The problem of solving the Schrodinger equation by a method related to the restrictive Pade approximation is considered. It yields more accurate results. The complex tridiagonal system which arises from the finite difference discretization of the considered equation is solved by Evans-Roomi [1] method. The restrictive Pade approach is applied successfully for the one and two dimensional Schrodinger equations. It is shown by numerical examples that it is more efficient and gives faster results compared with classical finite difference methods.

The aggregate - matrix interface plays a leading role in the fracture mechanisms and in the fracture response of concrete. In this work, the influence of the interface on the macroscopic fracture parameters of concrete is investigated. Eleven concrete batches were cast with the same matrix. Different-crushed or rounded-aggregates from the same quarry were used, and several surface treatments were applied to improve or degrade the bond between the matrix and the particles. Fracture tests (three-point bending tests and Brazilian splitting tests) were carried out to determine the fracture energy and other relevant fracture parameters of the concrete batches. The modulus of elasticity and the compressive strength were obtained from uniaxial compression tests. The macroscopic fracture behaviour was modeled by the cohesive crack model with a bilinear softening curve. The results show that concretes with the same matrix and aggregates, and similar behaviour under uniaxial compression, can give very different fracture responses, The work shows how fracture behaviour is governed by the interfacial properties that are also behind the cracking mechanism, (C) 2002 Elsevier Science Ltd. All rights reserved.

The decentralised treatment of concentrated sewage (about 3,600 mgCOD/1) at low temperature was investigated in a two-step anaerobic system: two-anaerobic hybrid (AH) septic tanks (each 0.575 m(3)). The two reactors were placed in a temperature controlled-room and the HRT was 2.5 days for each reactor. The system was fed with concentrated domestic sewage, mainly black water from about 40 toilets flushed with only 4 litre of water and a limited amount of grey water. The system showed high removal efficiency for the different COD fractions. Mean removal efficiencies in the two-step AH-septic tank at 5 days HIRT and 13degreesC were 94, 98, 74 and 78% for total COD, suspended COD, colloidal COD and dissolved COD respectively. The results of short run experiments indicated that the presence of reticulated polyurethane foam (RPF) media in the AH-septic tank improved the removal of suspended COD by 22%. The first AH-septic tank was full of sludge after 4 months of operation due to the high removal of particulate COD and the limited hydrolysis at low temperature conditions. Therefore, a simple mathematical model was developed based on ADM1 (the IWA model in 2002). Based on the experimental results and the mathematical model, only a one-step AH septic tank is required. An HRT of 5.5-7.5 days is needed for that one-step AH septic tank to treat concentrated sewage at a low temperature of 13degreesC. Such a system can provide a total COD removal as high as 87% and will be full of sludge after a period of more than a year.

The treatment of domestic sewage at low temperature was studied in a two-anaerobic-step system followed by an aerobic step, consisting of an anaerobic filter (AF) + an anaerobic hybrid (AH) + polyurethane-foam trickling filter (PTF). The AF+AH system was operated at a hydraulic retention time (HRT) of 3+6 h at a controlled temperature of 13degreesC, while the PTF was operated without wastewater recirculation at different hydraulic loading rates (HLR) of 41, 15.4 and 2.6 m(3)/m(2)/d at ambient temperature (ca. 15-18degreesC). The AF reactor removed the major part of the total and suspended COD, viz. 46 and 58% respectively. The AH reactor with granular sludge was efficient in the removal and conversion of the anaerobically biodegradable COD. The AF+AH system removed 63% of total COD and converted 46% of the influent total COD to methane. At a HLR of 41 m(3)/m(2)/d, the COD removal was limited in the PTF, while at HLR of 15.4 and 2.6 m3/M2/d, a high total COD removal of 54-57% was achieved without a significant difference between the two HLRs. The PTF was mainly efficient in the removal of particles (suspended and colloidal COD removal were 75-90% and 75-83% respectively), which were not removed in the anaerobic two-step. The overall total COD removal in the AF+AH+PTF system was 85%. Decreasing the HLR from 15.4 to 2.6 m3/M2/d, only increased the nitrification rate efficiency in the PTF from 22% to 60%. Also, at HLR of 15.4 and 2.6 m3/M2/d, PTF showed a similar removal for E coli by about 2 log. Therefore, the effluent of AF+AH+PTF system can be utilised for restricted irrigation in order to close water and nutrients cycles. Moreover, such a system represents a high-load and a low-cost technology, which is a suitable solution for developing countries.

The anaerobic biodegradability of domestic sewage for four Egyptian villages and four Egyptian cities was determined in batch experiments. The results showed that the biodegradability of the Egyptian-villages sewage (73%) was higher than that of the cities (66%). The higher biodegradability of the soluble COD of village sewage (69%) as compared to that of the cities (46%) was the reason for the higher biodegradability of the total COD of the villages sewage. The biodegradability of suspended COD was similar for the sewage of both villages and cities (73-74%). The results of a mathematical-model, developed based on anaerobic digestion model number 1, indicate that at applying a UASB reactor for the treatment of Egyptian villages and cities sewage, an optimum HRT of, respectively, 16 and 8 h is required. At these HRTs, a total COD removal and a conversion to methane of, respectively, 62-70% and 59-64% can be achieved for the sewage of cities and, respectively, 71-77% and 67-69% for the villages sewage. The model results also show that in the treatment of villages sewage in a two-step (anaerobic filter + UASB reactor) system a higher total COD removal can be obtained (77-81%) at a short HRT of 10 h (4 + 6 h). However, the excess sludge from the first-step of the two-step system will be less stabilized.

This paper describes a high performance single-chip FPGA implementation of the new Advanced Encryption Standard (AES) algorithm dealing with 128-bit data/key blocks and operating in Counter (CTR) mode. Counter mode has a proven-tight security and it enables the simultaneous processing of multiple blocks without losing the feedback mode advantages. It also gives the advantage of allowing the use of similar hardware for both encryption and decryption parts. The proposed architecture is modular. The architecture basic module implements a single round of the algorithm with the required expansion hardware and control signals. It gives very high flexibility in choosing the degree of pipelining according to the throughput requirements and hardware limitations and this gives the ability to achieve the best compromised design due to these aspects. The FPGA implementation presented is that of a pipelined single chip Rijndael design which runs at a rate of 10.8 Gbits/sec for full pipelining on an ALTERA APEX-EP20KE platform.

Adomian Decomposition method (ADM) is an approximate method, which can be adapted to solve nonlinear partial differential equations. In this paper, we solve the KdV and modified KdV (mKdV) equations using ADM-Pade technique, which gives the approximate solution with fast convergence rate and high accuracy in the case of solitary wave solution and closed form solution in the case of rational polynomial solution.

In this paper, a model for electron distribution in the direction perpendicular to the interface (transverse direction) of a DG-MOSFET is proposed The model is based on multiplying the classically-calculated electron density by a correction term to account for quantum-mechanical effects. The correction term is chosen to guarantee zero carrier density at the interface and assumes an effective bandgap widening resulting from splitting of the conduction band into subbands. The model has fitting parameters that were optimized with numerical simulation results. It has continuous derivative and works well over a wide range of gate biases and Si-film thicknesses including both volume and surface inversion regions.

In this paper, we shall develop a new explicit method for solve the convection-diffusion equation, which will exhibit several advantageous features: highly accurate, fast and with good results whatever the exact solution is too large. The stability region is discussed. The error upper bound is proved. The obtained results for a test problem compared with the exact solution and its Douglas approximation, it proves the mentioned advantages. (C) 2002 Elsevier Inc. All rights reserved.

A method of analysis is developed for studying the whirl stability of rotor-bearing systems without the need to solve the governing differential-equations of motion of such systems. A mathematical model, comprised of an axially-symmetric appendage at the mid-span of a spinning shaft mounted on two dissimilar eight-coefficient bearings, is used to illustrate the method. Sufficient conditions for asymptotic stability of both the translational and rotational modes of motion of the system have been derived. The system's stability boundaries, presented graphically in terms of the various system non-dimensionalized parameters, afford a comprehensive demonstration of the effects of such parameters on the system's stability of motion. (C) 2003 Elsevier Ltd. All rights reserved.

From 1995 to 2002 the author and others succeeded to apply a new approach for approximation which called restrictive Pade approximation and restrictive Taylor approximation. Almost the work is summarized in the nine papers [J. Faculty Educat. (1995) 63; Int. J. Comput. Math. 66 (1998) 343; Int. J. Comput. Math. 72 (1999) 271; Int. J. Comput. Math. 77 (2000) 251; J. lust. Math. Comput. Sci. 11 (1) (2000) 63; J. Inst. Math. Comput. Sci. India 11 (2) (2000) 159; Int. J. Comput. Math. 78 (2001) 73; Int. J. Inst. Math. Comput. Sci. 12 (2) (2001) 153; Int. J. Comput. Math. 79 (5) (2002) 603]. It Lives a lot of highly accurate, efficient and distinguished finite difference methods for numerical solutions of initial-boundary-value problerns for parabolic and hyperbolic partial differential equations. Now this paper derived a general theory for solvability and uniqueness of tile mentioned restrictive Pade and restrictive Taylor's approximations. A survey of the individual necessary and sufficient solvability and uniqueness conditions for several 15 examples of these approximations are given. (C) 2003 Elsevier Inc. All rights reserved.

Solving generalized Fisher and Burger-Fisher equations by the finite difference technique yields difficult nonlinear system of equations. In this paper linearization and restrictive Pade approximation is considered. It yields more accurate and faster results. Also the stability analysis is discussed. Numerical results are treated. (C) 2003 Elsevier Inc. All rights reserved.

In recent publications [Chaos, Solitons Fractals 12 (2001) 2283; Int. J. Appl. Math. 3 (4) (2000) 361], we have dealt with the numerical solutions of the Korteweg-De-Vries (KDV) and modified Korteweg-De-Vries (MKDV) equations. We extend this study to a more general nonlinear equation, which is the general Korteweg-De-Vries (GKDV) equation, in which the previous Studies is a special case of it. The method applied here is Adomian decomposition method, which has been developed by George Adomian [Solving Frontier Problems of Physics: The Decomposition Method, Kluwer Academic Publishers, Boston, MA, 1994]. Numerical examples are tested to illustrate the pertinent feature of the proposed algorithm. (C) 2003 Elsevier Inc. All rights reserved.

An experimental evaluation of using jojoba oil as an alternate Diesel engine fuel has been conducted in the present work. Measurements of jojoba oil chemical and physical properties have indicated a good potential of using jojoba oil as an alternative Diesel engine fuel. Blending of jojoba oil with gas oil has been shown to be an effective method to reduce engine problems associated with the high viscosity of jojoba oil. Experimental measurements of different performance parameters of a single cylinder, naturally aspirated, direct injection, Diesel engine have been performed using gas oil and blends of gas oil with jojoba oil. Measurements of engine performance parameters at different load conditions over the engine speed range have generally indicated a negligible loss of engine power, a slight increase in brake specific fuel consumption and a reduction in engine NO, and soot emission using blends of jojoba oil with gas oil as compared to gas oil. The reduction in engine soot emission has been observed to increase with the increase of jojoba oil percentage in the fuel blend. (C) 2003 Elsevier Ltd. All rights reserved.

In the present study, a two-phase closed thermosyphon flat-plate solar collector with a shell and tube heat exchanger was investigated experimentally under the field conditions of Cairo, Egypt. The collector was designed, constructed, and tested at transient conditions to study its performance for different cooling water mass flow rates at different inlet cooling water temperatures. Also the effect of the number of the thermosyphon tubes on the performance of the collector was investigated. Under different climate conditions, the experimental results showed that the optimal mass flow rate is very close to the ASHRAE standard mass flow rate for testing conventional flat-plate solar collectors. Also, the experimental results indicated that the number of the thermosyphon tubes has a significant effect on the collector efficiency. The performance of the present collector with optimum number of thermosyphon tubes was compared with the performance of two-phase closed thermosyphon flat-plate solar collectors with tube in tube heat exchangers of previous investigators and a better performance for the present collector was obtained at high inlet water temperature. (C) 2004 Elsevier Ltd. All rights reserved.

The transfer matrix method (TMM) has been extensively used to investigate quantum-mechanical tunnelling through potential barriers. Reported is the application of TMM, for the first time, to solve the Schrodinger equation in double-gate MOSFETs. The method is shown to be more accurate than the conventional finite difference method, especially for high energy levels.

Free convection from a tilted rectangular enclosure heated at the bottom wall and vented by uniform slots opening at different walls of the enclosure was experimentally investigated. The experiments were carried out to study the effects of venting arrangement, opening ratio and enclosure's tilt angle on the passive cooling of the enclosure. The experiments were carried out at a constant heat flux of 250 W/m(2) and for enclosure tilt angles ranging from 0degrees to 180degrees. Three different venting arrangements of the air from the enclosure were studied: (1) top-venting arrangement, (2) side-venting arrangement, and (3) top and side-venting arrangement. Each venting arrangement was studied at different opening ratios of 1, 0.75, 0.5 and 0.25. The results showed that: (1) for top-venting arrangement, the Nusselt number decreases as the tilt angle of the enclosure increases, (2) for side-venting and side and top-venting arrangements, the Nusselt number increases as the tilt angle increases in the range [0degrees, 90degrees], then it decreases with the increase of the tilt angle, (3) for the three venting arrangements and at any tilt angle, the Nusselt number increases with the increase of the opening ratio of the slots, (4) for any tilt angle and at any opening ratio, the top and side-venting arrangement has the highest rate of cooling of the enclosure, and (5) for small tilt angles, the rate of cooling of the enclosure for top-venting arrangement was higher than that for side-venting arrangement, but with increasing tilt angle, the rate of cooling for side-venting arrangement becomes higher than that for top-venting arrangement. Correlations were developed for the three venting arrangements to predict the average Nusselt number of the enclosure in terms of the opening ratio and the enclosure tilt angle. (C) 2004 Elsevier Inc. All rights reserved.

The approximate solutions for the Burger's-Huxley and Burger's-Fisher equations are obtained by using the Adomian decomposition method [Solving Frontier Problems of Physics: the Decomposition Method, Kluwer, Boston, 1994]. The algorithm is illustrated by studying an initial value problem. The obtained results are presented and only few terms of the expansion are required to obtain the approximate solution which is found to be accurate and efficient. (C) 2003 Elsevier Inc. All rights reserved.

This paper presents experimental study to simulate the natural pollution conditions of high voltage polluted insulators. The effects of some factors on the leakage current bursts (number and magnitudes) are studied. Like these factors are the effect of polluted layer conductivity on the leakage current bursts, the effect of wetting method of polluted layer of high voltage insulators on the leakage current bursts, effect of the method of applying the high voltage on leakage current bursts and effect of pollution layer material on the leakage current bursts. In these tests the investigated insulators are covered with a homogenous layer according to IEC. The degree of severity is evaluated by surface layer conductivity. The paper contains also high voltage tests to simulate the desert conditions in which the dew is usually formed when the air temperature drops sharply while the humidity is high.

Numerical experiments have been carried out to investigate natural convection heat transfer and fluid flow characteristics from a horizontal fluid layer with finned bottom surface. The effects of fin height and fin spacing have been investigated for a sufficiently wide range of Rayleigh number. Quantitative comparisons of heat transfer rates and finned surface effectiveness have been reported. The insertion of heat conducting fins has been found to induce an upward fluid motion along the fin walls. For a given value of fin spacing, the number of convection cells between two adjacent fins is function of the values of fin height and Rayleigh number. In comparison with a bare plate, the heat transfer rates for low values of fin height may be decreased by the insertion of fins. For high values of fin height, the finned surface effectiveness is greater than one for a wide range of fin spacing. or low values of Rayleigh number and high values of fin. height, the finned surface effectiveness increases linearly with the decrease of fin spacing. Useful guidelines have been suggested to enhance the heat transfer rates from the finned surface. (C) 2004 Elsevier SAS. All rights reserved.

The switching frequency of a conventional direct torque control (DTC) strategy which is based on hysteresis controllers results in a variable switching frequency which depends on the mechanical speed. stator flux, stator voltage, and the hysteresis band of the comparator. In this paper, a DTC scheme using space vector modulator (SVM) and fuzzy logic controller (FLC) is suggested. A comparison with the classical DTC is presented. The suggested control strategy guarantees very good dynamic and steady state characteristics with low sampling rate and a constant switching frequency. The experimental results are presented to validate the scheme. Copyright (C) 2005 John Wiley Sons, Ltd.

The potential of anaerobic digestion in ecological and decentralised sanitation has been investigated in this research. Different anaerobic digestion systems were proposed for the treatment of sewage, grey water, black water and faeces. Moreover, mathematical models based on anaerobic digestion model no.1 (ADM1) were developed for determination of the suitable design for each system. For stable performance of an upflow anaerobic sludge blanket (UASB) reactor treating sewage, the model results indicated that optimisation of wastewater conversion to biogas (not COD removal) should be selected for determination of the hydraulic retention time (HRT) of the reactor. For the treatment of sewage or black water in a UASB septic-tank, the model results showed that the sludge removal-period was the main parameter for determination of the HRT. At such HRT, both COD removal and wastewater conversion are also optimised. The model results demonstrated that for treatment of faeces in an accumulation (AC) system at temperature >= 25 degrees C, the filling period of the system should be higher than 60 days. For maximisation of the net biogas production (i.e. reduction of biogas losses as dissolved in the effluent), the separation between grey water, urine and faeces and reduction of water consumption for faeces flushing are required. Furthermore, the faeces + kitchen organic wastes and grey water are digested in, respectively, AC system and UASB reactor, while the urine is stored.

Hardware Description Languages (RDLs) are commonly used to construct hardware systems. Reuse of the design is a common practice to improve the productivity nowadays. In this paper, an implementation of a fully pipelined ARM compatible processor core, which can be embedded into System-on-Chips (SOCs) is presented. The implementation aims to support research, education, and development by opening the source codes. The logic description of the core is based on VHDL. Therefore, the core can be applied to design tools of many vendors and can be easily reused.

This paper is concerned with theoretical and experimental investigations of the onset voltage of positive corona as influenced by coating the coronating electrodes. Dielectric-coated hemispherically-capped rod-plane gaps positioned in air are investigated. The onset voltage is determined when a developed primary avalanche triggers successor avalanches to sustain the discharge process. Laboratory measurements of the onset voltage on bare and coated electrodes were carried out. The effects of varying field nonuniformity, thickness and permittivity of coating material on the onset voltage values were investigated. The results show that coating the electrodes with a dielectric material is effective in increasing the onset voltage of corona. The calculated onset voltage values for coated and bare electrodes agreed satisfactorily with those measured experimentally within 10%.

This paper deals with the novel idea of controlling the electric stress in a hybrid air-solid dielectric insulation. In a parallel-plate electrode system, the electric stress can be reduced if the electrodes are covered with thick non-conducting dielectric coatings. Free charges are generated by microdischarges developing between the electrodes and are deposited at the dielectric Surfaces. As a consequence,, a counteracting electric field component results, which causes a reduction of the electric field in the air gap and an enhancement of the field in the dielectric coatings: i.e. the electric stress is forced into the dielectric coatings by the charges. A computation of the threshold voltage of the microdischarges is presented. The charge simulation technique IS used for field calculation. irrespective of the thickness of the dielectric layer and the values of the charges deposited on the dielectric surfaces. The calculated threshold voltages are compared with those estimated before analytically and those measured for different gap lengths.

A fixed-domain numerical model for microsegregation during alloy solidi. cation is developed. The phenomena of solute partitioning at the moving solid/liquid interface and subsequent redistribution by diffusion in the solid and liquid phases have been formulated using volumetric terms. A solute balance equation valid for the whole domain comprising the solid and liquid phases has been obtained in terms of the liquid concentration. The effects of microstructure coarsening on microsegregation has been described and included in the present model. Numerical experiments and comparisons have been carried out between the present fixed-domain model, previous deforming-domain models, and the exact analytical solutions available in the literature. Good agreement has been observed between the predictions of the present fixed-domain model and the exact analytical solutions. Further extensions of the present model for the analysis of two-dimensional microsegregation have been also reported.

Different relationships have been proposed by codes and researchers for predicting the shear capacity of members without transverse reinforcement. In this paper, the applicability of the artificial neural network (ANN) technique as an analytical alternative to existing methods for predicting this shear capacity is investigated using a critically reviewed and agreed upon database of experimental work that serves as a basis of comparison and (or) assessment of existing and new relationships. Both ANN and eight different codes and researcher's predictions of the shear capacity of the specimens of the database were compared. The ANN predictions are much superior to those of any of the current available relationships.

Some accurate finite difference sophisticated methods for solving initial boundary value problem for partial differential equations gives its exact solution with certain values of the mesh sizes of space and time as done [H.N.A. Ismail, On the convergence of the restrictive Pade approximation to the exact solutions of IBVP of parabolic and hyperbolic types, Appl. Math. Comput., accepted; H.N.A. Ismail, G.S.E. Salem, On the convergence of the restrictive Taylor approximation to the exact solutions of IBVP for parabolic, hyperbolic, convection diffusion, and KdV equations, Appl. Math. Comput., in press]. The restrictive Pade and restrictive Taylor approximations are very promising methods. In recent publications [H.N.A. Ismail, K.R. Raslan, G.S.E. Salem, Solitary wave solutions for the General KdV equation by Adomian decomposition method, 28th International Conference for Statistics and Computer Science and its Applications, Cairo, Appl. Math. Comput., June, accepted; A.M. Wazwaz, Construction of solitary wave solutions and rational solutions for the KdV equation by Adomian decomposition method, Chaos, Soliton. Fract. 12 (2001) 2283-2293; A.M. Wazwaz, Solitary wave solutions for the modified KdV equation by Adomian decomposition method, Int. J. Appl. Math. 3(4) (2000) 361-368], we have dealt with the numerical solutions of the Korteweg-de-Vries (KdV) and modified Korteweg-de-Vries (MKdV) equations. We extend this study to a more general nonlinear equation, which is the General Korteweg-de-Vries (GKdV) equation. The method applied here is Adomian decomposition method, which has been developed by George Adomian [Solving Frontier Problems of Physics: the Decomposition Method, Kluwer Academic Publishers, Boston, MA, 1994], restrictive Taylor and restrictive Pade approximations. Numerical examples are tested to illustrate the pertinent feature of the proposed algorithms. (c) 2004 Elsevier Inc. All rights reserved.

A performance comparison study of four HDM systems is presented. The four systems studied are hybrid companding delta modulation (HCDM), hybrid constant factor incremental DM (HCFIDM), song hybrid companding DM (SHCDM) and modified SHCDM (MSHCDM). The study was done at low bit rates with three different input signals. According to our results, the MSHCDM always performs better while the HCDM systems may not always be good. Further, for low frequency input signals the dynamic range of SHCDM and HCFIDM is much wider than that of HCDM. In a noisy channel, the results for HCDM at a bit rate of 24 kbs s-1 indicate that the values of SNR at an error rate of 0.001 and 0.01 are, respectively, 15 dB and 6 dB, whereas in the case of HCFIDM and SHCDM they are 16 dB and 10 dB.

This paper is concerned with an efficient algorithm for the computation of frequency response matrices for single-input control systems of the form C(jwI - A)-1b. A reduction of the matrix A is achieved using Arnoldi's algorithm where (jwI - H) remains in upper Hessenberg form of less dimension as w varies over a desired range. Simple and faster computation can then be used to solve an upper Hessenberg system of smaller dimension.

N-butyric, n-heptanoic, and n-nonanoic acids (3.9 moles) were esterified by trimethylolpropane (1 mol.) in presence of metal halide (Mcl 200) as catalyst and an azeotropic agent which facilitates the continuous separation of water of the reaction using a Dean Stark apparatus at about 170-degrees-C under agitation. About 98.5 wt% in 5.5 hours, 98.1 wt% in 6 hours, and 96.8 wt% in 6.5 hours conversions were verified for the C4, C-7 and C-9 acids respectively. The structures of the prepared esters were outlined by elementary analysis, molecular weight determination, and infra-red studies. The measurements of the variation of the viscosity with temperature for the prepared ester suggest their suitability as excellent base lubricant. The comparative study of the physico-chemical characteristics of the prepared esters and those of the commercial turbo-engine oil (turbonycoil 13 B) suggest their probable use as base lubricant in the formulation of turbo-engines lubricant according to the French specification Air 3514 for turbo-jet aircraft of supersonic speed regimes.

Natural convection from uniformly heated helicoidal pipes oriented vertically and horizontally is experimentally studied. Four helicoidal pipes of different parameters are presented. The effects of pitch to pipe diameter ratio, coil diameter to pipe diameter ratio and length to pipe diameter ratio on the average heat transfer coefficient are found. The experiments covered a range of Rayleigh number based on tube diameter from 1.5 x 10(3) to 1.1 x 10(5). The results showed that the overall average Nusselt number, Nu(m), increases with the increase in pitch to pipe diameter ratio, coil diameter to pipe diameter ratio and length to pipe diameter ratio for vertical helicoidal pipes. For horizontal helicoidal pipes, the overall average Nusselt number, Nu, increases with the increase in pitch to pipe diameter ratio and length to pipe diameter ratio, but it decreases with the increase in coil diameter to pipe diameter ratio. New correlations are presented, and they can be used in HVAC applications. (c) 2005 Elsevier Ltd.

The post-treatment of domestic sewage pretreated in a 6 m(3) UASB was investigated in two high-rate anaerobic filter (AF) reactors operated in parallel. The difference between the two AF reactors was only the addition of cationic polymer to the second reactor (AF + P). The reactors were operated at low temperatures, ranged between 13 and 20 degrees C. The media in each AF reactor consisted of vertical sheets of reticulated-polyurethane foam (RPF) with knobs. The results demonstrated that the AF + P reactor (HRT = 3 h) with cationic polymer addition (2 mg/L) was an efficient system for post-treatment. The removal efficiencies for total, suspended, colloidal and dissolved COD were, respectively, 41, 86 and 76 and 1296 in the AF + P reactor and they were, respectively, 80, 97, 77 and 6696 in the UASB + (AF + P) system. The removal of total, suspended and colloidal COD in the UASB + (AF + P) system were significantly higher than those achieved in the UASB + AF system. As hardly any nutrient was removed in the UASB + (AF + P) system, the effluent after pathogen removal is a valuable product for irrigation and fertilisation to close the water and nutrients cycle.

The feasibility of two accumulation-systems (AC) for anaerobic digestion and storage of concentrated black water with (A,Cl) or without (AC2) urine + kitchen organic-wastes was investigated. The waste(water) 0 was collected by two vacuum toilet/transport systems. The influent-total COD of the AC2 (53,000 mg/L) was more concentrated by four times than that of the AC1. The suspended COD represented the major part (71-73%) of influent total COD of the two systems. The batch-experiments results showed a high anaerobic biodegradability of the waste(water) (> 85%). The AC systems demonstrated stable performance. There was no inhibition effect of NH4 and VFA concentration decreased in time. Total COD removal of 58% was achieved in both systems, after 105 days at 20 degrees C. Moreover, if only the supernatant in AC1 is withdrawn and the settled sludge stays for the next runs, only 20% of the influent total COD will be in the supernatant. In AC2, 74% of influent ortho-P was removed by precipitation. Therefore, the settled sludge in the AC2 had a high total-P concentration of 1,300 mg/L. The C:N:P ratios of the supernatant and the sludge were 26:13:1 and 35:4.5:1, respectively, in the AC1, and were 28:14:1 and 32:2.4: 1, respectively, in AC2.

Anaerobic digestion of concentrated domestic wastewater streams - black or brown water, and solid fraction of kitchen waste is considered as a core technology in a source separation based sanitation concept (DESAR - decentralised sanitation and reuse). A simple anaerobic digester can be implemented for an enhanced primary treatment or, in some situations, as a main treatment. Two reactor configurations were extensively studied; accumulation system (AC) and UASB septic tank at 15, 20 and 25 C. Due to long retention times in an AC reactor, far stabilisation of treated medium can be accomplished with methanisation up to 60%. The AC systems are the most suitable to apply when the volume of waste to be treated is minimal and when a direct reuse of a treated medium in agriculture is possible. Digested effluent contains both liquid and solids. In a UASB septic tank, efficient separation of solids and liquid is accomplished. The total COD removal was above 80% at 25 degrees C. The effluent contains COD and nutrients, mainly in a soluble form. The frequency of excess sludge removal is low and sludge is well stabilised due to a long accumulation time.

The potential of anaerobic digestion in ecological and decentralised sanitation has been investigated in this research. Different anaerobic digestion systems were proposed for the. treatment of sewage, grey water, black water and faeces. Moreover, mathematical models based on anaerobic digestion model no.1 (ADM1) were developed for determination of a suitable design for each system. For stable performance of an upflow anaerobic sludge blanket (UASB) reactor treating sewage, the model results indicated that optimisation of wastewater conversion to biogas (not COD removal) should be selected for determination of the hydraulic retention time (HRT) of the reactor. For the treatment of sewage or black water in a UASB septic-tank, the model results showed that the sludge removal period was the main parameter for determination of the HRT. At such HRT, both COD removal and wastewater conversion are also optimised. The model results demonstrated that for treatment of faeces in an accumulation (AC) system at temperature >= 25 degrees C, the filling period of the system should be higher than 60 days. For maximisation of the net biogas production (i.e. reduction of biogas losses as dissolved in the effluent), the separation between grey water, urine and faeces and reduction of water consumption for faeces flushing are required. Furthermore, the faeces and kitchen organic wastes and grey water are digested in, respectively, an AC system and UASB reactor, while the urine is stored.

The flow field through a transonic linear turbine cascade is studied in this paper at design and off-design conditions. The compressible flow field is obtained by solving the equations governing the fluid flow and heat transfer. Two eddy-viscosity turbulence models are used to simulate the turbulence in turbine cascades: the standard k-epsilon model and the Spalart-Allmaras model. The standard k-epsilon model is the most universal and popular model for industrial flow and heat transfer simulations. It has the shortcoming of accurately predicting the profile loss in turbomachinery applications. The Spalart-Allmaras model is a relatively recent and simple one-equation model. In this paper, the model is tested for turbomachinery applications. The ability of the model to accurately predict the flow field in turbine cascade is tested. Blade loading, downstream wake distribution, total pressure loss coefficient, and exit flow angle are used in this study with comparisons to the standard k-epsilon model and experimental data. The design condition and the off-design conditions are considered.

Entropy generation for a viscous, forced convection through enhanced rough tubes subjected to constant heat flux was numerically investigated. The entropy generation and exergy destruction due to the flow friction and heat transfer was proposed to evaluate the benefits of the utilisation of different enhanced tubes. The model was based on either measurements or empirical correlations for both the flow and heat transfer characteristics in plain and enhanced tubes. Flow of different fluids in rough tubes with threedimensional internal extended surfaces (3-DIES) were studied. Enhanced rough tubes, either with continued or regularly spaced tape inserts were investigated. Based on exergy performance, it was found that the use of hollow 3-DIES tubes in water turbulent flow regime is preferable while segmented twistedtape inserts is attractive in laminar flow. Also, inline 3-DIES rough tubes indicate a lower exergy destruction rate when compared with that of staggered alignments. The correlation for both optimum Reynolds number (Re-*) and minimum percentage exergy destruction (Psi(min) %) were obtained for oil and Ethylene Glycol flows in inline 3-DIES rough tubes as a function of the exposed heat flux, Prandtl number and the tube ratio (L/D).

Natural convection from the inside surface of a horizontal elliptic tube of axis ratio (major to minor axis) 2:1 with a uniformly heated surface was investigated experimentally. The effect of angle of attack on the heat transfer rate was studied. The angle of attack (alpha) was varied from 0 (when the major axis was horizontal) to 90 (when the major axis was vertical) with steps of 15. The experiments covered a range of Rayleigh number Ra from 1.45 x 10(6) to 1.78 x 10(7). The local and average heat transfer coefficients and Nusselt number were estimated for different angles of attack at different Rayleigh numbers. The results obtained showed that the effect of angle of attack on the heat transfer coefficient is significant. The temperature distributions increase with the increase of axial distance from both ends of the tube until a maximum value at the middle of the tube. Also, the local Nu increases with the increase of a at the same axial distance. The average Nu(m), increases with the increase of alpha at the same Ra. The results obtained were correlated by dimensionless groups and with the available data of the horizontal elliptic tube. (c) 2005 Elsevier Ltd. All rights reserved.

Rigorous assessment of uncertainties associated with capacitor installation in distribution systems is the aim of the present paper. Interval mathematics provides a powerful tool for modeling uncertainties. To account for such uncertainties, a heuristic method coupled with interval mathematics is developed with the aim of maximizing a cost saving function. The effects of uncertain inputs within the proposed model are examined for various assumed levels of overall uncertainties. To assess the relative contribution of each uncertain input, an interval sensitivity analysis is carried out. While catering for uncertainties, the proposed method offers utilities with alternatives for selecting the standard capacitor sizes to be used and the associated costs to be saved. This should enable utilities to make informed decisions regarding installing capacitors for reactive power compensation in their distribution systems. A procedure is devised in order to produce sharp bounds of the interval outcomes. Successful implementation of the proposed method is described using a nine- bus radial distribution system.

Numerical simulation of nanoscale double gate MOSFET depends mainly on the accurate representation of quantum-mechanical effects. These effects include, mainly, the quantum confinement of carriers by gate-oxides in the direction normal to the interfaces, and the quantum transport of carriers along the channel. In a previous work, the use of Transfer Matrix Method (TMM) was proposed for the simulation of the first effect. In this work, TMM is proposed to be used for the solution of Schrodinger equation with open boundary conditions to simulate the second quantum-mechanical effect. Transport properties such as transmission probability, carrier concentration, and I-V characteristics resulting from quantum transport simulation using TMM are compared with that using the traditional tight-binding model (TBM). Comparison showed that, when the same mesh size is used in both methods, TMM gives more accurate results than TBM.

In the present study, two numerical approaches for single-domain modelling of microsegregation during solidification of binary alloys are presented. In the first approach, the concentration jump at the moving solid/liquid interface is formulated using a volumetric term and a Boolean function. The governing solute redistribution equation, valid for the whole domain comprising the solid and liquid regions, is derived in terms of the liquid phase composition. The effects of microstructure coarsening on microsegregation has been described and included in the model. In the second approach, the continuum mixture theory is utilized to derive a single domain solute redistribution equation in terms of the mixture composition. The solidification front motion and dendrite arm coarsening effects are accommodated by considering the representative elementary volume to consist of solid, interdendritic, and extradendritic liquid phases. Numerical solutions have been obtained using a control-volume based finite-difference method with a fixed grid. Good agreement has been observed between the predictions of the present fixed-domain models and the exact analytical and experimental results.

An enthalpy-porosity fixed-grid method has been applied to the melting and solidification of pure metals in a rectangular cavity. Flow structures and isotherms are compared with literature information based on multidomain analysis. During solidification, recirculation cells are observed to vanish with time, whereas the multidomain method predicted their enlargement. The cell near the interface significantly affects the local solidification rate at the cavity top. Results of the present study agree well with the experimental data in the literature. The effect of neglecting the viscous diffusion term for a phase change problem involving low Prandtl number liquid metals is also studied. The maximum value of the stream function is higher by 10% and the melt volume by 5%, in the absence of viscous effects.

A conjunction T ties an implication operator A if the identity A(a, A(b, z)) = A(T(a, b), z) holds [A.A. Abdel-Hamid, N.N. Morsi, Associatively tied implications, Fuzzy Sets and Systems 136 (2003) 291-311]. We study the class of tied adjointness algebras (which are five-connective algebras on two partially ordered sets), in which the implications are tied by triangular norms. This class contains, besides residuated implications, several other implications employed in fuzzy logic. Nevertheless, we show that the algebraic inequalities of residuated algebras remain true for our tied implications, but in forms that distribute roles over the five connectives of the algebra. We apply the properties of tied implications to a generalized modus ponens inference scheme with two successive rules. We prove its equivalence to a scheme with one compound rule, when both schemata are interpreted by the compositional rule of inference, and all connectives are taken from one tied adjointness algebra. Then we quote another application of this rich theory, a notion of many-valued rough sets, which exhibit the basic mathematical behaviour of the rough sets of Pawlak. A comparator His said to be prelinear if it satisfies H(y, z) boolean OR H(z, y) = 1 for all y, z (Hajek). We introduce prelinear tied adjointness algebras, in which two comparators are prelinear. We provide a representation of those algebras, as subdirect products of tied adjointness chains, on the lines of Hajek's representation of BL-algebras. But our representations are more economical, because we employ minimal prime filters (on residuated lattices) only; rather than all prime filters. (c) 2005 Elsevier B.V. All rights reserved.

We study the propagation of electromagnetic waves in infinite lines with grafted finite lines in a frequency regime, where the grafted lines have negative phase velocity. The physical properties of such a structure with negative phase velocity materials have not been investigated before, to the best of our knowledge. The theory uses a Green's function formalism. For a single resonator structure we calculate the transmission intensity, and for periodic systems, we determine the transmission intensities and the miniband structures as functions of the number of resonators. In a single resonator structure, resonances are manifested as dips in the transmission, which evolve into stopping minigaps for periodic systems. The dispersion relations of collective normal modes exhibit new allowed minibands or stopping minigaps for the electromagnetic wave propagation, which depend on the number of resonators and the resonator size. These results are in agreement with the features of the transmission spectra. We also investigate the effects of dissipation on the transmission spectra of such structures.

Cobalt ferrite nanoparticles, CoFe2O4, are one of the important spinel ferrites due to their high cubic magnetocrystalline anisotropy, high coercivity and moderate saturation magnetization. CoFe2O4 nanoparticles have been known to be a photomagnetic material which shows an interesting light induced coercivity change. In this study, various preparation techniques were used to produce cobalt ferrite nanoparticles namely, (i) ball milling of a homogeneous mixture of cobalt(II) acetate, and iron(Ill) acetate (basic) treated by a novel self flash combustion, (ii) precipitation of cobalt(II) chloride (CoCl(2)(.)6H(2)O) and iron(111) chloride (FeCl3), and (iii) ceramic method by firing of cobalt oxide (CoO) and iron oxide (Fe2O3). These techniques help to obtain particle sizes ranging from a few micrometers to about 20 nm. Thermal analysis (TGA and DTA), X-ray diffraction, SEM, TEM, magnetic and surface area measurements have been used for characterization of the prepared samples. Results showed that saturation magnetic flux density (Bs) and remnant magnetic flux density (Br) varied with crystallite size from 6.929 to 14.91 and 2.73 to 8.146emu/g, respectively. The measured surface area (S-BET) for the prepared Co-ferrite particles ranged from 5.327 to 47 m(2)/g. The effect of different nanosizes on the total pore volume, adsorption energy, average pore diameter, micro pore volume, have been studied. Nanocrystalline CoFe2O4 showed a catalytic activity towards CO2 decomposition with the formation of carbon nanotubes. (c) 2006 Elsevier B.V.

The efficiency and cost-effectiveness of H2O2/UV for the complete decolorization and mineralization of wastewater containing high concentrations of the textile dye Reactive Black 5 was examined. Oxidation until decolorization removed 200-300 mg g(-1) of the dissolved organic carbon (DOC). The specific energy consumption was dependent on the initial dye concentration: the higher concentration required a lower specific energy input on a weight basis (160 W h g(-1) RB5 for 2.1 g L-1 versus 354 W h g(-1) RBS for 0.5 g L-1). Biodegradable compounds were formed, so that DOC removal could be increased by 30% in a following biological stage. However, in order to attain 800 mg g(-1) overall mineralization, 500 mg g(-1) of the DOC had to be oxidized in the H2O2/UV stage. A cost analysis showed that although the capital costs are much less for a H2O2/UV stage compared to ozonation, the operating costs are almost double those of ozonation. Thus, while H2O2/UV can compete with ozonation when the treatment goal only requires decolorization, ozonation is more cost-effective in this case when mineralization is desired. (c) 2006 Society of Chemical Industry.

An experimental study of cooling an array of multiple heat sources simulating electronic equipment by a single row of slot air jets positioned above a critical row (row having maximum heat dissipation rate) of the array was conducted. The other low power rows of the array were cooled by the spent air flow from the air jets. The experimental work was carried out in two phases. In the first phase, each block of the array was heated at a time and the other blocks of the array were kept unheated. The Nusselt number of each heated block and the thermal wake effect on downstream blocks were investigated and correlated for different values of jet Reynolds number, position of the block with respect to the jet impingement point and the separation distance between the orifice plate and the impingement surface. A superposition technique was implemented to demonstrate the practical importance of the present correlations in predicting the operating temperature of any block in an array with multiple heated blocks. In the second phase, the experiments were carried out with heating all the blocks at the same time. This phase was carried out to verify the superposition technique used to predict the operating temperature of the blocks of the array in the case of the multiple heating. (c) 2006 Elsevier Ltd

In the present study, the effect of wickless heat pipe cross section geometry and its working fluid filling ratio on the performance of flat plate solar collectors has been investigated experimentally. Three groups of wickless heat pipes having three different cross section geometries (namely, circular, elliptical and semi-circular cross sections) were designed and manufactured. Each group of three wickless heat pipes was charged with three different distilled water filling ratios of 10%, 20% and 35%. Each wickless heat pipe was then incorporated into a prototype flat plate solar collector developed for the purpose of the present study. The prototypes wickless heat pipe flat plate solar collectors have been investigated experimentally at different inlet cooling water temperatures, two different cooling water mass flow rates and under the meteorological conditions of Cairo, Egypt. The experimental results indicate that the elliptical cross section wickless heat pipe flat plate solar collectors have better performance than the circular cross section ones at low water filling ratios. The optimum water filling ratio of the elliptical cross section wickless heat pipe solar collector is about 10%, while it is very close to 20% for the circular cross section one. Also, the water filling ratio corresponding to the flooding limit of the elliptical wickless heat pipe solar collector is lower than that of the circular one. At 20% water filling ratio, the semi-circular cross section wickless heat pipe solar collector has bad performance compared with that of the other cross sections. (c) 2005 Elsevier Ltd. All rights reserved.

An implication operator A is said to be tied if there is a binary operation T that ties A; that is, the identity A (a, A (b, z)) = A (T (a, b), z) holds for all a, b, z. We aim at the construction of a complete predicate logic for prelinear tied adjointness, algebras. We realize this in three steps. In the first step, we establish a propositional calculus AdjTPC, complete for the class of all tied adjointness algebras on partially ordered sets; without prelinearity and ignoring the lattice operations. For that we supply a Hilbert system based on seven axioms and one deduction rule (modus ponens). In the second and third steps, we extend AdjTPC to propositional and predicate calculi; complete for prelinear tied adjointness algebras. We apply a duality principle, due to Morsi, in all three calculi; through which we manage to cut down the number of proofs. (c) 2006 Elsevier B.V. All rights reserved.

Clusters of microcalcifications in mammograms are an important early sign of breast cancer in women. Comparing with microcalcifications, the breast background tissues have high local self-similarity, which is the basic property of fractal objects. A fast fractal modeling method of mammograms for detecting the presence of microcalcifications is proposed in this paper. The conventional fractal modeling method consumes too much computation time. In the proposed method, the image is divided into shade (homogeneous) and non-shade blocks based on the dynamic range and only the non-shade blocks are modeled. Reducing the number of the processed blocks reduces the encoding time to 6.372% compared to the conventional modeling method. The modeled mammograms were investigated for microcalcifications detection and the results show that the sensitivity is 92% for 25 abnormal mammograms were obtained.

In this paper, simulation and implementation of Asymmetric Digital Subscriber Line (ADSL) modem is presented which can be applied to different telephone networks. The ADSL modem is modeled and simulated under the MATLAB version 7.3 (R2006b) environments by which the simulation is achieved for both the downstream and upstream directions of the modem. The ADSL modern with a transmission throughput between 690 kbps and 6 Mbps operating over most of existing telephone subscriber loops has been implemented on TI TMS320C6713 DSP for consumer multimedia applications. Except the Analog Front End, all the basic building blocks of the ADSL modem functionalities are implemented with DSP platform. We use Real-Time Data Exchange (RTDX) as a way to debug and test our DSP designs.

Face verification has been widely studied during the past two decades. One of the challenges is the rising concern about the security and privacy of the template database. In this paper, we propose a secure face verification system which employs a user dependent one way transformation based on a two stage hashing algorithm. We first hash the face image using a two stages robust image hashing technique, then the result hash vector is encrypted using Advanced Encryption Standard (AES). Both the hashing and the encryption/decryption keys are generated from the user claimed ID, using a modified password-based key driven algorithm. The proposed system is tested on the ORL (AT&T) face database.

The increasing demand for portable computing has elevated power consumption to be one of the most critical embedded systems design parameters. In this paper, we present a qualitative study wherein we examine the impact of code transformations on the energy and power consumption. Three main categories of code transformations are investigated, namely data, loop and procedural oriented transformations. Moreover, we evaluate the influence of employing Single Instruction Multiple Data (SIMD) on energy and power dissipation via the utilization of compiler intrinsic C-functions. Results show that a trade-off between power and performance can be achieved by employing the intrinsic C-functions in conjunction with some transformations such as loop unrolling and procedure integration.

The present article reports on the feasibility of using encapsulated phase change materials (EPCMs) in the dehumidifying bed of a desiccant cooling system. The mathematical model used to simulate the coupled non-equilibrium heat and moisture transfer processes in the porous composite structure containing the EPCM and desiccant particles is presented. Numerical investigations of heat and mass transfer in a desiccant dehumidifying bed composed of silica gel and EPCM particles have been carried out for different values of process parameters. Careful choices of EPCM volume fraction and thermo physical characteristics have been found to increase the overall effectiveness of the desiccant dehumidifier with negligible loss in the dehumidification efficiency. The air stream exits the desiccant/EPCM bed at relatively lower temperature and slightly higher moisture content than from purely desiccant bed. Desiccant cooling systems with less sensible heating and higher cooling capacity can be obtained by employing EPCM in the dehumidifier. (C) 2008 Elsevier Ltd. All rights reserved.

Enhanced efficiency of the adsorption process in the dehumidifier is a key element for improved performance of desiccant cooling systems. Due to the exothermic nature of the adsorption process, the dehumidification and cooling capacity are limited by significant temperature changes in the adsorption column. In the present study, the effects of integration of sensible and latent heat storage particles in the desiccant bed for in situ management of released adsorption heat are investigated. For this purpose, column experiments are performed using an initially dry granular bed made of silica-gel particles or a homogeneous mixture of silica gel and inert sensible or latent heat storage particles. The packed bed is subject to a sudden uniform air flow at selected values of temperature and humidity. Also, a packed bed numerical model is developed that includes the coupled non-equilibrium heat and moisture transfer in the solid and gas phases. Investigations of the heat and mass transfer characteristics are reported using the composite structure and the results are compared with the base case of simple silica gel bed. Improved desiccant cooling system performance can be obtained by appropriate adjustment of desiccant cycle operation and proper choice of the volume ratio of thermal energy storage particles.

This paper shows how water permeability may be calculated from measurements of drying under a vacuum. The results obtained are for water vapour transport at low pressures and gas slippage theory is then used to compare them with liquid water permeability measurements on samples of the same mixes. The experimental work includes the drying procedure and also the initial surface absorption test (ISAT), a standard absorption test using a partially immersed sample and a 'through flow' high-pressure test for direct permeability measurements. The results from these tests are compared and additional gas and liquid permeability data from the literature is included for comparison. It is concluded that, with appropriate analysis, all of the procedures give comparable values for intrinsic permeability.

Characterization of the phase changing behavior of granular materials is an important issue for design and optimization of latent heat thermal energy storage (LHTES) systems. In the present work, differential scanning calorimetry, (DSC) has been used to study the phase changing behavior of granular composites consisting of ceramic encapsulated phase change material (EPCM) with particle diameters of 1-3 mm. The obtained DSC curves characterizing melting and solidification of the composite material are shown to be dependent upon the values of heating and cooling rates. Direct utilization of the measured DSC curves could result in an inexact representation of the sample enthalpy change. A simple procedure has been advised to obtain accurate quantitative results from the DSC measurements based on the estimation of the thermal resistance between the sample and its enclosure. Analysis of the evolution of latent heat of EPCM with temperature at different values of cooling/heating rates is presented. (C) 2009 Elsevier Ltd. All rights reserved.

The present article reports on heat transfer characteristics associated with multiple laminar impinging air jet cooling a hot flat plat at different orientations. The work aims to study the interactions of the effects of cross flow, buoyancy induced flow, orientation of the hot surface with respect to gravity, Reynolds numbers and Rayleigh numbers on heat transfer characteristics. Experiments have been carried out for different values of jet Reynolds number, Rayleigh number and cross flow strength and at different orientations of the air jet with respect to the target hot plate. In general, the effective cooling of the plate has been observed to be increased with increasing Reynolds number and Rayleigh number. The results concluded that the hot surface orientation is important for optimum performance in practical applications. It was found that for Re a parts per thousand yen 400 and Ra a parts per thousand yen 10,000 (these ranges give 0.0142 a parts per thousand currency sign Ri a parts per thousand currency sign 1.59 the Nusselt number is independent on the hot surface orientation. However, for Re a parts per thousand currency sign 300 and Ra a parts per thousand yen 100,000 (these ranges give 1.59 a parts per thousand currency sign Ri a parts per thousand currency sign 42.85): (i) the Nusselt number for horizontal orientation with hot surface facing down is less that that of vertical orientation and that of horizontal orientation with hot surface facing up, and (ii) the Nusselt number of vertical orientation is approximately the same as that of horizontal orientation with hot surface facing up. For all surfaces orientations and for the entire ranges of Re and Ra, it was found that increasing the cross flow strength decreases the effective cooling of the surface.

The extraction equilibria of copper(II) with Cyanex 301, LIX (R) 984N, and their mixtures have been investigated. Extraction was studied as a function of organic phase composition, sulfuric acid concentration, pH, temperature, initial copper concentration, mixing speed, and aqueous/organic volume ratio. Considerable synergistic enhancement has been observed in the extraction of Cu(2+) with mixtures of Cyanex 301 and LIX (R) 984N. The results demonstrate that copper ion is extracted as CuRL(2)H with synergistic mixture. The thermodynamic parameter, enthalpy change (Delta H) of Cyanex 301, LIX (R) 984N, and their mixtures have been determined and the enclothermic process has been found. The synergistic enhancement factor of copper(II) with mixtures is higher at more acidic solutions, which suggests that it is a promising synergistic extraction system for the separation of copper(II) from more acidic medium. HCl was found to be more efficient for copper stripping from loaded synergistic mixtures. (C) 2008 Elsevier B.V. All rights reserved.

We study the computational complexity of some axiomatic extensions of the monoidal t-norm based logic (MTL), namely NM corresponding to the logic of the so-called nilpotent minimum t-norm (due to Fodor in Fuzzy Sets Syst 69:141-156, 1995); and SMTL corresponding to left-continuous strict t-norms, introduced by Esteva (and others) (Fuzzy Sets Syst 132(1):107-112, 2002; 136(3):263-282, 2003). In particular, we show that the sets of 1-satisfiable and positively satisfiable formulae of both NM and SMTL are NP-complete, while the set of 1-tautologies of NM and the set of positive tautologies of both NM and SMTL are co-NP-complete. The set of 1-tautologies of SMTL is only shown to be co-NP-hard, and it remains open if this set is in co-NP. Also, some results on the relations between these sets are obtained. We point out that results about 1-satisfiability and 1-tautology for NM are already well-known. However, in this paper, those results are proved in different ways.

Video-based Automatic Incident Detection ( AID) systems are widely deployed in many cities for detecting traffic incidents to provide smoother, safer and congestion free traffic flow. However, the accuracy of an AID system operating in an outdoor environment suffers from high false alarm rates due to environmental factors. These factors include snow movement, static shadow and static glare on the roads. In this paper, a robust real-time algorithm is proposed to detect snow movement in video streams to improve the rate of detection. This is done by having the AID system reducing its sensitivity in the areas that have snow movements. The feasibility of the proposed algorithm has been evaluated using traffic videos captured from several cameras at the City of Calgary.

The equations governing the flow of an electrically conducting, incompressible viscous fluid over an infinite flat plate in the presence of a magnetic field are investigated using the homotopy perturbation method (HPM) with Pade approximants (PA) and 4(th) order Runge-Kutta method (4RKM). Approximate analytical and numerical Solutions for the velocity field and heat transfer are obtained and compared with each other, showing excellent agreement. The effects of the magnetic parameter and Prandtl number on velocity field, shear stress, temperature and heat transfer are discussed as well.

This study is to experimentally investigate the heat transfer enhancement by perforation in air cooling of two in-line rectangular heat sources module. Two separation distances between the heat sources were investigated at s/L = 0.5 and 1.0. The area between the heat sources in both cases were perforated in aligned arrangement such that the holes open area ratio (p) are of 0, 0.0736, 0.1472 and 0.2944. The dimensionless temperature distribution and the average Nusselt number are considered at different values of Reynolds number (3391

This paper presents fuzzy goal programming (FGP) algorithm for solving decentralized bi-level multi-objective programming (DBL-MOP) problems with a single decision maker at the upper level and multiple decision makers at the lower level. A FGP algorithm for DBL-multi-objective linear programming (DBL-MOLP) problems is proposed. This algorithm is extended to solve bi-level multi-objective linear fractional programming (DBL-MOLFP) problems. In the proposed algorithm, the membership functions for the defined fuzzy goals of all objective functions at the two levels as well as the membership functions for vector of fuzzy goals of the decision variables controlled by ULDM are developed in the model formulation of the problem. Then FGP approach is used to achieve highest degree of each of the membership goals by minimizing their deviational variables and thereby obtaining the most satisfactory solution for all decision makers. Illustrative numerical examples are given to demonstrate the proposed algorithm. (C) 2009 Published by Elsevier B.V.

The present paper reports on the utilization of granular phase change composites (GPCC) of small particle diameter (1-3 mm) in latent heat thermal energy storage (LHTES) systems. The phase changing parameters (phase change temperature, latent heat, and energy storage capacity) of GPCC have been determined using differential scanning calorimeter (DSC) and temperature-history methods. Further analysis of measurement results has been conducted to describe the evolution of latent heat with temperature during phase change in terms of liquid fraction-temperature relationships. Charging and discharging packed bed column experiments have been also carried out for different operating conditions to analyze the potential of GPCC for packed bed thermal energy storage. The present column results clearly demonstrate the dependence of temperature variation along the packed bed and the overall performance of the storage unit on the phase change characteristics of GPCC. Small and non-uniform particles diameters of GPCC and heterogeneity of the bed material complicate the phenomena of heat transfer and evolution of latent heat in the packed bed. Mathematical modeling of the packed bed that considers the GPCC and air as two separate phases with inter-phase heat transfer is presented. Comparisons between experimental and numerical results are used to evaluate the sensitivity of numerical simulations to different model parameters. (C) 2009 Elsevier Ltd. All rights reserved.

he reduction of one of the greenhouse gases, CO2, has been a current subject in the field of environmental chemistry. Cobalt ferrite nanoparticles with different sizes were prepared by the thermal decomposition of acetate precursors and wet method techniques. CoFe2O4 nanoparticles were compacted, then isothermally reduced in H-2 flow at 400-600 degrees C. The isothermal reduction profiles obtained show that a topochemical mode of reduction is developed as the process proceeds. The metallic phases of iron and cobalt, produced from the complete reduction of CoFe2O4 are in nanosize form. The prepared, completely reduced and reoxidized CoFe2O4 compacts were characterized by XRD, SEM and reflected light microscope. The reoxidation process is affected by both particle size and reoxidation temperature. At the initial stages, the reaction was controlled by the interfacial chemical reaction mechanism with some contribution of the gaseous diffusion mechanism. On the other hand, at the final stages the mechanism by which the reoxidation process proceeds was found to be the solid-state diffusion. CO2 decomposes on the surface of metallic phases with 99% conversion at 550 degrees C to form single- and multi-walled carbon nanotubes. (c) 2006 Elsevier B.V. All rights reserved.

We study theoretically the plasmon mediated propagation of light through a chain of metallic nanoparticles along which a small chain (called a resonator) is attached vertically. The effect of this vertical resonator is to induce peaks and zeros in the transmission power. We show that, with a resonator constituted of two metallic clusters, an appropriate choice of the geometrical parameters can lead to a narrow peak in the transmission spectrum. This may be realized for this device by adjusting the distances between the two resonator clusters and the chain cluster to which they are attached. This enables us to get, in particular, a sharp peak between two zeros of transmission close to each other or sharp dips between two transmission ones. Such a device can be useful as a selecting or rejecting plasmon filter.

The design of a model-free fuzzy power system stabilizer (PSS) lacks systematic stability analysis and performance guarantees. This paper provides a step toward the design of a model-based fuzzy PSS that guarantees not only robust stability but also robust performance of power systems. A new practical and simple design based on dynamic output feedback is proposed. The design model is approximated by a set of Takagi-Sugeno (T-S) fuzzy models to account for nonlinearities and uncertainties. The proposed stabilizer is based on parallel distributed compensation efficient design conditions are presented as (PDC). Sufficient linear matrix inequalities (LMIs). The design procedure leads to a tractable convex optimization problem in terms of the stabilizer gain matrices. The design guarantees robust pole clustering, in an acceptable region in the open left half of the complex plane, and robust performance in terms of H(2) and H(infinity) measures, over a wide range of operating conditions. Simulations results of both single-machine and multi-machine power systems confirm the effectiveness of the proposed PSS design.

A fundamental understanding of nanoscaled materials has become an important challenge for any technical applications. For magnetic nanoparticles, the investigations are in particular stimulated by the magnetic storage devices. In this paper we present a theory of the magnon propagation in a nanometric chain and of the effects of neighbor magnetic clusters. We show that with an appropriate choice of the additional clusters, it is possible to control the transmission spectrum of the magnons. The additional clusters can also create a resonator with zero of transmission. This model could be useful to construct device to transmit or stop the magnon signal. (c) 2006 Elsevier B.V. All rights reserved.

The fractional Fokker-Planck equation (FFPE) has been used in many physical transport problems which take place under the influence of an external force field and other important applications in various areas of engineering and physics. In this paper, by means of the homotopy perturbation method (HPM), exact and approximate solutions are obtained for two classes of the FFPE initial value problems. The method gives an analytic solution in the form of a convergent series with easily computed components. The obtained results show that the HPM is easy to implement, accurate and reliable for solving FFPEs. The method introduces a promising tool for solving other types of differential equation with fractional order derivatives.

The present article reports on the utilization of multiple granular phase change composites (GPCC) with different ranges of phase change temperatures in a packed bed thermal energy storage system. Small particle diameter of GPCC allows simple mixing of two or three ranges of GPCCs in a packed bed for enhancement of storage unit performance. Experiments have been carried out to characterize the phase changing characteristics of two GPCCs chosen for this purpose. Packed bed column experiments have been carried out to provide basic understanding of the heat transfer process in the composite bed consisting of a mixture of GPCCs at different values of mixing ratio. A mathematical model has been developed for the analysis of charging and discharging process dynamics. Once validated, the model has been used to perform a parametric study to investigate the overall bed performance at different values of mixing ratio and Reynolds number. An optimization of the value of mixing ratio has been obtained based on the overall charging and discharging times as well as the exergy efficiency. It has been demonstrated that, as compared to the use of single GPCC, careful choice of the mixing ratio of GPCCs in a composite bed can result in a significant enhancement of the overall storage unit performance. As compared to the use of multiple sequential layers of GPCCs, using units composed of a mixture of GPCCs with an optimized mixing ratio results in a remarkable improvement of the unit performance without limitations on the charging and discharging directions during practical applications. (C) 2009 Elsevier Ltd. All rights reserved.

The finite-element floating frame of reference (FFR) formulation is used, for the most part, in the small deformation analysis of flexible bodies that undergo large reference displacements. This formulation allows for filtering out systematically complex shapes associated with high frequencies that have no significant effect on the solution in the case of small deformations. The resulting low-order FFR models have been widely used to obtain efficient and accurate solutions for many engineering and physics applications. In this investigation, the use of the FFR formulation in the large deformation analysis is examined, and it is demonstrated that large deformation FFR models can be accurate in applications, where the deformation can be described using simple shapes as it is the case in robot system manipulators. In these cases, the standard finite-element FFR formulation must be used with non-linear strain displacement relationships that account for the geometric non-linearities. The results obtained using the large deformation FFR models are compared with the results obtained using the large deformation absolute nodal coordinate formulation (ANCF), which does not allow for the use of linear modes. The ANCF models are developed using two different methods for formulating the elastic forces: the basic continuum mechanics approach (ANCF-BC) and the elastic line method (ANCF-EL). While the explicit Adams method can be used to obtain the numerical solution of the FFR model, two implicit integration methods are implemented in order to be able to obtain an efficient solution of the FFR and ANCF models. These implicit integration methods are the RADAU5 method and the Hilber-Hughes-Taylor (HHT) method. In the case of simple large deformation shapes, the simulation results obtained in this study show a good agreement between the FFR and the ANCF solutions. The results also show that, in the case of thin and stiff beams, the coupled deformation modes that result from the use of the ANCF-BC can be a source of numerical and locking problems, as reported in the literature. These ANCF-BC numerical problems can be circumvented using the implicit HHT integration method. Nonetheless, the HHT integrator does not capture high-frequency FFR axial modes which are necessary in order to obtain accurate solutions for high-speed rotating beams. In addition to the comparison with the ANCF solutions, experimental results of a forward dynamics model are used in this study to validate the large deformation FFR numerical solutions. The experimental set-up used in the validation of the numerical solutions is also described in this investigation.

Modern RF Radar signal processing has been receiving much attention for wide range of domains that include industrial, environmental, and military applications. Inherently, the received raw spatial-temporal signals can be 1-D, 2-D, or 3-D and are usually of uncertain nature, because of changing conditions and optical background variations. In this paper, we apply novel concepts for hyper-neural theory that allow for incorporation of variables attribute definitions and uncertainties for the purpose of effective evidential learning and subsequent key output features determination in the radar processing. Application to wide-band angle of arrival data sets at several carrier frequencies has been carried out in order to illustrate the strengths as well weakness of the approach. Using interval set-based operations together with segmentation of the data is proved useful and gave good sensitivity of detection.

Experimental study has been carried out to investigate performance parameters, emissions, cylinder pressure, exhaust and wall temperatures at different engine speeds and different percentage of EGR using sunflower and jojoba/diesel (B20) blend in comparison to diesel fuel. Sunflower oil and B20 were selected for the study because of its being widely used in Egypt and world. Tests were conducted for three different fuels with different engine speeds. Also, series of tests were conducted at same previous conditions with different percentage of exhaust gas recirculation (EGR) rates from 0 to 12 % of inlet mass of air fresh charge. Results indicate that sunflower or B20 blend gives lower brake thermal efficiency, brake power, brake mean effective pressure, and higher BSFC due to lower heating value compared to diesel fuel. Sunflower or B20 blend gives lower NO(X) concentration due to lower gases temperature. Sunflower or B20 blend gives higher wall/exhaust temperatures due to incomplete combustion inside engine cylinder. Sunflower or B20 blend gives higher CO and CO(2) concentrations due to higher carbon/hydrogen ratio. The position of maximum pressure change for diesel fuel is earlier than for sunflower and B20 blend. The results show that sunflower and B20 blend are promising as alternatives fuel for diesel engine. One of the main advantages of vegetable oil is not requiring significant modification of existing engine hard wares. On contrast, the main disadvantages of biodiesel fuels are high viscosity, drying with time, thickening in cold conditions, flow and atomization characteristics.

A comparative study between type-1 and type-2 fuzzy sets, introducing the main differences in membership functions and operations done on these fuzzy sets, is introduced in this paper. The idea of fuzzy sets and both membership functions of type-1 and type-2 are illustrated along with the idea of foot print of uncertainty (FOU). A new fuzzy controller is proposed which is based on type-1 fuzzy controller, with both double number of membership functions and rules. Application of the proposed hyper-fuzzy controller on a simple plant which could be a resonator in a bio-inspired system, a spring-mass system or even a DC machine is introduced and better response of the new proposed controller is shown.

We consider, in the frame of long-wavelength Heisenberg model, the effect of a pinning field on the spin wave band gaps and transmission spectra of a simple magnonic device. This simple device is composed of an infinite one dimensional (1D) monomode waveguide (the backbone) along which N (N') side resonators are grafted at two sites. Using a Green's function method, we obtained closed-form expressions for the transmission coefficients for various systems of this kind. The amplitude, the phase, and the phase time of the transmission are discussed as a function of frequency and the strength of the pinning field parameter. In the presence of the pinning field at the ends of the side branches, the transmission probability may exhibit resonances of the Fano type. It is shown that the transition from strong to weak pinning leads to Fano line shapes with gradually smaller asymmetry. This also results in a modification of the position and the width of the resonance but the transmission amplitude remain unaffected. Furthermore, it is shown that the presence of the pinning field causes systematic collapse of certain Fano resonances. These results may provide useful means for the design of narrow-frequency optical or microwave filters.

The present article reports on the characterization of granular phase changing composites using the T-history method. Further modifications and improvements of the method are employed to handle granular materials undergoing phase change over a temperature range. The accuracy of the T-history method is shown to be limited by the assumption of temperature-independent specific heats and the difficulty of determining the limits of solid and liquid phases. The concept of enthalpy and its relationship with temperature has been employed in the analysis to overcome these difficulties. Enthalpy-temperature and apparent heat capacity curves similar to those obtained using IDSC have been developed. These characteristic curves are necessary for accurate design, modeling, and optimization of latent heat thermal energy storage systems. Experiments have been also carried out to measure the transient temperature distribution inside a cylindrical packed bed using phase changing granulates. Analysis of temperature variation along the bed shows good agreement with the measured phase change characteristics. Copyright (C) 2009 John Wiley & Sons, Ltd.

Efficient numerical methods for solving nonlinear wave equations and studying the propagation and stability properties of their solitary waves (solitons) are applied to a Boussinesq type equation in one space dimension. These methods use a pseudospectral (Fourier transform) treatment of the space dependence, together with (a) finite differences, or (b) a fourth-order Runge-Kutta scheme (RK4), for the time evolution. Our schemes follow very accurately single solitons, which are given by simple closed formulas and are known to be stable for all allowed velocities. However, as a parameter of the problem tends to the critical value b = 0.5, where the velocity of the exact soliton vanishes, our solutions destabilize due to numerical errors, producing two small solitons in the place of the exact one. On the other hand, when we study the interaction of two such solitons, starting far apart from each other, we find in the b(1), b(2) parameter plane a curve beyond which the solution becomes unstable by exponential blow-up of the amplitudes, independently of our space and time discretization. We claim that this is due to a dynamical resonance rather than the accumulation of numerical errors, in agreement with theoretical predictions. Our implementation relies on the fast Fourier transform (FFT) algorithm and no major differences are observed, when either scheme (a) or (b) is used for the evolution of time.

An efficient numerical method is developed for solving nonlinear wave equations by studying the propagation and stability properties of solitary waves (solitons) of the regularized long wave (RLW) equation in one space dimension using a combination of leap frog for time dependence and a pseudospectral (Fourier transform) treatment of the space dependence. Our schemes follow very accurately these solutions, which are given by simple closed formulas. Studying the interaction of two such solitons and three solitary waves interaction for the RLW equation. Our implementation employs the fast Fourier transform (FFT) algorithm.

Corrosion of reinforcing steel in concrete structures is a major problem affecting North American infrastructure. Fiber-reinforced polymers (FRPs) have outstanding properties such as high strength, durability, and resistance to electrochemical corrosion. The use of FRP wraps and their effectiveness in restoring the integrity of corroded reinforced concrete structures, as well as their impact on corrosion activity, is still in question. This paper focuses on inducing corrosion in columns using an aggressive environment that simulates natural corrosion, and the use of carbon FRP (CFRP) wraps in repair of corrosion-damaged reinforced concrete columns. The experiment included 12 large-scale circular columns 300 x 1200 nun (12 x 48 in.). Ten columns were cast with 3% NaCl (by weight of cement) premixed with the mixing water in the outer 75 mm (3 in.) thick ring. The two remaining columns were uncontaminated and used as control specimens (one wrapped and one unwrapped). The ten chloride-laden columns were corroded using an aggressive environment. The experiment incorporated electrochemical chloride extraction (ECE) treatment on four of the columns followed by CFRP wrapping on eight columns. The research concluded that the CFRP wraps applied over. corrosion-damaged reinforced concrete columns will decrease the corrosion rate of the reinforcement and restore the structural integrity of the column. The ECE and wrapping combination provided the best protection against future corrosion. The application of the wraps will be more effective when applied at earlier stages of the corrosion. The strength of the wrapped columns was also very close to that of the wrapped control column.

Heat transfer characteristics of a slot/slots jet air impinging on a cylinder have been experimentally investigated for two different orientations of slot/slots jet plan with respect to cylinder axis. The experiments were carried out to study the effects of orientation of slot/slots jet plan with respect to cylinder axis on the rate of heat transfer from the cylinder. Two different jet-cylinder configurations were studied: (1) single slot jet aligned with cylinder axis (slot length = cylinder length), and (2) multiple slot jets equally spaces distributed orthogonal to cylinder axis (each slot length = cylinder diameter and sum of slots lengths = cylinder length). For each configuration, parametric effects of Reynolds numbers (Re) ranging from 1,000 to 10,000, dimensionless slot widths (W/d) ranging from 0.125 to 0.5, and dimensionless slot orifice-to-cylinder spacing (Z/W) ranging from 1 to 12 on local and average Nusselt numbers around cylinder surface have been investigated. The results showed that: (1) cooling the cylinder by multiple slots jets situated orthogonal to cylinder axis gave more uniform surface temperature distributions and higher heat transfer rate than the case of cooling the cylinder by single slot jet aligned with cylinder axis, (2) for both configurations the Nusselt number around the cylinder increased with increasing Re and W/d, and (3) for both configurations there was a certain Z/W in the range 4 < Z/W < 6 at which the stagnation and mean Nusselt number were maximum. Correlations for the mean Nusselt numbers around cylinder surface have been presented for both configurations. Comparisons between the correlations predictions and the present and other previous experimental data have been conducted.

Intrusion detection systems (IDS) have become a major focus of computer scientists and practitioners as computer attacks have become an increasing threat to commercial business as well as our daily lives. Classification mining is one of the most important data mining tasks that classify intruders in IDS. Classification mining task faces several challenges as noisy data, huge transactions and many other challenges. Therefore conventional (crisp classification models) became unable to overcome such challenges. The art of fuzzy classes is that the element may belong to one or more classes with a different membership. The goal of this paper is to apply fuzzy decision trees to find a good classifier to improve the performance of intrusion detection process. The paper introduces also the application of the crisp decision trees to find the crisp classes of intruders and presents also the comparison and analysis of results of two methods. The results analysis shows that; the fuzzy decision trees is more better than the crisp decision trees and produces an accurate classes, which increase the system performance and accuracy. Moreover fuzzy decision trees are more complex than crisp decision trees.

In this paper, the homotopy perturbation method (HPM) is extended to obtain analytical solutions for some nonlinear differential-difference equations (NDDEs). The discretized modified Kortewegde Vries (mKdV) lattice equation and the discretized nonlinear Schrodinger equation are taken as examples to illustrate the validity and the great potential of the HPM in solving such NDDEs. Comparisons between the results of the presented method and exact solutions are made. The results reveal that the HPM is very effective and convenient for solving such kind of equations.

Speed of intruder's detection in intrusion detection systems is one of the most important factors, which gives the system the ability to minimize intruder activities. The work in this paper aims at improving the detection process by introducing a hybrid of artificial intelligence techniques to provide a good features subset selection process; this hybrid consists of rough set theory, decision tree, and a heuristic methods. The classifier-learning algorithm based on good features selection that maximizing an information measure and providing a good classifier. In this work, we introduce five methods for selecting the relevant feature. KDDCUP99data set used to evaluate the goodness of the hybrid methods abilities of selecting relevant features. Neural network classifier built to differentiate between the different methods used. The experiments design and results analysis is presented. The results show that hybrid of AI methods is better than using each one individual and the hybrid of decision tree and rough set is better than the hybrid of rough set and decision tree. The heuristic method used in this work provides good results as rough sets and decision tree; but still need improvement.

In this paper, the feasibility of grey water treatment in a UASB reactor was investigated. The batch recirculation experiments showed that a maximum total-COD removal of 79% can be obtained in grey-water treatment in the UASB reactor. The continuous operational results of a UASB reactor treating grey water at different hydraulic retention time (HRT) of 20, 12 and 8 hours at ambient temperature (14-24 degrees C) showed that 31 -41% of total COD was removed. These results were significantly higher than that achieved by a septic tank (11-14%), the most common system for grey water pre-treatment, at HIRT of 2-3 days. The relatively lower removal of total COD in the UASB reactor was mainly due to a higher amount of colloidal COD in the grey water, as compared to that reported in domestic wastewater. The grey water had a limited amount of nitrogen, which was mainly in particulate form (80-90%). The UASB reactor removed 24-36% and 10-24% of total nitrogen and total phosphorus, respectively, in the grey water, due to particulate nutrients removal by physical entrapment and sedimentation. The sludge characteristics of the UASB reactor showed that the system had stable performance and the recommended HIRT for the reactor is 12 hours.

process for recovery of zinc from acid solution with di(2-ethyl hexyl phosphoric acid) (D2EHPA) dissolved in iso-dodecane was carried out at 20 degrees C in a countercurrent tubular membrane extractor using a hollow fiber as solid support. Experiments were performed at different aqueous metal concentrations (0.1-1.0 g/L), pH 0.1-2.1, and D2EHPA concentrations (2-8 v%). It was found that both the flux of metal and the extraction extent was highly influenced by the extractant concentration and the pH of the feed solution. Overall mass transfer coefficients were determined and related to the tube side, the membrane, and the shell side mass transfer by varying the aqueous flow rate (0.38-0.80 L/min) and organic flow rate (0.22-0.57 L/min) in countercurrent flow. The overall mass transfer coefficient for zinc extraction ranged from 6.2 x 10(-6) m/s to 25.3 x 10(-6) m/s. It was concluded that extraction kinetics were a major contributor to the overall resistance to mass transfer.

Recently, a special algebra called EQ-algebra ( we call it here commutative EQ-algebra since its multiplication is assumed to be commutative) has been introduced by Novak ( Proceedings of the Czech-Japan seminar, ninth meeting, Kitakyushu and Nagasaki, 18-22 August, 2006), which aims at becoming the algebra of truth values for fuzzy type theory. Its implication and multiplication are no more closely tied by the adjunction and so, this algebra generalizes commutative residuated lattice. One of the outcomes is the possibility to relax the commutativity of the multiplication. This has been elaborated by El-Zekey et al. ( Fuzzy Sets Syst 2009, submitted). We continue in this paper the study of EQ-algebras (i.e., those with multiplication not necessarily commutative). We introduce prelinear EQ-algebras, in which the join-semilattice structure is not assumed. We show that every prelinear and good EQ-algebra is a lattice EQ-algebra. Moreover, the {boolean AND, boolean OR, ->, 1}-reduct of a prelinear and separated lattice EQ-algebra inherits several lattice-related properties from product of linearly ordered and separated EQ-algebras. We show that prelinearity alone does not characterize the representable class of all good ( commutative) EQ-algebras. One of the main results of this paper is to characterize the representable good EQ-algebras. This is mainly based on the fact that {->, 1} reducts of good EQ-algebras are BCK-algebras and run on lines of van Alten's (J Algebra 247: 672-691, 2002) characterization of representable integral residuated lattices. We also supply a number of potentially useful results, leading to this characterization.

In this paper, two new algorithms are presented to solve multi-level multi-objective linear programming (ML-MOLP) problems through the fuzzy goal programming (FGP) approach. The membership functions for the defined fuzzy goals of all objective functions at all levels are developed in the model formulation of the problem: so also are the membership functions for vectors of fuzzy goals of the decision variables, controlled by decision makers at the top levels. Then the fuzzy goal programming approach is used to achieve the highest degree of each of the membership goals by minimizing their deviational variables and thereby obtain the most satisfactory solution for all decision makers. The first suggested algorithm groups the membership functions for the defined fuzzy goals of the objective functions at all levels and the decision variables for each level except the lower level of the multi-level problem. The second proposed algorithm lexicographically solves MOLP problems of the ML-MOLP problem by taking into consideration the decisions of the MOLP problems for the upper levels. An illustrative numerical example is given to demonstrate the algorithms. (C) 2009 Elsevier Inc. All rights reserved.

Construction contractors often finance projects using bank credit lines that allow contractors to withdraw money up to certain credit limits. Finance-based scheduling provides schedules that ensure that the contractor's indebtedness at any time during the construction stage does not exceed the credit limit. Generally, constricted credit limits tend to yield prolonged schedules. Provided that credit limits can be adequately relaxed, compressed schedules of compressed-duration activities can be attained. Devising a compressed schedule calls for the incorporation of time-cost trade-off (TCT) analysis to strike a balance between the decreased overhead costs and the increased direct costs of the activities. Since employing TCT analysis usually causes great fluctuations in the daily resource requirements by mixing compressed-duration activities of high resource demand with others of low resource demand, therefore, the need for resource management techniques becomes inevitable to ensure efficient utilization of resources. This note used genetic algorithms to expand finance-based scheduling to devise schedules for relaxed credit limits. A prototype system was developed and coded using VISUAL BASIC, then demonstrated using a five-activity example project. The prototype was validated by comparing the results with those obtained by using the integer programming. Expanding finance-based scheduling to handle the whole spectrum of credit limits helps devise overall-optimized schedules that consider cash, time, cost, and resources.

Pure Fe2O3 and Fe2O3 doped with either 2, 4, or 6 mass% MnO2 annealed at 1 473 K for 6 h were isothermally reduced with carbon monoxide at 1 073-1 373 K. The oxygen weight loss resulted from the reduction at a given temperature was continuously recorded as a function of time. Reflected and scanning electron microscopes were used to characterize the annealed and reduced samples whereas the different phases developed were identified by X-ray phase analysis technique. The external volume of partially and completely reduced samples was measured by displacement method and the volume change (Delta V%) was calculated. At a given temperature, the influence of MnO2 mass% on the reduction behaviour and volume change of Fe2O3 compacts was investigated. The doping of MnO2 showed different effects during the reduction of Fe2O3 which is temperature dependant. At

A performance evaluation based on exergy analysis was proposed to evaluate the benefits of different enhancement techniques for flow inside tubes. The present performance evaluation was developed based on the application of the principle of entropy generation. A semi-analytical model was developed to predict the entropy generation and the exergy destruction rates associated with both flow friction and heat transfer. This model was based on measurements and empirical Correlations for both flow and heat transfer characteristics. The present performance evaluation was applied on flow through tubes enhanced with twisted-tapes inserts, spirally internal fins and conical turbulators for three different fluids. It was found that using specific types of enhancement techniques reduces the irreversibility owing to heat transfer across a finite temperature difference and in the same time increases that part of irreversibility resulting from the flow friction. Therefore, a thermodynamic optimum at a minimum exergy destruction rate can be achieved for different enhancement techniques and different flow conditions.

Steganography gained importance in the past few years due to the increasing need for providing secrecy in an open environment like the internet. With almost anyone can observe the communicated data all around, steganography attempts to hide the very existence of the message and make communication undetectable. Many techniques are used to secure information such as cryptography that aims to scramble the information sent and make it unreadable while steganography is used to conceal the information so that no one can sense its existence. In most algorithms used to secure information both steganography and cryptography are used together to secure a part of information. Steganography has many technical challenges such as high hiding capacity and imperceptibility. In this paper, we try to optimize these two main requirements by proposing a novel technique for hiding data in digital images by combining the use of adaptive hiding capacity function that hides secret data in the integer wavelet coefficients of the cover image with the optimum pixel adjustment (OPA) algorithm. The coefficients used are selected according to a pseudorandom function generator to increase the security of the hidden data. The OPA algorithm is applied after embedding secret message to minimize the embedding error. The proposed system showed high hiding rates with reasonable imperceptibility compared to other steganographic systems.

In this paper, a secure face recognition system is presented, in which face detection is performed with skin color detection followed by light normalization and normalized cross correlation. Principal component analysis (PCA) is used for face verification. Due to the rising concern about the security and privacy of the biometric system, we offer a secure storage for user records by encrypting them using Advanced Encryption Standard (AES). A different encryption/decryption key is used for each user, and that key is-not stored in the database, it is extracted by expanding the submitted user identification (ID). A simulation of AES algorithm using field programmable gate array (FPGA) and the very high speed integrated circuit hardware description language (VHDL) is performed.

This paper introduces a hybridization approach of AI techniques and statistical tools to evaluate and adapt the e-learning systems including e-learners. Learner's profile plays a crucial role in the evaluation process and the recommendations to improve the e-learning process. This work classifies the learners into specific categories based on the learner's profiles; the learners' classes named as regular, workers, casual, bad, and absent. The work extracted the statistical usage patterns that give a clear map describing the data and helping in constructing the e-learning system. The work tries to find the answers of the question how to return the bad students who are away back to be regular ones and find a method to evaluate the e-learners as well as to adapt the content and structure of the e-learning system. The work introduces the application of different fuzzy clustering techniques (FCM and KFCM) to find the learners profiles. Different phases of the work are presented. Analysis of the results and comparison: There is a match with a 78% with the real world behavior and the fuzzy clustering reflects the learners' behavior perfectly. Comparison between FCM and KFCM proved that the KFCM is much better than FCM. (C) 2010 Elsevier Ltd. All rights reserved.

In the present investigation, the mechanical and microstructural characteristics of friction stir welded AA7020-O Al plates were investigated. The influence of the tool rotational and welding speeds such characteristics was studied. The friction stir welding (FSW) was conducted at tool rotational speeds of 1120, 1400, and 1800 rpm and at welding speeds of 20, 40 and 80 mm/min. It has been found that increasing the tool rotational speed and/or reducing the welding speed increases the primary Al phase grain size as well as the size of the precipitates at the center of the stirred zone (SZ). The tensile characteristics of the friction stir welded tensile samples depend significantly on both the tool rotational and welding speeds. (C) 2010 Elsevier B.V. All rights reserved.

Thanks to its essential functionality and structure simplicity, proportional-integral-derivative (PID) controllers are commonly used by industrial utilities. A robust PID-based power system stabilizer (PSS) is proposed to properly function over a wide range of operating conditions. Uncertainties in plant parameters, due to variation in generation and load patterns, are expressed in the form of a polytopic model. The PID control problem is firstly reduced to a generalized static output feedback (SOF) synthesis. The derivative action is designed and implemented as a high-pass filter based on a low-pass block to reduce its sensitivity to sensor noise. The proposed design algorithm adopts a quadratic Lyapunov approach to guarantee a-decay rate for the entire polytope. A constrained structure of Lyapunov function and SOF gain matrix is considered to enforce a decentralized scheme. Setting of controller parameters is carried Out via an iterative linear matrix inequality (ILMI). Simulation results, based on a benchmark model of a two-area four-machine test system, are presented to compare the proposed design to a well-tuned conventional PSS and to the standard IEEE-PSS4B stabilizer. (C) 2010 Elsevier B.V. All rights reserved.

In this paper, we have extended the homotopy perturbation method (H PM) to find approximate analytical solutions for some nonlinear differential-difference equations (NDDEs). The discretized modified Korteweg-de Vries (mKdV) lattice equation and the discretized nonlinear Schrodinger equation are taken as examples to demonstrate the validity and the great potential of the HPM in solving such NDDEs. Comparisons are made between the results of the presented method and exact solutions. The obtained results reveal that the HPM is a very effective and convenient tool for solving such kind of equations.

Purpose - The paper proposes to present the effect of the high voltage transmission lines on the metallic pipelines by calculating the induced voltage due to mutual inductance between the two circuits especially in short circuit conditions of high voltage overhead transmission lines. Design/methodology/approach - The electro magnetic transient program (EMTP) is used to simulate the high voltage transmission lines in normal case and in different faulty case conditions. A software is built on MATLAB program (M-file) to study the effects of various parameters on the magnitude of the induced voltage such as: separation distance between the high voltage transmission line and the metallic pipeline (horizontal distance), different cases of short circuits and normal operation case, the screening factor, and the soil resistivity. Findings - The three-phase to ground fault gives the least induced voltage, and phase to ground fault case is the most serious case. The induced voltage decreases with increasing the soil resistivity until 400 Omega m and after this, the induced voltage in the metallic pipeline increases with increasing the soil resistivity for all phase fault types. Research limitations/implications - It does not deal with all types of interference such as capacitive interference. Practical implications - This technique helps to know the electrical influence exerted by power line on a pipeline. So it can prevent the pipeline from posing a shock hazard rather than corrosion. Originality/value - This paper presents the effect of the high voltage transmission lines on the metallic pipelines by calculating the induced voltage due to mutual inductance between the two circuits especially in short circuit conditions of high voltage overhead transmission lines.

Theoretical investigation of the onset voltage of negative corona on stranded conductors is described in this paper. The method of calculation is based on the criterion developed for the formation of repetitive negative corona Trichel pulses. This calls first for an accurate calculation of the electric field in the vicinity of stranded conductors. The investigated gap is a three-dimensional field problem. To solve this problem, a new modification of the charge simulation technique is presented, where the simulation charges are helical of infinite length. Laboratory measurements of the onset voltage on stranded conductors are carried out to check the accuracy of the present calculations. The effects of varying the field nonuniformity on the onset voltage values are investigated. The calculated onset voltage values for stranded conductors agree satisfactorily with those measured experimentally.

ADM-Pade technique is a combination of Adomian decomposition method (ADM) and Pade approximants. It is an approximate method, which can be adapted to solve nonlinear partial differential equations. In this paper, we solve Burgers' and Boussinesq equation using ADM-Pade technique which gives the approximate solution with faster convergence rate and higher accuracy than using ADM alone. (c) 2005 Elsevier Ltd. All rights reserved.

Natural convection heat transfer and fluid flow characteristics in horizontal and vertical narrow enclosures with heated rectangular finned base plate have been experimentally investigated at a wide range of Rayleigh number (Ra) for different fin spacings and fin lengths. Quantitative comparisons of finned surface effectiveness (epsilon) and heat transfer rate between horizontal and vertical enclosures have been reported. In comparison with enclosure of a bare base plate, insertion of heat conducting fins always enhances heat transfer rate. Optimization of fin-array geometry has been addressed. The results gave an optimum fin spacing at which Nusselt number (NUH) and finned surface effectiveness (e) are maximum. It has been found that: (1) increasing fin length increases NUH and epsilon; (2) increasing Ra increasesNuH for any fin-array geometries and (3) for any fin-array geometry and at Ra > 10,000, increasing Ra decreases - while for fin-array geometries of large fin spacing and at Ra < 10,000, increasing Ra increases e. Useful design guidelines have been suggested. Correlations of NUH have been developed for horizontal and vertical enclosures. Correlations predictions have been compared with previous data and good agreement was found. (c) 2006 Elsevier Ltd. All rights reserved.

Feasibility of grey water treatment in an upflow anaerobic sludge blanket (UASB) reactor operated at different hydraulic retention time (HRT) of 16, 10 and 6h and controlled temperature of 30 degrees C was investigated. Moreover, the maximum anaerobic biodegradability without inoculum addition and maximum removal of chemical oxygen demand (COD) fractions in grey water were determined in batch experiments. High values of maximum anaerobic biodegradability (76%) and maximum COD removal in the UASB reactor (84%) were achieved. The results showed that the colloidal COD had the highest maximum anaerobic biodegradability (86%) and the suspended and dissolved COD had similar maximum anaerobic biodegradability of 70%. Furthermore, the results of the UASB reactor demonstrated that a total COD removal of 52-64% was obtained at HRT between 6 and 16 h. The UASB reactor removed 22-30% and 15-21% of total nitrogen and total phosphorous in the grey water, respectively, mainly due to the removal of particulate nutrients. The characteristics of the sludge in the UASB reactor confirmed that the reactor had a stable performance. The minimum sludge residence time and the maximum specific methanogenic activity of the sludge ranged between 27 and 93 days and 0.18 and 0.28 kg COD/ (kg VS d). (c) 2007 Elsevier Ltd.

A simple electronic circuit consisting of a single symmetric or asymmetric loop with dangling resonators is designed to obtain possibly large stop bands (where the propagation of electrons is forbidden). Contrary to all known systems of this kind, a spectral transmission gap of nonzero width occurs here even with a single loop. This is obtained by combining appropriately the zeros of transmission of the loop and of the dangling resonators. Sharp resonant electronic states inside the gaps can be achieved without introducing any defects in the structure. This results from an internal resonance of the structure when such a resonance is situated in the vicinity of a zero of transmission or squeezed between two zeros of transmission, the so-called Fano resonances. A general expression for the transmission coefficient is given for various systems of this kind within the framework of the interface response theory. The amplitude and the phase of the transmission are discussed as a function of the wave vector or energy and it is shown that the width of the stop bands is very sensitive to the number of grafted resonators, while the magnitude of the resonant states in the transmission coefficient is very sensitive to the lengths of the different arms constituting the loop and the dangling resonators. These structures may have potential applications in microelectronic devices.

Airside heat and mass transfer and fluid flow characteristics of a wavy-finned-tube direct expansion air coil under cooling and dehumidifying condition have been experimentally investigated. Experiments were carried out to study the effects of operating conditions such as: air temperature, air relative humidity, air face velocity, and evaporator pressure on the airside performance (cooling capacity, dehumidification capacity, pressure drop, and heat transfer coefficient) of the coil. Charts for coil wet conditions, partially wet or totally wet, were conducted to identify the coil wet conditions in terms of the operating conditions. Two techniques, enthalpy potential method and equivalent dry-bulb temperature method, were used to analyze the data and to deduce correlations for Colburn factors for the different coil wet conditions. Comparison between the correlations predictions of the two techniques was presented. (c) 2006 Elsevier Ltd and IIR.

Experimental study has been carried out to investigate performance parameters, emissions, cylinder pressure, exhaust gas temperature (T(exhaust)) and engine wall temperatures (T(wall)) for direct injection diesel engine. Tests were conducted for sunflower oil (S100) and 20% jojoba oil + 80% pure diesel fuel (B20) in comparison to pure diesel fuel with different engine speeds. S100 and B20 were selected for the study because of its being widely used in Egypt and in the world. Also, series of tests are conducted at same previous conditions with different percentage of exhaust gas recirculation (EGR) from 0% to 12% of inlet mass of air fresh charge. Results indicate that S100 or B20 gives lower brake thermal efficiency (eta(B)), brake power (BP), brake mean effective pressure (BMEP), and higher brake specific fuel consumption (BSFC) due to lower heating value compared to pure diesel fuel. S100 or B20 gives lower NO(X) concentration due to lower gas temperature. S100 or B20 gives higher T(wall) and T(exhaust) due to incomplete combustion inside engine cylinder. S100 or B20 gives higher CO and CO(2) concentrations due to higher carbon/hydrogen ratio. The position of maximum pressure (P(max)) change for pure diesel fuel is earlier than for S100 or B20. The results show that S100 or B20 are promising as alternative fuel for diesel engine. The utilization of vegetable oils does not require a significant modification of existing engines. This can be seen as the main advantage of vegetable oils. The main disadvantages of biodiesel fuels are high viscosity, drying with time, thickening in cold conditions, flow and atomization characteristics. (C) 2010 Elsevier Ltd. All rights reserved.

In this study a copper wire is proposed as a tool electrode in electrochemical groove turning process (WECGT). The working parameters, namely, radial feed rate, wire diameter, and rotational speed are investigated to study the performance criteria via MRR, groove width, and roundness error. An experimental study is presented through performing series of designed experiments. Key features of a WECGT setup that was designed and developed incorporating several unique features are also highlighted. The experimental results are statistically analyzed and mathematically modeled through response surface methodology (RSM). The mathematical model adequacies are checked using analysis of variance (ANOVA). Furthermore, optimal combination of working parameters has been evaluated to maximize MRR and minimize roundness error. The results reveal that using wire as an electrode in electrochemical turning instead of using a profiled tool proved its powerfulness to produce circular grooves. The results also demonstrate that the groove width has greatly increased by increasing the wire diameter, while it is decreased by increasing both the radial feed rate and rotational speed. Lower roundness errors are obtained by increasing both radial feed rate and wire diameter. The optimum combination of parameters setting is: radial feed rate of 0.08 mm min(-)1, wire diameter of 2.3 mm, and rotational speed of 578 rpm.

In the frame of the long-wavelength Heisenberg model, a simple magnonic mono-mode circuit is designed to obtain transmission stop (pass) bands where the propagation of spin waves is forbidden (allowed). This simple device is composed of an infinite one-dimensional monomode waveguide (the backbone) along which side resonators (symmetric or asymmetric loops) are grafted. These circuits are usually mono-mode when the lateral dimensions of the conducting wires are small as compared to the magnon wavelength. Their production utilizes the most advanced surface technologies and represents one of the most important challenges for the next decade. In all these circuits, the interfaces between the different wires out of which the circuits are made, play a fundamental role. All such circuits exhibit a variety of interference effects in their transport properties. Emphasis in this review article is placed on the network creations, which include stubs or resonators, closed symmetric or asymmetric loops and interconnecting branched networks. In other words, a fundamental understanding of nanoscaled materials has become an important challenge for any technical applications. For magnetic nanoparticles, the investigations are in particular stimulated by the magnetic storage devices. Then we present a theory of the magnon propagation in a quasi-one-dimensional resonant structure, composed of one nanometric magnetic cluster chain and adsorbed clusters near the chain. Results for the transmission and reflection properties of such circuits (nanometric networks) are discussed, as a function of the frequency of the excitations and the physical or geometrical properties of the circuits. In the last part of this report, we review magnonic crystals. These man-conceived materials should be useful for many applications and, in particular, for designing the mono-mode circuits reviewed in the first part of this paper. These magnonic materials and circuits may have uses for the design of integrated devices such as narrow-frequency optical or microwave filters, high-speed switches, multiplexers, storage devices, .... (C) 2010 Elsevier B.V. All rights reserved.

Design of experiments (DOE) and statistical process control (SPC) have been separately used in many traditional and non-traditional machining processes, but recently these two approaches are being combined and reevaluated for more effective use and accurate conclusions. DOE and SPC are very efficient tools to maintain the process on target and within boundaries of natural variations and to achieve the maximum accuracy and effectiveness of an experimental program. This paper proposes an integrated framework of SPC and DOE to execute the experimental procedures and to investigate a reliable mathematical model for optimizing the wire electrochemical turning process (WECT). WECT is a non-traditional machining process which has tremendous applications in modern industries especially in the aerospace and military industries. Response surface methodology is used to determine the sufficient number of experiments and also the recommended values of the input parameters. Univariate and multivariate control charts are used to assess the statistical control of the output parameters. Multi-objective optimization is conducted for determining the optimum values of the input parameters.

Electrochemical machining (ECM) has become one of the most widely spread techniques of the non-traditional processes. The main problem of ECM is that of choosing the correct working parameters to attain a high degree of accuracy under fine surface finish conditions. Recently, electrochemical turning has gained attention as a finishing process. By feeding a shaped tool into a rotating workpiece, axially symmetric turned parts can be manufactured. In this way, large symmetric workpiece can be made with small tools. This paper discusses the feasibility of using a wire as a tool in electrochemical turning process (WECT). The present study measures the performance criteria of the WECT process through investigating the effect of working parameters, namely, applied voltage, wire feed rate, wire diameter, workpiece rotational speed, and overlap distance, on metal removal rate, surface roughness, and roundness error. The experimental results are statistically analyzed and modeled through response surface methodology. The regression model adequacies are checked using analysis of variance. Furthermore, the optimal combination of these parameters has been evaluated to maximize metal removal rate and minimize surface roughness and roundness error. The study reveals the ability of using a wire as a tool in WECT and its productivity; the shape errors can be controlled through the mentioned input parameters. The results show that the increase of wire feed rate enhances the productivity of the process and improves both surface quality and roundness error. Also, the increase of rotational speed improves both the productivity of the process and geometrical error of the produced parts.

Many factors affect the loading of the underground power cables, such as ambient temperature, depth of laying of cable, number of parallel circuits of cable, and thermal resistivity of the surrounding soil. One important factor, usually ignored, is the formation of dry zones around the underground power cables. Dry zones are usually formed around underground power cables under loading conditions due to the migration of moisture within the soil. In this paper, the effect of the formation of the dry zone on the ampacity of underground power cables is investigated. The derating factor for the formation of dry zones around underground power cables is suggested and calculated for different types of natural backfill soil. IEC 60287-1-3 is taken as a reference. Experimental work was conducted to study the phenomena of the dry zone as related to different types of soils.

This paper presents accurate solutions for nonlinear transcendental equations of the selective harmonic elimination technique used in three-phase PWM inverters feeding the induction motor by particle swarm optimization (PSO). With the proposed approach, the required switching angles are computed efficiently to eliminate low order harmonics up to the 23(rd) from the inverter voltage waveform, whereas the magnitude of the fundamental component is controlled to the desired value. A set of solutions and the evaluation of the proposed method are presented. The obtained results prove that the algorithm converges to a precise solution after several iterations. The salient contribution of the paper is the application of the particle swarm algorithm to attenuate successfully any undesired low-order harmonics from the inverter output voltage. The current paper demonstrates that the PSO is a promising approach to control the operation of a three-phase voltage source inverter with a selective harmonic elimination strategy to be applied in induction motor drives.

In this paper, we use homotopy analysis method (HAM) to solve two-point nonlinear boundary value problems that have at least one solution. The new approach provides the solution in the form of a rapidly convergent series with easily computable components using symbolic computation software. The scheme shows importance of choice of convergence-control parameter h to guarantee the convergence of the solutions of nonlinear differential equations. This scheme is tested on three nonlinear exactly solvable differential equations. Two of the examples are practical in science and engineering. The results demonstrate reliability, simplicity and efficiency of the algorithm developed. Copyright (C) 2011 John Wiley & Sons, Ltd.

The design of complex systems-on-chip (SoCs) in the upcoming complementary metal-oxide-semiconductor (CMOS) technologies has become increasingly challenging due to the high levels of integration, the excessive energy consumption, the clock distribution problems and the increased process variability impact. To deal with these issues, we consider network-on-chip (NoC) architectures partitioned into several voltage-frequency domains and propose an efficient control algorithm for on-the-fly workload monitoring and management. This algorithm is able to cope with the technology-related variability and with the variable workload of the system. It dynamically controls the speed of the different voltage-frequency islands with respect to the process variability impact on each island. Within this work, a new clock synchronization scheme is also presented. Simulation results demonstrate the effectiveness of our approach in guarantying the average speed performance of the system under different cases of the process variability effect while keeping reduced the overall system energy consumption. Moreover, this is achieved with a small area overhead. The results are validated on a MIPS R2000 processor node using the 45 nm CMOS technology from STMicroelectronics.

Compacts made from chemically grade Fe2O3 were fired at 1473K for 6 hrs. The fired compacts were isothermally reduced either by hydrogen or carbon monoxide at 1073-1373K. The O-2 weight-loss resulting from the reduction process was continuously recorded as a function of time using TGA technique, whereas the volume change at different reduction conditions was measured by displacement method. Porosity measurements, microscopic examination and X-ray diffraction analysis were used to characterize the fired and reduced products. The rate of reduction at both the initial and final stages was increased with temperature. The reduction mechanism deduced from the correlations between apparent activation energy values, structure of partially reduced compacts and application of gas-solid reaction models revealed the reduction rate (dr/dt) at both the initial and final stages. At early stages, the reduction was controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanism, while at the final stages the interfacial chemical reaction was the rate determining step. In H-2 reduction, maximum swelling (80%) was obtained at 1373K, which was attributed to the formation of metallic iron plates. In CO reduction, catastrophic swelling (255%) was obtained at 11 98K due to the formation of metallic iron plates and whiskers.

The present article reports on the fluid flow and heat transfer characteristics associated with cooling an in-line array of discrete protruding heated blocks in a channel by using a single laminar slot air jet. Numerical experiments have been carried out for different values of jet Reynolds number, channel height, slot width, spacing between blocks, block height, and block thermal conductivity. The effects of variation of these parameters are detailed to illustrate important fundamental and practical results that are relevant to the thermal management of electronic packages. In general, the effective cooling of blocks has been observed to increase with the increase of Reynolds number and the decrease of channel height. Heat transfer rates are enhanced for shorter and widely spaced heated blocks. Circulation cells that may appear on the top surface of the downstream blocks have been shown to decrease the value of Nusselt number for these blocks. The values of surface averaged Nusselt number attain their maximum at the block just underneath the impinging air jet, decrease for the downstream blocks, and approximately reach a constant value after the third block. Useful design correlations have been obtained for the mean Nusselt number for the heated blocks underneath and downstream the impinging jet. (c) 2006 Elsevier Inc.

Fatigue behavior of unidirectional glass fiber reinforced polyester (GFRP) composites at room temperature under in-phase combined torsion/bending loading was investigated. All fatigue tests were carried out on constant-deflection fatigue machine with frequency of 25 Hz. A 30% reduction from the initial applied moments was taken as a failure criterion in the combined torsion/bending fatigue tests of the composite materials. A series of pure torsional fatigue tests were conducted to construct the failure contour of GFRP composites using different failure theories. The obtained S-N curves from combined torsion/bending tests were compared with both, pure torsion fatigue test results and published results of pure bending fatigue tests of GFRP rods. Pictures by scanning electron microscope were used to closely examine the failure mode of the tested specimens under combined torsion/bending loading. The results showed that, the unidirectional glass fiber reinforced polyester composites have poor torsional fatigue strength compared with the published results of pure bending fatigue strength. Endurance limit value (calculated from S-N equation at N = 10(7) cycles) of GFRP specimens tested under combined torsion/bending loading equals 8.5 times the endurance limit of pure torsion fatigue. On the other hand the endurance limit of combined torsion/bending fatigue strength approximately half the fatigue limit of pure bending fatigue strength. The predicted values of combined torsion/bending fatigue strength at different number of cycles, using the published failure theory are in good agreement with the experimental data. For the investigated range of fiber volume fractions (V-f) it was found that higher stress levels are needed to produce fatigue failure after the same number of cycles as V-f increases. (C) 2006 Elsevier Ltd. All rights reserved.

Fluid flow and heat transfer characteristics around a semi-circular tube in cross flow were experimentally and numerically investigated. Three different tube-flow arrangements were considered. Firstly, the flat surface of the tube was placed parallel to the freestream flow; secondly, the flat surface of the tube was facing the upstream flow and thirdly, the curved surface of the tube was facing the upstream flow. For the second and the third arrangements, different angles of attack were studied. Flow visualization was carried out to illustrate streamlines around the tube and to verify flow patterns obtained from the numerical calculations. It was found that: (1) for any angle of attack, the arrangement of the curved surface facing the flow gave higher average Nusselt number than the arrangement of the flat surface facing the flow and (2) for all tube-flow arrangements, increasing the angle of attack slightly increases the average Nusselt number. Correlations of Nusselt numbers in terms of Reynolds number and angle of attack were deduced from the experimental results for the three arrangements. The comparisons between the experimental data, correlations' predictions and numerical results showed reasonable agreements.

Quantum effects play an important role in determining the double-gate (DG) MOSFETs characteristics. The non-equilibrium Green's function formalism (NEGF) in real-space (RS) representation provides a rigorous description of quantum transport in nanoscale devices. Unfortunately, the traditional NEGF framework has the disadvantage of being heavy in computations. Methods that reduce the computations exist in the literature like the recursive Green's Function (RGF) algorithm, the contact block reduction (CBR) method, and Gauss elimination (GE) method. Comparison of the simulation time of the traditional NEGF, the RGF algorithm, the CBR method, and the GE method was always theoretical and based on approximate estimates. In this work, we carry out a real comparison between the four methods by implementing them inside the same simulator, using them to simulate the same device dimensions and parameters on the same machine. It is demonstrated that the RGF algorithm or the GE method introduce about one order of magnitude reduction in simulation time below that traditional NEGF, whereas the CBR method yields the smallest simulation time with about two orders of magnitude reduction. Copyright (C) 2010 John Wiley & Sons, Ltd.

Low alloy steels are processed to fulfill the requirements of low temperature applications. Besides the chemical composition, the steel should receive a suitable heat treatment to ensure the targeted mechanical properties at low temperature. In other words, the steels are designed to delay the ductile to brittle transition temperature to resist dynamic loading at subzero temperatures. Steel alloys processed for liquefied gas pipeline fittings are examples for applications that need deep subzero impact transition temperature (ITT). The main purpose of the present work was to find a suitable heat treatment sequence for alloys LC2 and LC2-1. Further, it aimed to correlate the impact toughness with the microstructure and the fracture surface at different sub-zero temperatures. The steels under investigation are carbon-low alloy grades alloyed with Ni, Cr and Mo. LC2 steel alloy has been successfully processed and then modified to LC2-1 alloy by addition of Cr and Mo. Oil quenching from 900 degrees C followed by tempering at 595 degrees C was used for toughness improvements. Hardness, tensile and impact tests at room temperature have been carried out. Further impact tests at subzero temperatures were conducted to characterize alloys behavior. Metallographic as well as SEM fractographic coupled with XRD qualitative analysis are also carried out. Non-homogenous martensite-ferrite cast structure in LC2 was altered to homogeneous tempered martensite structure using quenching-tempering treatment, which is leading to shift the ITT down to -73 degrees C. Addition of Cr and Mo creates a very fine martensitic structure in LC2-1 alloy. Quenching-tempering of LC2-1 accelerates ITT to -30 degrees C. It is expected that the steel was subjected to temper embrittlement as a result of phosphorus segregation on the grain boundary due to Cr and Mo alloying, as it was concluded in reference no. [6]. Published by Elsevier B.V.

In the present investigation, A390/graphite and A390/Al2O3 surface composite (SC) layers were fabricated using friction stir processing (FSP). The effect of tool rotational and traverse speeds on the microstructural, mechanical and wear characteristics of the surface layers was studied. The results revealed that increasing the tool rotational speed increases the hardness of the composite layers. The traverse speed has less significant influence on the hardness of the composite layer than the tool rotational speed. The A390/Al2O3 surface composites exhibited higher hardness than the A390/graphite surface composites. The surface composites exhibited better wear resistance than the matrix alloy. The A390/Al2O3 surface composites exhibited lower wear rates than the A390/graphite surface composites. Increasing the tool rotational reduces the wear rate of both A390/Al2O3 and A390/graphite surface composites. (C) 2011 Elsevier B.V. All rights reserved.

A wideband perforated rectangular dielectric resonator antenna (RDRA) reflectarray is presented. The arrays of RDRA are formed from one piece of materials. Air-filled holes are drilled into the material around the RDRA. This technique of fabricating RDRA reflectarray using perforations eliminates the need to position and bond individual elements in the reflectarray and makes the fabrication of the RDRA reflectarray feasible. The ground plane below the reflectarray elements is folded as a rectangular concave surface so that an air-gap is formed between the RDRA elements and the ground plane in order to increase the bandwidth. Full-wave analysis using the finite integration technique is applied. Three cases are studied. In the first one, the horn antenna is placed at the focal point to illuminate the reflectarray and the main beam in the broadside direction. In the second one, the horn antenna is placed at the focal point and the main beam at 30 degrees off broadside direction. In the third one, an offset feed RDRA reflectarray is considered. A variable length RDRA provides the required phase shift at each cell on the reflectarray surface. The normalized gain patterns, the frequency bandwidth, and the aperture efficiency for the above cases are calculated.

In this study a mathematical model has been developed to simulate two dimensional fluidized beds with uniform fluidization. The model consists of two sub models for hydrodynamic and thermal behavior of fluidized beds on which a FORTRAN program entitled (NEWFLUIDIZED) is devolved .The program is used to predict the volume fraction of gas and particle phases, the velocity of the two phases, the gas pressure and the temperature distribution for two phases. Also the program calculates the heat transfer coefficient. Besides that, the program predicts the fluidized bed stability and determines the optimum input gas velocity for fluidized beds to achieve the best thermal behavior. The hydrodynamic model is verified by comparing its results with the computational fluid dynamic code MFIX [1]. The thermal model was tested and compared to the available previous experimental correlations. The model results show good agreement with MFIX results and the thermal model of the present work confirms Zenz [2] and Gunn [3] equations.

The variational iteration method (VIM) attracted much attention in the past few years as a promising method for solving nonlinear differential equations. It is shown in this paper that the application of VIM to a special kind of nonlinear differential equations leads to calculation of unneeded terms and more time consumed in repeated calculations for series solutions. A modified VIM is introduced to eliminate the shortcomings; and its effectiveness is illustrated by some examples. (C) 2006 Elsevier B.V. All rights reserved.

This paper applies the modified variational iteration method to solve a class of nonlinear partial differential equations. Boussinesq equation is used as a case-study to illustrate the simplicity and effectiveness of the method. Comparison between variational iteration method and Adomian decomposition method is made. (c) 2007 Elsevier Ltd. All rights reserved.

In this paper, the variational iteration method (VIM) is reintroduced with Laplace transforms and the Pade technique treatment to obtain closed form solutions of nonlinear equations. Some examples, including the coupled Burger's equation, compacton k(n, n) equation, Zakharov-Kuznetsov Zk(n, n) equation, and KdV and mKdV equations are given to show the effectiveness of the coupled VIM-Laplace-Pade and VIM-Pade techniques. (c) 2007 Elsevier Ltd. All rights reserved.

Natural convection heat transfer in a horizontal elliptic annulus filled with saturated porous media is investigated experimentally and numerically. The inner horizontal elliptic tube is heated under constant heat flux conditions and is located concentrically in a larger isothermally cooled horizontal cylinder. Both ends of the water-saturated porous annulus are closed. The heated elliptic tube was made of copper material and has an axis ratio (AR = a/b) of 3.0. The porous media used in the experiments were made of sandstone and glass materials with different solid thermal conductivities and particle diameters. The elliptic tube orientation angle is varied from 0 degrees to 9 degrees, and the hydraulic radius ratio, HRR = R-o/R-i, is 6.85. The numerical solution scheme is based on a two-dimensional model, which is governed by Darcy-Boussinseq equations. The inner elliptic cylinder is heated isothermally, while the outer circular cylinder is also cooled isothermally. Discretization of the governing equations is achieved using a finite element scheme based on Galerkin method of weighted residuals. The effect of pertinent parameters such as modified Rayleigh number, Ra (Rayleigh-Darcy), orientation angle of the elliptic cylinder, delta, and the axis ratio of the elliptic cylinder, AR, is investigated. The numerical results obtained from the present model are compared with the available published results and with the present experimental results, and good agreement is found. The variation of the average Nusselt number with the investigated parameters is presented. It is concluded that the effect of modified Rayleigh number, which includes the effect of fluid properties, porous medium properties, and operating conditions on the average Nusselt number, is more significant than the effect of the geometric parameters such as the elliptic cylinder orientation angle and the elliptic cylinder axis ratio. The results showed that the average Nusselt number increases with the increase of the modified Rayleigh number. Also, the flow and heat transfer characteristics are illustrated via stream function and isotherms contours. Moreover, an empirical correlation for the average Nusselt number is obtained as a function of Rayleigh number, elliptic cylinder orientation angle, and elliptic cylinder axis ratio.

The optical properties and photovoltaic characterization of CdS quantum dots sensitized solar cells (QDSSCs) were studied. CdS QDs were prepared by the chemical solution deposition (CD) technique. Photoacoustic spectroscopy (PA) was employed to study the optical properties of the prepared samples. The sizes of the CdS QDs were estimated from transmission electron microscope (TEM) micrographs gives radii ranged from 1.57 to 1.92 nm. The current density-voltage (J-V) characteristic curves of the assembled QDSSCs were measured. Fluorine doped Tin Oxide (FTO) substrates were coated with 20 nm-diameter TiO2 nanoparticles (NPs). Presynthesized colloidal CdS quantum dots of different particles size were deposited on the TiO2-coated substrates using direct adsorption (DA) method. The FTO counter electrodes were coated with platinum, while the electroelectrolyte containing I-/I-3(-) redox species was sandwiched between the two electrodes. The short current density (J(sc)) and efficiency (eta) increases as the particle size increases. The values of J(sc) increases linearly with increasing the intensities of the sun light which indicates the greater sensitivity of the assembled cells.

this paper introduces a new technique for Key Generation based on fingerprints, Genetic Algorithms, and pseudorandom generator. The proposed technique can be applied in block ciphering techniques to enhance its performance (increase its complexity space). The paper introduces the different stages of the key generation sub-system; including: preprocessing and features extraction to represent the fingerprints signature (ID). Secondly the computation of genetic biometric signature ID, the third stage is computation of the pseudorandom generator to generate the different keys for 3DES. Results analysis proved that; the generated keys were strong when compared with the weak or semi weak keys. The proposed key generation technique increases the key space as well as it increases the total overheads on the encryption system due to the extra operations added but these overheads can be neglected when compared with the strong generated keys and its high complexity space.

This paper presents theoretical and experimental investigations of the onset voltage of conducting particle-initiated negative corona in air insulated co-axial cylindrical configurations. The conducting particles are spheres or wires of varying dimensions. The particle is fixed either on the inner or outer cylinder. The calculated onset voltage of negative corona is based on the criterion developed for the formation of repetitive negative corona Trichel pulses. This calls at first for an accurate calculation of the electric field in the vicinity of the particle. The investigated gap in the presence of particle is a three-dimensional field problem, due to the asymmetric position of particle inside the gap. The electric field is calculated using the charge simulation technique with a new charge distribution. The effect of varying field nonuniformity, particle shape, size and position on negative corona onset voltage is investigated. Laboratory measurements of negative corona onset voltage as influenced by particle position, shape and dimensions in air insulated co-axial configurations are carried out and compared with the present calculations. The calculated values agreed well with those measured experimentally.

Most Bluetooth implementations focus on architecture, routing protocols, encryption, and performance evaluation of the network. This paper provides a brief description of the Bluetooth standard including the physical layer. It focuses on developing MatLab/Simulink models for the Bluetooth transceivers utilizing different modulation schemes and the performance evaluation of these models. Different pulse shaping waveforms are utilized in our Matlab/Simulink Bluetooth models. The performance of our Bluetooth transceiver models with AWGN channel is evaluated by means of the BER.

The Absolute Nodal Coordinate Formulation (ANCF) has been initiated in 1996 by Shabana (Computational Continuum Mechanics, 3rd edn., Cambridge: Cambridge University Press, 2008). It introduces large displacements of planar and spatial finite elements relative to the global reference frame without using any local frame. A sub-family of beam, plate and cable finite elements with large deformations are proposed and employed the 3D theory of continuum mechanics. In the ANCF, the nodal coordinates consist of absolute position coordinates and gradients that can be used to define a unique rotation and deformation fields within the element. In contrast to other large deformation formulations, the equations of motion contain constant mass matrices as well as zero centrifugal and Coriolis inertia forces. The only nonlinear term is a vector of elastic forces. This investigation concerns a way to generate new finite element in the ANCF for laminated composite plates. This formulation utilizes the assumption that the bonds between the laminae are thin and shear is non-deformable. Consequently, the Equivalent Single Layer, ESL model, is implemented. In the ESL models, the laminate is assumed to deform as a single layer, assuming a smooth variation of the displacement field across the thickness. In this paper, the coupled electromechanical effect of Piezoelectric Laminated Plate is imposed within the ANCF thin plate element, in such a way as to achieve the continuity of the gradients at the nodal points, and obtain a formulation that automatically satisfies the principle of work and energy. Convergence and accuracy of the finite-element ANCF Piezoelectric Laminated Plate is demonstrated in geometrically nonlinear static and dynamic test problems, as well as in linear analysis of natural frequencies. The computer implementation and several numerical examples are presented in order to demonstrate the use of the formulation developed in this paper. A comparison with the commercial finite element package COMSOL MULTIPHYSICS (http://www.comsol.com/) is carried out with an excellent agreement.

In the frame of the discrete dipole approximation, the propagation of magnons in quasi-one-dimensional resonant structures made of nanometric magnetic clusters is examined theoretically. These resonant structures, composed of a nanometric magnetic cluster chain and adsorbed clusters near the chain, may exhibit sharp peaks (dips) in the magnon transmission spectrum. Stop bands and sharp resonant magnonic states in the gaps can be created with an appropriate choice of the geometrical or magnetic parameters of the structure. These resonant states result from an internal resonance of the structure when such a resonance is situated in the vicinity of a zero of transmission or placed between two zeros of transmission. This model may have potential applications in constructing magnon filter devices. (c) 2007 Elsevier B.V. All rights reserved.

Numerical simulation of nanoscale double-gate Sol (Silicon-on-Insulator) greatly depends on the accurate representation of quantum mechanical effects. These effects include, mainly, the quantum confinement of carriers by gate-oxides in the direction normal to the interfaces, and the quantum transport of carriers along the channel. In a previous work, the use of transfer matrix method (TMM) was proposed for the simulation of the first effect. In this work, TMM is proposed to be used for the solution of Schrodinger equation with open boundary conditions to simulate the second quantum-mechanical effect. Transport properties such as transmission probability, carrier concentration, and I-V characteristics resulting from quantum transport simulation using TMM are compared with that using the traditional tight-binding model (TBM). Comparison showed that, when the same mesh size is used in both methods, TMM gives more accurate results than TBM. Copyright (C) 2007 John Wiley & Sons, Ltd.

This study implements the genetic algorithm (GA) method in the optimization of steel telecommunication poles subjected to normal operating loads. In formulating the optimization problem, the objective function is defined as the pole weight. The imposed constraints on the design are: interaction ratios, sway angle limitations, minimum and maximum pole bottom diameters, and segment heights. The formulated problem is a mixed continuous-discrete problem where the main dimensions of the pole, top and bottom diameters, and segment heights are continuous variables whereas other variables are discrete. A Microsoft (R) Visual Basic (R) computer program is written implementing the requirements of TIA/EIA-222-G standards and using genetic algorithms (GAs). A verification problem and a generic telecommunication pole example are presented that show the effectiveness of the proposed approach. This program can be extended to cover other design standards of telecommunication poles as well as different types of poles, such as lighting and transmission poles.

Pure Fe2O3 and Fe2O3 doped with either 2.5-75mass% SiO2, 6.0 mass% MnO2 and (6.0%MnO2+ 7.5%SiO2) compacts annealed at 1 473 K for 6 h were prepared. The different phases were identified by X-ray diffraction (XRD) and their structures were examined by optical and scanning electron microscopes. The magnetic properties were measured with Vibrating Sample Magnetometer (VSM). Total porosity and pore size distribution were determined and their external volume was also measured. Unlike in SiO2 doped samples where no new phases were detected, manganese ferrite (MnFe2O4) was identified in MnO2-containing samples. Annealed compacts were isothermally reduced with CO at 1 073-1 373 K and the O-2-weight loss was continuously recorded. It was found that the reduction rate Of SiO2-Fe2O3 samples increases at the early stages with SiO2 mass% due to the increase in their original porosity. At final stages, the rate was retarded due to the formation of hardly reducible fayalite (Fe2SiO4) In MnO2-containing samples, the reduction rate was retarded at initial stages due to the presence of manganese ferrite. At later stages, the formation of fayalite-manganoan [(Fe, Mn)(2)SiO4] greatly hindered the reduction process. A catastrophic swelling (Delta V= 405%) was recorded in 6%MnO2-Fe2O3 compacts and was greatly diminished to 55.95% in presence of 75% SiO2 due to the decrease in size and number of metallic iron whiskers and plates. The reduction mechanism of pure and doped samples was predicted from the correlations between reduction kinetics and the microscopic examinations of partially and completely reduced samples.

Experimental and numerical studies for natural convection in two dimensional regions formed by a constant flux heat horizontal elliptic tube concentrically located in a larger, isothermally cooled horizontal cylinder were investigated. Both ends of the annulus are closed. Experiments were carried out for the Rayleigh number based on the equivalent annulus gap length ranges from 1.12x10(7) up to 4.92x10(7); the elliptic tube orientation angle varies from 0 degrees to 90 degrees and the hydraulic radius ratio, HRR, was 6.4. These experiments were carried out for the axis ratio of an elliptic tube (minor/major= b/c) of 1:3. The numerical simulation for the problem is carried out by using commercial CFD code. The effects of the orientation angle as well as other parameters such as elliptic cylinder axis ratio and hydraulic radius ratio on the flow and heat transfer characteristics are investigated numerically. The numerical simulations covered a range of elliptic tube axis ratios from 0.1 to 0.98 and for the hydraulic radius ratios from 1.5 to 6.4. The results showed that the average Nusselt number increases as the orientation angle of the elliptic cylinder increases from 0 degrees (the major axis is horizontal) to 90 degrees ( the major axis is vertical) and with the Rayleigh number as well. Also, the average Nusselt number decreases with the increase of the hydraulic radius ratio. An increase up to 1.75 and further increases in the hydraulic radius ratio leads to an increase in the average Nusselt number. The axis ratio of the elliptic cylinder has an insignificant effect on the average Nusselt number. Both the average and local Nusselt number from the experimental results are compared with those obtained from the CFD code. Both the fluid flow and heat transfer characteristics for different operating and geometric conditions are illustrated velocity vectors and isotherm contours that were obtained from the CFD code. Also, two correlation equations that relate the average Nusslet number with the Rayleigh number, orientation angle, and hydraulic radius ratio and axis ratio are obtained.

An analysis is carried out to study the flow and heat transfer characteristics of a non-Newtonian power-law fluid over a stretching surface in the presence of radiation and slip condition at the surface. The local similarity solution is used to transform the system of partial differential equations, describing the problem, into a system of highly coupled non-linear ordinary differential equations. The transformed system of equations is solved numerically using the fourth order Runge-Kutta method coupled with the shooting technique. The effects of the radiation parameter and the slip parameter on both the flow and the heat transfer are investigated and discussed. Also, it is found that the local skin-friction coefficient decreases as the slip parameter increases. However, it is found that increasing the slip parameter or the radiation parameter has the effect of decreasing the local Nusselt number.

The determination of burning velocity is very important for the calculations used in hazardous waste explosion protection and fuel tank venting, which has a direct impact on environmental protection. The scope of the present study encompass an extensive study to map the variations of the laminar burning velocity and the explosion index of LPG-air and propane-air mixtures over wide ranges of equivalence ratio (Phi = 0.7-2.2) and initial temperature (T-i = 295-400 K) and pressure (P-i = 50-400 kPa). For this purpose a cylindrical combustion bomb was developed. The reliability and accuracy of the built up facility together with the calculation algorithm are confirmed by comparing the values of the laminar burning velocity obtained for a standard fuel (propane at normal pressure normal temperature conditions, NPT) with those available in the literature. The burning velocity was determined using different models depending on the pressure history (P-t) of the central ignition combustion process at the minimum ignition energy. The data obtained for the laminar burning velocity is correlated to S-L = S-L0(T/T-0)(alpha)(P/P-0)(beta) where S-L0 is the burning velocity at NPT, alpha nd beta are the temperature and pressure exponents respectively. The value of beta is observed to slightly vary with the equivalence ratio for both fuels. However, propane exhibits higher pressure dependency than that of LPG. The maximum laminar burning velocity found for propane is nearly 455 mm/s at Phi = 1.1, hile that for LPG is nearly 432 mm/s at 4.5% fuel percent ((Phi approximate to 1.5). The maximum explosion index, commonly called the "explosion severity parameter", is calculated from the determined laminar burning velocity and is found to be 93 bar m/s for propane, and nearly 88 bar m/s for LPG. (c) 2007 Elsevier Ltd. All rights reserved.

Photoacoustic absorption spectra of the porous silicon samples ( P-Si) of different thickness and porosity percentage were measured at different modulation frequency. The absorption edge of the P-Si layer for all samples shows a blue shift from that of crystalline silicon ( C-Si) at 1.1 eV. At low modulation frequency the estimated energy gap ( 1.88 eV) is almost the same for all samples and the PA signal increases as the porosity percentage increases. At the higher modulation frequency, the spectra show an increase in the energy gap indicating the effect of quantum confinement as the porosity increasing. The Raman shifts of the P-Si samples are correlated with the particle size leading to an estimated average particle size. The quantum confinement interpretation of the PA results is in agreement with the Raman measurements that indicate the presence of such nanostructure in the P-Si layer.

Single-phase induction motors are widely used in many applications. Improvements in its performance means a great saving in electrical energy consumption. An inverter-fed variable frequency motor is a typical example of such improvement. In this regard, the paper presents a comprehensive analysis of the performance of the single-phase induction motor when it is fed with an inverter. Dynamic models and analysis of the motor behavior during transient and steady state phases are presented. A speed controller based on slip frequency technique is proposed. The controlled motor exhibited better performance at both staring and steady state.

Mammogram - breast x-ray imaging - is considered the most effective, low cost, and reliable method in early detection of breast cancer. Clustered Microcalcifications are an important early sign of breast cancer. In this paper, we are introducing, as an aid to radiologists, a computer-aided diagnosis (CAD) system, which could be helpful in detecting microcalcifications faster than traditional screening program without the drawback attribute to human factors. The techniques used in this paper for feature extraction is based on the fractal modeling of locally processed image (ROI). Classification between normal and microcalcification is done using the voting K-Nearest Neighbor classifier and the support vector machine classifier. The two classification techniques used were compared through the system to reach a better classification decision.

Emulsion liquid membranes (ELMs) can contribute to process intensification of zinc extraction, by significantly reducing the solvent and carrier requirements in comparison with conventional solvent extraction. Di(2-ethylhexyl)phosphoric acid (D2EHPA) was used as a highly selective carrier for the transport of zinc ions through the emulsified liquid membrane. The hollow-fiber extractor appears to offer significant advantages over conventional liquid-liquid contactors for this separation because emulsion leakage and swell are practically eliminated even when treating high concentration feeds. Various hydrodynamic and chemical parameters, such as variation in feed pH; zinc concentration in feed; variation in concentrations of D2EHPA; variation in feed/emulsion volume ratios and variation in feed and emulsion flow rates, were investigated. The content of sulfuric acid as an internal did not show in the studied range any significant influence on zinc extraction through the ELM, although a minimum hydrogen ion concentration is suggested in the internal aqueous solution to ensure acidity gradient between both aqueous phases to promote the permeation of zinc ions toward the internal phase. The experimental mass-transfer coefficients have shown a stronger dependence on hydrodynamic conditions in both the external feed phase and emulsion among the parameters studied. For emulsion flow rate, mass-transfer coefficient increased from 16.3 x 10(-6) m/s at 200 ml/min to 31.2 x 10(-6) m/s at 640 ml/min. Significant increasing in mass-transfer coefficient observed with increasing aqueous flow rate from 9.7 x 10(-6) m/s at 170ml/min to 37.2 x 10(-6) m/s at 740 ml/min. The overall mass-transfer coefficient increases from 12 x 10-6 m/s at 2% D2EHPA to 28 x 10-6 m/s at 8% D2EHPA. This means that this process is chemically controlled and the interfacial resistance has a more significant role in the extraction of zinc by emulsion liquid membrane through hollow-fiber contactor. From the results obtained, it seems that the diffusion processes in aqueous feed phase and the membrane phase have the same importance as the chemical process. (C) 2007 Elsevier B.V. All rights reserved.

Comprehensive analysis of the starting period of inverter-fed large induction motors reveals that these motors are subjected to additional components of pulsating torsional torque. These torque pulsations may coincide with the natural torsional frequency of the large motor system and produce hazardous shaft torque oscillations. To alleviate the torsional toque problem and limit the motor starting current, a constant air-gap flux using slip frequency control scheme is proposed to operate the motor inverter. Simulation results show that the proposed scheme is capable of drastically reducing the torsional torque oscillations and limiting the motor line current to approximately 22% of its direct online starting value without prolonging its starting period.

In this paper, a new technique of homotopy analysis method (nHAM) is proposed for solving second order nonlinear differential equations. This method improves the convergence of the series solution, eliminates the unneeded terms and reduces time consuming in the standard homotopy analysis method (HAM). The proposed provides an approximate solution by rewriting the second order nonlinear differential equation in the form of two first order differential equations. The solution of these two differential equations is obtained as a power series solution. This scheme is tested on four non-linear exactly solvable differential equations. Three of the examples are initial value problems and the fourth is boundary value problem. The results demonstrate reliability and efficiency of the algorithm developed. (C) 2012 Elsevier Inc. All rights reserved.

The present research is devoted to the investigation of electron spin transmission through a nanoelectronic device. This device is modeled as nonmagnetic semiconductor quantum dot coupled to two diluted magnetic semiconductor leads. The spin transport characteristics through such a device are investigated under the effect of an ac-field of a wide range of frequencies. The present result shows a periodic oscillation of the conductance for both the cases of parallel and antiparallel spin alignment. These oscillations are due to Fano-resonance. Results for spin polarization and giant magneto-resistance show the coherency property. The present research might be useful for developing single spin-based quantum bits (qubits) required for quantum information processing and quantum spin-telecommunication.

This study introduces the application for the mixture model to simulate the liquid-liquid flow through complex pipeline configurations. The model is validated by comparing model predictions with published experimental data and showed reasonable agreement. The model is used to calculate the naphtha-water flow through a complex pipeline configuration with straight pipes and elbow fittings. The selected pipeline suffers from corrosion problems. The effect of different fittings on the pipeline is taken into account. The results obtained here showed that the mixture model is appropriate two-phase flow model and could be used to explain the reasons why specific locations in the pipeline suffer from corrosion problems while other locations do not suffer from these problems. These locations are predicted with good agreement with field measurements of corrosion distribution. It was concluded through this study that the mixture model can predict the two-phase flow features with reasonable accuracy and during relatively short computational time. (C) 2012 Elsevier Inc. All rights reserved.

He's homotopy perturbation method (HPM) is applied to linear and nonlinear Schrodinger equations for obtaining exact solutions. The HPM is used for an analytic treatment of these equations. The results reveal that the HPM is very effective, convenient and quite accurate to such types of partial differential equations.

The separation of zinc and copper ions from sulfuric acid solutions by an emulsion liquid membrane (ELM), using di-(2-ethylhexyl) phosphoric acid (D2EHPA) as a carrier, has been investigated. The batch extraction of zinc and copper was carried out while varying a selection of experimental conditions, i.e., stirring speed, treatment ratio, concentrations of metal ions in the feed phase, carrier and Span 80 concentration in the membrane, and internal phase concentration. The results obtained demonstrate the effectiveness of D2EHPA as a carrier for the separation of zinc and copper from sulfuric acid media using an ELM. An increase of the D2EHPA concentration beyond 2 vol.-% does not result in the improved extraction of zinc because the viscosities of the membrane and emulsion have a trend to increase for higher carrier concentrations. It was found that the extraction rate of copper was affected by the carrier concentration in the liquid membrane and by the pH and metal content in the external phase. A 3 vol.-% concentration of surfactant in the organic phase was required to stabilize the emulsion. The number of stages required for the extraction of zinc and copper by an ELM was determined from McCabe-Thiele plots.

In this paper, the equations describing the performance of the electric vehicle are derived. Performance characteristics for each part in the vehicle system are obtained when the vehicle is accelerated under voltage, turn on, and turn off angle control. A comparison between the different methods of control is established. From these comparisons, it can be noticed that the acceleration time, for the case at which the turn on angle is controlled, will be smaller than that for the other cases; also the motor efficiency, at the voltage control method, has the highest value especially at the higher values of the vehicle speed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772964]

In this paper, a dynamic modeling and power control scheme for doubly-fed induction generator (DFIG) for variable speed wind power generation is proposed. A detail dynamic model of a DFIG-based, wind turbine and grid-connected system is presented in the d-q-synchronous reference frame. A robust controller based on sliding mode controller (SMC) is applied in order to control the power flowing between the stator of the DFIG and the power network. To improve the controller performance in steady state the integral sliding mode controller (ISMC) is used. Also, ISMC is used to achieve the controller robustness. Its respective performance is compared in terms of power reference tracking, sensitivity to perturbations in sub-synchronous and super-synchronous modes and robustness against machine parameters variations. Moreover, the proposed ISMC performance is compared with the conventional proportional-integral control. (C) 2012 Elsevier Ltd. All rights reserved.

Tungsten-copper composites with various copper nano-particles volume fractions were manufactured and examined. Tungsten-copper composites with 20 pct, 25 pct, and 30 pct volume fractions were mechanically mixed and sintered. spark plasma sintering (SPS) method was used for samples preparation at two different sintered temperatures 1273 K and 1373 K (1000 degrees C and 1100 degrees C). The effect of copper nano-particles on the bulk density, hardness, the coefficient of thermal expansion (CTE), electrical conductivity, and stress-strain behavior of the produced composites were studied. The hardness was found to decrease with the increase of the copper volume fraction in the composites. Conversely, the CTE and electrical conductivity increases with the increase of the copper volume fraction in the composites. Furthermore, the elastic modulus were extracted from tensile stress-strain behavior were found to increase with the increase of the copper volume fraction in the composites. Finally, the fracture surface roughness was studied using high resolution optical investigations and was noticeably higher with the increase of the copper volume fraction in the composites. DOI: 10.1007/s11661-012-1396-x (C) The Minerals, Metals & Materials Society and ASM International 2012

A routing algorithm is proposed to increase link reliability in smart metering over low-tension power line grid. The algorithm assumes data concentrator (DC) is polling meters connected to the power line to send energy consumption, loading profile and any other crucial data to the utility. The proposed algorithm is designed to keep the needed complexity at the meters at minimum, while moving the intelligence up to the DC. The protocol accounts for asymmetric characteristics of the power line channel, where some nodes couldn't receive data from DC and neighbor nodes (deaf nodes), while its transmission could be received properly. Special packet structure is proposed to minimize algorithm overhead. Performance comparison with AODV protocol in terms of average throughput, reachability, and protocol overhead is in progress.

Although the septic tank is the most applied on-site system for wastewater pre-treatment, limited research has been performed to determine sludge accumulation and biogas production in the tank. Therefore a dynamic mathematical model based on the Anaerobic Digestion Model No. 1 (ADM1) was developed for anaerobic digestion of the accumulated sludge in a septic tank treating domestic wastewater or black water. The results showed that influent chemical oxygen demand (COD) concentration and hydraulic retention time (HRT) of the tank mainly control the filling time with sludge, while operational temperature governs characteristics of the accumulated sludge and conversion to methane. For obtaining stable sludge and high conversion, the tank needs to be operated for a period more than a year without sludge wasting. Maximum conversion to methane in the tank is about 50 and 60% for domestic wastewater and black water, respectively. The required period for sludge wasting depends on the influent COD concentration and the HRT, while characteristics of the wasted sludge are affected by operational temperature followed by the influent COD concentration and the HRT. Sludge production from the tank ranges between 0.19 to 0.22 and 0.13 to 0.15 L/(person. d), for the domestic wastewater and black water, respectively.

Design of conventional power system stabilizers (PSSs) is load-dependent and thus has to be adjusted at every operating condition. An interval arithmetic (IA) based approach is proposed, to rigorously address load uncertainties associated with the design of PSS. The proposed approach characterizes the set of all robust stabilizing PSSs computed for a single-machine infinite-bus system. A robust PSS can properly function over the full range of operating conditions. An interval plant transfer function is determined over the operating range where upper and lower bounds of the coefficients are precisely computed. Using a proportional-derivative (PD) PSS, an interval characteristic polynomial for the closed loop system is generated. Interval Routh-Hurwitz array is developed to determine the boundaries of robust stability region in Kp-Kd plane via IA computation. Thereafter, the results obtained by interval Routh array are relaxed using degenerate interval array with an image-set polynomial of the plant where the boundaries of the robust stability region is exactly computed. Simulation results confirm the effectiveness of a sample controller, which lies within the solution set, as it is applied to the original nonlinear system model under wide loading conditions.

In this paper, a new efficient H. 264 intra prediction scheme is introduced. The new prediction scheme is called Best Prediction Matrix Mode (BPMM). The main idea behind the new prediction scheme is to combine the most usable intra prediction modes, {vertical - horizontal - DC}, into a new efficient prediction mode. The performance of our proposed prediction scheme is evaluated using VHDL implementation benchmark with respect to compression ratio, Peak Signal to Noise Ratio (PSNR) and bit rate. The results show that our BPMM enhances the compression ratio and correspondingly the bit rate and it increases the PSNR.

Iris recognition is one of the most reliable biometric technologies. In order to improve the accuracy of iris recognition systems, and according to the variations in iris data, due to noises of the eyelids and eyelashes or inappropriate image acquisition environment, multiple iris images per person are enrolled. Therefore, these systems suffer from storage and computational overheads. This paper presents a new technique for generating a reliable reference iris image per person rather than maintaining multiple images. The proposed technique enhances the performance of iris recognition systems regardless of the feature extraction method in use. Moreover, it has the advantage of reducing the amount of data storage, computational complexity and the matching time. The achieved results assure that our proposed approach results in very high recognition rate as well as it decreases the matching threshold.

This paper presents a theoretical and experimental study of the effect of conducting particles on the onset voltage of a negative corona in air-insulated co-axial cylindrical configurations. The conducting particles are spheres or wires of varying dimensions. The particle is fixed either on the inner or the outer cylinder. The calculated onset voltage of the negative corona is based on the criterion developed for the formation of repetitive negative coronas, Trichel pulses. This calls first for an accurate calculation of the electric field in the vicinity of the particle where avalanches grow. The investigated gap in the presence of a particle is a three-dimensional field problem due to the asymmetrical position of the particle inside the gap. The three-dimensional electric field is calculated using the charge simulation technique with a new charge distribution. An experimental set-up is built up to measure the onset voltage of a negative corona initiated by particles in an air-insulated co-axial configuration to check the accuracy of the present calculation. The effect of varying field nonuniformity, particle shape, size and position on the onset voltage of the negative corona is investigated. The calculated onset voltage values agree well with those measured experimentally.

Automatic license plate recognition (ALPR) is the extraction of vehicle license plate information from an image or a sequence of images. The extracted information can be used with or without a database in many applications, such as electronic payment systems (toll payment, parking fee payment), and freeway and arterial monitoring systems for traffic surveillance. The ALPR uses either a color, black and white, or infrared camera to take images. The quality of the acquired images is a major factor in the success of the ALPR. ALPR as a real-life application has to quickly and successfully process license plates under different environmental conditions, such as indoors, outdoors, day or night time. It should also be generalized to process license plates from different nations, provinces, or states. These plates usually contain different colors, are written in different languages, and use different fonts; some plates may have a single color background and others have background images. The license plates can be partially occluded by dirt, lighting, and towing accessories on the car. In this paper, we present a comprehensive review of the state-of-the-art techniques for ALPR. We categorize different ALPR techniques according to the features they used for each stage, and compare them in terms of pros, cons, recognition accuracy, and processing speed. Future forecasts of ALPR are given at the end.

In this contribution, the well-known ordinal sum technique of posets is generalized by allowing for a lattice ordered index set instead of a linearly ordered index set, and we argue for the merits of this generalization. We will call such a proposed sum-type construction a lattice-based sum. Our new approach of lattice-based sum extends also the horizontal sum. We show that the lattice-based sum of posets is again a poset. Subsequently, we apply the results for constructing new lattices by investigating lattice-based sums when the summand posets are lattices. We show that under certain assumptions, the lattice-based sum of lattices will be a lattice. (C) 2012 Elsevier Inc. All rights reserved.

This paper presents the behavior and design of axially loaded normal and steel fiber reinforced concrete in-filled steel tube (SFRCFT) columns, to examine the contribution of steel fibers on the compressive strength of the composite columns. Non-linear finite element analysis model (FEA) using ANSYS software has been developed and used in the analysis. The confinement effect provided by the steel tube is considered in the analysis. Comparisons of the analytical model results, along with other available experimental outputs from literature have been done to verify the structural model. The compressive strength and stiffness of SFRC composite columns were discussed, and the interpretation of the FEA model results has indicated that, the use of SFRC as infill material has a considerable effect on the strength and stiffness of the composite column. The analytical model results were compared with the existing design methods of composite columns - (EC4, AISC/LRFD and the Egyptian code of Practice for Steel Construction, ECPSC/LRFD). The comparison indicated that, the results of the FEA model were evaluated to an acceptable limit of accuracy. The code design equations were modified to introduce the steel fiber effect and compared with the results of the FEA model for verification.

The absolute nodal coordinate formulation (ANCF) has been used in the analysis of large deformation of flexible multibody systems that encompass belt drive, rotor blade, and cable applications. As demonstrated in the literature, the ANCF finite elements are ideal for isogeometric analysis. The purpose of this investigation is to establish a relationship between the B-splines, which are widely used in the geometric modeling, and the ANCF finite elements in order to construct continuum models of large-deformation geometries. This paper proposes a simplified approach to map the B-spline surfaces into ANCF thin plate elements. Matrix representation of the mapping process is established and examined through numerical examples successfully. The matrix representation of the mapping process is used because of its suitability of computer coding and to minimize the calculation time. The error estimation is carried out by analyzing the gap between the points of each ANCF element and the corresponding points of the portion of the B-spline surface. The Hausdorff distance is used to study the effect of the number of control points, the degree of interpolation, and the knot multiplicity on the mapped geometry. It is found that cubic interpolation is recommended for optimizing the accuracy of mapping the B-spline surface to ANCF thin plate elements. It is found that thin plate element in ANCF missing a number of basis functions which considered a source of error between the two surfaces, as well as it does not allow to converting the ANCF thin plate elements model to B-spline surface. In this investigation, an application example of modeling large-size wind turbine blade with uniform structure is illustrated. The use of the continuum plate elements in modeling flexible blades is more efficient because of the relative scale between the plate thickness and its length and width and the high flexibility of its structure. The numerical results are compared with the results of ANSYS code with a good agreement. The dynamic simulation for mapped surface model shows a numerical convergence, which ensures the ability of using the proposed approach for applications of dynamics for design and computer-aided design.

Cyclone performance is determined by pressure drop and collection efficiency. This study aims to optimize the dimensions of the exit pipe to improve cyclone performance. A numerical technique was used which is based on an Eulerian-Lagrangian approach. The behavior of the cyclone was studied by solving the three-dimensional, incompressible turbulent flow governing equations. The turbulent flow was modeled by using Reynolds Stress Model. Particle trajectories were obtained by solving the particle equation of motion. The collection efficiency was obtained by releasing a specified number of particles at the inlet of the cyclone and by counting the collected particles. The model was verified by comparing the numerical results to published experimental measurements. It was found through this study that increasing exit pipe diameter decreases the pressure drop through the cyclone and affects also the collection efficiency while exit pipe length does not affect cyclone performance significantly. It was concluded that the performance of the standard cyclone can be improved by prober selection for the diameter of the exit pipe. The data obtained through this study was represented in performance maps. These maps allowed the selection of the exit pipe diameter to obtain the maximum collection efficiency while avoiding excessive pressure drop. (C) 2012 Elsevier Inc. All rights reserved.

Rather than using graphene oxide, which is limited by a high defect concentration and cost due to oxidation and reduction, we adopted cost-effective, 3.56 nm thick graphene platelets (GnPs) of high structural integrity to melt compound with an elastomer-ethylene-propylene-diene monomer rubber (EPDM)-using an industrial facility. An elastomer is an amorphous, chemically crosslinked polymer generally having rather low modulus and fracture strength but high fracture strain in comparison with other materials; and upon removal of loading, it is able to return to its original geometry, immediately and completely. It was found that most GnPs dispersed uniformly in the elastomer matrix, although some did form clusters. A percolation threshold of electrical conductivity at 18 vol% GnPs was observed and the elastomer thermal conductivity increased by 417% at 45 vol% GnPs. The modulus and tensile strength increased by 710% and 404% at 26.7 vol% GnPs, respectively. The modulus improvement agrees well with the Guth and Halpin-Tsai models. The reinforcing effect of GnPs was compared with silicate layers and carbon nanotube. Our simple fabrication would prolong the service life of elastomeric products used in dynamic loading, thus reducing thermosetting waste in the environment.

The connection of small-scale embedded generation to the grid may influence the frequency and voltage stability of the power system. A load-frequency control technique for systems with high penetration of small-scale wind generation is proposed. The proposed controller has been successfully implemented and tested using PSCAD/EMTDC (PSCAD Power System Simulation, HVDC Research Centre, Manitoba, Canada). In this study, the impact of small-scale wind turbines on frequency stability of the system is studied in detail. This study shows that large penetration of small-scale wind turbines with load and frequency has a significant impact on the stability and security level of electrical network. Copyright (c) 2012 John Wiley & Sons, Ltd.

Electrothermal plasma sources have been introduced as a method to propel frozen hydrogenic pellets for fueling of future magnetic fusion reactors. These sources are also useful as mini-thrusters in space shuttles, pre-injectors in hypervelocity launchers and igniters in electrothermal-chemical Guns. The source is a capillary discharge that generates the plasma from the ablation of a liner in an ablation-dominated regime, or from the flow of gas into the capillary in an ablation-free regime. Most electrothermal plasma sources uses pulse power delivery system with a pulse length in the range of 100 mu s with FWHM of 50 mu s. This research is a computational study on the effect of extending the top of the discharge current pulse to the range of 1,000 mu s on the source exit parameter to achieve higher pressures and better exit velocities. Calculations using 0.4 cm diameter, 9.0 cm length Lexan polycarbonate capillary source, using ideal and nonideal plasma models, show that extended flattop pulses at fixed amplitude produce more ablated mass which scales linearly with increased pulse length, however, other plasma parameters remain almost constant. Results suggest that quasi-steady state operation of an electrothermal plasma source may provide constant exit pressure and velocity for pellet injectors for future magnetic fusion reactors deep fueling.

Electrically and thermally conductive elastomers are highly desired in industries, since they can prevent static electricity accumulation and reduce internal heat build-up. Previous methodologies using carbon black, metal nanoparticles and carbon nanotubes are either ineffective or expensive. By contrast, we in this study developed electrically and thermally conductive, high-mechanical performance elastomers, by adopting cost-effective, high-structural integrity graphene platelets (GnPs) of 3.55 +/- 0.32 nm in thickness and employing an industrial compatible method. A percolation threshold of electrical conductivity was observed at 16.5 vol% GnPs, and the elastomer thermal conductivity improved 240% at 41.6 vol%. At 24 vol%, tensile strength, Young's modulus, and tear strength improved 230%, 506% and 445%, respectively. By comparing the reinforcement effect of GnPs with those of carbon black, multi-walled carbon nanotubes and silicate layers, we found that GnPs are a promising candidate for developing cost-effective, functional, high-mechanical performance elastomers. (C) 2013 Elsevier Ltd. All rights reserved.

Glasses with composition xBi(2)O(3)-24Na(2)O-(75 - x)B2O3-1Er(2)O(3) (where x = 0, 5, 10, 15, 25, 33, 40 mol%), were prepared by the melt quenching technique. The effect of Bi2O3 content on thermal stability, optical properties and structures of these glasses is systematically investigated by X-ray diffraction, infrared spectroscopy and DTA techniques. The variations in the optical band gap energies, with Bi2O3 content have been discussed in terms of changes in the glass structure. Urbach energy increases with increasing Bi2O3 content in the present glass system. It is found that the density, molar volume and optical basicity increase with increasing Bi2O3. The glass transition temperature (T-g) of the samples was found to decrease with the Bi2O3 content. IR measurements revealed an existence of trigonal BO3 pyramid, tetrahedron BO4, pyramidal BiO3 and octahedron BiO6 structural units in the network of the investigated glass. Furthermore, a decrease in BO4 and an increase in BO3 take place against the increase of x which means that, Bi2O3 plays the role of network modifier in the structural network. (c) 2013 Elsevier B.V. All rights reserved.

Accurate modeling of large wind turbine blades is an extremely challenging problem. This is due to their tremendous geometric complexity and the turbulent and unpredictable conditions in which they operate. In this paper, a continuum based three dimensional finite element model of an elastic wind turbine blade is derived using the absolute nodal coordinates formulation (ANCF). This formulation is very suitable for modeling of large-deformation, large-rotation structures like wind turbine blades. An efficient model of six thin plate elements is proposed for such blades with non-uniform, and twisted nature. Furthermore, a mapping procedure to construct the ANCF model of NACA (National Advisory Committee for Aeronautics) wind turbine blades airfoils is established to mesh the geometry of a real turbine blade. The complex shape of such blades is approximated using an absolute nodal coordinate thin plate element, to take the blades tapering and twist into account. Three numerical examples are presented to show the transient response of the wind turbine blades due to gravitational/aerodynamics forces. The simulation results are compared with those obtained using ANSYS code with a good agreement.

We present a multiplexing device made of nanometric magnetic cluster chains and adsorbed clusters near the chains. We show that this nanosystem can transfer one magnon frequency from one chain to the other. With an appropriate choice of the geometrical or magnetic parameters of the structure, it is possible to control the desired magnon ejection. These results should have important consequences for designing integrated devices such as narrow-frequency microwave multiplexers. (C) 2008 Elsevier B.V. All rights reserved.

The greatest challenge in developing polymer/graphene nanocomposites is to prevent graphene layers stacking; in this respect, we found effective solution-mixing polymers with cost-effective graphene of hydrophobic surface. Since graphene oxide is hydrophilic and in need of reduction, highly conducing graphene platelets (GnPs) of similar to 3 nm in thickness were selected to solution-mix with a commonly used elastomer - styrene-butadiene rubber (SBR). A percolation threshold of electrical conductivity was observed at 5.3 vol% of GnPs, and the SBR thermal conductivity enhanced three times at 24 vol%. Tensile strength, Young's modulus and tear strength were improved by 413%, 782% and 709%, respectively, at 16.7 vol%. Payne effect, an important design criteria for elastomers used in dynamic loading environment, was also investigated. The comparison of solution mixing with melt compounding, where the same starting materials were used, demonstrated that solution mixing is more effective in promoting the reinforcing effect of GnPs, since it provides more interlayer spacing for elastomer molecules intercalating and retains the high aspect ratio of GnPs leading to filler-filler network at a low volume fraction. We also compared the reinforcing effect of GnPs with those of carbon black and carbon nanotubes. (C) 2013 Elsevier Ltd. All rights reserved.

In this work the effect of the structure of water-in-diesel fuel emulsion (WFE) on a three cylinder diesel engine performance has been investigated. Based on membrane emulsification, two different membranes of pore sizes of 0.2 mu m and 0.45 mu m has been individually used to change the emulsion structure while keeping the same WFE volumetric content (at 17% water volumetric content and 0.5% mixing emulsifier content). The Results showed that emulsions with large size of water droplets resulted in greater reduction in NOx emissions up to 25%. While, emulsions with finer droplets not only gave reductions in engine smoke and unburned hydrocarbons of values greater than 80% and 35% respectively, but also resulted in an increase of the engine effective efficiency up to 20%. (C) 2013 Elsevier Ltd. All rights reserved.

Purpose - The paper aims to find an accurate analytic solution (series solution) for the micropolar flow in a porous channel with mass injection for different values of Reynolds number. Design/methodology/approach - In this paper, the homotopy analysis method (HAM) with different numbers of unknown convergence-control parameters has been used to derive accurate analytic solution for micropolar flow in a porous channel with mass injection. The possible optimal value of convergence-control parameter determined by minimizing the averaged residual error. Findings - The results obtained from HAM solution with two parameters are compared with numerical results and that obtained from HAM solution with only one parameter. The results show that this method gives an analytical solution with high order of accuracy with a few iterations. As shown in this paper, by minimizing the averaged residual error, the authors can get the possible optimal value of the convergence-control parameters which may give the fastest convergent series. Practical implications - The HAM with different numbers of unknown convergence-control parameters can be used to obtain analytic solutions for many problems in sciences and engineering. Originality/value - This paper fulfils an identified need to evaluate the accurate analytic solution (series solution) of practical problem.

Time diversity is achieved in direct sequence spread spectrum by receiving different faded delayed copies of the transmitted symbols from different uncorrelated channel paths when the transmission signal bandwidth is greater than the coherence bandwidth of the channel. In this paper, a new time diversity scheme is proposed for spread spectrum systems. It is called code-time diversity. In this new scheme, N spreading codes are used to transmit one data symbol over N successive symbols interval. The diversity order in the proposed scheme equals to the number of the used spreading codes N multiplied by the number of the uncorrelated paths of the channel L. The paper represents the transmitted signal model. Two demodulators structures will be proposed based on the received signal models from Rayleigh flat and frequency selective fading channels. Probability of error in the proposed diversity scheme is also calculated for the same two fading channels. Finally, simulation results are represented and compared with that of maximal ration combiner (MRC) and multiple-input and multiple-output (MIMO) systems.

The greatest challenge in developing polymer/graphene nanocomposites is to prevent graphene layers stacking; in this respect, we found effective solution-mixing polymers with cost-effective graphene of hydrophobic surface. Since graphene oxide is hydrophilic and in need of reduction, highly conducing graphene platelets (GnPs) of similar to 3 nm in thickness were selected to solution-mix with a commonly used elastomer - styrene-butadiene rubber (SBR). A percolation threshold of electrical conductivity was observed at 5.3 vol% of GnPs, and the SBR thermal conductivity enhanced three times at 24 vol%. Tensile strength, Young's modulus and tear strength were improved by 413%, 782% and 709%, respectively, at 16.7 vol%. Payne effect, an important design criteria for elastomers used in dynamic loading environment, was also investigated. The comparison of solution mixing with melt compounding, where the same starting materials were used, demonstrated that solution mixing is more effective in promoting the reinforcing effect of GnPs, since it provides more interlayer spacing for elastomer molecules intercalating and retains the high aspect ratio of GnPs leading to filler-filler network at a low volume fraction. We also compared the reinforcing effect of GnPs with those of carbon black and carbon nanotubes. (C) 2013 Elsevier Ltd. All rights reserved.

In the present study, an experimental investigation of heat transfer and fluid flow characteristics of buoyancy-driven flow in horizontal and inclined annuli bounded by concentric tubes has been carried out. The annulus inner surface is maintained at high temperature by applying heat flux to the inner tube while the annulus outer surface is maintained at low temperature by circulating cooling water at high mass flow rate around the outer tube. The experiments were carried out at a wide range of Rayleigh number (5 x 10(4) < Ra < 5 x 10(5)) for different annulus gap widths (L/D-o = 0.23, 0.3, and 0.37) and different inclination of the annulus (alpha = 0 degrees, 30 degrees and 60 degrees). The results showed that: (1) increasing the annulus gap width strongly increases the heat transfer rate, (2) the heat transfer rate slightly decreases with increasing the inclination of the annulus from the horizontal, and (3) increasing Ra increases the heat transfer rate for any L/D-o and at any inclination. Correlations of the heat transfer enhancement due to buoyancy driven flow in an annulus has been developed in terms of Ra, L/D-o and alpha. The prediction of the correlation has been compared with the present and previous data and fair agreement was found.

A simple acoustic device consisting of two dangling side resonators grafted at two sites on a slender tube is designed possibly to obtain transmission stop bands (where the propagation of longitudinal acoustic waves is forbidden). In contrast to all known systems of this kind, a spectral transmission gap of nonzero width occurs here even with this simple structure. This is obtained by combining appropriately the zeros of transmission of the side resonators. Sharp resonant states inside the gaps can be achieved without introducing any defects in the structure. This results from an internal resonance of the structure when such a resonance is situated in the vicinity of a zero of transmission or placed between two zeros of transmission, the so-called Fano resonances. A general analytical expression for the transmission coefficient is given for various systems of this kind within the framework of the Green's function method. The amplitude and the phase of the transmission are discussed as a function of frequency and it is shown that the width of the stop bands is very sensitive to the number of side resonators. These results should have important consequences for the suppression of low-frequency noise and for designing filters.

In this paper, a new finite difference called the Restrictive Taylor approximation (RTA) is implemented to find numerical solution of KdV-Burgers, this method is a new explicit method. The accuracy of the method is assessed in terms of the absolute error which is very close to zero and the error norms L-2, L-infinity. (c) 2014 Elsevier Inc. All rights reserved.

The CoLaPipe is a novel test facility at the Department of Aerodynamics and Fluid Mechanics, Brandenburg University of Technology Cottbus-Senftenberg (BTU Cottbus-Senftenberg), set up to investigate fully developed pipe flow at high Reynolds numbers (Re-m

In the frame of long-wavelength Heisenberg model, a simple magnonic device is designed to obtain possibly transmission stop bands (where the propagation of spin waves is forbidden). This simple device is composed of an infinite one-dimensional mono-mode waveguide (the backbone) along which N(N') side resonators are grafted at two sites. Contrary to all known systems of this kind, a spectral transmission gap of nonzero width occurs here even with this simple structure. This is obtained by combining appropriately the zeros of transmission of the side resonators. Sharp resonant states inside the gaps can be achieved without introducing any defects in the structure. This results from an internal resonance of the structure when such a resonance is situated in the vicinity of a zero of transmission or placed between two zeros of transmission, the so-called Fano resonances. A general analytical expression for the transmission coefficient is given for various systems of this kind within the framework of the Green's function method. The amplitude, the phase, and the phase time of the transmission are discussed as a function of frequency and it is shown that the width of the stop bands is very sensitive to the number of the side resonators. These results should have important consequences for designing integrated devices such as narrow-frequency optical or microwave filters and high-speed switches.

This paper describes and evaluates the use of the Absolute Nodal Coordinate Formulation (ANCF) in modeling large size wind turbine blades. Modern blade model can be divided into two regions classified by aerodynamic and structural function. The aerodynamic region, blade-span, is utilizing the thinnest possible airfoil section. On the other hand, the transition between the circular mount and the first airfoil profile is referred as blade-root region, which carries highest loads along the blade. In this investigation, an efficient procedure is developed for mapping NACA airfoil wind-turbine blades into ANCF thin plate models. The procedure concerns a complete wind turbine blade structure, blade-root as well as the blade-span regions with non-uniform and twisted nature. As a result, the slope discontinuity problem arises in both chord-wise and span-wise directions, and consequently presents numerical errors in dynamic simulation. The paper investigates the methods of modeling slope discontinuity resulting from the variations of the cross-sectional layouts across the blade. The developed method is applied for the gradient-deficient thin plate element in order to account for structural discontinuity. In addition, the aerodynamic loads are precisely expressed and the aerodynamic characteristics of such blades are examined with the ANCF and with the classical finite element method. The static and dynamic solutions of different operating conditions are obtained and results are compared with those obtained using ANSYS code. Both the limitations and advantages of using the ANCF in modeling large size wind turbine blades are concluded and discussed. A Dynamics for Design (DFD) procedure is presented with numerical example concerning large-rotation, large deformation wind turbine blades.

Pure Fe(2)O(3) and Fe(2)O(3) doped with 2, 4, and 6 mass% of MnO(2) (>99%) compacts annealed at 1473 K for 6 h were isothermally reduced with H(2) at 1073-1373 K. The O(2) weight loss resulted from the reduction of compacts was continuously recorded as a function of time using thermogravimetric analysis (TGA). High pressure mercury porosimeter, optical and scanning electron microscopes, X-ray phase analysis and vibrating sample magnetometer were used to characterise both the annealed and reduced samples. In MnO(2) containing samples, manganese ferrite (MnFe(2)O(4)) was identified. The rate of reduction of pure and doped compacts increased with temperature and decreased with the increase in MnO(2) content. Unlike in pure compacts, the reduction of MnO(2) containing samples was not completed and stopped at different extents depending on MnO(2) (mass%). At initial reduction stages, the decrease in the rate was due to the presence of poorly reducible manganese ferrite (MnFe(2)O(4)) phase which was partially reduced to iron manganese oxide (FeO(0.899), MnO(0.101)) at the final stages. The reduction mechanism was predicted from the correlation between the reduction kinetics and the structure of partially reduced samples at different temperatures. The reduction of pure and doped samples was controlled by a combined effect of interfacial chemical reaction and gaseous diffusion mechanism at their initial stages. At final stages, the interfacial chemical reaction was the rate controlling mechanism.

Power system perturbations are due to many reasons; one of the most common perturbation causes is switching off/on the power capacitors. This paper monitors and discusses the overvoltages which appear on local and remote capacitor connected buses in power systems. Using the Fast Fourier Transfer (FFT), the total harmonic content of voltages and currents waveforms is also estimated at all buses. The power factor during different cases of switching modes "off/on" is monitored. The monitoring technique tackles not only the longitudinal long distance mutual effects of switching power capacitors between different buses but also evaluates the overvoltage durations. A relative long term monitoring is implemented using the Matlab/Simulink environment to show severity assessments in different switching modes on the transformers' voltages and currents' waveforms.

In the present study, computational fluid dynamics (CFD) methodology is used to investigate the confined non-premixed jet flames in rotary kilns. Simulations are performed using ANSYS-Fluent, a commercial CFD package. A two-dimensional axisymmetric model is conducted to understand the main operational and geometrical parameters of rotary kilns, which affect the flame behaviors, including the aerodynamics and heat transfer. Three kinds of fuels are employed in this study; Methane (CH4), Carbon Monoxide (CO) and Biogas (50% CH4 and 50% CO2). Confined jet flame length correlations are developed and presented in terms of kiln operational and geometrical parameters. Previous 2-D simulation results of free jet flames are used to select and validate the turbulence model, which applied in this study. The present simulation results are compared with available experimental data and previous analytical results, which show satisfactory agreement (C) 2014 Elsevier Ltd. All rights reserved.

An experimental study of quenching of a hot vertical tube by sudden introduction of a falling liquid film was investigated under different methods of venting the generated steam. The steam generated during the quenching process may form a countercurrent vapor velocity which exceeds the onset of flooding limit causing flooding of the liquid film and resisting the propagation of the quench front delaying the rewetting process. To study the effect of this steam countercurrent flow, experiments were carried out in three stages. In the first stage, the tube was closed from top to force the steam generated to be vented from bottom. In the second stage, both ends of the tube were opened to allow venting of the steam from both ends. In the third stage, the tube was closed at bottom and the steam was vented from top. The results showed that, the rewetting velocity in case of bottom steam-venting is higher than that in case of top and bottom steam-venting which in turn is higher than that in case of top steam-venting. For the three methods of steam venting, the quenching velocity decreases with increasing the initial tube temperature and the inlet liquid temperature and decreasing the liquid flow rate. Experimental correlations for rewetting velocities were deduced from experimental data for different cases of steam venting directions. Predictions of equations were compared with the present and previous experimental data and good agreement was found. (C) 2014 Elsevier Masson SAS. All rights reserved.