Articles in This Issue
Abstract
A five-phase two-motor drive system with a series connection of stator windings and decoupled dynamic control is considered in the present paper. The two-motor drive system is supplied from a single five-phase Space Vector Pulse Width Modulation (S VPWM) Voltage Source Inverter (VSI) and controlled using a vector control scheme, provided that the stator windings are connected in series with appropriate phase transposition. The concept has been developed under the assumption that the inverter voltages are controlled in the stationary dq-reference frame. A fuzzy logic-based speed controller has been constructed and used to drive the two-motor in this work. The two-motor system, inverter system, and fuzzy controller models are implemented and tested using Simulink/Matlab facilities. 1be presented results show the validity of the model to do well for the sake of speed control in wider different operating conditions.
Abstract
Orthogonal frequency division multiplexing (OFDM) has become a popular modulation method in high-speed wireless communication systems due to its high data rate transmission capability and robustness against multipath fading effects. One of the major drawbacks of OFDM at the transmitter side is the high peak-to-avenge power ratio (PAPR) of the OFJ)M signal. In this paper, an algorithm is proposed to reduce the peak-to-average power ratio of OFDM signal with a large number of sub-carriers. This algorithm is based on the tone reservation method. The computer simulation tests show that the suggested algorithm reduces the PAPR to a factor of S.2S dB and needs less number of iterations as compared with the traditional tone reservation algorithm.
Abstract
In this article, a hybrid optimization method has been proposed consisting of Adaptive Genetic Algorithms (AGAs) and Constrained Nonlinear Programming (NLP) to solve the problems of performance optimization of circular array antenna consisting paraOel center feeding short dipoles elements with two complex nonlinear optimization problems. In the first problem. the hybrid optimization algorithm is used to reduce the value of sidelobe level in the circular array radiation pattern by finding the oPtlmal values of the excitation coefficients of each element in the clrcular array. In the second problem, a synthesis of circular array with different forms of the desired radiation pattern is considered. Several examples are considered here to verify the validlty of this method. Comparisons were made between the results of this method and the results obtained by {SGA) Standard Genetic Algorithm, and it is clearly shown that this method is more efficient and flexible in solving the problems of performance optimization of circular array antenna .
Abstract
The excitation and governing control of generator play an important role in improving the dynamic and transient stability of power system. Typically the excitation control and governing control are designed independently. This paper, presented Neuro-Fu;,.zy methods for the excitation and governing control . Neuro-Fuz.zy system is applied to generate two compensating signals to modify the controls dwing system disturbances. A single machine to infinite bus (SMIB) system is applied in simulation. The MATLAB SIMULIK and S-function technique is used to simulate the system and controllers
Abstract
Tn this paper, a hierarchical phoneme recognition system is proposed. The hierarchical approach is applied here to recursively partition the recognition problem into smaller and smaller sub-problems those are independently handled at the di~tinct nodes of the hierarchy. The nodes are individually set to chara~erize different properties of the input phoneme, or more precisely to make separate d~isioos on its pertinence to the different reference subgroups of phonemes. The full characteri:zation of the input phoneme is achieved by traversing some root-to-leaf path through the hierarchy. The relationships between the different features of phonemes and their pertinence to the different reference subgroups. are to be objectively characteriz.ed ttnd optimized here. This involves specifying the decisive subset of features for each pertinence decision and neglecting the remaining features those are irrelevam to (or probably have negative effect on) that decision, at each node of the hierarchy. The optimization applied through the feature election process here, is not aimed at reducing the amount of feamres to be used in the recognition process, for the purpose of decreasing the time-complexity of the systcn1, but, is interested in enhancing the decision making accuracy of the system by avoiding the misleading features.
Abstract
This paper deals with the modeling and control strategics of the motion of wheeled mobile robot. The model of the mobile robot has two driving wheels and the azimuth and velocity are dependently controlled by two PID controllers. The PID controller is one of the earliest and famous industrial controllers. It has many advantages: It is economic, simple easy to be tuned and robu.~t. The tuning of these controllers is governed by system nonlinearities and continuous parameter variations. lbis paper deals with the optimal design of a PID controller for path tracking of mobile robot by using genetic algorithms (GA). The designed controller is tested for different paths.
Abstract
A novel hiding system is proposed in this work which is based on Least Significant Bits (LSB) embedding of information such as speech in gray scale images. The proposed hiding algorithm embeds the secrete infonnation message bits in the least significant bits of the cover image pixels such that the number of secrete infurmation bits to he embedded in least significant bits of cover image pixel is variable and detennined randomly. So that cover image pixel may contain no secrete information bit, one bit, two bits , or three bits according to the pseudo random nwnber generator that generates integer numbers randomly between O and 3. The resulting image (the cover image within which the secret information is hidden) is called stego_image. Stego_image is closely related to the cover image and does not show any details of the secret infonnation. It ensures that the eavedroppers will not have any suspicion that message bits are hidden in the illll!ge and standard steganography detection methods can not estimate the locations in which the secret message bits are embedded and can not estimate the locations in which the secrete information bits are hidden nor the number of bits embedded in oover image . The proposed system achieves perfect reconstruction of the secret message.
Abstract
The present study deals with the analysis of short reinforced concrete columns subjected to axial load. One of the efficient techniques is applied, known as artificial neural networks. The descent gradient backpropagation algorithm is employed for analysis. The optimum topology (which gives the least mean square error for both training and testing with a fewer number of epochs) is presented. The effects of the number of nodes in input and hidden layer(s), and selecting of leaming rate and momentum coefficient, on the behavior of the neural network, have been investigated. Due to the slow convergence of results when using descent gradient backpropagation, the faster algorithm called "resilient backpropagation algorithm" has been used to improve the performance of the neural network and the results have been compared with those obtained using the descent gradient backpropagation algorithm.
Abstract
In this investigation, the bond stresses between the reinforcement and concrete was studied by using non-material interface elements that are able to produce the bond stresses for the reinforced concrete beam gradually loaded from zero to failure. Depending on (Jawad) program, which is a non-linear analysis program of plain and reinforced concrete beams through a discrete-crack approach by using the finite element method. The stiffness matrix derivation of the interface element and the way of non-linear treatment were explained. The distribution of bond stress drawings along the steel reinforcement for different values of loading was achieved before and after cracking.
Abstract
The main objective of this study is to investigate the effect of repeated load on the strength and behavior of the spandrel beam by considering eight specimens divided into four groups based on the design methods; type of cross-section of the spandrel beam and the type of loading. Two design methods, two types of loading and two types of cross sel.1ions for spandrel beam are considered, the first is a solid rectangular section, while the other is a hollow rectangular section. The effect of repeated loads on the crack's width, deflections, torque, and angle of twist is studied using two stages of loading, the first stage is at the soft-cracking stage after the occurring of cracks in the spandrel beam and the second stage is the yielding of the bottom longitudinal reinforcement of the floor beam.
Abstract
Hydrodynamics and heat transfer in a fully developed laminar incompressible reciprocating channel flow subjected to a constant heat flux have 'been investigated analytically using similarity transfo1mat ion. An exact analytical solution for the velocity, local, and bulk temperature as well as the Nusselt number has been obtained. The effect of the parameters Pr, Ao, y, and X/Dh on u, T, Tt, Nux, and Nux are presented. The results showed that the local Nusselt number is increased with increasing Womersly number (A.) while the dimensionless temperature is increased with Womersly and decreases with amplitude (Ao). The Prandtl number has a significant effect on the local Nusselt number. The results were found in very good agreement with those obtained numerically using the finite volume method. The comparison with the experimental results of other authors gave a reasonable identification.
Abstract
The weight function prescribing the sensitivity of the electromagnetic flowmeter (EM}') to the changes in the velocity profiles must be as much as possible uniformly distributed through the measuring volume. The most commonly used criterion of the weight function distribution is a statistical quantity ( e criterion) which deals with only the axial component of the weight vector. In the present work, attempt 10 introduces a more revealing and accurate criterion to the EMF performance was studied. The curl of the weight function vector over the measuring volume has been considered and formulated (and termed as e ) in such a mathematical expression that takes Into account the contributions of the three components of the weight vector regardless of the geometry of the cross-sectional area of the flow. In addition, a numerical solution of a previously defined criterion (ey) is presented here for the first time in order to compare the validity of the newly introduced criterion. The results showed that the present new criterion e is closely harmonious with the previously defined criteria 8 and Si.. in the conventional flow cases. The results and the configuration of the formula of the present criterion, which is independent of the flow cross-sectional led us to conclude that is more reliable and applicable than other existing criteria.
Abstract
The effect of thermal aging on the tensile properties of cast stainless steel during service in light water reactors has been evaluated and recorded by the Argonne National Laboratory. Tensile data for several experimental and commercial heats of cast stainless steel (CF-8M) are presented for predicting the change in tensile flow and yield stresses and engineering stress-strain curve as a function of time and temperature of service in the light water reactors using Neural Networks. Thermal aging increases the tensile strength of this type of steel. The result and correlation described by this work may be used for assessing thermal embitterment of cast stainless steel components.
Abstract
The study focuses on using sand and activated carbon filters for treating of A l-Kasak refinery wastewater. The wastewater contains many contaminants and organic and chemical materials. Many tests were performed such as pH, E.C, T.S, COD, BOD, Phenole, Oil, and NH3, after and before treatment with a filter in order to determine effluent characteristics. The highest T.S removal efficiency with sand filter was 93% and 90% for oil. The highest removal efficiency with activated carbon filter happened to Phenol, which was 99%, and for COD and BOD was(81- 90) % and (77-9 1)% continuously. The study shows that the cycle time of 9 hr gives the best removal efficiency for organic wastewater, especially for high organic load. It was recommended to use a sand-activated carbon filter to treat refinery wastewater because the effluents were within the Limits of refinery waste water casting and river casting.