فهرست مطالب

  • Volume:7 Issue: 4, 2014
  • تاریخ انتشار: 1392/11/11
  • تعداد عناوین: 9
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  • Hassan Farsi, Pouriya Etezadifar Page 1
    Progress of technology in recent decades causes that video transmission via communication channels has met high demands. Therefore, many methods have been proposed to improve the quality of video under channel errors. The aim of this paper is to increase PSNR for video reconstructed by the receiver; this is achieved by increasing channel encoder rate but in constant transmission rate. In the proposed method the video frames’ parts containing more energy are coded by local channel coding inside source encoder. Then, the resulted data is embedded in low power frames’ parts. The proposed method is able to increase channel coding rates without increasing the amount of information for any frame. This method provides more robustness for video frames against channel errors. The proposed method is tested for different source coding rates and several SNRs for channel and the obtained results are compared with a new method.
  • Amin Zafarian, Iraj Kalali Fard, Abbas Golmakani, Jalil Shirazi Page 11
  • Babak Sadeghi Page 17
    In this paper, reliability of power system has been studied based on different Static Var Compensator (SVC) locations in power system. First, reliability model of SVC has been presented and then reliability indices of power system have been introduced. Furthermore, three different scenarios have been considered for SVC placement and these scenarios have been compared based on different reliability factors and losses of power system. It has been shown that each scenario may give unique solution for optimization problem based on reliability indices and losses. Also, it has been discussed that number of SVCs directly affects reliability and losses of power system, but increases cost of operation.
  • Ashkan Ghanbari Page 27
    In present study, we intend to investigate the evolution of supercontinuum generation (SCG) through triangular photonic crystal fiber (PCF) at 1310nm by using both full-vector multipole method (M.P.M) and novel concrete algorithms: symmetric split-step fourier (SSF) and fourth order runge kutta (RK4) which is an accurate method to solve the general nonlinear schrodinger equation (GNLSE). We propose an ideal solid-core PCF structure featuring a minimum anomalous group velocity dispersion (GVD), small higher order dispersions (HODs) and enhanced nonlinearity for appropriate supercontinuum generation with low input pulse energies over discrete distances of the PCF. We also investigate the impact of linear and nonlinear effects on supercontinuum spectra in detail and compare the results with different status.
  • Alireza Siadatan Page 37
    The switched reluctance motor is a singly excited, doubly salient machine which can be used in generation mode by selecting the proper firing angles of the phases. Due to its robustness, it has the potential and the ability to become one the generators to be used in harsh environment.This paper briefly discusses energy conversion by a switched reluctance generator (SRG) when two switches per phase converter circuit and discrete position sensors are employed. It is well known fact that, as the generator’s speed increases by a prime mover the shape of current waveform changes in such a way that limits the production of generating voltage. At high speeds, it is possible for the phase current never reaches the desired value to produce enough back-EMF for sufficient voltage generation, therefore, the output power falls off. In order to remedy this problem, the phase turn on angle is advanced in a way that the phase commutation begins sooner. Since one of the advantages of this type of generator is its variable speed then, the amount of advancing for the turn on angle should be accomplished automatically to obtain the desired output voltage according to the speed of the generator, meaning, as the generator speed increases so should the turn on angle and vice versa. In this respect, this paper introduces an electronic circuit in conjunction with time reshaping of the command pulses obtained from position sensors and the drive converter to achieve this task for a desired output voltage when a SRG feeding a resistive load.To evaluate the generator performance, two types of analysis, namely numerical technique and experimental studies have been utilized on a 6 by 4, 30 V, SRG. In the numerical analysis, due to highly non-linear nature of the motor, a three dimensional finite element analysis is employed to calculate some of motor parameters and then using these parameter current shape and magnitude is computed, whereas in the experimental study, a proto-type generator and its circuitries have been built and tested using two switch per phase converter. A linear analysis of the current waveform for the generator under different advancements of the turn on angle has been performed numerically and experimentally and the results are presented.
  • Mohsen Biglari, Faezeh Mirzaei, Hossein Ebrahimpour, Komleh Page 47
    Face recognition under uneven illumination is still an open problem. One of the main challenges in real-world face recognition systems is illumination variation. In this paper, a novel illumination invariant face recognition approach based on Self Quotient Image (SQI) and weighted Local Binary Pattern (WLBP) histogram has been proposed. In this system, the performance of the system is increased by using different sigma values of SQI for training and testing. Furthermore, using two multi-region uniform LBP operators for feature extraction simultaneously, made the system more robust to illumination variation. This approach gathers information of the image in different local and global levels. The weighted Chi square statistic is used for histogram comparison and NN (1-NN) is used as classifier. The weighted approach emphasizes on the more important regions in the faces. The proposed approach is compared with some new and traditional methods like QI, SQI, QIR, MQI, DMQI, DSFQI, PCA and LDA on Yale face database B and CMU-PIE database. The experimental results show that the proposed method outperforms other tested methods.
  • Leila Esteki, Abas Ali Zamani, Seyed Mohammad Kargar, Seyed Ali Mousavi Page 55
    In this paper, an auto tuned load frequency controller based on Fuzzy Wavelet Neural Network (FWNN) and Shuffled Frog Leaping Algorithm (SFLA) is employed to damp the deviations in frequency and tie line power due to load disturbances in a multi-area power system. Optimal tuning of FWNN parameters is very important to improve the design performance and achieving a satisfactory level of robustness, for a particular operation. In this work, a new systematic tuning method is developed for designing the FWNN load frequency controller. For this, the error between desired system output and output of control object is employed to tune the FWNN parameters. Tuning rule is accomplished based on SFLA approach by minimizing a compound of control error. To show the effectiveness of the proposed method, some numerical results are presented for a two area power system with considerations regarding governor saturation and the results are compared to the one obtained by a classic PI controller and a fuzzy load frequency controller. Moreover, the robustness of the proposed method is tested against change of parameters. The simulation studies show that the designed controller by proposed method has a very desirable dynamic performance, better operation and improved system parameters such as settling time and step response rise time even when the system parameters change.
  • Durai Kalyan Kumar Page 65
    A parabolic concentrating solar collector was fabricated and anlyzed through experimental evaluation, performed for several days under different conditions, for optimisation of the performance efficiency.The real time results were brought out in this paper to show the novelty for enhancing the efficiency of the performance.References The National Institute of Technology -Environmental Engineering laboratory,Trichirapalli, Tamilnadu,India, was utilized for the measurement of solar radiations using Pyranometer for different days and for the various timings.
  • Hamidreza Fardad, Hadi Khosravi, Farsani, Mohammadali Nematbakhsh Page 75
    With an increase of available datasets in web of data, ranking the datasets will be of prime importance. In this article, the famous PageRank algorithm is extended and a new link-based method is proposed for ranking the datasets in web of data. In this method, the number of links to the dataset, the type of the links, and the number of each type of the links have been considered and a new hyper-linked based approach name as DSRank is proposed. The suggested algorithm has been implemented on datasets collected from the web amounting to 20 GB. All of the datasets is arranged using suggested method. For evaluation, the access log files of Dbpedia, DBTune, and Dog Food is used. Number of requests by users in one day for these datasets is calculated and then datasets are organized based on user’s opinion. The results of comparing our suggested algorithm with the number of the requests by the users in a day indicate that the order of the assigned ranks in the dataset using the proposed method is correct.