per Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-06628393articleS. Shaerbafsa_sh13@um.ac.ir1M. Khademikhademi@um.ac.ir2Mohammad Molavimolavi@um.ac.ir3Ferdosi UniversityFerdowsi University of MashhadFerdosi UniversityAutomatic modulation type classifier is a system which recognizes the modulation type of received signal automatically from some possible, pre-assumed types. Automatic modulation classification has applications such as spectrum surveillance, signal confirmation, interference identification, software radio, etc. This paper, proposes a new method for recognition of 9 famous digital and analog modulations, which no need for prior knowledge of the signal to be recognized. This system is used to separate AM, FM, DSB and SSB in Analog modulations and 2ASK, 2PSK, 2FSK, 4PAM and 16QAM in digital modulations. Support Vector Machines (SVM) is used to classify these modulations and Genetic Algorithm is used to optimize Classifier Structure. Simulation results show that proposed algorithms have a good performance in comparison with other algorithms. Computational simplicity, High training speed and High classification rate, are the advantages of proposed algorithms.http://ijece.org/Article/27899Genetic algorithmsupport vector machinemodulation recognitionpattern recognitionper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-066294102articleM. F. Sabahim_sabahi@eng.ui.ac.ir1M. Modarres Hashemimodarres@cc.iut.ac.ir2a. sheikhisheikhi@shirazu.ac.ir3In many of detection problems the received signals models under two hypotheses, H0 and H1, are the same except that some model parameters have fixed value under H0. These models are so called Nested Models. One of the most important examples is detection of a target with unknown amplitude in the clutter. In this problem, one can assume similar models for received signals under H0 and H1 unless the target amplitude is assumed to be zero under H0. If the Bayesian approach used for treating unknown parameters, it can be shown that the likelihood ratio can be calculated as the ratio of the posterior and the prior probability of unknown parameters. Using this method a new detector for detection in Gaussian clutter is presented in this paper. Simulation results show that the proposed detector has much better performance compared with conventional GLRT detectors. It is also shown that a CFAR property is achieved provided that a small modifications in decision rule.http://ijece.org/Article/27900Radar detectionBayesian estimationautoregressive clutterper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662103110articleS. S. Fadaeisadegh_fadaei@yahoo.com1M. H. Kahaeikahaei@iust.ac.ir2University of Science and TechnologyTo separate speech signals using blind techniques, the DUET algorithm is used in which each source signal is separated by masking the mixed signals in the Time-Frequency domain. To do so, a two dimensional Histogram of mixed parameters is generated which is computationally burden, and thus, can not be used in real-time. In this paper, we introduce a new algorithm in which the separation process can be carried out online. Also, simulation results show that this algorithm has a comparable precision with respect to the DUET algorithm.http://ijece.org/Article/27901Time-frequencyDUEThistogramBSSper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662111118articleA. Jahanbeigimsheikhn@azad.ac.ir1M. E. Kalantarikalantari@eetd.kntu.ac.ir2K.N. Toosi University of TechnologyEstimating the number of basic telephony services (fixed and mobile) and also residential users and enterprise subscribers of data services for the next years (up to 1389), is the goal of this paper. To predict the number of basic telephony services, the Cobb-Douglas model, which uses the two important factors (the subscriber’s income and charge of service), is utilized. An increase of 18.48 and 27.18 million subscribers for fixed and mobile telephony services is predicted, respectively (in the time interval of 1385-89). The accuracy of estimates is also validated by comparing the results with actual numbers of subscription in the past years and also with global norms in the world (published by International Telecommunication Union). The potential number of residential users of data services is estimated to be about 14.43 million (or penetration rate of 19.6 percent for internet users), and enterprise subscribers about 217 thousand (in addition to governmental organizations) at the end of 1389. Finally, a range of demanded data services along with their required bit rates are identified in order to be used in bandwidth forecast and allocation in the next generation networks.http://ijece.org/Article/27902Fixed and mobile telephony servicesdata servicesresidential usersenterprise subscribersper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662119125articleH. Samimisamimi@itrc.ac.ir1P. Azmipazmi@modares.ac.ir2An approximate analytical method for the evaluation of the cumulative distribution function (CDF) of the sum of L independent random variables (RVs) is presented. The proposed method is based on the convergent infinite series approach, which makes it possible to describe the CDF in the form of an infinite series. The computation of the coefficients of this series needs complicated integrations over the RV’s probability density function (PDF). In some cases, the required integrations have closed-form in terms of confluent hypergeometric function and in other cases, the required integrations can not be analytically solved and have not a closed-form solution. In this paper, an approximation method for computation of the coefficients of the CDF series is presented that only needs the mean and the variance of the RV, so it has low computational complexity; it eliminates the need for calculation of complex functions and can be used as a unified tool for determining CDF of a sum of statistically independent RVs. To present an application for the developed approximation method, it is used to find the distribution of the sum of generalized Gamma (GG) RVs. The derived approximate expressions are used in the performance analysis of equal-gain combining (EGC) receivers operating over GG fading channels. The accuracy of the developed approximation method is verified by performing comparisons between exact existing results in the literature and computer simulations results.http://ijece.org/Article/27903Equal-gain combininggeneralized gamma distributionWeibull distributionNakagami distributionper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662126135articleS. Seyedshenavashenava@modares.ac.ir1H. Seifiseifi_ho@modares.ac.ir2S. M. SepasianSepasian@pwut.ac.ir3Tarbiat Modares UniversityTarbiat Modares UniversityA hybrid genetic algorithm (GA)–simulated annealing (SA) approach, incorporating Differential Evolution (DE), fencing method (FM) as well as implicit enumeration method (IEM) is proposed in this paper for transmission expansion planning (TEP) of a grid, involving both HVAC and HVDC links. The use of these algorithms makes a robust proposed approach by which for a hybrid HVAC-HVDC network, TEP may be performed fast and accurately. The proposed approach is assessed and evaluated for three test systems.http://ijece.org/Article/27904Evolutionary algorithmsdifferential evolution methodHVDC transmission expansion planningper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662136143article rahmati@iust.ac.ir1S. A. Abrishamifarabrishamifar@iust.ac.ir2E. Abiriabiri@sutech.ac.ir3University of Science and TechnologyUniversity of Science and TechnologyIn this paper voltage source converter based HVDC (VSC-HVDC) is used for power transmission in asynchrony distribution systems. Direct power control (DPC) of three-phase space vector modulation (SVM) is employed for this control scheme. It is economically motivated to replace the AC line voltage sensors with a virtual flux (VF) estimator. The control system is resistant to the majority of line voltage disturbances using by the idea of virtual flux. It is also effective to damp system oscillations and enhance power quality when power flow is reversed. Superior advantages of this method are good dynamic response and unity power factor of rectifier.http://ijece.org/Article/27905Distribution systemsstabilityDPCVSC-HVDCper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662144149articleB. vahidivahidi@aut.ac.ir1Gh. Rasuli Hashemabadrasouliqadir@yahoo.com2Static electrification due to oil flow is the main reason for several electrical breakdown in large transformers. In the present paper this phenomenon has been investigated by the aid of open cycle system. Finally from tests results obtained by authors, the effects of applied electric field, temperature and oil flow velocity on static electrification have been investigated.http://ijece.org/Article/27906Transformer oilstatic electrificationelectrical breakdownoil flowopen cycleper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662150161articleM. Davoodabadidavoodabadi@qom.ac.ir1M. Palhangpalhang@cc.iut.ac.ir2The process of the comprehension of written natural language texts is usually called text understanding. Text understanding includes different processes and has many applications. One of the applications of natural language understanding systems is executing the imperative sentences which has a wide usage in dialog based systems and robotics. Numerous works have been done in processing of Persian language but a few of them has considered the subject of Persian text understanding and performing actions after it. In this paper reports an implementation of a Persian understanding system called DANA. DANA accepts an imperative sentence or a question, applies morphological, syntactic and semantic analysis on it and creates a meaning representation. This system is able to understand some simple Persian sentences, responds to a few orders issued in Persian and answers some of user questions. The results of this project can be used for developing other types of natural language processing systems such as machine translation or question answering systems.http://ijece.org/Article/27907Morphological analysistext understandingunification grammarsemantic representationper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662162171articleH. Sadoghi Yazdisadoghi@sttu.ac.ir1Studying of classifier behavior is interested from viewpoint of error checking and presentation of suitable solution for decreasing error rates and decreasing performance. Weakness operation of recognition system is because of small number of training samples, noisy samples, unsuitable extracted features, method of determining of system response. Presentation of suitable model for behavior or response of recognition system, we can improve operation of recognition system. In this paper, a new hidden Markov model based decision template is generated for modeling of neurons behavior in neural network. In existing methods, relation of neurons and interaction between them is not studied whereas; response of neural network includes response value of all neurons. So, relations of neurons are modeled using new hidden Markov decision templates. This method is used into three applications include recognition of Farsi number images, normal traffic in internet network, and recognition of types of vehicles. Increasing performance of neural network indicates to superiority of the proposed system.http://ijece.org/Article/27908Classifiers behaviorpattern recognitiondecision templateshidden Markov modelback propagation neural networksper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662172178articleP. Moallemp_moalloem@eng.ui.ac.ir1A. Shiri Sichanialielectronic2003@yahoo.com2The Fabrication of switch capacitor Filters and continuous time CMOS circuits, with a suitable unity gain bandwidth, a high DC gain and a high quality factor are a major challenge in integrated circuits design basically. This article is proposed a novel positive feedback topology for designing of OPAMP kernel and then a sample of OPAMP based on this method by tuning of the fabrication parameters is designed. The results of simulations which are done in frequency and time domain demonstrate that unity gain bandwidth of the designed OPAMP is greater than 1.4GHz and DC gain is greater than 108dB that in comparison with similar designs based on positive feedback can demonstrate there are plentiful increment in unity gain bandwidth and suitable increment in DC gain. The phase margin of the designed OPAMP is greater than 170 degree. Moreover, investigation of the proposed design outputs in time domain demonstrates the stability of the proposed OPAMP.http://ijece.org/Article/27909Unity gain bandwidthDC gainpositive feedbackper Iranian Research Institute for Electrical Engineeringفصلنامه مهندسی برق و مهندسی کامپيوتر ايران16823745168237452008-0662179186articleSeyed-Hamid Zahirihzahiri@birjand.ac.ir1University of BirjandIn this paper a novel technique for automatic data clustering based on the artificial immune algorithm is proposed. The lengths of the antibodies are dynamically changed based on inter-clusters and intra-clusters distances by means of a fuzzy controller which has been added to the immune algorithm to provide, also, a soft computing approach for data clustering. This idea leads to proper number of clusters and effective and powerful clustering process without any additional try and error efforts. Also the manual setting of the number of clusters is available in the proposed algorithm (like other unsupervised clustering approaches) after removing the fuzzy controller from the proposed clustering system. The method has been tested on the different kinds of the complex artificial data sets and well known benchmarks. The experimental results show that the performance of the proposed technique is much better than the k-means clustering algorithm (as a conventional one), specially for huge data sets with large feature vector dimensions. Furthermore, it is found that the performance of the proposed approach is comparable, sometimes better than the genetic algorithm based clustering technique (as an evolutionary clustering algorithm).http://ijece.org/Article/27910Automatic clusteringartificial immune algorithmfuzzy controllersoft computing