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Showing 663 results for Type of Study: Research Paper

A. Moosavienia, K. Mohammadi,
Volume 1, Issue 1 (1-2005)
Abstract

In this paper we first show that standard BP algorithm cannot yeild to a uniform information distribution over the neural network architecture. A measure of sensitivity is defined to evaluate fault tolerance of neural network and then we show that the sensitivity of a link is closely related to the amount of information passes through it. Based on this assumption, we prove that the distribution of output error caused by s-a-0 (stuck at 0) faults in a MLP network has a Gaussian distribution function. UDBP (Uniformly Distributed Back Propagation) algorithm is then introduced to minimize mean and variance of the output error. Simulation results show that UDBP has the least sensitivity and the highest fault tolerance among other algorithms such as WRTA, N-FTBP and ADP. Then a MLP neural network trained with UDBP, contributes in an Algorithm Based Fault Tolerant (ABFT) scheme to protect a nonlinear data process block. The neural network is trained to produce an all zero syndrome sequence in the absence of any faults. A systematic real convolution code guarantees that faults representing errors in the processed data will result in notable nonzero values in syndrome sequence. A majority logic decoder can easily detect and correct single faults by observing the syndrome sequence. Simulation results demonstrating the error detection and correction behavior against random s-a-0 faults are presented too.
J. Poshtan, H. Mojallali,
Volume 1, Issue 1 (1-2005)
Abstract

We give a general overview of the state-of-the-art in subspace system identification methods. We have restricted ourselves to the most important ideas and developments since the methods appeared in the late eighties. First, the basis of linear subspace identification are summarized. Different algorithms one finds in literature (Such as N4SID, MOESP, CVA) are discussed and put into a unifying framework. Further, a comparison between subspace identification and prediction error methods is made on the basis of computational complexity and precision of methods by applying them to a glass tube manufacturing process.
,
Volume 1, Issue 1 (1-2005)
Abstract

In an environment such as underwater channel where placing test equipments are difficult to handle, it is much practical to have hardware simulators to examine suitably designed transceivers (transmitter/receiver). The simulators of this kind will then allow researchers to observe their intentions and carry out repetitive tests to find suitable digital coding/decoding algorithms. In this paper, a simplified shallow water digital data transmission system is first introduced. The transmission channel considered here is a stochastic DSP hardware model in which signal degradations leads to a severe distortion in phase and amplitude (fades) across the bandwidth of the received signal. A computer base-band channel model with frequency non-selective feature is derived by the authors [10-11]. This system was based on fullraised cosine channel modelling and proved to be the most suitable for vertical and shortrange underwater communication csdfher), with a reflected path (specula component, when the acoustic hydrophone receives reflected signals from surface and bottom of the sea) and a random path (diffused component, when the acoustic hydrophone receives scattered signals from the volume of the sea). The model assumed perfect transmitter-receiver synchronization but utilized realistic channel time delays, and demonstrated the timevarying characteristics of an underwater acoustic channel observed in practice. In this paper, they are used to provide a full system simulation in order to design an adaptive receiver employing the most advanced digital signal processing techniques in hardware to predict realizable error performances.
M. A. S. Masoum, M. Sarvi,
Volume 1, Issue 1 (1-2005)
Abstract

A new fuzzy maximum power point tracker (MPPT) for photovoltaic systems is proposed. Fuzzy controller input parameters dI dP , ) dI dP ( D and variation of duty cycle ( DC D ) are used to generate the optimal MPPT converter duty cycle, such that solar panel maximum power is generated under different operating conditions. A photovoltaic system including a solar panel, a fuzzy MPP tracker and a resistive load is designed, simulated and constructed. The fuzzy MPP tracker includes a buck dc/dc converter, fuzzy controller and interfacing circuits. Theoretical and experimental results are used to indicate the advantages and limitations of the proposed technique.
Sh. Mohammad Nejad, M. H. Haji Mirsaeidi,
Volume 1, Issue 1 (1-2005)
Abstract

In this paper altitude measurement from water surface using laser beam is presented. Research data indicate that the reflection of infrared waves from water surface is about zero and it is less than 2% for visible radiations. Phase-shift and heterodyne technique was used for the measurement, and the laser beam ( mW p nm 10 , 700 = = l ) was modulated by a sine wave having a fixed frequency. The optimum design and low-noise elements made it possible to detect a light power about 20 nW at operating frequency.
M. Kalantar, M. Sedighizadeh,
Volume 1, Issue 1 (1-2005)
Abstract

A dynamic reduced order model using integral manifold theory has been derived, which can be used to simulate the DOIG wind turbine using a double-winding representation of the generator rotor. The model is suitable for use in transient stability programs that can be used to investigate large power systems. The behavior of a wind farm and the network under various system disturbances was studied using this dynamic model. Simulation results of the proposed method represents that integral manifold method results fit the detailed model results with a higher precision than other methods.
H. Mahdavi-Nasab, Shohreh Kasaei,
Volume 1, Issue 2 (4-2005)
Abstract

Motion estimation and compensation is an essential part of existing video coding systems. The mesh-based motion estimation (MME) produces smoother motion field, better subjective quality (free from blocking artifacts), and higher peak signal-to-noise ratio (PSNR) in many cases, especially at low bitrate video communications, compared to the conventional block matching algorithm (BMA). However, the iterative refinement process of MME is computationally much costly and makes the method impractical in real- (or near real-) time systems. Also, eliminating the iterative refinement step deteriorates the motion estimation result. In this paper, we propose motion adaptive interpolation schemes for noniterative MME, which use BMA to compute the motion vectors (MVs) of mesh nodes. The proposed algorithm aims at compromising the MME and BMA by modifying the interpolation patterns (IPPs) of the MME in an adaptive manner, based on the MVs of mesh nodes. Experimental results show notable rate-distortion improvement over both BMA and conventional non-iterative MME, with acceptable visual quality and system complexity, especially when applied to sequences with medium to high motion activities.
S.m.reza Soroushmehr, Shadrokh Samavi, Shahram Shirani,
Volume 1, Issue 2 (4-2005)
Abstract

In this paper a new method for determining the search area for motion estimation algorithm based on block matching is suggested. In the proposed method the search area is adaptively found for each block of a frame. This search area is similar to that of the full search (FS) algorithm but smaller for most blocks of a frame. Therefore, the proposed algorithm is analogous to FS in terms of regularity but has much less computational complexity. To find the search area, the temporal and spatial correlations among the motion vectors of blocks are used. Based on this, the matched block is chosen from a rectangular area that the prediction vectors set out. Simulation results indicate that the speed of the proposed algorithm is at least 7 times better than the FS algorithm.
H. Monsef, N.t. Mohamadi,
Volume 1, Issue 2 (4-2005)
Abstract

Electric power restructuring offers a major change to the vertically integrated monopoly. The change manifests the main part of engineers’ efforts to reshape the three components of today’s vertically integrated monopoly: generation, distribution and transmission. In a restructured environment, the main tasks of these three components will remain the same as before, however, to comply with FERC orders, new types of unbundling, coordination and rules are to be established to guarantee competition and non-discriminatory open access to all users. This paper provides the generation schedule of a GENCO in a deregulated power system. It is shown that the goal of generation schedule in the new structure is different from the traditional centralized power systems. The modeling of generation scheduling problem in a competitive environment is demonstrated by taking into account the main purposes of GENCOs which are selling electricity as much as possible and making higher profit. The GENCOs of an area are introduced via a model whose objective function consists of hourly spot market price as income and different kinds of costs. The constraints are the general ones of such a problem e.g. minimum up/down time, minimum and maximum generation and ramp rate. Using one of the classical optimization methods, the hourly generation schedule of the generating units will be obtained in this competitive environment. The results of this section will be used by ISO. The ISO will finalize the schedules of GENCOs by taking into account the technical considerations like the power flow of transmission lines. The model and the optimization methods are implemented on IEEE-RTS benchmark with 24 buses and 32 generating units.
S.jadid, S.jalilzadeh,
Volume 1, Issue 2 (4-2005)
Abstract

This paper presents a new composite index to analyze power system transient stability. Contingency ranking in power system transient stability is a complicated and time consuming task. To prevail over this difficulty, various indices are used. These indices are based on the concept of coherency, transient energy conversion between kinetic and potential energy and three dot products of the system variables. It is well known that some indices work better than others for a particular power system. This paper along with test results using two practical 230 kV Sistan and 400 kV Khorasan power system in Iran, and 9 bus IEEE test system demonstrates that combination of indices provides better ranking than a single one. In this paper two composite indices ( CI ) is presented and compared. One composite index is based on Least Mean Square algorithm (LMS) and other based on summing indices by equal weights. Numerical simulations of the developed index, demonstrate that composite index is more effective than other indices.
A.vahedi, M.ramezani,
Volume 1, Issue 2 (4-2005)
Abstract

Dc excitation of the field winding in a synchronous machine can be provided by permanent magnets. Permanent magnet synchronous machine (PMSM) can offer simpler construction, lower weight and size for the same performance, with reduced losses and higher efficiency. Thanks to the mentioned advantages these motors are widely used in different application, therefore analysis and modeling of them, is very important. In this paper a new, fast and simple method is presented to study performance of a PMSM connected to the converter. For this purpose, average-value modeling and related analytical relations which leads to the desired characteristics such as electromagnetic torque, dc current and dc voltage is presented and applied to PMSM & converter system. The advantage of this model lie in reduction of computation time compares to the other dynamic models while keeping accuracy quite acceptable. This model is applicable for studying the steady-state performance of systems as well as dynamic performance.
A Ayatollahi, N Jafarnia Dabanloo, Dc McLernon, V Johari Majd, H Zhang,
Volume 1, Issue 2 (4-2005)
Abstract

Developing a mathematical model for the artificial generation of electrocardiogram (ECG) signals is a subject that has been widely investigated. One of its uses is for the assessment of diagnostic ECG signal processing devices. So the model should have the capability of producing a wide range of ECG signals, with all the nuances that reflect the sickness to which humans are prone, and this would necessarily include variations in heart rate variability (HRV). In this paper we present a comprehensive model for generating such artificial ECG signals. We incorporate into our model the effects of respiratory sinus arrhythmia, Mayer waves and the important very low frequency component in the power spectrum of HRV. We use the new modified Zeeman model for generating the time series for HRV, and a single cycle of ECG is produced using a radial basis function neural network.
F. Hojjat Kashani, A. A. Lotfi Neyestanak, K. Barkeshli,
Volume 1, Issue 2 (4-2005)
Abstract

A modified circular patch antenna design has been proposed in this paper, the bandwidth of this antenna is optimized using the genetic algorithm (GA) based on fuzzy decision-making. This design is simulated with HP HFSS Program that based on finite element method. This method is employed for analysis at the frequency band of 1.4 GHz- 2.6 GHz. It gives good impedance bandwidth of the order of 15.5% at the frequency band of 1.67GHz- 1.95GHz and 10.6% at 2.23GHz- 2.48GHz. It means that impedance bandwidth increases above 4.9% than the impedance bandwidth of ordinary circular patch antennas and band width rise from 1.78GHz- 1.98GHz (10.6%) to 1.67GHz- 1.95GHz (15.5%) and 2.23GHz- 2.48GHz (10.6%). The antenna fabricated with two slots on circular patch antenna. The measured results of the optimized antenna validate a high compatibility between the simulation and the measurements.
S. H. Zahiri, H. Rajabi Mashhadi, S. A. Seyedin,
Volume 1, Issue 3 (7-2005)
Abstract

The concepts of robust classification and intelligently controlling the search process of genetic algorithm (GA) are introduced and integrated with a conventional genetic classifier for development of a new version of it, which is called Intelligent and Robust GA-classifier (IRGA-classifier). It can efficiently approximate the decision hyperplanes in the feature space. It is shown experimentally that the proposed IRGA-classifier has removed two important weak points of the conventional GA-classifiers. These problems are the large number of training points and the large number of iterations to achieve a comparable performance with the Bayes classifier, which is an optimal conventional classifier. Three examples have been chosen to compare the performance of designed IRGA-classifier to conventional GA-classifier and Bayes classifier. They are the Iris data classification, the Wine data classification, and radar targets classification from backscattered signals. The results show clearly a considerable improvement for the performance of IRGA-classifier compared with a conventional GA-classifier.
P. Khadivi, S. Samavi, H. Saidi, T. D. Todd,
Volume 1, Issue 3 (7-2005)
Abstract

Multi-constraint quality-of-service routing will become increasingly important as the Internet evolves to support real-time services. It is well known however, that optimum multi-constraint QoS routing is computationally complex, and for this reason various heuristics have been proposed for routing in practical situations. Among these methods, those that use a single mixed metric are the most popular. Although mixed metric routing discards potentially useful information, this is compensated for by significantly reduced complexity. Exploiting this tradeoff is becoming increasingly important where low complexity designs are desired, such as in battery operated wireless applications. In this paper, a novel single mixed metric multi-constraint routing algorithm is introduced. The proposed technique has similar complexity compared with existing low complexity methods. Simulation results are presented which show that it can obtain better performance than comparable techniques in terms of generating feasible multi-constraint QoS routes.
A. Abadpour, S. Kasaei,
Volume 1, Issue 3 (7-2005)
Abstract

A robust skin detector is the primary need of many fields of computer vision, including face detection, gesture recognition, and pornography filtering. Less than 10 years ago, the first paper on automatic pornography filtering was published. Since then, different researchers claim different color spaces to be the best choice for skin detection in pornography filtering. Unfortunately, no comprehensive work is performed on evaluating different color spaces and their performance for detecting naked persons. As such, researchers usualy refer to the results of skin detection based on the work doen for face detection, which underlies different imaging conditions. In this paper, we examine 21 color spaces in all their possible representations for pixel-based skin detection in pornographic images. Consequently, this paper holds a large investigation in the field of skin detection, and a specific run on the pornographic images.
H. Abdi, M. Parsa Moghaddam, M. H. Javidi,
Volume 1, Issue 3 (7-2005)
Abstract

Restructuring of power system has faced this industry with numerous uncertainties. As a result, transmission expansion planning (TEP) like many other problems has become a very challenging problem in such systems. Due to these changes, various approaches have been proposed for TEP in the new environment. In this paper a new algorithm for TEP is presented. The method is based on probabilistic locational marginal price (LMP) considering electrical loss, transmission tariffs, and transmission congestion costs. It also considers the load curtailment cost in LMP calculations. Furthermore, to emphasize on competence of competition ability of the system, the final plan(s) is (are) selected based on minimization of average of total congestion cost for transmission system.
F. Namdari, S. Jamali, P. A. Crossley,
Volume 1, Issue 3 (7-2005)
Abstract

Current differential based wide area protection (WAP) has recently been proposed as a technique to increase the reliability of protection systems. It increases system stability and can prevent large contingencies such as cascading outages and blackouts. This paper describes how power differential protection (PDP) can be used within a WAP and shows that the algorithm operates correctly for all types of system faults whilst preventing unwanted tripping, even if the data has been distorted by CT saturation or by data mismatches caused by delays in the WAP data collection system. The PDP algorithm has been simulated and tested on an Iranian 400kV transmission line during different fault and system operating conditions. The proposed operating logic and the PDP algorithm were also evaluated using simulation studies based on the Northern Ireland Electricity (NIE) 275 kV network. The results presented illustrate the validity of the proposed protection.
A. Kazemi, A. Badri, S. Jadid,
Volume 1, Issue 4 (10-2005)
Abstract

In this paper, two vector control systems for investigating the performance of Static Synchronous Series Compensators (SSSC) in steady state conditions are presented that are based on famous d-q axis theory. The workability of proposed method to simplify the SSSC mathematical expressions is shown. The performance of SSSC with two different vector controllers, first based on d-q line currents(indirect control) and the second a heuristic vector control based on real and reactive line powers (direct control), are investigated through simulation. It is found that the new introduced direct control produces better performance in controlling AC power system. Finally the simulation results of an elementary two-machine system with SSSC in different cases are investigated.
A. Saberkari, S. B. Shokouhi,
Volume 1, Issue 4 (10-2005)
Abstract

In this paper, an imaging chip for acquiring range information using by 0.35 μm CMOS technology and 5V power supply has been described. The system can extract range information without any mechanical movement and all the signal processing is done on the chip. All of the image sensors and mixed-signal processors are integrated in the chip. The design range is 1.5m-10m with 18 scales.

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© 2022 by the authors. Licensee IUST, Tehran, Iran. This is an open access journal distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.