بایگانی بخش Ph.D thesis

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چهارشنبه ۲۶ مهر ۱۳۹۱ -

Mehdi Savaghebi Firoozabadi

Electrical Engineering Department PhD Thesis Defense Session Coordinated Control Design of Distributed Generators Interface Converters and Power Quality Conditioners in MicrogridsAbstract: In recent years, distributed generators have proliferated in electrical systems. In this regard, the concept of microgrid has been newly proposed. A microgrid is a small local grid which comprises distributed resources and loads and is able to operate in grid-connected and islanded modes. Distributed generators are often interfaced to the electrical system by power-electronic converters. The main role of the interface converter is to control power injection. In the present thesis, the control of distributed generators interface converters in order to improve microgrid power quality is addressed. This way, the need for dedicated power quality conditioners such as active power filters will be alleviated. The control of interface converters is coordinated in a way that the distributed generators cooperate in compensating power quality problems and supporting loads demands in proportion with their rated powers. The proposed control structures can be classified as hierarchical (centralized) and local (decentralized) control schemes. In the hierarchical scheme, the power quality enhancement is managed by a central controller which sends proper control signals to distributed generators while in the other scheme local controllers are in charge of compensation control. Various methods are proposed to provide virtual impedance by distributed generators aiming to improve the sharing of load current components and to enhance microgrid power quality. Furthermore, the coordinated control of distributed generators converters and active filters is presented in order to provide more options for power quality compensation. The proposed approaches are applicable in both grid-connected and islanded operation modes of microgrid. Control systems design procedures are discussed in detail and simulations (using Matlab/Simulink software package) and experiments are performed in different cases to validate the proposed control approaches. Ph.D. Candidate : Mehdi Savaghebi FiroozabadiSupervisor : Dr. Alireza JalilianAdvisor: Dr. Josep M. Guerrero

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یکشنبه ۱۴ اسفند ۱۳۹۰ -

Payman Rezaee

Electrical Engineering Department PhD Thesis Defense Session A Novel Approach For Designing Microstrip Bandpass Filters By The Aid of Fuzzy Inferences Method With Some PrototypesAbstract: In the final step of any filter design process, the desired center frequency, coupling factor and external quality factor (Qext) are used to determine the physical parameters of the filter. Although in the most cases the physical dimensions of a single resonator for a given center frequency are determined using exact analytical or simple approximate equations, usually such simple equations cannot be found to easily relate the required coupling factor and Qext to the physical parameters of the filter. Analytical calculation of coupling factor and Qext versus dimensions are usually complicated due to the geometrical complexities or in some cases such as microstrip resonators due to the lack of exact solution for the field distribution. Therefore coupling factor and Qext of various kinds of resonators, especially microstrip resonators, are related to the physical parameters of the structure by the use of time consuming full wave simulations. In this dissertation a surprisingly fast and completely general approach based on a soft computing pattern-based processing technique, called active learning method (ALM) and spatial membership functions is proposed to overcome the time consuming process of coupling factor and Qext determination. ALM is an adaptive recursive fuzzy learning algorithm based on brain functionality and specifications which models a complex multi-input single-output (MISO) function or system as a fuzzy combination of some single-input single-output (SISO) one. In the modeling process the multi-dimensional functions of coupling factor and Qext are broken down into their simpler aspects, their behaviors are extracted and then final model will be constructed by combining these simpler aspects.Ph.D. Candidate : Payman RezaeeSupervisor : Dr. Majid TayaraniExamining Committee : Prof. Hojjat Kashani, Dr. Komjani, Dr. Khalaj Amirhoseini, Prof. Kamyab, Dr. BrishamianDate: 2012/3/6 MondayLocation: Room 302 Electrical Engineering Faculty

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یکشنبه ۱۴ اسفند ۱۳۹۰ -

Mahdi Rajabi

Electrical Engineering Department PhD Thesis Defense Session Improvement of TLM Algorithm Frequency Response in Microstrip Discontinuities and Metamaterials Abstract: The design of high performance electronic components and systems such as waveguide structures, digital systems interfaces and connections, RF circuits and systems requires careful attention to physical modeling. In this way, the intrinsic physical inherent limitations of implementation processes can be accounted for, and adverse effects such as substrate coupling, electromagnetic interference (EMI) and metallic edges effects can be minimized. A high degree of physical fidelity of the models is necessary and can only be achieved by detailed analysis employing electromagnetic field solvers. The time domain Transmission Line Matrix (TLM) method has proven to be a powerful tool for solving electromagnetic field problems and has been successfully applied to the analysis of various complicated planar and general three-dimensional structures.The design of complex systems operating at high frequencies requires that the design and analysis tools can handle circuit and field analysis at the same time since the design system may include a combination of lumped circuits, transmission line components such as couplers, power dividers, interconnections, and waveguide components that may contain field singularities due to metallic sharp edges or corners. The field analysis of such a hybrid system is a difficult task for a space and time discrete numerical method like FDTD or TLM method. Existence of field singularities, complex media and materials such as dispersive materials, metamaterials and ferrite is one of the main problems in using such methods to simulate the desired structures. What is intended in this project is to efficiently eliminate the effects of singularities while increasing the accuracy of results without any additional computational cost. In addition, the ability to simulate dispersive materials and complex structures such as metamaterials using TLM algorithm is another main objectives of this project.Ph.D. Candidate : Mahdi RajabiSupervisor : Dr. Nader KomjaniExamining Committee : Prof. Hojjat Kashani, Prof. Orazi, Dr. Khalaj Amirhoseini, Prof. Rashed Mohasel, Prof. ForooraghiDate: 2012/3/14 WednesdayLocation: Ebnesina Conference Hall, Electrical Engineering Faculty

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سه شنبه ۹ اسفند ۱۳۹۰ -

Yasser Attar Izi

Electrical Engineering Department PhD Thesis Defense Session Multiple Antenna Multiple Relay Cooperative Systems in Wireless Fading ChannelsAbstract: In cooperative networks a nodes (source) can exploit other nodes (relay) antennas to obtain spatial diversity. In such networks the source broadcast its symbols and the relays receive the transmitted symbols, and after applying their designed algorithm, forward them to the destination node.In this thesis, a Multi-Antenna Multiple Relay Network (MAMR) in which the source and the destination have the same number of antennas (M) and each transmit antenna is virtually paired to a different destination antenna is investigated. Amplify and forward (AF) strategy is used in the relays where the relays multiply the received vector by a matrix, dubbed the relay matrix, and forward the resulting vector to the destination. In this thesis, the aim is to find the optimized relay matrix.The main contribution of this thesis is presented in three parts: In the first part, by applying ZF algorithm in the reception and transmission for each relay, the MAMR network is transformed to M Single-Antenna Multiple Relay Networks (SAMR). In consequence, the network beamforming proposed for SAMR network can be deployed.In the second part, the optimal relay matrix in MAMR network is obtained for two assumptions of complete and partial channel state information (CSI). It is assumed that a parameter (η) that control signal to noise ratio at destination is known. In the optimization problem, the Mean Square Error (MSE) is minimized as the object function subject to individual power constraint at each relay. The duality is used to solve the problem and the parametric relay matrices are obtained where the parameters are Lagrange multipliers. Then these parameters are computed numerically using Active Set method. To obtain η a method based on its statistical properties is proposed. Then we show that problem with partial CSI is a generalization of the complete CSI case and by changing some variables the partial CSI problem is converted to the completed CSI problem. Thus the same approach of the complete CSI can be use to obtain the relay matrices in partial CSI case.At the end, the parametric relations are achieved for special cases: two relays network and a network with high SNR. The obtained matrices are similar to precoding matrix in MIMO systems.Student: Yasser Attar IziDirecting Proffessor: Dr. Abolfazl FalahatiDr. Paeez Azmi, Dr. Soroush Akhlaghi, Dr. Vahid Tabataba Vakili, Dr. Mohammad Kahaei, Dr. Bahman Abolhasani Date: 2012/7/3,Wednesday  Time: 16:30Place: Ibn Sina Amphitheater  Electrical Engineering Department

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دوشنبه ۱ اسفند ۱۳۹۰ -

Seyed Alireza Davari

Electrical Engineering Department PhD Thesis Defense Session Simulation and Implementation of Sensorless PTC method for Induction MotorAbstract: The predictive torque control (PTC) method is being implemented by means of speed sensor in most cases. Also, in model predictive control, adjusting the weighting factor is an important challenge. Therefore, the PTC method has not succeeded to pave its way to the industrial applications.The contributions of this dissertation are categorized to two main parts. In the first part, two novel methods for weighting factor calculation are developed. In the first method, weighting factor of the cost function is calculated via an optimization method in order to minimize the torque ripple. In the second method, a look-up table base method for two-step prediction method is developed. The second part of the dissertation is dedicated to the proposed sensorless predictive torque control methods. Finite control set model predictive control (FCS-MPC) method and dead-beat method are combined with full order and voltage model observers. In order to reduce the effect of sensorless estimation on sensorless prediction, a robust prediction model is proposed for FCS-MPC and an inherently sensorless prediction model is proposed for dead-beat control. For precise estimation of the states, robust full order observer and robust reduced order observer are developed. The robustness of the prediction model and observers is achieved by H-infinity analysis.In order validate the proposed methods, simulation and experimental results are presented and analyzed. Low speed performance, robustness against the variation of the stator and rotor resistances and robustness against current measurement offset are examined to select the most useful method.Ph.D. candidate: Seyed Alireza DavariSupervisor: Dr. Arab Khaburi Examining committee: Dr. Mili Monfared, Dr. Vaez Zadeh, Dr. Shoulaei, Dr. Vahedi, Dr. JalilianDate: 2012/102/26 SundayLocation: Room 304 Electrical Engineering Faculty

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شنبه ۱ بهمن ۱۳۹۰ -

Roshanak Rezaeipour

Electrical Engineering Department PhD Thesis Defense Session Modeling  And Allocation of RHFC as a New Member of FACTS Devices for Static StudyAbstract: Steady-state and dynamic power-flow control, particularly under heavily loaded system conditions, is an indispensable operational requirement for an interconnected power system. One of the most conventional FACTS devices used to control and transfer the power through certain paths is Phase Shifting Transformer (PST) but it is only more effective to control steady-state power control because of its large time constant. Rotary Hybrid Flow Controller (RHFC) as a new member of  Flexible AC Transmission System (FACTS) controllers  is formed of combination of RPST and other power flow controllers for providing dynamic power flow control. This thesis describes the steady state single phase equivalent circuit and P-Q operational characteristics of RHFC based on power injection model. However OPF makes an objective function to be optimal in the network but it causes other objectives diverge from their optimal value. Therefore, it has been made most of multiobjective optimal power flow to fix all of function in admitting limits from their optimal value. The optimal location and setting of RHFC incorporated in Optimal Power Flow (OPF) problem are found to optimize the total fuel cost, power losses, system loadability in the IEEE 14-, 30- and 118-bus test systems. Furthermore, the results obtained by these devices have been compared to that of PST, HFC  and UPFC. The optimization problem is solved in MATLAB and GAMS softwares using Non Linear Programming (NLP) and Mixed Integer Non Linear Programming (MINLP) as solution procedures. Simulation results show that RHFC has  desirable operation in technical and economical point of views. Student: Roshanak  RezaeipourSupervisor: Mr. Ahad KazemiCommittee Judges: Mr. Jalali, Mr. Kalantar, Mr. Arab Khabouri, Mr. Golkar, Mr. ShayeghiDay: Jan. 31, 13:00 Afternoon Class: 305

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یکشنبه ۱۸ دی ۱۳۹۰ -

Mahdi Hariri

Electrical Engineering Department PhD Thesis Defense Session Robust Combination Methods for Biometric SystemsAbstract: Designing multi modal biometric systems proposes more precise and confident technique than single systems, with one biometric modality and one matcher, for authentication. Because absolute security is impossible, investigation of various invasions to these systems and analyzing vulnerability of systems against these attacks cause proposing suitable methods for designing secure authentication systems and increment their robustness. This thesis introduces the possibility and probability of spoof attacks to each modality of biometric matchers and investigates the vulnerability of combined biometric systems against spoofing of their matchers' modalities. In this research for case study face and fingerprint traits are fused in score level for generation of bimodal biometric systems. For studying the vulnerability of systems, we have simulated spoofed scores of each matcher, up on proposed parameters by a novel method, then imposed invasion to authentication systems by these simulated scores, and at last calculated the vulnerability of them by an applicable method. Vulnerability of biometric systems is evaluated in individual and bimodal forms by the most common fusion rules, included fixed combination rules contained analytic and fuzzy rules, and linear and nonlinear trainable rules against various possibilities and probabilities of spoofing and experimental results have been analyzed and compared. Comparison of quality and quantity outcomes of various fusion rules shows the robustness and vulnerability of each of them. In this thesis, spoofed scores database has been constructed from real standard scores database with various possibilities and probabilities of spoofing. Following the goal of research and for improve the robustness of biometric systems against spoofing, rules and guidelines include: finding suitable biometric modality and its matcher, robust combination rule and its robustness conditions are proposed as the contribution of these research.Novel applied experimental researches and extraction method of their results show the importance of consideration to and more investigation the robustness of biometric systems and can help to development of security and creation the appropriate robustness in biometric systems by investigation their vulnerabilities with fusion rules and biometric traits.Mahdi HaririSupervisor: Dr Shahriar Baradaran ShokouhiAdvisor :Dr Sattar MirzakuchakiThe Jury:Dr Ehsanollah Kabir, Dr Nasrollah Moghaddam, Dr Karim Mohammadi, Dr Ahmad Ayatollahi, Dr Golam ali Rezaei RadViva Date:   Sunday 8 Jan 2012Place: Electrical Engineering faculty, Seminar Room (Class 303)

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شنبه ۱۷ دی ۱۳۹۰ -

Amirkeyvan Momtaz

Electrical Engineering Department PhD Thesis Defense Session Design and Simulation of an intelligent Algorithm for Defects Detection in Ultrasound Images Abstract: In non-destructive testing, detection and clustering of defects is an important issue. One of the exploited methods to determine the defects is the use of c-scan images obtained from ultrasound test. The goal of the thesis is detection and clustering of defetcts in ultrasound images. Since the quality of the obtained image is not suitable for processing, it is necessary to enhance the quality of images before applying clustering method. The proposed denoising method in preprocessing step is based on the denoising the wavelet coefficients of the image by the use of independent component analysis and a spatial filter. The filter is used to determine the homogenous areas from the areas containing image details. The method has the capability to reduce different kind of noises including Gaussian, speckle and the noise with weak Gaussian distribution. The proposed clustering algorithm is based on the rosette pattern. For this purpose, by the use of the rosette pattern, the image is sampled and according to the rosette pattern characteristics, the samples are mapped to the two dimensional linear space. In this stage, based on the neighborhood property of the samples, the clustering is performed. Finally, the clustered samples are remapped to the main space. Unlike the conventional clustering methods such as k-means and FCM algorithms requiring the number of clusters as one of the initializing parameters, in the proposed method, there is no need to initialize any parameter. Based on different data sets, the results show that the algorithm improves the capability of clustering, run time and determining the optimal number of clusters about 92%, 99% and 71% compared to k-means and FCM algorithms, rspectively. Moreover, in dealing with high resolution data sets, the efficiency of the algorithm in clusters detection and run time improvement increases considerably.Phd Student : Amirkeyvan MomtazSupervisor: Dr. Ali SadrJudges: Dr. Mahloojifar, Dr. Setaredan, Dr. Ayatollahi, Dr. Mirzakochaki and Dr. AbrishamifarDay: Wednesday, Date: 2012/01/11 Time: 17Class: 303

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دوشنبه ۵ دی ۱۳۹۰ -

Mehdi Alemi Rostami

Electrical Engineering Department PhD Thesis Defense Session Dynamic Analysis, Design and Implementation of Induction Motor Control Based on the Singular Perturbation Theory with Consideration Iron Losses and Core SaturationAbstract: Control of Induction motor due to it’s the nonlinear property is one of the most popular research topics recently. Vector control based algorithms which are used for proper functioning need to estimate the rotor speed and magnetic flux. In many applications, flux and speed must be estimated without using sensors. Thus, in these cases, it is necessary to obtain speed and flux by measuring voltage and current. In this thesis, a nonlinear observer for estimating motor parameters based on Lyapunov function is presented. Using the Lyapunov theory, inputs regulating system and control system are earned which improve increases system performance. Moreover a novel control speed sensorless indirect field-oriented control for the full-order model of the induction motor is presented. It provides local exponential tracking of smooth speed and flux amplitude reference signals together with local exponential field orientation, on the basis of stator current measurements only and under assumption of unknown constant load torque.The absence of the flux model in the proposed algorithm allows for simple and effective time-scale separation between the speed–flux tracking error dynamics (slow subsystem) and the current error dynamics (fast subsystem). This property is exploited to obtain a high performance sensorless controller, with features similar to those of standard field-oriented induction motor drives. The theoretical analysis based on the singular perturbation method enlightens that a persistency of excitation condition is necessary for the asymptotic stability.Extensive simulation and experimental tests confirm the effectiveness of the proposed approach. These results show the advantages of proposed observer in control of induction motor transient performances. The merits of the proposed control system are also indicated in comparison with a traditional optimal control system.Phd Student : Mehdi Alemi RostamiSupervisor: Dr. Adib Abrishamifar Advisor : Dr . Rajaei SalmasiJudges : Dr. Rahmati , Dr. Arabkhaboori , Dr. Vahedi , Dr. mohammadian, Dr. Radan Day : Wednesday     Date: 2011/12/28    Time:15 Class : 305

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یکشنبه ۱۵ آبان ۱۳۹۰ -

Mostafa Shahnazari

Electrical Engineering Department PhD Thesis Defense Session Modeling and Parameter Identification of Brushless Synchronous GeneratorAbstract: In this Thesis, a new average modeling approach for brushless excitation system with improved dynamics was developed using mathematical derivation method. Using an efficient VBR model of the generator and taking into account the dynamics of a variable excitation current during the averaging period are the main features of the presentedmodel. Moreover, the analytic nature of this model makes it suitable for analysis of variable frequency systems as well as control and identification purposes. The proposed model simulation results compared with laboratory tests and experimental studies carried out in an actual power plant confirm the validity of the suggested model in steady state and transient operation. The developed excitation system model is an appropriate model for large disturbance simulations and transient stability studies, where a computationally efficient exciter representation is necessary.By: Mostafa ShahnazariSupervisor: Dr. Abolfazl VahediReferees boards: Prof. Lesani, Prof. Milimonfared, Dr. Shahrtash, Dr. Jalilian, Dr. Arab KhaburiDate: Sunday 13 Nov. 2011   Time: 15:00Room: Class 301, Department of Electrical Engineering

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یکشنبه ۱ آبان ۱۳۹۰ -

Mahdi Khodabandeh

Electrical Engineering Department PhD Thesis Defense Session Uncertainty Measurement and Improvement in Evidential Reasoning Problems using Sensor FusionAbstract: Uncertainty evaluation for sensor fusion results as an open problem to justify the results in an efficient manner is concentrated in this thesis. The Aggregate uncertainty measure, AU, which is presented in Dempster-Shafer (DST) framework, is generalized in two procedures to be applicable to the fusion theories based on free and hybrid Dezert-Smarandache model. These fusion theories are Dezert-Smarandache Theory (DSmT) of combination including DSmC and DSmH also Proportional Conflict Redistribution (PCR) rules of combination. The new developed uncertainty measures are called Generalized Aggregate Uncertainty measure-1 (GAU1) and Generalized Aggregate Uncertainty measure-2 (GAU2). Requirements for these uncertainty measures are discussed theoretically. Additionally, modified forms of the AU measure, GAU1 measure and GAU2 measure are presented. Moreover, in order to achieve a well-organized decision making, a hierarchical sensor fusion framework with supervision of an uncertainty evaluator is introduced which it utilizes the uncertainty measures. Capabilities of the developed uncertainty measures in order to evaluate the DSmT-based fusion results in the information fusion framework are verified by two experimental studies. The designed experiments are target differentiation using ultrasonic sensors and localization problem using cameras’ images. Sensors’ data in these experiments are fused by fusion rules based on the obtained models and then the fusion outcomes are evaluated by the associated uncertainty measures in uncertainty point of view. The results are discussed to illustrate high performance of the new developed generalized aggregate uncertainty measures in the introduced decision making systemStudent : Mahdi KhodabandehSupervisor : Dr. Alireza Mohammad-ShahriAssessment committee: Dr. Behzad Moshiri, Dr. Hamidreza Momeni, Dr. Mohammadreza Jahed-Motlagh, Dr. Aliakbar Jalali, Dr. Mohammad FarrokhiDefense Date: Sunday, October 23, 2011 at 5 PMRoom 303, Electrical Engineering Department

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دوشنبه ۱۸ مهر ۱۳۹۰ -

Khalil Monfaredi

Electrical Engineering Department PhD Thesis Defense Session Low Voltage Low Power Digital to Analog Converter Design for Video ApplicationAbstract: Considering the subject of this thesis which is about low voltage low power current steering digital to analog converters design for high definition video applications, in first step with a wide and comparative approach different types of DACs and more specially the well improved ones are investigated. This procedure resulted in selection of appropriate DAC type for intended high precision and high speed application. Then, considering the fact that every DAC includes two digital and analog parts, and since the analog part has more tremendous effect than digital part on DAC’s overall performance, we focused mainly on improving current mirror, current buffer, and deglitching parts and successfully designed some novel structures which resulted in several international papers. Some achievements of this thesis are the design of high performance current mirrors as one of the main building blocks of current steering DACs. Ultra high output resistance (400GΩ), low voltage supply (0.9V), Ultra low current transfer error (3*10-3%), very low input resistance (0.0058Ω), ultra high input and output compliance (0.058V and 0.055V, respectively), very low offset and power dissipation (0.4aA and 86nW, respectively), wide dynamic range and bandwidth (150dB and 210MHz, respectively) are some of improvements we achieved during current mirror design phase in this thesis. One of the current mirrors which was the perfect choice for providing ultra wide dynamic range, low power consumption, very high output resistance, good precision and minimum voltages at input and output nodes was selected for designing the current steering DAC promised in this thesis. The other important and determinative analog part of current steering DAC is its output section which has a tremendous effect on producing glitch, speed and the effective number of bits. This forced us to put a strong emphasis on proposing improved structures for this (output) part. Utilizing the mentioned current mirror with ultra wide dynamic range, low power consumption, very high output resistance, good precision and minimum voltages at input and output nodes, and also the novel current buffer cell with outstanding deglitching scheme whose wonderful capability is mainly due to its ultra fast settling time, local deglitching, and statistical glitch division schemes, realized most of the aforementioned goals and resulted in design of ultra high speed current steering DAC (2GS/s) with 12Bit precision and high SFDR (73.43dB), very low glitch (0.42PV*s), low supply voltage (1V) and low power consumption (3.446mW). This DAC is perfectly suitable for mixed mode, HDTV, and high speed applications in which large glitch energy is considered as the main issues. Whereas most of the previously reported artworks suffer from high power consumption and high glitch energy. The operation of proposed structures is proved by HSPICE simulations in TSMC 0.18 μm CMOS, BSIM3 and Level49 technology.Student : Khalil MonfarediSupervisor : Dr. Seyed Javad AzhariAssessment committee: Dr. Ahmad Ayatollahi, Dr. Sattar Mirzakuchaki, Dr. Seyed Adib Abrishamifar, Dr. Omid Hashemipour, Dr. Hossein GhezelayaghDefense Date: 19 October 2011 Time: 14 Location: Seminar Hall, Electronic Research Center, Iran University of Science and Technology, Narmak, Tehran, Iran

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سه شنبه ۲۹ شهریور ۱۳۹۰ -

Mohammad Amin Amiri

Electrical Engineering Department PhD Thesis Defense Session Analysis, Simulation and Realization of Single Aperture Monopulse Antenna with Circular PolarizationAbstract: Quantum Cellular Automata (QCA) is an emerging technology which utilizes quantum dots in digital computations. Utilizing the QCA technology for implementing logic circuits is one of the approaches which in addition to decreasing the size of logic circuits and increasing the clock frequency of these circuits, reduces the power consumption of these circuits.Power consumption, Area, Latency, Throughput, Clock frequency and Resistance against attacks are main parameters which are used to evaluate the hardware implementation of a cryptographic algorithm. Using the quantum cellular automata will enhance the mentioned parameters.Hardware design and implementation of A5/1 and Trivium from the stream ciphers and Serpent and Rijndael from the block ciphers and simulation of these implementations are discussed by three methods. These methods involve "implementation using VHDL and simulation by ModelSim", "modular implementation in QCA and simulation by QCADesigner" and "modeling QCA circuits by VHDL and simulation by ModelSim".Student : Mohammad Amin AmiriSupervisor : Dr. MirzakuchakiAvisor: Dr. Rashed MohasselAssessment committee: Dr. Ebrahimi Atani, Prof. Raeesi, Dr. Ayatollahi,Prof. Mohammad Nejad, Prof. Mohammadi: Date of Defense: Monday 90/7/4 , 13 pmElectrical Engineering Department, Class No. 303

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سه شنبه ۲۹ شهریور ۱۳۹۰ -

Mohseni Armaki

Electrical Engineering Department PhD Thesis Defense Session Analysis, Simulation and Realization of Single Aperture Monopulse Antenna with Circular PolarizationAbstract: This thesis describes the design and realization of a multi-mode tracking feed antenna system, for a circularly polarized wave, which can generate sum and difference patterns suitable for monopulse tracking in remote sensing earth stations. It uses TE11 and TE21 modes, in a smooth circular waveguide, to obtain the sum and difference patterns. The higher order mode, TE21 generated within the feed is separated from the fundamental mode, TE11 by using a mode coupler. Circular polarization is converted to linear polarization by pin polarizer septum. The design of the multimode corrugated horn, optimum TE21 mode coupler and polarizer are described in some details. The size and shape of the sidewall slots of mode coupler is optimized to provide an efficient coupling. The use of compact mode coupler with a conical corrugated horn makes the design particularly simple and inexpensive. The prototyped horn designed here operates in the frequency range of 7.2-8.8GHz. Sum and delta patterns and polarizer axial ratio are presented. The close agreement between measured and simulated data validates the present designStudent : S.H. Mohseni ArmakiSupervisor : Dr. Farrokh Hojjat-KashaniAvisor: Dr. Rashed MohasselAssessment committee: Dr. M. Khalaj-Amirhoseini, Dr. N. Komijani,Dr. Kamyab, Dr. Moghaddasi: Date of Defense Monday, 26 Sep. 2011, at 15:30Room , Department of Electrical Engineering

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شنبه ۱۲ شهریور ۱۳۹۰ -

Majid Ardestani

Electrical Engineering Department PhD Thesis Defense Session Adaptive Multiple Description Scalable Coding for Peer-to-Peer Video StreamingAbstract: Multiple description scalable coding based on T+2D wavelet decomposition provides a flexible structure for peer-to-peer video streaming with lossy links and heterogeneous nodes. In the present thesis, two different strategies are proposed; one based on segmentation and unequal loss protection of the embedded video bit stream and another based on truncation of the scalable bit stream of each code block. In the first strategy, it is important to find the suboptimal sizes of the bit stream segments. To this end, an analytical relation is found between the optimal sizes of any two successive segments which is the result of analysis of the optimization cost function around the optimal point and smart search of the state space. This idea yields a progressive solution with low computational complexity and identical performance as the local search algorithm.In the second strategy, it is necessary to find the optimal truncation point of each code block within each description. This is a complicated problem requiring a full search in a huge dimensional state space. To design an adaptive low-complexity encoder with arbitrarily unbalanced descriptions, a simple clustering algorithm is proposed for partitioning the CBs into a limited number of clusters. This simple and efficient clustering algorithm significantly reduces the size of redundancy-rate assignment matrix, such that one can find the optimal channel-aware cluster-level redundancy-rate assignment matrix using a low-complexity full search approach. This approach improves the decoding quality compared to the co-echelon adaptive frameworks. In addition, the proposed clustering approach (along with an experimental rate-distortion modeling) may be analytically represented by closed-form relations for low-complexity computation of the optimal encoding parameters. Therefore, an efficient real-time post-encoding adaptation mechanism may be realized.Student : Majid Roohollah Ardestani Supervisor : Dr. Ali Asghar Beheshti ShiraziJury: Dr. V. Tabataba Vakili; Dr. A. Falahati; Dr. B. Abolhassani; Dr. E. Kabir; Dr. H. Aghaei Nia: Date of Defense Sunday, September 11, 2011Classroom No. 302, Faculty of Electrical Engineering

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چهارشنبه ۲ شهریور ۱۳۹۰ -

Asghar Taheri

Electrical Engineering Department PhD Thesis Defense Session Efficiency and Torque Ripple Improvement of Six-phase induction motor Abstract: Recently, multiphase machines have been received great deal of attention. Some of the advantages of these machines can be listed as: higher redundancy and reliability under fault conditions, lower torque pulsations, reduced rotor harmonic currents, lower DC-link voltage requirement, lower power per phase, and a reduction in the stator copper loss. The six-phase induction machine (6PIM) is known as an interesting and the most discussed types of multi-phase machines. Until recent years, the literature of 6PIM drives has covered different issues.  Some papers addressed the multi-phase drive efficiency; improving efficiency of six-phase induction machine is an important issue that addressed less in the articles. Six-phase induction motor has 64 space voltage vectors which causes more complexity in selecting of inverters switching. Unsuitable selection of switching table leads to large harmonics especially in low speed and it reduces drive efficiency. The six-phase induction machine has large zero sequence harmonic currents of order . These harmonic currents are varied in various techniques. Decreasing this loss is so essential in six-phase induction machine. Improving of ST-DTC of Six-phase induction machine to reduce voltage and current harmonics and torque pulsation is addressed newly in this thesis. Selecting a suitable method by minimizing these harmonics is very important in DTC of six-phase induction motor. Motors are designed to have maximum efficiency at their nominal point. If the motor load or velocity is under this point, flux should be reduced to have appropriate efficiency. There are a number of approaches for choosing a suitable control method including Loss Model based Control (LMC), Search Control (SC). A flux search controller is proposed to improve the efficiency of direct torque control and field oriented control of six-phase induction machine. The proposed flux search controller is based on adaptive gradient descent of motor flux value with fast response and easy implementation. A proper loss model of six phase induction motor in conjunction with the proposed method has been presented. Stator frequency variation with respect to flux reduction is considered as a new aspect of fast flux search control. Reduction of the flux in the search control technique leads an increase in stator frequency and an error in core loss calculation is occurred if the frequency variation is ignored. The proposed search controller greatly improves efficiency by reducing core loss as well as harmonics loss. The approach not only is easy to implement and adaptive about parameter variations but also requires no additional hardware for practical implementation. The simulation and experimental results presented in this paper verify the effectiveness of the proposed method in improving efficiency of direct torque control and field oriented control of six-phase induction motor drive. Adaptive gradient variation of flux technique decreases the convergence time, noise impact, and increases accuracy of algorithm.  Although using the frequency variation affects the core loss calculation, the SC technique causes an increase in accuracy of the core loss calculation. The proposed loss modeling of DTC of 6PIM can describe dynamic variation of losses in the SC technique not only in 6PIM but also in IM. Flux variation in the SC technique results in variation of core loss; a matter previously worked in literature. However, the flux variation leads to a variation in frequency as well as core loss coefficients. In this thesis, the accuracy of loss calculation and efficiency in the SC technique is improved considering the frequency. Student : Asghar Taheri Supervisor : Dr. Abdolreza RahmatiCo supervisor : Dr. Shahriyar KaboliJury:Dr. Vahedi, Dr. Arabkhabouri,  Dr. Abrishamifar, Dr. Mohammadian, Dr. Kianinezhad:  Date of Defense Saturday 3 sep. 2011, 15 pmElectrical Engineering Department, class NO. 305

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سه شنبه ۱ شهریور ۱۳۹۰ -

Ali Mosallanejad

Electrical Engineering Department PhD Thesis Defense Session Optimal Design and Construction of Multi Level Tubular Linear Reluctance MotorAbstract:Operation of the tubular linear reluctance motor depends strongly on the motor inductance profile. Therefore, calculating the motor inductance with a good accuracy is very important.in this thesis The exact method for calculating the minimum and maximum inductance is proposed  and field intensity inside the iron core is achieved with regard to eddy current. Finite element method is used for motor simulation and its inductance calculation in every plunger position. For evaluating simulation and calculation results, a prototype TLRM was built and its inductance was measured. Also dynamic modeling of tubular linear reluctance motor is performed considering different conditions, such as eddy current effect, skin & proximity effect , different length condition, the current source inverter fed, plunger lock effect  stability curve.This thesis represents a method for increasing the magnetic force and velocity in tubular linear reluctance motor by implementing step winding structure. Moreover the methods used in inductance calculation and the novel motor modeling are presented. The performance improvements in the proposed motor are proved using experimental results and FEM analysis. At the end, the simulation results are compared with experimental results. Good agreement between experimental and simulation results has been observed.Also in this thesis all methods of increase efficiency of tubular linear reluctance motor are introduced, then optimal design of this motor is preformed and Optimal design method of motor are described by algorithms.In the end, Multi Level Tubular Linear Reluctance Motor with control system and the equipment are made and experimental results are compared with dynamic modeling results. Good agreement between experimental and simulation results has been observed.Student : Ali MosallanejadSupervisor : prof. abbas shoulaieJury: prof. vaezzadeh , Dr fathi , Dr vahedi , Dr arabkhabouri,  Dr JaliliyanDate of Defense:Monday 90/06/14 , 9 amElectrcal Engineering Department, class NO. 303.

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سه شنبه ۲۵ مرداد ۱۳۹۰ -

Khoshnam Shojaei

Electrical Engineering Department PhD Thesis Defense Session Adaptive-Robust Control of Nonholonomic Wheeled Mobile Robots in Presence of Parametric and Non-parametric Uncertainties with Practical ConsiderationsAbstract: In this thesis, the trajectory tracking problem of nonholonomic wheeled mobile robots (WMRs) in presence of both parametric and non-parametric uncertainties is addressed. A combination of adaptive and robust control is employed using input-output feedback linearization, backstepping control technique and Lyapunov-based control techniques of robotic manipulators in order to solve the trajectory tracking control of uncertain nonholonomic mobile robots. At first, an adaptive-robust backstepping-based controller is proposed to solve global tracking problem of all WMR states for every arbitrary initial condition. The complexity of the proposed backstepping-based controller motivates us to design a simpler unified tracking controller in chapter 5. Therefore, an adaptive-robust feedback linearizing controller is proposed to provide a unified tracking controller with minimum complexity and less design parameters for an integrated formulation of uncertain kinematics and, dynamics of WMRs and uncertain actuator dynamics. Simulation and experimental results are presented to evaluate the proposed tracking controller. Since most of commercial WMRs are not equipped with velocity sensors, an output feedback tracking controller is proposed in chapter 6. This controller only requires position measurements of WMRs. The controller design task is accomplished by using control techniques of robotic manipulators. For this reason, a new input-output model is proposed in this thesis which allows the designer to directly apply the control techniques of robotic manipulators to control nonholonomic WMRs. Simulation results are also presented to evaluate the controller performance. Student: Khoshnam ShojaeiSupervisor: Dr. Mohammad ShahriAdvisor: Dr. FarrokhiReferee Committee Members: Dr. Jahed Motlagh, Dr. Jalali, Dr. Davaei Markazi, Dr. Khaki Sedigh, Dr. MousavianDate: Wednesdayu 24 Agust 2011, Time: 10:00Place: Electrical Engineering Department, Room 305.

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یکشنبه ۲۳ مرداد ۱۳۹۰ -

Mohammad Mehdi Arefi

Electrical Engineering Department PhD Thesis Defense Session Adaptive Robust Control of a Class of Complex Systems in Presence of Time-varying UncertaintiesAbstract: In this thesis, first, an adaptive robust stabilization algorithm is presented for a class of nonlinear systems with mismatched uncertainties. In this regard, a new controller based on the Lyapunov stability theory is proposed in order to covercome the problem of stabilizing nonlinear time-varying systems with mismatched uncertainties. This method is such that the stability of the closed-loop system is guaranteed in the absence of triangularity assumption. The proposed approach leads to asymptotic convergence of the states of the closed-loop system to zero for unknown but bounded uncertainties. Then, this method is modified so that all the signals in the closed-loop system are uniformly ultimately bounded. Numerical simulation for two different examples, and also for synchronization of time-varying Rossler systems shows the effectiveness of the given algorithm. Next, a method for stabilization of nonlinear systems with non-parametric mismatched uncertainties is introduced. This method is also based on Lyapunov stability theory, and the uncertainty of the system is approximated via an adaptive neural network. The method can be applied to Multi-input systems. Numerical simulations on a vertical take-off and landing helicopter and also two numerical examples show that the presented algorithm has a good performance in the face of mismatched uncertainties.   Finally, the previous algorithm is developed for the systems when all the states are not available. To this end, an observer-based stabilization algorithm based on strictly positive real (SPR)-Lyapunov design is presented. Results show that if the SPR condition is satisfied, one can apply the stabilization algorithm using available outputs.     By:Mohammad Mehdi ArefiSupervisor:Dr. Mohammad Reza Jahed-MotlaghReferee committee Dr. Ali Khaki-Sedigh, Dr. Vahid Johari-Majd, Dr. Mohammad Farrokhi, Dr. Javad Poshtan, Dr. Ali Akbar JalaliDate: August 20, 2011,    Time: 10:00Place: Electrical Engineering Department, Room 305. 

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شنبه ۲۲ مرداد ۱۳۹۰ -

Majid Hajatipour

Electrical Engineering Department PhD Thesis Defense Session  Design of State Observer in Nonlinear Systems Based on Switching MethodAbstract: Nowadays considerable amount of researches belongs to the sliding mode observers (SMOs) since they have good characteristics such as fast estimation, robustness to the uncertainties. But their sensitivity to the measurement noise degrades their quality. In this thesis, SMOs are analyzed from point of view of relay feedback systems. That is, based on the new structure, the relation between frequency of oscillations and accuracy or effecting from measurement noise are analyzed and discussed. Hence this thesis is based on three stages of design. In the first stage, it shows that by appropriate design of a compensator in the frequency domain, estimation of SMO becomes less affected from the measurement noise. However this design results some estimation errors. In the second stage of design, using another compensator, accuracy of SMOs is increased, but it results increasing of sensitivity of SMOs to the measurement noise. At the final stage of design, designing two different compensators, both increasing of accuracy and decreasing of sensitivity to the measurement noise are added to the SMOs.  Simulations show the acceptable performance of proposed method, compared to the conventional SMOs.Keywords: sliding mode observers, nonlinear system, relay feedback, frequency of oscillation, linear compensator.  Student: Majid HajatipourSupervisor: Dr Mohammad FarrokhiReviewers: Dr Javad Poshtan; Dr Jahed Motlagh; Dr Davayi Markazi; Dr khaloozadeh; Dr Khaki seddighDefense Date: Sunday 1390/5/30Time: 10:00 Place : Electrical department- 305

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چهارشنبه ۱۱ اسفند ۱۳۸۹ -

Mahdi Moradian

Department of Electrical Engineering PhD Defence 396 Improving the radiation characteristics of waveguide feed longitudinal slotted arrayAbstract: A suitable centered longitudinal shunt slot is proposed. It is shown that the proposed slot antenna can be an effective candidate for replacing the conventional longitudinal shunt slot. The proposed structure is realized by adding the V-shaped to the ridge of the single ridge waveguide. The wiggly ridge is placed exactly under the slot. It has been shown that the radiation characteristic of the slot can be varied by changing both slot length and V-shaped depth. In order to design a high performance array composed of the proposed slots, two methods are proposed which both are based on the well known Elliott’s design procedure. One of the methods is called semi-analytical and the other called analytical method. In the semi-analytical method, general relation connecting the backward- and forward-scattering dominant mode coefficients to the slot voltage is derived using available electromagnetic field simulator and by fitting some proper polynomials to the derived data. In analytical method, the V-shaped ridge is approximated by discrete steps. Then, the electric field at each step is found by defining a suitable scalar potential ional and solving it. Finally, the electric field in V-shaped wiggly ridge waveguide is found by considering previously obtained electric fields for each step. The general relation connecting the backward- and forward-scattering dominant mode coefficients to the slot voltage is found using reciprocity theorem and by fitting some proper polynomials to the derived data. The Elliott’s design procedure is used to design some slot antenna using analytical and semi-analytical results. The simulation results show that the butterfly lobe suppression of the proposed array is better than 6dB in comparison to the single ridge waveguide fed array while allowing the beam to scan to a relatively wide angle of 40 degrees. By: Mahdi Moradian Supervisor: Dr. Mohammad Khalaj-Amirhosseini Advisor: Dr. Majid Tayarani Assessment Committee: Dr. Farrokh Hodjat Kashani, Dr. Homayoon Oraizi, Dr. Hashem Vajed Samiei, Dr. Jalil Rashed-Mohassel, Dr. Manouchehr Kamyab THE DEFENCE TAKES PLACE: Monday 7 March 2011, at 15.00 Room 303, Department of Electrical Engineering

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چهارشنبه ۱۱ اسفند ۱۳۸۹ -

Reza Sharifi

Iran University of Science and Technology Electrical Engineering Department PhD Thesis Defense Session 396 Optimal Design Algorithm of Superconducting Fault Current Limiters via Multi Criteria Decision Making Techniques Abstract: Superconducting fault current limiters (SFCL), connected in series with the transmission and distributions lines, are one of the important protection devices in future power systems. Considering unique characteristics of materials in superconducting state, several configurations including resistive and inductive types are presented to limit the fault current based on this phenomenon. The main purpose of this thesis is to propose an algorithm for optimal design of resistive and inductive SFCLs via multiple criteria decision making techniques. To achieve this goal, after a comprehensive survey of previous works, an appropriate model describing electrical, thermal and magnetic behavior of the mentioned SFCLs will be presented to analyse their performance in normal and faulty conditions and to choose important parameters. In the next step, using multiple criteria decision making methods the optimal design process of SFCLs will be explained considering some objectives including optimal limiting performance, minimum losses and voltage sag, appropriate response to transient faults and minimum cost. Then, an improved meta-heuristic multi-objective algorithm will be presented based on simulated annealing to be employed in this purpose. Furthermore, a combined algorithm will be offered to optimize number, size and location of SFCL in power system and the results for the standard IEEE 30-bus test system will be appeared. As an additional study, two new configurations based on autotransformer introduced as well as a modified configuration based on magnetic switch and their performances are analyzed. Electro-thermal modeling and optimization algorithm are made in PSCAD/EMTDC environment and the results are compared by FLUX/2D finite element software. By: Reza Sharifi Supervisor: Dr. Hossein Heydari Referee committee: Dr. Gholami ; Dr. Jadid ; Dr. Shahrtash; Dr. Amjadi; Dr. Javadi Defense Date: Sunday 27/02/2011 Time: 17:00 Place : Electronic Research Center, Seminar Room

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پنجشنبه ۲۸ بهمن ۱۳۸۹ -

Mostafa Sarlak

Electrical Engineering Department PhD Thesis Defense Session 396 High Impedance Fault Detection and Branch Identification in Distribution Networks Abstract High Impedance Faults (HIFs) usually occur in distribution networks and, generally, cannot activate conventional protection relays because of high impedance at the fault point. These faults often occur when an overhead conductor breaks down and touches high impedance surfaces and/or where the conductors become in contact with a high impedance object such as a tree. The main purpose in HIF detection, in contrary to short circuit faults, is not to protect the system, but to protect the human lives and preventing fire hazards due to arcing phenomenon . In this thesis , for the first time a high impedance fault indicator (HIFI), to be mounted on the poles, is proposed to detect and track down the faulted branch. The main contribution of this thesis is the investigation of employing the magnetic field strength signal (MFSS), measured in the vicinity of the conductors of a feeder as a new signature, to detect HIFs based on a novel pattern recognition method. The proposed HIFI is capable of discriminating HIFs (with broken and unbroken conductor) from other similar phenomena, including capacitor switching, feeder switching, load switching, insulator leakage currents and harmonic load. Also , a new multi criteria pattern recognition based algorithm is presented to detect high impedance fault in distribution feeders. This method has three stages: feature generation, feature extraction and classification. The proposed feature sets are generated by applying the multi-resolution morphological gradient to each of the first three half cycles of the post-disturbance current and MFSS signatures . T hese feature sets are fed to support vector machines with r adial b asis f unction (RBF), as the kernel function, for distinguishing HIFs . Applying the data for HIF, insulator leakage current and harmonic load from field tests and for other similar phenomena from simulations has shown high security and dependability of the proposed method . By: Mostafa Sarlak Supervisor: Dr. Seyyed Mohammad Shahrtash Referee committee: Dr. Kazemi ; Dr. Jamali ; Dr. Analuee ; Dr. Haghifam ; Dr. Khederzadeh Defense Date: Wednesday 11/12/1389 Time: 15:00 Place : Electrical Engineering Department, Room 303

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دوشنبه ۲۵ بهمن ۱۳۸۹ -

Mohammad Reza Zoghi

Electrical Engineering Department PhD Thesis Defense Session Sensor Selection in Wireless Sensor Networks for Target Tracking Abstract: Wireless sensor networks formed using unattended ground sensors promise to provide an effective low cost solution for observing a physical phenomenon. Due to the energy limitation of WSN , for such a network to be effective over an extended time, power conservation is an absolute necessity. On the other hand, due to the high density in the network topology, it may not be necessary to active all the sensors in each time instance. This work is concerned with the selection of a subset of sensors for a target tracking. To do so, it is assumed that the locations of all sensors are, a priori, known and the predicted target state obtained from the tracking algorithm is used to approximate the target position. Therefore, the criterion for sensor selection is defined by considering the location of all the sensors relative to the target position. Accordingly, a cost function is proposed based on the spatial correlation obtained using the best estimation of the event source. Then, another cost function is derived using the geometrical dilution of precision (GDOP) metric for power measuring sensors. As a result, a sensor selection algorithm is proposed which adaptively determines the number of active sensors and finds the best active set topology for target tracking. The sensor selection methods are evaluated in terms of event distortion, their RMS errors of the target position, energy consumption, percent of intersection between the active set selected by each approach to the best active set and the execution time. First, It is shown that the distortion achieved by the proposed spatial-based cost function and its corresponding minimum number of active sensors for a given distortion constraint was less than those obtained using the suboptimum distortion function. Moreover, the proposed distortion function is less sensitive to the sensor density and range parameter. Also, simulation results are revealed that the performance of the sensor selection algorithm evaluated by the MSE and also computational burden has been improved compared with other algorithms. By: Mohammad Reza Zoghi Supervisor: Dr. Kahaei Referee committee: Dr. Tabatabavakili ; Dr. Falahati; Dr. Abolhasani; Dr. Olfat; Dr. Navaie Defense Date: Monday 25/11/1389 Time: 17:00 Place : Electrical Engineering Department, Room 214

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چهارشنبه ۲۰ بهمن ۱۳۸۹ -

Jafar Zarei

Electrical Engineering Department PhD Thesis Defense Session Robust observer-based fault diagnosis in nonlinear systems Abstract: Fault diagnosis of complex control systems is one of the most important research topics among control engineering community during the last half century. In recent years, attention has tend ed towards designing of robust fault detection and diagnosis approaches both for linear and nonlinear systems. Many of the proposed methods in this field are based on robust observers which can efficiently estimate system states, in the presence of a wide class of modeling uncertainty and external disturbances. It should be noted that robust state estimation needs special conditions, which will limit its implementation. For nonlinear systems complexity is higher. One of the goals of this thesis is to present a robust method with good accuracy and simplicity compared to the so far presented methods for robust fault detection of nonlinear system. For this purpose, first, a method using the Unscented Kalman Filter (UKF) algorithm for detection of faults in nonlinear systems is proposed. Then convergence of the unscented Kalman filter is investigated and its local convergence conditions are obtained. To show the ability and performance of the presented method it is applied to detect and isolate faults of a nonlinear process, and it is shown that the presented method is superior to linearization-based methods such as Extended Kalman Filter (EKF). Since this filter lonely cannot solve the problem related to presence of uncertainty in the model, the concept of unknown input is introduced, and Unknown Input Observer (UIO) is used for fault detection of linearized model of the presented nonlinear system around the point of operation. It is shown that by considering an unknown input in the system and tacking into account its effect on the design of the observer, both unknown input effects and uncertainties can be decoupled from fault effects. UIO is then extended to a more general case and it will be shown that the algorithm presented by Kalman can be used to calculate the observer gain. Therefore, if the extended Kalman methods for nonlinear systems; such as EKF or UKF is used, UIO can be designed without linearization for fault detection purposes in nonlinear systems. Finally, convergence of the proposed observer will be studied and to demonstrate its ability it is applied to the introduced system. It is shown that the proposed observer is able to distinguish between fault effects and uncertainties or unknown inputs. By: Jafar Zarei Supervisor: Dr. Poshtan Referee committee: Dr. Jahed-motlagh ; Dr. Jalali; Dr. Sadjadian; Dr. Momeni; Dr. Khaloozadeh Defense Date: Monday, February 14, 2011 Time: 17:00 Place : Electrical Engineering Department, Room 305

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یکشنبه ۱۰ بهمن ۱۳۸۹ -

Hamid Khodabakhshi

Iran University of Science and Technology Electrical Engineering Department PhD Thesis Defense Session Analysis of the electromagnetic waves effects of wireless communications on human head Abstract: In recent years, the rapidly increasing use of mobile phone operating nearby the human head has caused public concern for the effects on human health. In this thesis, after studying of general considerations of biological effects of electromagnetic waves, a new analytical method has been introduced to analyze the interaction between a six-layered lossy spherical human head model and a half-wave dipole antenna. In this method, a simple form of quasi-Green's function for a six-layered lossy sphere has been presented based on the sommerfeld integral. The method of auxiliary sources was then applied to model the half-wave dipole antenna. In the numerical results, the antenna radiation patterns and the local SAR have been calculated at 900 and 1900 MHz. In the second section, a fast numerical simulation of the human head coupling with a PIFA structure based on the CIE/MoM approach to study the effects of the EM coupling on the antenna performance. A mix-potential integral equation (MPIE) for the surface current of the PIFA and volume electric field integral equation (VEFIE) for the head have been extracted. After finding the antenna current distribution, the antenna performance parameters such as input impedance, radiation patterns and radiation effeciency have been calculated. Finally, simulation of mobile phone with dual-band patch antenna in the vicinity of the anatomical model of head has been performed using FDTD methodology. Then, the electric field, local SAR and 1gr-averaged SAR distribution have been calculated at 900 and 1800 MHz. Thereafter, temperature-rise of head tissues due to the radiation of mobile phone has been estimated using the bio-heat equation. It was observed that the peak of the temperature-rise in the brain region is very lower than the allowable values of temperature-rise in the brain tissue. To validate the proposed method, the mobile phone in the proximity of the spherical head phantom has been simulated and the results have been compared with the results of XFDTD and CST softwares. By: Hamid Khodabakhshi Supervisor: Dr. Ahmad Cheldavi Referee committee: Dr. Kamarei ; Dr. Orazi ; Dr. Rashed-Mohassel ; Dr. Komjani ; Dr. Saraf shirazi Defense Date: Wednesday 20/11/1389 Time: 16:00 Place : Electrical Engineering Department, Room 305

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شنبه ۴ دی ۱۳۸۹ -

Shamsolah Salemian

Electrical Engineering Department Ph.D. Thesis Defense Session 396 Design and Modeling of Quantum Repeater in Long-distance Quantum CommunicationAbstract Quantum communication system transmits quantum information from one point to another point. Distribution and control of entanglement in global scale is required in long-distance quantum communication. Now, the only suitable system for long-distance quantum communication is photon. Photon-based protocols suffer from photon loss and quantum decoherence in quantum channels. These problems limit range of single photon transmission up to several tens of kilometers in silica fibers. This problem can be solved by dividing the long distances into shorter intervals, so that the entanglement can be preserved in the shorter distances. System, which is responsible for this task, is called quantum repeater. In this thesis, quantum repeater design is done and its components are introduced. Relation between the components and performance of quantum repeater are described. Then design, simulation and implementation of some subsystem of the quantum repeater are done. Two distinct methods are presented for entangled photon pair source. First method is based on optical integrated circuits and other is based on the linear optic components. In the scheme based on optical integrated circuits, the grating waveguides are used and entangled photon pairs with wavelengths 692 nm and 950 nm are produced. Method Based on linear optics devices is experimentally done on the optical table in the Laboratory. Laser diode with 405 nm wavelength and BBO nonlinear crystal are used in experiment. Entangled photon pair is produced in wavelength of 810 nm. Total 88 pairs of entangled photon are measured at time interval of 30 sec. On the other hand, quantum gates such as NOT and CNOT are designed and simulated based on planar lightwave circuits. By using these gates, a scheme is presented for quantum state swapping. Polarization beam splitter is used as a key element in Bell states measurement. By using integrated optics method, an optical polarization filter is designed that its function is equivalent to the polarization beam splitter. Distribution of quantum entanglement is the main infrastructure of quantum communication and quantum repeater. New protocol will presented for the distribution of entanglement. This protocol can detect and correct qubit error in the quantum channel. Student: Shamsolah SalemianSupervisor: Dr. Shahram Mohammadnejad Referees: Dr. S. mirzakuchaki, Dr. S. A. Abrishami far, Dr. A. Sadr, Dr. M. Hakkak, Dr. A. Malahzadeh Date: Wednesday 29 Dec. 2010 Time: 13:00Place: Room 305, School of Electrical Engineering

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شنبه ۱ آبان ۱۳۸۹ -

Mahmoud Reza Shakarami

Electrical Engineering Department Ph.D. Thesis Defense Session 396 Design and Coordination of Inter-Area Oscillations Controllers in Stressed Power SystemsAbstract Nowadays, because of economic problems on restructured power systems, also environmental pollution problems, interconnected power systems are operated close to their stability limits. These power systems are called stressed power systems. In large power systems, high power may be transferred between generating stations through weak transmission lines. This subject may produce low frequency oscillations ranging 0.2 to 0.8 Hz in power system facing a disturbance. These oscillations appear in oscillating of angles of a group of generators in an area against angels of generators in other or others areas. Inter-area oscillations with no sufficient damping cause major problems in the power systems. They can fatigue in turbine-generator axis of electrical machines or threaten security of power systems. Also, they have negative effects on power quality, like as flicker. Power system stabilizers (PSSs) are the oldest devices to improve damping of these oscillations. Studies shows that in stressed power systems, these oscillations cannot be damped effectively by only PSSs. Nowadays, FACTS devices with high speed of performance have shown their ability to damp these oscillations effectively. Static synchronous series compensator (SSSC) is one of the new FACTS devices that generates a series voltage synchronized with transmission line voltage. Unlike others FACTS devices, less attention has been done on SSSC to damp electromechanical, particularly inter-area, oscillations. Modeling of SSSC to study of dynamic stability in a multi-machine power system, presentation of a method to design of a lead-lag stabilizer for SSSC and its coordination with PSSs have been studied in this dissertation. Also, analysis and studying on SSSC stabilizer in different control channels on damping inter-area oscillations, investigation on different operation modes of SSSC and analysis of effect of SSSC stabilizers in these modes on damping inter-area oscillations in large and small samples of multi-machine power systems are studied in this research. Studies show that, in the stressed power systems, modal interactions can affect noticeably on dynamic behavior and performance of stabilizers. One of the methods to analysis modal interactions phenomenon is modal series (MS) method. In this dissertation, for the first time, the MS method is expanded to a power system installed with a SSSC stabilizer. Modal interactions between an inter-area mode and control modes related to SSSC stabilizers are studied in the samples of stressed multi-machine power systems. A method to design of SSSC stabilizer and its coordination with PSS to improve damping inter-area oscillations considering modal interactions is presented and tested on IEEE 4 and 50-machine power System. Student: Mahmoud Reza ShakaramiSupervisor:Ahad KazemiExamining Committee : Dr. Heydar Ali Shayanfar, Dr. Mohsen kalantar, Dr. Alireza Jalilian, Dr. Mohammad Tavakoli Bina, Dr. Seyed Hossein HosseinianDate: Oct. 27, 2010, 17:00 Place: Department of Electrical Engineering, Room: 305

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چهارشنبه ۱۷ شهریور ۱۳۸۹ -

Seyyed Javad Seyyed Mahdavi Chabok

Electrical Engineering Department Ph.D. Thesis Defense Session 396 Evolutionary Design of Digital Reliable Circuits Abstract Reliability is currently a new factor in designing integrated circuits. In order to design a reliable circuit, effective methods for reliability analysis apart from its manufacturing technology are required. Due to recent developments in manufacturing of reconfigurable hardware, the evolutionary approach for designing circuits is of interest . This thesis considers reliability improvement of digital circuits by evolutionary approach. An appropriate environment is proposed for evolutionary design of combinational and sequential circuits which has features such as proper chromosome structure for applying evolutionary operators, using general VHDL file for nonstop circuit simulation and possibility of slicing the initial set of elements to reduce GA’s search space. T o attain thesis aims, methods for reliability analysis of combinational and sequential digital circuits are presented. Results show that improved single-pass method is fast and dependable for reliability analysis of combinational circuits and it can reduce maximum error from 50% to 7% in a circuit with large number of re-convergent fan-outs such as C1355 with gate failure rate of 0.1. Multiple-pass method also has mean absolute error near 5 percent in all nodes reliability analysis of a sequential circuit with 150 gates and 4 D-flip-flops. In addition to improving circuit’s reliability, the proposed method is also capable of optimizing other parameters such as power consumption, speed and silicon area with less priority to reliability. By applying proposed method to a set of benchmark circuits, it is shown that more reliable circuits (about 20 percent improvement) can be generated by this method in comparison to primary circuits. Moreover, the scalability issue limits this method to be applied only to basic digital circuits such as multiplexers, decoders and flip-flops. Candidate: Seyyed Javad Seyyed Mahdavi Chabok Supervisor: Dr. K. Mohammadi Examining Committee : Dr. H. Taheri, Dr. A. Khademzadeh, Dr. S. Baradaran Shokouhi, Dr. S. Shah Hoseini, Dr. S. Mirza Kuchaki Date: Wed, 2010-09-15 16:30 Place: Conference room of Electrical Engineering Dep.

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سه شنبه ۲۶ مرداد ۱۳۸۹ -

Mojtaba Barkhordari Yazdi

Iran university of Science and Technology Electrical Engineering Department PhD Defense Presentation 396 Control of Nonlinear Hybrid Systems under Constrained Switching Abstract: In this thesis, the stabilization problem of a class of nonlinear hybrid systems is considered. The complex behavior of hybrid systems originates from the interaction of continuous and discrete event dynamics. Stabilization of switched nonlinear systems with nonlinear subsystems is a challenging problem. The stabilizing controller consists of a switching law and a continuous control law. Moreover, the switching signal has some constraints. The new concept of modal state feedback linearization is proposed. The objective is to find a suitable state feedback for each subsystem and a common diffeomorphism state transformation to transform each of the closed-loop subsystems to an equivalent linear one in a way that the resulted switched linear system is controllable. Using this technique we can reduce the complexity of the design procedure by transforming the switched nonlinear system into an equivalent controllable switched linear system. The necessary and sufficient conditions for modal state feedback linearizability of single-input affine switched nonlinear systems are given. This result is extended for the general case, namely switched nonlinear systems with arbitrary number of subsystems and dynamical dimension. In order to simplify the verification of conditions, similar results are developed for some special cases. The developed results are based on a differential geometry. Our approach is constructive in nature in the sense that once the conditions are satisfied, the state transformation is obtained and this leads to modal state feedback linearization. A method to design stabilizing controller for switched nonlinear systems in partial-linear triangular form is proposed to handle partial modal feedback linearizable systems. An approach to design a stabilizing switching law for a class of switched linear systems with constrained switching is developed as the second stage of designing the controller. The existence of solution can be verified using some geometrical properties and graph theory. An algorithm is proposed to generate all of the solutions. Mojtaba Barkhordari Yazdi Supervisor: Dr. M.R. Jahed-Motlagh Examination committee: Dr. A. Afzalian, Dr. A. Khaki-sedigh, Dr. J. Poshtan, Dr. A. Jalali, Dr. M. Farrokhi Date: 29th August Time: 2 pm Place: seminar room

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یکشنبه ۲۰ تیر ۱۳۸۹ -

Mohammad Hosein Khanzade

Iran University of Science and Technology Electrical Engineering Department PhD. Defense Session Dynamic Modeling of Helical Flux Compression Generators Abstract Magnetic flux compression generators offer the largest pulsed power output per unit size or weight when compared with other more conventional systems. These generators are capable of producing voltages of tens kV and currents of tens to hundreds MA. The variety types of flux compression generators have been developed and tested during the past five decades. The most successful types of them , is the helical flux compression generator which is capable of producing a high energy output into large impedance loads, just as it is needed for a practical pulsed power source. In this thesis, we have modeled the helical flux compression generator, using the tow-dimensional filamentary method. The state equations of the generator have been solved by using an approach, which is based on the dynamic matrix concept . The most important source of the losses in a helical flux compression generator is the flux loss due to turn skipping phenomenon (flux that is left behind the conductors and lost for compression). A method has been introduced to calculate this loss. In addition, this work also presents an approach for modeling the eddy current effects in helical flux compression generators accurately. This approach based on the filamentary method in the frequency domain . Due to eddy current effects, the resistances of a helical flux compression generator are frequency dependent. Therefore, it is important to consider a proper frequency in calculation of them. On the other hand, this generator is a pulsed device and its operating frequency can not be determined explicitly. It is usual that these parameters are calculated at an averaged frequency approximately but we have introduced an equivalent frequency and a method for calculation it. To verify our modeling and simulations, experimental models of helical flux compression generator were built and tested. The simulation results demonstrate a good agreement with the experiment results. Student: Mohammad Hosein Khanzade Supervisors : Dr. Abbas Shoulaie, Dr. Yousef Alinejad Refrees: Dr. Mojtaba Mirsalim, Dr. Sadegh Vaezzade, Dr. Homayoon Oreizi, Dr. Heydarali Shayanfar, Dr. Alireza Jalilian Date of defense: July 4, 2010, 10 a.m. Location: Seminar room

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سه شنبه ۱۵ تیر ۱۳۸۹ -

Doctoral thesis defence

Mr. Nasour BAgheri will defend his doctoral thesis on Monday July 12, 2010 . His thesis title is " Analysis and designing of Cryptographic Hash Functions ". His advisor is Dr. Majid Naderi . wish him success from almighty God. ...

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سه شنبه ۱۵ تیر ۱۳۸۹ -

Nasour BAgheri

Electrical Engenieering Department Oral Defense Notice 396 Analysis and designing of Cryptographic Hash Functions In this thesis we conceder the designing and analysis of cryptographic hash functions. Our analysis leads to variety of successful attacks for the known hash functions, includes: ¨ multicollision attack on ZIPPER HASH, SFRH, and MFRH ¨ Collision, preimage and second preimage on CRUSH. In addition, we study the relationship between information theoretic attack costs and real costs. We show that in the information theoretic model, many well-known and commonly used hash functions such as MD5 and SHA-256 fail to be preimage resistant. We propose a generic n -bit iterated hash function framework based on n -bit compression function called Suffix-free-Prefix-free (SFPF) which works for arbitrary IV s and does not possess MD strengthening. We formally prove that SFPF is indifferentiable from the random oracle (RO) when the compression function is viewed as a fixed input-length random oracle (FIL-RO). We also design a concrete hash constriction which fits the SFPF. A hash function with free IV has many benefits such as speedup for the short messages up to two times and applications in randomized hashing. We propose a permutation based compression function and prove its security with respect to collision and (second) preimage attacks in the ideal permutation model. The proposed compression function can be seen as a generalization of the compression function of MD6 hash function. By: Nasour BAgheri Supervisor: Dr. Majid Naderi Advisor: Dr Babak Sadeghiyan Referees : Dr. Taba Taba Vakioli, Dr. Beheshti Shirazi, Dr. Shahossaini, Dr. Ahmadian, Dr. Eghlidos Date: Monday July 12, 2010 Time: 5:00PM Location: The seminar room of E.E. Dept

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سه شنبه ۸ تیر ۱۳۸۹ -

M asoumeh Shafieian Bajestani

Electrical Engineearing Department Viva Session for Dissertation 396 Sound Diffusion Design Using Enclosed Space’s Transfer Function and Wave-Based Numerical Method Abstract Room acoustic design has a very important role to enhance objective and subjective characteristics of the space. Acoustic simulation before implementation is one of the main steps. Boundary Element Method (BEM) is the most accurate method in indoor sound field predictions. In this dissertation we have implemented BEM for predicting sound field inside a room (especially for this research). To provide some basic validation of the accuracy of the numerical models, sound field measurements were carried out in two rooms. The measurements results show great accuracy of the implemented program. Distribution of diffusive and nondiffusive surfaces on room walls affect sound diffusion in room, but the amount, combination, and location of these surfaces are still the matter of question. We investigated effects of these issues on room acoustic frequency response in different parts of the room with different source-receiver locations. Different distributions of acoustic surfaces on room walls have been introduced to the model and room frequency response results are calculated. Finally for more smooth frequency response in small and medium rooms, some suggestions are made. Then, evaluations of the predictions from the room acoustic modeling program have been run using two source types with the same sound power: (a) an omni-directional source; (b) a realistically-directional source with different directionalities together with different combination of diffusive surfaces on room’s walls. The results also confirm the relation of sound diffusion to surface diffusivity and show what combinations of surface diffusivity and source directivity could lead to a more smooth frequency response. The written program is also capable of predicting the scattered sound from diffusing surfaces like schroeder’s. Some of the predicted results of some diffusers are presented. Student: M asoumeh Shafieian Bajestani Supervisor: Dr. Farokh Hodjat Kashani Viva Committee: Dr. Homayoun Oraisi; Dr. Mohammad Hakkak; Dr. Jalil Rashed Mohasel; Dr. Mohammad Hosein Kahaei; Dr. Mohammad Hashem Vajed Samiei Date: Wednesday Tir 4th 1389 Time: 5 pm Place: Seminar room of Electrical Engineering Department

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سه شنبه ۱۴ اردیبهشت ۱۳۸۹ -

Reza Ebrahimi Atani

Electrical Engineering Department Final Defense session of The PhD Thesis 396 Design and Implementation of a Stream Cipher for Mobile Communication Abstract: Stream ciphers are fast cryptographic primitives to provide confidentiality of electronically transmitted data. They can be very suitable in environments with restricted resources, such as mobile devices or embedded systems. Practical examples are cell phones, RFID transponders, smart cards or devices in sensor networks. Besides efficiency, security is the most important property of a stream cipher. In the thesis first we address the classical methods in design and analysis of stream ciphers. The third section of this thesis specifies Alamout, a new hardware oriented synchronous stream cipher with an associated authentication mechanism. The design is small in hardware and it targets environments with limited resources. Alamout supports key size of 80 bits and IV size of 128 bits. The Alamout cipher has been designed to produce keystream with guaranteed randomness properties. Simulation with ENT randomness test program confirms randomness of output keystream with very good results The threat of DPA attacks is of crucial importance when designing cryptographic hardware. The forth chapter of the thesis discusses the DPA-resistant implementation of two eSTREAM finalists using SABL and WDDL logic styles. Particularly, two Feedback Shift Register (FSR) based stream ciphers, Grain v.1 and Trivium are designed in both BSim3 130nm and typical 350nm technologies and simulated by HSpice software. Circuit simulations and statistical power analysis show that DPA resistivity of SABL implementation of both stream ciphers has a major improvement. In the next chapter of this thesis a compact implementation of the SBox of Pomaranch stream cipher using composite field arithmetic in 12GF((23)3)'> is presented. It describes a systematic exploration of different choices for the irreducible polynomials that generate the extension fields. It also examines all possible transformation matrices that map one field representation to another. We evaluated the optimal candidates using Xilinx and Altera FPGA implementations. And finally in the last section of the thesis two public key cryptography protocols are introduced: Public key cryptography based on semi modules over quotient semi rings and also Public Key Cryptography using Semi-Group Actions and Semi-Rings. Student: Reza Ebrahimi Atani Supervisor: Dr. Sattar Mirzakuchaki Advisor: Dr. Shahabaddin Ebrahimi Atani Referees: Dr. Ahmadian; Dr. Raeesei; Dr. Sadr; Dr Shokouhi; Dr. Shahhosseini Defense date: 12th of May by 8 AM Auditorium of Electrical Engineering Department

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سه شنبه ۳۱ فروردین ۱۳۸۹ -

Farhad Haghjoo

Electrical Eng. Departement PhD Thesis Defense Session 396 Online Detection and Location of Partial Discharges in Cable Networks Abstract Partial Discharge (PD) is the most important phenomenon in deterioration of XLPE cable insulation. Then, the PD detection and especially online PD monitoring is an important idea for MV or HV cable networks protection, where are developed recently. Of course, the proper PD detection needs suitable noise reduction procedure and an appropriate algorithm for diagnosis of multi and simultaneous PDs that are generated by not only different defects along the protected cable, but also adjacent equipments. Moreover, the PD signals should be obtained without distortion due to intermediate equipments. High frequency inductive and capacitive electrical sensors which are used to current and voltage PD pulses, respectively, have related transfer functions; therefore, the output of any sensor is frequency dependent that applies a distortion on the primary signals. In this thesis: 1. First, a comprehensive lumped model for PD is proposed which is able to show and justify the PD treatment due to the changing of not only the voltage amplitude, the power frequency and the temperature, but also the shape, size and the location of the cavity inside the cable insulation. This model can also consider the electrical field distortion in adjacent the cavity. Based on this model, a novel differential model is proposed to show the transient behavior of non-homogenous and distorted electrical field due to multi cavities in the cable insulation. 2. Second, the frequency dependent and distributed model of the XLPE cables is analyzed. The attenuation and distortion of PD signals, when travel along the cable, are studied; and a novel algorithm is proposed to reconstruct PD current signals in the related defect point. The proposed algorithm is based on travelling wave theory and is applicable to simultaneous defects. 3. Third, the sensors distortion is analyzed and a new method is introduced to compensate the related distortion in online conditions. Compensation is done using the inverse of sensor transfer function, and therefore, the PD signals can be obtained as the similar to the original waveform. The performance of the proposed method is approved, experimentally. 4. A novel filtering procedure for extraction of the PD signals through the ambient noises, as the biggest problem in online PD detection, is proposed as the fourth step. A new wavelet transform based filter is constructed to decompose any primary non-stationary signal in any arbitrary frequency spectrum, without need to use previous approximate components with very low calculation burden (less than 50%). Also, an online adaptive noise reduction procedure is developed that is able to follow the ambient noise levels and adjust the threshold levels in any frequency spectrum, separately. Moreover, a mixing procedure to reconstruct broadband filtered components is proposed. 5. As the final and the main step, an algorithm for online location of simultaneous PDs is proposed, based on travelling wave theory. This algorithm uses the pulses train (generated by defects) along the protected cable. Both elimination of the fundamental frequency component and discrimination of PD pulses with reverse polarities are done using Mathematical Morphology idea. The simulation results show the high accuracy (more than 99%) for multi PDs locations even in noisy conditions. Student: Farhad Haghjoo Supervisor: Dr. Sayyed Mohammad Shahrtash Reviewers : Prof. H. Mohseni, Prof. M. Vakilian, Dr. A. Gholami, Dr. H. Heydari, Dr. M. H. Mahdieh Date: Sunday 2 May 2010 Place: Electrical Eng. Dep./ Seminar Room

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سه شنبه ۱۸ اسفند ۱۳۸۸ -

Yasser Baleghi Damavandi

Electrical Department PhD Thesis Defense Session Design and Simulation of Evolvable Hardware and Its Communication Protocol Abstract A Permanent physical fault in the communication line between two agents can usually lead to failure. In this thesis a kind of self organized communication is proposed to defeat the problem. In this case, the communication protocol that emerges between the agents can adapt itself to environmental changes like physical faults. To evolve such an emergent communication, agents should have knowledge representation language, be purposeful and rational. Evolvable hardware agents own all of the mentioned properties. Evolvable hardware is a concept that aims the use of evolutionary algorithms in the hardware design. In this thesis, the mentioned agents are simulated and implemented to emerge a self organized protocol which is expected to be fault tolerant. The simulations show good results in gate level evolution of a fault tolerant serial adder. However, the idea of hierarchical level evolution is proposed in this dissertation and tested in another experiment to defeat the shortcomings of gate level and functional level evolution in the application of transferring video streams. Using hierarchical level evolution in genetic algorithm, stalling effect is removed to some extent and a self organized, fault tolerant communication is emerged to transmit the images between evolvable hardware agents. In this system, redundancies are added autonomously to hardware and consequently to the communication protocol. The agents emerged variant mappings to tolerate different faults at the expense of more evolution time. Student: Yasser Baleghi Damavandi Supervisor: Dr. Karim Mohammadi Advisor: Dr. Caro Lucas Reviewers: Dr.Sahebzamani, Dr.Taheri, Dr.Shokouhi,Dr. Sadr, Dr. ShahHosseini Date : 2010/03/07 Time: 16:30 Place: Seminar Conference Room

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سه شنبه ۱۸ اسفند ۱۳۸۸ -

Ali Abdolali

Iran University of Science and Technology Department of Electrical Engineering DEFENCE SESSION OF Ph.D. Dissertation 396 Radar Cross Section Reduction by Metamaterials Metamaterials have been recently the subject of intensive research. We investigate the applicability of nondispersive and dispersive metamaterials for the reduction (or increasing) of the radar cross section. The addition theorems for the multilayered structures are used for the EM wave analysis. As a result, a new class of radar absorbing materials (RAM) are obtained by the application of DPS,DNG, MNG,ENG metamaterials in the ultra wide band and a wide interval of incident angles and for arbitrary polarization. Exact mathematical formulation for the design of new reflectionless structures and their notable applications are derived. We prove several interesting theorems for the reflection and transmission coefficients for the planar multilayered metamaterial structures. These theorems reveal some type of duality between DPS and DNG media and also between ENG and MNG media. Then we introduce a new class of materials called double zero metamaterials (DZR) and investigate the applications of double zero (DZR) metamaterials as radar absorbing materials. In addition several new applications for multilayer metamaterial structures are obtained, like radar cross section reduction, invisibility, directive scattering, metamaterial hat, etc. Finally, propagation, reflection and transmission of electromagnetic waves in isotropic and anisotropic multilayer structures are investigated. BY: Ali Abdolali Supervisor: Dr. Homayoon Oraizi Jury members: Dr. Farokh Hojjat Kashani Dr. Ahmad Cheldavi Dr. Ahad Tavakoli Dr. Mohammad Hakkak Dr. Asghar Keshtkar March 2010 Date : 2010/MARCH/13 Saturday Conference Room- Department of Electrical Engineering

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چهارشنبه ۵ اسفند ۱۳۸۸ -

Masoud Esmaili

Iran University of Science and Technology Electrical Engineering Department Ph.D. Thesis Defense 269 Congestion Management in Restructured Power Systems Considering Voltage and Angle Stability Abstract Congestion management in power markets plays a vital role in both the operation and the planning of transmission networks. In order to prevent blackouts, which are recently occurred in some deregulated power markets, it is essential to incorporate power system security into power market solutions. In this thesis, some novel methods are proposed to perform congestion management considering voltage and transient stability as the most prevalent stability problems. Using the effect of each individual generator or demand on the voltage stability margin or loading margin, a single-objective optimization problem is proposed for congestion management. The bids received from generation and demand sides are so adjusted that a sufficient level of voltage security is established after congestion management. Also, using this concept, the bids from participating parties in the congestion market are penalized according to their effect on the transient stability; then, congestion management is so done that an enough level of transient stability margin is retained. In addition, a multi-objective congestion management framework based on the e -constraint method is proposed in order to simultaneously establish an adequate level of voltage and transient stability margins while keeping the congestion management cost at a minimum value. Moreover, a new version of the e -constraint method is introduced; it results in a higher preference for Pareto optimal solutions because of considering the relative importance of objective functions in Pareto optimal solutions. In the next stage, the proposed methods for congestion management considering voltage and transient stability are implemented in the stochastic framework using Monte-Carlo Simulation in order to get more realistic solutions compared with deterministic solutions. All proposed methods are tested on a well-known test system and obtained results are thoroughly discussed and compared with those of previous methods. By: Masoud Esmaili Supervisor: Dr. Heidarali Shayanfar Advisor: Dr. Nima Amjady Reviewers: Dr. S. Jadid, Dr. M. Kalantar, Mr. A. Kazemi, Dr. M. ParsaMoghadam, Dr. A. Rahimikiyan Date: Saturday, 1388.12.15 Time: 7:30 AM – 10:00 AM Place: Seminar saloon, Electrical Engineering Department

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سه شنبه ۲۷ بهمن ۱۳۸۸ -

Vahid Vahidinasab

Electrical Engineering Department Ph.D. Thesis Defense Optimal Bidding Strategy of Power Producers in Joint Energy and Spinning Reserve Markets Abstract In competitive electricity markets, electric power producers compete through energy and ancillary services and therefore, in order to maximize their profit , they need to make decisions on energy and ancillary services bidding, arbitraging, and risk management. In this thesis, new methods are developed to guide power producers in day-ahead market. At first, a new method for forecasting based bidding strategy is presented which applies Bayesian neural networks to forecast electricity prices using published historical data and the bidding strategy index as input. The forecasted price is then used to develop the optimal bidding strategy for two types of participants, i.e. risk averse and risk seeker. Besides, influence of suppliers’ emission of pollutants and transmission lines congestion on market participant bidding behavior is analyzed in the framework of game theory to assess the equilibrium methods for price makers’ bidding strategy. In an attempt to achieve a model that covers different type of requirements for various power producers, a new model for the static self-scheduling based bidding strategy in the joint energy and reserve market is proposed. The proposed model, not only considers all the operational constraints of generating units for supplying energy and reserves, but also incorporates line flow constraints to ensure network security. Moreover, the uncertainties of electricity prices as well as forced outage of generating units and transmission lines are also incorporated to the proposed model. A new multiobjective viewpoint which deals with the objective functions related to emission of pollutants and risk is also proposed which includes both environmental and techno-economical aspects of generation companies. Several case studies with different complexity are simulated on two IEEE test systems to test the proposed models. The results indicate the effectiveness and capability of the proposed techniques. By: Vahid Vahidinasab Supervisor: Dr. Shahram Jadid Date: Saturday, 27 Feb. 2010, 7:30 a.m. Electrical Engineering Department, Seminar Room

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سه شنبه ۲۷ بهمن ۱۳۸۸ -

Behrooz Rezaie

Electrical Engineering Department PhD Thesis Defense Session 396 Global Stability Analysis and Controlling Chaotic Nonlinear Behaviors in High-Speed Communication Networks Abstract In this thesis, we carry out global stability analysis, bifurcation study, and control design for a nonlinear delayed model of congestion control system in computer communication networks namely Kelly model. The model covers the system dynamics for a network including arbitrary number of sources and links. First, sufficient conditions for global stability of the system in steady state are derived by considering time-variability of some parameters such as link capacities and time-delays in Kelly model. Then, Hopf bifurcation analysis is studied for Kelly model of general networks with a delay parameter. By choosing the gain vector and the delay parameters as the bifurcation parameters, the conditions and properties of Hopf bifurcation are obtained. In the next part, Hopf bifurcation control is studied to postpone the onset of the bifurcation and thereby to avoid nonlinear dynamical behaviors. First, we propose a dynamic delayed feedback control scheme which consists of a combination of the delayed control feedback method and a washout filter. Then, an adaptive control method is proposed for tuning the control parameters such that the closed loop system copes with the effect of changes in the system parameters by updating the control gains. When the parameters of the system are not known, the problem can be solved by adding a parameter identification algorithm to the control scheme. Finally, the proposed control methods are numerically studied using simulation results for different scenarios. The simulation results show that the proposed control methods can effectively enhance the system behavior. Student: Behrooz Rezaie Supervisor: Dr. Jahed Motlagh Consultant: Dr. Analoui, Dr. Khorsandi Refrees: Dr. Poshtan, Dr. Johari Majd, Dr. Haeri, Dr. Farokhi, Dr. Mohammad Shahri Date: Momnday 22 Feb 2010 Place: Classroom No. 101, Electrical Engineering department

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چهارشنبه ۷ بهمن ۱۳۸۸ -

Morteza Kazerooni

Iran University of Science and Technology Electrical Engineering Faculty Defense Session of PhD Thesis ANALYSIS AND MODELING OF EBG AND DGS STRUCTURES AND THEIR APPLICATION IN MICROSTRIP WIDEBAND ANTENNA OPTIMUM DESIGN Abstract In this thesis some electromagnetic bandgap(EBG) structures such as defected microstrip structure(DMS) , cacadesd defected microstrip structure(CDMS) and defected ground structure(DGS) are analyzed and modeled by some new approaches. The physical dimensions and how current circulations are used for modeling. The frequency responses of proposed models show good agreement with full wave simulations. To verify these models, the comparison in response not only has been considered in amplitude but also in phase of all S-parameters of proposed model and full wave analysis. Also some modeling results are validated simultaneously by comparison with simulations of the structures and experimental results. Throughout the thesis many new applications for DMS, CDMS and DGS such as all types filtering, noise and harmonic suppressing, improvement input impedance of narrow and broad band microstrip antenna, very compact filter called island DMS (I-DMS) with more than 900% compactness, millimeter filter design and so on are introduced. Also to model these structures, some useful formulas are extracted to obtain the lumped element parameters. Also the error diagrams are presented for better comparison. By: Morteza Kazerooni Supervisor : Dr. Ahmad Cheldavi Advisor : Dr. Mahmoud Kamarei Control by: Dr. J. Rashed Mohassel, Dr. A. A. Abdipour, Dr. H. Oraizi, Dr. M. Tayarani, Dr. N. Komijani Defense date: Wednesday, 14/11/1388 at 18:00 O'clock Place: Seminar Room of Electrical Faculty

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چهارشنبه ۷ بهمن ۱۳۸۸ -

Alireza Saberkari

Electrical Engineering Department Ph.D. Thesis Defense Design and Simulation of a Single-Chip CMOS RF Transmitter for Wireless Communications with DCS1800 Standard Abstract In recent years, demand for wireless communication systems has been increased, tremendously and many types of mobile communication devices have been introduced in which transceivers are used as a main hardware. There are some significant challenges to use CMOS technology in designing radio frequency RF circuits that require finding new techniques at both the circuit and architectural level. On the other hand to prolong the battery life, low power and low voltage RF circuits should be utilized. In this thesis, design of the IF and RF mixers and also power control block of a transmitter is done, while enabling single chip integration, high performance, and also low voltage and low power operation. In this research a low voltage IF mixer with inherent harmonic rejection is designed by changing the structure of the mixer and also utilizing the harmonic rejection logic. Also, a low voltage highly linear image rejection RF mixer is designed. In addition, a new method based on the current steering approach is used to connect the IF and RF mixers that helps to improve the system linearity even at low supply voltage. The transmitter architecture based on these mixers is presented while provides single chip integration and high performance in CMOS technology. Also, a fast transient and high regulation low-dropout (LDO) regulator based on the current feedback amplifier is designed to control the output power of RF switching power amplifier according to the timing mask requirement of DCS1800 standard and also provide the supply voltage of mixers for rejecting their power supply ripple. The proposed circuits of IF and RF mixers and also LDO regulator are designed and simulated by Cadence in AMS 0.35 µ m CMOS process. The comparisons between performance of the proposed circuits with the most recently published works show better performance of the proposed circuits while consume less power. Student: Alireza Saberkari Supervisor: Dr. Baradaran Shokouhi Advisor: Dr. Abrishamifar Referees: Dr. Azhari; Dr. Mirzakouchaki; Dr. Sadr; Dr. Afzali-Kousha; Dr. Hashemipour Date: Wednesday 3/2/2010 Time: 10:30 AM Class No. 206, Faculty of Electrical Engineering

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سه شنبه ۲۹ دی ۱۳۸۸ -

Ahmad Afifi

Iran University of Science and Technology Electrical Engineering Faculty Defense Session of PhD Thesis Design and Simulation of neuromorphic networks in CMOS/Nano hybrids Abstract During the past several decades, the semiconductor industry has integrated more than two billion transistors on a single chip. However, this industry no longer relies on only transistor scaling for higher computing performance. It has been projected that in 2016 most CMOS circuits will be manufactured with 22 nm process. The CMOS circuits will have a large number of defects and can provide for the continuation of the Moore's Law only for the next few years . Especially when the transistor goes below sub-micron, the original deterministic circuits will start having probabilistic characteristics. Hence, it would be challenging to map traditional Von-Neuman computational models onto probabilistic circuits, suggesting a need for fault-tolerant computational algorithms. Biologically inspired algorithms, or spiking neural networks (SNNs), exhibit a remarkable match to the nano-scale electronics, besides having great fault-tolerance ability. Research on the potential mapping of the SNNs onto a recently developed technology called hybrid CMOS/Nano circuits (such as CMOL) provides useful insight into the development of neuromorphic architectures that has a significant impact on the Intelligent Signal Processing (ISP) and the future of the nano-computer industry. In CMOL two-terminal nanodevices are arranged into a single layer as an add-on to a CMOS sub-system. In this thesis, we investigated asynchronous implementations of adaptive SNNs on different CMOS/Nano platforms, including molecular and memristive based crossbars. We provide spike-timing dependent plasticity (STDP) rule by modifying Integrate-and-Fire (I&F) type neurons in a biologically inspired and plausible approach. We show that the STDP rule can be provided using a crossbar array combined with neurons that asynchronously generate spikes of a given shape, similar to biological action potentials, and send them to both forward and backward directions along their axon and dendrites, simultaneously. The method eliminates storage circuits per synapse and so it can be mapped to crossbar-based CMOS/Nano hybrids rather easily. The obtained STDP learning function is exactly that of the STDP learning function obtained from neurophysiological experiments on real synapses. In this thesis, we draw the conclusion that the STDP rule in memristive based (analog) crossbars exhibit better performance in comparison to molecular (binary) crossbars. We also highlighted a number of options for cost-effective computational resources and power consumption. The simulated results show that the size and complexity of the proposed architecture have been improved in order of {O(N2)-O(N)} (where N is the network size) in comparison to regular CMOS based adaptive SNNs implementations. Furthermore, the performance of the rule as spike-timing correlation learning of synchrony detection and character recognition in winner-take-all (WTA) networks are demonstrated as case examples. By: Ahmad Afifi Supervisor : Dr. Ahmad Ayatollahi Advisor : Dr. Farshid Raissi Control by: Dr. M. Teshnehlab, Dr. H. Shamsi, Dr. A. Erfanian, Dr. S. Mirzakouchaki, Dr. S.A. Abrishamifar Defense date: Saturday, 10/11/1388 at 13:30 Oclock Place: Seminar Room of Electrical Faculty