Journal Papers (19) Details

1 Indoor Non-directed Optical Wireless Communications - Optimization of the Lambertian Order , Z. Ghassemlooy1,*, D. Wu1, M. A. Khalighi2, and X. Tang3For an indoor non-directed line of sight optical wireless communication (NLOS-OWC) system we investigate the optimized Lambertian order (OLO) of light-emitting diodes (LEDs). We firstly derive an expression for the OLO from a conventional Lambertian LED model. Then, we analyze the indoor multi-cell NLOS-OWC channel characteristics including the optical power distribution and the multipath time dispersion for two cases of one-cell and four-cell configurations. Furthermore, we estimate the transmission bandwidth by simulating the channel frequency response. Numerical results presented show that, by using OLO a significant improvement of the transmission bandwidth can be achieved for an indoor NLOS-OWC system, in particular, for multi-cell configurations. |
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2 3D Hand Motion Evaluation Using HMM, A.Safaei1,*and M.Jahed2Gesture and motion recognition are needed for a variety of applications. The use of human hand motions as a natural interface tool has motivated researchers to conduct research in the modeling, analysis and recognition of various hand movements. In particular, human-computer intelligent interaction has been a focus of research in vision-based gesture recognition. In this work, we introduce a 3-D hand model recognition method that offers flexible and elaborate representation of hand motion. We used landmark points on the tips and joints of the fingers and calculated the 3-D coordinates of these points through a stereo vision system followed by a Hidden Markov Model (HMM) to recognize hand motions. Experimentally, in an effort to evaluate the formation of hand gestures similar to those used in rehabilitation sessions, we studied three evolving motions. Given the natural hand features and uncontrolled environment, we were able to classify and differentiate unnatural slowness or rapidness in the performance of such motions, ranging from 45% to 93%. |
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3 High Speed Delay-Locked Loop for Multiple Clock Phase Generation, A. Ghanbari1,*,A. Sadr2, andM. Nikoo3In this paper, a high speed delay-locked loop (DLL) architecture ispresented which can be employed in high frequency applications. In order to design the new architecture, a new mixed structure is presented for phase detector (PD) and charge pump (CP) which canbe triggered by double edges of the input signals. In addition, the blind zone is removed due to the elimination of reset signal. Therefore, operating frequency of the whole system isimproved which canbe mentioned as notable advantage of the proposed DLL. To obtain more accurate phases at the output signal, a new delay cell is introduced which is controlled by a single voltage. This control voltage, through equalizing the rise and fall time, regulate duty cycle of output clock. These features along with simplicity and low power consumption qualify the proposed architecture to be widely used in high speed systems. For better realization of the designed circuit’s behavior, simulation results are presented based on TSMC 0.35µm CMOS technology and 3.3-V power supply for a type II filter which demonstrate accuracy and perfect performance of this work. |
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4 Rateless Coding over Wireless Relay Networks Using Amplify/Decode and Forward Relays, M. Shirvanimoghaddam1,*and S. Movassaghi2In this paper two different rateless transmissionschemes are developed. In the proposed scheme, relay node candecode and forward the message to the destination if they areable to decode it, or amplify and forward the message to thedestination. Based on the analysis and simulation resultsprovided in this paper, the proposed method has bettertransmission time than the scheme which only the relay nodesthat have already decoded the message participate in the secondphase. Due to the simplicity of the amplify and forwardtransmission, adding this feature to the network can result inbetter performance without any additional complexity. |
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5 Driving/Regeneration and Stability Enhancement of a 4WD Hybrid Vehicles Using Multi-Stage Fuzzy Controller, S. M. Sharouni1,*, P. Naderi2,and N. Taghizadegan3In front wheels driven vehicles, fuel economy can be obtained by summing torques applied to rear wheels. On the other hand, unequal torques applied to rear wheels provides enhanced safety. In this paper, a model with seven degrees of freedom is considered for the vehicle body. Thereafter, power-train subsystems are modeled. Considering an electrical machine on each rear wheel, a fuzzy controller is designed for each driving, braking, and stability conditions. Another fuzzy controller recognizes the vehicle requirements between the driving/regeneration and stability modes. The simulations performed in MATLAB/Simulink environment show that the proposed structure can effectively enhance vehicle performance in different modes. |
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6 RTDGPS Implementation by Online Prediction of GPS Position Components Error Using GA-ANN Model, M.H. Refan1,* andA. Dameshghi2If both Reference Station (RS) and navigational device in Differential Global Positioning System (DGPS) receive signals from the same satellite, RS Position Components Error (RPCE) can be used to compensate for navigational device error. This research used hybrid method for RPCE prediction which was collected by a low-cost GPS receiver. It is a combination of Genetic Algorithm (GA) computing and Artificial Neural Network (ANN). GA was used for weight optimization and RS and Mobile Station (MS) were implemented by the software. The experimental results demonstrated which GA-ANN had great approximation ability and suitability in prediction; GA-ANNs prediction' RMS errors were less than 0.12 m. The simulation results with real data showed that position components' RMS errors in MS were less than 0.51 m after RPCE prediction. |
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7 The Sine-Cosine Wavelet and Its Application in the Optimal Control of Nonlinear Systems with Constraint , R. Hajmohammadi1, H. NasiriSoloklo2,*, and M.M. Farsangi3In this paper, an optimal control of quadratic performance index with nonlinear constrained is presented. The sine-cosine wavelet operational matrix of integration and product matrix are introduced and applied to reduce nonlinear differential equations to the nonlinear algebraic equations. Then, the Newton-Raphson method is used for solving these sets of algebraic equations. To present ability of the proposed method, two classes, first order system and second order system, are considered. The obtained results show that the proposed method offers improved performance |
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8 Fuzzy Logic Based Life Estimation of PWM Driven Induction Motors , T. G. Arora, M. V. Aware, and D. R. Tutakne Pulse-width modulated (PWM) adjustable frequency drives (AFDs) are extensively used in industries for control of induction motors. It has led to significant advantages in terms of the performance, size, and efficiency but the output voltage waveform no longer remains sinusoidal. Hence, overshoots, high rate of rise, harmonics and transients are observed in the voltage wave. They increase voltage and thermal stresses; resulting into accelerated insulation aging. This paper presents the application of fuzzy logic to life estimation of PWM driven induction motors. Insulation stress parameters are experimentally computed for wide range of switching frequency and used in fuzzy logic based life estimation algorithms. The results obtained with the fuzzy expert system show a performance approaching that attainable for the life model based on the inverse power law. |
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9 A High Efficiency Low-Voltage Soft Switching DC–DC Converter for Portable Applications, P. Amiri1,* and M. Sharafi1This paper presents a novel control method to improve the efficiency of low-voltage DC-DC converters at light loads. Pulse Width Modulation (PWM) converters have poor efficiencies at light loads, while pulse frequency modulation (PFM) control is more efficient for the same cases. Switching losses constitute a major portion of the total power loss at light loads. To decrease the switching losses and to increase efficiency, converters based on soft-switching are utilized. This paper presents the design of a soft-switching DC-DC buck converter in a 90-nm CMOS technology. Simulation results by HSPICE shows a 21 mV output ripple on a 0.5 V output voltage for an input voltage of 1.4 V. Finally, the efficiency of 95% at a load current of 50 mA having 74 mA of current ripple is achievable. |
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10 Mitigation of Switching Harmonics in Shunt Active Power Filter Based on Variable Structure Control Approach , S. Mohammadi1,*, H. R. Mosaddegh2, and M.Yousefian3This paper presents a novel control approach used in shunt active power filter based on variable structure control combined with Random PWM technique (RVSC) that provides robust, fast, and more favorable performance for active power filter. This control strategy is compared with two other strategies to show the effectiveness of the introduced methods; pulse width modulated proportional-integral control (PIC), and Random Pulse Width Modulated proportional-integral control (RPIC). The simulation results with and without the shunt active power filter in the system are presented and analyzed. The simulation results show that the RVSC controller has a better performance than other control strategies, allowing compensation of reactive power, reducing high frequency harmonics thus overcoming the problem of electromagnetic interference (EMI), reducing dc current injection below the limit specified in IEEE-1547 standard, and also reducing the harmonic level below the limit specified in IEEE-519 standard. |
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11 An Improved Time-Reversal-Based Target Localization for Through-Wall Microwave Imaging , A. B. Gorji1,* and B. Zakeri1Recently, time reversal (TR) method, due to its high functionality in heterogeneous media has been widely employed in microwave imaging (MI) applications. One of the applications turning into a great interest is through-wall microwave imaging (TWMI). In this paper, TR method is applied to detect and localize a target obscured by a brick wall using a numerically generated data. Regarding this, it is shown that when the signals acquired by a set of receivers are time reversed and backpropagated to the target-embedded media, finding the optimum time frame which the constituted image represents a true location of the target becomes infeasible. Indeed, there are situations pertinent to the target distance ratio that the previously-used Maximum field method and Entropy-based methods may fail to select the optimum time frame. As a result, an improved method which is based on initial reflection from the target is proposed. According to different target locations described in this research, the results show this method prevails over the shortcomings of the former methods. |
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12 Automatic Sleep Stages Detection Based on EEG Signals Using Combination of Classifiers, R. Kianzad1,* and H. Montazery Kordy1Sleep stages classification is one of the most important methods for diagnosis in psychiatry and neurology. In this paper, a combination of three kinds of classifiers are proposed which classify the EEG signal into five sleep stages including Awake, N-REM (non-rapid eye movement) stage 1, N-REM stage 2, N-REM stage 3 and 4 (also called Slow Wave Sleep), and REM. Twenty-five all night recordings from Physionet database are used in this study. EEG signals were decomposed into the frequency sub-bands using wavelet packet tree (WPT) and a set of statistical features was extracted from the sub-bands to represent the distribution of wavelet coefficients. Then, these statistical features are used as the input to three different classifiers: (1) Logistic Linear classifier, (2) Gaussian classifier and (3) Radial Basis Function classifier. As the results show, each classifier has its own characteristics. It detects particular stages with high accuracy but, on the other hand, it has not enough success to detect the others. To overcome this problem, we tried the majority vote combination method to combine the outputs of these base classifiers to have a rather good success in detecting all sleep stages. The highest classification accuracy is obtained for Slow Wave Sleep as 81.68% in addition to the lowest classification accuracy of 43.68% for N-REM stage 1. The overall accuracy is 70%. |
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13 A Comparison of Different Control Design Methods for the Linearized CSTR Temperature Model, A. D. Shakib JooContinuous Stirred Tank Reactor (CSTR) has particular importance in chemical industry. CSTR has usually a nonlinear behavior which makes it difficult to control. The reactor has two parameters: the concentration and temperature of mixture both of which are uncertain. This case of CSTR has large disturbance in domain. In order for disturbance rejection, a controller has to be designed. In this paper, for modeling the CSTR system, first, the PI and PID controllers are designed by two methods, the automatic with Matlab Simulink and Ziegler-Nichols (Z-N) method. Then, reset control is replaced and tuned by their parameters. The main aim of this work is to compare the output responses (temperatures) of controllers with each other. In this work a reset controller is proposed for the thermal reactor model. Due to complexity of control of this plant, different design methods should be evaluated for disturbance rejection and input tracking. The results show that the reset controller is better than the PI controller in disturbance elimination. Finally, controller’s output response is investigated for improvement in disturbance rejection and change in the set-point. |
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14 THD Analysis in Closed-Loop Analog PWM Class-D Amplifiers, P. Amiri, M. Kohestani , M. SeiforiIn this paper, we investigate the parameters affecting Total Harmonic Distortion (THD) and Power Supply Rejection Ratio (PSRR) in PWM Class D Amplifiers (CDAs) on the basis of linear models with feedback. From our mathematical analysis, we show that the THD of a PWM Class D amplifier with feedback can be improved by increasing the gain of the integrator through adding another amplifier at the output of the integrator. We also show that the THD can be further improved by means of two cascaded amplifiers with a single pole. We verify our analysis by means of PSPICE simulations. Simulation results show that the THD of the gain boosting and the two cascaded amplifiers with a single pole CDAs can be improved by as much as 1.4 times and 2 times, respectively. |
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15 A New Closed-form Mathematical Approach to Achieve Minimum Phase Noise in Frequency Synthesizers, B. Zakeri, S. Samadi, M. ZahabiThe aim of this paper is to minimize output phase noise for the pure signal synthesis in the frequency synthesizers. For this purpose, first, an exact mathematical model of phase locked loop (PLL) based frequency synthesizer is described and analyzed. Then, an exact closed-form formula in terms of synthesizer bandwidth and total output phase noise is extracted. Based on this formula, the phase noise diagram as a function of bandwidth is plotted. From the analysis and simulation results, it is observed that the synthesizer has a minimum phase noise at a particular bandwidth. |
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16 Control strategies for performance assessment of an autonomous wind energy conversion system, M.R. HojatyDana, M.R. AlizadehPahlavaniRenewable energy sources like wind, sun, and hydro are considered as a reliable alternative to the traditional energy sources such as oil, natural gas, or coal. This paper describes modeling and simulations to determine a method for the power performance evaluation of autonomous wind turbine system. A speed control regulator is utilized to control the DC bus voltage. The inverter gate’s signals are generated by decoding the Hall effect signals of the motor. The three-phase output of the inverter is applied to the permanent magnet synchronous generator (PMSG) block's stator windings. This study shows that the use of resonant controllers ensures the stability of the three-phase source supplying the load which may be unbalanced and subjected to abrupt variations. It also shows that use of PI controller ensures the regulation of DC bus to a reference voltage. |
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17 DALD: Distributed Asynchronous Local Decontamination Algorithm in Arbitrary Graphs, M. Rahmaninia, E. Bigdeli, M. ZakerNetwork environments always can be invaded by intruder agents. In networks where nodes are performing some computations, intruder agents might contaminate some nodes. Therefore, problem of decontaminating a network infected by intruder agents is one of the major problems in these networks. In this paper, we present a distributed asynchronous local algorithm for decontaminating a network. In most of prior algorithms, there is a coordinator agent that starts from a node and decontaminates the network. Since this procedure is handled by an agent and in centralized mode decontamination algorithm is very slow. In our algorithm, the network is decomposed to some clusters and a coordinator is advocated to each cluster. Therefore, there is more than one coordinator that each of them starts from different nodes in the network and decontaminates network, independently. In this case, network is decontaminated faster. In addition, in previous works the upper bound of the number of moves and the number of cleaner agents required to decontaminate network are given only for networks with special structures such as ring or tori while our algorithm establishes these upper bounds on networks with arbitrary structure. |
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18 Optimum Design of a SRM Using FEM and PSO, M. Ranjkesh, E. FallahChoolabi * , M. PourjafariNowadays the use of the Switched Reluctance Motors (SRMs) has been considerably increased in various home and industrial applications. Despite of many advantages of this type of motors, such as simple structure, low cost, and high reliability, the main disadvantage of them is the generation of high torque pulsation. This paper presents a novel method to optimize a typical SRM such that the torque ripple reaches its minimum value. Meanwhile, the torque average and the motor efficiency become maximum. It is shown that the pole width to the pole pitch ratio, for both stator and rotor poles, have a great impact on the torque ripple and torque average. Finite Element Method (FEM) is used to obtain the torque ripple, the torque average and the motor efficiency for a large number of ratios. A functional relationship is developed between the input and the output parameters. Normalized summation of the torque ripple minus the torque average and the efficiency is considered to be the cost function, which must be minimized. Then, the Particle Swarm Optimization (PSO) is used to find the optimum ratio of pole width to pole pitch, for both stator and rotor. The optimum design is verified by FEM. |
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19 The Application of Multi-Layer Artificial Neural Networks in Speckle Reduction (Methodology), M.R. Pishgoo, M.R.N Avanaki, R. EbrahimpourOptical Coherence Tomography (OCT) uses the spatial and temporal coherence properties of optical waves backscattered from a tissue sample to form an image. An inherent characteristic of coherent imaging is the presence of speckle noise. In this study we use a new ensemble framework which is a combination of several Multi-Layer Perceptron (MLP) neural networks to denoise OCT images. The noise is modeled using Rayleigh distribution with the noise parameter, sigma, estimated by the ensemble framework. The input to the framework is a set of intensity and wavelet statistical features computed from the input image, and the output is the estimated sigma value for the noise model. In this article the methodology of this technique is explained. |