مهندسی برق مجلسی
سال:1387 | دوره:2 | شماره:2 |تعداد مقالات:18

This paper presents a square lattice of two-dimensional photonic crystal in the design of NOT and XOR logic gates. The important characteristic of this method is that the one structure allows implementation of two types of logic gate. The structure consists of two inputs and one output; thus, whenever it is used as a NOT gate, one of the entrances acts as a controller for the input. The Plane Wave Expansion (PWE) method is used to calculate the frequency band structure of the proposed lattice. The Finite Difference Time Domain (FDTD) method is used to calculate the optical power distribution in waveguide paths. The smaller size and simple structure of the design are advantages which make the proposed structure suitable for using in optical integrated circuits. In addition, the optical power transmitted to the output in "0" logic state is very close to zero.

In this paper, dynamic comparators structure, by employing two methods for power consumption reduction with applications in low-power high-speed analog-to-digital converters, have been presented. The proposed comparators have low consumption thanks to power reduction methods. They have the ability for adjusting the offset. The comparators consume 14. 3 and 24 μ W at 100 MHz, which is equal to 3. 7 and 11. 8 fJ. The comparators are designed and simulated in 180 nm CMOS. Layouts occupy 210 and 240 μ m2, respectively.

The multi machine power system, with the interconnection of number of generators and loads, has the dynamic stability as the important factor for maintaining the step with respect to the generators connected to it. The stability of individual machine, as well as, the stability of a generator with the other generators are more important terms. The supply of the damping torque required for getting the desired condition of stability enhancement is done by the power system stabilizer. In this paper a new method is proposed for stability enhancement of a three machine nine bus system by using the coordinated application of the unified power flow controller and the power system stabilizer designed by using the Firefly algorithm. The improved stability performance of the tested multi machine system was compared with Genetic search algorithm approach without and with the application of the unified power flow controller. From the pseudo spectrum analysis, it is observed that the better improvement of the stability of the multi machine system is achieved by using the proposed method. From the step responses it can be deduced that the relative variations of inter machine states with unified power flow controller and firefly-based power system stabilizer are settled at a faster rate. The contingency analysis is performed to consider the non-linearity problem. The responses of the system with unified power flow controller and firefly based power system stabilizer are settled at a faster rate in the normal case, as well as, in the contingency cases, respectively.

The development of miniature antennas is the key requirement for radio frequency identification applications in various fields. In this paper, a new design of a compact metamaterial microstrip antenna based CSRR resonators is proposed. The proposed metamaterial antenna has a simple structure. It is formed by a rectangular patch embedded a T-shaped slot in one side, and a two metamaterial unit cells formed by CSRR etched from the ground plane in the other side. The designed antenna is printed on an epoxy Frame Resistant 4 substrate by using CST Microwave Studio. It operates at two RFID bands around 5. 8GHz and 2. 45GHz. The designed antenna is fabricated by using an LPKF machine. The simulation results have been justified by measuring the parameters, respectively.

In this paper, a novel compact microstrip Low-Pass Filter (LPF) with sharp roll-off and ultra-wide stopband with high suppression level is presented. In the proposed filter, square-shaped resonators are used. The cut-off frequency at 3dB is 1. 88GHz. The maximum insertion loss of this filter is less than 0. 1dB and the return loss is also less than 16dB in the passband. In the proposed structure, the stopband extends from 2. 07 to 29. 5 GHz at 24dB level of suppression and is considered as an ultra-wide stopband. There is a significant relationship between simulation and fabrication results, which have justified the functionality of the proposed LFP, respectively.

In in-wheel Electrical Vehicle (EV) applications, Axial Flux Switched Reluctance Motor (AFSRM) is a more suitable solution compared to Radial Flux Switched Reluctance Motor (RFSRM); due to higher outer diameter to axial length ratio with, lower flux length and higher flux density. Switched Reluctance Motor (SRM) attract more attention due to its Permanent Magnet (PM) free structure. In view of this, C-core RFSRM is proposed; which offers combined advantages of radial and axial flux SRM. In this paper, based on a 12/16 pole three-phase structure, C-core RFSRM is compared with conventional RFSRM. Average torque and phase inductance are calculated with mathematical modeling. Computer Added Design (CAD) is verified with 2D and 3D Finite Element (FE) analysis. Based on simulation result, it has been observed that C-core RFSRM offers higher torque compared to conventional RFSRM; with removable wheel/rotor facility, without disturbing the stator. Prototype hardware is designed for feasibility testing of the proposed C-core RFSRM for in-wheel EV applications.

The application of communication between human and computer has been emerging as an important matter in communication with the surrounding environment. If the computer could sense the human’ s emotion, it would be easier to establish a connection between the computer and human. Therefore, the extraction of emotions is an important topic in communication between them. For extracting an emotion, which is absolutely undeniable, various biological signals are used. One of the simple and high-precision methods to acquire data from these signals is to implement the eye tracking and the concentration on the screen technique. In this paper, the eye tracking technique is used to extract emotions for the communication between the human and computer. According to the acquired data from the persons and videos, some of the characteristics of signals, including focus areas, pupil diameter, statistical features, and features of videos are extracted. In addition, in order to improve the results, combining the features are proposed. Afterwards, based on two distinct outputs i. e. Arousal and Valence, and employing a linear combination and reducing the dimension, some features are selected separately. Finally, to classify the two-axes associated with the Arousal and Valence in the range of 0 to 9, which is divided into three equal parts; special types of KNN and SVM methods combined with AdaBoost classifier are used. The numerical studies have shown that the average extraction accuracy is 68. 66% for Arousal axis, and 74. 66% for Valence axis. As a result, the overall accuracy is improved 5. 5% compared to the previous works, respectively.

Among various types of Distributed Generations, Microturbine (MT) Generation (MTG) systems are known as highly reliable and efficient sources. The MT must support demands in different conditions, which requires its proper control. In this paper, hybrid operation of the MTG is considered which is initially isolated from utility grid, and after that it is connected to the distribution network. A robust control method is used for stand-alone mode and a novel power-voltage control strategy is applied to grid-tied inverter. In stand-alone mode, the voltage, frequency and current are used as control parameters instead of traditional voltage-frequency control. In grid-connected novel controller, the inner voltage loop is substituted with the current loop, so it is based on powers and voltage. The simulations are performed by MATLAB/Simulink, with the results indicating proper power sharing as well as load-following performance with the minimum level of distortion. The proposed strategy can be used in hybrid operations of the MTG.

Nowadays, energy supplied by the reliable manner is one of the important challenges of the distribution company in the radial distribution system. Therefore, this paper considers these challenges by the optimal DG placement to minimize power losses with considering the analysis related to the reliability and voltage profile. In this paper, exchange market algorithm (EMA) is used as a powerful tool to solve the optimization problem. In order to extract the global optimum point, EMA uses two searching operators and two absorbent operators based on the generation of random numbers. To evaluate the goals of this paper, EMA is successfully implemented on 10, 33, and 69 bus IEEE test systems. Simulation results have illustrated that power losses are reduced by the optimal DG placement and size. Finally, the analysis of obtained results has shown the system’ s reliability; voltage profile can be improved if the DGs are allocated optimally in the radial network.

A new emerging solution to prolong the lifetime of the energy-constrained wireless networks is energy harvesting. In this paper, an Amplify-and-Forward (AF) relaying network in downlink phase is proposed. The relay harvests energy through Free Space Optical (FSO) link from the source and uses it to forward information to the destination through the RF link. In addition, there is a direct RF link between the source and destination. The FSO link experiences Gamma-Gamma atmospheric turbulence conditions with pointing errors and Rayleigh fading is considered for RF channels. In this system, a closed-form expression for outage probability in the form of Meijer’ s-G function is derived.

The aim of this research is to improve the quality of input current for AC/DC PWM converter, in case of grid imbalance with high dynamic transient. This can be achieved by joining compensating power with finite set model predictive control (FSMPC) based on voltage sensor-less technique. The control scheme proposed in this paper is divided into two steps. First, a double second order generalized integrator is used to estimate the virtual-flux and separate sequences of grid current and then the compensating power necessary to obtain sinusoidal input current is calculated. In the second step, the current is regulated via FSMPC, where, the switching state is determined directly. MATLAB/Simulink is selected to simulate and verify the effectiveness of the proposed control scheme; with and without virtual flux estimation. Simulation results are compared to confirm the validity of the algorithm.

The recent realm and leader technology in advanced manufacturing of critical components, and optical surfaces is ultra-precision Single-Point Diamond Turning (SPDT). This state-of-the-art technology enables machining optical surfaces with nanometric accuracies and surface roughness from order of nanometers. However, there are drawbacks in this process and SPDT is limited when machining brittle-and difficult-to-cut materials. Non-conventional assisted technologies have been developed and used to assist SPDT for extending turning limitations. Recently, application of novel hybrid platforms for SPDT has been emerging to achieve the best possible outcome in optical surface generation. Hybrid controllers are playing the main role in a hybrid platform. Main tasks of a hybrid controller in a hybrid SPDT platform include; real-time assisted technologies performance control, setting working parameters, and effective communication with implemented sensors for on-machine metrology. Hybrid processes in SPDT are recently emerging and there have been a few studies on designing and developing such novel platforms for SPDT. The purpose of this study is to design and simulate a Multi-Axis Automatic Hybrid Controller (MAAHC) to be used in a hybrid platform for assisting SPDT technologies. MAAHC has three process cores which work independently and communicate simultaneously. The designed MAAHC has different capabilities; MAAHC can control and drive ultrasonic vibration system, laser beam system, cold plasma system, and on-machine metrology systems i. e. vibration and force sensors. In addition, MAAHC is capable to control and drive two stepper motors in two independent linear axes. Electronic switches, communication ports, and high-performance switching have provided a full control on secondary technologies assisting in realizing a hybrid SPDT platform. Theoretical equations, design specifications, and simulation results have revealed that the proposed MAAHC is functional and has met all requirements to control such a hybrid SPDT process.