نشریه مهندسی برق
سال چهل و هشتم شماره 4 (پیاپی 86، زمستان 1397)

The goal of this paper is improvement of the operation of networked control systems using optimized fuzzy logic controlled communication. Network traffic is reduced with optimal kalman filter estimator and fuzzy logic. It should be explained, there is no need to send information on the network continuously and the measurements are processed locally before sending. In this paper, population based optimization algorithms are used to set the parameters of fuzzy system for control the communication logic. The performance of regulated controllers are compared by the results of Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Biogeography Based Optimization (BBO), Imperialist Competitive Algorithm (ICA) and Ant Colony Optimization with continuous domain (ACOR) algorithms. The proposed method is simulated on two overhead cranes over a network with nonlinear features. Simulation results prove the validation of the proposed solution. While the results of all algorithms are reasonable but PSO algorithm has best result in reducing tracking error and fitness function point of view. Simulation results illustrate the effectiveness of proposed control system in coordination of two cranes over the network in moving heavy loads.

In recent cellular networks, the real-time broadcast of multimedia contents such as VoIP and Video traffics is increasingly becoming common. In this regard, 4G/LTE networks have been introduced due to providing high speed data along with QoS assurance, more security, and ultimately customer satisfaction. To accomplish these goals, radio resources management is a critical requirement and then schedulers are used in order to allocate the resources as Channel-Aware/QoS-Aware for the various traffics. One of the most important and effective schedulers is known as EXP RULE method; however these networks requires to improve in some of QoS parameters such as Packet Loss Rate (PLR) and Delay values to achieve further real-time information. In this paper, a new scheduling called Hybrid Weighted Exponential-Logarithm (HWEL) scheduler has been proposed to improve the PLR and Delay especially and improve the other QoS parameters generally in 4G/LTE networks. By performing simulations and comparisons between EXP-Rule and HWEL methods using LTE-Sim package for VoIP and Video traffics, it is observed that the proposed scheduler is a very good candidate to improve delay, PLR, throughput and fairness in the video traffics up to 21%, 29.8%, 7.8% and 1.1% and improve delay and PLR in the VoIP traffics up to 23.5% and 0.7% respectively.

Power line communication (PLC) channel as a medium for high speed data communication transmission based on orthogonal frequency division multiplexing (OFDM) is considered. It is an environment with frequency selective and multipath fading features which has been contaminated by impulsive noise. These deficiencies in power line communications degrade the accuracy of channel estimation. In this article, an efficient channel estimation method based on Bayesian inference is presented. A new proposed kernel function with proper hyper-parameters in relevance vector machine (RVM) is used to estimate the PLC channel impulse response. It is shown that bit error rate (BER) and mean square error (MSE) in proposed method, are significantly decreased. Proposed channel estimation algorithm achieves good results respected to reported approaches as Huang channel estimation method.

Load balancing is an important issue in distributed systems. In addition, using distributed generation sources such as photovoltaic is increasing. This paper presents a photovoltaic grid interface inverter with compensation of load active and reactive power Imbalance for three-phase four-wire distribution networks. An improved control strategy based on instantaneous active and reactive current component method with variable reference frame in single-phase systems is proposed. Two DC/DC and DC/AC converters have been utilized for connecting PV to the grid. DC/DC converter is responsible for maximum power point tracking (MPPT) and DC/AC converter is responsible for injecting power to the grid as well as balancing load. Using the structure of 3H-bridge converter for grid interface inverter, it is possible to achieve control objectives in three-phase four-wire low voltage distribution networks is provided. The proposed control has been verified by simulation using MATLAB/SIMULINK software and the simulation results indicate the ability of the proposed method to achieve control objectives.

In this paper, a new metasurface is proposed for miniaturization of patch antenna. The metasurface is placed on top of the patch antenna (working as a superstrate). The main purpose of this paper is to reduce dimensions of antenna. So the metasurface superstrate is placed on top with no air gap and is in direct contact with the radiating patch. For affirming the reduction in size, another patch antenna, which has the same shape with primary antenna, is designed without using superstrate to operate with approximate similar performance at the frequency of the first antenna with metasurface superstrate. The results show that this method brings size reduction about 50% in the surface of antenna. In this method of miniaturization, the only factor in reducing the resonant frequency of primary antenna is metasurface superstrate (place of feed line and the values of antenna dimensions are not changed). Therefore the antenna radiating parameters are affected just by metasurface superstrate. Consequently simulation measurement results, show effects of metasurface superstrate on the patch antenna characteristic and performance parameters.

Polar codes were recently proposed by Arikan and are constructed based upon a phenomenon that called channel polarization. The basic polarization matrix is given as . A challenging problem related to the design of polar codes is choose a suitable generator matrix , where is an arbitrary integar and , since in this state we have several choices for , unlike Arikan works that has only just one linear form. In this paper, we have compared status , that is simplest case from changing matrix with Arikan's work. As carry out simulations for this schema to show that there is eventuality selection unsuitable channel for the transmission information and find the best generator matrix. Finally have been proposed a briefly on the probability of error and complexity in this schema.

Combination method, including chemotherapy and immunotherapy, is one of the most effective treatment approaches suggested for cancer. In this study, a nonlinear multi-input model including chemotherapy and immunotherapy is considered for treatment of cancerous tumor growth. Due to side effects of chemotherapy and drug resistance effects, the level of used drug should be limited. In addition, the treatment should be performed in limit time. One of the solutions, which can be selected for this purpose, is the optimal treatment protocol. State dependent Riccati equation is the optimal strategy of this paper, which is designed for the tumor growth model. Afterwards, in order to show the flexibility of controller designing, several values for input weighting matrices are selected and the sensitivity of the proposed controller is analyzed. System is stabilized around the equilibrium point without tumor. Simulation results demonstrate the cancer treatment using the proposed controller could be performed in less time and by using lower drug dosage in comparison to the used method of reference model.

This paper presents an improved Flying Capacitor based multilevel converter to link ac and dc subgrids of a hybrid Medium Voltage )MV ( microgrid. Increase in the number of output voltage levels with lower size of filters, increase in the number of combinations to obtain a desired voltage level (redundancy), lower voltage and power rating of components and natural self-balancing of flying capacitors and dc link voltage compared to other conventional converters are the main properties of proposed interlinking converter. The proposed multilevel converter can decrease the limitations on power transfer between ac and dc subgrids, which can significantly complicate the power management and control of hybrid systems. The interlinking converter plays both inverter-based and rectifier-based roles in hybrid system, depending on the power transfer direction. Multilevel based interlinking converters can improve the power quality of hybrid system especially during islanded modes. Furthermore, a modified control strategy has been presented for the interlinking converter. The proposed structure is simulated using PSCAD/EMTDC software and simulation results are presented to validate the effectiveness and advantages of the proposed configuration

In this article, an end-fire microstrip dipole antenna, with high gain and capability of operating in millimeter-wave frequency band (57-64 GHz) is designed. The high gain of the antenna, with concept of negative permeability is achieved by the proposed metamaterial slabs embedded in horizontal plane of the dipole antenna. Each slab is loaded by a novel unit-cell. The result of the full-wave simulation presents the fact that the proposed design, would cause a better gain of 6.2 dBi in comparison with conventional dipole antenna without using metamaterial structures. In this structure, 28 metamaterial slabs from proposed unit-cells are used. These unit-cells are capable of creating two magnetic resonances that can play an important role to improve the gain in a wide frequency band. How to achieve this gain enhancement, depends on the number and decoration of metamaterial slabs around the antenna. These proposed metamaterial slabs are placed on top of the horizontal plane of the antenna, and also on the bottom of the antenna plane. This would cause the main lobe to stay still to the desired direction.

Audio event detection (AED) is addressed by using a segment mapping on the NMF dictionary in the sparse representation. One problem with dictionary methods is the lack of controls in the decomposition process of the input signal, so the process yields some unstructured sound pieces that are not the valid audio events. We proposed an algorithm which uses sparsity constraint and beta-divergence to decompose the input segments into the predefined dictionary atoms instead. Here, the sparsity control in each segment decomposes it into a linear combination of basis vectors thereby the segment is approximated into a hypothetical audio event. This method is applied to the recognition of variety live official sound events and has promising results.

In the power system, usually the reactance of transmission line is greater than its resistance and thereby power flow algorithms such as Newton Raphson methods and newton based methods can easily converged. However, in the case of series compensation such as series capacitor, the reactance of transmission line is decreased and accordingly the ratio of R/X is increased. In such case system condition is changed and therefore Newton based power flow methods will converged hardly or even diverged. In fact, with increase of R/X ratio, conventionally the system condition number (the ratio of maximum to minimum eigenvalue of Jacobian matrix) is increased and Newton Raphson method is not converged. In this paper, a new iterative based method is present to solve power flow of system with high ratio of R/X. The main advantage of the proposed method is its independence to R/X ratio and will converged even for system with high ratio of R/X. The suggested method is studied based on IEEE 9-bus, 30-bus and 118-bus also 11-bus and 2383-bus test systems. The obtained results show the effectiveness and accuracy of the proposed method in solving power flow problem of power systems, independent to R/X ratio.

In distributed generations (DG) such as wind turbines (WT) and photovoltaic systems (PV), since power production is directly dependent on weather conditions and wind speed, their powers have an intermittent nature. This intermittent characteristic can lead to power fluctuation, frequency deviation, reduction of power quality and reliability indexes at the Point of Common Coupling (PCC). In this paper, a grid-tied microgrid including WT and PV is studied and the effect of weather conditions and wind speed changes on power fluctuation and frequency deviatiom is investigated. In order to smooth the power fluctuations, a battery energy storage system (BESS) is used. Control system of this BESS consists of three control levels. Through the first two control levels, the DGs reference power is calculated aiming to smooth the network power. Effective life and protection of the BESS is considered in reference power calculation process. Afterward, the generated reference power is injected to the grid proper control system of voltage source converter connecting battery storage to PCC. In order to validate the effectiveness of BESS control system for smoothing power fluctuations of DGs, simulations studies have been done in MATLAB/ Simulink software. The results confirm that the proposed BESS control system is capable to reduce the output power fluctuations of DGs, Such a way that the average frequency of the fluctuations harmonic content reduce from 15.5 to 5.4 percent.

With increase of wind power penetrations into the power system, attention to power quality becomes an important issue. Important aspects of power quality are flicker and harmonics. There are numerous factors that affect on flicker emission and power oscillations of grid-connected wind turbines for example wind characteristics (mean wind speed, tower shadow and wind shear effects and type of used wind turbine) and the grid conditions (short circuit capacity ratio and grid impedance angle) and type of the maximum power point tracking. In the present paper, performances of two maximum power point tracking methods (TSR and OTC) in fluctuations emission are evaluated and fluctuations caused by the tower shadow are then reduced by adding filter when the best MPPT method and grid conditions are selected. All aerodynamic, mechanical and electrical aspects of a wind farm connected to the grid are modeled using FAST and MATLAB/SIMULINK. The simulation results are given and they show well the effectiveness of the method proposed for improvement of power fluctuations.

Techno-economic performance indices of an active power filter are affected by power losses of the converters that are used in its structure. In this paper, the equations needed to calculate the losses in both conventional VSC and CSC based and also VCSC based filters which has been recently proposed in valuable references, are derived. Despite the significant advantages in a VCSC filter, there are always doubt and concern for the losses due to the use of two different converters. With this motivation, the losses are divided into four main sections including AC losses, DC losses, conducting and switching losses in semiconductors. These equations provide the possibility of relative comparison of losses between traditional filters and VCSC one. Simulation of various structures of active filter in a typical test system in MATLAB/SIMULINK environment shows that total losses in the proposed VCSC based filter is near to VSC based and much lower than CSC based one. This is on condition that the simultaneously use of two converters in a unified filter and with a same THD, increases the reliability and aggregates benefits of both conventional filters. Also, for validating the computations, power losses of filters are assessed in half of the nominal load power and for five switching frequencies.

Through the numerous solutions for active and reactive power flow control in power systems, flexible ac transmission system (FACTS) devices have been in the center of attention in the last two decades. Although these devices are recognized as the utmost and modern technologies for power flow control, there is a very lukewarm reception in power systems. The main hurdles are known as high cost implementation, sophisticated design and control requirements, and long-duration interruptions for maintenance purposes. In this study, controllable network transformer (CNT) is first introduced as a suitable alternative of FACTS devices which is deemed for power flow control in power systems. This devise contains an under load tap changing (ULTC) transformer followed with a biridectional low rated AC-AC converter. Simplicity of structure and hence a low cost implementation of this device ends in a suitable solution for bidirectional power flow control. To end in effective switching parameters, dual virtual quadrature sources (DVQS) approach is utilized. Meanwhile, a fuzzy logic controller (FLC) is devised for active and reactive power flow controls in faulty situations. To evaluate performance of the proposed approach, simulation studies are conducted on a typical power system. The obtained results demonstrate outperformance of the proposed approach in effective power flow control.

Image retrieval is an important issue of machine vision and image processing. Many researches have been done in image retrieval. In 70’s, Text-Based image retrieval had been created before Content-Based image retrieval have been introduced since 90’s cause of large amount of data stored and inefficient previous methods. On this way, researcher reached better conclusion by extracting features from pictures. Semantic gap between these features and human concept, and burst increase in amount of images which were saved, caused researchers to think about new algorithms. Excellent successes on deep learning algorithms encourage us to implant a new method for image retrieval based on deep learning. In this paper, after reviewing deep convolutional neural networks as a kind of deep learning methods, we introduce a new retrieval system based on deep convolutional neural networks and by testing it on three famous databases, ALOI, Corel and MPEG7, computing P(0.5), P(1) and ANMRR and comparing them with other methods which have been used since recent years, we show the superior accuracy of this method in comparison to the other methods.

Achieving an appropriate level of reliability in electrical distribution systems is one of the main goals toward smart distribution grid. Moreover, self-healing is a significant features of smart distribution grid. Self-healing can be improved through installation of remote-controlled switches, which leads to an increase in availability and reliability. Thus, it is important to install controllable equipment in distribution grid. In this paper, a mixed integer linear program (MIP) is introduced to allocate remote-controlled and manual switches. In addition, reliability-centered approach is considered to find the best arrangement of switches in distribution grid. A sensitivity analysis is conducted on maximum investment cost, leads to a comprehensive analysis on installation of switches in distribution grid. Moreover, the objective function includes investment cost, customer interruption cost and maintenance cost. The formulation is solved by CPLEX solver.

In this paper, the impacts of energy policies on environmental and economic issues are investigated in the context of generation expansion planning (GEP) problem. Furthermore, detailed explanations on how these policies work is elaborated. For this purpose, first, by incorporating some of the most popular energy policies into the GEP problem, a comprehensive model is proposed. Named Integrated Renewable-Conventional Generation Expansion Planning (IRCGEP), the model is based on a suitably modified objective function and additional constraints. The IRCGEP model is formulated as a mixed integer non-linear programming problem and solved in several scenarios using GAMS optimization package from a generation company point of viewed. Then, regarding the obtained optimized expansion strategies, the effects of the policies on the generation company’s profit, electricity consumers surplus, and environmental damages cost is examined. In this framework, to analyze the consumer surplus affected by financial burden of the policies, an appropriate price criterion, the so called “virtual price”, is also proposed. Analyzing the cost of environmental damages derived from power sector emission is accomplished by the estimated social cost of carbon. Obtained results reveal that the energy policies have positive impacts on renewable energy promotion as well as emission mitigation. In addition, among considered policies, the most effective policy is introduced from an economic-environmental perspective.

In this paper, a new guidance law based on Robust Model Predictive Control (RMPC) is proposed for intercepting flying maneuvering targets. The presented guidance law is calculated by nonlinear kinematics. The design is based on a state feedback control law in which Linear Matrix Inequalities (LMI) has been used in order to optimize a cost function, subject to constraint on the control input. This Robust MPC method is utilized to obtain optimal Line Of Sight (LOS) angle tracking performance for maneuvering flying vehicle. It is shown that the control signal obtained from the problem stabilizes the nonlinear plant. Numerical simulations are implemented to the nonlinear plant and the effectiveness of the guidance law has been demonstrated.

Induction motors have numerous applications in various industries. In order to avoid industrial processes failures, fast and timely fault detection of motors is essential. In this paper, a novel method is presented for on-line detection of broken rotor bars which is a common rotor faults in induction motors. The method is based on the stator current analysis and signal processing using continuous wavelet transform (CWT). The most advantage of the method is that it detects the broken rotor bars in normal operations and at different loading conditions. In this method, the stator current signal should first be analyzed in the healthy and faulty conditions and then the broken bar can be diagnosed using a proposed index. Finite element method (FEM) is applied to simulate the motor under healthy and faulty conditions.

In this paper, a new closed-loop stator flux observer based on the voltage model (reduced-order) in direct torque control (DTC) applications for induction motors is proposed. The rule of DTC is based on controlling flux and its angle. Therefore, flux estimation is one of the fundamental issues in this method. Using the conventional open-loop voltage model observers can cause some problems such as, appearing dc offset in output, integrator saturation and incorrect estimation in low-speeds. One of the available solutions for compensating these shortcomings and improving the drive system performance is using closed-loop observers. The proposed observer in this paper is a novel closed-loop reduced-order observer based on shifting poles of its transfer function to the left in the complex plane. The simulation results show that the DTC performance is improved in different operation points, especially in low-speeds and also the observer is able to keep its stability in critical conditions.

In this paper, a new protocol to select cluster-heads and improve the Bee algorithm in order to routing in Vehicular Ad Hoc Networks (VANETs), which utilizes fuzzy set theory, is proposed. As regards the rapid topology change and congestion in VANETs lead to links failure, the proposed protocol calculates the validity value of each node and link based on the connectivity and the congestion level of the links of the route. Despite the importance of achieving optimal membership function in fuzzy inference system, Gravitational Search Algorithm (GSA) is employed to tune the fuzzy membership functions (MFs). Finally, the proposed protocol is simulated by MATLAB and compared with other routing protocols such as AODV, VANET QoS-OLSR and Bee algorithm that experimental results show that this algorithm achieves high data packet delivery ratio and low end to end delay.

In this paper, a novel pulse width modulation strategy based on circuit level decoupling concept is presented for Vienna rectifier as an alternative of conventional discontinuous modulation methods. Based on the proposed strategy, the Vienna rectifier can be decoupled into two two-level boost converters in every defined operating section, and though the controller design will be simplified. Moreover, compared to conventional continuous PWM methods, the proposed scheme, can also results in reduction of the switching loss by one third at the same switching frequencies. In this paper, the software implementation of the control technique has been carried out on Vienna rectifier under 882w output power and10 KHz switching frequency. The simulation results prove the effectiveness of the proposed method over other continuous and discontinuous modulation schemes, in terms of loss reduction and reduced complexity in control structure.

In this paper, a bidding strategy model is presented for electric vehicles’ (EVs) aggregator to sell the aggregated energy in the distribution network. The bidding price of the EVs’ Aggregator is determined through the Stackelberg game theory. It is modeled based on a bilevel programming problem between distribution system operator (DSO) and the aggregator. In the upper level of proposed bilevel model, the aggregator offered its optimal bidding price and EVs’ charge and discharge scheduling to maximize its profit. On the other hand, according to the price of the electricity market and bidding by the aggregator, DSO tries to optimally schedule the portion of energy which is supplied from either main grid or EVs’ aggregator to minimize its cost. In the equilibrium point of the problem, the optimal bidding price of the aggregator and the purchased energy from the aggregator and main grid is determined. The proposed bilevel programming problem is transformed into a single level mathematical programming problem with equilibrium constraints (MPEC) using the Karush-Kuhn-Tucker optimality conditions. The obtained numerical results is used to assess the proposed bidding strategy of EVs’ aggregator.

This paper presents the design of an element of a steerable 2×2 array antenna for GPS and BGAN applications. The element is a printed quadrifilar helical antenna which an integrated sequential phase shift rotation feed employed to enhance the circular polarization (CP) characteristics of the antenna. The integrated feed network is designed to provide a balanced RF signal to the four helical arms with a 90ᵒ sequential phase difference between them. The antenna maintains a low cross polarization up to ±60ᵒ, over transmit and receive frequency coverage from 1525 MHz to 1660 MHz, a return loss better than 11 dB with RHCP performance, and an axial ratio below 1.9 dB. The proposed antenna has a compact size, low cost and light-weight, with a relatively wide bandwidth, and almost-hemispherical radiation pattern with excellent right hand CP radiation that is suitable for L1-band GPS and BGAN satellite communications.

Today, PV systems have been widely used in power networks. The important issues about them are efficiency and power quality. In this way, inverters have the important role to achieve high efficiency, control power injected into the grid and improve power quality. The selection of inverter topology and the control strategy are two necessary factors to achieve the specified performance objectives. In this way, multilevel inverters with modularity and low cost can be a good choice for the next generation of efficient and reliable solar power stations. This paper introduces the improved topology of the photovoltaic supported MMC for grid interface. To observe all the control requirements simultaneously, only with one controller, FCS-MPC is used. It satisfies the control objectives like constant power in grid voltage sag/swell, synchronizing grid utility voltage with output current and low total harmonic distortion. The validity of the proposed system and the comparison with conventional topology is confirmed by MATLAB/SIMULATION.

In this paper, Extended Harmonic Domain is used in order to simulate and exact harmonic analysis of five-limb core type transformers during the transients in addition to steady state. To this aim, low frequency model of transformer along with considering magnetic circuit, appropriate for studies in the range of power system frequency, are used. Then, modeling procedure of non-ideal core is mentioned and required mathematical equations for their appropriate implementation in extended harmonic domain will be expanded. Finally, analyzing of inrush current of a sample transformer by implementing the equations in Matlab software is simulated and in order to investigate the accuracy of the proposed method, results of the performed simulation are compared with those results derived from transient analysis in power systems software.

Mild cognitive impairment )MCI( is an early stage of Alzheimer's disease)AD). Early diagnosis of this disease increases the likelihood of the treatment and prevents its conversion to dementia. The purpose of this study is the discrimination and the classification of two groups of healthy and MCI subjects by an advanced method of extracting spatial spectral features from electroencephalographic (EEG) signals. Filter bank common spatial pattern (FBCSP) has been recently used for classifying motor imagery EEG data in brain-computer interface researches. Here, we propose using FBCSP for classifying EEG data from healthy and MCI subjects. The proposed method was tested and compared to the popular method of frequency band-power and to the classic common spatial pattern (CSP) using a dataset of 9 MCI patients and 12 healthy subjects. A leave-one-out cross validation, using FBCSP resulted in a classification accuracy of 100% and outperformed both the frequency band-power and classic CSP methods. These results reveal the important role of using the learned spatial combinations of EEG signals in different frequency bands as effective features for discrimination of MCI and normal subjects.

One of the main factors that lead to the reduction of the potential, electric field distribution and the insulating level is surface charge accumulation on insulators .In this paper, the effect of surface charges on potential and electric field distribution along an outdoor polymeric insulator under DC voltage is studied by computer simulations. Research has shown that the accumulation of electrical charges on the surface of insulators can affect the performance of the flashover. So to avoid the occurrence of unexpected flashover must have a thorough understanding of surface charge to be examined its impact on insulation performance under various stresses. In this current paper, electric field and potential distribution along standard polymeric insulator with different geometry were investigated in the presence of surface charges. Calculations of the potential and electric field are performed based on Finite Element Method (FEM). Numerical simulations were carried out in COMSOL Multiphysics® to study the effect of the positive and negative surface charges on potential distribution under DC positive and negative applied voltage. Simulation results show the importance of surface charges effect in potential and electric field variations and the performance of the flashover.

One of the solutions for implementing IPTV service is applying the simple structure of Ethernet Passive Optical Networks. In such networks, scheduling algorithms play an important role for providing required levels of Quality of Service. Among them, Weighted Round Robin, is one of the commonly used ones. In this paper, a new weight allocation scheme is proposed in which, the weight of each queue would be allocated dynamically in each round. This strategy, reduces packet loss ratio for bursty traffics entering each queue. Simulation results with NS-2, show that the proposed scheme results in better packet loss ratio for bursty traffic compared to previous methods.

In this paper, two slow-light photonic crystal waveguides are designed based on a directional coupler. For the coupling of the waveguides to the conventional photonic crystal W1 waveguide, matching structures are proposed. For simulating the proposed structures, finite difference time domain and plane wave expansion methods are used. For the first structure, a group-index of 18.05 and a GBP equal to 0.278 and for the second structure, by modifying a section of photonic crystal lattice structure from hexagonal to square, a group-index of 11.37 and a GBP equal to 0.255 is obtained. For matching these waveguides to the W1 waveguide, a matching stage based on a Y-splitter is designed and proposed. Gradual change technique at the intersection of slow-light waveguide and coupling stage are used in order to maximize the waveguides coupling within the photonic crystal waveguide frequency range. For this purpose, a light pulse is inserted to the structure and the transmitted and reflected powers are calculated for each case. The bandwidth obtained for the first structure is equal to 28 nm and for the second structure it is equal to 7 nm. For the first structure, the maximum simulated transmittance is equal to 97.3% and for the second structure it is equal to 98.5%. Due to the 28 nm bandwidth obtained for the first structure, the proposed slow-light waveguide is well suited for the 1550 nm wavelength which is used in optical communications.

System resilience as a new concept in the power industry becomes important recently. This paper with consider to the rate of change of frequncey as a new system resilience index, introduces a resilient constraint unit commitment model to increase resilience against rare and severe events that ultimately lead to outages and frequency instabilities. This model offers an effective approach to solve unit commitment problem to prevent frequency instability by using optimal distributed generation switching problem, emergency interruptible load contracts and adaptive automatic frequency load shedding and when the event occurs, it places the system’s operating point in a stable state close to its optimal point. All simulation steps in the MATLAB software were conducted on 57-bus IEEE standard system. Simulation results of the proposed method, when compared with the conventional unit commitment approach without optimal distributed generation switching, imply the effectiveness of this innovative approach in the power system frequency stability enhancement.

Different storage systems have developed as the key solution for the growing demand of electric power. To this aim, the flywheel storage systems are gaining a wide acceptance for their higher power density and fast dynamic response. In this paper, a novel power electronic topology is proposed for connecting the flywheel storage systems to the distribution systems. This topology provides high dc-link voltage for the power electronic circuit required for driving BLDC motors in flywheel. Consequently, larger power can be stored in flywheel storage system. Since, it is desired to fully exploit the stored energy in flywheel systems, the proposed topology have ZVS feature, which leads to increase of power conversion efficiency. Moreover, the proposed topology is a bidirectional converter for charging and discharging purposes.Also, when the converter is in discharging mode its output voltage remains constant with changes of load. The small signal and fundamental frequency analysis is performed to model the proposed converter. The converter is simulated in Matlab environment to validate its convincing performance.

With the growth of information technology, network security is raised as one of the most important issues and challenges. Anomaly-based intrusion detection system is a valuable technology for network protection against malicious activities. In this paper a new approach is proposed based on hidden Markov model (HMM) and extreme learning machine (ELM) for intrusion detection. In the proposed model, the data that have been collected from network traffic are preprocessed at first. Then, the sequence of observations, are fed into HMM and the model is trained using Baum-Welch algorithm. In the recognition phase, Viterbi algorithm is used and the optimal state sequences are extracted from the input observations. Then, the sequence of states is considered as the input of ELM network and classified to normal or attack classes. Darpa98 dataset which is network trafic data is used to evaluate the approach. We evaluated the approach on this data set for challenges such as insufficient training data and the effect of training samples insufficiency, for which the proposed model provided satisfacory results. Experiments show that our approach has higher accuracy and lower false positive as compared with other methods and the accuracy of the proposed intrusion detection system is 98 percent.

Indoor localization and navigation of mobile robots has remained as a challenging problem. Vision-based navigation systems have been utilized as a promising solution. But they come with deficiencies such as weak robustness against camera failures. In this paper a vision-based 3D localization and control method for aerial robots is proposed. This method addresses several key features such as higher precision, real-time processing, full area coverage, reduced camera costs and robustness against asynchronized images and camera failures. Most of the processes of the proposed method, including image preprocessing, object recognition and 2D target localization are carried out separately for each camera. Then the acquired data are fused by a distributed Kalman filter to estimate the 3D location of the robot. The method has been experimentally verified by controlling the indoor position of a small aerial robot.

A Fully Differential latched comparator using a new offset cancellation technique is presented. The comparator consists of three stages: the input pre-amplifier, a latch stage and the offset cancellation circuitry. The kick-back noise can be significantly reduced by using a pre-amplifier stage. Also, the offset and noise of the latch and offset cancellation stages are attenuated by the gain of the pre-amplifier when referred to the input. Latches regenerate faster than pre-amplifiers and provide a full swing digital output for the comparator. The last stage is the offset cancellation circuitry. The main advantage of the proposed offset cancellation technique is that it does not need to make any interrupt in normal operation of comparator to eliminate offset error. In order to evaluate the performance of the comparator, simulations are performed in a 0.18µm standard CMOS technology. Simulation results show that the offset of the pre-amplifier and latch stages are significantly eliminated by this cancellation technique and only about 450µv offset voltage will be referred to the input. The proposed comparator operates at 500MHz clock frequency and dissipates 373µw from a 1.8v supply. Also, it has a propagation delay of 138ps and kick-back noise of 0.54mv.

In this paper, a voltage-controlled oscillator is provided by a triple frequency. Second harmonic frequency (2fo) is used directly for mixing with the frequency f0. The VCO consists of a detector and a comparator to shift LC-VCO bias condition from initial Class-AB start-up to steady class-C low current oscillation. The frequency of the VCO from 5.93 to 6.39 GHz has shown that the frequency tripling to 17.8 GHz - 19.19 GHz. This work has been simulated in a standard 0.18µm CMOS process. The simulated VCO achieves a phase noise of -114.7 dBc/Hz at 1 MHz offset and -135.1 dBc/Hz at 10 MHz offset from the 17.8 GHz carrier that Monte Carlo and corners analysis confirmed the obtained values. Circuit layout area is 443 × 547.47 , while the power consumption is 13.4 mw from a 1V supply.

In this paper, a probabilistic model for joint scheduling of energy and reserve (spinning and non-spinning) of an islanded microgrid is proposed considering demand response programs and security constraints. The objective of the problem is to maximize the expected profit of the microgrid operator with considering voltage and frequency security constraints. The presence of stochastic sources such as renewable resources and loads made the nature of the scheduling problem stochastic which is required to be formulated and solved in a scenario-based model. In the proposed method, to minimize the adverse effects of unfavorable scenarios, the cconditional value at risk (CVaR) criteria is used in the probabilistic model. In this method, the sensitivity of operator’s profit and the microgrid security margin in the cases with/ without the participation of responsive loads are assessed with considering risk criteria. Using this method, makes the operator capable to choose a proper risk factor as well as maximizing its expected profit and improving the security margin of voltage and frequency of the microgrid. In addition, in order to assess the system security more precisely and to determine the voltage and frequency deviations in each scenario, the AC optimal power flow (AC-OPF) is applied. Considering the security constraints of voltage and frequency simultaneously (at each hour) is a benefit of this method.

An analytical current model has been presented for an undoped symmetric double gate MOSFET based on the drift and diffusion of the inversion charges. First, using the one dimensional long channel (1D) Poisson’s equation perpendicular to the channel with mobile charges, a differential equation for charge of the channel is achieved which its solution gives the variation of the long channel charge concentration perpendicular to the channel. The 1D long channel potential is calculated by this long channel charge. The 2D short channel potential caused by the lateral electric field (which is important in short channel devices) is the solution of the 2D Laplace’s equation. Using this potential, the 2D variation of the short channel charge is extracted. Using the total calculated charge and the Gauss’s law at each point along the channel under the gate, the inversion charge in that point is calculated. Despite the existing models in which the inversion charge is calculated from the long channel charge perpendicular to the channel, in the proposed method it is shown that the 2D short channel charge (introduced by the lateral electric field) varies perpendicular to the channel too which affects calculating the inversion charge and must be taken into account in short channel devices. Finally, using the total inversion charge, the current is calculated. Good agreement between the results of the model and the results obtained by the Atlas software shows the validity of the proposed method.