فهرست مطالب

  • Volume:15 Issue:3, 2019
  • تاریخ انتشار: 1398/06/10
  • تعداد عناوین: 13
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  • N. Mansouri*, M. M. Javidi Pages 282-293
    As grow as the data-intensive applications in cloud computing day after day, data popularity in this environment becomes critical and important. Hence to improve data availability and efficient accesses to popular data, replication algorithms are now widely used in distributed systems. However, most of them only replicate the static number of replicas on some requested chosen sites and it is obviously not enough for more reasonable performance. In addition, the failure of request is one of the most common issue within the data centers. To compensate these problems, we, propose a new data replication strategy to provide cost-effective availability, minimize the response time of applications and make load balancing for cloud storage. The proposed replication strategy has three different steps which are the identification of data file to replicate, placing new replicas, and replacing replicas. In the first step, it finds the most requested files for replication. In the second step, it selects the best site by consideration of the frequency of requests for replica, the last time the replica was requested, failure probability, centrality factor and storage usage) for storing new replica to reduce access time. In the third step, the replacement decision is made in order to provide better resource usage. The proposed strategy can ascertain the importance of valuable replicas based on the number of accesses in future, the availability of the file, the last time the replica was requested, and size of replica. Our proposed algorithm evaluated by CloudSim simulator and results confirmed the better performance of hybrid replication strategy in terms of mean response time, effective network usages, replication frequency, degree of imbalance, and number of communications.As grow as the data-intensive applications in cloud computing day after day, data popularity in this environment becomes critical and important. Hence to improve data availability and efficient accesses to popular data, replication algorithms are now widely used in distributed systems. However, most of them only replicate the static number of replicas on some requested chosen sites and it is obviously not enough for more reasonable performance. In addition, the failure of request is one of the most common issue within the data centers. To compensate these problems, we, propose a new data replication strategy to provide cost-effective availability, minimize the response time of applications and make load balancing for cloud storage. The proposed replication strategy has three different steps which are the identification of data file to replicate, placing new replicas, and replacing replicas. In the first step, it finds the most requested files for replication. In the second step, it selects the best site by consideration of the frequency of requests for replica, the last time the replica was requested, failure probability, centrality factor and storage usage) for storing new replica to reduce access time. In the third step, the replacement decision is made in order to provide better resource usage. The proposed strategy can ascertain the importance of valuable replicas based on the number of accesses in future, the availability of the file, the last time the replica was requested, and size of replica. Our proposed algorithm evaluated by CloudSim simulator and results confirmed the better performance of hybrid replication strategy in terms of mean response time, effective network usages, replication frequency, degree of imbalance, and number of communications.
    Keywords: Data Replication, Cloud Computing, CloudSim, Replica Placement
  • M. Naderan*, E. Namjoo, S. Mohammadi Pages 294-309
    Social networks have become the main infrastructure of today’s daily activities of people during the last decade. In these networks, users interact with each other, share their interests on resources and present their opinions about these resources or spread their information. Since each user has a limited knowledge of other users and most of them are anonymous, the trust factor plays an important role on recognizing a suitable product or specific user. The inference mechanism of trust in social media refers to utilizing available information of a specific user who intends to contact an unknown user. This mostly occurs when purchasing a product, deciding to have friendship or other applications which require predicting the reliability of the second party. In this paper, first the raw data of the real world dataset, Epinions, is examined, and the feature vector is calculated for each pair of social network users. Next, fuzzy logic is incorporated to rank the membership of trust to a specific class, according to two-, three- and five-classes classification. Finally, to classify the trust values of users, three machine learning techniques, namely Support Vector Machine (SVM), Decision Tree (DT), and k-Nearest Neighbors (kNN), are used instead of traditional weighted sum methods, to express the trust between any two users in the presence of a special pattern. The results of simulation show that the accuracy of the proposed method reaches to 91%, and unlike other methods, does not decrease by increasing the number of samples.
    Keywords: Trust Inference, Social Networks, Feature Vector, Fuzzy Logic, Epinions
  • S. M. Razavi Pages 310-320
    Probabilistic-based methods have been used for designing noise tolerant circuits recently. In these methods, however, there is not any reliability mechanism that is essential for nanometer digital VLSI circuits. In this paper, we propose a novel method for designing reliable probabilistic-based logic gates. The advantage of the proposed method in comparison with previous probabilistic-based methods is its ultra-high reliability. The proposed method benefits from Markov random field (MRF) as a probabilistic framework and triple modular redundancy (TMR) as a reliability mechanism. A NAND gate is used to show the design methodology. The simulation results verify the noise immunity of the proposed MRF-based gate in the presence of noise. In addition, the values from reliability estimation program show the reliability of 0.99999999 and 0.99941316 for transistor failure rates of 0.0001 and 0.001, respectively, which are much better as compared with previous reported MRF-based designs.
    Keywords: Reliability, Noise Tolerance, Markov Random Field (MRF), Triple Modular Redundancy (TMR)
  • H. Faraji Baghtash*, Kh. Monfaredi Pages 321-329
    A novel active feedback frequency compensation scheme is presented in this work. Based on the proposed technique, an amplifier with two main poles in its frequency bandwidth can be easily compensated by introducing a pole-zero pair in a local feedback. The proposed method is mathematically analyzed and then based on the derived formulations, a design procedure is established. The capability of the proposed technique is examined considering a well-known two-stage amplifier, considering just a trivial modification on its input stage. To gain an analogous and fair insight, the performance of the proposed structure is compared with that is of the optimally designed miller-compensated two-stage amplifier. The post-layout simulations are accomplished with TSMC 180nm CMOS standard technology. The Spectre post-layout simulations show that the proposed structure outperforms the traditional structure in terms of power consumption and gain bandwidth product. The robustness of the design is checked with Monte Carlo simulations.
    Keywords: Low Voltage, Low Power, Frequency Compensation, Operational Amplifier
  • S. Mavaddati* Pages 330-342
    Blind voice separation refers to retrieve a set of independent sources combined by an unknown destructive system. The proposed separation procedure is based on processing of the observed sources without having any information about the combinational model or statistics of the source signals. Also, the number of combined sources is usually predefined and it is difficult to estimate based on the combined sources. In this paper, a new algorithm is introduced to resolve these issues using empirical mode decomposition technique as a pre-processing step. The proposed method can determine precisely the number of mixed voice signals based on the energy and kurtosis criteria of the captured intrinsic mode functions. Also, the separation procedure employs a grey wolf optimization algorithm with a new cost function in the optimization procedure. The experimental results show that the proposed separation algorithm performs prominently better than the earlier methods in this context. Moreover, the simulation results in the presence of white noise emphasize the proper performance of the presented method and the prominent role of the presented cost function especially when the number of sources is high.
    Keywords: Voice Separation, Empirical Mode Decomposition, Grey Wolf Optimization, Equiangular Tight Frames, Correlation
  • M. Srivastava*, K. Bhardwaj Pages 343-351
    In this paper two R‑L network simulator configurations employing a single VDDIBA, one resistance and one grounded capacitance are presented. The first configuration is a grounded series resistor-inductor (R‑L) network simulator and the second configuration is intended for grounded parallel resister-inductor (R‑L) circuit simulation. Both the proposed circuits enjoy several beneficial features such as: 1) compact structure employing only one VDDIBA and two passive elements, 2) electronic tuning of inductive part of realized series/parallel R‑L impedances, 3) independent control of inductive and resistive parts of realized parallel R‑L impedance, 4) no requirement of any component matching, and 5) un-deviated performance in non-ideal environment. By choosing appropriate values of active/passive elements, a series R‑L circuit for simulating resistance of 7.742 kΩ and inductance of value 7.742 mH has been developed. Similarly a parallel R‑L simulation circuit to simulate a resistance of value 1 kΩ and inductance of value 77.4 µH is implemented. To study the influence of parasitics on developed lossy inductances, the behavior of these configurations has been studied keeping terminal parasitics of VDDIBAs under consideration. To check the performance and usefulness of the proposed configurations some second-order filtering circuits have been designed. To confirm the theoretical analysis, PSPICE Simulation results have been included.
    Keywords: Active RL Networks, Compact Circuit, Electronic Control, VDDIBA
  • E. Bounadja*, Z. Boudjema, A. Djahbar Pages 352-363
    This paper proposes a novel wind energy conversion system based on a Five-phase Permanent Magnetic Synchronous Generator (5-PMSG) and a Five to three Matrix Converter (5-3MC). The low cost and volume and also eliminating grid side converter controller are attractive aspects of the proposed topology compared to the conventional with back-to-back converters. The control of active and reactive power injected to the grid from the proposed system is carried out by a Direct Power Control (DPC) combined with a Space Vector Modulation (SVM). An advantage of this control, compared with the Conventional Direct Power Control (C-DPC) method, is that it eliminates the lookup table and lowers grid powers and currents harmonics through the use of a standard PI controller instead of hysteresis comparators. The efficiency of proposed whole system has been simulated by using MATLAB/Simulink environment.
    Keywords: Five-Phase Permanent Magnetic Synchronous Generator (5-PMSG), Five to Three-Phase Matrix Converter (5-3MC), Grid Active, Reactive Powers, Direct Power Control (DPC), Space Vector Modulation (SVM), Wind Turbine
  • B. Tousi, M. Farhadi, Kangarlu*, M. Farzinnia Pages 364-374
    In this paper a new topology for Dynamic Voltage Restorer (DVR) with high frequency link is proposed. This topology is able to compensate different types of voltage disturbances such as voltage sag, voltage swell and voltage harmonics. According to the obtained equations, this topology operates as a controllable current source to charge the series capacitor. Due to using High Frequency Transformer (HFT), the volume and the weight of the proposed DVR is decreased in comparison with conventional DVRs. This topology contains two ac/ac converters which are using in the input and output of the device. The absence of DC link capacitors and storage elements is the other advantage of using the proposed structure. In order to verify the claimed features, the proposed topology has been simulated by PSCAD/EMTDC software and examined under several disturbance conditions. In addition, an experimental prototype has been designed and tested. The results of the simulation and experimental cases are presented.
    Keywords: Dynamic Voltage Restorer, High-Frequency Link, Power Quality
  • S. Hajiaghasi, Z. Rafiee*, A. Salemnia, T. Soleymani Aghdam Pages 375-385
    Since the insulators of transmission lines are exposed to different environmental conditions, it is important task to study insulators performance under different conditions. In this paper, silicone rubber insulators performance under different environmental conditions including rainy, icy, salt and cement are proposed and exactly is studied. Electric fields (E-fields) and voltage distributions along the insulator under various conditions have been evaluated. Moreover, the corona rings effects on insulator performance under these conditions have been presented. A 230 kV silicone rubber insulator is selected, modeled and simulated with finite element method (FEM) using the COMSOL software. The simulation is repeated for different environmental conditions and efficiency of corona ring for each scenario is evaluated. The results indicate that environmental conditions have a significant effect on the insulator performance and the corona ring somewhat alleviate the adverse effect of environmental conditions on the insulator performance.
    Keywords: Corona Ring, Electric Field, Finite Element Method (FEM), Insulator, Potential Distribution, Rubber Insulator
  • M. Sanatgar, M. R. Alizadeh Pahlavani*, A. Bali Lashak Pages 386-400
    This paper presents the control approach for single inverter dual coupled brushless DC motors (DCBLDC) drive system. One of the basic requirements of such systems, is the power balance between two motors and on the other hand, minimizing mechanical fluctuations in order to avoid mechanical equipment damage especially in the state of mechanical resonance. This paper also presents an improved form of the conventional direct torque control (IDTC) for the DCBLDC, which can be used on nine-switch inverters (NSIs). The conventional approaches used in the coupled motors are considered, and then a combination of torque and velocity control is proposed for DCBLDC. After theoretical analysis and drive modeling, whose performance has been simulated by MATLAB/Simulink in terms of dispatching balanced power as well as dealing with transient phenomena owing to malfunctioning of the mechanical connection line. Finally, experiments with the 120W BLDC motors are executed to verify the feasibility of the proposed approach.
    Keywords: Coupled Motors, Double Drive, DTC, Load Balance Distribution, Nine-Switch Inverter
  • P. Intra*, P. Wanusbodeepaisarn, T. Siri, Achawawath Pages 401-410
    The object of the present work was to design, construct and evaluate a cylindrical tri-axial charger for charging of submicron aerosol particles by unipolar ions. The corona discharge characteristics, the intrinsic and extrinsic particle charging efficiencies, and the losses of aerosol particles were experimentally evaluated for particle diameters in the range between 50 nm and 500 nm under different operating conditions. The conditions included the corona voltages of about 7.0 to 8.0 kV, the mesh screen voltages of about 100 to 300 V and the aerosol flow rate was set at 1.5 L/min. It was found that the ion current increased from 2.90´10-10 to 3.66´10-8 A and 2.40´10-10 to 1.36´10-7 A and the number concentration of ions increased from 7.50´109 to 5.92´1011 ions/m3 and 6.21´109 to 2.19´1012 ions/m3 when the corona voltage increased from 5.5 to 8.0 kV at the mesh screen voltage between 100 and 300 V, respectively. The intrinsic charging efficiency of particles introduced a constant value of about 99% for particle diameter in the range between 50 nm and 200 nm and decreased with particle diameter in the range between about 300 nm and 500 nm at a given corona voltage. The best extrinsic charging efficiency of the studied charger occurred between 1.32% and 38% for particle diameter in the range from 50 nm to 500 nm at corona and ion trap voltages of about 7.0 kV and 300 V respectively. The highest electrostatic loss of particles was observed at 50 nm particles and it was about 89.08, 90.73 and 91.91% at a mesh screen voltage of about 300 V for corona voltages of about 7.0, 7.5 and 8.0 kV, respectively. Finally, the highest diffusion losses were at about 28.88, 23.03 and 11.15% for singly charged, neutralized and non-charged particles of 500, 500 and 50 nm, respectively.
    Keywords: Aerosol, Corona Discharge, Unipolar Charging, Particle Charging
  • H. Benbouhenni* Pages 411-419
    This article presents a sliding mode control (SMC) with artificial neural network (ANN) regulator for the doubly fed induction generator (DFIG) using two-level neural pulse width modulation (NPWM) technique. The proposed control scheme of the DFIG-based wind turbine system (WTS) combines the advantages of SMC control and ANN regulator. The reaching conditions, robustness and stability of the system with the proposed control are guaranteed. The SMC method which is insensitive to uncertainties, including parameter variations and external disturbances in the whole control process. Finally, the SMC control with neural network regulator (NSMC) is used to control the stator reactive and a stator active power of a DFIG supplied by the NPWM strategy and confirms the validity of the proposed approach. Results of simulations containing tests of robustness and tracking tests are presented.
    Keywords: Doubly Fed Induction Generator, Neural Pulse Width Modulation, Artificial Neural Network, Sliding Mode Control, Neuro-Sliding Mode Control
  • H. Kiani Rad, Z. Moravej* Pages 420-433
    In this paper, a new method is conducted for incorporating the forecasted load uncertainty into the Substation Expansion Planning (SEP) problem. This method is based on the fuzzy clustering, where the location and value of each forecasted load center is modeled by employing the probability density function according to the percentage of uncertainty. After discretization of these functions, the location and value of each of the new load centers are determined based on the presented fuzzy clustering based algorithm. A Genetic Algorithm (GA) is used to solve the presented optimization problem in which the allocations and capacities of new substations as well as the expansion requirements for the existing ones are determined. With the innovative presented method, the impact of uncertainty of the power and location of the predicted loads on the results of SEP is measured, and finally, it is possible to make a proper decision for the SEP. The significant features of this method can be outlined as its applicability to large-scale networks, robustness to load changes, the comprehensiveness and also, the simplicity of applying this method to various problems. The effectiveness of proposed method is demonstrated by application on a real sub-transmission system.
    Keywords: Genetic Algorithm, Fuzzy Clustering, Load Uncertainty, Probability Density Function, Substation Expansion Planning