فهرست مطالب

  • Volume:7 Issue: 2, 2013
  • تاریخ انتشار: 1392/04/15
  • تعداد عناوین: 9
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  • Hassan Farsi, Samana Kuhimoghadam Page 1
    This paper proposes a new feature extraction algorithm which is robust against noise using histogram compensation and asymmetric filter. Temporal masking would be provided to improve ASR systems specifically in matched and multistyle training conditions. Nonlinear filtering and temporal masking are used in this algorithm. By matching the power histograms of the input in each frequency band to those obtained over clean training data, and then mixing together the processed and unprocessed spectra can be increased appropriately speech recognition accuracy. Obtaining results show that recognition accuracy in compare with MFCC, PLP and PNCC has been improved in various training conditions.
  • Nagu Bhookya Page 12
    In this paper, investigation is carried out for the improvement of power system stability by utilizing auxiliary controls for controlling HVDC power flow. The current controller model and the line dynamics are considered in the stability analysis. Transient stability analysis is done on a multi-machine system, where, a neural network controller is developed to improve the stability of the power system and to improve the response time of the controller to the changing conditions in power system. The results show the application of the neural network controller in AC-DC power systems.
  • Ali Badri, Mahdy Norouzi Page 21
    DG (dispersed generation) application has received increasing attention during recent years. The impact of DG on various aspects of distribution system characteristics depends highly on DG location in distribution feeder. This paper presents an optimization method to determine long term optimal DG placement in distribution systems in which system reliability and operational constraints as well as environmental constraints are taken into account. In order to get more realistic results impact of load uncertainty is modeled using normal distribution function. Furthermore, DG transactions with the market and corresponding payoffs are calculated. Despite, most of studies dealing with the problem from cost minimization point of view in a short term period, here DG placement is investigated from long term perspective. To get more accurate results the model considers both DG benefits and costs and the objective function is based on DG profit maximization. Benefits of using DG consist of loss reduction revenue, reducing in costumers'' interruption costs, power purchase saving as well as green house gas and fossil fuel reductions. Whereas, the costs consist of initial costs, maintenance and operating costs and DG transition costs as well. The proposed model is simulated on a standard IEEE test system to obtain the results and show the accuracy of the model.
  • Monika Gupta, Smriti Srivastava, J.R.P. Gupta Page 31
    In this paper, a hybrid of Neural Network (NN) and Fast Traversal Filter (FTF) based controller is used to determine the optimal parameters of Load Frequency Control (LFC) of a realistic two area power system. The two area power system is modeled considering the various non -linearities like governor dead band, generation rate constraint (GRC) and boiler dynamics. Input to the controller i.e. the error signal is divided into two parts- linear and non- linear. The linear part of the input signal is minimized by the FTF algorithm, whereas the non- linear part is minimized by the NN algorithm. The output of the controller is the sum of the outputs of NN and FTF networks. The proposed hybrid controller requires less number of samples for training of weights, thus making the system fast. This is highly desirable in power quality problems. The various components of power system are reduced to transfer functions and the system performance is analyzed for 1% step load perturbation in area1 with different controllers- proportional and integral (PI), neural network (NN) and NN+FTF based controllers. The simulations demonstrate the fast and smooth performance of the power system with the proposed controller. Simulated results evince the superiority of the proposed hybrid controller.
  • Saber Arabi Page 41
    Application of renewable energy sources have shown perfect potential as a form of contribution to conventional power generation systems. This paper presents an hybrid system based on photovoltaic (PV) module and PEM (proton exchange membrane) fuel cell (FC) with the aim of selling electricity to distribution network (DN) and improve its reliability. In this paper proposed system, moreover supply the load electricity of system, capable to sale electricity to DN and by electricity injection causes DN reliability improvement. The revenue from selling electricity to DN is considered as the system profit (SP). An optimization to maximize the SP using GAMS environment is applied. This study claims that moreover load electricity provision, electricity can also be sold to DN by proposed hybrid system and by injection the electricity to that increased, its reliability in consumer load supplement.
  • Maryam Monemian Page 48
    With respect to the increasing growth in the subscribers of wireless cellular networks and the necessity of providing network services with reasonable quality in any location, the importance of enhancement in the wireless network services is deeply felt. This means that network users expect to receive voice, data, and multimedia services with reasonable QoS, regardless of their locations and mobility patterns. Therefore, failures which may occur in mobile wireless network and may inhibit communication or result in loss of critical data will be not tolerated. Hence, providing wireless networks services in the presence of network failures has a great importance and can cause the networks to avoid from reducing their subscribers. In this paper, two main schemes are proposed, in order to reduce bad effects which can be generated in the case of network failures. These schemes try to reduce dropping probabilities and cause mobile hosts in the failed cell to continue their calls with high probability in the case of failure. One of the proposed schemes uses ad hoc relaying and the other uses bandwidth degradation, in order to improve network performance in the case of failure. Simulation results show that these two schemes have great impacts in improving network performance in the case of failure.
  • Razieh Jalalivarnamkhasti, Hamidreza Reza, Alikhani, Alireza Naghsh Page 58
    In this paper an approach is presented for edge detection of noisy images that have been degraded by impulsive noise. It uses Fuzzy Inference System (FIS) and Ant Colony Optimization (ACO). Starting with, using the FIS with 12 simple rules is to identify the noisy pixels in order to perform the filtering operation only for the noisy pixels. Probable edge pixels in 4 main directions for filtered image are detected using fuzzy rules and then ACO is applied by assigning a higher pheromone value for the probable edge pixels rather than other pixels so that the ant’s movement toward edge pixels gets faster. Another factor is the influence of the heuristic information in the movement of any ant that is considered to be proportional to local change in intensity of each pixel in order to the possibility of movement of ants increased toward pixels that have more change in their local intensity. Finally, by using an intelligent thresholding technique which is provided by training a neural network, the edges from the final pheromone matrix are extracted. Experimental results are provided in order to demonstrate the superior performance of the proposed approach.
  • Ali Hashemi, Amir Hossein Sarhaddi, Hossein Emami Page 68
    The demand for RFID tags has recently increased due to the development of the RFID. Over the past decade, great efforts have been devoted to the design of RFID tags without chip inside. The concept of chipless RFID tags appears to be a promising solution for low cost item tagging because the cost of active RFID tag depends mainly on the chip used in them. This paper presents the progress of the chipless RFID tag and introduces major studies in this filed. Advantages and disadvantages of these methods are pointed out.
  • Ali Ebadi, Mohammad Mirzaie, Sayyed Asghar Gholamian Page 76
    Induction motors are widely used in industrial, commercial and residential applications. An induction motor may exposed to the unbalanced voltage in the various operating conditions. Therefore, it is vital to investigate influences of voltage unbalance on performance of induction motors. In this paper, the performance of a three-phase squirrel cage induction motor has been simulated using Finite Element Method(FEM) supplied by different unbalanced voltages with the same Voltage Unbalance Factor(VUF) as well as the same positive-sequence phase voltage components. In addition, power, losses and efficiency of the simulated motor under mentioned conditions have been studied.