فهرست مطالب

Majlesi Journal of Electrical Engineering - Volume:3 Issue: 1, 2009
  • Volume:3 Issue: 1, 2009
  • 80 صفحه،
  • تاریخ انتشار: 1388/03/20
  • تعداد عناوین: 8
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  • Mehrdad Jafarboland, Abdolamir Nekoubin Page 1
    Effective parameters in performance of linear induction motors such as air gap, number of poles and the thickness of secondary must be selected and optimized to increase power coefficients and motor performance significantly. In this paper a double sided linear induction motor in different conditions is designed and next by finite element method analyzed. Then for comparing analytical model and numerical model a linear motor using Matlab software is simulated in different condition. It is clear from the results that with optimal value of effective parameters, power losses decreased the performance of motor is improved and efficiency of linear motor is increased.
  • Ghazanfar Shahgholiyan, Mohamadamin Heidari, Mehdi Mahdavi Page 11
    The recent development in renewable energy systems and the high demand for having clean and low cost energy sources encourage people to use distributed generator (DG) systems. Proper addition and placement of DG units can increase reliability and reduce the loss and production cost. In this paper using Ant Colony method, we developed an optimum placing scheme for DGs. The proposed method is tested on an IEEE 34-shinhe system. Results show that if DGs are able to generate active power, their effectiveness will increase.
  • Mansour Sheikhan, Davood Gharavian, Ali Eslamzadeh Page 19
    The speech spectrum is very sensitive to linear predictive coding (LPC) parameters, so small quantization errors may cause unstable synthesis filter. Line spectral pairs (LSPs) are more efficient representations than LPC parameters. On the other hand, artificial neural networks (ANNs) have been used successfully to improving the quality and also reduction the computational complexity of speech coders. This work proposes an efficient technique to reduce the bit rate of FS-1015 speech coder, while improving the performance. In this way, LSP parameters are used instead of the LPC parameters. In addition, neural vector quantizers based on Kohonen self-organizing feature map (KSOFM), with a modified-supervised training algorithm, and fuzzy ARTMAP are also employed to reduce the bit rate. By using the mentioned neural vector quantizer models, the quality of synthesized speech, in terms of mean opinion score (MOS), is improved 0.13 and 0.26, respectively. The execution time of proposed models, as compared to FS-1015 standard, is also reduced 27% and 43%, respectively.
  • Arash Daghighi, Azar Farajzadeh Page 27
    The self-heating effects (SHE) in 45nm Silicon-on-Insulator (SOI) and Silicon-on-Diamond (SOD) structures were investigated. As a result of high thermal conductivity of diamond, SHE is much less pronounced in SOD structures. This makes SOD transistors suitable for high power applications were large power density is required. It was shown that in SOD substrate the generated heat in active transistors not only spreads away in the substrate but also transfers to the auxiliary non-active transistors on the same die through the diamond film. Our hydrodynamic simulation results showed 8 times more off-current in auxiliary transistors than SOI substrate. The thermal coupling between the neighboring devices in SOD structures represent device miss-match in analog circuits were high degree of matching is required.
  • Ali Esmaiili, Mehdi Mahdavi, Pejman Khadivi Page 33
    The expansion of Internet, increases the number of users and applications. Having higher speed and better quality are the main chalanges of computer network development. Using MPLS and proper traffic design, it is possible to improve the quality of service and reduce the possibility of congestion. It is possible to use MPLS in a BGP/MPLS VPN network for data transmition. In this paper we explain BGP/MPLS VPN and we implement an MPLS network based on Diffserv over VPN services. Using OPNET various senarios are simpulated. In most of the previous proposed systems, with incressing the number of low traffic priority sources like BE and AF, higher priority traffic like EF faces difficulty. Our simulation shows with using traffic engineering, congestion control for low priority sourses and management methods, it is possible to have better quality of services for those traffics which are sensitive to delay.
  • Saeed Abazari, Ghazanfar Shahgholian, Omid Ghanaati Page 45
    With increase energy consumption in the world, power network development is necessary but creating a new transmission line is very costly. Therefore increasing line transmission capability is economic. We propose a method to FACTS device to the power network, in this paper and resulted in introducing decrease power network loss's and increase transmission capability with optimal choice and allocation of FACTS device by using genetic algorithm. We examine, proving this method by simulation IEEE6 bus system and using the genetic algorithm for optimal choice and allocation of FACTS device in this system.
  • Mohammadreza Soltani, Rasoul Amirfattahi, Mohammadreza Zadhosh Page 53
    In this paper we study various techniques of power RF amplifier linearization and analyze the most effective circuits of predistortion digital circuits. We propose a method for adapting this circuit and compare the advantages and disadvantages of this circuit with conventional predistortion circuit. The main problem with predisrortion circuit is the memory effect. We propose a new circuit to overcome the above problem based on digital signal processing techniques. Finally we compare results of our simulation with previous results. Our simulation shows an 8dB reductional in power ratio of adjacent channel.
  • Mohammadali Saghafi, Rasoul Amirfattahi, Mojtaba Mansouri, Mohsen Kazemi Page 61
    In this paper a new method approach is proposed for automatic segmentation of heart sounds (S1, S2) based on wavelet transform. Unlike many other approaches, this method does not use ECG as reference for detection. The applied criterion for segmentation is based on a very important physiologic attribute of heart which is the difference between the pressure of heart valves while opening and closing which causes high frequency components in heart sound. The main idea in this paper is to extract detail and approximation wavelet coefficients of heart sound (PCG) to detect the heart cycle via the Shannon energy of coefficients and then segment S1 and S2. The results show the present algorithm is capable of accurate segmentation of 90% of first heart sounds (S1) and 88.9% of second heart sounds (S2).