Sharif Digital Repository

Background & Objective: A sensor network is composed of a large number of sensor nodes that are deployed to perform measurement and/or command and control in a field. Sensor nodes are battery powered devices and replacement or recharging of their batteries may not be feasible. One of the major challenges with sensory wireless networks is excessive energy consumption in nodes. Clustering is one of the methods that has been offered for resolving this issue. In this paper, we pursue evolutionary clustering and propose a new fitness function that har-nesses multiple propagation indices. Methods: In this paper we develop an efficient fitness function by first selecting the best clusters, and then... 

Quality and continuity of electrical power to sensitive loads especially in power plants and industrial sectors is of great importance. For this reason, bus transfer is used. During the bus transfer interval, sensitive loads especially motors will be interrupted, and may encounter difficulties. So, it is used reactive power compensator and custom power devices to mitigate stress in motors and improve power quality indices. This paper presents the effect of reactive power compensator and custom power devices paralleling with motor in process of bus transfer which is done in two methods: EMTS and STS. Also, it is investigated dynamic performance of induction motor and spin-down curves in... 

Growing interest in high-temperature superconducting (HTS) power devices is the result of commercial availability of the HTS tapes. One of the most promising applications of the HTS technology is HTS transformer. Flux diverters are used for critical current elevation in HTS transformer windings. In this paper multilayered flux diverter arrangements have been introduced to reduce weight and losses of conventional solid flux diverter arrangement. Horizontal and vertical multilayered arrangements have been investigated and compared with solid arrangement. Two dimensional (2D) finite element method (FEM) simulations have been used for comparison between different arrangements  

LLC resonant converter has been used widely as dc-dc converter for achieving constant dc voltage. In this paper, an LLC resonant converter, by adding an inductance to its conventional topology and considering the rectifying stage stray inductances, is proposed for an adjustable wide range regulated current source (20-200 A dc) for using as ion implanter's filament power supply. The additional inductor increases output current adjustment range and efficiency, especially at light loads. Transformer's leakage inductances and rectifying stage stray inductances have been considered. Because of these inductances, the rectifier stage always works in continuous conduction mode, and its conduction... 

In this paper, the FHA and a simple TDA approaches have been used to derive the normalized maximum switching frequency of wide adjustable range LLC resonant converter for realizing the ZVS operation even under the worst-case conditions. By accounting the resonant current higher harmonics, more accurate expressions are derived. These analyses demonstrate that the normalized maximum switching frequency depends on the dead-time and the converter inductance ratio. It also depends on the ratio of the converter resonant capacitor and the effective capacitance appeared in parallel with the power MOSFETs drain-sources. The simulated and experimental results are in good agreement with the derived... 

LLC-LC resonant converter is a suitable circuit topology to design switched-mode power supplies for wide-output-voltage and wide-output-load applications. In this paper, a design procedure is introduced to optimize this converter. Unlike soft switching techniques for pulse width modulated converters, which usually apply an active auxiliary circuit to reduce switching losses and EMI, in the proposed converter, not only such circuits are not used, but also all of the parasitic elements are merged to the converters main components. Zero-voltage switching (ZVS) operation is realized for all power devices under all operating conditions. Thus, this converter is a suitable choice for...