International Journal of Research in Science & Technology

Number 3, 2015

5
NEUTRON STARS - UNIQUE COMPACT OBJECTS OF THEIR OWN

Authors: R. Sashikanth

Abstract

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Number of views: 342

This paper outlines the study of neutron stars right from the early theoretical predictions and observations by various astrophysicists which gradually aroused huge interests among the scientific community, to the latest developments in the scientific analysis of the behavior of the different categories of compact objects. Although white dwarfs, neutron stars, brown dwarfs, Black Holes etc.fall under the category of compact objects, each of them is unique in its own way.

6-11
A Study on the Local Property of indexed Summability of a factored Fourier Series

Authors: B.P.Padhy, S.K.Nayak, Mahendra Misra and U.K.Misra

Abstract

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Number of views: 355

In this paper we have established a theorem on the local property of k n n N, p , ; summability of a factored Fourier series.

12-15
Improving the Signal Quality of Multistream Data Transmission in 4G Services

Authors: Ms. Emil Jenitta.R and Mrs. Sherin Shibi

Abstract

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Number of views: 322

Relaying is one of the key feature in wireless standards that expand the coverage of wireless networks. The ever increasing demand for very high data rate servicesmake use of multicarrier modulation techniques. This project explains about the improvement in bit error rate and elimination of interference. Conjugate Cancellation scheme for transmitter design, Phase Rotated Conjugate Cancellation scheme for receiver design and Equalize and Forward relay provides an efficient method for interference cancellation. In transmitter side only one phase rotation is applied and two phase rotations are applied at the receiver side. With such rotations the mismatch between the transmitter and the receiver can be tracked. The optimal solutions can be obtained by Block least mean square algorithm. Simulation results using the metrics viz. SNR, BER shows the performance of the proposed scheme achieves the interference free transmission and improvement in bit error rate.

16-21
Analysis of Voltage and Current Variations in Hybrid Power System

Authors: M .N .V .Subbarayudu, M. L .Pravalika, P.V.Avinash, P.Bhavya Sree N.Chaitanya and V.Sarayu

Abstract

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Number of views: 378

In this paper, a detailed dynamic model and simulation of a solar cell/wind turbine/fuel cell hybrid power system is Developed using a novel topology to complement each other and to alleviate the effects of environmental variations. Comparing with the nuclear energy and thermal power, the renewable energy is inexhaustible and has non-pollution Characteristics. Here Ultra-capacitors are used in power applications requiring short duration peak power. The voltage variation at the output is found to be within the acceptable range. The output fluctuations of the wind turbine varying with wind speed and the solar cell varying with both environmental temperature and sun radiation are reduced using a fuel cell. Therefore, this system can tolerate the rapid changes in load and environmental conditions, and suppress the effects of these fluctuations on the equipment side voltage. The proposed system can be used for off-grid power generation in non interconnected areas or remote isolated communities. Modeling and simulations are conducted using MATLAB/Simulink software packages to verify the effectiveness of the proposed system. The results show that the proposed hybrid power system can tolerate the rapid changes in natural conditions and suppress the effects of these fluctuations on the voltage within the acceptable range.

22-27
DTC Scheme for a Four-Switch Inverter-Fed PMBLDC Motor Emulating the Six-Switch Inverter Operation

Authors: A. Rani, A. Amarendra

Abstract

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Number of views: 346

The paper deals with the direct torque control (DTC) of brushless DC (BLDC) motor drives fed by four-switch three phase inverters (FSTPI) rather than six-switch inverters (SSTPI) in conventional drives. For any three phase inverter require six switches, but these switches are reduced to four. This reduction of power switches from six to four improves the reliability of the inverter, size of the inverter is reduced and cost of the inverter is also reduces. The FSTPI could be regarded as a reconfigured topology of the SSTPI in case of a switch/leg failure which represents a crucial reliability benefit for many applications especially in electric and hybrid propulsion systems. The DTC of FSTPI-fed BLDC motor drives is treated considering two strategies, such as: 1) DTC-1: a strategy inspired from the one intended to SSTPI-fed BLDC motor drives; 2) DTC-2: a strategy that considers a dedicated vector selection subtable in order to independently control the torques developed by the phases connected to the FSTPI legs during their simultaneous conduction. The operational principle of the four-switch BLDC motor drive and the developed control scheme are theoretically analyzed and the performance is demonstrated by simulation.