NISCAIR Online Periodicals Repository Collection: IJEMS Vol.19(2) [April 2012]
http://nopr.niscair.res.in/handle/123456789/14123
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Class-E power amplifier and its linearization using analog predistortion
http://nopr.niscair.res.in/handle/123456789/14151
Title: Class-E power amplifier and its linearization using analog predistortion
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<br/>Authors: Sampath, P; Gunavathi, K
<br/>
<br/>Abstract: In this paper,
power amplifier operating with center frequency of 947.5 MHz, which can be used
for the transmitter in beamforming systems, is proposed. The power amplifier
implemented provides high power added efficiency (PAE) of 71.967% and low noise
figure (NF) as low as 1.525. The linearity of the power amplifier is improved
by using square law and cubic law analog predistortion techniques. The power
amplifier is designed and implemented using 0.35 µm CMOS technology. The power
amplifier implemented provides high SNR of 82.723 and the linearity is improved
by suppressing the power in the 2<sup>nd</sup> and 3<sup>rd</sup> order
harmonics.
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<br/>Page(s): 144-152FEM modeling of compressive deformation behaviour of aluminum cenosphere syntactic foam (ACSF) under constrained condition
http://nopr.niscair.res.in/handle/123456789/14150
Title: FEM modeling of compressive deformation behaviour of aluminum cenosphere syntactic foam (ACSF) under constrained condition
<br/>
<br/>Authors: Khedle, Raghvendra; Mondal, D P; Verma, S N; Panthi, Sanjay
<br/>
<br/>Abstract: The deformation behavior of aluminum
cenosphere syntactic foam (ACSF) as a function of porosity, shell thickness,
shell volume fraction and cenosphere volume fraction has been studied using
finite element modeling<sup> </sup>of a representative unit cell of the
respective material under both constrained and unconstrained conditions.<sup> </sup>The
volume fraction of cenosphere and its shell thickness varies from 5% to 65% and
1 µm to 4 µm, respectively. It has been noted that as cenosphere volume
fraction decreases, the plateau stress and Young’s modulus of these materials
increases. While these values increase with increase in the shell thickness,
i.e., shell volume fraction. The modulus and plateau stress increase
considerably under constrained condition especially at low cenosphere volume
fraction. The FEM predicted values are validated with experimental results and
it is noted that the FEM predicted values are within the 12% variation of the
experimental values. The proposed study thus shows that unit representative
shell techniques are reasonably ideal and rapid method for predicting
compressive deformation behavior of ACSF.
<br/>
<br/>Page(s): 135-143Prediction performance of various numerical model training algorithms in solidification process of A356 matrix composites
http://nopr.niscair.res.in/handle/123456789/14149
Title: Prediction performance of various numerical model training algorithms in solidification process of A356 matrix composites
<br/>
<br/>Authors: Shabani, Mohsen Ostad; Mazahery, Ali
<br/>
<br/>Abstract: This
paper reports the microstructural and mechanical properties of casting Al
matrix composite such as porosity, hardness and tensile strength. The numerical
model and finite element method are applied to simulate the solidification of
the composites. The finite element analysis involves a
number of steps such as finite-element discretization,
imposition of boundary conditions and solution of assembled equations. The
mathematical formulation of this solidification problem is given. The neural
network predictions are directly compared with the experimentally obtained data
to evaluate the learning performance. In this investigation the MAPE is used to
evaluate the performance of model. The results show that Levenberg-Marquardt
learning algorithm
give the best prediction for UTS, hardness and porosity of A356 composite
reinforced with B<sub>4</sub>C particulates.
<br/>
<br/>Page(s): 129-134An investigation on the workability of sintered copper-silicon carbide preforms during cold axial upsetting
http://nopr.niscair.res.in/handle/123456789/14148
Title: An investigation on the workability of sintered copper-silicon carbide preforms during cold axial upsetting
<br/>
<br/>Authors: Sumathi, M; Selvakumar, N
<br/>
<br/>Abstract: An
investigation has been carried out for the determination of the workability
behaviour of Cu-SiC composites under two different stress conditions namely
plane and tri-axial state. Cylindrical preforms with 95% initial preform
density possessing aspect ratio of 0.60 are prepared from copper with various
percent content of silicon carbide (up to 20%) metal matrix composites using a
die and punch assembly with a 1.0 MN capacity Universal Testing Machine. The
sintering operation is carried out in an electric furnace at 850 ± 10°C for a
period of one hour in argon inert atmosphere and subsequently they are furnace
cooled. Each sintered preform is subjected to an incremental compressive
loading under zinc stearate as lubricant. Based on the experimental results,
the phenomenon like axial strain (ε<sub>z</sub>), various stress ratio
parameters (namely (σ<sub>m</sub>/σ<sub>eff</sub>) and (σ<sub>θ</sub>/σ<sub>eff</sub>))
and the formability stress index (β) under two different stress state
conditions are systematically analysed considering the barreling effects.
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<br/>Page(s): 121-128