NOPR Collection:

Class-E power amplifier and its linearization using analog predistortion

2016-07-20T04:45:35Z

Title: Class-E power amplifier and its linearization using analog predistortion Authors: Sampath, P; Gunavathi, K 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^nd and 3^rd order harmonics. Page(s): 144-152

FEM modeling of compressive deformation behaviour of aluminum cenosphere syntactic foam (ACSF) under constrained condition

2016-07-20T04:44:50Z

Title: FEM modeling of compressive deformation behaviour of aluminum cenosphere syntactic foam (ACSF) under constrained condition Authors: Khedle, Raghvendra; Mondal, D P; Verma, S N; Panthi, Sanjay 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 modelingof a representative unit cell of the respective material under both constrained and unconstrained conditions.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. Page(s): 135-143

Prediction performance of various numerical model training algorithms in solidification process of A356 matrix composites

2016-07-20T04:44:10Z

Title: Prediction performance of various numerical model training algorithms in solidification process of A356 matrix composites Authors: Shabani, Mohsen Ostad; Mazahery, Ali 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 B₄C particulates. Page(s): 129-134

An investigation on the workability of sintered copper-silicon carbide preforms during cold axial upsetting

2016-07-20T04:43:34Z

Title: An investigation on the workability of sintered copper-silicon carbide preforms during cold axial upsetting Authors: Sumathi, M; Selvakumar, N 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_z), various stress ratio parameters (namely (σ_m/σ_eff) and (σ_θ/σ_eff)) and the formability stress index (β) under two different stress state conditions are systematically analysed considering the barreling effects. Page(s): 121-128