Indiana University-Purdue University Indianapolis (IUPUI) / This study presents a novel converter configuration that is related to the area DC-DC power converters. To begin with, a brief introduction is given by stating the importance of power electronics. Different types of converters, their operating principles and several new topologies that are being proposed over the years, to suit a particular application with specific advantages are listed in detail. In addition, pro- cedure for performing small signal analysis, which is one among the several averaging techniques is summarized in the first chapter. In the second chapter, small signal modeling is carried out on the single input dual output DC-DC buck converter. This analysis is performed to get a clear un- derstanding on the dynamics of this novel configuration. Routh stability criterion is also applied on this converter topology to determine the limiting conditions for operating the converter in its stability. Third chapter proposes the single input multiple output DC-DC synchronous buck converter. It’s operation, implementation and design are studied in detail. In further, small signal analysis is performed on this topology to determine the transfer function. In the following chapter, results obtained on comparison of a losses between the conventional and traditional topologies are presented in detail. In addition, results achieved during the analysis performed in the previous chapter are displayed. In the end, advantages and its highlights of this novel configuration proposed in this study is summarized. Future course of actions to be done, in bringing this configuration in to practice are discussed as well.

Micromechanics theories have been used to develop macro-level constitutive relations for infinitesimal elastoplastic deformations of unidirectional fiber reinforced laminates. The matrix is assumed to be isotropic and deform elasto-plastically and the fibers transversely isotropic and linear elastically. We have analyzed damage initiation, damage progression, and failure of 16-ply unidirectional fiber reinforced laminates impacted at normal incidence by a rigid sphere. The damage is assumed to initiate when at least one of Hashin's failure criteria is satisfied with the evolving damage modeled by an exponential relation. Transient three dimensional impact problems have solved using the finite element method (FEM) by implementing the material damage model as a user defined subroutine in the FE software ABAQUS. From strains supplied by ABAQUS the subroutine uses the free shear traction technique and values of material parameters of the constituents to find average stresses in a FE, and checks for Hashin's failure criteria. If the damage has initiated, the subroutine evaluates the damage developed, computes resulting stresses, and provides them to ABAQUS. The irreversibility of the damage is satisfied by requiring that the damage evolved does not decrease during unloading. The delamination failure mode is simulated by using the cohesive zone model and the degradation of material properties already available in ABAQUS. The computed time histories of the axial load acting on the impactor are found to agree well with the experimental ones available in the literature. The effect of stacking sequence in the laminate upon the impact load has been ascertained. / Ph. D.

A vibration isolator is designed to reduce the vibration and structure borne noise transmitted from a vibratory source, such as machinery and equipment, to the supporting structure. The vibration and structure borne noise transmitted depends upon the dynamic properties of the foundation, the source mounting point and the vibration isolator. Therefore knowledge of the frequency dependent dynamic properties of vibration isolators is a necessary part of the acoustic prediction and control/reduction process. Vibration isolators may be characterised by measuring their four-pole parameters. A measurement procedure is proposed that employs the floating mass method, measures the direct forces and corrects for the errors introduced by the direct force measurement. Compared to the basic method, it extends the frequency limits of measurement in both directions. The development of a novel vibration isolator test facility that implements the proposed measurement procedure is described, and its satisfactory operation is experimentally demonstrated. The vibration isolator test facility is capable of characterizing vibration isolators commonly used in industrial and maritime applications, under service conditions. A method is proposed for measuring the four-pole parameters of a uni-directional asymmetrical vibration isolator under static load. The method is called the two masses method, and is suitable for determining the four???pole parameters of active vibration isolators with feedback control. The method is also applicable to uni-directional symmetrical and bi-directional symmetrical and bi-directional asymmetrical vibration isolators. It may be regarded as a universal method for characterising vibration isolators. Experimental data is presented and the method is validated. Modelling of vibration isolators is complicated by the highly non-linear nature of their rubber elements. The notion of an effective rubber cylinder is proposed to account for the barrelling of rubber elements under static load. Consequently, a general static compression model is proposed that applies to vibration isolators having unfilled and filled rubber elements of regular prismatic shapes. The model predicts the dependence of the four-pole parameters on the compression ratio of the rubber element. The predictions derived from the effective rubber cylinder and general static compression model agree excellently with experimental work of this study and other researchers.

A vibration isolator is designed to reduce the vibration and structure borne noise transmitted from a vibratory source, such as machinery and equipment, to the supporting structure. The vibration and structure borne noise transmitted depends upon the dynamic properties of the foundation, the source mounting point and the vibration isolator. Therefore knowledge of the frequency dependent dynamic properties of vibration isolators is a necessary part of the acoustic prediction and control/reduction process. Vibration isolators may be characterised by measuring their four-pole parameters. A measurement procedure is proposed that employs the floating mass method, measures the direct forces and corrects for the errors introduced by the direct force measurement. Compared to the basic method, it extends the frequency limits of measurement in both directions. The development of a novel vibration isolator test facility that implements the proposed measurement procedure is described, and its satisfactory operation is experimentally demonstrated. The vibration isolator test facility is capable of characterizing vibration isolators commonly used in industrial and maritime applications, under service conditions. A method is proposed for measuring the four-pole parameters of a uni-directional asymmetrical vibration isolator under static load. The method is called the two masses method, and is suitable for determining the four???pole parameters of active vibration isolators with feedback control. The method is also applicable to uni-directional symmetrical and bi-directional symmetrical and bi-directional asymmetrical vibration isolators. It may be regarded as a universal method for characterising vibration isolators. Experimental data is presented and the method is validated. Modelling of vibration isolators is complicated by the highly non-linear nature of their rubber elements. The notion of an effective rubber cylinder is proposed to account for the barrelling of rubber elements under static load. Consequently, a general static compression model is proposed that applies to vibration isolators having unfilled and filled rubber elements of regular prismatic shapes. The model predicts the dependence of the four-pole parameters on the compression ratio of the rubber element. The predictions derived from the effective rubber cylinder and general static compression model agree excellently with experimental work of this study and other researchers.

The thesis is focused on special corrugated reflectors for ultra-wideband antennas. Corrugated reflectors are divided into a type H and a type E. Both these types are mutually combined. All those reflectors are simulated and subsequently analyzed. The thesis also deals with different types of broadband dipoles, which are completed by investigated types of reflectors. Created reflector antennas are then compared. For antennas exhibiting the best parameters, we performed simulations of the transmission between two antennas. For the simulations, we used CST Microwave Studio. Selected antennas were manufactured and measured. Consequent simulations were aimed to detect differences between the simulated and measured results.