Symbolic framework for linear active circuits based on port equivalence using limit variables

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Time-Response Functions of Mechanical Networks with Inerters and Causality

This paper derives the causal time-response functions of three-parameter mechanical networks that have been reported in the literature and involve the inerter-a two-node element in which the force-output is proportional to the relative acceleration of its end-nodes. This two-terminal device is the mechanical analogue of the capacitor in a force-current/velocity-voltage analogy. The paper shows that all frequency-response functions that exhibit singularities along the real frequency axis need to be enhanced with the addition of a Dirac delta function or with its derivative depending on the strength of the singularity. In this way the real and imaginary parts of the enhanced frequency response functions are Hilbert pairs; therefore, yielding a causal time-response function in the time domain. The integral representation of the output signals offers an attractive computational alternative given that the constitutive equations of the three-parameter networks examined herein involve the third derivative of the nodal displacement which may challenge the numerical accuracy of a state-space formulation when the input signal is only available in digital form as in the case of recorded seismic accelerograms

The Response of Normal Shocks in Diffusers

The frequency response of a normal shock in a diverging channel is calculated for application to problems of pressure oscillations in ramjet engines. Two limits of a linearized analysis arc discussed: one represents isentropic flow on both sides of a shock wave; the other may be a crude appr'l'I;imation to the influence of flow separation induced hy the wave. Numerical results arc given, and the influences of the shock wave on oscillations in the engine are discus,ed

Analysis and design of Piezoelectric sonar transducers.

PhDIn this study techniques are developed for the analysis and design of piezoelectric sonar transducers based on equivalent circuit representations. For the purposes of analysis, equivalent circuits capable of accurately representing every element of a transducer in the full operating frequency range, are developed. The most convenient fashion in which these equivalents could be derived is also discussed. For the purposes of design the accurate equivalents are approximated by L-C-R circuits. The limits of both representations are discussed in detail. The technique of analysis developed is capable of determining the frequency characteristics as well as the transient response to any electrical or acoustic input which can be specified analytically or numerically in the time domain. The design technique is based on the formulation of a ladder-type generalized circuit incorporating the essential components of any transducer. The generalised circuit is then used to extract particular bandpass filter designs which possess wide passbands and which are mechanically realizable. By this procedure it is found possible to design transducers exhibiting bandwidths of around 100%. The performance of a 'test' transducer constructed to verify both analysis and design theories is also discussed

Bordered Block-Diagonal Preserved Model-Order Reduction for RLC Circuits

This thesis details the research of the bordered block-diagonal preserved model-order reduction (BVOR) method and implementation of the corresponding tool designed for facilitating the simulation of industrial, very large sized linear circuits or linear sub-circuits of a nonlinear circuit. The BVOR tool is able to extract the linear RLC parts of the circuit from any given typical SPICE netlist and perform reduction using an appropriate algorithm for optimum efficiency. The implemented algorithms in this tool are bordered block-diagonal matrix solver and bordered block-diagonal matrix based block Arnoldi method

Lossy Filter Synthesis

All telecommunication systems, such as cellular mobile networks (cellphones), object-detection systems (radars), and navigation systems that include satellite positioning systems (GPS), base their functioning on radio wave radiation with pre-defined frequencies and thus require a microwave filter to select the most appropriate frequencies. Generally speaking, the more highly-selective a filter is, the less non-useful frequencies and interference it picks up. Recent advances in microwave instruments, semiconductors, fabrication technologies and microwave filters applications have ushered in a new era in performance but have also brought significant challenges, such as keeping fabrication costs low, miniaturizing, and making low-profile devices. These challenges must be met while at the same time maintaining the performance of conventional devices. The thesis proposes use of lossy filter concepts to maintain high quality filtering frequency response flatness and selectivity regardless of the filter’s physical size. The method is applied to lumped element filters. It introduces resistances to the physical structure of the filter and hence a certain amount of loss to the frequency response of the filter. The lossy filter synthesis is based on the coupling matrix mode. The thesis also proposes modifications to the traditional lossy filter design techniques, to improve the filter performance in the stopband

Program in electro-physical studies - Microcircuit models and diagnostic techniques for environmental failure mode prediction

Microcircuit models and computer program for predicting failure modes under adverse environmental condition

PC programs for the prediction of the linear stability behavior of liquid propellant propulsion systems and application to current MSFC rocket engine test programs, volume 1

Research on propulsion stability (chugging and acoustic modes), and propellant valve control was investigated. As part of the activation of the new liquid propulsion test facilities, it is necessary to analyze total propulsion system stability. To accomplish this, several codes were built to run on desktop 386 machines. These codes enable one to analyze the stability question associated with the propellant feed systems. In addition, further work was adapted to this computing environment and furnished along with other codes. This latter inclusion furnishes those interested in high frequency oscillatory combustion behavior (that does not couple to the feed system) a set of codes for study of proposed liquid rocket engines

Design and control of reconfigurable bed/chair system with body pressuring sensing

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1997.Includes bibliographical references (leaf 68).by Joseph S. Spano.M.S