Digital Commons Network^™

Analysis Of Radiation From An Open-Ended Coaxial Line Into Stratified Dielectrics, Sasan Bakhtiari, Stoyan I. Ganchev, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Radiation from an open-ended coaxial transmission line into an N-layer dielectric medium is studied in application to nondestructive evaluation of materials. Explicit formulations for two cases of layered media, one terminated into an infinite half-space and the other into a conducting sheet are addressed in general form. In the theoretical derivations it is assumed that only the fundamental TEM mode propagates inside the coaxial line. The terminating admittance of the line is then formulated using the continuity of the power flow across the aperture. The admittance expressions for specific cases of two-layer dielectric composite with generally lossy dielectric properties, and …

Simulation Of Communication Systems, William H. Tranter, Kurt Louis Kosbar

Electrical and Computer Engineering Faculty Research & Creative Works

When both a complex system and a complex channel model are encountered, the result is typically a design or analysis problem that cannot be solved using traditional (pencil and paper) mathematical analysis. Computer-aided techniques, which usually involve some level of numerical simulation, can be a very valuable tool in these situations. The purpose of this article is to provide a tutorial review of some of the basic techniques of communication system simulation. The authors consider the basic techniques used to represent signals, generate signals, and model linear systems, nonlinear systems, and time-varying systems within a simulation. They consider the important …

Transient Simulations And Modelling Of Semi-Insulating Gaas Photoconductive Switches, Prasun Kumar Raha

Electrical & Computer Engineering Theses & Dissertations

The primary objective of this thesis is to develop a one-dimensional transient simulator for Photoconductive Semiconductor Switches (PCSS) taking into consideration the material characteristics, the internal physical effects, and the external circuit. Simulations have been performed to study the device behavior at different voltage levels for copper-doped silicon-compensated GaAs material, though other materials could easily be simulated by changing the parameters. The model includes hole transport, and the results demonstrate the effect of hole injection, with and without recombination centers. In addition to developing a one-dimensional transient simulator, the role of various physical effects, such as the field-dependence of trapping …

Hardware Assists For High Performance Computing Using A Mathematics Of Arrays, H. Pottinger, W. Eatherton, L. Mullin, T. Schiefelbein

Computer Science Technical Reports

Work in progress at the University of Missouri - Rolla on hardware assists for high performance computing and communication is presented. This research consists of a field programmable gate array based rapid prototyping environment (Chameleon) being used to evaluate hardware architectures for speedup of array partitioning and routing algorithms. These algorithms have been developed using a Mathematics of Arrays (MOA) and are optimal in the sense that they reduce normal array indexing operations to a series of primitive additions based on array shape. The method is simple yet powerful, produces algorithms which are provably correct, and are independent of dimensionality. …

An Fpga Based Reconfigurable Coprocessor Board Utilizing A Mathematics Of Arrays, H. Pottinger, W. Eatherton, T. Schiefelbein, L. Mullin, R. Ziegler

Computer Science Technical Reports

Work in progress at the University of Missouri-Rolla on hardware assists for high performance computing is presented. This research consists of a novel field programmable gate array (FPGA) based reconfigurable coprocessor board (the Chameleon Coprocessor) being used to evaluate hardware architectures for speedup of array computation algorithms. These algorithms have been developed using a Mathematics of Arrays (MOA) and are optimal in the sense that they reduce normal array cartesian indexing operations to a series of primitive additions and offsets based on array shape. The method is simple yet powerful, produces algorithms which are provably correct, and are independent of …

Spatio-Temporal Pattern Recognition Using Hidden Markov Models, Kenneth H. Fielding

Theses and Dissertations

A new spatio-temporal method for identifying 3D objects found in 2D image sequences is presented. The Hidden Markov Model technique is used as a spatio-temporal classification algorithm to identify 3D objects by the temporal changes in observed shape features. A new information theoretic argument is developed that proves identifying objects based on image sequences can lead to higher classification accuracies than single look methods. A new distance measure is proposed that analyzes the performance of Hidden Markov Models in a multi-class pattern recognition problem. A three class problem identifying moving light display objects provides experimental verification of the sequence processing …

A Diffraction-Based Model Of Anisoplanatism Effects In Adaptive Optic Systems, Steven E. Troxel

Theses and Dissertations

This dissertation presents a new model for computing the angle dependent performance measures of an adaptive-optics system. By incorporating diffraction caused by the index-of-refraction variations of the atmosphere, the phase and amplitude fluctuations of the propagating wave are computed. New theory is presented, that uses the diffraction-based propagation model to yield optical transfer function (OTF) expressions that are more accurate as compared to current theory that neglects diffraction. An evaluation method for calculating the OTF is presented that utilizes a layered atmospheric model and normalized OTF expressions. The diffraction model is also used to present the first OTF signal-to-noise ratio …

H2 Optimal Control With H∞, Μ, And L1 Constraints, David E. Walker

Theses and Dissertations

H₂ optimization with convex constraints is considered. The optimal order-free solution is shown to be unique through convex analysis. H_∞ constraints with feedforward terms and singular constraints are also allowed. The optimal fixed-order solution is shown to have the same characteristics as a mixed problem with regular H_∞ constraints. Furthermore, these results are shown to hold for controller orders as low as the optimal H₂ order. A numerical method is developed based on analytical gradients which results in sub- and super-optimal fixed-order controllers. The problem is extended to include an upper bound on a mu constraint …

Noise Reduction For Speech Enhancement Using Non-Linear Wavelet Processing, Hassan Dehmani

Theses and Dissertations

The problem of speech enhancement presents many obstacles in the speech processing field. This thesis develops several speech de-noising systems that can be used in the time, fourier, and wavelet domains. We present two thresholding techniques soft and hard. The application of these thresholding techniques to noisy speech data is discussed. The combination of both wavelets and the Fourier domains with noisy phase restoration proves to yield the best results in terms of intelligibility. Informal listening tests were conducted in order to compare the effects and differences between the speech de-noising systems.

Mixed H2-H∞ Optimization With Multiple H Infinity Constraints, Julio C. Ullauri

Theses and Dissertations

A general mixed H₂/H_∞ optimal control design with multiple H_∞ constraints is developed and applied to two systems, one SISO and the other MIMO. The SISO design model is normal acceleration command following for the F- 16. This design constitutes the validation for the numerical method, for which boundaries between the H₂ design and the H_∞ constraints arc shown. The MIMO design consists of a longitudinal aircraft plant (short period and phugoid modes) with stable weights on the H₂ and H_∞ transfer functions, and is linear- time-invariant. The controller order is reduced …

Motion Estimation Using Optical Flow Field, Jingning Pan

Dissertations

Over the last decade, many low-level vision algorithms have been devised for extracting depth from intensity images. Most of them are based on motion of the rigid observer. Translation and rotation are constants with respect to space coordinates. When multi-objects move and/or the objects change shape, the algorithms cannot be used.

In this dissertation, we develop a new robust framework for the determination of dense 3-D position and motion fields from a stereo image sequence. The framework is based on unified optical flow field (UOFF). In the UOFF approach, a four frame mode is used to compute six dense 3-D …

Estimation And Cancellation Of Friction In Control Systems, Sofia Mentzelopoulou

Dissertations

The research reported in this dissertation concerns the estimation and cancellation of friction in control systems. For purposes of analysis, the Coulomb friction model, the "extended" Coulomb friction model as well as dynamic friction models are used. In addition, for systems with multiple degrees-of-freedom, a general matrix representation of friction is presented.

For the design of the friction estimators, the theory of nonlinear observers is applied. In particular, for a system with multiple degrees-of-freedom, holonomic constraints, and multiple friction sources, three different observers are presented to estimate the friction force or torque. The first (Generalized Coulomb Friction Observer) is designed …

Heart Rate Variability Study Using Phase Response Curve, Peizhuan Zhang

Dissertations

A noninvasive phase resetting experiment on human subjects was investigated. The phase response curve was estimated and was used to demonstrate cardiac phase resetting due to a vagal input. The estimated running phase response curve showed that the cardiac cycle resetting depended on the time and the amplitude of the vagal stimulation. The phase response curve was then studied using time circle analysis, topological analysis and nonlinear dynamics analysis. Also phase entrainment and stimulus frequency dependence of the phase response were evaluated. Further, the Van Der Pol model, Generalized Additive model and Knight and Peskin's model were used to simulate …

Performance Analysis Of The "Fiber Distributed Data Interface (Fddi) Network" Using Petri Nets And Spnp Software Package, Savvas Eteoclis Christodoulou

Theses

The main purpose of this thesis is to model a "Fiber Distributed Data Interface" (FDDI) Network using Petri Nets, and to analyze its performance with the help of the SPNP software package. The verification of a communication protocol, by modeling it as a discrete-event system using Petri Nets is a new approach.

The correlation between the throughput rate, voice and data throughput, and the parameters of the system, such as the network load and the network speed are investigated. An overview of the "Fiber Distributed Data Interface" is provided, along with its network protocol and the limitations of its operating …

Multi-Disk Subsystem Organizations For Very Large Databases, Zhiyi Huang

Theses

This thesis investigates efficient mappings of very large databases with non-uniform access to its data. to a. multi-disk subsystem.

Two algorithms are developed to distribute the database across multiple disks, possibly with replication, in order to minimize latency and maximize throughput. These algorithms are compared with respect to the amount of replication overhead incurred to achieve desired throughput.

A simulator is developed to simulate these two mapping algorithms and investigate the efficiency of these two mappings.

Fast Adaptive Algorithms For Signal Separation, Robert A. Manzo

Theses

LMS and RLS type algorithms are suggested for decorrelation of multi-channel systems outputs. These algorithms act as signal separators when applied to unknown linear combinations of the inputs. The performance of the suggested algorithms is compared with that of the conventional LMS and RLS algorithms that minimize the mean square error. It. is shown that the correlation matrix eigenvalue spread associated with the LMS decorrelator is always smaller than the eigenvalue spread corresponding to the conventional LMS. resulting in faster convergence speed for the decorrelator. A new RLS type decorrelator algorithm is suggested. The RLS decorrelator is shown to be …

Interference Cancellation By Time Adjustable Sampling, Josko Zec

Theses

The problem of improving the frequency response of linear arrays is addressed in this thesis. The improvement is measured in the level of rejection of the undesired sources. A new, simple, and practical method is suggested. It is based on adjusting the sampling time in selected channels. Interference cancellation for finite bandwidth signals is accomplished only at, or close to, the carrier frequency. Wideband cancellation requires additional hardware and computational complexity. Conventional way of the wideband interference cancellation utilizes tapped delay line adaptive filters in each channel.

The Time Adjustable Sampling (TAS) method achieves a part of the tapped delay …

Characterization Of Lightning Induced Voltages On Overhead Power Lines, Wen-Ta Hsiao

Theses

The transient voltage surge caused by lightning is the major source contributed to the disturbance on power systems. The calculation of induced voltages, which is the propagated voltage surge on overhead power lines due to indirect lightning strokes, has been the subject of theoretical and experimental studies. The objective of this research is to develop a comprehensive numerical method to study the induced voltages on an overhead power line caused by a lightning return stroke with arbitrary shapes, for examples inclined lightning, zigzag lightning, etc.

A finite-length lightning channel of any direction in 3-D space has been modelled and closed-form …

On Issues Of Equalization With The Decorrelation Algorithm : Fast Converging Structures And Finite-Precision, Andrew James Bateman

Theses

To increase the rate of convergence of the blind, adaptive, decision feedback equalizer based on the decorrelation criterion, structures have been proposed which dramatically increase the complexity of the equalizer. The complexity of an algorithm has a direct bearing on the cost of implementing the algorithm in either hardware or software. In this thesis, more computationally efficient structures, based on the fast transversal filter and lattice algorithms, are proposed for the decorrelation algorithm which maintain the high rate of convergence of the more complex algorithms. Furthermore, the performance of the decorrelation algorithm in a finite-precision environment will be studied and …

Constraint Objects, Divesh Srivastava, Raghu Ramakrishnan, Peter Revesz

School of Computing: Conference and Workshop Papers

We describe the Constraint Object Data Model (CODM), which enhances an object-based data model with existential constraints to naturally represent partially specified information. We present the Constraint Object Query Language (COQL), a declarative, rule-based query language that can be used to infer relationships about and monotonically refine information represented in the CODM. COQL has a model-theoretic and an equivalent fixed-point semantics, based on the notions of constraint entailment and "proofs in all possible worlds." We also provide a novel polynomial-time algorithm for quantifier elimination for set-order constraints, a restricted class of set constraints that uses membership of subset-equal.

Fluttering Fountains: Stability Criteria, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The fluttering oscillations that have long been seen in falling sheets of water have recently been subjected to detailed theoretical analysis. In this study stability criteria for these oscillations are derived and discussed. These criteria provide insight into the physical mechanisms of the instability and may be employed in the design of fluttering waterfall systems.

Multirate Time-Frequency Distributions, John R. O'Hair

Theses and Dissertations

Multirate systems, which find application in the design and analysis of filter banks, are demonstrated to also be useful as a computational paradigm. It is shown that any problem which can be expressed a set of vector-vector, matrix-vector or matrix-matrix operations can be recast using multirate. This means all of numerical linear algebra can be recast using multirate as the underlying computational paradigm. As a non-trivial example, the multirate computational paradigm is applied to the problem of Generalized Discrete Time- Frequency Distributions GDTFD to create a new family of fast algorithms. The first of this new class of distributions is …

Logic Synthesis With High Testability For Cellular Arrays, Andisheh Sarabi

Dissertations and Theses

The new Field Programmable Gate Array (FPGA) technologies and their structures have opened up new approaches to logic design and synthesis. The main feature of an FPGA is an array of logic blocks surrounded by a programmable interconnection structure. Cellular FPGAs are a special class of FPGAs which are distinguished by their fine granularity and their emphasis on local cell interconnects. While these characteristics call for specialized synthesis tools, the availability of logic gates other than Boolean AND, OR and NOT in these architectures opens up new possibilities for synthesis. Among the possible realizations of Boolean functions, XOR logic is …

An Analysis Of The Linked-Pulse In Steady-State Free Precession In Mri, Fang Li

Dissertations and Theses

The steady-state free precession (SSFP) is one type of the fast scanning technique in MRI. So far most of its analysis are concentrated on the gradient echo SSFP (GR SSFP), very few paper discuss the spin echo SSFP (SE SSFP), and they are usually based on the simplified the hard pulse assumption. The advantage of the SE SSFP is that it can refocus the dephasing caused by the magnetic field inhomogeneity, which is the disadvantage of the GR SSFP. Also the hard pulse model can provide very limited information.

The purpose of this paper is to establish the soft pulse …

Developing A Benchmark For Evaluating The Performance Of Parallel Computers, D. Ladd Williamson

Undergraduate Honors Capstone Projects

This paper discusses the development of a portable suite of benchmarking programs for parallel computers. Comparative measurement of the performance of parallel computing systems has been limited because of the great diversity of architectures and of processor interconnection schemes. One solution is to translate benchmark codes into a consistent and portable parallel language. This paper reports on progress in developing such a portable suite of benchmarks. An extensive introduction to parallel computing is included as an appendix, to provide a thorough understanding of the factors complicating development of the performance suite. Key to the development was the use of p4, …

A State Architecture Notation Specification Of The Electronic Industries Association Rs-232-C Generic Interchange Circuit, Nelson E. Hastings

Masters Theses

The Electronic Industries Association (BIA) RS-232-C recommendation is an interface specification which was introduced in August 1969 and presents a natural language specification of a 25 pin binary serial data interface between a Data Communication Equipment (DCE) and a Data Terminal Equipment (DTE). The exchange of data signals between a DCE and a DTE ultimately provides the means for DTEs to communicate on networks of DCEs interconnected by different transmission mediums possibly over great distances. The exchange of data signals between a DCE and a DTE occurs at an interface via interchange circuits.

In this thesis we will create a …

Dynamic Task Scheduling For The Atamm Multicomputer Operating System Using Embedded Firmware On Microcontrollers, Sudhir Sastry

Electrical & Computer Engineering Theses & Dissertations

A dynamic task scheduling strategy for the distributed processing of large grain dataflow algorithms using embedded firmware on an ATAMM testbed consisting of interconnected microcontrollers is presented in this thesis. The ODU/NASA developed Algorithm to Architecture Mapping Model, ATAMM, uses marked graph models to specify data and control flow for the execution of iterative, deterministic large grain dataflow algorithms in a multicomputing environment. The testbed consists of a bank of four 68HC11 microcontrollers that communicate over a token bus. The token bus arbitration scheme used is contention free and well suited for real-time computing applications. The execution of data flow …

Optimization Of Electron-Beam Activated Gaas Switches, Raymond Jack Allen Iii

Electrical & Computer Engineering Theses & Dissertations

The use of electron induced luminescence (cathodoluminescence) in gallium arsenide offers the possibility to modulate the conductance of the material on a timescale of nanoseconds and with a pulse rate of MHz, through modulation of an electron-beam current. This ionization mechanism allows the utilization of semi-insulating GaAs in fast, high power closing and opening switches. The efficiency of the switches is determined by the hold-off voltage of the GaAs switches, and by the conversion efficiency of electron energy into (useful) photon energy. Studies of the dark-current and the electron-beam induced conductance in semi-insulating GaAs have been performed in order to …

Diamond Thin Film Sensors For Hypersonic Flow Studies, Bhaskar Kumar Bulusu

Electrical & Computer Engineering Theses & Dissertations

Conventional metal film sensors can measure flow instabilities of the order of 60 kHz. The turbulence fluctuations in the hypersonic regime are of the order of 200- 400 kHz. To measure these fluctuations, sensors with an enhanced frequency response are required. Therefore, it is required to identify the parameters to enhance the frequency response. These include parameters such as the temperature sensitivity, the resistivity, the thermal conductivity, the diffusivity, specific heat capacity and the geometric size and shape of the film and the substrate. A selection of materials was then carried out to maximize the frequency response. Diamond was identified …

Derivative Absorption Spectroscopy With Tunable Laser Diodes, Andrew D. Jackson

Electrical & Computer Engineering Theses & Dissertations

Derivative Absorption Spectroscopy using tunable diode lasers provides a non­ intrusive, sensitive, and convenient method for monitoring gaseous characteristics such as concentration, temperature, and flow velocity. In addition, the specie type can be identified, and if the equation of state is known, pressure may be deduced.

This technique was used on molecular oxygen, in which the rovibronic transitions of the A-band ( b ¹ ∑_g ⁺ ← X ³ ∑g ^- ; v^II = O, v^I = O) were probed. Phase sensitive detection with a lock-in amplifier provides the flexibility to examine lineshape derivatives; several such derivative …