Digital Commons Network^™

Design And Implementation Of Fuzzy Logic Controllers, Osama A. Abihana

Electrical & Computer Engineering Theses & Dissertations

The main objectives of our research are to present a self-contained overview of fuzzy sets and fuzzy logic, develop a methodology for control system design using fuzzy logic controllers, and to design and implement a fuzzy logic controller for a real system. In this thesis we first present the fundamental concepts of fuzzy sets and fuzzy logic. Fuzzy sets and basic fuzzy operations are defined. In addition, for control systems, it is important to understand the concepts of linguistic variables, linguistic values, term sets, fuzzy rule base, inference methods, and defuzzification methods. Second, we introduce a four-step fuzzy logic control …

The Effect Of Contacts On The Performance Of Electron-Beam Controlled Gaas And Diamond Switches, Michael Kevin Kennedy

Electrical & Computer Engineering Theses & Dissertations

The performance of GaAs and diamond as electron-beam controlled closing and opening switches has been studied. An emphasis has been placed on the effect of contacts on the current-voltage characteristics. The two materials studied were GaAs and diamond. Using the same semi-insulating GaAs wafer as a source of material, a bulk device and a p-i-n device have been fabricated and compared. The asymmetry of the pin diode allows operation at higher voltage because of the ability to suppress the lock-on effect. Whereas GaAs was ionized through cathodoluminescence; diamond, in the form of thin films, has been directly ionized by the …

Analysis Of Heat Pump Cycles Using Thermodynamic Equations Of State, Stephen C. Ericson

Mechanical & Aerospace Engineering Theses & Dissertations

In this study, thermal performance of heat pump cycles is analyzed by employing several equations of state. The analysis presented here is particularly useful for applications where refrigerant properties need to be calculated from a thermodynamic equation of state. Such a situation, for example, would arise during a long-term numerical simulation of a solar-assisted heat pump system. In these cases, the direct use of thermodynamic property tables of refrigerants would not be possible in a computational procedure. The approach of using equations of state to predict thermodynamic properties is also useful for applications where new refrigerants or blends of refrigerants …

Transient Simulation Of A Trombe Wall Passive Heating System Coupled To A Thermally Stratified Room, Ali Saleh Kheireddine

Mechanical & Aerospace Engineering Theses & Dissertations

Thermal performance of a Trombe-wall space heating system has been studied numerically for one-day and multiple-day periods. This study analyzes the system performance by simultaneously considering the coupled nature of the channel convection, wall heat conduction and transient room energy balance. A computer program has been written and implemented to assess the effects of system parameters, weather conditions and peak temperature control strategies on the system performance.

The system performance is influenced by such system parameters as the storage wall thickness, channel width and the temperature stratification in the room. Increasing the wall thickness decreases the temperature swings considerably, but …

Multiple Learner Systems Using Resampling Methods, Binyun Xie

Computer Science Theses & Dissertations

The N-Learners Problem deals with combining a number of learners such that the resultant system is "better", under some criterion, than the best of the individual learners. We consider a system of probably approximately correct concept learners. Depending on the available information, there are several methods to make the composite system better than the best of the individual learners. If a sample and an oracle that generates data points (but, not their classification) is available, then we show that we can achieve arbitrary levels of the normalized confidence of the composite system if (a) a robust learning algorithm is available, …

Multigrid Algorithms For Massively Parallel Machines, Satyanarayan Gupta

Computer Science Theses & Dissertations

Numerical solutions of partial differential equations (pde's) are required in many physical problems arising in areas such as computational fluid dynamics, atmospheric sciences, electromagnetics etc. One of the most popular methods of solving pde's is the use of the multigrid algorithm. However, the implementation of the multigrid algorithm on massively parallel machines is not very efficient because of (i) low processor utilization and (ii) high communication overheads. These problems need to be addressed to make better use of massively parallel machines for solving pde's using the multigrid algorithm.

In this dissertation, we present three parallel multigrid algorithms which …

High Performance Issues On Parallel Architectures, Peter J. Looges

Computer Science Theses & Dissertations

In an effort to reduce communication latency in mesh-type architectures, these architectures have been augmented by various types of global and reconfigurable bus structures. The static bus structures provide excellent performance in many areas of computation especially structured numerical computations, but they lack the flexibility required of many large numerical and non-numerical applications. Reconfigurable bus systems have the dynamic adaptability to handle a much wider range of applications. While reconfigurable meshes can often yield constant time results for many problems, the cost of this performance is paid in the number of processors required. While in actuality the majority of these …

Investigation Of Alignment Dynamics In Mg-Ne And Mg-Ar Two-Photon Fractional Collisions, David Allen Olsgaard

Physics Theses & Dissertations

A new technique is used to observe the dynamics of electronic alignment in a dissociating collision complex. The technique requires the absorption of two optical photons during a single binary collision. Two exciting light fields are tuned into the wings of the 3s¹s₀-3p₁ and 3p¹p₁-5s¹s₀ resonances of Mg where strong collisions with rare gas atoms induce transitions between corresponding molecular states. The alignment produced in the intermediate state by the first excitation is probed by the second laser as a function of relative linear laser polarization and laser …

Visual Graphic Knowledge Management Methodology, Jih-Shih Hsu

Computer Science Theses & Dissertations

As computer technology evolves, graphic workstations are becoming more popular. They support more friendly user interfaces than do conventional terminals. The better user interfaces require more effort to develop. Therefore, many user interface (UI) design systems have been developed to facilitate the creation of modern user interfaces, but not very successfully. Many of them either provide limited features or are difficult to use. Besides, these UI design systems are actually like black boxes to their users because the underlying technology is opaque; their users cannot learn how to utilize the underlying window systems through user interface design sessions. In a …

Mat Movement In Coastal Louisiana Marshes: Effect Of Salinity And Inundation On Vegetation And Nutrient Levels, Christopher Martin Swarzenski

Biological Sciences Theses & Dissertations

The present research compared and contrasted the physical structure of floating and rooted marshes, their differing responses to open-water salinities and inundation, as well as the nutrient distribution in the porewaters and sediment. The effects of the physical differences in the two marsh types on the ocurrence of the dominant emergent vegetation was discussed.

The main difference in physical structure of the two marsh types was the presence of a mineral, non-buoyant layer at 25-45 cm depth in the rooted marsh, which could serve as an anchor for the overlying highly organic mat layer found in both marsh types. Porewater …

Text-Independent Automatic Speaker Identification Using Partitioned Neural Networks, Laszlo Rudasi

Electrical & Computer Engineering Theses & Dissertations

This dissertation introduces a binary partitioned approach to statistical pattern classification which is applied to talker identification using neural networks. In recent years artificial neural networks have been shown to work exceptionally well for small but difficult pattern classification tasks. However, their application to large tasks (i.e., having more than ten to 20 categories) is limited by a dramatic increase in required training time. The time required to train a single network to perform N-way classification is nearly proportional to the exponential of N. In contrast, the binary partitioned approach requires training times on the order of N². …

A Responsive Evaluation In Two Hampton Roads Museums: The Development Of A Performance Assessment System For Museum Volunteers, Joan Fishman Hecht

Theses and Dissertations in Urban Services - Urban Education

The purpose of this study is to evaluate volunteer performance in two Hampton Roads museums. The research question was: How can managers of museum volunteer services evaluate volunteer performance? The research design was a naturalistic, responsive, utilization-focused evaluation in response to the research question. The data was collected with a systematic examination of volunteer performance activities using techniques of in-depth interviews, participant observations, a questionnaire, documents and records. The data was analyzed by categorizing, sorting and characterizing the categories, conducting member checks, and prioritizing the data. Triangulation was used to verify the collected information. This study determined important traits, performance …

Analysis Of Impact Damage Of Composite Laminates Using Five-Point Bending, Mark Edward Robeson

Mechanical & Aerospace Engineering Theses & Dissertations

The low-velocity impact of composite laminates can induce high transverse shear strains, resulting in severe damage within the laminate. This type of damage may be studied in a quasi-static manner by use of a multi-span beam shear test in five-point bending configuration. A five-point bending arrangement induces high transverse shear strains in sections of the laminate, causing failures, such as intraply cracks and delaminations, that are similar to those caused by low-velocity impact. Stress distributions in the laminate can be calculated using a potential energy approach, and these stress distributions can be correlated with failure locations in the five-point bending …

Experimental Investigation Of Crossflow Instability Waves In Rotating Disk Flow, Alan E. Blanchard

Mechanical & Aerospace Engineering Theses & Dissertations

For the past 40 years, the crossflow (or inflectional) instability associated with rotating disk flow has been generally assumed to be a pure vortex that is fixed with respect to the disk; however, the terms "wave" and "vortex" have also been used interchangeably throughout the computational and experimental literature to describe this instability. Through the use of both hot-wire surveys and smoke-wire flow visualizations in the present investigation, the existence of crossflow instability waves prior to vortex formation has been shown. The results of the hot-wire surveys and smoke-wire flow visualizations for both a "clean" disk case and a disk …

Direct Measurement Of The Van Der Waals Interaction Between An Atom And Its Images In A Micron-Sized Cavity, V. Sandoghdar, C. I. Sukenik, E. A. Hinds, S. Haroche

Physics Faculty Publications

The authors have measured by laser spectroscopy the energy of interaction between a sodium atom and its images in the walls of a micron-sized cavity. This cavity-QED study is the first direct quantitative test of the Lennard-Jones van der Waals interaction as a function of controlled atom-surface separation and mean-square electric dipole moment.

Single Object Detection Using Multiple Sensors With Unknown Noise Distributions, Shaofen Chen

Computer Science Theses & Dissertations

We consider the design of an object classification system that identifies single objects using a system of sensors; each sensor outputs a random vector, according to an unknown (noise) probability distribution, in response to a sensed object. We consider a special class of systems, called the linearly separable systems, where the error-free sensor outputs corresponding to distinct objects can be mapped into disjoint intervals on real line. Given a set of sensor outputs corresponding to known objects, we show that a detection rule α_emp that approaches the correct rule with a high probability can be computed. We show …

An Assessment Of Food Sanitation Knowledge And Practice Of Restaurant Workers In Taichung City, Taiwan, Shiow-Fu Sheu

Community & Environmental Health Theses & Dissertations

Taichung city is located in the western middle part of Taiwan, with a population of nearly 800,000. The total number of food service establishments in Taichung City is more than 10,000. Among these, nearly 2000 of the food establishments are considered restaurants. For such a large number of restaurants, the total number of food sanitation inspectors is 16. In order to overcome the shortage of the food inspector manpower problem, Taichung City Health Department has set up a "Food Sanitation Self-inspection Program", in an effort to encourage the restaurants to direct more attention to food sanitation problems. In the meantime, …

Factors Affecting The Kinetics Of Light Intensity Adaptation In Marine Phytoplankton, Chunzhi Guo

OES Theses and Dissertations

It has been suggested that the recent light history of phytoplankton and the kinetics of photoadaptation can be used to provide information about the vertical mixing processes in the upper mixed layer. To be useful as a parameter in a model of photoadaptation and vertical mixing, the response of a photoadaptive variable to changes in growth irradiance must be monotonic, significant, and comparable in time rate scale to mixing processes. Previous studies of photoadaptation kinetics have focused on the response of phytoplankton to changes in light intensity under continuous illumination. This dissertation attempts to elucidate the effects of light:dark cycle, …

Materially Nonlinear Finite Element Analyses Of Trusses And Slab-On-Grade Problems, Moayyad Moh'd Al-Nasra

Civil & Environmental Engineering Theses & Dissertations

The overall approach is to employ the finite-element method along with specified material models to account for material nonlinearity. This study includes two different applications: truss structures and slabs-on-grade.

Procedures for materially nonlinear analysis of truss structures, which apply for both determinate and indeterminate cases are proposed. The proposed procedures are simple and can handle a variety of different stress-strain functions, and the applied load does not have to be incremental. Proposed procedures results are verified with the output of NASTRAN.

A finite-element model for slab-on-grade is introduced. The concrete slab is represented by eight-node brick elements, and the joints …

Unsteady Euler And Navier-Stokes Computations Around Oscillating Delta Wing Including Dynamics, Ahmed Abd-El-Bar Ahmed Salman

Mechanical & Aerospace Engineering Theses & Dissertations

Unsteady flows around rigid or flexible delta wings with and without oscillating leading-edge flaps are considered. These unsteady flow problems are categorized under two classes of problems. In the first class, the wing motion is prescribed a priori and in the second class, the wing motion is obtained as a part of the solution. The formulation of the first class includes either the unsteady Euler or unsteady Navier-Stokes equations for the fluid dynamics and the unsteady linearized Navier-displacement (ND) equations for the grid deformation.

The problem of unsteady transonic flow past a bicircular-arc airfoil undergoing prescribed thickening-thinning oscillation is studied …

Some Solutions To A Lens Model With Applications To Warm-Core Eddies, Juping Liu

OES Theses and Dissertations

A model of lens-shaped anticyclonic eddies based on nonlinear shallow water equations is developed. The model is a three-layer fluid and allows for one asymmetric mode as well as specified environmental flows. The solution scheme is a polynomial expansion of the field variables. When inserted into the hydrographic equations, the expansion yields eight first-order differential equations for the time dependent amplitudes. This system of ordinary differential equations is numerically tractable. As long as the initial values meet the requirement of elliptical structure and the prescribed external force is tolerable for the initial values, the numerical solutions are stable. Numerical solutions …

Ring Dynamics In The Western Gulf Of Mexico, Adolphe W. Indest

OES Theses and Dissertations

The interaction of a recently-formed Loop Current ring and a fossil ring is studied using observations and a two-layered eddy-resolving general circulation model of the Gulf of Mexico. This interaction is investigated by following the evolution of volume, energy, potential vorticity, angular momentum and enstrophy within a model ring as it moves westward and encounters a fossil ring along the continental slope of the Gulf of Mexico. By comparing the model results with drifter and hydrographic data several new insights into ring/ring and ring/slope interactions are seen. A Loop Current ring may merge with a fossil ring along the slope. …

Reasoning By Analogy In A Multi-Level System Architecture For The Design Of Mechanisms, Ghassan F. Issa

Computer Science Theses & Dissertations

Since the first attempts to integrate AI technology and engineering design nearly two decades ago, few expert systems have been shown to demonstrate sufficient reasoning capabilities to solve real-world design problems. The complex nature of design, the lack of understanding of the design process, and the limitations of current expert system technology have all been shown to have adverse effects on the maturity of this research area. Therefore, our direction in this research concentrates on understanding the design process, investigating a novel area of research focusing on creative design, and incorporating the results into a system model feasible for production …

Evaluation Of Late Mesozoic And Cenozoic Tectonism: Atlantic Inner Coastal Plain Margin Near Richmond, Virginia, Andrew A. Gremos

OES Theses and Dissertations

A combined geologic, geophysical, and geomorphic analysis of the Virginia Inner Coastal Plain margin near Richmond was conducted to investigate the presence of basement structures and to evaluate their influence on the overlying sedimentary package and present-day landscape. Basement structures identified included north-northeast and northwest oriented faults that appear to bound and transect a north-northeast trending early Mesozoic basin or basins and other pre-existing zones of weakness. Observed offsets are propagated upward through the pre-Miocene strata in the form of reverse faults and flexuring. Fracture sets measured in the Petersburg Granite and overlying Coastal Plain units, stream drainage lines, and …

Search For The Mössbauer Effect In 109ag, Shokrollah Rezaie-Serej

Physics Theses & Dissertations

The 88-keV first-excited nuclear state in ¹⁰⁹Ag has a mean lifetime of 57.1 sec and a corresponding natural linewidth of 1.15 x 10^-17 eV which is nearly six orders of magnitude narrower than the width for the 93-keV 13.2-μsec state in ⁶⁷Zn. The 93-keV transition in ⁶⁷Zn has the narrowest linewidth for which the Mossbauer effect has been observed. The 88-keV transition in ¹⁰⁹Ag is obviously a very difficult case for the observation of the Mossbauer effect and provides a stringent test for exploring the practical limits of inhomogeneous line broadening in real single …

Monitoring Computer Systems: An Intelligent Approach, Myron Zhihong Xu

Computer Science Theses & Dissertations

Monitoring modern computer systems is increasingly difficult due to their peculiar characteristics. To cope with this situation, the dissertation develops an approach to intelligent monitoring. The resulting model consists of three major designs: representing targets, controlling data collection, and autonomously refining monitoring performance. The model explores a more declarative object-oriented model by introducing virtual objects to dynamically compose abstract representations, while it treats conventional hard-wired hierarchies and predefined object classes as primitive structures. Taking the representational framework as a reasoning bed, the design for controlling mechanisms adopts default reasoning backed up with ordered constraints, so that the amount of data …

Formant Estimation From Dctc's Using A Feedforward Neural Network, Shubhangi U. Kelkar

Electrical & Computer Engineering Theses & Dissertations

Formants are the natural frequencies of the human vocal tract. Existing methods for estimating formants from speech signals are computationally complex and subject to errors for certain type of speech sounds. This thesis describes a method for estimating vowel formant frequencies from Discrete Cosine Transform Coefficients (DCTC's), a form of cepstral coefficients, using a feedforward neural network with back-propagation training. Experimental results are based on a large multispeaker data base. The results are obtained for both a linear transformation and a feedforward neural network with a nonlinear hidden layer. In general, the neural network transformation is superior to the linear …

Development Of A Model Updating Technique For Controls-Structures Integrated Design Optimization, Angela Georges

Mechanical & Aerospace Engineering Theses & Dissertations

A model updating technique is developed with the intent of providing an efficient means of improving the accuracy of the modelling of the vibrational qualities of a large, flexible structure as it undergoes an integrated controls-structures design optimization. The proposed technique utilizes eigenvalue/eigenvector sensitivity information, two different model reduction methods which assign weights of importance to the vibrational modes of the structure, and modal switching based upon the modal weights determined by the model reduction methods. Issues associated with the numerical implementation of the proposed technique, such as discontinuities induced by modal switching, are also addressed.

The proposed model updating …

Shape Sensitivity Analysis And Optimization Of Skeletal Structures And Geometrically Nonlinear Solids, Ching-Hung Chuang

Mechanical & Aerospace Engineering Theses & Dissertations

Formulations and computational schemes for shape design sensitivity analysis and optimization have been developed for both skeletal structures and geometrically nonlinear elastic solids. The continuum approach, which is based on the weak variational form of the governing differential equation and the concept of the material derivative, plays a central role in such a development.

In the first part of this work, the eigenvalue and eigenvector sensitivity equations for skeletal structures are derived with respect to configuration variables of joint and support locations. This derivation is done by the domain method as well as the boundary method. The discrete approach for …

The Growth And Bioenergetics Of Callinectes Sapidus Larvae And The Effects Of Diet Quality On Larval Physiology, James J. Pletl

OES Theses and Dissertations

Food quality, especially ω3 polyunsaturated fatty acids (PUFA), can affect the physiology and metabolic efficiency of larvae of the blue crab, Callinectes sapidus. These affects may correlate with success in development and juvenile recruitment.

Larvae were exposed to two diets differing quantitatively in ω3 PUFA and respiration, excretion, growth, and feeding rates were measured for each larval stage and the megalopal stage. The energy partitioned to molts and specific dynamic action was also measured. T

he ω3 PUFA enriched diet resulted in a lower respiration rate when compared to the unsupplemented diet, but there was little differences in excretion …