Engineering Commons^™

Economic Analysis Of Costs Incurred From Chemical Exposures In The Workplace Resulting In Non-Carcinogenic Responses As Additional Justification For Pollution Prevention Projects, Michael L. Forcht, Timothy D. Neu

Theses and Dissertations

This research determines the applicability of using costs associated with chemical exposures in the workplace for financial justification of pollution prevention projects. Specifically, this thesis looks at costs incurred due to noncarcinogenic effects caused by chemical exposures. Average costs are determined through researching applicable statistical cost data. Acute effects are analyzed using an analysis of available statistical accident data from multiple sources. Expected values are then calculated based upon the projected cost of an accident and the probability of having an accident. Chronic effects are analyzed using an empirical analysis. A risk assessment is used to determine the likelihood of …

Automatic Tuning Of Integrated Filters Using Neural Networks, Lutz Henning Lenz

Dissertations and Theses

Component values of integrated filters vary considerably due to· manufacturing tolerances and environmental changes. Thus it is of major importance that the components of an integrated filter be electronically tunable. The method explored in this thesis is the transconductance-C-method.

A method of realizing higher-order filters is to use a cascade structure of second-order filters. In this context, a method of tuning second-order filters becomes important.

The research objective of this thesis is to determine if the Neural Network methodology can be used to facilitate the filter tuning process for a second-order filter (realized via the transconductance-C-method). Since this thesis is, …

Unified Bias Analysis Of Subspace-Based Doa Estimation Algorithms, Yang Lu

Dissertations and Theses

This thesis presents the unified bias analysis of subspace-based DOA estimation algorithms in terms of physical parameters such as source separation, signal coherence, number of senors and snapshots. The analysis reveals the direct relationship between the performance of the DOA algorithms and signal measurement conditions. Insights into different algorithms are provided. Based upon previous first-order subspace perturbations, second-order subspace perturbations are developed which provide basis for bias analysis and unification. Simulations verifying the theoretical bias analysis are presented.

Detecting Chaotic Signals With Nonlinear Models, Qin Cai

Dissertations and Theses

In this thesis we apply chaotic dynamic data analysis to the area of discrete time signal processing. A newly developed Hidden Filter Hidden Markov Model is introduced in detection of chaotic signals. Numerical experiments have verified that this novel nonlinear model outperforms linear AR model in detecting chaotic signals buried by noise having similar power spectra. A simple Histogram Model is proposed which can also be used to do detection on the data sets with chaotic behavior. Receiver Operating Characteristics for a variety of noise levels and model classes are reported.

A New Approach To The Optimal Filtering Of Differential Phase Measurements Of Gps Signal In The Precision Survey, Shengan Wang

Dissertations and Theses

The Global Positioning System (GPS) has become popular research and application interests in surveying and many other areas. Nowadays, the accuracy of the Differential GPS can easily reach the order of a few meters. Yet, there are still many ways to exploit the GPS system signal carrier to improve the accuracy to less than meter level. In this thesis, a new approach to improve the accuracy to less than meter level is presented while the observer is in the dynamic situation. In order to reach the sub-meter accuracy, we measure on the carrier phase difference (The L1 carrier frequency is …

Single Scheduling Problem With Dependent Setup Cost, Mohamed Mahmoud Zaki

Archived Theses and Dissertations

No abstract provided.

Application Of Sequence Comparison Methods To Multisensor Data Fusion And Target Recognition, Edmund W. Libby

Theses and Dissertations

This research addresses methods for exploiting the joint likelihood of observed kinematic and nonkinematic (sensor signature) physical events to improve dynamic object and target recognition. A principal direction is the application of dynamic programming sequence comparison techniques to condition matching of object signatures to known models according to observed kinematics. A second direction is the application of kinematic/aspect-angle Kalman filter trackers to condition kinematic tracking according to observed signatures. These conditioning processes dramatically reduce ambiguity in object recognition, and can be used together or separately to allow computation of a posterior probabilities of object class membership using Bayesian methods. Proposals …

Comparison Of A Distributed Kalman Filter Versus A Centralized Kalman Filter With Fault Detection Considerations, Paul J. Lawrence Jr.

Theses and Dissertations

This project examined the results obtained by simulating an aircraft navigation system with a partial complement of a typical avionics sensor array. Two different techniques of estimation processes were utilized and compared: the conventional Kalman and the federated filter architectures. Areas of interest include error state estimation accuracy and overall performance, residual behavior under normal and induced sensor failure conditions, and potential for failure detection and isolation. Several simulations were accomplished for each filter design and the results were compared in order to verify the validity of the newly developed federated filter architecture. Comparison of the error state estimation accuracies …

Finite Element Analysis For An Involute Spur Gear Noise Excitation By Impact Effects, Wenbeen Li

Electronic Theses & Dissertations

The purpose of this study includes (1) to identify the relationship between the impact loads or backlash and the sound field pressure of impact direct noise of meshing gears, (2) to show that impact whether or not the impact direct noise contributes to the noise of overall gear system, and (3) to demonstrate how impact direct noise can be predicted. The method used to predict was finite element analysis and numerical solution. This research presents the analytical model of impact direct noise prediction for meshing gear teeth based on the data that the tooth vibration and surface are known by …

Boundary Value Problems In Rectilinearly Anisotropic Thermoelastic Solids, Gilbert Kerr

Mathematics & Statistics Theses & Dissertations

The boundary value problems which are considered are the type that arise due to the presence of a Griffith crack (or cracks) in an anisotropic thermoelastic solid. The thermoelastic field, in such materials, when the infinitesimal theory is employed, is governed by a set of elliptic partial differential equations. The general solution of these equations is expressed in terms of arbitrary analytic functions whose real parts, in turn, are expressed in terms of Fourier type integrals or Fourier series. Integral transform techniques are then used to determine the stress intensity factors (and other pertinent information) for various crack geometries. In …

Boundary Layer Influences On The Subsonic Near-Wake Of A Family Of Three-Dimensional Bluff Bodies, Charles Willliam Alcorn

Mechanical & Aerospace Engineering Theses & Dissertations

A study is reported on subsonic bluff body near-wake flows. It has been determined that one family of bluff bodies, namely slanted-base ogive cylinders, can experience either a closed recirculating near-wake, or a longitudinal vortex near-wake depending on the base slant-angle and the Reynolds number. This suggests a dependence of near-wake parameters on the state of the boundary layer ahead of separation. This report addresses the influence of the boundary layer on the near-wake of slanted-base bluff bodies. Experiments were conducted in two facilities, the 6-inch Magnetic Suspension and Balance System (MSBS) at NASA Langley Research Center and the Old …

Studies On Nonequilibrium Phenomena In Supersonic Chemically Reacting Flows, Rajnish Chandrasekhar

Mechanical & Aerospace Engineering Theses & Dissertations

This study deals with a systematic investigation of nonequilibrium processes in supersonic combustion. The two-dimensional, elliptic Navier-Stokes equations are used to investigate supersonic flows with nonequilibrium chemistry and thermodynamics, coupled with radiation, for hydrogen-air systems. The explicit, unsplit MacCormack finite-difference scheme is used to advance the governing equations in time, until convergence is achieved.

For a basic understanding of the flow physics, premixed flows undergoing finite rate chemical reactions are investigated. Results obtained for specific conditions indicate that the radiative interactions vary substantially, depending on reactions involving HO$\sb2$ and NO species, and that this can have a noticeable influence on …

A Computer-Based Strategy To Facilitate Organizational Learning Process, Charles B. Keating

Engineering Management & Systems Engineering Theses & Dissertations

This research investigated the development of Organizational Learning Process (OLP) through the application of a computer-based strategy in an organizational setting. OLP is developed from the organizational learning literature as an integration of similar concepts of organizational processes of inquiry essential to organizational learning. These concepts included: organizational dialectic (Argyris and Schon 1978), surfacing and testing mental models (Senge 1990a,1990b), and interpretation process (Daft and Weick 1984). A qualitative research methodology was developed within a participatory action research framework (Whyte 1989). A six phase research project, designed as a computer-based strategy to generate OLP, was applied in an organizational setting. …

A Multivariate Quality Control Approach For Automated Manufacturing Systems, Hisham Naim Ashur

Engineering Management & Systems Engineering Theses & Dissertations

In today's competitive manufacturing environment, effective and practical statistical quality control approaches are essential. A successful process control approach needs to provide on line real time monitoring of quality related characteristics.

No longer acceptable is an approach that analyzes quality related data only after the product is produced. A statistical process control approach that monitors the process during production and that reports trouble spots before bad products are made is necessary in an automated manufacturing environment.

An automated manufacturing environment is characterized by high volume production runs and short production cycles. Traditional statistical process control approaches are not capable of …

Fiber Enhanced Viscoelastic Damping Polymers And Their Application To Passive Vibration Control, Houchun Xia

Mechanical & Aerospace Engineering Theses & Dissertations

A new composite damping material is investigated, which consists of a viscoelastic matrix and high elastic modulus fiber inclusions. This fiber enhanced viscoelastic damping polymer is intended to be applied to light-weight flexible structures as surface treatment for passive vibration control. A desirable packing geometry for the composite material is proposed, which is expected to produce maximum shear strain in the viscoelastic damping matrix. Subsequently, a micromechanical model is established in which the effect of fiber segment length and relative motion between neighboring fibers are taken into account. Based on this model, closed form expressions for the effective storage and …

Three-Dimensional Transport Simulations Of The Dispersal Of Volcanic Aerosol From Mount Pinatubo, T. Duncan A. Fairlie

Mechanical & Aerospace Engineering Theses & Dissertations

A global finite-difference model that simulates the large-scale dynamics of the Earth's stratosphere and mesosphere is combined with a global spectral transport model to investigate aspects of the initial dispersal of the volcanic aerosol plume from the Mount Pinatubo eruption in 1991. Results of the modelling study are found to compare well with observations of the volcanic plume made from satellite instruments. Dynamical quantities, diagnosed from the simulated fields are used to provide insight into the evolution of the volcanic plume. Lagrangian trajectory analysis is used to help assess the performance of the Eulerian transport model and to highlight small-scale …

Study Of Algebraic Reynolds Stress Models For The Computation Of Secondary Motion In Channels, Tomas Chylek

Mechanical & Aerospace Engineering Theses & Dissertations

A three-dimensional computer code for solving Reynolds equations of turbulent flow at high Reynolds numbers in generalized curvilinear coordinates is used to study the engineering applications of several variants of linear and nonlinear second moment algebraic Reynolds stress models based on pressure-strain correlation of Launder, Recce and Rodi (1975) and Speziale, Sarkar and Gatski (1991). A new form of algebraic Reynolds stress equation in generalized curvilinear coordinates is derived based on simplification of Reynolds stress transport equations. Two implicit and two explicit implementations are explored in three different geometries of straight channel flows. The predictions of secondary motion driven by …

Light Injection From An Active Cladding To The Core Of A Fiber Optic Fluorosensor, Alvin Leon Bryant

Electrical & Computer Engineering Theses & Dissertations

A fluorosensor works on the basis of light injection from the clad into the core of an optical fiber. The sensitivity of such a sensor depends on the efficiency of light injection. Conditions necessary for a high injection efficiency are experimentally determined. The refractive index difference between the core and the clad,ⁿcore ^-nclad, must be maximized to achieve a high injection efficiency. Since an air clad has the least refractive index, a bare core fiber will have a maximum efficiency. Standard optical fibers used for communication employ a minimum value for ⁿcore ^-nclad, in order …

Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen

Electrical & Computer Engineering Theses & Dissertations

Fiber optic sensors are widely used in today's technological applications, providing many advantages that conventional sensors lack. In particular, there is a demand in hypersonic applications to develop microphones to measure acoustic pressure that performs in high temperature and noisy surroundings. This thesis analyzes fiber optic lever microphones (FOLM), since they perform at high temperatures. An FOLM system is an intensity modulated sensor, which is simple to implement and is small in size. Two models of the FOLM have been fabricated and calibrated. The first model uses a seven-element fiber array while the second uses a single-fiber to transmit and …

Absorption Imaging Studies On Intrinsic Gaas, John Samuel Kenney

Electrical & Computer Engineering Theses & Dissertations

A diagnostic technique has been developed which allows recording of the temporal and spatial development of electric field structures in GaAs photoconductive switches. The optical method is based on the Franz-Keldysh effect. Measurements were performed with a Nd:YAG activation laser and a GaAs laser diode as the probe laser. At low applied voltages a 100 atm wide region of high electric field is seen at the cathode only. With increasing voltage strong domain like structures emerge at the anode also. A calibration measurement shows that the electric fields in these domains are well above 50 kV/cm. At a threshold voltage, …

Development Of A Knowledge Based System For Wastewater Pipeline Failure Risk Assessment, Adam Mayanzani Ngaliga

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this thesis was to study and analyze the wastewater pipeline failure risk assessment process, and then design and develop an effective and efficient wastewater pipeline risk assessment tool for the Hampton Roads Sanitation District, in Virginia, U.S.A. A knowledge based system was developed using an expert system building shell (Xi-Plus).

The system design is based on the knowledge elicited from the experts and literature in sanitary pipeline failure risk evaluation. The knowledge base contains both heuristics and procedural rules. The system interprets the information provided by the user and reasons from that information to reach conclusions on …

Predicting Seepage Of Leachate From The St. Johns Landfill To Ground And Surface Water Systems, Kevin A. Schock

Dissertations and Theses

Determination of the vertical and horizontal groundwater hydraulic gradient within a landfill is the first step in determining the potential of groundwater contamination from the landfill leachate. The length of a study and the frequency at which measurements are recorded can greatly affect the description of the local groundwater environment. A more comprehensive analysis can be preformed for longer periods of study and greater measurement frequency. The intent of this study was to install a continuous groundwater level monitoring system around the st. Johns Landfill for a minimum study length of one year. This would allow a more thorough study …

Performance Analysis Of A Hierarchical, Cache-Coherent, Shared Memory Based, Multi-Processor System, Raman Nayyar

Dissertations and Theses

We have conducted a performance analysis of a large scale multiprocessor system based on shared buses organized in a hierarchical fashion and employing an easy to implement snoopy cache protocol. · This arrangement, named TREEBUS [ 5], presents a logical extension path for multiprocessor systems based on a single shared bus whose scalability is limited by the available system bus bandwidth [26]. The multiple, independent, hierarchical buses overcome the bus bandwidth limitation and the architecture can scale to relatively large sizes. We have developed an easy to use, reasonably accurate and computationally efficient analytic model for analyzing the performance of …

Waveform Estimation With Jitter Noise By Pseudo Symmetrical Probability Density Function, Wei-Da Hao

Dissertations and Theses

A new method for solving jitter noise in estimating high frequency waveform is proposed. It reduces the bias of the estimation in those points where all the other methods fail to achieve. It provides preliminary models for estimating percentiles in Normal, Exponential probability density function. Based on the model for Normal probability density function, a model for any probability density function is derived. The resulting percentiles, in turn, are used as estimates for the amplitude of the waveform. Simulation results show us with satisfactory accuracy.

Measurement Techniques For Noise Figure And Gain Of Bipolar Transistors, Wayne Kan Jung

Dissertations and Theses

First, the concepts of reflection coefficients, s-parameters, Smith chart, noise figure, and available power gain will be introduced. This lays out the foundation for the presentation of techniques on measuring noise figure and gain of high speed bipolar junction transistors. Noise sources in a bipolar junction transistor and an equivalent circuit including these noise sources will be presented. The process of determining the noise parameters of a transistor will also be discussed. A Pascal program and several TEKSPICE scripts are developed to calculate the stability, available power gain, and noise figure circles. Finally, these circles are plotted on a Smith …

Study Of Single-Electron Capture From He, Ne And Ar By Low-Energy Ne^Q+ Recoil Ions Using Translational Energy Spectroscopy, Renad Qubaj-Said

Masters Theses

No abstract provided.

Experimental And Analytical Analysis Of The Response Of A Smart Beam To Rate Feedback, Terance J. Hoffman

Theses and Dissertations

A smart beam with embedded sensors and actuators was analyzed and tested. The smart beam studied was constructed from graphite and epoxy with piezoceramic actuators and NiTiNOL sensors embedded. It was mounted vertically and subjected to transverse dynamic loading at the free end. Analytic expressions for the open loop and closed loop response (using strain rate feedback control) of the beam (including internal damping) to external forcing were derived in detail. Experimental testing of the beam verified the accuracy of the predicted open loop response.

Experimental Investigation Of The Effects Of Blowing Ratio Parameter On Heat Transfer To A Film-Cooled Flat Plate, Marco R. Valencia

Theses and Dissertations

The effects of blowing ratio on film cooling effectiveness were investigated. Two round-nosed test plates were used. One made of aluminum and the second of corian (low thermal conductivity). Injection at 35 degrees in the downstream direction was studied. Helium was mixed with air to produce a density ratio (coolant to mainstream) of 1.6 and 2.0, while the blowing ratio varied from 0.3 to 2.2. Surface temperature was measured by thin film gages located up to a nondimensional downstream distance X/D of 30. Two injection regimes, weak and strong, were found. In the weak regime, film cooling reduced gage heat …

Thermal Behavior Of A Stratified Cylindrical Energy Storage Tank, Sheherazad Youssef Ezz Eldeen Ahmed Korayem

Archived Theses and Dissertations

No abstract provided.

Evaluation Of Dynamic Stresses And Fatigue Life Prediction For Randomly Loaded Structure, Walied Ahmed Moussa

Archived Theses and Dissertations

No abstract provided.