Engineering Commons^™

The Effects Of Risk Management Program Implementation On Worker Safety Knowledge, John C. Donnelly

Community & Environmental Health Theses & Dissertations

This study examined the effect of the implementation of a risk management program tool on worker safety knowledge in a composite building material fabrication facility whose workers suffered from an increasingly high injury (incidence) rate in recent years. Risk assessment codes (RACs) and job safety analyses (JSAs) were the primary tools used to introduce workers to the concept of risk. Because employee involvement is a crucial element in JSA development. employee input was frequently solicited throughout JSA development.

The study instrument consisted of a pre-test and post-test survey, to which an experimental and control group were subjected. The instrument was …

Atomic Broadcast In Heterogeneous Distributed Systems, Osman Zeineldine

Computer Science Theses & Dissertations

Communication services have long been recognized as possessing a dominant effect on both performance and robustness of distributed systems. Distributed applications rely on a multitude of protocols for the support of these services. Of crucial importance are multicast protocols. Reliable multicast protocols enhance the efficiency and robustness of distributed systems. Numerous reliable multicast protocols have been proposed, each differing in the set of assumptions adopted, especially for the communication network. These assumptions make each protocol suitable for a specific environment. The presence of different distributed applications that run on different LANs and single distributed applications that span different LANs mandate …

System Dynamic Modeling Of Activity And Flow Relationships In Plant Layout Problems, Gary Allen Weaver

Engineering Management & Systems Engineering Theses & Dissertations

The problem of determining an optimal plant layout involves the distribution of machinery, service areas, and storage spaces. The solution is usually determined for a specific period of time and static in nature. Planning for the plant layout is normally performed at the onset of new construction, or major refurbishment of an existing facility. In addition, plant layouts are renewed when a significant productivity decrease is experienced over long periods of time and linked to material flow problems, and when an expanding company plans for major capital expenditures in equipment and space. Due to the dynamic nature of business the …

An Experimental Investigation Of Wall Cooling Effects On Hypersonic Boundary Layer Stability In A Quiet Wind Tunnel, Alan E. Blanchard

Mechanical & Aerospace Engineering Theses & Dissertations

One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, 'quiet' Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same 'N=10' criterion used to predict boundary-layer transition in subsonic, transonic, and …

Buckling Analysis And Optimum Design Of Multidirectionally Stiffened Composite Curved Panel, Navin R. R. Jaunky

Mechanical & Aerospace Engineering Theses & Dissertations

Continuous filament grid-stiffened structure is a stiffening concept that combines structural efficiency and damage tolerance. However, buckle resistant design optimization of such structures using a finite element method is expensive and time consuming due to the number of design parameters that can be varied. An analytical optimization procedure which is simple, efficient and supports the preliminary design of grid-stiffened structures for application to combined loading cases is needed.

An analytical model for a general grid-stiffened curved panel is developed using an improved smeared theory with a first-order, shear-deformation theory to account for transverse shear flexibilities and local skin-stiffener interaction effects. …

Dynamic Unstructured Method For Prescribed And Aerodynamically Determined Relative Moving Boundary Problems, Kamakhya Prasad Singh

Mechanical & Aerospace Engineering Theses & Dissertations

A new methodology is developed to simulate unsteady flows about prescribed and aerodynamically determined moving boundary problems. The method couples the fluid dynamics and rigid-body dynamics equations to capture the time-dependent interference between stationary and moving boundaries. The unsteady, compressible, inviscid (Euler) equations are solved on dynamic, unstructured grids by an explicit, finite-volume, upwind method. For efficiency, the grid adaptation is performed within a window around the moving object. The Eulerian equations of the rigid-body dynamics are solved by a Runge-Kutta method in a non-inertial frame of reference. The two-dimensional flow solver is validated by computing the flow past a …

Numerical Investigation Of Shock-Induced Combustion Past Blunt Projectiles, Jagjit K. Ahuja

Mechanical & Aerospace Engineering Theses & Dissertations

A numerical study is conducted to simulate shock-induced combustion in premixed hydrogen-air mixtures at various free-stream conditions and parameters. Two-dimensional axisymmetric, reacting viscous flow over blunt projectiles is computed to study shock-induced combustion at Mach 5.11 and Mach 6.46 in hydrogen-air mixture. A seven-species, seven reactions finite rate hydrogen-air chemical reaction mechanism is used combined with a finite-difference, shock-fitting method to solve the complete set of Navier-Stokes and species conservation equations. In this approach, the bow shock represents a boundary of the computational domain and is treated as a discontinuity across which Rankine-Hugoniot conditions are applied. All interior details of …

Nonlinear Transient Thermal Analysis By The Force-Derivative Method, Narayani V. Balakrishnan

Mechanical & Aerospace Engineering Theses & Dissertations

The force-derivative method (FDM) represents a series of higher-order modal methods which offer an increasingly improved approximation of the higher modes neglected in the basic mode-displacement method (MDM). The FDM includes additional terms which involve the forcing function and derivatives of the forcing function with respect to time. The mode-acceleration method (MAM), extensively used in structural analysis, is a first-order form of the FDM which includes only one correction term that depends on the forcing function itself. The success of the FDM in many structural dynamic applications has prompted its application for solving transient thermal problems. The superior convergence of …

Studies Of Mixing Processes In Gases And Effects On Combustion And Stability, Frank Paul Kozusko Jr.

Mathematics & Statistics Theses & Dissertations

Three physical models of laminar mixing of initially separated gases are studied. Two models study the effects of the mixing dynamics on the chemical reactions between the gases. The third model studies the structure and stability of a laminar mixing layer in a binary gas. The three models are:

1. Two ideal and incompressible gases representing fuel and oxidizer are initially at rest and separated across an infinite linear interface in a two dimensional system. Combustion, expected as the gases mix, will lead to a rapid rise in temperature in a localized area, i.e. ignition. The mixing of the gases …

Development Of A Knowledge-Based System For Generating Process Plans Using Group Technology: A Study For Norfolk Naval Shipyard, William P. Keene Jr.

Engineering Management & Systems Engineering Theses & Dissertations

The purpose of this research was to study and analyze the Norfolk Naval Shipyard's manufacturing methods of determining part families and generating part process plans for parts in the machine shop. A knowledge-based decision support system was designed based on knowledge acquired from machinist experts and documented sources of the Norfolk Naval Shipyard. The system interprets specific part information provided by the user, categorizes parts into part families and generates process plans to manufacture the parts. The system was evaluated and tested for parts provided by Norfolk Naval Shipyard.

Identification And Characterization Of The Iron-Zinc Intermetallics Formed In Galvanneal Steel, Richard Frederick George Grant

Physics Theses & Dissertations

The demand to improve the corrosion resistance of steel sheet, particularly for use within the automotive industry, has led to a dramatic increase in the use of coated steels in place of cold-rolled sheet steel. Galvanneal steel results from the post annealing of the zinc-coated steel sheet, in which iron and zinc are interdiffused to form an iron-zinc alloy coating. Within this alloy coating, four main iron-zinc phases, Zeta, Delta, Gamma-1, and Gamma may be present. Manufacture of the most suitable coating requires identifying which phases form during the galvannealing process, an understanding of the properties of each phase and …

Closed-Loop Identification Of Unstable Systems In Time And Frequency Domains, Hyun Chang Lee

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation presents closed-loop identification algorithms of an unstable system in the time and frequency domains. In the time domain, the projection filter, which is a linear transformation which projects (transforms) a finite number of input-output data of a system into its current space, is used to relate the state-space model with a finite difference model. The method developed can take into account the effects of process noise as well as measurement noise and identify open-loop systems with unknown feedback dynamics in the closed-loop operation. Then the recursive relations between Markov parameters and the ARX model are derived to identify …

An Investigation Of The Speed And Power Limitations Of A Copper-Doped Gallium Arsenide Photoconductive Switch, David Clifton Stoudt

Electrical & Computer Engineering Theses & Dissertations

The processes of persistent photoconductivity followed by photo-quenching are demonstrated in copper-compensated, silicon-doped, semi-insulating gallium arsenide. These processes allow a switch to be developed that can be closed by the application of one laser pulse (λ = 1.06 μm) and opened by the application of a second laser pulse with a wavelength equal to twice that of the first laser (λ= 2.13 μm). Switch closure is primarily achieved by elevating electrons from a deep copper center which has been diffused into the material. The opening phase is a two-step process which relies initially on the absorption of the 2-μm laser …

Aerodynamic Design Optimization With Consistently Discrete Sensitivity Derivatives Via The Incremental Iterative Method, Vamshi M. Korivi

Mechanical & Aerospace Engineering Theses & Dissertations

In this study which involves advanced fluid-flow codes, an incremental iterative formulation (also known as the "delta" or "correction" form), together with the well-known spatially split approximate-factorization algorithm, is presented for solving the large, sparse systems of linear equations that are associated with aerodynamic sensitivity analysis. For the smaller two dimensional problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. However, iterative methods are needed for larger two-dimensional and three dimensional applications because direct methods require more computer memory than is currently …

Component Mode Synthesis-Based Design Methodology For Structural Modification And Synthesis, Venkateshwarlu Maroju

Mechanical & Aerospace Engineering Theses & Dissertations

In this work, structural modification and synthesis techniques based on component mode synthesis are presented. The component mode synthesis method formulates the eigenvalue equation of an entire structure in terms of the vibration characteristics of individual components in the assembly. Through this functional relationship, the individual components are successfully treated as the design entities in the proposed methodology. Unlike conventional design modification techniques that can only treat the properties of the finite elements as the design variables, this technique uses the vibration and static responses of the individual components as the design entities. The sensitivity derivatives of the global responses …

Understanding Collaborative Writing Of Technical Proposals With A Process/Product Model, Frank Joseph Greco

Engineering Management & Systems Engineering Theses & Dissertations

Group work creates concerns with respect to performance, collaboration, and conflict management. Writing technical proposals creates appropriate settings for gaining insight into work group efficiencies and project conflict. The research involved different work groups preparing responses to Federal Government solicitations. A proposed Process/Product model was applied to create a new framework and perception of the technical proposal development effort. There exists a rich dialectic between the forces of Process, (how the effort is accomplished), and, Product, (what the effort will produce.) The investigation attempted to learn if the P/P model provides explanations for project conflict during technical collaborative writing.

The …

Knowledge Acquisition And Structuring By Multiple Experts In A Group Support Systems Environment, Bernard Lee Lewis

Engineering Management & Systems Engineering Theses & Dissertations

This study addresses the impact of Group Decision Support Systems (GDSS) on expert system development by multiple Domain Experts. Current approaches to building expert systems rely heavily on knowledge acquisition and prototyping by a Knowledge Engineer working directly with the Domain Expert. Although the complexity of knowledge domains and new organizational approaches demand the involvement of multiple experts, standard procedures limit the ability of the Knowledge Engineer to work with more than one expert at a time.

Group Decision Support Systems offer a networked computerized environment for group work activities, in which multiple experts may express their ideas concurrently and …

Finite Element Nonlinear Random Response Of Composite Panels Of Arbitrary Shape To Acoustic And Thermal Loads Applied Simultaneously, Roger R. Chen

Mechanical & Aerospace Engineering Theses & Dissertations

The nonlinear random response of composite plates to the simultaneously applied, combined acoustic/thermal loads are investigated in this dissertation. A finite element formulation for the nonlinear random response is developed. The three-node Mindlin plate element with improved transverse shear is extended and employed. The extension includes the development of the thermal geometric matrix, the mass matrix, the first- order and second-order nonlinear stiffness matrices, and the thermal and mechanical load vectors. An innovative solution procedure has been created which is believed to be the first attempt to analyze nonlinear random response of complex composite panels subjected to simultaneous acoustic and …

Electric Field Mapping System With Nanosecond Temporal Rosolution, F. E. Peterkin, R. Block, K. H. Schoenbach

Bioelectrics Publications

The electric field dependence of the absorption coefficient in semi‐insulating GaAs at the absorption edge was measured in a high‐voltage pulsed experiment. Pulse duration was kept below 50 ns in order to avoid thermal effects. A GaAs laser diode was used as a probe light source with wavelength varied from 902 to 911 nm. For fields up to 40 kV/cm the absorption coefficient increased from 3 to 17 cm⁻¹ at 902 nm, with smaller absolute increases evident at the longer wavelengths. Calculation from theory was consistent with this behavior. The spatial variation of the electric field was also recorded …

Supralinear Photoconductivity Of Copper Doped Semi-Insulating Gallium Arsenide, K. H. Schoenbach, R. P. Joshi, F. Peterkin, R. L. Druce

Bioelectrics Publications

We report on the intensity dependent supralinear photoconductivity in GaAs:Si:Cu material. The results of our measurements show that the effective carrier lifetime can change over two orders of magnitude with variations in the intensity of the optical excitation. A threshold intensity level has been observed and can be related to the occupancy of the deep copper level. Numerical simulations have also been carried out to analyze the trapping dynamics. The intensity dependent lifetimes obtained from the simulations match the experimental data very well. Finally, based on the nonlinear intensity dependence of the effective lifetimes, a possible low‐energy phototransistor application for …

Does Junk Dna Regulate Gene Expression In Humans, M. A. Hulten, Michael W. Stacey, S. J. Armstrong

Bioelectrics Publications

No abstract provided.

A Nonlinear Dynamic Method For Supporting Large-Scale Decision-Making In Uncertain Environments, Wayne Woodhams

Engineering Management & Systems Engineering Theses & Dissertations

This research developed a methodology for supporting decision making by reducing uncertainty in decision environments which are too large, dynamic and complex to be treated by traditional quantitative and simulation techniques. These environments are complex because of the free choice associated with human involvement, and the existence of a large number of interrelated factors which influence the outcomes of the decision process. They are dynamic because the ground rules affecting those interrelationships are constantly changing. Uncertainty cannot be treated probabilistically, since identification of a full set of outcomes and factors of influence is not possible.

The venue for the investigation …

Effects Of Large Aspect Ratios And Fluctuations On Hard X-Ray-Detection In Lower Hybrid Driven Divertor Tokamaks, Linda L. Vahala, George Vahala, Paul Bonoli

Electrical & Computer Engineering Faculty Publications

It is shown that lower hybrid wave scattering from fluctuations plays a critical role in large aspect ratio divertor plasmas even through the edge density fluctuation levels are only at 1%. This is seen in the theoretically calculated electron power-density profiles which can be directly correlated to the standard experimental chordal hard x-ray profiles. It thus seems that fluctuation effects must be included in determining rf current-density profiles.

Compensation And Characterization Of Gallium Arsenide, Randy A. Roush

Electrical & Computer Engineering Theses & Dissertations

The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the shallow …

Scanning-Tunneling-Microscopy Study Of Pb On Si(111), D. Tang, H. E. Elsayed-Ali, J. Wendelken, J. Xu

Electrical & Computer Engineering Faculty Publications

Scanning-tunneling microscopy has been used to study temperature and coverage dependence of the structure of lead on the Si(111)-7×7 surface. For low Pb coverage, the Pb atoms favored the faulted sites. The ratio between the number of Pb atoms on faulted to unfaulted sites increased after sample annealing. An energy difference of 0.05 eV associated with a Pb atom on these two sites is estimated. The mobility of Pb atoms on Si(111) was observed at a temperature as low as 260°C for a coverage of 0.1 and 1 ML. © 1995 The American Physical Society.

A Diamond Thin Film Flow Sensor, Sacharia Albin, John C. Hagwood, John B. Cooper, David L. Gray, Scott D. Martinson, Michael A. Scott

Electrical & Computer Engineering Faculty Publications

We present the results of theoretical modeling and experimental testing of a diamond thin film sensor for flow studies. It is shown that the high thermal conductivity of a diamond film can enhance the frequency response of the flow sensor. One-dimensional heat diffusion equation was solved using the finite difference method for determining the frequency response. Two different sensor structures were analyzed: a Ni film on a quartz substrate (Ni/Q) and an intermediate layer of diamond film between the Ni film and quartz substrate (Ni/D/Q). The theoretical model predicts a frequency response for the Ni/D/Q sensor higher than that of …

Comparing Traditional Statistical Models With Neural Network Models: The Case Of The Relation Of Human Performance Factors To The Outcomes Of Military Combat, William Oliver Hedgepeth

Engineering Management & Systems Engineering Theses & Dissertations

Statistics and neural networks are analytical methods used to learn about observed experience. Both the statistician and neural network researcher develop and analyze data sets, draw relevant conclusions, and validate the conclusions. They also share in the challenge of creating accurate predictions of future events with noisy data.

Both analytical methods are investigated. This is accomplished by examining the veridicality of both with real system data. The real system used in this project is a database of 400 years of historical military combat. The relationships among the variables represented in this database are recognized as being hypercomplex and nonlinear.

The …

Nozzle Flow With Vibrational Nonequilibrium, John Gary Landry

Mathematics & Statistics Theses & Dissertations

Flow of nitrogen gas through a converging-diverging nozzle is simulated. The flow is modeled using the Navier-Stokes equations that have been modified for vibrational nonequilibrium. The energy equation is replaced by two equations. One equation accounts for energy effects due to the translational and rotational degrees of freedom, and the other accounts for the affects due to the vibrational degree of freedom. The energy equations are coupled by a relaxation time which measures the time required for the vibrational energy component to equilibrate with the translational and rotational energy components. An improved relaxation time is used in this thesis. The …