Engineering Commons^™

Numerical Prediction Of Turbulent Diffusion Flames Formed By Cylindrical Tube Injector, Ali S. Kheireddine

Mechanical & Aerospace Engineering Theses & Dissertations

This work summarizes numerical results for a diffusion flame formed from a cylindrical tube fuel injector, issuing gaseous fuel jet vertically in a quiescent atmosphere. Both pure fuels as well as fuel mixtures are examined. The primary objective is to predict the flame base height as a function of the jet velocity. A finite volume scheme is used to discretize the time-averaged Navier-Stokes equations for the reacting flow, resulting from the turbulent fuel jet motion. The turbulent stresses, and heat and mass fluxes are computed from the Reynolds stress turbulence model. A chemical kinetics model involving a two-step chemical reaction …

Comprehensive Conjunctive-Use Management Of Connected Surface Water Groundwater Systems Using Stochastic Inputs And Uncertainties, Seshadri Suryanarayana

Civil & Environmental Engineering Theses & Dissertations

A comprehensive conjunctive-use management model is developed. The dynamics of flow and solute transport processes in connected surface water groundwater systems are integrated by a dual programming management model. The governing aquifer flow parameters and streamflows are treated as stochastic random processes. Multiple realizations of the random field are generated and are explicitly incorporated in a non-linear optimization model along with other system, environmental, and management constraints. To facilitate management of large aquifer systems, a linked simulation-optimization approach is used. The simulation program generates the response matrices for flow and transport processes. The management model then determines optimal well discharges …

Exploring Knowledge Processes For Technology Assimilation, Rochelle K. Young

Engineering Management & Systems Engineering Theses & Dissertations

In the emerging knowledge society, the ability to make the experience and expertise of those involved in and affected by new technology unconditionally available to all members of an organization is becoming increasingly important. One of the problems in developing such knowledge processes for technology assimilation is that current social structures do not easily accommodate unconditional participation. Since the implementation of modern information technology is changing the workplace and the nature of work itself, alternative social structures are needed. This research takes as given that deep questions concerning knowledge processes and social transformation are in principle undecidable; and, only questions …

An Artificial Life Model Of Engineering Attrition Contemplation: Why Do Federally Employed Civilian Engineers Think Of Quitting?, John William Herweg

Engineering Management & Systems Engineering Theses & Dissertations

The research objective is, using engineer turnover, to develop an Artificial Life (A-Life) model and simulation methodology useful for studying behavioral variables of individuals in an organization.

One consequence of work stress is burnout, and its extreme expression is quitting or turnover. Various models have been used to explain and predict this behavior. Behavior models are useful tools to explore the ability of organizational policies to reduce stress levels and turnover. Advancing the usefulness of models is a goal which assists all research on human behavior. A-Life offers a new and different methodology for this purpose. It provides an ability …

A Progressive Damage Methodology For Residual Strength Predictions Of Center-Crack Tension Composite Panels, Timothy William Coats

Mechanical & Aerospace Engineering Theses & Dissertations

An investigation of translaminate fracture and a progressive damage methodology was conducted to evaluate and develop residual strength prediction capability for laminated composites with through penetration notches. This is relevant to the damage tolerance of an aircraft fuselage that might suffer an in-flight accident such as an uncontained engine failure. An experimental characterization of several composite materials systems revealed an R-curve type of behavior. Fractographic examinations led to the postulate that this crack growth resistance could be due to fiber bridging, defined here as fractured fibers of one ply bridged by intact fibers of an adjacent ply.

The progressive damage …

The Noaa Corps A Participant Action Research Of A Uniformed Service Facing Termination, Richard Eugene Marriner Ii

Engineering Management & Systems Engineering Theses & Dissertations

The NOAA Corps is a uniformed service of the Federal Government. It is composed of officers commissioned by the President of the United States as are the officers of the Air Force, Army, Coast Guard, Marines, Navy, and Public Health Service. "NOAA" is the acronym for the National Oceanic and Atmospheric Administration, an agency within the U.S. Department of Commerce.

On January 24, 1996 the Clinton administration formally proposed that the NOAA Corps be terminated on October 1, 1996. If this were to become reality it would be the first time in U.S. History that a uniformed service has been …

Organic Matter Characterization Of Virginia Rivers And Reservoirs, Susanne Margaret Lockhart

Civil & Environmental Engineering Theses & Dissertations

Research was conducted on characterizing the DOC characteristics and to discern whether spatial and temporal variations exist in these characteristics as impacted by seasonal, hydrologic or other factors. Data was cumulative of two studies: the State-Wide Survey in which water samples were taken in March and July 1995 from surface waters in four physiographic regions of Virginia and the James River Peninsula Survey concentrating on reservoirs and rivers on the James River Peninsula.

Results illustrate that the two largest fractions of DOC were the hydrophilic and hydrophobic acid fractions. An increase in DOC was observed between the mountains and the …

Petrochemical Analysis By Remote Fiber-Optic Raman Spectroscopy And Partial Least Squares Regression Analysis, Philip Edmund Flecher Jr.

Chemistry & Biochemistry Theses & Dissertations

A dispersive Raman system with charge coupled device (CCD) detection, distributed Bragg reflector (DBR) diode laser excitation, and a fiber optic probe has been developed for the rapid analysis of petrochemicals and fuels. Initially, mock petroleum fuels with analyte concentrations from 1.S - 16% were prepared and analyzed with the system. The inability of the original index guided diode laser to maintain a constant frequency during the mock petroleum analysis was a recurrent problem. The DBR laser was subsequently shown to have stability superior to index guided lasers, and was used in the remainder of the research.

Real gasoline samples …

A Total Systems Analysis Method For The Conceptual Design Of Spacecraft: An Application To Remote Sensing Imager Systems, Knut I. Oxnevad

Engineering Management & Systems Engineering Theses & Dissertations

Increased emphasis is being placed on improving the performance of space projects, within tighter budgets and shorter development times. This has led to a need for more efficient space system design methods. The research described here represents an effort to develop and evaluate such a method.

Systems engineering and concurrent engineering together provide the theoretical foundation for the method. The method, derived from both this theoretical foundation and ideas from experts in the space industry, emphasizes a total systems analysis approach, taking into account given mission requirements, and the mathematical modeling of interactions between system variables and between subsystems. The …

Dynamic Lot Sizing And Scheduling In A Multi-Item Production System, Padmanabhan Soundar

Engineering Management & Systems Engineering Theses & Dissertations

In this research, algorithms are developed to address the problem of dynamic lot sizing and scheduling in a single level (or single operation) production system. This research deviates from previous research in this area in that it does not have the kind of assumptions regarding the real world production system that normally were made to reduce the complexity of the problem. Specifically, this research explicitly considers finite capacity, multiple items, known deterministic dynamic demand, sequence dependent setup times and setup costs, setup carryover and variable backlogging. The objective is to simultaneously determine the lot size and the sequence of production …

Sensitivity Analysis And Optimization Of Aerodynamic Configurations With Blend Surfaces, Almuttil Mathew Thomas

Mechanical & Aerospace Engineering Theses & Dissertations

A novel (geometrical) parametrization procedure using solutions to a suitably chosen fourth order partial differential equation is used to define a class of airplane configurations. Inclusive in this definition are surface grids, volume grids, and grid sensitivity. The general airplane configuration has wing, fuselage, vertical tail and horizontal tail. The design variables are incorporated into the boundary conditions, and the solution is expressed as a Fourier series. The fuselage has circular cross section, and the radius is an algebraic function of four design parameters and an independent computational variable. Volume grids are obtained through an application of the Control Point …

Gamma-Ray Optical Studies Of ⁷³Ge And ⁵⁷Fe, Walter Carlton Mcdermott Iii

Physics Theses & Dissertations

The research described herein is among the first attempts to test one of the more popular theories for development of a gamma-ray laser. This work is a "marriage" between the Borrmann effect, which is a consequence of the dynamical theory of x-ray diffraction, and time-filtering which comes from time-domain Mossbauer spectroscopy.

Our experiments involved the search for a nuclear Borrmann effect and the subsequent time-filtering effect using ⁵⁷Fe and ⁷³Ge. In both cases, no nuclear Borrmann effect was observed; however, the methodology and criteria necessary for such an observation with any isotope were documented. The procedures necessary for …

Unsteady, Transonic Flow Around Delta Wings Undergoing Coupled And Natural Modes Response: A Multidisciplinary Problem, Margaret Anne Menzies

Mechanical & Aerospace Engineering Theses & Dissertations

The unsteady, three-dimensional Navier-Stokes equations coupled with the Euler equations of rigid-body dynamics are sequentially solved to simulate and analyze the aerodynamic response of a high angle of attack delta wing undergoing oscillatory motion. The governing equations of fluid flow and dynamics of the multidisciplinary problem are solved using a time-accurate solution of the laminar, unsteady, compressible, full Navier-Stokes equations with the implicit, upwind, Roe flux-difference splitting, finite-volume scheme and a four-state Runge-Kutta scheme, respectively. The primary model under consideration consists of a 65° swept, sharp-edged, cropped delta wing of zero thickness at 20° angle of attack. In a freestream …

The Progressive Failure Analysis Of Cut Slope In Anisotropic Strain Softening Soils, Jong Woon Choi

Civil & Environmental Engineering Theses & Dissertations

The failure phenomena in earth structures such as slopes and embankments on clay foundations are a consequence of the formation of failure surfaces.

A finite difference computer code, FLAC (Itasca Consulting Group, 1993), with the isotropic Mohr-Coulomb plasticity model, is used to analyze the undrained progressive failure of a strain softening soil during a slope excavation process. The focus of the study is on the short-term stability of slopes. In the first series of analyses, which are aimed at the evaluation of anisotropic strength effect on slope stability, the isotropic Mohr-Coulomb plasticity model is slightly modified to implement the anisotropic …

Exact Solutions For Orthogonal And Non-Orthogonal Magnetohydrodynamic Stagnation-Point Flow, Shahrooz Moosavizadeh

Mathematics & Statistics Theses & Dissertations

The viscous plane flow of an electrically conducting fluid towards an infinite wall is solved in the presence of a magnetic field which is aligned with the flow far from the wall. The problem has two dimensionless parameters-- ε, the magnetic Prandtl number, and β, the square of the ratio of Alfven velocity to fluid velocity far from the wall. The problem has a similarity solution which reduces the governing equations to a system of coupled ordinary differential equations which can be solved numerically. For extreme values of ε, both large and small, singular perturbation techniques are used to derive …

Developing Methods To Measure And Project Levels Of Combat Readiness In A Naval Aviation Squadron At The Unit Level, Michael Lawrence White

Engineering Management & Systems Engineering Theses & Dissertations

Among the various missions and levels in a military organization, the term "Combat Readiness" is defined in many ways. To a unit-level command, such as an aircraft squadron, it simply refers to the unit's capability to perform its assigned mission when called upon. The proof of that capability is evident in the aftermath of combat, however, it is too late at that point to address any shortcomings that may exist. The problem is, how can the unit effectively define, continuously measure, and confidently forecast its ability to perform in combat? A quantitative model based upon historical data that encompasses all …

A One-Dimensional Model For Storm Breaching Of Barrier Islands, Cheol Shik Shin

Civil & Environmental Engineering Theses & Dissertations

A set of numerical models is developed for simulating the four stages of barrier breaching characterized by one horizontal spatial dimension.

The SBEACH model is employed for the first stage of dune/beach erosion. The Lax-Wendroff two-step explicit scheme for Stage II is developed to simulate initiation of ocean flood propagation on initially dry barrier islands and the method of characteristics (MOC), is employed to compute additional boundary data. The development of the Preissmann implicit scheme for water motion and a forward time centered space explicit scheme for sediment motion in Stages III and IV provide a tool to study the …

Variational Methods In Sensitivity Analysis And Optimization For Aerodynamic Applications, Adem Ibrahim Hussen

Mechanical & Aerospace Engineering Theses & Dissertations

Variational methods (VM) sensitivity analysis, which is the continuous alternative to the discrete sensitivity analysis, is employed to derive the costate (adjoint) equations, the transversality conditions, and the functional sensitivity derivatives. In the derivation of the sensitivity equations, the variational methods use the generalized calculus of variations, in which the variable boundary is considered as the design function. The converged solution of the state equations together with the converged solution of the costate equations are integrated along the domain boundary to uniquely determine the functional sensitivity derivatives with respect to the design function.

The determination of the sensitivity derivatives of …

Microhollow Cathode Discharges, K. H. Schoenbach, R. Verhappen, R. Tessnow, F. E. Peterkin, W. W. Byszewski

Bioelectrics Publications

The current–voltage characteristics of hollow cathode discharges and their predischarges in argon under dc and pulsed conditions were found to have a positive slope at pressures up to approximately 50 Torr, and currents up to 20 mA, at a hole diameter of 0.7 mm. In this range of pressure and current, parallel operation of hollow cathode discharges, without ballast, was demonstrated. Scaling to higher pressure is possible by reducing the hole diameter. Pulsed experiments with an array of cathode rings of 75 μm diameter allowed us to obtain parallel operation of more than 50 discharges at a pressure of 350 …

Long-Term Performance Of Old Dominion Technology Graduates, William D. Stanley, Alok K. Verma

Engineering Technology Faculty Publications

The long-term career patterns of Old Dominion University's engineering technology baccalaureate graduates have been studied extensively. Results from approximately 400 alumni have been analyzed. The results of the analysis are presented and conclusions are drawn from the trends. The results indicate that the career progress of engineering technology graduates over a nearly twenty-year period is substantial and that they are performing effectively in a variety of career patterns.

The Modeling Of Structural-Acoustic Interaction Using Coupled Fe/Be Method And Control Of Interior Acoustic Pressure Using Piezoelectric Actuators, Yucheng Shi

Mechanical & Aerospace Engineering Theses & Dissertations

A coupled finite element (FE) and boundary element (BE) approach is presented to model full coupled structural/acoustic/piezoelectric systems. The dual reciprocity boundary element method is used so that the natural frequencies and mode shapes of the coupled system can be obtained, and to extend this approach to time dependent problems. The boundary element method is applied to interior acoustic domains, and the results are very accurate when compared with limited exact solutions. Structural--acoustic problems are then analyzed with the coupled finite element/boundary element method, where the finite element method models the structural domain and the boundary element method models the …

Mechanical Alloying Of Nitrogen Into Iron Powders, J. Rawers, D. Govier, D. Cook

Physics Faculty Publications

Mechanical alloying of nitrogen into bcc-fe powder is a very effective and efficient means of obtaining very high concentration of nitrogen in micron-size iron particles. Mechanical alloying increases the concentration of nitrogen in the iron powder far in excess of the bcc-Fe lattice low nitrogen solubility, however most of the infused nitrogen resides on the nano-size grain boundaries and in nano-size bct-fe that forms during mechanical alloying.

A Decision Support Model For Large Systems Using Quality Function Deployment And Goal Programming: A Capital Budgeting Problem, Kenneth Lindsey Jr.

Engineering Management & Systems Engineering Theses & Dissertations

Effective planning for the modernization of U.S. Air Force fighter aircraft requires a perception of the future tasks these aircraft will be called upon to perform, and the improvements and modifications that will be required to successfully accomplish those tasks. A great deal of research has been done in the areas of military strategy, quality function deployment, capital budgeting, and goal programming, as separate areas of study. This thesis details the research and analysis performed for a project called The Fighter Configuration Plan (FICOP), in which these areas were integrated in a decision support model to aid the Air Force …

Numerical Simulation Of Complex, Three-Dimensional, Turbulent-Free Jets, Robert V. Wilson

Mechanical & Aerospace Engineering Theses & Dissertations

Three-dimensional, incompressible turbulent jets with rectangular and elliptical cross-section are simulated with a finite-difference numerical method. The full Navier-Stokes equations are solved at low Reynoids numbers, whereas at high Reynolds numbers filtered forms of the equations are solved along with a sub-grid scale model to approximate the effects of the unresolved scales. A 2-N storage, third-order Runge-Kutta scheme is used for temporal discretization and a fourth-order compact scheme is used for spatial discretization. Although such methods are widely used in the simulation of compressible flows, the lack of an evolution equation for pressure or density presents particular difficulty in incompressible …

Modelling An Optical Fiber Bragg Grating, Claudio Oliveira Egalon

Electrical & Computer Engineering Theses & Dissertations

A theoretical investigation of a single mode optical fiber with one and two superimposed Bragg grating is presented. The formulation relies in the determination of an approximate solution in the asymptotic region of one of the fiber parameters. A correction is then applied to the asymptotic solution using the Method of the Successive Approximations also known as the Piccard Method. The approximation was then compared to the numerical solution using the Runge-Kutta method. Assuming that each Bragg grating has modulation frequencies given by Ω₁ and Ω₂, it has been found that the second Bragg grating shifts the …

Optical Fiber Fourier Transform Infrared Evanescent Wave Absorption Spectroscopy Of Aluminum Hydroxide And Natural Corrosion, Juock S. Namkung

Electrical & Computer Engineering Theses & Dissertations

A new technique for continuous, real-time, in-situ detection of natural corrosion of aluminum alloys is presented. The technique is a generalized version of attenuated total reflectance (ATR) spectroscopy, that combines optical fibers and a Michelson interferometer spectrometer to make evanescent wave absorption measurements. Aluminum hydroxide is one of the major corrosion products of aluminum. Absorption spectra of powdered samples of aluminum corrosion, in the spectral region around three micrometers have been studied and compared with the spectra from pure powdered aluminum hydroxide. A chalcogenide optical fiber was used as an attenuated total reflectance (ATR) optical element. The same samples were …

Application Of Reanalysis Techniques For Pattern Design Of Spot Welds, Young San Kim

Mechanical & Aerospace Engineering Theses & Dissertations

Extensive benchmarking on competitive cars has shown that the durability of vehicles, assembly-induced variations, and assembly cost are directly related to the quality and number of spot welds. On most luxury cars, approximately 4,500 to 5,000 spot welds are found. On less expensive cars, the range is from 3,500 to 4,500. These cars usually inherit more noise, rattles, squeaks, and other quality-related problems. These problems have motivated the search for a new capability to systematically place welds in the most critical areas, with a minimum number of welds for car bodies, while satisfying all performance requirements (e.g., stiffness, stress distribution, …

Dynamic Scale Genetic Algorithm: An Enhanced Genetic Search For Discrete Optimization, Bela Dange Joshi

Engineering Management & Systems Engineering Theses & Dissertations

The minimization of operations and support resources of reusable launch vehicles is a complex task, involving discrete optimization and the simulation domain. Genetic algorithms, offering a robust search strategy suitable for integer variables and the simulation domain, can be applied to minimize these resources. This research developed an enhanced genetic algorithm for problems with a linear objective function, the most common class of discrete optimization problems. The dynamic scale genetic algorithm developed here incorporates concepts of implicit enumeration to enhance search. This is achieved by utilizing problem specific information to refine the solution space over successive generations. The utility of …

Surface Debye Temperature Measurement With Reflection High-Energy Electron Diffraction, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Measurement of the surface mean-square atomic vibrational amplitude, or equivalently the surface Debye temperature, with reflection high-energy electron diffraction is discussed. Low-index surfaces of lead are used as examples. Particular details are given about the temperature-dependent diffraction pattern of Pb(100) in the Debye-Waller region. The use of reflection high-energy electron diffraction for measurement of the substrate surface temperature in thin-film deposition chambers is suggested. © 1996 American Institute of Physics.