Engineering Commons^™

Vehicle Performance Optimization Utilizing The Air Turbo-Ramjet Propulsion System; Methodology Development And Applications, Kirk Christensen

Doctoral Dissertations

"The ATR (Air TurboRocket) is an air breathing propulsion system in which the turbocompressor turbine is powered by a hot drive gas which is generated independently of the air flow through the compressor. The ATR has a lower specific impulse (Isp) and higher thrust compared to a similar size turbojet but a lower thrust and higher Isp compared to similar size solid rocket motor (SRM). This work defines the benefits of ATR propulsion for tactical vehicles.

ATR simulation codes were developed to support analysis of hypothetical ATR powered vehicles. Both turbojet powered and SRM powered vehicles were also evaluated against …

Service Quality Using The Deviation-Score Approach To Fit In Contingency Theory In A U.S. Army Corps Of Engineers Setting, Donald Robert Groh

Doctoral Dissertations

"The purpose of this study is to learn how organizational work unit context, structure, and processes relate to service quality. The theoretical basis for the research is that organizational work units should be structured based on the work that they perform. If the work that a unit performs is highly variable, then the work unit should be structured in such a way as to provide flexibility, that is, few rules and procedures and highly decentralized decision making. If the work that a unit performs is not variable, then the work unit should be structured to provide a non-varying product or …

Multiobjective Optimum Design Of Static And Seismic-Resistant Structures With Genetic Algorithm, Fuzzy Logic And Game Theory, Dan Li

Doctoral Dissertations

"The goal of this research is to develop a constrained multiobjective optimization method in the form of a robust, practical, problem-independent algorithm, and to investigate the effect of multiobjective optimization on structural design.

This research studies the properties and characteristics of multiobjective optimization and solutions. Design objectives, constraints and design variables as well as their effect on structural design and behaviors are investigated. Dynamic input energy for a multidegree-of-freedom structure is formulated. A multiobjective optimization algorithm based on game theory is developed. Fuzzy set theory is introduced to construct a fuzzy constrained environment. A Pareto genetic algorithm is developed based …

Heat Transfer In Microchannels, Xianming Wang

Doctoral Dissertations

The objective of this research was to develop an analytical solution to the heat transfer problem in microchannels with slip-flow--a heat transfer problem for gases at low pressures or in extremely small geometries, and to verify this solution experimentally. In this investigation, an analytical expression for the velocity distribution with slip-flow was obtained which involved the Knudsen (Kn) number in an infinite series form. The result showed that the velocity always increased as the Knudsen number was increased. The Knudsen number for extremely small channels may become large enough to affect significantly the velocity distribution and consequently affect the heat …

Implementation Of Alf Results To Designing Flexible Pavements In Louisiana, Ludfi Djakfar

Doctoral Dissertations

The Louisiana Transportation Research Center (LTRC) recently conducted a research effort using the Accelerated Loading Facility (ALF). The objective of the research was to evaluate a limited number of alternative base materials and construction techniques envisioned to provide a significant reduction in the occurrence of shrinkage and reflected block cracking in the cement-stabilized bases. Nine test sections were constructed for this research, using the same wearing course material but having different thicknesses of crushed stone and soil cement bases and subbases. The soil cement base is the most commonly used base material in Louisiana, whereas crushed stone is a preferred …

The Application Of Markov State Probabilities In Developing Artificially Intelligent Managerial Strategies: A Case Study Based On Major League Baseball, Arnold Vincent Arconati

Doctoral Dissertations

"Baseball is a very large industry that influences the lives and financial assets of millions of people.

Many baseball analysts estimate that even the best Major League player can increase his team's expected number of yearly wins by only 3 or 4 games. In 1993 Bobby Bonilla, a New York Mets National League outfielder, earned $5,200,000 more than the average Major League player earned. The Mets apparently believed that expenditure of this money was worth his expected additional victories. If the strategy of an Artificially Intelligent baseball manager could produce 4 more team victories than the corresponding human baseball manager, …

A Model Of Electronic Warfare Systems Acquisition And Engineering For Saudi Arabia, Negaa M. Albegami

Doctoral Dissertations

"A major activity within the systems engineering process is the requirements definition and analysis phase. In technical systems, planning this phase looks too technical for top management and too broad for the engineers specialized in narrow technical fields. This categorization (too technical/too broad) represents a gap between top management and specialized engineering. In Saudi Arabia, such a gap is believed to be very wide.

The main objective of this research is to find a way to narrow this gap between management and engineering when planning government systems, especially in electronic warfare (EW) systems. A solution in this effort is to …

Galvanic Stripping Of Fe⁺³ And Pb⁺² Ions And Dissolution Of Metallic Fe, Zn, Pb And Cd Using Di(2-Ethylhexyl)Phosphoric Acid, Luis Miguel Chia Aquije

Doctoral Dissertations

"Two systems were evaluated using the principles of the galvanic stripping process. One of them, the removal of Pb⁺² ions from di-2(ethylhexyl) phosphoric acid (D2EHPA) was performed using metallic zinc. The other, the removal of Fe⁺³ ions from D2EHPA used metallic iron as reductant and was performed simultaneously with the organic phase using a slightly acidic aqueous solution of hydrochloric acid. In addition, the dissolution of metallic zinc, iron, lead, and cadmium in D2EHPA was studied in order to better understand the anodic step in the mechanism of the galvanic stripping process.

Increased temperature was found to dramatically …

Transition From Laminar To Turbulent Flow Around An Airfoil, Chang-Ren Chen

Doctoral Dissertations

"A computational fluid dynamics (CFD) code has been developed for two-dimensional incompressible turbulent flows and employed to solve the Navier Stokes equations around an airfoil of arbitrary shape. A low-Reynolds-number k — e turbulence model including curvature effect was used to consider the gain and loss of turbulent kinetic energy. To include laminar sublayer into the computational domain, a multi-layer grid and a cubic-slpine grid were introduced through a conservative form of coordinate transformation. The flow structure varies with the Reynolds numbers. For an airfoil at low Reynolds numbers (below ten thousand), distinct vortex shedding patterns can be found in …

Toughening Mechanisms In Weak Matrix Ceramic Composites, Jowoong Ha

Doctoral Dissertations

"Tough behavior of ceramic matrix composites is closely related to the weak interface between fiber and matrix. The weak interfaces in composites have been provided by reducing the chemical bonding and the residual thermal stresses between constituents. A new way to introduce the weak interface by induced porosity or damaged zones, so called porosity toughening or damage toughening respectively, was proposed in this study to provide the rationale for guiding development of oxide/oxide composites. The existence of porosity toughening was examined by qualitative theoretical consideration and experiments. Porous oxide/oxide composites were fabricated using alumino-silicate fibers (Nextel 440) and magnesium alumino-silicate …

Toward The Development Of Decision Support Tools To Manage The Catis Project Life Cycle, Steven Wayne Mccrary

Doctoral Dissertations

"The American Public Works Administration (1987) states that communities' infrastructures are in need of repair and better management and recommends CATIS (Computer-Assisted Terraspatial Information Systems) as an excellent tool to assist in that endeavor. Small communities have several voids that CATIS technology can fill. This research reports on a life-cycle approach to CATIS adoption that will help small communities to better manage their infrastructure.

It is important for small communities to become aware of the types of systems available and what each system can do. This study presents a straightforward, understandable discussion of CATIS technologies, features, and applications. Justifying the …

Time Characteristics Of Small Watersheds In Response To The Probable Maximum Precipitation, Brian Jay Swenty

Doctoral Dissertations

"The EPA Storm Water Management Model (SWMM) was used to perform single event simulations of Probable Maximum Precipitation (PMP) level rainfall events on the Loss Lake watershed in southcentral Missouri. Overland flow was simulated using kinematic wave routing and channel flow was simulated using dynamic wave routing.

Lag time was defined as the time between the centroid of the excess rainfall hyetograph and the centroid of the direct runoff hydrograph.

Rainfall depth, rainfall duration, and the distribution of rainfall intensity were found to be significant predictor variables for lag time. Defined as hydrologic parameters for this study, channel flow roughness, …

Mixed Convection In Laminar/Turbulent Separated Backward-Facing Step Flows, Jen-Tai Lin

Doctoral Dissertations

"Mixed convective heat transfer results for two-dimensional laminar/turbulent flow in a duct with a backward-facing step are reported. The two walls forming the duct are maintained at uniform but different temperatures. The straight wall is maintained at the inlet air temperature, while the downstream section of the stepped wall is heated to a higher temperature. This study focuses on a backward-facing step geometry with an expansion ratio of two. The present laminar study examines a wide range of inlet flow and wall temperature conditions to cover the domain from buoyancy-assisting mixed convective flow, pure forced convective flow, buoyancy-opposing mixed convective …

Toward The Development Of A Knowledge-Based Construction Schedule Planning System, Nordin Bin Yunus

Doctoral Dissertations

"This research attempts to model and prototype a knowledge-based system for use in the construction industry to accomplish the automatic generation of initial construction schedules. The schedule can be transformed into a logical network that provides a physical representation of the construction operations plan. The prototype system, which requires symbolic processing and reasoning, is developed based on an intensive modeling that rationally examines industry practice.

The model identifies work breakdown and precedence relationship as the two major concepts in schedule planning. Work breakdown is concerned with the identification of construction activities that result in the completion of project elements. Precedence …

Bubble Formation, Movement And Distortion In Viscous Glass, Simon Cheng-Ping Wang

Doctoral Dissertations

"A study of bubble formation, movement and distortion in viscous glass is described. A glass rod containing an irregularly shaped hole is heated to a temperature at where the glass viscosity is low enough to let the hole form a spherical bubble. Spheration occurs as the bubble moves upward in the glass rod. At the proper time, the rising bubble is decelerated and brought to a stop by increasing the glass viscosity by slowly reducing the temperature. The entrapped bubble is then cut from the glass rod and heated again, if necessary, to a lower temperature, to reduce distortion of …

Studies Of Defect Structure And Oxidation-Reduction Behavior Of Undoped Lamno₃, Sr-Doped Lamno₃ And Mg-Doped Lamno₃, Jen-Ho Kuo

Doctoral Dissertations

"Undoped LaMnO₃, Sr-doped LaMnO₃ and Mg-doped LaMnO₃ showed reversible oxidation-reduction behavior. These perovskites can be excess, stoichiometric or deficient in oxygen content depending on the specific conditions. Under very reducing conditions these oxides will decompose into new phases. Phase stabilities for these oxides were determined. The results showed that both Sr and Mg doping caused the LaMnO₃ to dissociate at higher oxygen activities than for undoped LaMnO₃.

Defect models were proposed to interpret the TG results, in which metal vacancies are assumed for the oxygen excess condition and oxygen vacancies are assumed for the oxygen deficient condition. Thermodynamic properties were …

Development Of Design Criteria For Ferritic Stainless Steel Cold-Formed Structural Members And Connections, Pieter Van Der Merwe

Doctoral Dissertations

"This dissertation describes the development of the basic criteria needed for the design of structural members cold-formed from certain ferritic stainless steels. The Allowable Stress Design method as well as the Load and Resistance Factor Design method receive attention. The ferritic stainless steels under consideration are: Types AISI 409 and 430 as well as a modified Type 409 steel, designated 3CR12 steel, developed and produced by the speciality steel producing company, Middelburg Steel and Alloys in South Africa.

The mechanical properties needed for structural design are established. It is shown through an experimental study that the design provisions for the …

Fundamental Study Of The Role Of Cathode Structure On Zinc Electrowinning, Horacio M. Aros

Doctoral Dissertations

"The influence of cathode macromorphology on the current efficiency of zinc electrowinning was determined.

The studies have shown that surface roughness affects current efficiency during zinc electrowinning, particularly when the electrolyte contains impurities such as nickel and antimony. Current efficiency does not change with surface roughness as long as the electrolyte is sufficiently pure.

Zinc deposited on smooth zinc cathodes tends to retain a more favorable structure and macromorphology, which is less sensitive to the effects caused by antimony and nickel. Glue helps to counteract the effect of the impurities; however, its presence in the electrolyte at certain combinations with …

Structural Behavior Of Members Consisting Of Flat And Curved Elements, M. Brad Parks

Doctoral Dissertations

"Local buckling of stiffened and unstiffened curved elements has been investigated both experimentally and analytically. Stiffened curved elements are supported on all four edges while unstiffened curved elements are supported along three edges with one longitudinal edge free.

A series of stub column, beam, and shear tests have been performed for sections containing curved elements. The tested specimens were formed from sheet steels with yield strengths ranging from 27 to 88 ksi. The radius-to-thickness, R/t, values of the curved elements varied from 12 to 438 whereas the arc length-to-thickness, bit, ratios ranged from 23 to 218.

As a result of …

Experimental Vapor-Liquid Equilibria Of Propyne With Propane, Propene And Propadiene, Edward Allen Kyser

Doctoral Dissertations

"Vapor pressures for pure propane, pure propene, impure propadiene and pure propyne and 19 binary mixtures of propane, propene, and propadiene with propyne are reported at -20, 5, 30, 55 and 80° C. An equation of state utilizing pure component saturated vapor and liquid densities is used to correlate all the data and the effect of the propadiene impurities was theoretically removed. The data of Burcham (1981) are recorrelated using new information about the impurities, and different results are obtained. Calculated relative volatilities and saturated densities are reported for the systems propane-propyne, propene-propyne, propadiene-propyne and propane-propadiene"-- Abstract, p. ii

Phase Equilibria From Pvt Measurements For Carbon Dioxide, Water And N-Decane, Michael Nduka Okafor

Doctoral Dissertations

"Phase equilibrium properties for the carbon dioxide - water - n-decane system were determined from pressure-temperature-volume (PVT) measurements. PVT properties were also obtained for pure carbon dioxide and water, and the binary mixtures of carbon dioxide - water and carbon dioxide - n-decane. The experiments were conducted at temperatures of 313.17, 353.15 and 393.15 Kelvin, and at pressures from 37 to 416 bar. Measurements for the mixtures were terminated when complete miscibility was observed.

The Perturbed-Hard-Chain (PHC) equation of state developed by Gmehling et al. (1979) was chosen to correlate the measured data because of its ability to handle the …

Effects Of The Luminous Environment On Managerial Decision Making, Marc Clay Belcher

Doctoral Dissertations

"Little is known about the influence the physical environment may have on the way a manager goes about making decisions. This work considers one element of the environment, lighting, and attempts to establish a relationship between that element and the decision strategy a manager may select.

From a review of the literature on the effects of light on man and from the field of decision making, a model is posited suggesting that the luminous environment affects decision making. Since others have established that mood influences how decisions are made, and since it is suggested in the literature that lighting affects …

An Investigation Of Signs For Median Crossovers, Gillian M. Worsey

Doctoral Dissertations

“This paper describes a study of advance warning signs for median crossovers on divided highways. Candidate crossover signs were identified from a literature review, survey of current State practices and discussions with FHWA personnel. Seven of these signs were selected for further testing in a laboratory study for legibility, understanding and driver preference. Sixty subjects representing a cross-section of drivers took part in the study, thirty at the Turner-Fairbanks Highway Research Center in McLean, Virginia and thirty at the University of Missouri--Rolla in Rolla, Missouri.

Two of the seven signs were word messages and five were symbolic signs. The results …

Web Crippling Of High Strength Cold-Formed Steel Beams, Chiravut Santaputra

Doctoral Dissertations

"The structural behavior of high strength cold-formed steel beams subjected primarily to web crippling was investigated analytically and experimentally. In this study hat sections and I-beams, formed from five different types of high strength sheet steels commonly used in the automobile industry, were investigated under various loading conditions. The yield strengths of these sheet steels vary from 58 to 165 ksi.

In addition to the test data gathered in this phase of study, the experimental results obtained from the beam tests conducted at Inland Steel Company and Ford Motor Company were carefully evaluated. The evaluation indicated that the present available …

The Modeling And Analysis Of Multi-Component, Multivalent Biospecific Adsorption, Bo Henrik Arve

Doctoral Dissertations

"A general model is presented and used to predict the dynamic behavior of the adsorption, wash, and elution stages of biospecific adsorption (affinity chromatography) in finite bath and column operations. The model accounts for film and pore diffusional mass transfer resistances and the rates of interaction between adsorbates and ligands. For column operations the effect of axial dispersion in the flowing fluid stream is included. The model is applicable to single and multi-component biospecific as well as non-specific adsorption, and the adsorbates may be monovalent or multivalent. In the elution stage both non-selective and selective elution of monovalent adsorbates is …

Structural Design Of Coal-Fueled Power Plant Ductwork, Stanley Pearce Rader

Doctoral Dissertations

"An absence of a comprehensive procedure for design of coal-fueled power plant ductwork currently exists in the publicly available literature. This dissertation presents such a procedure.

An overview of the ductwork design environment, including major components of the air and flue gas flow paths, design loads and temperatures, corrosion considerations, and physical configurations, is given. Design criteria for materials, corrosion inhibition, minimum plate thicknesses, temperature effects, allowable stresses and deflections, and vibrations are proposed. A detailed design procedure based on the allowable stress design philosophy is presented, and computer programs implementing the design procedure are provided. An alternate design procedure …

Oxidation Kinetics Of Polycrystalline Srtio₃ And Lacro₃, Chi-Kung Jerry Yu

Doctoral Dissertations

"The oxidation kinetics of polycrystalline SrTiO₃ and LaCrO₃ were determined by measuring the time and temperature dependence of the weight and conductivity change of reduced samples. A region of fast diffusion followed by a reduced diffusion tail was observed in the TGA measurements. This observation can be interpreted as the initial diffusion along the boundaries and then spreading out into the lattice. The absence of the tail in the conductivity measurements is due to the high electron and hole mobility at the boundaries. The electrical conductivity and TGA results on Nb-doped LaCrO₃ show that at low oxygen …

Numerical Simulation Of Mixing Processes In Two-Dimensional Channel Flows, Milan Karel Straka

Doctoral Dissertations

"Recently, considerable interest has arisen in the numerical simulation of laminar and turbulent transport phenomena. More knowledge in this field is needed to improve predictions of heat and mass transfer processes in a variety of technical fields.

In this work a new computationally efficient transport model is developed. It consists of partially parabolized time-dependent equations of motion, continuity, and concentration of nonconservative species. Pertinent equations are solved numerically for both laminar and turbulent flow.

Results of calculations of laminar flow in the entry region of a parallel-plate channel agree well with the work of other authors. For turbulent flows, the …

Kinetics And Reactor Design In The Pyrolysis Of Tar Sands, Charles Arthur Lechner

Doctoral Dissertations

"Data from the thermal decomposition of bitumen from Utah tar sands was obtained and analysed with both isothermal and non-isothermal chemical reaction models. The use of a power rate law to describe the complex kinetics of pyrolysis gave agreement with the experimental data that was approximate, but adequate for design purposes. The results indicated a reaction rate that was second order in bitumen content, with an activation energy of about 17 to 20 kcal/gmol.

Data for the boiling point distribution of the products was consistent with a change of mechanism from vaporization to pyrolysis as the samples are heated. Higher …

A Management Training Model For Engineers In Saudi Arabia, Majid Al-Kassabi

Doctoral Dissertations

“Great economic growth has occurred in Saudi Arabia in the last decade creating overwhelming demands for professionally trained people. The emerging Saudi professionals are mostly engineers who have been put in managerial positions without the benefit of managerial training.

Objectives of this research were 1) To identify the skills needed by engineers to become managers; 2) To identify problems and constraints inherent in management training programs; 3) To identify the impact of a model training program on the individual; and 4) The impact of a model training program on the firm.

A training program was implemented using an experimental group …