Digital Commons Network^™

Modeling Of The Electromagnetic Radiation From Shielded Enclosures With Apertures And Attached Wires In A Real-World Environment, Bruce Roy Archambeault

Doctoral Dissertations

A hybrid modeling technique using the Finite-Difference Time-Domain (FDTD) approach in conjunction with the Method of Moments (MoM) approach was developed to allow simulation of electromagnetic interference (EMI) emissions through apertures due to sources within a shielded enclosure. These apertures can include air ventilation openings, option card slots, mating cover seams, or any other opening in the metal shielded enclosure. Modeled emission results can now be directly compared to U.S. and other countries' regulations to allow engineers to predict compliance before hardware prototypes are built. The effects of the test environment, including ground plane and specified measurement distance, as well …

Numerical Analysis For Blood Distribution In Complete Flow Cross-Section Microvascular Networks, Jewen Xiao

Doctoral Dissertations

As the blood flows through a bifurcation, the axisymmetric red blood cell concentration profile is skewed by plasma skimming. In the downstream segment of the bifurcation the concentration profile of red blood cells recovers symmetry by the red blood cell dispersion process.

In this study, the concentration convective equation, which models the red blood cell dispersion process, is solved with the method of finite differences in cylindrical coordinates. In the computation, a shear-induced diffusivity coefficient is used. The computed hematocrit ratios at the second bifurcation are compared with in vitro experimental data obtained from 50 $\mu$m serial trees with two …

Construction Of An X-Band Electron Nuclear Double Resonance Spectrometer And Partial Characterization Of An Iron Nitrosyl Complex Of Transferrin, Pamela Marie Proulx-Curry

Doctoral Dissertations

An X-band Electron Nuclear Double Resonance (ENDOR) spectrometer was constructed, tested at both room and liquid helium temperatures, and characterized at liquid helium temperature using a vanadyl-imidazole standard.

An iron nitrosyl complex of transferrin was studied. Three methods of generating nitric oxide gas were tested and resulted in no differences in product formation. The g-factors for the rhombic complex--prepared with and without carbonate addition to the buffer--were determined. For the complex prepared with carbonate g$\sb{\rm x}$ = 2.052, g$\sb{\rm y}$ = 2.028, and g$\sb{\rm z}$ = 2.013. For the complex prepared without addition of carbonate g$\sb{\rm x}$ = 2.051, g$\sb{\rm …

Relativistic Thinking And Identity Development In College Students, Rebecca Anne Regeth

Doctoral Dissertations

The relationship between relativistic thinking and identity formation was examined. Relativistic thinking is the ability to accept the subjective nature of knowledge and values and has been shown to develop during college. It was predicted that as students become more relativistic in their thinking, they also realize that their own perception of reality is relative too. This causes an identity crisis, resulting in a mature identity. A one-year longitudinal study showed that changes in identity (increased moratorium) were related to changes in thinking (increased relativism). Students in different college majors were shown to think differently about the nature of knowledge …

Composition As A Mode Of Being: Politics, Ethics, And History In The Writing Classrooms Of Postmodernity, Lance Michael Svehla

Doctoral Dissertations

Henry Louis Gates, Jr. once commented that while he did not "deny the importance, on the level of theory, of the (postmodern) project," such a project did not help him when he was "trying to get a taxi on the corner of 125th and Lenox Avenue" (Loose Canons 37-38). The postmodern project lacked what Gates calls "practical performative force." The purpose of this dissertation is to establish postmodernity's practical performative force for the composition classroom. It addresses four central questions: What is postmodernity? What is its relationship to composition? Why should composition teachers and students care about this relationship? How …

Foraging Strategies Of Two Sympatric Lagomorphs: Implications Of Habitat Fragmentation, Douglas Foxall Smith

Doctoral Dissertations

I studied the effects of variation in food patch quality and predation risk on the foraging patterns and measures of foraging behavior of New England (S. transitionalis) and eastern (S. floridanus) cottontails, and their survivorship and weight change during these experiments. I then superimposed the results of these experiments onto real habitat patches to determine the amount of habitat each species could occupy and maintain similar survivorship. Finally, I measured an adaptation (eye size), and predator detection of both species in an effort to explain the difference in survival between S. floridanus and S. transitionalis.

In outdoor enclosures (5.7 x …

The Use Of An Artificial Light System To Assess The Influence Of Relative Light Change On Diel Activity Cycles Of Nymphs Of The Mayfly, Stenonema Modestum, In The Presence And Absence Of Predators, Annette L. Schloss

Doctoral Dissertations

A mechanism by which light controls diel changes in locomotor activity and surface location of mayfly nymphs (Stenonema modestum Banks), named the Stimulus-based Timing and Activity-Rate (STAR) Model, was tested. Nymph movements were video-recorded in time-lapse from underneath unglazed artificial substrates in a laboratory stream. Light/dark cycles were simulated using computer-controlled halogen lamps. Light increases and decreases were generated to maintain constant rates of relative light change throughout simulated twilight periods. Nymph locomotor activity and position on the substrate were measured in response to rate of light change. Experiments tested whether adaptation light intensity (10$\sp{-4}$ or 10$\sp{-6}$ W cm$\sp{-2}$), time …

Analysis Of Cured-In-Place Pipes (Cipp) Installed In Circular And Oval Deteriorated Host Pipes, Abdel-Aziz Mabrouk Omara

Doctoral Dissertations

This dissertation presents new analytical models for the structural analysis of Cured-In-Place Pipes (CIPP) used in the rehabilitation process of deteriorated pipelines. Both cases of partially and fully deteriorated pipelines are considered. Specifically, analytical models for the stability of CIPP encased in either circular or oval partially deteriorated host pipes are presented. The proposed models for the case of partially deteriorated host pipes were compared with the results of experimental works. Results of the experimental work, which was done during the course of this research, were used in the comparison. Other, previously done, related experimental work were also added to …

An Experimental Investigation Of Thermally-Induced Deformation Of 1 Micron Thick Copper/Tantalum/Polymide High-Density Interconnect Structures, Dmitry V. Zhmurkin

Doctoral Dissertations

A new technique to estimate the out-of-plane thermal expansion coefficient (CTE) of several 1 $\mu$m thick, spin-coated polyimides is introduced. Arrays of parallel copper and polyimide lines of various aspect ratios on Si substrate were imaged in air at room temperature and at 97$\sp\circ$C using an atomic force microscope (AFM). The out-of-plane CTE of the polyimides was estimated by matching the experimental results with the predictions of finite element models with different out-of-plane parameters. For FPI-135 (6FCDA-TMOB) polyimide the out-of-plane CTE was found to be $\approx$260 ppm/$\sp\circ$C, for FPI-136 (PMDA-6FDA-TFMOB) polyimide $\approx$120 ppm/$\sp\circ$C. Polyimide lines with widths equal to or …

Immobilization Of Radioactive Materials In Iron Phosphate Glass, Melissa G. Mesko

Doctoral Dissertations

"The current study investigates the feasibility of using iron phosphate glass for the immobilization of radioactive wastes considered incompatible with borosilicate glass. Wastes may be incompatible with borosilicate glass due to high phosphorus content (Hanford tank sludges), the presence of halides (CsCl and SrF₂ capsules), or large amounts of uranium (SNF).

Between 20 and 60 wt% Hanford tank sludge was vitrified with an iron phosphate glass at ≤ 1200°C in 1 hour. The chemical durability of iron phosphate glassy wasteforms was as good as, or better than a reference borosilicate glass (10^-9 g/cm²/min) in distilled water …

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 …

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 …

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 …

Assessing Land Use/Cover Change In Costa Rica, Gerardo-Arturo Sanchez-Azofeifa

Doctoral Dissertations

The need for accurate estimates of forest cover and forest fragmentation is a critical issue for developing countries such as Costa Rica. Accurate estimates of forest cover can help in several sectors related to the environment and economic development. This dissertation focuses on providing an accurate and precise estimate of forest cover in Costa Rica. The year 1991 was used as a baseline. Landsat Thematic Mapper was the remote sensing sensor used in this analysis. This dissertation concludes that: (1) Twenty-nine percent ($\sim$1,400,000 ha) of the country was under primary forest (80% canopy closure) in 1991. Of the total forest …

Biped Dynamic Walking Using Reinforcement Learning, Hamid Benbrahim

Doctoral Dissertations

This thesis presents a study of biped dynamic walking using reinforcement learning. A hardware biped robot was built. It uses low gear ratio DC motors in order to provide free leg movements. The Self Scaling Reinforcement learning algorithm was developed in order to deal with the problem of reinforcement learning in continuous action domains. A new learning architecture was designed to solve complex control problems. It uses different modules that consist of simple controllers and small neural networks. The architecture allows for easy incorporation of modules that represent new knowledge, or new requirements for the desired task. Control experiments were …

Ecophysiology Of Metal-Reducing Aeromonas And Shewanella Strains From Great Bay Estuary, Victoria Knight

Doctoral Dissertations

The seasonal abundance and distribution of mesophilic aeromonads at seven sites in Great Bay Estuary, NH were monitored over a 24 month period. Total heterotrophic bacteria, total and fecal coliforms, salinity, temperature, pH, total suspended solids, and chlorophyll were also measured in the samples. Aeromonads were isolated at each site throughout the year with the highest incidence and population density in the late summer to early fall. Aeromonad abundance correlated positively with the incidence of coliforms, temperature, and salinity.

Aeromonas hydrophila ATCC 7966 grew anaerobically by using NO$\sb3\sp-$, fumarate, Fe (III), Co (III), or Se (VI) as terminal electron acceptors. …

Polymer Substrates For Optical Chemical Sensing, Michael Thomas Rooney

Doctoral Dissertations

Membranes for chemical sensing based on changes in light reflectance from amine-modified, porous, rubber-toughened poly(vinylbenzyl chloride-co-divinyl benzene) were prepared by bulk free radical polymerization. Xylene and dodecane were used as porogenic solvents and solutions were prepolymerized to viscous solutions prior to forming membranes. The crosslinked membranes are turbid and scatter light when unswollen. They swell in response to increases in hydrogen ion concentration, causing the membrane to reflect less light. Turbidity is ascribed mainly to scattering by water-filled macropores within the amine-functionalized membranes. Swelling decreases the refractive index of porous, hydrated polymers with 2% crosslinking by approximately 0.04 units, bringing …

Analysis And Design Of Ac Induction Motors With Squirrel Cage Rotors, Shine Ho

Doctoral Dissertations

The traditional approach to modelling the AC induction motor revolves around the well-known equivalent "T" circuit model. In this approach, the direct connection from geometry to performance is suppressed. For better understanding of magnetic, electrical, and thermal behaviors, three lumped models based on the actual geometry are developed in this dissertation. Based on these lumped models, an iterative design model is also developed.

In order to analyze and design induction motors, the relationships of basic motor variables to motor performance must be known. For determining the relationships, three new mathematical lumped models are developed. The magnetic model describes flux behavior. …

Full-Scale Comparative Evaluation Of Two Slow Sand Filter Cleaning Methods, Jan A. Kem

Doctoral Dissertations

Slow sand filters are an established treatment method for water with low turbidity. They usually are effective for the removal of turbidity, microorganisms (including cysts of Giardia and Cryptosporidium), and particles, but they require significant periods of time for cleaning. In the 1950's, West Hartford, CT developed a harrowing process to reduce the time and labor required for cleaning at that plant. A 1988 study observed those filters had higher removal rates for non-particulate dissolved organic carbon and UV absorbing materials, surrogates for trihalomethane formation, than did filters at two other plants cleaned by the conventional scraping method.

This study …

The Generation Of Predictive Inferences And The Availability Of Contextual Information, Michelle Lenore Rizzella

Doctoral Dissertations

Five experiments were conducted to determine whether readers generate predictive inferences when biasing context was available at either a local level (i.e., in short-term memory) or global level (i.e., in long-term memory). Subjects read passages that described two characters; one description contained contextual information supporting a predictive inference and the other description did not. Experiments 1 and 2 examined whether subjects generated a predictive inference when biasing context was locally available. Reading time differences in Experiment 1 demonstrated that subjects experienced comprehension difficulty when critical sentences were inconsistent with biasing context. Experiment 2 showed that subjects had generated a predictive …

Fume Generation In Gas Metal Arc Welding, Robert V. Albert

Doctoral Dissertations

This investigation studied fume generated from Gas Metal Arc Welding (GMAW). Through an extensive literature review, experimental measurements and analytical reasoning this dissertation answers four questions. Why and how does oxygen content of the shield gas effect fume generation? Why is more fume generated with helium than with argon as a shield gas? Why and how does welding mode affect fume rate? Why and how does pulsing the current lower fume generation rate?

An extensive literature survey was conducted. The current view of GMAW indicates that four modes exist in metal transfer across the arc. Each mode selects from several …

Molecular Identification, Coastal Distribution And Recruitment Of Cucmaria Frondosa Larvae In The Western Gulf Of Maine, Dorothy E. Medeiros-Bergen

Doctoral Dissertations

Understanding of the physical transport of larvae requires information on adult source populations, larval distributions, larval behavior and physical oceanography. Identification of three species (Cucumaria frondosa, Psolus fabricii and Chiridota laevis) of holothurian larvae in the western Gulf of Maine was done with a simple detection protocol, using oligonucleotide probes, for the 16S rRNA portion of the mitochondrial DNA genome. More than 2000 larvae and new recruits were analyzed. This technique revealed that of the three species present in the plankton, Cucumaria larvae dominated the samples comprising $>$90% of the larvae and 95% of new recruits during 1993. Cucumaria …

Profiles Of Reform In The Teaching Of Calculus: A Study Of The Implementation Of Materials Developed By The Calculus Consortium Based At Harvard (Cch) Curriculum Project, Alice Darien Lauten

Doctoral Dissertations

The research question addressed in this study is: What profiles of interpretation and implementation of reform in the teaching of calculus emerge from data obtained from mathematics faculty members using Calculus Consortium Based at Harvard (CCH) Curriculum Project materials? Site liaisons from mathematics departments using CCH Curriculum Project materials in 117 academic institutions, consisting of 13 secondary schools, 30 two-year colleges, 19 doctoral and research universities, and 55 other colleges and universities, completed Initial and Site Liaison Surveys. Site liaisons and 266 other instructors from 117 academic institutions completed a Faculty Survey. Six clustering scales were developed from the survey …

Nitrogen Oxide Decomposition By Barrier Discharge, Christopher Rob Mclarnon

Doctoral Dissertations

Nitrogen oxides have been linked to numerous air pollution problems including the production of ozone in the troposphere and acid rain. Annual nitrogen oxides emissions in the United States exceed 21 million tons and are primarily a result of the high temperature combustion of fossil fuel. Recent regulations in the U.S., both federal and state, require that nitrogen oxides emissions be reduced over the next several years.

Control of nitrogen oxide emissions is difficult in combustion exhaust gases because of their low concentration and reactivity. Numerous technologies have been developed to reduce emissions but the costs are generally high and …

Ultrasonically Initiated Free Radical Catalyzed Emulsion Polymerization Of Methyl Methacrylate, H. C. Joe Chou

Doctoral Dissertations

"The emulsion polymerization of methyl methacrylate initiated by ultrasound has been studied at ambient temperature using sodium lauryl sulfate as the surfactant.

The source of the free radical for the initiation process was found to come from the degradation of the sodium lauryl sulfate presumably in aqueous phase. The weight average molecular weight (Mw) of the poly (methyl methacrylate) obtained varied from 2,500,000 to 3,500,000 g mole^-1 and the conversion for the polymerization was up to 70%.

The polymerization rate, the number of polymer particles generated and the free radical concentration in initiation process were found to increase with …

Analysis And Design Considerations Of A High-Power Density, Dual Air Gap, Axial-Field, Brushless, Permanent Magnet Motor, Chahee Peter Cho

Doctoral Dissertations

Until recently, brush dc motors have been the dominant drive system because they provide easily controlled motor speed over a wide range, rapid acceleration and deceleration, convenient control of position, and lower product cost. Despite these capabilities, the brush dc motor configuration does not satisfy the design requirements for the U.S. Navy's underwater propulsion applications.

Technical advances in rare-earth permanent magnet materials, in high-power semiconductor transistor technology, and in various rotor position-sensing devices have made using brushless permanent magnet motors a viable alternative. This research investigates brushless permanent magnet motor technology, studying the merits of dual-air gap, axial-field, brushless, permanent …

Experimental And Numerical Studies On Pattern Formation In Electrochemical Deposition, Zhenqiu Liu

Doctoral Dissertations

An experimental and theoretical investigation on pattern formation in electrochemical deposition from copper and zinc binary sulfate electrolyte in two dimensional cells was carried out in this study. Aggregates were produced by electrochemical deposition. An interferometric setup was developed to measure the concentration boundary layer around the aggregates produced during growth.

Convection is observed during electrodeposition from binary sulfate solution of zinc and copper with the concentration of 0.04M and higher in horizontal cells. The theoretical and experimental investigation indicates that natural convection is much stronger in a horizontal cell than that in a vertical cell. Channel growth is observed …

Forest Floor Leachate Biogeochemistry And Decomposition Dynamics, William S. Currie

Doctoral Dissertations

Forest floor biogeochemistry was studied in combined field and modeling research in ecosystems representative of forests of the Northeastern U.S. The field study, conducted at the Harvard Forest, MA, focused on changes to organic and inorganic chemistry of forest-floor leachate under experimentally elevated N inputs meant to simulate effects of acid deposition in the region.

Concentrations of dissolved organic carbon and nitrogen (DOC and DON) increased substantially in N treatments in the first year of the study. I attributed this to an increase in production of soluble organics in the forest floor due to an interaction between increased N availability …