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Cathodoluminescence Spectroscopy Of Zinc Germanium Phosphide Zngep2, Michael R. Gregg

Theses and Dissertations

Zinc Germanium Phosphide (ZnGeP₂) is a nonlinear semiconductor suitable for use as a laser tuning element over the two to six micron wavelength range. Although this crystal has been studied in the past, its luminescent properties are not yet well understood. In this present study, ZnGeP₂ has been examined using cathodoluminescence spectroscopy (CL). Specifically, the spectral dependence of the CL was obtained as a function of electron beam energy, beam current and temperature. The resulting CL was found to be polarized with a peak structure that was dependent on the polarization. This peak structure observed by CL …

Computational And Experimental Investigation Into Fracture Of Brittle Fiber - Brittle Matrix Composite Systems, James P. Solti

Theses and Dissertations

Experimental and computational analyses provided an improved understanding of quasi-static fracture in model composite systems. Constant displacement compression tests using borosilicate glass double cleavage drilled compression test templates provided qualitative assessments of localized toughening for crack growth near cylindrical inclusions. Large crack-tip stress fields induced interfacial slip and separation prior to arrival of the main crack. Debonding and the proliferation of secondary matrix cracks characterized the role of bridging fibers along weak interfaces. Strong residual normal compressive interfacial stresses diminished the influence of crack-tip stresses; however, slip was still observed. VHS tape and computer enhanced photos record a history of …

Methods For Viewing Radar Cross Section Data In Three Dimensions, David J. Tisdale

Theses and Dissertations

Radar Cross Section data is an important factor in the design of modern fighter and bomber aircraft. Minimization of the reflected radar energy is one of the key issues when choosing shapes and materials in new aircraft. Visualization of the energy scattered back to a radar is neither intuitive nor easy. The mission planner and pilot need to gain an understanding of the vulnerabilities inherent in the design of the systems they use. The advent of relatively low cost graphics workstations has made their use affordable in applications inconceivable only a few short years ago. This thesis examines three graphics …

Design And Characterization Of Optically Pumped Vertical Cavity Surface Emitting Lasers, Richard J. Bagnell

Theses and Dissertations

Vertical Cavity Surface Emitting Lasers (VCSELs) are a form of semiconductor laser which have their cavity oriented orthogonally to the plane of the wafer. The orientation necessitates short cavities, highly reflective mirrors and a relatively high gain/loss ratio. Even so, the resultant superior exit beam characteristics and the tight packing density of the finished lasers provide strong motivation for pursuing the growth of these structures. This thesis details the design of an optically pumped InGaAs multiple quantum well periodic gain structure VCSEL with a 950 nm lasing wavelength. These growths were to be a first attempt at VCSEL construction, so …

Cepstral And Auditory Model Features For Speaker Recognition, John M. Colombi

Theses and Dissertations

The TIMIT and KING databases, as well as a ten day AFIT speaker corpus, are used to compare proven spectral processing techniques to an auditory neural representation for speaker identification. The feature sets compared were Linear Predictive Coding (LPC) cepstral coefficients and auditory nerve firing rates using the Payton model. This auditory model provides for the mechanisms found in the human middle and inner auditory periphery as well as neural transduction. Clustering algorithms were used to generate speaker specific codebooks - one statistically based and the other a neural approach. These algorithms are the Linde-Buzo-Gray (LBG) algorithm and a Kohonen …

Satcom General Purpose Modem Dscs Iii Sct Beacon Telemetry Display, James D. Coppola

Theses and Dissertations

This thesis documents the design and implementation of a DSCS III single Channel Transponder (SCT) beacon telemetry display. The system is a personal computer based design which interfaces to three SCT beacon receiver/demodulators. The software was designed to decode and display both the DSCS III A and DSCS HI B satellite beacons. Recordings of the SCT beacon display can be made on paper and/or magnetic media when triggered by the user, a watchdog timer, or the SCT command accept telemetry bit. In addition, the system can be configured with an IRIG B Universal Time Coordinates (UTC) card which enables the …

Face Recognition With Neural Networks, Dennis L. Krepp

Theses and Dissertations

This study investigated neural networks for face verification and classification. The research concentrated on developing a neural network based feature extractor and/or classifier to perform authorized user verification in a realistic work environment. Recognition accuracy, system assumptions, training time, and execution time were analyzed to determine the feasibility of a neural network approach. Data was collected using a camcorder and two segmentation schemes: manual segmentation and motion-based, automatic segmentation. Data consisted of over 2000. 32x32 pixel, 8 bit gray scale images of 52 subjects; each subject had two to ten days worth of images collected. Several training and test sets …

Photopolymer-Based Stratified Volume Holographic Optical Elements, Gregory P. Nordin, A. R. Tanguay

Faculty Publications

We report the implementation of stratified volume holographic optical elements (SVHOE's) using DuPont's Omnidex holographic photopolymer material and an in situ exposure technique for simultaneous multilayer grating recording. Experimental measurement of the +1-order angular sensitivity of a seven-layer SVHOE structure shows remarkable agreement with both theory and numerical simulation for incidence angles near the Bragg angle. For SVHOE's having modulation layers that individually operate in the Bragg or transition diffraction regimes, the envelope of the SVHOE angular sensitivity is experimentally shown to approximate closely that of a single modulation layer.

Diffraction Properties Of Stratified Volume Holographic Optical Elements, Gregory P. Nordin, R. V. Johnson, A. R. Tanguay

Faculty Publications

We present a unified treatment of the diffraction properties of stratified volume holographic optical elements (SVHOE's). We show that the relative phasing of the diffraction orders as they propagate from layer to layer gives rise to a unique notched diffraction response of the +1 order (for the case of Bragg incidence) as a function of the normalized buffer-layer thickness, the grating spatial frequency, and the readout wavelength. For certain combinations of these parameters Bragg diffraction behavior characteristic of volume holographic optical elements (VHOE's) is observed, whereas for other combinations pure Raman-Nath behavior periodically recurs. By using these same relative-phasing arguments, …

Oxidative Mechanisms In Arterial Distension Injury: Observations Relevant To Restenosis After Angioplasty, Charles F. Babbs, Yuan Zhong

Weldon School of Biomedical Engineering Faculty Working Papers

Background: To explore the hypothesis that tissue iron and reactive oxygen species, including superoxide (O2), mediate acute inflammatory and late hyperplastic responses to vascular injury, we studied experimental overdistension of normal carotid and femoral arteries in dogs. Experimental design: Arterial segments isolated in situ were distended with Ringer solution at 2 atmospheres pressure. In initial experiments the arteries were excised immediately after distension and immersed in diaminobenzidine solutions containing Mn++ ions to initiate histochemical reactions for O2. In other experiments distended arterial segments were reperfused with arterial blood in the presence or absence of the iron chelator, deferoxamine, or the …

Nsf Sponsored Innovation In Engineering And Cornputer Science, Jacob Abel, Patricia Daniels, James G. Harris, Harry Hedges

Electrical Engineering

No abstract provided.

Model For The Infrastructure Of Engineering Education, James G. Harris, Karen Frair, Win Aung, Susan T. Hill

Electrical Engineering

There are many ways to describe and model physical systems. The infrastructure of engineering education in the United States is an example of such a system, and it is the intent of this report to describe and model this infratructure. The means for doing this starts with the graduation statistics for the year 1989 given by the Computer Aided Science Policy Analysis & Research Database System (CASPAR) developed for the National Science Foundation by Quantum Research Corporation [1], and uses a simple categorization for the institutions that contribute to those statistics. This categorization sorts the post -secondary institutions in the …

Acuta Enews November 1992, Vol. 21, No. 11

ACUTA Newsletters

In This Issue

Interchangeable NPA, NNX

President's Message

Permanent 800 numbers

Industry/ Regulatory updates

Making voice mail effective

The fax-on-demand solution

A Study On Radical Scavenging And Magnetic Resonance Imaging Characteristics Of Stable Radical Nitroxides, Shiey-Shiun Horng

Dissertations

Several nitroxides have been prepared for study of their image enhancement capability. These nitroxides contain different nitroxyl moieties within one molecule. On MRI examination for the nitroxides prepared, TEMPO and HPTPO are better due to their better water solubility, even though some of the others have more nitroxyl centers available. The intensity response is linear with respect to concentration in the range studied in most of the cases except for HPTPO, whose intensity finally reaches maximum when its concentration is higher than 10 mM.

Three sources of biomass, namely, liver microsomes, whole-cell yeast and a bacterial activated sludge consortium, have …

Bragg Reflection Grating Waveguide, Wei Zhong

Theses

Bragg reflection waveguides (BRW) are non-conventional optical guides in which optical confinement is achieved via periodic set of grooves or stratified media along the guiding path. BRW may also serve as optical filters, because of spectral discrimination of the guiding process. A novel UV laser ablation technique was used in this thesis to fabricate periodic metal-clad polymeric waveguides. Spin-on technique was applied to fabricate the waveguide core on glass substrates, evaporation of metal film and selective ablation process defined the optical guides. Various periodicities have been fabricated and the near field patterns have been measured to compare the different guiding …

Mineralization Of 2-Chlorophenol Using A Hollow Fiber Ultrafiltration System In Combination With A Reactor Containing An Immobilized White Rot Fungus, Sheau-Ming Tung

Theses

Phanerochaete chrysosporium, a white rot fungus was immobilized on a packed-bed reactor, and was used to mineralize an aqueous stream contaminated with 50 ppm of 2-chlorophenol. Hollow fiber ultrafiltration membranes (for 5,000 daltons and 10,000 daltons molecular weight cut-oft) were utilized to retain the extracellular enzyme resulting from the immobilized fungus in a recirculation loop outside of the reactor.

It was found here that the concentration of proteins (roughly proportional to the extracellular enzyme releasd by the fungus) does not correlate with the rate of degradation of 2-chlorophenol in the system. The protein was concentrated 1.5 fold in the recycle …

Application Of Desktop Manufacturing System (Sla) For The Manufacturing Of A Centrifugal Pump Impeller Using Cad (I-Deas), Wasimuddin Azam Muhammad Syed

Theses

Desktop Manufacturing (DTM) systems which combine personal computer, laser and other technologies are being used to sculpt objects from computer generated models created on computer aided design (CAD) workstations. As a member of DTM systems, StereoLithography Apparatus (SLA) transforms 3-dimensional designs into a 3-D output. This can substantially reduce the time required to produce a prototype through the process of photopolymerization. The process involves the transfer of a liquid plastic monomer into a solid polymer by exposing it to ultraviolet light.

Although the process looks productive, inefficiencies can occur, if incorrect parameters are selected before its application for a particular …

Acuta Enews October 1992, Vol. 21, No. 10

ACUTA Newsletters

In This Issue

CMSU testing VISIT

President's message

A telecom intern's report

Annual ACUTA budget

Answers from "Regional Feud"

Membership Director's report

Bulletin - Fall, 1992, Civil Aviation Medical Association

Browse all Civil Aviation Medical Association Newsletters

A sixteen page newsletter of the Civil Aviation Medical Association. The newsletter provided news about civil aviation medicine and information related to the organization.

Interaction Of Profiled Light With Contrapropagating Acoustic Waves: Fourier Transform Approach, Partha P. Banerjee, Chen-Wen Tarn, Jaw-Jueh Liu

Electrical and Computer Engineering Faculty Publications

A straightforward Fourier-transform approach is employed to investigate acousto-optic interaction between an input optical beam with arbitrary profile and contrapropagating cw sound in the Bragg regime. The process can be analyzed in terms of the simultaneous scattering of light by the two sound waves in the interaction region. Analytic expressions for the equivalent transfer functions are obtained and the scattered light profiles are plotted.

An Experimental Study For The Effect Of Specimen Size On Shear Behavior Of Granular Materials, Clifton Linwood Parker Iv

Civil & Environmental Engineering Theses & Dissertations

An experimental study was undertaken to look into the effect of specimen size on the volumetric behavior of granular triaxial specimens. It was hypothesized that the specimen preparation mold creates a unique particle arrangement near the perimeter of the specimen and thus, for smaller specimen diameter relative to the particle size, it will exhibit a greater effect of the unique particle arrangement on the volumetric behavior. particles was used A single distribution of spherical glass throughout the testing. The tested specimens were 3.6, 2.8, 2.0, 1.4, 1.0, and 0.6 inches in diameter with a fixed two to one specimen height …

Retention Of Cellular Viability And Growth Potential In Cryopreserved Bovine Arterial Tissue: Implications For Clinical Use Of Cryopreserved Vascular Allografts, Kip G. Gardner

Biological Sciences Theses & Dissertations

Segments of bovine calf aortas and pulmonary arteries were cryopreserved at -196° C for two weeks to 18 months and subsequently thawed. Cellular morphology, viability, and growth potential in these segments were then compared with the same attributes in segments from fresh (control) arteries. Scanning electron microscopy revealed no disruption of intimal surfaces attributable to cryopreservation. Endothelial cells were successfully cultured from all cryopreserved arterial segments. Endothelial monolayers grown from cryopreserved arteries had a cobblestone appearance and expressed Factor VIII antigen but not smooth muscle alpha-actin. Plating efficiency in primary cultures of endothelial cells was lower for cryopreserved arteries than …

Understanding Transportation In The Commonwealth: How Decisions Of The Past Affect Us Today: National Overview, Lester P. Lamm

Kentucky's Annual Forum on Transportation

No abstract provided.

The Management Of Replicated Data, Hsueh-Chi Shih, C. Y. Ho, S. Alptekin

Computer Science Technical Reports

Data replication, which has the benefits of improving system availability and read performance, proved to be indispensable to many database applications. In a replicated database, the one-copy serializability of transaction executions can be ensured by employing a replica control mechanism on top of the traditional concurrency control mechanism. This work contains two replica control algorithms and a read-only transaction processing algorithm. Both replica control algorithms handle multiple site, communication and partitioning failures. The replica control algorithms achieve read operation efficiency by always translating a logical read operation into one local physical read operation and by taking advantage of the locality …

Methanotrophic Bacteria For Nutrient Removal From Wastewater: Attached Film System, William J. Jewell, Yarrow M. Nelson, Mark S. Wilson

Civil and Environmental Engineering

It was hypothesized that nutrient removal from wastewater could be achieved by using methane oxidizing bacteria (methanotrophs). Because methane is inexpensive. it can be used as an energy source to encourage bacterial growth to assimilate nitrogen and phosphorus and other trace elements. This initial feasibility study used synthetic nutrient mixtures and secondary sewage effluent as feed to a laboratory-scale methanotrophic attached-film expanded bed (MAFEB) reactor operated at 35°C and 20°C. The MAFEB system operated successfully at low nutrient concentrations under a variety of nutrient-limited conditions. Using a synthetic nutrient mixture with a nitrogen:phosphorus feed ratio (w/w) …

Acuta Enews Septmber 1992, Vol. 21, No. 9

ACUTA Newsletters

In This Issue

Merging technologies to compete

President's column

Award, election winners

Innovation spurs productivity

Conference evaluations

Welcome to new members

A Comparison Of Computer And Paper Media In Psychological Testing, Anthony C. Hensley, Timothy R. Morris

Theses and Dissertations

This study examined differences based on computer and paper modes of administration in psychological testing. The hypotheses tested were the expectations that scores on the computer Wonderlic Personnel Test (WPT) would be higher than the paper version and subjects would report higher levels on the computer Vocational Preference Inventory (VPI) scales. A counterbalance experimental design with two experimental groups was used. The subjects were volunteers from the Air Force Institute of Technology (AFIT) and Wright State University (WSU); 90 subjects completed the study. This included 75 students from AFIT and 15 from WSU; 69 subjects were male and 21 were …

An Analysis Of Strategic Planning To Support The United States Special Operations Forces' C3 Interoperability, George M. Pierce Ii

Theses and Dissertations

The purpose of this study was to analyze the strategic plans of USSOCOM to determine its role in resolving the C3 interoperability issues. A model using strategic controls and Theory of Constraints was used as a standard to evaluate USSOCOM's management plans. A literature search revealed that hardware and new technology were the primary concerns of previous studies. However, the literature did not address whether the lack of a formal strategy contributed to the C3 interoperability problems. Therefore, the determination was to adopt a fresh approach to the C3 interoperability issues and analyze the strategic process. The data analysis of …

An Analysis Of The Potential Use Of Red Horse Capabilities And Training Activities To Perform Or Accelerate Air Force Environmental Cleanups, E. Alexander Stokes Iii, Randy A. Carpenter

Theses and Dissertations

There are more than 4,000 Air Force (AF) sites requiring restoration due to hazardous waste contamination. The AF goal is to completely restore all sites by 2000. One method of achieving this ambitious goal is to use in-house capabilities. This study examined the potential use of RED HORSE capabilities and training activities to assist with cleanup of contaminated sites. RED HORSE capabilities and training requirements were compared to the primary cleanup needs of the AF. One finding of this study suggests cleanup of sites contaminated by volatile organic chemicals (VOCs) is the primary need of the AF. The findings also …

Development Of A Heuristic Knowledge Base For The Selection Of Applicable Or Relevant And Appropriate Environmental Requirements, Scott J. Borg, Gerald B. Puetz

Theses and Dissertations

Applicable or Relevant and Appropriate Requirements (ARARs) are the basis used in establishing threshold limits for hazardous waste cleanups performed under the Comprehensive Environmental Response, Compensation and Liability Act (CERCIA). ARARs selections must be applied consistently at numerous cleanup locations concurrently. The purpose of this research was to analyze activities required for the development of a heuristic knowledge base used for selection of The problem domain for the research was limited CERCLA cleanups of contaminated groundwater, through the use of a pump and treat strategy, using air stripping as the as the cleanup technology. The research examined literature concerning the …