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Articles 9601 - 9630 of 11503

Full-Text Articles in Engineering

A Multiobjective Approach Applied To The Protein Structure Prediction Problem, Richard O. Day Mar 2002

A Multiobjective Approach Applied To The Protein Structure Prediction Problem, Richard O. Day

Theses and Dissertations

Interest in discovering a methodology for solving the Protein Structure Prediction problem extends into many fields of study including biochemistry, medicine, biology, and numerous engineering and science disciplines. Experimental approaches, such as, x-ray crystallographic studies or solution Nuclear Magnetic Resonance Spectroscopy, to mathematical modeling, such as minimum energy models are used to solve this problem. Recently, Evolutionary Algorithm studies at the Air Force Institute of Technology include the following: Simple Genetic Algorithm (GA), messy GA, fast messy GA, and Linkage Learning GA, as approaches for potential protein energy minimization. Prepackaged software like GENOCOP, GENESIS, and mGA are in use to …

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Compare And Complexity - When Is Compare Not Enough?, Chris E. Greiman Mar 2002

Compare And Complexity - When Is Compare Not Enough?, Chris E. Greiman

Theses and Dissertations

The purpose of this case study research is to determine the utility of COMPARE, the DoD approved software for conducting A-76 competitions, in the more complex world of public-private competition. COMPARE serves as the baseline for establishing cost factors, while two Air Force Depots are used as a basis of comparison. Research questions answered are: 1. What are the baseline cost comparison factors established in COMPARE? 2. What are the common cost factors found in the Air Force Depot public-private competitions? 3. What are the similarities and differences between the cost factors established in COMPARE and those used in the …

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Experimental Vibration Analysis Of Inflatable Beams For An Afit Space Shuttle Experiment, Thomas G. Single Mar 2002

Experimental Vibration Analysis Of Inflatable Beams For An Afit Space Shuttle Experiment, Thomas G. Single

Theses and Dissertations

This study investigated the use of MEMS based devices to control the boundary layer separation from a circular cylinder in cross flow. Velocity profiles were measured experimentally in a low speed wind tunnel. Momentum thickness was measured as the primary way to determine a change in the flow field. The goal was to determine the angular location and frequency of operation that would provide an effect on the boundary layer of the cylinder. A 25% reduction of momentum loss in the cylinder wake was detected with an optimal angle of 69 degrees and an optimal frequency of operation equal to …

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Broadcast Vs Precise Gps Ephemerides: A Historical Perspective, David L. M. Warren Mar 2002

Broadcast Vs Precise Gps Ephemerides: A Historical Perspective, David L. M. Warren

Theses and Dissertations

In most recent years, both high-resolution imagery systems and images were only available to military and national security organizations. Distinctive changes within the commercial image industry allowed space-borne pioneers to provide high-resolution images. Space-borne Image Company's Ikonos satellite provides a 1-meter resolution for the past 3 years. Current development of .5-meter resolution will be offered in the near future. Access of these images is available in ground stations located worldwide in different regions. Studies have shown that these high quality images are eye-catching and may serve a purpose through its design; on contrary high cost and accessibility does not met …

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The Investigation Of Hypervelocity Gouging, David J. Laird Mar 2002

The Investigation Of Hypervelocity Gouging, David J. Laird

Theses and Dissertations

The slipper/rail interface of a hypervelocity rocket sled is subject to immense forces due to dynamic loads and impact of the slipper with the rail, and tremendous heating due to aerodynamic and frictional effects is produced at the interface. Under these severe loading conditions, the material in the rail will sometimes experience large non-linear deformations known as gouging. Hydrocodes are computational solvers designed to handle such non-linear, large deformation, high shock, hydrodynamic applications. The ability of the hydrocode CTH to handle gouge modeling is considered, as well as the manner in which temperature environments affect deformation and plastic strain. The …

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Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey Mar 2002

Design And Fabrication Of Micro-Electro-Mechanical Structures For Tunable Micro-Optical Devices, Michael C. Harvey

Theses and Dissertations

Tunable micro-optical devices are expected to be vital for future military optical communication systems. In this research I seek to optimize the design of a microelectromechanical (MEM) structure integrated with a III-V semiconductor micro-optical device. The resonant frequency of an integrated optical device, consisting of a Fabry-Perot etalon or vertical cavity surface emitting laser (VCSEL), may be tuned by applying an actuation voltage to the MEM Flexure, thereby altering the device's optical cavity length. From my analysis I demonstrate tunable devices compatible with conventional silicon 5V integrated circuit technology. My design for a Fabry-Perot etalon has a theoretical tuning range …

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Fretting Fatigue Behavior Of A Titanium Alloy Ti-6al-4v At Elevated Temperature, Onder Sahan Mar 2002

Fretting Fatigue Behavior Of A Titanium Alloy Ti-6al-4v At Elevated Temperature, Onder Sahan

Theses and Dissertations

The purpose of this research is to investigate the fretting fatigue behavior of the titanium alloy Ti-6Al-4V at elevated temperature is investigated. Fretting and plain fatigue experiments are conducted at 260 °C. Crack initiation location and crack initiation orientation is measured and fretting and plain fatigue life data of the specimens from these tests are obtained. Fatigue parameters capable of predicting the number of cycles to specimen failure, the crack location and the crack orientation along the contact surface are analyzed. The parameters are calculated by using the computed stresses and strains obtained from the finite element analysis. The mechanisms …

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An Analytical Study Of T-38 Drag Reduction In Tight Formation Flight, Eugene H. Wagner Jr. Mar 2002

An Analytical Study Of T-38 Drag Reduction In Tight Formation Flight, Eugene H. Wagner Jr.

Theses and Dissertations

This thesis explores the benefits of flying in a tight formation, mimicking the natural behavior of migratory birds such as geese. The first phase of the research was to determine an optimal position for the wingman of a tight formation flight of T-38 Talon aircraft using the HASC95 vortex lattice code. A second wingman was then added to determine the benefit derived by increasing formation size. The second wingman was predicted to derive an even greater induced drag benefit than the first wingman for T-38s operating at Mach 0.54 at a 10,000-foot altitude. The predicted values were 17.5% savings for …

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Orbital Maneuvering Using Electrodynamic Tethers, Hakan San Mar 2002

Orbital Maneuvering Using Electrodynamic Tethers, Hakan San

Theses and Dissertations

Considerably short electrodynamic tethers can be used as a low-thrust propulsion system with minimum or no mass expenditure. The propulsive force is generated by inducing a current flow through the tether which interacts with the magnetosphere of the planet (i.e. Earth, Jupiter and other planetary bodies with magnetosphere). The basics of electrodynamic tether systems have been studied and successful experiments such as boost and de-boost of spacecraft have been conducted in the past. This study presents a simple guidance scheme for the current in the tether in order to perform orbital maneuvers. The general perturbation equations are used to develop …

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Estimating Engineering Cost Risk Using Logistic And Multiple Regression, Vincent P. Sipple Mar 2002

Estimating Engineering Cost Risk Using Logistic And Multiple Regression, Vincent P. Sipple

Theses and Dissertations

This study explores a two-step procedure for assessing defense acquisition program cost growth using historical data. Specifically, we seek to predict whether a program will experience cost growth and, if applicable, how much costs will increase. We compile programmatic data from the Selected Acquisition Reports (SARs) between 1990 and 2000 for programs from all defense departments. We focus our analysis on cost growth in research and development dollars for the Engineering Manufacturing Development phase of acquisition. We further limit our study to only one of the seven SAR categories of cost growth engineering cost growth. We explore the use of …

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A Life Cycle Cost Analysis Of The Proposed Replacement Of Pope Air Force Base's C-130e Fleet Using A Fleet Replacement Model, Lance R. French Mar 2002

A Life Cycle Cost Analysis Of The Proposed Replacement Of Pope Air Force Base's C-130e Fleet Using A Fleet Replacement Model, Lance R. French

Theses and Dissertations

The 43rd Airlift Wing at Pope AFB, NC, possesses 33 E-model C-130 aircraft. The airplanes range in age from 30-36 years old. Current plans call for replacing Pope's aging fleet of tactical airlifters with new C-130J model planes in FY11. There are two replacement alternatives proposed in this research. The first is to calls for replacing the C-130Es with C-130Js now. The second option is upgrade the C-130Es to C-130Xs and replace them in 10 years with the C-130J. The results indicate that the least cost solution is to upgrade Pope's fleet of C-130Es to C-130Xs now. However, after conducting …

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The Management Of Energy Savings Performance Contracts (Espcs), Ericka M. Dailey Mar 2002

The Management Of Energy Savings Performance Contracts (Espcs), Ericka M. Dailey

Theses and Dissertations

Energy Savings Performance Contracts (ESPCs) originated to accomplish several objectives: (1) to meet energy efficiency goals mandated by executive orders and energy policies; (2) to improve federal government facilities using funds allocated for utility bills; and (3) to receive repayment of expenditures through energy savings reflected in reduced utility bills. In ESPC's, the contractor guarantees savings to the federal government agency. 10 CFR 436 limits the time necessary for payback. However, this regulation and others were written prior to the deregulation of utility companies. This theory is based on the underlying premise that the contractor payback is a direct result …

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A System Dynamics Approach To Modeling Aircraft System Production Break Costs, John J. Dubelko Mar 2002

A System Dynamics Approach To Modeling Aircraft System Production Break Costs, John J. Dubelko

Theses and Dissertations

This research effort employs a System Dynamics methodology to model Air Force aircraft production break costs. The Air Force currently used the Anderlohr, Modified Anderlohr, and Retrograde methods for the estimation of aircraft production breaks. These methods offer little insight into the dynamic behavior of an aircraft production break. System Dynamics offers a unique way of capturing expert opinions in this area and dynamically presenting behaviors of an Air Force aircraft production line during a production break. Development of this model followed a four-step process of conceptualization, formulation, testing, and implementation. Five Air Force aircraft production break experts in were …

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Spectrum Management And The Global Positioning System: A Case Study In Interagency Coordination, John A. Enis Mar 2002

Spectrum Management And The Global Positioning System: A Case Study In Interagency Coordination, John A. Enis

Theses and Dissertations

At the 2000 World Radio Conference (WRC), a European initiative resulted in the approval of resolutions 605 and 606 (agenda item 1.15), which the United States opposed. These resolutions established provisional power flux density (PFD) limits on the L2 and L5 frequencies of the Global Positioning System. These limits will negatively affect the $1.2B GPS modernization. The United States will have to present its positions and rationale regarding the PFD limits to international meetings, including the 2003 World Radio Conference, to persuade the international community to adopt that U.S. view. Developing the U.S. view and conducting the supporting technical work …

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Admissions Criteria And Academic Performance In The Afit Graduate Cost Analysis Program, Kenneth R. Garwood Mar 2002

Admissions Criteria And Academic Performance In The Afit Graduate Cost Analysis Program, Kenneth R. Garwood

Theses and Dissertations

This research examined the admissions criteria used by the Air Force Institute of Technology (AFIT) to determine academic eligibility for the in-residence Graduate Cost Analysis (GCA) master's degree program. Using the cumulative graduate grade point average earned at AFIT as the measure of academic performance, comparisons were made between the predictive capability of the current criteria and other potential factors. Factors considered included scores from the Graduate Record Examination (GRE) and the Graduate Management Admissions Test (GMAT), undergraduate cumulative and math grade point averages, applicant's age and gender, ratings of the undergraduate school's admissions competitiveness, undergraduate degree type, and various …

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An Evaluation Of Public And Private Sector Housing Alternatives For Military Families, Lawrence P. Kokocha Jr. Mar 2002

An Evaluation Of Public And Private Sector Housing Alternatives For Military Families, Lawrence P. Kokocha Jr.

Theses and Dissertations

This study explored the three primary housing alternatives along with their associated benefits and costs for military members at Robins Air Force Base. Using a case study methodology, qualitative and quantitative data were collected from contract documents, cost records, statements and testimonies to Congress, literature, census data, and interviews with civil engineering, contracting, financial management and legal professionals. This data was analyzed to determine which housing alternative seems to provide the best benefits at the lowest costs for military members and the government. The results of the study indicated that private sector alternatives are less expensive than government provided housing. …

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An Empirical Investigation Of Critical Factors Affecting The Ability Of Public Entities To Compete In Public Private Competitions, Timothy J. Gilbride Mar 2002

An Empirical Investigation Of Critical Factors Affecting The Ability Of Public Entities To Compete In Public Private Competitions, Timothy J. Gilbride

Theses and Dissertations

In 1996, the Commandant of the U.S. Coast Guard initiated the largest ever service acquisition program to re-capitalize Coast Guard assets. Called the Integrated Deepwater System or IDS, this acquisition effort seeks to renovate, modernize, and or replace the Coast Guard s entire portfolio of ships, aircraft, and support facilities. The IDS contractor will be responsible for designing and constructing the system, as well as, sharing responsibility for supporting and disposing of it. This poses a significant threat to the USCG Aircraft Repair and Supply Center (AR&SC), the Coast Guard s aircraft depot located in Elizabeth City, North Carolina. The …

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How Can The Air Force Maximize The Value Of Reverse Auctioning As A Pricing Technique?, Cynthia L. Marion-Mullins Mar 2002

How Can The Air Force Maximize The Value Of Reverse Auctioning As A Pricing Technique?, Cynthia L. Marion-Mullins

Theses and Dissertations

This research examines the pricing tool reverse auctioning. In a reverse auction buyers state the item they wish to buy and the sellers compete with each other for the sale, driving the price steadily down until no seller is willing to go any lower. Darleen A. Druyun, Principal Deputy Assistant Secretary of the Air Force for Acquisition and Management, Washington, D.C., launched the Air Force acquisition reform "Lightning Bolts" initiatives. These initiatives jump-start acquisition reform to find processes leading towards a better, faster, and cheaper way of conducting business. A reverse auction is one of these processes. A review of …

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The Predictive Validity Of The Afit Graduate Engineering And Environmental (Geem) Admission Requirements, Charles C. Zitzmann Mar 2002

The Predictive Validity Of The Afit Graduate Engineering And Environmental (Geem) Admission Requirements, Charles C. Zitzmann

Theses and Dissertations

Recognizing that a strong commitment to advanced technical and management education (Van Scotter, 1993, p. 1) serves to maintain the capability and strength of the United States Air Force (USAF), the Air Force Institute of Technology (AFIT) Graduate School of Engineering and Management (GSEM) offers a full-time, eighteen-month, Graduate Engineering and Environmental Management (GEEM) program to military officers and Department of Defense (DoD) civilian employees. The AFIT uses the applicant's undergraduate grade-point average (UGPA), Graduate Record Examination (GRE) General Test verbal and quantitative scores, and undergraduate mathematics course grade-point average (UMGPA) to select applicants for admission. This study analyzed how …

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Integrated Manet Mutual Authentication System, Jason T. Ballah Mar 2002

Integrated Manet Mutual Authentication System, Jason T. Ballah

Theses and Dissertations

The Integrated MANET Mutual Authentication System (IMMAS) provides implied mutual authentication of all routing and data traffic within a Mobile Ad Hoc Network (MANET) by combining Elliptic Curve Cryptography, a public-key cryptosystem, with the Dynamic Source Routing (DSR) Protocol. IMMAS provides security by effectively hiding network topology from adversaries while reducing the potential for, among other things, traffic analysis and data tampering, all while providing a graceful degradation for each of the authentication components. Current research in MANETs tends to focus primarily on routing issues leaving topics such as security and authentication for future research. IMMAS focuses on achieving a …

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Ontological Engineering And Mapping In Multiagent Systems Development, Jonathan M. Dileo Mar 2002

Ontological Engineering And Mapping In Multiagent Systems Development, Jonathan M. Dileo

Theses and Dissertations

Multiagent systems have received much attention in recent years due to their advantages in complex, distributed environments. Previous work at the Air Force Institute of Technology has developed a methodology for analyzing, designing, and developing multiagent systems, called Multiagent Systems Engineering (MaSE). MaSE currently does not address the information domain of the system, which is an integral part of designing proper system execution. This research extends the MaSE methodology to include the use of ontologies for information domain specification. The extensions allow the designer to specify information flow by using objects from the ontology as parameters in agent conversations. The …

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Space Time Adaptive Processing And Clutter Classification Integration And Evaluation, Nathan A. Jensen Mar 2002

Space Time Adaptive Processing And Clutter Classification Integration And Evaluation, Nathan A. Jensen

Theses and Dissertations

Radar is a fundamental technology in today's military and civilian environment, and continuing development of this technology is of utmost importance to maintaining technological advantages this realm. Current radar technologies suffer from jamming and clutter limitations. STAP is a statistical method to remove this noise, however it is extremely computationally intensive, and presents several real time processing hurdles. Clutter Classification is another method to classify the radar returns that are found according to the best fit statistical distribution that the return follows. This research investigation attempts to use this clutter classification technology to aid in the detection of targets by …

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Performance Analysis Of A Dynamic Bandwidth Allocation Algorithm In A Circuit-Switched Communications Network, Timothy M. Schwamb Mar 2002

Performance Analysis Of A Dynamic Bandwidth Allocation Algorithm In A Circuit-Switched Communications Network, Timothy M. Schwamb

Theses and Dissertations

Military communications networks typically employ a gateway multiplexer to aggregate all communications traffic onto a single link. These multiplexers typically use a static bandwidth allocation method via time-division multiplexing (TDM). Inefficiencies occur when a high-bandwidth circuit, e.g., a video teleconferencing circuit, is relatively inactive rendering a considerable portion of the aggregate bandwidth wasted while inactive. Dynamic bandwidth allocation (DBA) reclaims unused bandwidth from circuits with low utilization and reallocates it to circuits with higher utilization without adversely affecting queuing delay. The proposed DBA algorithm developed here measures instantaneous utilization by counting frames arriving during the transmission time of a single …

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Groundwater Flow Through A Constructed Treatment Wetland, Andrew C. Entingh Mar 2002

Groundwater Flow Through A Constructed Treatment Wetland, Andrew C. Entingh

Theses and Dissertations

This study examines the flow of groundwater through one of the treatment cells. A major goal of the study is to determine whether the system design facilitates uniform vertical flows through the subsurface soil sediments or if preferential flows occur. Conceptually, uniform flows will achieve the most efficient degree of contaminant removal possible by evenly dispersing the groundwater contaminants throughout the full volume of the subsurface media. A three-dimensional grid of piezometers is used to generate potentiometric contour maps, and in-situ tests of hydraulic conductivity facilitate construction of a numerical computer model. The contours of hydraulic head, measured conductivities, and …

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An Evaluation Of Geobest Contingency Beddown Planning Software Using The Technology Acceptance Model, Shawn J. Jensen Mar 2002

An Evaluation Of Geobest Contingency Beddown Planning Software Using The Technology Acceptance Model, Shawn J. Jensen

Theses and Dissertations

GeoBEST is a software program designed to simplify the contingency beddown planning process through application of geographic information technology. The purpose of this thesis was to thoroughly evaluate GeoBEST using prospective GeoBEST users in a realistic beddown planning scenario. The Technology Acceptance Model (TAM) was applied, which measures a prospective user's perceptions of the technology's usefulness and ease-of-use and predicts their intentions to use the software in the future. The evaluations also included a qualitative evaluation of specific software features. The test group for this thesis was seventy-one Civil Engineering students attending contingency skills training at the Silver Flag training …

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Decision Analysis With Value Focused Thinking As A Methodology To Select Force Protection Initiatives For Evaluation, David M. Jurk Mar 2002

Decision Analysis With Value Focused Thinking As A Methodology To Select Force Protection Initiatives For Evaluation, David M. Jurk

Theses and Dissertations

Current emphasis on homeland security/defense is high. Decision makers responsible for enhancing the protection of both military and civilian personnel require additional insight when selecting ideas, concepts, or technologies to pursue with constrained resources. They are faced with multiple criteria and multiple objectives; yet they have no defensible, objective, and repeatable selection process to assist them in making their decisions. This thesis explores whether the value-focused thinking (VFT) process is appropriate for providing the necessary insight to those decision makers. To prove the VFT process is appropriate and viable; this thesis focuses on constructing a value model, scoring alternatives, and …

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Decision Analysis With Value-Focused Thinking As A Methodology In Structuring The Civil Engineer Operations Flight, Dee Jay Katzer Mar 2002

Decision Analysis With Value-Focused Thinking As A Methodology In Structuring The Civil Engineer Operations Flight, Dee Jay Katzer

Theses and Dissertations

The civil engineer operations flight organizational structure has been in a state of change since the flight's inception and is currently prescribed only to the element level. Therefore, an operations flight commander must determine the organizational structure best suited for their unique situation without any guidance or support. To provide insight and defensible support for an operations flight commander faced with this decision, a value-focused thinking process was used to create a value model that aids in evaluating possible organizational structures. To ensure that the results of this research are applicable across the Air Force, the value model was created …

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Determination Of Chlorinated Solvent Contamination In An Upward Flow Constructed Wetland, Bryan C. Opperman Mar 2002

Determination Of Chlorinated Solvent Contamination In An Upward Flow Constructed Wetland, Bryan C. Opperman

Theses and Dissertations

The purpose of this study is to determine chlorinated solvent contamination levels in an upward flow constructed wetland at Wright-Patterson Air Force Base (WPAFB), Ohio. A stratified grid sampling methodology will be used in sampling the contaminated groundwater. Analysis will be accomplished by means of purge-and-trap gas chromatography. The contaminant concentration levels will be used to enhance the design and construction of man-made wetlands used to remove chlorinated solvents from aquifers. PCE levels declined from an average of 33.97 ppb in the inflow stream to an average of 3.65 ppb in the upper layer, a 91% reduction. High concentrations occurred …

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Hexavalent Chromium Dissociation From Overspray Particles Into Fluid For Three Aircraft Primers, Richard A. Schilke Mar 2002

Hexavalent Chromium Dissociation From Overspray Particles Into Fluid For Three Aircraft Primers, Richard A. Schilke

Theses and Dissertations

DOD and industry use chromate-containing primers extensively to inhibit corrosion on metal assets. Chromate contains Cr6+, a human carcinogen, but there is little epidemiological evidence of increased lung cancer among spray painters. Using bio-aerosol impingers, overspray particles from three primers (solvent-borne epoxy, water-borne epoxy, and solvent-borne polyurethane) were collected into water to test the hypothesis that the paint matrix inhibits Cr6+ release into water, under the premise that this simulates Cr6+ release from particles into lung fluid. Particles were allowed to reside in water for 1 or 24 hours, then separated from the water by centrifugation, …

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Fabrication Techniques For Micro-Optical Device Arrays, Ryan D. Conk Mar 2002

Fabrication Techniques For Micro-Optical Device Arrays, Ryan D. Conk

Theses and Dissertations

Micro-optical devices are vital components of conventional military data storage, sensor, and communication systems. Two types of micro-optical device arrays exist: individually addressable and matrix addressable. The matrix addressable array has a drastically reduced number of metal lines and can potentially be fabricated into large, dense (over 1k elements) arrays. Such arrays are expected to enable the development of extremely high bandwidth optical interconnect systems for future military applications including optical computing and short-haul fiber optical communication systems. I investigate new fabrication techniques for the assembly of dense matrix-addressed arrays of micro-optical devices such as vertical-cavity surface-emitting lasers. Using a …

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