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Air Force Institute of Technology

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Articles 5251 - 5280 of 5698

Full-Text Articles in Engineering

A Radiosity Approach To Realistic Image Synthesis, Richard L. Remington Dec 1992

A Radiosity Approach To Realistic Image Synthesis, Richard L. Remington

Theses and Dissertations

The Air Force Institute of Technology (AFIT) has not had the capability to generate photorealistic images. This thesis is a research effort to implement such a system at AFIT, and to apply knowledge from the particle transport community to this problem. Investigation into various techniques for generating photorealistic images led to the conclusion that the radiosity method would serve as the foundation for development. This is because of the increased accuracy of the diffuse reflections with the radiosity method and the fact that the images produced with radiosity axe view-independent. Two distinct tools to generate photorealistic images axe described. The …

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Generalization And Parallelization Of Messy Genetic Algorithms And Communication In Parallel Genetic Algorithms, Laurence D. Merkle Dec 1992

Generalization And Parallelization Of Messy Genetic Algorithms And Communication In Parallel Genetic Algorithms, Laurence D. Merkle

Theses and Dissertations

Genetic algorithms (GA) are highly parallelizable, robust semi- optimization algorithms of polynomial complexity. The most commonly implemented GAs are 'simple' GAs (SGAs). Reproduction, crossover, and mutation operate on solution populations. Deceptive and GA-hard problems are provably difficult for simple GAs. Messy GAs (MGA) are designed to overcome these limitations. The MGA is generalized to solve permutation type optimization problems. Its performance is compared to another MGA's, an SGA's, and a permutation SGA's. Against a fully deceptive problem the generalized MGA (GMGA) consistently performs better than the simple GA. Against an NP-complete permutation problem, the GMGA performs better than the other …

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Development Of A Protocol Usage Guideline For Conservative Parallel Simulations, Prescott J. Van Horn Dec 1992

Development Of A Protocol Usage Guideline For Conservative Parallel Simulations, Prescott J. Van Horn

Theses and Dissertations

The objective of distributed simulation is to speedup simulation execution by partitioning the simulation processing load over multiple processors, This thesis reviews current synchronization protocol methods for distributed simulations, and proposes guidelines for obtaining optimal conservative simulation partitionings using empirical evidence. An analysis is performed using three protocol variations of the Chandy-Misra HULL message algorithm, two using a pending message blocking strategy, and the other using a safetime blocking strategy. A fourth protocol evaluated is based on the SRADS algorithm proposed by Reynolds. The analysis involves a study of all possible 2 and 4 node configurations, for three queuing simulations, …

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Parallel Simulation Of Structural Vhdl Circuits On Intel Hypercubes, Thomas A. Breeden Dec 1992

Parallel Simulation Of Structural Vhdl Circuits On Intel Hypercubes, Thomas A. Breeden

Theses and Dissertations

Many VLSI circuit designs are too large to be simulated with VHDL in a reasonable amount of time. One approach to reducing the simulation time is to distribute the simulation over several processors. This research creates an environment for designing and simulating structural VHDL circuits on the Intel iPSC/2 and iPSC/860 Hypercubes. Logic gates and system behaviors are partitioned among the processors, and signed changes are shared via event messages. Circuit simulations are run over the SPECTRUM parallel simulation testbed, and the null- message paradigm is used to avoid deadlock. Structural circuits ranging from forty to over one thousand logic …

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Automated Control Of Aircraft In Formation Flight, Louis E. Buzogany Dec 1992

Automated Control Of Aircraft In Formation Flight, Louis E. Buzogany

Theses and Dissertations

In this study, an automated formation control system for an aircraft formation comprised of one lead and multiple wing aircraft is analyzed. Second- order models of the C-130 aircraft are developed in order to accurately model the flying qualities of large aircraft. This automated formation control system is capable of controlling the C-130 aircraft in maneuvering formation flight, thus reducing the wing's pilot workload. During formation flight, the wing aircraft continuously measures the lead aircraft's relative position with an ideal on-board position sensor. This information, in addition to Proportional Plus Integral feedback control, is used to maintain the aircraft in …

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Scientific Visualization Of Volumetric Radar Cross Section Data, Thomas G. Wojszynski Dec 1992

Scientific Visualization Of Volumetric Radar Cross Section Data, Thomas G. Wojszynski

Theses and Dissertations

For aircraft design and mission planning, designers, threat analysts, mission planners, and pilots require a Radar Cross Section (RCS) central tendency with its associated distribution about a specified aspect and its relation to a known threat, Historically, RCS data sets have been statically analyzed to evaluate a d profile. However, Scientific Visualization, the application of computer graphics techniques to produce pictures of complex physical phenomena. appears to be a more promising tool to interpret this data. This work describes data reduction techniques and a surface rendering algorithm to construct and display a complex polyhedron from adjacent contours of RCS data. …

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Design And Characterization Of Optically Pumped Vertical Cavity Surface Emitting Lasers, Richard J. Bagnell Dec 1992

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 …

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High Range Resolution Radar Target Identification Using The Prony Model And Hidden Markov Models, Mark R. Dewitt Dec 1992

High Range Resolution Radar Target Identification Using The Prony Model And Hidden Markov Models, Mark R. Dewitt

Theses and Dissertations

Fully polarized Xpatch signatures are transformed to two left circularly polarized signals. These two signals are then filtered by a linear FM pulse compression ('chirp') transfer function, corrupted by AWGN, and filtered by a filter matched to the 'chirp' transfer function. The bandwidth of the 'chirp' radar is about 750 MHz. Range profile feature extraction is performed using the TLS Prony Model parameter estimation technique developed at Ohio State University. Using the Prony Model, each scattering center is described by a polarization ellipse, relative energy, frequency response, and range. This representation of the target is vector quantized using a K-means …

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Enhancement Of Audio Localization Cue Synthesis By Adding Environmental And Visual Cues, Eric L. Scarborough Dec 1992

Enhancement Of Audio Localization Cue Synthesis By Adding Environmental And Visual Cues, Eric L. Scarborough

Theses and Dissertations

An audio localization cue synthesizer, the DIRectional Audio Display (DIRAD) was used to simulate auditory distance, room reflections, and to provide spatial audio for computer graphics images. The DIRAD processes input audio signals to generate spatially located sounds for headphone listening. The DIRAD can position audio sources around the head and these sounds are stable with respect to the listener's head position. An interactive, real-time simulation of auditory distance and room reflections was accomplished using the DIRAD in combination with a Silicon Graphics audio processor board installed in a Personal Iris 4D/35. Several demonstrations of auditory distance and the effects …

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A Generic Template Extractor (Gentex) In C For Vlsi Design Verification, Kenneth J. Mcclellan Jr. Dec 1992

A Generic Template Extractor (Gentex) In C For Vlsi Design Verification, Kenneth J. Mcclellan Jr.

Theses and Dissertations

The problem of VLSI design verification through circuit extraction was analyzed. The problems of creating a simple template format, the permutability of pins, maintaining connectivity, and performance were focused on. A generic template extractor (GENTEX) was developed in the C programming language for use as a testbed to find solutions to these problems. Six different extraction algorithms were tested with GENTEX and compared based on performance. EDIF translation programs were used to interface with GENTEX on both the input and output sides. One translation program converted an EDIF representation of a schematic into the template format used by GENTEX. The …

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Radar Cross Section Models For Limited Aspect Angle Windows, Mark C. Robinson Dec 1992

Radar Cross Section Models For Limited Aspect Angle Windows, Mark C. Robinson

Theses and Dissertations

This thesis presents a method for building Radar Cross Section (RCS) models of aircraft based on static data taken from limited aspect angle windows. These models statistically characterize static RCS. This is done to show that a limited number of samples can be used to effectively characterize static aircraft RCS. The optimum models are determined by performing both a Kolmogorov and a Chi-Square goodness-of-fit test comparing the static RCS data with a variety of probability density functions (pdf) that are known to be effective at approximating the static RCS of aircraft. The optimum parameter estimator is also determined by the …

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Real Image Visual Display System, James R. Brandt Dec 1992

Real Image Visual Display System, James R. Brandt

Theses and Dissertations

This thesis investigates a technique for improving the perception of three-dimensionality in images generated by a Silicon Graphics workstation. The technique involves using a spherical mirror into which the graphics from the CRT are projected. A real image of the graphic is formed by the mirror and it appears to be floating at the image plane. The three-dimensional effect is improved by adding reflections or shadows of the displayed object. Additionally, a method of using real objects with computer generated shadows and computer generated objects with real shadows is investigated. This is done in an effort to quantify how far …

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The Effect Of Oxide Layers And Boron Doping On The Breakdown Of High Purity Silicon, Brian A. Hibbeln Dec 1992

The Effect Of Oxide Layers And Boron Doping On The Breakdown Of High Purity Silicon, Brian A. Hibbeln

Theses and Dissertations

For many applications such as lasers and radar drive circuits, there exists a need for solid state high voltage, high current switches. Current gaseous discharge switches fail to satisfy the ruggedness, reliability, and lifetime requirements of today's systems. A promising alternative is the Photoconductive Semiconductor Switch (PCSS). The limiting factor in the operation of these switches is the occurrence of breakdown through channels formed slightly below the surface. A theory on the formation of these channels is presented based upon band bending at the metal-semiconductor interface, a nonhomogeneous space charge due to irregular trap distributions, and thermal runaway in localized …

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Total Hemispherical Emittance Of Niobium-1% Zirconium Fuel Cladding For The Sp-100 Space Reactor, John E. Thomason Iii Dec 1992

Total Hemispherical Emittance Of Niobium-1% Zirconium Fuel Cladding For The Sp-100 Space Reactor, John E. Thomason Iii

Theses and Dissertations

Total hemispherical emittance was measured for the SP-100 reactor fuel cladding alloy (Nb-l% Zr). Based on a standard test method (ASTM C 835-82), experiments were conducted on a reference sample of oxidized stainless steel and then on a sample of actual cladding. The sample is heated in a vacuum by passing DC current through it until reaching equilibrium. Measurements are made of the electrical power dissipated in the sample and of the surface temperature. Using the Stefan-Boltzmann Law and some key assumptions concerning conductive and radiative heat transfer, the measured quantities are used to calculate emittance. Calculated values for unoxidized …

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Spectral And Spatial Pattern Recognition In Digital Memory, John M. Amrine Dec 1992

Spectral And Spatial Pattern Recognition In Digital Memory, John M. Amrine

Theses and Dissertations

The main purpose of this research is to develop a model that can be used to solve combined spectral and spatial pattern recognition problems. The basis of my model is a multiobjective discrete programming model developed by Benabdullah and Wright (B and W). The model will be modified and then tested by solving a real world problem with SPOT multispectral imagery. Several improvements were added to the B and W model, namely standard border length accounting and control over which pixels are selected by the model. The model was also improved to process more than one channel of imagery at …

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Correlation Based Target Location And Identification, Richard A. Wenzel Dec 1992

Correlation Based Target Location And Identification, Richard A. Wenzel

Theses and Dissertations

Correlation was investigated as a technique for locating and identifying visible light terrain board images of tanks, airplanes, and trucks. A correlator was built which utilizes the Fast Fourier Transform. The 180 images in the image set were correlated in both the raw form and after pre-processing via energy normalization and local energy normalization. The correlation of the raw images led to development of quantitative and heuristic rules for possible inclusion in a rule based expert system. The correlation of the local energy normalized images resulted in a 100 percent target location rate and can be used as a baseline …

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Locating An Imaging Radar In Canada For Identifying Spaceborne Objects, William G. Schick Dec 1992

Locating An Imaging Radar In Canada For Identifying Spaceborne Objects, William G. Schick

Theses and Dissertations

This research presents a study of the maximal coverage p-median facility location problem as applied to the location of an imaging radar in Canada for imaging spaceborne objects. The classical mathematical formulation of the maximal coverage p-median problem is converted into network-flow with side constraint formulations that are developed using a scaled down version of the imaging radar location problem. Two types of network-flow with side constraint formulations are developed: a network using side constraints that simulates the gains in a generalized network; and a network resembling a multi-commodity flow problem that uses side constraints to force flow along identical …

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The Adaptation Of The Sei's Capability Maturity Model To The Air Force Software Acquisition Management Process, William G. Dickerhoff Jr., William J. Sommers Dec 1992

The Adaptation Of The Sei's Capability Maturity Model To The Air Force Software Acquisition Management Process, William G. Dickerhoff Jr., William J. Sommers

Theses and Dissertations

This study develops an Air Force Software Acquisition Maturity Framework (SAMF) by adapting the Software Engineering Institute's (SEI) capability Maturity Model (CMM) to the Air Force software acquisition process. The SAMFs purpose is to provide the Air Force Materiel Command's product centers and program off ices with criterion to assess their software acquisition maturity in a similar fashion as the SEI's CMM provides companies a benchmark to measure their organization's software production maturity. The research was accomplished through a combination of information gathering techniques and data analysis. A literature search of documentation, both within and external to the Department of …

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Analysis Of Kriging Applied To Resolution Enhancement Of Digital Satellite Imagery, David J. Blaufuss Dec 1992

Analysis Of Kriging Applied To Resolution Enhancement Of Digital Satellite Imagery, David J. Blaufuss

Theses and Dissertations

To aid the viewer in interpreting the information contained in an image, spatial resolution of the image can be increased. One way to increase the resolution is to improve the optics and sensors of the imaging system. Another is to process the data on the ground by computer. Enhancement techniques can be employed to alter the image and extract necessary data. Current techniques to manipulate and enlarge an image are nearest-neighbor, bilinear interpolation, and cubic convolution which can give greater clarity and readability. To satisfy the growing demand for quality (high-resolution) remotely sensed images, new techniques to enhance images need …

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The Efficacy Of Group Decision Support Systems: A Field Experiment To Evaluate Impacts On Air Force Decision Makers, Benjamin C. Huff Dec 1992

The Efficacy Of Group Decision Support Systems: A Field Experiment To Evaluate Impacts On Air Force Decision Makers, Benjamin C. Huff

Theses and Dissertations

The research contributed to the study of Group Decision Support Systems (GDSS) in field experiments involving real managers making real decisions. This research was conducted by the Air Force Institute of Technology with the Air Force Armstrong Laboratory to evaluate the efficacy of using GDSS technology in an Air Force decision making environment. This study compared facilitated GDSS, facilitated manual, and unfacilitated manual decision making processes. This study focused on performance and secondary outcomes resulting from GDSS effects versus process structure effects. The research evaluated two performance outcomes: GDSS efficiency in terms of decision speed and effectiveness in terms of …

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Shock Tube Study Of The Effects Of Large Density Differences And Blowing Ratio On Heat Transfer To A Film-Cooled Flat Plate, Thomas A. Eads Nov 1992

Shock Tube Study Of The Effects Of Large Density Differences And Blowing Ratio On Heat Transfer To A Film-Cooled Flat Plate, Thomas A. Eads

Theses and Dissertations

The effects of coolant-to-mainstream density ratio (D.R.) and mass flux (blowing) ratio (Mb) on flat plate heat transfer were investigated in a shock tube. The round-nosed plate has a single row of holes inclined 35° downstream with two-diameter lateral spacing and hole length of three diameters. Mixing helium with air in the shock tube produced a D.R. range of 1.2 to 2.1. The parameters studied approach those of film-cooled turbine components. For an Mb range of 0.4 to 3 and 10% mainstream turbulence, heat flux was measured with thin-film heat flux gauges located 4 to 30 hole diameters downstream of …

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Thrust Vector Control Using Internal Airfoils, Eric J. Herup, Milton E. Franke, Jerold H. Friddell Oct 1992

Thrust Vector Control Using Internal Airfoils, Eric J. Herup, Milton E. Franke, Jerold H. Friddell

AFIT Patents

A thrust vectoring exhaust nozzle structure for an engine, such as a ramjet, rocket or turbojet, which generates thrust by expulsion of gaseous fuel combustion products along a thrust axis is described which comprises a generally axisymmetric housing defined along a central thrust axis including a wall structure defining an exhaust duct, and an axially spaced radially inwardly convergent portion, throat and radically outwardly divergent portion, and at least one airfoil disposed on the wall structure of the divergent portion and mounted for rotation about an axis substantially perpendicular to the thrust axis.

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A Model For Determining Modular Heat Recovery Incinerator Feasibility On Air Force Installations, Arthur H. Anderson Jr., Paul R. Munnell Sep 1992

A Model For Determining Modular Heat Recovery Incinerator Feasibility On Air Force Installations, Arthur H. Anderson Jr., Paul R. Munnell

Theses and Dissertations

This study constructed a model to determine the feasibility of building municipal solid waste (MSW) fired modular heat recovery incinerators (HRIs) on Air Force installations. The model consisted of three gates. Gate one identified current federal regulatory air emission requirements for various HRI pollutants. It also specified two air pollution control configurations with emission reduction efficiencies capable of achieving these requirements. Gate two presented a life-cycle cost (LCC) economic analysis methodology. Operational and cost data for existing modular HRIs located in the United States facilitated the development of regression equations that estimate capital and annual operating costs for a modular …

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A Comparison Of Computer And Paper Media In Psychological Testing, Anthony C. Hensley, Timothy R. Morris Sep 1992

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 …

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The Development Of An Expert System For Hazardous Cargo Compatibility, Douglas A. Furst, Ronald E. Smith Sep 1992

The Development Of An Expert System For Hazardous Cargo Compatibility, Douglas A. Furst, Ronald E. Smith

Theses and Dissertations

This research demonstrates the application of expert system technology to automate the aircraft load selection process performed when transporting hazardous cargo. The resulting computer program is an expert system named HAZARD. This system incorporates the regulations governing hazardous cargo compatibility with the heuristics used by experts in loadplanning operations. The impetus to develop such a system is the January 1993 conversion of regulation guidelines for hazardous cargo classification and management in Air Force Regulation 71-4, to a universal international standard. The Cargo Operations Division of Headquarters Air Mobility Command at Scott AFB, was concerned that this change in procedures and …

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A Technical And Practical Study Of Composting As A Solid Waste Management Alternative For The Air Force, Donald R. Abrams, Timothy D. Brecheen Sep 1992

A Technical And Practical Study Of Composting As A Solid Waste Management Alternative For The Air Force, Donald R. Abrams, Timothy D. Brecheen

Theses and Dissertations

This thesis reviews composting as a solid waste management option for the Air Force. The Air Force's Pollution Prevention Program Mandates composting as an opportunity to reduce landfill disposal and save future environmental costs. This research considers composting technologies used in mixed municipal solid waste and yard waste applications. The thesis presents technical aspects of composting and also summarizes operational techniques of successful composting sites across the United States. Composting is a biological process for converting organic waste into a stable product for use as a soil amendment or mulch. The Air Force should immediately begin yard waste composting programs …

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Analysis Of Standard Type Unit Development, Jeffrey M. Hess, Merry D. Wermund Sep 1992

Analysis Of Standard Type Unit Development, Jeffrey M. Hess, Merry D. Wermund

Theses and Dissertations

This research study examined the standard type unit development process for the Air Force. Current standard type unit development procedures were determined by a literature review. The literature review, with the interviews, provided information regarding the history of, purpose for, and possible alternatives for developing standard type units. A Delphi questionnaire was developed to determine how well the current process works, how standard type units worked for Desert Shield/Storm, and possible ways to improve the development process. This questionnaire was distributed to F-15 units, F-16 units, and major command personnel in Tactical Air Command (now Air Combat Command). All three …

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Development Of A Heuristic Knowledge Base For The Selection Of Applicable Or Relevant And Appropriate Environmental Requirements, Scott J. Borg, Gerald B. Puetz Sep 1992

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 …

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An Assessment Of The Options Available To Air Forces' Commanders To Suppress Smoke From Oil Well Fires, William B. Owens, Richard D. Taylor Sep 1992

An Assessment Of The Options Available To Air Forces' Commanders To Suppress Smoke From Oil Well Fires, William B. Owens, Richard D. Taylor

Theses and Dissertations

The particulates in smoke from oil well fires can obscure targets and inhibit the use of precision-guided munitions. The purpose of this research was to develop a decision support matrix to aid commanders of air forces select methodologies for controlling oil well fire smoke through fire suppression. Through interviews with military experts and fire-fighters, a set of situational factors affecting the employment of these technologies was developed. Technologies for extinguishing oil well fires were investigated by conducting expert interviews and studying research data, periodical literature, and proposals suggesting means to control the Kuwaiti oil well fires. Over 200 proposals from …

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Issues Affecting Acquisition Strategies For Remedial Action Projects At Installation Restoration Program Sites, John E. Keoshian, William A. Kolakowski Sep 1992

Issues Affecting Acquisition Strategies For Remedial Action Projects At Installation Restoration Program Sites, John E. Keoshian, William A. Kolakowski

Theses and Dissertations

Most, if not all, of Air Force IRP restoration work is accomplished through contracting avenues. The present system of cleanup and close out of these IRP sites is inefficient, time consuming, and costly. Expedient cleanup of contaminated sites will depend in large part upon on how effectively the USAF manages its restoration contracts. Difficulties are encountered due to differences in interpretation and/or vagueness of contracting and environmental information by all parties involved. Additionally, numerous conflicts arise when different agencies apply different acquisition strategies to similar remedial actions. To compound the problem, there are few definitions and little guidance from the …

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