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Theses and Dissertations

Air Force Institute of Technology

2001

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Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell Dec 2001

Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell

Theses and Dissertations

The influence of stimulated scattering on laser intensity in fiber optic waveguides is examined. Stimulated Brillouin scattering (SBS) in long, multimode optical waveguides is found to generate a Stokes beam that propagates in the fiber LP01 mode. Additionally, the same process is found to combine multiple laser beams into a single spatially coherent source. Limitations in beam cleanup and combining are also investigated to identify ways to overcome them. The last portion of the dissertation theoretically examines suppression of stimulated Raman scattering in fibers to eliminate the restriction this imposes on the power of a fiber laser or amplifier. The …

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Air Vehicle Path Planning, Jeffrey M. Hebert Dec 2001

Air Vehicle Path Planning, Jeffrey M. Hebert

Theses and Dissertations

This dissertation explores optimal path planning for air vehicles. An air vehicle exposed to illumination by a tracking radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An analytic solution yielding the trajectory minimizing the received radar energy reflected from the target is derived using the Calculus of Variations. Additionally, the related problem of an air vehicle tracked by a passive sensor is also solved. Using the insights gained from the single air vehicle radar exposure minimization problem, a hierarchical cooperative control law is formulated to determine the optimal trajectories that …

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Nonlinear Suppression Of Range Ambiguity In Pulse Doppler Radar, Jon M. Anderson Dec 2001

Nonlinear Suppression Of Range Ambiguity In Pulse Doppler Radar, Jon M. Anderson

Theses and Dissertations

Coherent pulse train processing is most commonly used in airborne pulse Doppler radar, achieving adequate transmitter/receiver isolation and excellent resolution properties while inherently inducing ambiguities in Doppler and range. First introduced by Palermo in 1962 using two conjugate LFM pulses, the primary nonlinear suppression objective involves reducing range ambiguity, given the waveform is nominally unambiguous in Doppler, by using interpulse and intrapulse coding (pulse compression) to discriminate received ambiguous pulse responses. By introducing a nonlinear operation on compressed (undesired) pulse responses within individual channels, ambiguous energy levels are reduced in channel outputs. This research expands the NLS concept using discrete …

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Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia Dec 2001

Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia

Theses and Dissertations

The use of Proper Orthogonal Decomposition (POD) for reduced order modeling (ROM) of fluid problems is extended to high-speed compressible fluid flows. The challenge in using POD for high-speed flows is presented by the presence of moving discontinuities in the flow field. To overcome these difficulties, a domain decomposition approach is developed that isolates the region containing the moving shock wave for special treatment. The domain decomposition implementation produces internal boundaries between the various domain sections. The domains are linked using optimization-based solvers which employ constraints to ensure smoothness in overlapping portions of the internal boundary. This approach is applied …

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Modeling And Analysis Of Social Networks, Robert S. Renfro Ii Dec 2001

Modeling And Analysis Of Social Networks, Robert S. Renfro Ii

Theses and Dissertations

This dissertation develops new methods for the modeling and analysis of social networks. Social networks describe the complex relationships of individuals and groups in multiple overlapping contexts. Influence in a social network impacts behavior and decision making in every setting in which individuals participate. This study defines a methodology for modeling and analyzing this complex behavior using a Flow-Model representation. Multiple objectives in an influencing effort targeted at a social network are modeled using Goal Programming. Value Focused Thinking is applied to model influence and predict decisions based on the reaction of the psychological state of individuals to environmental stimuli. …

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Electrical Activation Studies Of Ion Implanted Gallium Nitride, James A. Fellows Nov 2001

Electrical Activation Studies Of Ion Implanted Gallium Nitride, James A. Fellows

Theses and Dissertations

A comprehensive and systematic electrical activation study of Si-implanted GaN was performed as a function of ion implantation dose, anneal temperature, and implantation temperature. Additionally, Mg-implanted GaN was also investigated. Temperature-dependent Hall effect measurements and photoluminescence (PL) spectra were used to characterize the samples. GaN wafers capped with AlN were implanted with Si ions at doses ranging from 1x1013 to 5x1015 cm-2 and annealed from 1050 to 1350 °C. The optimum anneal temperature for samples implanted with the higher Si doses is around 1350 °C, exhibiting nearly 100% electrical activation efficiency. Exceptional mobilities and carrier concentrations were …

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Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr. Oct 2001

Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr.

Theses and Dissertations

The US Department of Defense (DOD), as well as the National Aeronautics and Astronautics Administration (NASA) and the Jet Propulsion Laboratory (JPL) are interested in developing and deploying precise, compliant, light-weight, space-based structures. More specifically, the Air Force’s core competencies ‘Aerospace Superiority’ and ‘Information Superiority’ demand ever-increasing depth and breadth of capability. Whether used for energy transmission or optical reconnaissance, current launch restraints limit rigid space-based optical reflector size. To support this requirement, the Air Force Research Laboratory (AFRL) is developing a large space-based optical membrane telescope. Inflatable reflectors can conceptually break this barrier, but controlling such a compliant structure …

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Techniques For Reduced Order Modeling Of Aeroelastic Structures With Deforming Grids, John S. R. Anttonen Oct 2001

Techniques For Reduced Order Modeling Of Aeroelastic Structures With Deforming Grids, John S. R. Anttonen

Theses and Dissertations

Reduced order modeling (ROM) seeks to make the modeling of aeroelastic behavior practical by reducing computation time for design codes. Deforming grids are often used in aeroelastic problems to account for the deformation of the structure. Proper Orthogonal Decomposition (POD/ROM) is a ROM technique that operates in an index-space for computations, not accounting for changes in grid dynamics, and must be modified to reflect grid deformation properly. To investigate and account for the effects of grid deformation on POD/ROM, a new algorithm is developed that incorporates modifications to the usual formulation. Evaluation of the new algorithm is accomplished through application …

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A Decomposition Approach For The Multi-Modal, Resource-Constrained, Multi-Project Scheduling Problem With Generalized Precedence And Expediting Resources, Michael L. Fredley Sep 2001

A Decomposition Approach For The Multi-Modal, Resource-Constrained, Multi-Project Scheduling Problem With Generalized Precedence And Expediting Resources, Michael L. Fredley

Theses and Dissertations

The field of project scheduling has received a great deal of study for many years with a steady evolution of problem complexity and solution methodologies. As solution methodologies and technologies improve, increasingly complex, real-world problems are addressed, presenting researchers a continuing challenge to find ever more effective means for approaching project scheduling. This dissertation introduces a project scheduling problem which is applicable across a broad spectrum of real-world situations. The problem is based on the well-known Resource-Constrained Project Scheduling Problem, extended to include multiple modes, generalized precedence, and expediting resources. The problem is further extended to include multiple projects which …

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Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe Sep 2001

Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe

Theses and Dissertations

In this research the electromagnetic scattering of a plane wave from a two-dimensional cavity embedded in an infinite, perfectly conducting ground plane is investigated. The plane wave is assumed to be under transverse electric (TE) polarization with respect to the x-axis. The cavity may be empty or filled with an arbitrary homogeneous, lossy material. A coupled set of scalar integral equations that govern the electromagnetic scattering is implemented. An approximate solution to the scalar integral equations is found via a Method of Moments (MoM) algorithm. The algorithm is implemented in a computer code, and approximations to the total magnetic field …

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Theater-Level Stochastic Air-To-Air Engagement Modeling Via Event Occurrence Networks Using Piecewise Polynomial Approximation, David R. Denhard Sep 2001

Theater-Level Stochastic Air-To-Air Engagement Modeling Via Event Occurrence Networks Using Piecewise Polynomial Approximation, David R. Denhard

Theses and Dissertations

This dissertation investigates a stochastic network formulation termed an event occurrence network (EON). EONs are graphical representations of the superposition of several terminating counting processes. An EON arc represents the occurrence of an event from a group of (sequential) events before the occurrence of events from other event groupings. Events between groups occur independently, but events within a group occur sequentially. A set of arcs leaving a node is a set of competing events, which are probabilistically resolved by order relations. An important EON metric is the probability of being at a particular node or set of nodes at time …

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Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange Jun 2001

Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange

Theses and Dissertations

As aircraft age, corrosion forms upon unobservable surfaces, particularly at the junction of the sheet aluminum and the steel rivets used to attach the sheets to the airframe, degrading the aircraft s airworthiness. Previous research developed a noninvasive technique for the evaluation of the material composition of aluminum surfaces, utilizing the information encoded in the energy spectra of Compton-scattered gamma emissions. The spectra are gathered by a six-element, high purity germanium detector array. A, first principles, deterministic computer code is used to reconstruct a two-dimensional map of the electron density of aluminum samples. Previous efforts, to image pure aluminum samples, …

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Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay Jun 2001

Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay

Theses and Dissertations

In the world of semiconductor photonic device fabrication, one important objective may be to extract as much light as possible from the device. In these devices, photons are created when electrons recombine with holes by transitioning from a high-energy state to a lower one. Unfortunately, electron-hole recombination does not always result in the formation of a photon. There are three basic types of recombination: the first results in the formation of a photon and is called radiative recombination; and the second and third, known as Shockley-Read-Hall and Auger recombination, result in the heating of the device and do not produce …

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Integer Approximation Of Real Valued Preference Curves, Richard M. Antoine May 2001

Integer Approximation Of Real Valued Preference Curves, Richard M. Antoine

Theses and Dissertations

A primary challenge of the AFIT Mission Resource Value Assessment Tool is to approximate a given preference curve with integer valued mission ready resources. This thesis evaluated four candidate methods of accomplishing this approximation. The thesis evaluated the implementation of the integer estimation approximation from a purely mathematical perspective. The models were measured against six quality and error measurement standards: convergence on an endpoint, convergence on any interior integer points, characterization of the overall error between the sequence of integer coordinates and the real valued linear function and characterization of the error in each individual dimension of the problem space. …

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Hidden Markov Models For Visual Speech Synthesis In Limited Data, Harold A. Arb Mar 2001

Hidden Markov Models For Visual Speech Synthesis In Limited Data, Harold A. Arb

Theses and Dissertations

This work presents a new approach for estimating control points (facial locations that control movement) to allow the artificial generation of video with apparent mouth movement (visual speech) time-synced with recorded audio. First, Hidden Markov Models (HMMs) are estimated for each visual speech category (viseme) present in stored video data, where a category is defined as the mouth movement corresponding to a given sound and where the visemes are further categorized as trisemes (a viseme in the context of previous and following visemes). Next, a decision tree is used to cluster and relate states in the HMMs that are similar …

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Spectroscopic Constants, Lifetimes And Predissociation Rates For Bi2A(0+U), Michael W. Dolezal Mar 2001

Spectroscopic Constants, Lifetimes And Predissociation Rates For Bi2A(0+U), Michael W. Dolezal

Theses and Dissertations

More than 100,000 spectral features from a Bi2(X1 Σ+g → A(0+u)) absorption spectrum, encompassing 0 ≤ v' ≤ 91, 0 ≤ v" ≤ 7 and J2(A). Ground state constants, reported by Barrow et al. [1], remain unchanged. The new constants are used to redefine the A-state potential using traditional RKR methods and to set the dissociation energy at De = 29,913 cm"1, which correlates A-state dissociation products to 4S + 2D atoms. A pulsed dye laser apparatus was used to obtain lifetime data for Bi2A(0+u) …

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Identification Of Preferred Operational Plan Force Mixes Using A Multiobjective Methodology To Optimize Resource Suitability And Lift Cost, David J. Wakefield Jr. Mar 2001

Identification Of Preferred Operational Plan Force Mixes Using A Multiobjective Methodology To Optimize Resource Suitability And Lift Cost, David J. Wakefield Jr.

Theses and Dissertations

AFIT research in support of the Advanced Logistics Project is directed at developing a Mission-Resource Value Assessment Tool for rationally assigning relative value to resources and identifying alternative force mixes to logistics and operational planners. Research of factors that affect force mix composition has been strictly limited to how the operating environment of USAF combat aircraft influences their performance in specified aerospace missions. In contrast, this research makes use of an aircraft's designed suitability to perform specified aerospace missions in order to examine the tradeoff between mission suitability and the amount of lift needed to deploy and operate the asset. …

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Jp-8+100lt: A Low Cost Replacement Of Jpts As The Primary Fuel For The U-2 Aircraft, Christian G. Simms Mar 2001

Jp-8+100lt: A Low Cost Replacement Of Jpts As The Primary Fuel For The U-2 Aircraft, Christian G. Simms

Theses and Dissertations

The Air Force currently spends approximately $ 10 million dollars annually on fuel support for the U-2 aircraft. The U-2 has used a jet fuel known as JPTS since the aircraft's development in the 1950's. JPTS is a specialty fuel used only by the U-2 and is produced by two oil refineries in the United States. As such, it has limited worldwide availability and costs over three times the per-gallon price of the Air Force's primary jet fuel, JP-8. Recent research performed at the Air Force Research Laboratory Propulsion Directorate suggests that additives could be added to JP-8, which would …

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Adaptive And Reconfigurable Flight Control, Yih Shiun Huang Mar 2001

Adaptive And Reconfigurable Flight Control, Yih Shiun Huang

Theses and Dissertations

An indirect adaptive and reconfigurable flight control system is developed. The three-module controller consists of: (1) a system identification module, (2) a parameter estimate smoother, and (3) a proportional and integral compensator for tracking control. Specifically: (1) The identification of a linear discrete-time control system's open-loop gain is addressed. The classical Kalman filter theory for linear control systems is extended and the control system's state and loop gain are jointly estimated on-line. Explicit formulae for the loop gain's estimate and estimation error covariance are derived. The estimate is unbiased and the predicted covariance is reliable. (2) An adaptive smoother is …

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Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman Mar 2001

Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman

Theses and Dissertations

Air Force operations are directly impacted by weather on a daily basis. Erroneous forecasts negatively impact mission readiness and consequently cost the government time, in terms of wasted man-hours, and money. Advanced forecast lead-time could make a difference to minimize loss to both USAF personnel and assets. This study examined lightning data from 64 storm events from 1995-2000 in search of unique lightning signatures indicative of tornadic activity. Overall flash rates, percentage of positive flashes, positive and negative peak currents and multiplicity for each case were separated into two categories based on tornado intensity and season of occurrence. Based on …

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Differences In Civil Engineer Perceptions Of Change Based On Prior Training And Experience, Steven W. Lo Mar 2001

Differences In Civil Engineer Perceptions Of Change Based On Prior Training And Experience, Steven W. Lo

Theses and Dissertations

The Department of Defense (DoD) and the United States Air Force (USAF) have moved toward an aggressive stance to competitively source and privatize (CS&P) support functions as much as possible. This move is intended to shrink support costs and redirect the savings to force and equipment modernization. In addition, the USAF hopes to realize improved services, gain access to technology, share risks with contractors, and allow its forces to focus on the core competencies. In order to implement OS&P, the USAF communicates information through two major pathways, passive and active. Passive communication is similar to traditional classroom learning where information …

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Fatigue Response Of Thin Stiffened Aluminum Cracked Panels Repaired With Bonded Composite Patches, Jason B. Avram Mar 2001

Fatigue Response Of Thin Stiffened Aluminum Cracked Panels Repaired With Bonded Composite Patches, Jason B. Avram

Theses and Dissertations

This research investigated the fatigue response of precracked and patched 2024-T3 Aluminum panels with stiffeners. Patches were single-sided, unidirectional three ply boron/epoxy. Stiffeners were 2024-T3 aluminum and were riveted and bonded on. Disbonds were introduced into the repair bondline by inserting teflon strips. Three disbond configurations were investigated rack tip disbond (CTD) located at the edge of the patch in the path of crack propagation, full-width disbond (FWD) covering the entire crack, and end disbond (ED) located at each end of the patch and covering the full width. Each repaired panel was subjected to tension/tension cyclic fatigue with a maximum …

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Optimization Of Palladium-Catalyzed In Situ Destruction Of Trichloroethylene-Contaminated Groundwater Using A Genetic Algorithm, Manuel Fernandez Mar 2001

Optimization Of Palladium-Catalyzed In Situ Destruction Of Trichloroethylene-Contaminated Groundwater Using A Genetic Algorithm, Manuel Fernandez

Theses and Dissertations

Conventional technologies for the treatment of groundwater contaminated with chlorinated solvents have limitations that have motivated development of innovative technologies. One such technology currently under development involves using palladium-on-alumina (Pd/Al) as a catalyst to promote dechlorination. Pd/Al catalyst may be used in-well as part of a re-circulating horizontal flow treatment well (HFTW) system. An HFTW system involves two or more dual-screened wells, with in-well reactors, to capture and treat contaminated groundwater without the need to pump the water to the surface. In this study, objective and fitness functions, based on system costs and TCE concentration requirements, were developed to optimize …

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Influence Of Personality Type And Anonymity On Participation In A Group Support System, Robert E. Hartmann Mar 2001

Influence Of Personality Type And Anonymity On Participation In A Group Support System, Robert E. Hartmann

Theses and Dissertations

A group support system (GSS) uses a combination of networked personal computers, software that collects, manipulates, and aggregates member's individual input, and human facilitation to improve the group decision-making process. A GSS has been promoted as a means of improving the quantity and quality of ideas within a decision-making meeting. Research into GSS has focused on the benefits of providing anonymity to improve participation. Anonymity in a GSS meeting has been offered as a means to improve participation, which in turn improves decision quality. To date this has not been proven through research. In fact, there is conflicting evidence as …

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Routing Of Time-Sensitive Data In Mobile Ad Hoc Networks, Necdet Kilic Mar 2001

Routing Of Time-Sensitive Data In Mobile Ad Hoc Networks, Necdet Kilic

Theses and Dissertations

This research focuses on routing of time-sensitive data in mobile ad hoc networks. Routing protocols that were developed for ad hoc networks have been reviewed. Ad Hoc On-demand Distance Vectoring (AODV) routing protocol, which is a prominent routing protocol among these protocols have been implemented in OPNET, a discrete-event simulation tool. Taking AODV as a point of departure, a routing protocol named Real Time Routing Protocol (RTRP) has been developed and also implemented in simulation environment. The performance of these routing protocols have been observed by simulating them in various experiments where the workload has been chosen to be time-sensitive …

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Using A Distributed Object-Oriented Database Management System In Support Of A High-Speed Network Intrusion Detection System Data Repository, Phillip W. Polk Mar 2001

Using A Distributed Object-Oriented Database Management System In Support Of A High-Speed Network Intrusion Detection System Data Repository, Phillip W. Polk

Theses and Dissertations

The Air Force has multiple initiatives to develop data repositories for high-speed network intrusion detection systems (IDS). All of the developed systems utilize a relational database management system (RDBMS) as the primary data storage mechanism. The purpose of this thesis is to replace the RDBMS in one such system developed by AFRL, the Automated Intrusion Detection Environment (AIDE), with a distributed object-oriented database management system (DOODBMS) and observe a number of areas: its performance against the RDBMS in terms of IDS event insertion and retrieval, the distributed aspects of the new system, and the resulting object-oriented architecture. The resulting system, …

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Minimum Distance Estimation For Time Series Analysis With Little Data, Hakan Tekin Mar 2001

Minimum Distance Estimation For Time Series Analysis With Little Data, Hakan Tekin

Theses and Dissertations

Minimum distance estimate is a statistical parameter estimate technique that selects model parameters that minimize a good-of-fit statistic. Minimum distance estimation has been demonstrated better standard approaches, including maximum likelihood estimators and least squares, in estimating statistical distribution parameters with very small data sets. This research applies minimum distance estimation to the task of making time series predictions with very few historical observations. In a Monte Carlo analysis, we test a variety of distance measures and report the results based on many different criteria. Our analysis tests the robustness of the approach by testing its ability to make predictions when …

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Analysis Of The Effect Of Centralizing Management Of Mobility Readiness Spares Package Assets, Ian R. Hester Mar 2001

Analysis Of The Effect Of Centralizing Management Of Mobility Readiness Spares Package Assets, Ian R. Hester

Theses and Dissertations

Air Force supply doctrine requires the management of large numbers of spare parts in Mobility Readiness Spares Packages (MRSPs). The MRSPs are designed to support deployed aircraft for the first 30 days of a conflict, and can be quite large. When units from several bases deploy to the same operating location, they each bring their full MRSP. This results in a large logistics footprint that may be reduced by taking a system-level approach. This thesis examined the impact of centralized MRSP management on kit size and cost. The Aircraft Sustainability Model (ASM) computer program was used to evaluate MRSPs for …

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Determining The Value Of Groundwater Contamination Source Removal: A Methodology, Benjamin C. Recker Mar 2001

Determining The Value Of Groundwater Contamination Source Removal: A Methodology, Benjamin C. Recker

Theses and Dissertations

Subsurface contamination by industrial chemicals is one of the most prevalent and costly environmental problems facing the United States government. This contamination problem must be managed to protect human health and the environment. Two basic strategies are used to deal with subsurface contamination: source removal and contaminant containment. While much cost and performance data are available for individual technologies associated with each of these strategies, there have been very few studies that have examined the benefits of implementing source removal technologies in order to reduce contaminant containment (and hopefully total) costs. This study examines the tradeoff between extent of source …

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A Multi-Objective Decision Support Model For The Turkish Armed Forces Personnel Assignment System, Zubeyir Cimen Mar 2001

A Multi-Objective Decision Support Model For The Turkish Armed Forces Personnel Assignment System, Zubeyir Cimen

Theses and Dissertations

The Turkish Armed Forces (TAF) assign more than 25,000 active duty personnel annually. TAF wants to obtain maximum utilization of its personnel by assigning the right person to the right job at the right time, To accomplish this task, decision-makers and personnel assignment staff should consider conflicting multiple objectives that create the widely known problem called "personnel assignment problem". To assist in this complicated task from a quantitative perspective, a preemptive goal programming approach was used to develop an integer programming (IP) model to capture the multiple objectives flexibly and interactively. A realistic size IP problem with random data was …

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