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Air Force Institute of Technology

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Articles 3751 - 3780 of 5699

Full-Text Articles in Engineering

Cross Range Smear Characterization In Xpatch Isar Images, Peter E. Muend Mar 2004

Cross Range Smear Characterization In Xpatch Isar Images, Peter E. Muend

Theses and Dissertations

This thesis investigates a cross range smear phenomenon seen in far field, frequency domain Xpatch calculations. The phenomenon is very subtle, manifesting itself in 2-D ISAR images as a low-level scatterer response smeared in the cross range direction. This cross range smear occurs only using complex target models with certain characteristics. It is also a mathematical construct, not occurring in physical SAR systems. Using a carefully constructed scattering target set, Xpatch-generated ISAR images are used to characterize cross range smear in terms of its input parameters. The characterization is done as a DOE-based polynomial approximation to the observed smear levels. …

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Evaluation Of Current Automated Civil Engineer System Non-Appropriated Funds Project Programming Procedures, Joshua C. Ligday Mar 2004

Evaluation Of Current Automated Civil Engineer System Non-Appropriated Funds Project Programming Procedures, Joshua C. Ligday

Theses and Dissertations

It is essential that businesses continually improve their automated information systems (AIS) to support the changing needs of the organization. The Air Force civil engineering organization is no exception since they have drastically improved their Automated Civil Engineer System (ACES) through end user support since its implementation in 2000. However, there are many problems associated with the non-appropriated funds (NAF) project programming business rules within ACES. These problem areas were not addressed until recently when an integrated process team met and proposed numerous changes to how NAF programming is accomplished in ACES. This research effort, through a web-based survey, focuses …

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An Electromagnetic Tool For Damping And Fatigue Analysis, Todd M. Hoover Mar 2004

An Electromagnetic Tool For Damping And Fatigue Analysis, Todd M. Hoover

Theses and Dissertations

An automated test system was developed by the USAF Turbine Engine Fatigue Facility (TEFF). This system was initially designed to reduce the time and manpower required to characterize damping treatments. It is based on a digitally controlled environmental chamber with automated data acquisition and processing. Several outputs are available including identification of natural frequencies, modal damping ratios from the acquired frequency responses, and changes in damping with response amplitude; however, the TEFF additionally desires the capability to study fatigue under a free boundary condition. The system consists of a test specimen suspended by a pendulum to closely simulate free boundary …

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Optimal Design Of Generalized Multiple Model Adaptive Controllers, Thomas E. Brehm Mar 2004

Optimal Design Of Generalized Multiple Model Adaptive Controllers, Thomas E. Brehm

Theses and Dissertations

Advanced analysis and optimal design techniques that achieve performance improvement for multiple model adaptive control (MMAC) and multiple model adaptive estimation (MMAE) based control are developed and tested for this dissertation research. An adjunct area of research yielded modified linear quadratic Gaussian (LQG) control design techniques that also can be applied to nonadaptive control. For the Modified LQG (MLQG) controller, the proposed designs remove the assumption that the Kalman filter as the observer and the controller gain matrix design are necessarily based on the same model as the best system model. The filter and controller gain matrices are both determined …

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A Rapidly-Converging Alternative To Source Iteration For Solving The Discrete Ordinates Radiation Transport Equations In Slab Geometry, Nicholas J. Wager Mar 2004

A Rapidly-Converging Alternative To Source Iteration For Solving The Discrete Ordinates Radiation Transport Equations In Slab Geometry, Nicholas J. Wager

Theses and Dissertations

I present a numerical technique to solve the time independent Boltzmann Transport Equation for the transport of neutrons and photons. The technique efficiently solves the discrete ordinates equations with a new iteration scheme. I call this new scheme the angle space distribution iteration method because it combines a non-linear, high angular-resolution flux approximation within individual spatial cells with a coarse angular-resolution flux approximation that couples all cells in a spatial mesh. This shown to be an efficient alternative to source iteration. The new method is implemented using the step characteristic and exponential characteristic spatial quadrature schemes. The latter was introduced …

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Effect Of Equivalence Ratio And G-Loading On In-Situ Measurements Of Chemiluminescence In An Ultra Compact Combustor, Jason M. Armstrong Mar 2004

Effect Of Equivalence Ratio And G-Loading On In-Situ Measurements Of Chemiluminescence In An Ultra Compact Combustor, Jason M. Armstrong

Theses and Dissertations

Using a spectrometer and high temperature fiber optics the relative intensities of the near-infrared, visible, and ultraviolet radiation emitted from the C2*, CH*, and OH* radicals were measured at eight discrete locations within the Ultra Compact Combustor test rig. Blackbody radiation in the near infrared also was observed. The tests were conducted at various g-loadings and overall equivalence ratios and with various air hole configurations. These measurements were compared to determine the effect of these changes on the radiation emitted. Local C2* intensities were used to estimate the flame location within the combustor and the local CH*/OH* ratio was used …

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Maneuver Design For Fast Satellite Circumnavigation, Stanley D. Straight Mar 2004

Maneuver Design For Fast Satellite Circumnavigation, Stanley D. Straight

Theses and Dissertations

The feasibility of satellite operations in close proximity to a reference satellite is of interest for both civilian and military applications. One such operation is circular circumnavigation in a time period less than the orbital period of the reference satellite. This thesis investigates a guidance scheme for such maneuvers involving impulsive burns at specific points within a specified toroidal region centered on the circular-orbiting reference satellite. Two analytical methods for determining the magnitude and direction of the impulses are demonstrated. These methods are then used as initial estimates in an optimization scheme to produce the minimum total required impulse.

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Effect Of A Variable Contact Load On Fretting Fatigue Behavior Of Ti-6al-4v, Andrew J. Jutte Mar 2004

Effect Of A Variable Contact Load On Fretting Fatigue Behavior Of Ti-6al-4v, Andrew J. Jutte

Theses and Dissertations

Effects of a variable contact load on the high cycle fretting fatigue behavior of Ti-6AL-4V were investigated. Experimental tests were performed using a new test setup capable of applying a contact load varying in amplitude, frequency, and phase and independently measuring shear forces on opposite sides of a specimen. Finite element analysis (FEA) of experimental and idealized loading conditions was performed and local mechanistic parameters and the Modified Shear Stress Range (MSSR) fatigue parameter were determined. Correlations between contact width, slip amplitude, fatigue life and a variable contact load were established with variable contact loading shown to have a damaging …

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Investigation Of Atmospheric Reentry For The Space Maneuver Vehicle, Dennis J. Mcnabb Mar 2004

Investigation Of Atmospheric Reentry For The Space Maneuver Vehicle, Dennis J. Mcnabb

Theses and Dissertations

This study investigated the atmospheric reentry of the Space Maneuver Vehicle from low-earth orbit using an entry guidance concept similar to the Space Shuttle. The Space Maneuver Vehicle was modeled as a point mass with aerodynamic properties as determined using Newtonian impact theory. For the rarefied-flow transition regime bridging formulae are used to capture the effects of both hypersonic continuum flow and free molecular flow. Constraints to the reentry are developed and a reentry corridor is defined in the drag-velocity plane. Bank angle modulation is established as the primary means for controlling drag and range. The guidance concept is applied …

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Geometric Approach To Orbital Formation Mission Design, Matthew J. Press Mar 2004

Geometric Approach To Orbital Formation Mission Design, Matthew J. Press

Theses and Dissertations

For distributed remote sensing architectures to be useful for collecting data, it is essential to have a methodology for relating orbital formation parameters to remote sensing requirements. Utilizing the characteristics of formation parameters, an orbital design approach is developed that establishes a satellite formation from a desired instantaneous spatial distribution as viewed from a target ground site. To maintain a conceptually basic representation, a geometric approach is used to develop the correlating algorithm. This tool will enable mission planning for orbital formations as well as future concept exploration.

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The Evaluation Of The Damping Characteristics Of A Hard Coating On Titanium, Christopher M. Blackwell Mar 2004

The Evaluation Of The Damping Characteristics Of A Hard Coating On Titanium, Christopher M. Blackwell

Theses and Dissertations

Engine failures due to fatigue have cost the Air Force an estimated $400 million dollars per year over the past two decades (Garrison, 2001). Damping treatments capable of reducing the internal stresses of fan and turbine blades to levels where fatigue is less likely to occur have the potential for reducing cost while enhancing reliability. This research evaluates the damping characteristics of magnesium aluminate spinel, MgO+Al2O3, (mag spinel) on titanium plates. The material and aspect ratio were chosen to approximate the low aspect ratio blades found in military gas turbine fans. The plates were tested with …

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Creating Cost Growth Models For The Engineering And Manufacturing Development Phase Of Acquisition Using Logistic And Multiple Regression, Brandon M. Lucas Mar 2004

Creating Cost Growth Models For The Engineering And Manufacturing Development Phase Of Acquisition Using Logistic And Multiple Regression, Brandon M. Lucas

Theses and Dissertations

Cost growth remains a concern for cost analysts, program managers, senior DoD decision-makers, Congress, and even the American public. All of these people have a vested interest in the cost of DoD programs and most would like to see those costs decrease; as such, we need additional tools to help combat cost growth. Previous research creates the foundation for the use of a two-step methodology to help predict cost growth, which we follow closely. First, utilizing logistic regression we analyze whether specific program characteristics predict cost growth within the Engineering and Manufacturing Development (EMD) phase for combined RDT&E and procurement …

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Estimating Cost Growth In Engineering And Schedule Cost Categories Using A Two-Pronged Regression Approach, Chris J. Mcdaniel Mar 2004

Estimating Cost Growth In Engineering And Schedule Cost Categories Using A Two-Pronged Regression Approach, Chris J. Mcdaniel

Theses and Dissertations

This research confirms the usefulness of the logistic and multiple regression two-step procedure for assessing cost growth in major DoD weapon systems. We compile programmatic data from the Selected Acquisition Reports (SARs) between 1990 and 2002 for programs covering all defense departments. Our analysis concentrates on cost growth in the procurement appropriations of the Engineering and Manufacturing Development phase of acquisitions. We investigate the use of logistic regression in cost growth analysis to predict whether or not cost growth will occur in a program. If applicable, multiple regression is implemented to predict how much cost growth will occur. Our study …

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Analysis And Forecasting Of Army Operating And Support Cost For Rotary Aircraft, John C. Hawkins Mar 2004

Analysis And Forecasting Of Army Operating And Support Cost For Rotary Aircraft, John C. Hawkins

Theses and Dissertations

This research explores forecasting techniques to estimate the Cost per Flying Hour (CPFH) for Army Helicopters. Specifically, three separate forecasting techniques were evaluated to better predict the CPFH for better estimating and budgeting by the U.S. Army. For forecasting purposes, actual CPFH figures were compiled from 1995 to 2003 for all MACOMs flying the AH-64A, the CH-47D, and the UH-60A helicopters. The number of MACOMs was then reduced to the top three with regard to total CPFH expenditure. The use of a 3-year moving average, the single exponential smoothing method, and Holt's linear method were explored for each helicopter's data. …

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Analysis And Forecasting Of Air Force Operating And Support Cost For Rotary Aircraft, Matthew E. Laubacher Mar 2004

Analysis And Forecasting Of Air Force Operating And Support Cost For Rotary Aircraft, Matthew E. Laubacher

Theses and Dissertations

This research explores forecasting techniques to estimate the Cost per Flying Hour (CPFH) for Air Force Helicopters. Specifically, this research evaluates three separate forecasting techniques to predict the CPFH for better estimating and budgeting by the U.S. Air Force. It starts by empirically analyzing the Operating and Support cost by CAIG categories for each helicopter. For forecasting purposes, the actual CPFH figures were compiled from FY96 to FY03 for a total of eight MAJCOMs flying the MH-53J/M, the HH-60G, or the UH-1N helicopters. The research explores the use of a 3-year moving average, the single exponential smoothing method, and Holt's …

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Reusable Space Vehicle Ground Operations Baseline Conceptual Model, Dennis R. Maynard, Patricia Pettit Mar 2004

Reusable Space Vehicle Ground Operations Baseline Conceptual Model, Dennis R. Maynard, Patricia Pettit

Theses and Dissertations

Modeling efforts for future space operation vehicles at the United States Air Force Research Labs Air Vehicles Directorate have been focused towards the in-flight mission. To better serve the research and development effort, a simulation of the ground operations is required allowing for trade-offs within turnaround operations and between the components that drive those procedures. However, before a simulation can be developed a conceptual model must be generated to guide the model building process. This research provides a baseline conceptual model for reusable space vehicles based on the space shuttle as the only operational vehicle of its kind. The model …

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Effects Of Duty Schedule Variance And Overtime On The Job Satisfaction And Turnover Intentions Of Usaf F-16 Crew Chiefs, Michael J. Shellhamer Mar 2004

Effects Of Duty Schedule Variance And Overtime On The Job Satisfaction And Turnover Intentions Of Usaf F-16 Crew Chiefs, Michael J. Shellhamer

Theses and Dissertations

This thesis empirically assessed how duty schedule variance and overtime affect the job satisfaction and turnover intentions of USAF F-16 crew chiefs. A survey was completed by 346 active duty USAF F-16 crew chiefs regarding their perceptions of duty schedule variance, overtime, job satisfaction and intent to leave the Air Force. Theory suggests that turnover behavior is a multistage process that involves organizational, individual, and attitudinal components. Using multivariate correlation and regression analyses, plausible evidence was found to support the idea that duty schedule variance and overtime plays a role in USAF F-16 crew chief turnover intentions via job satisfaction. …

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Age Replacement And Service Rate Control Of Stochastically Degrading Queues, Patrick S. Chapin Mar 2004

Age Replacement And Service Rate Control Of Stochastically Degrading Queues, Patrick S. Chapin

Theses and Dissertations

This thesis considers the problem of optimally selecting a periodic replacement time for a multiserver queueing system in which each server is subject to degradation as a function of the mean service rate and a stochastic and dynamic environment. Also considered is the problem of optimal service rate selection for such a system. In both cases, the performance metric is the long-run average cost rate. Analytical expressions are obtained, in terms of Laplace transforms, for the nonlinear objective functions, necessitating the use of numerical Laplace transform inversion to evaluate candidate solutions in conjunction with standard numerical algorithms. Due to the …

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Effects Of Uncertainty On Real World Aerospace Mission Data, Steven J. Barosko Mar 2004

Effects Of Uncertainty On Real World Aerospace Mission Data, Steven J. Barosko

Theses and Dissertations

Uncertainty is an age old element of warfare. How does one measure success or failure on the battlefield? This thesis explores the effect of uncertainty on real world aerospace mission data from Operation Iraqi Freedom (OIF). Sources of uncertainty are identified during data preparation and the effects of uncertainty are investigated using multivariate analysis techniques. Two distinct cases are analyzed: one case with a low level of uncertainty in predicting whether or not a mission is pre-planned or alert generated, and another case with a high level of uncertainty in predicting whether or not a mission is a success or …

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Agent Based Simulation Seas Evaluation Of Dodaf Architecture, Gregory V. Destefano Mar 2004

Agent Based Simulation Seas Evaluation Of Dodaf Architecture, Gregory V. Destefano

Theses and Dissertations

With Department of Defense (DoD) weapon systems being deeply rooted in the command, control, communications, computers, intelligence, surveillance, and reconnaissance (C4ISR) structure, it is necessary for combat models to capture C4ISR effects in order to properly assess military worth. Unlike many DoD legacy combat models, the agent based model System Effectiveness and Analysis Simulation (SEAS) is identified as having C4ISR analysis capabilities. In lieu of requirements for all new DoD C4ISR weapon systems to be placed within a DoD Architectural Framework (DoDAF), investigation of means to export data from the Framework to the combat model SEAS began. Through operational, system, …

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An Investigation Of The Effects Of Correlation, Autocorrelation, And Sample Size In Classifier Fusion, Nathan J. Leap Mar 2004

An Investigation Of The Effects Of Correlation, Autocorrelation, And Sample Size In Classifier Fusion, Nathan J. Leap

Theses and Dissertations

This thesis extends the research found in Storm, Bauer, and Oxley, 2003. Data correlation effects and sample size effects on three classifier fusion techniques and one data fusion technique were investigated. Identification System Operating Characteristic Fusion (Haspert, 2000), the Receiver Operating Characteristic Within Fusion method (Oxley and Bauer, 2002), and a Probabilistic Neural Network were the three classifier fusion techniques; a Generalized Regression Neural Network was the data fusion technique. Correlation was injected into the data set both within a feature set (autocorrelation) and across feature sets for a variety of classification problems, and sample size was varied throughout. Total …

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Phase-Type Approximations For Wear Processes In A Semi-Markov Environment, Christopher J. Solo Mar 2004

Phase-Type Approximations For Wear Processes In A Semi-Markov Environment, Christopher J. Solo

Theses and Dissertations

The reliability of a single-unit system experiencing degradation (wear) due to the influence of a general, observable environment process is considered. In particular, the failure time distribution is evaluated using only observations of the unit's current operating environment which is characterized as a finite semi-Markov process (SMP). In order to impose the Markov property, generally distributed environment state sojourn times are approximated as phase-type (PH) random variables using observations of state holding times and transition rates. The use of PH distributions facilitates the use of existing analytical results for reliability evaluation of units subject to an environment process that evolves …

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Measuring The Risk Of Shortfalls In Air Force Capabilities, William E. Woodward Mar 2004

Measuring The Risk Of Shortfalls In Air Force Capabilities, William E. Woodward

Theses and Dissertations

The U.S. Air Force seeks to measure and prioritize risk as part of its Capabilities Review and Risk Assessment (CRRA) process. The goal of the CRRA is to identify capability shortfalls, and the risks associated with those shortfalls, to influence future systems acquisition. Many fields, including engineering, medicine and finance, seek to model and measure risks. This research utilizes various risk measurement approaches to propose appropriate risk measures for a military context. Specifically, risk is modeled as a non-negative random variable of severity. Four measures are examined: simple expectation, a risk-value measure, tail conditional expectation, and distorted expectation. Risk measures …

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Forward Looking Radar: Interference Modelling, Characterization, And Suppression, James T. Caldwell Mar 2004

Forward Looking Radar: Interference Modelling, Characterization, And Suppression, James T. Caldwell

Theses and Dissertations

This research characterizes forward looking radar performance while noting differences with traditionally examined sidelooking radar. The target detection problem for forward looking radar is extremely difficult due to the severe, heterogeneous and range dependent ground clutter. Consequently, forward looking radar detection represents an important but overlooked topic because of the increased difficulty compared to sidelooking radar. This void must be filled since most fighter aircraft use forward looking radar, making this topic intensely interesting to the Air Force. After characterizing forward looking radar performance, basic radar concepts along with advanced adaptive interference suppression techniques improve the output Signal-to-Interference-plus-Noise Ratio (SINR) …

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Thin Film Encapsulation Of Radio Frequency (Rf) Microelectromechanical Systems (Mems) Switches, Eric D. Marsh Mar 2004

Thin Film Encapsulation Of Radio Frequency (Rf) Microelectromechanical Systems (Mems) Switches, Eric D. Marsh

Theses and Dissertations

Microelectromechanical systems (MEMS) radio frequency (RF) switches have been shown to have excellent electrical performance over a wide range of frequencies. However, cost-effective packaging techniques for MEMS switches do not currently exist. This thesis involves the design of RF-optimized encapsulations consisting of dielectric and metal layers, and the creation of a novel thin film encapsulation process to fabricate the encapsulations. The RF performance of several encapsulation designs are evaluated with an analytical model, full wave electromagnetic simulation, and laboratory testing. Performance degradation due to parasitic and reflection losses due to the package is considered, and RF feed-throughs of the transmission …

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Enhancing The Instantaneous Dynamic Range Of Electronic Warfare Receivers Using Statistical Signal Processing, Bryan E. Smith Mar 2004

Enhancing The Instantaneous Dynamic Range Of Electronic Warfare Receivers Using Statistical Signal Processing, Bryan E. Smith

Theses and Dissertations

Accurately processing multiple, time-coincident signals presents a challenge to Electronic Warfare (EW) receivers, especially if the signals are close in frequency and/or mismatched in amplitude. The metric that quantifies an EW receiver's ability to measure time-coincident signals is the Instantaneous Dynamic Range (IDR), defined for a given frequency estimation accuracy, a given frequency separation and a given SNR as the maximum signal amplitude ratio that can be accommodated. Using a two sinusoid time-series model, this thesis analyzes IDR for ideal intercept and parametric digital EW receivers. In general, the number of signals contained in the EW receiver measurement interval is …

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An Analysis Of The Effects Of Low Energy Electron Radiation Of AlXGa1-XN/Gan Modulation-Doped Field-Effect Transistors, James M. Sattler Mar 2004

An Analysis Of The Effects Of Low Energy Electron Radiation Of AlXGa1-XN/Gan Modulation-Doped Field-Effect Transistors, James M. Sattler

Theses and Dissertations

The effects of radiation on AlxGa1-xN/GaN MODFETs is an area of increasing interest to the USAF as these devices become developed and integrated in satellite-based systems Irradiation is also a valuable tool for analyzing the quantum-level characteristics and properties that are responsible for device operation AlxGa1-xN/GaN MODFETs were fabricated and irradiated at liquid nitrogen temperatures by 0,45-1,2MeV electrons up to doses of 6*1016 e/cm2. Following irradiation, low temperature I-V measurements were recorded providing dose-dependent measurements Temperature-dependent I-V measurements were also made during room temperature annealing following irradiation I-V measurements …

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Cross-Service Investigation Of Geographical Information Systems, Matthew H. Beverly Mar 2004

Cross-Service Investigation Of Geographical Information Systems, Matthew H. Beverly

Theses and Dissertations

This research investigated the armed services current uses of GIS, and asked the question whether or not a joint GIS program could benefit the DOD. An information technology implementation model was presented as a framework to implement a joint GIS program. It was found that all four armed services use GIS for forward deployments. The Army has its Combat Terrain Information System (CTIS). The Navy's digital nautical charts are a GIS. The Marine Corps has created their Geographically Linked Information Display Environment (GLIDE) program, which is similar to a map repository. Finally, the Air Force has its GeoBase program for …

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Modeling A Field Application Of In Situ Bioremediation Of Perchlorate-Contaminated Groundwater Using Horizontal Flow Treatment Wells (Hftws), Peter G. Chosa Mar 2004

Modeling A Field Application Of In Situ Bioremediation Of Perchlorate-Contaminated Groundwater Using Horizontal Flow Treatment Wells (Hftws), Peter G. Chosa

Theses and Dissertations

Perchlorate contaminated groundwater is rapidly becoming a significant environmental remediation issue for the Department of Defense. In this study, an existing numerical model that simulates the operation of a Horizontal Flow Treatment Well (HFTW) system to effect the in situ biodegradation of perchlorate through the addition of an electron donor is modified to include a submodel that describes bioclogging. Bioclogging restricts flow out of the HFTW due to the accumulation of biomass directly adjacent to the well. The modified model is then applied to an existing perchlorate contaminated site that will be used for an evaluation of the HFTW technology. …

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Making The Business Case For Sustainable Design In The Department Of Defense, David M. Warnke Mar 2004

Making The Business Case For Sustainable Design In The Department Of Defense, David M. Warnke

Theses and Dissertations

Buildings are one of the largest consumers of natural resources, a major source of ecological pollution, and occasionally toxic to human health. Sustainable design is the common term associated with buildings which, during their construction, use, and eventual disposal, seek to minimize their negative impact on the environment and human health. The U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED) rating system helps to assess a building's sustainability level. In the Federal Government's push to set the example for the rest of the nation, nearly every Federal Agency has chosen to adopt the LEED assessment tool. Each …

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