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Air Force Institute of Technology

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Articles 3151 - 3180 of 5700

Full-Text Articles in Engineering

Investigation Of Gate Current In Neutron Irradiated AlXGa1-XN/Gan Heterogeneous Field Effect Transistors Using Voltage And Temperature Dependence, Thomas E. Gray Mar 2007

Investigation Of Gate Current In Neutron Irradiated AlXGa1-XN/Gan Heterogeneous Field Effect Transistors Using Voltage And Temperature Dependence, Thomas E. Gray

Theses and Dissertations

The gate current of Al27Ga73N/GaN heterogeneous field effect transistors (HFETs) is investigated using current-voltage (IV) and current-temperature (IT) measurement demonstrating that trap assisted tunneling (TAT) is the primary current mechanism. A thermionic trap assisted tunneling (TTT) model is used with variables of Schottky barrier height, trap energy, donor density and trap density. This results in a sigma of 1.38x10-8 A for IT data measured between 85K and 290K and for IV data measured between 0.0 V and -4.0 V. High energy (>0.5 MeV) neutron irradiation confirms an increase of gate current with fluence. An …

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High Resolution Mesoscale Weather Data Improvement To Spatial Effects For Doserate Contour Plot Predictions, Christopher P. Jones Mar 2007

High Resolution Mesoscale Weather Data Improvement To Spatial Effects For Doserate Contour Plot Predictions, Christopher P. Jones

Theses and Dissertations

Reanalysis weather data is obtained for dates surrounding historical nuclear tests and processed through Regional Atmospheric Modeling System (RAMS) software to produce a high-resolution weather forecast. Output from RAMS is visualized to check for validity and input into Hazard Prediction and Assessment Capability (HPAC) software and modeled predictions are compared to historical observation data. Simulations are conducted using constant high resolution weather and varying terrain resolution. The HPAC prediction is numerically compared to historical observation data. The result of this research culminated in the knowledge that early-time, low-altitude wind data was neglected by HPAC's incorporation of the Defense Land Fallout …

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Optimal Spacecraft Attitude Control Using Aerodynamic Torques, Michael L. Gargasz Mar 2007

Optimal Spacecraft Attitude Control Using Aerodynamic Torques, Michael L. Gargasz

Theses and Dissertations

This thesis introduces a method of three-axis spacecraft attitude control using only aerodynamic torques. Attitude actuation is achieved using four control panels mounted on the rear of a cubical spacecraft bus. The controller consists of an outer loop using linear state feedback to determine desired control torque and an inner loop to choose appropriate control panel angles. The inner loop uses a Jacobian-based approach to invert the nonlinear relationship between panel angles and generated torque. Controller performance is evaluated via simulations, which show that three-axis control is possible over a range of initial angles and angular rates. The analysis used …

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A Modular Mixed Signal Vlsi Design Approach For Digital Radar Applications, Brian M. Brakus Mar 2007

A Modular Mixed Signal Vlsi Design Approach For Digital Radar Applications, Brian M. Brakus

Theses and Dissertations

This study explores the idea of building a library of VHDL configurable components for use in digital radar applications. Configurable components allows a designer to choose which components he or she needs and configures those components for a specific application. By doing this, design time for ASICs and FPGAs is shortened because the components are already designed and tested. This idea is demonstrated with a configurable dynamic pipelinable fast fourier transform. Many FFT implementations exist, but this implementation is both configurable and dynamic. Pre-synthesis customization allows the FFT to be tailored to almost any DSP application, and the dynamic property …

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Parametric Reliability Of Space-Based Field Programmable Gate Arrays, Joseph C. Pomager Mar 2007

Parametric Reliability Of Space-Based Field Programmable Gate Arrays, Joseph C. Pomager

Theses and Dissertations

The high cost of failure for microelectronic devices operating in the space environment has led to a need for an accurate characterization of a device's reliability prior to being deployed. In addition, significant cost savings can be achieved by determining this reliability prior to fabrication. With the increased performance needs required for many missions, designers are seeking to utilize devices that have smaller and smaller feature sizes. Specifically, feature sizes as small as 130, 90, and 65 nm. A characterization of the space environment is constructed specifically to address the extreme conditions that can affect the performance and functionality of …

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Optimal Sensor Threshold Control And The Weapon Operating Characteristic For Autonomous Search And Attack Munitions, Roland A. Rosario Mar 2007

Optimal Sensor Threshold Control And The Weapon Operating Characteristic For Autonomous Search And Attack Munitions, Roland A. Rosario

Theses and Dissertations

This Thesis considers the optimal employment of a wide area search munition in a battlespace where a target is known to be uniformly distributed among false targets which are Poisson distributed. The Poisson distribution's parameter is obtained from readily available battlespace intelligence. This work formulates and solves the optimal control problem for deriving the optimal sensor threshold schedule in order to maximize the probability of attacking the target during the battlespace sweep while constraining the probability of attacking a false target. The efficiency gained by optimally varying the sensor threshold is compared against the performance achieved with a static, optimum …

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Developing A Framwork For Evaluating Organizational Information Assurance Metrics Programs, Adam R. Bryant Mar 2007

Developing A Framwork For Evaluating Organizational Information Assurance Metrics Programs, Adam R. Bryant

Theses and Dissertations

The push to secure organizational information has brought about the need to develop better metrics for understanding the state of the organization’s security capability. This thesis utilizes case studies of information security metrics programs within Department of Defense organizations, the United States Air Force (USAF), and the National Aeronautics and Space Administration’s (NASA’s) Jet Propulsion Lab to discover how these organizations make decisions about how the measurement program is designed, how information is collected and disseminated, and how the collected information supports decision making. This research finds that both the DOD and USAF have highly complex information security programs that …

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Hardware Virtualization Applied To Rootkit Defense, Douglas P. Medley Mar 2007

Hardware Virtualization Applied To Rootkit Defense, Douglas P. Medley

Theses and Dissertations

This research effort examines the idea of applying virtualization hardware to enhance operating system security against rootkits. Rootkits are sets of tools used to hide code and/or functionality from the user and operating system. Rootkits can accomplish this feat through using access to one part of an operating system to change another part that resides at the same privilege level. Hardware assisted virtualization (HAV) provides an opportunity to defeat this tactic through the introduction of a new operating mode. Created to aid operating system virtualization, HAV provides hardware support for managing and saving multiple states of the processor. This hardware …

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Multi-Dimensional Classification Algorithm For Automatic Modulation Recognition, Ouail Albairat Mar 2007

Multi-Dimensional Classification Algorithm For Automatic Modulation Recognition, Ouail Albairat

Theses and Dissertations

This thesis proposes an approach for modulation classification using existing features in a more efficient way. The Multi-Dimensional Classification Algorithm (MDCA) treats features extracted from signals of interest as elements with irrelevant identities, hence eliminating any dependence of the classifier on any particular feature. This design enables the use of any number of features, and the MDCA algorithm provides the capability to classify modulations in higher dimensions. The use of multiple features requires an equal number of data dimensions, and thus classification in as high a dimensional space as possible can improve final classification results. Finally, the MDCA algorithm uses …

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Characterization Of Intercalated Graphite Fibers For Microelectromechanical Systems (Mems) Applications, Bryan W. Winningham Mar 2007

Characterization Of Intercalated Graphite Fibers For Microelectromechanical Systems (Mems) Applications, Bryan W. Winningham

Theses and Dissertations

Research was accomplished to characterize the electrical and physical characteristic changes of the Thornel® P-100 carbon fiber and five variants when intercalated with 96% sulfuric acid and incorporated the use of Microelectromechanical Systems (MEMS) structures for testing purposes. The five fiber variants were oxidized in 1 M nitric acid at 0.5 A for 30 seconds, 1 and 2 minutes, the last two samples were detreated at 1150 °C for one hour prior to the nitric acid treatment. The fibers were mounted onto a MEMS die, placed into a chip carrier, sulfuric acid added, the chip carrier sealed and testing accomplished. …

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Implementation And Optimization Of The Advanced Encryption Standard Algorithm On An 8-Bit Field Programmable Gate Array Hardware Platform, Ryan J. Silva Mar 2007

Implementation And Optimization Of The Advanced Encryption Standard Algorithm On An 8-Bit Field Programmable Gate Array Hardware Platform, Ryan J. Silva

Theses and Dissertations

The contribution of this research is three-fold. The first is a method of converting the area occupied by a circuit implemented on a Field Programmable Gate Array (FPGA) to an equivalent as a measure of total gate count. This allows direct comparison between two FPGA implementations independent of the manufacturer or chip family. The second contribution improves the performance of the Advanced Encryption Standard (AES) on an 8-bit computing platform. This research develops an AES design that occupies less than three quarters of the area reported by the smallest design in current literature as well as significantly increases area efficiency. …

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Price Vs. Performance: The Value Of Next Generation Fighter Aircraft, John M. Stelly Mar 2007

Price Vs. Performance: The Value Of Next Generation Fighter Aircraft, John M. Stelly

Theses and Dissertations

The United States Department of Defense (DoD) is currently recapitalizing its aging fighter aircraft inventory with the F-22A and F-35. While the DoD may consider cost and performance issues, it does not use a quantitative model that effectively measures the tradeoffs between the two. This thesis constructs a hedonic model of the fighter aircraft market to measure the implicit price on fighter performance characteristics and specifically applies it to next-generation aircraft. Data from 50 aircraft from 1949-present were used to construct two models – one based on procurement costs and one based on research, design, test, and evaluation (RDT&E) costs. …

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Beyond Passswords: Usage And Policy Transformation, Alan S. Alsop Mar 2007

Beyond Passswords: Usage And Policy Transformation, Alan S. Alsop

Theses and Dissertations

The purpose of this research is to determine whether the transition to a two-factor authentication system is more secure than a system that relied only on what users “know” for authentication. While we found that factors that made passwords inherently vulnerable did not transfer to the PIN portion of a two-factor authentication system, we did find significant problems relating to usability, worker productivity, and the loss and theft of smart cards. The new authentication method has disrupted our ability to stay connected to ongoing mission issues, forced some installations to cut off remote access for their users and in one …

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Using Concept Maps To More Efficiently Create Intelligence Information Models, Christopher E. Coryell Mar 2007

Using Concept Maps To More Efficiently Create Intelligence Information Models, Christopher E. Coryell

Theses and Dissertations

Information models are a critical tool that enables intelligence customers to quickly and accurately comprehend U.S. intelligence agency products. The Knowledge Pre-positioning System (KPS) is the standard repository for information models at the National Air and Space Intelligence Center (NASIC). The current approach used by NASIC to build a KPS information model is laborious and costly. Intelligence analysts design an information model using a manual, butcher-paper-based process. The output of their work is then entered into KPS by either a single NASIC KPS "database modeler" or a contractor (at a cost of roughly $100K to the organization). This thesis proposes …

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Characterizationn Of Polumer-Based Mems Pyroelectic Infrared Detector, Mark E. Allard Mar 2007

Characterizationn Of Polumer-Based Mems Pyroelectic Infrared Detector, Mark E. Allard

Theses and Dissertations

AFRL/MLPJE had developed a novel thermal sensing material termed protein-impregnated-polymer (PIP). Thus far, a proof-of-concept has been demonstrated using a macro-sized pixel (0.64 mm2) as a bolometric detector. In an effort to better characterize this novel thermal sensing material, experimental data was used to determine figures of merit (FOMs) comparative to off-the-shelf thermal detectors. Microelectromechanical (MEMS) pixels were designed and used as the support structure for an inkjet-deposited droplet of the PIP. During the material characterization, two observations were made: PIP is a pyroelectric material, and the polymer (polyvinyl alcohol (PVA)) without the protein was found to be …

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Toward A Flying Mems Robot, Nathan E. Glauvitz Mar 2007

Toward A Flying Mems Robot, Nathan E. Glauvitz

Theses and Dissertations

The work in this thesis includes the design, modeling, and testing of motors and rotor blades to be used on a millimeter-scale helicopter style flying micro air vehicle (MAV). Three different types of motor designs were developed and tested, which included circular scratch drives, electrostatic motors, and comb drive resonators. Six different rotor designs were tested; five used residual stress while one design used photoresist to act as a hinge to achieve rotor blade deflection. Two key parameters of performance were used to evaluate the motor and rotor blade designs: the frequency of motor rotation and the angle of deflection …

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Thermally Activated, Variable Blazed Grating For Coherent Beam Steering, Matthew T. Johnson Mar 2007

Thermally Activated, Variable Blazed Grating For Coherent Beam Steering, Matthew T. Johnson

Theses and Dissertations

The ability to perform non-mechanical optical beam steering is of critical importance in laser communication and remote sensing; it is as vital as a phased-array antenna is for RADAR. Directed energy transmission and direction-selective reception increase performance and produce tactical advantage in DoD applications. However, specific geometric features of non-mechanical beam steering devices must be designed in proportion to the wavelength of the monochromatic light to be steered. Also, the ability to handle higher energies by reducing the energy per unit requires large areas of uniform properties on the micrometer scale. These challenges have been addressed in the past using …

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Material Characterization Improvement In High Temperature Rectangle Waveguide Measurements, Eric A. Buschelman Mar 2007

Material Characterization Improvement In High Temperature Rectangle Waveguide Measurements, Eric A. Buschelman

Theses and Dissertations

This research presents a method by which electromagnetic characterization of materials in a partially filled waveguide can be accurately performed. Higher order modes are excited by the geometry, which are not accounted for in most algorithms. A correction must consider the power transmitted by higher-order modes. Modal solutions, using reference plane independence, for a single top air gap between the material sample and the waveguide wall, are also presented. Characterization is performed on samples of acrylic and rubberized magnetic radar absorbing material. Calculation of the complex permittivity and permeability of shielding material, within 10% of the true value, was achieved …

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Sub-Surface Navigation Using Very-Low Frequency Electromagnetic Waves, Alan L. Harner Mar 2007

Sub-Surface Navigation Using Very-Low Frequency Electromagnetic Waves, Alan L. Harner

Theses and Dissertations

This research proposes two schemes utilizing very-low frequency (VLF) electromagnetic waves to navigate underground. The first scheme consists of using above-ground beacon transmitters to broadcast VLF signals to an underground mobile receiver which uses methods such as triangulation and trilateration to obtain a position solution. The second scheme consists of using above-ground reference receivers along with an underground mobile receiver to form time-difference- of-arrival measurements of incoming VLF signals of opportunity, such as lightning strike emissions, to calculate a position solution. The objective of this thesis is to develop positioning algorithms and use simulations as a tool to characterize the …

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Exploring Hardware Based Primitives To Enhance Parallel Security Monitoring In A Novel Computing Architecture, Stephen D. Mott Mar 2007

Exploring Hardware Based Primitives To Enhance Parallel Security Monitoring In A Novel Computing Architecture, Stephen D. Mott

Theses and Dissertations

This research explores how hardware-based primitives can be implemented to perform security-related monitoring in real-time, offer better security, and increase performance compared to software-based approaches. In doing this, we propose a novel computing architecture, derived from a contemporary shared memory architecture, that facilitates efficient security-related monitoring in real-time, while keeping the monitoring hardware itself safe from attack. This architecture is flexible, allowing security to be tailored based on the needs of the system. We have developed a number of hardware-based primitives that fit into this architecture to provide a wide array of monitoring capabilities. A number of these primitives provide …

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Assessment Of Optical Turbulence Profiles Derived From Probabilistic Climatology, Brett W. Wisdom Mar 2007

Assessment Of Optical Turbulence Profiles Derived From Probabilistic Climatology, Brett W. Wisdom

Theses and Dissertations

This research effort assesses the performance of the High Energy Laser End-to-End Operational Simulation (HELEEOS) Climatological C2n optical turbulence model. Path-integrated C2n values of two HELEEOS optical turbulence pro les at 3 distinct operational altitudes are compared to values determined from measured thermosonde data. HELEEOS desert and mid-latitude sites are selected from the Extreme and Percentile Environmental Reference Tables (ExPERT) database for comparison to the thermosonde data. Statistical equivalence of the two datasets is determined through a Design of Experiments (DOE) factorial test to within 80% confidence. The HELEEOS profiles are shown to be equivalent to …

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Use Of Two-Way Time Transfer Measurements To Improve Geostationary Satellite Navigation, Benjamin G. Dainty Mar 2007

Use Of Two-Way Time Transfer Measurements To Improve Geostationary Satellite Navigation, Benjamin G. Dainty

Theses and Dissertations

An emerging use of GPS is to provide accurate navigation information for satellites in orbit. The GPS satellites are designed to provide service to terrestrial users, so the antenna array points directly towards the Earth and uses a narrow primary beamwidth. Because GEO altitudes are well above the GPS constellation, the Earth occludes most of the GPS signals to the satellite. Decreased satellite visibility is debilitating, as GPS navigation requires at least four visible satellites to determine position. To assist with the visibility problem, the receiver can look at the GPS satellite transmit antenna side lobes, but this does not …

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A Study Of Rootkit Stealth Techniques And Associated Detection Methods, Daniel D. Nerenberg Mar 2007

A Study Of Rootkit Stealth Techniques And Associated Detection Methods, Daniel D. Nerenberg

Theses and Dissertations

In today's world of advanced computing power at the fingertips of any user, we must constantly think of computer security. Information is power and this power is had within our computer systems. If we cannot trust the information within our computer systems then we cannot properly wield the power that comes from such information. Rootkits are software programs that are designed to develop and maintain an environment in which malware may hide on a computer system after successful compromise of that computer system. Rootkits cut at the very foundation of the trust that we put in our information and subsequent …

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Information Management Principles Applied To The Ballistic Missile Defense System, John M. Koehler Ii Mar 2007

Information Management Principles Applied To The Ballistic Missile Defense System, John M. Koehler Ii

Theses and Dissertations

Information systems (IS) have evolved over the last 50 plus years from individual components with single functionality to grand architectures that integrate multiple individual business functions into global organizational enterprises. Similarly several military systems with the single mission of missile defense have evolved in service stovepipes, and are now being integrated into a national and global missile defense architecture. The Missile Defense Agency (MDA) is currently tasked with developing an integrated Ballistic Missile Defense System (BMDS) capable of defending against all ranges of ballistic missiles in all phases of flight in defense of the homeland, our deployed forces, and our …

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Distributed Fault-Tolerant Quality Of Service Routing In Hybrid Directional Wireless Networks, Larry C. Llewellyn Ii Mar 2007

Distributed Fault-Tolerant Quality Of Service Routing In Hybrid Directional Wireless Networks, Larry C. Llewellyn Ii

Theses and Dissertations

This thesis presents a distributed fault-tolerant routing protocol (EFDCB) for QoS supporting hybrid mobile ad hoc networks with the aim of mitigating QoS disruption time when network failures occur. The experimental design presented in this thesis describes 22 experiments aimed at illustrating EFDCB's ability to handle fault-tolerance. The interpreted results show that EFDCB excels over a global rerouting protocol at this challenge which is the goal of this work.

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Biological Cell Identification By Integrating Micro-Fluidics, Electrical Impedance Spectroscopy And Stochastic Estimation, Karl R. Schwenn Mar 2007

Biological Cell Identification By Integrating Micro-Fluidics, Electrical Impedance Spectroscopy And Stochastic Estimation, Karl R. Schwenn

Theses and Dissertations

The integration of micro-fluidics, electrical impedance spectroscopy and stochastic estimation will lead to a device with enhanced detection capabilities. The goal of this thesis was to build a micro-fluidic electrical impedance measurement device that can be used in combination with a stochastic estimator to accurately identify living cells. A microdevice capable of making impedance measurements on individual living cells was designed and built using a series of standard microelectronic fabrication techniques. A microchannel was patterned in SU-8 photoresist between two gold microelectrodes on a two inch Pyrex 7740 wafer. The design process, the fabrication techniques for the microchannel, the fluid …

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Effective Mobile Routing Through Dynamic Addressing, Heungsoon Park Mar 2007

Effective Mobile Routing Through Dynamic Addressing, Heungsoon Park

Theses and Dissertations

Military communications has always been an important factor in military victory and will surely play an important part in future combat. In modern warfare, military units are usually deployed without existing network infrastructure. The IP routing protocol, designed for hierarchical networks cannot easily be applied in military networks due to the dynamic topology expected in military environments. Mobile ad-hoc networks (MANETs) represent an appropriate network for small military networks. But, most ad-hoc routing protocols suffer from the problem of scalability for large networks. Hierarchical routing schemes based on the IP address structure are more scalable than ad-hoc routing but are …

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Characterization Of Chlorinated Ethene Degradation In A Vertical Flow Constructed Wetland, James M. Waldron Mar 2007

Characterization Of Chlorinated Ethene Degradation In A Vertical Flow Constructed Wetland, James M. Waldron

Theses and Dissertations

Chlorinated solvents, including perchloroethene (PCE) and trichlorethene (TCE), are among the most common groundwater contaminants found in the United States. Once released into the environment, chlorinated solvents are extremely persistent and often require costly and lengthy remedial actions. The use of constructed wetlands has shown promise as an effective and less costly alternative for the treatment of chlorinated solvent contaminated groundwater. This study characterized and evaluated the concentration of chlorinated ethenes within a vertical flow constructed wetland, fed with PCE contaminated groundwater, at Wright-Patterson Air Force Base (WPAFB), Ohio. Chlorinated ethene concentrations were characterized within three distinct layers of the …

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A Decision Model For Selecting Energy Efficient Technologies For Low -Sloping Roof Tops Using Value-Focused Thinking, Michael J. Mccourt Mar 2007

A Decision Model For Selecting Energy Efficient Technologies For Low -Sloping Roof Tops Using Value-Focused Thinking, Michael J. Mccourt

Theses and Dissertations

The Air Force has a large inventory of low-sloping built up roofs (BURs) and millions of dollars are spent each year retrofitting these systems. The DOD has been directed to reduce non-renewable energy consumption by using energy-efficient technologies. These two details present a great opportunity to use the open roof space to install energy-efficient roofing technologies. The purpose of this research is to provide Air Force decision makers with a tool to assist them in deciding what roofing technologies should be installed on facilities. Value Focused-Thinking is the methodology used to construct the model, in which values were used, instead …

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Planning And Assessing Stability Operations: A Proposed Value-Focused Thinking Approach, Gerald D. Fensterer Mar 2007

Planning And Assessing Stability Operations: A Proposed Value-Focused Thinking Approach, Gerald D. Fensterer

Theses and Dissertations

Stability operations are vital to establish peace in the aftermath of conflict. The United States is often called in for military support during conflict. The new American military paradigms include establishing peace through stability operations after a military conflict. Due to this new role, military decision makers face many difficulties in conducting successful stability operations. Compounding this problem is the limited number of resources pertaining to stability operations: experts, doctrine, knowledge, and technology. Two overarching challenges of stability operations facing decision makers are planning and prioritizing of stability operations and determining progress. This thesis applies a structured analytical approach to …

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