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Articles 3571 - 3600 of 5699
Full-Text Articles in Engineering
A Comparison Of The Heft Subsurface And Delfic Particle Size Distributions And Effects In Hpac, Eric T. Skaar
A Comparison Of The Heft Subsurface And Delfic Particle Size Distributions And Effects In Hpac, Eric T. Skaar
Theses and Dissertations
The Heft subsurface three component lognormal fallout particle size distribution is compared and contrasted with the single lognormal fallout particle size distribution used by the Defense Land Fallout Interpretive Code (DELFIC). Comparison of the two distributions is accomplished with results from the AFIT smear code and the Hazard Prediction and Assessment Capability (HPAC). The effect of the distributions is explored in HPAC for varying yield weapons, varying surfaces, precipitation conditions, varying wind effects and varying dose rate times. The results from the two distributions are quantitatively compared using the concepts of grounded source normalization constant and the rate at which …
Temperature Dependent Current-Voltage Measurements Of Neutron Irradiated Al0.27Ga0.73N/Gan Modulation Doped Field Effect Transistors, Troy A. Uhlman
Temperature Dependent Current-Voltage Measurements Of Neutron Irradiated Al0.27Ga0.73N/Gan Modulation Doped Field Effect Transistors, Troy A. Uhlman
Theses and Dissertations
In this research, the first ever neutron irradiation study of AlGaN/GaN MODFETs was conducted. Devices irradiated to a total 1 MeV Eq (Si) neutron fluence of 1.2x1016 n/sq cm demonstrated the temperature dependence of irradiation and annealing. Devices irradiated at 80 K exhibited significant persistent electrical degradation at only 5.4 rad (Si), whereas those irradiated at elevated temperatures exhibit transient increases in gate and drain current up to 400 krad (Si). I-V measurements indicate substantial radiation-induced increased gate and drain currents occur only at low-temperature irradiations. The introduction of a high-density of donor defects is hypothesized as the primary …
Modeling Groundwater Flow And Contaminant Transporting Fractured Aquifers, Jason M. Bordas
Modeling Groundwater Flow And Contaminant Transporting Fractured Aquifers, Jason M. Bordas
Theses and Dissertations
The hybrid discrete fracture network/equivalent porous medium (DFN/EPM) model was selected for analysis and application to simulate a contaminated site in this study. The DFN/EPM was selected because it appeared to have the potential to aid decision making by remedial project managers at contaminated DoD fractured aquifer sites. This model can use data that are typically available at a site while incorporating the important processes relevant to describing contaminant transport in a fractured medium. The model was applied to simulate the operation of a pump-and-treat remedial action at a trichloroethene-contaminated fractured aquifer at Pease AFB. The model was able to …
Using Value-Focused Thinking To Evaluate The Practicality Of Ground-Source Heat Pumps At Military Installations, Jimmy J. Jeoun
Using Value-Focused Thinking To Evaluate The Practicality Of Ground-Source Heat Pumps At Military Installations, Jimmy J. Jeoun
Theses and Dissertations
Because of potential cost and energy savings, military decision-makers may want to consider the use of energy-efficient heating, ventilating, and air-conditioning (HVAC) systems at their installations. Ground source heat pumps (GSHPs), in particular, show great promise because of their low energy requirements and low life-cycle costs. However, there currently exists no design guidance or established criteria for HVAC selection. Consequently, military decision-makers have no basis for comparing conventional HVAC systems and GSHPs. The Value-Focused Thinking (VFT) methodology was used to create a multi-objective decision analysis model that measures the value of different HVAC systems. Consisting of five bottom-tier values and …
Comparing Management Approaches For Automatic Test Systems: A Strategic Missile Case Study, William C. Ford
Comparing Management Approaches For Automatic Test Systems: A Strategic Missile Case Study, William C. Ford
Theses and Dissertations
From 1980 to 1992, the DoD spent over $50 billion acquiring Automatic Test Systems (ATS) used to test weapon systems. At that time, procuring unique ATS to support single weapon systems was the norm. In 1994, the DoD made a dramatic change to their ATS acquisition policy; common ATS that supported multiple weapon systems was preferred over ATS tailored to support a single weapon system. Expected benefits of this new policy included: more reliable equipment, increased supportability, decreased cost, smaller logistics footprint, and decreased manning. To date, the common ATS initiative has garnered little support AF-wide due to lack of …
Output Analysis And Comparison Of Deployment Models With Varying Fidelity, Matthew M. Gill
Output Analysis And Comparison Of Deployment Models With Varying Fidelity, Matthew M. Gill
Theses and Dissertations
This thesis explores the changes in insights that result from using different types of models to assess the capability of deploying the Stryker Brigade within specific timeline goals. The thesis uses as its primary base a study conducted in 2002 by USTRANSCOM to evaluate the ability of Stryker to meet stated deployment timeline goals. Specifically, the author compares the outputs from four different models as they change over three different deployment scenarios and 10 different routes. The study investigates the relationships among the outputs of spreadsheet models, spreadsheet models with elements of variability added, and low- and high-level discrete-event simulations. …
Evaluating Management Strategies For Automated Test Systems/Equipment (Ats/E): An F-15 Case Study, Jeremy A. Howe
Evaluating Management Strategies For Automated Test Systems/Equipment (Ats/E): An F-15 Case Study, Jeremy A. Howe
Theses and Dissertations
The management of United States Air Force ATS/E presents a variety of issues that affect the long-term capability and mission readiness of weapon systems. Traditional procurement processes suggest that individual aircraft platform System Program Offices (SPOs) developed, improved and replaced ATE on an "as-required" basis. Increased obsolescence, however, and a concern for maintaining longer-term viability provided the necessary inertia for a movement towards the procurement and development of consolidated, common test equipment that would support multiple weapon systems. In 1998, the Air Force Chief of Staff directed HQ AFMC to establish a Common Support Equipment office to facilitate the combination …
Estimating Resource Requirements To Support Multi-Echelon F-15e Deployments, David R. Maxwell
Estimating Resource Requirements To Support Multi-Echelon F-15e Deployments, David R. Maxwell
Theses and Dissertations
Since the end of the Cold War, the United States has become focused on developing the capability to rapidly respond to emerging crises. Strategic and operation planning play key roles in order to effectively implement this concept. During the planning process, separate courses of action (COAs) are developed. These COAs are evaluated based upon their operational effect, resource availability, nuclear and transportation feasibility. Currently, transportation feasibility assessments are based on the resources contained within a full Unit Type Code (UTC). Some COAs are eliminated based on these factors. However, most deployments occur at reduced levels. Situational factors, such as the …
Determining Pacaf Transportation Alternatives To The General Purpose Vehicle, Andrew H. Pate
Determining Pacaf Transportation Alternatives To The General Purpose Vehicle, Andrew H. Pate
Theses and Dissertations
Vehicle fleets under gird the mission of Air Force bases. Under funding for vehicle replacement requirements raised concerns and has led to purchasing alternative vehicles classified as equipment items to supplement budget shortfalls. In order to effectively use funds and meet mission requirements, Pacific Air Force (PACAF) commanders need an adjustable multifactor decision tool that will allow them to make an informed purchasing decision from among appropriately classified equipment item vehicles. This research will discuss existing regulatory restrictions to alternative transportation purchases, consider available alternative vehicles, and determine the attributes important to vehicle purchases. A review of current Air Force …
Optimization Model For Base-Level Delivery Routes And Crew Scheduling, Young-Ho Cha
Optimization Model For Base-Level Delivery Routes And Crew Scheduling, Young-Ho Cha
Theses and Dissertations
In the U.S. Air Force, a Logistic Readiness Squadron (LRS) provides material management, distribution, and oversight of contingency operations. Dispatchers in the LRS must quickly prepare schedules that meet the needs of their customers while dealing with real-world constraints, such as time windows, delivery priorities, and intermittent recurring missions. Currently, LRS vehicle operation elements are faced with a shortage of manpower and lack an efficient scheduling algorithm and tool. The purpose of this research is to enhance the dispatchers' capability to handle flexible situations and produce "good" schedules within current manpower restrictions. In this research, a new scheduling model and …
Stochastic Capability Models For Degrading Satellite Constellations, Cole W. Gulyas
Stochastic Capability Models For Degrading Satellite Constellations, Cole W. Gulyas
Theses and Dissertations
This thesis proposes and analyzes a new measure of functional capability for satellite constellations that incorporates the instantaneous availability and mission effectiveness of individual satellites. The capability measure yields a continuous score between zero and one accounting for the degree to which the constellation meets operational requirements. The measure is computed from an average of satellite capabilities, composed of the product of the satellite's instantaneous availability and value score. Instantaneous availability is acquired by modeling the satellite degradation status as either a time-homogenous, continuous-time Markov chain (CTMC) if it possesses functions with exponential lifetime distributions, or as a time-homogenous, semi-Markov …
An Investigation Of The Effects Of Correlation And Autocorrelation In Classifier Fusion With Non-Declarations, Frank M. Mindrup
An Investigation Of The Effects Of Correlation And Autocorrelation In Classifier Fusion With Non-Declarations, Frank M. Mindrup
Theses and Dissertations
Air Force doctrine requires reliable and accurate information when striking targets. Further, this doctrine states that fusion should be utilized whenever possible to ensure the best possible information is conveyed; there is no specific guidance as to how to fuse this information. This thesis extends the research found in Leap, Bauer, and Oxley (2004) to include a non-declared class. The Identification system operating characteristic (ISOC) was adapted to allow for non-declarations both at the individual sensor level as well as the fused output level. A probabilistic neural network (PNN) was also used as a fusion technique. A cost function was …
Selection And Application Of Distorted Risk Measures, Edwin J. Offutt
Selection And Application Of Distorted Risk Measures, Edwin J. Offutt
Theses and Dissertations
This thesis develops and illustrates a methodology for the selection of probability distributions and distortion functions associated with risk scenarios resulting from military capability shortfalls. Distorted (or transformed) risk measures are analyzed and applied to account for loss scenarios that may occur with low frequency but result in catastrophic outcomes. After reviewing the rudimentary concepts of distortion, four well-known continuous distributions, suitable for modeling risk scenarios, are chosen using defined criteria. Based on subject matter expert inputs, a simple method for assigning exactly one of the four distributions to any risk scenario is proposed. Four parametric distortion functions from the …
Optimal Sampling Of A Chemical Hazard Area, Jennifer R. Plourde
Optimal Sampling Of A Chemical Hazard Area, Jennifer R. Plourde
Theses and Dissertations
This thesis proposes a methodology for optimally sampling a chemical hazard area subsequent to a chemical weapons attack. The objective is to identify the maximum number of areas that no longer require protective gear for safe operations. We model the area as an undirected graph and employ network analysis techniques to provide a methodological framework for identifying an optimal sampling sequence within a fixed time limit. We propose four models that characterize the secondary vapor concentrations: i) static and deterministic, ii) static and stochastic, iii) dynamic and deterministic, and iv) dynamic and stochastic. Comparisons of the static cases and their …
Strategic Airlift En Route Analysis And Considerations To Support The Global War On Terrorism, Michael C. Sere
Strategic Airlift En Route Analysis And Considerations To Support The Global War On Terrorism, Michael C. Sere
Theses and Dissertations
The Global War on Terrorism has mandated the need for additional global en route airfields. En route airfields consist of bases that are strategically located at intermediate locations between the Continental United States and the intended theater of operations. These airfields serve as refueling, crew staging, or maintenance stops for strategic airlift aircraft flying transoceanic routes. The focus of this study is to examine concepts to meet this need and to address important aspects that should be considered in devising new en route strategies. Based on various important factors associated with potential en route airfields, a goal programming methodology was …
An Evaluation Of Wind Turbine Technology At Peterson Afb, Randy C. Combs
An Evaluation Of Wind Turbine Technology At Peterson Afb, Randy C. Combs
Theses and Dissertations
Wind energy technology is a viable source for attaining the emission reduction and renewable energy use goals set forth by the executive office. In accordance with Executive Orders, the Air Force must reduce greenhouse emissions and energy consumption, and expand the use of renewable energy sources within its facilities nation-wide by year 2010. This mandate requires that the Air Force look at alternative electrical production and rely more on such renewable energy resources as wind power. The specific problem addressed by this research is whether on-site wind energy generation can be more economically feasible than the conventional energy consumption at …
A Qualitative Study Of Industry And Air Force Commodity Council Processes, Robert J. Irvine
A Qualitative Study Of Industry And Air Force Commodity Council Processes, Robert J. Irvine
Theses and Dissertations
The purpose of this research was to compare industry and Air Force commodity council processes. More specifically, this research used a survey to gather strategic sourcing philosophies and procedures (with respect to small business participation in procurement strategies) from successful industry firms. Industry source selection documentation, applicable government contracting guidelines, and a literature review of strategic sourcing materials were also reviewed. The current Air Force commodity council process and associated historical documents were then studied using a business process modeling tool. It was determined that the Air Force process differs from industry in how small business participation is addressed, the …
An Analysis Into The Effectiveness Of Aircraft Maintenance Under The Combat Wing Structure, Derrick R. Barthol
An Analysis Into The Effectiveness Of Aircraft Maintenance Under The Combat Wing Structure, Derrick R. Barthol
Theses and Dissertations
Organizational structure builds the foundation from which organizations operate. To gain full potential of structural efficiencies in the current operating environment, public and private firms are continually modifying their organizational structure. The U.S. Air Force is no different and underwent its most recent reorganization in the fall of 2002 replacing the post-Gulf War format of the previous decade. Air Force leadership needs to understand how well the current structure is performing at achieving its intended objectives. This research investigates the effectiveness of the recent change to Air Force organizational structure on aircraft maintenance performance through an analysis of aircraft maintenance …
An Approach For Optimizing The On-Orbit Servicing Architecture For The Space-Based Radar Constellation, Michael L. Mcconnell
An Approach For Optimizing The On-Orbit Servicing Architecture For The Space-Based Radar Constellation, Michael L. Mcconnell
Theses and Dissertations
Satellite systems, once operational, are essentially a consumable item with no capacity to maintain, repair, or upgrade them while on-orbit. In order to avoid having to replace costly space assets, the Defense Advanced Research Projects Agency (DARPA) and Air Force Space Command (AFSPC) are looking to developing programs to provide an on-orbit servicing capability for future satellite systems under development, such as the Space-Based Radar (SBR) system. DARPA and AFSPC are studying on-orbit servicing using the Orbital Express platform as part of an Analysis of Alternatives for the SBR program. Like their satellite clients, on-orbit servicing assets are expected to …
Barriers To Electronic Records Management (Erm): An Exploratory Case Study Investigating Erm In The Deployed Environment During Operations Enduring Freedom And Iraqi Freedom, Brian G. Hobbs
Theses and Dissertations
Corporate and government organizations can use electronic records as an important strategic resource, if the records are managed properly. In addition to meeting legal requirements, electronic records can play a vital role in the management and operation of an organization's activities. Corporate America is facing challenges in managing electronic records, and so too is the U.S. Air Force (USAF). The deployed environment is particularly problematic for electronic records management (ERM). This research, thus, investigates ERM in the deployed environment to identify and characterize the barriers faced by USAF personnel who deployed to locations supporting Operations Enduring Freedom and Iraqi Freedom. …
Tensile Stress Rupture Behavior Of A Woven Ceramic Matrix Composite In Humid Environments At Intermediate Temperature, Kevin J. Larochelle
Tensile Stress Rupture Behavior Of A Woven Ceramic Matrix Composite In Humid Environments At Intermediate Temperature, Kevin J. Larochelle
Theses and Dissertations
Stress rupture tests on the SylramicTM fiber with an in-situ layer of boron nitride, boron nitride interphase, and SiC matrix ceramic matrix composite were performed at 550°C and 750°C with 0.0, 0.2, or 0.6 atm partial pressure of water vapor, pH2O. The 550°C, 100-hr strengths were 75%, 65% and 51% of the monotonic room temperature tensile strength, respectively. At 750°C, the strengths were 67%, 51%, and 49%, respectively. Field Emission Scanning Electron Microscopy analysis estimated the total embrittlement times for 550°C with 0.0, 0.2, and 0.6 atm pH2O were >63 hrs, >38 hrs, and between …
Pulse Detonation Engine Thrust Tube Heat Exchanger For Flash Vaporization And Supercritical Heating Of Jp-8, Christen L. Miser
Pulse Detonation Engine Thrust Tube Heat Exchanger For Flash Vaporization And Supercritical Heating Of Jp-8, Christen L. Miser
Theses and Dissertations
Research has shown that performance of liquid hydrocarbon fueled pulse detonation engines is limited by the time required to evaporate liquid fuel droplets within the mixture. Vaporization of liquid fuels prior to injection has been shown to decrease ignition times and also increases fuel efficiency; however, the size and efficiency of the vaporization system used are not feasible for use in future pulse detonation aircraft concepts. The purpose of this research is to harness the waste heat of pulse detonation engine thrust tubes to generate a steady-state, self-sustained flash vaporization and supercritical heating system using JP-8 as the working fluid …
Computational Model Of One-Dimensional Dielectric Barrier Discharges, Krista G. Marchand
Computational Model Of One-Dimensional Dielectric Barrier Discharges, Krista G. Marchand
Theses and Dissertations
As theory lags experiment for dielectric barrier discharge flow control, two different computational methods are implemented to give further insight into characteristics of the dielectric barrier discharge (DBD). A one-dimensional fluid model of a surface-type dielectric barrier discharge is created using He as the background gas. This simple model, which only considers ionizing collisions and recombination in the electropositive gas, creates an important framework for future studies into the origin of experimentally observed flow-control effects of the DBD. The two methods employed in this study include the semi-implicit sequential algorithm and the fully implicit simultaneous algorithm. The first involves consecutive …
Development Of 2-Dimensional Cloud Rise Model To Analyze Initial Nuclear Cloud Rise, Karson A. Sandman
Development Of 2-Dimensional Cloud Rise Model To Analyze Initial Nuclear Cloud Rise, Karson A. Sandman
Theses and Dissertations
The objective of this research is to create a two-dimensional cloud rise model that could be used instead of the current one-dimensional cloud rise model in the Defense Land Fallout Intepretive Code (DELFIC) option of the Hazard Prediction and Assessment Capability (HPAC). The model includes numerical analysis of partial differential equations involving pressure, potential temperature, horizontal and vertical winds, and specific humidity. The 2-D model developed provides a much more detailed definition of the physical properties within the mushroom cloud than the 1-D DELFIC option. This is particularly useful in fallout studies on particle formation, fractionation, and particle location within …
Development Of A Higher-Order Upwind Algorithm For Compressible Fluid Flow, Barry A. Croker
Development Of A Higher-Order Upwind Algorithm For Compressible Fluid Flow, Barry A. Croker
Theses and Dissertations
A global fourth-order solution method that incorporates compact differencing with Roe's approximate Riemann solver was investigated. This method was incorporated into a one-dimensional numerical simulation of the compressible Euler equations, and applied to a one-dimensional shock tube problem. The method was also extended to two dimensions, and applied to a two-dimensional shock tube problem and an advecting vortical structure problem on both rectilinear and curvilinear meshes. The results were compared to a third-order Roe scheme and a fourth-order compact difference scheme. An order of accuracy determination showed that it has an order of accuracy somewhere near fourth order, with absolute …
A Study In Drag Reduction Of Close Formation Flight Accounting For Flight Control Trim Positions And Dissimilar Formations, Michael T. Morgan
A Study In Drag Reduction Of Close Formation Flight Accounting For Flight Control Trim Positions And Dissimilar Formations, Michael T. Morgan
Theses and Dissertations
This thesis further defines the position of greatest fuel savings benefit for the trail aircraft flying in a two-ship formation. The HASC95 vortex lattice code was used for the examination. Investigations of a similar formation of F-16 aircraft and a dissimilar formation of a lead KC-135 aircraft and a trail F-16 aircraft were conducted. The analyses determined the effects of varying airspeed on the optimal position. In addition, flight control surface deflections were taken into account during the analyses. Both investigations trimmed the aircraft in the yaw and roll axes to determine the optimal savings. The similar analysis was conducted …
Full Capability Formation Flight Control, Ryan K. Osteroos
Full Capability Formation Flight Control, Ryan K. Osteroos
Theses and Dissertations
The subject of automatic formation flight control is of current interest to the development of Unmanned Aerial Vehicles (UAV). Previous control approaches have been refined in this work to allow more robust maneuvering and to include a fourth control parameter. The equations of motion for each aircraft as a point mass, expressed in a wind-axis coordinate system, are coupled into differential equations that model the two aircraft system dynamics. Control laws are developed that include proportional and integral action. Gains are determined based on formation performance. Lead maneuvers are simulated and the controller is gauged on its ability to maintain …
Parachute Extraction Of A Generic Store From A C-130; A Cfd Proof Of Concept, Stephen C. Platt
Parachute Extraction Of A Generic Store From A C-130; A Cfd Proof Of Concept, Stephen C. Platt
Theses and Dissertations
This thesis encompasses a feasibility analysis of a parachute extracted generic precision guided munition from the cargo bay of a C-130 aircraft in flight. This analysis utilizes the USAF Beggar code and incorporates full physics effects as well as aerodynamic loading assuming an inviscid aircraft and viscous store for a time-accurate solution. Both an immediate and time varying application of the parachute force are utilized as well as two different ordnance body styles at zero and 5 degrees AOA with the store placed on centerline and offset in the cargo bay. The time accurate parachute model is based on empirical …
An Investigation Of A Simplified Gouging Model, Gregory S. Rickerd
An Investigation Of A Simplified Gouging Model, Gregory S. Rickerd
Theses and Dissertations
Gouging is a type of structural failure that becomes important when two metals slide against each other at velocities in the range of 1.5 kilometers per second. A computer model has previously been used to model the development of gouging at the Holloman High Speed Test Track. This model has not been experimentally verified to be correct, due to the complexity of the model. This research develops a simplified model that can be experimentally verified. The computer program utilized in this research was studied to determine the most appropriate options to use in simulations. This was accomplished by modeling a …
Controlling Sideslip Angle To Reduce The Radar Exposure Of A Tactical, Rotary Winged Uav, Jonathan D. Bulseco
Controlling Sideslip Angle To Reduce The Radar Exposure Of A Tactical, Rotary Winged Uav, Jonathan D. Bulseco
Theses and Dissertations
This work investigates another way of contributing to the radar minimization solution for air vehicles in a threat environment. While much research has been conducted on structural solutions to radar exposure minimization, not much work has been done in the area of using control to continuously assess and present the smallest radar cross section of an air vehicle to oncoming threat radar systems by changing the aircraft's orientation. This work looks at the application of sideslip/beta angle feedback control of an unmanned helicopter to minimize radar cross section exposure in a hostile radar environment. A new way of controlling aircraft …