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2011

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Articles 3031 - 3060 of 5806

Full-Text Articles in Engineering

A Simulation Of The Ecss Help Desk With The Erlang A Model, Michael E. Chua Mar 2011

A Simulation Of The Ecss Help Desk With The Erlang A Model, Michael E. Chua

Theses and Dissertations

During steady states, the Level 1 help desk might expect about 500 to 600 calls per month. That is about 0.39 to 0.46 calls per user per month, which represents the workload once ECSS is established and most of the users have already received training for the system. The optimal level for this workload is about 12 agents to operate the entire 24 hour period. At this level, the Level 1 help desk would minimize the amount of customers that renege from the system to about 15 to 22 percent and still maintain acceptable utilization percentages of about 52% to …

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Tailoring The Statistical Experimental Design Process For Lvc Experiments, Casey L. Haase Mar 2011

Tailoring The Statistical Experimental Design Process For Lvc Experiments, Casey L. Haase

Theses and Dissertations

The use of Live, Virtual and Constructive (LVC) Simulation environments are increasingly being examined for potential analytical use particularly in test and evaluation. The LVC simulation environments provide a mechanism for conducting joint mission testing and system of systems testing when scale and resource limitations prevent the accumulation of the necessary density and diversity of assets required for these complex and comprehensive tests. The statistical experimental design process is re-examined for potential application to LVC experiments and several additional considerations are identified to augment the experimental design process for use with LVC. This augmented statistical experimental design process is demonstrated …

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Determining Pilot Manning For Bomber Longevity, Jason S. Hamilton Mar 2011

Determining Pilot Manning For Bomber Longevity, Jason S. Hamilton

Theses and Dissertations

In support of US Air Force efforts to conserve resources without sacrificing capability, this research examines the question of whether the 509th Bomb Wing could continue to provide maximum combat capability with fewer assigned pilots. During peacetime, pilot proficiency training comprises the majority of annual flying hours for the small B-2 bomber fleet. Optimal pilot manning will decrease the accumulation of excess wear on the airframes; helping to extend the viable life of the B-2 fleet and preserve the deterrent and combat capabilities that it provides to the United States. The operations and maintenance activity flows for B-2 aircraft and …

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A Methodology Using Simulation Results For Test And Evaluation, Jonathon S. Hosket Mar 2011

A Methodology Using Simulation Results For Test And Evaluation, Jonathon S. Hosket

Theses and Dissertations

Each year the Air Force spends billions of dollars on Test and Evaluation to ensure acquisition programs roll out the best possible products. In 1997, the National Research Council assembled to evaluate the overall procedure used in procuring various platforms with system planning, research, development and engineering (SPRDE) and program management (PM) processes. In their final report, they claimed that the full advantages of statistical practices, simulation, model-test-models, and incorporation of prior test information into current test practices have not been fully utilized. To examine one of the report's recommendations, this thesis defines and explores a methodology using simulation to …

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Optimal Ch-47 And C-130 Workload Balance, Dustin P. Jones Mar 2011

Optimal Ch-47 And C-130 Workload Balance, Dustin P. Jones

Theses and Dissertations

The Air Force can save thousands of dollars by reducing the number of blade hours on the CH-47 through finding an optimal mixture of CH-47s and C-130s to conduct current operations in Afghanistan and Iraq. Ultimately these savings will relieve maintenance operations for the CH-47 and lengthen the lifespan of the CH-47 airframe. Moreover, incorporating C-130s into the operations will reduce cargo transit time from supply depots. This study looks at the involvement of the C-130 in CH-47 airlift operations to reduce CH-47 usage and increase supply efficiency. The research focus is narrowed to current airlift operations in Afghanistan and …

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Measure Of Effectiveness For Jstars Ground Moving Target Indicator: A Value Focused Thinking Approach, Gardner J. Joyner Mar 2011

Measure Of Effectiveness For Jstars Ground Moving Target Indicator: A Value Focused Thinking Approach, Gardner J. Joyner

Theses and Dissertations

As the nature of warfare has shifted from a conventional approach to more guerilla type warfare, intelligence has become more important than at any other time in the history of the United States Military. With the stochastic nature of intelligence gathering, it is almost impossible to know with any degree of certainty where and when the next piece of information that could possibly change the course of the battle or war will be obtained. US intelligence gathering assets have long been plagued with using useless measures of performance rather than measures of effectiveness to determine their worth. This research uses …

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Multi Criteria Decision Support Model For The Turkish Air Force Personnel Course/Education Planning System, Cem Malyemez Mar 2011

Multi Criteria Decision Support Model For The Turkish Air Force Personnel Course/Education Planning System, Cem Malyemez

Theses and Dissertations

Many personnel are assigned to different courses and educational opportunities in the Turkish Air Force every year. This daunting process requires a great deal of time and does not currently seek to find an optimal solution. The Turkish Air Force has a database for all personnel information, but the officials use just a few quantitative personnel data points to complete their tasks. Moreover, the matching process is done by hand. Therefore there is a need for a model, which supports the Decision Makers, to cover the some of the other quantitative data points and also add some qualitative data for …

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Weighted Key Player Problem For Social Network Analysis, Ryan M. Mcguire Mar 2011

Weighted Key Player Problem For Social Network Analysis, Ryan M. Mcguire

Theses and Dissertations

Social network analysis is a tool set whose uses range from measuring the impact of marketing campaigns to disrupting clandestine terrorist organizations. Social network analysis tools are primarily focused on the structure of relationships between actors in the network. However, characteristics of the actors, such as importance or status, are generally the output of the social network analysis rather than an input. Characteristics of actors can come from a number of sources to include information gathering, subject matter experts or social network analysis. Further, the strength of relationships between actors in social networks are often assumed to be all equal. …

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Contextual Detection Of Anomalies In Hyperspectral Images, Adam J. Messer Mar 2011

Contextual Detection Of Anomalies In Hyperspectral Images, Adam J. Messer

Theses and Dissertations

The majority of anomaly detectors in Hyperspectral Imaging use only the statistical aspects of the spectral readings in the image. These detectors fail to use the spatial context that is contained in the images. The use of this information can yield detectors that out perform their spatially myopic counterparts. To demonstrate this, we will use an independent component analysis based detector, autonomous global anomaly detector (AutoGAD), developed at AFIT augmented to account for the spatial context of the detected anomalies. Through the use of segmentation algorithms, the anomalies identified are formed into regions. The size and shape of these regions …

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Application Of Post Modern Portfolio Theory To Mitigate Risk In International Shipping, Michael R. Quashne Mar 2011

Application Of Post Modern Portfolio Theory To Mitigate Risk In International Shipping, Michael R. Quashne

Theses and Dissertations

This research uses asset allocation concepts to determine the correct amount of cargo to send down the PAKGLOC and NDN to minimize the risk of loss or damage. Loss and Damage data is used from Transportation Discrepancy Reports and overall value is assumed to match the industry standard. Using assumed levels of pilferage along the NDN, a Monte Carlo simulation is run at each level of pilferage, and a Co-Lower Partial Moment model is solved. Analysis of the data shows a wide spread of possible optimal solutions at each level of pilferage. Due to the low levels of risk along …

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Empirical Characterization Of Ballistic Impact Flash, Thomas P. Talafuse Mar 2011

Empirical Characterization Of Ballistic Impact Flash, Thomas P. Talafuse

Theses and Dissertations

Fires onboard aircraft are leading mechanisms for mishaps and losses during peacetime and combat operations. Typical ignition sources causing fires onboard aircraft include electrical sparks and hot surfaces. However, impact and penetration of common threats encountered during combat operations, such as armor piercing incendiary projectiles and missile fragments, generate short-lived, but thermally-intense clouds (flashes) capable of igniting fires. Fire simulations supporting system-level survivability analyses depend on accurate characterization of these flash clouds, however, such accurate representations are not currently available. This research presents the modeling approach developed to estimate the boundary model representations of impact flashes. The research presents generalized …

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Migration Issues In The Democratic Republic Of Congo, Michael J. Thompson Mar 2011

Migration Issues In The Democratic Republic Of Congo, Michael J. Thompson

Theses and Dissertations

Since the end of the Cold War, the number of weak and failing states has increased significantly. The United States (US) military has been deployed in multiple nation states in an effort to prevent these weak states from collapsing into chaos. This thesis explores one of the driving factors of state collapse, net migration, to gauge how US foreign policy might be employed to reduce the flow of people out of a country. To demonstrate the foreign policies and their effects, a pilot model was constructed using a system dynamics methodology. The Democratic Republic of Congo (DRC) was selected as …

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Depot-Level Simulation And Multivariate Analysis On B-1 High Velocity Maintenance, Florence K. Yee Mar 2011

Depot-Level Simulation And Multivariate Analysis On B-1 High Velocity Maintenance, Florence K. Yee

Theses and Dissertations

The objective of this thesis is to gain insights on the B-1B depot maintenance operations, with a focus on direct maintenance hours or burn rate, under the implementation of High Velocity Maintenance (HVM). Based on historical depot maintenance data and the current B-1 depot HVM prototype data, a discrete-event simulation model is developed using Arena 12.0. Some United States Air Force supply chain influences, such as manning levels and kitting characteristics of the B-1 depot operations, are incorporated in our models as design factors. The model captures the stochastic nature of 30 HVM tasks performed on one B-1 aircraft in …

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Understanding Schedule Forecasting Shortfalls In Federal Design-Build Facility Procurement, Timothy W. Gannon Mar 2011

Understanding Schedule Forecasting Shortfalls In Federal Design-Build Facility Procurement, Timothy W. Gannon

Theses and Dissertations

This research explores whether initial schedules provide reliable forecasting for project control in federal design build facility procurement. The purpose of this research is to understand how scheduling operates in the Department of Defense environment and identify how project change underscores schedule uncertainty. The research methodology involves a comparative analysis of project schedule data from three case studies. The investigation documents how initial project schedules fail to sufficiently forecast and provide a reliable baseline for total cost, final duration, and activity count for three design-build projects. Most schedule variability occurs after the 100% design benchmark. Furthermore, activity growth highlights the …

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A Century Long Pursuit Of Alternative Fuels And Feedstocks: A Content Analysis, Elias J. Halvorson Mar 2011

A Century Long Pursuit Of Alternative Fuels And Feedstocks: A Content Analysis, Elias J. Halvorson

Theses and Dissertations

he United States has dramatically increased its production of alternative fuels over the past seven years. With the passing of the Energy Independence and Security Act of 2007 (EISA), alternative fuel production will increase in the United States over 700% from 2005 levels. However, the pursuit of petroleum alternatives is not a recent trend. Over the last 100 years, various nations have pursued petroleum alternatives with varying levels of success. This research focuses on the historical development of 10 leading alternative fuels and feedstocks. Through a thorough literature review we will identify commonalities among these fuels and feedstocks which have …

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Application Of Relational Contracting Methods To Federal Construction Projects, Travis R. Johnson Mar 2011

Application Of Relational Contracting Methods To Federal Construction Projects, Travis R. Johnson

Theses and Dissertations

Relational contracting is a method designed to improve relationships between contracted parties. The federal construction sector was a leader in the development and implementation of an early form of relational contracting known as partnering. Since then, alliancing has emerged as the new evolution of relational contracts. While it provides many potential benefits to contracting parties, alliancing has not yet been utilized in federal construction procurement, which is subject to stringent regulations. A commercially available standard form alliancing contract was selected for analysis against the Federal Acquisition Regulation. Key practices that characterize the alliancing method were identified. Utilizing a panel of …

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Composite Aircraft Life Cycle Cost Estimating Model, Daniel B. Lambert Mar 2011

Composite Aircraft Life Cycle Cost Estimating Model, Daniel B. Lambert

Theses and Dissertations

Composite materials are beginning to comprise a greater percentage of structural materials used throughout aircraft production. The increased usage of composites has led individuals within the Air Force community to revisit aircraft life cycle cost, LCC, models. A series of affordability initiatives has culminated in significant evidence over the last decade to better quantify the impact of primarily composite structures in aircraft. The Advanced Composite Cargo Aircraft, ACCA, a research effort sponsored by the Air Force Research Lab, attempted to determine the impact of part size and large scale composite components on LCC for cargo aircraft. This research evaluates the …

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Modeling Enhanced Storage Of Groundwater Contaminants Due To The Presence Of Cracks In Low Permeability Zones Underlying Contaminant Source Areas, Jeremy M. Miniter Mar 2011

Modeling Enhanced Storage Of Groundwater Contaminants Due To The Presence Of Cracks In Low Permeability Zones Underlying Contaminant Source Areas, Jeremy M. Miniter

Theses and Dissertations

Throughout DoD, chlorinated aliphatic hydrocarbons (CAHs), a type of Dense Non-Aqueous Phase Liquid (DNAPL), have been frequently used. In the subsurface, spilled DNAPLs may pool atop low permeability clay layers. In this study a numerical model is constructed using the Groundwater Modeling System to assess how cracks in the clay, either pre-existing or the result of DNAPL-clay interactions, might impact a dissolved CAH plume generated by the DNAPL source. The conceptual model posits a DNAPL source in a high permeability sand aquifer sitting atop a low permeability clay layer. The model assumes dissolved CAH generated by the DNAPL is transported …

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A Primary Care Workload Production Model For Estimating Relative Value Unit Output, Rachel G. Murphy Mar 2011

A Primary Care Workload Production Model For Estimating Relative Value Unit Output, Rachel G. Murphy

Theses and Dissertations

Health care costs have grown to unsustainable levels nationally and within the Department of Defense. Military health care costs have historically been difficult to isolate, causing budget cuts to be the vehicle for cost control. Maximum efficiency, therefore, is the goal in order to show improvement. With the Air Force’s new preventive health plan, they aim to drive a long-term posture for cost reduction through prevention. This research effort aimed to develop a tool to assist in future efforts to understand and improve efficiency in workload output, and whether a relationship exists between patient workload demand and the per-encounter variables …

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Degradation Modeling Of Polyurea Pavement Markings, Jonathan D. Needham Mar 2011

Degradation Modeling Of Polyurea Pavement Markings, Jonathan D. Needham

Theses and Dissertations

Polyurea is a long life pavement marking material used for assets requiring long periods of uninterrupted accessibility. Knowing the performance characteristics of such markings is critical to asset management planning focused on maximizing marking material life-cycles. This paper presents the performance characteristics of polyurea pavement markings in North Carolina using linear regression models. The models generated by this research provide pavement marking managers with tools to better allocate limited manpower and resources in order to optimize budgets while meeting newly proposed pavement marking retroreflectivity levels of service as proposed by the Federal Highway Administration. This research constructed performance models for …

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Measuring The Utility Of A Cyber Incident Mission Impact Assessment (Cimia) Process For Mission Assurance, Christy L. Peterson Mar 2011

Measuring The Utility Of A Cyber Incident Mission Impact Assessment (Cimia) Process For Mission Assurance, Christy L. Peterson

Theses and Dissertations

Information is a critical asset on which virtually all modern organizations depend upon to meet their operational mission objectives. Military organizations, in particular, have embedded Information and Communications Technologies (ICT) into their core mission processes as a means to increase their operational efficiency, exploit automation, improve decision quality, and shorten the kill chain. However, the extreme dependence upon ICT results in an environment where a cyber incident can result in severe mission degradation, or possibly failure, with catastrophic consequences to life, limb, and property. These consequences can be minimized by maintaining real-time situational awareness of mission critical resources so appropriate …

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Modeling Vertical Flow Treatment Wetland Hydraulics To Optimize Treatment Efficiency, David T. Roen Ii Mar 2011

Modeling Vertical Flow Treatment Wetland Hydraulics To Optimize Treatment Efficiency, David T. Roen Ii

Theses and Dissertations

An upward Vertical Flow Treatment Wetland (uVFTW) at Wright Patterson AFB designed to bioremediate contaminated groundwater exhibits hydraulic short-circuiting. Prior studies estimated that groundwater flowed through less than 50% of the wetland’s volume, and that the mean residence time was significantly less than the nominal residence time, which was calculated assuming flow through the entire wetland volume. The objective of this research was to investigate how uVFTW hydraulics affects treatment efficiency, and to propose design strategies to maximize treatment efficiency. A groundwater flow and contaminant transport model of a uVFTW that couples hydraulics and degradation kinetics was built and applied …

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Retrospective Geospatial Modeling Of Pm10 Exposures From Open Burning At Joint Base Balad, Iraq, John P. Rinker Mar 2011

Retrospective Geospatial Modeling Of Pm10 Exposures From Open Burning At Joint Base Balad, Iraq, John P. Rinker

Theses and Dissertations

Predicting, determining, and linking theater-related source-specific exposures to health effects has proven difficult. The purpose of this research is to delineate retrospective exposure zones using spatially interpolated particulate air sampling point data from Joint Base Balad, create burn pit exposure isopleths from dispersion model outputs, and merge into a combined exposure model in GIS. Interpolated monitoring results and dispersion modeled results were combined to compare modeled exposures across base. Burn pit contribution to total PM10 was also modeled. The combined dispersion and interpolation map showed elevated concentrations within a 1 kilometer buffer of the burn pit. Buildings within this area …

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Improving The Relevance Of Cyber Incident Notification For Mission Assurance, Stephen M. Woskov Mar 2011

Improving The Relevance Of Cyber Incident Notification For Mission Assurance, Stephen M. Woskov

Theses and Dissertations

Military organizations have embedded Information and Communication Technology (ICT) into their core mission processes as a means to increase operational efficiency, improve decision making quality, and shorten the kill chain. This dependence can place the mission at risk when the loss, corruption, or degradation of the confidentiality, integrity, and/or availability of a critical information resource occurs. Since the accuracy, conciseness, and timeliness of the information used in decision making processes dramatically impacts the quality of command decisions, and hence, the operational mission outcome; the recognition, quantification, and documentation of critical mission-information resource dependencies is essential for the organization to gain …

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Characterization Of Graphite Composite Material Particulates From Usaf Aircraft Maintenance Operations, Richard E. Yon Mar 2011

Characterization Of Graphite Composite Material Particulates From Usaf Aircraft Maintenance Operations, Richard E. Yon

Theses and Dissertations

Due to the benefits of their material properties, advanced composite materials (ACM) are increasingly being used as structural components on aircraft, especially within the United States Air Force. As a result, the potential exists for occupational exposures to structural maintenance employees while repairing and fabricating aircraft components. Two field studies were conducted for this thesis in order to characterize ACM aerosol size distribution, determine the feasibility of utilizing direct reading instruments (DRIs) in the field, and ensure workers are protected with adequate controls. In order to characterize exposure, traditional integrated air sampling and DRIs were positioned together near an ACM …

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Application And Validation Of Concept Maturity Assessment Framework, Mathews C. Scharch, Jeremy J. Homan Mar 2011

Application And Validation Of Concept Maturity Assessment Framework, Mathews C. Scharch, Jeremy J. Homan

Theses and Dissertations

Far too often decision makers select concepts based on insufficient data, resulting in projects that are over-budget, over-schedule, and not what the customer wants. Research efforts have proposed a stage-gated concept maturity framework as a tool to assess and increase the maturity of concepts. This research uses multiple validation techniques to demonstrate the value this framework can provide. Interviews with acquisition professionals capture qualitative and quantitative data on the utility of the elements of the framework and the acquisition process. This research also applies the framework to a current acquisition program to determine if it can be broadly applied for …

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Analysis Of Flow Migration In An Ultra-Compact Combustor, Brian T. Bohan Mar 2011

Analysis Of Flow Migration In An Ultra-Compact Combustor, Brian T. Bohan

Theses and Dissertations

One of the major efforts for turbine engine research is to improve the thrust to weight of the system. One novel concept for accomplishing this is the use of an Ultra-Compact Combustor (UCC). The UCC attempts to shorten the overall combustion length (thereby reducing weight) by performing the combustion in the circumferential direction along the outside diameter of the core flowpath. One of the major benefits of this design is enhanced combustion due to the establishment of a high-g field in the circumferential cavity. AFIT and the Air Force Research Laboratory (AFRL) have been teamed for several years in understanding …

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Creep Performance Of Oxide Ceramic Fiber Materials At Elevated Temperature In Air And In Steam, Clinton J. Armani Mar 2011

Creep Performance Of Oxide Ceramic Fiber Materials At Elevated Temperature In Air And In Steam, Clinton J. Armani

Theses and Dissertations

The effects of steam on the creep performance for several ceramic materials were investigated at temperatures in the 1100-1300 deg. C range. Experimental programs were designed to explore both tensile and compressive creep behaviors as well as the response in monotonic tension. Subcritical crack growth was determined to be the dominant failure mechanism in ceramic fibers at elevated temperatures in steam. The creep life prediction analysis of ceramic fiber tows was performed using linear elastic fracture mechanics and a power-law crack velocity model. Additionally, the effects of steam at 1300 deg. C on creep performance of high-purity polycrystalline yttrium aluminum …

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Time Resolved Filtered Rayleigh Scattering Measurement Of A Centrifugally Loaded Buoyant Jet, Firas Benhassen Mar 2011

Time Resolved Filtered Rayleigh Scattering Measurement Of A Centrifugally Loaded Buoyant Jet, Firas Benhassen

Theses and Dissertations

The combustion process within the Ultra-Compact Combustor (UCC) occurs in the circumferential direction. The presence of variable flow density within the circumferential cavity introduces significant buoyancy issues. On the other hand, G-loading caused by the presence of centrifugal forces, ensures the circulation of the flow in the circumferential cavity and enhances the completion of the combustion process before allowing the exit of the hot gases to the main flow. The coupling between buoyancy and high G-loading is what predominately influences the behavior of the flow within the UCC. In order to better understand the combustion process within the UCC, three …

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Airborne Wind Energy: Implementation And Design For The U.S. Air Force, Troy L. Cahoon Mar 2011

Airborne Wind Energy: Implementation And Design For The U.S. Air Force, Troy L. Cahoon

Theses and Dissertations

Excitement among researchers about Airborne Wind Energy (AWE) technology matches DoD aims to advance and employ renewable energy. AWE seeks to cost-effectively tap the vast supply of wind energy available at altitudes high above the reach of conventional, ground-based wind turbines (e.g. 500-12,000m). This paper explores viability and implementation of AWE technology for fulfilling USAF energy needs. Characteristics, potential, and developmental status of the AWE resource are presented. A design tool for a rotor-based AWE system is developed, facilitating the analysis of blade performance to simplify design and provide the best efficiencies for a range of conditions. USAF bases are …

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