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Articles 1 - 30 of 122
Full-Text Articles in Engineering
Network Security Versus Network Connectivity: A Framework For Addressing The Issues Facing The Air Force Medical Community, Franklin E. Cunningham Jr.
Network Security Versus Network Connectivity: A Framework For Addressing The Issues Facing The Air Force Medical Community, Franklin E. Cunningham Jr.
Theses and Dissertations
The Air Force has instituted Barrier Reef to protect its networks. The Air Force medical community operates network connections that are incompatible with Barrier Reef. To overcome this problem, OASD(HA) directed the Tri-Service Management Program Office (TIMPO) to develop an architecture that protects all military health systems and allows them to link with all three services and outside partners. This research studied the underlying networking issues and formed a framework based on data from network experts from the Air Force's medical centers and their base network organizations. The findings were compared TIMPO and a composite framework was developed that more …
Power, Performance, And Perception (P3): Integrating Usability Metrics And Technology Acceptance Determinants To Validate A New Model For Predicting System Usage, Alan P. Fiorello
Power, Performance, And Perception (P3): Integrating Usability Metrics And Technology Acceptance Determinants To Validate A New Model For Predicting System Usage, Alan P. Fiorello
Theses and Dissertations
Currently, there are two distinct approaches to assist information technology managers in the successful implementation of office automation software. The first approach resides within the field of usability engineering, while the second approach is derived from the discipline of management information systems (MIS). However, neither approach has successfully produced conclusive evidence that explains what characteristics facilitate system use as well as influence user acceptance of the system. This study reports on the validity of a new model, entitled the Power, Performance, Perception (P3) model, that links the constructs of usability engineering to user acceptance. Additionally, speech recognition software (SRS) was …
Effects Of Foreign Object Damage From Small Hard Particles On The High-Cycle Fatigue Life Of Ti-6a1-4v, Joseph L. Hamrick Ii
Effects Of Foreign Object Damage From Small Hard Particles On The High-Cycle Fatigue Life Of Ti-6a1-4v, Joseph L. Hamrick Ii
Theses and Dissertations
Thin rectangular samples of Ti-6Al-4V were damaged by four methods to represent foreign object damage found in turbine engine blades: 1) impact with 2 mm and 5 mm diameter glass spheres at 305 m/s, 2) impact with 2 mm and 4 mm diameter steel spheres at 305 m/s, 3) quasi-static displacement controlled indentation using steel chisels with 1 mm, 2 mm and 5 mm diameter tips and 4) shearing notches with a 2 mm diameter chisel point under a quasi-static loading condition. Finite element analysis was used to study the relationship between the stress state created by the plastic damage …
Reverse Engineering Of Foreign Missiles Via Genetic Algorithm, Jon D. Wollam
Reverse Engineering Of Foreign Missiles Via Genetic Algorithm, Jon D. Wollam
Theses and Dissertations
One mission of the National Air Intelligence Center (NAIC) is the reverse engineering of foreign missile weapon systems from incomplete observational data. In the past, intuition and repeated runs of a missile performance model were required to converge to a solution compatible with observed flight characteristics. This approach can be cumbersome and time consuming, as well as being subject to undesirable influences from the analyst's preconceptions and biases. An alternative approach has been created to apply genetic algorithm (GA) techniques to allow automation of the process, wider exploration of the design space, and more optimal solutions matching the observational data. …
Electrical And Optical Characterization Of Intrinsic And Ion-Implantation Induced Defects In 6h- And 4h-Sic, Michael B. Scott
Electrical And Optical Characterization Of Intrinsic And Ion-Implantation Induced Defects In 6h- And 4h-Sic, Michael B. Scott
Theses and Dissertations
Deep level transient spectroscopy (DLTS), Hall effect, and cathodolummescence (CL) measurements are used to characterize the intrinsic and ion-implantation induced defects in high-temperature (475 and 500 °C) ion-implanted epitaxial n-type 6H- and 4H-SiC, ion-implanted with Cr, Mg, Ar, N, and P atoms. Comparison of room-temperature and high-temperature ion-implanted 6H-SiC:Mg and :Cr indicate the significance of high-temperature ion implantation on the activation of the ion-implanted atoms and damage-recovery of the crystalline lattice. The effects of high-temperature annealing on both damage-recovery and implanted ion activation are detected and analyzed, from 1200 to 1800 °C. Trap parameters of both damage-related and species-related defects …
Defining Virtual Interactions: A Taxonomy For Researchers And Practitioners, Glade G. Oxborrow
Defining Virtual Interactions: A Taxonomy For Researchers And Practitioners, Glade G. Oxborrow
Theses and Dissertations
Many uses for virtual technology are being identified by diverse organizational entities around the world. Before these technologies can be fully utilized, it is important to have a common definition and understanding of what is meant by the term virtual. It is also important to understand the structural configurations possible using virtual technology and the types of virtual interactions that may occur using these technologies. This thesis will define the basic premises, structures, and definitions applicable to vial interactions. It also defines various types of virtual interactions that may occur using virtual technology. These designations will help both practitioners and …
Approximation And Optimization Of An Auditory Model For Realization In Vlsi Hardware, Samuel L. Sangregory
Approximation And Optimization Of An Auditory Model For Realization In Vlsi Hardware, Samuel L. Sangregory
Theses and Dissertations
The Auditory Image Model (AIM) is a software tool set developed to functionally model the role of the ear in the human hearing process. AIM includes detailed filter equations for the major functional portions of the ear. Currently, AIM is run on a workstation and requires 10 to 100 times real-time to process audio information and produce an auditory image. An all-digital approximation of the AIM which is suitable for implementation in very large scale integrated circuits is presented. This document details the mathematical models of AIM and the approximations and optimizations used to simplify the filtering and signal processing …
Cost-Benefit Analysis Of Leasing Versus Buying Air Force General Purpose Vehicles In The Continental United States, Robert J. Neal Jr.
Cost-Benefit Analysis Of Leasing Versus Buying Air Force General Purpose Vehicles In The Continental United States, Robert J. Neal Jr.
Theses and Dissertations
Given the increasingly aging vehicle fleet and declining vehicle budget, this research performed a cost-benefit analysis of leasing versus buying various Air Force general purpose vehicles for the entire continental United States (CONUS). In contrast to previous analyses, which have examined the leasing versus buying issue on a base-by-base basis, this analysis studies the issue from an Air Force-wide perspective using a cost-buying model. Costs and benefits are calculated for three purchasing options (Air Force ownership, GSA leasing, and commercial leasing) to determine and recommend the best alternative for the Air Force. Finally, a sensitivity analysis is to test the …
The Challenge Of Maintaining Or Replacing An Aging Airlift Fleet: A Cost/Capability Analysis For The Brazilian Air Force Mobility System, Julio C. Messias
The Challenge Of Maintaining Or Replacing An Aging Airlift Fleet: A Cost/Capability Analysis For The Brazilian Air Force Mobility System, Julio C. Messias
Theses and Dissertations
Despite the high Operational and Support costs incurred, the Brazilian Air Force's (BAF) declining budget has led to the establishment of conservative policies that favor short run solutions for a critical BAF airlift problem of operating an aging fleet. As a result of this policy, service life extensions of older airlift aircraft are the preferred solution. Using an equal airlift capacity approach to examine the Brazilian Air Force mobility system, this research performs a cost comparison analysis between two aircraft currently in operation at Brazilian's airlift command: C-130 Hercules and C-95 Bandeirante. To accomplish the cost analysis, this research develops …
An Ex Post Facto Analysis Of E-3 Maintenance Indicators In The 552d Air Control Wing Since Reorganization Under An Aircraft Generation Squadron Concept, Larry J. Stetz
Theses and Dissertations
Organizational restructuring sometimes occurs in the aircraft maintenance field, yet seldom are in-depth analyses performed after the fact to see if productivity improved. In December 1995, the 552D Air Control Wing restructured its flight line maintenance into an aircraft generation squadron concept. This study looked at before and after maintenance indicators to see if productivity improved. Maintenance data was collected from December 1993 to December 1997. Nineteen maintenance indicators were identified, and the key indicators were analyzed using means comparison and regression analysis to determine if efficiency and effectiveness had increased. The variables Mission Capable rate and Man-hours per Flying …
Space-Available Transportation: An Analysis Of The Cost Of Providing 'Free' Travel, Frank J. Long
Space-Available Transportation: An Analysis Of The Cost Of Providing 'Free' Travel, Frank J. Long
Theses and Dissertations
The purpose of this study is to estimate the costs borne by the government for providing space-available travel to eligible uniformed services personnel and their dependents. As the primary provider of the space-available privilege, it is important that the Air Force have an estimate of the burden that the administration of that privilege places on the budget. In January 1993, the Air Force discontinued its 15-year-old practice of charging a fee for space-available travel aboard AMC-owned or controlled aircraft. The fee had been set at $10 in 1978 and was collected to recover a portion of the costs associated with …
Operational Risk Management And Military Aviation Safety, Park D. Ashley
Operational Risk Management And Military Aviation Safety, Park D. Ashley
Theses and Dissertations
The Air Force Class A aviation mishap rate has hovered around 1.5 mishaps per 100,000 flight hours since 1985. Recent attention on Air Force accidents has caused the leadership to seek to reduce its mishap rate. The Army's Class A aviation mishap rate declined after it implemented risk management (RM) principles in 1987. This reduction caught the attention of Air Force leadership who have since stated that the application of operational risk management (ORM) is how the Air Force will reduce, even eliminate, mishaps. With current budget constraints, ORM is considered to be the most cost-effective way the Air Force …
An Exploratory Analysis Of The Responsiveness Capability Of The Air Expeditionary Wing (Aew) Concept, Robert L. Charlesworth
An Exploratory Analysis Of The Responsiveness Capability Of The Air Expeditionary Wing (Aew) Concept, Robert L. Charlesworth
Theses and Dissertations
Seven AEF deployments have been accomplished in the Southwest Asia area of responsibility; none have met the Air Force's stringent 72 hour criterion. This exploratory study quantifies the responsiveness capability of the AEW concept. Based on a Monte Carlo simulation methodology this study concludes that the on call AEW at Mountain Home AFB does not have the capability to meet the 72 hour criterion. Additionally, this study examined the effect of three departures from the baseline model on responsiveness capability. These departures included: increasing airlift throughput capacity, incorporating limited airlift failure, and employing an air refueling scenario. The simulation models …
Reparable Inventory Reduction: Impacts On Air Force Fighter Aicraft Mission Capability, Gregory E. Hutson
Reparable Inventory Reduction: Impacts On Air Force Fighter Aicraft Mission Capability, Gregory E. Hutson
Theses and Dissertations
During the 1990's the Air Force experienced severe declines in serviceable inventory levels and a rise in their TNMCS rates. Air Force predictions of TNMCS hours during this time period did not account for the upward trend in TNMCS rates. The Air Force uses a regression equation, consisting of possessed hours, flying hours, and sorties, to predict TNMCS hours. This research, through simple linear regression, found a significant relationship between serviceable inventory levels and TNMCS rates for 8 of the 10 aircraft studied. Using this relationship, serviceable inventory levels were then added to the Air Force equations and new multiple …
The Privatization Of The Aerospace Guidance And Metrology Center At Newark Air Force Base, Richard H. Fillman Jr.
The Privatization Of The Aerospace Guidance And Metrology Center At Newark Air Force Base, Richard H. Fillman Jr.
Theses and Dissertations
The Aerospace Guidance and Metrology Center (AGMC) at Newark AFB was privatized in place as a result of the 1993 BRAC process. This was a first of a kind for the DoD repair depot system. The justification was too much excess depot capacity and by closing Newark the Air Force would rid itself of this excess capacity and obtain savings by privatizing the repair workload. This thesis concentrates on whether excess capacity at AGMC was as large as it was identified and if cost saving had materialized at the depot since the privatization. To determine how well the depot repairs …
Professional Contracting Certification: An Examination And Model Development, Robert D. Lorton, Daniel I. Dunn
Professional Contracting Certification: An Examination And Model Development, Robert D. Lorton, Daniel I. Dunn
Theses and Dissertations
This study compared the elements of existing contracting certification programs to an ideal contracting certification model developed by experts. The expert panel responded to an open-ended electronic interview to convey their ideas regarding the individual elements for the model. Input received from the initial interviews was used to develop a survey for the panel members. The surveys were completed and results were recorded and conveyed back to the panel members. This process was repeated until a majority was reached on each individual element of the model, resulting in the ideal certification model. The final model contained elements of both the …
The Effect Of Action Workouts On Aircraft Mission Capability Measurements, Michael P. Allison
The Effect Of Action Workouts On Aircraft Mission Capability Measurements, Michael P. Allison
Theses and Dissertations
Previous studies concerning quality improvement and the Action Workout Process attempted to define and describe the difficult concept of quality. A logical next step is to study to what extent implementation of a quality improvement program, such as ACC's Action Workout Process, positively or negatively affects performance factors within an Air Force organization. This study focused on exploring the fundamental question of whether there was, as a result of the Action Workout, a noticeable, statistically verifiable, positive or negative change in the mission capability of aircraft assigned to the units carrying out this quality improvement initiative. Research questions were developed …
Comparison Of The Effects Of Eight-Hour And Twelve-Hour Shifts On Air Force Aircraft Maintenance Production Levels, David P. Collette
Comparison Of The Effects Of Eight-Hour And Twelve-Hour Shifts On Air Force Aircraft Maintenance Production Levels, David P. Collette
Theses and Dissertations
his is a follow-on study that examined the effects of converting a large aircraft maintenance squadron from 8-hour shifts to 12-hour shifts. The squadron studied converted its 24-hour maintenance work force from three 8-hour work shifts to two 12-hour work shifts. Data was collected from four different time periods. Three time periods were used for a primary analysis and all four time periods were used for trend analysis. To determine if the 12-hour work shift was effective, workforce productivity was measured during the different work shift periods. Results showed an increase in two productivity measurements, no-change in two productivity measurements, …
A Methodology For The Analysis And Prediction Of Air Force Enlisted Aircraft Maintenance Personnel Retention Rates Using Economic Statistics, Peter D. Lommen
A Methodology For The Analysis And Prediction Of Air Force Enlisted Aircraft Maintenance Personnel Retention Rates Using Economic Statistics, Peter D. Lommen
Theses and Dissertations
The purpose of this study is to investigate the effects of certain national economic indicators on enlisted aircraft maintenance personnel retention rates. To fulfill this purpose, this study builds a linear regression equation that can predict the retention rate using the civilian unemployment rate and the index of 11 leading economic indicators as the independent variables. Journal literature and economic texts were reviewed to identify the indicators as good predictors for changes in employee turnover. The method of linear regression was used to build the model needed to predict the changes in the retention rate. The equation developed with this …
Flow Separation Prevention On A Turbine Blade In Cascade At Low Reynolds Number, James P. Lake
Flow Separation Prevention On A Turbine Blade In Cascade At Low Reynolds Number, James P. Lake
Theses and Dissertations
The problem of flow separation from a low pressure turbine blade was investigated. The operating conditions under which the separation occurred were documented through measurement of surface pressure coefficients, boundary layer velocity and turbulence profiles, total pressure loss coefficient and wake velocity momentum deficit. Three different means for reducing the losses associated with the flow separation were also investigated. A boundary layer trip, dimples, and V-grooves were studied as passive means requiring no additional energy to reduce the separation losses. The boundary layer trip was only successful for an inlet and axial chord Reynolds number of 50k with a reduction …
Closely Supervised Reactive Control Of An Uninhabited Aerial Vehicle, Roy G. Glassco
Closely Supervised Reactive Control Of An Uninhabited Aerial Vehicle, Roy G. Glassco
Theses and Dissertations
Closely Supervised Reactive Control is an alternative control method for uninhabited aerial vehicles that incorporates some of the benefits of both manual and autonomous operations. Utilizing an onboard camera, an operator can control a UAV by manually choosing desired targets. The flight path of the uninhabited vehicle is determined autonomously from the camera gimbal angles. The operator of the payload (i.e. camera), has close supervision of the aircraft. The aircraft, using an onboard computer, is given autonomous control to alter flight path to fly towards a target and at a specified range, loiter over the target. In the basic mode …
Dual Channel Matched Filtering And Space-Time Adaptive Processing, Scott D. Berger
Dual Channel Matched Filtering And Space-Time Adaptive Processing, Scott D. Berger
Theses and Dissertations
We propose a dual channel matched filtering system that addresses two key challenges in the practical implementation of a single channel matched filtering system: secondary data support and computational cost. We demonstrated that the dual channel system requires half the secondary data to achieve nearly the same signal-to-interference plus noise ratio (SINR) as an equivalent single channel system. The key to the dual channel system is the block diagonalization of the interference plus noise correlation matrix with a fixed transformation. We investigated the application of this dual channel concept to the problem of space-time adaptive processing (STAP), referring to the …
Timed Safety Automata And Logic Conformance, Frank C. D. Young
Timed Safety Automata And Logic Conformance, Frank C. D. Young
Theses and Dissertations
Timed Logic Conformance (TLC) is used to verify the behavioral and timing properties of detailed digital circuits against abstract circuit specifications when both are modeled as Timed Safety Automata (TSA) with real-valued clocks. TLC is a bisimulation-style partial order relationship defined over TSA state space. In contrast to timed simulation, Calculus of Timed Refinement, and time-abstracted bisimulation, TLC defines when one system is an acceptable implementation of another by asymmetric action-matching requirements for specification inputs and implementation outputs. TLC intuitively and pragmatically supports writing abstract specifications and verifying them against implementations. TLC scales up by substituting verified specifications for implementations …
Wind Tunnel Investigation Of Joined Wing Configurations, Jennifer Corneille
Wind Tunnel Investigation Of Joined Wing Configurations, Jennifer Corneille
Theses and Dissertations
The Air Force Research Laboratory's Munitions Directorate is looking to extend the range of its small smart bomb. One proposed idea is to retrofit the bombs with a wing kit, particularly a joined wing configuration. A typical joined wing configuration is one where the wings are positioned in such a way that they form a diamond in both plan and front views. The purpose of this study is to conduct low speed wind tunnel testing of the joined wing configuration to help determine if the joined wing is more beneficial than a single wing configuration. Configurations with differing sweep angles …
A Performance Analysis Of A Low Earth Orbit Satellite System, Korkut A. Ercakar
A Performance Analysis Of A Low Earth Orbit Satellite System, Korkut A. Ercakar
Theses and Dissertations
This thesis provides a performance analysis of the TELEDESIC® Low Earth Orbit Satellite System. It analyzes the system's performance to meet the real-time communications constraints with a full satellite constellation. Computer simulation results are the sources to evaluate delays associated with packets transmitted from source to destination earth stations. The simulation is run at low, medium and high loading levels with two different, uniform and non-uniform, traffic distributions. The evaluated results are end-to-end packet delays and packet rejection rate. The results show that the TELEDESIC® satellite system network is capable of meeting the real-time communication requirements with delay values much …
Parallel Digital Signal Processing On A Network Of Personal Computers Case Study: Space-Time Adaptive Processing, Fernando Silva
Parallel Digital Signal Processing On A Network Of Personal Computers Case Study: Space-Time Adaptive Processing, Fernando Silva
Theses and Dissertations
Network based parallel computing using personal computers is currently a popular choice for concurrent scientific computing. This work evaluates the capabilities and the performance of the AFIT Bimodal Cluster (ABC); a heterogeneous cluster of PCs connected by switched fast Ethernet and using MPICH 1.1 for interprocess communication for parallel digital signal processing using Space Time Adaptive Processing (STAP) as the case study. The MITRE RT_STAP Benchmark version 1.1 is ported and executed on the ABC, as well as on a cluster of six Sun SPARC workstations connected by a Myrinet network (the AFIT NOW), and on a IBM SP for …
Bistatic Radar Cross Section (Rcs) Characterization Of Complex Objects, Robert L. Eigel Jr.
Bistatic Radar Cross Section (Rcs) Characterization Of Complex Objects, Robert L. Eigel Jr.
Theses and Dissertations
This research addresses some phenomenological aspects of bistatic scattering from a complex object with an emphasis on specular, shadowing, dihedral, and cavity effects. Five targets are investigated for their simplicity and ability to highlight certain scattering phenomena. Direct measurements of scattered electromagnetic energy and simulation data is gathered for a frequency bandwidth of 6-18 GHz. Both ray tracing and scattering center approaches are used to describe the bistatic mechanisms. An appraisal of the effectiveness and utility of the monostatic-to-bistatic equivalence theorems (Kell's and Crispin's) and several commercial scattering prediction codes is also accomplished. Simulation data is generated from two different …
Solving An Inverse Control Problem Using Predictive Methods, Chad J. Davis
Solving An Inverse Control Problem Using Predictive Methods, Chad J. Davis
Theses and Dissertations
Model Predictive Control is the class of control methods that optimizes a specified performance index in order to minimize the weighted future output deviations from a setpoint trajectory. This thesis applies MPC in the inverse sense -- known aircraft outputs are applied in the performance index as setpoints in an attempt to determine what control histories caused those outputs. Using this method, aircraft mishap investigators could then have a means of determining what the control surface deflections were throughout an incident since Flight Data Recorder data does not include control surface deflections. The actual Flight Data Recorder data from aircraft …
Close Formation Flight Control, Andrew W. Proud
Close Formation Flight Control, Andrew W. Proud
Theses and Dissertations
In this research the close formation flight control problem is addressed. The formation consists of a lead and wing aircraft, where the wing flies in close formation with the lead, such that the lead's vortices produce aerodynamic coupling effects, and a reduction in the formation's drag is achieved. A controller, i.e., a formation-hold autopilot for the wing aircraft, is designed such that the formation's geometry is maintained in the face of lead aircraft maneuvers. In the formation flight control system, the wing and lead aircraft dynamics are coupled due to kinematic effects, and, in the case of close formations, additional …
Positive Anisotropic Group Scattering Cross Sections For Radiation Transport, J. Mark Delgrande
Positive Anisotropic Group Scattering Cross Sections For Radiation Transport, J. Mark Delgrande
Theses and Dissertations
In solving the Boltzmann transport equation, most discrete ordinates codes calculate the source term by first approximating the scattering cross section using a Legendre polynomial expansion. Such expansions are insufficient when scattering is anisotropic and the Legendre expansion is truncated prematurely. This can lead to nonphysical negative cross sections, negative source terms and negative angular fluxes. While negative sources are problematic for standard discrete ordinates methods leading to poor convergence or convergence to incorrect results, they are of particular concern to exponential methods, causing such calculations to fail. We've developed and tested a new technique to solve this problem called …