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Articles 5551 - 5580 of 5697
Full-Text Articles in Engineering
A Network Flow And Goal Programming Approach To Modeling The Impact Of Pre-Accession Training To The Trained Personnel Requirements Process, William J. Beveridge
A Network Flow And Goal Programming Approach To Modeling The Impact Of Pre-Accession Training To The Trained Personnel Requirements Process, William J. Beveridge
Theses and Dissertations
HQ ATC was tasked to analyze the impact of pre-accession training to the Trained Personnel Required (TPR) and training production process. Pre- accession training is a policy of providing contracted initial skills training to enlistees prior to entering basic military training. The purpose of this study was to develop a method to model the impact of pre-accession training. A network modeling and goal programming approach was used. Comparisons between the current training policy and a pre-accession training policy were made. Sensitivity was conducted on the impact of a balk rate on the new policy. The balk rate is the percent …
A Study Of Variables To Help Predict Navigator Training Success And Classification, Gary A. Hagler
A Study Of Variables To Help Predict Navigator Training Success And Classification, Gary A. Hagler
Theses and Dissertations
This study attempted to build statistical models which could possibly be used to help predict an individual's final outcome of pass or fail from Undergraduate Navigator Training (UNT). Also, the research tried to develop models to help place a potential trainee into one of the three training tracks at UNT. The variables studied were test scores from a computerized testing device which measured psychomotor and cognitive skills of individuals entering training. The Air Force Officers Qualifying Test (AFOQT) scores were also variables considered. Data was from 317 trainees from the years 1988 to 1990. Discriminant analysis was applied in an …
A Solution Methodology For The Variable-Level Scheduling Problem, Dennis R. Benson
A Solution Methodology For The Variable-Level Scheduling Problem, Dennis R. Benson
Theses and Dissertations
This study looked at a specific scheduling problem for a Department of Defense agency. A heuristic algorithms was developed to solve a general variable-level scheduling problem and was applied to this specific problem. This heuristic used linear programming and integer programming to find the minimum number of weekly billable hours for five alternative schedules. The best alternative schedule was further developed into a spreadsheet designed, squad level, master schedule. The result of this study was a proposed schedule that would save the United States government 8.2% of their security costs for this one part of the governmental agency. These savings …
The Utility Of Elliptical And Circular Confidence Regions For Hfdf Receivers, Paul T. Nemec
The Utility Of Elliptical And Circular Confidence Regions For Hfdf Receivers, Paul T. Nemec
Theses and Dissertations
This thesis investigates HFDF confidence region (CR) shape exhibited by geolocations in a search-and-rescue context. In Phase I, a Keeney-Raiffa multiattribute utility function was developed which allowed an analytical measure of preference between elliptical and equivalent- probability circular CRs. Phase II utilized a likelihood approach to establish CR shape for sample operational geolocations having multiple points of bearing intersections. For 12 sample Phase I geolocations, the elliptical CR always had higher utility than its corresponding circular CR. For accepted sample geolocations, a preference condition was developed whereby a circular CR would only be preferred over the corresponding elliptical CR if …
Multicriteria Network Routing Of Tactical Aircraft In A Threat Radar Environment, Ernst K. Isensee
Multicriteria Network Routing Of Tactical Aircraft In A Threat Radar Environment, Ernst K. Isensee
Theses and Dissertations
Real-time route planning for tactical aircraft has established a requirement for analytical tools which prescribe optimal solutions. The Air Force Electronic Warfare Center has developed a computerized routing aid which enhances the ability to plan tactical flight missions under real-time constraints. The decision aid known as the Improved Many-on-Many (IMOM) allows the user to subjectively evaluate flight routes within enemy radar coverages. However, the mission planner is required to intuitively assesses the survivability risks associated for each user defined route. As an alternative to this method, the deterministic procedures of dynamic programming and the shortest path algorithms offer techniques which …
Incorporating Value Systems In Strategic Force Analysis, Nancy D. Snyder
Incorporating Value Systems In Strategic Force Analysis, Nancy D. Snyder
Theses and Dissertations
Deterring potential Soviet aggression depends on our ability to hold at risk those assets they value most. This research investigates target valuation as an added dimension to force structure analysis. An extensive literature review is followed by the development and demonstration of a methodology defining development and use target values. The literature review covers arms control concepts to give a foundation for an important use of force structure analysis. It also covers measures of effectiveness. The final part of the review is comprised of definitions of perspectives on nuclear war. The methodology defines motivations for force structuring in the form …
Effects Of Colocation And Non-Colocation Of Sensors And Actuators On Flexible Structures, W. C. Lee
Effects Of Colocation And Non-Colocation Of Sensors And Actuators On Flexible Structures, W. C. Lee
Theses and Dissertations
This thesis compares the performance and robustness of colocated and non-colocated sensor/actuator pairs. Linear quadratic Gaussian and loop transfer recovery (LOG/LTR) procedures are used to design optimum controllers for three example problems. The first example is a single motion degree-of-freedom system having motion only about one axis. This type of system does not have any right half plane zeros for the non-colocated case; however, the thesis shows it behaves as a non minimum phase system. The second example is a Bernoulli-Euler beam which does not have RHP zeros. An optimum LOG/LTR controller can not improve the robustness of non minimum …
A Prolog-Based System For Hardware Verification, Kevin L. Sparks
A Prolog-Based System For Hardware Verification, Kevin L. Sparks
Theses and Dissertations
With the expanding number of components provided on a single digital chip, verification of digital designs is becoming a major problem. The more circuits one places on a single chip, the greater the number of input/output combinations which need to be checked. A paper by Barrow in 1984 discusses a Prolog-based hierarchical formal verification system which he calls VERIFY. Barrow provided a lot of information on what VERIFY can and cannot do, and on projected enhancements. He does not, however, mention how VERIFY actually performs the task of formal verification. This thesis will provide a description of one possible implementation …
Sensitivity Analysis For The Selection Of Linear Quadratic Regulator Weighing Parameters Q And R For Active Vibration Suppression Of A Cantilevered Beam, Steven L. Story
Sensitivity Analysis For The Selection Of Linear Quadratic Regulator Weighing Parameters Q And R For Active Vibration Suppression Of A Cantilevered Beam, Steven L. Story
Theses and Dissertations
There has been much interest during the past decade to develop and launch large space structures. The high cost of launching material into orbit will require that these structures be assembled in space using light weight elements which are vulnerable to dynamic excitations. Active control may be necessary to rapidly attenuate large amplitude vibrations. The active vibration control system is usually designed after the structure has been optimized. The integrated design of the control system and the structure may provide additional weight savings. This thesis presents a sensitivity analysis of the structure/ control optimization problem. The structure used is an …
A Common Interface Real-Time Multiprocessor Operating System For Embedded Systems, Michael S. Rottman
A Common Interface Real-Time Multiprocessor Operating System For Embedded Systems, Michael S. Rottman
Theses and Dissertations
Large real time applications such as aerospace avionics systems, battle management, and factory automation place many demands and constraints on the computing system not found in other applications. Software development is hindered by software dependence on the computer architecture and the lack of portability between systems. This thesis specifies and designs a real time multiprocessor operating system (RTMOS) that implements a consistent programming model, enabling the development of real time parallel software independent of the target architecture. The RTMOS defines the core functionality required to demonstrate the programming model. The RTMOS functional requirements are specified using Structured Analysis and Design …
An Environmentally Controlled Chamber For The Study Of Radon Detection, William R. Wharton Jr.
An Environmentally Controlled Chamber For The Study Of Radon Detection, William R. Wharton Jr.
Theses and Dissertations
A system was developed to dynamically control and monitor the environment and radon concentration within a glovebox chamber for the study of radon. The system is designed around a personal computer workstation which automates the entire system. The radon concentration is determined by monitoring the count rate from radon and its progeny which are continuously circulated from the radon chamber through a Lucas Cell detection system. This information is then used as a base for controlling a radon injection system. When the concentration within the glovebox drops, the system injects a precisely-measured volume of high activity radon gas into the …
An Assessment Of The Accuracy Of Semi-Empirical Quantum Chemistry Calculations Of The Mechanical Properties Of Polymers, James R. Shoemaker
An Assessment Of The Accuracy Of Semi-Empirical Quantum Chemistry Calculations Of The Mechanical Properties Of Polymers, James R. Shoemaker
Theses and Dissertations
The ultimate mechanical properties of polymers, assuming perfect morphology, will be limited by the mechanical properties of a single, ideal polymer chain. Previous calculations of polymer chain moduli using semi- empirical (SE) quantum chemistry methods have resulted in modulus values much higher than experimentally measured. This study investigated the error in the calculated inherent to the method of calculation by comparing SE results for C-C bond potentials in two well characterized polymers, polyethylene and polydiacetylene. It was found that the SE calculation systematically overpredicted bond stiffness in these polymers by approximately 25% to 30%. This is the upper limit on …
Agility: Presentation And Flight Test Methods For The Operational Fighter Pilot, William R. Langdon
Agility: Presentation And Flight Test Methods For The Operational Fighter Pilot, William R. Langdon
Theses and Dissertations
This thesis develops both metrics and flight test techniques to measure agility. During development of both the agility metrics and the flight test techniques, previous work conducted by the agility community and the Flight Test Center at Edwards Air Force Base was used as a lessons learned tool to insure favorable results. Both simulator and flight testing was performed to validate the flight test techniques. During simulator testing several problems with the original flight test techniques were noted. Flight testing on the pitch agility flight test technique solved most of its problems but problems found during roll testing in the …
Optimal Iterative Task Scheduling For Parallel Simulations, Joann M. Sartor
Optimal Iterative Task Scheduling For Parallel Simulations, Joann M. Sartor
Theses and Dissertations
The ultimate purpose of this research is to reduce the time needed for execution of parallel computer simulations. In particular, the impact of task assignment strategies is determined for parallel VHDL circuit simulations. The classical scheduling problem, which assigns n precedence-constrained tasks to m processors is NP-complete in all but the simplest cases. The problem of assigning simulation tasks is further complicated by the iterative nature of computer simulations: each task is required to execute multiple times as the simulation executes. This investigation develops a polynomial-time algorithm (the level strategy) which provides optimal assignment for iterative systems with specific constraints. …
Construction, Calibration And Use Of A Neutron Time-Of-Flight Spectrometer, Charles L. Wood
Construction, Calibration And Use Of A Neutron Time-Of-Flight Spectrometer, Charles L. Wood
Theses and Dissertations
The energy spectrum of a 5 curie Pu-Be neutron source is determined by use of a neutron time-of-flight spectrometer. This spectrometer measures the time it takes for a neutron to travel between two plastic scintillator detectors. Using a fixed distance for travel, a time spectrum is generated which is then unfolded into the energy spectrum of the source. The different aspects of equipment selection, connection and calibration of the system are described. With the resolved spectrum the energy resolution of the spectrometer is determined by using a Monte Carlo simulation of the experimental set-up. A dual- parameter experiment is conducted …
Development Of An Angular Distribution Function For The Study Of Atomic Lattice Structures Used In Atomistic Simulation, David Wesley
Development Of An Angular Distribution Function For The Study Of Atomic Lattice Structures Used In Atomistic Simulation, David Wesley
Theses and Dissertations
An angular distribution function (ADF) was developed as a tool to be used in atom simulation. The ADF lets us easily distinguish between different lattice structures for systems of atoms by looking at the distribution of bond angles. The ADF is also a useful tool for determining the amount of order in a system. First, model structures of simple cubic, FCC, BCC, and diamond were developed. Then, the ADF was used on these model structures so that a set of model graphs of the ADF could be used to compare to real systems. Finally, simulated systems of Ferric Titanate, Nickel …
Location And Routing Of The Defense Courier Service Aerial Network, Steven F. Baker
Location And Routing Of The Defense Courier Service Aerial Network, Steven F. Baker
Theses and Dissertations
This study extends work done by the Military Airlift Command's Analysis Group on reducing the operating costs of the Defense Courier Service aerial network. The study's primary focus is to minimize those costs by varying the number and location of servicing depots, and the routes flown from those depots. The theoretical algorithm used in the methodology is an expansion of Laporte's (1986) formulation of the multiple depot multiple travelling salesmen facility-location problem. Multiple servicing frequency is addressed by clustering co-located demands with Kulkarni's (1985) subtour breaking constraint. Vehicle range is considered by redressing a shortfall of the subtour breaking constraint, …
Investigation Of A Zero-One Integer Programming Approach To Automating The Scheduling Process At The Usaf Test Pilot School, Lisa M. Hassel
Investigation Of A Zero-One Integer Programming Approach To Automating The Scheduling Process At The Usaf Test Pilot School, Lisa M. Hassel
Theses and Dissertations
This thesis investigated models that could be used to determine a feasible schedule for the Test Pilot School (TPS) training program and form the basis for an automated scheduling system. The TPS problem is formulated as a 0-1 integer linear program and is solved using preprocessing techniques and the Branch-and-Bound algorithm. The method produced feasible solutions for small problems that equate to portions of the TPS schedule but cannot efficiently solve large problems like the full TPS problem. More investigation should be conducted to alter the method developed in the study so it could be used for large problems. A …
Thermo-Mechanical Fatigue Of A Fiber Reinforced Titanium Aluminide Composite, Mark A. Bates
Thermo-Mechanical Fatigue Of A Fiber Reinforced Titanium Aluminide Composite, Mark A. Bates
Theses and Dissertations
The thermo-mechanical fatigue behavior of a specific unidirectional fiber reinforced titanium aluminide composite was investigated. Three test specimens were subjected to in-phase thermo-mechanical cycling and four to out- of-phase thermo-mechanical cycling. The applied maximum mechanical stresses ranged from 500-800 MPa. The stress ratio of 0.1 was used for all tests. The temperature range was from 150-650 C and the resulting fatigue lives were in the 58-1487 cycles range. The out-of-phase test specimens failed sooner compared to their respective in-phase counterparts. In order to find out why, the test results were analyzed using a simple micromechanics analysis and compared. The fracture …
Development Of A Personal Computer Based Approach To Aircraft Parameter Identification, Mark S. Erickson
Development Of A Personal Computer Based Approach To Aircraft Parameter Identification, Mark S. Erickson
Theses and Dissertations
This thesis develops and tests a personal computer based approach to the aircraft parameter identification problem. The approach was tested analytically at the Air Force Institute of Technology, Wright-Patterson AFB, Ohio. These tests were conducted using simplified short period approximation and second-order transfer function models of longitudinal aircraft response. Initial evaluations were accomplished using simulated, noise free data. The longitudinal aircraft model was modified prior to flight test, for both convenience and necessity. This more complex model was evaluated during a flight test program at the USAFTPS, Edwards AFB, California. A T-38A aircraft was used as a tool to demonstrate …
The Self-Shielding Of Fallout Gamma Rays By Terrain Roughness, Mark S. Herte
The Self-Shielding Of Fallout Gamma Rays By Terrain Roughness, Mark S. Herte
Theses and Dissertations
The study presents a first order calculation of the self-shielding of nuclear weapon fission fragment gamma rays by surface roughness (microscopic terrain irregularities). To simulate fallout particles, polymer microspheres were deposited on slides containing samples of soil, concrete and asphalt roofing shingles. Scanning electron microscopy was used to photographically map the surfaces. The thickness of surface irregularities at various angles was measured by converting the photographs to digital images. Measurements showed a dependence upon the surface type, but not upon particle size. Average values of the measurements were modelled using a homogeneous buried source. With this geometry, dose rates were …
The Optimal Location Of Geodss Sensors In Canada, Pierre J. Forgues
The Optimal Location Of Geodss Sensors In Canada, Pierre J. Forgues
Theses and Dissertations
This thesis studies the maximal coverage p-median and the set covering facility location problems as applied to the GEODSS location problem. The classical single-objective mathematical formulations of the p-median and set covering problems are converted into network-flow formulations and various solution methods are developed using a scaled-down version of the GEODSS problem. The next step is the introduction of a second criterion function into the problem. This second function consists of minimizing the sum of the variance in coverage at the selected locations. Research reveals the deficiencies of MOLP (multiobjective linear programming) techniques in generating the efficient frontier of an …
Hybrid Wafer Scale Microcircuit Integration -- [ 4989063 ], Edward S. Kolesar Jr.
Hybrid Wafer Scale Microcircuit Integration -- [ 4989063 ], Edward S. Kolesar Jr.
AFIT Patents
A wafer scale integration arrangement wherein integrated circuit die of varying size, fabrication processes, and function are commonly mounted in the same host wafer using a filled epoxy material of special characteristics. The mounting epoxy material also serves as a substrate for the die interconnecting conductors in regions adjacent the mounted die. The described assembly also includes a newly available photosensitive polyimide material as a planarization and passivation covering for the die and host wafer and as a mounting surface for an interconnecting metal conductor array. Multiple levels of interconnection metal. Fabrication processes for the die to host wafer attachment …
Three Degrees Of Freedom Compliant Motion Control For Robotic Aircraft Refueling, Clayton M. Andersen
Three Degrees Of Freedom Compliant Motion Control For Robotic Aircraft Refueling, Clayton M. Andersen
Theses and Dissertations
The Air Force Institute of Technology (AFIT) supports on-going research in application of robotic technology to enhance assembly tasks. As a testbed, AFIT supports the ground-based aerial refueling project, with an emphasis on visual servoing techniques and compliant motion control. This thesis focuses on compliant motion control. Previous research developed the testing environment, which includes a PUMA-560 industrial manipulator, and a half scale mock-up of an aerial refueling system. This effort corrected and expanded the existing two degree of freedom (DOF) compliant controller to three DOF. Three DOF compliance was demonstrated by inserting the refueling nozzle into the receiver port. …
Analysis Of Visual Illusions Using Gabor Filters, Richard A. Oberndorf
Analysis Of Visual Illusions Using Gabor Filters, Richard A. Oberndorf
Theses and Dissertations
This thesis has demonstrated the correctness of using spatial filters in the analysis of various visual illusions; the specific form of filter has been derived from a Gabor equation model of simple cell response on the visual cortex. The Gabor Low Pass Filter (GLPF) applied to these anomalies was derived from proposals made that simple cell response on the visual cortex may be modeled by a set of equations originally proposed by Gabor in the 1940's. Based upon the extension of these equations into two dimensions, a GLPF process was applied to computer-generated black and white illusions (the Kanizsa Triangle, …
Quantization Noise Characteristics Resulting From Gaussian, Negative- Exponential, And Sinusoidal Random Input Signals, Van N. Osborne
Quantization Noise Characteristics Resulting From Gaussian, Negative- Exponential, And Sinusoidal Random Input Signals, Van N. Osborne
Theses and Dissertations
The purpose of this study was to investigate the trade-off between the number of quantization levels and the resulting noise characteristics for three classes of commonly occurring input signals, namely, those signals possessing Gaussian, negative-exponential and random sinusoidal distributions. This study derived expressions for the mean-squared error, output spectrum and error spectrum by expanding the nonlinear quantization function into a summation of orthogonal polynomials matched to the corresponding input signal distribution. Once accomplished, orthogonality properties were applied to provide usable expressions. A set of three Fortran 77 programs were developed- each of which applied to one of the studied input …
Speech Coding And Compression Using Wavelets And Lateral Inhibitory Networks, Richard Ricart
Speech Coding And Compression Using Wavelets And Lateral Inhibitory Networks, Richard Ricart
Theses and Dissertations
The purpose of this thesis is to introduce the concept of lateral inhibition as a generalized technique for compressing time/frequency representations of electromagnetic and acoustical signals, particularly speech. This requires at least a rudimentary treatment of the theory of frames-which generalizes most commonly known time/frequency distributions--the biology of hearing, and digital signal processing. As such, this material, along with the interrelationships of the disparate subjects, is presented in a tutorial style. This may leave the mathematician longing for more rigor, the neurophysiological psychologist longing for more substantive support of the hypotheses presented, and the engineer longing for a reprieve from …
Radar Image Processing For The Afit Anechoic Chamber, Brian K. Sanders
Radar Image Processing For The Afit Anechoic Chamber, Brian K. Sanders
Theses and Dissertations
The purpose of this study was to begin development of an Inverse Synthetic Aperture Radar imaging capability for the AFIT anechoic chamber. This began with an evaluation of the capabilities and limitations of the existing radar system and the chamber itself for this application. Then, after deciding on the image processing approach, software had to be written to collect the data necessary for image processing. This constituted the majority of this study, and resulted in a versatile, user-friendly program that automates the process of collecting data for high-resolution radar images. The program checks that the data to be collected will …
A Method Of Moments Solution For The Electric Currents On An Aperture-Fed, Stacked Patch Microstrip Antenna, William L. Irvin
A Method Of Moments Solution For The Electric Currents On An Aperture-Fed, Stacked Patch Microstrip Antenna, William L. Irvin
Theses and Dissertations
This study presents a method of moments solution for the surface currents and charge distributions on an aperture-fed, stacked patch antenna. To make the solution independent of the antenna excitation technique, an aperture magnetic current distribution is assumed, and the spatial Green's functions of the antenna are used to calculate the tangential fields on the antenna patches and coefficients for a finite series expression of the surface currents and charge densities. The Green's functions of the antenna are modeled with polynomials that are a function of the radial distance separating observer and source locations. The method of moments solution is …
Characterization Of An Air-To-Air Optical Heterodyne Communication System, Rebecca N. Seeger
Characterization Of An Air-To-Air Optical Heterodyne Communication System, Rebecca N. Seeger
Theses and Dissertations
The primary goal of this research was to determine the feasibility of air-to-air optical communications systems using coherent detection in a turbulent environment. Secondary goals were to determine (1) the signal-to-noise ratio (SNR) degradation due to turbulence and (2) the effect of varying the wavelength (1.5, 830, 904 nm), altitude (5000-12500 m), path length (40-160 km) and aperture side length (1-15 cm) on the turbulence affected SNR. The research was conducted under the following assumptions: (1) ideal transmitter and receiver, (2) equally sized, uniformly weighted, square transmitter and receiver apertures, (3) ideal tracking by the receiver, and (4) zero losses …