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Articles 11011 - 11040 of 11490
Full-Text Articles in Engineering
Development Of An Analog Mimo Quantitative Feedback Theory (Qft) Cad Package, Richard R. Sating
Development Of An Analog Mimo Quantitative Feedback Theory (Qft) Cad Package, Richard R. Sating
Theses and Dissertations
This thesis describes the development of an analog MIMO Quantitative Feedback Theory (QFT) CAD package for the automation of the multivariable control design process. The CAD package is capable of carrying a design from problem setup through the design process to a frequency domain analysis of the compensated MIMO system. The package automates the selection of the weighting matrix, formation of the square effective plants, the polynomial matrix inverse required to form the equivalent plants, generation of stability, tracking, disturbance, gamma, and composite bounds, loop shaping, design of the prefilter elements, and the frequency domain analysis of the completed design. …
Neutron Fluence And Dose From A Varian Clinic 1800 Accelerator, Richard A. Jackson
Neutron Fluence And Dose From A Varian Clinic 1800 Accelerator, Richard A. Jackson
Theses and Dissertations
The goals of this study were (1) to verify calibration factors determined by previous experiment for relating counts from activated gold foils to neutron fluences, and (2) to use the method to determine neutron fluences under various operating conditions of the Varian Clinac 1800 (18-MeV) electron accelerator at the WPAFB Medical Center. For comparison similar measurements were made of the CGM Saturne 1 at Kettering Memorial Hospital, Dayton, Ohio. Cadmium-difference pairs in a standard graphite pile were employed to verify the counting efficiency of the Geiger-Mueller beta counting system used to count the foil activity. They were also used to …
Multiple Model Adaptive Estimation Applied To The Vista F-16 With Actuator And Sensor Failures, Timothy E. Menke
Multiple Model Adaptive Estimation Applied To The Vista F-16 With Actuator And Sensor Failures, Timothy E. Menke
Theses and Dissertations
A Multiple Model Adaptive Estimation (MMAE) algorithm is applied to the Variable Stability In-flight Simulator Test Aircraft (VISTA) F-16 at a low dynamic pressure flight condition (0.4 Mach at 20000 ft). A complete F-16 flight control system is modeled containing the longitudinal and lateral-directional axes. Single and dual actuator and sensor failures are simulated including: complete actuator failures, partial actuator failures, complete sensor failures, increased sensor noise, sensor biases, dual complete actuator failures, dual complete sensor failures, and combinations of actuator and sensor failures. Failure scenarios are examined in both maneuvering and straight and level flight conditions. The system performance …
A Modal Analysis And Modelling Of A Lightly Damped Large Space Structure, Scott E. George
A Modal Analysis And Modelling Of A Lightly Damped Large Space Structure, Scott E. George
Theses and Dissertations
This study involves the modification to the PACOSS Dynamic Test Article to create a lightly damped representative large space structure with closely spaced, low frequency modes. An experimental modal analysis is performed to recharacterize the low frequency flexible vibration modes. A finite element model is created using MSC/NASTRAN to predict low frequency behavior using both real eigenvalue analysis and frequency response analysis. Then a reduced order model is created and fine-tuned to represent the dynamics of the structure for the identified low frequency modes.
A Method For Determining Schedule Delay Information In A Channel Cargo Route Network Schedule, Justin E. Moul
A Method For Determining Schedule Delay Information In A Channel Cargo Route Network Schedule, Justin E. Moul
Theses and Dissertations
This research develops a method for measuring schedule effectiveness by determining the amounts of enroute, cargo delay caused by a given aircraft mission schedule. The method is designed to generate information which helps identify flights for which different scheduling might decrease overall cargo delay in the entire network, given that all non-scheduling factors are held constant. The research uses a simplified twelve-airport cargo route network to test the methodology.
Wing Rock Prediction Method For A High Performance Fighter Aircraft, Robert C. Nolan Ii
Wing Rock Prediction Method For A High Performance Fighter Aircraft, Robert C. Nolan Ii
Theses and Dissertations
This study is a limited investigation of the nonlinear aircraft behavior known as wing rock. An eight state F-15 model is analyzed using bifurcation theory. The wing rock onset point is identified and small perturbation analysis is used to linearize the equations of motion about this point. The eigenstructure of the model is analyzed and is used to identify the stability modes involved in this motion. A procedure is developed to predict wing rock onset and frequency and the critical stability derivatives involved in this motion are identified. The developed procedure is applied to existing F-4J data and a flight …
A General Three Dimensional All Quadrilateral Surface Mesh Generation Algorithm, Roger Cass
A General Three Dimensional All Quadrilateral Surface Mesh Generation Algorithm, Roger Cass
Theses and Dissertations
Among the available all-quadrilateral mesh generation algorithms progressive-front offers the best quality and robustness. The paving algorithm is a progressive-front technique that generates a two dimensional mesh of all quadrilaterals on planar surfaces. The technique is particularly suited to meshing irregular boundaries with interior holes. This thesis presents an extension of the paving algorithm to generalized three dimensional surfaces. The major problems in three-dimensional surface mesh generation are projection of nodes, calculation of interior angles, and connection of mesh fronts. The solutions to these problems are presented. This work is part of the ongoing CUBIT project at Sandia Labs. The …
Strategic Deterrence In The Post-Start Era, David C. Mccormick
Strategic Deterrence In The Post-Start Era, David C. Mccormick
Theses and Dissertations
With the Soviet Union's fall there have been widespread calls for drastic reductions in the United States military's strategic nuclear forces. Although a major threat to the United States has been greatly reduced, the number of strategic targets will not decrease as rapidly as the number of available weapons. This research considers how the United States should think about strategic forces in the rapidly changing world order of the 1990s. An extensive literature review of deterrence concepts and conventional weapons capabilities is conducted with special attention paid to the role that precision guided munitions played in the 1991 Persian Gulf …
Comparison Of Synchronization Techniques For The Afit Direct Sequence Spread Spectrum System, Edward A. Bednar
Comparison Of Synchronization Techniques For The Afit Direct Sequence Spread Spectrum System, Edward A. Bednar
Theses and Dissertations
The purpose of this study is to analyze and evaluate the performance of several code synchronization methods that could be used in the Air Force Institute of Technology's (AFIT) Direct-Sequence Spread Spectrum (DSSS) communication system. These methods include the sliding correlator, transmitted reference, sequential estimation, and three types of matched filters. The matched filters are the baseband matched filter, delay line matched filter, and the convolver. The criteria used for the evaluation of these synchronization methods are theoretical synchronization times and probability of bit-error. Advantages and disadvantages of each synchronization method are described and a method is recommended to be …
Experimental Evaluation Of Incorporating Digital And Analog Integrated Circuit Die On A Common Substrate Utilizing Silicon-Hybrid Wafer-Scale Integration Technology, Philip C. Reamy
Theses and Dissertations
The objective of this research effort was to investigate the implementation of analog circuits in a wafer scale integration system. A test circuit composed of analog and digital subsystems was designed and tested through simulation. IC die containing this test circuit were utilized in the WSI system fabrication. Preliminary investigations were conducted to evaluate the potential improvements to the IC die mounting procedure, a key step in fabricating functional WSI systems. These investigations demonstrated a procedure which produced repeatable results in achieving acceptable planarization of IC die and host substrate surfaces. These investigations also demonstrated the successful application of a …
Development Of A Stratified Plate Model For Composite Panels, Alan L. Lesmerises
Development Of A Stratified Plate Model For Composite Panels, Alan L. Lesmerises
Theses and Dissertations
A new model for composites represents a composite panel as an alternating stack of isotropic matrix and orthotropic fiber-dominated layers. An energy approach results in a set of partial differential equations and boundary conditions where the mechanical properties of the matrix and fibers appear separately. Two solution methods are developed. The first, called Strata Theory is developed for general applications, while the second, called the Exact Stratified Plate, is used as a benchmark for comparison to Strata Theory. Both solutions assume zero gradients of displacement through the thickness of a fiber layer. They are compared for an isotropic material and …
Effects Of Facility Configurations And Scheduling Techniques On Aircraft Throughput For Warner Robins Alc Paint/Depaint Facilities, David V. Mcelveen
Effects Of Facility Configurations And Scheduling Techniques On Aircraft Throughput For Warner Robins Alc Paint/Depaint Facilities, David V. Mcelveen
Theses and Dissertations
The purpose of this research was to determine the effects of configuration options and dispatching rules on aircraft throughput for the WR- ALC paint/depaint facilities. A simulation model was constructed and used for this analysis as the primary means to conduct the research. The dispatching rules considered were first come first served, largest number in queue, shortest processing time, and a look ahead heuristic. Due to a reduction in the number of paint aircraft, no configuration option differing from the baseline significantly affected aircraft throughput. Dispatching rules were also found to produce no significant differences on aircraft throughput. Configuration options …
Quantifying The Impact Of The Acquisition Professional Development Program Certification Requirements On The Air Force Institute Of Technology, Paul A. Nicholson
Quantifying The Impact Of The Acquisition Professional Development Program Certification Requirements On The Air Force Institute Of Technology, Paul A. Nicholson
Theses and Dissertations
The purpose of this research is to determine the impact of implementing the Acquisition Professional Development Program on the Air Force Institute of Technology. APDP is part of a DOD-wide effort to decrease inefficiency in the procurement process. The program encompasses a tri-level certification process based on experience, training, and educational standards. APDP serves as a guideline for professional development of acquisition personnel from entry to senior level management. Many of the courses required for certification are offered through AFIT School of Systems and Logistics. Integrating the new educational requirements as a standard for career development is expected to produce …
An Analysis Of Escort Formations, Mustafa Ilhan
An Analysis Of Escort Formations, Mustafa Ilhan
Theses and Dissertations
This study used computer simulation to investigate escort fighter formations unknown interceptor threat environment. A USAF computer simulation model, TAC, was used to simulate air combat between the escorts and the interceptors in several different combat scenarios. The escort formations were defined by the vertical and horizontal distances of the escort fighters from the main strike body. Interceptors were characterized as one of two types of fighters with dissimilar aircraft frames and missile firing ranges. A central composite design was used to mathematically model the effect of escort formations and interceptor type on the survivability of the bombers and escorts. …
An Improved Scheduling Algorithm For Eglin Afb Test Ranges, Jeffrey S. Antes
An Improved Scheduling Algorithm For Eglin Afb Test Ranges, Jeffrey S. Antes
Theses and Dissertations
This research develops an algorithm that integrates into an existing computerized scheduling system to improve the mission scheduling function for Eglin AFB test ranges. The primary objective of this research was to design an improved computerized scheduling aid. The measure of performance for this approach is the number of missions scheduled using this aid as compared to current Eglin capabilities. Constructive heuristics are used in the algorithm to schedule missions according to critical resource groups while ensuring mission priority is not violated. The success of this new interactive scheduling algorithm is measured against a schedule produced by the current computer …
A Decision-Theoretic Approach To Recommending Action In The Air-To- Ground Aircraft Of The Future, Garrison H. Flemings
A Decision-Theoretic Approach To Recommending Action In The Air-To- Ground Aircraft Of The Future, Garrison H. Flemings
Theses and Dissertations
Designers of air-to-ground fighters of the future should consider including decision support systems to relieve pilots of some of the present workload. Those decision support systems should use utility theory. This work reviews two techniques of utility theory (decision trees and influence diagrams) and a new technique due to Morlan (probability ratio nets). The work includes a proposed structure for action recommendation systems in air-to-ground fighters of the future. The work describes an implementation of probability ratio nets. The work demonstrates the value of decision theory to air-to-ground fighters of the future by way of solving an example problem and …
A Response Surface Methodology Study Of Ferroelectric Memory Devices, Kevin C. Smith
A Response Surface Methodology Study Of Ferroelectric Memory Devices, Kevin C. Smith
Theses and Dissertations
Fatigue in ferroelectric memory devices was studied. The application of fatigue pulses to a ferroelectric sample was controlled by the RT-66 Ferroelectric Tester, a variation of the Sawyer-Tower circuit. The RT-66 also controlled data collection following the fatiguing process. Seven variables were evaluated for their potential- affect on fatigue. A sequence of fatigue tests, which varied the settings of these variables, was developed using Response Surface Methodology (RSM) experimental designs. Least-squares regression models were developed once a particular RSM set of design experiments was completed. These models were evaluated using RSM tools, and the analysis of these models allowed the …
A Sensitivity Analysis Of Circular Error Probable Approximation Techniques, Peter Puhek
A Sensitivity Analysis Of Circular Error Probable Approximation Techniques, Peter Puhek
Theses and Dissertations
Several algebraic CEP estimates models were examined in this study. Each assumes that the crossrange and downrange miss distances of the sample data follow a bivariate normal distribution. The analysis determined the sensitivities of these models to changes in the parameters of sample size, bias, correlation, and ellipticity. The accuracy of each model is expressed in terms of relative error, and the parameter regions in which a certain method dominated as the most accurate were noted. In general, it was found that bias was the most significant parameter in determining the best CEP method. A simple method, based on the …
Implementation And Analysis Of Np-Complete Algorithms On A Distributed Memory Computer, Joel S. Garmon
Implementation And Analysis Of Np-Complete Algorithms On A Distributed Memory Computer, Joel S. Garmon
Theses and Dissertations
The purpose of this research is to explore methods used to parallelize NP-complete problems and the degree of improvement that can be realized using different methods of load balancing. A serial and four parallel A* branch and bound algorithms were implemented and executed on an Intel iPSC/2 hypercube computer. One parallel algorithm used a global, or centralized, list to store unfinished work and the other three parallel algorithms used a distributed list to store unfinished work locally on each processor. the three distributed list algorithms are: without load balancing, with load balancing, and with load balancing and work distribution. The …
Development Of A System For Survey Of Radon Concentration Of The Dayton Area Using A Liquid Scintillation Counter And Analysis Of The Data, Taewon Kim
Theses and Dissertations
A system to do a large scale survey was developed. The data obtained from the survey was analyzed using a database. The database incorporated an equation for converting cpm into radon concentration pCi/ℓ). The equation of conversion, protocol for measuring radon concentration, survey form, and a database program were modified (from previous theses) or developed for this thesis. The elution time constant, adsorption time constant, and calibration factor were calculated for equation of conversion. Two surveys were during the course of the thesis. On the first survey, the arithmetic average radon concentration with standard error of the mean was 2.9 …
Model Of A Nuclear Thermal Test Pipe Using Athena, Mark J. Dibben
Model Of A Nuclear Thermal Test Pipe Using Athena, Mark J. Dibben
Theses and Dissertations
Nuclear thermal propulsion offers significant improvements in rocket engine specific impulse over rockets employing chemical propulsion. The computer code ATHENA (Advanced Thermal Hydraulic Energy Network Analyzer) was used in a parametric analysis of fuelpipe. The fuelpipe is an annular particle bed fuel element of the reactor with radially inward flow of hydrogen through it. The outlet temperature of the hydrogen is parametrically related to key effects, including the effect of reactor power at two different pressure drops, the effect of the power coupling factor of the Annular Core Research Reactor, and the effect of hydrogen flow. Results show that the …
An Examination Of The Feasibility Of A Nuclear-Pumped Laser-Driven Inertial Confinement Fusion Reactor With Magnetically Protected Walls, John M. Jacobson
An Examination Of The Feasibility Of A Nuclear-Pumped Laser-Driven Inertial Confinement Fusion Reactor With Magnetically Protected Walls, John M. Jacobson
Theses and Dissertations
A preliminary design study of a nuclear-pumped laser-driven inertial confinement fusion reactor with a magnetically protected first wall using an advanced DT-ignited, DD-fueled pellet demonstrated the feasibility of such a concept. This paper presents a parametric study of the required energy multiplication in the blanket, the pellet injection rate, and the net efficiency of this is conceptual reactor for advanced pellet yields. A model of the reactor energy balance yields a required energy multiplication of 2.4. A cylindrical design for a helium-cooled blanket demonstrates that natural uranium micropellets in a laser pump region provide a multiplication of 2.9 with a …
Design And Construction Of A Channel Electron Multiplier Based Mossbauer Spectroscopy System, Daniel J. Robbins
Design And Construction Of A Channel Electron Multiplier Based Mossbauer Spectroscopy System, Daniel J. Robbins
Theses and Dissertations
A channel electron multiplier (cem) detector system was designed and built to provide a signal to a Mossbauer spectroscopy system in an effort to obtain a better signal-to-noise ratio than achievable with a proportional counter system. Three cems are contained in a vacuum chamber built using standard components. Gamma, rays of 14.4-keV energy from a 57Co source enter from outside the chamber through a window and are absorbed by an 57Fe target near the cems. The target emits internal conversion electrons which are collected by the cems and a Mossbauer spectrometer collects the signal. The system produces a …
Design Of A Warm X-Ray Radiation Environment For Nuclear Weapons Effects Testing In The Nova-Upgrade Facility, Jeffrey E. Malapit
Design Of A Warm X-Ray Radiation Environment For Nuclear Weapons Effects Testing In The Nova-Upgrade Facility, Jeffrey E. Malapit
Theses and Dissertations
This engineering design project examined the creation of a radiation environment for warm x-ray effects testing in the Nova Upgrade laser facility. With the use of the MORSE Monte Carlo Code and the DABL69 Broad-group cross section library, the ignition of an inertial confinement fusion pellet using D-T fuel in a test cassette was modeled in the Nova Upgrade's target chamber. Various x-ray scattering materials were used in the test cassette to include enriched lithium hydride, polyethylene, liquid hydrogen, liquid helium, and liquid methane. The lithium hydride produced the best warm x-ray doses and least neutron dose. The predicted x-ray …
Multilayer Perceptrons For Classification, Lisa M. Belue
Multilayer Perceptrons For Classification, Lisa M. Belue
Theses and Dissertations
Techniques for training, testing, and validating multilayer perceptrons are thoroughly examined. Results obtained using perceptrons are compared and contrasted with two multivariate discriminant analysis techniques- logistic regression and k neighbor. Methods for determining significant input features are investigated and a procedure for examining the confidence to place in the significance of these features is developed. Procedures to evaluate the applicability of high-order feature inputs are examined. These methods and procedures are applied to two very different applications. The first application concerns the prediction of Air Force pilot retention/separation rates for input to force projection models. The second application concerns the …
An Analysis Of The Endurance Of Mobile Satellite Command And Control Systems, Steven O. Brown
An Analysis Of The Endurance Of Mobile Satellite Command And Control Systems, Steven O. Brown
Theses and Dissertations
This study investigated the endurance of a single deployed generic mobile space (GMS) command and control (C2) system. Specifically, factors which affect overall system performance were examined. The analysis began with the development of a simulation model for a GMS C2 system. Optimal settings of factor levels were determined by using the model to find peak system endurance and availability. Factors set were field support vehicle (FSV) access, numbers of maintenance personnel, and numbers of spare components available. After optimum values were chosen for these factors, an experimental design was conducted to determine factor effect between maintenance manpower and the …
Transformation Of Combat Data In Support Of Battle Trace, Hyoung-Kyu Choi
Transformation Of Combat Data In Support Of Battle Trace, Hyoung-Kyu Choi
Theses and Dissertations
The purpose of this study was to find an appropriate way of characterizing battle data as a function of time. This study was initially designed to remove the numerical instability problem cited in Barr's battle trace methodology as suggested by TRAC-MTRY. The research focused on the instability problem and identifying/recommending a technique that improved the efficiency of computation, and enhanced an analyst's ability to meaningfully interpret the battle trace. Two Lanchester's Square Law based methodologies are introduced and analyzed. The results of this analysis indicate that the battle trace of a constant value generated by Lanchester's Square Law integration seemed …
Feasibility Of An Antiproton Catalyzed Fission Fragment Rocket, David S. Hidinger
Feasibility Of An Antiproton Catalyzed Fission Fragment Rocket, David S. Hidinger
Theses and Dissertations
The purpose of this project was to investigate the feasibility of an antiproton catalyzed fission fragment rocket (FFR). The FFR is characterized by the extraction of fission fragments from the fuel, and the utilization of their kinetic energy for thrust generation. A significant drawback to previous FFR designs was the required critical nuclear pile as the fission fragment source. The author examined the possibility of replacing the critical pile with a sub- critical pile driven by antiprotons. Recent experiments have revealed that antiprotons stimulate highly energetic fissions in 238U, with a neutron multiplicity of 13.7 neutrons per fissions. This interaction …
Visual Information Processing And Response Time In Traffic-Signal Cognition, Hasan H. Demirarslan
Visual Information Processing And Response Time In Traffic-Signal Cognition, Hasan H. Demirarslan
Theses and Dissertations
In man-machine design, it is important to quantify the reaction time components instead of simply determining the lump-sum reaction time to stimulus. The primary purpose of this thesis was to investigate the reaction time components, such as visual perception and muscle response time, and to quantify them by separating from their aggregated sum. The prime example, traffic-signal cognition simulation was used to examine human reaction time to signal change. With a modified computer program that stimulates the driver's approach to the intersection, we measured the subject's reaction times and examined behavioral patterns. Twelve subjects were involved in the experiment. A …
An Investigation Of Modifications To The Tac Campaign Model, Efgan Denguer
An Investigation Of Modifications To The Tac Campaign Model, Efgan Denguer
Theses and Dissertations
This research investigates the cost and budget modifications to Mixmaster which is an aggregate version of the Theater Attack Model (TAM). Seven simple cost employment methods, a goal programming approach, a probabilistic approach for determining cost coefficients, and goal programming version of that probabilistic approach were applied to Mixmaster. Also, Mixmaster was enhanced with an additional leading constraint to incorporate the Air Force tactical considerations in a campaign scenario. The results favor the advantages of the goal programming approaches. In addition, the probabilistic approach introducing the time factor in the computations promises more accurate results, given that the required parameters …