Digital Commons Network^™

Multicriteria Mission Route Planning Using A Parallel A* Search, Michael S. Gudaitis

Theses and Dissertations

The Mission Route Planning (MRP) Problem falls into the general class of multicriteria path search problems. Multiple criteria are evaluated to select an optimal aircraft mission route through a hostile environment. Criteria for distance travelled and radar exposure are combined into a single cost function for route evaluation. Radar calculations are performed dynamically. The A* search algorithm is applied to the MRP problem, and a parallel implementation is developed and tested. A unique combination of distributed OPEN lists with a global CLOSED list strategy produced fast execution times on the Paragon. Test cases for scenarios with 15 radars took less …

The Role Of The Gso Program In The Space Operations Career Field, Gregory J. Beloyne

Theses and Dissertations

The number of Air Force officers graduating from the Air Force Institute of Technology's Graduate of Space Operations master's degree program is declining. Furthermore, the number of advanced academic degree jobs these officers fill within the Space Operations career field has been reduced. These events question the role the GSO program has in the Space operations career field. This research surveys the GSO populations to determine how useful their master's degrees have been in providing the skills and knowledge needed to fill the advanced degree positions. This research also addresses the number of officers entering the GSO program each year. …

Generation Of A Single-Lobe, Far-Field Intensity Pattern From A Laser Diode Array Using An Optical Delay Line, Thomas A. Summers

Theses and Dissertations

A simple and practical technique is demonstrated to generate a stable, single-lobe, far-field intensity pattern from a one-dimensional, antiphased, laser diode array with gain-guided elements. The two far-field lobes of the array are combined after introducing an optical delay line into the path of one of the lobes to make the lobes mutually incoherent. The incoherent superposition of intensities produces a near-diffraction-limited, single-lobe, far-field intensity pattern containing 84% of the power, exceeding any previous (known) phase control experiments. This technique compares favorably with more elaborate schemes advanced previously using integrated phase plates, etc. The method is directly applicable to one-dimensional …

Superintendent Selection In North Dakota: Practices And Criteria, O. Kent Hjelmstad

Theses and Dissertations

The purpose of this study was to learn how North Dakota school board members who had recendy participated in the selection of a school superintendent perceived the relative importance of (a) hiring practices, (b) administrative skills, and (c) superintendent attributes. Analyses of individual items and clusters of items were conducted. In addition to the general purpose, analyses were conducted by gender, by duration of board incumbency, and by school enrollment size.

Data for the study consisted of responses from 124 school board members from 39 school districts. (The universe of districts which had hired a superintendent during the 1990-1993 time …

The Constituency's Role In Congressional Decision Making: A Case Study Of Constituent Correspondence And Its Effect On Roll Call Voting, Sarah Ann Carlson

Theses and Dissertations

There has been a recent explosion in the volume of communication between constituents and their representatives in Congress. There is an intradisciplinary disagreement about what—if any—role this communication plays in the federal legislative decision making process. David Mayhew makes a persuasive argument based on reelection realities that this input from constituents affects the legislative decisions made by members of Congress. However, others, such as Robert Bernstein, maintain there is no causal relationship between constituent input and the decisions made by members of Congress.

In order to ascertain the degree to which this causal relationship exists—if it exists at all—comparative content …

Smoltification And Imprinting In Introduced, Land-Locked Chinook Salmon (Oncorhynchus Tshawytscha), Timothy L. Hoffnagle

Theses and Dissertations

The period of smoltification is crucial to the maintenance of a self-supporting salmon population. This study addresses the physiological and behavioral changes that occur during smoltification and the environmental cues which induce this metamorphosis in Chinook salmon (Oncorhynchus tshawytscha). The timing of imprinting in this species is also investigated.

The effects of novel water chemistry, increased stream flow rate, photoperiod and age and size on plasma levels of thyroxine, triiodothyronine and cortisol, hematocrit, condition factor and hepatosomatic index were examined. Exposure to a novel water source was found to induce smoltification while doubling the stream flow rate had no effect. …

The Lived Experience Of Caring And Knowing In Senior Nursing Students, Sherry Neil-Urban

Theses and Dissertations

Caring is identified as a central and defining feature of professional nursing. Yet, there is little explicit emphasis on the philosophy and substance of caring in the traditional nursing program. Rather, caring is subsumed by the pressing need to stay current with expanding definitions of nursing competence and increased knowledge required by licensing boards. The purpose of this phenomenological investigation was to better understand the lived experiences of caring and knowing as expressed by senior nursing students near completion of the nursing program. Eighteen sen ior nursing students, within one month of graduation, participated in this interview study in which …

Who's Speaking Whose Language? A Study Of Contact Signing Between Deaf And Hearing Co-Workers, Marilyn K. Plumlee

Theses and Dissertations

This study documents signed communication between a deaf woman and five hearing co-workers who have worked together for periods ranging from two and a half to twenty-three years.

The study has two primary foci:

(1) to describe the linguistic features observed during contact signing between deaf and hearing interlocutors, all fluent in English, who communicate in a manual, visual channel, and

(2) to identify the dynamics affecting the linguistic choices made by both the hearing and deaf signers during contact signing.

The primary data base for this study were videotaped recordings of conversational dyads consisting of the deaf woman and …

Effects Of Blowing Ratio On Heat Transfer To The Throat Region Of A Porous-Walled Nozzle, Joseph L. Lenertz

Theses and Dissertations

This experiment analyzed the effects of blowing ratio on heat transfer to the throat region of a porous-walled nozzle, using the AFIT low speed shock tube. Heat flux data were taken from both sides of a two-dimensional Mach 2.0 Re-m=5.2x10⁷ nozzle using thin film resistance thermometers. One side was transpiration-cooled by secondary air injection through a sintered wall, while the other side served as a control. Control results were validated using empirical relations, and cooled side results showed up to a 14% reduction in heat transfer coefficient at blowing ratios of only 0.51%. The linear nature of cooling effectiveness …

An Investigation Of The Afit 2-Inch Shock Tube As A Flow Source For Supersonic Testing, Kevin M. Vlcek

Theses and Dissertations

An investigation of the AFIT high pressure shock tube was conducted to determine how closely it followed ideal shock tube theory and to determine the available test times for an attached Mach 3 nozzle. The driver section was five feet (1.52 m) long and the driven section was 25 feet (7.62 m) long. The driver gas used for this study was helium while the driven gas was atmospheric air. The pressure rise measured behind the incident shock wave was, on average, 30% lower than predicted by the ideal shock tube relations. Behind the reflected shock, the pressure rise was 65% …

Investigation Into The Behavior Of Geometrically Nonlinear Composite Arches, John C. Bailey

Theses and Dissertations

This research modifies the existing finite element formulation of a potential energy based large deformation and moderate rotation theory. Hermitian shape functions replace the existing linear bending angle interpolations. Negligible differences between the two formulations indicate the underlying kinematics limit the accuracy, not the finite element interpolations. Using the new program, numerous nonlinear arch geometries are modeled to investigate the effects of arc length and thickness variations. Local and global snapping phenomena are captured as well as through the thickness shear driven nonlinearities.

The Design And Development Of A Low-Speed, Low-Force Wind Tunnel Data Acquisition System With An Application To Bicycle Front Fork Spacing, Alan W. Elledge

Theses and Dissertations

This thesis encompassed the design, development, and application of a low-speed, low-force data acquisition system for the AFIT 5-ft Wind Tunnel. The new data acquisition system was designed and developed to measure approximately 0.045 N (about 0.01 lb_f) at nearly 64.4 km/h (40 mph). Verification of the capability was obtained through testing of a cylindrical model. As part of a technology transition program with Wright Laboratory, this new system was used to investigate bicycle front fork blade spacing in order to determine the optimal spacing for minimum drag. As for the minimum drag of a bicycle with an …

An Experimental Investigation Of Sandwich Flat Panels Under Low Velocity Impact, Timberlyn M. Harrington

Theses and Dissertations

This study evaluated the failure modes and mechanisms associated with increasing face sheet thickness of flat sandwich panels under low velocity impact. The sandwich panels were fabricated using 1.27 cm thick, 145 kg-m³ (9 lb-ft³), 3.175 mm (1-8 in.) cell size Nomex honeycomb core, FM 300-2 film adhesive and AS4-3501-6 graphite-epoxy face sheets. The thickness of the core remained 1.27 cm, and the thickness of the adhesive remained 0.25 mm. The thickness of the face sheets varied using the following stacking sequences: [0-90]_s, [0-90]_2s, [0-90]_4s, [0-90]_8s, and [0-90]_{12s …}

Performance Characterization Of A Highly-Offset Diffuser With And Without Blowing Vortex Generator Jets, Michael B. Senseney

Theses and Dissertations

The effect of blowing vortex generator jets (VGJs) on the performance of a highly-offset (s-duct) diffuser was investigated experimentally. VGJs are pitched, skewed jets which generate streamwise vortices as well as injecting high-momentum fluid into the boundary layer. Diffuser performance with and without VGJs was measured for an inlet Mach number of 0.6 (Re/x = 1.27x10⁷ per cm). Pitot static and hot-film instrumentation was used to measure flow properties at the diffuser inlet and exit planes. Without blowing, the flow on the lower surface of the diffuser was massively separated. Blowing at 0.48% mass flow ratio through three lower-surface …

Improved Numerical Solution Of Mixed H2/H∞ Optimization With Applications, Linda D. Smith

Theses and Dissertations

This study improved the numerical optimization technique used to compute mixed H₂/H_∞ controllers. The run time to generate the full curve of an H₂/H_∞ design was reduced by a factor of almost 200 for a specific example. This was accomplished by improving gradient calculations, upgrading the H_∞ norm calculation to capture multiple peaks in the singular value plot and using routines that minimized processing time. The optimization routine used was the MATLAB CONSTR' Sequential Quadratic Programming (SQP) routine. This SQP routine was compared to a FORTRAN SQP numerical optimizer, IMSL-DNCONG. The method was …

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperature Under Tension-Tension Loading, Craig D. Steiner

Theses and Dissertations

This study investigated the fatigue behavior and damage mechanisms of a [0-90]_4s SiC-MAS ceramic matrix composite under tension-tension loading at two elevated temperatures and two frequencies. Stress and strain hystereses, maximum and minimum strain, and modulus of elasticity were evaluated to characterize the material behavior. Microscopy and fractography were used to evaluate damage progression and mechanisms. Fatigue life was independent of frequency at both temperatures.

Generalized Probabilistic Reasoning And Empirical Studies On Computational Efficiency And Scalability, Eric P. Baenen

Theses and Dissertations

Expert Systems are tools that can be very useful for diagnostic purposes, however current methods of storing and reasoning with knowledge have significant limitations. One set of limitations involves how to store and manipulate uncertain knowledge: much of the knowledge we are dealing with has some degree of uncertainty. These limitations include lack of complete information, not being able to model cyclic information and limitations on the size and complexity of the problems to be solved. If expert systems are ever going to be able to tackle significant real world problems then these deficiencies must be corrected. This paper describes …

Unification Of Larch And Z-Based Object Models To Support Algebraically-Based Design Refinement: The Larch Perspective, Catherine J. Lin

Theses and Dissertations

This research describes the feasibility of developing object-oriented LARCH specifications, part of a dual approach for formally extending object-oriented analysis models using LARCH and Z. The first phase consisted of two steps establishing a set of transformation heuristics for algebraically representing object models and implementing a robust LARCH parser. The LARCH parser produced abstract syntax trees ASTs of objects forming the basis for analyzing the similarities and differences between Z-based and LARCH-based object representations. The second phase used the analysis of LARCH and Z to identify fundamental core constructs in the languages and abstract syntax trees. These core constructs consisted …

The Photo-Realistic Afit Virtual Cockpit, Milton E. Diaz

Theses and Dissertations

The Air Force Institute of Technology (AFIT) has pursued research in virtual environments since 1988. This research expands the current capabilities of the AFIT Virtual Cockpit (VC) by increasing the realism of the cockpit environment and improving the pilot's command interface. Realism is improved creating console elements from texture maps and polygonal models; these elements include working dials, switches and circuit breakers. The pilot command interface is improved in part by adapting the AFIT Information Pod using a two-dimensional mouse input to the virtual three-dimensional environment. This immersive virtual environment is also improved by modifications to the Head Mounted Display …

Predicting Protein Structure Using Parallel Genetic Algorithms, George H. Gates Jr.

Theses and Dissertations

The protein folding problem is a biochemistry Grand Challenge problem. The challenge is to reliably predict natural three-dimensional structures of polypeptides. Genetic algorithms (GAs) are robust, semi-optimal search techniques modeling natural evolutionary processes. Fast messy GAs (fmGAs) are variants of messy GAs that reduce the exponential time complexity to polynomial. This investigation evaluates the merits of parallel SGAs and fmGAs for minimizing the potential energy of a pentapeptide, (Met)-enkephalin. AFIT's energy model is compared to a similar model in a commercial package called QUANTA. Differences between the two models are identified and resolved to enhance GAs' abilities to correctly fold …

Modeiing Operational Task Assignment In Air Force Wing Command And Control, Robert J. Hunt

Theses and Dissertations

This research investigated the feasibility of applying software engineering technology to the Air Force wing command and control (C2) domain. As part of this research, domain analysis and object-oriented techniques were investigated and a specific approach was chosen to analyze the domain. Analysis of the domain resulted in an object-oriented domain model that captured the key objects, operations, and associations, and behavior of wing C2. The domain model was used to design and implement a prototype software tool that enables wing decision makers to assign resources to mission tasks and to make assessments about automation's impact on wing C2 operations.

Improving Intrusion Detection In Unix-Based Networks, David R. Landry

Theses and Dissertations

Computer security has not kept pace with the rapid growth of networked systems. Through its connection to the Internet, the Department of Defense is vulnerable to computer-based attacks. Current intrusion detection systems are still unproven, too complicated, or too costly for most system security officers to implement. The attack methods used by system intruders are known and can be represented as groups of commands called attack signatures. This thesis investigates methods for detecting intruders by monitoring command usage. Testing was conducted in both controlled and uncontrolled circumstances. With controlled testing, it was shown that 7 of the 11 signatures could …

Development Of A Mammographic Image Processing Environment Using Matlab, John L. Kelley

Theses and Dissertations

Breast cancer is a disease that accounts for a disturbingly large number of deaths in females each year. Its prevalence is a topic of concern to all of us since it can affect our families, friends, and coworkers. Although mammographic screening is the most effective method currently available for the early detection of breast cancer, it is far from being an infallible procedure. Mammographic reading is error prone, partly because of the complexity of the task and partly because of the variability in human performance. Computers offer high reproducibility, and when used as an adjunct by the radiologist, may improve …

Designing And Implementing An Ada Language Binding Specification For Odmg-93, Stephen R. Lindsay

Theses and Dissertations

Object-oriented database management systems (ODBMSs) represent the latest advancement in database technology, combining the reusability and maintainability of the object-oriented programming paradigm with the ability to efficiently store and retrieve a wide range of data types as well as code to manipulate stored data. Unfortunately, programmers developing software in the Ada programming language do not have the ability to interface to object databases without significant customized code development. One important reason for this has been the absence of a standard defining the constructs accessing ODBMS functionality. This thesis documents the creation of an Ada language binding to the ODMG-93 standard …

The Re-Engineering Of The Air Force Institute Of Technology Student Information System, Douglas J. Wu

Theses and Dissertations

This research describes the design and implementation issues associated with re-engineering the Air Force Institute of Technology Student Information System (AFITSIS). Currently, AFITSIS executes on aging relational database technology and has unfriendly user interface mechanisms. The two research objectives met were to research current AFITSIS requirements, design, and implementation, and use object-oriented methods to design an alternative implementation based on proposed object database management system standards. This research explores how AFITSIS performance and capabilities might be enhanced by taking advantage of new object-oriented software engineering techniques. One of the primary benefits of this research is a detailed object modeling technique …

Classification Of Ultra High Range Resolution Radar Using Decision Boundary Analysis, Christopher L. Eisenbies

Theses and Dissertations

This thesis examines the discrimination of targets with Ultra High Range Resolution (UHRR) radar data. Using these measured signals from frontal aspect angles of four aircraft classes, the baseline performance of the Adaptive Gaussian Classifier (AGC) is tested with respect to aligning exemplars to templates. Alignment plays a crucial role in the AGC's classification performance which can degrade by 11% for a target class. The AGC is compared to non-parametric classifiers, but no statistically significant degradation of performance is found. Data separability is analyzed by hounding the Bayes error. The data is well separated in a statistical sense. A feature …

Roc Analysis Of Ir Segmentation Techniques, Georgia K. Harrup

Theses and Dissertations

Receiver Operating Characteristic (ROC) curves are used to compare the effectiveness of IR image processing techniques. Two non-parametric error estimation techniques (k-Nearest Neighbor and Parzen Window) are used to create estimates of the probability density functions for the data. These pdfs are used in the creation of the ROC curves for both resubstitution and leave-one-out estimates. These estimates generate the upper and lower bounds, respectively, on the ROC curves. The ROC curve analysis is performed on the outputs of various image processing techniques and the resulting ROC curves are used to compare the techniques. Of the image processing techniques used …

Electro-Hydrostatic Actuator Controller Design Using Quantitative Feedback Theory, Ki Ho Kang

Theses and Dissertations

The Electro-Hydrostatic Actuator (EllA) technology offers a higher degree of combat survivability and easier maintainability of the aircraft flight control system, because all the components necessary to operate the actuator are collocated with the actuator. Quantitative Feedback Theory (QFT) is used to design a control system for the EHA. The impact of parameter variations, sensor noise, and flight conditions are explicitly considered in the design process. The solution utilizes a two loop QFT feedback structure. The inner loop structure stabilizes the motor's angular velocity and decreases the outer loop's uncertainty. The outer loop structure controls the RAM piston's position to …

Adaptive Beamforming In Frequency-Dispersive Multipath Environments, David A. Murray

Theses and Dissertations

It is well known that an antenna array with N degrees of freedom (DOF) can cancel N - 1 interferers if they approach the array from directions other than that of the desired signal. It has been shown that there are cases in which it is possible for an array with N DOF to effectively cancel more than N - 1 interferers. Specifically, we show how this can be done when there is incident upon an N-element array not only the desired signal and a jammer signal, but more than N - 1 Doppler-shifted multipath copies of the jammer signal …

Compensated Deconvolution From Wavefront Sensing, Lori A. Thorson

Theses and Dissertations

The U.S. Air Force has a continuing mission to obtain imagery of earth-orbiting objects. One of the means for obtaining this imagery is through the use of ground-based observatories. A fundamental problem associated with imaging objects through the atmosphere is that atmospheric turbulence inflicts a large, random aberration on the telescope which effectively limits the realizable resolution to that of a much smaller telescope. Several approaches have been taken to overcome these effects including pure post processing, pure adaptive optics, and hybrid techniques involving both adaptive optics and image post processing. One key result from past approaches is that partially …