Digital Commons Network^™

Advanced Formation Flight Control, Michael J. Veth

Theses and Dissertations

In this thesis, the formation flight control problem is continued from four previous theses. Automatic formation flight involves controlling multiple aircraft equipped with standard Mach-hold, altitude hold, and heading-hold autopilots to maintain a desired distance from a lead aircraft or "rabbit". Changes in the rabbit's states are treated as disturbances to the system and rejected. Previous research is advanced in the following areas: Higher-order aircraft-autopilot models are included into the design and a new feedback control law is employed, resulting in more accurate simulations. An energy tracking scheme is developed and is shown to reduce wing aircraft energy excursions. Finally, …

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. …

Voice Analysis Using The Bispectrum, Deborah A. Douglass

Theses and Dissertations

The theory of the bispectrum has been studied, though very few practical applications have yet been considered in any depth. One application mentioned in the literature is the use of the bispectrum for voice signal processing. The aim of this thesis was to research the bispectrum towards the particular application of speech enhancement. The technique is based on the fact that the bispectrum is zero for a Gaussian white noise signal, arid the bispectrum of two signals added together is the sum of the two signal bispectra. Theoretically, processing signals in the bispectra domain should increase the signal-to-noise ratio of …

A Methodology To Assess The Utility Of Future Space Systems, Bruce Rayno

Theses and Dissertations

This research identifies the assumptions and simplifications in the SPACECAST 2020 value model and assesses modifications. The model determines and prioritizes future space systems' utility toward controlling and exploiting space. This study shows that the assumption of using an additive utility function is valid. This research shows that the mission areas are mutually utility independent allowing the use of the multiplicative utility function. This research also uses the multilinear function, which requires utility independence implied in mutual utility independence. This study makes modifications to the 98 SPACECAST 2020 measure of merit scoring functions. These scoring functions all used the same …

The Junction Characteristics And Current Conduction Mechanisms Of Gainp2 N+P Diodes And Solar Cells, Kitt C. Reinhardt

Theses and Dissertations

This work involves an investigation of GaInP₂ n⁺p diode and solar cell dark current mechanisms, the defect centers that affect these mechanisms, and the response of dark current and solar cell photovoltaic parameters to I MeV electron irradiation and thermal annealing. Dark current due to carrier diffusion, recombination, and tunneling were identified, and recombination current was found to dominate at the maximum power-point voltage of the GaInP2 solar cells. Carrier recombination was found to occur via defect centers at the perimeter and within the bulk of the junction. Two deep majority-hole trap centers were found at E …

Life Cycle Costs Of Alternatives For F-16 Printed Circuit Board Diagnosis Equipment, Kent R. Montgomery, Clifford B. Thorstenson

Theses and Dissertations

This study analyzes two alternatives for printed circuit board (PCB) diagnosis for the F-16 depot PCB repair shop from a life cycle cost (LCC) perspective. Alternative 1 assumes the use of the current F-16 automatic test equipment (ATE) while Alternative 2 augments the current ATE with infrared imaging test equipment. Infrared imaging is a developed technology that is currently available to the Air Force in a commercial-off-the-shelf (COTS) form. Using the Cost Analysis and Strategy Assessment (CASA) Life Cycle Cost (LCC) Model and data from the DL41 database on F-16 PCBs this study determined that over the current expected life …

An Analysis Of The Extent To Which Humor Is Accepted And Employed In The Workplace For The Enhancement Of Productivity And Creativity, Jonathan R. Specht, Paul D. Tobin

Theses and Dissertations

Today's business literature is filled with discussions of the many benefits humor can bring to the work environment. Two of these purported benefits, namely, the enhancement of workplace productivity and the enhancement of workplace creativity, have attracted the attention of modern managers challenged with keeping their organizations competitive despite dwindling financial and human resources. Unfortunately, little research has been done to date which actually demonstrates a link between the existence of workplace humor and improved levels of productivity and creativity. Without this demonstration of causality, most managers are reluctant to invest corporate resources in pursuit of workplace humor despite its …

An Experimental Study Of Planar Heterogeneous Supersonic Confined Jets, Frederick J. Tanis Jr.

Theses and Dissertations

The effects of varying the exit pressure of a supersonic helium jet exhausting coaxially with two parallel supersonic air streams into a constant area duct were investigated. The method used to evaluate the mass entrainment rate was to measure helium molar concentration profiles and mass flux across the duct using a binary gas probe then calculate the mass entrainment into the helium jet. In order to conduct this study a novel binary gas probe was developed which allowed helium concentration and mass flux data to be obtained during continuous traverses across the supersonic flowfield. High exit pressure ratio (EPR) led …

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 …

Telepresent Spacecraft Docking With Object-Based Bilateral Control (Obbc), Paul Woznick

Theses and Dissertations

The concept of object-based control is extended to the field of teleoperation, specifically to accomplish the task of spacecraft docking via a bilateral manual controller. An object-based controller with bilateral feedback controls the motion of the grasped object, not the trajectory of the manipulator. For this reason it can be designed with feedback that is intricately linked with the task kinematics. The benefits derived from anthropomorphicity and force feedback are possible without kinematically-geometrically similar master-slave systems, complex calibration and joint mapping schemes, or expensive, high degree-of-freedom force reflection. Object-based control is ideal for low-level telerobotic interfaces. A hand controller and …

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 …

Finite Element Methods For Nonlinear Static Analysis Of Sandwich Plates, Damin J. Siler

Theses and Dissertations

A finite element method, developed for static analysis of composite plates, was enhanced to be used with sandwich plates. The theory considers geometric nonlinearity and transverse shear. Furthermore, a new postprocessor was written to check for initial failure using the maximum stress criteria. It also includes a procedure for evaluating transverse normal stresses by enforcing equilibrium. The code modifications for sandwiches were verified by comparing finite element solutions to closed-form sandwich theories. Both methods showed good correlation. In addition, comparisons between one type of composite plate and a similar sandwich plate found that the sandwich had better specific stiffness for …

Model Of A Single Impurity In A Wide Bandgap Semiconductor Describing Electric Field Screening, Anthony N. Dills

Theses and Dissertations

A mathematical model of the influence on electric field screening arising from a single impurity in a wide bandgap semiconductor has been numerically investigated and compared with analytically derived solutions. The parameter set chosen to perform the comparison of analytical solution and numerical solution is based upon a bismuth silicate crystal. Both the analytical calculations and the numerical calculations are an attempt to mathematically model the internal electric field within a semiconductor. Two types of impurities were looked at: a single donor level and a single trap impurity level. In general, after an abrupt application of a voltage across the …

An Analysis Of Bayesian Networks As Classifiers, Gregory C. Ahlquist

Theses and Dissertations

An analysis of Bayesian networks as classifiers is presented. This analysis results in an algorithm and several tools related to Bayesian network classifiers. The tools calculate and display the decision regions for two level Bayesian network classifiers. They collectively provide an approach to analyze the effects of changing network parameters on the network's decision regions. The algorithm defines a Bayesian network classifier to solve traditional classification problems. The algorithm is data driven, meaning that the resulting Bayesian network classifier is uniquely tuned to the classification problem at hand. Also, the algorithm contains procedures for defining the topology of a Bayesian …

A General Object Model Transformation System, John P. Mullaney

Theses and Dissertations

Cecil and Fullenkamp developed a program that transforms knowledge captured in an object-model in one environment into a different object-model in a different environment. This program worked well for the intended purpose, but if one of the object-models is replaced by a different object-model then this transformation program has to be re-engineered. As the object-modeling paradigm becomes more prevalent, many systems are experiencing this problem. The primary goal of this research was to determine what reusable knowledge could be extracted from these types of program and used to build a general object-model transformer that generalizes such transformation programs. Toward this …

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 …

Selection Of Secondary School Teachers: Perceptions Of School Adminstrators Concerning Criteria, Procedures, And Problems, James Paul Haussler

Theses and Dissertations

Tills study of secondary teacher selection ascertained which selection criteria administrators regarded as important and which criteria were used, ascertained which procedures administrators regarded as important and which procedures were used, and ascertained which problems administrators encountered in selecting secondary teachers. An Analysis of Variance procedure was conducted to ascertain whether differences existed in administrators' perceptions related to the size of school, to the location of the school, and to administrative role.

Data were collected by securing responses to a questionnaire mailed to a stratified (by enrollment size) random sample of 768 public school administrators in North Dakota, South Dakota, …

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 …

An Exploration Of Technology Transfer Control: A Case Study Of Wright Laboratory, William K. West

Theses and Dissertations

Federal laboratories, system product centers, and military logistics centers are being challenged to leverage national investments in technology beyond their traditional customer base--technology transfer. Participation in domestic technology transfer is growing at an astounding rate. Additionally, the federal government has invested and continues to invest billions of dollars into active defense conversion, dual-use technology, and technology transfer. The objective of this research is to explore how one government laboratory controls its technology transfer process, in both the near and long terms. This research examines the motives for participating in technology transfer. The researcher presents several of the processes that are …

A State-Space Model Of A Large, Lightly Damped Space Structure Using The Eigensystem Realization Algorithm, Robert D. Woods

Theses and Dissertations

Large, lightweight space structures of the future will require state-of-the-art vibration suppression systems. To design such a system, it is necessary to have a mathematical model that adequately describes the motion of the system. Coulomb damping compensation was utilized to remove a known nonlinearity from the frequency response functions obtained from the Passive and Active Control of Space Structures (PACOSS) Dynamic Test Article (DTA). Via the Eigensystem Realization algorithm (ERA), the frequency response functions were then used to generate a mathematical representation of the structure's dynamics. Two models were obtained. The first model, without friction compensation, acted as a baseline. …

Comparative Analysis Of Content For An Occupational Safety Health Program As Perceived By Industrial And Educational Enterprises, Christopher K. Trostad

Theses and Dissertations

No abstract provided.

The Impact Of Judicial Sentencing: An Analysis, Scott K. Johnson

Theses and Dissertations

No abstract provided.

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 …

Perceptions About Ethical Decision-Making Among North Dakota Elementary Principals, Isabel Patricia Hovel

Theses and Dissertations

The perceptions of North Dakota elementary principals about ethics and ethical decisions in the workplace were examined in the light of a similar national study. The purpose of the study was to analyze the perceptions of elementary principals of North Dakota to develop a clearer view of what would be considered ethical behaviors and ethical concerns among North Dakota elementary principals. The cumulative perceptions helped clarify the general consensus regarding ethical standards for principals in North Dakota schools. A secondary purpose was to disseminate the results of this analysis in order to help elementary principals in North Dakota in their …

Survey And Implementation Of Commercial Manual Controllers For A Generic Telerobotics Architecture, Thomas E. Deeter

Theses and Dissertations

The purpose of this study is to determine an input device for the Air Force's generic telerobotics architecture for large aircraft maintenance and repair. One area of concern is the human to machine interface, more specifically, which manual controller should be used for the specified tasks in this architecture. We mailed a survey to 68 companies in order to compile a list of possible input devices that the telerobotics architecture could use. 32 companies responded which gave me enough data to generate a list that described the physical traits of the input devices. We then divided the required tasks into …

Multiclassifier Fusion Of An Ultrasonic Lip Reader In Automatic Speech Recognition, David L. Jennnings

Theses and Dissertations

This thesis investigates the use of two active ultrasonic devices in collecting lip information for performing and enhancing automatic speech recognition. The two devices explored are called the 'Ultrasonic Mike' and the 'Lip Lock Loop.' The devices are tested in a speaker dependent isolated word recognition task with a vocabulary consisting of the spoken digits from zero to nine. Two automatic lip readers are designed and tested based on the output of the ultrasonic devices. The automatic lip readers use template matching and dynamic time warping to determine the best candidate for a given test utterance. The automatic lip readers …

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 …

Business Process Re-Engineering Applied To The Air Force Institute Of Technology Office Of The Registrar, Records Management, Connie C. Hutchinson, Alison F. Mccoy

Theses and Dissertations

This study analyzed the processes performed by the Officer Academic Education Repository at the Air Force Institute of Technology at Wright-Patterson Air Force Base, Ohio. Business Process Re-engineering (BPR) methodology was used to define tile existing processes. IDEFO (Integrated Computer Aided Manufacturing Definition Language) and Activity Based Costing techniques were used to map the flow of activities and to determine the costs for handling one education record. The cost for processing one education record averaged approximately $69.95. Under BPR, the functional expert team evaluates the existing processes to determine which processes are value-added and which are non-value added and generate …

Fatigue Behavior Of A Cross-Ply Metal Matrix Composite At Elevated Temperature Under Strain Controlled Mode, Leon B. Dennis

Theses and Dissertations

This research extends the existing knowledge of cross-ply metal matrix composites (MMC) to include fatigue behavior under strain-controlled fully reversed loading. This study investigated fatigue life, failure modes and damage mechanisms of the SCS-6-Ti-15-3, [O-9O]_2s, MMC. The laminate was subjected to fully reversed fatigue at elevated temperature (427° C) at various strain levels. Stress, strain and modulus data were analyzed to characterize the macro-mechanical behavior of the composite. Microscopy and fractography were accomplished to identify and characterize the damage mechanisms at the microscopic level. Failure modes varied according to the maximum applied strain level showing either mixed mode …