Digital Commons Network^™

Compressible Turbulence Measurements In A Supersonic Boundary Layer Including Favorable Pressure Gradient Effects, Raymond S. Miller

Theses and Dissertations

The effect of a favorable pressure gradient on the turbulent flow structure in a Mach 2.9 boundary layer (R_e/m approx. 1.5 x 10⁷) is investigated experimentally. Conventional flow and hot film measurements of turbulent fluctuation properties have been made upstream of and along an expansion ramp. Upstream measurements were taken in a zero pressure gradient boundary layer 44 cm from the nozzle throat in a 6.35 cm square test section. Measurements are obtained in the boundary layer, above the expansion ramp, 71.5 cm from the nozzle throat. Mean flow and turbulent flow characteristics are measured in …

Parallelization Of The 2d Roe Scheme On The Intel Paragon, John R. Graham Iii

Theses and Dissertations

This study presented a methodology for determining the general performance characteristics of a computational fluid dynamics (CFD) algorithm on the Intel Paragon. By performing a rigorous time complexity analysis of a parallel CFD algorithm, the general performance could be characterized before the code was actually parallelized. This was shown by implementing a serial version of the 2-D Roe Scheme on the Paragon. This explicit code was parallelized by the addition of generic yet efficient routines that decomposed the domain, automatically adjusted partition indices, and performed 2-D and 3-D buffer exchanges. Additionally, efficient global routines available for the Paragon were used …

An Analysis Of The Effectiveness Of Records Management, Dale R. Austin, Peter M. Moseley

Theses and Dissertations

This research was performed for the dual purpose of defining effectiveness as it applies to the field of records management (RM) and studying the impact of Document Librarian (DL) on the productivity of Air Force records managers. The main thrust of the study was to define effectiveness for RM because no standard existed. The definition was generated through a Delphi process with a group of RM experts and took four rounds to achieve acceptable consensus. The Delphi process evaluated major areas which a RM system must perform. DL is a RM software package developed jointly by Air Force Material Command …

The Relationship Of Parental Conflict And Parent-Child Relationship To The Sense Of Coherence Of Young Adult Children Of Divorce, Bruce K. Retterath

Theses and Dissertations

Early investigations of children and adolescents of divorce focused on the short-term negative influence of divorce on children and adolescents from "broken homes." Divorce is still seen as an important mediator in children's development, but other variables dealing with the family dynamics have been shown to be significant factors in the response of children to parental divorce. Few studies have considered the long-term influences of parental conflict and the parent-child relationship on young adults, and no studies have examined their relationship with the development of sense of coherence (SOC).

This study investigated the long-term relationship of parents' marital status, parental …

A Gain Scheduling Optimization Method Using Genetic Algorithms, Robert C. Martin Iv

Theses and Dissertations

Gain scheduling. the traditional method of providing adaptive control to a nonlinear system, has long been an ad hoc design process. Until recently; little theoretical guidance directed this practitioners' art. For this reason a systematic study of this design process and its potential for optimization has never been accomplished. Additionally, the nonlinearities and the large search space involved in gain scheduling also precluded such an optimization study. Traditionally, the gain scheduling process has been some variation of a linear interpolation between discrete design points. By using powerful non-traditional optimization tools such as genetic algorithms there are ways of improving this …

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 …

Using Object-Oriented Database Technology To Develop A Multiple Domain Capability For Domain-Oriented Application Composition Systems, Alfred W. Harris Jr.

Theses and Dissertations

This thesis describes the design and implementation of a multiple domain capability for a domain-oriented application composition system, named Architect. The research goal was to show how object-oriented database management system (OODBMS) technology can be used to provide simultaneous access to multiple domain-oriented knowledge bases. Since the Architect system was originally designed using the object-oriented paradigm, insertion of OODBMS technology was relatively simple and many of the object-oriented concepts, such as inheritance and aggregation, proved beneficial. Inheritance was used to encapsulate domain knowledge by defining each domain as a subclass of Architect's software architecture. Aggregation was used to allow applications …

Analytic Performance Models For Parallel Discrete Event Battlefield Simulation With Conservative Synchronization, James B. Hiller

Theses and Dissertations

This study investigated the development and use of analytic models for performance analysis of parallel discrete event battlefield simulation using conservative synchronization. A simulation architecture with layered application, simulation, and host machine services provided the model development basis. Simulation entities were modeled with set-theoretic definitions. Deterministic performance models using these definitions were developed for event prediction, scheduling, and execution in sequential battlefield simulation. The sequential model was expanded to include relative bounds for overhead factors introduced when the simulation is spatially decomposed for a parallel distributed memory machine. Comparison of sequential and parallel models instantiated for a simulation with uniform …

Accelerating Conservative Parallel Simulation Of Vhdl Circuits, Joel F. Hurford

Theses and Dissertations

This research effort considers heuristic and cost model based techniques for the optimal partitioning of VHDL circuits for parallel simulation. Correlation statistics are gathered on a wide variety of graph-based a priori parameters. Linear regression is used to identify significant parameters for inclusion in a representative cost model. Driving a greedy search, this cost model is used to improve upon initial heuristic partitions. The influence of feedback dominated previous research so a no-feedback algorithm is used to create the initial partition The circuits studied range from 1,050 to 4,243 gates.

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.

Unification Of Larch And Z-Based Object Models To Support Algebraically-Based Design Refinement: The Z Perspective, Kathleen M. Wabiszewski

Theses and Dissertations

This research established a foundation for formalizing the evolution of based object models to theories, part of a dual approach for formally extending object-oriented analysis models using the Z and LARCH languages. For the initial phase, a comprehensive, consistent, and correct Z language parser was implemented within the SOFTWARE REFINERY™ Programming Environment. The Z parser produced abstract syntax trees (ASTs) of objects, thereby forming the basis for analyzing the similarities and differences between the based and LARCH-based object representations. The second phase used the analysis of the two languages to identify fundamental core constructs that consisted of similar syntactic and …

A Correlational Study Of The Sei's Capability Maturity Model And Software Development Performance In Dod Contracts, Robert M. Flowe, James B. Thordahl

Theses and Dissertations

The Software Engineering Institute's (SEl's) Capability Maturity Model (CMM) is to measure an organization's software development process maturity. The Department of Defense (DoD) has model with the belief that a more mature software development process will result in a more successful software subject. Although there is a growing body of anecdotal evidence supporting this presumed correlation, there is empirical evidence. Thus, the goal of our research was to determine the nature of the correlation, if any, :ware process maturity and software project success, where process maturity is based on a CMM rating and success based on the parameters of cost …

Evaluation Of An Air Force Information Resources Management (Irm) Overview Course, Joseph L. Cox, Brenda R. Forcht

Theses and Dissertations

The federal government has passed laws and issued directives recognizing that information is a valuable national resource. To help assure that Air Force information managers are capable of implementing policy in support of such laws and directives, the Secretary of the Air Force's Directorate of Information Management (SAF-AAI) directed a team from the Air Force Institute of Technology (AFIT) to design and construct an exportable course to provide an overview of information resources management (IRM) concepts and principles. Such an IRM overview course was completed in the Summer of 1994. The authors evaluated this course quantitatively and qualitatively. During a …

A Model For Merging Information Systems: A Case Study Of The Air Force Material Command Merger, John A. Ellis, Matthew T. Pirko

Theses and Dissertations

As the Department of Defense continues to shrink, downsizing and rightsizing are terms that often indicate that changes are inevitable to many military units and organizations, some of these changes result in organizational mergers. One of the critical areas for such mergers lies within getting the information systems of the premerger organizations to work together. This thesis presents a model for merging information systems as part of an organizational merger. The proposed model, synthesized from existing technical and non- technical models and guidelines, addresses five key areas for consideration for a successful information systems merger. Those areas are: (1) Organizational …

Advanced Educational Methods In The Department Of Defense: Application Of Case Theory And Computer-Assisted Instruction To Business Process Reengineering, Brian A. Brown, Susan M. Brown, Karen L. Cook

Theses and Dissertations

The goal of this research was to create a computer-assisted instruction (CAI) prototype tutorial to teach the fundamental principles of integrated, computer-aided manufacturing definition activity modeling (IDEFO), a component of business process reengineering within the Department of Defense. To accomplish this, the authors evaluated current instructional material related to IDEFO, then adapted the material to a computerized learning environment using the Authorware Professional™ authoring software and a hybrid methodology which incorporated elements both of instructional design and software development. One of the most notable characteristics of this hybrid model was a series of iterations at each phase of development, which …

Factors In Human-Computer Interface Design (A Pilot Study), Susan Stewart

Theses and Dissertations

The DoD has budgeted over $9.8 billion for 1995 for information technology, yet many government office workers let their existing systems sit idle. This thesis explores why these computers are sitting idle. This researcher's initial hypothesis was that certain features of the human-computer interface can positively or negatively affect efficiency, retention, and satisfaction level of workers. Although some research is being done in this area, interfaces continue to be of poor quality, especially in the DoD, where long procurement cycles, forced purchases, and limited budgets result in out-of-date software. Intuitively most programmers know the human-computer interface impacts on a person's …

An Experimental Investigation Of The Time-Dependent Separation Of Tangent Bodies In Supersonic Flow, Neal A. Mosbarger

Theses and Dissertations

An experimental, time-dependent separation of tangent bodies was performed in a supersonic wind tunnel (Mach 1.5 and 1.9) to investigate the significance of transient effects and the suitability of using steady-state assumptions to predict a dynamic even. The model configurations consisted of two bodies placed in a near tangent position. A stationary body, plate or ogive, was instrumented to obtain dynamic surface pressures, while a second body, a wedge attached to an air cylinder, was plunged in a constrained motion away from and towards the stationary model. Three-dimensional flow expansion around the edge of the wedge reduced the strength of …

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 …

A Numerical Model To Predict The Fate Of Jettisoned Aviation Fuel, Karl D. Pfeiffer

Theses and Dissertations

While airborne, military and civilian aircraft must occasionally jettison unburned aviation fuel into the atmosphere. This research investigates the fate of a jettisoned fuel (e.g. JP-4, JP-8, etc.) from initial release to final ground fall by numerically modeling the physical phenomena governing the fate of this fuel: evaporation, advection, and dispersion. Using previous work in evaporation and free fall of fuel droplets as a foundation, this thesis presents an integrated evaporation advection and dispersion model designed to run under the resources of a typical personal computer. This integrated model is capable of using near real-time meteorological data (i.e. vertical profiles …

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 …

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 …

Modeling Workload Effectiveness And Efficiency Of Air Force Wing Command And Control, Michael D. Sarchet

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 of wing C2. The domain model was used to design and implement a prototype software tool that enables wing decision makers to make assessments about automation's impact on wing C2 operations.

Analysis And Simulation Of Narrowband Gps Jamming Using Digital Excision Temporal Filtering, Gerald L. Falen

Theses and Dissertations

The purpose of this thesis is to investigate the performance of the Digital Excision Temporal Filter (DETF) to reject narrowband jammers used against the Global Positioning System (GPS). The DETF takes the Fast Fourier Transform (FFT) of the GPS signal and excises any FFT bins that are above a preselected threshold level. Then the excised signal is Inverse Fourier Transformed and fed to the GPS receiver. Several jammer types are simulated including Continuous Wave (CW), Pulse CW, Swept CW, Narrowband Spot Noise, and Wideband Barrage Noise jammers. Cases are also simulated using all but the Wideband Barrage Noise jammer at …

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 …

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 …

The Enhanced Performance Of An Integrated Navigation System In A Highly Dynamic Environment, Brian J. Bohenek

Theses and Dissertations

For the U.S. Air Force to maintain an accurate and reliable Navigation Reference System (NRS) with Carrier-Phase Global Positioning System (CPGPS) measurements, it must develop an accurate and robust NRS in the face of cycle slips caused by highly dynamic maneuvers. This research investigates the implementation of a double differencing between receivers-satellites scheme to improve the accuracy of current NRS models. The removal of the 'perfect Doppler velocity aiding measurements' (a very poor assumption of past research) was completed with stable and accurate results. The double differencing implemented showed improvement in the accuracy of the NRS. An investigation of two …

Minimizing The Impact Of Synchronization Overhead In Parallel Discrete Event Simulations, Andrew C. Walton

Theses and Dissertations

A Parallel Discrete Event Simulation Coprocessor was designed for conservative synchronization protocols and was implemented in software using some of a parallel computer's nodes to act as coprocessors. The coprocessor was designed to offload synchronization overhead and next event queue management from the nodes running the simulation. The coprocessor was designed to accelerate simulations based on the Simulation Protocol Evaluation on a Concurrent Testbed with ReUsable Modules (SPECTRUM) environment. The research was conducted in three steps: the SPECTRUM environment was ported from an Intel iPSC-2 to an Intel Paragon XP-S, the coprocessor was designed and the simulations were timed, with …

Easy-Sim: A Visual Simulation System Software Architecture With An Ada 9x Application Framework, Jordan R. Kayloe

Theses and Dissertations

Software architectures increase productivity when used as the basis for developing applications in a problem domain. This thesis describes the creation of Easy-Sim, an object-oriented software architecture for visual simulation systems, and its corresponding implementation as an application framework in Ada 9X. The research built upon ObjectSim, an existing object-oriented simulation architecture implemented as a application framework. Both ObjectSim and Easy-Sim operate on Silicon Graphics platforms and use the IRIS Performer graphics programming library. Easy-Sim is implemented using version 1.83 of the GNAT compiler. The investigation for this thesis involved honing ObjectSim's design, implementing the improved result in both C++ …

Multiple Model Adaptive Estimation And Head Motion Tracking In A Virtual Environment: An Engineering Approach, James E. Russell

Theses and Dissertations

Software engineering tools and techniques were applied to design and implement an application that reduces lag typically present in virtual environment displays. The application was a Multiple Model Adaptive Estimator (MMAE), composed of three Kalman filters, that predicted head orientation one sample period into the future. The environment rendering software used these predictions to generate the environment display. Each of the filters in the MMAE was designed for a different assumed head motion type (benign, moderate, or heavy), which allowed the MMAE to adapt to changes in head movement characteristics. The use of Ada 9X as an implementation language for …

A 3-D Finite Difference Time Domain Investigation Of Microwave Propagation Through Inhomogeneous Biological Materials, David B. Dunn Jr.

Theses and Dissertations

This paper extends past analysis of an optimal source distribution around a homogeneous sphere of muscle tissue by using a 3-D finite difference time domain (FDTD) scenario in which an anatomically correct human head model is irradiated. It first duplicates the analytical solution within an FDTD space using an FDTD computer code developed at Penn State University. This duplication uses a 9.45 cm radius sphere represented in an FDTD space of 2.35 mm cubic cells. FDTD simulations are then performed on four, three, and two layer laminated spheres, designed to provide simple models of a head. Finally, four simulations were …