Computer Sciences Commons^™

The Simulation, Modeling And Analysis Of Wireless Local Area Networks Supporting The Ieee 802.11 Standard, Jaikwan Joo

Theses and Dissertations

Research to improve the performance of the IEEE 802.11 has been ongoing since 1990. The focus of this research has investigated the use of the MAC and Physical layers for improving throughput. An adaptive MAC protocol, CATER (Code Adapts To Enhance Reliability) is based on the proposed MAC standard for wireless local area networks (WLAN)-802. 11. IEEE 802.11 uses a fixed Pseudo-Noise (PN) code for spreading the information signal, implying a fixed process gain at the receiver. When the channel degrades, IEEE 802.11 offers only retransmissions at the MAC layer to contend with the corrupted medium. However, CATER allows communicating …

A Web-Based Prototype For Afit Edplan Administration, Tien-Chen Lee

Theses and Dissertations

This document details the design, development, and evaluation of a prototype course registration and reporting system for the students and faculty of the United States Air Force Institute of Technology. The web-based system provides HTML-based client interfaces and Active Server Page server processes for interaction with the relational databases used to manage course and personnel data. The system prototype was developed following the "Engineering Software Components for Web-Database Access" methodology of Dipiro. A survey of modern web-based database access techniques is first provided and Dipiro's methodology is reviewed as background. The remainder of the document details the application of the …

Radial Complexity Estimation For Improved Generalization In Artificial Neural Networks, Lemuel R. Myers Jr.

Theses and Dissertations

When training an artificial neural network (ANN) for classification using backpropagation of error, the weights are usually updated by minimizing the sum-squared error on the training set. As training ensues, overtraining may be observed as the network begins to memorize the training data. This occurs because, as the magnitude of the weight vector, W, grows, the decision boundaries become overly complex in much the same way as a too-high order polynomial approximation can overfit a data set in a regression problem. Since w grows during standard backpropagation, it is important to initialize the weights with consideration to the importance of …

The Effects Of Three Media Presentation Systems On Maintenance Task Performance, John W. Chastain

Theses and Dissertations

Wearable computers and Portable Maintenance Aids (PMAs) may soon be the normal way of doing aircraft maintenance in the Air Force. Currently, the Air Force uses the paper form of Technical Orders (TO's) while doing aircraft maintenance. The purpose of this thesis was to compare the effects of three different media presentations of the information used during aircraft maintenance. The three different presentations compared are the current paper form, a Head Mounted Display (HMD), and an auditory mode. An experiment was conducted to determine if there was a significant difference between the systems (in terms of task completion times and …

A Decision Theoretic Approach For Interface Agent Development, Scott M. Brown

Theses and Dissertations

The complexity of current software applications is overwhelming users. The need exists for intelligent interface agents to address the problem of increasing taskload that is overwhelming the human user. Interface agents could help alleviate user taskload by extracting and analyzing relevant information, and providing information abstractions of that information, and providing timely, beneficial assistance to users. These agents could communicate with the user through the existing user interface and also adapt to user needs and behaviors. Central to providing assistance to a user is the issue of correctly determining the user's intent. This dissertation presents an effective, efficient, and extensible …

Automatic Target Cueing Of Hyperspectral Image Data, Terry A. Wilson

Theses and Dissertations

Modern imaging sensors produce vast amounts data, overwhelming human analysts. One such sensor is the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) hyperspectral sensor. The AVIRIS sensor simultaneously collects data in 224 spectral bands that range from 0.4µm to 2.5µm in approximately 10nm increments, producing 224 images, each representing a single spectral band. Autonomous systems are required that can fuse "important" spectral bands and then classify regions of interest if all of this data is to be exploited. This dissertation presents a comprehensive solution that consists of a new physiologically motivated fusion algorithm and a novel Bayes optimal self-architecting classifier …

Representations, Approximations, And Algorithms For Mathematical Speech Processing, Laura R. Suzuki

Theses and Dissertations

Representing speech signals such that specific characteristics of speech are included is essential in many Air Force and DoD signal processing applications. A mathematical construct called a frame is presented which captures the important time-varying characteristic of speech. Roughly speaking, frames generalize the idea of an orthogonal basis in a Hilbert space, Specific spaces applicable to speech are L₂(R) and the Hardy spaces H_p(D) for p> 1 where D is the unit disk in the complex plane. Results are given for representations in the Hardy spaces involving Carleson's inequalities (and its extensions), …

Singularity Avoidance Strategies For Satellite Mounted Manipulators Using Attitude Control, Nathan A. Titus

Theses and Dissertations

Control concepts for satellite mounted manipulators (SMM) are examined. The primary focus is on base actuated concepts, which eliminate singularity problems associated with free floating SMMs. A new form of the equations of motion for an n-link SMM is developed using a quasi coordinate form of Lagrange's Equation. Alternative free floating SMM designs are presented which eliminate dynamic singularities, but still experience difficulties due to the unactuated base. A new generic SMM controller is developed as a framework for various control concepts with and without base actuation. Momentum constrained Jacobians are shown to produce better SMM tracking than fixed base …

New Algorithms For Moving-Bank Multiple Model Adaptive Estimation, Juan R. Vasquez

Theses and Dissertations

The focus of this research is to provide methods for generating precise parameter estimates in the face of potentially significant parameter variations such as system component failures. The standard Multiple Model Adaptive Estimation (MMAE) algorithm uses a bank of Kalman filters, each based on a different model of the system. A new moving-bank MMAE algorithm is developed based on exploitation of the density data available from the MMAE. The methods used to exploit this information include various measures of the density data and a decision-making logic used to move, expand, and contract the MMAE bank of filters. Parameter discretization within …

Methodology For The Analysis And Design Of Internet Software Components Providing Relational Database Access Through The World Wide Web, Daniel L. Dipiro

Theses and Dissertations

This work examines the application of Internet software technologies to provide access to remote relational databases via the World Wide Web. The research applies these software technologies to assist the Air Force Institute of Technology Civilian Institute Program in improving operations and student to staff communication. An analysis of the existing Internet software technologies revealed several competing technologies capable of performing the same database access functions. The analysis further revealed weaknesses and inconsistencies in the existing AFIT/CI database. A methodology is proposed to assist in analyzing an existing development environment and in selecting among the competing technologies to provide the …

An Advanced Visualization Method For An Operations Research Analysis, Steven C. Oimoen

Theses and Dissertations

Visualizing multidimensional data using only two dimensions and conventional visualization techniques limits the understanding of the data set. Underlying structures or patterns within the data can easily go unnoticed. In order to gain additional insight into an analysis, incorporation of visualization and multidimensional graphics into the analysis results should be accomplished. The results must ensure that the information portrayed is not misleading or misunderstood. The integrity of the data must be preserved throughout the transformation. The primary objective of this research effort is to identify techniques to visualize multidimensional data and then develop a software tool to display the multidimensional …

Aegis Data Analysis And Reduction (Adar) In Support Of The Aegis Weapon System (Aws), June Bullard Gaines

Theses and Dissertations

The AEGIS Weapons System (AWS), part of the AEGIS Combat System (ACS), is an integral part of the defense system on U.S. Navy AEGIS-class ships. AEGIS Data Analysis and Reduction (ADAR) has been developed to assist in the evaluation of the AWS data. ADAR, along with the AWS and ACS, has evolved through the years to accommodate advances in technology and computer programming languages. Additionally, ADAR has evolved so that users located at sites other than the Naval Surface Warfare System Dahlgren Division (NSWCDD), Dahlgren, Virginia, can reduce tactical system data and perform data analysis using the reduced data.

This …

Concept Vectors: A Synthesis Of Concept Mapping And Matrices For Knowledge Representation In Intelligent Tutoring Systems, Mark L. Dyson

Theses and Dissertations

A review of the literature relating to intelligent tutoring systems (ITS) reveals that the bulk of research to date is focused on the student, and on methods for representing the knowledge itself. From student models to learning schemas to presentation methods, comparatively little attention has been paid to the problem of educators attempting to build viable lesson plans for use in an ITS environment--yet when this problem is addressed in the literature, it is recognized as a potentially daunting one. This thesis addresses the problem of ITS lesson plan development by proposing a practical, computable approach for knowledge engineering that …

An Incompleteness Handling Methodology For Validation Of Bayesian Knowledge Bases, David J. Bawcom

Theses and Dissertations

The PESKI (Probabilities, Expert Systems, Knowledge, and Inference) system attempts to address some of the problems in expert system design through the use of the Bayesian Knowledge Base (BKB) representation. Knowledge gathered from a domain expert is placed into this framework and inferencing is performed over it. However, by the nature of BKBs, not all knowledge is incorporated, i.e. the representation need not be a complete representation of all combinations and possibilities of the knowledge, as this would be impractical in many real-world systems. Therefore, inherent in such a system is the problem of incomplete knowledge, or spaces within the …

Developing A Corpus Specific Stoplist Using Quantitative Comparison, Craig N. Berg

Theses and Dissertations

We have become overwhelmed with electronic information and it seems our situation is not going to improve. It is becoming increasingly common for people to work with information on a daily basis. We seem to spend more and more time looking for information, and it is taking longer because more information is available. This thesis will look at how we can provide faster access to the information we want to find. Today's requirements are closely related to searching for information using queries. At the heart of the query process is the removal of search terms having little or no significance …

Visualization And Animation Of A Missile/Target Encounter, Jeffrey T. Bush

Theses and Dissertations

Existing missile/target encounter modeling and simulation systems focus on improving probability of kill models. Little research has been done to visualize these encounters. These systems can be made more useful to the engineers by incorporating current computer graphics technology for visualizing and animating the encounter. Our research has been to develop a graphical simulation package for visualizing both endgame and full fly-out encounters. Endgame visualization includes showing the interaction of a missile, its fuze cone proximity sensors, and its target during the final fraction of a second of the missile/target encounter. Additionally, this system displays dynamic effects such as the …

An Examination Of Multi-Tier Designs For Legacy Data Access, Michael L. Acker

Theses and Dissertations

This work examines the application of Java and the Common Object Request Broker Architecture (CORBA) to support access to remote databases via the Internet. The research applies these software technologies to assist an Air Force distance learning provider in improving the capabilities of its World Wide Web-based correspondence system. An analysis of the distance learning provider's operation revealed a strong dependency on a non-collocated legacy relational database. This dependency limits the distance learning provider's future web-based capabilities. A recommendation to improve operation by data replication is proposed, and the implementation details are provided for two alternative test systems that support …

Breast Cancer Mass Detection Using Difference Of Gaussians And Pulse Coupled Neural Networks, Donald A. Cournoyer

Theses and Dissertations

CAD, serving as a second reader, has been shown to improve the success of radiologists at detecting breast cancer. This thesis will develop a new algorithm to identify masses in mammograms. The system developed for this thesis will be capable of assisting a radiologist in making decisions.

A Single Chip Low Power Implementation Of An Asynchronous Fft Algorithm For Space Applications, Bruce W. Hunt

Theses and Dissertations

A fully asynchronous fixed point FFT processor is introduced for low power space applications. The architecture is based on an algorithm developed by Suter and Stevens specifically for a low power implementation. The novelty of this architecture lies in its high localization of components and pipelining with no need to share a global memory. High throughput is attained using large numbers of small, local components working in parallel. A derivation of the algorithm from the discrete Fourier transform is presented followed by a discussion of circuit design parameters specifically, those relevant to space applications. The generic architecture is explained with …

A Representational Approach To Knowledge And Multiple Skill Levels For Broad Classes Of Computer Generated Forces, Larry J. Hutson

Theses and Dissertations

Current computer generated forces (CGFs) in the 'synthetic battlespace', a training arena used by the military, exhibit several deficiencies. Human actors within the battlespace rapidly identify these CGFs and defeat them using unrealistic and potentially fatal tactics, reducing the overall effectiveness of this training arena. Simulators attached to the synthetic battlespace host local threat systems, leading to training inconsistencies when different simulators display the same threat at different levels of fidelity. Finally, current CGFs are engineered 'from the ground up', often without exploiting commonalities with other existing CGFs, increasing development (and ultimately training) costs. This thesis addresses these issues by …

A Model For Determining Information To Be Captured Regarding Unauthorized Computer Entry Of An Air Force Computer System, Leslie F. Himebrook

Theses and Dissertations

This thesis presents a model of information to capture regarding unauthorized computer systems access attempts. This model takes a management focus, and incorporates the technical focus, intelligence focus, and legal focus as inputs. The author used an exploratory, qualitative methodology consisting of an extensive literature review and interviews with experts in the field. These efforts produced the proposed model, which was reviewed by experts in the field using a delphi technique. The model consists of information that is divided into the following areas: 1. What information was compromised. 2. What type of intrusion occurred. 3. How the intrusion was attempted. …

A Modeling And Simulation Approach To Characterize Network Layer Internet Survivability, Leif S. King

Theses and Dissertations

The Air Force Core Competency of Information Superiority will be achieved in an age of decreasing AF manpower and corporate expertise. Increased AF reliance on COTS solutions, coupled with nearly ubiquitous points of entry to communication networks, create unique challenges in maintaining the Information Superiority edge. The protection of the internet is part of this equation. The internet supports the daily business traffic of the Air Force. Personnel, finance, and supply data flow through its routers. Controlling an adversary's access to our information systems, either the data, or the hardware and software that control the data and transform it into …

Requirements, Design And Prototype Of A Virtual User Interface For The Afit Virtual Spaceplane, John M. Lewis

Theses and Dissertations

The United States Air Force is evaluating the feasibility of designing a military spaceplane capable of accomplishing military objectives from a low earth orbit and atmospheric flight regimes. Current efforts are involved in determining the scientific, operational, and budgetary constraints associated with this concept. This thesis looks at the exploration of new interface techniques associated with the design of a virtual spaceplane and is a subset of the overall virtual spaceplane effort which will assist researchers in determining the feasibility of a military spaceplane. Interface techniques are integrated into a virtual user interface that is designed to accommodate expected operations …

Architecture, Design, And Implementation Of A Rapidly Prototyped Virtual Environment For A Military Spaceplane, Scott A. Rothermel

Theses and Dissertations

The new Global Engagement vision places increased emphasis on the Air Force's ability to control and exploit space. A military spaceplane combining reliable access to space, high operational tempos, and multi-mission capabilities is in conceptual stages of development. Virtual environment technology provides an opportunity to investigate system requirements and unconventional interface paradigms for this unique vehicle. A virtual environment architecture and design based on support for a rapid prototyping development process, separation of concerns, and user interface development is presented. The rapid prototyping process allowed management of changing requirements via an evolutionary approach to implementation. Separation of the activities performed …

Modeling And Simulation Support For Parallel Algorithms In A High-Speed Network, Dustin E. Yates

Theses and Dissertations

This thesis investigates the ability of a simulation model to compare and contrast parallel processing algorithms in a high-speed network. The model extends existing modeling, analysis, and comparison of parallel algorithms by providing graphics based components that facilitate the measurement of system resources. Simulation components are based on the Myrinet local area network standard. The models provide seven different topologies to contrast the performance of five variations of Fast Fourier Transform (FFT) algorithms. Furthermore, the models were implemented using a commercially developed product that facilitates the testing of additional topologies and the investigation of hardware variations. Accurate comparisons are statistically …

Subjective Quality Of Experience With The Internet: Accounting For Temporal Changes In User Acceptance Of Information Technology, Jason M. Turner

Theses and Dissertations

Contemporary information technology (IT) related research has focused on use as a key dependent measure for valuing IT. By understanding the determinants of IT use, we gain descriptive information about successful IT, and prescriptive information for better deploying IT resources. Although there are several competing theories regarding IT use, research findings often cite their inability to account for temporal changes in usage behaviors. This thesis introduces quality of experience as a potential moderator between the determinants of use and actual usage behaviors. A pilot survey concerning Internet usage generated potentially relevant items which were later refined into a questionnaire assessing …

Microprogramming A Writeable Control Memory Using Very Long Instruction Word (Vliw) Compilation Techniques, Randall S. Whitman

Theses and Dissertations

Microprogrammed Digital Signal Processors (DSP) are frequently used as a solution to embedded processor applications. These processors utilize a control memory which permits execution of the processor's instruction set architecture (ISA). The control memory can take the form of a static, read only memory (ROM) or a dynamic, writeable control memory (WCM), or both. Microcoding the WCM permits redefining the processor's ISA and provides speedup due to its instruction level parallelism (ILP) potential. In the past, code generation efforts for microprogrammable processors focused on creating assembly and microcode as two separate steps. In this thesis an alternative approach was chosen …

Pseudorandom Code Generation For Communication And Navigation System Applications, John F. Brendle Jr.

Theses and Dissertations

This research project investigated the design, construction and evaluation of a pseudorandom code generator for communication and navigation system applications. These types of codes include spreading codes, Gold codes, Jet Propulsion Laboratory (JPL) ranging codes, syncopated codes, and nonlinear codes. Such waveforms are typically used in communication and navigation system applications. The code generator uses the Stanford Telecom STEL-1032 Pseudorandom Number (PRN) coder. A coder interface was designed and constructed for manual data entry to the registers of the PRN coder. The code generator is capable of independently clocking and generating all possible codes with lengths up to 4,294,967,295 bits. …

Applications Of Unsupervised Clustering Algorithms To Aircraft Identification Using High Range Resolution Radar, Dzung Tri Pham

Theses and Dissertations

Identification of aircraft from high range resolution (HRR) radar range profiles requires a database of information capturing the variability of the individual range profiles as a function of viewing aspect. This database can be a collection of individual signatures or a collection of average signatures distributed over the region of viewing aspect of interest. An efficient database is one which captures the intrinsic variability of the HRR signatures without either excessive redundancy typical of single-signature databases, or without the loss of information common when averaging arbitrary groups of signatures. The identification of 'natural' clustering of similar HRR signatures provides a …

An Investigation Into The Use Of Software Product Metrics For Cobol Systems, Richard E. Boone

Theses and Dissertations

This thesis investigated several hypotheses that specific product measures could be used to predict later software lifecycle process or product measures. It collected software product and process measures from four consecutive major releases of a large Cobol legacy system (400K LOC). The types of product measures used were size and specific complexity measures. A statistical software package was used to calculate sample correlation coefficients between the measures. A 95% confidence interval was computed for each sample correlation coefficient that showed a strong or moderate linear correlation. The maintenance process measures provided were manhours used for each program changed or added, …