Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Air Force Institute of Technology

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 2341 - 2370 of 3052

Full-Text Articles in Physical Sciences and Mathematics

Analysis Of Usaf Battlelabs' Communication Infrastructure Over Various Protocols, Rocky A. Favorito, David M. Mcillece Mar 1999

Analysis Of Usaf Battlelabs' Communication Infrastructure Over Various Protocols, Rocky A. Favorito, David M. Mcillece

Theses and Dissertations

As a result of the doctrines exposed in the Air Force's "Global Engagement: A Vision for the 21st Century Air Force," the concept of a "Battlelab" was devised to support and develop the key warfighting capabilities needed in the next century. Although geographically separated, these labs must have the capability to exchange information with each other in a "Virtual Battlelab Environment" (VBE). Although many types of data will be exchanged, only variable-bit-rate (VBR) video and distributed interactive simulation (DIS) traffic are modeled in the VBE. The research described in this thesis utilizes a systems engineering approach to investigate the performance …

Go to article

Band Structure Anisotropy In Semiconductor Quantum Wells, Steven J. Novotny Mar 1999

Band Structure Anisotropy In Semiconductor Quantum Wells, Steven J. Novotny

Theses and Dissertations

The focus of this research is an investigation of energy band anisotropy in simple quantum well structures. This anisotropy results from the asymmetry of the periodic potential within the crystal lattice. For sufficiently high doping levels, band structure anisotropy is expected to play an important role in the evaluation of the electronic and optical properties of the quantum well structures. The analysis uses a model based on a 6x6 Luttinger-Kohn k.p approach for bulk material valence band structure together with the Envelope Function Approximation. The model is used to analyze Si/SiGe, AlGaAs/GaAs, and GaAs/InGaAs quantum wells for the 001 and …

Go to article

A Continuous Wave Atomic Bromine Laser Produced By Photolysis Of Iodine Monobromide, Brian A. Smith Mar 1999

A Continuous Wave Atomic Bromine Laser Produced By Photolysis Of Iodine Monobromide, Brian A. Smith

Theses and Dissertations

An apparatus to generate continuous wave (CW) lasing at 2.714 µm by Br(2P1/2) atoms produced from photodissociation of IBr was designed, constructed and tested. A frequency doubled Nd:YAG laser firing 8 ns, 850 mJ pulses at 532 nm was used to photodissociate static IBr vapor inside a flow nozzle. The CaF2 windows on either side of the nozzle proved to have a damage threshold below the threshold for lasing. Pulsed lasing in static mode was not observed. Therefore, CW lasing in flow mode, using an Ar+ laser at 488 nm, could not be investigated.

Go to article

Laser Beam Combining And Cleanup Via Stimulated Brillouin Scattering In Multi-Mode Optical Fibers, Blake C. Rodgers Mar 1999

Laser Beam Combining And Cleanup Via Stimulated Brillouin Scattering In Multi-Mode Optical Fibers, Blake C. Rodgers

Theses and Dissertations

The main objective of this thesis was to demonstrate the feasibility of combining and cleaning up multiple laser beams via Stimulated Brillouin Scattering (SBS) in a multi-mode optical fiber. Beam combining via SBS in an optical fiber is of interest because of the low SBS threshold power in an optical fiber allowing low power diode laser beams to be combined into one high power beam. SBS theory and some of the important historical results are described briefly. The experimental results clearly indicate that SBS in multi-mode optical fiber can indeed combine laser beams and clean up the beams at the …

Go to article

A Java Based Human Computer Interface For A Uav Decision Support Tool Using Conformal Mapping, Randy A. Flood Mar 1999

A Java Based Human Computer Interface For A Uav Decision Support Tool Using Conformal Mapping, Randy A. Flood

Theses and Dissertations

This paper describes the development of the Human Computer Interface (HCI) for a Decision Support System for routing Unmanned Aerial Vehicles (UAVs). This problem is a multi-vehicle routing problem with time-windows. Because of the unique nature of UAVs, a tool is needed to support dynamic re-routing. We solve the problem in two ways. First, we create a UAV Decision Support Tool (UAV DST) that uses a set of Java software objects to display maps and convert between latitude-longitude coordinates and x-y coordinates. Secondly, this library provides the ability for the user to dynamically reoptimize large UAV routing problems through a …

Go to article

An Interactive Tool For Refining Software Specifications From A Formal Domain Model, Gary L. Anderson Mar 1999

An Interactive Tool For Refining Software Specifications From A Formal Domain Model, Gary L. Anderson

Theses and Dissertations

This work examines the process for refining a software specification from a formal object-oriented domain model. This process was implemented with interactive software to demonstrate the feasibility and benefits of automating what has been a tedious and often error-prone manual task. The refinement process operates within the framework of a larger Knowledge-Based Software Engineering system. A generic object-oriented representation is used to store a domain model, which allows the specification tool to access, select, and manipulate the required objects to form a customized specification. The specification is also stored as an object-oriented model, which in turn can be accessed by …

Go to article

Methodology For Application Design Using Information Dissemination And Active Database Technologies, Robert H. Hartz Mar 1999

Methodology For Application Design Using Information Dissemination And Active Database Technologies, Robert H. Hartz

Theses and Dissertations

In dynamic data environments, the large volume of transactions requires flexible control structures to effectively balance the flow of information between producers and consumers. Information dissemination-based systems, using both data push and pull delivery mechanisms, provide a possible scalable solution for data-intensive applications. In this research, a methodology is proposed to capture information dissemination design features in the form of active database rules to effectively control dynamic data applications. As part of this design methodology, information distribution properties are analyzed, data dissemination mechanisms are transformed into an active rule framework, and the desired reactive behavior is achieved through rule customization. …

Go to article

Protein Structure Prediction Using Parallel Linkage Investigating Genetic Algorithms, Karl R. Deerman Mar 1999

Protein Structure Prediction Using Parallel Linkage Investigating Genetic Algorithms, Karl R. Deerman

Theses and Dissertations

AFIT has had a long-standing interest in solving the protein structure prediction (PSP) problem. The PSP problem is an intractable problem that if "solved" can lead to revolutionary new techniques for everything from the development of new medicines to optical computer switches. The challenge is to find a reliable and consistent method of predicting the 3-dimensional structure of a protein given its defining sequence of amino acids. PSP is primarily concerned with predicting the tertiary protein structure without regards to how the protein came to this folded state. The tertiary structure determines the protein's functionality.

Go to article

Transforming Cobol Legacy Software To A Generic Imperative Model, Dina L. Moraes Mar 1999

Transforming Cobol Legacy Software To A Generic Imperative Model, Dina L. Moraes

Theses and Dissertations

Legacy COBOL code presents challenges for organizations wishing to increase their effectiveness and improve their efficiency. The systems that utilize this code are vital to enterprise operations, yet maintenance of code is expensive. This research presents an alternative that overcomes some of the problems of legacy COBOL code through the use of software reengineering techniques. This research develops a transformation system to convert COBOL code into a generic imperative model, recapturing the initial design and deciphering the requirements implemented by the legacy code, thereby making possible the documentation of legacy systems, design restructuring, and the re-design of a new, enhanced …

Go to article

Extensible Multi-Agent System For Heterogeneous Database Association Rule Mining And Unification, Christopher G. Marks Mar 1999

Extensible Multi-Agent System For Heterogeneous Database Association Rule Mining And Unification, Christopher G. Marks

Theses and Dissertations

The Probabilities, Expert System, Knowledge, and Inference (PESKI) System uses the data mining of association rules to fill incompleteness in the knowledge of an expert system. The rules are mined from transactional data sources and then incorporated using an existing link to PESKI. One method of providing a system that will easily allow new data sources to be added is using an information gathering agent-based system. This research first develops a methodology for designing and creating a multi-agent system. It then applies this methodology to design a platform independent means of data mining data sources of any format. The use …

Go to article

Improving Cape Canaveral's Next-Day Thunderstorm Forecasting Using A Meso-Eta Model-Based Index, John C. Crane Mar 1999

Improving Cape Canaveral's Next-Day Thunderstorm Forecasting Using A Meso-Eta Model-Based Index, John C. Crane

Theses and Dissertations

Reliable thunderstorm forecasts are essential to safety and resource protection at Cape Canaveral. Current methods of forecasting day-2 thunderstorms provide little improvement over forecasting by persistence alone and are therefore in need of replacement. This research focused on using the mesoscale eta model to develop an index for improved forecasting of day-2 thunderstorms. Logistic regression techniques were used to regress the occurrence of a thunderstorm at Cape Canaveral against day-2 forecast variables output, or derived, from the mesoscale eta model. Accuracy and bias scores were calculated for the forecasts made by the regression equations, and the forecast results were compared …

Go to article

A Comparison Of Horizontal Cloud-To-Ground Lightning Flash Distance Using Weather Surveillance Radar And The Distance Between Successive Flashes Method, Christopher C. Cox Mar 1999

A Comparison Of Horizontal Cloud-To-Ground Lightning Flash Distance Using Weather Surveillance Radar And The Distance Between Successive Flashes Method, Christopher C. Cox

Theses and Dissertations

On April 29th, 1996 an airman servicing a C-130 aircraft on Huriburt AFB Florida was struck and killed by a lightning flash that traveled an estimated 7 to 10 miles from storms south of the airfield. Ten other workers were injured in the incident. The fatal flash occurred just 8 minutes after the base weather station allowed a lightning advisory to expire. The incident brought to question the adequacy of lightning advisory criteria. Very little research has been done on the horizontal distance that cloud-to-ground lightning flashes occurs from the center of a thunderstorm. This thesis used the WSR-88D method, …

Go to article

Predicting Launch Pad Winds At The Kennedy Space Center With A Neural Network Model, Steven J. Storch Mar 1999

Predicting Launch Pad Winds At The Kennedy Space Center With A Neural Network Model, Steven J. Storch

Theses and Dissertations

This thesis uses neural networks to forecast winds at the Kennedy Space Center and the Cape Canaveral Air Station launch pads. Variables are developed from WINDS tower observations, surface and buoy observations, and an upper-air sounding. From these variables, a smaller set of predictive inputs is chosen using a signal-to-noise variable screening method. A neural network is then trained to forecast launch pad winds from the inputs. The network forecasts are compared to persistence, and peak wind predictions are found skillful compared to persistence. An ensemble modeling technique using Toth's and Kalnay's breeding of growing modes method is explored with …

Go to article

Using The Wsr-88d To Forecast Downburst Winds At Cape Canaveral Air Station And The Kennedy Space Center (Ccas/Ksc), Gerald D. Sullivan Jr. Mar 1999

Using The Wsr-88d To Forecast Downburst Winds At Cape Canaveral Air Station And The Kennedy Space Center (Ccas/Ksc), Gerald D. Sullivan Jr.

Theses and Dissertations

The 45 Weather Squadron is tasked with providing several convective wind warnings in support of the U. S. Space Program. The forecasters use a radar-based forecast technique to determine if a thunderstorm has the potential to produce a gust that meets warning criteria. This technique, the Echo Top/Vertically Integrated Liquid Wind Gust Potential (ET/VIL WGP), has not previously been evaluated for use in the Cape Canaveral Air Station and Kennedy Space Center (CCAS/KSC) locale. Additionally, there are two other radar-based forecast techniques that required evaluation for possible inclusion into the 45 WS forecast process. These are the Maximum Reflectivity / …

Go to article

Computation Of Scattering From Bodies Of Revolution Using An Entire-Domain Basis Implementation Of The Moment Method, Arthur P. Ford Iv Mar 1999

Computation Of Scattering From Bodies Of Revolution Using An Entire-Domain Basis Implementation Of The Moment Method, Arthur P. Ford Iv

Theses and Dissertations

Research into improved calibration targets for measurement of radar cross-section has created a need for the ability to accurately compute the scattering from perfectly conducting bodies of revolution. Common computational techniques use Moment Method codes that employ subdomain basis functions to expand the unknown current density. This approach has its shortcomings. Large numbers of basis functions are required, and increasing the number of basis functions to improve accuracy after an initial computation requires re-computation of previous results and lost processing time. This research involves using basis functions that have as their domain the entire length of the surface. Entire-domain basis …

Go to article

Graphical User Interface And Microprocessor Control Enhancement Of A Pseudorandom Code Generator, John M. Kos Mar 1999

Graphical User Interface And Microprocessor Control Enhancement Of A Pseudorandom Code Generator, John M. Kos

Theses and Dissertations

Modern digital communication techniques often require the generation of pseudorandom numbers or sequences. The ability to quickly and easily produce various codes such as maximal length codes, Gold codes, Jet Propulsion Laboratory ranging codes, syncopated codes, and non-linear codes in a laboratory environment is essential. This thesis addresses the issue of providing automated computer control to previously built, manually controlled hardware incorporating the Stanford Telecom STEL-1032 Pseudo-Random Number (PRN) Coder. By incorporating a microcontroller into existing hardware, the STEL-1032 can now be conveniently controlled from a MATLAB Graphical User Interface (GUI). The user can quickly create, save, and recall various …

Go to article

Gps Signal Offset Detection And Noise Strength Estimation In A Parallel Kalman Filter Algorithm, Barry J. Vanek Mar 1999

Gps Signal Offset Detection And Noise Strength Estimation In A Parallel Kalman Filter Algorithm, Barry J. Vanek

Theses and Dissertations

Measurements from Global Positioning System (GPS) satellites are subject to corruption by signal interference and induced offsets. This thesis presents two independent algorithms to ensure the navigation system remains uncorrupted by these possible GPS failures. The first is a parameter estimation algorithm that estimates the measurement noise variance of each satellite. A redundant measurement differencing (RMD) technique provides direct observability of the differenced white measurement noise samples. The variance of the noise process is estimated and provided to the second algorithm, a parallel Kalman filter structure, which then adapts to changes in the real-world measurement noise strength. The parallel Kalman …

Go to article

A New Sequential Goodness-Of-Fit Test For A Family Of Two Parameter Gamma Distributions With Known Shape Based On Skewness And Q-Statistic, Jae Suk Park Mar 1999

A New Sequential Goodness-Of-Fit Test For A Family Of Two Parameter Gamma Distributions With Known Shape Based On Skewness And Q-Statistic, Jae Suk Park

Theses and Dissertations

The objective of this research is to develop a new goodness-of-fit test for the gamma distribution. The gamma distribution is widely used for reliability and failure time estimations in the real world. Several methods to measure the fit of data to a hypothesized distribution are commonly used such as the chi-squared test, and Anderson- Darling test. The most important aspect of these tests is how well the results reflect the distribution family. This research will use the sequential test with skewness and Q- statistic as test statistics for fitting a gamma distribution. The main idea of a sequential test is …

Go to article

Kinetic Model Of A Space-Based, Br (4 2P1/2 → 4 2P3/2) Laser Pumped By Solar Photolysis Of Ibr, Barry N. Behnken Mar 1999

Kinetic Model Of A Space-Based, Br (4 2P1/2 → 4 2P3/2) Laser Pumped By Solar Photolysis Of Ibr, Barry N. Behnken

Theses and Dissertations

A kinetic model of the directly solar-pumped, atomic bromine laser-operating on the Br (4 2P1/2 → 4 2P3/2) transition under IBr photolysis-was developed, executed, and interpreted. In recognition of an evolving national interest in space-based laser development, the model presumed operation on a space station platform. Results indicate that a well-engineered IBr laser is capable of generating 1.2 kilowatts of continuous-wave (CW) power under a pumping concentration of 20,000 solar units. Such performance translates to an efficiency of roughly 0.29%, appreciably better than the 0.1% ascribed to the heretofore leading solar-pumped competitor. An extensive analysis …

Go to article

Strategies For Steganalysis Of Bitmap Graphics Files, Christopher J. Fogle Mar 1999

Strategies For Steganalysis Of Bitmap Graphics Files, Christopher J. Fogle

Theses and Dissertations

Steganography is the art and science of communicating through covert channels. The goal of steganography is to hide the fact that a message is even being transmitted. In the context of today's digital world, this ancient practice is enjoying resurgence due to the plethora of hiding places made possible by modern information media. Of particular concern is the use of graphics image files to conceal both legitimate and criminal communications.

Go to article

Characterization Of The Double Scatter Spectrum In Multiplexed Compton Scatter Tomography, David W. Gerts Mar 1999

Characterization Of The Double Scatter Spectrum In Multiplexed Compton Scatter Tomography, David W. Gerts

Theses and Dissertations

The Multiplexed Compton Scatter Tomograph (MCST) uses single back-scattered photons to image electron density in aluminum. A source of error in this imaging technique is the presence of multiple scatters. This thesis studies the double scatter spectrum as an approximation of the multiple scatter spectrum. A deterministic code called Monte Carlo Double Scatter (MOCADS) was developed to investigate the double scatter spectrum. The code includes calculations of the Rayleigh scatter, Compton scatter, Doppler broadening effects of the spectrum, and polarization effects following the Compton scatter. The Doppler broadening portion of the code was validated by a deterministic code called Scatgram. …

Go to article

Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath Mar 1999

Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath

Theses and Dissertations

Electrical characterization has been performed on ion-implanted p-type 4H-SiC to assess the activation efficiency and implantation-related damage recrystallization with the intention of developing an implantation/annealing scheme. Low doped (Na - Nd = 5x10(exp 15)/cu cm) epitaxial p-type layers grown by MOCVD were implanted with Al or B at doses ranging from 1x10(exp 13) to 1x10(exp 14)/sq cm at room temperature or 500 deg. C. The electrical technique of Temperature Dependent Hall Effect (TDHE) indicated that Al and B act as shallow acceptors 4H-SiC with ionization energies of ^252 and ^285 meV, respectively. The highest activation efficiency for Al and B …

Go to article

Double Layer Effects On Shock Wave Propagation, Shannon L. Walker Mar 1999

Double Layer Effects On Shock Wave Propagation, Shannon L. Walker

Theses and Dissertations

An analysis and assessment of two mechanisms in plasma shock interactions was conducted under conditions typically encountered in a weakly ionized glow discharge. The mechanisms of a spatially-dependent electron temperature and additional electron impact ionization at the shock front were examined for effects on shock structure and propagation. These mechanisms were incorporated into an existing one-dimensional, time-dependent, fluid dynamics code that uses the Riemami problem as a basis and numerically solves the Euler equations for two fluids: the neutral gas and the charged component. The spatial variation in electron temperature was modeled as a shock-centered rise in temperature. Additional ionization …

Go to article

Optimization Of A Multilayer Photothermal Sensor For Infrared Spectroscopy, Janine O.J. Wiggins Mar 1999

Optimization Of A Multilayer Photothermal Sensor For Infrared Spectroscopy, Janine O.J. Wiggins

Theses and Dissertations

Tri-layer thermal diffusion modeling was applied to the optimization of a multi-layer reed sensor for use in a photothermal infrared detector. The multi-layer reed sensor deflects in response to increased temperature. Deflection, of angstroms or larger, is measured using an atomic force microscope. A newly developed thermal diffusion model for three layer reeds was combined with an existing two-layer cantilever model, in order to explore the effects of length, operating frequency, and layer thickness on signal to noise ratio. Model behavior is presented, and compared to laboratory results.

Go to article

Modeling Chemical Absorption Through Membranes, Jeffrey M. Hemmes Mar 1999

Modeling Chemical Absorption Through Membranes, Jeffrey M. Hemmes

Theses and Dissertations

Understanding the processes involved in dermal penetration of chemicals and drugs is important to both toxicologists and pharmacologists. Researchers developing new drugs are interested in enhancing the penetration of chemicals through the skin, while environmental professionals are interested in limiting such penetration. For both types of applications, predictive biologically-based mathematical models can be very useful in understanding the processes involved, particularly when such models are based on physiological and biochemical parameters which can be measured experimentally. In this thesis we study two existing physiologically-based pharmacokinetic (PBPK) models that predict concentrations of neat and aqueous dibromomethane (DBM) absorbed into and through …

Go to article

Target Pose Estimation From Radar Data Using Adaptive Networks, Andrew W. Learn Mar 1999

Target Pose Estimation From Radar Data Using Adaptive Networks, Andrew W. Learn

Theses and Dissertations

his research investigates and extends recent work by J.C. Principe at the University of Florida in target pose estimation using adaptive networks. First, Principe's technique is successfully extended to estimate both azimuth and elevation using SAR images. A network trained and tested using MSTAR data yields mean errors of less than six degrees in azimuth and five degrees in elevation. Second, the technique is applied to high-range resolution radar (HRR) signatures. Ground target (azimuth only) testing yields mean errors of less than 11 degrees for most classes. Air target testing for networks trained and tested on the same aircraft class …

Go to article

Incorporating Scene Mosaics As Visual Indexes Into Uav Video Imagery Databases, Timothy I. Page Mar 1999

Incorporating Scene Mosaics As Visual Indexes Into Uav Video Imagery Databases, Timothy I. Page

Theses and Dissertations

The rise of large digital video archives has strengthened the need for more efficient ways of indexing video files an accessing the information contained in them. Reconnaissance platforms, such as the Predator UAV, are contributing thousands of hours of video footage that require analysis, storage, and retrieval. A process is proposed for converting a video stream into a series of mosaic and selected still images that provide complete coverage of the original video. The video mosaic images can be utilized as visual indexes into a video database. In addition, mosaic images contain information from an entire sequence of video frames …

Go to article

Analysis Of The Applicability Of Video Segmentation To Unmanned Aerial Vehicle Surveillance Video, Bradley L. Pyburn Mar 1999

Analysis Of The Applicability Of Video Segmentation To Unmanned Aerial Vehicle Surveillance Video, Bradley L. Pyburn

Theses and Dissertations

The focus of this research is to determine if applying edge detection segmentation (proposed by Ramin Zabih, Justin Miller, and Kevin Mai) to Unmanned Aerial Vehicle (UAV) video footage can provide meaningful segments for database storage and retrieval. The edge detection segmentation algorithm is applied to fifty-four UAV video sequences containing visual effects such as abrupt camera changes, camera zooms, motion (rapid and gradual), and cloud cover while varying the frame rate from 5 fps to 30 fps. An analysis of the results is performed to compare actual versus expected outcomes, similar sequences, and scenes with motion, along with explaining …

Go to article

Generating Executable Code From Formal Specifications Of Primitive Objects, Travis W. Tankersley Mar 1999

Generating Executable Code From Formal Specifications Of Primitive Objects, Travis W. Tankersley

Theses and Dissertations

The concept of developing a model for producing compilable and executable code from formal software specifications has long been a goal of software engineers. Previous research at the Air Force Institute of Technology (AFIT) has been focused on specification and domain analysis. An analysis model is populated using specifications written in Z. Then, a set of preliminary design transforms refines the specification in the analysis model. This research bridges the gap between analysis and design, allowing source code to be produced from formal specifications of primitive objects using transformational programming. The contribution of this thesis is to transform the analysis …

Go to article

An Efficient Gps Position Determination Algorithm, Carlos R. Colon Mar 1999

An Efficient Gps Position Determination Algorithm, Carlos R. Colon

Theses and Dissertations

The use of detect, or closed-form solutions of the trilateration equations used to obtain the position fix in GPS receivers is investigated. The paper is concerned with the development of an efficient new position determination algorithm that uses the closed-form solution of the trilateration equations and works in the presence of pseudorange measurement noise and for an arbitrary number of satellites. in addition, an initial position guess is not required and good estimation performance is achieved even under high GDOP conditions. A two step GPS position determination algorithm which 1) entails the solution of a linear regression problem and, 2) …

Go to article

First Prev Next Last