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Air Force Institute of Technology

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Articles 2011 - 2040 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Evolving Compact Decision Rule Sets, Robert E. Marmelstein Jun 1999

Evolving Compact Decision Rule Sets, Robert E. Marmelstein

Theses and Dissertations

While data mining technology holds the promise of automatically extracting useful patterns (such as decision rules) from data, this potential has yet to be realized. One of the major technical impediments is that the current generation of data mining tools produce decision rule sets that are very accurate, but extremely complex and difficult to interpret. As a result, there is a clear need for methods that yield decision rule sets that are both accurate and compact. The development of the Genetic Rule and Classifier Construction Environment (GRaCCE) is proposed as an alternative to existing decision rule induction (DRI) algorithms. GRaCCE …

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Multiobjective Evolutionary Algorithms: Classifications, Analyses, And New Innovations, David A. Van Veldhuizen Jun 1999

Multiobjective Evolutionary Algorithms: Classifications, Analyses, And New Innovations, David A. Van Veldhuizen

Theses and Dissertations

This research organizes, presents, and analyzes contemporary Multiobjective Evolutionary Algorithm (MOEA) research and associated Multiobjective Optimization Problems (MOPs). Using a consistent MOEA terminology and notation, each cited MOEAs' key factors are presented in tabular form for ease of MOEA identification and selection. A detailed quantitative and qualitative MOEA analysis is presented, providing a basis for conclusions about various MOEA-related issues. The traditional notion of building blocks is extended to the MOP domain in an effort to develop more effective and efficient MOEAs. Additionally, the MOEA community's limited test suites contain various functions whose origins and rationale for use are often …

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Cobol Reengineering Using The Parameter Based Object Identification (Pboi) Methodology, Sonia De Jesus Rodrigues Jun 1999

Cobol Reengineering Using The Parameter Based Object Identification (Pboi) Methodology, Sonia De Jesus Rodrigues

Theses and Dissertations

This research focuses on how to reengineer Cobol legacy systems into object oriented systems using Sward's Parameter Based Object Identification (PBOI) methodology. The method is based on relating categories of imperative subprograms to classes written in object oriented language based on how parameters are handled and shared among them. The input language of PBOI is a canonical form called the generic imperative model (GIM), which is an abstract syntax tree (AST) representation of a simple imperative programming language. The output is another AST, the generic object model (GOM), a generic object oriented language. Conventional languages must be translated into the …

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Implementation Of A Two-Dimensional Hydrodynamic Shock Code Based Upon The Weighted Average Flux Method, Mark P. Wittig Jun 1999

Implementation Of A Two-Dimensional Hydrodynamic Shock Code Based Upon The Weighted Average Flux Method, Mark P. Wittig

Theses and Dissertations

Numerical modeling of shock propagation and reflection is of interest to the Department of Defense (DoD). Propriety state-of-the-art codes based upon E. F. Toro's weighted average flux (WAF) method are being used to investigate complex shock reflection phenomena. Here we develop, test, and validate a one-dimensional hydrodynamic shock code. We apply WAF to Gudonov's first-order upwind method to achieve second-order accuracy. Oscillations, typical of second-order methods, are then removed using adaptive weight limiter functions based upon total variation diminishing (TVD) flux limiters. An adaptive Riemann solver routine is also implemented to improve computational efficiency. This one-dimensional code is then extended …

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Image Fusion Using Autoassociative-Heteroassociative Neural Networks, Claudia V. Kropas-Hughes May 1999

Image Fusion Using Autoassociative-Heteroassociative Neural Networks, Claudia V. Kropas-Hughes

Theses and Dissertations

Images are easily recognized, classified, and segmented; in short, analyzed by humans. The human brain/nervous system; the biological computer, performs rapid and accurate image processing. In the current research the concepts of the biological neural system provide the impetus for developing a computational means of fusing image data. Accomplishing this automatic image processing requires features be extracted from each image data set, and the information content fused. Biologically inspired computational models are examined for extracting features by transformations such as Fourier, Gabor, and wavelets, and for processing and fusing the information from multiple images through evaluation of autoassociative neural networks …

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Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott Apr 1999

Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott

AFIT Patents

An improved intracavity sensor based output power control for microcavity light emitting devices. An improved phototransistor transducer is both configured and physically disposed so that it passively transmits the spurious optical energy output of the microcavity light emitting device while simultaneously generating a light determined electrical signal of easily used large magnitude that is nearly free of error. The base-collector region of the transistor is disposed with a quantum well absorbing layer and produces a signal responsive to a selected emission wavelength. The configuration of the optical energy communicating transducer is arranged so that it is improved in sensitivity and …

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Fan-Beam Multiplexed Compton Scatter Tomography For Single-Sided Noninvasive Inspection, Brian L. Evans Apr 1999

Fan-Beam Multiplexed Compton Scatter Tomography For Single-Sided Noninvasive Inspection, Brian L. Evans

Theses and Dissertations

Multiplexed Compton Scatter Tomography (MCST) is explored as a method of nondestructively generating cross-sectional images of a sample's electron density. MCST is viable when access is available to only one side of the sample because it registers scattered gamma radiation. Multiplexing in scattered photon energy and in detector position allows simultaneous interrogation of many voxels with comparatively wide collimation. Primary components include a radioisotope source, fan beam collimators, and energy-discriminating detectors. The application of MCST to inspecting aluminum airframes for corrosion is considered. This application requires source gammas near 100 keV where the scattered gamma energy is severely broadened by …

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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 …

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Use Of Diffuse Reflectance Spectroscopy To Determine Desorption Coefficients Of Trichioroethylene From Powdered Soils, Jay H. Foil Mar 1999

Use Of Diffuse Reflectance Spectroscopy To Determine Desorption Coefficients Of Trichioroethylene From Powdered Soils, Jay H. Foil

Theses and Dissertations

This laboratory thesis investigated the applicability of reflectance spectroscopy as a tool to measure desorption rates by directly observing the change in trichloroethylene bound to surface sites. Diffuse reflectance spectroscopy holds the promise of being a faster technique with minimal sample preparation time. Reflectance spectroscopy's dependence on the surface of the sample is its greatest advantage, as well as its greatest disadvantage. Both high and low resolution scans were made of different soil samples contaminated by trichloroethylene. After the technique of spectral subtraction was used, potential TCE signals were observed from the dolomitic limestone sample. Unfortunately, due to the low …

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Space Charge Structure Of A Glow Discharge In The Presence Of A Longitudinal Inhomogeneity, Frank A. Tersigni Mar 1999

Space Charge Structure Of A Glow Discharge In The Presence Of A Longitudinal Inhomogeneity, Frank A. Tersigni

Theses and Dissertations

A survey of space charge structures arising due to inhomogeneities in glow discharges was conducted. Space charge structures associated with tube geometries, the cathode sheath, striations, and shockwaves were examined. Space charge effects on the Electron Energy Distribution Function (EEDF) were explored for a geometric inhomogeneity using an approximate nonlocal solution to the one dimensional Boltzmann equation after Godyak. The approximate solution partially captured qualitative aspects of space charge effects on the EEDF. Simplification of collisional effects and adaptation of an approximate electric field restricted quantitative comparisons with experimental data. It is recommended that any future analysis of space charge …

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Parallel Data Mining With The Message Passing Interface Standard On Clusters Of Personal Computers, Lonnie P. Hammack Mar 1999

Parallel Data Mining With The Message Passing Interface Standard On Clusters Of Personal Computers, Lonnie P. Hammack

Theses and Dissertations

Piles of personal computers (PoPCs) have begun to challenge the performance of the traditional Massively Parallel Processors (MPPs) and the less traditional networks of workstations (NOWs) as platforms for parallel computing. Large clusters of PCs have reached and at times exceeded the performance of modern MPPs at a fraction of the cost. Built with commodity components, these clusters can be constructed for about half the cost of a comparable NOW. The primary competing operating systems (OIS) in use on PoPCs are Linux and Windows NT. This thesis investigation compares the performance of an NT cluster with that of a Linux …

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A Modeling And Simulation Approach To Analyze The Workload Associated With The Growth Of Network Router Access Control Lists, Douglas R. Lomsdalen Mar 1999

A Modeling And Simulation Approach To Analyze The Workload Associated With The Growth Of Network Router Access Control Lists, Douglas R. Lomsdalen

Theses and Dissertations

Organizations can no longer isolate their networks from the rest of the world and still remain competitive. An organization willing to compete in the world market must take the necessary precautions to protect its network, the systems located on those networks, and its mission critical data. There are performance issues associated with the use of access control lists (ACL); however, if ACLs are implemented properly and periodically reviewed, a secure network can be attained. This research attempts to determine how the growth of an ACL affects packet flow and router CPU consumption, and also identify the specific length of an …

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An Improved Thunderstorm Forecast Index For Cape Canaveral, Florida, James A. Everitt Mar 1999

An Improved Thunderstorm Forecast Index For Cape Canaveral, Florida, James A. Everitt

Theses and Dissertations

This thesis creates a new algorithm to replace the Neumann-Pfeffer Thunderstorm Index (NPTI). The 45th Weather Squadron at Patrick AFB, Florida, uses the NPTI as an objective means of determining the probability of thunderstorm occurrence at Cape Canaveral. The probability is used for mission planning and resource protection, and increasing the accuracy of NPTI can potentially save billions of dollars for the United States space program. Stratified logistical regressions are performed and probability equations are derived for May through September using upper air data and surface observations for Cape Canaveral. A logistical regression of NPTI was also performed. Variables include …

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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 …

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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.

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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 …

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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, …

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A Validation Study Of Cloud Scene Simulation Model Temporal Performance, Glenn Kerr Mar 1999

A Validation Study Of Cloud Scene Simulation Model Temporal Performance, Glenn Kerr

Theses and Dissertations

Cloud Scene Simulation Model (CSSM) temporal performance was validated by comparing the cloud forcing signatures on observed radiometric time series with those derived from CSSM output for initial conditions similar to that for the observed data. Observed radiometric data was collected by a normal incidence pyraheliometer sensitive to wavelengths in the range .3mm to 3mm. Simulation radiometric time series data was derived by applying the following process to each case study. CSSM cloud liquid water content (CLWC) grids were converted to grids of slant path optical depth values by the Fast Map post processor to the CSSM. A ray tracing …

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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 …

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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 …

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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 …

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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 …

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Numerical Solutions To The Two Dimensional Boltzmann Equation, Christopher G. Smithtro Mar 1999

Numerical Solutions To The Two Dimensional Boltzmann Equation, Christopher G. Smithtro

Theses and Dissertations

A strict kinetic, two-dimensional model of the electron kinetics within a glow discharge positive column is developed. The problem is solved in cylindrical geometry using the standard two-term Legendre expansion of the electron velocity distribution function. The model establishes a steady state solution, such that the net ionization rate is exactly balanced by the wall loss. In addition to a thorough analytic development, we present the numerical techniques used to solve the resulting elliptic partial differential equation, including an efficient method to treat sparse banded matrices. The model is validated against published results, local and nonlocal kinetic approximations, and a …

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Structural Emergence And The Collaborative Behavior Of Autonomous Nano-Satellites, Daniel J. Petrovich Mar 1999

Structural Emergence And The Collaborative Behavior Of Autonomous Nano-Satellites, Daniel J. Petrovich

Theses and Dissertations

The collaborative behavior of nano-satellites in a zero-gravity environment is explored, and satellite characteristics are proposed that maximize constellation robustness and minimize manufacturing costs. Behavioral algorithms are proposed to facilitate both swarming and structural formation and are validated using the Structural Emergence Simulator (STEMS) Graphical User Interface (GUl). A payload of multiple satellites is placed in a zero-gravity environment and released to re-configure autonomously into a pre-designed structure. Data transmission between satellites is not permitted during the swarming phase of the structure formation mission. A binary behavior algorithm is invented that produces a direction and magnitude solution to the satellite …

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High-Grade Paper Recycling: A Program Management Perspective, Rodger L. Carter Mar 1999

High-Grade Paper Recycling: A Program Management Perspective, Rodger L. Carter

Theses and Dissertations

Recycling of high-grade paper is one method of reducing the use of natural resources and the amount of waste being emitted into the environment, both in the process of manufacturing and in the disposal of unneeded documents. The Air Force Materiel Command (AFMC) is a significant user of high-grade paper, thus recycling represents a potential saving to society in the form of lessened negative impact on the environment as the result of AFMC operations. The possibility also exists for AFMC to reduce operating costs. The purpose of this study is to explore means of reducing high-grade paper disposal by AFMC, …

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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 …

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Inelastic Scattering Matrix Elements For The Collision B (2P1/2) + H2(J) → B (2P3/2) + H2(J'), Thomas A. Niday Mar 1999

Inelastic Scattering Matrix Elements For The Collision B (2P1/2) + H2(J) → B (2P3/2) + H2(J'), Thomas A. Niday

Theses and Dissertations

Initial efforts to characterize the scattering dynamics of B + H2 focus on computing scattering matrix elements for the fine structure transition B (2P1/2) --> B (2P3/2) in collisions with H2, allowing for rotational excitation. Using a new application of the time dependent Channel Packet Method (CPM), reactant and product wave packets are prepared in the asymptotic limit on the B (2P1/2) and B (2P3/2) surfaces. They are propagated using the split operator method together wit a unitary transformation between the …

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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 …

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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.

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Transforming Aggregate Object-Oriented Formal Specifications To Code, John A. Kissack Mar 1999

Transforming Aggregate Object-Oriented Formal Specifications To Code, John A. Kissack

Theses and Dissertations

The feasibility of a transformational formal-based software engineering tool has been the focus of AFIT research for several years. Until now, the main research emphasis has been placed on the individual components that would comprise such a transformational system; therefore, this research demonstrates how a representative collection of aggregate objects would be transformed from specification to code. The research focused on critical integration issues associated with a formal-based software transformation system, such as the source specification, the problem space architecture, design architecture, design transforms, and target software transforms. Software is critical in today's Air Force, yet its specification, design, and …

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