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

Articles 2161 - 2190 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Analyzing And Improving Stochastic Network Security: A Multicriteria Prescriptive Risk Analysis Model, David L. Lyle Mar 1997

Analyzing And Improving Stochastic Network Security: A Multicriteria Prescriptive Risk Analysis Model, David L. Lyle

Theses and Dissertations

This research optimized two measures of network security by hardening components and improving their reliability. A common measure of effectiveness (MOE) for networks is statistical reliability, which ignores the effects of hostile actions. A new MOE which includes hostile actions was developed. Both measures require component reliability functions, derived using fault trees. Fuzzy Logic and Monte Carlo simulation were used to quantify uncertainty. Results from the model are compared to traditional Risk Assessment results.

Go to article

A Validation Study Of The Ssm/I Temperature Algorithm And Comparison With The Cal/Val Land Surface Temperatures, Ronald L. Comoglio Mar 1997

A Validation Study Of The Ssm/I Temperature Algorithm And Comparison With The Cal/Val Land Surface Temperatures, Ronald L. Comoglio

Theses and Dissertations

The USAF operational cloud model, the Real-Time Nephanalysis (RTNEPH), requires infrared and visual scene scans as well as input from the Special Sensor Microwave Imager (SSM/I), featured on the Defense Meteorological Satellite Program (DMSP) polar orbiters. Additionally, SSM/I provides input to the Air Force Global Weather Center (AFGWC) surface temperature model (SFCTMP). The global surface temperatures are required for identifying which pixel of a scene is cloud and which is ground and as a first guess input to initialize NWP models. The SSM/I provides brightness temperatures sampled at four discrete: frequencies and dual polarizations to produce surface temperatures. Two algorithms …

Go to article

Optimization Of The Velocity Azimuth Display (Vad) Algorithm's Adaptable Parameters In The Wsr-88d System, Donald R. Farris Mar 1997

Optimization Of The Velocity Azimuth Display (Vad) Algorithm's Adaptable Parameters In The Wsr-88d System, Donald R. Farris

Theses and Dissertations

Meteorologists have encountered problems with the Velocity Azimuth Display (VAD) algorithm in the Weather Surveillance Radar - 1988 Doppler (WSR-88D) System. Under certain meteorological conditions, forecasters have observed differences between the radar's wind profiles and wind profiles from rawinsonde upper-air soundings, or wind profilers. One of the main causes of this problem is inversions in the atmosphere which cause the radar beam to subrefract or superefract, causing the VAD winds to be inaccurately reported at a particular height. This thesis used the WSR-88D Algorithm Testing and Display System (WATADS) to compare VAD winds from recorded Level 2 NEXRAD data at …

Go to article

A Comparison Of Circular Error Probable Estimators For Small Samples, Charles E. Williams Mar 1997

A Comparison Of Circular Error Probable Estimators For Small Samples, Charles E. Williams

Theses and Dissertations

Several previous studies investigated the performance of competing circular error probable (CEP) estimators for small samples. This estimation is important in ICBM analysis because, due to expense, there are a limited number of ICBM test launches. In the most recent previous study (1993), Tongue considered five CEP estimators in a simulation test, attempting to determine the behavior of these estimators for populations of various bias, ellipticity, correlation, and sample size. In this paper, we build on Tongue's findings in three ways: (1) The number of estimators compared is expanded to eight. (2) Different factors and factor levels are used. (3) …

Go to article

Automatic Digital Processing For Calibration Data Of Open Skies Treaty Sensors, Donna D. Keating Mar 1997

Automatic Digital Processing For Calibration Data Of Open Skies Treaty Sensors, Donna D. Keating

Theses and Dissertations

The Open Skies Treaty provides guidelines allowing participants to fly in air space over other participants' countries to monitor strategic military placement and development. The treaty restricts the ground size of the smallest detail recorded by these aerial imaging systems to any size larger than 30 cm. This restriction is enforced by placing a lower limit on the altitude at which a participating aircraft can fly and it is computed as the value of Hmin. Current techniques rely on human photographic interpreters to select the value of Hmin for every calibration pass and is very resource intensive. The Open Skies …

Go to article

An Atmospheric Sensitivity And Validation Study Of The Variable Terrain Radio Parabolic Equation Model (Vtrpe), Matthew K. Doggett Mar 1997

An Atmospheric Sensitivity And Validation Study Of The Variable Terrain Radio Parabolic Equation Model (Vtrpe), Matthew K. Doggett

Theses and Dissertations

The Variable Terrain Radio Parabolic Equation (VTRPE) computer model is a powerful and flexible program that provides calculations of the radar propagation conditions of the atmosphere. It is limited however, by the accuracy and resolution of the input data. This study quantifies the sensitivity of the VTRPE model to the accuracy and resolution of the atmospheric parameters that go into it. Also, two case studies are examined to test the utility of VTRPE in operational use. The sensitivity to measurements of pressure, temperature, and humidity was found to be dependent on the meteorological environment. In standard and subrefractive environments, average …

Go to article

Development And Implementation Of An Isentropic Potential Vorticity Algorithm For Use At Air Force Global Weather Center, Jay B. Desjardins Jr. Mar 1997

Development And Implementation Of An Isentropic Potential Vorticity Algorithm For Use At Air Force Global Weather Center, Jay B. Desjardins Jr.

Theses and Dissertations

This thesis presents and validates methods for calculating isentropic potential vorticity (IPV) and applies these methods in software programs planned for implementation at the Air Force Global Weather Center (AFGWC). The IPV programs will provide Air Force Weather forecasters additional tools to diagnose atmospheric kinematics and understand atmospheric dynamics. A FORTRAN program is recommended using mandatory-level isobaric data projected to be available on AFGWC computer systems, specifically, from the Navy Operational Global Atmosphere Prediction System and Medium Range Forecast models. Program development and analysis consists of three main steps: (1) data retrieval; (2) IPV calculations; and, (3) interpolation to an …

Go to article

Moisture Sensitivity Of Contrail Forecast Algorithms, Allen C. Rabayda Mar 1997

Moisture Sensitivity Of Contrail Forecast Algorithms, Allen C. Rabayda

Theses and Dissertations

This thesis looked at using new relative humidity (RH) climatologies to improve the Air Force Global Weather Center's (AFGWC) contrail forecasts. To study the effect of the new RH climatolgies, the currently used empirical relative humidity (RH) profile is replaced with a more accurate climatological one, the Stratospheric And Gaseous Experiment II (SAGE II). The study begins by examining accuracy and bias of forecast contrail bases generated by the empirical and SAGE II RH profiles on 42 days. Both sets of forecast bases are shown to be statistically similar with a series of hypothesis tests. Additional RH profiles, from 0% …

Go to article

Experiments In Aggregating Air Ordnance Effectiveness Data For The Tacwar Model, James E. Parker Feb 1997

Experiments In Aggregating Air Ordnance Effectiveness Data For The Tacwar Model, James E. Parker

Theses and Dissertations

An interactive MS Access&trademark; based application that aggregates the output of the SABSEL model for input into the TACWAR model is developed. The application was developed following efforts to create a functional approximation of the SABSEL data using neural networks, statistical networks, and traditional statistical techniques. These approximations were compared to a look-up table methodology on the basis of accuracy, (RMSE

Go to article

Response Surface Methodology: An Analytical Method For Locating Migrated Contaminant Sources, Orlando J. Dona Jr. Jan 1997

Response Surface Methodology: An Analytical Method For Locating Migrated Contaminant Sources, Orlando J. Dona Jr.

Theses and Dissertations

The use and storage of hazardous chemicals at U.S. military facilities often adversely affect the groundwater when contaminants infiltrate the subsurface as a result of leaks and accidental spills. These contaminants, if not located and remediated in a relatively short time, may move and settle unpredictably, essentially creating a source some distance from the original leak or spill. An example of this phenomenon is found with migrating dense nonaqueous phase liquid (DNAPL) contaminants. Although various methods for estimating the present day locations of these migrated contaminants are in use, accurately pinpointing the source of contaminants remains a difficult problem in …

Go to article

Spectroscopic And Kinetic Studies Of Bismuth Dimers, Robert Eugene Frankin Jan 1997

Spectroscopic And Kinetic Studies Of Bismuth Dimers, Robert Eugene Frankin

Theses and Dissertations

The spectroscopy of high rotational levels (J ≤ 211) in Bi2 X(Og+) and A(Ou+) was investigated for 2≤v"≤5 and 0≤v'≤4 by observing total fluorescence from laser excitation. Dunham coefficients were derived that fit all observed rotational lines to within 0.01 cm-1. Franck-Condon factors were calculated and experimentally verified for transitions originating from the initially populated levels 0≤v'≤5. Vibrational energy transfer upon collision with rare gas collision partners was investigated for the low-lying vibrational levels of the A-state using spectrally resolved, continuous wave laser induced fluorescence. Vibrational transfer was adequately modeled by …

Go to article

Investigation Of The Optical Properties Of Ordered Semiconductor Materials, Jack E. Mccrae Jr. Jan 1997

Investigation Of The Optical Properties Of Ordered Semiconductor Materials, Jack E. Mccrae Jr.

Theses and Dissertations

Optical studies have been conducted upon CdGeAs2 and ZnGeP2, two of the most promising semiconductors being developed for mid-infrared non-linear optics applications. These experiments included photoluminescence (PL) studies of both compounds as well as photoreflectance (PR) measurements upon CdGeAs2. In addition, Hall effect measurements were carried out upon CdGeAs2, to aid in interpretation of the optical data. PL was measured as a function of laser power, sample temperature, and crystal orientation for CdGeAs2. One broad weak peak near 0.38 eV, and another somewhat narrower and often far brighter peak near 0.57 …

Go to article

Four-Wave Mixing And Optical Phase Conjugation In Vertical Cavity Surface Emitting Devices, Gregory J. Vansuch Jan 1997

Four-Wave Mixing And Optical Phase Conjugation In Vertical Cavity Surface Emitting Devices, Gregory J. Vansuch

Theses and Dissertations

Four-wave mixing (FWM), a nonlinear optical process, was investigated in resonant cavity light emitting diodes (RCLEDs) and vertical cavity surface emitting lasers (VCSELs) below lasing threshold. These semiconductor photonic devices consisted of an optical gain region of quantum wells sandwiched between two distributed Bragg reflector (DBR) mirrors. Pump and probe lasers were injected into the devices to generate FWM. The dependence of FWM on bias current, pump laser power, and spectral and spatial separation between pump and probe lasers was investigated experimentally. A computer model of FWM based on the wave and carrier density equations was developed and agreed well …

Go to article

Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts Dec 1996

Modeling And Simulation Of Optical Characteristics Of Microelectromechanical Mirror Arrays, Peter C. Roberts

Theses and Dissertations

MEMS (Micro-Electro-Mechanical Systems) micromirror devices can be used to control the phase of a propagating light wavefront, and in particular to correct aberrations that may be present in the wavefront, due to either atmospheric turbulence or any other type of fixed or time and space varying aberrations. In order to shorten the design cycle of MEMS micromirror devices, computer software is developed to create, from MEMS micromirror device design data, a numerical model of the MEMS device. The model is then used to compute the far field diffraction pattern of a wavefront reflected from the device, and to predict the …

Go to article

On Unifying Time And Uncertainty: The Probabilistic Temporal Network, Joel D. Young Dec 1996

On Unifying Time And Uncertainty: The Probabilistic Temporal Network, Joel D. Young

Theses and Dissertations

Complex real-world systems consist of collections of interacting processes/events. These processes change over time in response to both internal and external stimuli as well as to the passage of time. Many domains such as real-time systems diagnosis, (mechanized) story understanding, planning and scheduling, and financial forecasting require the capability to model complex systems under a unified framework to deal with both time and uncertainty. Existing uncertainty representations and existing temporal models already provide rich languages for capturing uncertainty and temporal information, respectively. Unfortunately, these partial solutions have made it extremely difficult to unify time and uncertainty in a way that …

Go to article

Student Modeling In An Intelligent Tutoring System, Jeremy E. Thompson Dec 1996

Student Modeling In An Intelligent Tutoring System, Jeremy E. Thompson

Theses and Dissertations

This thesis explores a new approach to modeling the student in an intelligent tutoring system (ITS), by providing a student model which learns new solutions from the student. A prototype of the new approach to ITS is demonstrated in the Euclidean geometry domain. Complete C++, CLIPS, and Tcl/Tk code listings are included in the appendices for reference. Adaptable multiple software agents were targeted for implementation, based on current literature. However, the student model is found to be maintainable without multiple software agents, while still allowing for tracking several possible solution paths when monitoring student solutions. This capability contradicts previous research …

Go to article

Investigation Of Ba, Bao, Sr And Sro Pulsed Laser-Induced Vapor Plumes In N2, O2, Microwave Discharged O2, And Vacuum At Low Laser Fluence, David L. Byers Dec 1996

Investigation Of Ba, Bao, Sr And Sro Pulsed Laser-Induced Vapor Plumes In N2, O2, Microwave Discharged O2, And Vacuum At Low Laser Fluence, David L. Byers

Theses and Dissertations

Ba, BaO, Sr and SrO were ablated by 248 nm laser pulses at fluences ranging from 270 mJ-/sq cm to 575 mJ-/sq cm in vacuum and in 25 mtorr atmospheres of N2, O2 and microwave-discharged O2. The spectral emissions of these plumes were compared for indications of ionization due to Ba or Sr collisions with each gas. The addition of a background gas increased the ion and neutral signature across the spectrum. SrO band emission was observed at 16,600-16,900/cm and possible BaO band emissions were observed in the 18,250-18,400/cm, 19,000-19700/cm and 19,800-20,000/cm regions. A screened plate ion probe was use …

Go to article

Theoretical Modeling Of Linear Absorption Coefficients In Si/Si1-Xgex Multiple Quantum Well Photodetectors, Kevin D. Greene Dec 1996

Theoretical Modeling Of Linear Absorption Coefficients In Si/Si1-Xgex Multiple Quantum Well Photodetectors, Kevin D. Greene

Theses and Dissertations

Si/Si1-xGex MQW Infrared Photodetectors offer the promise of normal incidence photodetection tunable over the range of 3-12 micrometers wavelength range at temperatures above 40 K. This system is attractive because the Si1-xGex offers greater compatibility with existing Si based signal processing circuitry. Band structures, momentum matrix elements and linear absorption coefficients are computed using a Luftinger-Kohn k/p analysis for Si/Si1-xGex quantum wells grown in the 110 direction. The absorption coefficient as a function of energy and wavelength is calculated by two methods: a delta function fit to intersubband transitions, and a …

Go to article

Dynamic Relevance Filtering In Asynchronous Transfer Mode-Based Distributed Interactive Simulation Exercises, David T. Hightower Dec 1996

Dynamic Relevance Filtering In Asynchronous Transfer Mode-Based Distributed Interactive Simulation Exercises, David T. Hightower

Theses and Dissertations

As Distributed Interactive Simulation (DIS) exercises continue to grow in scale, the need to support a large number of players has become apparent. The demands on the network and the simulation hosts in large exercises, though, have proved to be prohibitive, requiring significant computational overhead to filter through the information and extract what is relevant to a particular simulation. Some mechanism is needed to reduce irrelevant network traffic received by a system, while increasing the bandwidth available for the DIS exercise. Previous research efforts in this area have centered primarily on fixed geographic partitions of the battlespace to reduce the …

Go to article

Simulation Based Performance Evaluation Of Resource Allocation Algorithms For Implementation In The Shf-Dama Satellite Network, Eric P. Hobson Dec 1996

Simulation Based Performance Evaluation Of Resource Allocation Algorithms For Implementation In The Shf-Dama Satellite Network, Eric P. Hobson

Theses and Dissertations

Sponsored by DISA, the SHF-DAMA Standard addresses the warfighter's requirements for flexible, reliable, and efficient (technically and fiscally) satellite communications. The Standard proposes a system supporting both packet data transfer and single-channel-per-carrier voice and data circuits assigned on a demand basis. The Standard does not address management of the DSCS 3 transponder's bandwidth and power resources among priority classes of users. This effort characterizes the SHF-DAMA system's performance over each combination of the following resource management algorithm features: (1) preemption enabled and disabled; (2) using the Standard-specified collision resolution technique and a binary exponential backoff; (3) using complete partitioning, complete …

Go to article

Integrating The Capability Maturity Model For Software And The Quality Air Force Criteria, Marshall B. Messamore Dec 1996

Integrating The Capability Maturity Model For Software And The Quality Air Force Criteria, Marshall B. Messamore

Theses and Dissertations

As defense budgets decrease and it is required to do more with less, the Air Force has chosen to use the Malcolm Baldrige National Quality Award (MBNQA) as the basis for implementing quality principles. The Air Force program is known as Quality Air Force (QAF), and the criteria are referred to as the QAF criteria DEPA95b. At about the same time the Department of the Air Force implemented QAF, the software leaders in the Air Force adopted the Capability Maturity Model for Software (CMM) as the internal standard for Air Force software organizations MOSE9l. Software organizations strapped with both sets …

Go to article

Utilizing Bayesian Techniques For User Interface Intelligence, Robert A. Harrington Dec 1996

Utilizing Bayesian Techniques For User Interface Intelligence, Robert A. Harrington

Theses and Dissertations

The purpose of this research is to study the injection of an intelligent agent into modern user interface technology. This agent is intended to manage the complex interactions between the software system and the user, thus making the complexities transparent to the user. The background study will show that while interesting and promising research exists in the domain of intelligent interface agents, very little research has been published that indicates true success in representing the uncertainty involved in predicting user intent. The interface agent architecture presented in this thesis will offer one solution for solving the problem using a newly …

Go to article

Solar System Modeler: A Distributed, Virtual Environment For Space Visualization And Gps Navigation, Gary E. Williams Dec 1996

Solar System Modeler: A Distributed, Virtual Environment For Space Visualization And Gps Navigation, Gary E. Williams

Theses and Dissertations

The Solar System Modeler (SM) extends the Space Modeler developed in 1994. It provides a virtual environment enabling an explorer to dynamically investigate near Earth satellites, deep space probes, planets, moons, and other celestial phenomena. The explorer navigates the virtual environment via mouse selected options from menu panels while wearing a tracked, head mounted display (HMD). Alternatively, a monitor may replace the HMD and keyboard controls replace head tracking. The SM's functionality is extended by the ability to broadcast simulated GPS satellite transmissions in compliance with Distributed Interactive Simulation (DIS) protocol standards. The transmissions include information found in true GPS …

Go to article

Design And Prototype Of The Afit Virtual Emergency Room: A Distributed Virtual Environment For Emergency Medical Simulation, Brian W. Garcia Dec 1996

Design And Prototype Of The Afit Virtual Emergency Room: A Distributed Virtual Environment For Emergency Medical Simulation, Brian W. Garcia

Theses and Dissertations

Due to the increasing complexity of emergency medical care, medical staffs require increasingly sophisticated training systems. Virtual environments offer a low cost means to achieve a widely usable yet sophisticated training capability. The Defense Advanced Research Projects Agency (DARPA) has sponsored the Virtual Emergency Room (VER) project to develop a simulation system that enables emergency department personnel within level I and II emergency rooms to practice emergency medical procedures and protocols. The VER is a simulation facility that uses a distributed virtual environment architecture to enable real-time, multi-participant simulations. The potential advantages of this system include the ability to evaluate …

Go to article

Neural Network Classification Of Environmental Samples, Jeffrey L. Blackmon Dec 1996

Neural Network Classification Of Environmental Samples, Jeffrey L. Blackmon

Theses and Dissertations

This research develops a general methodology for designing neural network classifiers for real-world environmental problems. This methodology is demonstrated through the design of a multi-layer perceptron to classify stainless steel and actinide samples. Neural networks, sometimes called artificial neural networks, have been shown capable of classifying complex patterns. Artificial neural networks are physiologically motivated computer algorithms which attempt to mimic the function of the large interconnected network of neurons in the human brain, which has extraordinary pattern recognition capabilities. These artificial neural networks learn to map a set of input features, elemental composition, onto a set of outputs such as …

Go to article

The Biodegradation Characteristics Of Proposed Fuel Systems Icing Inhibitors (Fsii), Charles E. Meshako Dec 1996

The Biodegradation Characteristics Of Proposed Fuel Systems Icing Inhibitors (Fsii), Charles E. Meshako

Theses and Dissertations

The biodegradation characteristics of three fuel system icing ihhibitors (FSII) were evaluated. FSII are jet fuel additives that partition into water readily and are present in the water drained from storage tank bottoms in concentrations approaching 40%. These concentrations raise concerns as to the disposal and handling of these wastes. The current FSII, DiEGME was evaluated along with two new candidates, dipropylene glycol and glycerol formal. DiEGME appeared to be moderately but not completely biodegradable. It is likely that much of it would be removed in a wastewater treatment plant. Dipropylene glycol only showed signs of degradation after more than …

Go to article

Surfactant Enhanced Microbial Degradation Of Jp-8 Contaminated Soil, John D. Thomas Dec 1996

Surfactant Enhanced Microbial Degradation Of Jp-8 Contaminated Soil, John D. Thomas

Theses and Dissertations

This research effort used an automated respirometer to evaluate the enhancement of JP-8 fuel biodegradation, from surfactant addition. Two nonionic surfactants, Novell 1412-7 and Alfonic 810-4.5 were chosen for addition to contaminated JP-8, microcosms at three levels of treatment. The three levels of treatment included sub-CMC, CMC, and supra-CMC concentrations for each surfactant. The Novell II, nonionic surfactant, exhibited inhibitory characteristics, and was eliminated from the study. The focus of the study was to determine if JP-8 was actually degraded, and if enhancement of JP-8 biodegradation would be achieved from surfactant addition. The respirometer was found to be repeatable within …

Go to article

Artificial Cochlea Design Using Micro-Electro-Mechanical Systems, George C. Dalton Ii Dec 1996

Artificial Cochlea Design Using Micro-Electro-Mechanical Systems, George C. Dalton Ii

Theses and Dissertations

The use of Micro-Electro-Mechanical Systems (MEMS) in the design of an artificial cochlea is investigated in depth. Interdigitated finger (comb), cantilever, bridge, and mirror resonators are presented as possible devices used to implement the artificial cochlea. These resonators are demonstrated to be extremely high Q devices, capable of being tuned with a simple DC bias. This suggests a possible change to existing cochlea models that claim highly complex AC feedback as being responsible for changes in the damping of the basilar membrane. The new cochlea model presented here, using MEMS to approximate the tuning of the basilar membrane, may be …

Go to article

An Approach To Evaluate Software Effectiveness, Timothy J. Schalick Dec 1996

An Approach To Evaluate Software Effectiveness, Timothy J. Schalick

Theses and Dissertations

The Air Force Operational Test and Evaluation Center (AFOTEC) is tasked with the evaluation of operational effectiveness of new systems for the Air Force. Currently, the software analysis team within AFOTEC has no methodology to directly address the effectiveness of the software portion of these new systems. This research develops a working definition for software effectiveness, then outlines an approach to evaluate software effectiveness-- the Software Effectiveness Traceability Approach (SETA). Effectiveness is defined as the degree to which the software requirements are satisfied and is therefore application-independent. With SETA, requirements satisfaction is measured by the "degree of traceability" throughout the …

Go to article

An Activity Driver Based Analysis Of Hazardous Materials Usage At Wright-Patterson Afb, Charles D. Perham Dec 1996

An Activity Driver Based Analysis Of Hazardous Materials Usage At Wright-Patterson Afb, Charles D. Perham

Theses and Dissertations

As the Air Force has progressed and succeeded in the realm of pollution prevention, the opportunities for further progress have become more challenging. With the 'low-hanging fruit' now gone from the pollution prevention tree, new methods to identify opportunities must be adopted. This research effort applied a subset of activity based costing, activity driver analysis, to reveal pollution prevention opportunities in regards to hazardous materials usage. A sample of base organizations (civil engineering and aircraft maintenance), and a sample of the hazardous chemicals (Class C or most hazardous) used by those organizations were investigated to determine the drivers behind usage.

Go to article

First Prev Next Last