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Air Force Institute of Technology

Theses/Dissertations

2001

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Articles 1 - 30 of 61

Full-Text Articles in Physical Sciences and Mathematics

Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell Dec 2001

Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell

Theses and Dissertations

The influence of stimulated scattering on laser intensity in fiber optic waveguides is examined. Stimulated Brillouin scattering (SBS) in long, multimode optical waveguides is found to generate a Stokes beam that propagates in the fiber LP01 mode. Additionally, the same process is found to combine multiple laser beams into a single spatially coherent source. Limitations in beam cleanup and combining are also investigated to identify ways to overcome them. The last portion of the dissertation theoretically examines suppression of stimulated Raman scattering in fibers to eliminate the restriction this imposes on the power of a fiber laser or amplifier. The …

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Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia Dec 2001

Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia

Theses and Dissertations

The use of Proper Orthogonal Decomposition (POD) for reduced order modeling (ROM) of fluid problems is extended to high-speed compressible fluid flows. The challenge in using POD for high-speed flows is presented by the presence of moving discontinuities in the flow field. To overcome these difficulties, a domain decomposition approach is developed that isolates the region containing the moving shock wave for special treatment. The domain decomposition implementation produces internal boundaries between the various domain sections. The domains are linked using optimization-based solvers which employ constraints to ensure smoothness in overlapping portions of the internal boundary. This approach is applied …

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Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr. Oct 2001

Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr.

Theses and Dissertations

The US Department of Defense (DOD), as well as the National Aeronautics and Astronautics Administration (NASA) and the Jet Propulsion Laboratory (JPL) are interested in developing and deploying precise, compliant, light-weight, space-based structures. More specifically, the Air Force’s core competencies ‘Aerospace Superiority’ and ‘Information Superiority’ demand ever-increasing depth and breadth of capability. Whether used for energy transmission or optical reconnaissance, current launch restraints limit rigid space-based optical reflector size. To support this requirement, the Air Force Research Laboratory (AFRL) is developing a large space-based optical membrane telescope. Inflatable reflectors can conceptually break this barrier, but controlling such a compliant structure …

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Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe Sep 2001

Analysis And Numerical Solution Of An Integral Equation Method For Electromagnetic Scattering From A Cavity In A Ground Plane, Eric T. Howe

Theses and Dissertations

In this research the electromagnetic scattering of a plane wave from a two-dimensional cavity embedded in an infinite, perfectly conducting ground plane is investigated. The plane wave is assumed to be under transverse electric (TE) polarization with respect to the x-axis. The cavity may be empty or filled with an arbitrary homogeneous, lossy material. A coupled set of scalar integral equations that govern the electromagnetic scattering is implemented. An approximate solution to the scalar integral equations is found via a Method of Moments (MoM) algorithm. The algorithm is implemented in a computer code, and approximations to the total magnetic field …

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Theater-Level Stochastic Air-To-Air Engagement Modeling Via Event Occurrence Networks Using Piecewise Polynomial Approximation, David R. Denhard Sep 2001

Theater-Level Stochastic Air-To-Air Engagement Modeling Via Event Occurrence Networks Using Piecewise Polynomial Approximation, David R. Denhard

Theses and Dissertations

This dissertation investigates a stochastic network formulation termed an event occurrence network (EON). EONs are graphical representations of the superposition of several terminating counting processes. An EON arc represents the occurrence of an event from a group of (sequential) events before the occurrence of events from other event groupings. Events between groups occur independently, but events within a group occur sequentially. A set of arcs leaving a node is a set of competing events, which are probabilistically resolved by order relations. An important EON metric is the probability of being at a particular node or set of nodes at time …

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Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange Jun 2001

Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange

Theses and Dissertations

As aircraft age, corrosion forms upon unobservable surfaces, particularly at the junction of the sheet aluminum and the steel rivets used to attach the sheets to the airframe, degrading the aircraft s airworthiness. Previous research developed a noninvasive technique for the evaluation of the material composition of aluminum surfaces, utilizing the information encoded in the energy spectra of Compton-scattered gamma emissions. The spectra are gathered by a six-element, high purity germanium detector array. A, first principles, deterministic computer code is used to reconstruct a two-dimensional map of the electron density of aluminum samples. Previous efforts, to image pure aluminum samples, …

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Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay Jun 2001

Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay

Theses and Dissertations

In the world of semiconductor photonic device fabrication, one important objective may be to extract as much light as possible from the device. In these devices, photons are created when electrons recombine with holes by transitioning from a high-energy state to a lower one. Unfortunately, electron-hole recombination does not always result in the formation of a photon. There are three basic types of recombination: the first results in the formation of a photon and is called radiative recombination; and the second and third, known as Shockley-Read-Hall and Auger recombination, result in the heating of the device and do not produce …

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Hidden Markov Models For Visual Speech Synthesis In Limited Data, Harold A. Arb Mar 2001

Hidden Markov Models For Visual Speech Synthesis In Limited Data, Harold A. Arb

Theses and Dissertations

This work presents a new approach for estimating control points (facial locations that control movement) to allow the artificial generation of video with apparent mouth movement (visual speech) time-synced with recorded audio. First, Hidden Markov Models (HMMs) are estimated for each visual speech category (viseme) present in stored video data, where a category is defined as the mouth movement corresponding to a given sound and where the visemes are further categorized as trisemes (a viseme in the context of previous and following visemes). Next, a decision tree is used to cluster and relate states in the HMMs that are similar …

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Spectroscopic Constants, Lifetimes And Predissociation Rates For Bi2A(0+U), Michael W. Dolezal Mar 2001

Spectroscopic Constants, Lifetimes And Predissociation Rates For Bi2A(0+U), Michael W. Dolezal

Theses and Dissertations

More than 100,000 spectral features from a Bi2(X1 Σ+g → A(0+u)) absorption spectrum, encompassing 0 ≤ v' ≤ 91, 0 ≤ v" ≤ 7 and J2(A). Ground state constants, reported by Barrow et al. [1], remain unchanged. The new constants are used to redefine the A-state potential using traditional RKR methods and to set the dissociation energy at De = 29,913 cm"1, which correlates A-state dissociation products to 4S + 2D atoms. A pulsed dye laser apparatus was used to obtain lifetime data for Bi2A(0+u) …

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Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman Mar 2001

Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman

Theses and Dissertations

Air Force operations are directly impacted by weather on a daily basis. Erroneous forecasts negatively impact mission readiness and consequently cost the government time, in terms of wasted man-hours, and money. Advanced forecast lead-time could make a difference to minimize loss to both USAF personnel and assets. This study examined lightning data from 64 storm events from 1995-2000 in search of unique lightning signatures indicative of tornadic activity. Overall flash rates, percentage of positive flashes, positive and negative peak currents and multiplicity for each case were separated into two categories based on tornado intensity and season of occurrence. Based on …

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Validation And Characterization Of Ionospheric Densities Measured By Dmsp, Herbert L. Keyser Mar 2001

Validation And Characterization Of Ionospheric Densities Measured By Dmsp, Herbert L. Keyser

Theses and Dissertations

Future models of the thermosphere-ionosphere-magnetosphere system will require near real-time assimilation of ionospheric parameters to specify% and forecast these regions One of the current sensors that will be used in the GAIM model is the DMSP SSIES. Knowledge of the SSIES's reliability and data characteristics is key to using the data when relying on automated processes to ingest the data. To validate the DMSP value, the DMSP-measured density is compared to ground-based ISR measurements from solar minimum to solar maximum. The DMSP data are compared to data from the ISRs located at the Millstone Hill Observatory in Massachusetts and Sondrestrom …

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Design And Specification Of Dynamic, Mobile And Reconfigurable Multiagent Systems, Athie L. Self Mar 2001

Design And Specification Of Dynamic, Mobile And Reconfigurable Multiagent Systems, Athie L. Self

Theses and Dissertations

Multiagent Systems use the power of collaborative software agents to solve complex distributed problems. There are many Agent-Oriented Software Engineering (AOSE) methodologies available to assist system designers to create multiagent systems. However, none of these methodologies can specify agents with dynamic properties such as cloning, mobility or agent instantiation. This thesis starts the process to bridge the gap between AOSE methodologies and dynamic agent platforms by incorporating mobility into the current Multiagent Systems Engineering (MaSE) methodology. Mobility was specified within all components composing a mobile agent class. An agent component was also created that integrated the behavior of the components …

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Transforming Analysis Models Into Design Models For The Multiagent Engineering Systems (Mase) Methodology, Clint H. Sparkman Mar 2001

Transforming Analysis Models Into Design Models For The Multiagent Engineering Systems (Mase) Methodology, Clint H. Sparkman

Theses and Dissertations

Agent technology has received much attention in the last few years because of the advantages that multiagent systems have in complex, distributed environments. For multiagent systems are to be effective, they must be reliable, robust, and secure. AFIT's Agent Research Group has developed a complete lifecycle methodology, called Multiagent Systems Engineering (MaSE), for analyzing, designing, and developing heterogeneous multiagent systems. However, developing multiagent systems is a complicated process, and there is no guarantee that the resulting system meets the initial requirements and will operate reliably with the desired behavior. The purpose of this research was to develop a semi-automated formal …

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Gss Technology As A Moderator Of Influence And Perceived Expertise, Kevin V. Thompson Mar 2001

Gss Technology As A Moderator Of Influence And Perceived Expertise, Kevin V. Thompson

Theses and Dissertations

Group Support System (355) research has found this content and process anonymity influence problem solving groups. However, previous studies report mixed results on how OSS technology changes social influence processes and recognition of expertise which affect group performance. This thesis explored content and process anonymity's affect on influence and perceived expertise using three treatments to derive possible explanations for the mixed results found in previous GSS research. The study developed a theoretical model of influence, perceived expertise, and performance. Using structural equation modeling the study tested the relationships between expertise and participation rates, and overall group performance. An experiment was …

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Investigation Of Gravity Waves Via The Rotational Temperature Of Hydroxyl Nightglow, Erin C. Willingham Mar 2001

Investigation Of Gravity Waves Via The Rotational Temperature Of Hydroxyl Nightglow, Erin C. Willingham

Theses and Dissertations

Measurement of the vibration and rotation bands of mesospheric hydroxyl radicals (OH) has been conducted during the past two decades using ground-based and space-based interferometers to take temperature and wind measurements from 70-100km in altitude. Gravity waves that pass through the mesosphere can be measured by determining the variance over time of the rotational temperature of the OH emissions. Several attempts were made to take spectrum measurements of the nightglow from hydroxyl radicals in the mesosphere using a custom hardware configuration that included a telescope and grating monochrometer optimized for the visible and near infrared. Quantifying gravity wave activity was …

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Assessment Of The Effects Of Entrainment And Wind Shear On Nuclear Cloud Rise Modeling, Daniel E. Zalewski Mar 2001

Assessment Of The Effects Of Entrainment And Wind Shear On Nuclear Cloud Rise Modeling, Daniel E. Zalewski

Theses and Dissertations

The Missile Defense Agency (MDA) plans to construct, during a two-week period, an X-Band Radar (XBR) on Shemya, AK. Wind speeds must not, at any time during the construction, exceed a 25 knot limit set by the MDA for lifting the massive dome panels into place. The goal of this research was to explore the possibilities of long-range forecasts to determine the feasibility of predicting any upcoming two-week windows of opportunity, well in advance, that will ensure the successful completion of constructing the XBR on Shemya. In order to reach this goal, the following objectives were achieved; (1) a climatological …

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Analyzing The Effects Of Meteorology On Radar Measured Index Of Refraction Structure Parameter, Jeffrey W. Budai Mar 2001

Analyzing The Effects Of Meteorology On Radar Measured Index Of Refraction Structure Parameter, Jeffrey W. Budai

Theses and Dissertations

Forecasting optical turbulence is essential for the Air Force's Airborne Laser program to optimize placement of aircraft. To find bow meteorology affects Cn2, the intensity of turbulence in the index of refraction, case studies of synoptically interesting times are first chosen. Correlation coefficients are then computed between radar measured Cn2 and meteorological quantities. The potential for mechanically turbulent activity is looked at. In the analysis of this work, six meteorological features were found likely to affect Cn2. Two features associated with affecting potential refractivity, and thus Cn2, are jets …

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Numerical Study Of Optical Delay In Semiconductor Multilayer Distributed Bragg Reflector And Tunable Microcavity Structures, Michael I. K. Etan Mar 2001

Numerical Study Of Optical Delay In Semiconductor Multilayer Distributed Bragg Reflector And Tunable Microcavity Structures, Michael I. K. Etan

Theses and Dissertations

The Air Force has a growing need for the greater bandwidth, speed, and flexibility offered by optical communication links. Future space systems and airborne platforms will most likely use optical signals for efficient power transmission and to minimize the possibility of spoofing and eavesdropping. Tunable optical delays play an important role in the implementation of free space optical communication links. The primary challenge in implementing these systems is the active maintenance of coherent wave fronts across the system's optical aperture. For space applications, this aperture may he hundreds of meters in diameter. Spatial segmentation of a large aperture into smaller …

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Comparative Analysis Of Traditional Versus Computer-Based Survey Instrument Response, Albert E. Franke Iv Mar 2001

Comparative Analysis Of Traditional Versus Computer-Based Survey Instrument Response, Albert E. Franke Iv

Theses and Dissertations

The purpose of this study was to determine if survey medium (paper versus computer) affected responses and response rates in Air Force personnel. The study compared responses and response rates from 900 randomly selected Air Force active-duty members using a paper-based survey, a computer-based survey, and a more complex computer-based survey. The first computer-based survey minimized the differences between itself and the paper-based survey to more accurately quantify any bias due solely to the computer medium. The more complex survey served to maximize differences between itself and the other computer-based survey to more accurately quantify any bias due to programmatic …

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Validation And Assessment Of Dmsp Electron Temperatures In The Topside Ionosphere, Bradford S. Green Mar 2001

Validation And Assessment Of Dmsp Electron Temperatures In The Topside Ionosphere, Bradford S. Green

Theses and Dissertations

Geomagnetic disturbances in the near earth space environment can adversely affect numerous military and Department of Defense (DoD) systems and operations. To improve the prediction accuracy of such disturbances, the next generation of space environment forecast models aims to automatically ingest real-time ionospheric measurements. This research validates and assesses one such measurement - the Defense Military Satellite Program (DMSP) measured electron temperature (Te). DMSP Te data were validated against near simultaneous incoherent scatter radar (ISR) Te measurements from Millstone Hill, MA and Sondrestrom, Greenland between Winter 1996 and Summer 2000. Of the 37 Millstone and six …

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Use Of Quantum Mechanical Calculations To Investigate Small Silicon Carbide Clusters, Jean W. Henry Mar 2001

Use Of Quantum Mechanical Calculations To Investigate Small Silicon Carbide Clusters, Jean W. Henry

Theses and Dissertations

Density Functional Theory (DFT) method was employed to model silicon carbide small clusters. Comparing the DFT calculation results with experimental results that observed by using photoelectron spectroscopy (PES), DFT predicts the same structures that experiment observed. For electron affinity, DFT results are in good agreement with experimental results, the root mean square negative offset 0.1 eV found using medium size of basis set (cc-pVDZ+) calculation. DFT results for vibrational frequencies are in good agreement with experiment results; the root mean square error is 72.5 cm-1 wave number. 16 ground state structures of SimCn (m ≤ 4, …

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Modeling Information Assurance, Joseph E. Beauregard Mar 2001

Modeling Information Assurance, Joseph E. Beauregard

Theses and Dissertations

The ever-increasing speed of information systems allows decision-makers around the world to gather, process, and disseminate information almost instantaneously. However, with this benefit there comes a price. Information is valuable and therefore a target to those who do not have it or wish to destroy it. The Internet has allowed information to flow freely, but it has also made information vulnerable to many forms of corruption. The U. S. military controls much of the world's most sensitive information, and since it cannot sacrifice losing the speed at which this information is currently processed and disseminated, it must find a way …

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A Process For Vectoring Offensive Information Warfare As A Primary Weapon Option Within The United States Air Force, Sheila G. Bennett Mar 2001

A Process For Vectoring Offensive Information Warfare As A Primary Weapon Option Within The United States Air Force, Sheila G. Bennett

Theses and Dissertations

Consistently and comprehensively using Information Operations (IO) capabilities as primary weapon option within the Air Force is the next step to operationalizing IO within the Air Force. Doctrine and official guidance has set the variables of mission and concepts of operations, organizational structure, and IW players in place. The missing variable to operationalizing IO and probably the most difficult is the 'how' or process of the equation. This research will introduce a useable process that can be incorporated within the Air Force for integrating offensive IW activities into the current and given environment. The process is the basis for further …

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A Traffic Pattern-Based Comparison Of Bulk Image Request Response Times For A Virtual Distributed Laboratory, David B. Hooten Mar 2001

A Traffic Pattern-Based Comparison Of Bulk Image Request Response Times For A Virtual Distributed Laboratory, David B. Hooten

Theses and Dissertations

Various agencies throughout the Department of Defense possess intelligence imagery and electrooptical signature data required by researchers in the field of automatic target recognition (ATR). The Air Force Research Laboratory, Sensors Directorate, as been tasked with creating a virtual distributed laboratory (VDL) which will make this data available to ATR researchers via high speed networks such as the defense research and engineering network (DREN). For this research, a model for simulating potential operational network configurations and collaboration scenarios was developed and implemented using OPNET. The results of the simulations were analyzed using statistical methods to determine the impact on performance …

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A Flexible Framework For Collaborative Visualization Applications Using Java Spaces, Sean C. Butler Mar 2001

A Flexible Framework For Collaborative Visualization Applications Using Java Spaces, Sean C. Butler

Theses and Dissertations

The complexity of modern tasks is rising along with the level of technology. Two techniques commonly used to deal with complexity are collaboration and information visualization. Recently, computer networks have arisen as a powerful means of collaboration, and many new technologies are being developed to better utilize them. Among the newer, more promising of these technologies is Sun Microsystems' JavaSpaces ™, a high-level network programming API. This thesis describes a tool for developing collaborative visualization software using JavaSpaces-an application framework and accompanying toolkit. In addition to a detailed description of the framework, the thesis also describes an application implemented using …

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Quantitative Validation Of A Model Of Chlorinated Ethene Natural Attenuation, Harold C. Young Mar 2001

Quantitative Validation Of A Model Of Chlorinated Ethene Natural Attenuation, Harold C. Young

Theses and Dissertations

Chlorinated ethenes are among the most prevalent groundwater contaminants at hazardous waste sites nationwide. In an attempt to manage the risks posed by these contaminants, while controlling costs, monitored natural attenuation (MNA) is being considered as a remediation strategy at many sites. MNA relies on naturally occurring physical, chemical, and biological processes in the subsurface to reduce the risk posed by the contamination. The implementation of MNA, however, requires a detailed understanding of these processes, and how they impact contamination at a particular site. One way to gain this understanding is through contaminant fate and transport modeling. In this study, …

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Optimization Of Palladium-Catalyzed In Situ Destruction Of Trichloroethylene-Contaminated Groundwater Using A Genetic Algorithm, Manuel Fernandez Mar 2001

Optimization Of Palladium-Catalyzed In Situ Destruction Of Trichloroethylene-Contaminated Groundwater Using A Genetic Algorithm, Manuel Fernandez

Theses and Dissertations

Conventional technologies for the treatment of groundwater contaminated with chlorinated solvents have limitations that have motivated development of innovative technologies. One such technology currently under development involves using palladium-on-alumina (Pd/Al) as a catalyst to promote dechlorination. Pd/Al catalyst may be used in-well as part of a re-circulating horizontal flow treatment well (HFTW) system. An HFTW system involves two or more dual-screened wells, with in-well reactors, to capture and treat contaminated groundwater without the need to pump the water to the surface. In this study, objective and fitness functions, based on system costs and TCE concentration requirements, were developed to optimize …

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Minimum Distance Estimation For Time Series Analysis With Little Data, Hakan Tekin Mar 2001

Minimum Distance Estimation For Time Series Analysis With Little Data, Hakan Tekin

Theses and Dissertations

Minimum distance estimate is a statistical parameter estimate technique that selects model parameters that minimize a good-of-fit statistic. Minimum distance estimation has been demonstrated better standard approaches, including maximum likelihood estimators and least squares, in estimating statistical distribution parameters with very small data sets. This research applies minimum distance estimation to the task of making time series predictions with very few historical observations. In a Monte Carlo analysis, we test a variety of distance measures and report the results based on many different criteria. Our analysis tests the robustness of the approach by testing its ability to make predictions when …

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An Analysis Of The Computer And Network Attack Taxonomy, Richard C. Daigle Mar 2001

An Analysis Of The Computer And Network Attack Taxonomy, Richard C. Daigle

Theses and Dissertations

The Air Force's dependence on the Internet continues to increase daily. However, this increased dependence comes with risks. The popularity and potential of the Internet attracts users with illegal as well as legal intentions. Since the Air Force considers the Internet an integral component of its information Operations strategy, the Air Force must be confident that it can trust the security of this component. Therefore, reliable methods and information that helps the Air Force classify the risks associated with the Internet can help the Air Force determine the best processes to assure the security of its use of this resource. …

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Analysis Of Cloud-Free Line-Of-Sight Probability Calculations, Joseph J. Golemboski Iii Mar 2001

Analysis Of Cloud-Free Line-Of-Sight Probability Calculations, Joseph J. Golemboski Iii

Theses and Dissertations

Cloud-free line-of-sight probabilities were calculated using two separate methods. The first was a variation of a method developed by the Rand Corporation in 1972. In it, CFLOS probabilities were calculated using empirical data based on five years of photograms taken over Columbia, Missouri and forecasted cloud amounts rather than climatological values. The second was a new approach using the Cloud Scene Simulation Model developed by Phillips Laboratory. Cloud scenes were generated using forecasted cloud fields, meteorological inputs, and thirty random numbers. Water content files were produced and processed through a follow-on program to determine the extinction coefficients at each grid …

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