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Air Force Institute of Technology

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Articles 1861 - 1890 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Categorizing Network Attacks Using Pattern Classification Algorithms, George E. Noel Iii Mar 2002

Categorizing Network Attacks Using Pattern Classification Algorithms, George E. Noel Iii

Theses and Dissertations

The United States Air Force relies heavily on computer networks for many day-to-day activities. Many of these networks are affected by various types of attacks that can be launched from anywhere on the globe. The rising prominence of organizations such as the AFCERT and the MAJCOM NOSCs is evidence of an increasing realization among the Air Force leadership that protecting our computer networks is vitally important. A critical requirement for protecting our networks is the ability to detect attacks and intrusion attempts. This research is an effort to refine a portion of an AFIT-developed intrusion detection system known as the …

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Verification Of Mm5 Cloud Microphysics Schemes For East Asia, Dean J. Carter Mar 2002

Verification Of Mm5 Cloud Microphysics Schemes For East Asia, Dean J. Carter

Theses and Dissertations

Using the 3-Dimensional Variational Analysis data assimilation scheme and the (MM5), input observations were denied in three different categories: total, upper air, and surface observation denial. Two control groups were run using all available data as received by AFWA. The main control group used a 6 hours old first guess as a baseline. The data denied test cases and the secondary control group used a 30-hour old first guess because it was not possible to deny data from the first guess. The secondary control group was used to estimate errors resulting from the use of different first guess forecasts between …

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Portable High-Performance Indexing For Vector Product Format Spatial Databases, Engin Colak Mar 2002

Portable High-Performance Indexing For Vector Product Format Spatial Databases, Engin Colak

Theses and Dissertations

Geo-spatial databases have an overall performance problem because of their complexity and large size. For this reason, many researchers seek new ways to improve the overall performance of geo-spatial databases. Typically, these research efforts are focused on complex indexing structures and query processing methods to capture the relationships between the individual features of fully-functional geo-spatial databases. Visualization applications, such as combat simulators and mission planning tools, suffer from the general performance problems associated with geo-spatial databases. This research focuses on building a high-performance geo-spatial database for visualization applications. The main approach is to simplify the complex data model and to …

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Exploration Of Teleconnection Indices For Long-Range Seasonal Temperature Forecasts, Robb M. Randall Mar 2002

Exploration Of Teleconnection Indices For Long-Range Seasonal Temperature Forecasts, Robb M. Randall

Theses and Dissertations

The goal of this research was to examine the possibility of establishing guidance for lightning avoidance and lightning warning criteria based upon lightning radar reflectivity signatures. Determining how far naturally occurring lightning normally travels from thunderstorms can provide insight to decision makers concerning in-flight and ground safety measures. 3D lightning data are merged with archived weather radar data. To analyze the radar characteristics of the lightning data, radar data are interpolated to a 3D grid of reflectivity. Lightning flashes were analyzed to resolve the reflectivity of the flash origin and to determine the distance of the flash origin from the …

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Multi-Objective Mission Route Planning Using Particle Swarm Optimization, Kursat Yavuz Mar 2002

Multi-Objective Mission Route Planning Using Particle Swarm Optimization, Kursat Yavuz

Theses and Dissertations

The Mission Routing Problem (MRP) is the selection of a vehicle path starting at a point, going through enemy terrain defended by radar sites to get to the target(s) and returning to a safe destination (usually the starting point). The MRP is a three-dimensional, multi-objective path search with constraints such as fuel expenditure, time limits, multi-targets, and radar sites with different levels of risks. It can severely task all the resources (people, hardware, software) of the system trying to compute the possible routes. The nature of the problem can cause operational planning systems to take longer to generate a solution …

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An Integrated Architecture And Feature Selection Algorithm For Radial Basis Neural Networks, Timothy D. Flietstra Mar 2002

An Integrated Architecture And Feature Selection Algorithm For Radial Basis Neural Networks, Timothy D. Flietstra

Theses and Dissertations

There are two basic ways to control an Unmanned Combat Aerial Vehicle (UCAV) as it searches for targets: allow the UCAV to act autonomously or employ man-in-the-loop control. There are also two target sets of interest: fixed or mobile targets. This research focuses on UCAV-based targeting of mobile targets using man-in-the-loop control. In particular, the interest is in how levels of satellite signal latency or signal degradation affect the ability to accurately track, target, and attack mobile targets. This research establishes a weapon effectiveness model assessing targeting inaccuracies as a function of signal latency and/or signal degradation. The research involved …

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The Horizontal Extent Of Cloud-To-Ground Lightning Over The Kennedy Space Center, Todd M. Mcnamara Jan 2002

The Horizontal Extent Of Cloud-To-Ground Lightning Over The Kennedy Space Center, Todd M. Mcnamara

Theses and Dissertations

The Air Force Weather Agency (AFWA) runs the Penn State/NCAR Mesoscale Model 5 (MM5) as their main mesoscale weather forecast model. One of the post-processing procedures is a diagnostic algorithm, which is used to help identify convective and non-convective wind gusts. O. Brassuer has identified a new Wind Gust Estimate (WGE), as a physically based method of computing non-convective wind gusts. The WGE surmises that Turbulent Kinetic Energy (TKE) transfers the momentum of faster upper-air winds to the surface, overcoming the buoyant energy of the surface layer. This work converts Brassuer's WGE to FORTRAN code and utilizing post-processed CONUS AFWA …

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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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Microcavity Surface Emitting Laser, Stewart Feld, John P. Loehr, James A. Lott Jul 2001

Microcavity Surface Emitting Laser, Stewart Feld, John P. Loehr, James A. Lott

AFIT Patents

A three-dimensional waveguiding structure for a microcavity surface-emitting laser is described in which native aluminum oxide layers provide control of intracavity waveguiding and the laser optical mode structure of the emitted beam. Microcavity lasers described herein account for the blueshift of the emission wavelength as the laser lateral dimensions are reduced to or below the emission wavelength.

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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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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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A Radial Basis Function Neural Network Approach To Two-Color Infrared Missile Detection, Kin-Weng Chan Mar 2001

A Radial Basis Function Neural Network Approach To Two-Color Infrared Missile Detection, Kin-Weng Chan

Theses and Dissertations

Multicolor infrared imaging missile-warning systems require real-time detection techniques that can process the wide instantaneous field of regard of focal plane array sensors with a low false alarm rate. Current technology applies classical statistical methods to this problem and ignores neural network techniques. Thus the research reported here is novel in that it investigates the use of radial basis function (RBF) neural networks to detect sub-pixel missile signatures. An RBF neural network is designed and trained to detect targets in two-color infrared imagery using a recently developed regression tree algorithm. Features are calculated for 3 by 3 pixel sub-images in …

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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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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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Models For Data Source Tracking With Xml, Teoman Yoruk Mar 2001

Models For Data Source Tracking With Xml, Teoman Yoruk

Theses and Dissertations

The Air Force Research arch Laboratory, Sensors Directorate Electronic Warfare Simulation Branch (APRL/SNZW) is responsible for developing and maintaining real-world and hypothetical scenarios for an array of threat engagement simulation systems. The general for scenario creation involves mapping from real-world databases and operations plans to specific fields in the input files represent the scenario. As part of the AFRL/SNZW's overall initiative for the development of a Concurrent Engineering Real-Time database CORrelation tool (CERCORT), as important to the scenario files themselves is the capability to trace hack to the source of data for the scenario fields. Acquiring this capability consequently results …

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Spectral And Temporal Characterization Of High Temperature Events, William F. Bagby Mar 2001

Spectral And Temporal Characterization Of High Temperature Events, William F. Bagby

Theses and Dissertations

The remote observations of the temporal and spectral characteristics of the infrared (IR) emissions from exploding ordnance have been correlated with explosion conditions. A Bomem MR-154 Fourier Transform Interferometer with two detectors, InSb and HgCdTe, was used to record spectra in the 1.3 - 20 micrometers range. Data was collected at spectral resolutions of 16/cm and 4/cm, and temporal resolutions of 0.045 sand 0.123 5, respectively. The data files range in size from 900 Kilobytes to several Megabytes. These are reduced to 2-dimensional representations of temporal features that are less than 100 Kilobytes. The data analysis indicates the possibility of …

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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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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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Lifecycle Energy And Air Emission Differences Between Electric And Internal Combustion Vehicles, David L. Mccleese Mar 2001

Lifecycle Energy And Air Emission Differences Between Electric And Internal Combustion Vehicles, David L. Mccleese

Theses and Dissertations

The U.S. Federal Government has encouraged shifting from internal combustion engine vehicles (ICEVs) to electric vehicles (EVs) with three objectives, reducing foreign oil dependence, greenhouse gas emissions, and criteria pollutant emissions. This thesis uses Monte Carlo simulation to predict lifecycle emissions and energy consumption differences per kilometer driven from replacing ICEVs with three EV options: lead acid, nickel cadmium (Ni-Cd), and nickel metal hydride (NiMH). All three EV options reduce U.S. foreign oil dependence by shifting to domestic coal. The probabilities that lifecycle energy consumption per km driven improve are lead acid 76%, Ni-Cd 64%, and NiMH 90%. The probabilities …

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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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Dissolution Of Chromium From Inhalable Primer Paint Particles Into A Simulated Lung Fluid, David A. Kauth Mar 2001

Dissolution Of Chromium From Inhalable Primer Paint Particles Into A Simulated Lung Fluid, David A. Kauth

Theses and Dissertations

The use of chromate as a corrosion inhibitor in primer paint is an essential component for the protection of aluminum-skinned aircraft and the primary source of hexavalent chromium (Cr (VI)) exposure to USAF aircraft painters. The objective of this research was to quantify the dissolution of chromate from freshly sprayed paint particles into a simulated lung fluid (SLF). Two primer paints were sprayed with a paint spray gun to generate overspray particles for collection into impingers filled with SLF. Particles were allowed to soak in SLF for 24 and 48 hours and then the particles were removed by centrifugation. The …

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Malicious Hackers: A Framework For Analysis And Case Study, Laura J. Kleen Mar 2001

Malicious Hackers: A Framework For Analysis And Case Study, Laura J. Kleen

Theses and Dissertations

Recent years have seen an increase in the number and severity of Information Operations (IO) attacks upon DoD resources. At a higher level, the US as a whole has come under cyber attack by individuals and groups seeking thrills, monetary gain, publicity for their causes, and myriad other goals. This effort develops a first cut model of individual hacker mentality that can be utilized to improve threat assessment, mitigate Information Assurance (IA) vulnerabilities, and improve risk assessment. Further, it is a first step toward automated characterization of Information Warfare (IW) attacks based upon hacker types. All hackers are not the …

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