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 1171 - 1200 of 2678

Full-Text Articles in Physical Sciences and Mathematics

Combating Biological Terrorism From Imported Food, Jeffrey S. Nelson Mar 2011

Combating Biological Terrorism From Imported Food, Jeffrey S. Nelson

Theses and Dissertations

There is a threat that a terrorist or terrorist organization will use access to the US food supply to kill or sicken Americans by contaminating imported food products from Mexico. The food that Americans eat is coming more and more often from foreign countries such as Mexico. Foodborne diseases infect nearly fifty million people in the US each year, resulting in over three thousand deaths. There are many terrorist organizations that would like to deliberately contaminate American food. Drug cartels and terrorist organizations currently operate in Mexico, one of the leading food importers into the US. The purpose of this …

Go to article

Cathodoluminescence Of Irradiated Hafnium Dioxide, Emily A. Purcell Mar 2011

Cathodoluminescence Of Irradiated Hafnium Dioxide, Emily A. Purcell

Theses and Dissertations

The purpose of this research is to understand the effect of radiation on HfO2 thin films, and to compare the quality of HfO2 thin films produced by both atomic layer deposition (ALD) and pulsed laser deposition (PLD); PLD samples had varying substrate temperatures during deposition (300°C, 500°C, and 750°C). The entirety of this research was conducted using cathodoluminescence (CL) as the examination method. The excitation source was a Kimball Physics EMG-12 electron gun. The photomultiplier tube contained a gallium arsenide photocathode. Measurements were made with beam energies ranging from 1 to 10 keV and beam currents ranging from …

Go to article

Optical And Electrical Characterization Melt-Grown Bulk Ingaas And Inasp, Jean W. Wei Mar 2011

Optical And Electrical Characterization Melt-Grown Bulk Ingaas And Inasp, Jean W. Wei

Theses and Dissertations

A new method to determine semiconductor bandgap energy directly from the easily measured transmission spectra was developed. The method was verified using many binary semiconductors with known properties and utilized to determine the unknown ternary semiconductors were determined at various wavelengths and temperatures. Photoluminescence and Hall-effect measurement were performed to identify various electronic transitions, as well as sample quality. The determination of electrical and optical properties of the material will provide important addition to the database of material properties for future optoelectronic device applications. In the near future, newer materials and their applications need to be developed, and often binary …

Go to article

Adaptive Imaging Methods Using A Rotating Modulation Collimator (Rmc), Daniel T. Willcox Mar 2011

Adaptive Imaging Methods Using A Rotating Modulation Collimator (Rmc), Daniel T. Willcox

Theses and Dissertations

The Rotating Modulation Collimator (RMC) belongs to a larger class of radiation imaging systems that rely on either temporal or spatial modulation of incident radiation through collimation to map the location of the incident radiation source. The strengths of these detection systems include their low cost and simplicity. A major drawback is the collection time required for low radiation intensities due especially to the loss of radiation information resulting from collimation. One method of addressing this drawback for the RMC is by applying an adaptive imaging approach. As with most system design theory, there are inherent design tradeoffs for the …

Go to article

Integration Of A Worldwide Atmospheric Based Model With A Live Virtual Constructive Simulation Environment, David B. Simmons Mar 2011

Integration Of A Worldwide Atmospheric Based Model With A Live Virtual Constructive Simulation Environment, David B. Simmons

Theses and Dissertations

Yearly DoD spends millions of dollars on Modeling and Simulation tools in order to accomplish two fundamental tasks: make better decisions and develop better skills. Simulators that are based on realistic models enable the USAF to properly train, educate, and employ military forces. LEEDR is an atmospheric model based on worldwide historic weather data that is able to predict the extinction, absorption, and scattering of radiation across a broad range of the electromagnetic spectrum. Through this study LEEDR models the propagation of 1.0642 micron laser radiation at worldwide locations and through various environmental conditions. This modeled laser transmission output, based …

Go to article

Immediate And Delayed Drug Therapy Effects On Low Dose Sarin Exposed Mice Myocardial Performance, Joshua T. Miller Mar 2011

Immediate And Delayed Drug Therapy Effects On Low Dose Sarin Exposed Mice Myocardial Performance, Joshua T. Miller

Theses and Dissertations

Recent studies have shown that a single asymptomatic dose exposure to the nerve agent sarin can lead to long term cardiac dysfunction. This study looked at immediate and delayed treatment therapies post exposure on cardiac function. The mice were studied using electrocardiography (QTc, STc, and Tc intervals) and histological techniques (hematoxylin and eosin staining and brain natriuretic peptide (BNP) staining). Male C57BL/6J mice were injected with sarin (0.4LD50) and studied up to 11 weeks. Mice which were given a single dose of the nerve agent treatment atropine/2PAMCL, showed significantly higher cell size and BNP levels than the control (p = …

Go to article

Cathodoluminescence And Photoemission Of Doped Lithium Tetraborate, Christina L. Dugan Mar 2011

Cathodoluminescence And Photoemission Of Doped Lithium Tetraborate, Christina L. Dugan

Theses and Dissertations

Lithium tetraborate (Li2B4O7) crystals are being developed for possible use in solid state neutron detectors. The 6Li(n,α)3H and 10B(n,α)7Li reactions are the basis for neutron detection, and a Li2B4O7 crystal enriched with Mn should show improved efficiency for neutron detection. There is a lack of fundamental characterization information regarding this useful material, particularly with regard to its electronic configuration. Photoemission spectroscopy was used to determine the energy level structure of the Mn doped Li2B4O7 crystals. …

Go to article

Radiation Effects On The Electrical Properties Of Hafnium Oxide Based Mos Capacitors, Jesse C. Foster Mar 2011

Radiation Effects On The Electrical Properties Of Hafnium Oxide Based Mos Capacitors, Jesse C. Foster

Theses and Dissertations

Hafnium oxide-based MOS capacitors were investigated to determine electrical property response to radiation environments. In situ capacitance versus voltage measurements were analyzed to identify voltage shifting as a result of changes to trapped charge with increasing dose of gamma, neutron, and ion radiation. In situ measurements required investigation and optimization of capacitor fabrication to include dicing, cleaning, metalization, packaging, and wire bonding. A top metal contact of 200 angstroms of titanium followed by 2800 angstroms of gold allowed for repeatable wire bonding and proper electrical response. Gamma and ion irradiations of atomic layer deposited hafnium oxide on silicon devices both …

Go to article

Radial Distribution Of Absorption In A Cesium Heat Pipe With Axial Laser Heating, Charles D. Fox Mar 2011

Radial Distribution Of Absorption In A Cesium Heat Pipe With Axial Laser Heating, Charles D. Fox

Theses and Dissertations

Diode Pumped Alkali Lasers (DPAL) have been scaled to greater than 100 W and exhibit slope efficiencies exceeding 80%, offering application for tactical laser weapons. The hybrid DPAL system combines efficient diode pumping with the good beam quality and thermal characteristics of gas lasers. Thermal effects on alkali concentration have been observed to degrade performance, while low speed flowing systems are in development. However, spatial gradients in temperature and concentrations have not previously been observed. In the present work, a 0.8 W/cm2 pump laser at the D1 frequency heats the medium in a T=50-100 °C cesium heat pipe …

Go to article

Sensitivity Analysis Of Empirical Parameters In The Ionosphere-Plasmasphere Model, Janelle V. Jenniges Mar 2011

Sensitivity Analysis Of Empirical Parameters In The Ionosphere-Plasmasphere Model, Janelle V. Jenniges

Theses and Dissertations

A sensitivity analysis of empirical parameters used in physics-based models was completed in this study to determine their effect on electron densities and total electron content (TEC) in the ionosphere. The model used was the Ionosphere-Plasmasphere Model (IPM) developed by Utah State University. The empirical parameters studied include the O+/O collision frequency, zonal wind, secondary electron production, nighttime ExB drifts, and tidal structure. The sensitivity analysis was completed by comparing a default run of the IPM to a run with the parameter adjusted for three geophysical cases. Many of the comparisons resulted in nonlinear changes to the model …

Go to article

Branch Point Mitigation Of Thermal Blooming Phase Compensation Instability, Mark F. Spencer Mar 2011

Branch Point Mitigation Of Thermal Blooming Phase Compensation Instability, Mark F. Spencer

Theses and Dissertations

Thermal blooming can have a major impact on high-energy laser (HEL) beam propagation in the atmosphere. In theory, an adaptiveoptics (AO) system can mitigate the nonlinear optical effects induced by thermal blooming; however, when a single deformable mirror is used for phase-only compensation, analysis predicts the possibility of instability. This instability is appropriately termed phase compensation instability (PCI) and arises with the time-dependent development of spatial perturbations found within the HEL beam. These spatial perturbations act as local hot spots that produce negative-lens-like optical effects in the atmosphere. An AO system corrects for the hot spots by applying positive-lens-like phase …

Go to article

Shack-Hartmann And Interferometric Hybrid Wavefront Sensor, Troy R. Ellis Mar 2011

Shack-Hartmann And Interferometric Hybrid Wavefront Sensor, Troy R. Ellis

Theses and Dissertations

This document reports results of wave-optics simulations used to test the performance of a hybrid wavefront sensor designed to combine the self-referencing interferometer and Shack-Hartmann wavefront sensors in an optimal way. Optimal hybrid-wavefront sensor design required a thorough analysis of the noise characteristics of each wavefront sensor to produce noise models that assist in the design of an optimal phase-estimation algorithm. Feasible architectures and algorithms for combining wavefront sensors were chosen, and the noise models of the individual wavefront sensors were combined to form a model for the noise-induced error of the resulting hybrid sensor. The hybrid wavefront sensor and …

Go to article

Spear Phishing Attack Detection, David T. Merritt Mar 2011

Spear Phishing Attack Detection, David T. Merritt

Theses and Dissertations

This thesis addresses the problem of identifying email spear phishing attacks, which are indicative of cyber espionage. Spear phishing consists of targeted emails sent to entice a victim to open a malicious file attachment or click on a malicious link that leads to a compromise of their computer. Current detection methods fail to detect emails of this kind consistently. The SPEar phishing Attack Detection system (SPEAD) is developed to analyze all incoming emails on a network for the presence of spear phishing attacks. SPEAD analyzes the following file types: Windows Portable Executable and Common Object File Format (PE/COFF), Adobe Reader, …

Go to article

A Multi Agent System For Flow-Based Intrusion Detection Using Reputation And Evolutionary Computation, David Hancock Mar 2011

A Multi Agent System For Flow-Based Intrusion Detection Using Reputation And Evolutionary Computation, David Hancock

Theses and Dissertations

The rising sophistication of cyber threats as well as the improvement of physical computer network properties present increasing challenges to contemporary Intrusion Detection (ID) techniques. To respond to these challenges, a multi agent system (MAS) coupled with flow-based ID techniques may effectively complement traditional ID systems. This paper develops: 1) a scalable software architecture for a new, self-organized, multi agent, flow-based ID system; and 2) a network simulation environment suitable for evaluating implementations of this MAS architecture and for other research purposes. Self-organization is achieved via 1) a reputation system that influences agent mobility in the search for effective vantage …

Go to article

A Multispectral Bidirectional Reflectance Distribution Function Study Of Human Skin For Improved Dismount Detection, Bradley M. Koch Mar 2011

A Multispectral Bidirectional Reflectance Distribution Function Study Of Human Skin For Improved Dismount Detection, Bradley M. Koch

Theses and Dissertations

In 2008, the Sensors Exploitation Research Group at the Air Force Institute of Technology began using spectral properties of skin for the detection and classification of humans. Since then a multispectral skin detection system was developed to exploit the optical properties of human skin at wavelengths in the visible and near infrared region of the electromagnetic spectrum. A rules-based detector, analyzing an image spectrally, currently bases its skin pixel selection criteria on a diffuse skin reflectance model. However, when observing skin in direct view of the sun, a glint of light off skin is common and indicates specularity. The areas …

Go to article

Characterization Of Neutron-Induced Defects In Isotopically Enriched Lithium Tetraborate, Brant E. Kananen Mar 2011

Characterization Of Neutron-Induced Defects In Isotopically Enriched Lithium Tetraborate, Brant E. Kananen

Theses and Dissertations

Lithium Tetraborate (LTB) is assessed for use as a material for neutron detection. LTB isotopically enriched in either Li-6 or B-10 provides a medium that efficiently captures and transmutes neutrons into more readily detected forms of material or energy. Neutron detection is desirable to detect elicit movement of special nuclear material or nuclear weapons. Single crystals of LTB, Li-6 or B-10 enriched, were neutron irradiated, and electron paramagnetic resonance was used to detect point defects induced by the neutrons. Multiple defects were noted in the irradiated crystals. Two particular defects, perturbed lithium vacancies and lithium clusters are proposed as induced …

Go to article

Investigation Of Yag:Ce Scintillating Fiber Properties Using Silicon Photomultipliers, Bradley S. Jones Mar 2011

Investigation Of Yag:Ce Scintillating Fiber Properties Using Silicon Photomultipliers, Bradley S. Jones

Theses and Dissertations

The properties of thin, cerium activated, yttrium aluminum garnet (YAG:Ce), scintillating fiber-shaped crystals were investigated for particle tracking and calorimetric applications such as Compton imaging of Special Nuclear Material from remote platforms at standoff ranges. Silicon photomultipliers (SiPMs) are relatively new, efficient, single photon sensitive, solid-state photodiode arrays which are well suited for the readout of scintillating fibers. Using SiPMs, the scintillation decay time profiles of six 400 micrometers YAG:Ce fiber crystals were measured under alpha and gamma irradiation. Interestingly, the observed decay times in the thin fibers were substantially slower than values for bulk single crystal YAG:Ce reported in …

Go to article

Analysis Of Plasma Bubble Signatures In The Ionosphere, Omar A. Nava Mar 2011

Analysis Of Plasma Bubble Signatures In The Ionosphere, Omar A. Nava

Theses and Dissertations

Plasma bubbles are large scale structures of depleted plasma density in Earth's ionosphere that disrupt radio and satellite communications, to include global navigation satellite systems. This study used the Ionospheric Forecast Model (IFM) to analyze affected look angles and total electron content (TEC) differences due to plasma bubbles of various sizes for 27 geophysical conditions consisting of different seasons and levels of solar and geomagnetic activity at 421 GPS ground stations worldwide. Overall, different geographic locations and plasma bubble configurations produced different affected look angle profiles. Bigger plasma bubbles, larger density depletion factors, higher levels of solar activity and the …

Go to article

Nuclear Weapon Yield Determination Through Nano Indentation Of Thermally Degraded Automobile Paint, Michael J. Richards Mar 2011

Nuclear Weapon Yield Determination Through Nano Indentation Of Thermally Degraded Automobile Paint, Michael J. Richards

Theses and Dissertations

This work investigated the suitability of automotive clearcoat as a nuclear weapon yield sensor, using the change in elastic modulus as the primary metric. The AFIT Xenon Thermal Simulator (AXTS) was used to simulate a nuclear thermal pulse. The elastic modulus of the clearcoat was measured using a nano indenter. During this research the power density of the AXTS beam was increased from 44.7 to 63.7 W/cm2. The morphological steps through which automobile paint proceeds as it thermally degrades were identified and correlated with temperatures. A computer model was created and used to ensure that the paint’s time-temperature …

Go to article

Improving The Efficiency Of Photon Collection By Compton Rescue, Alexander W. Stevenson Mar 2011

Improving The Efficiency Of Photon Collection By Compton Rescue, Alexander W. Stevenson

Theses and Dissertations

A method to improve the efficiency of photon collection in thin planar HPGe detectors was investigated. The method involved implementing a second HPGe detector to collect Compton scattered photons from the primary detector and incorporating coincident interactions in the two detectors that sum to the full energy event into the energy spectrum. This method is termed Compton rescue because the Compton scattered photons make a partial energy deposition in the primary detector and are added back to the spectrum after being detected by the second detector. This research has implications on improving the efficiency of positron annihilation spectroscopy (PAS) techniques …

Go to article

Passive Ranging Of Dynamic Rocket Plumes Using Infrared And Visible Oxygen Attenuation, Robert Anthony Vincent Mar 2011

Passive Ranging Of Dynamic Rocket Plumes Using Infrared And Visible Oxygen Attenuation, Robert Anthony Vincent

Theses and Dissertations

Atmospheric oxygen absorption bands in observed spectra of boost phase missiles can be used to accurately estimate range from sensor to target. This work compares two oxygen absorption bands in the near-infrared (NIR) and visible (Vis) spectrum, centered at 762nm and 690 nm, to passively determine range. Spectra were observed from static tests of both surface-to-air missile simulators at 405m range and a full-scale solid rocket motor at 900m range. The NIR O2 band provided range estimates accurate to within 3% for both tests, while the Vis O2 band had range errors of 77% and 15 %, respectively. …

Go to article

Comparison Of Development Test And Evaluation And Overall Program Estimate At Completion, William R. Rosado Mar 2011

Comparison Of Development Test And Evaluation And Overall Program Estimate At Completion, William R. Rosado

Theses and Dissertations

Historically, cost growth regression models analyze aggregate, program-level information. Initiatives by the Office of Secretary of Defense, Cost Assessment and Program Evaluation (OSD CAPE) require direct, centralized reporting of the complete Work Breakdown Structure (WBS) Earned Value (EV) data. Centralized reporting allows access to unfiltered, unaltered, EV data for multiple programs. Using regression, we evaluate if WBS element Development Test and Evaluation (DT&E) EV data is related to program estimate at completion (EAC). Identifying a relationship provides evidence validating pertinence and reliability of low level EV data. Additionally, a relationship between a specific WBS element and program EAC establishes a …

Go to article

Measuring The Utility Of A Cyber Incident Mission Impact Assessment (Cimia) Process For Mission Assurance, Christy L. Peterson Mar 2011

Measuring The Utility Of A Cyber Incident Mission Impact Assessment (Cimia) Process For Mission Assurance, Christy L. Peterson

Theses and Dissertations

Information is a critical asset on which virtually all modern organizations depend upon to meet their operational mission objectives. Military organizations, in particular, have embedded Information and Communications Technologies (ICT) into their core mission processes as a means to increase their operational efficiency, exploit automation, improve decision quality, and shorten the kill chain. However, the extreme dependence upon ICT results in an environment where a cyber incident can result in severe mission degradation, or possibly failure, with catastrophic consequences to life, limb, and property. These consequences can be minimized by maintaining real-time situational awareness of mission critical resources so appropriate …

Go to article

Software And Critical Technology Protection Against Side Channel Analysis Through Dynamic Hardware Obfuscation, John R. Bochert Mar 2011

Software And Critical Technology Protection Against Side Channel Analysis Through Dynamic Hardware Obfuscation, John R. Bochert

Theses and Dissertations

Side Channel Analysis (SCA) is a method by which an adversary can gather information about a processor by examining the activity being done on a microchip though the environment surrounding the chip. Side Channel Analysis attacks use SCA to attack a microcontroller when it is processing cryptographic code, and can allow an attacker to gain secret information, like a crypto-algorithm's key. The purpose of this thesis is to test proposed dynamic hardware methods to increase the hardware security of a microprocessor such that the software code being run on the microprocessor can be made more secure without having to change …

Go to article

Overcoming Pose Limitations Of A Skin-Cued Histograms Of Oriented Gradients Dismount Detector Through Contextual Use Of Skin Islands And Multiple Support Vector Machines, Jonathon R. Climer Mar 2011

Overcoming Pose Limitations Of A Skin-Cued Histograms Of Oriented Gradients Dismount Detector Through Contextual Use Of Skin Islands And Multiple Support Vector Machines, Jonathon R. Climer

Theses and Dissertations

This thesis provides a novel visualization method to analyze the impact that articulations in dismount pose and camera aspect angle have on histograms of oriented gradients (HOG) features and eventual detections. Insights from these relationships are used to identify limitations in a state of the art skin cued HOG dismount detector's ability to detect poses not in a standard upright stances. Improvements to detector performance are made by further leveraging available skin information, reducing false detections by an additional order of magnitude. In addition, a method is outlined for training supplemental support vector machines (SVMs) from computer generated data, for …

Go to article

Simulating The Effects Of An Extended Source On The Shack-Hartmann Wavefront Sensor Through Turbulence, Jeffery S. Dennison Mar 2011

Simulating The Effects Of An Extended Source On The Shack-Hartmann Wavefront Sensor Through Turbulence, Jeffery S. Dennison

Theses and Dissertations

Perspective elongation in Shack-Hartmann wavefront sensor (SHWFS) spots is a phenomenon caused by an extended three-dimensional scattering beacon in the mesosphere (80-100km). Elongated spots cause errors in wavefront sensor measurements, which leads to poor turbulence compensation and decreased image resolution of the optical system. In order to compensate for elongated spots, a proper beacon model must be developed to simulate the error. In this paper, a documented theory for modeling an elongated sodium beacon and elongated SHWFS spots using sodium layer slices was tested. It was found that nine evenly-spaced slices were adequate to model the elongated beacon in the …

Go to article

Development Of An Interference Lithography Capability Using A Helium Cadmium Ultraviolet Multimode Laser For The Fabrication Of Sub-Micron-Structured Optical Materials, Stanley D. Crozier Mar 2011

Development Of An Interference Lithography Capability Using A Helium Cadmium Ultraviolet Multimode Laser For The Fabrication Of Sub-Micron-Structured Optical Materials, Stanley D. Crozier

Theses and Dissertations

The goal of this work is to develop unique holograms on a semiconductor-metal thin films to characterize as potential metamaterials. This is achievable by developing a fabrication recipe to include exposure methods, exposure dosages, and material development. This study developed an interference lithography capability at AFIT for the first time with period resolution below 230nm. It also identified initial acceptable photoresist materials and exposure dosages, and a path to follow to optimize this process. The potential impact of this is to make IL a standard in optical meta-material fabrication, which decreases manufacturing time and allows for less error in production. …

Go to article

Evaluating Information Assurance Control Effectiveness On An Air Force Supervisory Control And Data Acquisition (Scada) System, Jason R. Nielsen Mar 2011

Evaluating Information Assurance Control Effectiveness On An Air Force Supervisory Control And Data Acquisition (Scada) System, Jason R. Nielsen

Theses and Dissertations

Supervisory Control and Data Acquisition (SCADA) systems are increasingly being connected to corporate networks which has dramatically expanded their attack surface to remote cyber attack. Adversaries are targeting these systems with increasing frequency and sophistication. This thesis seeks to answer the research question addressing which Information Assurance (IA) controls are most significant for network defenders and SCADA system managers/operators to focus on in order to increase the security of critical infrastructure systems against a Stuxnet-like cyber attack. This research applies the National Institute of Science and Technology (NIST) IA controls to an attack tree modeled on a remote Stuxnet-like cyber …

Go to article

Characterization Of A Boron Carbide Heterojunction Neutron Detector, James E. Bevins Mar 2011

Characterization Of A Boron Carbide Heterojunction Neutron Detector, James E. Bevins

Theses and Dissertations

New methods for neutron detection have become an important area of research in support of national security objectives. In support of this effort, p-type B5C on n-type Si heterojunction diodes have been built and tested. This research sought to optimize the boron carbide (BC) diode by coupling the nuclear physics modeling capability of GEANT4 and TRIM with the semiconductor device simulation tools. Through an iterative modeling process of controllable parameters, optimal device construction was determined such detection efficiency and charge collection were optimized. This allows an estimation of expected charge collection and efficiency given a set of operating …

Go to article

Remote Quantification Of Smokestack Total Effluent Mass Flow Rates Using Imaging Fourier-Transform Spectroscopy, Jacob L. Harley Mar 2011

Remote Quantification Of Smokestack Total Effluent Mass Flow Rates Using Imaging Fourier-Transform Spectroscopy, Jacob L. Harley

Theses and Dissertations

A Telops Hyper-Cam midwave infrared (1.5 − 5.5μm) imaging Fourier-transform spectrometer (IFTS) was used to estimate industrial smokestack total effluent mass flow rates by combining spectrally-determined species concentrations with flow rates estimated via analysis of sequential images in the raw interferogram cube. Strong emissions from H2O, CO2, CO, SO2, and NO were observed in the spectrum. A previously established plume radiative transfer model was used to estimate gas concentrations, and a simple temporal cross-correlation analysis of sequential imagery enabled an estimation of the flow velocity. Final effluent mass flow rates for CO2 and …

Go to article

First Prev Next Last