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2008

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Articles 2491 - 2520 of 4190

Full-Text Articles in Engineering

Simulation Modeling And Analysis Of F-16 Pilot Training Squadron, Adem Okal Mar 2008

Simulation Modeling And Analysis Of F-16 Pilot Training Squadron, Adem Okal

Theses and Dissertations

The need for fighter pilots in the Turkish Air Force is expected to increase with the planned acquisition of Joint Strike Fighters, ongoing new F-16 purchases, and other upgrades to the Turkish Air Force fighter inventory. This increased demand will affect the current fighter training squadron curriculum and scheduling. This study focuses on issues related to 143rd Oncel squadron F-16 Pilot Training with this projected increase in number of student pilots (SP). Completing the training periods on time is an important issue along with maintaining effective training performance. In our study the Total Time of the training period serves …

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Assessing Capabilities Of The High Energy Liquid Laser Area Defense System Through Combat Simulations, Ryan S. Ponack Mar 2008

Assessing Capabilities Of The High Energy Liquid Laser Area Defense System Through Combat Simulations, Ryan S. Ponack

Theses and Dissertations

High Energy Laser (HEL) technology continues to improve and its place in the battlefield is ever evolving. By combining the high energy delivery of solid state laser technology with the efficient thermal management of liquid laser technology, HELLADS has two main advantages over any HEL predecessors. One, the configuration is small and light enough to be carried on more tactical aircraft such as fighters. Two, the thermal management greatly increases HEL fire power by increasing dwell time on target. To assess HELLADS operational capabilities the test community has been challenged with how to effectively examine the advantages and limitations through …

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A Simulation Optimization Approach To The Design Of Unmanned Aircraft Systems, Emily C. Evans Mar 2008

A Simulation Optimization Approach To The Design Of Unmanned Aircraft Systems, Emily C. Evans

Theses and Dissertations

Military strategy and operations have evolved significantly over the past decade. This evolution has led to a change in the military resources required to carry out missions successfully. In line with these requirements, demand has increased for unmanned aerial vehicles (UAV) with enhanced capability to perform surveillance and to strike targets of interest. This research effort aids in the design of a next generation UAV by employing a simulation optimization approach. The goal of this research is to maximize the number of targets destroyed in a conflict scenario by a newly designed UAV that is subject to size, weight, and …

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A Decision Tool To Evaluate Budgeting Methodologies For Estimating Facility Recapitalization Requirements, Krista M. Hickman Mar 2008

A Decision Tool To Evaluate Budgeting Methodologies For Estimating Facility Recapitalization Requirements, Krista M. Hickman

Theses and Dissertations

The purpose of this research was to develop a decision tool to assist in the evaluation of facility recapitalization budget estimation models to determine which model was best suited for a particular organization. Specifically, this thesis sought to answer an overarching research question addressing the importance of recapitalization and the best method to estimate the facility recapitalization budget using the Department of Defense (DoD) as the subject of the research. A comprehensive literature review revealed ten existing recapitalization model alternatives to consider for implementation. The methodology used to develop a decision tool was based on the Value Focused Thinking (VFT) …

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The Impact Of Operations Tempo (Optempo) On Intentions To Depart The Military. Does The Increase Of Optempo Cause Action, Nathan P. Olsen Mar 2008

The Impact Of Operations Tempo (Optempo) On Intentions To Depart The Military. Does The Increase Of Optempo Cause Action, Nathan P. Olsen

Theses and Dissertations

Recent information in the field of Operations Tempo (OPTEMPO) has resulted in conflicting information on its effect on turnover intentions. This study evaluated the August 2004 Status of Forces Survey to determine if the sample demonstrated OPTEMPO had a curvilinear effect on turnover intentions when accounting for the moderators job satisfaction and organizational commitment while controlling for rank and gender. Linear regressions were used to determine if the relationship between OPTEMPO and turnover intentions were significant. When accounting for job satisfaction and organizational commitment the relationship between OPTEMPO and turnover intentions is not significant, this indicated that OPTEMPO and turnover …

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Linking Embeddedness And Macroinvertebrate In Two Southwest Ohio Streams, Jonathan P. Kochersberger Mar 2008

Linking Embeddedness And Macroinvertebrate In Two Southwest Ohio Streams, Jonathan P. Kochersberger

Theses and Dissertations

Environmental managers utilize a variety of tools when assessing lotic systems for stressors attributed to anthropogenic sources. Stream deposited sediment has been recognized as one of the major stressors affecting streams in the U.S. The detrimental effect on aquatic biota of sediment depositing within the interstitial spaces of stream substrate (embeddedness) has been established, yet lacking is an effective in situ method of quantifying embeddedness over short time periods. The goal of this research was to develop a short-term embeddedness (EMB) quantification method that can be linked to benthic macroinvertebrate health. Such a method would be a valuable tool when …

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Molecular Characterization Of Wetland Soil Bacterial Communities In Constructed Mesocosms, Elisabeth M. Leon Mar 2008

Molecular Characterization Of Wetland Soil Bacterial Communities In Constructed Mesocosms, Elisabeth M. Leon

Theses and Dissertations

16S rRNA gene analysis was performed on soil samples from a subsurface flow mesocosm experiment, mimicking a constructed wetland. Three typical wetland species of plant were used in nine of the columns and three columns were unplanted controls. Analyses showed that plant presence, plant species, and depth did not have a significant effect on microbial community composition. However, richness analyses illustrated that plant presence had a positive effect on richness, plant species analyses indicated that there was evidence that plant species affected richness in a significant manner, and lastly richness was negatively affected in the bottom depth for the control …

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Intelligence Surveillance And Reconnaissance Asset Assignment For Optimal Mission Effectiveness, Ryan D. Kappedal Mar 2008

Intelligence Surveillance And Reconnaissance Asset Assignment For Optimal Mission Effectiveness, Ryan D. Kappedal

Theses and Dissertations

This research develops mathematical programming techniques to solve an intelligence, surveillance, and reconnaissance sensor assignment problem for USSTRATCOM. The problem as specified is hypothesized to be difficult (i.e. np-hard). With the smallest test cases, the true optimal solution is found using simple optimization techniques, but, due to intractability, the optimal solutions for larger test cases are not found using these same techniques. Instead, heuristic techniques are applied to several test cases in order to determine the best, robust methodologies to find true or near optimal solutions. Specifically, simulated annealing (SA) is tested for convergence properties across several different parameter settings. …

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Risk-Based Comparison Of Classification Systems, Seth B. Wagenman Mar 2008

Risk-Based Comparison Of Classification Systems, Seth B. Wagenman

Theses and Dissertations

Performance measures for families of classification system families that rely upon the analysis of receiver operating characteristics (ROCs), such as area under the ROC curve (AUC), often fail to fully address the issue of risk, especially for classification systems involving more than two classes. For the general case, we denote matrices of class prevalences, costs, and class-conditional probabilities, and assume costs are subjectively fixed, acceptable estimates for expected values of class-conditional probabilities exist, and mutual independence between a variable in one such matrix and those of any other matrix. The ROC Risk Functional (RRF), valid for any finite number of …

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Velocity Estimate Following Air Data System Failure, Scott A. Mclaren Mar 2008

Velocity Estimate Following Air Data System Failure, Scott A. Mclaren

Theses and Dissertations

Modern high performance aircraft can provide amazing performance due in part to their advanced flight control systems that require gain scheduling to provide optimum performance over a huge flight envelope. In modern fighter aircraft, this gain scheduling is a function of airspeed, and almost all of the research involving aircraft gain scheduling assumes aircraft airspeed to be a known quantity. The purpose of this research was to investigate a method of determining an aircraft’s airspeed in the event of total air data system failure. The process began by combining known aircraft information following an air data system failure to determine …

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Handling Qualities Evaluation Of A Supersonic Tailless Air Vehicle, Steven W. Speares Mar 2008

Handling Qualities Evaluation Of A Supersonic Tailless Air Vehicle, Steven W. Speares

Theses and Dissertations

This thesis presents the results of a handling qualities evaluation of a supersonic tailless air vehicle. The 2006 Quadrennial Defense Review mandated the need for the next generation of long-range strike aircraft by 2018. Due to speed and stealth requirements, this resulted in a tailless aircraft with an instantaneous center of rotation located well forward of that of a conventional aircraft. This thesis examines how this center of rotation affected pilot handling qualities ratings. This effect should have been the most pronounced during approach and landing, and was where the testing focused. The goal of this research was to develop …

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Design Of An Oxygen Turbopump For A Dual Expander Cycle Rocket Engine, William S. Strain Mar 2008

Design Of An Oxygen Turbopump For A Dual Expander Cycle Rocket Engine, William S. Strain

Theses and Dissertations

The design of a pump intended for use with a dual expander cycle (LOX/H2) engine is presented. This arrangement offers a number of advantages over hydrogen expander cycles; among these are the elimination of gearboxes and inter-propellant purges and seals, an extended throttling range, and higher engine operating pressures and performance. The target engine has been designed to meet the needs of Phase III of the Integrated High Payoff Rocket Propulsion Technology (IHPRPT) program; thus, this pump must meet the program’s reliability, maintainability, and service life goals. In addition, this pump will be driven by warm gaseous oxygen. …

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Real-Time Navigation And Flight Path Generation For Tracking Stop-And-Go Targets With Miniature Air Vehicles, Nate A. Terning Mar 2008

Real-Time Navigation And Flight Path Generation For Tracking Stop-And-Go Targets With Miniature Air Vehicles, Nate A. Terning

Theses and Dissertations

This research effort focuses on using a heuristic approach to determine the optimal flight path required to put an Unmanned Aircraft System’s (UAS) sensor on a moving target in the presence of a constant wind field. This thesis builds on past work using dynamic optimization techniques to calculate minimum time to target. The computationally intensive dynamic optimization routines in their current form take a prohibitive amount of time to calculate and ultimately result in erroneous flight path predictions due to inherent execution time latencies. Therefore an iterative, suboptimal heuristic approach was explored to mitigate excessive calculation times and ultimately yield …

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Investigation Into Fretting Fatigue Under Cyclic Contact Load And In Conjuction With Fatigue Of Titanium Alloy, Abdulla A. Al-Noaimi Mar 2008

Investigation Into Fretting Fatigue Under Cyclic Contact Load And In Conjuction With Fatigue Of Titanium Alloy, Abdulla A. Al-Noaimi

Theses and Dissertations

Fretting fatigue is the surface damage that occurs at the interface between two components that are undergoing a small amplitude oscillatory movements. It results in a reduction of the material life comparing to the plain fatigue. Most of the previous works were accomplished under a constant applied contact load and a little effort has been done under a variable contact load, while none of these studies have taken the phase difference between the axial and the contact load. The primary goal of this study is to investigate the effect of phase difference between axial and contact loads on fretting fatigue …

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Space Based Satellite Tracking And Characterization Utilizing Non-Imaging Passive Sensors, Bradley R. Townsend Mar 2008

Space Based Satellite Tracking And Characterization Utilizing Non-Imaging Passive Sensors, Bradley R. Townsend

Theses and Dissertations

A technique is developed to determine the orbit of a sunlight illuminated satellite passing through the field-of-view of a sensor platform in a Highly Elliptical Orbit (HEO) and Geosynchronous orbit (GEO). The technique develops two different methods of initial orbit determination. The first relies on the Gauss initial orbit determination method to develop an estimate of the state from angular data. The second method relies on positional data of the target relative to the Earth’s background to determine an estimate of the state. These estimates are then refined in a non-linear least squares routine. This estimate of the state is …

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Network Visualization Design Using Prefuse Visualization Framework, John Mark Belue Mar 2008

Network Visualization Design Using Prefuse Visualization Framework, John Mark Belue

Theses and Dissertations

Visualization of network simulation events or network visualization is an effective and low cost method to evaluate the health and status of a network and analyze network designs, protocols, and network algorithms. This research designed and developed a network event visualization framework using an open source general visualization toolkit. This research achieved three major milestones during the development of this framework: A robust network simulator trace file parser, multiple network visualization layouts {including user-defined layouts, and precise visualization timing controls and integrated display of network statistics. The parser architecture is extensible to allow customization of simulator trace formats that are …

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Digital Fingerprinting Of Field Programmable Gate Arrays, James W. Crouch Mar 2008

Digital Fingerprinting Of Field Programmable Gate Arrays, James W. Crouch

Theses and Dissertations

Commercial off-the-shelf (COTS) component usage is becoming more prevalent in military applications due to current Department of Defense (DoD) policies. The easy accessibility of COTS will give reverse engineers a higher probability of successfully tampering, coping, or reverse engineering circuits that contain critical capabilities. To prevent this and verify the trustworthiness of hardware, circuit identification tags or serials numbers can be used. However, these values can be easily obtained and forged. To protect critical DoD technologies from possible exploitation, there is an urgent need for a reliable method to confirm a circuit’s identity using a set of unique unforgettable metrics. …

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Signal Processing Design Of Low Probability Of Intercept Waveforms, Nathaniel C. Liefer Mar 2008

Signal Processing Design Of Low Probability Of Intercept Waveforms, Nathaniel C. Liefer

Theses and Dissertations

This thesis investigates a modification to Differential Phase Shift Keyed (DPSK) modulation to create a Low Probability of Interception/Exploitation (LPI/LPE) communications signal. A pseudorandom timing offset is applied to each symbol in the communications stream to intentionally create intersymbol interference (ISI) that hinders accurate symbol estimation and bit sequence recovery by a non-cooperative receiver. Two cooperative receiver strategies are proposed to mitigate the ISI due to symbol timing offset: a modified minimum Mean Square Error (MMSE) equalization algorithm and a multiplexed bank of equalizer filters determined by an adaptive Least Mean Square (LMS) algorithm. Both cooperative receivers require some knowledge …

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Development And Flight Of A Robust Optical-Inertial Navigation System Using Low-Cost Sensors, Michael B. Nielsen Mar 2008

Development And Flight Of A Robust Optical-Inertial Navigation System Using Low-Cost Sensors, Michael B. Nielsen

Theses and Dissertations

This research develops and tests a precision navigation algorithm fusing optical and inertial measurements of unknown objects at unknown locations. It provides an alternative to the Global Positioning System (GPS) as a precision navigation source, enabling passive and low-cost navigation in situations where GPS is denied/unavailable. This paper describes two new contributions. First, a rigorous study of the fundamental nature of optical/inertial navigation is accomplished by examining the observability grammian of the underlying measurement equations. This analysis yields a set of design principles guiding the development of optical/inertial navigation algorithms. The second contribution of this research is the development and …

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Hyperspectral-Augmented Target Tracking, Neil A. Soliman Mar 2008

Hyperspectral-Augmented Target Tracking, Neil A. Soliman

Theses and Dissertations

With the global war on terrorism, the nature of military warfare has changed significantly. The United States Air Force is at the forefront of research and development in the field of intelligence, surveillance, and reconnaissance that provides American forces on the ground and in the air with the capability to seek, monitor, and destroy mobile terrorist targets in hostile territory. One such capability recognizes and persistently tracks multiple moving vehicles in complex, highly ambiguous urban environments. The thesis investigates the feasibility of augmenting a multiple-target tracking system with hyperspectral imagery. The research effort evaluates hyperspectral data classification using fuzzy c-means …

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Scripted Mobile Network Routing In A Contested Environment, Anthony R. Otto Mar 2008

Scripted Mobile Network Routing In A Contested Environment, Anthony R. Otto

Theses and Dissertations

Mobile wireless network protocols currently run on optimistic routing algorithms, adjusting node connectivity only when the chosen connectivity metrics, such as signal strength, pass beyond minimum thresholds. Optimistic routing has several weaknesses. Optimistic routing suffers from increased network overhead during increased frequency of node movement and increased node density per area, and optimistic routing also suffers from non-optimistic access change for individual nodes. The overall communication throughput of a network may be increased if the network topology change is scripted; a scripted plan can allow messages to travel along a more efficient topological path while creating less topology control traffic. …

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Integration Of Information Operations Theory Into The Corporate Air Force, Thomas R. Kettles Jr. Mar 2008

Integration Of Information Operations Theory Into The Corporate Air Force, Thomas R. Kettles Jr.

Theses and Dissertations

The purpose of this research was to determine the desired end-state for company grade officers in terms of an information operations education. Specifically, an examination of company grade officer curricula from the pre-commissioning sources to the Squadron Officer College was performed. This assessment was then compared to the Air Force Institute of Technology Cyber Competency Areas Framework. Any areas that were missing from the current company grade officer curricula were identified and a proposed implementation plan was presented to correct these deficiencies. To aid in developing an implementation plan, redundancies between the two Squadron Officer College courses were identified. Furthermore, …

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Achieving Complex Motion With Fundamental Components For Lamina Emergent Mechanisms, Brian Geoffrey Winder Mar 2008

Achieving Complex Motion With Fundamental Components For Lamina Emergent Mechanisms, Brian Geoffrey Winder

Theses and Dissertations

Designing mechanical products in a competitive environment can present unique challenges, and designers constantly search for innovative ways to increase efficiency. One way to save space and reduce cost is to use ortho-planar compliant mechanisms which can be made from sheets of material, or lamina emergent mechanisms (LEMs). This thesis presents principles which can be used for designing LEMs. Pop-up paper mechanisms use topologies similar to LEMs, so it is advantageous to study their kinematics. This thesis outlines the use of planar and spherical kinematics to model commonly used pop-up paper mechanisms. A survey of common joint types is given, …

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Bottom Profiling By Correlating Beam-Steered Noise Sequences, Chris H. Harrison, Martin Siderius Mar 2008

Bottom Profiling By Correlating Beam-Steered Noise Sequences, Chris H. Harrison, Martin Siderius

Electrical and Computer Engineering Faculty Publications and Presentations

It has already been established that by cross-correlating ambient noisetime series received on the upward and downward steered beams of a drifting vertical array one can obtain a subbottom layer profile. Strictly, the time differential of the cross correlation is the impulse response of the seabed. Here it is shown theoretically and by simulation that completely uncorrelated surfacenoise results in a layer profile with predictable amplitudes proportional to those of an equivalent echo sounder at the same depth as the array. The phenomenon is simulated by representing the sound sources as multiple random time sequences emitted from random locations in …

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Design And Optimization Of Broadband High Impedance Ground Planes (Higp) For Surface Mount Antennas, Murat Dogrul Mar 2008

Design And Optimization Of Broadband High Impedance Ground Planes (Higp) For Surface Mount Antennas, Murat Dogrul

Theses and Dissertations

Gain and bandwidth metrics of broad-band low-profile antennas severely deteriorate when they are placed conformally onto the conductive skins of air, sea, and ground platforms. This detrimental effect is primarily due to out-of-phase reflections from the conductive body interfering with the antenna’s self radiation. Furthermore, lateral waves launched by the antenna couple into the thin substrate placed between the antenna and the platform, giving rise to surface waves resulting in significant diffraction from the edges of the substrate. To remedy these two major mechanisms degrading antenna performance, high impedance ground planes (HIGP) were designed. HIGPs made of a 2-dimensional periodic …

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Developing An Excel Decision Support System Using In-Transit Visibility To Decrease Dod Transportation Delays, Brian B. Stone Mar 2008

Developing An Excel Decision Support System Using In-Transit Visibility To Decrease Dod Transportation Delays, Brian B. Stone

Theses and Dissertations

The United States Air Force's Air Mobility Command (AMC) is responsible for efficiently transporting military personnel and cargo throughout the world. Organizations throughout the transportation system search for ways to decrease cargo transportation time as part of their ongoing mission to provide timely airlift services to the DoD. As cargo is transported through the transportation system it is in one of two states; waiting at an air base for transportation or in some phase of the loading, transportation, or unloading process. The loading and unloading process has been streamlined throughout the transportation system to a point which leaves little room …

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Impacts Of Weather Variations On Energy Consumption Efforts At U.S. Air Force Installations, James S. Griffin Mar 2008

Impacts Of Weather Variations On Energy Consumption Efforts At U.S. Air Force Installations, James S. Griffin

Theses and Dissertations

Energy consumption is a national concern, as evidenced by federal laws aimed toward facility energy conservation measures for federal organizations. Factors, primarily weather variables, that significantly impact energy consumption must be addressed and understood to align resources and programs to meet federal energy reduction goals. An energy model was created and tested to produce an appropriate forecasting tool for energy consumption. Energy demand at Air Force installations primarily depends on climatic conditions, with a small portion attributed to a base level of non-climatic conditions, such as interior lighting and appliance loads. By gathering all energy consumption and meteorological data covering …

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Embedded Noninteractive Continuous Bot Detection, Roman V. Yampolskiy, Venu Govindaraju Mar 2008

Embedded Noninteractive Continuous Bot Detection, Roman V. Yampolskiy, Venu Govindaraju

Faculty and Staff Scholarship

Multiplayer online computer games are quickly growing in popularity, with millions of players logging in every day. While most play in accordance with the rules set up by the game designers, some choose to utilize artificially intelligent assistant programs, a.k.a. bots, to gain an unfair advantage over other players. In this article we demonstrate how an embedded noninteractive test can be used to prevent automatic artificially intelligent players from illegally participating in online game-play. Our solution has numerous advantages over traditional tests, such as its nonobtrusive nature, continuous verification, and simple noninteractive and outsourcing-proof design. © 2008 ACM.

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Semantic Components: A Model For Enhancing Retrieval Of Domain- Specific Information, Susan Loucette Price Mar 2008

Semantic Components: A Model For Enhancing Retrieval Of Domain- Specific Information, Susan Loucette Price

Dissertations and Theses

Despite the success of general Internet search engines, information retrieval remains an incompletely solved problem. Our research focuses on supporting domain experts when they search domain-specific libraries to satisfy targeted information needs. The semantic components model introduces a schema specific to a particular document collection. A semantic component schema consists of a two-level hierarchy, document classes and semantic components. A document class represents a document grouping, such as topic type or document purpose. A semantic component is a characteristic type of information that occurs in a particular document class and represents an important aspect of the document’s main topic. …

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Structural Identification Of Cubic Iron-Oxide Nanocrystal Mixtures: X-Ray Powder Diffraction Versus Quasi-Kinematic Transmission Electron Microscopy, Peter Moeck Mar 2008

Structural Identification Of Cubic Iron-Oxide Nanocrystal Mixtures: X-Ray Powder Diffraction Versus Quasi-Kinematic Transmission Electron Microscopy, Peter Moeck

Physics Faculty Publications and Presentations

Two novel (and proprietary) strategies for the structural identification of a nanocrystal from either a single high-resolution (HR) transmission electron microscopy (TEM) image or a single precession electron diffraction pattern are proposed and their advantages discussed in comparison to structural fingerprinting from powder X-ray diffraction patterns. Simulations for cubic magnetite and maghemite nanocrystals are used as examples.

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