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Articles 2611 - 2640 of 4566

Full-Text Articles in Engineering

Phase Shaping In The Infrared By Planar Quasi-Periodic Surfaces Comprised Of Sub-Wavelength Elements, James Ginn Jan 2009

Phase Shaping In The Infrared By Planar Quasi-Periodic Surfaces Comprised Of Sub-Wavelength Elements, James Ginn

Electronic Theses and Dissertations

Reflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time--at frequencies as high as 194 THz. Relevant aspects of computational electromagnetic modeling are explored, to yield design procedures optimized for these high frequencies. Modeling is also utilized to demonstrate the phase response of a generalized …

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Electronic Properties And Microstructures Of Amorphous Sicn Ceramics Derived From Polymer Precursors, Tao Jiang Jan 2009

Electronic Properties And Microstructures Of Amorphous Sicn Ceramics Derived From Polymer Precursors, Tao Jiang

Electronic Theses and Dissertations

Polymer-derived ceramics (PDCs) are a new class of high-temperature materials synthesized by thermal decomposition of polymeric precursors. These materials possess many unique features as compared with conventional ceramics synthesized by powder metallurgy based processing. For example, PDCs are neither amorphous nor crystalline. Instead, they possess nano-domain structures. Due to the direct chemical-to-ceramic processing, PDCs can be used for making components and devices with complex shapes. Thus, understanding the properties and structures of these materials are of both fundamental and practical interest. In this work, the structures and electronic behavior of polymer-derived amorphous silicon carbonitrides (SiCNs) were investigated. The materials were …

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Stress Intensity Factor Dependence Of Hg-Al Liquid Metal Embrittlement, Scott Keller Jan 2009

Stress Intensity Factor Dependence Of Hg-Al Liquid Metal Embrittlement, Scott Keller

Electronic Theses and Dissertations

When high strength aluminum alloys are subjected to liquid metals, physical and chemical reactions ensue resulting in what is known as liquid metal embrittlement (LME). A subset of environmentally-assisted cracking, LME is exhibited when a liquid metal, e.g. Hg or Ga, comes into intimate contact with a solid metal having significant susceptibility. As mechanical loads are applied, the interaction between the two metals results in a reduction in the flow properties of the solid metal. Several theories have been proposed to identify the underlying microstructural failure mechanism; however, none have been widely accepted, as failures can typically incorporate features common …

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Pressure Drop And Endwall Heat Transfer Effects Of Porous Turbulators In A Rectangular Channel, Jared Pent Jan 2009

Pressure Drop And Endwall Heat Transfer Effects Of Porous Turbulators In A Rectangular Channel, Jared Pent

Electronic Theses and Dissertations

This study examines the local and averaged endwall heat transfer effects of a staggered array of porous pin fins within a rectangular channel. The porous pin fins were made from aluminum and had a pore density of 10 pores per inch (PPI). The pressure drop through the channel was also determined for several flow rates and presented in terms of the friction factor. Local heat transfer coefficients on the endwall were measured using Thermochromic Liquid Crystal (TLC) sheets recorded with a charge-coupled device (CCD) camera. Static and total pressure measurements were taken at the entrance and exit of the test …

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Geometric Invariance In The Analysis Of Human Motion In Video Data, Yuping Shen Jan 2009

Geometric Invariance In The Analysis Of Human Motion In Video Data, Yuping Shen

Electronic Theses and Dissertations

Human motion analysis is one of the major problems in computer vision research. It deals with the study of the motion of human body in video data from different aspects, ranging from the tracking of body parts and reconstruction of 3D human body configuration, to higher level of interpretation of human action and activities in image sequences. When human motion is observed through video camera, it is perspectively distorted and may appear totally different from different viewpoints. Therefore it is highly challenging to establish correct relationships between human motions across video sequences with different camera settings. In this work, we …

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A Statistical Approach To View Synthesis, Phillip Berkowitz Jan 2009

A Statistical Approach To View Synthesis, Phillip Berkowitz

Electronic Theses and Dissertations

View Synthesis is the challenging problem of predicting a new view or pose of an object given an exemplar view or set of views. This thesis presents a novel approach for the problem of view synthesis. The proposed method uses global features rather than local geometry to achieve an effect similar to that of the well known view morphing method . While previous approaches to the view synthesis problem have shown impressive results, they are highly dependent on being able to solve for epipolar geometry and therefore have a very precise correspondence between reference images. In cases where this is …

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Realization Of Power Factor Correction And Maximum Power Point Tracking For Low Power Wind Turbines, Gustavo Gamboa Jan 2009

Realization Of Power Factor Correction And Maximum Power Point Tracking For Low Power Wind Turbines, Gustavo Gamboa

Electronic Theses and Dissertations

In recent years, wind energy technology has become one of the top areas of interest for energy harvesting in the power electronics world. This interest has especially peaked recently due to the increasing demand for a reliable source of renewable energy. In a recent study, the American Wind Energy Association (AWEA) ranked the U.S as the leading competitor in wind energy harvesting followed by Germany and Spain. Although the United States is the leading competitor in this area, no one has been able successfully develop an efficient, low-cost AC/DC convertor for low power turbines to be used by the average …

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Evaluating The Impact Of Oocea's Dynamic Message Signs (Dms) On Travelers' Experience Using Multinomial And Ordered Logit For The Post-Deployment Survey, Taylor Lochrane Jan 2009

Evaluating The Impact Of Oocea's Dynamic Message Signs (Dms) On Travelers' Experience Using Multinomial And Ordered Logit For The Post-Deployment Survey, Taylor Lochrane

Electronic Theses and Dissertations

The purpose of this thesis was to evaluate the impact of dynamic message signs (DMS) on the Orlando-Orange County Expressway Authority (OOCEA) toll road network using the Post-Deployment DMS Survey analysis. DMS are electronic traffic signs used on roadways to give travelers information about travel times, traffic congestion, accidents, disabled vehicles, AMBER alerts, and special events. The particular DMS referred to in this study are large rectangular signs installed over the travel lanes and these are not the portable trailer mount signs. The OOCEA has added twenty-nine fixed DMS to their toll road network from 2006-2008. At the time of …

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Nonlinear Stabilization And Control Of Medium Range Surface To Air Interceptor Missiles, Mark Snyder Jan 2009

Nonlinear Stabilization And Control Of Medium Range Surface To Air Interceptor Missiles, Mark Snyder

Electronic Theses and Dissertations

Nonlinear stabilization and control autopilots are capable of sustaining nominal performance throughout the entire fight envelope an interceptor missile may encounter during hostile engagements and require no gain scheduling to maintain autopilot stability. Due to non minimum phase conditions characteristic of tail controlled missile airframes, a separation of time scales within the dynamic equations of motion between rotational and translational differential equations was enforced to overcome unstable effects of non minimum phase. Dynamic inversion techniques are then applied to derive linearizing equations which, when injected forward into the plant result in a fully controllable linear system. Objectives of the two …

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Characterization And Aqueous Colloidal Processing Of Tungsten Nano-Powders, Zhengtao Yang Jan 2009

Characterization And Aqueous Colloidal Processing Of Tungsten Nano-Powders, Zhengtao Yang

Electronic Theses and Dissertations

Extensive attention has been paid to consolidate nanoparticles into nanocrystalline components that possess better properties than their coarse-grained counterparts. Nanocrystalline monolithic tungsten (W) has been envisaged to possess better properties than coarse-grained tungsten and to improve the performance of many military components. Commercially available nano-W powders were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Brunauer, Emmett, and Teller (BET) measurement. While the bulk of nano-W powders consisted of bcc-W as confirmed by XRD and TEM, much of their surface consisted of WO3 with traces of …

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Sintering Additives For Nanocrystalline Titania And Processing Of Porous Bone Tissue Engineering Scaffolds, Arun Menon Jan 2009

Sintering Additives For Nanocrystalline Titania And Processing Of Porous Bone Tissue Engineering Scaffolds, Arun Menon

Electronic Theses and Dissertations

Titania (Titanium dioxide, TiO2) has been researched as a promising biomaterial due to its excellent biocompatibility. However, the main limitation of titania is its poor mechanical properties which limit its use in many load-bearing applications. In this thesis report, the properties of titania were improved by doping with small quantities of MgO, ZnO and SiO2 as sintering additives. Nanocrystalline powder was selected, as it possesses outstanding properties over conventional coarse-grained powders due to reduced grain size. Nanocrystalline anatase powder of size 5-15 nm was synthesized via a simple sol-gel technique. Small quantities of dopants were introduced into pure titania powder, …

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Safety Improvements On Multilane Arterials A Before And After Evaluation Using The Empirical Bayes Method, Prem Chand Devarasetty Jan 2009

Safety Improvements On Multilane Arterials A Before And After Evaluation Using The Empirical Bayes Method, Prem Chand Devarasetty

Electronic Theses and Dissertations

This study examines the safety effects of the improvements made on multi-lane arterials. The improvements were divided into two categories 1) corridor level improvements, and 2) intersection improvements. Empirical Bayes method, which is one of the most accepted approaches for conducting before-after evaluations, has been used to assess the safety effects of the improvement projects. Safety effects are estimated not only in terms of all crashes but also rear-end (most common type) as well as severe crashes (crashes involving incapacitating and/or fatal injuries) and also angle crashes for intersection improvements. The Safety Performance Functions (SPFs) used in this study are …

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Occupational Lower Extremity Risk Assessment Modeling, Christopher Reid Jan 2009

Occupational Lower Extremity Risk Assessment Modeling, Christopher Reid

Electronic Theses and Dissertations

Introduction: Lower extremity (LE) work-related musculoskeletal disorders (WMSDs) are known to occur with cumulative exposure to occupational and personal risks. The objective of this dissertation study was to find if creating a quantifiable risk detection model for the LE was feasible. The primary product of the literature review conducted for this study resulted in focusing the attention of the model development process onto creating the initial model of the LE for assessing knee disorder risk factors. Literature Review: LE occupational disorders affect numerous industries and thousands of people each year by affecting any one of the musculoskeletal systems deemed susceptible …

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The Effect Of Heat Transfer Coefficient On High Aspect Ratio Channel Accompanied By Varying Rib Aspect Ratio, An Le Jan 2009

The Effect Of Heat Transfer Coefficient On High Aspect Ratio Channel Accompanied By Varying Rib Aspect Ratio, An Le

Electronic Theses and Dissertations

Heat transfer and pressure data were performed and reported on two different rigs. The first rig has an aspect ratio of (19:1) with two different inlet conditions and the second rig is composed of two different aspect ratio channels, (1:8) and (1:4). Rib turbulators were used as a flow disruptor scheme to enhance the heat transfer and friction factor. Rib aspect ratios ranging from (1:1) to (1:5) rib-height-to-width ratio were used. The first channel rib-width-to-pitch (Wr/P) ratio was kept at 1/2 where flow was kept at relatively low Reynolds numbers, between 3000 and 13000. Results from the current tests showed …

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Characterizing Spontaneous Fires In Landfills, Shadi Moqbel Jan 2009

Characterizing Spontaneous Fires In Landfills, Shadi Moqbel

Electronic Theses and Dissertations

Landfill fires are relatively common incidents that landfill operators encounter which have great impact on landfill structure and the environment. According to a U.S. Fire Administration report in 2001, an average of 8,300 landfill fires occurs each year in the United States, most of them in the spring and summer months. Subsurface spontaneous fires are considered the most dangerous and difficult to detect and extinguish among landfill fires. Few studies have been conducted on spontaneous fires in landfills. Information regarding the thermal behavior of solid waste is not available nor have measurements been made to evaluate spontaneous ignition of solid …

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Safety And Operational Evaluation Of Dynamic Lane Merging In Work Zones, Rami Harb Jan 2009

Safety And Operational Evaluation Of Dynamic Lane Merging In Work Zones, Rami Harb

Electronic Theses and Dissertations

Traffic safety and mobility of roadway work zones have been considered to be one of the major concerns in highway traffic safety and operations in Florida. In intent to expose Florida's work zones crash characteristics, the Florida Traffic Crash Records Database for years 2002, 2003 and 2004 were explored. Statistical models were estimated and Florida's work zone crash traits for single vehicle crashes and two-vehicle crashes were drawn. For the single-vehicle crashes, trucks were found more likely to be involved in single vehicle crashes in freeway work zones compared to freeways without work zones. Straight level roadways are significantly affected …

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Spatio-Temporal Analyses For Prediction Of Traffic Flow, Speed And Occupancy On I-4, Srinivasa Ravi Chandra Chilakamarri Venkata Jan 2009

Spatio-Temporal Analyses For Prediction Of Traffic Flow, Speed And Occupancy On I-4, Srinivasa Ravi Chandra Chilakamarri Venkata

Electronic Theses and Dissertations

Traffic data prediction is a critical aspect of Advanced Traffic Management System (ATMS). The utility of the traffic data is in providing information on the evolution of traffic process that can be passed on to the various users (commuters, Regional Traffic Management Centers (RTMCs), Department of Transportation (DoT), ... etc) for user-specific objectives. This information can be extracted from the data collected by various traffic sensors. Loop detectors collect traffic data in the form of flow, occupancy, and speed throughout the nation. Freeway traffic data from I-4 loop detectors has been collected and stored in a data warehouse called the …

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Providing A Better Understanding For The Motorist Behavior Towards Signal Change, Noor Elmitiny Jan 2009

Providing A Better Understanding For The Motorist Behavior Towards Signal Change, Noor Elmitiny

Electronic Theses and Dissertations

This research explores the red light running phenomena and offer a better understanding of the factors associated with it. The red light running is a type of traffic violation that can lead to angle crash and the most common counter measure is installing a red light running cameras. Red light running cameras some time can reduce the rates of red light running but because of the increased worry of the public towards crossing the intersection it can cause an increase in rear end crashes. Also the public opinion of the red light running cameras is that they are a revenue …

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An Integrated Hydrology/Hydraulic And Water Quality Model For Watershed-Scale Simulations, Cheng Wang Jan 2009

An Integrated Hydrology/Hydraulic And Water Quality Model For Watershed-Scale Simulations, Cheng Wang

Electronic Theses and Dissertations

This dissertation presents the design of an integrated watershed model, WASH123D version 3.0, a first principle, physics-based watershed-scale model of integrated hydrology/hydraulics and water quality transport. This numerical model is comprised of three modules: (1) a one-dimensional (1-D) simulation module that is capable of simulating separated and coupled fluid flow, sediment transport and reaction-based water quality transport in river/stream/canal networks and through control structures; (2) a two-dimensional (2-D) simulation module, capable of simulating separated and coupled fluid flow, sediment transport, and reactive biogeochemical transport and transformation in two-dimensional overland flow systems; and (3) a three-dimensional (3-D) simulation module, capable of …

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Structural Health Monitoring With Emphasis On Computer Vision, Damage Indices, And Statistical Analysis, Ricardo Zaurin Jan 2009

Structural Health Monitoring With Emphasis On Computer Vision, Damage Indices, And Statistical Analysis, Ricardo Zaurin

Electronic Theses and Dissertations

Structural Health Monitoring (SHM) is the sensing and analysis of a structure to detect abnormal behavior, damage and deterioration during regular operations as well as under extreme loadings. SHM is designed to provide objective information for decision-making on safety and serviceability. This research focuses on the SHM of bridges by developing and integrating novel methods and techniques using sensor networks, computer vision, modeling for damage indices and statistical approaches. Effective use of traffic video synchronized with sensor measurements for decision-making is demonstrated. First, some of the computer vision methods and how they can be used for bridge monitoring are presented …

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Classical Size Effect In Copper Thin Films: Impact Of Surface And Grain Boundary Scattering On Resistivity, Tik Sun Jan 2009

Classical Size Effect In Copper Thin Films: Impact Of Surface And Grain Boundary Scattering On Resistivity, Tik Sun

Electronic Theses and Dissertations

Surface and grain boundary electron scattering contribute significantly to resistivity as the dimensions of polycrystalline metallic conductors are reduced to, and below, the electron mean free path. A quantitative measurement of the relative contributions of surface and grain boundary scattering to resistivity is very challenging, requiring not only the preparation of suitably small conductors having independent variation of the two relevant length scales, namely, the sample critical dimension and the grain size, but also independent experimental quantification of these two length scales. In most work to date the sample grain size has been either assumed equal to conductor dimension or …

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Comprehensive Analytical Investigation Of The Safety Of Unsignalized Intersections, Kirolos Haleem Jan 2009

Comprehensive Analytical Investigation Of The Safety Of Unsignalized Intersections, Kirolos Haleem

Electronic Theses and Dissertations

According to documented statistics, intersections are among the most hazardous locations on roadway systems. Many studies have extensively analyzed safety of signalized intersections, but did not put their major focus on the most frequent type of intersections, unsignalized intersections. Unsignalized intersections are those intersections with stop control, yield control and no traffic control. Unsignalized intersections can be differentiated from their signalized counterparts in that their operational functions take place without the presence of a traffic signal. In this dissertation, multiple approaches of analyzing safety at unsignalized intersections were conducted. This was investigated in this study by analyzing total crashes, the …

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A Study Of Central Florida Nonroad Voc And Nos Emissions And Potential Actions To Reduce Emissions, Michael Radford Jan 2009

A Study Of Central Florida Nonroad Voc And Nos Emissions And Potential Actions To Reduce Emissions, Michael Radford

Electronic Theses and Dissertations

Ground-level ozone is harmful to the human respiratory system, as well as the environment. The national EPA 8-hour ozone standard for ground-level ozone was reduced from 85 parts per billion (ppb) to 75 ppb in 2008, and trends from previous years show that some of the counties in Central Florida could be in danger of violation. Violation means "non attainment" status; in which the county is ordered by EPA to develop specific implementation plans to reduce its emissions. The objective of this study was to compile an emissions inventory of volatile organic compounds (VOCs) and nitrogen oxides (NOx) from nonroad …

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Design, Analysis, And Optimization Of Diffractive Optical Elements Under High Numerical Aperture Focusing, Toufic Jabbour Jan 2009

Design, Analysis, And Optimization Of Diffractive Optical Elements Under High Numerical Aperture Focusing, Toufic Jabbour

Electronic Theses and Dissertations

The demand for high optical resolution has brought researchers to explore the use of beam shaping diffractive optical elements (DOEs) for improving performance of high numerical aperture (NA) optical systems. DOEs can be designed to modulate the amplitude, phase and/or polarization of a laser beam such that it focuses into a targeted irradiance distribution, or point spread function (PSF). The focused PSF can be reshaped in both the transverse focal plane and along the optical axis. Optical lithography, microscopy and direct laser writing are but a few of the many applications in which a properly designed DOE can significantly improve …

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Macroscopic Traffic Safety Analysis Based On Trip Generation Characteristics, Chowdhury Siddiqui Jan 2009

Macroscopic Traffic Safety Analysis Based On Trip Generation Characteristics, Chowdhury Siddiqui

Electronic Theses and Dissertations

Recent research has shown that incorporating roadway safety in transportation planning has been considered one of the active approaches to improve safety. Aggregate level analysis for predicting crash frequencies had been contemplated to be an important step in this process. As seen from the previous studies various categories of predictors at macro level (census blocks, traffic analysis zones, census tracts, wards, counties and states) have been exhausted to find appropriate correlation with crashes. This study contributes to this ongoing macro level road safety research by investigating various trip productions and attractions along with roadway characteristics within traffic analysis zones (TAZs) …

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Vectorpad: A Tool For Visualizing Vector Operations, Jared Bott Jan 2009

Vectorpad: A Tool For Visualizing Vector Operations, Jared Bott

Electronic Theses and Dissertations

Visualization of three-dimensional vector operations can be very helpful in understanding vector mathematics. However, creating these visualizations using traditional WIMP interfaces can be a troublesome exercise. In this thesis, we present VectorPad, a pen-based application for three-dimensional vector mathematics visualization. VectorPad allows users to define vectors and perform mathematical operations upon them through the recognition of handwritten mathematics. The VectorPad user interface consists of a sketching area, where the user can write vector definitions and other mathematics, and a 3D graph for visualization. After recognition, vectors are visualized dynamically on the graph, which can be manipulated by the user. A …

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Modeling Microbiological And Chemical Processes In Municipal Solid Waste Bioreactor: Development And Applications Of A Three-Pha, Nitin Gawande Jan 2009

Modeling Microbiological And Chemical Processes In Municipal Solid Waste Bioreactor: Development And Applications Of A Three-Pha, Nitin Gawande

Electronic Theses and Dissertations

The numerical computer models that simulate municipal solid waste (MSW) bioreactor landfills have mainly two components--a biodegradation process module and a multi-phase flow module. The biodegradation model describes the chemical and microbiological processes of solid waste biodegradation. The models available to date include predefined solid waste biodegradation reactions and participating species. In a bioreactor landfill several processes, such as anaerobic and aerobic biodegradation, nitrogen and sulfate cycling, precipitation and dissolution of metals, and adsorption and gasification of various anthropogenic organic compounds, occur simultaneously. These processes may involve reactions of several species and the available biochemical models for solid waste biodegradation …

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Vibrational And Mechanical Properties Of 10 Mol % Sc2o3-1 Mol % Ceo2- Zro2 Electrolyte Ceramics For Solid Oxide Fuel Cells, Svetlana Lukich Jan 2009

Vibrational And Mechanical Properties Of 10 Mol % Sc2o3-1 Mol % Ceo2- Zro2 Electrolyte Ceramics For Solid Oxide Fuel Cells, Svetlana Lukich

Electronic Theses and Dissertations

Solid Oxide Fuel Cells (SOFCs) are emerging as a potential breakthrough energy conversion technology for clean and efficient production of electricity and heat from hydrogen and hydrocarbon fuels. Sc0.1Ce0.01ZrO2 electrolytes for Solid Oxide Fuel Cells are very promising materials because their high ionic conductivity in the intermediate temperature range 700°C-800°C. The vibration response of cubic and rhombohedral (β) 10 mol%Sc2O3 - 1 mol%CeO2 - ZrO2(Sc0.1Ce0.01ZrO2 ) both at room and high-temperatures is reported. The in-situ heating experiments and ex-situ indentation experiments were performed to characterize the vibrational behavior of these important materials. A temperature and stress-assisted phase transition from cubic …

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Saw Reflective Transducers And Antennas For Orthogonal Frequency Coded Saw Sensors, Bianca Maria Santos Jan 2009

Saw Reflective Transducers And Antennas For Orthogonal Frequency Coded Saw Sensors, Bianca Maria Santos

Electronic Theses and Dissertations

Passive sensors that vary its impedance per measured parameter may be used with surface acoustic wave (SAW) reflective transducers (SRT) for wireless acquisition of the measurand. The device is composed of two transducers, where one, which may be attached to an antenna, is used to launch the wave within the device substrate, and the other is where the sensor load is attached to. The latter is able to reflect the incident wave. How much power is reflected is determined by the attached sensor load. Amplitude variations as well as peak frequency variations of the SRT reflectivity response are explored in …

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Emergency Evacuation Route Planning Considering Human Behavior During Short- And No-Notice Emergency Situations, Suebpong Kittirattanapaiboon Jan 2009

Emergency Evacuation Route Planning Considering Human Behavior During Short- And No-Notice Emergency Situations, Suebpong Kittirattanapaiboon

Electronic Theses and Dissertations

Throughout United States and world history, disasters have caused not only significant loss of life, property but also enormous financial loss. The tsunami that occurred on December 26, 2004 is a telling example of the devastation that can occur unexpectedly. This unexpected natural event never happened before in this area. In addition, there was a lack of an emergency response plan for events of that magnitude. Therefore, this event resulted not only in a natural catastrophe for the people of South and Southeast Asia, but it is also considered one of the greatest natural disasters in world history. After the …

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