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Articles 2161 - 2190 of 4566

Full-Text Articles in Engineering

Numerical Study On Reinforcement Mechanism Of Copper/Carbon Nanotubes Composite, Xiang Long Jan 2012

Numerical Study On Reinforcement Mechanism Of Copper/Carbon Nanotubes Composite, Xiang Long

Electronic Theses and Dissertations

Because of its high stiffness, carbon nanotubes (CNTs) are considered as one of the widely used reinforcement materials in the metal matrix composites. In this thesis, finite element (FE) models were built in Ls-Dyna3D to simulate Copper/CNTs composite deformation and fracture, and to explore CNTs reinforcement mechanisms. Several possible mechanisms were discussed. Deformation and failure of Cu/CNT composites were studied numerically using unit cell FE models, which consist of both metal matrix and CNTs. The simulation results have been verified by existing experiment data reported by Chen’s group. The matrix material was modeled as elasto-plastic ductile solids. The CNTs material …

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Characterization, Morphology, Oxidation, And Recession Of Silicon Nanowires Grown By Electroless Process, Robert G. Mertens Jan 2012

Characterization, Morphology, Oxidation, And Recession Of Silicon Nanowires Grown By Electroless Process, Robert G. Mertens

Electronic Theses and Dissertations

This dissertation presents heretofore undiscovered properties of Silicon Nanowires (SiNWs) grown by electroless process and presents mathematical solutions to the special problems of the oxidation and diffusion of dopants for SiNWs. Also presented here is a mathematical description of morphology of oxidized SiNWs. This dissertation is comprised of several discussions relating to SiNWs growth, oxidation, morphology and doping. In here is presented work derived from a long-term study of SiNWs. Several important aspects of SiNWs were investigated and the results published in journals and conference papers. The recession of SiNWs was heretofore unreported by other research groups. In our investigations, …

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Bootstrapping Cognitive Radio Networks, Brent Horine Jan 2012

Bootstrapping Cognitive Radio Networks, Brent Horine

Electronic Theses and Dissertations

Cognitive radio networks promise more efficient spectrum utilization by leveraging degrees of freedom and distributing data collection. The actual realization of these promises is challenged by distributed control, and incomplete, uncertain and possibly conflicting knowledge bases. We consider two problems in bootstrapping, evolving, and managing cognitive radio networks. The first is Link Rendezvous, or how separate radio nodes initially find each other in a spectrum band with many degrees of freedom, and little shared knowledge. The second is how radio nodes can negotiate for spectrum access with incomplete information. To address the first problem, we present our Frequency Parallel Blind …

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A New Quasi Resonant Dc-Link For Photovoltaic Micro-Inverters, Anna Grishina Jan 2012

A New Quasi Resonant Dc-Link For Photovoltaic Micro-Inverters, Anna Grishina

Electronic Theses and Dissertations

PV Inverters have the task of tracking the maximum power point (MPP), and regulating the solar energy generation to this optimal operation point. The second task is the conversion of direct current produced by the solar modules into alternating current compatible with the grid. A new inverter approach such as a single phase micro inverter is emerging aimed to overcome some of the challenges of centralized inverters. As a counterpart to the central inverter, a micro inverter is a small compact module attached directly to each solar panel. To provide for the constantly increasing demand for a small size, light …

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Turbidity Removal Efficiency And Toxicity Issues Associated With The Chitosan-Based Dual Bio-Polymer Systems, Rylee Hernandez Jan 2012

Turbidity Removal Efficiency And Toxicity Issues Associated With The Chitosan-Based Dual Bio-Polymer Systems, Rylee Hernandez

Electronic Theses and Dissertations

Stormwater runoff can be a great concern in the State of Florida due to the impact the quality of the runoff water can have on the natural water bodies. Stormwater runoff can carry pollutants and sediments which can cause both physical and biological risks in an aquatic ecosystem such as a lake, river, or pond. Polymers, namely the chitosan-based dual polymer system, can be used remove the sediment from this runoff to ensure the safety of the state’s water bodies. Three soils are used in this testing: AASTO soil classifications A-3(sandy soil) and A-2- 4 (silty-sand), and a soil with …

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Wireless Power Transfer For Space Applications: System Design And Electromagnetic Compatibility Compliance Of Radiated Emissions, Ramos Gabriel Vazquez Jan 2012

Wireless Power Transfer For Space Applications: System Design And Electromagnetic Compatibility Compliance Of Radiated Emissions, Ramos Gabriel Vazquez

Electronic Theses and Dissertations

This dissertation evaluates the possibility of wireless power transfer (WPT) systems for space applications, with an emphasis in launch vehicles (rockets). After performing literature review for WPT systems, it was identified that magnetic resonance provides the more suited set of characteristics for this application. Advanced analysis, simulation and testing were performed to magnetic resonance WPT systems to acquire system performance insight. This was accomplished by evaluating/varying coupling configuration, load effects and magnetic element physical characteristics (i.e. wire material, loop radius, etc.). It was identified by analysis, circuit simulation and testing that the best coupling configuration for this application was series-series …

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Implementation And Performance Comparisons For The Crisfield And Stiff Arc Length Methods In Fea, Thomas W. Silvers Jan 2012

Implementation And Performance Comparisons For The Crisfield And Stiff Arc Length Methods In Fea, Thomas W. Silvers

Electronic Theses and Dissertations

In Nonlinear Finite Element Analysis (FEA) applied to structures, displacements at which the tangent stiffness matrix KT becomes singular are called critical points, and correspond to instabilities such as buckling or elastoplastic softening (e.g., necking). Prior to the introduction of Arc Length Methods (ALMs), critical points posed severe computational challenges, which was unfortunate since behavior at instabilities is of great interest as a precursor to structural failure. The original ALM was shown to be capable in some circumstances of continued computation at critical points, but limited success and unattractive features of the formulation were noted and addressed in extensive subsequent …

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Co Florida 2012, A Moves-Based, Near-Road, Screening Model, Mark David Ritner Jan 2012

Co Florida 2012, A Moves-Based, Near-Road, Screening Model, Mark David Ritner

Electronic Theses and Dissertations

Citizens in the United States are fortunate to have an excellent system of roadways and the affluence with which to afford automobiles. The flexibility of travel on demand for most allows for a variety of lifestyles, assists with conducting business, and contributes to the feeling of freedom that most citizens enjoy. The current vehicle fleet, which is primarily powered by internal combustion engines burning fossil fuels, does however contribute to the deterioration of air quality. This effect is particularly significant in metropolitan areas. Motor vehicle exhausts contain several combustion bi-products that pose harmful effects to the environment and human health, …

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Incorporating Remotely Sensed Data Into Coastal Hydrodynamic Models: Parameterization Of Surface Roughness And Spatio-Temporal Validation Of Inundation Area, Stephen Conroy Medeiros Jan 2012

Incorporating Remotely Sensed Data Into Coastal Hydrodynamic Models: Parameterization Of Surface Roughness And Spatio-Temporal Validation Of Inundation Area, Stephen Conroy Medeiros

Electronic Theses and Dissertations

This dissertation investigates the use of remotely sensed data in coastal tide and inundation models, specifically how these data could be more effectively integrated into model construction and performance assessment techniques. It includes a review of numerical wetting and drying algorithms, a method for constructing a seamless digital terrain model including the handling of tidal datums, an investigation into the accuracy of land use / land cover (LULC) based surface roughness parameterization schemes, an application of a cutting edge remotely sensed inundation detection method to assess the performance of a tidal model, and a preliminary investigation into using 3-dimensional airborne …

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A Framework For Process Data Collection, Analysis, And Visualization In Construction Projects, Reza Akhavian Jan 2012

A Framework For Process Data Collection, Analysis, And Visualization In Construction Projects, Reza Akhavian

Electronic Theses and Dissertations

Automated data collection, simulation and visualization can substantially enhance the process of designing, analysis, planning, and control of many engineering processes. In particular, managing processes that are dynamic in nature can significantly benefit from such techniques. Construction projects are good examples of such processes where a variety of equipment and resources constantly interact inside an evolving environment. Management of such settings requires a platform capable of providing decision-makers with updated information about the status of project entities and assisting site personnel making critical decisions under uncertainty. To this end, the current practice of using historical data or expert judgments as …

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Deformation And Phase Transformation Processes In Polycrystalline Niti And Nitihf High Temperature Shape Memory Alloys, Othmane Benafan Jan 2012

Deformation And Phase Transformation Processes In Polycrystalline Niti And Nitihf High Temperature Shape Memory Alloys, Othmane Benafan

Electronic Theses and Dissertations

The unique ability of shape memory alloys (SMAs) to remember and recover their original shape after large deformation offers vast potential for their integration in advanced engineering applications. SMAs can generate recoverable shape changes of several percent strain even when opposed by large stresses owing to reversible deformation mechanisms such as twinning and stress-induced martensite. For the most part, these alloys have been largely used in the biomedical industry but with limited application in other fields. This limitation arises from the complexities of prevailing microstructural mechanisms that lead to dimensional instabilities during repeated thermomechanical cycling. Most of these mechanisms are …

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Thermally Annealled Plasmonic Nanostructures, Chaoming Wang Jan 2012

Thermally Annealled Plasmonic Nanostructures, Chaoming Wang

Electronic Theses and Dissertations

Localized surface plasmon resonance (LSPR) is induced in metal nanoparticles by resonance between incident photons and conduction electrons in nanoparticles. For noble metal nanoparticles, LSPR can lead to strong absorbance of ultraviolet-violet light. Although it is well known that LSPR depends on the size and shape of nanoparticles, the inter-particle spacing, the dielectric properties of metal and the surrounding medium, the temperature dependence of LSPR is not well understood. By thermally annealing gold nanoparticle arrays formed by nanosphere lithography, a shift of LSPR peak upon heating has been shown. The thermal characteristics of the plasmonic nanoparticles have been further used …

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An Index To Measure Efficiency Of Hospital Networks For Mass Casualty Disasters, Maria Bull Torres Jan 2012

An Index To Measure Efficiency Of Hospital Networks For Mass Casualty Disasters, Maria Bull Torres

Electronic Theses and Dissertations

Disaster events have emphasized the importance of healthcare response activities due to the large number of victims. For instance, Hurricane Katrina in New Orleans, in 2005, and the terrorist attacks in New York City and Washington, D.C., on September 11, 2001, left thousands of wounded people. In those disasters, although hospitals had disaster plans established for more than a decade, their plans were not efficient enough to handle the chaos produced by the hurricane and terrorist attacks. Thus, the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) suggested collaborative planning among hospitals that provide services to a contiguous geographic area …

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Real-Time Open Source Traffic Control Software For The Advance Traffic Controller, Justin Key Jan 2012

Real-Time Open Source Traffic Control Software For The Advance Traffic Controller, Justin Key

Electronic Theses and Dissertations

Under the initiative of Department of Transportation (DOT) a safety-critical, dual redundant, open source traffic signal control application is currently being developed. The system named SCOPE, for Signal Control Program Environment, currently implements standard 8-phase NEMA logic and the National Cooperative Highway Research Program 3-66 preemption logic. SCOPE is designed to be part of the Advanced Traffic Controller (ATC), making use of API standard 2.06b to integrate with the hardware. Safety-critical status is achieved through redundancy of application logic that constantly compares expected signal phase information. From baseline requirements, engineers independently program application code, one using Ada95 and the other …

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Structural Identification Through Monitoring, Modeling And Predictive Analysis Under Uncertainty, Hasan Burak Gökçe Jan 2012

Structural Identification Through Monitoring, Modeling And Predictive Analysis Under Uncertainty, Hasan Burak Gökçe

Electronic Theses and Dissertations

Bridges are critical components of highway networks, which provide mobility and economical vitality to a nation. Ensuring the safety and regular operation as well as accurate structural assessment of bridges is essential. Structural Identification (St-Id) can be utilized for better assessment of structures by integrating experimental and analytical technologies in support of decision-making. St-Id is defined as creating parametric or nonparametric models to characterize structural behavior based on structural health monitoring (SHM) data. In a recent study by the ASCE St-Id Committee, St-Id framework is given in six steps, including modeling, experimentation and ultimately decision making for estimating the performance …

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Forecasting Volcanic Activity Using An Event Tree Analysis System And Logistic Regression, William N. Junek Jan 2012

Forecasting Volcanic Activity Using An Event Tree Analysis System And Logistic Regression, William N. Junek

Electronic Theses and Dissertations

Forecasts of short term volcanic activity are generated using an event tree process that is driven by a set of empirical statistical models derived through logistic regression. Each of the logistic models are constructed from a sparse and geographically diverse dataset that was assembled from a collection of historic volcanic unrest episodes. The dataset consists of monitoring measurements (e.g. seismic), source modeling results, and historic eruption information. Incorporating this data into a single set of models provides a simple mechanism for simultaneously accounting for the geophysical changes occurring within the volcano and the historic behavior of analog volcanoes. A bootstrapping …

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A Bench Top Study Of The Optimization Of Lvad Cannula Implantation To Reduce Risk Of Cerebral Embolism, William D. Clark Jan 2012

A Bench Top Study Of The Optimization Of Lvad Cannula Implantation To Reduce Risk Of Cerebral Embolism, William D. Clark

Electronic Theses and Dissertations

Physical bench top experiments are performed to validate and complement ongoing computational fluid dynamics (CFD) analyses of ventricular assist device (VAD) circulation. VADs are used in patients whose hearts do not function to their maximum potential due advanced stages of heart disease and, consequently, are unable to adequately supply blood to the systemic circulation. VADs are commonly utilized as a bridge-to-transplantation, meaning that they are implanted in patients while waiting for a heart transplant. In such cases of long term utilization of VADs, it has been reported in the literatures that thrombo-embolic cerebral events occur in 14-47% of patients over …

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A Study Of Localization And Latency Reduction For Action Recognition, Syed Zain Masood Jan 2012

A Study Of Localization And Latency Reduction For Action Recognition, Syed Zain Masood

Electronic Theses and Dissertations

The success of recognizing periodic actions in single-person-simple-background datasets, such as Weizmann and KTH, has created a need for more complex datasets to push the performance of action recognition systems. In this work, we create a new synthetic action dataset and use it to highlight weaknesses in current recognition systems. Experiments show that introducing background complexity to action video sequences causes a significant degradation in recognition performance. Moreover, this degradation cannot be fixed by fine-tuning system parameters or by selecting better feature points. Instead, we show that the problem lies in the spatio-temporal cuboid volume extracted from the interest point …

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Engineering Evaluation Of Multi-Beam Satellite Antenna Boresight Pointing Using Land/Water Crossings, Catherine Susan May Jan 2012

Engineering Evaluation Of Multi-Beam Satellite Antenna Boresight Pointing Using Land/Water Crossings, Catherine Susan May

Electronic Theses and Dissertations

The Microwave Radiometer (MWR) on the Aquarius/SAC-D mission measures microwave radiation from earth and intervening atmosphere in terms of brightness temperature (Tb). It takes measurements in a push-broom fashion at K (23.8GHz) and Ka (36.5 GHz) band frequencies using two separate antenna systems, each producing eight antenna beams. Pre-launch knowledge of the alignment of these beams with respect to the space-craft is used to geolocate the antenna footprints on ground. As a part of MWR’s on-orbit engineering check-out, the verification of MWR’s pointing accuracy is discussed here. The technique used to assess MWR’s pointing involved comparing the radiometer image of …

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Variance In Fade-Time Of A Gamma-Gamma Distributed Irradiance Signal, Troy T. Leclerc Jan 2012

Variance In Fade-Time Of A Gamma-Gamma Distributed Irradiance Signal, Troy T. Leclerc

Electronic Theses and Dissertations

Free-space optical communications are predominantly hindered by optical turbulence, an effect caused by temperature and pressure variations within the atmosphere. The result is an optical wave interfering with itself due to multipath propagation via tiny refractive-index fluctuations across the wave-front. Optical communication systems are affected when the channel conditions induce fading in the irradiance signal that is received at the detector. The nature of optical interference imparted by the atmosphere is a random process and therefore the received irradiance signal is often characterized by an appropriate probability density function (PDF). Data collected during past free-space optical experiments in the atmosphere …

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Financial Evaluation Of Milege Based User Fees For Florida's Transportation Funding, Massoud Moradi Jan 2012

Financial Evaluation Of Milege Based User Fees For Florida's Transportation Funding, Massoud Moradi

Electronic Theses and Dissertations

Motor fuel taxes have been collected as a principal source of highway funding for close to a century. They account for approximately two thirds of all the highway user fees and about half of all highway expenditures. Federal fuel taxes have not kept pace with the inflation in general and increasing traffic demand and resulting construction, maintenance and operation costs of the transportation assets in particular. Lack of political will, combined with rising anti-tax sentiment among the populace, has kept the federal tax level not only well below its initial intents, but also at a unsustainable level in future. Mileage …

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Synchronous Communication System For Saw Sensors Interrogation, Maxim Troshin Jan 2012

Synchronous Communication System For Saw Sensors Interrogation, Maxim Troshin

Electronic Theses and Dissertations

During past two decades a variety of SAW based wireless sensors were invented and research is still in progress. As different frequencies, varied bandwidths, coding techniques and constantly changing post processing algorithms are being implemented, there is a constant need for a universal and adjustable synchronous communication system able to interrogate new generations of SAW sensors. This thesis presents the design of a multiple FPGA based communication system with an operational frequency range of 450MHz-2.2GHz capable of producing user programmed modulated signal. The synchronous receiver is designed to have interchangeable chip, replacement of which would allow adjustment of the receiver’s …

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Towards Real-Time Mixed Reality Matting In Natural Scenes, Nicholas Beato Jan 2012

Towards Real-Time Mixed Reality Matting In Natural Scenes, Nicholas Beato

Electronic Theses and Dissertations

In Mixed Reality scenarios, background replacement is a common way to immerse a user in a synthetic environment. Properly identifying the background pixels in an image or video is a dif- ficult problem known as matting. Proper alpha mattes usually come from human guidance, special hardware setups, or color dependent algorithms. This is a consequence of the under-constrained nature of the per pixel alpha blending equation. In constant color matting, research identifies and replaces a background that is a single color, known as the chroma key color. Unfortunately, the algorithms force a controlled physical environment and favor constant, uniform lighting. …

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Multiscale Simulation Of Laser Ablation And Processing Of Semiconductor Materials, Lalit Shokeen Jan 2012

Multiscale Simulation Of Laser Ablation And Processing Of Semiconductor Materials, Lalit Shokeen

Electronic Theses and Dissertations

We present a model of laser-solid interactions in silicon based on an empirical potential developed under conditions of strong electronic excitations. The parameters of the interatomic potential depends on the temperature of the electronic subsystem Te, which is directly related to the density of the electron-hole pairs and hence the number of broken bonds. We analyze the dynamics of this potential as a function of electronic temperature Te and lattice temperature Tion. The potential predicts phonon spectra in good agreement with finite-temperature densityfunctional theory, including the lattice instability induced by the high electronic excitations. For 25fs pulse, a wide range …

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Numerical Simulation Of Conventional Fuels And Biofuels Dispersion And Vaporization Process In Co-Flow And Cross-Flow Premixers, Xin Gu Jan 2012

Numerical Simulation Of Conventional Fuels And Biofuels Dispersion And Vaporization Process In Co-Flow And Cross-Flow Premixers, Xin Gu

Electronic Theses and Dissertations

In order to follow increasingly strict regulation of pollutant emissions, a new concept of Lean Premixed pre-vaporized (LPP) combustion has been proposed for turbines. In LPP combustion, controlled atomization, dispersion and vaporization of different types of liquid fuel in the premixer are the key factors required to stabilize the combustion process and improve the efficiency. A numerical study is conducted for the fundamental understanding of the liquid fuel dispersion and vaporization process in pre-mixers using both cross-flow and co-flow injection methods. First, the vaporization model is validated by comparing the numerical data to existing experiments of single droplet vaporization under …

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Optical Fluid-Based Photonic And Display Devices, Su Xu Jan 2012

Optical Fluid-Based Photonic And Display Devices, Su Xu

Electronic Theses and Dissertations

Conventional solid-state photonic devices exhibit an ultra-high optical performance and durability, but minimal adaptability. Recently, optical fluid-based photonic and display devices are emerging. By dynamically manipulating the optical interface formed by liquids, the optical output can be reconfigured or adaptively tuned in real time. Such devices exhibit some unique characteristics that are not achievable in conventional solid-state photonic devices. Therefore, they open a gateway for new applications, such as image and signal processing, optical communication, sensing, and lab-on-a-chip, etc. Different operation principles of optical fluidbased photonic devices have been proposed, for instance fluidic pressure, electrochemistry, thermal effect, environmentally adaptive hydrogel, …

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Non-Reciprocal Wave Transmission In Integrated Waveguide Array Isolators, Tony Yatming Ho Jan 2012

Non-Reciprocal Wave Transmission In Integrated Waveguide Array Isolators, Tony Yatming Ho

Electronic Theses and Dissertations

Non-reciprocal wave transmission is a phenomenon witnessed in certain photonic devices when the wave propagation dynamics through the device along one direction differs greatly from the dynamics along the counter-propagating direction. Specifically, it refers to significant power transfer occurring in one direction, and greatly reduced power transfer in the opposite direction. The resulting effect is to isolate the directionality of wave propagation, allowing transmission to occur along one direction only. Given the popularity of photonic integrated circuits (PIC), in which all the optical components are fabricated on the same chip so that the entire optical system can be made more …

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Infrared Tapered Slot Antennas Coupled To Tunnel Diodes, Louis A. Florence Jan 2012

Infrared Tapered Slot Antennas Coupled To Tunnel Diodes, Louis A. Florence

Electronic Theses and Dissertations

Tapered slot antennas (TSAs) have seen considerable application in the millimeter-wave portion of the spectrum. Desirable characteristics of TSAs include symmetric E- and H-plane antenna patterns, and broad non-resonant bandwidths. We investigate extension of TSA operation toward higher frequencies in the thermal infrared (IR), using a metal-oxide-metal diode as the detector. Several different infrared TSA design forms are fabricated using electronbeam lithography and specially developed thin-film processes. The angular antenna patterns of TSA-coupled diodes are measured at 10.6 micrometer wavelength in both E- and H-planes, and are compared to results of finite-element electromagnetic modeling using Ansoft HFSS. Parameter studies are …

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High-Efficiency Blue Phase Liquid Crystal Displays, Yan Li Jan 2012

High-Efficiency Blue Phase Liquid Crystal Displays, Yan Li

Electronic Theses and Dissertations

Blue phase liquid crystals (BPLCs) have a delicate lattice structure existing between chiral nematic and isotropic phases, with a stable temperature range of about 2 K. But due to short coherent length, these self-assembled nano-structured BPLCs have a fast response time. In the past three decades, the application of BPLC has been rather limited because of its narrow temperature range. In 2002, Kikuchi et al. developed a polymer stabilization method to extend the blue-phase temperature range to more than 60 K. This opens a new gateway for display and photonic applications. In this dissertation, I investigate the material properties of …

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Laser Filamentation Interaction With Materials For Spectroscopic Applications, Matthew Weidman Jan 2012

Laser Filamentation Interaction With Materials For Spectroscopic Applications, Matthew Weidman

Electronic Theses and Dissertations

Laser filamentation is a non-diffracting propagation regime consisting of an intense core that is surrounded by an energy reservoir. For laser ablation based spectroscopy techniques such as Laser Induced Breakdown Spectroscopy (LIBS), laser filamentation enables the remote delivery of high power density laser radiation at long distances. This work shows a quasiconstant filament-induced mass ablation along a 35 m propagation distance. The mass ablated is sufficient for the application of laser filamentation as a sampling tool for plasma based spectroscopy techniques. Within the scope of this study, single-shot ablation was compared with multi-shot ablation. The dependence of ablated mass on …

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