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Articles 1711 - 1740 of 4566

Full-Text Articles in Engineering

Integrated Remote Sensing And Forecasting Of Regional Terrestrial Precipitation With Global Nonlinear And Nonstationary Teleconnection Signals Using Wavelet Analysis, Lee Mullon Jan 2014

Integrated Remote Sensing And Forecasting Of Regional Terrestrial Precipitation With Global Nonlinear And Nonstationary Teleconnection Signals Using Wavelet Analysis, Lee Mullon

Electronic Theses and Dissertations

Global sea surface temperature (SST) anomalies have a demonstrable effect on terrestrial climate dynamics throughout the continental U.S. SST variations have been correlated with greenness (vegetation densities) and precipitation via ocean-atmospheric interactions known as climate teleconnections. Prior research has demonstrated that teleconnections can be used for climate prediction across a wide region at sub-continental scales. Yet these studies tend to have large uncertainties in estimates by utilizing simple linear analyses to examine chaotic teleconnection relationships. Still, non-stationary signals exist, making teleconnection identification difficult at the local scale. Part 1 of this research establishes short-term (10-year), linear and non-stationary teleconnection signals …

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Sps: An Sms-Based Push Service For Energy Saving In Smartphone's Idle State, Erich Dondyk Jan 2014

Sps: An Sms-Based Push Service For Energy Saving In Smartphone's Idle State, Erich Dondyk

Electronic Theses and Dissertations

Despite of all the advances in smartphone technology in recent years, smartphones still remain limited by their battery life. Unlike other power hungry components in the smartphone, the cellular data and Wi-Fi interfaces often continue to be used even while the phone is in the idle state to accommodate unnecessary data traffic produced by some applications. In addition, bad reception has been proven to greatly increase energy consumed by the radio, which happens quite often when smartphone users are inside buildings. In this paper, we present a Short message service Push based Service (SPS) to save unnecessary power consumption when …

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A Framework For Assessing The Quality And Effectiveness Of A National Employment System: A Case Study Of Saudi Arabia, Hemaid Alsulami Jan 2014

A Framework For Assessing The Quality And Effectiveness Of A National Employment System: A Case Study Of Saudi Arabia, Hemaid Alsulami

Electronic Theses and Dissertations

National employment systems have been established in several countries to tackle the unemployment dilemma between citizens while the labor market flooded by expatriates. Lack of performance measurement indices among these systems caused failure to provide jobs to citizens and caused a state of confusion and dissatisfaction among employing entities. In Saudi Arabia, unemployment rate has increased in the last few decades and have since become a very political issue for the Saudi government. Compared to other countries, the problem is different since many expatriates in Saudi Arabia are already employed in their markets while citizens are seeking jobs. In Saudi …

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Investigation Of Dual-Stage High Efficiency And Density Micro Inverter For Solar Application, Lin Chen Jan 2014

Investigation Of Dual-Stage High Efficiency And Density Micro Inverter For Solar Application, Lin Chen

Electronic Theses and Dissertations

Module integrated converters (MIC), also called micro inverter, in single phase have witnessed recent market success due to unique features (1) improved energy harvest, (2) improved system efficiency, (3) lower installation costs, (4) plug-N-play operation, (5) and enhanced flexibility and modularity. The MIC sector has grown from a niche market to mainstream, especially in the United States. Due to the fact that two-stage architecture is commonly used for single phase MIC application. A DC-DC stage with maximum power point tracking to boost the output voltage of the Photovoltaic (PV) panel is employed in the first stage, DC-AC stage is used …

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Optimization Of Block Layout And Evaluation Of Collection Mat Materials For Polyacrylamide Treatment Channels, Alicia Mcdougal Jan 2014

Optimization Of Block Layout And Evaluation Of Collection Mat Materials For Polyacrylamide Treatment Channels, Alicia Mcdougal

Electronic Theses and Dissertations

Construction sites are frequently cited as major sources of pollution that degrade the quality of surface water. The highly erodible topsoil is transported off site by stormwater runoff causing negative effects downstream. Research has shown that the small particles, which are the most susceptible to erosive forces, have more pollutants associated with them than larger soil particles. Currently, in the state of Florida, it is not permissible to discharge water to a receiving water body if the turbidity is more than 29 Nephelometric Turbidity Units (NTUs) above background or higher than background for an outstanding Florida water body. The removal …

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Mechanical And Thermal Characterization Of Continuous Fiber-Reinforced Pyrolysis-Derived Carbon-Matrix Composites, Donovan Lui Jan 2014

Mechanical And Thermal Characterization Of Continuous Fiber-Reinforced Pyrolysis-Derived Carbon-Matrix Composites, Donovan Lui

Electronic Theses and Dissertations

Maturity of high-temperature polymer-reinforced composites defer to conventionally expensive and intensive methods in both material and manufacturing aspects. Even traditional carbon-carbon, aerogel, and ceramic approaches are highly limited by difficult manufacturing techniques and are subject to sensitive handling throughout their processing and lifetime. Despite their utility in extreme environments, the high costs of existing high-temperature composites find limited practical applicability under high-performance applications. The development of continuous fiber-reinforced pyrolysis-derived carbon-matrix composites aim to circumvent the issues surrounding the manufacturing and handling of conventional high-temperature composites. Polymer matrix composites (PMCs) have a number of attractive properties including light weight, high stiffness-to-weight …

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Injection-Locked Vertical Cavity Surface Emitting Lasers (Vcsels) For Optical Arbitrary Waveform Generation, Sharad Bhooplapur Jan 2014

Injection-Locked Vertical Cavity Surface Emitting Lasers (Vcsels) For Optical Arbitrary Waveform Generation, Sharad Bhooplapur

Electronic Theses and Dissertations

Complex optical pulse shapes are typically generated from ultrashort laser pulses by manipulating the optical spectrum of the input pulses. This generates complex but periodic time-domain waveforms. Optical Arbitrary Waveform Generation (OAWG) builds on the techniques of ultrashort pulse-shaping, with the goal of making non-periodic, truly arbitrary optical waveforms. Some applications of OAWG are coherently controlling chemical reactions on a femtosecond time scale, improving the performance of LADAR systems, high-capacity optical telecommunications and ultra wideband signals processing. In this work, an array of Vertical Cavity Surface Emitting Lasers (VCSELs) are used as modulators, by injection-locking each VCSEL to an individual …

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An Uncooled Mid-Wave Infrared Detector Based On Optical Response Of Laser-Doped Silicon Carbide., Geunsik Lim Jan 2014

An Uncooled Mid-Wave Infrared Detector Based On Optical Response Of Laser-Doped Silicon Carbide., Geunsik Lim

Electronic Theses and Dissertations

This dissertation focuses on an uncooled Mid-Wave Infra-Red (MWIR) detector was developed by doping an n-type 4H-SiC with Ga using the laser doping technique. 4H-SiC is one of the polytypes of crystalline silicon carbide, a wide bandgap semiconductor. The dopant creates an energy level of 0.30 eV, which was confirmed by optical spectroscopy of the doped sample. This energy level corresponds to the MWIR wavelength of 4.21 µm. The detection mechanism is based on the photoexcitation of electrons by the photons of this wavelength absorbed in the semiconductor. This process modifies the electron density, which changes the refraction index and, …

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Study Of The Formation And Control Of Disinfection By-Products Originating From A Surface Water Supply On The Volcanic Island Of Guam, Erica Laberge Jan 2014

Study Of The Formation And Control Of Disinfection By-Products Originating From A Surface Water Supply On The Volcanic Island Of Guam, Erica Laberge

Electronic Theses and Dissertations

Three oxidants have been evaluated for use as alternative chemical pretreatments for Fena Lake, a surface water that supplies the U.S. Navy's Public Water System (PWS) on the volcanic island of Guam. The study consisted of two investigative components. The first and primary component included a bench-scale evaluation to study the effects of different pre-oxidant chemicals on the formation of chlorinated disinfection by-products (DBPs). The second and ancillary component included a series of water treatment and distribution system management studies that analyzed DBP formation within the treatment plant and water distribution system. The goal of this research was to reduce …

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Pen-Based Methods For Recognition And Animation Of Handwritten Physics Solutions, Salman Cheema Jan 2014

Pen-Based Methods For Recognition And Animation Of Handwritten Physics Solutions, Salman Cheema

Electronic Theses and Dissertations

There has been considerable interest in constructing pen-based intelligent tutoring systems due to the natural interaction metaphor and low cognitive load afforded by pen-based interaction. We believe that pen-based intelligent tutoring systems can be further enhanced by integrating animation techniques. In this work, we explore methods for recognizing and animating sketched physics diagrams. Our methodologies enable an Intelligent Tutoring System (ITS) to understand the scenario and requirements posed by a given problem statement and to couple this knowledge with a computational model of the student's handwritten solution. These pieces of information are used to construct meaningful animations and feedback mechanisms …

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An Unsupervised Consensus Control Chart Pattern Recognition Framework, Siavash Haghtalab Jan 2014

An Unsupervised Consensus Control Chart Pattern Recognition Framework, Siavash Haghtalab

Electronic Theses and Dissertations

Early identification and detection of abnormal time series patterns is vital for a number of manufacturing. Slide shifts and alterations of time series patterns might be indicative of some anomaly in the production process, such as machinery malfunction. Usually due to the continuous flow of data monitoring of manufacturing processes requires automated Control Chart Pattern Recognition(CCPR) algorithms. The majority of CCPR literature consists of supervised classification algorithms. Less studies consider unsupervised versions of the problem. Despite the profound advantage of unsupervised methodology for less manual data labeling their use is limited due to the fact that their performance is not …

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Automatic Detection Of Brain Functional Disorder Using Imaging Data, Soumyabrata Dey Jan 2014

Automatic Detection Of Brain Functional Disorder Using Imaging Data, Soumyabrata Dey

Electronic Theses and Dissertations

Recently, Attention Deficit Hyperactive Disorder (ADHD) is getting a lot of attention mainly for two reasons. First, it is one of the most commonly found childhood behavioral disorders. Around 5-10% of the children all over the world are diagnosed with ADHD. Second, the root cause of the problem is still unknown and therefore no biological measure exists to diagnose ADHD. Instead, doctors need to diagnose it based on the clinical symptoms, such as inattention, impulsivity and hyperactivity, which are all subjective. Functional Magnetic Resonance Imaging (fMRI) data has become a popular tool to understand the functioning of the brain such …

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Large Area Conformal Infrared Frequency Selective Surfaces, Jeffrey D'Archangel Jan 2014

Large Area Conformal Infrared Frequency Selective Surfaces, Jeffrey D'Archangel

Electronic Theses and Dissertations

Frequency selective surfaces (FSS) were originally developed for electromagnetic filtering applications at microwave frequencies. Electron-beam lithography has enabled the extension of FSS to infrared frequencies; however, these techniques create sample sizes that are seldom appropriate for real world applications due to the size and rigidity of the substrate. A new method of fabricating large area conformal infrared FSS is introduced, which involves releasing miniature FSS arrays from a substrate for implementation in a coating. A selective etching process is proposed and executed to create FSS particles from crossed-dipole and square-loop FSS arrays. When the fill-factor of the particles in the …

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Bio-Inspired Attitude Control Of Micro Air Vehicles Using Rich Information From Airflow Sensors, He Shen Jan 2014

Bio-Inspired Attitude Control Of Micro Air Vehicles Using Rich Information From Airflow Sensors, He Shen

Electronic Theses and Dissertations

Biological phenomena found in nature can be learned and customized to obtain innovative engineering solutions. In recent years, biologists found that birds and bats use their mechanoreceptors to sense the airflow information and use this information directly to achieve their agile flight performance. Inspired by this phenomenon, an attitude control system for micro air vehicles using rich amount of airflow sensor information is proposed, designed and tested. The dissertation discusses our research findings on this topic. First, we quantified the errors between the calculated and measured lift and moment profiles using a limited number of micro pressure sensors over a …

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Self-Heating Control Of Edge Emitting And Vertical Cavity Surface Emitting Lasers, Yu Zhang Jan 2014

Self-Heating Control Of Edge Emitting And Vertical Cavity Surface Emitting Lasers, Yu Zhang

Electronic Theses and Dissertations

Self-heating leads to temperature rise of laser diode and limits the output power, efficiency and modulation bandwidth due to increased loss and decreased differential gain. The main heat sources in laser diode during continuous wave operation are Joule heating and free carrier absorption loss. To control device self-heating, the epi structure needs to be designed with low electrical resistance and low absorption loss, while the heat flux must spread out of the device efficiently. This dissertation presents the control of self-heating of both edge emitting laser diodes and vertical cavity surface emitting lasers (VCSELs). For the 980nm high power edge …

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Particle Manipulation Via Optical Forces And Engineering Soft-Matter Systems With Tunable Nonlinearities., Shima Fardad Jan 2014

Particle Manipulation Via Optical Forces And Engineering Soft-Matter Systems With Tunable Nonlinearities., Shima Fardad

Electronic Theses and Dissertations

One of the most intriguing properties of light-matter interaction is the ability of an electromagnetic field to exert mechanical forces on polarizable objects. This phenomenon is a direct consequence of the fact that light carries momentum, which in turn can be transferred to matter. Mediated by scattering, this interaction usually manifests itself as a “pushing force” in the direction of beam propagation. However, it is possible to judiciously engineer these optical forces, either by tailoring particle polarizability, and/or by structuring the incident light field. As a simple example, a tightly focused laser beam demonstrates strong gradient forces, which may attract …

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Frequency Selective Detection Of Infrared Radiation In Uncooled Optical Nano-Antenna Array, Sushrut Modak Jan 2014

Frequency Selective Detection Of Infrared Radiation In Uncooled Optical Nano-Antenna Array, Sushrut Modak

Electronic Theses and Dissertations

Mid-infrared (mid-IR) detection and imaging over atmospheric transparent 3-5 μm and 8-12 μm bands are increasingly becoming important for various space, defense and civilian applications. Various kinds of microbolometers offer uncooled detection of IR radiation. However, broadband absorption of microbolometers makes them less sensitive to spectrally resolved detection of infrared radiation and the fabrication is also very tedious involving multiple complex lithography steps. In this study, we designed an optical nano-antenna array based detector with narrow frequency band of operation. The structure consists of a two-element antenna array comprised of a perforated metallic hole array coupled with an underneath disk …

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Control Based Soft Switching Three-Phase Micro-Inverter: Efficiency And Power Density Optimization, Ahmadreza Amirahmadi Jan 2014

Control Based Soft Switching Three-Phase Micro-Inverter: Efficiency And Power Density Optimization, Ahmadreza Amirahmadi

Electronic Theses and Dissertations

In the field of renewable energy, solar photovoltaic is growing exponentially. Grid-tied PV micro-inverters have become the trend for future PV system development because of their remarkable advantages such as enhanced energy production due to MPPT implementation for each PV panel, high reliability due to redundant and distributed system architecture, and simple design, installation, and management due to its plug-and-play feature. Conventional approaches for the PV micro-inverters are mainly in the form of single-phase grid connected and they aim at the residential and commercial rooftop applications. It would be advantageous to extend the micro-inverter concept to large size PV installations …

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Human-Robot Interaction For Multi-Robot Systems, Bennie Lewis Jan 2014

Human-Robot Interaction For Multi-Robot Systems, Bennie Lewis

Electronic Theses and Dissertations

Designing an effective human-robot interaction paradigm is particularly important for complex tasks such as multi-robot manipulation that require the human and robot to work together in a tightly coupled fashion. Although increasing the number of robots can expand the area that the robots can cover within a bounded period of time, a poor human-robot interface will ultimately compromise the performance of the team of robots. However, introducing a human operator to the team of robots, does not automatically improve performance due to the difficulty of teleoperating mobile robots with manipulators. The human operator’s concentration is divided not only among multiple …

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Design And Development Of Heterogenous Combustion Systems For Lean Burn Applications, Anthony Terracciano Jan 2014

Design And Development Of Heterogenous Combustion Systems For Lean Burn Applications, Anthony Terracciano

Electronic Theses and Dissertations

Combustion with a high surface area continuous solid immersed within the flame, referred to as combustion in porous media, is an innovative approach to combustion as the solid within the flame acts as an internal regenerator distributing heat from the combustion byproducts to the upstream reactants. By including the solid structure, radiative energy extraction becomes viable, while the solid enables a vast extension of flammability limits compared to conventional flames, while offering dramatically reduced emissions of NOx and CO, and dramatically increased burning velocities. Efforts documented within are used for the development of a streamlined set of design principles, and …

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A Lab-Scale Experimental Framework For Studying The Phenomenon Of Autorotation, Sigitas Rimkus Jan 2014

A Lab-Scale Experimental Framework For Studying The Phenomenon Of Autorotation, Sigitas Rimkus

Electronic Theses and Dissertations

While wind energy has emerged as a popular source of renewable energy, the traditional wind turbine has an inherent limitation, namely that it only generates power in the presence of sufficiently high and consistent wind speeds. As a result, wind farms are typically built in areas with a high probability of the required wind speeds, which are geographically sparse. One way of overcoming this drawback is to tap into the energy available in winds at high altitudes which are not only consistent and of high magnitude, but also globally pervasive. An airborne wind energy device based upon the phenomenon of …

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Learning Collective Behavior In Multi-Relational Networks, Xi Wang Jan 2014

Learning Collective Behavior In Multi-Relational Networks, Xi Wang

Electronic Theses and Dissertations

With the rapid expansion of the Internet and WWW, the problem of analyzing social media data has received an increasing amount of attention in the past decade. The boom in social media platforms offers many possibilities to study human collective behavior and interactions on an unprecedented scale. In the past, much work has been done on the problem of learning from networked data with homogeneous topologies, where instances are explicitly or implicitly inter-connected by a single type of relationship. In contrast to traditional content-only classification methods, relational learning succeeds in improving classification performance by leveraging the correlation of the labels …

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Nonlinear Integrated Photonics On Silicon And Gallium Arsenide Substrates, Jichi Ma Jan 2014

Nonlinear Integrated Photonics On Silicon And Gallium Arsenide Substrates, Jichi Ma

Electronic Theses and Dissertations

Silicon photonics is nowadays a mature technology and is on the verge of becoming a blossoming industry. Silicon photonics has also been pursued as a platform for integrated nonlinear optics based on Raman and Kerr effects. In recent years, more futuristic directions have been pursued by various groups. For instance, the realm of silicon photonics has been expanded beyond the well-established near-infrared wavelengths and into the mid-infrared (3 - 5 µm). In this wavelength range, the omnipresent hurdle of nonlinear silicon photonics in the telecommunication band, i.e., nonlinear losses due to two-photon absorption, is inherently nonexistent. With the lack of …

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Spectrum Map And Its Application In Cognitive Radio Networks, Saptarshi Debroy Jan 2014

Spectrum Map And Its Application In Cognitive Radio Networks, Saptarshi Debroy

Electronic Theses and Dissertations

Recent measurements on radio spectrum usage have revealed the abundance of underutilized bands of spectrum that belong to licensed users. This necessitated the paradigm shift from static to dynamic spectrum access. Cognitive radio based secondary networks that utilize such unused spectrum holes in the licensed band, have been proposed as a possible solution to the spectrum crisis. The idea is to detect times when a particular licensed band is unused and use it for transmission without causing interference to the licensed user. We argue that prior knowledge about occupancy of such bands and the corresponding achievable performance metrics can potentially …

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Specialty Fiber Lasers And Novel Fiber Devices, Clemence Jollivet Jan 2014

Specialty Fiber Lasers And Novel Fiber Devices, Clemence Jollivet

Electronic Theses and Dissertations

At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs. As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the …

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Visual Analysis Of Extremely Dense Crowded Scenes, Haroon Idrees Jan 2014

Visual Analysis Of Extremely Dense Crowded Scenes, Haroon Idrees

Electronic Theses and Dissertations

Visual analysis of dense crowds is particularly challenging due to large number of individuals, occlusions, clutter, and fewer pixels per person which rarely occur in ordinary surveillance scenarios. This dissertation aims to address these challenges in images and videos of extremely dense crowds containing hundreds to thousands of humans. The goal is to tackle the fundamental problems of counting, detecting and tracking people in such images and videos using visual and contextual cues that are automatically derived from the crowded scenes. For counting in an image of extremely dense crowd, we propose to leverage multiple sources of information to compute …

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Role Of Force Resultants Interaction On Fiber Reinforced Concrete, Titchenda Chan Jan 2014

Role Of Force Resultants Interaction On Fiber Reinforced Concrete, Titchenda Chan

Electronic Theses and Dissertations

Ultra-high performance concrete (UHPC) is a recently developed concrete gaining a lot of interest worldwide, and a lot research has been conducted to determine its material properties. UHPC is known for its very high strength and high durability. Association Francaise de Genie Civil (AFGC) has defined UHPC as a concrete exhibiting compressive strength greater than 150 MPa (22 ksi). To utilize the full compressive strength of UHPC, complementary tension reinforcement is required. A recent research study to find light weight yet high strength alternative deck systems for Florida movable bridges demonstrated that a composite UHPC and high strength steel (HSS) …

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Lp Fiber Mode Converters Using Holographic Phase Mask In Photo-Thermo-Refractive Glass, Aniket Patil Jan 2014

Lp Fiber Mode Converters Using Holographic Phase Mask In Photo-Thermo-Refractive Glass, Aniket Patil

Electronic Theses and Dissertations

In this study, an investigation was undertaken to research the use of holographic phase masks (HPMs) in photo-thermo-refractive (PTR) glass as mode converters for linearly polarized (LP) fiber modes. A Spatial Light Modulator (SLM) was used to generate higher-order transverse fiber modes LPm,n. Under proper incidence condition on the holographic device, LPm,n modes are diffracted and simultaneously converted into higher order or lower order LP modes. The process was analyzed by imaging the far field on a CCD camera. It is demonstrated that using this novel method of converting transverse fiber modes several combinations of LP modes can be converted …

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A Short Window Granger Causality Approach To Identify Brain Functional Pattern Associated With Changes Of Performance Induced By Sleep Deprivation, Muyuan Li Jan 2014

A Short Window Granger Causality Approach To Identify Brain Functional Pattern Associated With Changes Of Performance Induced By Sleep Deprivation, Muyuan Li

Electronic Theses and Dissertations

The comprehensive effect of sleep deprivation on biological and behavioral functions largely remains unknown. There is evidence to support that human sleep must be of sufficient duration and physiological continuity to ensure neurocognitive performance while we are waking. Insufficient sleep would lead to high risk of human-error related to accidents, injuries or even fatal outcomes. However, in modern society, more and more people suffer from sleep deprivation because of the increasing social, academic or occupational demand. It is important to study the effect of sleep deprivation, not only on task performance, but also on neurocognitive functions. Recent research that has …

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Advanced Liquid Crystal Materials For Display And Photonic Applications, Yuan Chen Jan 2014

Advanced Liquid Crystal Materials For Display And Photonic Applications, Yuan Chen

Electronic Theses and Dissertations

Thin-film-transistor (TFT) liquid crystal display (LCD) has been widely used in smartphones, pads, laptops, computer monitors, and large screen televisions, just to name a few. A great deal of effort has been delved into wide viewing angle, high resolution, low power consumption, and vivid color. However, relatively slow response time and low transmittance remain as technical challenges. To improve response time, several approaches have been developed, such as low viscosity liquid crystals, overdrive and undershoot voltage schemes, thin cell gap with a high birefringence liquid crystal, and elevated temperature operation. The state-of-the-art gray-to-gray response time of a nematic LC device …

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