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Articles 3721 - 3750 of 4180
Full-Text Articles in Engineering
Ultrashort, High Power, And Ultralow Noise Mode-Locked Optical Pulse Generation Using Quantum-Dot Semiconductor Lasers, Myoung-Taek Choi
Ultrashort, High Power, And Ultralow Noise Mode-Locked Optical Pulse Generation Using Quantum-Dot Semiconductor Lasers, Myoung-Taek Choi
Electronic Theses and Dissertations
This dissertation explores various aspects and potential of optical pulse generation based on active, passive, and hybrid mode-locked quantum dot semiconductor lasers with target applications such as optical interconnect and high speed signal processing. Design guidelines are developed for the single mode operation with suppressed reflection from waveguide discontinuities. The device fabrication procedure is explained, followed by characteristics of FP laser, SOA, and monolithic two-section devices. Short pulse generation from an external cavity mode-locked QD two-section diode laser is studied. High quality, sub-picosecond (960 fs), high peak power (1.2 W) pulse trains are obtained. The sign and magnitude of pulse …
Prototype Of Coupling Unit Network For Power Line Communications, Bharath Srinivasan
Prototype Of Coupling Unit Network For Power Line Communications, Bharath Srinivasan
Electronic Theses and Dissertations
Power Line Communications has made impressive strides since its introduction. Power Line Communications (PLC) or Broadband over Power Lines (BPL) is the method of transmitting broadband signals over the power lines and making it available at the power outlet in homes. It provides last mile communication and makes use of existing power lines to transmit signals, thereby eliminating the need to lay cables all over again. PLC is fast becoming a commercial reality in the United States. The Federal Communications Commission (FCC) is working toward making PLC a standard with particular emphasis on power emission issues and interference with nearby …
A New Approach To Identify The Expected Crash Patterns Based On Signalized Intersection Size And Analysis Of Vehicle Movements, Hari Salkapuram
A New Approach To Identify The Expected Crash Patterns Based On Signalized Intersection Size And Analysis Of Vehicle Movements, Hari Salkapuram
Electronic Theses and Dissertations
Analysis of intersection crashes is a significant area in traffic safety research. This study contributes to the area by identifying traffic-geometric characteristics and driver demographics that affect different types of crashes at signalized intersections. A simple methodology to estimate crash frequency at intersections based on the size of the intersection is also developed herein. First phase of this thesis used the crash frequency data from 1,335 signalized intersections obtained from six jurisdictions in Florida, namely, Brevard, Seminole, Dade, Orange, and Hillsborough Counties and the City of Orlando. Using these data a simple methodology has been developed to identify the expected …
A Holistic Usability Framework For Distributed Simulation Systems, Jeffrey Dawson
A Holistic Usability Framework For Distributed Simulation Systems, Jeffrey Dawson
Electronic Theses and Dissertations
This dissertation develops a holistic usability framework for distributed simulation systems (DSSs). The framework is developed considering relevant research in human-computer interaction, computer science, technical writing, engineering, management, and psychology. The methodology used consists of three steps: (1) framework development, (2) surveys of users to validate and refine the framework, and to determine attribute weights, and (3) application of the framework to two real-world systems. The concept of a holistic usability framework for DSSs arose during a project to improve the usability of the Virtual Test Bed, a prototypical DSS, and the framework is partly a result of that project. …
Multiobjective Simulation Optimization Using Enhanced Evolutionary Algorithm Approaches, Hamidreza Eskandari
Multiobjective Simulation Optimization Using Enhanced Evolutionary Algorithm Approaches, Hamidreza Eskandari
Electronic Theses and Dissertations
In today's competitive business environment, a firm's ability to make the correct, critical decisions can be translated into a great competitive advantage. Most of these critical real-world decisions involve the optimization not only of multiple objectives simultaneously, but also conflicting objectives, where improving one objective may degrade the performance of one or more of the other objectives. Traditional approaches for solving multiobjective optimization problems typically try to scalarize the multiple objectives into a single objective. This transforms the original multiple optimization problem formulation into a single objective optimization problem with a single solution. However, the drawbacks to these traditional approaches …
Hurricane Wind Retrieval Algorithm Development For An Airborne Conical Scanning Scatterometer, Santhosh Vasudevan
Hurricane Wind Retrieval Algorithm Development For An Airborne Conical Scanning Scatterometer, Santhosh Vasudevan
Electronic Theses and Dissertations
Reliable ocean wind vector measurements can be obtained using active microwave remote sensing (scatterometry) techniques. With the increase in the number of severe hurricanes making landfall in the United States, there is increased emphasis on operational monitoring of hurricane winds from aircraft. This thesis presents a data processing algorithm to provide real-time hurricane wind vector retrievals (wind speed and direction) from conically scanning airborne microwave scatterometer measurements of ocean surface backscatter. The algorithm is developed to best suit the specifications for the National Oceanic and Atmospheric Administration (NOAA) Hurricane Research Division's airborne scatterometer Integrated Wind and Rain Airborne Profiler …
Using The Software Adapter To Connect Legacy Simulation Models To The Rti, Deepak Kumar Rachapalli
Using The Software Adapter To Connect Legacy Simulation Models To The Rti, Deepak Kumar Rachapalli
Electronic Theses and Dissertations
The establishment of a network of persistent shared simulations depends on the presence of a robust standard for communicating state information between those simulations. The High Level Architecture (HLA) can serve as the basis for such a standard. While the HLA is architecture, not software, use of Run Time Infrastructure (RTI) software is required to support operations of a federation execution. The integration of RTI with existing simulation models is complex and requires a lot of expertise. This thesis implements a less complex and effective interaction between a legacy simulation model and RTI using a middleware tool known as Distributed …
Experimental Analysis And Evaluation Of Tidy Tree Drawing Algorithms, Pankaj Mahajan
Experimental Analysis And Evaluation Of Tidy Tree Drawing Algorithms, Pankaj Mahajan
Electronic Theses and Dissertations
Tree Drawings have been used extensively in software engineering and many other business and computer applications. The basic structure of a tree allows for the organization and representation of complex information. Many commercial tools allow their users to draw or construct trees to represent a problem and/or its solution. Our focus is on dynamic trees - trees subject to frequent changes and redisplay in highly user-friendly interactive computer applications. Tree presentations in such interactive tools have to be precise and maintainable, which means, the tree presentations should maintain a particular structure so that user's mental perception of the tree is …
Automated Scenario Generation System In A Simulation, Hajime Tomizawa
Automated Scenario Generation System In A Simulation, Hajime Tomizawa
Electronic Theses and Dissertations
Developing training scenarios that induce a trainee to utilize specific skills is one of the facets of simulation-based training that requires significant effort. Simulation-based training systems have become more complex in recent years. Because of this added complexity, the amount of effort required to generate and maintain training scenarios has increased. This thesis describes an investigation into automating the scenario generation process. The Automated Scenario Generation System (ASGS) generates expected action flow as contexts in chronological order from several events and tasks with estimated time for the entire training mission. When the training objectives and conditions are defined, the ASGS …
Design And Implementation Of An Emission Spectroscopy Diagnostic In A High-Pressure Strand Burner For The Study Of Solid Propell, Jason Arvanetes
Design And Implementation Of An Emission Spectroscopy Diagnostic In A High-Pressure Strand Burner For The Study Of Solid Propell, Jason Arvanetes
Electronic Theses and Dissertations
The application of emission spectroscopy to monitor combustion products of solid rocket propellant combustion can potentially yield valuable data about reactions occurring within the volatile environment of a strand burner. This information can be applied in the solid rocket propellant industry. The current study details the implementation of a compact spectrometer and fiber optic cable to investigate the visible emission generated from three variations of solid propellants. The grating was blazed for a wavelength range from 200 to 800 nm, and the spectrometer system provides time resolutions on the order of 1 millisecond. One propellant formula contained a fine aluminum …
Automated Visual Database Creation For A Ground Vehicle Simulator, Pedro Claudio
Automated Visual Database Creation For A Ground Vehicle Simulator, Pedro Claudio
Electronic Theses and Dissertations
This research focuses on extracting road models from stereo video sequences taken from a moving vehicle. The proposed method combines color histogram based segmentation, active contours (snakes) and morphological processing to extract road boundary coordinates for conversion into Matlab or Multigen OpenFlight compatible polygonal representations. Color segmentation uses an initial truth frame to develop a color probability density function (PDF) of the road versus the terrain. Subsequent frames are segmented using a Maximum Apostiori Probability (MAP) criteria and the resulting templates are used to update the PDFs. Color segmentation worked well where there was minimal shadowing and occlusion by other …
Design And Optimization Of Nano-Optical Elements By Coupling Fabrication To Optical Behavior, Raymond Rumpf
Design And Optimization Of Nano-Optical Elements By Coupling Fabrication To Optical Behavior, Raymond Rumpf
Electronic Theses and Dissertations
Photonic crystals and nanophotonics have received a great deal of attention over the last decade, largely due to improved numerical modeling and advances in fabrication technologies. To this day, fabrication and optical behavior remain decoupled during the design phase and numerous assumptions are made about "perfect" geometry. As research moves from theory to real devices, predicting device behavior based on realistic geometry becomes critical. In this dissertation, a set of numerical tools was developed to model micro and nano fabrication processes. They were combined with equally capable tools to model optical performance of the simulated structures. Using these tools, it …
Predicting Surface Scatter Using A Linear Systems Formulation Of Non-Paraxial Scalar Diffraction, Andrey Krywonos
Predicting Surface Scatter Using A Linear Systems Formulation Of Non-Paraxial Scalar Diffraction, Andrey Krywonos
Electronic Theses and Dissertations
Scattering effects from rough surfaces are non-paraxial diffraction phenomena resulting from random phase variations in the reflected wavefront. The ability to predict these effects is important in a variety of applications including x-ray and EUV imaging, the design of stray light rejection systems, and reflection modeling for rendering realistic scenes and animations of physical objects in computer graphics. Rayleigh-Rice (small perturbation method) and Beckmann-Kirchoff (Kirchhoff approximation) theories are commonly used to predict surface scatter effects. In addition, Harvey and Shack developed a linear systems formulation of surface scatter phenomena in which the scattering behavior is characterized by a surface transfer …
Probing Random Media With Singular Waves, Chaim Schwartz
Probing Random Media With Singular Waves, Chaim Schwartz
Electronic Theses and Dissertations
In recent years a resurgence of interest in wave singularities (of which optical vortices are a prominent example), light angular momentum and the relations between them has occurred. Many applications in various areas of linear and non-linear optics have been based on studying effects related to angular momentum and optical vortices. This dissertation examines the use of such wave singularities for studying the light propagation in highly inhomogeneous media and the relationship to angular momentum transfer. Angular momentum carried by light can be, in many cases, divided in two terms. The first one relates to the polarization of light and …
Identifying Common Ultrasonic Predictive Failure Signatures In Bearing Elements For The Development Of An Automated Condition Based Ultrasonic Monitoring Controller., Jason Eric Johnson
Identifying Common Ultrasonic Predictive Failure Signatures In Bearing Elements For The Development Of An Automated Condition Based Ultrasonic Monitoring Controller., Jason Eric Johnson
Electronic Theses and Dissertations
This thesis presents a new method for Condition Based Ultrasonic Monitoring to be applied in conjunction with a lubrication distribution controller. As part of this thesis, algorithms were developed using ultrasonic sensors to control the application of lubrication to machinery. The controller sensors detect an ultrasonic signal from rolling or sliding machine elements. This signal then alerts the controller to dispense the proper amount of lubrication when needed, as opposed to a time schedule based on average performance or history. The work from this thesis will be used to help reduce equipment downtime and maintenance cost when utilized in an …
Cost Effective Human Protein C Purification From Cohn Fraction Iv-1 Using Mini-Antibody., Doh Gyeuhn Ahn 1969-
Cost Effective Human Protein C Purification From Cohn Fraction Iv-1 Using Mini-Antibody., Doh Gyeuhn Ahn 1969-
Electronic Theses and Dissertations
Protein C (PC) is an important anticoagulant, antithrombotic, and antiinflammatory in blood plasma. PC deficiency can lead to severe venous thrombotic events, including lung embolism, stroke, and heart attack. In the body, PC is activated only when it is needed, and, therefore, PC does not cause bleeding problems that currently available anticoagulants may do. Purification of PC from plasma is currently done by immunoaffinity chromatography using monoclonal antibodies (Mabs), which is very expensive. Single chain variable regions (mini-Mab) with a PC binding capability, which can be produced in recombinant E. coli , were developed for PC purification. Compared to Mabs, …
Design And Development Of A Mems-Based Capacitive Bending Strain Sensor And A Biocompatible Housing For A Telemetric Strain Monitoring System., Julia Marie Weyer Aebersold 1969-
Design And Development Of A Mems-Based Capacitive Bending Strain Sensor And A Biocompatible Housing For A Telemetric Strain Monitoring System., Julia Marie Weyer Aebersold 1969-
Electronic Theses and Dissertations
Lumbar arthrodesis or spinal fusion is usually performed to relieve back pain and regain functionality from ruptured discs, disc degenerative disease, trauma and scoliosis. Metal rods are often fixed to the spine with screws or hooks, while fusion develops on the affected vertebrae. Fusion is determined by visual examination of radiographic images (X-ray), computed tomography (CT) scans or magnetic resonance imaging (MRI), yet these inspection procedures are subjective methods of review. They do not objectively confirm the presence of spinal fusion, which can lead to exploratory surgery to determine if fusion has occurred. Therefore, a need has arisen to develop …
Digital Control Of Half-Bridge Dc-Dc Converters With Current Doubler Rectification, Liangbin Yao
Digital Control Of Half-Bridge Dc-Dc Converters With Current Doubler Rectification, Liangbin Yao
Electronic Theses and Dissertations
DC-DC power converters play an important role in powering telecom and computing systems. Complex systems, including power electronics systems, are increasingly using digital controllers because of the major advancements in digital controllers and DSP as well as there ability to perform sophisticated and enhanced control schemes. In this thesis, the digital controller is investigated for DC-DC converters in high current low voltage applications. For an optimal design of a regulated DC-DC converter, it is necessary to derive a valid model. The current doubler rectified half bridge (CDRHB) DC-DC converter is suitable for high current low voltage applications. In this thesis, …
An Optimized Kinetics Model For Oh Chemiluminescence At High Temperatures And Atmospheric Pressures, Joel Hall
An Optimized Kinetics Model For Oh Chemiluminescence At High Temperatures And Atmospheric Pressures, Joel Hall
Electronic Theses and Dissertations
Chemiluminescence from the OH(A-X) transition near 307 nm is a commonly used diagnostic in combustion applications such as flame chemistry, shock-tube experiments, and reacting-flow visualization. Measurements of the chemiluminescent intensity provide a simple, cost-effective, non-intrusive look at the combustion environment. The presence of the ultra-violet emission is often used as an indicator of the flame zone in practical combustion systems, and its intensity may be correlated to the temperature distribution or other parameters of interest. While absolute measurements of the ground-state OH(X) concentrations are well-defined, there is no elementary relation between emission from the electronically excited state (OH*) and its …
Transform Based And Search Aware Text Compression Schemes And Compressed Domain Text Retrieval, Nan Zhang
Transform Based And Search Aware Text Compression Schemes And Compressed Domain Text Retrieval, Nan Zhang
Electronic Theses and Dissertations
In recent times, we have witnessed an unprecedented growth of textual information via the Internet, digital libraries and archival text in many applications. While a good fraction of this information is of transient interest, useful information of archival value will continue to accumulate. We need ways to manage, organize and transport this data from one point to the other on data communications links with limited bandwidth. We must also have means to speedily find the information we need from this huge mass of data. Sometimes, a single site may also contain large collections of data such as a library database, …
Seawinds Radiometer Brightness Temperature Calibration And Validation, Mayank Rastogi
Seawinds Radiometer Brightness Temperature Calibration And Validation, Mayank Rastogi
Electronic Theses and Dissertations
The NASA SeaWinds scatterometer is a radar remote sensor which operates on two satellites; NASA's QuikSCAT launched in June 1999 and on Japan's ADEOS-II satellite launched in December 2002. The purpose of SeaWinds is to provide global measurements of the ocean surface wind vector. On QuikSCAT, a ground data processing algorithm was developed, which allowed the instrument to function as a QuikSCAT Radiometer (QRad) and measure the ocean microwave emissions (brightness temperature, Tb) simultaneously with the backscattered power. When SeaWinds on ADEOS was launched, this same algorithm was applied, but the results were anomalous. The initial SRad brightness temperatures exhibited …
Unified Large And Small Signal Discrete-Space Modeling For Pwm Converters In Ccm, Ehab Hamed Shoubaki
Unified Large And Small Signal Discrete-Space Modeling For Pwm Converters In Ccm, Ehab Hamed Shoubaki
Electronic Theses and Dissertations
In this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter states at steady-state is done for steady-state waveform acquisition , …
Alternative Foam Treatments For The Space Shuttle's External Tank, Kirsten Dreggors
Alternative Foam Treatments For The Space Shuttle's External Tank, Kirsten Dreggors
Electronic Theses and Dissertations
The Space Shuttle Columbia accident and the recent excitement surrounding Discovery's return to space brought excessive media attention to the foam products used on the External Tank (ET). In both cases, videos showed chunks of foam or ablative material falling away from the ET during lift off. This led to several years of investigation and research into the exact cause of the accident and potential solutions to avoid the problem in the future. Several design changes were made prior to the return to flight this year, but the ET still shed foam during lift off. Since the Columbia accident, the …
Background Stabilization And Motion Detection In Launch Pad Video Monitoring, Kaushik Gopalan
Background Stabilization And Motion Detection In Launch Pad Video Monitoring, Kaushik Gopalan
Electronic Theses and Dissertations
Automatic detection of moving objects in video sequences is a widely researched topic with application in surveillance operations. Methods based on background cancellation by frame differencing are extremely common. However this process becomes much more complicated when the background is not completely stable due to camera motion. This thesis considers a space application where surveillance cameras around a shuttle launch site are used to detect any debris from the shuttle. The ground shake due to the impact of the launch causes the background to be shaky. We stabilize the background by translation of each frame, the optimum translation being determined …
Slope Stability Of Laterite Soil Embankments, Ikiensinma Gogo-Abite
Slope Stability Of Laterite Soil Embankments, Ikiensinma Gogo-Abite
Electronic Theses and Dissertations
Embankments are key elements in the infrastructural development of structures such as dams, bridges, and roads. Residual soils are generally used as fills in the construction of embankments in areas were residual soils such as laterite is the dominant soil types. Laterite soils have the characteristics of losing its shear strength with time and in fully saturated conditions and its properties varies from region to region. The soil property is influenced by the chemical composition and the environment. The binding agent iron oxide in such soils changes its composition with time and in the presence of moisture. Sudden failures of …
Investigations On Rf Sputter Deposited Sicn Thin Films For Mems Applications, Ravi Todi
Investigations On Rf Sputter Deposited Sicn Thin Films For Mems Applications, Ravi Todi
Electronic Theses and Dissertations
With the rapid increase in miniaturization of mechanical components, the need for a hard, protective coatings is of great importance. In this study we investigate some of the mechanical, chemical and physical properties of the SiCN thin films. Thin films of amorphous silicon carbide nitride (a-SiCxNy) were deposited in a RF magnetron sputtering system using a powder pressed SiC target. Films with various compositions were deposited on to silicon substrate by changing the N2/Ar gas ratios during sputtering. Nano-indentation studies were performed to investigate the mechanical properties such as hardness and reduced modulus of the SiCN films. Surface morphology of …
Predictive Control For Dynamic Systems To Track Unknown Input In The Presence Of Time Delay, Yulan Li
Predictive Control For Dynamic Systems To Track Unknown Input In The Presence Of Time Delay, Yulan Li
Electronic Theses and Dissertations
This study investigated a tracking system to trace unknown signal in the presence oftime delay. A predictive control method is proposed in order to compensate the time delay. Root locus method is applied when designing the controller, parameter setting is carried out through error and trail technique in w-plane. State space equation is derived for the system, with special state chose of tracking error. To analyze the asymptotic stability of the proposed predictive control system, the Lyapunov function is constructed. It is shown that the designed system is asymptotically stable when input signal is rather low frequency signal. In order …
An Investigation Of The Autoignition Of Power Generation Gas Turbine Fuel Blends Using A Design Of Experiments Approach, Jaap De Vries
An Investigation Of The Autoignition Of Power Generation Gas Turbine Fuel Blends Using A Design Of Experiments Approach, Jaap De Vries
Electronic Theses and Dissertations
Natural gas has grown in popularity as a fuel for power generation gas turbines. However, changes in fuel composition are a topic of concern since fuel variability can have a great impact on the reliability and performance of the burner design. In particular, autoignition of the premixed fuel and air prior to entering the main burner is a potential concern when using exotic fuel blends. To obtain much-needed data in this area, autoignition experiments for a wide range of likely fuel blends containing CH4 mixed with combinations of C2H6, C3H8, C4H10, C5H12, and H2 were performed in a high-pressure shock …
Analysis And Simulation Tools For Solar Array Power Systems, Nattorn Pongratananukul
Analysis And Simulation Tools For Solar Array Power Systems, Nattorn Pongratananukul
Electronic Theses and Dissertations
This dissertation presents simulation tools developed specifically for the design of solar array power systems. Contributions are made in several aspects of the system design phases, including solar source modeling, system simulation, and controller verification. A tool to automate the study of solar array configurations using general purpose circuit simulators has been developed based on the modeling of individual solar cells. Hierarchical structure of solar cell elements, including semiconductor properties, allows simulation of electrical properties as well as the evaluation of the impact of environmental conditions. A second developed tool provides a co-simulation platform with the capability to verify the …
International Space Station Remote Sensing Pointing Analysis, Craig Jacobson
International Space Station Remote Sensing Pointing Analysis, Craig Jacobson
Electronic Theses and Dissertations
This paper analyzes the geometric and disturbance aspects of utilizing the International Space Station for remote sensing of earth targets. The proposed instrument is SHORE (Station High-Sensitivity Ocean Research Experiment), a multi-band optical spectrometer with 15 m pixel resolution. The analysis investigates the contribution of the error effects to the quality of data collected by the instrument. The analysis begins with the discussion of the coordinate systems involved and then conversion from the target coordinate system to the instrument coordinate system. Next the geometry of remote observations from the Space Station is investigated including the effects of the instrument location …