Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network™

Open Access. Powered by Scholars. Published by Universities.®

University of Texas at Arlington

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 7651 - 7680 of 8681

Full-Text Articles in Entire DC Network

Visualization Of Monitor-Based Executions, Keerthika Koteeswaran Mar 2008

Visualization Of Monitor-Based Executions, Keerthika Koteeswaran

Computer Science and Engineering Theses - Archive

Concurrent programs play a vital role in the world of software engineering. Concurrent programs are used in various fields such as safety critical applications, applications involving advanced graphical user interface, operating system implementation etc. Concurrent programs due to their inherent multi-threaded nature pose a challenge to software engineers not only in coding but also in ensuring data consistency and accuracy. One of the important software constructs used by concurrent programmers to handle critical sections and data synchronization is monitors. A monitor is an encapsulation of shared data, operations on the data and any synchronization required to access the data~\cite{CarTai06:ModMulti}. Monitors …

Go to article

Simulation Analysis Of Orthogonal Frequency Division Multiplexing Systems With Diversity Reception, Sai Sravan Bharadwaj Karri Feb 2008

Simulation Analysis Of Orthogonal Frequency Division Multiplexing Systems With Diversity Reception, Sai Sravan Bharadwaj Karri

Electrical Engineering Theses - Archive

With the rapid increase in the utility of voice and data services, there is a demand for higher data rates and reliability in wireless communications. A wireless communication channel is prone to degrading effects such as multi-path fading, ISI etc. Orthogonal Frequency Division Multiplexing (OFDM), a candidate for the 4^{th} generation wireless systems, mitigates these effects and supports higher data rates.The performance analysis of a complex system like OFDM,is a challenging task where analytical methods become cumbersome to be used. Simulation based approaches provide a fair estimate of the performance in such cases. In this thesis, the performance of an …

Go to article

Semi-Analytical Complex Variable Based Stochastic Finite Element Method, Weiya Jin Jan 2008

Semi-Analytical Complex Variable Based Stochastic Finite Element Method, Weiya Jin

Mechanical and Aerospace Engineering Dissertations - Archive

The stochastic finite element method (SFEM) is an approach that allows an analyst to define material, load, and geometry parameters as random variables to represent uncertainty in an engineering problem. The method is then used to estimate the probability of exceeding specified performance thresholds. A necessary ingredient for this analysis is consistent, accurate and efficient algorithms for computing finite element response sensitivities. In this work, the semi-analytical complex variable method (SACVM) is introduced as a method for computing accurate response sensitivities of stochastic models. The SACVM incorporates the complex variable method (CVM) with the semi-analytical method (SAM). It takes advantage …

Go to article

Corrosion Behavior Of Zn-Ni Coatings Deposited By Electrolytic Plasma Processing, Giancarlo Rios Jan 2008

Corrosion Behavior Of Zn-Ni Coatings Deposited By Electrolytic Plasma Processing, Giancarlo Rios

Material Science and Engineering Theses - Archive

In the current research project, three groups of Zn-Ni coatings of various Ni contents were deposited on comercial carbon steel by electrolytic plasma processing (EPP), a novel surface modification technique. The coating characteristics were studied along with their corrosion behavior in order to determine their potential as electroplated Cd coating replacements. The latter electroplated coatings are currently used in aerospace applications but are toxic and hazardous to humans and the environment. Coating surfaces and cross sections were analyzed by scanning electron microscopy (SEM) while compositional analysis was conducted by energy-dispersive spectroscopy (EDS). Phase structure analysis was carried out by x-ray …

Go to article

Fabrication And Characterization Of Cobalt-Diamond-Like-Carbon (Co-Dlc) Nanocomposites, Gunjan Shebe Jan 2008

Fabrication And Characterization Of Cobalt-Diamond-Like-Carbon (Co-Dlc) Nanocomposites, Gunjan Shebe

Material Science and Engineering Theses - Archive

In recent years, synthesis of magnetic nanocomposites has been receiving significant attention. These nanocomposites offer opportunities to develop active nanomaterials with various applications like magnetic data storage and biomedical applications. They can be designed to provide excellent magnetic properties. However, high saturation magnetization materials, such as Co are not biocompatible. Thus, designing nanocomposites with magnetic phase embedded in biocompatible protective shells is of immense interest. In this study, Co-DLC nanocomposites were synthesized using a hybrid CVD/PVD technique and different combination of processing parameters were used to vary the concentration of Co in the nanocomposites. X-ray photoelectron spectroscopy showed, that with …

Go to article

Effects Of Edge Distance, Hole Size Ratio And Hole Spacing On Peak Stresses Of Composite Laminate With Multiple Holes, Manishkumar Kheradiya Jan 2008

Effects Of Edge Distance, Hole Size Ratio And Hole Spacing On Peak Stresses Of Composite Laminate With Multiple Holes, Manishkumar Kheradiya

Mechanical and Aerospace Engineering Theses - Archive

Unlike isotropic material, the stress distribution of laminate with a hole varies with its size, its material properties and fiber orientations of each layer. Moreover, presence of a hole in the neighborhood of another hole may also affect their stress distribution, too. The major objective of this study is to determine stress distribution of finite width laminated composite having multiple holes. The effect of stress concentration due to presence of holes in each angle ply of laminated composite is a focus of this study. Three dimensional finite element models are developed to determine the stress distribution in laminate using commercial …

Go to article

Characterization And Cooling Capacity Enhancement Of A Porous Ceramic Wick Based Coldplate, Mauricio Adrian Salinas Jan 2008

Characterization And Cooling Capacity Enhancement Of A Porous Ceramic Wick Based Coldplate, Mauricio Adrian Salinas

Mechanical and Aerospace Engineering Dissertations - Archive

Current passive cooling methods of aerospace and military, high heat-flux electronics include the use of thermal planes made of exotic metal alloys, which have been designed, at a great expense, to have high thermal conductivity and low density (i.e. light weight). Also, phase change modules composed of a metal matrix saturated with a solid phase change material are being employed for systems requiring a transient cooling scheme such as expendable weapons. This method requires the heat to be transferred from the source location, through the metal matrix (typically a porous aluminum foam), to the available phase change material. Preliminary empirical …

Go to article

Thermal Design Optimization Of Internally Cooled Turbine Blades, James Daniel Ruiz Jan 2008

Thermal Design Optimization Of Internally Cooled Turbine Blades, James Daniel Ruiz

Mechanical and Aerospace Engineering Theses - Archive

This paper outlines the use of Computational Fluid Dynamics (CFD) and Genetic Algorithm (GA) Optimization to enhance the design of a 3-dimensional internally cooled turbine blade. The optimization code utilizes principles of Genetic Algorithms to optimize (i.e. minimize) the integrated heat flux through the turbine blade. The optimization is accomplished by adjusting the size and position (within pre-determined constraints) of cooling passages internal to the turbine blade. Starting with an aerodynamically optimized airfoil shape, cooling passage designs are generated by the optimization process and coupled with boundary and airfoil domains. The analysis becomes a Conjugate Heat Transfer (CHT) problem analyzing …

Go to article

Increasing Localization Precision In Sensor Networks With Mobile Beacons - A Genetic Path Planning Approach, Awais Iqbal Jan 2008

Increasing Localization Precision In Sensor Networks With Mobile Beacons - A Genetic Path Planning Approach, Awais Iqbal

Computer Science and Engineering Theses - Archive

This work describes a genetic algorithm based approach to approximate an optimal path for a mobile beacon node in a grid of stationary wireless sensors. As the beacon moves over the field of sensors it broadcasts its location. Sensors that are currently in the proximity of the beacon will receive this communication and can then use several of these messages to compute estimates on their locations. An optimal path is defined as a path that will result in the highest overall precision of location estimates among sensors given a maximum path length for the beacon. We assume that sensors are …

Go to article

Development Of Spectral And Wavelet Time-Of-Flight Methods For Propagating Shock And Detonation Waves, Alfredo Albert Ortiz Jan 2008

Development Of Spectral And Wavelet Time-Of-Flight Methods For Propagating Shock And Detonation Waves, Alfredo Albert Ortiz

Mechanical and Aerospace Engineering Theses - Archive

An accurate time delay estimate for a propagating disturbance, including an estimate of its uncertainty, is important in many areas of science. Several techniques were developed for determining the propagation time of a shock and detonation wave. The speed of the propagating wave was then determined by the time delay estimates provided for the best techniques. The techniques used ranged from the commonly used time-of-flight method to a nonstationary cross-spectral density phase method that provided a statistical estimation of the propagation time. The time delay results for a shock tube experiment showed that most of the methods had difficulties in …

Go to article

Thermal Analysis Of Pulse Detonation Engines, Raghu Raman Ghandikota Jan 2008

Thermal Analysis Of Pulse Detonation Engines, Raghu Raman Ghandikota

Mechanical and Aerospace Engineering Theses - Archive

The pulse detonation engine (PDE) is a compact system that can be modeled thermodynamically by the Humphrey cycle and is capable of high efficiency. The rapid heat release for stochiometric fuel/oxidizer ratios results in developing high temperatures. The high temperatures produced during its operation can cause the engine to fail. Thus, operating this engine for a longer duration would become dubious if the temperatures are not dissipated from it. The current research aims to perform a preliminary thermal analysis. This analysis consists of two steps. The first step is to determine the heat dissipated from the engine using the unsteady …

Go to article

Effect Of Pullout And Torsional Strength Of Composites With Co-Molded Thread Inserts, Dan L. Reller Jan 2008

Effect Of Pullout And Torsional Strength Of Composites With Co-Molded Thread Inserts, Dan L. Reller

Mechanical and Aerospace Engineering Theses - Archive

Rotorcraft transmission housings and drive system components are typically made from cast metals due to their highly complex geometries. Utilizing composite materials offers potential to reduce weigh and manufacturing cost while increasing corrosive resistance and extending part life. Traditional compression molded composites have not been utilized in aerospace because they typically experience low fiber volume fraction. Currently there are numerous materials which offer opportunities for composites in drive system housing applications and also offer the ability to co-mold details to reduce post mold operations. One of the issues associated with composite structures is the ability to fasten them to one …

Go to article

Electromagnetic Flow Control: A Review And Experimental Development And Testing Of A Compact Actuator, Eric Braun Jan 2008

Electromagnetic Flow Control: A Review And Experimental Development And Testing Of A Compact Actuator, Eric Braun

Mechanical and Aerospace Engineering Theses - Archive

This thesis is divided into two sections which both relate to the field of magnetohydrodynamics and particularly electromagnetic flow control (EMFC). The first section contains a review of recent research in EMFC. The second section presents the experimental results of a compact EMFC actuator designed for use at low speeds where the flow conductivity is raised by conductive seed particle injection.Fifty years ago, publications began to discuss the possibilities of using EMFC to improve aerodynamic performance. This led to an era of research that focused on coupling the fundamentals of magnetohydrodynamics (MHD) with propulsion, control, and power generation systems. Unfortunately, …

Go to article

Finite Element Analysis Of Helicopter Main Rotor Hub Plates To Evaluate The Possibility Of Increasing The Time To Retirement, Douglas Wittig Jan 2008

Finite Element Analysis Of Helicopter Main Rotor Hub Plates To Evaluate The Possibility Of Increasing The Time To Retirement, Douglas Wittig

Mechanical and Aerospace Engineering Theses - Archive

Rotorcraft main rotor systems have multiple components that are subject to very high loads and moments. These loads and moments dictate the life expectancy of the parts based upon the components material of composition. This project will primarily focus on the upper and lower hub plates on the main rotor system of a typical four bladed commercial helicopter. The upper and lower plates are machined from 7075-T73 aluminum forgings. The upper and lower plates were laboratory fatigue tested during product development as supporting parts in the test of the main rotor assembly. With recent advances in finite element analysis, there …

Go to article

Fabrication And Characeterization Of Granular Magnetic Gold Nanoparticles, Rishi Wadhwa Jan 2008

Fabrication And Characeterization Of Granular Magnetic Gold Nanoparticles, Rishi Wadhwa

Material Science and Engineering Theses - Archive

In recent years, gold and magnetic nanoparticles have showed great potential in biomedical applications. Magnetic nanoparticles can be used in both in- vivo and in-vitro applications such as drug and gene delivery, hyperthermia treatment of cancer, MRI contrast enhancement, cell labeling and magnetic separation. Due to the surface plasmon resonance effect (SPR), gold nanoparticles strongly absorb and scatter visible and infrared light in resonance with SPR. They have been exploited for bioimaging and photothermal therapy applications. This is why different sizes and shapes of Au nanoparticles exhibit different colors.In this thesis, we are investigating a new type of nanoparticles, granular …

Go to article

Clay Mineralogy Effects On Long-Term Performance Of Chemically Treated Expansive Clays, Bhaskar Chandra Srinivas Chittoori Jan 2008

Clay Mineralogy Effects On Long-Term Performance Of Chemically Treated Expansive Clays, Bhaskar Chandra Srinivas Chittoori

Civil Engineering Dissertations - Archive

Stabilization of expansive soils using chemical additives such as cement and lime had been in use for several decades and these treatments provide riding comforts to travelers. However, many state Departments of Transportation (DOTs) in the United States have had problems with subgrade failure even after stabilization with chemical additives due to a loss of stabilizer over time, or a stabilizer being ineffective in some soils while other soils with the same index properties respond well to that stabilizer. These problems are attributed to the limitations of the current procedures of stabilization for pavement subsoil layers. One such limitation is …

Go to article

Construction Cost Of Underground Infrastructure, Seyed Behnam Hashemi Jan 2008

Construction Cost Of Underground Infrastructure, Seyed Behnam Hashemi

Civil Engineering Theses - Archive

Renewal of aging underground infrastructure is a major challenge that municipalities inNorth America face every day. Traditional replacement or renewal of these underground utilitiesuses open-cut excavation methods that can be disruptive to everyday life of citizens andexpensive, particularly in built-up areas and in projects with difficult ground and site conditions. Incontrast, trenchless technologies use innovative methods, materials, and equipment that requireminimum surface excavation to renew and construct aging underground infrastructure. Thesenew methods are considered to be more safe, cost-effective, efficient and productive thanconventional open-cut projects. However, to select trenchless technologies in utility design,consulting engineers and utility owners need to compare …

Go to article

Adsorption Curve Fits For Landfill Vocs On Bituminous Coal Based And Coconut Shell Based Activated Carbon, Annaprabha Athappan Jan 2008

Adsorption Curve Fits For Landfill Vocs On Bituminous Coal Based And Coconut Shell Based Activated Carbon, Annaprabha Athappan

Civil Engineering Theses - Archive

This study explores adsorption as a method of controlling hazardous gas emissions from Municipal Solid Waste Landfills (MSWL). In particular, the hazardous air pollutants (HAPs) para, meta, and ortho-xylene, ethylbenzene and methyl ethyl ketone are selected for experimental study. Activated carbon is a good adsorbent and well known for its high surface area. Among the many varieties of activated carbon, bituminous coal based activated carbon (BPL) and coconut shell based activated carbon (OVC) are compared in this study. Each experiment was conducted in a vial with a known amount of carbon in it. The pollutant concentration remaining in the vial …

Go to article

Optimization Of Reconstruction Parameters In Brain Activation Studies, Aswini Kanneganti Jan 2008

Optimization Of Reconstruction Parameters In Brain Activation Studies, Aswini Kanneganti

Bioengineering Theses - Archive

Diffuse Optical Imaging (DOI) is being extensively used in brain activation studies for the quantification of hemodynamic changes in the cerebral cortex. Many investigators have utilized the commercially available CW5 DOI device to attain cortical activation maps. However, the localization and spatial resolution in the resulting activation images remains poor. These limitations arise due to the large source detector separations required for light to reach the brain's surface and the limited number of detector channels in the CW5 system, which result in sparse spatial sampling of the cortical activation regions. In this thesis we assess the feasibility of using denser …

Go to article

Assessing Control Strategies For Ground Level Ozone, Neelesh Vijay Sule Jan 2008

Assessing Control Strategies For Ground Level Ozone, Neelesh Vijay Sule

Civil Engineering Dissertations - Archive

Developing cost effective control strategies for ozone has been a challenge to air quality modelers. Conventionally, the control strategies are applied across-the board to the region. The main aim of this research was to develop a Decision-Making Framework (DMF) for evaluating and optimizing the selection of ozone control strategies. Conventional across-the-board reductions conduct emission reductions uniformly throughout the region and throughout the day. By contrast, this dissertation studied targeted reductions, in which emission sources of various types are reduced at various times and locations. The proposed DMF comprised of four phases: (1) Initialization, (2) Mining, (3) Metamodeling, and (4) Optimization. …

Go to article

Measured And Theoretical Response Of Perpetual Pavement Structures, Miguel M. Portillo Jan 2008

Measured And Theoretical Response Of Perpetual Pavement Structures, Miguel M. Portillo

Civil Engineering Theses - Archive

The Kansas Perpetual Pavement experiment includes the construction of four pavement sections on the US-75 highway designed according to the perpetual pavement concept. The sections were instrumented with strain gauges and pressures cells to measure strains and stress at the bottom of the base layer and at the top of the subbase layer. Pavement response measurements were carried out in seven occasions between July 2005 and October 2007 with a loaded truck. Measured values obtained show that longitudinal and transverse values were almost always below the average endurance limit of 70 microstrains. The measurements also showed that temperature and vehicle …

Go to article

Fano Resonance Filters On Patterned Silicon Photonic Crystal Nanomembranes, Santhad Chuwongin Jan 2008

Fano Resonance Filters On Patterned Silicon Photonic Crystal Nanomembranes, Santhad Chuwongin

Electrical Engineering Theses - Archive

Recently broadband reflectors and guided-resonance narrowband filters have been proposed to be the major components in communication and optical interconnect systems. Most work reported so far are based on free-standing membranes. Recent advances in the fabrication process have made it possible to pattern crystalline silicon nanomembranes (NMs) and transfer to foreign substrates. These NMs are transferable, stackable, bondable and manufacturable. In this thesis, we present two-dimensional photonic crystal broadband reflectors and narrowband filters based on Fano resonances on patterned silicon nanomembranes, on Si, glass, and polyethylene terephthalate (PET) substrates. For broadband reflectors, spectral trimming was achieved by partially or even …

Go to article

Collision Response Of Surface Modeled Organs For Virtual Laparoscopic Surgery, Dibbesh Sharma Adhikari Jan 2008

Collision Response Of Surface Modeled Organs For Virtual Laparoscopic Surgery, Dibbesh Sharma Adhikari

Electrical Engineering Theses - Archive

Laparoscopic surgery is a modern surgical procedure in which, operations are performed in the abdomen by monitoring the image from a laparoscope: a telescopic rod lens system, which is usually connected to a video camera with a halogen or xenon light source, and is inserted into the abdomen through a small incision. Generally, laparoscopic surgeries are chosen over open surgery because of lower pain and speedier recovery process. However, the surgeon needs additional training in performing such surgery since laparoscopic camera reflects 2D mirror image of hand movement and depth information of the scene is harder for the surgeon to …

Go to article

Collision Detection And Penetration Depth Calculation In Virtual Surgical Simulation, Rupin Pavithran Jan 2008

Collision Detection And Penetration Depth Calculation In Virtual Surgical Simulation, Rupin Pavithran

Electrical Engineering Theses - Archive

Virtual Reality (VR) based surgical simulators create a simulated, realistic three dimensional surgical environments using advanced graphic and haptic rendering techniques. Virtual objects, which are geometric surface polygonal models of different human organs and instruments, are rendered in a common viewing volume. Such deformable or non-deformable polygonal models interact with each other. In order to provide a realistic response in real-time, detection of collisions in such models is the greatest challenge in the field of VR based simulators. Once collision is detected, the overlapping region and the largest penetration distance for a pair of intersecting objects need to be determined …

Go to article

The Design Of A Precision Current Miror Using A High-Gain Current Amplifier, Mei-Ping Pua Jan 2008

The Design Of A Precision Current Miror Using A High-Gain Current Amplifier, Mei-Ping Pua

Electrical Engineering Theses - Archive

An improved high gain, precision, low sensitivity current mirror is designed around a feedback circuit. This mirror utilizes a buffered Widlar current mirror to drive the constant input reference current, two beta helpers to compensate for the loss of base current and an active load, and a feedback loop in the amplifier. This design provides a comparison node for detecting the input error signal. The output collector current is substantially equal to the input reference current when driving multiple transistor loads. The circuit has been fabricated with National's VIP10 process, which caters to the high gain bipolar technology. Measurement results …

Go to article

Development Of A New Procedure For Assessing Power System Reliability In Preparation For Nerc's Standards Compliance, Frederico Von Pinho Jan 2008

Development Of A New Procedure For Assessing Power System Reliability In Preparation For Nerc's Standards Compliance, Frederico Von Pinho

Electrical Engineering Theses - Archive

In response to historical reliability issues of the past and following the evolution of newly developing power system markets, NERC has created new standards for maintaining and enforcing power system reliability. Entities are still reviewing the standards and finding ways to comply with the same. Non-compliance can result in financial penalties that can add-up to $1M per day per violation.The aim of this thesis is to propose a procedure to be followed by entities wishing to comply with NERC's reliability requirements for a preliminary determination/understanding of the current reliability situation of the system and therefore foresee any difficulties might appear …

Go to article

Evaluation Of Iso 18000-6 Type C Class 1 Generation 2 Rfid Protocol Artifacts, Nikhil Ayer Jan 2008

Evaluation Of Iso 18000-6 Type C Class 1 Generation 2 Rfid Protocol Artifacts, Nikhil Ayer

Electrical Engineering Theses - Archive

In this thesis, we have identified the effect on the performance of the RFID system when ISO 18000-6 Class 1 Gen 2 RFID protocol's parameters are changed. The protocol parameters we considered changing for the conformance testing are Tari, operating frequency, pulse width and modulation index at the constant transmitted power. The range of frequencies used in the experiments does fall outside the specification of ISO 18000-6 Type-C Class-1 Gen-2 protocol; but the power transmited by the RFID reader is under the FCC regulations. The research gives the detail behavior of the RFID signal propagation both from the reader to …

Go to article

Nonrigid Image Registration By The Deformation Based Grid Generation, Chih-Yao Hsieh Jan 2008

Nonrigid Image Registration By The Deformation Based Grid Generation, Chih-Yao Hsieh

Computer Science and Engineering Dissertations - Archive

A novel nonrigid image registration algorithm is developed using a well-established mathematic work known as deformation based grid generation. The deformation based grid generation is capable to generate a grid free of mesh folding, which is achieved by devising a positive monitor function describing the anticipated grid point density in the computational domain. Based on this method, a novel nonrigid image registration algorithm is successfully developed with many interesting features. First of all, the functional to be optimized during the image registration process consists of only one term — the similarity term. Thus, no regularization functional is required in this …

Go to article

Searching And Ranking Xml Data In A Distributed Environment, Weimin He Jan 2008

Searching And Ranking Xml Data In A Distributed Environment, Weimin He

Computer Science and Engineering Dissertations - Archive

Due to the increasing number of independent data providers on the web, there is a growing number of web applications that require searching and querying data sources distributed at different locations over the internet. Since XML is rapidlygaining in popularity as a universal data format for data exchange and integration, locating and ranking distributed XML data on the web are gaining importance in the database community. Most of existing XML indexing techniques combine structure indexes and inverted lists extracted from XML documents to fully evaluate a full-text query against these indexes and return the actual XML fragments of the query …

Go to article

Regridding In Nonrigid Image Registration, Ting-Hung Lin Jan 2008

Regridding In Nonrigid Image Registration, Ting-Hung Lin

Computer Science and Engineering Dissertations - Archive

Regridding was first introduced in viscous fluid registration for preventing folding of the transformation and for maintaining the admissible deformation field in large-deformation nonrigid image registration applications. We investigated the application of regridding to leading nonrigid image registration algorithms, including elastic, fluid, diffusion, curvature, and demons algorithms, and compared the performance and accuracy in each case.We also introduce a grid repairing mechanism based on the adaptive grid-generation method to prevent the transformation from folding. The grid repairing method can be used in conjunction with the proposed regridding scheme to set bounds on the Jacobian determinant of the transformation. We showed …

Go to article

First Prev Next Last