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Articles 1 - 30 of 74
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Error Estimation And Grid Adaptation For Functional Outputs Using Discrete-Adjoint Sensitivity Analysis, Ravishankar Balasubramanian
Error Estimation And Grid Adaptation For Functional Outputs Using Discrete-Adjoint Sensitivity Analysis, Ravishankar Balasubramanian
Theses and Dissertations
Within the design process, computational fluid dynamics is typically used to compute specific quantities that assess the performance of the apparatus under investigation. These quantities are usually integral output functions such as force and moment coefficients. However, to accurately model the configuration, the geometric features and the resulting physical phenomena must be adequately resolved. Due to limited computational resources a compromise must be made between the fidelity of the solution obtained and the available resources. This creates a degree of uncertainty about the error in the computed output functions. To this end, the current study attempts to address this problem …
Evaluation Of The Effectiveness Of Radar Obstacle Detection Systems When Used On Industrial Lift Trucks, Oluwatosin Toluwalase Odetola
Evaluation Of The Effectiveness Of Radar Obstacle Detection Systems When Used On Industrial Lift Trucks, Oluwatosin Toluwalase Odetola
Theses and Dissertations
This study addresses the application and the effectiveness of radar obstacle sensors for forklift trucks during reverse travel. Two different discriminating radar obstacle sensors with different outputs are evaluated. This study reviews the safety of human exposure to emissions from these radar sensors; documents the field of view obtained from experiments with the two systems; gives the results from experiments with sensors on lift trucks. The influence of obstacle reflectivity, composition and area on the size and shape of the radar detection zone are discussed. An experimental setup for measuring position and velocity of the obstacle crossing the truck path …
Surface Mesh Generation Using Curvature-Based Refinement, Bhaskar Sinha
Surface Mesh Generation Using Curvature-Based Refinement, Bhaskar Sinha
Theses and Dissertations
Surface mesh generation is a critical component of the mesh generation process. The objective of the described effort was to determine if a combination of constrained Delaunay triangulation (for triangles), advancing front method (for quadrilaterals), curvature-based refinement, smoothing, and reconnection is a viable approach for discretizing a NURBS patch holding the boundary nodes fixed. The approach is significant when coupled with recently developed geometry specification that explicitly identifies common edges. This thesis describes the various techniques used to achieve the above objectives. Application of this approach to several representative geometries demonstrates that it is an effective alternative to traditional approaches.
Self-Smoothing Functional Estimation, Bronson Thomas Yake
Self-Smoothing Functional Estimation, Bronson Thomas Yake
Theses and Dissertations
Analysis of measured data is often required when there is no deep understanding of the mathematics that accurately describes the process being measured. Additionally, realistic estimation of the derivative of measured data is often useful. Current techniques of accomplishing this type of data analysis are labor intensive, prone to significant error, and highly dependent on the expertise of the engineer performing the analysis. The ?Self-Smoothing Functional Estimation? (SSFE) algorithm was developed to automate the analysis of measured data and to provide a reliable basis for the extraction of derivative information. In addition to the mathematical development of the SSFE algorithm, …
Code Verification Using The Method Of Manufactured Solutions, Vasanth Kumar Murali
Code Verification Using The Method Of Manufactured Solutions, Vasanth Kumar Murali
Theses and Dissertations
Implementations of numerical simulations for solving systems of partial differential equations are often not verified and are falsely assumed to work correctly. As a result, the implementations are prone to coding errors that could degrade the accuracy of the solution. In order to ensure that a code is written correctly, rigorous verification of all parts of the code is necessary. Code verification is the task of ascertaining whether a numerical algorithm is solving the governing equations of the problem correctly. If an exact solution existed for the governing equations then verification would be easier but these solutions are rare because …
Condensation Heat Transfer In Horizontal Micro-Fin Tubes, Chea-Chun Kung
Condensation Heat Transfer In Horizontal Micro-Fin Tubes, Chea-Chun Kung
Theses and Dissertations
Three existing condensation heat transfer models are validated using 544 experimental data points for pure refrigerants and refrigerant mixtures. The Cavallini et al. (1999) model predicts well with the pure-refrigerant data sets. However, the Cavallini et al. (1999) model fails to predict the refrigerant-mixture data sets. The Yu and Koyama (1998) model, which is applicable for the pure refrigerants only, fails to predict most of the R22 data sets. The Kedzierski and Goncalves (1999) model, which is applicable for both pure refrigerants and refrigerant mixtures, yields relatively high mean absolute deviations for most of the pure-refrigerant data sets. The Kedzierski …
Growth Of 6h-Sic Homoepitaxy On Substrates Off-Cut Between The [01-10] Planes, James Dennis Vandersand Jr
Growth Of 6h-Sic Homoepitaxy On Substrates Off-Cut Between The [01-10] Planes, James Dennis Vandersand Jr
Theses and Dissertations
The wide band-gap semiconductor silicon carbide has tremendous potential for use in high power, high temperature, and high frequency electronic devices. One of the more important design factors for these devices is the epitaxial layer. It is desirable that this thin film have uniform polytype, thickness, and impurity concentration, as well as be defect free. One method used for SiC to ensure epitaxial layers with homogenous polytype is to cut wafers from a boule that has been tilted towards a specific crystallographic face at a fixed angle (known as ?off cut?). The purpose of this thesis was to investigate the …
Two And Three-Dimensional Finite Element Analysis Of Plasticity-Induced Fatigue Crack Closure: A Comprehensive Parametric Study, Kiran N. Solanki
Two And Three-Dimensional Finite Element Analysis Of Plasticity-Induced Fatigue Crack Closure: A Comprehensive Parametric Study, Kiran N. Solanki
Theses and Dissertations
Finite element analyses are frequently used to model growing fatigue cracks and the associated plasticity-induced crack closure. Two-dimensional, elastic-perfectly plastic finite element analyses of middle-crack tension (M(T)), bend (SEB), and compact tension (C(T)) geometries were conducted to study fatigue crack closure and to calculate the crack opening values under plane-strain and plane-stress conditions. The loading was selected to give the same maximum stress intensity factor in both geometries, and thus similar initial forward plastic zone sizes. Mesh refinement studies were performed on all geometries with various element types. For the C(T) geometry, negligible crack opening loads under plane-strain conditions were …
Integration Of Zero-Valent Metals And Chemical Oxidation For The Destruction Of 2,4,6-Trinitrotoluene Within Aqueous Matrices, Rafael Hernandez
Integration Of Zero-Valent Metals And Chemical Oxidation For The Destruction Of 2,4,6-Trinitrotoluene Within Aqueous Matrices, Rafael Hernandez
Theses and Dissertations
The Department of Defense (DoD) has numerous sites that contain groundwater contaminated with 2,4,6-trinitrotoluene (TNT). The currently applied technologies for treating TNT contaminated waters are carbon adsorption and chemical oxidation. Carbon adsorption is a non-destructive technology, which could create future liability issues and is inefficient at relatively low TNT concentrations. On the other hand, application of chemical oxidation for the treatment of TNT contaminated water generates trinitrobenzene (TNB), a by-product of the incomplete oxidation of TNT. TNB is regulated as strictly as TNT. Additionally, over 70% of the reactor required treatment time for meeting target levels is due solely for …
Experimental Studies Of The Drag Of An Axisymmetric Submarine Hull, John Lindsley Freudenthal
Experimental Studies Of The Drag Of An Axisymmetric Submarine Hull, John Lindsley Freudenthal
Theses and Dissertations
The purpose of these studies was to measure the drag coefficient of a small model submarine to add data to a Reynolds number study. First, a laser Doppler velocimeter (LDV) was used to measure the flow characteristics of the Mississippi State University water tunnel. The velocity and turbulence intensity profiles were measured for a range of freestream velocities of 8.6 m/s to 10.7 m/s. Several wake velocity profiles were taken for a model submarine at downstream distances of x/d = 10 to x/d = 28, with a freestream velocity of 8.6 m/s. A formula for the drag coefficient that uses …
Adsorption Of Organic Pollutants Onto Natural Adsorbents, Arun Subramani
Adsorption Of Organic Pollutants Onto Natural Adsorbents, Arun Subramani
Theses and Dissertations
In this research, the adsorptive capacities of kenaf, peat moss, hay, and peanut hulls were evaluated for the removal of TNT and 2,4-DCP from aqueous solutions. Adsorbent loading capacities determined by batch studies were verified by continuous column experiments. It was found that the adsorption capacity of the candidate adsorbents were significantly lower than granular activated carbon (GAC). The impact of surface modification techniques, such as surface oxidation, were evaluated to study the effect on adsorption capacity. At lower equilibrium concentrations of the adsorbate (less than 10 ppb), surface oxidation by ozone showed an increase in the adsorption capacity. The …
An Analysis For Evaluating The Cost/Profit Effectiveness Of Parallel Systems, Maria Teran
An Analysis For Evaluating The Cost/Profit Effectiveness Of Parallel Systems, Maria Teran
Theses and Dissertations
A new domain of commercial applications demands the development of inexpensive parallel computing platforms to lower the cost of operations and increase the business profit. The calculation of returns on an IT investment is now important to justify the decision of upgrading or replacing parallel systems. This thesis presents a framework of the performance and economic factors that are considered when evaluating a parallel system. We introduce a metric called the cost/profit effective metric, which measures the effectiveness of a parallel system in terms of performance, cost and profit. This metric describes the profit obtained from the performance of three …
Sic Etch Development In A Lam Tcp 9400se Ii System, Janna Rea Bonds
Sic Etch Development In A Lam Tcp 9400se Ii System, Janna Rea Bonds
Theses and Dissertations
SiC etch development has been performed in a Lam TCP 9400SE II system (a system meant for polysilicon etching and modified for SiC etching). SiC etching has never been reported in this particular system. Various parameters (carrier material, pressure, gas additives, gas flow, and electrode power) were examined and their effects determined on etch rate and resulting surface morphology. An efficient carrier material (graphite), operating pressure (25 mTorr), and gas flow rate (30 sccm) for obtaining peak etch rates were determined for this system. Peak etch rates of 1254 Å/min. in CHF3:O2, 4314 Å/min. in SF6:O2, and 1255 Å/min. in …
Application Of Generalized Grids To Turbomachinery Cfd Simulations, Rajkeshar Singh
Application Of Generalized Grids To Turbomachinery Cfd Simulations, Rajkeshar Singh
Theses and Dissertations
A generalized grid based technique was developed for handling the relative motion of grids in CFD simulations involving rotating machineries. In the present method, the relative motion between the grid blocks is handled by splitting the cellaces at the interface and updating the grid data structure appropriately. The resulting grid will have cells and cellaces with an arbitrary number of nodes and which are stored in a cellace based data structure. The current methodology is developed for cells with any number of nodes. However, the present work supports only tetrahedral elements at the interface of the rotating grid-blocks at the …
Best Effort Mpi/Rt As An Alternative To Mpi: Design And Performance Comparison, Raghavendra Angadi
Best Effort Mpi/Rt As An Alternative To Mpi: Design And Performance Comparison, Raghavendra Angadi
Theses and Dissertations
The Real-Time Message Passing Interface (MPI/RT) is an emerging real-time communications middleware standard for distributed real-time applications. The Message Passing Interface (MPI) is the de facto standard for high performance parallel application development. In this thesis, we describe how MPI/RT with best effort quality of service can be used as an alternative for MPI. Mercury Computer Systems' RACE embedded parallel computer is used as the platform for comparison of design and performance of these two standards. The main advantages MPI/RT has over MPI are its explicit support for communication channels and its emphasis on early binding. Design and implementation of …
Development Of Application Program For Harmonic Analysis, Sunitha Uppalapati
Development Of Application Program For Harmonic Analysis, Sunitha Uppalapati
Theses and Dissertations
Increased power quality problems due to intensive usage of power electronic devices resulted in development of software applications to perform quick harmonic analysis. However, the present harmonic analysis applications have special software or computer locks requirements and occupy huge memory and cost high. An application program (using Microsoft Visual C++) that is simple yet accurate in calculations; with no special software or high memory requirements is developed in this thesis work. The program uses the automatic acceptance criteria (AAC) and the harmonic penetration techniques in calculating the system voltages. Several userriendly features and tools that aid in better understanding of …
Dimensionality Reduction Of Hyperspectral Signatures For Optimized Detection Of Invasive Species, Abhinav Mathur
Dimensionality Reduction Of Hyperspectral Signatures For Optimized Detection Of Invasive Species, Abhinav Mathur
Theses and Dissertations
The aim of this thesis is to investigate the use of hyperspectral reflectance signals for the discrimination of cogongrass (Imperata cylindrica) from other subtly different vegetation species. Receiver operating characteristics (ROC) curves are used to determine which spectral bands should be considered as candidate features. Multivariate statistical analysis is then applied to the candidate features to determine the optimum subset of spectral bands. Linear discriminant analysis (LDA) is used to compute the optimum linear combination of the selected subset to be used as a feature for classification. Similarly, for comparison purposes, ROC analysis, multivariate statistical analysis, and LDA are utilized …
Efficient Reliability Estimation Approach For Analysis And Optimization Of Composite Structures, Mukti Nath Singh
Efficient Reliability Estimation Approach For Analysis And Optimization Of Composite Structures, Mukti Nath Singh
Theses and Dissertations
The efficient evaluation of reliability index is of considerable importance in the assessment of component reliability and reliability-based structural optimization. In this thesis, the structural reliabiltiy analysis is performed using the random sampling techniques such as traditional Monte Carlo simulation and the analytical techniques such as first-order reliability method. The feasibility of Gauss quadrature points as means of target sampling of design space and generating accurate first- and second-order response surface models of failure functions is examined. Parametric uncertainty is considered by probabilistic modeling of design parameters. Various alternative approaches for estimation of component reliability index are examined with application …
A Framework For Automatic Ontology Generation From Autonomous Web Applications, Giovanni Modica
A Framework For Automatic Ontology Generation From Autonomous Web Applications, Giovanni Modica
Theses and Dissertations
Ontologies capture the structure, relationships, semantics and other essential meta information of an application. This thesis describes a framework to automate application interoperability by using dynamically generated ontologies. We propose a set of techniques to extract ontologies from data accessible on the Web in the form of semi-structured HTML pages. Ontologies retrieved from similar applications are matched together to create a general ontology describing the application domain. Information retrieval and graph matching techniques are used to match and measure the usefulness of the ontologies created. Matching algorithms are combined together to produce global ontologies based on local ontologies inherently present …
Short Term Observations Of In Vitro Biocorrosion Of Two Commonly Used Implant Alloys, Hsin-Yi Lin
Short Term Observations Of In Vitro Biocorrosion Of Two Commonly Used Implant Alloys, Hsin-Yi Lin
Theses and Dissertations
Orthopedic metal implant materials may mediate a variety of adverse tissue reactions by releasing ions through corrosion. Adverse tissue reactions include inflammation, fibrosis and hypersensitivity. All of these reactions eventually lead to implant failure. The goal of this study was to provide a better understanding of the cellular-material interaction at the metal surface. The hypotheses were that 1. the attachment of cells and their released reactive inflammatory compounds (e.g. hydrogen peroxide H2O2, superoxide O2. and nitric oxide NO.) on the surfaces alter the alloys? corrosion and surface properties and 2. the changes in corrosion and chemical properties of the surfaces …
Small Signal Stability Of An Unregulated Power System, Vikas Singhvi
Small Signal Stability Of An Unregulated Power System, Vikas Singhvi
Theses and Dissertations
Rotor angle stability is the ability of the interconnected synchronous machines of a power system to remain in synchronism. This stability problem is concerned with the behavior of one or more synchronous machine after they have been perturbed. These perturbations can be small or large depending upon the type of disturbances considered. The work presented in this thesis is focused on the power system behavior when subjected to small disturbances. The ?small signal? disturbances are considered sufficiently small for the linearization of system equations to be permissible for the purpose of the analysis. The first step in the small signal …
Linear Unmixing Of Hyperspectral Signals Via Wavelet Feature Extraction, Jiang Li
Linear Unmixing Of Hyperspectral Signals Via Wavelet Feature Extraction, Jiang Li
Theses and Dissertations
A pixel in remotely sensed hyperspectral imagery is typically a mixture of multiple electromagnetic radiances from various ground cover materials. Spectral unmixing is a quantitative analysis procedure used to recognize constituent ground cover materials (or endmembers) and obtain their mixing proportions (or abundances) from a mixed pixel. The abundances are typically estimated using the least squares estimation (LSE) method based on the linear mixture model (LMM). This dissertation provides a complete investigation on how the use of appropriate features can improve the LSE of endmember abundances using remotely sensed hyperspectral signals. The dissertation shows how features based on signal classification …
Modeling Of Evaporation And Condensation Pressure-Drop In Micro-Fin Tubes, Meng-Onn Tan
Modeling Of Evaporation And Condensation Pressure-Drop In Micro-Fin Tubes, Meng-Onn Tan
Theses and Dissertations
Three existing pressure-drop models are validated and analyzed with experimental data compiled from the research database. From the analysis, it was found that the pressure-drop prediction results from the models are not very accurate and not consistent with all experimental datasets. A new pressure-drop model was consequently created based on the findings from the study, and experimental data from the database were used to validate the model to produce more accurate and consistent predictions. The new pressure-drop model was tested on experimental datasets that were in the database and also with experimental datasets that were not in the database. Good …
Relationships Between Reflectance And Soil Physical And Chemical Properties, Abdulrahman Mohammed Alrajehy
Relationships Between Reflectance And Soil Physical And Chemical Properties, Abdulrahman Mohammed Alrajehy
Theses and Dissertations
Soil chemical and physical properties are important to farm productivity, and they vary within fields, so farmers are interested in managing inputs like fertilizer according to local soil conditions within fields. Thus, they must have knowledge of soil conditions of interest, which have historically been measured at a few locations with tedious soil sampling and laboratory analyses. Advantageous to farmers would be a measurement method that provided more geographically detailed information at similar or lower cost. Remote and ground-based optical sensing are possibilities for gathering detailed soil information rapidly and inexpensively. This study considers the possibility of optically measuring soil …
Scheduling For Proportional Differentiated Services On The Internet, Manimaran Selvaraj
Scheduling For Proportional Differentiated Services On The Internet, Manimaran Selvaraj
Theses and Dissertations
Proportional Differentiated Services can be provisioned in terms of bandwidth, delay, or packet loss. Several studies contributed schedulers and packet droppers that achieved proportional bandwidth, delay, or loss differentiation. However, all these schemes differentiated in terms of only one of the three metrics. A simple, unified, scalable, and robust scheme to simultaneously control all three metrics was felt important. By controlling just delay and packet loss, proportional differentiation can be achieved in terms of all three metrics. A robust adaptive scheduler for proportional delay differentiation services is presented. Proportional services are further policed by a class based packet dropper. The …
Volute And Diffuser Performance Analysis For High Turning Turbine System, Runsong Xu
Volute And Diffuser Performance Analysis For High Turning Turbine System, Runsong Xu
Theses and Dissertations
Test results from a rocket turbine test model, called the Oxidizer Technology Turbine Rig (OTTR), are discussed in this paper. The turbine was designed to support the development of advanced turbines for future liquid rocket engines. It is a highly loaded single stage liquid oxygen pump drive turbine which uses inlet and exit volutes to provide optimum performance in a compact configuration. The system design creates high pressure and temperature gradients as well as high Mach number flow. These factors make it especially difficult to accurately measure the flowfield. Test issues such as probe calibration; probe interference, rake blockage, and …
A Trusted Environment For Mpi Programs, German Florez-Larrahondo
A Trusted Environment For Mpi Programs, German Florez-Larrahondo
Theses and Dissertations
Several algorithms have been proposed to implement intrusion detection systems (IDS) based on the idea that anomalies in the behavior of a system might be produced by a set of actions of an intruder or by a system fault. Almost no previous research has been conducted in the area of anomaly detection for high performance clusters. The research reported in this thesis demonstrates that the analysis of sequences of function calls issued by one or more processes can be used to verify the correct execution of parallel programs written in C/C++ with the Message Passing Interface (MPI) in a cluster …
Accuracy Study Of A Free Particle Using Quantum Trajectory Method On Message Passing Architecture, Ravi K. Vadapalli
Accuracy Study Of A Free Particle Using Quantum Trajectory Method On Message Passing Architecture, Ravi K. Vadapalli
Theses and Dissertations
Bhom's hydrodynamic formulation (or quantum fluid dynamics) is an attractive approach since, it connects classical and quantum mechanical theories of matter through Hamilton-Jacobi (HJ) theory, and quantum potential. Lopreore and Wyatt derived and implemented one-dimensional quantum trajectory method (QTM), a new wave-packet approach, for solving hydrodynamic equations of motion on serial computing environment. Brook et al. parallelized the QTM on shared memory computing environment using a partially implicit method, and conducted accuracy study of a free particle. These studies exhibited a strange behavior of the relative error for the probability density referred to as the transient effect. In the present …
An Advanced Signal Processing Toolkit For Java Applications, Vijay Pravin Shah
An Advanced Signal Processing Toolkit For Java Applications, Vijay Pravin Shah
Theses and Dissertations
The aim of this study is to examine the capability, performance, and relevance of a signal processing toolkit in Java, a programming language for Web-based applications. Due to the simplicity, ease and application use of the toolkit and with the advanced Internet technologies such as Remote Method Invocation (RMI), a spectral estimation applet has been created in the Java environment. This toolkit also provides an interactive and visual approach in understanding the various theoretical concepts of spectral estimation and shows the need to create more application applets to better understand the various concepts of signal and image processing. This study …
Upgrading And Qualification Of A Turbulent Heat Transfer Test Facility, Olumide Folorunso Odetola
Upgrading And Qualification Of A Turbulent Heat Transfer Test Facility, Olumide Folorunso Odetola
Theses and Dissertations
The Turbulent Heat Transfer Test Facility (THTTF) has been refurbished and the data acquisition system upgraded. The THTTF is now controlled by a LabView 4.1 program which replaces the old program in BASIC. Heat transfer data acquired using this new program is presented as Stanton number distributions. The new data set is compared to previously reported data obtained with this facility and other wellepted published data. This project has successfully qualified the THTTF for zero-pressure gradient, isothermal wall temperature, incompressible boundary-layer flow over smooth flat plates without transpiration. The THTTF is now set to accommodate modifications which will facilitate heat …