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2009

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Articles 3331 - 3360 of 4158

Full-Text Articles in Engineering

Low Temperature And Reduced Length Scale Behavior Of Shape Memory And Superelastic Niti And Nitife Alloys, Radhakrishnan Manjeri Jan 2009

Low Temperature And Reduced Length Scale Behavior Of Shape Memory And Superelastic Niti And Nitife Alloys, Radhakrishnan Manjeri

Electronic Theses and Dissertations

Shape memory and superelastic applications of NiTi based alloys have typically been limited to near room temperature or to bulk length scales. The objective of this work is two-fold: first, to investigate shape memory behavior at low temperatures in the context of the R-phase transformation in NiTiFe alloys by recourse to arc-melting, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and mechanical testing at low temperatures; and second, to investigate superelasticity and two-way shape memory behavior at reduced length scales in the context of NiTi by recourse to micro-compression, micro-indentation and TEM studies. Selected compositions of ternary NiTiFe shape memory …

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Design, Fabrication And Testing Of A Low Temperature Heat Pipe Thermal Switch With Shape Memory Helical Actuators, Othmane Benafan Jan 2009

Design, Fabrication And Testing Of A Low Temperature Heat Pipe Thermal Switch With Shape Memory Helical Actuators, Othmane Benafan

Electronic Theses and Dissertations

This work reports on the design, fabrication and testing of a thermal switch wherein the open and closed states are actuated by shape memory alloy elements while heat is transferred by a heat-pipe. The motivation for such a switch comes from NASA's need for thermal management in advanced spaceport applications associated with future lunar and Mars missions. For example, as the temperature can approximately vary between 40 K to 400 K during lunar day/night cycles, such a switch can reject heat from a cryogen tank in to space during the night cycle while providing thermal isolation during the day cycle. …

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Magnetically Deflectable Mems Actuators For Optical Sensing Applications, Matthew Montgomery Jan 2009

Magnetically Deflectable Mems Actuators For Optical Sensing Applications, Matthew Montgomery

Electronic Theses and Dissertations

In this work, new small deflection magnetic actuators have been proposed, designed, and tested for applications in Surface Enhanced Raman Scattering optical sensors. Despite the fact that SERS sensors have been shown to increase Raman over ten orders of magnitude for molecular detection, several technological challenges have prevented the design of practical sensors, such as making SERS sensors that can efficiently detect a wide variety of molecules. Since the optimum signal-to-noise in SERS occurs at different excitation wavelengths for different molecules, individual metal nanostructures need to be designed and fabricated for each independent chemical species. One possible solution to this …

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Numerical Solution Of The Two-Phase Incompressible Navier-Stokes Equations Using A Gpu-Accelerated Meshless Method, Jesse Kelly Jan 2009

Numerical Solution Of The Two-Phase Incompressible Navier-Stokes Equations Using A Gpu-Accelerated Meshless Method, Jesse Kelly

HIM 1990-2015

This project presents the development and implementation of a GPU-accelerated meshless two-phase incompressible fluid flow solver. The solver uses a variant of the Generalized Finite Difference Meshless Method presented by Gerace et al. [1]. The Level Set Method [2] is used for capturing the fluid interface. The Compute Unified Device Architecture (CUDA) language for general-purpose computing on the graphics-processing-unit is used to implement the GPU-accelerated portions of the solver. CUDA allows the programmer to take advantage of the massive parallelism offered by the GPU at a cost that is significantly lower than other parallel computing options. Through the combined use …

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Automatic Graphics And Game Content Generation Through Evolutionary Computation, Erin Hastings Jan 2009

Automatic Graphics And Game Content Generation Through Evolutionary Computation, Erin Hastings

Electronic Theses and Dissertations

Simulation and game content includes the levels, models, textures, items, and other objects encountered and possessed by players during the game. In most modern video games and simulation software, the set of content shipped with the product is static and unchanging, or at best, randomized within a narrow set of parameters. However, ideally, if game content could be constantly and automatically renewed, players would remain engaged longer in the evolving stream of content. This dissertation introduces three novel technologies that together realize this ambition. (1) The first, NEAT Particles, is an evolutionary method to enable users to quickly and easily …

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Unsupervised Building Detection From Irregularly Spaced Lidar And Aerial Imagery, Nicholas Shorter Jan 2009

Unsupervised Building Detection From Irregularly Spaced Lidar And Aerial Imagery, Nicholas Shorter

Electronic Theses and Dissertations

As more data sources containing 3-D information are becoming available, an increased interest in 3-D imaging has emerged. Among these is the 3-D reconstruction of buildings and other man-made structures. A necessary preprocessing step is the detection and isolation of individual buildings that subsequently can be reconstructed in 3-D using various methodologies. Applications for both building detection and reconstruction have commercial use for urban planning, network planning for mobile communication (cell phone tower placement), spatial analysis of air pollution and noise nuisances, microclimate investigations, geographical information systems, security services and change detection from areas affected by natural disasters. Building detection …

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Detecting Malicious Software By Dynamicexecution, Jianyong Dai Jan 2009

Detecting Malicious Software By Dynamicexecution, Jianyong Dai

Electronic Theses and Dissertations

Traditional way to detect malicious software is based on signature matching. However, signature matching only detects known malicious software. In order to detect unknown malicious software, it is necessary to analyze the software for its impact on the system when the software is executed. In one approach, the software code can be statically analyzed for any malicious patterns. Another approach is to execute the program and determine the nature of the program dynamically. Since the execution of malicious code may have negative impact on the system, the code must be executed in a controlled environment. For that purpose, we have …

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Exploring Additional Factors Of Presence, Dustin Chertoff Jan 2009

Exploring Additional Factors Of Presence, Dustin Chertoff

Electronic Theses and Dissertations

One of the oft cited reasons for virtual environments is that they provide experiences with places one would never be able to visit and to perform tasks that would otherwise be dangerous, or inaccessible. The ability to become transported to another environment, such that you think you are "there," is known as presence. Existing presence literature focuses largely on the sensory aspects of virtual environment experiences. However, there is more to experience than what is sensed. This dissertation investigates the theoretical components of holistic experiences in virtual environments. In order to explore the relationship between experiential design and presence, a …

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Study Of Gate Oxide Breakdown And Hot Electron Effect On Cmos Circuit Performances, Jun Ma Jan 2009

Study Of Gate Oxide Breakdown And Hot Electron Effect On Cmos Circuit Performances, Jun Ma

Electronic Theses and Dissertations

In the modern semiconductor world, there is a significant scaling of the transistor dimensions--The transistor gate length and the gate oxide thickness drop down to only several nanometers. Today the semiconductor industry is already dominated by submicron devices and other material devices for the high transistor density and performance enhancement. In this case, the semiconductor reliability issues are the most important thing for commercialization. The major reliability issues caused by voltage are hot carrier effects (HCs) and gate oxide breakdown (BD) effects. These issues are recently more important to industry, due to the small size and high lateral field in …

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Using Student Mood And Task Performance To Train Classifier Algorithms To Select Effective Coaching Strategies Within Intelligent Tutoring Systems (Its), Robert Sottilare Jan 2009

Using Student Mood And Task Performance To Train Classifier Algorithms To Select Effective Coaching Strategies Within Intelligent Tutoring Systems (Its), Robert Sottilare

Electronic Theses and Dissertations

The ultimate goal of this research was to improve student performance by adjusting an Intelligent Tutoring System's (ITS) coaching strategy based on the student's mood. As a step toward this goal, this study evaluated the relationships between each student's mood variables (pleasure, arousal, dominance and mood intensity), the coaching strategy selected by the ITS and the student's performance. Outcomes included methods to increase the perception of the intelligent tutor to allow it to adapt coaching strategies (methods of instruction) to the student's affective needs to mitigate barriers to performance (e.g. negative affect) during the one-to-one tutoring process. The study evaluated …

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Data Entry Error In Mobile Keyboard Device Usage Subject To Cognitive, Environmental, And Communication Workload Stressors Present In Fully Activated Emergency Operations Centers, Samiullah Durrani Jan 2009

Data Entry Error In Mobile Keyboard Device Usage Subject To Cognitive, Environmental, And Communication Workload Stressors Present In Fully Activated Emergency Operations Centers, Samiullah Durrani

Electronic Theses and Dissertations

The diversity and dynamic nature of disaster management environments necessitate the use of convenient, yet reliable, tools for technology. While there have been many improvements in mitigating the effects of disasters, it is clearly evident by recent events, such as Hurricane Katrina that issues related to emergency response and management require considerable research and improvement to effectively respond to these situations. One of the links in a disaster management chain is the Emergency Operations Center (EOC). The EOC is a physical command center responsible for the overall strategic control of the disaster response and functions as an information and communication …

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Multicomponent Interdiffusion In Austenitic Ni-, Fe-Ni-Base Alloys And L12-Ni3al Intermetallic For High-Temperature Applications, Narayana Garimella Jan 2009

Multicomponent Interdiffusion In Austenitic Ni-, Fe-Ni-Base Alloys And L12-Ni3al Intermetallic For High-Temperature Applications, Narayana Garimella

Electronic Theses and Dissertations

Interdiffusion in multicomponent-multiphase alloys is commonly encountered in many materials systems. The developments of multicomponent-multiphase alloys require control of microstructure through appropriate heat treatment, involving solid-state transformations, precipitation processes, and surface modification, where the interdiffusion processes play a major role. In addition, interdiffusion processes often control degradation and failure of these materials systems. Enhanced performance and reliable durability always requires a detailed understanding of interdiffusion. In this study, ternary and quaternary interdiffusion in Ni-Cr-X (X = Al, Si, Ge, Pd) at 900°C and 700°C, Fe-Ni-Cr-X (X = Si, Ge) at 900°C, and Ni3Al alloyed with Ir, Ta and Re at …

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Attacks On Difficult Instances Of Graph Isomorphism: Sequential And Parallel Algorithms, Greg Tener Jan 2009

Attacks On Difficult Instances Of Graph Isomorphism: Sequential And Parallel Algorithms, Greg Tener

Electronic Theses and Dissertations

The graph isomorphism problem has received a great deal of attention on both theoretical and practical fronts. However, a polynomial algorithm for the problem has yet to be found. Even so, the best of the existing algorithms perform well in practice; so well that it is challenging to find hard instances for them. The most efficient algorithms, for determining if a pair of graphs are isomorphic, are based on the individualization-refinement paradigm, pioneered by Brendan McKay in 1981 with his algorithm nauty. Nauty and various improved descendants of nauty, such as bliss and saucy, solve the graph isomorphism problem by …

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Concept Learning By Example Decomposition, Sameer Joshi Jan 2009

Concept Learning By Example Decomposition, Sameer Joshi

Electronic Theses and Dissertations

For efficient understanding and prediction in natural systems, even in artificially closed ones, we usually need to consider a number of factors that may combine in simple or complex ways. Additionally, many modern scientific disciplines face increasingly large datasets from which to extract knowledge (for example, genomics). Thus to learn all but the most trivial regularities in the natural world, we rely on different ways of simplifying the learning problem. One simplifying technique that is highly pervasive in nature is to break down a large learning problem into smaller ones; to learn the smaller, more manageable problems; and then to …

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Dod Acquisition Workforce Education: An Sba Education Case Study, Richard Davenport Jan 2009

Dod Acquisition Workforce Education: An Sba Education Case Study, Richard Davenport

Electronic Theses and Dissertations

A Department of Defense (DoD) M&S education task force is in the process of studying the Modeling and Simulation (M&S) education of the acquisition workforce. Historically, DoD acquisition workforce education is not referred to as education, but rather what the Defense Acquisition University (DAU) refers to as "practitioner training, career management, and services." The DAU is the organization primarily responsible for training the DoD acquisition corps in conjunction with service schools and strategic partners in the civilian sector. DAU programs primarily focus on program management, contracting, and management of logistics across the system life cycle. Further, the examples and cases …

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An Architecture For High-Performance Privacy-Preserving And Distributed Data Mining, James Secretan Jan 2009

An Architecture For High-Performance Privacy-Preserving And Distributed Data Mining, James Secretan

Electronic Theses and Dissertations

This dissertation discusses the development of an architecture and associated techniques to support Privacy Preserving and Distributed Data Mining. The field of Distributed Data Mining (DDM) attempts to solve the challenges inherent in coordinating data mining tasks with databases that are geographically distributed, through the application of parallel algorithms and grid computing concepts. The closely related field of Privacy Preserving Data Mining (PPDM) adds the dimension of privacy to the problem, trying to find ways that organizations can collaborate to mine their databases collectively, while at the same time preserving the privacy of their records. Developing data mining algorithms for …

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Validation Of Quickscat Radiometer (Qrad) Microwave Brightness Temperture Measurments, Rafik Hanna Jan 2009

Validation Of Quickscat Radiometer (Qrad) Microwave Brightness Temperture Measurments, Rafik Hanna

Electronic Theses and Dissertations

After the launch of NASA's SeaWinds scatterometer in 1999, a radiometer function was implemented in the Science Ground Data Processing Systems to allow the measurement of the earth's microwave brightness temperature. This dissertation presents results of a comprehensive validation to assess the quality of QRad brightness temperature measurements using near-simultaneous ocean Tb comparisons between the SeaWinds on QuikSCAT (QRad) and WindSat polarimetric radiometer on Coriolis. WindSat was selected because it is a well calibrated radiometer that has many suitable collocations with QuikSCAT; and it has a 10.7 GHz channel, which is close to QRad frequency of 13.4 GHz. Brightness temperature …

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Visual Inspection Of Railroad Tracks, Pavel Babenko Jan 2009

Visual Inspection Of Railroad Tracks, Pavel Babenko

Electronic Theses and Dissertations

In this dissertation, we have developed computer vision methods for measurement of rail gauge, and reliable identification and localization of structural defects in railroad tracks. The rail gauge is the distance between the innermost sides of the two parallel steel rails. We have developed two methods for evaluation of rail gauge. These methods were designed for different hardware setups: the first method works with two pairs of unaligned video cameras while the second method works with depth maps generated by paired laser range scanners. We have also developed a method for detection of rail defects such as damaged or missed …

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An Improved Hurrican Wind Vector Retrieval Algorithm Using Sea Winds Scatterometer, Peth Laupattarakasem Jan 2009

An Improved Hurrican Wind Vector Retrieval Algorithm Using Sea Winds Scatterometer, Peth Laupattarakasem

Electronic Theses and Dissertations

Over the last three decades, microwave remote sensing has played a significant role in ocean surface wind measurement, and several scatterometer missions have flown in space since early 1990's. Although they have been extremely successful for measuring ocean surface winds with high accuracy for the vast majority of marine weather conditions, unfortunately, the conventional scatterometer cannot measure extreme winds condition such as hurricane. The SeaWinds scatterometer, onboard the QuikSCAT satellite is NASA's only operating scatterometer at present. Like its predecessors, it measures global ocean vector winds; however, for a number of reasons, the quality of the measurements in hurricanes are …

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Design And Analysis Of Effective Routing And Channel Scheduling For Wavelength Division Multiplexing Optical Networks, Xingbo Gao Jan 2009

Design And Analysis Of Effective Routing And Channel Scheduling For Wavelength Division Multiplexing Optical Networks, Xingbo Gao

Electronic Theses and Dissertations

Optical networking, employing wavelength division multiplexing (WDM), is seen as the technology of the future for the Internet. This dissertation investigates several important problems affecting optical circuit switching (OCS) and optical burst switching (OBS) networks. Novel algorithms and new approaches to improve the performance of these networks through effective routing and channel scheduling are presented. Extensive simulations and analytical modeling have both been used to evaluate the effectiveness of the proposed algorithms in achieving lower blocking probability, better fairness as well as faster switching. The simulation tests were performed over a variety of optical network topologies including the ring and …

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Integrated Servomechanism And Process Control For Machining Processes, Yan Tang Jan 2009

Integrated Servomechanism And Process Control For Machining Processes, Yan Tang

Electronic Theses and Dissertations

In this research, the integration of the servomechanism control and process control for machining processes has been studied. As enabling strategies for next generation quality control, process monitoring and open architecture machine tools will be implemented on production floor. This trend brings a new method to implement control algorithm in machining processes. Instead of using separate modules for servomechanism control and process control individually, the integrated controller is proposed in this research to simultaneously achieve goals in servomechanism level and the process level. This research is motivated by the benefits brought by the integration of servomechanism control and process control. …

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Variable Resolution & Dimensional Mapping For 3d Model Optimization, Joseph Venezia Jan 2009

Variable Resolution & Dimensional Mapping For 3d Model Optimization, Joseph Venezia

Electronic Theses and Dissertations

Three-dimensional computer models, especially geospatial architectural data sets, can be visualized in the same way humans experience the world, providing a realistic, interactive experience. Scene familiarization, architectural analysis, scientific visualization, and many other applications would benefit from finely detailed, high resolution, 3D models. Automated methods to construct these 3D models traditionally has produced data sets that are often low fidelity or inaccurate; otherwise, they are initially highly detailed, but are very labor and time intensive to construct. Such data sets are often not practical for common real-time usage and are not easily updated. This thesis proposes Variable Resolution & Dimensional …

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Modeling Scenes And Human Activities In Videos, Arslan Basharat Jan 2009

Modeling Scenes And Human Activities In Videos, Arslan Basharat

Electronic Theses and Dissertations

In this dissertation, we address the problem of understanding human activities in videos by developing a two-pronged approach: coarse level modeling of scene activities and fine level modeling of individual activities. At the coarse level, where the resolution of the video is low, we rely on person tracks. At the fine level, richer features are available to identify different parts of the human body, therefore we rely on the body joint tracks. There are three main goals of this dissertation: (1) identify unusual activities at the coarse level, (2) recognize different activities at the fine level, and (3) predict the …

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Formation Of Lyotropic Liquid Crystals Through The Self-Assembly Of Bile Acid Building Blocks, Karan Tamhane Jan 2009

Formation Of Lyotropic Liquid Crystals Through The Self-Assembly Of Bile Acid Building Blocks, Karan Tamhane

Electronic Theses and Dissertations

Liquid crystalline materials (LCMs) have gained much popularity over the past century. The thermotropic forms of these materials have been extensively studied and employed in a range of innovative applications. The lyotropic liquid crystal systems that have been studied in the past have often been formed by the organization of natural and synthetic small molecules in solutions. In this study, we use self-assembled supramolecular structures as building blocks to fabricate lyotropic liquid crystals. We investigate the self-assembly of a naturally occurring bile acid called lithocholic acid (LCA), to form supramolecular fibrous and tubular structures in basic aqueous solutions. We control …

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Determining Emissions From Landfills And Creating Odor Buffer Distances, Nicholas Guarrieloo Jan 2009

Determining Emissions From Landfills And Creating Odor Buffer Distances, Nicholas Guarrieloo

Electronic Theses and Dissertations

With population growing every year, more and more people are looking for places to live. This can lead to construction of houses near and around landfills. As homes get closer to landfills, the odors these landfills produce become more of a problem, and lead to an increase in odor complaints. Modeling these odors and recommending odor buffer distances will help determine limits on how close to landfills new homes should be allowed. This should help reduce future odor complaints. To solve this problem one must accurately estimate odorous gas emissions from the landfill. Often odors can be indicated by methane …

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Analyses Of Crash Occurence And Injury Severities On Multi Lane Highways Using Machine Learning Algorithms, Abhishek Das Jan 2009

Analyses Of Crash Occurence And Injury Severities On Multi Lane Highways Using Machine Learning Algorithms, Abhishek Das

Electronic Theses and Dissertations

Reduction of crash occurrence on the various roadway locations (mid-block segments; signalized intersections; un-signalized intersections) and the mitigation of injury severity in the event of a crash are the major concerns of transportation safety engineers. Multi lane arterial roadways (excluding freeways and expressways) account for forty-three percent of fatal crashes in the state of Florida. Significant contributing causes fall under the broad categories of aggressive driver behavior; adverse weather and environmental conditions; and roadway geometric and traffic factors. The objective of this research was the implementation of innovative, state-of-the-art analytical methods to identify the contributing factors for crashes and injury …

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Phase Shaping In The Infrared By Planar Quasi-Periodic Surfaces Comprised Of Sub-Wavelength Elements, James Ginn Jan 2009

Phase Shaping In The Infrared By Planar Quasi-Periodic Surfaces Comprised Of Sub-Wavelength Elements, James Ginn

Electronic Theses and Dissertations

Reflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time--at frequencies as high as 194 THz. Relevant aspects of computational electromagnetic modeling are explored, to yield design procedures optimized for these high frequencies. Modeling is also utilized to demonstrate the phase response of a generalized …

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Electronic Properties And Microstructures Of Amorphous Sicn Ceramics Derived From Polymer Precursors, Tao Jiang Jan 2009

Electronic Properties And Microstructures Of Amorphous Sicn Ceramics Derived From Polymer Precursors, Tao Jiang

Electronic Theses and Dissertations

Polymer-derived ceramics (PDCs) are a new class of high-temperature materials synthesized by thermal decomposition of polymeric precursors. These materials possess many unique features as compared with conventional ceramics synthesized by powder metallurgy based processing. For example, PDCs are neither amorphous nor crystalline. Instead, they possess nano-domain structures. Due to the direct chemical-to-ceramic processing, PDCs can be used for making components and devices with complex shapes. Thus, understanding the properties and structures of these materials are of both fundamental and practical interest. In this work, the structures and electronic behavior of polymer-derived amorphous silicon carbonitrides (SiCNs) were investigated. The materials were …

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Stress Intensity Factor Dependence Of Hg-Al Liquid Metal Embrittlement, Scott Keller Jan 2009

Stress Intensity Factor Dependence Of Hg-Al Liquid Metal Embrittlement, Scott Keller

Electronic Theses and Dissertations

When high strength aluminum alloys are subjected to liquid metals, physical and chemical reactions ensue resulting in what is known as liquid metal embrittlement (LME). A subset of environmentally-assisted cracking, LME is exhibited when a liquid metal, e.g. Hg or Ga, comes into intimate contact with a solid metal having significant susceptibility. As mechanical loads are applied, the interaction between the two metals results in a reduction in the flow properties of the solid metal. Several theories have been proposed to identify the underlying microstructural failure mechanism; however, none have been widely accepted, as failures can typically incorporate features common …

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Pressure Drop And Endwall Heat Transfer Effects Of Porous Turbulators In A Rectangular Channel, Jared Pent Jan 2009

Pressure Drop And Endwall Heat Transfer Effects Of Porous Turbulators In A Rectangular Channel, Jared Pent

Electronic Theses and Dissertations

This study examines the local and averaged endwall heat transfer effects of a staggered array of porous pin fins within a rectangular channel. The porous pin fins were made from aluminum and had a pore density of 10 pores per inch (PPI). The pressure drop through the channel was also determined for several flow rates and presented in terms of the friction factor. Local heat transfer coefficients on the endwall were measured using Thermochromic Liquid Crystal (TLC) sheets recorded with a charge-coupled device (CCD) camera. Static and total pressure measurements were taken at the entrance and exit of the test …

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