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Articles 1171 - 1189 of 1189
Full-Text Articles in Engineering
The Effect Of Process Variables On Microstructure In Laser-Deposited Materials, Srikanth Bontha
The Effect Of Process Variables On Microstructure In Laser-Deposited Materials, Srikanth Bontha
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The ability to predict and control microstructure in laser deposition processes requires an understanding of the thermal conditions at the onset of solidification. The focus of this work is the development of thermal process maps relating solidification cooling rate and thermal gradient (the key parameters controlling microstructure) to laser deposition process variables (laser power and velocity). The approach employs the well-known Rosenthal solution for a moving point heat source traversing an infinite substrate. Cooling rates and thermal gradients at the onset of solidification are numerically extracted from the Rosenthal solution throughout the depth of the melt pool, and dimensionless process …
A Formal Language Approach For Detecting Texture Paths And Patterns In Images, Prithviraj S. Patil
A Formal Language Approach For Detecting Texture Paths And Patterns In Images, Prithviraj S. Patil
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This Master thesis considers the use of formal languages representation for image processing, especially texture patterns and determining texture paths in them. The texture paths are detected and extracted by using image processing techniques, such as image segmentation to isolate regions of interest, and then the extraction of repeating textures. The detection of the texture blocks is obtained by recursively using 27 X 27, 9 X 9, and 3 X 3 windows. Predefined repeating texture patterns are also searched for in each of the sets. For each set of texture blocks with similar or same characteristics, curve fitting techniques are …
Investigation Into The Behavior Of Bolted Joints, Steven M. Page
Investigation Into The Behavior Of Bolted Joints, Steven M. Page
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Models to capture the physics of jointed structures have been proposed for over 40 years. These models approximate the behavior of the joint under carefully developed operating conditions. When these conditions change, the model has to be changed. Recent developments in numeric codes like finite elements have created interest in incorporating joint models into the design process but joint models need to represent the joined structure over a broader operating range. This work investigates the dynamic response of a structure with a joint. Isolation of a few dominant effects may give way to a model able to capture a broader …
An (R,S)-Inventory Policy For Winter Maintenance Materials For The State Of Ohio, Nicholas Andrew Brown
An (R,S)-Inventory Policy For Winter Maintenance Materials For The State Of Ohio, Nicholas Andrew Brown
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Winters in Ohio mean snow and ice, and with snow and ice come treacherous roads. Roads that become treacherous or impassable cost the state economically and socially. Thus to prevent this from happening road crews are out spreading salt on the roads before, during, and after a storm to promote safe travel. To provide the amount of salt needed to all counties of Ohio; individual counties stock up during the summer and fall, re-order to maintain inventory through the winter time, and finally allowing inventories to reduce towards the end of winter. During a mild winter salt not used and …
Robust Estimation Of Reliability In The Presence Of Multiple Failure Modes, Phani R. Adduri
Robust Estimation Of Reliability In The Presence Of Multiple Failure Modes, Phani R. Adduri
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In structural design, every component or system needs to be tested to ascertain that it satisfies the desired safety levels. Due to the uncertainties associated with the operating conditions, design parameters, and material systems, this task becomes complex and expensive. Typically these uncertainties are defined using random, interval or fuzzy variables, depending on the information available. Analyzing components or systems in the presence of these different forms of uncertainty increases the computational cost considerably due to the iterative nature of these algorithms. Therefore, one of the objectives of this research was to develop methodologies that can efficiently handle multiple forms …
Investigating The Male-Driven Evolution Hypothesis Using Human AluRepeat Elements, Sridhar Ramachandran
Investigating The Male-Driven Evolution Hypothesis Using Human AluRepeat Elements, Sridhar Ramachandran
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Thousands of copies of short interspersed repeats (SINEs) are scattered essentially ran-domly through the human genome. Although copies of each repeat subfamily are identical at the time of their insertion, they become subject to individual substitutions after insertion. As the relative time of insertion is known for many of these repeats, such "junk DNA" can be used to provide a sizeable number of time-series data points for studying substitution effects in a variety of genomic contexts. This dissertation specifically discusses the usefulness of the Alufamily of SINE repeats towards addressing open problems in genomics, population genetics, and biology in …
Computational Study Of Ring-Cusp Magnet Configurations That Provide Maximum Electron Confinement, Taiwo A. Ogunjobi
Computational Study Of Ring-Cusp Magnet Configurations That Provide Maximum Electron Confinement, Taiwo A. Ogunjobi
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Enhancing the confinement of primary electrons within the plasma in a discharge chamber of an ion thruster improves plasma ionization and consequently the thruster's performance. This work computationally calculates the location, position, and orientation of the permanent magnets that provide a ring-cusp magnetic field that maximizes electron confinement in an axi-symmetric cylindrical aluminum-wall discharge chamber. Small samarium cobalt magnets are circumferentially arranged in a ring around the front, side, or back wall of the chamber. The generated ring-cusp magnetic field for any specified magnet configuration is calculated using MAXWELL2D, a two dimensional electromagnetic field simulation computer code. For various magnet …
Methodology For Quantifying Biomechanical Bone Movement Of Transtibial Amputations, Johanna C. Bell
Methodology For Quantifying Biomechanical Bone Movement Of Transtibial Amputations, Johanna C. Bell
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A controversy has long existed about an alternate below knee amputation procedure that may be more beneficial than the traditional transtibial amputation. The proponents of this alternate procedure that stabilizes the distal tibia and fibula claim it reduces excessive movement of the fibula relative to the tibia that occurs with common movements, such as walking. The purpose of this study is to develop a methodology for quantifying excessive movement of the fibula bone relative to the tibia bone in traditional below the knee amputations. The methodology will measure the movement and rotation of the fibula relative to the tibia. These …
A Field Programmable Gate Array Architecture For Two-Dimensional Partial Reconfiguration, Fei Wang
A Field Programmable Gate Array Architecture For Two-Dimensional Partial Reconfiguration, Fei Wang
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Reconfigurable machines can accelerate many applications by adapting to their needs through hardware reconfiguration. Partial reconfiguration allows the reconfiguration of a portion of a chip while the rest of the chip is busy working on tasks. Operating system models have been proposed for partially reconfigurable machines to handle the scheduling and placement of tasks. They are called OS4RC in this dissertation. The main goal of this research is to address some problems that come from the gap between OS4RC and existing chip architectures and the gap between OS4RC models and practical applications. Some existing OS4RC models are based on an …
Topology Optimization Of Engine Exhaust-Washed Structures, Mark A. Haney
Topology Optimization Of Engine Exhaust-Washed Structures, Mark A. Haney
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Aircraft structure subjected to elevated temperature and acoustic loading present a challenging design environment. Thermal stress in a structural component has typically been alleviated by allowing thermal expansion. However, very little work has been done which directly addresses the situation where such a prescription is not possible. When a structural component has failed due to thermally-induced tensile stresses, the answer to the question of how best to stiffen the structure is far from trivial. In this work, we demonstrate that conventional stiffening techniques, for example, those which add material to the thickness of a failing panel, may actually increase the …
Using In-Situ Error Tracking For Mode Selection In Proper Orthogonal Decomposition Reduced Order Modelling, Michael Richard Maddux
Using In-Situ Error Tracking For Mode Selection In Proper Orthogonal Decomposition Reduced Order Modelling, Michael Richard Maddux
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Proper Orthogonal Decomposition (POD) provides a method of analyzing data and/or creating a Reduced Order Model (ROM). In this thesis, POD is used to create a ROM comprised of basis functions onto which the governing equations of a Computational Fluid Dynamics (CFD) problem are projected via Galerkin's method. The model is of reduced order since the basis functions span a space smaller than the space from which they were created. A full order simulation called the training period is conducted first to obtain data to be used for creating the ROM using POD. The dominant characteristics are extracted from the …
System Analysis And Rf-Floodlight Exploitation Of Short-Range Gotcha Repeaters, Jose A. Montes De Oca
System Analysis And Rf-Floodlight Exploitation Of Short-Range Gotcha Repeaters, Jose A. Montes De Oca
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Emerging wide-area synthetic aperture radar (SAR) system concepts call for a single data collection platform to orbit a large ( e.g., 20-km) spot at a nominal range of 40-km. The large standoff distance and desire for fine resolution, coupled with a need for persistent real-time sensing, pose a significant challenge in terms of clutter-to-noise ratio (CNR) performance and data processing. Increased CNR and reduced processing load can be achieved by decreasing the range of the SAR system and the size of the area of interest. Employing multiple cooperating SAR systems allows the same overall coverage area to be maintained …
Large Scale Visualization Of Pulsed Vortex Generator Jets, Kenneth Jay Moore Jr.
Large Scale Visualization Of Pulsed Vortex Generator Jets, Kenneth Jay Moore Jr.
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The use of small jets of air has proven to be an effective means of flow control on low Reynolds number turbine blades. Pulsing of these jets has also shown benefits in reducing the amount of air needed to achieve the same level of flow control. An experiment using Hot Wire Anemometry and Particle Image Velocimetry (PIV) has been used to investigate how these pulsed jets interact with the boundary layer to help keep the flow attached. A 25x scaled jet in a flat plate has been utilized. The 25.4 mm diameter jet has a pitch angle of 30° and …
Pattern Recognition Via Machine Learning With Genetic Decision-Programming, Carl C. Hoff
Pattern Recognition Via Machine Learning With Genetic Decision-Programming, Carl C. Hoff
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In the intersection of pattern recognition, machine learning, and evolutionary computation is a new search technique by which computers might program themselves. That technique is called genetic decision-programming. A computer can gain the ability to distinguish among the things that it needs to recognize by using genetic decision-programming for pattern discovery and concept learning. Those patterns and concepts can be easily encoded in the spines of a decision program (tree or diagram). A spine consists of two parts: (1) the test-outcome pairs along a path from the program's root to any of its leaves and (2) the conclusion in that …
Nano-Coatings On Carbon Structures For Interfacial Modification, Rajasekhar Venkata Pulikollu
Nano-Coatings On Carbon Structures For Interfacial Modification, Rajasekhar Venkata Pulikollu
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Surface modification of materials is a rapidly growing field as structures become smaller, more integrated and complex. It opens up the possibility of combining the optimum bulk properties of a material with optimized surface properties such as enhanced bonding, corrosion resistance, reactivity, stress transfer, and thermal, optical or electrical behavior. Therefore, surface functionalization or modification can be an enabling step in a wide variety of modern applications. In this dissertation several surface modification approaches on carbon foam and carbon nano-fibers will be discussed. These are recently developed sp 2 graphitic carbon based structures that have significant potential in aerospace, automotive …
Feasibility Of Radiographic Absorptiometry Of The Mandible As An Osteoporosis Screening Method, Julie A. Skipper
Feasibility Of Radiographic Absorptiometry Of The Mandible As An Osteoporosis Screening Method, Julie A. Skipper
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The purpose of this work was to develop and evaluate single- and dual-energy radiographic absorptiometry (RA) for the measurement of mandibular bone mineral density (BMD), using standard dental equipment, that would allow for inexpensive and widespread osteoporosis screening. Accurately measured x-ray tube spectra are important for validating the simulations used in the design of the method. A constrained least-squares deconvolution technique for reducing the detector-induced blurring of the energy spectrum was developed. Application of this analytic correction to spectra acquired with a NaI-photomultiplier detector improved the measured data by 20-60%. Implementation of the screening method is accomplished by simultaneously acquiring …
Innovative Forced Response Analysis Method Applied To A Transonic Compressor, Timothy M. Hutton
Innovative Forced Response Analysis Method Applied To A Transonic Compressor, Timothy M. Hutton
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A set of inlet guide vane (IGV) unsteady surface pressure measurements of a transonic compressor is presented. Using a flexible pressure sensor array, unsteady IGV suction-surface and pressure-surface pressures are acquired for six spanwise by five chordwise locations for various speed lines and throttle settings. Measurements from this sensor array are used to investigate unsteady vane/blade interaction aeromechanical forcing functions in a modern, highly loaded compressor stage. A significant effect is shown on the unsteady forced response of the IGV with changes in compressor operating point and IGV/rotor axial spacing for various span and chord locations. In particular, variations in …
Plastic Dissipation Energy In Mixed-Mode Fatigue Crack Growth On Ductile Bimaterial Interfaces, Jeremy S. Daily
Plastic Dissipation Energy In Mixed-Mode Fatigue Crack Growth On Ductile Bimaterial Interfaces, Jeremy S. Daily
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A new theory of fatigue crack growth in ductile solids has recently been proposed based on the total plastic energy dissipation per cycle ahead of the crack. This and previous energy-based approaches in the literature suggest that the total plastic dissipation per cycle can be closely correlated with fatigue crack growth rates under Mode I loading. The goal of the current study is to extend the dissipated energy approach to steady-state crack growth under mixed-mode loading conditions, with application to cyclic delamination of ductile interfaces in layered materials. The total plastic dissipation per cycle is obtained by 2-D elastic-plastic finite …
Defining Benthic Organism Exposure: Bioavailability And Effects Of Non-Polar Organics, Marc Samuel Greenberg
Defining Benthic Organism Exposure: Bioavailability And Effects Of Non-Polar Organics, Marc Samuel Greenberg
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Laboratory and field tests were conducted to evaluate the hypothesis that factors such as the total organic carbon (TOC) contents and groundwater-surface water interactions (GSI) in the sediments can affect chemical desorption, bioavailability and benthic organism exposure. Laboratory studies were conducted with the polycyclic aromatic hydrocarbon fluoranthene (FLU) and the herbicide trifluralin (TF). Toxicokinetic parameters were determined for Lumbriculus variegatus and Hyalella azteca in water-only exposures to 0, 5, 20 and 50 µg/L of the compounds and bioaccumulation was measured during exposures to 0, 100 and 200 mg/kg of FLU and TF spiked onto sediments from Lakes Erie and Huron. …