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Articles 1 - 30 of 162
Full-Text Articles in Engineering
Characterization And Evaluation Of A Novel Tissue Engineered Aortic Heart Valve Construct, Mary Tedder
Characterization And Evaluation Of A Novel Tissue Engineered Aortic Heart Valve Construct, Mary Tedder
All Dissertations
Tissue engineering holds great promise for treatment of valvular diseases. Scaffolds for engineered heart valves must function immediately after implantation, but must also permit repopulation with autologous host cells and facilitate gradual remodeling.
Native aortic heart valves are composed of three layers, i.e. two strong external fibrous layers (ventricularis and fibrosa) separated by a central, highly hydrated spongiosa. The fibrous layers provide strength and resilience while the spongiosa layer facilitates shearing of the external layers. Our working hypothesis is that partially cross-linked collagen scaffolds that closely mimic the layered histo-architecture of the native valve would fulfill these requirements. To test …
An Investigation Of Metaheuristics Using Path- Relinking On The Quadratic Assignment Problem, Thashika Rupasinghe
An Investigation Of Metaheuristics Using Path- Relinking On The Quadratic Assignment Problem, Thashika Rupasinghe
All Dissertations
The Quadratic Assignment Problem (QAP) is a widely researched, yet complex, combinatorial optimization problem that is applicable in modeling many real-world problems. Specifically, many optimization problems are formulated as QAPs. To resolve QAPs, the recent trends have been to use metaheuristics rather than exact or heuristic methods, and many researchers have found that the use of hybrid metaheuristics is actually more effective. A newly proposed hybrid metaheuristic is path relinking (PR), which is used to generate solutions by combining two or more reference solutions. In this dissertation, we investigated these diversification and intensification mechanisms using QAP. To satisfy the extensive …
Sensitivity Analysis Of Uranium Speciation Modeling In Groundwater Systems With A Focus On Mobility, Andrew Scott
Sensitivity Analysis Of Uranium Speciation Modeling In Groundwater Systems With A Focus On Mobility, Andrew Scott
All Dissertations
Uranium is an important natural resource used in production of nuclear reactor fuel and nuclear weapons. The mining and processing of uranium has left a legacy of environmental contamination that remains to be addressed. There has been considerable interest in manipulating the oxidation state of uranium in order to put it into an environmentally immobile form. Uranium forms two stable oxidation states in nature, uranium (IV) being much less soluble than uranium (VI), and therefore the preferred state with regard to limiting the potential exposure of man. One of the tools used in evaluating potential effects of manipulating the natural …
Novel Vascular Grafts Based On Polyphenol-Stabilized Acellular Tissue Scaffolds, Ting-Hsien Chuang
Novel Vascular Grafts Based On Polyphenol-Stabilized Acellular Tissue Scaffolds, Ting-Hsien Chuang
All Dissertations
The Cardiovascular diseases (CVDs) continue to be the leading cause of morbidity and mortality worldwide. The most common form of CVDs is occlusion of blood flow thus limiting blood supply to specific tissues or organs. Atherosclerosis is a leading cause of coronary heart disease and stroke, which were responsible for more than 25% of deaths in 2004.
The demand for vascular graft is huge. In United States alone, approximately 500,000 coronary artery bypass graft surgeries are performed annually. Synthetic polymers such as Dacron and ePTFE have been successfully applied in large diameter blood vessel prosthesis; however, for small diameter (inner …
Effect Of Impurities On Performance Of Proton Exchange Membrane Fuel Cell Components, Kitiya Hongsirikarn
Effect Of Impurities On Performance Of Proton Exchange Membrane Fuel Cell Components, Kitiya Hongsirikarn
All Dissertations
It is believed that proton–exchange membrane fuel cells (PEMFCs) are going to be exploited as power generation devices for stationary, automotive, and portable applications in the near future because of their high performance and environmental friendliness. Up to the present, wide spread utilization of PEMFCs is not viable because of their cost and durability in the presence of fuel and oxidant stream impurities. These impurities include NH3, hydrocarbons, CO, CO2, halogenated compounds, cations, etc. The objective of this research was to investigate the effect of these harmful contaminants containing in the H2 fuel stream on …
Studies Relevant To The Design Of Reliable Automotive Electronics, Hua Zeng
Studies Relevant To The Design Of Reliable Automotive Electronics, Hua Zeng
All Dissertations
This dissertation describes three independent studies related to the design of reliable automotive electronics. The topics covered are: the estimation of the radiated emissions from power bus structures, EM propagation of tire pressure monitoring systems (TPMS), and examinations of corrosion-induced faults in a connector.
The first chapter describes a method for estimating the maximum possible radiated emissions from a printed circuit board power bus. An analysis based on a lossy cavity model is performed to determine the maximum possible radiated field corresponding to a given power bus noise voltage. A closed-form expression relating the maximum power bus noise voltage to …
A Self Organization-Based Optical Flow Estimator With Gpu Implementation, Manish Shiralkar
A Self Organization-Based Optical Flow Estimator With Gpu Implementation, Manish Shiralkar
All Dissertations
This work describes a parallelizable optical flow estimator that uses a modified batch version of
the Self Organizing Map (SOM). This gradient-based estimator handles the ill-posedness in motion
estimation via a novel combination of regression and a self organization strategy.
The aperture problem is explicitly modeled using an algebraic framework
that partitions motion estimates obtained from regression into two sets, one (set Hc) with estimates
with high confidence and another (set Hp) with low confidence estimates. The self organization step
uses a uniquely designed pair of training set (Q=Hc) and the initial weights set …
Circuit Modules For Broadband Cmos Six-Port Systems, Chaojiang Li
Circuit Modules For Broadband Cmos Six-Port Systems, Chaojiang Li
All Dissertations
This dissertation investigates four circuit modules used in a CMOS integrated six-port measurement system. The first circuit module is a wideband power source generator, which can be implemented with a voltage controlled ring oscillator. The second circuit module is a low-power 0.5 GHz - 20.5 GHz power detector with an embedded amplifier and a wideband quasi T-coil matching network. The third circuit module is a six-port circuit, which can be implemented with distributed or lumped- lement techniques. The fourth circuit module is the phase sifter used as calibration loads. The theoretical analysis, circuit design, simulated or experimental verifications of each …
Comprehensive Thermal Modeling Of Power Split Hybrid Power-Train And Electronics, Abdel Mayyas
Comprehensive Thermal Modeling Of Power Split Hybrid Power-Train And Electronics, Abdel Mayyas
All Dissertations
Hybrid electric vehicle (HEV) uses both internal combustion engine (ICE) with an electric system. The combination of the electric power train with the ICE is intended to achieve both better fuel economies than the conventional vehicles and better performance. Several types of HEV exist with different layouts. Recent HEVs' make use of regenerative braking, which converts the vehicles' kinetic energy into electric energy instead of wasting it as heat as conventional brakes do. A hybrid-electric is more fuel efficient than ICE and has less environmental impact.
The new HEV with its new Key Characteristics and Configurations (i.e. Mechanical complexity, Multiple …
Packet Error Rate Predictive Model For Sensor Radios On Fast Rotating Structures, Lei Tang
Packet Error Rate Predictive Model For Sensor Radios On Fast Rotating Structures, Lei Tang
All Dissertations
Wireless sensing technologies have raised widespread interests in the applications for monitoring fast rotating or moving machinery structures in manufacturing environments. Over the past five years, a few wireless sensor systems have been implemented and proven to feasibly work under fast rotation conditions. However, few of these studies evaluated data transmission performance of the wireless communication systems. Although the manufacturing environments are known to be harsh for wireless communication, in many cases, an excellent data throughput is critical for such systems. Conventional statistical methods for studying wireless communication channels are not sufficient in this specific field.
This dissertation presents systematic …
Synthesis, Stabilization, And Characterization Of Metal Nanoparticles, Gregory White Ii
Synthesis, Stabilization, And Characterization Of Metal Nanoparticles, Gregory White Ii
All Dissertations
Wet chemical synthesis techniques offer the ability to control various nanoparticle characteristics including size, shape, dispersibility in both aqueous and organic solvents, and tailored surface chemistries appropriate for different applications. Large quantities of stabilizing ligands or surfactants are often required during synthesis to achieve these nanoparticle characteristics. Unfortunately, excess reaction byproducts, surfactants, and ligands remaining in solution after nanoparticle synthesis can impede application, and therefore post-synthesis purification must be employed. A liquid-liquid solvent/anti-solvent pair (typically ethanol/toluene or ethanol/hexane for gold nanoparticles, GNPs) can be used to both purify and size-selectively fractionate hydrophobically modified nanoparticles. Alternatively, carbon dioxide may be used …
Modulated Properties Of Fully Absorbable Bicomponent Meshes, Shawn Peniston
Modulated Properties Of Fully Absorbable Bicomponent Meshes, Shawn Peniston
All Dissertations
Current meshes used for soft-tissue repair are mostly composed of single component, nonabsorbable yarn constructions, limiting the ability to modulate their properties. This situation has left the majority of soft tissue repair load-bearing applications to suffer distinctly from undesirable features associated, in part, with mesh inability to (1) possess short-term stiffness to facilitate tissue stability during the development of wound strength; (2) gradually transfer the perceived mechanical load as the wound builds mechanical integrity; and (3) provide compliance with load transfer to the remodeling and maturing mesh/tissue complex. The likelihood of long-term complications is reduced for fully absorbable systems with …
Predictive Energy Management In Connected Vehicles: Utilizing Route Information Preview For Energy Saving, Chen Zhang
Predictive Energy Management In Connected Vehicles: Utilizing Route Information Preview For Energy Saving, Chen Zhang
All Dissertations
This dissertation formulates algorithms that use preview information of road terrain and traffic flow for reducing energy use and emissions of modern vehicles with conventional or hybrid powertrains. Energy crisis, long term energy deficit, and more restrictive environmental protection policies require developing more efficient and cleaner vehicle powertrain systems. An alternative to making advanced technology engines or electrifying the vehicle powertrain is utilizing ambient terrain and traffic information in the energy management of vehicles, a topic which has not been emphasized in the past. Today's advances in vehicular telematics and advances in GIS (Geographic Information System), GPS (Global Positioning Systems), …
Modeling Microbial And Nutrient Dynamics In Zero-Discharge Aquaculture Systems, Kendall Kirk
Modeling Microbial And Nutrient Dynamics In Zero-Discharge Aquaculture Systems, Kendall Kirk
All Dissertations
A finite element, finite difference model was developed to predict nutrient and microbial dynamics in recirculating aquaculture systems. Total ammonia nitrogen, nitrite, nitrate, chemical oxygen demand, and dissolved oxygen concentrations are predicted in addition to growth and decay of algae, Nitrosomonas, Nitrobacter, denitrifying heterotrophs, and aerobic heterotrophs. Inputs to the model include temperature, photosynthetically available radiation, feed application rate, pH, aeration/mixing energy, water exchange configuration, water exchange rate, tilapia biomass, and dissolved oxygen concentration. Up to 10 exchanged units may be included, user-definable as continuous stirred tank reactors or sequencing batch reactors. Demonstration of the model's utility was demonstrated through …
Assortment Planning For Multiple Quality Levels Using Locational Choice, Mark Mcelreath
Assortment Planning For Multiple Quality Levels Using Locational Choice, Mark Mcelreath
All Dissertations
Assortment planning is the process in which a retailer selects a product line to offer to customers and is a key determinant of a retailer's profit. We consider the assortment planning problem using a locational choice model for customer product selection and allow for both horizontal and vertical product differentiation. When the distribution of customer preference is unimodal, the optimal solutions for this problem are unknown. We propose two solution philosophies for generating product assortments. First, we introduce a metaheuristic representation for the problem and test the performance of three metaheuristic techniques. We suggest that a tabu search or genetic …
A Study Of The Statistics Of The Air/Water Interfacial Temperature Field During Mixed Convection Heat Transfer, Jie Kou
All Dissertations
Heat transfer across an air/water interface is of particular importance to limnology, oceanography and some industrial applications. The relationship between the statistics of the air/water interfacial temperature field and the interfacial heat flux is poorly understood, particularly for the mixed convection condition, which is a common heat transfer mechanism for small inland lakes. The few studies that have been conducted under mixed convection conditions have been limited to an uncontrolled surfactant condition (tap water). Therefore, in this dissertation research two sets of experiments for wind speeds from 0 to 4 m/s were conducted: controlled surfactant contaminated conditions (with oleyl alcohol) …
Evaluation Of Factors That Modulate Cellular Adipogenesis For Breast Tissue Engineering Strategies, Cheryl Gomillion
Evaluation Of Factors That Modulate Cellular Adipogenesis For Breast Tissue Engineering Strategies, Cheryl Gomillion
All Dissertations
It is estimated that this year more than 200,000 women in the United States will be diagnosed with breast cancer. Treatment for most occurrences of breast cancer will often include surgical removal of the tumorigenic tissue, resulting in a soft tissue defect within the subcutaneous tissue of the skin. Post-surgical reconstruction methods are often sought by patients to restore the aesthetic function of the breast via cellular or non-cellular methods; however, because of complications associated with currently used methods for breast reconstruction, researchers are investigating tissue engineering methods to produce viable autologous adipose tissue for breast reconstruction.
Previous research in …
Offshore Wind Power Integration Into The South Carolina Power System, Mountaga Fane
Offshore Wind Power Integration Into The South Carolina Power System, Mountaga Fane
All Theses
The steady state analysis of the impact of offshore wind on the South Carolina power transmission was conducted in three phases of incremental wind energy injection into the system using forecasted base power flow. The simulation of Phase I involved the generation capacity of 80 MW projected for 2014 in state water. The modeling Phases II and III, which will distribute the energy among neighboring utilities, involve a supplementary capacity of 1000 MW projected for 2020 and 2000 MW for 2030 in federal water. In addition to this steady state investigation, a contingency analysis was performed on the power system …
Design Decisions Under Risk And Uncertainty, Sravya Thoomu
Design Decisions Under Risk And Uncertainty, Sravya Thoomu
All Theses
In the contemporary world of engineering, engineers strive towards designing reliable and robust artifacts while considering and attempting to control manufacturing costs. In due course they have to deal with some sort of uncertainty. Many aspects of the design are the result of properties that are defined within some tolerances, of measurements that are appropriate, and of circumstances and environmental conditions that are out of their control. This uncertainty was typically handled by using factors of safety, and resulted in designs that may have been overly conservative. Therefore, understanding and handling the uncertainties is critical in improving the design, controlling …
Determination Of Sorption Coefficients For Neptunium, Plutonium, Iodine, And Technetium In Engineered And Natural Systems Under Oxidizing And Reducing Conditions, Michael Lilley
All Theses
Plutonium, neptunium, technetium, and iodine present appreciable risks at nuclear waste disposal sites around the world due to their potential mobility. Sorption of each of these radionuclides is profoundly influenced by oxidation/ reduction reactions. Therefore, the mobility of each radionuclide may be greatly influenced by redox conditions of the natural or engineered system. The primary focus of this study was to determine distribution coefficients (Kd) for each radionuclide for engineered concrete and saltstone systems with varying amounts of reducing slag (a cement additive to create a reducing environment), and for iodide/iodate in natural sediments. Saltstones are a mixture …
Optimizing The Mechanical Properties Of Partially Yttria Stabilized Zirconia With Alumina Additions, Ramanaganapathy Kandaswamy
Optimizing The Mechanical Properties Of Partially Yttria Stabilized Zirconia With Alumina Additions, Ramanaganapathy Kandaswamy
All Theses
Zirconia is one of the extensively studied solid oxide ceramics with respect to its use in various industrial applications like electrolyte in fuel cells, sensors, refractories and exhaust chamber in automobile industry. It can be found from the literature 1-4 that are contradictory results on the mechanical properties when alumina is added. There are several factors like microstructure, phase composition and method of processing that affects the mechanical properties of the material. The focus of this research is to examine how hardness, tensile strength and other properties varies with alumina content and deduce the optimal amount of alumina that is …
Influence Of Topography Of Endovascular Stent Material On Smooth Muscle Cell Response, Vipul Taneja
Influence Of Topography Of Endovascular Stent Material On Smooth Muscle Cell Response, Vipul Taneja
All Theses
Although implantation of endovascular stents for the treatment of coronary and peripheral artery diseases has been one of the most rapidly used medical interventions, significant limitations in terms of a restenosis rate of 10-30% still persists. Neointimal hyperplasia characterized by a phenotypic shift of smooth muscle cells from contractile to synthetic type, has been deemed to be the predominant cause of restenosis. A number of stent surface parameters, including topography, have been attributed to play an important role in stent performance. Although endothelial cell and thrombotic response to surface roughness have been well evaluated, the effect of topography of the …
Vena Cava As An Alternative To Pericardium In Bioprosthetic Percutaneous Heart Valves, Amy Munnelly
Vena Cava As An Alternative To Pericardium In Bioprosthetic Percutaneous Heart Valves, Amy Munnelly
All Theses
Valve disease is a specialized form of cardiovascular disease that specifically affects the heart valves. Heart valves serve the vital function of maintaining unidirectional blood flow through the chambers of the heart during the cardiac cycle; however, as valve disease progresses, this function can become severely compromised [1]. Currently, the only cure for valve disease is to replace the defective valve with an engineered substitute. Each year, over 300,000 heart valve replacement surgeries are performed worldwide [2], and this number is expected to continue growing as life expectancies increase [3].
In the United States, the most common form of valve …
On The Use Of Natural-Mode Basis Functions For Electromagnetic Analysis Of Arbitrary Conducting Surfaces, Joshua Lawrence
On The Use Of Natural-Mode Basis Functions For Electromagnetic Analysis Of Arbitrary Conducting Surfaces, Joshua Lawrence
All Theses
The natural modes defined in the singularity expansion method (SEM) are used as basis functions for the frequency- and time-domain current responses of arbitrary perfect electrically conducting (PEC) surfaces in this work. First, a method of determining the natural frequencies and corresponding modes which employs the electric field integral equation is presented. These quantities are then calculated for several geometries and the currents induced due to an incident plane wave in the frequency and time domains are approximated by a weighted sum of the natural modes. Additionally, the modal weights prescribed by SEM are compared to a set of weights …
Identifying Barriers To Address During The Delivery Of Sustainable Building Renovation Projects, Corey Cattano
Identifying Barriers To Address During The Delivery Of Sustainable Building Renovation Projects, Corey Cattano
All Theses
Architects, engineers, and contractors are continuously searching for tools and methods to reduce the unique risks associated with the delivery of construction projects. Since national policies to reduce carbon emissions and energy consumption will require drastic improvements to the existing building stock, one specific area in need of such tools is the sustainable renovation of existing buildings. The purpose of this research is to identify the barriers to address during the delivery of sustainable renovation projects and offer solutions that overcome these barriers. For example, typical renovation projects do not coordinate energy retrofits with building system renovations, resulting in poor …
Discontinuous Galerkin Method For 1d Shallow Water Flow With Water Surface Slope Limiter, Wencong Lai
Discontinuous Galerkin Method For 1d Shallow Water Flow With Water Surface Slope Limiter, Wencong Lai
All Theses
A water surface slope limiting scheme is applied to numerically solve the one dimensional shallow water equations with bottom slope source term. The total variation diminishing Runge-Kutta discontinuous Galerkin finite element method with slope limiter schemes based on water surface and water depth are investigated for solving one-dimensional shallow water equations. For each slope limiter, three different Riemann solvers based on HLL, LF, and Roe flux functions are used. The three different solvers with slope limiters based on water surface and water depth are applied to simulate idealized dambreak problem, hydraulic jump, quiescent flow, subcritical flow, supercritical flow, and transcritical …
Mapping Problem And Requirements To Solution: Document Analysis Of Senior Design Projects, Shraddha Joshi
Mapping Problem And Requirements To Solution: Document Analysis Of Senior Design Projects, Shraddha Joshi
All Theses
Formulating and solving engineering problems and designing solutions that meet the established requirements are important skills that graduating engineering students need to possess. However, there are noticeable gaps in the literature with respect to understanding how the formulation of design problems and establishment of requirements affect the final design solution. This thesis is an initial attempt to understand the influence of level of detail of problem statement and requirements on the level of detail of final solution. In doing so, a document analysis of final reports from senior design class collected over a period of ten years from 1999 to …
Molecular Characterization Of Enrichment Cultures That Grow On Tetrachloroethene, 1,2 Dichloroethane And Ethylene Dibromide, Hari Shankar Peethambaram
Molecular Characterization Of Enrichment Cultures That Grow On Tetrachloroethene, 1,2 Dichloroethane And Ethylene Dibromide, Hari Shankar Peethambaram
All Theses
Halogenated aliphatic hydrocarbons are among the most common contaminants in soil and groundwater found at hazardous waste sites throughout the United States. Among them are tetrachloroethene (PCE), 1,2-dichloroethane (1,2-DCA) and ethylene dibromide (EDB). Organohalide respiration of each compound has been reported. However, considerably less information is known about EDB than PCE and 1,2-DCA, including the yield that occurs during growth with EDB as the sole TEA. The main objective of this project was to determine which types of chlororespiring microbes predominate during growth of enrichment cultures when PCE, 1,2-DCA and EDB served as the TEA, and what their yield is. …
Neomycin-Enhanced Carbodiimide Cross-Linking For Glycosaminoglycan Stability In Bioprosthetic Heart Valves, Joshua Leong
Neomycin-Enhanced Carbodiimide Cross-Linking For Glycosaminoglycan Stability In Bioprosthetic Heart Valves, Joshua Leong
All Theses
Valvular heart diseases lead to over 290,000 heart valve replacements worldwide each year, and approximately half of these involve replacement with a bioprosthetic heart valve (BHV) [1]. BHVs exhibit excellent hemocompatibility, but suffer from inadequate long-term durability with most adult implanted valves failing within 12 to 15 years after implantation [2]. Although this may be adequate for some individuals, BHV implantation may be contraindicated in younger individuals to avoid reoperation. Even in elder recipients, valve dysfunction can still cause death or reoperation that could be avoided with increased BHV durability. Therefore, investigation into methods of increasing BHV durability can not …
Advanced Automotive Thermal Management - Operation Of An Electric Radiator Fan Array For Reduced Electric Power Consumption, Amit Jagarwal
Advanced Automotive Thermal Management - Operation Of An Electric Radiator Fan Array For Reduced Electric Power Consumption, Amit Jagarwal
All Theses
The depletion of fossil fuel reserves and the limited renewable energy resources have raised public awareness about the need to improve fuel efficiency in ground transportation vehicles. The internal combustion engine remains one of the primary industrial machines using gasoline or diesel fuel to produce mechanical work. In these engines, the cooling system performs the vital role of removing waste heat to ensure normal combustion processes in the cylinders. To accomplish this task, the radiator, the radiator fan(s), the thermostat valve, and the water pump operated by circulating cooling fluid through the engine block and rejecting heat to the atmosphere. …