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Articles 1 - 30 of 57
Full-Text Articles in Engineering
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 …
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 …
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 …
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 …
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 …
Characterization Of Anti-Proteolytic And Anti-Proliferative Activities Of Pentagalloylglucose; Its Potential Application As A Therapeutic Agent In Vascular Diseases, Chaitra Cheluvaraju
Characterization Of Anti-Proteolytic And Anti-Proliferative Activities Of Pentagalloylglucose; Its Potential Application As A Therapeutic Agent In Vascular Diseases, Chaitra Cheluvaraju
All Dissertations
Cardiovascular diseases are the leading causes of mortality in the United States and will cost around $500 billion this year alone. Elevated proteolytic activity, increased proliferation and migration of vascular smooth muscle cells are hallmarks of atherosclerosis, stenosis and aortic aneurysms. These diseases often manifest the transdifferentiation of vascular smooth muscle cells into osteoblast-like cells followed by deposition of hydroxyapatite–like mineral in the arterial walls.
Currently, there are no standard treatments available for vascular calcification or aneurysms. Atherosclerosis treatment options are limited to statins while balloon angioplasty and stenting – surgical procedures for stenosis, often end in restenosis. Therefore, we …
A Meta-Analysis Of Human Factors Analysis And Classification System Causal Factors: Establishing Benchmarking Standards And Human Error Latent Failure Pathway Associations In Various Domains, Katherine Berry
All Dissertations
Many models of accident investigation have been created and have served as the basis for other tools and techniques. One of the most prominent techniques, Reason's Swiss Cheese Model (1990), is based on the idea of active and latent failures. Expanding on this idea, the Human Factors Analysis and Classification System (HFACS) was created with the idea to associate contributing factors and errors (Wiegmann & Shappell, 2003).
While HFACS has been frequently applied in the field of aviation in literature, other industry types are under-represented. Seventeen data sources encompassing various industry types were collected and included in this dissertation analysis. …
Production And Characterization Of Aramid Copolymer Fibers For Use In Cut Protection, Jeffrey Moreland
Production And Characterization Of Aramid Copolymer Fibers For Use In Cut Protection, Jeffrey Moreland
All Dissertations
High-performance fibers such as para-aramids are used extensively in gloves for cut protection. However, the inherent cut resistance of these fibers and the relationship between cut resistance and other material properties is not known. To better understand cut resistance at the material level, an experiment was conducted using a lab-scale wet spinning system to produce and characterize aramid copolymer fibers.
To facilitate the use of lab-scale equipment, the experiment was conducted as a four-factor split-plot response surface design. The four treatment factors studied were solvent concentration in the coagulation bath, the amount of salt in the coagulation bath, the degree …
Utilizing Copper(I) Catalyzed Azide-Alkyne Huisgen 1,3-Dipolar Cycloaddition For The Surface Modification Of Colloidal Particles With Electroactive And Emissive Moieties, Parul Rungta
All Dissertations
The development of charge–transporting and fluorescing colloidal particles that can be directly printed into electroluminescent devices may result in a broad impact on the use of electrical energy for illumination. The objective of this work was to design and synthesize electroactive & fluorescing colloidal particles; establish their optical, electronic, and thermodynamic properties; and transition them into a device format for potential applications. The original intended application of this work was to build “better” colloidally–based organic light emitting devices (OLEDs) by creating functional particles with superior electrical and optical performance relative to commercially available technologies, but through the course of the …
Molecular Physics Of Electrical Double Layers In Electrochemical Capacitors, Guang Feng
Molecular Physics Of Electrical Double Layers In Electrochemical Capacitors, Guang Feng
All Dissertations
At present, electrochemical capacitors (ECs) are emerging as a novel type of energy storage devices and have attracted remarkable attention, due to their key characteristics, such as high power density and excellent durability. However, the moderate energy density of ECs restricts their widespread deployment in everyday technology. To surmount this limitation, four strategies are adopted: (1) to reduce the total system mass, (2) to increase the specific surface area of electrodes, (3) to enhance normalized capacitance, and (4) to expand the range of potentials applied on electrodes. The implementation of these approaches critically relies on the fundamental understanding of physical …
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 …
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 …
High Frequency Ferromagnetic Inductive Elements For On-Chip Integration And Their Magnetization Dynamics, Hanqiao Zhang
High Frequency Ferromagnetic Inductive Elements For On-Chip Integration And Their Magnetization Dynamics, Hanqiao Zhang
All Dissertations
The dissertation focuses on the broadband characterization of magnetization dynamics of submicron (200-550 nm wide, 10 µm long, 100 nm thick) and micron (2-10 µm wide, 100 µm long, 100 nm thick) size patterned ferromagnetic material (Permalloy, Py) with low frequency and microwave measurement methods. Particularly the ferromagnetic resonance (FMR), damping process, magnetization reversal, mag-noise, and 1/f noise in different pattern geometry, DC current and external magnetic field bias situations are investigated. In addition to simple microwave transmission line measurements, a sensitive on-chip microwave interferometer is proposed and fabricated by means of nano-fabrication techniques. The FMR properties of an individual …
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 …
Pulsed-Laser Direct Writing Of Biological Materials, Yafu Lin
Pulsed-Laser Direct Writing Of Biological Materials, Yafu Lin
All Dissertations
Laser direct writing, developed based on modified laser-induced forward transfer (LIFT), has been emerging as one of the most promising biofabrication techniques. While some studies have been conducted to investigate laser direct writing of biological materials, there are some key challenges such as mechanisms of bubble formation, droplet formation and process-induced cell injury that have not been well elucidated. The objective of this dissertation is to study laser-induced droplet formation dynamics and process-induced cell injury in pulsed-laser direct writing of biological materials, and improve the existing laser direct-write techniques.
Phase explosion is identified as the dominant bubble formation mechanism in …
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 …
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 …
Order Picking And Storage Using Stackable Pallets In A Warehouse, Ahmed Hassan Aly
Order Picking And Storage Using Stackable Pallets In A Warehouse, Ahmed Hassan Aly
All Dissertations
Quarter Billion dollars could be saved annually by double stacking pallets. A forklift storing 100 double stacked pallets saves 2.5 working hours versus single pallets. More than one billion pallets and cases handled between Wal-Mart distribution centers according to BEA White Paper (2006) [1], assume only 500 million were stackable pallets. This translates to 12.5 million working hours. If a forklift driver earns $20 per hour, then $250 million can be saved.
Moreover, handling double stacked pallets takes up to 46 % of total time to pick and store. This is a significant element that was ignored in literature. All …
Investigation Of Subgrid-Scale Mixing And Turbulence-Chemistry Interaction In Turbulent Partially Premixed Flames Using Experimental Data, Jian Cai
All Dissertations
The filtered mass density function (FMDF) of mixture fraction, temperature and species used in large eddy simulation (LES) of turbulent combustion is studied experimentally using line images obtained in turbulent partially premixed methane flames (Sandia flames D and E). Cross-stream filtering is employed to obtain the FMDF and other filtered variables. The mean of the FMDF conditional on the subgrid-scale (SGS) scalar variance at a given location are found to vary from unimodal to bimodal, corresponding to quasi-equilibrium distributed reaction zones and laminar flamelets (including extinguished flamelets), respectively. The conditionally filtered mixture fraction dissipation for small SGS variances has a …
Robust Analysis Of Electromagnetic Responses Of Resonant Structures Using Early-Time And Low-Frequency Data, James Frye, Jr.
Robust Analysis Of Electromagnetic Responses Of Resonant Structures Using Early-Time And Low-Frequency Data, James Frye, Jr.
All Dissertations
The rapid increase of affordable computing resources combined with the continued development and refinement of computational electromagnetic (CEM) methods has yielded a wide range of accurate and well-verified EM modeling tools; however, improvements are required to keep pace with the current and future requirements of EM systems. One such need is the development of robust, computationally-efficient methods which provide one the means to understand complex resonant systems through the by analyzing EM responses. The characteristics of resonant systems often make the determination of a wideband response with CEM methods computationally very intensive. Also, a numerical solution may not directly provide …
Probing The Mechanisms Of Platelet Adhesion To Adsorbed Plasma Proteins, Balakrishnan Sivaraman
Probing The Mechanisms Of Platelet Adhesion To Adsorbed Plasma Proteins, Balakrishnan Sivaraman
All Dissertations
Despite over three decades of research in blood-material interactions, the biomaterials field has been unsuccessful in developing a truly non-thrombogenic biomaterial. This is due to an incomplete understanding of the factors underlying biomaterial-associated thrombosis, especially the mechanisms mediating the interactions of platelets with the adsorbed plasma protein layer(s) on the implant surface. The work presented here is motivated by the primary goal of delineating these mechanisms, and understanding the platelet receptors involved, as well as the domains/amino acid sequences they bind to in the protein molecules.
It is critical to differentiate between the amount and the conformation of the adsorbed …
Simulation And Mathematical Modeling To Support Community-Wide Evacuation Decisions For Multiple Population Groups, Jun Duanmu
All Dissertations
Evacuating a large population from an at-risk area has been the subject of extensive research over the past few decades. In order to measure trip completion and total evacuation times accurately, most researchers have implemented some combination of simulation and optimization methods to provide vehicular flow and congestion data. While the general at-risk population comprises the majority of travelers on the road network, there are often specific groups to consider when assessing the ability to evacuate an entire population. In particular, healthcare facilities (e.g., hospitals) may require evacuation, and the trip times may become an important health issue for patients …
Principal Component Analysis Based Image Fusion Routine With Application To Stamping Split Detection, Yi Zhou
Principal Component Analysis Based Image Fusion Routine With Application To Stamping Split Detection, Yi Zhou
All Dissertations
This dissertation presents a novel thermal and visible image fusion system with application in online automotive stamping split detection. The thermal vision system scans temperature maps of high reflective steel panels to locate abnormal temperature readings indicative of high local wrinkling pressure that causes metal splitting. The visible vision system offsets the blurring effect of thermal vision system caused by heat diffusion across the surface through conduction and heat losses to the surroundings through convection. The fusion of thermal and visible images combines two separate physical channels and provides more informative result image than the original ones.
Principal Component Analysis …