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Articles 31 - 60 of 63
Full-Text Articles in Engineering
Laboratory Characterization And Theoretical Analysis Of Contaminant Mass Transfer, Xiaoling Liu
Laboratory Characterization And Theoretical Analysis Of Contaminant Mass Transfer, Xiaoling Liu
All Dissertations
Chlorinated volatile organic compounds (CVOCs) in fractured, low permeability material can be a long-term source of groundwater contaminants and they are among the most difficult remediation challenges. Thermal methods are a possible remediation option, where heat is used to boil water and the volatile compounds are stripped out by partitioning into the resulting water vapor. Theoretical analysis indicates that only a small fraction of pore water removal may lead to a significant geometric reduction in the dissolved concentration [(Udell(, 1998]. Previous modeling studies [(Falta and Murdoch(, 2011; (Pruess(, 1983] suggest that a lower permeability limit exists for effective mass transfer …
Propagation Of Uncertainty In Light-Frame Wood Buildings, Seyed Masood Hassanzadehshirazi
Propagation Of Uncertainty In Light-Frame Wood Buildings, Seyed Masood Hassanzadehshirazi
All Dissertations
Light-frame wood construction is the most common form of construction for residential and low-rise commercial buildings (e.g. hotels and motels) in North America. In these buildings, shearwalls are the primary systems resisting lateral loads induced by earthquakes and winds. Past earthquake events have revealed that the structural performance of nominally identical light-frame wood buildings varied significantly. Although much research has been conducted investigating the uncertainty in the performance of wood shearwalls and buildings under earthquake loading, the focus of many of these studies was on the uncertainty due to the earthquake motions, referred as earthquake-to-earthquake uncertainty, the influences of variability …
Districting And Dispatching Policies To Improve The Efficiency Of Emergency Medical Service (Ems) Systems, Damitha Bandara
Districting And Dispatching Policies To Improve The Efficiency Of Emergency Medical Service (Ems) Systems, Damitha Bandara
All Dissertations
The major focus of Emergency Medical Service (EMS) systems is to save lives and to minimize the
effects of emergency health incidents. The efficiency of the EMS systems is a major public concern. Thus,
over the past three decades a significant amount of research studies have been conducted to improve the performance
of EMS systems. The purpose of this study is also to improve the performance of EMS system.
The contribution of this research towards improving the performance of EMS systems is twofold. One area
is to implement optimal or near optimal dispatching strategies for EMS systems and the other …
Elasto-Capillarity In Fibrous Materials, Daria Monaenkova
Elasto-Capillarity In Fibrous Materials, Daria Monaenkova
All Dissertations
Current advances in the manufacture of nanoporous and nanofibrous materials with high absorption capacity open up new opportunities for the development of fiber-based probes and sensors. Pore structures of these materials can be designed to provide high suction pressure and fast wicking. During wicking, due to the strong capillary action, the liquids exert stresses on the fiber network, thus the stressed state of dry and wet parts of the material differs. In this work the effect of stress reduction in fibrous materials due to the presence of wetting liquid in the pore structure is studied in details for both static …
Prediction Of The Wear & Evolution Of Cutting Tools In A Carbide / Ti-6al-4v Machining Tribosystem By Volumetric Tool Wear Characterization & Modeling, Mathew Kuttolamadom
Prediction Of The Wear & Evolution Of Cutting Tools In A Carbide / Ti-6al-4v Machining Tribosystem By Volumetric Tool Wear Characterization & Modeling, Mathew Kuttolamadom
All Dissertations
The objective of this research work is to create a comprehensive microstructural wear mechanism-based predictive model of tool wear in the tungsten carbide / Ti-6Al-4V machining tribosystem, and to develop a new topology characterization method for worn cutting tools in order to validate the model predictions. This is accomplished by blending first principle wear mechanism models using a weighting scheme derived from scanning electron microscopy (SEM) imaging and energy dispersive x-ray spectroscopy (EDS) analysis of tools worn under different operational conditions. In addition, the topology of worn tools is characterized through scanning by white light interferometry (WLI), and then application …
Probing And Controlling Fluid Rheology At Microscale With Magnetic Nanorods, Alexander Tokarev
Probing And Controlling Fluid Rheology At Microscale With Magnetic Nanorods, Alexander Tokarev
All Dissertations
This Dissertation is focused on the development of new methods for characterization and control of fluid rheology using magnetic nanorods. This Dissertation consists of five chapters. In the first chapter, we review current microrheologial methods and develop a Magnetic Rotational Spectroscopy (MRS) model describing nanorod response to a rotating magnetic field. Using numerical modeling, we analyze the effects of materials parameters of nanorods and fluids on the MRS characteristic features. The model is designed for a specific experimental protocol. We introduce and examine physical parameters which can be measured experimentally. The model allows identification of MRS features enabling the calculation …
Design Of Advanced Fouling-Resistant And Self-Cleaning Membranes For Treatment Of Oily And Impaired Waters, Daniel Wandera
Design Of Advanced Fouling-Resistant And Self-Cleaning Membranes For Treatment Of Oily And Impaired Waters, Daniel Wandera
All Dissertations
The overall goal of my Doctor of Philosophy (PhD) research was to design and develop advanced anti-fouling and self-cleaning membranes for treating impaired waters. Initial work focused on the development of membranes to treat produced water, which is oily wastewater that is co-produced during oil and gas exploration. Economical, environmentally sustainable treatment of the large volumes of produced water is a grand challenge for oil and gas companies. While membranes offer many advantages over more conventional treatment methods, membrane-based treatment processes for oily waters often fail due to membrane fouling. Therefore, the primary objective of my doctoral research was to …
Resource Allocation Framework: Validation Of Numerical Models Of Complex Engineering Systems Against Physical Experiments, Joshua Hegenderfer
Resource Allocation Framework: Validation Of Numerical Models Of Complex Engineering Systems Against Physical Experiments, Joshua Hegenderfer
All Dissertations
An increasing reliance on complex numerical simulations for high consequence decision making is the motivation for experiment-based validation and uncertainty quantification to assess, and when needed, to improve the predictive capabilities of numerical models. Uncertainties and biases in model predictions can be reduced by taking two distinct actions: (i) increasing the number of experiments in the model calibration process, and/or (ii) improving the physics sophistication of the numerical model. Therefore, decision makers must select between further code development and experimentation while allocating the finite amount of available resources. This dissertation presents a novel framework to assist in this selection between …
Surface Damage In Retrieved Total Knee Replacement Femoral Components, Estefania Alvarez
Surface Damage In Retrieved Total Knee Replacement Femoral Components, Estefania Alvarez
All Dissertations
The metallic femoral components of total knee replacements are subject to in vivo surface damage and roughening that can severely limit the service lifetime of the bearing system. To date, there are no national standards by which to characterize the severity and damage modes of these critical bearing surfaces, and therefore it remains difficult to accurately assess how femoral damage influences total joint replacement bearing longevity. In vitro and in vivo studies have shown that severe surface damage of the femoral component can occur, however, there is still no defined test methodology that can identify or replicate the types of …
Nanopillar Based Electrochemical Biosensor For Monitoring Microfluidic Based Cell Culture, Rajan Gangadharan
Nanopillar Based Electrochemical Biosensor For Monitoring Microfluidic Based Cell Culture, Rajan Gangadharan
All Dissertations
In-vitro assays using cultured cells have been widely performed for studying many aspects of cell biology and cell physiology. These assays also form the basis of cell based sensing. Presently, analysis procedures on cell cultures are done using techniques that are not integrated with the cell culture system. This approach makes continuous and real-time in-vitro measurements difficult. It is well known that the availability of continuous online measurements for extended periods of time will help provide a better understanding and will give better insight into cell physiological events.
With this motivation we developed a highly sensitive, selective and stable microfluidic …
Evaluation Of A Bisphosphonate Enriched Ultra-High Molecular Weight Polyethylene For Enhanced Total Joint Replacement Bearing Surface Functionality, Cassandra Wright-Walker
Evaluation Of A Bisphosphonate Enriched Ultra-High Molecular Weight Polyethylene For Enhanced Total Joint Replacement Bearing Surface Functionality, Cassandra Wright-Walker
All Dissertations
Each year in the United States there is an increasing trend of patients receiving total joint replacement (TJR) procedures. Approximately a half million total knee replacements (TKRs) are performed annually in the United States with increasing prevalence attributed to baby-boomers, obesity, older, and younger patients. This trend is also seen for total hip replacements (THRs) as well. The use of ultra high molecular weight polyethylene (UHMWPE) inserts in TJRs results in wear particle-induced osteolysis, which is the predominant cause for prosthesis failure and revision surgery. Sub-micron size particle generation is inevitable despite the numerous efforts in improving this bearing material. …
Applying Chaotic Advection To Rheology: An In Situ Structuring Rheometer, Ramaswami Subrahmanian
Applying Chaotic Advection To Rheology: An In Situ Structuring Rheometer, Ramaswami Subrahmanian
All Dissertations
A prototype In Situ Structuring Rheometer (ISSR) was designed and implemented to study changes in shear viscosity of polymer blends and composites while processing them in such a way as to control the evolution of microstructure. The ISSR is based on a regime of fluid mechanics known as chaotic advection, in which simple time-periodic flow fields can cause fluid particles to move chaotically. Chaotic advection is also the basis of Smart Blending, a technology employed to process polymer blends having a variety of morphologies at a fixed composition, and polymer composites in which the additives have been arranged into layered …
Modeling One- And Two-Dimensional Shallow Water Flows With Discontinuous Galerkin Method, Wencong Lai
Modeling One- And Two-Dimensional Shallow Water Flows With Discontinuous Galerkin Method, Wencong Lai
All Dissertations
Numerical models for one- and two-dimensional shallow water flows are developed using discontinuous Galerkin method. Formulation and characteristics of shallow water equations are discussed. The well-balanced property and wetting/drying treatment are provided in the numerical models. The shock-capturing property is achieved by the approximate Riemann solvers in the schemes. Effects of different approximate Riemann solvers are also investigated. The Total Variation Diminishing property is achieved by adoption of slope limiters. Different slope limiters and their effects are compared through numerical tests. Numerical tests are performed to validate the models. These tests include dam-break flows, hydraulic jump and shocks in channels, …
First Generation College Students In Engineering: A Grounded Theory Study Of Family Influence On Academic Decision Making, Denise Simmons
First Generation College Students In Engineering: A Grounded Theory Study Of Family Influence On Academic Decision Making, Denise Simmons
All Dissertations
This work develops a constructivist grounded theory describing the influence of family and those that serve a role similar to family on the academic decision making of undergraduate first generation in college (FGC) students majoring in engineering. FGC students, in this study, are students with neither parent having attained a bachelor's degree.
FGC students are an untapped talent pool with the potential to diversify and increase the number of engineers, which are both urgent national priorities. Much is known about FGC students with respect to their academic preparation, transition to postsecondary education, and progress toward degree attainment. However, the literature …
Grain Boundaries Structures And Wetting In Doped Silicon, Nickel And Copper, Kaveh Meshinchi Asl
Grain Boundaries Structures And Wetting In Doped Silicon, Nickel And Copper, Kaveh Meshinchi Asl
All Dissertations
This thesis reports a series of fundamental investigations of grain boundary wetting, adsorption and structural (phases) transitions in doped Ni, Cu and Si with technological relevance to liquid metal embrittlement, liquid metal corrosion and device applications. First, intrinsically ductile metals are prone to catastrophic failure when exposed to certain liquid metals, but the atomic level mechanism for this effect is not fully understood. A nickel sample infused with bismuth atoms was characterized and a bilayer interfacial phase that is the underlying cause of embrittlement was observed. In a second related study, we showed that addition of minor impurities can significantly …
Algebraic Approaches To Stochastic Optimization, Katherine Hastings
Algebraic Approaches To Stochastic Optimization, Katherine Hastings
All Dissertations
The dissertation presents algebraic approaches to the shortest path and maximum flow problems in stochastic networks. The goal of the stochastic shortest path problem is to find the distribution of the shortest path length, while the goal of the stochastic maximum flow problem is to find the distribution of the maximum flow value. In stochastic networks it is common to model arc values (lengths, capacities) as random variables. In this dissertation, we model arc values with discrete non-negative random variables and shows how each arc value can be represented as a polynomial. We then define two algebraic operations and use …
Further Investigation On Magnetically Induced Subsequent Fault And Study On Electromagnetic Scattering Of Objects Buried Below A Random Rough Surface, Haiyan Yang
All Dissertations
This dissertation contains two subjects: further development of numerical
technique for the analysis of magnetically induced subsequent fault (MISFault) in overhead power lines and its implementation into a software upgrade; and first-phase of study on the electromagnetic scattering from objects buried below a random rough surface making use of the multidomain pseudospectral time domain (PSTD) method and Monte-Carlo simulation. An initial electric fault can result in strong magnetic torque on the overhead power line conductors, which will make them swing and may bring them to close proximity or in contact with one another, causing a subsequent fault. In Chapter 2, …
Quantitative, Spatial Imaging Based Measurements To Assess Cellular Health And Oxygenation In A Tissue Engineered Test System, Erik Bland
All Dissertations
Three-dimensional in vitro tissue test systems are employed to examine cell behavior, test responses to drugs and vaccines, and answer basic biological questions. These systems are more physiologically relevant than two-dimensional cell cultures, and are more relevant, easier and less expensive to maintain than animal models. However, methods used to measure cell behavior and viability have been developed specifically for two-dimensional cell cultures or animal models, and are often not optimally translated to three-dimensional in vitro test systems. The purpose of this work was to aid in the development of three-dimensional, spatially controlled in vitro test systems, and to develop …
Assembly And Disassembly Of Myofibrils In Dissociated Cardiomyocytes, Honghai Liu
Assembly And Disassembly Of Myofibrils In Dissociated Cardiomyocytes, Honghai Liu
All Dissertations
Significance
1) We have developed a hybrid TPEF-SHG imaging system with an onstage incubator for long-term living-cell imaging. Using the imaging system, the assembly of myosin filaments onto the myofibrils can be investigated without fluorescently labeling the specific proteins, which enabled us to study the dynamic process of the assembly and dedifferentiation of myofibrils in living cardiomyocytes without labeling any sarcomeric proteins for long time.
2) We observed the addition of new sarcomeres during myofibrillogenesis while neonatal cardiomyocytes were spreading on the substrate for up to 10 hours under the customized TPEF-SHG imaging system. New-sarcomere addition at both the ends …
A Comprehensive Human Factors Analysis Of Off-Duty Motor Vehicle Crashes In The United States Military, Rebecca Iden
A Comprehensive Human Factors Analysis Of Off-Duty Motor Vehicle Crashes In The United States Military, Rebecca Iden
All Dissertations
Researchers have always had great interest in traffic safety and the phenomenon of motor vehicle crashes (MVCs). Though scores of service members are severely injured or killed in off-duty MVCs each year, few studies have addressed the MVC phenomenon within the military population and none have conducted a comprehensive evaluation of the causal factors associated with MVCs involving military personnel.
The main purpose of this dissertation was to gain a greater understanding of the causal factors associated with serious and fatal off-duty personal MVCs for military service members with the ultimate goal of preventing future losses. The HFACS-MVC framework was …
Compressive Strength Of Continuous Fiber Unidirectional Composites, Ronald Thompson
Compressive Strength Of Continuous Fiber Unidirectional Composites, Ronald Thompson
All Dissertations
Dow and Rosen's work in 1965 formed an intellectual framework for compressive strength of unidirectional composites. Compressive strength was explained in terms of micro-buckling, in which filaments are beams on an elastic foundation. They made simplifying assumptions, with a two dimensional idealization and linearized material properties. This study builds on their model, recognizing that the shear mode of instability drives unidirectional compressive strength. As a necessary corollary, the predictive methods developed in this study emphasize correct representation of composite shear stiffness. Non-linear effects related to matrix material properties, fiber misalignment, three dimensional representation, and thermal prestrains are taken into account. …
Assessing Ongoing Sources And Fate Of Dissolved Polychlorinated Biphenyls (Pcbs) In A Stream, Viet Dang
Assessing Ongoing Sources And Fate Of Dissolved Polychlorinated Biphenyls (Pcbs) In A Stream, Viet Dang
All Dissertations
Polychlorinated biphenyls (pcbs) contamination remains a concern due to their persistence and the risk to human health associated with them. Once released into the environment, these substances are mainly associated with sediment particles and sediment organic carbon matter. They bioaccumulate in organisms via contaminated food and only a small faction is desorbed from sediment into the water column. Given the discontinuity of active discharge, pcbs are currently entering the water via groundwater inputs, soil erosion, and/or ongoing leakage from the point source. It is the dissolved form that 1) can be either absorbed by biofilm attached to stream leaves, which …
Flushing Of A Dense Fluid From An Isolated Urban Canyon, Zahra Baratian-Ghorghi
Flushing Of A Dense Fluid From An Isolated Urban Canyon, Zahra Baratian-Ghorghi
All Dissertations
The mechanics of shear-driven flushing of a dense fluid from a canyon is investigated through a series of laboratory experiments. Such a flow has many environmental applications including the removal of dense pollutants trapped in urban canyons and the purging of salt water from bed depressions at river mouths. While there is an extensive literature on flow in canyons and cavities for the neutrally buoyant case, the problem of flushing a dense fluid from canyon has received considerably less attention. To understand the dynamics of the mixing and to quantify the buoyant contaminant flushing rate, a broad range of experimental …
Glottal Excitation Extraction Of Voiced Speech - Jointly Parametric And Nonparametric Approaches, Yiqiao Chen
Glottal Excitation Extraction Of Voiced Speech - Jointly Parametric And Nonparametric Approaches, Yiqiao Chen
All Dissertations
The goal of this dissertation is to develop methods to recover glottal flow pulses, which contain biometrical information about the speaker. The excitation information estimated from an observed speech utterance is modeled as the source of an inverse problem.
Windowed linear prediction analysis and inverse filtering are first used to deconvolve the speech signal to obtain a rough estimate of glottal flow pulses. Linear prediction and its inverse filtering can largely eliminate the vocal-tract response which is usually modeled as infinite impulse response filter. Some remaining vocal-tract components that reside in the estimate after inverse filtering are next removed by …
Bioengineering Approach To Understanding Tmj Pathobiology, Jonathan Kuo
Bioengineering Approach To Understanding Tmj Pathobiology, Jonathan Kuo
All Dissertations
The temporomandibular joint (TMJ) is a load-bearing joint consisting of the condyle of the mandibular bone, the fossa eminence of the temporal bone, and a fibrocartilaginous disc held in between the bone surfaces by ligaments. The TMJ disc serves to distribute stress, lubricate movement, and protect the articular surfaces of the joint. Over ten million Americans suffer from TMJ disorders (TMD) that affect the movement and function of the joint, making everyday tasks like talking and eating difficult and painful. A wide variety of treatments and surgeries have been proposed and undertaken with limited success based on the varying degree …
Clustering And Classification Of Multivariate Stochastic Time Series In The Time And Frequency Domains, Ryan Schkoda
Clustering And Classification Of Multivariate Stochastic Time Series In The Time And Frequency Domains, Ryan Schkoda
All Dissertations
The dissertation primarily investigates the characterization and discrimination of stochastic time series with an application to pattern recognition and fault detection. These techniques supplement traditional methodologies that make overly restrictive assumptions about the nature of a signal by accommodating stochastic behavior. The assumption that the signal under investigation is either deterministic or a deterministic signal polluted with white noise excludes an entire class of signals -- stochastic time series. The research is concerned with this class of signals almost exclusively. The investigation considers signals in both the time and the frequency domains and makes use of both model-based and model-free …
Computational Representation And Reasoning Support For Requirements Change Management In Complex System Design, Beshoy Morkos
Computational Representation And Reasoning Support For Requirements Change Management In Complex System Design, Beshoy Morkos
All Dissertations
Requirements play a critical role within any design process and the activity of identifying and maintaining a system's requirements is essential to. However, design is a complex and iterative process, where requirements are continuously evolving and are volatile. This change, if not managed, may result in undesired uncertainty within the design process leading to monetary losses and time delays, as the changing of requirements has been recognized as a major cause of project failure. In order to mitigate issues that arise due to requirement change propagation, this research presents a computational reasoning tool to help designers and engineers predict change …
Expert System Based Approach For Material Selection Of Automobile Body-In-White Structural Panels Using Numerical Ranking And Sustainability Indices, Ahmad Mayyas
All Dissertations
The goal of this work is to establish a set of quantifiable measures for design for sustainability (DFS) that can be applied to automotive applications in terms of environmental, social, economic and technical aspects. In this study, a comprehensive analysis was made in order to develop a methodology that can evaluate different body-in-white designs in terms of major sustainability aspects. Besides the complete life cycle analysis, environmental impacts and cost factors will be analyzed over vehicle's entire life-cycle (fuel extraction and refining, Pre-manufacturing, Manufacturing, Use, and
Post-use stages). The considered material options include: conventional steel, high strength steel, aluminum, magnesium, …
Design Of Meta-Materials Outside The Homogenization Limit Using Multiscale Analysis And Topology Optimization, Christopher Czech
Design Of Meta-Materials Outside The Homogenization Limit Using Multiscale Analysis And Topology Optimization, Christopher Czech
All Dissertations
The field of meta-materials engineering has largely expanded mechanical design possibilities over the last two decades; some notable design advances include the systematic engineering of negative Poisson's ratio materials and functionally graded materials, materials designed for optimal electronic and thermo-mechanical performances, and the design of materials under uncertainty. With these innovations, the systematic engineering of materials for design-specific uses is becoming more common in industrial and military uses. The motivation for this body of research is the design of the shear beam for a non-pneumatic wheel. Previously, a design optimization of a finite element model of the non-pneumatic wheel was …
Research And Development Effort In Developing The Optimal Formulations For New Tablet Drugs, Zhe Li
Research And Development Effort In Developing The Optimal Formulations For New Tablet Drugs, Zhe Li
All Dissertations
Seeking the optimal pharmaceutical formulation is considered one of the most critical research components during the drug development stage. It is also an R&D effort incorporating design of experiments and optimization techniques, prior to scaling up a manufacturing process, to determine the optimal settings of ingredients so that the desirable performance of related pharmaceutical quality characteristics (QCs) specified by the Food and Drug Administration (FDA) can be achieved. It is widely believed that process scale-up potentially results in changes in ingredients and other pharmaceutical manufacturing aspects, including site, equipment, batch size and process, with the purpose of satisfying the clinical …