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Articles 1 - 30 of 51
Full-Text Articles in Engineering
Synthesis And Characterization Of Polymer Brushes For Controlled Adsorption Of Proteins, Olha Hoy
Synthesis And Characterization Of Polymer Brushes For Controlled Adsorption Of Proteins, Olha Hoy
All Dissertations
Performance of biomedical devices to a large extent depends on the interactions between the device surface and the biological liquids/protein molecules. To achieve controllable interactions between the device and biomolecules and still retain the required mechanical strength on the whole, modification of the surface is often done.
In the present study surface properties were modified through a polymer brush approach. After the modification, surfaces gain tunability toward protein adsorption. Mixed polymer brushes consisting of protein repelling and protein attractive components were used, with a 'grafting to' method employed for the synthesis of polymer layers. First, poly(ethylene glycol), the protein repelling …
The Development Of Hyaluronic Acid Biomaterials For Vascular Tissue Engineering, Samir Ibrahim
The Development Of Hyaluronic Acid Biomaterials For Vascular Tissue Engineering, Samir Ibrahim
All Dissertations
Current vascular implant materials poorly interact with medial smooth muscle cells (SMCs) allowing the permanent loss of vascular elastin, eliminated by trauma or disease, a crucial element in maintaining the natural biomechanics of the blood vessel and overall vascular homeostasis. In addition, these materials insufficiently recruit vascular endothelial cells (ECs) to form a normally functional, confluent endothelium that acts as the interface between the blood and vascular tissue and regulates numerous vital vascular processes. As a result, the restenosis, or re-occlusion, rate within these devices has remained fairly high stimulating the investigation of numerous new materials capable of providing the …
Effect Of Clinically Relevant Mechanical Forces On Smooth Muscle Cell Response In Model Of Balloon Angioplasty, Kara Acampora
Effect Of Clinically Relevant Mechanical Forces On Smooth Muscle Cell Response In Model Of Balloon Angioplasty, Kara Acampora
All Dissertations
Restenosis remains a common problem affecting the patency of endovascular intervention such as balloon angioplasty and stent placement as treatments for atherosclerosis. Denudation of the endothelial layer and the increased injury from balloon deployment can cause phenotypic changes in surrounding vascular smooth muscle cells (SMCs) in vivo. The presented work modeled this mechanical environment in vitro to investigate the role of the altered mechanical environment on the phenotypic response of SMCs. Through the system design and CFD channel characterization, a six-independent-channel system providing low oscillating wall shear stress (WSS) was manufactured to apply concurrent shear and tensile forces with uniform …
Modeling And Control Of Piezoactive Micro And Nano Systems, Saeid Bashash
Modeling And Control Of Piezoactive Micro And Nano Systems, Saeid Bashash
All Dissertations
Piezoelectrically-driven (piezoactive) systems such as nanopositioning platforms, scanning probe microscopes, and nanomechanical cantilever probes are advantageous devices enabling molecular-level imaging, manipulation, and characterization in disciplines ranging from materials science to physics and biology. Such emerging applications require precise modeling, control and manipulation of objects, components and subsystems ranging in sizes from few nanometers to micrometers. This dissertation presents a comprehensive modeling and control framework for piezoactive micro and nano systems utilized in various applications.
The development of a precise memory-based hysteresis model for feedforward tracking as well as a Lyapunov-based robust-adaptive controller for feedback tracking control of nanopositioning stages are …
Development And Characterization Of Moisture- And Heat- Activated Oxygen Scavenging Nanoparticle, Youngjae Byun
Development And Characterization Of Moisture- And Heat- Activated Oxygen Scavenging Nanoparticle, Youngjae Byun
All Dissertations
Alpha-tocopherol and a transition metal, iron, mixture was evaluated as a possible oxygen scavenger. The effects of moisture, amount of transition metal, and thermal processing on oxygen scavenging capability were also investigated. Results showed that alpha-tocopherol and transition metal had 6.72 cc oxygen per gram of oxygen scavenging capacity and 0.11 cc oxygen per gram per day of oxygen scavenging rate.
Nanoencapsulation technology was adopted for the possible oxygen scavenging activation system. Alpha-tocopherol-loaded poly caprolactone (PCL) nanoparticles were prepared by oil in water (O/W) emulsion solvent evaporation with ultrasonification. The effects of PCL concentration, solvent in oil phase, and ultrasonification …
Ecm Stabilization Strategies For Bioprosthetic Heart Valves For Improved Durability, Devanathan Raghavan
Ecm Stabilization Strategies For Bioprosthetic Heart Valves For Improved Durability, Devanathan Raghavan
All Dissertations
Abstract
Approximately 85,000 heart valve replacement surgeries are performed every year in United States and about 300,000 surgeries worldwide. It is estimated that half of them are mechanical valve replacements and the other half bioprosthetic valve replacements. The use of bioprosthetic heart valves is slowly increasing. Bioprosthetic heart valves are made from porcine aortic valves or bovine pericardium. Commercially these bioprostheses are currently crosslinked using glutaraldehyde (GLUT) to prevent tissue degradation and reduce tissue antigenicity. GLUT crosslinks these bioprostheses by stabilizing the collagen present in the tissue via a Schiff base reaction of the aldehyde with the hydroxylysine / lysine …
'Fabrication And Characterization Of Polymer Blends And Composites Derived From Biopolymers', Suraj Sharma
'Fabrication And Characterization Of Polymer Blends And Composites Derived From Biopolymers', Suraj Sharma
All Dissertations
This research focuses on fabricating blends and composites from natural polymers especially from proteins and natural epoxy, and describing the properties of plastics made from them. Specifically, plastic samples from partially denatured feathermeal and bloodmeal proteins, derived from the animal co-products (rendering) industry, were successfully produced through a compression molding process. The modulus (stiffness) of the material obtained was found to be comparable with that of commercial synthetic materials, such as polystyrene, but was found to have lower toughness characteristics, which is a common phenomenon among plastics produced from animal and plant proteins. Therefore, this study explored blending methods for …
Real-Time Automatic Linear Feature Detection In Images, Guang Zeng
Real-Time Automatic Linear Feature Detection In Images, Guang Zeng
All Dissertations
Linear feature detection in digital images is an important low-level operation in
computer vision that has many applications. In remote sensing tasks, it can be used
to extract roads, railroads, and rivers from satellite or low-resolution aerial images,
which can be used for the capture or update of data for geographic information and
navigation systems. In addition, it is useful in medical imaging for the extraction of
blood vessels from an X-ray angiography or the bones in the skull from a CT or MR
image. It also can be applied in horticulture for underground plant root detection in
minirhizotron images. …
Human Microvasculature Fabrication Using Thermal Inkjet Printing Technology, Xiaofeng Cui
Human Microvasculature Fabrication Using Thermal Inkjet Printing Technology, Xiaofeng Cui
All Dissertations
The current tissue engineering paradigm is that successfully engineered thick tissues must include vasculature. As biological approaches alone such as VGEF have fallen short of their promises, one may look for an engineering approach to build microvasculature. With the advent of cell printing, one may be able to build precise human microvasculature with suitable bio-ink. Human Microvascular Endothelial Cells (HMVEC) and fibrin were studied as bio-ink for microvasculature construction. Endothelial cells are the only cells to compose the human capillaries and also the major cells of blood vessel intima layer. Fibrin has been already widely recognized as tissue engineering scaffold …
Characterization Of Vascular Smooth Muscle Cell Mechanical And Frictional Properties Using Atomic Force Microscopy, Jason Hemmer
Characterization Of Vascular Smooth Muscle Cell Mechanical And Frictional Properties Using Atomic Force Microscopy, Jason Hemmer
All Dissertations
A working hypothesis within the Laboratory of Vascular Research is that mechanical loading on vascular smooth muscle cells (VSMCs), especially due to solid contact from endovascular devices, contributes to the development of restenosis. In order to better understand the role of mechanical loading on VSMCs in vascular disease development, it is imperative to understand the mechanical properties of VSMCs themselves. To measure the viscoelastic and frictional properties of living VSMCs in an in vitro setting, an atomic force microscope (AFM) was utilized, thereby allowing for mechanical testing of living cells in a fluid environment. In the first phase of research, …
Aperture Coupling And Penetration In Various Configurations, Jason Keen
Aperture Coupling And Penetration In Various Configurations, Jason Keen
All Dissertations
The problem of a slot in a perfectly conducting surface is addressed for a variety of configurations using both integral equation and transmission line techniques. The use of Bethe hole theory to model short slots is discussed and utilized where appropriate. Primary problems of discussion are a slot array, wires coupling through slots in a ground plane, and wires coupling through slots in a bent ground plane. Additionally, the use of the extended BLT formulation for incorporation of slot effects in a transmission line problem is addressed. In this manuscript, the work of Bethe is extended to include cross-aperture coupling …
Synthesis And Characterization Of Macromolecular Layers Grafted To Polymer Surfaces, Oleksandr Burtovyy
Synthesis And Characterization Of Macromolecular Layers Grafted To Polymer Surfaces, Oleksandr Burtovyy
All Dissertations
The composition and behavior of surfaces and interfaces play a pivotal role in dictating the overall efficiency of the majority of polymeric materials and devices. Surface properties of the materials can be altered using surface modification techniques. It is necessary to highlight that successful methods of surface modification should affect only the upper layer of the polymer material without changing bulk properties. The processes must introduce new functionalities to the surface, optimize surface roughness, lubrication, hydrophobicity, hydrophilicity, adhesion, conductivity, and/or biocompatibility.
Research presented in this dissertation is dedicated to the synthesis, characterization, and application of thin macromolecular layers anchored to …
Experimental And Modeling Studies For Optimizing Flocculant-Aided Sediment Retention Ponds, Byung Joon Lee
Experimental And Modeling Studies For Optimizing Flocculant-Aided Sediment Retention Ponds, Byung Joon Lee
All Dissertations
Attempts to control sediment-containing runoff and associated water quality problems have involved the establishment of many small to medium sediment retention ponds and the injection of nonionic and anionic polyacrylamide (PAM) flocculants to enhance colloid removal. However, to date use has been driven more by practicing engineers and trial-and-error approaches than by logical and consistent design approaches. Therefore, the purpose of this research was to optimize colloidal clay removal in PAM-aided sediment retention ponds by applying experimental and theoretical methodologies.
Initially, simple measurement techniques for the molecular weight (MW) and charge density (CD) of various PAMs were tested and their …
Vascular Tissue Engineering: The Creation Of Living, Non-Thrombogenic, Functional Blood Vessels Based On Elastin Scaffolds, Aditee Kurane
Vascular Tissue Engineering: The Creation Of Living, Non-Thrombogenic, Functional Blood Vessels Based On Elastin Scaffolds, Aditee Kurane
All Dissertations
Cardiovascular diseases are the leading cause of death worldwide. Blood vessel replacement is a common treatment for vascular diseases such as atherosclerosis, restenosis and aneurysm, with over 300,000 bypass procedures performed each year. However, vein grafts are limited due to their availability. Although synthetic vascular replacements have been successful for large diameter arteries, they have shown minimal success in arteries with diameters <6mm. This is because most synthetic materials induce thrombus formation which, within a few months of implantation, causes failure of the vascular graft due to occlusion. Tissue engineering is a promising approach to the fabrication of non-thrombogenic vascular grafts, but a reliable and expandable cell source for tissue-engineered vascular graft (TEVG) has not been established.
The work presented here is motivated by the current unavailability of an ideal tissue engineered blood vessel replacement. Our overall goal is to create a living tissue engineered vascular graft that is biodegradable, non-thromobogenic, presents low antigenicity and …
Computional Modeling Of Precision Molding Of Aspheric Glass Optics, Balajee Ananthasayanam
Computional Modeling Of Precision Molding Of Aspheric Glass Optics, Balajee Ananthasayanam
All Dissertations
In this dissertation, research in two parallel directions is presented; the first involves the prediction of the final size and shape of a glass lens during a precision glass lens molding process and the second introduces a method to compute and quantify the importance of higher order terms in fracture mechanics for different modes of fracture.
The process of precision lens molding has received attention in recent years due to its potential to mass produce aspherical lenses. Aspherical lenses have significantly better optical properties and conventional lens making techniques are limited to manufacturing of spherical lenses only. The conventional technique …
Effective Vr: Interplay Of Presence, Perception, Fidelity And Transfer Effects In The Development Of Inspection Training Simulators, Sajay Sadasivan
Effective Vr: Interplay Of Presence, Perception, Fidelity And Transfer Effects In The Development Of Inspection Training Simulators, Sajay Sadasivan
All Dissertations
Increased emphasis on aircraft inspection to ensure aviation safety has resulted in the need for a better trained workforce of aircraft maintenance personnel. Aircraft inspection is mostly visual in nature. Thus it has led to the development of computer simulators to train human inspectors performing the inspection task. However, the lack of immersion and interaction in such simulators has led to limited effectiveness and adoption. Using advances in graphics and virtual reality technology, there is an increase the sense of involvement in using these simulators. Though technology is available to provide higher levels of immersion, it is expensive. It is …
High Temperature Wetting And Multilayer Adsorption In Oxide Systems, Haijun Qian
High Temperature Wetting And Multilayer Adsorption In Oxide Systems, Haijun Qian
All Dissertations
The primary objective of this thesis research is to greatly advance the knowledge of the formation mechanism and thermodynamic stability of a unique class of surficial amorphous films (SAFs) and analogous intergranular films (IGFs) via critical experiments and modeling. These quasi-liquid IGFs and SAFs films exhibit the following distinct characteristics: 1) self-regulating (equilibrium) thicknesses on the order of 1 nm, 2) structures and compositions that are neither found nor stable as bulk phases, and 3) thermodynamic stability below the bulk solidus lines.
The first part of this study examines anisotropic wetting of ZnO single crystals by Bi2O3-rich liquid with and …
Inferring Mechanical Resonances In Micro - And Nanocantilevers Using The Harmonic Detection Of Resonance (Hdr) Method To Develop A Novel Sensing Platform, Gayatri Keskar
All Dissertations
During the past two decades, advances in microelectromechanical systems (MEMS) have spurred efforts worldwide to develop sensing platforms based on smart microcantilevers. A microcantilever beam is one of the simplest MEMS structures which forms the basis for portable, fast and highly sensitive schemes that are capable of measuring small deflections in static or dynamic response due to changes in external parameters such as mass, pressure, charge, etc.
In this dissertation, I mainly focus on MEMS sensors with transducers in the form of microcantilevers. Variations in the microcantilever's response such as resonant frequency, amplitude, phase and quality factor when exposed to …
Performance Based Decisions Under Uncertainty And Risk, Sundeep Samson
Performance Based Decisions Under Uncertainty And Risk, Sundeep Samson
All Dissertations
Decision making has became increasingly complex as risky decisions are made in uncertain environments. To minimize risk, the problem of quantifying risk becomes very significant. In our review of the literature, we found a number of different risk measures. A closer study reveals that most of these risk measures define both risk and uncertainty in many different ways.
In this dissertation, we model uncertainty and risk based on the Knightian definition of uncertainty and risk. We propose this alternative modeling paradigm and introduce our decision making methodology by solving an illustrative problem presented by a group of decision makers from …
Similarity Metrics Applied To Graph Based Design Model Authoring, Srinivasan Anandan
Similarity Metrics Applied To Graph Based Design Model Authoring, Srinivasan Anandan
All Dissertations
Model reuse is typically facilitated by search and retrieval tools, matching the sought model with models in a database. This research aims at providing similar assistance to users authoring design exemplars, a data structure to represent parametric and geometric design problems. The design exemplar represents design problems in the form of a bi-partite graph consisting of entities and relations. Authoring design exemplars for relatively complex design problems can be time consuming and error prone. This forms the motivation of developing a search and retrieval tool, capable of retrieving exemplars that are similar to the exemplar that a user is trying …
Modeling Systems For Optimal Resource Allocation, Scheduling, And Decision Making, Esengul Tayfur
Modeling Systems For Optimal Resource Allocation, Scheduling, And Decision Making, Esengul Tayfur
All Dissertations
This dissertation focuses on the resource requirements and scheduling problem for logistic systems. We investigate solutions to this problem in two different logistic systems: logistic system of the health care facilities during emergency evacuations and delivery and distribution system of production industries. All hospitals must have an evacuation plan to ensure the safety of patients and prevent the loss of life. However, hospital operators have not been able to quantify how resource availability, the cost of acquiring those resources, and evacuation completion time are related. This research addresses this problem and contributes two methodologies to solve this problem. In the …
The Effects Of Crumb Rubber Particles On Highway Noise Reduction - A Laboratory Study, Khaldoun Shatanawi
The Effects Of Crumb Rubber Particles On Highway Noise Reduction - A Laboratory Study, Khaldoun Shatanawi
All Dissertations
Traffic noise is a major setback to the life quality of residents living in the vicinity of highways. Over the past 40 years, much legislation has been passed to regulate sound levels to which residents are exposed. Among the many approaches adopted to alleviate the problem, crumb rubber modified asphalt has been proposed as a measure to reduce highway traffic noise.
The use of crumb rubber modified asphalt to reduce traffic noise on pavements had not been evaluated in great detail prior to this study. This research investigates the effects of crumb rubber particles on asphalt pavement noise absorption ability. …
Evaluation Of Warm Asphalt Additives On Performance Properties Of Crm Binders And Mixtures, Chandra Akisetty
Evaluation Of Warm Asphalt Additives On Performance Properties Of Crm Binders And Mixtures, Chandra Akisetty
All Dissertations
The Warm Mix Asphalt (WMA) technologies have gained increasing popularity in recent years because of its unique property to allow the reduction in mixing and compaction temperatures of Hot Mix Asphalt (HMA) mixtures without compromising the quality of the mix. On the other hand, one of the reasons for utilizing the Crumb Rubber Modified (CRM) asphalt mixtures is that it increases the durability of the pavement by reducing the cracking and rutting potential of the pavement. However the CRM mixtures require a high mixing and compaction temperatures compared to the conventional HMA. Since the temperature requirements for CRM mixtures are …
The Spaceflight Environment And The Skeletal System, Eric Bandstra
The Spaceflight Environment And The Skeletal System, Eric Bandstra
All Dissertations
The spaceflight environment presents many challenges to the human body. Bone loss in astronauts is a well known consequence of reduced loading in the weightless environment of low-earth orbit. Recent studies have also indicated that spaceflight relevant types of radiation (at relatively high doses) have deleterious effects on trabecular bone. Both of these represent potential skeletal challenges during long-duration spaceflight. The objective of these studies is to examine the response of bone to models of the spaceflight environment.
Astronauts will likely absorb doses of protons and heavy ions during lengthy missions outside the Earth's magnetosphere. Following exposure to a range …
Engineered Micro-Environments And Vibrational Culture Systems For Vocal Fold Tissue Engineering, Jaishankar Kutty
Engineered Micro-Environments And Vibrational Culture Systems For Vocal Fold Tissue Engineering, Jaishankar Kutty
All Dissertations
Voice is produced by the conversion of aerodynamic energy from exhalation to acoustical energy for voice production by the vocal folds (membranous connective tissue) located in the larynx. The quality of voice depends on the biomechanical properties of the multi-layered vocal fold tissue which derive from its extracellular matrix (ECM) organization and composition. The wound healing response to vocal fold injuries is characterized by scarring and subsequent dysphonia due to alterations in the biomechanical properties of the tissue.
The work presented here is motivated by the importance of voice in maintaining quality of life and the inability of current treatment …
Cues For Cellular Assembly Of Vascular Elastin Networks, Chandrasekhar Kothapalli
Cues For Cellular Assembly Of Vascular Elastin Networks, Chandrasekhar Kothapalli
All Dissertations
Elastin, a structural protein distributed in the extracellular matrix of vascular tissues is critical to the maintenance of vascular mechanics, besides regulation of cell-signaling pathways involved in injury response and morphogenesis. Thus, congenital absence or disease-mediated degradation of vascular elastin and its malformation within native vessels due to innately poor elastin synthesis by adult vascular cells compromise vascular homeostasis. Current elastin regenerative strategies using tissue engineering principles are limited by the progressive destabilization of tropoelastin mRNA expression in adult vascular cells and the unavailability of scaffolds that can provide cellular cues necessary to up-regulate elastin synthesis and regenerate faithful mimics …
Revenue And Order Management Under Demand Uncertainty, Kiran Chahar
Revenue And Order Management Under Demand Uncertainty, Kiran Chahar
All Dissertations
We consider a firm that delivers its products across several customers or markets, each with unique revenue and uncertain demand size for a single selling season. Given that the firm experiences a long procurement lead time, the firm must decide, far in advance of the selling season not only the markets to be pursued but also the procurement quantity. In this dissertation, we present several operational scenarios in which the firm must decide which customer demands to satisfy, at what level to satisfy each customer demand, and how much to produce (or order) in total.
Traditionally, a newsvendor approach to …
Some Problems In Statistical Mechanics With Applications To Materials Science, Ethan Ballard
Some Problems In Statistical Mechanics With Applications To Materials Science, Ethan Ballard
All Dissertations
In this work, some problems in statistical mechanics related to condensed matter physics and of general interst in materials science, physics, chemistry and polymer science are considered. In chapters 1-4, the work by E.M. Lifshitz on the group-theoretical refinements of the Landau theory of phase transitions is brought to completion. Based on mathematical results obtained by Yamabe, Osgood, Phillips, Sarnak, and Kholodenko analytical results for determinants were developed which allows for prediction of the symmetry of the phase after a phase transition provided that the symmetry prior to the phase transition is known. Numerical results are presented which are in …
Framework For Probabilistic Analysis Of Recurrent Landslides: A Case Study Of El Berrinche, Raul Flores
Framework For Probabilistic Analysis Of Recurrent Landslides: A Case Study Of El Berrinche, Raul Flores
All Dissertations
Assessment of slope stability or landslide is a complex geotechnical problem that involves much uncertainty. To consider combined effects of the uncertainties in soil parameters and changes in pore water pressure, reliability theory may be employed. In this dissertation study, a reliability-based framework for the probabilistic analysis of recurrent landslides is developed.
Generally, the stability of a slope is analyzed deterministically with methods of limit equilibrium and a factor of safety is computed. This approach is referred to as the deterministic approach. However, a deterministic analysis alone may not be sufficient in assessing the risk level of a landslide in …
Framework For The Fully Probabilistic Analysis Of Excavation-Induced Serviceability Damage To Buildings In Soft Clays, Matt Schuster
Framework For The Fully Probabilistic Analysis Of Excavation-Induced Serviceability Damage To Buildings In Soft Clays, Matt Schuster
All Dissertations
In this dissertation, a framework for a fully-probabilistic analysis of the potential for building serviceability damage induced by an excavation in soft clays is established. This analysis framework is established based on the concept of a serviceability limit state where the resistance is represented by the capacity of a building to resist serviceability damage, and the loading is represented by the demand on a building due to excavation-induced ground movements. In this study, both the resistance and the loading are treated as a random variable; the resistance is characterized empirically based on a database of the observed building performance while …