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Articles 31 - 51 of 51
Full-Text Articles in Engineering
Kinetics Of Preferential Adsorption And Equilibrium Properties Of Interfacial Layers Formed From Polymer Chains That Tether By Multiple Ends, Jose Alonzo Calderon
Kinetics Of Preferential Adsorption And Equilibrium Properties Of Interfacial Layers Formed From Polymer Chains That Tether By Multiple Ends, Jose Alonzo Calderon
All Dissertations
Due to their ability to straddle phase boundaries, polymer brushes represent a model system for studies of polymer-modified surfaces. The research presented in this dissertation focuses on understanding a special type of polymer brushes formed at the solid-fluid interface by self-assembly of block copolymer chains that have the ability to tether by multiple ends, thus creating loops on the surface. Specifically, I study the self-assembly of a series of poly(2-vinylpyridine)-polystyrene-poly(2-vinylpyridine) (PVP-b-PS-b-PVP) triblock copolymers and PVP-b-PS star block copolymers adsorbed from the selective solvent toluene onto silicon and mica surfaces. The triblock and star copolymers have different molecular weights and PS/PVP …
Chitosan Derivatives For Tissue Engineering, Yongzhi Qiu
Chitosan Derivatives For Tissue Engineering, Yongzhi Qiu
All Dissertations
Chitosan, a naturally occurring polysaccharide, and its derivatives have been widely explored for biomedical applications due to their biocompatibility and biodegradability. In our studies, we developed a series of chitosan derivatives through chemical modifications. These chitosan derivatives not only possess better processibility in scaffolds fabrication, but also show excellent potentials in tissue engineering applications, including blood vessel and bone tissue engineering.
The excellent antithrombogenic property is crucial for vascular engineering applications, especially in engineering small-diameter blood vessels. In our studies, chitosan was chemically modified by phthalization and the phthalized chitosan exhibited great antithrombogenic property. Through a wet- phase-inversion process, tubular …
A Comprehensive Multiphysics, Multiscale Modeling Framework For Carbon Nanotube Fabrication Process By Chemical Vapor Deposition, Mahmoud Reza Hosseini
A Comprehensive Multiphysics, Multiscale Modeling Framework For Carbon Nanotube Fabrication Process By Chemical Vapor Deposition, Mahmoud Reza Hosseini
All Dissertations
Carbon nanotubes (CNTs) are among the most promising nanosize materials as evidenced by the attention they have received since their discovery in 1991 and a wide range of scientific and industrial applications. Each of these applications requires unique CNTs with specific length, diameter and chirality. However, control of these parameters is considered as one of the main challenges for large scale production of CNTs. Furthermore, these processes are not well designed so as to limit the number of CNT defect sites or the production of unwanted byproducts such as amorphous carbon. Therefore, it is crucial to develop a controlled CNTs …
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 …
A Real-Time Traffic Condition Assessment And Prediction Framework Using Vehicle-Infrastructure Integration (Vii) With Computational Intelligence, Yongchang Ma
All Dissertations
This research developed a real-time traffic condition assessment and prediction framework using Vehicle-Infrastructure Integration (VII) with computational intelligence to improve the existing traffic surveillance system. Due to the prohibited expenses and complexity involved for the field experiment of such a system, this study adopted state-of-the-art simulation tools as an efficient alternative.
This work developed an integrated traffic and communication simulation platform to facilitate the design and evaluation of a wide range of online traffic surveillance and management system in both traffic and communication domain. Using the integrated simulator, the author evaluated the performance of different combination of communication medium and …
Radiation-Induced Osteoporosis: Bone Quantity, Architecture, And Increased Resorption Following Exposure To Ionizing Radiation, Jeffrey Willey
Radiation-Induced Osteoporosis: Bone Quantity, Architecture, And Increased Resorption Following Exposure To Ionizing Radiation, Jeffrey Willey
All Dissertations
Skeletal complications from radiation therapy have been described for breast, brain, pelvic, and blood cancers. These problems include atrophy, fractures, and osteoradionecrosis. Improved survivorship rates of cancer patients receiving radiotherapy increases the importance of understanding the causal mechanisms and long-term effects of radiation-induced bone loss. One such long-term effect is bone fractures following radiation therapy for cancer treatment. The incidence of hip fractures is significantly increased following targeted radiotherapy for cancer. This decline in bone health can have a severe impact on the patient's functional capabilities. This damage to bone following irradiation is thought to involve damage to both osteoblasts …
Renewable Resource Lactide Derived Materials: Scaled-Up Synthesis, Characterization And Applications, Akhilesh Singh
Renewable Resource Lactide Derived Materials: Scaled-Up Synthesis, Characterization And Applications, Akhilesh Singh
All Dissertations
Renewable resource monomer, lactide, derived copolymers and terpolymers were synthesized on a few hundred gram scale with specialty/commodity co-monomers such as perfluoropolyether and bisphenol A derivatives. The modifications resulted in improved properties such as surface energy, crystallization, and glass transition temperature of the polylactide.
Ring-opening polymerizations of L-lactide were performed using different block length perfluoropolyethers as macro-initiators and tin octoate as the catalyst. The resultant polylactide-perfluoropolyether-polylactide block copolymers were characterized by various analytical and microscopic techniques such as differential scanning calorimetry, thermogravimetric analysis, nuclear magnetic resonance spectroscopy, dynamic mechanical analysis, wide-angle x-ray diffraction spectroscopy, polarized optical microscopy, etc.
The incorporation …
Protocols For Dynamic Spectrum Access, Thomas Royster
Protocols For Dynamic Spectrum Access, Thomas Royster
All Dissertations
Protocols for modulation selection, initial transmitter power adjustment, modulation and coding adaptation, and transmitter power adaptation are presented. Most adaptive protocols in the literature are for full-duplex communication and they require channel estimation (e.g., using training symbols); however, our protocols are for half-duplex packet radios and they do not require estimation of the channel for adaptation. Instead, our protocols are driven by statistics that can be derived from the receiver's demodulator or decoder. We present the protocols in the context of their application to dynamic spectrum access networks. Our protocols are designed for adaptive radios, of which software-defined radios and …
Effects Of Warm Asphalt Additives On Asphalt Binder And Mixture Properties, Tejash Gandhi
Effects Of Warm Asphalt Additives On Asphalt Binder And Mixture Properties, Tejash Gandhi
All Dissertations
With increasing concerns of global warming and increasing emissions, the asphalt industry is making a constant effort to lower its emissions by reducing the mixing and compaction temperatures of the asphalt mixture without affecting the properties of the mix. Several proprietary chemicals are available in the industry that can help reduce the mixing and compaction temperatures. A significant reduction of required heat can be achieved in most cases. While some studies have been conducted to evaluate the properties of warm mix asphalt; properties of binders and mixtures, in fresh and aged conditions, containing these chemicals have not been studied in …
Formation Of Active Catalytic Sites In Hydrocarbon Synthesis And Reaction, Nattaporn Lohitharn
Formation Of Active Catalytic Sites In Hydrocarbon Synthesis And Reaction, Nattaporn Lohitharn
All Dissertations
Acid and metal catalysis are considerably important in the chemical industry especially, for the production of transportation fuels. Since a serious concern on the world environment has infringed on the restriction of aromatics contained in gasoline, the demand for clean high-octane branched alkanes for gasoline upgrading has significantly increased. This process involves acid catalyzed n-butane isomerization in which n-butane is converted to isobutane, a primary feedstock for the production of high-octane species. In addition, due to the unpredictable price and the limited resource of petroleum fuel derived crude oil, the attention has shifted to synthetic liquid fuels derived from other …
Biodiesel Production From High Free Fatty Acid Content Feedstocks, Kaewta Suwannakarn
Biodiesel Production From High Free Fatty Acid Content Feedstocks, Kaewta Suwannakarn
All Dissertations
Biomass, such as animal fats and grease, is one of the better sources for transportation fuels, e.g. biodiesel. Use of such biomass in the biodiesel synthesis decreases the need for fossil energy, provides an outlet for utilizing the abundant resources effectively and economically, results in a cleaner fuel that is biodegradable, renewable, and non-toxic. Free fatty acid (FFA) esterification and triglyceride (TG) transesterification with low molecular weight alcohols are the central reactions for the biodiesel production. The focus of this research is to establish a better fundamental insight into heterogeneous catalysis for biodiesel forming reactions, in an attempt to design …
Vibration Analysis Of Piezoelectric Microcantilever Sensors, Amin Salehi-Khojin
Vibration Analysis Of Piezoelectric Microcantilever Sensors, Amin Salehi-Khojin
All Dissertations
The main objective of this dissertation is to comprehensively analyze vibration characteristics of microcantilever-based sensors with application to ultra small mass detection and low dimensional materials characterization. The first part of this work focuses on theoretical developments and experimental verification of piezoelectric microcantilevers, commercially named Active Probes, which are extensively used in most today's advanced Atomic Force Microscopy (AFM) systems. Due to special geometry and configuration of Active Probes, especially multiple jump discontinuities in their cross-section, a general and comprehensive framework is introduced for forced vibration and modal analysis of discontinuous flexible beams. More specifically, a general formulation is obtained …
Study Of Electrospinning Of Property-Modulated Biomedical Microfibers, Scott Taylor
Study Of Electrospinning Of Property-Modulated Biomedical Microfibers, Scott Taylor
All Dissertations
Electrospinning technologies have been of great interest in recent years, due in large part to developments in the field of Bioengineering, including the preparation of novel polymers and advances in tissue engineering, specifically for therapeutic applications. The electrospinning process is, in general, a very benign process that allows the preparation, under mild conditions, of micro- and nano-scale fibers from fiberforming materials, as well as traditionally non-fiber forming materials. This process is of specific interest to the biomedical community because it affords an opportunity to create highly-tailored novel constructs with a multitude of possible uses. Some proposed uses for these materials …
Anaerobic Biodegradation Of Ethylene Dibromide And 1,2-Dichloroethane In The Presence Of Fuel Hydrocarbons, James Henderson
Anaerobic Biodegradation Of Ethylene Dibromide And 1,2-Dichloroethane In The Presence Of Fuel Hydrocarbons, James Henderson
All Dissertations
Field evidence from underground storage tank (UST) sites where leaded gasoline leaked indicates the lead scavengers 1,2-dibromoethane (ethylene dibromide, or EDB) and 1,2-dichloroethane (1,2-DCA) may be present in groundwater at levels that pose unacceptable risk. These compounds are seldom tested for at UST sites. Although dehalogenation of EDB and 1,2-DCA is known to occur, the effect of fuel hydrocarbons on their biodegradability under anaerobic conditions is poorly understood. Microcosms (2 L glass bottles) were prepared with soil and groundwater from a UST site in Clemson, South Carolina, using samples collected from the source (containing residual fuel) and less contaminated downgradient …
Incorporation Of Polydiacetylene Sensors Into Commercial Polymers, Jennifer Kauffman
Incorporation Of Polydiacetylene Sensors Into Commercial Polymers, Jennifer Kauffman
All Dissertations
Polydiacetylenes (PDAs) exhibit a chromatic response to solvents, temperature, strain and other environmental perturbations. When formed in a solid-state polymerization, the backbone of the polymer is planar and continuous π-overlap is observed. However, when the PDA backbone is distorted by an outside force the extended conjugation is interrupted and an optical shift from blue to red occurs. By exploiting the PDAs properties within polymer systems, smart fibers and films have been created that enhance the original intention of the host. Under this umbrella, a strain sensitive polydiacetylene-polyurethane blend was created using 3 and 4-butoxycarbonylmethylurethane PDA and a medical grade polyurethane, …
Optimal Fleet Size Of An Integrated Production And Distribution Scheduling Problem For A Single Perishable Product, Priyantha Devapriya
Optimal Fleet Size Of An Integrated Production And Distribution Scheduling Problem For A Single Perishable Product, Priyantha Devapriya
All Dissertations
This dissertation focuses on a practical production problem in which a perishable product must be produced and distributed at minimum cost. The problem has some features of the integrated production and distribution scheduling problem in that we seek to determine the fleet size and their routes subject to a planning horizon constraint but there are significant differences as well. In particular, this research differs because the product has a limited lifetime, the total demand must be satisfied within a planning horizon, multiple trucks can be used, and the production schedule and the distribution sequence are considered. Two mixed integer programming …
Physics-Based Shape Morphing And Packing For Layout Design, Hong Dong
Physics-Based Shape Morphing And Packing For Layout Design, Hong Dong
All Dissertations
The packing problem, also named layout design, has found wide applications in the mechanical engineering field. In most cases, the shapes of the objects do not change during the packing process. However, in some applications such as vehicle layout design, shape morphing may be required for some specific components (such as water and fuel reservoirs). The challenge is to fit a component of sufficient size in the available space in a crowded environment (such as the vehicle under-hood) while optimizing the overall performance objectives of the vehicle and improving design efficiency. This work is focused on incorporating component shape design …
Development Of Prediction Models Of High Temperature Crumb Rubber Modified Binders, Carl Thodesen
Development Of Prediction Models Of High Temperature Crumb Rubber Modified Binders, Carl Thodesen
All Dissertations
The purpose of this research was to identify and model critical elements of the asphalt rubber matrix contributing to the crumb rubber modified (CRM) binder properties as measured by Superpave testing procedures. Current models are neither applicable (due to new testing procedures) nor practical (due to the difficulty of application or lack of accuracy). Therefore, this research investigated the development of predictive models for estimating binder properties within a specified range of accuracy.
Multiple crumb rubber sources were evaluated in order to gain an understanding of the differences between the various crumb rubbers. This analysis permitted identification of the important …
Real-Time Raman Spectroscopy And Wide-Angle X-Ray Diffraction During Single-Layer And Multi-Layer Blown Film Extrusion, Giriprasath Gururajan
Real-Time Raman Spectroscopy And Wide-Angle X-Ray Diffraction During Single-Layer And Multi-Layer Blown Film Extrusion, Giriprasath Gururajan
All Dissertations
Properties exhibited by blown films are controlled by the microstructure developed during their processing. Therefore, real-time measurement of microstructure during the blown film extrusion can help in better control and optimization of the process needed to obtain desired properties. The objectives of this research were (i) to conduct real-time microstructural measurements during single-layer and multi-layer blown film extrusion of polypropylene (PP) and low-density polyethylene (LDPE) using real-time Raman spectroscopy; (ii) to conduct real-time wide-angle X-ray diffraction (WAXD) during single-layer blown film extrusion of LDPE to obtain crystallinity and orientation values during the process; and (iii) to investigate the effect of …
Laboratory Evaluation Of Chlorinated Ethene Transformation Processes In Fractured Sandstone, Ramona Darlington
Laboratory Evaluation Of Chlorinated Ethene Transformation Processes In Fractured Sandstone, Ramona Darlington
All Dissertations
A fractured sandstone aquifer at an industrial site in southern California is contaminated with trichloroethene (TCE) to depths in excess of 244 m. Field monitoring data suggest that TCE is undergoing reduction to cis-DCE and that additional attenuation is occurring. However, vinyl chloride (VC) and ethene have not been detected in significant amounts, so that if transformation is occurring, a process other than reductive dechlorination must be responsible. The overall objective of this study was to evaluate the occurrence of biotic and abiotic transformation processes at this site for TCE, cis-DCE and VC. Anaerobic microcosms were constructed with site groundwater …
Modeling Of The Effect Of Tool Wear On Cutting Forces In Turning, Yu Long
Modeling Of The Effect Of Tool Wear On Cutting Forces In Turning, Yu Long
All Dissertations
Machining is the most widely used and efficient material removal process, and tool wear in machining is usually of great interest in order to improve machining efficiency and effectiveness. Cutting tool wear patterns such as the flank and crater wear and the dead metal zone (DMZ) may induce the cutting tool geometry variation in machining. As a result, cutting forces may increase or decrease due to the change of tool effective cutting geometry during machining operations. A quantitative understanding of and the ability to predict cutting forces in relation to tool wear are important to the tool life estimation, chatter …