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Articles 1 - 16 of 16
Full-Text Articles in Engineering
Structure-Property Evolution During Polymer Crystallization, Deepak Arora
Structure-Property Evolution During Polymer Crystallization, Deepak Arora
Open Access Dissertations
The main theme of this research is to understand the structure-property evolution during crystallization of a semicrystalline thermoplastic polymer. A combination of techniques including rheology, small angle light scattering, differential scanning calorimetry and optical microscopy are applied to follow the mechanical and optical properties along with crystallinity and the morphology. Isothermal crystallization experiments on isotactic poly-1-butene at early stages of spherulite growth provide quantitative information about nucleation density, volume fraction of spherulites and their crystallinity, and the mechanism of connecting into a sample spanning structure. Optical microscopy near the fluid-to-solid transition suggests that the transition, as determined by time-resolved mechanical …
Diffusion And Structure In Complex Fluids: I. Axial Diffusion In Membranes Ii. Proteins In Ionic Liquids, Malvika Bihari
Diffusion And Structure In Complex Fluids: I. Axial Diffusion In Membranes Ii. Proteins In Ionic Liquids, Malvika Bihari
Open Access Dissertations
Geometrically hindered motions of a single large solute (particle or polymer) can be imaged in real time via optical microscopy. The dynamics of fluorescent colloidal particles near surfaces and in porous membranes were monitored using confocal microscopy. A method of analysis to estimate diffusivity of particles in the axial direction by observing their intensity fluctuations was developed. The intensity fluctuations correspond to the Brownian motion of the particles in the axial direction. The method was successful in capturing the hindered diffusion of particles close to surfaces and in pores. This study provides a novel route to monitor the dynamics of …
Hole Mobility In Strained Ge And Iii-V P-Channel Inversion Layers With Self-Consistent Valence Subband Structure And High-K Insulators, Yan Zhang
Open Access Dissertations
We present a comprehensive investigation of the low-¯eld hole mobility in strained Ge and III-V (GaAs, GaSb, InSb and In1¡xGaxAs) p-channel inversion layers with both SiO2 and high-· insulators. The valence (sub)band structure of Ge and III-V channels, relaxed and under strain (tensile and compressive) is calculated using an effcient self-consistent method based on the six-band k ¢ p perturbation theory. The hole mobility is then computed using the Kubo-Greenwood formalism accounting for non-polar hole-phonon scattering (acoustic and optical), surface roughness scatter- ing, polar phonon scattering (III-Vs only), alloy scattering (alloys only) and remote phonon scattering, accounting for multi-subband dielectric …
Catalytic Fast Pyrolysis Of Biomass For The Production Of Fuels And Chemicals, Torren Ryan Carlson
Catalytic Fast Pyrolysis Of Biomass For The Production Of Fuels And Chemicals, Torren Ryan Carlson
Open Access Dissertations
Due to its low cost and large availability lignocellulosic biomass is being studied worldwide as a feedstock for renewable liquid biofuels. Currently there are several routes being studied to convert solid biomass to a liquid fuel, which involve multiple steps at long residence times thus greatly increasing the cost of biomass processing. Catalytic fast pyrolysis (CFP) is a new promising technology to convert directly solid biomass to gasoline-range aromatics that fit into the current infrastructure. CFP involves the rapid heating of biomass (~500˚C sec-1) in an inert atmosphere to intermediate temperatures (400 to 600 ˚C) in the presence of zeolite …
Bench-Scale Assessment Of Low Pressure Membrane Fouling: Characterization And Examination The Role Of Organic Nitrogen Compounds, Anh Hai Nguyen
Bench-Scale Assessment Of Low Pressure Membrane Fouling: Characterization And Examination The Role Of Organic Nitrogen Compounds, Anh Hai Nguyen
Open Access Dissertations
The primary goal of this research was to improve understanding of the fouling of low pressure hollow fiber membranes used in drinking water treatment. The major difference of this study compared to other reported studies was the use of a hollow fiber membrane module at operating conditions mimicking those of full-scale practice. Two poly(vinylidene-fluoroethylene) based hollow fiber membranes (A and B) were tested. Different types of fouling indices (total, hydraulic irreversible, chemical irreversible) developed based on a resistance in series model were used to assess membrane performance. Data from bench-scale and full-scale plants were compared to validate the use of …
Stochastic Modeling Of The Equilibrium Speed-Density Relationship, Haizhong Wang
Stochastic Modeling Of The Equilibrium Speed-Density Relationship, Haizhong Wang
Open Access Dissertations
Fundamental diagram, a graphical representation of the relation among traffic flow, speed, and density, has been the foundation of traffic flow theory and transportation engineering for many years. For example, the analysis of traffic dynamics relies on input from this fundamental diagram to find when and where congestion builds up and how it dissipates; traffic engineers use a fundamental diagram to determine how well a highway facility serves its users and how to plan for new facilities in case of capacity expansion. Underlying a fundamental diagram is the relation between traffic speed and density which roughly corresponds to drivers’ speed …
On Detection, Analysis And Characterization Of Transient And Parametric Failures In Nano-Scale Cmos Vlsi, Alodeep Sanyal
On Detection, Analysis And Characterization Of Transient And Parametric Failures In Nano-Scale Cmos Vlsi, Alodeep Sanyal
Open Access Dissertations
As we move deep into nanometer regime of CMOS VLSI (45nm node and below), the device noise margin gets sharply eroded because of continuous lowering of device threshold voltage together with ever increasing rate of signal transitions driven by the consistent demand for higher performance. Sharp erosion of device noise margin vastly increases the likelihood of intermittent failures (also known as parametric failures) during device operation as opposed to permanent failures caused by physical defects introduced during manufacturing process. The major sources of intermittent failures are capacitive crosstalk between neighbor interconnects, abnormal drop in power supply voltage (also known as …
Prediction And Manipulation Of Drop Size Distribution Of Emulsions Using Population Balance Equation Models For High-Pressure Homogenization, Neha B. Raikar
Prediction And Manipulation Of Drop Size Distribution Of Emulsions Using Population Balance Equation Models For High-Pressure Homogenization, Neha B. Raikar
Open Access Dissertations
Emulsions constitute a wide range of natural as well as processed products. Pharmaceutical applications of emulsions include oral administration, parenteral delivery, ophthalmic medicine, topical and transdermal creams, and fluorocarbon-in-water emulsions for blood oxygenation. In the foods area many of the products like mayonnaise, margarine, ice-creams are emulsions by nature and some products can also be used for delivery of active ingredients (e.g. nutraceuticals) with potential health benefits. Emulsions are also encountered at many stages of petroleum recovery, transportation, and processing. Typically, emulsions are manufactured in a two-step process. First a coarse emulsion called a premix is made which is passed …
Diversifying The Internet, Yong Liao
Diversifying The Internet, Yong Liao
Open Access Dissertations
Diversity is a widely existing and much desired property in many networking systems. This dissertation studies diversity problems in Internet, which is the largest computer networking system in the world. The motivations of diversifying the Internet are two-fold. First, diversifying the Internet improves the Internet routing robustness and reliability. Most problems we have encountered in our daily use of Internet, such as service interruptions and service quality degradation, are rooted in the inter-domain routing system of Internet. Inter-domain routing is policy-based routing, where policies are often based on commercial agreements between ASes. Although people know how to safely accommodate a …
A Hardware/Software Co-Design Architecture For Thermal, Power, And Reliability Management In Chip Multiprocessors, Omer Khan
Open Access Dissertations
Today’s designs are being shaped by the challenges of nano-CMOS technologies: increased power density, rising junction temperatures, and rising rate of errors and device failures that constrain average rate of power dissipation, and design technologies that limit peak power delivery. This thesis focuses on how to leverage the hardware and software abstraction layers of today’s systems. Several of the low level hardware details such as power, hotspots, and faults are tightly correlated to interactions within the system including application and hardware behavior. The conventional approach to tackling such problems come with additional costs and design complexity, and they are limited …
Polymer Composites And Porous Materials Prepared By Thermally Induced Phase Separation And Polymer-Metal Hybrid Methods, Joonsung Yoon
Polymer Composites And Porous Materials Prepared By Thermally Induced Phase Separation And Polymer-Metal Hybrid Methods, Joonsung Yoon
Open Access Dissertations
The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the composition of …
Quantifying Defects In Zeolites And Zeolite Membranes, Karl Daniel Hammond
Quantifying Defects In Zeolites And Zeolite Membranes, Karl Daniel Hammond
Open Access Dissertations
Zeolites are crystalline aluminosilicates that are frequently used as catalysts to transform chemical feedstocks into more useful materials in a size- or shape-selective fashion; they are one of the earliest forms of nanotechnology. Zeolites can also be used, especially in the form of zeolite membranes (layers of zeolite on a support), to separate mixtures based on the size of the molecules. Recent advances have also created the possibility of using zeolites as alkaline catalysts, in addition to their traditional applications as acid catalysts and catalytic supports. Transport and catalysis in zeolites are greatly affected by physical and chemical defects. Such …
Water-In-Oil Microemulsions: Counterion Effects In Aot Systems And New Fluorocarbon-Based Microemulsion Gels, Xiaoming Pan
Water-In-Oil Microemulsions: Counterion Effects In Aot Systems And New Fluorocarbon-Based Microemulsion Gels, Xiaoming Pan
Open Access Dissertations
Microemulsions have important applications in various industries, including enhanced oil recovery, reactions, separations, drug delivery, cosmetics and foods. We investigated two different kinds of water-in-oil microemulsion systems, AOT (bis(2-ethylhexyl) sulfosuccinate) microemulsions with various counterions and perfluorocarbon-based microemulsion gels with triblock copolymers. In the AOT systems, we investigated the viscosity and interdroplet interactions in Ca(AOT)2, Mg(AOT)2 and KAOT microemulsions, and compared our results with the commonly-studied NaAOT/water/decane system. We attribute the differences in behavior to different hydration characteristics of the counterions, and we believe that the results are consistent with a previously proposed charge fluctuation model. Perfluorocarbons (PFCs) are of interest …
Modeling Of Thermal Non-Equilibrium In Superheated Injector Flows, Shivasubramanian Gopalakrishnan
Modeling Of Thermal Non-Equilibrium In Superheated Injector Flows, Shivasubramanian Gopalakrishnan
Open Access Dissertations
Among the many factors that effect the atomization of a fuel spray in a com- bustion chamber, the flow characteristics of the fuel inside the injector nozzle play significant roles. The enthalpy of the entering fuel can be elevated such that it is higher than the local or downstream saturation enthalpy, which will result in the flash-boiling of the liquid. The phase change process dramatically effects the flow rate and has the potential to cause subsonic two-phase choking. The timescale over which this occurs is comparable to the flow-through time of the nozzle and hence any attempt to model this …
Protocol And System Design For A Service-Centric Network Architecture, Xin Huang
Protocol And System Design For A Service-Centric Network Architecture, Xin Huang
Open Access Dissertations
Next-generation Internet will be governed by the need for flexibility. Heterogeneous end-systems, novel applications, and security and manageability challenges require networks to provide a broad range of services that go beyond store-and-forward. Following this trend, a service-centric network architecture is proposed for the next-generation Internet. It utilizes router-based programmability to provide packet processing services inside the network and decompose communications into these service blocks. By providing different compositions of services along the data path, such network can customize its connections to satisfy various communication requirements. This design extends the flexibility of the Internet to meet its next-generation challenges. This work …
Evaluating Alternative Public-Private Partnership Strategies For Existing Toll Roads: Toward The Development Of A Decision Support System, Christopher John Ahmadjian
Evaluating Alternative Public-Private Partnership Strategies For Existing Toll Roads: Toward The Development Of A Decision Support System, Christopher John Ahmadjian
Open Access Dissertations
Many claim that, with regard to transportation infrastructure, only partnerships between public and private entities, which draw on the strengths of both, can achieve the goals of enhancing operational efficiency, increasing service delivery, improving asset maintenance, and stretching scarce federal, state, and local tax dollars. While some completed public-private partnership (P3) agreements on existing toll roads in the United States have seen a measure of success, others have raised critical questions pertaining to the true costs and benefits associated with these agreements for all stakeholders. Of particular concern is an apparent reliance on monetary calculations alone to determine toll road …