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    Synthesis And Characterization Of Platinum And Carbon Nanoparticle In Benzene By Electric Plasma Discharge In Ultrasonic Cavitation
    (Materials Science & Engineering, 2011-07-14)
    Nanoparticles are of interest due to the high number of atoms located on the surface. This high surface area is conductive to higher catalytic efficiency than normal seen in bulk metals. Of numerous Nanoparticles catalysts studied, Platinum (Pt) nanoparticles have attracted particular interest due to their superior catalysis for many chemical reactions, especially for fuel cell reactions including hydrogen oxidation and oxygen reduction. Carbon supported Pt nanoparticles are active anode catalysts for fuel cells. In this thesis nano-sized Pt particles have been synthesized by an advanced and cost effective method. Pt nanoparticles embedded in carbon matrix were synthesized by an electric plasma discharge generated in the ultrasonic cavitation field of benzene. Several material characterization techniques such as Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to study the particle size and structure of the synthesized nanoparticles. X-ray photoelectron Spectroscopy (XPS) and Energy dispersive X-ray Spectroscopy (EDX) analysis were used to study the chemical composition of the synthesized nanoparticles. Magnetic nanoparticles are of considerable interest owing to their potentials application in magnetic fluids, magnetic recording materials, biomedicine, and other applications. In particular magnetic nanoparticles offer attractive possibilities in biomedicine. The size of magnetic nanoparticles range from few nanometers up to tens of nanometers, which places them at dimensions of biological entity such as a cell, a virus, a protein and a gene. Magnetic nanoparticles can be manipulated using an external magnetic field, which provides applications such as tagging of biomolecules, efficient bioseparation, sensitive biosensing, magnetic resonance imaging and drug delivery. These applications require particles to be biocompatible, stable and biodegradable. Carbon nanoparticles are potentially biocompatible, chemically stable and nontoxic .In this work Graphite nanoparticles and iron doped carbon nanoparticles were synthesized by an electric plasma discharge generated in the ultrasonic cavitation field of benzene. Several material characterization techniques such as High Resolution Transmission Electron Microscopy (HRTEM) and XRD were used to study the particle size and structure of the synthesized nanoparticles.XPS and EDX analysis were used to study the chemical composition of the synthesized nanoparticles. Raman spectroscopy was used to characterize carbon nanoparticles. Magnetic measurement of iron doped carbon and graphite nanoparticles were measured using Vibrating sample magnetometer (VSM).
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    New Macrocyclic Glycopeptide Antibiotic For Chiral HPLC Stationary Phases And Ionic Liquids In Analytical Chemistry
    (Chemistry & Biochemistry, 2011-07-14)
    The main focus of this dissertation is on the development of new chiral stationary phases for HPLC and GC and the application of ionic liquids in analytical chemistry. They will be discussed separately in two parts. Enantiomeric separations continue to be of great interest to the pharmaceutical industry. It is because drug molecules of opposite chirality often possess distinctive effects in biological environments. Direct chromatography is one of the major techniques used to address the challenge of enantiomeric analysis. Macrocyclic glycopeptides are a very useful class of chiral selectors for HPLC stationary phases because of their broad enantioselectivity. A study of a new macrocyclic glycopeptide antibiotic, dalbavancin, as chiral selector for HPLC will be described in part one. Two stationary phases based on dalbavancin were synthesized via two different binding strategies and compared against with commercial teicoplanin column. The application of Ionic liquids in analytical chemistry is growing rapidly due to their valuable properties such as wide liquid temperature range, high thermal stability, inflammability etc. Several techniques based on ionic liquids are maturing into commercialized products. In part two, the synthesis, physical properties, and the use as ion pairing reagent for anion detection in ESI-MS of linear tricationic ionic liquids will be presented. In chapter 7, a study of new chiral GC columns using ionic liquids as matrices and methylated ionic cyclodextrin as chiral selector will be discussed.
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    Some Problems Of Integral Geometry In Advanced Imaging
    (Mathematics, 2011-07-14)
    During the past decade, our society has become dependent on advanced mathematics for many of our daily needs. Mathematics is at the heart of the 21st century technologies and more specifically the emerging imaging technologies from thermoacoustic tomography (TAT) and ultrasound computed tomography (UCT) to non-destructive testing (NDT). All of these applications reconstruct the internal structure of an object from external measurements without damaging the entity under investigation. The basic mathematical idea common to such reconstruction problems is often based upon Radon integral transform.The Radon integral transform Rf puts into correspondence to agiven function f its integrals over certain subsets. In this work,we will focus on the situation when the subsets are circles. Themajor problems related to this transform are the existence anduniqueness of its inversion, inversion formulas and the rangedescription of the transform. When Rf is known for circles of allpossible radii, there are well developed theories now addressingmost of the questions mentioned above. However, many of thesequestions are still open when Rf is available for only a part ofall possible radii, or when the support of f is outside the circle.The aim of my dissertation is to derive some new results about theexistence and uniqueness of the representation of a function by itscircular Radon transform with radially partial data for bothinterior and exterior problems. The presented new results open newfrontiers in the field of medical imaging such as intravascularultrasound (IVUS) and transrectal ultrasound (TRUS).
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    A Snapshot Of Advanced High School Students' Understanding Of Continuity
    (Mathematics, 2011-07-14)
    We report on a study of sixteen high school calculus and seven precalculus students' concept image and concept definition of continuity after one-trimester of instruction at a large suburban high school in the southwestern United States. The researchers developed a questionnaire based upon the work of Tall and Vinner (1981) to determine if calculus students had developed a more sophisticated concept image and concept definition of continuity than students in pre-calculus after a typical treatment in both courses. Using data from the written assessment it was not evident that calculus students demonstrated a more sophisticated concept image and concept definition than pre-calculus students. However, findings suggest that a weak concept image or concept definition of continuity reflects practices in precalculus and calculus instruction.
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    High Detectivity Pyroelectric Infrared Detector
    (Electrical Engineering, 2011-07-14)
    The sensors which measure physical quantities by sensing them as thermal quantities and then converting the thermal signals into electrical signals are called thermal sensors. One such type of thermal sensor is a pyroelectric infrared sensor. Thermal sensors are not popular mainly because they are slow devices, and they have low sensitivity when compared to photon detectors. One major advantage of thermal detectors over photon detectors is that they can operate at room temperature. This is one of the main motivations for this research. The aim of the thesis is to design an uncooled, high detectivity pyroelectric infrared detector. The high detectivity is obtained by reducing the thermal conductivity from the sensor to the substrate or the heat sink. Pyroelectricity is defined as the change in polarization with corresponding change in temperature. Lead calcium titanate (PCT) is a material which is a ferroelectric perovskite. It has a very high pyroelectric co-efficient, high dielectric constant and if deposited in a proper ratio could yield a very high pyroelectric response in the range of 6 x106 V/W. The thermal conductance between the sensor and the substrate using the proposed design is found to be as low as 9.51x10-9 W/K, less than the radiative thermal conductance 3.69x10-7 W/K. Two kinds of absorber designs are proposed with this detector. The efficiency of the design and the directivity of the top surface of the infrared sensor are found to have 55° field of view on both sides. Various fabrication methods for fabricating the device have been discussed in detail and the best methods have been mentioned in comparison over the other types. The development of the absorber and its application in the detection mechanism is discussed in detail.
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    Temperature And Frequency Dependence Of Thermal Impedance In Dielectrically Isolated SiGe HBTs
    (Electrical Engineering, 2011-07-14)
    Silicon Germanium (SiGe) heterojunction bipolar transistors (HBTs) have been designed to cater the demand of high speed circuits having applications in wireless and optical communication. Due to higher cut-off frequencies and high speed applications, self heating plays a significant role in the performance of SiGe HBTs. This thesis paper does an extensive analysis on the effect of self heating and used different DC, time domain and frequency domain methods to extract the self heating parameters thermal resistance (Rth) and thermal capacitance (Cth). The VBIC (Vertical Bipolar Inter Company) model is used for all the simulations. Simulations are performed using ICCAP (Integrated Circuit Characterization and Analysis Program) tool. Measurements are done using HP 4142 DC source module, Agilent 6000 series oscilloscope and Agilent 8753 ES s-parameter network analyzer. National Semiconductor Corporation's SiGe LV (low voltage) NPN HBT with emitter dimensions 10um×0.25um from their CBC8 process is used for getting real data.
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    Mathematical Optimization Techniques For Managing Selective Catalytic Reduction For Coal-fired Power Plants
    (Industrial & Manufacturing Engineering, 2011-07-14)
    Coal is one of the most important energy sources in the U.S. However, it is also one of the biggest air polluters where the major emissions generated from coal combustion are oxides of nitrogen (NOx). NOx leads to ozone formation and make people more susceptible to respiratory illness. The US Environmental Protection Agency (EPA) has steadily tightened the regulation for NOx emissions that can be discharged into the atmosphere. Many techniques and technologies can all assist with NOx removal. However, to meet upcoming EPA mandates, more aggressive technique such as Selective Catalytic Reduction (SCR) is highly recommended. SCR is an emissions control technique that primarily reduces harmful emissions of NOx. To maintain SCR performance, catalyst layers may be added or replaced to improve NOx reduction efficiency. To make these changes, power plants must be temporarily shut down, and SCR maintenance during scheduled power plant outages can be very expensive. Consequently, developing fleet-wide SCR management plans that are both efficient at reducing NOx and limiting operating costs would be extremely de-sirable. In this dissertation, we propose an SCR management framework that finds an optimal SCR management plan for the fleet number of plants that minimizes NOx emissions or total operating costs using mathematical optimization techniques. In the first part of this dissertation, we propose an SCR schedule generation and optimization algorithm (SGO) to solve the fleet SCR management problem. SCR schedule generation enumerates the set of possible outage schedules by recursion. An optimal set of these generated schedules are then selected by a 0-1 large scale integer program. The main approaches for SGO are recursion, branch-and-bound, and Pareto efficient frontiers. Although SGO is very effective and can yield a good result within a reasonable amount of time, the problem size can get larger and the computational time can increase exponentially. In the second part of this dissertation, we address this limitation by replacing SGO with a multi-commodity network flow problem (MCFP). We first formulated the MCFP as a relaxed problem to solve the fleet SCR management problem without a constraint on average daily NOx. Edges are generated instead of schedules to represent the flow of all SCR catalyst layers for the fleet. The MCFP relaxed problem is solved by a 0-1 integer program. We then address the average daily NOx constraint limitation by introducing MCFP with schedule elimination constraints (MCFPwSEC). The MCFPwSEC algorithm uses a single cut per iteration to incorporate an average daily NOx constraint into the model. We then reduce the computational time further with the introduction of a multi-cut MCFPwSEC. Multi-cut MCFPwSEC similarly eliminate infeasible solutions per iteration based on a heuristic algorithm. Then, we further explore additional ways to reduce the computational time further with discussions on a reactor potential (RP) constraint. Finally, we discuss future extensions of this research.
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    The Translator's Assistant: A Multilingual Natural Language Generator Based On Linguistic Universals, Typologies, And Primitives
    (Linguistics, 2011-07-14)
    The Translator's Assistant (TTA) is a multilingual natural language generator (NLG) designed to produce initial drafts of translations of texts in a wide variety of target languages. The four primary components of every NLG system of this type are 1) the ontology, 2) the semantic representations, 3) the transfer grammar, and 4) the synthesizing grammar. This system's ontology was developed using the foundational principles of Natural Semantic Metalanguage theory. TTA's semantic representations are comprised of a controlled, English influenced metalanguage augmented by a feature system which was designed to accommodate a very wide variety of target languages. TTA's transfer grammar incorporates many concepts from Functional-Typological grammar as well as Role and Reference grammar. The synthesizing grammar is intentionally very generic, but it most closely resembles the transformational-generative model. The meaning-based theory of translation underlies the TTA system. The fundamental question that this research proposes to answer is as follows: if the semantic representations contain sufficient information, and if the grammar possesses sufficient capabilities, then is TTA able to generate drafts of sufficient quality that they improve the productivity of experienced mother-tongue translators? To answer this question, software was developed that allows a linguist to build a lexicon and grammar for a particular target language. Then semantic representations were developed for one hundred and five chapters of text. Two unrelated languages were chosen to test the system, and a partial lexicon and grammar were developed for each test language: English and Korean. Fifty chapters of text were generated in Korean, and all one hundred and five chapters were generated in English. Then extensive experiments were performed to determine the degree to which the computer generated drafts improve the productivity of experienced mother-tongue translators. Those experiments indicate that when experienced mother-tongue translators use the rough drafts generated by TTA, their productivity is typically quadrupled without any loss of quality.
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    The Analysis And Testing Of The Quaife Torque-biasing Differential
    (Mechanical Engineering, 2011-07-14)
    The purpose of this thesis is to analyze and test the Quaife torque biasing differential. The differential was modeled mathematically and equations were formulated. Experiments were then performed on a Formula SAE car to see how the output torque of each axle would react to modified preload torques. The results of these tests were then compared with the mathematical models. Overall, it was found that the there are two equations that govern the differential: one for traction and one for slip, and that the derived model correlates well with the experimental results.
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    The Complex Gaussian Scale Mixtures Of Complex Wavelet Coefficients And Applications
    (Electrical Engineering, 2011-07-14)
    In this thesis, the complex Gaussian scale mixture (CGSM), which is an extension of the Gaussian scale mixture (GSM) for real-valued random variables to the complex case, is presented to model the complex wavelet coefficients. Along with some related propositions and miscellaneous results, the probability density functions (pdf) of the magnitude and phase of the complex random variable are presented. Specifically, the closed forms of the magnitude pdf for the case of complex generalized Gaussian distribution (CGGD) and the phase pdf for the general case are presented. Subsequently, the pdf of the relative phase is derived.Moreover, parameter estimation methods in the presence of noise for several magnitude pdf's which are special cases of the magnitude pdf related to the CGSM, and for the relative phase pdf (RP pdf) are proposed. In addition, the parameter estimation of the RP pdf is investigated, and a non-iterative estimator for the relative phase pdf's parameters is also proposed.To show the usefulness of the proposed model, the CGSM is then applied to image denoising using Bayes least square estimator. The experimental results show that using the CGSM of complex wavelet coefficients visually improves the quality of denoised images from the real case. Moreover, the derived magnitude pdf of the CGGD is then utilized in texture image retrieval that uses complex coefficient magnitude to improve the accuracy rate from using the real or imaginary parts. Finally, the problem of noisy texture retrieval, where the query image is contaminated by noise, is studied. This texture retrieval scheme is based on the proposed parameter estimation methods in the presence of noise. The retrieval results show that using both magnitude and phase information of complex coefficients improves the accuracy rate from solely using the magnitude or phase information, and also from using the real or the imaginary parts. These simulation results are also consistent in several complex transform domains.
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    Distributed Model For Thermal Characterization Of Oxide Isolated Silicon Germanium Heterojunction Bipolar Transistors
    (Electrical Engineering, 2011-07-14)
    Demand for high-speed and cost-effective devices has resulted in the development of smaller, high frequency devices. Since semiconductor devices are getting smaller, self-heating effects have become more important. This is especially true in BJTs/HBTs since the base-emitter voltage and hence collector current are sensitive to temperature variations. Self-heating increases the temperature of the devices and results in variations in the electrical properties of the circuit in which these devices are used. Hence, it is important to accurately characterize the self-heating effects and develop reliable models, so that these effects can be taken into consideration in the simulations during the design process. With the development of Silicon on Insulator (SOI) technology, self-heating is even more dominant because the oxide is a poor conductor of heat, and the heat tends to get trapped within the device resulting in much longer time constants. This work deals with the development of the Vertical Bipolar Inter-Company (VBIC) model parameters to characterize self-heating in SOI SiGe transistors which have been fabricated by National Semiconductors (NSC).
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    Unsaturated Soil Behavior Under Large Deformations Using A Fully Servo/suction-controlled Ring Shear Apparatus
    (Civil & Environmental Engineering, 2011-07-14)
    In recent years, the key hypotheses of most elasto-plastic constitutive frameworks postulated for unsaturated soils have been validated via suction-controlled oedometer, triaxial, and direct shear testing. These techniques, however, allow for the application of loads along limited modes and levels of soil deformation. Today, it is well known that most geotechnical infrastructure resting on unsaturated ground involves a wide range of deformations. Calculation of foundation settlement, for instance, requires a good estimation of soil stiffness at relatively small strains. Analysis of slopes, embankments, and soil bearing capacity, on the other hand, requires an adequate estimation of shear strength, from peak to residual. To date, however, there is very limited experimental evidence of unsaturated soil response under mid-to-large strain levels under controlled-suction states. This paper introduces a novel suction-controlled ring shear apparatus suitable for modeling unsaturated soil response over a whole range of deformations using the axis-translation technique. The apparatus features a 113 N-m torque motor along with a 360-degree-range angular deformation sensor. The lower annular shear platen accommodates a 15.24-cm OD x 9.65-cm ID x 1.5-cm thickness specimen and also features custom-made grooves to house a full set of six 5-bar or 15-bar ceramics as well as diffused-air flushing ports. A series of suction-controlled ring shear tests was accomplished on several identically prepared, ring-shaped specimens of compacted silty sand (SM) and silty clayey sand (SC-SM). Matric suction was found to exert a critical influence on soil's peak and residual strength responses under constant-suction ring shear testing. Residual shear strength parameters, residual friction angle and residual intercept cohesion, showed a significant increase with applied suction. A comparison of results with literature allowed determining than high suction has a significant influence on the residual strength and residual friction angle of plastic material, but any effect on the cohesion intercept, which is predominantly close to zero.
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    A Comparison Method To Evaluate Motion Splicing Techniques
    (Electrical Engineering, 2011-07-14)
    The development of methods for the re-use and modification of motion data is an activearea of research. Among these methods, we find automatic techniques to generate a spliced motion by combining different actions recorded in separate sessions. Motion splicing allows capturing motion independently and later combining them to create a new natural looking motion. Even though there have been a lot of research on motion editing techniques, less focus has been given to evaluate these edited motions. In this thesis, we present a novel methodology to quantitatively evaluate the synthesized motion generated by different motion editing techniques. We implemented three splicing algorithms to perform a comparison study based on our evaluation methodology. The splicing algorithms considered are spatial body alignment, segmentation-based method, and naïve DOF replacement. We use 39 sets of motions in the Human Motion Database specifically collected for testing splicing. The motion sets consist of two actions performed individually and then in combination to each other. This data served as the ground truth in our comparison. The motions synthesized using the above splicing techniques were then evaluated using our quantitative evaluation method. The spatial body alignment performs best since it accounts for the correlation between joints. Due to poor segmentation, the segmentation-based method generated too much jerkiness in the synthesized motion which was demonstrated with a poor result in our evaluation
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    Hybrid Dynamic Simulation For Performance Optimization Of Legged Mechanisms
    (Mechanical Engineering, 2011-07-14)
    Agile locomotion is needed for mobile robots to efficiently navigate challenging terrain. The ability of an agile legged mobile robot to abruptly change trajectory allows it toquickly react to obstacles and successfully operate in environments usually more suited forlegged animals. The research presented herein aims to increase the agility and performanceof legged robots.Using hybrid dynamic simulation, novel methods are developed to model the inter-action of a legged robot with the ground. In considering robot agility, an accurate model ofthe events that occur while in contact is needed. Methods are developed to model groundinteraction where oblique angled impacts occur, and to address the well known issues withenergy consistency when using rigid body models for dynamic systems.The contact model in this work is investigated with three multibody benchmark cases.A cable driven single leg jumping robot is modeled to research agility. An optimizationof the initial posture of the robot, and its effect on jumping performance and agility ispresented. Configuration optimization during the stance phase of a non-periodic jumpingmotion is performed, utilizing the directional dynamic capability equations. This optimization maximizes the time the mechanism is in contact with the ground, minimizes actuationeffort, and reduces the likelihood of slipping and stumbling.
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    Comparison Of Dust Generation From Open Cut And Trenchless Technology Methods For Utility Construction
    (Civil & Environmental Engineering, 2011-07-14)
    Construction industry has changed many aspects of human life and is still evolving at a rapid pace. New and better technologies which are environmentally friendly and safe are being introduced in this industry. But with the passage of time, this industry has got riddled with loss of human life and quality due to various scenarios. One of the major contributors to such conditions is dust generated on a construction site. The amount of dust a worker inhales during his whole career is very dangerous. This research has found out that using trenchless technology, this exposure to dust can be reduced drastically. Also, during this study, it was noted that sites which are using open cut methodologies, have higher percentage of generating dust.
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    Stress Analysis For A Three Phase Plate With A Concentric Circular Inclusion By Deriving An Airy Stress Function
    (Mechanical Engineering, 2011-07-14)
    This thesis derives the Airy stress function for a three phase plate that consists of two concentric circular inclusions and a matrix phase. It incorporates the elastic property of each phase as well as the geometry of the inclusions. An Airy stress function has been derived that satisfies the continuity conditions of the displacement and traction across the phase interface precisely. The obtained results are new and could not have been possible without a computer algebra system (Mathematica).
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    Parametric And Performance Analysis Of A Hybrid Pulse Detonation / Turbofan Engine
    (Aerospace Engineering, 2011-07-14)
    The performance of a hybrid pulse detonation engine (PDE), with the PDE tubes installed in the bypass duct of a turbofan engine is investigated in this study. Performance parameters for the duct burning PDE engine are compared with a baseline turbofan engine. The PDE analysis is based on an updated numerical analysis by Endo-Fujiwara, whereas the turbofan calculations are based on Mattingly's gas turbine model. The calculations were done with MATLAB 2010 as a platform. A mixer analysis was performed for the hybrid engine concept. In the duct burning PDE, the PDE exhaust was mixed with the turbine exhaust prior to entering the nozzle. For this configuration, core air was mixed with the PDE exhaust to cool the flow prior to entering the turbine. The performance of both configurations was compared for parametric variations of compressor and fan pressure ratio, bypass ratio, PDE tube length and frequency. A performance analysis was carried out for the resulting hybrid baseline engine at different altitudes and Mach numbers.
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    High Order Compact Scheme For Discontinuous Differential Equations
    (Mathematics, 2011-07-14)
    A high order implicit second derivative compact method is given which is similar the Adams-Moulton method, but requiring only two steps for sixth order. This method is used in both predictor-corrector and Newton's method formulations, and although the compact scheme is not A-stable or stiffly stable, it's region of stability is over six times greater than the Sixth order Adams-Moulton method. This compact method has a small truncation error coefficient, and is more accurate than Enright's method within the region of stability. Fourth and sixth order explicit compact methods are derived as well, and the three step sixth order explicit method is used as the predictor for the harmonic oscillator equation with Coulomb damping. Consistency and rate of convergence conditions are derived for these compact methods, and convergence is proved as well. There region of stability is plotted for the sixth order implicit case. The two step sixth order implicit compact method is compared against the five step stiffly-stable Enright method and the five step Adams-Moulton scheme on three test problems, and is shown to be more accurate than Enright's method, and has better accuracy and is more stable than Adams-Moulton. The predictor-corrector compact formulation is tested on two Coulomb friction problems, and the difficulties caused by the discontinuous right-hand side is avoided by breaking the problem into segments between the discontinuities.
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    Numerical Modeling Of A Parallel Plate Electrowetting-on-Dielectric (EWOD) Device
    (Mechanical Engineering, 2011-07-14)
    Numerical modeling and simulations have been performed in this study that focuses on modeling the fluid dynamics of an Electrowetting-on-Dielectric (EWOD) device. The case to be modeled in the present study is a droplet cutting problem where a droplet is sandwiched between two plates of Teflon and an electrical actuation will cause the droplet to cut or split into two smaller droplets. A finite difference method has been used to solve the Navier-Stokes equations, along with the continuity equation. An algorithm used for tracking the free surface is the Volume of Fluid (VOF) method. Along with using the VOF method a Continuum Surface Force (CSF) model is implemented to accurately predict the physics of the surface tension on the free surface. The finalized algorithm used for solving the fluid flow is known as the Coupled Level Set - Volume of Fluid (CLSVOF) method. The physics of the fluid dynamics within a EWOD device have been investigated and adaptations have been made to the CLSVOF method to accurately predict the displacement and motion of the fluid. The accuracy of the numerical model has been validated using comparisons with published experimental data. A parametric study has been performed on the effects of various parameters.
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    Contracting Institutions And Foreign Direct Investment: Evidence From The U.S. Mulitnationals
    (Economics, 2011-07-14)
    Development Economics studies have highlighted the importance of both property rights and contracting institutions for attracting foreign direct investment. However, to the best of our knowledge, none of the previous studies has examined the separate FDI impacts of these institutions. Using country level data, this thesis examines the effects that both contracting and property rights institutions have on United States multinationals' foreign direct investment decisions. We control for potential endogeneity by using indigenous population density and country latitude, along with a British legal origin dummy variable as instruments for property rights and contracting institutions, respectively. We find strong evidence that weak contracting institutions are a deterrent to US firms' investment. We believe US multinationals place high importance on formal contracting institutions because of the quantity, size, and complexity of their transactions.