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Title: THE PATH TO HIGH Q-FACTORS IN SUPERCONDUCTING ACCELERATING CAVITIES: FLUX EXPULSION AND SURFACE RESISTANCE OPTIMIZATION
Creator: Martinello, Martina
Date: 2016, 2016-12
Description: Accelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators....
Show moreAccelerating cavities are devices resonating in the radio-frequency (RF) range used to accelerate charged particles in accelerators. Superconducting accelerating cavities are made out of niobium and operate at the liquid helium temperature. Even if superconducting, these resonating structures have some RF driven surface resistance that causes power dissipation. In order to decrease as much as possible the power losses, the cavity quality factor must be increased by decreasing the surface resistance. In this dissertation, the RF surface resistance is analyzed for a large variety of cavities made with different state-of-the-art surface treatments, with the goal of finding the surface treatment capable to return the highest Q-factor values in a cryomodule-like environment. This study analyzes not only the superconducting properties described by the BCS surface resistance, which is the contribution that takes into account dissipation due to quasi-particle excitations, but also the increasing of the surface resistance due to trapped flux. When cavities are cooled down below their critical temperature inside a cryomodule, there is always some remnant magnetic field that may be trapped increasing the global RF surface resistance. This thesis also analyzes how the fraction of external magnetic field, which is actually trapped in the cavity during the cooldown, can be minimized. This study is performed on an elliptical single-cell horizontally cooled cavity, resembling the geometry of cavities cooled in accelerator cryomodules. The horizontal cooldown study reveals that, as in case of the vertical cooldown, when the cooling is performed fast, large thermal gradients are created along the cavity helping magnetic flux expulsion. However, for this geometry the complete magnetic flux expulsion from the cavity equator is more difficult to achieve. This becomes even more challenging in presence of orthogonal magnetic field, that is easily trapped on top of the cavity equator causing temperature rising. The physics behind the magnetic flux expulsion is also analyzed, showing that during a fast cooldown the magnetic field structures, called vortices, tend to move in the same direction of the thermal gradient, from the Meissner state region to the mixed state region, minimizing the Gibbs free energy. On the other hand, during a slow cool down, not only the vortices movement is limited by the absence of thermal gradients, but, also, at the end of the superconducting transition, the magnetic field concentrates along randomly distributed normal-conducting region from which it cannot be expelled anymore. The systematic study of the surface resistance components performed for the different surface treatments, reveals that the BCS surface resistance and the trapped flux surface resistance have opposite trends as a function of the surface impurity content, defined by the mean free path. At medium field value, the BCS surface resistance is minimized for nitrogen-doped cavities and significantly larger for standard niobium cavities. On the other hand, Nitrogen-doped cavities show larger dissipation due to trapped flux. This is consequence of the bell-shaped trend of the trapped flux sensitivity as a function of the mean free path. Such experimental findings allow also a better understanding of the RF dissipation due to trapped flux. The best compromise between all the surface resistance components, taking into account the possibility of trapping some external magnetic field, is given by light nitrogen-doping treatments. However, the beneficial effects of the nitrogen-doping is completely lost when large amount of magnetic field is trapped during the cooldown, underlying the importance of both cooldown and magnetic field shielding optimization in high quality factors cryomodules.
Ph.D. in Physics, December 2016
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Title: ASSESSMENT OF MICROGRIDS FOR DEVELOPED AND DEVELOPING COUNTRIES
Creator: Vyas, Kohil
Date: 2013, 2013-12
Description: Today’s world essentially runs on electricity, in some form or the other. From the introduction of the concept of electricity by William...
Show moreToday’s world essentially runs on electricity, in some form or the other. From the introduction of the concept of electricity by William Gilbert to thousands of invention by Thomas Edison, there have been great changes in the world of electricity. The life of every living being is directly affected by these changes. Various electrical problems have surfaced because of these changes. Microgrids have been considered as a solution to these problems, and have been assessed and evaluated in this research. To realize the effectiveness of microgrids as a solution, initially problems were explored. It was found that there are two perspectives of the problems faced by electrical world. One being: problems seen from the view point of developed countries, and the other: problems seen from the view point of developing countries. Assessment of microgrids was accordingly branched during the research. In the case of the developed countries, the basic infrastructure of electrical system which was built long ago, demands an upgrade now. Problems like blackouts and brownouts have risen and the frequency of their occurrence is growing with time. Owing to these problems, there has been a loss of billions of dollars, as well as critical loads like research facilities, military bases, data centers etc… are severely affected. Microgrids installed in military bases, a university campus and a jail were assessed to analyze how they are implemented, the benefits reaped from them and how they can be a viable solution to the problems faced by the developed countries. In the case of the developing countries, the fact stands that they are yet to reach a state where they can serve their entire load by themselves. This results into regular load shedding. Also, there are some areas where there is no electrical infrastructure and this restricts many from even having xi the access to the electricity. For this research, microgrids installed in villages of Africa, India, and on the islands of Maldives were assessed. Their application and revolutionary impacts on the developing countries were explored. The research indicates that in the developed countries, owing to the gargantuan increase in power consumption, several electrical problems have arisen. Microgrids were able to solve these problems and save millions of dollars. Whereas, in developing countries, people still are in need of a 24-hours access to electricity for their progress. Electricity is required for basic necessities like pumping water, cooking, and activities carried out at night which requires light. Implementation of microgrids by providing electricity removes the bottleneck to their progress.
M.S. in Electrical Engineering, December 2013
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Title: P-DOPED STRONTIUM TITANATE GROWN USING TWO TARGET PULSED LASER DEPOSITION FOR THIN FILM SOLAR CELLS
Creator: Man, Hamdi
Date: 2015, 2015-12
Description: Thin-film solar cells made of Mg-doped SrTiO3 (STO) p-type absorbers are promising candidates for clean energy generation. This material shows...
Show moreThin-film solar cells made of Mg-doped SrTiO3 (STO) p-type absorbers are promising candidates for clean energy generation. This material shows p-type conductivity and also demonstrates reasonable absorption of light. In addition, p-type SrTiO3 can be deposited as thin films so that the cost can be lower than the competing methods. In this work, Mg:SrTiO3 (Mg:STO) thin-films were synthesized and analyzed in order to observe their potential to be employed as the base semiconductor in photovoltaic applications. Mg:STO thin-films were grown with pulsed laser deposition (PLD) using a frequency quadrupled Yttrium Aluminum Garnet (YAG) laser and with a substrate that was heated by back surface absorption of infrared (IR) laser light. The samples were characterized using X-ray photoelectron spectroscopy (XPS) and it was observed that Mg atoms were incorporated in the STO films. Reflection high energy electron diffraction (RHEED) spectroscopy proved that the thin films were polycrystalline. Calculations showed that the lattice constant of Mg:STO/SSF is slightly greater than that of STO/SSF, therefore, the conservation of the characteristic ring pattern for STO suggests of doping by substitution, which is consistent with the examples in literature. Kelvin Probe work function measurements indicated that the work function of the films were 4.167 eV after annealing. EDS spectroscopy showed that Mg was present in the thin films.
M.S. in Physics, December 2015
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Title: Modeling and Optimization of Embedded Active Flow Control Systems
Creator: Henry, James M.
Date: 2024
Description: This thesis presents research focused on the aerodynamic performance of circulation control on two-dimensional and quasi-two-dimensional wings...
Show moreThis thesis presents research focused on the aerodynamic performance of circulation control on two-dimensional and quasi-two-dimensional wings. Aerodynamic loads, namely lift, drag, and moment coefficients, are measured through Reynolds Averaged Navier Stokes (RANS) modeling and wind tunnel experiment. A simplified and parameterized RANS model is presented as a rapidly iterable approach to estimating the performance of trailing-edge circulation control on two dimensional airfoils, with the hypothesis that an optimized airfoil shape can be found which maximizes the lift coefficient increment generated by circulation control, through modification of the wing profile. The simplified modeling setup is compared with more conventional approaches to numerical simulation of circulation control. The performance of the simplified modeling scheme is then compared with wind tunnel studies, for both steady-state and dynamic performance, as functions of both momentum coefficient dCμ and chord-based Reynolds number Re_c. The dynamic performance for the model is studied to find an analog to the theoretical unsteady models of Wagner and Theodorsen. An adjoint optimization framework is used to find an optimal airfoil profile for circulation control. The optimized profile is then compared in both a simulation and a wind tunnel test study against a NACA0015 airfoil. In simulation, improvement between 12% and 15% is seen for the lift control authority for all values of dCμ and Re_c tested. In experiment, the optimized profile demonstrated improvements of up to 28% in lift control authority, dCL/dCμfor values of Cμ, and decreased performance for higher values of Cμ.
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Title: Utilizing Concurrent Data Accesses for Data-Driven and AI Applications
Creator: Lu, Xiaoyang
Date: 2024
Description: In the evolving landscape of data-driven and AI applications, the imperative for reducing data access delay has never been more critical,...
Show moreIn the evolving landscape of data-driven and AI applications, the imperative for reducing data access delay has never been more critical, especially as these applications increasingly underpin modern daily life. Traditionally, architectural optimizations in computing systems have concentrated on data locality, utilizing temporal and spatial locality to enhance data access performance by maximizing data and data block reuse. However, as poor locality is a common characteristic of data-driven and AI applications, utilizing data access concurrency emerges as a promising avenue to optimize the performance of evolving data-driven and AI application workloads.This dissertation advocates utilizing concurrent data accesses to enhance performance in data-driven and AI applications, addressing a significant research gap in the integration of data concurrency for performance improvement. It introduces a suite of innovative case studies, including a prefetching framework that dynamically adjusts aggressiveness based on data concurrency, a cache partitioning framework that balances application demands with concurrency, a concurrency-aware cache management framework to reduce costly cache misses, a holistic cache management framework that considers both data locality and concurrency to fine-tune decisions, and an accelerator design for sparse matrix multiplication that optimizes adaptive execution flow and incorporates concurrency-aware cache optimizations.Our comprehensive evaluations demonstrate that the implemented concurrency-aware frameworks significantly enhance the performance of data-driven and AI applications by leveraging data access concurrency.Specifically, our prefetch framework boosts performance by 17.3%, our cache partitioning framework surpasses locality-based approaches by 15.5%, and our cache management framework achieves a 10.3% performance increase over prior works. Furthermore, our holistic cache management framework enhances performance further, achieving a 13.7% speedup. Additionally, our sparse matrix multiplication accelerator outperforms existing accelerators by a factor of 2.1.As optimizing data locality in data-driven and AI applications becomes increasingly challenging, this dissertation demonstrates that utilizing concurrency can still yield significant performance enhancements, offering new insights and actionable examples for the field. This dissertation not only bridges the identified research gap but also establishes a foundation for further exploration of the full potential of concurrency in data-driven and AI applications and architectures, aiming at fulfilling the evolving performance demands of modern and future computing systems.
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Title: THE ROLE OF MOLECULAR MOTORS IN THE MECHANICS OF ACTIVE GELS AND THE EFFECTS OF INERTIA, HYDRODYNAMIC INTERACTION AND COMPRESSIBILITY IN PASSIVE MICRORHEOLOGY
Creator: Uribe, Andres Cordoba
Date: 2014, 2014-07
Description: The mechanical properties of soft biological materials are essential to their physiological function and cannot easily be duplicated by...
Show moreThe mechanical properties of soft biological materials are essential to their physiological function and cannot easily be duplicated by synthetic materials. The study of the mechanical properties of biological materials has lead to the development of new rheological characterization techniques. In the technique called passive microbead rheology, the positional autocorrelation function of a micron-sized bead embedded in a viscoelastic fluid is used to infer the dynamic modulus of the fluid. Single particle microrheology is limited to fluids were the microstructure is much smaller than the size of the probe bead. To overcome this limitation in two-bead microrheology the cross-correlated thermal motion of pairs of tracer particles is used to determine the dynamic modulus. Here we present a time-domain data analysis methodology and generalized Brownian dynamics simulations to examine the effects of inertia, hydrodynamic interaction, compressibility and non-conservative forces in passive microrheology. A type of biological material that has proven specially challenging to characterize are active gels. They are formed by semiflexible polymer filaments driven by motor proteins that convert chemical energy from the hydrolysis of adenosine triphosphate (ATP) to mechanical work and motion. Active gels perform essential functions in living tissue. Here we introduce a single-chain mean-field model to describe the mechanical properties of active gels. We model the semiflexible filaments as bead-spring chains and the molecular motors are accounted for by using a mean-field approach. The level of description of the model includes the end-toend length and attachment state of the filaments, and the motor-generated forces, as stochastic state variables which evolve according to a proposed differential Chapman- Kolmogorov equation. The model allows accounting for physics that are not available in models that have been postulated on coarser levels of description. Moreover it allows the prediction of observables at time scales that will be too difficult to achieve in multi-chain simulations.
Ph.D. in Chemical Engineering, July 2014
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Title: An Integrated Cell Culture-PCR Assay for the Detection of Viable Coxiella Burnetii Nine Mile Phase II RSA 439 in Fluid Dairy Products
Creator: Kukreja, Ankush
Date: 2011-12, 2011-12
Description: Coxiella burnetii, an obligate intracellular bacterium, has been used as the reference organism for defining milk pasteurization conditions....
Show moreCoxiella burnetii, an obligate intracellular bacterium, has been used as the reference organism for defining milk pasteurization conditions. With renewed interest in minimizing processing times and temperatures, and in ensuring product safety, development of an Integrated Cell Culture-PCR (ICC-PCR) assay may be useful for evaluating C. burnetii inactivation in fluid dairy products. The purpose of this research was to develop an ICC-PCR assay to determine viability and detection limit of C. burnetii and characterize inhibiting effects contributed by various milk formulations. Coxiella burnetii was inoculated on Vero cell culture with PBS and whole milk, incubated for 48 hours to allow infection, and then incubated for 11 days to allow propagation. The propagated C. burnetii mix was subjected to freeze-thaw followed by DNA extraction with Autogen Blood & Tissue DNA Extraction Kit using Quickgene Mini80. Extracted DNA was amplified using TaqMan-MGB based qPCR targeting published primers for the IS1111a transposase gene to verify C. burnetii growth/infectivity. For detection limit determination, serial dilutions of C. burnetii in RPMI were mixed separately in whole milk, cream, chocolate milk and eggnog. The mix was overlaid on sub-confluent Vero cell monolayers, subjected to freeze-thaw followed by DNA extraction using Autogen Blood & Tissue DNA Extraction Kit and PCR. Uninoculated wells were evaluated for dairy sample background signal, and inhibition was evaluated by comparison to purified DNA. Duplicate trials using 6 replicates per sample were performed.
M.S. in Food Safety & Technology, December 2011
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Title: DESIGN OF MODERN HIGH NB-CONTENT ,-,' NI-BASE SUPERALLOYS
Creator: Antonov, Stoichko
Date: 2017, 2017-07
Description: Superalloy design can prove to be a very complex and challenging task, as certain elemental additions can significantly improve properties...
Show moreSuperalloy design can prove to be a very complex and challenging task, as certain elemental additions can significantly improve properties when added in high contents, however, exceeding their solubility limits can promote the formation of undesired phases at grain boundaries as well as grain interiors, and can quickly deteriorate the high temperature structural integrity and stability of the alloy, resulting in a catastrophic failure. Precipitate phases, such as " and ⌘, appear similar and are often mistaken for one another, leading to the need for a better fundamental understanding of their formation, required for developing innovative new classes of Ni-base superalloys. The morphology, formation, and composition of precipitate phases in a number of experimental alloys spanning a broad range of compositions were explored and compositional relationships were developed to facilitate the design of !-!0-("/⌘) Ni-base superalloys. The e↵ect of increasing Nb alloying additions on the formation and long term phase stability of topologically close packed (TCP) phases was studied. Elevated levels of Nb can result in increased matrix supersaturation and promote the precipitation of ⌘-Ni6AlNb along the grain boundaries in powder processed, polycrystalline Ni-base superalloys, while reduced Nb levels favored the precipitation of blocky Cr and Mo rich $ phase precipitates along the grain boundary. Evaluation of the thermodynamic stability of these two phases using Thermo-Calc showed that while $ phase predictions are fairly accurate, predictions of the ⌘ phase are limited. In addition, atom probe tomography (APT) was used to quantitatively assess grain boundary phase compositions and local segregation along the grain boundary before and after a 1000 hour thermal exposure at 800 "C. The complex network of $ phase precipitates that formed upon the thermal exposure and the characteristic interfacial segregation profiles were studied. In addition, elemental boron was observed to segregate to the grain boundary and phase interfaces, but did not form borides, due to the relatively low concentration of B atoms, resulting from a higher B concentration in the matrix. APT studies were also performed on MC carbides of the alloys and the formation kinetics and morphological differences between NbC and Hf doped NbC were explained using density functional theory (DFT) calculations of the formation energies of different facets of the MC carbide. Detailed electron microscopy and APT techniques were then used to systematically quantify the chemical and morphological instabilities that occur during aging of polycrystalline !-!0 Ni-base superalloys containing elevated levels of refractory alloying additions. The morphological changes and splitting phenomenon associated with the secondary !0 precipitates were related to the discrete chemical compositions of the secondary and tertiary !0 along with the phase compositions of the ! matrix and the ! precipitates that form within the secondary !0 particles. Compositional phase inhomogeneities led to the precipitation of finely dispersed tertiary !0 particles within the ! matrix and secondary ! particles within the secondary !0 precipitates, which, along with surface grooving of the secondary !0 particles, contributed to the inverse coarsening or splitting of the precipitates during aging. As recent studies have shown that polycrystalline Ni-base superalloys containing elevated levels of Nb additions exhibit superior properties at elevated temperatures when compared to existing commercial Ni-base superalloys, understanding of elemental partitioning to each phase is essential and was studied via APT. Compositions of the constituent phases were measured in four high Nb-content !-!0 Ni-base superalloys and the results were compared to thermodynamic database models from Thermo-Calc. Results were also used to predict the solid solution strength behavior of the four alloys. The di↵erences in phase composition predictions from thermodynamic models resulted in dissimilarities between the generated strength behavior curves and those from the experimental work. Finally, creep behavior of high Nb-content !-!0 Ni-Based superalloys was related to the formation of secondary phases mainly at grain boundaries. As secondary phases form, their brittle nature leads to crack formation, which can propagate under the tensile load and lead to premature failure of the alloy.
Ph.D. in Materials Science and Engineering, July 2017
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Title: DESIGN AND PERFORMANCE ASSESSMENT OF MULTI-MODAL MOBILE ROBOTS
Creator: Kalantari, Arash
Date: 2015, 2015-05
Description: This thesis is focused on developing multi-modal mobile robots, i.e. robots that can operate in more than one domain. For decades, researchers...
Show moreThis thesis is focused on developing multi-modal mobile robots, i.e. robots that can operate in more than one domain. For decades, researchers have been trying to improve locomotion capabilities of robots that operate in a single domain: on the ground, on inclined surfaces, in the air, or in water. A prevailing approach in design of hybrid robots is to simply attach systems designed for a single domain together. In order to reduce the complexity of the hybrid robot, a different design approach is taken in this thesis by attempting to keep the hardware resources on the system as low as possible. To this end, two hybrid aerial and terrestrial platforms have been developed: the walking quadrotor and the HyTAQ, the Hybrid Terrestrial and Aerial Quadrotor. In both platforms, ight is achieved through a quadrotor configuration; four actuators provide the required thrust. The walking quadrotor uses a single actuator set for both walking and ying by means of a unique compliant mechanism. This mechanism uses two separate linear movements to make walking possible. The horizontal movement of the leg is driven by running the propellers in reverse and the vertical movement is actuated by shape memory alloy (SMA) wires. An experimental prototype of this robot proves the functionality of the design. However, the experiments suggest that the application of the robot is efficient only where ground movement is a small portion of the whole mission. This is mainly due to the low efficiency of the propellers rotating in reverse and large time constant of the SMA wires, which makes walking slow. The terrestrial locomotion of HyTAQ has been made possible by adding a cylindrical cage, connected to the quadrotor through a revolute joint. This allows the cage to roll freely with respect to the body of the quadrotor, making the terrestrial locomotion possible. Moreover, the same ight actuators and control commands can be used to control terrestrial mode. An analysis of the system's energy consumption shows that the addition of the terrestrial locomotion improves the efficiency of the aerial-only quadrotor by increasing the overall operation range and time. This has been experimentally verified by showing that the HyTAQ's terrestrial range is 11 times greater compared to ight range of the quadrotor at the same speeds. Developing a hybrid aerial and scansorial robot is the next goal of this research. The first step toward this goal has been taken as part of this thesis by developing a method that enables a quadrotor to land and take-off from smooth vertical surfaces autonomously. A Microsoft Kinect sensor is used to localize the MAV and a PID controller is used to control the perching maneuver. A servo actuated gripper, mounted in front of the robot, makes attachment and detachment possible. The experimental results show that the robot can perch successfully in more than 90% of the experiments, which indicates the robustness of the proposed method.
Ph.D. in Mechanical and Aerospace Engineering, May 2015
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Title: Achipelago the Future City
Creator: Song, Gil Ryong
Date: 2011-12-05, 2011-12
Description: We are in search for many who are thinking about the methods of achieving an international sustainable environment internationally. The low...
Show moreWe are in search for many who are thinking about the methods of achieving an international sustainable environment internationally. The low carbon green city is one of the most advanced models to deal with thus related urban issues. The approach this thesis has been to find a new traditional city model for Korea that’s amalgamated with the latest technology. Until recently from the recent liberation from the Japanese colonial rule, the top priority of any policies of Korea were economic growth and national development which has enabled the nation to achieve rapid economic growth over past decades. However, through this urban transforming process we have lost our city identity. In order to achieve the nation’s quality based growth, designing the low carbon green city with a traditional identity is essential.
M.S. in Architecture, December 2011
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Title: CARRIER AGGREGATION BASED SCHEDULING FOR COORDINATED MULTIPOINT TRANSMISSION IN LTE ADVANCED SYSTEMS
Creator: Raj, Avneet
Date: 2012-04-04, 2012-05
Description: Long term Evolution Advanced(LTE-A) was introduced to eliminate the short comings of Long term Evolution(LTE).LTE uses orthogonal frequency...
Show moreLong term Evolution Advanced(LTE-A) was introduced to eliminate the short comings of Long term Evolution(LTE).LTE uses orthogonal frequency division multiplexing(OFDM) for its downlink transmission. But OFDM suffers from inter cell interference which means that cell edge suffer from a low throughput, hence LTE-A has come up with certain new techniques to solve this problem which are Carrier Aggregation(CA) and Coordinated multipoint transmission (CoMP).There are certain resource allocation techniques been currently used in CoMP which are either throughput based or fairness based .In my Thesis I have made a new resource allocation scheme which is throughput based and is aimed to provide the cell edge users with optimum data rate.To achieve this I have used soft frequency re-use pattern and to achieve higher throughput also used the CA technology. For simulation of the system I used Matlab,the simulation results show that the cell edge users in my scheme achieve higher Signal to noise ratio(SINR) optimum throughput. I have also compared my results with the existing joint proportional fairness scheme(JPF) and found that I achieve a higher overall throughput compared to the JPF scheme. viii
M.S. in Electrical Engineering, May 2012
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Title: REVIEW OF THE AC/DC MICROGRID OPERATION AND CONTROL
Creator: Bahramirad, Sheida
Date: 2016, 2016-07
Description: As defined by the U.S department of energy, a microgrid is a group of interconnected loads and distributed energy resources (DERs) with the...
Show moreAs defined by the U.S department of energy, a microgrid is a group of interconnected loads and distributed energy resources (DERs) with the ability of self-supply and islanding. The significant advantages of microgrids have resulted in extensive research and development efforts and rapidly growing implementation in electric power systems. There are, however, still many challenges to be addressed in order to efficiently design, control, and operate microgrids when connected to the grid, and also when in islanded mode. Based on the type of voltages and currents in the network, different microgrid types can be considered, including AC microgrids, DC microgrids, and Hybrid AC/DC microgrids. This thesis presents a review of AC, DC and Hybrid microgrids with a focus on control, operation, and planning issues. A thorough comparison between these microgrid types is further provided based on the system layout and the type of DERs that are commonly utilized. Communication issues are also investigated to demonstrate and compare the existing deployment practices. The thesis is concluded by providing a list of potential areas of research associated with AC, DC, and hybrid microgrids.
M.S. in Electrical Engineering, July 2016
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Title: GRAIN BOUNDARY ENGINEERING IN INCONEL 600
Creator: Li, Baishun
Date: 2013, 2013-12
Description: Grain Boundary Engineering (GBE) is a process consisting of deformation-anneal iterations that increase special boundaries, especially the...
Show moreGrain Boundary Engineering (GBE) is a process consisting of deformation-anneal iterations that increase special boundaries, especially the fraction of Σ3 boundaries, to improve material properties such as corrosion resistance, intergranular fracture resistance or ductility. In this work, Inconel 600 super alloy was chosen as the research material. Different levels of compression at various temperatures followed by a subsequent anneal were used on the Inconel 600 to investigate the respective Σ3 boundary fractions as a function of processing. Orientation Image Microscopy (OIM) was applied to scan, observe and analyze the microstructures of the samples before and after deformation. The work was aimed at investigating the effect of hot deformation on the Σ3 boundary fraction in Inconel 600 and understanding the mechanisms of Grain Boundary Engineering. The formation of twins was studied with emphasis on their formation following elevated temperature deformation.
M.S. in Material Science and Engineering, December 2013
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Title: GETTING RID OF THE WIRES: A TRANSCUTANEOUS POWER AND WIDEBAND TELEMETRY SYSTEM FOR MULTI-CHANNEL NEURAL RECORDING IMPLANTS
Creator: Rush, Alexander Daniel
Date: 2012-08-08, 2012-07
Description: This dissertation focuses on development of wireless power and data transmission hardware for use in a wireless neural recording system. This...
Show moreThis dissertation focuses on development of wireless power and data transmission hardware for use in a wireless neural recording system. This involves a comprehensive review of the applications requiring or strongly benefiting from wireless power and high data rate outward telemetry, multiparametric analysis of a system for wireless power and data transmission, and a detailed description of external and implanted hardware composing such a system. In this document “implanted” or “implantable” means that the hardware referred to by these terms is designed with the intention of being fully contained within the body with no physical connections crossing the skin.
Ph.D. in Biomedical Engineering, July 2012
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Title: MECHANICAL PROPERTIES AND DEFORMATION MECHANISMS OF TERNARY γ-γ’-δ NICKEL-BASED SUPERALLOYS
Creator: Di Sciullo Jones, Alexander
Date: 2012-12-03, 2012-12
Description: The primary drive towards the continued development of nickel-based superalloys lies in the turbine industry, both for propulsion and power...
Show moreThe primary drive towards the continued development of nickel-based superalloys lies in the turbine industry, both for propulsion and power generative uses, where approximately 90% of such materials are used. The ongoing trend is to increase the temperature, increase the rotational speed, and decrease the weight of turbines to increase their efficiency. Thus, much of the improvement of the efficiency of these machines rests on what materials are available to the industry. This has led to the design of superalloys specifically tailored to withstand the varied and increasingly demanding properties of turbine parts. Turbine discs, as one such part, experience substantially lower temperatures than the turbine blades, thus the creep properties of materials to be used in such an application are not quite as important. However, in the drive to increase turbine rotation speed and reduce weight, the industry is looking for materials which can withstand higher stresses. It is with this goal in mind that the material focused on in this work, V204H, was designed. The material utilizes a novel, three-phase microstructure consisting of γ-γ’-δ rather than a conventional two-phase γ-γ’ microstructure. It has been theorized that the addition of δ precipitates, formed through the addition of niobium, will behave as a reinforcement phase as in a particulate composite. The material was also heavily alloyed to increase strengthening and improve creep behavior via the addition of elements which decrease diffusion rate and deter grain boundary damage. It was discovered that this material has a fourth phase between the γ’ precipitates, and this was identified using SAD to be γ”. Flow stress tests over a range of temperatures and creep tests, both performed in compression, were conducted. These properties were seen to be exemplary for use in a turbine disc. It was, however, found that such properties deteriorated when the testing was conducted in tension. This xv
M.S. in in Materials Science and Engineering, December 2012
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Title: MABC2 REGULATES CELLULAR AND MITOCHONDRIAL HEME CONTENT IN CARDIOMYOCYTES
Creator: Khechaduri, Arineh
Date: 2011-04-20, 2011-05
Description: mABC2 (ABCB10) protein is a mitochondrial inner-membrane ATP-binding cassette transporter. The structure of mABC2 is similar to that of ABCB8 ...
Show moremABC2 (ABCB10) protein is a mitochondrial inner-membrane ATP-binding cassette transporter. The structure of mABC2 is similar to that of ABCB8 (mABC1), which was shown to export iron from mitochondria into the cytoplasm. Based on the structural similarities we hypothesized that mABC2 is involved in export of heme from mitochondria into the cytoplasm for subsequent use in cytosolic enzymes. To study the role of mABC2 in cellular and mitochondrial iron homeostasis, we modulated the expression of the protein in neonatal rat cardiomyocytes (NRCM). We found that downregulation of mABC2 led to significant decrease in total cellular heme content. There was a trend toward increase in total cellular heme content with overexpression of mABC2, however the finding was not statistically significant (p=0.36). To measure mitochondrial heme content with mABC2 modulation we have successfully isolated mitochondria from NRCM. Overexpression of mABC2 significantly elevated mitochondrial heme content. It has been shown that mABC2 and mitoferrin-1 (Mfrn1) interact and form an oligomeric complex with ferrochelates to enhance mitochondrial iron importation for heme biosynthesis. Our findings are inconsistent with the proposed function of mABC2 in heme export out of the mitochondria, but support the hypothesis that mABC2 modulates heme synthesis via regulation of stability and activity of Mfrn1 and ferrochelatase in cardiomyocytes. This suggests that mABC2 may play a role in regulation of cellular iron homeostasis by regulating expression of cellular iron import and/or export.
M.S. in Biology, May 2011
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Title: SUPERVISED AND INTERACTIVE IMAGE SEGMENTATION TECHNIQUES WITH AN APPLICATION TO PROSTATE CANCER
Creator: Artan, Yusuf Oguzhan
Date: 2013, 2013-05
Description: Prostate cancer is a leading cause of cancer death for men in the United States. Fortunately, the survival rate for early diagnosed patients...
Show moreProstate cancer is a leading cause of cancer death for men in the United States. Fortunately, the survival rate for early diagnosed patients is relatively high. Accurate prostate cancer localization with noninvasive imaging using MRI can be used to guide biopsy, radiotherapy, and surgery as well as to monitor disease progression. However, in general, a single type of MRI is not sufficient for reliable tumor localization. As an alternative, multispectral MRI, i.e., the use of multiple MRI-derived datasets, has emerged as a promising noninvasive imaging technique for the localization of prostate cancer; however almost all studies are with human readers. There is a significant inter and intra-observer variability for human readers, and it is substantially difficult for humans to analyze the large dataset of multispectral MRI. To solve these problems, this thesis presents various novel supervised and semi- supervised (interactive) segmentation techniques. Initially, we develop a supervised segmentation method by combining conditional random fields (CRF) and support vector machines (SVM) with a cost-sensitive framework, and show that proposed method further improves classical and cost-sensitive SVM results by incorporating spatial information. Next, we propose an extension of popular semi-supervised seg- mentation method, namely random walker (RW) algorithm, with automated seed initialization for multispectral MRI images. We also present an automated shape and boundary based segmentation approach for prostate segmentation from T2-weighted MRI. Proposed method is based on a banded geocuts algorithm that utilizes bound- ary and shape information to yield prostate segmentation. Finally, we develop a novel method that has the ability to design classifiers obtained from one imaging protocol and/or MRI device to be used on a dataset from another protocol and/or imaging device. In order to evaluate the performance of the proposed methods, we utilize multispectral MRI datasets acquired from 21 biopsy-confirmed cancer patients. Our results show that multispectral MRI helps to increase the accuracy of prostate cancer xiv localization when compared to single MR images; and that using advanced proposed methods for prostate cancer localization performs better than available methods in the literature.
PH.D in Electrical Engineering, May 2013
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Title: MATHEMATICAL MODELING AND ANALYSIS OF WASTEWATER TREATMENT PROCESSES
Creator: Raju Ganesan, Arun Kumar
Date: 2013-04-25, 2013-05
Description: The activated sludge process is the most commonly used biological waste water treatment system. Mathematical modeling of this process is...
Show moreThe activated sludge process is the most commonly used biological waste water treatment system. Mathematical modeling of this process is important for improving its treatment efficiency and thus the quality of the effluent released into the receiving water body. These models can help the operator predict the performance of the plant to take cost-effective and timely remedial actions that would ensure consistent treatment efficiency and meeting discharge requirements. However, due to the highly complex and non-linear characteristics of this biological system, mathematical modeling of this treatment process has remained a challenge. The first part of this study is to build fundamental grey-box models to predict the raw influent quality and the preliminary effluent of the plant for any given day using historical data. The thesis is an attempt to model the various waste water treatment processes and validate the model with the historical data available for the Stickney Water Reclamation Plant, Chicago. This model has been further used to analyze the plant on both dry and wet weather conditions. Wastewater treatment processes utilize approximately 3% of the energy consumption in the US. A detailed study of the aeration required for the activated sludge tanks has been performed. The plant has been operated at a far higher aeration compared to the minimum required aeration which has increased the operating costs tremendously. A description of cost reduction by minimizing aeration usage without compromising on the discharge limits has been provided. Finally, storms are one of the biggest challenges faced by the operators in treatment plants. Dynamic simulations of storms have been described using the model to understand and control storm events in a more robust manner.
M.S. in Chemical Engineering, May 2013
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Title: VALIDATION AND CHARACTERIZATION OF TURBULENCE IN AN AORTIC COARCTATION
Creator: Arzani, Amirhossein
Date: 2012-04-25, 2012-05
Description: Image based, patient speci c computational uid dynamics (CFD) modeling has gained dramatic attention in evaluation of health and disease...
Show moreImage based, patient speci c computational uid dynamics (CFD) modeling has gained dramatic attention in evaluation of health and disease progression. With the popularity of these techniques in clinical settings the need to address how these numerical predictions validate against the empirical data becomes more imperative. Validation studies have primarily been used in vitro models, since experiments are dif- cult to control in vivo, and in vivo conditions are challenging to replicate numerically. However, in vivo validations are essential for a more reliable assessment. Moreover, direct quanti cation of turbulence, necessary for diagnostic purposes, makes the validation process more challenging in turbulent ows. A phase-contrast magnetic resonance imaging (PCMRI) method was used to obtain turbulent kinetic energy (TKE) in an aortic coarctation, a congenital disease, where the aorta narrows blocking the passage of blood to a great portion of the body. A 3D patient-speci c computer model of the aortic coarctation was constructed from the MRI data. Direct numerical simulation was performed to solve the Navier-Stokes equations using a stabilized nite element method. Based on the PCMRI procedures, di erent methods were used to compute TKE from the CFD velocity data, and were compared to the PCMRI data. The velocity data obtained from CFD was also used to study the ow topology by computing the Finite-Time Lyapunov Exponent (FTLE) eld, and the Lagrangian coherent structures (LCS). The TKE results showed relative good agreement between the in vivo measurements and the CFD predictions of TKE. Observed di erences were within expectations due to modeling, measurement and numerical errors.
M.S. in Mechanical, Materials, and Aerospace Engineering, May 2012
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Title: A TASK-BASED APPROACH TO PARAMETRIC IMAGING WITH DYNAMIC CONTRAST-ENHANCED MRI
Creator: Haleem, Muhammad Salman
Date: 2011-07-28, 2011-07
Description: In this thesis, we propose a task-based approach to parametric imaging with dynamic image sequences and apply the proposed method to an...
Show moreIn this thesis, we propose a task-based approach to parametric imaging with dynamic image sequences and apply the proposed method to an example problem of prostate cancer segmentation with dynamic contrast enhanced Magnetic Resonance Imaging (DCE MRI). Traditionally, the time activity curve obtained from dynamic series of MR images is modeled without considering a specific task in order to obtain the kinetic parameters and to construct the parametric images. This mostly consists of estimating parameters based on minimizing the error between the model and measurement. Unfortunately, this method results in noisy images and performances of the task in hand e.g. tumor segmentation suffers. Therefore, we develop a new method for the estimation of kinetic parameters based on the maximization of tumor segmentation performance. The kinetic parameters are estimated with a weighted approach such that the performance of the particular task is maximized. The mathematical criterions used to quantify the performance are Fisher Ratio, Area Under the Curve (AUC) and the Dice Measure. The proposed method of parametric imaging is tested with the problem of prostate cancer localization with DCE MRI. We use Linear Discriminant Analysis (LDA) as a segmentation tool and use quantitative measures to compare segmentation results, such as Fisher Ratio, Dice Measure, Sensitivity, Specificity and Area Under the Curve (AUC). Our results show that the proposed method is able to improve the prostate cancer localization for certain patients.
M.S. in Electrical Engineering, July 2011
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