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Title: A NOVEL FIXED DISPLACEMENT ELECTRIC-HYDRAULIC HYBRID (EH2) DRIVETRAIN CONCEPT FOR CITY VEHICLES
Creator: Sun, Yingguang
Date: 2013, 2013-07
Description: With growing emphasis on energy independence and environmental issues, alternative energy vehicles, especially Electric Vehicles (EV), Hybrid...
Show moreWith growing emphasis on energy independence and environmental issues, alternative energy vehicles, especially Electric Vehicles (EV), Hybrid Electric Vehicles (HEV) and Plug-in Hybrid Electric Vehicles (PHEV) have received significant attention. Though these solutions can have significant an impact on the environment, economy and efficiency, some challenges still exist in the widespread acceptance of EVs and HEVs. Some issues include low power density of the battery and low battery durability caused by frequent charging and discharging. This can be especially significant for city use owing to typical drive cycles. In order to address this problem, this work proposes a novel electric-hydraulic hybrid (EH2) drivetrain for PHEVs, HEVs and EVs. An EH2 drivetrain is comprised of an electric traction motor and a hydraulic system that uses a combination of hydraulic pump, motor and accumulator. All the components and their operation theory are introduced in this work. In the proposed system, a hydraulic accumulator is used for energy storage during the regenerative braking process. The energy stored in the accumulator will be released to the hydraulic motor during the power assistance process [1]. In this drivetrain, two 6 HP axial flux permanent magnet (AFPM) brushless machines are selected as the traction motor and hydraulic drive. This kind of motor is very suitable for electric vehicles, pump, valve control, fans, etc. due to its pancake shape, compact structure and high torque density [2]. To validate the proposed design, the mathematical model of the hydraulic energy storage system is built in Matlab/Simulink environment and the simulation results are given both for the regenerative braking process and power assistance process. The xiv models of the axial flux permanent magnet brushless machines and its drive system are also built in the Matlab/Simulink. The simulation results are compared with the experimental testing results from the motor test bed built in the lab. Preliminary simulation and experimental results show in the regenerative braking process, 5332 J energy is stored in the accumulator and the energy conversion efficiency is 64.39%. In power assistance process, all the energy stored in the accumulator is released and the vehicle accelerates from 0 m/s to 5.2 m/s. The energy conversion efficiency is 50.71%. These results prove that the hydraulic energy storage system can be used in power assistance and energy storage. The charging and discharging time is very short compared with other energy storage systems. More importantly, the stored energy can reduce the number of times the battery is charged and discharged. In this way the battery size can be reduced and the battery life can be extended. The parallel hydraulic-electric configuration is proved to be a promising solution towards energy storage and power assistance for electric vehicles. Finally, the electric and hydraulic components have been implemented on a go-kart setup built in the lab for future complete drivetrain testing. From the conducted research, it can be concluded that successful implementation of this concept can lead to a wider acceptance of electric vehicles.
M.S. in Electrical Engineering, July 2013
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Title: NONLINEAR SIMULATIONS OF MULTI-VESICLE DYNAMICS
Creator: Hamiilton, Caleb
Date: 2015, 2015-07
Description: Vesicles in biology are closed forms of membranes. The dimensions of vesicles can vary in terms of surface area and enclosed volume. Examples...
Show moreVesicles in biology are closed forms of membranes. The dimensions of vesicles can vary in terms of surface area and enclosed volume. Examples range from small organelles to large cell bodies which all play a variety of resource transportation roles in biological systems. Research from the fields of chemistry and physics helps mathematical modeling by providing the mechanisms behind certain observed morphologies. Mathematical models and methods for simulating vesicle dynamics have produced accurate numerical solutions to verify experimental data and can be used to design new experiments that lead to more discoveries. The most researched case has been a single vesicle under shear flow. However, recent numerical and experimental results consider extensional flows on a single vesicle and hydrodynamic interactions among multiple vesicles. This thesis extends work on hydrodynamic interactions between vesicles in viscous fluid. We investigate numerically cases with multiple vesicles relaxing in asymmetrical configurations, time-dependent flow with more oscillation, and stochastic dynamics. Subjecting vesicles to these various cases reveals sensitivity to initial conditions such as distance and relative orientation. The effects from adding more vesicles are: increased time before equilibrium for the relaxation tests, and distributive wrinkling dynamics for the extensional flow tests. In stochastic cases, there are similar wrinkling distributions. However, initial conditions like distance and orientation have less important effects when competing with influence from thermal fluctuations. Additionally, in the presence of other vesicles under extensional flow, a vesicle may change the number and amplitude of wrinkles it would have experienced alone.
M.S. in Applied Mathematics, July 2015
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Title: EFFICACY OF PULSED LIGHT TECHNOLOGY FOR THE INACTIVATION OF SALMONELLA ENTERITIDIS PT 30 ON ALMOND KERNEL SURFACE
Creator: Harguindeguy, Maite
Date: 2016, 2016-05
Description: Almond surfaces can be contaminated with pathogens such as Salmonella. Traditional thermal processing technologies used for inactivation of...
Show moreAlmond surfaces can be contaminated with pathogens such as Salmonella. Traditional thermal processing technologies used for inactivation of Salmonella on almonds can adversely impact the quality. Therefore, there is a need to investigate the efficacy of alternative technologies for inactivation of Salmonella on almonds without adversely affecting the quality. Pulsed light, a novel technology, can potentially be used to achieve this. Therefore, this study evaluated the efficacy of three pulsed light systems (operating at 1.8, 3, or 100 Hz) under various electrical input powers (1000, 1250 and 1500 W) and treatment times for inactivation of Salmonella Enteritidis PT 30 on almond surfaces. More than 4-log reduction was achieved at different treatment conditions for each of the control units. For instance, a 160 s treatment at 1500 W (100 Hz system) resulted in a 4.3 log CFU/almond reduction. Whereas, similar reductions were achieved in a shorter time with the lower frequency systems (1.8 or 3 Hz). Reductions of 4.6 and 5.9 log CFU/almond were achieved after 80 and 100 s treatment, respectively with the 1.8 Hz system (1250 W). Similarly, a 100 s treatment with the 3 Hz system (1000 W) resulted in a reduction of 4.7 log CFU/almond. Statistical analysis showed that the effect of equipment, treatment time, and electrical power input were significant (p<0.05). The D-values of 1.8, 3, and 100 Hz systems were 0.24, 0.53 and 0.73 min, respectively at 1500 W. In general, lower frequencies resulted in increased inactivation in shorter time. This can be attributed to the higher instantaneous power at lower frequencies. Similar trends were observed at other electrical input powers. The D-values found using pulsed light treatment are lower than the conventional dry heat treatment ones. Also, minimal color change was observed for treated almonds. These results indicate that pulsed light is efficacious for decontaminating almond surfaces within a relatively short time.
M.S. in Food Process Engineering, May 2016
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Title: CHILD TEMPERAMENT AND PARENTING BEHAVIOR AT AGE 5: DO THEY PREDICT CHILD COPING AT AGE 6?
Creator: Hwang, Maria D’aniello
Date: 2014, 2014-07
Description: Coping has been shown to be related to many positive outcomes in children, including better psychological adjustment, positive social...
Show moreCoping has been shown to be related to many positive outcomes in children, including better psychological adjustment, positive social relationships and higher achievement. Additionally, coping abilities in childhood and adolescence can serve as risk or protective factors for psychopathology. Both parenting and child temperament have been shown to be related to child coping; however, these variables have never been examined simultaneously. The transition from kindergarten to grammar-school is considered to be important because children must learn to adjust to this critical, more structured environment. As a result, it is important to determine what factors contribute to adaptive coping at the time when children begin formal school. The aim of this study was to: (a) examine the relationship between child negative affect (NA), effortful control (EC), parenting variables (support/scaffolding, support/engagement, and hostility/coercion), and child coping; and (b) to determine if parenting moderates the effects of temperament on adaptive coping. Participants included 796 (391 males and 405 females) children and their primary caregivers. Children were assessed at ages 5 and 6 years. NA and EC were assessed by parent-report with the Child Behavior Questionnaire. EC also was assessed with an observer-rated task, Gift Delay, which measures the child’s ability to delay a prepotent response, and with two subtests from the NEPSY; Knock and Tap, and Statue. Parenting variables (support/engagement and hostility/coercion) were assessed by parent-report with the Parenting Behavior Inventory and through an observation task, which was assessed by a factor-analyzed composite of variables rated during the National Institute for Child Health and Human Development 3-Boxes Task (support/scaffolding). Coping adaptability was assessed using the Early Childhood Coping Puppet Interview. Results of hierarchical regression analyses indicated that NA, EC, support/scaffolding, support/engagement, and hostility/coercion were not related to child coping adaptability. There also was no evidence of moderation of the relationship between temperament and coping by parenting. Post hoc analyses indicated that for males, lower SES was related to more adaptive coping. Implications of these findings and suggestions for further research are discussed.
Ph.D. in Psychology, July 2014
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Title: REVISITING THE URBAN BLOCK IN THE LIGHT OF CLIMATE CHANGE A CASE STUDY OF BUDAPEST
Creator: Gal, Csilla Viktoria
Date: 2014, 2014-07
Description: Since the beginning of the twentieth century, the urban block configuration of free-standing buildings has been deemed superior to other built...
Show moreSince the beginning of the twentieth century, the urban block configuration of free-standing buildings has been deemed superior to other built forms, as it provided the necessities of modern healthy living: sunlight and fresh air. In light of climate change, the dissertation aims to reevaluate these long held beliefs and to reintroduce microclimate as an urban design consideration. The study takes four metropolitan block typologies of Budapest as cases to clarify the microclimate influence of key urban design parameters by means of a numerical simulation study. The effects of built form, orientation, vegetation and facade properties are evaluated for a typical summer day. The cases are assessed on the basis of diurnal potential air and mean radiant temperatures within the urban canopy layer. Numerical modeling is performed by ENVI-met and analysis is conducted with MATLAB. The findings indicate that built form and vegetation are key factors governing the microclimate. During the day, intraurban cool island develops between dense configurations and in tree-shaded urban canopies. Orientation is decisive in configurations with large open spaces, where east-west alignment corresponds with peak radiant and air temperatures. Apart from albedo, facade properties have little effect on the microclimate. The rise of air temperature with facade albedo is the outcome of canopy floor heating, resulting from the increased ratio of reflected shortwave radiation. A short-term field experiment was conducted in Budapest to complement the numerical simulation study and to evaluate ENVI-met. The measurement campaign utilized six air temperature and humidity loggers. Additionally, wind speed, air temperature and humidity were recorded at the pedestrian level during an anticyclonic period. In courtyards, thermal stratification developed by day with cool island intensities up to 7 C. In the case of open configurations, neither cool island, nor stratification was observed. The comparison of measured and predicted air temperatures revealed the strengths and weaknesses of the numerical model. In general, predicted temperatures had a decreased diurnal range with maximum values systematically underestimated. ENVI-met also failed to reproduce the thermal stratification in courtyards. Despite these shortcomings, the predicted trends and the relative microclimate differences between the configurations agreed with observations reasonably well.
Ph.D. in Architecture, July 2014
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Title: THE LENGTH-TENSION CURVE OF FLIGHT MUSCLE IN MANDUCA SEXTA
Creator: Wang, Geng
Date: 2015, 2015-05
Description: The synchronous indirect flight muscle (DLM1) is located in the thorax of the Hawk moth, Manduca sexta. It has the potential to be a model...
Show moreThe synchronous indirect flight muscle (DLM1) is located in the thorax of the Hawk moth, Manduca sexta. It has the potential to be a model system for cardiac muscle because both muscles have similar length-tension curves and they have similar passive properties (Tu & Daniel, 2004). An important and valuable property of the muscle is the temperature gradient between dorsal and ventral muscles which have a corresponding functional gradient between them. The functions of dorsal and ventral muscle appear to be regulated by the temperature gradient and changes in the phase of activation (N. T. George, Sponberg, & Daniel, 2012). Very little is known, however, about its other physiological properties. Here I measured the relation between tetanic tension and sarcomere length in chemical skinned dorsal and ventral muscle in order to further characterize the properties of the two muscle parts. Analysis of the results showed similarities and differences in the length of thick and thin filaments, maximum force, and rates of force generation between dorsal and ventral muscles. Maximal force was also plotted as a function of temperature in order to inquire into the physiological changes of muscle at various temperatures. The potential of DLM1 to be a model system for some aspects of cardiac muscle research was supported by the results of this study. The hypothesis that functions of dorsal and ventral muscle is regulated by the temperature gradient and changes in the phase of activation also was verified.
M.S. in Biology, May 2015
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Title: BARRIERS TO TREATMENT FOR INNER-CITY CHILDREN WITH DISRUPTIVE BEHAVIOR DISORDERS AND THEIR FAMILIES: AN EVALUATION OF FACTORS THAT INFLUENCE TREATMENT PARTICIPATION
Creator: Gibson, Lynda L.
Date: 2015, 2015-12
Description: Despite the prevalence of disruptive behavior diagnoses in inner-city children, research findings have consistently shown that African...
Show moreDespite the prevalence of disruptive behavior diagnoses in inner-city children, research findings have consistently shown that African-Americans and individuals from inner-city populations tend to utilize mental health services significantly less than other racial and income groups. The primary aim of this study was to identify child, parent, and contextual factors that predicted duration oftreatment in a manualized family therapy intervention for disruptive behavior disorders in children and adolescents. Findings from this study revealed that higher levels of treatment participation were significantly predicted by increased severity of externalizing symptoms and lower levels ofstress present within the home. These fmdings indicate that families whose children have more severe problems are more likely to stay in treatment and that treatment participation may be enhanced by offering case management to families to reduce their levels of stress.
M.S. in Psychology, December 2015
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Title: MODELING THE IMPACT OF NATURAL GAS VARIATION ON COMBUSTION IN A DUAL FUEL ENGINE
Creator: Hulbert, Matthew Calvin
Date: 2017, 2017-07
Description: The desire to meet rising energy demands while simultaneously adhering to stringent climate policies have propelled several advanced...
Show moreThe desire to meet rising energy demands while simultaneously adhering to stringent climate policies have propelled several advanced combustion technologies. The utilization of alternative fuels in internal combustion engines is a relevant solution to the immediate problems facing the transportation sector. Natural gas (NG) is an attractive alternative as it is economically and environmentally versatile, geographically diverse, and has clean-burning qualities which when coupled with dual fuel technologies has shown significant positive impacts on combustion characteristics. The present work describes the setup of an experimental test cell that contains a modern 2.0-liter 4-cylinder turbocharged direct-injected diesel engine that will be modified for dual fuel capability. The initial stages of a computationally efficient simulation model that represents the experimental engine are also presented and a discussion on the model’s development ensues. A dual fuel simulation model was created and calibrated against experimental data obtained from a heavy-duty 6-cylinder duel fuel engine. The objective of this work is to assess the affects different NG compositions have on the combustion process. Natural gas has shown to vary significantly, depending on where the fuel is acquired. The results show that methane content plays a significant role on combustion. As methane content increases, start of combustion (SOC) shifts and peak cylinder pressure decreases. The premixed combustion phase is shown to increase with decreasing methane content, while the mixing-controlled combustion phase decreases. Nitrogen oxides (NOx), carbon monoxide (CO), and carbon dioxide (CO2) emissions have demonstrated to be dependent on methane content. NG compositions with low methane content show increased amounts of CO2 emissions while high methane content shows a decrease in nitric oxide (NO) emissions.
M.S. in Mechanical and Aerospace Engineering, July 2017
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Title: House museums In Chicago: a re-examination of motives, origins, and transformations of the institutions
Creator: Whittaker, Daniel Joseph
Date: 2018
Description: A house museum is a former residence converted into a publicly accessible structure, which preserves an identity of its original domestic...
Show moreA house museum is a former residence converted into a publicly accessible structure, which preserves an identity of its original domestic history. These houses shelter a wide variety of institutions with a diverse range of imperatives and services. With a focus on Chicago house museums, this dissertation seeks an overarching pattern underlying this conversion and reuse of residential buildings. This dissertation focuses on six house museums in Chicago: the Palmer Castle, the Harding Castle, the Clarke House, the Glessner House, the Madlener House and the Robie House. The Palmer and Harding Castles ceased to exist as house museums and are no longer standing.Conventional archival research conducted during the initial phases yielded historiographies that corroborate as well as contradict popular stories about the process by which the houses were preserved, salvaged and converted. Key primary-source research includes interviews with persons involved in—and observant of—motivations and forces in play upon these six case studies. Texts of the interviews are included in appendices. The dissertation reveals how select individuals (acting variously as architects, historians, concerned citizens, and leaders of institutions) influenced the creation of the six house museums. This dissertation contains a chronicle and an evaluation of the values which informed and influenced the house museum condition in Chicago in an environment which largely pre-dated the historic building preservation movement in America. The case studies show that the persons and parties involved in saving various houses for reuse did not generally execute definitive plans, in full, with a clear ultimate goal. Instead, in all cases, individuals and small groups of people fought an array of idiosyncratic battles, often yielding short-term victories. Economic pressures, political conditions, and societal values evolve, ushering in new opportunities and new dangers for nascent institutions inhabiting former residences. As each generation of directors, curators and governing boards mature and matriculate, the goals and objectives which influenced the reuse of their house museums changed. The very notion of attaining some sort of permanent statis has been found, through this research, to be elusive. Dynamism in both the people and the institution reusing these house museums can yield positive outcomes ensuring preservation of the institution of the house museum.
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Title: Sustainable Solutions in Complex Spaces of Innovation
Creator: Nogueira, André Martins
Date: 2019
Description: Even though the interconnectivity between human activities and the integrity of ecological systems has long been recognized, the development...
Show moreEven though the interconnectivity between human activities and the integrity of ecological systems has long been recognized, the development of design practices that account for such interconnectivity can be considered relatively new. As such, contemporary institutions and their arrangements were not designed accordingly to their potential to promote sustainable and equitable flows of different types of resources; they lack the capability and structure to operate in the speed and scale in which humans are dynamically interacting with themselves, and with the natural environment. As the world has passed the 7.5 billion mark, such a condition is generating unintended socio-ecological-technical consequences being empowered by the fast-changing technology industry. New lenses and models for understanding the connectivity of social, ecological and technical systems underlying contemporary institutional arrangements are required to advance expertise in redirecting the flow of different types of resources for the sustainability of these systems. However, how humans perceive systems is largely framed by who is included in the discussion and the experiences and interests that they bring to bear. Even though there will always be a discrepancy between what is perceived, and the actual system at play, there are greater opportunities to expand such perception by drawing more deeply on systems thinking and the notion of resources. This dissertation advances design knowledge in the pursuit of bridging the gap between theoretical discourses and the pragmatism necessary to intervene socio-ecological-technical dynamics by exploring how designers might embed principles of sustainability into choice-making processes for innovation, and it proposes a new approach through which designers can advance their practices in enabling more sustainable flows of resources.
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Title: Entangled Polymer Rheology: Efficient Algorithms and Coarse-Graining of Slip-Link Model
Creator: Taletskiy, Konstantin
Date: 2018
Description: This manuscript presents the work done with the Discrete Slip-Link model (DSM) and efforts to improve it through new theoretical derivations...
Show moreThis manuscript presents the work done with the Discrete Slip-Link model (DSM) and efforts to improve it through new theoretical derivations and computational algorithms. New results are presented for melts of broadly polydisperse linear chains as well as for monodisperse star-branched chains. Significant portion of this work is dedicated to the development of the new method for coarse-graining physical models and application of it to the problem of mechanical relaxation of star-branched polymers in DSM.
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Title: ENHANCING PRIVACY AND SECURITY IN IOT-BASED SMART HOME
Creator: Du, Haohua
Date: 2019
Description: The IoT-based smart home is envisioned as a system that augments everyone’s daily life. In the past few years, the smart home attracted...
Show moreThe IoT-based smart home is envisioned as a system that augments everyone’s daily life. In the past few years, the smart home attracted immense attention from the industrial organizations and has been considered as one of the principal pillars of the fourth industrial revolution. However, while the rapidly increasing number of Internet-connected smart devices expends the functionalities of smart homes, it also raises substantial security and privacy concerns.Commonly, a smart home system is composed of three major components, smart devices, communication among devices, and smart applications connecting the devices. Thus, this dissertation aims to enhance the security and privacy of the smart home system without weakening its functionalities from the perspectives of these three components. First, I improve the security of smart devices within the smart home by monitoring their behaviors based on the contextual environment. Then, I enhance the security of the communications among the devices through visible light communication, whose receivers have to be physically visible to senders and avoid possible eavesdropping. Finally, I study two popular smart applications – the augmented reality assistant and the cloud-based surveillance system, to discuss how to define privacy, how to reduce the leakage, and how to balance the privacy and security in the smart home. This dissertation proposes the mechanisms for each component, respectively, and it also implements the design in the real-world for evaluating their effectiveness and efficiency.
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Title: Electronically Assisted Direct Current Circuit Breakers
Creator: Feng, Yanjun
Date: 2019
Description: DC power is gaining tractions recently, however, DC fault protection remains a major technical challenge. Popular and cost-effective AC...
Show moreDC power is gaining tractions recently, however, DC fault protection remains a major technical challenge. Popular and cost-effective AC mechanical circuit breakers do not offer sufficient DC interruption capability. Solid state circuit breakers have drawbacks of high cost and high conduction loss. The reported hybrid circuit breakers solutions require fast responding current sensors and mechanical actuation mechanism vastly different from and far more complex than the conventional AC circuit breakers.This thesis introduces a new DC hybrid circuit breaker concept termed Electronically Assisted Circuit Breaker (EACB). A conventional AC mechanical circuit breaker (MCB) is used to interrupt DC fault currents with the assistance of an electronic commutation circuit, which is activated for a short time period only during the late phase of the breaking process. Unlike other prior art HCB concepts, an EACB uses (1) a conventional thermal-magnetic AC baseline breaker design with minimal modification; and (2) an electronic commutation circuit which only needs to commutate a fault current already reduced from its peak for a very short duration (~100µs), both contributing to significant cost savings. While an EACB does not facilitate arc-free or ultrafast breaking, it does provide a simple and cost-effective way to enhance the DC current interruption capability of conventional thermal-magnetic AC circuit breakers currently dominating the low voltage circuit breaker market. The EACB concept has been validated both experimentally and by simulation. A 600VDC/250A (nominal) EACB prototype is designed and tested. It has experimentally demonstrated a fault current interruption capability of over 8kA at a DC voltage of 600V within 6 milliseconds.
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Title: Wireless Body Sensor Network for Tracking Human Mobility using Long Short-Term Memory Neural Network for Classification
Creator: Gupta, Saumya
Date: 2019
Description: A large number of sensors are used without justification of the number chosen or placement choice. Many papers about body sensor networks...
Show moreA large number of sensors are used without justification of the number chosen or placement choice. Many papers about body sensor networks explore how to capture a type or types of motion, but all their sensors are placed in different locations; making their algorithms very specific to that movement. In this research, we explore the enhancement of human activity classification algorithm using long short-term memory (LSTM) neural network and wearable sensor network. There are five identical nodes used in the body sensor network to collect data. Each node incorporates an ESP8266 Microcontroller with Wi-Fi which is connected to an inertial measurement unit consisting of triple axis accelerometer and gyroscope sensor board. An analysis on the accuracy that each sensor node provides separately and in different combinations has been conducted to allow future research to focus their positioning in optimal positions. A Robot Operating System (ROS) central node is used to illustrate the in-built multi-threading capability. For demonstration, the positions chosen are waist, ankles and wrists. The raw sensor data can be observed on screen while it is being labelled live to create fitting dataset for developing an artificial neural network. Expectation is that increasing the number of sensors should raise the overall accuracy of the output but that isn’t the case observed, positioning of the sensor is pertinent to improvement. These platforms can be further extended to understand different motions and different sensor positions, also expanded to include other sensors.
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Title: SINGLE-POINT MUTATION OF UBL4A ABOLISHES ITS INTERACTION WITH THE ARP2/3 COMPLEX
Creator: Yao, Qi
Date: 2018
Description: Ubl4A is a member of the ubiquitin-like protein family with multiple functions, such as pro-survival and anti-tumor. Our group previously...
Show moreUbl4A is a member of the ubiquitin-like protein family with multiple functions, such as pro-survival and anti-tumor. Our group previously found that Ubl4A directly interacts with actin-related protein Arp2/3 complex to promote Arp2/3-dependent actin “Y shape” branching formation. However, the binding region of Ubl4A for Arp2/3 still remains unknown. To address this question, we generated several Ubl4A mutant and truncated constructs, and cloned them into a GST vector in which GST was fused in-frame with Ubl4A at the N-terminus. We used Glutathione-beads to purify GST fusion proteins and performed pull-down assay with purified Arp2/3 complex. We show that C-terminus of Ubl4A is the region where the Arp2/3 complex interacts with. A single point mutation (D122A) in Ubl4A C-terminal “DYD” motif can abolish Ubl4A ability to bind Arp2/3. These results indicate that C-terminus, especially D122, is critical for Ubl4A association with Arp2/3.
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Title: IN SITU X-RAY ABSORPTION SPECTROSCOPY STUDY OF TIN-BASED GRAPHITE COMPOSITE ANODES FOR LITHIUM-ION BATTERIES
Creator: Ding, Yujia
Date: 2019
Description: Sn-based anode materials such as Sn, SnO2, Sn4P3, and SnS2 that exhibit large theoretical capacities are promising alternatives to traditional...
Show moreSn-based anode materials such as Sn, SnO2, Sn4P3, and SnS2 that exhibit large theoretical capacities are promising alternatives to traditional graphite anodes for Li-ion batteries. However, their capacities fade drastically in a few cycles due to substantial volume changes during the lithiation/delithiation process resulting in cracking and pulverization of the electrode. A graphite matrix is introduced by high-energy ball milling to obtain a graphite composite and enhance the electrochemical performance. Indeed, Sn4P3/graphite composite exhibits a reversible capacity of 651 mA h g-1 in the 100th cycle, and SnS2/graphite composite shows 591 mA h g-1 in the 50th cycle.To obtain a better understanding of the improved performance of the composite materials and the reason for the more gradual capacity fading, in situ EXAFS is used to investigate these mechanisms using in situ coin cells and in situ vacuum-sealed pouch cells. The collected EXAFS data were analyzed by modeling to extract detailed local environment changes during the lithiation/delithiation process.In the crystalline phases of Sn-based materials, the conversion reaction forming metallic Sn is partially reversible and partially irreversible, and the subsequent alloying/dealloying reaction forming LiSn alloys is reversible. Introducing the graphite matrix increases electrical conductivity and prevents aggregation of intermediate Sn clusters. The graphite matrix also plays a significant role in transforming composites into highly dispersed amorphous phases. These amorphous phases, formed in the first few cycles of Sn4P3/graphite and SnS2/graphite composites, exhibit excellent reversibility in both conversion and alloying/dealloying reactions, which is the main reason for the significant improvements in electrochemical performance. The slow growth of metallic Sn clusters and the slight reduction in amorphous phases result in gradual capacity loss over long-term cycling. Introducing the graphite matrix and creating highly dispersed composite samples are the successful strategies that can be scaled up to develop new battery materials in the future.
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Title: Physicochemical Characterization of the SiC Barrier Layer of Irradiated TRISO Fuel
Creator: Seibert, Rachel
Date: 2018
Description: Tristructural-isotropic (TRISO) nuclear fuel is designed to be an inherently safe microencapsulated fuel for use in advanced nuclear reactors...
Show moreTristructural-isotropic (TRISO) nuclear fuel is designed to be an inherently safe microencapsulated fuel for use in advanced nuclear reactors. TRISO fuel is comprised of an uranium-carbide/uranium-oxide mixed kernel, surrounded subsequently by a porous carbon buffer layer, pyrolytic carbon, silicon carbide, and pyrolytic carbon. The silicon carbide layer acts as both the structural backbone and the main barrier to non-gaseous fission product release from the kernel. During operation, fission products are known to release from intact fuel (silver) and to locally corrode the silicon carbide layer (palladium). Release of silver can pose a threat to safety and maintenance workers due to plate-out on reactor components, while palladium corrosion leads the possibility of failure of the SiC layer. An understanding of the silver release mechanism, the diffusion of palladium and fuel kernel components, and their possible correlation is necessary to understand envelopes for safe operation using these fuels.This work focuses on analysis of the reactivity of silver, palladium, and fissile inventory with silicon carbide to determine potential mechanisms and interactions. Irradiated TRISO particles and model thin film cubic silicon carbide (3C-SiC) surfaces were studied to compare and understand the reaction mechanisms of these fission products. Analysis on both systems involved X-ray Absorption Fine Structure Spectroscopy (XAFS) measurements to determine the local atomic structure of the bulk material and electron microscopy studies to observe the microstructure and fission product location. Additionally, x-ray photoelectron spectroscopy (XPS) was used to study the fundamental surface science of silver and palladium in the 3C-SiC thin films. From the comparative studies in this work, the interaction of silver, palladium, and fuel kernel products has been observed. Palladium silicides are preferentially formed, but silver remains metallic and diffuses through both bulk SiC, through material defects, and through grain boundary diffusion. Uranium preferentially forms carbides with increasing temperature. Plutonium primarily forms silicides, but with short carbon bonds. All fission products and fissile inventory were observed to be segregated along grain boundaries in the SiC. This work did not measure a single release mechanism, but suggests multiple mechanisms work together simultaneously. It also presents the first evidence of uranium carbide formation at elevated temperatures and of silver as a metal in irradiated TRISO fuel, to the best of the author's knowledge.
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Title: Enhancing Charge/Discharge Cycle Stability of NaCrO2 Cathode for Na-ion Batteries via Carbon Coatings
Creator: Shi, Zhepu
Date: 2018
Description: In this study, we report the effects of carbon coating on the electrochemical cycle stability of Na-ion batteries made of NaCrO2 cathodes....
Show moreIn this study, we report the effects of carbon coating on the electrochemical cycle stability of Na-ion batteries made of NaCrO2 cathodes. Various coating approaches and conditions have been investigated for 10-h high energy ball milled NaCrO2. It is shown that mixing the carbon source with NaCrO2 particles before the high-temperature carbonization reaction is a critical step. The solution-based mixing of the carbon source with NaCrO2 leads to the best carbon coating uniformity. Furthermore, carbonization treatment should be limited to 10 min at 650 ℃ in order to prevent the reaction between carbon and NaCrO2 to form chromium carbides. Uniform carbon coating can improve the capacity retention of NaCrO2 over charge/discharge cycles and the best capacity retention achieved in this study is 70% after 50 cycles. Furthermore, once the coating is uniformly distributed, NaCrO2 exhibits a very high specific capacity (140 mAh/g) which is significantly higher than the typical value of 110 mAh/g reported in the literature. The unusually high specific capacity observed is attributed to the enhancement of Na-ion intercalation and de-intercalation rates at the electrode/electrolyte interface because of the presence of the carbon coating.
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Title: Electron Cloud studies at Fermilab
Creator: Ji, Yichen
Date: 2019
Description: The presence of unwanted electrons in an accelerator vacuum chamber, known as E-cloud (E-cloud) can potentially cause operational problems in...
Show moreThe presence of unwanted electrons in an accelerator vacuum chamber, known as E-cloud (E-cloud) can potentially cause operational problems in the Fermilab Main Injector (MI) and Recycler Ring (RR). E-cloud has caused instability in the RR in the past, and although it is not currently a problem, there is measurable E-cloud in the MI accelerator. There are planned beam intensity increases due to upgrades of the Fermilab accelerator complex, so E-cloud could become a problem. Some work has been done by others previously to understand how low SEY (Secondary Electron Yield coefficient) coatings might mitigate production of E-cloud, and to model the mechanism whereby E-cloud causes beam instability. Using previous studies as a base, this research took several approaches toward understanding the risk of E-cloud at Fermilab. The evolution of the SEY of the SS316L (stainless steel), TiN coated SS316L, and amorphous carbon coated SS316L were measured in-situ using a SEY measurement station in the MI tunnel. The SEY of these materials change over time either due to bombardment of the E-cloud, or disruption of vacuum conditions. The SEY evolution was tracked over a several year period to find out how long it takes for the SEY of each material to reach its lowest level, and how much the SEY rises during deconditioning periods of poor vacuum. The SEY measurement results can be used to determine whether the SS316L will be a problem at upgrade intensities, and if so, whether or not TiN and A-Carbon coatings can mitigate E-cloud related problems sufficiently. Direct measurements of the E-cloud were done as well, and compared to simulation. The E-cloud bombardment rate was measured at different beam intensities and bunch lengths. It was possible to get detailed information on how the E-cloud varies over the acceleration cycle, where sensitivity to bunch length is reflected in the evolution of the E-cloud. The Retarding Field Analyzer (RFA) measuring the E-cloud bombardment rate was near the instrument that is used to measure the SEY of the beam pipe material. This proximity provided an accurate SEY value for simulations, so that the simulated E-cloud bombardment rate could be better compared to measurement. Bunch length measurements and computations generated accurate bunch length information also needed as input for simulations. After this careful control of the input parameters, the POSINST simulations of E-cloud were a good match to direct measurements. This gave confidence that predictions could be made concerning the E-cloud densities at upgrade intensities. These densities were compared against corresponding proton densities to predict the SEY required to avoid instabilities. That prediction and the information provided by the SEY measurements provide helpful information regarding the risks of E-cloud effects at future beam intensities at Fermilab.
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Title: Capillary Rise of Common Liquids and Nanofluids: Experiments and Modeling
Creator: Wu, Pingkeng
Date: 2018
Description: Capillary dynamics of common liquids and nanofluids is a ubiquitous everyday phenomenon. It has practical applications in diverse fields,...
Show moreCapillary dynamics of common liquids and nanofluids is a ubiquitous everyday phenomenon. It has practical applications in diverse fields, including ink-jet printing, lab-on-a-chip, biotechnology, and coating. Important as it is, this phenomenon has not been fully understood and requires tremendous effort in theoretical analysis and experimental investigations to gain further knowledge and guide the design of practical precesses whenever capillarity is essential.The rise of the main meniscus in rectangular capillaries is important in interpreting the phenomenon of fluid flow in porous media. This thesis presents an experimental study on the rise of the main meniscus in rectangular borosilicate glass and plastic (polystyrene) capillaries using three different liquids (water, ethanol, and hexadecane). A universal model (an extended two-wall model) based on the Laplace equation was developed to predict the equilibrium height of the main meniscus in rectangular capillaries. In capillary dynamics, it is crucial to understand the interaction between fluid molecules and a solid substrate (the wall) in molecular scale. Recent studies reveal that a layered molecularly thin wetting film (LMTWF) will develop ahead of the apparent three-phase contact line for the spreading of a wetting liquid on solid surfaces. Based on this fact, a novel molecular self-layering model is proposed to explain the dynamic wetting considering the role of the molecular shape on self-layering and its effect on the molecularly thin film viscosity in regards to the advancing (dynamic) contact angle. The proposed molecular self-layering model is then incorporated into the Lucas-Washburn-Rideal (LWR) equation to explain the capillary rise dynamics of fluids of spherical, cylindrical, and disk shape molecules in borosilicate glass capillaries. The abilities of the other popular dynamic contact angle models to correct the dynamic contact angle effect in the capillary rise process were also investigated. The LWR equation modified by molecular self-layering model predicts well the capillary rise of carbon tetrachloride, octamethylcyclotetrasiloxane and n-alkanes with the molecular diameter or measured solvation force data. The molecular self-layering model modified LWR equation also has good predictions on the capillary rise of silicone oils covering a wide range of bulk viscosities with the same key parameter W(0), which results from the molecular self-layering. Besides the open capillaries, the proposed molecular self-layering model is applied to explain the spontaneous rise of Newtonian liquids in closed-end capillaries. Contribution of the compressed air inside the closed capillaries is also modeled and experimentally verified. Finally, the research is extended to a liquid phase displacing another immiscible liquid in capillaries with the focus on surfactant solutions containing polymeric nanoparticles (nanofluids), which have been shown to have an improved wetting and spreading on solid surfaces. The polymeric nanoparticles can reduce the frictional coefficient by as much as four times by forming structured layers in the confined wedge film. The role of the interfacial tension on the frictional coefficient is also demonstrated.In summary, this thesis presents the physics of liquid rise in rectangular capillaries, effect of molecular self-layering in capillary dynamics in open and closed-end capillaries, and the contribution of nanofluids in the two-phase displacement dynamics.
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