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Title: Physics at the MeV-Scale in Liquid Argon Time Projection Chambers
Creator: Lepetic, Ivan Thomas
Date: 2020
Description: The liquid argon time projection chamber (LArTPC) is the detection technology chosen for several Fermilab-based neutrino experiments. This...
Show moreThe liquid argon time projection chamber (LArTPC) is the detection technology chosen for several Fermilab-based neutrino experiments. This technology will be used in studies of neutrino cross-sections and oscillations, neutrinos from supernovae as well as a variety of studies of beyond the Standard Model physics. This thesis explores the use of these detectors to study MeV-scale activity. MeV-scale electrons arising from Compton scatters of deexcitation photons and photons from inelastic neutron scattering in neutrino-nucleus interactions are reconstructed using novel methods presented here. This work represents the first demonstration of MeV-scale physics capabilities in a LArTPC neutrino experiment as well as the first observation of neutrino-produced photons from nuclear de-excitation and inelastic neutron scattering. A search for millicharged particles, postulated by theories of beyond the standard model physics, is also performed using data from a LArTPC and the low-energy reconstruction techniques developed. The results set world-leading bounds on the parameter space of millicharged particles. The work in this thesis demonstrates that studies of MeV-scale activity and new physics are possible with LArTPC technology and provides the foundation for future LArTPC studies of low energy neutrinos and new physics.
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Title: A MULTIPLE CASE STUDY OF COLLEGE MATHEMATICS INSTRUCTORS’ TECHNOLOGICAL PEDAGOGICAL CONTENT KNOWLEDGE (TPACK) AND ITS RELATIONSHIP TO THE INTEGRATION OF INFORMATION AND COMMUNICATIONS TECHNOLOGY (ICT) IN THEIR TEACHING PRACTICES AND STUDENTS’ LEARNING
Creator: Alhejoj, Kawkab
Date: 2020
Description: This multiple-case study aimed to investigate the following essential aspects of instructors’ ICT integration in higher education: self...
Show moreThis multiple-case study aimed to investigate the following essential aspects of instructors’ ICT integration in higher education: self-reported technological pedagogical content knowledge (TPACK), level of ICT integration, and motivations-challenges to integrate specific ICT tools to teach particular mathematics concepts. Four college math instructors were selected purposefully from four community colleges. The TPACK conceptual framework was adopted through the use of the TPACK-M self-assessment survey to understand the perceived TPACK knowledge of the instructors. The model of Niess et al (2009), which describes the teacher’s level of practical ICT integration in the light of their TPACK, assisted in exploring the way college math instructors used ICT. Data collection involved surveys, semi-structured interviews, and direct classroom observations. Quantitative data was analyzed using descriptive statistics, while Atlas.ti software was applied for qualitative data. The findings showed that the total TPACK-M was rated high, with TPK the lowest among all the constructs. In terms of the ICT integration model, one instructor fitted into the recognizing level, another into the adapting level, and two others into the accepting level. There was a misalignment between the self-reported TPACK knowledge and the in-class level of ICT integration. Instructors need more support in developing practical TPACK abilities via effective PD and activating the “teacher model” to help college math instructors integrate ICT in creative and successful practice. Also, more research in higher education is recommended using a larger sample in the area of designing a TPACK instrument for college math instructors to help capture their perceptions and recognize any gap between what they know and what they do in higher education contexts.
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Title: Implementation of a multisensor wearable artificial pancreas platform: ensuring safety with communication robustness and cyber security
Creator: Lazaro Martinez, Carmen Caterina
Date: 2019
Description: Advances in IoT technologies and new sensor capabilities contributed to the rapid growth of wearable medical devices. Today, mobile sensor...
Show moreAdvances in IoT technologies and new sensor capabilities contributed to the rapid growth of wearable medical devices. Today, mobile sensor platforms can be effectively, cost efficiently integrated in healthcare applications. However, the increased risks of these devices, inherent vulnerabilities of mobile operating systems and open nature of the wireless protocols call for improved safety and security measures to prioritize patient's well-being. In the field of type 1 diabetes, blood glucose level management with insulin control algorithms are available in diabetes therapy systems, though none are fully automated and require extra announcements (such as meal and exercise) to operate. A mobile artificial pancreas (AP), based on Android smartphone, is developed: such a platform relies on off-the-shelf components and receives in real-time the physiological measurements from the wrist worn physical activity tracker and the glucose measurements, then used in a predictive control algorithm (originally developed and tested on a laptop), to compute the optimal amount of insulin to administer via an insulin pump. A dedicated remote server provides additional support for registration, authentication and data backup.The nature of the algorithm required a fast, reliable method to translate its inherent functions. Therefore, we implement a new semi-automatic conversion mechanism which ports MATLAB to Android as native C code. Validation tests of the mobile version confirm there are no deviations in the results.Moreover, in order to enhance safety guarantees for the patient, this cyber-physical system needs a robust implementation also resilient to attacks and failures. A central monitor module is introduced, wherein wireless devices and communications channels are integrated with complementary alarm and safety subsystems. The parameterization of the AP as a state machine demonstrates the efficiency to detect and react to possible errors, since any state change triggers the appropriate correcting response. The result is a protected and fail-safe environment, further expanded with security modules enforcing encryption, authenticated access and data-flow rules for intrusion detection.Overall, this research demonstrates, in the case of an AP, how challenges in diverse fields such as sensor fusion, control systems, wireless communications and cybersecurity can be addressed with a holistic approach for mobile health (mHealth).
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Title: USING COMPUTATIONAL MOLECULAR MODELING TO STUDY TRANSPORT PROCESSES OF INTEREST IN SEPARATIONS
Creator: Wang, Xiaoyu
Date: 2020
Description: Separation processes are widely used in chemical productions. The further development of membrane-based separation processes, compared with...
Show moreSeparation processes are widely used in chemical productions. The further development of membrane-based separation processes, compared with thermal separations, can lead to significant energy savings in chemical process industries. However, the main obstacle of experiments is that many separation processes are not well understood at the fundamental molecular level. In this dissertation, we use computational molecular modeling tools, mainly classical molecular dynamics (MD), to clarify molecular forces and provide detail at a molecular level, which can aid in the understanding of transport process and designing materials for a proposed application.In the first study, we investigated separation of water/alcohol vapor using zeolite membranes. Experimentally, the separation of water/isopropanol (IPA) mixtures shows a dramatic decrease in selectivity due to increase of IPA flux as the feed water concentration decrease when using the sodium A zeolite membrane. We used molecular dynamics simulations to help our experimental collaborators understand these puzzling results. The MD results reveal that the water molecules gather around the defect pores on the zeolite membrane, which stops the IPA from going through the membrane and has a positive effect on separation.Then, we studied the HPLC used to separate chiral drug mixtures. One popular chiral stationary phase, amylose tris(3,5-dimethylphenyl carbamate) (ADMPC), has been investigated using both experimental and computational methods; however, the dynamic nature of the interaction between enantiomers and ADMPC, as well as the solvent effects on the ADMPC-enantiomer interaction, are currently absent from the chiral recognition mechanism. We used MD simulations to model the ADMPC in different solvents to elucidate the chiral recognition mechanism from a new dynamic perspective. The ADMPC is found to hold the left-handed helical structure in both methanol and heptane/IPA (90/10); however, the ADMPC has a more extended average structure in heptane/IPA. We developed a model where the ADMPC atoms were restricted in the MD simulation. To better understand the molecular dynamic chiral recognition that provides the retention factor and the elution order in HPLC, we examined hydrogen bonding lifetimes, and mapped out ring-ring interactions between the drugs and the ADMPC. We discover several MD metrics related to hydrogen-bonding lifetimes and correlate them with HPLC results. One metric provides a prediction of the correct elution order 90%, and the ratios of these quantities for the enantiomers provide linear correlation (0.85 coefficient) with experimental retention factors.In the following study, we presented an improved model wherein multiple ADMPC polymer strands are coated on an amorphous silica slab. Using various MD techniques, we successfully coated ADMPCs onto the surface without losing the structural character of the backbone in the solvent. This model provides more opportunities for chiral molecules interacting with ADMPC, resulting in a better agreement compared with experiment when using the overall average metric. The new model also provides the possibility for drug molecules to interact with two polymer strands simultaneously, which is not possible in the previous single-strand model. For a better understanding of why some metrics are better predictors than others, we used charts of the distribution of hydrogen bonding lifetimes to display the information for various donor-acceptor pairs. The results are more consistent than the previous models and resolves the problematic cases of thalidomide and valsartan.Besides the membrane-based separations, immiscible liquid-liquid equilibrium states were also studied. We successfully predicted results based on MD simulations and showed comparable accuracy with experimental data. This method has applications in liquid-liquid extraction which is widely used in industrial separation process.
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Title: A FRAMEWORK FOR MANAGING UNSPECIFIED ASSUMPTIONS IN SAFETY-CRITICAL CYBER-PHYSICAL SYSTEMS
Creator: Fu, Zhicheng
Date: 2020
Description: For a cyber-physical system, its execution behaviors are often impacted by its operating environment. However, the assumptions about a cyber...
Show moreFor a cyber-physical system, its execution behaviors are often impacted by its operating environment. However, the assumptions about a cyber-physical system’s expected environment are often informally documented, or even left unspecified during the system development process. Unfortunately, such unspecified assumptions made in cyber-physical systems, such as medical cyber-physical systems, can result in patients’ injures and loss of lives. Based on the U.S. Food and Drug Administration (FDA) data, from 2006 to 2011, there were 5,294 recalls and 1,154,451 adverse events resulting in 92,600 patient injuries and 25,800 deaths. One of the most critical reasons for these medical device recalls is the violations of unspecified assumptions. These compelling data motivated us to research unspecified assumptions issues in safety-critical cyber-physical systems, and develop approaches to reduce the failures caused by unspecified assumptions.In particular, this thesis is to study the issues of unspecified assumptions in cyber-physical system design process, and to develop an unspecified assumption management framework to (1) identify unspecified assumptions in system design models; (2) facilitate domain experts to perform impact analysis on the failures caused by violating unspecified assumptions; and (3) explicitly model unspecified assumptions in system design models for system safety validation and verification.Before starting to develop the unspecified assumption management framework, we first need to study how unspecified assumptions may be introduced into cyber- physical systems. We took cases from the FDA medical device recall database to analyze the root causes of medical device failures. By analyzing these cases, we found two important facts: (1) one of the major reasons that causes medical device recalls is violation of some unspecified assumptions; and (2) unspecified assumptions are often introduced into the system design models through syntactic carriers. Based on the two findings, we propose a framework for managing unspecified assumption in cyber- physical system development process. The framework has three components. The first component is called the Unspecified Assumption Carrier Finder (UACFinder), which is to identify unspecified assumptions in system design models through automatically extracting syntactic carriers associated with unspecified assumptions. However, as the number of unspecified assumptions identified from system design models can be large, and it may not be always feasible for domain experts to validate and address the most safety-critical assumptions at different system development phases. Therefore, the second component of the framework is a methodology that uses the Failure Mode and Effects Analysis (FMEA) based prioritization approach to facilitate domain experts to perform impact analysis on unspecified assumptions identified by the UACFinder and asses their safety-critical level. The third component of the framework describes a model architecture and corresponding algorithms to model and integrate assumptions into system design models, so that system safety associated with these unspecified assumptions can be validated and formally verified by existing tools.We also have conducted case-studies on representative system models to demonstrate how UACFinder can identify unspecified assumptions from system design mod- els, and how the FMEA based prioritizing approach can facilitate domain experts to verify the appropriateness of identified assumptions. In addition, case studies are also conducted to demonstrate how system safety properties can be improved by modeling and integrating unspecified assumptions into system models. The results of case-studies indicate that the unspecified assumption management framework can identify unspecified assumptions, facilitate domain experts to validate and verify the appropriateness of identified assumptions, and explicitly specify assumptions that would cause defects in these systems.
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Title: Regenerating the Jordan River: Through Ecological and Sociocultural Interventions
Creator: Shadid, Rula
Date: 2019
Description: The Jordan River is often described as one of the world’s most unique eco-systems and is attributed to serving as a cradle of history, culture...
Show moreThe Jordan River is often described as one of the world’s most unique eco-systems and is attributed to serving as a cradle of history, culture, and spirituality in the ancient and modern times. Archaeological evidence on its banks reveal signs of some of the world’s earliest existences of civilization. Its history as a meeting place for the crossing and exchange between plants, animals, and human societies, along with its strong association to three of the world’s great religions – Christianity, Islam, and Judaism – has made it a world known and important site. Being located in the Middle East, in the heart of a complex political conflict that has been ongoing since the middle of the last century, years of war, political clashes, and water and resource exploitation has reduced the river from a once lush and bio-diverse ecosystem to nothing but a polluted stream. Today the river is a “hydro-border” that divides the competing nations around it and segregates the people of the Jordan Valley in which the river runs via militarized security efforts. The conflict has left the region politically and socially segregated and has eliminated the productive exchange which once allowed the valley to thrive while efforts to protect, preserve, or rehabilitate the river are given little chance to succeed. The thesis addresses river degradation and social segregation as two interdependent issues in the Jordan Valley. It highlights saving the Jordan River as a driver for integration between the conflicting society and points to the Jordan Valley river border as a site for regenerative interventions that suggest an alternative and productive way of life in an area filled with conflict, economic distress, and spatial divide through the collaboration and exchange of efforts, ideas, and resources.
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Title: FABRICATION, CHARACTERIZATION AND RELEASE STUDIES OF LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES
Creator: Zhao, Ziqian
Date: 2015, 2015-07
Description: Nanocomposites exhibit enhanced physical properties including mechanical strength, thermal stability, and gas barrier properties. The...
Show moreNanocomposites exhibit enhanced physical properties including mechanical strength, thermal stability, and gas barrier properties. The development of nanocomposites has led to applications in food industry, mostly in food packaging. The application of nanocomposites in food packaging may extend the shelf life of a food, thus increasing the market value for manufactures. However, there is limited data and research to assess the risk of exposure of nanomaterials to consumers. This project aims at evaluating the factors that can influence the release of nanomateirals in low density polyethylene/clay nanocomposites films. Nanocomposites based on low density polyethylene (LDPE), containing 1, 3, 5 and 7 wt.% of Cloisite 20A and maleic anhydride-grafted polyethylene (MAPE) as a compatibilizer were prepared by melt compounding and characterized in this thesis project. Cloisite 20A is mostly composed of montmorillonite (MMT), which is commonly used as a nanoscale size filler. LDPE/Clay nanocomposite films containing MMT and three mass equivalents of MAPE were successfully extruded into thin films with good optical clarity. The materials were characterized by using transmission electron microscope (TEM), thermogravimetric analysis (TGA), oxygen permeation analysis and a material testing machine. Important properties such as tensile modulus, oxygen transmission rate, thermal resistance and glass transition temperature were measured. Nanocomposite films were immersed in three kinds of food simulants (absolute ethanol, 3% acetic acid and deionized water). Storage time, storage temperature and percent fill of clay were evaluated as the factors that can influence the release of nanomaterials. The content of released of Al, Mg, and Si was quantified using inductively coupled plasma mass spectrometry (ICP-MS). Mg, Al and Si were continuously released from nanocomposite films in duration of 30 days. Fastest releasing speed was found in 3% aqueous acid at 75 °C, and lower temperature can largely decrease the release of nanoparticles. This project is an initial attempt to assess the risks from the use of nanocomposites as food packaging.
M.S. in Food Safety and Technology, July 2015
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Title: COMPUTATION AND ANALYSIS OF TUMOR GROWTH
Creator: Turian, Emma
Date: 2016, 2016-05
Description: The ability of tumors to metastasize is preceded by morphological instabilities such as chains or fingers that invade the host environment....
Show moreThe ability of tumors to metastasize is preceded by morphological instabilities such as chains or fingers that invade the host environment. Parameters that control tumor morphology may also contribute to its invasive ability. In this thesis, we investigate tumor growth using a two-phase Stokes model. We first examine the morphological changes using the surface energy of the tumor-host interface and investigate its nonlinear dynamics using a boundary integral method. In an effort to understand the interface stiffness, we then model the tumor-host interface as an elastic membrane governed by the Helfrich bending energy. Using an energy variation approach, we derive a modified Young-Laplace condition for the stress jump across the interface, and perform a linear stability analysis to evaluate the effects of viscosity, bending rigidity, and apoptosis on tumor morphology. Results show that increased bending rigidity versus mitosis rate contributes to a more stable growth. On the other hand, increased tumor viscosity or apoptosis may lead to an invasive fingering morphology. Comparison with experimental data on glioblastoma spheroids shows good agreement especially for tumors with high adhesion and low proliferation. Next, we evaluate tumor regression during cancer therapy by a combined modality involving chemotherapy and radiotherapy. The goal is to address the complexities of a vascular tumor (e.g. apoptosis and vascularization) during treatment. We introduce an apoptotic time delay and study its impact on tumor regression using numerical and asymptotic techniques. In particular, we implement the linear-quadratic model and identify two extreme sets of parameter data, namely the slow, and fast tumor response to therapy. Numerical simulations for the slow response set show good agreements with data representing non-small cell lung carcinoma. Using the evolution equation for tumor radius with time delay, we find that tumors with shorter time interval to the onset of apoptosis shrink faster.
Ph.D. in Applied Mathematics, May 2016
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Title: DEVELOPMENT OF AN EMBEDDED CONTROLLER FOR TWO QUADRANT OPERATION OF BLDC MOTORS IN AUTOMOTIVE APPLICATIONS
Creator: Liu, Yizhe
Date: 2011-07-06, 2011-07
Description: Due to growing concerns over the availability of non-renewable petroleum products and the increasing emphasis on protecting our environment...
Show moreDue to growing concerns over the availability of non-renewable petroleum products and the increasing emphasis on protecting our environment from green house gas emissions, plug-in hybrid electric vehicle and hybrid electric vehicles have been gaining increasing popularity over recent years. This has led to the design of advanced drive systems using different electric motors such as BLDC, PMSM, IM and SRM. An electric motor/generator requires controller that not only has a strong I/O control function, but also high speed signal processing ability for realizing real time control. Therefore, a DSP (Digital Signal Processors), which integrates flexible multiple PWM signal generator, high speed high precision ADC and encoder interface for motor speed and position feedback, is considered as one of the strongest controllers for electric motor control. Owing to a growing emphasis on identification, interference, and communication of security services of drive train in intelligent PHEVs and HEVs, a DSP can also be used to identify and isolate security issues in the integrity of the drive train in PHEVs and EVs. This thesis has two main contributions: a) it focuses on the development of an embedded controller using TMS320LF2812 DSP to realize two quadrant control of the BLDC; and b) it develops an automotive test bench to identify and investigate some potential security issues using the embedded controller’s eCAN communication function.
M.S. in Electrical Engineering, May 2011
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Title: AN EVALUATION OF THE FEASIBILITY OF AN ONLINE FAMILY-BASED INDICATED PREVENTION PROGRAM FOR ADOLESCENT EATING DISORDERS
Creator: Lebow, Jocelyn R.
Date: 2011-10, 2011-12
Description: Adolescent eating disorders are highly impairing class of mental illness, marked by chronicity and recurrence. Data indicate that early...
Show moreAdolescent eating disorders are highly impairing class of mental illness, marked by chronicity and recurrence. Data indicate that early intervention, before anorexia nervosa (AN) or bulimia nervosa (BN) symptoms become entrenched, leads to an increased likelihood of positive outcomes (Fisher, Schneider, Burns, Symons & Mandel 2001; Le Grange, Loeb, Van Orman & Jellar, 2004). As such, numerous prevention programs have been developed for adolescent eating disorders, with mixed success (Shaw, 2008, Stice, Shaw & Marti, 2007). Most recently, programs have utilized the technology of the Internet to make prevention and early intervention more accessible and cost effective for affected teens and families. The current study assessed the feasibility of an original Internet-based indicated prevention program for families of adolescents with subsyndromal eating disorders. The program was based on the empirically-supported Family Based Treatment (FBT) for adolescent AN and BN. Seven families (comprised of 7 caregivers and 7 adolescents with subthreshold levels of eating disorder symptoms) were enrolled in the study, and 4 families successfully completed all program requirements. Four separate aims were assessed including: evaluation of program acceptability, identification of recruitment and retention patterns, assessment of program compliance and dosage received, and analysis of preliminary outcomes. Results suggested that the program was acceptable to all participants, and that the program format and content were positively received. Preliminary outcome data was limited due to the small sample size, however, descriptive analyses showed that the program had a significant effect on the reduction of all cognitive and behavioral eating disorder symptoms, as well as on the reduction of adolescent depressive symptoms. Adolescent ix self esteem was not significantly impacted by program participation. Compliance results were less straightforward. Program adherence was mixed, and further investigation is needed to clarify patterns of compliance and retention. Finally, the recruitment strategies used were found to not be feasible. Despite a wide-ranging and multi-faceted recruitment strategy, rates were very slow. Further, a large percentage of interested potential participants had to be excluded, calling into question the appropriateness of the applicant pool that was accessed through the implemented program of recruitment. Implications of these findings, possible explanations and suggestions for future research are discussed.
Ph.D. in Psychology, December 2011
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Title: Polymorphic Network-on-Chip Datapath Architecture for Reconfigurable Computing Machines
Creator: Weber, Joshua
Date: 2012-04-18, 2012-05
Description: Polymorphic processors have considerable advantages in performance over existing reconfigurable designs. Polymorphic processors combine the...
Show morePolymorphic processors have considerable advantages in performance over existing reconfigurable designs. Polymorphic processors combine the flexibility and ease of a general purpose processor with the performance optimizations made possible through reconfigurable arrays. Polymorphic processors provide all the ease of programming from a traditional general purpose processor while incorporating the significant performance gains that can be realized using reconfigurable arrays. Polymorphic processors can be categorized by the level of integration between the general purpose processor and the reconfigurable array. At coarse levels of integration, the processor and reconfigurable array execute independently and exchange data utilizing bus structures. These systems perform robustly for high level datadriven optimizations, allowing large segments of processing to be quickly performed on fast reconfigurable resources. However, the overhead of data transfer between the processor and array limits the benefit to fine grained optimizations. Other architectures attempt a tight coupling of reconfigurable arrays, placing them within the processor as reconfigurable coprocessors and functional units. This technique allows fine grained optimizations of small scale, highly repeated computations, but finds it difficult to replicate the gains made in large coarse grained optimizations. To achieve an even more tightly coupled design than any prior work, the fundamental architecture of the processor is changed. The datapath of the processor is eliminated and replaced with a network-on-chip communications framework. This framework connects a system of reconfigurable arrays. Some of these reconfigurable blocks are tasked with execution of standard, general purpose processor computations, emulating the standard pipeline stages of a SPARC processor. Additional reconfigurable blocks are available to the end-user to incorporate custom application specific optimizations. This new polymorphic NoC datapath (PolyNoC) processor is able to provide a more tightly integrated architecture with significant performance advantages. The PolyNoC processor is able to incorporate both fine and coarse grained optimizations, producing a polymorphic processor able to provide performance improvements for a wide range of target applications. This thesis presents the architectural design of the PolyNoC processor. The unique design constraints resulting from the use of the NoC as a datapath will be fully explored. The impact of these constraints will be incorporated into the design of a suitable NoC for the PolyNoC processor. A cycle-accurate simulator of the PolyNoC processor has been constructed. This simulator is used to examine the performance of the PolyNoC processor when executing unmodified, industry standard benchmark programs. To demonstrate the advantages of application specific extensions to the processor, accelerators are added for each benchmark. The performance of the Poly- NoC processor is promising.
Ph.D. Computer Science, May 2012
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Title: A SPECTRAL ELEMENT SOLVER FOR SIMULATING TURBULENT FLOWS IN COMPLEX GEOMETRIES
Creator: Kandala, Sriharsha
Date: 2015, 2015-07
Description: Flows in urban street canopies are quite complex both physically and geometrically and often unique to the specific canopy. Understanding the...
Show moreFlows in urban street canopies are quite complex both physically and geometrically and often unique to the specific canopy. Understanding the physics of these flows is important for various applications like prediction and control of dispersion in urban environments and efficient navigation of Micro-Air Vehicles (MAV) in gusty velocity fields among others. These flows are turbulent and the velocity fields are characterized by a wide range of spatial and temporal scales. Traditionally, given the exorbitant number of grid points required for accurate resolution of all flow features in computer simulations, experimental measurements supplemented with theory were the only feasible choice for understanding these flows. However with rapid increase in computing power and development of highly scalable algorithms to harness this power, numerical simulations are increasingly becoming feasible for higher Reynolds number flows. In the current work, flow in a model urban street canyon is studied using high-fidelity three-dimensional computational fluid dynamics simulations. Specsolve, a parallel spectral element solver capable of running parallel simulations utilizing thousands of processors, is developed for this purpose. The simulation domain used in this study consists of a 5 by 7 array of obstacles representative of a typical urban environment with the canyon aspect ratio corresponding to the skimming flow regime. These simulations do not use any turbulence model and are stabilized using a filtering procedure. Hot-wire data obtained from the wind tunnel experiments performed on an identical domain are used to prescribe realistic inflow boundary conditions upstream of the array. Numerical simulations were performed for cases where the flow is perpendicular to the array and with the flow at 15 degree angle of incidence. A grid resolution study is conducted to zero-in on the spectral element mesh required to resolve all important flow features for the 0 degree angle of incidence case. Mean velocity, coherent-structures and turbulence characteristics are used to describe the most important flow features in the domain. Streetwise evolution of flow is studied and the results indicate that flow reaches an equilibrium state by the third street.
Ph.D. in Mechanical and Aerospace Engineering, July 2015
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Title: POWDER CHARACTERIZATION AND PROCESS OPTIMIZATION FOR COLD COMPACTION AND SINTER APPLICATIONS OF COMMERCIALLY PURE TITANIUM POWDERS
Creator: Araci, Kerem
Date: 2011-08, 2011-07
Description: Near net shape manufacturing using powder metallurgy (P/M) technology and processes can significantly reduce material waste and cost during...
Show moreNear net shape manufacturing using powder metallurgy (P/M) technology and processes can significantly reduce material waste and cost during component fabrication. This study includes all the efforts to evaluate near net shape consolidation processes utilizing several different commercially pure titanium (CP-Ti) powders, focusing on the one produced by Armstrong Process® technology. Powder characteristics were studied in terms of morphology, particle size distribution, apparent and tap densities, and chemistry. Desired particle size distributions and higher powder densities were observed for HDH powders, while unique coral-like morphology was examined for the Armstrong Process® powder. Ball milling of the Armstrong Process® powder was systematically investigated by evaluating the impact on the particle size distribution, powder density and chemistry. Cold-uniaxial compaction of the milled powders was also evaluated in terms of theoretical density and green strength as a function of compaction pressure and lubrication techniques. Green densities were varied from 79 % to 91% for different powder compacts in different compaction conditions. Excellent green compaction of 145 MPa was approached by green compacts of Armstrong Process® powder. Sinter processing of the green compacts was investigated to approach relatively advanced tensile and flexural properties as a function of process temperature, time and heating rate. Near net-shape components which were fabricated by pressing and sintering were shown to achieve near-full densification with up to 97% of the theoretical density. Properties of P/M materials after the consolidation process were characterized and compared to those of conventionally produced materials.
M.S. in Materials Science and Engineering, July 2011
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Title: DEVELOPMENT OF ADVANCED PACKAGING, FABRICATION AND RELIABILITY METHODS FOR SUBMINIATURE IMPLANTABLE NEURAL PROSTHESES
Creator: Kim, Taehyung
Date: 2011-08, 2011-07
Description: The main purpose of the present thesis is to study the critical reliability issues of polymeric encapsulated electronic devices for visual...
Show moreThe main purpose of the present thesis is to study the critical reliability issues of polymeric encapsulated electronic devices for visual prosthesis. Visual prosthesis has been compatibly studied over twenty years in many professional research labs. The electric design of circuit for the visual prosthesis has been well studied so far. However, the device packaging design and reliability have been not studied extensively. In particular, failure analysis and reliability using non-hermetic packaging for long lifetime visual prosthesis have been poorly studied. The first step of the research for this thesis was to create a mechanical design of a visual prosthesis prototype. The prototype device was created by fabricate a multi-layer structure consisting of electrodes, substrate, and integrated circuit chip with silicone encapsulated packaging. The interconnection between the chip and electrodes used Au wire and Al bonding pad. The prototype devices were tested in a liquid water. This water environment is not a common reliability test for commercial electronic packaging. Relative humidity testing is a common and widely used testing methods, but the visual prosthesis device cannot be applied to gas phase relative humidity testing due to the environment condition. Water absorption in polymeric material in the liquid water is higher than in the vapor water. After water penetrated interconnection interface, the Au-Al intermetallic compound becomes oxidized and generates bonding die open failure. From these unusual testing results, we were conformed the failure mechanism and predicted the lifetime using Au-Al imtermetallic growth pattern and oxidation. Additional discussions include transition metal ions in CSF to expect the other failure mechanisms. Wafer and packaging level xiii failure mechanisms by Cu and Fe ions are also discussed in this thesis. The end of this thesis discuss possible fabrication processing to protect overall external environment effects for polymeric packaging visual prosthesis. Overall this thesis study, which uses polymeric packaging electronic devices for bio-implant research, concluded that devices may not make good reliability devices in the CSF environment. The corrosion, oxidation and metallization on or in metal surfaces and interconnection interfaces should continually be studied to produce longer lasting electronic devices over 30 years. The reliability of the visual prosthesis has not been well studied in any other professional research labs, so this thesis may give or address some initial guidelines to help save time for the project decision in the future to develop advanced hermetic packaging for bioimplantable electronic devices.
Ph.D. in Materials Science and Engineering, July 2011
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Title: UNMANNED AIRCRAFT SYSTEM SENSE AND AVOID INTEGRITY AND CONTINUITY
Creator: Jamoom, Michael B.
Date: 2016, 2016-05
Description: This thesis describes new methods to guarantee safety of sense and avoid (SAA) functions for Unmanned Aircraft Systems (UAS) by evaluating...
Show moreThis thesis describes new methods to guarantee safety of sense and avoid (SAA) functions for Unmanned Aircraft Systems (UAS) by evaluating integrity and continuity risks. Previous SAA e↵orts focused on relative safety metrics, such as risk ratios, comparing the risk of using an SAA system versus not using it. The methods in this thesis evaluate integrity and continuity risks as absolute measures of safety, as is the established practice in commercial aircraft terminal area navigation applications. The main contribution of this thesis is a derivation of a new method, based on a standard intruder relative constant velocity assumption, that uses hazard state estimates and estimate error covariances to establish (1) the integrity risk of the SAA system not detecting imminent loss of “well clear,” which is the time and distance required to maintain safe separation from intruder aircraft, and (2) the probability of false alert, the continuity risk. Another contribution is applying these integrity and continuity risk evaluation methods to set quantifiable and certifiable safety requirements on sensors. A sensitivity analysis uses this methodology to evaluate the impact of sensor errors on integrity and continuity risks. The penultimate contribution is an integrity and continuity risk evaluation where the estimation model is refined to address realistic intruder relative linear accelerations, which goes beyond the current constant velocity standard. The final contribution is an integrity and continuity risk evaluation addressing multiple intruders. This evaluation is a new innovation-based method to determine the risk of mis-associating intruder measurements. A mis-association occurs when the SAA system incorrectly associates a measurement to the wrong intruder, causing large errors in the estimated intruder trajectories. The new methods described in this thesis can help ensure safe encounters between aircraft and enable SAA sensor certification for UAS integration into the National Airspace System.
Ph.D. in Mechanical and Aerospace Engineering, May 2016
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Title: UNDERSTANDING DELIBERATIVE AND INTUITIVE DECISION MAKING ABOUT HAZARDS ON CONSTRUCTION SITES
Creator: Saxena, Jaya
Date: 2013, 2013-12
Description: During the course of performing daily tasks, construction workers encounter numerous hazards, such as ladders that are too short to reach the...
Show moreDuring the course of performing daily tasks, construction workers encounter numerous hazards, such as ladders that are too short to reach the work area, energized electrical lines, or inadequate fall protection. When a hazard is encountered, the worker must make a rapid decision about how to respond and whether to take or avoid the risk. The goal of this researchwas to construct a theory about the influence of decision cues on intuitive and deliberative decision-making in high-hazard construction environments. Drawing from Cognitive Continuum Theory, the study specifies a framework for understanding why and how construction workers make decisions that lead to taking or avoiding physical risks when they encounter daily hazards. A secondary aim of the research was to construct a set of hypotheses about how specific decision cues influence whether a worker is more likely to engage their intuitive impulses or to use careful deliberationwhen responding to a hazard. These hypotheses are described and the efficacy of the hypotheses was evaluated using cross-tabulations and nonparametric measures of association. While most of the associations between decision cues and decision mode (i.e., intuition or deliberation) identified in this data set were generally modest, none of the associations were statistically zero, thus indicating that further research is warranted based on theoretical grounds. The qualitative data set was analysed using Decision Trees and Recognition Primed Decision Models.A rigorous program of theory testing is the next logical step to the research, and the thesis thus concludes with numerous suggestions for extending the research and testing the proposed hypotheses
M.S. in Civil Engineering, December 2013
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Title: FPGA IMPLEMENTATION OF ULTRASONIC FLAW DETECTION ALGORITHM BASED ON SUPPORT VECTOR MACHINE CLASSIFICATION
Creator: Jiang, Yiyue
Date: 2016, 2016-12
Description: In this study, a Support Vector Machine (SVM) classification method used for analyzing Ultrasound signals is implemented by FPGAs based on...
Show moreIn this study, a Support Vector Machine (SVM) classification method used for analyzing Ultrasound signals is implemented by FPGAs based on Xilinx Zynq SoC. The SVM processor aims at classifying A-scan data obtained by an ultrasonic sensor. For reducing development time, hardware software co-design tools such as Xilinx System Generator and Vivado have been used. SVM kernel function is implemented by DSP slices and block RAMs. Advanced Extensible Interface bridges the ARM core and FPGAs for more convenient communication. The main objective of this study is to achieve robust detection of ultrasonic flaw echoes in real-time using an SVM algorithm. The implementation on the FPGA shows that the architecture can be realized with a Xilinx Zedboard FPGA. It runs at 100MHz clock frequency and can calculate the SVM classification for 1024 feature space points under 0.02ms.
M.S. in Electrical Engineering, December 2016
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Title: SERVICEABILITY REQUIREMENTS FOR FLOOR SYSTEMS - A REVIEW OF CURRENT STANDARDS AND PRACTICES
Creator: Jaafari, Chaimaa
Date: 2017, 2017-07
Description: Serviceability requirements are considered in any design to maintain the occupants’ comfort in buildings. Specifically, issues such as floor...
Show moreServiceability requirements are considered in any design to maintain the occupants’ comfort in buildings. Specifically, issues such as floor system deflections and vibrations are two important considerations for design as relate to serviceability. Design codes primarily address the deflection control yet rarely address the vibration. Although the vibration may be related to deflection, maintaining the comfort of occupants will require a detailed study on the level of vibration and its frequency that would be comfortable to the occupants. This research will examine and summarize the serviceability requirements as suggested by various codes and standards and also as suggested by published papers. Specifically, the research focuses on deflection and vibration control for floor systems based on the occupancy and usage and the types of structures and sources of vibrations. Methods to alter existing floor system designs to control vibrations will also be presented. The final research outcome will be a complete document summarizing the findings on what is perceived as good practice for deflection and vibration control for floor system designs in buildings.
M.S. in Civil Engineering, July 2017
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Title: ELECTROCATALYSTS FOR ALKALINE WATER ELECTROCATALYSIS
Creator: Jain, Anchal
Date: 2016, 2016-07
Description: Hydrogen is an attractive energy carrier and is part of an idealistic future wherein it serves as a clean energy source. In the presence of...
Show moreHydrogen is an attractive energy carrier and is part of an idealistic future wherein it serves as a clean energy source. In the presence of oxygen, it can be converted to water in fuel cells with the release of heat and electrical work. Electrolysis of water is an important route to hydrogen generation. Alkaline water electrolysis is preferred over electrolysis in acidic medium due to the possibility of lowering stack costs and enhancing the library of stable electrocatalyst materials available for the electrochemical reactions. The high anode overpotential arising from the sluggish oxygen evolution reaction (OER) has led to significant interest in developing stable and active OER electrocatalysts. IrO2 (state of the art catalyst), RuO2 and PGM-based pyrochlores are suitable catalyst materials that exist today, but there is benefit in finding cost-effective alternatives. In this study, the pyrochlore oxides containing non- Platinum Group Metals (non-PGM) metals were synthesized by solid state reaction and were tested for their OER activity but none of the materials tested, exhibited OER activity and a comparison was attempted between the pyrochlores containing PGM metals as against those containing non-PGM metals. Additionally, perovskite oxides of the form La[Ni(1-x-y)CoxFey]O3 (where 0≤x≤1 and 0≤y≤1) were synthesized by the co-precipitation method. Many of these perovskites exhibited electron conductivities greater than 0.1S/cm, eliminating the need to add carbon for OER studies and implying the likelihood of making conducting electrodes with these materials without the additives like carbon. The perovskites LaNi0.6Co0.4O3 or LaNi0.6Fe0.4O3 with x/y =0.4 had conductivities of the order of 10S/cm. The electrocatalytic activity for the OER was studied using a rotating disk electrode (RDE) in 0.1M KOH and catalyst loading of ~100μg/cm2. The perovskite LaNi0.5Co0.5O3 (x=0.5, y=0) had the onset potential of ~1.50V against RHE, and all these perovskites had onset potentials ~0.1-0.15V higher than the benchmark IrO2 that has an onset potential of ~1.43V. Few of the perovskites were also evaluated for their oxygen reduction activity (ORR) implying that these materials can be used as bi-functional catalysts.
M.S. in Chemical Engineering, July 2016
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Title: DYNAMIC ANALYSIS OF UNCERTAIN STRUCTURES USING IMPRECISE PROBABILIY
Creator: Bergerson, Joshua D.
Date: 2014, 2014-05
Description: A new method for dynamic response spectrum analysis of structures with uncertainty in their mechanical properties utilizing the notion of...
Show moreA new method for dynamic response spectrum analysis of structures with uncertainty in their mechanical properties utilizing the notion of imprecise probability is developed. This finite-element-based method is capable of obtaining probabilistic bounds of the dynamic response of the structure with uncertainty defined by enveloping p-boxes. The developed method obtains probabilistic bounds on 1) the mode shapes, 2) modal coordinates, and 3) modal participation factor, leading to the p-boxes of modal responses. Finally maximum modal responses are combined to obtain the structure’s maximum total response with consideration of uncertainty. Numerical examples demonstrating the developed method are included. Keywords: Structural Dynamics, Uncertainty, Imprecise Probability, P-Box.
PH.D in Civil Engineering, May 2014
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