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Title: THE DEVELOPMENT OF A CRYOGENIC OVER-PRESSURE PUMP
Creator: Alvarez, Matthew L.
Date: 2001-07-17, 2012-07
Description: The Dark Energy Survey (DES) project will study the accelerated expansion of the universe. In order to further study this phenomenon,...
Show moreThe Dark Energy Survey (DES) project will study the accelerated expansion of the universe. In order to further study this phenomenon, scientists have devised a method of creating an array of charged couple devices (CCD) to capture images that will be studied. These CCDs must be cooled and remain at 173K to eliminate thermal gradients and dark current. Therefore, a two-phase CCD liquid nitrogen (LN2) cooling system was designed to maintain the array of CCDs at a constant temperature. However, the centrifugal pump used to supply LN2 has a mean time between failure (MTBF) of approximately two thousand-eight hundred hours (116 days). Because of the low MTBF of the centrifugal pump, a new pump is being considered to replace the existing one. This positive displacement pump is a simpler design that is expected to have a MTBF that will exceed 116 days (2800hrs). This positive displacement reciprocating pump, also known as, the cryogenic over-pressure pump (OPP), was tested in February 2012 and successfully cooled the CCD array to 173K. Though un t for service for DES CCD cooling system, the overall concept of this pump has been proven. Typical ow rates, pressures, and temperatures trends have been captured via instrumentation and are speci c to the operation of future over-pressure pumps.
M.S. in Mechanical and Aerospace Engineering, July 2012
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Title: THE GARDEN BLOCK: A NEW MODEL OF SUPERBLOCKS TOWARDS SOCIO-ECOLOGICAL COHESION
Creator: Sharari Alzraikat, Saly Azmi
Date: 2016, 2016-12
Description: It is said that the contemporary Chinese city is a global model of future urban development, in terms of superblocks’ development, advanced...
Show moreIt is said that the contemporary Chinese city is a global model of future urban development, in terms of superblocks’ development, advanced technological applications and accelerated expansion. However, this model’s characteristics can be perceived as its own challenges; this mono-functional gated community is built on a blank slate without taking into consideration culture, transportation and socio-ecological infrastructure, creating bedroom communities that lack social cohesion, and ecological sensitivity and awareness. A hybrid typology is a potential adaptive prototype that generates community stability, public benefit and sustainable practices. Chinese authorities proposed the "Sponge City" initiative to ensure healthy urban expansion, control water flooding and diminish pollution. By proposing a “Garden System” as a solution that responds to the "Sponge City" objectives, quality of life of the block's users can be enhanced by juxtaposing contemporary garden applications that would directly target the current superblock conditions in China, and produce a superblock model that balances the socio-ecological infrastructure with density, culture, program and context.
M.S. in Architecture, December 2016
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Title: EFFECTS OF ARRAY SCALING ON THE ANGULAR RESOLUTION OF MICROPHONE ARRAY SYSTEMS
Creator: Aldeman, Matt
Date: 2016, 2016-12
Description: Array detection systems have been in use for nearly a century and have proven useful in a variety of applications. The most ubiquitous form of...
Show moreArray detection systems have been in use for nearly a century and have proven useful in a variety of applications. The most ubiquitous form of array is the active radar array, but in the past four decades microphone arrays have become increasingly common. Microphone arrays have traditionally been very large devices. This is because of the limited angular resolution of the traditional Delay-and-Sum (DAS) beamforming algorithm. Improved frequency-domain beamforming (FDBF) methods were developed in the 1980’s using the Fast Fourier Transform. More advanced methods have been developed in the past decade, including deconvolution methods (DAMAS, DAMAS2), methods based on the spatial coherence of point sources and sidelobes in the frequency domain (CLEAN-SC), and spatial coherence methods in the time domain (TIDY). In this investigation two sets of experiments were carried out to better understand the angular resolution characteristics of scaled microphone arrays and associated beamforming algorithms. In the first experiment five scaled microphone arrays with diameters from 0.73m to 10.98m were constructed and tested, and the data was analyzed with a variety of beamforming algorithms. In the second experiment three scaled microphone arrays and one alternative array geometry were tested with both free-field and reflective boundary conditions. The results show that the Rayleigh criterion can be exceeded under certain conditions. However, several other parameters are also important. For example, Signal-to-Noise Ratio (SNR), z-axis correction, and reflective boundaries all impact aspects of the array’s performance. In addition to increasing the array diameter and the signal frequency, results show that effective strategies to improve the angular resolution performance of an array include careful selection of beamforming algorithm, the use of appropriate beamforming integration times, and minimizing boundary reflections. The DAS algorithm is shown to offer the lowest angular resolution performance because it does not separate the acoustic source map from the point spread function of the array. The DAMAS algorithm offers the greatest angular resolution because it numerically deconvolutes the acoustic source map from the point spread function. However, deconvolution-based algorithms are the most negatively affected by the boundary reflection effects commonly seen with larger arrays. This is because the pressure field becomes contaminated with reflections and image sources, and the deconvolution approach does not make use of significant simplifying assumptions as several of the other algorithms do. The logarithmic spiral array is shown to offer versatile performance across a wide range of frequencies, while an alternative quasiperiodic array yields results that are highly frequency-dependent. It is demonstrated that this is because of gaps in the source-to-element differences coverage, and the gaps in coverage correspond to half-wavelengths of frequency bands with significantly lower angular resolution performance.
Ph.D. in Mechanical and Aerospace Engineering, December 2016
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Title: THERMO-RESPONSIVE HYDROGELS FOR INTRAVITREAL INJECTION AND BIOMOLECULE RELEASE
Creator: Drapala, Pawel
Date: 2011-04-20, 2011-05
Description: In this dissertation, we develop an injectable polymer system to enable localized and prolonged release of therapeutic biomolecules for...
Show moreIn this dissertation, we develop an injectable polymer system to enable localized and prolonged release of therapeutic biomolecules for improved treatment of Age-Related Macular Degeneration (AMD). Thermo-responsive hydrogels derived from N-isopropylacrylamide (NIPAAm) and cross-linked with poly(ethylene glycol) (PEG) poly(L-Lactic acid) (PLLA) copolymer were synthesized via free-radical polymerization. These materials were investigated for (a) phase change behavior, (b) in-vitro degradation, (c) capacity for controlled drug delivery, and (d) biocompatibility. The volume-phase transition temperature (VPTT) of the PNIPAAm-co-PEG- b-PLLA hydrogels was adjusted using hydrophilic and hydrophobic moieties so that it is ca. 33 C. These hydrogels did not initially show evidence of degradation at 37 C due to physical cross-links of collapsed PNIPAAm. Only after addition of glutathione chain transfer agents (CTA)s to the precursor did the collapsed hydrogels become fully soluble at at 37 C. CTAs signi cantly a ected the release kinetics of biomolecules; addition of 1.0 mg/mL glutathione to 3 mM cross-linker accelerated hydrogel degradation, resulting in 100 % release in less than 2 days. This work also explored the e ect of PEGylation in order to tether biomolecules to the polymer matrix. It was demonstrated that non-site-speci c PEGylation can postpone the burst release of solutes (up to 10 days in hydrogels with 0.5 mg/mL glutathione). Cell viability assays showed that at least two 20-minute bu er extraction steps were needed to remove cytotoxic elements from the hydrogels. Clinically-used therapeutic biomolecules Lucentis® and Avastin® were demonstrated to be both stable and bioactive after release form PNIPAAm-co-PEG-b-PLLA hydrogels. The thermo-responsive hydrogels presented here o er a promising platform for the localized delivery of proteins such as recombinant antibodies.
Ph.D. in Chemical and Biological Engineering, May 2011
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Title: STRESS DISTRIBUTION IN A WELDED TRUSS CONNECTION
Creator: Lesbekov, Arman
Date: 2011-11-30, 2011-12
Description: Trusses, although geometrically simple, constitute rather complex structures when one considers their true behavior. Even though they are...
Show moreTrusses, although geometrically simple, constitute rather complex structures when one considers their true behavior. Even though they are designed considering pin connections for their joints, in practice joints are neither pinned nor fixed. For this reason, the behavior of a truss at its joints is rather complicated; and to a great extent depends on the method of fabrication used including the weld patterns and the geometry and design of gusset plates used. This study focuses on the behavior of welded truss joints by using a three-dimensional finite element analysis in an effort to provide an insight into how stress patterns are developed at a joint when it is subject to loads from adjoining truss members. The research included a series of simulation analyses on a simple truss joint with welded connections. The typical joint is those that can be found in the lower chords of trusses used in highway bridges. The simulations employed linear finite element analyses utilizing solid elements to model the weld, connecting elements and the gusset plates. Stresses obtained from these analyses were compared with those through conventional methods. At points of stress concentrations, stresses from the finite element (FE) analyses showed stresses can be as high as 5 – 10 orders of magnitude higher than those from conventional methods. The results are presented in the form of graphs showing the ratio of FE-based results to those from conventional methods for several different configurations for weld length.
M.S. in Civil Engineering, December 2011
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Title: AUTOMATED MANIPULATION OF NANOSCALE STRUCTURES VIA AN ATOMIC FORCE MICROSCOPE
Creator: Xu, Kangmin
Date: 2013, 2013-05
Description: As a useful tool for both imaging and modifying nanoscale structures, atomic force microscopes (AFM) have drawn many researchers’ attention,...
Show moreAs a useful tool for both imaging and modifying nanoscale structures, atomic force microscopes (AFM) have drawn many researchers’ attention, but there are still many challenges such as lack of visual feedback during manipulation. In this dissertation, an AFM based nano manipulation system has been developed to modify the nanoscale structures including manipulation of nano particles, carbon nanotubes (CNTs) and indentation of the polymer substrate. These operations have been further assisted by real-time feedback such that AFM can be used to image, sense and manipulate nanoscale objects simultaneously. To address critical issues in AFM based nano manipulation, several methods have been developed to enhance the process of manipulation. In nano particle manipulation, a method called sequential parallel pushing (SPP) is presented for efficient and automated nano particle manipulation. Instead of using tip scanning to fully locate the particle center, this method uses contact loss detection to get the longitudinal position of particle and one scan line perpendicular to the pushing direction to determine the lateral position of the particle center. In nano indentation, computer-aided design (CAD) geometry processing has been integrated with an AFM based nano indentation process which enables the fabrication of complex geometric features. Machining parameters have been investigated and procedure to determine them have been demonstrated. In the localization of deformable nanoscale objects, two localization methods for localizing CNTs and nanowires have been introduced. They can perform accurate positioning and reconstruction of sample shapes while being manipulated. Successive manipulation strategies thus can be developed based on the developed fast localization schemes.
PH.D in Mechanical Engineering, May 2013
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Title: CLONING AND CHARACTERIZATION OF HOTSPOT II EXON EDITED DYSTROPHIN RODS
Creator: Kuruba, Balaganesh
Date: 2014, 2014-05
Description: Duchenne muscular dystrophy, DMD, is an X–link recessive disorder with an incidence of 1 in 3500 male births worldwide. This fatal condition...
Show moreDuchenne muscular dystrophy, DMD, is an X–link recessive disorder with an incidence of 1 in 3500 male births worldwide. This fatal condition has no effective treatment, but due to its high incidence and severity, several strategies are the subject of on-going clinical trials including gene therapy (delivery of replacement genes via viral vector systems) and exon skipping (administration of therapeutic compounds to mask certain exons and so repair the defective gene). Both of these approaches result in the production of modified dystrophin proteins with deletions in the central rod region. It is unknown how such edits will affect protein structure, although it has been shown that the nature of the edit is related to clinical severity. DMD defects are non-randomly distributed along the gene, being clustered in two regions: the so-called hotspot region I (Exons 11 – 22) and the hotspot region II (Exons 45 – 55). We are producing alternative exon skipped proteins in the hotspot II region and are characterizing them with respect to biophysical and biochemical stability by thermal denaturation and proteinase challenge studies in order to determine which of these potential edits are most similar to native, undamaged dystrophin.
M.S. in Cell and Molecular Biology, May 2014
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Title: ACOUSTICALLY FORCED EXTERNAL PULSED COMBUSTION
Creator: Karuppiah, Manikandan
Date: 2011-04-25, 2011-05
Description: Pulsed combustion is one of the most energy-efficient and less polluting ways to produce a hot gas stream for heating purposes. It is usually...
Show morePulsed combustion is one of the most energy-efficient and less polluting ways to produce a hot gas stream for heating purposes. It is usually limited, however, by the need to confine the combustion within a resonant tube. In the experiments presented here, pulsed combustion was achieved in the open air by means of upstream acoustic forcing of a porous matrix burner. Using metal matrices at least 20 mm thick, with pore densities of 60 pores per inch, a stoichiometric mixture of air and natural gas at a constant rate of 217.5 standard cubic feet per hour was forced by a speaker mounted on the plenum upstream of the matrix by means of sinusoidal waves of variable amplitude, at 10 to 150 Hz. Instantaneous surface temperature, as well as pressures upstream and downstream of the matrix were acquired. Phase-locked photographs of the combustion zone were acquired by means of a mechanical stroboscope synchronized to the forcing signal. It was found that, as the forcing amplitude increases, the mode of combustion switches from continuous to oscillating flame, to pulsed combustion consisting of a series of ignitions and extinctions. The change of combustion mode was accompanied by substantial changes in matrix surface temperature, with the pulsed mode reaching temperatures 170°C higher than steady-state combustion and 70% increase in radiant heat flux emitted. This was usually accompanied by a contraction in the size of the hot part of the matrix, resulting in an overall increase in radiant heat output of 5%, for our experiments. Maximum surface temperature was reached for a 35 mm thick matrix, which is hereby recommended for practical radiant heaters using this process. The mechanism hypothesized earlier was nearly proved with pending confirmation from reverse velocity measurements.
M.S. in Mechanical and Aerospace Engineering, May 2011
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Title: ELECTROSTATIC SPRAY DEPOSITION OF SOLID OXIDE FUEL CELL ELECTROLYTE
Creator: He, Quanzhi
Date: 2013-04-30, 2013-05
Description: 8mol% yttria-stabilized zirconia (YSZ) is the most currently used electrolyte material for solid oxide fuel cell (SOFC) due to is chemical and...
Show more8mol% yttria-stabilized zirconia (YSZ) is the most currently used electrolyte material for solid oxide fuel cell (SOFC) due to is chemical and thermal stability and its high oxygen ion conductivity at high temperature. However, SOFC based on YSZ electrolyte operate generally at very high temperatures (900-1000℃) for adequate oxygen conductivity, therefore the selection of materials for other cell components has a lot of problems, such as high materials costs and degradation of performance. To avoid the problem associated with high temperatures, it would be desirable to reduce the operating temperature from 900℃ to intermediate temperatures, typically 600-800℃. But, at these temperature, the ohmic losses due to the low ionic conductivity of the electrolyte become too high for thick (100μm) YSZ electrolyte. Therefore, a thin (less than 10μm) but dense and tight electrolyte is needed. Because the thin film YSZ electrolyte makes the oxygen ions have a shorter conducting path, unit cells have less ohmic resistance at a reduced temperature. To make SOFC working at intermediate temperature, a thin (less than 10μm) but dense and tight electrolyte is needed. This work takes a closer look at electrostatic spraying of ceramic suspensions and the ability of sprayed layer to sinter into dense layer under the 10μm thickness range. In this study, a new ESD deposition system was designed and produced, the relationship between ESD parameters and the deposition results was established, most of all, pore free and complete dense ultra-thin YSZ electrolyte thin film (less than 1μm) was successfully made with ESD technique.
M.S. in MaterialsS ciencea ndE ngineering, May 2013
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Title: Modeling and Control of Boundary Constrained Granular Swarm Robots
Creator: Mulroy, Declan Augustine
Date: 2023
Description: Soft robots offer many advantages that traditional robotic systems do not. Soft robotic systems are able to safely interact with their...
Show moreSoft robots offer many advantages that traditional robotic systems do not. Soft robotic systems are able to safely interact with their environment and tolerate large deformations. This is due to being composed of soft materials, which allows them to be subjected to and experience large deformations. However, they still have limitations in their maneuverability, locomotion, and force exertion. Moreover, they usually require external tethering or other specialized systems, such as pneumatic devices, to function. To address some of these limitations, a novel class of robotic systems has emerged called a boundary-constrained granular swarm robot.A boundary-constrained granular swarm robot is composed of a closed-loop series of active sub-robots, each with the ability to locomote. Each sub-robot is connected to its neighbors with an elastic membrane, which forms a single robot. The membrane encloses a passive granular interior, which provides structure and allows the robot to switch between rigid and soft states via granular jamming phase transitions. This allows for the robotic system to exploit the desirable characteristics of both soft and rigid robots. However, there is limited research with regards to modeling and controlling this system due to its novelty. This thesis addresses this gap by presenting several simulation frameworks, which incorporates multi-body dynamics and non-smooth contact dynamics to model the forward dynamics of the system. These models are able to account for the frictional effects, and the contact forces experienced by the system. The developed models are verified through experimental prototypes to ensure the models are able to capture the general behaviors of the system. Additionally, gradient-based control algorithms are presented and applied to simulated and experimental systems to have each of them form arbitrary shapes, morph between shapes, grasp arbitrarily shaped objects, and navigate narrow corridors. All of these objectives have been accomplished in previous systems, however, this thesis will demonstrate this system is one of the first to be able to accomplish all four. Moreover, it is able to by using a single control framework. In addition, this thesis will present the application distance functions, R-functions, and space-time transfinite interpolation for control purposes. These techniques are commonly utilized in graphics and animation theory, and will be applied to gradient-based controllers. These controllers will be used for boundary constrained granular swarms to form desired shapes and morph between shapes in both 2D and 3D simulated systems and experimental systems. Moreover, this thesis will explore the use of grasping metrics for boundary-constrained granular swarms. The Ferrari Canny metric, a well-established tool for assessing grasp quality in robotic manipulators, is utilized to evaluate the system’s grasp performance. This thesis will also demonstrate the application of this metric for boundary-constrained swarms to find the optimal angle of approach for the system to grasp a target object.
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Title: Effects of Microstructure Engineering on Laser Powder Bed Fusion Processed Superalloy IN718 through Inoculant Addition
Creator: Ho, I-Ting
Date: 2023
Description: Additive manufacturing (AM) techniques can now be utilized as innovative tools that provide unlimited design flexibility for the fabrication...
Show moreAdditive manufacturing (AM) techniques can now be utilized as innovative tools that provide unlimited design flexibility for the fabrication of geometrically complex metallic structures. For production of Ni-base superalloy components used in advanced gas turbine engines, laser powder bed fusion (L-PBF), which is one of the AM techniques, is frequently used as it allows good metallurgical bonding of powder feedstock and simultaneously enables development of ultra-efficient power systems for aerospace propulsion, space exploration and power generation. One of the major challenges associated with additively manufactured Ni-base superalloy components is that the extreme temperature gradients encountered during processing negatively impact the underlying microstructure and mechanical properties of the material. Although the macroscopic shape and chemistry of the additively fabricated part may be identical to the conventionally manufactured part, the resulting properties are usually compromised. In an effort to make Ni-base superalloys more amenable for processing via additive manufacturing, varying levels of benign inoculants that promote may heterogeneously grain nucleation were blended into Inconel 718 (IN718) powder feedstock and used for processing via L-PBF to characterize the microstructural evolution. In the first study, 0.2 wt. % of micron-sized CoAl2O4 flakes was found to effectively change the grain morphology during the L-PBF process leading to significant reduction in crystallographic texture and thus resulting elastic anisotropy. Dispersion of nano-oxides resulting from the reduction of CoAl2O4 particles also contributed to improved tensile strength and steady creep strain rate. It should be noted, however, that, the multiple iterations of remelting as the result of deposition of new layers dissolved the Co-rich particles reduced from CoAl2O4 inoculants. Instead of having nucleation events contributed by elemental Co, the oxide agglomerates as a result of Marangoni convection seemed to be the major contribution to facilitating grain refinement by inhibiting the heat transfer in the surroundings. On the other hand, addition CoAl2O4 particles appeared to generally reduce the melt pool width while increase the melt pool depth by inhibiting the degree of heat transfer and Marangoni flow. The changes in melt pool dimension aided in improving the relative density and surface roughness of the bulk samples by generating better metallurgical bonding to the subsequent layers. As the trade-off, however, the changes in melt pool physics also enhanced the tendency for epitaxial growth and hence retarded the columnar-to-equiaxed transition unless oxide agglomerates are present. In addition to CoAl2O4, candidates including Co, TaCr2, TiB2, and CeO2 particles were also considered to be blended with the powder feedstock of IN718. After the L-PBF process, different degree of microstructural evolution was characterized with the addition of Co, TaCr2, TiB2, or CeO2 particles. It was found that the physical presence of inoculants may change the melt pool geometries that accounted for a comparatively more columnar-grained structure with <101> texture in samples containing Co and TaCr2 particles while a relatively equiaxed-grained structure with <001> texture in samples containing TiB2. The comparison between samples containing TiB2 and CeO2 further indicates that the phase transformation induced agglomeration will also reduce the effectiveness of inoculants due to decreasing nuclei density. Findings from this investigation demonstrate the resulting grain structure upon L-PBF can be profoundly impacted by both chemistry and physical properties of the inoculants. These effects may potentially be harnessed to effectively engineer the microstructure and optimize the properties of L-PBF processed Ni-base superalloys.
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Title: Growth Kinetics of Listeria monocytogenes and Salmonella enterica on Rehydrated Enoki and Wood Ear Mushrooms during Storage
Creator: George, Josephina
Date: 2023
Description: Plant foods, such as fruits and vegetables, that have been dehydrated do not support the growth of pathogenic microorganisms. Recent...
Show morePlant foods, such as fruits and vegetables, that have been dehydrated do not support the growth of pathogenic microorganisms. Recent listeriosis and salmonellosis outbreaks in the U.S. have been associated with imported specialty mushrooms. These mushrooms are commonly sold fresh or dehydrated. This study evaluated the survival and growth of two foodborne pathogens Listeria. monocytogenes and Salmonella. enterica on dehydrated mushrooms during both rehydration at 25 or 5℃ and storage at 5, 10, or 25℃. Fresh enoki and wood ear mushrooms were dehydrated for 24 h at 60°C. Dehydrated mushrooms were inoculated with a four-strain cocktail of S. enterica or L. monocytogenes at 4 log CFU/g. Mushrooms were dried for 1 h, followed by rehydration for 2 h with 5 or 25°C (water and air temperature). Rehydrated mushrooms were stored at 5, 10, or 25°C for up to 14 d. The pathogens were enumerated at 0, 1, 3, 6, 9 and 14 d. Three independent trials with triplicate samples at each time point were completed. Population differences were evaluated via Student’s t-test; p<0.05 was considered significant. The growth rates were determined by DMFit in Excel. Overall, the growth rates of L. monocytogenes and S. enterica on enoki mushrooms were significantly higher when the mushrooms were rehydrated at 25℃ and stored at 25℃ (P<0.05). The growth rates were 2.69 log CFU/g per day and 3.56 log CFU/g per day, for L. monocytogenes and S. enterica respectively. Since the growth of pathogens on wood ear mushrooms during rehydration and storage was considerably less and below the level of enumeration, enrichment of the pathogens was conducted. The pathogens could be suppressed during rehydration due to less nutrient contents and antimicrobial properties of wood ear. The result of this study outlines the importance of refrigerated storage temperature and time combination for safety during rehydration and subsequent storage of the mushrooms.
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Title: MACHINE VISION NAVIGATION SYSTEM FOR VISUALLY IMPAIRED PEOPLE
Creator: Yang, Guojun
Date: 2021
Description: Visually impaired people are often challenged in the efficient navigation of complex environments. Moreover, helping them navigate intuitively...
Show moreVisually impaired people are often challenged in the efficient navigation of complex environments. Moreover, helping them navigate intuitively is not a trivial task. Cognitive maps derived from visual cues play a pivotal role in navigation. In this dissertation, we present a sight-to-sound human–machine interface (STS-HMI), a novel machine vision guidance system that enables visually impaired people to navigate with instantaneous and intuitive responses. This proposed system extracts visual context from scenes and converts them into binaural acoustic cues for users to establish cognitive maps. The development of the proposed STS-HMI system encompasses four major components: (i) a machine vision–based indoor localization system that uses augmented reality (AR) markers to locate the user in GPS-denied environments (e.g., indoor); (ii) a feature-based object detection and localization system called the simultaneous localization and mapping (SLAM) algorithm, which tracks the mobility of users when AR markers are not visible; (iii) a path-planning system that creates a course towards a destination while avoiding obstacles; and (iv) an acoustic human–machine interface to navigate users in complex navigation courses. Throughout the research and development of this dissertation, each component is analyzed for optimal performance. The navigation algorithms are used to evaluate the performance of the STS-HMI system in a complicated environment with difficult navigation paths. The experimental results confirm that the STS-HMI system advances the mobility of visually impaired people with minimal effort and high accuracy.
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Title: Fate of Listeria Monocytogenes on Hard-cooked Eggs Treated With Citric Acid
Creator: Zeng, Hui
Date: 2021
Description: Commercially-prepared hard-cooked eggs are available for foodservice and to the public in retail grocers. Potential contamination with...
Show moreCommercially-prepared hard-cooked eggs are available for foodservice and to the public in retail grocers. Potential contamination with Listeria monocytogenes during or after the cooking and peeling steps is of concern since this pathogen can proliferate at refrigeration temperatures. Citric acid is a common preservative used in the food industry to treat hard-boiled eggs (HBEs). The purpose of this project was to evaluate the efficacy of citric acid treatment of HBEs to reduce the population levels of L. monocytogenes during 24 h (treatment trials) and 28 d storage (storage trials) at 5 or 25°C. Fresh eggs were boiled for 12 min, cooled to 4°C, peeled, and stored at 5°C for 24 h prior to experiments. In treatment trials, HBEs were dip inoculated with a 4-strain cocktail of rifampicin-resistant L. monocytogenes resulting in either 4 (low) or 7 (high) log CFU/egg. Eggs were air-dried 10 min, followed by treatment with pH 2.5 citric acid (PHCA) or 0.2 M citric acid (calculated as the molarity resulting in pH 2.5: MCA) at 5 or 25°C for 24 h. In treatment-storage trials, citric acid treatment of HBEs occurred before or after inoculation, followed by 28-d storage at 5 or 25°C. L. monocytogenes populations were enumerated by homogenization of eggs with BLEB and cultivation on BHI/rifampicin agar. Enrichment in BLEB was conducted if the pathogen was below the level of enumeration. Significant differences in the populations of L. monocytogenes due to temperature of the acid treatment (5 or 25°C) or the two citric acids (MCA and PHCA) were determined using Student’s T-test and ANOVA with Tukey’s post-test, p ≤ 0.05. Overall, the largest L. monocytogenes reduction occurred after 6 h treatment of HBEs with PHCA at 25°C (1.59 ± 0.00 log CFU/egg) and after 24 h with MCA at 5°C (1.23 ± 0.54 log CFU/egg) when the pathogen was inoculated at the low and high levels, respectively. In treatment-storage trials, citric acid treatment after HBE contamination resulted in a fewer number of samples where the pathogen was detected compared to when treatment occurred before contamination. Citric acid treatment for 24 h also resulted in a greater number of samples where L. monocytogenes was not detected than the 1 h treatment. The results of this study determined that L. monocytogenes could survive on HBEs treated with citric acid, regardless of treatment or storage temperature and acid concentration (PHCA or MCA).
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Title: ANALYTIC STUDY OF THE CELLULAR FUNCTIONS OF UBL4A
Creator: Zhang, Huaiyuan
Date: 2021
Description: Ubiquitin-like protein 4A (Ubl4A) is a small protein encoded by a “housekeeping” gene that locates on the X chromosome. As a multi-functional...
Show moreUbiquitin-like protein 4A (Ubl4A) is a small protein encoded by a “housekeeping” gene that locates on the X chromosome. As a multi-functional protein, it has roles in a variety of cellular events including anti-tumorigenesis, response to DNA damage, inhibiting the fusion between autophagosome and lysosome, and docking of the tail-anchored proteins to the endoplasmic reticulum. We have previously reported that the newborns from Ubl4A-deficient mice had a high rate of mortality due to defect of AKT-dependent glucose metabolism. At the molecular level, Ubl4A directly binds with the actin related protein (Arp) 2/3 complex to accelerate the building up of the actin branching network, which further promotes the translocation and activation of the Akt, a key kinase for multiple cellular processes, from the cytosol to the plasma membrane.In further exploration of the molecular basis of Ubl4A in cell survival, here, we demonstrated that Ubl4A is critical for mitochondrial fusion and cell survival under nutrient depletion. In WT (wild-type) cells, the association of Ubl4A and the Arp2/3 complex serves as a primed “pool” of the actin branching network near mitochondria and enables mitochondria to fuse quickly for energy conservation upon starvation insult. However, such a “ready-to-go pool” of mitochondria was significantly decreased in the Ubl4A-deficient cells. As the result, the mitochondria became fragmentated, exhibited decreased trans-membrane potential, and accumulated ROS (reactive oxygen species), consequently, initiated mitochondria-mediated apoptosis. In this study, we also observed that Ubl4A-deficient mice displayed type II diabetic phenotype under a high-fat diet feeding. The preliminary results showed that these Ubl4A-deficient mice were more sensitive to glucose intolerance than their WT littermates, most likely owing to a delay in glucose uptake, and/or insulin secretion, both of which require the Arp2/3-actin branching network. We speculated that Ubl4A might be involved in cellular vesicle formation and/or secretion, but further investigation is needed to approve this hypothesis. Taken together, these findings provide a novel function of Ubl4A and further insight into the multi-functional roles of Ubl4A in mammalian cells, as well as the molecular basis for understanding the clinical relevance of Ubl4A in related human diseases.
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Title: Modeling and Control Methods for Boundary Constrained Soft Robots
Creator: Zhou, Qiyuan
Date: 2021
Description: Soft and deformable robots have been an active field of research in the past few years. However, they are limited in that they cannot apply...
Show moreSoft and deformable robots have been an active field of research in the past few years. However, they are limited in that they cannot apply much force to an environment due to the limitations of the flexible materials from which they are made of. To help overcome this limitation, a new architecture named the Jamming and Morphing Enabled Bot Array (JAMoEBA) system was conceived. This system consists of a flexible outer membrane which encloses an interior composed of a granular medium. Active sub-units along the flexible outer membrane allow for actuation and locomotion of the system. The granular material coupled with the flexible outer membrane allows the robot to maintain the characteristics typically associated with soft robots (continuum, compliant, configurable). At the same time, the granular material is also able to undergo a solid phase transition with the application of pressure to the flexible outer membrane and allow the system to behave more like a rigid robot if needed. This allows for the robot system to exploit the desirable characteristics of both soft and rigid robots in its tasks.The purpose of this thesis is to offer a discussion and demonstration of various simulation methods for the physically accurate modeling of the JAMoEBA constrained boundary robotic system and to show some of the control methods which have been investigated within the selected modeling framework. Simulation methods based on Lennard-Jones (L-J) potentials, non-smooth contact dynamics (NSCD), as well as the discrete element methods based on complementarity (DEM-C) and penalty (DEM-P) conditions as implemented in the open source physics library Project Chrono are considered. Comparisons are made in the areas of physical accuracy, computational efficiency, and feature availability in the consideration of the best simulation method for the JAMoEBA system. Investigations of control strategies such as leader-follower and heuristics based approaches are carried out using the selected simulation method. Finally, a framework for self contained localization which relies on measurements from onboard sensors and linear Kalman filtering is tested within the simulation framework, and the effectiveness of approximating the shape of the JAMoEBA system using elliptical Fourier descriptors is shown.The main contributions made in this thesis are in the areas of suitable modeling methods, controls strategies, and localization techniques for the novel boundary constrained JAMoEBA soft robot architecture. The work done serves as a solid foundation for the future study of this novel soft robotic architecture due to the demonstration of successful methods for modeling, control, and localization of the system. The work presented is not meant to be a comprehensive or deep dive into any one specific area, but rather a jumping off point for future areas of research.
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Title: BLOCKCHAIN FOR TRANSACTIVE ENERGY MARKET WITH NETWORKED MICROGRIDS
Creator: Yan, Mingyu
Date: 2021
Description: Transactive energy, which allows and incentivizes microgrids (MGs) to trade energy with each other, is regarded as the next-generation energy...
Show moreTransactive energy, which allows and incentivizes microgrids (MGs) to trade energy with each other, is regarded as the next-generation energy management scheme to accommodate the penetration of distributed energy resources (DERs). Blockchain provides an effective and decentralized strategy, which can address the operational challenges introduced by the transactive energy market. This thesis is aimed at providing effective transactive energy markets for incentivizing MGs to trade energy and utilizing blockchain technologies to provide a secure and efficient energy trading environment for all participants.First, this thesis offers a centralized transactive market for networked MGs to transact energy through the centralized distribution system operator (DSO) while ensuring the power network limits. All MGs cooperate in this market and the cooperative behaviors are captured using the cooperative game with externalities. A two-level problem is studied to allocate the total payoff to all participating MGs. Numerical results for a 4-MG system and the IEEE 33-bus show the validity of the centralized transactive energy model. Second, this thesis proposes a two-level network-constrained peer-to-peer (P2P) transactive energy for multi-MGs, which guarantees the distribution power network security and allows MGs to trade energy with each other flexibly. At the lower level, a P2P transactive energy is employed for multi-MGs to trade energy with each other. A multi-leader multi-follower (MLMF) Stackelberg game approach is utilized to model the energy trading process among MGs. At the upper level, the DSO reconfigures the distribution network based on the P2P transactive energy trading results by applying the AC optimal power flow considering the distribution network reconfiguration. If there are any network violations, the DSO requests energy trading adjustments at the lower level for network security. Numerical results for a 4-MG system, the modified IEEE 33-bus, and the 123-bus distribution power systems show the effectiveness of the proposed transactive energy model and its solution technique. Third, this thesis adopts the blockchain for the peer-to-peer transactive energy market among MGs. A two-level integrated blockchain-power system is provided, in which all MGs and the DSO are equipped with blockchain. At the lower level, MGs trade energy with each other through the lower-level MG blockchain, while the DSO manages the network security through the upper level DSO blockchain. We illustrate how to utilize blockchain technologies, i.e., public and private keys and smart contracts, to provide an efficient and secure energy trading environment for all MGs. Last, this thesis applies the blockchain for transacting energy and carbon right for networked MGs. MGs transact energy and carbon right through the centralized DSO while ensuring the power network limits. The introduction of blockchain achieves secure and decentralized market settlements in this centralized market. Numerical results for a 4-MG system and modified IEEE 33-bus systems show the effectiveness of the proposed transactive energy and carbon market.
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Title: Quantifying Localization Safety for State-of-the-Art Mobile Robot Estimation Algorithms
Creator: Abdul Hafez, Osama Mutie Fahad
Date: 2023
Description: In mobile robotics, localization safety is quantified using covariance matrix or particle spread.However, such methods are insufficient for...
Show moreIn mobile robotics, localization safety is quantified using covariance matrix or particle spread.However, such methods are insufficient for mission or life-critical applications, like Autonomous Vehicles (AVs), because they only reflect nominal sensor noise without considering sensor measurement faults. Sensor faults are unknown deterministic errors that cannot be modeled using a zero mean Gaussian distribution. Ignoring sensor faults, in such applications, might result in large localization errors, which in turn deceives other reliant systems, like the controller, leading to catastrophic consequences, such as traffic accidents for AVs. Thus, other techniques need to be used to conservatively quantify pose safety.This thesis builds upon previous research in aviation safety, or what is referred to as \textit{integrity monitoring}, to quantify localization safety for mobile robots that use state-of-the-art state estimators (as localizers).Specifically, this thesis utilizes the localization \textit{integrity risk} metric, as a measure of localization safety, which is defined as the probability of the robot's pose estimate error to lie outside pre-determined acceptable limits while an alarm is not triggered. Unlike open-sky aviation applications, where Global Navigation Satellite Systems (GNSS) signals are available, mobile robots operate in GNSS-denied, or in the best case GNSS-degraded, environments, which demands utilizing more complex set of sensors to guarantee an acceptable level of localization safety. This thesis provides a conservative measure of localization safety by rigorously upper-bounding the integrity risk while accounting for both nominal lidar noise and unmodeled lidar measurement faults.The contributions of this thesis include the design and analysis of practical integrity monitoring and failure detection procedures for mobile robots utilizing map-based particle filtering, a recursive integrity monitoring method for mobile robots utilizing map-based fixed lag smoothing for both solution-separation and chi-squared as failure detectors, the synthesis of an integrity monitoring procedure for mobile robots utilizing Extended Kalman Filter-based Simultaneous Localization And Mapping (EKF-based SLAM), and a Model Predictive Control (MPC) framework that is capable of planning mobile robot's trajectory to follow a predefined robot path while maintaining a predefined minimum level of mobile robot localization safety. The proposed methodologies are validated using both simulation and experimental results conducted in real-world urban university campus environments.
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Title: Efficacy of Power Ultrasound Technology on the Reduction of Listeria monocytogenes and Salmonella enterica on Produce Matrices
Creator: Biswas, Priya
Date: 2023
Description: Fresh produces are considered as ready-to-eat (RTE) and are minimally processed before the distribution to retailers and consumers. Fresh...
Show moreFresh produces are considered as ready-to-eat (RTE) and are minimally processed before the distribution to retailers and consumers. Fresh produce recalls are frequently linked with pathogenic bacteria like Salmonella enterica and Listeria monocytogenes because of minimal processing. This study evaluated the use of power ultrasound coupled with organic acids like citric, acetic, and lactic acid which are generally recognized as safe and often helps to maintain the quality and prolong the shelf life of fresh RTE fruits and vegetables.All the produce matrices which include cucumbers, romaine lettuce, tomatoes, and strawberry were inoculated with four-strain cocktails of rifampicin-resistant S. enterica or L. monocytogenes at approximately 8 log CFU/ matrix. The produce matrices were dried for 1 h and treated for 2 minutes using 2 % or 5 % citric, lactic, or malic acid. This treatment was conducted with or without power ultrasound treatment at 40 kHz. Samples were taken in sets of three and placed into a stomacher bags. The bag contained 225 ml of water or acid. Following a 2 min treatment period, the samples were placed in separate stomacher bags, each containing 225ml of BPB or BLEB, for S. enterica or L. monocytogenes respectively. Followed serial dilutions, samples were then plated on BHIARif plates. For each condition, triplicate samples were taken, and three separate trials were conducted. The use of Student's t-test allowed for the evaluation of population differences, with a significance level of p<0.05 being deemed significant. Cucumber, romaine lettuce, tomatoes, and strawberries treated with 5 % concentration of citric, lactic, and malic acids, with addition of ultrasound showed a greater result in reductions of S. enterica to populations of 5.54 ± 0.47, 4.54 ± 0.83, and 4.69 ± x 0.36, log CFU/cucumber, 6.66 ± 0.51, 4.12 ± 0.32, and 5.51 ± 0.68, log CFU/ lettuce, 4.38 ± 0. 47, 3.12, and 5.04 ± 0.37 log CFU/ tomato, 4.66 ± 0.49, 4.69 ± 0.06, and 6.22 ± 0.39, log CFU/ strawberries, respectively. For L. monocytogenes, 5 % concentration of acids with the addition of ultrasound resulted in populations of 7.69 ± 0.35, 6.04 ± 0.24, and 6.96 ± 0.41, log CFU/ cucumbers, 7.57 ± 0.12, 5.49 ± 0.55, and 5.78 ± 0.73 log CFU/ lettuce, 6.44 ± 0.13, 5.08 ± 0.12, and 6.04 ± 0.22 log CFU/ tomato, 6.16 ± 0.37, 5.18 ± 0.22, and 5.64 ± 0.50, log CFU/ strawberries, respectively. The most effective acid was lactic when compared with citric and malic acids. The objective of this study is to investigate the effectiveness of power ultrasound as a novel non-thermal processing technology, in order to contribute to the existing knowledge base on this topic.
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Title: Structural Condition Assessment for Wind Turbine Towers
Creator: Zahraee, Afshin
Date: 2019
Description: Wind-based energy generation has special priority in efforts related to global sustainability. Based on this priority and the desire for...
Show moreWind-based energy generation has special priority in efforts related to global sustainability. Based on this priority and the desire for increase in electricity generation, the size of wind turbines has been tremendously increased in recent years. Moreover, larger wind turbines have access to more stable wind speeds which assists in electricity generation consistency. However, larger wind turbines are more prone to exhibit structural failure due to the increase of size as well as presence of complexities in the structure and wind load interaction. As such, condition monitoring and fault diagnosis of wind turbines are crucial in their sustainable operation. In this work, a new framework for condition assessment of wind turbine towers is developed. This framework enhances the ability to assess the structural condition of in-service wind turbine towers. Using this framework: 1) the wind data for the wind turbine location is collected, 2) a series of numerical modeling and analysis for the wind turbine tower for various wind velocities are performed to obtain the maximum induced stresses and their corresponding critical fatigue components (hot spots), and 3) fatigue analysis is performed leading to prediction for the remaining life of the wind turbine tower. To illustrate the capability of the present method, a case study is performed on an existing wind turbine. The obtained analytical results are compared and verified by the original design parameters. The results obtained for life prediction of the wind turbine tower correlate with life predictions of other existing wind turbine towers. It is anticipated that application of this framework for existing and future wind turbines will enhance their inspection planning as well as offer a more cost-effective process for repair and rehabilitation of wind turbine towers. This will ultimately increase the overall safety of wind turbine systems and enhance their reliability of performance.Keywords: Wind Turbine Tower, Condition Assessment, Life Prediction.
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