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Description
This dissertation studies the methods to enhance the performance of foldable robots manufactured by laminated techniques. This class of robots are unique in their manufacturing process, which involves cutting and staking up thin layers of different materials with various stiffness. While inheriting the advantages of soft robots -- low weight, affordable manufacturing cost and a fast prototyping process -- a wider range of actuators is available to these mechanisms, while modeling their behavior requires less computational cost.The fundamental question this dissertation strives to answer is how to decode and leverage the effect of material stiffness in these robots. These robots' stiffness is relatively limited due to their slender design, specifically at larger scales. While compliant robots may have inherent advantages such as being safer to work around, this low rigidity makes modeling more complex. This complexity is mostly contained in material deformation since the conventional actuators such as servo motors can be easily leveraged in these robots. As a result, when introduced to real-world environments, efficient modeling and control of these robots are more achievable than conventional soft robots.
Various approaches have been taken to design, model, and control a variety of laminate robot platforms by investigating the effect of material deformation in prototypes while they interact with their working environments. The results obtained show that data-driven approaches such as experimental identification and machine learning techniques are more reliable in modeling and control of these mechanisms. Also, machine learning techniques for training robots in non-ideal experimental setups that encounter the uncertainties of real-world environments can be leveraged to find effective gaits with high performance. Our studies on the effect of stiffness of thin, curved sheets of materials has evolved into introducing a new class of soft elements which we call Soft, Curved, Reconfigurable, Anisotropic Mechanisms (SCRAMs). Like bio-mechanical systems, SCRAMs are capable of re-configuring the stiffness of curved surfaces to enhance their performance and adaptability. Finally, the findings of this thesis show promising opportunities for foldable robots to become an alternative for conventional soft robots since they still offer similar advantages in a fraction of computational expense.
ContributorsSharifzadeh, Mohammad (Author) / Aukes, Daniel (Thesis advisor) / Sugar, Thomas (Committee member) / Zhang, Wenlong (Committee member) / Arizona State University (Publisher)
Created2021
Description
Corrosion is one of the key failure modes for stainless steel (SS) piping assets handling water resources managed by utility companies. During downtime, the costs start to incur as the field engineer procures its replacement parts. The parts may or may not be in stock depending on how old, complex, and common the part model is. As a result, water utility companies and its resilience to operate amid part failure are a strong function of the supply chain for replacement piping. Metal additive manufacturing (AM) has been widely recognized for its ability to (a) deliver small production scales, (b) address complex part geometries, (c) offer large elemental metal and alloy selections, (d) provide superior material properties. The key motive is to harvest the short lead time of metal AM to explore its use for replacement parts for legacy piping assets in utility-scale water management facilities. In this paper, the goal was to demonstrate 3D printing of stainless steel (SS) 316L parts using selective laser melting (SLM) technology. The corrosion resistance of 3D printed SS 316L was investigated using (a) Chronoamperometry (b) Cyclic Potentiodynamic Polarization (CPP) and Electrochemical Impedance Spectroscopy (EIS) and its improved resistance from wrought (conventional) part was also studied. Then the weldability of 3D printed SS 316L to wrought SS 316L was illustrated and finally, the mechanical strength of the weld and the effect of corrosion on weld strength was investigated using uniaxial tensile testing. The results show that 3D printed part compared to the wrought part has a) lower mass loss before and after corrosion, (b) higher pitting potential, and (c) higher charge transfer resistance. The tensile testing of welded dog bone specimens indicates that the 3D printed parts despite being less ductile were observed to have higher weld strength compared to the wrought part. On this basis, metal AM holds great value to be explored further for replacement piping parts owing to their better corrosion resistance and mechanical performance.
ContributorsSampath, Venkata Krishnan (Author) / Azeredo, Bruno (Thesis advisor) / Torres, Cesar (Committee member) / Mu, Bin (Committee member) / Arizona State University (Publisher)
Created2021
Description
Image segmentation is an important and challenging area of research in computer vision with various applications in medical imaging. Image segmentation refers to the process of partitioning an image into meaningful parts having similar attributes. Traditional manual segmentation approaches rely on human expertise to outline object boundaries in images which is a tedious and expensive process. In recent years, Deep Convolutional Neural Networks have demonstrated excellent performance in tasks such as detection, localization, recognition and segmentation of objects. However, these models require a large set of labeled training data which is difficult to obtain for medical images. To solve this problem, interactive segmentation techniques can be used to serve as a trade-off between fully automated and manual approaches. This allows a human expert in the loop as a form of guidance and refinement together with deep neural networks. This thesis proposes an interactive training strategy for segmentation, where a robot-user is utilized during training to mimic an actual annotator and provide corrections to the predicted masks by drawing scribbles. These scribbles are then used as supervisory signals and fed to the network; which interactively refines the segmentation map through several iterations of training. Further, the conducted experiments using various heuristic click strategies demonstrate that user interaction in the form of curves inside the organ of interest achieve optimal editing performance. Moreover, by using the popular image segmentation architectures based on U-Net as base models, segmentation performance is further improved; signifying that the accuracy gain of the interactive correction conform to the accuracy of the initial segmentation map.
ContributorsGoyal, Diksha (Author) / Liang, Jianming Dr. (Thesis advisor) / Wang, Yalin Dr. (Committee member) / Demakethepalli Venkateswara, Hemanth Kumar Dr. (Committee member) / Arizona State University (Publisher)
Created2021
Description
Granular materials demonstrate complexity in many physical attributes with various shapes and sizes, varying from several centimeters down to less than a few microns. Some materials are highly cohesive, while others are free-flowing. Despite such complexity in their physical properties, they are extremely important in industries dealing with bulk materials. Through this research, the factors affecting flowability of particulate solids and their interaction with projectiles were explored. In Part I, a novel set of characterization tools to relate various granular material properties to their flow behavior in confined and unconfined environments was investigated. Through this work, a thorough characterization study to examine the effects of particle size, particle size distribution, and moisture on bulk powder flowability were proposed. Additionally, a mathematical model to predict the flow function coefficient (FFC) was developed, based on the surface mean diameter and moisture level, which can serve as a flowability descriptor.
Part II of this research focuses on the impact dynamics of low velocity projectiles on granular media. Interaction of granular media with external foreign bodies occurs in everyday events like a human footprint on the beach. Several studies involving numerical and experimental methods have focused on the study of impact dynamics in both dry and wet granular media. However, most of the studies involving impact dynamics considered spherical projectiles under different conditions, while practical models should involve more complex, realistic shapes. Different impacting geometries with conserved density, volume, and velocity on a granular bed may experience contrasting drag forces upon penetration. This is due to the difference in the surface areas coming into contact with the granular media. In this study, a set of non-spherical geometries comprising cuboids, cylinders, hexagonal prisms and triangular prisms with constant density, volume, and impact velocities, were released onto a loosely packed, non-cohesive, dry granular bed. From these experimental results, a model to determine the penetration depth of projectiles upon impact was developed and how it is influenced by the release height and surface area of the projectiles in contact with the granular media was studied.
ContributorsVajrala, Spandana (Author) / Emady, Heather N (Thesis advisor) / Marvi, Hamidreza (Committee member) / Jiao, Yang (Committee member) / Arizona State University (Publisher)
Created2021
Description
This research focuses mainly on employing tunable materials to achieve dynamic radiative properties for spacecraft and building thermal management. A secondary objective is to investigate tunable materials for optical propulsion applications. The primary material investigated is vanadium dioxide (VO2), which is a thermochromic material with an insulator-to-metal phase transition. VO2 typically undergoes a dramatic shift in optical properties at T = 341 K, which can be reduced through a variety of techniques to a temperature more suitable for thermal control applications. A VO2-based Fabry-Perot variable emitter is designed, fabricated, characterized, and experimentally demonstrated. The designed emitter has high emissivity when the radiating surface temperature is above 345 K and low emissivity when the temperature is less than 341 K. A uniaxial transfer matrix method and Bruggeman effective medium theory are both introduced to model the anisotropic properties of the VO2 to facilitate the design of multilayer VO2-based devices. A new furnace oxidation process is developed for fabricating high quality VO2 and the resulting thin films undergo comprehensive material and optical characterizations. The corresponding measurement platform is developed to measure the temperature-dependent transmittance and reflectance of the fabricated Fabry-Perot samples. The variable heat rejection of the fabricated samples is demonstrated via bell jar and cryothermal vacuum calorimetry measurements. Thermal modeling of a spacecraft equipped with variable emittance radiators is also conducted to elucidate the requirements and the impact for thermochromic variable emittance technology.
The potential of VO2 to be used as an optical force modulating device is also investigated for spacecraft micropropulsion. The preliminary design considers a Fabry-Perot cavity with an anti-reflection coating which switches between an absorptive “off” state (for insulating VO2) and a reflective “on” state (for metallic VO2), thereby modulating the incident solar radiation pressure. The visible and near-infrared optical properties of the fabricated vanadium dioxide are examined to determine if there is a sufficient optical property shift in those regimes for a tunable device.
The potential of VO2 to be used as an optical force modulating device is also investigated for spacecraft micropropulsion. The preliminary design considers a Fabry-Perot cavity with an anti-reflection coating which switches between an absorptive “off” state (for insulating VO2) and a reflective “on” state (for metallic VO2), thereby modulating the incident solar radiation pressure. The visible and near-infrared optical properties of the fabricated vanadium dioxide are examined to determine if there is a sufficient optical property shift in those regimes for a tunable device.
ContributorsTaylor, Sydney June (Author) / Wang, Liping (Thesis advisor) / Wells, Valana (Committee member) / Yu, Hongbin (Committee member) / Wang, Robert (Committee member) / Thangavelautham, Jekanthan (Committee member) / Massina, Christopher J (Committee member) / Arizona State University (Publisher)
Created2020
Description
Vinegar is gaining popularity as a natural and proven treatment for common diseases and conditions ranging from high blood pressure to diabetes. While the evidence to support the benefits of vinegar is growing, few studies have considered possible negative consequences. One concern relates to the effect of vinegar on saliva pH and dental erosion. The aim of this study is to explore this relationship as well as unsubstantiated claims that vinegar, although acidic, has an alkalizing effect on the overall body, specifically looking at its effect on resting saliva pH. Healthy adults aged 18-45 were recruited for this trial. Twenty-two participants completed this eight-week, parallel-arm, randomized, double blinded study that looked at the effect that regular consumption of red wine vinegar (two tablespoons taken two times per day before a meal) had on resting salivary pH and dental erosion compared to a control (low dosage vinegar pill taken two times a day before a meal). Resting saliva pH was measured at home using the pH20H application and pH strips at week 0 and 8 of the trial. Erosion was noted using the Basic Erosive Wear Examination (BEWE) by a registered dental hygienist at week 1 and 8 of trial. Results indicate no mean difference in resting salivary pH in either treatment group after eight weeks (p value, 0.49). However, there was a statistical significant mean difference in dental erosion between the VIN and CON group (p value, 0.05). Statistical significance in dental erosion, typically a gradual process, in just eight weeks is a significant finding and warrants concern about long time use of vinegar and dental health. Further exploration into this relationship is needed.
ContributorsAnderson, Summer Lynn (Author) / Johnston, Carol (Thesis advisor) / Whisner, Corrie (Committee member) / Alexon, Christy (Committee member) / Arizona State University (Publisher)
Created2019
Description
Background: Research has found that nearly a quarter of the American population follows a gluten-free diet in some capacity, while only about 1% of the population is diagnosed with celiac disease. Although the amount of research-based evidence supporting any health benefits of a gluten-free diet in an individual without a gluten- related disorder is limited, the number of people claiming to follow a gluten-free diet continues to rise. Also, despite an increasing belief that gluten is harmful for health, the potentially undesirable effects of gluten substitutions used in gluten-free foods are largely unknown. Due to the protein network encapsulating starch granules, gluten is thought to lengthen the amount of time needed during starch digestion, thereby reducing postprandial glycemia. Therefore, it is predicted that breads containing gluten will produce a lower glycemic response compared to gluten-free breads. Aim: The aim of this study was to investigate the glycemic response of gluten-free bread made with different types of flour compared to bread made with gluten-containing wheat flour. Methods: This study involved a 3-week, randomized, single blind crossover study in which 17 healthy individuals were asked to consume a different type of bread each week, 2 of which were gluten-free. Blood glucose was taken by finger prick at fasting as a baseline measurement, then for 2 hours after bread consumption in 30-minute increments. Results: Across the three groups, there was no significant difference in iAUC values after 120 minutes (p=0.192 ). The greatest mean was seen in the gluten-containing bread (145.3 ± 82.6), then the gluten-free bread made with rice flour (125.5 ± 62.8), and lastly the gluten-free bread made with potato and fava bean flour (112.4 ± 64.5). Conclusion: The inconsistent results of this study compared to previous, similar studies suggests that the postprandial glycemic response of gluten-free products can not be generalized as a whole, but instead is dependent on the type of product and the ingredients used to replace the gluten. Although the results did not show a significant difference, it does argue against the belief that gluten-free products are invariably better for health in the general, non-gluten sensitive population.
ContributorsWaznik, Lauren LaRue (Author) / Johnston, Carol (Thesis advisor) / Mayol-Kreiser, Sandra (Committee member) / Dixon, Kathleen (Committee member) / Arizona State University (Publisher)
Created2019
Description
Food insecurity and childhood obesity are both major public health concerns in the United States of America. Research has not found a definite relationship between childhood obesity and food insecurity to date, with conflicting results being found due to differences in sample sizes and protocol for measuring key variables. Preschoolers (children aged 2-5 years) are a population of particular interest as there tends to be improved health behaviors and greater adaptability to change at this period of growth and development. This study aims to evaluate if there is a relationship between food insecurity and childhood obesity with diet quality as a mediator among preschoolers in the Phoenix area. A secondary data analysis from participants (n=154) from the SAGE (Sustainability via Active Garden Education) research project was used to evaluate food insecurity status, diet quality components (kcal, saturated fat, added sugars, and servings of juice, fruits, and vegetables), and anthropometrics (waist circumference and BMI percentile). No significant associations between food insecurity status, diet quality components, and anthropometric data were found. There was an increased rate of food insecurity and childhood overweight/obesity in this sample compared to state and national averages. Further research of high quality is necessary to determine whether a relationship exists between childhood obesity and food insecurity exists and in what context. Additionally, practice and policy will need to be implemented to decrease rates of food insecurity and childhood obesity among Phoenix preschoolers.
ContributorsGutierrez, Marisa (Author) / Bruening, Meg (Thesis advisor) / Whisner, Corrie (Committee member) / Lee, Rebecca E (Committee member) / Arizona State University (Publisher)
Created2020
Description
Historically, researchers in the gut microbiome have deemed the composition of the microbiome as being adult by the age of two. However, recent studies have contradicted this, demonstrating statistically significant differences in the microbiome even through childhood and adolescence. This difference is important in the field of microbiome research, particularly in studies examining this relationship with weight, because even though there have been significant associations between the gut microbiome and weight, they have been largely studied in adults. The freshman year of college is an interesting time to study this relationship in younger populations, due to the lifestyle changes that make them vulnerable to weight gain. This study included N=139 participants, a majority female (N=97, 69.8%), white (N=59, 42.4%), and non-Hispanic (N=89, 64%). Participants were only included in this analysis if they gave 2 or more fecal samples over the 4 timepoint study. Samples were sequenced using the Illumina MiSeq instrument after polymerase chain reaction (PCR) amplification was performed on the V4 region of the 16S rRNA gene sequence. Statistical analysis was performed using the longitudinal plugin of QIIME2. Results demonstrate that low abundance features seemed to drive a majority of the differences in variability between those who maintained their weight over the course of the study and those who gained weight. This was demonstrated through many significant Unweighted UniFrac results with corresponding nonsignificant Weighted UniFrac data. This study demonstrated that changes in lower abundance features may have driven the significant differences in weight status in this study. This study emphasized the importance of low abundance features and how this relates to changes in weight status during a period of major lifestyle changes. Further work is needed to confirm these findings and explore how gut microbes change in free-living individuals gaining weight over time.
ContributorsAhern, Mary (Author) / Whisner, Corrie (Thesis advisor) / Bruening, Meg (Committee member) / Sears, Dorothy (Committee member) / Arizona State University (Publisher)
Created2021
Description
The first task faced by many teams endeavoring to solve complex scientific problems is to seek funding for their research venture. Often, this necessitates forming new, geographically dispersed teams of researchers from multiple disciplines. While the team science and organizational management fields have studied project teams extensively, nascent teams are underrepresented in the literature. Nonetheless, understanding proposal team dynamics is important because if left unaddressed, obstacles may persist beyond the funding decision and undermine the possibility of team successes adjunctive to funding. Participant observation of more than 100 multi-investigator proposal teams and semi-structured interviews with six leaders of multidisciplinary proposal teams identified investigator motivations for collaboration, obstacles to collaboration, and indicators of proposal team success. The motivations ranged from technical interests in the research question to a desire to have impact beyond oneself. The obstacles included inconsistent or non-existent communication protocols, unclear processes for producing and reviewing documents, ad hoc file and citation management systems, short and stressful time horizons, ambiguous decision-making procedures, and uncertainty in establishing a shared vision. While funding outcome was the most objective indicator of a proposal team’s success, other success indicators emerged, including whether the needs of the team member(s) had been met and the willingness of team members to continue collaborating. This multi-dimensional definition of success makes it possible for teams to simultaneously be considered successes and failures. As a framework to analyze and overcome obstacles, this work turned to the United States military’s command and control (C2) approach, which relies on specifying the following elements to increase an organization’s agility: patterns of interaction, distribution of information, and allocation of decision rights. To address disciplinary differences and varied motivations for collaboration, this work added a fourth element: shared meaning-making. The broader impact of this work is that by implementing a C2 framework to uncover and address obstacles, the proposal experience—from team creation, to idea generation, to document creation, to final submittal—becomes more rewarding for faculty, leading to greater job satisfaction. This in turn will change how university research enterprises create, organize, and share knowledge to solve complex problems in the post-industrial information age.
ContributorsPassantino, Laurel (Author) / Seager, Thomas P (Thesis advisor) / Cantwell, Elizabeth R (Committee member) / Johnston, Erik (Committee member) / Arizona State University (Publisher)
Created2021