• Western State FFA State Officer Selection Process: A Case Study Analysis

      Rice, Amber; Troub, Joshua; Molina, Quintin; Torres, Robert (The University of Arizona., 2020)
      Leadership selection within Western State FFA was qualitatively researched through individual interviews and focus groups with state FFA nominating committees from 2017, 2018, and 2019. A document analysis of nominating committee documents was also completed. The main question addressed was how do Western State FFA nominating committees determine quality youth leadership? Secondary research questions included: (1) What attributes do Western State FFA nominating committees’ value for quality youth leadership? and (2) How do Western State FFA nominating committees determine if state officer candidates possess these attributes? The information gleaned from this study may potentially be used by future nominating committees, leaders, and state FFA staff to inform decisions related to the leadership selection of state officers. The findings from the document analysis, interviews, and focus groups were divided into the three following categories: Nominating Committees’ Overarching Priorities for Candidate Selection, Objectivity and Subjectivity of the Nominating Committee Process, and Nominating Committees’ Skepticism towards the Selection Process. The attributes sought by the nominating committees under study did not always align with the attributes listed in state officer selection documents and loosely matched current youth leadership models. Suggestions for changing the current nominating committee process to align with the findings of this study and youth leadership research are therefore also discussed.
    • Focal Volume Characterization of a Laser Scanning System

      Ellis, Jonathan D.; Whitsitt, Rebecca; Schwiegerling, James T.; Dubin, Matthew B. (The University of Arizona., 2020)
      Knife edge testing of a focused laser beam is a well-known method of observation of the position of focus. When this test is paired with pinhole scanning, a representation of the focal volume can be observed. These two methods are discussed and applied to an optical system that mimics laser-induced refractive index change (LIRIC), a femtosecond micromachining system developed at the University of Rochester to write diffractive patterns into ophthalmic hydrogels for vision correction. The focused, 405 nm, single-mode diode laser beam is modeled as Gaussian with a beam waist of 1.5 μm, and the experimentally measured waist was found to be between 8 μm. The beam quality is assessed in terms of Gaussian beam waist and the estimated beam quality factor M2, and the possibility of full characterization of the focal volume is explored. An f-theta lens is used to scan the beam, and the properties of f-theta lenses are discussed and modeled.
    • A Standard Methodology Enabling Execution of Models Described in Sysml Demonstrated in a Model Based Systems Engineering Approach Toward Developing a Space Situational Awareness System Implemented in Cubesats

      Valerdi, Ricardo; Lutfi, Mostafa; Bruyere, Donald; Lepore, Robert (The University of Arizona., 2020)
      As systems grow in complexity, Systems Engineers have embraced Model-Based Systems Engineering (MBSE) to tackle this complexity. The Systems Modeling Language (SysML) is the most commonly used language by the Systems Engineers to implement MBSE. SysML can highly express conceptual models, but struggles to demonstrate executable models. In order to perform requirements/behavior verifications, systems engineers/designers mostly use separate simulation tools. Hence, the efficiency of the systems engineering process is often reduced due to the isolated and consecutive use of both SysML modeling tool and other simulation tools, for example defining simulation inputs to each simulation tool separately. Hence, Executable SysML is the next logical step towards achieving true MBSE support for all Systems Engineering activities in the life cycle phases- system requirements, analysis, design, implementation, integration, verification, transition, validation, acceptance testing, training and maintenance. Therefore, various research efforts are being conducted to develop executable SysML Modeling approaches. This thesis paper develops a SysML Executable Modeling Methodology (SEMM), which is demonstrated by modeling a CubeSat based Space Situational Awareness (SSA) system in SysML. The SysML SSA-CubeSat System model is made executable by integrating with Commercial-Off-The-Shelf (COTS) simulation software, namely - Systems Tool Kit (STK) and MATLAB, following the approaches defined in the SEMM.
    • An Evaluation of Municipal Adaptation Planning in California: Climate Information Use, Access, and the Integration of Social Vulnerability

      Liverman, Diana M.; Cunningham, James; Gerlak, Andrea K.; Keith, Ladd (The University of Arizona., 2020)
      Urban adaptation plans are often predicated on knowledge of climate risks, requiring municipal planners to engage in novel ways of gathering data and using climate information, a term used for current and future climate projections and their impacts. However, few studies have assessed if and how municipal governments are acquiring and integrating climate information and how this might impact strategy development. Using content analysis and selected interviews to evaluate 26 of California’s 2012-2017 municipal adaptation plans, this study identifies (1) what climate information is used and how it supports strategy development (2) the networks and sources that provide climate information, and (3) the integration of social vulnerability concerns and public participation. I find that California’s municipalities rely on qualitative and quantitative descriptions of future climate to frame generalized threats to urban sectors and inhabitants. However, apart from sea level rise, plans do not address the location of magnitude of climate impacts within a municipality. As a result, climate information is mainly used to create a sense of urgency around climate change and support the low-cost capacity building solutions that dominate California’s urban adaptation strategies. While most municipalities consult information from state climate assessments and online climate wizards, to a lesser extent, municipalities form connections with regional commissions and local universities. These partnerships resulted in locally specific impact assessments that were used to produce tailored adaptation strategies. Despite the frequent integration of climatic variables, few plans take additional steps to identify and account for vulnerable populations within their jurisdictions. Similarly, public participation techniques are rarely incorporated into adaptation strategies but are more common in plans created by municipal staff as opposed to environmental consultants. As a result, key policy considerations for California include providing support for understanding the location and magnitude of climate impacts for multiple climate hazards, supporting the creation of additional regional commissions that can assist a greater number of municipalities, and providing incentives and tools for integrating social vulnerability and public participation into adaptation plan development.
    • Soil Dwelling Streptomyces Inhibit Arabidopsis Seed Germination

      Baltrus, David A.; White, Aaron R.; Woodson, Jesse D.; Beilstein, Mark A. (The University of Arizona., 2020)
      Streptomyces are a cosmopolitan and economically important genus of Actinobacteria known for producing an array of secondary metabolites, including many clinically relevant antibiotics. Streptomyces are ubiquitous in soil environments throughout the world and have been identified as prominent members of the microbiomes of diverse plant species. The presence of Streptomyces around and within plants has been shown to provide a wide variety of fitness benefits including increases in disease resistance and abiotic stress tolerance. Despite recent increased interest in the benefits of these bacteria to associated plants, relatively little is known about the genetic basis for the plant growth promotion capabilities shown by Streptomyces, or about the traits that facilitate plant interaction. In this work plant phenotypes resulting from inoculation with isogenic bacterial cultures are quantified and correlated with the genetic background of the bacteria used. The 9 isolates of soil derived Streptomyces influence the early growth phenotypes of co-cultured Arabidopsis thaliana Columbia-0 seedlings in a manner consistent with previously identified phylogenetic clade associations. Quantification of phenotypes of seedlings growing in association with bacterial cultures, and correlation of those phenotypes with the genetic backgrounds of associated isolates, demonstrates how results from an in vitro plant assay can be used to elucidate genomic regions with implication for plant colonization and interaction among closely related Streptomyces bacteria.
    • Creating an Empirically Based Model to Assess Infiltration Rates During Artificial Recharge at CAVSARP from 2013-2018

      Ferre, Paul; Solis-Arroyo, Sheila Sarai; Whitaker, Martha; Meixner, Thomas (The University of Arizona., 2020)
      Artificial recharge of groundwater is often achieved by infiltrating surface water into surface structures such as spreading basins. Tucson Water manages several artificial recharge projects including the Central Avra Valley Storage and Recovery Project (CAVSARP). CAVSARP consists of an intermittent multi-basin system responsible for the recharge of Central Arizona Project (CAP) water, originating from the Colorado River. Recharge basins are preferred structures for artificial recharge because they require little maintenance and are relatively easy to service. The main limit on spreading basins can be reduction in hydraulic conductivity over time due to suspended solids in surface water and anaerobic conditions. The purpose of this study is to create a simple, yet robust model that can interpret a time series of stage in the basin and measured inflow during artificial recharge periods to characterize whether the hydraulic conductivity is changing significantly over time. This could be used to trigger more detailed investigations by Tucson Water personnel to determine if a basin needs maintenance. The results of the study are in general agreement with a simpler assessment that is routinely performed by Tucson Water. However, with further refinement, it appears that the model developed here could be used to augment operational monitoring of basin performance.
    • Quantitative Microbial Risk Assessment and Community-Based Risk Perception of Sewage Overflows by Naco Elementary

      Ramirez-Andreotta, Monica D.; Gerba, Charles; Anides Morales, Alma; Reynolds, Kelly (The University of Arizona., 2020)
      Transboundary sanitary sewage overflows (SSO) have recurrently affected Ambos Nacos, sister border towns, since the late 1970s. Wastewater pollution is a major issue of concern worldwide because of the presence of pathogens and infectious microorganisms in polluted waters. The proximity of the sewage overflows to Naco Elementary School, has raised questions as to the potential health risks to the students. This is a community-inspired research project and a collaborative effort with Cochise Health and Social Services (CHSS) and Naco Elementary School. The purpose of this study was to assess the potential health risks to the students and improve understanding of risk perception and communication preferences among the school community. Following the quantitative microbial risk assessment (QMRA) paradigm, a single school day risk during a SSO event ranging from 5.08E-04 to 1 far exceeding the accepted annual risk of 1E-04. Inputs in the QMRA model included microbial analyses from superficial soil samples, and student behavior data from survey responses from teachers and parents. Qualitative coding found that approximately half of parents are not concerned or are unsure about SSO related concerns, and those who expressed concern pertained to the health and safety of their community and children, and groundwater contamination. Furthermore, 68% of parents and 50% of teachers said they had been aware of SSOs, highlighting the need for improved communication among all stakeholders (county, school, and parents). Results suggest improved communication during the occurrence of SSOs as well as action steps on how to prevent accidental exposure can mitigate a high risk of infection as calculated by the QMRA. Complementing QMRA studies with ethnographic methods to gather site-specific information can improve exposure data and inform future risk communication and management efforts.
    • The White Whale: A Case Study of Sight-Singing Philosophies and Practices of Two Secondary Choral Music Educators

      Corso, Dawn T.; Campman, Jennifer Brobeck; Cossey, Alyssa J.; Williams, Matthew (The University of Arizona., 2020)
      Within the American secondary choral classroom, sight-singing instruction is a common practice, with many teachers touting its connection to building music literacy for singers. Given the plethora of available sight-singing curricula, as well as the many possible musical and instructional systems that can be used in sight-singing instruction, choir teachers can approach this subject in a variety of ways. This thesis sought to delve deeper into the backgrounds, philosophies, and rationales of two Tucson, Arizona-area secondary choir teachers in regard to the instruction of sight-singing in their choir classes. The two teachers, Mrs. Julia Higgins of Esperero Canyon Middle School and Mrs. Sarah Ross of Marana High School, were first interviewed one-on-one to gain a foundational understanding of their personal musical backgrounds, teaching philosophies and instructional choices. They were then each observed teaching “standard sight-singing lessons” to three of their choir classes. After their observations, each participant made a self-reflection in the form of a vlog to discuss the rationales behind the lessons that they taught. After analyzing the data, several categories emerged: teacher identity (subcategories: personal musical experience, instrumental music connections, perception of self, and relationship to students), musical systems and curriculum (subcategories: solfege, establishing the key, tuning and intervals, beat and rhythm, and curriculum choices), pedagogical strategies (subcategories: structure and repetition, variety in approach, modeling, feedback and assessment), and philosophy (subcategories: efficiency and fluency, connecting the mind and the voice, artistic significance and application to repertoire, fun, and student independence and growth over time). This led to a discussion of each teacher’s music teaching philosophies as they relate to sight-singing, their pedagogical strategies used when teaching sight-singing, and how these two categories connect. This study provides only a snapshot of two teacher’s backgrounds and methods, and further, broader research can and should be done to comprehensively investigate how and why secondary choral educators teach sight-singing.
    • College Students’ Academic Entitlement, Lifestyles, and Parents

      Burross, Heidi L.; Ringquist, Austin Paul; Erbacher, Monica K.; Good, Thomas L. (The University of Arizona., 2020)
      Academic entitlement is an increasingly disrupting characteristic, affecting students, peers, teachers and professors in many different academic environments. This study reviewed the background of entitlement, investigated factors that may impact academic entitlement, as well as identified key characteristics to look for while searching for academic entitlement. A survey was administered to 397 college undergraduate students at a major southwestern university. Results from the survey used on this study included demographic items, parenting style measures, and academic entitlement items. Results from a series of separate linear regression models indicated academic entitlement is most predictive by anxious intrusiveness parenting style variable and the ethnicity variable, specifically Asian or Asian American group categorized. While these results were not statistically nor practically significant, it is worth noting future research is necessary further investigating these two variables across a wider sample. Additionally, limitations are discussed, and future research ideas are mentioned.
    • A Grammar Sketch of Tutelo-Saponi

      De Lima Silva, Wilson; Roberts, Corey; Zepeda, Ofelia; Fountain, Amy (The University of Arizona., 2020)
      This is a sketch grammar of the Tutelo-Saponi language, a preliminary examination of the history, phonology, morphology, and syntax of the Southeastern Siouan language and its speakers. While previous works have presented the corpus’ data in the North American Phonetic Alphabet, this study presents data primarily in a combination of the International Phonetic Alphabet (for the phonology portion of the grammar) and the writing system currently being developed for the Occaneechi Band of the Saponi Nation (a derivation of the orthography of the 19th-century philologist Horatio Hale). Included later in the sketch are methods currently being used to enrich the Tutelo-Saponi lexicon. Finally, this sketch presents a sample opening prayer in the language created in conjunction with an Occaneechi language consultant, as well as a land acknowledgment of the Tohono O’odham people created by Corey Roberts to open a linguistics presentation at the University of Arizona.
    • Calcium Homeostasis Modulator (CALHM1/2) in Pulmonary Arterial Hypertension

      Yuan, Jason X.-J.; Garcia, Joe G.N.; Rodriguez, Marisela; Vanderpool, Rebecca; Carew, Jennifer S. (The University of Arizona., 2020)
      Calcium Homeostasis Modulator in Pulmonary Arterial Hypertension byMarisela Rodriguez Master of Science (M.S.) in Clinical Translational Sciences University of Arizona, Tucson 2020 Professor Jason Yuan, Co-Chair Professor Joe G.N. Garcia, Co-Chair Pulmonary arterial hypertension (PAH) is a progressive and fatal disease that predominantly affects women. The increased pulmonary arterial pressure (PAP) in patients with PAH is mainly generated by increased pulmonary vascular resistance (PVR) (18, 70, 103). Sustained pulmonary vasoconstriction, excessive pulmonary vascular remodeling, in situ thrombosis, and increased pulmonary vascular wall stiffness are the major causes for the elevated PVR and PAP in patients with PAH. Concentric pulmonary vascular remodeling is among one of the major causes for the elevated pulmonary vascular resistance (PVR) and pulmonary arterial pressure (PAP), also one the major causes for increasing afterload of right ventricle (RV) and inducing right heart failure leading to death if untreated (103). Excessive pulmonary artery smooth muscle cell (PASMC) proliferation and inhibited PASMC apoptosis have been implicated in the development and progression of pulmonary vascular wall thickening in patients with PAH and animals with severe experimental pulmonary hypertension (PH). An increase in cytosolic free Ca2+ concentration ([Ca2+]cyt) in PASMCs is not only a trigger for PASMC contraction and pulmonary vasoconstriction, but also an important stimulus for PASMC proliferation, migration, and pulmonary vascular remodeling (16, 83, 85). [Ca2+]cyt in PASMCs is increased by Ca2+ influx through Ca2+-permeable cation channels in the plasma membrane (PM) and Ca2+ release or mobilization from the intracellular Ca2+ stores, mainly the sarcoplasmic (SR) or endoplasmic (ER) reticulum. There are at least three classes of Ca2+-permeable cation channels identified in human and animal PASMCs that are responsible for Ca2+ influx associated with excitation-concentration coupling (EC-coupling) and Ca2+-mediated PASMC proliferation and migration: (i) voltage-dependent Ca2+ channels (VDCC), (ii) receptor-operated Ca2+ channels (ROCC), and (iii) store-operated Ca2+ channels (SOCC) (50, 57). VDCC are opened or activated by membrane depolarization due to, for example, decreased activity or downregulated K+ channels (57) while ROCC is opened or activated by ligand-mediated binding to membrane receptors including G protein-coupled receptors (GPCR) and tyrosine kinase receptors (TKR). Activation of GPCR or TKR upon binding to respective ligands increases production of diacylglycerol (DAG) and inosital 1,4,5-triphosphate (IP3), two important intracellular second messengers. DAG then activates ROCC and introduces receptor-operated Ca2+ entry (ROCE), while IP3 activates IP3 receptors, also referred to as Ca2+ release channels, in the SR/ER membrane and induces Ca2+ release from the intracellular stores to the cytosol contributing to increasing [Ca2+]cyt. Depletion or significant reduction of Ca2+ levels in the ER/SR due to Ca2+ mobilization or release leads to Ca2+ influx through SOCC, commonly referred to as store-operated Ca2+ entry (SOCE). Active depletion of intracellularly stored Ca2+ in the SR/ER then also results in the dimerization and translocation of STIM1 (and/or STIM2) in the SR/ER membrane and forms STIM protein puncta close to the SR/ER-plasma membrane junctions. Then the multimer STIM1/2 proteins in the ER-PM recruit Orai proteins in the plasma membrane to form SOCC responsible for SOCE (16). It has been shown that transient receptor potential (TRP) channels are involved in forming ROCC in PASMCs and can be activated directly by DAG. In our previous publishing, we have determined that the proliferative phenotype of PASMCs employs SOCC leading to increased expression levels of STIM2, not STIM1, and also Orai2 and TRPC6 expressions from IPAH patients- altogether providing an underlying mechanism for enhanced SOCE. TRP channels are also reported to participate in the regulation of SOCE in many cell types (21). In addition to TRP channels, many other types of Ca2+-permeable cation channels may also participate in ROCE and SOCE. Calcium homeostasis modulators (CALHM) including CALHM1 and CALHM2, have been identified as a family of physiologically important plasma membrane ion channels that are permeable to both cations and anions. These channels are allosterically regulated by membrane voltage (or membrane potential) and extracellular Ca2+; CALHM1 and CALHM2 channels are closed at the resting membrane potential but can be opened by strong membrane depolarization. Reduction of extracellular [Ca2+] increases the probability for CALHM channels to open, which allow the channels to be activated at a negative potential. Ultimately, it is widely known that the increased [Ca2+]cyt due to upregulated and activated Ca2+-permeable cation channels contribute to pulmonary vasoconstriction and excessive proliferation of PASMCs (and other cell types, for example fibroblasts and myofibroblasts) in patients with PAH, eventually this leads to concentric pulmonary vascular remodeling (17). Therefore, a rise in intracellular [Ca2+] and activated Ca2+ in PASMC via upregulated and/or activated Ca2+-permeable cation channels play a major role. CALHM1 and CALHM2 have a significant impact on the pathogenesis that lead to the development and progression of PAH. As discussed earlier, sustained pulmonary vasoconstriction and excessive pulmonary vascular remodeling comprise of two major causes for the elevated PVR and PAP in patients with PAH and animals with experimental PH (50). Pulmonary vasoconstriction is certainly a major cause for increasing PVR and PAP at the early stage of disease development, while concentric pulmonary vascular remodeling and obliterative intima and plexiform lesions are made up of the late state pathological changes that contribute to maintaining high PVR and PAP (57). The transition from the contractile or differentiated phenotype to the synthetic or proliferative phenotype of PASMC is thus an important pathogenic process that promotes vascular remodeling (62) in which we aimed at investigating. In this study, I hypothesized that CALHM1 and/or CALHM2 are involved in PASMC phenotypical transition from the contractile or differentiated phenotype to the synthetic or proliferative phenotype, while CALHM1/2 are upregulated in PASMC from patients with PAH and animals with experimental PH.
    • Examining the Double-Consciousness: Portraits of Americana in the Works of Ulysses Kay

      Mugmon, Matthew; Knox, Grant Stephen; Brobeck, John T.; Rosenblatt, Jay (The University of Arizona., 2020)
      Ulysses Simpson Kay, Jr. (1917–1995) was a distinguished American composer, conductor and professor. Having composed approximately 140 works throughout his lifetime, Kay established himself as a prominent figure within the scope of twentieth-century American composition. An African American composer, Kay often seemed to downplay the role of race in his music, an approach perhaps best articulated by his categorical definition of Black music as “music written or conceived by blacks.” Indeed, scholars have debated the role of Kay’s racial identity in his music. An examination of selected works by Ulysses Kay, and their contexts, reveals that his American and African American musical identities coexist. This finding suggests Kay’s music to be a case study in the musical expression of W.E.B. DuBois’s (1868–1963) term “double-consciousness.” DuBois’s writings, particularly his 1903 collection of essays The Souls of Black Folk offer a framework for understanding the role of racial identity in Kay’s music. This study will look at Kay’s Danse Calinda (1941), Lift Every Voice & Sing (1943), Harlem Children’s Dance Suite (1973), and Frederick Douglass (1991) as works that are evocative of the African American identity, while A Lincoln Letter (1953), FDR: From Third Term to Pearl Harbor (1958), Forever Free (1962), Presidential Suite (1965), Southern Harmony (1975) represent the broader American identity. Each of these compositions implies the duality of identities through its subjects, contexts, and/or specific musical details. As a result, we are able to arrive at a more nuanced understanding of the role of racial identity in Ulysses Kay’s music.
    • Estimation of Mechanical and Thermal Properties of Porous Aluminosilicate Foam

      Momayez, Moe; Chaurasia, Akash; Muralidharan, Krishna; Waqas, Muhammad (The University of Arizona., 2020)
      Aluminosilicates are naturally occurring minerals with low thermal conductivity due to the presence of variable size pores in their structure. Because they are found in abundance in nature, they could be an economical alternative for the fabrication of thermal insulators used in the buildings and underground mines. In this study, the thermal and mechanical properties of amorphous porous aluminosilicate structures (PAS) were investigated using computational and experimental methods. Molecular Dynamics (MD) simulation was used to characterize the thermal conductivity at the atomistic scale. MD simulations were performed to identify the suitable Al-Si ratio that yields the lowest possible thermal conductivity as well as high mechanical strength. The effect of density on the thermal conductivity of aluminosilicate structures was characterized. It was observed that the thermal conductivity of the Aluminosilicate structures has a linear dependence on the densities varying between 0.4 g/cc and 2.62 g/cc. In addition, for a given porosity, a larger distribution of smaller pores results in lower thermal conductivity. This observation is correlated with the presence of phonon-scattering centers in such systems. The data obtained from MD simulations were used to physically fabricate the foams with similar densities in laboratory, and their associated thermal conductivity was experimentally measured. MD simulations and experimental data show a high degree of agreement. The ultrasound non-destructive technique (NDT) was used to transmit wave energy in the 1 MHz frequency range to measure dynamic mechanical properties experimentally. Porosity was varied by changing the composition of the blowing agent and surfactant. P-wave and S-wave velocities were measured using the time of flight of the ultrasonic energy through the sample. The Finite Element Method (FEM) provided in the COMSOL Multiphysics platform was used to verify the bulk mechanical and thermal properties of the amorphous porous aluminosilicate materials. Acoustic and stress analysis were performed at different porosities to determine P-wave and S-wave velocities, and other elastic properties. Symmetric spherical pores were introduced to simulate porosity. We also generated a high-fidelity model of the foam using micro-CT scans. Volume meshing was created in the Simpleware ScanIp software and subsequently exported as a COMSOL supported file to perform the modeling. Next, FEM models were set up to determine the acoustic and elastic properties at different porosity ranges. The data produced in this analysis demonstrated a good agreement between numerical and experimental tests. The findings from this research project will be used to design and fabricate a cost-effective thermal insulator.
    • Examining the Relationship between Pesticide Exposure and Negative Health Outcomes among Farmworkers

      Estrada, Antonio; Aguilar Buenrostro, Mario Alberto; Martínez, Daniel E.; Téllez, Michelle (The University of Arizona., 2020)
      Farmworkers in the agriculture sector work in one of the most dangerous occupations in the country. Farmworkers are highly exposed to occupational pesticides that can result in various negative health outcomes. Drawing on the National Agricultural Workers Survey (NAWS), this thesis examines the relationships between lifetime asthma diagnoses, pain/discomfort, pesticide exposure, occupational factors, and socio-demographic factors. Logistic regression results suggest that farmworkers who handled pesticides within the past 12 months preceding the survey have higher odds of having received a lifetime health care provider diagnosis of asthma, as well as higher odds of reporting experiencing pain and discomfort during the prior year. The findings produced in this research provide further knowledge to farmworkers, employers, and society about occupational health disparities and exposure to pesticides.
    • Strategies for Two Alternative Forced Choice Navigation Tasks

      Reverdy, Paul B.; Lei, Henry; Thanga, Jekan; Butcher, Eric (The University of Arizona., 2020)
      In the engineering community, there has been a growing interest in emulating robust continuous decision mechanisms, often found implicitly in biological systems, in engineered autonomous systems. The Two Alternative Forced Choice navigation problem, where an agent is required to decide between two possible navigation tasks based on a noisy signal, is a natural model problem for studying such mechanisms. In this thesis, we aim to generate and systematically study a variety of decision-making strategies in terms of the expected time, distance and error rates. We look at five in particular; the first four are preliminary, based off of various heuristics, while the fifth follows a model predictive control framework with a novel adaptive cost function that penalizes the control magnitude and deviation from a dynamic “artificial” goal. The strategies are studied using a variety of computational and analytic methods; for the model predictive control strategy in particular, closed form results for the expected trajectory in both deterministic and stochastic environments are presented.
    • Rapid Geodetic Shortening, Northwest Argentina

      Bennett, Richard A.; McFarland, Phillip Kenneth; Decelles, Peter G.; Beck, Susan L. (The University of Arizona., 2020)
      Continuous global navigation satellite system (cGNSS) ground tracking station data are commonly used in the study of active tectonics to measure crustal deformation at plate boundaries. In this work, surface crustal velocities for 29 cGNSS stations from the southern central Andes are presented in a South-America-fixed frame for a transect across the Puna Plateau, Eastern Cordillera, and Santa Barbara System for the time span between two major megathrust earthquakes: the 27 February 2020 Maule and the 1 April 2014 Iquique earthquakes. The surface crustal velocities exhibit a systematic decrease in magnitude from roughly 35 mm/yr near the Peru-Chile trench to less than 1 mm/yr within the stable craton. The contribution to the velocity field due to loading on the Nazca-South America (NZ-SA) subduction interface was modeled using back-slip on elastic dislocations to approximate a fully locked interface from 10 to 50 kilometers depth. For this modeling, an ensemble of models was generated by iterating over the percentage of NZ-SA convergence accommodated at the subduction interface. Velocity residuals calculated for each model demonstrate that locking on the NZ-SA interface is insufficient to reproduce the observed velocities. In order to fully fit the velocity field, a supplemental back-arc décollement model was employed comprising an edge dislocation for which parameters were estimated using the velocity residuals for each forward model of the subduction interface ensemble using a Bayesian approach. The best fit to the thrust-perpendicular velocity field was realized with 70 ± 5 % of NZ-SA convergence accommodated at the subduction interface and a slip rate of 9.1 ± 0.9 mm/yr on the fold-thrust belt décollement. The locking depth for the décollement was estimated to be 14 ± 9 km, which places the down-dip extent of the locked zone 135 ± 20 km from the thrust front. The thrust-parallel component of the velocity field was fit by a constant shear strain rate of -19×〖10〗^(-9) yr¬-1, equivalent to clockwise rigid-block rotation of the back arc at a rate of 1.1 /Myr.
    • Optimization of Blockage on Solar Panel Systems and Concentrated Solar Power (CSP) Systems

      Li, Peiwen; Chen, Guangji; Hao, Qing; Zohar, Yitshak (The University of Arizona., 2020)
      It is well-established that renewable energy is produced from sources that do not deplete or can be replenished within a human’s lifetime. Collecting solar energy through solar panels faces a significant utilization efficiency problem. As collectors direct to collect solar energy, solar panels are sometimes blocked by other surrounding solar panels because of sunlight shifting angles. Other surrounding heliostats also block heliostats to reflect sunlight in concentrated solar power systems as sunlight shifting angles. For these reasons, it is essential to estimate the mutual blocking rate and find the optimum row-spacing for a solar panel field or geometrical layout for a heliostat field. The available literature regarding mutual blocking analysis or optimizations of a solar field usually discusses an algorithm of estimating mutual blocking rate with many abstract calculations or a series of geometrical layouts under fixed conditions. But this paper presents a straightaway geometric algorithm that collaborated with MATLAB to approach the mutual blocking rate, accompanied by the amount of monthly/yearly energy collected. Also, it demonstrates different optimizing thoughts based on utilization efficiency and the cost of energy collected for the solar panel in a solar field to optimize the row spacing. Moreover, it also provides this algorithm’s wide range of applications for heliostats in a CSP system to estimate the mutual blocking rate. In this context, the distance ratio (Ds Ratio), as an optimizing value about row spacing, is defined the ratio of the distance between two solar panels and the width of the solar panel. A MATLAB computer model was created to simulate these situations and find the optimum Ds Ratios based on the mutual blocking analysis. The yearly energy harvested from a solar panels field simulated at Tucson in 2019 can be estimated. And developed model estimated instantaneous blockage of a heliostat in a CSP system anytime and anywhere. The results showed that blockage could almost be avoided at setting a Ds Ratio of 1.83 for a solar panels field at Tucson with an average solar panels utilization efficiency of 99.5%. Also, the Ds ratio of 1.15 is the most optimal value to build a solar panels field with the lowest economic cost and utilization rate of 94.8% in Tucson. These results gave suggestions to those investors who consider the solar panels blockage to build a lar solar panels field. These results can also provide estimated heliostat blockage to researchers to optimize a CSP system’s heliostat layout.
    • Analytical and Experimental Study on the Effect of Discontinuities on Cast Steel Component Performance

      Fleishcman, Robert; Moya, Joseph; Jo, Hongki; Kundu, Tribikram (The University of Arizona., 2020)
      An experimental and analytical study is performed to investigate the effect of different discontinuities on the yield strength, ultimate strength and ductility of steel cast components. Steel plates containing various discontinuities were cast in sand molds, cut to size, and tested in monotonic tension to fracture. Radiographic imaging was used to identify, classify, and rate discontinuities. Three different types of discontinuity and three different ASTM 2868 indication levels were tested. The discontinuities varied in size from 0.46 percent to 9.09 percent of the average gross-section area of the specimens. Specimens rated Level 2 or lower tended to fracture at the minimum section, not at the discontinuity. Specimens with Level 5 indications tended to fracture at the discontinuity. Specimens that fractured at the discontinuity had reduced ductile capacity. Elongation was reduced by Level 5 indications by between 45.7 to 70.0 percent. Ductile fracture predictive models were used in finite-element analysis to predict component performance. Models used color data from radiography for discontinuity size. Good agreement is obtained between experimental and predicted elongation at fracture. The analytical modeling methods used in this thesis allow for accessible prediction of ductile capacity of a cast component.
    • A Theory of Nature Architecture through Indigenous Knowledge: Evaluation with Post-Disaster Building Design

      Ida, Aletheia; Lin, ChungTse; Trumble, Christopher D.; Robinson, Clare M. (The University of Arizona., 2020)
      Humans are continuously developing new technologies to transform buildings into comfortable fortresses that are not affected by the outdoor environment. But this modality of environmental control also makes architecture a barrier to the relationship between nature and humans. Although the topic of green architecture or sustainable building is becoming ever more prevalent, the focus tends to primarily be on physical impacts such as energy-reduction and carbon footprint minimization. However, the early and long-standing important relationship between humans and nature is not well considered through these contemporary sustainable architecture practices. This research seeks to develop a built environment theory, identified as Nature Architecture, that focuses on establishing the relationship between humans and nature. This relationship has the capacity to bring humans back to natural systems and help situate human considerations, reflections, and actions for and with nature in the future. Nature Architecture is a metaphorical bridge connecting people directly with nature, rather than a barrier that isolates humans from nature due to technological developments. In order to identify human and nature relationships in architecture, this research analyzes the indigenous architecture from three different geographic regions: Arizona, Alaska, and Taiwan. By comparing and contrasting ancient people's dwellings, which were built with early construction techniques, a symbiotic relationship between indigenous people and the balance of nature for thousands of years is identified. Fundamental defining characteristics are elicited from this symbiotic relationship, including form, material, condition, and space. These foundational aspects are then applied to post-disaster architecture's conceptual design process with three demonstrations that show more connection with nature that improve psychological and physical health for refugees.
    • Mulch and Compost for Restoration of Soil Health in a Semi-Arid Rangeland

      Blankinship, Joseph C.; Leger, Ariel Marc; Gornish, Elise; Rasmussen, Craig (The University of Arizona., 2020)
      Between one quarter and one half of dryland (P:PET<0.65) soils are degraded. Soil organic amendments (amendments) can improve soil health, increase plant productivity, and increase soil organic carbon (SOC) content. This has led to a recent surge in research into the use of amendments. However, more research is needed to identify locally appropriate amendments and applications for dryland restoration. My thesis work addresses this need by surface applying (mulching) two locally abundant amendments in a degraded section of a semi-arid rangeland. The amendments used were mesquite branches and a compost of woodchips and manure. The first section of this thesis assesses the effects of amendments on soil health and plant establishment. The second section focuses on the ability of amendments to increase SOC in stable soil fractions that can protect SOC for decades to centuries. We found that mesquite mulch alone increased soil moisture, plant available nitrogen, cover and abundance of plants. However, mulch alone did not increase total soil carbon or carbon content of any measured soil fraction. When combined with compost, total SOC, the carbon in labile pools, and the SOC in stable aggregate and mineral protected pools increased. However, we found that the carbon in protected pools did not resist high levels of dispersion. Furthermore, although compost increased mean soil moisture, it could not do so during dry times of the year in response to small rain events and it. Compost also reduced the cover and abundance of plants at 6 cm applications but did increase the growth and cover of seeded grasses at 3 cm applications. Overall, the use of mesquite branch mulch was found to be highly promising as a method to improve key aspects of soil health and the short-term establishment of plants. Compost on the other hand is not recommended at either 3 cm or 6 cm rates of application, but may be promising at lower application rates. Although longer-term observations are needed to confirm, neither amendment seemed likely to result in persistent soil carbon gains unless careful management actions are taken to prevent soil disturbance and prevent loss of carbon from the weakly bound aggregates and mineral associations we found.