• Modeling Orbital Motion in a Circular Conic Reference Frame

      May, Douglas H.; University of Arizona (American Institute of Aeronautics and Astronautics, 2022-12-29)
      Two-body orbital trajectories conform to conic sections. However, typically in the literature their motion is analyzed in a plane. Kepler modeled elliptic orbital motion in a plane, stated his second law, and derived the geometric position-time relationship as the uniform change in area with respect to time. Kepler’s equation has been applied extensively and proven to give time as a function of position for exact solutions to orbital problems. An identical equation has been derived without reliance on geometry alone by applying basic principle of classical mechanics and the calculus. When the elliptic orbit is analyzed as a section of a circular cone and represented in three dimensions, additional variables relate position and time. In a conical reference frame, the planar and conic representations merge. This paper combines the conic section knowledge and characteristics of the cone to introduce a third dimension to modeling orbital motion. Force and potential energy have indeterminate limits because potential energy approaches zero as the radius approaches infinity and the gravitational force approaches infinity as the radius vector approaches zero, a singularity. The conic frame includes the apex where the singularity of a radius of zero is an established point in the reference system.
    • Development and Flight Performance of the Autonomous Navigation Feature Catalog for OSIRIS-REx Asteroid Sample Collection

      Mario, Courtney; Miller, Curtis; Norman, Chris; Olds, Ryan; Palmer, Eric; Weirich, John; Lorenz, David A.; Barnouin, Olivier; Bos, Brent J.; Rizk, Bashar; et al. (American Institute of Aeronautics and Astronautics, 2022-12-29)
      The OSIRIS-REx spacecraft successfully collected a sample from the asteroid Bennu in October 2020, enabled by the vision navigation system Natural Feature Tracking (NFT). NFT autonomously provided state updates by matching features defined from Bennu shape model data to onboard camera images and allowed the spacecraft to touch down within 1 meter of the targeted location. This paper presents the development process and flight performance of the feature catalog used for navigation, including findings about terrain characteristics of robust features, validation methodologies despite limited test imagery, and trends between feature terrain content and final feature performance.
    • Adaptive Scale Factor Compensation for Missiles with Strapdown Seekers via Predictive Coding

      Gaudet, Brian; Drozd, Kris; Furfaro, Roberto; University of Arizona (American Institute of Aeronautics and Astronautics, 2022-12-29)
      In this work we present a method to adaptively compensate for scale factor errors in both rotational velocity and seeker angle measurements. The adaptation scheme estimates the scale factor errors using a predictive coding model implemented as a deep neural network with recurrent layer, and then uses these estimates to compensate for the error. During training, the model learns over a wide range of scale factor errors that ideally bound the expected errors that can occur during deployment, allowing the deployed model to quickly adapt in real time to the ground truth error. We demonstrate in a realistic six degrees-of-freedom simulation of an exoatmospheric intercept that our method effectively compensates for concurrent rotational velocity and seeker angle scale factor errors. The compensation method is general in that it is independent of a given guidance, navigation, and control system implementation. Although demonstrated using an exoatmospheric missile with strapdown seeker, the method is also applicable to endoatmospheric missiles with both gimbaled and strapdown seekers, as well as general purpose inertial measurement unit rate gyro compensation.
    • Integrated Guidance and Control for Lunar Landing using a Stabilized Seeker

      Gaudet, Brian; Furfaro, Roberto; University of Arizona (American Institute of Aeronautics and Astronautics, 2022-12-29)
      We develop an integrated guidance and control system that in conjunction with a stabilized seeker and landing site detection software can achieve precise and safe planetary landing. The seeker tracks the designated landing site by adjusting seeker elevation and azimuth angles to center the designated landing site in the sensor field of view. The seeker angles, closing speed, and range to the designated landing site are used to formulate a velocity field that is used by the guidance and control system to achieve a safe landing at the designated landing site. The guidance and control system maps this velocity field, attitude, and rotational velocity directly to a commanded thrust vector for the lander’s four engines. The guidance and control system is implemented as a policy optimized using reinforcement meta learning. We demonstrate that the guidance and control system is compatible with multiple diverts during the powered descent phase, and is robust to seeker lag, actuator lag and degradation, and center of mass variation induced by fuel consumption. We outline several concepts of operations, including an approach using a preplaced landing beacon.
    • Singlet Oxygen Leads to Structural Changes to Chloroplasts during their Degradation in the Arabidopsis thaliana plastid ferrochelatase two Mutant

      Fisher, Karen E; Krishnamoorthy, Praveen; Joens, Matthew S; Chory, Joanne; Fitzpatrick, James A J; Woodson, Jesse D; School of Plant Sciences, University of Arizona (Oxford University Press, 2022-11-24)
      During stress, chloroplasts produce large amounts of reactive oxygen species (ROS). Chloroplasts also contain many nutrients, including 80% of a leaf's nitrogen supply. Therefore, to protect cells from photo-oxidative damage and to redistribute nutrients to sink tissues, chloroplasts are prime targets for degradation. Multiple chloroplast degradation pathways are induced by photo-oxidative stress or nutrient starvation, but the mechanisms by which damaged or senescing chloroplasts are identified, transported to the central vacuole and degraded are poorly defined. Here, we investigated the structures involved with degrading chloroplasts induced by the ROS singlet oxygen (1O2) in the Arabidopsis thaliana plastid ferrochelatase two (fc2) mutant. Under mild 1O2 stress, most fc2 chloroplasts appeared normal, but had reduced starch content. A subset of chloroplasts was degrading, and some protruded into the central vacuole via 'blebbing' structures. A 3D electron microscopy analysis demonstrated that up to 35% of degrading chloroplasts contained such structures. While the location of a chloroplast within a cell did not affect the likelihood of its degradation, chloroplasts in spongy mesophyll cells were degraded at a higher rate than those in palisade mesophyll cells. To determine if degrading chloroplasts have unique structural characteristics, allowing them to be distinguished from healthy chloroplasts, we analyzed fc2 seedlings grown under different levels of photo-oxidative stress. A correlation was observed among chloroplast swelling, 1O2 signaling and the state of degradation. Finally, plastoglobule (PG) enzymes involved in chloroplast disassembly were upregulated while PGs increased their association with the thylakoid grana, implicating an interaction between 1O2-induced chloroplast degradation and senescence pathways.
    • Titan's haze at opposite seasons from HST-STIS spectroscopy

      Karkoschka, Erich; Lunar and Planetary Laboratory, University of Arizona (Elsevier BV, 2022-11)
      We present an analysis of three new image cubes of Titan by the Space Telescope Imaging Spectrograph taken in 2017, 2018, and 2019, half a Titan year after previously analyzed image cubes. Both data sets probe periods when Titan's seasonal north-south-asymmetry switched. The new observations show that the new reversal came exactly half a Titan year after the previous opposite reversal. On the other hand, the phase lag of the reversals with respect to Titan's equinoxes was different indicating that the seasonal variation is close to harmonic and does not follow variations due to Saturn's orbital eccentricity. The reversal had two components, a major one at altitudes below 80 km reversing two years after a minor one above 150 km. The observations further revealed small temporary deviations of <10% of the seasonal amplitude. The new observations provide an improved seasonal model of Titan that gives accurate constraints for future global circulation models.
    • Thermal rectification in polytelescopic Ge nanowires

      Molaei, Fatemeh; Farzadian, Omid; Zarghami Dehaghani, Maryam; Spitas, Christos; Hamed Mashhadzadeh, Amin; Mining and Geological Engineering Department, The University of Arizona (Elsevier BV, 2022-11)
      Herein we served non-equilibrium molecular dynamics (NEMD) approach to simulate thermal rectification in the mono- and polytelescopic Ge nanowires (GeNWs). We considered mono-telescopic structures with different Fat-Thin configurations (15-10 nm-nm or Type (I); 15-5 nm-nm or Type (II); and 10–5 or Type (III) nm-nm) as generic models. We simulated the variation of thermal conductivity against interfacial cross-sectional temperature as well as the direction of heat transfer, where a higher thermal conductivity correlating to thicker nanowires, and a more significant drop (or discontinuity) in the average interface temperature in the positive (or negative) direction were detected. Noticeably, interfacial thermal resistance followed the order of Type (II) (48 K/μW, maximal) ˃ Type (III) ˃ Type (I) (5 K/μW, minimal). In the second stage, a series of polytelescopic nanostructures of GeNWs were born with consecutive cross-sectional interfaces. Surprisingly, larger interfacial cross-sectional areas equivalent to smaller diameter changes along the GeNWs were responsible for higher temperature rectification. This led to a very limited thermal conductivity loss or a very high unidirectional heat transfer along the polytelescopic structures - the key for manufacturing next generation high-performance thermal diodes.
    • A finite volume algorithm for the dynamics of filaments, rods, and beams

      Ryan, Paul M.; Wolgemuth, Charles W.; Department of Physics, University of Arizona; Department of Molecular and Cellular Biology, University of Arizona (Elsevier BV, 2022-10)
      Filaments, rods, and beams are ubiquitous in biology and in many man-made products and structures. While a substantial amount of research has been done to understand the statics and dynamics of these long, thin objects, there remain many unanswered and unstudied problems related to the dynamics of bending and twisting filamentary objects. Simulating the general dynamics of these structures in 3D remains challenging. For example, the net force and torque on a free filament immersed in fluid at low Reynolds number must be zero. However, standard finite difference approaches will often fail to preserve the zero force and torque conditions. These numerical artifacts cause spurious rotations and translations that prohibit, or at least limit, their accuracy in simulating the dynamics of filaments, rods, and beams in these contexts (such as the free-swimming motion of a filamentary microorganism). Here we develop a finite volume discretization based on the Kirchoff equations that naturally guarantees the correct total integral of the forces and torques on filaments, rods, or beams. We then couple this discretization to resistive force theory to develop a stable, accurate dynamic algorithm of filament motion at low Reynolds number. We use a range of sample problems to highlight the utility, stability, and accuracy of this method. While our sample problems focus on low Reynolds number dynamics in the context of resistive force theory (RFT), our discretized finite volume algorithm is general and can be applied to inertial dynamics, immersed boundary methods, and boundary integral methods, as well.
    • Directed energy deposition GRCop-42 copper alloy: Characterization and size effects

      Demeneghi, Gabriel; Barnes, Baxter; Gradl, Paul; Ellis, David; Mayeur, Jason R.; Hazeli, Kavan; Aerospace and Mechanical Engineering Department, University of Arizona (Elsevier BV, 2022-10)
      Laser Powder Direct Energy Deposition (LP-DED) allows for manufacturing of large components while still maintaining internal thin walls for heat exchanger applications. The LP-DED process has been matured for alloys including stainless steels, superalloys, and titanium, but has had very limited research using copper-based alloys, which are important for applications that require high thermal conductivity. This study quantifies the size effects on microstructure, surface metrology, microhardness, and mechanical response to tensile loads for different thicknesses and powder compositions of hot isostatic pressed (HIP) LP-DED Copper-Chromium-Niobium alloy, specifically GRCop-42. To accomplish this, tensile specimens were sectioned from single track build walls in both horizontal and vertical orientations to also investigate possible anisotropic behavior in the part. Results show that microstructure, hardness, surface metrology, and porosity are independent of wall thickness. Uniaxial loading response showed some variations with specimens orientation and size effects. For vertical specimens, thicker specimens showed a 6% higher elongation than thinner specimens. Horizontal specimens showed close to double the elongation when compared to vertical specimens, where thinner specimens had a higher reduction in elongation than thicker specimens. Additionally, removing the surface effects through polishing practically eliminated the anisotropic behavior between horizontal and vertical specimens along with the observed size effects. To demonstrate size effects dependency on the manufacturing process comparison is made between GRCop-42 alloy produced by Laser Powder Bed Fusion (L-PBF) and LP-DED.
    • Late Oligocene - Miocene morpho-tectonic evolution of the central Gangdese batholith constrained by low-temperature thermochronology

      Su, Wenbo; He, Zhiyuan; Zhong, Linglin; Glorie, Stijn; Zhong, Kanghui; Jepson, Gilby; De Grave, Johan; Department of Geosciences, University of Arizona (Elsevier BV, 2022-10)
      The morpho-tectonic evolution of the Tibetan Plateau is controlled by complicated interactions between tectonic uplift and surface erosion. The Gangdese batholith in the southern Lhasa terrane is a key orogenic belt for exploring the complicated morpho-tectonic evolution of the Tibetan Plateau. In this contribution, we apply apatite fission track (AFT) thermochronology to constrain the thermo-tectonic evolution of the central segment of the Gangdese batholith. Twenty-four granitoid samples were collected from both river valleys (e.g., the Yarlung and Xiang Rivers) and from the internal batholith areas located farther from river drainage (and/or local faults) networks. All samples exhibit Miocene AFT ages between ∼19.9 and ∼ 6.1 Ma. Inverse thermal history modeling results reveal that the central Gangdese batholith underwent a two-stage accelerated basement cooling in the Miocene. The first cooling stage took place during the late Oligocene to middle Miocene (∼25–15 Ma), this period of moderate to rapid basement cooling coincides with activity along the Gangdese thrust and Great Counter thrust system, and the Oligocene-Miocene delamination of the Lhasa lithosphere and concomitant asthenosphere upwelling. These tectonic processes acted as first-order control on regional basement uplift, denudation and exhumation. Second, a middle-late Miocene (∼14–5 Ma) rapid cooling is widely recognized in the whole Gangdese batholith. We suggest that this middle-late Miocene cooling is due to exhumation in response to tectonic and surface erosion processes such as N-S normal faults and enhanced river incision induced by the intensification of Asian monsoon. Finally, in combination with published low-temperature thermochronological and paleoaltimetry data, it is deduced that the present-day low-relief landscape of the southern Lhasa terrane resulted from a long-term balance between intense regional tectonic activity and surface erosion.
    • Computational Thinking for Using Models of Water Flow in Environmental Systems: Intertwining Three Dimensions in a Learning Progression

      Gunckel, Kristin, l.; Covitt, Beth; Berkowitz, Alan; Caplan, Bess; Moore, John; Department of Teaching, Learning, & Sociocultural Studies, University of Arizona (Wiley, 2022-09-20)
      Nearly a decade ago, the Framework for K-12 Science Education argued for the need to intertwine science and engineering practices, disciplinary core ideas, and crosscutting concepts in performance expectations. However, there are few empirical examples for how intertwining three dimensions facilitates learning. In this study, we used a learning progressions approach to examine how student engagement in computational thinking (science and engineering practice) intertwines with learning about the flow of water through environmental systems (disciplinary core ideas) and understanding of systems and system models (crosscutting concept). We developed three secondary-level curriculum units situated in current groundwater contamination and urban flooding contexts. Units included specially designed NetLogo computational models. Post-assessments measured student performances in computational thinking processes and understanding of hydrologic systems. Using item response theory in our analysis, we identified distinct levels of performance on a learning progression. At the lower end, Literal Model Users interacted with models and manipulated model interfaces to achieve a specified goal. In the middle, Model Technicians used computational models to solve real-world problems. At the upper end, Principle-Based Model Users used computational thinking processes and principles related to systems modeling and hydrology to explain how the models worked to predict water flow. Differences between performances of Literal Model Users, Model Technicians, and Principle-based Model Users reflected shifts in how students made sense of the systems and system models crosscutting concept. These shifts in performances aligned with progress in computational thinking practices and finally with use of hydrology disciplinary core ideas. These findings contribute to understanding of how science and engineering practices, disciplinary core ideas, and crosscutting concepts intertwine during learning; how computational thinking practices develop; and how computational thinking about system models facilitates learning for environmental science literacy.
    • Stability and bifurcation of Mathieu–Duffing equation

      Azimi, Mohsen; Department of Aerospace and Mechanical Engineering, University of Arizona (Elsevier BV, 2022-09)
      Various phenomena in science, physics, and engineering result in the Mathieu equation with cubic nonlinear term, known as the Mathieu–Duffing equation. In previous works, different perturbation methods have been used to investigate the stability and bifurcation of this equation in the vicinity of the first unstable tongue and for relatively small values of natural frequency. The primary goal of this paper is to adapt the Strained Parameters Method to investigate the stability and bifurcation associated with stability change around the second unstable tongue. In addition, this work shows that the Strained Parameters Method is able to obtain the same results previously obtained by other perturbation techniques with minimum computational effort. An inductive approach is used to express the multipliers of the transition curves and the location of the newborn equilibria as a function of the parametric frequency. Lastly, the Floquet theory and Poincaré map are used to validate the analytical results.
    • An evaluation of carbon indicators of soil health in long-term agricultural experiments

      Liptzin, Daniel; Norris, Charlotte E.; Cappellazzi, Shannon B.; Bean, G. Mac; Cope, Michael; Greub, Kelsey L.H.; Rieke, Elizabeth L.; Tracy, Paul W.; Aberle, Ezra; Ashworth, Amanda; et al. (Elsevier BV, 2022-09)
      Soil organic carbon (SOC) is closely tied to soil health. However, additional biological indicators may also provide insight about C dynamics and microbial activity. We used SOC and the other C indicators (potential C mineralization, permanganate oxidizable C, water extractable organic C, and β-glucosidase enzyme activity) from the North American Project to Evaluate Soil Health Measurements to examine the continental-scale drivers of these indicators, the relationships among indicators, and the effects of soil health practices on indicator values. All indicators had greater values at cooler temperatures, and most were greater with increased precipitation and clay content. The indicators were strongly correlated with each other at the site-level, with the strongest relationship between SOC and permanganate oxidizable C. The indicator values responded positively to decreased tillage, inclusion of cover crops, application of organic nutrients, and retention of crop residue, but not the number of harvested crops in a rotation. The effect of decreased tillage on the C indicators was generally greater at sites with higher precipitation. The magnitude and direction of the response to soil health practices was consistent across indicators within a site but measuring at least two indicators would provide additional confidence of the effects of management, especially for tillage. All C indicators responded to management, an essential criterion for evaluating soil health. Balancing the cost, sensitivity, interpretability, and availability at commercial labs, a 24-hr potential C mineralization assay could deliver the most benefit to measure in conjunction with SOC.
    • Privacy protection, measurement error, and the integration of remote sensing and socioeconomic survey data

      Michler, Jeffrey D.; Josephson, Anna; Kilic, Talip; Murray, Siobhan; Department of Agricultural and Resource Economics, University of Arizona (Elsevier BV, 2022-09)
      When publishing socioeconomic survey data, survey programs implement a variety of statistical methods designed to preserve privacy but which come at the cost of distorting the data. We explore the extent to which spatial anonymization methods to preserve privacy in the large-scale surveys supported by the World Bank Living Standards Measurement Study-Integrated Surveys on Agriculture (LSMS-ISA) introduce measurement error in econometric estimates when that survey data is integrated with remote sensing weather data. Guided by a pre-analysis plan, we produce 90 linked weather-household datasets that vary by the spatial anonymization method and the remote sensing weather product. By varying the data along with the econometric model we quantify the magnitude and significance of measurement error coming from the loss of accuracy that results from privacy protection measures. We find that spatial anonymization techniques currently in general use have, on average, limited to no impact on estimates of the relationship between weather and agricultural productivity. However, the degree to which spatial anonymization introduces mismeasurement is a function of which remote sensing weather product is used in the analysis. We conclude that care must be taken in choosing a remote sensing weather product when looking to integrate it with publicly available survey data.
    • An isotope study of the Shule River Basin, Northwest China: Sources and groundwater residence time, sulfate sources and climate change

      Xie, Cong; Zhao, Liangju; Eastoe, Christopher J.; Wang, Ninglian; Dong, Xiying; Department of Geosciences, University of Arizona (Elsevier BV, 2022-09)
      Isotopes (δ18O and δD, δ34SSO4 and δ18OSO4, tritium and 14C) were employed to reveal moisture sources in precipitation and sources of surface water and groundwater, as well as groundwater residence times and sulfate sources in the Shule River Basin (SRB). Groundwater originates in the Qilian Mountains as high-altitude precipitation and meltwater from ice archives. The local meteoric water line (LMWL) is δD = 7.8δ18O + 18.1. Precipitation from westerly circulation has a characteristic annual cycle of δ18O and δD, high (δ18O > −5‰) in summer and low (δ18O < −10‰) at other times. This pattern was interrupted by an incursion of the Indian summer monsoon in August 2018, resulting in abnormally low δ18O and δD values. Surface water in the upper SRB yields an evaporation trend of slope near 5, with an origin near δ18O = −10‰ on the LMWL. Other catchments of similar altitude in the Qilian Mountains have evaporation trends with different origin points, indicating different input fractions of meltwater from ancient ice for each catchment. Groundwater δ18O and δD data plot along mixing trends, different in each sub-basin, between three water types: (1) recent Shule River runoff; (2) water like that archived in the Dunde ice sheet, representing precipitation over the last 12 ka; and (3) evaporated water that cannot be explained as precipitation from the last 12 ka. Type (3) water originated as water with δ18O values between −14 and −20‰ on the LMWL, and may represent incursion of monsoonal circulation prior to 12 ka. Tritium and 14C data identify post-bomb recharge, but 14C is of limited use in dating older groundwater mixtures. Sulfate isotopes (δ34SSO4 and δ18OSO4) in dissolved sulfate from groundwater and surface water indicate mixing of sulfur derived from evaporite and sulfide, but do not identify sulfate pollution from fertilizer. Future climate change may lead to water shortage as ancient ice is consumed by melting.
    • The process mineralogy of leaching sandstone-hosted uranium-vanadium ores

      Radwany, Molly R.; Barton, Isabel F.; Department of Mining & Geological Engineering, University of Arizona (Elsevier BV, 2022-09)
      In the United States, sandstone-hosted ore deposits of the Paradox Basin (Colorado Plateau) are major resources of uranium and vanadium, two metals important to green energy among other applications. Despite historic and current mining interest, and their significance as major domestic resources of critical elements, the geometallurgy of these deposits has received little study. This article documents the geometallurgy and process mineralogy of the U-V ores and identifies the principal barriers to optimal recovery by acid leaching. Most of the metals occur as pitchblende (mixed uranium oxide-silicate), V-hydroxides, V-bearing phyllosilicates, and diverse vanadates of U, Pb, Cu, and other metals. Commercial extraction is by two-stage heated tank leaching with H2SO4 and NaClO3, yielding high U but lower V recovery (70–75% in the industrial operation). Laboratory leaching experiments coupled with comparisons of head and residue mineralogy indicate that the unrecovered U consists of micron-scale pitchblende grains locked within quartz and other insoluble minerals. The principal cause of suboptimal V recovery is the V-phyllosilicates, which show variable but generally poor solubility at room temperatures. An ancillary cause is locking of a small amount of fine-grained V-hydroxide and pitchblende by authigenic quartz and V-phyllosilicates. Comparison with other global V resources suggests that variable solubility of V-phyllosilicate ore minerals may also diminish recovery from more common ore deposit types, such as V hosted in black shales or stone coal, particularly in heap leaching of low-grade ores at coarse grain sizes.
    • The assessment of memes as digital multimodal composition in L2 classrooms

      Ryu, Jieun; Kim, Young Ae; Eum, Seungmin; Park, Seojin; Chun, Sojung; Yang, Sunyoung; University of Arizona (Elsevier BV, 2022-09)
      Digital multimodal writing has become predominant in our students’ lives in and outside the L2 classrooms. While many L2 educators integrate various multimodal projects into their curriculum, internet memes and their assessment have not been explored in depth in L2 settings, although memes have potential to be valuable multimodal writing tasks. The purpose of this study is to better understand how memes can be incorporated and assessed in L2 classrooms. Twenty-seven student-created memes in a low-intermediate Korean as a Foreign Language course at a large university were collected and analyzed. The findings indicated that the student-created memes successfully addressed the multimodal aspect of the meme genre, universal and specific cultural references, and language aspects specific to the genre of memes. Our analyses of the memes suggest three key components to assess this multimodal writing project in addition to its overall task/functions: 1) multimodal aspects that include understanding the interplay between multiple modes for an effective message in a given context; 2) cultural aspects, demonstrating cultural knowledge and its application, recognizing the semiotic importance of multimodal expression in the target community; and 3) language aspects as an effective communication medium, demonstrating genre knowledge of the specific task and language accuracy.
    • ‘Earning your scars’: An exploratory interview study of design for manufacturing at hardware startups

      Budinoff, Hannah D.; Kramer, Julia; Department of Systems and Industrial Engineering, University of Arizona (Springer Science and Business Media LLC, 2022-08-26)
      Although many design for manufacturing tools and methods have been developed, it is unclear if engineers at startups widely use these design support techniques. We interviewed twelve engineers employed at startups to better identify common practices related to design for manufacturing. Specifically, we sought to learn the design for manufacturing strategies and tools used, and the timing of considering manufacturing constraints—such as process cost and geometry restrictions—in startups’ new product development processes. Interviews were analyzed using an inductive coding approach. All interviewees viewed design for manufacturing as being necessary for a successful product launch, but the implementation of considering manufacturing constraints varied. Interviewees mainly learned of the importance of design for manufacturing through negative personal design experiences where they did not emphasize the consideration of manufacturing constraints, a process which was described as “earning scars.” Formal education was viewed by interviewees as having limited practical utility, and startups’ staffing and funding constraints contributed to informal new product development processes and design practices. We identified ten emergent informal design for manufacturing strategies employed at startups, with most strategies relying heavily on consulting external manufacturing experts. We noted only a limited use of design for manufacturing tools, such as manufacturing simulation software and cost modeling. Insights from this paper can lead to better educational practices, contribute to more contextualized advising of startups, and guide other resource-constrained design teams.
    • Determinant of the Finite Volume Laplacian

      Doehrman, Thomas; Glickenstein, David; Mathematics Department, University of Arizona (Springer Science and Business Media LLC, 2022-08-26)
      The finite volume Laplacian can be defined in all dimensions and is a natural way to approximate the operator on a simplicial mesh. In the most general setting, its definition with orthogonal duals may require that not all volumes are positive; an example is the case corresponding to two-dimensional finite elements on a non-Delaunay triangulation. Nonetheless, in many cases two- and three-dimensional Laplacians can be shown to be negative semidefinite with a kernel consisting of constants. This work generalizes work in two dimensions that gives a geometric description of the Laplacian determinant; in particular, it relates the Laplacian determinant on a simplex in any dimension to certain volume quantities derived from the simplex geometry.
    • Incorporating habitat suitability, landscape distance, and resistant kernels to estimate conservation units for an imperiled terrestrial snake

      Bauder, Javan M.; Chandler, Houston C.; Elmore, Michele L.; Jenkins, Christopher L.; U.S. Geological Survey, Arizona Cooperative Fish and Wildlife Research Unit, University of Arizona; School of Natural Resources and the Environment, University of Arizona (Springer Science and Business Media LLC, 2022-08-25)
      Context: Wildlife distributions are often subdivided into discrete conservation units to aid in implementing management and conservation objectives. Habitat suitability models, resistance surfaces, and resistant kernels provide tools for delineating spatially explicit conservation units but guidelines for parameterizing resistant kernels are generally lacking. Objectives: We used the federally threatened eastern indigo snake (Drymarchon couperi) as a case study for calibrating resistant kernels using observed movement data and resistance surfaces to help delineate habitat-based conservation units. Methods: We simulated eastern indigo snake movements under different resistance surface and resistant kernel parameterizations and selected the scenario that produced simulated movement distances that best approximated the maximum observed annual movement distance. We used our calibrated resistant kernel to model range-wide connectivity and compared delineated conservation units to Euclidean distance-based population units from the recent eastern indigo snake species status assessment (SSA). Results: We identified a total of 255 eastern indigo snake conservation units, with numerous large (2500–5000 ha of suitable habitat) conservation units across the eastern indigo snake distribution. There was substantial variation in the degree of overlap with the SSA population units likely reflecting the spatial heterogeneity in habitat suitability and landscape resistance. Conclusion: Our calibration approach is widely applicable to other systems for parameterizing biologically meaningful resistant kernels. Our conservation units can be used to prioritize future eastern indigo snake conservation efforts, identify areas where more survey work is needed, or identify small, isolated populations with high extinction risks.