Thermomechanical Characterization and Modeling of Superelastic Shape Memory Alloy Beams and Frames.

Of existing applications, the majority of shape memory alloy (SMA) devices consist of beam (orthodontic wire, eye glasses frames, catheter guide wires) and framed structures (cardiovascular stents, vena cava filters). Although uniaxial tension data is often sufficient to model basic beam behavior (which has been the main focus of the research community), the tension-compression asymmetry and complex phase transformation behavior of SMAs suggests more information is necessary to properly model higher complexity states of loading. In this work, SMA beams are experimentally characterized under general loading conditions (including tension, compression, pure bending, and buckling); furthermore, a model is developed with respect to general beam deformation based on the relevant phenomena observed in the experimental characterization. Stress induced phase transformation within superelastic SMA beams is shown to depend on not only the loading mode, but also kinematic constraints imposed by beam geometry (such as beam cross-section and length). In the cases of tension and pure bending, the structural behavior is unstable and corresponds to phase transformation localization and propagation. This unstable behavior is the result of a local level up-down-up stress/strain response in tension, which is measured here using a novel composite--based experimental technique. In addition to unstable phase transformation, intriguing post-buckling straightening is observed in short SMA columns during monotonic loading (termed unbuckling here). Based on this phenomenological understanding of SMA beam behavior, a trilinear based material law is developed in the context of a Shanley column model and is found to capture many of the relevant features of column buckling, including the experimentally observed unbuckling behavior. Due to the success of this model, it is generalized within the context of beam theory and, in conjunction with Bloch wave stability analysis, is used to model and design SMA honeycombs.PHDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113455/1/watkinrt_1.pd

Photometric Investigations of Lunar Landing Sites and Silicic Regions using LRO Narrow Angle Camera Images

The reflectance properties of a planetary surface are related to the physical and compositional properties of that body. Photometry is a powerful method for determining differences in composition and regolith structure, and photometric data from orbital images coupled with soil sample data can greatly enhance our understanding of the regolith properties of our nearest neighbor, the Moon. At the time of writing, the United States has no operating missions on the Moon and no future plans to send robots or humans to study our nearest neighbor, so we must rely on remote sensing data to provide us with information about the lunar surface. This dissertation uses photometric studies of high-resolution Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) images and Hapke photometric modeling to understand the behavior and composition of lunar soil at spacecraft landing sites and areas of non-mare volcanism on the Moon. This work has implications for future mission planning and implementation, including landing site selection, landing safety, and sampling strategies. Topics include: i) the effects of rocket exhaust on lunar soil reflectance properties at the Apollo, Luna, and Surveyor landing sites, ii) photometric analysis of the recent Chang\u27e-3 landing site and comparison of reflectance alterations with those of older landing sites, and iii) compositional variations at regions of non-mare volcanism using NAC photometry and spectral analysis of glassy analog materials. Rocket exhaust from the Apollo, Luna, and Surveyor descent engines disturbed the regolith at their landing sites, causing the soil to become more reflective. These surface alterations, which we call blast zones , are still evident in NAC images, and I use photometry and Hapke modeling to show that the increase in reflectance was caused by smoothing, destruction of fine-scale surface structure (i.e., fairy-castle structure), and possibly redistribution of fine particles. The recent Chinese Chang\u27e-3 spacecraft also disturbed the soil at its landing site in the same fashion, and I show that the reflectance changes and area of disturbance are in family with those of older landing sites, indicating reflectance changes have not changed on the order of decades. I determine the relationship between lander mass and blast zone area and use this to make predictions of the area of soil disturbance for future missions. Finally, using photometric methods optimized from landing site studies, I place compositional constraints on areas of non-mare and intrusive volcanism and confirm that these areas exhibit a range of evolved silicic compositions (dacite, andesite, and rhyolite) and pyroclastic deposits, and should be considered as scientific targets for future landed sample-return missions

Lunar Crater Identification in Digital Images

It is often necessary to identify a pattern of observed craters in a single image of the lunar surface and without any prior knowledge of the camera's location. This so-called "lost-in-space" crater identification problem is common in both crater-based terrain relative navigation (TRN) and in automatic registration of scientific imagery. Past work on crater identification has largely been based on heuristic schemes, with poor performance outside of a narrowly defined operating regime (e.g., nadir pointing images, small search areas). This work provides the first mathematically rigorous treatment of the general crater identification problem. It is shown when it is (and when it is not) possible to recognize a pattern of elliptical crater rims in an image formed by perspective projection. For the cases when it is possible to recognize a pattern, descriptors are developed using invariant theory that provably capture all of the viewpoint invariant information. These descriptors may be pre-computed for known crater patterns and placed in a searchable index for fast recognition. New techniques are also developed for computing pose from crater rim observations and for evaluating crater rim correspondences. These techniques are demonstrated on both synthetic and real images

Microbial therapeutics designed for infant health

Acknowledgment of the gut microbiome as a vital asset to health has led to multiple studies attempting to elucidate its mechanisms of action. During the first year of life, many factors can cause fluctuation in the developing gut microbiome. Host genetics, maternal health status, mode of delivery, gestational age, feeding regime, and perinatal antibiotic usage, are known factors which can influence the development of the infant gut microbiome. Thus, the microbiome of vaginally born, exclusively breastfed infants at term, with no previous exposure to antibiotics, either directly or indirectly from the mother, is to be considered the “gold standard.” Moreover, the use of prebiotics as an aid for the development of a healthy gut microbiome is equally as important in maintaining gut homeostasis. Breastmilk, a natural prebiotic source, provides optimal active ingredients for the growth of beneficial microbial species. However, early life disorders such as necrotising enterocolitis, childhood obesity, and even autism have been associated with an altered/disturbed gut microbiome. Subsequently, microbial therapies have been introduced, in addition to suitable prebiotic ingredients, which when administered, may aid in the prevention of a microbial disturbance in the gastrointestinal tract. The aim of this mini-review is to highlight the beneficial effects of different probiotic and prebiotic treatments in early life, with particular emphasis on the different conditions which negatively impact microbial colonisation at birth

Performance of a Quaternary Logic Design

This paper analyzes the performance of a quaternary logic circuit and its components. The multi-valued logic design consisting of two drivers and a transistor matrix is simulated using Mentor Graphic software. Functional operation of the circuit is shown and propagation delay and power consumption are determined. The design is dependent on the voltage values for the multi-valued logic. Three logic cases are investigated. The performance of the logic circuit as a quaternary difference calculator is described

Effects of sample handling and storage on quantitative lipid analysis in human serum

There is sparse information about specific storage and handling protocols that minimize analytical error and variability in samples evaluated by targeted metabolomics. Variance components that affect quantitative lipid analysis in a set of human serum samples were determined. The effects of freeze-thaw, extraction state, storage temperature, and freeze-thaw prior to density-based lipoprotein fractionation were quantified. The quantification of high abundance metabolites, representing the biologically relevant lipid species in humans, was highly repeatable (with coefficients of variation as low as 0.01 and 0.02) and largely unaffected by 1-3 freeze-thaw cycles (with 0-8% of metabolites affected in each lipid class). Extraction state had effects on total lipid class amounts, including decreased diacylglycerol and increased phosphatidylethanolamine in thawed compared with frozen samples. The effects of storage temperature over 1week were minimal, with 0-4% of metabolites affected by storage at 4°C, −20°C, or −80°C in most lipid classes, and 19% of metabolites in diacylglycerol affected by storage at −20°C. Freezing prior to lipoprotein fractionation by density ultracentrifugation decreased HDL free cholesterol by 37% and VLDL free fatty acid by 36%, and increased LDL cholesterol ester by 35% compared with fresh samples. These findings suggest that density-based fractionation should preferably be undertaken in fresh serum samples because up to 37% variability in HDL and LDL cholesterol could result from a single freeze-thaw cycle. Conversely, quantitative lipid analysis within unfractionated serum is minimally affected even with repeated freeze-thaw cycle

The Plethora of Science Afforded by a Lunar Swirl : A White Paper to the Planetary Science Decadal Survey Committee

Whitepaper #166 submitted to the Planetary Science and Astrobiology Decadal Survey 2023-2032. Topics: surface/geological evolution; Mercury and/or the Moon; other science themes: Physics, Heliophysics, Magnetohydrodynamics, Volcanology, ISRU, PhotometryLunar swirls should be the top priority target of the next lunar mission. The swirls are a fascinating lunar feature, as well as a laboratory to study the solar wind, space weathering, plasma weathering, and plasma kinetics. In this white paper we present examples of broad scientific interest in lunar swirls as well as some example mission types

Activities of the Grand Portage Reservation (Minnesota) to Protect and Restore the Aquatic Habitat in Lake Superior

Presented at the National Forum on Tribal Environmental Science, September 27, 2006.This is a 30-slide Powerpoint presentation summarizing the Grand Portage natural resources, wetlands, air quality, energy, solid waste and water quality program details; the cooperative agreement between the Grand Portage tribal authority and Minnesota Pollution Control Agency; the no discharge zone; and nonpoint source pollution efforts. Also briefly summarizes activities of the 1854 Treaty Authority

Relaxed blue ellipticals: accretion-driven stellar growth is a key evolutionary channel for low mass elliptical galaxies

How elliptical galaxies form is a key question in observational cosmology. While the formation of massive ellipticals is strongly linked to mergers, the low mass (Mstar < 10^9.5 MSun) regime remains less well explored. In particular, studying elliptical populations when they are blue, and therefore rapidly building stellar mass, offers strong constraints on their formation. Here, we study 108 blue, low-mass ellipticals (which have a median stellar mass of 10^8.7 MSun) at z < 0.3 in the COSMOS field. Visual inspection of extremely deep optical HSC images indicates that less than 3 per cent of these systems have visible tidal features, a factor of 2 less than the incidence of tidal features in a control sample of galaxies with the same distribution of stellar mass and redshift. This suggests that the star formation activity in these objects is not driven by mergers or interactions but by secular gas accretion. We combine accurate physical parameters from the COSMOS2020 catalog, with measurements of local density and the locations of galaxies in the cosmic web, to show that our blue ellipticals reside in low-density environments, further away from nodes and large-scale filaments than other galaxies. At similar stellar masses and environments, blue ellipticals outnumber their normal (red) counterparts by a factor of 2. Thus, these systems are likely progenitors of not only normal ellipticals at similar stellar mass but, given their high star formation rates, also of ellipticals at higher stellar masses. Secular gas accretion, therefore, likely plays a significant (and possibly dominant) role in the stellar assembly of elliptical galaxies in the low mass regime.Comment: Published in MNRA