Thermodynamic Modeling of Uranium and Oxygen Containing Ternary Systems with Gadolinium, Lanthanum, and Thorium

The CALPHAD method is used to assess the thermodynamic properties and phase relations in the U-M-O system where M = Gd, La, and Th. A compound energy formalism (CEF) model for fluorite UO2±x [urania] is extended to represent the complex U1-yMyO2±x [urania solid solution] phases. The lattice stabilities for fictive GdO2 [gadolinia] and LaO2 [lanthana] fluorite structure compounds are calculated from density functional theory (DFT) for use in the CEF for U1-yMyO2±x [urania solid solution phase] while U6+ [uranium 6 plus cation] is introduced into the cation sublattice of the CEF for U1-yMyO2±x [urania solid solution phase] to better reproduce phase relations in U-Ln-O systems at high fixed trivalent Ln [lanthanide] compositions. Tentative Gibbs functions and CEF representations for the fluorite derivative rhombohedral phases were developed and the two-sublattice liquid model (TSLM) was used to describe the melt. Equilibrium oxygen pressures over U1-yThyO2±x [urania thoria solid solution] were obtained from thermogravimetric measurements and used together with those reported in the literature, phase relations, and other experimentally determined thermodynamic values to fit adjustable parameters of the CEF and TSLM along with the standard state enthalpy and entropy of the Gibbs functions representing the stoichiometric compounds. The models can be extended to include other actinides and fission products to develop higher order multi-component system assessments to support further experimental efforts and the development of multi-physics fuel performance simulation codes

Examining the accuracy of the normal approximation to the poisson random variable

Because the Poisson distribution is discrete, it is sometimes useful to use the continuous normal distribution as an approximation. In doing so, determining the accuracy of the approximation is important. Some issues of interest include: knowing how the error depends on the Poisson parameter, knowing when the approximation overestimates or underestimates the distribution, bounding the magnitude of the error, and determining if the approximation can be improved. This paper addresses these issues by examining how two types of absolute error measurements are affected by variations in the Poisson parameter; changes in the relative error are also examined. Generally, the error decays much like a power function of the parameter; therefore, curve fitting is used to bound the error. Finally, variations on the approximation are examined; these variations are often more accurate than the standard approximation

The Spacecraft Challenge: A Student Satellite Program Accelerator

Brigham Young University’s first smallsat project, like many university smallsat projects, faced significant personnel challenges. The time required for inexperienced undergraduates to become contributing team members, combined with moderate turnover, caused overruns in the budget and schedule. To find and train future team members for employment, the student team formed a club and instituted a peer-mentored, introductory-level challenge to design, build, and fly a miniature, fully-functional model spacecraft, in one semester. At very low cost, two annual rounds of the challenge provided more than 30 students with full-cycle, design-to-flight engineering experience. Leveraging this introductory experience, many participants have now contributed to more advanced smallsat projects. We describe the low-cost project and implementation of the challenge format along with recommendations for starting similar programs at other schools

Tools and terms for understanding illegal wildlife trade

Illegal wildlife trade (IWT) is a global conservation issue that threatens thousands of species, including fish, fungi, medicinal plants, and charismatic mammals. Despite widespread recognition of the problem, debates on the science and policy of IWT generally concentrate on a few high- profile species (eg rhinoceros, tigers, elephants) and often overlook or conflate complex IWT products, actors, networks, and contexts. A poor understanding of IWT is aggravated by the lack of systematic vocabulary and conceptual tools with which to analyze complex phenomena in a more structured way. We synthesize the available evidence on IWT across taxa and contexts into a typology- based framework that considers (1) the diversity of wildlife products; (2) the roles of various actors involved with IWT, including harvesters, intermediaries, and consumers; and (3) common IWT network configurations. We propose ways in which these tools can inform structured analyses of IWT, to help ensure more nuanced, appropriate, targeted, and effective responses to illegal wildlife harvest, trade, and use

Quantum Catalysis of Magnetic Phase Transitions in a Quantum Simulator

We control quantum fluctuations to create the ground state magnetic phases of a classical Ising model with a tunable longitudinal magnetic field using a system of 6 to 10 atomic ion spins. Due to the long-range Ising interactions, the various ground state spin configurations are separated by multiple first-order phase transitions, which in our zero temperature system cannot be driven by thermal fluctuations. We instead use a transverse magnetic field as a quantum catalyst to observe the first steps of the complete fractal devil's staircase, which emerges in the thermodynamic limit and can be mapped to a large number of many-body and energy-optimization problems.Comment: New data in Fig. 3, and much of the paper rewritte

Resolution independent curved seams in clothing animation using a regular particle grid

We present a method for representing seams in clothing animation, and its application in simulation level of detail. Specifically we consider cloth represented as a regular grid of particles connected by spring-dampers, and a seam specified by a closed set of parametric trim curves in the cloth domain. Conventional cloth animation requires the tessellation of seams so that they are handled uniformly by the dynamics process. Our goal is a seam definition which does not constrain the attached clothing panels to be of the same resolution, or even constant resolution, while not being a hindrance to the dynamics process. We also apply our seams to cloth defined on a regular grid, as opposed to the irregular meshes commonly used with seams. The determination of particles interior to the cloth panel can be done using wellknown graphics operations such as scan-conversion. Due to the particle-based nature of the simulation, the dynamics approach combines easily with existing implicit and explicit methods. Finally, because the seams are resolution independent, the particle density per clothing panel can be adjusted as desired. This gives rise to a simple application of the given seams approach illustrating how it may be used for simulation level of detail

Bud Bank Density Regulates Invasion by Exotic Plants

Grasslands and savannas, which cover as much as 30-50% of the earth's ice-free land area, are affected by global environmental changes including biological invasions. To test the role of bud banks, an important feature of native prairie communities, in regulating invasion by exotic plants under three levels of simulated grazing (no clipping, 28 day clipping interval, and 14 day clipping interval) I conducted a greenhouse microcosm study. Using native rhizomes planted into native prairie soil, I established bud bank densities of 0, 30, 60, and 100% of mean tallgrass prairie bud bank density. Seeds of three exotic species were sown into each microcosm. The number of emerging and established exotic plants in each microcosm was counted every 14 days. I measured the aboveground biomass of each species at the end of the growing season (22 weeks). Assessments of exotic plant emergence, establishment, survivorship, reproduction, and biomass based on these measurements were compared using analysis of variance. The effects of the bud bank on exotic plant emergence, establishment, and survivorship were inconsistent and relatively weak. However, reproduction and biomass of exotic species were strongly influenced by bud bank density. In the absence of clipping, the biomass of exotic species was 675% higher at the lowest bud bank density than at the highest density. Furthermore, I found evidence for an invasibility threshold between 0-30% of mean field bud bank density in tallgrass prairie. These findings improve our understanding of plant invasion and suggest that restoring and maintaining bud banks should be a priority for land managers seeking to prevent and limit plant invasions.Department of Natural Resource Ecology and Managemen

UNCOVERING THE TRADE OF WILD-COLLECTED ORNAMANTAL PLANTS IN THAILAND, INCLUDING IMPORTS FROM MYAN MAR AND LAO PDR

Ph.DDOCTOR OF PHILOSOPH

How do Microservices Evolve?:An Empirical Analysis of Changes in Open-Source Microservice Repositories

Context.Microservice architectures are an emergent service-oriented paradigm widely used in industry to develop and deploy scalable software systems. The underlying idea is to design highly independent services that implement small units of functionality and can interact with each other through lightweight interfaces.Objective.Even though microservices are often used with success, their design and maintenance pose novel challenges to software engineers. In particular, it is questionable whether the intended independence of microservices can actually be achieved in practice.Method.So, it is important to understand how and why microservices evolve during a system’s life-cycle, for instance, to scope refactorings and improvements of a system’s architecture or to develop supporting tools. To provide insights into how microservices evolve, we report a large-scale empirical study on the (co-)evolution of microservices in 11 open-source systems, involving quantitative and qualitative analyses of 7,319 commits.Findings.Our quantitative results show that there are recurring patterns of (co-)evolution across all systems, for instance, “shotgun surgery” commits and microservices that are largely independent, evolve in tuples, or are evolved in almost all changes. We refine our results by analyzing service-evolving commits qualitatively to explore the (in-)dependence of microservices and the causes for their specific evolution.Conclusion.The contributions in this article provide an understanding for practitioners and researchers on how microservices evolve in what way, and how microservice-based systems may be improved

Rogue Rotary - Modular Robotic Rotary Joint Design

This paper describes the design process from ideation to test validation for a singular robotic joint to be configured into a myriad of system level of robots