Multi-phase-field analysis of short-range forces between diffuse interfaces

We characterize both analytically and numerically short-range forces between spatially diffuse interfaces in multi-phase-field models of polycrystalline materials. During late-stage solidification, crystal-melt interfaces may attract or repel each other depending on the degree of misorientation between impinging grains, temperature, composition, and stress. To characterize this interaction, we map the multi-phase-field equations for stationary interfaces to a multi-dimensional classical mechanical scattering problem. From the solution of this problem, we derive asymptotic forms for short-range forces between interfaces for distances larger than the interface thickness. The results show that forces are always attractive for traditional models where each phase-field represents the phase fraction of a given grain. Those predictions are validated by numerical computations of forces for all distances. Based on insights from the scattering problem, we propose a new multi-phase-field formulation that can describe both attractive and repulsive forces in real systems. This model is then used to investigate the influence of solute addition and a uniaxial stress perpendicular to the interface. Solute addition leads to bistability of different interfacial equilibrium states, with the temperature range of bistability increasing with strength of partitioning. Stress in turn, is shown to be equivalent to a temperature change through a standard Clausius-Clapeyron relation. The implications of those results for understanding grain boundary premelting are discussed.Comment: 24 pages, 28 figure

Distinguished non-Archimedean representations

For a symmetric space (G,H), one is interested in understanding the vector space of H-invariant linear forms on a representation \pi of G. In particular an important question is whether or not the dimension of this space is bounded by one. We cover the known results for the pair (G=R_{E/F}GL(n),H=GL(n)), and then discuss the corresponding SL(n) case. In this paper, we show that (G=R_{E/F}SL(n),H=SL(n)) is a Gelfand pair when n is odd. When $n$ is even, the space of H-invariant forms on \pi can have dimension more than one even when \pi is supercuspidal. The latter work is joint with Dipendra Prasad

Pengaruh Variasi Masssa Serbuk Arang dan Kalsium Karbonat (Caco3) pada Proses Karburasi terhadap Sifat Mekanik Baja Karbon Sedang

The aim of this research is to acknowledge the insluence of the variation in the mass of CaCO3 as an energizer in the process of carburizing on the mechanical properties of medium carbon steel. The process of a carburizing uses a temperature of 9500C with a time holding of 3 hours. In this process, carbon is retrieved from a charcoal wood which then is extracted into fine powder, and it is mixed with CaCO3 as its energizer. The mass of calcium carbonate varies at 0%, 5%, 10%, and 15%, each mixed into the charcoal powder in different basins for the carburizing process. In this research, the mixture of characoal powder and the CaCO3 is added into the carbon steel in a furnace which is then heated at 9500C and it is quenched immediately after it is leated. Later on, the quenched material is tested for its hardnss Vickers and its tensile strength. The hardness Vickers of the unquenched carbon steel is 1478,57 N/mm2 and for tensile strength is 477,905 N/mm2. The result of the hardness Vickers before quenching is 967,52 N/mm2, 953,113 N/mm2, 963,644 N/mm2 for the various samples of 5%, 10%, and 15% of CaCO3. And the result after the material is quenched, is at 1585,307 N/mm2, 2143,142 N/mm2, 1883,442 N/mm2. The result for the tensile strength before quenching is at 465,625 N/mm2, 541,3 N/mm2, 492,535 N/mm2. Whereas after the process of quenching, the reading shows 502,285 N/mm2, 541,3 N/mm2 and 501,31 N/mm2

Financial Analysis of New Medicare and Medicaid Guidelines, Reimbursement Rates, and Increased Enrollment on Four Nebraska Clinics

Government health insurance plans such as Medicaid and Medicare were created with the intention of providing elderly, low-income, or disabled citizens with affordable and quality health insurance through government-contracted providers (Baicker et al., 2013). Medicare is a government health insurance program that provides healthcare to United States citizens 65 years and older, regardless of their income or past medical history. Medicaid was implemented as an assistance program to provide health insurance for low-income Americans and their families. Medicaid is administered by each state independently, which creates variation in reimbursement rates, services, and structure. (Grabowski, 2007). Providers accepting Medicare and Medicaid payments agree to receive lower reimbursement rates in comparison to private insurance. Private insurance programs offer providers rates based on group contracts and affiliated capitation programs and typically reimburse higher than government payment models (Mark et al., 2020). Providers see a significant revenue difference between private pay and government reimbursement. For an established patient office visit, commercial insurers paid an average of 126 percent of Medicare rates (Mark et al., 2020). For many providers, especially if they have an overabundance, or their patient base skews heavily on government patients, their revenues and financial well-being can be strained (Mark et al., 2020). Lower reimbursement, coupled with higher expenses of caring for these patients, complex CMS guidelines, and increased Medicare and Medicaid enrollment, often can jeopardize providers financially. This project aims to complete a financial impact assessment of four clinics to determine the impact of Medicare and Medicaid guidelines, reimbursement rates, and increased enrollment and apply that data to a financial decision tool that can assist in determining clinic decisions

Relativistic quantum plasma dispersion functions

Relativistic quantum plasma dispersion functions are defined and the longitudinal and transverse response functions for an electron (plus positron) gas are written in terms of them. The dispersion is separated into Landau-damping, pair-creation and dissipationless regimes. Explicit forms are given for the RQPDFs in the cases of a completely degenerate distribution and a nondegenerate thermal (J\"uttner) distribution. Particular emphasis is placed on the relation between dissipation and dispersion, with the dissipation treated in terms of the imaginary parts of RQPDFs. Comparing the dissipation calculated in this way with the existing treatments leads to the identification of errors in the literature, which we correct. We also comment on a controversy as to whether the dispersion curves in a superdense plasma pass through the region where pair creation is allowed.Comment: 16 pages, 1 figur