Ninth and Tenth Order Virial Coefficients for Hard Spheres in D Dimensions

We evaluate the virial coefficients B_k for k<=10 for hard spheres in dimensions D=2,...,8. Virial coefficients with k even are found to be negative when D>=5. This provides strong evidence that the leading singularity for the virial series lies away from the positive real axis when D>=5. Further analysis provides evidence that negative virial coefficients will be seen for some k>10 for D=4, and there is a distinct possibility that negative virial coefficients will also eventually occur for D=3.Comment: 33 pages, 12 figure

Dynamics of Change in Spatial Dependencies in Blood Donation System in Poland

Blood donation allows to obtain blood and its components from healthy people in a bid to help treatment of anonymous individuals, relying on timely and sufficient supplies of matching blood. Being a social initiative, it depends on multiple factors. Those factors are possible to be shaped and are subject to research. This paper aims to present the dynamics of change in spatial dependencies determining development of blood donation in Poland from 2005 to 2010. Spatial analysis of data enables identification of similarities and differences between voivodeships in a given period. Testing of hypothesis concerning spatial autocorrelation was carried out using tools of spatial statistics. This paper's subject matter concentrates on pointing towards the direction and extent of changes illustrated with an example of analysis investigating the number of blood donations per hospital bed in wards with high demand on blood and its components. The number of blood donors per 1000 residents in 18 - 65 age was also analysed.Krwiodawstwo jest sposobem pozyskiwania krwi i jej składników od osób zdrowych na rzecz anonimowych osób, których leczenie jest uwarunkowane podaniem właściwej krwi w odpowiednim czasie oraz ilości. Jako akcja społeczna uwarunkowana jest od wielu czynników, będących przedmiotem kształtowania oraz badania. Celem niniejszego opracowania jest przedstawienie dynamiki zmian zależności przestrzennej w zakresie poziomu rozwoju krwiodawstwa w Polsce w latach 2005 - 2010. Analiza przestrzenna danych umożliwia określenie podobieństw i różnic między województwami w badanym okresie. Za pomocą narzędzi statystyki przestrzennej została zweryfikowana hipoteza o występowaniu autokorelacji przestrzennej. Przedmiotem opracowania jest wskazanie kierunku oraz zakresu zmian na przykładzie analizy zróżnicowania liczby donacji krwi przypadającej na łóżko szpitalne w oddziałach o wysokim zapotrzebowaniu na krew i jej składniki oraz liczby dawców przypadających na 1000 mieszkańców w wieku 18 -65

Solving large scale linear programming problems

The interior point method (IPM) is now well established as a computationaly com-petitive scheme for solving very large scale linear programming problems. The leading variant of the IPM is the primal dual predictor corrector algorithm due to Mehrotra. The main computational efforts in this algorithm are the repeated calculation and solution of a large sparse positive definite system of equations. We describe an implementation of this algorithm for vector processors. At the heart of the implementation is a vectorized matrix multiplication and Cholesky factorization for sparse matrices. We identify the parts where vectorization can be beneficial and discuss in details the merits of alternative vectorization techniques. We show that the best way to utilize a vector processor is by exploiting dense computation within the sparse framework and by unrolling loop operations. We further present an extended definition of supernodes, and describe an implementation based on this new approach. We show that although this approach requires more memory it can increase the scope of dense computation substantially with out adding extra operations. Performance results on standard industrial test problems and comparison between an algorithm that utilizes the extended supernodes and one that utilizes standard supernodes are presented and discussed

Summary of investigations of light scattering in highly reflecting pigmented coatings

Light scattering in highly reflecting pigmented coatings - silver bromide and particle suspensions and paint film

Water vapor diffusion in Mars subsurface environments

The diffusion coefficient of water vapor in unconsolidated porous media is measured for various soil simulants at Mars-like pressures and subzero temperatures. An experimental chamber which simultaneously reproduces a low-pressure, low-temperature, and low-humidity environment is used to monitor water flux from an ice source through a porous diffusion barrier. Experiments are performed on four types of simulants: 40–70 µm glass beads, sintered glass filter disks, 1–3 µm dust (both loose and packed), and JSC Mars–1. A theoretical framework is presented that applies to environments that are not necessarily isothermal or isobaric. For most of our samples, we find diffusion coefficients in the range of 2.8 to 5.4 cm^2 s^-1 at 600 Pascal and 260 K. This range becomes 1.9–4.7 cm^2 s^-1 when extrapolated to a Mars-like temperature of 200 K. Our preferred value for JSC Mars–1 at 600 Pa and 200 K is 3.7 ± 0.5 cm^2 s^-1. The tortuosities of the glass beads is about 1.8. Packed dust displays a lower mean diffusion coefficient of 0.38 ± 0.26 cm^2 s^-1, which can be attributed to transition to the Knudsen regime where molecular collisions with the pore walls dominate. Values for the diffusion coefficient and the variation of the diffusion coefficient with pressure are well matched by existing models. The survival of shallow subsurface ice on Mars and the providence of diffusion barriers are considered in light of these measurements

Simulating Three-Dimensional Hydrodynamics on a Cellular-Automata Machine

We demonstrate how three-dimensional fluid flow simulations can be carried out on the Cellular Automata Machine 8 (CAM-8), a special-purpose computer for cellular-automata computations. The principal algorithmic innovation is the use of a lattice-gas model with a 16-bit collision operator that is specially adapted to the machine architecture. It is shown how the collision rules can be optimized to obtain a low viscosity of the fluid. Predictions of the viscosity based on a Boltzmann approximation agree well with measurements of the viscosity made on CAM-8. Several test simulations of flows in simple geometries -- channels, pipes, and a cubic array of spheres -- are carried out. Measurements of average flux in these geometries compare well with theoretical predictions.Comment: 19 pages, REVTeX and epsf macros require

Bulk and shear relaxation in glasses and highly viscous liquids

The ratio between the couplings of a relaxational process to compression and shear, respectively, is calculated in the Eshelby picture of structural rearrangements within a surrounding elastic matrix, assuming a constant density of stable structures in distortion space. The result is compared to experimental data for the low-temperature tunneling states in glasses and to Prigogine-Defay data at the glass transition from the literature.Comment: 6 pages, 2 figures, 53 references; version after understanding the Prigogine-Defay ratio at the glass transition in the accompanying paper arXiv:1203.3555 [cond-mat.dis-nn

Effect of pressure on the electronic structure of hcp Titanium

The effect of pressure on the hexagonal close-packed structure of titanium is investigated. The lattice parameters of the equilibrium structure were determined in terms of the Gibbs free energy using the Epitaxial Bain Path method. When this process was repeated for several pressures, the effect of pressure on the lattice parameters was revealed. The calculated lattice parameters were in good agreement with the experimental and theoretical results. The effects of pressure on parameters depending on the electronic structure such as conductivity and resistivity in the ground state were also investigated up to 30 GPa using density functional theory.Comment: 7 pages, 7 figure