The impact of supercomputers on experimentation: A view from a national laboratory

The relative roles of large scale scientific computers and physical experiments in several science and engineering disciplines are discussed. Increasing dependence on computers is shown to be motivated both by the rapid growth in computer speed and memory, which permits accurate numerical simulation of complex physical phenomena, and by the rapid reduction in the cost of performing a calculation, which makes computation an increasingly attractive complement to experimentation. Computer speed and memory requirements are presented for selected areas of such disciplines as fluid dynamics, aerodynamics, aerothermodynamics, chemistry, atmospheric sciences, astronomy, and astrophysics, together with some examples of the complementary nature of computation and experiment. Finally, the impact of the emerging role of computers in the technical disciplines is discussed in terms of both the requirements for experimentation and the attainment of previously inaccessible information on physical processes

THE IMPACTS OF MARKET POWER AND EXCHANGE RATES ON PRICES OF EUROPEAN UNION SOYBEAN IMPORTS..

This study examines whether the EU, the world's largest importer, exercises market power over soybean imports. Results, based on 1975-2000 data, suggest that the EU has practiced price discrimination against imports from Argentina and Brazil. The evidence for the practice of pricing-to-market based on exchange rate changes is mixed.International Relations/Trade,

Strong Correlations Produce the Curie-Weiss Phase of Nax_{x}CoO2_2

Within the t-J model we study several experimentally accessible properties of the 2D-triangular lattice system Na$_x$CoO$_2$, using a numerically exact canonical ensemble study of 12 to 18 site triangular toroidal clusters as well as the icosahedron. Focusing on the doping regime of $x\sim0.7$, we study the temperature dependent chemical potential, specific heat, magnetic susceptibility and the dynamic Hall coefficient $R_H(T,\omega)$ as well as the magnetic field dependent thermopower. We find a crossover between two phases near $x \sim 0.75$ in susceptibility and field suppression of the thermopower arising from strong correlations. An interesting connection is found between the temperature dependence of the diamagnetic susceptibility and the Hall-coefficient. We predict a large thermopower enhancement, arising from {\em transport corrections} to the Heikes-Mott formula, in a model situation where the sign of hopping is reversed from that applicable to Na$_x$CoO$_2$.Comment: 5 pages, 4 figure

The Electrostatic Persistence Length Calculated from Monte Carlo, Variational and Perturbation Methods

Monte Carlo simulations and variational calculations using a Gaussian ansatz are applied to a model consisting of a flexible linear polyelectrolyte chain as well as to an intrinsically stiff chain with up to 1000 charged monomers. Addition of salt is treated implicitly through a screened Coulomb potential for the electrostatic interactions. For the flexible model the electrostatic persistence length shows roughly three regimes in its dependence on the Debye-H\"{u}ckel screening length, $\kappa^{-1}$.As long as the salt content is low and $\kappa^{-1}$ is longer than the end-to-end distance, the electrostatic persistence length varies only slowly with $\kappa^{-1}$. Decreasing the screening length, a controversial region is entered. We find that the electrostatic persistence length scales as $sqrt{\xi_p}/\kappa$, in agreement with experiment on flexible polyelectrolytes, where $\xi_p$ is a strength parameter measuring the electrostatic interactions within the polyelectrolyte. For screening lengths much shorter than the bond length, the $\kappa^{-1}$ dependence becomes quadratic in the variational calculation. The simulations suffer from numerical problems in this regime, but seem to give a relationship half-way between linear and quadratic. A low temperature expansion only reproduces the first regime and a high temperature expansion, which treats the electrostatic interactions as a perturbation to a Gaussian chain, gives a quadratic dependence on the Debye length. For a sufficiently stiff chain, the persistence length varies quadratically with $\kappa^{-1}$ in agreement with earlier theories.Comment: 20 pages LaTeX, 9 postscript figure

Ecological Studies of Wolves on Isle Royale, 1995-1996

Annual Report 1995-1996https://digitalcommons.mtu.edu/wolf-annualreports/1025/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 1991-1992

Annual Report 1991-1992https://digitalcommons.mtu.edu/wolf-annualreports/1029/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 1996-1997

Annual Report 1996-1997https://digitalcommons.mtu.edu/wolf-annualreports/1024/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 1989-1990

Annual Report 1989-1990 (Covering the thirty-second year of research)https://digitalcommons.mtu.edu/wolf-annualreports/1031/thumbnail.jp

Ecological Studies of Wolves on Isle Royale, 1997-1998

Annual Report 1997-1998https://digitalcommons.mtu.edu/wolf-annualreports/1023/thumbnail.jp