Statistical Analysis of Winter Sulphur Dioxide Concentration Data in Vienna

The paper describes two nonlinear regression models, applied to winter daily SO2 concentration data and to the corresponding meteorological data from the metropolitan area of Vienna. The first model accounts for the role of wind speed and temperature (a proxy for emissions due to residential heating) on average SO2 concentration in the area. The second regression has an additional wind direction input and tries to point out the contribution by the industrial emissions (located primarily near the south-eastern border of the area) to concentration in the most polluted subarea. Both models offer a satisfactory fitting performance (e.g., correlations around 0.85 between observed and regression values). However, since model validation is a critical point for regressions, sensitivity tests of model fitting performance are carried out by using various data sets for the estimation of regression coefficients. One of such tests points out that there is an "optimal length" of the data set to be used, namely neither a too short set nor a set including "too past" data offer a satisfactory fitting quality

Establishing Operational Models for Dynamic Compilation in a Simulation Platform

Abstract. In this paper we introduce a new approach to dynamic converting conceptual models in a simulation platform as the GAMA platform (represented in form of GAML syntax) into corresponding oper-ational models (represented in form of Java syntax). This approach aims at providing a more flexible solutions to actual simulation models imple-mented in a simulation platform as the GAMA. This new approach will facilitate the exhibits of a simulation platform to work with different types of simulation models represented in different forms of syntax

Large-Scale First-Principles Molecular Dynamics Simulations on the BlueGene/L Platform using the Qbox Code

We demonstrate that the Qbox code supports unprecedented large-scale First-Principles Molecular Dynamics (FPMD) applications on the BlueGene/L supercomputer. Qbox is an FPMD implementation specifically designed for large-scale parallel platforms such as BlueGene/L. Strong scaling tests for a Materials Science application show an 86% scaling efficiency between 1024 and 32,768 CPUs. Measurements of performance by means of hardware counters show that 37% of the peak FPU performance can be attained

Wigner high-electron-correlation regime of nonuniform density systems: A quantal-density-functional-theory study

The Wigner regime of a system of electrons in an external field is characterized by a low electron density and a high electron-interaction energy relative to the kinetic energy. The low-correlation regime is in turn described by a high electron density and an electron-interaction energy smaller than the kinetic energy. The Wigner regime of a nonuniform-electron-density system is investigated via quantal density functional theory (QDFT). Within QDFT, the contributions of electron correlations due to the Pauli exclusion principle, Coulomb repulsion, and correlation-kinetic effects are separately delineated and explicitly defined. The nonuniform-electron-density system studied is that of the Hooke\u27s atom in the Wigner regime, for which the exact wave function is derived. As such, the results of the QDFT analysis are exact. It is observed that in comparison to the low-correlation case, not only is the electron-interaction energy greater than the kinetic energy as a fraction of the total energy, but so are its individual Hartree, Pauli, and Coulomb components. The ionization potential as a fraction of the total energy too is greater. But most significantly, in the Wigner regime, the correlation-kinetic energy as a fraction of both the electron-interaction and the total energy is substantially greater than in the low-correlation case. Hence, we propose that the Wigner regime now also be characterized by a high correlation-kinetic energy. The kinetic energy as a fraction of the total energy, however, is less than in the low-correlation case. This fact and the high correlation-kinetic energy value in the Wigner regime is explained by the concept of “quantal compression” of the kinetic energy density derived from QDFT. The corresponding results for the low-correlation case are in turn a consequence of a “quantal decompression” of the kinetic energy density. From the QDFT analysis, the exact values for the Kohn-Sham theory “exchange-correlation” and “correlation” energy functionals of the density and their respective functional derivatives are also obtained. These results ought to be of value in the construction and testing of approximate energy functionals valid for the Wigner regime