Fast Fourier Transform simulation techniques for Coulomb gases

An improved approach to updating the electric field in simulations of Coulomb gases using the local lattice technique introduced by Maggs and Rossetto [A.C. Maggs, V. Rossetto, Phys. Rev. Lett. 88 (2002) 196402] is described and tested. Using the Fast Fourier Transform (FFT) an independent configuration of electric fields subject to Gauss' law constraint can be generated in a single update step. This FFT based method is shown to outperform previous approaches to updating the electric field in the simulation of a basic test problem in electrostatics of strongly correlated systems.     

A low-cost, accurate and non-intercepting continuous method for beam current measurements in a high-current ion implanter

The development of a low-cost, accurate, non-intercepting continuous method for measuring the beam current in a high-current ion implanter is described. The method, named a differential current monitor, is based on the electric charge conservation principle, applied to the currents that flow in the implanter electrical system, due to the acceleration voltage applied to the ion beam and the leakage currents to ground. This method allows for continuous measurement of the ion beam current without intercepting it. Since its installation, it is possible to accurate measure ion beam currents from tens of μA to mA, which is the normal range for this type of system.     

Implementing peridynamics within a molecular dynamics code

Peridynamics (PD) is a continuum theory that employs a nonlocal model to describe material properties. In this context, nonlocal means that continuum points separated by a finite distance may exert force upon each other. A meshless method results when PD is discretized with material behavior approximated as a collection of interacting particles. This paper describes how PD can be implemented within a molecular dynamics (MD) framework, and provides details of an efficient implementation. This adds a computational mechanics capability to an MD code, enabling simulations at mesoscopic or even macroscopic length and time scales.     

一种提高Power VDMOSFET栅电荷性能的新结构

文章提出一种减小VDMOSFET栅电荷（Qg）的新结构，通过二维数值模拟：相对于常规VDMOSFET，该结构将栅电荷降低42．93％，器件优值（FOM=Qg＊Ron）降低37．05％。我们分析了新结构的主要特性，并与常规VD-MOSFET进行了比较和参数优化分析。     

Application of a chronoamperometric measurement to the on-line monitoring of a lithium metal reduction for uranium oxide

Both a potentiometric and a chronoamperometric electrochemical technique have been applied in an attempt to develop an efficient method for an on-line monitoring of a lithium metal reduction process of uranium oxides at a high-temperature in a molten salt medium. As a result of this study, it was concluded that the chronoamperometric method provided a simple and effective way for a direct on-line monitoring measurement of a lithium metal reduction process of uranium oxides at 650 °C by the measuring electrical currents dependency on a variation of the reduction time for the reaction. A potentiometric method, by adopting a homemade oxide ion selective electrode made of ZrO₂ stabilized by a Y₂O₃ doping, however, was found to be inappropriate for an on-line monitoring of the reduction reaction of uranium oxide in the presence of lithium metal due to an abnormal behavior of the adopted electrodes. The observed experimental results were discussed in detail by comparing them with previously published experimental data.     

A program to generate a basis set adaptive radial quadrature grid for density functional theory

We present an automatic quadrature routine (AQR) which generates an atomic basis set adaptive radial quadrature grid for the numerical evaluation of molecular integrands in density functional theory. Unlike the popular radial grids that are tuned to a particular class of integrands and rely on a fixed selection of points, our grid adapts itself automatically to the atomic shell structure of any radial integrand and determines the best number of quadrature points that provides user specified accuracy. We evaluate the performance of our radial grid on various tight, diffuse, and noble gas atom radial integrands. We conclude that the radial quadrature grid generated by our AQR is generally comparable to and sometimes better than the best ranked popular radial grids in efficiency and reliability.     

An enhanced version of SMMP—open-source software package for simulation of proteins

We describe a revised and updated version of the program package SMMP (Simple Molecular Mechanics for Proteins) [F. Eisenmenger, U.H.E. Hansmann, Sh. Hayryan, C.-K. Hu, Comput. Phys. Comm. 138 (2001) 192-212]. SMMP is an open-source FORTRAN package for molecular simulation of proteins within the standard geometry model. It is designed as a simple and inexpensive tool for researchers and students to become familiar with protein simulation techniques. This announcement describes the first major revision of this software package and its newly added features.

Program summary

Title of program:SMMPCatalogue identifier:ADOJ₋v2₋0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADOJ_v2_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandOperating system under which the program has been tested:LINUX systemProgramming language used:FORTRANComputer:PC PentiumNumber of lines in distributed program, including test data, etc.:18 492Number of bytes in distributed program, including test data, etc.:278 995Distribution format:ASCIICard punching code:ASCIICatalogue Identifier of previous version:ADOJJournal Reference of previous version:F. Eisenmenger, U.H.E. Hansmann, Sh. Hayryan, C.-K. Hu, Comput. Phys. Comm. 138 (2001) 192-212Does the new version supersede the previous version?:YesNature of physical problem:Molecular mechanics computations and Monte Carlo simulation of proteinsReasons for the new version:Increased functionalitySummary of revisions:Changes in energy function and protein representation; differences in program structure and organization; new functionalities added; miscellaneous changes and additionsMethod of solution:Utilizes ECEPP2/3 and FLEX potentials. Includes Monte Carlo simulation algorithms for canonical, as well as for generalized ensemblesRestrictions on the complexity of the problem:The consumed CPU time increases with the size of protein moleculeTypical running time:Depends on the size of the molecule under simulationUnusual features of the program:No     

Molecular dynamics simulation of the pressure-volume-temperature data of xenon for a nuclear fuel

The exact equation of state for the fission gas is necessary for the accurate prediction of the fission gas behavior in a nuclear fuel. However, certain kinds of extrapolating data are used to construct and verify the equations of state for the fission gas because experimental data are very limited at high temperatures and pressures that are encountered in the nuclear fuel. To fill the lack of experimental data for the fission gas, the behavior of Xe gas atoms was investigated by molecular dynamics simulation assuming an exponential-six potential. The molecular dynamics simulation produced reasonable pressure-volume-temperature data for Xe and the simulation results were compared with existing equations of state for Xe.     

Interference and shadow effects in the production of light by charged particles in optical fibers

A charged particle passing through or near a narrow optical fiber induces, by polarisation, coherent light guided by the fiber. In the limit of zero crossing angle, the radiation tends towards a Cherenkov radiation with a discrete spectrum, studied by different authors. If the particle crosses a bent fiber at regularly spaced points, interference gives quasi-monochromatic lines. If the particle passes near an end of the fiber, light is produced by the capture of virtual photons through the end face. An alternative way consists in sticking a metallic ball to the fiber: the passing particle induces plasmons which are then evacuated as light in the fiber. Interferences can occur between lights from several ends or balls. Applications of these various light signals to beam diagnostics are discussed. The shadow effect, which reduces the photon yield when the particle runs parallel to a row of balls, is pointed out and an upper bound -dE/dz≤C(Ze/b)² for the particle energy loss is conjectured (Ze is the particle charge, b the impact parameter and C a numerical constant). This bound should also apply to other kinds of light sources, in particular to Smith-Purcell radiation.