4,585 research outputs found
An Overview of a Grid Architecture for Scientific Computing
This document gives an overview of a Grid testbed architecture proposal for
the NorduGrid project. The aim of the project is to establish an inter-Nordic
testbed facility for implementation of wide area computing and data handling.
The architecture is supposed to define a Grid system suitable for solving data
intensive problems at the Large Hadron Collider at CERN. We present the various
architecture components needed for such a system. After that we go on to give a
description of the dynamics by showing the task flow
Sliding of Electron Crystal of Finite Size on the Surface of Superfluid He-4 Confined in a Microchannel
We present a new study of the nonlinear transport of a two-dimensional
electron crystal on the surface of liquid helium confined in a 10
micrometer-wide channel in which the effective length of the crystal can be
varied from 10 to 215 micrometers. At low driving voltages, the moving electron
crystal is strongly coupled to deformation of the liquid surface arising from
resonant excitation of surface capillary waves, ripplons, while at higher
driving voltages the crystal decouples from the deformation. We find strong
dependence of the decoupling threshold of the driving electric field acting on
the electrons, on the size of the crystal. In particular, the threshold
electric field significantly decreases when the length of the crystal becomes
shorter than 25 micrometers. We explain this effect as arising from weakening
of surface deformations due to radiative loss of resonantly-excited ripplons
from an electron crystal of finite size, and we account for the observed effect
using an instructive analytical model.Comment: 5 figure
Isochoric thermal conductivity of solid nitrogen
The isochoric thermal conductivity of solid nitrogen has been investigated on
four samples of different densities in the temperature interval from 20 K to
the onset of melting. In alfa-N2 the isochoric thermal conductivity exhibits a
dependence weaker than 1/T; in beta-N2 it increases slightly with temperature.
The experimental results are discussed within a model in which the heat is
transported by low-frequency phonons or by "diffusive" modes above the mobility
boundary. The growth of the thermal conductivity in beta-N2 is attributed to
the decreasing "rotational" component of the total thermal resistance, which
occurs as the rotational correlations between the neighboring molecules become
weaker.Comment: Postscript 12 pages, 3 figures, 1 table. To be published in 200
Causal signal transmission by quantum fields. IV: The causal Wick theorem
Wick's theorem in the Schwinger-Perel-Keldysh closed-time-loop formalism is
written in a form where the place of contractions is taken by the linear
response function of the field. This result demonstrates that the physical
information supplied by Wick's theorem for operators is propagation of the free
field in space and time.Comment: Final version, to appear in Phys Rev
Measurement of young's modulus and hardness of Al-50 wt % Sn alloy phases using nanoindentation
The nanoindentation method was used to measure the Young's modulus and hardness of the phases of the alloy Al-50 wt % Sn: α-aluminum and eutectic. Samples are obtained in different ways, i.e., traditionally via the transition of the melt into a homogeneous structural state by heating to a certain temperature, followed by cooling using the cooling rate greater by the order than that of the traditional method and via the addition of 0.06 wt % Ti and 1 wt % Zr to the binary alloy. It has been found that the most significant effect of the Al-50 wt % Sn phases on the Young's modulus is the transition of the melt into a homogeneous structural state and the introduction of Zr into the melt. As part of the mathematical theory of elasticity, a numerical evaluation of the interfacial pressure that arises due to the difference between Young's modulus of α aluminum and eutectic has been performed. The calculation has showed that the extra pressure is nine times less for the alloy formed through the transition of the melt into a homogeneous structural state than for the alloy produced via a traditional way. © 2013 Pleiades Publishing, Ltd
Method for obtaining ingots of the A34 solder based on an investigation into the relation between the structure and properties of liquid and solid metals
A comparative analysis of the influence of the modifying method on the structure and phase composition of the ingots of the A34 solder is performed. Modification is performed by force of heating the melt to 1000°C and introducing the fine-crystalline remelt in an amount of 5% of the charge amount into the melt. The investigation is performed using DTA and metallographic analysis. The structure of the ingot of the A34 solder is additionally investigated at elevated temperatures (150 and 300°C) by the sc-AFM method using the NTEGRA Therma probe nanolaboratory, and recommendations are given to optimize the modes of casting and thermal treatment. © 2013 Allerton Press, Inc
Dephasing of qubits by transverse low-frequency noise
We analyze the dissipative dynamics of a two-level quantum system subject to
low-frequency, e.g. 1/f noise, motivated by recent experiments with
superconducting quantum circuits. We show that the effect of transverse linear
coupling of the system to low-frequency noise is equivalent to that of
quadratic longitudinal coupling. We further find the decay law of quantum
coherent oscillations under the influence of both low- and high-frequency
fluctuations, in particular, for the case of comparable rates of relaxation and
pure dephasing
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