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911.
912.
Boris Tomášik Ulrich Heinz 《The European Physical Journal C - Particles and Fields》1998,4(2):327-338
A comprehensive model study of Bose-Einstein correlation radii in heavy ion collisions is presented. The starting point is
a longitudinally and transversally expanding fireball, represented at freeze-out by an azimuthally symmetric emission function.
The freeze-out temperature is allowed to feature transverse and temporal gradients. Their effects on the correlation radii
are studied. In particular, we evaluate numerically their dependence on the transverse mass of the particle pairs and check
a recent suggestion, based on analytical approximations, that for certain reasonable source parameters all three correlation
radii satisfy simultaneously a scaling.
Received: 2 July 1997 / Revised version: 25 September 1997 / Published online: 23 February 1998 相似文献
913.
914.
In this paper, we develop a tabu search procedure for solving the uniform graph partitioning problem. Tabu search, an abstract heuristic search method, has been shown to have promise in solving several NP-hard problems, such as job shop and flow shop scheduling, vehicle routing, quadratic assignment, and maximum satisfiability. We compare tabu search to other heuristic procedures for graph partitioning, and demonstrate that tabu search is superior to other solution approaches for the uniform graph partitioning problem both with respect to solution quality and computational requirements. 相似文献
915.
Czechoslovak Journal of Physics - 相似文献
916.
917.
918.
The case of small defect with the transition temperature higher than in the bulk is studied. It is shown that localized superconductivity appears in magnetic field — in zero field it does not exist. The percolation mechanism as well as anisotropic character resistivity is studied. 相似文献
919.
The previously described reduction of the effective rotational Hamiltonian for semirigid molecules of C3v or D3 point group symmetry [M. R. Aliev and V. T. Aleksanyan, Opt. Spectrosc.24, 201–206 (1968)] has been extended to nonrigid molecules with a significant inversion splitting of the energy levels (e.g., NH3, H3O+, CH3?, or SiH3 molecules). Although for semirigid molecules like PH3 or AsH3, the parameters α and η′3 which appear in the terms α[J+3 + J?3, Jz]+ and η′3(J+6 + J?6) are almost completely correlated, the effects of the inversion splitting and the accidental resonance which can occur between the interacting rotational levels in nonrigid molecules make it possible to determine α and η′3 separately. The results of fitting the experimental data for 14NH3 and 15NH3 [?. Urban, Romola D'Cunha, K. Narahari Rao, and D. Papou?ek, Canad. J. Phys.62, 1775–1791 (1984); Romola D'Cunha, ?. Urban, K. Narahari Rao, L. Henry, and A. Valentin, J. Mol. Spectrosc.111, 352–360 (1985)] are in agreement with this conclusion. The possibility of the determination of the sign of η3 from a simultaneous analysis of the allowed and Δk = ±3 forbidden transitions in semirigid XY3 molecules has been discussed. 相似文献
920.
The fluorescence spectra were measured of nine alkali halides with a low concentration of monovalent copper. Relations analogous to Mollwo-Ivey law for F-centers and for lead doped alkali halides were found to be satisfied by the measured wavelengths corresponding to the emission band maxima. The Stokes shifts, however, were here essentially larger as compared to those of lead doped alkali halides. Their order of magnitude is about the same as for F-centers.Dedicated to Prof. Dr. I. Tarján on occasion of his 60th birthday.Cukrovarnická 10, Praha 6, Czechoslovakia.The authors wish to express their appreciation to Dr. M. Lébl, CSc., and Ing. . Barta, CSc., for growing the crystals and to Mrs. I. Velická for the polarographic analysis. 相似文献