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901.
Hypothetical helical organic polymers with localized electrons, charges, and/or atoms are described, in which these localized substructures can move along the backbones of the polymers via sigmatropic H shifts. 相似文献
902.
Li Changjun; Li Zheng; Evans David J.; Zhang Tie 《IMA Journal of Numerical Analysis》2003,23(4):581-592
Golub et al. (2001, BIT, 41, 7185) gave a generalizedsuccessive over-relaxation method for the augmented systems.In this paper, the connection between the SOR-like method andthe preconditioned conjugate gradient (PCG) method for the augmentedsystems is investigated. It is shown that the PCG method isat least as accurate (fast) as the SOR-like method. Numericalexamples demonstrate that the PCG method is much faster thanthe SOR-like method. 相似文献
903.
Effect of track stiffness on vibration levels in railway tunnels 总被引:1,自引:0,他引:1
The paper discusses the difficulties in comparing and drawing conclusions from vibration measurements made in different railway tunnels. A number of new measurements are presented, which have been made and analyzed on a consistent basis. The track stiffness has been determined for each of the measurements. Graphs are presented which indicate the level of rail and tunnel floor vibration likely to occur for different track stiffnesses. The variance in the measurement results also indicates the potential error in using the data to predict vibration levels in new situations. 相似文献
904.
J. Wambach 《The European Physical Journal A - Hadrons and Nuclei》2003,18(2-3):453-458
Theoretical issues and perspectives of hadronic matter at high baryon density are discussed with focus on the restoration of chiral symmetry and observable consequences.Received: 30 September 2002, Published online: 22 October 2003PACS:
25.75.-q Relativistic heavy-ion collisions - 21.65. + f Nuclear matter 相似文献
905.
906.
We present a review of our recent measurements of total cross sections (Q
T's) for the scattering of positrons by Na, K, and Rb, and positronium-formation cross sections (Q
Ps's) for Na and K. For our total cross section measurements, a beam transmission technique has been used. For ourQ
Ps measurements, our approach involves setting upper and lower limits onQ
Ps using a combination of (1) measuring the transmission of the positron beam with the angular discrimination of the apparatus made as poor as possible, and (2) measuring the 511 keV annihilation gamma rays in coincidence produced by the decay of para-Ps formed in the scattering cell. Comparison with theoretical calculations shows that our measuredQ
T's andQ
Ps's for Na and K agree reasonably well with a close coupling approximation (CCA) calculation which takes into account the formation of Ps in then=1 andn=2 states. In the 3–10 eV energy range, this calculation predicts a peak in theQ
T's andQ
Ps's for K which also appears in our measurements. The absence of such a peak in our measuredQ
T's andQ
Ps's (preliminary) for Na in this energy range is also consistent with the same theory. Comparisons with five-state CCA calculations ofQ
T which do not take Ps-formation into account also show good agreement with our positron-Na, K, and RbQ
T measurements for energies above 20 eV, but show dramatic departures from our measurements below 10 eV for K and Rb. 相似文献
907.
908.
E. A. Davis A. Singh S. F. J. Cox S. R. Kreitzman T. L. Estle B. Hitti R. L. Lichti R. DuVarney 《Hyperfine Interactions》1994,86(1):705-710
Studies of the muonium fractions in the amorphous oxide a-SiO have been carried out by RF resonance at TRIUMF, Canada and LF repolarization techniques at RAL, U.K. The resonance measurements confirm the presence of the interstitial Mu centre in this intermediate oxide of silicon. Analysis of the data gathered at RAL, using a recently-developed fitting technique, reveals that the Mu* state is present here as well, but with lower relative fractions than in a-Si. However, as in the latter material, but in contrast to c-Si, this bond-centre species appears to be stable up to room temperature. 相似文献
909.
R. Silvennoinen K. -E. Peiponen T. Asakura Yan-Fang Zhang Cong Gu K. Ikonen E. J. Morley 《Optics and Lasers in Engineering》1992,17(2)
The specular reflectance of cold-rolled aluminum surface is studied using a fiber optic system. An approximation for the determination of surface roughness is presented. 相似文献
910.