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901.
A time-of-flight mass spectrometer combined with a pulsed laser system has been used for determination of krypton isotope ratios of air samples containing 106-107 krypton atoms. A three-color, doubly resonant ionization scheme employing a 116.48 nm transition from the ground into the first 4s24p5(2P°1/2)5s J = 1 excitation level has been applied. The magnitude of a hyperfine splitting of this level has been estimated for 81Kr, 83Kr and 85Kr isotopes. Hyperfine structure induced isotopic effects have been investigated under different saturation conditions and found to be negligible when the first and the second transitions are strongly saturated. 相似文献
902.
903.
Convex geometry of max-stable distributions 总被引:1,自引:0,他引:1
Ilya Molchanov 《Extremes》2008,11(3):235-259
It is shown that max-stable random vectors in [0, ∞ )
d
with unit Fréchet marginals are in one to one correspondence with convex sets K in [0, ∞ )
d
called max-zonoids. The max-zonoids can be characterised as sets obtained as limits of Minkowski sums of cross-polytopes
or, alternatively, as the selection expectation of a random cross-polytope whose distribution is controlled by the spectral
measure of the max-stable random vector. Furthermore, the cumulative distribution function P
ξ ≤ x of a max-stable random vector ξ with unit Fréchet marginals is determined by the norm of the inverse to x, where all possible norms are given by the support functions of (normalised) max-zonoids. As an application, geometrical
interpretations of a number of well-known concepts from the theory of multivariate extreme values and copulas are provided.
相似文献
904.
Elena B. Averina Kseniya N. Sedenkova Ilya S. Borisov Yuri K. Grishin Tamara S. Kuznetsova Nikolai S. Zefirov 《Tetrahedron》2009,65(29-30):5693-5701
A series of novel gem-bromofluorospiropentanes were synthesized and investigated in the reaction with methyllithium. Either substitution of the fluorine atom for a methyl group or rearrangement into methylated cyclobutene derivatives occurred under these conditions. 相似文献
905.
906.
The present paper deals with element‐based algebraic multigrid (AMGe) methods that target linear systems of equations coming from finite element discretizations of elliptic partial differential equations. The individual element information (element matrices and element topology) is the main input to construct the AMG hierarchy. We study a number of variants of the spectral agglomerate AMGe method. The core of the algorithms relies on element agglomeration utilizing the element topology (built recursively from fine to coarse levels). The actual selection of the coarse degrees of freedom is based on solving a large number of local eigenvalue problems. Additionally, we investigate strategies for adaptive AMG as well as multigrid cycles that are more expensive than the V‐cycle utilizing simple interpolation matrices and nested conjugate gradient (CG)‐based recursive calls between the levels. The presented algorithms are illustrated with an extensive set of experiments based on a matlab implementation of the methods. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
907.
Vasil Tiberkevich Ilya Krivorotov Andrei Slavin 《Journal of magnetism and magnetic materials》2009,321(16):L53
A theory of generation linewidth of a spin-torque oscillator (STO) based on an in-plane-magnetized nano-pillar with an anisotropic “free” magnetic layer has been developed. It is predicted that by choosing the direction of the in-plane bias magnetic field H0 along the “hard” anisotropy axis of the STO “free” layer and the magnitude of this field to be four times larger than the anisotropy field HA (H0=4HA) it would be possible to compensate the nonlinear phase noise and to achieve the minimum value of the generation linewidth, characteristic for an auto-oscillator without a nonlinear frequency shift. 相似文献
908.
Robert Pollice Felix Fleckenstein Ilya Shenderovich Peter Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14419-14426
The importance of London dispersion for structure and stability of molecules with less than about 200 atoms has been established in recent years but the quantitative understanding is still largely based on computations because of a persistent lack of suitable experimental data. We herein report a comprehensive computational and experimental study of the compensation of London dispersion in proton‐bound dimer dissociations showing that total compensation is largely invariant in both polar and nonpolar aprotic solvents spanning a wide range of bulk polarizabilities. Additionally, we find that compensation by solvent (which is about 40–80 %) largely dominates over compensation in the gas phase (which is about 0–40 %) for typical experimental temperatures. 相似文献
909.
Konstantin L. Kuzmin Ilya A. Timoshkin Evgeniya S. Zhukovskaya Yakov V. Lipatov Bogdan I. Lazoryak 《Composite Interfaces》2017,24(1):13-34
The present study explains the role of surface modification of constituent materials on composite material performance. The influence of silane and nano-hybrid coatings on mechanical properties of basalt fibers and composite materials on their base was investigated. Infrared spectroscopy indicated that modification of basalt fiber surface and nano-SiO2 was successfully applied. The surface modification leads to the significant increase in the tensile strength of basalt fibers compared to the non-coated fibers. The tensile strength of silane-treated fibers was established 23% higher than the non-coated fibers, indicating that silane plays a critical role in the strength retention of basalt fibers. Also it was pointed out that silane coupling agents can be used for the preparation of the nano-hybrid coating. Addition of SiO2 nanoparticles into the fiber surface was incorporated to enhance the interfacial bonding of basalt fiber reinforced epoxy composite. 相似文献
910.