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991.
J.-Q. Shen H.-Y. Zhu P. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(2):305-313
There exist a number of typical and interesting systems and/or models, which possess three-generator Lie-algebraic structure,
in atomic physics, quantum optics, nuclear physics and laser physics. The well-known fact that all simple 3-generator algebras
are either isomorphic to the algebra sl (2, C) or to one of its real forms enables us to treat these time-dependent quantum systems in a unified way. By making use of
both the Lewis-Riesenfeld invariant theory and the invariant-related unitary transformation formulation, the present paper
obtains exact solutions of the time-dependent Schr?dinger equations governing various three-generator Lie-algebraic quantum
systems. For some quantum systems whose time-dependent Hamiltonians have no quasialgebraic structures, it is shown that the exact solutions can also be obtained by working in a
sub-Hilbert-space corresponding to a particular eigenvalue of the conserved generator (i.e., the time-independent invariant that commutes with the time-dependent Hamiltonian). The topological property of geometric phase factors and its adiabatic limit in time-dependent systems is briefly
discussed.
Received 6 July 2002 / Received in final form 21 October 2002 Published online 11 February 2003 相似文献
992.
József Kaizer József Pap Gábor Speier Marius Réglier Michel Giorgi 《Transition Metal Chemistry》2004,29(6):630-633
The preparation, spectroscopic properties, and crystal structure of [Cu(ind)(mco)] [ind is the anion of 1,3-bis(2-pyridylimino)isoindoline and mco is the anion of 3-hydroxy-(4H)-benzopyran-4-one] are reported. The complex exhibits a distorted square pyramidal geometry. The oxygenation of the title compound results in oxidative cleavage of the heterocyclic ring to give the (acetylsalicylato)copper(II) complex [Cu(asp)(ind)] (asp is the anion of acetylsalicylic acid) and CO as primary products, which reaction resembles the enzymatic reaction of quercetinase. 相似文献
993.
I T Vieira P R Harper A K Shahani V De Senna 《The Journal of the Operational Research Society》2003,54(7):713-722
Mother-to-child transmission (MTCT) of HIV is the most significant source of HIV infection in children below the age of 15 years. In 2000 alone, about 600 000 new infections occurred, the vast majority from mothers living in developing countries who were not aware of their HIV-positive status. To date, at least 4.3 million children have died from AIDS. In this paper, we discuss the development of an operational model that can be used to evaluate intervention options for the prevention of MTCT of HIV. The problem was approached by defining suitable pregnancy risk groups, prevention options and the required model outputs to evaluate different intervention strategies. The method chosen to approach the problem was a discrete-event, three-phase simulation, built in Visual Basic, with a stochastic semi-Markov structure. The developed model takes individual pregnant women through each stage of their pregnancy, labour and birth. Different intervention strategies may be modelled at any time, including short-course antiretroviral drugs and cessation of breastfeeding. The model is demonstrated with data from Botswana, which has one of the highest HIV-infection rates in the world. 相似文献
994.
995.
996.
Stephen P. Humphries 《Israel Journal of Mathematics》2004,143(1):189-222
We prove that (with two possible exceptions) the Hurwitz braid group action on the sequence of standard generators of an irreducible
Artin group has a finite orbit if and only if the Artin group is of finite type (i.e., the corresponding Coxeter group is
finite). 相似文献
997.
Oleg Safronov 《Arkiv f?r Matematik》2004,42(2):363-377
We study the spectral properties of Jacobi matrices. By combining Killip's technique [12] with the technique of Killip and
Simon [13] we obtain a result relating the properties of the elements of Jacobi matrices and the corresponding spectral measures.
This theorem is a natural extension of a recent result of Laptev-Naboko-Safronov [17].
The author thanks Sergei Naboko for useful discussions and Barry Simon for pointing out the conjecture. 相似文献
998.
Effects of barium on the nonlinear electrical characteristics and dielectric properties of SnO2-based varistors 下载免费PDF全文
The effects of barium on electrical and dielectric properties of the SnO_2·Co_2O_3·Ta_2O_5 varistor system sintered at 1250℃ for 60min were investigated. It is found that barium significantly improves the nonlinear properties. The breakdown electrical field increases from 378.0 to 2834.5V/mm, relative dielectric constant (at 1kHz) falls from 1206 to 161 and the resistivity (at 1kHz) rises from 60.3 to 1146.5kΩ·cm with an increase of BaCO_3 concentration from 0mol% to 1.00mol%. The sample with 1.00mol% barium has the best nonlinear electrical property and the highest nonlinear coefficient (α=29.2). A modified defect barrier model is introduced to illustrate the grain-boundary barrier formation of barium-doped SnO_{2}-based varistors. 相似文献
999.
On the characterisation of paired monotone metrics 总被引:1,自引:1,他引:0
Paolo Gibilisco Tommaso Isola 《Annals of the Institute of Statistical Mathematics》2004,56(2):369-381
Hasegawa and Petz introduced the notion of paired monotone metrics. They also gave a characterisation theorem showing that
Wigner-Yanase-Dyson metrics are the only members of the paired family. In this paper we show that the characterisation theorem
holds true under hypotheses that are more general than those used in the above quoted references. 相似文献
1000.