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71.
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M.A. Kaashoek 《Journal of Functional Analysis》2005,228(1):207-233
A discrete analog of a skew self-adjoint canonical (Zakharov-Shabat or AKNS) system with a pseudo-exponential potential is introduced. For the corresponding Weyl function the direct and inverse problem are solved explicitly in terms of three parameter matrices. As an application explicit solutions are obtained for the discrete integrable nonlinear equation corresponding to the isotropic Heisenberg magnet model. State-space techniques from mathematical system theory play an important role in the proofs. 相似文献
74.
The value of the central density is of key importance for annihilation processes. For the ground state we discuss its determination from the moments of the ground state density. We first review the way of reaching the moments from the spectrum. In particular we show how to get the lowest moments in D = 3, namely 〈r−2〉 and 〈r−1〉 from the series expansion of the Laplace transform of the density. We then recall a method to obtain the central density based on the Stieltjes moment problem. If the number of known moments is finite, this technique yields a lower bound. We investigate the possibilities to estimate the accuracy of the bound and the corresponding asymptotic value. An application to the muonic 208Pb atom is presented. 相似文献
75.
K. -M. Haendel U. Denker O. G. Schmidt A. G. M. Jansen R. J. Haug 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):487
We use magneto-transport spectroscopy to study a dramatic instability between a low and high conductivity mode in Si/SiGe-based resonant tunneling diodes with an embedded layer of self-assembled Ge hut cluster quantum dots in the Si barrier. In the low current regime a simple activation-type behavior with an astonishingly low activation energy in the order of 0.1 meV is determined. In the high current regime a region of negative differential conduction can be observed. We discuss the influence of different layer structures and magnetic fields. 相似文献
76.
F. Fu L.-H. Liu L. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):367-372
We focus on the heterogeneity of social networks and its
role to the emergence of prevailing cooperators and sustainable
cooperation. The social networks are representative of the
interaction relationships between players and their encounters in
each round of games. We study an evolutionary Prisoner's Dilemma
game on a variant of Newman-Watts small-world network, whose
heterogeneity can be tuned by a parameter. It is found that
optimal cooperation level exists at some intermediate topological
heterogeneity for different temptations to defect. That is,
frequency of cooperators peaks at a certain specific value of
degree heterogeneity — neither the most heterogeneous case nor
the most homogeneous one would favor the cooperators. Besides, the
average degree of networks and the adopted update rule also affect
the cooperation level. 相似文献
77.
78.
We have analyzed the optical properties of a-Ge30-xSbxS70 chalcogenide glass films (x=0,10,20 and 30 at%); the chalcogenide films were prepared by vacuum thermal evaporation. The optical-absorption data indicate that the absorption mechanism is non-direct transition. We found that the optical band gap, Eopt, decreases from 2.04±0.01 to 1.74±0.01 eV, whereas the refractive index increases with increasing Sb content. Data are analyzed by the Wemple equation, which is based on the single-oscillator model. 相似文献
79.
S. Sree Ranjani 《Annals of Physics》2005,320(1):164-174
We analyze the Scarf potential, which exhibits both discrete energy bound states and energy bands, through the quantum Hamilton-Jacobi approach. The singularity structure and the boundary conditions in the above approach, naturally isolate the bound and periodic states, once the problem is mapped to the zero energy sector of another quasi-exactly solvable quantum problem. The energy eigenvalues are obtained without having to solve for the corresponding eigenfunctions explicitly. We also demonstrate how to find the eigenfunctions through this method. 相似文献
80.
研究了退火温度对Se0.70Ge0.15Sb0.15薄膜的影响.通过热蒸发技术,在300K温度下将大块无定形Se0.70Ge0.15Sb0.1s沉积在石英和玻璃衬底上.研究发现,未经过退火处理的薄膜结构和在300K,1.33×10-5Pa下退火1小时后的薄膜结构都是无定形结构,而在同样气压470K温度下退火1小时的薄膜有结晶现象.通过在300 2 500nm范围内垂直入射光方向上透射率和反射率的测试,研究了薄膜的一些光学参数,如消光系数(k),折射系数(n)和吸收系数(a).研究发现,n和k同热处理温度有关.通过光学数据的分析,得到了不同条件下薄膜的间接带隙宽度(Enong),未经过热处理薄膜的Enong是1.715±0.021eV,300K下退火薄膜的Enong是1.643±0.021eV,470K下退火的Enong是1.527±0.021eV.退火温度降低了带隙宽度Enong,但增加了带尾eo这种效应可以根据Mott和Davis提出的多晶体系中态密度来解释. 相似文献