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51.
We find a lower bound for the proportion of face boundaries of an embedded graph that are nearly light (that is, they have bounded length and at most one vertex of large degree). As an application, we show that every sufficiently large k‐crossing‐critical graph has crossing number at most 2k + 23. © 2006 Wiley Periodicals, Inc. J Graph Theory 53: 151–156, 2006 相似文献
52.
Let τ be some stopping time for a random walk S
n
defined on transitions of a finite Markov chain and let τ(t) be the first passage time across the level t which occurs after τ. We prove a theorem that establishes a connection between the dual Laplace-Stieltjes transforms of the joint distributions of (τ, S
τ) and (τ(t), S
τ(t)). This result applies to the study of the number of crossings of a strip by sample paths of a random walk.Original Russian Text Copyright © 2005 Lotov V. I. and Orlova N. G.The authors were partially supported by the Russian Foundation for Basic Research (Grant 05-01-00810) and the Grant Council of the President of the Russian Federation (Grant NSh-2139.2003.1).__________Translated from Sibirskii Matematicheskii Zhurnal, Vol. 46, No. 4, pp. 833–840, July–August, 2005. 相似文献
53.
C.M. Marian F. Schneider M. Kleinschmidt J. Tatchen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):357-367
Electronic spectra of uracil in its diketo (lactam) form and five enol (lactim) tautomeric forms have been investigated by
means of combined density functional and configuration interaction methods. We have simulated the effects of hydrogen bonding
with a protic solvent by recomputing the spectrum of uracil in the presence of two, four, or six water molecules. Geometries
of the electronic ground state and several low-lying excited states have been optimized. Spin-orbit coupling has been determined
for correlated wavefunctions employing a non-empirical spin-orbit mean-field approach. In accord with experiment, we find
the diketo tautomer to be the most stable one. The calculations confirm that the first absorption band arises from the 1( π↦π*) S
0↦S
2 excitation. The experimentally observed vibrational structure in this band originates from a breathing mode of the six ring.
Complexation with water molecules is seen to cause a significant blue shift of n↦π* excitations while leaving π↦π* excitations nearly uninfluenced. Computed radiative lifetimes are presented for the experimentally known weak phosphorescence
from the π↦π* excited T1 state. Among the uracil lactim tautomers, one is particularly interesting from a spectroscopic point of view. In this tautomer,
the π↦π* excitation gives rise to the S1 state.
Received 18 February 2002 / Received in final form 5 June 2002 Published online 13 September 2002 相似文献
54.
Ting LI 《数学学报(英文版)》2007,23(7):1217-1232
In this paper, a class of morphisms which have a kind of singularity weaker than normal crossing is considered. We construct the obstruction such that the so-called semi-stable log structures exists if and only if the obstruction vanishes. In the case of no power, if the obstruction vanishes, then the semi-stable log structure is unique up to a unique isomorphism. So we obtain a kind of canonical structure on this family of morphisms. 相似文献
55.
Richard Barakat 《Stochastic Processes and their Applications》1978,8(1):77-85
The average frequency with which a trigonometric sum having linearly independent frequencies achieves a given value in a specified time interval was solved by Kac in the form of a double integral. In the present paper, Kac's solution is generalized by allowing the amplitudes of the sinusoidal terms to be statistically independent random variables possessing compact probability density functions. The average frequency is expressed as a Fourier cosine series. Representative numerical calculations are shown. The asymptotic form of the average frequency is also discussed. 相似文献
56.
J. Scott Carter Masahico Saito Shin Satoh 《Proceedings of the American Mathematical Society》2006,134(9):2779-2783
We prove that a crossing change along a double point circle on a -knot is realized by ribbon-moves for a knotted torus obtained from the -knot by attaching a -handle. It follows that any -knots for which the crossing change is an unknotting operation, such as ribbon -knots and twist-spun knots, have trivial Khovanov-Jacobsson number.
57.
58.
The nonlinear optical nonlinearities of a fluorine-containing azoic dye in tetrahydrofuran have been investigated by using Z-scan technique with picosecond and nanosecond lasers. The experimental results reveal that the azoic dye has large optical nonlinearity under the excitations of picosecond and nanosecond 532 nm. At the picosecond 532 nm the solution presents negative nonlinear refraction due to the electronic effect, while the larger nonlinear refraction under nanosecond laser excitation is induced by thermal effect. Moreover, the different nonlinear absorption behavior under picosecond and nanosecond excitations is analyzed. 相似文献
59.
60.
1000多年前,英国著名学者Alcuin曾提出一个古老的渡河问题,即狼、羊和卷心菜的渡河问题。2006年,Prisner把该问题推广到任意的冲突图上,考虑了一类情况更一般的渡河运输问题。所谓冲突图是指一个图G=(V,E),这里V代表某些物品的集合,V中的两个点有边连结当且仅当这两个点是冲突的,即在无人监管的情况下不允许留在一起的点。图G=(V,E)的一个可行运输方案是指在保证不发生任何冲突的前提下,把V的点所代表的物品全部摆渡到河对岸的一个运输方案。图G的Alcuin数定义为它存在可行运输方案时所需船的最小容量。本文讨论了覆盖数不超过3的连通图的Alcuin数,给出了该类图Alcuin数的完全刻画。 相似文献