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41.
苏振华 《数学的实践与认识》2017,(12):182-188
目前关于积图的交叉数的研究已经推广到六阶图与星图的积图.研究得到了一个特殊六阶图Q与n个孤立点nK_1的联图交叉数,然后通过收缩的方法,得到了Q与星图S_n的积图交叉数. 相似文献
42.
早在20世纪50年代,Zarankiewicz 猜想完全2-部图K_{m,n}(m\leq n)的交叉数为\lfloor\frac{m}{2}\rfloor\times \lfloor\frac{m-1}{2}\rfloor\times\lfloor\frac{n}{2}\rfloor\times\lfloor\frac{n-1}{2}\rfloor (对任意实数x,\lfloor x\rfloor表示不超过x的最大整数). 目前这一猜想的正确性只证明了当m\leq6时成立. 假定著名的Zarankiewicz的猜想对m=7的情形成立,确定了6-轮W_{6}与星S_{n}的笛卡尔积图的交叉是 cr(W_{6}\times S_{n})=9\lfloor\frac{n}{2}\rfloor\times\lfloor\frac{n-1}{2}\rfloor+2n+5\lfloor\frac{n}{2}\rfloor. 相似文献
43.
44.
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
45.
在二维渗流中,设rn是矩形[O,n]2的最低水平开穿透,令ξn=max{y:(xy)∈rn}.本文证明了在临界状态p=pc时,存在常数0<C1<C2<1,当n充分大时有存在,而在上临界状态p>pc时,有存在]=0. 相似文献
46.
采用密度泛函UB3 LYP/6-311+ G(2d)方法研究了Fe+在基态和激发态与CO与N2O反应的反应机理.全参数优化了反应势能面上各驻点的几何构型,用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证,并用UB3LYP/6-311++G(3df,3pd)、单点垂直激发等方法分别进行各驻点单点能校正,四重态和六重态反应势能面交叉点CP确定,计算结果表明,该反应为两步反应,且反应机理都为插入一消去反应,势能面上的两个交叉点能够有效降低反应的活化能,这在动力学和热力学上都是有利的. 相似文献
47.
Harry Kesten R. A. Maller 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》1999,35(6):685
We show that the passage time, T*(r), of a random walk Sn above a horizontal boundary at r (r≥0) is stable (in probability) in the sense that
as r→∞ for a deterministic function C(r)>0, if and only if the random walk is relatively stable in the sense that
as n→∞ for a deterministic sequence Bn>0. The stability of a passage time is an important ingredient in some proofs in sequential analysis, where it arises during applications of Anscombe's Theorem. We also prove a counterpart for the almost sure stability of T*(r), which we show is equivalent to E|X|<∞, EX>0. Similarly, counterparts for the exit of the random walk from the strip {|y|≤r} are proved. The conditions arefurther related to the relative stability of the maximal sum and the maximum modulus of the sums. Another result shows that the exit position of the random walk outside the boundaries at ±r drifts to ∞ as r→∞ if and only if the random walk drifts to ∞. 相似文献
48.
P. Cacciani J. Cosléou F. Herlemont M. Khelkhal J. Legrand 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(2):199-207
When a gas sample of 13CH3F is prepared with a population of isomers (ortho and para forms) far from the equilibrium given by nuclear spin statistics,
it relaxes towards this equilibrium with an exponential decay rate. This phenomenon called nuclear spin conversion is mainly
governed by intramolecular spin-spin and spin-rotation interactions. In the quantum relaxation model [P.L. Chapovsky, Phys.
Rev. A 43, 3624 (1991)], two pairs of ortho-para levels (J
= 9, K
= 3; J'
= 11, K'
= 1) and (J
= 20, K
= 3; J'
= 21, K'
= 1) are principally responsible for the conversion. The levels of the second pair are coupled by both spin-spin and spin-rotation
interactions. The application of an electric field (up to 10 kV/cm) induces a crossing of the Stark components of this pair,
which is observed for the first time. A specific experimental set-up based on an electric field of alternating triangular
shape is used, which allows the determination of the strength of both interactions via the measurement of the spin conversion decay rates. This work yields the first experimental value for the electronic contribution
to the spin-rotation interaction in 13CH3F.
Received 23 May 2002 / Received in final form 18 September 2002 Published online 21 January 2003
RID="a"
ID="a"e-mail: Patrice.Cacciani@univ-lille1.fr 相似文献
49.
R. Unanyan S. Guérin B. W. Shore K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(3):443-449
In traditional schemes of multilevel multilaser excitation, each laser pulse interacts with only one pair of states, and the
rotating wave approximation (RWA) is applicable. Here we study the population transfer process in a three-state system when
each of the two lasers interacts with each of the pair of states and when the Rabi frequencies characterizing the interaction
strengths of the system are comparable to or larger than the difference of the transition frequencies. We show that complete
and robust population transfer is possible under conditions more general than those hitherto considered necessary for stimulated
Raman adiabatic passage (STIRAP) or for successive π pulses. Using adiabatic Floquet theory we show that successful population transfer can be interpreted as adiabatic passage
by means of a transfer state which connects the initial and final states. The Floquet picture offers a convenient interpretation
of the population transfer as accompanied by multiple absorption of photons from or emission into the laser fields. 相似文献