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991.
The performance of a superheated alkali vapor cell, with a geometry suitable for x-ray photoionization experiments, is described. An internal heater was used to superheat sodium vapor in a split-wick heat pipe. At a Na pressure of 20 Torr, the transmission through the cell in the region of theC–X molecular band of Na2 increased to 50% from the 5% observed when the cell was operated in a conventional heat-pipe mode. In the presence of a Na atom density of 2×1017 cm–3, the average molecule density over the length of the cell was measured to be 2.5×1015 cm–3. In the hot central region of the superheated cell, the molecule density was predicted to have been reduced by a factor of 50 to 3×1014 cm–3. 相似文献
992.
Summary. This is a continuation of our previous work [6] on the investigation of intermittency for the parabolic equation (∂/∂t)u=Hu on ℝ+×ℤ
d
associated with the Anderson Hamiltonian H=κΔ+ξ(·) for i.i.d. random potentials ξ(·). For the Cauchy problem with nonnegative
homogeneous initial condition we study the second order asymptotics of the statistical moments <u(t,0)
p
> and the almost sure growth of u(t,0) as t→∞. We point out the crucial role of double exponential tails of ξ(0) for the formation of high intermittent peaks of the
solution u(t,·) with asymptotically finite size. The challenging motivation is to achieve a better understanding of the geometric structure
of such high exceedances which in one or another sense provide the essential contribution to the solution.
Received: 10 December 1996 / In revised form: 30 September 1997 相似文献
993.
赵爱威 《科技情报开发与经济》2002,12(6):64-65,67
随着我国经济的不断发展,财政、金融手段在宏观调控中的作用明显增强。目前的财政调控手段主要有税收调控、财政支出调控、财政信用调控、财政补贴调控。金融调控手段主要有法定存款准备金率调控、再贴现率调控、公开市场业务调控等。 相似文献
994.
证明了若 G是 3连通无爪图 ,且 G的每个同构于 A的导出子图都满足 ( a1,a2 ) ,则 G是泛连通图 (除了 u,v∈ V( G) ,d( u,v) =1时 ,G中可能不存在 ( u,v)—k路外 )。由此立得C.Thomassen猜想 :每个 4连通线图均是 Hamilton图 相似文献
995.
报导高温超导体 TlBaCaCuO 系的制备工艺与电磁测试的结果。实验证明,我们制备出了稳定的零电阻转变温度为112K 的新超导体。 相似文献
996.
Summary. Necessary and sufficient conditions for the existence of moments of the first passage time of a random walk S
n
into [x, ∞) for fixed x≧ 0, and the last exit time of the walk from (−∞, x], are given under the condition that S
n
→∞ a.s. The methods, which are quite different from those applied in the previously studied case of a positive mean for the
increments of S
n
, are further developed to obtain the “order of magnitude” as x→∞ of the moments of the first passage and last exit times, when these are finite.
A number of other conditions of interest in renewal theory are also discussed, and some results for the first time for which
the random walk remains above the level x on K consecutive occasions, which has applications in option pricing, are given.
Received: 18 September 1995/In revised form: 28 February 1996 相似文献
997.
Summary In this paper we suggest the use of complete families of solutions of the heat equation for the numerical solution of the inverse Stefan problem. Our approach leads to linear optimization problems which can be established and solved easily. Convergence results are proved. In a final section the method is applied to some examples. 相似文献
998.
999.
A carefully controlled interlaboratory comparison of analyses by size exclusion chromatography of a poly(vinyl acetate) whole polymer showed that compatible measurements could be made of the molar mass distribution. The characterized sample is available as a Community Bureau of Reference (BCR) test material. 相似文献
1000.
Summary A nonlinear approximation technique for the numerical solution of certain free boundary problems is proposed. The method is shown for a degenerate one-dimensional Stefan problem. For this problem, an error estimate, which is independent of the used algorithm, is derived. Numerical examples are discussed.This paper was written when the author held a 1 1/2 year postdoctoral position at the Department of Mathematics and Applied Mathematics Institute of the University of Delaware 相似文献