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61.
62.
Using Monte Carlo molecular dynamics, a new, careful study is made of the approach of the trajectory of a typical particle in a hard sphere fluid to that of a Brownian particle, discussed before by Powles and Quirke and Rapaport. The apparent fractal dimension of the trajectory, as a function of reduced length scale,(), characterizes the transition from mechanical to Brownian motion and differs markedly from 2 in all present computer simulations. 相似文献
63.
We derive rigorously general results on the critical behavior of the magnetization in Ising models, as a function of the temperature and the external field. For the nearest-neighbor models it is shown that ind4 dimensions the magnetization is continuous atT
c and its critical exponents take the classical values=3 and=1/2, with possible logarithmic corrections atd=4. The continuity, and other explicit bounds, formally extend tod>3 1/2. Other systems to which the results apply include long-range models ind=1 dimension, with 1/|x–y|
couplings, for which 2/(–1) replacesd in the above summary. The results are obtained by means of differential inequalities derived here using the random current representation, which is discussed in detail for the case of a nonvanishing magnetic field.Research supported in part by NSF grant PHY-8301493 A02, and by a John S. Guggenheim Foundation fellowship (M.A.). 相似文献
64.
Raoul Kopelman 《Journal of statistical physics》1986,42(1-2):185-200
Heterogeneous kinetics are shown to differ drastically from homogeneous kinetics. For the elementary reaction A + A products we show that the diffusion-limited reaction rate is proportional tot
– h[A]2 or to [A]x, whereh=1- d
s/2, X=1+2/d
s
=(h-2)(h-1), andd
s
is the effective spectral dimension. We note that ford = d
s
=1, h =1/2 andX = 3, for percolating clustersd
s = 4/3,h = 1/3 andX = 5/2, while for dust ds <1, 1 >h > 1/2 and >X > 3. Scaling arguments, supercomputer simulations and experiments give a consistent picture. The interplay of energetic and geometric heterogeneity results in fractal-like kinetics and is relevant to excitation fusion experiments in porous membranes, films, and polymeric glasses. However, in isotopic mixed crystals, the geometric fractal nature (percolation clusters) dominates. 相似文献
65.
Ole Toft Sørensen 《Journal of Thermal Analysis and Calorimetry》2005,80(3):793-794
Summary An enormous development has taken place within the last five years in synchronous teaching over the Internet, i.e. both the teacher and the students are simultaneously in direct communication with each other as in a normal class-room or auditorium. With this concept it is possible to communicate orally, to exchange Power Point Presentations, documents, programmes and live web-camera pictures. It is even possible to use an electronic black board on which both the teacher and the students can work simultaneously. The great advantage with this type of teaching is that it is not restricted to a single class-room/auditorium with limited access, but in a virtual room accessible to everybody in principle all over the world, and which certainly open up new possibilities in teaching. The purpose of this paper is to present and to discuss the concept of virtual class-room teaching, how the system operates in practice, its advantages and, finally, how its inherent limitations can be overcome. 相似文献
66.
原油三维荧光分析中猝灭现象辨析 总被引:5,自引:0,他引:5
研究了原油的三维荧光猝灭现象,指出浓度过高是原油产生荧光猝灭的主要原因,将会造成三维荧光等值线图畸变,致使定量分析数据失真,谱图特征变异,难以获取原油特征三维指纹图。提出了避免荧光猝灭的预试方法,并列出了不同类型原油的最佳测试浓度。 相似文献
67.
Gun'ko VM Villiéras F Leboda R Marciniak M Charmas B Skubiszewska-Zi&ecedil;ba J 《Journal of colloid and interface science》2000,230(2):320-327
Adsorbents synthesized by grafting of titania onto mesoporous silica gel surfaces at different temperatures were studied by means of nitrogen adsorption–desorption and water desorption. The pore size distribution f(Rp) of titania/silica gel depends on the titania concentration (CTiO2) and the temperature of titania synthesis. Nonuniformity of TiO2 phase is maximal at a low CTiO2 value (3.2 wt.% anatase deposited at 473 K), and two peaks of the fractal dimension distribution f(D) are observed at such a concentration of titania, but at larger CTiO2 values, only one f(D) peak is seen. More ordered filling of pores and adsorption sites by nitrogen, reflecting in the shape of adsorption energy distributions f(E) at different pressures of adsorbate, is observed for adsorbent with titania (rutile+anatase) grafted on silica gel at a higher temperature (673 K). 相似文献
68.
煤微孔表面的分形维数及其变化规律的研究 总被引:4,自引:2,他引:4
本文利用气体吸附数据确定了各种煤阶煤(从褐煤到无烟煤)和煤焦气化反应过程中微孔表面的分形维数及其变化规律。这有助于进一步认识煤的孔结构特征。 相似文献
69.
设M=(m_(ij))是一个b×b阶矩阵且m_(ij)∈{0,1},∑_(M)是矩阵M=(m_(ij))诱导产生的有限型,σ是其上左推移算子.本文主要研究的是有限型动力系统(∑_(M),σ)上的首次返回速度问题.令τ_(k)(x)是点x∈∑_(M)首次返回到包含x的k阶柱集时间,且E_(α,β)={x∈∑_(M):lim inf_(k→∞)(logτ_(k)(x))/k=α,lim sup_(k→∞)(logτ_(k)(x))/k=β}.我们证明了:当M是不可约矩阵时,对任意0≤α≤β≤+∞,集合E_(α,β)的Markov测度要么等于0要么等于1并且具有满的Hausdorff维数. 相似文献
70.
有阻尼Sine-Gordon方程的全局吸引子的维数 总被引:2,自引:0,他引:2
本文通过引入新范数,得到有阻尼Sine-Gordon方程的Dirichlet问题的全局吸引子的维数的一个估计.结果表明:当“阻尼”与“扩散”同时增大或正弦项系数减小时,吸引子的维数减小.特别地,得到了零维吸引子存在的参数条件. 相似文献