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91.
Jayanth R. Banavar Oscar Gonzalez John H. Maddocks Amos Maritan 《Journal of statistical physics》2003,110(1-2):35-50
Physical strands or sheets that can be modelled as curves or surfaces embedded in three dimensions are ubiquitous in nature, and are of fundamental importance in mathematics, physics, biology, and engineering. Often the physical interpretation dictates that self-avoidance should be enforced in the continuum model, i.e., finite energy configurations should not self-intersect. Current continuum models with self-avoidance frequently employ pairwise repulsive potentials, which are of necessity singular. Moreover the potentials do not have an intrinsic length scale appropriate for modelling the finite thickness of the physical systems. Here we develop a framework for modelling self-avoiding strands and sheets which avoids singularities, and which provides a way to introduce a thickness length scale. In our approach pairwise interaction potentials are replaced by many-body potentials involving three or more points, and the radii of certain associated circles or spheres. Self-interaction energies based on these many-body potentials can be used to describe the statistical mechanics of self-interacting strands and sheets of finite thickness. 相似文献
92.
The authors study the bifurcation problems of rough heteroclinic loop connecting three saddle points for the case β1 > 1, β2 > 1, β3 < 1 and β1β2β3 < 1. The existence, number, coexistence and incoexistence of 2-point-loop, 1-homoclinic orbit and 1-periodic orbit are studied. Meanwhile, the bifurcation surfaces and existence regions are given. 相似文献
93.
K. S. Birdi 《Colloid and polymer science》1997,275(6):561-566
The surface tension versus temperature data of homologous series of n-alkanes and n-alkenes is analyzed. Critical temperatures are shown to be predicted from these data, with a very high precision, after some
corrections are made. The corrections are shown to arise from the effect of the critical pressure on the extrapolated data
to surface tension approaching zero.
Received: 29 October 1996 Accepted: 13 December 1996 相似文献
94.
95.
以金刚石压腔高压装置为工具,用Ⅱ型金刚石作压砧兼红外窗口,对本征态聚苯胺进行了高压(0~8.4 GPa)就位红外光谱测试。结果表明:在4.8~5.2 GPa压力区间,代表醌环振动的吸收峰相对代表苯环振动的吸收峰变小,表明聚苯胺在此压力区间结构上发生了显著变化,且这种变化是不可逆的。聚苯胺的高压(0~14.5 GPa)电阻测量结果表明:当压力小于7.5 GPa时,电阻随压力升高而显著降低,据此认为聚苯胺为电子性导电物质;在7.5 GPa处电阻出现极小值,然后又缓慢升高,至10 GPa后基本不变。推测聚苯胺电阻极小值是由结构变化引起的。至于红外光谱与电阻测量结果反映聚苯胺结构变化的压力值不一致,可能是由于测试条件不同所致。 相似文献
96.
97.
本文给出了对高功率横流CO_2激光器脉冲预电离过程的理论和实验研究.表明了预电离过程中光电离的重要作用.实验结果表明,脉冲预电离可增大高功率横流CO_2.激光器的pd值(p为放电气压、d为放电间隔),增大放电区注入功率密度.对于提高此类型激光器的放电稳定性和输出激光功率是一种技术简单而有效的手段. 相似文献
98.
A novel type of corner reflector for the reflection of surface plasmon polariton (SPP) is proposed. The reflector consists
of two layers of compensatory media whose permittivity and permeability take opposite signs to that of the corresponding layer
of the SP waveguide. By rigorously solving Maxwell's equations, the reflected SPP is proved to exist. The transverse wave
vector of the reflected SPP is always antiparallel to that of the incident SPP and no phase retardation is introduced. 相似文献
99.
Longlan Cui Hong Xu Ping He Keiko Sumitomo Yoshinori Yamaguchi Hongchen Gu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5285-5295
A hybrid emulsion polymerization was formulated for synthesizing Fe3O4/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)‐droplets with a diameter of 100–200 nm and styrene (St)‐droplets with a diameter of 3–4 μm, was obtained by mixing Mag‐miniemulsion and St‐macroemulsion. With extremely low surfactants concentration (?critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag‐droplets, as the result of smaller droplet size and larger surface ratio. Both water‐soluble potassium persulfate (KPS) and oil‐soluble 2,2′‐azobis(2‐isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60–200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe3O4/polystyrene latices assembled into well‐ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as‐synthesized Fe3O4/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag‐miniemulsion and St‐macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285–5295, 2007 相似文献
100.
Many recent algorithmic approaches involve the construction of a differential equation model for computational purposes, typically
by introducing an artificial time variable. The actual computational model involves a discretization of the now time-dependent differential system, usually
employing forward Euler. The resulting dynamics of such an algorithm is then a discrete dynamics, and it is expected to be
“close enough” to the dynamics of the continuous system (which is typically easier to analyze) provided that small – hence
many – time steps, or iterations, are taken. Indeed, recent papers in inverse problems and image processing routinely report
results requiring thousands of iterations to converge. This makes one wonder if and how the computational modeling process
can be improved to better reflect the actual properties sought.
In this article we elaborate on several problem instances that illustrate the above observations. Algorithms may often lend
themselves to a dual interpretation, in terms of a simply discretized differential equation with artificial time and in terms
of a simple optimization algorithm; such a dual interpretation can be advantageous. We show how a broader computational modeling
approach may possibly lead to algorithms with improved efficiency.
AMS subject classification (2000) 65L05, 65M32, 65N21, 65N22, 65D18 相似文献