Some Isoperimetric Inequalities in Electrochemistry and Hele Shaw Flows

Isoperimetric inequalities are applied to a moving-boundaryproblem for doubly-connected domains. This problem occurs forexample in electrochemistry, in which case the domains in questionare the electrolyte of an electrolytic cell. The two electrodessurrounding the electrolyte are assumed to grow or dissolve,at different rates in general, by electrochemical reaction.We obtain optimal estimates showing, for example, that the leastchange in volume of each electrode always occurs in sphericalsymmetry.     

The crystal and molecular structures of the compounds [(η5-C5H5)Fe(CO)2]2(CH2)n, where 0 n = 3 and 4

The crystal stuctures of [(η⁵-C₅H₅)Fe(CO)₂]₂(CH₂)_n, n = 3 and 4, have been determined.[(η⁵-C₅H₅)Fe(CO)₂]₂(CH₂)₃: a = 21.20, b = 10.39, c = 7.88Å, β = 101.6°, U = 1699ų, C2/c, Z = 4, R = 0.059, 1036 observed data.[(η⁵-C₅H₅)Fe(CO)₂]₂(CH₂)₄: a = 7.63, b = 10.54, c = 21.87Å, β = 96.4°, U= 1748ų, P2₁/c, Z = 4, R = 0.051, 1418 observed data.In each compound the iron atoms are joined by simple chains of sigma bonded CH₂ groups. Bond lengths are similar in both: mean Fe-CO 1.75, C-O 1.15, FeC(cp) 2.11, FeCH₂ 2.08, (cp)CC(cp) 1.41, CH₂CH₂ 1.55Å. The (CH₂)₃ compound retains a 2-fold axis of symmetry in the crystal. The (CH₂)₄ compound has no imposed symmetry, but closely approximates centrosymmetry. The effects of molecular symmetry on the IR spectrum between 2100 and 1900 cm^-1 are discussed. The¹³C and₁H (270 MHz) NMR spectra in solution are shown to be consistent with the structures found crystallographically.     

Bi2223带材临界电流沿长度方向的统计分布

本文采用四引线法测量了Bi2223带材临界电流沿长度方向的分布,采用正态分布、对数正态分布、威布尔分布和最小极值分布对临界电流分布进行了拟合检验,确定了临界电流的最优统计分布模型.