Random Lattices with Fractal Bond Permeabilities

The macroscopic permeability of random lattices has been studied when the permeability of each link is a power law of its length with an exponent . When they are sufficiently long, the link lengths are shown to follow exponential laws which depend on the density. The macroscopic permeability is studied as a function of ; it is compared to a modified effective medium theory (EMT).*Author for correspondence: e-mail: adler@ipgp.jussieu.fr**e-mail: le_chic@mail.ru     

Diffusion-controlled smoulder propagation in a semi-infinite solid: The asymptotic temperature distribution

The authors consider the steady propagation of a two-dimensionaldiffusioncontrolled smouldering reaction front parallel to theplane boundary of a semi-infinite nonporous reactant. The reactionfront is assumed to be a sheet of line heat sources of variablestrength. The distribution of oxidizer concentration and temperaturein the porous burnt char and of the temperature in the reactantis determined in the form of an asymptotic expansion involvinga similarity variable. The temperature on the reaction frontin the asymptotic region is found to be constant to high order.The dependence of this temperature on the Lewis numbers associatedwith the reactant and the char is found to be in general agreementwith observations.     

聚吡咯薄膜的电特性

含有不同的链长的w-吡咯烷基二甲基氯硅烷作为粘合剂通过自组装（SAMs）吸附于二氧化硅表面,然后聚吡咯膜化学沉积于该粘合剂修饰的表面。化学沉积的聚吡咯膜的表面形貌用扫描电镜（SEM）及原子力显微镜（AFM）表征。除短链外不同链长的粘合剂对聚吡咯膜的厚度影响不大。聚吡咯膜的电特性用电流-电压表征。结果显示电流与粘合剂的链长无关。电特性表明载流子迁移率为1.4 ´ 10-4 cm2×V-1.s –1。     

A Criticality Criterion for Thermal Explosions in Well-stirred Systems with Reactant Consumption: Addendum

OUR attention has been drawn to the fact that the criticalitycondition ^* = 1 of Adler & Herbert (1985), for well-stirredreactive systems, has been derived previously (Gray, 1975).It arises from an examination of trajectories in the temperaturereactant phase plane when a tube stability argument is employed.Using the criterion ^* = 1, values of the critical Semenov numberhave also been obtained numerically (Gray & Jones, 1981). Our work on criticality for systems with reactant consumptioncame about by trying to reconcile the inflection criterion ofBoddington et al. (1983), for finite B, with the correspondingmaximum criterion in the limit B . Our contribution was to showthat the Semenov number versus maximum temperature ^* curvehas a bifurcation at ^* = 1 for all B. Both Gray's work and ourown are attempting to resolve the same problem; the approachesare, however, quite distinct and complement each other     

Thermal Conductivity of a Single Fracture

The macroscopic conductivity of fractures is determined for Gaussian and self-affine fractures by solving the three-dimensional Laplace equation. Results are discussed and compared with various analytical or two-dimensional approximations. They are shown to be in good agreement with some existing experimental data.     

The Critical Conditions in a Reactive Slab with Slowly Varying Surface Temperature

Liouville's non-linear partial differential equation is consideredfor an infinite rectangular strip domain with a slowly varyingboundary condition. The equation describes a layer of chemicallyreactive material under conditions where the resistance to surfaceheat transfer is negligible and the ambient temperature variesslowly along the surface. Symmetrical heating by a zero orderexothermic reaction is assumed. If is a small dimensionlesstemperature difference between regions where the surface temperatureis effectively constant, a perturbation series solution in may be determined provided the Frank-Kamenetskii parameter satisfies _c(). It is shown that a plausible value for thecritical parameter is _c() = _c(0) e^–e,where _c(0) = 0.878.The corresponding critical temperature distribution is shownto have a dependence on different from that for subcriticalcases.     

3-烷基取代吡咯单体的合成

通过电聚合沉积在基底上的聚吡咯膜容易剥离的问题可以通过粘合增强剂解决。我们设计并合成一类新化合物w-3-吡咯烷基磷酸将聚吡咯膜 通过化学键键合到金属基底上。本文描述了合成含有表面反应功能团的3-取代吡咯的过程。1-苯磺酰吡咯作为起始物经付-克反应得到3-取代吡咯。两种方法可以合成w-3-吡咯烷基磷酸酯。一种路线是：先磷酸化然后脱保护基最后还原羰基。这种方法适用于含有六个碳及以上的取代基。另一种路线是：先还原羰基然后磷酸化及脱保护。这种方法适用于短链及长链取代基。最后水解得到w-3-吡咯烷基磷酸。