The Transport Properties of Hot Electrons in a Xenon/Methane Mixture

The results are given of numerical solution of the Boltzmann equation in a binomial approximation in view of elastic and inelastic electron collisions in Xe+CH₄ mixtures and in pure methane. The electron energy distribution functions obtained are used to calculate the electron transport coefficients for E/N values of up to several Townsends, i.e., the drift velocity, mobility, average and characteristic energies, diffusion coefficient. The results of calculation for pure methane fit the available experimental data. A similarity rule is found for the electron transport coefficients in a Xe+CH₄ mixture with different concentrations of methane molecules, which enables one to determine the values of transport coefficients in a mixture with a minor (less than 30 percents) methane content.     

Midplane-symmetry breaking in the flow between two counter-rotating disks

This paper considers the axisymmetric steady flow driven by exact counter rotation of two co-axial disks of finite radius. At the edges of the rotating disks one of three conditions is (typically) imposed: (i) zero velocity, corresponding to a stationary, impermeable, cylindrical shroud (ii) zero normal velocity and zero tangential fluid traction, corresponding to a (confined) free surface and (iii) an edge constraint that is consistent with a similarity solution of von Kármán form. The similarity solution is valid in an infinite geometry and possesses a pitchfork bifurcation that breaks the midplane symmetry at a critical Reynolds number. In this paper, similar bifurcations of the global (finite-domain) flow are sought and comparisons are made between the resulting bifurcation structure and that found for the similarity solution. The aim is to assess the validity of the nonlinear similarity solutions in finite domains and to explore the sensitivity of the solution structure to edge conditions that are implicitly neglected when assuming a self-similar flow. It is found that, whilst the symmetric similarity solution can be quantitatively useful for a range of boundary conditions, the bifurcated structure of the finite-domain flow is rather different for each boundary condition and bears little resemblance to the self-similar flow.     

On a three-dimensional axisymmetric boundary-value problem of nonlinear elastic deformation: Asymptotic solution and exponentially small error

In this paper, we study a three-dimensional axisymmetric boundary-value problem of a slender cylinder composed of a nonlinearly elastic material subjected to an axial force. Starting from the field equations, after a transformation and proper scalings, we identify a small variable and two small parameters, which characterize the present problem. Then, by an approach involving compound series-asymptotic expansions, a nonlinear ODE is derived, which governs the axial strain (the first-term in the series expansion). By imposing the zero radial displacement conditions at two ends, we manage to get the analytical solution of the axial strain, from which all other physical quantities can be deduced and thus the three-dimensional displacement field can be determined. Graphical results are presented, which show that there are two boundary layers near the two ends while the middle part is in a state of almost uniform extension. The asymptotic structure of the analytical solution is derived, which offers clear explanations to the structure of the deformed configuration and shows that the thickness of both boundary layers is of the order of the radius. We also point out the relevance of the present results to the St. Venant’s problem. In particular, we obtain the explicit uniformly-valid exponentially small error term, when the obtained deformed configuration is compared to the configuration of a uniform extension.     

化学还原法制备纳米铜粉的研究

本文采用KBH4在液相中化学还原CuSO4,并加入KOH和络合剂EDTA ,制得了纳米级的纯净的铜粉 ,通过调整反应物的浓度 ,可以消除Cu2 O等杂质。制备的纳米铜粉还存在一定程度的团聚 ,需试验加入分散剂来改善。     

求非线性方程近似解的逐次迭代法

本文提出了求解非线性问题的一种新方法——逐次迭代法，本方法先是给出一个初始近似解，然后将这个近似解进行校正迭代，使之接近于真实解，把一个非线性问题转化为一个线性问题来解决。     

胡状集油田胡5-15井区天然混合羧酸盐/黄胞胶驱油先导试验

报道了在室内实验研究中得到的混合天然羧酸盐/烷基磺基甜菜碱/黄胞胶复合驱油段塞结构:预冲洗段塞,10g/LKCl溶液;前置聚合物段塞,1500mg/L黄胞胶溶液;主驱油段塞,1.5×104mg/L混合天然羧酸盐+800mg/L烷基磺基甜菜碱DSB+800mg/L黄胞胶+5×103mg/L复碱(质量比1∶1的Na2CO3+NaHCO3)溶液;后置聚合物段塞,1000mg/L黄胞胶溶液。在岩心流动实验中0.3PV主段塞在水驱基础上提高采收率18.19%。胡状集油田胡5 15井区采出程度18.48%,油藏温度86℃,地层水矿化度1.7×105mg/L,Ca2+浓度4799mg/L,Mg2+浓度830mg/L,有油、水井各5口,综合含水已达96%(92%～99%)。从2000 01 24到2001 03 20,在5口注水井中依次注入预冲洗液2920m3,前置液2920m3,主驱油液49640m3(除一口井外均不加复碱),后置液2920m3,5口油井均见效,一些油井有效期超过20个月,油井产油量增加,含水下降,自然递减降低62.7%,采油速度升高0.46%。图3表2参3。     

PVDF中空纤维滤膜的形态结构

用Ｌ－Ｓ相转换法制备了聚偏氟乙烯（ＰＶＤＦ）中空纤维不对称滤膜。铸膜液由聚合物、溶剂和添加剂组成。用电子显微镜（ＳＥＭ）考察了聚合物浓度、添加剂用量及种类对膜形态结构的影响。实验结果表明，聚合物浓度对膜形态结构有显著影响，当铸膜液中聚合物浓度较低时，无论用什么种类添加剂，都能形成大、且多的孔，但孔的形状随添加剂不同而异。当恒定聚合物浓度时，添加剂的用量对膜形态结构有很大的影响，但孔的大小及多少与添加剂含量的多少不成正比。     

一类广义耦合的KdV方程组的整体吸引子

利用Sobolev插值不等式和关于时间t的先验估计，研究了一类广义耦合的具有周期初值问题的KdV方程，得到了整体解和整体吸引子的存在性。     

糠醛注水——润滑油糠醛精制装置的节能途径

介绍了用水稀释糠醛使润滑油糠醛精制装置节能的途径。通过注水——糠醛－水溶液（含水９５％左右），可降低糠醛的气化沸点，增大换热系统的传热温差，改善换热效果，更多地回收能量，达到节约能源的目的。     

RADIATION FIELD FROM A RECTANGULAR PLAQUE SOURCE FOR RADIATION PROCESSING

Evaluation of the Hubbell integral for an omnidirectional detector response to a rectangular plaque gamma emitting radiation source using a different numerical computation method on a personal computer was made. For a plaque consisting of several strip gamma emitters, exposure rates at different positions above the source were calculated using 'exact' evaluation and an approximate method. Optimization method is used to find source activity of each strip, so as to acquire desirable dose uniformity of the irradiated products. In uses of the Hubbell integral, by introducing appropriate programming, computation time can be saved.