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991.
992.
Diffusiophoresis of colloidal spheres in nonelectrolyte gradients at small but finite Péclet numbers
The diffusiophoretic motion of a spherical particle in a uniform imposed gradient of a nonionic solute is analyzed for small
but finite Péclet numbers. The range of the interaction between the solute molecules and the particle surface is assumed to
be small relative to the radius of the particle, but the polarization effect of the mobile solute in the thin diffuse layer
surrounding the particle caused by the strong adsorption of the solute is incorporated. A normal flux of the solute and a
slip velocity of the fluid at the outer edge of the diffuse layer are used as the boundary conditions for the fluid domain
outside the diffuse layer. Through the use of a method of matched asymptotic expansions along with these boundary conditions,
a set of transport equations governing this problem is solved in the quasisteady situation and an approximate expression for
the diffusiophoretic velocity of the particle good to O(Pe
2) is obtained analytically. The analysis shows that the first correction to the particle velocity is O(Pe
2). The normalized particle velocity is found to decrease monotonically with the Péclet number and to increase monotonically
with the dimensionless relaxation coefficient. The stronger the polarization effect in the diffuse layer, the weaker the convective
effect on the diffusiophoresis.
Received: 25 May 2000 Accepted: 6 September 2000 相似文献
993.
994.
By means of1H,13C,11B NMR, polar transfer DEPT135, DEPT90 and 2D NMR experiments, IR, etc, the structure of the diaminodihydroxyl ligand and its
derivatives used in the asym-metric reduction of prochiral ketones were detected. The catalysts derived from the ligand and
borane formedin situ were also studied and the structure transformations in solution were monitored. The structure of the catalyst was proved
to be a new type of dual-centered catalyst — bisoxazaborolidine. 相似文献
995.
996.
PAN基活性炭纤维的表面及其孔隙结构解析 总被引:5,自引:0,他引:5
通过氮吸附等温线、X射线光电子能谱以及扫描电子显微镜(SEM)对聚丙烯腈(PAN-Polyacrylonitrile)-基活性炭纤维(ACF-Activated Carbon Fiber)的表面和孔隙结构进行了分析,结果表明吸附测量可以提供有关碳质吸附剂的孔结构复杂性;通过XPS对PAN基ACF的表面官能团的种类及含量进行了表征,由SEM对PAN基ACF的表面以及断面的孔隙结构进行了直接观察,提供了有关孔隙结构的直接证据。 相似文献
997.
材料物性参数识别的梯度正则化方法 总被引:12,自引:1,他引:11
本文对梯度正则化方法(Gradient-Regularization Method)作了进一步的研究,给出一种建立了梯度正则化迭代算法和选择正参数的简明实用方法。文中椭圆算子方程参数识别算例不仅说明了GR法具有广泛的适应性和一定的抗噪声能力,而且收敛速度较快,具有较大的收敛范围。 相似文献
998.
Theoretical Efficiency of an Inexact Newton Method 总被引:6,自引:0,他引:6
We propose a local algorithm for smooth unconstrained optimization problems with n variables. The algorithm is the optimal combination of an exact Newton step with Choleski factorization and several inexact Newton steps with preconditioned conjugate gradient subiterations. The preconditioner is taken as the inverse of the Choleski factorization in the previous exact Newton step. While the Newton method is converging precisely with Q-order 2, this algorithm is also precisely converging with Q-order 2. Theoretically, its average number of arithmetic operations per step is much less than the corresponding number of the Newton method for middle-scale and large-scale problems. For instance, when n=200, the ratio of these two numbers is less than 0.53. Furthermore, the ratio tends to zero approximately at a rate of log 2/logn when n approaches infinity. 相似文献
999.
We propose an implementable BFGS method for solving a nonsmooth convex optimization problem by converting the original objective function into a once continuously differentiable function by way of the Moreau–Yosida regularization. The proposed method makes use of approximate function and gradient values of the Moreau-Yosida regularization instead of the corresponding exact values. We prove the global convergence of the proposed method under the assumption of strong convexity of the objective function. 相似文献
1000.
On the truncated conjugate gradient method 总被引:7,自引:0,他引:7
Y. Yuan 《Mathematical Programming》2000,87(3):561-573
In this paper, we consider the truncated conjugate gradient method for minimizing a convex quadratic function subject to a
ball trust region constraint. It is shown that the reduction in the objective function by the solution obtained by the truncated
CG method is at least half of the reduction by the global minimizer in the trust region.
Received January 19, 1999 / Revised version received October 1, 1999?Published online November 30, 1999 相似文献