电感耦合等离子体原子发射光谱法及离子选择电极法测定荧光级氧化钇中痕量铈的研究

文章描述了荧光级氧化钇中痕量稀土铈的测定方法,在溴酸钾存在下,5摩尔/升HNO_3介质中,以P507萃取微量铈,然后有机相用硝酸、过氧化氢反萃取、再将水相浓缩定容,然后以电感耦合等离子体原子发射光谱法分析。同时用铈的离子选择电极以二次标准加入法作第二种手段分析。样品溶液以乙醇预去溶方式引入等离子体,测定下限为2微克/克,方法简单、快速、准确。离子选择电极法测定铈离子下限1×10～(-5)摩尔/升,回收率为94-101%,方法简单,结果满意、价格便宜。     

用有限元法分析多波导耦合系统本征模的模式特性

本文应用有限元法(FEM),计算和分析了多波导耦合系统的本征模(超模)的模式特性及其变化规律,得到了强度均匀分布的基超模,克服了微扰理论计算这类问题的局限性.     

Finite element simulation of dip coating,I: Newtonian fluids

A finite element simulation of the dip coating process based on a discretization of the continuum with discontinuous pressure elements is presented. The algorithm computes the flow field from natural boundary conditions while an extra condition provided by the existence of free surface is employed to displace the meniscus location towards the actual position. The process is iterative and uses a pseudo-time stepping technique coupled to a cubic spline fitting of the free surface. Numerical predictions exhibit good agreement with experimental data for Newtonian fluids in the case of flat plate dip coating as well as in the case of wire dip coating.     

单纯形法计算薄膜常数

本文首次报道了用单纯形加速法计算正常兔ＩｇＧ抗原与羊－抗兔抗体反应的抗体层厚度和光学常数，该方法假定抗体层厚度、光学常数均为时间的函数，避免了以往只假定厚度为时间函数所造成的误差。结果表明该方法计算抗体层薄膜常数是可行的。     

On the convergence of a class of algorithms using linearly independent search directions

Powell has shown that the cyclic coordinate method with exact searches may not converge to a stationary point. In this note we consider a more general class of algorithms for unconstrained minimization, and establish their convergence under the assumption that the objective function has a unique minimum along any line.     

A bump triangular dynamic factorization algorithm for the simplex method

A dynamic factorization algorithm is developed which algebraically partitions the basis inverse in such a manner so that the simplex method can be executed from a series of small inverses and the basis itself. This partition is maintained dynamically so that the additional memory required to represent the basis inverse reduces to this series of small inverses for in-core implementations.The algorithm is intended for use in solving general large-scale linear programming problems. This new method of basis representation should permit rather large problems to be solved completely in-core.Preliminary computational experience is presented and comparisons are made with Reid's sparsity-exploiting variant of the Bartels—Golub decomposition for linear programming bases. The computational experience indicated that a significant reduction in memory requirements can usually be obtained using the dynamic factorization approach with only a slight (up to about 20%) degradation of execution time.This research was supported in part by the Air Force Office of Scientific Research, Air Force System Command, USAF, under AFOSR Contract/Grant Number AFOSR-74-2715.     

Numerical modelling of viscous non-Newtonian effects in lubricating systems

Modern lubricants often exhibit shear-thinning due to the presence of high molecular weight polymers as additives. Therefore the influence of such non-Newtonian effects on the performances of lubricating systems must be predicted. The corresponding fluid film flow is governed by a non-linear partial differential equation, which generalizes the classical Reynolds equation. Having prescribed adequate boundary conditions, this equation is solved by a finite element method with optimal control. The problem of the square slider bearing lubricated by the Rabinowitsch fluid is solved in order to test the accuracy of the numerical scheme. The pressure and velocity fields are given and compared with the corresponding ones obtained for the Newtonian fluid.     

Studies on Fast Algorithm for the Scattering of a Large Array of Waveguide-Fed Wide-Slot Antennas in Millimeter Wave Region

We present an effective numerical technique to characterize the scattering of wide-slot antennas fed by waveguides with arbitrary terminations in terms of the method of moment (MoM) and the mixed potential integral equation (MPIE). In particular, the precorrected-fast Fourier transform (P-FFT) eliminates the need to generate and store the usual square impedance matrix andthus leads to speed up the matrix-vector multiplication in the resultant system. This property makes the Rao-Wilton-Glisson (RWG) functions to be useful in simulating electrically large-scale problems. In addition, the scattering from the finite ground surfaces is accounted for in the total scattered field by using the method of equivalent edge currents. The numerical results are presented and compared with both the traditional method of moment results obtained using the entire-domain basis functions and the experimental results, to demonstrate the proposed method to be a good candidate for study on the scattering of arbitrary wide-slot large array.     

Visualization of shock-wave formation processes during shock reflection at obstacles with multiple steps

According to standard textbooks on compressible fluid dynamics, a shock wave is formed by an accumulation of compression waves. However, the process by which an accumulated compression wave grows into a shock wave has never been visualized. In the present paper, the authors tried to visualize this process using a model wedge with multiple steps. This model is useful for generating a series of compression waves and can simulate a compression process that occurs in a shock tube. By estimating the triple-point trajectory angle, we demonstrated visually that an accumulated compression wave grows into a shock wave. Further reflection experiments over a rough-surface wedge confirmed the tendency for the triple point trajectory angle to reach the asymptotic value _s in the end.This work was first presented at the Symposium on Shock Waves, Japan 2002     

The method of lines applied to nonlinear nonlocal functional differential equations

This paper discusses nonlinear functional differential equation in a real reflexive Banach space with nonlocal history condition. By using the method of lines, the existence and uniqueness of a strong solution are established. Finally, some applications of the abstract results are presented.