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881.
Two phase immiscible flow in petroleum reservoirs is considered. Various formulations of the governing equations that describe this flow, including phase, global, and weighted formulations, are numerically experimented. Mixed finite element methods are used to solve these formulations. Our experiments show that the numerical results obtained using the phase and global formulations match well in terms of production rates, characterization curves, and water cuts. 相似文献
882.
883.
884.
The problems of a computational procedure in modeling structural isomer–isomer transitions in multiatomic molecules are considered. A number of approximations that allow one to considerably simplify calculation of the probabilities of these transformations are suggested. In comparison with traditional calculations of potential surfaces and determination of their saddle points, in the proposed approach the relationship between the electronic and vibrational components of a general problem is virtually changed. A particular emphasis is put on the vibrational part, which seems to be more physical. It is shown that the problem of structural isomer–isomer conversions can be solved without resorting at all to explicit calculation of the contribution of an electronic matrix element to the probability of transition. There is no need to study in detail the shapes of potential surfaces; it suffices only to know the positions of their minima. The calculation of multidimensional vibrational integrals is replaced by calculation of one-dimensional integrals. The results obtained form a basis for constructing methods for modeling the dynamic spectra of complex molecules considering their structural transformations. 相似文献
885.
Hai-Lun Lin 《Theoretical chemistry accounts》1991,79(1):43-52
Summary This is the first paper of a series of two, which enables the evaluation ofU(n) generator matrix elements in the non-canonical Weyl tableau basis adapted to subgroupU(n
1)×U(n
2). In this paper the explicit closed formulae for subduction coefficients are presented. These formulae will become useful through an inductive method to be presented in the second paper. 相似文献
886.
三元复合表面膜反射光谱的计算 总被引:1,自引:1,他引:0
将二元的金属-介质非均匀复合物的等效介质理论推广到三元的情况,并由此计算出两种铝阳极氧化着色谱试样的反射谱。与实验结果对比可看出,计算曲线与实验曲线大致相符,表明该计算方法在一定范围和条件下的适用性,从而为多元复合表面材料光特性的理论研究提供了一种可行的方法。 相似文献
887.
测定并讨论了产自四川冕宁矿区的氟碳铈矿和产自内蒙白云鄂博稀土矿区的黄河矿、氟碳钙铈矿、氟碳铈钡矿的光致发光谱。结果表明,稀土氟碳酸盐矿物在488.0nm和514.5nm激光激发下的光致发光中心是Nd3+,发光谱中的所有谱带均出自Nd3+的辐射跃迁。在488.0nm激光激发下,稀土氟碳酸盐矿物在495nm到733nm谱区的发光谱带强而尖锐,但在514.5nm激光激发下,这个谱区的谱带明显变弱或消失,转而出现783nm到907nm谱区的强发光谱带。可见光吸收谱表明稀土氟碳酸盐矿物对可见光的吸收也与矿物中的Nd3+有关。 相似文献
888.
For many clinical purposes various artificial devices are applied, which contact human tissue and can thus cause adverse reactions between prosthetic surfaces and body components. Of the many materials applied for orthopaedic joint replacements the most common are cobalt-chromium-molybdenum alloys. In these cases considerable amounts of cobalt-chromium-molybdenum wear particles are released from the prostheses which have to be regarded as a cause of long-time problems for the patient.Since these particles are dissolved in body fluids of the surrounding area they are distributed in the whole body via blood. Elevated metal concentrations have been found in blood and urine of persons with endoprostheses. Partly the metals are excreted via urine, but to some extend they accumulate in different organs.Therefore this study dealt with the development of an analytical method for the determination of seven relevant trace elements, namely Al, Co, Cr, Mo, Nb, Ni, and Ti in nine kinds of human tissue (brain, heart, kidney, liver, lung, muscle, lymphatic nodes, spleen, body fat) starting with drawing of the sample, sample work up and finally analysis by means of atomic spectrometry. The optimized method was then applied to determine the metal contents in organs of persons (post mortem) with total hip replacements with metal on metal bearing surfaces. Comparison of the data obtained with those of persons without hip-endoprostheses shows that brain and lung are the main targets for elemental accumulation in persons with hip-endoprostheses. Mo and Nb represent the elements with the highest tendency to be accumulated. 相似文献
889.
890.
La、Ce和Pr对甲基丙烯醛氧化酯化催化剂性能的影响 总被引:2,自引:0,他引:2
国内目前主要采用丙酮氰醇法(ACH法)生产甲基丙烯酸甲酯(简称MMA),此法工艺流程长、原子经济性低(约47%)、经济效益差、环境污染严重[1]. 相似文献