Stability properties of collocation methods

Lower bounds for are given for which equidistant s-point collocation methods areA()-stable for arbitrarys.     

Adaptive boundary element methods for strongly elliptic integral equations

Summary Integral operators are nonlocal operators. The operators defined in boundary integral equations to elliptic boundary value problems, however, are pseudo-differential operators on the boundary and, therefore, provide additional pseudolocal properties. These allow the successful application of adaptive procedures to some boundary element methods. In this paper we analyze these methods for general strongly elliptic integral equations and obtain a-posteriori error estimates for boundary element solutions. We also apply these methods to nodal collocation with odd degree splines. Some numerical examples show that these adaptive procedures are reliable and effective.This work was carried out while Dr. De-hao Yu was an Alexander-von-Humboldt-Stiftung research fellow at the University of Stuttgart in 1987, 1988     

What do multistep methods approximate?

Summary Standard analysis of multistep methods for ODE's assumes the application of an initialization routine that generates the starting points. Here ak-step method is considered directly as a mappingR ^kn R ⁿ . It is shown to approximate a mapping which is expressible directly in terms of the flow of the vector field. Some useful properties of that mapping are shown and for strictly stable methods these are applied to the question of invariant circles near a hyperbolic periodic solution.     

Convolution quadrature and discretized operational calculus. I

Numerical methods are derived for problems in integral equations (Volterra, Wiener-Hopf equations) and numerical integration (singular integrands, multiple time-scale convolution). The basic tool of this theory is the numerical approximation of convolution integrals

On the generation and annealing of dangling bond defects in hydrogenated amorphous silicon

We show that, through the diffusive re-arrangement of Si-H bonds, the a-SiH lattice is able to establish thermal equilibrium between the densities of band tail trapped charge carriers and dangling bond defects. When this equilibrium is disturbed by changes in temperature, carrier injection or illumination, dangling bond defects have to be generated or annealed out via H-diffusion processes. Based on the concept of charge-induced bond breaking, we develop a mathematical formalism for the diffusive re-arrangement of Si-H bonds and show that our formalism can account for a variety of observations that have been made in the context of defect-generation and annealing experiments.     

Influence of end reflectivity on gain saturation in a planar distributed feedback laser

An approximate method for the analysis of planar-waveguide distributed-feedback lasers is extended to include a nonvanishing reflectivity at the ends of the structure. An index grating structure with parasitic losses is investigated. An expression for the small-signal gain coefficient ^0MN as a function of the output power P ^MNout normalized to the saturation power P ^s , coupling coefficient K, complex reflectivity R of end reflectors, and waveguide parameters is presented.     

缬草根化学成分的研究

本文报道了湖南花坦县产的缬草根的化学成分，用气相色谱－色谱－计算机联用和波谱技术鉴定了缬草根中的４４个组分，其中乙酸里哪醇酯，２－蒈烯，马拶铃烯，瓦伦烯，香橙烯，愈创木烯，异尼醇，乙酸金合欢酯，邻苯二甲酸二异辛酯，６，１３－二甲基－十四烷酸和２－甲基十六烷酸甲酯等化合物是在缬草根中首次发现的，对缬草根中的氨基酸和微量元素也进行了测定。     

Charge donation to and dearomatization of benzene attending complexation: DFT estimates of binding energies of TpMXO(L) with benzene, for Tp = hydridotris(pyrazolyl) borate, MXO = MoNO, ReCO, and WNO, and L = ammonia, N-methylimidazole, pyridine, phosphine, methyl isocyanide, and carbon monoxide

By density functional methods we characterize the bonding and charge distribution in complexes of benzene with dearomatizing agents tpReCO(L), tpMoNO(L), and tpWNO(L), where tp = hydrido Tris (pyrazolyl)borate), for a range of ligands L. Our LSDA and B3LYP density functional calculations use the Spartan LACVP+ basis and pseudopotential on Re, Mo, and W and 6-31G* on light atoms. The binding energy is strongly dependent on the nature of the ligand L, being greatest for L = ammonia and N-methylimidazole and weakest for CH3NC and CO. We find a correlation between strength of binding and electron transfer from the dearomatizing agents toward benzene. For the most strongly bound systems we find substantial (up to 500 millielectrons) charge transfer towards benzene, while for the most weakly bound systems charge is withdrawn from benzene. Structural details illustrate the ability of Re, Mo, and W species to dearomatize complexed benzene, which is extensive for all but the most weakly bound species with L = MeNC and CO. Re and W dearomatizing agents, which are computed and observed to form stable complexes with benzene, may be economic alternatives to osmium dearomatizing agents.     

马齿苋及其籽中脂肪酸的比较研究

本实验利用ＧＣ－ＭＳ分析技术对马齿苋全草及其籽中的脂肪酸（以甲酯的形式）进行了分析，共鉴定出８种脂肪酸。全草中以亚麻酸（４７．１６％）、亚油酸（２２．００％）及棕榈酸（１７．４％）为主，籽中以亚油酸（４５．８６％）及亚麻酸（３０．６１％）为主。     

反相高效液相色谱法同时测定决明子中芦荟大黄素和大黄素

用反相高效液相色谱法分离并测定了决明子中芦荟大黄素和大黄素，建立了该中药中芦荟大黄素、大黄素分离、测定的色谱方法。色谱条件：ＯＤＳ柱，甲醇－水（８０∶２０Ｖ／Ｖ）为流动相，检测波长２２３ｎｍ。本研究为决明子的质量评价提供了科学依据。