Formation of Supersonic Zones and Local Separation Zones in Transonic Steady-State Flow Past Surface Roughness in the Free Interaction Regime

Within the framework of free interaction theory numerical methods are used to investigate the occurrence of supersonic zones with shocks in the outer inviscid region for flow past roughness in the lower viscous sublayer, with and without the formation of local separation zones.     

半导体中多光子吸收跃迁速率的全量子理论分析

本文从非线性光学中辐射跃迁速率的表达式出发,在全量子理论下,导出了半导体中任意阶多光子吸收跃迁速率的一般表达式。理论分析结果表明,n光子吸收跃迁速率与光强的n次方和n阶光子相干度成正比。本文在多能带及二能带理论模型下,对多光子吸收跃迁速率的一般表达式进行了化简,并对非线性相互作用项对跃迁速率的贡献,作了讨论。     

自由电子激光振荡器的二维数值模拟

在柱二维坐标系中,用数值计算方法求解了摇摆器内电子模拟方程组、光场方程组和无源区(不含摇摆器区)经非自适应方法变换后的无源旁轴波动方程并设计了相应的程序R_2D。用该程序计算的数值结果表明,在有源条件下二维数值模拟结果与高斯光束近似下的数值模拟结果符合较好;取完全相同的计算条件R-2D程序与洛斯阿拉莫斯实验室(LANL)的FELEX程序的计算结果符合较好;初步认为LANL实验数据的物理图象合理,数值结果基本可信;最后给出北京自由电子激光器(BFEL)的一些物理数据。     

自由电子激光的医学应用

自由电子激光这种新型光源非常适合于医学应用。通过对医用自由电子激光器的简要介绍,探讨了自由电子激光与人体组织的相互作用及其在医学上的应用前景。     

Viscosity solution theory of a class of nonlinear degenerate parabolic equations II. Lipschitz continuity of free boundary

In [1] we construct a unique bounded Hölder continuous viscosity solution for the nonlinear PDEs with the evolutionp-Laplacian equation and its anisotropic version as typical examples. In this part, we investigate the Lipschitz continuity of the free boundary of viscosity solution and its asymptotic spherical symmetricity, however, this result does not include the anisotropic case.This research is supported by the National Natural Sciences Foundation of China.     

负电子亲和势GaAs光电阴极中的三光子激发和发射的理论研究

将三阶微扰理论应用于单晶GaAs半导体,结合与实际相接近的能带结构,得到了GaAs中三光子吸收系数的解析式表达式,在考虑了激发电子的逃逸过程的情况下,进而推导了负电子亲和势GaAs光电阴极中三光子光电发射的发射系数的解析表达式.两表达式得到的理论数值分别与用ns量级脉宽、2.06μm波长的激光测得的GaAs中三光子吸收系数和GaAs(Cs,O)光电阴极中三光子发射系数的实验值相比较,吻合较好.     

Determination of tributyltin oxide in coastal marine sediments and mussels by electrothermal atomic absorption spectrometry

We have devised a new method for bis(tributyltin)oxide (TBTO) determination in marine sediments and mussels. This technique involves an n-hexane/methylene chloride mixture extraction and extract purification with a sodium hydroxide wash in order to eliminate interfering compounds. TBTO is then extracted again by nitric acid and converted into an inorganic tin species; the analysis has been effected using Zeeman graphite furnace-atomic absorption spectrophotometry. The method detection limit for the matrices examined is 0.004 μg TBTO g^?1 (wet weight) and is sufficient for the analysis in real samples. The percentage recovery of TBTO from sediments and mussels samples is higher than 85% and 95% respectively. This method has been applied to TBTO level determination in sediments and mussels (Mytilus galloprovincialis) sampled in the harbour area in Taranto, where mussel culture activities are much developed; the TBTO levels obtained in sediments and mussels were in the range 15-47 ng g^?1 (wet weight) and 11-30 ng g^?1 (wet weight) respectively. Such values are comparable with those found in other harbour areas in the Mediterranean Sea.     

Bivariate Free Knot Splines

We consider the least squares approximation of gridded 2D data by tensor product splines with free knots. The smoothing functional to be minimized—a generalization of the univariate Schoenberg functional—is chosen in such a way that the solution of the bivariate problem separates into the solution of a sequence of univariate problems in case of fixed knots. The resulting optimization problem is a constrained separable least squares problem with tensor product structure. Based on some ideas developed by the authors for the univariate case, an efficient method for solving the specially structured 2D problem is proposed, analyzed and tested on hand of some examples from the literature.     

Orbifold fibrations of Eschenburg spaces

Most of the few known examples of compact Riemannian manifolds with positive sectional curvature are the total space of a Riemannian submersion. In this article we show that this is true for all known examples, if we enlarge the category to orbifold fibrations. For this purpose we study all almost free isometric circle actions on positively curved Eschenburg spaces, which give rise to principle orbifold bundle structures, and we examine in detail their geometric properties. In particular, we obtain a new family of 6-dimensional orbifolds with positive sectional curvature whose singular locus consists of just two points.