非齐次微分方程两点边值问题正解的存在性及多重性

本文考虑一类非齐次微分方程的两点边值问题,得到了一些有关其正解存在性与多重性的精确条件．     

橙皮素A的NMR研究

橙皮素A是从中药北沙参(Glehnia littoralis Fr. Schmidt ex Miquel)的正丁醇萃 取物中分离得到的一种8-O-4′-型异木脂素苷类化合物. 通过化学方法和波谱分析鉴 定了该 化合物的结构. 采用2D NMR技术对其NMR信号进行了全归属. DMSO-d₆代替CD₃OD作为溶剂，并利用重水交换，能准确读出偶合常数J_7,8值.      

高温超导薄膜微波非线性研究的进展

文章介绍了高温超导薄膜微波非线性的主要特征，阐述了高温超导薄膜微波非线性产生的原因和相关的研究现状，指出了高温超导薄膜非线性研究中遇到的困难和尚未解决的问题．     

Effect of carbon content on the microstructure and the cracking susceptibility of Fe-based laser-clad layer

The laser cladding of Fe-based alloys on a medium carbon steel substrate was performed using a CO₂ laser and Ar shielding gas that was blown into a molten pool. The microstructure and cracking susceptibility of the laser-clad layers were studied in terms of carbon additions. Results show that the small change of the carbon content in the alloy powders can obviously change the microstructure and properties of the layers. When the carbon content is in the range of 0.3–0.4 wt.%, the decrease of the carbon content in alloy powders will increase the hardness and toughness of the layers simultaneously under the same process parameters. As a result, crack-free coatings with high hardness can be obtained. As the carbon content increases from 0.2 wt.% to 0.4 wt.%, the segregation ratio of chromium increases, while the segregation ratios of nickel, manganese, and silicon first decrease and then increase. At the same time, a new designing principle concerning the composition and microstructure has been put forward, and the principal mechanisms of strengthening and toughening of the layers are fine-grain strengthening and low carbon martensitic phase transformation strengthening.     

一类退化型Schrodinger方程解的连续性

该文通过一种基本的分析方法,得到了一类退化型Schrodinger方程解的连续性结果,方程的类型为:Lu+vu=(f_i)_{x_i},其中L为一退化椭圆算子,v属于某一Kato类的类比,而f_i 属于某一加权L^p空间.     

人原始生殖细胞的分离和体外培养

从4～10周龄药物流产胚胎的生殖嵴和肠系膜组织中分离原始生殖细胞(primordial germ cells,PGCs),培养在添加人重组白血病抑制因子(rh LIF)、人重组碱性成纤维细胞生长因子(rh bFGF)和Forskolin的小鼠饲养层细胞上.经过4～7 d培养,PGCs形成典型的鸟巢状集落.集落在传代过程中保持碱性磷酸酶活性,且胚胎阶段性特异抗原1(SSEA-1)、胚胎阶段性特异抗原3(SSEA-3)免疫荧光染色呈阳性.具有分化潜能的PGCs能在体外连续传代培养12代.结果表明从药物流产胚胎中分离的人类PGCs可以在体外培养成为具有分化潜能的多能性干细胞.     

内源全息术的原理和数学描述

以往的全息术在对原子成像时,在相干光源、探测器空间分辨和信号强度三个方面遇到了难以克服的困难. 阐述了内源全息术克服这些困难的原理,研究了内源全息术的记录和再现全过程,推导出内源球面全息图的再现公式,并在散射因子球对称近似和能量无关近似下,推导出以δ函数表示原子全息再现像的解析表达式. 关键词： 内源全息术 同步辐射 晶体结构 傅里叶变换     

Bis[μ‐1‐(1,10‐phenanthrolin‐2‐yl)‐2‐pyridone]bis{aqua[1‐(1,10‐phenanthrolin‐2‐yl)‐2‐pyridone]cadmium(II)} tetrakis(perchlorate)

In the title centrosymmetric binuclear complex, [Cd₂(C₁₇H₁₁N₃O)₄(H₂O)₂](ClO₄)₄, the Cd^II ion assumes a distorted octahedral geometry. There are π–π stacking interactions between the pyridine and 1,10‐phenanthroline ring systems of adjacent ligands at the same Cd^II centre. Intermolecular hydrogen bonds between the coordinated aqua ligand and the O atom of a keto group connect adjacent complex cations into extended chains. Hydrogen bonds also exist between the complex cations and the perchlorate anions. Compared with the fluorescence spectrum of the organic ligand, the complex displays strong fluorescent emission and an ipsochromic shift of the emission peaks, which may be attributed to the structural character.     

A projection method for solving incompressible viscous flows on domains with moving boundaries

In this paper, a projection method is presented for solving the flow problems in domains with moving boundaries. In order to track the movement of the domain boundaries, arbitrary‐Lagrangian–Eulerian (ALE) co‐ordinates are used. The unsteady incompressible Navier–Stokes equations on the ALE co‐ordinates are solved by using a projection method developed in this paper. This projection method is based on the Bell's Godunov‐projection method. However, substantial changes are made so that this algorithm is capable of solving the ALE form of incompressible Navier–Stokes equations. Multi‐block structured grids are used to discretize the flow domains. The grid velocity is not explicitly computed; instead the volume change is used to account for the effect of grid movement. A new method is also proposed to compute the freestream capturing metrics so that the geometric conservation law (GCL) can be satisfied exactly in this algorithm. This projection method is also parallelized so that the state of the art high performance computers can be used to match the computation cost associated with the moving grid calculations. Several test cases are solved to verify the performance of this moving‐grid projection method. Copyright © 2004 John Wiley Sons, Ltd.     

Numerical analysis of the rotating viscous flow approaching a solid sphere

A numerical simulation is performed to investigate the flow induced by a sphere moving along the axis of a rotating cylindrical container filled with the viscous fluid. Three‐dimensional incompressible Navier–Stokes equations are solved using a finite element method. The objective of this study is to examine the feature of waves generated by the Coriolis force at moderate Rossby numbers and that to what extent the Taylor–Proudman theorem is valid for the viscous rotating flow at small Rossby number and large Reynolds number. Calculations have been undertaken at the Rossby numbers (R_o) of 1 and 0.02 and the Reynolds numbers (R_e) of 200 and 500. When R_o=O(1), inertia waves are exhibited in the rotating flow past a sphere. The effects of the Reynolds number and the ratio of the radius of the sphere and that of the rotating cylinder on the flow structure are examined. When R_o ? 1, as predicted by the Taylor–Proudman theorem for inviscid flow, the so‐called ‘Taylor column’ is also generated in the viscous fluid flow after an evolutionary course of vortical flow structures. The initial evolution and final formation of the ‘Taylor column’ are exhibited. According to the present calculation, it has been verified that major theoretical statement about the rotating flow of the inviscid fluid may still approximately predict the rotating flow structure of the viscous fluid in a certain regime of the Reynolds number. Copyright © 2004 John Wiley & Sons, Ltd.