Triterpenoid Constituents of Huperzia miyoshiana

Thirteen triterpenoids, including three new ones, miyoshianois A (1), B (2) and C (3), were isolated from Huperzia miyoshiana. The structures of these new compounds were established as 3-O-dihydroferuloyltohogenol (1), 16-oxo-3β,21β-dihydrox-y-serrat-14-en-24-ferulate (2) and 16-oxo-3a, 21β-dihydroxy-serrat-14-en-24-ferulate (3), respectively, on the basis of their spectroscopic analysis.     

毛细管放电X光激光中的预脉冲研究

 为研究毛细管放电X光激光中预脉冲放电对增益的影响，用简化的XDCH程序，模拟计算了聚乙烯毛细管充Ar气、2μs脉宽的预脉冲放电过程，把预放电之后的等离子体温度、密度和电离度作为初始条件，输入XDCH程序，进行40kA典型主脉冲放电的计算模拟，给出了一些典型预放电幅度下的增益和电子密度分布情况。比较分析的结果发现，对2μs脉宽的预脉冲，100A的电流将得到较好的增益，并且预言激光线时间谱可能出现双峰结构，空间谱会出现环状结构。     

会聚厄米-双曲余弦高斯光束的光强分布和焦移

 基于厄米-双曲余弦高斯光束通过无光阑限制薄透镜聚焦的解析传输公式，研究了厄米-双曲余弦高斯光束聚焦区域的光强分布，并对光束的焦移进行了分析，讨论了偏心参数对光强主极大位置的影响。结果表明：TEM₁₁模厄米-双曲余弦高斯光束的相对焦移（绝对值）随偏心参数和菲涅尔数的减小而增大，菲涅尔数较大时相对焦移趋于零。TEM₂₂模光束在偏心参数小于0.54时，轴外与轴上光强极大值的比值大于1，此时光强主极大在轴外，偏心参数大于0.54时则相反；在偏心参数等于0.54时比值为1，此时光束有两个主极大，偏心参数愈大光强愈集中于轴上。使用LW法和GH法得到的TEM₂₂模光束的相对焦移（绝对值）随偏心参数和菲涅尔数的变化规律与TEM₁₁模光束一致，但相同参数下使用这两种方法得出的具体结果不同。     

Synthesis,X-Ray Structure and Characterization of a Triruthenium Cluster Complex Ru_3~Ⅲ(μ_3-O)(μ-CH_3COO)_6(py)_2Cl with Four Steps One-electron Redox Processes

Great attention is currently paid to the synthesis of polynuclear transition metal complexes as well as their photochemical, photophysical, and electrochemical properties. The design of multicomponent systems capable of performing useful light- and/or redox-induced function is of special interest1. The oxo-centered carboxylate-bridge trinuclear ruthenium clusters have been investigated extensively during recent decades because they have remarkable electron-transfer properties, intense visibl…     

Time-Resolved Femtosecond Degenerate Four-Wave Mixing in LiNbO3：Fe,Mg Crystal

Forward degenerate four-wave mixing （DFWM） processes are investigated with a femtosecond pulsed laser in lithium niobate crystal doubly-doped with magnesium and iron （LiNbO3：Fe, Mg）. The pulse energy dependence reveals a pure third-order nonlinear response, and the third-order nonlinear susceptibility x^（3） in the material is evaluated to be 4.96 × 10^-13 esu. The time-resolved DFWM process shows a response time of x^（3） shorter than 100fs, which is due to the nonresonant electronic nonlinearities. Our results indicate that LiNbO3 crystals have potentials for ultrafast real-time optical processing systems, which require a large and fast x^（3） optical nonlinearity.     

Endpoint estimates for certain commutators of fractional and singular integrals

In this paper, the authors obtain the endpoint estimates for a class of non-standard commutators with higher order remainders and their variants. Moreover, the authors show that these operators are actually not bounded in certain cases.

     

聚苯硫醚／石墨基双极板复合材料性能的研究

以聚苯硫醚树脂和人造石墨为原料一次模压成型制备双极板复合材料.研究了模压成型过程中加压时机、冷却方式及人造石墨原料对复合材料电导率和弯曲强度的影响.结果表明,制备聚苯硫醚/石墨基双极板材料宜选用石墨化程度较高且结构密实的石墨粉料;采用保温后加压及空气中冷却方式制备的复合材料的综合性能较优.     

Na离子和Cl离子引起He原子直接多重电离过程的研究

利用2～8 MeV的Naq+、Clq+(q=2,3,4,5)轰击氦原子,对碰撞的直接多重电离过程进行研究.实验采用反冲离子-散射离子飞行时间符合技术,通过反冲离子飞行时间谱区分不同价态反冲离子;利用静电偏转和位置灵敏探测技术区分不同电荷态散射离子;结合CAMAC-PC多参数获取系统得到一定价态散射离子所对应的反冲离子电荷态分布谱;经分析该谱得到直接多重电离截面与直接单电离截面之比R21.讨论了R21随入射离子速度和电荷态的变化关系.     

有向图上的随机游动

设G=(V,Г)是有向图,G上的随机游动X(G)定义如下:位于某个顶点上的一个粒子将以等概率转移到该顶点的所有后继顶点.令M(j,n)表示随机游动X(G)在前n步内访问顶点j的平均次数,用W(j)表示随机游动X(G)到达顶点j所需要的平均步效.我们对M(j,n)和W(j)的值进行了估计,证明了M(j,n)=O(n),并给出了W(j)的上界.