峰形类比巧析法在红外光谱实验教学中的应用

通过红外光谱实验教学,把理论知识贯穿于实验操作和解析中,选取典型的化合物,采用峰形比较法,让学生掌握解析红外谱图的一般规律。     

关于一类拟线性抛物方程解的Blow—up问题

本文利用Ｆｏｕｒｉｅｒ空间的比较原理研究一类拟线性抛物方程解的Ｂｌｏｗ－ｕｐ问题，并给出了其解在有限时刻Ｂｌｏｗ－ｕｐ的条件。     

Synthesis of cyclicβ-silylenones via oxidative rearrangement of tertiaryα-hydroxy allylsilanes with PCC

An oxidative rearrangement of cyclic tertiary a-hydroxy allylsilanes has been carried out in refluxing ClCH₂CH₂Cl with pyridinium chlorochromate（PCC）.The reaction provides a convenient method to synthesize cyclicβ-silylenones in modest to excellent yields.     

Analytical and experimental studies on nonlinear characteristics of an L-shape beam structure

This paper focuses on theoretical and experimental investigations of planar nonlinear vibrations and chaotic dynamics of an L-shape beam structure subjected to fundamental harmonic excitation,which is composed of two beams with right-angled L-shape.The ordinary differential governing equation of motion for the L-shape beam structure with two-degree-of-freedom is firstly derived by applying the substructure synthesis method and the Lagrangian equation.Then,the method of multiple scales is utilized to obtain a four-dimensional averaged equation of the L-shape beam structure.Numerical simulations,based on the mathematical model,are presented to analyze the nonlinear responses and chaotic dynamics of the L-shape beam structure.The bifurcation diagram,phase portrait,amplitude spectrum and Poincare map are plotted to illustrate the periodic and chaotic motions of the L-shape beam structure.The existence of the Shilnikov type multi-pulse chaotic motion is also observed from the numerical results.Furthermore, experimental investigations of the L-shape beam structure are performed,and there is a qualitative agreement between the numerical and experimental results.It is also shown that out-of-plane motion may appear intuitively.     

A novel antimicrobial flavonoidic glycoside from the leaves of Alstonia macrophylla Wall ex A. DC (Apocynaceae)

<正>A new flavonoidic glycoside,tricin-4'-O-β-L-arabinoside(1) was isolated from the leaves of Alstonia macrophylla along with two known flavonoids,vitexin and myricetin-3′-rhamnoside-3-O-galactoside.Their structures were established by chemical and spectral evidences.The known compounds were reported for the first time from this plant.Moreover compound 1 was tested for antifungal and antibacterial activities.     

广义拟变分不等式及其选择映射

本文引进了映射Q相对于另一映射 T 是下半连续的概念。在此条件下,讨论了广义拟变分不等式的选择映射的连续性问题。并得到了一个广义拟变分不等式解的存在性定理。     

A NOVEL TITANIUM COMPLEX WITH LINKED β-DIKETONATO-INDENYL LIGAND FOR CATALYTIC SYNDIOSPECIFIC POLYMERIZATION OF STYRENE

A novel ligand (3), in which the indenyl group is linked to a β-diketone moiety through a three-carbon bridge, andits titanium complex (4) were synthesized. The titanium complex was employed as a metallocene analog with co-catalystmethylaluminoxane (MAO) in catalytic syndiospecific polymerization of styrene to give highly syndiotactic polystyrene(s-PS, 96%-97%). Polymerization temperature (T_p) strongly influenced the catalytic activity and syndiotacticity of theproduced PS. The activities of catalyst 4 increase from 1.84×10~6 to 3.26×10~6 gPS/molTi·h with the increase of T_p from60℃ to 80℃ and the syndiotacticities of the produced s-PS also increase slightly. Then, both the catalytic activity and thesyndiotacticity of PS decrease at T_p of 90℃.     

研究平抛物体运动实验的新设计

“研究平抛物体运动”的实验现行高中物理教材均采用了有孔卡片漏球找轨迹点的方法(图1)。根据我们的教学体会,“漏球”的方法存在如下问题: 一、“用硬纸做有孔的卡片,并折成直角”,当把折成直角的卡片放在图1的位置时,有孔面在重力作用下,要下沉,就难以保证与竖直面成直角。二、在竖直的木板上用手按住卡片也很     

流形上广义扩张自映射

本文将紧流形上的扩张自映射推广到广义的扩张自映射.一方面,广义扩张自映射的一系列动态性质与扩张自映射的表现类似,参考文 M.Shub[3],并且任何扩张自映射在一定的 Riemann 度量下均可成为广义扩张自映射.另一方面,在这两类自映射之间存在着一个重要的差别,这就是扩张自映射是结构稳定的,而广义扩张自映射可以不是.本文所有的术语均可在文 S.Smale[4]中找到.     

二维抛物型方程的高精度多重网格解法

提出了数值求解二维抛物型方程的一种新的高精度加权平均紧隐格式，利用Fourier分析方法证明了该格式是无条件稳定的，为了克服传统迭代法在求解隐格式是收敛速度慢的缺陷，利用了多重网格加速技术，大大加快了迭代收敛速度，提高了求解效率，数值实验结果验证了方法的精确性和可靠性。