硅胶担载四核羰基钴催化剂的EXAFS和IR研究

本文以透射法EXAFS和IR等手段研究了四核羰基钴金属簇Co_4(CO)_(10)(PPh)_2担载在SiO_2上以后及用于烯烃醛化反应前后的变化,确定了相应的结构参数并探讨了催化活性与结构的关系。     

Global axisymmetric classical solutions of full compressible magnetohydrodynamic equations with vacuum free boundary and large initial data

In this paper,the global existence of the classical solution to the vacuum free boundary problem of full compressible magnetohydrodynamic equations with large initial data and axial symmetry is studied.The solutions to the system(1.6)–(1.8) are in the class of radius-dependent solutions,i.e.,independent of the axial variable and the angular variable.In particular,the expanding rate of the moving boundary is obtained.The main difficulty of this problem lies in the strong coupling of the magnetic field,velocity,temperature and the degenerate density near the free boundary.We overcome the obstacle by establishing the lower bound of the temperature by using different Lagrangian coordinates,and deriving the uniform-in-time upper and lower bounds of the Lagrangian deformation variable r;by weighted estimates,and also the uniform-in-time weighted estimates of the higher-order derivatives of solutions by delicate analysis.     

用EXAFS研究NiO在γ-Al2O3表面上的分散

本文使用EXAFS方法研究NiO在γ-Al_2O_3的表面上的分散情况。文章讨论了Ni含量为7%、13%、18%、26%、35%的NiO/γ-Al_2O_3体系的径向结构函数图以及Ni含量为13%、26%的NiO/α-Al_2O_3样品的径向结构函数图,认为NiO能在γ-Al_2O_3表面上成单层分散。分散后的Ni-O距离接近NiO晶体的Ni-O距离,表明Ni离子和γ-Al_2O_3表面上的氧有很强的相互作用。     

Aligned CuO nanorod arrays: fabrication and anisotropic ferromagnetism

Copper oxide (CuO) is a p-type semiconductor with a band gap of 1.2 eV, which is well known in high-temperature superconductor and antiferromagnetic (AFM) materials through Cu–O–Cu super-exchange interaction. In this paper, we report the strong anisotropic ferromagnetism (FM) in aligned CuO nanorod arrays synthesized by a microwave-assisted hydrothermal method. The transmission electron microscopy (TEM) image shows that the CuO nanorod consists of a large number of smaller nanorods with almost the same growth direction. The X-ray diffraction (XRD) pattern indicates that the CuO nanorods are well crystallized with highly preferred orientation of the [020] direction. These CuO nanorod arrays show room-temperature ferromagnetism, with strong magnetic anisotropy when the magnetic field is applied perpendicular or parallel to the rod axis. This phenomenon of room-temperature ferromagnetism in those aligned CuO nanorods might originate from uncompensated surface spins and shape anisotropy of the nanorods.     

表面熔化

对近年来人们十分关注的表面熔化问题，从理论和实验上进行了综述性讨论。综述了一些金属晶体、冰及石墨吸附Ａｒ膜表面熔化的特征及其热力学理论解释。评述了半导体Ｇｅ（１１１）表面熔化的独特性质。     

Multiple homoclinic solutions for singular differential equations

The homoclinic bifurcations of ordinary differential equation under singular perturbations are considered. We use exponential dichotomy, Fredholm alternative and scales of Banach spaces to obtain various bifurcation manifolds with finite codimension in an appropriate infinite-dimensional space. When the perturbative term is taken from these bifurcation manifolds, the perturbed system has various coexistence of homoclinic solutions which are linearly independent.     

A fixed point index for generalized inward mappings of condensing type

A fixed point index is defined for mappings defined on a cone which do not necessarily take their values in but satisfy a weak type of boundary condition called generalized inward. This class strictly includes the well-known weakly inward class. New results for existence of multiple fixed points are established.

     

Existence of nonzero positive solutions of systems of second order

Existence of nonzero positive solutions  of systems of second order elliptic boundary value problems under sublinear conditions is obtained. The methodology is to establish a new result on existence of nonzero positive solutions of a fixed point equation in real Banach spaces by using the well-known theory of fixed point index for compact maps defined on cones, where the fixed point equation involves composition of a compact linear operator and a continuous nonlinear map. The conditions imposed on the nonlinear maps involve the spectral radii of the compact linear operators. Moreover, the nonlinear maps are not required to be increasing in  ordered Banach spaces.     

导电高聚物的EXAFS 研究(Ⅰ)铂氯酸(H2PtCl6·6H2O)掺杂的聚乙炔

在实验室EXAFS装置上测量了一种导电高聚物——H_2PtCl_6·6H_2O掺杂聚乙炔和模型化合物(K_2PtCl_6)的PtL_Ⅲ吸收谱。用高功率的施转阳极靶X射线发生器(RigakuRU-1000)作为X射线源。观测到的EXAFS数据分析表明, Pt原子在试样中有两种配位状态。一种是PtCl_6~(2-)离子, Pt—Cl键长为0.233 nm, 另一种是Pt在0.228 nm附近有两个最近邻的Cl原子。实验结果提供了支持下述观点的直接结构信息: 随着电子从(CH)_x链向铂盐的转移, 发生下列反应:2H_2PtCl_6+2e~-→PtCl_6~(2-)+PtCl_2+4HCl     

New fixed point theorems for a family of mappings and applications to problems on sets with convex sections

Some new fixed point theorems for a family of mappings are obtained and applied to problems on sets with convex sections that were first studied by Ky Fan.