纳米三苯环分子带不对称电子传导特性

利用基于Green Function的Tight-binding方法,对由三个苯分子环耦合成的输入与输出电极不对称纳米分子带进行了理论研究.通过数值计算,得出了入射电子通过分子带传输到不对称端点的电子传输谱.利用Fisher-Lee 关系式和量子流密度理论,在传输峰值的六个能量点E=±0.45eV、E=±1.06eV和E=±1.46eV处,分别计算了分子带内的电子流分布,并且给出了分子带内电子流分布的模拟结果.对电子通过分子带的传输特性和键电子流生成的物理原因给出了合理的解释.     

磺酸功能化三维有序大孔材料的制备与催化性能研究

采用模板法, 用正硅酸乙酯和3-巯丙基-三甲氧基硅烷的混合溶胶, 在聚苯乙烯胶晶间隙中原位转化, 除去模板后用双氧水将巯基氧化成磺酸基, 首次成功地制备了大孔规整排列的3DOM SiO₂-SO₃H材料. 样品用SEM, EDS, FT-IR等方法进行了测试表征. 结果表明, 所得到材料的三维大孔结构规整性十分好, 大孔孔径大约250 nm, 并由大约80 nm的小孔相连; 磺酸基很好地嵌入孔壁基质中, 吡啶吸附测定显示了典型的质子酸特征, 而且酸中心随硫含量增加而增多. 对乙酸与正丁醇的酯化反应显示了良好的催化性能, 磺酸含量越大, 催化活性越高. 这一研究为开发新型高效的固体酸催化剂提供了很有意义的结果.     

基于三维评价的区域不平衡发展研究——以福建省外商投资环境为例

从一定时空粒度三维评价切入,决策矩阵预处理后,利用频率法变换为概率,再根据玻尔兹曼熵函数与对立概念变换为有序度,使不同时间截面、不同对象时间序列间均可比较.经时空权变灵敏分析,利用公因子方差赋权法确定权矩阵,建立三维评价模型,提出基于三维评价的诊断和表达区域不平衡发展的方法、定量指标.根据2000～2007年福建统计年鉴,从1999～2006年福建省地级市外商投资环境三维评价切入,分析福建省外商投资环境不平衡发展特征.     

Semianalytic wave functions for highly rotational states of antiprotonic He

The structural and magnetic evolution in magnesium ferrite (MgFe₂O₄) caused by high-energy milling is investigated by Mössbauer spectroscopy.     

我国经济增长与产业结构演进关系的研究——基于面板数据模型的实证分析

本文运用面板数据模型,对我国各省1996-2005年人均GDP及三次产业产值比重的关系分别进行了模型拟合,结论认为:我国经济增长对产业结构变化的影响显著,而后者对前者的影响在统计上并不显著,我国经济增长模式是需求导向型的。其次,就各次产业与人均GDP的关系看,第一产业与人均GDP呈现负相关关系,而第二、三产业与人均GDP呈现正相关关系。     

Solvent‐free synthesis of α‐aminonitriles from aldehydes,amines and trimethylsilyl cyanide catalyzed by thallium(III) chloride tetrahydrate

A straightforward and efficient method has been developed for the synthesis of α‐aminonitriles by combining aldehydes, amines and trimethylsilyl cyanide in the presence of a catalytic amount of thallium(III) chloride tetrahydrate (1 mol%) under solvent‐free conditions at room temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Parameter estimation for a three‐dimensional numerical barotropic tidal model with adjoint method

The parameters of a three‐dimensional (3‐D) barotropic tidal model are estimated using the adjoint method. The mode splitting technique is employed in both forward and adjoint models. In the external mode, the alternating direction implicit method is used to discretize the two‐dimensional depth‐averaged equations and a semi‐implicit scheme is used for the 3‐D internal mode computations. In this model the bottom friction is expressed in terms of bottom velocity which is different from the previous works. Besides, the bottom friction coefficients (BFCs) are supposed to be spatially varying, i.e. the BFC at some grid points are selected as the independent BFC, while the BFC at the other grid points can be obtained through linear interpolation with these independent BFCs. On the basis of the simulation of M₂ tide in the Bohai and North Yellow Seas (BNYS), twin experiments are carried out to invert the prescribed distributions of model parameters. The parameters inverted are the Fourier coefficients of open boundary conditions (OBCs), the BFC and the vertical eddy viscosity profiles. In these twin experiments, the real topography of BNYS is installed. The ‘observations’ are produced by the tidal model and recorded at the position of TOPEX/Poseidon altimeter data, tidal gauge data and current data. The experiments discuss the influence of initial guesses, model errors and data number. The inversion has obtained satisfactory results and the prescribed distributions have been successfully inverted. The results indicate that the inversion of BFC is more sensitive to data error than that of OBC and the vertical eddy viscosity profiles. Copyright © 2007 John Wiley & Sons, Ltd.     

A hybrid vortex method for the simulation of three‐dimensional flows

This paper presents an integral vorticity method for solving three‐dimensional Navier–Stokes equations. A finite volume scheme is implemented to solve the vorticity transport equation, which is discretized on a structured hexahedral mesh. A vortex sheet algorithm is used to enforce the no‐slip boundary condition through a vorticity flux at the boundary. The Biot–Savart integral is evaluated to compute the velocity field, in conjunction with a fast algorithm based on multipole expansion. This method is applied to the simulation of uniform flow past a sphere. Copyright © 2007 John Wiley & Sons, Ltd.     

透视画法的几何研究与计算机作图

对文艺复兴时写实绘画所采用的透视画法进行了精确的数学描述,并利用所得结论给出了使用计算机进行作图的方法.