石墨和纳米碳中缺陷和电子动量的研究

用正电子湮没技术研究了石墨和纳米碳中的缺陷和电子动量. 结果表明, 纳米碳中缺陷的开空间和缺陷浓度分别大于和高于石墨晶体. 纳米碳中存在开空间小于单空位的自由体积以及开空间相当于约10个空位聚集体的微孔洞. 石墨晶体中的自由电子动量分布表现出显著的各向异性: 沿石墨晶体的\[0 001\]晶向的自由电子(即2Pz电子)的动量最大; 偏离该方向越大, 自由电子的动量越小; 垂直于\[0 001\]晶向的自由电子的动量最小. 而纳米碳中自由电子动量的分布表现出各向同性. The defects and electronic momenta in graphite and nanocrystalline carbon have been studied by positron annihilation techniques. The results show that the concentration and open volume of defects in nanocrystalline carbon are higher/larger than that in graphite. Two kinds of microdefects were found in the nanocrystalline carbon: free volume (with a size of smaller than that of a monovacancy) and microvoids (with a size of about ten monovacancies). The anisotropic distribution of electronic momentum was found in single crystalline graphite, the momentum of free electron shows a maximum value in \[0001\] direction, and decreases with the increase of the angle deviation from \[0001\] direction and then reaches a minimum value in the direction perpendicular to \[0001\]. However, this phenomenon was not found in nanocrystalline carbon since the distribution of electronic momentum is isotropic.     

甲醇氧化羰化反应中含氮配体助催化剂的空间及电子效应

甲醇氧化羰化反应中含氮配体助催化剂的空间及电子效应;含氮配体;空间结构;电子效应;氧化羰化;甲醇     

关于薄板的无网格局部边界积分方程方法中的友解

无网格局部边界积分方程方法是最近发展起来的一种新的数值方法,这种方法综合了伽辽金有限元、边界元和无单元伽辽金法的优点,是一种具有广阔应用前景的、真正的无网格方法．把无网格局部边界积分方程方法应用于求解薄板问题,给出了薄板无网格局部边界积分方程方法所需要的友解及其全部公式．     

Rotation and Its Realization on Noncommutative Space R2N

In this paper,we present the realization of unitary transformation that is corresponding to symplectic transformation of coordinate on noncommunicative R^2N,and give out the transformation of wave function caused by the unitary transformation,i,e.,it is the matrix unit of unitary transformation.     

Studies on Adsorption Behavior and Mechanism of Copper（ Ⅱ ） onto Amino Methylene Phosphonic Acid Resin

IntroductionThe adsorption ability of the functional poly-mer used to enrich metal ions is strong and the op-eration of the functional polymer is convenient.The polymer having adsorbed metal ions can be re-covered by means of an acid or an alkaline solutionand the recovered polymeric material can bereused.The adsorption ability of the polymer withvarious functional groups is different for differentmetals.Because nucleophilic atoms such as oxy-gen,nitrogen,sulphur and phosphorous atoms cancoord…     

Dirac Operator on Fuzzy Sphere with U（1） Dirac Monopole Background

We treat the Dirac operator on the Fuzzy sphere with the help of the generalized coherent state. It is shown that the derivatives can be constructed by Moyal product with symbol of the operator. We obtain the eigenvalue of the free fermion Dirac operator as same as the result by [Hajime Aoki, Satoshi Iso, and Kelichi Nagao, Phys. Rev.D67 (2003) 065018]. Meanwhile, we also give the eigenvalue of Dirac operator with U(1) Dirac monopole background.     

内部荷载作用下圆柱形孔洞的动力响应解答

考虑土与衬砌结构的动力相互作用,本文研究了内源荷载作用下,圆柱形孔洞的动力响应问题.将土体和衬砌结构视为弹性均匀介质,通过引入势函数将位移控制方程化为二维轴对称波动方程.采用拉普拉斯变换,得到土体及衬砌的位移应力的表达式.利用土体与衬砌结构之间的连续性条件和衬砌结构内边界上的边界条件,可确定表达式的未知系数.采用逆拉普拉斯变换的数值方法,给出了问题的数值解.分析了土中圆形衬砌结构的动力响应随土体和衬砌结构参数的变化规律.     

多体动力学的几何积分方法研究进展

动力系统的几何积分研究是近20年来工程计算领域非常活跃的方向.多体动力学方程(微分方程, 微分代数方程)是一类典型的动力系统,将其从Lagrange体系向Hamilton系统过渡,目的在于从欧氏几何过渡到辛几何形态, 将对偶变量引入到力学研究中,然后利用辛几何的数学框架对多体系统动力学方程进行数值计算,可以预知多体动力学系统的一些定性信息,并在数值离散时能保持这些定性性质特征,尤其在表示关键的物理意义时需要强调保持这些几何性质.简要介绍多体系统(无约束多刚体系统、完整约束多刚体系统和柔性多体系统)的Hamilton正则方程的建立和几何积分方法的构造,着重介绍了在多体动力学计算中非常有应用前景的高阶辛算法(合成辛算法、分裂合成辛算法和辛精细积分法)、多辛算法,以及广义Hamilton 系统与Lie 群积分方法等计算几何力学方法, 并对Lie群积分的投影方法、流形局部坐标法等方法进行了阐述.      

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

Y掺杂Ba0.90Sr0.08Ca0.02TiO3固溶体纳米晶粒尺寸 对其晶体结构的影响

The title nanocrystalline powders were prepared by sol-gel method, the influences of grain size on crystal structure were investigated by XRD and DSC techniques.The experiment results show that the tetragonal ferroelectric phase content of the powders and the Curie temperature Tc are increased with the increase of grain size.When the grain size is less than 34.7nm, crystal structure of the particle changes into cubic paraelectric phase and the transition of ferro-paraelectric phase disappears as well.