A new heptacoordinated organogermanium compound; trichlorogermyl[tris(2-methoxyphenyl)]methane

A new hypercoordinated organogermanium compound, trichlorogermyl[tris(2-methoxyphenyl)]methane (4) was prepared, and its tricapped tetrahedral structure was confirmed by X-ray crystallographic analysis. All interatomic oxygen?germanium distances are shorter than the sum of van der Waals radii of O and Ge (3.62 Å).     

四配位配合物结构的讨论

本文从金属离子在正方形和四面体场中的ＣＦＳＥ以及配体间的排斥作用出发，讨论了四配位配合物的空间结构。ｄ０、ｄ１０及弱场ｄ５、ｄ７等组态的离子，形成排斥作用较小的四面体配合物；而ｄ８、ｄ９组态的离子，多数都形成ＣＦＳＥ特别有利的平面正方形配合物，只有Ｎｉ（Ⅱ）、Ｃｕ（Ⅱ）与弱场配体Ｃｌ－、Ｂｒ－等形成的配合物为四面体结构，对此可用分裂能△的大小来说明。     

二元碱金属硅酸盐精细结构和拉曼光谱的从头计算研究

应用量子化学从头计算方法研究了二元碱金属硅酸盐的精细结构,对典型的系列二元碱金属硅酸盐离子簇模型采用6-31G(d)基组和闭壳层Hartree-Fock(RHF)方法优化构型,并计算了二元碱金属硅酸盐的拉曼光谱,采用硅氧四面体应力指数这一精细结构参数分析和讨论了计算得到的非桥氧高频区对称伸缩振动频率和其拉曼光学活性,以及不同阳离子对该拉曼光学活性的影响。研究表明,二元碱金属硅酸盐非桥氧高频区对称伸缩振动频率与其精细结构密切相关,而且与Q₃相连的Q₄会对该Q₃的拉曼光学活性表现出增强作用。这说明二元碱金属硅酸盐的拉曼散射等性质主要依赖于其精细结构而非其初级结构单元-硅氧四面体。研究还表明,半径较大的阳离子有利于增强离子簇的拉曼光学活性,但对于小的离子簇,过多的电荷迁移反而会起到抑制作用。     

三角形法和四面体法优化选择毛细管区带电泳背景电解质

建立了两种高效、快速的毛细管区带电泳背景电解质(BGE)的优化方法三角形优化法和四面体优化法。以色谱指纹图谱指数F和色谱指纹图谱相对指数Fr作为评价毛细管电泳分析系统的目标函数,以雪莲药材水提取液为样品,考察一定浓度的硼砂、硼酸、磷酸氢二钠和磷酸二氢钠溶液按三角形优化法和四面体优化法构成背景电解质时对样品的分离情况,通过添加有机改性剂和调节pH进行再优化。用三角形法优化出以50 mmol/L硼砂-含3%乙腈的150 mmol/L磷酸二氢钠(体积比为1∶1)作为BGE时分离效果最佳,用四面体法优化出以50 mmol/L硼砂-150 mmol/L磷酸二氢钠-200 mmol/L硼酸(体积比为1∶1∶2,用0.1 mol/L氢氧化钠调pH 8.55)作为BGE时分离效果最佳,分别获得28个和25个电泳峰。所建立的方法操作简捷,适用于中药材水提取液或醇提取液的毛细管区带电泳BGE的选择。     

Unstructured pressure‐correction solver based on a consistent discretization of the Poisson equation

A finite volume incompressible flow solver is presented for three‐dimensional unsteady flows based on an unstructured tetrahedral mesh, with collocation of the flow variables at the cell vertices. The solver is based on the pressure‐correction method, with an explicit prediction step of the momentum equations followed by a Poisson equation for the correction step to enforce continuity. A consistent discretization of the Poisson equation was found to be essential in obtaining a solution. The correction step was solved with the biconjugate gradient stabilized (Bi‐CGSTAB) algorithm coupled with incomplete lower–upper (ILU) preconditioning. Artificial dissipation is used to prevent the formation of instabilities. Flow solutions are presented for a stalling airfoil, vortex shedding past a bridge deck and flow in model alveoli. Copyright © 2000 John Wiley & Sons, Ltd.     

Electric Field Induced Changes of Spin Lattice Relaxation Time T1 in Polar Liquids

T ₁ was found to change linearly with applied electric field for the liquids nitrobenzene, chlorobenzene, ether and dioxane: no change was observed in hexane and cyclohexane. These substantial reductions in T ₁ are explained in terms of quasi-crystalline structures in the liquid.     

网络形成体对重金属氧化物玻璃形成的影响

利用红外吸收光谱和喇曼散射光谱考察了PbO-Bi2O3-B2O3,PbO-Bi2O3-B2O3-SiO2及PbO-Bi2O3-P2O5系统中B3+,Si4+,P5+离子的配位状态,比较了不同玻璃形成体氧化物在重金属氧化物玻璃形成中的作用.研究结果表明在上述各系统重金属氧化物玻璃中,B3+,Si4+,P5+分别以孤立的[BO3]三角体、[SiO4]四面体及不带PO双键的[PO4]四面体形式存在;重金属氧化物玻璃的形成主要取决于[BO3]三角体、[SiO4]和[PO4]四面体的含量,这些氧多面体的作用是对Pb2+,Bi3+,O2-的积聚起阻隔作用,使之难以排列成晶格结构,从而形成非晶态玻璃.     

Effects of stacking fault energy on defect formation process in face-centered cubic metals

To elucidate the effect of stacking fault energies (SFEs) on defect formation by the collision cascade process for face-centred cubic metals, we used six sets of interatomic potentials with different SFEs while keeping the other properties almost identical. Molecular dynamic simulations of the collision cascade were carried out using these potentials with primary knock-on atom energies (E_PKA) of 10 and 20 keV at 100 K. Neither the number of residual defects nor the size distributions for both self-interstitial atom (SIA) type and vacancy type clusters were affected by the difference in the SFE. In the case of E_PKA = 20 keV, the ratio of glissile SIA clusters increased as the SFE decreased, which was not expected by a prediction based on the classical dislocation theory. The trend did not change after annealing at 1100 K for 100 ps. For vacancy clusters, few stacking fault tetrahedrons (SFTs) formed before the annealing. However, lower SFEs tended to increase the SFT fraction after the annealing, where large vacancy clusters formed at considerable densities. The findings of this study can be used to characterise the defect formation process in low SFE metals such as austenitic stainless steels.     

面向大规模科学计算的三维Delaunay快速插点算法

该文提出一种快速、稳定的Delaunay插点算法.这一算法提高了单机有元建模的规模,可在PC计算机生成千万级有元四面体网格.算法通过点与点之间位置关系,建立对位置信息;据这些信息在查找BASE单元时,提高＂walk-through＂点定位算法的速度.而在生成新单元和建立邻接关系过程中,算法利用CORE表面的三角网格,在性时间内完成CORE附近的新旧单元更新操作,并出算法时间复杂度证明.本文以分别以空间任意点集、正文体删格和机械模三角面片为例,测试应用Delaunay逐点插入算法.算例表明,本算法在一台Intel（R） Core（TM）2 Duo CPU E7200@2.53GHz,1.98GB内存的PC上可生成千万单元量级四面体网格,生成速度达11-15万单元/秒.     

The Design of Non-standard Dice （ I ）

在文献中,Galllan Joseph A.,Duane M.Broline和唐高华、李云慧、韦丹妮小组分别给出了所有正多面体骰子的等价设计.该文考虑与标准骰子等价的非标准的骰子,证明了有恰有两对非标准骰子与标准正四面体骰子等价,恰有九对非标准骰子与标准正八面体骰子等价.