Indexing Non-merohedrally Twinned Crystals by Bruker＇sAPEX2 and Agilent＇s CrysAlis~（PRO）, an Example of a Crystal Structure That Can Be Refined through Either the PLATONRoute or the ＇HKLF 5＇ Route,and, Simultaneous Data Collection of Two Crystals in a Two-in-one Run

The first part of this report describes the data reduction of non-merohedrally twinned crystals measured on Bruker and Agilent area-detector diffractometers. The image frames of methyl-2-aminopyrazine-3-carboxylate were processed with APEX2 to furnish a set of overlapping diffraction indices that were used for solution and refinement. CrysAlisPRO was used for processing the frames of bis（diethyldicarbamato）nickel, which exists in monoclinic and tetragonal polymorphs, and in untwinned and twinned forms. In the second part, the crystal structure of [（3-formyl-4- hydroxyphenyl）methyl]triphenylphosphanium chloride was refined through the ‘HKLF 5＇（based on a combined set of diffraction indices） and PLATON（based on one set of diffraction indices） routes to give identical outcomes because the amount of overlap of the twin domains is small. For the third part, in a proof-of-concept investigation, the diffraction pattern of untwinned and twinned 4-{（E）-（4-aminophenyl）diazenyl]phenylamine was recorded simultaneously in one run; the three domains could be indexed and the crystal structure satisfactorily refined. The refinement was identical to those derived from independent measurements; the crystal structure features two independent centrosymmetric molecules, one of which is ordered and the other whole-molecule-disordered. This two-in-one run opens up the possibility that two or more crystals having different atomic compositions can be measured simultaneously if their reciprocal lattices do not overlap significantly.     

Extended finite element method for viscous flow inside complex three‐dimensional geometries with moving internal boundaries

A three‐dimensional extended finite element method is presented to simulate Stokes flow in complex geometries with internal moving parts. Instead of re‐meshing the flow domain, the kinematics of the internal objects are imposed on the conservation equations using a constraint, implemented with a Lagrangian multiplier. To capture discontinuities of field variables, such as pressure and velocity, on the intersected elements, XFEM is used. To validate our method, it is first applied to a relatively simple problem, that is, the flow around a cylinder in a channel. The results are verified by comparing with a boundary‐fitted solution. After validation of the model and its implementation, the three‐dimensional flow in a twin‐screw extruder is simulated and the results are compared with experimental data from literature. XFEM shows very good accuracy for complex geometries with internal moving parts and narrow gap regions where the shear rate is orders of magnitude higher than in other regions. Copyright © 2011 John Wiley & Sons, Ltd.     

基于双剪统一强度理论的复式钢管混凝土轴压承载力计算

考虑内、外钢管对混凝土的双重约束作用, 分析复式钢管混凝土的轴压应力状态, 采用双剪统一强度理论分析混凝土和钢管各自的极限轴压强度, 得出复式钢管混凝土轴压承载力公式; 通过推导钢管在极限状态的强度折减系数及钢管与混凝土之间的紧箍力值, 计算出的轴压承载力与试验数据进行对比, 吻合较好, 验证了双剪统一强度理论在复式钢管混凝土轴压承载力计算中的适用性; 并给出了内圆钢管的径厚比和直径与轴压承载力提高系数的关系, 为复式钢管混凝土的优化设计提供理论依据.     

Crystal structure of a new double salt hydrate SrCd2Cl6⋅8H2O

SrCd₂Cl₆8H₂O crystallizes in the space group and has the unit cell dimensions a = 9.688(2) Å, b = 11.212(2) Å, c = 7.732(3) Å, = 99.85(21)°, = 89.95(22)°, = 75.81(13)°, and Z = 2. After refinement through full-matrix least-squares methods, the reliability factor R in the final cycle is 4.65%. A very persistent occurrence of twinning by pseudosymmetry was observed. The twin element is a twofold axis [001]. The title compound exhibits five endothermic peaks, which have been detected by differential scanning calorimetry and interpreted from thermogravimetry.     

数学优生与差生的素质差异的比较研究

本文通过对初中学生基础素质指标与学习成绩的多元统计分析,探讨了数学差生与优生的素质差异,从不同群体的基础素质对数学学习成绩的影响,研究培养优生与转化差生的不同策略。 本项研究得到世界银行贷款的资助,获96年山东省普通高等学校优秀教学成果二等奖;98年1月通过了国家教委世行贷款办主持的鉴定。99年3月获“1998年度全国师范院校基础教育改革实验优秀成果”二等奖及世界银行贷款“师范教育发展”改革课题实验研究优秀项目二等奖。     

Improved twin support vector machine

We improve the twin support vector machine(TWSVM)to be a novel nonparallel hyperplanes classifier,termed as ITSVM(improved twin support vector machine),for binary classification.By introducing the diferent Lagrangian functions for the primal problems in the TWSVM,we get an improved dual formulation of TWSVM,then the resulted ITSVM algorithm overcomes the common drawbacks in the TWSVMs and inherits the essence of the standard SVMs.Firstly,ITSVM does not need to compute the large inverse matrices before training which is inevitable for the TWSVMs.Secondly,diferent from the TWSVMs,kernel trick can be applied directly to ITSVM for the nonlinear case,therefore nonlinear ITSVM is superior to nonlinear TWSVM theoretically.Thirdly,ITSVM can be solved efciently by the successive overrelaxation(SOR)technique or sequential minimization optimization(SMO)method,which makes it more suitable for large scale problems.We also prove that the standard SVM is the special case of ITSVM.Experimental results show the efciency of our method in both computation time and classification accuracy.     

Na5[B2P3O13]晶体双晶结构的研究

采用泡生法和b向籽晶生长出尺寸为22mm×24mm×20mm的透明Na5[B2P3O13]晶体.晶体定向中发现(100)和(001)晶面的一级衍射出现双峰;正交偏光显微镜下观察晶体的(010)切片,看到清晰的明暗条纹;当一束激光正入射(010)切片时,产生衍射现象;用同步辐射白光X射线形貌术拍摄了(100)、(010)和(001)切片的Laue像,观察到了晶体的孪晶结构,再借助(010)切片的化学腐蚀研究,推出该晶体为规则的聚片双晶,其结合面为(001).     

Abundances of heavy elements in ultra-metal-poor star CS 22892-052

Based on the heavy element nucleosynthesis theory, with the solar heavy-nuclide abundances and the observed abundances of three elements which are the representatives of the individul neutron-capture processes, a method to determine the relative contributions from the individul neutron-capture processes to the abundances of heavy elements in metal-poor stars is applied. With this method, the abundances of heavy elements in ultra-metal-poor star CS 22892-052 are calculated. It is found that the observed abundances of heavy elements in this star are well matched by our calculations in error limits, except for thorium Project supported by the National Natural Science Foundation of China (Grant No. 19673008). The visiting scholar of Shijiazhuang Teacher’s College.     

Embeddings of Twin Trees

In this article we provide sufficient conditions for when a pair of trees having a semi-codistance function can be embedded in a twin tree with codistance function extending . We use these conditions to show that given a twin tree T of bidegree (d1,d2) there exists a twin tree of bidegree (e1,e2) containing T as a substructure as long as di ei.