采用电感耦合等离子体质谱测定化肥中微量Cr、Cd、As、Pb、Hg元素

采用电感耦合等离子体质谱法测定化肥中微量Cr、Cd、As、Pb、Hg元素。仪器经条件优化，以In为内标，样品的基体效应和仪器漂移能得到很好的补偿。微波消解和敞开酸溶两种样品处理方法比较可知，微波法具有更高的精密度和准确度。方法的标准加入回收率在85-120％，RSD％〈15％，误差完全符合GB18877-2002的规定，方法简便快速。     

Dynamic soil–structure interaction analysis of layered unbounded media via a coupled finite element/boundary element/scaled boundary finite element model

In this paper, a coupled model based on finite element method (FEM), boundary element method (BEM) and scaled boundary FEM (SBFEM) (also referred to as the consistent infinitesimal finite element cell method) for dynamic response of 2D structures resting on layered soil media is presented. The SBFEM proposed by Wolf and Song (Finite‐element Modelling of Unbounded Media. Wiley: England, 1996) and BEM are used for modelling the dynamic response of the unbounded media (far‐field). The standard FEM is used for modelling the finite region (near‐field) and the structure. In SBFEM, which is a semi‐analytical technique, the radiation condition at infinity is satisfied exactly without requiring the fundamental solution. This method, also eliminates the need for the discretization of interfaces between different layers. In both SBFEM and BEM, the spatial dimension is decreased by one. The objective of the development of this coupled model is to combine advantages of above‐mentioned three numerical models to solve various soil–structure interaction (SSI) problems efficiently and effectively. These three methods are coupled (FE–BE–SBFEM) via substructuring method, and a computer programme is developed for the harmonic analyses of SSI systems. The coupled model is established in such a way that, depending upon the problem and far‐field properties, one can choose BEM and/or SBFEM in modelling related far‐field region(s). Thus, BEM and/or SBFEM can be used efficiently in modelling the far‐field. The proposed model is applied to investigate dynamic response of rigid and elastic structures resting on layered soil media. To assess the proposed SSI model, several problems existing in the literature are chosen and analysed. The results of the proposed model agree with the results presented in the literature for the chosen problems. The advantages of the model are demonstrated through these comparisons. Copyright © 2004 John Wiley & Sons, Ltd.     

Mixed finite element method for coupled thermo‐hydro‐mechanical process in poro‐elasto‐plastic media at large strains

A mixed finite element for coupled thermo‐hydro‐mechanical (THM) analysis in unsaturated porous media is proposed. Displacements, strains, the net stresses for the solid phase; pressures, pressure gradients, Darcy velocities for pore water and pore air phases; temperature, temperature gradients, the total heat flux are interpolated as independent variables. The weak form of the governing equations of coupled THM problems in porous media within the element is given on the basis of the Hu–Washizu three‐filed variational principle. The proposed mixed finite element formulation is derived. The non‐linear version of the element formulation is further derived with particular consideration of the THM constitutive model for unsaturated porous media based on the CAP model. The return mapping algorithm for the integration of the rate constitutive equation, the consistent elasto‐plastic tangent modulus matrix and the element tangent stiffness matrix are developed. For geometrical non‐linearity, the co‐rotational formulation approach is utilized. Numerical results demonstrate the capability and the performance of the proposed element in modelling progressive failure characterized by strain localization and the softening behaviours caused by thermal and chemical effects. Copyright © 2005 John Wiley & Sons, Ltd.     

萃取分离ICP-AES法测定二氧化锆中镧和钇

利用1－苯基－3－甲基－4－苯甲酰基－吡唑酮[5](PMBP)-氯仿溶液在高酸度下对锆的选择性萃取，使基体与待测元素分离，然后以电感耦合等离子体原子发射光谱（ICP－AES）法，测定了高纯二氧化锆中痕量杂质元素La和Y的含量，样品分析结果满意。     

氟化电热蒸发ICP-AES中的基体干扰及机理研究

对氟化辅助电热蒸发电感耦合等离子体原子发射光谱(FETV-ICP-AES)中的基体效应及其机理进行了初步探讨。考察了基体元素Na、Ca、Zn对待测难熔元素Y的语线强度、蒸发过程和激发过程的影响。所得实验结果表明，与常规ICP-AES相比，在FETV-ICP-AES中的基体效应明显降低，其主要原因与试样的蒸发和激发(电离)分步进行，ETV-ICP体系具有更高的激发温度以及待测物和基体在蒸发过程中发生了选择挥发有关。     

干旱灾害成灾过程数值模拟研究

以有限区域大气运动模式和土壤水热传导模式为基础,采用地表水分蒸发、地表水渗透、植被的蒸腾作用与根系吸水作用、地面风场4种过程作为模型的耦合方案,建立了用于干旱灾害成灾过程数值模拟的数学耦合模型.利用该数学模型模拟计算了1995年7月1～30日发生在长江中下游地区的干旱灾害,其干旱过程可分为土壤可供水量满足农作物需水量阶段、根系层土壤供水量小于农作物需水量阶段、农作物干旱阶段3个阶段,实践证明该模型对干旱灾害的发生发展过程具有很好的模拟能力.     

在线群体交互的影响模型及其学习算法

在线群体交互有助于数字图书馆发挥其服务人类需求的潜力，但如何量化在线群体交互对个人信息访问方面的影响还有待进一步研究．该文用隐Markov模型(HMM)来建模交互用户的状态序列及其相应的信息搜索行为，并基于影响模型理论提出了一个在线群体交互影响模型来分析用户在从数字图书馆选择资料和搜索所需信息时的相互影响．为满足本应用问题中增量模型学习的需要，文章还从耦合隐Markov模型(CHMM)学习算法引申出基于梯度的方法来进行在线群体交互影响模型参数的训练．实验结果显示，本文所提出的模型和算法能较准确地刻画在线群体交互对个人信息访问行动的影响．     

载流梁在磁场中的变形计算

研究载流弹性梁在外加磁场中的磁弹性变形问题。用两种方法分析计算了载流梁磁弹性变形的挠度，给出了考虑耦合效应时磁弹性梁挠度的表达式，通过对计算结果的分析比较发现：忽略耦合效应的分析方法得到的结果有时大于耦合模型的结果，有时小于耦合模型的结果。对复杂结构的磁弹性变形问题，要得到问题的准确解则必须采用耦合型的分析模型。     

衍射图像的信号采集和数据处理

针对衍射图像边缘弥散状态不易切准的问题，运用光电积分的方法确定采集点，然后将二值化的数据通过计算机采用最小二乘法进行计算，从而保证了测量结果的正确性     

Controlling Spin Qubits in Quantum Dots

We review progress on the spintronics proposal for quantum computing where the quantum bits (qubits) are implemented with electron spins. We calculate the exchange interaction of coupled quantum dots and present experiments, where the exchange coupling is measured via transport. Then, experiments on single spins on dots are described, where long spin relaxation times, on the order of a millisecond, are observed. We consider spin-orbit interaction as sources of spin decoherence and find theoretically that also long decoherence times are expected. Further, we describe the concept of spin filtering using quantum dots and show data of successful experiments. We also show an implementation of a read out scheme for spin qubits and define how qubits can be measured with high precision. Then, we propose new experiments, where the spin decoherence time and the Rabi oscillations of single electrons can be measured via charge transport through quantum dots. Finally, all these achievements have promising applications both in conventional and quantum information processing. PACS: 03.67.Lx, 03.67.Mn, 73.23.Hk, 85.35.Be