一个线性约束优化问题的广义梯度投影法

本文对线性约束优化问题提出了一个新的广义梯度投影法，该算法采用了非精确线性搜索，并在每次迭代运算中结合了广义投影矩阵和变尺度方法的思想确定其搜索方向．在通常的假设条件下，证明了该算法的整体收敛性和超线性收敛速度．     

Structure and electrochemical behaviour of 4,7-diazaheptyl-trimethoxy-silane and vinyl-trialkoxy-silane adsorbed at silver surface

Novel self-assembled monolayers were obtained on silver using 4,7-diazaheptyl-trimethoxy-silane (SiN) and vinyl-trialkoxy-silane (SiVA, where the alkyl group is 3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60-eicozaoxa- hexaheptaconan). It was shown that thus modified metal surface was protected against electrooxidation. A densely packed monolayer remained stable and did not desorb from the Ag electrode on the potential cycling. The structure of SiN and SiVA as well as their complexes with Li⁺ cations were calculated and visualised by the AM1d and PM5 semi-empirical methods.     

Electrical properties of neodymium doped CaBi4Ti4O15 ceramics

Neodymium doped bismuth layer structure ferroelectrics (BLSFs) ceramics CaBi_4−xNd_xTi₄O₁₅ (x=0, 0.25, 0.50, 0.75) were prepared by solid-state reaction method. X-ray diffraction pattern showed that single phase was formed when x=0-0.75. The refined lattice parameters showed that a (b) axes decrease at x=0.25 and increase with more Nd³⁺ dopant. The effects of Nd³⁺ doping on the dielectric and ferroelectric properties of CaBi₄Ti₄O₁₅ ceramics are studied. Nd³⁺ dopant decreased the Curie temperature linearly, and the dielectric loss, tan δ, as well. The remnant polarization of Nd³⁺ doped CaBi₄Ti₄O₁₅ ceramics was increased by 80% at x=0.25, while more Nd³⁺ dopant decreased the remnant polarization. CaBi_3.75Nd_0.25Ti₄O₁₅ ceramics had the largest piezoelectric constant d₃₃. The structure and properties of CaBi_4−xNd_xTi₄O₁₅ ceramics showed that Nd³⁺ may occupy different crystal locations when Nd³⁺ content x is less than 0.25 and more than 0.50.     

量子算法的NMR实现方法

量子计算机是一种以量子耦合方式进行信息处理的装置[1 ] 。原则上 ,它能利用量子相干干涉方法以比传统计算机更快的速度进行诸如大数的因式分解、未排序数据库中的数据搜索等工作[2 ] 。建造大型量子计算机的主要困难是噪音、去耦和制造工艺。一方面 ,虽然离子陷阱和光学腔实验方法大有希望 ,但这些方法都还没有成功实现过量子计算。另一方面 ,因为隔离于自然环境 ,核自旋可以成为很好的“量子比特” ,可能以非传统方式使用核磁共振 (NMR)技术实现量子计算。本文介绍一种用NMR方法实现量子计算的方法 ,该方法能够用比传统方法少的步骤解决一个纯数学问题。基于该方法的简单量子计算机使用比传统计算机使用更少的函数“调用”判断一未知函数的类别。     

Hydrothermal Synthesis and Structure of [Mn(C_8H_5NO_4)·H_2O]_n·2nH_2O

1 INTRODUCTION The self-assembly of organic-inorganic hybrid ma- terials is an intriguing area, which is yielding new generations of supramolecular architectures[1, 2]. Coor- dination by transition metals with multifunctional ligands is one of the main design principles. As a rigid multi-dentate ligand, 5-aminoisophthalic acid (AIP) has received considerable attention owing to the variety of bridging abilities[3~8]. It can engage in three types of intermolecular interactions: (1) M-L b…     

SPME-GC-MS快速分析炼油厂废水中痕量VOCs

采用固相微萃取-气相色谱-质谱联用(SPME-GC-MS)对炼油厂废水中痕量挥发性有机化合物(VOCs)进行了定性分析,简化了预处理过程,总分析时间为1h左右.对比处理前后的废水样品的MS定性结果,为废水处理工艺的评价以及有机物降解机理提供了依据.     

解线性最小二乘问题的一个新并行算法

讨论了求解无约束线性最小二乘问题的一种并行单纯形法以及对它的改进算法并行共轭梯度—单纯形法 .算法本身具有很强的并行机制 ,能够充分地发挥并行机快速省时的特点 .本文也对算法做了理论分析 ,对算法的收敛性给予了证明 (在二维情形下 ) .最后做了数值实验 (由于软硬件条件的限制 ,并行算法未能在并行计算机上实现 ,鉴于这种情况 ,我们所做的数值实验均是在串行机上完成的 )     

基因组重排问题的一个近似算法

分子生物学中基因无方向的反向基因组重排问题在数学上已被证明是一个NP困难问题．基于断点图的概念，给出一个时间复杂性为O(max{b^(π)，nb(π)})，空间复杂性为0(n)的求其近似最优解的算法．其中n为基因组中基因个数，π=(π1,π2，…，πn)表示n个基因的一种排列，b(π)表示排列π中的断点数．数据实验的结果表明，该近似算法可以求得较好的结果．     

Polyaniline/12-phosphotungstic acid/V<Subscript>2</Subscript>O<Subscript>5</Subscript> nanocomposite and its platinum analog as oxygen reduction electrocatalysts

A guest-host nanocomposite based on electroconducting polyaniline doped with 12-phosphotungstic acid and V₂O₅ as well as its bifunctional analog containing not more than 5 mass% nanosized platinum were obtained. A study was carried out on the structure of these nanocomposites, their redox characteristics, and electrocatalytic activity in the reduction of oxygen. These nanocomposites were found to display catalytic properties in the electrochemical reduction of oxygen, while the presence of even a slight amount of nanosized platinum in the bifunctional composite leads to a significant increase in its electrocatalytic activity. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 307–314, September–October, 2007.     

Characterization of a 4-miktoarm star copolymer of the (PS-b-PI)3 PS type by temperature gradient interaction chromatography

Temperature gradient interaction chromatography (TGIC) was applied for the separation of a complex miktoarm star copolymer which has one polystyrene (PS) arm and three polystyrene-b-polyisoprene (PS-b-PI) diblock copolymer arms. Such miktoarm star polymers are much more difficult to characterize than branched homopolymers since the byproduct, typically polymers with missing arm(s) or coupled products, have not only different molecular weights but also different compositions. TGIC was able to fully separate the byproducts, and the composition of the molecular species corresponding to the different separated elution peaks was determined by two methods, fractionation/NMR and multiple detection (UV and RI). A reasonable agreement between the results of the two methods was obtained. By using the composition found, the corresponding molecular weights were determined by multi-angle light scattering detection. Based on the composition and the molecular weight we were able to identify the structure of the different molecular species.