《材料力学》竞赛主要题型分析

在分析前五届全国力学竞赛中《材料力学》试题的基础上,对竞赛主要题型进行了总结,并给出了相应例题的解题方法和思路,最后指出了参赛大学生应具备的基本条件.     

中空Ta_2O_5/TiO_2复合光催化剂的可控氧化制备及性能

以钛粉、钽粉为原料,炭黑作为反应性模板,通过熔盐法在炭黑表面原位生长了TaTiC_2纳米碳化物涂层,并以所得TaTiC_2/C复合物为碳化物前驱体,再经可控氧化制备出中空Ta_2O_5/TiO_2复合光催化剂。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见(UV-Vis)漫反射(DRS)及N2物理吸附等手段对所制备的光催化剂进行形貌、显微结构及孔结构表征。以高压汞灯为紫外光源,以亚甲基蓝为目标降解物,通过光催化降解实验评价中空Ta_2O_5/TiO_2复合光催化剂的光催化活性。结果表明,熔盐法生长碳化物涂层厚度均匀(20~30 nm),碳化物主要以TaTiC_2晶相存在且具有纳米级的颗粒尺寸。中空Ta_2O_5/TiO_2复合光催化剂同时具有200 nm左右的中空大孔结构及壳层10 nm左右的介孔结构。中空大孔和介孔的存在提高了所制备催化剂对亚甲基蓝的吸附能力。此外,TiO_2与Ta2O5通过电子能带结构的耦合,有效提高了光生电子和空穴的分离效率,从而显著提高了光催化活性。nTi∶nTa=2.5∶1.5时,相应的中空Ta_2O_5/TiO_2复合光催化剂表现出最佳的光催化活性,对亚甲基蓝的紫外光催化降解率高达97%。     

内蒙古段黄河水系放射性水平调查研究

给出了内蒙古段黄河水平中总α，总β，＾９０Ｓｒ，＾１３７Ｃｓ，＾４０Ｋ，＾３Ｈ，＾２１０Ｐｂ，＾２１０Ｐｏ，＾２３８Ｕ，＾２３２Ｔｈ、＾２２６Ｒａ放射性水平，结果基本为正常水平，找出了污染源，为内蒙古段黄河水中放射性监督监测建立了全面的背景材料。     

无定形TiO2可见光敏化降解染料污染物

采用一步水解法制备了无定形TiO2(Am-TiO2),并运用X射线衍射、X射线光电子能谱、N2吸附-脱附和紫外-可见漫反射光谱等手段对其进行了表征.结果表明,Am-TiO2具有大的比表面积(216m2/g)和丰富的表面羟基/化学吸附的水.与晶态TiO2相比,Am-TiO2的吸收带边明显蓝移(411nm→378nm),禁...     

New bifurcations of basin boundaries involving Wada and a smooth Wada basin boundary

This paper demonstrates and analyses double heteroclinic tangency in a three-well potential model, which can produce three new types of bifurcations of basin boundaries including from smooth to Wada basin boundaries, from fractal to Wada basin boundaries in which no changes of accessible periodic orbits happen, and from Wada to Wada basin boundaries. In a model of mechanical oscillator, it shows that a Wada basin boundary can be smooth.     

Synthesis, structure, and electrocatalysis of diiron C-functionalized propanedithiolate (PDT) complexes related to the active site of [FeFe]-hydrogenases

New C-functionalized propanedithiolate-type model complexes (1-8) have been synthesized by functional transformation reactions of the known complex [(mu-SCH2)2CH(OH)]Fe2(CO)6 (A). Treatment of A with the acylating agents PhC(O)Cl, 4-pyridinecarboxylic acid chloride, 2-furancarbonyl chloride, and 2-thiophenecarbonyl chloride in the presence of Et3N affords the expected C-functionalized complexes [(mu-SCH2)2CHO2CPh]Fe2(CO)6 (1), [(mu-SCH2)2CHO2CC5H4N-4]Fe2(CO)6 (2), [(mu-SCH2)2CHO2CC4H3O-2]Fe2(CO)6 (3), and [(mu-SCH2)2CHO2CC4H3S-2]Fe2(CO)6 (4). However, when A is treated with the phosphatizing agents Ph2PCl, PCl3 and PBr3, both C- and Fe-functionalized complexes [(mu-SCH2) 2CHOPPh2-eta1]Fe2(CO)5 (5), [(mu-SCH2) 2CHOPCl2-eta1]Fe2(CO)5 (6), and [(mu-SCH2) 2CHOPBr2-eta1]Fe2(CO)5 (7) are unexpectedly obtained via intramolecular CO substitution by P atoms of the initially formed phosphite complexes. The simplest C-functionalized model complex [(mu-SCH2) 2CO]Fe2(CO)6 (8) can be produced by oxidation of A with Dess-Martin reagent. While 8 is found to be an electrocatalyst for proton reduction to hydrogen, starting complex A can be prepared by another method involving the reaction of HC(OH)(CH2Br)2 with the in situ generated (mu-LiS) 2Fe2(CO)6. X-ray crystallographic studies reveal that the bridgehead C atom of 8 is double-bonded to an O atom to form a ketone functionality, whereas the bridgehead C atoms of A, 1, 3, and 4 are equatorially-bonded to their functionalities and those of 5-7 axially-bonded to their functionalities due to formation of the corresponding P-Fe bond-containing heterocycles.     

高压密闭消解-电感耦合等离子体质谱法测定青藏高原气溶胶样品中磷及其他18种元素

气溶胶中磷（P）的准确测定是评估磷沉降对青藏高原生态效应及磷的生物地球化学循环的重要前提。针对青藏高原气溶胶中磷含量低及滤膜单个样品量有限的特征,本文建立了高压密闭消解-电感耦合等离子体质谱法测定气溶胶中磷及其他元素含量的方法。电感耦合等离子体质谱法（ICP-MS）测得P元素的检出限为3.5 μg/L,优于电感耦合等离子体发射光谱仪（ICP-OES）的检测限（89 μg/L）,其他元素检出限均达到μg/L（ppb）级（0.013-36 μg/L）,部分元素如Co、Cd、Pb等达到ng/L（ppt）级（2-7 ng/L）。各元素线性关系良好,测定结果的相对标准偏差(RSD) < 5%,磷的加标回收在90-103%, 方法准确度和精密度满足分析要求。该方法成功地测定了青藏高原实际气溶胶样品中磷及其他元素,具有良好的可靠性和实用性。     

宽波段高分辨率小型紫外成像光谱仪光学系统研究

结合小型紫外光谱仪器设计原理对紫外成像光谱仪进行了研究。以离轴抛物镜为望远镜,超环面光栅为成像光谱系统设计了系统方案;该光学系统的优化设计就是对超环面光栅的参数设计。分析了光栅的光程函数和像差方程,总结了单超环面光栅结构的完善聚焦条件和完善成像条件;这两种条件无法在代数计算下得到完善代数解,限制了光谱仪的工作波段和视场,引入遗传算法解决了这个问题。以一工作波段为200~280 nm的日盲紫外成像光谱仪为例对设计理论进行验证,根据优化理论计算了初始结构最优解并进行光线追迹模拟,成功得到了F数为5.7,焦距为102 mm,全视场全波段调制传递函数值在奈奎斯特频率(20 lp·mm-1)下大于0.65的高分辨率成像光谱仪光学系统。设计结果表明这种光学系统设计理论适用于小型宽波段高分辨率紫外成像光谱仪。     

镧-依文思蓝-氨基糖苷类抗生素的显色反应及其分析应用

分光光度法;镧-依文思蓝-氨基糖苷类抗生素的显色反应及其分析应用     

Tensor density matrix theory for determining population and alignment of symmetric top molecule using rotationally unresolved fluorescence

General expressions used for transforming raw laser-induced fluorescence (LIF) intensity into the population and alignment parameters of a symmetric top molecule are derived by employing the density matrix approach. The molecular population and alignment are described by molecular state multipoles. The results are presented for a general excitation-detection geometry and then applied to some special geometries. In general cases, the LIF intensity is a complex function of the initial molecular state multipoles, the dynamic factors and the excitation-detection geometrical factors. It contains a population and 14 alignment multipoles. How to extract all initial state multipoles from the rotationally unresolved emission LIF intensity is discussed in detail.