Impedance spectroscopy study of gadolinia-doped ceria

The electrical properties of Gd_0.1Ce_0.9O_1.95 were investigated in various gas atmospheres using a.c. impedance spectroscopy. In dry oxygen, impedance spectra consisted of two arcs at low temperatures corresponding to bulk and grain boundary behaviour, respectively, and only one arc at high temperatures (T>550 °C). The results showed a high oxygen ion conductivity in oxygen atmosphere more than 10⁻² S/cm at 600 °C. In water atmospheres, the bulk arc in dry oxygen was reduced by 30 %, and an additional arc corresponding to the grain boundary effect appeared. It seems that the presence of water may decrease the bulk resistance, but causes an additional grain boundary resistance and thus increase in the total resistance. In hydrogen atmosphere, a conductivity enhancement up to one order of magnitude was observed. In hydrogen there is a reduction of Ce⁴⁺ to Ce³⁺ in the sample, which involves defect formation generating e.g. electrons, additional oxygen vacancies and at the same time protons in the lattice. These new charge carriers are responsible for a significant conductivity enhancement. Therefore, in a hydrogen atmosphere the material is a mixed (oxygen ion + proton + electron) conductor. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

高校人力资源管理中的模糊综合评判

人力资源管理是高校管理的重要组成部分。本简要介绍了高校人力资源的状况，讨论了模糊综合评判理论在人力资源管理中的应用。     

Potential measurement in ECT system

Potential measurement can be applied to electrical capacitance tomography (ECT) systems. However, the relationship between potential and the capacitance is not well understood. This paper reveals that a potential is dependent on the capacitance ratio for a given excitation voltage, independent of capacitance themselves. The conditions for using this method are discussed. Finally, image reconstruction based on the Generic Algorithm for Electrical Capacitance Tomography (GA-ECT) is implemented satisfactorily for square and circular sensors respectively.     

一个新的高维向量Lie代数及其应用

构造了一个新的8维向量Lie代数,通过适当设计等谱问题,利用屠格式和扩展的迹恒等式得到了AKNS族的可积耦合及Hamilton结构.     

溶液中pH对蛋白质乳化能力影响的拉曼光谱研究

本工作采用 FT- Raman光谱仪对不同的 p H值的蛋白质水溶液多次扫描 ,采用酰胺 带的谱图作曲线拟合 ,并以子峰面积表征对应二级结构含量 ,得出二级结构的变化与蛋白质水溶液与乙酸丁酯混合后乳化能力变化的关系。结果表明 :蛋白质分子对 p H变化的敏感程度不一样。蛋白质分子结构的改变是引起蛋白质水溶液在有机溶液中乳化的一个重要因素     

动能定理应用探讨

应用动能定理解质点系运动问题时，不能随意假定质点系的始末状态，而必须全过程进行分析。本给出了一个只考虑想象中的、并不存在的始末状态而得出错误结论的例子。     

Synthesis,Structure,and Ring-opening Metathesis Polymerization of η~5-Pentamethylcyclopentadienyl-(η~5-exo-tricyclo [5.2.1.0~(2,6)]deca-2,5,8-trien-6-yl) Iron

η5-Pentamethylcyclopentadienyl-(η5-exo-tricyclo[5.2.1.02,6]deca-2,5,8-trien-6-yl) iron(3) was synthesized and characterized by 1H NMR, 13C NMR, MS, elemental analysis, IR, UV and X-ray diffraction analysis. Compound 3 was polymerized with ring-opening metathesis polymerization(ROMP) initiator (PCy3)2Cl2Ru=CHPh. 1H NMR and IR spectra revealed the presence of CH=CH units in the polymer and supported the ROMP mechanism. GPC analysis of the polymer showed that the weight-average molecular weights(Mw) was 5967, ...     

Structures and Absolute Configurations of Three 7,8‐Secolabdane Diterpenes from the Chinese Liverwort Pallavicinia ambigua

The known 7,8‐secolabdane type diterpenoids neopallavicinin ( 1 ), pallavicinin ( 2 ), and 18‐hydroxypallavicinin ( 3 ) were isolated from Pallavicinia ambigua, and their structures were determined. The X‐ray crystal structure of 1 was solved, and, in combination with CD and NMR studies, the absolute configurations of 1 – 3 were established. A possible biogenetic pathway for 1 and 2 from a single labdane precursor is proposed.