无催化剂条件下环辛烯环氧化反应

以O2气为氧源,在无溶剂无引发剂条件下,研究了非催化剂体系中环辛烯环氧化反应,并考察了反应温度、时间、压力、自由基引发剂以及自由基阻聚剂对环辛烯环氧化反应的影响. 实验结果表明,在无催化剂条件下,当反应初压0.60 MPa,反应时间2.0 h时,在140 ℃的较高温度下,以分子氧为氧源,环辛烯的转化率为44.5%,环氧环辛烷的选择性可达到64.4%.     

可转换债券:参数估计与定价实证

金融产品的定价,是金融工程研究的核心问题之一,同样可转换债券的定价也引起国内外学者们的关注.本文试图借鉴国内外研究成果,在分析股价及利率特性的基础上,运用推导出基于股价和利率的双因素定价模型;从中国实情出发,运用广义自回归条件异方差模型(简称GARCH)得出长期波动率,通过将可转债条款转化为边界终值条件并利用数值方法对可转债定价.     

固体酸WO3/TiO2负载锂锰催化剂组成对其甲烷氧化偶联反应性能的影响

The selective oxidation of methane to basic petrochemicals (ethylene and ethane) is desirable and has attracted extensive research attention. The oxidative coupling of methane (OCM) is considered a promising one-step route for the production of C₂ compounds (ethylene and ethane) from methane, and has been the focus of industrial and fundamental studies. It is widely accepted that the composition is a crucial factor governing the activity of a catalyst system. It was found that the phase structures, basicity, existing status and distribution of the active components, oxygen species, and chemical states of the catalyst were influenced by the composition and ratio, resulting in different catalytic performances for the OCM. In this study, a series of solid acid WO₃/TiO₂-supported lithium-manganese oxide catalysts for OCM were synthesized via the impregnation method. The impacts of diverse compositions, such as the individual contents (Li and Mn) and dual contents (Li-Mn), on the OCM were investigated in detail, using inductively coupled plasma optical emission spectrometry, X-ray diffraction, high-resolution transmission electron microscopy, CO₂-temperature-programmed desorption, O₂-temperature-programmed desorption, H₂-temperature-programmed reduction, Raman spectroscopy, X-ray photoelectron spectroscopy, and CH₄-temperature-programmed surface reaction. The addition of Li content to the catalyst not only led to the anatase-to-rutile crystal structure transformation of TiO₂, and the reduction of the high-valence-state Mn species to low-valence-state Mn, but also increased the content of surface lattice oxygen and decreased the surface basicity. The observed effects on the structures and catalytic performance suggest that the Li content is helpful in suppressing the formation of completely oxidized CO₂, and increases the C₂ selectivity. Moreover, increasing the Li content of the catalyst facilitated the mobility of the lattice oxygen, which triggered the promotion of CH₄ activation, thereby enhancing the OCM catalytic performance. The Mn content acted as the active sites for OCM; therefore, the performance of the catalyst was closely related to the Mn concentration and valence state. However, the WO₃/TiO₂-supported catalyst with excessive Mn content exhibited a high surface basicity, high valence state of Mn, and low abundant lattice oxygen, which was unfavorable for C₂ selectivity. The Raman spectroscopy results revealed that MnTiO₃ was formed due to the co-existence of Li and Mn on WO₃/TiO₂, and played an essential role in improving the low-temperature OCM performance. There was a synergic effect of the Li and Mn components on the OCM. The optimal performance (16.3% C₂ yield) was achieved over the WO₃/TiO₂-supported lithium-manganese catalyst with n(Li) : n(Mn) = 2 : 1 at 750 ℃.     

硷金属卤化物离子晶体的科希关系式

本文在二级微扰的近似下,具体导出一个离子在其它离子(看作是点电荷)的晶体场中作用能的一般表达式,写出晶体的能密度函数,从而导出硷金属卤化物离子晶体的各弹性系数的表达式,对于科希关系式的偏离作了数值计算,并与实验结果进行比较。     

钼单晶体的冷轧及再结晶织构

本文研究了(110)[001]和(111)[112]取向的钼单晶体,在经过70％、80％和85％冷轧后的加工織构,以及退火后的再结晶織构。分析了(111)[112]取向晶体在轧制变形时,由于各组滑移系间的交互作用而引起晶体取向的转动,从定向生核的观点,能够比较满意地解释这类取向的晶体随着压下量从70％增加到85％,再结晶織构从(221)[114]、(110)[001]向着(320)[001]和(210)[001]逐渐变化的现象。 关键词：     

铁硅合金(110)[001]单晶体的形变和再结晶

本文研究了含硅3.25％铁硅合金(110)[001]的单晶,在压下量为5—50％范围内的形变和再结晶。沿样品轴向冷轧2—16％后,测出的滑移面为(101),(101),(011)和(011),孿生面为(112)和(112),这很好地解释了本文所得冷轧机构的来源。样品经过35％和50％冷轧后,在退火时再结晶晶粒形成的部位和生长的情况有所不同:前者在孿晶界上领先形成,并沿孿晶界择尤生长;而后者除了观察到在孿晶界和形变带附近形成外,还观察到一种通过亚晶粒长大而成的晶粒,它们择尤生长的趋势也不如前者明显。     

关于μ俘获中有效赝标量耦合项的符号

最近的实验有迹象表明,μ俘获中有效赝标量项的符号与从V-A理论用色散关系求得的相反。本文对这个符号的差别提出了一个可能的解释。在本文中指出,汉密顿量中一很小的赝标耦合项(约为有效赝标耦合项的1/100)即能改变有效赝标耦合项的符号。将这一赝标项加以变换,使之成为普适赝矢量电流的一部分,则可证明新添的这一项对β衰变和π→e+v衰变不产生任何可观察的效应,因而不破坏V-A理论的普适性。文章最后讨论了超子对对有效赝标项符号的影响的问题。     

无机化学实验成绩评价标准与考核方式初探

根据我院实际情况,对无机化学实验考核方式进行了探讨,将实验教学考核成绩分成平时成绩、阶段成绩和结课成绩三个部分,建立了注重实验结果的同时更注重实验过程及实验技能的考核体系。     

NEB NONLINEAR σ MODELS ON SYMMETRIC SPACES

Two new nonlinear σ models, defined on the symmetric coset spaces GL (n,c). ⊕ GL(n,c)/GL (n,c) and GL (n,c)/U(n) respectively, are formulated in this paper.The latter may be useful in discus-sing the four-dimensional Yang-Mills fields.