金红石TiO_2中本征缺陷扩散性质的第一性原理计算

基于密度泛函理论的爬坡弹性带方法,对金红石相二氧化钛晶体中钛间隙、钛空位、氧间隙、氧空位4种本征缺陷的扩散特征进行了研究.对比4种本征缺陷在晶格内部沿不同扩散路径的过渡态势垒后发现,缺陷扩散过程呈现出明显的各向异性.其中,钛间隙和氧间隙沿[001]方向具有最小的扩散势垒路径,激活能分别为0.505 eV和0.859 eV;氧空位和钛空位的势垒最小的扩散路径分别沿[110]方向和[111]方向,激活能分别为0.735 eV和2.375 eV.     

郡县制国家现代化：中央政府如何扩大公共事务治理职能

郡县制国家的传统职能是“管人”,但是在当代,为了适应现代世界,需要加强和完善“管事”的职能。然而,加强“管事”的职能遇到的一大障碍,是“管事”与“管人”通常难以分开,带来管事与管人的冲突。在全国性公共事务上,面对管事与管人的冲突,郡县制国家的一种改革方向,即建立中央统一管理与地方属地管理相结合的体制,既扩大中央政府的治理职能,同时又发挥纵向约束机制的作用,从而能改善全国性公共事务治理。此种中央统一管理与地方属地管理相结合的体制,通常不是中央政府事先设计出来的,而是在改革过程中,经由中央政府与地方政府的策略性互动过程,逐渐建立起来的。因此,郡县制国家蕴含着一种潜力,即在公共事务治理上,包括地方公共事务和全国性公共事务,可以引入和发挥“纵向约束机制”的作用,使得国家既保持“管人”的基本体制不变,又能提高治理能力。     

Evaluation of a Novel Dechlorination Reaction as an Analytically Useful Derivatization Reaction Part 1. Stoichiometry,Mechanism and Yield Optimization

Abstract

A novel reaction for the dechlorination of polychlorinated biphenyls (PCBs) as well as most other chlorinated aromatic and aliphatic compounds is evaluated and discussed in terms of its potential for analytical purposes. The active dechlorinating agent is prepared through the reaction of molten sodium or potassium with polyethylene glycols (MW >200), in the absence of oxygen, to form the corresponding alkali metal glycolate, a powerful nucleophilic agent. Special emphasis is given to the mechanistic aspects of the reaction and their importance in terms of achieving high and reproducible yields with analytical quantities of substrate, in short periods of time. The contribution of the techniques: ESR, NMR, IR, UV, MS, GC-ECD, LC-EC, CIDNP-NMR, conductimetry and chloride analysis (amperometric) in elucidating the reaction mechanism and providing valuable kinetic data is illustrated. This reaction can potentially be applied to the determination of PCBs in waste oils.     

对氨基酚络合萃取机理的探讨

对氨基酚络合萃取机理的探讨;对氨基酚; 络合萃取; 萃取机理; 萃取反应热     

过渡金属氢化物和聚集双键化合物反应的研究Ⅲ.用ESR方法考察二茂锆氢化物与RNCS的反应机理

本文用ESR方法考察了Cp₂ZrH) Cl与RNCSR=C₆H₅,c-C₆H₁₁,n-C₄H₉)的反应的过程,结果表明,在这类反应过程中,Zr-H键发生均裂,中心金属锆经过+4-→+3-→+4的价态变化,反应通过自由基机理进行.     

Random walk properties of lattices and correlation factors for diffusion via the vacancy mechanism in crystals

Random walk properties and correlation factors for diffusion via the vacancy mechanism are calculated and compared for various three-dimensional lattices. By applying the theory of random walks on an imperfect lattice, the correlation factor for impurity diffusion is calculated rigorously for the five jump frequency model in the fee lattice.Presented at the Symposium on Random Walks, Gaithersburg, MD, June 1982.     

小间隙高放大多丝室及其放电机制

对以强猝灭气体工作的小间隙多丝室及其放电机制进行了研究,实验表明,因为工作在饱和模式区,这种室同时具有很高的气体放大和相当快的时间特性.文中探讨了放电机制,雪崩中空间电荷效应以及电离光子的产生和作用是重要的因素,而其中后一因素又受到强猝灭气体的抑制.     

预裂爆破设计参数的理论分析

本文在分析不偶合装药爆破物理过程和动态冲击压力的基础上,研究了预裂孔的破坏型态;利用相应的破坏准则,推导了预裂孔临界和允许体积装药密度的理论计算式,并在总结已有的预裂成缝理论和实验成果的基础上,用裂断力学理论对成缝机理作了进一步探讨。考虑了岩体初始应力的影响,对裂缝扩展进行了定量描述,提出了预裂爆破炮孔间距的计算表达式。     

Analysis and modeling of resistive switching mechanisms oriented to resistive random-access memory

With the progress of the semiconductor industry,the resistive random-access memory(RAM) has drawn increasing attention.The discovery of the memristor has brought much attention to this study.Research has focused on the resistive switching characteristics of different materials and the analysis of resistive switching mechanisms.We discuss the resistive switching mechanisms of different materials in this paper and analyze the differences of those mechanisms from the view point of circuitry to establish their respective circuit models.Finally,simulations are presented.We give the prospect of using different materials in resistive RAM on account of their resistive switching mechanisms,which are applied to explain their resistive switchings.     

金属催化制备石墨烯的研究进展

石墨烯作为一种新兴的碳素材料,从一出现就引起了众多学者的关注.石墨烯具有许多新奇的特性,使得石墨烯在光电领域及微电子工业等有极大的应用潜力.但是目前难以实现大尺寸、高质量、宏量石墨烯的可控制备,限制了石墨烯的广泛应用.本文分析了各种石墨烯制备方法的利弊,重点从层数控制及大面积制备等方面对金属催化法进行了阐述,固态碳源金属催化法可以实现宏量制备大尺寸、高质量、薄且均匀的石墨烯.综述了金属催化制备石墨烯的相关机理研究,指出了目前研究的局限,并对石墨烯相变机理的下一步研究方向进行了展望.