From designer Lewis acid to designer Brønsted acid towards more reactive and selective acid catalysis

This review focuses on the development of acid catalysis for selective organic transformations conducted in our laboratories for the past 30 years. Several important concepts in designing of catalysts are described with some examples. Further, recent developments in super Brønsted acid and their applications in a one-pot procedure to construct complex molecules with high diastereoselectivities are described.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Theory of electrically controlled exhibition of circular Bragg phenomenon by an obliquely excited structurally chiral material – Part 2: Arbitrary dc electric field

Numerical examination of the solution of the boundary-value problem of the reflection and transmission of a plane wave due to a slab of an electro-optic structurally chiral material (SCM) indicates that the exhibition of the circular Bragg phenomenon by the SCM can be controlled not only by the sign and the magnitude of a dc electric field but also by its orientation in relation to axis of helicoidal non-homogeneity of the SCM. Thereby, the possibility of electrical control of circular-polarization filters has been extended.     

生态旅游与非生态现象--问题与对策

生态旅游作为一种新的旅游形态备受各国关注,我国开展生态旅游有着良好的资源条件。文章在扼要分析了发展中国生态旅游优势的基础上,重点主中国开展生态旅游所出现的问题。认为加强环境教育和生态管理是搞好中国生态旅游的有效策略 。     

超大径圆钢机械连接接头试验研究

介绍超大径圆钢(Φ75/45A)机械连接接头试验方法和特点,本试验组研制的大吨位加力装置,解决了超大径圆钢机械连接接头变形性能单向拉伸试验的难题,填补了国内该项试验的空白.对试验测取的数据进行对比分析,其机械连接接头抗拉性能指标满足<钢筋机械连接技术规程>JGJ 107(2007年征求意见稿)的相关技术要求.     

理学ZSX PrimusⅡX射线荧光光谱仪日常维护及常见故障维修

主要介绍了理学ZSX PrimusⅡX射线荧光光谱仪的一些日常保养和出现故障的现象及处理方法。     

基于空间自适应正则化的超分辨率重建算法

针对模糊图像的复原问题,从正则化技术克服问题病态性的思想出发,研究了一种有效的超分辨率重建算法。该算法充分考虑了图像的局部特性,引入了空间自适应加权矩阵,采用全局正则化参数与局部正则化参数矩阵相结合的方法,弥补了传统正则化方法所带来的正则化误差以及噪声放大误差。实验结果表明,该算法能够有效地减少重建误差,保护图像的细节信息。     

C/N/O centred metal clusters: super valence bonding and magic structure with 26 valence electrons

By using genetic algorithm combined with B3LYP and QCISD methods, this paper investigates the stabilities and electronic structures of Al₆OM_m (M?=?Na, K; m?=?2,4,6) and a few other Al_nXNa_m (X?=?C, N, O) clusters. The results show that the nonmetal doped metal clusters with 26 valence electrons have enhanced stabilities and large energy gaps. This paper extends the Jellium model for the application to the nonmetal doped metal clusters and explains the electronic origin of this strong magic structure. The nonmetal X atom is situated in the centre of the magic clusters. The 2s/2p orbitals of the central atom interact strongly with the superatomic 1S/1P orbitals and form bonding and antibonding orbitals. The bonding orbitals make the C/N/O atoms form s²p⁶ shell closure, and the antibonding orbitals make the metal moieties form closed 2S²2P⁶ shells. The 26 valence electrons form closed s²p⁶S²P⁶D¹⁰ shells, and this electronic configuration can be taken as the combination of the octet rule and 18-electron rule. The octahedral Al₆O^2? core is a superatomic anion with great stability, and it can be used as building blocks to assemble Zintl phase materials by interaction with alkali metals.     

准噶尔盆地玛湖——盆1井西复合含油气系统地层高压分布与成因

玛湖——盆1井西复合含油气系统是准噶尔盆地油气分布最集中的地质单元．研究表明该地区地层压力类型丰富,侏罗系底部及以下地层在凹陷内一定深度以下普遍发育高压,在莫索湾凸起的中南部侏罗系则整体处于超压状态．沉积型欠压实作用使得凹陷内侏罗系底部及以下储层流体以高压分布为主,腹部4400m以下地层中的高压形成则与成岩型欠压实作用有关,而构造挤压及叠置作用对西北缘高压的形成起主要作用．     

关于随机现象的评估模型

利用一种新的Fuzzy综合评判方法,对于市场研究中的随机现象进行综合评判,提出一种评估模型.使用这种模型,可以使评估结果更切合实际,更具有使用价值.