Recent progress in the plastic methods of structural analysis

The techniques described in Part I of this paper for the calculation of plastic failure loads under proportional loading are further exemplified by indicating solutions for a rectangular building frame, a Vierendeel girder, and a shed-type portal frame. A method for estimating deflections of a frame just as the collapse load is attained is then described, with some indications as to its reliability. More general conditions of loading than proportional loading are next discussed, and generalized load and failure concepts are defined. The theorems and techniques for determining critical shakedown loads under variable, repeated loading are then described and illustrated. The relation of the elastic-plastic shakedown analysis to the much simpler analysis for failure under single load applications is discussed.     

Recent progress in the chemistry of the sugars

This paper reviews the work of Emil Fischer upon sugars and ferments. The synthesis of monoses, disaccharides and glucosides are described. The fermentation of the sugars and the action of the various inverting enzymes are discussed, as is also the lock-and-key theory of enzyme action. The splitting of racemic sugar derivatives into their active components, and asymmetric syntheses within the sugar group are also considered.     

中国碳排放增长的多层递进动因——基于SDA和SPD的实证研究

研究碳排放增长的多维、多层动因,识别关键的增排产业链和增排路径,对于宏观减排政策制定和微观减排路径选择都具有较强的现实意义。本文基于非竞争型投入产出模型,利用结构分解和结构路径分解的分析方法,从总体、生产阶段、产业链3个层次对中国碳排放增长进行了递阶分解分析,识别出了2010—2015年中国碳排放增长的主要动因和路径。研究结论表明：①需求规模变化是中国总体、生产阶段、产业链碳排放增加的主导影响因素;②煤炭消费发挥着减排作用且贡献巨大,但其他能源的增排效应使煤炭的减排贡献大打折扣;③能源效率变化对各生产阶段的影响为正且呈递减趋势,最终需求结构变化对第一生产阶段的碳排放具有显著减排效应,对其他生产阶段具有轻微增排效应;④需求规模变化和直接消耗系数变化是多数增排产业链的最大影响因素,30条增排路径占中国2010—2015年碳排放增加量的25.7%,构成了碳排放增加的关键路径和动因。最后,从宏观和微观两方面提出了相应的减排政策建议。     

Recent progress in the study of transition in the hypersonic boundary layer

Turbulence is a universal form of fluid motion. It is the key issue in fluid mechanics. Very recently, it has become a bottleneck in some key engineering research of national importance, such as aeronautics, astronautics and navigation. Developed turbulence and the onset of turbulence, i.e. transition, are two interrelated parts of turbulence. The hypersonic boundary-layer transition is a strategic focus in the fluid mechanics community. This article reviews recent developments in the study of the hypersonic boundary-layer transition, research facilities and experimental techniques. The hypersonic quiet wind tunnel is introduced as a necessary device to obtain real flight data in near space. Near-wall measurement techniques, such as temperature-sensitive paint, near-wall particle image velocimetry and Rayleigh-scattering visualization, are shown. The most important issues in the recent development of the transition in the hypersonic boundary layer are addressed. The instability and nonlinear interaction of different instability modes are discussed. The recent contributions from China, especially at Peking University, are also introduced.     

Recent advances in structural studies of the CRISPR-Cas-mediated genome editing tools

Clustered regularly interspaced short palindromic repeats (CRISPR) and accompanying CRISPR-associated (Cas) proteins provide RNA-guided adaptive immunity for prokaryotes to defend themselves against viruses. The CRISPR-Cas systems have attracted much attention in recent years for their power in aiding the development of genome editing tools. Based on the composition of the CRISPR RNA-effector complex, the CRISPR-Cas systems can be divided into two classes and six types. In this review, we summarize recent advances in the structural biology of the CRISPR-Cas-mediated genome editing tools, which helps us to understand the mechanism of how the guide RNAs assemble with diverse Cas proteins to cleave target nucleic acids.     

人才测评方法研究的新进展

结合大量的国外文献,对心理测验、面试、评价中心和履历分析四种普遍应用的测评方法的研究进行了总结,并展望未来测评方法研究的方向,介绍了人才测评方法领域的新进展。     

Recent progress in reactivity study and synthetic application of N-heterocyclic phosphorus hydrides

N-heterocyclic phosphines (NHPs) have recently emerged as a new group of promising catalysts for metal-free reductions, owing to their unique hydridic reactivity. The excellent hydricity of NHPs, which rivals or even exceeds those of many metal-based hydrides, is the result of hyperconjugative interactions between the lone-pair electrons on N atoms and the adjacent σ^*(P–H) orbital. Compared with the conventional protic reactivity of phosphines, this umpolung P–H reactivity leads to hydridic selectivity in NHP-mediated reductions. This reactivity has therefore found many applications in the catalytic reduction of polar unsaturated bonds and in the hydroboration of pyridines. This review summarizes recent progress in studies of the reactivity and synthetic applications of these phosphorus-based hydrides, with the aim of providing practical information to enable exploitation of their synthetically useful chemistry.     

浅析构造地质学新进展及应用研究

当今世界,地学面临新的需求和新的机遇。构造地质学是传统地质学的三个重要支柱之一,因而笔者认为对构造地质学的相关应用研究要高度重视,尤其是目前在我国经济快速发展,但面临着资源和能源的匮乏,国内急缺重要固体矿产资源,矿山勘探和开采难度加大。我国在基础地质、矿产资源、地质灾害、全球气候变化等重大地学领域将积极参与全球地学合作,此时地质构造学的应用研究显得更为重要。笔者在文中对构造地质学作用、研究的发展历程及特点进行了浅析,就构造地质学研究新进展及应用作了五个方面的重点阐述。     

基于知识的公司战略的结构化阐释

为了给战略管理提供知识视角的理论启发,本文认为,企业是知识一体化组织,公司战略是由公司战略要素构成的结构性系统,基于这样的认识,在简要探讨关于“知识”的基本内容的基础上,通过分析知识和每个公司战略要素的联系而得出公司战略的知识维度的结构,据此推出对于基于知识的公司战略过程理论的启示。     

技术创新、产业结构与劳动生产率

本文运用传统的份额变化分析方法,通过细分工业各产业和把工业作为整体细分各地区两种方法,论证了从1986年到2001年技术创新和产业结构对中国经济增长的影响,得出如下结论:在中国技术创新对生产率增长有重要影响;从总体来说,产业结构对生产率的影响较微弱,但细化到各地区则有较大差别。