Marked Advance in Widths and Heights of Harmonic Plateau

We propose a scheme to simultaneously widen and heighten the high-order harmonic plateau on a large scale. More specifically, by adopting a united two-atom system with a suitable inter-nuclear separation instead of a single-atom, the harmonic plateau is widened from I_p + 3.2U_p to I_p + 8.5U_p; further, by adopting the combined pulse, the extended plateau (harmonics near I_p + 5.6U_p) is selectively heightened in excess of 4 orders of magnitudecompared with the case of the low-frequency pulse alone. By means ofthe wavelet transform for the induced dipole of these harmonics, asingle x-ray pulse as short as 210 asec is achieved.     

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.     

On‐line optical and X‐ray spectroscopies with crystallography: an integrated approach for determining metalloprotein structures in functionally well defined states

X‐ray‐induced redox changes can lead to incorrect assignments of the functional states of metals in metalloprotein crystals. The need for on‐line monitoring of the status of metal ions (and other chromophores) during protein crystallography experiments is of growing importance with the use of intense synchrotron X‐ray beams. Significant efforts are therefore being made worldwide to combine different spectroscopies in parallel with X‐ray crystallographic data collection. Here the implementation and utilization of optical and X‐ray absorption spectroscopies on the modern macromolecular crystallography (MX) beamline 10, at the SRS, Daresbury Laboratory, is described. This beamline is equipped with a dedicated monolithic energy‐dispersive X‐ray fluorescence detector, allowing X‐ray absorption spectroscopy (XAS) measurements to be made in situ on the same crystal used to record the diffraction data. In addition, an optical microspectrophotometer has been incorporated on the beamline, thus facilitating combined MX, XAS and optical spectroscopic measurements. By uniting these techniques it is also possible to monitor the status of optically active and optically silent metal centres present in a crystal at the same time. This unique capability has been applied to observe the results of crystallographic data collection on crystals of nitrite reductase from Alcaligenes xylosoxidans, which contains both type‐1 and type‐2 Cu centres. It is found that the type‐1 Cu centre photoreduces quickly, resulting in the loss of the 595 nm peak in the optical spectrum, while the type‐2 Cu centre remains in the oxidized state over a much longer time period, for which independent confirmation is provided by XAS data as this centre has an optical spectrum which is barely detectable using microspectrophotometry. This example clearly demonstrates the importance of using two on‐line methods, spectroscopy and XAS, for identifying well defined redox states of metalloproteins during crystallographic data collection.     

The Modified Rockwell Test: A New Probe for Mechanical Properties of Metals

In the present work a novel methodology is proposed, based on the combination of the Rockwell and the Vickers tests, to provide estimates of the mechanical properties of metal substrates. The analysis is based on some novel invariants obtained from the finite element solution of the Vickers indentation (the imprint diagonal relates to the maximum indentation depth and the residual indentation depth with the average pressure and the elastic modulus). Several other useful results are discussed and experiments are performed with a modified Rockwell apparatus on steel and aluminium alloys. The results are important for the interpretation of micro indentation tests. Inverting the indentation data, reasonably accurate results can be obtained for strain hardening properties for “power law” behaviour, whereas more complex strain hardening would require further investigation.     

高职产学研结合的内涵与模式探讨

高职产学研合作教育是以就业为导向,培养技术应用性人才的重要途径,其内涵是利用高职和企业的教育资源,发挥双方各自优势,将学校课堂上理论知识学习为主与企业生产场所实践技能培训为主两种教学形式有机结合,培养企业需求的技术应用性人才。由于高职学院和企业的具体条件不同,决定其合作模式是多层次、多方位、多形式,产学研合作教育主要内容是:(1)加强专业建设;(2)推动职业培训合作;(3)加快科技开发合作;(4)增加学生就业渠道。     

SS304不锈钢高温非比例多轴循环变形行为的粘塑性本构描述

在350℃和700℃下SS304不锈钢的非比例多轴循环变形行为进行了系统的实验研究。在此基础上,在统一粘塑性本构理论的框架下改进和发展了一个新的循环本构模型。该模型给出了新的背应力演化方程,引入了非比例度参量,考虑了温度效应和最大塑性应变幅值记忆效应,能够对材料的高温非比例多轴应变循环变形行为和棘轮行为进行统一描述。模型的模拟结果与实验结果比较表明:该模型对SS304不锈钢高温非比例多轴循环变形行为的描述比较合理。     

Effect of temper rolling on the bake-hardening behavior of low carbon steel

In a typical process, low carbon steel was annealed at two different temperatures (660℃ and 750℃), and then was temper rolled to improve the mechanical properties. Pre-straining and baking treatments were subsequently carried out to measure the bake-hardening (BH) values. The influences of annealing temperature and temper rolling on the BH behavior of the steel were investigated. The results indicated that the microstructure evolution during temper rolling was related to carbon atoms and dislocations. After an apparent increase, the BH value of the steel significantly decreased when the temper rolling reduction was increased from 0% to 5%. This was attributed to the increase in solute carbon concentration and dislocation density. The maximum BH values of the steel annealed at 660℃ and 750℃ were 80 MPa and 89 MPa at the reductions of 3% and 4%, respectively. Moreover, increasing the annealing temperature from 660 to 750℃ resulted in an obvious increase in the BH value due to carbide dissolution.     

铅芯橡胶耗能器与油阻尼器组合耗能系统的振动台试验与分析

在一座三层单跨的钢结构模型中安装了铅芯橡胶耗能器及其和油阻尼器并联组合。对这两种耗能体系进行了振动台试验,以研究组合耗能体系的动力特性,检验其减振效果,试验结果表明：组合耗能体系对位移和加速度有良好的减振效果;在合适的刚度范围内,增加适当的阻尼可提高耗能器的减振效果,进行了数值分析,并与试验结果进行了比较,验证了本文提出的计算模型与方法的正确性。     

群决策中基于判断相似度的专家聚类及群体意见集结方法

针对大规模群决策问题,提出了一种基于专家意见相似度的群体判断信息逐步集结规划的方法。首先利用备选方案序关系向量的灰色关联度和夹角余弦构造两两专家判断信息的组合相似度;其次以判断相似度为标准,采用一种广度邻居搜索算法对专家进行聚类;然后以判断偏差最小为目标,构造非线性的约束规划模型对每一类专家意见进行集结,从而获得类内专家的集结信息;最后从专家数量最多的类别开始,依次对每类专家集结后的判断信息进行再次集结,从而获得最终的评判结果。该方法将大规模的复杂群决 策转化为低复杂度的多阶段专家信息集结问题,并保证了群体结果的一致性。算例分析验证了方法的可行性和有效性。     

新型双燃料重整联合循环发电系统

本文提出了一种新型双燃料重整联合循环发电系统。该系统通过重整反应实现了煤和天然气的综合利用,煤的燃烧过程为天然气/水蒸汽重整反应提供了高温反应热,通过双燃料重整煤的部分化学能间接转化到合成气中,然后合成气进入联合循环燃烧作功。研究结果表明双燃料联合循环的供电效率为49.4%-53.2%,煤的折合供电效率为42.4%-44.6%,与IGCC(动力部分相同时为44%-46%)相比供电效率降低1-2个百分点,但是投资大约降低30%。本文的研究开拓性地为煤的清洁高效利用提供了新途径。