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Duo-Duo Hu Qian Gao Jing-Cheng Dai Ru Cui Yuan-Bo Li Yuan-Ming Li Xiao-Guo Zhou Kang-Jie Bian Bing-Bing Wu Kai-Fan Zhang Xi-Sheng Wang Yan Li 《中国科学:化学(英文版)》2022,65(4):753-761
A light-induced, nickel-catalyzed three-component arylsulfonation of 1,3-enynes in the absence of photocatalyst is reported.This methodology exhibited mild conditions, broad scope and high efficiency, and its synthetic utility has been demonstrated by a concise total synthesis of sulfone-containing drug molecule. Detailed mechanistic studies indicated that this light induced nickel catalysis is autopromoted by in situ produced allene, which plays a key role as co-ligand in the photoactive excite... 相似文献
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Bo Wang Peng Hao Gang Li Jia-Xin Zhang Kai-Fan Du Kuo Tian Xiao-Jun Wang Xiao-Han Tang 《Acta Mechanica Sinica》2014,30(3):391-402
A concept of hierarchical stiffened shell is proposed in this study, aiming at reducing the imperfection sen- sitivity without adding additional weight. Hierarchical stiffened shell is composed of major stiffeners and minor stiff- eners, and the minor stiffeners are generally distributed between adjacent major stiffeners. For various types of geo- metric imperfections, e.g., eigenmode-shape imperfections, hierarchical stiffened shell shows significantly low imper- fection sensitivity compared to traditional stiffened shell. Furthermore, a surrogate-based optimization framework is proposed to search for the hierarchical optimum design. Then, two optimum designs based on two different opti- mization objectives (including the critical buckling load and the weighted sum of collapse loads of geometrically imperfect shells with small- and large-amplitude imperfections) are compared and discussed in detail. The illustrative example demonstrates the inherent superiority of hierarchical stiffened shells in resisting imperfections and the effectiveness of the proposed framework. Moreover, the decrease of imperfection sensitivity can finally be converted into a decrease of structural weight, which is particularly important in the development of large-diameter launch vehicles. 相似文献
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杨凯凡 《数学的实践与认识》2010,40(16)
对算子方程X+A~*X~(-2)A=Q有正算子解的条件做了进一步的研究,得到了方程有正算子解时A,Q,X的范数、谱半径之间新的关系.并给出了算子方程X+A~*X~(-t)A=Q有正算子解的一些条件. 相似文献
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Guo-Bin Jung Kai-Fan Lo Shih-Hung Chan 《Journal of Solid State Electrochemistry》2007,11(10):1435-1440
An important objective in the development of solid oxide fuel cell (SOFC) is to produce thin stabilized zirconia electrolytes
that are supported upon the nickel–zirconia composite anode. Although this will reduce some of the problems associated with
SOFCs by permitting lower temperature operation, this design may encounter problems during start- up. The first step in a
start-up involves the reduction of nickel oxide in the anode to metallic nickel and increase of three-phase boundary will
be beneficial for further reaction. In this study, two pretreatment methods are investigated for their effects on the performances
of SOFC. Performances of the SOFCs are influenced by the pretreatment conditions, which included exposure of the cells to
dilute H2/O2 either under open-circuit or closed-circuit conditions before their performance studies. By carrying out the methods, the
pretreatment using the closed circuit is found to attain much higher performances effectively and efficiently. Accompanying
with SEM and element analysis, increase of three-phase boundary is considered to give rise to changes in the anode microstructure,
leading to activation of the anode. Mechanisms of NiO in anode reducing to Ni and porous structure via different pretreatments
and their effects on the anode microstructure are proposed. 相似文献
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Kang-Jie Bian Yan Li Kai-Fan Zhang Yan He Tian-Rui Wu Cheng-Yu Wang Xi-Sheng Wang 《Chemical science》2020,11(38):10437
As an alternative approach to traditional C–H activation that often involved harsh conditions, and vicinal or primary C–H functionalization, radical relay offers a solution to these long-held problems. Enabled by 1,n (n = 5, 6)-hydrogen atom transfer (HAT), we use a most prevalent moiety, alkene, as the precursor to an sp3 C-centered radical to promote selective cleavage of inert C(sp3)–H bonds for the generation of azidotrifluoromethylated molecules. Mild conditions, broad scope and excellent regioselective control (>20 : 1) are observed in the reactions. Deuterium labelling studies disclose the kinetic characteristics of the transformations and verify a direct 1,n-HAT pathway. The key to this C-centered radical relay is that iron plays a dual role as a radical initiator and terminator to incorporate the azide functionality through radical oxidation via azido–ligand-transfer. The methods and the later derivatization promise expeditious synthesis of CF3-containing organic azides, γ-lactam and triazoles that are widely used in designing new fluorescent tags and functional materials.Remote functionalization of inert C(sp3)–H bonds is described via iron-catalyzed sp3 C-centered radical relay. 相似文献
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