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An efficient one-pot three-component stepwise approach for the synthesis of N-2-aryl-substituted-1,2,3-triazoles has been developed. By using this azide-chalcone oxidative cycloaddition and post-triazole arylation, a series of N-2-aryl-substituted-1,2,3-triazoles are readily prepared under mild conditions in excellent yields and high regioselectivity. Both the catalyst and substrates are readily available. 相似文献
64.
Ming Gao Jinghai Yang Lili Yang Yongjun Zhang Jihui Lang Huilian Liu Hougang Fan Yunfei Sun Zhiqiang Zhang Hang Song 《Superlattices and Microstructures》2012
The Zn1−xYxO nanoparticles with good optical properties have been prepared by sol–gel method. The yttrium doping effect on the structures and optical properties were investigated by XRD, SEM, XPS and low temperature photoluminescence. The UV emission intensity of yttrium doped ZnO was over 300 times stronger than that of pure ZnO, which was an exciting result in enhancing the ultraviolet near band edge emission in photoluminescence from ZnO nanoparticles. The UV emission band of doped ZnO nanoparticles exhibits a red shift from 388 to 398 nm, indicating a shallow energy level near valence band has been formed due to the yttrium doping into ZnO lattices. The defect-related band is suppressed (ID/IUV = 1–0.83) considerably in Zn1−xYxO nanoparticles, revealing the quenching of the broad yellow-orange emission. The doping effect on the optical properties is investigated by temperature dependent photoluminescence. The experimental results indicated that the donor level of yttrium is deeper than that of undoped ZnO. 相似文献
65.
LetG be a simple graph with vertex setV(G) and edge setE(G). A subsetS ofE(G) is called an edge cover ofG if the subgraph induced byS is a spanning subgraph ofG. The maximum number of edge covers which form a partition ofE(G) is called edge covering chromatic number ofG, denoted by χ′c(G). It known that for any graphG with minimum degreeδ,δ -1 ≤χ′c(G) ≤δ. If χ′c(G) =δ, thenG is called a graph of CI class, otherwiseG is called a graph of CII class. It is easy to prove that the problem of deciding whether a given graph is of CI class or CII class is NP-complete. In this paper, we consider the classification of nearly bipartite graph and give some sufficient conditions for a nearly bipartite graph to be of CI class. 相似文献
66.
Monomials are widely used. They are basic structural units of geometric programming. In the process of optimization, many
objective functions can be denoted by monomials. We can often see them in resource allocation and structure optimization and
technology management, etc. Fuzzy relation equations are important elements of fuzzy mathematics, and they have recently been
widely applied in fuzzy comprehensive evaluation and cybernetics. In view of the importance of monomial functions and fuzzy
relation equations, we present a fuzzy relation geometric programming model with a monomial objective function subject to
the fuzzy relation equation constraints, and develop an algorithm to find an optimal solution based on the structure of the
solution set of fuzzy relation equations. Two numerical examples are given to verify the developed algorithm. Our numerical
results show that the algorithm is feasible and effective. 相似文献
67.
Jihui Ni Hu Jia Wanfen Pu Hang Jiang Jianjun Yang Qiang Ren 《Journal of Thermal Analysis and Calorimetry》2014,117(3):1349-1355
In this study, the oxidation behavior of crude oils in the presence and absence of rock cuttings was investigated by thermogravimetry/derivative thermogravimetry (TG/DTG) techniques. Prior to these tests, the composition of cuttings and properties of crude oils were analyzed. Three obvious reaction regions were observed from the TG/DTG curves which are recognized as low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation. The effects of light components (C7–15), heavy fractions (asphaltene, paraffin, resin), and cutting on oil oxidation behavior were analyzed. Kinetic analysis of crude oils and oil + cutting mixtures was performed by Arrhenius method, and the data were analyzed at last. Results show that high content C7–15 hydrocarbons can provide negative effect on the LTO behavior of crude oil. On the contrary, the high content unsaturated heavy hydrocarbons including asphaltene, paraffin, and resin are benefit for the oxidation performance. In addition, a shortened FD stage and higher peak temperature in LTO region are observed by addition of cutting. Cutting especially clay in it plays an active role of catalyzing in oil oxidation reaction. 相似文献
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A one-pot method for the synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles via carbonylative Sonogashira reaction/1,3-dipolar cycloaddition of terminal acetylenes, carbon monoxide, aryl iodides, and sodium azide was developed. A series of new 4,5-disubstituted-1,2,3-(NH)-triazoles were prepared readily under mild conditions. 相似文献
70.
Nonlinear Dynamics - This article proposes a fixed-time adaptive fault-tolerant control methodology for a larger class of high-order (powers are positive odd integers) nonlinear systems subject to... 相似文献