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951.
Zuzhen Zhao Xiang Fang Yongliang Li Yi Wang Pei Kang Shen Fangyan Xie Xin Zhang 《Electrochemistry communications》2009,11(2):290-293
The Pt supported on WC modified MWCNT catalysts (PtWC/MWCNT) were synthesized by the combination of organic colloidal and intermittent microwave heating (IMH) methods for the first. The results proved the better performance of the PtWC/MWCNT catalyst than that of Pt/C for methanol oxidation in terms of the onset potential and peak current density. The synergistic effect between Pt nanoparticles and WC and the structure effect of the MWCNTs could be the reasons to result in the high activity. The CO stripping test provided the evidence that the onset potential shift for methanol oxidation is consistent with the reduction in the overpotential for the CO oxidation on PtWC/MWCNT catalyst. Therefore, the mechanism of the high performance for methanol oxidation on PtWC/MWCNT catalyst is probably the easier oxidation of CO-like species which cause high overpotential for further oxidation of methanol. 相似文献
952.
953.
954.
Hui Fang Pi Peng Zhang Han Li Ruan Yong Hui Zhang Han Dong Sun Ji Zhou Wu 《中国化学快报》2009,20(11):1319-1320
A new alkaloid was isolated from the bulbs of Lycoris aurea(L'Herit.) Herb.Its structure was established as 3-o-ethyltazettinol through chemical and spectroscopic studies including 2D NMR. 相似文献
955.
956.
On the resolution and optimization of a system of fuzzy relational equations with sup-T composition 总被引:3,自引:2,他引:1
This paper provides a thorough investigation on the resolution of a finite system of fuzzy relational equations with sup-T composition, where T is a continuous triangular norm. When such a system is consistent, although we know that the solution set can be characterized
by a maximum solution and finitely many minimal solutions, it is still a challenging task to find all minimal solutions in
an efficient manner. Using the representation theorem of continuous triangular norms, we show that the systems of sup-T equations can be divided into two categories depending on the involved triangular norm. When the triangular norm is Archimedean,
the minimal solutions correspond one-to-one to the irredundant coverings of a set covering problem. When it is non-Archimedean, they only correspond to a subset of constrained irredundant coverings of a set covering problem. We then show that the problem of minimizing a linear objective function subject to a system of sup-T equations can be reduced into a 0–1 integer programming problem in polynomial time. This work generalizes most, if not all,
known results and provides a unified framework to deal with the problem of resolution and optimization of a system of sup-T equations. Further generalizations and related issues are also included for discussion. 相似文献
957.
958.
The title complex {[Co(dimb)2(H2O)2]·(NO3)2·(H2O)2}n ( 1 ) (dimb = 1,3‐di(imidazol‐1‐ylmethyl)‐5‐methylbenzene) has been hydrothermally synthesized by the reaction of dimb with Co(NO3)2·6H2O in aqueous solution. The cobalt(II) atoms are linked by bridging dimb ligands to form 2D corrugated and wavy networks containing Co4(dimb)4 macrocyclic motifs. Two neighboring independent layers interlinked each other in a parallel fashion to construct three‐dimensional structure by O–H···O, N–H···O and C–H···O hydrogen bonds. Magnetic measurement shows the weak antiferromagnetic interaction with a one‐dimensional chain model in the range of 5–300 K, with J of –0.68 cm−1. 相似文献
959.
拟共形映射和John域 总被引:1,自引:0,他引:1
本文研究了(R)∫ΩBn中的John域与一致域和线性局部连通域的关系.利用平面中John域和拟圆的关系,获得了(R)∫ΩBn中的John域成为一致域和线性局部连通域的几个充分条件,它们是(R)2的推广. 相似文献
960.
Wang FangFang Wang Yi Wang BingQiang Wang YinFeng Ma Fang Li ZhiRu 《中国科学:化学(英文版)》2009,52(11):1980-1986
The optimized structure of the tetrathiafulvalence radical-cation dimer (TTF·+-TTF·+) with all-real frequencies is obtained at MP2/6-311G level, which exhibits the attraction between two molecular cation TTF·+. The new attraction interaction is a 20-center-2-electron intermolecular covalent π/π bonding with a telescope shape. The covalent π/π bonding has the bonding energy of about ?21 kcal·mol?1 and is concealed by the Coulombic repulsion between two TTF·+ cations. This intermolecular covalent attraction also influences the structure of the TTF·+ subunit, i.e., its molecular plane is bent by an angle θ = 5.6°. This work provides new knowledge on intermolecular interaction.
相似文献