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Cu2O and Ag/Cu2O composite octahedra were synthesized via a hydrothermal reaction of CuAc2 with urea in H2O–propanetriol binary solution by adjusting the quantity of AgNO3 at 180 °C for 10 h. The influence of reaction temperature and time on the morphology and phase of the products was investigated, and a possible growth mechanism of Cu2O octahedron was also proposed. The photocatalytic activities of the as-prepared Cu2O and Ag/Cu2O octahedra for the degradation of methyl orange aqueous solution were studied. The results show that they are effective photocatalysts for the degradation of methyl orange, and the photocatalytic ability of Ag/Cu2O composite is stronger than that of Cu2O octahedra, which are expected to be useful in the treatment of wastewaters.  相似文献   
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图G的一个pebbling移动是从一个顶点移走2个pebble, 而把其中的1个pebble移到与其相邻的一个顶点上. 图G 的pebbling数f(G)是最小的正整数n, 使得不论n个pebble 如何放置在G的顶点上, 总可以通过一系列的pebbling移动, 把1个pebble移到图G的任意一个顶点上. 图G 的中间图M(G) 就是在G 的每一条边上插入一个新点, 再把G 上相邻边上的新点用一条边连接起来的图. 对于任意两个连通图G和H, Graham猜测f(G\times H)\leq f(G)f(H). 首先研究了圈的中间图的pebbling 数, 然后讨论了一些圈的中间图满足Graham猜想.  相似文献   
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Let U(n,d) be the set of unicyclic graphs on n vertices with diameter d. In this article, we determine the unique graph with minimal least eigenvalue among all graphs in U(n,d). It is found that the extremal graph is different from that for the corresponding problem on maximal eigenvalue as done by Liu et al. [H.Q. Liu, M. Lu, F. Tian, On the spectral radius of unicyclic graphs with fixed diameter, Linear Algebra Appl. 420 (2007) 449-457].  相似文献   
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For a given graph G of order n, a k-L(2,1)-labelling is defined as a function f:V(G)→{0,1,2,…k} such that |f(u)-f(v)|?2 when dG(u,v)=1 and |f(u)-f(v)|?1 when dG(u,v)=2. The L(2,1)-labelling number of G, denoted by λ(G), is the smallest number k such that G has a k-L(2,1)-labelling. The hole index ρ(G) of G is the minimum number of integers not used in a λ(G)-L(2,1)-labelling of G. We say G is full-colorable if ρ(G)=0; otherwise, it will be called non-full colorable. In this paper, we consider the graphs with λ(G)=2m and ρ(G)=m, where m is a positive integer. Our main work generalized a result by Fishburn and Roberts [No-hole L(2,1)-colorings, Discrete Appl. Math. 130 (2003) 513-519].  相似文献   
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给出Modified Korteweg-de Vries方程(MKdV)and Sine-Gordon(SG)方程n重达布交换后的孤子解和孤子曲面的表达式.进一步,分析了孤子曲线和曲面在达布变换下的性质和变化规律.  相似文献   
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BaCl2·2H2O和配体3,4-吡啶二酸在溶剂热条件下反应生成了配合物[Ba2(pdc)2(H2O)3] n (1)(H2pdc=3, 4-吡啶二酸), 用单晶X-射线、元素分析和FT-IR对生成的晶体进行了表征。Ba1和Ba2分别采取了八配位扭曲四方反棱柱和十配位的双帽四棱柱几何构型, 整个pdc2-作为四齿桥联配体连结4个不同的Ba(Ⅱ)原子形成二维网结构, O-H…N氢键将二维网结合在一起形成三维结构。还研究了配合物1的荧光和热重性质。  相似文献   
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Two new Fe3O4 microspheres‐supported semi‐homogeneous catalysts, namely Fe3O4‐G4‐polyaminoamido (PAMAM) dendrimers‐Pd(0) and Fe3O4‐polyethylene glycols (PEGs)‐Pd(0) were synthesized and characterized by X‐ray powder diffraction, infrared spectrum, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and thermal gravimetric analysis, which can catalyze Suzuki coupling reactions. The performance of catalysts was tested for the reactions of aryl halides with phenyl boronic acid and compared with a heterogeneous catalyst Fe3O4‐(3‐aminopropyl)triethoxysilane (APTS)‐Pd(0), in which Fe3O4‐G4‐PAMAM dendrimers‐Pd(0) shows the best activity among the three catalysts. The order of the catalytic activities is Fe3O4‐G4‐PAMAM dendrimers‐Pd(0)>Fe3O4‐PEGs‐Pd(0)>Fe3O4‐APTS‐Pd(0). The catalysts can be quickly and completely recovered by simply applying a magnet of 105 mT and the efficiencies remain unaltered even after four recycles.  相似文献   
30.
Let R be a 2-torsion free prime ring, d1 a nonzero derivation, -γ a generalized derivation associated with a nonzero derivation d2, U a square closed Lie ideal of R. In the present paper,we prove that if [di^2(u), u] ∈ Z(R) or γ acts as a homomorphism (or an antihomomorphism) on U, then U Z(R).  相似文献   
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