Pd改性多活性位点催化剂NH3-SCR脱硝反应机理研究

低温SCR脱硝技术具有效率高、能耗低、无二次污染等优点,是很有前途的脱硝净化技术.我们制备了一系列多活性位点催化剂（Pd_xV_y/TiO₂）,并对其NH₃-SCR脱硝性能进行了测试分析.结果表明,Pd_0.12V₄/TiO₂催化剂在250℃时可达到接近100%的NO_x转化率和N₂选择性.结合XRD、TEM、XPS、H₂-TPR、in situ DRIFT和DFT分析,考察了催化剂表面NO_x催化脱除机理.所得数据表明,该催化剂对NH₃、O₂和NO_x等反应气体分子表现出强烈的吸附性能,且均为化学吸附,所有组分（Pd O_x和VO_x）在NO_x的催化脱除中发挥着不可或缺的作用,而氧化还原循环(2V⁴⁺(Ti     

Ag/CuI-Mischbesetzung in den Kristallstrukturen der Kupfer(II)-cyanoargentate Cu(NH3)(py)Ag3-xCux(CN)5 · py

Ag/Cu^I Mixed Occupancy in the Crystal Structures of the Copper(II) Cyanoargentates Cu(NH₃)(py)Ag_3?xCu_x(CN)₅ · py From pyridine and ammonia containing Cu^II solutions, to which K[Ag(CN)₂] and in part KCu(CN)₂/KCN has been added, we obtained single crystals of mixed-valent copper compounds of variable composition Cu(NH₃)-(py)Ag_3-xCu_x(CN)₅ · py. The phases corresponding to x = 0.39(1) ( I ) and to x = 1.243(6) ( II ) were characterized by X-ray structure analysis. They are isomorphous and crystallize with Z = 4 in the monoclinic space group P2₁/c. The lattice constants for I [and II , resp.] are: a = 923.8(2) [901.4(2)], b = 1226.8(2) [1227.3(2)], c = 1809.8(4) [1783.5(2)] pm, β = 91.41(3) [91.02(1)]°. The Cu^II cation shows trigonal bipyramidal [CuN₅] coordination, with the neutral ligands in axial positions (mean value Cu? N for II : 201 pm), three N atoms of cyano bridges in equatorial ones (Cu? N: 206 pm). One of these bridges stems from a trigonal unit [AgCN(NC)₂], the central atom of which is substituted by Cu^I to an extent of 39% in I , and completely in II . The two other bridges originate from two [Ag(CN)₂]^? groups, of which the more bent one may be partially occupied by Cu^I as well (24% in II ). The units mentioned are connected into meshes of elongated hexagons and further into puckered layers within the (010) plane, interpenetrating each other in pairs. A threedimensional linking of layers occurs by the trigonal Ag/Cu^I species forming centrosymmetric dimers, in which the metal coordination is completed to tetrahedral by a C-atom of the corresponding neighbouring group and short metal-metal distances of 279.1(3) pm in I and 264.1(1) pm in II appear. Details and relations are discussed.     

Site engineering in chemical-solution-deposited Bi<Subscript>3.25</Subscript>La<Subscript>0.75</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> thin films using Ce,Zr, Mn and Si atoms

Ferroelectric Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films were fabricated by depositing sol-gel solutions on Pt(111)/Ti/SiO₂/Si (100) substrates. Crystallographic orientations of the BLT films were random, but the preferred orientations along (00l) and (117) axes were found. All films showed a single-phase bismuth-layered structure but the orientation in the films could be engineered by optimizing the growth condition, as well as by introducing dopant atoms such as Ce and Zr in the films, which in turn influenced the ferroelectric properties of the films significantly. The shape of c-axis-oriented grains was more plate-like, while that of (117)-oriented grains was rod-like. Small % substitution of Ce, Mn, and Zr atoms at Ti site enhanced the remanent polarization by approximately 20%, while substitution of Si atoms reduced the remanent polarization in BLT films but improved insulating properties. It was also demonstrated that fatigue endurance could be controlled by the concentration of dopant atoms, which was thought to be due to the decrease in oxygen vacancy concentration.     

可变高度激光里程计在室内不平整地面环境下的地图构建

针对可变高度激光雷达的结构特点提出了一种基于线、面特征的匹配算法, 并应用于存在不平整地面的结构化的室内环境. 首先提取激光点云中的边缘点和平面点, 并使用随机抽样一致性算法拟合成线段和平面; 然后根据线段与平面几何关系提出特征匹配条件, 完成特征之间的匹配; 利用特征间的匹配关系构建约束方程求解机器人位姿; 最后把机器人竖直方向位姿变换信息补偿到激光点云中, 并把纠正后的有一定高度的激光点云压缩成二维激光构建室内栅格地图. 实验结果表明, 与常用的二维激光同时定位与构图算法Gmapping对比, 在地面不平整的室内环境构建的地图得到了改善, 提高了移动机器人的构图精度.     

C60分子在有序-无序和玻璃态相变间的取向概率与弛豫行为

用极限动力学模型研究了Ｃ₆₀分子在有序-无序相变和玻璃态相变温度区间取向 角为98°和38°的取向概率与温度的关系.计算结果在玻璃态相变点附近的85K,90K和有序- 无序相变点的260K分别与实验值相吻合,取向概率对实验值更精确的拟合及其对温度的二阶 导数预言玻璃态相变点在84K.导出了弛豫规律,其结果表明：双能级的Ｃ₆₀分子从非平衡态到平衡态的弛豫行为与非指数因子β有关,其总的弛豫时间决定于其中一个较 短的弛豫时间,展宽指数形式保持不变.讨论了KWW方程的非 关键词： 60')" href="#">Ｃ₆₀ 取向概率 非平衡态弛豫     

不同笼占据率Ⅰ型甲烷水合物结构和光学性质的第一性原理研究

本文基于第一性原理计算,对三种不同结构的Ⅰ型甲烷水合物进行弛豫,得到优化后的结构、电子态密度及光学性质,通过对结果的分析揭示不同笼子占据率对水合物的结构和相关性质的影响。这三种结构分别为:(cI)只有一个大笼未被占据;(cII)只有一个小笼未被占据;(cIII)每个笼子都被甲烷分子占据。结果显示,cIII是最稳定的,因为它有完美的晶体结构;cII和cI相对较不稳定,其中cI在缺失一个甲烷分子的情况下,结构出现了较大的变形,这导致它成为三种情况中最不稳定的结构;相反,同样缺失了一个甲烷分子的cII的结构变形就很小。cII和cI的体积变化分别是0.56%和2.1%,cII的电子态密度和能带几乎与cIII的一致,而cI的则与前两者差别很大。计算结果表明,相对于电子转移,质子无序对水合物的介电常数的影响更为主要;甲烷水合物只对紫外光有响应,无论结构和占据率差异如何,甲烷水合物都具有相近的光学性质。本文的结果证明,缺失一个甲烷分子,对cII造成的影响很小,其晶体结构、介电常数和光学性质与cIII的一致,然而同样缺失一个甲烷分子的cI的结构及性质却出现了巨大变化。这些结果可为水合物探测提供有价值的参考。     

Interaction of the atoms in molecules of pyridine and its derivatives according to the results of ab initio calculations

Nonempirical quantum-chemical calculations of pyridine and its 2-, 3-, and 4-X-substituted derivatives (X = F, Cl, Br, Me, and Et) by RHF/6-311G(d) and MP2/6-311G(d) methods indicate an alternation of charges on the atoms of the pyridine ring and of the occupancy of their valence p_y-orbitals. This is caused by the polarization of bonds under the action of the charges of the atoms geminal to C(n). Bonding molecular orbitals in these molecules, formed as a result of the p_y-orbitals, occurring in the plane of the pyridine ring, are not an indication (characteristic) of p, π-conjugation between the unshared electron pair of the heteroatom of a substituent X and the π-electron system of the ring. The results of the calculations by these methods did not differ in principle. Dedicated to Academician of the Russian Academy of Sciences M. G. Voronkov in honor of his 85^th birthday. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1671–1681, November, 2006.     

On the expected number of distinct points in a subset visited by anN-step random walk

Many investigators have calculated asymptotically valid expressions for the expected number of distinct points visited by ann-step random walk on a lattice. In this note we point out that the same formalism can be used to study the expected number of distinct points in a subset of lattice points. We also calculate the expected occupancy of the subset and give sufficient conditions for the ratio of the two calculated quantities to have the same asymptotic time dependence as for the full lattice. Specific examples are considered.     

Three-dimensional site percolation problem and effective-medium theory: A computer study

A site percolation approach to classical transport in disordered two-phase materials is presented. A Monte Carlo computer experiment gives the bulk conductivity of a 30 x 30 x 30 site simple cubic resistor network consisting of two kinds of unit resistor with different conductance. A modified effective-medium theory predicts very accurately the bulk conductivity of the network. This theory is found to agree well with available data for the thermal conductivity of real two-phase materials: glass particle-silicon rubber; glass fiber-plastics; air-saturated porous sandstone; and air-saturated fire brick.