Dynamics of shock induced ignition in Fickett’s model: Influence of χ

Using Fickett’s model for reactive compressible flows, i.e., the reactive form of Burgers’ equation, we address the problem of shock induced ignition by a piston in a reactive medium characterized by a 2 step induction-reaction kinetics. Owing to the model’s simplicity, the ignition and acceleration mechanism is explained using the two families of characteristics admitted by the model. The energy release along the particle paths provides the amplification of forward-traveling pressure waves. These waves pre-compress the medium in the induction layer ahead of the reaction zone, therefore changing the induction delays of successive particles. The variation of the induction delay provides the modulation of the amplification of the forward traveling pressure waves by controlling the residence time of the pressure waves in the reaction zone. A closed form analytical solution is obtained by the method of characteristics and high activation energy asymptotics. The acceleration of the reaction zone was found to be proportional to the product of the activation energy, the ratio of the induction to reaction time and the heat release. This finding provides a theoretical justification for the previous use of this non-dimensional number to characterize the ignition regimes observed experimentally in detonations and shock induced ignition phenomena. Numerical simulations are presented and analyzed. Both subsonic and supersonic internal flame propagation are observed, consistent with experiment and previous reactive Euler models.     

New reactivities of deltaline analogs: an efficient O-demethylation at C-1 and an unusual extrusion of the C-14 atom

O-Demethylation at C-1 in the C₁₉-diterpenoid alkaloids is very challenging. In this paper, it was firstly observed that 10-OH group in deltaline (1) is a determining factor for the O-demethylation reaction. After removal of this hydroxyl group, 1-O-methyl group in the corresponding deltaline analogs can be readily removed by treatment with HBr–HOAc. Meanwhile, the C-14 atom in bromides 18 or 20 can be extruded under basic condition probably via a sequence, including Grob fragmentation, aerobic oxidation, deformylation, and S_N2 nucleophilic substitution, to give enone 21 (70%) and oxetane 22 (14%). The structure of compound 22 was confirmed by X-ray crystallographic analysis of its derivative 21.     

Organophosphine/phosphite‐stabilized silver(I) complexes bearing N‐acetylbenzamide ligand: synthesis,characterization and potential application in metal organic chemical vapor deposition

New N‐silver(I) acetylbenzamide complexes of type L_n?AgNC₉H₈O₂ (L = PPh₃; n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)₃; n = 1, 2d; n = 2, 2e; n = 3, 2f) were prepared. These complexes were obtained in high yields and characterized by elemental analysis, ¹H NMR, ¹³C{H} NMR, ³¹P{H} NMR and IR spectroscopy, respectively. The molecular structure of 2b has been determined by X‐ray single‐crystal analysis in which the silver atom is in a distorted tetrahedral geometry and crystallizes as cis–trans. New N‐silver(I) acetylbenzamide complexes have a four‐membered ring, which could influence their chemical and physical properties and modulate volatility. Metal organic chemical vapor deposition experiments were carried out successfully at 400°C and 450°C using 2e as precursor for the deposition of silver films, respectively. The high‐purity silver film obtained at 400°C is dense and homogeneous. Copyright © 2012 John Wiley & Sons, Ltd.     

亚硝基甲胺异构化的量子化学研究

此文用ＭＮＤＯ方法研究了亚硝基甲胺异构化反应的机理。     

解大型线性方程组的ATOR方法

本文提出了一种数值求解大型稀疏线性方程组Ax=b的具有三个参数的迭代法,我们称之为ATOR法,并且指出,熟知的Jacobi法、Gauss-Seidel法,SOR法,AOR法和TOR法为其特例.同时,我们对具有某些性质的系数矩阵A——Hermite正定矩阵、H-矩阵、L-矩阵和对角占优矩阵,讨论了ATOR法的收敛性以及给出了迭代矩阵谱半径的表达式和上界估计。     

SO_4~(2-)_TiO_2-SnO_2、SO_4~(2-)_ZrO_2-SnO_2、SO_4~(2-)_SnO_2催化剂的制备与物性测试研究

制备了SO_4~(2-)/TiO_2-SnO_2、SO_4~(2-)/ZrO_2-SnO_2、SO_4~(2-)/SnO_2催化剂,对它们进行了部分物性测试,并测定了它们对酯化反应的催化活性.发现此类催化剂的酸性很强,远远超过SiO_2-Al_2O_3固体酸催化剂,对酯化反应具有良好的活性.红外光谱测定结果证明,SO_4~(2-)以双配位形式结合在催化剂金属离子上,未生成硫酸盐.同一组成的催化剂的活性与催化剂中的SO_4~(2-)％含量,脱附温度有较大的关系.     

最近邻强交换相互作用对spin-1纳米管热力学性质的影响

利用有效场理论研究了纳米管上最近邻强交换相互作用下Blume-Capel模型的内能、比热和自由能,得到了系统的内能、比热和自由能与最近邻强交换相互作用、晶场强度和温度的关系.结果表明:最近邻强交换相互作用、晶场强度和温度等诸多因素相互竞争,使系统表现出比J_1=J_2=J=1时的BC模型更为丰富的热力学性质;系统内能随温度的变化曲线表现出不连续性;比热随温度的变化出现奇异性;一定条件下,基态时的自由能会发生突变.