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51.
José Rogan Alejandro Varas Juan Alejandro Valdivia Miguel Kiwi 《Journal of computational chemistry》2013,34(29):2548-2556
An unbiased strategy to search for the global and local minimal energy structures of free standing nanoclusters is presented. Our objectives are twofold: to find a diverse set of low lying local minima, as well as the global minimum. To do so, we use massively the fast inertial relaxation engine algorithm as an efficient local minimizer. This procedure turns out to be quite efficient to reach the global minimum, and also most of the local minima. We test the method with the Lennard–Jones (LJ) potential, for which an abundant literature does exist, and obtain novel results, which include a new local minimum for LJ13, 10 new local minima for LJ14, and thousands of new local minima for . Insights on how to choose the initial configurations, analyzing the effectiveness of the method in reaching low‐energy structures, including the global minimum, are developed as a function of the number of atoms of the cluster. Also, a novel characterization of the potential energy surface, analyzing properties of the local minima basins, is provided. The procedure constitutes a promising tool to generate a diverse set of cluster conformations, both two‐ and three‐dimensional, that can be used as an input for refinement by means of ab initio methods. © 2013 Wiley Periodicals, Inc. 相似文献
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[structure: see text]. The first study on enantioselective oxidation of functionalized sterically hindered disulfides is reported. This study shows that the Shi organocatalytic system using carbohydrate-derived ketone with oxone is superior to the Ellman-Bolm vanadium catalyst in terms of chemical yield and enantioselectivity. Whereas the latter system afforded mostly racemic thiosulfinates in low to moderate yields, the former one afforded thiosulfinates with up to 96% ee. 相似文献
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A comparative study on the allylation of a benzoyl hydrazone with allyl trichlorosilane using monosulfoxides, methylene-bridged C2-symmetric bissulfoxides, and ethylene-bridged C2-symmetric bissulfoxides shows that the enantioselectivity of the process is highly dependent on the spacer between the two sulfinyl sulfurs and the concentration of the reaction. 相似文献
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Karina Valdivia Delgado Leliane Nunes de BarrosFabio Gagliardi Cozman Scott Sanner 《International Journal of Approximate Reasoning》2011,52(7):1000-1017
This paper investigates Factored Markov Decision Processes with Imprecise Probabilities (MDPIPs); that is, Factored Markov Decision Processes (MDPs) where transition probabilities are imprecisely specified. We derive efficient approximate solutions for Factored MDPIPs based on mathematical programming. To do this, we extend previous linear programming approaches for linear approximations in Factored MDPs, resulting in a multilinear formulation for robust “maximin” linear approximations in Factored MDPIPs. By exploiting the factored structure in MDPIPs we are able to demonstrate orders of magnitude reduction in solution time over standard exact non-factored approaches, in exchange for relatively low approximation errors, on a difficult class of benchmark problems with millions of states. 相似文献
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Nonthermal plasma technologies are often used for cleaning toxic gases. In this work, we will present an optical emission spectroscopy (OES) study in a dielectric barrier discharge (DBD) used to remove NO x specifically. Rotational temperatures are calculated from the UV-OH band (A 2Σ, ν = 0 → X 2Π ν′ = 0) situated between 306–310 nm; for the rotational temperature, a fitting method was employed (comparison between experimental data with a synthetic molecular spectrum). Excitation temperatures were calculated using OII atomic lines situated in a wavelength range of 300–700 nm using a Boltzman’s plot method. From calculated temperatures, a thermal inequity characteristic of nonthermal plasma discharges has been high-lighted. The influence of the percentage of water added to the DBD reactor is also studied in the removal efficiency and in the OH band intensities and temperatures. 相似文献
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电感耦合等离子体原子发射光谱法测定钛酸钡纳米粉体中7种杂质元素 总被引:3,自引:0,他引:3
钛酸钡纳米粉体样品用盐酸溶解,在所得样品溶液中用电感耦合等离子体原子发射光谱法测定了以氧化物存在于样品中的7种杂质元素(包括镁、锶、钾、钠、铝、硅及铁),对测定的光谱条件进行了试验并优化达到上述各元素的测定上限为0.1%(质量分数).测得方法的检出限(3S/b)为(单位μg·L-1):2.0(铝),1.0(铁),20.0(钾),0.2(镁),4.0(钠),3.0(硅)及0.5(锶).应用此方法分析了两件实样,所得结果的相对标准偏差(n=6)小于等于2.0%,对其中4种杂质元素(镁、钾、钠和锶)同时用HG/T 3587-1999标准中的方法作分析校核,所得结果与此方法结果一致. 相似文献