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A Two-Dimensional Photonic Crystal Slab Mirror with Silicon on Insulator for Wavelength 1.3μm 下载免费PDF全文
A concrete two-dimensional photonic crystal slab with triangular lattice used as a mirror for the light at wavelength 1.3μm with a silicon-on-insulator (SOI) substrate is designed by the three-dimensional plane wave expansion method. For TE-like modes, the bandgap in the Г-K direction is from 1087nm to 1559nm. The central wavelength in the bandgap is about 1.3μm, hence the incident light at wavelength 1.3μm will be strongly reflected. Experimentally, such a photonic crystal slab is fabricated on an SOI substrate by the combination of EBL and ICP etching. The measurement of its transmission characteristics shows the bandgap edge in a longer wavelength is about 1540 nm. The little discrepancy between the experimental data and the theoretical values is mainly due to the size discrepancy of the fabricated air holes. 相似文献
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用电子探针定量分析超轻元素中的几个问题 总被引:2,自引:0,他引:2
碳,硼,氮及氧等元素在电子探针分析中常称之为超轻元素,这些元素的定量分析还存在许多包括测量和定量修正方面的困难。本文就质量吸收系数的不准确,超轻元素谱线的化学位移,及重元素的L,M及N系谱线对其干扰等方面的问题进行研究和讨论,并分别提出了解决这些问题的方法。选择合适的标样是获得准确定量分析结果的关键。 相似文献
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A copper(Ⅱ) complex 1 of a novel macrocyclic polyamine ligand with hydroxylethyl pendant groups, 4,11-bis(hydroxylethyl)-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (L) has been synthesized and characterized. Rate enhancement for hydrolysis of p-nitrophenyl picolinate (PNPP) catalyzed by 1 was studied kinetically under Brij35 micellar condition. For comparision, the catalytic activity of corresponding copper(Ⅱ) complex 2 of non-substituted macrocyclic polyamine ligand, 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane (L') toward the hydrolysis of PNPP was also investigated. The results indicate that the macrocyclic polyamine copper(Ⅱ) complex 1 effectively catalyzed the hydrolysis of PNPP, and the pendant ligand hydroxyl group or deprotonated pendant ligand hydroxyl group can act as catalytically active species in the reaction. A ternary Complex kinetic model involving metal ion, ligand and substrate has been proposed, and the results confirmed the reasonability of such kinetic model. 相似文献
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采用分子动力学方法结合嵌入原子势, 对Pt-Au核-壳纳米粒子的热稳定性进行了研究. 计算结果表明: Pt-Au纳米粒子的熔点明显高于Au纳米粒子而低于Pt纳米粒子. 通过计算Lindemann指数发现: 壳层中的Au首先熔化, 然后逐渐向内部扩展, 最终导致核中的Pt完全熔化; 熔化所经历的温度区间明显宽于单质纳米粒子, 而且该熔化过程呈现典型的两阶段熔化特征; 在两次熔化之间, 存在着固(核)液(壳)共存的结构.
关键词:
纳米粒子
熔化
分子动力学 相似文献
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We investigate the size effect on melting of metal nanoclusters by molecular dynamics simulation and thermodynamic theory based on Kofman‘s melt model. By the minimization of the free energy of metal nanoclusters with respect to the thickness of the surface liquid layer, it has been found that the nanoclusters of the same metal have the same premelting temperature Tpre = To - To(γsu - γlu - γsl)/(ρLξ) (To is the melting point of bulk metal, γsu the solid-vapour interracial free energy: γlu the liquid-vapour interracial free energy, γsl the solid-liquid interracial free energy, p the density of metal, L the latent heat of bulk metal, and ξ the characteristic length of surface-interface interaction) to be independent of the size of nanoclusters, so that the characteristic length ξ of a metal can be obtained easily by Tpre, which can be obtained by experiments or molecular dynamics (MD) simulations. The premelting temperature Tpre of Cu is obtained by MD simulations, then ξ is obtained.The melting point Tcm is further predicted by free energy analysis and is in good agreement with the result of our MD simulations. We also predict the maximum premelting-liquid width of Cu nanoclusters with various sizes and the critical size, below which there is no premelting. 相似文献