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211.
212.
介绍了平台式和斜坡式两种结构的表面放电辐射源,研究了在1.0 μF和1.5 μF储能电容、15~30 kV充电电压等实验条件下两种辐射源的放电特性,并对实验结果进行了比较分析。得到如下结论:对于斜坡式辐射源,增加电极间距可导致放电回路面积增大,因此等效电阻和等效电感也将增加;在相同电压及电容值条件下,斜坡式辐射源的放电电流、平均沉积功率均小于平台式辐射源的相应值,但放电沉积效率略大;电压升高使放电周期、电流达到峰值时间及放电沉积效率呈减小趋势,对于同一种辐射源,使用1.5 μF电容时放电回路参数更加匹配,放电沉积效率得到提高。 相似文献
213.
In this paper, we propose a nonlinear PDE model for reconstructing a regular surface from sampled data. At first, we show the existence and the uniqueness of a viscosity solution to this problem. Then we propose a numerical scheme for solving the nonlinear level set equation on unstructured triangulations adapted to the data sample. We show the consistency of this scheme. In addition, we show how to compute nodewise first and second order derivatives. Some application examples of curve or surface construction are provided to illustrate the potential and to demonstrate the accuracy of this method. 相似文献
214.
Anwar Latif M. Khaleeq-ur-RahmanM.S. Rafique K.A. Bhatti 《Physica B: Condensed Matter》2011,406(9):1713-1716
The microstructural morphological changes in laser irradiated targets are investigated. Nd:YAG laser (1064 nm, ∼12 ns nominal, 1.1 MW) is used to irradiate 4 N pure (99.99%) fine polished and annealed silver samples in ambient air and under vacuum ∼10−6 Torr. The laser spot size and power density at tight focus are 12 μm and 3×1011 W/cm2, respectively. SEM micrographs and X-ray diffractograms of the exposed and unexposed targets reveal the surface texture and structural changes, respectively. Amongst the ablation mechanisms involved, exfoliation and hydrodynamic sputtering are found to be dominant. Surface modifications appear in the form of craters and ripples formation. Heat is conducted non-uniformly through narrow channels at the surface. Thermal stresses induced by the laser do not disturb inter planar distance of the target. On the other hand irradiation causes significant variations in grain size and diffracted X-rays intensities. 相似文献
215.
利用密度泛函理论计算六角NiAs型和立方闪锌矿型MnSb的电子和电磁特性,研究闪锌矿MnSb与GaSb(001)界面,并采用广义渐变近似计算了交换-相关项.闪锌矿结构的MnSb具有半金属铁磁特性,单分子磁矩4μB,MnSb/GaSb(001)界面同样具有半金属特性.界面中Mn原子的磁矩减小,界面中Sb原子磁矩等于两个相应界面磁矩的平均值.另外计算了能带排列在异质结中价带偏移大约1.25 eV. 相似文献
216.
Surface tensions of some Pb-free solder systems such as Ag–Bi–Sn with cross-sections Ag/Bi = 1/1, Ag/Bi = 1/2, Ag/Bi = 2/1, In–Sn–Zn with cross-sections Sn/In = 1/1, Sn/In = 1/3 and (Ag7Cu3)100?x Snx with cross-section Ag/Cu = 7/3 are calculated from the sub-binary surface tension data using the models, such as the Muggianu, Kohler, Toop models, Butler’s equation and Chou’s General Solution Model (GSM) at 873, 923 and 1073 K, respectively. The surface tension of In–Sn–Zn increases wavily with increasing amount of Zn and it is found that the best models are the GSM for both cross-sections in question while GSM becomes the best model for (Ag7Cu3)100?x Snx alloy in the whole experimental range. Moreover, the surface tension of (Ag7Cu3)100?x Snx decreases slightly with increasing amount of Sn. The Muggianu, Butler and Butler models are determined as the best models for the cross-sections in the order given above for entire measurement range, respectively, and the surface tension of Ag–Bi–Sn decreases slightly with an increasing amount of Bi and Ag but increases with increasing Sn in liquid alloys. 相似文献
217.
218.
搭建了一套研究金属和金属氧化物表面的超快激发态电子动力学和光化学动力学的飞秒双光子光电子能谱仪. 该装置将半球形电子能量分析仪和成像技术相结合,同时测量光电子的能量和角度分布.通过Mach-Zehnder干涉仪测量时间分辨的双光子光电子能谱获得超快激发电子态的动力学信息. 这一功能在Cu(111)上得到了证实. 另外还发展了一个通过实时测量双光子光电子能谱来研究表面光化学的方法,并成功应用到CH3CH2OH/TiO2(110)体系. 研究表明,只有将两种方法结合起来才能正确地研究光诱导的表面激发共振的动力学. 相似文献
219.
Steps, ledges and kinks on the surfaces of platinum nanoparticles of different shapes 总被引:1,自引:0,他引:1
Platinum nanoparticles with a high percentage of cubic-, tetrahedral- and octahedral-like shapes, respectively, have been synthesized by a shape-controlling technique that we developed recently [Ahmadi et al., Science 272 (June 1996) 1924]. High resolution transmission electron microscopy (HRTEM) is used here to directly image the atomic scale structures of the surfaces of these particles with different shapes. The truncated shapes of these particles are mainly defined by the {100}, {111}, and {110} facets, on which numerous atom-high surface steps, ledges and kinds have been observed. This atomic-scale fine structure of the surfaces of these particles is expected to play a critical role in their catalytic activity and selectivity. 相似文献
220.
Surface defects created on Ge(001) exposed to low energy Xe ions are characterized by in situ scanning tunneling microscopy (STM). The temperature of the sample during ion bombardment is 165 C and ion energies range from 20 to 240 eV. The ion collisions create defects (vacancies and adatoms) which nucleate and form vacancy and adatom islands. For fixed total vacancy creation, the vacancy island number density increases with increasing ion energy: the vacancy island number density is 1.6 × 10−20 cm−2 for 40 eV ion bombardment and increases to 4.4 × 10−20 cm−2 for 240 eV ion bombardment. The increased nucleation rate for vacancies is attributed to clustering of defects. The sputtering yield of Ge(001) is also measured by STM. The sputtering yield for 20 eV ions is approximately 10−3 per ion but the net yield for surface defects (sum of adatoms and vacancies) is an order of magnitude higher, 10−2, due to adatom-vacancy pair creation. 相似文献