Spin effects in the screening and Auger neutralization of He ions in a spin-polarized electron gas

The screening of a He⁺ ion embedded in a free electron gas is studied for different spin-polarizations of the medium. Density functional theory and the local spin density approximation are used to calculate the induced electronic density for each spin orientation, i.e. parallel or antiparallel to the spin of the electron bound to the ion. Since both the He⁺ ion and the electron gas are spin-polarized, we analyze in detail the spin state of the screening cloud for the two different possibilities: the spin of the bound electron can be parallel to either the mayority spin or the minority spin in the medium. Finally, the spin-dependent Kohn–Sham orbitals are used to calculate the Auger neutralization rate of the He⁺ ion. The polarization of the Auger excited electron is influenced by the spin-polarization of the medium. The results are discussed in terms of the spin-dependent screening and the indistinguishability of electrons with the same spin state.     

Electronic energy-density effects in ion tracks of metals

High resolution Auger-electron spectroscopy has been applied to the interaction of swift heavy ions with atomically clean metallic solids. Spectra have been taken for fast projectile electrons and for charge-state equilibrated ions at normal incidence on microcrystalline beryllium samples, Al(1 0 0) single crystals and several metallic glasses (Al₈₇La₇Ni₅Zr₁, Ni₇₈B₁₄Si₈, Co₆₆Si₁₆B₁₂Fe₄Mo₂). From the energy shift and from the Auger-line width we have extracted ion-track potentials and also electron temperatures inside ion tracks. A first determination of the angular distribution of multiple-ionization lines is presented as well.     

汉语属性库OLAP系统的设计

本文介绍了一个基于C/ S 结构的汉语属性库联机分析处理(OLAP) 系统的设计。文中详细阐述了汉语属性库的存储结构和系统工作平台。同时,文中给出了客户机端和服务器端应用系统的设计思想及实现方法。     

一个基于C/S模式的汉字词属性分析和重组系统的数据模型

随着ＩＳＯ１０６４６的出台，庞大的汉字词集的属性分析是一个迫切需要解决的难题，本文主要阐述了采用Ｃ／Ｓ模式的汉字词属性分析和重组系统的数据模型，并简单介绍了系统的设计要点。     

Thermal stability of the Ta (1 1 1) surface covered with Pd

The thermal stability of Ta(1 1 1) face covered with Pd layers of different thickness was examined by the complementary scanning tunnelling microscope (STM), low-energy electron diffraction (LEED), Auger electron spectroscopy and Δφ techniques. It has been found that for thin layers of θ<3 monolayer (ML) heated to 450 K, uplifts appear on the surface that may be treated as an agglomerated form of Pd adsorbate. For layers thicker than θ>3 ML, facets of the {1 1 0} type were observed upon heating to 700 K. Regardless of the conditions of investigation the faceting of the {2 1 1} type did not appear. During the adsorbate desorption the STM images revealed an ordered arrangement of surface atoms in the form of micropyramids composed of 10 atoms each and equally oriented towards the substrate. The appearance of the pyramids on the surface did not affect the observed LEED pattern.     

高分辨光电里程仪中的弹簧效应研究

高分辨光电里程仪是地面车辆定位系统中的测速测距元件,该元件具有极高的分辨率,并且从工作原理上看,其测速误差不随时间累积,因此在车辆导航系统中有很大的潜力。研究了弹簧效应对里程仪测速精度的影响,并且提出了数据重构的软件降噪去抖算法,根据运动状态不同,从缩短样本和提高拟合阶次两个方面选取了40样本三阶拟合数据重构算法。结果表明,该数据算法能够有效抑制里程仪的弹簧效应,将里程仪的测速精度由0.2 m/s提高到0.038 m/s,同时满足了快速跟踪的要求。     

改进区块遗传算法解决分布式车间调度问题

针对分布式车间调度问题,提出了改进区块遗传算法(modified block-genetic algorithm,MBGA).用NEH和随机性两种方式得到高质量的初始解,然后进行统计分析,选出精英染色体,建立工件-车间分配矩阵和工件-机器排序矩阵,挖掘联系紧密的基因链组成区块.构建基于区块的人工染色体,并进行基因重组,...     

热壁外延生长 ZnSe 薄膜的质量研究

研究了热壁外延法（ＨＷＥ）在经两种不同处理方法的ＧａＡｓ衬底上生长的ＺｎＳｅ薄膜质量．俄歇电子能谱图（ＡＥＳ）分析表明,经Ｓ纯化的ＧａＡｓ表面大约由一层单原子层所覆盖,从而减少了ＺｎＡｓ／ＧａＡｓ界面态密度．用喇曼光谱（Ｒａｍａｎ）的空间相干模型,对不同处理方法的ＧａＡｓ上生长的ＺｎＳｅ处延膜的一级ＬＯ声子喇曼谱线形变化进行分析,定量判断出ＺｎＳｅ外延膜质量的优劣．分析认为,经Ｓ纯化ＺｎＳｅ／ＧａＡｓ具有较好的质量．理论分析与实验分析相一致．     

Grain boundary microstructure and fatigue crack growth in Allvac 718Plus superalloy

The correlation between grain boundary microstructure and fatigue crack growth with hold-times was investigated for two conditions of the superalloy Allvac 718Plus; a Standard condition with the recommended distribution of grain boundary phases and a Clean condition with virtually no grain boundary phases. Fatigue testing was performed at 704 °C using 10 Hz cyclic load with intermittent hold-times of 100 s at maximum tensile load. Microstructural characterization and fractography were conducted using scanning- and transmission electron microscopy techniques. Auger electron- and X-ray photoelectron spectroscopy techniques were used for oxide analyses on fracture surfaces. It was found that in the Standard condition crack growth is mostly transgranular for 10 Hz loading and intergranular for hold-times, while for the Clean condition crack growth is intergranular in both load modes. The lower hold-time crack growth rates in the Standard condition are attributed to grain boundary δ-phase precipitates. No effect of δ-phase was observed for 10 Hz cyclic loading crack growth rates. Two different types of oxides and oxide colours were found on the fracture surfaces in the Standard condition and could be correlated to the different loading modes. For cyclic loading a bright thin Cr-enriched oxide was dominate and for hold-times a dark and slightly thicker Nb-enriched oxide was dominant These oxide types could be related to the oxidation of δ-phase and the matrix respectively. The influence of δ-phase precipitates on crack propagation is discussed.