免费办公软件专题

以前，在我国，主流办公软件出奇一致。但是，近几年随着各大企业对知识产权、信息化体系的不断重视。在企业内部系统平台和办公软件方面，都逐步呈现出按需配置、不拘一格的态势。     

Vista系统工作站安全防护有高招

为了保证工作站系统的安全,相信不少人都掌握了有关工作站系统安全设置的许多妙招!不过,伴随着Vista系统的正式发布,局域网中安装了Vista系统的工作站数量是越来越多,我们以前掌握的许多安全设置妙招对于Vista工作站系统来说几乎都已失效,所以为了保证Vista工作站系统的安全,我们还需要掌握一些新的安全设置技巧.这不,本文下面为各位贡献的几则Vista工作站安全防护措施,表面上看上去很平常、很简单,可是这些安全防护措施的具体设置过程却与我们平时见到的并不一样,希望各位能在这些安全防护措施的帮助下更好地保证Vista工作站系统的安全.     

瞬态C-V方法对Al_xGa_(1-x)As中DX中心的研究

本文指出DX中心电容测量中边区的重要性,提出一种新的瞬态C-V方法,可以用来测量DX中心浓度、导带电子浓度和边区的空间电荷分布及导带电子浓度随温度的变化关系,并由此导出测量DX中心热电离能的方法。另外,还对DX中心正∪和负∪两种模型的理论分析和实验结果进行了比较,得出不同模型所应满足的附加条件。     

AlGaAs:Si中与DX中心有关的光生电子陷阱特性研究(英文)

A new electron trap state SD was found by DLTS measurement under light illumination in Si doped A.lxGa1-xAs. This new trap energy level ESD is shallower than the DX center energy in the gap and the concentration of SD is comparable to that of DX centers. The emission activation energy Ec=0.20±0.05eV and capture activation energy Ec= 0.17±0.05eV. The SD DLTS peak has never been detected previously because under dark and thermal equilibrium condition most of the electrons occupy the deeper DX states and most of SD states are empty. However, when the sample is illuminated by light, electrons are excited to the conduction band and then re-captured by SD since the deeper DX states have a slower electron capture rate, thus a new DLTS peak corresponding to SD appears. Constant temperature capacitance transient C-t and transient C-V measurements were also used to further confirm the existence of SD states.     

MBE MD AlGaAs/GaAs调制反射谱及其与2DEG浓度的关系(英文)

The two-dimensional electron gas concentration dependence of photore-flectance of n-AlGaAs/GaAs heterostructures is reported and explained by analysing the physical process induced by photo-modulation. Comparison of the experimental results and energy level calculations based on a triangular potential well approximation shows good agreement.     

瞬态C-V法测量AlGaAs:Si中DX中心的电离能(英文)

The thermal ionization energy ET of DX centers in AlxGa1-xAs and its dependence with the value of x and the pressure are very important for estab- lishing the model of DX centers. The conventional DLTS and Hall methods used to DX center measurement have some ambiguities in theoretical analysis and experiments and the values of ET determined are different with those methods. The new constant temperature transient C-V measurement is based on the fact that at low temperature both electron capture and emission rates of DX centers are very slow. During the transient C-V measurement, change; of bias voltages and capacitance measurements are completed in a time duration much shorter than the electron capture and emission time constants, therefore the electrons occupied on the DX centers are considered to be frozen. The density of DX centers, the distribution profile of electrons on DX centers in the depletion region of a Schottky diode at a constant reverse bias, and the density of free electrons in conduction band in the bulk and their temperature dependence have been measured.     

幼儿电子成长档案制作初探

幼儿成长档案是反映幼儿学习与发展状况的资料，是对幼儿成长过程的评价和记录。《幼儿园教育指导纲要》中指出，对幼儿的评价应是一个动态评价，是一个持续的过程，它对幼儿发展的分析包含了过去、现在和未来。为每位幼儿建立成长档案能为教师因材施教提供依据；为幼儿提供自我展示的舞台；让家长更加了解自己的孩子；也为幼儿留下美好的回忆。     

如何选择集散控制系统

介绍了一种定量比较不同集散控制系统优劣的方法－－矩阵法，并详细阐述了其使用方法。     

Al_xGa_(1-x)As-GaAs多层量子阱结构的流体静压光荧光研究

本文对Al_xGa_(1-x)As-GaAs多层量子阱结构的子带间跃迁能的压力关系做了77K低温下的光荧光光谱研究.实验结果表明,未掺杂的量子阱的非本征发光主要来自缺陷的束缚激子d~ox.d~ox束缚激子态在量子阱中的压力系数(5meV/kbar)与体材料中的压力系数(2.7meV/kbar)的比较表明,在量子阱中深中心发生了浅化.通过对不同子带间跃迁能的压力关系测量给出了GaAs Γ谷相应能量点的压力系数,结果表明Γ谷并不是以同一压力系数移动的刚性球.最后测量了量子阱的发光强度随压力的变化.