Effects of Microstructural Heterogeneity on the Spallation Behavior of Materials

It is of utmost importance to understand the spallation behaviour of heterogeneous materials. In this paper, a driven nonlinear threshold model with stress fluctuation is presented to study the effects of microstructural heterogeneity on continuum damage evolution. The spallation behavior of heterogeneity material is analyzed with this model. The heterogeniety of mesoscopic units is characterized in terms of Weibull modulus m of strength distibution and stress fluctuation parameter k. At high stress, the maximum damage increases with m; while at low stress, the maximum damage decreases. In addition, for low stress, severe stress fluctuation causes higher damage; while for high stress, causes lower damage.

基于PROFIBUS-DP的激光加工系统数字化控制

提出采用PROFIBUS-DP现场总线技术实现对激光柔性加工系统的数字化控制，给出了控制实现过程中的DL动态链接库方案，详述了控制中的同步问题，并将其应用于汽车覆盖件模具激光表面硬化，编程采用VC++面向对象工具加以实现。

Characteristics of the interface of a laser-quenched steel substrate and chromium electroplate

The interface of a laser-discrete-quenched steel substrate and as-deposited chromium electroplate was investigated by ion beam etching, dissolving-substrate-away and using a Vickers microhardness tester, in an attempt to reveal the mechanism that the service life of the chromium-coated parts is increased by the duplex technique of laser pre-quenching plus chromium post-depositing. The laser quenching of the steel substrate can reduce the steep hardness gradient at the substrate/chromium interface and improve the load-bearing capacity of chromium electroplate. Moreover, the laser quenching prior to plating has an extremely great effect on the morphologies and microstructure of the substrate/chromium interface: there is a transient interlayer at the original substrate/chromium interface while there is not at the laser-quenchedzone/chromium interface; the near-substrate surface microstructure and morphologies of the free-standing chromium electrodeposits, whose substrate was dissolved away with nital 30% in volume, inherit the periodically gradient characteristics of the laser-discrete-quenched substrate surface. (c) 2006 Elsevier B.V. All rights reserved.

Effects of Microstructural Heterogeneity on The Spallation Behavior of Materials

It is of utmost importance to understand the spallation behaviour of heterogeneous materials. In this paper, a driven nonlinear threshold model with stress fluctuation is presented to study the effects of microstructural heterogeneity on continuum damage evolution. The spallation behavior of heterogeneity material is analyzed with this model. The heterogeniety of mesoscopic units is characterized in terms of Weibull modulus m of strength distibution and stress fluctuation parameter k. At high stress, the maximum damage increases with m; while at low stress, the maximum damage decreases. In addition, for low stress, severe stress fluctuation causes higher damage; while for high stress, causes lower damage.

Guiding neutral atoms with two current-carrying wires and a vertical bias field on the atom chip

We demonstrate the guiding of neutral atoms with two parallel microfabricated current-carrying wires on the atom chip and a vertical magnetic bias field. The atoms are guided along a magnetic field minimum parallel to the current-carrying wires and confined in the other two directions. We describe in detail how the precooled atoms are efficiently loaded into the two-wire guide. We present a detailed experimental study of the motional properties of the atoms in the guide and the relationship between the location of the guide and the vertical bias field. This two-wire guide with vertical bias field can be used to realize large area atom interferometer.

Improvement of sensitivity and refractive-index changes in LiNbO3 : Ce : Cu crystals with UV light

A nonvolatile recording scheme is proposed using LiNbO3:Ce:Cu crystals and modulated UV light to record gratings simultaneously in two centres and using red light to bleach the grating in the shallow centre to realize persistent photorefractive holographic storage. Compared with the normal UV-sensitized nonvolatile holographic system, the amplitude of refractive-index changes is greatly increased and the recording sensitivity is significantly enhanced by recording with UV light in the LiNbO3:Ce:Cu crystals. Based on jointly solving the two-centre material equations and the coupled-wave equations, temporal evolutions of the photorefractive grating and the diffraction effciency are effectively described and numerically analysed. Roles of doping levels and recording-beam intensity are discussed in detail. Theoretical results confirm and predict experimental results.

小麦光系统I的分离纯化及其光合特性的研究

从不同基因型的小麦京411和小偃54中分离纯化了PSI颗粒并研究了PSI颗粒的一些光合特性： 1. 测定了两种基因型小麦PSI颗粒的室温吸收光谱、低温荧光光谱，并进行了SDS-PAGE多肽分析。吸收光谱显示了红区680nm和蓝区439nm的两个最大吸收峰，低温荧光光谱显示了PSI特征的位于735nm左右的发射峰，同时SDS-PAGE也显示我们的制备物包括PsaA、PsaB、LHCI以及一些其它小分子量蛋白亚基。这些都表明我们从不同基因型小麦中获得了比较理想的PSI颗粒制备物。 2. 测定了京411类囊体膜和PSI颗粒的脂类组成和脂肪酸成分，发现PSI颗粒中也存在着类囊体膜中的五种膜脂，即：MGDG、DGDG、PG、SQDG、PC，但PSI颗粒的MGDG含量比类囊体膜高，而DGDG含量较类囊体低。PSI颗粒和类囊体膜的脂肪酸组成也有差异。 3. 运用光谱学手段，研究两种基因型小麦PSI颗粒光破坏过程的异同。发现在经过强光破坏后，两种小麦PSI颗粒都发生叶绿素漂白现象，在各种状态叶绿素中，683nm状态的Chl a对强光最为敏感，受到光破坏的程度最大，而649nm Chl b和667nm Chl a分子变化较小。结合吸收光谱和低温荧光光谱我们提出了PSI中可能存在的能量传递途径。比较两种小麦PSI颗粒光破坏在低温荧光光谱上的不同，我们初步认为，小偃54可能通过将能量较多地分配给予长波长Chl而一定程度的避免过多能量向P700反应中心传递，从而起到对P700的保护作用。 4. 研究了不同表面活性剂SDS和Triton X-100对PSI颗粒色素结合状态和能量传递的影响。发现表面活性剂对色素状态和PSI中的能量传递都有很大的影响。并且Triton X-100的作用较SDS强烈。紫外荧光显示PSI蛋白结构也发生了显著变化。

加速器束流阻挡板

本实用新型涉及一种加速器束流阻挡板，含有固定板等；在固定板下活动联接有两动杆，并在其上固定联有两定杆，在动杆的另一端联有阻挡板；在阻挡板上还设有定位板；在动杆上还联有动杆横拉杆，在动杆横拉杆上通过传力叉与上电磁铁的柱销上的调拉杆相联；另在定杆的另一端还联有定位槽钢，在定位槽钢上还联有下电磁铁的下电磁铁架；下电磁铁与定杆横拉杆相联；本实用新型的结构紧凑、动作灵活、方便准确、可保证被辐照物的辐照剂量的均匀性、避免浪费束流。

昆明山海棠片对小鼠淋巴细胞体外增殖活化影响的研究

目的:研究昆明山海棠片对小鼠脾淋巴细胞增殖、活化标志CD69和CD25及细胞因子IL-4及IFN-γ的影响.方法:无菌分离小鼠脾淋巴细胞,加入不同浓度的昆明山海棠溶液,MTT法检测刀豆蛋白A刺激的小鼠脾淋巴细胞增殖;流式细胞仪检测活化标志CD69及CD25;酶联免疫法检测细胞因子IL-4及IFN-γ.结果:昆明山海棠片对脾淋巴细胞增殖活化及分泌均有抑制作用.

基于Weil对的成对密钥协商协议

为了实现网络安全，一个重要的方法是网络用户传送加密和可鉴定的消息．此时，用来加密和鉴定的密钥应该由网络中的用户协商得到．提出了3个基于Weil对的成对密钥协商协议．在协议中，所有用户共享一个秘密信息，通过较少的步骤，同时实现密钥协商和用户认证．提出的协议满足如下的安全特性：部分密钥泄漏的安全性、完备的前向安全性、个人密钥泄漏的安全性、无不明的密钥共享和无法控制密钥等．