REGULARITY CRITERIA FOR WEAK SOLUTION TO THE 3D MAGNETOHYDRODYNAMIC EQUATIONS＊

In this article,regularity criteria for the 3D magnetohydrodynamic equations are investigated.Some sufficient integrability conditions on two components or the gradient of two components of u + B and u...     

ON THE CAUCHY PROBLEM FOR IMBQ SYSTEM ARISING FROM DNA

In this article, we focus on the Cauchy problem for the generalized IMBq system in n-dimensional space, which arises from DNA. We show the global existence and decay estimates of solution for a class of initial velocity, provided that the initial value is suitably small.     

Quantitative evaluation of equatorial small-angle X-ray scattering for cylindrical fibers

Elongated microvoids, internal fibrillar structure, and edge scattering from both surface refraction cause an equatorial streak in small angle X-ray scattering. A model for analyzing the edge scattering of fibers is proposed. Simulation results indicate that the intensity of edge scattering from surface refraction of a cylindrical fiber is strong and makes an important contribution to the equatorial streak. Two factors influence edge scattering intensity. One is the sample-to-detector distance (D); edge scattering intensity increases with increasing D. The equatorial streak becomes weak when D is shortened. The other factor is the refraction index. Edge scattering intensity increases as the real component of the refraction index decreases. In experiment, weak or even no equatorial streaks were found for samples measured in a roughly index-matching fluid. Edge scattering can be eliminated or weakened, and it can be calculated by comparing the intensities of a cylindrical fiber when it is measured in air and in index-matching fluid. The simulation data are basically in agreement with the experimental data.     

CardBus信令接口卡驱动程序开发

CardBus信令接口卡可以方便地接入七号信令网,对信令网进行有效的测试和维护.文中开发实现了该接口卡的wDM驱动程序.使该接口卡可以在Windows 2000/XP平台上稳定地运行,实现各种管理和控制功能.     

一种VDL mode 2高动态接收前端的设计

针对VDL mode 2接收机前端信号强度变化大、容易造成信道失真的问题,本文设计了一种高线性的动态接收前端。射频前级利用数字增益控制实现增益的快速控制响应,中频则采用模拟自动增益控制电路,进一步提高动态范围。实验结果表明,动态范围达到110dB,并实现了±1dB的线性精度,满足VDL mode 2数据链系统对接收前端的要求。     

同步辐射小角和广角X射线散射在高分子材料研究中的应用

同步辐射X射线散射是研究高分子材料不可替代的重要工具。第三代同步辐射光源—上海光源的成功建设,标志着我国进入国际先进光源俱乐部,为我国高分子材料研究大发展提供了一个契机。本文结合作者和国内外同行的工作,以具体案例的形式介绍了同步辐射小角和广角X射线散射在高分子材料研究中的一些应用,阐述了同步辐射高亮度原位在线研究高分子材料结构形成和演化动力学以及结构与性能关系的独特优势。同时介绍几种自主研制的原位装置和常用的X射线散射数据处理方法。希望本文能起到抛砖引玉的作用,吸引更多的高分子研究同行利用同步辐射开展研究。     

基于Kirkpatrick-Baez镜聚焦的X射线小角散射显微层析成像

X射线小角散射显微层析成像(SAXS-CT)是一种无损的结构表征技术,用于研究非均匀物质纳米结构信息及其空间分布;在上海同步辐射光源(SSRF)设计并搭建了基于Kirkpatrick-Baez(KB)镜聚焦的SAXS-CT成像系统,并选取毛竹和注塑聚乳酸样品进行实验验证。结果表明:该SAXS-CT成像系统的聚焦光斑尺寸可以达到20μm以下;对于毛竹样品,得到了其内部维管束和薄壁细胞的位置分布及散射差异,同时获取了内部纳米纤维的取向特点;对于注塑聚乳酸样品,发现其内部片晶结构具有分层分布特征,获取了片晶结构的分布图像以及长周期分布图像;实验结果验证了该SAXS-CT成像系统的可靠性及实用性。     

微波宽带固态高功率合成关键技术的探析

随着现代通信技术的发展与测量需求不断增加,为满足系统对输出功率、宽带、性能等方面的需求,诸多技术人员对微波系统可以运用的技术进行了相关分析.基于当前的发展,本文阐述了高功率合成相关技术的具体运用,从而实现系统宽带、多路、高功率的设计目标.针对固态功率合成技术进行分别阐述,根据芯片、电路、空间功率等角度出发进行分析,以及...