Preparation and characterization of amphiphilic block copolymer of polyacrylonitrile‐block‐poly(ethylene oxide)

The synthesis of polyacrylonitrile‐block‐poly(ethylene oxide) (PAN‐b‐PEO) diblock copolymers is conducted by sequential initiation and Ce(IV) redox polymerization using amino‐alcohol as the parent compound. In the first step, amino‐alcohol potassium with a protected amine group initiates the polymerization of ethylene oxide (EO) to yield poly(ethylene oxide) (PEO) with an amine end group (PEO‐NH₂), which is used to synthesize a PAN‐b‐PEO diblock copolymer with Ce(IV) that takes place in the redox initiation system. A PAN‐poly(ethylene glycol)‐PAN (PAN‐PEG‐PAN) triblock copolymer is prepared by the same redox system consisting of ceric ions and PEG in an aqueous medium. The structure of the copolymer is characterized in detail by GPC, IR, ¹H‐NMR, DSC, and X‐ray diffraction. The propagation of the PAN chain is dependent on the molecular weight and concentration of the PEO prepolymer. The crystallization of the PAN and PEO block is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1753–1759, 2003     

三高气井管柱损伤研究现状

目前国内"高温、高压、高产"气井主要存在油套管强度降低、油管损坏、油管冲蚀等一系列安全问题。三高井内各种杆管柱处于复杂变形和运动状态,外载荷成为影响其力学行为的主要因素之一。国内外关于管柱力学、动力学、冲蚀等方面的研究成果卓著,但在解释油管柱的瞬态动力学、油管柱疲劳等方面仍显不足。在管柱力学分析的基础上进行冲蚀分析和振动分析应该是三高气井管柱损伤理论的研究趋势。     

个性化搜索引擎推荐算法研究*

将个性化引入搜索引擎出现了稀疏性、精确性、扩展性等新问题。针对以上问题,提出了一种基于SVD（单值分解）影响集的协作过滤推荐算法,在利用矩阵相关技术以及扩大影响的基础上,将用户潜在感兴趣的资源推荐给用户。实验表明,该算法可有效解决以上存在的问题,显著提高个性化系统的推荐质量。     

植物病害图像压缩与传输的研究

为实现植物病害监控,研究了基于DSP的图像压缩编码,构建植物病害监测系统．系统通过CCD进行视频信息的采集,基于TMS320DM642DSP多媒体处理芯片采用H．263编码技术进行压缩编码,并将压缩后的数据经以太网传输至控制中心,进行图像识别分析,从而实现病害监控．测试表明,系统可成功进行图像的采集、压缩编码,并在PC端接收到压缩的图像．     

T-S模糊控制方法在生物流化床系统中的应用

针对生物流化床污水处理系统的非线性、时滞、时变等问题,提出采用T-S模糊控制方法,将复杂的非线性系统模糊化为局部线性模型,并引入积分环节,降低T-S模糊控制器维数,简化规则.最后,通过实验进行理论验证.实验结果表明,该方法可行且有效.     

Analysis Model on Penetration Depth of Concrete by Eroding Long-Rod Projectiles

Mass loss should be considered while calculating the penetration depth of concrete by eroding long-rod projectiles of high velocity.The penetration process is divided into two phases:eroding phase and rigid phase.During eroding phase,a model to predict the penetration depth is established on the assumption that there is a chipping region in the bottom of crater.During rigid phase,Forrestal formula is adopted to calculate the penetration depth.Using this model,the depth of concrete penetration by a tungsten alloy long-rod projectile is calculated.When the critical eroding velocity is between 950 m/s and 1 000 m/s,the result is in good agreement with the experimental data.     

Deformation resistance effect of PAN-based carbon fibers

The deformation resistance effect of polyacrylonitrile (PAN)-based carbon fibers was investigated, and the variatipn law of electrical resistivity under tensile stress was analyzed. The results show that the gauge factor (fractional change in resistance per unit strain) of PAN-based carbon fibers is 1.38, which is lower than that of the commonly-used resistance strain gauge. These may due to that the electrical resistivity of carbon fibers decreases under tensile stress. In addition when the carbon fibers are stretched, the change of its resistance is caused by fiber physical dimension and the change of electric resistivity, and mainly caused by the change of physical dimension. The mechanical properties of carbon fiber monofilament were also measured. Funded by the National Natural Science Foundation of China (No. 10672128 and 50878170)     

基于Morlet小波变换和改进遗传算法的动态识别

如何合理地识别大型复杂结构的动力参数一直是工程领域关心的问题.为此,以Morlet小波变换和采用单亲遗传算子的改进遗传算法为基础,构造一结构动态参数识别模型.并且以C++为平台,通过计算机内部命令调用ANSYS等软件,实现识别模型的程序化.通过模拟算例计算,计算结果与理论值一致.同时,结合一水电站厂房现场振动试验,对该大型结构进行动态参数识别,识别结果与工程经验值基本吻合.     

配HRBF500级钢筋混凝土梁受弯承载力试验

试验设计制作了7根配有500 MPa细晶粒高强钢筋的钢筋混凝土梁,通过变化保护层厚度、纵筋配筋率、混凝土强度等因素,分析研究高强钢筋混凝土梁的承载力.试验结果表明,应用了500 MPa细晶粒高强钢筋的混凝土梁承载力的实测结果与计算值比较接近,可以继续沿用现有的规范计算模式.     

离子液体中棒状ZnO粉体的制备及光催化性能

制备了离子液体1-乙基-3-甲基咪唑溴盐([emin]Br),以该离子液体为模板剂,采用水热法制备了亚微米级棒状ZnO粉体。经扫描电子显微镜(SEM)、X射线衍射(XRD)、傅立叶转换红外光谱(FT-IR)等对样品进行了表征和分析。结果表明,该方法制备出具有六方纤锌矿结构的棒状亚微米级ZnO粉体,棒长为2~3μm,直径为500~600 nm;以高压汞灯为光源,以ZnO粉体为光催化剂,对有机染料罗丹明B进行了光降解实验,光降解90 min后,其去除率达到93.3%。