Grafting of maleic anhydride onto polyethylene through a green chemistry approach

The grafting of a polymer can lead to the improvement and modification of the polymer and thus expand its applications. Grafting methods include solution grafting in organic solvents, melt grafting at high temperatures, and light grafting with radioactive sources. These methods have their advantages and disadvantages. The disadvantages include waste treatment, consumption of energy, and so on. In this study, a hydrothermal process which is called the green approach, was developed to prepare graft copolymers. The effect of various factors on the grafting degree was investigated in detail. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A simple method of rapid and automatic color image segmentation for serialized Visible Human slices

In this paper, a rapid and automatic color image segmentation method for the serialized slices of the Visible Human is proposed. The main strategy is based on region growing and pixel color difference. A rapid color similarity computing method is improved and applied for classifying different pixels. An algorithm based on corrosion from four directions is proposed to automatically extract the seed points for the serialized slices. Utilizing this method, the color slice images of the Visible Human body can be segmented in series automatically. Also, the multithreading frame of parallel computing is introduced in the entire segmentation process. This method is simple but rapid and automatic. The primary organs of the Visible Human can be segmented clearly and accurately. The 3D models of these organs after 3D reconstruction are satisfactory. This novel method can provide support to the Visible Human research.     

7A04铝合金应力腐蚀过程中裂纹萌生和扩展规律研究

为了研究不同拉伸速率对应力腐蚀敏感性及应力腐蚀过程(SCC)中裂纹萌生与扩展规律的影响,本文选用7A04铝合金在3.5%wt NaCl溶液中进行慢应变速率拉伸实验(SSRT),采用扫描电子显微镜(SEM)、体式显微镜、电化学方法、高分辨透射电子显微镜(HRTEM)等方法进行研究;提出一种原位预测裂纹萌生和扩张的新方法即相移与电化学阻抗谱相结合的方法来系统研究应力腐蚀过程(SCC)中裂纹萌生和扩展规律.结果表明:当拉伸速率为3.0 um/min时,在3 h附近裂纹开始萌生,在8 h附近裂纹发生明显扩展;通过高分辨透射电子显微镜(HRTEM)对裂纹萌生和扩展机理进行研究,验证了新方法的可行性,推测裂纹的萌生和扩展机理可能是由晶界出产生的析出物引起的.     

铝合金在盐水环境中腐蚀性能的电化学研究

为了深入研究温度对铝合金材料的腐蚀行为和机理,采用盐水腐蚀方法研究了其在高温条件下的电化学特性及腐蚀机理.选用7A04和5A06铝合金作为研究对象,在质量分数为3.5%的氯化钠溶液中,利用增重法、蔡司显微镜并结合电化学测试方法研究了其在20~80 ℃范围内的腐蚀性能,分析了腐蚀产物的微观形貌,探讨了腐蚀机理.结果表明：两种铝合金试样的腐蚀速率均随温度升高而增大.在Tafel极化曲线图中,对于同一种铝合金,自腐蚀电位随腐蚀温度增加向负方向移动,自腐蚀电流密度和年腐蚀深度随腐蚀温度增加而减小.对同一腐蚀温度下的两种铝合金,5A06铝合金自腐蚀电位低于7A04铝合金,腐蚀电流密度和年腐蚀深度均小于7A04铝合金.电化学阻抗图谱中,两种铝合金在不同条件下的Nyquist图均存在一个容抗弧,极化电阻随腐蚀温度增加而减小.对于同一种铝合金,在3.5%氯化钠溶液中的腐蚀速率会随着温度的升高而增大;在同一腐蚀温度下,5A06铝合金比7A04铝合金更容易发生腐蚀,但腐蚀速率比7A04铝合金慢.     

Large capacitance and fast polarization response of thin electrolyte dielectrics by spin coating for two-dimensional MoS2 devices

Nano Research - A spin-coating method was applied to obtain thinner and smoother PEO/LiClO4 polymer electrolyte films (EFs) with a lower level of crystallization than those obtained using a...     

一种亚稳型β钛合金在高应变率下的多种变形机制

以二元Ti-16V合金为研究对象,采用霍普金森压杆装置、光学显微镜、电子背散射衍射技术以及透射电子显微镜,分别测量并分析了高应变率下Ti-16V合金的动态力学性能、微观组织演变以及塑性变形机制。得出如下结论:Ti-16V合金的流变抗力与应变硬化速率对应变率不敏感;Ti-16V合金的临界失稳应变率约为3000 s~(-1);{332}113型孪生与应力诱发ω相变为Ti-16V合金高应变率下的主导塑性变形机制;通过本研究构建的孪生Schmid因子计算模型,定量核算与模拟{332}113型孪生的Schmid因子,结合实验结果表明Schmid因子是决定晶粒是否发生孪生的重要参数。     

挣值分析在深圳地铁9号线BT项目中的应用

随着国内经济的高速发展,大型城市的基础设施建设全面铺开,地铁建设项目正在逐步开展。地铁项目建设期较长(普遍为3~8年),项目的进度管理及成本管理面临较大挑战。在项目管理中应用挣值分析,有助于管理者更加直观地了解项目的进度和成本使用情况。基于深圳地铁9号线BT项目,研究挣值分析在该项目进度管理和成本控制中的具体应用。     

新型表面活性剂对铝合金的复配缓蚀行为

以异丙基亚氨基(>NCH(CH3)2)作为连接基团,通过二步法合成了一种新型双季铵盐阳离子表面活性剂--二[2-羟基-3-(十二烷基二甲基季铵基)丙基]-异丙胺二氯化表面活性剂,进而用各种实验方法对合成产物进行结构表征;分别将其与阴离子表面活性剂十二烷基苯磺酸钠(SDBS)和稀土元素氯化铈进行复配,研究复配体系对铝合金在盐酸溶液中的缓蚀性能和机理。结果表明:两复配体系均能产生良好的协同作用:当合成产物与SDBS配比为3∶4时,缓蚀效率为97.4%;当合成产物与氯化铈配比为1∶1时,缓蚀效率为96.4%。合成产物与SDBS复配的缓蚀机理为利用静电吸附作用在铝合金表面形成致密吸附膜;合成产物与氯化铈复配的缓蚀机理为氯化铈可先在溶液中形成配合物,该配合物进一步吸附于金属表面从而起到协同缓蚀作用。     

基于振动能量采集器的无源无线传感节点技术研究

随着以MEMS技术为依托,结合压电效应的振动能量采集技术的日臻完善,如何利用振动能量采集器构成高效的无源无线传感节点成为近期研究热点,而能量采集器输出的电能储存控制和低功耗发射技术是实现该节点的难点。在设计出对储能电容电压具有双阈值检测与控制功能的低功耗电路基础上,给出了一种自报警、无源无线低功耗传感节点。实验表明,在频率52 Hz正弦振动、振动加速度幅值为5 gn激励下,经过125 s的能量储存,节点能够以+10 dBm功率在16 ms内完成发射及无线报警,发射距离可达1.31 km。该节点构成的无线传感网络可广泛应用于石油管线、桥梁和军事侦察等外部供电极度受限环境的现场监控等用途。     

A stretching transform‐based automatic nonrigid registration system for cerebrovascular digital subtraction angiography images

In the cerebrovascular digital subtraction angiography (DSA), patient motion is the primary cause of image quality degradation. In this article, we describe a nonrigid image registration system for motion artifact reduction in DSA which is fully automatic, effective, and computationally very efficient. In this system, the mask image is partitioned to generate the appropriate control points. The energy of histogram of differences method is adopted as similarity measurement, and the Powell algorithm is utilized for acceleration. A forward stretching transformation is used to complete the motion estimation, and an inverse stretching transformation is used to generate the target image by pixel mapping strategy. The method of this system is effective to maintain the topological relationships of the gray value before and after the image deformation. Preliminary experiments on the cerebrovascular DSA images illustrate the applicability of the system. After the deformation, the mask image remains clear and accurate contours, and the quality of the subtraction image after the registration is favorable. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 171–187, 2013