Fe/Si多层膜的层间耦合与界面扩散

对以本征Si及重掺杂ｐ型和ｎ型Si作为中间层的Fe/Si多层膜的层间耦合进行研究，并通过退火，增大Fe，Si之间的扩散，分析界面扩散对层间耦合的影响. 实验结果表明，层状结构良好的制备态的多层膜，Fe，Si之间也存在一定程度的扩散，它是影响层间耦合的 主要因素，远远超过了半导体意义上的重掺杂，使不同种类的Si作为中间层的层间耦合基本 一致.进一步还发现，在一定范围内增大Fe，Si之间的扩散，即使多层膜的层状结构已经有了相当的退化，Fe/Si多层膜的反铁磁耦合强度基本保持不变. 关键词： Fe/Si多层膜 层间耦合 界面扩散     

Electrochemical characterization of poly(vinylidenefluoride)-zinc triflate gel polymer electrolyte and its application in solid-state zinc batteries

Gel polymer electrolyte (GPE) films comprising of poly(vinylidenefluoride), propylene carbonate, ethylene carbonate and zinc trifluoromethane sulfonate are prepared and characterized. The composition of GPE is optimized to contain minimum liquid components with a maximum specific conductivity of 3.94×10⁻³ S cm⁻¹ at (25±1) °C. A detailed investigation on the properties such as ionic conductivity, transport number, electrochemical stability window, reversibility of Zn/Zn²⁺ couple and Zn/gel electrolyte interfacial stability have been carried out. The ionic conductivity follows a VTF behaviour with an activation energy of about 0.0014 eV. Cationic transport number varies from 0.51 at 25 °C to 0.18 at 70 °C. Several cells have been assembled with GPE as the electrolyte, zinc as the anode, γ-MnO₂ as the cathode and their charge–discharge behaviour followed. Capacity values of 105, 82, 64 and 37 mAh/g of MnO₂ have been achieved at 10, 50, 100 and 200 μA/cm² discharge current densities, respectively. The discharge capacity values are almost constant for about 55 cycles for all values of current densities. Cyclic voltammetric study of MnO₂ electrode in Zn/GPE/MnO₂ cell clearly shows intercalation/deintercalation of Zn²⁺.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶 凝胶法以磷钼酸 (MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2 催化剂 .使用ICP、XRD、TG DTA、IR、TPD MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能 .杂多钼酸盐与TiO2 通过O2 -在TiO2 表面发生了键合 .在 6 2 3K下 ,杂多阴离子仍保持原有的Keggin结构 .CO2 在Lewis酸位Ni(Ⅱ )和Lewis碱位Ni-O -Mo的桥氧协同作用下生成CO2 卧式吸附态Ni(Ⅱ )←O - (CO)← (O--Ni) .丙烯有多种吸附态在催化剂上吸附 .在 5 6 3K、1MPa和空速 15 0 0h-1的反应条件下 ,丙烯的摩尔转化率为 3.2 % ,产物MAA选择性为 95 % .     

基于MPEG-4的视频流式传输系统及动态带宽分配方法

提出了一个基于MPEG 4精细可分级编码技术的视频流式传输系统。介绍了系统中主要模块的作用,并重点研究了速率控制模块。速率控制模块采用了适合视频流式传输的动态带宽分配方法。它可以根据实时的网络通道波动状况来动态调整滑动参数,以适应网络波动和高效地利用网络的有限资源。实验结果表明,动态带宽分配方法在动态带宽波动条件下不仅可以使相邻帧间的视频质量更加平滑,而且可以大大提高解码视频图像的总体质量,也就是说可同时改善解码视频的主客观性能。     

Total synthesis of (±) maculalactone A, maculalactone B and maculalactone C and the determination of the absolute configuration of natural (+) maculalactone A by asymmetric synthesis

Maculalactones A, B and C from the marine cyanobacterium Kyrtuthrix maculans are amongst the only compounds based on the tribenzylbutyrolactone skeleton known in nature and (+) maculalactone A from the natural source possesses significant biological activity against various marine herbivores and marine settlers. We now report a concise synthesis of racemic maculalactone A in five steps from inexpensive starting materials. Maculalactones B and C were synthesized by a minor modification to this procedure, and the synthetic design also permitted an asymmetric synthesis of maculalactone A to be achieved in around 85% ee. The (+) and (−) enantiomers of maculalactone A were assigned, respectively, to the S and R configurations on the basis of the chiral selectivity expected for catecholborane reduction of an unsymmetrical ketone in the presence of Corey's oxazoborolidine catalyst. Surprisingly, it appeared that natural (+) maculalactone A was biosynthesized in K. maculans in a partially racemic form, comprising ca. 90-95% of the (S) enantiomer and 5-10% of its (R) enantiomer. Coincidentally therefore, the percentage enantiomeric excess of the product obtained from asymmetric synthesis almost exactly matched that found in nature.     

Radiation‐induced migration of additives in PVC‐based biomedical disposable devices. Part 1. Surface morphology by AFM and SEM/XEDS

Two different types of plasticized poly(vinyl chloride) (PVC) used for biomedical disposable devices—extruded and injection moulded—were studied in the non‐sterilized condition and after 25 and 50 kGy of beta irradiation. The polymer surfaces were analysed by scanning electron microscopy (SEM) equipped with an x‐ray energy‐dispersive spectroscopy (XEDS) and by atomic force microscopy (AFM). The inner surface of two parts of a venous line showed a different morphology according to their original formulation (for extrusion or injection moulding process) and reacted differently on sterilization with beta irradiation. Moulded parts were affected only slightly by the radiation step, whereas the variations were bigger for the extruded parts. In order to gain the best performances for the medical devices studied, the utmost care must be taken in the sterilization step, which should be optimized as well as the other steps of the manufacturing process. Copyright © 2003 John Wiley & Sons, Ltd.     

4英寸热氧化硅衬底上磁性隧道结的微制备

就如何在4英寸热氧化硅衬底上沉积高质量的磁性隧道结纳米多层薄膜材料和如何利用光刻方法微加工制备均匀性较好的磁性隧道结方面做了初步研究，并对磁性隧 道结的磁电性质及其工作特性进行了初步测量和讨论.利用现有的光刻设备和工艺条 件在4英寸热氧化硅衬底上直接制备出的磁性隧道结，其结电阻与面积的积 矢的绝对误差在10% 以内，隧穿磁电阻的绝对误差在7% 以内，样品的磁性隧道结性质具有较好的均匀性和一致性，可以满足研制磁随机存储器存储单元演示器件的基本要求. 关键词： 磁性隧道结 隧穿磁电阻 磁随机存储器 4英寸热氧化硅衬底     

Intermittency in the Slow Particle Emission During Hadron–Nucleus Interactions

The study of the angular distribution of slow particles during high energy hadron-nucleus interaction indicates that emission of slow particles takes place from a thermally non-equilibrated system. This evidence has come out from the presence of intermittency - a phenomenon that reveals a fractal structure and represents a self-similarity in the particle production process. Hence, this study highlights inadequacy of cascade-evaporation model and advocates the need of its refinement.     

ICP-AES测定钛基复合材料中镍、钕和铁的研究

采用ICP－AES法对钛基复合材料中的合金元素镍、钕、铁的测定进行了研究，着重进行了基体元素及待测元素镍、钕、铁之间干扰试验及各元素在测定浓度范围内的线性相关性试验，进行了酸度试验，测定了钛基复合材料中3种元素的含量，得到了较好的精密度和准确度。方法简便、可靠，获得满意的分析结果。