溶胶-凝胶法制备纳米多孔SiO2薄膜

以正硅酸乙酯(TEOS)为原料，采用旋转涂敷的方法，结合溶胶-凝胶技术在硅衬底上制备超低介电常数多孔SiO₂薄膜.采用两种不同的改性方法对薄膜表面进行改性，傅里 叶变换红外光谱分析发现改性后薄膜中含有大量的—CH₃键，从而减少了孔洞塌陷.用扫 描电子显微镜观察薄膜的表面形貌，发现薄膜内孔洞尺寸在70—80 nm之间.调节溶胶pH值，发现pH值越小凝胶时间越长.对改性样品热处理的结果表明，在300 ℃时介电常数最低达2.05. 关键词： 2')" href="#">多孔SiO₂ 低介电常数 溶胶-凝胶     

Electron Injection by E—Field Drift and its Application in Starting—up Tokamaks at Low Loop Voltage

We propose an innovative method of election injection by E-field drift into a plasma device and discuss its application in starting-up tokamak plasmas at low loop voltage.The experimental results obtained from HT-6M Tokamak are also presented.The breakdown loop voltage is obviously reduced and the discharge performance is improved by using the electron injection method.It could be applied to some other types of plasma device.     

Modification of Boundary Fluctuations by LHCD in the HT—7 Tokamak

Measurements of boundary fluctuations and fluctuation driven electron fluxes have been performed in ohmic and lower hybrid current drive enhanced confinement plasma using a graphite Langmuir probe array on HT-7 tokamak. The fluctuations are significantly suppressed and the turbulent fluxes are remarkably depressed in the enhanced plasma. We characterized the statistical properties of fluctuations and the particle flux and found a non-Gaussian character in the whole scrape-off layer with minimum deviations from Gaussian in the proximity of the velocity shear layer in ohmic plasma. In the enhanced plasma the deviations in the boundary region are all reduces obviously. The fluctuations and induced electron fluxes show sporadic bursts asymmetric in time and the asymmetry is remarkably weakened in the lower hybrid current driving (LHCD) phase. The results suggest a coupling between the statistical behaviour of fluctuations and the turbulent flow.     

Epoxy Resin-Photopolymer Composite with None-Shrinkage for Volume Holography

A novel photopolymer storage medium for holographic storage is presented. In particular, the refractive in-dex of the monomer methyl methacrylate is much lower than that of the binder epoxy resin solidified by m-xylylenediamine, and the material can be developed into samples with dimension stability and high optical quality and thickness of several millimetres or more. Some none-polymeric macromolecule impurity is uniformly mixed into the medium to aid the monomer diffusing and to enhance the diffraction efficiency. A holographic recording medium of 0.8 mm thickness has been fabricated, and relative theoretical analysis and experiments are presented.     

Measurements of Boundary Plasma in Synergy Discharges of IBW and LHCD on the HT-7 Tokamak

By applying ion Bernstein wave (IBW) heating into the lower hybrid current drive (LHCD) plasma, improved confinements have been obtained in the HT-7 tokamak. The central electron temperature was doubled and the storage energy was increased significantly. The core electron density and temperature were broadened and ther profiles near the edge were steepened. A transport barrier has been formed in the vicinity of the limlter radial location. An enhanced shear in poloidal phase velocity was found in the same region with reduction of the fluctuation levels and the coherences between fluctuations. The results suggest that the improved confinement in the IBW and LHCD plasma is at least partially due to the modification of shear in poloidal velocity and then the suppression of fluctuations and fluctuation induced fluxes via de-correlation effect.     

掺CH4的SiCOH低介电常数薄膜结构与介电性能研究

以十甲基环五硅氧烷和甲烷作为反应气体，采用电子回旋共振等离子体化学气相沉积(ECR-C VD)方法制备了k = 2.45，485℃下的热稳定性优良的SiCOH低介电常数薄膜.通过薄膜结构的 FTIR谱分析，比较了十甲基环五硅氧烷(D5)液态源和不同甲烷流量下制备的薄膜的键结构差 异，发现在沉积过程中甲烷含量的增大，一方面有利于D5源环结构的保留，另一方面有利于 薄膜中形成高密度的CH_n基团.高密度碳氢大分子基团的存在降低了薄膜密度， 结合薄膜中形成的本构孔隙、低极化率Si—C键以及—OH键减少的共同作用，导致薄膜介电 常数的降低. 关键词： 低介电常数 SiCOH薄膜 碳氢掺杂     

过渡金属化合物OsB2与OsO2低压缩性的第一性原理计算研究

利用基于密度泛函理论平面波赝势法的第一性原理计算,研究了过渡金属化合物OsB2和OsO2的金红石相、黄铁矿相与萤石相三种结构在高压下的状态方程和结构特性以及OsO2可能的高压相变.理论计算结果支持OsB2与OsO2的萤石相是潜在超低可压缩性的硬性材料.同时,也分析了它们的电子结构,力求理解大体变模量和高硬度的微观机制.结果表明,可以利用过渡金属高的价电子浓度,掺入硼、氧、碳、氮等轻的元素形成强的方向键,这可能提供了一种合成超硬材料的新途径.     

CsI/MCP X射线阴极及其在低强度X射线影像仪中的应用

报道了X射线阴极的光电发射原理,给出CsI／MCPX射线阴极的制作方法。分析了反射式和透射式X射线阴极的量子效率和噪声特点,提出了改进工艺,给出CsI／MCP的输出特性和扫描电镜正面和剖面照片,且指出Lixiscope的发展以及在生物医学中的应用前景。     

第四讲语音信号处理的现状和展望

文章简要介绍了“语音信号处理”这一分支学科形成和发展的历史过程．指出了它在现代信息科学技术中的地位和作用．介绍了语音信号处理在应用领域的一些重要课题，如语音的低速率编码，语音的规则合成和文一语转换系统，语音识别和人一机语音对话等，这些仍然是当前研究的热点．文章最后展望了语音信号处理的发展前景，指出在这个领域还有很多难题等待人们去研究探索．     

无线视频传感阵列低复杂度多视点视频编码方案

基于网络中心节点的运动矢量外推技术,提出了一种无线视频传感阵列的低复杂度多视点视频编码方法。该方法考虑到密集型视频传感阵列各视点间通信复杂、布线繁重、且位于各相机节点内的编码器由于计算能力、功耗等限制难以完成复杂的编码过程等特点,利用运动矢量外推逼近技术将大量的运动估计运算从视频编码端移到了网络中心节点,使得新编解码框架下编码器的运动估计的计算复杂度只有传统全搜索运动估计运算的0.3%,降低了系统传感阵列编码端功耗。实验结果表明,该方法的率失真性能比H.264-I帧高出4 dB以上,接近H.264-P帧编码,优于基于Wyner-Ziv理论的分布式多视点视频编码方法。