Graphitic nanofillers in PMMA nanocomposites—An investigation of particle size and dispersion and their influence on nanocomposite properties

Mechanical, thermal, and electrical properties of graphite/PMMA composites have been evaluated as functions of particle size and dispersion of the graphitic nanofiller components via the use of three different graphitic nanofillers: “as received graphite” (ARG), “expanded graphite,” (EG) and “graphite nanoplatelets” (GNPs) EG, a graphitic materials with much lower density than ARG, was prepared from ARG flakes via an acid intercalation and thermal expansion. Subsequent sonication of EG in a liquid yielded GNPs as thin stacks of graphitic platelets with thicknesses of ～10 nm. Solution‐based processing was used to prepare PMMA composites with these three fillers. Dynamic mechanical analysis, thermal analysis, and electrical impedance measurements were carried out on the resulting composites, demonstrating that reduced particle size, high surface area, and increased surface roughness can significantly alter the graphite/polymer interface and enhance the mechanical, thermal, and electrical properties of the polymer matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2097–2112, 2007     

Solvothermal synthesis of TiO2: anatase nanocrystals and rutile nanofibres from TiCl4 in acetone

This work reports a new synthetic approach for single‐phase TiO₂ nanomaterials by solvothermal treatment of titanium tetrachloride in acetone at 80–110 °C. Small, uniform, and yet size‐tunable (5–10 nm) anatase titania nanocrystallites were obtained using a low concentration of TiCl₄ in acetone (i.e., at molar ratios of TiCl₄/acetone ≤ 1:15) in the temperature range of 80–110 °C, while rutile nanofibers were synthesized using a high concentration of TiCl₄ (e.g., TiCl₄/acetone = 1:10) at 110 °C. Copyright © 2007 John Wiley & Sons, Ltd.     

会议电视系统及其发展现状

讨论会议电视系统的组成，种类及设计标准，介绍其发展现状及应用中存在的问题。     

求通信网生存能力的一种分裂二叉树算法

本文研究了布尔代数方法在通信网生存能力分析中的应用，提出了一种求布尔代数式不交化变换的分裂二叉树算法，与现有的同类算法相比，该算法具有结构清晰、执行效率高、易于实现等优点。     

A numerical study of an unsteady laminar flow in a doubly constricted 3D vessel

Unsteady flow dynamics in doubly constricted 3D vessels have been investigated under pulsatile flow conditions for a full cycle of period T. The coupled non‐linear partial differential equations governing the mass and momentum of a viscous incompressible fluid has been numerically analyzed by a time accurate Finite Volume Scheme in an implicit Euler time marching setting. Roe's flux difference splitting of non‐linear terms and the pseudo‐compressibility technique employed in the current numerical scheme makes it robust both in space and time. Computational experiments are carried out to assess the influence of Reynolds' number and the spacing between two mild constrictions on the pressure drop across the constrictions. The study reveals that the pressure drop across a series of mild constrictions can get physiologically critical and is also found to be sensitive both to the spacing between the constrictions and the oscillatory nature of the inflow profile. The flow separation zone on the downstream constriction is seen to detach from the diverging wall of the constriction leading to vortex shedding with 3D features earlier than that on the wall in the spacing between the two constrictions. Copyright © 2002 John Wiley & Sons, Ltd.     

ISDN的现状和发展

９０年代将是ＩＳＤＮ和宽带ＩＳＤＮ迅速发展的年代，本文介绍了国外Ｎ－ＩＳＤＮ和Ｂ－ＩＳＤＮ的发展动向，并结合我国通信网的现状，对发展ＩＳＤＮ（Ｂ－ＩＳＤＮ）提出若干建议。     

四方向上的任意角度扇形数字滤波器的设计

具有任意角度（扇形所围成的角度）和任意方向（扇形所取方向）的扇形数字滤波器在图像数据压缩和地质、地震等方面的数据处理中有着广泛的应用。目前，大多数的工作多集中于水平及垂直方向的９０°扇形数字滤波器的设计，因而有必要研究任意方向上的任意角度的扇形数字滤波器的设计。本文介绍利用ＭｃＣｌｅｌｌａｎ交换法设计具有垂直，水平及±４５°方向上的任意角度的扇形数字滤波器的设计方法，垂直水平方向上的扇形滤波器的设     

IPA模型对Hopfield模型神经网络的改进

考虑Ｈｏｐｆｉｅｌｄ模型中假态之间的布尔逻辑关系，提出利用ＩＰＡ模型对神经网络中的假态进行抑制，并和原网络的性能进行了比较，结果表明：改进后的网络性能比Ｈｏｐｆｉｅｌｄ模型和ＩＰＡ模型均有较大提高。     

介质加载圆柱腔的场分析

本文应用严格场匹配法解决了介质加载圆柱腔的本征问题，计算了圆柱腔在纵向部分填充介质后ＴＥ０１ｎ模和ＴＭ０１ｎ模的本征频率和本征场型的变化。特别分析了本征模式在空气段为截止模的情况。本文的分析方法亦可应用到纵向部分填充介质的传输线和其它形状的谐振腔。     

陶瓷传感器的微型化与集成化

本文主要介绍陶瓷传感器在微型化及集成化方面的进展；指出了集成化多功能传感器存在的技术问题及未来发展趋势。