家庭听音室的声学设计(三)--分散吸声型简易听音室(下)

如果只使用一种全频带吸声材料，利用赛宾公式一下子即可算出材料用量。材料种类一多，吸声特性各异，配合在一起使用就要考虑相互对材料用量的影响。为了获得预期的混响特性，通常要进行反复的试差计算，才能达到比较满意的结果。下面的计算次序仅供参考，读者也可寻找更好的计算次序。     

要闻回顾

工业和信息化部最新统计数据显示2月份通信业发展保持平稳 工业和信息化部最新统计数据显示，2010年2月份，全国电信业务量完成2203.1亿元，电信主营业务收入完成662.5亿元。     

直面广电网络生存现状,沉着应对三网融合挑战

三网融合这个提法已经十余年了，只有电信在悄无声息地低调实验性、试探性开展一些业务，多数广电企业一直在埋头大睡。2009年也只是在说三网融合如箭在弦，直到关于三网融合的国务院常务会议召开后，广电才有了新的认识。是觉醒还是被吵醒，是沉着应对还是手忙脚乱，是底气十足还是一惊一乍，各地广电人就如同分散管理的广电网络一样，表现不一。无论如何，三网融合，箭已发出，且没有回头路。     

互联网分层或解“中立”困局

＂分层的互联网（Tiered Internet）＂是通信行业提议的一种新的互联网架构,这种架构将允许电信业务提供商将业务量分成不同的层次,这样就可以允许把话音、视频以及重要的行业应用放在＂高速通道＂内,给与它们更大的带宽。     

把握图形特征巧解角度问题

求某一个角的度数是初中数学竞赛考查的一个重要题型.这类问题具有的一个鲜明特点是:条件分散,不易直接运用.解决这类问题的关键是根据图形的不同特征,采取对图形进行不同的变化方式,使分散的条件集中化,从而便于我们揭示其中隐藏的关系,进而可有效地解决有关角度的计算问题.现列举对图形进行变化的几种方式,供参考.     

Solitons and Waves in （2＋l）-Dimensional Dispersive Long-Wave Equation

For a higher-dimensional integrable nonlinear dynamical system, there are abundant coherent soliton excitations. With the aid of an improved projective Riccati equation approach, the paper obtains several types of exact solutions to the （2＋l）-dimenslonal dispersive long-wave equation, including multiple-soliton solutions, periodic soliton solutions, and Weierstrass function solutions. From these solutions, apart from several multisoliton excitations, we derive some novel features of wave structures by introducing some types of lower-dimensional patterns.     

Two classes of fractal structures for the （2＋1）-dimensional dispersive long wave equation

Using the mapping approach via a Riccati equation, a series of variable separation excitations with three arbitrary functions for the (2+1)-dimensional dispersive long wave (DLW) equation are derived. In addition to the usual localized coherent soliton excitations like dromions, rings, peakons and compactions, etc, some new types of excitations that possess fractal behaviour are obtained by introducing appropriate lower-dimensional localized patterns and Jacobian elliptic functions.     

Yield stress measurements and microstructure of colloidal kaolin powders clusterized and dispersed in different liquids

Rheologicat measurements of four colloidal kaolin powders dispersed in water, paraffinic oil and liquid rubber have been done at solid concentration （9 （VS/VL） in the range 8-33%. In quasi-static conditions the yield stress τ° values were derived. An S-shaped relationship between τ° and （9 exists, that allows to evaluate the percolation threshold θc values. In water θc ranges between 29% and 33%, while it is between 17% and 21% in oil and in liquid rubber. In water the microstructure units, i.e. the primary clusters among kaolin crystallites, are denser and bigger than the ones in the two other liquids. Furthermore, in quasistatic condition, the aqueous microstructure units have less tendency to cling together to form a network that can span all over the liquid phase. The different kaolin dispersions at θ equal to 22% are characterized by yield stress ranging between 7.S Pa and 59 Pa in water, 66-250 Pa in oil and 230-770 Pa in liquid rubber. It has been found that for any kaolin types the log τ°/ θ evaluated near to the percolation threshold is a conservative parameter of the three different liquids. These results are useful to design colloidal dispersions with selected microstructure.     

分散体系形成中表面活性剂使用量的判据

通过对甲苯等有机溶剂/水/表面活性剂体系的水基化分散,利用MalvernMicroplus型激光粒度仪对乳化后的分散相粒子大小及其分布进行研究.结果表明,表面活性剂的使用量对分散结果的影响具有局限性,对于具体体系,表面活性剂的临界胶束浓度[CMC(CMC_O+CMC_W)是这种局限性的量化标志,超出CMC的表面活性剂是多余的,对最终的分散结果无作用,同时也会影响分散体系的稳定性.     

无皂相反转乳化法制备高分子水基分散体系

高分子树脂水基分散体系是指高分子树脂以微粒形式分散于水中 ,包括高分子乳液、高分子悬浮液等体系 .由于高分子树脂水基分散体系具有低成本 ,高性能 ,无污染等优点 ,一直受到普遍关注 .高分子树脂乳液一般通过乳液聚合制备 .该方法只适用于由含双键的单体制备的加聚产物 .而在制备缩聚产物的乳液时 ,乳液聚合方法局限性很大 ,而最近发展起来的相反转乳化技术 ,适用于制备包括加聚产物和缩聚产物在内的大多数高分子水基分散体系 ,拓宽了高聚物水基分散体系的范围 [1] .杨振忠等 [2～ 5] 利用相反转乳化技术制备了未固化和可固化的环氧树脂…