相对分子质量对聚丙烯结晶和熔融行为的影响

在中试装置上合成了一系列相对分子质量不同但相对分子质量分布相似的均聚聚丙烯。利用GPC,MFR,SAXS,DSC等方法考察了相对分子质量对聚丙烯晶体结构、结晶和熔融行为的影响。表征结果显示,相对分子质量越大,聚丙烯注塑样条的片晶越容易沿剪切方向取向,且其片晶厚度和非晶层厚度也越大。随着相对分子质量下降,聚丙烯的结晶温度和熔融温度降低,而结晶度增大。等规聚丙烯的平衡熔点为188.2℃。     

非对称中间包稳态浇铸与换包操作的冶金效果

??To rationally assess and optimize the metallurgical effect of an industrially used three- strand asymmetric tundish?? the mixing characteristics of molten steel with different tundish configurations were investigated by residence time distribution??RTD??curves based on the analysis of fluid flow and temperature distribution at four flow control schemes?? and the behavior of the tundish level was tracked by employing volume- of- fluid??VOF??model. The fluid dynamics behavior of the tundish was studied in term of both steady and unsteady service situations with and without fluid flow control devices?? which made it possible to assess comprehensively the metallurgical effect of the given tundish. The results show that the flow control effect of bare tundish is weak. It is observed that there are distinct short- circuit flow and large proportion of dead zone?? together with the non- uniform temperature distribution and the flow state discrepancy among the three strands?? which will accordingly lead to the quality difference of the bloom castings. The improvements on the fluid flow characteristics and the temperature distribution have been observed in tundish with the combined application of baffles and turbulence inhibitor. The proportion of dead zone is decreased by 13. 28%?? the temperature difference is only 0. 5K among three outlets?? along with an improved fluid flow consistency. Additionally?? studies also show that this arrangement may have large steel level velocity and level fluctuation during ladle change period. That is likely to bring about exposure?? reoxidation and even slag entrainment of molten steel. Attentions should be paid to the control of the ladle change interval?? inlet flowrate and the moment height of liquid level.     

关于主动式建筑能耗检测方法问题的讨论

主动式建筑能耗检测方法是最近提出的一种新建筑能耗检测方法.该方法用相关系数作为建筑能耗的指标.文中对该方法以下几点不完善处进行了分析:在理论推导中忽略了围护结构热容的影响;测试所用的热源形式未作界定;未考虑被测房间邻室的影响;相关系数不能反映建筑节能的比率.     

寒冷地区空调设计中应注意的几个问题

本文针对我国寒冷地区冬季室外空气干燥,气温低且持续时间长的特点,讨论了在这一地区进行舒适性空调设计时,在空气的加热、加湿处理、换热设备防冻和新风的合理利用等方面应注意的几个问题,并提出了解决办法.     

固体核磁在共聚聚丙烯快速分析中的应用

使用固体核磁建立了抗冲聚丙烯二甲苯可溶物含量的快速测试方法,成核剂的加入对测试结果有影响。研究了固体核磁信号与丙丁无规聚丙烯结晶性能的关系,二者线性相关。     

简易通用铣夹具

我们在加工蝶阀转轴,均压球等工件上的四方或六方头时,经常遇到如何提高工效的问题。这类工件的共同特点是生产批量较大,但分度精度要求不高,采用万能分度头做夹具既不经济又不方便。为此,我们设计了简易通用铣夹具,解决了这个矛盾。     

基于模糊数据库构建的听觉定位方法

针对场景分析方法中因高密度参考点和数据采集带来的离线指纹数据库构建工作量大和在线定位复杂度高的问题,提出了一种基于特征模糊C均值聚类的声音位置指纹数据库构建方法。该方法使用少量位置标定参考点建立的模糊数据库来降低特征匹配的计算量,在使用加权K近邻算法定位的同时,根据定位误差大小采用迭代插值算法矫正定位精度偏低的测试点位置。实验结果表明,该方法相较于传统指纹定位方法在减少了数据库构建开销的同时,显著提高了机器人听觉定位系统的精度和效率。     

福建漳州歌剧院结构设计

漳州歌剧院采用的花朵式造型使其结构具有框架柱外倾、大空间的特点,造型复杂.根据建筑造型及功能布局,结构采用了钢桁架与混凝土框架-剪力墙结构相结合的结构体系.对其结构体系、多道防线设置及抗震性能目标进行介绍,对结构整体的受力特性进行总结,重点对设置楼层框架环箍抵抗外倾拉力、关键构件的抗震性能及钢桁架与混凝土结构交接部位处理等关键问题进行论述.结果表明,该结构对建筑形体适应性强,抗震性能良好,满足抗震性能化设计要求,结构安全度较高.