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81.
The blends composed of polyamide 6 (PA6) and polyamide 66 (PA66) were obtained using two different preparation methods, one of which was the melt‐mixing through a twin‐screw extruder and the subsequent injection molding; and the other, the in situ blending through anionic polymerization of ε‐caprolactam in the presence of PA66. For the former, there existed a remarkable improvement in toughness but a drastic drop in strength and modulus; however, for the latter, a reverse but less significant trend of mechanical properties change appeared. Various characterizations were conducted, including the analyses of crystalline morphology, crystallographic form, and crystallization and melting behaviors using polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC), respectively; observation of morphology of fractured surface with scanning electron microscope (SEM); measurement of glass transition through dynamic mechanical analysis (DMA); and the intermolecular interaction as well as the interchange reaction between the two components by Fourier transform infrared spectrometry (FT‐IR) and 13C solution NMR. The presence and absence of interchange reaction was verified for the in situ and melt‐mixed blends, respectively. It is believed that the transreaction resulted in a drop in glass transition temperature (Tg) for the in situ blends, contrary to an increase of Tg with increasing PA66 content for the melt‐mixed ones. And the two kinds of fabrication methods led to significant differences in the crystallographic form, spherulite size and crystalline content and perfection as well. Accordingly, it is attempted to explain the reasons for the opposite trends of changes in the mechanical properties for these two blends. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1176–1186, 2007 相似文献
82.
首先将无线传感器网络的路由问题转化成求解最小Steiner树问题,然后给出了求解无线传感器网络路由的蚁群优化算法,并对算法的收敛性进行了证明.最后对找到最优解后信息素值的变化进行了分析.即在限制信息素取值的条件下,当迭代次数充分大时,该算法能以任意接近于1的概率找到最优解,并且当最优解找到后,最优树边上的信息素单调增加,而最优解以外边上的信息素在有限步达到最小值. 相似文献
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The spin coating method was used to assemble polymer (Poly (2,5-dibutoxy-1,4-phenylenevinylene)) (DBO-PPV) into the pores of porous alumina which was prepared by anodization. Four peaks in the photoluminescence (PL) spectra of the composite, with contributions from the DBO-PPV and porous alumina, were found. It was also found that the light emitting from the porous alumina could excite the photoluminescence of DBO-PPV. The nanometer effect of the porous alumina can lead to a blue shift of 90 nm of the PL peaks of DBO-PPV. 相似文献
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本文利用85年5—6月间对乌鲁木齐市主要商业区及部分中、小商业区的实地调查资料,对乌市商业中心等级系统进行了定性和定量的分级分类,将全市商业中心划分为五个等级,八组商业中心,对已形成的商业中心分布现状进行了初步探讨,并对今后商业网点的合理布局提出了建议。 相似文献
89.
提出了一种基于模型驱动的元数据管理方案.方案采用了基于模型的形式化描述方法,统一了专业网管子系统间的元数据模式;通过引入模型驱动技术,从元模型的抽象层次消除了不同专业网管子系统之间存在的“信息孤岛”;方案还对综合网管环境下的元数据理论和交换机制进行了研究,并给出了元数据的管理框架以及元数据交换的Java接口映射. 相似文献
90.
Crystal-Orientation Dependent Evolution of Edge Dislocations from a Void in Single Crystal Cu 下载免费PDF全文
The micro-void growth by dislocation emission under tensile loading is explored with focus on the influence of crystal orientations. Based on the elastic theory, a dislocation emission criterion is formulated. It is predicted that the preferential location of dislocation nucleation and its threshold stress are dependent on the crystal orientation. Large-scale molecular dynamics (MD) simulations are also performed for single crystal copper to illustrate the dislocation evolution pattern associated with a nano-void growth. The results are in line with those given by the theoretical prediction. As revealed by MD simulations, the characteristics of void growth at micro-scale depend greatly on the crystal-orientation. 相似文献