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151.
The long‐term thermal‐oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
152.
Biphenol monoacrylate (AL) was combined with a traditional hindered phenolic‐based binary antioxidant system to form a ternary stabilization system for the purpose of further improving the thermal–oxidative stability of polyamide 6 (PA6). The thermal stabilization effect of the antioxidant AL on PA6 was studied in terms of the reduced viscosity, the chemical structure, the yellow index, and the mechanical properties. The results showed that the antioxidant AL, with the proper chemical structure, could improve the thermal stability of PA6 effectively through a unique bifunctional stabilizing mechanism. The interaction of the molecules of PA6 with the antioxidant AL was investigated. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
153.
2005年4月9日下午,广州市番禺区灵山镇一在建厂房突然倒塌,三面高约11m的墙轰然倒下,造成4死3失踪28伤的重大安全事故。据了解,该厂房长90m、宽24m、高11m,事发时三面墙已经封顶,只剩下一面墙还差3m多(以上二引自广州《南方都市报》2005年4月10日A04版)。 相似文献
154.
Global adaptive control of nonlinearly parametrized systems 总被引:1,自引:0,他引:1
Xudong Ye 《Automatic Control, IEEE Transactions on》2003,48(1):169-173
In this paper, we consider global adaptive control of nonlinearly parametrized systems in parametric-strict-feedback form. Unlike previous results, we do not require a priori bounds on the unknown parameters, which is as in the linear parametrization case. We also allow unknown parameters to be time-varying provided they are bounded. Our proposed adaptive controller is a switching type controller, in which the controller parameter is tuned in a switching manner via a switching logic. Global stability results of the closed-loop system have been proved. 相似文献
155.
“两步法”求取双目视觉传感器中摄象机位置关系 总被引:2,自引:1,他引:1
根据平行线“消隐点”理论,提出了用于双目视觉传感器自标定的“两步法”。该方法仅需4对消隐点象面坐标便可线性求解出旋转矩阵,再用2个空间点坐标便可线性求解出平移矢量。 相似文献
156.
介绍一种利用径向矢量提取形状特征的方法,着重于分析二维图形的不变性,提出一种带有方向因子的径向矢量描述,该矢量以图形边界弧长为自变量,完整地刻画了图形特点,克服了非凸图形识别中存在的多义性,以归一化的特征矢量的输入,采用三层神经网络为分类器,在字符及军事目标不变性识别中取得了令人满意的结果。 相似文献
157.
Four low rank coals (peat and lignite) and their derived humic acids have been investigated by thel3C CP/MAS/TOSS NMR technique. The NMR analysis indicates that the peat contains a significant amount of unaltered plant components including cellulose, hemicellulose, lignin, waxes, and resins.
Variable contact time and dipolar dephasing experiments were performed on each sample. The data from above experiments, together with normal CP/MAS integration over selected chemical shift range, were used to derive 12 parameters of carbon skeletal structure including the aromaticity.From the ratio of aromatic bridgehead carbons, facp, to the aromatic peripheral carbons, fcpxBp as measured by NMR, the aromatic cluster size may be estimated for each coal. 相似文献
Variable contact time and dipolar dephasing experiments were performed on each sample. The data from above experiments, together with normal CP/MAS integration over selected chemical shift range, were used to derive 12 parameters of carbon skeletal structure including the aromaticity.From the ratio of aromatic bridgehead carbons, facp, to the aromatic peripheral carbons, fcpxBp as measured by NMR, the aromatic cluster size may be estimated for each coal. 相似文献
158.
159.
船体水上防锈漆体系加速试验方法研究 总被引:1,自引:1,他引:0
根据船舶水线漆和船壳漆的使用环境和主要破坏因素,设计了一套以盐雾-人工加速老化(紫外光/冷凝)交替暴露和带人造缺陷样板的加速暴露试验方法为主,结合海水冲刷、附着力等主要力学性能测定的试验方案。对8种国内外船体水上部份防锈漆体系的性能进行综合评定,其结果采用数字量化评分。试验结果表明,该试验方法可在相当短的时间内对各类船体水上防锈漆体系的综合性能作出正确的评定。 相似文献
160.