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描述了一种适用于机敏材料及其结构中应力、应变等状态探测与损伤估计的新颖的光纤传感阵列,采用的是周期性不对称刻纹多光纤组成的传感阵列,探讨了其信号的神经网络处理方法,给出了BP网的仿真结果。 相似文献
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Induction of angiogenesis during the transition from hyperplasia to neoplasia 总被引:147,自引:0,他引:147
It is now well established that unrestricted growth of tumours is dependent upon angiogenesis. Previous studies on tumour growth, however, have not revealed when or how the transition to an angiogenic state occurs during early tumour development. The advent of transgenic mice carrying oncogenes that reproducibly elicit tumours of specific cell types is providing a new format for studying multi-step tumorigenesis. In one of these models, transgenic mice expressing an oncogene in the beta-cells of the pancreatic islets heritably recapitulate a progression from normality to hyperplasia to neoplasia. We report here that angiogenic activity first appears in a subset of hyperplastic islets before the onset of tumour formation. A novel in vitro assay confirms that hyperplasia per se does not obligate angiogenesis. Rather, a few hyperplastic islets become angiogenic in vitro at a time when such islets are neovascularized in vivo and at a frequency that correlates closely with subsequent tumour incidence. These findings suggest that induction of angiogenesis is an important step in carcinogenesis. 相似文献
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A SERIES of acylic isoprenoid alkanes, of which pristane and phytane are typical, frequently occurs in crude oils, shales, coals, bitumens and so on. It is generally agreed that the primary source of these compounds is the phytyl side chain of chlorophyll(1,2) although the mechanisms of its incorporation into sediments and its subsequent diagenesis, are not completely understood. At present, little is known about the role of kerogen as a source, or sink, of isoprenoid moieties and we report here that the principal isoprenoid, obtained by the high temperature (600 degrees C) pyrolysis of kerogens has been identified as prist-1-ene. 相似文献
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对事故多发点进行改造是减少事故的发生、增强交通安全的重要措施。其中增加标志标线等交通安全设施是常见的改造方式。由于驾驶行为是影响交通安全的重要因素,因此有必要从驾驶员角度对改造效进行评价。研究了某二级公路的事故多发点特点。在现场实验的基础上结合驾驶员眼动注视点的特征分析,分别从驾驶员注视特征、运营速度、改造前后的事故分析,综合评价事故多发点的改造效果。同时分析驾驶员负荷特征,为未来事故多发点的安全改造方案提出可行建议。 相似文献
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