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长期湿热老化对塑料的影响 被引量:3
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作者 j. r. martin r. j. GArDNEr 董志鸿 《合成材料老化与应用》 1983年第1期34-51,共18页
在老化试样的试验周期从十个月到三年的规划中,评价了30多种塑料的耐湿热性能。本试验中包括了热固性和热塑性塑料。所有这些材料除了吸水作用降低玻璃化转变温度足够引起畸变的外,均能在中温高湿下短期间使用。其中有几个商业产品在接... 在老化试样的试验周期从十个月到三年的规划中,评价了30多种塑料的耐湿热性能。本试验中包括了热固性和热塑性塑料。所有这些材料除了吸水作用降低玻璃化转变温度足够引起畸变的外,均能在中温高湿下短期间使用。其中有几个商业产品在接近100℃下呈现优良的长期耐湿热性能。但有些长期曝露在湿热条件下发生降解。能够预期这种水解效应能导致使用寿命远比以传统的干热烘箱老化试验反映的寿命短。大量基础数据可为湿热环境下使用塑料的选择提供一种依据。 展开更多
关键词 湿热老化 抗张性能 尼龙 屈服强度 抗张强度 力学性能 扯断强度 力学强度 玻璃纤维增强 树脂 聚合物 塑料
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Interacting with Text:The Role of Dialogue in Learning to Read and Write 被引量:25
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作者 j. r. martin David rose 《中国外语》 2007年第5期66-80,共15页
English language teachers in China are expressing growing interest in the model of language provided by systemic functional linguistics and genre theory. This paper offers further insights into the methods developed i... English language teachers in China are expressing growing interest in the model of language provided by systemic functional linguistics and genre theory. This paper offers further insights into the methods developed in this framework,for teaching reading and writing in school and academic contexts. These methods involve carefully planned interactions between teachers and students,that enable all students in a class to successfully practise skills in academic reading and writing. The paper outlines the models of language and language learning that underpin the methods,and illustrates the kinds of classroom interactions used for writing and reading. It concludes with a discussion of the implications of these methods for language teaching in China. 展开更多
关键词 GENRE LITERACY reading writing PEDAGOGY functional LINGUISTICS SCAFFOLDING classroom discourse DIALOGUE
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