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在新学期即将开始的时候,我们向同学们简要地介绍一下“数字电子技术基础”课的特点、主要内容和学习方法。一、课程的主要特点数字电子技术基础和模拟电子技术基础一样,也是一门实践性很强的课程,两者有许多共同之处,然而也有着明显的区别。1.在模拟电子电路中,工作的信号是模拟信号,这种信号在时间上和数量上都是连续的。而在数字电子电路中,工作的信号则是二进制的数字信号,这种信号在时间上和数量上都是离散的,其取值只有“1”和“0”两种可能,反映到电路上就是高电平和低电平。 相似文献
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当前,小学作文教学在探索中不断前进,在前进中不断探索,取得了许多可喜的成就;但是也还存在着两种令人忧虑的现象。其一是有人认为:“文无定法,只能靠自己去摸索,熟能生巧。”于是,作文课只是出一个题目叫学生去写,不加任何指导,任其“自由发展”。批改作文,也只是将病句、错别字改改,笼统地写上“较 相似文献
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The functional piezoelectric ceramic smart aggregate(SA) sensors and actuators,based on piezoelectric ceramic materials such as lead zirconium titanate(PZT),were embedded into the reinforced concrete beams with three-point bending under static loading for purposes of damage detection.The SA actuators generated the desired sine sweep excitation signals online and the SA sensors received and detected real-time signals before and after damage.The wavelet analysis and statistical characteristics about damage signals were used as a signal processing and analysis tool to extract the optimal damage information and establish a statistical damage detection algorithm.The damage index-based wavelet analysis and damage probability-based probability and statistics were proposed by PZT wavebased theory and active health monitoring technology.The results showed that the existence of cracks inside largely attenuated the amplitude of active monitoring signal after the damage of beam and the attenuation was related to the severity degree of damage.The innovative statistical algorithm of damage pattern detection based PZT-SA can effectively determine damage probability and damage degree,and provide a prediction for the critical damage location of reinforced concrete structures.The developed method can be utilized for the structural health comprehensive monitoring and damage detection on line of various large-scale concrete structures. 相似文献
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阎石 《全国优秀作文选(高中)》2000,(10)
终于,我也走进了高三。带着彷徨、忧郁、畏惧,我走进了高三。曾几何时,每当我从远处眺望高三这片陌生的界域时,它总是那样朦胧,那样神秘,还有一种让人敬畏的感觉。于是,我便向曾经的高三学生们询问,它究竟是怎样的。答案却不一:有人说它是戈壁,淡漠、枯荒;有人说它是 相似文献
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