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学习平面解析几何的读者一定解决过许多与椭圆离心率相关的问题,并熟悉一些相关的特殊值,但也许并未留意过(更少研究过)每个特殊值背后所蕴含的丰富深刻的本质内涵和形形色色的背景特征.作为研究性学习与数学兴趣小组活动的极好素材,本文旨在通过对椭圆离心率的几种特殊值的种种背景研究,揭示其趣味性、广泛性、深刻性,以利于培养学生综合应用与创新思维的能力. 相似文献
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利用北京同步辐射光源,对居里点在室温附近的掺铁钽铌酸钾光折变晶体进行了X射线白光形貌术研究.观察显示,晶体内部除了杂质偏析物和一组沿[010]方向的生长层外,还有一组与之正交的畴组态,后者被发现不满足一般面缺陷的衬度消光规律,仅有异常散射效应揭示其衬度.利用同步辐射波长的可调谐性,揭示了该组畴随波长改变其衍时衬度变化的规律,而且畴的衍射强度被发现违背Friedel定律.依据实验证据,这组畴被确认为180°铁电畴.对畴形成原因和晶体生长特性进行了讨论. 相似文献
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重在提高辨析能力-排列、组合应用题教学有感蒋建华(江苏海安高级中学226600)在历年数学高考中,“排列、组合应用题”一直作为考查考生分析问题、解决问题能力以及数学应用意识的极好素材.由于这部分内容与其它数学知识相比,不论是思想方法还是解题方法均较为... 相似文献
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Near-field thermophotovoltaic systems functioning at 400-900 K based on graphene-hexagonal-boron-nitride heterostructures and thin-film InSb p-n junctions are investigated theoretically.The performances of two near-field systems with different emitters are examined carefully.One near-field system consists of a graphene-hexagonalboron-nitride-graphene sandwiched structure as the emitter,while the other system has an emitter made of the double graphene-hexagonal-boron-nitride heterostructure.It is shown that both systems exhibit higher output power density and energy efficiency than the near-field system based on mono graphene-hexagonal-boron-nitride heterostructure.The optimal output power density of the former device can reach 1.3 × 105 W/m2,while the optimal energy efficiency can be as large as 42% of the Carnot efficiency.We analyze the underlying physical mechanisms that lead to the excellent performances of the proposed near-field thermophotovoltaic systems.Our results are valuable toward high-performance moderate temperature thermophotovoltaic systems as appealing thermal-to-electric energy conversion(waste heat harvesting) devices. 相似文献
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利用同步辐射对天然金刚石晶体进行了形貌学研究,在近完事晶体内观察到晶体以平行{100}生长为主的正常生长,而不是前人所常见的平行{111}生长。生长带方向平行于(100)、(100)和(010)、(010)。生长带分布在偏离晶体中心的曲面内。由生长带的分布与形态可以观察到晶体不同晶面的生长速度具有明显差异。 相似文献
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