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问题是认识世界和改造世界的原始动力,数学科目也不例外.本文中以“相似三角形的判定”一课的教学设计为例,结合问题法应用的两个原则,从“在现实情境中发现数学问题”和“利用新旧知识间的联系生成和解决问题”这两个方面探讨了在数学单元教学活动中运用问题法的实践和探索. 相似文献
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基于Bitaper-LPFG-Bitaper结构的全光纤Mach-Zehnder干涉仪的温度传感特性 总被引:1,自引:1,他引:0
提出并制作出一种基于锥体光纤-长周期光纤光栅-锥体光纤结构的全光纤Mach-Zehnder(M-Z)干涉仪传感器,并对其温度传感特性进行了研究.实验结果表明,固定光纤锥体和长周期光纤光栅的结构,仅改变两个光纤锥体之间的距离,对应不同的M-Z干涉谐振峰呈现出不同的温度传感特性:随着两个光纤锥体之间的距离增加,位于短波长处的谐振峰,传感器的温度灵敏度减小,而位于长波长处的谐振峰,传感器的温度灵敏度增加.当传感器长度为16.5 cm时,在1 680 nm附近的温度灵敏度达到0.102 06 nm/℃.实验结果对于锥体光纤-长周期光纤光栅组合型温度传感器的优化设计具有重要参考价值. 相似文献
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软段对水性聚氨酯结构与性能的影响 总被引:15,自引:0,他引:15
以低聚物多元醇、异氟尔酮二异氰酸酯(IPDI)、亲水单体二羟甲基丙酸(DMPA),乙二胺为主要原料,制备了一组不同组成的聚氨酯乳液。通过粘度测定、粒度分析、力学性能和耐水性能测试、原子力显微镜(AFM)分析,研究了软段类型、软段分子量对乳液及其胶膜性能的影响。结果表明,分子结构规整、易结晶的软段合成的聚氨酯树脂力学性能和耐水性能都较好,对聚己二酸酯而言,分子量减小,其合成的水性聚氨酯拉伸强度提高,耐水性能却有很大程度的下降。 相似文献
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Compact and tunable mid-infrared source based on a 2 μm dual-wavelength KTiOPO4 intracavity optical parametric oscillator 下载免费PDF全文
Using a double resonant KTiOPO 4 (KTP) intracavity optical parametric oscillator operating at degenerated point of 2 μm,we demonstrate a unique mid-infrared source based on difference frequency generation in GaSe crystal.The output tuning range is 8.42-19.52 μm,and a peak power of 834 W for type-I phase matching scheme and 730 W for type-II phase matching scheme are achieved.Experimental results show that this oscillator is a good alternative to the generator of a compact and tabletop mid-infrared radiation with a widely tunable range. 相似文献
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A simplified scheme of bend-induced mode distortion is introduced into bent holey fibres, the distorted mode distribution and mode effective area reduction are investigated using the finite difference method. Numerical results show that the modes of bent holey fibres with small bend radius shift away from the core and are deformed greatly, and the mode areas drop significantly as the bend radius decreases, which severely affects the fibre laser performance. The propagation characteristics of bent holey fibres at given wavelength are determined by fill factor and normalized bend radius. Finally, the transition normalized bend radius that represents the location of the mode area beginning to fall off is obtained. 相似文献
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Continuous-wave green laser with a maximum power of 34 W has been obtained by intracavity frequency doubling with KTP in diode-side-pumped Nd:YAG. The Nd:YAG/KTP green laser has a simple three- mirror V-fold cavity structure. The optical-to-optical conversion efficiency is 9.5%. The instability of the laser is measured when the output powers are near 16, 21, 30, and 34 W after the beam is filtered. At the maximum output power, the M^2 factor is measured to be 8. 相似文献
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