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近年来涌现了关于"学习困难生"问题的众多研究成果,但是,许多研究大多集中于一般心理学层面上的讨论,而缺乏与具体数学学科的结合.虽然有学者联系到数学学科研究学习困难学生问题,但是针对高中"数困生"的深入研究却很少,尤其是从归因角度研究"数学学习困难生"的转化策略更是少之又少. 相似文献
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Application of Ultra-Compact Single Negative Waveguide Metamaterials for a Low Mutual Coupling Patch Antenna Array Design 下载免费PDF全文
A novel ultra-compact single-negative waveguide metamaterial (WG-MTM) based on a complementary anti- parallel-spiral line (CAPAL) is proposed and investigated by circuit model analysis, electromagnetic simulation and extraction of the effective parameters. The cell is ultra-compact with dimensions of λ0/22.08 × λo/22.08, which advances a step further toward homogenized concept. Two band-gaps attributing to the negative permeability and negative permittivity appear when the CAPAL-WG-MTM cells response to the time-varying perpendicular E-field and parallel H-field, and thus a high decoupling efficiency is obtained. Mutual coupling reduction of about 8.27dB is realized by inserting 7 ×1 CAPSL-WG-MTM cells between two closely placed antenna elements with an edge-to-edge separation of only λ0/19.23. Moreover, the radiation characteristics are improved for both the patch element and the antenna array. A higher front-to-back ratio is obtained for the patch element and an increase of 0.64dB for the gain of the antenna array by using the CAPAL-WG-MTM structure. 相似文献
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羊毛表面改性对拒水拒油整理的作用及机理研究 总被引:1,自引:0,他引:1
应用扫描电镜(SEM)、X射线光电子能谱(XPS)和衰减全反射红外光谱(FTIR-ATR)等现代表面分析技术研究不同改性处理羊毛表面的化学和物理结构特性.SEM研究结果表明,经低温等离子体表面改性或特定化学改性后的羊毛鳞片表面呈现纳米尺度的沟槽和凹凸结构,应用Wenzel公式和Cassie and Baxter公式阐述了表面粗糙度与接触角的关系,揭示了羊毛表面改性对于提高拒水拒油整理效果的原因所在.XPS和FTIR-ATR研究表明,上述物理和化学的表面改性技术使羊毛表面的二硫键氧化断裂和表面类脂物质改性/除去,促进拒水拒油整理剂的吸附和固着.表面改性和拒水拒油整理的协同效应赋予羊毛类荷叶效应,使其呈现超级拒水拒油拒污功能. 相似文献
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傅种孙关于"中学数学基础"的思想初探 总被引:1,自引:0,他引:1
傅种孙 (1 898— 1 962 ) ,字仲嘉 ,江西高安县朱湖村人氏 ,1 92 0年毕业于北京高等师范数理部 ,留附中任教 ,次年任高师数理部讲师 ,1 92 8年升任教授 ,1 93 5年当选为中国数学会评议委员 ,1 945— 1 947年赴英考察 ,回国后任北平师院数学系主任、北京师范大学教务长、副校长 ,1 95 0年任中国及北京市数学会常务理事、《中国数学杂志》(现《数学通报》)总编辑 .傅种孙是土生土长的中国数学家 ,又是有为有守的数学教育家 .从2 0世纪 2 0— 5 0年代 40余年的时间里 ,他亲历数学教育的每个环节 ,通过数学研究 ,译介名著 ,撰写教材 ,一线教学 ,… 相似文献
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火焰原子吸收光谱法间接测定碘:NCP—Cu(Ⅱ)—I^—反应体系 总被引:6,自引:0,他引:6
应用NCP-Cu(Ⅱ)-I~-反应体系,采用火焰原子吸收测定与碘定量反应的铜,从而间接测定碘。对反应体系的显色剂和还原剂用量、pH、稳定时间做了选择试验。方法相对标准偏差<3%,回收率93%~110%。线性范围0~5.0μg·ml~(-1),用于生物试样(海带、紫菜)和药品(西地碘片)中碘的测定,结果满意。 相似文献
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Metamaterial beam scanning leaky-wave antenna based on quarter mode substrate integrated waveguide structure 下载免费PDF全文
In this paper, we first propose a metamaterial structure by etching the same two interdigital fingers on the upper ground of quarter mode substrate integrated waveguide(QMSIW). The simulated results show that the proposed QMSIWbased metamaterial has a continuous phase constant changing from negative to positive values within its passband. A periodic leaky-wave antenna(LWA), which consists of 11 QMSIW-based metamaterial unit cells, is designed, fabricated,and measured. The measured results show that the fabricated antenna achieves a continuous beam scanning property from backward-43° to forward +32° over an operating frequencyrange of 8.9 GHz–11.8 GHz with return loss better than 10 d B.The measured antenna gain keeps consistent with the variation of less than 2 d B over the operating frequency range with a maximum gain of 12 d B. Besides, the measured and simulated results are in good agreement with each other, indicating the significance and effectiveness of this method. 相似文献
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