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研究了铋离子掺杂磷铝酸盐玻璃近红外发光与光学碱度的反常现象. 研究发现, 通过改变碱金属离子半径调节玻璃基质光学碱度, 在808 nm激光激发下铋离子位于1300 nm波段的近红外宽带发光强度随光学碱度的增大而增强, 而在690 nm激光激发下得到的1100 nm波段近红外发光强度则随着光学碱度的增大而减弱. 该玻璃1300 nm波段近红外发光强度与光学碱度依存关系与以往报道结果相反, 且也与1100 nm波段发光特性相反. 根据上述结果可以推测玻璃中1100和1300 nm波段的近红外发光源于不同价态的铋离子, 而该玻璃体系的基质结构自还原作用是导致上述现象产生的主要原因. 相似文献
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城镇化是改善城乡二元结构的重要途径,小城镇在城乡统筹发展中的作用日益突出。本文以淮安车桥镇为例,充分考虑欠发达地区小城镇发展动力不足,基础条件差、区域支撑能力弱的特点,在城乡统筹背景下,分析了城镇职能、不同发展阶段的增长机制和发展路径、城乡空间布局、设施配套、以及政策保障等方面内容,为欠发达地区小城镇发展与转型提供有益借鉴。 相似文献
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大都市郊区是城市化近域推进表现最为强烈。也是城乡统筹发展建设中最复杂、最富变化的地区。本文对大都市郊区的空间演变、城镇模式、产业结构、交通组织以及公共设施进行研究,以更好地发挥大都市郊区城镇在城乡统筹发展中的重要作用。 相似文献
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A series of single-phased Ca2Al2SiO7:Eu2+ phosphors were synthesized by the solid-state reaction. Their structure and photolumi-nescence properties were investigated by the X-ray powder diffraction (XRD) and excitation and emission spectra in detail. The emission spectra of Ca2Al2SiO7:Eu2+ phosphors consisted of blue and green band located at419 and542 nm, respectively. The relative intensities of the blue and green emission changed with Eu2+ concentration and were sensitive to the excitation wavelength. The unique photoluminescence property originated from the 4f7→4f65d transition of Eu2+ at different energy levels, on which the effect of the crystal field strength was con-sidered to be tailed by adjusting the host composition. 相似文献
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The up-conversion of Er3+/Yb3+co-doped transparent glass-ceramics 50SiO2-10AlF3-5TiO2-30BaF2-4LaF3-0.5ErF3-0.5YbF3 containing Ba2 LaF7 nanocrystals under the changing of heat treatment temperature and time were investigated.The Ba2 LaF7 nanocrystals precipitated from the glass matrix was confirmed by X-ray diffraction(XRD).The structural investigation carried out by XRD and transmission electron microscopy(TEM) evidenced the formation of cubic Ba2 LaF7 nanocrystals with crystal size of about 14 nm.Comparing with the samples before heat treatment,the high efficiency up-conversion emission of Er3+/Yb3+co-doped samples was observed in the glass-ceramics under 980 nm laser diode excitation.The increase in red emission intensity bands was stronger than the green bands when the crystal size increased.The mechanism for the up-conversion process in the glass-ceramics and the reasons for the increase of Er3+/Yb3+co-doped up-conversion intensity after heat treatment were discussed. 相似文献
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由于中央空调系统的时滞性、时变性、非线性和大惰性等特性,使得当前采用的中央空调负荷预测算法精度并不高,本文在江阴某楼宇空调系统节能改造项目的基础上,从中央空调系统的组成和特性出发,提出了基于支持向量回归机(Support Vector Regression SVR)理论的中央空调负荷预测模型。对项目楼宇历史负荷数据进行分析,分别采用SVR负荷预测模型和BP神经网络负荷预测模型进行了训练和预测。预测结果表明:基于SVR负荷预测模型较BP神经网络负荷预测模型精度更高,具有较强的实用性和可行性。 相似文献
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我校在2009年8月至2010年6月通过对涉外护理专业学生《护理学基础》的双语教学,实践出了适合我校涉外护理学生的护理教学内容和教学方法在学校与中华护士基金会合办的赴英实习,99%通过了考试,成效显著。 相似文献
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