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改革开放30年以来,我国经济发展取得了巨大成就。其中重要的一个标志体现在城市的发展,城市化进程加快,城市用地规模急剧扩大,城市人口迅速增加。然而在‘系列的增长的背后,也给我国带来了日益严重的城市环境问题,在我国城市环境管理的道路上,应该怎么管理,采取何种对策,这将是本文探讨的问题。 相似文献
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研究了预时效处理工艺对汽车用6016铝合金板烘烤硬化性能的影响,试验结果表明,经过预时效处理可明显改善人工时效过程中合金软化现象。160℃、7 min预时效处理后板材硬度值高于T4态且呈现增长趋势,有效的抵消了自然时效过程中的合金软化现象。DSC结果表明,预时效处理可加快Mg2Si相析出速度,提高人工时效效果。拉伸结果表明,预时效后烤漆试样屈服强度达到321 MPa,相比自然时效烤漆试样硬度提高了60 MPa,降低自然时效对板材烤漆硬化性能的影响。对6016铝板材采用固溶处理+预时效+烤漆硬化工艺流程,有利于获得良好的板材冲压成形性能以及烘烤硬化处理效果。 相似文献
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Photoluminescence enhancement of YAG:Ce~(3+) phosphor prepared by co-precipitation-rheological phase method 总被引:1,自引:0,他引:1
YAG:Ce3+ phosphor was prepared by a novel co-precipitation-rheological phase method.The resulting YAG:Ce3+ phosphor was characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM) and photoluminescent emission spectra.By using acetic acid as solvent,YAG:Ce3+ powder with small particle size(≤2 μm) was obtained at a relatively lower sintering temperature of 1400 oC.With the content of acetic acid increasing,small particles dissolved and disappeared,but larger particles grew up and changed its shape from spherical to partially rectangular.Meanwhile,the emission intensity of the sample prepared by co-precipitation-rheological phase method was about 43% higher than that of the sample prepared by co-precipitation method.It was assumed that the significant improvement of luminescence was mainly because the rheological phase presented a better diffusion environment,and therefore,a better homogeneity of activators of Ce3+. 相似文献
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根据推导出的局部坐标系下曲线线路测设点直角坐标计算公式,利用CASIO fx-4800P计算器的编程功能,计算出测设点与置镜点的距离及测设方向与后视方向的夹角,然后利用全站仪测设点位,以推广CASIO fx-4800P计算器在测量中的应用。 相似文献
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