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目的:连续多年监测彭州敖平镇川芎药材栽培土壤中重金属镉的含量,分析其对川芎药材中镉含量的影响。方法根据前期研究结果选取敖平镇部分川芎种植地固定采集样品。按照国家标准方法,采取0~20 cm连续根系土柱和川芎药材。采用火焰法对抽样土壤及川芎药材中镉的含量进行检测分析。结果采样区域内土壤中镉含量均符合国家二级土壤环境质量标准;部分土壤中镉的含量呈明显增长趋势。结论川芎种植土壤中镉含量与环境有较高关联,水泥厂粉尘等污染源是土壤中镉含量增加的重要来源。 相似文献
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川芎中有毒重金属元素镉含量超过国家GAP标准,严重影响其出口创汇,也成为制约川芎走向现代化和国际化的瓶颈。介绍了目前对川芎的消化及重金属元素镉的检测方法,并对各方法的利弊进行了分析,从而为准确、高效地检测药材中重金属元素镉的含量提供了有力的参考依据。 相似文献
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In this study, we design periodic grille structures on a single homogenous thin plate to achieve anisotropic acoustic metamaterials that can control flexural waves. The metamaterials can achieve the bending control of flexural waves in a thin plate at will by designing only one dimension in the thickness direction, which makes it easier to use this metamaterial to design transformation acoustic devices. The numerical simulation results show that the metamaterials can accurately control the bending waves over a wide frequency range. The experimental results verify the validity of the theoretical analysis. This research provides a more practical theoretical method of controlling flexural waves in thin-plate structures. 相似文献
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Transformation acoustics are concentrated for the purpose of designing novel acoustic devices to tailor acoustic waves to achieve desirable characteristics. However, these devices require fluid or fluid-like materials with an anisotropic density that generally does not exist in nature. Therefore, we introduce pentamode metamaterials into an alternating multilayer isotropic medium model to build fluid-like metamaterials with an anisotropic density. A 2D acoustic bending based on transformation acoustics is established and investigated to verify our method. This idea provides a method to design broadband and physically realizable acoustic metamaterials with an anisotropic density and is meaningful for the design of acoustic metamaterials. 相似文献
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设计了一种新型高功率光纤隔离器.其以球面透镜和铽镓石榴石(TGG)晶体作为器件核心,能较好地满足高功率光纤激光器的要求.测试结果湿示,在1064±15 nm的范围内,隔离器所能承受的最高功率为45 W,插入损耗(IL)小于0.61 dB,隔离度(JSO)大于24.5 dB. 相似文献
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