A variety of environmental problems have been observed in the Changjiang River Estuary and adjacent coastal area, including eutrophication, harmful algal blooms（HABs）, and hypoxia in recent decades. Application of s...A variety of environmental problems have been observed in the Changjiang River Estuary and adjacent coastal area, including eutrophication, harmful algal blooms（HABs）, and hypoxia in recent decades. Application of sedimentary biogenic element indicators on the study of paleoenvironment can reconstruct environmental evolution history of waters. Two 210Pb-dated cores were collected from the Changjiang River Estuary（S3） and adjacent coastal area（Z13）, and total organic carbon（TOC）, total nitrogen（TN）, biogenic silicon（BSi）, total phosphorus（TP） and phosphorus（P） species were analyzed. Three stages of environmental changes are deduced by the nutrient sedimentary records. First, nutrient concentration increased rapidly since the 1950 s, which attributed to agriculture development and overused chemical fertilizers. Second, nutrient concentration kept high and primary production began to promote during the 1960 s to 1980 s, while diatom abundance and proportion began to decline since the 1970 s, accompanied by reduced 23 Si O- concentration and flux from the river. Third, due to several dams and bridges constructed, river runoff and coastal hydrodynamic conditions reduced to a certain extent since the 1990 s, which aggravated the unbalance in nutrient structure. Multi-nutrient proxies in sediment can reflect the natural environm-ental changes as well as influence of human activities.展开更多
激光诱导石墨烯由于其制备便捷,物理化学特性可调节,兼容性强等特点,已被广泛应用于微电子、储能器件和柔性可穿戴设备等领域,获取高质量的激光诱导石墨烯是进一步推广其应用的重要前提。本文重点关注激光诱导石墨烯碳化过程,基于Reax F...激光诱导石墨烯由于其制备便捷,物理化学特性可调节,兼容性强等特点,已被广泛应用于微电子、储能器件和柔性可穿戴设备等领域,获取高质量的激光诱导石墨烯是进一步推广其应用的重要前提。本文重点关注激光诱导石墨烯碳化过程,基于Reax FF反应力场搭建分子动力学模型,通过调整聚酰亚胺热解的控制参数对碳化过程进行了分析,结合分子构型演变和结晶特性分析研究了石墨烯簇的生长机制。仿真结果表明:提高反应温度或延长反应时间有助于增加产物中六元环的数量。基于仿真结论,应用较高的激光功率,降低扫描速度,制备LIG超级电容器,获得了良好的倍率性能(500 m V·s^(-1)扫描速率下保持初始容量的70%)和较低的等效串联电阻(52Ω)。展开更多
基金The Environmental Protection Public Welfare Project of China under contract No.201309008the Environmental Protection Research Project of Zhejiang Province under contract No.200830
文摘A variety of environmental problems have been observed in the Changjiang River Estuary and adjacent coastal area, including eutrophication, harmful algal blooms（HABs）, and hypoxia in recent decades. Application of sedimentary biogenic element indicators on the study of paleoenvironment can reconstruct environmental evolution history of waters. Two 210Pb-dated cores were collected from the Changjiang River Estuary（S3） and adjacent coastal area（Z13）, and total organic carbon（TOC）, total nitrogen（TN）, biogenic silicon（BSi）, total phosphorus（TP） and phosphorus（P） species were analyzed. Three stages of environmental changes are deduced by the nutrient sedimentary records. First, nutrient concentration increased rapidly since the 1950 s, which attributed to agriculture development and overused chemical fertilizers. Second, nutrient concentration kept high and primary production began to promote during the 1960 s to 1980 s, while diatom abundance and proportion began to decline since the 1970 s, accompanied by reduced 23 Si O- concentration and flux from the river. Third, due to several dams and bridges constructed, river runoff and coastal hydrodynamic conditions reduced to a certain extent since the 1990 s, which aggravated the unbalance in nutrient structure. Multi-nutrient proxies in sediment can reflect the natural environm-ental changes as well as influence of human activities.
文摘激光诱导石墨烯由于其制备便捷,物理化学特性可调节,兼容性强等特点,已被广泛应用于微电子、储能器件和柔性可穿戴设备等领域,获取高质量的激光诱导石墨烯是进一步推广其应用的重要前提。本文重点关注激光诱导石墨烯碳化过程,基于Reax FF反应力场搭建分子动力学模型,通过调整聚酰亚胺热解的控制参数对碳化过程进行了分析,结合分子构型演变和结晶特性分析研究了石墨烯簇的生长机制。仿真结果表明:提高反应温度或延长反应时间有助于增加产物中六元环的数量。基于仿真结论,应用较高的激光功率,降低扫描速度,制备LIG超级电容器,获得了良好的倍率性能(500 m V·s^(-1)扫描速率下保持初始容量的70%)和较低的等效串联电阻(52Ω)。
