2017年厦门金砖会晤期间气象因素与管控措施对空气质量的影响

2017年厦门金砖会晤期间采取了大气污染临时管控措施,使AQI小时值和日均值均达到了双优的预期目标.本文根据管控措施实施的前、中、后阶段,厦门及周边城市大气污染物浓度的变化,对气象因素和人为因素的影响分别进行分析.结果发现,气态污染物对临时管控措施的敏感性最强,SO2和NO2的降幅（39.9%和25.6%）明显高于PM2.5和PM10的降幅（5.5%和4.8%）,台风外围带来的大风和降水可显著改变大气污染物的周期性变化规律.大气PM2.5组成及SO2/NO2、SO【math395z】/NO【math396z】、OC/EC和WSOC/OC等比值变化显示机动车（尤其是柴油货车）是本地区大气污染物的重要来源.控制变量分析显示,厦门金砖会晤期间气象因素对颗粒物和NO2削减的贡献更大（20.3%）,而临时管控措施对SO2的削减效果更明显（23.2%）,且有一半以上（51%～64%）的大气污染物来自外来源输送.国家重点研发计划(No.2016YFC0502901);;国家自然科学基金(No.41471390);;厦门大学校长基金本科生项目(No.20720162006)~

Impacts of Spartina alterniflora invasion on the benthic food web in the Yellow River Delta during autumn

Spartina alterniflora was introduced into the Yellow River Delta(YRD)in 1990 with the purpose of shore protection and siltation accretion.However,it spread rapidly and became a severe threat to the local coastal wetland ecosystem.To assess the impacts of S.alterniflora invasion on the benthic food web,we sampled the potential food sources of macrobenthos in November 2020,analyzed the trophic level and the benthic food web structure based on stable isotope technique.Results showed that the average delta~(13) C values of macrobenthic food sources followed an order:sediment organic matter(SOM)>S.alterniflora >benthic microalgae >particulate organic matter(POM)>Suaeda salsa.The average delta~(15) N values significantly differed among food sources,ranging from 1.24 to 9.03.The trophic levels of different macrobenthos ranged from 1.73 to 4.19,of which the bivalve species was the lowest one.S.alterniflora and the decayed debris were the most important food sources for macrobenthos,but without any impact on the trophic level structure of macrobenthos.In conclusion,Spartina alterniflora invasion distinctly changed the composition of food sources of macrobenthos through a bottom-up effect,which would probably impact the local food web structure in the YRD wetland

Fast construction of 2D offset curve based on distance field(基于距离场的二维偏移曲线快速生成方法)

提出了一种快速生成二维偏移曲线的方法.对于无自相交的二维多边形曲线，该方法能构造无自相交、保留准确尖锐特征的二维等距偏移曲线.算法的基本思想：先在一个均匀网格上根据给定的曲线采样一个局部有向距离场，然后使用等值线抽取方法从有向距离场中获取偏移曲线.在构造局部距离场时引入3个过滤器，在远离偏移曲线的区域消除大量冗余计算.采用经典MS(marching square)方法抽取初始多边形偏移曲线，通过一个混合解析解和二分搜索方法，快速计算得到偏移曲线与网格边的准确交点.根据最近点位置信息对初始多边形偏移曲线进行简化和特征重构（如尖角和圆弧），构造无自相交、顶点数少、具有尖锐特征、含混合直线和圆弧段的准确偏移曲线.大量数据实例说明该方法性能良好

Porous-Electrode Theory of Lithium Ion Battery: Old Paradigm and New Challenge

本文总结了Newman多孔电极理论的基本内容,提出若干改进思路. 提出基于离子-空穴耦合传输机制描述浓电解质中的离子输运过程,在此基础上引入离子-电子耦合转移反应的思想处理电极材料中的离子传输问题,并通过计算嵌锂材料的离子扩散系数验证其合理性. 总结了描述多孔电极多尺度结构的相关理论和技术,表明均质化方法和基于结构重建的介观模拟方法均能给出比较合理的有效输运参数,从而提高多孔电极理论模拟结果的准确性.A critical review on the porous electrode theory developed by Newman and his colleagues is presented. We propose several ideas for further development of this theory by analyzing its limitations. The classical Newman theory does not consider ion steric effect in describing ion transport in electrolyte solutions, which can be amended by a newly developed ion-vacancy coupled charge transfer model for ion transport in concentrated solutions. Ion transport in solid particles of active materials is essentially an ion-electron coupled transport process, and its rationality is verified by comparing the calculated and experimental diffusion coefficients of Li + ion in intercalation materials. The methods for describing multiscale structures of porous electrodes and the theories of porous structure reconstruction are summarized, and their applications in determining the effective transport parameters are presented and discussed. We would like to point out that further development remains necessary for porous electrode theory, especially with the emerging of new materials and systems to meet high energy and power density. A number of issues associated with/raised by high working current densities should be considered, for instances, nonlinear non-equilibrium mass transportation, overlapping of electrical double layer (EDL) and mass transport layer, the interfacial charge transfer kinetics, the fusion of phase and interface, the phase transformation of electrode materials in the process of charging and discharging, and the coupling among electrochemical, thermal and mechanical properties and processes. It is our consensus to build a universal theoretical framework that can contain electrochemistry, thermodynamics and mechanics in the electrochemical systems, with careful consideration of microscopic mechanisms for charge and mass transfer in different spatial and temporal domains.国家自然科学基金项目(21832004);国家自然科学基金项目(21773175);国家自然科学基金项目(21673163)通讯作者:黄俊,陈胜利E-mail:[email protected];[email protected]:HUANGJun,CHENSheng-liE-mail:[email protected];[email protected].武汉大学化学与分子科学学院,湖北 武汉 4300722.中南大学化学化工学院,湖南 长沙 4100831. Hubei Key Laboratory of Electrochemical Power Sources, Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), Department of Chemistry, Wuhan University, Wuhan 430072, China2. Hunan Provincial Key Laboratory of Chemical Power Sources, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Chin