针对红树林叶面积指数(Leaf Area Index,LAI)实地测量难度大、无法快速大范围LAI估算的问题。该研究以广西北部湾红树林为研究对象,以无人机(Unmanned Aerial Vehicle,UAV)和哨兵二号(Sentinel-2A,S2)多光谱影像为数据源,整合原始光谱...针对红树林叶面积指数(Leaf Area Index,LAI)实地测量难度大、无法快速大范围LAI估算的问题。该研究以广西北部湾红树林为研究对象,以无人机(Unmanned Aerial Vehicle,UAV)和哨兵二号(Sentinel-2A,S2)多光谱影像为数据源,整合原始光谱波段、植被指数和组合植被指数构建高维数据集,并进行数据降维和特征优选。定量评估6种机器学习算法(XGBoost、前馈反向传播神经网络(Back Propagation,BP)、支持向量机(SVM)、岭回归(Ridge)、Lasso和弹性网络(ElasticNet))对不同红树林树种LAI的估算能力;探究UAV和Sentinel-2A影像对红树林树种LAI估算的精度差异。研究结果表明:1)基于XGBoost算法构建的模型实现了红树林LAI高精度估算,R^(2)均高于0.70,RMSE均低于0.349;2)在UAV和Sentinel-2A影像下,XGBoost模型对不同红树林树种LAI的估算精度(R^(2))比其他5种模型分别提高了0.105~0.365和0.283~0.540,RMSE降低了0.100~0.392和0.102~0.518;3)UAV影像数据与XGBoost算法构建的模型对海榄雌LAI的估算精度优于其他组合(R^(2)=0.821、RMSE=0.288),Sentinel-2A影像数据与XGBoost算法构建的模型对秋茄和桐花树LAI的估算精度优于其他组合(R^(2)=0.940~0.979、RMSE=0.142~0.104),不同红树林树种LAI的估算精度依次为桐花树>秋茄>海榄雌;4)SNAP-SL2P算法整体性低估红树林LAI值,UAV影像红树林树种LAI的平均估算精度(R^(2)=0.677~0.713)均优于Sentinel-2A影像,实现了不同红树林树种LAI的高精度估算。展开更多
基于Web of Science核心合集数据库,利用VOSviewer和CiteSpace软件,对2000—2020年有关垃圾填埋场污染物的文献进行了计量分析。结果表明:(1)2000—2020年,垃圾填埋场污染物领域的发文量总体呈逐年增加态势,2015年后中国的发文量直线上...基于Web of Science核心合集数据库,利用VOSviewer和CiteSpace软件,对2000—2020年有关垃圾填埋场污染物的文献进行了计量分析。结果表明:(1)2000—2020年,垃圾填埋场污染物领域的发文量总体呈逐年增加态势,2015年后中国的发文量直线上升;(2)中国的机构虽然发文量多,但均篇被引频次不是很高,影响力还有待进一步提升;(3)垃圾填埋场污染物研究的热点包括城市固体废弃物及其处置过程,垃圾渗滤液或污废水中有机污染物的去除、降解,垃圾填埋场周边地表水和地下水中污染物的环境行为,无机污染物氮元素的去除,垃圾填埋场中新污染物的环境行为和去除5大类;(4)垃圾填埋场污染物主要分为重金属和有机污染物两大类,其中重金属在不同环境介质中出现的频次高于有机污染物,填埋气等气态污染物造成的环境问题也不容忽视。展开更多
针对国内外已有的复杂工业产品多学科设计仿真优化框架与平台在多学科模型集成能力、计算能力、协同能力方面的不足,研究和开发国产自主的新一代复杂工业产品多学科设计仿真优化框架与平台UniXDE(unified exploration and design enviro...针对国内外已有的复杂工业产品多学科设计仿真优化框架与平台在多学科模型集成能力、计算能力、协同能力方面的不足,研究和开发国产自主的新一代复杂工业产品多学科设计仿真优化框架与平台UniXDE(unified exploration and design environment)。本平台基于微服务云架构技术构建整体框架,提供低代码仿真优化流程编排、组件化CAD/CAE参数化集成接口、丰富的多学科设计优化算法库、分布式高性能优化计算引擎、可视化计算监控和报告自动生成等功能。通过白车身轻量化、船型优化、飞行器起落架性能优化等工程应用,表明UniXDE可显著提升产品综合性能和设计成功率。展开更多
We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge system.They are studied using a...We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge system.They are studied using an intensified charge-coupled device camera and photomultiplier tubes.The three novel types of patterns are a square pattern with one structure,a square superlattice pattern with four sublattices and a(1/4)K_(grid)(K_(grid)is the basic wave vector of the grid),and another square pattern with a complex inversion discharge sequence.From the application viewpoint,the five types of patterns can be used as plasma photonic crystals(PPCs).Their band diagrams under a transverse-magnetic wave simulated by the finite element method show that there are a large number of band gaps.Compared with the original PC with only a unidirectional band gap,the five types of PPCs have tunable and omnidirectional band gaps,which is very important in controlling the propagation of electromagnetic waves in the mm-wave region.The experimental results enrich the pattern types in the dielectric barrier discharge system and provide a method for obtaining PPCs with symmetry controllability and bandgap tunability.展开更多
文摘基于Web of Science核心合集数据库,利用VOSviewer和CiteSpace软件,对2000—2020年有关垃圾填埋场污染物的文献进行了计量分析。结果表明:(1)2000—2020年,垃圾填埋场污染物领域的发文量总体呈逐年增加态势,2015年后中国的发文量直线上升;(2)中国的机构虽然发文量多,但均篇被引频次不是很高,影响力还有待进一步提升;(3)垃圾填埋场污染物研究的热点包括城市固体废弃物及其处置过程,垃圾渗滤液或污废水中有机污染物的去除、降解,垃圾填埋场周边地表水和地下水中污染物的环境行为,无机污染物氮元素的去除,垃圾填埋场中新污染物的环境行为和去除5大类;(4)垃圾填埋场污染物主要分为重金属和有机污染物两大类,其中重金属在不同环境介质中出现的频次高于有机污染物,填埋气等气态污染物造成的环境问题也不容忽视。
文摘针对国内外已有的复杂工业产品多学科设计仿真优化框架与平台在多学科模型集成能力、计算能力、协同能力方面的不足,研究和开发国产自主的新一代复杂工业产品多学科设计仿真优化框架与平台UniXDE(unified exploration and design environment)。本平台基于微服务云架构技术构建整体框架,提供低代码仿真优化流程编排、组件化CAD/CAE参数化集成接口、丰富的多学科设计优化算法库、分布式高性能优化计算引擎、可视化计算监控和报告自动生成等功能。通过白车身轻量化、船型优化、飞行器起落架性能优化等工程应用,表明UniXDE可显著提升产品综合性能和设计成功率。
基金supported by National Natural Science Foundation of China(No.12075075)the Natural Science Foundation of Hebei Province, China(Nos.2020201016 and A2018201154)。
文摘We report five types of patterns with square symmetry,including three novel types obtained by inserting a specially designed grid photonic crystal(PC)into a dielectric barrier discharge system.They are studied using an intensified charge-coupled device camera and photomultiplier tubes.The three novel types of patterns are a square pattern with one structure,a square superlattice pattern with four sublattices and a(1/4)K_(grid)(K_(grid)is the basic wave vector of the grid),and another square pattern with a complex inversion discharge sequence.From the application viewpoint,the five types of patterns can be used as plasma photonic crystals(PPCs).Their band diagrams under a transverse-magnetic wave simulated by the finite element method show that there are a large number of band gaps.Compared with the original PC with only a unidirectional band gap,the five types of PPCs have tunable and omnidirectional band gaps,which is very important in controlling the propagation of electromagnetic waves in the mm-wave region.The experimental results enrich the pattern types in the dielectric barrier discharge system and provide a method for obtaining PPCs with symmetry controllability and bandgap tunability.
