The Zongwulong Shan-Qinghai Nanshan tectonic belt of the northern Xizang Plateau experienced a protracted tectonica history,including the openings and closures of the Proto-and Paleo-Tethyan Oceans.Although the tecton...The Zongwulong Shan-Qinghai Nanshan tectonic belt of the northern Xizang Plateau experienced a protracted tectonica history,including the openings and closures of the Proto-and Paleo-Tethyan Oceans.Although the tectonic belt has been extensively studied,details regarding the tectonic processes involved in its development remain controversial.To better constrain the tectonic processes of this tectonic belt,we conducted detailed field geological mapping,zircon U-Pb geochronology,and whole-rock geochemical and Sr-Nd isotopic analyses.Our results show that intrusive rocks in the tectonic belt crystallized in ca.292-233 Ma,perhaps in an arc/subduction setting.Geochemical and Sr-Nd isotopic data suggest that Early Permian-Late Triassic ultramaficintermediate intrusions were sourced from the enriched mantle,whereas intermediate-acidic rocks were sourced from mixed crust-mantle.We present the tectonic model that involves:(1)Early Devonian-Early Permian intracontinental extension occurred in the northern margin of the Qaidam continent(ca.416-292 Ma);(2)Early Permian-Late Triassic northward subduction of the Paleo-Tethyan Ocean resulted in arc magmatism(ca.292-233 Ma);and(3)subsequent Late Triassic intracontinental extension(ca.233-215 Ma).Our results suggest that the Late Paleozoic-Early Mesozoic development of the Zongwulong Shan-Qinghai Nanshan was related to the opening,subduction,and slab retreat of the Paleo-Tethyan Ocean,which has key implications for the tectonic evolution of the northern Tibetan Plateau.展开更多
作为人们日常生活和休闲娱乐活动的重要场所,城市公园绿地活力的提升对优化公共空间布局、提高居民生活质量及推动城市可持续发展具有重要意义。当前,其已成为城市空间研究的热点议题,研究成果数量和社会关注度持续增长。本研究首先,基...作为人们日常生活和休闲娱乐活动的重要场所,城市公园绿地活力的提升对优化公共空间布局、提高居民生活质量及推动城市可持续发展具有重要意义。当前,其已成为城市空间研究的热点议题,研究成果数量和社会关注度持续增长。本研究首先,基于CNKI(中国知网)和WOS(Web of Science)数据库,使用CiteSpace知识图谱工具,系统分析了城市公园绿地活力研究的演进脉络;其次,根据国家政策导向和文献计量法分析了突变节点,并将其分为3个阶段:初步理论探索阶段(2012年以前)、中期实证阶段(2012—2019年)和信息深化阶段(2019年至今);再次,总结了各阶段的研究重点与发展方向,并识别了当前研究中存在的不足;最后,提出了未来深化路径。展开更多
近年来,随着高频电力电子磁元件不断发展,双有源桥变换器(dual active bridge,DAB)拓扑受到广泛应用。DAB传递功率需要变压器串联较大电感,传统分立磁件方案采用变压器及独立电感串联,功率密度低,而现有磁集成结构存在励磁电感下降、损...近年来,随着高频电力电子磁元件不断发展,双有源桥变换器(dual active bridge,DAB)拓扑受到广泛应用。DAB传递功率需要变压器串联较大电感,传统分立磁件方案采用变压器及独立电感串联,功率密度低,而现有磁集成结构存在励磁电感下降、损耗高等问题。为此,文中研究一种磁芯中柱设置分布式气隙的磁集成结构,建立其励磁电感解析模型,对分立磁件方案、传统磁集成方案与所提结构进行系统比较,并制作样机证明所提结构具有低损耗、小体积等优点;此外,为准确计算该结构漏感并在优化设计中实现漏感精准控制,提出基于双二维法的漏感建模方法。首先,针对所提结构建立主视图和左视图的双二维计算模型,为考虑三维下气隙扩散磁通影响,提出气隙修正系数以改进双二维计算精度;其次,针对影响漏感因素进行系统的参数灵敏度分析,以此进行归一化处理及参数扫描;然后,采用基于蚁群算法的BP神经网络建立漏感计算模型;最后,通过3台样机测试,验证漏感模型的准确性。展开更多
基金supported by the National Natural Science Foundation of China(No.42372256)the Basic Science Center for Tibetan Plateau Earth System(No.41988101)the Second Tibetan Plateau Scientific Expedition and Research Program(No.2019QZKK0708)。
文摘The Zongwulong Shan-Qinghai Nanshan tectonic belt of the northern Xizang Plateau experienced a protracted tectonica history,including the openings and closures of the Proto-and Paleo-Tethyan Oceans.Although the tectonic belt has been extensively studied,details regarding the tectonic processes involved in its development remain controversial.To better constrain the tectonic processes of this tectonic belt,we conducted detailed field geological mapping,zircon U-Pb geochronology,and whole-rock geochemical and Sr-Nd isotopic analyses.Our results show that intrusive rocks in the tectonic belt crystallized in ca.292-233 Ma,perhaps in an arc/subduction setting.Geochemical and Sr-Nd isotopic data suggest that Early Permian-Late Triassic ultramaficintermediate intrusions were sourced from the enriched mantle,whereas intermediate-acidic rocks were sourced from mixed crust-mantle.We present the tectonic model that involves:(1)Early Devonian-Early Permian intracontinental extension occurred in the northern margin of the Qaidam continent(ca.416-292 Ma);(2)Early Permian-Late Triassic northward subduction of the Paleo-Tethyan Ocean resulted in arc magmatism(ca.292-233 Ma);and(3)subsequent Late Triassic intracontinental extension(ca.233-215 Ma).Our results suggest that the Late Paleozoic-Early Mesozoic development of the Zongwulong Shan-Qinghai Nanshan was related to the opening,subduction,and slab retreat of the Paleo-Tethyan Ocean,which has key implications for the tectonic evolution of the northern Tibetan Plateau.
文摘作为人们日常生活和休闲娱乐活动的重要场所,城市公园绿地活力的提升对优化公共空间布局、提高居民生活质量及推动城市可持续发展具有重要意义。当前,其已成为城市空间研究的热点议题,研究成果数量和社会关注度持续增长。本研究首先,基于CNKI(中国知网)和WOS(Web of Science)数据库,使用CiteSpace知识图谱工具,系统分析了城市公园绿地活力研究的演进脉络;其次,根据国家政策导向和文献计量法分析了突变节点,并将其分为3个阶段:初步理论探索阶段(2012年以前)、中期实证阶段(2012—2019年)和信息深化阶段(2019年至今);再次,总结了各阶段的研究重点与发展方向,并识别了当前研究中存在的不足;最后,提出了未来深化路径。
文摘近年来,随着高频电力电子磁元件不断发展,双有源桥变换器(dual active bridge,DAB)拓扑受到广泛应用。DAB传递功率需要变压器串联较大电感,传统分立磁件方案采用变压器及独立电感串联,功率密度低,而现有磁集成结构存在励磁电感下降、损耗高等问题。为此,文中研究一种磁芯中柱设置分布式气隙的磁集成结构,建立其励磁电感解析模型,对分立磁件方案、传统磁集成方案与所提结构进行系统比较,并制作样机证明所提结构具有低损耗、小体积等优点;此外,为准确计算该结构漏感并在优化设计中实现漏感精准控制,提出基于双二维法的漏感建模方法。首先,针对所提结构建立主视图和左视图的双二维计算模型,为考虑三维下气隙扩散磁通影响,提出气隙修正系数以改进双二维计算精度;其次,针对影响漏感因素进行系统的参数灵敏度分析,以此进行归一化处理及参数扫描;然后,采用基于蚁群算法的BP神经网络建立漏感计算模型;最后,通过3台样机测试,验证漏感模型的准确性。
