新元古代末期高家山生物群的生态多样性     

华洪  蔡耀平  闵筱  柴姝  代乔坤  崔再航 《地学前缘》2020,27(6):28-46

新元古代末期是生命演化的关键转折期,也是以微生物占主导的生态系统向显生宙以后生动物占主导的生态系统的转变期,埃迪卡拉纪大型软躯体生物以固着、底栖、食悬浮为特色,普遍缺乏运动能力。作为这一时期特殊代表的高家山生物群,是目前新元古代唯一一个以黄铁矿化三维保存的管状和锥管状化石为主导,兼有骨骼生物、原生动物、钙化蓝细菌类及遗迹化石的多门类生物组合,是研究埃迪卡拉纪末期生命演化和生态系统演变十分重要的载体。本文通过对高家山生物群古生态学的初步研究,揭示出在前寒武纪—寒武纪之交,生态系统已显示一定的多样性。为适应平底面上(level-bottom)微生物席的发育,高家山生物群的许多生物采取了适应性的生存策略,通过黏附或插入微生物席中,营底栖固着食悬浮(如Cloudina、Conotubus)或化学共生(可能的Shaanxilithes)或平躺(如Gaojiashania和Sinotubulites)食碎屑生活。底内遗迹化石表明存在可能的表栖和半内栖、可自由运动、食碎屑的造迹生物。Conotubus中常见的“回春”或“复苏”现象,Gaojiashania和Sinotubulites的身体扭转或生活姿态调整则是对频繁风暴事件的被动适应。  相似文献   

基于手机位置数据的地震灾情指标选择     

庞晓克  聂高众  张昕  李华癑  夏朝旭  范熙伟  魏本勇 《中国地震》2019,35(1):144-157

选取四川阿坝州九寨沟县MS7.0地震、新疆博尔塔拉州精河县MS6.6地震、四川广元市青川县MS5.4地震作为案例分析,绘制活跃Wi Fi数量、无线网络联网设备数量、汇总在线设备数量、活跃基站数量等4种地震灾情指标在地震发生前后数量变化的折线图。根据与地震前1天变化情况的对比分析,验证地震灾情指标的可用性,选取出效果好的指标,这对进一步研究震后快速获取极震区位置、影响场方向等具有重要意义。  相似文献   

Mapping 3D visibility in an urban street environment from mobile LiDAR point clouds     

Yi Zhao  Jianping Wu  Song Shu  Handong Liang  Min Liu 《地理信息系统科学与遥感》2020,57(6):797-812

ABSTRACT

Visibility determination is a key requirement in a wide range of national and urban applications, such as national security, landscape management, and urban design. Mobile LiDAR point clouds can depict the urban built environment with a high level of details and accuracy. However, few three-dimensional visibility approaches have been developed for the street-level point-cloud data. Accordingly, an approach based on mobile LiDAR point clouds has been developed to map the three-dimensional visibility at the street level. The method consists of five steps: voxelization of point-cloud data, construction of lines-of-sight, construction of sectors of sight, construction of three-dimensional visible space, and calculation of volume index. The proposed approach is able to automatically measure the volume of visible space and openness at any viewpoint along a street. This approach has been applied to three study areas. The results indicated that the proposed approach enables accurate simulation of visible space as well as high-resolution (1 m × 1 m) mapping of the visible volume index. The proposed approach can make a contribution to the improvement of urban planning and design processes that aim at developing more sustainable built environments.  相似文献   

The Callander (Auchenlaich) moraine: A new site report for the Western Highland Boundary block of the Quaternary of Scotland Geological Conservation Review (GCR)     

John Lowe  Vanessa Brazier 《Proceedings of the Geologists' Association. Geologists' Association》2021,132(1):24-33

  相似文献   

Intergenerational relations and the power of the cell phone: Perspectives on young people’s phone usage in sub-Saharan Africa     

《Geoforum》2015

Cell phones present new forms of sociality and new possibilities of encounter for young people across the globe. Nowhere is this more evident than in sub-Saharan Africa where the scale of usage, even among the very poor, is remarkable. In this paper we reflect on the inter-generational encounters which are embedded in young people’s cell phone interactions, and consider the wider societal implications, not least the potential for associated shifts in the generational balance of power. An intriguing feature of this changing generational nexus is that while many young people’s phone-based interactions, from their mid-teens onwards, are shifting away from the older generation towards friendship networks in their own age cohort, at the same time they are repositioning themselves – or becoming repositioned – as family information hubs, as a consequence of their phone expertise. The paper draws on mixed-methods research with young people aged c. 9–25 years and in-depth interviews with older age-groups in 24 sites (ranging from high density poor urban to remote rural) across Ghana, Malawi and South Africa.  相似文献   

青藏高原东缘重力导纳模型均衡异常时空特征   总被引：13，自引：7，他引：6       下载免费PDF全文

陈石  王谦身  祝意青  蒋长胜  王武星  卢红艳  刘端法  郭凤义 《地球物理学报》2011,54(1):22-34

青藏高原东缘地处南北地震带,在卫星自由空气重力异常图上对应明显的正负异常梯级带变化特征,沿着异常梯级带分布多条深大断裂,属于构造单元的边界区域.本文利用重力导纳分析方法,计算了该区重力导纳模型均衡异常背景场;通过与Airy模型和弹性板模型的均衡重力异常特征对比,结合地震活动性分布特点,评价均衡重力异常计算结果和选择计算...  相似文献   

基于CCD的高精度水管倾斜仪研制          下载免费PDF全文

杨江  王平 《地震工程学报》2011,33(4):359-362

CCD技术近年来已发展的非常成熟,应用范围广泛.本文介绍了利用CCD技术实现的高精度水管倾斜仪测量系统,其采用非接触式测量方法降低了测量过程中浮子干扰对测量精度的影响,体积小,安装简单,可用于流动观测中.  相似文献   

基于CORS的移动GIS采集系统设计与实现     

方浩天  彭树标 《现代测绘》2011,34(1):37-40

本文介绍了Ntrip协议以及基于该协议通过GPRS向VRS控制中心上传用户授权信息和概略位置并下载差分改正的信息的方法,通过串口模块将RTCM差分改正信息发送到GPS接收机从而实现差分,提高了GPS数据采集的精度。阐述了基于ArcGIS Mobile的移动GIS系统的开发与实现,对开发中的遇到的问题和关键技术进行了总结。  相似文献   

移动道路测量在高速公路养护中的应用研究     

张延波  曲林  于曼竹  殷福忠 《测绘与空间地理信息》2011,34(5):65-66,70

阐述了移动道路测量系统在高速公路养护应用中的关键部分,包括高速公路发展现状的总结、数据采集的作业准备、实测的采集过程、对测区数据的集成处理以及养护系统研发要点等。除总结研究理论外,还对系统研发的各模块组成进行了探讨,为后续实际应用和功能定制打下良好实验基础。  相似文献   

关于建立测绘产品生产过程质量监控系统的研究     

蒋勇  张鑫 《测绘与空间地理信息》2015,(6):92-93

通过分析测绘产品生产过程质量管理现状,阐述了建立生产过程质量监控系统的必要性,并重点介绍了测绘产品生产过程质量管理监控系统的工作流程和具体功能。  相似文献