近地质时期岩石圈板块构造运动的力学分析

运用相对运动的地球动力学理论，把软流圈以上的岩石圈和软流圈以下的地球内圈，作为两个独立的运动单元来考察它们随地球自转时所发生的变化和各自的运动状态。完整的岩石圈碎裂成岩石块之后，它们各自作为独立的单元，在纬向西漂力、经向离极力和洋底扩张力联合作用下，产生相对运动。     

人类圈·智慧圈·人类世

文章讨论了人类圈、智慧圈、人类世及其关系。作为独立地球圈层的人类圈是以人类为自然实体的地球圈层,它是由需求圈、技术圈和思维圈构成的统一整体,它的研究拓宽和加深了人们对地球以及地球科学概念的理解,对推动人地关系的协同共进有着重要的意义。智慧圈强调智力在现代地球演变中的巨大作用,这是重要的,但狭义智慧圈只是人类圈的一个构成部分,而广义智慧圈则是人类地球的一种可能的未来状态。人类世强调人类在地质和生态中的核心作用,这也是重要的,但作为新的地质时代,它是否能在科学上站得住脚,还需要进行论证。     

全球表层系统研究的思考

1900年前后,以徐士、阿尔冈、魏格纳、李四光等为代表的先驱们从不同视角开始了对地球表层的整体性研究。20世纪人造卫星的应用和板块理论的建立,推动了全球整体观思想的发展。进入21世纪后,伴随社会全球化进程,地球整体观在科学前沿领域显示出极为重要的导向作用。在这个思想引导下的广义地球系统科学是关于地球多圈层的整体研究,但由于涉及人类生存的资源、环境、灾害问题的紧迫性,在未来10至20年内地球系统科学的优先领域之一应是整体观指导下的地球表层系统的研究,它涉及大气层、海洋、地壳、生物和人类。目前可列举出4个重大问题:(1)全球变暖引起的大范围灾害与环境变化;(2)以SARS和禽流感为代表的全球性生物病毒传播灾患;(3)影响人类生存的全球性水资源短缺;(4)导致严重损失和全球性影响的大地震的频繁发生。厄尔尼诺现象与地震的相关性,全球大地震十几年尺度的幕式活动与区域间交替变换,十几年尺度的大范围旱、涝交替变换,表明上述全球性异常变化都是地球表层系统整体性动力过程的表现。应从全球尺度研究包含气体、液体、固体的地球表层系统的微动态变化,分析它们与地、水、大气和生物各圈层之间的相互作用及物质与能量交换的关系,加深对地球表层相互联系的系统过程的理解。     

黄河中游的侵蚀环境与植被恢复前景

黄土高原的土壤侵蚀和生态环境问题世界瞩目。在保证蓄水拦沙效益基础上,提高林、草保存率,使植被恢复得到最佳的生态效益,是黄土高原环境整治中亟待解决的关键问题。本文根据黄土高原不同空间地理位置的流域、重点县水文监测资料,研究了气候、地表覆被、土地利用方式的变化对流域侵蚀产沙的影响以及流域产沙与地理环境要素间的耦合关系,定量分析了黄土高原,特别是多沙粗沙区自然与人文要素对流域侵蚀产沙的综合影响和因子的权重分析,并利用天然降雨植被生态需水适宜性系数和林、草恢复度的概念,重点探讨了黄河中游主要产沙区、尤其是多沙粗沙区退耕还林等土地利用方式宏观格局变化与植被恢复前景。研究表明,在植被生长主要依赖天然降雨的黄土高原,生物措施(植被类型)要与自然带相适应,应根据植被恢复度和植被生态需水适应性系数来进行宏观植被的恢复与实施。这是目前在不断增长的人口压力下,进行水土保持,解决好经济发展与环境保护、减少垦殖率与保证老百姓的基本农田、造林种草与植被类型的自然适应性、以及控制泥沙作用中生物措施与工程措施合理布局等诸多矛盾的关键所在。     

基于三维激光扫描仪的建筑物建模应用研究

为分析三维激光扫描仪在建筑物建模方面的精度,针对传统实测的建模方式,采用基于三维激光扫描理论技术对某建筑进行扫描,从其数据获取、数据分析处理,到获得该建筑物的表面三维模型的过程入手,对比、分析与传统测量的建模方法所获得模型的精度及可靠性。结果表明,三维激光扫描仪所获得数据的精度完全达到了预期的要求,且可以大大节省数据建模的时间,突显了三维激光扫描技术的优势,也为三维激光扫描技术在其他领域的应用提供了科学参考。     

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MetroIn在大尺寸天线罩安装测量中的应用

阐述大尺寸天线罩的高精度安装测量方案,基于MetroIn工业测量软件平台对测量数据进行处理和分析,全方位实时指导天线罩的现场安装.通过对一台口径为5m的天线进行防护罩安装测量,验证方案的正确性,表明其理论和技术成功可行.     

各向异性ATI介质剪切位错点源P波远场辐射

假设震源区为ATI介质,传播介质为全空间各向同性介质情况下,给出了剪切位错源P波远场辐射解析表达式,讨论了震源区各向异性对远场P波振幅和震源球的影响。结果表明,震源区裂隙密度,裂隙方位等参数的动态变化导致P波远场辐射花样也随之动态变化,同时也会造成非双力偶百分含量的动态变化。研究认为,在井中对中小地震的非双力偶机制进行...     

Detection of a Satellite Orbiting The Nucleus of Comet Hale–Bopp (C/1995 O1)

This paper reports on the detection of a satellite around the principal nucleus of comet Hale-Bopp. As shown elsewhere, a successful morphological model for the comet's dust coma necessitates the postulation of overlapping jet activity from a comet pair. The satellite has been detected digitally on images taken with the Hubble Space Telescope's Wide Field Planetary Camera 2 in the planetary mode on five days in May–October 1996. An average satellite-to-primary signal ratio is 0.21 ± 0.03, which implies that the satellite is ∼30 km in diameter, assuming the main nucleus is ∼70 km across. To avoid collision, the separation distance must exceed 50–60 km at all times. The satellite's projected distances on the images vary from 160 to 210 km, or 0.06 to 0.10 arcsec. The satellite was not detected in October 1995, presumably because of its subpixel separation from the primary. The radius of the gravitational sphere of action of the principal nucleus 70 km in diameter is 370–540 km at perihelion, increasing linearly with the Sun's distance: the satellite appears to be in a fairly stable orbit. Its orbital period at ∼180 km is expected to be ∼2–3 days, much shorter than the intervals between the HST observations. If the main nucleus should be no more than 42 km across, Weaver et al.'s upper limit, the satellite's orbit could become unstable, with the object drifting away from the main nucleus after perihelion. Potentially relevant ground-based detections of close companions are reported. Efforts to determine the satellite's orbit and the total mass of the system will get under way in the near future. This revised version was published online in July 2006 with corrections to the Cover Date.     

Geography of Protest: Places of Demonstration in Buenos Aires and Seoul

Demonstrations shape the urban landscape and affect the normal functions of a city. They disrupt traffic, make marginalized people and neglected areas visible in city centers, and challenge élite designs of urban landscape both visually and functionally. Demonstrations question élite norms by using city space in nonconformist ways for making claims, and by charging places with demonstrators' own meanings. Differences between Buenos Aires and Seoul show that historically developed conventions and symbolic readings of city space matter in the strategic choice of places to protest. Yet most demonstration sites belong to the same major categories. Demonstrators may gather outside governmental buildings to communicate with the authorities; at centers of commercial activity to appeal to the public; to places that link them historically, culturally or morally with symbolically important events; or at places connected with a particular grievance. Along with local traditions, an internationally shared demonstration culture determines what kinds of places are suitable for demonstrations.