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901.
磁重联被认为是太阳耀斑的产生机制,本文数值模拟在日冕中发生在磁重联过程,结果表明耀斑环的表观运动是磁重联的自洽结果;由重联点发出的慢激波对耀斑环的加热有贡献;耀斑环的上升并不意味着重联点的上升。 相似文献
902.
903.
MA Xingyu WANG Lanmin WANG Qian WANG Ping ZHONG Xiumei PU Xiaowu LIU Fuqiang XU Xiaowei 《中国地震研究》2020,34(4):469-481
Based on the dynamic triaxial liquefaction test of the loess samples which are taken from Shibei tableland, Guyuan City, Ningxia, China, the characteristics of dynamic strain, dynamic stress and pore water pressure are studied under cyclic loading. Triaxial shear test is conducted immediately after the sample reaches liquefaction point. During the test, the property of the liquefied soil is analyzed through fluid mechanics method, whereby the fluidity of the liquefied soil is represented by apparent viscosity.The results show that the fluidity of liquefied loess changes from "shear thickening" to "shear thinning" as the shear force continues, and the fluidity of liquefied loess is closely related to its structure. In addition, in the process of forming a new stable state, the apparent viscosity and deviant stress change with axial strain in a similar approach. When the sample reaches its stable state, it meanwhile shows a relatively stable apparent viscosity. According to the fluid mechanics and the law of conservation of energy, the slip distance of the liquefied soil is estimated, and the results are in good agreement with the field investigation results. 相似文献
904.
ABSTRACTThis paper presents a brief overview of the geospatial technologies developed and applied in Chang’e-3 and Chang’e-4 lunar rover missions. Photogrammetric mapping techniques were used to produce topographic products of the landing site with meter level resolution using orbital images before landing, and to produce centimeter-resolution topographic products in near real-time after landing. Visual positioning techniques were used to determine the locations of the two landers using descent images and orbital basemaps immediately after landing. During surface operations, visual-positioning-based rover localization was performed routinely at each waypoint using Navcam images. The topographic analysis and rover localization results directly supported waypoint-to-waypoint path planning, science target selection and scientific investigations. A GIS-based digital cartography system was also developed to support rover teleoperation. 相似文献
905.
利用GNSS三维水汽层析技术全天候地获取高时空采样率的水汽垂直分布信息,已成为GNSS气象学中一大研究热点。当前,基于单一导航系统的传统层析方法存在观测数据利用率低、观测分布不均等不足。本文设计和实现了一种顾及边界入射信号的多模水汽层析方法,采用香港CORS网观测数据和无线电探空产品进行精度验证,并详细分析边界入射信号和多模层顶信号的引入对层析水汽结果的改善程度。结果表明:相较于传统GPS层析方法,本文采用的融合两类多模层顶信号和边界入射信号的新水汽层析方法,兼备边界入射信号和多模层顶信号的优点,可得到更高精度和更可靠的三维水汽信息。 相似文献
906.
在ANUSPLIN薄盘光滑样条插值中,高相关协变量的选取决定了插值结果的精确性。本文选取2017—2019年大雾和霾能见度较差的天气过程,利用183个能见度观测站点对能见度进行插值,引入Himawari-8卫星的通道数据和DEM数据作为协变量对能见度的插值结果进行改进,并对能见度插值结果进行对比分析。研究表明,引入Himawari-8数据和DEM数据作为协变量的能见度插值结果在精度上有显著提高,尤其对雾区和霾区的边界范围和纹理的反演更为准确,基于Himawari-8卫星数据和气象监测站点的观测数据,使用协变量的方法进行能见度插值可以做为能见度监测网格化的一种有效途径。 相似文献
907.
908.
为了解河北省雷电灾害事件的时空分布、行业分布、经济损失及人员伤亡等,对2006—2017年(不包括2013、2016年)河北省雷电灾害事件资料进行统计分析。结果表明:河北省近10 a雷电灾害事件呈逐年波动递减的趋势,主要发生在6—8月,占全年雷电灾害事件总数的81.34%,唐山、保定和石家庄市为雷电灾害事件的高发区。雷电灾害事件最为严重的是电力行业达382起,人员伤亡事故主要发生在乡村。 相似文献
909.
Chen Hong-Fei Xu Wen-Yao Chen Geng-Xiong Hong Ming-Hua Peng Feng-Lin 《Solar physics》2001,204(1-2):339-349
In this paper geomagnetic disturbances at middle and low latitudes are discussed by using geomagnetic data of the magnetic
storm of 15–16 July 2000. This storm is a response to the solar Bastille Day flare on 14 July. Generally, the geomagnetic
disturbances at middle and low latitudes during a storm are mainly caused by three magnetospheric–ionospheric current systems,
such as the ring current system (RC), the partial ring current and its associated region II field-aligned currents (PR), and
the region I field-aligned currents (FA). Our results show that: (1) The northward turning of IMF-Bz started the sudden commencement of the storm, and its southward turning caused the main phase of the storm. (2) The PR- and
FA-currents varied violently in the main phase. In general, the field of the FA-current was stronger than that of the PR-current.
(3) In the first stage of the recovery phase, the RC-field gradually turned anti-parallel to the geomagnetic axis from a 15°
deviation, and the local time (Λ) pointed by the RC-field stayed at 16:00. After that, Λ rotated with the stations, and the
RC-field was not anti-parallel to the geomagnetic axis, but 5°–10° deviated. These facts suggest that the warped tailward
part of the ring current decays faster than the symmetric ring current. 相似文献
910.