The Southwest Pacific GPS Project: Geodetic results from Burst 1 of the 1990 Field Campaign     

B. Schutz  M. Bevis  F. Taylor  D. Kuang  P. Abusali  M. Watkins  J. Recy  B. Perin  O. Peyroux 《Journal of Geodesy》1993,67(4):224-240

The Southwest Pacific GPS Project (SWP) is using the Global Positioning System (GPS) to monitor crustal motion across and within a plate boundary complex between the Australian and Pacific plates. GPS field campaigns were conducted in 1988, 1989 and 1990, to observe networks of increasing size and complexity. The 1990 campaign consisted of two periods, or Bursts, and this paper focuses on the analysis of data collected during the nine day Burst 1 in July, 1990, a period in which GPS Selective Availability was activated. During Burst 1, baselines that spanned the Tonga Trench and the Lau Basin were observed, and only one station (Espiritu Santo, Vanuatu) was located west of Fiji in the network. The lengths of the baselines observed fall mainly between 300 km and 1600 km, but some lines are as long as 3500 km. A total of 78 station-days of field site data and approximately 150 station-days of global fiducial data were processed from predominantly codeless receivers. A global fiducial network of 20 sites was used to provide orbit control and accuracy assessment for the 13 available satellites. The daily solutions for 45 baselines between 10 SWP sites have an RMS scatter in the length of 24 mm plus 6 parts per billion. This scatter provides an estimate of baseline precision for the Burst 1 nominal solution. Experiments were conducted to investigate a variety of possible effects on the SWP Network baseline estimates, including the influence of a reduced global fiducial network for the purpose of assessing the quality of results obtained in 1988 and 1989 in which the fiducial network was smaller than in 1990. These experiments produced results that agreed with the nominal solution at the level of the precision estimate. Furthermore, estimates for selected baselines in Australia, the Central Pacific, North America and Europe, also measured by VLBI and SLR, were used for an external accuracy evaluation. The GPS and VLBI or SLR determinations of length agreed at a level consistent with the nominal solution precision estimate.  相似文献   

数字逻辑理论及其在气象预报集成中的应用     

张选民  文强  邹希云  张家望  匡昌武 《气象》2002,28(6):8-10

以数字逻辑理论为基础，采用逻辑电路设计方法，对二级（0，1）气象要素预报多种方法进行预报集成尝式，效果令人满意。该方法理论依据充分，计算简单，易于编程，为预报集成开辟了一条新的途径。  相似文献   

Adaptive evolution of the rural human–environment system in farming and pastoral areas of northern China from 1952–2017     

LI Wenlong  KUANG Wenhui  LYU Jun  ZHAO Zhonghua  ZHANG Boyuan 《地理学报(英文版)》2021,31(6):859-877

The theory on the cyclic adaptation between society and ecosystems sheds new light on the evolution and internal structure of human–environment systems. This paper introduces the risk index(RI) and adaptation capacity index(ACI) to evaluate the rural human–environment system. An evaluation index system for the adaptability of rural human–environment systems is configured in the context of climate change and policy implementation. On this basis, the stages, features, dominant control factors, and evolution mechanism were examined vis-à-vis the adaptability of the rural human–environment system in Darhan Muminggan Joint Banner from 1952 to 2017. The main results are as follows:(1) The evolution of the rural human–environment system can be divided into three stages, namely, the reorganization and rapid development stage(1952–2002) with population, cultivated land, livestock and degraded grassland increasing by 260%, 13%, 134% and 16.33%, respectively. The rapid to stable development stage(2003–2010) with population increasing by 2.8%; cultivated land, livestock and degraded grassland decreasing by 2.3%, 13.6% and 10.7%, respectively. The stable to release stage(2011–2017) with population, cultivated land, livestock and degraded grassland decreasing by 2.6%, 0.2%, 10.6% and 3.8%, respectively.(2) With the passage of time, the ACI of the rural human–environment system first increased slightly(–0.016–0.031), followed by a slight decline(0.031–0.003), and culminating in a rapid increase(0.003–0.088). In terms of spatial patterns, adaptability is high in the middle, moderate in the north, and low in the south.(3) The evolution of adaptability in the rural human–environment system was mainly controlled by the per capita effective irrigation area(22.31%) and the per capita number of livestock(23.47%) from 1990 to 2000, the desertified area(25.06%) and the land use intensity(21.27%) from 2000 to 2005, and the per capita income of farmers and herdsmen(20.08%) and the per capita number of livestock(18.52%) from 2010 to 2007.(4) Under the effects of climate change and policy interventions, the cyclic adaptation of the rural human–environment system was propelled by the interactions between two kinds of subjects: farmers and herdsmen on the one hand and rural communities on the other hand. The interaction affects the adaptive behavior of the two kinds of subjects, which in turn drives the cyclic evolution of the system. As a result, the system structure and functions developed alternatively between coordinated and uncoordinated states. Small-scale adaptive behaviors of farmers and herdsmen have a profound impact on the evolution of the rural human–environment system.  相似文献   

玉林市低温、霜冻的统计分析     

肖世芳  匡昭敏 《气象研究与应用》2000,21(1):22-24

通过对玉林市各站建站至1999年12月的霜冻及低温日(日极端最低气温≤5℃的低温天气)天气的分析,得出了平均初、终霜日的出现日期和平均低温日的开始和终止日期。  相似文献   

志留纪以来的云开地块   总被引：16，自引：1，他引：15  

吴浩若  邝国敦  王忠诚 《古地理学报》2001,3(3):32-40

桂南－粤西的云开地块,位于特提斯构造带和环太平洋构造带的交汇处。其变质基底仅出露于两广边境的云开大山地区,但古生代海相沉积盖层分布广泛,甚至跨越北部湾。地块北缘的古生代深水沉积带,也延展到越南东北沿海地区。云开地块的范围,可能西起红河三角洲,东达珠江三角洲。晚古生代时,它可能为地处南纬低纬度海域的碳酸盐台地。古南海于中晚二叠世开始张开,使云开地块北移,与大明山地体碰撞,形成云开北缘的造山带。中晚三叠世,古南海的进一步扩张和桂西－越北的古特提斯向南消减,又形成晚二叠世造山带以北的印支期岩浆弧和磨拉石。也是东古特提斯闭合过程的重要部分。新生代早期南海张开前,古南海北侧的南沙地块可能和云开地块相接,总面积可能超过50万km2,在东南亚地质演化中起重要作用。  相似文献   

GIS在农业生态地质调查中的应用   总被引：1，自引：0，他引：1  

宋泽峰  栾文楼  崔邢涛 《化工矿产地质》2005,27(4):221-225

GIS凭借其所具有的科学可视化功能,区域性、多层次、易操作等特点,能够将各种空间、 数字数据分类存储并进行分析,以上优点使GIS能够在农业地质调查项目中起到存储信息、分析态 势、辅助决策等重要作用,并能够在此基础上建立数据库辅助管理决策系统,在农业生态地质调查 中发挥了巨大作用。  相似文献   

Numerical studies of vertical Cl−, δ2H and δ18O profiles in the aquifer–aquitard system in the Pearl River Delta,China          下载免费PDF全文

Xingxing Kuang  Jiu Jimmy Jiao  Kun Liu 《水文研究》2015,29(19):4199-4209

Sedimentation may have a significant effect on the transport of solutes and environmental isotopes in sediment. The depth profiles of the Cl^?, δ²H and δ¹⁸O in a borehole in the aquifer–aquitard system in the Pearl River Delta (PRD), China, were obtained by centrifuging the core sediment samples. A one‐dimensional model based on the sedimentation and sea level changes of the PRD during the Holocene was built to investigate numerically the transport mechanisms of Cl^?, δ²H and δ¹⁸O. The sedimentation process was modelled as a moving boundary problem with the moving rate equal to the sedimentation rate. The model was calibrated and the parameters were obtained by comparing simulated and measured data. Very good agreement between all the three observed profiles and the simulated ones demonstrates the reliability of the model and the parameters. Simulation results show that the shapes of the curves are controlled by the combination of sedimentation and upper boundary conditions. Diffusion solely is adequate to reconstruct the observed profiles, which indicates that diffusion is the dominant vertical transport mechanism. The effective diffusion coefficients of the aquitard and the aquifer equal to 5.0 × 10^?11 and 2.0 × 10^?10 m²/s, respectively. The results of this study will help in understanding the transport mechanisms of solutes and environmental tracers in deltas with geology and hydrogeology similar to the PRD. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

地理学视角下数字创业生态系统的理论框架和研究展望     

汪明峰  匡爱平  计怡村 《地理科学》2023,43(1):31-40

中国数字经济方兴未艾,推动数字创业生态系统发展成为社会各界关注的热点议题。在系统梳理有关创业研究的相关文献基础上,建构地理学视角下的数字创业生态系统研究框架,探究数字化嵌入到创业过程中各行动主体的构成,以及新要素建构创业生态系统的空间过程和机制,并且分析总结数字创业生态系统与地方发展的交互动态。最后基于中国情境,着眼于中国创业发展的地方实践,提出未来的研究展望,以期为数字化时代创业地理学研究提供新的理论视角,也为指导中国创新创业发展提供实践指引。  相似文献   

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¬����  �����  �Ž���  ����� 《大地测量与地球动力学》2014,34(6):44-49

???????????TEC????????????????????SSA????????TEC????У???SSA??????????????????ARMA???????????????????????????????IGS????2010??????TEC?????????飬???????????????????????5 d??TEC????????????92%???????ARMA??????4%??  相似文献   

济南市人口城市化和土地城市化的关系研究     

刘匡  王璐 《山东国土资源》2014,30(12)

改革开放以来,济南市社会经济发展迅速,城市化水平大幅度提高。选取济南市1996—2010年间的总人口、非农业人口、建成区面积等相关数据,运用Excel和SPSS对数据进行处理和相关分析,定量地探讨了济南市人口城市化和土地城市化之间的关系。研究结果表明,济南市的土地城市化速度明显快于人口城市化速度,并因此导致一系列的社会、经济等问题,并在对这些问题的分析基础上提出了相应的对策建议。  相似文献