利用空间投影理论求解RPC模型     

樊沛  黄文骞  于彩霞 《海洋测绘》2007,27(6):8-11

利用遥感影像成像时的空间投影模型并顾及全球DEM建立了一组虚拟的三维控制点,用于求解RPC模型,解决了控制点数量严重不足时RPC模型的求解问题。试验证明该方法理论严密、精度较高。  相似文献   

气候变化科学方面的几个最新认知   总被引：1，自引：0，他引：1  

翟盘茂  周佰铨  陈阳  余荣 《气候变化研究进展》2021,17(6):629-635

IPCC第六次评估报告(AR6)第一工作组报告主要从以下几个方面的进展提升了我们对气候系统变化、气候变化原因以及预估未来气候系统变化等方面的认知,对过去气候变化及其与人类活动的关系有了更加清晰、可靠的认识.综合多重证据评估指出,全球气候正经历着前所未有的变化;包括极端事件在内的归因进展已把人类活动对气候系统影响的认识从...  相似文献   

如何提高调绘质量     

谷锦平 《测绘与空间地理信息》2008,31(3)

从生产实际出发,对基于航测法成图原理和全数字摄影测量工作站的功能,进行调绘片制作的方法及其基本内容进行了阐述,从中得到提高目前调绘质量和效率的较好办法。  相似文献   

A stabilized extended finite element framework for hydraulic fracturing simulations          下载免费PDF全文

Fushen Liu  Peter Gordon  Holger Meier  Dakshina Valiveti 《国际地质力学数值与分析法杂志》2017,41(5):654-681

We present a stabilized extended finite element formulation to simulate the hydraulic fracturing process in an elasto‐plastic medium. The fracture propagation process is governed by a cohesive fracture model, where a trilinear traction‐separation law is used to describe normal contact, cohesion and strength softening on the fracture face. Fluid flow inside the fracture channel is governed by the lubrication equation, and the flow rate is related to the fluid pressure gradient by the ‘cubic’ law. Fluid leak off happens only in the normal direction and is assumed to be governed by the Carter's leak‐off model. We propose a ‘local’ U‐P (displacement‐pressure) formulation to discretize the fluid‐solid coupled system, where volume shape functions are used to interpolate the fluid pressure field on the fracture face. The ‘local’ U‐P approach is compatible with the extended finite element framework, and a separate mesh is not required to describe the fluid flow. The coupled system of equations is solved iteratively by the standard Newton‐Raphson method. We identify instability issues associated with the fluid flow inside the fracture channel, and use the polynomial pressure projection method to reduce the pressure oscillations resulting from the instability. Numerical examples demonstrate that the proposed framework is effective in modeling 3D hydraulic fracture propagation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Projection of glacier runoff in Yarkant River basin and Beida River basin,Western China     

Shiqiang Zhang  Xin Gao  Xiaowen Zhang  Stefan Hagemann 《水文研究》2012,26(18):2773-2781

Potential changes in glacier area, mass balance and runoff in the Yarkant River Basin (YRB) and Beida River Basin (BRB) are projected for the period from 2011 to 2050 employing the modified monthly degree‐day model forced by climate change projection. Future monthly air temperature and precipitation were derived from the simple average of 17, 16 and 17 General Circulation Model (GCM) projections following the A1B, A2 and B1 scenarios, respectively. These data were downscaled to each station employing the Delta method, which computes differences between current and future GCM simulations and adds these changes to observed time series. Model parameters calibrated with observations or results published in the literature between 1961 and 2006 were kept unchanged. Annual glacier runoff in YRB is projected to increase until 2050, and the total runoff over glacier area in 1970 is projected to increase by about 13%–35% during 2011–2050 relative to the average during 1961–2006. Annual glacier runoff and the total runoff over glacier area in 1970 in BRB is projected to increase initially and then to reach a tipping point during 2011–2030. There are prominent increases in summer, but only small increase in May and October of glacier runoff in YRB, and significant increases during late spring and early summer and significant decreases in July and late summer of glacier runoff in BRB. This study highlights the great differences among basins in their response to future climate warming. The specific runoff from areas exposed after glacier retreat relative to 1970 is projected to general increasing, which must be considered when evaluating the potential change of glacier runoff. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Tides—a modern perspective     

Lakshmi H. Kantha 《Marine Geodesy》2013,36(4):275-297

Progress in tidal science has been rapid in recent years. The advent of precision altimetry has enabled, for the very first time in tidal history, an accurate measurement of tides in most of the global oceans. This has revolutionized our knowledge of tides and tidal processes. Combined with high‐resolution numerical models of tides (and other recent advances in astronomy and geodesy), this increased knowledge is providing valuable assistance in effecting closure on many outstanding problems in this three‐centuries‐old science. For example, we now know the dissipation rate of lunar tides to be 3.17 TW to within 2%. However, there do remain some outstanding issues. While we know the rate at which tidal energy is being dissipated in the global oceans, there is still considerable uncertainty as to the mechanisms, locations, and magnitudes of various tidal energy sinks. Imminent advances in shallow‐water barotropic and deep‐water baroclinic tides hold the prospect of a better understanding of these also. Improved knowledge of oceanic tides and high‐precision satellite measurements of tides are enabling better assessment of some matters of geophysical interest, such as the anelasticity and the length‐of‐day fluctuations of the Earth's mantle. It has been possible to map long‐period lunar tides more accurately and derive their contribution to the Earth's rotation rate fluctuations and its anelasticity at these frequencies. We discuss various aspects related to tides, including tidal dissipation and its consequences, as well as several other topics such as tidal energetics, internal tides, and long‐period tides, where considerable progress has been made in the last decade. Both oceanographic and geophysical implications are mentioned.  相似文献   

南极中山站极区空间环境观测系统   总被引：1，自引：0，他引：1       下载免费PDF全文

黄德宏胡红桥  刘瑞源杨惠根胡泽骏  刘建军何昉刘勇华  韩德胜 《极地研究》2016,28(1):1-10

中国南极中山站位于极隙区纬度,可以观测到丰富的日地能量传输过程的电离层征兆和极光现象,非常适合开展极区空间环境观测研究。自1989年开始建设以来,中山站极区空间环境观测系统经历了观测设备的不断完善和发展,现已建立了涵盖地面极光、电离层和地磁观测多要素、多手段的自主观测体系,实现了极区空间环境的连续监测并建立了数据库。所有观测设备的运行状态可实时监控,地磁、宇宙噪声吸收等数据实现了准实时远程传输。最后展望中国极区空间环境观测研究的发展前景。  相似文献   

极地雪冰中过量~(17)O研究进展   总被引：1，自引：1，他引：1       下载免费PDF全文

何静庞洪喜  侯书贵 《极地研究》2015,27(4):392-401

过量~(17)O是当前水体稳定同位素研究的前沿领域,在极地雪冰研究中备受关注。本文系统地介绍了水循环过程中过量~(17)O研究的基本原理和实验方法,在此基础上,重点评述了极地雪冰中过量~(17)O研究的最新进展,包括过量~(17)O的影响因素、空间分布特征、季节变化、末次冰盛期-全新世过量~(17)O演化特征,并针对极地雪冰过量~(17)O研究尚未解决的科学问题对未来的工作进行了展望。  相似文献   

汶川地震区映秀——卧龙公路边坡崩塌类型的赤平投影解法   总被引：1，自引：0，他引：1  

王孝健  苏生瑞  成良霞 《中国地质灾害与防治学报》2012,23(1):48-54

汶川地震后,公路岩质边坡结构面发育,极易失稳形成崩塌。从发育的多组结构面中选取典型的结构面作为形成崩塌的控崩结构面,并通过对结构面所处边坡的工程地质条件分析得出控崩结构面的选取原则;考虑控崩结构面与边坡临空面的空间位置关系,运用赤平投影解法重点分析一组和两组控崩结构面与边坡临空面的图解关系;将震后公路边坡发生崩塌分为三种类型：滑移式、坠落式和倾倒式,结合边坡岩性、坡形、坡度、坡高等因素,得到了震后公路边坡崩塌三种类型的判据;将其应用到汶川地震后映秀—卧龙公路沿线边坡发育的典型崩塌中,得出的崩塌类型与实际相符。  相似文献   

基于极射赤平投影的岩质边坡稳定性评价和防治措施     

刘洪  陈福春 《地质灾害与环境保护》2012,23(3):93-98

岩质边坡破坏主要由结构切割形成的楔形体失稳造成.通过对无锡滨湖区-露天采矿形成的岩质边坡稳定性的评价,介绍利用极射赤平投影法评价岩质边坡稳定性和提出不稳定岩质边坡防治措施的基本原理和方法.  相似文献