ȷ��1���1�����׼�ȫ����ˮ׼���ģ��ʵ��   总被引：2，自引：0，他引：2  

韩建成  申文斌 《大地测量与地球动力学》2007,27(5):38-43

???????????????1???1??(10 ^-5 ms ^-2 ??)??????????????????????????????????????????????,????????????????????????1???1??????????????????????????????÷??????????衣 ????????????????????????????????????÷??????1???1???????????????????????????  相似文献   

Groundwater Depletion and Agricultural Land Use Change in the High Plains: A Case Study from Wichita County,Kansas*     

Nathan Kettle  Lisa Harrington  John Harrington Jr. 《The Professional geographer》2007,59(2):221-235

Shifts in resource availability and resulting land use changes are important research themes for coupled human and natural systems and human dimensions of global environmental change. This study examines the relationship between groundwater depletion and agricultural land use change within a single county in the High Plains, where agro-economic systems and populations are dependent on access to reliable groundwater supplies. Results indicate a significant relationship between high proportionate decreases in groundwater and land being removed from irrigation. This case study strengthens the links among local, regional, and global environmental change, and contributes to a greater understanding of the High Plains in the context of regional sustainability and vulnerability concerns.  相似文献   

Impacts of climate variability on stream-flow in the Yellow River     

Guobin Fu  Stephen P. Charles  Neil R. Viney  Shulin Chen  Joan Q. Wu 《水文研究》2007,21(25):3431-3439

This paper examines the impacts of climate variability upon the regional hydrological regimes of the Yellow River in China. Results indicate that the average annual precipitation is 494·8 mm in La Niña years and only 408·8 mm in El Niño years. The difference is 86·0 mm, or 18·8% over the long-term average. The stream-flows in the La Niña years are higher than that in El Niño years: 9·2% at the Lan-Zhou station, 9·5% for Tou-Dao-Guai station, 11·8% for Long-Men, 17·6% for San-Men-Xia, 19·2% at the Hua-Yuan-Hou station, and 22·0% at the Li-Jin station. Both precipitation and stream-flow responses show temporal and spatial patterns. The relationship among the stream-flow, precipitation, and temperature, which was obtained by ArcGIS Geostatistical Analyst based on observed data, indicates stream-flow is sensitive to both precipitation and temperature. For small precipitation increases (less than 13%), the stream-flow percentage change is less than the precipitation change for the Yellow River. The results of this paper can be used as a reference for watershed water resources planning and management to maintain the healthy life and proper function of the river. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

GPS网中已知点间兼容性检验的探讨   总被引：1，自引：0，他引：1  

胡新玲  谭世波 《测绘科学》2009,34(4)

为各项测绘工程建立的GPS控制网都应以一定的已知点作为约束数据进行约束平差,求得网中各点在国家坐标系统或地方独立坐标系统中的坐标成果并得以应用,所以已知点间的兼容性对于保证GPS控制网的整体精度和点位坐标值的正确性非常重要。本文就相关规范的规定提出坐标及边长回归分析法进行已知点间兼容性检验,并使用几种常用的GPS平差软件结合实例进行计算和分析,成功地选定相兼容的已知点;并就实际生产中对已知点的联测和使用提出了建议。  相似文献   

高寒草旬地区沙漠化发展过程及成因分析——以黄河源区玛多县为例   总被引：1，自引：1，他引：1  

薛娴 郭坚张芳  宗莉韩邦帅  黄翠华 《中国沙漠》2007,27(5):725-732

遥感监测和野外调查研究结果表明：玛多县的沙漠化经历了由迅速发展到急剧逆转的过程，其中，20世纪80年代到2000年是沙漠化迅速发展的时期，沙漠化土地面积从1987年的12827．6km^2增加到16330．7km^2，达到全县土地总面积的64．7％，而在此后的6a里，沙漠化状况得以有效逆转，在2006年，沙漠化土地下降到12977．2km^2，年均逆转面积为559km^2；研究区沙漠化发生、发展的主要原因是气候变暖引起的冻土退化，以及随之引起的表土干旱化、草场退化、鼠害等；人类活动虽然在研究区沙漠化发生、发展过程中没有起到主导作用，但是可以通过以草定畜、围栏、灭鼠等措施有效控制沙漠化的发展，并使其得到逆转。  相似文献   

Institutions, the governance of quality and on-farm value retention for Indonesian specialty coffee     

Jeff Neilson 《Singapore journal of tropical geography》2007,28(2):188-204

Fluctuating global commodity prices affect the livelihoods of millions of tropical farmers worldwide. In recent years, systemic oversupply of many tropical agricultural products, grown in countries such as Indonesia, has meant that agricultural incomes have continuously fallen below subsistence levels. Within an increasingly open global trade regime, along with the limited ability of governments to protect domestic farm prices, quality-informed product differentiation appears to offer an escape route from the trap of low commodity prices. However, ownership and governance of quality constructions are fundamental to determining who benefits from such differentiation. This paper examines the use of geographical identities as a specific tool for value-adding in agricultural produce, presenting the case of specialty coffee production in South Sulawesi, Indonesia. The potential for producer-driven geographical indications compete with corporate-driven quality constructions, where the latter are able to appropriate place-related quality associations by using trademarks, vertical integration and tightly coordinated supply chain controls. An emergent politic of quality governance and ownership in global commodity chains reveals the highly restricted institutional terrain within which growers of specialty coffee might attempt to retain a higher share of the economic rent associated with quality production.  相似文献   

Spherical-earth Fréchet sensitivity kernels     

Tarje Nissen-Meyer  F. A. Dahlen  Alexandre Fournier 《Geophysical Journal International》2007,168(3):1051-1066

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Defining the translational velocity of the reference frame of Earth   总被引：2，自引：0，他引：2  

Donald F. Argus 《Geophysical Journal International》2007,169(3):830-838

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Second order homogenization of the elastic wave equation for non-periodic layered media     

Y. Capdeville  J.-J. Marigo 《Geophysical Journal International》2007,170(2):823-838

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Relocating Global Cities: From the Center to the Margins by M. Mark Amen,Kevin Archer,and M. Martin Bosman,eds     

Murray D. Rice 《The Professional geographer》2007,59(3):400-402

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