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991.
边坡岩体结构的三维失稳形式及稳定性分析研究 总被引:2,自引:0,他引:2
由两组结构面控制的四面体块体是岩体中最基本的结构体, 其稳定性取决于块体所受荷载及结构面上的摩阻力。正确判定边界面上摩阻力分布是评价块体稳定性的关键。本文提出的块体稳定性分析适用于岩体所受荷载为三维非共点力系。在不同外力作用下块体可产生平动、转动、翘扭及倾倒等各种三维失稳组合形式, 从而得到更为合理的块体稳定性评价。 相似文献
992.
南极长城站地磁观测站是我国首次建成的地磁自动化台站。本文简要地叙述了系统的构成、工作原理和设计思路。地磁自动化台站系统包括3台GM-2单分量磁通门磁力仪,用来记录地磁场三分量的变化,分辨率为0.05nT,采样间隔为6s,1台分量质子磁力仪,用于进行基线值测量,分辨率0.1nT,采样间隔为6min。安装在PC机内的数据采集卡进行A/D转移和数采采集,本文还介绍了地磁数据采集和常规处理的程序 相似文献
993.
994.
Problems of Artisanal Marine Fishermen in Ghana: The Way Ahead 总被引:1,自引:0,他引:1
John Victor Mensah & Barima Kwabina Antwi 《Singapore journal of tropical geography》2002,23(2):217-235
Marine fishing is an important traditional economic activity of the coastal communities in Ghana and contributes over 80 per cent of the total fish catch. The traditional sector accounts for over 75 per cent of the marine catch. The small-scale artisanal marine fishing communities, which contribute less than 30 per cent of the traditional sector landings, are generally characterised by low levels of production and, hence, low incomes, poor living conditions and chronic indebtedness. Based on field data on artisanal fishing communities in the Ahanta West and Gomoa districts, this paper summarises the chronic problems of artisanal fishermen that perpetuate their precarious existence in the coastal environment. Overcoming the problems of these increasingly marginalised and migrant communities calls for the provision of supplementary employment opportunities, improved social services and the formation of solidarity groups to enhance access to micro credit. These would require technical and management training as well as support services from government and non-governmental organisations (NGOs). 相似文献
995.
996.
基于MRF的航空影像理解的知识获取 总被引:1,自引:0,他引:1
讨论了基于MRF影像理解的3种知识——同类影像的距离最短、近邻像元个别特征参数的显著性和影像的方向性在航空影像理解中如何获取和应用。通过航空影像试验,表明影像理解的正确率大大提高。 相似文献
997.
van Hoof A.A.M. Langereis C.G. Joosten I. Thijssen J.R.A.M. Nijhof E. Groenendijk H.A. van den Eynde G.R.M. 《Geologie en Mijnbouw》1997,76(1-2):155-162
The palaeomagnetic directions of seven Dutch fireplaces are compared with the archaeological age estimates which range from the first to the 17th century AD. A comparison with the British master curve of secular variation for archaeomagnetic dating results in a refinement of the archaeological age estimates in two cases, while four other archaeological age estimates can be confirmed. For one fireplace only one sample is reliable, resulting in a very poorly defined archaeomagnetic age of 2 to 3 centuries younger than the expected age (i.e. late Middle Ages). On the other hand, accepting the archaeological age estimates, the palaeomagnetic directions can contribute to the database that is used to construct the British secular-variation master curve. We applied the classification grades proposed by Tarling & Dobson (1995) which range from unreliable (grade 1) to reliable (grade 5). Three fireplaces have grades 5, one has grade 4, one grade 3, one grade 1 and for one case no grade was assigned. 相似文献
998.
泥沙模型试验测控系统 总被引:5,自引:0,他引:5
本文介绍了成功地应用于国家“八五”重点科技攻关项目——三峡工程回水变动区涪陵河段泥沙模型试验的测控系统,简述了对模型试验进口的含沙量、流量和泥沙颗粒级配的控制原理和方法,重点介绍了微机尾水位自动控制以及流速、水位和波浪的多点同步采集与处理系统。 相似文献
999.
1000.
In the United Kingdom responsibility for the management of national catch quotas has since 1984 been extensively devolved to producers' organizations, Institutions created by the European Community in order to implement the common organization of the Community market for fish. The paper describes the development of the UK quota management system and the approaches adopted by different producers' organizations to the internal management of their quota allocations. Because of changes in the UK fishing vessel licensing rules as well as developments in the quota allocation system, there is an emerging market in quotas at both individual and collective levels. The implications of these developments are discussed, including the possible evolution, largely through industry-led innovation, of some sort of individual transferable quota (ITQ) system for the UK. 相似文献