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331.
三峡库区土地持续利用潜力与途径模式 总被引:16,自引:6,他引:16
建立了量化评价模型,对三峡库区土地资源持续利用的潜力及其差异性进行了评价与分析。指出库区土地利用总体上处于弱持续发展的阶段,而且地区差异悬殊、面临的障碍因素多。因此,未来库区土地利用优化决策的关键在于遵照因地制宜和分类指导的原则,正确处理生态建设、移民安置和经济协调发展的关系。主要的途径模式包括植树造林、坡地改梯田、优化结构和产业突破等四个方面。 相似文献
332.
Wang Mingyu The University of Arizona Tucson Arizona USA Department of Water Resources Environmental Engineering China University of Geosciences Beijing Chen Jinsong Wan Li Department of Water Resources Environmental Engineering 《中国地质大学学报(英文版)》2001,12(3)
INTRODUCTIONGroundwaterorfluidflowmodelinginfracturedrocksisacomplicatedtheoreticalandappliedtopic.Boththeoreticallyandoperationally ,itisimportantinmanyfieldssuchasgeologicalandhydrogeologicalengineering ,environmentalengineeringandpetroleumengineerin… 相似文献
333.
中国外商直接投资的地域结构研究 总被引:19,自引:2,他引:19
改革开放以来,我国引进外资工作取得了较大进展。然而,外资地域分布的不平衡,成为导致区域经济发展水平差距拉大的一个重要原因。如何改善外资地域分布结构,成为各界关注的焦点之一。文中采用定量和定性相结合的方法,研究了中国外资地球分布的现状及特点,分析了外资地域分布的动态变化趋势,并在此基础上提出若干改善外资地域分布结构的举措。 相似文献
334.
335.
Origin and occurrence of 25-norhopanes: a statistical study 总被引:1,自引:0,他引:1
The alkane fraction of more than 200 rocks, biodegraded oils and non-biodegraded oils, have been analysed by means of computerized GC-MS, in order to investigate the effect of natural biodegradation on the occurrence of “demethylated hopanes”, i.e. 17α-25-norhopanes. The results obtained indicate that 25-norhopanes are preexisting biomarkers the concentration of which is enhanced by selective biodegradation of more readily degradable homologs, i.e. regular hopanes, rather than by demethylation of hopanes in reservoirs. However, the use of 25-norhopane enrichment as a palaebiodegradation indicator in apparently non-biodegraded oils is still valuable providing the initial background content in the corresponding source rocks is known. Furthermore, 25-norhopanes appear to be diagnostic of specific environmental conditions (marine and lacustrine source rocks, dysoxic and not very hypersaline). Lastly, one other (novel) bacterially resistant rearranged hopanoic compound, namely a C29 neohopane, is applicable for both biodegradation and maturation evaluation. 相似文献
336.
本文研究涉及生态水文学中生态需水问题的一般认知。探讨了生态系统动态变化与水流驱动力因素之间的关系,重点探讨水流驱动因素中的关键指标——流速,通过分析流速与生态系统相互作用,从生态水文学动力因素出发估算生态需水;基于生态流速和水力半径,提出考虑河道内生态需水与水力因素关系的生态水力半径法,充分利用水生生物信息(鱼类产卵洄游流速)与河道信息(水位、流速、糙率等)估算河道内生态需水;归纳生态水力半径法在生态需水计算中的初步应用:考虑污染物降解耦合水量水质的生态需水计算、考虑鱼类等生物对流速要求的生态需水计算、考虑河道冲淤平衡的输沙需水量计算等方面。本文提出的生态流速研究既包括生物生长发育适宜的流速,又包括流速大小变化所涉及的许多动力因素,旨在延伸与扩展生态水文学的内涵与应用。 相似文献
337.
Livio Sirovich 《Natural Hazards》1996,14(1):23-37
Comparison between the observed and the synthesized isoseismals of the relatively small earthquake of Sierra Madre (1991) and of the big one in San Francisco (1906), California, suggests that sometimes the areal shapes of the territories damaged by earthquakes might be synthetically traced out with a simple kinematic function which, following the asymptotic approach, takes into account some gross features of the sources. The rather good fits presented herein may indicate the possibility of substituting in some regions the so-called empirical attenuation relations, which are currently used in regional seismic hazard studies, by new more source-dependent algorithms. Conversely, the technique could help in retrieving information about sources of earthquakes from the pre-instrumental era, (i) in areas where it could be proved that the effects due to the travel paths and to local site conditions are negligible, (ii) when the detailed modelling techniques nowadays available are inapplicable due to lack of data, or (iii) for saving time and money. It seems that the algorithm gives rather stable results.Formerly: LIVIO SIRO. 相似文献
338.
C. Z. Zhang 《Earth, Moon, and Planets》1996,75(1):17-24
This paper is concerned with the interior structure of Uranus and Neptune. Our approach is three-fold. First, a set of three-layer models for both Uranus and Neptune are constructed using a method similar to that used in the study of the terrestrial planets. The variations of the mass density (s) and flattening e(s) with fractional mean radius s for two representative models of Uranus and Neptune are calculated. The results are tabulated. A comparison of these models shows that these two planets are probably very similar to each other in their basic dynamical features. Such similarity is very seldom seen in our solar system. Secondly, we check the conformance between the theoretical results and observational data for the two planets. And thirdly, the 6th degree Stokes zonal parameters for Uranus and for Neptune are predicted, based on the interior models put forward in this paper. 相似文献
339.
2014年云南鲁甸地震触发地质灾害发育分布规律及与景谷、盈江地震对比研究 总被引:6,自引:0,他引:6
2014年8月3日16时30分,云南省鲁甸县龙头山镇Ms 6.5级地震造成617人死亡,触发1700多处崩塌滑坡等地质灾害点,同年,该省又发生了Ms 6.6级景谷地震和Ms 6.1级盈江地震。笔者在对鲁甸等3次地震区次生地质灾害现场调查和遥感解译的基础上,研究了鲁甸地震触发地质灾害的发育分布规律,首次提出了地震“干滑坡”的概念,并从震级、地形地貌、活动构造、人口密度等多个方面对比了鲁甸地震、景谷地震和盈江地震触发地质灾害的异同点。主要结论有:(1)鲁甸地震后新增地质灾害数量显著增加,其主要分布在水系的深切峡谷区,表现为“干滑坡”特征;(2)大型、特大型崩塌滑坡灾害点主要受活动断裂控制;(3)地震地质灾害的发育特征与地貌高程和微地貌具有很好的响应关系;(4)鲁甸震区的地形坡度明显大于景谷和盈江震区,地形坡度是鲁甸地震区地质灾害发育的主要控制因素;(5)我国西南高山峡谷区的断层、河流、阶地和城镇是相互依存,不可分割的地质环境载体,震后房屋选址、重建规划不仅要注意房屋抗震问题,还应充分考虑地质环境安全问题。 相似文献
340.
《Marine Policy》2016
Public organizations involved in marine management are increasingly confronted with coordination challenges in marine governance. This study examines why and how the Norwegian Institute of Marine Research (IMR) reorganized its formal coordination structures between the areas of fisheries management and marine environmental management. The findings indicate that organizing efficient and, at the same time, legitimate coordination structures between different areas of marine governance is a “wicked” organizational problem with no ultimate and single optimal solution. In contrast to the assumptions of classical organization and management theory, the study finds that the reorganization of formal coordination structures is not necessarily driven for reasons of efficiency and perceived coordination problems. Instead, public marine management organizations also change their organizational structures to live up to external expectations to adopt modern management concepts, such as the Ecosystem Approach to Management (EAM). However, the study indicates that the adoption of the EAM has stimulated coordination and integration efforts in the research and advisory activities of the IMR. 相似文献