唐山震区深反射剖面分析   总被引：14，自引：2，他引：14       下载免费PDF全文

陆涵行  曾融生  郭建明  林中洋 《地球物理学报》1988,31(1):27-36

为了进一步研究唐山地区深部地壳构造与唐山大地震孕育及发生的关系,国家地震局地球物理研究所在石油部物探局的协助下,于1985年1月在唐山震区完成了64km长的深反射剖面野外观测,获得了高分辨率的整个地壳结构的详细资料。分析结果表明,唐山震区内深度500m以上的沉积层十分破碎;结晶基底为前震旦纪地层,埋深2-7km不等,覆盖地层倾斜,且断层发育,其中陡河断裂为正断层,延深至6-7km,推断该断层为1976年唐山发震的重要构造之一。测线上大约21km深处普遍存在一反射层;莫霍面深度在31-32km左右,与该地区折射剖面得到的结果相当一致。  相似文献   

Approximation of interfacial properties in multiphase porous medium systems     

J.E. McClure  D. Adalsteinsson  C. Pan  W.G. Gray  C.T. Miller 《Advances in water resources》2007

We investigate the estimation of interfacial areas, curvatures, and common curve lengths in multiphase porous medium systems. Algorithms are developed to obtain estimates of these quantities based upon a variety of potential data sources and estimation approaches. The accuracy of the derived approximations are evaluated as a function of the data type and resolution of the data. The methods advanced improve upon standard approaches now in use and show excellent accuracy at resolutions on the order of five lattice points per minimum radius of curvature of the object being resolved. Finally, we suggest a promising class of extensions that could lead to further improvements in the accuracy of such methods.  相似文献   

Dietary studies on exotic carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) from two lakes of western Victoria,Australia     

Tariq A. Khan 《Aquatic Sciences - Research Across Boundaries》2003,65(3):272-286

  相似文献   

Defending community? Indigeneity, self-determination and institutional ambivalence in the restoration of Lake Whakaki     

Brad Coombes 《Geoforum》2007,38(1):60-72

Conservation practitioners have scrutinized the credibility and effectiveness of community-based natural resource management, noting its romantic misconceptions about communities and their capacities. Early approaches failed to acknowledge the heterogeneity of collective agents, the synergy between decentralization and neoliberalism, or the need to affirm rural peoples’ entitlements to resources. A Maori community’s attempt to restore Lake Whakaki on New Zealand’s east coast confirms many of these critiques. The restoration confronts institutional ambivalence, obstructive forces from beyond the zone of Maori influence and non-correspondence between community and catchment dynamics. Fulfilment of the project requires exogenous resources and authority, but state conservation agencies are ambivalent towards local demands for self-determined development. Nonetheless, an uncommon degree of agency which is grounded within community aspirations for sovereignty suggests that the motivational characteristics of community retain their importance in debates about integrated conservation and development.  相似文献   

洞庭青鲫(Carassius auratus var.Dongtingking)与三个鲫品系群体遗传多样性的ISSR分析   总被引：2，自引：1，他引：1  

刘良国  杨品红  谢春华  王晓艳  徐黎明 《海洋与湖沼》2015,46(2):426-431

采用ISSR分子标记技术,对洞庭青鲫(Carassius auratus var.Dongtingking)、野生二倍体和三倍体鲫(C.auratus)、彭泽鲫(C.auratus var.Pengze)4个鲫品系群体共120个个体的遗传多样性进行分析。9个ISSR引物在四个鲫品系群体中共获得1637个扩增位点,其中多态位点1572个,多态位点比例为96.03%。4个鲫品系群体内的多态位点比例分别为46.14%、65.40%、73.76%和51.94%,遗传距离分别为0.0905、0.1186、0.1351和0.1056。在4个鲫品系群体之间,洞庭青鲫与彭泽鲫的遗传距离最小(0.1191),二倍体鲫和三倍体鲫的遗传距离次之(0.1336),而洞庭青鲫、彭泽鲫与二倍体鲫的遗传距离(分别为0.1377、0.1367)略小于它们与三倍体鲫的遗传距离(均为0.1378)。UPGMA聚类结果为洞庭青鲫与彭泽鲫聚成一个分支,二倍体鲫与三倍体鲫聚成另一个分支。结果表明,洞庭青鲫、彭泽鲫等养殖群体内的遗传多样性明显低于野生鲫群体;四个鲫品系中,洞庭青鲫与彭泽鲫的亲缘关系较近,二倍体鲫与三倍体鲫的亲缘关系较近,推测洞庭青鲫、彭泽鲫、三倍体鲫均起源于二倍体鲫。二倍体洞庭青鲫和二倍体野生鲫资源的保护必须引起重视。  相似文献   

Results based management in fisheries: Delegating responsibility to resource users     

《Marine Policy》2015

While the notion of results based management has been devoted recent attention in the context of reforming European fisheries management, it remains unclear what it entails. A conceptual model of results based management in fisheries is proposed as a way for public authorities to delegate specific management and documentation responsibilities to resource users. The model comprises three defining features: (1) That authorities define measurable objectives for the utilization of fisheries resources; (2) that resource users are made responsible for achieving these objectives and for (3) providing documentation that allows for an audit of the extent to which they are met. Selected cases are used to illustrate these features. Rationales and prospects of introducing results based management as an alternative in a European fisheries management context are discussed, giving consideration to how it may be pursued under the reformed common fisheries policy.  相似文献   

ENCLOSURE EXPERIMENTS ON AND LACUSTRINE PRACTICE FOR ELIMINATING MICROCYSTIS BLOOM   总被引：2，自引：0，他引：2  

刘建康  谢平 《中国海洋湖沼学报》2002,20(2):113-117

Microcystis bloom, one of the most objectionable characteristics of eutrophication in tropical and subtropical waters, occurred in Donghu Lake (East lake) of Wuhan every summer from the 1970s up to 1984, but from 1985 up to now failed to occur there. The cause of its disappearance rema-ined in obscurity until recently. In situ enclosure experiments in the lake for three years showed that the stocking of the filter-feeding silver carp ( Hypophthalmichthys molitrix ) and big-head carp (Aristichthys nobilis ) played a decisive role in eliminating Microcystis bloom from the lake; but that recurrence of the bloom is possible under certain conditions. This paper presents the details and the results of enclosure ex-periments. The authors‘ analysis of fish biomass data obtained by echo-sounding and the fishery produc-tion of the lake over the years, revealed that the recurrence of Microcystis bloom can be prevented so long as the combined biomnss of silver carp and big-head carp remains at or exceeds 50 g per cubic meter of lakewater, as was the case in the lake‘s 1985 fish yield of 1015 t.  相似文献   

COMPARATIVE STUDIES ON THE FEEDING CAPACITY OF SILVER CARP AND BIGHEAD CARP   总被引：1，自引：0，他引：1  

董双林  李德尚 《中国海洋湖沼学报》1994,12(2):185-190

Study of the feeding capacity of silver carp and bighead carp by means of experimental ecologyshowed that the filtering frequency of silver carp was slightly greater than that of bighead carp,but thatthe latter's suction volume was much greater than the former's so the filtering rate(filtering frequency mul-tiplied by the suction volume)of silver carp was smaller than that of bighead carp.The filtering efficien-cy of silver carp for phytoplankton was greater than that of bighead carp for them.The removal ratesof silver carp for phytoplankton were greater than those of bighead carp,but for zooplankton the formerwere smaller than the latter.For food particles about 70 μm both removal rates were almost equal.The feeding habits of the two species in natural waters is also discussed in the paper.  相似文献   

Urban green commons: Insights on urban common property systems   总被引：1，自引：0，他引：1  

Johan Colding  Stephan Barthel  Pim Bendt  Robbert Snep  Wim van der Knaap  Henrik Ernstson 《Global Environmental Change》2013,23(5):1039-1051

The aim of this paper is to shed new light on urban common property systems. We deal with urban commons in relation to urban green-space management, referring to them as urban green commons. Applying a property-rights analytic perspective, we synthesize information on urban green commons from three case-study regions in Sweden, Germany, and South Africa, and elaborate on their role for biodiversity conservation in urban settings, with a focus on business sites. Cases cover both formally established types of urban green commons and bottom-up emerged community-managed habitats. As our review demonstrates, the right to actively manage urban green space is a key characteristic of urban green commons whether ownership to land is in the private, public, the club realm domain, or constitutes a hybrid of these. We discuss the important linkages among urban common property systems, social–ecological learning, and management of ecosystem services and biodiversity. Several benefits can be associated with urban green commons, such as a reduction of costs for ecosystem management and as designs for reconnecting city-inhabitants to the biosphere. The emergence of urban green commons appears closely linked to dealing with societal crises and for reorganizing cities; hence, they play a key role in transforming cities toward more socially and ecologically benign environments. While a range of political questions circumscribe the feasibility of urban green commons, we discuss their usefulness in management of different types of urban habitats, their political justification and limitation, their potential for improved biodiversity conservation, and conditions for their emergence. We conclude by postulating some general policy advice.  相似文献   

基于CC的防火墙安全功能分析   总被引：1，自引：0，他引：1  

梁思  刘嘉勇  胡勇  陈波 《成都信息工程学院学报》2006,21(4):519-522

防火墙是网络安全的核心手段。依据基于CC（Common Criteria）制订的国家标准——包过滤防火墙安全技术要求和应用级防火墙安全技术要求，提出每项安全功能要求对应的实际安全措施，并分析当前防火墙未实现的安全功能要求。  相似文献