EAF implementation in Southern Africa: Lessons learnt     

Barbara Paterson  Samantha L. Petersen   《Marine Policy》2010,34(2):276-292

The practical implementation of an ecosystem approach to fisheries (EAF) management has proved difficult to achieve. Without simple and structured guidelines for implementing an EAF, managers are grappling with the complexity of implementation and the need to prioritise resources and management actions. Ecological risk assessment has been put forward as a structured procedure. There is a need to review regularly whether progress is being made in addressing the issues and priorities identified through ecological risk assessment. Such reviews require a framework providing clear objectives for the respective fishery and delineating the steps required towards their achievement. This paper proposes a generic framework for reviewing ecological risk assessments through stakeholder workshops. This framework is aided by a fuzzy logic tool to track EAF implementation and informs the development of proactive work plans which incorporate EAF objectives. The advantages and disadvantages of a generic and participatory approach are discussed and compared with other related methods for evaluating progress in implementing an EAF.  相似文献   

The probabilistic distinct element method     

P. Moarefvand  T. Verdel 《国际地质力学数值与分析法杂志》2008,32(5):559-577

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Burial and scour of short cylinders under combined random waves and currents including effects of second order wave asymmetry     

Dag Myrhaug  Muk Chen Ong 《Coastal Engineering》2009

This paper provides an approach by which the burial and scour of short cylinders under combined second order random waves and currents can be derived. Here the formulas for burial and scour for regular waves plus currents presented by Catano-Lopera and Garcia [Catano-Lopera, Y.A. and Garcia, M.H. (2006). Burial of short cylinders induced by scour under combined waves and currents. ASCE J. Waterway, Port, Coastal and Ocean Eng. 132(6), 439–449., Catano-Lopera, Y.A. and Garcia, M.H. (2007). Geometry of scour hole around, and the influence of the angle of attack on the burial of finite cylinders under combined flows. Ocean Eng. 34(5, 6), 856–869.] are used together with Stokes second order wave theory by assuming the basic harmonic wave motion to be a stationary Gaussian narrow-band random process. An example of calculation is also presented.  相似文献   

Evaluations and Ensemble Approaches of Western-Pacific Subtropical High and South-Asian High Ensemble Forecasting in GRAPES-GEPS     

Li Gao  Pengfei Ren  Fang Zhou  Jiawen Zheng  Hongli Ren 《地球科学进展》1986,35(7):715-730

Based on the operational standard indices, the prediction skills of the Western-Pacific Subtropical High (WPSH) and South-Asian High (SAH) using 2019 real-time forecasts derived from the Global Ensemble Prediction System of GRAPES (GRAPES-GEPS) in China Meteorological Administration (CMA) Numerical Prediction Center were evaluated and the effects of different ensemble approaches on the prediction skills of WPSH and SAH indices were further investigated in this study. The results show that for WPSH, the GRAPES-GEPS has its highest prediction skill for the ridge line index, considerably high skill for the intensity and area indices, but relatively low skill for the western boundary index, and for SAH, it has comparatively high skill for the intensity and center latitude indices, but relatively lower skill for the center longitude index. Prediction errors of the GRAPES-GEPS for the WPSH forecasts are featured by the weaker intensity and area and the more eastward center position, compared with the observation, which can be effectively reduced by employing the maximum/minimum approach from ensemble members, relative to the ensemble mean approach. By direct comparison, prediction errors of the GRAPES-GEPS for the SAH forecasts are featured by the weaker intensity and the more southward center position, which tends to be slightly reduced using the ensemble mean approach. Finally, for the extreme forecast, the maximum approach provides superior performance for both WPSH and SAH than the ensemble mean approach, which can be validated in terms of the two extreme cases. These results clearly indicate that the maximum approach could better improve the GRAPES-GEPS performance for the extreme forecasting of the two primary circulation patterns than the traditional ensemble mean approach.  相似文献   

21世纪初大连市水资源供需保障与解决途径研究   总被引：3，自引：1，他引：3  

王茂军  张学霞  盖美  宋薇  赵雅静 《地域研究与开发》2001,20(1):65-69

在简要论述大连市资源基本特点和利用现状的基础上，分析了区域供水系统，城市供水系统和农村用水系统的供需平衡状况，研究表明前二者供不应求，后者供大于求，并提出了解决供需矛盾的主要途径，包括：超前研究地表水源地，扩大海水利用范围，提高中水利用量等开源措施，结构调整，技术挖潜等节流措施以及差异提价和尝试工业用水配额交易等市场措施。  相似文献   

Elemental composition of sediment cores from a mangrove environment using neutron activation analysis     

Julio Cesar Wasserman  Ana Maria G Figueiredo  Fabio Pellegatti  Emmanoel V Silva-Filho 《Journal of Geochemical Exploration》2001,72(2):1013

The geochemistry of Sepetiba Bay was studied in four sediment cores using a multi-element approach. Two cores were sampled in the more contaminated eastern part of the bay and two cores were sampled in the western region. The aim was to determine whether less common elements like the rare earths or the actinides are associated with contaminant metals like zinc in the Bay. Samples were analysed by instrumental neutron activation analysis that permits the quantification of total concentrations of metals (Ba, Co, Cr, Cs, Fe, Hf, Rb, Sc, Zn), rare earth elements (Ce, Eu, La, Lu, Sm and Yb), actinides (Th, U), non-metals and semi-metals (As, Br). Organic carbon and total sulphur were also analysed. The results show very strong zinc contamination in the top layers (more than 1000 μg g⁻¹) and background concentrations in the bottom (15 μg g⁻¹). Elements like chromium which would be expected to be released by the heavy industries of Sepetiba Bay, did not show a contamination profile, and concentrations remained close to those of natural environments. No evidence of any association between the zinc and other potential contaminant elements could be identified in this work.  相似文献   

青藏线客城区段沙害成因与防治途径的研究     

于云江  鲁春霞 《干旱区地理》2001,24(3):236-242

青藏铁路哈（尔盖）－格（尔木）段位于青藏高原，横穿柴达木沙漠，不少地段曾因沙害造成中断行车和机车掉道等事故，其中以客城最为突出。对青藏线客城区段气候、地质、地貌等自然因素和人为因素的研究表明：风大多风是该区段风沙猖獗的动力因素，分布广泛的洪积沙层则构成了风沙流的物质基础，不适当的人为活动加剧了当地的沙漠化，致使线路沙害日趋严重。在该锻铁路防沙中，采用的竹片栅栏与碎石方格相结合的机械措施取得较好的防沙效果，经过观测，阻沙措施降低了风速；固沙措施增加了地面的粗糙度，减少了沙面的流动性，为植物的生长创造了有利条件。植物固沙试验表明，白刺是当地最佳的治沙植物种，它具有冠幅大，根系发达、固沙效果好等特点，虽然地下水矿化度高，但用它浇灌，可提高白刷成活率。防沙措施取得了明显的防沙效果和经济效益，确保了该段行车安全。  相似文献   

地球化学反应平衡模型的建模方法   总被引：1，自引：1，他引：1  

陈家玮  鲍征宇 《地质科技情报》2001,20(3):41-46

简要介绍了各种地球化学反应模型及建模思想 ,重点介绍了最基本的地球化学反应平衡模型建立过程中的一些基本概念和建模的一般方法 ,并就模型实际应用中 ,在概念模型的确立、热力学数据资料的使用范围、模型计算中离子强度、温度、压力、p H值等方面存在的问题和影响因素 ,作了较为全面的说明。  相似文献   

评析西方城市土地利用的理论研究   总被引：46，自引：7，他引：46  

刘盛和  吴传钧  陈田 《地理研究》2001,20(1):111-119

综述了西方城市土地利用理论研究的最新进展,较深入地评析了各种研究方法与理论派系的独到功力及其局限性。并结合中国城市土地利用的研究进展,提出今后应加强城市土地利用区位经济的理论与实证研究及城市土地开发过程的政治经济分析  相似文献   

地震特征拾取及其在解释应用中的新进展   总被引：1，自引：0，他引：1  

吴雨梅  吴律 《地球物理学进展》1996,11(2):123-136

本文通过对瞬时振幅、瞬时相应、瞬时频率的应用研究的回顾，进一步论述了对这三种瞬时特征在地震记录分析中，如何利用模式识别技术和引用最新的ＰＰ方法即投影寻踪方法，同时介绍了倾角和方位角在三维 震资料解释中的应用，文中给出了每一种特征的应用实例。  相似文献