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1.
Modelers often need to quantify the rates at which zooplankton consume a variety of species, size classes and trophic types. Implicit in the equations used to describe the multiple resource functional response (i.e. how nutritional intake varies with resource densities) are assumptions that are not often stated, let alone tested. This is problematic because models are sensitive to the details of these formulations. Here, we enable modelers to make more informed decisions by providing them with a new framework for considering zooplankton feeding on multiple resources. We define a new classification of multiple resource responses that is based on preference, selection and switching, and we develop a set of mathematical diagnostics that elucidate model assumptions. We use these tools to evaluate the assumptions and biological dynamics inherent in published multiple resource responses. These models are shown to simulate different resource preferences, implied single resource responses, changes in intake with changing resource densities, nutritional benefits of generalism, and nutritional costs of selection. Certain formulations are further shown to exhibit anomalous dynamics such as negative switching and sub-optimal feeding. Such varied responses can have vastly different ecological consequences for both zooplankton and their resources; inappropriate choices may incorrectly quantify biologically-mediated fluxes and predict spurious dynamics. We discuss how our classes and diagnostics can help constrain parameters, interpret behaviors, and identify limitations to a formulation's applicability for both regional (e.g. High-Nitrate-Low-Chlorophyll regions comprising large areas of the Pacific) and large-scale applications (e.g. global biogeochemical or climate change models). Strategies for assessing uncertainty and for using the mathematics to guide future experimental investigations are also discussed.  相似文献   
2.
李郇  符文颖 《地理研究》2010,29(7):1269-1280
Hedonic价格模型在西方发达国家是分析住房市场的常用工具,具有较高的针对性和实时性,并且是衡量外部性的定量科学方法。通过2005年、2006年和2007年三个独立的时间截面数据,建立广州住宅市场的Hedonic模型,揭示了广州居民住宅偏好随时间变化的方向和程度及发生变化的原因,并重点衡量了城市政府的基础设施投资在住宅市场中的资本化程度。结果显示广州居民对于中心区位、良好的交通通达性、大规模的小区和水景景观具有持续上升的偏好,而对于城市政府来说,在地铁建设、景观改造、教育质量提升等方面的长期性公共投资,反映在住宅市场中,即是对此不断增长的住房偏好,并通过模型也对这种投资效用的程度进行了较准确的定量测算。  相似文献   
3.
This paper draws on trade data to examine the degree of upgrading of China’s trade structure with the world as a whole and in particular with the European Union (EU). More specifically it examines the evolution of the industrial structure of China’s trade with the world and with the EU between 1996 and 2008 and of the underlying dynamic indicators of revealed comparative advantage. This method of analysing China’s industrial structure provides clear evidence of upgrading into more advanced industries without at present losing significant competitive advantage in industries employing unskilled workers. The examination of revealed comparative advantage indices for world and Sino-EU trade also indicates an increasingly high degree of interdependence between the EU and China between 1996 and 2008. The EU (especially Germany, the UK, and France) is China’s most important export market, though it is also much more important as a market for China’s exports than the EU is as a supplier for China. China’s consequent trade surplus with the EU has gradually shifted from textiles and clothing to machinery and furniture. Further investigation reveals that the complementary Sino-EU bilateral trade is moving towards intra-industry trade at the 4-digit level of HS (Harmonization System) commodity classification. Although China is still a ‘global sweatshop’ with a strong specialization in labour-intensive commodities produced for economically developed countries (by importing machinery, raw materials and exporting processed goods), there are signs of technological upgrading in number of selected sectors in China, noticeably electronics, computers and telecommunications equipment. China’s reliance of imports of minerals indicates however that energy and resource security could be an important constraint on China’s long-term economic development.  相似文献   
4.
以实现对极轨气象卫星应用系统健康程度进行综合评价为目的,提出结合主观分析的层次分析法(Analytic Hierarchy Process,AHP)和客观分析的熵权法(Entropy Weight,EW)确定待评价系统指标值的综合权重,再采用逼近理想解排序法(Technique for Order Preference by Similarity to an Ideal Solution,TOPSIS)对系统的指标进行多角度评价排序来作为最终评价结果。本文根据连续5个月3颗极轨气象卫星在实际业务系统运行中异常指标样本进行实证分析。结果表明该方法较为全面考虑了影响应用系统的多种因素,避免了单一判据的局限性,并对各指标的重要性进行综合对比分析,使得评价结果更科学准确,可以作为构建极轨气象卫星应用系统健康程度评价指标体系的一种方法。  相似文献   
5.
Conventional sectoral management and piecemeal governance are considered less and less appropriate in pursuit of sustainable development. Ecosystem based marine spatial management (EB-MSM) is an approach that recognizes the full array of interactions within an ecosystem, including human uses, rather than considering single issues, species, or ecosystem services in isolation. Marine spatial planning and ocean zoning are emerging concepts that can support EB-MSM. EB-MSM is driven by high-level goals that managers aim to achieve through the implementation of measures. High-level goals and objectives need to be translated into more operational objectives before specific targets, limits and measures can be elaborated.Monitoring, evaluation and adaptation are necessary to ensure that marine management measures are both effective and efficient. Solid monitoring frameworks are the foundation of adaptive management, as they provide the necessary information to evaluate performance and the effectiveness of management actions. Marine protected areas (MPAs) - possibly set up in networks - constitute a key component in EB-MSM policies and practises and have been applied as a cornerstone in conservation of marine biodiversity, management of fish populations, development of coastal tourism, etc. Moreover, MPA experiences have provided methods and concepts (such as zoning) to a wider EB-MSM context. The assignment of values to biophysical features of the marine environment allows the direct assessment of related management choices and may assist EB-MSM.A range of monetary valuation techniques have been proposed to reduce attributes of goods and services to a single metric. However, in the marine environment such an approach is often over simplistic, and thus less reductive techniques may be necessary. Rather than producing a single metric, the results of non-monetary assessments guide policy allowing weight to be given as necessary to potential areas of conflict and consensus.Strategies to take into account climate change effects and geohazard risks in EB-MSM have been applied or proposed worldwide. EB-MSM regimes must be alert to such risks and flexible to account for changes.  相似文献   
6.
基于偏好度与竞争态的中国区域外资利用研究   总被引:1,自引:0,他引:1  
将偏好度和竞争态模型引入外资利用研究中,并据此对2000和2009年中国24个地区的外资利用情况进行实证研究,结论为:1)偏好度和竞争态是一种有效分析区域外资利用变化趋势和特征的方法,能更全面地把握外资来源地的时空结构及其演变特征,建立合理的区域外资来源地结构体系;2)各地外资偏好度和竞争态结构基本健全,类型分布和成员组成虽不理想但日趋合理,区域外资利用总体呈“欧洲偏爱北方、亚洲偏爱南方”特征,外资引进重心长期稳定于香港、日本、新加坡、台湾等亚太或毗邻地区,地缘作用影响显著,近年向欧洲和美洲集聚,尤其是美国,但不同地区外资竞争态和偏好度各类型内成员分化显著,且同一地区内不同外资来源地的偏好度和竞争态差异悬殊;3)2000年以来中国区域外资偏好度普遍下降,尤其是东部和西部,各类偏好度和竞争态的成员数量变化剧烈,且偏好度类别演替和竞争态转移现象显著,尤其是强偏好和金牛及明星引资地;4)外资竞争态和偏好度及其变化的相关性不显著,西部尤其是西北地区被边缘化,港澳台对外资利用贡献差异明显,香港最优而澳门最差;5)外资引进目标地分类及其战略选择为优势稳定型——收获性和开拓性:战略、优势增长型——开拓性和扩张性战略、优势下降型——选择性战略、劣势稳定型——选择性和撤退性战略。  相似文献   
7.
The social acceptability of aquaculture is linked to its perceived environmental impact, and this clearly poses a challenge to policy makers in deciding what weight to attach to such a concern within a governance framework for the industry. Using salmon farming in Scotland as a case study, we have developed a survey-based approach to evaluating public and stakeholder attitudes towards the environmental performance of aquaculture. The survey of the general public finds marked regional variations in attitudes towards salmon farming, while the results of the stakeholder survey raise issues over how far the preferences of particular interest groups are truly representative of the community as a whole.  相似文献   
8.
Monitoring and assessment of landslide hazard is an important task for decision making and policy planning in the landslide area. Massive landslides, caused by the catastrophic Chi‐Chi earthquake in 1999, occurred in Central Taiwan, especially at Chiufenershan area in Nantou county. This study proposed two useful indicators coupled with the Self‐organizing map (SOM) neural network and the Preference Ranking Organization METHod for Enrichment Evaluations (PROMETHEE) technique to quickly extract accurate post‐quake landslides from multi‐temporal Système Probatoire de l'Observation de la Terre (SPOT) images. A GIS‐based system was developed to simplify and integrate the procedures such as image pre‐processing, the SOM training, the PROMETHEE calculation, landslide extraction and accuracy assessment. The evaluated result shows that the landslide area soon after the earthquake is 209.50 ha (Kappa coefficient 96.88%). Over seven years of vegetation recovery, the denudation area has declined to 112.64 ha (Kappa coefficient 90.64%). Most earthquake‐induced landslides could be restored by natural vegetation succession. The developed system is a useful decision‐making tool for landslide area planning.  相似文献   
9.
Voluntary offsetting of flight-related emissions is an important cornerstone of passengers’ individual efforts to contribute to climate change mitigation. Hence, many scientific studies have tried to assess people’s willingness-to-pay to offset their own flight-related carbon emissions. Up-to-date, these studies are overwhelmingly grounded in hypothetical stated-preference approaches, with very limited knowledge about external validity. Here, we report on an observational field study involving a final sample of 63,520 bookings made with a European airline, allowing us to gauge actual willingness-to-pay for carbon dioxide compensation in a revealed-preference approach. Our pre-registered study shows that the median willingness-to-pay to voluntarily offset a ton of carbon dioxide from flight-related emissions is zero, with the mean willingness-to-pay being around 1 EUR. Aggregated voluntary willingness-to-pay thus dramatically falls short of current prices to offset carbon dioxide, for example through the EU-ETS. Our results thereby question the suitability of self-reported, hypothetical assessments of offsetting and raise caution about the effectiveness of offsetting schemes, which currently do not very successfully internalize flight-related cost of emissions.  相似文献   
10.
针对山区公路沿线复杂地质生态环境动态变化等问题, 以都江堰 - 汶川公路沿线区域为研究对象, 提出了一种基于承载力综合质量和空间聚类关系对区域地质生态环境承载力评价的方法, 实现了对具有地质灾害易发特点的山区公路沿线区域承载力状况的科学评价。通过自然 - 环境 - 人文模型构建区域承载力状况评估指标体系, 借助层次分析法确定各评价指标因子的权重, 采用TOPSIS算法(逼近理想解排序方法)进行计算并加权叠加得到承载力综合质量状况, 结合热点分析的结果对研究区的承载力状况进行等级划分。结果表明: 研究区的地质环境、 生态环境、 社会经济承载力质量空间分布皆呈现出高度聚集性, 划入适宜建设区的面积占比31.12%, 后备调控区的面积占比31.98%, 不宜建设区面积占比36.79%, 研究区内的映秀镇、 漩口镇和都江堰所组成的三角区呈现大面积的高值聚集区, 承载力综合质量好, 空间聚集度高, 利于规划建设。评价结果为区域承载力准确评价和空间利用格局研究提供了新思路, 也可为防灾减灾工作提供参考。  相似文献   
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