Numerical and experimental study of a flapping foil generator     

《Applied Ocean Research》2017

The energy extraction performance of a flapping foil generator is studied through experiment and numerical simulation. A practical flapping foil generator has been proposed. The heave motion and the pitch motion of the foil are adjusted through a crankshaft-like structure. The heave and pitch motions of the foil are transferred to the rotational motion of the main shaft. A pair of gears is adopted to increase the pitch angle. A prototype with pitch amplitude θ₀ = 60^∘ has been built and the experiment is carried out in a tunnel. The overall performance of the mechanism has been analysed. Good agreement of numerical results and experiment data has been found. Further simulations with larger pitch amplitudes are carried out. It is found that higher efficiency can be achieved with larger pitch amplitude at medium frequency.  相似文献   

从经验性预报向以物理为基础的概率预报过渡的若干问题   总被引：1，自引：0，他引：1  

韩渭宾 《内陆地震》1990,4(4):319-331

前言 地震预报是一个既古老又年轻的课题。早在二千七百多年前我国就开始有地震记载。公元132年,东汉张衡发明了世界上最早的地震仪——候风地动仪。但是,世界性的比较科学的地震预报研究大体上从本世纪六十年代开始。日本从1965年开始执行第一个地震预报五年计划。苏联虽自1948年阿什哈巴德地震之后就提出地震预报,但是,在地震学、地球物理和地球化学等方面探索前兆,真正取得进展也始于六十年代末。我国有计划大规模开展地震预报从1966年邢台地震现场开始。美国地震预报起步稍晚,但进展很快。 二十多年的观测、研究和预报实践推动了地震预报事业的发展。地震预报已从束手无策的  相似文献   

The role of moral economy in two British Columbia fisheries: Confronting neoliberal policies     

《Marine Policy》2015

What have been the moral values and practices allowing equitable economic opportunities and a sense of fairness in North American small-scale fisheries? How have these “moral economies” been affected by neoliberal policies with their emphasis on efficiency, rational self-interest, and wealth accumulation? Focusing especially on the salmon and halibut fisheries in British Columbia, Canada, this discussion summarizes key findings on the manner in which small-scale fisheries and their moral practices tend to be marginalized and undervalued under neoliberal regimes. The paper considers the value of these moral economies for promoting social, economic, and ecological welfare as grounds for the expansion of small-scale fisheries.  相似文献   

流气式正比计数管效率标定     

任基 《成都信息工程学院学报》1990,(1)

本文介绍了一种新的标定流气式正比计数管的方法。此方法的特点是把正比管作为吸收体,利用He气对光子较为透明的原理,标定正比管的探测效率。方法简便实用,并对P-10(90%Ar+10%CH_4)为工作气体的正比管进行了标定。  相似文献   

Decomposing productivity and efficiency changes in the Alaska head and gut factory trawl fleet     

《Marine Policy》2015

Fishing fleets are subject to numerous factors that affect economic performance, making identification and attribution of such impacts difficult. This paper separately identifies the effects of changing input and output prices, fishery management, and quota allocations on total factor productivity using a Lowe Index. Indices account for technical change and decompose productivity estimates into its technical, environmental, and scale-mix components. This results in measures that reflect shifts in the production frontier, and movements by vessels toward and around the frontier, to capture economies of scale and mix after a policy shift to a catch share program that includes fishing cooperatives and a limited access fishery. The difference between cooperative and limited access vessels is exploited to compare the changes in economic performance between the groups after the introduction of the shift to catch shares and cooperative management, which allowed the vessels to improve the timing and coordination across multi-species fisheries and to decrease incidental catch of quota-limited bycatch species that had closed the target fisheries prematurely in the past. Results indicate that total factor productivity increased significantly after the move to a catch share program, largely due to increases in technical change that shifted out the production frontier of the fishery.  相似文献   

Juggling multiple dimensions in a complex socio-ecosystem: The issue of targeting in payments for ecosystem services     

《Geoforum》2015

Proponents of payments for ecosystem services (PES) schemes advocate targeting payments to geographical areas that can: (a) maintain or enhance ecosystem services, (b) permit economically efficient arrangements and (c) address poverty objectives. The location of these efficient, effective and equitable (or triple-win) solutions is viewed as the ‘holy grail’ of PES and is often sought in isolation to broader socio-economic pressures, political relationships, or local cultural conditions. While the plethora of PES design perspectives often follow the concepts of efficiency and effectiveness, they seldom relate to pluralistic value systems and may disparage local self-determination for influencing the form and terms of negotiation. This paper critically analyses the assumptions underpinning the design of PES schemes which seek to optimise or target efficient, effective and poverty objectives. Using a case study for a proposed PES initiative in the Kathmandu Valley of Nepal, we employ spatial analysis to geographically visualise the discrepancy between the location for a typology of targeted objectives and actual preferences which support local perceptions of natural resource use and conservation. The case study highlights the inequity inherent in targeting payments under a neoliberal framing. Instead, spatially differentiating incentives according to socially determined priorities and collective management is suggested.  相似文献   

Thirteen plus one: a comparison of global climate policy architectures     

Joseph E. Aldy  Scott Barrett  Robert N. Stavins 《Climate Policy》2013,13(4):373-397

We critically review the Kyoto Protocol and thirteen alternative policy architectures for addressing the threat of global climate change. We employ six criteria to evaluate the policy proposals: environmental outcome, dynamic efficiency, cost-effectiveness, equity, flexibility in the presence of new information, and incentives for participation and compliance. The Kyoto Protocol does not fare well on a number of criteria, but none of the alternative proposals fare well along all six dimensions. We identify several major themes among the alternative proposals: Kyoto is “too little, too fast”; developing countries (DCs) should play a more substantial role and receive incentives to participate; implementation should focus on market-based approaches, especially those with price mechanisms; and participation and compliance incentives are inadequately addressed by most proposals. Our investigation reveals tensions among several of the evaluative criteria, such as between environmental outcome and efficiency, and between cost-effectiveness and incentives for participation and compliance.  相似文献   

海南地下流体台网现状分析及改进建议     

刘阳 《高原地震》2012,24(3):26-29

依据中国地震局地下流体学科技术协调组制定的《地下流体观测站(点)质量与效能评估方案》,从5个方面对海南省地下流体3个固定观测网三大测项的监测效能进行了评估,较全面地分析了海南地震地下流体监测网存在的问题,并针对存在问题提出了建议性的改进措施。  相似文献   

一种多站雷电定位系统探 测效率的估算方法     

陈明理  郭昌明 《高原气象》1991,10(3):287-292

通过分析多站雷电定位系统MDF的特点,提出影响多站雷电定位系统探测效率的因素主要有两个方面:1)波形判据及阈值的设置;2)DF场地环境及其本身的时间分辨率。本文提出了一种估算系统因第二种因素存在时的探测效率的方法。用此方法分别计算和分析了北京DF网络三年来的探测效率。结果表明:1)该系统中各DF站在正常情况下(不考虑第一种因素)探测效率约为70％左右;2)若有大量干扰DF的探测效率会大大降低。  相似文献   

基于湿位涡和积雪效率的降雪预报技术探讨     

姜有山  束宇  李力  刘冬晴 《气象科学》2017,37(5):659-665

本文对南京地区2015年的一次强降雪过程进行了湿位涡诊断分析,根据2008—2015年的57次强降雪个例归纳出了积雪效率与地面2 m气温的关系。结果表明:湿位涡正压项对降雪强度变化有较好的指示意义;结合湿位涡斜压项和地面气温可以较好地判断降雪落区,且强降雪落区和湿位涡斜压项的大值中心对应较好;积雪效率和地面2 m气温是分段函数关系,利用该统计关系及气温、降雪量的预报,可以作出积雪深度的预报。  相似文献