Optimal gas detector placement under uncertainty considering Conditional-Value-at-Risk

A stochastic programming formulation considering Conditional-Value-at-Risk (CVaR) is developed for the optimal placement of gas detectors in petrochemical process facilities. A rigorous gas dispersion simulator, FLACS, is used to generate release scenario data for a real process geometry. We consider two problem formulations: minimization of expected detection time and minimization of expected detection time subject to a restriction on CVaR across the scenario set. The extensive form of each stochastic program is formulated in Pyomo and solved using CPLEX. Considering all scenarios, we compare key values and histograms of detection times for both formulations. Minimizing the mean detection time only can lead to optimal detector placements with a good expected behavior, but unacceptable worst-case behavior. The formulations that minimize or constraint CVaR produce sensor placements with significantly better worst-case behavior and fewer scenarios having high detection times. Considering these results, a strong case for the use of optimal sensor placement using stochastic programming considering CVaR is made for improving safety systems.     

Responses of benthic insect communities to effluent from the abandoned Ferris-Haggarty copper mine in southeast Wyoming, USA

This study provided information about the benthic insect communities that are present in the impacted reaches of Haggarty Creek.     

Why most conservation monitoring is, but need not be, a waste of time

Ecological conservation monitoring programmes abound at various organisational and spatial levels from species to ecosystem. Many of them suffer, however, from the lack of details of goal and hypothesis formulation, survey design, data quality and statistical power at the start. As a result, most programmes are likely to fail to reach the necessary standard of being capable of rejecting a false null hypothesis with reasonable power. Results from inadequate monitoring are misleading for their information quality and are dangerous because they create the illusion that something useful has been done. We propose that conservation agencies and those funding monitoring work should require the demonstration of adequate power at the outset of any new monitoring scheme.     

Impact of climate change and seasonal trends on the fate of Arctic oil spills

We investigated the effects of a warmer climate, and seasonal trends, on the fate of oil spilled in the Arctic. Three well blowout scenarios, two shipping accidents and a pipeline rupture were considered. We used ensembles of numerical simulations, using the OSCAR oil spill model, with environmental data for the periods 2009–2012 and 2050–2053 (representing a warmer future) as inputs to the model. Future atmospheric forcing was based on the IPCC’s A1B scenario, with the ocean data generated by the hydrodynamic model SINMOD. We found differences in “typical” outcome of a spill in a warmer future compared to the present, mainly due to a longer season of open water. We have demonstrated that ice cover is extremely important for predicting the fate of an Arctic oil spill, and find that oil spills in a warming climate will in some cases result in greater areal coverage and shoreline exposure.     

经合组织的可持续农业思路

经合组织为其29个成员国提供了一个论坛,来讨论以经济分析和共享各国经验为基础的经济政策与社会政策,以期向各国政府提供政策忠告和建议.近年来,已经更多地注意到经合组织国家与非经合组织国家之间的彼此相互作用,在市场、贸易和投资的全球化与自由化范畴内尤其如此. 　　目前,正在进行一个关于可持续发展的重大经合组织项目,利用经合组织中范围广泛的社会经济人才,准备2001年向经合组织部长会议的报告,并作为对2002年“里约+10”联合国会议的投入.在考察到底发生了什么的基础上,旨在概述提请政策制定者努力保持和加强可持续发展的方式——覆盖经济方面、环境方面和社会方面.1999年向经合组织部长会议的中期报告可上网浏览：www.oecd.org/subject/sustdev.......     

Oil spill response capabilities and technologies for ice-covered Arctic marine waters: A review of recent developments and established practices

Renewed political and commercial interest in the resources of the Arctic, the reduction in the extent and thickness of sea ice, and the recent failings that led to the Deepwater Horizon oil spill, have prompted industry and its regulatory agencies, governments, local communities and NGOs to look at all aspects of Arctic oil spill countermeasures with fresh eyes. This paper provides an overview of present oil spill response capabilities and technologies for ice-covered waters, as well as under potential future conditions driven by a changing climate. Though not an exhaustive review, we provide the key research results for oil spill response from knowledge accumulated over many decades, including significant review papers that have been prepared as well as results from recent laboratory tests, field programmes and modelling work. The three main areas covered by the review are as follows: oil weathering and modelling; oil detection and monitoring; and oil spill response techniques.     

经合组织的可持续农业思路

经合组织为其29个成员国提供了一个论坛,来讨论以经济分析和共享各国经验为基础的经济政策与社会政策,以期向各国政府提供政策忠告和建议.近年来,已经更多地注意到经合组织国家与非经合组织国家之间的彼此相互作用,在市场、贸易和投资的全球化与自由化范畴内尤其如此.