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151.
Time discounting is central to the valuation of future health and mortality risks in public sector allocative decision-making, particularly for environmental policies with delayed health impacts. Using a Risk-Risk trade-off survey, we elicit discount rates for fatality risks and establish discounting functional forms on both a sample and an individual level. We find wide variation in implicit discount rates for fatality risk between individuals, as well as between-individual heterogeneity in discounting functional forms. In aggregate, the sample is best characterised by subadditive discounting. Our work has implications for the academic investigation of intertemporal choice involving mortality risks, and potentially for the evaluation of policy options with delayed mortality risk outcomes. A thought experiment cautions against the standard practice of assuming that exponential discounting characterises society's time preferences. 相似文献
152.
In the real industrial process, alarm threshold optimization is an important part of alarm system rationalization. If the design of alarm threshold is unreasonable, it would result in nuisance alarms, among which the critical alarms are overwhelmed. In order to alleviate this phenomenon, we propose a method of multivariate alarm thresholds optimization to reduce the nuisance alarms. Firstly, causal relationship between process variables is constructed based on the time delay estimation method, thus we can determine the alarms propagation path and then select the optimized variables. Secondly, in order to guarantee both the process safety and correlation consistency, three factors - false alarm probability (FAP), missed alarm probability (MAP), and the correlation between the alarm information and process information – are combined to establish the objective function of the optimization process for the first time. Then, the optimal thresholds are obtained by the genetic algorithm. Finally, the validity and effectiveness of the developed method are illustrated by the Tennessee Eastman process. 相似文献
153.
Introduction
The current study explored the association between the business cycle and the incidence of workplace injuries to identify cyclically sensitive industries and the relative contribution of physical capital and labor utilization within industries.Method
Bureau of Labor Statistics nonfatal injury rates from 1976 through 2007 were examined across five industry sectors with respect to several macroeconomic indicators. Within industries, injury associations with utilization of labor and physical capital over time were tested using time series regression methods.Results
Pro-cyclical associations between business cycle indicators and injury incidence were observed in mining, construction, and manufacturing but not in agriculture or trade. Physical capital utilization was the highest potential contributor to injuries in mining while labor utilization was the highest potential contributor in construction. In manufacturing each effect had a similar association with injuries.Conclusion
The incidence of workplace injury is associated with the business cycle. However, the degree of association and the mechanisms through with the business cycle affects the incidence of workplace injuries was not the same across industries.Impact on Industry
The results suggest that firms in the construction, manufacturing, and mining industries should take additional precautionary safety measures during cyclical upturns. Potential differences among industries in the mechanisms through which the business cycle affects injury incidence suggest different protective strategies for those industries. For example, in construction, additional efforts might be undertaken to ensure workers are adequately trained and not excessively fatigued, while safety procedures continue to be followed even during boom times. 相似文献154.
北京平原区地下水污染源识别与危害性分级 总被引:7,自引:6,他引:1
地下水污染源的有效识别与分级对地下水污染风险源识别和地下水污染防控区划具有重要意义.本研究通过对北京市平原区主要污染源进行解析,构建了以特征污染物属性与污染物排放量计算污染源危害性的量化计算方法.运用ARCGIS 9.3软件实现了北京市平原区的污染负荷空间分布和污染物属性的叠加分析,得到地下水污染源识别与危害性分级.结果表明,该方法能够较为细致准确地反映出污染源的危害性分级,识别结果表明工业污染源对北京平原区地下水污染贡献最大,其次是城镇居民区和垃圾场. 相似文献
155.
Sébastien Denys Claire Rollin Francis Guillot Hafid Baroudi 《Water, Air, & Soil Pollution: Focus》2006,6(3-4):299-315
Phytoremediation of pollutants in soils is an emerging technology, using different soil-plant interaction properties. For
organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), phytodegradation seems to be the most promising approach.
It occurs mostly through an increase of the microbial activity in the plant rhizosphere, allowing the degradation of organic
substances, a source of carbon for soil microbes. Despite a large amount of available data in the literature concerning laboratory
and short term PAH phytodegradation experiments, no actual field application of such technique was previously carried out.
In the present study, a soil from a former coking plant was used to evaluate the feasibility and the efficiency of PAH phytodegradation
in the field during a three years trial and following a bioremediation treatment. Before the phytoremediation treatment, the
soil was homogenized and split into six independent plots with no hydrological connections. On four of these plots, different
types of common plant species were sowed: mixture of herbaceous species, short cut (P1), long cut (P2), ornamental plants
(P3) and trees (P4). Natural vegetation was allowed to grow on the fifth plot (P5), and the last plot was weeded (P6). Each
year, representative sampling of two soil horizons (0–50 and 50–100 cm) was carried out in each plot to characterize the evolution
of PAHs concentration in soils and in soils solution obtained by lixiviation. Possible impact of the phytoremediation technique
on ecosystems was evaluated using different eco- and genotoxicity tests both on the soil solid matrix and on the soil solution.
For each soil horizon, comparable decrease of soil total PAHs concentrations were obtained for three plots, reaching a maximum
value of 26% of the initial PAHs concentration. The decrease mostly concerned the 3 rings PAHs. The overall low decrease in
PAHs content was linked to a drastic decrease in PAHs availability likely due to the bioremediation treatment. However, soil
solutions concentration showed low values and no signficant toxicity was characterized. The mixture of the herbaceous species
seemed to be the most promising plants to be used in such procedure. 相似文献
156.
Raymond H. G. Klaassen Roine Strandberg Mikael Hake Thomas Alerstam 《Behavioral ecology and sociobiology》2008,62(9):1427-1432
We used novel Global Positioning System-based satellite telemetry to reconstruct daily time budgets on travelling days of
a long-distance migrant, the Osprey Pandion haliaetus, to reveal how landscape affects migratory performance. We compared daily travel routines between the Ospreys’ passage of
Europe and the Sahara. In Europe, where feeding habitat is abundant, Ospreys fed both before–after flights and during interruptions,
thus, combining migration with foraging. This resulted in a 2.7-h shorter daily flight period in Europe than in the Sahara.
A calculated energy budget indicated that a ‘fly-and-forage migration strategy’ is favourable in Europe because associated
benefits (energy intake) more than outweigh costs (reduced flight time). The much shorter flight time in Europe was the main
explanation why Ospreys covered on average 78 km less distance on a travelling day in Europe than in the Sahara. In addition,
there were regional differences in hourly flight speeds that are most probably the result of variation in thermal soaring
conditions. We conclude that landscape properties have a profound effect on migration through regional variation in daily
routines. 相似文献
157.
JONATHAN V. HIGGINS‡ MARK T. BRYER† MARY L. KHOURY THOMAS W. FITZHUGH‡ 《Conservation biology》2005,19(2):432-445
Abstract: Freshwater biodiversity is highly endangered and faces increasing threats worldwide. To be complete, regional plans that identify critical areas for conservation must capture representative components of freshwater biodiversity as well as rare and endangered species. We present a spatially hierarchical approach to classify freshwater systems to create a coarse filter to capture representative freshwater biodiversity in regional conservation plans. The classification framework has four levels that we described using abiotic factors within a zoogeographic context and mapped in a geographic information system. Methods to classify and map units are flexible and can be automated where high-quality spatial data exist, or can be manually developed where such data are not available. Products include a spatially comprehensive inventory of mapped and classified units that can be used remotely to characterize regional patterns of aquatic ecosystems. We provide examples of classification procedures in data-rich and data-poor regions from the Columbia River Basin in the Pacific Northwest of North America and the upper Paraguay River in central South America. The approach, which has been applied in North, Central, and South America, provides a relatively rapid and pragmatic way to account for representative freshwater biodiversity at scales appropriate to regional assessments. 相似文献
158.
A full probabilistic Explosion Risk Analysis (ERA) is commonly used to establish overpressure exceedance curves for offshore facilities. This involves modelling a large number of gas dispersion and explosion scenarios. Capturing the time dependant build up and decay of a flammable gas cloud size along with its shape and location are important parameters that can govern the results of an ERA. Dispersion simulations using Computational Fluid Dynamics (CFD) are generally carried out in detailed ERA studies to obtain these pieces of information. However, these dispersion simulations are typically modelled with constant release rates leading to steady state results. The basic assumption used here is that the flammable gas cloud build up rate from these constant release rate dispersion simulations would mimic the actual transient cloud build up rate from a time varying release rate. This assumption does not correctly capture the physical phenomena of transient gas releases and their subsequent dispersion and may lead to very conservative results. This in turn results in potential over design of facilities with implications on time, materials and cost of a project.In the current work, an ERA methodology is proposed that uses time varying release rates as an input in the CFD dispersion simulations to obtain the fully transient flammable gas cloud build-up and decay, while ensuring the total time required to perform the ERA study is also reduced. It was found that the proposed ERA methodology leads to improved accuracy in dispersion results, steeper overpressure exceedance curves and a significant reduction in the Design Accidental Load (DAL) values whilst still maintaining some conservatism and also reducing the total time required to perform an ERA study. 相似文献
159.
以2008年南京北郊大气中O3 质量浓度观测资料和常规观测资料为基础,利用Matlab小波分析工具,对O3浓度的年时间序列进行分析,得出该地区的O3 日均浓度的变化特征:春、夏季节O3浓度大于秋、冬季节,最高浓度出现在春末夏初,最低浓度出现在冬季;并且全年共有5个突变点;弱高压的天气系统、较高的温度、较低的湿度和晴朗少云的天气是造成南京北郊O3浓度突变的主要气象因素。结合HYSPLIT气流后向轨迹模拟,对污染源来源进行追踪,结果表明:南京北郊O3高浓度污染来源主要分为本地局地污染和外来污染物输送两类;垂直方向上,O3的区域尺度或中尺度的输送主要稳定在混合层的底层。 相似文献
160.
The ability of free and polysulphone immobilized biomass of Arthrobacter sp. to remove Cu2+ ions from aqueous solution was studied in batch and continuous systems. The Langmuir and Freundlich isotherm models were applied to the data. The Langmuir isotherm model was found to fit the sorption data indicating that sorption was monolayer and uptake capacity (Qo) was 175.87 and 158.7 mg/g for free and immobilized biomass respectively at pH 5.0 and 30 °C temperature, which was also confirmed by a high correlation coefficient, a low RMSE and a low Chi-square value. A kinetic study was carried out with pseudo-first-order reaction and pseudo-second-order reaction equations and it was found that the Cu2+ uptake process followed the pseudo-second-order rate expression. The diffusivity of Cu2+ on immobilized beads increased (0.402 × 10−4 to 0.435 × 10−4 cm2/s) with increasing concentration from 50 to 150 mg/L. The maximum percentage Cu2+ removal (89.56%) and uptake (32.64 mg/g) were found at 3.5 mL/min and 20 cm bed height. In addition to this the Bed Depth Service Time (BDST) model was in good agreement with the experimental data with a high correlation coefficient (>0.995). Furthermore, sorption and desorption studies were also carried out which showed that polysulphone immobilized biomass could be reused for up to six sorption–desorption cycles. 相似文献