Effects of tour boats on dolphin activity examined with sensitivity analysis of Markov chains

In Patagonia, Argentina, watching dolphins, especially dusky dolphins (Lagenorhynchus obscurus), is a new tourist activity. Feeding time decreases and time to return to feeding after feeding is abandoned and time it takes a group of dolphins to feed increase in the presence of boats. Such effects on feeding behavior may exert energetic costs on dolphins and thus reduce an individual's survival and reproductive capacity or maybe associated with shifts in distribution. We sought to predict which behavioral changes modify the activity pattern of dolphins the most. We modeled behavioral sequences of dusky dolphins with Markov chains. We calculated transition probabilities from one activity to another and arranged them in a stochastic matrix model. The proportion of time dolphins dedicated to a given activity (activity budget) and the time it took a dolphin to resume that activity after it had been abandoned (recurrence time) were calculated. We used a sensitivity analysis of Markov chains to calculate the sensitivity of the time budget and the activity-resumption time to changes in behavioral transition probabilities. Feeding-time budget was most sensitive to changes in the probability of dolphins switching from traveling to feeding behavior and of maintaining feeding behavior. Thus, an increase in these probabilities would be associated with the largest reduction in the time dedicated to feeding. A reduction in the probability of changing from traveling to feeding would also be associated with the largest increases in the time it takes dolphins to resume feeding. To approach dolphins when they are traveling would not affect behavior less because presence of the boat may keep dolphins from returning to feeding. Our results may help operators of dolphin-watching vessels minimize negative effects on dolphins.     

城市天然气管道泄漏数值模拟

针对城市天然气管道和城市周围环境的特点,进行了城市管道天然气泄漏事故动态数值模拟,得到了天然气泄漏5,10,15,20 s时甲烷浓度分布图和安全区域图,结果显示城市天然气管道泄漏的规律不同于在平坦地势的泄漏规律,模拟结果可以为城市管道设计和事故求援提供指导依据。     

安全生产违章行为的人口因素影响模型研究——基于省级面板数据的协整方法

为了探讨人口因素对安全生产违章行为的影响,基于省级面板数据,构建安全生产违章行为数量与作业人员人口因素之间的固定效应变系数模型。实证研究,从业者的受教育程度、第二产业在岗职工平均工资以及人员数量规模等因素,影响违章行为方式及程度。结果表明:受教育程度的提高将显著抑制违章行为的发生;提高作业人员工资将增加违章行为的成本进而遏制违章行为的产生,但这一效果会受到作业人员所持有的风险态度的影响;作业人员规模的增加将提高工伤事故率。建议从提供受培训教育机会、提高违章成本、降低第二产业比重、减少高危行业作业人员数量等方面采取措施遏制违章行为。     

响应面法建立不同经口介质中邻苯二甲酸酯生物有效性预测模型及相关因素

运用响应面法对不同消化基质下邻苯二甲酸酯(PAEs)生物有效性的相关因素进行筛选建立预测模型,并对主要因素设定值进行分析.研究表明,3种模型中因变量与自变量之间的相关性较好(土壤:R2=0.959;农作物及植物:R2=0.973;脂肪:R2=0.862),模型拟合度较高.通过多次试验模拟,初步认为在土壤消化基质中,设置人体摄入PAEs经口摄入浓度为10μg·g-1,基质质量为0.4g,pH值约为7时,生物吸收量最高.在植物源基质下,污染物浓度在10—11μg·g-1,消化时间在6—7h,基质质量为0.4g为生物吸收量最高.脂肪源中,基质质量在0.4g,污染物浓度在10μg·g-1,脂肪量在10%—11%时,PAEs生物吸收量最高.研究通过重复试验,充分体现了该模型的准确性,及设定条件的可靠性.但本研究仅考虑摄入介质相对单一,污染物化合形态等未在考虑范围内,在后期研究中将补充试验.     

INTERPLAY BETWEEN PARAMETER UNCERTAINTY AND MODEL AGGREGATION ERROR1

ABSTRACTS: Modeling error can be divided into two basic components: use of an incorrect model and input parameter uncertainty. Incorrect model usage can be further subdivided into inappropriate model selection and inherent modeling error due to process aggregation. Total modeling error is a culmination of these various modeling error components, with overall optimization requiring reductions in all. A technique, utilizing Monte Carlo analysis, is employed to investigate the relative importance of input parameter uncertainty versus process aggregation error. An expanded form of the Streeter-Phelps dissolved oxygen equation is used to demonstrate the application of this technique. A variety of scenarios are analyzed to illustrate the relative obfuscation of each modeling error component. Under certain circumstances an aggregated model performs better than a more complex model, which perfectly simulates the real system. Alternately, process aggregation error dominates total modeling error for other situations. The ability to differentiate modeling error impact is a function of the desired or imposed model performance level (accuracy tolerance).     

Assessing Public Perceptions of Computer-Based Models

Although there is a solid body of research on both collaborative decision-making and on processes using models, there is little research on general public attitudes about models and their use in making policy decisions. This project assessed opinions about computer models in general and attitudes about a specific model being used in water planning in the Middle Rio Grande Region of New Mexico, United States. More than 1000 individuals were surveyed about their perceptions of computer-based models in general. Additionally, more than 150 attendees at public meetings related to the Middle Rio Grande planning effort were surveyed about their perceptions of the specific Rio Grande-based model. The results reveal that the majority of respondents are confident in their ability to understand models and most believe that models are appropriate tools for education and for making policy decisions. Responses also reveal that trust in who develops a model is a key issue related to public support. Regarding the specific model highlighted in this project, the public revealed tremendous support for its usefulness as a public engagement tool as well as a tool to assist decision-makers in regional water planning. Although indicating broad support for models, the results do raise questions about the role of trust in using models in contentious decisions.     

Nature and fate of Hudson Bay permafrost

Two aspects of the permafrost of the Hudson Bay region are examined. The first is the climatological conditions that support permafrost especially along the southwestern shore of Hudson Bay. The second is the fate of the permafrost using recent climate change scenarios. The continuous permafrost along the shores of southwestern Hudson Bay is examined from a climatological perspective. Two hypotheses are explored to explain the presence of continuous permafrost in this region in spite of the relatively "warm" local climate. Possible errors in the calculation of thawing degree days and the asymmetries in frozen and unfrozen soil thermal conductivities are successively examined. Only the second hypothesis is likely to explain the presence of permafrost in southwestern Hudson Bay. Sophisticated climate models are used to assess the potential change in permafrost distribution in the Hudson Bay region. Nine simulations using three different versions of the Canadian Centre of Climate Modelling and Analysis (CCCma) general circulation model are used to project permafrost distribution. Two surface temperature thresholds, –5 and –10 °C, are used to diagnose permafrost grid points. All simulations, including those that include reduction of CO₂ emissions, showed at least a 50% reduction of permafrost by 2100 using these temperature thresholds. Electronic Publication     

Spatial-Scale Effects on Relative Importance of Physical Habitat Predictors of Stream Health

A common theme in recent landscape studies is the comparison of riparian and watershed land use as predictors of stream health. The objective of this study was to compare the performance of reach-scale habitat and remotely assessed watershed-scale habitat as predictors of stream health over varying spatial extents. Stream health was measured with scores on a fish index of biotic integrity (IBI) using data from 95 stream reaches in the Eastern Corn Belt Plain (ECBP) ecoregion of Indiana. Watersheds hierarchically nested within the ecoregion were used to regroup sampling locations to represent varying spatial extents. Reach habitat was represented by metrics of a qualitative habitat evaluation index, whereas watershed variables were represented by riparian forest, geomorphology, and hydrologic indices. The importance of reach- versus watershed-scale variables was measured by multiple regression model adjusted-R² and best subset comparisons in the general linear statistical framework. Watershed models had adjusted-R² ranging from 0.25 to 0.93 and reach models had adjusted-R² ranging from 0.09 to 0.86. Better-fitting models were associated with smaller spatial extents. Watershed models explained about 15% more variation in IBI scores than reach models on average. Variety of surficial geology contributed to decline in model predictive power. Results should be interpreted bearing in mind that reach habitat was qualitatively measured and only fish assemblages were used to measure stream health. Riparian forest and length-slope (LS) factor were the most important watershed-scale variables and mostly positively correlated with IBI scores, whereas substrate and riffle-pool quality were the important reach-scale variables in the ECBP.     

逆向物流与再生资源回收利用

逆向物流是重新挖掘产品使用价值,节约资源,保护环境,实施可持续发展的重要战略措施.论述了逆向物流与再生资源回收利用之间的关系,分析了再生资源企业开展逆向物流的优劣势,提出了再生资源企业参与逆向物流的模式.     

Regional Assessment of Nutrient and Pesticide Leaching in the Vegetable Production Area of Rattaphum Catchment, Thailand

Regional groundwater vulnerability maps to indicate the impact of leaching of chemicals under different management scenarios were prepared for the Rattaphum Catchment using several leaching models and GIS techniques. The Attenuation Factor (AF) model was used to simulate the leaching potential of several pesticides for selected soils in the catchment under different rates of recharge from irrigation. The LEACHN model was used to simulate the NO₃ ⁻ leaching potential and LEACHP was used to simulate leaching potential of metolachlor under different management scenarios. The results showed that only a small number of pesticides have the potential to contaminate the shallow groundwater. However, the risk of contamination with nutrients is much higher due to the mobility and conservative nature of the NO₃ ⁻. The LEACHP results indicated that the intensive use of agrochemicals in the vegetable growing area, especially during the rainy season when the groundwater is near the surface, increases the risk of pesticide contamination. The results of upscaling from the farm to the catchment scale using soil maps and GIS techniques under various management scenarios and chemical application rates showed that the most effective strategy to reduce chemical leaching is by reducing pesticide application rates and optimizing the application of irrigation water. The identification of potential high risk farms by ranking soils and agricultural practices could be used to formulate management practices that reduce pesticide contamination of the surface and ground water resources in the area.