Response of the buried steel pipeline caused by perilous rock impact: Parametric study

One of threatening buried steel pipeline in bad geological regions is collapsed rock. Buckling behavior of a buried pipeline impacted by a perilous rock with spherical shape was investigated by numerical simulation. Effects of pipeline parameters (internal pressure, wall thickness, diameter, buried depth) and perilous rock parameters (impact velocity, radius, eccentric distance) on deformation, stress and strain of the buried pipeline were discussed. Buckling behaviors of the buried pipeline under transverse and longitudinal inclined impacts also were studied. The results show that cross section shape of the buried pipeline becomes to an oval, then to a peach shape, and finally to a crescent shape or gourd shape in the process of rock’s impact. The deformation process of a buried pipeline can be divided into four stages. They are elastic deformation stage, buckling stage, elastic recovery stage and final deformation stage. Buckling mode of no-pressure pipeline is more serious than the pressure pipeline. The impact dent’s length and depth increase with the decreasing of buried depth, wall thickness and internal pressure. But they increase with the increasing of impact velocity, perilous rock’s radius and pipeline’s diameter. The maximum stress and plastic strain decrease with the increasing of buried depth and wall thickness. Under rock’s eccentric impact, impact dent trends to one side. Stress and plastic deformation decrease with the eccentric distance increases. Under rock’s transverse and longitudinal inclined impacts, cross section shape of the buried pipeline is an oval shape when the incidence angle α ≤ 45°, and there is no plastic deformation. When α > 45°, impact dent appears. Buckling is more serious with the incidence angle increases. Destructive powers of transverse and longitudinal inclined impacts are smaller than the vertical impact.     

Environment-specific elasticity and sensitivity analysis of the stochastic growth rate

For matrix population models, analyses of how sensitive the population growth rate is to changes in vital rates (i.e. perturbations) are important for studies of life history evolution as well as for management and conservation of threatened species. There are two types of sensitivity analyses corresponding to absolute (sensitivity) or relative (elasticity) changes in the vital rates and both types can be applied to both deterministic and stochastic matrix population models. To date, most empirical studies of elasticity and sensitivity of the stochastic growth rate have examined the response to perturbations in the vital rates in a complete set of possible environments. However, it is often of interest to examine the response to perturbations occurring in only a subset of the possible environments. This has been done for periodic time-varying models elsewhere, but here we describe a recently published method for calculating the environment-specific sensitivity and elasticity of the stochastic growth rate and apply this method to data. These environment-specific perturbation analyses provide a logical way of dividing the sensitivity and elasticity among the environments. They give important insight into the selection regime in different environments and can provide valuable information for making management decisions and management evaluations in stochastic environments.     

Uncertainty evaluation in air quality planning decisions: a case study for Northern Italy

In recent years, evaluating the robustness of environmental models results has become essential in order to effectively support decision makers to define suitable emission control strategies. This evaluation is performed in literature through uncertainty and sensitivity analyses. Therefore, the application of such methodologies to air quality Integrated Assessment Models (IAMs) is extremely challenging. In fact, in this case uncertainty and sensitivity analyses should be assessed not only for each single component of the system, but also for the overall IAM. In the paper, an attempt is made to extend and systematize the information available on uncertainty/sensitivity analysis, at first considering environmental models in general, and then focusing on air quality IAMs. The study aims to offer a tentative framework addressed to modelers and decision makers in the implementation of IAM and evaluation of its results. The framework has been tested on Lombardy region (Northern Italy). The results show how the uncertainty on Drivers of emissions propagates on the whole modelling chain characterizing an integrated assessment study.     

用酶联免疫吸附法测定鱼类体内金属硫蛋白

用酶联免疫吸附法测定鱼体内（肝,肾）MT。鱼组织经匀浆、加热、离心、将上清液以包被液稀释后,与一抗、二抗反应,求得MT含量。与镉／血红蛋白饱和法比较、本法显示了特异、简便、及灵敏的特点。同时,用酶联免疫吸附法测定了取自武汉东湖不同水域的鱼类、不同种类的鱼类的组织脏器的MT的含量,用以研究水体质量。     

受限空间中CO与水蒸汽阻尼瓦斯爆炸的反应动力学模拟研究

为了探求一氧化碳与水蒸汽参与瓦斯爆炸的化学反应动力学过程的阻尼效应,建立了受限空间中瓦斯爆炸反应的数学模型。数值计算结果表明,结果表明在瓦斯爆炸过程中,瓦斯-空气混合气体含有10%的一氧化碳,虽然会延迟瓦斯爆炸时间,抑制瓦斯爆炸,但是H、O自由基浓度、瓦斯爆炸温度和压力比不加入一氧化碳时升高,同时对CO2、NO的生成起促进作用;当混合气体中含有10%的水蒸汽时,H、O自由基浓度降低,瓦斯爆炸温度和压力也随之降低,致灾性气体CO2、NO的生成得到抑制。虽然一氧化碳对瓦斯爆炸有一定的阻尼效应,但是由于一氧化碳对部分致灾性气体的生成有促进作用,因此,在阻尼瓦斯爆炸方面,水蒸汽的效果要好于一氧化碳。     

Optimization of an artificial neural network for identifying fishing set positions from VMS data: An example from the Peruvian anchovy purse seine fishery

The spatial behavior of numerous fishing fleets is nowadays well documented thanks to satellite Vessel Monitoring Systems (VMS). Vessel positions are recorded on a frequent and regular basis which opens promising perspectives for improving fishing effort estimation and management. However, no specific information is provided on whether the vessel is fishing or not. To answer that question, existing works on VMS data usually apply simple criteria (e.g. threshold on speed). Those simple criteria generally focus in detecting true positives (a true fishing set detected as a fishing set); conversely, estimation errors are given no attention. For our case study, the Peruvian anchovy fishery, those criteria overestimate the total number of fishing sets by 182%. To overcome this problem an artificial neural network (ANN) approach is presented here. In order to set both the optimal parameterization and use “rules” for this ANN, we perform an extensive sensitivity analysis on the optimization of (1) the internal structure and training algorithm of the ANN and (2) the “rules” used for choosing both the relative size and the composition of the databases (DBs) used for training and inferring with the ANN. The “optimized” ANN greatly improves the estimates of the number and location of fishing events. For our case study, ANN reduces the total estimation error on the number of fishing sets to 1% (in average) and obtains 76% of true positives. This spatially explicit information on effort, provided with error estimation, should greatly reduce misleading interpretations of catch per unit effort and thus significantly improve the adaptive management of fisheries. While fitted on Peruvian anchovy fishery data, this type of neural network approach has wider potential and could be implemented in any fishery relying on both VMS and at-sea observer data. In order to increase the accuracy of the ANN results, we also suggest some criteria for improving sampling design by at-sea observers and VMS data.     

C2H6/CO2组分构成对瓦斯着火延迟时间的影响规律研究

为进一步研究多种不同性质的气体对瓦斯着火过程的影响,采用CHEMKIN-PRO Release软件,选择CH_4燃烧化学反应机理USC Mech 2.0模型对不同组分构成的C_2H_6/CO_2与甲烷混合气体进行数值模拟,然后分析不同组分下瓦斯着火延迟时间的变化趋势,并利用SENKIN程序对其进行敏感性分析。计算结果表明:当C_2H_6百分比小于CO_2百分比时,随着CO_2百分比的增加,瓦斯着火延迟时间略有增加,且其在T=1200K下延长了17.0%,在T=2200K下延长了8.4%,同时抑制CH_4生成的关键反应步敏感性系数下降幅度略大,其协同抑制瓦斯爆炸;当C_2H_6百分比大于CO_2百分比时,随着C_2H_6百分比的增加,瓦斯着火延迟时间大幅缩短,且其在T=1200K下缩短了63.7%,在T=2200K下缩短了35.5%,同时促进CH_4生成的关键反应步敏感性系数下降幅度大,其协同促进瓦斯爆炸。     

Total alkalinity of surface waters: a map of the upper midwest region of the United States

This map (see the inside back cover of this issue) illustrates the regional patterns of mean annual alkalinity of surface water in the northern portions of Minnesota, Wisconsin, and Michigan, USA. It provides a qualitative graphic overview of the relative potential sensitivity of surface waters to acidic input in the upper midwest portions of the United States. The map is based on data from approximately 14,000 lakes and streams and the apparent spatial associations between these data and macroscale watershed characteristics that are thought to affect alkalinity.For the map of the Upper Midwest Region of the United States, see the inside back cover of this issue.     

Land use change and carbon exchange in the tropics: III. Structure,basic equations,and sensitivity analysis of the model

The rationale, assumptions, structure and basic mathematical functions of the model used to produce the simulation results reported in the first two articles of this series are described in detail. Sensitivity analysis indicates that the most important parameters in the model, and, presumably, in the carbon exchange between tropical forests and the atmosphere, are: (a) the conversion rate of forests to permanent pasture and agriculture, (b) the changes that are occurring and have occurred in the shifting cultivation system, and (c) the fate of cleared vegetation. Although it is not possible to validate the model against direct measurements of carbon exchange, the model has been proven robust when subject to a series of explicit analyses and comparisons with other assessments.