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511.
固体和液体化学品仓库火灾是企业安全面临的经常性威胁之一,需考虑火灾中毒性燃烧产物释放和非燃烧产生的毒性物质释放。结合火灾风险分析方法,阐述火灾场景中各要素及相互关系,主要包括火灾场景、物质、燃烧速率、源项、毒性、扩散、概率和风险之间的关系,火灾场景考虑持续时间、面积和通风率的影响,物质中考虑平均结构式和燃烧方程,源项中考虑形成的产物、燃烧物质每千克的散发和活性物质百分比,毒性中考虑HCl,NO2,SO2和非燃烧产生的物质。基于储存物质平均结构式,建立燃烧关系方程。燃烧速率计算取决于可用的氧气量和需要的氧气量,分为面积受限的燃烧速率和氧气受限的燃烧速率。最后给出毒性燃烧产物HCl,NO2,SO2释放量和非燃烧产生的毒性物质释放量的计算方法,同时以毒性燃烧产物释放场景后果模拟为例说明仓库发生火灾的后果严重性,为仓库火灾风险分析提供借鉴。 相似文献
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Thomas J. Habib Evelyn H. MerrillM.J. Pybus David W. Coltman 《Ecological modelling》2011,222(15):2722-2732
Managing wildlife diseases requires an understanding of disease transmission, which may be strongly affected by host population density and landscape features. Transmission models are typically fit from time-series disease prevalence data and modelled based on how the contact rate among hosts is affected by density, which is often assumed to be a linear (density-dependent transmission) or constant (frequency-dependent transmission) relationship. However, long-term time-series data is unavailable for emerging diseases, and this approach cannot account for independent effects of landscape. We developed a mechanistic model based on ecological data to empirically derive the contact rate-density relationship in white-tailed and mule deer in an enzootic region of chronic wasting disease (CWD) in Alberta, Canada and to determine whether it was affected by landscape. Using data collected from aerial surveys and GPS-telemetry, we developed empirical relationships predicting deer group size, home range size, and habitat selection to iteratively simulate deer distributions across a range of densities and landscapes. We calculated a relative measure of total per-capita contact rate, which is proportional to the number of other deer contacted per individual per unit time, for each distribution as the sum of pairwise contact rates between a target deer and all other individuals. Each pairwise contact rate was estimated from an empirical relationship developed from GPS-telemetry data predicting pairwise contact rates as a function of home range overlap and landscape structure. Total per-capita contact rates increased as a saturating function of density, supporting a transmission model intermediate between density- and frequency-dependent transmission. This pattern resulted from group sizes that reached an asymptote with increasing deer density, although this relationship was mediated by tree and shrub coverage in the landscape, such that in heavily wooded areas, the contact rate saturated at much lower densities. These results suggest that CWD management based on herd reductions, which require a density-dependent contact rate to be effective, may have variable effects on disease across a single management region. The novel mechanistic approach we employed for estimating effects of density and landscape on transmission is a powerful complement to typical data-fitting approaches for modelling disease transmission. 相似文献
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Integrating soil carbon cycling with that of nitrogen and phosphorus in the watershed model SWAT: Theory and model testing 总被引:1,自引:0,他引:1
Armen R. Kemanian Stefan Julich Valipuram S. ManoranjanJeffrey R. Arnold 《Ecological modelling》2011,222(12):1913-1921
In this paper we describe and test a sub-model that integrates the cycling of carbon (C), nitrogen (N) and phosphorus (P) in the Soil Water Assessment Tool (SWAT) watershed model. The core of the sub-model is a multi-layer, one-pool soil organic carbon (SC) algorithm, in which the decomposition rate of SC and input rate to SC (through decomposition and humification of residues) depend on the current size of SC. The organic N and P fluxes are coupled to that of C and depend on the available mineral N and P, and the C:N and N:P ratios of the decomposing pools. Tillage explicitly affects the soil organic matter turnover rate through tool-specific coefficients. Unlike most models, the turnover of soil organic matter does not follow first order kinetics. Each soil layer has a specific maximum capacity to accumulate C or C saturation (Sx) that depends on texture and controls the turnover rate. It is shown in an analytical solution that Sx is a parameter with major influence in the model C dynamics. Testing with a 65-yr data set from the dryland wheat growing region in Oregon shows that the model adequately simulates the SC dynamics in the topsoil (top 0.3 m) for three different treatments. Three key model parameters, the optimal decomposition and humification rates and a factor controlling the effect of soil moisture and temperature on the decomposition rate, showed low uncertainty as determined by generalized likelihood uncertainty estimation. Nonetheless, the parameter set that provided accurate simulations in the topsoil tended to overestimate SC in the subsoil, suggesting that a mechanism that expresses at depth might not be represented in the current sub-model structure. The explicit integration of C, N, and P fluxes allows for a more cohesive simulation of nutrient cycling in the SWAT model. The sub-model has to be tested in forestland and rangeland in addition to agricultural land, and in diverse soils with extreme properties such high or low pH, an organic horizon, or volcanic soils. 相似文献
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以山地长寿沙田柚成年果树为对象,研究不同生境和季节对丛枝菌根(Arbuscular mycorrhiza,AM)真菌侵染以及根围土壤中AM真菌孢子密度的影响.试验结果表明,不同生境下,菌根侵染率和AM真菌孢子密度都是以梯田最高,坡地次之,洼地最低;在坡地和洼地生境下,生草区均高于清耕区.两块试验地AM真菌的菌丝侵染率均为夏季最高(16.8%±1.9%和16.0%±1.8%),秋季次之,冬季最低;丛枝和泡囊的形成也是夏/秋季较高,春/冬季较低;而根围土壤中AM真菌孢子密度则是秋季最高[(159±19)个/100 g和(167±17)个/100 g],夏季次之,冬季最低.总之,对于长寿沙田柚成年果树,AM真菌的菌根侵染率在夏季梯田最高,根围土壤中的AM真菌孢子密度在秋季梯田最高;在坡地和洼地生境中,生草处理均可显著提高菌根侵染率和AM真菌孢子密度.图4参27 相似文献
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UV-B辐射增强对不同大麦品种生理特性的影响 总被引:1,自引:0,他引:1
通过大田试验,研究了UV-B辐射增强对不同生育期3个大麦(Hordeum vulgare)品种光合和蒸腾生理特性的影响。试验设对照(自然光)和辐射增强(辐照强度14.4 kJ.m-2.d-1)2个UV-B辐射水平。结果表明,UV-B辐射增强明显抑制大麦光合作用和蒸腾作用。与对照相比,UV-B辐射增强可降低叶片叶绿素含量、气孔导度、净光合速率和蒸腾速率,但对胞间CO2摩尔分数基本没有影响。不同大麦品种对UV-B辐射增强响应的敏感性存在差异,单2号对UV-B辐射增强较为敏感,而苏啤4号较不敏感。 相似文献
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研究了未处理的腐殖酸(HA)和不溶性腐殖酸(IHA)对Cr(Ⅵ)的吸附作用.进行了反应时间、pH值、IHA投加量、温度等对去除效率的影响研究,确定了两种吸附剂最佳反应条件,并通过对比实验,分析了两种吸附剂吸附Cr(Ⅵ)的特点.实验表明,HA达到最大吸附量时所需要的反应时间(180 min左右)远远高于IHiA的反应时间... 相似文献
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