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Organic flammable liquids and their mixtures, which possess high risk of combustion and explosion, are widely used as raw materials and solvents in chemical and pharmaceutical industries. Lower flammability limits (LFL) is one of the most important parameters to characterize the combustion and explosion hazards of combustible gases and liquid vapors. The LFL of various ternary organic mixtures consist of ketone (acetone and butanone), ester (ethyl acetate) and alcohol (ethanol and isopropanol) were tested at 25 °C and atmospheric pressure. The results showed that resulted LFL values of the experiment were always lower than those calculated by volume fraction weighting method when the volume fraction of alcohol was less than 20 vol% but more than 10 vol%. The co-existence of alcohol and ethyl acetate had synergistic effect on reducing the LFL values of ternary organic mixtures and thus increased their explosive risk. The mechanism of synergistic effect was analyzed, and the results showed that the OH· and H· radicals produced by the oxidation decomposition of alcohols and esters accelerated the oxidation process of ternary organic mixtures, which led to the decrease of experimental LFL values and thus corresponding increased of their explosive risk. This study would be expected to provide some guidance for designing or choosing safer and more suitable ternary organic mixtures prior to their applications for engineering. 相似文献
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By varying inert gas content, equivalence ratio and initial pressure, this study is aimed at investigating flame propagation behaviors and explosion pressure characteristics near suppression limit. For carbon dioxide, the weakest flame floating phenomenon is observed at Φ = 1.5 and the buoyant instability is enhanced when the equivalent ratio deviates to the rich and lean sides. For nitrogen, the buoyant instability decreases with increasing equivalent ratio. Both maximum explosion pressure and maximum pressure rise rate increase firstly and then decrease with the increase of equivalence ratio, and they decrease significantly with increasing content of carbon dioxide and nitrogen. For carbon dioxide, the critical suppression ratio of Φ = 0.6, 0.8, 1.0, 1.5 and 2.0 is 7.50, 7.18, 5.74, 3.83, and 2.87. For nitrogen, the critical suppression ratio of Φ = 0.6, 0.8, 1.0, 1.5 and 2.0 is 15.83, 11.87, 9.50, 6.33 and 4.75. Compared to nitrogen, the carbon dioxide is more effective on suppressing hydrogen explosion pressure. The adiabatic flame temperature, thermal diffusivity and mole fraction of active radicals continue to decrease with increasing content of carbon dioxide and nitrogen, which contributes to the decrease of laminar burning velocity. 相似文献
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为探究铁磁流体对煤体瓦斯解吸性能的影响,采用水浴恒温吸附解吸系统,开展0.44,0.65,1.14 MPa 3组不同平衡压力下加铁磁流体前后的瓦斯解吸对比实验,根据Langmuir方程经验公式计算瓦斯极限解吸量和初始扩散系数,分析铁磁流体对煤体瓦斯解吸影响的机理。结果表明:在3组不同平衡压力下加入铁磁流体后瓦斯极限解吸量由2.5,10,20 mL/g降低为2.22,3.33,10 mL/g,降低11.2%,66.7%,50%;初始扩散系数由0.997 1,1.629 9,3.888 3 μm2·s降低为0.685 5,0.997 1,2.933 5 μm2·s,降低31.25%,38.82%,24.56%。在铁磁流体的作用下,煤体瓦斯解吸性能得到大幅降低。 相似文献
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近年来,由个人护理品及废旧塑料直接或间接产生的微塑料不断地在各种环境介质中被检出,且微塑料会对生态系统产生各种危害,因此对微塑料的研究受到越来越广泛的关注。阐述了微塑料在水体、沉积物、沙滩和生物体中的赋存情况,介绍了微塑料的采集与分离方法,以及定性与定量分析方法。指出微塑料对环境及生物体产生的危害,提出现阶段研究存在的主要问题,并对今后的研究方向进行了展望。 相似文献
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从仪器精密度、方法检出限、准确度等角度对吹扫捕集浓缩仪Stratum PTC与Eclipse 4660的性能进行比较。结果表明,大部分分析物用Stratum PTC的方法检出限略高于Eclipse 4660,但精密度比Eclipse 4660稍差;Eclipse 4660用于分析极性的、水溶性物质的效果比Stratum PTC好,回收率更高。两种吹扫捕集仪的测试结果均满足《土壤和沉积物挥发性有机物的测定吹扫捕集/气相色谱-质谱法》(HJ 605-2011)标准方法的指标要求。 相似文献
59.
To detect threats and reduce predation risk prey animals need to be alert. Early predator detection and rapid anti-predatory action increase the likelihood of survival. We investigated how foraging affects predator detection and time to take-off in blue tits (Parus caeruleus) by subjecting them to a simulated raptor attack. To investigate the impact of body posture we compared birds feeding head-down with birds feeding head-up, but could not find any effect of posture on either time to detection or time to take-off. To investigate the impact of orientation we compared birds having their side towards the attacking predator with birds having their back towards it. Predator detection, but not time to take-off, was delayed when the back was oriented towards the predator. We also investigated the impact of foraging task by comparing birds that were either not foraging, foraging on chopped mealworms, or foraging on whole ones. Foraging on chopped mealworms did not delay detection compared to nonforaging showing that foraging does not always restrict vigilance. However, detection was delayed more than 150% when the birds were foraging on whole, live mealworms, which apparently demanded much attention and handling skill. Time to take-off was affected by foraging task in the same way as detection was. We show that when studying foraging and vigilance one must include the difficulty of the foraging task and prey orientation.Communicated by P.A. Bednekoff 相似文献
60.
László Z. Garamszegi Thorsten J. S. Balsby Ben D. Bell Marta Borowiec Bruce E. Byers Tudor Draganoiu Marcel Eens Wolfgang Forstmeier Paolo Galeotti Diego Gil Leen Gorissen Poul Hansen Helene M. Lampe Stefan Leitner Jan Lontkowski Laurent Nagle Erwin Nemeth Rianne Pinxten Jean-Marc Rossi Nicola Saino Aurélie Tanvez Russell Titus János Török Els Van Duyse Anders P. Møller 《Behavioral ecology and sociobiology》2005,57(4):305-317
Repertoire size, the number of unique song or syllable types in the repertoire, is a widely used measure of song complexity in birds, but it is difficult to calculate this exactly in species with large repertoires. A new method of repertoire size estimation applies species richness estimation procedures from community ecology, but such capture-recapture approaches have not been much tested. Here, we establish standardized sampling schemes and estimation procedures using capture-recapture models for syllable repertoires from 18 bird species, and suggest how these may be used to tackle problems of repertoire estimation. Different models, with different assumptions regarding the heterogeneity of the use of syllable types, performed best for different species with different song organizations. For most species, models assuming heterogeneous probability of occurrence of syllables (so-called detection probability) were selected due to the presence of both rare and frequent syllables. Capture-recapture estimates of syllable repertoire size from our small sample did not differ significantly from previous estimates using larger samples of count data. However, the enumeration of syllables in 15 songs yielded significantly lower estimates than previous reports. Hence, heterogeneity in detection probability of syllables should be addressed when estimating repertoire size. This is neglected using simple enumeration procedures, but is taken into account when repertoire size is estimated by appropriate capture-recapture models adjusted for species-specific song organization characteristics. We suggest that such approaches, in combination with standardized sampling, should be applied in species with potentially large repertoire size. On the other hand, in species with small repertoire size and homogenous syllable usage, enumerations may be satisfactory. Although researchers often use repertoire size as a measure of song complexity, listeners to songs are unlikely to count entire repertoires and they may rely on other cues, such as syllable detection probability.Communicated by A. Cockburn 相似文献