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991.
Susan D. Shaw Michelle L. Berger Kurunthachalam Kannan Olaf Päpke 《The Science of the total environment》2009,407(10):3323-3329
Seven species of teleost fishes comprising major prey of northwest Atlantic harbor seals were analyzed for polybrominated diphenyl ethers (PBDEs). PBDE concentrations in whole fish samples (n = 87) were compared with those measured previously in harbor seal blubber to evaluate the transfer of PBDEs from prey to predator. Hexabromocyclododecane (HBCD) concentrations were measured in three fish species to provide an initial estimation of HBCD contamination in this ecosystem. HBCD was detected in 87% of the fish samples at concentrations ranging from 2.4 to 38.1 ng/g, lw (overall mean 17.2 ± 10.2 ng/g, lw). ∑PBDE concentrations in fish ranged from 17.9 to 94 ng/g, lw (overall mean 62 ± 34 ng/g, lw). ∑PBDE concentrations in the harbor seals were two orders of magnitude higher than levels in the fish. Biomagnification factors (BMFs) from fish to seals averaged from 17 to 76, indicating that tetra- to hexa-BDEs are highly biomagnified in this marine food web. BDE-47 was the dominant congener in all samples, suggesting exposure to the penta-BDE mixture. The presence of higher brominated congeners including BDE-209 at measurable levels in fish and seal tissue, along with the very high biomagnification of BDE-153, as well as − 155, and − 154, suggests recent exposure to the octa- and deca-BDE formulations in this US coastal marine food web, as well as the additional contribution of BDE-209 debromination in fish to the loading of persistent PBDEs in the seals. This is the first study to report the occurrence of BDE-209 and other higher BDEs in commercially important marine fishes from the northwest Atlantic. 相似文献
992.
993.
Modeling the trajectory of window flames with regard to flow attachment to the adjacent wall 总被引:1,自引:0,他引:1
A model for predicting the trajectory of window flame ejected from a fire compartment was formulated incorporating the effect of wall above the opening. Based on the observation in the reduced scale experiments, window flames were divided into the following categories with regard to its trajectory configuration: the flow which ascends almost vertically up after ejection maintaining a certain separation from the wall; and the flow which ascends upward after ejection and gradually approaches to the wall in the downstream. In the model, trajectories of these flows were approximated by cubic polynomials whose coefficients were given as functions of a dimensionless parameter F*. The parameter F* was derived from the conservation equation of momentum which incorporates the effect of pressure gradient across the ascending flows. Critical condition for the occurrence of flow attachment was described as a proportion of the maximum separation from the wall versus the opening width. Trajectories predicted by the proposed model were then compared with the measurement data which indicated reasonable agreements. 相似文献
994.
A series of reduced-scale experiments were carried out in order to investigate thermal behaviors of window flame, which exposes the upper floors as well as the adjacent buildings to potential risks of fire spread. A stainless pan filled with alcohol was used as the fire source and was placed inside a cubic compartment of 900 mm side. Temperatures and velocities at various points inside and outside of the compartment were measured. The compartment was pressurized during the experiment by mechanically supplying air at several mass inflow rates through an inlet duct set at the bottom part of the compartment. This was for simulating fire conditions under the effect of external wind pressure. On the basis of the experimental observation, line (i.e., two-dimensional) heat source assumption was adopted for developing a model of window flame behavior. A dimensionless parameter Q′* was derived from the governing differential equations in order to generalize the measurement results. Expressions for temperature rise along the trajectory ΔTm and characteristic flame width bT were developed incorporating the parameter Q′*. 相似文献
995.
One previous experimental study has reported a width effect for upward flame spread rate on thermally thin fuels. A similar effect is expected for thermally thick fuels. This study revisited this topic by developing a hypothesis and performing experiments with sidewalls using 18 mm thick, 1000 mm tall PMMA slabs of widths 100, 200, 300, 500 and 700 mm. In the hypothesis, a lateral diffusion throughout the flame width was proposed to cause thicker flame along its centerline for wider flames and enhance combustion efficiency. Higher heat release rate per unit width, larger flame height, higher flame temperature and more heat feedback to the surface were consequently present. The corresponding flame spread rate was also increased and a power value of 0.35 existed between the flame spread rate and width in this study. All the experimental results clearly supported the hypothesis. 相似文献
996.
选取聚磷酸铵(APP)/季戊四醇(PER)/三聚氰胺(MEL)组成膨胀阻燃体系,采用马来酸酐接枝聚丙烯(MAH-g-PP)为增容剂,研究了三种膨胀阻燃成分及MAH-g-PP的含量的变化对阻燃聚丙烯力学性能的影响。研究结果表明:随着MAH-g-PP含量的增加,阻燃聚丙烯的力学性能有所改善,在10%以前提高较大,在10%以后增幅趋缓。 相似文献
997.
环氧树脂改性水性聚氨酯阻燃涂料的研究 总被引:3,自引:0,他引:3
以E-44环氧树脂改性水性聚氨酯为基料,三聚氰胺、季戊四醇为阻燃剂,制备了一种阻燃涂料.测试了该涂料的附着力、耐水性、吸水率、阻燃性及热失重.结果表明,改性后涂料的涂膜附着力达到1级,耐水时间为240 h,吸水率16.5%,阻燃时间可达10 min以上,耐高温及阻燃性能明显提高. 相似文献
998.
999.
1000.
微胶囊红磷膨胀型阻燃剂的制备及应用 总被引:2,自引:0,他引:2
制备了微胶囊红磷/季戊四醇/三聚氰胺膨胀型阻燃剂(IFR)。采用吸湿性、抗氧化性、SEM、TG等测试方法对阻燃剂进行了表征。结果表明:微胶囊红磷的吸湿性减小、抗氧化性增强;TG分析显示,微胶囊红磷在385~422℃、470~553℃有两个失重阶段;600℃时,未包覆红磷残重仅为6%,而微胶囊包覆红磷的残重为12%;微胶囊红磷膨胀型阻燃剂的最佳组成为:微胶囊红磷:季戊四醇:三聚氰胺=4.00:0.75:2.00(摩尔比);500℃下,IFR残重高达65.06%;当IFR添加量为30%时,阻燃环氧树脂的氧指数从未添加IFR时的19.0%提高到26.3%。 相似文献