高层建筑火灾风险评估中一种具有置信度和方差的权系数

对评估中的权系数引入置信度和方差两个概念 ,为权系数提供更多的信息 ,便于决策者采用 ;针对作者在香港所作的高层建筑火灾风险因子评估系数 ,得到 16个风险因子的带置信度和方差的权系数 ,为火灾风险评估提供重要依据     

Statistical method for the determination of the ignition energy of dust cloud-experimental validation

Powdery materials such as metallic or polymer powders play a considerable role in many industrial processes. Their use requires the introduction of preventive safeguard to control the plants safety. The mitigation of an explosion hazard, according to the ATEX 137 Directive (1999/92/EU), requires, among other things, the assessment of the dust ignition sensitivity. PRISME laboratory (University of Orléans) has developed an experimental set-up and methodology, using the Langlie test, for the quick determination of the explosion sensitivity of dusts. This method requires only 20 shots and ignition sensitivity is evaluated through the E₅₀ (energy with an ignition probability of 0.5). A Hartmann tube, with a volume of 1.3 l, was designed and built. Many results on the energy ignition thresholds of partially oxidised aluminium were obtained using this experimental device (Baudry, 2007) and compared to literature. E₅₀ evolution is the same as MIE but their respective values are different and MIE is lower than E₅₀ however the link between E₅₀ and MIE has not been elucidated.In this paper, the Langlie method is explained in detail for the determination of the parameters (mean value E₅₀ and standard deviation σ) of the associated statistic law. The ignition probability versus applied energy is firstly measured for Lycopodium in order to validate the method. A comparison between the normal and the lognormal law was achieved and the best fit was obtained with the lognormal law.In a second part, the Langlie test was performed on different dusts such as aluminium, cornstarch, lycopodium, coal, and PA12 in order to determine E₅₀ and σ for each dust. The energies E₀₅ and E₁₀ corresponding respectively to an ignition probability of 0.05 and 0.1 are determined with the lognormal law and compared to MIE find in literature. E₀₅ and E₁₀ values of ignition energy were found to be very close and were in good agreement with MIE in the literature.     

Combining material characterization with single and multi-oxyanion adsorption for mechanistic study of chromate removal by cationic hydrogel

Cationic hydrogel with magnetic property was synthesized via radical polymerization and its removal capacity of chromate from contaminated water was found to be 200 mg/g. Using Fourier transform infrared spectroscopy (FT-IR) study, the mechanism of chromate removal by hydrogel was found to be non-specific adsorption, mainly due to ion exchange, as evidenced by the positively charged functional group, trimethyl ammonium –N+(CH3)3; in the monomer. Verifications were accordingly determined by testing different oxyanion adsorption onto the hydrogel. The results of the chromate adsorption experiments illustrated that the amount of chromate adsorbed was nearly equal to that of the chloride released from the hydrogel, which is part of the evidence for ion exchange. Single and multi-oxyanion adsorption experiments were also performed, and it was demonstrated that ion removal was species independent, but charge dependent, another characteristic of the ion exchange process. It was found that the same Langmuir model can be applied to best fit the findings of single and multi-oxyanion adsorption, which further indicates the mechanism of chromate removal is attributed to ion exchange. In view of the above, the background anions compete for adsorption sites with chromate, evidenced by inhibitive chromate removal in the presence of background electrolytes in the batch studies, further echoing the ion exchange mechanism.     

城市灾时大范围人员应急疏散探讨

人类面临着许多自然的和人为的灾害,比如最近发生的印度洋大海啸和2001年的美国"9·11"恐怖袭击事件等.当这类重大灾害性事件发生时,在短时间内安全地大范围疏散转移高密集人群,实施科学的应急救灾策略,是减轻灾害后果严重性的重要措施之一.探讨了如何建立一个综合性的疏散规划模型,为人员应急疏散管理提供决策支持.     

Contributions of biofilm and suspended sludge to nitrogen transformation and nitrous oxide emission in hybrid sequencing batch system

Hybrid system combines the nature of suspended growth and attached growth has been widely applied to wastewater treatment. In this research, the contributions to N transformation and N2O emission by biofilm and suspended sludge in the hybrid sequencingbatch reactor for a simultaneous nitrification, denitrification and phosphorus removal process were investigated. For the hybrid system, nitrification occurred mostly in the suspended sludge, while the biofilm played the major role in denitrification. The interaction of the biofilm and the suspended sludge in the same reactor resulted in a better overall nitrogen removal performance with simultaneous nitrification and denitrification. However, N2O emission was the main end product of nitrogen removal for the hybrid system; while it was N2 for the biofilm. The relative low N2O emissions from the pure biofilm and the pure suspended sludge corresponded to the relatively high nitrate at the end of the aeration period compared with the hybrid system.