基于MODIS数据的森林火险时空分异规律研究

森林火灾严重危害生态环境,引起了全球的高度重视。将从MODIS(MODerate-resolution imaging spectroradiometer)中提取的活动火点与历史火烧痕迹进行比较研究,发现MOD14A1(火掩膜数据产品a daily Level 3 1-km fire hot spot product)中提取的8+9波段适合消防监测,与现场勘察数据相比较吻合度高达0.83。使用MOD14A1中8+9波段结合相关数据对这个区域的长达11年(2000—2010年)的森林火灾发生的时间和空间分析,结果表明：火灾发生频率最多的是春季,秋季次之,夏天概率最低,除非干旱。通过对研究区域黑龙江省分析,针叶林和温带针阔混交林过火面积所占比例分别为53.68%,44%,草原区过火面积较小为2.32%。大兴安岭是主要的燃烧区域,面积达到64.74%,小兴安岭约为23.49%,而其他区域面积不超过5%。且火灾发生的较大部分森林有个平缓的斜坡(≤5°),大部分处于中海拔(200 m≤H≤500 m)。因此,通过卫星遥感对森林火区区域的时间序列分析,阐明火灾活动规律和气候、地形、植被类型的相互关系,有助于预测火灾区域危险性等级。     

Fire impact on forest soils evaluated using near-infrared spectroscopy and multivariate calibration

The assessment of physico-chemical properties in forest soils affected by fires was evaluated using near infrared reflectance (NIR) spectroscopy coupled with chemometric methods. In order to describe the soil properties, measurements were taken of the total organic carbon on solid phase, the total nitrogen content, the organic carbon and the specific absorbences at 254 and 280 nm of humic substances, organic carbon in humic and fulvic acids, concentrations of NH₄⁺, Ca²⁺, Mg²⁺, K⁺ and phosphorus in addition to NIR spectra. Then, a fire recurrence index was defined and calculated according to the different fires extents affecting soils. This calculation includes the occurrence of fires as well as the time elapsed since the last fire. This study shows that NIR spectroscopy could be considered as a tool for soil monitoring, particularly for the quantitative prediction of the total organic carbon, total nitrogen content, organic carbon in humic substances, concentrations of phosphorus, Mg²⁺, Ca²⁺ and NH₄⁺ and humic substances UVSA₂₅₄. Further validation in this field is necessary however, to try and make successful predictions of K⁺, organic carbon in humic and fulvic acids and the humic substances UVSA₂₈₀. Moreover, NIR coupled with PLS can also be useful to predict the fire recurrence index in order to determine the spatial variability. Also this method can be used to map more or less burned areas and possibly to apply adequate rehabilitation techniques, like soil litter reconstitution with organic enrichments (industrial composts) or reforestation. Finally, the proposed recurrence index can be considered representative of the state of the soils.     

Preparation and characterisation of a novel fire retardant PET/α-zirconium phosphate nanocomposite

The preparation of a novel fire retardant nanocomposite of poly(ethylene terephthalate) (PET) using nanoscopic α-zirconium phosphate (α-ZrP), by in situ polymerisation was investigated. The novel fire retarded PET nanocomposite, PET-co-DDP/α-ZrP, was synthesized by the direct condensation of terephthalic acid, ethylene glycol, 9,10-dihydro-10[2,3-di(hydroxycarbonyl)propyl]-10-phosphaphenanthrene-10-oxide (DDP) and nano α-ZrP. The morphology, thermal stability and burning behaviour of the nanocomposite with 1 wt% α-ZrP loading was investigated. The extent of dispersion of the nanofillers was quantified by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Significant improvements in fire retardant performance were observed for the nanocomposite from limiting oxygen index (increased from 21.2 to 32.6), UL-94 (achieving V-0), and cone calorimetry (reducing both the heat release rate and the total heat released, without reducing the time to ignition).     

微波消解-火焰原子吸收光谱法测定下火药材中的微量元素

微波消解样品,火焰原子吸收光谱法测定下火药材中5种微量元素的含量。菊花中钙、镁、铁、锌、锰的含量分别为15.80,31.42,7.68,0.935,0.105g/kg;桑叶中钙、镁、铁、锌、锰的含量分别为195.6,33.69,7.02,0.839,2.21g/kg;夏枯草中钙、镁、铁、锌、锰的含量分别为110.9,38.69,14.75,1.24,0.112g/kg。该方法加标回收率在90.1%—106.3%之间,方法简单、灵敏、准确,可为下火药材的基础研究提供依据。     

火试金法测定铅冶炼渣中的金、银含量

建立了铅冶炼渣中的金银含量的测定方法,采用火试金法富集铅冶炼渣中的金、银,铅扣经灰吹后,形成金银合粒,合粒中除有金银外,还残留微量的铅铋杂质,合粒经硝酸分金后,实现金银分离,得到金粒和分金溶液。合粒中杂质保留在分金溶液中,分金溶液经酸处理,采用电感耦合等离子体发射光谱(ICP-OES)法测定其中杂质量和微量的金量。金粒质量补正分金溶液中微量金量即为样品中的金量,合粒质量减去金粒质量和杂质量即为银量。ICP-OES法测定杂质解决了合粒中铅铋残留和分金失误造成微量金进入分金溶液现象。方法精密度较好,加标回收率分别为银98.6%～100%,金96.2%～102%。方法准确、方便、快捷,能很好地满足铅冶炼渣中金、银含量的测定。     

火试金重量法与AAS湿法结合测定砂金矿中金的含量

砂金矿中二氧化硅和金的含量较高,本文用传统的火试金重量法与AAS湿法相结合来测定砂金矿中的金含量,用以得到较为精确的结果。本文用科学的配料方法,调节好熔渣的硅酸度,得到品质更好的熔渣与铅扣。再通过二次补正收集分散在熔渣中的金,之后进行三次补正收集灰皿中残留的金含量,然后用原子吸收光谱—AAS湿法测定三次补正得到的金银合粒与分金液中金的含量,从而得到更精确的结果。此方法操作简便、适用性广、精密度与准确度较高。通过加标测试此方法金的回收率在99.2%～100.3% 之间,金的相对标准偏差(RSD)在0.24%～0.6%之间。     

基于锥形量热仪试验的聚合物材料火灾危险评价研究

简述了锥形量热仪的试验原理,以聚合物材料锥形量热仪试验数据为基础,导出了火势增长指数（FGI）、放热指数（THRI6min）、发烟指数（TSPI6min）和毒性气体生成速率指数（ToxGI）4个评价聚合物材料火灾危险的参数,并利用这四个参数对ABS、PS、PVC、PA 4类16种商用塑料样品的火灾危险性逐项进行了分析评价.在此基础上,采用层次分析法的原理对样品的火灾危险进行了综合评价,结果表明,ABS、PS、PVC、PA四类样品的火灾综合危险依次减小.     

Coupled fire dynamics and thermal response of complex building structures

Simulation of the effects of severe fires on the structural integrity of buildings requires a close coupling between the gas phase energy release and transport phenomena, and the stress analysis in the load-bearing materials. The connection between the two is established primarily through the interaction of the radiative heat transfer between the solid and gas phases with the conduction of heat through the structural elements. This process is made difficult in large, geometrically complex buildings by the wide disparity in length and time scales that must be accounted for in the simulations. A procedure for overcoming these difficulties used in the analysis of the collapse of the World Trade Center towers is presented. The large scale temperature and other thermophysical properties in the gas phase are predicted using the NIST Fire Dynamics Simulator. Heat transfer to subgrid scale structural elements is calculated using a simple radiative transport model that assumes the compartment is locally divided into a hot, soot laden upper layer and a cool relatively clear lower layer. The properties of the two layers are extracted from temporal averages of the results obtained from the Fire Dynamics Simulator. Explicit formulae for the heat flux are obtained as a function of temperature, hot layer depth, soot concentration, and orientation of each structural element. These formulae are used to generate realistic thermal boundary conditions for a coupled transient three-dimensional finite element code. This code is used to generate solutions for the heating of complex structural assemblies.     

Fire retardant systems in poly(methyl methacrylate): Interactions between metal oxide nanoparticles and phosphinates

In the course of our investigations on halogen-free fire-retardant solutions for PMMA, the influence of oxide nanoparticles (TiO₂, Al₂O₃) on the thermal stability and fire behaviour of PMMA blended with phosphinate additives (Exolit OP930 and OP1311) has been studied by thermogravimetric analysis and cone calorimetry. For each mixture, the residues obtained after combustion were examined and characterized by SEM, X-ray diffraction and X-ray microprobe analysis. Some synergistic effects were obtained between nanometric alumina and OP930 additive leading to the reduction of peak of heat released rate and of total heat released up to 30% and to the increase of time to ignition. From the results obtained, it can be proposed that OP930 and OP1311 act principally in the condensed phase, the presence of oxides playing a reinforcement role in the carbonaceous layer promoted by the phosphinate additives.