Retrospective analysis of two northern California wild-land fires via Landsat five satellite imagery and Normalized Difference Vegetation Index (NDVI)

Wild-land fires are a dynamic and destructive force in natural ecosystems. In recent decades, fire disturbances have increased concerns and awareness over significant economic loss and landscape change. The focus of this research was to study two northern California wild-land fires: Butte Humboldt Complex and Butte Lightning Complex of 2008 and assessment of vegetation recovery after the fires via ground based measurements and utilization of Landsat 5 imagery and analysis software to assess landscape change. Multi-temporal and burn severity dynamics and assessment through satellite imagery were used to visually ascertain levels of landscape change, under two temporal scales. Visual interpretation indicated noticeable levels of landscape change and relevant insight into the magnitude and impact of both wild-land fires. Normalized Burn Ratio (NBR) and delta NBR (DNBR) data allowed for quantitative analysis of burn severity levels. DNBR results indicate low severity and low re-growth for Butte Humboldt Complex “burned center” subplots. In contrast, DNBR values for Butte Lightning Complex “burned center” subplots indicated low-moderate burn severity levels.

The impact of climate change on fire risk in Daxing'anling,China

Daxing’anling is a key region for forest fire prevention in China. Assessing changes in fire risk in the future under multiple climatic scenarios will contribute to our understanding of the influences of climate change for the region and provide a reference for applying adaptive measures for fire management. This study analyzed the changes in fire weather indices and the fire season under four climate scenarios (RCP2.6, RCP4.5, RCP6.0, RCP8.5) for 2021-2050 using data from five global climate models together with observation data. The results showed that the analog data could project the average state of the climate for a given period but were not effective for simulating extreme weather conditions. Compared with the baseline period (1971-2000), the period 2021-2050 was predicted to have an increase in average temperature of 2.02-2.65 °C and in annual precipitation 25.4-40.3 mm, while the fire weather index (FWI) was predicted to increase by 6.2-11.2% and seasonal severity rating (SSR) by 5.5-17.2%. The DMC (Duff moisture code), ISI (initial spread index), BUI (build-up index), FWI and SSR were predicted to increase significantly under scenarios RCP4.5, RCP6.0, and RCP8.5. Furthermore, days with high or higher fire danger rating were predicted to be prolonged by 3-6 days, with the change in the southern region being greater under scenarios RCP4.5, RCP6.0, and RCP8.5.

Spatiotemporal variation in forest fire danger from 1996 to 2010 in Jilin Province,China

We evaluated the spatial and temporal patterns of forest fires in two fire seasons (March to June and September to November) from 1996 to 2010 in Jilin Province, China, using the Canadian Forest Fire Weather Index System. Fire data were obtained from the Provincial Fire Agency, and historical climate records of daily weather observations were collected from 36 weather stations in Jilin and its neighboring provinces. A linear regression model was used to analyze linear trends between climate and fire weather indices with time treated as an independent variable. Correlation analysis was used to detect correlations between fire frequency, areas burned, and fire weather indices. A thin-plate smooth spline model was used to interpolate the point data of 36 weather stations to generate a surface covering the whole province. Our analyses indicated fire frequency and areas burned were significantly correlated with fire weather indices. Overall, the Canadian Forest Fire Weather Index System appeared to be work well for determining the fire danger rating in Jilin Province. Also, our analyses indicated that in the forthcoming decades, the overall fire danger in March and April should decrease across the province, but the chance of a large fire in these months would increase. The fire danger in the fall fire season would increase in the future, and the chance of large fire would also increase. Historically, because most fires have occurred in the spring in Jilin Province, such a shift in the future fire danger between the two fire seasons would be beneficial for the province's fire management.

STUDY ON FOREST FIRE DANGER MODEL WITH REMOTE SENSING BASED ON GIS

Forest fire is one of the main natural hazards because of its fierce destructiveness. Various researches on fire real time monitoring, behavior simulation and loss assessment have been carried out in many countries. As fire prevention is probably the most efficient means for protecting forests, suitable methods should be developed for estimating the fire danger. Fire danger is composed of ecological, human and climatic factors. Therefore, the systematic analysis of the factors including forest characteristics, meteorological status, topographic condition causing forest fire is made in this paper at first. The relationships between biophysical factors and fire danger are paid more attention to. Then the parameters derived from remote sensing data are used to estimate the fire danger variables, According to the analysis, not only PVI (Perpendicular Vegetation Index) can classify different vegetation but also crown density is captured with PVI. Vegetation moisture content has high correlation with the ratio of actual evapotranspiration (LE) to potential ecapotranspiration (LEp). SI (Structural Index), which is the combination of TM band 4 and 5 data, is a good indicator of forest age. Finally, a fire danger prediction model, in which relative importance of each fire factor is taken into account, is built based on GIS.

Investigation on Fire Protection System of Highrise Buildings in the Context of Bir Uttam Aminul Haque Avenue in Dhaka, Bangladesh

Rapid high-rise building construction of different occupancies is becoming popular in Dhaka due to its economic gain and functional flexibility. Fire prevention poses a significant difficulty to this type of construction due to its complexity and economic worth as well. Therefore, construction of high-rise building without following the proper fire safety measures, is a common practice at present in the city and it poses a greater threat to urban life considering its associated loss. Even though, most of the owners or authorities do not respect the construction code and the majority of them lack sufficient awareness and basic fire control knowledge and practice. More often, they are unable to comprehend the magnitude and severity of severe fire hazards, and recognize the causes and implementing effective mitigation measures are rare. As a result, the number of fire hazard in high-rise construction is increasing day by day. Hence, investigating the present condition of high-rise buildings (already built) in terms of Fire Protection System is imperative to prevent the upcoming fire hazard. An urban chunk of 33 plots along with Bir Uttam Aminul Haque Avenue, located in Banani, has been chosen for the study area considering its vulnerability to fire hazard. Among these buildings, STAR Tower and HBR Tower, these two high-rise buildings are assessed thoroughly using FRI (Fire Risk Index) Method. The method is semi-quantitative in nature with seventeen parameters associated with fire protection. This assessment represents a scenario in what extent fire codes are being followed in the selected area. It concludes that most of the buildings lack in providing protection against fire hazards for not following the code strictly. This research provides some recommendations which can be followed to improve the fire safety measures in this existing context. It is expected that this research could be a unique addition to firefighting knowledge by contributing to mitigating the consequences of fire related hazards in any densely populated city like Dhaka.

Study on Forecasting Method of Forest Fire Risk Grade in Putian City, China

From January 1, 2014, the basic stations of meteorological observation countries have changed from small evaporation observations to large-scale evaporation observations. National general weather stations have canceled observations on evaporation, but small evaporation is very important for forest fire risk prediction. In order to make the prediction of forest fire risk level objectively, weather data in Putian City, China and the multi-linear regression analysis method is used to calculate the daily evaporation amount in the more advanced SPSS16.0 software (English version), and the data of the last 5 years of each site are selected and fitted. Results showed that we accurately calculated the evaporation of the next day to make up for the lack of data due to the adjustment of the evaporation observation project. According to the forest fire risk weather index corresponding to many meteorological factors such as evaporation, temperature, humidity, sunshine and wind speed, the forest fire risk meteorological grade standard was designed to make a more accurate forest fire risk grade forecast.

基于机器学习的CFST柱高温剩余强度系数预测方法

目的 为提高计算精度和速度,利用机器学习模型泛化数据,以预测CFST柱的高温剩余强度系数。方法 利用生成对抗网络将搜集到的110个试验结果泛化生成407组数据,据此训练机器学习模型,并使用试验结果评估其性能,以确定最优模型;然后使用生成数据输入建立的模型预测CFST柱高温剩余强度系数,并和现有计算方法进行对比。结果 建立的随机森林模型在性能度量上表现最好,拟合优度达到0.947 7,均方误差为0.001 8,精度为94.7%;预测结果误差在±10%内的数据为83%,在±20%内的数据为100%;剩余强度系数主要影响因素依次为温度、钢材屈服强度、混凝土抗压强度和横截面积,钢管厚度影响很小。结论 提出的预测方法优于现有计算方法,具有更快的计算速度、更小的结果误差以及更强的模型可解释性,该方法可为CFST柱抗火设计提供参考。

基于隐马尔可夫模型的火灾风险评估研究

近年来全球气候变化越来越复杂,自然灾害频发,森林防火形式日益严峻,森林火灾风险评估工作越来越重要。为此,基于隐马尔可夫模型(Hidden Markov Model, HMM)提出一种森林火险评估模型。首先构建森林火灾风险指标体系,将其分为气象条件、森林特征以及防火意识和能力3类12个指标,并根据层次分析法计算指标权重。同时,针对HMM模型求解过程中Baum-Welch算法对初始值有较强的依赖性且容易陷入局部最优的问题,提出通过粒子群优化算法搜索全局最优解作为HMM初始值,再使用Baum-Welch算法进行局部校正,使其快速收敛到全局最优解。利用优化前后的2个模型分别对重庆市森林火灾风险数据开展评估,验证优化后的模型能够有效地评估森林火灾风险,并且与改进前相比更精确,可为区域森林防火工作提供有效指导。

野外-城市界域森林火险时空演变趋势及火险等级划分

野外-城市界域(WUI)人类活动密集,火灾风险极大,在该区域进行森林火险的合理性评价和时空演变趋势分析,对保护区域生态环境和社会经济可持续发展具有重要意义。以北京近郊九龙山林场为研究对象,基于相关火险驱动因子指标数据,运用层次分析法评估研究区2004、2009、2014、2019年森林火险指数,通过Theil-Sen Median趋势分析、全局莫兰指数和局部莫兰指数分析探究森林火险指数的变化趋势及空间聚集性,并基于历史火情数据和地理探测器模型验证火险区划的合理性和准确性。结果表明:(1)九龙山林场内火险指数整体的集聚特征变化较大,61.58%的区域火险指数不显著增加,5.62%的区域微显著增加,32.80%区域为不显著减少和微显著减少。(2)森林火险指数空间上呈正相关,森林火险高值聚集区域分布于东部低海拔地区,在研究时间段内面积减少4.89%,低值聚集区域分布于西部高海拔地区,面积减少2.19%。(3)森林火险区划结果显示,九龙山林场森林高火险区域面积占比最小,主要分布于研究区中部,由于人类活动的影响,高火险区覆盖范围扩大。(4)区划合理性验证结果显示,研究区森林火险等级空间分异性较好,与实际火点分布具有高度一致性。研究结果较好的反应了研究区森林火险时空格局变化,为九龙山林场进一步合理规划防火设施布局,加强火险管控力度,完善防火应急能力奠定数据基础,提示管理部门应加强防火宣传,以最大限度发挥九龙山的生态环境效益,保障林区周边人民生命财产安全。

考虑多火灾场景的古城镇消防供水可靠性评估

针对云南省火灾事故频发的现状,评估古城镇消防安全对人民生命财产安全和文化遗产保护具有重要现实意义。提出火灾失效指数以筛选火灾失效风险高的建筑及组合。首先,利用美国联邦保险事务所的消防流量计算方法评估火灾时重要单体建筑的消防需水量。然后,构建水力模型评估消防管网供水能力。最后,通过计算建筑火灾失效指数以识别危险建筑及危险组合。将所提出的算法应用于云南省丽江市大研古城的消防管网。结果表明:单火灾场景的失效指数不仅与管道的管径、建筑附近消火栓数量和建筑的耐火等级相关,还与建筑的位置相关;随着火灾场景数量的增加,各建筑的失效指数均呈现不同程度的上升,最高可超过30%;建议在消火栓较少的区域增设消防管网附近的消火栓,以增强消防供水量,并优化远离水源建筑的消防设施。

Structure changes and succession dynamic of the natural secondary forest after severe fire interference

The structure and dynamic succession law of natural secondary forest after severe fire interference in recent 20 years were studied by adopting the method of deducing time series from the spatial sequence of vegetation in Heihe region, Heilongjiang, China.Two typical and widely distributed forest types in the study area, namely forest type A and forest type B, were selected as study subjects.Forest type A is pure broadleaf forest or broadleaf mixed forest mainly composing of superior Betula platyphylla and Populus davidiana in the area with gradient <25°, while forest type B is pure forest or mixed forest composing of superior Quercus mongolica and Betula davurica in the area with gradient >25°.Species richness, vegetation coverage, important value, and similarity index of community in different layers(Herb, shrub, small tree, and arbor layers) were investigated and analyzed for the two typical forests.The results show that after fire interference, the species richness and coverage in each layer in forest type A were higher than that in forest type B.Both for forest type A and B, with elapse of post-fire years, the species richness and coverage of herbs and shrubs showed a decline tendency, while those of arbor layer present a rising tendency.Through comparison of the important values of species in each layer and analysis of community structure changes, the dynamic process of post-fire vegetation succession for forest type A and B was separately determined.Post-fire 80 years' succession tendency of forest type A is B.platyphylla and Larix gmelinii mixed forest.Its shrub layer is mainly composed of Corylus heterophylla and Vaccinium uliginosum, and herb layer is dominated by Carex tristachya, Athyrium multidentatum, and Pyrola incarnate;whereas, the post-fire 80 years' succession of forest type B is Q.mongolica and B.davurica mixed forest.Its shrub layer is mainly composed of lespedeza bicolar and corylus heterophylla and herb layer is dominated by Carex tristachya, Asparagus densiflorus, and Hemerocallis minor.

基于Sentinel-2影像的火烧迹地生态指数提取及植被恢复影响评价--以浑南区棋盘山为例

火灾对生态环境的损害是最明显最直接的,对火灾地区生态环境质量变化及灾后植被恢复的研究具有重要意义。以沈阳市棋盘山附近2019年火灾形成的火烧迹地为研究对象,基于Sentinel-2遥感影像,对比分析dNBR、NDVI、EVI、BAI、BADI 5种植被指数对火烧迹地的提取能力,筛选出最佳指数;依据遥感生态指数RSEI,综合考虑火灾对生态环境质量的短期影响;同时运用归一化植被指数NDVI和林分恢复指数SRI观察植被恢复情况。结果表明:BADI指数结合Sentinel-2数据提取火烧迹地面积最优,与官方数据相符;火灾对生态环境破坏程度严重,灾后3年RSEI呈现先快后慢的上升趋势;NDVI与SRI呈现轻度火烧迹地恢复速度最快,重度、中度火烧迹地稳步恢复的趋势。

300 MW超临界二氧化碳燃煤发电机组热经济性分析

针对300 MW超临界二氧化碳(SCO_(2))部分冷却循环和部分冷却再热循环燃煤发电系统,建立了热经济性数学模型,以循环热效率η_(t)、系统㶲效率η_(ex)及平准化度电成本C_(LCOE)为评价指标,对不同系统和不同关键参数进行热经济性对比分析。结果表明:在设计工况下,与部分冷却循环系统相比,在部分冷却再热循环下η_(t)高0.33%,η_(ex)高0.35%;在相同参数条件下,2个发电机组燃煤消耗成本占比均超过70%,锅炉成本远高于其他设备成本;存在最优的主压缩机入口压力,使得η_(t)、η_(ex)达到最大,同时C_(LCOE)达到最小;随着主压缩机入口温度的增大,η_(t)、η_(ex)逐渐减小,C_(LCOE)则逐渐增大;η_(t)、η_(ex)随着透平入口温度的增大线性提升,C_(LCOE)则先减小后增大。

中南半岛野火变化特征及其与土壤水分的相互作用

[目的]分析野火变化特征并探讨火点数与不同深度土壤水分的关联性,为评价生态文明建设和人类生产生活提供科学依据。[方法]基于SNPP/ⅦRS卫星火点监测、火烧迹地和SMAP土壤水分等数据,使用统计方法多角度对2016—2021年中南半岛野火变化特征进行分析,探讨不同干湿条件下火点数与0—5cm和0—100cm2个不同深度土壤水分的相互作用。[结果]①中南半岛火点数和火烧迹地年内主要出现在2—4月,二者在时空分布上具有较高的一致性,多集中在缅甸西部与印度接壤区域、缅甸中部以东和老挝北部。②2—4月火点主要出现在林地、灌木地和耕地,而易发生在归一化植被指数(NDVI)为如下3个等级的区域:0.2<NDVI≤0.4,0.4<NDVI≤0.6,0.6<NDVI≤0.8,但其所占比例随地表覆盖类型和月份的不同存在一定差异。③特旱和重旱条件下火点区明显较无火点区广,火点数集中程度更高;土壤水分随火点数的增加整体呈减少趋势,但极端干湿条件下,土壤水分随火点数变化存在由减转增的“拐点”,且“拐点”值随时间延后而减小。④滞后1~2个月的火点数与土壤水分相关程度最高;日时间尺度上土壤水分对火点数变化同期响应快,且土壤水分和NDVI高的区域关联性更强。[结论]土壤水分亏缺是中南半岛火点高发的重要驱动力。火点数与土壤水分之间相互作用,二者之间存在显著负向关联性。

地铁站消防应急火灾逃生虚拟教学实证研究

为探究地铁站消防应急火灾逃生教学过程中,不同学习场景对学习者学习效果的影响,发掘虚拟现实学习优势,采用调查问卷和MP160生理仪,获取纸质学习、移动端视频学习和虚拟现实学习场景下,学习者不同的行为反应数据,并处理和分析这些数据。研究结果表明:3种学习场景下,学习者的学习成绩存在显著差异,相较于移动端视频学习和纸质学习场景,虚拟现实学习场景能够促进学习者对地铁火灾逃生知识的理解,显著提高学习成绩;3种学习场景下,学习者的学习兴趣存在显著差异,虚拟现实学习场景在提升学习者对地铁火灾逃生知识的学习兴趣方面表现出显著优势;虚拟现实学习场景在生理指标方面体现出更高水平的生理唤醒。

五里堠煤矿3号煤层工作面煤自燃特征及分级预警体系研究

为了研究确定五里堠煤矿3号煤层工作面煤自燃预警指标体系,采用程序升温试验系统测试煤样氧化自燃过程中特征气体生成规律;得到了煤自燃标志性气体,建立了煤自燃分级预警指标体系。结果表明:煤样氧化过程中随温度升高氧化活性增强,耗氧速率不断增大。在常温下,煤氧化产生了CO、CO_(2)和C_(2)H_(6),随煤氧化温度升高气体产生量不断增大;氧化温度升高到110℃时才氧化产生了C_(2)H_(4).为了提高煤自燃风险的预警准确性,研究确定了煤自燃格氏火灾系数和气体比值及变化规律。得到了五里堠煤矿3号煤层工作面煤自燃预警的关键指标为CO、ΔCO/ΔO_(2)、C_(2)H_(4)、C_(2)H_(4)/C_(2)H_(6),提出了3号煤层工作面“灰、蓝、黄、橙、红”五级预警指标体系,结合现场确定了工作面煤自燃分级指标阈值,形成了3号煤层工作面煤自燃分级预警指标体系。

投影寻踪模型在偏氟乙烯储罐单元火灾爆炸指数评价中的应用

采用道化学公司的火灾爆炸指数法对偏氟乙烯(VDF)储罐单元进行危险分析与评价,定量得出采取安全补偿措施前后的单元火灾、爆炸危险指数,结果显示,采取安全补偿措施前单元的危险等级为Ⅴ级,采取安全补偿措施后单元的危险等级降为Ⅱ级。根据道化学的安全补偿指标体系,建立了基于遗传算法的投影寻踪评价模型,包括工艺、物质隔离和火灾控制3个维度,共24个评价指标,并制定了相应的评价标准。研究结果表明:计算机控制、其他工艺过程风险分析、标准操作程序(SOP)等几项指标对目标层的影响较大并依据评价结果提出了几项提升单元安全水平的建议措施。

燃煤发电安全应急管理评价方法研究

为提升煤电应急管理水平,保障煤电行业安全稳定,从应急准备能力、应急预防与预警能力、应急响应能力、应急保障能力和应急恢复能力等方面,建立燃煤电厂应急管理能力评价的指标体系,构建基于熵权的改进模糊综合评价方法,并从系统角度综合评价分析某燃煤电厂安全应急管理能力,提出安全应急管理优化的措施和建议。结果表明:燃煤电厂应急管理能力评价指标影响权重由大到小依次为应急恢复能力(0.269)、应急保障能力(0.227)、应急准备能力(0.197)、应急预防与预警能力(0.172)和应急响应能力(0.135);模糊综合评价模型能有效分析多因素、多层次复杂问题,可为提升燃煤电厂应急管理评价的客观性和科学性提供依据。

云南红河州森林火灾风险评估研究

以全国森林火灾风险评估技术体系为架构,基于红河州森林火灾风险普查数据对红河州森林火灾危险性、综合风险进行了评估和研究。结果表明:红河州森林火灾危险性指数最高的是石屏县,为0.3494,最低的是金平县,为0.1880,全州各县(市)平均值为0.2543,处于平均值附近的是开远市。全州森林火灾风险指数最高的是绿春县0.3283,最低的是蒙自市,为0.1987,全州各县(市)平均值为0.2469,处于平均值附近的是弥勒市。综合风险评估结果与红河州森林防火实际情况有所差异,主要原因是从指标体系和指标权重来看,森林资源总量对森林火灾综合风险评估结果影响较大。通过红河州森林火灾风险评估结果,与实际情况相互对比印证,为进一步优化森林火灾风险评估体系提供参考。

煤自燃火区启封条件的商磋

通过煤自然发火全过程实验,对现行《煤矿安全规程》(2022版)第二百七十九条规定的火区熄灭条件进行深入分析,探讨其在实际应用中可能存在的问题,并提出相应的修改建议。实验结论表明,煤着火后,当O_(2)浓度降到5%以下时,煤自燃指标气体浓度快速降低,但仍可维持阴燃状态,恢复供氧后很快会复燃,说明在此条件下测定的指标气体不能准确表征煤自燃状态。因此,认为:《煤矿安全规程》(2022版)第二百七十九条规定的火区熄灭条件,将指标气体的观测限定在“火区内空气中的O_(2)浓度降到5.0%以下”不妥,或者改为“火区内空气达到新鲜空气要求,即O_(2)浓度达到21%”。