公路隧道火灾逃生疏散研究

以苍岭隧道为背景,首先采用经验计算理论和计算软件building EXODUS相结合的方式,从被困人员的安全疏散时间、高温烟气的影响、隧道横通道的利用率以及人员的疏散行为特性进行了研究。结果表明:中小规模火灾情况下的安全疏散时间控制在8 min之内,高温烟气影响不大,但横通道的利用率不平均,且人员疏散路线相对集中。然后对存在的逃生疏散问题提出针对性建议以及其他相关建议,旨在为更大程度降低事故的严重性和经济财产损失。     

公共建筑火灾中人员生命风险分析

结合国内公共建筑火灾中影响人员生命安全的因素,提出一种公共建筑火灾中人员生命风险分析的方法。该方法根据人员生命危险出现的临界时间和疏散公式,可以定量计算出人员的伤亡率,以公共建筑火灾中可能的人员伤亡率大小评价公共建筑火灾中人员生命风险大小,进而分析出公共建筑火灾中可能影响人员伤亡的主要因素,最后提出减少人员伤亡的对策。结果表明该方法可以快速地估算出公共建筑物发生火灾的伤亡,并分析提出减少人员伤亡的方法。     

超细水雾抑制酒精火有效性实验研究

为了研究超细水雾对酒精火的抑制效果,通过搭建超细水雾抑制受限空间酒清火燃烧的小尺寸实验平台,利用基于质量损失速率的热释放速率计算方法,研究超细水雾与酒精火焰相互作用时,酒精火火焰的变化规律及酒精火的热释放速率,与此同时,采用高速摄像仪对火焰进行拍摄,利用Matlab图像处理程序对采集的火焰图片剖面进行处理.研究发现:施...     

高层建筑火灾安全疏散研究述评

火灾条件下的高层建筑安全疏散研究已成为国内外研究的热点。介绍了高层建筑安全疏散设计及高层建筑人员疏散模拟两种主要研究方法在高层建筑安全疏散研究上的应用。首先说明了高层建筑安全疏散设计经历了一个从处方式安全疏散设计到性能化安全疏散设计的转变,分析了国内外在高层建筑性能化安全疏散设计上的发展,并列出了性能化安全疏散设计在实施中存在的问题;其次介绍了应用于高层建筑人员疏散的仿真模型,设想了高层建筑计算机模型的发展趋势;最后结合高层建筑火灾安全疏散目前存在的问题和不足,对高层建筑火灾安全疏散做出展望。     

Estimating California ecosystem carbon change using process model and land cover disturbance data: 1951-2000

Land use change, natural disturbance, and climate change directly alter ecosystem productivity and carbon stock level. The estimation of ecosystem carbon dynamics depends on the quality of land cover change data and the effectiveness of the ecosystem models that represent the vegetation growth processes and disturbance effects. We used the Integrated Biosphere Simulator (IBIS) and a set of 30- to 60-m resolution fire and land cover change data to examine the carbon changes of California's forests, shrublands, and grasslands. Simulation results indicate that during 1951-2000, the net primary productivity (NPP) increased by 7%, from 72.2 to 77.1 Tg C yr⁻¹ (1 teragram = 10¹² g), mainly due to CO₂ fertilization, since the climate hardly changed during this period. Similarly, heterotrophic respiration increased by 5%, from 69.4 to 73.1 Tg C yr⁻¹, mainly due to increased forest soil carbon and temperature. Net ecosystem production (NEP) was highly variable in the 50-year period but on average equalled 3.0 Tg C yr⁻¹ (total of 149 Tg C). As with NEP, the net biome production (NBP) was also highly variable but averaged −0.55 Tg C yr⁻¹ (total of -27.3 Tg C) because NBP in the 1980s was very low (-5.34 Tg C yr⁻¹). During the study period, a total of 126 Tg carbon were removed by logging and land use change, and 50 Tg carbon were directly removed by wildland fires. For carbon pools, the estimated total living upper canopy (tree) biomass decreased from 928 to 834 Tg C, and the understory (including shrub and grass) biomass increased from 59 to 63 Tg C. Soil carbon and dead biomass carbon increased from 1136 to 1197 Tg C.Our analyses suggest that both natural and human processes have significant influence on the carbon change in California. During 1951-2000, climate interannual variability was the key driving force for the large interannual changes of ecosystem carbon source and sink at the state level, while logging and fire were the dominant driving forces for carbon balances in several specific ecoregions. From a long-term perspective, CO₂ fertilization plays a key role in maintaining higher NPP. However, our study shows that the increase in C sequestration by CO₂ fertilization is largely offset by logging/land use change and wildland fires.     

Grass feedbacks on fire stabilize savannas

Savannas commonly consist of a discontinuous cover of overstory trees and a groundcover of grasses. Savanna models have previously demonstrated that vegetation feedbacks on fire frequency can limit the density of overstory trees, thereby maintaining savannas. Positive feedbacks of either savanna trees alone or trees and grasses together on fire frequency have been shown to result in a stable savanna equilibrium. Grass feedbacks on fire frequency, in contrast, have resulted in stable equilibria in either a grassland or forest state, but not in a savanna. These results, however, were derived from a system of differential equations that assumes that fire occurrence is strictly deterministic and that vegetation losses due to fire are continuous in time. We develop an alternative formulation of the grass-fire feedback model that assumes that fires are discrete and occur stochastically in time to examine the influence of these assumptions on the predicted state of the system. We show that incorporating fire as a discrete event can produce a recurring temporal refuge in which both grass and trees co-occur in a stable, bounded savanna. In our model, tree abundance is limited without invoking demographic bottlenecks in the transition from fire-sensitive to fire-resistant life history stages. An increasing strength of grass feedback on fire results in regular, predictable fires, which suggests that the system can also be modeled using a set of difference equations. We implement this discrete system using modified Leslie/Gower difference equations and demonstrate the existence of a bounded savanna state in this model framework. Our results confirm the potential for grass feedbacks to result in stable savannas, and indicate the importance of modeling fire as a discrete event rather than as a loss rate that is continuous in time.     

农村灾害避难场所布局规划评价研究——以四川省小鱼洞镇为例

灾害避难场所不仅在灾中或灾后能为农村灾民提供一个临时安置或生存场所,而且更是农村整合其有限资源开展防灾减灾工作的平台,在农村社区减灾中工作发挥着重要的作用,然而相关研究工作较少。以四川省彭州市小鱼洞镇为例,通过对政府既定的避难场所进行安全性、通达性、收容性、生活性等分析,综合评价这些避难场所的布局合理性。以期为该区避难所的进一步建设提供科学依据,也为农村灾害避难所的规划和评价提供参考实例。     

The loss of an indigenous constructed landscape following British invasion of Australia: An insight into the deep human imprint on the Australian landscape

Indigenous people play an integral role in shaping natural environments, and the disruption to Indigenous land management practices has profound effects on the biosphere. Here, we use pollen, charcoal and dendrochronological analyses to demonstrate that the Australian landscape at the time of British invasion in the 18th century was a heavily constructed one—the product of millennia of active maintenance by Aboriginal Australians. Focusing on the Surrey Hills, Tasmania, our results reveal how the removal of Indigenous burning regimes following British invasion instigated a process of ecological succession and the encroachment of cool temperate rainforest (i.e. later-stage vegetation communities) into grasslands of conservation significance. This research provides empirical evidence to challenge the long-standing portrayal of Indigenous Australians as low-impact ‘hunter-gatherers’ and highlights the relevance and critical value of Indigenous fire management in this era of heightened bushfire risk and biodiversity loss.     

Evaluation of fire as a management tool for controllingSchinus terebinthifolius as secondary successional growth on abandoned agricultural land

Schinus terebinthifolius, native to South America, has become an aggressive woody weed in southern Florida, displacing native vegetation as well as rapidly invading disturbed sites. Studies to evaluate the effectiveness of fire as a management option for controllingSchinus on abandoned farmland in Everglades National Park, known as the “Hole-in-the-Donut,” began in 1979. Study plots were established to monitor any change(s) in herbaceous cover and in numbers and size ofSchinus stems. Except in the control plot (which was not burned), each site was burned as often as fuel conditions permitted (usually once every one or two years), through 1985. Results indicated that both the number and density ofSchinus stems increased over the course of the study. While plots that burned showed a reduction in the rate ofSchinus invasion, invasion still progressed rapidly with or without the occurrence of fire. The increase inSchinus stem density from 1980 to 1985 was highly significant in all transects except one. Herbaceous cover showed no clear trends relative to burning.     

预应力预制叠合楼板耐火性能参数分析

在合理选择混凝土和预应力筋材料的热工参数、高温力学参数的基础上,采用有限元分析软件ABAQUS建立底面受火的预应力预制叠合楼板的高温热力学模型,计算结果得到已有试验结果的验证。对影响预应力预制叠合楼板高温力学性能的各参数进行有限元分析,结果表明:荷载水平和耐火保护层厚度对叠合楼板耐火性能的影响显著,混凝土强度、预应力筋截面配筋率等参数对叠合楼板的耐火性能影响较小,可以忽略不计;耐火保护层厚度一定时,叠合楼板的耐火极限随荷载水平的提高而降低;荷载水平一定时,叠合楼板的耐火极限随耐火保护层厚度的增加呈非线性提高。在ISO-834标准火灾作用下,叠合楼板跨中挠度变化率速率大于L2/(9000d)可作为其达到耐火极限的判别标准。选取荷载水平、混凝土保护层厚度两个重要影响参数进行分析,提出了叠合楼板的耐火极限取值建议,为预应力预制叠合楼板的抗火设计提供技术参考。