Assessing drought-related ecological risk in the Florida Everglades

In the winter-spring of 2001, South Florida experienced one of the worst droughts in its recorded history. Out of a myriad of ecological concerns identified during this time, the potential for catastrophic peat fire and negative impacts to wading bird reproduction emerged as critical issues. Water managers attempted to strike a balance between the environment and protection of water supplies for agriculture and urban interests. It became evident, however, that a broad-scale, integrated way to portray and prioritise ecological stress was lacking in the Florida Everglades, despite this being considered a necessary tool for addressing issues of environmental protection. In order to provide a framework for evaluating various water management operations using real-time information, we developed GIS-based indices of peat-fire risk and wading bird habitat suitability. These indices, based on real physical, chemical, and biological data, describe two ecological conditions that help define the physical and biological integrity of the Everglades. In addition to providing continuous, updated assessments throughout the drought period, we incorporated predictive models of water levels to evaluate how various water management alternatives might exacerbate or alleviate ecological stress during this time.     

基于BP神经网络的机车车辆智能火灾防控系统设计

设计了一种分布式模块化机车车辆智能火灾防控系统,该系统由车载主处理器、多个车载现场处理器、多个传感器和多个执行器构成,各控制单元可根据各种机车车辆车型灵活配置。车载主处理器通过BP人工神经网络算法实现对火警的智能识别,可根据环境因素调节火警判断时的相关参数,适用性强,有效提高火灾防控的准确性,进而更好地保障机车车辆的运行安全。     

火灾科学的发展前景

本文研究了火灾科学的发展前景，指出了火灾科学必然包括各种领域并列举了课题的分类，阐明了每一领域的研究都是防止火灾损失必不可少的。通过分析火灾科学近年来的工作，阐述了火灾研究的现状。大多数研究都是以最近的火灾为背景展开的，虽然其中许多侧重于基础研究，并未针对某一特定火灾。最后本文提出了火灾研究的将来需要。由于未来技术的发展和生活方式的改变有的难以预测，与之紧密相关的未来火灾也难以想象，因此，只能试从当前火灾研究去推测将来。本文认为将来的火灾研究课题大多数为基础研究，虽然它也或多或少与未来火灾有关系。并且预测随着新概念的引入，将来的火灾研究的数据和方法都活发生很大变化。     

Consequence modeling of explosion at Azad-Shahr CNG refueling station

Safety of people has been the most important concern since the onset of commercial use of Compressed Natural Gas¹ as a novel type of vehicle fuel. Provided a car vessel bursts, irreversible consequences will surface. The most important hazard threatening people and their properties in CNG distribution stations is pressurized natural gas in station storage vessels and car vessels. Storage vessels are far from people; however, they may damage other properties such as pipes, valves, electrical equipment, and etc. Owing to the distance between storage vessels and the hive, the risk is not considered a big concern; on the contrary, car storage vessel is very close to the passengers sitting in the car and those standing around the car. The proximity heightens the risk as the consequences caused by vessel burst can be more catastrophic than the former condition. Taken together, the car CNG vessel burst may be regarded as the most hazardous event at CNG distribution centers. It is believed that modeling the mentioned events can illustrate risky conditions. The present study was formulated in order to model one of such accidents occurring in Azad-Shahr in the winter 2010. The obtained results provided useful points and recommendations like the minimum safe distance from rupture center depending on such outcomes as overpressure, types of fire, or toxic release. The recommendations provided by the present study can prevent people from calamitous events and they can be adopted so as to reduce severity of possible events.     

基于风暴识别算法的森林火灾识别

采用风暴识别算法对森林火灾进行了识别。首先根据参数阈值调整后的风暴识别算法,得到二维分量,结合不同云回波与火灾回波的差异,对火灾回波进行识别。根据算法对浙江省温州市三次森林火灾过程进行识别,结果显示:对于三次火灾过程都能够有效识别。对于火灾发生初期和熄灭时,由于回波强度较弱,回波结构松散,与小范围弱回波混合,导致漏识别。当回波中存在小范围地物杂波时,由于其尺度与小面积火灾接近,最终导致误识别。在森林火灾发生时,该算法可以帮助识别发生火灾的位置,为消防人员提供及时可靠的火灾地点及起火时间。     

燃烧烟尘凝团形貌的分形辨别方法研究

对火灾现场常见聚合物材料和易燃液体燃烧烟尘凝团进行了分形研究,通过线性回归得到了描述其形貌特征的分形维数和分形前置因子。研究发现大多数材料烟尘凝团的分形维数在1.5~2.0之间,燃烧时发烟量较大的材料通常具有较高的分形维数值。利用分形分析结论,对烟尘进行判别分析,可以准确判别烟尘种类。     

外立面作用下水平湍流浮力射流火焰的附壁研究

用防火板模拟建筑外立面,设计了可控流速和开口尺寸的气体燃烧器产生水平湍流浮力射流火焰,系统研究了外立面抑制火焰卷吸所导致的水平湍流浮力射流火焰附壁规律。将火焰流场演变分为两个阶段:(1)出口到流场水平动量衰减为零(等价点)的阶段;(2)火焰附壁或不附壁的阶段。其中,火焰附壁与否很大程度上取决于等价点到出口的水平距离LE。通过分析,我们发现雷诺应力是导致流场水平动量衰减和火焰附壁的主要原因。由此,我们基于普朗特混合长度理论推导了雷诺应力的近似表达式并结合动量控制方程,获得了LE与修正弗洛德数Fr*的线性关系,从理论上解释了出口宽高比n(n=B/H,B是开口宽度;H是开口高度)越大,火焰越容易附壁的现象,并确定了不同开口及流速条件下,火焰附壁的临界条件。     

纸面石膏板受热痕迹的数值重构研究

利用锥形量热仪实验测定了纸面石膏板暴露在不同辐射热通量、不同暴露时间下的烧损程度,基于火灾烈度理论对实验数据进行拟合,建立石膏板受热痕迹的半经验模型。通过修改FDS(Fire Dynamics Simulator)的源代码,将模型嵌入到软件中,与自身功能相结合,实现重现石膏板受热痕迹的功能。同时进行了石膏板受热痕迹的实体实验,研究了不同油盘面积、受热时间和相对位置对石膏板受热痕迹形成过程和结果的影响。利用增加了新功能的FDS软件对实体实验进行了数值重构,对比实验和模拟的结果,证明了该模型可用于石膏板受热痕迹的重现。该技术完善了火灾的数值重构技术,作为火灾调查的一种新兴的技术手段,对于完善事故调查的证据链,辅助火灾调查工作具有重要意义。     

Knowing fire incidence through fuel phenology: A remotely sensed approach

Fire is a basic ecological factor that contributes to determine vegetation diversity and dynamics in time and space. Fuel characteristics play an essential role in fire ignition and propagation; at the landscape scale fuel availability and flammability are closely related to the vegetation phenology that directly affects wildfire pattern in time and space. In this view, the annual normalized difference vegetation index (NDVI) profiles derived from high temporal resolution satellites, like SPOT Vegetation, represent an effective tool for monitoring the coarse-scale vegetation seasonal timing. The objective of this study thus consists in quantifying the explanatory power of multitemporal NDVI profiles on the fire regime characteristics of the potential natural vegetation (PNV) types of Sardinia (Italy) over a 5-year period (2000-2004). The results obtained show a good association between the NDVI temporal dynamics of the PNV of Sardinia and the corresponding fire regime characteristics, emphasizing the role of the bioclimatic timing of the vegetation in controlling the coarse-scale wildfire spatio-temporal distribution of Sardinia. By providing a sound phytogeographical framework for describing different wildfire regimes, PNV maps can thus be considered helpful cartographic documents for fire management strategies at the landscape scale.     

Combined effect of fire and water scarcity on vegetation patterns in arid lands

In many arid zones around the word, the vegetation spontaneously forms regular patterns to optimize the use of the scarce water resources. The patterns act as early warning signal that fragile ecosystems may suddenly undergo irreversible shifts, thus, interpreting the structural shape of vegetation patterns is crucial to deciphering the ecosystem history and its expected further development. The sudden and irreversible shift of delicate ecosystems as a consequence of minor variation of the climatic forcing has been studied extensively in the past. The attitude of the ecosystem to recover after a catastrophic event, such as fire, did not receive as much attention so far. Here we modelled fire, as a sudden shift of the ecosystem state variables and functionality and evaluated post-fire scenarios under the hypothesis that two major feedbacks shaped the vegetation patterns: a positive feedback between preferential infiltration and plant growth, and a second feedback between infiltration and vegetation burning. A simple model solving a set of partial differential equations for soil moisture, plant biomass, surface water and dead biomass balance predicted significantly diverse post-fire vegetation patterns depending on the fire severity and on the degree of soil water repellency induced by the vegetation burning.