A case study on fractal simulation of forest fire spread

This paper relates to the semi-empirical model based on fire field energy balance and the physical model based on land temperature, aiming to provide a practical way of describing fire spread. Fire spread is determined by the characteristics of combustible materials and the agency of meteorological factors and terrains. Combustible materials, such as surface area, have no featured scale, yet the process of forest fire spread contains the self-replicating feature, both of which contribute to the self-similarity of fire spread. Consequently, fire behavior can be described by fractal geometry. In this research, we select Wuchagou forest in Da Hinggan Mountains as the experimental site where a forest fire took place three years ago. The forest fire was detected on low-resolution NOAA-AVHRR images, and fire spread was simulated on high-resolution TM images as another attempt to merge information. Based on remote sensing and GIS, we adopted the method of limited spreading lumping (DLA) to describe growing phenomenon to simulate the dynamic process of fire spread and adjusting shape of the result of fire simulation by the scale rule. As a result, the simulated fire and the actual fire manifest the self-similarity in their spreading shapes as well as the quantitative similarity in their areas.     

Arrangement of the computer code for the prediction of forest fire spread

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Experimental study and numerical simulation of spread law for fire on tunnel

In order to research spread law and distribution law of temperature nearby fire sources on roadway in mine, according to combustion theory and other basic, the theory model of temperature attenuation was determined under unsteady heat-exchange between wind and roadway wall. The full-size roadway fire simulation experiments were carried out in Chongqing Research Institute of China Coal Technology & Engineering Group Corporation. The development processes of mine fire and flow pattern of high temperature gas were analyzed. Experimental roadway is seen as physical model, and through using CFD software, the processes of mine fire have been simulated on computer. The results show that, after fire occurs, if the wind speed is less than the minimum speed which can prevent smoke from rolling back, then the smaller wind speed can cause smoke to roll back easily. Hot plume will lead to secondary disasters in upwind side. Because of roadway wall, hot plume released from roadway fire zone has caused the occurrence of the ceiling jet, and the hot plume has been forced down. Whereas, owing to the higher temperature, buoyancy effect is more obvious. Therefore, smoke rises gradually along the roadway in the flow process, and the hierarchical interface appears wavy.Oxygen-enriched combustion and fuel-enriched combustion are the two kinds of combustion states of fire. The oxygen content of downwind side of fire is maintained at around 15% for oxygen-enriched combustion, and the oxygen content of downwind side of fire is maintained at around 2% for fuel-enriched combustion. Furthermore, fuel-enriched combustion can lead to secondary disasters easily.     

冶金多孔介质散料层分形结构计算机模拟

研究了计算机模拟多孔介质散料层分形结构的方法，用这种方法模拟了高炉散料层中焦炭和矿石床层的分形结构，模拟结果与实验结果基本一致．     

基于分形理论的人体骨二维微观结构建模方法研究

利用人体骨二维微观结构多区域上的自相似这一分形特性，采用分形理论和蒙特卡罗（Monte-Carlo)模拟法来代替传统建模方法建立人体骨微观结构的二维模型。     

基于分形理论的电站燃烧稳定性监测

针对电站锅炉状态监测中无法定量评价燃烧稳定性能的不足,研究基于分形原理的炉膛压力R/S分析,计算相应的Hurst指数。根据电站常规运行方式,定义稳态、变负荷和异常三种典型工况,指出典型工况的燃烧稳定性能优劣可由计算得到的Hurst指数近似衡量。以一台600 MW电站锅炉为例,验证了该指数对于燃烧状态实时监测的有效性和实用性。     

基于分维的遥感影像最佳分割尺度研究

针对面向对象的遥感技术中对象最优分割尺度难题,提出了基于分维的定量确定最优分割尺度算法。算法通过分析分维值变化规律和最优分割尺度之间的定量关系,发现分维值变化稳定区间与遥感对象最佳分割尺度范围相对应,因此可以通过对象分维-尺度关系,确定遥感对象的最佳分割尺度,一定程度上解决了最优分割尺度难于确定的难题。     

一种基于对象的分形视频压缩算法研究

基于分形视频压缩的典型方法,提出了一种改进并提高其压缩性能的方法,用更有效的宏块划分规则替代传统的四叉树划分规则、简化块的搜索策略和范围、使用类似H.264标准的I帧和减少重复计算等。提出了一种在分形视频压缩算法中的基于对象(OB)压缩的实现方法,可以对任意对象单独进行压缩编码,极大地提高压缩比和压缩速度,降低比特率并节省数据传输时的带宽。实验结果表明,相比典型的方法,本文提出的分形视频压缩算法,压缩比提高了近4倍,压缩速度快近10倍,图像质量提高了3～5dB,显著地提高了分形视频压缩算法的性能;同时,OB的压缩方法简单有效,压缩比和压缩速度又有大幅度提高,使分形视频压缩的应用具有更大的灵活性和实用性。     

Numerical simulation of bistatic scattering from fractal rough surface in the finite element method

By using the Monte Carlo method and numerical finite element approach, bistatic scattering from the fractal and Gaussian rough surfaces is studied. The difference between these two surfaces and their functional dependence on the surface parameters are discussed. Angular variation of bistatic scattering from the fractal surface is very significant, even for fairly smooth surface, whilst scattering from the Gaussian rough surface tends to the specular reflection. The slope of angular variation is linearly related with the fractal dimension. If an electrically-large target is placed over the rough surface, the fractal dimension inverted from bistatic scattering would be reduced. As the surfaces become very rough, scattering from different fractal and Gaussian surfaces would be not identified.     

分形编码技术在图像型火灾烟雾探测中的应用研究

图像型火灾探测技术是火灾探测领域中近几年发展起来的较新的技术分支，由于其自身非接触性探测等优越性，成为国内外火灾探测领域关注的焦点。文章介绍了图像型火灾烟雾探测技术的发展和现状，并针对火灾烟雾的分形特征引入分形编码技术，分析了通过基于K均值聚类方法的分形编码技术进行烟雾图像分割的实用性。     

高光谱遥感数据光谱曲线分形特征研究

提出一种基于分形分析的高光谱遥感数据处理方法．从反射光谱的产生机理、全色影像与单色影像表现出来的自相似现象以及用不同尺度量尺测量曲线所表现出来的幂指数关系三个方面,说明高光谱遥感数据中像元中光谱曲线具有分形的特征,简述了研究光谱曲线分形特征在高光谱遥感数据处理中的意义．     

裂隙分布的分形特征与岩石强度的相关性研究

依据分形几何学的基本观点对岩石中的裂隙分布进行了观测研究，提出了描述裂隙分布规律的分形维数Ｄ及度量裂隙发育程度的指数Ｑ、Ｋ，并建立了裂隙发育指数与岩石单轴抗压强度之间的相关规律     

某办公室火灾数值模拟研究

本文以某办公室为背景,根据具体情况,在最有可能发生火灾的两个火灾场景下利用火灾动力学软件——FDS进行数值模拟分析。得出在两个不同火灾场景下的安全疏散时间,以及房间发生轰然的时间。并对两个火灾场景结果进行对比。发现发生在房间中间某处的火灾比发生在靠墙处的火灾危险性大,火势易蔓延,容易轰然。     

基于可视化的森林火灾监测节点优化部署策略

由于森林防火传感器节点成本高、部署区域大,优化部署效率是其应用时所面临的主要问题。为使节点部署成本与覆盖效率之间相互协调,提出一种基于可视化的森林火灾监测节点优化部署策略。以实际森林环境为基础,对预置节点做可视域分析;通过建立节点可视域面积关联矩阵,使用互信息算法贪婪地选择覆盖效率最高的预置节点;在预算受限时利用子模算法预估最佳的节点部署数量。该策略既保证了覆盖效率,又减少了部署成本,是一种高性价比的森林火灾监测节点部署策略。     

三维分形地形生成技术综述

简述了三维地形生成的几种常用方法，重点介绍了三维分形地形建模方法，并对利用中点位移法生成三维分形地形图的数学模型作了具体探讨。     

基于分形理论的谱峰检测方法研究

在拓展分形维数概念的基础上,提出曲线的点盒维数定义,并以此构筑判峰算法,发展了一种新的谱峰检测理论及实现途径．与现有谱峰检测技术相比,该算法具有判据阈值设定简单可靠、适应范围广、谱峰识别准确等显著特点．实践表明,这种新的谱峰检测法能满意地用于色谱、光谱等仪器分析数据的自动处理．     

基于多源遥感数据融合的SVM分类研究

针对SVM对遥感数据进行分类时出现的“同谱异物”和“椒盐现象”,提出利用LiDAR数据和遥感影像相融合的分类方法.实验结果表明：该方法在有效提高分类精度和解决“同谱异物”与“椒盐现象”的同时,还可以加快分类速度.     

农业干旱监测指标研究进展

从传统监测指标和遥感监测指标两个方面对农业干旱表征指标进行了综述.传统农业干旱监测指标主要包括降水量指标、土壤含水量指标以及作物需水量指标等;遥感监测指标包含基于裸露地表和基于有植被覆盖地表的干旱遥感监测指标两大类.由于遥感方法具有大范围、宏观、动态监测的优势,目前得到了较为广泛的使用.未来农业干旱监测应建立广义的、适合于作物各时期的监测模型,并在此基础上对双层模型进一步简化.     

分维散射定律的模拟检验

模拟辐射在Ｐａｒｔｉｃｌｅ－ＣｌｕｓｔｅｒＣｌｕｓｔｅｒ（Ｐ－Ｃ凝块）的散射表明，对单个Ｐ－Ｃ凝块，ｌｏｇ（ｓ（ｑ））～ｌｏｇ（ｑ）没有直线关系，这里散射波矢量的模ｑ为４πλ－１ｓｉｎ（θ／２），λ为辐射波长，θ为相对于入射方向的散射角，ｓ为散射强度．对于由大小相近，位置和取向随机分布凝块构成的体系，ｌｏｇ（ｓ（ｑ））～ｌｏｇ（ｑ）有直线关系，但斜率不是其分数维值（Ｄ为２．５），而是大约为１．７５，即分维散射定律ｓ（ｑ）～ｑ－Ｄ，对Ｐ－Ｃ凝块不成立