图像型火灾探测技术研究

提出基于DSP（数字信号处理）和GPRS（通用无线分组业务）技术的图像型火灾报警系统,详细叙述了系统网络的搭建、系统的设计、火灾识别和火源定位方式。火灾模拟实验表明,系统能有效感知并识别火灾种类,实现火源的定位。     

Fire detection using smoke and gas sensors

Fire detection systems located in aircraft cargo compartments are currently based only on smoke detectors. They generate about 200 false alarms per year for US registered aircraft. The number of false alarms is growing as more planes are outfitted with smoke detectors and air travel expands. Moreover, the survivability of an aircraft in a fire scenario depends on the early detection of the fire. A fire detection system is developed based on the simultaneous measurements of carbon monoxide, carbon dioxide, and smoke. The combination of the rates of rise of smoke and either carbon monoxide or carbon dioxide concentration provides a potential fire alarm algorithm to increase the reliability of aircraft smoke detectors, and to reduce the time to alarm. The fire detection system with the alarm algorithm detected fires that were not alarmed by smoke sensors, and alarmed in shorter times than smoke sensors operating alone.     

A reference model of fire detection and monitoring system using BACnet

The objective of this paper is to introduce a reference model of BACnet-based fire detection and monitoring system using MS/TP and ARCNET protocols. The reference model is designed to satisfy the requirements of response time, survivability and flexibility. The reference model is operated on the basis of BACnet, a standard communication protocol for building automation systems. In this study, a simulator for the reference model of fire detection and monitoring system was developed. Using the simulator, this study examined the validity of the reference model proposed in this study. This study also evaluated the performance of the BACnet-based fire detection and monitoring system in terms of network-induced delay. Simulation results show that the reference model satisfies the requirements of fire detection and monitoring system.     

Fire detection based on vision sensor and support vector machines

This paper proposes a new vision sensor-based fire-detection method for an early-warning fire-monitoring system. First, candidate fire regions are detected using modified versions of previous related methods, such as the detection of moving regions and fire-colored pixels. Next, since fire regions generally have a higher luminance contrast than neighboring regions, a luminance map is made and used to remove non-fire pixels. Thereafter, a temporal fire model with wavelet coefficients is created and applied to a two-class support vector machines (SVM) classifier with a radial basis function (RBF) kernel. The SVM classifier is then used for the final fire-pixel verification. Experimental results showed that the proposed approach was more robust to noise, such as smoke, and subtle differences between consecutive frames when compared with the other method.     

视频检测在高速公路交通事件中的应用研究

对高速公路交通事件的特点及影响因素进行了分析,阐述了交通事件中视频检测原理及各种检测算法的优点,并以某路段为例,探讨了基于视频的交通事件检测系统模型的构成及性能提高方法,以指导实践。     

Multi-feature fusion based fast video flame detection

A video flame detection method based on the multi-feature fusion is presented in this paper. The temporal and spatial characteristics of flames, such as ordinary flame movement and color clues, a flame flickering detection algorithm is incorporated into the scheme to detect fires in color video sequences. An improved Gaussian mixture model method is firstly adopted to extract moving foreground objects from the still background of detection scenes; secondly, detected moving objects are then categorized into candidate and non-candidate flame regions by using a flame color filtering algorithm; finally, a flame flicker identification algorithm based on statistical frequency counting is used to distinguish true flames from fire-like objects in video images. Testing results show that the proposed algorithms are effective, robust and efficient. The processing rate of the flame detection method can achieve 24 fps with image size of 320 × 240 pixels on a PC with an AMD 2.04 GHz processor.     

Numerical modelling of timber connections under fire loading using a component model

This paper describes a component model for dowelled timber connections under fire loading. The component model of the dowelled connection is first developed and calibrated for room temperature. The constitutive relations for dowel–timber interaction are detailed and compared with experimental results. In the fire situation, a two-step approach is used: first, three-dimensional (3D) thermal analysis of the connection is performed using a conductive model with timber properties defined in Eurocode 5 in order to calculate the temperatures in the fasteners and timber; afterwards, the mechanical analysis using a component model is carried out using mechanical properties of the steel dowel and of timber adjusted to the temperatures obtained by the thermal analyses. These properties are reduced according to Eurocode 3 and Eurocode 5, respectively. Numerical simulations are presented that allow evaluation of the model behaviour and performance. Obtained results show good agreement with available experimental data, indicating that regardless of its simplicity, the component model has the capability to accurately model timber connections under fire loading.     

基于足尺抗火试验的三维框架结构消防安全分析

分析三维框架结构(如工业厂房)的消防安全。冷弯薄钢板作为结构构件使用,并对建筑进行了足尺抗火试验。利用有限元模型SAFIR进行盲预测分析,对火灾荷载密度为625MJ/m2、通风系数为0.009m1/2的标准火灾和自然火灾下结构构件的热响应进行预测。与预期一样,由于是薄钢板,冷弯截面的温度或多或少与防火分区内气体温度相关。力学响应的预测结果给出了27min(标准火灾)和54min(自然火灾)的抗火能力。利用足尺抗火试验结果对模型进行了验证,证明了62min的抗火能力。与一个简单的2.5D模型进行比较,证明了所提供的结果足够精确、适用于日常设计。     

火灾中端板连接件的屈服线模型的研究进展

特定温度下连接件的设计一般只考虑初始刚度和塑性抗力,然而结构在高温作用下发生大变形时其延性和破坏模式就显得更为重要。本文通过对T型连接模型的分析得到大变形,包括发生破坏的部位处端板连接件的性能。基于虚功原理建立的该模型,能很容易地应用于端板连接,而且能考虑到T型连接的翼缘和螺栓同时屈服后的材料硬化。同时还包括对这两个构件相容性的分析。对常温和升温环境中T型连接试验的验证表明:提出的模型可以预测T型连接的多种性能特征。通过与有限元分析结果对比发现:该模型可以很好地反映端板连接的性能。     

面向新世纪的我国消防机器人展望

本文论述了在各类危险场合使用消防机器人进行灭火、侦察,洗消、破拆和救人等作业的必要性以及消防机器人应该具备的各种功能,并对消防机器人进行了分类;论述了国外消防机器人的发展历史和现状以及我国发展消防机器人已经具备的条件。     

Flame and smoke detection method for early real-time detection of a tunnel fire

This paper presents an image-processing technique for automatic real-time flame and smoke detection in a tunnel environment. To avoid the large-scale damage caused by fire occurring in different environments, there are many studies about discovering and minimizing an incident as fast as possible. However, we need an original algorithm specialized for a tunnel fire, because this environment is quite different and it is difficult to apply existing fire detection algorithms to a tunnel environment. Therefore, this paper proposes an original algorithm that applies to a tunnel environment. Color and motion information are used to minimize false detections in tunnels, and this information enables us to detect the exact position of an event at an early stage, by detection, test, and verification procedures. The experimental results show the validity and efficiency of the proposed algorithms by a comparison of the characteristics of each algorithm.     

基于数字图像处理的火灾探测技术

文章运用数字图像处理技术对火灾火焰的图像特性作了分析，根据火焰蔓延时的面积、相似度的变化来识别火灾的发生。图像处理技术在消防报警领域中的应用，具有一定的意义和价值。     

终南山公路隧道火灾探测系统简介

针对公路隧道的火灾特点,采用光纤感温探测线缆作为探测器构成的消防探测系统。介绍了该探测系统的网络结构、安装方式、报警区域设定、报警显示等。     

Structural parameter identification and damage detection for a steel structure using a two-stage finite element model updating method

A two-stage eigensensitivity-based finite element (FE) model updating procedure is developed for structural parameter identification and damage detection for the IASC-ASCE structural health monitoring benchmark steel structure on the basis of ambient vibration measurements. In the first stage, both the weighted least squares and Bayesian estimation methods are adopted for the identification of the connection stiffness of beam-column joints and Young’s modulus of the structure; then the damage detection is conducted via the FE model updating procedure for detecting damaged braces with different damage patterns of the structure. Comparisons between the FE model updated results and the experimental data show that the eigensensitivity-based FE model updating procedure is an effective tool for structural parameter identification and damage detection for steel frame structures.     

Microbiological Events After a Fire in a High-rise Building

Water used to control a fire on an upper floor in a highrise office building wetted furnishings and construction materials on lower floors and resulted in the amplification of microorganisms especially mesophilic and thermotolerant fungi. Concentrations of fungi in indoor air including Aspergillus, Penicillium and Paecilomyces approached or exceeded 10⁴ colony forming units per cubic meter (cfu/m³). Airborne endotoxin levels increased about 1 order of magnitude over background levels. Sampling for fungi using both culture plate impactors and spore traps showed that spores were migrating from water damaged to undamaged areas in the office complex. Elevator shafts traversing water damaged floors likely provided the major dispersion pathway of spores into occupied areas. Construction materials such as plaster ceilings that had been wetted during the fire but were free of visual fungal contamination were found to be strong fungal reservoirs after the building had thoroughly dried. Management of microbial contaminants after a fire in a highrise building is an important public health concern and therefore an essential aspect of building restoration.     

Fire resistance of compartments within a high-rise steel frame: New sub-frame and isolated member models

To study the structural response of a fire compartment within a steel frame, it is expensive and time-consuming to conduct full-frame finite element (FE) analyses, although they can better represent the actual behaviour. For design purposes, engineers have recourse to an isolated member or sub-frame model. Although such an approach is relatively quick, it does not simulate the effects of boundary restraints exerted on heated members. Thus, based on a simple design approach, this paper proposes a new sub-frame model and isolated member model to ascertain the fire resistance of beams and columns subjected to compartment fires. The boundary restraints are represented as a combination of linear and rotational springs, where the spring stiffnesses are derived based on the assumption of semi-rigid beam-to-column connections. The proposed models are verified using a two-dimensional (2D) full-frame analysis. The comparison shows that the member internal forces and displacements predicted by both sub-frame and isolated-member models agree well with the 2D full-frame predictions. The limitations of the proposed methods are also discussed.     

Development of a yield-line model for endplate connections in fire

Connection designs at ambient temperature generally consider only the initial stiffness and the plastic resistance, whereas ductility and failure modes are more important for connections in fire, as large deformations are generally experienced. This paper describes the development of a T-stub model to capture the behaviour of endplate connections at large deformations, including failure wherever relevant. The model is based on the virtual work principle, which allows it to be easily applied to endplate connections, and considers material hardening after yielding for both the T-stub flange and the bolts. Compatibility between these two components is also maintained. Validation against T-stub tests at both ambient and elevated temperatures shows that the proposed model can predict the behaviour of T-stubs of various characteristics. Comparison with finite element analysis results shows that this model represents the behaviour of endplate connections very well.     

Mercury storage in surface soils in a central Washington forest and estimated release during the 2001 Rex Creek Fire

Recent investigations indicate that wildfires provide a significant flux of mercury (Hg) from terrestrial ecosystems to the atmosphere. However, little is known about how geographic location, climate, stand age, and tree species affect Hg accumulation prior to burning and loss during burning. Soil cores collected in sites burned during the summer 2001 Rex Creek Fire in the eastern Cascade Mountains (Washington State, USA) and in adjacent unburned control sites indicate that Hg loss from soils during the Rex Creek Fire averaged 6.7 (+/-2.5) g Hg ha(-1). This soil profile-based estimate of Hg release is higher than a previous estimate for the same fire based on airborne measurements of Hg and CO concentrations in smoke. This study has implications for global estimates of Hg storage in forests and release to the atmosphere during wildfires.     

约束钢框架角钢抗剪连接节点的抗火性能

就双角钢连接节点在热诱导负荷下的试验结果进行了分析。2个梁组件被放入1个熔炉内进行测试,以模拟典型的建筑火灾情形。这些梁组件使用双角钢连接节点与熔炉外1个约束钢框架相连。试验参数包括火灾场景,负荷等级以及由梁板效应引起的综合作用。火灾试验中产生的数据表明,尽管只是简单的剪切连接的设计,双角钢连接节点有其固有的转动刚度并且能够传递热诱导弯矩。尽管产生了永久变形,试验组件并没有破坏,从而说明了双角钢连接节点具有较好的韧性。