火灾探测器误报警成因分析及改进措施

火灾自动报警系统是通过火灾探测器,向报警控制器发送火灾信号,向人们报警。火灾探测器是一种灵敏度非常高的探测设备,它受环境因素影响非常多,因此常有误报警发生。笔者根据多年来对自动报警系统运行情况的分析,发现造成误报警的原因也很多,本文主要研究了探测器误报警的主要原因及降低误报警而进行的相关改进措施。     

浅谈PIC16C71单片机在智能型火灾探测器中的应用

本文介绍了火灾报警系统中的火灾探测器的工作原理及存在的问题,如何对火灾信号的探测、判断和处理是解决智能型火灾探测器的误报问题的关键。因此,我采用美国MICROCHIP公司生产的PIC16C71单片机进行软件编程的方法来解决智能型火灾报警探测器在探测火灾过程中出现的误报、不报等问题。     

高层建筑火灾自动报警设备探测器安装施工方法

本文以杭州国际博览中心为例,为了让高层建筑火灾探测器实现实时自动报警,通过布置各类自动报警探测器,为自动报警探测器安装高密度钢管金属线槽,布设实时探测消防桥架维持探测器并配置探测器敏感性管线等,设计一种新型高层建筑火灾自动报警设备探测器安装工艺。使用设计的安装工艺后,探测器在多次报警探测中的探测延时均低于消防验收规范规定的最大允许延时,实施效果较好,具有实时性,符合高层建筑的火灾自动报警需求,有一定的应用价值。     

火灾探测及报警系统产品采用国际标准提高企业竞争力

1火灾探测及报警系统产品采标情况对于火灾探测及报警系统产品,目前ISO正在制定相应的系列标准并陆续发布,主要包括感烟探测器、感温探测器、线型光束探测器、手动报警按钮、声报警器、电源、火灾报警控制装置等。笔者所在公司生产的火灾探测及报警系统的采标产品主要针对欧盟市场及美洲市场,公司感烟探测器、感温探测器产品顺利通过德国莱茵(TUV)认证机构CE认证和英国防损认证协会(LPCB)的认证并取得了证书,产品全面符合欧盟关于安全、电磁兼容、火灾探测性能三个方面的要求。与此同时,产品又通过了美国安全检测实验室公司(UL)认证。…     

基于光声技术的火灾气体探测系统设计

近年来，针对标识性气体的探测成为火灾探测技术中发展最活跃的领域之一。将可检测极低浓度的某一气体的光声检测技术应用于极早期火灾气体产物的检测是一个新的尝试，将可能实现高灵敏度、高可靠性的火灾探测。但常规光声气体检测设备结构复杂、价格昂贵，必须恰当的重新设计才能应用到火灾探测系统中。分析了该技术在火灾探测中应用的关键问题,并提出了一种利用光声腔和光源间的“自由吸收路径”进行测量的光声气体探测系统，避免了对光源的窄带滤波要求，实现了在线式的气体检测。起始状态下，光声腔密封有纯CO气体，吸收光源中4.6 μm的辐射，产生一定强度的初始光声信号；当火灾气体产物流经吸收路径时，其中的CO气体吸收使到达光声腔的光辐射在4.6 μm波长上发生衰减，导致光声信号减弱，这个信号的变化量就反映了吸收路径中的CO气体浓度。     

机载火警探测系统的改进研究

目前民航飞机货舱火警探测器普遍采用红外光电感烟器,存在响应慢和误报率高的缺陷.文中引入火灾发生早期出现的一氧化碳气体浓度/浓度变化量作为新的火警探测标志量,设计了烟气复合火警探头.提出了两维输入复合偏置滤波自动火警报警算法,设计了火警报警阈值调节模糊系统,根据烟雾浓度变化量和一氧化碳气体浓度变化量等动态参量,智能调整火警报警阈值,拟解决货舱单一使用红外光电感烟火警探测器误报率高和响应慢的问题.模拟实验结果表明:新研制的烟气复合火警探测器比现有的红外光电感烟探测器有更低的火警误报率和更快的响应速度.     

吸气式感烟火灾探测器在地铁车站中的应用

根据建筑形式、设备布置等特点,介绍了火灾自动报警系统采用传统的点型火灾探测器在某些特定场所进行火灾探测的缺陷,通过分析吸气式感烟火灾探测器的技术特点,从工程的可实施性、可靠性和可行性等方面提出了针对性解决措施,并从设备的运营维护工作量、维护成本等多方面进行了分析,以实现火灾的早期预警和报警,为快速灭火提供了依据。     

基于R2868型传感器的紫外火焰探测器设计

针对现有火焰探测器响应时间长、探测灵敏度低、探测距离短等问题,本文设计了基于R2868型传感器的火灾监测用紫外火焰探测器.采用具有光能量汇聚功能的光学前窗结构,增大了探测器光学窗口.通过脉冲信号调理电路对传感器输出的脉冲信号进行整形,利用窗口识别算法有效判别火焰状态,可及时响应声光报警.为了满足不同工作条件需求,探测器设有3档灵敏度开关.经试验验证,该火焰探测器能够滤除环境干扰,探测灵敏度高,有效探测距离可达27 m,报警时间小于2 s,具有良好的环境适应性和可靠性.     

基于微控制器2051实现的探测器设计

本文探讨一种智能型火灾探测器的设计过程。通过对火灾报警控制器配套的光电感烟火灾探测器的设计。探讨利用AT89C2051微处理器芯片完成信息的探测、多地址信息的发送控制及分析、判断、报警等功能。     

基于微控制器2051实现的探测器设计

本文探讨一种智能型火灾探测器的设计过程.通过对火灾报警控制器配套的光电感烟火灾探测器的设计.探讨利用AT89C2051微处理器芯片完成信息的探测、多地址信息的发送控制及分析、判断、报警等功能.     

ZnO纳米线CO气敏性能与气体浓度的关系研究

以采用物理热蒸发法制备的纯ZnO纳米线和掺杂Ni、Al的ZnO纳米线为气敏基料,以蒸馏水调和制备成旁热式气敏元件,用静态配气法对一系列浓度的一氧化碳气体进行了气敏性能的测试。结果表明掺杂的纳米ZnO元件与纯的纳米ZnO元件相比对CO气体的灵敏度更高,三种元件的灵敏度与所测气体浓度均呈现先上升后下降的变化趋势,且在同一浓度下出现最高值。     

Bacterial detection using a carbon nanotube gas sensor coupled with a microheater for ammonia synthesis by aerobic oxidisation of organic components

In this study, the authors propose a new bacteria detection method using a carbon nanotube (CNT) gas sensor and a microheater, which were coupled into a Bio-MEMS (microelectromechanical systems)-type device. Bacteria were heated by the microheater in air so that ammonia (NH₃) gas can be generated by the oxidation reaction of organic components of bacteria. Thus generated NH₃ gas was detected by using the CNT gas sensor, which was fabricated by dielectrophoresis (DEP) and combined with the microheater to form a small chamber. Cyclic pulsed heating operation was employed so that the CNT response to elevated temperature did not mask NH₃ response. It was demonstrated that the proposed device could detect and quantify 10⁷ bacteria cells (Escherichia coli). Possible application of DEP to trap and enrich target bacteria on the microheater was also discussed.     

气相色谱法测定环境空气与废气中氯乙烯

环境空气或工业废气中氯乙烯以活性炭吸附采集后,用二硫化碳解吸,直接经聚乙二醇6000不锈钢填充柱分离,氢焰离子化检测器检测。方法最低检出浓度0.15mg/m3,相对标准偏差1.9%-5.8%,平均解吸率93.7%,本方法操作简便、快速,灵敏度完全能满足环境监测要求。     

Sensitivity analysis for PCA-based chiller sensor fault detection

This paper presents an algebraic solution of erroneous sensor's undetectable boundary to evaluate the sensitivity of chiller sensor fault detection based on principal component analysis. Q-statistic of PCA is normally applied as a collective statistical index to detect sensor fault by comparing its value with the threshold. However, Q-statistic has no specific physical meaning and cannot evaluate the sensitivity of the provided method for sensor fault detection. We analyzed the definition of Q-statistic and derived the numerical value of the minimum range not to detect sensor fault. Bias sensor fault of a fielded screw chiller was studied for each sensor in PCA model by introducing different severity levels. Results showed that each sensor has different fault detection sensitivity using the same PCA model. The undetectable boundary can be a criterion used to evaluate the detection sensitivity of PCA-based method easily.     

火灾探测的人工神经网络方法

火灾早期探测是较复杂和有重大义意的问题，本文指出了传统火灾探测方法所存在的问题，在分析火灾实验数据的基础上，提出了一种新的火灾探测方法，即人工神经网络（ＡＮＮ）方法。由于ＡＮＮ方法具有自学习能力，能适应各种复杂条件，因此它能克服传统火灾探测方法的缺陷，摸拟实验结果也表明ＡＮＮ方法在火灾自动探测中是一种十分有效的方法     

一种基于多传感器信息融合的火灾探测系统

根据火灾的特征与燃烧产物,设计了一种基于多传感器信息融合的火灾探测系统.该系统以DSP TMS320LF2407A为处理器,包括一氧化碳传感器模块、温度传感器模块和紫外火焰传感器模块.紫外火焰传感器可以很好地区分闪燃火和阴燃火,一氧化碳传感器和温度传感器能够对闪燃火和阴燃火产生不同的反应,因此系统采用两种不同的算法来探测闪燃火和阴燃火.该火灾探测系统在燃烧室中通过了实验验证.实验表明,该火灾探测系统比通用的感烟型探测器具有更快的探测速度和准确度,且不会在常见干扰源的干扰下产生误报警.     

A Novel DDoS Attack Detection Method Using Optimized Generalized Multiple Kernel Learning

Distributed Denial of Service (DDoS) attack has become one of the most destructive network attacks which can pose a mortal threat to Internet security. Existing detection methods cannot effectively detect early attacks. In this paper, we propose a detection method of DDoS attacks based on generalized multiple kernel learning (GMKL) combining with the constructed parameter R. The super-fusion feature value (SFV) and comprehensive degree of feature (CDF) are defined to describe the characteristic of attack flow and normal flow. A method for calculating R based on SFV and CDF is proposed to select the combination of kernel function and regularization paradigm. A DDoS attack detection classifier is generated by using the trained GMKL model with R parameter. The experimental results show that kernel function and regularization parameter selection method based on R parameter reduce the randomness of parameter selection and the error of model detection, and the proposed method can effectively detect DDoS attacks in complex environments with higher detection rate and lower error rate.     

A carbon based spintronic material Fe(x)-C(1-x)/Si structure

The decay of spin polarization poses serious problems for spintronic devices. It will be greatly helped by the availability of spintronic materials with a long spin diffusion length. Carbon has small spin-orbital interaction and longer coherent length. This makes carbon suitable material for exploitation in the spintronic materials and devices. A great deal of magnetoresistance (MR) research has been carried out in carbon nanotubes, grapheme and small carbon molecules. However, the MRs of these materials are normally observed at low temperature, making these carbon materials difficult used in information industry. In this paper, we introduce a novel class of carbon based hybrid materials Fe(x)-C(1-x)/Si structure which show larger MR at room temperature. These materials have also some other novel physical properties, such as electromagnetoresistance, switch effect, pressure sensitivity, gas sensitivity and photoconductivity. This kind of carbon based materials has shown early sign of being excellent candidates for spintronic materials operating at room temperature.     

Carbon analysis for inspecting carbonation of concrete using a TEA CO2 laser-induced plasma

It has been demonstrated that a spectrochemical analysis of carbon using the laser plasma method can be successfully applied to inspect the carbonation of concrete by detecting carbon produced in aged concrete by a chemical reaction of Ca(OH)2 with CO2 gas in environmental air, turning into CaCO3, which induces degradation of the quality of building concrete. A comparative study has been made using a TEA CO2 laser (500-1000 mJ) and a Q-switched Nd-YAG laser (50-200 mJ) to search for the optimum conditions for carbon analysis, proving the advantage of the TEA CO2 laser for this purpose. Also, it was clarified that laser irradiation with suitable defocusing conditions is a crucial point for obtaining high sensitivity in the detection of carbon. Practical experiments on the inspection of carbonation were carried out using both a concrete sample that had been intentionally carbonated by exposure to high concentrations of CO2 gas and a naturally carbonated concrete sample. As a result, good coincidence was observed between the laser method and the ordinary method, which uses the chemical indicator phenolphthalein, implying that this laser technique is applicable as an in situ quantitative method of inspection for carbonation of concrete.     

Development of sensors based on CuO-doped SnO2 hollow spheres for ppb level H2S gas sensing

An effort has been made to develop a new kind of SnO₂–CuO gas sensor which could detect an extremely small amount of H₂S gas at relatively low working temperature. The sensor nanomaterials were prepared from SnO₂ hollow spheres (synthesized by employing carbon microspheres as temples) and Cu precursor by dipping method. The composition and structural characteristics of the as-prepared CuO-doped SnO₂ hollow spheres were studied by X-ray photoelectron spectroscopy, X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. Gas-sensing properties of CuO-doped SnO₂ hollow sphere were also investigated. It was found that the sensor showed good selectivity and high sensitivity to H₂S gas. A ppb level detection limit was obtained with the sensor at the relatively low temperature of 35 °C. Such good performances are probably attributed to the hollow sphere nanostructures. Our results imply that materials with hollow sphere nanostructures are promising candidates for high-performance gas sensors.