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15 April 2022, Volume 41 Issue 4 Previous Issue    Next Issue

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Multiscale image enhancement and flame segmentation of ant colony algorithms under strong light HU Yan, MA Zong-fang, WEN Hao 2022, 41 (4):  435-439.  Abstract ( 1600 )   Aiming at the problem of incomplete flame image segmentation under low contrast, the threshold adaptive segmentation method for color flame image enhancement and the improvement of ant colony algorithm is proposed. First, the multi-scale Retinex enhancement with color recovery is designed for RGB images captured by the acquisition device. The brightness of the background pixel is raised through the brightness control factor. Adding the high-frequency information to the original image from three different scales dynamically improves the local visibility of the flame, thus making the color, texture, and edge information of the flame more prominent. Then, to avoid the randomness of ants during path selection, and enhance ant search efficiency and excellence search, based on the maximum class variance method, the segmentation threshold is automatically obtained from single images by improving the initial pheromone concentration and update rules and inspiration function in the ant colony algorithm, greatly improving the segmentation accuracy and speed. Finally, the proposed algorithm is compared with similar algorithms under different strong light, different scenes and different interference. The experimental results show that the average segmentation accuracy has improved by nearly 1.96 times while ensuring the segmentation speed. Related Articles | Metrics

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Study on fire behavior of linear fire source along the wall in cable cabin of utility tunnel LIU Xin, ZHU Guo-qing, WANG Pu-fan, XU Gang, 2022, 41 (4):  440-443.  Abstract ( 1532 )   The cable fire test was carried out in the scaled utilitytunnel model. Linear fire sources were placed on the wall at 15 ,45, 75 ,105 cm from the bottom of utility tunnel to study the fire behavior of the linear fire sources at different heights. It is found that the heat release rate of the linear fire source decreases with the increase of the height, which is different from the point fire source. The effective flame height was modified and the prediction formula of the effective flame height was obtained by fitting. The prediction formulas of the temperature distribution are obtained by analyzing the transverse temperature in plume region and jet region respectively. It provides technical support for the design of utility tunnel fire detection system and automatic fire extinguishing system. Related Articles | Metrics

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Effect of toluene content on the fire smoke characteristic of n-heptane fire YANG Xin-yan, WANG Shi-xu, LU Yong-li, XIN Long 2022, 41 (4):  444-447.  Abstract ( 1557 )   In engineering applications, the same content of fuel may not lead to uniform results in order to obtain the standard effective test fire, depending on the infrastructure conditions of the standard fire test room. Based on the specific test conditions, experimental research was carried out on the change of the linearity of the fire smoke characteristic curve caused by different toluene contents, and the volume ratio of toluene solution was 3.1%, 8.1% ,13.1%, respectively. The change law and the linearity of the ratio curve of m value to test time and m value to y value were obtained. The results show that by increasing the toluene content, the rate of smoke release could be quantitatively increased, and the linearity of the smoke characteristic curve becomes worse. For achieving the effective test of the smoke characteristics, the upper and lower limits of the toluene ratio in the fuel are limited by the linearity of the characteristic curve and the rate of smoke release. Related Articles | Metrics

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Overcharge-induced thermal runaway characteristics of pouch cells XU Hui-yong, ZHANG Zhi-ping, HU Ren-zong, FAN Ya-fei 2022, 41 (4):  448-451.  Abstract ( 1585 )   This paper studies the overcharge-induced thermal runaway characteristic of LiNi0.8Mn0.1O0.1O2-SiOx/graphite system 25 Ah pouch-shaped traction cells. Combined with the analysis results of the thermal characteristics of the electrode materials and gas production components during the thermal runaway process, the internal microscopic changes and dynamic heat generation characteristics of the cells during the thermal runaway triggered by overcharge in adiabatic and non-adiabatic environments was revealed. The path of overcharge triggering thermal runaway is: when overcharge causes the battery to exceed the safety margin voltage, side reaction and micro-short circuit of the pole piece occurred inside the cells, which generate gas and heat, and finally the cells overheat and reach the critical point of triggering thermal runaway. The trigger temperature of thermal runaway in adiabatic environment is 37.5 ℃ higher than that in non-adiabatic environment, and the triggering time in an adiabatic environment is shortened to varying degrees (about 90~500 s). In the end, the safety boundary and failure boundary of the cells were defined. Related Articles | Metrics

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Research on the electrostatic properties and hazards of polyvinyl alcohol MENG He, LI Liang-liang, GONG Hong, LIU Quan-zhen, 2022, 41 (4):  452-455.  Abstract ( 1564 )   In view of the potential safety hazards of ignition caused by electrostatic discharge of polyvinyl alcohol (PVA) during the packaging process, the resistivity, the the static decay time of two types of PVA dust layer, the static charge-mass ratio of the materials during the packaging process, and the surface potential of the packing bag were tested and analyzed，and the concentration of combustible volatile matter near the discharge port during the PVA packaging process was sampled and analyzed. The results showed that the particle size， polarity of the electrostatic charge carried and the environmental humidity all affected the electrostatic decay rate of PVA. In a humid environment, the charge-to-mass ratio of PVA during the packaging process and the the surface potential of the packing bag respectively exceeded 1 μC/kg and 20 kV. There are three types of flammable volatiles sampled and the methanol concentration was higher than the lower explosive limit. There's a risk of igniting the flammable volatiles due to electrostatic discharge. Combustible gas monitoring should be added to the PVA packaging process and electrostatic prevention and control measures should be strengthened. Related Articles | Metrics

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Improvement effect analysis of side-by-side distribution smoke exhaust pipe to the lateral smoke exhaust efficiency HUANG Yi-long, ZHANG Shao-gang, SHI Yan-li, LIU Jia-hao 2022, 41 (4):  456-461.  Abstract ( 1567 )   To further improve the lateral smoke exhaust efficiency of tunnel fire, taking the Hong Kong-Zhuhai-Macao Bridge submarine immersed tube tunnel as the research object, FDS numerical simulation software is used to carry out isometric modeling. Set the heat release rate of the fire source to 10, 20, 50 MW, the smoke exhaust rate to 4, 6, 8, 10 m/s, and the aspect ratio to 1:2, 1:1, 2:1, 3:1, a total of 48 sets of the scenarios. Install the "side by side distributed smoke exhaust pipe" at each side exhaust vent, the influence of the aspect ratio of the side-by-side distribution smoke exhaust pipe and the heat release rate(HRR) of the fire source on the smoke exhaust efficiency is explained through control variate method, and analyze the influence of the aspect ratio of this pipe on the improvement rate of the lateral smoke exhaust efficiency. The results show that: （1）Under the condition of the same exhaust rate when the aspect ratio of this pipe is small and the aspect ratio increases from 1:2 to 2:1, the vertical interception range of smoke decreases, and the exhaust efficiency gradually decrease. At this time, the amount of smoke absorbed dominates the exhaust efficiency. When the aspect ratio of this pipe is large, and the aspect ratio is increased from 2:1 to 3:1, the pipe becomes flattered making the exhaust efficiency gradually increase. At this time, the concentration of the smoke absorbed dominates the exhaust efficiency. Therefore, the laterals moke exhaust efficiency first decreases and then increases with the increase of the aspect ratio of this pipe and the minimum value is obtained when the aspect ratio is 2:1.（2）Under the same conditions of smoke exhaust rate and aspect ratio of the pipe, the total amount of smoke generated by combustion increases with the increase of the HRR, while the smoke absorption of the pipe quickly reaches the saturated state, the smoke absorbed by the pipe does not increase significantly, but the total amount of smoke generated by combustion increases, so the exhaust efficiency decreases with the increase of the HRR; Furthermore, under the conditions of the same smoke exhaust rate and different aspect ratios of the pipes, since the smoke absorbed by the pipe has not reached saturation when the HRR is small, there are obvious differences in the exhaust efficiency corresponding to the different aspect ratio. With the increase of the HRR, the smoke exhaust volume of the pipe reaches saturation at this time. Both of the smoke absorbed by the pipe and the total amount of smoke generated by combustion tend to be the same, thus making the smoke extraction efficiency tend to be consistent with the increase of the HRR. In this case, the aspect ratio of the pipe is no longer the main factor affecting the exhaust efficiency, and it should be considered to increase the number of pipes to improve the exhaust efficiency substantially. （3）By comparing the smoke extraction efficiency of the original lateral smoke exhaust system, the lateral smoke exhaust efficiency can be increased by a maximum of 4.3 times after the “distributed smoke exhaust pipe” is installed (the HRR is 10 MW, the smoke exhaust rate is 8 m/s, and the aspect ratio of the pipe is 1:2), and the minimum can be increased by 0.5 times. According to the power function fitting, the functional relationship between the aspect ratio and the improvement rate of the lateral exhaust efficiency is obtained. The improvement rate of smoke extraction efficiency gradually decreases with the increase of the aspect ratio, and finally converges to a certain limit value. The data show that when the aspect ratio is greater than 2:1, the improvement rate is very close to the limit. Although there is a maximum improvement rate when the aspect ratio is 2:1, it will affect the tunnel headroom. Considering economy and practicality, setting the aspect ratio to 1:1 is an optimized design solution. Related Articles | Metrics

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Research on the effectiveness of spatial directional information transmission of fire safety evacuation signs FAN Rui-wen, DAI Zhang-yin, ZHOU Hui, TIAN Shi-xiang 2022, 41 (4):  462-467.  Abstract ( 1545 )   To explore the effectiveness of spatial directional information transmission of fire safety evacuation signs, we designed a simulation experiment on the effectiveness of spatial directional information transmission by using two types of commonly used fire safety evacuation signs: hangtag and embedded, and the countermeasures were put forward. The results indicate that the spatial angle of the hangtag fire safety evacuation signs is inversely proportional to the effectiveness of spatial direction information transmission. When the spatial angle of embedded fire safety evacuation signs is 10°, the spatial direction information transmission effectiveness is the strongest. But when the spatial angle is 5°, the practical degree is the best. Suitable spatial angle can increase the visual area of fire safety evacuation signs, thus enhance its transmission effectiveness. Related Articles | Metrics

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Fire and smoke law of A320 cabin in low pressure environment WANG Zhi-yu, ZHU Jie, 2022, 41 (4):  468-471.  Abstract ( 1556 )   Airbus A320 series aircraft is taken as the research object to explore the influence of low pressure on the smoke movement of fire. Using FDS numerical simulation, the law of smoke and temperature inside the cabin of the aircraft is analyzed. The results show that in a low-pressure environment, the fire heat release rate, temperature and CO concentration inside the aircraft cabin are reduced in varying degrees, and the peak end time is advanced. The smoke sinking speed and lateral spreading speed increase, but the smoke concentration decreases. It is inferred that the smoke generation rate has slowed down. Related Articles | Metrics

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Review on the fire prevention and control technology for lithium-ion battery energy storage power station CAI Jing-jing 2022, 41 (4):  472-477.  Abstract ( 1641 )   Against the fire hazard of lithium-ion battery energy storage power station, related literatures both domestic and foreign countries have been reviewed. Research on the disaster-causing mechanism of thermal runaway, technical methods of firefighting and safety standards in energy storage field were summed up, and the present research status and future development tendency have been summarized in this paper. The analysis can provide an effective reference for the safe and healthy development of energy storage industry. Related Articles | Metrics

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Discussion on problems and countermeasure of steel structure buildings fire protection WANG Jin-ping, YE Yi-fan, CHU De-wen, BAI Yun-long 2022, 41 (4):  478-480.  Abstract ( 1540 )   Through analysis of the steel structure buildings fire protection situation, based on the occupy life of steel structure buildings, the paper put forward that the durability of the protective materials should be considered in the steel structure design phase, and analyzed the illegal operations of fire resistive material manufacturers and steel structure engineering constructors, focused on scene supervision and detection means improvement in the project construction stage, and put forward practical control measures for building acceptance and project management. Based on engineering examples, the key points of steel structure fire protection was proposed, and the corresponding solutions for design, construction, inspection and acceptance was discussed. Related Articles | Metrics

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Study on building evacuation based on fire scenarios YANG Qiang, LI Yi-fan, YAN Xiao-jie, ZHANG Zhong-ren 2022, 41 (4):  481-487.  Abstract ( 1503 )   A university library in Nanjing was taken as an example. According to the principle of Most Adverse Impact, fully consider meteorological factors, building structures, combustibles and other environmental factors, the building information model and spatiotemporal analysis model are used to simulate the spatiotemporal law of fire generating factors and build fire risk scenarios. By analyzing the threshold of hazard sources that people can bear during evacuation, the dangerous areas inside buildings in four seasons are obtained. Combined with the indoor road network model and path search algorithm, the life safety assurance path for personnel evacuation is planned and designed, which is compared with the shortest time path and the shortest distance path, and the evacuation effect of life safety assurance path is evaluated. Through the above research, the space-time simulation of building fire and the dynamic planning of personnel evacuation are realized, which provides theoretical basis and technical support for the formulation of adaptive measures for urban fire emergency response. Related Articles | Metrics

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Knowledge mapping analysis of fire risk assessment research based on CiteSpace XIANG Yue, CHEN Yue, QIAN Yi-nuo, QIN Yi 2022, 41 (4):  486-490.  Abstract ( 1591 )   In order to understand the overall situation of the field of fire risk assessment, this paper searched CNKI and Web of Science databases, analyzed 1 250 literatures from 1999 to 2020 based on the CiteSpace software, and drew its knowledge map. The results show that the number of publications about fire risk analysis is increasing steadily; the high-yield core authors are Tian Yu-min and Matthew P. Thompson; the core institutions are the Chinese People’s Armed Police Forces Academy （China People's Police University now）and University of Science and Technology of China; the high-yield core countries are China and the United States; and through the comprehensive analysis of key words, it is concluded that the hot spots of future research mainly include the following aspects: in theoretical research, the randomness and uncertainty of fire will continue to be studied; in terms of assessment methods, a fire risk assessment method based on the law of fire dual attributes will be constructed; in terms of evaluation practice, intelligent evaluation software will be developed. Related Articles | Metrics

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Risk assessment method of emergency evacuation in public buildings based on neural network LI Jia-feng, HU Yu-ling, LI Jia-xu, 2022, 41 (4):  491-495.  Abstract ( 1534 )   Public buildings have large spaces, densely populated people, and long horizontal evacuation distances. There are certain risks in the evacuation in emergency situations. This paper proposes an emergency evacuation risk assessment method based on deep neural network (DNN). The establishment method of DNN prediction model is given, and a university gymnasium is used as a case to illustrate the whole evaluation process of model data acquisition, model training, and model testing. The results show that compared with traditional evaluation methods, this deep learning method overcomes the shortcomings of subjectivity and difficulty in risk assessment of complex evacuation systems centered on people, and can realize rapid and effective evaluation of emergency evacuation in public buildings. Related Articles | Metrics

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Simplified assessment method of fire spread risk of village buildings based on network model ZHENG Fei-yang, ZHANG Liang, SONG Zhi-gang, ZHANG Jian 2022, 41 (4):  496-499.  Abstract ( 1519 )   In view of the heavy workload of fire spread simulation and insufficient consideration of fire prevention structure, this paper proposes a simplified analysis method of fire spread of village buildings based on network model combined with the fire spread risk assessment of Mengka Village in Yunnan Province. Based on the field investigation and simplified calculation of Mengka Village, this method determines the path of building fire spreading to the surrounding area, establishes the adjacency matrix of building fire spreading network, and further determines the spreading range of different fire scenarios combined with network node traversal algorithm. On this basis, the fire spreading risk of different fire scenarios and different areas is analyzed. Related Articles | Metrics

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Influencing of design mode of the protected stairway on the evacuation efficiency in buildings XING Lu-ning, LI Guo-hui 2022, 41 (4):  500-504.  Abstract ( 1472 )   In order to explore the influence of different evacuation stair design modes on evacuation, five evacuation models were constructed, and the numerical simulation method were used to compare and analyze the correlation between different stair forms and the number of stair transition platforms and evacuation efficiency. The results indicate that the form of stairs and the number of conversion platforms are directly related to the average evacuation distance of people in the buildings, the efficiency of people evacuate to the stairwell and the efficiency of people evacuate to the outdoor. The average evacuation distance is the shortest when the 4 stairs are scattered and no transfer platform is provided in the stairwell. The evacuation efficiency of all people step into the stairwell is the highest when 4 stairs are scattered and 2 transfer platforms are provided. The evacuation efficiency of all people step to the outside is the highest when 4 stairs are scattered and 1 transfer platform is provided. Related Articles | Metrics

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Effectiveness and parameter optimization of water mist control system for exhaust duct fire in high-rise residential WEI Ze, LI Zi-jian, ZHANG Pei-hong 2022, 41 (4):  505-509.  Abstract ( 1537 )   In order to effectively control the kitchen flue fire in high-rise residential buildings, the water mist fire control simulation models for cooking oil fire and cooking grease fire of flue with branches in kitchen in high-rise residential buildings were established based on FDS. The effectiveness and the optimum parameters of the water mist fire suppression system were analyzed. The results show that once a cooking oil fire in the kitchen on the ground floor of a high-rise residential buildings was not suppressed in time, the hot flame and smoke will ignite the cooking grease in the flue under the effect of the strong chimney effect, and the exhaust duct fire will spread immediately. In the fire simulation model of the 30 m height kitchen flue with branches established in this paper, the optimum operation mode of the water mist fire suppression system is to shut down the exhaust fan in the kitchen, start the water mist spray nozzles of 0.6 L/min which are arranged directly above the oil pan and nozzles of 10 L/min at different positions of the main flue of the high-rise residential buildings. The best spray velocity should be 10 m/s with spray angle 60° and 500 μm diameter of water mist particle size. Related Articles | Metrics

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Effect of gas-liquid flow rate on field characteristics of low-pressure twin-fluid water mist WANG Kang, WANG Jing-dong, TAO Bo, HE Yuan-hua 2022, 41 (4):  510-515.  Abstract ( 1529 )   Since there are few studies on low-pressure twin-fluid water mist with different gas-liquid flow rates in civil aircraft cargo tanks, and the quantitative and qualitative analysis of single nozzle mist flux and mist momentum is not perfect, it is necessary to design and carry out experiments for further research. Referring to the relevant standards formulated by the Federal Aviation Administration (FAA), a low-pressure twin-fluid water mist experimental platform for aircraft cargo tanks was designed and built, mainly including the FAA full-scale aircraft cargo tanks and low-pressure twin-fluid water mist system. The nozzle was different from the conventional nozzle. The spray of water mist is a circular plane with excellent dispersion and stagnation. Malvin particle size analyzer combined with Spraytec software was used to measure the droplet size of water mist under different gas-liquid flow rates. It was found that when the gas flow rate increased from 250 to 350 L/min and the liquid flow rate remained 0.5 L/min, the droplet size decreased from 130 to 95 μm. When the liquid flow rates were 0.75 and 1.0 L/min, the particle sizes decreased from 161 to 110 μm and 201 to 142 μm, respectively. According to the standards of the National Fire Protection Association, the water mist flux under different gas-liquid flow rates was measured by the cup collection method. It was found that the water mist flux increased with the increase of gas flow or liquid flow alone.When the gas flow rate was 350 L/min and the liquid flow rate was 1.0 L/min, the water mist flux reached the maximum value of 0.255 L/(min·m2). The velocity of droplet was measured by using the high speed camera of Particle Image Velocimetry. The results showed that when the gas flow rate increased from 250 to 350 L/min under three different liquid flow conditions, the corresponding droplet velocity increased approximately with the growth rate of 0.04 with a minimum value of 8.5 m/s and a maximum value of 16 m/s. Assuming that the shape of water mist droplets was spherical, the relationship of mist momentum was obtained by the product of droplet mass and velocity. The maximum value of droplet velocity was selected and substituted into the formula to obtain the variation curve of mist momentum of single droplet under different gas-liquid flow rates. When the gas flow was 250 L/min and the liquid flow was 1.0 L/min, the momentum of single droplet was the maximum as 3.6×10-8 kg.m/s. The influence of gas and liquid flow on the mist feild characteristies of low pressure twin fluid water mist was studied by experiments. The results showed that when the liquid flow rate was constant and the gas increased from 250 to 350 L/min with a gradient of 25 L/min, the droplet size and momentum decreased gradually, while the droplet velocity and flux increased gradually. When the gas flow rate was constant and the liquid increased from 0.5 to 1.0 L/min with a gradient of 0.25 L/min, the droplet size, momentum and flux increased gradually, while the droplet velocity decreased gradually. For a single droplet, the droplet momentum depended on the droplet size ; for all the droplets emitted by the nozzle, the droplet velocity determined the overall fog momentum. In the future, water mist fire extinguishing experiment will be carried out to explore the gas-liquid flow rate to achieve the best fire extinguishing effect. The conclusion can be used for the design and improvement of low pressure water mist fire extinguishing system in aircraft cargo compartment, which provides experimental and theoretical basis for the development of water mist system driven by low pressure. Related Articles | Metrics

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Experimental study on aquatic biotoxicity of class A foam extinguishing agent ZHANG Xian-zhong, KE Xin, ZHAO Ting-ting, BAO Zhi-ming 2022, 41 (4):  516-519.  Abstract ( 1576 )   The fine extinguishing capability of class A foam extinguishing agents are rapidly gaining acceptance. However, with the increasing environmental awareness, recent concern has focused on the potential adverse environmental impact of class A foam discharges. The aim of this study was to evaluate the acute toxicity of class A foam concentrates and solutions used in China. Laboratory studies were conducted to determine the acute toxicity of twelve class A foam extinguishing agents. The organism tested was zebrafish (Brachydanio rerio), and the median lethal concentration (LC50) was calculated and reported. The acute fish toxicity data of Class A foam extinguishing agents both in China and other countries were compared, and the effects of the discharge of class A foam concentrates and solutions on aquatic ecological environment were analyzed. The test results indicate that the 96 h LC50 values of twelve class A foams in China on zebrafish are at the range of 12.85~121.42 mg/L. The acute fish toxicity of Class A foam is significantly higher than that of aqueous film-forming foam (AFFF)(232.57~6 003.25 mg/L). Wetting agents are highly toxic, and they are the most important components affecting the toxicity of Class A foam extinguishing agents, while antifreeze has little influence on the acute toxicity. The acute toxicity values of class A foam both in China and other countries are at the same level, which are mainly within 10~100 mg/L. The 96 h LC50 values of samples meet the acute toxicity limit requirements for class A foam extinguishing agent in NFPA 1150, USDA 5100-307b and other relevant specifications and standards. The concentrate of class A foam extinguishing agent has higher aquatic toxicity than other types of extinguishing agents. According to the guidelines for the hazard evaluation of new chemical substances, it is classified as medium to high toxic substances, and may cause the death of aquatic organisms. So it needs to pay attention to the aquatic toxicity of the concentrate of class A foam. It is advised to operate cautiously in the transportation, storage and transfer of class A foam extinguishing agent concentrates so as to prevent the leakage of concentrates from poisoning natural organisms. The toxicity of class A foam solution is relatively low after being mixed with water at the ratio of 0.1%~1% and then further diluted by natural water body. However, the potential toxic effects of foam solution still exist in the environment. In order to reduce the environmental risk after use of class A foam extinguishing agent, the unnecessary foam disposal should be minimized during fire fighting activities. It is suggested that the foam solution and runoff water should be collected after use and biochemically treated before discharging into the natural environment. In the future research, environment-friendly class A foam extinguishing agent should be developed to reduce the aquatic toxicity and environmental risk of products through formula optimization. Related Articles | Metrics

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Study on fire extinguishing performance of hexafluoropropylene CHEN Lu, WANG Xing-gu, HUANG Xin, KAN Qiang 2022, 41 (4):  520-525.  Abstract ( 1603 )   Hexafluoropropylene(HFP) meets the environmental friendly requirements of Halon alternative fire extinguishing agent due to the existence of the C=C double bond. However, there are few studies focus on its fire extinguishing performance, and the interaction with flame is still unclear. In this paper, the fire extinguishing performance of HFP on methane and propane flames is studied by cup burner, and it was compared with saturated fluoroalkane, hexafluoropropane(HFC-236fa) and heptafluoropropane(HFC-227ea). The results indicated that HFP has an earlier trend of decreasing flame height and brightness than HFC-236fa and HFC-227ea, and has a more obvious effect on the increase or decrease of flame temperature.The C=C double bond structure of HFP makes it easier for fluorine-containing groups to react with free radicals in the flame, resulting in a sharp rise in the flame temperature, and then consume a lot of free radicals in the flame, resulting in a sudden drop in the temperature. Related Articles | Metrics

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Design of multi parameter fire detection system based on neural network algorithm JIA Rong-tian, YUAN Chun-miao, CAI Jing-zhi, ZHENG Hao-tian 2022, 41 (4):  526-529.  Abstract ( 1554 )   To further broaden the application of neural network algorithms in the field of fire detection, a national standard fire experimental data with a smoldering fire, open fire, and no fire occurrence probability as output results was used to train a multi-layer BP neural network on the MATLAB platform. The decisive coefficients of the network for the sample fitting of the test set are more than 0.95. Using AT89C52 as the main control chip, a simulation circuit diagram which can meet the purpose of fire detection is designed in Proteus. By introducing the trained BP neural network parameters into the simulation formula of the neural network, the software program that can drive the circuit action is designed, and the circuit simulation test of the fire detection system is realized. Related Articles | Metrics

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Research on key points and typical hidden problems of fire protection supervision and inspection of automatic fire alarm system CUI Peng-fei 2022, 41 (4):  530-532.  Abstract ( 1609 )   Automatic fire alarm system is a common building fire protection facility in modern buildings. This paper summarized the fire supervision and inspection experience of automatic fire alarm systems in recent years, and deeply studied the types, distribution characteristics and search methods of hidden problems, and formed a set of inspection methods for automatic fire alarm systems. Based on a large number of sample data from fire supervision and inspection in many provinces and cities in recent years, the analysis and calculation of the correlation between the number of hidden dangers of the automatic fire alarm system and the per capita GDP have been carried out. Systematic statistics and analysis of the inspection situation was shown in this paper, and it was discovered that the automatic fire alarm system mainly has three types of hidden problems: fire protection control room equipment, field equipment, and system function. From the five aspects of initial design, installation and commissioning, equipment selection, maintenance and safety management, each category of hidden dangers was analyzed and researched, and reasonable suggestions were put forward. The research results can be directly applied to our country's fire protection supervision and management policy formulation, development planning and daily supervision and inspection work, providing scientific technical support and data foundation for fire protection supervision and inspection. Related Articles | Metrics

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Development of intelligent fire fighting device for oil-immersed transformer fire in transformer substation CHEN Qing-wei, XIE Dan, HONG Wei-yi, HAO Xin 2022, 41 (4):  533-537.  Abstract ( 1457 )   This paper analyzes the cause of fire of oil-immersed transformer in multi-station fusion substation and develops a set of intelligent fire-fighting device for oil-immersed transformer in substation. The device uses LoRa wireless communication technology to remotely monitor the temperature, flame and smoke status of oil-immersed transformer, and uses multi-stage fire warning algorithm to judge and identify the fire situation, so as to improve the ability of early detection, early warning and timely extinguishing of the fire to ensure the safe and stable operation of oil-immersed transformer.The device was tested in transformer fire simulation field. The test results show that the device has sensitive communication and can extinguish the fire timely . Related Articles | Metrics

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Design of a multi-hazard emergency rescue simulation training platform based on scenario construction LIAO Guang-xuan, FENG Kai, CHEN Qin-pei, ZHANG Xiao-chun 2022, 41 (4):  538-541.  Abstract ( 1747 )   Multi-hazard emergency rescue simulation training based on scenario construction is an important way to innovate fire rescue drill methods, and the key technical support to realize the new rescue situation of "All Kinds of Disasters, Big Emergency". Starting from the needs of the fire rescue in the new era, this paper analyzes the traditional simulation training mode and its shortcomings, investigates the advanced concepts and methods of scenario construction abroad that can be used for reference, analyzes the necessity and urgency of the transformation of simulation training from "plan response" to "scenario response". At the same time, the scheme, mode and system composition of multi-hazard emergency rescue simulation training based on scenario construction are put forward, and the platform function is discussed. Related Articles | Metrics

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Effect of forest fire on soil stability of pinus massoniana plantation PENG Xu-jian, ZHANG Shui-feng, ZHANG Si-yu, Liu Xin 2022, 41 (4):  542-545.  Abstract ( 1453 )   The number of aggregate fractal dimension and soil erodibility K index were used to study the characteristics of soil erodibility of various layers of soil after fire under different simulated rainfall conditions. The results showed that the content of soil organic matter in burned sites has the greatest influence on soil erodibility, and the restoration effect of burned sites determines the soil's water erosion resistance. Among them, the 0～5 cm soil layer of the burned plots 1, 2 and 3 maintained the K value below 0.031 under the three different treatments of FW, SW and WS, and compared with the 0～5 cm and 5～10 cm soil layers, the K value of the 10～20 cm soil layer under the three different treatments were significantly increased, and the 10～20 cm soil layer of the fired plots 1 and 2 had the lowest corrosion resistance. The overall soil erodibility K value of plot 3 and control plot 3' were relatively lower, and their corrosion resistance were relatively stronger. Related Articles | Metrics

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Study on the effect mechanism of low voltage bare wire on forest fire LI Jin-song, YANG Dong-dong, YU Hua, LIU Wen-hao 2022, 41 (4):  546-550.  Abstract ( 1497 )   In recent years, the risk of fire in forest grassland caused by power transmission and distribution lines in China is increasing. In order to explore the characteristics and mechanism of low-voltage overhead bare wire fire, a 380/220 V low-voltage line simulation experiment platform was built. Branches short-circuiting lines and two phase contact short circuit tests were carried out. The phenomenon of short-circuited melted marks often occurred in the close place between low voltage bare wire crossing forest area and trees was analyzed by the experiments and simulation. The results indicate that there were no spark discharges when normal twig and rain-soaked twig overlapped line. The temperature of the splash beads generated by the contact short-circuit discharge between two phase lines falling to the ground is low, which can not ignite the combustible material on the ground. Combined with the investigation results of low-voltage line fire causes in recent years, the line overcurrent protection plays a significant role in preventing low-voltage line fire. In strong wind and heavy rain, the twigs and leaves short-circuit two phase line, which may lead to short-circuit discharge and obvious melted marks on the wire. The research can provide technical reference for low-voltage line fire cause investigation and prevention. Related Articles | Metrics

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The problems and countermeasures on the construction of full-time government fire brigades ZHANG Quan-ling1, WANG Dong2 2022, 41 (4):  551-553.  Abstract ( 2477 )   The main problems of the full-time fire brigades were pointed out from the brigade quantity, construction quality, logistical support level, management system etc., its main reasons were dissected from the aspects of system design, performing the functions according to law, ideological understanding, organization construction, and then the probable results of ignoring the construction of full-time government fire brigades were indicated. The countermeasures and suggestions for strengthening the construction of full-time government fire brigades were put forward from the ways of perfecting laws and regulations, establishing management organization, clarifying identity and attribute, strengthening cadre team, clarifying relevant responsibilities, strengthening organizational construction, standardizing management according to law and strengthening comprehensive guarantee. Related Articles | Metrics

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Safety education courses effect evaluation basedon "behavior-state" associated data WANG Fei, WEN Zhi-qiang, YANG Nan 2022, 41 (4):  554-558.  Abstract ( 1468 )   To ensure the effectiveness of safety education is of great significance to protect people's life and property safety and maintain social harmony and stability. By visiting 116 classes of 1 064 teachers and students, the study obtained the "behavior-state" associated data law of the actual classroom, combined with the existing teaching evaluation research results, and adopted a variety of wisdom perception technologies to carry out the evaluation of specific learning effects. Experimental results show that the accuracy of this method is about 80%. This method provides a reference for the realization of a more objective and scientific quantitative evaluation of the whole process of safety education, and helps improve the safety awareness of the whole people. Related Articles | Metrics

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Research on the construction method of fire rescue situation awareness system QU Zuo-dong1, SHI Cheng-tao2,LI You-dong3, ZHANG Wei4 2022, 41 (4):  559-561.  Abstract ( 1580 )   Analyzing the needs of fire rescue situational awareness circle, fusion circle, display circle, prediction circle, decision circle and evaluation circle model, the application demand of fire rescue situational awareness system in advance, in and after the event, the difficulties of constructing fire rescue situational awareness system were analyzed from the aspects of cross-cutting system convergence, intelligent equipment research and development, perception technology, data fusion, mathematical modeling and communication support, etc. From the formulation of regulatory standards, breakthrough key technologies, to increasing the strength of equipment research and personnel team construction， the construction of fire rescue situational awareness system countermeasures was explored. Related Articles | Metrics

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Exploration and thoughts on the cross-regional railway transportation of emergency rescue forces for the all-disaster relief-Taking the delivery of flood fighting forces of Hunan Fire and Rescue Brigade to Henan Province as an example GAO Ning-yu, LIU Ding-ming 2022, 41 (4):  562-565.  Abstract ( 1759 )   ?After the reform of the fire rescue team, the construction of cross-regional mobile power in the country has strengthened, and the cross-regional combat of large troop formation has become an emergency rescue normality. The establishment of a complete cross-regional power delivery plan is the basic premise and important guarantee of serious calamity accidents such as earthquakes, floods, mudslide, typhoons, forest and grassland fires. Therefore, it is imminent to explore cross-regional power delivery model, establish one circle of personnel, vehicle, and equipment, and improve the air-rail-highway integrated delivery system. This paper analyzed the practical experience of highway delivery and rail delivery when the Hunan Provincial Fire Rescue Corps reinforced the flood rescue in Henan Province and put forward exploratory suggestions on strengthening the construction of cross-regional railway transmission ability of emergency power deliver. Related Articles | Metrics

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Reflection on the influence of the new provisions on fault imputation in the Administrative Punishment Law of the PRC on the fire law enforcement HUANG Pei-yun 2022, 41 (4):  566-568.  Abstract ( 1635 )   For a long time, there are some different understandings about the fault imputation principle in administrative law enforcement in the academic circles at home and abroad, and it is reflected differently in the legal provisions of various countries including our country. As one of the types of administrative law enforcement, the fire law enforcement will also have some significant impact on the fact determination, law application and evidence collection and application of fire administrative penalty cases after the new provisions on subjective fault attribution in the Administrative Punishment Law of the People's Republic of China are put forward. In view of these situations and problems, combined with the actual work, this paper discusses countermeasures and puts forward corresponding suggestions. Related Articles | Metrics

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Path and thoughts on fire investigation big data construction WANG Xin, LU Zhi-bao, WANG Yu-ling, HAN Chong 2022, 41 (4):  569-571.  Abstract ( 1532 )   This paper put forward many thoughts and suggestions on the fire investigation big data system from the aspects of existing system, construction objectives, construction ideas and construction deployment by analyzing the current development status of fire investigation data in order to provide more references for the construction of fire investigation big data. Related Articles | Metrics

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Discussion on fire extension investigation based on working condition of fixed fire extinguishing system LIU Lian-xi, TIAN Li-wei, YI Cheng-yi, XIAN Xue-lei 2022, 41 (4):  572-574.  Abstract ( 1440 )   Based on the investigation and analysis of the working conditions of in-service fixed fire extinguishing systems such as gas fire extinguishing system and sprinkler system, this paper clarifies the factors affecting the failure of fixed fire extinguishing system to implement effective fire extinguishing at the fire site, and puts forward the possibility and ideas of extended fire investigation from the aspects of product producers, design, construction and maintenance, management and maintainers. It provides technical support for expanding and enhancing the means and scope of fire investigation. Related Articles | Metrics

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Investigation and test technology of gas deflagration accident CHANG Ying, LIANG Guo-fu, WU Xian 2022, 41 (4):  575-578.  Abstract ( 1540 )   In order to reduce and avoid gas explosion accidents, find out the causes of accidents, prevent and reduce gas accident rate, this paper introduces the propagation mode and characteristics of gas explosion. On this basis, it expounds the investigation method and test technology of gas explosion. Through analysis of explosion gas, initiation position, leakage point and leakage cause, it completely describes the whole explosion accident investigation and test technology. The study can provide a technical support and investigation means for gas explosion accidents, and lay a foundation for the accurate investigation of gas explosion accidents. Related Articles | Metrics