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15 September 2023, Volume 42 Issue 9 Previous Issue    Next Issue

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Study on the over temperature alarm device of structural members under fire Xiang Kai, Pan Yanchong, Song Tianyi, Hu Shengli, 2023, 42 (9):  1167-1173.  Abstract ( 304 )   In order to realize the over temperature alarm when the structural members in the building reach the failure temperature, based on the characteristics of high temperature melting of solid metal, over temperature alarm device and high temperature protection method of structural members are developed with the experimental research and finite element analysis. The research results show that the developed over temperature alarm device can realize the over temperature alarm when the structural member reaches the failure temperature. The high temperature protection of the over temperature alarm device can be effectively realized by using the thermal insulation protection method of the combination of fireproof board and aerogel blanket. Related Articles | Metrics

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Numerical study on the release pressures effect on the high-pressure hydrogen spontaneous ignition Wang Zongcheng, Li Quan, Wang Changjian 2023, 42 (9):  1174-1179.  Abstract ( 222 )   The valve is susceptible to damage caused by the instantaneous impact of high-pressure hydrogen during operation, resulting in spontaneous ignition of high-pressure hydrogen release. In this paper, an in-house solver is developed within OpenFOAM framework. The Fuller-Schettler-Giddings diffusion coefficient model and 21-step hydrogen/air chemical reaction mechanism is used to describe the diffusion and chemical reaction of spontaneous ignition process. Meanwhile, this paper carries out the numerical study on spontaneous ignition of high-pressure hydrogen release from valve and analyses the influence law of 4~10 MPa release pressures on spontaneous ignition of high-pressure hydrogen release. The critical pressure for spontaneous ignition of high-pressure hydrogen release though a valve is given. The investigation shows that, compared with straight tube leaks, when the high-pressure hydrogen release though a valve, the complex structure inside the valve causes the reflection and bypassing of the leading shock wave, which raises the shock-heated air temperature and promotes the occurrence of spontaneous ignition of high-pressure hydrogen inside the valve. When the release pressure reaches 6 MPa, spontaneous ignition occurs at the center of the valve. In addition, the increase in release pressure increases the likelihood of spontaneous ignition, as the release pressure increases from 6 MPa to 10 MPa, the time required for ignition decreases from 26 μs to 10 μs and the distance required for ignition decreases from 24 mm to 10 mm. Related Articles | Metrics

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Experimental study on combustion characteristics of single and row multifunctional massage seats Gu Sinian, Bu Xuemin, Yang Zhijun, 2023, 42 (9):  1180-1186.  Abstract ( 154 )    Experiments of single and two multifunctional massage seats were carried out. The essential parameters of fire spread behaviors, heat release rate, external field temperature and heat flux distribution were analyzed. The main conclusions are as follows: When the single and two seats are burning, the heat release rate experiences two rapid growth stages. The first corresponding peak values are 351， 392 kW, and the second are 572， 968 kW, the fire growth coefficient belongs to the range of slow and medium fire. Before reaching the peak value of heat release rate, the variation of theoretical heat release rate obtained by superposition principle is basically consistent with the experimental data, and the peak of heat release rate is qualitatively similar to the experimental results. The temperature of the fire plume decreases with height, and the attenuation of the fire plume temperature for two seat is slower than that for single seat. The longitudinal temperature of the external field accords with the Gaussian function distribution with the distance from the fire source, and its attenuation coefficient is 2.859. The variation of radiant heat flux experiences two peak values, which is similar to that of heat release rate. The point source radiation model can be used to calculate the external radiant heat flux, but the radiation coefficient should considered as 0.60~0.86 for the fire of multifunctional massage seat. Related Articles | Metrics

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Experimental study on combustion characteristics and heat transfer of 220 kV high-voltage cable Fire Yu Wei, Tu Yue, Yi Tao, Gao Fei 2023, 42 (9):  1187-1191.  Abstract ( 164 )   In order to study the heat transfer mechanism and combustion characteristics of 220 kV high-voltage cables fire, a full-scale fire experiment was carried out. The internal temperature distribution and combustion phenomenon were recorded, and the longitudinal temperature propagation progress of cable cores, cross-linked polyethylene (XLPE), filler materials and outer sheaths were analyzed. The results show that: there will be voids between the copper core and the extruded corrugated aluminum sheath during the combustion progress. After the high-voltage cable was heated, the heating response time of the inner copper core at different longitudinal positions is basically the same. In addition, in the heating stage of the cable, the average temperature gradient of the core, cross-linked polyethylene,filling material and outer sheath is 2.125,1.938, 1.688 and 1.375 ℃/cm respectively. In the continuous stage of the fire, due to the poor thermal conductivity of XLPE, with the increasing distance from the fire source, there is an obvious hysteresis phenomenon in the temperature change, and the average speed of combustion spread of XLPE is about 3.6 cm/min. The XLPE insulation part of the high-voltage cable will melt when heated, and will accumulate at the cable end. When its gravity is greater than the surface tension, it will form high-temperature molten droplets, which are easy to ignite the combustibles. Related Articles | Metrics

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Study on the effect of HFO-1234ze(E) on heptane flame suppression Yin Yixuan, Yang Ke, Ji Hong, Shu Zhongjun 2023, 42 (9):  1192-1196.  Abstract ( 174 )    With the implementation of the Kigali Amendment, the currently widely used hydrofluoropropane gas fire extinguishing agent represented by heptafluoropropane, as a typical non-carbon dioxide greenhouse gas, will be restricted and phased out, and it is of great significance to find alternative new chemical gas fire extinguishing agents. The environmentally friendly HFO-1234ze(E) has been widely used as a new refrigerant, and it is also within the screening range of alternative fire extinguishing agents as a fluoroolefin. In this paper, the extinguishing concentration of HFO-1234ze(E) was determined by cup burner. At the same time, the influence of air flow on its fire extinguishing concentration was studied, and its possible fire extinguishing mechanism was analyzed. The experimental results show that the critical extinguishing volume fraction of HFO-1234ze(E) on heptane flame is 11.5%, which has a strong inhibitory effect on the flame and is not greatly affected by the air flow. Its possible main fire extinguishing mechanism is to use the fluorine-containing group produced by its high-temperature decomposition to capture the free radicals of the combustion reaction and terminate the chain reaction to extinguish the flame. Therefore, HFO-1234ze(E) can be further studied as an environmentally friendly alternative fire extinguishing agent. Related Articles | Metrics

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Study on the combustion characteristics of cable fire under different ambient pressure and inclination angle Ding Chao, Li Yuyao, He Lingfeng, Jiao Yan 2023, 42 (9):  1197-1200.  Abstract ( 164 )   In this paper, cable combustion experiments were conducted in a variable pressure experimental chamber. We measured the burning rate of the cable and the combustion characteristics parameters such as temperature and radiant heat above the cable during the fire spread by changing the ambient pressure and the cable placement angle in the chamber, and processed and analyzed the measured data. The results show that the decrease in pressure affects the heat feedback of the flame. When the inclination is 90°, the burning rates corresponding to different environmental pressures are 0.019 96, 0.020 55, 0.021 26 g/s and 0.023 60 g/s, and the two are positively correlated. When the ambient pressure is 101 kPa, the burning rates corresponding to different inclination angles are 0.009 41, 0.017 28, 0.020 29 g/s and 0.023 60 g/s, and the burning rate accelerates with increasing inclination angle. The relationship between the peak burning rate and the combustion enhancement factor reflects the growth of fire spread. Related Articles | Metrics

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Technology of fire reconnaissance through fire and smoke based on laser range gate imaging Li Ziting, Chu Yuxi, Chen Ye, 2023, 42 (9):  1201-1204.  Abstract ( 228 )   In view of the difficulty of firefighters' search and rescue due to the extremely low visibility in the dense smoke environment of fires, we proposed a fire penetration and smoke detection technology based on laser range gate imaging, and carried out physical experiments on imaging through wood pallets, n-heptane fires and smoke in confined spaces, which can image through 1.5 m longitudinal flame and improve the visibility in dense smoke environment by 3 times, solving the current problem that fires and smoke cannot be penetrated due to surface/interface reflection and serious backward scattering. Based on the experimental results, the application prospect of laser range gate imaging in firefighting visualization reconnaissance and rescue is discussed, and the future development direction of this research field is further clarified. The future development of fire reconnaissance and rescue equipment based on laser range gate imaging technology provides "perspective eyes" for fire rescue personnel, which is expected to effectively improve the fire control, rapid internal attack and personnel rescue capabilities in the initial battle and night environment. Related Articles | Metrics

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Study on the influence of multi-sided restricted boundaries on the temperature characteristics of horizontal jet flames Huang Youbo, Wang Bin, Dong Bingyan, Liu Xi 2023, 42 (9):  1205-1209.  Abstract ( 131 )    To investigate the temperature field characteristics of the flame jet after impacting adjacent buildings in a confined space, experimental studies were conducted to explore the temperature distribution features of the flame jet under bi-lateral and tri-lateral restricted boundaries. The results indicate that the wall temperature of the obstacle is significantly affected by the form of the obstacle, the distance between the hole and the plate, and the leakage rate. When the distance between the two obstacles is small, the lateral diffusion of the jet flame is obstructed. When the distance between the hole and the plate is small, the high-temperature zone under the double-sided obstacle is located at the center of the wall and has a smaller thickness. As the leakage rate increases, the flame height under three-sided confinement is significantly higher than that under double-sided confinement, and the temperature inside the confined area is higher. Increasing the spacing between the plates leads to an upward displacement of the high-temperature region. Moreover, there exists a positive correlation between temperature and leakage rate. As the spacing increases, the area of temperature rise expands, although the magnitude of temperature rise diminishes. Furthermore, the introduction of multiple lateral obstacles has an impact on the migration of the high-temperature region. Related Articles | Metrics

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Numerical simulation of the combustion behavior of gas-liquid two-phase dimethyl ether jet flame Hou Zhihao, Bi Mingshu, Hao Qiangqiang, Ren Jingjie, 2023, 42 (9):  1210-1216.  Abstract ( 138 )    In order to analyze the combustion behavior and hazard range of gas-liquid two-phase jet flame produced by liquid hazardous chemicals tank leakage, a numerical calculation model of gas-liquid two-phase combustion was established based on Euler-Lagrange system by numerical simulation method. the effects of different nozzle diameter and injection pressure on the flame shape, droplet distribution and thermal radiation hazard range of gas-liquid two-phase dimethyl ether injection flame were studied. The results show that the higher the injection pressure and the larger the diameter of the nozzle, the longer the flame length, and the predictive correlation between mass flow rate and flame length is proposed. With the increase of injection pressure and nozzle diameter, the droplet evaporation intensity increases, and the average droplet size and velocity near the nozzle increase. The maximum thermal radiation hazard range of downstream and side of flame is 9.5 m and 5 m respectively. Related Articles | Metrics

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Fire resistance test study on Douglas-fir timber beam elements Liu Jiyang, Yin Liang, 2023, 42 (9):  1217-1222.  Abstract ( 133 )    Currently raw timber frame buildings are still widely used and face the need for fire resistance assessment and upgrading. This paper provides a brief overview of the current methods and status of research into the fire resistance of wood components, and designs and implements ambient temperature tests as well as fire resistance tests based on hydrocarbon (HC) and standard heating curves for small-section (200 mm×100 mm) log beam components of Douglas-fir. It was found that: the beam members were brittle at ambient temperature and failed in overall bending at both temperature rising conditions, with fire resistance limits of 17 min and 20 min respectively; the cross-sectional temperature characteristics and the measured charring results showed that the charring rate was greater near the mid-span section. It is recommended that the charring characteristics be obtained by inversion of the overall fire resistance test to cover random effects such as non-uniformity of the component material, and that a charring assessment method based on the whole process of fire temperature rise and fall also be developed. Related Articles | Metrics

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Experimental study on fire-resistance performance of cross-laminated timber floor under non-load bearing conditions Peng Lei, Qiu Peifang, Liu Yongli 2023, 42 (9):  1223-1227.  Abstract ( 166 )    Experiments were carried out to study the fire-resistance performance of cross-laminated timber （CLT） floor under non-loading conditions, by using a fire-resistance furnace and the standard fire curve. The tested specimens consisted of 5 layers of CLT laminates, with a thickness of 35 mm for each layer and an overall thickness of 175 mm. The temperature profiles at different depths within the CLT specimens, charring depths and charring rates were obtained in the tests. The effect of different types of adhesives on delamination and charring rate were also studied and analyzed. The test results show that the fire insulation and integrity of the tested floor specimens were not less than 2.00 h. For specimens using ordinary PUR adhesive, the first layer delaminated at about 58~69 minutes, and the second layer delaminated at about 110~113 minutes. The charring rates of the specimens were higher than the nominal charring rate given in Eurocode 5. For the specimen using heat-resistant PUR adhesive, there was no obvious layer delamination being observed. The charting rate remained respectively constant. Related Articles | Metrics

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Research on ancient building fire prevention and control technology based on BIM and simulation technology Liu Hui, Li Ting, Zhong Chen 2023, 42 (9):  1228-1232.  Abstract ( 180 )   Most ancient buildings in China are wooden structures, which are vulnerable to fire threat. At present, the experience of fire prevention and control technology for ancient buildings is insufficient, and it is impossible to carry out relevant experimental research using real ancient buildings. In order to solve the above problems, based on BIM and simulation technology, the fire prevention and control technology of ancient buildings is studied through computer simulation. Firstly, BIM is used to build three-dimensional models of four typical ancient buildings, and based on this model, CFD is used to study the natural ventilation and fire smoke spread. The experimental results show that the natural ventilation conditions of the outdoor wind field of ancient buildings with different roof types are significantly different, and the climate conditions also have a great impact on the indoor fire smoke diffusion. The simulation method can be used to simulate the fire smoke spread, and obtain the smoke temperature, velocity, distribution and other parameters, so as to provide reasonable suggestions for the layout of fire-fighting facilities. Related Articles | Metrics

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Fire resistance analysis of suspension bridge based on temperature equivalence section Duo Fei, Yang Qingtian, Hou Liqun, Chen Shicai 2023, 42 (9):  1233-1240.  Abstract ( 111 )   Abstract: In order to analyze the fire resistance of suspension bridge structure, a fire resistance analysis method based on the equivalent temperature section is proposed. The temperature calculation model of cable section composed of parallel steel strands is deduced based on the heat conduction theory, and a simplified equivalent temperature calculation method is further established. Then the finite element model of the cable bridge with equivalent cable area is established, and the temperature rise curve of the main cable at the fire position is determined according to the equivalent temperature calculation method. Finally, the fire response process and fire resistance performance of the suspension bridge structure are studied through thermal coupling analysis. The results show that for the four-layer cable of the main cable of the suspension bridge, there is an obvious uneven temperature field before 50 minutes in the vehicle fire. There are obvious differences between the overall bridge structural response when considering the uneven temperature field of cable section and when not considering it. The layered cable temperature equivalent method based on equivalent area and equivalent strength can consider the uneven distribution of cable section, simplify the finite element model of cable bridge and avoid the complex heat conduction analysis of the whole cable bridge. Related Articles | Metrics

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Analysis of the influence and countermeasure of starting temperature on the effectiveness of glass curtain wall protection cooling water curtain Shao Guangzheng 2023, 42 (9):  1241-1245.  Abstract ( 124 )   The protective cooling water curtain can play a good role in protecting the glass curtain wall at the initial stage of fire. However, if the water curtain is delayed to start, the heated glass may be accelerated to crack and fall off under the instantaneous action of cooling water. The experiment verified that the tempered glass and low-radiation (Low-E) glass can withstand the critical temperature range of the water curtain protection: in the control group without starting the water curtain, the tempered glass of 6 mm did not break until the fuel burned out, the highest temperature of the glass over 400 ℃, but the glass temperature over 250 ℃ opening the water curtain will accelerate its rupture; 6 mm low-E glass temperature over 70 ℃ after the same is no longer suitable for direct cooling with water curtain cooling. Starting the water curtain in time within the critical temperature can play a good protective cooling effect, but beyond the critical temperature, other measures should be taken. Based on the above research conclusions, the countermeasures and suggestions on the revision of relevant standards, engineering application and improvement of spray products are put forward. Related Articles | Metrics

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Experimental study on the effect of external wind speed on the spray intensity of transformer water mist system Chen Qiang, Shi Xiaolong, Lin Gang, Wang Dong 2023, 42 (9):  1246-1251.  Abstract ( 138 )   In order to study the change law of the spray intensity of the transformer water mist system under different external wind speeds, a 110 kV transformer physical experiment platform was built. Using the water mist nozzles with two flow coefficients, five cold spray experiments of water mist under different wind speeds were designed. The influence of different wind speeds on the spray intensity of the transformer water mist system was analyzed. The results show that when the applied wind speed exceeds 4 m/s, the effect of water mist is obviously affected, and the spray intensity on the transformer starts to decrease. In addition, with the increase of the applied wind speed, the spray intensity showed a decreasing trend. In addition, under the same external wind speed, nozzle with a flow coefficient of K=2.0 has a better spray effect than that with a flow coefficient of K=1.7 under the same working pressure and wind speed, and its "resistance" to external wind speed is stronger than the nozzle with a flow coefficient of K=1.7 under its own advantage of larger flow. Related Articles | Metrics

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A-IACO: A new algorithm for fire evacuation path planning Chao Wei, Xu Yong, Xu Le, 2023, 42 (9):  1252-1258.  Abstract ( 174 )   In a complex building, the traditional fire evacuation system cannot plan an optimal evacuation direction in real time, and sometimes misleads people to dangerous areas. To solve this problem, this paper proposes an A*-IACO algorithm that combined A* algorithm with an improved ant colony optimization （IACO）. The A*-IACO introduces a new heuristic function to weaken the influence of heuristic values on path planning. It uses the improved pheromone increment and pheromone range to overcome the local optimal problem and at the meanwhile utilizes segmentation rule to avoid the searching suspension phenomenon. Thereby it can enhance the path planning ability in fire environments. In addition, it adopts a hybrid optimal control strategy to further improve the results. The experiment results show that the proposed A*-IACO obtains the shortest evacuation path with fewest inflection point and performs high accuracy in various fire environments. According to fire environment 4, A*-IACO achieves not only best evacuation path selection but also lowest iteration times comparing to ACO and IACO. As a result, it illustrates good performance on path planning ability. Related Articles | Metrics

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A petrochemical fire fighting tactics auto-planning method basing on Agent Li Jibao, Li Dapeng, Wan Zijing, Dong Tingting, 2023, 42 (9):  1259-1264.  Abstract ( 138 )    In order to improve the details of petrochemical fire fighting plan, this paper proposed an automatic planning method of fire fighting tactics based on multi-agent system. This method was mainly oriented to fire fighting tasks in the chemical industry park scene, including basic fire fighting tactics, task dynamic planning and tactical simulation functions. Even it contained the characteristics of flexible configuration and intuitive simulation process, this method could solve the problem that the common fire fighting tactic simulation tools were lack of space environment simulation, and the psychological state, travel ability, work loss and other personnel attributes were formulated. In this paper, an oil tank fire scenario was simulated to verify the rationality of our proposed tactic planning and task allocation methods, and the simulated fire fighting process could be intuitively displayed. Related Articles | Metrics

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Identification of cigarette ashes by time-of-light mass spectrometry combined with machine learning Wang Jingtong, Liu Shujun, Yang Ming, Xu Zhiqian 2023, 42 (9):  1265-1269.  Abstract ( 129 )   In order to accurately and quickly identify cigarette ash from different brands and manufacturers, 58 types of cigarettes, 26 different interfering substances, and mixed cigarette ash samples from different brands and manufacturers were collected. The corresponding time-of-flight mass spectrometry data was obtained through a time-of-flight mass spectrometer, and then the time-of-flight mass spectrometry data was classified through system clustering. The characteristic peaks of the mass spectrometry were compared. Finally, principal component analysis and partial least squares discriminant analysis methods of machine learning are used to establish discriminant analysis for different methods. The results of principal component analysis indicate that this model has good reliability and predictive ability; partial least squares discriminant analysis indicates that the model is reliable and has good ability to predict cigarettes and interfering substance smoke ash. In addition, the model was verified for 200 times, and the results showed that the partial least squares discriminant model did not have overfitting when it was established. Therefore, combining time-of-flight mass spectrometry with two machine learning algorithms can help surveyors accurately and quickly identify and detect cigarette ash samples. Related Articles | Metrics

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Experimental study on extinguishing EVA shoe material with water-based fire extinguishing agent Zhang Xianzhong, Yu Jun, Bao Zhiming, Hu Cheng, 2023, 42 (9):  1270-1274.  Abstract ( 120 )   In this study, ethylene-vinyl acetate copolymer (EVA) shoe material stacking fire model was established because of its high fire risk and difficult to extinguish. The influence of fire extinguishing agent flow rate on the fire extinguishing effect of EVA shoe materials was investigated, and the difference of fire extinguishing efficiency between foam fire extinguishing agent and water-based extinguishing agent was compared. The results show that the flow rate of fire extinguishing agent is the key factor affecting its extinguishing efficiency on Class A fire, and the difference in fire extinguishing and cooling effect of water and AFFF can be effectively distinguished at the flow rate of 0.80 L/min. The fire control performance and cooling effect of high expansion foam and water-based fire extinguishing agent are significantly better than that of AFFF and AFFF/AR. The formation of fire extinguishing foam is conducive to improve the utilization rate of fire extinguishing water. Wetting performance is an important parameter affecting the water-based fire extinguishing agent to EVA shoe material fire fighting. Related Articles | Metrics

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Thermal decomposition behavior of phenolic resin impregnated quartz fiber composites Bai Bingyue, Liu Dan, Yang Jinjun, Wang Junsheng, 2023, 42 (9):  1275-1279.  Abstract ( 128 )   The thermal decomposition behavior and composition of gas phase products of phenolic resin quartz fibers during thermal decomposition at a heating rate of 20 ℃/min and 20 ℃/ms to a certain temperature were investigated by thermogravimetric analysis-mass spectrometry (TG-MS) and pyrolysis-gas chromatography-mass spectrometry (Py-GCMS). The results show that the thermal decomposition process of phenolic resin impregnated quartz fiber composites is consistent with that of phenolic resin, and can be divided into three stages: dehydration and gas loss stage at 20~400 ℃; The main stage of pyrolysis is from 400 ℃ to 800 ℃, and the main gaseous products are water, methane, carbon dioxide, benzene, phenol, and derivatives of benzene and phenol; When the temperature exceeds 800 ℃, the pyrolysis has basically completed. The main thermal decomposition products and relative content of phenolic resin impregnated quartz fiber composites at 600, 800, and 1 000 ℃ are basically the same as those of phenolic resin; This indicates that the pyrolysis of phenolic resin impregnated quartz fiber composites is mainly due to the pyrolysis of phenolic resin, and quartz fibers do not participate in the pyrolysis reaction. Related Articles | Metrics

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Flame retardancy of DOPO modified by zinc phytate coated with Schiff base in epoxy resin Kong Qinghong, Huang Shuai, Chai Huiyu, Liu Hong 2023, 42 (9):  1280-1286.  Abstract ( 141 )   A compound (PAPDO) containing phosphorus and nitrogen was synthesized from 9, 10-dihydro-9-oxa-10vphosphozaphene-10-oxide (DOPO), 3, 4-dihydroxybenzaldehyde and p-phenylenediamine in a one-pot method. A hybrid flame retardant (ZnPA@PAPDO) was prepared by coating PAPDO on zinc phytate using the force between the phenol hydroxyl group of protoca-techualdehyde and metal ions. EP/ZnPA@PAPDO was prepared with ZnPA@PAPDO as the flame retardant, epoxy resin (EP) as the base material and diaminobenzene methane (DDM) as the epoxy curing agent. The effect of ZnPA@PAPDO on the flame retardant property of EP was studied. Thermogravimetric results showed that the addition of ZnPA @ PAPDO advanced the initial decomposition temperature of the composite, promoted the charring of the polymer and formed a char layer on the surface to effectively protect the matrix. The addition of ZnPA@PAPDO can increase the residual amount at high temperature, and the residual amount of EP/8% ZnPA@ APDO increased by 31.0%. In addition, the addition of ZnPA@PAPDO greatly improved the flame retardant property of EP. The t1+t2 of EP/8% ZnPA@PAPDO is 11.6 s, reaching V-1 level, and the LOI value is 32.8%. The excellent thermal and flame retardant properties of EP/ZnPA@PAPDO are attributed to the double barrier action of organic coke and metal protective layer, phosphorous nitrogen synergism and free radical quenching. Related Articles | Metrics

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Research on the prediction method of spot fire based on conditional random field Huang Qiong, Si Ying, Bai Ye 2023, 42 (9):  1287-1291.  Abstract ( 151 )    The occurrence of flying fire in forest fire greatly accelerates the spreading speed of forest fire and seriously threatens the life safety of firemen. It is of great significance to forecast and early warning of spot fire. Most studies ignore the correlation between physical characteristics in the formation of spot fire, it is not enough to provide effective judgment basis for its prediction. A prediction model of spot fire based on linear-chain conditional random field is proposed. Combined with the temporal characteristics of the formation of spot fire, the prediction of the state sequence of each stage in the formation of spot fire is completed, and the prediction of spot fire is realized. The experimental results show that the model has high prediction accuracy, which is basically above 75%. The response time is controlled within 10 ms, which is lower than the time difference between two spot fire and the formation of fire lines. To a certain extent, it can meet the real-time requirement. It provides useful key information for the efficient fighting of natural fires in forest and grassland, and also provides important decision-making basis for the command and dispatch of fire fighting. Related Articles | Metrics

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Study on ignition probability of Larix gmelinii litter based on GA-BP neural network Jia Huimin, Xin Ying, Chi Hongying, Zhang Dexin 2023, 42 (9):  1292-1297.  Abstract ( 121 )   Based on indoor experimental data, study the effects of wind speed, moisture content of fuel and size of flying fire source on the ignition probability, and explore the applicability of GA-BP neural network model to predict the ignition probability, to provide a theoretical basis for the study of forest flying fire behavior. Using the surface fuel of Larix gmelinii as the combustion material and the branches of Larix gmelinii as the flying fire source, the combustion experiment was conducted by adjusting the wind speed, moisture content of fuel and the size of the flying fire source. SPSS is used to analyze the influence of various factors on the ignition probability. Genetic algorithm is used to optimize the BP neural network, and GA-BP neural network model is established to predict the ignition probability. The model takes wind speed, moisture content of fuel and the size of the ignition source as input variables, and the ignition probability as output variables. The optimized number of neurons in the hidden layer is selected to train and predict the model, and the prediction ability is compared with the BP neural network model. Results showed that, the ignition probability has a positive correlation with the wind speed and a negative correlation with the moisture content of the fuel. The ignition probability of the large-diameter flying ignition source is significant; The single factor ignition ability from strong to weak is as follows: wind speed>size of fly ignition source>moisture content of fuel; The strong or weak ignition ability of multi-factor interaction is: wind speed and fly ignition source size>moisture content of combustible and flying fire source size>wind speed and moisture content of combustible>wind speed, moisture content of combustible and size of flying fire source; the prediction ability of the model is good, which is conducive to the prediction of forest fires. Related Articles | Metrics

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Research on the influencing factors of firefighters' physical fitness development based on integrated DEMATEL-ISM Liu Bo, Wang Tongling, Zhu Guoqing, Chen Wenjia 2023, 42 (9):  1298-1303.  Abstract ( 139 )   In order to promote the development of firefighters' physical fitness, an index system of influencing factors of firefighters' physical fitness development is constructed from five dimensions: self, training, management, security, and fire protection characteristics. The degree of influence, affected degree, centrality, and cause of 22 influencing factors are calculated by using the decision test and evaluation laboratory method (DEMATEL), and the multi-level hierarchical structure model of influencing factors of firefighters' physical fitness development is constructed by combining the interpretative structural model method (ISM), so as to realize a comprehensive understanding of the importance, causal attribute, logic and hierarchical structure of the factors in the system. The research shows that the 22 influencing factors include 12 cause indicators and 10 outcome indicators, of which 13 indicators such as health status and training recovery support are the key factors affecting the physical development of firefighters. In the multi-layer hierarchical structure model, the physical training load is the most critical indicator at the surface factor level, the physical recovery status is the most critical indicator at the middle factor level, and the health status is the most critical indicator at the secondary factor level, the comprehensive environment of physical training is the most critical indicator at the level of essential factors. Related Articles | Metrics

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How to correctly understand and apply XF 703-2007 in the governance of "shared premises" Wang Haixiang 2023, 42 (9):  1304-1308.  Abstract ( 141 )   This article analyzed the current situation of fire safety management in accommodation, production, storage, and operation shared spaces, as well as the problems existing in the practical application of current fire rescue industry standards. Expounded the three necessary conditions for the formation of "shared spaces" and the four different forms in the governance process, and analyzed the external manifestations and root causes of "shared spaces" and "small fires that kill people" fires, summarize and organize the four aspects that should be paid attention to in the practical application of fire rescue industry standards in the management of accommodation, production, storage and operation shared places. Propose four principles for the management of accommodation, production, storage and operation shared places, and clarify the specific governance measures and responsibilities that should be taken for accommodation, production, storage and operation shared places in different periods. Related Articles | Metrics

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Research on optimization of Huizhou fire station location considering accessibility Zhang Jingdu, Li Chengyue 2023, 42 (9):  1309-1314.  Abstract ( 153 )   The reasonable accessibility of the distribution of fire station is of great significance for preventing and resolving the hidden dangers to urban safety. Traditional fire station distribution rarely considers residents' fire resource demand, resulting in structural problems caused by mismatching supply and demand. This paper improves the traditional site selection model from the aspects of supply and demand. In terms of supply, the best explanatory variable combination and its weight for fire occurrence are determined through exploratory analysis and generalized linear regression, so as to accurately assess the regional fire risk, and the reasonably determine the proposed location of the fire station. In terms of demand, by introducing an accessibility factor to increase the consideration of the location model for residents' demand for fire station. Then take Huizhou as an example to carry out the research on location optimization of the fire station, and verify the optimization effect of the improved location strategy by designing two other location strategies, so as to verify the effectiveness of the text improvement model. Related Articles | Metrics