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15 April 2024, Volume 43 Issue 4 Previous Issue    Next Issue

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Study on the performance of fluorocarbon⁃hydrocarbon surfactant foam by gas source and nanoparticles Shang Fengju, Zhang Jiaqing, Li Kaiyuan, Li Yaoqiang, 2024, 43 (4):  433-438.  Abstract ( 233 )   In this study, environmentally friendly foam dispersions were prepared using twin?chain fluorocarbon surfactants (Gemini) and amphoteric hydrocarbon surfactants (LAMC) as core components. The influence of nanoscale SiO2 particles and the type of compressed gas on the foaming properties, stability, and spreading characteristics of the foam dispersion were investigated. The results revealed that nanoscale SiO2 particles exhibited molecular interactions with short?chain fluorocarbon surfactants, leading to an approximately 5.8% increase in the height of compressed nitrogen foam compared to compressed air foam when 3% nanoscale SiO2 particles were added within the experimental range. The foaming performance of the dispersion slightly decreased after the addition of 3% nanoscale SiO2 particles. However, foam stability significantly increased with the incorporation of nanoscale SiO2 particles, resulting in a 5% improvement in the stability of nitrogen foam compared to air foam. Nanoscale SiO2 particles formed a network?like structure, aggregating within the Plateau borders, effectively delaying foam drainage and coarsening, thereby enhancing foam stability. Due to the inherent differences in density and permeability of foam liquid films between nitrogen and air, the average spreading rate of compressed air foam on the oil surface increased by 2.6% compared to compressed nitrogen foam. The findings of this study provide theoretical guidance for the development and firefighting applications of environmentally friendly foam extinguishing agents containing nanoscale SiO2 particles. Related Articles | Metrics

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Study on the correlation between position of indoor low-level flame and the light characteristics through the door slits Gao Yang, Chen Haohui, Li Yang, Liu Yixiang 2024, 43 (4):  439-444.  Abstract ( 158 )   In order to study how to locate the indoor low-level flame through the door slit light characteristics under the full occlusion environment, a ISO 9705 standard room was constructed, with a 90 cm×2 cm slit between the door and the floor, and a 0.5A standard wood stack fire was used to simulate the indoor low-level fire. The change of the door slit light characteristics was recorded by the outdoor video, and the change rule of door slit light characteristics and the correlation between the indoor low-level flame position and the door slit light characteristics was analyzed, coupled with the MATLAB luminance recognition and image processing technology. The results show that the geometry of the door slit light was roughly quadrilateral under a certain luminance threshold, when the flame is located in the center axis of the door, the geometry is isosceles trapezoidal, and when the flame is biased to the side, the door slit light is deflected to its opposite side. As the distance of the flame from the door increased, the angle of the quadrilateral girdle decreased, while the extension distance of the door slit light first increased and then decreased. The correlation was obtained between the indoor low-level flame position and the geometric parameters of the door slit light. The distance of the flame from the door and the extension distance of the door slit light can be characterized by the segmentation function. The study can provide a technical reference for locating the position of indoor fire after a fire accident by video. Related Articles | Metrics

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Experimental study on the morphology and thermal radiation of jet fire in sub high-pressure natural gas pipelines Jiang Yi, Li Youlv, Wang Binbin, Liu Yuting 2024, 43 (4):  445-450.  Abstract ( 124 )   When a gas pipeline leaks and comes into contact with an external fire source, it may lead to the formation of jet fire, which poses a huge risk to nearby workers and equipment. Therefore, it is particularly crucial to conduct in-depth research on the combustion behavior of jet flames in gas pipelines. Six types of pore sizes were selected, including 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm, with pressures of 0.5, 0.8, 1.0, 1.2, and 1.5 MPa, respectively, to conduct jet fire experiments on gas pipelines under different operating conditions. The results show that when natural gas combustion reaches stability, the flame height and thermal radiation gradually increase with the increase of injection pressure and nozzle diameter; At a 3 mm aperture, the flame reaches a maximum length of 4.32 m, and the maximum thermal radiation reaches 552 W/m2 at a horizontal position of 1m from the leakage hole; When the aperture is 1.5 mm and the pressure is 1.2 MPa, the flame begins to rise. As the pressure and aperture increase, the rise phenomenon becomes more pronounced. When the leakage aperture is 3 mm and the pressure is 1.5 MPa, the maximum lift is 0.4 m. The experimental values provide guidance for dealing with the situation of jet fire caused by natural gas pipeline leakage. Related Articles | Metrics

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Study on the influence range of fire radiation of steel box girder inner cable Zhu Kai, Zong Xiaoyu, Chen Xiaofeng, Wu Ke 2024, 43 (4):  451-456.  Abstract ( 106 )   To reveal the radiation distribution characteristics of cable fires inside steel box girders, FDS was used to simulate and study the radiation influence range under different fire source powers and diaphragm spacing. The flame radiation and smoke radiation characteristics received by targets in the fire chamber of steel box girders were analyzed, and the radiation prediction formula was constructed to obtain the critical safety distance. The results show that with the increase of the ignition source power and the decrease of the diaphragm spacing, the radiation influence range increases significantly, and the temperature error of the modified McCaffrey flue gas layer can be less than 5% considering the heat transfer characteristics of the multi-chamber steel box girder and the steel structure. The radiation distribution prediction model considering flame radiation and flue gas radiation can effectively predict the radiation distribution in the area of the steel box girder in the area greater than 0.6m from the center of the fire source. Using 10 kW/m2 as the critical ignition heat flux to define the critical safety distance of box girder cable, the minimum safety distance of cable laying in steel box girder is 0.8m. Related Articles | Metrics

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Analysis of the influence of vegetation size on the characteristics of high resistance ground of wire touching tree Wen Jiaguo, Wang Disheng, Wang Jun, Ning Xin 2024, 43 (4):  457-462.  Abstract ( 76 )   In response to the unclear impact of vegetation size on the characteristics of high impedance ground fault (THIF) caused by wire tree contact and the difficulty in predicting ignition, this article deeply analyzes the ignition phenomenon and the variation of leakage current during the THIF fault process. Explored the relationship between different vegetation sizes and leakage current, and studied the influence of vegetation size on arc discharge characteristics at tree line contact positions. On this basis, the numerical relationship between vegetation size parameters and leakage current was derived, and a leakage current prediction model at open flame time was established that comprehensively considers vegetation diameter and length. The research results can provide important basis for vegetation management and mountain fire prevention in distribution line corridors. Related Articles | Metrics

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Research on construction, optimization and prediction of firefighters' thermal physiology model in high temperature environment Hong Shiyi, Yan Xiaobo, Gao Haoxiang, Hong Yinzheng 2024, 43 (4):  463-468.  Abstract ( 131 )   In order to study the thermophysiological response of firefighters during training and rescue operations in high-temperature environments, this paper constructs a thermophysiological model applicable to firefighting and rescue operations based on the human body's thermoregulatory mechanism, correcting the surface area of the human body, the performance of the clothing, and the convective heat transfer coefficient of the human body and the environment in the two-node model, as well as controlling the maximal blood flow rate, and selecting the skin and core tuning temperatures. The predictive accuracy of the improved thermophysiological model was verified by comparative analysis with human thermophysiological test data in the literature, and the verified model was used to predict the core temperatures and safe sustained operating time of firefighters in high-temperature environments (40 °C and 60 °C). The results showed that: under four different test conditions, the maximum error between the simulated value and the test value of core temperature and skin temperature did not exceed 1.24 ℃ and 1.57 ℃ respectively, and the constructed thermophysiological model had a high reliability; it was found that, by predicting the change of the core temperature of firefighters under two high-temperature conditions (40 ℃, 50% relative humidity; 60 ℃, 50% relative humidity), the longest time for rescue personnel to safely continue the operation under 40 ℃ and 60 ℃ is 12 min and 6 min, respectively. Related Articles | Metrics

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Experimental study on the dimensional effect of splitting tensile of 3D printed cement⁃based material after high temperature Wang Xu, Chen Lin 2024, 43 (4):  469-474.  Abstract ( 74 )   In order to explore the size effect of splitting tensile of 3D printed cement?based materials after high temperature, the splitting tensile mechanical properties of 3D printed cement?based materials were tested by hydraulic servo machine under five temperature and three size conditions. The influence of high temperature and size effect on the splitting tensile mechanical properties of 3D printed cement?based materials is analyzed. The main conclusions of this paper are as follows: with the increase of temperature, the tensile strength of specimens decreases gradually, and the tensile strength of specimens with different sizes is basically the same under the influence of high temperature, with the maximum decrease of 87.97%. With the increase of size, the tensile strength of the specimen gradually decreases, and the increase of temperature leads to the increase of the tensile strength affected by the size effect. Affected by the size effect, the tensile strength of the specimen changes in the range of 18.488%~26.165% after different high temperatures. At the same time, based on the size effect law, a calculation model of tensile strength of 3D printed cement?based materials considering the influence factors of high temperature is proposed, and the evolution mechanism of its mechanical properties is revealed by microscopic testing technology. Related Articles | Metrics

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Experimental study on ceiling temperature distribution under branch pipe smoke exhaust in double⁃deck tunnel Chen Wanhong, Yu Pei, Wang Zhan, Tang Zhi, Fang Zheng, 2024, 43 (4):  475-481.  Abstract ( 74 )   Aiming at the double?deck shield tunnel with branch pipe exhaust mode in the lower tunnel, a reduced size model experiment was carried out to systematically study the smoke temperature distribution under branch pipe exhaust mode, and the influence of key factors such as fire source power, smoke outlet opening scheme (number and distance of smoke outlet) and smoke exhaust volume on the fire smoke temperature distribution was discussed. The results show that the ceiling smoke temperature gradually decreases with the increase of smoke exhaust volume, and gradually increases with the increase of the distance of smoke exhaust outlets in the area away from the fire source. The ceiling smoke temperature is the lowest when the two vents closest to the fire source are opened. The temperature below the upper and lower ceiling of the fire source presents an exponential attenuation law along the longitudinal tunnel, and the relative temperature attenuation ∆Tx /∆T max has little change under different smoke emission and fire source power. Based on the fitting analysis of the experimental data, the longitudinal attenuation prediction model of ceiling smoke temperature of upstream and downstream of the fire source is derived. Related Articles | Metrics

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Research on hose stream impact test of glass components for fire separation Xu Wenfei, Guo Zhansheng, Wang Zhenxiang, 2024, 43 (4):  482-486.  Abstract ( 456 )   Glass components are widely used in large commercial complexes as fire partitions. After the fire broke out, the water strike behavior during the fire fighting and rescue may cause damage to the glass components, resulting in the spread of the fire. According to the standard hose stream method of building components, hose stream test after fire resistance test of glass components is carried out in this paper. The results show that when the glass insulation performance of the glass component is lost, the glass will open and collapse when the over temperature area touches the water, resulting in the loss of the fire separation function. The fire resistance of the glass component does not reach the fire resistance limit, and the glass component may collapse. Water impact test is necessary after fire resistance test of glass components. Related Articles | Metrics

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The effect of natural aging on the combustion and mechanical properties of ancient architectural Pinus massoniana Long Miaotian, Yi Liang, Yan Long, Zheng Jiaxin 2024, 43 (4):  487-491.  Abstract ( 95 )   The Pinus massoniana inside and outside the Qing Dynasty wooden building from approximately 170 years ago was taken as the research object to systematically analyzes the effects and regulations of natural aging on the microstructure, combustion behavior and mechanical properties of the Pinus massoniana . The results show that natural aging can significantly damage the cellular structure of the pine, where indoor pine is susceptible to significant surface wormholes due to insect infestation and fungal parasitism during service, while outdoor pine is susceptible to more significant degradation of internal organic constituents due to UV light. Compared to the degradation of internal organic components, the surface wormholes can deteriorate the mechanical properties of the pine to a greater extent. The tensile and bending strengths of outdoor Qing Dynasty pine are lower than those of modern pine by 34.1% and 34.7%, respectively, while those of indoor Qing Dynasty pine are reduced by 48.2% and 31.6%, respectively. Combustion performance analysis reveals that the natural aging effect weakens the combustion strength and thermal stability of the wood, with the peak heat release rate （PHRR） being reduced by 8.4% and 15.4%, and the initial decomposition temperature （T5%） being reduced by 19.2 and 10.1 ℃, for the indoor Qing Dynasty pine and outdoor Qing Dynasty pine, respectively, compared to the modern pine. In addition, compared with the outdoor Qing Dynasty pine, the indoor Qing Dynasty pine has lower T5% and higher CO2 and CO production rate, which is mainly related to the greater destruction of the cellular structure of indoor Qing Dynasty pine, thereby indicating that the indoor Qing Dynasty pine has lower thermal stability and stronger fire smoke toxicity. Related Articles | Metrics

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Simulation study on fire temperature and internal air pressure of air⁃supported membrane structure coal storage shed Zhang Yu 2024, 43 (4):  492-497.  Abstract ( 67 )   In recent years, the country has continuously put forward new requirements for high?quality and green development. The novel air?supported membrane structure in building forms has been widely used in coal storage yards due to its unique advantages, but it corresponds to special fire safety issues. This article conducts numerical simulation research on the temperature distribution and pressure changes inside the membrane of air?supported membrane structure coal storage shed. The results show that the maximum temperature near the membrane surface depends on the distance between the fire source and the membrane surface. When the fire source is too close to the membrane surface, the membrane material will be heated and perforated, with a maximum perforation area of 29.75 m2. Most of the hot smoke will be discharged with the perforation, and the overall temperature inside the membrane will be greatly reduced. When the membrane material is not burned through, the trend of pressure changes inside the membrane at different fire source positions is similar, and the maximum value of internal pressure does not differ significantly. When the membrane material is burned through, the pressure inside the membrane rapidly decreases, which will affect the stability of the membrane structure and may lead to building collapse. Related Articles | Metrics

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Research on factors affecting flame suppression of external insulation system by sprinkler based on orthogonal experiments Hao Jiahang, Liu Zhiyi, Chen Yujia, Du Peng 2024, 43 (4):  498-503.  Abstract ( 90 )   The parameter setting of water sprinkler has a significant effect on the fire control effectiveness, but due to the large number of setting parameters, the method of numerical simulation is the most convenient and efficient. In order to study the influence of water sprinkler parameters on the flame spread suppression effect of external wall insulation system, this paper establishes a fire dynamics simulation model for the window fire test based on the GB/T 29416-2012， Test method for fire?resistant performance of external wall insulation systems applied to building facade. The effects of four water sprinkler parameters, namely, spray flow rate, horizontal angle, vertical angle and droplet size, on the fire control effect were investigated by orthogonal experiments, and the optimal parameter combinations were obtained by applying the extreme difference analysis and analysis of variance, and the optimal parameters were compared with the case of no sprinkler. The study shows that the appropriate water sprinkler parameters are particularly important for its fire extinguishing efficiency; with the increase of spray flow rate, the peak heat release rate of the exterior insulation system gradually decreases; when the spray flow rate is 140 L/min, the horizontal and vertical angles are 140°, and the droplet size is 0.5 mm, the fire control efficiency of sprinkler is the best. Related Articles | Metrics

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Study on retarding effect of water mist containing additive on thermal runaway of lithium battery Zhang Yan, Peng Wei, Liu Xiaoyong, Zhuo Hui 2024, 43 (4):  504-509.  Abstract ( 102 )   In order to investigate the retarding effect of water mist containing a nonionic surfactant on the thermal runaway phenomenon in lithium battery，this study focuses on optimizing the cooling and fire extinguishing performance of water mist by incorporating nonionic surfactants （FS 3100, Tween 80, APG 0810） into the water mist for 18650 ternary lithium?ion battery. The effects of different additives on the maximum temperature, average heating rate, average cooling rate, and cooling time of the lithium battery were compared and analyzed. Additionally, the cooling mechanism and reasons for negative inhibition were examined from the perspectives of surface tension, contact angle, and foaming properties. The results demonstrate that the three nonionic surfactants effectively enhance the capacity of water mist to suppress thermal runaway in lithium battery: FS 3100 < Tween 80 < APG 0810. APG 0810 primarily reduces the surface tension and contact angle of water mist to enhance the wettability and heat absorption capacity of water mist towards lithium battery. The main function of Tween 80 is to enhance foaming ability. The foam generated by Tween 80 exhibits low stability and brittleness, leading to significant heat dissipation during foam bursting and making it difficult for the foam to adhere to the surface of the battery. Consequently, this effectively improves the suppression of lithium battery heating rate during thermal runaway. Therefore, in order to enhance the retarding effect of water mist on the thermal runaway of lithium battery through the addition of nonionic surfactants, it is necessary to not only reduce surface tension but also appropriately increase the foaming multiple and the brittleness of the foam. Related Articles | Metrics

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Study on sealing performance of compressed air foam to solvent oil vapour Jing Lishuai, Bao Zhiming, Zhao Tingting, Ke Xin, 2024, 43 (4):  510-515.  Abstract ( 479 )   Based on the flux chamber test model of the United States Environmental Protection Agency, an evaluation test method was established to assess the foam sealing performance. This study investigates the impact of expansion and foam thickness on the sealing performance of film-forming compressed air foam. The evaporation rate of oil vapor and the effective evaporation inhibition time were measured and calculated. Additionally, the main control mechanism of foam sealing performance was explained by analyzing the effects of expansion and the droplet dropping behavior of foam drainage. The results demonstrate that the film-forming compressed air foam can effectively inhibit the evaporation of 120# solvent oil vapor. Specifically, the effective inhibition time of 3 cm 6.5 times foam exceeds 30 minutes. It was observed that the sealing performance of compressed air foam increases as the expansion decreases. Therefore, it is recommended to use foam with an expansion of less than 15 times to address 120# solvent oil leakage accidents. Furthermore, for film-forming compressed air foam, the difference in oil vapor sealing performance due to different foaming ratios is small, and the liquid film within the foam layer is found to be the main factor controlling oil vapor volatilization. Notably, the foam with lower expansion contains a higher liquid content, resulting in a stronger inhibition effect on oil vapor volatilization. Related Articles | Metrics

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Study on preparation of silicone-hydrocarbon surfactant compound foaming agent Wang Guangniu, Zhang Leilin, 2024, 43 (4):  516-521.  Abstract ( 193 )   As the core component of aqueous film-forming foam extinguishing agent, fluorocarbon surfactant is strictly restricted because of its difficulty in biodegradation and serious harm to the environment. A fluorine-free and environmentally friendly foaming agent compounded with silicone-hydrocarbon surfactant was developed. Several commercially available green and easily degradable silicone surfactants and hydrocarbon surfactants were selected, and their surface activity and foam properties were studied by foam scanner and interface rheometer. The single surfactant was optimized by single factor experiment method. The preferred silicone surfactant Silok 8022 and hydrocarbon surfactants AOS and LAMC were compounded by orthogonal experiment method, and the best foaming agent combination was obtained by range analysis of the results. The results showed that the optimal combination of three kinds of silicone-hydrocarbon surfactants as foaming agents had excellent foaming properties. Compared with the fluorocarbon surfactant FS-61 foaming agent, the maximum foam volume of the silicone-hydrocarbon surfactant compound foaming agent increased by 7 mL, the maximum foam liquid content increased by 2.28 mL and the 300 s drainage rate decreased by 3%. The fire extinguishing time of fluorine-free foam extinguishing agent is 4 s shorter than that of commercial 3% aqueous film-forming foam extinguishing agent. Therefore, the compound foaming agent has good foam performance and fire extinguishing effect while being environmentally friendly. Related Articles | Metrics

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Preparation and characterization of a new high efficiency fluorine-free foam extinguishing agent Xi Zhilin, Zhang Xuesong, Qian Kai 2024, 43 (4):  522-527.  Abstract ( 324 )   A new environment-friendly foam extinguishing agent composed of xanthan gum, nano-silica particles and compound surfactants is proposed to quickly extinguish flammable liquid fires. The surface properties, aggregation characteristics and foaming behavior of foam extinguishing agent were studied by fluorescence spectrophotometer, droplet shape analyzer, lubricant anti-foam property tester and binocular transmission polarization microscope. The results showed that the stability of the foam remained above 85% with the addition of xanthan gum and silica nanoparticles. Through the foam performance test, the best foam performance is matched, the initial foam volume is 905 mL, the 25% drainage time is 300 s, and the displacement is 105 mL within 10 min. The foaming performance and foam stability of the foam are significantly improved. Subsequently, by using the formula to carry out small fire extinguishing experiments, the fire extinguishing time is 18 s, and the reignition time is 650 s, this fire extinguishing agent has the potential for fire protection applications. Related Articles | Metrics

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Selection and structural optimization of thermal insulation materials for fire-fighting robots Zhang Hui, Cheng Guangwei, Zhang Yongbo, Ma Limin, Xu Liyou 2024, 43 (4):  528-534.  Abstract ( 144 )   The more and more extensive application of firefighting robots in fire disposal reduces the risk of firefighters in fire rescue, and also brings the demand for high temperature resistance and thermal protection technology. This paper takes the chassis body of a tracked fire fighting robot as the research object, in order to protect its internal electronic components from high temperature damage, and analyzes the distribution law of the body temperature field under the condition of fire field. Based on the orthogonal test design of the thermal protection structural materials of the fire robot chassis, the thermal protection performance of the combination of different thermal barrier coating materials, base materials and thermal insulation materials was analyzed by using ANSYS Workbench software, and the optimal combination scheme of the thermal protection structure was proposed.On the premise of ensuring the thermal protection performance of the firefighting robot, response surface optimization analysis was used to optimize the thickness of thermal barrier coating and thermal insulation layer. The thickness of thermal barrier coating and thermal insulation layer were reduced by 3.4 mm and 4 mm respectively. The internal volume of the chassis body was expanded by 11.74% and the mass was reduced by 15.83%. Related Articles | Metrics

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Research on optimization of task scheduling for forest fire rescue helicopter bucket firefighting Xu Hao, Qu Jingjing, Wang Minghui, Zhu Xinping 2024, 43 (4):  535-540.  Abstract ( 109 )   In view of the characteristics of forest fires, such as strong sudden occurrence and difficult disposal, and the current situation that helicopter task scheduling efficiency needs to be improved in fire rescue, in order to reduce the loss caused by forest fires, the optimization method of helicopter bucket fire extinguishing task scheduling was studied. Combined with fire area, fire situation, rescue force and other factors, a grid model of fire airspace was established. Aiming at the dynamic changes of fire sites in forest fire scenes, a dynamic task scheduling optimization method based on deep reinforcement learning (DQN) is proposed. The method continuously updates the global environment, forms a dynamic decision basis, and generates a task scheduling scheme by quantifying the burning time constraints of the fire grid and the water required for extinguishing the fire in real time. Improve the efficiency of helicopter bucket fire fighting. The simulation results show that compared with the greedy algorithm in the traditional algorithm, the proposed method can reduce the fire loss rate by 15.4% under the dynamic change of fire site, and effectively reduce the resource loss caused by forest fires. Related Articles | Metrics

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Study on ignition probability of typical bryophytes in northwest Yunnan Xu Xingjian, Bai Lei, Pu Siwei, Li Shiyou, 2024, 43 (4):  541-545.  Abstract ( 64 )   In order to study the ignition characteristics of surface bryophyte, Dicranum majus and Actinothuidium hookeri, which are widely distributed in northwest Yunnan, were taken as the test objects, and cigarettes and incense were used as ignition sources. The ignition ratio of two bryophytes under different experimental conditions was determined. The multiple linear regression equation was established by SPSS Statistics 27.0, and the regression equation was tested. The results showed that the order of influencing factors on ignition rate of Dicranum majus is: heat release rate > fire burning rate > moisture content > fire diameter > temperature > relative humidity. The order of influence degree of ignition rate of Actinothuidium hookeri is: moisture content > temperature > ignition rate > diameter of fire source > relative humidity > heat release rate. The goodness-fit of the model was 0.820 and 0.893, respectively. Residual analysis showed that the predicting deviation of ignition rate was ±8.895% and ±5.845% respectively. The research results can provide a basis for the management of surface fuels and fire risk warning in northwest Yunnan, and lay a foundation for further identification and evaluation of bryophyte fire risk. Related Articles | Metrics

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Mental health status and coping style of firefighters after emergency rescue Yang Weili, Zhang Jianhong, Wang Huiying, Wang Changhong, 2024, 43 (4):  546-550.  Abstract ( 113 )   To explore the mental health status and coping style of firefighters after emergency rescue, and analyze the correlation between mental health status and coping style of firefighters. A cluster sampling method was used to evaluate the mental health status of the firefighters in Henan province who were responding to the "7.20" rainstorm by SRQ-20,GAD-7, PHQ-9, SRSS and PTSD-7 scales. CSQ scale assessed the coping style characteristics of firefighters, and explored the correlation between mental health status and coping style. Among 5 332 fire fighters, 19.70% had emotional pain, 32.06% had anxiety symptoms and 38.14% had depression symptoms, 41.06% had sleep disorders, and 991 (20.89%) were suspected positive for post-traumatic stress disorder. The correlation analysis between coping styles and mental health status shows that the mental health level of firefighters with different coping styles is different. When the coping styles are mainly self-blame, fantasy, retreat and rationalization, the mental health level of firefighters is lower; The level of mental health of firefighters is better when solving problems and asking for help are the main coping methods. Firefighters have different degrees of mental health problems after emergency rescue, so it is necessary to cultivate their mental health literacy from time to time, intervene psychological assistance in early rescue, cultivate constructive coping styles, and conduct timely psychological intervention and treatment for high-risk personnel. Related Articles | Metrics

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Practice of optimizing the layout of urban fire stations by integrating multiple factors Wang Yarong, Zhao Haipeng, Zhou Weitao, Cheng Quanying 2024, 43 (4):  551-556.  Abstract ( 155 )   In order to scientifically plan the number and spatial location of urban fire stations, improve the coverage of responsibility areas at the same time, ensure the timeliness of emergency rescue, and avoid possible greater casualties and property losses, this study is based on the Urban Fire Station Construction Standards, uses geographic information systems (GIS), increases the weight of key units of hazardous chemicals, and proposes a 90% coverage rate within 10 minutes as the consideration standard based on research results. It fully considers the economic cost of retaining existing fire stations while constructing new stations and the harm of unreasonable layout to the health of firefighting and rescue personnel, and optimizes the layout of urban fire stations. Based on this approach, a practical study was conducted using Kun District in Baotou City as an example. The results showed that after optimizing the layout of fire stations in Kun District, under the same impedance interruption, the area of fire stations that can be reached and the coverage rate of responsible areas have increased significantly. Therefore, applying this approach to optimize the layout of urban fire stations has certain scientific significance. Related Articles | Metrics

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Fire risk identification and prevention measures in medical institutions Kang Jie 2024, 43 (4):  557-561.  Abstract ( 146 )   Taking a tertiary hospital in Shanghai as an example, the author combines the operation system of specialized medical institutions with the fire safety management system, carries out fire risk identification and screening by department and ward as a unit, comprehensively applies the questionnaire survey method, the safety checklist method and the operating conditions hazard analysis method, systematically combs through the fire risks of medical institutions, and evaluates the fire risk level of each department and, on this basis, proposes preventive measures and disposal countermeasures from four aspects, including top-level design for fire safety, management of key fire safety departments, all-staff hierarchical fire safety training, and emergency disposal system. Related Articles | Metrics

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Thinking on the construction of fire rescue command system Ji Jiacai 2024, 43 (4):  562-565.  Abstract ( 208 )   After the reform and transfer, the functional positioning of the national comprehensive fire rescue team has expanded from traditional fire supervision and firefighting to responding to "all types of disasters and major emergencies". In order to further adapt to the needs of emergency rescue tasks in the new situation, enhance the combat capability and literacy of the fire rescue team, and improve the team's ability to "extinguish fires and fight big battles", this article takes the fire rescue command system as the research object, analyzes and studies the current situation and problems of the fire rescue command system, and proposes 6 countermeasures including firmly establish the awareness of "all types of disasters and major emergencies", strengthen the application of information technology means, alleviate duty pressure through multiple channels, promote the recognition of professional qualifications for firefighting and rescue positions, scientifically formulate force composition, and explore the implementation of professional command models, providing theoretical support for the construction of the command system of firefighting and rescue teams. Related Articles | Metrics

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Analysis of the characteristics of short circuit melt marks and holes in copper conductors based on Micro CT Chen Ke, Guo Yuhang, Deng Songhua, Wang Xuanlei, Zhang Liangliang, Zhang Bin, 2024, 43 (4):  566-571.  Abstract ( 572 )   Short circuit of wires is one of the important causes of electrical fires. The current national standard divides wire short circuit marks into primary short circuit marks before ignition and secondary short circuit marks caused after ignition. However, the identification in the current national standard only stays at the stage of qualitative judgment. The quantitative analysis of the characteristics of short circuit marks on copper wires at fire sites has become the main focus of attention for China and other countries researchers. This paper applies Micro CT technology to perform fault scanning detection on copper wire short circuit melt marks and reconstruct 3D image data of copper wire short circuit melt marks. Based on this, the internal pore morphology and distribution of copper wire short circuit melt marks are statistically analyzed, summarized, and summarized. Research has shown that Micro CT can comprehensively collect the overall morphology and internal pore characteristics of copper wire short-circuit melt marks. There are differences in the characteristic data of pore radius, surface area, and tightness between primary and secondary short-circuit melt marks, which can provide new theoretical basis for qualitative analysis methods and quantitative analysis criteria of short-circuit melt marks. Related Articles | Metrics

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The impact of conductor length on the ignition and combustion behavior of overcurrent polyvinyl chloride copper conductors Jia Yizhuo, Li Changzheng, Wang Jingwu, Mi Wenzhong 2024, 43 (4):  572-577.  Abstract ( 412 )   To thoroughly investigate the impact of conductor length on the ignition, combustion, and fire propagation behavior of overcurrent polyvinyl chloride copper conductors, an electrical fire fault simulation apparatus was utilized to simulate overcurrent faults in copper conductors of varying lengths. The analysis focused on the effects of conductor length on the ignition and combustion processes, as well as the maximum distance of fire spread, with fire spread rate analyzed using video image stacking techniques. The results indicate that, with a constant overcurrent value, the maximum distance of fire spread initially increases and then decreases with an elongation of the conductor length. For the 2.5 mm2 multi-core polyvinyl chloride copper conductors used in the study, at a constant overcurrent value and a conductor length of 240 cm, the maximum fire spread distance is observed, with the flame reaching full-line combustion at 200 A. The fire spread rate is fastest at the moment of conductor melting, spreading rapidly to both sides. As one moves away from the melting point, there is a decreasing trend in the fire spread rate, coinciding with a decline in combustible gas concentration and temperature in the unburned zone, accompanied by significant fluctuations. Related Articles | Metrics