China Safety Science Journal

Research on airport safety performance evaluation index system based on criteria for performance excellence and G1 method

YANG Xiaoqiang, ZHANG Zhihua, JIANG Haoran, YANG Chenguang

2020, 30(3): 1-7. doi:10.16265/j.cnki.issn1003-3033.2020.03.001

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In order to explore airport safety performance evaluation index system for the sake of improving airport safety management quality and level, evaluation index system of civil transportation airport was studied based on CPE. Then, key safety performance dimensions were established from a multicriteria perspective, and an index system, through filtered statistical analysis, was constructed, which consisted of 6 first-level indicators (category), 17 second-level indicators, and 81 third-level indicators. Finally, weights of each index were calculated through G1, and the system and weights were applied in an airport. The results show that customers and corresponding indicators play little role in the evaluation index system, and CPE can be combined with it. Multidimensional evaluation index system satisfies actual needs in safety management of civil aviation airports.

Evaluation method of ATCO's task performance based on operation data

YANG Yue, HUANG Yigang, SONG Xiangbo, WANG Jianzhong

2020, 30(3): 8-14. doi:10.16265/j.cnki.issn1003-3033.2020.03.002

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In order to address the common problem of strong subjectivity and obvious differences in monitoring and evaluating ATCO's work performance by air traffic management organizations in China, an assessment index system was designed based on flight tracks, controlling airspaces, device operation data and instruction release data. Then, assessment procedure and calculation method of indexes were studied from aspects of flight safety, operational efficiency and controlling rules, and their value was quantified by utilizing fuzzy synthetic evaluation method. Finally, the evaluation system was released on Matlab platform and validated with simulative operation data in certain sector of China. The research shows that this objective data-based assessment method makes more integrated, quantitative and intelligent evaluation of ATCO's operational skills and decision-making capacity compared with traditional checklist assessment method, therefore it can help obtain evaluation results more quickly and accurately.

Impact of coal dust concentration on gas explosion in vertical pipelines

JING Guoxun, ZHANG Shengqi, DUAN Xinwei, GUO Shaoshuai, LIU Chuang

2020, 30(3): 15-20. doi:10.16265/j.cnki.issn1003-3033.2020.03.003

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In order to study impact of coal dust concentration on gas explosion, experiments were conducted in a self-built vertical pipeline with coal dust concentration of 25, 50, 100 and 200 g/m³ and volume fraction of 9%. Then, change features of gas explosion pressure and flame propagation in explosion chamber and pipeline were analyzed. The results show that as coal dust concentration increases, mixed explosion pressure decreases. Explosion pressure in chambers and pipelines have different sensitivity to coal dust, with the former one being more sensitive to high-concentration coal dust while the latter more sensitive to low-concentration coal dust. It is also found that participation of coal dust can promote development of flames in chambers and pipelines, and an increase in its concentration mainly affects flame development in rear section of chambers, but can obviously promote flame development in pipelines which reaches the fastest as the concentration is 50 g/m³.

Effect of SDBS of different mass fractions on coal's wettability by molecular simulation

LI Shugang, GUO Doudou, BAI Yang, YAN Min, LIN Haifei, SHI Yu

2020, 30(3): 21-27. doi:10.16265/j.cnki.issn1003-3033.2020.03.004

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In order to study effects of surfactant on coal's wettability, with SDBS taken as research object, Wiser coal chemical structure model and Material Studio molecular simulation software were used to establish a system where SDBS of six different mass fractions coexisted with water and coal. Then, the system's adsorption configuration, energy changes, relative concentration distribution as well as mean square displacement (MSD) of water molecules were analyzed. The results show that hydrophobic alkyl chains of SDBS molecules are adsorbed on coal surface, and hydrophilic group with benzene ring warps to water phase, which reduces liquid-solid interfacial tension of water and coal. As mass fraction of SDBS increases, the system's total energy decreases, but interaction energy between SDBS and coal increases, indicating that adsorption between molecules is more stable and wettability is enhanced. Spatial distribution difference of hydrophobic alkyl chains of SDBS molecules is one of the main factors affecting wettability. Diffusion coefficient of water molecules increases along with the growth of SDBS mass fraction, which has a significant effect on wettability of coal.

Research on thermal runaway expansion barrier technology of NCM power battery

ZHANG Shaoyu, XIAN Xuelei, DONG Haibin, LI Yi, YU Dongxing

2020, 30(3): 28-34. doi:10.16265/j.cnki.issn1003-3033.2020.03.005

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In order to effectively control thermal runaway expansion of high energy density lithium ion batteries (LIBs), a composite barrier technology was proposed. With soft NCM811 battery as research object, existing fire prevention and control method of LIBs was analyzed and relationship between surface temperature and thermal runaway trigger time was determined by studying its thermal runaway characteristics. Then, thermal insulation tests for materials of different microstructures and sizes, represented by aerogels, asbestos and rock wool, were conducted to determine relationship between microstructure size and thermal barrier characteristics. Finally, thermal resistance characteristics of different barrier schemes were studied through thermal isolation tests with different thickness and number of layers. The results show that the smaller microstructure of barrier material is (less than 70 nm of average free path of air molecules), the thinner it is, and the more layers and better thermal barrier effect it has.

Immersion acoustic positioning method of corrosion for large tank bottom plate

ZHANG Ying, ZHANG Xiao, ZHU Zidong, DANG Na, CHEN Xiaolong

2020, 30(3): 35-40. doi:10.16265/j.cnki.issn1003-3033.2020.03.006

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In order to avoid detection dead zone in corrosion detection of large-scale storage tank floor, an immersion acoustic method is proposed, of which locating corrosion sound source is a key. Based on a passive source localization algorithm featuring time delay estimation and considering characteristics of immersed acoustic detection of tank floor, a mobile planar five-element cross array acoustic method was applied to simulate positioning of bottom plate and verify the test. The results show that this method meets the requirement of corrosion detection in accuracy of direction finding and distance measurement. Direction finding accuracy is not affected by sound source angle φ and distance r while distance accuracy is only positively related to r and independent of φ. With the fitting relationship between relative error of distance and r obtained from experiment, the maximum effective radius of immersed acoustic detecting unit can be determined.

Identification of miners' unsafe behaviors based on transfer learning and residual network

WEN Tingxin, WANG Guitong, KONG Xiangbo, LIU Mengxiao, BO Jingkai

2020, 30(3): 41-46. doi:10.16265/j.cnki.issn1003-3033.2020.03.007

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In order to accurately identify unsafe behaviors of miners and reduce occurrence of accidents in coal mines, an image recognition method combining transfer learning and deep residual network is proposed. Firstly, behavior instances of miners were divided into three dimensions, namely completely safe behaviors, relatively safe behaviors, and unsafe behaviors, among which completely safe behaviors included walking, sitting and standing, relatively safe behaviors included bending, squatting, lifting, pushing, pulling, waving and clapping, and unsafe behaviors included falling and throwing. Then, ResNet50 network was used for training, and transfer learning weight parameters of ImageNet data set were fine-tuned. Finally, 12 classification was conducted through full connection layer, and final classification results were checked against test data. The results show that residual network model based on transfer learning is superior to other deep neural network models in identification accuracy of falling and throwing movements, and it can effectively identify unsafe behaviors, thus avoiding accidents caused by human factors.

Trajectory planning model for lifting operation considering spatial conflict

JIN Lianghai, LI Jiaxin, ZHENG Xiazhong, CHEN Shu, CHEN Yan'gao

2020, 30(3): 47-52. doi:10.16265/j.cnki.issn1003-3033.2020.03.008

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In order to ensure safety and efficiency of lifting operation and reduce risks of its spatial conflicts, Manhattan plane of lifting operation was designed. Then, OARMST model of lifting trajectory was constructed by analyzing spatial conflict factors, mechanical operation conditions and construction organization conditions. Finally, lifting trajectory planning system was developed to explore safe moving trace of lifting objects under multiple sites and obstacles by integrating Dijkstra heuristic algorithm and ultra wide band (UWB) positioning technology. The research shows that the optimal moving trace obtained from OARMST model can avoid spatial conflicts, prevent multiple sudden suspensions of hanging objects and redundant operation of drivers by reducing turns and displacement of objects, therefore improving safe dispatching of lifting operation.

Study on performance of gas-liquid extinguishing agent for lithium iron phosphate battery modules

HUANG Qiang, TAO Fengbo, LIU Yang, SUN Lei, NIU Zhiyuan, JIN Yang

2020, 30(3): 53-59. doi:10.16265/j.cnki.issn1003-3033.2020.03.009

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In order to study performance of different extinguishing agents for energy storage battery modules, an energy storage cabin test platform was built. With lithium iron phosphate energy storage battery module of 8.8 kWh as research object, fire was induced by thermal runaway from 0.5 C rate constant current overcharge, and experiments were conducted to compare performance of four fire-extinguishing agents, including medium-pressure water mist, Novec1230, heptafluoropropane and hexafluoropropane. The results show that hexafluoropropane can not extinguish battery fire within a short time while Novec1230 and heptafluoropropane can extinguish it quickly but can not cool it effectively with a tendency to reignite, all of which are not suitable to be fire extinguishing agent for lithium iron phosphate battery modules. However, medium-pressure water mist can quickly extinguish fire and prevent re-ignition with its continuous injection, thus making an ideal fire extinguishing material.

Safety evaluation method based on acoustic emission technology for large-scale storage tanks

SONG Gaofeng, ZHANG Yanbing, SUN Peipei, SHEN Shuoxun, WANG Zhirong

2020, 30(3): 60-66. doi:10.16265/j.cnki.issn1003-3033.2020.03.010

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In order to explore variation characteristics of related parameters of corrosion acoustic emission signals, experiment was carried out with a common vertical metal storage tank as research object to study characteristics of its acoustic emission source for corrosion. Then, a safety evaluation model based on BP neural network was established, and case study of its application was carried out. The results show that acoustic emission activity and intensity will change along with severity of corrosion reaction, and wave forms of corrosion signals in different periods of corrosion activity will exhibit three types, continuous, abrupt and hybrid types with its frequencies mainly concentrating between 20-60 kHz. The output of BP neural network model is consistent with actual evaluation results, which proves its feasibility and effectiveness.

Deformation mechanism and repairing technology for coal-rock uphill roadway under influence of dynamic pressure

GAO Lin, WANG Jiachen, KONG Dezhong, WU Guiyi, MA Zhenqian

2020, 30(3): 67-73. doi:10.16265/j.cnki.issn1003-3033.2020.03.011

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In order to solve difficulty of surrounding rock control under influence of dynamic pressure, with uphill coal transportation roadway of a mine in Guizhou province as engineering background, main features of surrounding rock deformation of such kind of roadway were clarified through field investigation. Then, spatial and temporal distribution characteristics of plastic zone, stress field and displacement field were obtained by numerical simulation analysis, and condition for shear-slip-fault occurrence of coal-rock interface was analyzed theoretically. Then, through analysis on action principle of overlap arch bearing structure, it was found that failure mechanism of original "bolt + mesh + shotcrete + anchor cable" support was disappearance of main compression arch and effect limitation of subordinate compression arch. Finally, repairing principle and a scheme were put forward with the core of collaborative control of"grouting after covering U-steel shed + asymmetric and inclined cross-layer locking clamp cables". The practice shows that serious asymmetric deformation of surrounding rock can be effectively controlled with the proposed scheme.

Experimental study on suppression of gas and coal dust explosion by powder clouds

HUANG Zichao, SI Rongjun

2020, 30(3): 74-81. doi:10.16265/j.cnki.issn1003-3033.2020.03.012

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In order to explore prevention and control measures for gas and coal dust explosion, explosion-proof performance of powder clouds is tested in roadways with large-scale sections. Firstly, an 2 m large pipe and its open space were used to study formation process and dynamic distribution characteristics of powder clouds. On this basis, with explosion pressure and flame velocity as characteristic parameters, gas and coal dust explosion and suppression experiments were conducted in a large roadway with a section of7.2 m². The results show that the powder can cover 7.4 m² section at 60 ms, and most of the powder is ejected at 1 200 ms, forming an effective explosion-proof barrier. When surface density of powder cloud reaches 8.1 kg/m², flame can be completely extinguished within 13 m, and maximum explosion pressure is reduced by 57.0% from 0.293 to 0.126 MPa while pressure rising time at 140 m is delayed by 137 ms. As power concentration increases, suppression effect of cloud curtain is enhanced, and it can extinguish flame in a short distance and greatly attenuate explosion pressure.

Measurement of stress-relief zone width of roadway by borehole gas continuous flow method

TIAN Shixiang, MA Ruishuai, ZOU Yihuai, XU Shiqing, LIN Huaying, YU Zhaoyang

2020, 30(3): 82-86. doi:10.16265/j.cnki.issn1003-3033.2020.03.013

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In order to accurately measure the width of stress-relief zone ahead of roadway working face, borehole gas continuous flow method was proposed based on the relationship between gas flow discharged from coals and in-suit stress, and its feasibility was verified theoretically. Then, borehole gas flow was measured in 2303 ventilating roadway of Xuehu coal mine by using outburst prediction device. The results show that gas flow increases first and then decreases with its peak being the boundary of stress-relief zone, and the width of the zone ahead of working face is determined to be 9-10 meter. Meanwhile, that measured by using drillings amount and drillings gas absorption index Δh₂ is 9.5-10 meter, consistent with results of borehole gas continuous flow method, therefore verifying its reliability in determining width of stress-relief zone.

Influence of cavity volume ratio on propagation of methane blast wave

SHI Benjun, MU Chaomin, ZHOU Hui, LI Zhongqing

2020, 30(3): 87-93. doi:10.16265/j.cnki.issn1003-3033.2020.03.014

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In order to study influence of relative volume ratio change of cavity on suppression of gas explosion shock wave, experiment was carried out by using Computational Fluid Dynamics (CFD) software and large-scale circular tube methane explosion test system. The results show that cavity's reduction effect on peak overpressure is strengthened as its relative volume ratio changes from 4.8 to 7.9, and continuous light intensity reduction of flame is suddenly enhanced. When the ratio increases to 12.7, fitting results indicate that attenuation factor of flame continuous light intensity presents a “L” curve, general reduction tends to be stable, and attenuation rate rises from 90.8% to 90.9%. Attenuation factor of peak overpressure is slow at first and then fast. It is found that cavity's explosion-suppressing effect is the best when its relative volume ratio reaches 12.7 with an general attenuation rate of continuous light intensity at 90.9% and and that of peak overpressure at 30.8%.

A PCA-LSTM neural network-integrated method for phreatic line prediction

DAI Jianfei, YANG Peng, ZHU Liyi, GUO Pan, GUAN Huaiguang

2020, 30(3): 94-101. doi:10.16265/j.cnki.issn1003-3033.2020.03.015

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In order to prevent dam-breaking accidents of tailings ponds, to excavate effective information of online monitoring system and improve prediction accuracy of phreatic lines, a prediction model was set up based on PCA and LSTM neural network. Then, with Chenkeng tailings pond as an example, Pearson correlation coefficient and variable combination method were introduced to determine 18 features of model inputs, including location of phreatic line of measuring point in the first three days, location of two adjacent surrounding saturation lines, water level of ponds, longitudinal displacement of dam body and rainfall. Finally, PCA was used to eliminate data redundancy between input variables, and LSTM neural network was applied to predict location of phreatic line for the next three days. The results show that PCA-LSTM neural network-based method presents higher predication accuracy with an average absolute error of 0.011 and a decision coefficient of 0.805. And it can achieve stable prediction of phreatic lines for tailings ponds under different rainfall conditions.

Effect of gas-containing cavity and its built-in ABC dry powder on gas explosion

HUANG Qiang, MU Chaomin, ZHOU Hui, LI Zhongqing, Shi Benjun, WANG Jinlai

2020, 30(3): 102-108. doi:10.16265/j.cnki.issn1003-3033.2020.03.016

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In order to explore a method for explosion suppression after gas leakage into chamber structure, a large-scale round tube explosion test system, 200 mm wide and 17 500 mm long with a 500 mm×500 mm×200 mm (length×width×height) cavity, was built. Then, explosion suppression effect of gas-containing cavity and its ABC dry powder was tested. And explosion propagation characteristics in the above-mentioned cavity was analyzed with numerical simulation. The results show that while gas-free cavity structure has a better suppression effect on gas explosion, gas-containing cavity structure is the opposite, and explosion flame and shock wave peak overpressure in the back of it increase by 1.68 and 1.45 times respectively compared to its front. When mass of ABC dry powder in gas-containing cavity structure is 400 g and 300 g, explosion flame and shock wave peak overpressure in its back change from increase to decrease compared to its front. When dry power is 600 g, suppression rates of flame and shock wave are increase by 108.4% and 77.46% respectively compared to those without ABC dry powder.

Experimental research on temporary closed wall constructed by graphene polyurethanen in coal mine

WANG Hua'e, TANG Yibo, GUO Pengwei, HU Shihua, ZHOU Jinqiang, GUO Qian

2020, 30(3): 109-114. doi:10.16265/j.cnki.issn1003-3033.2020.03.017

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In order to address problems of heavy materials and inefficient construction of traditional mine ventilation structures, a new type of graphene polyurethane foam was developed and its performance for various structures was tested. Firstly, new graphene polyurethane foam was prepared using one-step method. Then, its hermeticity was tested through gas permeability experiments of plastic films and sheets. Finally, its structures were analyzed by using a comprehensive thermal analyzer, a Fourier transform infrared spectrometer and a metallographic microscope. The results show that the density of new graphene polyurethane foam is only 40 kg/m³. Infrared spectrum shows that it is rich in organic functional groups such as C=C, C=O, -OH, -CO and -NH, and based on observation of metallurgical microscope, distribution of 160 μm foam is uniform and stable. And the new material remains highly efficient and hermetic within 30 days of simulation test, maintains excellent thermal stability within 400 ℃, and can extinguish within 0.13 s from fire, thus reducing fire risks during its use as a temporary ventilation structure in the mine.

Energy characteristics of AE signal frequency band during coal rupture in mines with gas

ZHAO Aohan, MA Yankun, LIU Jian, CHEN Dezhong, YUAN Hongyong, FU Ming

2020, 30(3): 115-121. doi:10.16265/j.cnki.issn1003-3033.2020.03.018

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In order to analyze gas's influence on AE band energy during coal rupture under loading, with structural coal as research object, uni-axial compression test was carried out by using self-developed gas-containing coal test device. Then, signal processing method of fast Fourier transform (FFT) and wavelet packet analysis was used to obtain characteristics of AE band energy during coal rupture under different gas pressure. The results show that the greater gas pressure is, the larger main frequency of AE signal is, the narrower frequency band is, and spectrum transforms gradually from a complex multi-peak form to a single peak form. When three is gas, with the increase of loading stress, frequency band enriches and spectrum shifts to left gradually. As gas pressure changes, energy of 2.92-4.38 kHz, 4.38-5.84 and 7.3-8.76 kHz changes significantly while that in 2.92-4.38 kHz is basically same as the sum of 4.38-5.84 and 7.3-8.76 kHz, showing an opposite trend. When stress of structural coal increases, 4.38-5.84 and 7.3-8.76 kHz indicate the largest increase and decrease of energy respectively. 2.92-4.38 kHz and 4.38-5.84 kHz can be used as characteristic frequency bands to study damage of structural coal under loading in mines with gas.

Dynamic vehicle speed control model of edge rate in long tunnel sections

ZHOU Can, WANG Hong, LU Hua, ZHU Shunying, XIAO Wenbin

2020, 30(3): 122-128. doi:10.16265/j.cnki.issn1003-3033.2020.03.019

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Currently, when static edge rate is used for vehicle speed control, cycle length of edge rate period and total length of pavement corresponding to all vehicle speeds are fixed, so it is not well-targeted and achieves no obvious effects in speed reduction. In order to make up for this defect, a dynamic speed control edge rate model for tunnel segment was established with minimum vehicle speed dispersion as objective function based on the positive correlation between accident rate and vehicle speed dispersion. Then, speed control system of dynamic edge rate was installed in central section of long tunnel on expressways for intelligent linkage studies between dynamic edge rate and traffic flow. Finally, vehicle speeds with or without control system of dynamic edge rate were compared and analyzed. The results show that speed control system based on dynamic edge rate model for tunnel sections can effectively control it with overspeed ratio decreasing by 16.69%, 85^th percentile speed, average speed and speed standard deviation decrease by 6.67%, 7.96% and 13.45% respectively, and its control effect is more remarkable than that of static edge rate.

Superposition analysis of individual risk matrix of oil and gas gathering and transportation station

ZHANG Peng, FAN Chaohai, CHEN Xiangsu

2020, 30(3): 129-136. doi:10.16265/j.cnki.issn1003-3033.2020.03.020

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In order to reduce accident risks in oil and gas gathering and transportation stations, situation of these stations is studied by using risk matrix superposition technology. Firstly, damage degree of hazard sources was analyzed based on boiling liquid extended vapor explosion (BLEVE) model and revised overpressure criteria, and damage areas of death zone, severe injury zone, light injury zone and safety zone were determined. Secondly, death probability matrix of each danger source was constructed by introducing Cartesian distance matrix and grid division technology, and regional grid risk matrix was obtained through equipment risk value and superposition principle of danger sources. Then, regional risk level map of station was drawn using risk classification principles modified by British welding society (TWI). Finally, with an oilfield gathering and transportation station in Xinjiang as example, acceptability of regional risk was quantified by determining its personal risk acceptability criteria. The results show that personal risk matrix analysis method can clarify security risk situation at various locations within station and improve its safety management.

Simulation study on fire evacuation of senior apartment

HUANG Lidi, LUO Kaizhou, LIU Ying, XU Jiejing, XU Xinxin, WANG Xichen

2020, 30(3): 137-142. doi:10.16265/j.cnki.issn1003-3033.2020.03.021

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In order to optimize fire safety design of senior apartments and reduce casualties, a fire and evacuation BIM was established, and evacuation was simulated. Then, influence of building layout on fire spread and that of temperature, visibility, CO concentration and smoke layer's height on evacuation behaviors of the elderly were analyzed. The results show that during fire development process, temperature difference is greater at height range between 0.5 m and 1.5 m for 3.3 m-high fire floor, smoke layer stays stable at height around 1.4 m in fire rooms, and forms of corridor have a great impact on fire temperature and propagation. Smoke, high temperature and other factors are unfavorable to evacuation of the elderly on fire floors and above, resulting in their inability to evacuate safely. Casualties can be effectively reduced by improving evacuation efficiency in vertical direction. And by increasing emergency exits and setting ramp type evacuation stairs in terms of building layout of apartments for the elderly, evacuation efficiency can be improved.

Simulation analysis on traffic safety of signal-coordinated arteries

JIANG Xinguo, REN Hankun, FAN Yingfei, LI Xiang, FU Chuanyun

2020, 30(3): 143-149. doi:10.16265/j.cnki.issn1003-3033.2020.03.022

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In order to reduce accidents of signal-coordinated arteries, changes of traffic safety performance before and after adopting coordinated signal control on arteries were explored. Then, with data from Shuhan road in Chengdu collected, SSAM was established based on traffic simulation conflicts. Finally, a kernel regression model was used to fit simulated traffic conflicts, and safety of arteries before and after coordinated signal control was evaluated based on fitting results. The results show that arteries with signal-coordinated control comparatively has worse safety performance when traffic volume is under 3 864 pcu/h. There are more conflicts as small cars reach a too high or too low proportion(P<0.73 or P>0.83)in traffic flow, and signal-coordinated arteries have fewer crossing conflicts and more rear-end conflicts.

Robustness analysis of railway express freight network

ZHANG Zhenjiang, ZHANG Yuzhao, WANG Xiaorong

2020, 30(3): 150-156. doi:10.16265/j.cnki.issn1003-3033.2020.03.023

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In order to ensure operation stability of railway express freight transport in the face of emergencies, theories of complex network and robust optimization are used to study topological characteristics and robustness of REFN. Firstly, statistical parameters of network characteristics were calculated and topological characteristics of REFN were analyzed. Then, important nodes were evaluated before a comprehensive evaluation index was established based on route grade, degree value and betweenness. Lastly, robustness evaluation index under different attack modes was calculated and REFN robustness with or without cascading failure was compared and analyzed. The results show that in contrast to traditional evaluation index of node importance for complex networks, important nodes calculated based on route grade have a greater impact on network robustness. REFN is robust under random attacks, but shows greater vulnerability under intentional attacks, and even more prominent vulnerability when there is cascading failure.

Slope displacement prediction method based on EEMD-PSO-ELM model

XIE Bo, SHI Fuqiang, LIAO Xueyan, MA Sheng, YANG Wei, LU Xiangxiang

2020, 30(3): 157-162. doi:10.16265/j.cnki.issn1003-3033.2020.03.024

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In order to solve the difficulty in predicting slope deformation and displacement, Beidou monitoring system was used to obtain slope displacement data, and EEMD method, PSO and ELM were introduced to build an EEMD-PSO-ELM model for displacement prediction. Then, with No. 5 monitoring point of Pangang Group limestone mine as an example, original data was denoised wavelet by, and displacement time series were decomposed into fluctuating displacement and trending displacement by EEMD method. Displacement in next period was predicted using PSO-ELM optimization model. Finally, cumulative displacement prediction of slope was obtained by combining the two results, and they were compared and analyzed. The research shows that the mean relative error(MRE), root mean square error(RMSE) and goodness of fit of EEMD-PSO-ELM model are 0.15%, 0.03 and 0.9999 respectively, indicating the model has certain accuracy and applicability.

Static risk analysis on rainstorm-agricultural disaster chain in mountainous areas based on complex network

LUO Junhua, LIN Xiaosong, MU Fengyun, LI Hongwei, ZHANG Li

2020, 30(3): 163-170. doi:10.16265/j.cnki.issn1003-3033.2020.03.025

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In order to provide guidance for prevention and control of agricultural economic damage in condition of mountainous rainstorm, static risk analysis of rainstorm-agricultural disaster chain is conducted by using complex network theory. Firstly, considering that risk evolution process of storm-agricultural disasters in mountainous areas has a chain law, 39 disaster events were identified based on basic factors like agricultural production, agro-ecological environment and crop itself, and a complex network model was developed with disaster events as nodes and event development connection as connecting edge. Then, node access and clustering coefficients were used to analyze risk evolution process and to identify key nodes in network that caused damage to agricultural economy, and some chain-breaking measures and chain control recommendations were proposed. Finally, risks of six types of secondary disaster chains that caused agricultural economic damage were identified by using the shortest path method. The results show that the overall clustering coefficient is 0.04 with low degree of grouping. There is only a clear "single node-single node" simple transfer relationship between most risk events, and disaster network shows obvious characteristics of small world networks.

Research on radon control performance of covering soil in uranium tailings reservoir under long time high temperature

LIU Yan, LIU Yong, XU Zhenghua, HONG ChangshouZHANG Qiucai, YUAN Jinfan

2020, 30(3): 171-177. doi:10.16265/j.cnki.issn1003-3033.2020.03.026

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In order to study variation characteristics of radon control performance of unsaturated covering soil on uranium tailings beach under long time high temperature, with uranium tailings pond as study subject, simulation experiments were carried out by using a self-made experimental device of radon exhalation from covering soil on the beach. Then, relationships between water content, degree of surface fissure development and radon exhalation rate of covering soil were studied with samples of tailing sand at a depth of 1.5 m from a uranium tailings pond in south China. The results show that the change of radon exhalation rate is divided into four stages, linear growth, linear decline, "step" growth and tending to stability. It increases with the increase of fracture rate of covering soil, and tend to be steady when shrinkage limit is reached and crack no longer develops. Moreover, the greater fractal dimension of cracks is, the more obvious soil cracking is, and the greater radon exhalation rate will be.

Effect of cooling vest on heat and humidity transfer of stab-resistant body armor

LI Nan, CHANG Suqin, GUO Zerong, HE Jingjie, YUAN Mengqi

2020, 30(3): 178-184. doi:10.16265/j.cnki.issn1003-3033.2020.03.027

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In order to quantitatively study the heat and moisture transfer performance of SRBA and improve the thermal comfort of SRBA, a thermal manikin was used to measure and analyze thermal insulation and evaporative resistance of cooling vest, SRBA and both stacks at different temperatures (25, 30, 40 ℃) and humidity (40%, 55%, 70%). It is found that the thermal insulation changes at the three temperatures measured as SRBA> both stacks > cooling vest, and the evaporative resistance follows this characteristic above 30 ℃, that the higher the temperature is, the greater the effect of the cooling vest on the heat transfer efficiency of the SRBA will be, and that the thermal insulation can be reduced by up to 46.75% and the evaporative resistance can be reduced up to 82.97%. The results show that at higher ambient temperature (＞30 ℃), the cooling vest can effectively reduce the thermal insulation and evaporative resistance of the SRBA and improve the heat and moisture transfer efficiency, and that the influence of the cooling vest on the heat and moisture transfer of the SRBA changes with the ambient temperature, humidity and design characteristics.

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