China Safety Science Journal

Research on system fault pattern recognition based on characteristic function and connection number

CUI Tiejun, LI Shasha

2021, 31(6): 1-6. doi:10.16265/j.cnki.issn 1003-3033.2021.06.001

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In order to study system fault pattern with certainty and uncertainty, a pattern recognition method was proposed. Firstly, fault sample patterns were identified by using existing fault standard pattern, and connection number of set pair analysis was used to represent certainty and uncertainty of identification. Secondly, component coefficients of connection number were calculated by utilizing characteristic function of space fault tree, andfault sample pattern was recognized by connection degree and recognition degree. Finally, through analysis on an electrical system example, its fault mode under influence of multiple factors was effectively identified. The results show that the proposed method, based on characteristic function and connection number, can express certainty and uncertainty of pattern recognition. It uses characteristic function to determine component coefficient of connection number and uses connection degree and recognition degree for pattern recognition.

FTA-BN model of risks causation for FOD intrusion in flight area

PAN Dan, LI Yongzhou, LUO Fan, ZHANG Panke, XIAO Qin

2021, 31(6): 7-13. doi:10.16265/j.cnki.issn 1003-3033.2021.06.002

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In order to explore safety risks of FOD intrusion in airport flight area, FTA and BN methods were integrated to build a risk causation analysis model. FTA was used to analyze causation structure of FOD intrusion events. BN was applied to express multimodal properties of risks, and FTA structural reasoning and BN bi-directional reasoning function were utilized to analyze, diagnose and evaluate system risk. The results show that position of violation factors is the most critical element from perspective of risk structure while from perspective of system sensitivity, pavement damage and flight flow are the most sensitive factors with probability of two nodes' most dangerous state increasing by 3.57% and 0.43% respectively, which means that FOD intrusion can occur. It is also found that from perspective of system contribution, nodes with violations and lack of skills make the greatest contribution, and when they are in the most dangerous state, probability of FOD intrusion reaches highest, which is 4.18% and 1.50% respectively. Moreover, FOD intrusion probability in sample airfield is 0.13%, and by operators enriching their working experience, it can be effectively reduced.

Review on resilience management of urban infrastructure system

BI Wei, TANG Yuchun, MAO Tingting, SUN Xinhong, LI Qiming

2021, 31(6): 14-28. doi:10.16265/j.cnki.issn 1003-3033.2021.06.003

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In order to explore significance of infrastructure systems in urban disaster prevention and mitigation from a resilience perspective, related research on resilience management method of urban infrastructure systems was reviewed. Firstly, 576 related literatures were screened out from core collection of Web of Science. Research status of urban infrastructure system resilience management was comprehensively analyzed from aspects of journal source, publication year, country, infrastructure type and disturbance type. Then, concept of resilience as well as its connection and difference with reliability, vulnerability and sustainability were defined, and key issues in resilience management were summarized. The results show that studies on resilience of urban infrastructure system have been getting increasing attention in the past decade, and of it, transportation infrastructure and natural disturbances have been studied most. Certain achievements have been made for such research in identification, assessment, improvement and simulation, yet it is necessary to strengthen resilience theory, explore quality assessment methods, and study coupling disturbances and internal interdependency of infrastructure system.

A new safety management model of intelligent mines in 5G era

NIU Lixia, LI Xiaomeng

2021, 31(6): 29-36. doi:10.16265/j.cnki.issn 1003-3033.2021.06.004

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In order to address problems of low efficiency and poor reliability of information transmission in traditional safety management mode under background of intelligent mines in 5G era. based on literature analysis, safety intelligence and smart services were introduced into safety management of intelligent mines. Firstly, overall architecture of mines was presented, and working mechanism of safety intelligence in safety information processing was analyzed. Then, a cyclic model of continuously improved safety management work was established. Finally, concept of intelligent service was introduced from technical subsystem of spatial deployment model, and a new safety management model was constructed, namely "sensing safety information - transmitting safety information - processing safety intelligence - providing safety service - realizing safety management" with three horizontal and three vertical directions. The results show that the optimized new model can handle safety information in a more refined and humanized way, improve management efficiency, and provide a new method for mine safety hazard diagnosis and emergency decision-making.

Simulation research on group subjective probability deviationfrom a perspective of death paradox

ZHANG Yu, QIAO Li, CEN Kang

2021, 31(6): 37-43. doi:10.16265/j.cnki.issn 1003-3033.2021.06.005

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In order to study formation and evolution of group subjective probability deviation in the process of safe production, a CA model of individual subjective probability was constructed and simulation experiments were conducted by using Netlogo simulation platform. Then, simulated graphics were compared and analyzed, and hierarchical regression method was used to analyze experiment data. The results show that evolution process of subjective probability of a group is divided into three periods, namely sudden change, fluctuation, and stability. Individual death will lead to a systematic underestimation of subjective probability, and aggravate its difference within the group. Reduction of objective accident probability will also increase difference in subjective probability. However, an increase in the number of group members helps to reduce such deviation and difference, and promotes a more objective and unified estimation of subjective probability of a group.

A literature review on antecedents of employees' safety behavior in construction projects

XIA Nini, LI Dezhi, YE Gui, YANG Jiawei

2021, 31(6): 44-55. doi:10.16265/j.cnki.issn 1003-3033.2021.06.006

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In order to systematically summarize current state of research on antecedents of construction employees' safety behavior, to identify future directions, and to explore specific problems for theoretical development, 55 Chinese papers and 85 English papers were reviewed by using both content and bibliometric analyses. The results indicate that number of related literatures is generally growing and antecedents have been identified from several aspects, including individual characteristics, team (group) interaction, workplace and work design, project and organization management, and family, industry, and society. However, much of such research is plagued by unclear conceptualization, undefined measures, and weak explanation of antecedents' influencing mechanism on safety behavior as well as inability of cross-sectional questionnaire survey in deducing cause and effect. The proposed the proposed integrated cross-level multi-path model can provide an idea for systematic studies on construction employees' antecedents of safety behavior in the future.

Research on early-warning index for deformation of integrated scaffoldingand formwork with steel platform based on risk management

SHEN Yang, XU Lei, WANG Shaochun

2021, 31(6): 56-63. doi:10.16265/j.cnki.issn 1003-3033.2021.06.007

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In order to provide early-warning for possible instability and damage of integrated scaffolding and formwork with steel platform during construction of super high-rise buildings, structural deformation under most unfavorable conditions is adopted as core index to evaluate safety risk of the scaffolding and formwork, and determination methods for early-warning indicators of deformation are put forward. Firstly, based on systematic analysis on equipment composition, failure modes were analyzed for normal states and limit states, and classification method of failure risk level was put forward. Secondly, determination method for four-level deformation early-warning indices based on risk management was established considering deformation developing characteristics. Finally, case study on a typical integrated steel platform project was carried out. The results show that by determining risk level standards and risk value, establishing conditions for analysis models can be obtained and hence early-warning deformation indices be acquired. Moreover, the proposed method is verified to be scientific and feasible as it, based on analysis of failure paths and modes, can obtain values of early-warning indices through calculation of finite element models.

Evaluation of coal mine safety management effect based on multi-source heterogeneous data

SU Guorui, JIA Baoshan, WANG Peng, SHEN Zhuo

2021, 31(6): 64-69. doi:10.16265/j.cnki.issn 1003-3033.2021.06.008

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In order to explore coal mine safety management model from a perspective of smart mines, a PSR model of coal mine safety management was established by introducing concept of PSR from the field of ecological safety in it, and relationship among risk factors, coal mine safety status and safety risk management & control was revealed. Then, multi-source heterogeneous data collected by coal mines was analyzed, and TF-IDF hidden danger classification model and PCA coal mine safety assessment model were constructed based on framework of the PSR model. Finally, this model was applied in a mine in Inner Mongolia to verify its effectiveness. The results show that TF-IDF algorithm-based hidden danger classification model and PCA safety assessment model can comprehensively analyze safety management effect of coal mines, and main hidden dangers can be checked according to analysis results.

Research on relationship between unsafe psychology and behavior of workers in confined space

CAO Lulu, LIU Yan

2021, 31(6): 70-75. doi:10.16265/j.cnki.issn 1003-3033.2021.06.009

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In order to explore status quo of unsafe psychology and behavior of workers in confined space and study relationship between them, a developed scale for unsafe psychology and behavior was used to investigate 206 frontline operators. Then, SPSS software was utilized to analyze variance of unsafe psychological scores of each demographic variable in collected questionnaire, and correlation analysis and regression analysis were performed on unsafe psychological scores and behavior scores of various dimensions. The results show that in addition to gender and age, level of unsafe psychology varies significantly in terms of service length, marital status, education level and unit attributes, and all dimensions of unsafe psychology have a strong positive correlation with unsafe behavior. Of seven kinds of unsafe psychology studied, four of them, including herd mentality, fluke, shortcut energy saving and boredom, have a significant impact on unsafe behavior of workers in confined space. Among them, herd mentality has the greatest influence, followed by fluke, shortcut energy saving and boredom in turn.

Influence of perceptions of organizational politics on counterproductive work behavior: chain mediating effect of psychological contract violation and miner cynicism

SANG Libin, LI Jizu

2021, 31(6): 76-82. doi:10.16265/j.cnki.issn 1003-3033.2021.06.010

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In order to effectively prevent and control counterproductive work behavior of new generation miners and reduce occurrence of safety accidents, starting from perspective of organizational situation perception, collecting data through questionnaire surveys, Bootstrap and other methods were used to conduct empirical tests, influence mechanism and internal mechanism of perceptions of organizational politics on counterproductive work behavior of new generation miners were studied, and a chain mediation model was constructed.The results show that counterproductive work behavior of new generation miners is significantly positively correlated with perceptions of organizational politics.

Causal analysis of strike accident of tower crane operating object based on D-I

ZHENG Xiazhong, ZHOU Jiali, SHAO Bo, YANG Ying, YANG Qiu, JIN Lianghai

2021, 31(6): 83-89. doi:10.16265/j.cnki.issn 1003-3033.2021.06.011

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To prevent SFO accident in tower crane operation, 19 high-frequency cause factors were extracted from investigation reports of tower crane accidents in the past five years.Decision-making trial and evaluation laboratory (DEMATEL) and interpretative structural modeling (ISM) were integrated to analyze mutual influence relationship between each cause, ladder level structure of causes were constructed, and key causes were found out. The results show that 19 high frequency causative factors are divided into 9 levels, among which improper use of safety protective equipment, illegal entry or in the danger zone and falling of hanging objects are apparent factors. Imperfection of safety management system is essential factor. Inadequate on-site supervision and management and missing or unqualified special construction scheme are deeper cause factors. And the key causing-factors of SFO accident are inadequate on-site supervision and management, inadequate safety technical disclosure, imperfect safety management system, insufficient safety awareness, skills or experience.

Evaluation of falling possibility at height in subway station construction based on HFACS-BN

WANG Junwu, WANG Mengyu, LIU Denghui, WU Han, HU Die

2021, 31(6): 90-98. doi:10.16265/j.cnki.issn 1003-3033.2021.06.012

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In order to accurately predict falling possibility at height in subway station construction, an evaluation model of it based on HFCAS-BN was constructed. Firstly, based on HFACS framework, causes of falling at height were identified, and the framework was mapped into BN. Secondly, group decision-making method based on normal distribution weight, fuzzy-BWM and global relative value were incorporated into BN to obtain prior probability of root nodes and conditional probability of intermediate nodes. Then, probability of falling nodes in various states was predicted and key causes were identified by using BN forward reasoning and sensitivity analysis. Finally, three stations of Chengdu Subway Line 11 were selected for case analysis. The results show that evaluations of most possible state of Huilonglu Stop, Diaoyuzui Stop and Lujiaocun Stop, respectively severe fault, fault free and fault free, are basically consistent with actual construction situation. Key causes of falling accidents include inadequate safety education and training, removal of falling prevention measures, losing one's footing, poor safety awareness, standing on unsafe places and inadequate lighting, so major efforts should be made on them.

Fault diagnosis method of rolling bearing based on Kurtogram and DSCN

GU Yingkui, LIU Ping, LIN Zhonghai, QIU Guangqi

2021, 31(6): 99-105. doi:10.16265/j.cnki.issn 1003-3033.2021.06.013

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In order to reveal fault characteristics of different bearing and improve accuracy and efficiency of fault diagnosis, a bearing fault diagnosis method based on Kurtogram and DSCN was proposed. After Kurtogram was generated with original vibration signals, its graphic features under different fault modes were studied and recognized by DSCN, and advantageous features were automatically extracted for fault classification. The results show that compared with other fault diagnosis methods, the proposed one has the highest recognition accuracy on test set, reaching as far as 97.28%, which also reflects obvious advantages of DSCN in reducing number of parameters and increasing training speed.

Research on dust removal characteristics under synergistic action of vibrating wire grid and high-pressure spray

DING Houcheng, LIAN Zhixu, DENG Quanlong, JIANG Zhongan, YANG Liwei, GE Mengyuan

2021, 31(6): 106-112. doi:10.16265/j.cnki.issn 1003-3033.2021.06.014

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In order to prevent and control pollution of dust from outlet of mine to surrounding atmospheric environment of mining area,based on theory of fluid dynamics, gas-liquid coupling and spray dust reduction and vibrating wire grid dust removal, computational fluid dynamics (CFD) three-dimensional numerical simulation method was used, dust removal characteristic parameters under synergistic effect of vibrating wire grid and high-pressure spray were optimized, effects of different atomization pressures on particle size distribution and mass concentration distribution of droplets were studied. Effects of diameter and spacing of vibrating string grid on droplets intercepting effect and effects of wind speed on water film of double-layer vibrating string grid were analyzed. The results show that with the increase of atomization pressure, the particle size of droplets decreases gradually and distribution becomes centralized. When atomization pressure exceeds 8 MPa, particle size distribution of droplets does not change significantly. Vibrating-string grids with different spacing have effect of blocking flow field and serious backflow phenomenon, while vibrating-string grids with spacing of 5 mm have the better effect of intercepting droplets with smaller particle size.When inlet wind speed is 3 m/s, water film on the surface of vibrating grating has the best effect, which is more conducive to dust collection. Variation trend of simulated data is basically consistent with experimental results.

High-speed railway emergency dispatching safety analysis based on STAMP/STPA

WU Haitao, LI Shuangxi

2021, 31(6): 113-120. doi:10.16265/j.cnki.issn 1003-3033.2021.06.015

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In order to overcome defect that traditional safety analysis models cannot evaluate complex interactions between components in the high-speed railway dispatching system, based on system theory, STAMP treats interaction safety between personnel and equipment in high-speed railway emergency command system as a system control and feedback problem, high-speed railway emergency dispatch control feedback model was constructed, and system safety risks and constrain were identified. STPA was used to analyze unsafe control behavior and control defects inducing unsafe control behavior. Validity of STAMP/STPA applied to safety analysis of high-speed railway emergency dispatch was verified based on case analysis of high-speed railway derailment accident in Taiwan. The results show that risk factors of emergency dispatch command of high-speed railway can be analyzed by feedback model of emergency dispatch control perception or execution error, decision-making error, receiving or execution delay. At the same time, failure path of safety constraint can be deduced by model.

Numerical simulation and experimental study on vortex blowing and suction dedusting technology during coal falling

JING Deji, JIA Xin, ZHANG Tian, MENG Xiangxi, MA Mingxing, WANG Zhiheng

2021, 31(6): 121-127. doi:10.16265/j.cnki.issn 1003-3033.2021.06.016

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In order to control dust in the process of coal falling, based on generation mechanism of vortex and migration feature of dust particles in vortex airflow field, a vortex blowing-suction dust removal technology was put forward to control dust dispersion during coal falling. Then, with a coal falling tower as an example, numerical simulation was used to analyze variance law of airflow field. Finally, a simulation experiment model was built, optimal vortex performance of devices was studied, and dust removal performance of proposed technology was compared with that of single suction one. The results show that vortex airflow is formed during coal falling process, and most of dust particles are collected by vortex, migrating bottom-up in a spiral pattern. Vortex performance will be the best at an optimal blowing ratio of 4.814. And dust removal performance of vortex blowing-suction dedusting technology is better than that of single one, with dust collection concentration per unit time being 314.27 and 191.94mg/m³, dust removal efficiency of 93.25% and 41.19%, and escape rate of 6.31% and 46.60% respectively.

Vehicle speed measurement based on vanishing points of driving videos and inverse perspective mapping

GUAN Chuang, FENG Hao, ZHANG Zhiyong, JIANG Zhenfei, ZHANG Zefeng

2021, 31(6): 128-135. doi:10.16265/j.cnki.issn 1003-3033.2021.06.017

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In order to overcome impact of camera jitter on speed measurement during driving, a general speed measurement method was proposed based on characteristics of driving video's vanishing points and inverse perspective mapping. Firstly, positions of those points and slope information of traffic lanes were obtained by detecting and identifying lane lines. Secondly, a three parameter model of cameras was established, and calculation formulas of pitch angle, yaw angle and height were derived by using perspective imaging principle. Then, velocity of self-driving vehicle and target vehicle were obtained through analyzing feature motion of forward projection image after reverse perspective transformation. Finally, a real vehicle test was carried out under conditions of self-driving speed 20, 25, 30, 35, 40, 50 km/h and front target vehicle at 10, 20, 30 km/h respectively. The results show that the average error of self-driving speed is less than 5%, while that of front vehicle is less than 7%, which can meet requirements of traffic accident speed measurement.

A method for determining safety capacity based on spatial-temporal distribution of crowds:case study in Shichahai scenic area, Beijing

HU Cheng, LI Junwei, LI Qiang, CHEN Jin

2021, 31(6): 136-143. doi:10.16265/j.cnki.issn 1003-3033.2021.06.018

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In order to prevent crowds gathering risks and trampling events in public places. Based on spatial-temporal distribution characteristics of crowds gathering in public places, unbalanced coefficient of spatial distribution and variation coefficient of temporal distribution of crowd gathering were proposed to improve safety capacity algorithm with consideration of evacuation time, basic algorithm of instantaneous safety capacity and daily safety capacity were improved. Taking Beijing Shichahai scenic spot as an example, corrected instantaneous safety capacity and daily safety capacity were respectively 47.8% and 33% of base value. The results show that difference of spatial and temporal distribution of population gathering is the root cause of high risk of population gathering in local time or specific region. Considering space unbalance and time fluctuation is helpful to improve accuracy of regional safety capacity, case proves that the improved method is more in line with the needs of safety management in public places.

Influence of auditory signals on pedestrians' perception of traffic signals

PENG Xing, TANG Xiaoyu, CHANG Ruosong, JIANG Hao, SHI Rong

2021, 31(6): 144-152. doi:10.16265/j.cnki.issn 1003-3033.2021.06.019

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In order to investigate influence of auditory signals on pedestrians' perception of audible traffic signals in different task stages (detection task, discrimination task), based on these two tasks (experiment 1 and 2), 2 (types of traffic lights: traditional traffic light and audible traffic light) × 2 (colors of traffic lights: red and green light) factorial design was adopted to explore whether audible signals can generate MSI. The results show that they do produce MSI with processing advantages in both detection and discrimination tasks. And red light produces psychological effect of red, due to which, pedestrians respond more quickly and accurately to it than green light. It is also found that in stage of discrimination, auditory signals can affect individual's reaction bias, and pedestrians are more inclined to report red audible signal light.

Research on passenger flow assignment for high-speed railwayunder public health emergencies

JIA Fei, MENG Xuelei, JIA Baotong, LI Tao, ZHANG Yang

2021, 31(6): 153-160. doi:10.16265/j.cnki.issn 1003-3033.2021.06.020

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In order to reasonably allocate passenger flow for high-speed railway under public health emergencies, a train service network was constructed considering physical network and operation plan of high-speed railways. Generalized expenses of passenger travel were divided into time cost, fare expenditure and congestion cost before its calculation method was determined, and it was defined as travel resistance. Then, a passenger flow distribution model was established with minimizing generalized travel cost as its goal, and was solved by an improved algorithm based on method of successive averages(MSA). Finally, Matlab programming was utilized to verify rationality of the model and algorithm with incidents in Wuhan as an example. The results show that occupancy rate of some high-speed railway trains is extremely high or large under conditions of public health emergencies, and it can be made more reasonable by increasing or reducing number of trains and adjusting stations' stop plan.

Research on damage resilience assessment of urban power networks under intentional attacks

HAN Lin, ZHAO Xudong, CHEN Zhilong, GONG Huadong, HOU Benwei

2021, 31(6): 161-169. doi:10.16265/j.cnki.issn 1003-3033.2021.06.021

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In order to improve effectiveness of damage resilience assessment of urban power networks under threat of intentional attacks, a performance response function(PRF) method was used in combination with strategy game model of attacker and defender to develop a damage resilience assessment method and procedure. At the same time, a new type of performance response function was designed by integrating power flow analysis to make resilience evaluation result better meet actual functional requirements of power network. Finally, with a power network in a city of China as an example, strategy game model was employed to solve Nash equilibrium strategies of attacker and defender, and damage resilience under different recovery conditions was evaluated. The results show that Nash equilibrium strategy is the most possible attack and defend strategy for both sides, and damage resilience of urban power network is jointly controlled by recovery resources and recovery budget. While the former decides recovery speed, the latter determines recovery level.

Development trend of global terrorist attacks and analysis on casualty risk

XU Xingpeng, XU Qingfeng, FANG Zhiming, LYU Wei, HUANG Rongyan

2021, 31(6): 170-175. doi:10.16265/j.cnki.issn 1003-3033.2021.06.022

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In order to reveal evolution trend of global terrorism, based on GTD, temporal and spatial evolution trends of terrorist attack numbers and causalities over last 50 years were analyzed. Then, characteristics of such attacks were analyzed from aspects of areas, weapon types and targets, and a quantitative model of casualty risk and a four-level risk classification standard for terrorist attacks were proposed. The results show that sub-Saharan Africa is at the highest risk geographically, while among all weapon types, transportation as a weapon features the highest risk of casualties. For attack targets, military, civilian and non-state militias are at the highest risk. In summary, global terrorist attacks still evolve in a grim way, and the quantitative model of casualties puts an end to subjectivity of experience assessment.

Research on visual load at entrance area of extra-long tunnel in different periods

MEI Jialin, DU Zhigang, ZHENG Haoran, XU Fuqiang

2021, 31(6): 176-181. doi:10.16265/j.cnki.issn 1003-3033.2021.06.023

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In order to study drivers' visual load when driving at tunnel entrances at different periods, real vehicle experiment was carried out at noon, dusk and night respectively in extra-long tunnels in Guizhou Province. Change rate of pupil area and frequency-weighted velocity of instantaneous pupil area were selected asevaluation indexes for the area's changes, and visual load of access zones, threshold zones and transition zones of entrance areas was analyzed. The results show that in the midday and evening, drivers' pupil area has no obvious change in access zones, but increases rapidly in threshold zones, and tends to be stable in transition zones. The distance between stable point of pupil area and portal in the midday period is longer than that in the evening. Visual load in different zones can be evaluated based on velocity of instantaneous pupil area, and it ranks as noon transition zone> noon threshold zone > night access zone ≈ night threshold zone ≈ night transition zone > noon access zone > evening transition zone> evening transition zone > evening access zone. In entrance areas, variation of drivers' visual load at different periods is more significant than that in different zones.

Research on urban flood and waterlog emergency scenario deductionbased on Bayesian network

WANG Zhe, KONG Weilei, FANG Danhui, DUAN Zhifei

2021, 31(6): 182-188. doi:10.16265/j.cnki.issn 1003-3033.2021.06.024

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In order to deal with complex evolution process of urban flood and waterlog disaster, Bayesian network was utilized in combination with evidence theory and knowledge meta-model for emergency scenario deduction research on urban flood and waterlog disasters. Then, their deduced elements were classified into disaster-pregnant environment, disaster-causing factors, disaster-bearing carrier and emergency management, and relationship between elements was analyzed. Finally, a Bayesian network of urban flood and waterlog disaster emergency scenarios was established to verify scientificity and effectiveness of emergency management measures through case study of flood disaster in Wuhan in 2016. The results show that the knowledge element model can construct a complex evolution path of urban flood and waterlog disaster emergency scenarios since evidence theory can deal with uncertain information in evolution of these scenarios while Bayesian network can effectively evaluate emergency management measures through simulation evolution.

Research on optimal information threshold of long straight section on grassland highway

SHANG Yan, ZHU Shoulin, QI Chunhua

2021, 31(6): 189-195. doi:10.16265/j.cnki.issn 1003-3033.2021.06.025

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In order to optimize monotonous landscape environment of grassland highways and improve driving safety of drivers, simulated driving experiment method was adopted to design a two-lane second-class grassland highway based on real road information. Different information densities were set for a range of 1-5/km, 40 subjects were selected and tested for four eye movement sensitivity indices including blink duration, fixation duration, pupil diameter and saccade range. Then, variation rules of their eye movement indices under different information amount environment were quantified, a relationship model between information content and indices was established, and derivative of the conic in terms of quasi combination was taken. The results show that relationship between information amount and eye movement indices is U-shaped, and 4/km makes the optimal information threshold under which change rate of indices reaches the largest with the utmost information extracted and landscape environment will not trigger "monotony". However, when it is greater than or less than 4/km, the change rate would decrease.

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