交通运输工程学报

Research progresses of prediction method and uncertainty of train-induced environmental vibration

MA Meng, LIU Wei-ning, LIU Wei-feng

Abstract: Various prediction methods and their uncertainty problems for the train-induced environmental vibration were summarized systematically. Various methods and models developed in the recent decade were summarized in three prediction classes such as the scoping prediction, determined prediction and detail prediction. The stochastic uncertainty of model input parameters was discussed, including the uncertainties caused by the difference between trains, the wheel and rail wear growth, and the input soil parameters in the prediction model. Based on the new measurement results, the influence of wheel and rail wear state on the uncertainty of vibration source intensity of metro was analyzed. Research result indicates that the machine learning method and analytical transfer function method of soil layers can be employed in the scoping prediction stage. In the determined prediction stage, various numerical and analytical models improve gradually, and their prediction efficiencies increase gradually. However, the wheel-rail excitation input method considering the developments of wheel and rail wear still needs to be further improved. The dynamics model of building structure with clear vibration propagation path and for the engineering prediction should still be further developed. In the detail prediction, the hybrid prediction method needs to be developed, and the application on the vibration prediction for underground metro lines should be investigated. Up to now, there is lack of researches on the accuracy and precision of prediction result and the reliability of prediction method. Most predictions can only provide results with determined values. The uncertainties of wheel and rail wear, operation maintenance level and vibration propagation in the soil layers cannot be considered. It is suggested to further develop the micro vibration acquisition device with remote intelligent offline sampling function, and it can be permanently installed on the building structures, so as to combine this technique with the machine learning method to adapt to the development requirements of intelligent prediction in future. It is suggested to develop the roughness spectrum that can describe the rail short-wave wear state grade and wheel out-of-round grade, and establish a dynamic environmental vibration prediction model in a whole maintenance and repair cycle. The intelligent prediction method with reliability and accuracy requirements should be developed, and the prediction should be fundamentally changed from the fixed value prediction to the probability prediction in future.More>

2020, 20(3): 1-16. doi: 10.19818/j.cnki.1671-1637.2020.03.001

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Research on crashworthiness of civil aircraft fuselage structures

MOU Hao-lei, JIE Jiang, FENG Zhen-yu

Abstract: The civil aircraft fuselage structure was considered as the study objective, according to the different levels of crashworthy building block approach, including coupons, elements, details, sub-components, components, and full-scale aircraft, the crashworthy tests and numerical simulation of civil aircraft fuselage structures were elaborated. The crashworthy researches on sub-components(sub-cargo fuselage sections) and components(fuselage sections) in the world were summarized, the crash failure modes of fuselage section were compared and analyzed, and the crashworthy design methods of fuselage sections were described. The crashworthy compliance verification and evaluation methods of civil aircraft fuselage structures were elaborated, and the prospect of future researches on the crashworthy design, verification and certification of civil aircraft fuselage structures was proposed. Research result shows that the failures of materials and connection structures are the main failure modes during the crash process of civil aircraft fuselage section, the material constitutive model and the connection structure failure model can significantly affect the crashworthy simulation analysis. The more accurate material constitutive models and connection structure modeling techniques need to be developed to improve the dynamic simulation maturity. The crashworthiness can be effectively improved by arranging the energy-absorbing structures in the fuselage structure, the more efficient and stable design scheme and layout of energy-absorbing structures need to be developed to maximize the crashworthy performance. The tests and simulation analysis of details and sub-components can provide the innovative solutions to evaluate the failure modes, damage mechanisms and energy-absorbing capabilities, and the high-precision test technology and finite element simulation analysis technology need to be developed to effectively support the crashworthy design, verification, and certification for the components and full-scale aircraft. The crashworthy evaluation methods and optimization methods with uncertain parameters need to be developed to avoid additional tests and later configuration changes. The crashworthy building block approach can be systematically conducted to effectively support the finite element model verification and evaluation, and the finite element simulation technology verified through the crashworthy building block approach needs to be developed to reduce the crashworthy verification time and cost, and to guide the crashworthy test design and structural design.More>

2020, 20(3): 17-39. doi: 10.19818/j.cnki.1671-1637.2020.03.002

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Safety evaluation and action mechanism of frost heave with local water storage in shallow tunnel

WANG Dao-yuan, YUAN Jin-xiu, ZHU Yong-quan, LUAN Yong-jun, CUI Hai-long, CUI Guang-yao

Abstract: To reveal the action mechanism of frost heave with local water storage and put forward the effective safety evaluation method of lining structure in cold region tunnels, the three-dimensional geomechanical model test was designed. By setting three different frost heave test conditions with different water accumulation ranges, the crack development and stress of lining structure were observed during the frost heave. The numerical calculation method of frost heave with local water storage was improved. The numerical model of frost heave based on the rock mechanics method and coupled with the frost heaving force and surrounding rock load was established. Under different locations, thicknesses and ranges of water storage, the change laws of tunnel frost heaving force and structural internal force were compared. The influence mechanism of frost heave with local water storage on the stress of tunnel was further revealed, and the safety of lining structure was evaluated. Analysis result shows that the frost heave with local water storage has significant regional characteristics, and the frost heave cracking of lining occurs at the junction between the local water storage and the non water storage, the magnitude of frost heave depends on the stress concentration effect caused by the frost heave at the junction. The lining cracks are mostly longitudinal and oblique. The most disadvantageous positions of local water storage frost heave of lining are the arch foot, side wall, invert arch, waist and vault from the best to the worst. The stress of lining increases with the increase of local water storage thickness. The stress of lining tends to be uniform with the increase of local water storage area. Under the conditions of frost heave with local water storage in different parts, the allowable pressure stress ratios of lining structure are less than 1, meeting the requirements of code. The allowable tensile stress ratios of vault, arch waist and invert are greater than 1, not meeting the requirements of code. In the actual project, the appropriate measures should be taken to prevent the frost heave in the above parts. The revealed action mechanism of frost heave with local water storage and the established safety evaluation method of lining structure can provide a certain theoretical basis for the prevention and control of tunnel frost damage in cold areas.More>

2020, 20(3): 40-50. doi: 10.19818/j.cnki.1671-1637.2020.03.003

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Train-induced vibration characteristics in throat area of sinking metro depot

CHEN Yan-ming, FENG Qing-song, LIU Qing-jie, LIU Wen-wu, LUO Xin-wei

Abstract: The vibration accelerations of rail, ballast bed, ground, floor and cover plate in the throat area of a sinking metro depot were measured on site by the trigger acquisition method. The field measured data were analyzed by the methods of insertion loss, one-third octave band spectrum and curve fitting of Z direction vibration level. Furthermore, the vibration source characteristics in the throat area of sinking metro depot and the transmission law of vibration along the cover plate and different floors were analyzed. Analysis result shows that in the frequency domain, the frequency band of rail vibration is wider than that of ballast bed, and there is no obvious main frequency band. The vibration distribution of rail is within 800 Hz. While the ballast bed has an obvious main frequency band within 80-200 Hz. The vibration attenuations from the rail to the ballast bed at the first and second floors underground are about 29.9 and 10.4 dB, respectively. The train-induced vibration response of cover plate decreases linearly with the increase of distance between the measuring point and the center line of running track, and the linear attenuation rate is about 0.2 dB·m^-1. Due to the reflection and refraction of the side wall to the vibration, the local amplification phenomenon occurs when the vibration is transmitted to the end of cover plate. No matter the train is running at the end of metro depot or in the middle track, with the increase of distance between the measuring point and the center line of running track, the vibration level of cover plate is basically the same at the low frequencies of 2.5 and 5.0 Hz, decreases slowly at 10 Hz, and decreases obviously at the middle and high frequencies of 25, 40 and 80 Hz. The upward propagation of train-induced vibration shows a floor-by-floor attenuation law. The vibration of cover plate caused by the train operation at the first floor underground is about 16.1 dB greater than that at the second floor underground. The characteristics of many rail joints and turnouts in the throat area of sinking metro depot lead to the prominent vibration response of cover plate in this area. It is necessary to focus on the vibration reduction design of this area.More>

2020, 20(3): 51-60. doi: 10.19818/j.cnki.1671-1637.2020.03.004

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Time series finite element analysis of support of slope excavation

YAN Qiang, LIAN Xiang-dong, LING Jian-ming

Abstract: In order to study the influence factors of slope stability of highway reconstruction and expansion project and to seek scientific support methods, the Liuzhou to Nanning Expressway K1456+800 left-hand reconstruction expansion slope was selected as the research subject, the finite element numerical model was built by using ANSYS, and two support methods were selected as the late support and timely support. The shear strain increment, horizontal and vertical displacement increments of the slope body during the excavation of 6-grade slope in the reconstruction and expansion project were simulated. For the quantitative analysis of the trend of displacement and stress during the excavation of slope under two support conditions, 6 special nodes were selected for the monitoring. The main monitoring contents include the displacement of measuring point(including the horizontal displacement and vertical displacement), and the change of principal stress(including the maximum principal stress and the minimum principal stress) with the excavation step. Analysis result shows that whether or not it is supported in time, the maximum shear strain at each step is at the foot of slope, however, the distribution area and shear strain increments of timely support are smaller than those of late support, and the probability of slope failure is low. With the excavation, the horizontal displacement increment decreases first and then increases slightly, the vertical displacement increment increases sharply first and then decreases slowly, and the final displacement of each measuring point under the timely support is smaller than the value under the late support. When it isn't supported in time, the safety factor is close to 1.0 finally. In case of timely support, the safety factor increases greatly at each step, basically greater than 1.35. As mentioned above, the timely support can reduce the shear strain of slope, limit the horizontal and vertical displacements, reduce the overall stress level, improve the safety factor, and significantly improve the stability of slope.More>

2020, 20(3): 61-71. doi: 10.19818/j.cnki.1671-1637.2020.03.005

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Model-free adaptive sliding mode vector control for podded propulsion motor

YAO Wen-long, WANG Jia-li, PANG Zhen, CHI Rong-hu, SHAO Wei

Abstract: To solve the problem of poor speed tracking performance caused by the load disturbance in the podded propulsion motor control system of semi-submersible ship, a speed vector control method for the podded propulsion motor was proposed based on the data-driven. The speed equation of propulsion motor with unknown load disturbance was discretized, and the nonlinear speed system about the output speed and input current after the discretization was given. Since multiple variables were in the nonlinear speed system equation and the load disturbance model was unknown, the model-free adaptive controller based on the data-driven was designed and the pseudo partial derivative estimation algorithm was given. The sliding mode observer was utilized to observe the propeller load disturbance and a sliding mode controller was given. Combining the model-free adaptive control with the sliding mode control, and the model-free adaptive sliding mode(MFASM) control scheme under the load disturbance was presented. The podded propulsion motor MFASM vector control speed governing system was constructed, and the simulation results were given in the MATLAB/Simulink environment. Research result shows that under the constant speed of ship in the normal operation and within the time range of 0.3-0.5 s, the speed errors of podded propulsion motor under the MFASM vector control scheme and the PI vector control scheme are 2 and 6 r·min^-1, respectively. Within the time range of 0.8-1.0 s, the speed errors of podded propulsion motor under the MFASM vector control scheme and the PI vector control scheme are 1 and 3 r·min^-1, respectively. For the variable speed case of ship operation, the time for the speed and torque of propulsion motor to the steady-state under the MFASM vector control scheme is 0.01-0.03 s less than that under the PI vector control scheme. Therefore, the speed tracking performance of podded propulsion motor can be improved by utilizing the MFASM vector control scheme, and the proposed method is an effective data-driven control method for suppressing the load disturbance.More>

2020, 20(3): 72-79. doi: 10.19818/j.cnki.1671-1637.2020.03.006

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Multi-objective optimization for dynamics parameters of high-speed trains under side wind

ZHAI Jian-ping, ZHANG Ji-ye, LI Tian

Abstract: To improve the dynamics property and the running stability and safety of high-speed train under side wind, the wheel shaft lateral force and the wheel load reduction rate were taken as the optimization goals, the multi-objective optimization design for the suspension parameters of high-speed train dynamics model was carried out, and the multi-body dynamics parameterized model of high-speed train was modeled. According to the wind speed limit standard, the aerodynamic data of high-speed train under side wind at different speeds were loaded. Total 11 variables were extracted such as the stop clearance, the first suspension longitudinal and vertical stiffnesses, the second suspension longitudinal and vertical stiffnesses, the first vertical shock absorber stiffness, the second lateral and vertical shock absorber stiffnesses, snake-resistant shock absorber stiffness and damping. The high-speed train dynamics model optimization platform was built. The correlation between the design parameters of multi-body dynamics parameterized model of high-speed train with the wheel shaft lateral force and the wheel load reduction rate was carried out, and the influence trend of suspension parameters on the wheel shaft lateral force and the wheel load reduction rate was obtained. Based on the correlation results, the optimization design for the high-speed train dynamics parameters was proceeded by using the NCGA, AMGA, and NSGA-Ⅱ genetic algorithm. Analysis result shows that the optimization result of NSGA-Ⅱalgorithm is ideal. The factor that has the biggest correlation with the wheel shaft lateral force and the wheel load reduction rate is the snake-resistant shock absorber stiffness, and with an adverse effect. After the optimization, the dynamics property of high-speed train has a marked improvement. The wheel load reduction rate decreases from the origin value 0.78 to 0.63 wholly, and the minimum value can be 0.49, reducing by up to 37.2%. The wheel shaft lateral force decreases from the origin value 16.8 kN to 9.6 kN wholly, and the minimum value can be 5.79 kN, reducing by up to 65.5%. The Pareto frontier optimal solution is got, the optimal solution set of each dynamics parameter design variable is determined, and the optimal solution sets with high applicability are verified at other wind speed and train speed states.More>

2020, 20(3): 80-88. doi: 10.19818/j.cnki.1671-1637.2020.03.007

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Emergency customized bus route optimization under public health emergencies

MA Chang-xi, WANG Chao, HAO Wei, LIU Jing, ZHANG Zhao-lei

Abstract: Considering the requirements of epidemic prevention and control under public health emergencies, an optimization method of emergency customized bus routes was constructed. The closed areas and road sections in the city were screened and set as the emergency customized bus forbidden areas. Taking the occupancy rate of passengers not exceeding the safety threshold as the constraint, and considering the matching of supply and demand, the optimization model of public health emergency customized bus route was constructed by minimizing the total running time of all emergency customized buses. The genetic algorithm was designed to solve the model. The chromosome was encoded by the three-segment hybrid coding method. The three chromosomes were composed of the customized bus parking lot number, boarding station number and alighting station number. The chromosomes were decoded by using the greedy strategy. A simulation case was used to verify the feasibilities of the optimization model and algorithm, and the optimization results were compared with the customized bus route optimization scheme based on the same passenger transport task under the normal circumstance. Research result shows that the number of vehicles required for the emergency customized bus route under public health emergencies is 2 more than that under the normal circumstance. The total travel time of vehicles increases by 6.997 h compared with that under the normal circumstance. The customized bus route optimization model under the normal circumstance cannot be directly used in public health emergency scenarios. The optimization model and algorithm of customized bus route based on the emergency scenario can obtain the optimized scheme from many alternatives through the fast calculation. It can not only meet the requirement of epidemic prevention, but also meet people's travel needs under public health emergencies.More>

2020, 20(3): 89-99. doi: 10.19818/j.cnki.1671-1637.2020.03.008

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System dynamics simulation on spread of COVID-19 by traffic and transportation

ZHONG Peng-yun, YIN Hui

Abstract: To research the influence of traffic and transportation on the spread of corona virus disease 2019(COVID-19), the model of COVID-19 spreaded by traffic and transportation was established based on the system dynamics. Based on the hypothesis of model, the population was divided into the susceptible individual, explored individual, infected individual and removed individual. According to the spreading characteristics of COVID-19, the modified susceptible-explored-infected-removed(SEIR) and susceptible-explored-infected(SEI) spreading dynamics equations of COVID-19 of epidemic area, port, station, car, ship and related area were established under the influence of traffic and transportation. Based on the analysis of spread process of COVID-19 by traffic and transportation, a causal loop of the system dynamics model of traffic and transportation spreading the COVID-19 was drawn, and a causality feedback loop was analyzed. The model of COVID-19 spreaded by traffic and transportation was established based on the system dynamics, and the dimensional consistency, mechanical error, model validity, and extreme condition of the model were tested. Taking the City A as the research example, the influence of traffic and transportation on the spread of COVID-19 was researched by establishing three simulation scenarios. Simulation result shows that the number of individuals infected with the COVID-19 in City A reaches a peak on the 32 nd day after the outbreak, and 77 726 people were infected, and that of the area outside the City A reaches the peak on the 30 th day after the outbreak, and 28 084 people were infected. The traffic and transportation have positive feedback effects on the spread of COVID-19. The peak volumes of infected and removed individuals of COVID-19 under the influence of traffic and transportation are 18.62 and 10.99 times of those without the participation of traffic and transportation, respectively. Therefore, the traffic control measures have a positive effect on controlling the development and preventing the spread of COVID-19. The increase of public transport proportion will accelerate the spread of COVID-19. Therefore, reducing people's travel demands and the proportion of public transport, and increasing the virus elimination work of public transportation car, ship, port and station can effectively slow down the spread of COVID-19.More>

2020, 20(3): 100-109. doi: 10.19818/j.cnki.1671-1637.2020.03.009

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Epidemic risk assessment and active protection strategy of high-speed train

XIE Guo, JIN Yong-ze, JI Wen-jiang, HEI Xin-hong, MA Wei-gang, WANG Dan, CHEN Pang, YE Min-ying

Abstract: Considering the danger of infectious disease in closed train compartment, the spatial distribution characteristics of the virus were studied. Combined with the correlation analysis result of the distances between passengers, the infection prediction model of passenger was constructed, and the risk of each passenger infected with virus in the case of existing multiple infections was evaluated. In order to reduce the infected risk of passenger, the active protection strategies for train passengers were formulated, and a hybrid heuristic algorithm based on greedy algorithm and variable neighborhood local search algorithm was proposed to optimize and solve the passenger seat arrangement problem. Through the distance-based greedy algorithm, the arrangement of passenger seats in the fixed coordinate was converted into the problem of the maximum number of passengers and the minimum number of virus overlapping areas, and the feasible solution of the seat was obtained. The feasible region was obtained by summing up the feasible solutions, the feasible solution of the seats was improved based on variable neighborhood local search algorithm, and the optimal scheme of seat arrangement was obtained. Research result shows that the risk of passengers infected with virus can be predicted effectively by the infection probability evaluation model, and the infection risk of passengers can be reduced effectively by the active protection measures combined with the hybrid heuristic algorithm. For the short-distance passengers, with the increase of the number of passengers and the number of people infected in the compartments, the number of people with high risk infection increases from 1 to 7, the number of people with medium risk infection increases from 0 to 3, and the number of people with low risk of infection increases from 47 to 83. Compared with the disordered sitting without control, the risk of passenger infection can be eliminated by the seat arrangement strategy.More>

2020, 20(3): 110-119. doi: 10.19818/j.cnki.1671-1637.2020.03.010

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Dynamic marshalling and scheduling of trains in major epidemics

CAO Yuan, WEN Jia-kun, MA Lian-chuan

Abstract: In order to reduce the infection risk of passengers who travel by urban rail transit in the context of the global epidemics outbreak, the marshalling and scheduling of trains were taking as the research objects, and a dynamic marshalling and scheduling method of trains based on the virtual coupling under the major epidemic was proposed. In order to improve the flexibility of train marshalling and scheduling in urban rail transit, the virtual coupling was applied to the train marshalling in urban rail transit. The nonlinear programming model of train dynamic marshalling based on the passenger flow was established to optimize the scheduling of urban rail transit trains, so as to improve the transport efficiency of urban rail transit, reduce the station personnel density and consequently reduce the risk of disease infection. The improved Wells-Riley model was used for the infection analysis. The pedestrian movement model based on the social force was used to calculate the parameters in the improved Wells-Riley model, so as to analyze the infection risk of passengers who travel under the dynamic marshalling of virtual coupling. The infection probability under the virtual coupling system was simulated and compared with the result under the traditional method by using the MATLAB. Analysis result shows that the virtual coupling technology can significantly improve the train transport efficiency of urban rail transit and shorten the tracking time interval between trains to 34.6 s. The dynamic marshalling and scheduling method of trains based on the virtual coupling can effectively reduce the infection risk of passengers. In the same conditions, the infection risk of passengers from the proposed method is only 85.1% of that from the traditional way, and the infection risks in the carriages and channel are 50.0% and 8.7% of those from the traditional way, respectively. If the proposed method is combined with the measures such as the control of off-peak travel and passenger flow, the in-station epidemic prevention and testing, the infection risk of passengers can reduce further.More>

2020, 20(3): 120-128. doi: 10.19818/j.cnki.1671-1637.2020.03.011

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Construction of evaluation index system for emergency rescue capacity of rail transit under serious epidemic situation

CHEN Ding-jun, SUN Yun-hao, LI Jun-jie, NI Shao-quan

Abstract: The pre-selection evaluation indicators of railway emergency rescue capability under serious epidemic situation were constructed from three aspects, including railway emergency preparation capability, railway emergency response capability and railway emergency recovery capability. In order to improve the scientificity, feasibility, independence and reliability of the indicators, the transitive closure method was used to select the indicators. The evaluation indicator system of railway emergency rescue capability under serious epidemic situation was established, including 3 first level indicators, 15 second level indicators and 49 third level indicators, and the indicator weights were calculated by analytic hierarchy process based on triangular fuzzy number. Analysis result shows that, in the first level indicators, the weights of railway emergency preparation capability, railway emergency response capability and railway emergency recovery capability are 0.26, 0.53 and 0.21, respectively, and the weight of railway emergency response capacity is the largest. During the epidemic period, the transportation of medical staff and materials should be guaranteed, and the effective measures are taken to prevent the further spread of the epidemic. Among the second level indicators of the railway emergency preparation capability, the weight of emergency materials indicator is the largest with the value of 0.29. In the preparation stage, it is necessary to prevent the situation from getting worse, do a good job in emergency materials storage, increase the proportion of emergency materials funds, clarify the right and responsibility of each emergency organization, and timely improve and update the emergency plan. The weight of operation recovery is 0.47, which accounts for the largest proportion in the second level indicators under the railway emergency recovery capacity. In the recovery stage, the number of operating trains should be increased, the information of operating trains should be open timely, and the resumption special train should be set up. The system provides a scientific and effective reference for improving the railway's emergency rescue capability under serious epidemic situations.More>

2020, 20(3): 129-138. doi: 10.19818/j.cnki.1671-1637.2020.03.012

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Modeling and forecasting of COVID-19 spread in urban rail transit system

LEI Bin, LIU Xing-liang, CAO Zhen, HAO Ya-rui, ZHANG Yuan, CHEN Xin-miao

Abstract: Passenger group in urban rail transit system under the COVID-19 epidemic was divided into susceptible, infected and exposed ones considering urban rail transit travel characters. In the research environment of COVID-19 free spread and the case sampling time of early spread, the infection probability of 0.41 was selected based on related studies. The urban rail transit ridership in COVID-19 case was divided into inbound/outbound phase and riding phase. Considering COVID-19 effective spread range, passengers distribution and moving characters, the COVID-19 spreading model in the urban rail transit system was built. Taking the metro system in a certain city as the simulation case, 13 patients in metro ridership cases were assumed. With the accessibility of historical passenger data, the parameters in the model were determined. The possible infections in different loading levels were forecasted, and the elements related to possible infections were discussed. Analysis result indicates that when the loading level decreases to 10% of the average level, the possible infections in most cases are less than 1, which proves the effectiveness of current urban rail transit passenger control strength. The change in possible infections caused by the reduction in passenger number in the start/terminal(less than 20%) is less than that caused by the reduction in passenger number in the vehicle(60%-80%). Therefore, the passenger density in the vehicle has more significant impact on the possible infection compared to the passenger number in the start/terminal. When passing the stop, if the ratio of the on/off board passenger numbers is no more than 1, the possible infections can be controlled effectively. If making the possible infections nonlinearly and positively correlate to the stop number, the function among the loading level, stop number and possible infections will have better performance(determination coefficient is 0.700 1).More>

2020, 20(3): 139-149. doi: 10.19818/j.cnki.1671-1637.2020.03.013

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Transmission mechanism of COVID-19 epidemic along traffic routes based on improved SEIR model

ZHANG Yu, TIAN Wan-li, WU Zhong-guang, CHEN Zong-wei, WANG Ji

Abstract: The characteristics of COVID-19, which is transmitted by contact and droplets and is infectious in the incubation period, were considered. Combined with the narrow space and airtight environment of the vehicle and based on SEIR model, the vehicle internal epidemic transmission model was established considering the factors of virus density, contact and infection rate among passengers, and travel time. Based on the internal epidemic transmission form in the vehicle, the epidemic transmission to the non-epidemic area in the process of the vehicle loading and unloading passengers at multiple stops was considered, and a model of epidemic spread along traffic routes based on population migration was established. The transmission mechanism of the epidemic along traffic routes was analyzed using the two models. Based on the population migration index and confirmed cases in Wuhan, the relationship between confirmed cases and population migration index was analyzed, and the transmission process of the epidemic along the high-speed railway was simulated. Research result shows that the cumulative confirmed cases of each provincial and municipal level have a strong positive correlation with the population migration index, indicating that transportation has a certain role in promoting the spread of the epidemic. There may be some passengers infected within the vehicle when there are infectives. With the backward effect of incubation period, to some extent, it explains that except for Wuhan, the number of newly confirmed cases in urban areas of other provinces in China was at a peak on January 31 to February 5 in 2020. The measures such as isolation and reducing passenger occupancy to reduce the contact between passengers can effectively reduce the infection risk of passengers, and the effect is significantly better than the ventilation and disinfection measures. Therefore, in order to reasonably control the spread of the epidemic along traffic routes, some measures should be taken to reduce the occupancy rate, increase the distance between passengers and reduce the contact rate, supplemented by the measures to increase ventilation and disinfection.More>

2020, 20(3): 150-158. doi: 10.19818/j.cnki.1671-1637.2020.03.014

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Influences and response measures of COVID-19 epidemic on shipping and port industry in China

ZHANG Yong-feng, GONG Jian-wei, YIN Ming

Abstract: The impact of the COVID-19 epidemic on economy, trade and industry was analyzed, and the transmission mechanism and visual impact of shipping and industry under epidemic condition were discussed. Based on Granger test, questionnaire survey, enterprise research and expert interview, the overall impacts of shipping and port industry were evaluated. Focusing on different market segments, the different impacts on ports, containers, tankers, dry bulk cargoes, cruise ships and other subdivisions were evaluated. Combined with the current difficulties of the shipping and port industry, major countermeasures were put forward. Research result shows that the COVID-19 epidemic has taken a severe recession on global economy, trade and industry, and has been transmitted to the shipping industry by global supply chains. There is a strong Granger causal relationship between the COVID-19 daily new cases and the Baltic Dry Index. In the first quarter of 2020, the throughput of cargo and containers of main monitored ports in China were 105 353×10⁴ t and 3 766.6×10⁴ TEU, respectively, and year-on-year decrease by 3.5% and 8.6%, respectively. The epidemic has a greater short-term impact on dry bulk cargo, containers and oil tankers. In February 2020, the throughput of the eight major container hub ports declined by 19.8% year-on-year, and cruise passenger transport was hit by the overall closure. The recovery will be a slow process, and the COVID-19 epidemic will continue to have a negative impact on the shipping and port industry. It is suggested that some measures are put forward such as strengthening overseas port policy and port linking tracking, avoiding ship charter disputes and legal risks, improving the system of prevention and control of cruise ships, and promoting the development of smart ports and smart shipping.More>

2020, 20(3): 159-167. doi: 10.19818/j.cnki.1671-1637.2020.03.015

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Distribution of emergency medical supplies in cities under major public health emergency

ZHAO Jian-you, HAN Wan-li, ZHENG Wen-jie, ZHAO Yang

Abstract: To improve the emergency rescue efficiency of medical supplies and reduce the casualties and economic losses in cities under the major public health emergency, based on the characteristics analyses of major public health emergencies and emergency logistics, the demand urgency was taken as the influencing factor of distribution. The evaluation index system for medical supplies demand points was proposed with the evaluation indexes of population within jurisdictions, confirmed and suspected cases of infection, scale of medical supplies demand point, number of medical staff and gap rate of medical supplies. According to the characteristics of emergency logistics of medical supplies, the time window parameters of medical supplies distribution were adjusted. The total distribution cost function composed of driving cost, penalty cost of distribution delay and subsidy without distribution delay was established. Considering the constraints of vehicle load, distribution time window, and demand urgency of medical supplies, a dual objective of priority distribution for demand points with the minimum total distribution cost and high demand urgency was constructed to optimize the distribution path of medical supplies. Relying on the software platforms of SPSS, Yaahp and MATLAB, and combining with examples, the analytic hierarchy process and genetic algorithm were used to solve the optimization models of emergency logistics distribution path of medical supplies with and without the consideration of demand urgency. Research result shows that under the major public health emergency, the optimal distribution path considering the demand urgency not only gives priority to the medical supplies demand points with higher demand urgency, but also reduces the total distribution cost by 5.8%, comparing with the distribution path without the consideration of demand urgency. The introduction of demand urgency can greatly reduce the blindness of scheduling. The dual objective optimization model restrained by the conditions of vehicle load, distribution time window and demand urgency of medical supplies can effectively improve the emergency rescue efficiency and reduce unnecessary scheduling costs.More>

2020, 20(3): 168-177. doi: 10.19818/j.cnki.1671-1637.2020.03.016

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Optimization model of electric coal ship scheduling under considering ship storage and port congestion

CHEN Kang, ZHAO Zi-zhou, WU Ming-hao, XIN Xu, CHEN Zi-gen

Abstract: In view of the actual characteristics of Chinese electric coal water transportation system, the factors of ship storage and port congestion were comprehensively considered, and a mixed integer programming optimization model was established to optimize the scheduling scheme of electric coal ships. Based on the interactive relationship among hard time window of transportation demand, waiting time of ship in unloading port and waterway-railway transportation collaboration, the minimum total cost of the transportation system was taken as objective to collaboratively optimize the freight sharing rates of waterway-railway transportation of electric coal and the task assignment, ship scheduling and storage/commissioning scheme in waterway transportation. Based on the improved column generation algorithm, a column generation algorithm was proposed to accurately solve the actual ship scheduling problem of electric coal transportation. The Gurobi was used to solve the master model generated by the column, and the dynamic programming labeling algorithm was used to solve the sub-model generated by the column. Based on the actual data of a thermal power group in Southern China, an example aimed at the proposed algorithm was analyzed. Calculation result shows that when the proposed algorithm is used to solve the middle-scale example, it takes only 73.61 s to obtain the optimal solution. Compared with the heuristic solution method based on the sequencing of traffic volume in transportation task(PHA), the solution efficiency improves by 18.1%. In a larger-scale example, the calculation time of the proposed algorithm is only 222.02 s, and the computational efficiency increases 19.1% compared with the PHA. In solving an actual scheduling problem, it is found that the proposed optimization model and algorithm can effectively shorten the waiting time of the ship at the unloading port and the active state time of the ship, and reduce the total cost of transportation by 17.13%. Therefore, they can achieve stable transportation of electric coal, improve the operating efficiency of enterprise, and reduce operating cost.More>

2020, 20(3): 178-191. doi: 10.19818/j.cnki.1671-1637.2020.03.017

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Optimization of VTS radar station location and configuration based on fine division of water area

HUANG Chuan, LYU Jing, AI Yun-fei

Abstract: In order to improve the efficiency of maritime safety supervision and ensure the safety production of maritime transportation, the vessel traffic service(VTS) radar station was viewed as the research object, the optimization of VTS radar station location based on the fine division of water area was studied. The effects of the occlusion factors in the actual environment and maritime risk factors on the monitoring performance of radar were considered, and a fine division of water area was proposed based on the software ArcGIS 10.4.1. The location of radar station and configuration type of radar were viewed as decision variables, the maximum coverage of water area and the lowest total cost were regarded as objective functions, then a mixed integer programming model was constructed. Based on the characteristics of the model, the multi-objective particle swarm optimization was designed, the heuristic rules for generating the initial particle swarms were proposed, and effective mutation operations were introduced into the algorithm. In order to verify the validity of the method, the series of ZDT test function were adopted to evaluate the performance of searching for the optimal solution and the convergence of algorithm. Research result shows that the spatial division of water area in consideration of occlusion factors and risk factors can be realized by the proposed method, and the water area monitored by the radar station is divided into 2 812 water area units in the example with 62 candidate radar stations. The global optimal solution in the ZDT test functions can be effectively found by the improved particle swarm algorithm, and the optimal solution with good convergence and average distribution is realized. 95.92% coverage of water area is achieved in the location optimization model of VTS radar station for the example. The total cost is 33 800 yuan. It can be seen that the location optimization model of VTS radar station considering the environmental occlusion and water risk factors is effective. The scientificity and rationality of VTS radar station location can be improved by the improved multi-objective particle swarm optimization algorithm, so it is an effective method to solve the location optimization problem of VTS radar station.More>

2020, 20(3): 192-205. doi: 10.19818/j.cnki.1671-1637.2020.03.018

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Explicit model predictive control of multi-objective adaptive cruise of vehicle

ZHAO Shu-en, LENG Yao, SHAO Yi-ming

Abstract: In order to coordinate both the tracking control effect and real-time performance of adaptive cruise control(ACC) system, a multi-objective adaptive cruise control method of vehicle was proposed via the explicit model predictive control(EMPC) theory. Based on the kinematic relationship between vehicles, an adaptive cruise control kinematics model was established. The tracking error prediction model was derived in the forecast time domain by the predictive control theory. The multi-performance objective functions and constraints of vehicle safety, tracking, economy and comfort were determined. The closed-loop model predictive control system based on the repeated online optimization calculation, was transformed into an equivalent explicit polyhedral piece-wise affine(PPWA) system by the multi-parameter programming theory of explicit model predictive control. The optimal control laws from the distance error, velocity error, self-vehicle acceleration and rear vehicle acceleration to the desired acceleration were obtained by the off-line calculation. The search process of the online control was designed. The adaptive cruise control was realized by the explicit control laws in the partition of the current state vector. The longitudinal tracking conditions were simulated and verified, and the EMPC-ACC was compared with the traditional MPC-ACC. Compared result shows that in the sinusoidal acceleration and deceleration condition of lead vehicle, the single-step operation speed of EMPC-ACC controller improves by 53.51% on average compared with the MPC-ACC controller. Under the EMPC-ACC, the average distance tracking error is 0.220 3 m, and the average speed error is 0.340 1 m·s^-1. In the step acceleration and deceleration condition of lead vehicle, the single-step operation speed of EMPC-ACC controller improves by 72.96% on average compared with the MPC-ACC controller. The average distance tracking error is 0.331 9 m, and the average speed error is 0.399 1 m·s^-1 under the EMPC-ACC. It can be seen that on the premise of guaranteeing the longitudinal tracking performance, the proposed EMPC-ACC controller can effectively improve the real-time performance of the ACC.More>

2020, 20(3): 206-216. doi: 10.19818/j.cnki.1671-1637.2020.03.019

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Collaborative method of vehicle conflict resolution in merging area for intelligent expressway

YANG Min, WANG Li-chao, ZHANG Jian, RAN Bin, WU Jing-xian

Abstract: According to the characteristics of the entire process of connected autonomous vehicles approaching the merging area, the coordination control process of the vehicles driving in the intelligent expressway merging area was set. Aiming at solving the problem of conflict risk in expressway merging area, the factors such as vehicle time demand intensity, vehicle type, and driving intention were considered, and the conflict resolution coordination method of connected autonomous vehicles in expressway merging area was proposed based on cooperative game theory. The vehicle passing merging area under different conditions was simulated and verified by using MATLAB. Simulation result shows that coordination rules of the vehicles driving in the intelligent expressway merging area can realize the coordination of connected autonomous vehicles' passing request. Under the action of cooperative game, the vehicle adjustment decision with the lowest virtual payment cost in the conflict system can be further realized. The degree of vehicle system virtual risk in merging area decreases with the decrease of speed. When the coordination decision is strictly implemented, the connected autonomous vehicles have higher stability in the process of passing merging area. When the length of potential conflict point is within a certain range, the cooperative game effect of two connected autonomous vehicles with the same speed is better than the effect of vehicles with different speeds. The cooperative method reduces the virtual payment cost of the conflict resolution process by 9%-14%, and greatly improves the safety of the process of passing merging area of connected autonomous vehicles.More>

2020, 20(3): 217-224. doi: 10.19818/j.cnki.1671-1637.2020.03.020

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A fast detection method of airport runway area based on region segmentation and Wishart classifier

HAN Ping, CHENG Zheng, WAN Yi-shuang, HAN Bin-bin, HAN Shao-cheng

Abstract: A fast detection method of airport runway area using polarimetric synthetic aperture radar images was proposed based on region segmentation and Wishart classifier. A simple liner iterative clustering algorithm was utilized to partition polarimetric synthetic aperture radar image into many super-pixels, and these super-pixels were regarded as basic units for subsequent classification processing. An optimized distance measurement method was adopted to assign appropriate category labels for the super-pixels, greatly solving the problem of large redundant computation of traditional Wishart distance measurement factor. The polarization scattering characteristics of the pixels in airport runway area were analyzed, and the interest regions were extracted from the classification results using the weak scattering characteristic of airport runway area. The structural characteristics of airport runway were used to select and identify the extracted interest regions, thereby the accurate location of airport runway region was determined. The validity of the proposed algorithm was tested by the measured data from polarimetric synthetic aperture radar, and the detection results were compared with the traditional pixel-based detection results. Experimental result shows that in the large complicated scenes, the algorithm can detect the runway area fast and effectively, and the detected runway has clear outline and relatively complete structure. Using the simple linear iterative clustering algorithm to preprocess the images reduces the complexity of subsequent processing significantly. Based on the experimental data in the Gulf of Mexico, the processing unit number of Wishart classifier is only 1.0% and 2.4% of the numbers of Freeman+Wishart algorithm and FCM+Wishart algorithm, respectively, and the whole detection time is 9.9% and 27.1% of those of Freeman+Wishart algorithm and FCM+Wishart algorithm, respectively. Based on the experimental data in the Big Island, the processing unit number of Wishart classifier is only 1.0% and 2.6% of those of Freeman+Wishart algorithm and FCM+Wishart algorithm, respectively, and the whole detection time is 14.0% and 31.8% of those of Freeman+Wishart algorithm and FCM+Wishart algorithm, respectively. Thus, the real-time performance of the proposed detection method is superior to that of the pixel-based detection method.More>

2020, 20(3): 225-236. doi: 10.19818/j.cnki.1671-1637.2020.03.021

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