交通运输工程学报

Development trends of waterway transportation technology

YAN Xin-ping, HE Ya-peng, HE Yi, FAN Ai-long, LIU Jia-lun, ZHANG Di

Abstract: A bibliometric analysis of literatures related to waterway transportation technology trends was carried out to sort out the research lineage in terms of major research countries, authors and keywords. The current development of waterway transportation technology was analyzed and summarized by comprehensively studying guiding policies, forward-looking reports and typical cases of waterway transportation development both in China and abroad, and the future development trend of waterway transportation technology was judged. Research results show that waterway transportation technology will develop in the following five directions. In terms of waterway carriers, transport vessels will gradually require less manpower, and inland river, offshore and deep-sea vessels will form a spectrum. In terms of shipping infrastructure, the waterway facilities, energy supply, and information networks will be integrated. The ship-shore collaboration ability will be strengthened, the ship remote control can be realized, and the construction of shore-based ship control centre will become an important part of waterway transport infrastructure. In terms of ship power, increasingly stringent emission reduction targets will promote the development of ship clean energy, and the ship power system will be driven by multi-diversified energy and electricity. In terms of ship navigation, multi-ship cooperative transportation can improve transportation efficiency, and the inland river and offshore ship formation navigation becomes a new mode of transportation. In terms of maritime supervision and safety, the application of intelligent system makes ship human-caused accidents gradually reduce, and intelligent unmanned system rescue becomes a reality. The research results can effectively guide the future planning, design, construction and application of waterway transportation system, and provide strong support for cultivating and developing new waterway transportation industry and gradually realizing the future new generation shipping system.More>

2022, 22(4): 1-9. doi: 10.19818/j.cnki.1671-1637.2022.04.001

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Overview on ship formation control

LIU Chen-guang, HE Zhi-bo, CHU Xiu-min, WU Wen-xiang, LI Song-long, XIE Shuo

Abstract: The characteristics of ship formation control were studied, and its current situation and methods were analyzed from the aspects of the structure of ship formation control, formation path planning, formation motion modeling, and formation motion control. The principle of ship formation control was introduced, and the mathematical representation methods and application scenarios of leader-follower structure, virtual structure, graph theory structure, and behavior-based structure of ship formations were described. For the path planning of ship formations, the latest methods and characteristics of formation environment modeling, global path planning, and local collision avoidance planning were summarized, and the local collision avoidance effect of ship formations based on the particle swarm optimization algorithm was demonstrated. For the motion modeling of ship formation control, a hydrodynamic model of ship formations considering the disturbance, control delay, and constraints was built and verified in the contral scenario of a ship formation passing through the lock waterway. For the motion control of ship formations, the characteristics of typical centralized, decentralized, and distributed formation controllers were summarized. It was pointed out that the distributed formation controller had better robustness and scalability, and hence, a formation navigation controller based on the distributed model predictive control was designed. Analysis results show that the technical bottleneck of ship formation control is mainly reflected in the aspects such as the integration of manned/unmanned formations, inland ship formation control mainly based on shore-side driving and control, ship formation control under uncertain disturbances, robust ship formation control under communication constraints, ship formation control in special waters, and consistency of ship formation control. In the future development of ship formations, the following key problems should be addressed: distributed collaborative control of ship formations, diversified control of ship formation tasks, ship formation control based on the biological group mechanism, ship formation control in special waters, and application of artificial intelligence technology in ship formation control.More>

2022, 22(4): 10-27. doi: 10.19818/j.cnki.1671-1637.2022.04.002

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Review on energy saving and emission reduction strategies of green container ports

PENG Yun, LI Xiang-da, WANG Wen-yuan, REN Li

Abstract: The energy saving and emission reduction strategies of green container ports were reviewed, the research achievements of the measures and effect quantification for energy saving and emission reduction in terms of ships, yard cranes, trucks, and quay cranes were summarized, and the future research directions were proposed. Research results show that marine alternative fuels, including liquefied natural gas (LNG), biofuels, and renewable energy show great potential in emission reduction. In terms of difficulties in the application of ships powered by alternative fuels, future research can be carried out to analyze the construction time sequence of supporting facilities by alternative fuels and the determination of subsidy policies. On the basis of different emission coefficients of different regions, CO₂ emissions of ships can be reduced by 48.0%-70.0% by applying shore power technologies. In view of the low utilization rate of shore power facilities, the pricing of shore power and the time sequence of retrofitting ship and port supporting facilities will become the focus of future research. Reducing ship speed can reduce 8.0%-20.0% CO₂ emission from ships at port. The CO₂ emissions of ships at port cannot be significantly cut by shortening unproductive waiting time and auxiliary operation time of ships, and how to reduce the waiting time of ships at port by reasonable scheduling of port resources can be studied in the future. SO₂ emission of ships can be cut by 33.0%-34.6% by setting up sulfur emission control areas, and research on the impact of emission control areas on ship operation and port operation can be carried out. Energy saving and emission reduction measures for yard cranes, trucks, and quay cranes mainly concentrate on equipment transformation and scheduling optimization, and research can be conducted on the time sequence of retrofitting existing facilities and equipments for energy saving, and the comprehensive emission reduction effect under the integration of various emission reduction measures of ships and loading/unloading equipments at port. The application of new energy supply system at port is still in its infancy, and the design method of new energy system can be studied to build a clean and low-carbon port energy system in future.More>

2022, 22(4): 28-46. doi: 10.19818/j.cnki.1671-1637.2022.04.003

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Review on key technologies of hydrogen fuel cell powered vessels

XU Xiao-jian, YANG Rui, JI Yong-bo, ZHANG Xin-yu, JIANG Lei, LI Kun

Abstract: Existing hydrogen fuel powered vessel types in the world were listed, and their characteristics were summarized. The research progress in the key technologies of hydrogen fuel cell powered vessels was analyzed in terms of standard specifications, power source, hydrogen production, hydrogen storage, and hydrogen safety. According to the navigation environment, structure, and operating condition of vessel, the challenges in the key technologies of hydrogen fuel cell powered vessels and the measures to deal with these challenges were proposed. Analysis results show that at present, the number of hydrogen fuel powered vessels in the world is limited. Most of them are small passenger vessels in inland rivers and lakes and are fueled mainly by hydrogen cells. The hydrogen is mostly stored in gas cylinders with high pressure of 35 MPa. The relevant standard specifications for hydrogen fuel cell powered vessels are still being formulated, and the standards and specifications for the building, testing, and application of vehicles fueled by hydrogen cells can be taken as references. Proton exchange membrane fuel cells (PEMFCs) are the most widely used hydrogen fuel cells. Catalyst, bipolar plate, membrane electrode, and sealing material all have important impacts on the performance of PEMFC. In order to increase the applicability of hydrogen fuel cells for vessels, it is suggested to develop high-power fuel cell modules, and the environmental suitability of fuel cells should be studied under the conditions of humidity, heat, salt spray, tilt, and swing. Currently, hydrogen production industries in China still focus on hydrogen production by coals, and it is necessary to produce hydrogen with renewable energy. In short term, compressed hydrogen is the most feasible way for hydrogen storage on board. Light and pressure-resistant storage tanks with high storage density should be developed to improve hydrogen storage density and safety. Furthermore, in order to ensure the safety of vehicles fueled by hydrogen cells, qualitative and quantitative risk analysis methods should be comprehensively utilized to identify risky scenarios, analyze the laws of development and consequence of leakage, diffusion, combustion and explosion of hydrogen by simulation, evaluate the risks, and propose risk mitigation measures.More>

2022, 22(4): 47-67. doi: 10.19818/j.cnki.1671-1637.2022.04.004

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Review on passenger boarding process optimization at civil airports

BAI Qiang, WU Shuai, CAO Rui, MENG Si-yuan, XU Zhi-man

Abstract: On the basis of the recent research on the optimization of passenger boarding process at civil airports, the research status and achievements in this area was analyzed from the aspects of passenger, aircraft, methodology, and COVID-19 pandemic, the methods and measures to optimize the passenger boarding process at civil airports were discussed, and the directions of future studies were explored according to the deficiency in current research. Research results show that in the passenger-oriented optimization studies, the group passengers are considered a significant factor. The minimum boarding time and boarding interference are used as the objective functions to build relevant models, and the passengers with different priorities and latecomers are often considered in groups. WilMA and RP are two boarding strategies with excellent comprehensive performance, and the new Side-Slip seat has the most significant influence on boarding time. The solution of passenger boarding optimization include model methods and simulation methods, in which models mainly include statistical physical model and mathematical model, and simulations include cellular automata and agents. In terms of the COVID-19 pandemic-oriented boarding studies, the health of passengers is the main consideration, where boarding time and health risks are the two primary indicators to evaluate the quality of passenger boarding. In future studies, the advantages of different boarding strategies should be combined to overcome the shortcomings of different individual strategies. The agent-based simulation with strong independence should be combined with the cellular automata simulation that does not highlight the individual heterogeneity. More factors should be considered in optimization models, and better heuristic algorithms should be explored to solve optimization models. Moreover, the impacts of the factors such as the safe social distance, the number of passengers wearing masks, and the number of group boarding passengers on the process of boarding should be attached more importance. It is also an important research direction to explore how to maximize passenger safety and boarding efficiency under the regular COVID-19 epidemic control.More>

2022, 22(4): 68-88. doi: 10.19818/j.cnki.1671-1637.2022.04.005

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Design of coarse-medium-fine aggregates proportion and analysis of air void contour curves

LIU Yu, ZHOU Yu-hui, HUANG Zi-run, MA Jia-ji, WANG Hai-nian, YOU Zhan-ping

Abstract: In order to make the mineral mixture meet the engineering requirements and reasonably match the aggregate particles with different particle sizes, the distribution range of aggregate particle sizes in the mineral mixture was analyzed. The aggregates were divided into three grades: coarse, medium and fine aggregates, and a triangular coordinate system with coarse aggregate proportion as horizontal axis, medium aggregate proportion as vertical axis and fine aggregate proportion as oblique axis was established. A design method of coarse, medium and fine aggregate ratios based on the triangular coordinate system was proposed. With the particle size ratio and initial particle size as indexes, a total of 27 combinations of coarse, medium and fine aggregates were built and each combination had 36 mixing proportions. Through the discrete element simulation, the air void ratios of 972 virtual samples were calculated and the results were plotted in contour maps. The influences of coarse, medium and fine aggregates combinations and mixing proportions on the mixture air voids were studied. Analysis results show that the initial particle size has negligible impact on the air void ratio. The particle size ratio has a great influence on the air void ratio, and gradually decreases with the increase of the particle size ratio. The air void ratio contours show obvious trend. The contours become denser and the regional rules become more and more obvious with the increase of the particle size ratio. The initial particle size and particle size ratio are two types of indexes for the mixture proportion, which have different effects on the void ratio, and the latter can be used as the main index. The influences of volume proportions of coarse, medium and fine aggregates on the void ratio show contour change with regional characteristics in the triangular coordinate system. The maximum void ratio appears near the apexes of the coordinate, and the minimum void ratio appears near the midpoint of the lateral axis. The void ratios on both sides against the oblique axis are significantly different, with a maximum of about 2.8%. The void ratio below the oblique axis is relatively small. The convex points of the void ratio contours point to the apexes of the vertical axis, the concaves point to the middle of the lateral axis, and the density of the curves indicates the difference degree of the void ratios.More>

2022, 22(4): 89-101. doi: 10.19818/j.cnki.1671-1637.2022.04.006

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Secondary aging performance of warm-mix recycled asphalt binder

LI Qiang, LU Yang, WANG Jia-qing, SUN Guang-xu, ZHAO Yao

Abstract: In order to investigate the secondary aging performance of warm-mix recycled asphalt binder, three different recycling schemes were proposed on the basis of two commonly used warm agents and considering the complex coupling effects of regenerants and different modifiers. By the dynamic shear rheological test, the change laws of viscoelasticity performance, rutting resistance performance, and fatigue resistance performance of asphalt binder were analyzed by using the three different warm-mix recycling schemes before and after secondary aging and under different secondary aging degrees. The change laws of surface chemical functional groups and microstructures of asphalt binder under different warm-mix recycling schemes were analyzed by the Fourier transform Infrared and environmental scanning electron microscopy (ESEM) test. Analysis results indicate that the elastic characteristics and rutting resistance performance of recycled asphalt binder after secondary aging are greatly improved by the warm agent Sasobit, but its fatigue life is less than 10 000 under the strain level of 5% and secondary aging. With the combination of Evotherm 3G with SBR latex and rubber powder, the high-temperature performance of recycled asphalt binder after secondary aging is promoted to some extent, and the original low-temperature performance is maintained. Under the combination of Evotherm 3G with SBR latex, the optimal viscoelastic performance is presented, while under the combination of Evotherm 3G with rubber powder, the irrecoverable creep compliance is still less than 0.05 after secondary aging, and excellent rutting resistance performance is shown. The secondary aging mechanisms under different recycling schemes are revealed by the analysis results of microchemical and microphysical properties, and the change laws of chemical functional groups and microstructure characteristics are well correlated with the change laws of dynamic shear rheological properties.More>

2022, 22(4): 102-116. doi: 10.19818/j.cnki.1671-1637.2022.04.007

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Damaged plastic analysis of concrete around dowel bars at joint in cement pavement

ZHOU Zheng-feng, LUO Jun-hao, KANG Yu-feng

Abstract: To reveal the mechanical characteristics and damage mechanism of concrete around the dowel bars at the joints in cement pavement, the concrete damaged plasticity (CDP) model and the method for determining its parameters were introduced on the basis of the finite element software ABAQUS. The uniaxial tension and compression tests of concrete specimens were simulated by the CDP model, and the accuracies of the CDP model parameters were verified by the comparison of model test results. On this basis, a three-dimensional finite element model of cement pavement with dowel bars at joints was built to analyze the distribution and development laws of the plastic strain, damage factor, and equivalent stress of concrete around the dowel bars at the joints subjected to different axle loads. Under the CDP model and elastic model of concrete, the difference between the two models in the stress of concrete around the dowel bars was compared. Analysis results show that for the uniaxial tension and compression specimens of concrete, the entire stress-deformation curves achieved by the simulation with the CDP model are consistent with the test results, indicating that the CDP model and its parameters are accurate. For the cement pavement with dowel bars at joints, when the load is applied at the edge of upper slab of the bonded end of a dowel bar, the stress in the concrete around the bonded end of the dowel bar is most disadvantageous. With the increase in the axle loads, the damaged plasticity is encountered first in the concrete at the bottom of bonded end of the dowel bar, and the equivalent stress reduces gradually. When the axle load raises from 100 kN to 250 kN, the range of plastic zone extends from 135°-225° at the bottom to 60°-300° for the concrete around the dowel bar. The concrete in the range of 150°-210° at the bottom is subjected to failure due to the complete damaged plasticity, and the equivalent stress becomes zero. More loads are borne by the concrete on both sides and at the top of the dowel bar due to the stress redistribution. If the elastic model is adopted for the concrete around the dowel bar, the equivalent stress of the concrete at the bottom of the dowel bar will be on the rise to exceed the ultimate strength. Therefore, the CDP model is recommended to analyze the stress concentration of concrete around the dowel bars.More>

2022, 22(4): 117-127. doi: 10.19818/j.cnki.1671-1637.2022.04.008

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Simulation on strength and thermal shrinkage property mechanisms of pre-cracked cement stabilized crushed stone

SU Pei-feng, LIU Yu, LI Miao-miao, HE Zhen-zhen, YOU Zhan-ping

Abstract: For the problem that the cement stabilized crushed stone tends to develop cracks, thus reducing the service life of pavements, an idea based on the coarse aggregate pretreatment technology was proposed to improve the pre-cracked cement stabilized crushed stone material. Some coarse aggregates of the cement stabilized crushed stone were pretreated to make their surfaces coated with a layer of new material, and thus a new interface was formed, to alleviate the influence of reducing cracks on the overall uniformity of the material during the shrinkage process. Then, the strength properties and the internal mechanism of crack development under the thermal shrinkage of new material were analyzed through simulations. A simulation model of the pre-cracked cement stabilized crushed stone was built based on the discrete element method. The virtual unconfined compression tests and restrained thermal shrinkage and cracking beam tests were conducted, respectively. Research results show that under the premise that the pretreatment of coarse aggregates only affects the interface strength of coarse aggregates, there is a good linear correlation between the unconfined compressive strength of the specimen and the two key parameters including the interface strength ratio, as well as the pretreated coarse aggregate replacement ratio. The unconfined compressive strength can be calculated and predicted through the regression formulas. When the interface strength ratio is higher than 40%, the increase in the pretreated coarse aggregate replacement ratio will only reduce the material's strength and cannot avoid the locally transverse cracks. When the interface strength ratio is lower than 40%, the cracks appearing during the shrinkage process of the specimen will change from the locally transverse cracks to the evenly distributed micro-cracks as the pretreated coarse aggregate percentage increases, thus ensuring the overall uniformity of the material after the shrinkage cracking. When the interface strength is less than 30% of that of the untreated material, and the coarse aggregate replacement ratio is higher than 30%, the internally transverse cracks of the specimen will be effectively reduced, and the thermal shrinkage cracking of the cement stabilized crushed stone can be alleviated.More>

2022, 22(4): 128-139. doi: 10.19818/j.cnki.1671-1637.2022.04.009

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Influence of geometric alignment of expressway superelevation transition section on hydroplaning speed of minibus

JIA Xing-li, CHEN Xing-peng, HUANG Ping-ming, MA Qing-wei, LI Shuang-qing, YAN Meng-hua

Abstract: In order to reveal the change laws of hydroplaning speed of minibus under different geometrical alignment factors at expressway superelevation transition section, the relationships among hydroplaning speed, water film thickness and superelevation transition geometric alignment factors were analyzed according to the tire force characteristics of minibus during hydroplaning process. Based on the multivariate linear regression and fluid simulation, a quantitative model of hydroplaning speed of minibus at superelevation transition section was established. Combined the rainfall intensity, longitudinal slope and superelevation transition rate, the critical hydroplaning speed of minibus was calculated. Taking the superelevation transition section of a typical four-lane expressway as an example, the influence law of rainfall intensity, longitudinal slope and superelevation transition rate on the hydroplaning speed of minibus was studied, and the recommended limit speed value at superelevation transition section was given. Research results show that the maximum value of hydroplaning speed of minibus is 115.5 km·h^-1 under the combination of longitudinal slope of 0.3%, superelevation transition rate of 1/200 and rainfall intensity of 20 mm·h^-1, and the minimum value of hydroplaning speed of minibus is 99.3 km·h^-1under the combination of longitudinal slope of 3.0%, superelevation transition rate of 1/330 and rainfall intensity of 80 mm·h^-1. Under the condition that rainfall intensity and superelevation transition rate are certain, the hydroplaning speed decreases gradually with the increase of longitudinal slope, and decreases by 2.68% when the longitudinal slope increases from 0.3% to 3.0%. Under the condition that the rainfall intensity and longitudinal slope are certain, the hydroplaning speed increases gradually with the increase of superelevation transition rate, and increases by 2.25% when the superelevation transition rate increases from 1/330 to 1/200. Increasing the longitudinal slope can reduce hydroplaning speed. However, when the rainfall intensity increases to a certain degree, the influence of longitudinal slope and superelevation transition rate on the hydroplaning speed tends to be flat. When the rainfall intensity is 20-80 mm·h^-1, the recommended limit speed is 95.0-115.0 km·h^-1, but not greater than the design speed.More>

2022, 22(4): 140-147. doi: 10.19818/j.cnki.1671-1637.2022.04.010

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Conversion relationship between uniaxial compressive strength and point load strength of sandy slate

CHEN Jian-xun, CHEN Li-jun, LUO Yan-bin, XIE Jiang-tao, WU Yun-fei, LIU Wei-wei

Abstract: The sandy slate exposed in the excavation of the Muzhailing Tunnel of Weiyuan-Wudu Expressway in Gansu Province was taken as the object, and the uniaxial compressive strength test and point load strength test of sandy slate were carried out. The uniaxial compressive strength and point load strength of sandy slate as well as their conversion relationship were obtained through a normal distribution test, highly abnormal data elimination, and confidence interval strength statistic analysis of the test data. In addition, the conversion formulas were compared with those recommended by relevant codes for rock tests and the International Society for Rock Mechanics (ISRM). Research results show that the uniaxial compressive strength of saturated sandy slate obeys the normal distribution, with an average value of 56.3 MPa and a confidence interval of 49.2-63.5 MPa under a confidence level of 95%. The point load strength of saturated sandy slates is not completely consistent with the normal distribution, with an average value of 7.36 MPa and a confidence interval of 6.50-8.22 MPa under a confidence level of 95%. There is a significant linear positive correlation between the point load strength and uniaxial compressive strength of the saturated sandy slate. The rock strength is affected by the direction, filler, width, and length of internal joints and fissures of each specimen, and the overall discreteness of the strength data is high. The conversion coefficients between the uniaxial compressive strength and point load strength of sandy slate in saturated and dryed states are 7.72 and 8.72, respectively. They are obviously smaller than the conversion coefficient ranging from 15 to 30 in most studies. The reason is that there are bedding or joints and fissures with different angles in the sandy slate, and the uniaxial compressive strength is greatly affected by the internal joints and fissures of the specimen, resulting in a low average strength, while the point load strength is less affected by the internal joints and fissures of the specimen. The uniaxial compressive strength of sandy slate predicted by the formulas recommended by codes and ISRM is 2-4 times the measured value and will inevitably lead to large deviations in tunnel designs. In comparison with the formulas recommended by codes and ISRM, the obtained relative error of the conversion relationship between the uniaxial compressive strength and point load strength is not more than 15%. It can be used as a useful supplement to the formulas in codes.More>

2022, 22(4): 148-158. doi: 10.19818/j.cnki.1671-1637.2022.04.011

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Dynamic response of bridge pile foundation near fault under strong earthquake

FENG Zhong-ju, ZHANG Cong, HE Jing-bin, GUAN Yun-hui, YUAN Feng-bin

Abstract: In order to find out the difference in the dynamic responses of bridge piles on the hanging wall and footwall of the fault under a strong earthquake, relying on the Haiwen Bridge project in Hainan Province, the shaking table model test was carried out to study the response differences of pile acceleration, pile top relative displacement and pile bending moment response laws, and the piles damage characteristics on the hanging wall and footwall of the fault under the action of 0.15g-0.60g ground motion intensity. Research result shows that the difference between pile top peak accelerations on the hanging wall and footwall of the fault is 0.291-0.488 m·s^-2, and the difference in the amplification factor of pile top acceleration is 0.067-0.195 under the different ground motion intensities. The reason is the difference in the influence range of the fault on the rock and soil mass on both sides and the "non-linear" difference of the rock and soil mass around the pile. With the increase of earthquake intensity, the difference between the pile top relative displacements on the hanging wall and footwall of the fault increases gradually, and the maximum difference is 0.77 mm. The difference between the maximum bending moments of the pile foundations on the hanging wall and footwall of the fault is 5.294-82.932 kN·m, and the maximum bending moment occurs at the interface of soft and hard soil and near the bedrock surface. The reason is that the footwall, as a stable plate, is squeezed by the soil mass of the hanging wall, which has a certain inhibitory effect on the vibration and shear of the rock and soil mass of the footwall. When the ground motion strength is 0.35g, the maximum bending moment of the pile on the hanging wall and footwall of the fault does not exceed the bending bearing capacity, which meets the requirement of seismic fortification intensity Ⅷ of Haiwen Bridge(0.35g). When the ground motion intensity is 0.35g-0.45g, the pile fundamental frequency on the hanging wall of the fault has a small variation range. When the ground motion intensity is 0.50g-0.60g, the pile foundation frequency on the hanging wall decreases significantly. The cracks appear at the connection between the pile top and cap, the interface between the soft and hard soil layer, and the bedrock surface, which shows that the piles have been damaged. In summary, the acceleration of pile, the relative displacement of pile top, and the bending moment of pile on the hanging wall are larger than those on the footwall. The dynamic response changes of the piles on the hanging wall and footwall of the fault are significantly different, which shows significant "the hanging wall effect of fault". Therefore, in the seismic design of bridge pile foundation near the fault under strong earthquake, the seismic capacity of hanging wall pile foundation should be considered.More>

2022, 22(4): 159-169. doi: 10.19818/j.cnki.1671-1637.2022.04.012

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Calculation method of post-tensioned prestressed anchorage loss considering influence of asymmetric friction

WANG Ling-bo, YUAN Hao-yun

Abstract: To improve the calculation method of prestressed anchorage loss of post-tensioned prestressed concrete beams with mixed straight lines and curves and enhance the theoretical calculation accuracy of the prestressed anchorage loss, an static equilibrium equation was established for the micro-segment of prestressed steel bundles. According to the deformation coordination relationship and stress continuity conditions between different steel bundle shapes, the actual influencing parameters of the mixed distribution of straight lines and curves of the prestressed steel bundles as well as the difference between the positive friction and anti-friction losses in design were considered. A piecewise approximation theory for calculating the anchorage loss of prestressed mixed bundles was established. The exact calculation formula of the prestressed anchorage loss was deduced, and a Python program was compiled to realize an automatic solution and simplified calculation. Through the field full-scale model test, the calculation errors of the exact formula and the theoretical algorithm for the prestressed anchorage loss in the current highway and railway bridge design codes were compared. Research results show that the anti-friction effect of post-tensioned prestressed bundles with mixed straight lines and curves for anchorage is smaller than the positive friction effect during the tensioning, and the actual anti-friction influence length greatly deviates from algorithms in the current bridge design codes. The anti-friction influence range calculated by the proposed method is generally closer to that in the Chinese railway bridge design code and is 16.7% and 14.9% higher than the current highway and railway bridge design codes in terms of accuracy and dispersion, respectively. Furthermore, it is highly correlated with the model test data, with small variability. In the related research on the post-tensioned prestressed concrete structures, the influences of the shape of actual prestressed mixed straight lines and curves, as well as the asymmetric positive friction and anti-friction effects, should be considered, and the piecewise approximation method should be used to calculate the prestressed anchorage loss of steel bundles. In the design of post-tensioned prestressed concrete structures, it is recommended to use the current railway bridge design code to calculate the anti-friction effect from the perspective of simplifying the calculation.More>

2022, 22(4): 170-185. doi: 10.19818/j.cnki.1671-1637.2022.04.013

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Abnormal fastener detection model based on deep convolutional autoencoder with structural similarity

LI Qing-yong, WANG Jian-zhu, ZHU Ye-zhou, HUANG Qi-long, PENG Wen-juan, WANG Sheng-chun, DAI Peng

Abstract: The basic functions of rail fastener system were presented, the existing detection technologies for abnormal rail fasteners were outlined, and the concerns and shortcomings of machine vision-based traditional methods and deep learning methods were summarized. The basic idea and formalization process of autoencoder were explained, and an abnormal fastener detection model based on an encoding-decoding architecture was proposed. The drawbacks of traditional pixel-level image similarity metrics were analyzed, and the loss function and image abnormality were determined according to the structural similarity. A dataset of rail fastener images was built and utilized to verify the performance of the proposed model. The representative false-positive and false-negative images were visualized, and their appearance features were described, and the possible reasons for the occurrence of false positives and false negatives were analyzed. According to the research results, the detection performance of the proposed model is significantly enhanced by the structural similarity index. The F-value of the proposed model is 14.5% and 16.2%, respectively, higher than those of the models that have the same network architecture but use the mean absolute error and mean square error as the similarity metrics. The highest detection precision and F-value, as high as 98.6% and 98.1%, respectively, are achieved by the proposed model when it is compared with the other models under comparison. They are found to be 6% and 9.8%, respectively, higher than those of the second-best RotNet model. The recall of the proposed model is 97.1%, slightly lower than the 98.4% of the deep support vector data description (DSVDD) model. On the whole, an F-value over 9% higher than those of all the other models under comparison is achieved by the proposed model, representing a significant performance advantage of the proposed model.More>

2022, 22(4): 186-195. doi: 10.19818/j.cnki.1671-1637.2022.04.014

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Numerical simulation of leakage and diffusion of hydrogen in cabin of fuel cell ship

YUAN Yu-peng, CUI Wei-yi, SHEN Hui, ZOU Zhi-xi, GUO Wei-yong

Abstract: The leakage/diffusion laws and distributions of hydrogen in the compartments of a fuel cell ship under different conditions were studied by the software FLUENT. On the basis of the transient gas leakage and diffusion model, the numerical simulation method was employed to build a numerical leakage and diffusion model of hydrogen in the compartments of the ship, and the effects of different factors on hydrogen leakage and diffusion in the compartments, such as the leakage location, leakage aperture, and ventilation condition, were compared and analyzed. As a result, the diffusion patterns and distributions of hydrogen in the compartments of the ship under different conditions were obtained. Analysis results show that the leakage and diffusion process of hydrogen in a ship compartment includes the initial spray, buoyancy rise, and turbulent diffusion. The top corner of the fuel cell compartment and the upper part between each row of the fuel cell power generation system are the best locations for the hydrogen detection alarms, and hydrogen is more accumulated at the top of the compartment under different leakage conditions. The risks of different locations and different apertures of leakage holes are different at the beginning of the leakage, but the risk evolution patterns are similar with the continuation of the leakage, and the hydrogen concentration near the leakage point is close to 100% after about 60 s. The diffusion of hydrogen to other compartments can be significantly reduced by the installation of explosion-proof exhaust fans in the fuel cell compartment and the adoption of forced air extraction measures to speed up the hydrogen discharge. When the air extraction speed is 1 m·s^-1, hydrogen is discharged from the fuel cell compartment to the outboard area of the ship, and no hydrogen is diffused into the control and passenger compartments. Hence, the safety of the control and passenger compartments can be effectively ensured. The diffusion of hydrogen to the stern, control, and passenger compartments, however, is accelerated by the forced air supply. Thus, the diffusion range of hydrogen is enlarged, and the risk of hydrogen leakage is aggravated.More>

2022, 22(4): 196-209. doi: 10.19818/j.cnki.1671-1637.2022.04.015

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Effect of upper and lower arms diameters on aerodynamic uplift force of high-speed pantograph

DAI Zhi-yuan, LI Tian, ZHOU Ning, ZHANG Ji-ye, ZHANG Wei-hua

Abstract: The pantograph models for the upper arms with seven different diameters and those for the lower arms with seven different diameters were built, and the aerodynamic numerical simulations of pantographs were carried out. The aerodynamic uplift forces of pantographs were calculated by using the multi-body dynamics method, and the effects of the upper and lower arm diameters on the aerodynamic performances and aerodynamic uplift forces of pantographs were studied from the perspective of the aerodynamic force and flow field characteristics. Research results show that both the aerodynamic lift force of the upper arm and the aerodynamic uplift force of the pantograph are larger with the rise of the upper arm diameter and are smaller with the rise of the lower arm diameter under the knuckle-downstream operating conditions, but the effect of the lower arm diameter on the aerodynamic uplift force of the pantograph is small. Moreover, both the aerodynamic lift force of the upper arm and the aerodynamic uplift of the pantograph lessens with the increase of the upper arm diameter and raises with the increase of the lower arm diameter under the knuckle-upstream operating conditions. The aerodynamic resistance of the bar of the upper arm only accounts for 3%-10% of that of the upper arm, and the aerodynamic lift force accounts for 26%-55% of that of the upper arm under both the knuckle-downstream and knuckle-upstream operating conditions. The aerodynamic resistance of the bar of the lower arm accounts for 10%-25% of that of the lower arm, and the aerodynamic lift force accounts for 43%-68% of that of the lower arm under the two conditions. The change of diameter has a great influence on the aerodynamic lift forces of the upper and lower arms and a small effect on the aerodynamic resistances. In addition, the absolute values of the aerodynamic resistances of the upper and lower arms under the knuckle-upstream operating conditions are greater than those under the knuckle-downstream operating conditions. 16 figs, 31 refs.More>

2022, 22(4): 210-222. doi: 10.19818/j.cnki.1671-1637.2022.04.016

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Optimal designs of hole shape and ply of composite plates with holes

QIN Guo-feng, QIN Rui-jian, MI Pei-wen, LI Ming

Abstract: For a larger bearing capacity of composite plates with holes, the hole shape and ply were optimized. On the basis of the damage mechanics model, the simulation analysis model of composite plates with holes was built, and its simulation accuracy was verified. Three kinds of composite plates with circular, triangle, and square holes were selected, and four optimization schemes were applied, i.e., hole shape optimization only, ply optimization only, hole shape optimization first and then ply optimization, and ply optimization first and then hole shape optimization. The failure analysis of composite plates with holes after optimization by different schemes was carried out. Analysis results show that the improvement in the failure load of composite plates with different holes by ply optimization only (7.6%-13.4%) is significantly greater than that by hole shape optimization only (2.0%-2.9%). The failure load of composite plates with triangle holes is improved the most by hole shape optimization only, while the failure load of composite plates with circular holes is improved the most by ply optimization only. When both hole shape optimization and ply optimization are adopted, the improvement effect is significantly better than that of a single optimization scheme, and the improvement in the failure load of composite plates with different holes by hole shape optimization first and then ply optimization is the greatest (11.6%-15.6%). The sequence of hole shape optimization and ply optimization has the greatest influence on composite plates with circular holes (a difference of 3.5%), but has relatively little influence on composite plates with triangle and square holes. Of the composite plates with three kinds of hole shapes, the failure load of composite plates with circular holes promotes the most (15.6%) after the optimization, and the performance of composite plates with circular holes is relatively good and stable in practical applications.More>

2022, 22(4): 223-231. doi: 10.19818/j.cnki.1671-1637.2022.04.017

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Mechanical characteristics test and nonlinear active controller design of energy-regenerative actuator for suspension

CHEN Shi-an, GUAN Yu-liang, REN Jie-yu, YAO Ming, JIANG Dong

Abstract: In order to improve the riding comfort and recover the vibration energy, the mechanical characteristics of a prototyped PMSM-ball screw energy-regenerative actuator were tested. The Coulomb damping and equivalent inertial mass of the actuator were identified, and the nonlinear controller for the corresponding energy-regenerative active suspension was designed. With electromagnetic dynamic modeling and electrical parameter calibration, the mechanical characteristic test on the actuator prototype with the triangle-wave and sine-wave displacement inputs was conducted by the experimental method of stepwise variable voltage charging. The Coulomb damping identification and equivalent inertial mass verification were carried out by the parameter fitting to make the modeling simulation curves of mechanical characteristics approximate the measured ones. For the mechanical active suspension model involving the Coulomb damping and equivalent inertial mass of the actuator, the nonlinear term was processed by the feedforward and feedback linearization, and the acceleration terms of the sprung mass or unsprung mass were normalized. On this basis, a dual-constraints-based H₂/H_∞ controller was developed according to the maximum output force of the actuator. A comprehensive performance comparison among the passive suspension, ideal active suspension, conventional active suspension with H₂/H_∞ control, and active suspension with dual-constraints-based H₂/H_∞ control was made through the numerical simulations for verification and energy-regenerative performance analysis. Analysis results show that compared with the passive suspension, the root mean square of sprung mass acceleration and the comprehensive performance index of the active suspension with dual-constraints-based H₂/H_∞ control reduce by 47.05% and 51.67%, respectively, which are just 1.86% and 1.34% inferior to those of the ideal active suspension, and 19.28% and 11.21% superior to those of the conventional active suspension with H₂/H_∞ control. The total absorption power of the actuator is consumed by the Coulomb damping and motor stator resistance by 18.99% and 20.19%, respectively. By contrast, the average power reclaimed to batteries is as high as 60.82%. 7 tabs, 11 figs, 35 refs.More>

2022, 22(4): 232-243. doi: 10.19818/j.cnki.1671-1637.2022.04.018

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Comprehensive influences of end cover grid on aerodynamic noise and temperature characteristics of an automobile alternator

HUANG Yan, WANG Shi-yu, JIANG Xiao-wen, DONG Da-wei

Abstract: To synchronically improve the aerodynamic noise performance and heat dissipation effect of the current alternator of new energy vehicles and meet the more stringent noise-, vibration-, and harshness- requirements. An alternator was taken as the research object, the comprehensive influence laws of end cover grids on the aerodynamic noise and temperature field distribution were analyzed by the bench experiment and numerical simulation method. The sound pressure level (SPL) distribution of noise was obtained by the five-point method, and the temperature distribution of key components was acquired on the basis of multi-thermocouple measurement points. The flow field, sound field, and temperature field distributions of the alternator were obtained by the computational fluid dynamics simulation software and electromagnetic Maxwell simulation software. The correctness of the numerical calculation model was verified by the experimental results. Upon the analysis of aerodynamic noise characteristics and temperature field characteristics of the original generator, the end covers with different angles of grid side walls were designed to reduce the kinetic energy loss caused by the cooling airflow impact. The reasonable matching of end cover grid angles and fan-blade airflow outlet angles was discussed, and with Newton's law of cooling, the effects of wavy end cover grids on the increase in the area of heat transfer surface and the reduction in aerodynamic noise were studied. Research results show that the end cover grid structure has a great contribution to the aerodynamic noise, and the cooling effect is also significantly affected by the structure. When the side wall of the end cover grid inclines at an angle of 40, a more reasonable match can be achieved with the airflow outlet angle of the fan blade, the energy loss caused by the cooling airflow impact can be effectively reduced. The maximum temperature of the three-phase stator winding reduces by 9.63 K, and the 12th-order aerodynamic noise lessenes by more than 3 dB(A). The wavy end cover grid increases the convective heat transfer area and airflow velocity, while reducing the aerodynamic impact. The heat dissipation of the end cover increases by 7.72 W, and the temperatures of stator core, end cover, and three-phase stator winding decrease by 5.12, 4.94, and 5.29 K, respectively. The 12th-order and 24th-order aerodynamic noises reduce by more than 3 dB(A) with the improvement in eddy currents by grids and the reduction of airflow impact on the grids. 4 tabs, 25 figs, 31 refs.More>

2022, 22(4): 244-258. doi: 10.19818/j.cnki.1671-1637.2022.04.019

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Trunk highway passenger flow forecasting method based on comprehensive transportation network

PEI Yu-long, YUWEN Chong, CHANG Zheng, GAO Zhi-xiang, LIU Tao

Abstract: A trunk highway passenger flow forecasting method integrating multiple transport modes was proposed. By introducing the standard passenger transport unit based on the man-time and the hub nodes conversion method from point to line, the sub-networks of different transport modes, such as highways, railways, airlines and waterways, were integrated, and the comprehensive transportation network model which can reflect the transfer relationship among different transport modes was built. By considering the travel economic cost, travel time, maximum travel recovery time, comfort level and other factors, the impedance functions of different transport modes in the comprehensive transportation network were constructed. The maximum capacities of different transport modes in the comprehensive transportation network were calibrated by using the rated passenger number and the number of departures per unit time. Based on the standard passenger transport unit and comprehensive transportation network model, the passenger flow distribution forecasting model considering the impedance of comprehensive transportation was proposed. On this basis, the passenger flow forecasting model considering the influence of different transport modes was realized. Taking Harbin, Daqing, Suihua and Qiqihar area in Heilongjiang Province as an example, the method was verified. Analysis results show that compared with the actual observation value in 2019, the average error of forecasting results of the passenger flow forecasting method based on the comprehensive transportation network is 5.47%, slightly lower than the 6.14% of the traditional four-stage method when there are no accompanying lines around the characteristic roads. However, the average error of forecasting results of the proposed method is 4.58% when the accompanying lines are around the characteristic roads, far less than the error value 11.89% of the traditional four-stage method. Compared with the traditional four-stage method, the proposed method can better reflect the influence of the transfer passenger on the traffic volume of the trunk highway after the structural change of comprehensive transportation network. Compared with adding waterways, adding high-speed or conventional railways accompanying lines have more obvious impact on the passenger flow of trunk highways, and can promote the transfer of passenger flow from highways to railways. 4 tabs, 12 figs, 32 refs.More>

2022, 22(4): 259-272. doi: 10.19818/j.cnki.1671-1637.2022.04.020

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Lagrangian relaxation heuristic algorithm of arc routing problem under time-space network

CHENG Lin, NING Yi-sen, SONG Mao-can

Abstract: The arc routing problem of road operating vehicles under the time-space network was studied to reduce the vehicle dispatching cost and optimize the vehicle transportation path. In view of the time variation of road travel and the time-space characteristics of vehicle operation, a time-space network was constructed, and a time-space network flow model for the arc routing problem was built. A heuristic algorithm based on Lagrangian relaxation was designed, and the Lagrangian multipliers were introduced to relax the coupling constraints to establish the Lagrangian relaxation problem. Furthermore, the relaxation problem was decomposed into the single vehicle shortest path problem by the Lagrangian decomposition. The sub-gradient algorithm was applied to update the multipliers, solve the Lagrangian dual problem, and update the lower bound of the optimal solution for the original problem. The heuristic algorithm was employed to produce a feasible solution and update the upper bound of the optimal solution for the original problem. Empirical analysis of the algorithm was carried out in different cases under the six-node transportation network and Sioux-Falls network. Calculation results show that the values of the gap between the upper and lower bounds of the six cases in the six-node transportation network are equal to 0 or close to 0. In the Sioux-Falls network, the gap value of Case 2 is 0.02%, and those of the remaining five cases are equal to 0. The approximate optimal solution with high quality can be obtained in all cases. In the most complex case (15 vehicles, 70 tasks), a solution without gap is obtained by the algorithm in an acceptable time, and the optimal vehicle paths are calculated. With the increase of the number of iterations, the Lagrangian multipliers will become fixed through gradual convergence. When the vehicle capacity increases from 50 to 100, the optimal solution reduces from 52 to 42, which shows that when the numbers of tasks and vehicles are constant, an appropriate increase in vehicle capacity is capable of reducing operating cost. Therefore, compared with commercial solvers, the heuristic algorithm based on the Lagrangian relaxation, featuring a smaller gap value and higher solution quality, is able to solve the arc routing problem more efficiently. 7 tabs, 11 figs, 33 refs.More>

2022, 22(4): 273-284. doi: 10.19818/j.cnki.1671-1637.2022.04.021

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Trip reservation and train operation plan optimization method of urban rail transit under demand responsive mechanism

ZHANG Song-liang, LI De-wei, YIN Yong-hao

Abstract: In rail transit systems, the planning of the supply side conflicts with the time-varying characteristics of the demand side. Therefore, an optimization method of trian operation plan for urban rail transit under a demand responsive mechanism was proposed to coordinate the supply and demand relationship. The optimization method includes two steps: trip reservation and demand response. A collaborative optimization model of demand response and train operation plan was established to minimize passenger trip cost and train operation cost, and the delay cost of passengers due to trip reservation was emphasized. The factors such as train operation, transport capacity, train marshalling and passenger distribution were considered, and an adaptive large-scale neighborhood search algorithm based on passenger priority was designed. It was featured with an outer layer optimizing the train operation plan and an inner layer optimizing the passenger allocation, which realizes the matching between the supply and demand of passenger flows. With Beijing Subway Batong Line as an example, a numerical experiment was carried out on its all-day demand management and transportation organization based on the demand responsive mechanism. The results were analyzed from three aspects including locomotive application, passenger waiting time and load rate distribution. Analysis results show that the optimization method can reduce the number of operation trains by 13.8%, and 29.8% of units can be saved by the multi-group mode, which can effectively reduce the operating miles of trains and cut down corporate expenses. Furthermore, the method can shorten the average passenger waiting time at stations by up to 35.3% while ensuring the basic trip of passengers, and the increase in the proportion of reservations has an obvious effect on the reduction of passenger waiting time. The optimized operation plan can make the train load rate maintain at a set level and effectively reduce personnel density to avoid large-scale gathering of passengers, which is a useful exploration and can effectively prevent and control the pandemic appearing in urban rail transit. 2 tabs, 8 figs, 31 refs.More>

2022, 22(4): 285-294. doi: 10.19818/j.cnki.1671-1637.2022.04.022

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Multi-parametric evaluation method of aircraft wake vortex encounter safety in cruise phase

WEI Zhi-qiang, LI Xiao-chen

Abstract: The response mechanism of aircraft after encountering wake vortices was analyzed. Considering the factors such as roll damping characteristics and handling qualities of aircraft, the calculation model for the roll angular acceleration of aircraft was constructed. Due to the change in the flight path and attitude after wake vortex encounters, several disturbance parameters were selected to evaluate the safety of wake vortex encounters, and the calculation model for aircraft dynamics parameters was built. For the determination of the acceptable safety level of wake vortex encounters, the computation data of the disturbance parameters for wake vortex encounters of aircraft combinations at medium and low altitudes were obtained on the basis of the current domestic standard of wake separation. The evolutionary characteristics of the flow fields of wake vortices at high altitudes were analyzed, the wake safety separation at high altitudes was studied, and the influence of different factors on flight safety was analyzed. Research results show that compared with the results at medium and low altitudes, the flow fields of wake vortices at high altitudes are characterized by larger initial strength and duration. Beyond the flight altitude of 9 000 m, the speed of wake vortex dissipation increases with the rise in height. When the leading aircraft is a super heavy aircraft or heavy aircraft, flight safety cannot be guaranteed by current wake separation, and the safety separation should increase by 1.4-2.1 km. When the flight altitude is beyond 13 800 and 14 400 m, the severity of wake vortex encounters reduces. When the leading aircraft is a general heavy aircraft, the wake safety separation can reduces by 1.5 km to improve airspace utilization efficiency. In the case of a medium-size leading aircraft, the safety of wake vortex encounters is high, but due to the limitation of the minimum radar separation, the distance between the leading and following aircraft cannot further reduce. A lower flight speed of the following aircraft is accompanied by more serious wake vortex encounters. When the initial roll bank angle of the following aircraft raises from 0 to 10°, the safety separation of wake vortices raises by 1.3 km, an increase of about 8.61%. It can be seen that the use of multiple disturbance parameters is effective in evaluating the severity of high-altitude wake vortex encounters. 4 tabs, 15 figs, 30 refs.More>

2022, 22(4): 295-305. doi: 10.19818/j.cnki.1671-1637.2022.04.023

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Expanding hub location-routing problem for hybrid hub-and-spoke multimodal transport network considering carbon emissions

LI Hui-fang, HU Da-wei, CHEN Xi-qiong, WANG Yin

Abstract: In view of the high hub saturation, as well as the high cost and low efficiency of direct transportation from a hub to cities of the existing multimodal transport network, a hybrid hub-and-spoke multimodal transport network was proposed to expand the hub locations and optimize the transportation routes. On the basis of the transport network allowing transfer between hubs and tours between cities and considering the low-carbon factors, a mathematical model was built to minimize costs including the total transportation cost, the construction cost to open secondary hubs, the transfer cost at hubs, and the total carbon emission cost. In this way, the problem was decomposed into two stages: the location-allocation and route optimization, and according to the characteristics of the two stages, a two-stage genetic algorithm using the 0-1 coding and digital coding was designed, respectively. The designed algorithm was applied to solve an existing real case, and the optimal transportation scheme obtained by the algorithm was compared with the actual scheme. Research results show that the difference percentage between the optimal solution and its average value obtained by 10 runs of the proposed algorithm is only 4.7%, and the average solution time is only 90.6 s. In the optimized network, two hubs are added, and an unreasonable hub is abandoned. The transfer capacity of the network improves by 11.3%, and the average saturation of hubs reduces by 15.7%. The saturations of different hubs are more balanced than that in the original network. The pressures of saturated hubs are relieved, and the turnover rates of idle hubs are raised to improve the transfer efficiency. The total cost, transportation cost, transfer cost, and carbon emission cost corresponding to the optimized transportation scheme reduce by 68.41%, 68.14%, 56.55%, and 86.76%, respectively, with the most prominent reduction in carbon emissions. It can be seen that the proposed model and algorithm have good performance in expanding the hub-and-spoke network locations and comprehensively optimizing the transportation scheme for the hybrid hub-and-spoke multimodal transport network. 7 tabs, 12 figs, 31 refs.More>

2022, 22(4): 306-321. doi: 10.19818/j.cnki.1671-1637.2022.04.024

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Wireless channel measurement and typical channel characteristics for intelligent inland navigation communications

LI Chang-zhen, CHEN Wei, WANG Jue, CHANG Fu-xing

Abstract: In order to clarify the mechanism of the new generation mobile communication technology in serving intelligent inland navigation, the 4G and 5G temporary wireless communication networks were built based on the development status and special communication environment of wireless communication for inland navigation. With the Wuhan Section of the Yangtze River as an example, the channel measurement work was carried out in typical communication scenarios of inland rivers to explore the influence factors on the wireless communication characteristics of the inland navigations. The channel parameters, such as channel transmission function, received signal strength, and delay, were collected by a high-precision wireless channel sounder. The typical wireless channel characteristics, such as transmission path loss, power delay distribution, delay spread, and Doppler spread, were extracted based on the wireless propagation theory and a tap delay line model. Based on the typical channel characteristic parameters, the effective coverage ranges and transmission rates of 4G and 5G wireless signals in inland river scenarios were predicted, and the multi-path sources and delay distribution of wireless communication for inland navigation were explored. Measurement and analysis results show that bridges, shore buildings, and large passing vessels are the main sources of the multi-path effect of wireless transmission signals in wireless communication for inland navigation. The maximum diffraction loss caused by bridges can reach 18.0 dB. The power attenuations caused by the block of shore buildings and passing vessels can reach 25.0 and 10.6 dB, respectively. The transmission rate of the wireless signals shows that the maximum measurement rate of 4G wireless communication is 95.32 Mb·s^-1, while that of 5G communication can reach 0.72 Gb·s^-1. In addition, the root mean square delay spread will be increased by about 754.94 ns under the influence of large passing vessels. Therefore, a private wireless communication network should be constructed appropriately according to the special environment of inland river communication, so as to provide better communication support services for intelligent navigation.More>

2022, 22(4): 322-333. doi: 10.19818/j.cnki.1671-1637.2022.04.025

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Semantic representation of ship behavior based on context autoencoder

MA Jie, HE Mu-rong, JIA Cheng-feng, LI Wen-kai, ZHANG Yu

Abstract: Considering the temporal correlation of ship behavior, a semantic representation model based on the context autoencoder (SRCAE) was proposed for ship behavior. The behavioral feature parameters, such as the longitude, latitude, speed, as well as the course, were extracted to establish the behavioral feature sequence. The behavioral feature sequence was divided into the center ship behavior and context ship behavior via the continuous bag-of-words (CBOW) model. The deep autoencoder (AE) networks were utilized to construct the semantic representation model of context ship behavior, and the encoded center ship behavior obtained from the model was output as the representation vector. The clustering algorithm was employed to establish the ship behavior dictionary. The South Passage Intersection Water of the Yangtze Estuary was selected as the research object, and the data from the automatic identification system (AIS) for ships were employed for verification of the proposed model and method. Analysis results show that the context relationships between ship behaviors can be effectively represented by the proposed SRCAE model, and the representation error of the SRCAE model is lower than that of the traditional AE model and long short-term memory autoencoder (LSTMAE) model. Three clustering algorithms, namely, k-means, Gaussian mixture model (GMM), and kernel k-means, were used to extract the ship behavior dictionary. Compared with the original data, the representation vectors generated by the SRCAE model are easier to distinguish different ship behavior patterns, among which the effect of k-means is the best, and the Silhouette coefficient (SC), Calinski-Harabasz index (CHI), and Davies-Bouldin index (DBI) of k-means reach 0.384, 18.308, and 0.531, respectively. A total of 30 types of composite behaviors are generated, such as steering acceleration, steering deceleration, straight-ahead acceleration, straight-ahead deceleration, and so on and the combination relationships of ship behavior words under different behavior patterns are effectively extracted.More>

2022, 22(4): 334-347. doi: 10.19818/j.cnki.1671-1637.2022.04.026

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Vehicle-infrastructure cooperative credible interaction method based on traffic business characteristics understanding

SHANGGUAN Wei, ZHA Yuan-yuan, FU Yao, ZHENG Si-fa, CHAI Lin-guo

Abstract: For the credible information interaction in vehicle-infrastructure cooperative environments, the processes of vehicle-vehicle and vehicle-infrastructure cooperative information interaction and the interaction requirements of different modes were analyzed, and a vehicle-infrastructure cooperative credible interaction framework was designed. A model of vehicle behavior state deduction and one of path perturbation factor quantification were constructed. A credibility calculation method for the vehicle object and level evaluation rules were designed. The credible authentication of vehicle object behavior was thereby achieved. A quantification model for the message urgency was built by understanding the effective traffic business characteristics. The low-resolution filtering strategy was used to preliminarily filter the message, and the message content was deeply understood on the basis of the support vector machine (SVM), thereby obtaining a multi-resolution interactive content cognition method. The Veins with OMNeT++ and SUMO simulators was used to build a simulation test environment. Simulation tests were carried out in open roads and intersection scenarios with different penetration rates of connected and automated vehicles (CAVs). The proposed vehicle-infrastructure cooperative credible interaction method was tested and verified. Research results show that the credibility identification for the vehicle-infrastructure cooperative information interaction can be effectively improved by understanding the traffic business characteristics. The average cognitive accuracy for the beacon location message achieved by the proposed method is 90.91%. It is 8.68% higher than that of the credible interaction method based on the timeliness detection. In the credible interaction verification experiment on the safety efficiency message, as the proportion of malicious vehicles increases, the traditional vehicle-infrastructure cooperative credible interaction method based on the voting mechanism is gradually held invalid. In contrast, an average accuracy of 94.96% is achieved by the proposed method under the condition that the single authentication delay is less than 13 ms. It is 3.05% higher than that of the traditional method based on the back propagation (BP) neural network. Moreover, a higher accuracy rate and a lower false negative rate of the credible interaction detection results can be obtained with a higher CAV penetration rate. Therefore, the needs of vehicle-infrastructure cooperative credible interaction can be met by the proposed method.More>

2022, 22(4): 348-360. doi: 10.19818/j.cnki.1671-1637.2022.04.027

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Communication delay compensation method of CACC platooning system based on model predictive control

TIAN Bin, YAO Ke, WANG Zi-jian, GU Gan, XU Zhi-gang, ZHAO Xiang-mo, JING Jun

Abstract: The model predictive control (MPC) and long short term memory (LSTM) methods were used to mitigate the impact of communication delay on the cooperative adaptive cruise control (CACC) platooning system. A communication delay compensation method was proposed to guarantee the string stability of the CACC platooning system. A system framework was designed including vehicle dynamics model, spacing strategy, information topology and MPC controller. Moreover, a quantitative indicator of the string stability was proposed by considering 2 norm and infinite norm conditions. Consequently, a modeling and evaluation methodology of the CACC platooning system was constructed. A MPC method was proposed to take the preceding vehicle acceleration trajectory (PVAT) of the preceding vehicle as reference trajectory, namely MPC-PVAT. The following, traffic safety, traffic efficiency and fuel consumption were considered comprehensively. An objective function was minimized to construct the optimal control. The Pontryagin maximum principle was used to efficiently solve the optimization problem. Furthermore, a long short term memory network was used on the MPC-PVAT. The PVAT was replaced by the predicted result in the MPC of the preceding vehicle. The MPC-PVAT was upgraded to the MPC-LSTM. Therefore, the effect of communication delay was further mitigated. Simulation results show that the upper bound of communication delay is more than 1.5 s by using the MPC-LSTM, and improves by 0.8 and 1.1 s compared with the MPC-PVAT and linear controller, respectively. For the field test results, when the communication delay is 1.2 s, the quantitative indicator of the string stability of the MPC-LSTM improves by 20.33% and 39.35% compared with the MPC-PVAT and linear controller, respectively. Consequently, the MPC-LSTM can guarantee the string stability of a CACC platooning system while the effect of communication delay is well tolerated.More>

2022, 22(4): 361-381. doi: 10.19818/j.cnki.1671-1637.2022.04.028

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Lane offset behavior and free driving trajectory model of hairpin curves of mountain roads

CHEN Ying, WANG Xiao-hui, ZHANG Xiao-bo, CHEN Hai-yuan, XU Jin, DU Zhi-gang

Abstract: A free driving track model was built to reveal the behavior of lane offset and the characteristics of vehicle tracks in hairpin curves of mountain roads. A real vehicle driving test was carried out on a complex mountainous linear road, and high-precision onboard equipment was used to collect vehicle track, speed, and offset data under natural driving conditions. By the relative position curves of the tracks, the free driving track patterns of left- and right-turning vehicles in the hairpin curves were defined. With the curve angle of 180° as the boundary, the fitting model of the relative position of a vehicle in a hairpin curve was constructed, and the calculation method of the free driving track based on the offset was designed. The model was verified by the examples of hairpin curves on other roads. Research results show that the left-turning vehicles in the hairpin curves have four track patterns, while the right-turning vehicles have three track patterns. The vehicle track has large offsets in the entrance, middle part, and exit of the hairpin curves, with an offset of more than 40%. As the opposite lane is occupied by vehicles, different offset features are presented for different track patterns. The distributions of speed and offset corresponding to different positions are discrete, and when the speed compensation is less than 6.5 km·h^-1, the driver can reduce speed loss in the hairpin curve by occupying the opposite lane. Among the track fitting models built on the basis of the lateral offset under different curve angles, the highest accuracy of the models can be achieved when the hairpin curve angle is about 180°, with the fitting precision for left-turning vehicles between 0.90-0.97 and that for right-turning vehicles between 0.65-0.97. When the hairpin curve angle is greater than 180°, the maximum fitting precision of the fitting models is 0.97, and can be observed in the case of right-turning vehicles. When the hairpin curve angle is less than 180°, the maximum fitting precision of the fitting models is 0.89, and can be observed in the left-turning case. Therefore, the proposed track model has strong applicability and can provide means and method for driving track prediction in hairpin curves of mountain roads.More>

2022, 22(4): 382-395. doi: 10.19818/j.cnki.1671-1637.2022.04.029

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Optimization method of long cycle high-level maintenance plan for high-speed EMUs

SHEN Yao-ming, LIN Bo-liang, XUE Jin-bo, WANG Zhong-kai, MENG Yu-fei, XU Zhi-quan

Abstract: The characteristics of different high-level maintenance plans for electric multiple units (EMUs) and their associated factors were analyzed, and the complexity of high-level maintenance planning problem was discussed. A method for scheduling a long cycle high-level maintenance plan for EMUs was proposed on the basis of rolling iteration method, and a complete long cycle high-level maintenance plan was made after the annual high-level maintenance profile plan was obtained for each planning year in the plan cycle in turn. 0-1 variables representing the repair time and maintenance state of EMUs were designed, and the maximization of the running kilometrage by EMUs in the interval between two adjacent high-level maintenance tasks was taken as the objective. The real-life requirements were used as constraints, including the upper maintenance rate limits of EMUs in different periods, the permitted receiving and the maximum maintenance capacities of the maintenance unit, the capital budget for high-level maintenance in the planning year, the allowed number of EMUs for high-level maintenance tasks per month, the average daily control kilometrage of EMUs, and the kilometrage of the train timetable. A linear 0-1 integer programming model was constructed for the optimization of high-level maintenance plans. Based on the historical running data and relevant parameters of 279 EMUs assigned to China Railway Beijing Group Co., Ltd., the model was accurately solved by Python calling commercial solvers to realize the optimization of the long cycle high-level maintenance plan of all EMUs in the railway group for the first time. Calculation results show that in the optimized long cycle high-level maintenance plan for EMUs, 19 high-level maintenance tasks are reduced compared with the manual plan, and the capital consumption of 150.5 million yuan is saved. In addition, the average annual operating time of EMUs is extended by 21 d during the planning period, and the average annual running kilometrage of EMUs increases by 46 080.21 km. Meanwhile, the exceeded maintenance rate and the maintenance capacity beyond the limit occurring in the manual scheme can be avoided, and the efficiency of EMUs operation improves with more scientific planning under the optimized scheme.More>

2022, 22(4): 396-407. doi: 10.19818/j.cnki.1671-1637.2022.04.030

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Academic influence analysis of Journal of Traffic and Transportation Engineering based on big data

ZHAO Zhi-hong, REN Lu, DAI Jie, WU Ming-qian

Abstract: In order to further improve the academic influence and promote the internationalized process of Journal of Traffic and Transportation Engineering, its published data since 2016 were studied based on the database platforms, its present situation, development direction, academic effect, contributions distribution and communication ability were analyzed, and its future development strategies were put forward. Research results show that: since 2016, in the field of comprehensive transportation, it ranks the first in impact factor and comprehensive index, and ranks the top 7% in the field of transportation. Its small number of annual published papers is only 48% of the transportation discipline mean, and its small number of annual highly cited papers is about 80% of the transportation discipline means of Peking University Core Periodical Catalogue and CSCD (Core Edition). So, they are the main influencing factors of impact factor and citation frequency of the journal. High-level special issues/columns, leading academic reviews and research teams' serialized core achievements contribute greatly to the improvement of the academic influence of the journal. Based on the successful experience and research result, the future development strategies of the journal are puts forward from four aspects: content quality construction, academic influence construction, publication team construction and communication capacity construction, namely: gathering publishing talents to improve publishing level, gathering academic resources to improving academic quality, enriching the display of information to enhance communication ability, and purifing the academic environment and optimizing the publishing mechanism.More>

2022, 22(4): 408-420. doi: 10.19818/j.cnki.1671-1637.2022.04.031

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2022 Vol. 22, No. 4

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