Table of Content

25 July 2023, Volume 51 Issue 7

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2023, 51(7):  0. 

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Mechanical Engineering

Design and Optimization of Liner TIG Welding Gun for Nuclear Heat Transfer Tube with Small Diameter



WANG Zhenmin, XIE Huimin, LI Xuyan, et al.

2023, 51(7):  1-11.  doi:10.12141/j.issn.1000-565X.220754

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As China’s nuclear industry enters the third 30 years of development, the maintenance need for nuclear equipment is becoming increasingly urgent. The internal structure of the nuclear steam generator is complex, and the key structure, namely the heat transfer tube, has the restrictions like small diameter, long pipeline and difficult disassembly and installation, which make traditional repair methods extremely difficult in implementation. In order to solve the problem of corrosion damage of small-diameter nuclear heat transfer tube due to long-term high temperature and high pressure condition, an all-position automatic TIG welding gun for liner repair was designed in this paper, and the gun reliability verification and welding repair test were carried out. Firstly, the overall structure design of the welding gun was presented, and the advantages of the designed welding gun comparing with the traditional tungsten electrode TIG welding gun were described. Next, the design and verification of the welding gun transmission system with small size and high space utilization were completed. Then, the stiffness of the key part of the welding gun, namely the conductive shaft, was modelled, analyzed and calculated, and the reliability of the theoretical model was verified by finite element solution. On this basis, an optimization method of the welding gun structure was proposed. Moreover, the field test of deflection and the welding test were carried out, finding that the stiffness of the conductive shaft satisfies the field welding conditions. Finally, linear regression equations and deflection correction formulas were used to quantitatively predict the deflection of the welding gun, and the results verify the rationality of the designed structure. Welding tests results show that the rotation speed of the transmission system is stable and controllable in working condition of welding gun, and the welding seam is well formed. The developed liner welding gun can satisfy the requirements of liner welding repair of the stainless-steel heat transfer tube inside the nuclear steam generator.

Influence of Inflow Direction on Thermal-Hydraulic Performance of Louvered Fin-Common Flow Down Vortex Generator



HU Xingjun, LUO Yufei, ZHANG Jinglong, et al.

2023, 51(7):  12-20.  doi:10.12141/j.issn.1000-565X.220701

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In order to improve the thermal-hydraulic performance of louvered fin and flat tube heat exchangers (LFHE), by arranging common flow down vortex generator (CFDVG) on LFHE’s flat tubes, this paper proposes louvered fin-common flow down vortex generator (LF-CFDVG). Then, considering the use of active grille air shutter (AGS) may change the inflow direction of air at the core of LFHE, the influence of inflow direction on the thermal-hydraulic performance of LF-CFDVG is further studied at the air velocity of 3 m/s. The results show that the pressure drop Δp of LF-CFDVG is always greater than that of Baseline (namely the LFHE without CFDVG) due to the impact of minimum free flow area reduction after the appearance of CFDVG, the increase in frictional resistance caused by the air velocity increment and the differential pressure resistance caused by CFDVG. In the process of γ (inflow direction angle) increasing from 0° to 30°, under the influence of air velocity reduction, Δp of both Baseline and LF-CFDVG decreases, so that increasing γ helps to reduce the resistance to air flow. At the same time, under the impact of high-speed and low-temperature main stream transported by the longitudinal vortices on the tube wall between CFDVGs, the convective heat transfer ability of LF-CFDVG is significantly enhanced, as compared with the Baseline. Moreover, in the process of γ increasing from 0° to 30°, the convective heat transfer coefficients of Baseline and LF-CFDVG both reduce due to the decrease of longitudinal vortex strength and scale, so that increasing γ impairs heat exchange ability. It is also found that the comprehensive performance of LF-CFDVG continuously decreases in the process of γ increasing from 0° to 30°. Thus, increasing γ is not conducive to the improvement of comprehensive performance.

Small-Sample Fault Diagnosis Method Based on Multi-Head Convolution and Differential Self-Attention



CHEN Xindu, FU Zhisen, WU Zhiheng, et al.

2023, 51(7):  21-33.  doi:10.12141/j.issn.1000-565X.220626

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Bearing is one of the most widely used rotating parts in industrial equipment. If the bearing runs in fault condition for a long time, it will cause huge economic loss and threaten personal safety, so that the investigation of bearing fault diagnosis is of great significance. Fault diagnosis technology based on deep learning is becoming more and more mature, but there are problems such as over-fitting, unstable effect and low accuracy in the case of small samples. In order to solve these problems, this paper proposes a Transformer variant model MDT (Multi-Head Convolution and Differential Self-Attention Transformer) to realize end-to-end few-shot fault diagnosis. This model combines the new data embedding algorithm of MC (Multi-Head Convolution) and the DSA (Differential Self-Attention) mechanism. The MC algorithm performs multi-path one-dimension convolution on the sample, extends the sample from one dimension to two dimensions by multi-channel output, and extracts rich fault information in each frequency domain in the original sample through multiple convolution kernel sizes. As compared with the original dot product self-attention in Transformer, the DSA mechanism obtains the corresponding attention weight vector for each feature through the difference, so as to extract deeper fault features from the sample. MDT inherits the powerful ability of Transformer to process sequence data, which can extract richer fault information from time-domain signals and avoid the overfitting problem common in small-sample models. Experimental results show that the proposed method can stably obtain more than 99% test accuracy in the bearing fault diagnosis task with only 100 training samples per fault type, and has strong anti-overfitting ability and strong robustness.

Experimental Investigation into Internal Stress Detection of Aluminum Alloy by Phased Array Longitudinal-Wave Ultrasonic Testing



ZOU Dapeng, ZENG Xinfa, REN Bin, et al.

2023, 51(7):  34-41.  doi:10.12141/j.issn.1000-565X.220322

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Aluminum alloy materials are widely used in the fields such as aerospace, automotive manufacturing and shipbuilding. However, the load stress and residual stress during the manufacturing and equipment process directly affect the mechanical properties and fatigue life of aluminum alloy components. In this paper, for the purpose of evaluating the internal stress of aluminum alloy and on the basis of acoustic elasticity principle, the phased array longitudinal-wave detection technology was studied, and an internal stress detection method of aluminum alloy was set up based on the time difference during longitudinal wave propagation. Then, an experimental system for phased array longitudinal-wave ultrasonic stress detection was set up, and calibration experiments were carried out to reveal the linear relationship between the internal stress of aluminum alloy and the time difference during longitudinal wave propagation, with the correlation equations being also formulated. The results show that, within the tensile stress range of 0~286 MPa, the absolute calibration errors of 5 mm and 3 mm aluminum alloy plates are respectively less than 2.85 MPa and 10.82 MPa, the corresponding relative errors are respectively not more than 2.36% and 13.93%, and the maximum relative errors of both specifications occur within the stress range of less than 28.58 MPa, meaning that it is necessary to improve the resolution and accuracy of ultrasonic measurement in small stress detection. The phased array longitudinal-wave system was then used to detect the stress 5 mm aluminum alloy plate specimens, and an average stress error of (1.174±4.567) MPa, an absolute error of less than 9.42 MPa as well as an estimated initial residual stress of 3.329 MPa was obtained. The experimental results show that the proposed phased array longitudinal-wave ultrasonic method is effective in detecting the average stress of 5 mm aluminum alloy plate; that the method based on the time difference during longitudinal wave propagation can be used to detect the stress type, stress size and residual stress; and that the proposed method is effective in improving the detection accuracy and efficiency of the internal stress detection of aluminum alloy.

Dielectric Behavior of Particles in Multi-Gap Serial Nanoelectrode System



DING Haitao, LIU Xiaofeng, ZHANG Jingran, et al.

2023, 51(7):  42-51.  doi:10.12141/j.issn.1000-565X.220483

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In order to explore the application of metal nanoparticles to the repair of microcircuits with multi-conducting elements and to analyze the motion trends during the dielectric serial assembly of nanoparticles, the dielectrophoretic serial assembly behavior of nanoparticles in a non-uniform electric field is investigated based on a multi-gap nanoelectrode system. In the investigation, first, the particle dielectrophoretic assembly experiments of the conductive island microelectrode system were conducted, finding that the molten nanoparticle wires obtained from the assembly could enhance the circuit conductivity. Then, a comparative experiment of dielectrophoretic serial assembly was conducted for the double-gap and the multi-gap serial nanoelectrode systems, finding that, with the increase of the number of conducting islands in the system, a body assembly phenomenon occurs in all nano-gaps, which helps realize the connection of conducting elements within the multi-gap serial nanoelectrode system. Finally, a simulation analysis was carried out not only for the electric field distribution but also for the dielectrophoretic force, alternating current electrothermal flow and their combined force during the dielectrophoretic assembly of nanoparticles. The results show that the average values of the dielectrophoretic force and the alternating current electrothermal flow inside the gap are both higher than those outside the gap at a frequency of 150 kHz; and that nanofluid pumping occurs in any gap of the multi-gap serial nanoelectrode system and the nanofluid pumping is not affected by the number of gaps. Moreover, the emergence of nanofluidic pumps indicates that metal nanoparticles in non-uniform electric field have an tendency of bulk and surface assembly during the dielectric serial assembly, and this tendency may directly affect the quality of generated nanoparticle wires.

Architecture & Civil Engineering

Carbonation Properties and Pore Characteristics of Different Interfaces in Recycled Lump/Aggregate Concrete



WU Bo, HUANG Tingting

2023, 51(7):  52-60.  doi:10.12141/j.issn.1000-565X.220637

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Scientifically grasping the durability performance of the recycled lump/aggregate concrete (RLAC) is of great significance for promoting the engineering application of this type of concrete. In this paper, to reveal the carbonation properties of the stone-mortar interface and the new mortar-old mortar interface in RLAC, rapid carbonation tests of these two kinds of interfaces and the mortar matrix were carried out, and the porosity of the new mortar-old mortar interfacial transition zone was investigated through backscatter electron images. The results show that the carbonization depth of the interfacial transition zone is greater than that of the mortar matrix, and the closer to the interface, the greater the degree of carbonization, showing an obvious two-dimension carbonization superposition phenomenon. The interface carbonization depths of the stone-mortar specimens vary from 26 to 46 mm, while those of the mortar-mortar specimens are only 7~15 mm. As compared with the new mortar-old mortar interface, the carbonization depth of the stone-mortar interface is much greater, indicating the latter interface having a weaker carbonization resistance. The water-to-cement ratio of the new mortar has a great influence on the carbonation performance of the new mortar-old mortar interface, and the related reduction in carbonization depth is between 15% and 52%, while the water-to-cement ratio of the old mortar has no obvious effect on the carbonation performance of such interface. When the water-to-cement ratio of the new mortar is fixed, the porosity of the new mortar-old mortar interface is almost unchanged with the water-to-cement ratio of the old mortar. However, when the water-to-cement ratio of the old mortar is fixed, the porosity of such interface decreases greatly with the reducing of the water-to-cement ratio of the new mortar. There thus comes to the conclusion that, in practical engineering, the carbonation performance of the new mortar-old mortar interface can be effectively improved by controlling the water-to-cement ratio of the new mortar.

Study on Natural Vibration Characteristics of Cable Network-Damper System



ZHEN Xiaoxia, LIU Guiyuan, DONG Chunguang, et al

2023, 51(7):  61-71.  doi:10.12141/j.issn.1000-565X.220631

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In cable-stayed bridges, multiple stay cables are connected with cross-ties and dampers to form a multilevel cable network-damper system, which can effectively reduce the vibration of stay cables. In order to deeply understand the real dynamic behavior of the system and grasp the interaction law of cross-ties and dampers, this paper proposes a model of multilevel cable network-damper system, which simplifies the cross-ties into linear spring elements, and obtains the complex characteristic equation of the system through theoretical derivation. Next, the natural frequency and damping ratio of each order of the system are solved, and local mode parameter is proposed to characterize the local vibration degree of different modes as well as the energy distribution rules of the system, and, furthermore, auxiliary estimate the vibration consistent of the system. Then, the proposed theoretical formulation is verified by the experiment and finite element simulation. Fnially, the changes of vibration mode, frequency, local mode parameter and damping ratio of the triple-layer cable network-single damper system during the change of cross-ties from flexible to rigid are investigated, and the effects of the cross-tie stiffness and damper position on the damping ratio of the system are analyzed. The results show that the multilevel cable networks-damper system decreases the amplitude of the cables and increases damping ratio of the system; that the stiffness change of the cross-tie and the set of damper at the cable end may both lead to corresponding change of multi-order system mode shape; that the change of anchoring position of the damper at the cable end may also cause individual mode shape change.; that the damping ratio is closely related to the amplitude of the section where the damper is located and to the stiffness change of the cross-tie; and that not all mode damping ratios benefit from the damper set at the cable end. In general, the farther the damper is from the bridge deck at the cable-end anchor point, the more favorable it is for the damper to play; the greater the stiffness of the auxiliary cable, the better the integrity of the vibration system; the higher the frequency, the stronger the mutual constraint between the cables.

Effect of Low Air Pressure on Performance and Pore Structure of Foamed Concrete in Pouring Period



LIU Xin, YAO Yunlong, YAO Zirui, et al

2023, 51(7):  72-80.  doi:10.12141/j.issn.1000-565X.220621

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Due to its advantages of light weight, adjustable strength, self-supporting after curing, good heat insulation and durability, etc., foamed concrete has been successfully used in soft foundation replacement, underground cavity and cavity filling, heat insulation and some other projects, especially in highway embankment filling projects, such as road reconstruction and expansion, bridge backfilling, subway space overlay’s load reduction, etc. If the foamed concrete is affected by such adverse environmental factor as low air pressure in the period from pouring to curing, performance degradation and deterioration of the cured foamed concrete may occur. However, there is a lack of research on the macroscopic properties and pore structure of foamed concrete after being affected by low air pressure in the pouring period. In order to investigate the service performance of foamed concrete after being affected by low air pressure in the pouring period, a simulation box of low air pressure environment was designed, and the evolution of macroscopic performance and pore structure of the foamed concrete at low air pressure (50, 60 and 80 kPa) were comparatively explored. The results show that the dry density and compressive strength of the foamed concrete decrease continuously, while the water absorption increases continuously as the air pressure decreases in the pouring period. Concretely, the dry density of the foamed concrete at 50 kPa is 63.9% of that at atmospheric pressure (101 kPa), the compressive strength is 15.8% of that at atmospheric pressure, and the water absorption of the foamed concrete reaches the maximum of 38.7% at 60 kPa. As the air pressure decreases, the equivalent pore size and the fractal dimension of pore distribution of foamed concrete both increase continuously. The number of large pores (more than 500 μm in diameter) at 50 kPa increases by 24% as comparing with that at atmospheric pressure, the number of irregular large pores and connected pores increases, and the distribution of small pores becomes more and more uneven. Moreover, in the range of pore roundness from 1.0 to 1.1, the percentage of pore number of the foamed concrete decreases gradually with the decrease of air pressure.

Experimental Investigation into Effect of Surface Roughness on Convective Heat Transfer of Concrete



ZHOU Linren, LI Shaoji, CHEN Lan

2023, 51(7):  81-89.  doi:10.12141/j.issn.1000-565X.220638

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The convective heat transfer coefficient (CHTC) is one of the important thermal parameters of concrete. At present, there are great differences in the selection of CHTC in the temperature-related research and engineering applications of building energy efficiency, structural temperature loading and temperature effects of concrete structures, and the influence of material surface conditions is not considered, all these directly affect the accuracy and reliability of the analysis results. In this paper, based on Newton's law of cooling and the principle of heat balance, a set of experimental determination system of CHTC of concrete surface was designed and constructed, and an experimental study on the CHTC of concrete surfaces with different roughness was carried out with a quantitative and controllable method of parameters to further improve and refine the quantitative calculation method of CHTC of concrete. The results show that the designed test system and method can well determine the CHTC of concrete surface in the component scale, and that the surface roughness significantly affects the convective heat exchange on concrete surface. At the wind speed of less than 10 m/s, the relative difference in CHTC of concrete surfaces with different roughness varies from 40.1% to 77.4%. The CHTC increases with the increase of surface roughness, and the forced convection is more greatly influenced by surface roughness than the natural convection. Moreover, based on the regression analysis of experimental data, the formulae for the CHTC of concrete surfaces with four typical roughness are derived, and the formulae for the CHTC of concrete considering the effects of coupled wind speed and surface roughness are also given. Some suggestions are finally given on how to determine the value of CHTC of concrete with the consideration of surface roughness in engineering.

Generalized Plastic Hinge Method for Ultimate Strength Analysis of Steel Frames Considering Residual Stress



BAI Dalian, YANG Lufeng, YIN Yuqi

2023, 51(7):  90-99.  doi:10.12141/j.issn.1000-565X.220423

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The first-order plastic hinge method (FPHM) is simple in theory and efficient in calculation because it can rapidly estimate the position of plastic hinges and the ultimate strength of steel frames according to the proportionality property between the external load and the linear elastic bending moment. However, it ignores the combined action of axial force and bending moment on the development of plastic hinge. The refined plastic hinge method (RPHM) overcomes the limitation of the FPHM, but it determines the position of plastic hinges and the ultimate strength of the structure only by incremental adjustment of external load and iterative trial calculation, which results in the loss of proportionality property and makes the formulation complex and the computation efficiency low. The generalized plastic hinge method (GPHM) possesses the advantages of both the FPHM and the RPHM but ignores the effect of the residual stress, which leads to the overestimating of the ultimate strength of frames with columns objected to large vertical concentrated loads. To solve these problems, this paper introduces the stability coefficient to modify the initial axial strength of the section under the generalized yield criterion, and then an improved GPHM is established to rapidly evaluate the ultimate strength of steel frames with the consideration of the influence of residual stress. In the investigation, firstly, each loading step’s modified section strength is established using the strength reduction factor. Next, the homogeneous generalized yield function is established through regression analysis and the element bearing ratio, which maintains the same proportional relationship with the external load, is defined. Then, the stability coefficient is introduced to modify the initial axial strength of the section to consider the influence of residual stress. Finally, according to the proportional relationship between the element bearing ratio and the external load, the position of the plastic hinge and the corresponding load increment in each loading step are determined. By comparing and analyzing several calibration examples in literatures with different methods, it is found that the computational efficiency of the proposed method is approximately 3~12 times that of the current general structural analysis method.

Traffic & Transportation Engineering

Precise Calculation Method of Traffic Carbon Emission in Expressway Segment Integrating Multi-Source Data



LIN Peiqun, ZHANG Yang, LUO Zhiqing, et al

2023, 51(7):  100-108.  doi:10.12141/j.issn.1000-565X.220627

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In the context of “dual-carbon” policy, the task of carbon emission reduction in transportation industry is arduous, but the vehicle carbon emission currently cannot be measured accurately at present. In order to realize the fine calculation of carbon emission, this paper proposes a precise calculation method of traffic carbon emission in expressway segment based on multi-source data. Firstly, KD-tree algorithm is used to match the GPS data of operational vehicles with the road points, thus implementing the real-time monitoring of dynamic vehicles. Then, the calculation model of vehicle carbon emission in road segment is established, and the relevant calculation process is designed. Finally, the main section of Humen Bridge is taken as an example to calculate the carbon emission of the section. Through VISSIM simulation and relative comparison experiments, the science and reliability of the proposed algorithm are verified. The results show that, for different vehicle types, the carbon emission of minibus is the highest, accounting for 74.36%; and that, for different fuel types, the carbon emission of gasoline automobile is the highest, accounting for 80.50%. The new energy vehicles in operation account for 12.60% of the total vehicles but the corresponding carbon emission only accounts for 4.27%, which means that energetically developing new energy trucks is the key to the carbon emission reduction of expressways. It is also found that, when the traffic saturation is controlled at 0.32~0.38, the average carbon emission of equivalent standard vehicle is lower; while when the traffic saturation is greater than 0.62, the average carbon emission of standard vehicle increases significantly. These conclusions provide theoretical basis for traffic management departments to formulate relevant strategies.

Activity Resilience of Urban Residents: Empirical Evidence Based on the Recovery of Rail Transit Ridership During the COVID-19 Pandemic



CHEN Xiaohong, TIAN Tiantian, ZHANG Hua

2023, 51(7):  109-119.  doi:10.12141/j.issn.1000-565X.220609

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Urban residents’ activity resilience is a vital component of society resilience. Based on the concept of society resilience, this paper qualitatively verified the existence of urban residents’ activity resilience during the COVID-19 pandemic, and quantitatively analyzed its evolution mechanism. Firstly, by using the daily rail transit ridership data of 28 cities in China in the two years before and after the outbreak of COVID-19, residents’ activity resilience was defined and measured, and a logistic function was introduced to model the ridership recovery process. Secondly, from the perspective of policy adjustment and behavior adaptation, this paper constructed and analyzed the action adjustment and learning adaptation process of plural subjects such as the government and the public. The results show that the larger the scale of rail transit network, the higher the residents’ activity resilience. As compared with the cities with a population of less than 5 million, the time for megacities with a population of more than 10 million to recover to 50%, 80%, 90% and 100% of the weekday ridership is 7 days, 15 days, 47 days and 95 days earlier, respectively. The later the recovery period, the greater the difference, and the weekend also shows a similar pattern. Rigid weekday activities have better resilience than flexible weekend activities, and the logistic function fitting parameters α of ridership recovery on weekdays and weekends are 0.019 and 0.016, respectively; H are 77.07 and 106.82 d, respectively. During the second outbreak after the first round of pandemic, the decline of rail transit ridership decreases, the average daily growth of ridership recovery rate in the second outbreak is 1~3 times that of the first round of pandemic, and residents’ activity resilience improves significantly. It concludes that the credibility created by accurate and effective interventions enhances the public compliance with policies, and that public awareness and learning about risks can significantly improve activity resilience. The research results provide a new perspective on how to estimate the travel demand and activity recovery and evaluate the impact of social interventions.

Reconstruction of Urban Vehicle Path Chain Based on Deep Inverse Reinforcement Learning



WANG Fujian, CHENG Huiling, MA Dongfang, et al

2023, 51(7):  120-128.  doi:10.12141/j.issn.1000-565X.220550

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With the improvement of urban traffic monitoring system, a large number of license plate recognition data are stored. This type of data has the advantages of strong temporal continuity, wide spatial range and multiple sample types, which provides an information foundation for studying urban traffic. However, due to the cost and technology in the process of information collection, the collected license plate data are discontinuous in time and space domains, thus limiting the application of the data. To solve this problem, a path chain extraction scheme is proposed in this paper to distinguish the complete path chain from the missing path chain for a single trip, and a reconstruction algorithm of urban vehicle travel path chain based on deep inverse reinforcement learning is proposed. This algorithm samples the complete path chain to obtain expert examples, uses deep inverse reinforcement learning to mine expert examples, and gives the potential route selection characteristics by fitting in the form of nonlinear reward function, which guides the agent to complete the missing path chain independently, and realizes the reconstruction of the missing path chain of vehicle travel. According to the experimental validation in the local road network of Xiaoshan District, Hangzhou City, it is found that the proposed reconstruction algorithm possesses good stability performance, with an average accuracy of 95%; and that the accuracy keeps more than 92% even in case of significant missing points, so that it is of significant advantages as compared with the traditional algorithms. Moreover, by analyzing the impact of the location distribution and number of expert examples on the algorithm, strong generalization ability of the proposed reconstruction algorithm is verified.

3D Modeling Method of Highway Based on Lidar Odometer



HUANG Yan, FU Xinsha, ZENG Yanjie, et al

2023, 51(7):  129-138.  doi:10.12141/j.issn.1000-565X.220583

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The construction of 3D road digital model is of great significance for intelligent vehicle service and road management. In this paper, to solve the problems such as fast running speed, interference noise, few features and no loopback detection assistance existing in different sections of highway application scenarios, a three-dimension highway modeling method with lidar information as the modeling data base is proposed, in which multi-sensor fusion based on lidar odometry and LOAM technology is adopted. In the investigation, firstly, the point cloud data in different road scenarios are obtained by lidar, and the lidar image segmentation technique is used to assign each point a label about the structure and exclude the information of other moving vehicles on the road to reduce the modeling noise. Then, an accurate synchronization strategy is developed to integrate the sensors such as GNSS, IMU and lidar. On this basis, by combining the inertial navigation pre-integration results, the position constraint based on feature point cloud and the RTK data, a three-dimension highway digital model with global consistency is constructed to eliminate the cumulative error of the lidar odometry. Moreover, in order to maintain a finite number of attitude estimates, a sliding window optimization strategy based on key frames is introduced. Finally, three common road sections (general, bridge and tunnel) in the highway scenario are collected for modeling analysis, and the results show that the proposed approach can effectively improve the robustness, accuracy and validity in the challenging highway scenario modeling.

Identification Model of Driver’s Cerebrovascular Diseases Based on PPG Pulse Signal Features



ZHANG Jiaxun, ZHENG Qiuna, YU Zhenyu, et al

2023, 51(7):  139-150.  doi:10.12141/j.issn.1000-565X.220571

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The physical condition of drivers is closely related to traffic safety, especially the driver’s cardiovascular health condition. Real-time monitoring of drivers’ health can help drivers understand their physical condition in time and reduce traffic accidents caused by sudden illnesses. In this study, firstly, 657 PPG (Photoplethysmography Signal) pulse wave datasets from Guilin People’s Hospital, Guangxi Zhuang Autonomous Region, China, were dichotomized numerically for cerebrovascular diseases after the noise reduction by Chebyshev Ⅱ filter and the extraction of time domain features, frequency domain features and wavelet packet features by fast Fourier method. Then, the numerically labeled cerebrovascular disease types were used as output parameters to construct driver cerebrovascular disease dataset. To solve the problem of unbalanced classification of samples in actual dataset, an oversampling supplement was performed by the SMOTE algorithm and a driver cerebrovascular disease classification model, namely SSA-DELM, was constructed based on PPG feature values, followed with model training and testing on actual datasets. The results show that the proposed classification model can provide comparatively accurate early warning for drivers suffering from cerebral infarction or cerebrovascular disease, with an accuracy of 83%, an average precision of 80%, a completeness of 76.6%, an F₁ score of 0.79, and a mean average precision of 0.80. This research can provide theoretical model basis and technical support for drivers’ dynamic health monitoring system based on PPG signal. The proposed model has a large application space in the software service and intelligent medical care of the new energy automobile industry, which is in line with the sales mode of the whole industry chain of “terminal + software + service” of new energy automobile enterprises, and is also in line with modern people’s attention to environmental protection, family health and intelligent transportation.