Field observations illustrated that, right-turn vehicles stopped at various positions when proceeding within the right-turn lanes, while some of them trespassed on the crosswalks with multiple stops. In this case, ped...Field observations illustrated that, right-turn vehicles stopped at various positions when proceeding within the right-turn lanes, while some of them trespassed on the crosswalks with multiple stops. In this case, pedestrians and bikes (ped/bike) are encountered unsmooth and hazardous crossings when right-turn vehicles encroaching their lanes. Meanwhile, this also causes conflicts between right-turn and through vehicles at the crossing street. To better protect ped/bike at crossings with right-turn vehicles, this paper proposes a concept of “right-turn vehicle box” (RTVB) as a supplemental treatment within right-turn lanes. Sight distance, geometric conditions, and behaviors of vehicles and ped/bike are key factors to consider so as to set up the criteria and to design the suitable treatment. A case study was conducted at an intersection pair in Houston, USA to shape the idea of RTVB, together with driving simulator tests under relevant scenarios. The preliminary crosscheck examination shows that the right-turn vehicle box could possibly provide ped/ bike with smoother and safer crossings. In the interim, the safety and efficiency of right-turn operations were also improved. To further validate the effects, implementation studies should be conducted before the RTVB can make its debut in practice. Future works will focus on the complete warrants and design details of this treatment. Moreover, the concept of “vehicle box” could also be transplanted to other places where turning movement(s) needs assistance or improvements.展开更多
This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with veh...This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with vehicle transverse distribution model(VTDM).A high-fidelity 3D FE model verified by the static load test is established to satisfy the fatigue analysis accuracy.The stress behavior of super-wide steel box girders under the vehicle load at different lane locations is investigated.Then,considering the effect of VTDM,the fatigue life analysis of four typical details is performed using the Miner cumulative damage rule.The results show that the vehicle transverse location has a great influence on the stress behavior of details with sharp influence surface,and the stress ranges in the outermost lane are larger than those in other lanes,indicating that the details of OSD in the outermost lane are prone to fatigue.The fatigue life analysis indicates that the diaphragm cutout is more prone to fatigue than other details,which should be carefully treated in bridge maintenance.展开更多
In this study, a dynamic modeling method for foil-like underwater vehicles is introduced and experimentally verified in different sea tests of the Hadal ARV. The dumping force of a foil-like underwater vehicle is sens...In this study, a dynamic modeling method for foil-like underwater vehicles is introduced and experimentally verified in different sea tests of the Hadal ARV. The dumping force of a foil-like underwater vehicle is sensitive to swing motion. Some foil-like underwater vehicles swing periodically when performing a free-fall dive task in experiments. Models using conventional modeling methods yield solutions with asymptotic stability, which cannot simulate the self-sustained swing motion. By improving the ridge regression optimization algorithm, a grey-box modeling method based on 378 viscous drag coefficients using the Taylor series expansion is proposed in this study. The method is optimized for over-fitting and convergence problems caused by large parameter matrices. Instead of the PMM test data, the unsteady computational fluid dynamics calculation results are used in modeling. The obtained model can better simulate the swing motion of the underwater vehicle. Simulation and experimental results show a good consistency in free-fall tests during sea trials, as well as a prediction of the dive speed in the swing state.展开更多
With the great development of unmanned aircraft system(UAS)over the last decade,sense and avoid(SAA)system has been a crucial technology for integrating unmanned aircraft vehicle(UAV)into national airspace with reliab...With the great development of unmanned aircraft system(UAS)over the last decade,sense and avoid(SAA)system has been a crucial technology for integrating unmanned aircraft vehicle(UAV)into national airspace with reliable and safe operations.This paper mainly focuses on intruder detection for SAA system.A robust algorithm based on the combination of edge-boxes and spatial pyramid matching using sparse coding(sc-SPM)is presented.The algorithm is composed of three stages.First,edge-boxes method is adopted to obtain a large number of proposals;Second,the optimization program is presented to obtain intruder area-of-interest(ROI)regions;Third,sc-SPM is employed for feature representation of ROI regions and support vector machines(SVM)is adopted to detect the intruder.The algorithm is evaluated under different weather conditions.The recall reaches to 0.95 in dawn and sunny weather and 0.9 in cloudy weather.The experimental results indicate that the intruder detection algorithm is effective and robust with various weather under complex background.展开更多
文摘Field observations illustrated that, right-turn vehicles stopped at various positions when proceeding within the right-turn lanes, while some of them trespassed on the crosswalks with multiple stops. In this case, pedestrians and bikes (ped/bike) are encountered unsmooth and hazardous crossings when right-turn vehicles encroaching their lanes. Meanwhile, this also causes conflicts between right-turn and through vehicles at the crossing street. To better protect ped/bike at crossings with right-turn vehicles, this paper proposes a concept of “right-turn vehicle box” (RTVB) as a supplemental treatment within right-turn lanes. Sight distance, geometric conditions, and behaviors of vehicles and ped/bike are key factors to consider so as to set up the criteria and to design the suitable treatment. A case study was conducted at an intersection pair in Houston, USA to shape the idea of RTVB, together with driving simulator tests under relevant scenarios. The preliminary crosscheck examination shows that the right-turn vehicle box could possibly provide ped/ bike with smoother and safer crossings. In the interim, the safety and efficiency of right-turn operations were also improved. To further validate the effects, implementation studies should be conducted before the RTVB can make its debut in practice. Future works will focus on the complete warrants and design details of this treatment. Moreover, the concept of “vehicle box” could also be transplanted to other places where turning movement(s) needs assistance or improvements.
基金supported by the National Natural Science Foundation of China(Grant Nos.51778135,52178119)the Distinguished Young Scientists of Jiangsu Province(Grant No.BK20190013)the National Key R&D Program Foundation of China(Grant No.2017YFC0806001).
文摘This study presents an investigation on the fatigue analysis of four types of details on orthotropic steel decks(OSDs)for a cable-stayed super-wide steel box girder bridge based on finite-element analysis(FEA)with vehicle transverse distribution model(VTDM).A high-fidelity 3D FE model verified by the static load test is established to satisfy the fatigue analysis accuracy.The stress behavior of super-wide steel box girders under the vehicle load at different lane locations is investigated.Then,considering the effect of VTDM,the fatigue life analysis of four typical details is performed using the Miner cumulative damage rule.The results show that the vehicle transverse location has a great influence on the stress behavior of details with sharp influence surface,and the stress ranges in the outermost lane are larger than those in other lanes,indicating that the details of OSD in the outermost lane are prone to fatigue.The fatigue life analysis indicates that the diaphragm cutout is more prone to fatigue than other details,which should be carefully treated in bridge maintenance.
基金financially supported by the National Key R&D Program of China(Grant No.2016YFC0300802)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB06050200)
文摘In this study, a dynamic modeling method for foil-like underwater vehicles is introduced and experimentally verified in different sea tests of the Hadal ARV. The dumping force of a foil-like underwater vehicle is sensitive to swing motion. Some foil-like underwater vehicles swing periodically when performing a free-fall dive task in experiments. Models using conventional modeling methods yield solutions with asymptotic stability, which cannot simulate the self-sustained swing motion. By improving the ridge regression optimization algorithm, a grey-box modeling method based on 378 viscous drag coefficients using the Taylor series expansion is proposed in this study. The method is optimized for over-fitting and convergence problems caused by large parameter matrices. Instead of the PMM test data, the unsteady computational fluid dynamics calculation results are used in modeling. The obtained model can better simulate the swing motion of the underwater vehicle. Simulation and experimental results show a good consistency in free-fall tests during sea trials, as well as a prediction of the dive speed in the swing state.
基金supported by the National Natural Science Foundation of China (Nos. 61673211, U1633105)the Fundamental Research Funds for the Central Universities of China (No. NP2019105)the Funding of Jiangsu Innovation Program for Graduation Education, Funding for Outstanding Doctoral Dissertation in NUAA (No.BCXJ18-11)
文摘With the great development of unmanned aircraft system(UAS)over the last decade,sense and avoid(SAA)system has been a crucial technology for integrating unmanned aircraft vehicle(UAV)into national airspace with reliable and safe operations.This paper mainly focuses on intruder detection for SAA system.A robust algorithm based on the combination of edge-boxes and spatial pyramid matching using sparse coding(sc-SPM)is presented.The algorithm is composed of three stages.First,edge-boxes method is adopted to obtain a large number of proposals;Second,the optimization program is presented to obtain intruder area-of-interest(ROI)regions;Third,sc-SPM is employed for feature representation of ROI regions and support vector machines(SVM)is adopted to detect the intruder.The algorithm is evaluated under different weather conditions.The recall reaches to 0.95 in dawn and sunny weather and 0.9 in cloudy weather.The experimental results indicate that the intruder detection algorithm is effective and robust with various weather under complex background.
