Shield machines are currently the main tool for underground tunnel construction. Due to the complexity and variability of the underground construction environment, it is necessary to accurately identify the ground in ...Shield machines are currently the main tool for underground tunnel construction. Due to the complexity and variability of the underground construction environment, it is necessary to accurately identify the ground in real-time during the tunnel construction process to match and adjust the tunnel parameters according to the geological conditions to ensure construction safety. Compared with the traditional method of stratum identifcation based on staged drilling sampling, the real-time stratum identifcation method based on construction data has the advantages of low cost and high precision. Due to the huge amount of sensor data of the ultra-large diameter mud-water balance shield machine, in order to balance the identifcation time and recognition accuracy of the formation, it is necessary to screen the multivariate data features collected by hundreds of sensors. In response to this problem, this paper proposes a voting-based feature extraction method (VFS), which integrates multiple feature extraction algorithms FSM, and the frequency of each feature in all feature extraction algorithms is the basis for voting. At the same time, in order to verify the wide applicability of the method, several commonly used classifcation models are used to train and test the obtained efective feature data, and the model accuracy and recognition time are used as evaluation indicators, and the classifcation with the best combination with VFS is obtained. The experimental results of shield machine data of 6 diferent geological structures show that the average accuracy of 13 features obtained by VFS combined with diferent classifcation algorithms is 91%;among them, the random forest model takes less time and has the highest recognition accuracy, reaching 93%, showing best compatibility with VFS. Therefore, the VFS algorithm proposed in this paper has high reliability and wide applicability for stratum identifcation in the process of tunnel construction, and can be matched with a variety of classifer algorithms. By combining 13 features selected from shield machine data features with random forest, the identifcation of the construction stratum environment of shield tunnels can be well realized, and further theoretical guidance for underground engineering construction can be provided.展开更多
低压微电网运行时,由于各分布式储能单元初始状态不一致和输出线路阻抗差异,采用传统阻性下垂控制易出现荷电状态(state of charge,SOC)不平衡问题,由此提出一种基于改进阻性下垂控制的储能系统SOC均衡策略。该策略首先引入动态虚拟复阻...低压微电网运行时,由于各分布式储能单元初始状态不一致和输出线路阻抗差异,采用传统阻性下垂控制易出现荷电状态(state of charge,SOC)不平衡问题,由此提出一种基于改进阻性下垂控制的储能系统SOC均衡策略。该策略首先引入动态虚拟复阻抗,消除各逆变器输出线路阻抗差异,实现阻性下垂控制功率解耦和有功功率精确均分。然后改进传统阻性下垂控制方程,通过各分布式储能单元的SOC变化自适应调整下垂系数,确保低压微电网各储能单元在充放电过程的SOC平衡,并对下垂控制过程中的电压与频率偏差进行补偿,进一步提升系统稳定性。最后,通过搭建仿真模型验证了所提策略的有效性。展开更多
Conventional filling therapy fails to fundamentally reduce oral cariogenic bacteria.Thus,oral microbiota follow-up intervention after filling would be necessary for improving dental caries prognosis.We recruited 9 car...Conventional filling therapy fails to fundamentally reduce oral cariogenic bacteria.Thus,oral microbiota follow-up intervention after filling would be necessary for improving dental caries prognosis.We recruited 9 caries-free individuals,and 89 dental caries subjects(5 dropouts).Eighty-nine patients were randomized into three groups:caries(n=8;no treatment),control(n=40;filling),and postbiotics(n=41;filling and 14-day Probio-Eco®intervention).Salivary samples were collected at 0 day(after filling)and 14 days.Our results showed that the diversity of dental caries oral microbiota was significantly increased compared with healthy subjects,and filling could restore a healthier oral microbiota partially and temporarily.Thepostbiotics intervention keeps a low alpha-diversity.Co-occurrence network analysis showed that a more stable oral microbiota structure after postbiotics intervention.Taxonomic and functional annotation of the microbiota revealed that postbiotics co-treatment significantly:increased the relative abundance of Pseudomonas and P.reactans,decreased the relative abundance of Prevotella shahii,and enriched the energy metabolism-related pathways.BugBase-predicted phenotypes inferred to an oral microbiota with decreased potential pathogenic bacteria and increased oxidative stress-tolerant bacteria after postbiotics intervention.Collectively,it suggested that postbiotics co-treatment could be a promising strategy that restores the oral microecological balance for dental caries.展开更多
Exoskeletons generally require accurate dynamic models to design the model-based controller conveniently under the human-robot interaction condition.However,due to unknown model parameters such as the mass,moment of i...Exoskeletons generally require accurate dynamic models to design the model-based controller conveniently under the human-robot interaction condition.However,due to unknown model parameters such as the mass,moment of inertia and mechanical size,the dynamic model of exoskeletons is difficult to construct.Hence,an enhanced whale optimization algorithm(EWOA)is proposed to identify the exoskeleton model parameters.Meanwhile,the periodic excitation trajectories are designed by finite Fourier series to input the desired position demand of exoskeletons with mechanical physical constraints.Then a backstepping controller based on the identified model is adopted to improve the human-robot wearable comfortable performance under cooperative motion.Finally,the proposed Model parameters identification and control are verified by a two-DOF exoskeletons platform.The knee joint motion achieves a steady-state response after 0.5 s.Meanwhile,the position error of hip joint response is less than 0.03 rad after 0.9 s.In addition,the steady-state human-robot interaction torque of the two joints is constrained within 15 N·m.This research proposes a whale optimization algorithm to optimize the excitation trajectory and identify model parameters.Furthermore,an enhanced mutation strategy is adopted to avoid whale evolution’s unsatisfactory local optimal value.展开更多
Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during ...Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.展开更多
基金Supported by National Natural Science Foundation of China and Shanxi Coalbased Low Carbon Joint Fund(Grant No.U1910211)National Natural Science Foundation of China(Grant Nos.51975024 and 52105044)National Key Research and Development Project(Grant No.2019YFC0121700).
文摘Shield machines are currently the main tool for underground tunnel construction. Due to the complexity and variability of the underground construction environment, it is necessary to accurately identify the ground in real-time during the tunnel construction process to match and adjust the tunnel parameters according to the geological conditions to ensure construction safety. Compared with the traditional method of stratum identifcation based on staged drilling sampling, the real-time stratum identifcation method based on construction data has the advantages of low cost and high precision. Due to the huge amount of sensor data of the ultra-large diameter mud-water balance shield machine, in order to balance the identifcation time and recognition accuracy of the formation, it is necessary to screen the multivariate data features collected by hundreds of sensors. In response to this problem, this paper proposes a voting-based feature extraction method (VFS), which integrates multiple feature extraction algorithms FSM, and the frequency of each feature in all feature extraction algorithms is the basis for voting. At the same time, in order to verify the wide applicability of the method, several commonly used classifcation models are used to train and test the obtained efective feature data, and the model accuracy and recognition time are used as evaluation indicators, and the classifcation with the best combination with VFS is obtained. The experimental results of shield machine data of 6 diferent geological structures show that the average accuracy of 13 features obtained by VFS combined with diferent classifcation algorithms is 91%;among them, the random forest model takes less time and has the highest recognition accuracy, reaching 93%, showing best compatibility with VFS. Therefore, the VFS algorithm proposed in this paper has high reliability and wide applicability for stratum identifcation in the process of tunnel construction, and can be matched with a variety of classifer algorithms. By combining 13 features selected from shield machine data features with random forest, the identifcation of the construction stratum environment of shield tunnels can be well realized, and further theoretical guidance for underground engineering construction can be provided.
文摘低压微电网运行时,由于各分布式储能单元初始状态不一致和输出线路阻抗差异,采用传统阻性下垂控制易出现荷电状态(state of charge,SOC)不平衡问题,由此提出一种基于改进阻性下垂控制的储能系统SOC均衡策略。该策略首先引入动态虚拟复阻抗,消除各逆变器输出线路阻抗差异,实现阻性下垂控制功率解耦和有功功率精确均分。然后改进传统阻性下垂控制方程,通过各分布式储能单元的SOC变化自适应调整下垂系数,确保低压微电网各储能单元在充放电过程的SOC平衡,并对下垂控制过程中的电压与频率偏差进行补偿,进一步提升系统稳定性。最后,通过搭建仿真模型验证了所提策略的有效性。
基金supported by the National Natural Science Foundation of China (31720103911)the China Agriculture Research System of MOF and MARAthe Science and Technology Major Projects of Inner Mongolia Autonomous Region (2021ZD0014)
文摘Conventional filling therapy fails to fundamentally reduce oral cariogenic bacteria.Thus,oral microbiota follow-up intervention after filling would be necessary for improving dental caries prognosis.We recruited 9 caries-free individuals,and 89 dental caries subjects(5 dropouts).Eighty-nine patients were randomized into three groups:caries(n=8;no treatment),control(n=40;filling),and postbiotics(n=41;filling and 14-day Probio-Eco®intervention).Salivary samples were collected at 0 day(after filling)and 14 days.Our results showed that the diversity of dental caries oral microbiota was significantly increased compared with healthy subjects,and filling could restore a healthier oral microbiota partially and temporarily.Thepostbiotics intervention keeps a low alpha-diversity.Co-occurrence network analysis showed that a more stable oral microbiota structure after postbiotics intervention.Taxonomic and functional annotation of the microbiota revealed that postbiotics co-treatment significantly:increased the relative abundance of Pseudomonas and P.reactans,decreased the relative abundance of Prevotella shahii,and enriched the energy metabolism-related pathways.BugBase-predicted phenotypes inferred to an oral microbiota with decreased potential pathogenic bacteria and increased oxidative stress-tolerant bacteria after postbiotics intervention.Collectively,it suggested that postbiotics co-treatment could be a promising strategy that restores the oral microecological balance for dental caries.
基金Supported by National Key Research and Development Program of China(Grant No.2022YFF0708903)Ningbo Municipal Key Technology Research and Development Program of China(Grant No.2022Z006)Youth Fund of National Natural Science Foundation of China(Grant No.52205043)。
文摘Exoskeletons generally require accurate dynamic models to design the model-based controller conveniently under the human-robot interaction condition.However,due to unknown model parameters such as the mass,moment of inertia and mechanical size,the dynamic model of exoskeletons is difficult to construct.Hence,an enhanced whale optimization algorithm(EWOA)is proposed to identify the exoskeleton model parameters.Meanwhile,the periodic excitation trajectories are designed by finite Fourier series to input the desired position demand of exoskeletons with mechanical physical constraints.Then a backstepping controller based on the identified model is adopted to improve the human-robot wearable comfortable performance under cooperative motion.Finally,the proposed Model parameters identification and control are verified by a two-DOF exoskeletons platform.The knee joint motion achieves a steady-state response after 0.5 s.Meanwhile,the position error of hip joint response is less than 0.03 rad after 0.9 s.In addition,the steady-state human-robot interaction torque of the two joints is constrained within 15 N·m.This research proposes a whale optimization algorithm to optimize the excitation trajectory and identify model parameters.Furthermore,an enhanced mutation strategy is adopted to avoid whale evolution’s unsatisfactory local optimal value.
基金National Key Research and Development Program of China under Grant No.2018YFC0705602。
文摘Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.
