Bone injury and implantation operation are often accompanied by microenvironment damage of bone tis-sue,which seriously affects the process of osseointegration of implants,especially for titanium(Ti)-based bioinert ma...Bone injury and implantation operation are often accompanied by microenvironment damage of bone tis-sue,which seriously affects the process of osseointegration of implants,especially for titanium(Ti)-based bioinert materials.Thus,repairing or improving the microenvironment of damaged bone tissue is of great significance for bone rescue,reconstruction,and regeneration,which is still a major medical challenge.Oxidative stress(OS)and oxygen(O_(2))deficiency are considered to be specific physiological signals of the bone-injury microenvironment.From the above background,a coating consisting of manganese dioxide(MnO_(2))nanoenzyme and strontium(Sr)ions was fabricated on the surface of the Ti implant via a one-step hydrothermal treatment.MnO_(2) nanoenzyme presented in the coating alleviated OS and O_(2) deficiency at the injury site by catalyzing the decomposition of abundant endogenous H_(2)O_(2) around the modified Ti implants into O_(2).In addition,Sr ions were released from the surface of the implant at a certain rate in a body-fluid environment,further promoting the adhesion,growth,and osteogenic differentiation of mesenchymal stem cells.More importantly,a Sprague Dawley rat femur model demonstrated that the modified Ti implant showed significant potential to accelerate bone tissue reconstruction in vivo.In sum-mary,the present system provides a new idea for the treatment of bone injury and the development of new orthopedic implants.展开更多
This paper addresses a learning-based discontinuous path following control scheme for a biomimetic underwater vehicle(BUV)driven by undulatory fins.Despite the flexibility of the BUV motion,it faces the challenge of d...This paper addresses a learning-based discontinuous path following control scheme for a biomimetic underwater vehicle(BUV)driven by undulatory fins.Despite the flexibility of the BUV motion,it faces the challenge of dealing with discontinuous paths affected by irregular seafloor topography and underwater vegetation.Therefore,BUV must employ path switching strategy to navigate to the next safe area.We introduce a discontinuous path following control method based on deep reinforcement learning(DRL).This method uses the line of sight(LOS)navigation algorithm to provide the Markov decision process(MDP)state inputs and the soft actor-critic(SAC)algorithm to train the control strategy of the BUV.Unlike the traditional fixed waveform control method,this method encourages the BUV to learn different waveforms and fluctuation frequencies through DRL.At the same time,the BUV has the ability to switch to a new path at necessary moments,such as when encountering underwater rocks.The results of simulations and experiments demonstrate the successful integration of the undulatory fins with the SAC controller,showcasing its efficacy and diversity in discontinuous underwater path following tasks.展开更多
基金financially supported by the National Natu-ral Science Foundation of China (Nos.32171327,21734002,and 51825302)the Natural Science Foundation of Chongqing (No.cstc2021jcyj-cxttX0002).
文摘Bone injury and implantation operation are often accompanied by microenvironment damage of bone tis-sue,which seriously affects the process of osseointegration of implants,especially for titanium(Ti)-based bioinert materials.Thus,repairing or improving the microenvironment of damaged bone tissue is of great significance for bone rescue,reconstruction,and regeneration,which is still a major medical challenge.Oxidative stress(OS)and oxygen(O_(2))deficiency are considered to be specific physiological signals of the bone-injury microenvironment.From the above background,a coating consisting of manganese dioxide(MnO_(2))nanoenzyme and strontium(Sr)ions was fabricated on the surface of the Ti implant via a one-step hydrothermal treatment.MnO_(2) nanoenzyme presented in the coating alleviated OS and O_(2) deficiency at the injury site by catalyzing the decomposition of abundant endogenous H_(2)O_(2) around the modified Ti implants into O_(2).In addition,Sr ions were released from the surface of the implant at a certain rate in a body-fluid environment,further promoting the adhesion,growth,and osteogenic differentiation of mesenchymal stem cells.More importantly,a Sprague Dawley rat femur model demonstrated that the modified Ti implant showed significant potential to accelerate bone tissue reconstruction in vivo.In sum-mary,the present system provides a new idea for the treatment of bone injury and the development of new orthopedic implants.
基金supported in part by Beijing Natural Science Foundation(grant 4222055)the National Natural Science Foundation of China(grants 62122087 and 62073316)+1 种基金the Youth Innovation Promotion Association CAS(grant Y2022053)the Scientific Research Program of Beijing Municipal Commission of Education-Natural Science Foundation of Beijing(KZ202210017024).
文摘This paper addresses a learning-based discontinuous path following control scheme for a biomimetic underwater vehicle(BUV)driven by undulatory fins.Despite the flexibility of the BUV motion,it faces the challenge of dealing with discontinuous paths affected by irregular seafloor topography and underwater vegetation.Therefore,BUV must employ path switching strategy to navigate to the next safe area.We introduce a discontinuous path following control method based on deep reinforcement learning(DRL).This method uses the line of sight(LOS)navigation algorithm to provide the Markov decision process(MDP)state inputs and the soft actor-critic(SAC)algorithm to train the control strategy of the BUV.Unlike the traditional fixed waveform control method,this method encourages the BUV to learn different waveforms and fluctuation frequencies through DRL.At the same time,the BUV has the ability to switch to a new path at necessary moments,such as when encountering underwater rocks.The results of simulations and experiments demonstrate the successful integration of the undulatory fins with the SAC controller,showcasing its efficacy and diversity in discontinuous underwater path following tasks.
