The increasing accumulation of space debris threatens the integrity and functionality of satellites and complicates orbital operations.This paper constructs an advanced rigid-flexible coupling dynamic model for tether...The increasing accumulation of space debris threatens the integrity and functionality of satellites and complicates orbital operations.This paper constructs an advanced rigid-flexible coupling dynamic model for tethered satellite systems,tailored to enhance space debris management.Utilizing the nodal position finite element method,the model significantly improves the precision of simulating tether dynamics and captures the complex interactions involving satellite and debris attitude dynamics.This advancement allows for detailed examination of potential tether entanglements and provides crucial data for optimizing deorbiting processes.To overcome the limitations of conventional control techniques,a robust adaptive sliding mode control strategy is developed.This approach is specifically designed to manage the unpredictable conditions of the low-Earth orbit and ensure precise satellite attitude control,critical for successful debris removal.Validated through extensive numerical simulations,our model and control strategy demonstrate substantial improvements in operational reliability and safety,significantly enhancing the success rate of deorbiting missions.展开更多
Dynamic analysis of the tethered satellite system(TSS)can provide a fundamental guideline to the evaluation of performance and robust design of the system examined.Uncertainties inherited with the parameters would ind...Dynamic analysis of the tethered satellite system(TSS)can provide a fundamental guideline to the evaluation of performance and robust design of the system examined.Uncertainties inherited with the parameters would induce unexpected variation of the response and deteriorate the reliability of the system.In this work,the effect of uncertain mass of the satellites on the deployment and retrieval dynamics of the TSS is investigated.First the interval mode is employed to take the variation of mass of satellite into account in the processes of deployment and retrieval.Then,the Chebyshev interval method is used to obtain the lower and upper response bounds of the TSS.To achieve a smooth and reliable implementation of deployment and retrieval,the nonlinear programming based on the Gauss pseudospectral method is adopted to obtain optimal trajectory of tether velocity.Numerical results show that the uncertainties of mass of the satellites have a distinct influence on the response of tether tension in the processes of deployment and retrieval.展开更多
Small molecule inhibitors have dominated the pharmaceutical landscape for a long time as the primary therapeutic paradigm targeting pathogenic proteins.However,their efficacy heavily relies on the amino acid compositi...Small molecule inhibitors have dominated the pharmaceutical landscape for a long time as the primary therapeutic paradigm targeting pathogenic proteins.However,their efficacy heavily relies on the amino acid composition and spatial constitution of proteins,rendering them susceptible to drug resistance and failing to target undruggable proteins.In recent years,the advent of targeted protein degradation(TPD)technology has captured substantial attention from both industry and academia.Employing an event-driven mode,TPD offers a novel approach to eliminate pathogenic proteins by promoting their degrada-tion,thus circumventing the limitations associated with traditional small molecule inhibitors.Hydropho-bic tag tethering degrader(HyTTD)technology represents one such TPD approach that is currently in the burgeoning stage.HyTTDs employ endogenous protein degradation systems to induce the degrada-tion of target proteins through the proteasome pathway,which displays significant potential for medical value.In this review,we provide a comprehensive overview of the development history and the reported mechanism of action of HyTTDs.Additionally,we delve into the physiological roles,structure-activity re-lationships,and medical implications of HyTTDs targeting various disease-associated proteins.Moreover,we propose insights into the challenges that necessitate resolution for the successful development of HyTTDs,with the ultimate goal of initiating a new age of clinical treatment leveraging the immense po-tential of HyTTDs.展开更多
For mitigating the libration angle fluctuation of the tethered satellite system,this paper discusses how to make the uniform velocity-deceleration separation scheme achieve the best effect.First,a judgment condition i...For mitigating the libration angle fluctuation of the tethered satellite system,this paper discusses how to make the uniform velocity-deceleration separation scheme achieve the best effect.First,a judgment condition is established to determine the tether state by comparing the tether length and the relative distance of the sub-satellite and the parent satellite.Based on the tethered satellite system dynamics equation and Clohessy-Wiltshire equation,dynamic models are given for four cases of tether states.Second,the influence of the uniform velocity-deceleration separation scheme on the libration angle is analyzed by taking the libration angle at the separation ending time and the mean absolute value of the libration angle as index functions.Then,the optimality problem of the uniform velocity-deceleration separation scheme is formulated as an optimization problem with constraints,and an approximate solution algorithm is given by combining the back propagation neural network and Newton-Raphson method of multiple initial values.Finally,the effectiveness of the proposed method is verified by a numerical simulation.展开更多
The Tethered Space Net Robot(TSNR)is an innovative solution for active space debris capture and removal.Its large envelope and simple capture method make it an attractive option for this task.However,capturing maneuve...The Tethered Space Net Robot(TSNR)is an innovative solution for active space debris capture and removal.Its large envelope and simple capture method make it an attractive option for this task.However,capturing maneuverable debris with the flexible and elastic underactuated net poses significant challenges.To address this,a novel formation control method for the TSNR is proposed through the integration of differential game theory and robust adaptive control in this paper.Specifically,the trajectory of the TSNR is obtained through the solution of a real-time feedback pursuit-evasion game with a dynamic target,where the primary condition is to ensure the stability of the TSNR.Furthermore,to minimize tracking errors and maintain a specific configuration,a robust adaptive formation control scheme with Artificial Potential Field(APF)based on a Finite-Time Convergent Extended State Observer(FTCESO)is investigated.The proposed control method has a key advantage in suppressing complex oscillations by a new adaptive law,thus precisely maintaining the configuration.Finally,numerical simulations are performed to demonstrate the effectiveness of the proposed scheme.展开更多
Rh/SiO2 catalysts with tethered-phosphines with different alkyl spacer lengths have been prepared,tested and characterized.Lengthening the alkyl spacer of the tethered-phosphine improved the flexibility of tethered-ph...Rh/SiO2 catalysts with tethered-phosphines with different alkyl spacer lengths have been prepared,tested and characterized.Lengthening the alkyl spacer of the tethered-phosphine improved the flexibility of tethered-phospine,promoted the formation of active species and enhanced the activity of hydroformylation over other tethered-phosphine modified Rh/SiO2 catalysts.展开更多
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.62173107 and 12202058)the Young Elite Scientists Sponsorship Program by Beijing Association for Science and Technology(Grant No.BYESS2023344).
文摘The increasing accumulation of space debris threatens the integrity and functionality of satellites and complicates orbital operations.This paper constructs an advanced rigid-flexible coupling dynamic model for tethered satellite systems,tailored to enhance space debris management.Utilizing the nodal position finite element method,the model significantly improves the precision of simulating tether dynamics and captures the complex interactions involving satellite and debris attitude dynamics.This advancement allows for detailed examination of potential tether entanglements and provides crucial data for optimizing deorbiting processes.To overcome the limitations of conventional control techniques,a robust adaptive sliding mode control strategy is developed.This approach is specifically designed to manage the unpredictable conditions of the low-Earth orbit and ensure precise satellite attitude control,critical for successful debris removal.Validated through extensive numerical simulations,our model and control strategy demonstrate substantial improvements in operational reliability and safety,significantly enhancing the success rate of deorbiting missions.
基金supported by the National Natural Science Foundation of China(Grant No.U21B2075)。
文摘Dynamic analysis of the tethered satellite system(TSS)can provide a fundamental guideline to the evaluation of performance and robust design of the system examined.Uncertainties inherited with the parameters would induce unexpected variation of the response and deteriorate the reliability of the system.In this work,the effect of uncertain mass of the satellites on the deployment and retrieval dynamics of the TSS is investigated.First the interval mode is employed to take the variation of mass of satellite into account in the processes of deployment and retrieval.Then,the Chebyshev interval method is used to obtain the lower and upper response bounds of the TSS.To achieve a smooth and reliable implementation of deployment and retrieval,the nonlinear programming based on the Gauss pseudospectral method is adopted to obtain optimal trajectory of tether velocity.Numerical results show that the uncertainties of mass of the satellites have a distinct influence on the response of tether tension in the processes of deployment and retrieval.
基金supported by grants from the National Natural Science Foundation of China(Nos.82103978,81874286)the Natural Science Foundation of Jiangsu Province(No.BK20210423)“Double-First-Class”University Project(Nos.CPU 2018PZQ02,CPU 2018GY07).
文摘Small molecule inhibitors have dominated the pharmaceutical landscape for a long time as the primary therapeutic paradigm targeting pathogenic proteins.However,their efficacy heavily relies on the amino acid composition and spatial constitution of proteins,rendering them susceptible to drug resistance and failing to target undruggable proteins.In recent years,the advent of targeted protein degradation(TPD)technology has captured substantial attention from both industry and academia.Employing an event-driven mode,TPD offers a novel approach to eliminate pathogenic proteins by promoting their degrada-tion,thus circumventing the limitations associated with traditional small molecule inhibitors.Hydropho-bic tag tethering degrader(HyTTD)technology represents one such TPD approach that is currently in the burgeoning stage.HyTTDs employ endogenous protein degradation systems to induce the degrada-tion of target proteins through the proteasome pathway,which displays significant potential for medical value.In this review,we provide a comprehensive overview of the development history and the reported mechanism of action of HyTTDs.Additionally,we delve into the physiological roles,structure-activity re-lationships,and medical implications of HyTTDs targeting various disease-associated proteins.Moreover,we propose insights into the challenges that necessitate resolution for the successful development of HyTTDs,with the ultimate goal of initiating a new age of clinical treatment leveraging the immense po-tential of HyTTDs.
基金supported by the National Key R&D Program of China(2018YFA0703800)the National Natural Science Foundation of China(62173030)the Beijing Natural Science Foundation(4222050).
文摘For mitigating the libration angle fluctuation of the tethered satellite system,this paper discusses how to make the uniform velocity-deceleration separation scheme achieve the best effect.First,a judgment condition is established to determine the tether state by comparing the tether length and the relative distance of the sub-satellite and the parent satellite.Based on the tethered satellite system dynamics equation and Clohessy-Wiltshire equation,dynamic models are given for four cases of tether states.Second,the influence of the uniform velocity-deceleration separation scheme on the libration angle is analyzed by taking the libration angle at the separation ending time and the mean absolute value of the libration angle as index functions.Then,the optimality problem of the uniform velocity-deceleration separation scheme is formulated as an optimization problem with constraints,and an approximate solution algorithm is given by combining the back propagation neural network and Newton-Raphson method of multiple initial values.Finally,the effectiveness of the proposed method is verified by a numerical simulation.
基金supported by the National Natural Science Foundation of China(Nos.62222313,62173275,62327809,62303381,and 62303312)in part by the China Postdoctoral Science Foundation(No.2023M732225).
文摘The Tethered Space Net Robot(TSNR)is an innovative solution for active space debris capture and removal.Its large envelope and simple capture method make it an attractive option for this task.However,capturing maneuverable debris with the flexible and elastic underactuated net poses significant challenges.To address this,a novel formation control method for the TSNR is proposed through the integration of differential game theory and robust adaptive control in this paper.Specifically,the trajectory of the TSNR is obtained through the solution of a real-time feedback pursuit-evasion game with a dynamic target,where the primary condition is to ensure the stability of the TSNR.Furthermore,to minimize tracking errors and maintain a specific configuration,a robust adaptive formation control scheme with Artificial Potential Field(APF)based on a Finite-Time Convergent Extended State Observer(FTCESO)is investigated.The proposed control method has a key advantage in suppressing complex oscillations by a new adaptive law,thus precisely maintaining the configuration.Finally,numerical simulations are performed to demonstrate the effectiveness of the proposed scheme.
基金financially supported by the National Natural Science Foundation of China(21273227,20903090)~~
文摘Rh/SiO2 catalysts with tethered-phosphines with different alkyl spacer lengths have been prepared,tested and characterized.Lengthening the alkyl spacer of the tethered-phosphine improved the flexibility of tethered-phospine,promoted the formation of active species and enhanced the activity of hydroformylation over other tethered-phosphine modified Rh/SiO2 catalysts.
