The estimation of the disturbance input acting on a vehicle from its given responses is an inverse problem.To overcome some of the issues related to ill-posed inverse problems,this work proposes a method of reconstruc...The estimation of the disturbance input acting on a vehicle from its given responses is an inverse problem.To overcome some of the issues related to ill-posed inverse problems,this work proposes a method of reconstructing the road roughness based on the Kalman filter method.A half-car model that considers both the vehicle and equipment is established,and the joint input-state estimation method is used to identify the road profile.The capabilities of this methodology in the presence of noise are numerically demonstrated.Moreover,to reduce the influence of the driving speed on the estimation results,a method of choosing the calculation frequency is proposed.A road vibration test is conducted to benchmark the proposed method.展开更多
Owing to the strong coupling among the hydrodynamic forces,aerodynamic forces and motion of amphibious aircraft during the water takeoff process,the water takeoff performance is difficult to calculate accurately and q...Owing to the strong coupling among the hydrodynamic forces,aerodynamic forces and motion of amphibious aircraft during the water takeoff process,the water takeoff performance is difficult to calculate accurately and quickly.Based on an analysis of the dynamics and kinematics characteristics of amphibious aircraft and the hydrodynamic theory of high-speed planing hulls,a suitable mathematical model is established for calculating the hydrodynamics of aircraft during water takeoff.A pilot model is designed to illustrate how pilots are affected by the lack of visual reference and the necessity to simultaneously control the pitch angle,flight velocity and other parameters during water takeoff.Combined with the aerodynamic model,engine thrust model and aircraft motion model,a digital virtual flight simulation model is developed for amphibious aircraft during water takeoff,and a calculation method for the water takeoff performance of amphibious aircraft is proposed based on digital virtual flight.Typical performance indicators,such as the liftoff time and liftoff distance,can be obtained via digital virtual flight calculations.A comparison of the measured flight test data and the calculation results shows that the calculation error is less than 10%,which verifies the correctness and accuracy of the proposed method.This method can be used for the preliminary evaluation of airworthiness compliance of amphibious aircraft design schemes,and the relevant calculation results can also provide a theoretical reference for the formulation of flight test plans for airworthiness certification.展开更多
RNA structures are essential to support RNA functions and regulation in various biological processes. Recently, a range of novel technologies have been developed to decode genome-wide RNA structures and novel modes of...RNA structures are essential to support RNA functions and regulation in various biological processes. Recently, a range of novel technologies have been developed to decode genome-wide RNA structures and novel modes of functionality across a wide range of species. In this review, we summarize key strategies for probing the RNA structurome and discuss the pros and cons of representative technologies. In particular, these new technologies have been applied to dissect the structural landscape of the SARS-CoV-2 RNA genome. We also summarize the functionalities of RNA structures discovered in different regulatory layers-including RNA processing, transport, localization, and mRNA translation-across viruses, bacteria, animals, and plants. We review many versatile RNA structural elements in the context of different physiological and pathological processes(e.g., cell differentiation, stress response, and viral replication). Finally, we discuss future prospects for RNA structural studies to map the RNA structurome at higher resolution and at the single-molecule and single-cell level, and to decipher novel modes of RNA structures and functions for innovative applications.展开更多
Due to elimination of horizontal and vertical tails,flying wing aircraft has poor longitudinal and directional dynamic characteristics.In addition,flying wing aircraft uses drag rudders for yaw control,which tends to ...Due to elimination of horizontal and vertical tails,flying wing aircraft has poor longitudinal and directional dynamic characteristics.In addition,flying wing aircraft uses drag rudders for yaw control,which tends to generate strong three-axis control coupling.To overcome these problems,a flight control law design method that couples the longitudinal axis with the lateraldirectional axes is proposed.First,the three-axis coupled control augmentation structure is specified.In the structure,a‘‘soft/hard"cross-connection method is developed for three-axis dynamic decoupling and longitudinal control response decoupling from the drag rudders;maneuvering turn angular rate estimation and subtraction are used in the yaw axis to improve the directional damping.Besides,feedforward control is adopted to improve the maneuverability and control decoupling performance.Then,detailed design methods for feedback and feedforward control parameters are established using eigenstructure assignment and model following technique.Finally,the proposed design method is evaluated and compared with conventional method by numeric simulations.The influences of control derivatives variation of drag rudders on the method are also analyzed.It is demonstrated that the method can effectively improve the dynamic characteristics of flying wing aircraft,especially the directional damping characteristics,and decouple the longitudinal responses from the drag rudders.展开更多
To enable diverse functions and precise regulation,an RNA sequence often folds into complex yet distinct structures in different cellular states.Probing RNA in its native environment is essential to uncovering RNA str...To enable diverse functions and precise regulation,an RNA sequence often folds into complex yet distinct structures in different cellular states.Probing RNA in its native environment is essential to uncovering RNA structures of biological contexts.However,current methods generally require large amounts of input RNA and are challenging for physiologically relevant use.Here,we report smartSHAPE,a new RNA structure probing method that requires very low amounts of RNA input due to the largely reduced artefact of probing signals and increased efficiency of library construction.Using smartSHAPE,we showcased the profiling of the RNA structure landscape of mouse intestinal macrophages upon inflammation,and provided evidence that RNA conformational changes regulate immune responses.These results demonstrate that smartSHAPE can greatly expand the scope of RNA structure-based investigations in practical biological systems,and also provide a research paradigm for the study of post-transcriptional regulation.展开更多
基金This work was supported by the Natural Science Foundation of Shaanxi Province(Grant No.2021KW-25)the Astronautics Supporting Technology Foundation of China(Grant No.2019-HT-XG)the Fundamental Research Funds for the Central Universities(Grant No.3102018ZY015).
文摘The estimation of the disturbance input acting on a vehicle from its given responses is an inverse problem.To overcome some of the issues related to ill-posed inverse problems,this work proposes a method of reconstructing the road roughness based on the Kalman filter method.A half-car model that considers both the vehicle and equipment is established,and the joint input-state estimation method is used to identify the road profile.The capabilities of this methodology in the presence of noise are numerically demonstrated.Moreover,to reduce the influence of the driving speed on the estimation results,a method of choosing the calculation frequency is proposed.A road vibration test is conducted to benchmark the proposed method.
文摘Owing to the strong coupling among the hydrodynamic forces,aerodynamic forces and motion of amphibious aircraft during the water takeoff process,the water takeoff performance is difficult to calculate accurately and quickly.Based on an analysis of the dynamics and kinematics characteristics of amphibious aircraft and the hydrodynamic theory of high-speed planing hulls,a suitable mathematical model is established for calculating the hydrodynamics of aircraft during water takeoff.A pilot model is designed to illustrate how pilots are affected by the lack of visual reference and the necessity to simultaneously control the pitch angle,flight velocity and other parameters during water takeoff.Combined with the aerodynamic model,engine thrust model and aircraft motion model,a digital virtual flight simulation model is developed for amphibious aircraft during water takeoff,and a calculation method for the water takeoff performance of amphibious aircraft is proposed based on digital virtual flight.Typical performance indicators,such as the liftoff time and liftoff distance,can be obtained via digital virtual flight calculations.A comparison of the measured flight test data and the calculation results shows that the calculation error is less than 10%,which verifies the correctness and accuracy of the proposed method.This method can be used for the preliminary evaluation of airworthiness compliance of amphibious aircraft design schemes,and the relevant calculation results can also provide a theoretical reference for the formulation of flight test plans for airworthiness certification.
基金supported by the National Key Research and Development Program of China(2021YFE0114900)the National Natural Science Foundation of China(91940303,91940306,32025008,32170262,31922039,U1832215,32170229)+6 种基金the Natural Science Foundation of Zhejiang Province(LD21C050002)the Starry Night Science Fund at Shanghai Institute for Advanced Study of Zhejiang University(SN-ZJU-SIAS-009)the Beijing Advanced Innovation Center for Structural Biology,Shenzhen Basic Research Project(JCYJ20180507181642811)Research Grants Council of the Hong Kong SAR,China Projects(City U 11100421,City U 11101519,City U 11100218,N_City U110/17)Croucher Foundation Project(9509003)State Key Laboratory of Marine Pollution Director Discretionary Fund,City University of Hong Kong Projects(7005503,9667222,9680261)the United Kingdom Biotechnology and Biological Sciences Research Council(BBSRC:BBS/E/J/000PR9788)。
文摘RNA structures are essential to support RNA functions and regulation in various biological processes. Recently, a range of novel technologies have been developed to decode genome-wide RNA structures and novel modes of functionality across a wide range of species. In this review, we summarize key strategies for probing the RNA structurome and discuss the pros and cons of representative technologies. In particular, these new technologies have been applied to dissect the structural landscape of the SARS-CoV-2 RNA genome. We also summarize the functionalities of RNA structures discovered in different regulatory layers-including RNA processing, transport, localization, and mRNA translation-across viruses, bacteria, animals, and plants. We review many versatile RNA structural elements in the context of different physiological and pathological processes(e.g., cell differentiation, stress response, and viral replication). Finally, we discuss future prospects for RNA structural studies to map the RNA structurome at higher resolution and at the single-molecule and single-cell level, and to decipher novel modes of RNA structures and functions for innovative applications.
基金supported by the Fundamental Research Funds for the Central Universities of China(No.:YWF-19-BJ-J-322)。
文摘Due to elimination of horizontal and vertical tails,flying wing aircraft has poor longitudinal and directional dynamic characteristics.In addition,flying wing aircraft uses drag rudders for yaw control,which tends to generate strong three-axis control coupling.To overcome these problems,a flight control law design method that couples the longitudinal axis with the lateraldirectional axes is proposed.First,the three-axis coupled control augmentation structure is specified.In the structure,a‘‘soft/hard"cross-connection method is developed for three-axis dynamic decoupling and longitudinal control response decoupling from the drag rudders;maneuvering turn angular rate estimation and subtraction are used in the yaw axis to improve the directional damping.Besides,feedforward control is adopted to improve the maneuverability and control decoupling performance.Then,detailed design methods for feedback and feedforward control parameters are established using eigenstructure assignment and model following technique.Finally,the proposed design method is evaluated and compared with conventional method by numeric simulations.The influences of control derivatives variation of drag rudders on the method are also analyzed.It is demonstrated that the method can effectively improve the dynamic characteristics of flying wing aircraft,especially the directional damping characteristics,and decouple the longitudinal responses from the drag rudders.
基金the National Key R&D Program of China(2019YFA0110002 and 2018YFA0107603 to Q.C.Z,and 2020YFA0509100 to X.H.)National Natural Science Foundation of China(Grants No.32125007,91940306,91740204,and 31761163007 to Q.C.Z,and 31725010,31821003,31991174,32030037,82150105 to X.H.)Research Grants Council of the Hong Kong SAR,China Project No.N_CityU110/17 to C.K.K.
文摘To enable diverse functions and precise regulation,an RNA sequence often folds into complex yet distinct structures in different cellular states.Probing RNA in its native environment is essential to uncovering RNA structures of biological contexts.However,current methods generally require large amounts of input RNA and are challenging for physiologically relevant use.Here,we report smartSHAPE,a new RNA structure probing method that requires very low amounts of RNA input due to the largely reduced artefact of probing signals and increased efficiency of library construction.Using smartSHAPE,we showcased the profiling of the RNA structure landscape of mouse intestinal macrophages upon inflammation,and provided evidence that RNA conformational changes regulate immune responses.These results demonstrate that smartSHAPE can greatly expand the scope of RNA structure-based investigations in practical biological systems,and also provide a research paradigm for the study of post-transcriptional regulation.