An output-feedback based partial integrated guidance and control (IGC) law for missile interceptor is proposed with the smooth finite time convergence property. Firstly, a novel outputfeedback based smooth sliding mod...An output-feedback based partial integrated guidance and control (IGC) law for missile interceptor is proposed with the smooth finite time convergence property. Firstly, a novel outputfeedback based smooth sliding mode control is proposed for a class of nonlinear systems in the presence of immeasurable state and disturbance. The finite time convergence property of this control scheme is proved based on the Lyapunov stability and homogeneous principle. Then, the proposed control method is applied to the design of partial IGC law. A kind of scaling methods is also developed to reach the rapid convergence of the system. An important dominance of this control scheme is the smooth characteristic, which may result in chattering free convergence. The simulation results indicate the high precision and smooth elevator deflection of the proposed output feedback base partial IGC law. ? 2016 Beijing Institute of Aerospace Information.展开更多
In order to solve four-bar straight-line guidance mechanism synthesis problem for the arbitrarily given straight-line’s"angle requirement"and"point-position requirement",a numerical comparison syn...In order to solve four-bar straight-line guidance mechanism synthesis problem for the arbitrarily given straight-line’s"angle requirement"and"point-position requirement",a numerical comparison synthesis method for single and double straight-line guidance mechanism is presented,which is convenient to realize by computer program.The basic idea of this method is:to select a four-bar linkage whose relative bar length of crank is 1 as a basic four-bar linkage.Then the other three relative bars’length is changed,and a lot of basic four-bar linkage can be obtained.There are many single and double ball-points of each basic four-bar linkage.With the motion of a basic four-bar linkage,there is straight-line segment of each Ball-point’s path.The data of these basic four-bar linkages is saved to a database.When designing a four-bar straight-line guidance mechanism,the design data is compared with the data in database and a satisfactory four-bar linkage can be obtained.The method effectively solves the straight-line guidance mechanism synthesis problem.展开更多
The appropriate catalysts can accelerate the reaction rate and effectively boost the efficient conversion of various molecules,which is of great importance in the study of chemistry,chemical industry,energy,materials ...The appropriate catalysts can accelerate the reaction rate and effectively boost the efficient conversion of various molecules,which is of great importance in the study of chemistry,chemical industry,energy,materials and environmental science.Therefore,efficient,environmentally friendly,and easy to operate synthesis methods have been used to prepare various types of catalysts.Although previous studies have reported the synthesis and characterization of the aforementioned catalysts,more still remain in trial and error methods,without in-depth consideration and improvement of traditional synthesis methods.Here,we comprehensively summarize and compare the preparation methods of the trial-and-error synthesis strategy,structure–activity relationships and density functional theory(DFT)guided catalysts rational design for nanomaterials and atomically dispersed catalysts.We also discuss in detail the utilization of the nanomaterials and single atom catalysts for converting small molecules(H_(2)O,O_(2),CO_(2),N_(2),etc.)into value-added products driven by electrocatalysis,photocatalysis,and thermocatalysis.Finally,the challenges and outlooks of mass preparation and production of efficient and green catalysts through conventional trial and error synthesis and DFT theory are featured in accordance with its current development.展开更多
基金supported by the National Natural Science Foundation of China(61273349)
文摘An output-feedback based partial integrated guidance and control (IGC) law for missile interceptor is proposed with the smooth finite time convergence property. Firstly, a novel outputfeedback based smooth sliding mode control is proposed for a class of nonlinear systems in the presence of immeasurable state and disturbance. The finite time convergence property of this control scheme is proved based on the Lyapunov stability and homogeneous principle. Then, the proposed control method is applied to the design of partial IGC law. A kind of scaling methods is also developed to reach the rapid convergence of the system. An important dominance of this control scheme is the smooth characteristic, which may result in chattering free convergence. The simulation results indicate the high precision and smooth elevator deflection of the proposed output feedback base partial IGC law. ? 2016 Beijing Institute of Aerospace Information.
文摘In order to solve four-bar straight-line guidance mechanism synthesis problem for the arbitrarily given straight-line’s"angle requirement"and"point-position requirement",a numerical comparison synthesis method for single and double straight-line guidance mechanism is presented,which is convenient to realize by computer program.The basic idea of this method is:to select a four-bar linkage whose relative bar length of crank is 1 as a basic four-bar linkage.Then the other three relative bars’length is changed,and a lot of basic four-bar linkage can be obtained.There are many single and double ball-points of each basic four-bar linkage.With the motion of a basic four-bar linkage,there is straight-line segment of each Ball-point’s path.The data of these basic four-bar linkages is saved to a database.When designing a four-bar straight-line guidance mechanism,the design data is compared with the data in database and a satisfactory four-bar linkage can be obtained.The method effectively solves the straight-line guidance mechanism synthesis problem.
基金supported by the National Key R&D Program of China(No.2018YFA0702003)the National Natural Science Foundation of China(Nos.21890383 and 22171157)+1 种基金L.G.W.acknowledges the funding support from the Project funded by China Postdoctoral Science Foundation(No.2022M711787)the Shuimu Tsinghua Scholar program(No.2021SM071)of Tsinghua University,China.
文摘The appropriate catalysts can accelerate the reaction rate and effectively boost the efficient conversion of various molecules,which is of great importance in the study of chemistry,chemical industry,energy,materials and environmental science.Therefore,efficient,environmentally friendly,and easy to operate synthesis methods have been used to prepare various types of catalysts.Although previous studies have reported the synthesis and characterization of the aforementioned catalysts,more still remain in trial and error methods,without in-depth consideration and improvement of traditional synthesis methods.Here,we comprehensively summarize and compare the preparation methods of the trial-and-error synthesis strategy,structure–activity relationships and density functional theory(DFT)guided catalysts rational design for nanomaterials and atomically dispersed catalysts.We also discuss in detail the utilization of the nanomaterials and single atom catalysts for converting small molecules(H_(2)O,O_(2),CO_(2),N_(2),etc.)into value-added products driven by electrocatalysis,photocatalysis,and thermocatalysis.Finally,the challenges and outlooks of mass preparation and production of efficient and green catalysts through conventional trial and error synthesis and DFT theory are featured in accordance with its current development.
