Energy harvesting induced from flowing fluids(e.g.,air and water flows)is a well-known process,which can be regarded as a sustainable and renewable energy source.In addition to traditional high-efficiency devices(e.g....Energy harvesting induced from flowing fluids(e.g.,air and water flows)is a well-known process,which can be regarded as a sustainable and renewable energy source.In addition to traditional high-efficiency devices(e.g.,turbines and watermills),the micro-power extracting technologies based on the flow-induced vibration(FIV)effect have sparked great concerns by virtue of their prospective applications as a self-power source for the microelectronic devices in recent years.This article aims to conduct a comprehensive review for the FIV working principle and their potential applications for energy harvesting.First,various classifications of the FIV effect for energy harvesting are briefly introduced,such as vortex-induced vibration(VIV),galloping,flutter,and wake-induced vibration(WIV).Next,the development of FIV energy harvesting techniques is reviewed to discuss the research works in the past three years.The application of hybrid FIV energy harvesting techniques that can enhance the harvesting performance is also presented.Furthermore,the nonlinear designs of FIV-based energy harvesters are reported in this study,e.g.,multi-stability and limit-cycle oscillation(LCO)phenomena.Moreover,advanced FIV-based energy harvesting studies for fluid engineering applications are briefly mentioned.Finally,conclusions and future outlook are summarized.展开更多
To achieve fast, smooth and accurate set point tracking in servo positioning systems, a parameterized design of nonlinear feedback controllers is presented, based on a so-called composite nonlinear feedback （CNF） co...To achieve fast, smooth and accurate set point tracking in servo positioning systems, a parameterized design of nonlinear feedback controllers is presented, based on a so-called composite nonlinear feedback （CNF） control technique. The controller designed here consists of a linear feedback part and a nonlinear part. The linear part is responsible for stability and fast response of the closed-loop system. The nonlinear part serves to increase the damping ratio of closed-loop poles as the controlled output approaches the target reference. The CNF control brings together the good points of both the small and the large damping ratio cases, by continuously scheduling the damping ratio of the dominant closed-loop poles and thus has the capability for superior transient performance, i.e. a fast output response with low overshoot. In the presence of constant disturbances, an integral action is included so as to remove the static bias. An explicitly parameterized controller is derived for servo positioning systems characterized by second-order model. Practical application in a micro hard disk drive servo system is then presented, together with some discussion of the rationale and characteristics of such design. Simulation and experimental results demonstrate the effectiveness of this control design methodology.展开更多
This paper is concerned with the problem of the full-order observer design for a class of fractional-order Lipschitz nonlinear systems. By introducing a continuous frequency distributed equivalent model and using an i...This paper is concerned with the problem of the full-order observer design for a class of fractional-order Lipschitz nonlinear systems. By introducing a continuous frequency distributed equivalent model and using an indirect Lyapunov approach, the sufficient condition for asymptotic stability of the full-order observer error dynamic system is presented. The stability condition is obtained in terms of LMI, which is less conservative than the existing one. A numerical example demonstrates the validity of this approach.展开更多
A robust control for uncertain nonlinear systems based on T-S fuzzy model is discussed in this paper. First, a T-S fuzzy system is adopted to model the uncertain nonlinear systems. Then, for the system with input vari...A robust control for uncertain nonlinear systems based on T-S fuzzy model is discussed in this paper. First, a T-S fuzzy system is adopted to model the uncertain nonlinear systems. Then, for the system with input variables adopting standard fuzzy partitions, the efficient maximal overlapped-rules group （EMORG） is presented, and a new sufficient condition to check the stability of T-S fuzzy system with uncertainty is derived, which is expressed in terms of Linear Matrix Inequalities. The derived stability condition, which only requires a local common positive definite matrix in each EMORG, can reduce the conservatism and difficulty in existing stability conditions. Finally, a simulation example shows the proposed approach is effective.展开更多
The current research of complex nonlinear system robust optimization mainly focuses on the features of design parameters, such as probability density functions, boundary conditions, etc. After parameters study, high-d...The current research of complex nonlinear system robust optimization mainly focuses on the features of design parameters, such as probability density functions, boundary conditions, etc. After parameters study, high-dimensional curve or robust control design is used to find an accurate robust solution. However, there may exist complex interaction between parameters and practical engineering system. With the increase of the number of parameters, it is getting hard to determine high-dimensional curves and robust control methods, thus it＇s difficult to get the robust design solutions. In this paper, a method of global sensitivity analysis based on divided variables in groups is proposed. By making relevant variables in one group and keeping each other independent among sets of variables, global sensitivity analysis is conducted in grouped variables and the importance of parameters is evaluated by calculating the contribution value of each parameter to the total variance of system response. By ranking the importance of input parameters, relatively important parameters are chosen to conduct robust design analysis of the system. By applying this method to the robust optimization design of a real complex nonlinear system-a vehicle occupant restraint system with multi-parameter, good solution is gained and the response variance of the objective function is reduced to 0.01, which indicates that the robustness of the occupant restraint system is improved in a great degree and the method is effective and valuable for the robust design of complex nonlinear system. This research proposes a new method which can be used to obtain solutions for complex nonlinear system robust design.展开更多
Based on the nonlinear error equation of deformation network monitoring, the mathematical model of nonlinear dynamic optimal design of class two was put forward for the deformation network monitoring, in which the tar...Based on the nonlinear error equation of deformation network monitoring, the mathematical model of nonlinear dynamic optimal design of class two was put forward for the deformation network monitoring, in which the target function is the accuracy criterion and the constraint conditions are the network’s sensitivity, reliability and observing cost. Meanwhile a new non derivative solution to the nonlinear dynamic optimal design of class two was also put forward. The solving model uses the difference to stand for the first derivative of functions and solves the revised feasible direction to get the optimal solution to unknown parameters. It can not only make the solution to converge on the minimum point of the constraint problem, but decrease the calculating load.展开更多
Optimal design theory for linear tuned mass dampers （TMD） has been thoroughly investigated, but is still under development for nonlinear TMDs. In this paper, optimization procedures in the time domain are proposed f...Optimal design theory for linear tuned mass dampers （TMD） has been thoroughly investigated, but is still under development for nonlinear TMDs. In this paper, optimization procedures in the time domain are proposed for design of a TMD with nonlinear viscous damping. A dynamic analysis of a structure implemented with a nonlinear TMD is conducted first. Optimum design parameters for the nonlinear TMD are searched using an optimization method to minimize the performance index. The feasibility of the proposed optimization method is illustrated numerically by using the Taipei 101 structure implemented with TMD. The sensitivity analysis shows that the performance index is less sensitive to the damping coefficient than to the frequency ratio. Time history analysis is conducted using the Taipei 101 structure implemented with different TMDs under wind excitation. For both linear and nonlinear TMDs, the comfort requirements for building occupants are satisfied as long as the TMD is properly designed. It was found that as the damping exponent increases, the relative displacement of the TMD decreases but the damping force increases.展开更多
A new preamble structure and design method for orthogonal frequency division multiplexing（OFDM）systems is described,which results a two-symbol long training preamble.The preamble contains four parts,the first part i...A new preamble structure and design method for orthogonal frequency division multiplexing（OFDM）systems is described,which results a two-symbol long training preamble.The preamble contains four parts,the first part is the same as the third,and the four parts are calculated by using nonlinear programming（NLP）model such that the moving correlation of the preamble results a steep rectangular-like pulse of certain width,whose step-down indicates the timing offset.Simulation results in AWGN channel are given to evaluate the perf o rmance of the proposed preamble design.展开更多
This paper presents a design method of H<sub>2</sub> and H<sub>∞</sub>-feedback control loop for nonlinear smooth gene networks that are in control affine form. Formulaic solution methodology ...This paper presents a design method of H<sub>2</sub> and H<sub>∞</sub>-feedback control loop for nonlinear smooth gene networks that are in control affine form. Formulaic solution methodology for solving the nonlinear partial differential equations, namely the Hamilton-Jacobi-Bellman and Hamilton-Jacobi-Isaacs equations through successive Galerkin’s approximation is implemented and the results are compared. Throughout the implementation, there were several caveats that need to be further resolved for practical applications in general cases. Such issues and the clarification of causes are mathematically established and reviewed.展开更多
海洋平台在地震的作用下会产生持续剧烈的振动,该振动会导致结构受到损耗,影响人员安全。提出一种基于非线性能量阱(nonlinear energy sink,NES)的海洋平台振动控制方法。建立了地震作用下基于NES的海洋导管架平台动力学模型。给出了NES...海洋平台在地震的作用下会产生持续剧烈的振动,该振动会导致结构受到损耗,影响人员安全。提出一种基于非线性能量阱(nonlinear energy sink,NES)的海洋平台振动控制方法。建立了地震作用下基于NES的海洋导管架平台动力学模型。给出了NES和TMD优化设计方案,得到地震载荷下NES和TMD的最优参数。最后,从平台结构刚度有无损耗以及系统初值角度,对NES和TMD的控制效果进行分析对比。结果表明:NES可以显著提高海洋平台稳定性;与TMD相比,NES具有更好的抗失谐性,抑制平台振动效果更好。展开更多
This study proposes a scheme for state estimation and,consequently,fault diagnosis in nonlinear systems.Initially,an optimal nonlinear observer is designed for nonlinear systems subject to an actuator or plant fault.B...This study proposes a scheme for state estimation and,consequently,fault diagnosis in nonlinear systems.Initially,an optimal nonlinear observer is designed for nonlinear systems subject to an actuator or plant fault.By utilizing Lyapunov's direct method,the observer is proved to be optimal with respect to a performance function,including the magnitude of the observer gain and the convergence time.The observer gain is obtained by using approximation of Hamilton-Jacobi-Bellman(HJB)equation.The approximation is determined via an online trained neural network(NN).Next a class of affine nonlinear systems is considered which is subject to unknown disturbances in addition to fault signals.In this case,for each fault the original system is transformed to a new form in which the proposed optimal observer can be applied for state estimation and fault detection and isolation(FDI).Simulation results of a singlelink flexible joint robot(SLFJR)electric drive system show the effectiveness of the proposed methodology.展开更多
In this paper,short pulse radiation in Shanghai Synchrotron Radiation Facility(SSRF)is generated by the low momentum compaction factor(α_C)optics,and three kinds of the low-α_C optics are found,with the very lowα_C...In this paper,short pulse radiation in Shanghai Synchrotron Radiation Facility(SSRF)is generated by the low momentum compaction factor(α_C)optics,and three kinds of the low-α_C optics are found,with the very lowα_C being adopted by reducing dispersion in the straight section to negative value in the SSRF.Energy acceptance is selected as objective functions in nonlinear optimization rather than the second orderα_C or other nonlinear driving terms.The optimal result is improved step-by-step by randomly setting harmonic sextupole strengths.Two optics modes,i.e.low positiveα_C and low negativeα_C,are analyzed.In order to get a large energy acceptance and only one stable point in longitudinal phase space,the low negativeα_C optics is taken as an operation mode for the short pulse radiation in the SSRF.展开更多
This paper presents a robust adaptive state feedback control scheme for a class of parametric-strict-feedback nonlinear systems in the presence of time varying actuator failures. The designed adaptive controller compe...This paper presents a robust adaptive state feedback control scheme for a class of parametric-strict-feedback nonlinear systems in the presence of time varying actuator failures. The designed adaptive controller compensates a general class of actuator failures without any need for explicit fault detection. The parameters, times, and patterns of the considered failures are completely unknown. The proposed controller is constructed based on a backstepping design method. The global boundedness of all the closed-loop signals is guaranteed and the tracking error is proved to converge to a small neighborhood of the origin. The proposed approach is employed for a two-axis positioning stage system as well as an aircraft wing system. The simulation results show the correctness and effectiveness of the proposed robust adaptive actuator failure compensation approach.展开更多
In the near future,the Phase-Ⅱ beamline project of Shanghai Synchrotron Radiation Facility(SSRF)will be implemented and some dipoles in the storage ring will be replaced by high field dipoles(super-bend),so as to lea...In the near future,the Phase-Ⅱ beamline project of Shanghai Synchrotron Radiation Facility(SSRF)will be implemented and some dipoles in the storage ring will be replaced by high field dipoles(super-bend),so as to leave room for short straight sections.In this way,the brightness of the hard x-ray emitted from the super-bends can be enhanced,and more insertion devices can be installed.In this paper,super-bends of two lengths are discussed and the corresponding lattices are presented.展开更多
The 285.5 m-high Xiluodu Arch Dam is located in a seismic region along the Jinsha River in China, where the horizontal components of peak ground accelerations for design and checking earthquakes have been estimated to...The 285.5 m-high Xiluodu Arch Dam is located in a seismic region along the Jinsha River in China, where the horizontal components of peak ground accelerations for design and checking earthquakes have been estimated to be 0.355 g and 0.423 g, respectively( g is the gravitational acceleration). The ground motion parameters of design and checking earthquakes are defined by exceedance probabilities of 2% over 100 years and 1% over 100 years, respectively. The dam shape was first selected and optimized through static analysis of the basic load combinations, and then adjusted after taking into account the seismic loads. The dam should be operational during and after the design earthquake with or without minor repairs, and maintain local and global stabilities during an extreme earthquake. Both linear elastic dynamic analysis and nonlinear dynamic analysis considering radiation damping, contraction joints, and material nonlinearity were conducted to assess the stress in the arch dam.The dynamic analysis shows that the maximum dynamic compressive stresses are less than the allowable levels, while the area with tensile stress over the limit is less than 15% of the dam surface and the maximum contraction openings range from 10 mm to 25 mm. The arch dam has sufficient earthquake-resistance capacity and meets the safety requirements. Nevertheless, steel reinforcement has been provided at the dam toe and in the zones of high tensile stress on the dam surface out of extra precaution.展开更多
Based on the improved particle swarm optimization(PSO) algorithm,an optimization approach for the cargo oil tank design(COTD) is presented in this paper.The purpose is to design an optimal overall dimension of the car...Based on the improved particle swarm optimization(PSO) algorithm,an optimization approach for the cargo oil tank design(COTD) is presented in this paper.The purpose is to design an optimal overall dimension of the cargo oil tank(COT) under various kinds of constraints in the preliminary design stage.A non-linear programming model is built to simulate the optimization design,in which the requirements and rules for COTD are used as the constraints.Considering the distance between the inner shell and hull,a fuzzy constraint is used to express the feasibility degree of the double-hull configuration.In terms of the characteristic of COTD,the PSO algorithm is improved to solve this problem.A bivariate extremum strategy is presented to deal with the fuzzy constraint,by which the maximum and minimum cargo capacities are obtained simultaneously.Finally,the simulation demonstrates the feasibility and effectiveness of the proposed approach.展开更多
An adaptive robust control algorithm for ship straight path control system in the presence of both modeling uncertainties and the bounded disturbances is proposed. Motivated by the backstepping approach, the algorithm...An adaptive robust control algorithm for ship straight path control system in the presence of both modeling uncertainties and the bounded disturbances is proposed. Motivated by the backstepping approach, the algorithm is developed by using the dissipation theory, such that the resulting dosed-loop system is both strictly dissipative and asymptotically adaptively stable for all admissible uncertainties. Also, it is able to steer an underactuated ship along a prescribed straight path with ultimate bounds under external disturbances induced by wave, wind and ocean current. When there are no disturbances, the straight path control can be implemented in a locally asymptotically stable manner. Simulation results on an ocean-going training ship ‘YULONG＇ are presented to validate the effectiveness of the algorithm.展开更多
The optimum design for flexible pavement structure is studied by using themethod of mathematical programming.The mathematical model is founded on the basisof“Design Code of Highway Flexible Pavement”issued by the Mi...The optimum design for flexible pavement structure is studied by using themethod of mathematical programming.The mathematical model is founded on the basisof“Design Code of Highway Flexible Pavement”issued by the Ministry of Communica-tions of China.The objective function is the cost of pavement structure.The optimal solu-tions of the mathematical model were searched successfully by flexiplex tolerance method.The relevant program has been developed on DPS-8 and IBM-PC computers.And thecalculated results show good convergence and accuracy for engineering applications.展开更多
基金the National Natural Science Foundation of China (Nos. 11972051 and 11672008)the Opening Project Foundation of the State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures of China (No. KF-2020-11)+1 种基金the Seed Foundation of Beijing University of Technology for International Research Cooperation of China (No. 2021A08)the Innovation and Technology Commission of the Hong Kong Special Administrative Region to the Hong Kong Branch of National Rail Transit Electrification and Automation Engineering Technology Research Center of China (No. K-BBY1)
文摘Energy harvesting induced from flowing fluids(e.g.,air and water flows)is a well-known process,which can be regarded as a sustainable and renewable energy source.In addition to traditional high-efficiency devices(e.g.,turbines and watermills),the micro-power extracting technologies based on the flow-induced vibration(FIV)effect have sparked great concerns by virtue of their prospective applications as a self-power source for the microelectronic devices in recent years.This article aims to conduct a comprehensive review for the FIV working principle and their potential applications for energy harvesting.First,various classifications of the FIV effect for energy harvesting are briefly introduced,such as vortex-induced vibration(VIV),galloping,flutter,and wake-induced vibration(WIV).Next,the development of FIV energy harvesting techniques is reviewed to discuss the research works in the past three years.The application of hybrid FIV energy harvesting techniques that can enhance the harvesting performance is also presented.Furthermore,the nonlinear designs of FIV-based energy harvesters are reported in this study,e.g.,multi-stability and limit-cycle oscillation(LCO)phenomena.Moreover,advanced FIV-based energy harvesting studies for fluid engineering applications are briefly mentioned.Finally,conclusions and future outlook are summarized.
文摘To achieve fast, smooth and accurate set point tracking in servo positioning systems, a parameterized design of nonlinear feedback controllers is presented, based on a so-called composite nonlinear feedback （CNF） control technique. The controller designed here consists of a linear feedback part and a nonlinear part. The linear part is responsible for stability and fast response of the closed-loop system. The nonlinear part serves to increase the damping ratio of closed-loop poles as the controlled output approaches the target reference. The CNF control brings together the good points of both the small and the large damping ratio cases, by continuously scheduling the damping ratio of the dominant closed-loop poles and thus has the capability for superior transient performance, i.e. a fast output response with low overshoot. In the presence of constant disturbances, an integral action is included so as to remove the static bias. An explicitly parameterized controller is derived for servo positioning systems characterized by second-order model. Practical application in a micro hard disk drive servo system is then presented, together with some discussion of the rationale and characteristics of such design. Simulation and experimental results demonstrate the effectiveness of this control design methodology.
基金supported by National Natural Science Foundation of China(Nos.61104072,61104210 and 61174211)Construct Program of the Key Discipline in Hunan Province
文摘This paper is concerned with the problem of the full-order observer design for a class of fractional-order Lipschitz nonlinear systems. By introducing a continuous frequency distributed equivalent model and using an indirect Lyapunov approach, the sufficient condition for asymptotic stability of the full-order observer error dynamic system is presented. The stability condition is obtained in terms of LMI, which is less conservative than the existing one. A numerical example demonstrates the validity of this approach.
基金supported by the National Natural Science Foundation of China (No.70471087)China Postdoctoral Science Foundation Funded Project(No.20080430929)Liaoning Province Education Bureau Foundation (No.20060106)
文摘A robust control for uncertain nonlinear systems based on T-S fuzzy model is discussed in this paper. First, a T-S fuzzy system is adopted to model the uncertain nonlinear systems. Then, for the system with input variables adopting standard fuzzy partitions, the efficient maximal overlapped-rules group （EMORG） is presented, and a new sufficient condition to check the stability of T-S fuzzy system with uncertainty is derived, which is expressed in terms of Linear Matrix Inequalities. The derived stability condition, which only requires a local common positive definite matrix in each EMORG, can reduce the conservatism and difficulty in existing stability conditions. Finally, a simulation example shows the proposed approach is effective.
基金Supported by National Natural Science Foundation of China(Grant No.51275164)
文摘The current research of complex nonlinear system robust optimization mainly focuses on the features of design parameters, such as probability density functions, boundary conditions, etc. After parameters study, high-dimensional curve or robust control design is used to find an accurate robust solution. However, there may exist complex interaction between parameters and practical engineering system. With the increase of the number of parameters, it is getting hard to determine high-dimensional curves and robust control methods, thus it＇s difficult to get the robust design solutions. In this paper, a method of global sensitivity analysis based on divided variables in groups is proposed. By making relevant variables in one group and keeping each other independent among sets of variables, global sensitivity analysis is conducted in grouped variables and the importance of parameters is evaluated by calculating the contribution value of each parameter to the total variance of system response. By ranking the importance of input parameters, relatively important parameters are chosen to conduct robust design analysis of the system. By applying this method to the robust optimization design of a real complex nonlinear system-a vehicle occupant restraint system with multi-parameter, good solution is gained and the response variance of the objective function is reduced to 0.01, which indicates that the robustness of the occupant restraint system is improved in a great degree and the method is effective and valuable for the robust design of complex nonlinear system. This research proposes a new method which can be used to obtain solutions for complex nonlinear system robust design.
文摘Based on the nonlinear error equation of deformation network monitoring, the mathematical model of nonlinear dynamic optimal design of class two was put forward for the deformation network monitoring, in which the target function is the accuracy criterion and the constraint conditions are the network’s sensitivity, reliability and observing cost. Meanwhile a new non derivative solution to the nonlinear dynamic optimal design of class two was also put forward. The solving model uses the difference to stand for the first derivative of functions and solves the revised feasible direction to get the optimal solution to unknown parameters. It can not only make the solution to converge on the minimum point of the constraint problem, but decrease the calculating load.
文摘Optimal design theory for linear tuned mass dampers （TMD） has been thoroughly investigated, but is still under development for nonlinear TMDs. In this paper, optimization procedures in the time domain are proposed for design of a TMD with nonlinear viscous damping. A dynamic analysis of a structure implemented with a nonlinear TMD is conducted first. Optimum design parameters for the nonlinear TMD are searched using an optimization method to minimize the performance index. The feasibility of the proposed optimization method is illustrated numerically by using the Taipei 101 structure implemented with TMD. The sensitivity analysis shows that the performance index is less sensitive to the damping coefficient than to the frequency ratio. Time history analysis is conducted using the Taipei 101 structure implemented with different TMDs under wind excitation. For both linear and nonlinear TMDs, the comfort requirements for building occupants are satisfied as long as the TMD is properly designed. It was found that as the damping exponent increases, the relative displacement of the TMD decreases but the damping force increases.
基金supported by the National Natural Science Foundation of China under Grant No. 60501018
文摘A new preamble structure and design method for orthogonal frequency division multiplexing（OFDM）systems is described,which results a two-symbol long training preamble.The preamble contains four parts,the first part is the same as the third,and the four parts are calculated by using nonlinear programming（NLP）model such that the moving correlation of the preamble results a steep rectangular-like pulse of certain width,whose step-down indicates the timing offset.Simulation results in AWGN channel are given to evaluate the perf o rmance of the proposed preamble design.
文摘This paper presents a design method of H<sub>2</sub> and H<sub>∞</sub>-feedback control loop for nonlinear smooth gene networks that are in control affine form. Formulaic solution methodology for solving the nonlinear partial differential equations, namely the Hamilton-Jacobi-Bellman and Hamilton-Jacobi-Isaacs equations through successive Galerkin’s approximation is implemented and the results are compared. Throughout the implementation, there were several caveats that need to be further resolved for practical applications in general cases. Such issues and the clarification of causes are mathematically established and reviewed.
文摘海洋平台在地震的作用下会产生持续剧烈的振动,该振动会导致结构受到损耗,影响人员安全。提出一种基于非线性能量阱(nonlinear energy sink,NES)的海洋平台振动控制方法。建立了地震作用下基于NES的海洋导管架平台动力学模型。给出了NES和TMD优化设计方案,得到地震载荷下NES和TMD的最优参数。最后,从平台结构刚度有无损耗以及系统初值角度,对NES和TMD的控制效果进行分析对比。结果表明:NES可以显著提高海洋平台稳定性;与TMD相比,NES具有更好的抗失谐性,抑制平台振动效果更好。
文摘This study proposes a scheme for state estimation and,consequently,fault diagnosis in nonlinear systems.Initially,an optimal nonlinear observer is designed for nonlinear systems subject to an actuator or plant fault.By utilizing Lyapunov's direct method,the observer is proved to be optimal with respect to a performance function,including the magnitude of the observer gain and the convergence time.The observer gain is obtained by using approximation of Hamilton-Jacobi-Bellman(HJB)equation.The approximation is determined via an online trained neural network(NN).Next a class of affine nonlinear systems is considered which is subject to unknown disturbances in addition to fault signals.In this case,for each fault the original system is transformed to a new form in which the proposed optimal observer can be applied for state estimation and fault detection and isolation(FDI).Simulation results of a singlelink flexible joint robot(SLFJR)electric drive system show the effectiveness of the proposed methodology.
文摘In this paper,short pulse radiation in Shanghai Synchrotron Radiation Facility(SSRF)is generated by the low momentum compaction factor(α_C)optics,and three kinds of the low-α_C optics are found,with the very lowα_C being adopted by reducing dispersion in the straight section to negative value in the SSRF.Energy acceptance is selected as objective functions in nonlinear optimization rather than the second orderα_C or other nonlinear driving terms.The optimal result is improved step-by-step by randomly setting harmonic sextupole strengths.Two optics modes,i.e.low positiveα_C and low negativeα_C,are analyzed.In order to get a large energy acceptance and only one stable point in longitudinal phase space,the low negativeα_C optics is taken as an operation mode for the short pulse radiation in the SSRF.
基金supported by Esfahan Regional Electric Company(EREC)
文摘This paper presents a robust adaptive state feedback control scheme for a class of parametric-strict-feedback nonlinear systems in the presence of time varying actuator failures. The designed adaptive controller compensates a general class of actuator failures without any need for explicit fault detection. The parameters, times, and patterns of the considered failures are completely unknown. The proposed controller is constructed based on a backstepping design method. The global boundedness of all the closed-loop signals is guaranteed and the tracking error is proved to converge to a small neighborhood of the origin. The proposed approach is employed for a two-axis positioning stage system as well as an aircraft wing system. The simulation results show the correctness and effectiveness of the proposed robust adaptive actuator failure compensation approach.
文摘In the near future,the Phase-Ⅱ beamline project of Shanghai Synchrotron Radiation Facility(SSRF)will be implemented and some dipoles in the storage ring will be replaced by high field dipoles(super-bend),so as to leave room for short straight sections.In this way,the brightness of the hard x-ray emitted from the super-bends can be enhanced,and more insertion devices can be installed.In this paper,super-bends of two lengths are discussed and the corresponding lattices are presented.
基金supported by the Program of Study on the Standard of Overall Safety Control of High Arch Dam of PowerChina Co.,Ltd.(Grant No.DJ-ZDXM-2014-19)
文摘The 285.5 m-high Xiluodu Arch Dam is located in a seismic region along the Jinsha River in China, where the horizontal components of peak ground accelerations for design and checking earthquakes have been estimated to be 0.355 g and 0.423 g, respectively( g is the gravitational acceleration). The ground motion parameters of design and checking earthquakes are defined by exceedance probabilities of 2% over 100 years and 1% over 100 years, respectively. The dam shape was first selected and optimized through static analysis of the basic load combinations, and then adjusted after taking into account the seismic loads. The dam should be operational during and after the design earthquake with or without minor repairs, and maintain local and global stabilities during an extreme earthquake. Both linear elastic dynamic analysis and nonlinear dynamic analysis considering radiation damping, contraction joints, and material nonlinearity were conducted to assess the stress in the arch dam.The dynamic analysis shows that the maximum dynamic compressive stresses are less than the allowable levels, while the area with tensile stress over the limit is less than 15% of the dam surface and the maximum contraction openings range from 10 mm to 25 mm. The arch dam has sufficient earthquake-resistance capacity and meets the safety requirements. Nevertheless, steel reinforcement has been provided at the dam toe and in the zones of high tensile stress on the dam surface out of extra precaution.
基金the National Special Fund for Agro-scientific Research in the Public Interest(No.201003024)
文摘Based on the improved particle swarm optimization(PSO) algorithm,an optimization approach for the cargo oil tank design(COTD) is presented in this paper.The purpose is to design an optimal overall dimension of the cargo oil tank(COT) under various kinds of constraints in the preliminary design stage.A non-linear programming model is built to simulate the optimization design,in which the requirements and rules for COTD are used as the constraints.Considering the distance between the inner shell and hull,a fuzzy constraint is used to express the feasibility degree of the double-hull configuration.In terms of the characteristic of COTD,the PSO algorithm is improved to solve this problem.A bivariate extremum strategy is presented to deal with the fuzzy constraint,by which the maximum and minimum cargo capacities are obtained simultaneously.Finally,the simulation demonstrates the feasibility and effectiveness of the proposed approach.
文摘An adaptive robust control algorithm for ship straight path control system in the presence of both modeling uncertainties and the bounded disturbances is proposed. Motivated by the backstepping approach, the algorithm is developed by using the dissipation theory, such that the resulting dosed-loop system is both strictly dissipative and asymptotically adaptively stable for all admissible uncertainties. Also, it is able to steer an underactuated ship along a prescribed straight path with ultimate bounds under external disturbances induced by wave, wind and ocean current. When there are no disturbances, the straight path control can be implemented in a locally asymptotically stable manner. Simulation results on an ocean-going training ship ‘YULONG＇ are presented to validate the effectiveness of the algorithm.
文摘The optimum design for flexible pavement structure is studied by using themethod of mathematical programming.The mathematical model is founded on the basisof“Design Code of Highway Flexible Pavement”issued by the Ministry of Communica-tions of China.The objective function is the cost of pavement structure.The optimal solu-tions of the mathematical model were searched successfully by flexiplex tolerance method.The relevant program has been developed on DPS-8 and IBM-PC computers.And thecalculated results show good convergence and accuracy for engineering applications.
