Dear Editor,This letter studies finite-time stability (FTS) of impulsive and switched hybrid systems with delay-dependent impulses. Some conditions, based on Lyapunov method, are proposed for ensuring FTS and estimati...Dear Editor,This letter studies finite-time stability (FTS) of impulsive and switched hybrid systems with delay-dependent impulses. Some conditions, based on Lyapunov method, are proposed for ensuring FTS and estimating settling-time function (STF) of the hybrid systems.When switching dynamics are FTS and impulsive dynamics involve destabilizing delay-dependent impulses, the FTS is retained if the impulses occur infrequently.展开更多
This article explores the existence results and finite time stability of nonlinear Riemann-Liouville fractional oscillatory differential equations of order 1<■<2 with pure delay.The approaches we adopted to exp...This article explores the existence results and finite time stability of nonlinear Riemann-Liouville fractional oscillatory differential equations of order 1<■<2 with pure delay.The approaches we adopted to explore the existence results are fixed point theorems.What’s more,based on some important inequalities,we explore the finite time stability of the system.In the end,the rationality of our conclusion is verified by a case.展开更多
This paper is concerned with fractional-order bidirectional associative memory(BAM) neural networks with time delays. Applying Laplace transform, the generalized Gronwall inequality and estimates of Mittag–Leffler fu...This paper is concerned with fractional-order bidirectional associative memory(BAM) neural networks with time delays. Applying Laplace transform, the generalized Gronwall inequality and estimates of Mittag–Leffler functions, some sufficient conditions which ensure the finite-time stability of fractional-order bidirectional associative memory neural networks with time delays are obtained. Two examples with their simulations are given to illustrate the theoretical findings. Our results are new and complement previously known results.展开更多
We study nonhomogeneous systems of linear conformable fractional differential equations with pure delay.By using new conformable delayed matrix functions and the method of variation,we obtain a representation of their...We study nonhomogeneous systems of linear conformable fractional differential equations with pure delay.By using new conformable delayed matrix functions and the method of variation,we obtain a representation of their solutions.As an application,we derive a finite time stability result using the representation of solutions and a norm estimation of the conformable delayedmatrix functions.The obtained results are new,and they extend and improve some existing ones.Finally,an example is presented to illustrate the validity of our theoretical results.展开更多
An autoregressive long-and short-term memory(ARLSTM)model was applied to develop a real-time probabilistic slope stability estimation model for the engineered barrier system(EBS)of a near surface radioactive waste dis...An autoregressive long-and short-term memory(ARLSTM)model was applied to develop a real-time probabilistic slope stability estimation model for the engineered barrier system(EBS)of a near surface radioactive waste disposal facility.The effectiveness of the developed model was verified using actual data acquired from South Korea,including precipitation,soil moisture contents,and inclinometer time-series data.The precipitation and the factor of safety(FS)ensemble results were used as the input and output variables of the AR-LSTM model,respectively,where the FS ensemble results were calculated by the Taylor model,integrating the Mualem-van Genuchten soil water retention model with consideration of the multivariate statistics on the hydrophysical properties of the soil.The estimation accuracy of the AR-LSTM model was reasonable by showing high correlation coefficient(0.9468)and low root mean squared error(0.0070)values between the actual and estimated FS values.Moreover,a significant correlation was observed between the estimated FS ensemble results and displacement events recorded by the inclinometer sensor.All the results suggest the effectiveness of the developed model for the long-term integrity assurance of the EBS.展开更多
Time-stability of sintered Nd-Fe-B magnet with lower content of oxygen at different temperatures and humidity conditions for 400 d was investigated.Results showed that the magnetic flux loss was-0.68% for the non-elec...Time-stability of sintered Nd-Fe-B magnet with lower content of oxygen at different temperatures and humidity conditions for 400 d was investigated.Results showed that the magnetic flux loss was-0.68% for the non-electroplating samples and-0.43% for the electroplating samples at room temperature and average humidity was 25% during 400 d,respectively.The magnetic flux loss of the plated samples was lower than non-plated samples under the conditions of room temperature and with the average humidity of 54%,but the magnetic flux loss of the plated samples was larger than that of the non-plated sample at 80 oC.The magnetic flux loss of electroplated and non-electroplated sintered Nd-Fe-B magnets was less than 1% for 400 d,which showed that the N40SH grade magnets have good time stability.展开更多
We discuss a filtration problem in a bounded one-dimensional porous medium. Suppose that the.volumetric moisture content at the surface is constant, and the bottom is impermeable. We prove thatthe solution will tend u...We discuss a filtration problem in a bounded one-dimensional porous medium. Suppose that the.volumetric moisture content at the surface is constant, and the bottom is impermeable. We prove thatthe solution will tend uniformly to a stable solution of the filtration equation as time tends to infinity.An explicit expression of the limiting profile is given.展开更多
Farinograph dough stability time is an important index for classifying wheat, and it often indicates the most appropriate end use for the wheat cultivars. This study aimed at the problem of large fluctuations in dough...Farinograph dough stability time is an important index for classifying wheat, and it often indicates the most appropriate end use for the wheat cultivars. This study aimed at the problem of large fluctuations in dough stability time that occurs during the commercial wheat production. The variations in the dough stability time and its consistency across locations and years were analyzed using 12 principal high-quality wheat cultivars （varieties） obtained from Shandong Province, China, which were grown at nine different locations for three successive years. The results showed that the coefficient of variation for the dough stability time ranged from 24.29 to 49.60% across different varieties, locations, and years. Additive main effects and multiplicative interaction （AMMI） analysis indicated that there were significant interactions for the dough stability time between the varieties, the growth locations, and the years. The genotype effect was the most noticeable, followed by the interaction of the genotype and the environment. The environmental effect was the least significant. The interactions between the varieties and the locations differ considerably, however, each cultivar （variety） apparently has a specific adaptability to the growth location. Therefore, for the successful commercial scale production of the high-quality wheat varieties, both the selection of proper cultivars and its most suitable growth locations to meet the desired requirements for the dough mixing stability time are important.展开更多
The problem of linear time-varying（LTV） system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system mo...The problem of linear time-varying（LTV） system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system modal analysis under the ＂frozen-time＂ assumption are not able to determine the dynamic stability of LTV systems. Time-dependent state space representations of LTV systems are first introduced, and the corresponding modal analysis theories are subsequently presented via a stabilitypreserving state transformation. The time-varying modes of LTV systems are extended in terms of uniqueness, and are further interpreted to determine the system＇s stability. An extended modal identification is proposed to estimate the time-varying modes, consisting of the estimation of the state transition matrix via a subspace-based method and the extraction of the time-varying modes by the QR decomposition. The proposed approach is numerically validated by three numerical cases, and is experimentally validated by a coupled moving-mass simply supported beam exper- imental case. The proposed approach is capable of accurately estimating the time-varying modes, and provides anew way to determine the dynamic stability of LTV systems by using the estimated time-varying modes.展开更多
In this paper, competitive neural networks with time-varying and distributed delays are investigated. By utilizing Lyapunov functional methods, the global exponential stability of periodic solutions of the neural netw...In this paper, competitive neural networks with time-varying and distributed delays are investigated. By utilizing Lyapunov functional methods, the global exponential stability of periodic solutions of the neural networks is discussed on time scales. In addition, an example is given to illustrate the effectiveness of the theoretical results.展开更多
Missile acceleration saturation in a practical terminal guidance process may significantly reduce the interception performance.To solve this problem,this paper presents an anti-saturation guidance law with finite-time...Missile acceleration saturation in a practical terminal guidance process may significantly reduce the interception performance.To solve this problem,this paper presents an anti-saturation guidance law with finite-time convergence for a three dimensional maneuvering interception.The finite time boundedness(FTB)theory and the input-output finite time stability(IO-FTS)theory are used,as well as the long short-term memory(LSTM)network.A sufficient condition for FTB and IO-FTS of a class of nonlinear systems is given.Then,an anti-acceleration saturation missile terminal guidance law based on LSTM,namely LSTM-ASGL,is designed.It can effectively suppress the effect of acceleration saturation to track the maneuvering target more accurately in the complex dynamic environment.The excellent performance of LSTM-ASGL in different maneuvering target scenarios is verified by simulation.The simulation results show that the guidance law successfully prevents acceleration saturation and improves the tracking ability of the missile system to the maneuvering target.It is also shown that LSTM-ASGL has good generalization and anti-jamming performance,and consumes less energy than the anti-acceleration saturation terminal guidance law.展开更多
Chattering phenomenon and singularity are still the main problems that hinder the practical application of sliding mode control. In this paper, a fixed time integral sliding mode controller is designed based on fixed ...Chattering phenomenon and singularity are still the main problems that hinder the practical application of sliding mode control. In this paper, a fixed time integral sliding mode controller is designed based on fixed time stability theory, which ensures precise convergence of the state variables of controlled system, and overcomes the drawback of convergence time growing unboundedly as the initial value increases in finite time controller. It makes the controlled system converge to the control objective within a fixed time bounded by a constant as the initial value grows, and convergence time can be changed by adjusting parameters of controllers properly. Compared with other fixed time controllers, the fixed time integral sliding mode controller proposed in this paper achieves chattering-free control, and integral expression is used to avoid singularity generated by derivation. Finally, the controller is used to stabilize four-order chaotic power system. The results demonstrate that the controller realizes the non-singular chattering-free control of chaotic oscillation in the power system and guarantees the fixed time convergence of state variables, which shows its higher superiority than other finite time controllers.展开更多
This paper concentrates on asymmetric barrier Lyapunov functions(ABLFs)based on finite-time adaptive neural network(NN)control methods for a class of nonlinear strict feedback systems with time-varying full state cons...This paper concentrates on asymmetric barrier Lyapunov functions(ABLFs)based on finite-time adaptive neural network(NN)control methods for a class of nonlinear strict feedback systems with time-varying full state constraints.During the process of backstepping recursion,the approximation properties of NNs are exploited to address the problem of unknown internal dynamics.The ABLFs are constructed to make sure that the time-varying asymmetrical full state constraints are always satisfied.According to the Lyapunov stability and finitetime stability theory,it is proven that all the signals in the closedloop systems are uniformly ultimately bounded(UUB)and the system output is driven to track the desired signal as quickly as possible near the origin.In the meantime,in the scope of finitetime,all states are guaranteed to stay in the pre-given range.Finally,a simulation example is proposed to verify the feasibility of the developed finite time control algorithm.展开更多
In this paper, a new approach is presented for finite-time control problems for linear systems subject to time-varying parametric uncertainties and exogenous disturbance. The disturbance is assumed to be time varying ...In this paper, a new approach is presented for finite-time control problems for linear systems subject to time-varying parametric uncertainties and exogenous disturbance. The disturbance is assumed to be time varying and bounded. Sufficient conditions are obtained for the existence of a linear parameter-dependent state feedback gain, which can ensure that the closed-loop system is finite-time bounded （FTB）. The conditions can be reduced to feasibility problems involving LMIs. Numerical examples show the validity of the proposed methodology.展开更多
We present a numerical study of the long time behavior of approxima- tion solution to the Extended Fisher-Kolmogorov equation with periodic boundary conditions. The unique solvability of numerical solution is shown. I...We present a numerical study of the long time behavior of approxima- tion solution to the Extended Fisher-Kolmogorov equation with periodic boundary conditions. The unique solvability of numerical solution is shown. It is proved that there exists a global attractor of the discrete dynamical system. Furthermore, we obtain the long-time stability and convergence of the difference scheme and the upper semicontinuity d（Ah,τ, .A） → O. Our results show that the difference scheme can effectively simulate the infinite dimensional dynamical systems.展开更多
For this investigation conventional polyamide 6 with monomodal molecular mass distribution, and the newly developed bimodal one were used. Conventional polyamide 6 was used as a reference material in order to emphasiz...For this investigation conventional polyamide 6 with monomodal molecular mass distribution, and the newly developed bimodal one were used. Conventional polyamide 6 was used as a reference material in order to emphasize prospects of using bimodal material for medical applications from the point of view of sterilization resistance and improved creep behavior. Time-dependent mechanical properties of testing samples were characterized by torsional creep measurements in non-sterilized state and after sterilization with three different techniques: with autoclave, ethylene oxide, and hydrogen peroxide plasma. Results show that the two materials exhibit pronounced difference in morphology and consequently, mechanical properties. Both of them were not significantly affected by any of used sterilization techniques. However, bimodal material, originally being noticeably more time-stable in comparison to monomodal one, retains these preferences also post sterilization.展开更多
This paper presents a new simple method of implicit time integration with two control parameters for solving initial-value problems of dynamics such that its accuracy is at least of order two along with the conditiona...This paper presents a new simple method of implicit time integration with two control parameters for solving initial-value problems of dynamics such that its accuracy is at least of order two along with the conditional and unconditional stability regions of the parameters. When the control parameters in the method are optimally taken in their regions, the accuracy may be improved to reach of order three. It is found that the new scheme can achieve lower numerical amplitude dissipation and period dispersion than some of the existing methods, e.g. the Newmark method and Zhai＇s approach, when the same time step size is used. The region of time step dependent on the parameters in the new scheme is explicitly obtained. Finally, some examples of dynamic problems are given to show the accuracy and efficiency of the proposed scheme applied in dynamic systems.展开更多
Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very import...Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very important theory put forward by biologists. In order to investigate the dynamical relationship between predators and their preys, a so-called Michaelis-Menten ratio-dependent predator-prey model is studied in this paper with gestation time delays of predators and preys taken into consideration. The stability of the positive equilibrium is investigated by the Nyquist criteria, and the existence of the local Hopf bifurcation is analyzed by employing the theory of Hopf bifurcation. By means of the center manifold and the normal form theories, explicit formulae are derived to determine the stability, direction and other properties of bifurcating periodic solutions. The above theoretical results are validated by numerical simulations with the help of dynamical software WinPP. The results show that if both the gestation delays are small enough, their sizes will keep stable in the long run, but if the gestation delays of predators are big enough, their sizes will periodically fluc-tuate in the long term. In order to reveal the effects of time delays on the ratio-dependent predator-prey model, a ratiodependent predator-prey model without time delays is considered. By Hurwitz criteria, the local stability of positive equilibrium of this model is investigated. The conditions under which the positive equilibrium is locally asymptotically stable are obtained. By comparing the results with those of the model with time delays, it shows that the dynamical behaviors of ratio-dependent predator-prey model with time delays are more complicated. Under the same conditions, namely, with the same parameters, the stability of positive equilibrium of ratio-dependent predator-prey model would change due to the introduction of gestation time delays for predators and preys. Moreover, with the variation of time delays, the positive equilibrium of the ratio-dependent predator-prey model subjects to Hopf bifurcation.展开更多
A time integration algorithm for structural dynamic analysis is proposed by uniform cubic B-spline functions. The proposed algorithm is successfully used to solve the dynamic response of a single degree of freedom （S...A time integration algorithm for structural dynamic analysis is proposed by uniform cubic B-spline functions. The proposed algorithm is successfully used to solve the dynamic response of a single degree of freedom （SDOF） system, and then is generalized for a multiple-degree of freedom （MDOF） system. Stability analysis shows that, with an adjustable algorithmic parameter, the proposed method can achieve both conditional and unconditional stabilities. Validity of the method is shown with four numerical simulations. Comparison between the proposed method and other methods shows that the proposed method possesses high computation accuracy and desirable computation efficiency.展开更多
In this paper,attitude tracking control with arbitrary convergence time for rigid spacecraft is considered.First,a novel time-varying sliding function is proposed to achieve free-will arbitrary time convergence when t...In this paper,attitude tracking control with arbitrary convergence time for rigid spacecraft is considered.First,a novel time-varying sliding function is proposed to achieve free-will arbitrary time convergence when the system states reside on the sliding surface.With such a sliding function,an attitude tracking controller is designed to guarantee that the states of the closed-loop system converge to the sliding surface within a predetermined time in the presence of external disturbances.The free-will arbitrary time convergences of the closed-loop system and sliding function are illustrated by numerical simulations.展开更多
基金supported by the National Natural Science Foundation of China(61833005)
文摘Dear Editor,This letter studies finite-time stability (FTS) of impulsive and switched hybrid systems with delay-dependent impulses. Some conditions, based on Lyapunov method, are proposed for ensuring FTS and estimating settling-time function (STF) of the hybrid systems.When switching dynamics are FTS and impulsive dynamics involve destabilizing delay-dependent impulses, the FTS is retained if the impulses occur infrequently.
基金Supported by the National Natural Science Foundation of China(Grant No.11871064).
文摘This article explores the existence results and finite time stability of nonlinear Riemann-Liouville fractional oscillatory differential equations of order 1<■<2 with pure delay.The approaches we adopted to explore the existence results are fixed point theorems.What’s more,based on some important inequalities,we explore the finite time stability of the system.In the end,the rationality of our conclusion is verified by a case.
基金Supported by National Natural Science Foundation of China under Grant Nos.61673008,11261010,11101126Project of High–Level Innovative Talents of Guizhou Province([2016]5651)+2 种基金Natural Science and Technology Foundation of Guizhou Province(J[2015]2025 and J[2015]2026)125 Special Major Science and Technology of Department of Education of Guizhou Province([2012]011)Natural Science Foundation of the Education Department of Guizhou Province(KY[2015]482)
文摘This paper is concerned with fractional-order bidirectional associative memory(BAM) neural networks with time delays. Applying Laplace transform, the generalized Gronwall inequality and estimates of Mittag–Leffler functions, some sufficient conditions which ensure the finite-time stability of fractional-order bidirectional associative memory neural networks with time delays are obtained. Two examples with their simulations are given to illustrate the theoretical findings. Our results are new and complement previously known results.
文摘We study nonhomogeneous systems of linear conformable fractional differential equations with pure delay.By using new conformable delayed matrix functions and the method of variation,we obtain a representation of their solutions.As an application,we derive a finite time stability result using the representation of solutions and a norm estimation of the conformable delayedmatrix functions.The obtained results are new,and they extend and improve some existing ones.Finally,an example is presented to illustrate the validity of our theoretical results.
基金supported by the Radioactive Waste Management of the Korea Institute of Energy Technology Evaluation and Planning grant funded by the Korea government Ministry of Knowledge(20193210100130)the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.202008980000).
文摘An autoregressive long-and short-term memory(ARLSTM)model was applied to develop a real-time probabilistic slope stability estimation model for the engineered barrier system(EBS)of a near surface radioactive waste disposal facility.The effectiveness of the developed model was verified using actual data acquired from South Korea,including precipitation,soil moisture contents,and inclinometer time-series data.The precipitation and the factor of safety(FS)ensemble results were used as the input and output variables of the AR-LSTM model,respectively,where the FS ensemble results were calculated by the Taylor model,integrating the Mualem-van Genuchten soil water retention model with consideration of the multivariate statistics on the hydrophysical properties of the soil.The estimation accuracy of the AR-LSTM model was reasonable by showing high correlation coefficient(0.9468)and low root mean squared error(0.0070)values between the actual and estimated FS values.Moreover,a significant correlation was observed between the estimated FS ensemble results and displacement events recorded by the inclinometer sensor.All the results suggest the effectiveness of the developed model for the long-term integrity assurance of the EBS.
基金Project supported by the National Natural Science Foundation of China (50761001)
文摘Time-stability of sintered Nd-Fe-B magnet with lower content of oxygen at different temperatures and humidity conditions for 400 d was investigated.Results showed that the magnetic flux loss was-0.68% for the non-electroplating samples and-0.43% for the electroplating samples at room temperature and average humidity was 25% during 400 d,respectively.The magnetic flux loss of the plated samples was lower than non-plated samples under the conditions of room temperature and with the average humidity of 54%,but the magnetic flux loss of the plated samples was larger than that of the non-plated sample at 80 oC.The magnetic flux loss of electroplated and non-electroplated sintered Nd-Fe-B magnets was less than 1% for 400 d,which showed that the N40SH grade magnets have good time stability.
文摘We discuss a filtration problem in a bounded one-dimensional porous medium. Suppose that the.volumetric moisture content at the surface is constant, and the bottom is impermeable. We prove thatthe solution will tend uniformly to a stable solution of the filtration equation as time tends to infinity.An explicit expression of the limiting profile is given.
文摘Farinograph dough stability time is an important index for classifying wheat, and it often indicates the most appropriate end use for the wheat cultivars. This study aimed at the problem of large fluctuations in dough stability time that occurs during the commercial wheat production. The variations in the dough stability time and its consistency across locations and years were analyzed using 12 principal high-quality wheat cultivars （varieties） obtained from Shandong Province, China, which were grown at nine different locations for three successive years. The results showed that the coefficient of variation for the dough stability time ranged from 24.29 to 49.60% across different varieties, locations, and years. Additive main effects and multiplicative interaction （AMMI） analysis indicated that there were significant interactions for the dough stability time between the varieties, the growth locations, and the years. The genotype effect was the most noticeable, followed by the interaction of the genotype and the environment. The environmental effect was the least significant. The interactions between the varieties and the locations differ considerably, however, each cultivar （variety） apparently has a specific adaptability to the growth location. Therefore, for the successful commercial scale production of the high-quality wheat varieties, both the selection of proper cultivars and its most suitable growth locations to meet the desired requirements for the dough mixing stability time are important.
基金Supported by the China Scholarship Council,National Natural Science Foundation of China(Grant No.11402022)the Interuniversity Attraction Poles Programme of the Belgian Science Policy Office(DYSCO)+1 种基金the Fund for Scientific Research–Flanders(FWO)the Research Fund KU Leuven
文摘The problem of linear time-varying（LTV） system modal analysis is considered based on time-dependent state space representations, as classical modal analysis of linear time-invariant systems and current LTV system modal analysis under the ＂frozen-time＂ assumption are not able to determine the dynamic stability of LTV systems. Time-dependent state space representations of LTV systems are first introduced, and the corresponding modal analysis theories are subsequently presented via a stabilitypreserving state transformation. The time-varying modes of LTV systems are extended in terms of uniqueness, and are further interpreted to determine the system＇s stability. An extended modal identification is proposed to estimate the time-varying modes, consisting of the estimation of the state transition matrix via a subspace-based method and the extraction of the time-varying modes by the QR decomposition. The proposed approach is numerically validated by three numerical cases, and is experimentally validated by a coupled moving-mass simply supported beam exper- imental case. The proposed approach is capable of accurately estimating the time-varying modes, and provides anew way to determine the dynamic stability of LTV systems by using the estimated time-varying modes.
基金Supported by the Fundamental Research Funds for the Central Universities(Grant No.JUSRP51317B)the National Natural Science Foundation of China(Grant No.60875036)
文摘In this paper, competitive neural networks with time-varying and distributed delays are investigated. By utilizing Lyapunov functional methods, the global exponential stability of periodic solutions of the neural networks is discussed on time scales. In addition, an example is given to illustrate the effectiveness of the theoretical results.
文摘Missile acceleration saturation in a practical terminal guidance process may significantly reduce the interception performance.To solve this problem,this paper presents an anti-saturation guidance law with finite-time convergence for a three dimensional maneuvering interception.The finite time boundedness(FTB)theory and the input-output finite time stability(IO-FTS)theory are used,as well as the long short-term memory(LSTM)network.A sufficient condition for FTB and IO-FTS of a class of nonlinear systems is given.Then,an anti-acceleration saturation missile terminal guidance law based on LSTM,namely LSTM-ASGL,is designed.It can effectively suppress the effect of acceleration saturation to track the maneuvering target more accurately in the complex dynamic environment.The excellent performance of LSTM-ASGL in different maneuvering target scenarios is verified by simulation.The simulation results show that the guidance law successfully prevents acceleration saturation and improves the tracking ability of the missile system to the maneuvering target.It is also shown that LSTM-ASGL has good generalization and anti-jamming performance,and consumes less energy than the anti-acceleration saturation terminal guidance law.
基金Project supported by the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.51521065)
文摘Chattering phenomenon and singularity are still the main problems that hinder the practical application of sliding mode control. In this paper, a fixed time integral sliding mode controller is designed based on fixed time stability theory, which ensures precise convergence of the state variables of controlled system, and overcomes the drawback of convergence time growing unboundedly as the initial value increases in finite time controller. It makes the controlled system converge to the control objective within a fixed time bounded by a constant as the initial value grows, and convergence time can be changed by adjusting parameters of controllers properly. Compared with other fixed time controllers, the fixed time integral sliding mode controller proposed in this paper achieves chattering-free control, and integral expression is used to avoid singularity generated by derivation. Finally, the controller is used to stabilize four-order chaotic power system. The results demonstrate that the controller realizes the non-singular chattering-free control of chaotic oscillation in the power system and guarantees the fixed time convergence of state variables, which shows its higher superiority than other finite time controllers.
基金supported in part by the National Natural Science Foundation of China(61803190,61973147,61773188)Liaoning Revitalization Talents Program(XLYC1907050)。
文摘This paper concentrates on asymmetric barrier Lyapunov functions(ABLFs)based on finite-time adaptive neural network(NN)control methods for a class of nonlinear strict feedback systems with time-varying full state constraints.During the process of backstepping recursion,the approximation properties of NNs are exploited to address the problem of unknown internal dynamics.The ABLFs are constructed to make sure that the time-varying asymmetrical full state constraints are always satisfied.According to the Lyapunov stability and finitetime stability theory,it is proven that all the signals in the closedloop systems are uniformly ultimately bounded(UUB)and the system output is driven to track the desired signal as quickly as possible near the origin.In the meantime,in the scope of finitetime,all states are guaranteed to stay in the pre-given range.Finally,a simulation example is proposed to verify the feasibility of the developed finite time control algorithm.
基金the Scientific Innovation Team Project of Hubei Provincial Department of Education (T200809)the Science Foundationof Education Commission of Hubei Province (No. D20081306)the Doctoral Pre-research Foundation of Three Gorges University
文摘In this paper, a new approach is presented for finite-time control problems for linear systems subject to time-varying parametric uncertainties and exogenous disturbance. The disturbance is assumed to be time varying and bounded. Sufficient conditions are obtained for the existence of a linear parameter-dependent state feedback gain, which can ensure that the closed-loop system is finite-time bounded （FTB）. The conditions can be reduced to feasibility problems involving LMIs. Numerical examples show the validity of the proposed methodology.
基金The NSF (10871055) of Chinathe Fundamental Research Funds (HEUCFL20111102)for the Central Universities
文摘We present a numerical study of the long time behavior of approxima- tion solution to the Extended Fisher-Kolmogorov equation with periodic boundary conditions. The unique solvability of numerical solution is shown. It is proved that there exists a global attractor of the discrete dynamical system. Furthermore, we obtain the long-time stability and convergence of the difference scheme and the upper semicontinuity d（Ah,τ, .A） → O. Our results show that the difference scheme can effectively simulate the infinite dimensional dynamical systems.
文摘For this investigation conventional polyamide 6 with monomodal molecular mass distribution, and the newly developed bimodal one were used. Conventional polyamide 6 was used as a reference material in order to emphasize prospects of using bimodal material for medical applications from the point of view of sterilization resistance and improved creep behavior. Time-dependent mechanical properties of testing samples were characterized by torsional creep measurements in non-sterilized state and after sterilization with three different techniques: with autoclave, ethylene oxide, and hydrogen peroxide plasma. Results show that the two materials exhibit pronounced difference in morphology and consequently, mechanical properties. Both of them were not significantly affected by any of used sterilization techniques. However, bimodal material, originally being noticeably more time-stable in comparison to monomodal one, retains these preferences also post sterilization.
基金The project supported by the National Key Basic Research and Development Foundation of the Ministry of Science and Technology of China （G2000048702, 2003CB716707）the National Science Fund for Distinguished Young Scholars （10025208）+1 种基金 the National Natural Science Foundation of China （Key Program） （10532040） the Research Fund for 0versea Chinese （10228028）.
文摘This paper presents a new simple method of implicit time integration with two control parameters for solving initial-value problems of dynamics such that its accuracy is at least of order two along with the conditional and unconditional stability regions of the parameters. When the control parameters in the method are optimally taken in their regions, the accuracy may be improved to reach of order three. It is found that the new scheme can achieve lower numerical amplitude dissipation and period dispersion than some of the existing methods, e.g. the Newmark method and Zhai＇s approach, when the same time step size is used. The region of time step dependent on the parameters in the new scheme is explicitly obtained. Finally, some examples of dynamic problems are given to show the accuracy and efficiency of the proposed scheme applied in dynamic systems.
基金supported by the National Natural Science Foundation of China (10702065 and 10532050)China National Funds for Distinguished Young Scientists (10625211)the Program of Shanghai Subject Chief Scientist (08XD14044)
文摘Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very important theory put forward by biologists. In order to investigate the dynamical relationship between predators and their preys, a so-called Michaelis-Menten ratio-dependent predator-prey model is studied in this paper with gestation time delays of predators and preys taken into consideration. The stability of the positive equilibrium is investigated by the Nyquist criteria, and the existence of the local Hopf bifurcation is analyzed by employing the theory of Hopf bifurcation. By means of the center manifold and the normal form theories, explicit formulae are derived to determine the stability, direction and other properties of bifurcating periodic solutions. The above theoretical results are validated by numerical simulations with the help of dynamical software WinPP. The results show that if both the gestation delays are small enough, their sizes will keep stable in the long run, but if the gestation delays of predators are big enough, their sizes will periodically fluc-tuate in the long term. In order to reveal the effects of time delays on the ratio-dependent predator-prey model, a ratiodependent predator-prey model without time delays is considered. By Hurwitz criteria, the local stability of positive equilibrium of this model is investigated. The conditions under which the positive equilibrium is locally asymptotically stable are obtained. By comparing the results with those of the model with time delays, it shows that the dynamical behaviors of ratio-dependent predator-prey model with time delays are more complicated. Under the same conditions, namely, with the same parameters, the stability of positive equilibrium of ratio-dependent predator-prey model would change due to the introduction of gestation time delays for predators and preys. Moreover, with the variation of time delays, the positive equilibrium of the ratio-dependent predator-prey model subjects to Hopf bifurcation.
基金Project supported by the National Natural Science Foundation of China(Nos.11602004 and11602081)the Fundamental Research Funds for the Central Universities(No.531107040934)
文摘A time integration algorithm for structural dynamic analysis is proposed by uniform cubic B-spline functions. The proposed algorithm is successfully used to solve the dynamic response of a single degree of freedom （SDOF） system, and then is generalized for a multiple-degree of freedom （MDOF） system. Stability analysis shows that, with an adjustable algorithmic parameter, the proposed method can achieve both conditional and unconditional stabilities. Validity of the method is shown with four numerical simulations. Comparison between the proposed method and other methods shows that the proposed method possesses high computation accuracy and desirable computation efficiency.
基金supported by Preeminent Youth Team Project of Guangdong Basic and Applied Basic Research Foundation with Project under Grant No.2024B1515040008the National Natural Science Foundation of China under Grant No.62173112+4 种基金the Science Center Program of National Natural Science Foundation of China under Grant No.62188101HIT Wuhu Robot Technology Research Institute with Project under Grant No.HIT-CXYCMP2-IARU-21-01Shenzhen Science and Technology Program under Grant Nos.RCJC20210609104400005 and KQTD20210811090146075the Joint Funds of the National Natural Science Foundation of China under Grant No.U2013203Innovation and Entrepreneurship Team Project of Chaozhou with Contract under Grant No.220217157150517。
文摘In this paper,attitude tracking control with arbitrary convergence time for rigid spacecraft is considered.First,a novel time-varying sliding function is proposed to achieve free-will arbitrary time convergence when the system states reside on the sliding surface.With such a sliding function,an attitude tracking controller is designed to guarantee that the states of the closed-loop system converge to the sliding surface within a predetermined time in the presence of external disturbances.The free-will arbitrary time convergences of the closed-loop system and sliding function are illustrated by numerical simulations.
