Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signal...Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signals, called as amendment estimation for short, is developed by introducing channel equalization technique to its conventional version, named as direct estimation in this paper, to improve the estimation stability. After inherent relationship between time delay and phase shift of signals is analyzed, an integer period error compensation method utilized the diversities of both contribution share and contribution mode of concerned estimates is proposed under the condition of high precision phase lag estimation. Finally, a cooperative multi-threshold estimation method composed of amendment and direct estimations to process impulse signals with three thresholds is established. In sea trials data tests of passive locating, this method improves the estimation precision of time delay difference efficiently. The experiments verify the theoretical predictions.展开更多
To improve the estimation accuracy,a novel time delay estimation(TDE)method based on the closed-form offset compensation is proposed.Firstly,we use the generalized cross-correlation with phase transform(GCC-PHAT)metho...To improve the estimation accuracy,a novel time delay estimation(TDE)method based on the closed-form offset compensation is proposed.Firstly,we use the generalized cross-correlation with phase transform(GCC-PHAT)method to obtain the initial TDE.Secondly,a signal model using normalized cross spectrum is established,and the noise subspace is extracted by eigenvalue decomposition(EVD)of covariance matrix.Using the orthogonal relation between the steering vector and the noise subspace,the first-order Taylor expansion is carried out on the steering vector reconstructed by the initial TDE.Finally,the offsets are compensated via simple least squares(LS).Compared to other state-of-the-art methods,the proposed method significantly reduces the computational complexity and achieves better estimation performance.Experiments on both simulation and real-world data verify the efficiency of the proposed approach.展开更多
The dynamics of discrete time delayed Hopfield neural networks is investigated. By using a difference inequality combining with the linear matrix inequality, a sufficient condition ensuring global exponential stabilit...The dynamics of discrete time delayed Hopfield neural networks is investigated. By using a difference inequality combining with the linear matrix inequality, a sufficient condition ensuring global exponential stability of the unique equilibrium point of the networks is found. The result obtained holds not only for constant delay but also for time-varying delays.展开更多
In this paper, we propose a method for the projective synchronization between two different chaotic systems with variable time delays. Using active control approach, the suitable controller is constructed to make the ...In this paper, we propose a method for the projective synchronization between two different chaotic systems with variable time delays. Using active control approach, the suitable controller is constructed to make the states of two different diverse time delayed systems asymptotically synchronize up to the desired scaling factor. Based on the Lyapunov stability theory, the sufficient condition for the projective synchronization is calculated theoretically. Numerical simulations of the projective synchronization between Maekey-Glass system and Ikeda system with variable time delays are shown to validate the effectiveness of the proposed algorithm.展开更多
Here several theorems are established to discuss uniform stability and uniformasymptotical stability of zero solution for difference equations with time delay. Thesetheorems extend Razumikhin Method from functional di...Here several theorems are established to discuss uniform stability and uniformasymptotical stability of zero solution for difference equations with time delay. Thesetheorems extend Razumikhin Method from functional differential equations to time delaydifference equations.展开更多
This paper studies the global exponential stability of competitive neural networks with different time scales and time-varying delays. By using the method of the proper Lyapunov functions and inequality technique, som...This paper studies the global exponential stability of competitive neural networks with different time scales and time-varying delays. By using the method of the proper Lyapunov functions and inequality technique, some sufficient conditions are presented for global exponential stability of delay competitive neural networks with different time scales. These conditions obtained have important leading significance in the designs and applications of global exponential stability for competitive neural networks. Finally, an example with its simulation is provided to demonstrate the usefulness of the proposed criteria.展开更多
Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4 (1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that there are two types of perio...Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4 (1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that there are two types of period bifurcations in the Nino indices and that period bifurcation points exist only in the region where the wavelet power is small. Interdecadal variation features of phase delays between the two indices vary with different time scales. In the periods of 40-72 months, the phase delay changes its sign in 1977: Nino 1+2 indices are 2-4 months earlier than Nino 3.4 indices before 1977, but 3-6 months later afterwards. In the periods of 20-40 months, however, the phase delay changes its sign in another way: Nino 1+2 indices are 1-4 months earlier before 1980 and during 1986-90, but 1-4 months later during 1980-83 and 1993-2001.展开更多
This paper presents a photonic crystal(PhC)line-defect slow-light waveguide modified by resonant rings.We introduce resonant rings into the line defect,constructing a slow-light waveguide with high normalized delay ba...This paper presents a photonic crystal(PhC)line-defect slow-light waveguide modified by resonant rings.We introduce resonant rings into the line defect,constructing a slow-light waveguide with high normalized delay bandwidth product(NDBP)and low group velocity dispersion(GVD).We simulate,analyze,and optimize the structural parameters of this slow-light waveguide using the finite difference time domain(FDTD)method,theoretically achieving a maximum group index of 3.7,maximum bandwidth of 15.6 nm,and maximum NDBP of 0.4416 for slow-light effect.The resonant ring-modified PhC slow-light waveguide designed in this paper exhibits GVD lower than the order of 10^(−20)s^(2)/m over a normalized frequency range from 0.3554 to 0.4175.This study is expected to provide theoretical references for the study of slow-light buffering devices based on PhCs with high NDBP values.展开更多
The proper phase difference of traffic signals for adjacent intersections could decrease the time of operational delay. Some theorems show how to minimize the total average delay time for vehicle operating at adjacent...The proper phase difference of traffic signals for adjacent intersections could decrease the time of operational delay. Some theorems show how to minimize the total average delay time for vehicle operating at adjacent intersections under given conditions. If the distance and signal cycles of adjacent intersections satisfy with specific conditions, the total average delay time would achieve zero. If the signal cycles of adjacent intersections and the phase difference of them are co-prime numbers, the total average delay time would be a constant. In general, if signal cycles of adjacent intersections and the phase difference of them are reducible numbers, the minimum total average delay time would be solved by the given algorithm. Numerical experiments have verified the rationality of these theorems.展开更多
This paper investigates pinning synchronization of discrete-time complex networks with differen t time-varying delays.An important lemma is presen ted and proved,t hen detailed analysis is given to yield some synchron...This paper investigates pinning synchronization of discrete-time complex networks with differen t time-varying delays.An important lemma is presen ted and proved,t hen detailed analysis is given to yield some synchronization criteria for this kind of net works.The results provide an effective way to synchronize discrete-time complex networks by reducing control cost.Furthermore,these theoretical results are illustrated by a complex network via two kinds of pinning schemes.Numerical simulations verify the feasibil计y of the proposed methods.展开更多
Interferometric measurements of high harmonics induced by multiple laser fields represent a burgeoning field of research,offering prospects for optimized harmonic yield and enabling time-and space-resolved nonlinear s...Interferometric measurements of high harmonics induced by multiple laser fields represent a burgeoning field of research,offering prospects for optimized harmonic yield and enabling time-and space-resolved nonlinear spectroscopy.While most investigations have focused on controlling the time delay between pulses,our study introduces a novel approach.By manipulating an additional parameter—the phase difference between the fields—we unveil detailed insights into the physical mechanisms governing the ultrafast processes underlying high harmonic generation.Leveraging high harmonic 2-dimensional interferograms,our method facilitates the streamlined analysis of attosecond electron dynamics in complex molecules and solids,marking an important advancement in this rapidly evolving field.展开更多
We present an approximation method for the non-stationary nonlinear in- compressible Navier-Stokes equations in a cylindrical domain （0, T） x G, where G C ]R3 is a smoothly bounded domain. Our method is applicable t...We present an approximation method for the non-stationary nonlinear in- compressible Navier-Stokes equations in a cylindrical domain （0, T） x G, where G C ]R3 is a smoothly bounded domain. Our method is applicable to general three-dimensional flow without any symmetry restrictions and relies on existence, uniqueness and rep- resentation results from mathematical fluid dynamics. After a suitable time delay in the nonlinear convective term v. ~7v we obtain globally （in time） uniquely solvable equations, which - by using semi-implicit time differences - can be transformed into a finite number of Stokes-type boundary value problems. For the latter a boundary element method based on a corresponding hydrodynamical potential theory is carried out. The method is reported in short outlines ranging from approximation theory up to numerical test calculations.展开更多
文摘Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signals, called as amendment estimation for short, is developed by introducing channel equalization technique to its conventional version, named as direct estimation in this paper, to improve the estimation stability. After inherent relationship between time delay and phase shift of signals is analyzed, an integer period error compensation method utilized the diversities of both contribution share and contribution mode of concerned estimates is proposed under the condition of high precision phase lag estimation. Finally, a cooperative multi-threshold estimation method composed of amendment and direct estimations to process impulse signals with three thresholds is established. In sea trials data tests of passive locating, this method improves the estimation precision of time delay difference efficiently. The experiments verify the theoretical predictions.
基金supported in part by National Key R&D Program of China under Grants 2020YFB1807602 and 2020YFB1807600National Science Foundation of China(61971217,61971218,61631020,61601167)+1 种基金the Fund of Sonar Technology Key Laboratory(Range estimation and location technology of passive target viamultiple array combination),Jiangsu Planned Projects for Postdoctoral Research Funds(2020Z013)China Postdoctoral Science Foundation(2020M681585).
文摘To improve the estimation accuracy,a novel time delay estimation(TDE)method based on the closed-form offset compensation is proposed.Firstly,we use the generalized cross-correlation with phase transform(GCC-PHAT)method to obtain the initial TDE.Secondly,a signal model using normalized cross spectrum is established,and the noise subspace is extracted by eigenvalue decomposition(EVD)of covariance matrix.Using the orthogonal relation between the steering vector and the noise subspace,the first-order Taylor expansion is carried out on the steering vector reconstructed by the initial TDE.Finally,the offsets are compensated via simple least squares(LS).Compared to other state-of-the-art methods,the proposed method significantly reduces the computational complexity and achieves better estimation performance.Experiments on both simulation and real-world data verify the efficiency of the proposed approach.
基金Project supported by the Program for New Century Excellent Talents in University (Grant No NCET-06-0298)the Program for Liaoning Excellent Talents in University (Grant No RC-05-07)+1 种基金the Program for Study of Science of the Educational Department of Liaoning Province, China (Grant No 05L020)the Program for Dalian Science and Technology of China (Grant No2005A10GX106)
文摘The dynamics of discrete time delayed Hopfield neural networks is investigated. By using a difference inequality combining with the linear matrix inequality, a sufficient condition ensuring global exponential stability of the unique equilibrium point of the networks is found. The result obtained holds not only for constant delay but also for time-varying delays.
基金Supported by Research Project of Hubei Provincial Department of Education under Grant No. Q20101609Foundation of Wuhan Textile University under Grant No. 105040
文摘In this paper, we propose a method for the projective synchronization between two different chaotic systems with variable time delays. Using active control approach, the suitable controller is constructed to make the states of two different diverse time delayed systems asymptotically synchronize up to the desired scaling factor. Based on the Lyapunov stability theory, the sufficient condition for the projective synchronization is calculated theoretically. Numerical simulations of the projective synchronization between Maekey-Glass system and Ikeda system with variable time delays are shown to validate the effectiveness of the proposed algorithm.
文摘Here several theorems are established to discuss uniform stability and uniformasymptotical stability of zero solution for difference equations with time delay. Thesetheorems extend Razumikhin Method from functional differential equations to time delaydifference equations.
基金supported by National Natural Science Foundation of China (Grant No 60674026)the Jiangsu Provincial Natural Science Foundation of China (Grant No BK2007016)Program for Innovative Research Team of Jiangnan University of China
文摘This paper studies the global exponential stability of competitive neural networks with different time scales and time-varying delays. By using the method of the proper Lyapunov functions and inequality technique, some sufficient conditions are presented for global exponential stability of delay competitive neural networks with different time scales. These conditions obtained have important leading significance in the designs and applications of global exponential stability for competitive neural networks. Finally, an example with its simulation is provided to demonstrate the usefulness of the proposed criteria.
基金This work was supported by the National Natural Science Foundation of China under Grant No．40035010
文摘Phase delays between two Nino indices-sea surface temperatures in Nino regions 1+2 and 3.4 (1950-2001)-at different time scales are detected by wavelet analysis. Analysis results show that there are two types of period bifurcations in the Nino indices and that period bifurcation points exist only in the region where the wavelet power is small. Interdecadal variation features of phase delays between the two indices vary with different time scales. In the periods of 40-72 months, the phase delay changes its sign in 1977: Nino 1+2 indices are 2-4 months earlier than Nino 3.4 indices before 1977, but 3-6 months later afterwards. In the periods of 20-40 months, however, the phase delay changes its sign in another way: Nino 1+2 indices are 1-4 months earlier before 1980 and during 1986-90, but 1-4 months later during 1980-83 and 1993-2001.
基金supported by the Graduate Student Innovation Fund of Xi’an Shiyou University(No.YCS21211087).
文摘This paper presents a photonic crystal(PhC)line-defect slow-light waveguide modified by resonant rings.We introduce resonant rings into the line defect,constructing a slow-light waveguide with high normalized delay bandwidth product(NDBP)and low group velocity dispersion(GVD).We simulate,analyze,and optimize the structural parameters of this slow-light waveguide using the finite difference time domain(FDTD)method,theoretically achieving a maximum group index of 3.7,maximum bandwidth of 15.6 nm,and maximum NDBP of 0.4416 for slow-light effect.The resonant ring-modified PhC slow-light waveguide designed in this paper exhibits GVD lower than the order of 10^(−20)s^(2)/m over a normalized frequency range from 0.3554 to 0.4175.This study is expected to provide theoretical references for the study of slow-light buffering devices based on PhCs with high NDBP values.
文摘The proper phase difference of traffic signals for adjacent intersections could decrease the time of operational delay. Some theorems show how to minimize the total average delay time for vehicle operating at adjacent intersections under given conditions. If the distance and signal cycles of adjacent intersections satisfy with specific conditions, the total average delay time would achieve zero. If the signal cycles of adjacent intersections and the phase difference of them are co-prime numbers, the total average delay time would be a constant. In general, if signal cycles of adjacent intersections and the phase difference of them are reducible numbers, the minimum total average delay time would be solved by the given algorithm. Numerical experiments have verified the rationality of these theorems.
基金supported by the National Natural Science Foundation of China under Grant Nos.61304022,61573262 and 61573011the Excellent Youth Foundation of Hunan Provincial Department of Education(16B141)
文摘This paper investigates pinning synchronization of discrete-time complex networks with differen t time-varying delays.An important lemma is presen ted and proved,t hen detailed analysis is given to yield some synchronization criteria for this kind of net works.The results provide an effective way to synchronize discrete-time complex networks by reducing control cost.Furthermore,these theoretical results are illustrated by a complex network via two kinds of pinning schemes.Numerical simulations verify the feasibil计y of the proposed methods.
基金support from the National Key Research and Development Program of China(grant no.2023YFA1407100)Guangdong Province Science and Technology Major Project(Future functional materials under extreme conditions-2021B0301030005)the Guangdong Natural Science Foundation(General Program project no.2023A1515010871).
文摘Interferometric measurements of high harmonics induced by multiple laser fields represent a burgeoning field of research,offering prospects for optimized harmonic yield and enabling time-and space-resolved nonlinear spectroscopy.While most investigations have focused on controlling the time delay between pulses,our study introduces a novel approach.By manipulating an additional parameter—the phase difference between the fields—we unveil detailed insights into the physical mechanisms governing the ultrafast processes underlying high harmonic generation.Leveraging high harmonic 2-dimensional interferograms,our method facilitates the streamlined analysis of attosecond electron dynamics in complex molecules and solids,marking an important advancement in this rapidly evolving field.
文摘We present an approximation method for the non-stationary nonlinear in- compressible Navier-Stokes equations in a cylindrical domain （0, T） x G, where G C ]R3 is a smoothly bounded domain. Our method is applicable to general three-dimensional flow without any symmetry restrictions and relies on existence, uniqueness and rep- resentation results from mathematical fluid dynamics. After a suitable time delay in the nonlinear convective term v. ~7v we obtain globally （in time） uniquely solvable equations, which - by using semi-implicit time differences - can be transformed into a finite number of Stokes-type boundary value problems. For the latter a boundary element method based on a corresponding hydrodynamical potential theory is carried out. The method is reported in short outlines ranging from approximation theory up to numerical test calculations.
