Finite-frequency travel time tomography is a newly developing method.The main procedure in this new method is to compute the traveltime sensitive kernel.The travel time of the same scatterer needs to be used for compu...Finite-frequency travel time tomography is a newly developing method.The main procedure in this new method is to compute the traveltime sensitive kernel.The travel time of the same scatterer needs to be used for computing the traveltime sensitive kernel many times.It is a time-consuming task.It is easy and fast to get the travel time from analytic equations in a simple model such as a homogenous or linear velocity media.However,most of the earth models are layered.It is cumbersome to get the travel time from analytic equations.In order to enhance the computation efficiency,we used the table look-up method to compute the finite-frequency travel time sensitive kernel for P-waves in a layered structure model.We chose the AK135 earth model for the velocity model.The table look-up method saved about 50% of the computation time.We enhanced the computation speed by using the table lookup method in the same velocity model,which was very useful for enhancing the computation efficiency for the finite-frequency travel time tomography.展开更多
This work proposes a robust fault detection and isolation scheme for discrete-time systems subject to actuator faults,in which a bank of H_/H∞ fault detection unknown input observers(UIOs) and a zonotopic threshold a...This work proposes a robust fault detection and isolation scheme for discrete-time systems subject to actuator faults,in which a bank of H_/H∞ fault detection unknown input observers(UIOs) and a zonotopic threshold analysis strategy are considered. In observer design, finite-frequency H_ index based on the generalized Kalman-Yakubovich-Popov lemma and H∞ technique are utilized to evaluate worst-case fault sensitivity and disturbance attenuation performance, respectively. The proposed H_/H∞ fault detection observers are designed to be insensitive to the corresponding actuator fault only, but sensitive to others.Then, to overcome the weakness of predefining threshold for FDI decision-making, this work proposes a zonotopic threshold analysis method to evaluate the generated residuals. The FDI decision-making relies on the evaluation with a dynamical zonotopic threshold. Finally, numerical simulations are provided to show the feasibility of the proposed scheme.展开更多
We investigate the two-mode quantum Rabi model(QRM)describing the interaction between a two-level atom and a two-mode cavity field.The quantum phase transitions are found when the ratioηof transition frequency of ato...We investigate the two-mode quantum Rabi model(QRM)describing the interaction between a two-level atom and a two-mode cavity field.The quantum phase transitions are found when the ratioηof transition frequency of atom to frequency of cavity field approaches infinity.We apply the Schrieffer–Wolff(SW)transformation to derive the low-energy effective Hamiltonian of the two-mode QRM,thus yielding the critical point and rich phase diagram of quantum phase transitions.The phase diagram consists of four regions:a normal phase,an electric superradiant phase,a magnetic superradiant phase and an electromagnetic superradiant phase.The quantum phase transition between the normal phase and the electric(magnetic)superradiant phase is of second order and associates with the breaking of the discrete Z_(2) symmetry.On the other hand,the phase transition between the electric superradiant phase and the magnetic superradiant phase is of first order and relates to the breaking of the continuous U(1)symmetry.Several important physical quantities,for example the excitation energy and average photon number in the four phases,are derived.We find that the excitation spectra exhibit the Nambu–Goldstone mode.We calculate analytically the higher-order correction and finite-frequency exponents of relevant quantities.To confirm the validity of the low-energy effective Hamiltonians analytically derived by us,the finite-frequency scaling relation of the averaged photon numbers is calculated by numerically diagonalizing the two-mode quantum Rabi Hamiltonian.展开更多
This article investigates the issue of event-triggered fault detection(FD)filter design for T-S fuzzy systems with local nonlinear models.A novel H−/H∞FD filter subject to the event triggering transmission mechanism ...This article investigates the issue of event-triggered fault detection(FD)filter design for T-S fuzzy systems with local nonlinear models.A novel H−/H∞FD filter subject to the event triggering transmission mechanism is designed in finite-frequency domain.Then,a novel lemma,in which the nonlinear part and the event triggering mechanism are dealt appropriately,is presented to capture the sensitivity and robustness performances.In addition,the slack matrices are utilised to derive optimal filter parameters by solving a convex optimisation problem.The less conservative FD method can get better detection performances than those entire-frequency methods.Finally,an example is introduced to verify the new results.展开更多
The Paleoproterozoic was a critical time in whether modern-style plate tectonics had become globally dominant(e.g.,Wan et al.,2020).The Capricorn Orogen witnessed the assembly of the Pilbara and Yilgarn Cratons and an...The Paleoproterozoic was a critical time in whether modern-style plate tectonics had become globally dominant(e.g.,Wan et al.,2020).The Capricorn Orogen witnessed the assembly of the Pilbara and Yilgarn Cratons and an exotic microcontinent,the Glenburgh Terrane,to form the West Australia Craton(WAC)through two collisional orogenic events,the 2215–2145 Ma Ophthalmian and 2005–1950 Ma Glenburgh Orogenies(Johnson et al.,2013;Fig.1).Compared to other Proterozoic orogenic belts in Australia,the Capricorn Orogen preserves‘complete'opposing continental margin successions,together with intervening arc fragments associated with oceanic closure and foreland basins associated with collisional loading(Cawood et al.,2009).展开更多
Wave front healing is a common natural phenomenon.To further investigate wave front healing,we simulated wave propagation in a spherical anomaly surrounded by homogeneous media using a high-order finite difference sol...Wave front healing is a common natural phenomenon.To further investigate wave front healing,we simulated wave propagation in a spherical anomaly surrounded by homogeneous media using a high-order finite difference solution of the acoustic equation.Furthermore,we analyzed the characteristics of the wave propagation in the anomaly,and found that they are related to the dominant frequency of the seismic wave and the dimensions of the anomaly.Through quantitative comparison of the wave front energy of the diffracted wave and transmitted wave,we summarized the influences of the wave front healing on seismic tomography.We conclude that,under the strong scattering condition,only positive anomalies can be inverted by ray-based tomography,only large anomalies can be inverted by finite-frequency tomography,and small negative anomalies cannot be inverted by any first-arrival traveltime tomographic methods.These conclusions are verified by tomographic experiments based on different theoretical models.Finally,we propose that more information besides the first-arrival traveltime should be used to invert the high wave number components of the media.Besides the above acquisitions of wave front healing on seismic tomography,we explain the banana-doughnut phenomena,and offer a new insight into the wave scattering,which should be important for better understanding the wave propagation and seismic inversion.展开更多
This paper addresses the fault detection(FD)problem for discretetime sector-bounded non-linear systems with finite-frequency servo inputs.The non-linear systems are firstly modelled as multi-models.The main contributi...This paper addresses the fault detection(FD)problem for discretetime sector-bounded non-linear systems with finite-frequency servo inputs.The non-linear systems are firstly modelled as multi-models.The main contributions are that a novel FD filter which combines the finite-frequency H∞and H−indices is designed.Different from the existing methods,the proposed FD scheme guarantees that the generated residuals are robust against the servo inputs in fault-free case and sensitive to them in faulty cases.Thus,the small sensor stuck faults including outagefaults can be detected.For this class of systems,the existing finite-frequency FD filter design methods are invalid.A new lemma is developed to characterise the system performances in finite-frequency domain.In addition,sufficient conditions for the existence of such a FD filter are derived by introducing slack variable and linear matrix inequalities techniques.Finally,an example is presented to demonstrate the method and its effectiveness.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 90814013)
文摘Finite-frequency travel time tomography is a newly developing method.The main procedure in this new method is to compute the traveltime sensitive kernel.The travel time of the same scatterer needs to be used for computing the traveltime sensitive kernel many times.It is a time-consuming task.It is easy and fast to get the travel time from analytic equations in a simple model such as a homogenous or linear velocity media.However,most of the earth models are layered.It is cumbersome to get the travel time from analytic equations.In order to enhance the computation efficiency,we used the table look-up method to compute the finite-frequency travel time sensitive kernel for P-waves in a layered structure model.We chose the AK135 earth model for the velocity model.The table look-up method saved about 50% of the computation time.We enhanced the computation speed by using the table lookup method in the same velocity model,which was very useful for enhancing the computation efficiency for the finite-frequency travel time tomography.
基金partially supported by National Key R&D Program of China(2018YFB1304600)National Natural Science Foundation of China(51805021,U1813220)+1 种基金China Postdoctoral Science Foundation Grant(2018M631311)the Fundamental Research Funds for the Central Universities(XK1802-4)
文摘This work proposes a robust fault detection and isolation scheme for discrete-time systems subject to actuator faults,in which a bank of H_/H∞ fault detection unknown input observers(UIOs) and a zonotopic threshold analysis strategy are considered. In observer design, finite-frequency H_ index based on the generalized Kalman-Yakubovich-Popov lemma and H∞ technique are utilized to evaluate worst-case fault sensitivity and disturbance attenuation performance, respectively. The proposed H_/H∞ fault detection observers are designed to be insensitive to the corresponding actuator fault only, but sensitive to others.Then, to overcome the weakness of predefining threshold for FDI decision-making, this work proposes a zonotopic threshold analysis method to evaluate the generated residuals. The FDI decision-making relies on the evaluation with a dynamical zonotopic threshold. Finally, numerical simulations are provided to show the feasibility of the proposed scheme.
基金supported by the National Natural Science Foundation of China(Grant No.12135003)。
文摘We investigate the two-mode quantum Rabi model(QRM)describing the interaction between a two-level atom and a two-mode cavity field.The quantum phase transitions are found when the ratioηof transition frequency of atom to frequency of cavity field approaches infinity.We apply the Schrieffer–Wolff(SW)transformation to derive the low-energy effective Hamiltonian of the two-mode QRM,thus yielding the critical point and rich phase diagram of quantum phase transitions.The phase diagram consists of four regions:a normal phase,an electric superradiant phase,a magnetic superradiant phase and an electromagnetic superradiant phase.The quantum phase transition between the normal phase and the electric(magnetic)superradiant phase is of second order and associates with the breaking of the discrete Z_(2) symmetry.On the other hand,the phase transition between the electric superradiant phase and the magnetic superradiant phase is of first order and relates to the breaking of the continuous U(1)symmetry.Several important physical quantities,for example the excitation energy and average photon number in the four phases,are derived.We find that the excitation spectra exhibit the Nambu–Goldstone mode.We calculate analytically the higher-order correction and finite-frequency exponents of relevant quantities.To confirm the validity of the low-energy effective Hamiltonians analytically derived by us,the finite-frequency scaling relation of the averaged photon numbers is calculated by numerically diagonalizing the two-mode quantum Rabi Hamiltonian.
基金the Funds of the Natural Science Foundation of Liaoning Province of China[grant number 2019-ZD-0118].
文摘This article investigates the issue of event-triggered fault detection(FD)filter design for T-S fuzzy systems with local nonlinear models.A novel H−/H∞FD filter subject to the event triggering transmission mechanism is designed in finite-frequency domain.Then,a novel lemma,in which the nonlinear part and the event triggering mechanism are dealt appropriately,is presented to capture the sensitivity and robustness performances.In addition,the slack matrices are utilised to derive optimal filter parameters by solving a convex optimisation problem.The less conservative FD method can get better detection performances than those entire-frequency methods.Finally,an example is introduced to verify the new results.
文摘The Paleoproterozoic was a critical time in whether modern-style plate tectonics had become globally dominant(e.g.,Wan et al.,2020).The Capricorn Orogen witnessed the assembly of the Pilbara and Yilgarn Cratons and an exotic microcontinent,the Glenburgh Terrane,to form the West Australia Craton(WAC)through two collisional orogenic events,the 2215–2145 Ma Ophthalmian and 2005–1950 Ma Glenburgh Orogenies(Johnson et al.,2013;Fig.1).Compared to other Proterozoic orogenic belts in Australia,the Capricorn Orogen preserves‘complete'opposing continental margin successions,together with intervening arc fragments associated with oceanic closure and foreland basins associated with collisional loading(Cawood et al.,2009).
基金supported by National Natural Science Foundation of China(Grant No. 40804023)National Basic Research Program of China (Grant No. 2006CB202402)+1 种基金Hi-tech R&D Program of China (Grant No.2008AA093001)Project of State Key Laboratory of Marine Geology of China (Grant No. MG200909)
文摘Wave front healing is a common natural phenomenon.To further investigate wave front healing,we simulated wave propagation in a spherical anomaly surrounded by homogeneous media using a high-order finite difference solution of the acoustic equation.Furthermore,we analyzed the characteristics of the wave propagation in the anomaly,and found that they are related to the dominant frequency of the seismic wave and the dimensions of the anomaly.Through quantitative comparison of the wave front energy of the diffracted wave and transmitted wave,we summarized the influences of the wave front healing on seismic tomography.We conclude that,under the strong scattering condition,only positive anomalies can be inverted by ray-based tomography,only large anomalies can be inverted by finite-frequency tomography,and small negative anomalies cannot be inverted by any first-arrival traveltime tomographic methods.These conclusions are verified by tomographic experiments based on different theoretical models.Finally,we propose that more information besides the first-arrival traveltime should be used to invert the high wave number components of the media.Besides the above acquisitions of wave front healing on seismic tomography,we explain the banana-doughnut phenomena,and offer a new insight into the wave scattering,which should be important for better understanding the wave propagation and seismic inversion.
基金This work was supported in part by the Funds of the National Natural Science Foundation of China[grant number 61621004],[grant number 61420106016]the Research Fund of State Key Laboratory of Synthetical Automation for Process Industries[grant number 2013ZCX01].
文摘This paper addresses the fault detection(FD)problem for discretetime sector-bounded non-linear systems with finite-frequency servo inputs.The non-linear systems are firstly modelled as multi-models.The main contributions are that a novel FD filter which combines the finite-frequency H∞and H−indices is designed.Different from the existing methods,the proposed FD scheme guarantees that the generated residuals are robust against the servo inputs in fault-free case and sensitive to them in faulty cases.Thus,the small sensor stuck faults including outagefaults can be detected.For this class of systems,the existing finite-frequency FD filter design methods are invalid.A new lemma is developed to characterise the system performances in finite-frequency domain.In addition,sufficient conditions for the existence of such a FD filter are derived by introducing slack variable and linear matrix inequalities techniques.Finally,an example is presented to demonstrate the method and its effectiveness.
