The low-frequency oscillation(LFO)has occurred in the train-network system due to the introduction of the power electronics of the trains.The modeling and analyzing method in current researches based on electrified ra...The low-frequency oscillation(LFO)has occurred in the train-network system due to the introduction of the power electronics of the trains.The modeling and analyzing method in current researches based on electrified railway unilateral power supply system are not suitable for the LFO analysis in a bilateral power supply system,where the trains are supplied by two traction substations.In this work,based on the single-input and single-output impedance model of China CRH5 trains,the node admittance matrices of the train-network system both in unilateral and bilateral power supply modes are established,including three-phase power grid,traction transformers and traction network.Then the modal analysis is used to study the oscillation modes and propagation characteristics of the unilateral and bilateral power supply systems.Moreover,the influence of the equivalent inductance of the power grid,the length of the transmission line,and the length of the traction network are analyzed on the critical oscillation mode of the bilateral power supply system.Finally,the theoretical analysis results are verified by the time-domain simulation model in MATLAB/Simulink.展开更多
There has been a lot of discussion about the atmospheric heat source over the Tibetan Plateau(TP)and the low-frequency oscillation of atmospheric circulation.However,the research on low-frequency oscillation of heat s...There has been a lot of discussion about the atmospheric heat source over the Tibetan Plateau(TP)and the low-frequency oscillation of atmospheric circulation.However,the research on low-frequency oscillation of heat source over TP and its impact on atmospheric circulation are not fully carried out.By using the vertically integrated apparent heat source which is calculated by the derivation method,main oscillation periods and propagation features of the summer apparent heat source over the eastern TP(Q1ETP)are diagnosed and analyzed from 1981 to 2000.The results are as follows:(1)Summer Q1ETP has two significant oscillation periods:one is 10-20d(BWO,Quasi-Biweekly Oscillation)and the other is 30-60d(LFO,Low-frequency Oscillation).(2)A significant correlation is found between Q1ETP and rainfall over the eastern TP in 1985 and 1992,showing that the low-frequency oscillation of heat source is likely to be stimulated by oscillation of latent heat.(3)The oscillation of heat source on the plateau mainly generates locally but sometimes originates from elsewhere.The BWO of Q1ETP mainly exhibits stationary wave,sometimes moves out(mainly eastward),and has a close relationship with the BWO from the Bay of Bengal.Showing the same characteristics as BWO,the LFO mainly shows local oscillation,occasionally propagates(mainly westward),and connects with the LFO from East China.In summary,more attention should be paid to the study on BWO of Q1ETP.展开更多
This study investigates the relationship between summer low-frequency rainfall over southern China and tropical intraseasonal oscillation(ISO) in the atmosphere by examining systematically the propagation features of ...This study investigates the relationship between summer low-frequency rainfall over southern China and tropical intraseasonal oscillation(ISO) in the atmosphere by examining systematically the propagation features of the tropical ISO in terms of focusing on five large-scale low-frequency rainfall regimes in summer over southern China. It is demonstrated that there is a close linkage between the five rainfall regimes over southern China and the northward propagation of the tropical ISO. The moist ISO signals, which influence the low-frequency rainfall events in different regions of southern China, mainly propagate northwestward from the tropical ocean to the southeast of China. The southeast China rainfall regime is intimately associated with the moist ISO signals propagating northwestward from the equatorial mid-western Pacific Ocean. For both the Yangtze River regime and South of Yangtze River regime, the moist ISO signals over the northern South China Sea show an evident northward propagation towards the Yangtze River region, and then propagate westward. It is further found that the interaction between the northward propagation of low-latitude ISO signals and the southward propagation of high-latitude ISO signals can also make a clear influence on the low-frequency rainfall in southern China. For the Southern China regime, the moist ISO signals show a significant northward propagation from the Philippines. Moreover, for the rainless regime, southern China is under dry ISO signals' control, and the latter shows no clear propagation to southern China. This study may provide insights for the extended-range forecasting of summer rainfall in southern China.展开更多
In practical operations,low-frequency oscillation(LFO)occurs and leads to converter blocking when multiple electrical rail vehicles at the platform are powered by the traction network.This paper proposes a small-signa...In practical operations,low-frequency oscillation(LFO)occurs and leads to converter blocking when multiple electrical rail vehicles at the platform are powered by the traction network.This paper proposes a small-signal model in state-space form for multiple vehicle-grid systems based on a dynamic phasor.This model uses the phasor amplitude and phase as variables to accurately describe the dynamics of the converter phase-domain control.An eigenvalue based-method is introduced to investigate the LFO with advantages of acquiring all oscillatory modes and analyzing participation factors.Two low-frequency dominant modes are identified by eigenvalues.Mode shape reveals that one of the modes involves the oscillations between the grid-connected converters and the traction network,and the other one involves the oscillations among these converters.Then the sensitivities of these two low-frequency modes to different system parameters are analyzed.Participation factors of system state variables,when the number of connected vehicle increases,are compared.Finally,the theoretical analysis is verified by nonlinear time-domain simulations and the modal analysis based on the estimation of signal parameters via the rotational invariance techniques(ESPRIT)method.展开更多
The mode-based damping torque analysis(M-DTA)method for studying the effect of an external controller on power system low-frequency oscillations is proposed in this paper.First,based on the interconnection model betwe...The mode-based damping torque analysis(M-DTA)method for studying the effect of an external controller on power system low-frequency oscillations is proposed in this paper.First,based on the interconnection model between the system and the controller in the frequency domain,the oscillation loop corresponding to the electromechanical oscillation mode is built,and then the mode-based damping torque of the controller can be calculated.Then,the application of the M-DTA method in the power system is illustrated.The derivation shows that in the single-machine infinite-bus power system,the M-DTA method is completely equivalent to the classical damping torque analysis(C-DTA)method.In the multi-machine power system,the mode-based damping torque directily reflects the effect of the controller on the oscillation mode,overcoming the shortcomings of the C-DTA method in which there is no direct correspondence between the damping torque and the oscillation mode.By deriving the relationship with the residue index,the M-DTA method shows higher accuracy than the residue method in applications,such as controller parameter adjustment.Finally,two example power systems are presented to demonstrate the application of the proposed M-DTA method.Index Terms-Electromechanical oscillation mode,FACTS,interconnection model in the frequency domain,mode-based damping torque analysis(M-DTA),power system low-frequency oscillation,PSS,residue method.展开更多
This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from ...This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from the Chengdu Institute of Plateau Meteorology to discuss modulation of the Madden-Julian Oscillation(MJO)on the Tibetan Plateau Vortex(TPV).Wavelet and composite analysis are used.Results show that the MJO plays an important role in the occurrence of the TPV that the number of TPVs generated within an active period of the MJO is three times as much as that during an inactive period.In addition,during the active period,the number of the TPVs generated in phases 1 and 2 is larger than that in phases 3 and 7.After compositing phases 1 and 7 separately,all meteorological elements in phase 1 are apparently conducive to the generation of the TPV,whereas those in phase 7 are somewhat constrained.With its eastward propagation process,the MJO convection centre spreads eastward,and the vertical circulation within the tropical atmosphere changes.Due to the interaction between the mid-latitude and low-latitude atmosphere,changes occur in the baroclinic characteristics of the atmosphere,the available potential energy and eddy available potential energy of the atmosphere,and the circulation structures of the atmosphere over the Tibetan Plateau(TP) and surrounding areas.This results in significantly different water vapour transportation and latent heat distribution.Advantageous and disadvantageous conditions therefore alternate,leading to a significant difference among the numbers of plateau vortex in different phases.展开更多
A modified slow-fast analysis method is presented for the periodically excited non-autonomous dynamical system with an order gap between the exciting frequency and the natural frequency.By regarding the exciting term ...A modified slow-fast analysis method is presented for the periodically excited non-autonomous dynamical system with an order gap between the exciting frequency and the natural frequency.By regarding the exciting term as a slow-varying parameter,a generalized autonomous fast subsystem can be defined,the equilibrium branches as well as the bifurcations of which can be employed to account for the mechanism of the bursting oscillations by combining the transformed phase portrait introduced.As an example,a typical periodically excited Hartley model is used to demonstrate the validness of the method,in which the exciting frequency is far less than the natural frequency.The equilibrium branches and their bifurcations of the fast subsystem with the variation of the slow-varying parameter are presented.Bursting oscillations for two typical cases are considered,which reveals that,fold bifurcation may cause the the trajectory to jump between different equilibrium branches,while Hopf bifurcation may cause the trajectory to oscillate around the stable limit cycle.展开更多
Based on dynamical characteristics of the tropical atmosphere, a mathematical model of low-frequency oscillation (LFO hereinafter) in low-latitudes has been developed. The analysis shows that the distributive fea- tur...Based on dynamical characteristics of the tropical atmosphere, a mathematical model of low-frequency oscillation (LFO hereinafter) in low-latitudes has been developed. The analysis shows that the distributive fea- tures (shear of wind speed) of easterlies and westerlies in low-latitudes, the divergence and convergence of meridional and zonal flow, the vertical structure of diabatic heating and the Coriolis parameter f are the basic factors resulting in the LFO, while quasi-periodical baroclinity development or index cycle of westerly waves in middle-latitudes of the Southern Hemisphere is an external forcing to the LFO in the tropical atmos- phere. The resonance on adequate condition makes LFO suddenly enhanced.展开更多
Extreme multistability has seized scientists’ attention due to its rich diversity of dynamical behaviors and great flexibility in engineering applications. In this paper, a four-dimensional(4D) memcapacitive oscillat...Extreme multistability has seized scientists’ attention due to its rich diversity of dynamical behaviors and great flexibility in engineering applications. In this paper, a four-dimensional(4D) memcapacitive oscillator is built using four linear circuit elements and one nonlinear charge-controlled memcapacitor with a cosine inverse memcapacitance. The 4D memcapacitive oscillator possesses a line equilibrium set, and its stability periodically evolves with the initial condition of the memcapacitor. The 4D memcapacitive oscillator exhibits initial-condition-switched boosting extreme multistability due to the periodically evolving stability. Complex dynamical behaviors of period doubling/halving bifurcations, chaos crisis, and initial-condition-switched coexisting attractors are revealed by bifurcation diagrams, Lyapunov exponents, and phase portraits. Thereafter, a reconstructed system is derived via integral transformation to reveal the forming mechanism of the initial-condition-switched boosting extreme multistability in the memcapacitive oscillator. Finally, an implementation circuit is designed for the reconstructed system, and Power SIMulation(PSIM) simulations are executed to confirm the validity of the numerical analysis.展开更多
Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic glasses.Here the effect of oscillation strain amplitude on ...Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic glasses.Here the effect of oscillation strain amplitude on the secondary relaxation of a typical Labased metallic glass was studied using the dynamic mechanical analysis method.The apparent activation energy of theβrelaxation is shown to increase with the oscillation strain amplitude.When it changes from 0.02%to 0.16%,the activation energy increases from 0.73 to 0.96 eV.Simultaneously,the intensity of theβrelaxation shifts toward high temperature.Additionally,the apparentβrelaxation is found to be sensitive to the physical aging below the glass transition temperature.The findings suggest a correlation between the inelastic deformation and the relaxation behavior of amorphous metals.展开更多
A baroclinic semi-geostrophic model with evaporation-wind feedback mechanism(EWFM) and CISK is established,two non-dimensional parameters a and η are introduced to represent EWFM and CISK,respectively.Analytic soluti...A baroclinic semi-geostrophic model with evaporation-wind feedback mechanism(EWFM) and CISK is established,two non-dimensional parameters a and η are introduced to represent EWFM and CISK,respectively.Analytic solutions of the model system are obtained,dynamics analyses and the model atmosphere calculations further confirm that EWFM and CISK are very important physical processes in leading to the low-frequency oscillations in the tropics.展开更多
In this paper, we describe a new silicon-die thermal monitoring approach using spatiotemporal signal processing technique for Wafer-Scale IC thermome- chanical stress monitoring. It is proposed in the context of a waf...In this paper, we describe a new silicon-die thermal monitoring approach using spatiotemporal signal processing technique for Wafer-Scale IC thermome- chanical stress monitoring. It is proposed in the context of a wafer-scale-based (WaferICTM) rapid prototyping platform for electronic systems. This technique will be embedded into the structure of the WaferIC, and will be used as a preventive measure to protect the wafer from possible damages that can be caused by excessive thermomechanical stress. The paper also presents spatial and spatiotemporal algorithms and the experimental results from an IR images collection campaign conducted using an IR camera.展开更多
[目的]虚拟惯性阻尼控制(Virtual Inertia and Damping Control,VIDC)潜在的正反馈可能加剧控制环路内部的相互作用进而引起母线电压低频振荡,破坏电动汽车直流充电站(Electric Vehicle DC Charging Station,EVCS)的稳定性。虽然已有多...[目的]虚拟惯性阻尼控制(Virtual Inertia and Damping Control,VIDC)潜在的正反馈可能加剧控制环路内部的相互作用进而引起母线电压低频振荡,破坏电动汽车直流充电站(Electric Vehicle DC Charging Station,EVCS)的稳定性。虽然已有多时间尺度阻抗模型解释VIDC的稳定机制和VIDC控制下EVCS的低频振荡机理,但其本质上是一个高阶传递函数,获取阻尼控制策略的解析表达式。[方法]针对这一问题,文章对环路虚拟阻抗进行了详细的阻抗分析,直观地揭示了每个控制环路阻抗高阶属性的根本原因。[结果]通过伯德图近似提出了控制环路闭环增益的降阶拟合方法,建立了低阶阻抗电路模型。[结论]通过Matlab/Simulation仿真结果验证了所提出的多时间尺度低阶阻抗电路模型的有效性。展开更多
基金This work was supported by the Applied Basic Research Program of Science and Technology Plan Project of Sichuan Province of China(No.2020YJ0252).
文摘The low-frequency oscillation(LFO)has occurred in the train-network system due to the introduction of the power electronics of the trains.The modeling and analyzing method in current researches based on electrified railway unilateral power supply system are not suitable for the LFO analysis in a bilateral power supply system,where the trains are supplied by two traction substations.In this work,based on the single-input and single-output impedance model of China CRH5 trains,the node admittance matrices of the train-network system both in unilateral and bilateral power supply modes are established,including three-phase power grid,traction transformers and traction network.Then the modal analysis is used to study the oscillation modes and propagation characteristics of the unilateral and bilateral power supply systems.Moreover,the influence of the equivalent inductance of the power grid,the length of the transmission line,and the length of the traction network are analyzed on the critical oscillation mode of the bilateral power supply system.Finally,the theoretical analysis results are verified by the time-domain simulation model in MATLAB/Simulink.
基金General Program from National Natural Science Foundation of China(40475029)Key Projects of the National Natural Science Foundation of China(40633018,90711003)
文摘There has been a lot of discussion about the atmospheric heat source over the Tibetan Plateau(TP)and the low-frequency oscillation of atmospheric circulation.However,the research on low-frequency oscillation of heat source over TP and its impact on atmospheric circulation are not fully carried out.By using the vertically integrated apparent heat source which is calculated by the derivation method,main oscillation periods and propagation features of the summer apparent heat source over the eastern TP(Q1ETP)are diagnosed and analyzed from 1981 to 2000.The results are as follows:(1)Summer Q1ETP has two significant oscillation periods:one is 10-20d(BWO,Quasi-Biweekly Oscillation)and the other is 30-60d(LFO,Low-frequency Oscillation).(2)A significant correlation is found between Q1ETP and rainfall over the eastern TP in 1985 and 1992,showing that the low-frequency oscillation of heat source is likely to be stimulated by oscillation of latent heat.(3)The oscillation of heat source on the plateau mainly generates locally but sometimes originates from elsewhere.The BWO of Q1ETP mainly exhibits stationary wave,sometimes moves out(mainly eastward),and has a close relationship with the BWO from the Bay of Bengal.Showing the same characteristics as BWO,the LFO mainly shows local oscillation,occasionally propagates(mainly westward),and connects with the LFO from East China.In summary,more attention should be paid to the study on BWO of Q1ETP.
基金973 Program of China(2015CB453203,2013CB430203)China Meteorological Special Project(GYHY201406022)China National Science Foundation(41505065,41375062)
文摘This study investigates the relationship between summer low-frequency rainfall over southern China and tropical intraseasonal oscillation(ISO) in the atmosphere by examining systematically the propagation features of the tropical ISO in terms of focusing on five large-scale low-frequency rainfall regimes in summer over southern China. It is demonstrated that there is a close linkage between the five rainfall regimes over southern China and the northward propagation of the tropical ISO. The moist ISO signals, which influence the low-frequency rainfall events in different regions of southern China, mainly propagate northwestward from the tropical ocean to the southeast of China. The southeast China rainfall regime is intimately associated with the moist ISO signals propagating northwestward from the equatorial mid-western Pacific Ocean. For both the Yangtze River regime and South of Yangtze River regime, the moist ISO signals over the northern South China Sea show an evident northward propagation towards the Yangtze River region, and then propagate westward. It is further found that the interaction between the northward propagation of low-latitude ISO signals and the southward propagation of high-latitude ISO signals can also make a clear influence on the low-frequency rainfall in southern China. For the Southern China regime, the moist ISO signals show a significant northward propagation from the Philippines. Moreover, for the rainless regime, southern China is under dry ISO signals' control, and the latter shows no clear propagation to southern China. This study may provide insights for the extended-range forecasting of summer rainfall in southern China.
基金This work was supported in part by the Fundamental Research Funds for the Central Universities of China(No.2682019CX20)in part by the Applied Basic Research Program of Science and Technology Plan Project of Sichuan Province of China(No.2020YJ0252)。
文摘In practical operations,low-frequency oscillation(LFO)occurs and leads to converter blocking when multiple electrical rail vehicles at the platform are powered by the traction network.This paper proposes a small-signal model in state-space form for multiple vehicle-grid systems based on a dynamic phasor.This model uses the phasor amplitude and phase as variables to accurately describe the dynamics of the converter phase-domain control.An eigenvalue based-method is introduced to investigate the LFO with advantages of acquiring all oscillatory modes and analyzing participation factors.Two low-frequency dominant modes are identified by eigenvalues.Mode shape reveals that one of the modes involves the oscillations between the grid-connected converters and the traction network,and the other one involves the oscillations among these converters.Then the sensitivities of these two low-frequency modes to different system parameters are analyzed.Participation factors of system state variables,when the number of connected vehicle increases,are compared.Finally,the theoretical analysis is verified by nonlinear time-domain simulations and the modal analysis based on the estimation of signal parameters via the rotational invariance techniques(ESPRIT)method.
基金supported in part by the National Natural Science Foundation of China under Grant No.U1766202,51907179 and 51977197.
文摘The mode-based damping torque analysis(M-DTA)method for studying the effect of an external controller on power system low-frequency oscillations is proposed in this paper.First,based on the interconnection model between the system and the controller in the frequency domain,the oscillation loop corresponding to the electromechanical oscillation mode is built,and then the mode-based damping torque of the controller can be calculated.Then,the application of the M-DTA method in the power system is illustrated.The derivation shows that in the single-machine infinite-bus power system,the M-DTA method is completely equivalent to the classical damping torque analysis(C-DTA)method.In the multi-machine power system,the mode-based damping torque directily reflects the effect of the controller on the oscillation mode,overcoming the shortcomings of the C-DTA method in which there is no direct correspondence between the damping torque and the oscillation mode.By deriving the relationship with the residue index,the M-DTA method shows higher accuracy than the residue method in applications,such as controller parameter adjustment.Finally,two example power systems are presented to demonstrate the application of the proposed M-DTA method.Index Terms-Electromechanical oscillation mode,FACTS,interconnection model in the frequency domain,mode-based damping torque analysis(M-DTA),power system low-frequency oscillation,PSS,residue method.
基金National Basic Research Program of China(2012CB417202)National Natural Science Foundation of China(41175045,91337215,Ul 133603)Special Fund for Meteorological Research in the Public Interest(GYHY201206042)
文摘This study uses NCEP/NCAR daily reanalysis data,NOAA outgoing long-wave radiation(OLR) data,the real-time multivariate MJO(RMM) index from the Australian Bureau of Meteorology and Tibetan Plateau vortex(TPV)data from the Chengdu Institute of Plateau Meteorology to discuss modulation of the Madden-Julian Oscillation(MJO)on the Tibetan Plateau Vortex(TPV).Wavelet and composite analysis are used.Results show that the MJO plays an important role in the occurrence of the TPV that the number of TPVs generated within an active period of the MJO is three times as much as that during an inactive period.In addition,during the active period,the number of the TPVs generated in phases 1 and 2 is larger than that in phases 3 and 7.After compositing phases 1 and 7 separately,all meteorological elements in phase 1 are apparently conducive to the generation of the TPV,whereas those in phase 7 are somewhat constrained.With its eastward propagation process,the MJO convection centre spreads eastward,and the vertical circulation within the tropical atmosphere changes.Due to the interaction between the mid-latitude and low-latitude atmosphere,changes occur in the baroclinic characteristics of the atmosphere,the available potential energy and eddy available potential energy of the atmosphere,and the circulation structures of the atmosphere over the Tibetan Plateau(TP) and surrounding areas.This results in significantly different water vapour transportation and latent heat distribution.Advantageous and disadvantageous conditions therefore alternate,leading to a significant difference among the numbers of plateau vortex in different phases.
基金supported by the National Natural Science Foundation of China(Grants11632008 and 11872189)
文摘A modified slow-fast analysis method is presented for the periodically excited non-autonomous dynamical system with an order gap between the exciting frequency and the natural frequency.By regarding the exciting term as a slow-varying parameter,a generalized autonomous fast subsystem can be defined,the equilibrium branches as well as the bifurcations of which can be employed to account for the mechanism of the bursting oscillations by combining the transformed phase portrait introduced.As an example,a typical periodically excited Hartley model is used to demonstrate the validness of the method,in which the exciting frequency is far less than the natural frequency.The equilibrium branches and their bifurcations of the fast subsystem with the variation of the slow-varying parameter are presented.Bursting oscillations for two typical cases are considered,which reveals that,fold bifurcation may cause the the trajectory to jump between different equilibrium branches,while Hopf bifurcation may cause the trajectory to oscillate around the stable limit cycle.
基金National Natural Science Foundation of ChinaMonsoon Research Fund s from State Meteorological Administration
文摘Based on dynamical characteristics of the tropical atmosphere, a mathematical model of low-frequency oscillation (LFO hereinafter) in low-latitudes has been developed. The analysis shows that the distributive fea- tures (shear of wind speed) of easterlies and westerlies in low-latitudes, the divergence and convergence of meridional and zonal flow, the vertical structure of diabatic heating and the Coriolis parameter f are the basic factors resulting in the LFO, while quasi-periodical baroclinity development or index cycle of westerly waves in middle-latitudes of the Southern Hemisphere is an external forcing to the LFO in the tropical atmos- phere. The resonance on adequate condition makes LFO suddenly enhanced.
基金Project supported by the National Natural Science Foundation of China (Nos. 51777016 and 61801054)the Natural Science Foundation of Jiangsu Province,China (No. BK20191451)+2 种基金the Natural Science Foundation of Changzhou,Jiangsu Province,China (No. CJ20190037)the Open Research Fund of Key Laboratory of MEMS of Ministry of EducationSoutheast University,China。
文摘Extreme multistability has seized scientists’ attention due to its rich diversity of dynamical behaviors and great flexibility in engineering applications. In this paper, a four-dimensional(4D) memcapacitive oscillator is built using four linear circuit elements and one nonlinear charge-controlled memcapacitor with a cosine inverse memcapacitance. The 4D memcapacitive oscillator possesses a line equilibrium set, and its stability periodically evolves with the initial condition of the memcapacitor. The 4D memcapacitive oscillator exhibits initial-condition-switched boosting extreme multistability due to the periodically evolving stability. Complex dynamical behaviors of period doubling/halving bifurcations, chaos crisis, and initial-condition-switched coexisting attractors are revealed by bifurcation diagrams, Lyapunov exponents, and phase portraits. Thereafter, a reconstructed system is derived via integral transformation to reveal the forming mechanism of the initial-condition-switched boosting extreme multistability in the memcapacitive oscillator. Finally, an implementation circuit is designed for the reconstructed system, and Power SIMulation(PSIM) simulations are executed to confirm the validity of the numerical analysis.
基金supported by the National Natural Science Foundation of China(Grant Nos.51971178 and 52271153)the Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province(Grant No.2021JC-12)+4 种基金the Natural Science Foundation of Chongqing(Grant No.cstc2020jcyj-jq X0001)financial support from“Proyecto PID2020-112975GB-I00 de investigación financiado por MCIN/AEI/10.13039/501100011033”Generalitat de Catalunya AGAUR 2021-SGR-343 grantsupported by the National Natural Science Foundation of China(Grant No.12072344)the Youth Innovation Promotion Association of the Chinese Academy of Sciences。
文摘Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic glasses.Here the effect of oscillation strain amplitude on the secondary relaxation of a typical Labased metallic glass was studied using the dynamic mechanical analysis method.The apparent activation energy of theβrelaxation is shown to increase with the oscillation strain amplitude.When it changes from 0.02%to 0.16%,the activation energy increases from 0.73 to 0.96 eV.Simultaneously,the intensity of theβrelaxation shifts toward high temperature.Additionally,the apparentβrelaxation is found to be sensitive to the physical aging below the glass transition temperature.The findings suggest a correlation between the inelastic deformation and the relaxation behavior of amorphous metals.
基金This work is supported by the National Natural Science Foundation of China.
文摘A baroclinic semi-geostrophic model with evaporation-wind feedback mechanism(EWFM) and CISK is established,two non-dimensional parameters a and η are introduced to represent EWFM and CISK,respectively.Analytic solutions of the model system are obtained,dynamics analyses and the model atmosphere calculations further confirm that EWFM and CISK are very important physical processes in leading to the low-frequency oscillations in the tropics.
文摘In this paper, we describe a new silicon-die thermal monitoring approach using spatiotemporal signal processing technique for Wafer-Scale IC thermome- chanical stress monitoring. It is proposed in the context of a wafer-scale-based (WaferICTM) rapid prototyping platform for electronic systems. This technique will be embedded into the structure of the WaferIC, and will be used as a preventive measure to protect the wafer from possible damages that can be caused by excessive thermomechanical stress. The paper also presents spatial and spatiotemporal algorithms and the experimental results from an IR images collection campaign conducted using an IR camera.
文摘[目的]虚拟惯性阻尼控制(Virtual Inertia and Damping Control,VIDC)潜在的正反馈可能加剧控制环路内部的相互作用进而引起母线电压低频振荡,破坏电动汽车直流充电站(Electric Vehicle DC Charging Station,EVCS)的稳定性。虽然已有多时间尺度阻抗模型解释VIDC的稳定机制和VIDC控制下EVCS的低频振荡机理,但其本质上是一个高阶传递函数,获取阻尼控制策略的解析表达式。[方法]针对这一问题,文章对环路虚拟阻抗进行了详细的阻抗分析,直观地揭示了每个控制环路阻抗高阶属性的根本原因。[结果]通过伯德图近似提出了控制环路闭环增益的降阶拟合方法,建立了低阶阻抗电路模型。[结论]通过Matlab/Simulation仿真结果验证了所提出的多时间尺度低阶阻抗电路模型的有效性。