This study focuses on the interdecadal changes in ENSO properties emerging around the year 2000. Compared to 1980-1999, after 2000, the ENSO amplitude weakened, the occurrence of the central Pacific （CP） Et Nino inc...This study focuses on the interdecadal changes in ENSO properties emerging around the year 2000. Compared to 1980-1999, after 2000, the ENSO amplitude weakened, the occurrence of the central Pacific （CP） Et Nino increased, and the eastern Pacific （EP） El Nino became suppressed. Meanwhile, the dominant period of ENSO shortened from quasi-quadrennial （QQ） to quasi-biennial （QB）. The authors show that these changes in ENSO properties are evidently consistent with the change in the stability of the ENSO mode through connecting the two ENSO types with the two coupled ENSO modes, i.e. the QQ and QB modes. It is suggested that the relative activity or stability of the two ENSO modes changed after the year 2000. The intensity of both the QQ and QB mode weakened. The QQ mode, which is linked to EP ENSO and was significantly strong during 1980-1999, became much weaker after 2000 in terms of the EP type almost disappearing. Compared with the weakness of the QQ mode, the QB mode, as manifested by the CP type, remained active and became dominant in the tropical Pacific after 2000. Analysis shows that the changes in mean states in the tropical Pacific were likely responsible for the interdecadal ENSO changes around the year 2000.展开更多
The skill of most ENSO prediction models has declined significantly since 2000.This decline may be due to a weakening of the correlation between tropical predictors and ENSO.Moreover,the effects of extratropical ocean...The skill of most ENSO prediction models has declined significantly since 2000.This decline may be due to a weakening of the correlation between tropical predictors and ENSO.Moreover,the effects of extratropical ocean variability on ENSO have increased during this period.To improve ENSO predictability,the authors investigate the influence of the extratropical Atlantic and Pacific oceans on ENSO during the pre-2000 and post-2000 periods,and find that the influence of the northern tropical Atlantic sea surface temperature(NTA SST)on ENSO has significantly increased since 2000.Furthermore,there is a much earlier and stronger correlation between NTA SST and ENSO over the central-eastern Pacific during June-July-August in the post-2000 period compared with the pre-2000 period.The extratropical Pacific SST predictors for ENSO retain an approximate 10-month lead time after 2000.The authors use SST signals in the extratropical Atlantic and Pacific to predict ENSO using a statistical prediction model.This results in a significant improvement in ENSO prediction skill and an obvious decrease in the spring predictability barrier phenomenon of ENSO.These results indicate that extratropical Atlantic and Pacific SSTs can make substantial contributions to ENSO prediction,and can be used to enhance ENSO predictability after 2000.展开更多
The four-particle EPR entangled state 【 p, X2,X3,X4 】 is constructed. Thecorresponding quantum mechanical operator with respect to the classical transformation p → e~(λ1)p, X2 → e~(λ2)X2, X3 → e~(λ3) X3, and ...The four-particle EPR entangled state 【 p, X2,X3,X4 】 is constructed. Thecorresponding quantum mechanical operator with respect to the classical transformation p → e~(λ1)p, X2 → e~(λ2)X2, X3 → e~(λ3) X3, and X4 → ee~(λ4) X4 in the state 【 p, X2, X3, X4 】 isinvestigated, and the four-mode realization of the S U(1, 1) Lie algebra as well as thecorresponding squeezing operators are presented.展开更多
We adopt a dynamical algebraic method to study a four-level excited-doublet atom model and obtain the explicit expressions of the time-evolution operator and the density operator for the system. The nonclassical effec...We adopt a dynamical algebraic method to study a four-level excited-doublet atom model and obtain the explicit expressions of the time-evolution operator and the density operator for the system. The nonclassical effects of the system, such as collapses and revivals of the atomic inversion and squeezing of the radiation field, are also discussed.展开更多
A novel hybrid robust three-axis attitude control approach, namely HRTAC, is considered along with the well-known developments in the area of space systems, since there is a consensus among the related experts that th...A novel hybrid robust three-axis attitude control approach, namely HRTAC, is considered along with the well-known developments in the area of space systems, since there is a consensus among the related experts that the new insights may be taken into account as decision points to outperform the available materials. It is to note that the traditional control approaches may generally be upgraded, as long as a number of modifications are made with respect to state-of-the-art, in order to propose high-precision outcomes. Regarding the investigated issues, the robust sliding mode finite-time control approach is first designed to handle three-axis angular rates in the inner control loop, which consists of the pulse width pulse frequency modulations in line with the control allocation scheme and the system dynamics. The main subject to employ these modulations that is realizing in association with the control allocation scheme is to be able to handle a class of overactuated systems, in particular. The proportional derivative based linear quadratic regulator approach is then designed to handle three-axis rotational angles in the outer control loop, which consists of the system kinematics that is correspondingly concentrated to deal with the quaternion based model. The utilization of the linear and its nonlinear terms, simultaneously, are taken into real consideration as the research motivation, while the performance results are of the significance as the improved version in comparison with the recent investigated outcomes. Subsequently, there is a stability analysis to verify and guarantee the closed loop system performance in coping with the whole of nominal referenced commands. At the end, the effectiveness of the approach considered here is highlighted in line with a number of potential recent benchmarks.展开更多
The paper presents physical and mathematical models of kinetic system, drive system （electric and combustion traction motors）, and also wheel and rails traction vehicle supply system （car, special vehicle, modern t...The paper presents physical and mathematical models of kinetic system, drive system （electric and combustion traction motors）, and also wheel and rails traction vehicle supply system （car, special vehicle, modern tram vehicle）. Selected predictive and quasi dynamic control system algorithms of traction vehicle are presented in the paper. For selected constructions of traction vehicle drive system are presented in simulation models and are results of calculations of different exploitations work state of wheel vehicle with hybrid drive system. Results of computer calculations are verified with laboratory measurement and suitable corrections coefficient to simulations models of vehicles is introduced.展开更多
基金jointly supported by the China Meteorological Special Projects[grant number GYHY201506013]the National Basic Reaseach Program of China(973)[grant number2015CB453203]+1 种基金the National Natural Science Foundation of China[grant numbers 41405080 and 41375062]partly supported by the UK-China Research&Innovation Partnership Fund through the Met Office Climate Science for Service Partnership China as part of the Newton Fund
文摘This study focuses on the interdecadal changes in ENSO properties emerging around the year 2000. Compared to 1980-1999, after 2000, the ENSO amplitude weakened, the occurrence of the central Pacific （CP） Et Nino increased, and the eastern Pacific （EP） El Nino became suppressed. Meanwhile, the dominant period of ENSO shortened from quasi-quadrennial （QQ） to quasi-biennial （QB）. The authors show that these changes in ENSO properties are evidently consistent with the change in the stability of the ENSO mode through connecting the two ENSO types with the two coupled ENSO modes, i.e. the QQ and QB modes. It is suggested that the relative activity or stability of the two ENSO modes changed after the year 2000. The intensity of both the QQ and QB mode weakened. The QQ mode, which is linked to EP ENSO and was significantly strong during 1980-1999, became much weaker after 2000 in terms of the EP type almost disappearing. Compared with the weakness of the QQ mode, the QB mode, as manifested by the CP type, remained active and became dominant in the tropical Pacific after 2000. Analysis shows that the changes in mean states in the tropical Pacific were likely responsible for the interdecadal ENSO changes around the year 2000.
基金This research was supported by the National Natural Science Foundation of China[grant number 41975070]the Identification and mechanism study of global warming‘hiatus’phenomenon of 973 project of China[grant number 2016YFA0601801].
文摘The skill of most ENSO prediction models has declined significantly since 2000.This decline may be due to a weakening of the correlation between tropical predictors and ENSO.Moreover,the effects of extratropical ocean variability on ENSO have increased during this period.To improve ENSO predictability,the authors investigate the influence of the extratropical Atlantic and Pacific oceans on ENSO during the pre-2000 and post-2000 periods,and find that the influence of the northern tropical Atlantic sea surface temperature(NTA SST)on ENSO has significantly increased since 2000.Furthermore,there is a much earlier and stronger correlation between NTA SST and ENSO over the central-eastern Pacific during June-July-August in the post-2000 period compared with the pre-2000 period.The extratropical Pacific SST predictors for ENSO retain an approximate 10-month lead time after 2000.The authors use SST signals in the extratropical Atlantic and Pacific to predict ENSO using a statistical prediction model.This results in a significant improvement in ENSO prediction skill and an obvious decrease in the spring predictability barrier phenomenon of ENSO.These results indicate that extratropical Atlantic and Pacific SSTs can make substantial contributions to ENSO prediction,and can be used to enhance ENSO predictability after 2000.
基金Open Foundation of Laboratory of High-intensity Optics，中国科学院资助项目
文摘The four-particle EPR entangled state 【 p, X2,X3,X4 】 is constructed. Thecorresponding quantum mechanical operator with respect to the classical transformation p → e~(λ1)p, X2 → e~(λ2)X2, X3 → e~(λ3) X3, and X4 → ee~(λ4) X4 in the state 【 p, X2, X3, X4 】 isinvestigated, and the four-mode realization of the S U(1, 1) Lie algebra as well as thecorresponding squeezing operators are presented.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10174066 and 10275055
文摘We adopt a dynamical algebraic method to study a four-level excited-doublet atom model and obtain the explicit expressions of the time-evolution operator and the density operator for the system. The nonclassical effects of the system, such as collapses and revivals of the atomic inversion and squeezing of the radiation field, are also discussed.
文摘A novel hybrid robust three-axis attitude control approach, namely HRTAC, is considered along with the well-known developments in the area of space systems, since there is a consensus among the related experts that the new insights may be taken into account as decision points to outperform the available materials. It is to note that the traditional control approaches may generally be upgraded, as long as a number of modifications are made with respect to state-of-the-art, in order to propose high-precision outcomes. Regarding the investigated issues, the robust sliding mode finite-time control approach is first designed to handle three-axis angular rates in the inner control loop, which consists of the pulse width pulse frequency modulations in line with the control allocation scheme and the system dynamics. The main subject to employ these modulations that is realizing in association with the control allocation scheme is to be able to handle a class of overactuated systems, in particular. The proportional derivative based linear quadratic regulator approach is then designed to handle three-axis rotational angles in the outer control loop, which consists of the system kinematics that is correspondingly concentrated to deal with the quaternion based model. The utilization of the linear and its nonlinear terms, simultaneously, are taken into real consideration as the research motivation, while the performance results are of the significance as the improved version in comparison with the recent investigated outcomes. Subsequently, there is a stability analysis to verify and guarantee the closed loop system performance in coping with the whole of nominal referenced commands. At the end, the effectiveness of the approach considered here is highlighted in line with a number of potential recent benchmarks.
文摘The paper presents physical and mathematical models of kinetic system, drive system （electric and combustion traction motors）, and also wheel and rails traction vehicle supply system （car, special vehicle, modern tram vehicle）. Selected predictive and quasi dynamic control system algorithms of traction vehicle are presented in the paper. For selected constructions of traction vehicle drive system are presented in simulation models and are results of calculations of different exploitations work state of wheel vehicle with hybrid drive system. Results of computer calculations are verified with laboratory measurement and suitable corrections coefficient to simulations models of vehicles is introduced.
