In late July and early August 2018,Northeast China suffered from extremely high temperatures,with the maxium temperature anomaly exceeding 6°C.In this study,the large-scale circulation features associated with th...In late July and early August 2018,Northeast China suffered from extremely high temperatures,with the maxium temperature anomaly exceeding 6°C.In this study,the large-scale circulation features associated with this heat wave over Northeast China are analyzed using station temperature data and NCEP–NCAR reanalysis data.The results indicate that strong anomalous positive geopotential height centers existed from the lower to upper levels over Northeast China,and the related downward motions were directly responsible for the extreme high-temperature anomalies.The northwestward shift of the western Pacific subtropical high(WPSH)and the northeastward shift of the South Asian high concurrently reinforced the geopotential height anomalies and descending flow over Northeast China.In addition,an anomalous Pacific–Japan pattern in the lower troposphere led to the northwestward shift of the WPSH,jointly favoring the anomalous geopotential height over Northeast China.Two wave trains emanating from the Atlantic region propagated eastwards along high latitudes and midlatitudes,respectively,and converged over Northeast China,leading to the enhancement of the geopotential height anomalies.展开更多
A chemical process may involve multiple adiabatic electronic states, and non-adiabatic couplings play an important role in the reaction mechanism. In this work, the effect of non-adiabatic couplings in the H+MgH;→Mg;...A chemical process may involve multiple adiabatic electronic states, and non-adiabatic couplings play an important role in the reaction mechanism. In this work, the effect of non-adiabatic couplings in the H+MgH;→Mg;+H;reaction are studied using the time-dependent wave packet method and trajectory surface hopping method. The calculated results show that the reaction follows a direct abstraction process when the non-adiabatic couplings are neglected. However, when non-adiabatic couplings are included in the calculations, a longlived excited state complex(MgH_(2)+)*can be formed during the reaction. These direct and complex-forming reaction pathways are revealed by trajectory surface hopping calculations.The non-adiabatic couplings induced complex-forming mechanism not only increases the reactivity but also has significant effect on the product vibrational state distribution.展开更多
Heat and energy are conceptually different, but often are assumed to be the same without justification. An effective method for investigating diffusion properties in equilibrium systems is discussed. With this method,...Heat and energy are conceptually different, but often are assumed to be the same without justification. An effective method for investigating diffusion properties in equilibrium systems is discussed. With this method, we demonstrate that for one-dimensional systems, using the indices of particles as the space variable, which has been accepted as a convention, may lead to misleading conclusions. We then show that though in one-dimensional systems there is no general connection between energy diffusion and heat conduction, however, a general connection between heat diffusion and heat conduction may exist. Relaxation behavior of local energy current fluctuations and that of local heat current fluctuations are also studied. We find that they are significantly different,though the global energy current equals the globe heat current.展开更多
Wide validation of self-developed program of natural circulation under oceanic conditions has been conducted compared with experimental data of inclination,zero-power condition and hot-state condition.Experiments were...Wide validation of self-developed program of natural circulation under oceanic conditions has been conducted compared with experimental data of inclination,zero-power condition and hot-state condition.Experiments were performed on a full-scale,whole parameterization natural circulation loop designed with reference to 5 MW experimental low temperature nuclear heating reactor(NHR)of Tsinghua University.Investigation of natural circulation and parameter effect under heaving motion was carried out using the program and comparison of heaving,inclination and rolling on natural circulation respectively to reveal the influence mechanism.Results indicate that:(1)significant influence of heaving motion on natural circulation was observed,and heaving motion with high level of strength and long cycle would lead to severe flow fluctuation;(2)slight effect was caused by short cycle heaving motion which was completely different from long cycle heaving motion;(3)comprehensive action of alternating force and flow density distribution would result in natural circulation under heaving motion;(4)most severe accidents maybe result from the long cycle heaving motion rather than inclination and rolling motion.Investigation of influence of heaving motion on natural circulation could have important reference significance in the optimization design of nuclear reactors.展开更多
基金supported by the National Natural Science Foundation of China under Grant 41775073
文摘In late July and early August 2018,Northeast China suffered from extremely high temperatures,with the maxium temperature anomaly exceeding 6°C.In this study,the large-scale circulation features associated with this heat wave over Northeast China are analyzed using station temperature data and NCEP–NCAR reanalysis data.The results indicate that strong anomalous positive geopotential height centers existed from the lower to upper levels over Northeast China,and the related downward motions were directly responsible for the extreme high-temperature anomalies.The northwestward shift of the western Pacific subtropical high(WPSH)and the northeastward shift of the South Asian high concurrently reinforced the geopotential height anomalies and descending flow over Northeast China.In addition,an anomalous Pacific–Japan pattern in the lower troposphere led to the northwestward shift of the WPSH,jointly favoring the anomalous geopotential height over Northeast China.Two wave trains emanating from the Atlantic region propagated eastwards along high latitudes and midlatitudes,respectively,and converged over Northeast China,leading to the enhancement of the geopotential height anomalies.
基金supported by the National Natural Science Foundation of China(No.11774043)。
文摘A chemical process may involve multiple adiabatic electronic states, and non-adiabatic couplings play an important role in the reaction mechanism. In this work, the effect of non-adiabatic couplings in the H+MgH;→Mg;+H;reaction are studied using the time-dependent wave packet method and trajectory surface hopping method. The calculated results show that the reaction follows a direct abstraction process when the non-adiabatic couplings are neglected. However, when non-adiabatic couplings are included in the calculations, a longlived excited state complex(MgH_(2)+)*can be formed during the reaction. These direct and complex-forming reaction pathways are revealed by trajectory surface hopping calculations.The non-adiabatic couplings induced complex-forming mechanism not only increases the reactivity but also has significant effect on the product vibrational state distribution.
基金the National Natural Science Foundation of China (Grant Nos. 10925525, 11275159 and 10805036)the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No.20100121110021)
文摘Heat and energy are conceptually different, but often are assumed to be the same without justification. An effective method for investigating diffusion properties in equilibrium systems is discussed. With this method, we demonstrate that for one-dimensional systems, using the indices of particles as the space variable, which has been accepted as a convention, may lead to misleading conclusions. We then show that though in one-dimensional systems there is no general connection between energy diffusion and heat conduction, however, a general connection between heat diffusion and heat conduction may exist. Relaxation behavior of local energy current fluctuations and that of local heat current fluctuations are also studied. We find that they are significantly different,though the global energy current equals the globe heat current.
基金supported by the National Science and Technology Major Project(Grant No.ZX06901)the National Natural Science Foundation of China(Grant No.11072131)
文摘Wide validation of self-developed program of natural circulation under oceanic conditions has been conducted compared with experimental data of inclination,zero-power condition and hot-state condition.Experiments were performed on a full-scale,whole parameterization natural circulation loop designed with reference to 5 MW experimental low temperature nuclear heating reactor(NHR)of Tsinghua University.Investigation of natural circulation and parameter effect under heaving motion was carried out using the program and comparison of heaving,inclination and rolling on natural circulation respectively to reveal the influence mechanism.Results indicate that:(1)significant influence of heaving motion on natural circulation was observed,and heaving motion with high level of strength and long cycle would lead to severe flow fluctuation;(2)slight effect was caused by short cycle heaving motion which was completely different from long cycle heaving motion;(3)comprehensive action of alternating force and flow density distribution would result in natural circulation under heaving motion;(4)most severe accidents maybe result from the long cycle heaving motion rather than inclination and rolling motion.Investigation of influence of heaving motion on natural circulation could have important reference significance in the optimization design of nuclear reactors.
