A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition （PIC） of the active region （AR） and discuss the PICs on diff...A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition （PIC） of the active region （AR） and discuss the PICs on different structures by changing structural parameters such as the widths of quantum wells or barriers in the AR. For some instances, the PIC can be simplified and is proportional to the spontaneous emission lifetime between the second and the first excited states, whereas some other instances imply that the PIC is proportional to the state lifetime of the second excited state.展开更多
The inversion reaction of hydroxy lamine was investigated by using the ab initiointrinsic reaction coordinate(IRC)method with 4-31G basis set.Our results indicate that the ∠H_1NO changes arastically in the vicinity o...The inversion reaction of hydroxy lamine was investigated by using the ab initiointrinsic reaction coordinate(IRC)method with 4-31G basis set.Our results indicate that the ∠H_1NO changes arastically in the vicinity of the transition state while the other bo-nd angles and bond lengths change little throughout the reaction process.展开更多
A 2-dimensional atmospheric transport model is deployed in a simplified CO 2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink i...A 2-dimensional atmospheric transport model is deployed in a simplified CO 2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible important role of Asian terrestrial ecosystems in carbon cycle.展开更多
The remote measurement of the vertical distribution of acoustical parameters of the sea bottom is an inverse method in acoustics. The existing methods can be divided into two types: the wave method and the ray method....The remote measurement of the vertical distribution of acoustical parameters of the sea bottom is an inverse method in acoustics. The existing methods can be divided into two types: the wave method and the ray method. The former usually does not apply to cases with discontinuity in acoustical parameter profiles[1] , whereas the latter usually ignores the contributions made by multiple reflections, resulting in the appearance of pseudo interfaces. However, under certain practical circumstances, the ray method can produce satisfactory results[2,3]. In this paper, at first we use the conception of equitime layer thickness to obtain the pulse response iteration method. The anti-interference capability of this method is poor. In order to improve this capability, we develope the sample iteration method and the sample-averaging iteration method. The sample-averaging iteration method introduces a way of statistical averaging, which can further improve the anti-interference capability.展开更多
Ring inversion of eight substituted 2-phenyl-4,4-dimethyloxazolidines in o-dichloro- benzene-d_4 was studied by ~H DNMR.Very high inversion barriers((?)G_c(?)=86.7—93.4 kJ·mol^(-1)) were found for these oxazolid...Ring inversion of eight substituted 2-phenyl-4,4-dimethyloxazolidines in o-dichloro- benzene-d_4 was studied by ~H DNMR.Very high inversion barriers((?)G_c(?)=86.7—93.4 kJ·mol^(-1)) were found for these oxazolidine rings.The magnitude of the inversion barrier is dependent on the polarity of the substituent on the phenyl group.A linear correlation is present between the (?)G_c(?) of the inversion and the substituent constant,σ^+,of the substituent.展开更多
基金supported by the National Natural Science Foundation of China(No.60976070)the Special Funds of China Academy of Engineering Physics(No.909)
文摘A population inversion study of GaAs/AlxGa1-xAs three-quantum-well quantum cascade structures is presented. We derive the population inversion condition （PIC） of the active region （AR） and discuss the PICs on different structures by changing structural parameters such as the widths of quantum wells or barriers in the AR. For some instances, the PIC can be simplified and is proportional to the spontaneous emission lifetime between the second and the first excited states, whereas some other instances imply that the PIC is proportional to the state lifetime of the second excited state.
文摘The inversion reaction of hydroxy lamine was investigated by using the ab initiointrinsic reaction coordinate(IRC)method with 4-31G basis set.Our results indicate that the ∠H_1NO changes arastically in the vicinity of the transition state while the other bo-nd angles and bond lengths change little throughout the reaction process.
文摘A 2-dimensional atmospheric transport model is deployed in a simplified CO 2 inverse study. Calculated carbon flux distribution for the interval from 1981 to 1997 confirms the existence of a terrestrial carbon sink in mid-high latitude area of North Hemisphere. Strong interannual variability exists in carbon flux patterns, implying a possible link with ENSO and other natural episodes such as Pinatubo volcano eruption in 1991. Mechanism of this possible link was investigated with statistic method. Correlation analysis indicated that in North Hemisphere, climatic factors such as temperature and precipitation, to some extend, could influence the carbon cycle process of land and ocean, thus cause considerable change in carbon flux distribution. In addition, correlation study also demonstrated the possible important role of Asian terrestrial ecosystems in carbon cycle.
文摘The remote measurement of the vertical distribution of acoustical parameters of the sea bottom is an inverse method in acoustics. The existing methods can be divided into two types: the wave method and the ray method. The former usually does not apply to cases with discontinuity in acoustical parameter profiles[1] , whereas the latter usually ignores the contributions made by multiple reflections, resulting in the appearance of pseudo interfaces. However, under certain practical circumstances, the ray method can produce satisfactory results[2,3]. In this paper, at first we use the conception of equitime layer thickness to obtain the pulse response iteration method. The anti-interference capability of this method is poor. In order to improve this capability, we develope the sample iteration method and the sample-averaging iteration method. The sample-averaging iteration method introduces a way of statistical averaging, which can further improve the anti-interference capability.
文摘Ring inversion of eight substituted 2-phenyl-4,4-dimethyloxazolidines in o-dichloro- benzene-d_4 was studied by ~H DNMR.Very high inversion barriers((?)G_c(?)=86.7—93.4 kJ·mol^(-1)) were found for these oxazolidine rings.The magnitude of the inversion barrier is dependent on the polarity of the substituent on the phenyl group.A linear correlation is present between the (?)G_c(?) of the inversion and the substituent constant,σ^+,of the substituent.
