The spatial propagation of meso-and small-scale errors in a Meiyu frontal heavy rainfall event,which occurred in eastern China during 4-6 July 2003,is investigated by using the mesoscale numerical model MM5.In general...The spatial propagation of meso-and small-scale errors in a Meiyu frontal heavy rainfall event,which occurred in eastern China during 4-6 July 2003,is investigated by using the mesoscale numerical model MM5.In general,the spatial propagation of simulated errors depends on their horizontal scales.Small-scale（L 〈 100 km） initial error may spread rapidly as an isotropic circle through the sound wave.Then,many scattered convection-scale errors are triggered in moist convection zone that will spread abroad through the isotropic,round-shaped sound wave further more.Corresponding to the evolution of the rainfall system,several new convection-scale errors may be generated continuously by moist convection within the propagated round-shaped errors.Through the above circular process,the small-scale error increases in amplitude and grows in scale rapidly.Mesoscale（100 km 〈 L 〈 1000 km） initial error propagates up-and down-stream wavelike through the gravity wave,meanwhile migrating down-stream slowly along with the rainfall system by the mean flow.The up-stream propagation of the mesoscale error is very important to the error growth because it can accumulate error energy locally at a place where there is no moist convection and far upstream from the initial perturbation source.Although moist convection plays an important role in the rapid growth of errors,it has no impact on the propagation of meso-and small-scale errors.The diabatic heating could trigger,strengthen,and promote upscaling of small-scale errors successively,and provide ＂error source＂ to error growth and propagation.The rapid growth of simulated errors results from both intense moist convection and appropriate spatial propagation of the errors.展开更多
Recently,the focus of semantic segmentation research has shifted to the aggregation of context prior and refined boundary.A typical network adopts context aggregation modules to extract rich semantic features.It also ...Recently,the focus of semantic segmentation research has shifted to the aggregation of context prior and refined boundary.A typical network adopts context aggregation modules to extract rich semantic features.It also utilizes top-down connection and skips connections for refining boundary details.But it still remains disadvantage,an obvious fact is that the problem of false segmentation occurs as the object has very different textures.The fusion of weak semantic and low-level features leads to context prior degradation.To tackle the issue,we propose a simple yet effective network,which integrates dual context prior and spatial propagation-dubbed DSPNet.It extends two mainstreams of current segmentation researches:(1)Designing a dual context prior module,which pays attention to context prior again with a shortcut connection.(2)The network can inherently learn semantic aware affinity values for each pixel and refine the segmentation.We will present detailed comparisons,which perform on PASCAL VOC 2012 and Cityscapes.The result demonstrates the validation of our approach.展开更多
The Kerr nonlinearity in two-dimensional(2D)nanomaterials is emerging as an appealing and intriguing research area due to their prominent light processing,modulation,and manipulation abilities.In this contribution,2D ...The Kerr nonlinearity in two-dimensional(2D)nanomaterials is emerging as an appealing and intriguing research area due to their prominent light processing,modulation,and manipulation abilities.In this contribution,2D black arsenic-phosphorus(B-AsP)nanosheets(NSs)were applied in nonlinear photonic devices based on spatial self-phase modula-tion(SSPM)method.By applying the Kerr nonlinearity in 2D B-AsP,an all-optical phase-modulated system is proposed to realize the functions of“on”and“off”in all-optical switching.By using the same all-optical phase-modulated system,another optical logic gate is proposed,and the logical“or”function is obtained based on the 2D B-AsP NSs dispersions.Moreover,by using the SSPM method,a 2D B-AsP/SnS_(2) hybrid structure is fabricated,and the result illustrates that the hybrid structure possesses the ability of the unidirectional nonlinear excitation,which helps in obtaining the function of spatial asymmetric light propagation.This function is considered an important prerequisite for the realization of diode functionalization,which is believed to be a factor in important basis for the design of isolators as well.The initial investig-ations indicate that 2D B-AsP is applicable for designing optical logical devices,which can be considered as an import-ant development in all-optical information processing.展开更多
The one-dimensional theory of sound propagation in ducts is generalized and investigated in this paper . It can be assumed that any duct system consists of two kinds of elementary structures : One is the piped structu...The one-dimensional theory of sound propagation in ducts is generalized and investigated in this paper . It can be assumed that any duct system consists of two kinds of elementary structures : One is the piped structure in which the characteristics , such as the acoustical parameter on the interior surface of the wall , the cross-section area and the aerodynamic parameters of the flow , etc., will vary continuously and slowly with distance along the axis of the duct . The other is the local structure with discontinuity in which the characteristics will change abruptly. The acoustical properties of both structures are analysed in general cases based upon the fundamental equations of aerodynamics , and their transmission matrixes are derived and discussed respectively . Two typical examples are analysed and discussed .展开更多
Time-mean global general circulation data are employed to analyze the temporal and spatial variations of the meridional gradient of zonal mean potential vorticity,the critical wavenumber n_s for horizontal wave- propa...Time-mean global general circulation data are employed to analyze the temporal and spatial variations of the meridional gradient of zonal mean potential vorticity,the critical wavenumber n_s for horizontal wave- propagation,and the critical wavenumber K_c for vertical wave-propagation.Thereby the kinematic charac- teristics in the propagation of atmospheric stationary waves and their annual variations are studied.Results show that in the troposphere n_s and K_c usually decrease with the increase of either latitude or altitude. Synoptic and near-resonant Rossby waves could be trapped during their upward and meridional propagations. These characteristics possess prominent annual variations,especially in the Northern Hemisphere.It is found that the spatial and temporal variations of these kinematic characteristics are in good agreement with those of the atmospheric wave patterns.展开更多
基金Supported by the National Natural Science Foundation of China (41130964)China Meteorological Administration Special Public Welfare Research Fund (GYHY201006004)Specialized Research Fund for the Doctoral Program of Higher Education of China (20080284019)
文摘The spatial propagation of meso-and small-scale errors in a Meiyu frontal heavy rainfall event,which occurred in eastern China during 4-6 July 2003,is investigated by using the mesoscale numerical model MM5.In general,the spatial propagation of simulated errors depends on their horizontal scales.Small-scale（L 〈 100 km） initial error may spread rapidly as an isotropic circle through the sound wave.Then,many scattered convection-scale errors are triggered in moist convection zone that will spread abroad through the isotropic,round-shaped sound wave further more.Corresponding to the evolution of the rainfall system,several new convection-scale errors may be generated continuously by moist convection within the propagated round-shaped errors.Through the above circular process,the small-scale error increases in amplitude and grows in scale rapidly.Mesoscale（100 km 〈 L 〈 1000 km） initial error propagates up-and down-stream wavelike through the gravity wave,meanwhile migrating down-stream slowly along with the rainfall system by the mean flow.The up-stream propagation of the mesoscale error is very important to the error growth because it can accumulate error energy locally at a place where there is no moist convection and far upstream from the initial perturbation source.Although moist convection plays an important role in the rapid growth of errors,it has no impact on the propagation of meso-and small-scale errors.The diabatic heating could trigger,strengthen,and promote upscaling of small-scale errors successively,and provide ＂error source＂ to error growth and propagation.The rapid growth of simulated errors results from both intense moist convection and appropriate spatial propagation of the errors.
文摘Recently,the focus of semantic segmentation research has shifted to the aggregation of context prior and refined boundary.A typical network adopts context aggregation modules to extract rich semantic features.It also utilizes top-down connection and skips connections for refining boundary details.But it still remains disadvantage,an obvious fact is that the problem of false segmentation occurs as the object has very different textures.The fusion of weak semantic and low-level features leads to context prior degradation.To tackle the issue,we propose a simple yet effective network,which integrates dual context prior and spatial propagation-dubbed DSPNet.It extends two mainstreams of current segmentation researches:(1)Designing a dual context prior module,which pays attention to context prior again with a shortcut connection.(2)The network can inherently learn semantic aware affinity values for each pixel and refine the segmentation.We will present detailed comparisons,which perform on PASCAL VOC 2012 and Cityscapes.The result demonstrates the validation of our approach.
基金supports from the National Natural Science Foundation of China(NSFC)(61435010 and 21773168)the Science and Technique Planning Project of Guangdong Province(Grant No.2016B050501005)+1 种基金the Science and Technology Innovation Commission of Shenzhen(JCYJ20170302153323978 and JCYJ201704101719588539)the Science and Technology Development Fund(No.007/2017/A1 and132/2017/A3),Ma-cao SAR,China.
文摘The Kerr nonlinearity in two-dimensional(2D)nanomaterials is emerging as an appealing and intriguing research area due to their prominent light processing,modulation,and manipulation abilities.In this contribution,2D black arsenic-phosphorus(B-AsP)nanosheets(NSs)were applied in nonlinear photonic devices based on spatial self-phase modula-tion(SSPM)method.By applying the Kerr nonlinearity in 2D B-AsP,an all-optical phase-modulated system is proposed to realize the functions of“on”and“off”in all-optical switching.By using the same all-optical phase-modulated system,another optical logic gate is proposed,and the logical“or”function is obtained based on the 2D B-AsP NSs dispersions.Moreover,by using the SSPM method,a 2D B-AsP/SnS_(2) hybrid structure is fabricated,and the result illustrates that the hybrid structure possesses the ability of the unidirectional nonlinear excitation,which helps in obtaining the function of spatial asymmetric light propagation.This function is considered an important prerequisite for the realization of diode functionalization,which is believed to be a factor in important basis for the design of isolators as well.The initial investig-ations indicate that 2D B-AsP is applicable for designing optical logical devices,which can be considered as an import-ant development in all-optical information processing.
文摘The one-dimensional theory of sound propagation in ducts is generalized and investigated in this paper . It can be assumed that any duct system consists of two kinds of elementary structures : One is the piped structure in which the characteristics , such as the acoustical parameter on the interior surface of the wall , the cross-section area and the aerodynamic parameters of the flow , etc., will vary continuously and slowly with distance along the axis of the duct . The other is the local structure with discontinuity in which the characteristics will change abruptly. The acoustical properties of both structures are analysed in general cases based upon the fundamental equations of aerodynamics , and their transmission matrixes are derived and discussed respectively . Two typical examples are analysed and discussed .
文摘Time-mean global general circulation data are employed to analyze the temporal and spatial variations of the meridional gradient of zonal mean potential vorticity,the critical wavenumber n_s for horizontal wave- propagation,and the critical wavenumber K_c for vertical wave-propagation.Thereby the kinematic charac- teristics in the propagation of atmospheric stationary waves and their annual variations are studied.Results show that in the troposphere n_s and K_c usually decrease with the increase of either latitude or altitude. Synoptic and near-resonant Rossby waves could be trapped during their upward and meridional propagations. These characteristics possess prominent annual variations,especially in the Northern Hemisphere.It is found that the spatial and temporal variations of these kinematic characteristics are in good agreement with those of the atmospheric wave patterns.
