It was proved by Bahouri et al.[9]that the Schrodinger equation on the Heisenberg group H^(d),involving the sublaplacian,is an example of a totally non-dispersive evolution equation:for this reason global dispersive e...It was proved by Bahouri et al.[9]that the Schrodinger equation on the Heisenberg group H^(d),involving the sublaplacian,is an example of a totally non-dispersive evolution equation:for this reason global dispersive estimates cannot hold.This paper aims at establishing local dispersive estimates on H^(d) for the linear Schrodinger equation,by a refined study of the Schrodinger ker-nel St on H^(d).The sharpness of these estimates is discussed through several examples.Our approach,based on the explicit formula of the heat kernel on H^(d) derived by Gaveau[19],is achieved by combining complex analysis and Fourier-Heisenberg tools.As a by-product of our results we establish local Stri-chartz estimates and prove that the kernel St concentrates on quantized hori-zontal hyperplanes of H^(d).展开更多
This paper is concerned with the low Mach number limit for the compressible Navier-Stokes equations in an exterior domain. We present here an approach based on Strichartz estimate defined on a non trapping exterior do...This paper is concerned with the low Mach number limit for the compressible Navier-Stokes equations in an exterior domain. We present here an approach based on Strichartz estimate defined on a non trapping exterior domain and we will be able to show the compactness and strong convergence of the velocity vector field.展开更多
Existing sequential parameter estimation methods use the acoustic pressure of a line array as observations. The modal dispersion curves are employed to estimate the sound speed profile（SSP） and geoacoustic parameter...Existing sequential parameter estimation methods use the acoustic pressure of a line array as observations. The modal dispersion curves are employed to estimate the sound speed profile（SSP） and geoacoustic parameters based on the ensemble Kalman filter. The warping transform is implemented to the signals received by a single hydrophone to obtain the dispersion curves. The experimental data are collected at a range-independent shallow water site in the South China Sea. The results indicate that the SSPs are well estimated and the geoacoustic parameters are also well determined. Comparisons of the observed and estimated modal dispersion curves show good agreement.展开更多
Abstract Sisorid catfishes are primarily limited in distribution to rivers of the Himalayan region and Tibetan Plateau. These species have external morphologies that are adapted for extremely fast-flowing riverine sys...Abstract Sisorid catfishes are primarily limited in distribution to rivers of the Himalayan region and Tibetan Plateau. These species have external morphologies that are adapted for extremely fast-flowing riverine systems. Given the diversity of the group and the above qualities of these catfishes, this lineage serves as an ideal group for inferring the geological history of this region based on their phylogenetic relationships reflecting evolu- tionary history. We sequenced the complete mitochondrial genome and four nuclear genes of representative sisorids distributed across river systems in China. Phylogenetic analyses strongly support the monophyly of the Sisoridae and the glyptosternoids. An analysis of the reconstructed ancestral states derived from inferred genealogical relationships suggests that the evolution of this lineage was accompanied by convergent evolution in morphological traits that were presumably in response to environmental pressure involving the rapid flowing river system that were generated during the uplift of the Tibetan Plateau （UTP）. Molecular dating indicates that the Chinese sisorids and the glyptosternoids originated at the later Miocene （~ 10.9-9.8 Mya）, and with further biogeographic analyses indicates that the species of Sisoridae likely originated from a widely distributed ancestor. Moreover, the divergence of the Sisoridae in China can be divided into two phases consis- tent with the UTP. All of these results indicate that the diversification and dispersal events in this lineage occurred as a result of drainage systems formed during and after the UTP in the late Miocene and Quaternary periods.展开更多
文摘It was proved by Bahouri et al.[9]that the Schrodinger equation on the Heisenberg group H^(d),involving the sublaplacian,is an example of a totally non-dispersive evolution equation:for this reason global dispersive estimates cannot hold.This paper aims at establishing local dispersive estimates on H^(d) for the linear Schrodinger equation,by a refined study of the Schrodinger ker-nel St on H^(d).The sharpness of these estimates is discussed through several examples.Our approach,based on the explicit formula of the heat kernel on H^(d) derived by Gaveau[19],is achieved by combining complex analysis and Fourier-Heisenberg tools.As a by-product of our results we establish local Stri-chartz estimates and prove that the kernel St concentrates on quantized hori-zontal hyperplanes of H^(d).
文摘This paper is concerned with the low Mach number limit for the compressible Navier-Stokes equations in an exterior domain. We present here an approach based on Strichartz estimate defined on a non trapping exterior domain and we will be able to show the compactness and strong convergence of the velocity vector field.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11434012,11774374,11404366 and41561144006
文摘Existing sequential parameter estimation methods use the acoustic pressure of a line array as observations. The modal dispersion curves are employed to estimate the sound speed profile（SSP） and geoacoustic parameters based on the ensemble Kalman filter. The warping transform is implemented to the signals received by a single hydrophone to obtain the dispersion curves. The experimental data are collected at a range-independent shallow water site in the South China Sea. The results indicate that the SSPs are well estimated and the geoacoustic parameters are also well determined. Comparisons of the observed and estimated modal dispersion curves show good agreement.
基金supported by the National Natural Science Foundation of China (31090254, 30770300 and U1036603)the Chinese Academy of Sciences (KSCX2-EW-Q-12)the endowment of William S. Barnickle, Saint Louis University, St. Louis, Missouri, USA
文摘Abstract Sisorid catfishes are primarily limited in distribution to rivers of the Himalayan region and Tibetan Plateau. These species have external morphologies that are adapted for extremely fast-flowing riverine systems. Given the diversity of the group and the above qualities of these catfishes, this lineage serves as an ideal group for inferring the geological history of this region based on their phylogenetic relationships reflecting evolu- tionary history. We sequenced the complete mitochondrial genome and four nuclear genes of representative sisorids distributed across river systems in China. Phylogenetic analyses strongly support the monophyly of the Sisoridae and the glyptosternoids. An analysis of the reconstructed ancestral states derived from inferred genealogical relationships suggests that the evolution of this lineage was accompanied by convergent evolution in morphological traits that were presumably in response to environmental pressure involving the rapid flowing river system that were generated during the uplift of the Tibetan Plateau （UTP）. Molecular dating indicates that the Chinese sisorids and the glyptosternoids originated at the later Miocene （~ 10.9-9.8 Mya）, and with further biogeographic analyses indicates that the species of Sisoridae likely originated from a widely distributed ancestor. Moreover, the divergence of the Sisoridae in China can be divided into two phases consis- tent with the UTP. All of these results indicate that the diversification and dispersal events in this lineage occurred as a result of drainage systems formed during and after the UTP in the late Miocene and Quaternary periods.
