The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI_(3)at the environmental temperatu...The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI_(3)at the environmental temperature(Te)ranging from 20 K to 300 K,and observed anomalous behaviors at cryogenic temperatures:The carrier temperature(Tc)of pure CsPbI_(3)exhibits a negative correlation with Te,accompanied by an expansion in Urbach tails of absorption spectra(Abs.)and excessive red-shifts at peak energy of PLs.These phenomena are also observed in those samples containing a certain amount of Cs_(4)PbI_(6),but to a lesser extent and occurs at lower temperatures.It is attributed to the intensified hot phonon bottleneck effect(HPB)in CsPbI_(3)at cryogenic Te,which hinders the energy transfer from hot carriers,via longitudinal optics(LO)phonons to longitudinal acoustic(LA)phonons,to the ambient.For samples under continuous-wave laser excitation,in specific,the barrier induced by the enhanced HPB at low Teprevents the effective thermalization among carriers,LO and LA phonons,which,therefore,form thermally isolated ensembles with different temperatures.At cryogenic Terange,the elevated temperatures of carrier and LO phonon expand the high-energy side of PLs and the low-energy tail of Abs.,respectively.For those samples in which the CsPbI_(3)is mixed with Cs_(4)PbI_(6),the interfacial LO-LO interaction across them provides a bypass for heat dissipation,mitigating the heat accumulation in LO-phonons of CsPbI_(3).The results suggest that a strong HPB effect may break the thermal equilibrium among different branches of phonons in the lattice under certain extreme conditions.展开更多
Environmental barriers and habitat fragmentation can restrict gene flow,leading to genetic divergence among animal populations.The golden snub-nosed monkey,Rhinopithecus roxellana,is endemic to China,and ranges ...Environmental barriers and habitat fragmentation can restrict gene flow,leading to genetic divergence among animal populations.The golden snub-nosed monkey,Rhinopithecus roxellana,is endemic to China,and ranges across 4 provinces.However,over the past 40 years its populations have become fragmented.We investigated the genetic diversity,demographic history and population structure of R.roxellana in 5 reserves in one of its strongholds,the Qinling Mountain forests of Shaanxi.We collected genetic material from 11 monkey bands(a group of individuals containing multiple 1-male units)with a total of 428 samples genotyped at 20 microsatellite loci.Allelic richness and heterozygosity suggested a relatively high level of intra-band genetic diversity.We found no evidence of any genetic bottleneck in these R.roxellana populations.AMOVA and Bayesian cluster analysis revealed that R.roxellana in the 5 reserves are highly structured and form at least 3 distinct subpopulations.These subpopulations concur with major topographical features in the study area,such as mountain ridges,suggesting that dispersal of R.roxellana may be restricted by geographical barriers.展开更多
The study of impacts of down-up hill road segment on the density threshold of traffic shock formation in ring road vehicular flow is helpful to the deep understanding of sags’bottleneck effect.Sags are freeway segmen...The study of impacts of down-up hill road segment on the density threshold of traffic shock formation in ring road vehicular flow is helpful to the deep understanding of sags’bottleneck effect.Sags are freeway segments along which the gradient increases gradually in the traffic direction.The main aim of this paper is to seek the density threshold of shock formation of vehicular flow in ring road with down-up hill segment,because down-up hill roadway segment is a source to cause capacity reduction that is an attractive topic in vehicular traffic science.To seek the density threshold numerically,a viscoelastic continuum model[1]is extended and used.To solve the model equations,a fifth-order weighted essentially non-oscillatory scheme for spatial discretization,and a 3rd order Runge-Kutta scheme for time partial derivative term are used.Validation by existing observation data and the Navier-Stokes like model[2]extended as EZM is done before conducting extensive numerical simulations.For ring road vehicular flow with three separated down-up hill segments,it is found that the density threshold of shock formation decreases monotonically with the relative difference of free flow speed,this variation can be simply fitted by a third order polynomial.展开更多
基金supported by the National Natural Science Foundation of China(Nos.62374142,12175189 and 11904302)External Cooperation Program of Fujian(No.2022I0004)+1 种基金Fundamental Research Funds for the Central Universities(Nos.20720190005 and 20720220085)Major Science and Technology Project of Xiamen in China(No.3502Z20191015)。
文摘The kinetic of low-temperature carrier and lattice of lead-halide perovskite is yet to be fully understood.In this work,we investigate the steady-state photoluminescences(PLs)of CsPbI_(3)at the environmental temperature(Te)ranging from 20 K to 300 K,and observed anomalous behaviors at cryogenic temperatures:The carrier temperature(Tc)of pure CsPbI_(3)exhibits a negative correlation with Te,accompanied by an expansion in Urbach tails of absorption spectra(Abs.)and excessive red-shifts at peak energy of PLs.These phenomena are also observed in those samples containing a certain amount of Cs_(4)PbI_(6),but to a lesser extent and occurs at lower temperatures.It is attributed to the intensified hot phonon bottleneck effect(HPB)in CsPbI_(3)at cryogenic Te,which hinders the energy transfer from hot carriers,via longitudinal optics(LO)phonons to longitudinal acoustic(LA)phonons,to the ambient.For samples under continuous-wave laser excitation,in specific,the barrier induced by the enhanced HPB at low Teprevents the effective thermalization among carriers,LO and LA phonons,which,therefore,form thermally isolated ensembles with different temperatures.At cryogenic Terange,the elevated temperatures of carrier and LO phonon expand the high-energy side of PLs and the low-energy tail of Abs.,respectively.For those samples in which the CsPbI_(3)is mixed with Cs_(4)PbI_(6),the interfacial LO-LO interaction across them provides a bypass for heat dissipation,mitigating the heat accumulation in LO-phonons of CsPbI_(3).The results suggest that a strong HPB effect may break the thermal equilibrium among different branches of phonons in the lattice under certain extreme conditions.
基金supported by the National Nature Science Foundation of China(31130061,31501872,31270441,31470455,31672301).
文摘Environmental barriers and habitat fragmentation can restrict gene flow,leading to genetic divergence among animal populations.The golden snub-nosed monkey,Rhinopithecus roxellana,is endemic to China,and ranges across 4 provinces.However,over the past 40 years its populations have become fragmented.We investigated the genetic diversity,demographic history and population structure of R.roxellana in 5 reserves in one of its strongholds,the Qinling Mountain forests of Shaanxi.We collected genetic material from 11 monkey bands(a group of individuals containing multiple 1-male units)with a total of 428 samples genotyped at 20 microsatellite loci.Allelic richness and heterozygosity suggested a relatively high level of intra-band genetic diversity.We found no evidence of any genetic bottleneck in these R.roxellana populations.AMOVA and Bayesian cluster analysis revealed that R.roxellana in the 5 reserves are highly structured and form at least 3 distinct subpopulations.These subpopulations concur with major topographical features in the study area,such as mountain ridges,suggesting that dispersal of R.roxellana may be restricted by geographical barriers.
基金supported by National Natural Science Foundation of China(NSFC No.11972341)fundamental research project of Lomonosov Moscow State University’s Mathematical models for multi-phase media and wave processes in natural,technical and social systems.
文摘The study of impacts of down-up hill road segment on the density threshold of traffic shock formation in ring road vehicular flow is helpful to the deep understanding of sags’bottleneck effect.Sags are freeway segments along which the gradient increases gradually in the traffic direction.The main aim of this paper is to seek the density threshold of shock formation of vehicular flow in ring road with down-up hill segment,because down-up hill roadway segment is a source to cause capacity reduction that is an attractive topic in vehicular traffic science.To seek the density threshold numerically,a viscoelastic continuum model[1]is extended and used.To solve the model equations,a fifth-order weighted essentially non-oscillatory scheme for spatial discretization,and a 3rd order Runge-Kutta scheme for time partial derivative term are used.Validation by existing observation data and the Navier-Stokes like model[2]extended as EZM is done before conducting extensive numerical simulations.For ring road vehicular flow with three separated down-up hill segments,it is found that the density threshold of shock formation decreases monotonically with the relative difference of free flow speed,this variation can be simply fitted by a third order polynomial.
