Mode matching method is used to analyze the scattering characteristics of thecircular-to-circular groove waveguide junction. Matching the electric fields and magnetic fields atthe boundary of the junction, and multipl...Mode matching method is used to analyze the scattering characteristics of thecircular-to-circular groove waveguide junction. Matching the electric fields and magnetic fields atthe boundary of the junction, and multiplying the mode functions of the circular waveguide andcircular groove waveguide on both sides of the boundary equation, the scattering matrix equation isobtained, the scattering coefficients can be obtained from the equation. Then the scatteringcharacteristics of the iris with circular window in circular groove waveguide are analyzed. At lastthe convergent problem is discussed; when choosing a suitable mode group, convergent numericalresults are obtained, and the frequency response of the iris' scattering coefficients is also given.展开更多
Measurements of neutron count rate （0.025 eV to 10 MeV） at ground level were performed with a single free （He-3） tube detectorthat is located near ground level in Aeronautical Institute of Technology （ITA） Silo ...Measurements of neutron count rate （0.025 eV to 10 MeV） at ground level were performed with a single free （He-3） tube detectorthat is located near ground level in Aeronautical Institute of Technology （ITA） Silo Jos6 dos Campos, SP, Brazil. The data were collected uninterruptedly since February 28, 2016 to March 11, 2016. Based on the analysis of data obtained in this period, was possible to observe the occurrence of events, backscattering for example,with significant increases in the neutron count rate during about 3 days of steady rain for all nearby regions. These events seem to be correlated with changes in local weather conditions such as cloud coverage or rain-precipitation of weak intensity. It was reported that the non-observation of a single event seems to be an indicative of the production of a burst of neutrons by a lightning discharge near the detector. Some explanations about the increasing of low energy neutrons are suggested in this article.展开更多
Elastic reverse-time migration can effectively deal with multicomponent seismic data in which the imaging condition based on energy norm can extract the scalar-imaging result from multicomponent data.However,the energ...Elastic reverse-time migration can effectively deal with multicomponent seismic data in which the imaging condition based on energy norm can extract the scalar-imaging result from multicomponent data.However,the energy cross-correlation imaging condition characterized by particle velocity and stress suffers from the problem of overdependence on the background elastic parameters.Therefore,we characterize the elastic-wave energy using the energy-flow vector,which is equal to the energy density,without background elastic parameters.According to the source and receiver wave fields,we propose an imaging energyflow vector and an elastic-wave energy imaging condition.Under the assumption of a planewave solution,the backscattering suppression is verified.The numerical simulations show that the elastic-energy imaging condition can obtain the energy image without backscattering.Compared with the cross-correlation imaging conditions in a vector-based wave field,the proposed imaging condition can eliminate the dependence on the background elastic parameters and effectively process seabed multicomponent data,which are conducive to further providing an interpretation of marine geological structures.展开更多
Dynamic changes in solar radiation have an important influence on ecosystem carbon sequestration,but the effects of changes caused by sky conditions on net ecosystem CO2 exchange(NEE)are unclear.This study analyzed th...Dynamic changes in solar radiation have an important influence on ecosystem carbon sequestration,but the effects of changes caused by sky conditions on net ecosystem CO2 exchange(NEE)are unclear.This study analyzed the effects of sunny,cloudy,and overcast sky conditions on NEE using carbon flux and meteorological data for a subtropical coniferous plantation in 2012.Based on one-year data,we found no seasonal variation in the light response curve under various sky conditions.Compared with sunny sky conditions,the apparent quantum yield(α)and potential photosynthetic rate at a light intensity of 150 and 750 W m^-2(P150 and P750)under cloudy sky conditions increased by an average of 82.3%,217.7%,and 22.5%;αand P150 under overcast sky conditions increased by 118.5%and 301%on average.Moderate radiation conditions were more favorable for maximum NEE,while low radiation conditions inhibited NEE.In most cases,when the sunny NEE was used as a baseline for comparison,the relative change in NEE(%NEE)was positive under cloudy sky conditions and negative under overcast sky conditions.The average maximal%NEE under cloudy sky conditions was 42.4% in spring,34.1% in summer,1.6% in autumn and –87.3% in winter.This study indicates that cloudy sky conditions promote photosynthetic rates and NEE in subtropical coniferous plantations.展开更多
An experimental study of compressible mixing layers(CMLs)was conducted using planar laser Mie scattering(PLMS)visualizations from condensed ethanol droplets in the flow.Large ensembles of digital images were collected...An experimental study of compressible mixing layers(CMLs)was conducted using planar laser Mie scattering(PLMS)visualizations from condensed ethanol droplets in the flow.Large ensembles of digital images were collected for two flow conditions at convective Mach numbers Mc=0.11 and 0.47.The coherent vortices,braids and eruptions in the mixing zone were observed,interpreted as evidence of multi-scale,three-dimensional structures at a high Reynolds number.The mixing layers with a large visualized range present two stages along the streamwise direction,corresponding to the initial mixing and the well-developed stage.A new method,the gray level ensemble average method(GLEAM),by virtue of the similarity of the mixing layer,was applied to measure the growth rate of the CML thickness.New evidence for a nonlinear growth of CML is reported,providing an interpretation of previous observations of the scattering of the growth rate.展开更多
The authors prove the uniqueness in the inverse acoustic scattering problem within convex polygonal domains by a single incident direction in the sound-soft case and the sound-hard case, and by two incident directions...The authors prove the uniqueness in the inverse acoustic scattering problem within convex polygonal domains by a single incident direction in the sound-soft case and the sound-hard case, and by two incident directions in the case of the impedance boundary condition. The proof is based on analytic continuation on a straight line.展开更多
文摘Mode matching method is used to analyze the scattering characteristics of thecircular-to-circular groove waveguide junction. Matching the electric fields and magnetic fields atthe boundary of the junction, and multiplying the mode functions of the circular waveguide andcircular groove waveguide on both sides of the boundary equation, the scattering matrix equation isobtained, the scattering coefficients can be obtained from the equation. Then the scatteringcharacteristics of the iris with circular window in circular groove waveguide are analyzed. At lastthe convergent problem is discussed; when choosing a suitable mode group, convergent numericalresults are obtained, and the frequency response of the iris' scattering coefficients is also given.
文摘Measurements of neutron count rate （0.025 eV to 10 MeV） at ground level were performed with a single free （He-3） tube detectorthat is located near ground level in Aeronautical Institute of Technology （ITA） Silo Jos6 dos Campos, SP, Brazil. The data were collected uninterruptedly since February 28, 2016 to March 11, 2016. Based on the analysis of data obtained in this period, was possible to observe the occurrence of events, backscattering for example,with significant increases in the neutron count rate during about 3 days of steady rain for all nearby regions. These events seem to be correlated with changes in local weather conditions such as cloud coverage or rain-precipitation of weak intensity. It was reported that the non-observation of a single event seems to be an indicative of the production of a burst of neutrons by a lightning discharge near the detector. Some explanations about the increasing of low energy neutrons are suggested in this article.
基金supported by the National Nature Science Foundation of China(No.61801275)Shangdong Provincial Natural Science Foundation(No.ZR2018BF002)+2 种基金China Postdoctoral Science Foundation(No.2017M622242)Basic Research Projects of Science,Education and Industry Integration Pilot Project of Qilu University of Technology(2022PX082)Qingdao Applied Research Projects.
文摘Elastic reverse-time migration can effectively deal with multicomponent seismic data in which the imaging condition based on energy norm can extract the scalar-imaging result from multicomponent data.However,the energy cross-correlation imaging condition characterized by particle velocity and stress suffers from the problem of overdependence on the background elastic parameters.Therefore,we characterize the elastic-wave energy using the energy-flow vector,which is equal to the energy density,without background elastic parameters.According to the source and receiver wave fields,we propose an imaging energyflow vector and an elastic-wave energy imaging condition.Under the assumption of a planewave solution,the backscattering suppression is verified.The numerical simulations show that the elastic-energy imaging condition can obtain the energy image without backscattering.Compared with the cross-correlation imaging conditions in a vector-based wave field,the proposed imaging condition can eliminate the dependence on the background elastic parameters and effectively process seabed multicomponent data,which are conducive to further providing an interpretation of marine geological structures.
基金National Key Research and Development Program of China(2017YFC0503801 2016YFA0600104)
文摘Dynamic changes in solar radiation have an important influence on ecosystem carbon sequestration,but the effects of changes caused by sky conditions on net ecosystem CO2 exchange(NEE)are unclear.This study analyzed the effects of sunny,cloudy,and overcast sky conditions on NEE using carbon flux and meteorological data for a subtropical coniferous plantation in 2012.Based on one-year data,we found no seasonal variation in the light response curve under various sky conditions.Compared with sunny sky conditions,the apparent quantum yield(α)and potential photosynthetic rate at a light intensity of 150 and 750 W m^-2(P150 and P750)under cloudy sky conditions increased by an average of 82.3%,217.7%,and 22.5%;αand P150 under overcast sky conditions increased by 118.5%and 301%on average.Moderate radiation conditions were more favorable for maximum NEE,while low radiation conditions inhibited NEE.In most cases,when the sunny NEE was used as a baseline for comparison,the relative change in NEE(%NEE)was positive under cloudy sky conditions and negative under overcast sky conditions.The average maximal%NEE under cloudy sky conditions was 42.4% in spring,34.1% in summer,1.6% in autumn and –87.3% in winter.This study indicates that cloudy sky conditions promote photosynthetic rates and NEE in subtropical coniferous plantations.
基金supported by the National Natural Science Foundation of China(Grant Nos.11172006,10572004 and 90716008)by the National Basic Research Program of China(Grant No.2009CB724100)
文摘An experimental study of compressible mixing layers(CMLs)was conducted using planar laser Mie scattering(PLMS)visualizations from condensed ethanol droplets in the flow.Large ensembles of digital images were collected for two flow conditions at convective Mach numbers Mc=0.11 and 0.47.The coherent vortices,braids and eruptions in the mixing zone were observed,interpreted as evidence of multi-scale,three-dimensional structures at a high Reynolds number.The mixing layers with a large visualized range present two stages along the streamwise direction,corresponding to the initial mixing and the well-developed stage.A new method,the gray level ensemble average method(GLEAM),by virtue of the similarity of the mixing layer,was applied to measure the growth rate of the CML thickness.New evidence for a nonlinear growth of CML is reported,providing an interpretation of previous observations of the scattering of the growth rate.
基金Project supported by the National Natural Science Foundation of China (No.10271032) the Nonlinear Mathematical Models and Methods Laboratory and the Grants 1534002715654015 from the Japan Society for the Promotion of Science and Sanwa Systems Development Co.Ltd. (Tokyo).
文摘The authors prove the uniqueness in the inverse acoustic scattering problem within convex polygonal domains by a single incident direction in the sound-soft case and the sound-hard case, and by two incident directions in the case of the impedance boundary condition. The proof is based on analytic continuation on a straight line.
