Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double-crystal X-ray diffraction measurement.The expected...Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double-crystal X-ray diffraction measurement.The expected high quality epitaxial DBR structure was verified.In the X-ray double-crystal rocking curves of DBR the zeroth-order peak,the first and second order satellite peaks were measured.Splitting of diffraction peak appeared in the rocking curves was analyzed.The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.展开更多
Knowledge of both vegetation distribution pattern and phenology changes is very important.Their complicated relationship with elevation and accessibility were explored through a geographically weighted regression(GWR)...Knowledge of both vegetation distribution pattern and phenology changes is very important.Their complicated relationship with elevation and accessibility were explored through a geographically weighted regression(GWR) framework in Fujian province,China.The 16-day time series of 250 m Moderate Resolution Imaging Spectroradiometer(MODIS) Enhanced Vegetation Index(EVI) dataset from 2000 to 2010 was applied.Wavelet transform method was adopted to decompose the original time series and construct the annual maximum EVI and amplitude of the annual phenological cycle(EVI).Candidate explaining factors included topographic conditions,accessibility variables and proportions of primary vegetation types.Results revealed very strong positive influence from parameters of elevation and accessibility to big rivers and negative effect from accessibility to resident on both maximum EVI and phenological magnitude through ordinary linear least square(OLS) regression analysis.GWR analysis revealed that spatially,the parameters of topography and accessibility had a very complex relationship with both maximum EVI and phenology magnitude,as a result of the various combinations of environmental factors,vegetation composition and also intensive anthropogenic impact.Apart from the continuously increasing trend of phenology magnitude with increasing altitude,the influence of topography and accessibility on maximum EVI and phenological magnitude generally decreased,even from strongly positive to negative,with increasing altitude or distance.Specially,the most rapid change of correlation coefficient between them was observed within a low elevation or close distance;less variation was discovered within a certain range of medium altitude or distance and their relationship might change above this range.Non-stationary approaches are needed to better characterize the complex vegetation dynamic pattern in Mountain-hill Region.展开更多
The measurement of emissions from the window material of sapphire was performed through multi-wavelength pyrometer and spontaneous spectroscopic techniques in the pressure range of 40 -120 GPa. The results showed that...The measurement of emissions from the window material of sapphire was performed through multi-wavelength pyrometer and spontaneous spectroscopic techniques in the pressure range of 40 -120 GPa. The results showed that the spectral distribution with wavelength clearly fit well with the grey-body spectrum. We have analyzed the emissions and discovered they mostly came from the shear banding, which is a typical thermal radiation. The radiance intensity changing linearly with time revealed it was a volume effect. All of the data from pyrometer can be explained by the model of Boslough＇s study, especially for pres- sures over megabar. The color temperature of shocked sapphire changing with increased stress disagrees with the computed melt curve which is likely explained by the differcnt phase structures of sapphire.展开更多
By using the Collins diffraction formula and expanding the aperture function into a fmite sum of complex Gaussian functions, an analytical formula of the time light intensity distribution for oblique Gaussian beams pa...By using the Collins diffraction formula and expanding the aperture function into a fmite sum of complex Gaussian functions, an analytical formula of the time light intensity distribution for oblique Gaussian beams passing through a moving cat-eye optical lens and going back along the entrance way is deduced. By numerical computation, the variation laws of the time intensity distributions of the cat-eye reflected light with the viewing angle, imaging distance, aperture and instantaneous field of view are given. The results show that the relationship between the light intensity at the return place and the detection time is linear, and it is of inverse proportion only when the viewing angle is very large. For the staring imaging optical lens, the nonlinear extent of the time distribution curve becomes larger with the decrease of the viewing angle. For the instantaneous imaging optical lens, there is still some cat-eye reflected light when the detection system is out of the viewing field of the target lens.展开更多
文摘Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double-crystal X-ray diffraction measurement.The expected high quality epitaxial DBR structure was verified.In the X-ray double-crystal rocking curves of DBR the zeroth-order peak,the first and second order satellite peaks were measured.Splitting of diffraction peak appeared in the rocking curves was analyzed.The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.
基金support forthis work from Chinese National Natural Science Foundation (Grant no. 41071267)Scientific Research Foundation for Returned Scholars,Ministry of Education of China ([2012]940)Science Foundation of Fujian province (Grant no.2012J01167,2012I0005)
文摘Knowledge of both vegetation distribution pattern and phenology changes is very important.Their complicated relationship with elevation and accessibility were explored through a geographically weighted regression(GWR) framework in Fujian province,China.The 16-day time series of 250 m Moderate Resolution Imaging Spectroradiometer(MODIS) Enhanced Vegetation Index(EVI) dataset from 2000 to 2010 was applied.Wavelet transform method was adopted to decompose the original time series and construct the annual maximum EVI and amplitude of the annual phenological cycle(EVI).Candidate explaining factors included topographic conditions,accessibility variables and proportions of primary vegetation types.Results revealed very strong positive influence from parameters of elevation and accessibility to big rivers and negative effect from accessibility to resident on both maximum EVI and phenological magnitude through ordinary linear least square(OLS) regression analysis.GWR analysis revealed that spatially,the parameters of topography and accessibility had a very complex relationship with both maximum EVI and phenology magnitude,as a result of the various combinations of environmental factors,vegetation composition and also intensive anthropogenic impact.Apart from the continuously increasing trend of phenology magnitude with increasing altitude,the influence of topography and accessibility on maximum EVI and phenological magnitude generally decreased,even from strongly positive to negative,with increasing altitude or distance.Specially,the most rapid change of correlation coefficient between them was observed within a low elevation or close distance;less variation was discovered within a certain range of medium altitude or distance and their relationship might change above this range.Non-stationary approaches are needed to better characterize the complex vegetation dynamic pattern in Mountain-hill Region.
基金support provided by the National Natural Science Foundation of China (Grant Nos. 10874141,10974160 and 10299040)the Foundation of Center Universities (Grant No.SWJTU112T23)
文摘The measurement of emissions from the window material of sapphire was performed through multi-wavelength pyrometer and spontaneous spectroscopic techniques in the pressure range of 40 -120 GPa. The results showed that the spectral distribution with wavelength clearly fit well with the grey-body spectrum. We have analyzed the emissions and discovered they mostly came from the shear banding, which is a typical thermal radiation. The radiance intensity changing linearly with time revealed it was a volume effect. All of the data from pyrometer can be explained by the model of Boslough＇s study, especially for pres- sures over megabar. The color temperature of shocked sapphire changing with increased stress disagrees with the computed melt curve which is likely explained by the differcnt phase structures of sapphire.
文摘By using the Collins diffraction formula and expanding the aperture function into a fmite sum of complex Gaussian functions, an analytical formula of the time light intensity distribution for oblique Gaussian beams passing through a moving cat-eye optical lens and going back along the entrance way is deduced. By numerical computation, the variation laws of the time intensity distributions of the cat-eye reflected light with the viewing angle, imaging distance, aperture and instantaneous field of view are given. The results show that the relationship between the light intensity at the return place and the detection time is linear, and it is of inverse proportion only when the viewing angle is very large. For the staring imaging optical lens, the nonlinear extent of the time distribution curve becomes larger with the decrease of the viewing angle. For the instantaneous imaging optical lens, there is still some cat-eye reflected light when the detection system is out of the viewing field of the target lens.
