The amount of photosynthetic radiation inter- cepted by a crop is a function of the incident solar radiation on the plants, the leaf area index （LAI）, and the light extinction coefficient （k）. We quantified LAI an...The amount of photosynthetic radiation inter- cepted by a crop is a function of the incident solar radiation on the plants, the leaf area index （LAI）, and the light extinction coefficient （k）. We quantified LAI and k in stands of black wattle （Acacia mearnsii De Wild.） over a 7-year growth cycle at two locations in the state of Rio Grande do Sul, Brazil. Our study was conducted in commercial stands in agroecological regions with high densities of black wattle plantations. LAI was calculated as the ratio between the leaf area of a tree and its planting space, and k was derived from Beer＇s law. LAI depends on the planting site and stand age. Between the two sites, the LAI was similar over time, the amount of variation differed. Values of k depended only on stand age, with the highest average observed for stands up to 5 years old. The trend of k during the plantation cycle was inversely proportional to LAI and was correlated with LAI, leaf area, leaf dry mass, canopy volume, height, branches dry mass, total dry mass, and crown diameter.展开更多
The utilization of blue lasers to excite phosphor materials holds great potential for the development of high-brightness laser-driven light sources.However,phosphor materials that can simultaneously constrain light sp...The utilization of blue lasers to excite phosphor materials holds great potential for the development of high-brightness laser-driven light sources.However,phosphor materials that can simultaneously constrain light spot expansion and enhance the maximum luminous flux have been elusive,thereby limiting the output luminance.In this study,optical fiber-inspired core–cladding phosphor ceramics(CCPC)of YAG:Ce@Al_(2)O_(3)wafers were engineered using a gel–casting technique to restrict light spot expansion.The smaller refractive index of Al_(2)O_(3),combined with the dense and sharp core–cladding interface of these CCPC,effectively confines the light spot area.The sample with a 1.0 mm core diameter has a small spot size nearly identical to that of the incident blue laser beam.Furthermore,the high thermal conductivity of the non-luminescent Al_(2)O_(3)cladding endows the CCPC with an impressive luminance saturation threshold of 30 W·mm^(-2)and a maximum luminous flux of 2100 lm for white light within a straightforward transmissive optical setup.The combination of a confined light-spot area and elevated luminous flux results in an ultra-high luminance of 3900 lm·mm^(-2),surpassing current reports.This research presents a pioneering approach to the design of phosphor materials,targeting the realization of light sources with unprecedented luminance for broad frontier applications.展开更多
文摘The amount of photosynthetic radiation inter- cepted by a crop is a function of the incident solar radiation on the plants, the leaf area index （LAI）, and the light extinction coefficient （k）. We quantified LAI and k in stands of black wattle （Acacia mearnsii De Wild.） over a 7-year growth cycle at two locations in the state of Rio Grande do Sul, Brazil. Our study was conducted in commercial stands in agroecological regions with high densities of black wattle plantations. LAI was calculated as the ratio between the leaf area of a tree and its planting space, and k was derived from Beer＇s law. LAI depends on the planting site and stand age. Between the two sites, the LAI was similar over time, the amount of variation differed. Values of k depended only on stand age, with the highest average observed for stands up to 5 years old. The trend of k during the plantation cycle was inversely proportional to LAI and was correlated with LAI, leaf area, leaf dry mass, canopy volume, height, branches dry mass, total dry mass, and crown diameter.
基金supported by the National Key R&D Program of China(MOSTNo.2022YFE0108800)+2 种基金the National Natural Science Foundation of China(No.52272165)the Fujian Provincial Natural Science Foundation of China(No.2024J09009)the Xiamen Major Science and Technology Project(No.3502Z20231050).
文摘The utilization of blue lasers to excite phosphor materials holds great potential for the development of high-brightness laser-driven light sources.However,phosphor materials that can simultaneously constrain light spot expansion and enhance the maximum luminous flux have been elusive,thereby limiting the output luminance.In this study,optical fiber-inspired core–cladding phosphor ceramics(CCPC)of YAG:Ce@Al_(2)O_(3)wafers were engineered using a gel–casting technique to restrict light spot expansion.The smaller refractive index of Al_(2)O_(3),combined with the dense and sharp core–cladding interface of these CCPC,effectively confines the light spot area.The sample with a 1.0 mm core diameter has a small spot size nearly identical to that of the incident blue laser beam.Furthermore,the high thermal conductivity of the non-luminescent Al_(2)O_(3)cladding endows the CCPC with an impressive luminance saturation threshold of 30 W·mm^(-2)and a maximum luminous flux of 2100 lm for white light within a straightforward transmissive optical setup.The combination of a confined light-spot area and elevated luminous flux results in an ultra-high luminance of 3900 lm·mm^(-2),surpassing current reports.This research presents a pioneering approach to the design of phosphor materials,targeting the realization of light sources with unprecedented luminance for broad frontier applications.
