In this paper, we demonstrate a scheme for compensating distorted optical vortex beams carrying orbital angular momentum. By inputting the intensity profile into the Gerchberg–Saxton algorithm [Optik 35, 237(1972)], ...In this paper, we demonstrate a scheme for compensating distorted optical vortex beams carrying orbital angular momentum. By inputting the intensity profile into the Gerchberg–Saxton algorithm [Optik 35, 237(1972)], the pre-compensation phase mask can be acquired. No additional probe beams are introduced, and all the computing is aiming at the transmitted vortex beams. The distorted vortex beams are investigated experimentally before and after pre-compensation, showing favorable compensation performance. This scheme will find applications in the areas of rotation detection, optical communications, and so on.展开更多
Over the last several decades,China has taken multiple measures for afforestation and natural forest protection,including setting the goal of carbon neutrality by the middle of 21th century.In order to support the pra...Over the last several decades,China has taken multiple measures for afforestation and natural forest protection,including setting the goal of carbon neutrality by the middle of 21th century.In order to support the practice of relevant policies from the scientific perspective,it is essential to precisely estimate the carbon storage of arbor forest,as it plays an important role in the carbon cycle of ecosystems.In this study,we first used the latest four phases of national forest inventory data to investigate the variation of carbon storage for both natural and planted arbor forest in China during the covered period(1999-2018).Then we used machine leaning methods to simulate the carbon density based on various kinds of environmental factors and analyzed the contribution of each influencing factor.Our results demonstrate that the total carbon storage for arbor forest in China kept increasing over the last two decades,but this increment was mainly brought about by the continuous expansion of forest land.The gap of carbon sequestration between natural forest and planted forest showed a significant trend of reduction.Additionally,tree age was identified as the dominant factor for influencing the spatiotemporal variation of carbon density among all the independent variables while the impact of climatic factor was limited.Therefore,the future improvement of carbon sequestration of arbor forest in should mainly rely on additional projects of afforestation,reforestation,green space conservation and reduction of emissions in China.Conclusions of this study have important implications for policy makers and other stakeholders to evaluate the previous achievement of environmental projects and can also help to set future plans and finally realize the goals of carbon neutrality.展开更多
基金National Basic Research Program of China(973 Program)(2014CB340002,2014CB340004)
文摘In this paper, we demonstrate a scheme for compensating distorted optical vortex beams carrying orbital angular momentum. By inputting the intensity profile into the Gerchberg–Saxton algorithm [Optik 35, 237(1972)], the pre-compensation phase mask can be acquired. No additional probe beams are introduced, and all the computing is aiming at the transmitted vortex beams. The distorted vortex beams are investigated experimentally before and after pre-compensation, showing favorable compensation performance. This scheme will find applications in the areas of rotation detection, optical communications, and so on.
基金supported by grants from the National Natural Science Foundation of China(Grants No.42171329,No.42071342,No.31870713).
文摘Over the last several decades,China has taken multiple measures for afforestation and natural forest protection,including setting the goal of carbon neutrality by the middle of 21th century.In order to support the practice of relevant policies from the scientific perspective,it is essential to precisely estimate the carbon storage of arbor forest,as it plays an important role in the carbon cycle of ecosystems.In this study,we first used the latest four phases of national forest inventory data to investigate the variation of carbon storage for both natural and planted arbor forest in China during the covered period(1999-2018).Then we used machine leaning methods to simulate the carbon density based on various kinds of environmental factors and analyzed the contribution of each influencing factor.Our results demonstrate that the total carbon storage for arbor forest in China kept increasing over the last two decades,but this increment was mainly brought about by the continuous expansion of forest land.The gap of carbon sequestration between natural forest and planted forest showed a significant trend of reduction.Additionally,tree age was identified as the dominant factor for influencing the spatiotemporal variation of carbon density among all the independent variables while the impact of climatic factor was limited.Therefore,the future improvement of carbon sequestration of arbor forest in should mainly rely on additional projects of afforestation,reforestation,green space conservation and reduction of emissions in China.Conclusions of this study have important implications for policy makers and other stakeholders to evaluate the previous achievement of environmental projects and can also help to set future plans and finally realize the goals of carbon neutrality.
