The pattern for utilization of rural space is closely related to rural transformationdevelopment (RTD). The problem of rural space utilization is an important manifestation of theuncoordinated relationship between lan...The pattern for utilization of rural space is closely related to rural transformationdevelopment (RTD). The problem of rural space utilization is an important manifestation of theuncoordinated relationship between land use patterns and rural development status during atransformation period. Considering the rural space utilization issue, this article seeks to analyzethe interaction mechanisms between land use transition (LUT) and rural spatial governanceand then build a rural spatial governance analysis framework based on LUT. Also, thepaper explores the internal relationship between rural spatial governance and rural vitalizationand discusses the research prospective of the interaction. The study found that: (1) Ruralspace utilization has systemic problems such as limited development space, ill-defined ownershipand poor organization, which have become important obstacles for rural development.(2) The uncoordinated relationship between LUT and RTD is an important reason for the dilemmasurrounding rural space utilization. (3) The LUT provides a basis for determining thetiming of rural spatial governance, specifying spatial governance objectives, and clarifyingrural spatial governance methods. (4) The construction of a comprehensive analysis frameworkof “matter-ownership-organization” of rural space based on the LUT has created conditionsfor the orderly promotion of rural spatial governance. (5) Rural spatial governance whichfacilitates the integration of urban-rural development is an important foundation for rural vitalization.(6) Interaction analysis of LUT, RTD and rural spatial governance is conducive tofacilitating research on the operational mechanism of rural regional systems and to expandingthe research field of rural geography.展开更多
Integrated photonics is expected to play an increasingly important role in optical communications,imaging,computing and sensing with the promise for significant reduction in the cost and weight of these systems.Future...Integrated photonics is expected to play an increasingly important role in optical communications,imaging,computing and sensing with the promise for significant reduction in the cost and weight of these systems.Future advancement of this technology is critically dependent on an ability to develop compact and reliable optical components and facilitate their integration on a common substrate.Here we reveal,with the utility of the emerging transformation optics technique,that functional components composed of planar gradient index materials can be designed and readily integrated into photonic circuits.The unprecedented design flexibility of transformation optics allows for the creation of a number of novel devices,such as a light source collimator,waveguide adapters and a waveguide crossing,which have broad applications in integrated photonic chips and are compatible with current fabrication technology.Using the finite-difference time-domain method,we perform full-wave numerical simulations to demonstrate their superior optical performance and efficient integration with other components in an on-chip photonic system.These components only require spatially-varying dielectric materials with no magnetic properties,facilitating low-loss,broadband operation in an integrated photonic environment.展开更多
基金National Natural Science Foundation of China,No.41901204,No.41871178China Postdoctoral Science Foundation,No.2019M660109+2 种基金The Foundation of Humanity and Social Sciences of the Ministry of Education of China,No.19YJCZH036Jiangsu Provincial Science Foundation,No.BK20190717Jiangsu Provincial Social Science Foundation,No.19GLC002。
文摘The pattern for utilization of rural space is closely related to rural transformationdevelopment (RTD). The problem of rural space utilization is an important manifestation of theuncoordinated relationship between land use patterns and rural development status during atransformation period. Considering the rural space utilization issue, this article seeks to analyzethe interaction mechanisms between land use transition (LUT) and rural spatial governanceand then build a rural spatial governance analysis framework based on LUT. Also, thepaper explores the internal relationship between rural spatial governance and rural vitalizationand discusses the research prospective of the interaction. The study found that: (1) Ruralspace utilization has systemic problems such as limited development space, ill-defined ownershipand poor organization, which have become important obstacles for rural development.(2) The uncoordinated relationship between LUT and RTD is an important reason for the dilemmasurrounding rural space utilization. (3) The LUT provides a basis for determining thetiming of rural spatial governance, specifying spatial governance objectives, and clarifyingrural spatial governance methods. (4) The construction of a comprehensive analysis frameworkof “matter-ownership-organization” of rural space based on the LUT has created conditionsfor the orderly promotion of rural spatial governance. (5) Rural spatial governance whichfacilitates the integration of urban-rural development is an important foundation for rural vitalization.(6) Interaction analysis of LUT, RTD and rural spatial governance is conducive tofacilitating research on the operational mechanism of rural regional systems and to expandingthe research field of rural geography.
基金Partial support for this work was provided by the NSF MRSEC(Grant No.DMR-0820404).We thank Peter Sieber for his assistance with some of the figure visualizations.
文摘Integrated photonics is expected to play an increasingly important role in optical communications,imaging,computing and sensing with the promise for significant reduction in the cost and weight of these systems.Future advancement of this technology is critically dependent on an ability to develop compact and reliable optical components and facilitate their integration on a common substrate.Here we reveal,with the utility of the emerging transformation optics technique,that functional components composed of planar gradient index materials can be designed and readily integrated into photonic circuits.The unprecedented design flexibility of transformation optics allows for the creation of a number of novel devices,such as a light source collimator,waveguide adapters and a waveguide crossing,which have broad applications in integrated photonic chips and are compatible with current fabrication technology.Using the finite-difference time-domain method,we perform full-wave numerical simulations to demonstrate their superior optical performance and efficient integration with other components in an on-chip photonic system.These components only require spatially-varying dielectric materials with no magnetic properties,facilitating low-loss,broadband operation in an integrated photonic environment.
