利用实验区环境星多光谱数据与Envisat ASAR VV极化数据进行融合,讨论了VV极化微波后向散射数据用于改善多光谱遥感数据农作物分类的精度,并比较了不同分类方法的分类精度。结果表明,两种数据之间的融合充分利用了环境星数据的光谱信息...利用实验区环境星多光谱数据与Envisat ASAR VV极化数据进行融合,讨论了VV极化微波后向散射数据用于改善多光谱遥感数据农作物分类的精度,并比较了不同分类方法的分类精度。结果表明,两种数据之间的融合充分利用了环境星数据的光谱信息和VV极化数据对于地物结构敏感的特征,不但增强了不同地物之间的光谱差异,而且提高了作物分类精度。两者融合后分类精度比单独使用环境星数据分类精度提高了约5个百分点,而且由于VV极化数据对田间非耕地信息的敏感性,对于田块边界的识别效果有很大的改善。通过该研究探讨了VV极化数据和多光谱数据融合在作物分类中的应用,拓展了遥感数据在农业领域应用的范围,具有推广价值。展开更多
In the current paper, we have primarily addressed one powerful simulation tool developed during the last decades-Large Eddy Simulation (LES), which is most suitable for unsteady three-dimensional complex turbulent flo...In the current paper, we have primarily addressed one powerful simulation tool developed during the last decades-Large Eddy Simulation (LES), which is most suitable for unsteady three-dimensional complex turbulent flows in industry and natural environment. The main point in LES is that the large-scale motion is resolved while the small-scale motion is modeled or, in geophysical terminology, parameterized. With a view to devising a subgrid-scale(SGS) model of high quality, we have highlighted analyzing physical aspects in scale interaction and-energy transfer such as dissipation, backscatter, local and non-local interaction, anisotropy and resolution requirement. They are the factors responsible for where the advantages and disadvantages in existing SGS models come from. A case study on LES of turbulence in vegetative canopy is presented to illustrate that LES model is more based on physical arguments. Then, varieties of challenging complex turbulent flows in both industry and geophysical fields in the near future-are presented. In conclusion; we may say with confidence that new century shall see the flourish in the research of turbulence with the aid of LES combined with other approaches.展开更多
Microstructure features of 12 MnNiVR pressure vessel steel welded joint deposited by the high heat input electrogas welding have been systematically investigated. It is revealed that the welded joint is featured by a ...Microstructure features of 12 MnNiVR pressure vessel steel welded joint deposited by the high heat input electrogas welding have been systematically investigated. It is revealed that the welded joint is featured by a heterogeneous juxtaposition. The coarse grained heat-affected zone(CGHAZ) primarily consists of lath bainites and minor granular bainites. The fine grained heat-affected zone(FGHAZ) is dominated by polygonal ferrites, pearlites, and fine cementite particles. Moreover, electron backscatter diffraction results further demonstrate that the CGHAZ is populated by coarse prior austenite grains(PAGs) with high frequency(61.3%) of low angle grain boundaries(LAGBs). On the other hand, the FGHAZ is filled with fine PAGs with a lower frequency(19.6%) of LAGBs. Such microstructural differences may likely contribute to differed mechanical properties for samples tested at designed positions.展开更多
Internet of Things (IoT) has attracted extensive interest from both academia and industries, and is recognized as an ultimate infrastructure to connect everything at anytime and anywhere. The implementation of IoT gen...Internet of Things (IoT) has attracted extensive interest from both academia and industries, and is recognized as an ultimate infrastructure to connect everything at anytime and anywhere. The implementation of IoT generally faces the challenges from energy constraint and implementation cost. In this paper, we will introduce a new green communication paradigm, the ambient backscatter (AmBC), that could utilize the environmental wireless signals for both powering a tiny-cost device and backscattering the information symbols. Specifically, we will present the basic principles of AmBC, analyze its features and advantages, suggest its open problems, and predict its potential applications for our future IoT.展开更多
Large intelligent surface/antennas(LISA),a two-dimensional artificial structure with a large number of reflective-surface/antenna elements,is a promising reflective radio technology to construct programmable wireless ...Large intelligent surface/antennas(LISA),a two-dimensional artificial structure with a large number of reflective-surface/antenna elements,is a promising reflective radio technology to construct programmable wireless environments in a smart way.Specifically,each element of the LISA adjusts the reflection of the incident electromagnetic waves with unnatural properties,such as negative refraction,perfect absorption,and anomalous reflection,thus the wireless environments can be software-defined according to various design objectives.In this paper,we introduce the reflective radio basics,including backscattering principles,backscatter communication,reflective relay,the fundamentals and implementations of LISA technology.Then,we present an overview of the state-of-the-art research on emerging applications of LISA-aided wireless networks.Finally,the limitations,challenges,and open issues associated with LISA for future wireless applications are discussed.展开更多
文摘利用实验区环境星多光谱数据与Envisat ASAR VV极化数据进行融合,讨论了VV极化微波后向散射数据用于改善多光谱遥感数据农作物分类的精度,并比较了不同分类方法的分类精度。结果表明,两种数据之间的融合充分利用了环境星数据的光谱信息和VV极化数据对于地物结构敏感的特征,不但增强了不同地物之间的光谱差异,而且提高了作物分类精度。两者融合后分类精度比单独使用环境星数据分类精度提高了约5个百分点,而且由于VV极化数据对田间非耕地信息的敏感性,对于田块边界的识别效果有很大的改善。通过该研究探讨了VV极化数据和多光谱数据融合在作物分类中的应用,拓展了遥感数据在农业领域应用的范围,具有推广价值。
基金The NSAF project supported by the NSFC and the Chinese Academy of Engineering Physics (10176032)
文摘In the current paper, we have primarily addressed one powerful simulation tool developed during the last decades-Large Eddy Simulation (LES), which is most suitable for unsteady three-dimensional complex turbulent flows in industry and natural environment. The main point in LES is that the large-scale motion is resolved while the small-scale motion is modeled or, in geophysical terminology, parameterized. With a view to devising a subgrid-scale(SGS) model of high quality, we have highlighted analyzing physical aspects in scale interaction and-energy transfer such as dissipation, backscatter, local and non-local interaction, anisotropy and resolution requirement. They are the factors responsible for where the advantages and disadvantages in existing SGS models come from. A case study on LES of turbulence in vegetative canopy is presented to illustrate that LES model is more based on physical arguments. Then, varieties of challenging complex turbulent flows in both industry and geophysical fields in the near future-are presented. In conclusion; we may say with confidence that new century shall see the flourish in the research of turbulence with the aid of LES combined with other approaches.
基金financially supported by the National Natural Science Foundation of China (Nos. 51622401, 51628402, 51861145312 and 51861130361)the National Key Research and Development Program of China (2016YFB0300602)+3 种基金the Research Fund for Central Universities (No. N172502004)State Key Laboratory of Solidification Processing, Northwestern Polytechnical University (No. SKLSP201805)the Global Talents Recruitment Program endowed by the Chinese Governmentsupport from Jiangyin Xingcheng Special Steel Works Co., Ltd.
文摘Microstructure features of 12 MnNiVR pressure vessel steel welded joint deposited by the high heat input electrogas welding have been systematically investigated. It is revealed that the welded joint is featured by a heterogeneous juxtaposition. The coarse grained heat-affected zone(CGHAZ) primarily consists of lath bainites and minor granular bainites. The fine grained heat-affected zone(FGHAZ) is dominated by polygonal ferrites, pearlites, and fine cementite particles. Moreover, electron backscatter diffraction results further demonstrate that the CGHAZ is populated by coarse prior austenite grains(PAGs) with high frequency(61.3%) of low angle grain boundaries(LAGBs). On the other hand, the FGHAZ is filled with fine PAGs with a lower frequency(19.6%) of LAGBs. Such microstructural differences may likely contribute to differed mechanical properties for samples tested at designed positions.
基金supported in part by National Key R&D Program of China under Grant 2016YFE0200900part by Scientific Research Program of Beijing Municipal Commission of Education under Grant KM201910853003part by Major projects of Beijing Municipal Science and Technology Commission under Grant Z181100003218010
文摘Internet of Things (IoT) has attracted extensive interest from both academia and industries, and is recognized as an ultimate infrastructure to connect everything at anytime and anywhere. The implementation of IoT generally faces the challenges from energy constraint and implementation cost. In this paper, we will introduce a new green communication paradigm, the ambient backscatter (AmBC), that could utilize the environmental wireless signals for both powering a tiny-cost device and backscattering the information symbols. Specifically, we will present the basic principles of AmBC, analyze its features and advantages, suggest its open problems, and predict its potential applications for our future IoT.
基金This work was supported by the National Natural Science Foundation of China under Grants U1801261,61631005,and 61571100.
文摘Large intelligent surface/antennas(LISA),a two-dimensional artificial structure with a large number of reflective-surface/antenna elements,is a promising reflective radio technology to construct programmable wireless environments in a smart way.Specifically,each element of the LISA adjusts the reflection of the incident electromagnetic waves with unnatural properties,such as negative refraction,perfect absorption,and anomalous reflection,thus the wireless environments can be software-defined according to various design objectives.In this paper,we introduce the reflective radio basics,including backscattering principles,backscatter communication,reflective relay,the fundamentals and implementations of LISA technology.Then,we present an overview of the state-of-the-art research on emerging applications of LISA-aided wireless networks.Finally,the limitations,challenges,and open issues associated with LISA for future wireless applications are discussed.
