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Deforestation in Latin America in the 2000s predominantly occurred outside of typical mature forests

The Innovation 2024年第3期5卷 88-98页

作者： Zhiyu Zhang Wenjian Ni Shaun Quegan Jingming Chen Peng Gong Luiz Carlos Estraviz Rodriguez Huadong Guo jiancheng shi Liangyun Liu Zengyuan Li Yating He Qinhuo Liu Yosio shimabukuro Guoqing Sun Key Laboratory of Remote Sensing and Digital Earth Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Shijingshan DistrictBeijing 100049China Chinal of Mathematics and Statistics University of SheffieldSheffield S37RHUK Department of Geography and Program in Planning University of TorontoTorontoON M5S 3G3Canada Department of Earth Sciences and Department of Geography University of Hong KongHong KongChina Forest Science Department Luiz de Queiroz College of AgricultureUniversity of São PauloAv.Pádua Dias11Piracicaba 13418-900Brazil National Space Science Center Chinese Academy of SciencesBeijing 100190China Institute of Forest Resource Information Techniques Chinese Academy of ForestryBeijing 100091China Research Institute of Forest Policy and Information Chinese Academy of ForestryBeijing 100091China Remote Sensing Department National Institute for Space Research(INPE)Av.dos Astronautas 1758São Josédos Campos 12227-010Brazil Department of Geographical Sciences University of MarylandCollege ParkMD 20742USA

The role of tropical forests in the global carbon budget remains controversial,as carbon emissions from deforestation are highly *** high uncertainty arises from the use of either fixed forest carbon stock density or maps generated from satellite-based optical reflectance with limited sensitivity to biomass to generate accurate estimates of emissions from *** space missions aiming to accurately map the carbon stock density rely on direct measurements of the spatial structures of forests using lidar and *** found that lost forests are special cases,and their spatial structures can be directly measured by combining archived data acquired before and after deforestation by space missions principally aimed at measuring ***,using biomass mapping,we obtained new estimates of carbon loss from deforestation ahead of forthcoming space ***,using a high-resolution map of forest loss and the synergy of radar and lidar to estimate the aboveground biomass density of forests,we found that deforestation in the 2000s in Latin America,one of the severely deforested regions,mainly occurred in forests with a significantly lower carbon stock density than typical mature forests.

关键词： forest Latin lidar

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先进通用核心机派生发展的理念、方法及实践

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航空学报 2024年第7期45卷 1-12页

作者：尹泽勇李概奇石建成银越千中国航发中国航空发动机研究院北京101304 中国航发湖南动力机械研究所株洲412002

概述了核心机派生发展发动机的历史背景和某些典型派生发展案例。阐明了先进通用核心机及其派生发展的理念及优势,给出了先进通用核心机派生发展的基本方法,包括通用核心机流量选择、热力循环参数选择、部件构型选择、部件高效稳定工作... 详细信息

概述了核心机派生发展发动机的历史背景和某些典型派生发展案例。阐明了先进通用核心机及其派生发展的理念及优势,给出了先进通用核心机派生发展的基本方法,包括通用核心机流量选择、热力循环参数选择、部件构型选择、部件高效稳定工作范围确定等。此外,从市场定位、先进性确定、核心机方案设计等方面介绍了某先进通用核心机的研发历程,并阐述了由其派生发展的飞机用涡轴、涡桨、涡扇航空发动机以及车用燃气轮机产品的研制。通过实践表明了先进通用核心机派生发展的可能性及由此带来的降低风险、缩短周期、节约经费等方面的优势。

关键词：先进通用核心机派生发展技术及经济优势航空发动机系列化

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面向电子装备装配引导的AR跟踪方法研究

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应用科学学报 2024年第3期42卷 416-424页

作者：杜小东王鹏史建成王月帅昊中国电子科技集团公司第二十九研究所四川成都610036 重庆邮电大学先进制造工程学院重庆400065

为了提高面向电子装备装配引导的增强现实(augmented reality,AR)跟踪方法的鲁棒性与适用性,在像素投票姿态估计网络结构的基础上,结合深度可分离卷积和通道注意力机制对AR跟踪算法进行优化。首先,针对电子装备六自由度姿态公共数据集... 详细信息

为了提高面向电子装备装配引导的增强现实(augmented reality,AR)跟踪方法的鲁棒性与适用性,在像素投票姿态估计网络结构的基础上,结合深度可分离卷积和通道注意力机制对AR跟踪算法进行优化。首先,针对电子装备六自由度姿态公共数据集稀缺与使用约束较多的问题,使用RGB-D相机采集并制作AR装配引导的电子装备的六自由度姿态训练数据集。然后,在基于像素投票的姿态估计网络结构基础上,使用深度可分离卷积对网络进行轻量化,并引入通道注意力机制对通道进行权重评估,以弥补网络轻量化造成的精度损失。最后,通过电子装备装配任务对提出的方法进行AR装配引导验证。实验结果表明:提出的跟踪注册方法相对于修改前的跟踪方法具有较好的鲁棒性,同时保持了装配引导的精度,能够对弱纹理的电子装备进行跟踪。

关键词：电子装备增强现实三维跟踪深度可分离卷积通道注意力

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Relationship between sea surface salinity and ocean circulation and climate change

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Science China Earth Sciences 2019年第5期62卷 771-782页

作者： Yan DU Yuhong ZHANG jiancheng shi State Key Laboratory of Tropical Oceanography South China Sea Institute of Oceanology Chinese Academy of Sciences University of Chinese Academy of Sciences State Key Laboratory of Remote Sensing Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences

Based on Argo sea surface salinity(SSS) and the related precipitation(P), evaporation(E), and sea surface height data sets, the climatological annual mean and low-frequency variability in SSS in the global ocean and their relationship with ocean circulation and climate change were analyzed. Meanwhile, together with previous studies, a brief retrospect and prospect of seawater salinity were given in this work. Freshwater flux(E-P) dominated the mean pattern of SSS, while the dynamics of ocean circulation modulated the spatial structure and low-frequency variability in SSS in most regions. Under global warming, the trend in SSS indicated the intensification of the global hydrological cycle, and featured a decreasing trend at low and high latitudes and an increasing trend in subtropical regions. In the most recent two decades, global warming has slowed down, which is called the"global warming hiatus". The trend in SSS during this phase, which was different to that under global warming, mainly indicated the response of the ocean surface to the decadal and multi-decadal variability in the climate system, referring to the intensification of the Walker Circulation. The significant contrast of SSS trends between the western Pacific and the southeastern Indian Ocean suggested the importance of oceanic dynamics in the cross-basin interaction in recent decades. Ocean Rossby waves and the Indonesian Throughflow contributed to the freshening trend in SSS in the southeastern Indian Ocean, while the increasing trend in the southeastern Pacific and the decreasing trend in the northern Atlantic implied a long-term linear trend under global warming. In the future, higher resolution SSS data observed by satellites, together with Argo observations, will help to extend our knowledge on the dynamics of mesoscale eddies, regional oceanography, and climate change.

关键词： Sea surface salinity Ocean circulation Climate change Multi-scale interaction

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Review of snow water equivalent microwave remote sensing

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Science China Earth Sciences 2016年第4期59卷 731-745页

作者： shi jiancheng XIONG Chuan JIANG LingMei State Key Laboratory of Remote Sensing Sciences Jointly Sponsored by Institute of Remote Sensing and Digital Earth of Chinese Academy of Sciences and Beijing Normal University and Joint Center for Global Change Studies State Key Laboratory of Remote Sensing Sciences Jointly Sponsored by Beijing Normal University and Institute of Remote Sensing and Digital Earth of Chinese Academy of Sciences School of Geography Beijing Normal Universityand Joint Center for Global Change Studies

Accurate quantitative global scale snow water equivalent information is crucial for meteorology, hydrology, water cycle and global change studies, and is of great importance for snow melt-runoff forecast, water resources management and flood control. With land surface process model and snow process model, the snow water equivalent can be simulated with certain accuracy, with the forcing data as input. However, the snow water equivalent simulated using the snow process models has large uncertainties spatially and temporally, and it may be far from the needs of practical applications. Thus, the large scale snow water equivalent information is mainly from remote sensing. Beginning with the launch of Nimbus-7 satellite, the research on microwave snow water equivalent remote sensing has developed for more than 30 years, researchers have made progress in many aspects, including the electromagnetic scattering and emission modeling, ground and airborne experiments, and inversion algorithms for future global high resolution snow water equivalent remote sensing program. In this paper, the research and progress in the aspects of electromagnetic scattering/emission modeling over snow covered terrain and snow water equivalent inversion algorithm will be summarized.

关键词： Snow Microwave remote sensing Model Inversion

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Enhancing remote sensing research on global change to improve our understanding on Earth system processes

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Science China Earth Sciences 2014年第10期57卷 2281-2282页

作者： shi jiancheng State Key Lab of Remote Sensing Science Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences

Global Change includes climate change and other environmental changes caused by the joint interaction among various layers of Earth. From the positive side, global change provides new opportunities to human and other living forms on Earth. In the meantime, it creates tremendous challenges and negative impact. At present, the negative impacts have reached all primary processes of the global ecosystem and every aspect of human society, especially causing degradation of the ecosys- tem. For instance, intensive deforestation causes decline of biodiversity; global warming causes sea level rise and increases the frequency of extreme weather and climate events （Yang et al., 2013）. Changing the natural environment also considerably affects the socio-economic development of the entire world. Prompt and adequate response to challenges of global change is essential to realizing sustainable development of human society （Xu et al., 2013）.

关键词：全球变化地球系统全球气候变化遥感人类社会全球生态系统生态系统退化全球气候变暖

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积雪季森林冠层微波透过率半经验模型

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遥感学报 2024年第4期28卷 981-994页

作者：杨建卫蒋玲梅武胜利栾英宏潘金梅施建成遥感科学国家重点实验室北京师范大学地理科学学部北京100875 国家卫星气象中心(国家空间天气监测预警中心) 北京100081 许健民气象卫星创新中心北京100081 上海航天电子技术研究所上海201109 中国科学院国家空间科学中心北京100190

星载被动微波遥感是获取宏观尺度雪深时空分布的重要手段。森林冠层不仅衰减了来自地表的微波辐射,同时自身也是一个热辐射源,因此森林冠层增加了被动微波遥感反演雪深的不确定性。本研究基于植被辐射传输tau-omega模型(τ-ω)提出了相... 详细信息

星载被动微波遥感是获取宏观尺度雪深时空分布的重要手段。森林冠层不仅衰减了来自地表的微波辐射,同时自身也是一个热辐射源,因此森林冠层增加了被动微波遥感反演雪深的不确定性。本研究基于植被辐射传输tau-omega模型(τ-ω)提出了相邻像元(森林和非森林)的冠层微波透过率提取方法,探索冠层微波透过率模型在卫星尺度的应用。该方法假设相邻的森林和非森林像元存在相同的积雪和环境参数,通过联立相邻像元的辐射传输方程从理论上推算冠层微波透过率,进而借助森林生物量建立森林透过率的半经验估算模型。通过对比微波辐射模型模拟亮温和AMSR2卫星观测亮温,发现未经过森林辐射校正的亮温(18.7 GHz和36.5 GHz)往往存在低估现象,而经过森林辐射校正后的模拟亮温更接近于卫星观测;通过留一法(Leave-One-Out Cross Validation)对发展的透过率半经验模型验证,发现反演的透过率与参考值相关性高于0.7,在18.7 GHz和36.5 GHz频段的均方根误差RMSE分别为0.0589和0.0787;通过分析高低频亮温差(Tb18.7V-Tb36.5V)与雪深的关系,发现相关系数由森林辐射校正前的0.26提高到校正后的0.46;最后利用传统的经验性雪深反演算法对森林辐射校正效果进行测试,发现雪深反演误差(unRMSE)由原来的8.9 cm降低到7.8 cm,相关系数由0.32提高到0.49。本研究发展的冠层微波透过率半经验模型可以实现卫星遥感尺度的应用,为提高林区的雪深反演精度提供了参考和支撑。

关键词：被动微波遥感森林冠层相邻像元法微波透过率雪深

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Reconstruction and analysis of temporal and spatial variations in surface soil moisture in China using remote sensing

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Chinese Science Bulletin 2012年第22期57卷 2824-2834页

作者： LU Hui shi jiancheng Ministry of Education Key Laboratory for Earth System Modeling and Center for Earth System Science Tsinghua University Beijing 100084 China The Institute of Remote Sensing Applications Chinese Academy of Sciences Beijing 100101 China

An ensemble method was used to combine three surface soil moisture products,retrieved from passive microwave remote sensing data,to reconstruct a monthly soil moisture data set for China between 2003 and *** the ensemble data set,the temporal and spatial variations of surface soil moisture were *** major findings were:(1) The ensemble data set was able to provide more realistic soil moisture information than individual remote sensing products;(2) during the study period,the soil moisture increased in semiarid regions and decreased in arid regions with anoverall drying trend for the whole country;(3) the soil moisture variation trends derived from the three retrieval products and the ensemble data differ from each other but all data sets show the dominant drying trend for the summer,and that most of the drying regions were in major agricultural areas;(4) compared with the precipitation trends derived from Global Precipitation Climatology Project data,it is speculated that climate change is a possible cause for the drying trend in semiarid regions and the wetting trend in arid regions;and (5) combining soil moisture trends with land surface temperature trends derived from Moderate Resolution Imaging Spectroradiomete,the study domain was divided into four *** with drying and warming trends cover 33.2%,the regions with drying and cooling trends cover 27.4%,the regions with wetting and warming trends cover 21.1% and the regions with wetting and cooling trends cover 18.1%.The first two categories primarily cover the major grain producing areas,while the third category primarily covers nonarable areas such as Northwest China and *** implies that the moisture and heat variation trends in China are unfavorable to sustainable development and ecology conservation.

关键词：土壤水分变化被动微波遥感中国西北时空变化表层半干旱地区干燥地区区域覆盖

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Contact State Estimation Based on Surface-matching in Virtual Assembly

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Chinese Journal of Mechanical Engineering 2012年第1期25卷 1-11页

作者： HOU Weiwei LIU Jianhua NING Ruxin shi jiancheng School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

Contact problems are one of the most challenging fields in virtual assembly. Information of contact states could be utilized to realize compliant motion of work pieces, to analyze the contact stress, to assist positioning parts and so on. Some methods have already been proposed to estimate contact states between objects and in most of these methods contact states between objects are simplified in order to realize real-time visual reality animation. While in virtual assembly contact states between parts are required to analyze contact stress, deformation and quality. Besides the contact state estimation method for virtual assembly should be able to handle a number of complex parts in real time. There are rarely known methods which could meet this requirement till now. In this study a contact state estimation algorithm based on surface-matching for virtual assembly is proposed. Contacts between parts are categorized into six basic types according to contact region of surfaces. Based on continuous collision detection of polyhedral models a novel contact state identification algorithm which is based on surface matching is proposed. Then contact evolution algorithm, which utilizes the extern force and contact information, is implemented to handle evolution of contact state. Finally a prototype system is developed to verify the above technologies. Experiment results reveal that contact state between parts could be estimated correctly in real time virtual assembly. The proposed contact state estimation algorithm provides a complete solution to obtain the contact state between parts in virtual assembly. Information of contact state between parts could be utilized to realize contact dynamic, contact stress analysis, assembly quality analysis, and so on.

关键词： virtual assembly contact state identification surface matching contact state evolution

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Retrieving dry snow density with SIR-C polarimetric SAR data

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Chinese Science Bulletin 2001年第14期46卷 1211-1214页

作者： Zhen Li Huadong Guo jiancheng shi Chinese Acad Sci Inst Remote Sensing Applicat Lab Remote Sensing Informat Sci Beijing 100101 Peoples R China

For a given incidence angle at the snow surface, a greater snow density causes a greater change in the incidence angle at the snow-ground interface; for a given snow density, however, a larger incidence angle at the snow surface results in a greater change in the refractive angle in the snow layer, by comparing the difference of incidence angle at the snow-ground interface and the air-snow interface with different snow density. Algorithm for estimating dry snow density used backscattering measurements with polarimetric SAR at L-band frequency is developed based on simulation of the surface backscattering components ghh,and gvv using the IEM model and regression analysis. The comparison of the estimated snow density from SAR L-band images with that from field measurements during the SIR-C/X-SAR overpass shows root means square error of 0.050 g/cm3. It shows that this algorithm can be accurately used to estimate dry snow density distribution.

关键词： polarimetric SAR dielectric constant backscattering dry snow density retrieving.

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