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Reconstructing forest and grassland cover changes in China over the past millennium

Science China Earth Sciences 2025年第1期68卷 94-110页

作者： Fanneng HE Fan YANG Yafei WANG Key laboratory of Land Surface pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing100101China Key Research Institute of Yellow River Civilization and Sustainable Development Henan UniversityKaifeng475001China University of Chinese Academy of Sciences Beijing100049China

Historical forest and grassland cover changes not only are critical indicators for quantifying ecological and environmental change processes but also serve as fundamental data for long-term climate change simulations and terrestrial ecosystem carbon emission ***,because of limitations in historical data,quantitative estimations and spatially gridded reconstructions of these changes remain challenging,necessitating further methodological *** study focused on China's present-day land area over the past millennium,objectively capturing the characteristics and drivers of forest and grassland cover *** this basis,using the forest transition theory and the space-for-time substitution method,we depicted the historical deforestation process as an inverted“S”curve and developed a model to reconstruct historical forest area changes based on the functional relationship between the forest area and population size ***,a gridded forest allocation model was established on the basis of deforestation *** the grassland cover,we implemented regionspecific methods,such as the cropland area deduction method and the habitat constraint method,to quantitatively reconstruct historical ***,we obtained provincial forest and grassland area changes over the past millennium and mapped 10-km-resolution gridded data of forest and grassland *** results indicated the following.(1)The methods developed using population data as a proxy objectively reproduced the spatiotemporal evolution of forest and grassland cover in China over the past *** feasible methods offer a novel pathway for the quantitative reconstruction of historical forest and grassland cover changes.(2)The data indicated that China's forest area generally decreased over the past millennium,characterized by a“decrease-then-increase”*** forest area experienced three distinct phases:a slow decline(AD 1000–1650),a rapid decline(AD 16

关键词： Land use and land cover change Forest Grassland Quantitative reconstruction Gridded reconstruction China historical period

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Clustering by data competition

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Science China(Information Sciences) 2013年第1期56卷 65-77页

作者： LU ZhiMao ZHANG Qi pattern recognition and natural computation laboratory Harbin Engineering University

Clustering analysis is an unsupervised method to find out hidden structures in *** partitional clustering algorithms are sensitive to the selection of initial exemplars,the outliers and *** this paper,a novel technique called data competition algorithm is proposed to solve the *** the concept of aggregation field model is defined to describe the partitional clustering ***,the exemplars are identified according to the data ***,the members will be assigned to the suitable *** competition algorithm is able to avoid poor solutions caused by unlucky initializations,outliers and noise,and can be used to detect the coexpression gene,cluster the image,diagnose the disease,distinguish the variety,*** provided experimental results validate the feasibility and effectiveness of the proposed schemes and show that the proposed approach of data competition algorithm is simple,stable and *** experimental results also show that the proposed approach of data competition clustering outperforms three of the most well known clustering algorithms K-means clustering,affinity propagation clustering,hierarchical clustering.

关键词： data mining clustering analysis partitional clustering data competition

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Latitudinal patterns of tree β-diversity and relevant ecological processes vary across spatial extents in forests of southeastern China

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Plant Diversity 2025年第1期47卷 89-97页

作者： Maochou Liu Wenxiang Wu Ke Wang Xinshuai Ren Xueqin Zhang Lei Wang Jing Geng Bo Yang Key laboratory of Land Surface pattern and Simulation Institute of Geographic and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Department of Environment and Resources University of Chinese Academy of SciencesBeijing 100049China Zhai Mingguo Academician Work Station Sanya UniversitySanya 572022China

Latitudinal patterns of treeβ-diversity reveal important insights into the biogeographical processes that influence forest *** previous studies have extensively documentedβ-diversity within relatively small spatial extents,the potential drivers ofβ-diversity along latitudinal gradients are still not well understood at larger spatial *** this study,we determined whether treeβ-diversity is correlated with latitude in forests of southeastern China,and if so,what ecological processes contribute to these patterns of treeβ-*** specifically aimed to disentangle the relative contributions from interspecific aggregation and environmental filtering across various spatial *** delineated regional communities comprising multiple nearby national forest inventory(NFI)plots around random focal *** number of NFI plots in a regional community served as a surrogate for spatial *** also used a null model to simulate randomly assembled communities and quantify the deviation(β-deviation)between observed and expectedβ-*** found thatβ-diversity decreased along a latitudinal gradient and that this pattern was clearer at larger spatial *** addition,latitudinal patterns ofβ-deviation were explained by the degree of species spatial *** also identified environmental factors that driveβ-deviation in these forests,including precipitation,seasonality,and temperature *** larger spatial extents,these environmental variables explained up to 84%of theβ-*** results reinforce that ecological processes are scale-dependent and collectively contribute to theβ-gradient in subtropical *** recommend that conservation efforts maintain diverse forests and heterogeneous environments at multiple spatial extents to mitigate the adverse effects of climate change.

关键词： Environmental filtering Latitudinal pattern Forest beta diversity Spatial extent Species spatial aggregation Regional community

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Spectroscopic Features of Quantum Many-Body Scar States

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Chinese Physics Letters 2025年第2期42卷 26-30页

作者： Wenjie Wei Long Zhang Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum computation University of Chinese Academy of SciencesBeijing 100190China Hefei National laboratory Hefei 230088China

We studied the dynamic correlations of non-integrable systems with quantum many-body scar(QMBS)states generated by a ladder *** ladder operator's spectral function has an exact δ-function peak induced by the QMBS *** a concrete example,we show that in the one-dimensional(1D)spin-1 Affleck-Kennedy-Lieb-Tasaki model,the spectral function of two-magnon excitations exhibits a characteristic bowtie shape composed of aδ-function resonance peak at momentum k=π and a continuum spectrum *** two-magnon excitations can be observed via resonant inelastic X-ray scattering spectroscopy on quasi-1D nickelates and other spin-1 antiferromagnetic ***,the findings of this study pave the way for detecting(approximate)QMBS states in realistic materials.

关键词： materials. excitation ladder

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Priority sources identification and risks assessment of heavy metal(loid)s in agricultural soils of a typical antimony mining watershed

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Journal of Environmental Sciences 2025年第1期147卷 153-164页

作者： Lianhua Liu You Li Xiang Gu Roberto Xavier Supe Tulcan Lingling Yan Chunye Lin Junting Pan Institute of Environment and Sustainable Development in Agriculture Chinese Academy of Agricultural SciencesBeijing 100081China Key laboratory of Land Surface pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China School of Environment Beijing Normal UniversityBeijing 100875China Yiyang Academy of Agricultural Sciences Yiyang 413099China Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural SciencesBeijing 100081China

Heavy metal(loid)(HM)pollution in agricultural soils has become an environmental concern in antimony(Sb)mining ***,priority pollution sources identification and deep understanding of environmental risks of HMs face great challenges due to multiple and complex pollution sources ***,an integrated approach was conducted to distinguish pollution sources and assess human health risk(HHR)and ecological risk(ER)in a typical Sb mining watershed in Southern *** approach combines absolute principal component score-multiple linear regression(APCS-MLR)and positivematrix factorization(PMF)models with ER and HHR *** pollution sources were distinguished for both models,and APCS-MLR model was more accurate and *** HM concentration source was natural source(39.1%),followed by industrial and agricultural activities(23.0%),unknown sources(21.5%)and Sb mining and smelting activities(16.4%).Although natural source contributed the most to HM concentrations,it did not pose a significant *** and agricultural activities predominantly contributed to ER,and attention should be paid to Cd and *** mining and smelting activities were primary anthropogenic sources of HHR,particularly Sb and As *** ER and HHR assessments,Sb mining and smelting,and industrial and agricultural activities are critical sources,causing serious ecological and health *** study showed the advantages of multiple receptor model application in obtaining reliable source identification and providing better source-oriented risk *** pollution management,such as regulating mining and smelting and implementing soil remediation in polluted agricultural soils,is strongly recommended for protecting ecosystems and humans.

关键词： Antimony Heavy metal(loid) Risk assessment Pollution sources Mining and smelting

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New progresses of fine-grained sediment gravity-flow deposits and their importance for unconventional shale oil and gas plays

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Petroleum Science 2025年第1期22卷 1-15页

作者： Tian Yang Ying-Lin Liu State Key laboratory of Oil and Gas Reservoir Geology and Exploitation (Chengdu University of Technology) Institute of Sedimentary Geology Key laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of natural Resources Chengdu University of Technology

Fine-grained sediments are widely distributed and constitute the most abundant component in sedimentary systems, thus the research on their genesis and distribution is of great significance. In recent years, fine-grained sediment gravity-flows(FGSGF) have been recognized as an important transportation and depositional mechanism for accumulating thick successions of fine-grained sediments. Through a comprehensive review and synthesis of global research on FGSGF deposition, the characteristics,depositional mechanisms, and distribution patterns of fine-grained sediment gravity-flow deposits(FGSGFD) are discussed, and future research prospects are clarified. In addition to the traditionally recognized low-density turbidity current and muddy debris flow, wave-enhanced gravity flow, lowdensity muddy hyperpycnal flow, and hypopycnal plumes can all form widely distributed FGSGFD. At the same time, the evolution of FGSGF during transportation can result in transitional and hybrid gravityflow deposits. The combination of multiple triggering mechanisms promotes the widespread development of FGSGFD, without temporal and spatial limitations. Different types and concentrations of clay minerals, organic matters, and organo-clay complexes are the keys to controlling the flow transformation of FGSGF from low-concentration turbidity currents to high-concentration muddy debris flows. Further study is needed on the interaction mechanism of FGSGF caused by different initiations, the evolution of FGSGF with the effect of organic-inorganic synergy, and the controlling factors of the distribution patterns of FGSGFD. The study of FGSGFD can shed some new light on the formation of widely developed thin-bedded siltstones within shales. At the same time, these insights may broaden the exploration scope of shale oil and gas, which have important geological significances for unconventional shale oil and gas.

关键词： Fine-grained sediment gravity-flow Depositional mechanism Transportation and evolution Distribution pattern Shale oil and gas

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Pushing one pair of labels apart each time in multi-label learning: from single positive to full labels

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Science China(Information Sciences) 2025年

作者： Xiang LI Xinrui WANG Songcan CHEN MIIT Key laboratory of pattern Analysis and Machine Intelligence College of Computer Science and Technology/College of Artificial Intelligence Nanjing University of Aeronautics and Astronautics

In multi-label learning (MLL), it is extremely challenging to accurately annotate every appearing object due to expensive costs and limited knowledge. When facing such a challenge, a more practical and cheaper alternative should be single positive multi-label learning (SPMLL), where only one positive label needs to be provided per sample. Existing SPMLL methods usually assume unknown labels as negatives, which inevitably introduces false negatives as noisy labels. More seriously, binary cross entropy (BCE) loss is often used for training, which is notoriously not robust to noisy labels. To mitigate this issue, we customize an objective function for SPMLL by pushing only one pair of labels apart each time to suppress the domination of negative labels, which is the main culprit of fitting noisy labels in SPMLL. To further combat such noisy labels, we explore the high-rankness of the label matrix, which can also push apart different labels. By directly extending from SPMLL to MLL with full labels, a unified loss applicable to both settings is derived. As a byproduct, the proposed loss can alleviate the imbalance inherent in MLL. Experiments on real datasets demonstrate that the proposed loss not only performs more robustly to noisy labels for SPMLL but also works well for full labels. Besides, we empirically discover that high-rankness can mitigate the dramatic performance drop in SPMLL. Most surprisingly, even without any regularization or fine-tuned label correction, only adopting our loss defeats state-of-the-art SPMLL methods on CUB, a dataset that severely lacks labels.

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Visual analytics for the clustering capability of data

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Science China(Information Sciences) 2013年第5期56卷 131-144页

作者： LU ZhiMao LIU Chen ZHANG Qi ZHANG ChunXiang FAN DongMei YANG Peng pattern recognition and natural computation laboratory Harbin Engineering University School of Computer Science and Technology Dalian University of Technology School of Software Harbin University of Science and Technology

Clustering analysis is an unsupervised method to find hidden structures in datasets and has been widely used in various ***,it is always difficult for users to understand,evaluate,and explain the clustering results in the spaces with dimension greater than *** high-dimensional visualization of clustering technology can express clustering results well,it still has significant *** this paper,a visualization cluster analysis method based on the minimum distance spectrum(MinDS) is proposed,aimed at reducing the problems of clustering multidimensional ***,the concept of MinDS is defined based on the distance between high-dimensional *** can map any dataset from high-dimensional space to a lower dimension to determine whether the data set is ***,a clustering method which can automatically determine the number of categories is designed based on *** method is not only able to cluster a dataset with clear boundaries,but can also cluster the dataset with fuzzy boundaries through the edge corrosion strategy based on the energy of each data *** addition,strategies for removing noise and identifying outliers are designed to clean datasets according to the characteristics of *** experimental results presented validate the feasibility and effectiveness of the proposed schemes and show that the proposed approach is simple,stable,and efficient,and can achieve multidimensional visualization cluster analysis of complex datasets.

关键词： data mining clustering analysis visual analysis minimum distance spectrum nearest neighbor spectrum outliers

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Degeneracy from Twisted Cubic Under Two Views

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Journal of Computer Science & Technology 2010年第5期25卷 916-924页

作者：吴毅红兰添胡占义 National laboratory of pattern recognition Institute of AutomationChinese Academy of Sciences

Fundamental matrix,drawing geometric relationship between two images,plays an important role in 3- dimensional computer *** configurations of the space points and the two camera optical centers affect stability of computation for fundamental *** order to robustly estimate fundamental matrix,it is necessary to study these degenerate *** analyze all the possible degenerate configurations caused by twisted cubic and give the corresponding degenerate rank for each *** with general degeneracies,the previous ruled quadric degeneracy and the homography degeneracy,are also reported.

关键词： fundamental matrix twisted cubic ruled quadric degenerate configuration

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Linguistic Theory Based Contextual Evidence Mining for Statistical Chinese Co-Reference Resolution

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Journal of Computer Science & Technology 2007年第4期22卷 608-617页

作者：赵军刘非凡 National laboratory of pattern recognition Institute of AutomationChinese Academy of Sciences

Under statistical learning framework, the paper focuses on how to use traditional linguistic findings on anaphora resolution as a guide for mining and organizing contextual features for Chinese co-reference resolution. The main achievements are as follows. （1） In order to simulate ＂syntactic and semantic parallelism factor＂, we extract ＂bags of word form and POS＂ feature and ＂bag of seines＂ feature from the contexts of the entity mentions and incorporate them into the baseline feature set. （2） Because it is too coarse to use the feature of bags of word form, POS tag and seme to determine the syntactic and semantic parallelism between two entity mentions, we propose a method for contextual feature reconstruction based on semantic similarity computation, in order that the reconstructed contextual features could better approximate the anaphora resolution factor of ＂Syntactic and Semantic Parallelism Preferences＂. （3） We use an entity-mention-based contextual feature representation instead of isolated word-based contextual feature representation, and expand the size of the contextual windows in addition, in order to approximately simulate ＂the selectional restriction factor＂ for anaphora resolution. The experiments show that the multi-level contextual features are useful for co-reference resolution, and the statistical system incorporated with these features performs well on the standard ACE datasets.

关键词： natural language processing information extraction co-reference resolution anaphora resolution

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