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Encroachment drives facilitation at alpine shrublines

Forest Ecosystems 2024年第1期11卷 62-72页

作者： Yafeng wang Eryuan Liang j.julio Camarero College of Ecology and Environment Nanjing Forestry UniversityNanjing210037China State Key Laboratory of Tibetan Plateau Earth System Environment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing100101China Instituto Pirenaico de Ecología(IPE-CSIC) Zaragoza50080Spain

Ongoing encroachment is driving recent alpine shrubline dynamics globally,but the role of shrub-shrub interactions in shaping shrublines and their relationships with stem density changes remain poorly ***,the size and age of shrubs from 26 Salix shrubline populations along a 900-km latitudinal gradient(30°-38°N)were measured and mapped across the eastern Tibetan *** pattern analyses were used to quantify the spatial distribution patterns of juveniles and adults,and to assess spatial associations between *** intensity of univariate and bivariate spatial patterns was related to biotic and abiotic *** mark correlation functions with a quantitative mark(shrub height,basal stem diameter,crown width)were also employed to investigate the spatial relationships between shrub traits of juveniles and *** equation models were used to explore the relationships among conspecific interactions,patterns,shrub traits and recruitment dynamics under climate *** shrublines showed clustered patterns,suggesting the existence of conspecific *** patterns of juveniles and conspecific interactions(potentially facilitation)tended to intensify with increasing soil moisture *** warming before 2010 triggered positive effects on population interactions and spatial patterns via increased shrub ***,summer warming after2010 triggered negative effects on interactions through reduced shrub ***,shrub recruitment shifts under rapid climate change could impact spatial patterns,alter conspecific interactions and modify the direction and degree of shrublines responses to *** changes would have profound implications for the stability of alpine woody ecosystems.

关键词： Alpine shrubline Positive interactions Facilitation Spatial clustering Point pattern analyses

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Granger causal representation learning for groups of time series

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Science China(Information Sciences) 2024年第5期67卷 56-68页

作者： Ruichu CAI Yunjin WU Xiaokai HUANG Wei CHEN Tom z.j.FU zhifeng HAO School of Computer Science Guangdong University of Technology Peng Cheng Laboratory College of Science Shantou University

Discovering causality from multivariate time series is an important but challenging *** existing methods focus on estimating the Granger causal structures among multivariate time series,while ignoring the prior knowledge of these time series, e.g., the group of the time series. Focusing on discovering the Granger causal structures among groups of time series, we propose a Granger causal representation learning method to solve this problem. First, we use the multiset canonical correlation analysis method to learn the Granger causal representation of each group of time series. Then, we model the Granger causal relationships among the learned Granger causal representations using a recurrent neural network with temporal information. Finally, we formulate the above two stages into one unified optimization problem, which is efficiently solved using the augmented Lagrangian method. We conduct extensive experiments on synthetic and real-world datasets to validate the correctness and effectiveness of the proposed method.

关键词： Granger causal discovery Granger causal representation learning time series data recurrent neural network multiset canonical correlation analysis

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Post-layout simulation driven analog circuit sizing

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Science China(Information Sciences) 2024年第4期67卷 289-300页

作者： Xiaohan GAO Haoyi zHANG Siyuan YE Mingjie LIU David z.PAN Linxiao SHEN Runsheng wang Yibo LIN Ru HUANG School of Integrated Circuits Peking University School of Computer Science Peking University Department of Electrical and Computer Engineering University of Texas at Austin Institute of Electronic Design Automation Peking University

Post-layout simulation provides accurate guidance for analog circuit design, but post-layout performance is hard to be directly optimized at early design stages. Prior work on analog circuit sizing often utilizes pre-layout simulation results as the optimization objective. In this work, we propose a post-layoutsimulation-driven(post-simulation-driven for short) analog circuit sizing framework that directly optimizes the post-layout simulation performance. The framework integrates automated layout generation into the optimization loop of transistor sizing and leverages a coupled Bayesian optimization algorithm to search for the best post-simulation performance. Experimental results demonstrate that our framework can achieve over 20% better post-layout performance in competitive time than manual design and the method that only considers pre-layout optimization.

关键词： analog EDA transistor sizing Bayesian optimization post-layout simulation

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Dedicated SiPM array for GRD of GECAM

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Radiation Detection Technology and Methods 2022年第1期6卷 63-69页

作者： D.L.zhang X.L.Sun z.H.An X.Q.Li X.Y.Wen K.Gong C.Cai z.Chang G.Chen C.Chen Y.Y.Du M.Gao R.Gao D.Y.Guo j.j.He D.j.Hou Y.G.Li C.Y.Li G.Li L.Li X.F.Li M.S.Li X.H.Liang X.j.Liu Y.Q.Liu F.j.Lu H.Lu B.Meng W.X.Peng F.Shi H.wang j.z.wang Y.S.wang H.z.wang X.Wen S.Xiao S.L.Xiong Y.B.Xu Y.P.Xu S.Yang1 X.zhou j.W.Yang Fan zhang S.N.zhang C.Y.zhang C.M.zhang Fei zhang X.Y.zhao Institute of High Energy Physics CASBeijing 100049China State Key Laboratory of Particle Detection and Electronics Beijing 100049China

Purpose The discovery of gravitational waves and gamma-ray bursts heralds the era of multi-messenger *** the adoption of two small satellites to achieve the all-sky monitoring of gamma-ray bursts,the gravitational wave highenergy electromagnetic counterpart all-sky monitor(GECAM)possesses a quasi-real-time early warning ability and plays an important role in positioning the sources of gravitational waves and in subsequent *** satellite of GECAM was fitted with 253-inch-diameter gamma-ray detectors(GRD),covering an energy range of 8–2 *** have adopted silicon photomultiplier tubes(SiPM)in lieu of photomultiplier tubes(PMT)to adapt to the dimensional limitations of *** A unique 3-inch circular SiPM array was *** this design,646×6 mm chips were arranged evenly in a circular manner with the seams filled with reflecting films,thus achieving satisfactory uniformity of light *** integrated pre-amplifier circuit on the back of the SiPM array adopted two-level grouping and summing;further,it achieved a satisfactory signal-to-noise *** high-gain and low-gain channels were adopted to achieve a large dynamic range,and two independent power supply units were used,where each unit can be closed separately,thus improving *** Performance studies show that this SiPM array meets the requirements of *** A 3-inch SiPM array have been developed that uses grouped summation,reflective films,a circular arrangement,two groups of independent power supplies,high-and low-gain signals,differential signal output technologies,*** solution can be used not only for GECAM,but also as a general solution for SiPM-based scintillation detectors.

关键词： SiPM GECAM Gamma-ray Signal-to-noise ratio Reflecting film Pre-amplifier

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A Sharding Scheme Based on Graph Partitioning Algorithm for Public Blockchain

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Computer Modeling in Engineering & Sciences 2024年第6期139卷 3311-3327页

作者： Shujiang Xu ziye wang Lianhai wang Miodrag j.Mihaljevi′c Shuhui zhang Wei Shao Qizheng wang Key Laboratory of Computing Power Network and Information Security Ministry of EducationShandong Computer Science CenterQilu University of Technology(Shandong Academy of Sciences)Jinan250014China Shandong Provincial Key Laboratory of Computer Networks Shandong Fundamental Research Center for Computer ScienceJinan250014China Mathematical Institute The Serbian Academy of Sciences and ArtsBelgrade11000Serbia

Blockchain technology,with its attributes of decentralization,immutability,and traceability,has emerged as a powerful catalyst for enhancing traditional industries in terms of optimizing business ***,transaction performance and scalability has become the main challenges hindering the widespread adoption of *** to its inability to meet the demands of high-frequency trading,blockchain cannot be adopted in many *** improve the transaction capacity,researchers have proposed some on-chain scaling technologies,including lightning networks,directed acyclic graph technology,state channels,and shardingmechanisms,inwhich sharding emerges as a potential scaling ***,excessive cross-shard transactions and uneven shard workloads prevent the sharding mechanism from achieving the expected *** paper proposes a graphbased sharding scheme for public blockchain to efficiently balance the transaction *** crossshard transactions and evening-out workloads among shards,the scheme reduces transaction confirmation latency and enhances the transaction capacity of the ***,the scheme can achieve a high-frequency transaction as well as a better blockchain *** results show that the scheme effectively reduces the cross-shard transaction ratio to a range of 35%-56%and significantly decreases the transaction confirmation latency to 6 s in a blockchain with no more than 25 shards.

关键词： Blockchain sharding graph partitioning algorithm

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The design and performance of charged particle detector onboard the GECAM mission

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Radiation Detection Technology and Methods 2022年第1期6卷 53-62页

作者： Y.B.Xu X.Q.Li X.L.Sun S.Yang H.wang W.X.Peng X.H.Liang K.Gong Y.Q.Liu D.Y.Guo X.Y.zhao C.Y.Li z.H.An j.j.He X.j.Liu X.Y.Wen S.L.Xiong Fan zhang D.L.zhang C.Y.zhang C.Cai z.Chang G.Chen C.Chen Y.Y.Du M.Gao R.Gao D.j.Hou Y.G.Li G.Li L.Li X.F.Li M.S.Li F.j.Lu H.Lu B.Meng F.Shi j.z.wang Y.S.wang H.z.wang X.Wen S.Xiao Y.P.Xu j.W.Yang Q.B.Yi S.N.zhang C.M.zhang F.zhang Y.zhao X.zhou Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

Background The Gravitational wave highly energetic Electromagnetic Counterpart All-sky Monitor(GECAM)is dedicated to detecting gravitational wave gamma-ray *** is capable of all-sky monitoring over and discovering gamma-ray bursts and new radiation *** consists of two microsatellites,each equipped with 8 charged particle detectors(CPDs)and 25 gamma-ray detectors(GRDs).Purpose The CPD is used to measure charged particles in the space environment,monitor energy and flow intensity changes,and identify between gamma-ray bursts and space charged particle events in conjunction with *** CPD uses plastic scintillator as the sensitive material for detection,silicon photomultiplier array as the optically readable device,and the inlaid Am-241 radioactive source as the onboard calibration *** In this paper,we will present the working principle,physical design,functional implementation and preliminary performance test results of the *** a result,the energy range of electron,gamma-ray detection efficiency and dead time are tested to be better than the indexes required through the ground calibration experiment.

关键词： GECAM CPD SiPM

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The data acquisition algorithm designed for the SiPM-based detectors of GECAM satellite

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Radiation Detection Technology and Methods 2022年第1期6卷 70-77页

作者： Y.Q.Liu K.Gong X.Q.Li X.Y.Wen z.H.An C.Cai z.Chang G.Chen C.Chen Y.Y.Du M.Gao R.Gao D.Y.Guo j.j.He D.j.Hou Y.G.Li C.Y.Li G.Li L.Li X.F.Li M.S.Li X.H.Liang X.j.Liu F.j.Lu H.Lu B.Meng W.X.Peng F.Shi X.L.Sun H.wang j.z.wang Y.S.wang H.z.wang X.Wen S.Xiao S.L.Xiong Y.B.Xu Y.P.Xu S.Yang j.W.Yang Q.B.Yi Fan zhang D.L.zhang S.N.zhang C.Y.zhang C.M.zhang Fei zhang X.Y.zhao Y.zhao X.zhou Key Laboratory of Particle Astrophysics Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Chinese Academy of SciencesBeijing 100049China Physics and Space Science College China West Normal UniversityNanchong 637002China

Background The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(GECAM)consists of 2 microsatellites,each of which contains 25 GRD(LaBr3)detectors and 8 CPD(plastic scintillator)*** silicon photomultiplier(SiPM)array is used to read each *** output signal of these detectors with SiPM array is very special and challenging to *** this study,a novel data acquisition(DAQ)algorithm for these detectors is designed and implemented,and the content of the output event packet is *** and Conclusion The performances,including the event acquisition efficiency of this DAQ algorithm,are extensively verified through experimental *** the on-ground and in-flight tests,this algorithm has excellent performance despite the very limited resources and short development time of GECAM mission.

关键词： Silicon photomultiplier Digital waveform processing Data acquisition

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Quality assurance test and failure analysis of SiPM arrays of GECAM satellites

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Radiation Detection Technology and Methods 2022年第1期6卷 35-42页

作者： D.L.zhang M.Gao X.L.Sun X.Q.Li z.H.An X.Y.Wen C.Cai z.Chang G.Chen C.Chen Y.Y.Du R.Gao K.Gong D.Y.Guo j.j.He D.j.Hou Y.G.Li C.Y.Li G.Li L.Li X.F.Li M.S.Li X.H.Liang X.j.Liu Y.Q.Liu F.j.Lu H.Lu B.Meng W.X.Peng F.Shi H.wang j.z.wang Y.S.wang H.z.wang X.Wen S.Xiao S.L.Xiong Y.B.Xu Y.P.Xu S.Yang j.W.Yang Fan.zhang S.N.zhang C.Y.zhang C.M.zhang Fei zhang X.Y.zhao X.zhou Institute of High Energy Physics CASBeijing 100049People’s Republic of China

Background The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)satellite developed a SiPM-based gamma-ray detector to monitor the gravitational wave-related GRBs and guide subsequent observations in other wavelengths of *** As all the available SiPM devices belong to commercial grade,quality assurance tests need to be performed in accordance with the aerospace *** In the SiPM application of GECAM,quality assurance experiments were *** mechanism of the failure of SiPM devices was analyzed during the development *** Based on the quality assurance test results,the fnal pass rate of SiPM array was 95%.Based on the failure analysis,it was found that a piece of SiPM had a leakage channel after longtime operation due to device *** According to the accumulated experience,in the reliability test of SiPM,it is necessary to pay special attention to test the impedance of each pin of SiPM to ground and confrm that the power switch state of SiPM is controllable.

关键词： Gravitational waves Gamma-ray detectors Silicon photomultipliers Quality assurance test Failure analysis

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Two-Mode Optical Fibers and Devices

Two-Mode Optical Fibers and Devices

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全国第十二次光纤通信暨第十三届集成光学学术会议

作者： W. jin j. ju z. wang ( Department of Electrical Engineering The Hong Kong Polytechnic University)

＜正＞Two-mode optical fibers have been studied extensively for telecommunication device and sensor applications. This paper overviews various types of two-mode fibers and their applications in tunable optical filters, dispersion compensators, non-linear frequency conversation, sensors, etc. Hong Kong PolyU’s work on two-mode photonic crystal fibers and elliptical-core fibers will be reported.

关键词： Circular-core fiber Elliptical-core fiber Photonic crystal fiber Two-mode fiber interferometric sensor

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The anode power supply for electron cyclotron resonance heating system on j-TEXT

The anode power supply for electron cyclotron resonance heat...

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第十八届全国等离子体科学技术会议

作者： C.H.Liu D.H.Xia F.T.Cui z.j.wang State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology

The electron cyclotron resonance heating(ECRH) system with 60 GHz/200 k W/0.5 s gyrotron donated by Culham Science Center is being developed on j-TEXT tokamak for plasma heating,current drive and MHD ***,an anode power supply(APS) has been rebuild and tested for the output power control of the gyrotron,which the input voltage is derived from an80 k V negative cathode power *** control strategy by controlling the grid voltage of the tetrode TH5186 is applied to get accurate anode climbing voltage,which the output voltage can be obtained from 0 to 30 k V with respect to cathode power *** characteristic of the APS,including control,protection,modulation,output waveform,were tested with the 100 k V/60 A negative cathode power supply,the dummy load and the ECRH control *** results indicating that the APS can meet the requirements of the ECRH system on j-TEXT.

关键词： j-TEXT ECRH APS TH5186 tetrode fiber isolation

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