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Identifying spatiotemporal traffic patterns in large-scale urban road networks using a modified nonnegative matrix factorization algorithm

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Journal of Traffic and Transportation Engineering(English Edition) 2020年第4期7卷 529-539页

作者： Xiaolei ma Yi Li Peng Chen School of Transportation Science and Engineering Beihang UniversityBeijing 100191China Beiing Advanced Innovation Center for Big Data and Brain Computing Beihang UniversityBeiing 100191China

The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and *** methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks,where traffic states exhibit high degrees of dynamics and ***,advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven ***,limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic *** this end,this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic *** matrix factorization,cluster analysis is conducted based on the obtained low-dimensional representative matrices,which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network *** applicability and effectiveness of the proposed approach are examined in a road network of Beijing,*** show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.

关键词： Large-scale network Traffic state Spatiotemporal patterns Nonnegative matrix factorization

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Symmetry and monotonicity of positive solutions to Schr?dinger systems with fractional p-Laplacians

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Applied mathematics(A Journal of Chinese universities) 2022年第1期37卷 52-72页

作者： ma Ling-wei ZHANG Zhen-qiu School of mathematical Sciences Tianjin Normal UniversityTianjin 300387China School of mathematical Sciences and LPMC Nankai UniversityTianjin 300071China

In this paper,we first establish narrow region principle and decay at infinity theorems to extend the direct method of moving planes for general fractional p-Laplacian *** virtue of this method,we investigate the qualitative properties of positive solutions for the following Schrodinger system with fractional p-Laplacian{(-△)^(s)_(p)u+au^(p-1)=f(u,v),(-△)^(t)_(p)v+bv(p-1)=g(u,v),where 0unit ball or the whole space R^(N)(N≥2),the monotonicity in the parabolic domain and the nonexistence on the half space for positive solutions to the above system under some suitable conditions on f and g,respectively.

关键词： fractional p-Laplacian Schr?dinger systems direct method of moving planes radial symmetry monotonicity nonexistence

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Net Pro: detecting attacks in maNET routing with provenance and verification

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Science China(Information Sciences) 2017年第11期60卷 253-255页

作者： Teng LI Jianfeng ma Cong SuN School of Computer Science and Technology Xidian University School of Cyber Engineering Xidian University

The Mobile Ad hoc Network(maNET)is a continuously self-configuring network of a collection of mobile devices with neither a defined infrastructure nor a central administration facility[1].The primary goal of maNET routing is to provide a secure,correct,and efficient path to the target node such that the data are transmitted quickly and are not *** a passive attack,in which the network intruder attempts to eavesdrop on the communication,there exist many types of active attacks that tend to damage the network by changing the data stored within the maNET.

关键词： maNET Net Pro detecting attacks in maNET routing with provenance and verification

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Antiferromagnetically ordered Mott insulator and d+id superconductivity in twisted bilayer graphene: a quantum Monte Carlo study

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Science Bulletin 2019年第5期64卷 310-314页

作者： Tongyun Huang Lufeng Zhang Tianxing ma Department of Physics Beijing Normal University

using exact quantum Monte Carlo method, we examine the recent novel electronic states seen in magicangle graphene superlattices. From the Hubbard model on a double-layer honeycomb lattice with a rotation angle θ=1:08°, we reveal that an antiferromagnetically ordered Mott insulator emerges beyond a critical u_c at half filling, and with a small doping, the pairing with d+id symmetry dominates over other pairings at low temperature. The effective d+id pairing interaction strongly increases as the on-site Coulomb interaction increases, indicating that the superconductivity is driven by electron-electron correlation. Our non-biased numerical results demonstrate that the twisted bilayer graphene shares the similar superconducting mechanism of high temperature superconductors, which is a new and ideal platform for further investigating the strongly correlated phenomena.

关键词： Twisted bilayer graphene Mott insulator Superconductivity Quantum Monte Carlo

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Dynamic Surface Antifouling materials

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Chinese Journal of Chemistry 2023年第21期41卷 2881-2888页

作者： man Wang Chunfeng ma Guangzhao Zhang Faculty of materials Science and Engineering South China University of TechnologyGuangzhouGuangdong510640 China

The colonization of marine microorganisms,animals and plants on underwater surface forms marine *** has profound effects on marine *** solve the problem,we proposed a strategy of Dynamic Surface Antifouling(DSAF),i.e.,continuously changing surfaces can effectively inhibit biofouling organisms landing and adhering,and developed degradable polymer based marine antifouling *** degradation of polymer chain enables the surface dynamic or self-renewing even on static *** final degradation products of these polymers are low molecular weight molecules,and do not produce marine ***,the degradable polymers act as carriers and controlled release systems for antifoulants,further improving the antifouling *** article reviews the development of dynamic surface antifouling materials.

关键词： marine biofouling Antifouling Biodegradable polymer Hydrolysis Synthesis design Polymerization

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Seed germination and seedling emergence of four tree species of southern China in response to acid rain

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Journal of Forestry Research 2021年第2期32卷 471-481页

作者： matoor Mohsin Gilani Mulualem Tigabu Bo Liu Taimoor Hassan Farooq Muhammad Haroon uRashid Muhammad Ramzan Xiangqing ma Forestry College Fujian Agriculture and Forestry UniversityFuzhou 350002People’s Republic of China Fujian Provincial Colleges and university Engineering Research Center of Plantation Sustainable management Fuzhou 350002People’s Republic of China Faculty of Forest Science Southern Swedish Forest Research CenterSwedish University of Agricultural SciencesP.O.Box 4923053 AlnarpSweden National Engineering Laboratory for Applied Technology of Forestry and Ecology in South China Central South University of Forestry and TechnologyChangsha 410000People’s Republic of China School of Soil and Water Conservation and Desertification Combating Beijing Forestry UniversityBeijing 100083People’s Republic of China

Acid rain has become a major concern due to increasing atmospheric pollution,particularly in *** investigated whether acid rain inhibits the germination of seeds and subsequent emergence of seedling of four tree species from southern China:Cunninghamia lanceolata,Fokienia hodginisi,Pinus massoniana and Phoebe zhennan by simulating acid rain with pH of 2.5,3.5,4.5 and *** hypothesized that the inhibitory effect of acid rain on germination of seeds and emergence of seedling varies between species and the degree of acidity.A solution of 1 N H2SO4 and 1 N HNO 3 in the ratio of 10–1 was prepared and diluted to four pH levels,and seeds were supplied with solutions of these pH values and distilled water as control and tested for germination in a controlled growth *** results revealed that simulated acid rain of pH 2.5 adversely affected the germination capacity of *** and ***;while all acid solutions significantly increased germination of ***;but had no effect on germination of *** *** acid solution(pH of 2.5)adversely affected elongation of radicle and hypocotyl as well as fresh and dry weights of radicle and hypocotyl of tender *** result demonstrated that seedling emergence is more sensitive than seed germination to simulated acid rain,and germination of conifer species are less sensitive than broad leaved species to simulated acid *** a whole,acid rain of pH of 3.5 is the threshold level and acid rain below this value will have a detrimental effect on seed germination and seedling emergence.

关键词： Cunninghamia lanceolata Fokienia hodginisi Pinus massoniana Phoebe zhennan Seed viability Simulated acid rain

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Poverty alleviation through e-commerce:Village involvement and demonstration policies in rural China

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Journal of Integrative Agriculture 2021年第4期20卷 998-1011页

作者： PENG Chao ma Biao ZHANG Chen Administration and management Institute Ministry of Agriculture and Rural AffairsBeijing 102208P.R.China School of Agricultural Economics and Rural Development Renmin University of ChinaBeijing 100872P.R.China Institute of Population and Labor Economics Chinese Academy of Social SciencesBeijing 100006P.R.China

The diffusion of e-commerce has played a significant role in recent rural economic development in China.E-commerce is also considered as an efficient channel to alleviate poverty in rural *** studies have investigated the contribution of e-commerce to agricultural development,yet it is lacking empirical evidence as to the effects of e-commerce on rural poverty *** the year of 2014,in order to develop rural e-commerce,Chinese government launched the National Rural E-commerce Comprehensive Demonstration *** gradual involvement policy offered a natural experiment for evaluation of *** on village-level survey data from rural China and Heckit method,our study finds that rural e-commerce has a significantly positive effect on rural ***,the effect is inverted u-shaped for the relative-poverty *** estimation of the propensity scores matching model confirms that the results are *** following policy recommendations are proposed:(1)policy support to rural e-commerce should prioritize the povertystricken *** doing so,the marginal income effects of e-commerce will be maximized.(2)Investment in internet infrastructure and establishment of human resources for e-commerce in rural areas will have spillover effects,increasing rural income through the"digital dividend".

关键词： poverty alleviation income National Rural E-commerce Comprehensive Demonstration Project Heckit method

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Provenance of Conglomerate and Sandstone from Early Permian Shoushangou Formation in Xi ujimqin,Inner Mongolia:Implications for understanding Paleo-Asian Ocean Subduction

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Acta Geologica Sinica(English Edition) 2024年第1期98卷 10-31页

作者： ZHANG Yingli GuO Xianqing ma Shouxian MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesCAGSBeijing 100037China Chinese Academy of Geological Sciences Beijing 100037China

During the Late Carboniferous to Early Permian,a rift was formed by post-collisional extension after ocean closure or an island arc-related basin formed by Paleo-Asian Ocean(PAO)subduction in the Xi ujimqin ***,the closure time of the PAO is still under ***,to identify the origin of the PAO,the geochemistry and u-Pb age of zircons were analyzed for the extra-large deep marine,polymict clastic boulders and sandstones in the Shoushangou Formation within the *** analyses revealed magmatic activity and tectonic *** conglomerates include megaclasts of granite(298.8±9.1 ma)and granodiorite porphyry(297.1±3.1 ma),which were deposited by muddy debris *** of this study demonstrated that the boulders of granitoids have the geochemistry of typical I-type granite,characterized by low Zr+Nb+Ce+Y and low Ga/Al *** granitoid boulders were formed in island arc setting,indicating the presence of arc magmatism in the area that is composed of the Late Carboniferous to Early Permian subduction-related granitoid in southern Xi *** diagrams for determining sedimentary provenance using major and trace elements indicate that Shoushangou sediments originated from continental island arc-related felsic *** zircon u-Pb age cluster of 330–280 ma was obtained,indicating input from granite,ophiolite,Xilin Gol complex,and Carboniferous sources to the *** basin was geographically developed behind the arc during the Early Permian period because the outcropped intrusive rocks in the Late Carboniferous to Early Permian form a volcanic *** comprehensive analyses of source areas suggest that Shoushangou sediments developed in a backarc basin in response to the northward subduction of the *** backarc basin and intrusive rocks,in addition to previously published Late Carboniferous to Early Permian magmatic rocks of arc unit in Xilin Gol,confirm the presence of an Early Permian trencharc-basin system in the region,r

关键词： provenance analysis backarc basin Shoushangou Formation Early Permian Central Asian Orogenic Belt

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A family of mixed finite elements for the biharmonic equations on triangular and tetrahedral grids

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Science China mathematics 2021年第12期64卷 2793-2816页

作者： Jun Hu Rui ma Min Zhang LmaM and School of mathematical Sciences Peking UniversityBeijing 100871China Fakultat fur mathematik Universitat Duisburg-EssenEssen 45127Germany Beijing Computational Science Research Center Beijing 100193China

This paper introduces a new family of mixed finite elements for solving a mixed formulation of the biharmonic equations in two and three *** symmetric stress σ=−∇^(2)u is sought in the Sobolev space H(divdiv,Ω;S)simultaneously with the displacement u in L^(2)(Ω).By stemming from the structure of H(div,Ω;S)conforming elements for the linear elasticity problems proposed by Hu and Zhang(2014),the H(divdiv,Ω;S)conforming finite element spaces are constructed by imposing the normal continuity of divσ on the H(div,Ω;S)conforming spaces of P_(k) symmetric *** inheritance makes the basis functions easy to *** discrete spaces for u are composed of the piecewise P_(k−2) polynomials without requiring any *** mixed finite elements are inf-sup stable on both triangular and tetrahedral grids for k≥3,and the optimal order of convergence is ***,the superconvergence and the postprocessing results are *** numerical experiments are provided to demonstrate the theoretical analysis.

关键词： biharmonic equation symmetric stress tensor conforming finite element mixed finite element method

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Trajectory Planning for OTFS-Based uAV Communications

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China Communications 2023年第1期20卷 114-124页

作者： Rui Han Jiahao ma Lin Bai Tsinghua Space Center Tsinghua UniversityBeijing 100084China School of Cyber Science and Technology Beihang UniversityBeijing 100191China

unmanned aerial vehicles(uAVs)have attracted growing research interests in recent years,which can be used as cost-effective aerial platforms to transmit collected data packets to ground access points(APs).Thus,it is crucial to investigate robust airto-ground(A2G)wireless links for high-speed ***,the A2G wireless link is unstable as it suffers from large path-loss and severe Doppler effect due to the high mobility of *** order to meet these challenges,we propose an orthogonal time frequency space(OTFS)-based uAV communication system to relief the Doppler ***,considering that the energy of uAV is limited,we optimize the trajectory planning of uAV to minimize the energy consumption under the constraints of bit error rate(BER)and transmission rate,where the Doppler compensation is taken into *** results show that the performance of OTFS-based uAV system is superior to orthogonal frequency division multiplexing(OFDM)-based uAV systems,which can accomplish transmission tasks over shorter distances with lower energy consumption.

关键词： orthogonal time frequency space(OTFS) orthogonal frequency division multiplexing(OFDM) unmanned aerial vehicle(uAV) 6G trajectory planning

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