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Application of Regularization Methods in the Sky Map Reconstruction of the Tianlai Cylinder Pathfinder Array

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Research in Astronomy and Astrophysics 2024年第2期24卷 24-35页

作者： kaifeng yu Shifan Zuo Fengquan Wu Yougang Wang Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Key Laboratory of Radio Astronomy and Technology Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Cosmology and Astrophysics(Liaoning)&College of Sciences Northeastern UniversityShenyang 110819China Center of High Energy Physics Peking UniversityBeijing 100871China

The Tianlai cylinder pathfinder is a radio interferometer array to test 21 cm intensity mapping techniques in the post-reionization *** works in passive drift scan mode to survey the sky visible in the northern *** deal with the large instantaneous field of view and the spherical sky,we decompose the drift scan data into m-modes,which are linearly related to the sky *** sky map is reconstructed by solving the linear interferometer *** to incomplete uv coverage of the interferometer baselines,this inverse problem is usually ill-posed,and regularization method is needed for its *** this paper,we use simulation to investigate two frequently used regularization methods,the Truncated Singular Value Decomposition(TSVD),and the Tikhonov regularization *** the regularization parameter is very important for its *** employ the generalized cross validation method and the L-curve method to determine the optimal *** compare the resulting maps obtained with the different regularization methods,and for the different parameters derived using the different *** both methods can yield good maps for a range of regularization parameters,in the Tikhonov method the suppression of noisy modes are more gradually applied,produce more smooth maps which avoids some visual artefacts in the maps generated with the TSVD method.

关键词： techniques interferometric-methods numerical-cosmology observations-radio continuum general

Heavy metals in a typical city-river-reservoir system of East China:Multi-phase distribution,microbial response and ecological risk

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Journal of Environmental Sciences 2022年第2期34卷 343-354页

作者： Jun Yang Mingrui Zhou kaifeng yu Karina Yew-Hoong Gin Muhammad Hassan Yiliang He School of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China NUS Environmental Research Institute National University of Singapore1-Create Way#15-02 Create TowerSingapore 138602Singapore China-UK Low Carbon College Shanghai Jiao Tong UniversityShanghai 200240China Department of Civil and Environmental Engineering National University of Singapore1 Engineering Drive 2Singapore 117576Singapore Ecology and Chemical Engineering Department South Ural State UniversityLenin Prospect 76Chelyabinsk 454080Russian Federation

The rapid construction of artificial reservoirs in metropolises has promoted the emergence of city-river-reservoir systems *** study investigated the environmental behaviors and risks of heavy metals in the aquatic environment of a typical system composed of main watersheds in Suzhou and Jinze Reservoir in *** shown that Mn,Zn and Cu were the dominant metals detected in multiple ***,Mn and Zn were mainly presented in exchangeable fraction and exhibited high *** proportion and high mobility of metals were found in suspended particulate matter(SPM),suggesting that SPM can greatly affect metal multi-phase distribution ***,city system(Ci S)exhibited more serious metal pollution and higher ecological risk than river system(Ri S)and reservoir system(Re S)owing to the diverse emission *** S and Re S were regarded as critical pollution source and sink,respectively,while Ri S was a vital transportation *** community in sediments exhibited evident spatial variation and obviously modified by exchangeable metals and *** particular,Bacteroidetes and Firmicutes presented significant positive correlations with most exchangeable *** assessment implied that As,Sb and Ni in water may pose potential carcinogenic risk to human ***,Re S was in a fairly safe *** was the main risk contributor in SPM,while Cu,Zn,Ni and Sb showed moderate risk in ***,Hg,Sb and Ci S were screened out as priority metals and system,*** attention should be paid to these priority issues to promote the sustainable development of the watershed.

关键词： Heavy metal Multi-phase Chemical fraction City-river-reservoir system Microbial community

A Simulation of Calibration and Map-making Errors of the Tianlai Cylinder Pathfinder Array

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Research in Astronomy and Astrophysics 2023年第10期23卷 281-298页

作者： kaifeng yu Fengquan Wu Shifan Zuo Jixia Li Shijie Sun Yougang Wang Xuelei Chen National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Key Laboratory of Radio Astronomy and Technology Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Cosmology and Astrophysics(Liaoning)&College of Sciences Northeastern UniversityShenyang 110819China Center of High Energy Physics Peking UniversityBeijing 100871China

The Tianlai cylinder array is a pathfinder for developing and testing 21 cm intensity mapping *** this paper,we use numerical simulation to assess how its measurement is affected by thermal noise and the errors in calibration and map-making process,and the error in the sky map reconstructed from a drift scan *** we consider only the single frequency,unpolarized *** beam is modeled by fitting to the electromagnetic simulation of the antenna,and the variations of the complex gains of the array elements are modeled by Gaussian *** visibility data are generated and run through our data processing *** find that the accuracy of the current calibration is limited primarily by the absolute calibration,where the error comes mainly from the approximation of a single dominating point *** then studied the m-mode map-making with the help of Moore-Penrose *** find that discarding modes with singular values smaller than a threshold could generate visible artifacts in the *** impacts of the residue variation of the complex gain and thermal noise are also *** thermal noise in the map varies with latitude,being minimum at the latitude passing through the zenith of the *** angular power spectrum of the reconstructed map show that the current Tianlai cylinder pathfinder,which has a shorter maximum baseline length in the North-South direction,can measure modes up to l■2πb_(NS)/λ~200 very well,but would lose a significant fraction of higher angular modes when noise is *** results help us to identify the main limiting factors in our current array configuration and data analysis procedure,and suggest that the performance can be improved by reconfiguration of the array feed positions.

关键词： techniques:interferometric telescopes cosmology:observations (cosmology:)diffuse radiation radio continuum:general

Review of trans-Mediterranean power grid interconnection:a regional roadmap towards energy sector decarbonization

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Global Energy Interconnection 2023年第1期6卷 115-126页

作者： kaifeng yu Paul van Son Global Energy Interconnection Development and Cooperation Organization Beijing 100031P.R.China Global Energy Interconnection Group Co.Ltd. Beijing 100031P.R.China Dii Desert Energy Dubai 487389United Arab Emirates

Climate change is becoming an important issue in all fields of infrastructure *** plays a core role in the decarbonized energy system’s path to a regional zero-emission pattern.A well-built trans-Mediterranean backbone grid can hedge the profound evolution of regional power generation,transmission,and *** date,only Turkey and the Maghreb countries(i.e.,Morocco,Algeria,and Tunisia)are connected with the Continental European Synchronous *** south-and east-shore countries have insufficient interconnection infrastructures and synchronization difficulties that have proven to be major hurdles to the implementation of large-scale solar and wind projects and achievement of climate *** study analyzes the current trans-boundary grid interconnections and power and carbon emission portfolios in the Mediterranean *** align with the recently launched new climate target‘Fit for 55’program and the accelerated large-scale renewables target,a holistic review of projected trans-Mediterranean grids and their market,technical,and financial obstacles of implementation was *** south-and east-shore countries,major legal and regulatory barriers encompassing non-liberalized market structure,regulation gaps of taxation and transmission tariffs,and the private sector’s access rights need to be *** of domestic grids,substations,and harmonized grid codes and frequency,voltage,and communication technology standards among all trans-Mediterranean countries are physical prerequisites for implementing the Trans-Mediterranean Electricity *** addition,the mobilization of capital instruments along with private and international investments is indispensable for the realization of supranational transmission *** the final section of the decarbonization roadmap,the development of electric appliances,equipment,and vehicles with higher efficiency is inevitable in the decarbonized building,transportation,and industry sec

关键词： Mediterranean Grid interconnection Regional roadmap Power system Decarbonization Climate change

Preparation of TiO2 Nanoflakes and Their Influence on Lithium Ion Battery Storage Performance

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Chemical Research in Chinese Universities 2015年第3期31卷 332-336页

作者： LI Yi HAN Xiangbo LIANG Jicai LENG Xuning YE Kaiqi HOU Changmin yu kaifeng Key Laboratory of Automobile Materials Ministry of Education College of Materials Science and EngineeringJilin University Changchun 130025 P.R.China State Key Laboratory of Supramolecular Structure and Materials College of Chemistry Jilin University Changchun 130012 P.R.China State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of Chemistry Jilin University Changchun 130012 P.R.China

TiO2 nanoflakes were prepared by hydrothermal precipitation method using Ti（SO4）2 as titanium source and NaOH solution as alkaline medium. Their surface morphology, grain size measured after high temperature calci- nation and effect on the electrochemical performance of Li ion battery were discussed. TiO2 nanoflakes were charac- terizated by means of transmission electron microscopy（TEM）, X-ray powder diffraction（XRD）, N2 adsorp- tion-desorption isothermal assay, cyclic voltammetry（CV） and cycle performance test. The result of electrochemical performance test shows that the prepared TiO2 nanoflakes have high discharge specific capacity and good cycle per- formance. Discharge specific capacity for the first circle at the discharge rate of 0.1 C is 261.5 mA·h·g-1. After 90 cycles, the discharge capacity reduces to 172.2 mA·h·g-1.

关键词： Heat treatment: TiO nanoflake: Lithium-ion battery

Evaluation of the Degree of Opening to the Outside World in Guizhou Province

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Asian Agricultural Research 2019年第7期11卷 1-4,7页

作者： kaifeng yu Institute of Industrial Economics Guizhou Academy of Social Sciences

The goal of economic opening to the outside world is an important basis for formulating and implementing the policy of opening. Different economic development strategies have different requirements for the degree of economic opening to the outside world. Guizhou should implement the open economy and adopt the export-oriented development strategy, which objectively requires Guizhou to gradually improve the degree of opening to the outside world.

关键词： Degree of opening to the outside world Foreign trade Utilization of foreign capital Guizhou

A Brief Talk on Absolute

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开封文化艺术职业学院学报 2000年第3期 37-38页

作者： MA Bing yu (kaifeng Institute of Education kaifeng 475000)

Absolute is an important grammatical construction. It is widely used for its toughness and economy in writing. This essay is intended to comment on the usage of absolute.

关键词： absolute toughness and economy vigorous subordination and lively description in writing

玉米秸秆基多孔生物质碳的制备、表征及电化学性能

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高等学校化学学报 2018年第4期39卷 607-613页

作者：李义李纯于开锋吉林大学材料科学与工程学院汽车材料教育部重点实验室长春130025

以玉米秸秆为原料,CaCl_2为活化剂,制备了多孔生物质碳.通过X射线衍射(XRD)、拉曼光谱、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和N_2吸附-脱附分析表征了其微观形貌和结构.结合微观形貌和结构分析了其电化学性能,并探究了多孔结构... 详细信息

以玉米秸秆为原料,CaCl_2为活化剂,制备了多孔生物质碳.通过X射线衍射(XRD)、拉曼光谱、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和N_2吸附-脱附分析表征了其微观形貌和结构.结合微观形貌和结构分析了其电化学性能,并探究了多孔结构的形成机理.在600℃下所得样品的比表面积为370.6m^2/g,平均孔径为9.65 nm.将该样品用作锂离子电池负极材料,在0.2C倍率下循环100次后其放电比容量为783 mA·h/g,在10C倍率下循环1000次后比容量为347 mA·h/g,表明样品具有良好的倍率性能和循环稳定性.该方法制备的样品具有较大的比表面积,能够提高电解液的渗透率和增加反应活性位点,而且丰富的孔结构增大了锂离子和电荷的自由运动空间,有利于电化学性能的提高.

关键词：玉米秸秆介孔结构生物质碳锂离子电池

The first occurrence of Scincomorpha lizard from Nenjiang Formation(lower Campanian)of Jilin,Northeast China

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Global Geology 2022年第4期25卷 255-263页

作者： YANG Jinyue WU Wenhao yu kaifeng SONG Qingqing College of Earth Sciences Jilin UniversityChangchun 130061China Research Centre of Palaeontology and Stratigraphy College of Earth SciencesJilin UniversityChangchun 130026China Xinjiang Branch Survey and Design Institute of Jiangxi ProvinceUrumqi 830000China

Fossil lizards are scarce in Jinlin Province,with only two jaws of Middle Eocene *** the authors report the first scincomorph lizard materials from the early Campanian Nenjiang Formation in Nong’an,Changchun,Jilin *** tooth morphologies of scincomorph lizards represented by fragmentary dentaries are tentatively identified as *** morphology of the crowns indicates probably the insectivorous and omnivorous diets of these small *** is the first lizard fossils discovered in the Late Cretaceous of Northeast China,extends the known paleogeographic distribution of scincomorph lizards,and provides new information about the terrestrial vertebrate fauna of the Cretaceous Songliao Basin.

关键词： Songliao Basin Nenjiang Formation Scincomorpha lower Campanian