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Interdecadal variation of drought patterns and associated influencing factors in the north-south transitional zone of China

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Journal of Geographical Sciences 2024年第7期34卷 1253-1279页

作者： DONG Qingdong ZHU Lianqi duan Zheng WANG Liyuan chen Chaonan LI Yanhong ZHU Wenbo GURUNG Sher Bahadur The College of Geography and Environmental Science Henan UniversityKaifengHenan475004China Department of Physical Geography and Ecosystem Science Lund UniversityLundS-22362Sweden Central Department of Geography Tribhuvan UniversityKathmandu44600Nepal

In the context of global warming,escalating water cycles have led to a surge in drought frequency and ***,multidecadal fluctuations in drought and their multifaceted influencing factors remain inadequately *** study examined the multidecadal changes in drought characteristics(frequency,duration,and severity)and their geographical focal points within China's north-south transitional zone,the Qinling-Daba Mountains(QDM),from 1960 to 2017 using the Standardized Precipitation Evapotranspiration Index(SPEI).In addition,a suite of eight scenarios,correlation analysis,and wavelet coherence were used to identify the meteorological and circulation factors that influenced drought *** results indicate the following:(1)From 1960 to 2017,the QDM experienced significant interdecadal variations in drought frequency,duration,and severity,the climate was relatively humid before the 1990s,but drought intensified ***,the 1990s marked the period of the longest drought duration and greatest severity,while the years spanning 2010 to 2017 experienced the highest frequency of drought events.(2)Spatially,the Qinling Mountains,particularly the western Qinling Mountain,exhibited higher drought frequency,duration,and severity than the Daba *** disparity can be attributed to higher rates of temperature increase and precipitation decrease in the western Qinling Mountain.(3)Interdecadal variations in droughts in the QDM were directly influenced by the synergistic effects of interdecadal fluctuations in air temperature and *** factors modulate temperature and precipitation through phase transitions,thereby affecting drought dynamics in the *** Atlantic Multidecadal Oscillation emerges as the primary circulation factors influencing temperature changes,with a mid-1990s shift to a positive phase favoring *** East Asian Summer Monsoon and El Ni?o-Southern Oscillation are the main circulation factors a

关键词： drought standardized precipitation evapotranspiration index multidecadal shift transitional zone Qinling-Daba Mountains

Development of a Front End Array for Broadband Phased Array Receiver

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Research in Astronomy and Astrophysics 2024年第4期24卷 60-70页

作者： Kai Wang Liang Cao Jun Ma Xue-Feng duan Hao Yan Mao-Zheng chen Yun-Wei Ning Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 8300lChina University of the Chinese Academy of Sciences Beijing 100049China Xinjiang Key Laboratory of Microwave Technology Urumqi 830011China

The receiver is a signal receiving device placed at the focus of the *** order to improve the observation efficiency,the concept of phased array receiver has been proposed in recent years,which places a small phased array at the focal plane of the reflector,and flexible pattern and beam scanning functions can be achieved through a beamforming *** combined with the element multiplexing,all beams within the entire field of view can be observed simultaneously to achieve continuous sky *** article focuses on the front-end array of phased array receiver at 0.7-1.8 GHz for QiTai Telescope,and designs a Vivaldi antenna array of PCB structure with dual line *** polarization antenna is designed to arrange in a rectangle manner by 11×*** on the simulation results of the focal field,32,18,and eight elements were selected to form one beam at 0.7,1.25,and1.8 *** analog beamforming network was constructed,and the measured gains of axial beam under uniform weighting were 19.32,13.72,and 15.22 *** the beam scanning method of reflector antenna,the pattern test of different position element sets required for PAF beam scanning was carried out under independent *** pattern optimization at 1.25 GHz was carried out by weighting method of conjugate field *** with uniform weighting,the gain,sidelobe level,and main beam direction under conjugate field matching have been *** the above test and simulation results are slightly different,which is related to the passive array and laboratory testing condition,the relevant work has accumulated experience in the development of the front-end array for the phased array receiver,and has good guiding significance for future performance verification after the array is installed on the telescope.

关键词： telescopes instrumentation:detectors techniques:radar astronomy

Assembly dynamics of East Asian subtropical evergreen broadleaved forests: New insights from the dominant Fagaceae trees

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Journal of Integrative Plant Biology 2022年第11期64卷 2126-2134页

作者： Lisi Hai Xiao-Qian Li Jing-Bo Zhang Xiao-Guo Xiang Rui-Qi Li Florian Jabbour Rosa del COrtiz An-Ming Lu Zhi-duan chen Wei Wang State Key Laboratory of Systematic and Evolutionary Botany Institute of BotanyChinese Academy of SciencesBeijing 100093China University of Chinese Academy of Sciences Beijing 100049China Jiangxi Province Key Laboratory of Watershed Ecosystem Change and Biodiversity Institute of Life Science and School of Life SciencesNanchang UniversityNanchang 330031China Institut de Systématique EvolutionBiodiversité(ISYEB)Muséum national d'Histoire naturelleCNRSSorbonne UniversitéEPHEUniversitédes AntillesParis 75005France Missouri Botanical Garden St.LouisMissouri 63166‐0299USA

The dominant species of a biome can be regarded as its genuine *** broadleaved forests(EBLFs) in subtropical East Asia harbor high levels of species biodiversity and endemism and are vital to regional carbon storage and ***,the historical assembly of this unique biome is still *** is the most essential family in East Asian subtropical EBLFs and its dominant species are vital for the existence of this ***,we used the dominant Fagaceae species to shed light on the dynamic process of East Asian subtropical EBLFs *** results indicate high precipitation in summer and low temperature in winter are the most influential climatic factors for the distribution of East Asian subtropical *** East Asian subtropical EBLFs did not begin to appear until 23 Ma,subsequently experienced a longlasting development in the Miocene and markedly deteriorated at about 4 Ma,driven jointly by orogenesis and *** also document that there is a lag time between when one clade invaded the region and when its members become dominant species within the *** study may improve our ability to predict and mitigate the threats to biodiversity of East Asian subtropical EBLFs and points to a new path for future studies involving multidisciplinary methods to explore the assembly of regional biomes.

关键词： biome climate change dominant species East Asia ecological niche modeling phylogeny

Clathrate structure of YB_(3)C_(3) for high-performance thermoelectrics with superior mechanical properties

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Journal of Materiomics 2024年第4期10卷 783-791页

作者： Yangfan Cui Shuai duan Xiaojun Wang Qinghang Tang Jinyang Xi Xiaobing Liu Yongsheng Zhang Xin chen Laboratory of High Pressure Physics and Material Science(HPPMS) School of Physics and Physical EngineeringQufu Normal UniversityQufuShandong273165China Materials Genome Institute Shanghai UniversityShanghai200444China Advanced Research Institute of Multidisciplinary Science Qufu Normal UniversityQufuShandong273165China

Exploring high-performance thermoelectric materials with improved mechanical properties is important for broadening the application scope and the assembly requirement of stable *** work presents an effective strategy to discover hard thermoelectric material by inserting foreign atoms in the rigid covalent *** demonstrate this in boron-carbon clathrate VII structure,showing a promising candidate for highly efficient thermoelectric energy conversion,especially with Y atom filled in the cage,with a peak zT of 0.73 at 1,000 *** ab initio calculations indicate that YB_(3)C_(3) system has low lattice thermal conductivity of 4.5 W/(m·K)at 1,000 K due to the strong rattling of encaged Y *** strongly covalent framework provides highly degenerate band structures consisting of heavy and light electron pockets,which can maintain high carrier mobility arising from small effective mass and thus large group ***,high power factor can be achieved in YB_(3)C_(3) for both electron and hole *** addition,it exhibits well mechanical properties and a Vickers hardness of 23.7 GPa because of the strong covalent boron-carbon *** work provides a novel avenue for the search of high-performance thermoelectric materials with excellent mechanical properties,based on boron-carbon clathrate structure.

关键词： Clathrate structure Thermoelectric performance First-principles calculations Mechanical properties Thermal conductivity

Chemodivergent Synthesis of Benzofurans and 2,3-Dihydrobenzofurans via Tandem Oxidative Annulation of Enaminones and Salicylaldehydes

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Chinese Journal of Chemistry 2024年第15期42卷 1727-1733页

作者： Xiyan duan Hui Li Junqi Wang Kun Liu Meixin Shi Weidong Lian Ran chen Pu Liu School of Chemistry&Chemical Engineering Henan University of Science and TechnologyLuoyangHenan 471003China

Chemodivergent synthesis of benzofurans and 2,3-dihydrobenzofurans has been *** a reaction system consisting of DBDMH and K_(2)CO_(3) as promotors,controlled conditions enabled the formation of two sets of valuable heterocycles from the tandem transformation of enaminones and *** key to success was the identification of the reaction parameters,in which the imine intermediate which was formed by transient halogenation coupling and substitution processes underwent either aldol condensation/annulation or imine hydrolysis/aldol *** additives NH_(4)Cl or Fe_(2)(SO_(4))_(3) controlled the unique selectivity of this reaction.A broad substrate scope of enaminones and salicylaldehydes has been employed in this reaction,demonstrating excellent functional group tolerance and versatility.

关键词： Cross-coupling Umpolung Domino reactions Enaminone Benzofurans 2,3-Dihydrobenzofurans

A 2D stability analysis of the rock surrounding underground liquified natural gas storage cavern based on COMSOL Multiphysics

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Energy Geoscience 2024年第3期5卷 351-361页

作者： Chao Zhang Pinjia duan Yuke cheng Na chen Huan Huang Feng Xiong Shaoqun Dong CNOOC Gas&Power Group Ltd. Beijing100028China School of Civil Engineering and Architecture Hubei University of TechnologyWuhan430068China State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing102249China College of Science China University of Petroleum(Beijing)Beijing102249China

Underground liquified natural gas(LNG)storage is essential in guaranteeing national energy strategic reserves,and its construction is being *** stability of surrounding rock of underground LNG storage caverns under stress-low temperature coupling effect is the key factor determining the feasibility of LNG ***,a mathematical model used for controlling the stress-low temperature coupling and the processes of rock damage evolution is given,followed by a 2-D numerical execution process of the mathematical model mentioned above described based on Comsol Multiphysics and Matlab ***,a series of 2-D simulations are performed to study the influence of LNG storage cavern layout,burial depth,temperature and internal pressure on the stability of surrounding rocks of these underground storage *** results indicate that all the factors mentioned above affect the evolution of deformation and plastic zone of surrounding *** research results contribute to the engineering design of underground LNG storage caverns.

关键词： Underground LNG storage Thermo-mechanical(TM)coupling Stability of surrounding rock Low temperature Comsol Multiphysics

CPL-active hybrid copper(Ⅰ)halides enabled by cation inclusion with chiral crown-ether

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Science China Chemistry 2024年第10期67卷 3283-3290页

作者： Peng Fan Li-Xuan Cai Xiao-Fang duan Fan Yin chen-chen Li Zhong-Hua Deng Xiao-Zhen Li Qing-Fu Sun College of Chemistry and Materials Science Fujian Normal UniversityFuzhou 350117China Strait Institute of Flexible Electronics(Future Technologies) Fujian Key Laboratory of Flexible ElectronicsFujian Normal University and Strait Laboratory of Flexible ElectronicsFuzhou 350117China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China Fujian College University of Chinese Academy of SciencesFuzhou 350002China

Chiral hybrid metal halides with high photoluminescence quantum yield(PLQY)and superior dissymmetry factor(g_(lum))are promising candidates for circularly polarized luminescence(CPL)emitting ***,it is a great challenge to achieve both high g_(lum)and large ***,we report a new supramolecular strategy to fabricate chiral hybrid Cu(Ⅰ)-halides with nearunity quantum yields and intense CPL *** dissymmetry factor can be dramatically modulated by tuning the hostguest *** to the chirality and variable conformations of the host-guest complexes,a series of chiral[G@L^(R/S)]_(2)Cu_(4)I_(6)have been *** incorporation of different cations within the chiral L^(R/S)hosts leads to variations of packing modes along the c-axis and different extent of distortions in the[Cu_(4)I_(6)]_(2)-*** them,[H_(3)O@L^(R/S)]+cations are stacked based on Van der Waals interactions and hierarchically self-assemble into a right/left-handed helix in[H_(3)O@L^(R/S)]_(2)Cu_(4)I_(6),which results in a high g_(lum)of-7×10^(-3)and a large PLQY of 96.92%.Notably,[G@L^(R/S)]_(2)Cu_(4)I_(6)shows promising applications in single-component white light emitting diodes(WLEDs),exhibiting a maximum dissymmetry factor of-1.2×10^(-3).The effective host-guest complexation and oriented hierarchical self-assembly provide an effective strategy for the development of high-performance CPL materials.

关键词： host-guest interaction circularly polarized luminescence copper iodide cluster hierarchical self-assembly chirality

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邻近基波/谐波的间谐波检测算法

电网技术 2019年第5期43卷 1818-1825页

作者：段晨杨洪耕四川大学电气信息学院四川省成都市610065

新能源大规模并网所引发的低频振荡,其频率分量通常可表现为一个低频信号对基波/谐波信号的调制,也即电力信号中会出现关于基波/谐波对称的邻近间谐波对。在使用离散傅里叶变换(DFT)对这类间谐波进行检测时,频域间的主瓣干扰会影响间谐... 详细信息

新能源大规模并网所引发的低频振荡,其频率分量通常可表现为一个低频信号对基波/谐波信号的调制,也即电力信号中会出现关于基波/谐波对称的邻近间谐波对。在使用离散傅里叶变换(DFT)对这类间谐波进行检测时,频域间的主瓣干扰会影响间谐波参数的准确估计。该文以单峰谱线插值算法为例,分析了传统插值算法在谐波和间谐波发生主瓣干扰时检测失效的原因,并提出了一种多分量频谱叠加算法对邻近基波/谐波的单个间谐波及间谐波对进行分析。首先根据信号DFT后紧邻基波/谐波的间谐波谱线的幅值特性,判别邻近基波/谐波的间谐波分量数;然后将间谐波的频谱按其频率分量数进行矢量叠加,并用紧邻基波/谐波的间谐波谱线构建谱线方程组得到其频率估计值;根据估计出的频率利用窗谱函数构建的关联矩阵求解其幅值和相位。仿真和工程实测分析表明,该方法能有效抑制由主瓣干扰引起的检测误差,在不增加采样数据长度的条件下准确检测出邻近基波或谐波的间谐波。

关键词：间谐波谐波快速傅里叶变换频谱分析主瓣干扰

Highly efficient three-dimensional solar evaporator for zero liquid discharge desalination of high-salinity brine

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Carbon Energy 2024年第9期6卷 52-65页

作者： Meichun Ding Demin Zhao Panpan Feng Baolei Wang Zhenying duan Rui Wei Yuxi Zhao chen-Yang Liu chenwei Li School of Chemistry and Pharmaceutical Engineering Shandong First Medical University&Shandong Academy of Medical SciencesJinanChina Medical Science and Technology Innovation Center Shandong First Medical University&Shandong Academy of Medical SciencesJinanChina Institut de Chimie Radicalaire Aix Marseille UniverisityMarseilleFrance CAS Key Laboratory of Engineering Plastics CAS Research/Education Center for Excellence in Molecular SciencesInstitute of Chemistrythe Chinese Academy of SciencesBeijingChina

Solar-driven interfacial evaporation is a promising technology for freshwater production from seawater,but salt accumulation on the evaporator surface hinders its performance and *** this study,we report a simple and green strategy to fabricate a three-dimensional porous graphene spiral roll(3GSR)that enables highly efficient solar evaporation,salt collection,and water production from near-saturated brine with zero liquid discharge(ZLD).The 3GSR design facilitates energy recovery,radial brine transport,and directional salt crystallization,thereby resulting in an ultrahigh evaporation rate of 9.05 kg m^(-2) h^(-1)6 in 25 wt%brine under 1-sun illumina-tion for 48 h ***,the directional salt crystallization on its outer surface not only enlarges the evaporation area but also achieves an ultrahigh salt collection rate of 2.92 kg m^(-2) h^(-1),thus enabling ZLD ***,3GSR exhibits a record-high water production rate of 3.14 kg m^(-2) h^(-1) in an outdoor *** innovative solution offers a highly efficient and continuous solar desalination method for water production and ZLD brine treatment,which has great implications for addressing global water scarcity and environmental issues arising from brine disposal.

关键词： graphene aerogels graphene composites solar desalination solar-driven interfacial evaporation