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A polynomial resultant approach to algebraic constructions of extremal graphs

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Science China Mathematics 2024年

作者： Tao Zhang Zixiang Xu Gennian Ge institute of Mathematics and Interdisciplinary sciences Xidian University School of mathematical sciences Capital Normal University

The Turan problem asks for the largest number of edges ex（n, H） in an n-vertex graph not containing a fixed forbidden subgraph H, which is one of the most important problems in extremal graph theory. However,the order of magnitude of ex（n, H） for bipartite graphs is known only in a handful of cases. In particular,giving explicit constructions of extremal graphs is very challenging in this field. In this paper, we develop a polynomial resultant approach to the algebraic construction of explicit extremal graphs, which can efficiently decide whether a specified structure exists. A key insight in our approach is the multipolynomial resultant, which is a fundamental tool of computational algebraic geometry. Our main results include the matched lower bounds on the Turan number of 1-subdivision of K3,t1and the linear Turan number of the Berge theta hypergraphΘ3B,t2, where t1= 25 and t2= 217. Moreover, the constant t1 improves the random algebraic construction of Bukh and Conlon（2018） and makes the known estimation better on the smallest value of t1 concerning a problem posed by Conlon et al.（2021） by reducing the value from a magnitude of 1056 to the number 25, while the constant t2improves a result of He and Tait（2019）.

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青藏高原地表变暗与北极气候变化间的共振

Science Bulletin 2024年第3期69卷 367-374页

作者：汤舒畅朴世龙 David M.Holland 阚飞汪涛姚檀栋李熙晨 Sino-French institute for Earth System Science College of Urban and Environmental SciencesPeking UniversityBeijing 100871China State Key Laboratory of Tibetan Plateau Earth System Resources and EnvironmentInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100085China courant institute of mathematical sciences New York UniversityNew YorkNY 0711USA institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029China

The Tibetan Plateau(TP)exerts a profound influence on global climate over million-year timescales due to its past ***,whether the ongoing climate changes over the TP,particularly the persistent reduction in its local albedo(referred to as“TP surface darkening”),can exert global impacts remains *** this study,a state-of-the-art coupled land–atmosphere global climate model has been employed to scrutinize the impact of TP darkening on polar climate *** indicate that the projected TP darkening has the potential to generate a stationary Rossby wave train,thereby modulating the atmospheric circulation in the high-latitudes of the Northern Hemisphere and instigating a dipole-like surface air temperature anomaly pattern around the Arctic *** additional experiment suggests that the projected Arctic warming may in return warm the TP,thus forming a bi-directional linkage between these two climate *** their association with vast ice reservoirs,the elucidation of this mechanism in our study is crucial in advancing our comprehension of Earth system climate projections.

关键词： Tibetan Plateau High-latitude Northern Hemisphere Arctic Climate change Albedo Surface darkening

青藏高原地表变暗与北极气候变化间的共振（英文）

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Science Bulletin 2024年第3期 367-374页

作者：汤舒畅朴世龙 David M.Holland 阚飞汪涛姚檀栋李熙晨 Sino-French institute for Earth System Science College of Urban and Environmental Sciences Peking University State Key Laboratory of Tibetan Plateau Earth System Resources and Environment Institute of Tibetan Plateau Research Chinese Academy of Sciences courant institute of mathematical sciences New York University institute of Atmospheric Physics Chinese Academy of Sciences

The Tibetan Plateau(TP) exerts a profound influence on global climate over million-year timescales due to its past uplift. However, whether the ongoing climate changes over the TP, particularly the persistent reduction in its local albedo(referred to as ‘‘TP surface darkening”), can exert global impacts remains elusive. In this study, a state-of-the-art coupled land–atmosphere global climate model has been employed to scrutinize the impact of TP darkening on polar climate changes. Results indicate that the projected TP darkening has the potential to generate a stationary Rossby wave train, thereby modulating the atmospheric circulation in the high-latitudes of the Northern Hemisphere and instigating a dipole-like surface air temperature anomaly pattern around the Arctic region. An additional experiment suggests that the projected Arctic warming may in return warm the TP, thus forming a bi-directional linkage between these two climate systems. Given their association with vast ice reservoirs, the elucidation of this mechanism in our study is crucial in advancing our comprehension of Earth system climate projections.

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How Does ESG Performance Impact Corporate Financing Costs?An Empirical Study in China

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Journal of Systems Science and Information 2024年第2期12卷 229-244页

作者： Wei LI Mei MEI Xiaoyan YU Jiahao WANG Tiangeng (Becky) GENG School of Economics and Management University of Chinese Academy of SciencesBeijing 100190China institute of Medical Information&Library Chinese Academy of Medical SciencesBeijing 100005China Business and Management Royal HollowayUniversity of LondonSurrey TW200EXUK Krieger School of Arts and sciences Johns Hopkins UniversityBaltimore MD 21218USA

In the background of the green transformation of the economy and society,the ESG performance of enterprises has been paid more and more attention in the investment ***,previous studies have inadequately explored how the ESG performance affects corporate financing *** on the information asymmetry theory,this paper analyzes the impact mechanism of ESG performance on corporate financing ***,taking 1044 A-share listed companies in2016–2020 as a sample,through the sorting and analysis of ESG report disclosure and rating data,the company’s ESG performance indicators are obtained,and an empirical model is built to test the relationship between ESG performance and corporate financing *** paper constructs a panel regression model using ESG rating data and corporate financial data and finds that in the overall sample,the higher the ESG performance,the lower the equity financing cost;The higher the ESG performance,the lower the debt financing *** addition,it also discussed the moderating effect of enterprise scale and media attention on the impact of ESG performance on enterprise financing *** empirical results show that the influence of company size on ESG performance on financing costs has a moderating effect and a positive moderating effect.

关键词： ESG performance financing cost corporate heterogeneity media attention

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Correcting Climate Model Sea Surface Temperature Simulations with Generative Adversarial Networks:Climatology,Interannual Variability,and extremes

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Advances in Atmospheric sciences 2024年第7期41卷 1299-1312页

作者： Ya WANG Gang HUANG Baoxiang PAN Pengfei LIN Niklas BOERS Weichen TAO Yutong CHEN BO LIU Haijie LI State Key Laboratory of Numerical Modeling for Atmospheric sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and TechnologyQingdao 266237China College of Earth and Planetary sciences University of Chinese Academy of SciencesBeijing 100049China Earth System Modelling School of Engineering and DesignTechnical University of MunichOttobrunn 85521Germany Potsdam institute for Climate Impact Research Potsdam 14412Germany Department of Mathematics and Global Systems institute University of ExeterExeter EX44QEUK CMA Earth System Modeling and Prediction Centre(CEMC) Chinese Academy of Meteorological SciencesBeijing 100081China

Climate models are vital for understanding and projecting global climate change and its associated ***,these models suffer from biases that limit their accuracy in historical simulations and the trustworthiness of future *** these challenges requires addressing internal variability,hindering the direct alignment between model simulations and observations,and thwarting conventional supervised learning ***,we employ an unsupervised Cycle-consistent Generative Adversarial Network(CycleGAN),to correct daily Sea Surface Temperature(SST)simulations from the Community Earth System Model 2(CESM2).Our results reveal that the CycleGAN not only corrects climatological biases but also improves the simulation of major dynamic modes including the El Niño-Southern Oscillation(ENSO)and the Indian Ocean Dipole mode,as well as SST ***,it substantially corrects climatological SST biases,decreasing the globally averaged Root-Mean-Square Error(RMSE)by 58%.Intriguingly,the CycleGAN effectively addresses the well-known excessive westward bias in ENSO SST anomalies,a common issue in climate models that traditional methods,like quantile mapping,struggle to ***,it substantially improves the simulation of SST extremes,raising the pattern correlation coefficient(PCC)from 0.56 to 0.88 and lowering the RMSE from 0.5 to *** enhancement is attributed to better representations of interannual,intraseasonal,and synoptic scales *** study offers a novel approach to correct global SST simulations and underscores its effectiveness across different time scales and primary dynamical modes.

关键词： generative adversarial networks model bias deep learning El Niño-Southern Oscillation marine heatwaves

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The exchange Attack and the Mixture Differential Attack Revisited: From the Perspective of Automatic Evaluation

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Chinese Journal of Electronics 2024年第1期33卷 19-29页

作者： Kexin QIAO Zhiyu ZHANG Zhongfeng NIU Liehuang ZHU School of Cyberspace Science and Technology Beijing Institute of Technology State Key Laboratory of Cryptology institute of Information Engineering Chinese Academy of Sciences School of Cryptography University of Chinese Academy of Sciences

Recent results show that the differential properties within quadruples boom as a new inspiration in cryptanalysis of Advanced Encryption Standard(AES)-like constructions. These methods include the exchange attack proposed in Asiacrypt’19, the mixture differential attack proposed in To SC’18, etc., where the essential properties are obtained by manually scrutinizing the structures of the AES-like constructions. This paper presents a novel framework and an automatic tool based on mixed integer linear programming to search for mixture differential distinguishers for general constructions. This framework considers what equality patterns among quadruples can make a distinguisher and traces how the patterns propagate through cipher components with accurate probability *** this tool, a 5-round AES distinguishing attack with lower complexity and more 6-round distinguishing attacks in the chosen plaintext scenarios are deduced. We prove that no exchange-type or mixture differential distinguisher exists for 7 and above rounds AES if the details of the Sbox and Mix Columns matrix are not taken into account.

关键词： Ciphers Estimation Encryption Mixed integer linear programming Complexity theory Standards

A near-zero quiescent power breeze wake-up anemometer based on a rolling-bearing triboelectric nanogenerator

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Microsystems & Nanoengineering 2024年第2期10卷 241-249页

作者： Xianpeng Fu Zhichao Jiang Jie Cao Zefang Dong Guoxu Liu Meiling Zhu Chi Zhang CAS Center for excellence in Nanoscience Beijing Key Laboratory of Micro-nano Energy and SensorBeijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing101400China School of Nanoscience and Engineering University of Chinese Academy of SciencesBeijing100049China Center on Nanoenergy Research Guangxi Colleges and Universities Key Laboratory of Blue Energy and Systems IntegrationSchool of Physical Science&TechnologyGuangxi UniversityNanning530004China institute of Intelligent Flexible Mechatronics Jiangsu UniversityZhenjiang212013China College of Engineering Mathematics and Physical ScienceUniversity of ExeterExeterEX44QFUK

Wind sensors have always played an irreplaceable role in environmental information monitoring and are expected to operate with lower power consumption to extend service ***,we propose a breeze wake-up anemometer(B-WA)based on a rolling-bearing triboelectric nanogenerator(RB-TENG)with extremely low static *** B-WA consists of two RB-TENGs,a self-waking-up module(SWM),a signal processing module(SPM),and a wireless transmission *** two RB-TENGs are employed for system activation and wind-speed *** the ambient wind-speed exceeds 2 m/s,the wake TENG(W-TENG)and the SWM can wake up the system within 0.96 *** the same time,the SPM starts to calculate the signal frequency from the measured TENG(M-TENG)to monitor the wind speed with a sensitivity of 9.45 Hz/(m/s).After the wind stops,the SWM can switch off the B-WA within 0.52 s to decrease the system energy *** quiescent on-duty mode,the operating power of the B-WA is less than 30 nW,which can greatly extend the service lifetime of the *** integrating triboelectric devices and rolling bearings,this work has realized an ultralow quiescent power and self-waked-up wireless wind-speed monitoring system,which has foreseeable applications in remote weather monitoring,IoT nodes,and so on.

关键词： generator power service

2023: Weather and Climate extremes Hitting the Globe with Emerging Features

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Advances in Atmospheric sciences 2024年第6期41卷 1001-1016页

作者： Wenxia ZHANG Robin CLARK Tianjun ZHOU Laurent LI Chao LI Juan RIVERA Lixia ZHANG Kexin GUI Tingyu ZHANG Lan LI Rongyun PAN Yongjun CHEN Shijie TANG Xin HUANG Shuai HU State Key Laboratory of Numerical Modeling for Atmospheric sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Met Office Hadley Centre Exeter EX13PBUK University of Chinese Academy of sciences Beijing 100049China Laboratoire de Météorologie Dynamique CNRSSorbonne UniversitéEcole Normale SupérieureEcole PolytechniqueParis 75230France Max Planck institute for Meteorology Hamburg 20146Germany Instituto Argentino de Nivología Glaciología Y Ciencias Ambientales(IANIGLA)CCT CONICETMendoza CP 5500Argentina Shanghai Typhoon institute China Meteorological AdministrationShanghai 200030China Asia-Pacific Typhoon Collaborative Research Center Shanghai 201306China

Globally,2023 was the warmest observed year on record since at least 1850 and,according to proxy evidence,possibly of the past 100000 *** in recent years,the record warmth has again been accompanied with yet more extreme weather and climate events throughout the ***,we provide an overview of those of 2023,with details and key background causes to help build upon our understanding of the roles of internal climate variability and anthropogenic climate *** also highlight emerging features associated with some of these extreme *** extremes are occurring earlier in the year,and increasingly simultaneously in differing parts of the world(e.g.,the concurrent hot extremes in the Northern Hemisphere in July 2023).Intense cyclones are exacerbating precipitation extremes(e.g.,the North China flooding in July and the Libya flooding in September).Droughts in some regions(e.g.,California and the Horn of Africa)have transitioned into flood *** extremes also show increasing interactions with ecosystems via wildfires(e.g.,those in Hawaii in August and in Canada from spring to autumn 2023)and sandstorms(e.g.,those in Mongolia in April 2023).Finally,we also consider the challenges to research that these emerging characteristics present for the strategy and practice of adaptation.

关键词： weather and climate extremes temperature extremes extreme precipitation drought wildfires

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Ternary layered boride MoAlB:A novel thermo-regulation microwave absorbing ceramic material

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Journal of Advanced Ceramics 2024年第5期13卷 699-710页

作者： Zhangjue Wang Fan Zhang Nannan Wang Wei Li Yongqiang Chen Hailong Wang Rui Zhang Yanqiu Zhu Bingbing Fan School of Material Science and Engineering Zhengzhou UniversityZhengzhou 450001China Henan Academy of sciences Zhengzhou 450046China State Key Laboratory of Featured Metal Materials and Life Cycle Safety for Composite Structures MOE Key Laboratory of New Processing Technology for Nonferrous Metals MaterialsSchool of ResourcesEnvironment and MaterialsGuangxi UniversityNanning 530004China Department of Materials and Earth sciences Technical University of DarmstadtDarmstadt 64287Germany School of Material Science and Engineering Luoyang Institute of Science and TechnologyLuoyang 471023China Department of Engineering Faculty of EnvironmentScience and EconomyUniversity of ExeterExeter EX44QFUK

In the context of the fifth-generation(5G)smart era,the demand for electromagnetic wave(EMW)-absorbing materials has become increasingly prominent,so it is necessary to explore promising candidate *** work focuses on the exploration of the material absorbing properties of a MoAlB MAB(MAB represents a promising group of alternatives,where M stands for a transition metal,A typically denotes Al,and B is boron)phase ***,the first-principles calculations were performed to reveal the unique crystal and layered structure of the MoAlB ceramics and to predict their potential for use as an EMW absorption ***,a series of MoAlB ceramics were synthesized at temperatures ranging from 800 to 1300℃,and the influence of temperature on the phase compositions and microstructures of the obtained MoAlB ceramics was characterized and ***,the practical EMW absorption performance of the prepared MoAlB ceramics was evaluated via a combination of experiments and radar cross-sectional *** MoAlB sample synthesized at 900℃ exhibits superior EMW absorption performance,achieving an impressive minimum reflection loss(RL)of−50.33 *** unique layered structure and good electrical conductivity of the MoAlB samples are the main reasons for their enhanced wave absorption performance,which provides interfacial polarization and multiple dielectric loss ***,this study not only contributes to the understanding of the preparation of MoAlB materials but also provides potential guidance for their utilization in the realm of electromagnetic wave absorption.

关键词： MoAlB electronic band structure electromagnetic wave(EMW)absorption layered ternary boride density of states