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Linear instability of hairy black holes in Horndeski theory

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Chinese Physics C 2024年第7期48卷 253-258页

作者：张超朱涛 Beijing Key Laboratory of Optical Detection Technology for Oil and Gas Basic Research Center for Energy InterdisciplinaryCollege of ScienceChina University of Petroleum-BeijingBeijing 102249China Institute for Theoretical Physics and Cosmology Zhejiang University of TechnologyHangzhou 310023China United Center for Gravitational Wave Physics(UCGWP) Zhejiang University of TechnologyHangzhou 310023China

Horndeski theory constitutes the most general model of scalar-tensor *** has attracted much attention in recent years in relation with black holes,celestial dynamics,stability analysis,*** is important to note that,for certain subclasses of Horndeski models,one can obtain analytic solutions for the background *** facilitates the investigation of the corresponding stability problems in *** particular,we aim to determine the constraints to the model or theory under which the stability conditions can be *** this study,we focused on a subclass of Horndeski theory and a set of analytic background *** addition,the odd-parity gravitational perturbation and 2nd-order Lagrangian were *** careful analysis,the instability was identified within the neighborhood of the event *** allows exclusion of a specific geometry for the *** an instability is implanted in the structure of the corresponding Lagrangian and is not erased by simply adding numerical constraints on the coupling *** a starting point of our research,the current study provides insights for further exploration of the Horndeski theory.

关键词： black holes black hole perturbations scalar-tensor theories Horndeski theory

Merger estimates for a disformal Kerr black hole in quadratic degenerate higher-order scalar-tensor theories

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Chinese Physics C 2024年第5期48卷 284-292页

作者：蒋洪鑫杜欣怡潘启沅陈松柏荆继良 Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education Synergetic Innovation Center for Quantum Effects and Applicationsand Department of PhysicsHunan Normal UniversityChangsha 410081China Institute of interdisciplinary Studies Hunan Normal UniversityChangsha 410081China Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We investigate the main features of a disformal Kerr black hole merger in quadratic degenerate higher-order scalar-tensor *** the ringdown stage of the black hole merger,for the prograde orbit,the real part of the quasinormal modes decreases with an increase in the disformal parameter,and the imaginary part also decreases,except in the Kerr case for a large spin ***,for the retrograde orbit,the real part increases with an increase in the disformal parameter,and the imaginary part always decreases with *** the approximate final spin,regardless of an equal spin,unequal spin,or generic spin configuration merger,the final black hole spin always increases with an increase in the disformal *** results show that the disformal parameter in the disformal Kerr solution and the MOG parameter in the Kerr-MOG case have obviously different effects on the black hole merger,which suggests the differences between these two spacetime structures.

关键词： black hole merger quasinormal modes final black hole spin disformal Kerr black hole quadratic degenerate higher-order scalar-tensor(DHOST)theory

Chiral bound states in a staggered array of coupled resonators

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Chinese Physics B 2024年第2期33卷 124-130页

作者：金伍林李静卢竞龚志瑞周兰 Synergetic Innovation Center for Quantum Effects and Applications Key Laboratory for Matter Microstructure and Function of Hunan ProvinceKey Laboratory of Low-Dimensional Quantum Structures and Quantum Control of the Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsInstitute of Interdisciplinary StudiesXiangjiang-Laboratory and Department of PhysicsHunan Normal UniversityChangsha 410081China College of Physics and Optoelectronic Engineering Shenzhen UniversityShenzhen 518060China

We study the chiral bound states in a coupled-resonator array with staggered hopping strengths,which interacts with a two-level small atom through a single coupling point or two adjacent *** addition to the two typical bound states found above and below the energy bands,this system presents an extraordinary chiral bound state located within the energy *** use the chirality to quantify the breaking of the mirror *** find that the chirality value undergoes continuous changes by tuning the coupling *** preferred direction of the chirality is controlled not only by the competition between the intracell and the intercell hoppings in the coupled-resonator array,but also by the coherence between the two coupling *** the case with one coupling point,the chirality values varies monotonously with difference between the intracell hopping and the intercell *** in the case with two coupling points,due to the coherence between the two coupling points the perfect chiral states can be obtained.

关键词： bound states two-level small atom coupled-resonator array chirality

Equilibrium Reinsurance Strategy and Mean Residual Life Function

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Acta Mathematicae Applicatae Sinica 2024年第3期40卷 758-777页

作者： Dan-ping LI Lv CHEN Lin-yi QIAN Wei WANG School of Statistics Key Laboratory of Advanced Theory and Application in Statistics and Data Science-MOEEast China Normal UniversityShanghai 200062China Academy of Statistics and interdisciplinary Sciences Key Laboratory of Advanced Theory and Application in Statistics and Data Science-MOEEast China Normal UniversityShanghai 200062China School of Mathematics and Statistics Ningbo UniversityNingbo 315211China

In this paper,we analyze the relationship between the equilibrium reinsurance strategy and the tail of the distribution of the *** Mean Residual Life(MRL)has a close relationship with the tail of the distribution,we consider two classes of risk distributions,Decreasing Mean Residual Life(DMRL)and Increasing Mean Residual Life(IMRL)distributions,which can be used to classify light-tailed and heavy-tailed distributions,*** assume that the underlying risk process is modelled by the classical CramérLundberg model *** the mean-variance criterion,by solving the extended Hamilton-Jacobi-Bellman equation,we derive the equilibrium reinsurance strategy for the insurer and the reinsurer under DMRL and IMRL,***,we analyze how to choose the reinsurance premium to make the insurer and the reinsurer agree with the same reinsurance *** find that under the case of DMRL,if the distribution and the risk aversions satisfy certain conditions,the insurer and the reinsurer can adopt a reinsurance premium to agree on a reinsurance strategy,and under the case of IMRL,the insurer and the reinsurer can only agree with each other that the insurer do not purchase the reinsurance.

关键词： mean residual life excess-of-loss reinsurance insurer reinsurer stochastic control

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A high-sensitive and self-selective humanoid mechanoreceptor for spatiotemporal tactile stimuli cognition

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Nano Research 2024年第5期17卷 4400-4409页

作者： Shuxin Bi Xuan Zhao Fangfang Gao Xiaochen Xun Bin Zhao Liangxu Xu Tian Ouyang Qingliang Liao Yue Zhang Academy for Advanced interdisciplinary Science and Technology Beijing Advanced Innovation Center for Materials Genome EngineeringUniversity of Science and Technology(Beijing)Beijing 100083China Key Laboratory of Advanced Materials and Devices for Post-Moore Chips Ministry of EducationBeijing Key Laboratory for Advanced Energy Materials and TechnologiesSchool of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083China

The cognition of spatiotemporal tactile stimuli,including fine spatial stimuli and static/dynamic temporal stimuli,is paramount for intelligent robots to feel their surroundings and complete manipulation ***,current tactile sensors have restrictions on simultaneously demonstrating high sensitivity and performing selective responses to static/dynamic stimuli,making it a challenge to effectively cognize spatiotemporal tactile ***,we report a high-sensitive and self-selective humanoid mechanoreceptor(HMR)that can precisely respond to spatiotemporal tactile *** HMR with PDMS/chitosan@CNTs(PDMS:polydimethylsiloxane;CNT:carbon nanotube)graded microstructures and polyurethane hierarchical porous spacer exhibits high sensitivity of 3790.8 kPa^(-1).The HMR demonstrates self-selective responses to static and dynamic stimuli with mono signal through the hybrid of piezoresistive and triboelectric ***,it can respond to spatiotemporal tactile stimuli and generate distinguishable and multi-type characteristic *** the assistance of the convolutional neural network,multiple target objects can be easily identified with a high accuracy of 99.1%.This work shows great potential in object precise identification and dexterous manipulation,which is the basis of intelligent robots and natural human-machine interactions.

关键词： mechanoreceptors self-selective high-sensitive spatiotemporal tactile stimuli cognition sensors

NONMONOTONE LOCAL MINIMAX METHODS FOR FINDING MULTIPLE SADDLE POINTS

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Journal of Computational Mathematics 2024年第3期42卷 851-884页

作者： Wei Liu Ziqing Xie Wenfan Yi South China Research Center for Applied Mathematics and interdisciplinary Studies South China Normal UniversityGuangzhou 510631China Key Laboratory of Computing and Stochastic Mathematics(Ministry of Education) Hunan Normal UniversityChangshaHunan 410081China Hunan Provincial Key Laboratory of Intelligent Information Processing and Applied Mathematics School of MathematicsHunan UniversityChangshaHunan 410082China

In this paper,by designing a normalized nonmonotone search strategy with the BarzilaiBorwein-type step-size,a novel local minimax method(LMM),which is a globally convergent iterative method,is proposed and analyzed to find multiple(unstable)saddle points of nonconvex functionals in Hilbert *** to traditional LMMs with monotone search strategies,this approach,which does not require strict decrease of the objective functional value at each iterative step,is observed to converge faster with less ***,based on a normalized iterative scheme coupled with a local peak selection that pulls the iterative point back onto the solution submanifold,by generalizing the Zhang-Hager(ZH)search strategy in the optimization theory to the LMM framework,a kind of normalized ZH-type nonmonotone step-size search strategy is introduced,and then a novel nonmonotone LMM is *** feasibility and global convergence results are rigorously carried out under the relaxation of the monotonicity for the functional at the iterative ***,in order to speed up the convergence of the nonmonotone LMM,a globally convergent Barzilai-Borwein-type LMM(GBBLMM)is presented by explicitly constructing the Barzilai-Borwein-type step-size as a trial step-size of the normalized ZH-type nonmonotone step-size search strategy in each ***,the GBBLMM algorithm is implemented to find multiple unstable solutions of two classes of semilinear elliptic boundary value problems with variational structures:one is the semilinear elliptic equations with the homogeneous Dirichlet boundary condition and another is the linear elliptic equations with semilinear Neumann boundary *** numerical results indicate that our approach is very effective and speeds up the LMMs significantly.

关键词： Multiple saddle points Local minimax method Barzilai-Borwein gradient method Normalized nonmonotone search strategy Global convergence

Atomically dispersed Mn enhanced catalytic performance for overall water splitting on graphdiyne-coated copper hydroxide nanowire

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Assessment of Rainwater Quality in Warri and Environ, Southern Nigeria for Domestic Purposes

结构化学 2024年第1期43卷 24-32页

作者： Lu Qi Zhaoyang Chen Xiaoyu Luan Zhiqiang Zheng Yurui Xue Yuliang Li Shandong Provincial Key Laboratory for Science of Material Creation and Energy Conversion Science Center for Materials Creation and Energy ConversionInstitute of Frontier and Interdisciplinary ScienceSchool of Chemistry and Chemical EngineeringShandong UniversityQingdao266237PR China Shandong Provincial Key Laboratory for Science of Material Creation and Energy Conversion Science Center for Materials Creation and Energy ConversionInstitute of Frontier and Interdisciplinary ScienceSchool of Chemistry and Chemical EngineeringShandong UniversityQingdao266237PR China CAS Key Laboratory of Organic Solids Institute of ChemistryChinese Academy of SciencesBeijing100190PR China University of Chinese Academy of Sciences Beijing100049PR China

Atomic catalysts(ACs)have been considered as promising catalysts for efficient hydrogen production through water ***,we report an AC with single Mn atoms highly dispersed on the surface of graphdiyne-coated copper hydroxide nanowire arrays(Mn-GDY/Cu(OH)x NWs).By anchoring Mn atoms on GDY,the specific surface area,the number of active sites,and the stability of catalyst are greatly *** characteri-zations reveal that the high hydrogen and oxygen evolution reaction(HER/OER)catalytic activity of the catalyst is induced by strong incomplete charge transfer effect between the metal atoms and *** advantages enable the electrocatalysts to drive a current density of 10 mA cm-2 at low overpotentials of 188 and 130 mV for OER and HER,respectively,together with excellent long-term ***,the alkaline electrolyzer using Mn-GDY/Cu(OH)x as both cathode and anode electrodes can reach 10 mA cm-2 only at a much low cell voltage of 1.50 V.

关键词： Graphdiyne Atom catalyst Electrocatalysis Hydrogen production Overall water splitting

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Journal of Geoscience and Environment Protection 2024年第6期12卷 255-268页

作者： Iwekumo E. Agbozu Tobore R. Maminor Uwem Bassey Department of Environmental Management and toxicology Federal University of Petroleum Resources Effurun Nigeria Department of Science Laboratory Technology Delta State University Abraka Nigeria

The study aimed at assessing the physiochemical characteristics of rainwater in Warri and it environ was investigated. Pb, Zn, Cd, Cu and Cr concentrations in rainwater from roof and non-roof sources were determined using Atomic Absorption Spectrophotometry. Three geospatial locations comprising Jakpa, Udu, and Ubeji were selected based on prevailing anthropogenic activities. The rainwater samples were systematically collected from (aluminum) roof and non-roof sources for the months of April, June, and August and October 2022, treated and analyzed in the laboratory for sixteen physicochemical parameters. Results were statistically analyzed using ANOVA, and T-test for the determination of the level of relationships and variations across geospatial locations. Significant correlations (r = 0.72) exist between Cr in rainwater from roof and non-roof sources. Implying point-source contaminations and may be emanating from the influence of roof materials. Furthermore, high concentrations of Cd and Pb in roof source above WHO standards were mostly in Jakpa and Ubeji. Calculated Health Risk Index (HRI) for children and adult is greater than 1. The results showed that most samples from the locations are considered not safe (HRI > 1) especially for Cd, which means that there are potential health risks consuming rainwater from Jakpa, Udu and Ubeji. Therefore, there is need for prompt sensitization program to dissuade people from directly drinking rainwater from these locations.

关键词： Water Quality Health Risks Rainwater Heavy Metals Warri Environs

Enhanced anomalous Hall effect in kagome magnet YbMn_(6)Sn_(6)with intermediate-valence ytterbium

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Chinese Physics B 2024年第5期33卷 43-50页

作者：李龙飞迟晟玮马文龙郭凯臻徐刚贾爽 International Center for Quantum Materials School of PhysicsPeking UniversityBeijing 100871China Wuhan National High Magnetic Field Center and School of Physics Huazhong University of Science and TechnologyWuhan 430074China interdisciplinary Institute of Light-Element Quantum Materials and Research Center for Light-Element Advanced Materials Peking UniversityBeijing 100871China Hefei National Laboratory Hefei 230088China

We report on the magnetization and anomalous Hall effect(AHE)in the high-quality single crystals of the kagome magnet YbMn_(6)Sn_(6),where the spins of the Mn atoms in the kagome lattice order ferromagnetically and the intermediate-valence Yb atoms are *** intrinsic mechanism plays a crucial role in the AHE,leading to an enhanced anomalous Hall conductivity(AHC)compared with the other rare-earth RMn_(6)Sn_(6)*** band structure calculation reveals a strong hybridization between the 4f electrons of Yb and conduction electrons.

关键词： anomalous Hall effect kagome magnet intermediate valence