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Causes of Differences in the Tropical Pacific SST Warming Pattern Projected by CMIP6 Models

Advances in Atmospheric Sciences 2025年第6期 1077-1091页

作者： Jun YING Matthew COLLINS Robin CHADWICK Shangfeng CHEN Xiaoming HU Tao LIAN Shangmin LONG State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural Resources Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) Department of Mathematics and Statistics University of Exeter Met Office Hadley Centre Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences School of Atmospheric Sciences Sun Yat-sen University School of Oceanography Shanghai Jiao Tong University Key Laboratory of Marine Hazards Forecasting Ministry of Natural Resources Hohai University College of Oceanography Hohai University

The inter-model difference in the tropical Pacific SST warming pattern is a big stumbling block for reliable projections of global climate change. Here by conducting an inter-model Empirical Orthogonal Function(EOF) analysis as well as an ocean mixed-layer heat budget, we find that the first two modes of inter-model difference in the SST warming pattern projected by 30 CMIP6 models, explaining more than three-quarters of the total inter-model variance, are both tied to different cloud–radiation feedbacks. The EOF1 mode that captures the different magnitudes of El Ni?o-like warming as well as the largest inter-model variance in the far eastern equatorial Pacific, is likely driven by highly diverse cloud–radiation feedbacks in the east and, to a lesser extent, by differing changes in the oceanic vertical temperature gradient. The EOF2 mode that mainly represents the different magnitudes of SST warming in the western equatorial Pacific, is associated with differing levels of negative cloud–radiation feedback over the central equatorial Pacific through a dynamic air–sea coupled process involving both the Bjerknes feedback and the wind–evaporation–SST *** in isolation the robust common model bias of a weak negative cloud–radiation feedback over the central equatorial Pacific, the projected SST warming in the western equatorial Pacific is likely to be smaller than the multi-model ensemble mean, thereby presenting a more weakeened zonal SST gradient than expected, implying the potential for more severe climate extremes under global warming.

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Security Performance Analysis for MIMO Systems: From Artificial Noise's Power and Dimension Perspective

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IEEE Transactions on Vehicular Technology 2025年

作者： Xu, Panpan Li, Zhenling Li, Chunguo Tan, Weijie Guizhou University School of Mathematics and Statistics Guiyang550025 China Southeast University School of Information Science and Engineering Nanjing210096 China Guizhou University State Key Laboratory of Public Big Data College of Computer Science and Technology Guiyang550025 China

This paper analyzes the influence of power and dimension of artificial noise (AN) on security performance of multiple-input multiple-output (MIMO) system with multiple randomly located eavesdroppers. We derive the closed-form expressions of the secrecy outage probability (SOP) and the optimal secrecy capacity by utilizing the irrelevance among transmission channels, and the orthogonality between AN and the basis vectors of the legitimate channel matrix's null space. We use the Poisson point process to determine the number and location of eavesdroppers, then analyze the security performance of the communication system under the 3D channel condition of probability-based line-of-sight (LoS) or non-line-of-sight (NLoS) channel. The simulation results show the following conclusions. When the AN dimension reaches 1/4 highest dimension (i.e., one quarter of the number of transmitting antennae less than one) and the power splitter factor (PSF) falls in the open interval (0.6, 0.9), we can achieve a trade-off between secrecy capacity and design complexity. © 1967-2012 IEEE.

关键词： Vector spaces

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Optimized thermoelectric generation for efficient low-medium temperature geothermal energy harvesting

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Renewable Energy 2025年 239卷

作者： Khan, Zafar Hayat Xie, Heping Sun, Licheng Yang, Wei Khan, Waqar A. Li, Bixiong Long, Xiting Wang, Jun Li, Cunbao Gao, Mingzhong Ruan, He Center for Applied Mathematics of Guangxi Nanning Normal University Nanning530100 China School of Mathematics and Statistics Nanning Normal University Nanning530100 China Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green Energy College of Civil and Transportation Engineering Shenzhen University Shenzhen518060 China State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource & Hydropower Sichuan University Chengdu610065 China Department of Mechanical Engineering College of Engineering Prince Mohammad Bin Fahd University Al Khobar31952 Saudi Arabia Key Laboratory of Deep Underground Science and Engineering for Ministry of Education Sichuan University Chengdu610065 China

This paper aims to design and evaluate a thermoelectric generation system optimized for low-to-medium temperature geothermal energy, focusing on maximizing power output and system efficiency. A one-dimensional mathematical model based on energy balance is employed for a single thermoelectric element and subsequently scaled to a 600 thermoelectric generators (TEGs) module. The Peltier, Fourier, and Joule heating effects are included in the analysis, whereas the radiation and convection effects are neglected. The impact of various 2D and 3D layouts of thermoelectric generators (TEGs) and temperature variations on power generation and performance is examined. An experiment is performed to observe the power capacity of a module consisting of five thermoelectric generators. These experimental observations validate the analytical model, and reference properties are adopted to predict more complex modules. This work aims to simulate the optimal design of a TEG module, utilizing the temperature difference to generate 1 kW of power. For this purpose, a module comprising of 600 TEGs is analyzed in various layouts. Based on experimental results for the temperature difference ΔT=96.4Co, it is proposed that a compact module consisting of 600 TEGs with a 3D design of 10 × 12 × 5 will be suitable and cost-effective to generate 1 kW power. © 2024 Elsevier Ltd

关键词： Geothermal Modeling Optimization Thermoelectric generator

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TVEG: Model Selection of the Time-Varying Exponential Family Distributions Graphical Models

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IEEE Transactions on Network Science and engineering 2025年

作者： Liu, Juan Mei, Guofeng Xia, Yuanqing Wu, Xiaoqun Lu, Jinhu Beijing Forestry University School of Technology Beijing100107 China Italy Zhongyuan University of Technology Henan 451191 China Wuhan University School of Mathematics and Statistics Wuhan430072 China Beihang University State Key Laboratory of Software Development Environment Beijing Advanced Innovation Center for Big Data and Brain Machine Intelligence School of Automation Science and Electrical Engineering Beijing100191 China

The undirected graphical model, a popular class of statistical model, offers a way to describe and explain the relationships among a set of variables. However, it remains a challenge to choose a certain graphical model to explain the relationships of variables adequately, especially when the relationships of variables are rewiring over time. This paper proposes the Time-Varying Exponential Family Distributions Graphical (TVEG) models, with time-varying structures and exponential family node-wise conditional distributions. TVEG models extend the scope of available graph models and can be applied to time-varying and exponential family distribution observation data in reality. We propose the Temporally Smoothed L1regularized exponential family graphical estimator (TSLEG), an estimator to infer the structure of TVEG from observations. We derive sufficient conditions for the TSLEG to recover the block partition and sparse pattern with high probability. We derive a message-passing optimization method to solve the TSLEG for time-varying Ising, Gaussian, exponential, and Poisson graphs based on the ADMM. The synthetic network simulations corroborate the theoretical analysis. Analysing of real data of stocks and the US Senate by the time-varying exponential model and Poisson model indicates the effectiveness and practicality of TVEG models. © 2025 IEEE. All rights reserved.

关键词： ADMM exponential family distributions Graphical model pseudo maximum likelihood estimation

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Delayed Pinning Control for Synchronization of Dynamical Networks

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IEEE Transactions on Automatic Control 2025年

作者： Zhu, Shuaibing Li, Feng Deng, Zhenhua Lü, Jinhu Hunan Normal University MOE-LCSM School of Mathematics and Statistics Changsha410081 China Anhui University of Technology School of Electrical and Information Engineering Ma'anshan243002 China Central South University School of Automation Changsha410075 China Beihang University School of Automation Science and Electrical Engineering State Key Laboratory of Software Development Environment Beijing100083 China

Though pinning control of dynamical networks with or without delay has been well explored in the past two decades, little attention has been paid to the delay originated from pinning control itself. This paper investigates the delayed pinning control scheme for lag synchronization and lag quasi-synchronization of dynamical networks. Two pinning control schemes with uniform delay and nonuniform delays are proposed, which are more practical than the widely-used delay-free pinning control scheme. For the two pinning control schemes, criteria for lag synchronization and lag quasi-synchronization of dynamical networks are derived by proposing a system of functional differential inequalities, and in the meantime, an upper bound of tolerable delays that allows synchronization is given. In particular, the ultimate bound of the synchronization error is estimated for lag quasi-synchronization. Finally, the theoretical results are demonstrated by two numerical examples. © 1963-2012 IEEE.

关键词： Delay control systems

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Two-mode terms in Wigner transport equation elucidate anomalous thermal transport in amorphous silicon

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Physical Review B 2025年第9期111卷 094206-094206页

作者： Jin Yang Xueyan Zhu Alan J. H. McGaughey Yee Sin Ang Wee-Liat Ong ZJU-UIUC Institute College of Energy Engineering Zhejiang University Jiaxing Haining Zhejiang 314400 China China Academy of Engineering Physics Software Center for High Performance Numerical Simulation Beijing 100088 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Department of Mechanical Engineering Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA Science Mathematics and Technology Singapore University of Technology and Design 487372 Singapore State Key Laboratory of Clean Energy Utilization Zhejiang University Hangzhou Zhejiang 310027 China

Over the past decades, our understanding of thermal transport in amorphous materials has predominantly relied on the inherently harmonic Allen-Feldman theory, which has been found to be insufficient. In this study, the Wigner transport formalism is adopted to explicitly account for anharmonicity. In studying the thermal transport in amorphous silicon, the results highlight that amorphous materials are not generally computationally equivalent to crystals with disordered primitive cells. A method that leverages the properties of the two-mode terms in the Wigner transport formalism is proposed to predict the bulk thermal conductivity of amorphous materials using finite-size models. In doing so, the need for mode classification schemes required in the Allen-Feldman theory is eliminated, and similarities are discovered between the two-mode terms and the carriers commonly used to describe thermal transport in amorphous materials, i.e., propagons, diffusons, and locons. Two competing trends are identified that shed light on the recently discovered anomalous decrease in the high-temperature thermal conductivity in some amorphous materials.

关键词： Heat transfer

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Fractional Cattaneo heat equation in a semi-infinite medium

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Chinese Physics B 2013年第1期22卷 338-343页

作者：续焕英齐海涛蒋晓芸 School of Mathematics and Statistics Shandong University Weihai State Key Laboratory for Turbulence and Complex Systems and Department of Mechanics and Aerospace Engineering College of Engineering Peking University School of Mathematics Shandong University

To better describe the phenomenon of non-Fourier heat conduction, the fractional Cattaneo heat equation is introduced from the generalized Cattaneo model with two fractional derivatives of different orders. The anomalous heat conduction under the Neumann boundary condition in a semi-infinity medium is investigated. Exact solutions are obtained in series form of the H-function by using the Laplace transform method. Finally, numerical examples are presented graphically when different kinds of surface temperature gradient are given. The effects of fractional parameters are also discussed.

关键词： Caputo fractional derivative non-Fourier heat conduction Cattaneo equation H-function

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Discovery of High-Temperature Superconducting Ternary Hydrides via Deep Learning

arXiv

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arXiv 2025年

作者： Wang, Xiaoyang Zhang, Chengqian Wang, Zhenyu Liu, Hanyu Lv, Jian Wang, Han Weinan, E. Ma, Yanming National Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Fenghao East Road 2 Beijing100094 China Academy for Advanced Interdisciplinary Studies Peking University Beijing100871 China Key Laboratory of Material Simulation Methods & Software of Ministry of Education State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun130012 China International Center of Future Science Jilin University Changchun130012 China HEDPS CAPT College of Engineering Peking University Beijing100871 China AI for Science Institute Beijing100080 China Center for Machine Learning Research Peking University Beijing100871 China School of Mathematical Sciences Peking University Beijing100871 China

The discovery of novel high-temperature superconductor materials holds transformative potential for a wide array of technological applications. However, the combinatorially vast chemical and configurational search space poses a significant bottleneck for both experimental and theoretical investigations. In this study, we employ the design of high-temperature ternary superhydride superconductors as a representative case to demonstrate how this challenge can be well addressed through a deep-learning-driven theoretical framework. This framework integrates high-throughput crystal structure exploration, physics-informed screening, and accurate prediction of superconducting critical temperatures. Our approach enabled the exploration of approximately 36 million ternary hydride structures across a chemical space of 29 elements, leading to the identification of 144 potential high-Tc superconductors with predicted Tc > 200 K and superior thermodynamic stability at 200 GPa. Among these, 129 compounds spanning 27 novel structural prototypes are reported for the first time, representing a significant expansion of the known structural landscape for hydride superconductors. This work not only greatly expands the known repertoire of high-Tc hydride superconductors but also establishes a scalable and efficient methodology for navigating the complex landscape of multinary hydrides. © 2025, CC BY.

关键词： High temperature superconductors

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The changes on synchronizing ability of coupled networks from ring networks to chain networks

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Science in China(Series F) 2007年第4期50卷 615-624页

作者： HAN XiuPing LU dunAn School of Mathematics and Statistics Wuhan University Wuhan 430072 China State Key Laboratory of Software Engineering Wuhan University Wuhan 430072 China

In this paper, two different ring networks with unidirectional couplings and with bidirectional couplings were discussed by theoretical analysis. It was found that the effects on synchronizing ability of the two different structures by cutting a link are completely opposite. The synchronizing ability will decrease if the change is from bidirectional ring to bidirectional chain. Moreover, the change on synchronizing ability will be four times if the number of N is large enough. However, it will increase obviously from unidirectional ring to unidirectional chain. It will be N^2/（π^2） times if the number of N is large enough. The numerical simulations confirm the conclusion in quality. This paper also discusses the effects on synchronization by adding one link with different length d to these two different structures. It can be seen that the effects are different. Theoretical results are accordant to numerical simulations. Synchronization is an essential physics problem. These results proposed in this paper have some important reference meanings on the real world networks, such as the bioecological system networks, the designing of the circuit, etc.

关键词： complex networks synchronizing ability unidirectional couplings bidirectional couplings ring chain coupling matrix

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A threshold effect of coupling delays on intra-layer synchronization in duplex networks

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Science China(Technological Sciences) 2018年第12期61卷 1907-1914页

作者： TANG LongKun LU JunAn Lü JinHu Fujian Province University Key Laboratory of Computation Science School of Mathematical Sciences Huaqiao University Department of Mathematics & Statistics Georgia State University School of Mathematics and Statistics Wuhan University School of Automation Science and Electrical Engineering State Key Laboratory of Software Development Environment and Beijing Advanced Innovation Center for Big Data and Brain Computing Beihang University

This paper investigates the impact of inter-layer coupling functions and intra-layer coupling delays on intra-layer synchronization regions and sychronizability. It is found that the inter-layer coupling functions have great influence on intra-layer synchronization regions, as well as on the intra-layer synchronizability. In particular, there exists an inter-layer coupling function such that the inter-layer coupling strength neither improves nor weakens the intra-layer synchronizability. Furthermore, no matter which one of three inter-layer coupling functions is chosen, a small intra-layer delay always keeps the intra-layer synchronized regions almost unchanged, implying that the small delay neither enhances nor suppresses the intra-layer synchronizability. At the same time the delay greatly frustrates the synchronizability in each layer when it is greater than some threshold. Our results may have potential applications for interconnected technological networks where communication delays are inevitably present.

关键词： multiplex network master stability function intra-layer synchronization synchronized region time delay

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