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Environmental Research Letters 2025年第2期20卷 029502-029502页

作者： Hanwoong Kim Yang Qiu Haewon McJeon Andres Clarens Parisa Javadi Can Wang Rui Wang Jiachen Wang Hanying Jiang Andy Miller Ryna Cui Jenna Behrendt Yang Ou Sha Yu Jay Fuhrman Joint Global Change Research Institute University of Maryland and Pacific Northwest National Laboratory College Park MD 20740 United States of America Graduate School of Green Growth and Sustainability (GGGS) Korea Advanced Institute of Science and Technology 291 Daehak-ro Yuseong-gu Daejeon 34141 Republic of Korea University of Virginia Department of Civil and Environmental Engineering University of Virginia Charlottesville VA 22904 United States of America State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University Beijing 100084 People’s Republic of China Department of Earth System Science Ministry of Education Key Laboratory for Earth System Modelling Institute for Global Change Studies Tsinghua University Beijing 100084 People’s Republic of China Center for Global Sustainability School of Public Policy University of Maryland College Park MD United States of America College of Environmental Sciences and Engineering Peking University Beijing People’s Republic of China Institute of Carbon Neutrality Peking University Beijing People’s Republic of China

Residual Networks for Light Field Image Super-Resolution

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Residual Networks for Light Field Image Super-Resolution

IEEE/CVF Conference on Computer Vision and Pattern Recognition

作者： Shuo Zhang Youfang Lin Hao Sheng Beijing Key Lab of Traffic Data Analysis and Mining School of Computer and Information Technology Beijing Jiaotong University Key Laboratory of Intelligent Passenger Service of Civil Aviation CAAC State Key Laboratory of Software Development Environment School of Computer Science and Engineering Beihang University Beijing Advanced Innovation Center for Big Data and Brain Computing Beihang University

Light field cameras are considered to have many potential applications since angular and spatial information is captured simultaneously. However, the limited spatial resolution has brought lots of difficulties in developing related applications and becomes the main bottleneck of light field cameras. In this paper, a learning-based method using residual convolutional networks is proposed to reconstruct light fields with higher spatial resolution. The view images in one light field are first grouped into different image stacks with consistent sub-pixel offsets and fed into different network branches to implicitly learn inherent corresponding relations. The residual information in different spatial directions is then calculated from each branch and further integrated to supplement high-frequency details for the view image. Finally, a flexible solution is proposed to super-resolve entire light field images with various angular resolutions. Experimental results on synthetic and real-world datasets demonstrate that the proposed method outperforms other state-of-the-art methods by a large margin in both visual and numerical evaluations. Furthermore, the proposed method shows good performances in preserving the inherent epipolar property in light field images.

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Harnessing non-local orbital-to-spin conversion of interfacial orbital currents for efficient spin-orbit torques

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arXiv 2020年

作者： Ding, Shilei Ross, Andrew Go, Dongwook Ren, Zengyao Freimuth, Frank Becker, Sven Kammerbauer, Fabian Yang, Jinbo Jakob, Gerhard Mokrousov, Yuriy Kläui, Mathias State Key Laboratory for Mesoscopic Physics School of Physics Peking University Beijing100871 China Institute of Physics Johannes Gutenberg-University Mainz Staudingerweg 7 Mainz55128 Germany Graduate School of Excellence Materials Science in Mainz Mainz55128 Germany Peter Grunberg Institut Institute for Advanced Simulation Forschungszentrum Jülich and JARA Jülich52425 Germany School of Materials Science and Engineering University of Science and Technology Beijing Beijing100083 China Collaborative Innovation Center of Quantum Matter Beijing100871 China Beijing Key Laboratory for Magnetoelectric Materials and Devices Beijing100871 China Center for Quantum Spintronics Department of Physics Norwegian University of Science and Technology TrondheimNO-7491 Norway

Current induced spin-orbit torques (SOT) allow for the efficient electrical manipulation of magnetism in spintronic devices. Engineering the SOT efficiency is a key goal that is pursued by maximizing the active interfacial spin accumulation or modulating the non-equilibrium spin-density that builds up through the spin Hall and inverse spin galvanic effects. Regardless of the origin, the fundamental requirement for the generation of the current-induced torques is a net spin accumulation. Here, we report the large enhancement of the SOT efficiency in TmIG / Pt by capping with a CuOx layer. Considering the weak spin-orbit coupling (SOC) of CuOx, these surprising findings are explained as a result of orbital current generated from CuOx in contact with Pt. This interface-generated orbital current is injected into Pt and converted into a spin current due to the large SOC of Pt. The converted spin current decays across the Pt and exerts a "non-local" torque on TmIG. This additional torque leads to a maximum enhancement of the SOT efficiency of a factor 16 for 1.5 nm of Pt at room temperature, thus opening a path to increase torques while at the same time offering insights into the underlying physics of orbital transport which has been elusive so far. Copyright © 2020, The Authors. All rights reserved.

关键词： Torque

Mechanism and propagation of characteristic frequency noise inner a high pressure compressor 25

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Mechanism and propagation of characteristic frequency noise ...

25th International Congress on Sound and Vibration 2018: Hiroshima Calling, ICSV 2018

作者： Zhao, Fengtong Jing, Xiaodong Sha, Yundong Luan, Xiaochi School of Energy and Power Engineering Beihang University Beijing100191 China Liaoning Province Key Laboratory of Advanced Measurement Test Technology of Aviation Propulsion Systems Shenyang Aerospace University Shenyang Liaoning110136 China

ISBN: (纸本)9781510868458

An acoustic experiment on a high pressure compressor is implemented to investigate noise mechanism and propagation corresponding to high level vibration occurred on rotor blades. The results show that, noise spectrum tested on the first stage rotor blades of high pressure compressor presents typical characteristics for discrete multi-tone in a pre-arranged structure adjustment and specific rotating speed. These discrete frequencies are composed with blade passing frequency of the first stage rotor blades and other special characteristic frequencies. And the amplitude of characteristic frequency 1402Hz will synchronously increase with the sharp vibration of the rotor blades. Rotating speed plays an important role on the characteristic frequency. This frequency merely occur on the specific speed range, and has relationship with structure adjustment of the compressor. With the rotating instability theory, the generation mechanism of the frequency can be explained with a rotating sound source having the same speed with the first stage rotor blades. The frequency of the rotating noise source will match with the characteristic frequency at a specific mode. Through the coherent analysis between the noise measured at different testing positions, this characteristic frequency noise source originates behind the first stage rotor blade at least. Therefore, the propagation state should be from back to forward with a circumferential speed. All these analysis reveal generation mechanism and propagation characteristic of the discrete frequency inner the compressor which may have an important reference value for Engineers. © 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling. All rights reserved.

关键词： Compressors

Rotation sensing in two coupled whispering-gallery-mode resonators with loss and gain

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Physical Review A 2019年第4期100卷 043810-043810页

作者： Tian Tian Zhihai Wang L. J. Song School of Science Changchun University Changchun 130022 China Key Laboratory of Materials Design and Quantum Simulation Changchun University Changchun 130022 China Center for Quantum Sciences and School of Physics Northeast Normal University Changchun 130024 China Center for Advanced Optoelectronic Functional Materials Research and Key Laboratory for UV-Emitting Materials and Technology of Ministry of Education Northeast Normal University Changchun 130024 China Jilin Engineering Normal University Changchun 130052 China

We theoretically propose a scheme to realize rotation sensing based on two coupled whispering-gallery-mode resonators with loss and gain. We consider that the active resonator with gain is rotated while the passive one with loss is stationary. The rotation will induce Sagnac effect and we show that the eigenfrequencies of the supermodes are sensitive to the Sagnac-Fizeau shift. Therefore, we can measure the average photon number in the steady state or the fluctuation spectrum of the output fields to detect the angular velocity of the rotation. We hope that our investigation will be useful in the design of a quantum gyroscope based on spinning resonators.

关键词： Quantum optics

Jacobi Spectral Collocation Method Based on Lagrange Interpolation Polynomials for Solving Nonlinear Fractional Integro-Differential Equations

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Advances in Applied Mathematics and Mechanics 2018年第6期10卷 1440-1458页

作者： Xingfa Yang Yin Yang Yanping Chen Jie Liu State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082HunanChina Hunan Key Laboratory for Computation and Simulation in Science and Engineering Key Laboratory of Intelligent Computing&Information Processing of Ministry of EducationSchool of Mathematics and Computational ScienceXiangtan UniversityXiangtan 411105HunanChina School of Mathematical Sciences South China Normal UniversityGuangzhou 510631GuangdongChina Center for Research on Leading Technology of Special Equipment School of Mechanical and Electric EngineeringGuangzhou UniversityGuangzhou 510006GuangdongChina

In this paper,we study a class of nonlinear fractional integro-differential equations,the fractional derivative is described in the Caputo *** the properties of the Caputo derivative,we convert the fractional integro-differential equations into equivalent integral-differential equations of Volterra type with singular kernel,then we propose and analyze a spectral Jacobi-collocation approximation for nonlinear integro-differential equations of Volterra *** provide a rigorous error analysis for the spectral methods,which shows that both the errors of approximate solutions and the errors of approximate fractional derivatives of the solutions decay exponentially in L^(∞)-norm and weighted L^(2)-norm.

关键词： Spectral method nonlinear fractional derivative Volterra integro-differential equations Caputo derivative

Is the existence of a J/ψJ/ψ bound state plausible?

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arXiv 2021年

作者： Dong, Xiang-Kun Baru, Vadim Guo, Feng-Kun Hanhart, Christoph Nefediev, Alexey Zou, Bing-Song CAS Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China Institut für Theoretische Physik II Ruhr-Universität Bochum BochumD-44780 Germany Institute for Theoretical and Experimental Physics NRC "Kurchatov Institute" Moscow117218 Russia Institute for Advanced Simulation Institut für Kernphysik Jülich Center for Hadron Physics Forschungszentrum Jülich JülichD-52425 Germany P.N. Lebedev Physical Institute of the Russian Academy of Sciences Moscow119991 Russia Moscow Institute of Physics and Technology Moscow141700 Russia School of Physics Central South University Changsha410083 China

In a recent measurement LHCb reported pronounced structures in the J/ψJ/ψ spectrum. One of the various possible explanations of those is that they emerge from non-perturbative interactions of vector charmonia. It is thus important to understand whether it is possible to form a bound state of two charmonia interacting through the exchange of gluons, which hadronise into two pions at the longest distance. In this paper, we demonstrate that, given our current understanding of hadron-hadron interactions, the exchange of correlated light mesons (pions and kaons) is able to provide sizeable attraction to the di-J/ψ system, and it is possible for two J/ψ mesons to form a bound state. As a side result we find from an analysis of the data for the ψ(2S) → J/ψππ transition including both ππ and KK¯ final state interactions an improved value for the ψ(2S) → J/ψ transition chromo-electric polarisability: |αψ(2S)J/ψ| = (1.8 ±0.1) GeV−3, where the uncertainty also includes the one induced by the final state interactions. © 2021, CC BY.

关键词： Hadrons

Studies on Artificial Neural Network Based Wind Power Grid-connected Harmonic Resonant Frequency Detection

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Studies on Artificial Neural Network Based Wind Power Grid-c...

IEEE Electronic Power Grid (eGrid)

作者： Dong Li Xueguang Wu Yang Gao Minxiao Han Dong Liu Chang Lin School of Electrical and Electronic Engineering North China Electric Power University Changping District Beijing China State Key Laboratory of Advanced Transmission Technology Global Energy Interconnection Research Institute Ltd. Changping District Beijing China Beijing Key Laboratory of DC Grid Technology and Simulation Global Energy Interconnection Research Institute Ltd. Changping District Beijing China

ISBN: (数字)9781728157047

ISBN: (纸本)9781728157054

With the wide utilization of wind resources, the penetration of wind power is ever increasing. Due to the influence of various uncertainties in the wind farm, the wind farm may generate harmonic oscillations randomly in the system. Accurate detection of the resonant frequency of the system is an important prerequisite for effective harmonic suppression. In response to the aforementioned issues, this paper proposes a wind power grid-connected harmonic resonant frequency measurement based on artificial neural network. It takes the instantaneous current values measured in a certain power frequency cycle as the model input, and uses the resonant frequency of the system as the model output. The accuracy and applicability of the proposed measurement method are verified by simulation studies in the MATLAB/Simulink. Results show that the detection method proposed in this paper is highly accurate and has the potential to be used in the wind farm.

关键词： Resonant frequency Artificial neural networks Harmonic analysis Wind power generation Neurons Wind farms Power system harmonics

Generalized Collision-free Velocity Model for Pedestrian Dynamics

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arXiv 2019年

作者： Xu, Qiancheng Chraibi, Mohcine Tordeux, Antoine Zhang, Jun Institute for Advanced Simulation Forschungszentrum Jülich GmbH Jülich52425 Germany School of Mechanical Engineering and Safety Engineering University of Wuppertal Wuppertal42119 Germany State Key Laboratory of Fire Science University of Science and Technology of China Hefei230027 China

The collision-free velocity model is a microscopic pedestrian model, which despite its simplicity, reproduces fairly well several self-organization phenomena in pedestrian dynamics. The model consists of two components: a direction sub-model that combines individual desired moving direction and neighbour’s influence to imitate the process of navigating in a two-dimensional space, and an intrinsically collision-free speed sub-model which controls the speed of the agents with respect to the distance to their neighbors. This paper generalizes the collision-free velocity model by introducing the influence of walls and extending the distance calculations to velocity-based ellipses. Besides, we introduce enhancements to the direction sub-module of the model that smooth the direction changes of pedestrians in the simulation;a shortcoming that was not visible in the original model due to the symmetry of the circular shapes. Moreover, the introduced improvements mitigate backward movement, leading to a more realistic distribution of pedestrians especially in bottleneck scenarios. We study by simulation the effects of the pedestrian’s shape by comparing the fundamental diagram in narrow and wide corridors. Furthermore, we validate our enhancements to the direction sub-model for bottleneck experiments with varying exit’s width. Copyright © 2019, The Authors. All rights reserved.

关键词： Velocity

Giant Anomalous Nernst Effect in Noncollinear Antiferromagnetic Mn-based Antiperovskite Nitrides

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arXiv 2019年

作者： Zhou, Xiaodong Hanke, Jan-Philipp Feng, Wanxiang Blügel, Stefan Mokrousov, Yuriy Yao, Yugui Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement Ministry of Education School of Physics Beijing Institute of Technology Beijing100081 China Peter Grünberg Institut Institute for Advanced Simulation Forschungszentrum Jülich and JARA Jülich52425 Germany Institute of Physics Johannes Gutenberg University Mainz Mainz55099 Germany

The anomalous Nernst effect (ANE)—the generation of a transverse electric voltage by a longitudinal heat current in conducting ferromagnets or antiferromagnets—is an appealing approach for thermoelectric power generation in spin caloritronics. The ANE in antiferromagnets is particularly convenient for the fabrication of highly efficient and densely integrated thermopiles as lateral configurations of thermoelectric modules increase the coverage of heat source without suffering from the stray fields that are intrinsic to ferromagnets. In this work, using first-principles calculations together with a group theory analysis, we systematically investigate the spin order-dependent ANE in noncollinear antiferromagnetic Mn-based antiperovskite nitrides Mn3XN (X = Ga, Zn, Ag, and Ni). The ANE in Mn3XN is forbidden by symmetry in the R1 phase but amounts to its maximum value in the R3 phase. Among all Mn3XN compounds, Mn3NiN presents the most significant anomalous Nernst conductivity of 1.80 AK−1m−1 at 200 K, which can be further enhanced if strain, electric, or magnetic fields are applied. The ANE in Mn3NiN, being one order of magnitude larger than that in the famous Mn3Sn, is the largest one discovered in antiferromagnets so far. The giant ANE in Mn3NiN originates from the sharp slope of the anomalous Hall conductivity at the Fermi energy, which can be understood well from the Mott relation. Our findings provide a novel host material for realizing antiferromagnetic spin caloritronics which promises exciting applications in energy conversion and information processing. Copyright © 2019, The Authors. All rights reserved.

关键词： Ferromagnetic materials