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Beam dynamics induced by the quantum metric of exceptional rings

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arXiv 2024年

作者： Zhang, Zhaoyang Septembre, Ismaël Liu, Zhenzhi Kokhanchik, Pavel Liang, Shun Liu, Fu Li, Changbiao Wang, Hongxing Liu, Maochang Zhang, Yanpeng Xiao, Min Malpuech, Guillaume Solnyshkov, Dmitry Key Laboratory for Physical Electronics and Devices The Ministry of Education Shaanxi Key Lab of Information Photonic Technique School of Electronic Science and Engineering Faculty of Electronics and Information Xi’an Jiaotong University Xi’an710049 China Institut Pascal PHOTON-N2 Université Clermont Auvergne CNRS Clermont INP Clermont-FerrandF-63000 France Naturwissenschaftlich-Technische Fakultät Universität Siegen Walter-Flex-Straße 3 Siegen57068 Germany International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Department of Physics University of Arkansas FayettevilleAR72701 United States Paris75231 France

Topological physics has broadened its scope from the study of topological insulating phases to include nodal phases containing band structure singularities. The geometry of the corresponding quantum states is described by the quantum metric which provides a theoretical framework for explaining phenomena that conventional approaches fail to address. The field has become even broader by encompassing non-Hermitian singularities: in addition to Dirac, Weyl nodes, or nodal lines, it is now common to encounter exceptional points, exceptional or Weyl rings, and even Weyl spheres. They give access to fascinating effects that cannot be reached within the Hermitian picture. However, the quantum geometry of non-Hermitian singularities is not a straightforward extension of the Hermitian one, remaining far less understood. Here, we study experimentally and theoretically the dynamics of wave packets at exceptional rings stemming from Dirac points in a photonic honeycomb lattice. First, we demonstrate a transition between conical diffraction and non-Hermitian broadening in real space. Next, we predict and demonstrate a new non-Hermitian effect in the reciprocal space, induced by the non-orthogonality of the eigenstates. We call it transverse non-Hermitian drift, and its description requires biorthogonal quantum metric. The non-Hermitian drift can be used for applications in beam steering. Copyright © 2024, The Authors. All rights reserved.

关键词： Topology

Direct reduction of iron-ore with hydrogen in fluidized beds: A coarse-grained CFD-DEM-IBM study

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arXiv 2023年

作者： Lan, Bin Xu, Ji Lu, Shuai Liu, Yige Xu, Fan Zhao, Bidan Zou, Zheng Zhai, Ming Wang, Junwu School of Energy Science and Engineering Harbin Institute of Technology Harbin150001 China State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences P. O. Box 353 Beijing100190 China School of Chemical Engineering University of Chinese Academy of Sciences Beijing100049 China Innovation Academy for Green Manufacture Chinese Academy of Sciences Beijing100190 China

Hydrogen metallurgy technology uses hydrogen as the reducing agent instead of carbon reduction, which is one of the important ways to reduce carbon dioxide emissions and ensure the green and sustainable development of iron and steel industry. Due to the advantages of high gas-solid contact efficiency and outstanding mass and heat transfer, direct reduction of iron ore in fluidized beds has attracted much attention. In this study, a coarse-grained CFD-DEM-IBM solver based on hybrid CPU-GPU computing is developed to simulate the direct reduction process of two kinds of iron ore with hydrogen in fluidized beds, where an unreacted shrinking core model based on multiple reaction paths is used to model the reduction reactions, a coarse-grained model and multiple GPUs enable the significant acceleration of particle computation, and the immersed boundary method (IBM) enables the use of simple mesh even in complex geometries of reactors. The predicted results of particle reduction degree are in good agreement with the experimental values, which proves the correctness of the CFD-DEM-IBM solver. In addition, the effects of reaction kinetic parameters and operating temperature on particle reduction degree are also investigated. Present study provides a method for digital design, optimization and scale-up of ironmaking reactors. Copyright © 2023, The Authors. All rights reserved.

关键词： Iron ores

Discrete Unified Gas-Kinetic Wave-Particle Method for flows in All flow Regimes

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SSRN

SSRN 2022年

作者： Yang, L.M. Li, Z.H. Shu, C. Liu, Y.Y. Liu, W. Wu, J. Department of Aerodynamics College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Nanjing210016 China State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Nanjing210016 China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing210016 China Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development Center Mianyang621000 China National Laboratory for Computational Fluid Dynamics Beijing100191 China Department of Mechanical Engineering National University of Singapore Singapore117576 Singapore

This work proposes a discrete unified gas-kinetic wave-particle (DUGKWP) method for simulation of flows in all flow regimes. Unlike the discrete velocity method (DVM) and the direct simulation Monte Carlo (DSMC) method which solve the governing equations by either the deterministic method or the stochastic method, the DUGKWP combines the advantages of these two methods. In the DUGKWP, the information of microscopic particles as well as macroscopic flow variables are both evolved. Specifically, the microscopic particles are updated by the free-transport and resampling processes, while the macroscopic flow properties are evolved through solving the macroscopic governing equations of conservation laws with the finite volume method. According to the discrete characteristic solution to the Boltzmann-BGK equation utilized in the DUGKWP, in the highly rarefied flow regime, the motion of microscopic particles greatly determines the fluxes for the macroscopic governing equations. Conversely, for the continuum flow, no microscopic particle exists in the computational domain and the DUGKWP is degraded to the Navier-Stokes’ solver. Numerical studies validate that the DUGKWP can accurately predict the flow properties in all flow regimes. Furthermore, compared with the deterministic method, the DUGKWP enjoys superior efficiency with less memory consumption for both high-speed rarefied flows and flows close to the continuum regime. © 2022, The Authors. All rights reserved.

关键词： Navier Stokes equations

Chargeable photoconductivity in Van der Waals heterojunctions

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arXiv 2020年

作者： Jiang, Yucheng He, Anpeng Chen, Yu Liu, Guozhen Lu, Hao Zhao, Run Long, Mingshen Gao, Ju Wu, Quanying Ge, Xiaotian Ning, Jiqiang Hu, Weida Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application School of Mathematics and Physics Suzhou University of Science and Technology Suzhou Jiangsu215009 China State Key Laboratory of Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences 500 Yu Tian Road Shanghai200083 China School for Optoelectronic Engineering Zaozhuang University Shandong277160 China Suzhou Jiangsu215009 China

Van der Waals (vdW) heterojunctions, based on two-dimensional (2D) materials, show great potential for the development of eco-friendly and high-efficiency nanodevices. Considerable research has been performed and has reported valuable applications of photovoltaic cells, photodetectors, etc. However, simultaneous energy conversion and storage in a single device has not been achieved. Here, we demonstrate a simple strategy to construct a vdW p-n junction between a WSe2 layer and quasi-2D electron gas. After once optical illumination, the device stores the light-generated electrons and holes for up to seven days, and then releases a very large photocurrent of 2.9 mA with bias voltage applied in darkness;this is referred to as chargeable photoconductivity (CPC), which completely differs from any previously observed photoelectric phenomenon. In normal photoconductivity, the recombination of electron-hole pairs takes place at the end of their lifetime, causing a release of heat;in contrast, infinite-lifetime photocarriers can be generated in CPC devices without a thermal loss. The photoelectric conversion and storage are completely self-excited during the charging process. The ratio between currents in full- and empty-energy states below the critical temperature reaches as high as 109, with an external quantum efficiency of 4410000% during optical charging. A theoretical model developed to explain the mechanism of this effect is in good agreement with the experimental data. This work paves a path towards storage-type photoconductors and high-efficiency entropy-decreasing devices. Copyright © 2020, The Authors. All rights reserved.

关键词： Van der Waals forces

Correction to: Modification of a first‑generation solid oxide fuel cell cathode with Co3O4 nanocubes having selectively exposed crystal planes

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Materials for Renewable and Sustainable Energy 2022年第3期11卷 299-299页

作者： Xu, Xi Wang, Chao Fronzi, Marco Liu, Xuehua Bi, Lei Institute of Materials for Energy and Environment College of Materials Science and Engineering Qingdao University Qingdao China State Key Laboratory of Multiphase Flow in Power Engineering International Research Centre for Renewable Energy Xi’an Jiaotong University Xi’an China

Direct numerical simulation of Taylor-Couette flow with vertical asymmetric rough walls

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arXiv 2023年

作者： Xu, Fan Su, Jinghong Lan, Bin Zhao, Peng He, Yurong Sun, Chao Wang, Junwu School of Energy Science and Engineering Harbin Institute of Technology Harbin150001 China State Key Laboratory of Multiphase Complex Systems Institute of Process Engineering Chinese Academy of Sciences P. O. Box 353 Beijing100190 China School of Chemical Engineering University of Chinese Academy of Sciences Beijing100049 China Innovation Academy for Green Manufacture Chinese Academy of Sciences Beijing100190 China Center for Combustion Energy Key Laboratory for Thermal Science and Power Engineering Ministry of Education Department of Energy and Power Engineering Tsinghua University Beijing100084 China Department of Engineering Mechanics School of Aerospace Engineering Tsinghua University Beijing100084 China

Direct numerical simulations are performed to explore the effects of the rotating direction of the vertically asymmetric rough wall on the transport properties of Taylor-Couette (TC) flow, up to a Taylor number of Ta = 2.39×107. It is shown that, compared to the smooth wall, the rough wall with vertical asymmetric strips can enhance the dimensionless torque Nuω. More importantly, at high Ta, clockwise rotation of the inner rough wall (where the fluid is sheared by the steeper slope side of the strips) results in a significantly greater torque enhancement compared to counter-clockwise rotation (where the fluid is sheared by the smaller slope side of the strips), due to the larger convective contribution to the angular velocity flux. However, the rotating direction has a negligible effect on the torque at low Ta. The larger torque enhancement caused by the clockwise rotation of the vertically asymmetric rough wall at high Ta is then explained by the stronger coupling between the rough wall and the bulk, attributed to the larger biased azimuthal velocity toward the rough wall at the mid-gap of the TC system, the increased turbulence intensity manifested by larger Reynolds stress and a thinner boundary layer, and the more significant contribution of the pressure force on the surface of the rough wall to the torque. Copyright © 2023, The Authors. All rights reserved.

关键词： Direct numerical simulation

A study of a computational BVP for heat transfer and friction drag in magnetohydrodynamics viscous flow of a nanofluid subject to the curved surface

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Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical engineering 2021年

作者： Khan, M Riaz Saleel, C Ahamed Saeed, Tareq Allehiany, F.M. El-Refaey, Adel M Jing, Dengwei Mahmoud, Emad E LSEC and ICMSEC Academy of Mathematics and Systems Science Chinese Academy of Sciences China School of Mathematical Science University of Chinese Academy of Sciences China Department of Mechanical Engineering College of Engineering King Khalid University Saudi Arabia -Research Group Department of Mathematics Faculty of Science King Abdulaziz University Saudi Arabia Department of Mathematical Sciences College of Applied Sciences Umm Al-Qura University Saudi Arabia Department of Basic and Applied Science College of Engineering and Technology Arab Academy for Science Technology Maritime Transport Smart Village Campus Egypt State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China Department of Mathematics and Statistics College of Science Taif University Taif Saudi Arabia

The ongoing work investigates the features of Joule heating and convective condition over a magnetohydrodynamic stagnation point flow of (Formula presented.) nanofluid moving across a curved surface. Moreover, mass suction is supposed through the stretching/shrinking surface. The initially developed model of partial differential equations is transformed into the ordinary ones assisted by suitable similarity variables. Subsequently, the ultimate nonlinear model of ordinary differential equations is solved with the help of a built-in function bvp4c package in MATLAB. Several graphical results are plotted to see the influence of various dimensionless parameters over the velocity, temperature, heat transfer, and friction drag. We found that there exists an escalation in temperature with increasing values of curvature, Eckert number, Hartmann number, and Biot number;however, the velocity profile declines with large curvature, ratio parameter, and high concentration of nanoparticles. It is also important to note that the friction drag rises with the mass suction, and reduces with vast curvature, whereas the rate of heat transfer improves with suction and Biot number but lowers with Eckert number and Hartmann number. © IMechE 2021.

关键词： Magnetohydrodynamics

Adsorption of Dibenzofuran by Modified Biochar Derived from Microwave Gasification

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SSRN

SSRN 2024年

作者： Ren, Jiyun Zhang, Yong Wang, Hui Huang, Xiaoming Jin, Xiaoling Zhang, Kai Li, Ruiyu Yang, Kaixuan Yue, Yang Deng, Lei Che, Defu State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China Yantai Longyuan Power Technology Co. Ltd Yantai264000 China West Pipeline Company of PipeChina Urumchi830000 China Jinggangshan Power Plant Huaneng Power International Inc Jiangxi 343009 China Shunde Institute of Inspection Guangdong Institute of Special Equipment Inspection and Research Foshan528300 China Shanghai Power Equipment Research Institute Co. Ltd. Shanghai200240 China

Dioxins, emanating from the waste incineration, constitutes an organic pollutant that poses considerable risks to human health and environment. In this study, the corn straw char (CSC) and oak char (OC) derived from the electric heating and microwave gasification, and the coconut-shell activated carbon (AC) are employed as absorbents for the adsorption of dibenzofuran (DBF, dioxins model compound). Characterization techniques including BET, X-ray CT, SEM-EDS, FTIR, and XPS are performed to identify the DBF adsorption mechanism on biochar. The results show that the biochar prepared by the microwave gasification has a more well-developed pore structure than that of the electric heating gasification. Higher porosity (16.94%) and lower mineral content (1.75%) are responsible for the effective adsorption of DBF onto AC. The adsorption capacity of CSC is proportional to the modified concentration of KOH. It is mainly ascribed to the decrement of carboxyl and lactone groups and the enhancement of alkaline functional groups on the biochar surface, which augments the hydrophobicity and π–π electron donor–acceptor (EDA) interaction. Instead, DBF adsorption capacity on the biochar is adversely affected by HNO3 modification. For all biochar samples, the corresponding maximum adsorption ratios are AC (87.11%) > KOH-modified CSC (77.14%) > unmodified CSC (49.11%) > unmodified OC (39.70%) > HNO3-modified CSC (36.09%). The adsorption mechanisms of DBF on the gasified biochar encompass pore filling, hydrophobicity, and π–π EDA interaction. A desirable adsorption capacity of DBF on the biochar prepared by the microwave gasification is attainable through augmenting the specific surface area while diminishing the oxygen-containing groups of the surface simultaneously. © 2024, The Authors. All rights reserved.

关键词： Potassium hydroxide

New technology of ionic liquid-based NH3/CO2 separation from melamine tail gas

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Green Chemical engineering 2020年第1期1卷 5-5页

作者： Shaojuan Zeng Haifeng Dong Yinge Bai Xiangping Zhang Suojiang Zhang CAS Key Laboratory of Green Process and EngineeringState Key Laboratory of Multiphase Complex SystemBeijing Key Laboratory of Ionic Liquids Clean ProcessInstitute of Process EngineeringChinese Academy of SciencesBeijing100190China

Melamine is an important industrial raw material,and widely used in the production of thermal insulation materials,adhesives,fiber materials and so ***,every 1 ton of melamine produced through decomposition and condensation reaction using urea generates about 2.2 tons of tail gas containing about 70%NH_(3)and 29%CO_(2).According to the phase diagram of NH_(3)–CO_(2)-AM(ammonium carbamate),NH_(3)and CO_(2)are easy to react and form AM solid under 63C at ambient pressure,which make it difficult to selective recovery of NH_(3).Water scrubbing is the mostly used technology in industries,but this method demands high energy consumption and discharges a large amount of NH_(3)-containg wastewater,which seriously restricts the sustainable development of industries.

关键词： insulation ambient restrict