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Singularity structure simplification of hexahedral mesh via weighted ranking

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arXiv 2019年

作者： Xua, Gang Ling, Ran Zhang, Yongjie Jessica Xiao, Zhoufang Ji, Zhongping Rabczuk, Timon School of Computer Science and Technology Hangzhou Dianzi University Hangzhou310018 China Key Laboratory of Complex Systems Modeling and Simulation Ministry of Education Hangzhou310018 China Department of Mechanical Engineering Carnegie Mellon University United States Institute of Structural Mechanics Bauhaus-Universitat Weimar Germany

In this paper, we propose an improved singularity structure simplification method for hexahedral (hex) meshes using a weighted ranking approach. In previous work, the selection of to-be-collapsed base complex sheets/chords is only based on their thickness, which will introduce a few closed-loops and cause an early termination of simplification and a slow convergence rate. In this paper, a new weighted ranking function is proposed by combining the valence prediction function of local singularity structure, shape quality metric of elements and the width of base complex sheets/chords together. Adaptive refinement and local optimization are also introduced to improve the uniformity and aspect ratio of mesh elements. Compared to thickness ranking methods, our weighted ranking approach can yield a simpler singularity structure with fewer base-complex components, while achieving comparable Hausdorff distance ratio and better mesh quality. Comparisons on a hex-mesh dataset are performed to demonstrate the effectiveness of the proposed method. Copyright © 2019, The Authors. All rights reserved.

关键词： Aspect ratio

Influences of weak disorder on dynamical quantum phase transitions of anisotropic XY chain

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arXiv 2019年

作者： Cao, Kaiyuan Li, Wenwen Zhong, Ming Tong, Peiqing Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

In this paper, the effects of disorder on the dynamical quantum phase transitions (DQPTs) in the transverse-field anisotropic XY chain are studied by numerically calculating the Loschmidt echo after quench. We obtain the formula for calculating the Loschmidt echo of the inhomogeneous system in real space. By comparing the results with that of the homogeneous chain, we find that when the quench crosses the Ising transition, the small disorder will cause a new critical point. As the disorder increases, more critical points of the DQPTs will occur, constituting a critical region. In the quench across the anisotropic transition, the disorder will cause a critical region near the critical point, and the width of the critical region increases by the disordered strength. In the case of quench passing through two critical lines, the small disorder leads to the system to have three additional critical points. When the quench is in the ferromagnetic phase, the large disorder causes the two critical points of the homogeneous case to become a critical region. And for the quench in the paramagnetic phase, the DQPTs will disappear for large disorder. Copyright © 2019, The Authors. All rights reserved.

关键词： Phase transitions

The effects of KSEA interaction on the ground-state properties of spin chains in a transverse field

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arXiv 2019年

作者： Fu, Hao Zhong, Ming Tong, Peiqing Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

The effects of symmetric helical interaction which is called the Kaplan, Shekhtman, Entin-Wohlman, and Aharony (KSEA) interaction on the ground-state properties of three kinds of spin chains in a transverse field have been studied by means of correlation functions and chiral order parameter. We find that the anisotropic transition of XY chain in a transverse field (XY TF) disappears because of the KSEA interaction. For the other two chains, we find that the regions of gapless chiral phases in the parameter space induced by the DM or XZY -Y ZX type of three-site interaction are decreased gradually with increase of the strength of KSEA interaction. When it is larger than the coefficient of DM or XZY - Y ZX type of three-site interaction, the gapless chiral phases also disappear. Copyright © 2019, The Authors. All rights reserved.

关键词： Spin dynamics

A Metal–Sulfur–Carbon Catalyst Mimicking the Two-Component Architecture of Nitrogenase

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Angewandte Chemie 2024年第45期136卷

作者： Junkai Xia Jiawei Xu Prof. Bing Yu Xiao Liang Dr. Zhen Qiu Prof. Hao Li Prof. Huajun Feng Prof. Yongfu Li Prof. Yanjiang Cai Prof. Haiyan Wei Prof. Haitao Li Prof. Hai Xiang Dr. Zechao Zhuang Prof. Dingsheng Wang State Key Laboratory of Subtropical Silviculture Zhejiang A&F University 311300 Hangzhou P. R. China College of Environment and Resources College of Carbon Neutrality Zhejiang A&F University 311300 Hangzhou P. R. China Jiangsu Key Laboratory of Numerical Simulation of Large Scale Complex Systems and School of Chemistry and Materials Science Nanjing Normal University 210023 Nanjing China Department of Chemistry Tsinghua University 100084 Beijing P. R. China Advanced Institute for Materials Research (WPI-AIMR) Tohoku University 980-8577 Sendai Japan Institute for Energy Research Jiangsu University 212013 Zhenjiang P. R. China Department of Chemical Engineering Columbia University 10027 New York NY USA

The production of ammonia (NH 3 ) from nitrogen sources involves competitive adsorption of different intermediates and multiple electron and proton transfers, presenting grand challenges in catalyst design. In nature nitrogenases reduce dinitrogen to NH 3 using two component proteins, in which electrons and protons are delivered from Fe protein to the active site in MoFe protein for transfer to the bound N 2 . We draw inspiration from this structural enzymology, and design a two-component metal–sulfur–carbon (M−S−C) catalyst composed of sulfur-doped carbon-supported ruthenium (Ru) single atoms (SAs) and nanoparticles (NPs) for the electrochemical reduction of nitrate (NO 3 − ) to NH 3 . The catalyst demonstrates a remarkable NH 3 yield rate of ~37 mg L −1 h −1 and a Faradaic efficiency of ~97 % for over 200 hours, outperforming those consisting solely of SAs or NPs, and even surpassing most reported electrocatalysts. Our experimental and theoretical investigations reveal the critical role of Ru SAs with the coordination of S in promoting the formation of the HONO intermediate and the subsequent reduction reaction over the NP-surface nearby. Such process results in a more energetically accessible pathway for NO 3 − reduction on Ru NPs co-existing with SAs. This study proves a better understanding of how M−S−Cs act as a synthetic nitrogenase mimic during ammonia synthesis, and contributes to the future mechanism-based catalyst design.

关键词： nitrogenase metal–sulfur–carbon nitrate reduction reaction ammonia synthesis synergistic interactions

Semileptonic decays B/Bs → (D(∗), Ds(∗))lνl in the PQCD approach with the lattice QCD input

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arXiv 2019年

作者： Hu, Xue-Qing Jin, Su-Ping Xiao, Zhen-Jun Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

In this paper, we studied the semileptonic B/Bs → (D(∗),Ds(∗))lνl decays in the framework of the standard model (SM), by employing the perturbative QCD (PQCD) factorization formalism combining with the lattice QCD inputs of the relevant transition form factors. We calculated the branching ratios B(B(s) → D((s∗))lνl) with l = (e,µ.τ), the ratios of the branching ratios R(D(∗)) and R(Ds(∗)) and other physical observables Pτ(D((s∗))), FL(D(∗s)) and AFB(τ). The "PQCD+Lattice" predictions for B(B → D(∗)lνl) and R(D(∗)) do agree well with those currently available experimental measurements within the errors. For the ratios R(Ds) and R(Ds∗), the"PQCD+Lattice" predictions agree well with other known predictions. For both Pτ(D∗) and FL(D∗), our theoretical predictions agree well with the measured values within errors. Our theoretical predictions about the considered semileptonic B/Bs decays could be tested in the near future LHCb and the Belle II experiments. Copyright © 2019, The Authors. All rights reserved.

关键词： Quantum theory

Semileptonic decays Bc → (ηc, J/ψ)lν¯l in the "PQCD + Lattice" approach

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arXiv 2019年

In this paper, we studied the semileptonic decays Bc− → (ηc,J/ψ)l−ν¯l by employing the PQCD factorization approach, using the newly defined distribution amplitudes of the Bc meson and the new kind of parametrization for extrapolation of the form factors, and also taking into account the lattice QCD results about the relevant form factors at several points. We found the following main results: (a) the PQCD predictions for the branching ratios of Bc → (ηc,J/ψ)lν¯ decays will become a little smaller by about (5 − 16)% when the lattice input are taken into account in the extrapolation of the relevant form factors;(b) the PQCD predictions for the ratio Rηc,J/ψ and the longitudinal polarization Pτ are Rηc = 0.34±0.01,RJ/ψ = 0.28±0.01, Pτ(ηc) = 0.37±0.01 and Pτ(J/ψ) = −0.55±0.01;and (c) after the inclusion of the lattice input the theoretical predictions changed slightly: Rηc = 0.31 ± 0.01, RJ/ψ = 0.27 ± 0.01, Pτ(ηc) = 0.36 ± 0.01 and Pτ(J/ψ) = −0.53 ± 0.01. The theoretical predictions for RJ/ψ agree with the measured one within errors, and other predictions could be tested in the near future LHCb experiments. Copyright © 2019, The Authors. All rights reserved.

关键词： Forecasting

QQs¯s¯ tetraquarks in the chiral quark model

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Physical Review D 2020年第5期102卷 054023-054023页

作者： Gang Yang Jialun Ping Jorge Segovia Department of Physics Zhejiang Normal University Jinhua 321004 China Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 People’s Republic of China Departamento de Sistemas Físicos Químicos y Naturales Universidad Pablo de Olavide E-41013 Sevilla Spain

The low-lying S-wave QQs¯s¯ (Q=c, b) tetraquark states with I(JP)=0(0+), 0(1+) and 0(2+) are systematically investigated in the framework of complex scaling range of chiral quark model. Every structure including meson-meson, diquark-antidiquark and K-type configurations, and all possible color channels in four-body sector are considered by means of a commonly extended variational approach, Gaussian expansion method. Within the studied mass region, several narrow and wide resonance states are obtained for ccs¯s¯ and bbs¯s¯ tetraquarks with I(JP)=0(0+) and 0(2+). Meanwhile, narrow resonances for cbs¯s¯ tetraquarks are also found in I(JP)=0(0+), 0(1+) and 0(2+) states. The possibility of finding tetraquark structures with masses ∼0.6 GeV above the non-interacting hadron-hadron thresholds (and not close to them) is a feature related with the absence of the one-pion exchange interaction in the QQs¯s¯ sector and thus it could deserve experimental confirmation.

关键词： Particle interactions Quantum chromodynamics Quark model Strong interaction

Superexponential diffusion in nonlinear non-Hermitian systems

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Physical Review A 2020年第6期102卷 062213-062213页

作者： Wen-Lei Zhao Longwen Zhou Jie Liu Peiqing Tong Kaiqian Huang School of Science Jiangxi University of Science and Technology Ganzhou 341000 China Department of Physics College of Information Science and Engineering Ocean University of China Qingdao 266100 China Graduate School of China Academy of Engineering Physics Beijing 100193 China CAPT HEDPS and IFSA Collaborative Innovation Center of the Ministry of Education Peking University Beijing 100871 China Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing 210023 China Jiangsu Provincial Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing Jiangsu 210023 China Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials SPTE South China Normal University Guangzhou 510006 China

We investigate the quantum diffusion of a periodically kicked particle subjected to both nonlinearity-induced self-interactions and PT-symmetric potentials. We find that, due to the interplay between the nonlinearity and non-Hermiticity, the expectation value of the mean square of momentum scales with time in a superexponential form 〈p2(t)〉∝exp[βexp(αt)], which is faster than any known rates of quantum diffusion. In the PT-symmetry-breaking phase, the intensity of a state increases exponentially with time, leading to the exponential growth of the interaction strength. The feedback of the intensity-dependent nonlinearity further turns the interaction energy into the kinetic energy, resulting in a superexponential growth of the mean energy. These theoretical predictions are in good agreement with numerical simulations in a PT-symmetric nonlinear kicked particle. Our discovery establishes a mechanism of diffusion in interacting and dissipative quantum systems. Important implications and possible experimental observations are discussed.

关键词： Anderson localization Atomic, optical & lattice clocks Diffusion Nonlinear optics Quantum transport Spatiotemporal chaos Wave chaos

Mass- and energy-preserving exponential Runge-Kutta methods for the nonlinear Schrödinger equation

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arXiv 2020年

作者： Cui, Jin Xu, Zhuangzhi Wang, Yushun Jiang, Chaolong Department of Basic Sciences Nanjing Vocational College of Information Technology Nanjing210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems School of Mathematical Sciences Nanjing Normal University Nanjing210023 China Department of Mathematics College of Liberal Arts and Science National University of Defense Technology Changsha410073 China School of Statistics and Mathematics Yunnan University of Finance and Economics Kunming650221 China

In this paper, a family of arbitrarily high-order structure-preserving exponential Runge-Kutta methods is developed for the nonlinear Schrödinger equation by combing the scalar auxiliary variable approach and the exponential Runge-Kutta method. By introducing an auxiliary variable, we first transform the original model into an equivalent system which admits both mass and modified energy. Then applying the Lawson method and the symplectic Runge-Kutta method in time, we derive a class of mass- and energy-conserving time-discrete schemes. Numerical experiments are addressed to demonstrate the accuracy and effectiveness of the newly proposed schemes. Copyright © 2020, The Authors. All rights reserved.

关键词： Runge Kutta methods