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Charge equilibration of laser-accelerated carbon ions in a porous-structure foam target

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Physical Review A 2024年第4期109卷 042810-042810页

作者： Bubo Ma Jieru Ren Lirong Liu Wenqing Wei Benzheng Chen Shizheng Zhang Hao Xu Zhongmin Hu Fangfang Li Xing Wang Wenxuan Li Qiuyan Li Shuai Yin Jianhua Feng Xianming Zhou Yifang Gao Yuan Li Xiaohua Shi Jianxing Li Xueguang Ren Zhongfeng Xu Zhigang Deng Wei Qi Shaoyi Wang Quanping Fan Bo Cui Weiwu Wang Zongqiang Yuan Jian Teng Yuchi Wu Zhurong Cao Zongqing Zhao Yuqiu Gu Leifeng Cao Shaoping Zhu Rui Cheng Yu Lei Zhao Wang Zexian Zhou Guoqing Xiao Hongwei Zhao Dieter H. H. Hoffmann Weimin Zhou Yongtao Zhao MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter School of Science Xi'an Jiaotong University Xi'an 710049 China Science and Technology on Plasma Physics Laboratory Laser Fusion Research Center China Academy of Engineering Physics Mianyang 621900 China Advanced Materials Testing Technology Research Center Shenzhen University of Technology Shenzhen 518118 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China Graduate School China Academy of Engineering Physics Beijing 100088 China Institute of Modern Physics Chinese Academy of Sciences Lanzhou 710049 China

The equilibrium charge state distribution of laser-accelerated carbon ions traversing a tri-cellulose-acetate (TCA, C9H16O8) foam target was measured experimentally. The ions were generated through the target normal sheath acceleration mechanism. This allowed us to obtain the equilibrium charge state for a wide energy range near the maximum energy loss within a single laser shot. The foam had a porous structure with 2 mg/cm3 volume density, which is between the typical density of gas- and solid-state matter. We found that the measured average equilibrium charge states were significantly underestimated by theoretical models applicable for gas targets, while were in close agreement with both semiempirical formulas and rate equation predictions based on ion-solid interactions. The solid-density fiber filaments in the current foam structure were attributed and demonstrated. The target density effects, which increase the ionization probability through frequent collisions and decrease the electron capture probability, were proven to play an important role in the foam target. Since the foam targets are widely used in laser plasma interaction experiments, our findings are relevant for a broad range of applications.

关键词： Atomic & molecular collisions Beam dynamics Beam injection, extraction & transport Lasers Ions Low- & intermediate-energy accelerators Atomic Properties Ab initio molecular dynamics Bragg spectroscopy Inner-shell processes

Semi-implicit energy-preserving numerical schemes for stochastic wave equation via SAV approach

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arXiv 2022年

作者： Cui, Jianbo Hong, Jialin Sun, Liying Department of Applied Mathematics The Hong Kong Polytechnic University Hung Hom Hong Kong Institute of Computational Mathematics and Scientific/Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing100190 China Institute of Applied Physics and Computational Mathematics Beijing100094 China

In this paper, we propose and analyze semi-implicit numerical schemes for the stochastic wave equation (SWE) with general nonlinearity and multiplicative noise. These numerical schemes, called stochastic scalar auxiliary variable (SAV) schemes, are constructed by transforming the considered SWE into a higher dimensional stochastic system with a stochastic SAV. We prove that they can be solved explicitly and preserve the modified energy evolution law and the regularity structure of the original system. These structure-preserving properties are the keys to overcoming the mutual effect of the noise and nonlinearity. By proving new regularity estimates of the introduced SAV, we establish the strong convergence rate of stochastic SAV schemes and the further fully-discrete schemes with the finite element method in spatial direction. To the best of our knowledge, this is the first result on the construction and strong convergence of semi-implicit energy-preserving schemes for nonlinear SWE. © 2022, CC BY.

关键词： Stochastic systems

Node-line Dirac semimetal manipulated by Kondo mechanism in nonsymmorphic CePt2Si2

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arXiv 2022年

作者： Ma, Hao-Tian Ming, Xing Zheng, Xiao-Jun Wen, Jian-Feng Wang, Yue-Chao Liu, Yu Li, Huan College of Science Guilin University of Technology Guilin541004 China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing100088 China

Dirac node lines (DNLs) are characterized by Dirac-type linear crossings between valence and conduction bands along one-dimensional node lines in the Brillouin zone (BZ). Spin-orbit coupling (SOC) usually shifts the degeneracy at the crossings thus destroys DNLs, and so far the reported DNLs in a few materials are non-interacting type, making the search for robust interacting DNLs in real materials appealing. Here, via first-principle calculations, we reveal that Kondo interaction together with nonsymmorphic lattice symmetries can drive a robust interacting DNLs in a Kondo semimetal CePt2Si2, and the feature of DNLs can be significantly manipulated by Kondo behavior in different temperature regions. Based on the density function theory combining dynamical mean-field theory (DFT+DMFT), we predict a transition to Kondo-coherent state at coherent temperature Tcoh ≈ 80 K upon cooling, verified by temperature dependence of Ce-4f self-energy, Kondo resonance peak, magnetic susceptibility and momentum-resolved spectral. Below Tcoh, well-resolved narrow heavy-fermion bands emerge near the Fermi level, constructing clearly visualized interacting DNLs locating at the BZ boundary, in which the Dirac fermions have strongly enhanced effective mass and reduced velocity. In contrast, above a crossover temperature TKS ≈ 600 K, the destruction of local Kondo screening drives non-interacting DNLs which are comprised by light conduction electrons at the same location. These DNLs are protected by lattice nonsymmorphic symmetries thus robust under intrinsic strong SOC. Our proposal of DNLs which can be significantly manipulated according to Kondo behavior provides an unique realization of interacting Dirac semimetals in real strongly correlated materials, and serves as a convenient platform to investigate the effect of electronic correlations on topological materials. Copyright © 2022, The Authors. All rights reserved.

关键词： Density functional theory

High-resolution CMB bispectrum estimator with flexible modal bases

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Physical Review D 2023年第6期108卷 063504-063504页

作者： Wuhyun Sohn James R. Fergusson E. P. S. Shellard Korea Astronomy and Space Science Institute Daejeon 34055 South Korea Centre for Theoretical Cosmology Department of Applied Mathematics and Theoretical Physics University of Cambridge Cambridge CB3 0WA United Kingdom

We present a new independent pipeline for the Cosmic Microwave Background bispectrum estimation of primordial non-Gaussianity and release a public code for constraining bispectrum shapes of interest based on the Planck 2018 temperature and polarization data. The estimator combines the strengths of the conventional Komatsu-Spergel-Wandelt and modal estimators at the cost of increased computational complexity, which has been made manageable through intensive algorithmic and implementation optimization. We also detail some methodological advances in numerical integration over a tetrapyd—domain where the bispectrum is defined on—via new quadrature rules. The pipeline has been validated both internally and against Planck. As a proof-of-concept example, we constrain some highly oscillatory models that were out of reach in conventional analyses using a targeted basis with a fixed oscillation frequency, and no significant evidence for primordial non-Gaussianity of these shapes is found. The methodology and code developed in this work will be directly applicable to future surveys where we expect a notable boost in sensitivity.

关键词： Cosmic microwave background Cosmological parameters Inflation

Influence of clustering round magnetic nano-dots on magnetization reversal 9

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Influence of clustering round magnetic nano-dots on magnetiz...

9th International Conference on Mathematical Modeling in Physical sciences, IC-MSQUARE 2020

作者： Blachowicz, T. Ehrmann, A. Institute of Physics - Center for Science and Education Silesian University of Technology Gliwice44-100 Poland Faculty of Engineering and Mathematics Bielefeld University of Applied Sciences Bielefeld33619 Germany

Square and round magnetic nano-dots of varying dimensions exhibit a large amount of possible magnetization reversal processes, from domain wall nucleation and propagation to multi-vortex states. Clustering such single nano-dots, however, may strongly modify these magnetization reversal processes due to the interactions between neighboring particles. Here we thus investigate the difference between magnetization reversal processes in clusters of hexagonally arranged round nano-dots under different orientations of the external magnetic field in comparison with single particle behavior. © Published under licence by IOP Publishing Ltd.

关键词： Magnetization reversal

Direct Optimization of Fast-Ion Confinement in Stellarators

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arXiv 2023年

作者： Bindel, David Landreman, Matt Padidar, Misha Department of Computer Science Cornell University IthacaNY14850 United States Institute for Research in Electronics and Applied Physics University of Maryland College ParkMD20742 United States Center for Applied Mathematics Cornell University IthacaNY14850 United States

Confining energetic ions such as alpha particles is a prime concern in the design of stellarators. However, directly measuring alpha confinement through numerical simulation of guiding-center trajectories has been considered to be too computationally expensive and noisy to include in the design loop, and instead has been most often used only as a tool to assess stellarator designs post hoc. In its place, proxy metrics, simplified measures of confinement, have often been used to design configurations because they are computationally more tractable and have been shown to be effective. Despite the success of proxies, it is unclear what is being sacrificed by using them to design the device rather than relying on direct trajectory calculations. In this study, we optimize stellarator designs for improved alpha particle confinement without the use of proxy metrics. In particular, we numerically optimize an objective function that measures alpha particle losses by simulating alpha particle trajectories. While this method is computationally expensive, we find that it can be used successfully to generate configurations with low losses. © 2023, CC BY.

关键词： Trajectories

Identiﬁcation of lead-free Rb2AgBiX6 (X=Cl, Br, I) double halide perovskites for promising photovoltaic applications: First-principles investigations

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Physica B: Condensed Matter 2024年 695卷

作者： Rehman, Muhammad Awais Rehman, Zia Ur Usman, Muhammad Bano, N. Riaz, Muhammad Ali, Syed Mansoor Farid, Ahsan Institute of Physics University of Silesia ul 75 Pulku Piechoty 1 Chorzów41-500 Poland Department of Mathematics Namal University 30km Talagang Road Mianwali42250 Pakistan Department of Applied Mechanics School of Mathematics and Physics University of Science and Technology Beijing Beijing100083 China Department of Physics and Astronomy College of Science King Saud University P.O. BOX 2455 Riyadh11451 Saudi Arabia Institute of Physics The Islamia University of Bahawalpur 63100 Pakistan Department of Materials Physics and Chemistry School of Materials Science and Engineering University of Science and Technology Beijing Beijing100083 China

This study examines double halide perovskites Rb2AgBiX6 (X = Cl, Br, I) using first-principles calculations, revealing their potential for various applications. The compounds demonstrate mechanical and thermodynamic stability, with lattice parameters aligning closely with previous reports. These semiconducting materials exhibit energy band gaps of 1.72, 1.27, and 0.82 eV for Cl, Br, and I variants, respectively. Their optical properties show maximum absorption between 2.50 and 3.50 eV, with refractive indices of 2.00–2.50 eV. Mechanically, they display high Young's moduli (78.3–82.6 GPa) and ductile characteristics. The photovoltaic properties, including the Shockley-Queisser limit efficiency (SLME), calculated for a thickness range of 10−2 μm–102 μm, yield promising values of 26.04 %, 30.87 %, and 24.57 % for Rb2AgBiCl6, Rb2AgBiBr6, and Rb2AgBiI6, respectively, showcasing their favorable properties for photovoltaic applications. © 2024

关键词： Chlorine compounds

Protein engineering in the deep learning era

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mLife 2024年第4期3卷 477-491页

作者： Bingxin Zhou Yang Tan Yutong Hu Lirong Zheng Bozitao Zhong Liang Hong Institute of Natural Sciences Shanghai Jiao Tong UniversityShanghaiChina Shanghai National Center for Applied Mathematics(SJTU center) Shanghai Jiao Tong UniversityShanghaiChina School of Information Science and Engineering East China University of Science and TechnologyShanghaiChina Shanghai Artificial Intelligence Laboratory ShanghaiChina School of Electronic Information and Electrical Engineering Shanghai Jiao Tong UniversityShanghaiChina Department of Cell and Developmental Biology University of Michigan Medical SchoolAnn ArborMichiganUSA School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghaiChina Zhangjiang Institute for Advanced Study Shanghai Jiao Tong UniversityShanghaiChina

Advances in deep learning have significantly aided protein engineering in addressing challenges in industrial production,healthcare,and environmental *** review frames frequently researched problems in protein understanding and engineering from the perspective of deep *** provides a thorough discussion of representation methods for protein sequences and structures,along with general encoding pipelines that support both pre‐training and supervised learning *** summarize state‐of‐the‐art protein language models,geometric deep learning techniques,and the combination of distinct approaches to learning from multi‐modal biological ***,we outline common downstream tasks and relevant benchmark datasets for training and evaluating deep learning models,focusing on satisfying the particular needs of protein engineering applications,such as identifying mutation sites and predicting properties for candidates'virtual *** review offers biologists the latest tools for assisting their engineering projects while providing a clear and comprehensive guide for computer scientists to develop more powerful solutions by standardizing problem formulation and consolidating data *** research can foresee a deeper integration of the communities of biology and computer science,unleashing the full potential of deep learning in protein engineering and driving new scientific breakthroughs.

关键词： artificial intelligence geometric deep learning protein engineering protein language model synthetic biology

Understanding Trade-offs in Stellarator Design with Multi-objective Optimization

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arXiv 2023年

作者： Bindel, David Landreman, Matt Padidar, Misha Department of Computer Science Cornell University IthacaNY14853 United States Institute for Research in Electronics and Applied Physics University of Maryland College ParkMD20742 United States Center for Applied Mathematics Cornell University IthacaNY14853 United States

In designing stellarators, any design decision ultimately comes with a trade-off. Improvements in particle confinement, for instance, may increase the burden on engineers to build more complex coils, and the tightening of financial constraints may simplify the design and worsen some aspects of transport. Understanding trade-offs in stellarator designs is critical in designing high performance devices that satisfy the multitude of physical, engineering, and financial criteria. In this study we show how multi-objective optimization (MOO) can be used to investigate trade-offs and develop insight into the role of design parameters. We discuss the basics of MOO, as well as practical solution methods for solving MOO problems. We apply these methods to bring insight into the selection of two common design parameters: the aspect ratio of an ideal magnetohydrodynamic equilibrium, and the total length of the electromagnetic coils. © 2023, CC BY.

关键词： Multiobjective optimization