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Increased neutron yield observed in indirect-drive double-shell experiments using high-energy x-ray preheat at the Shenguang laser facility

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Physical Review E 2024年第6期110卷 L063201-L063201页

作者： J. W. Li J. Yan C. S. Wu Z. S. Dai L. F. Wang J. Qi B. L. Chen X. Zhang G. Li Institute of Applied Physics and Computational Mathematics Beijing 100094 China Laser Fusion Research Center China Academy of Engineering Physics Mianyang 621900 China HEDPS Center for Applied Physics and Technology and College of Engineering Peking University Beijing 100871 China

In traditional indirect-drive double-shell inertial confinement fusion, high-energy x-ray preheat has always been identified as a major source of degrading implosion performance. However, a significant increase of the neutron yield is observed in ignition-like double-shell implosion experiments performed at Shenguang laser facility by intentionally utilizing high-energy x-ray preheat, mostly from the M-band. Permission of more M-band x-ray absorption inside the inner shell can both significantly mitigate the mix between the fuel and shell with a more stable Awtood number at the fuel-shell interface during the shell deceleration and slightly improve the symmetry of the imploding shell with a high entropy state of the shell, and the contribution outweighs the potential detriment to destabilizing the inner shell from the M-band preheat, which is consistent with radiation-hydrodynamics simulations and theoretical analysis. This novel understanding of the favorable impact of high-energy x-ray preheat on double-shell implosion could facilitate to achieve volumetric ignition and burn with high-Z shells.

关键词： Inertial confinement fusion

New-record-Tc and three-gap 2D superconductors with electronic and phononic topology: KB2C2

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arXiv 2024年

作者： Liu, Hao-Dong Fu, Xin-Peng Fu, Zhen-Guo Lu, Hong-Yan Zhang, Ping Institute of Applied Physics and Computational Mathematics National Key Laboratory of Computational Physics Beijing100088 China Graduate School China Academy of Engineering Physics Beijing100088 China School of Physics and Physical Engineering Qufu Normal University Qufu273165 China

Pursuing higher-temperature superconductors under ambient pressure continues to be a prominent topic in materials discovery. Isomorphic structures like MgB2 exhibit potential for conventional BCS-type superconductivity, but their transition temperatures (Tc) have remained below 100 K based on both experimental findings and theoretical predictions. In this study, two new two-dimensional (2D) superconductors with sandwich structures, KB2C2, featuring BC layers in AA and AB stacking configurations, are designed, whose Tc can exceed 112 K, setting a new record in 2D superconductors. The analyses suggest that electrons in σ-states covalent bonds and high-frequency E phonon modes dominated by the in-plane vibrations of B/C atoms are predominately responsible for electron-phonon coupling (EPC). An exciting robust three-gap superconducting nature stems from the strong and evident three-region distribution characteristic of electronic EPC parameters λelk . When biaxial tensile strain (BTS) is applied, their Tc are boosted above 153 K. The increase in Tc originates from the softening of optical E phonon modes around the Γ point and acoustic modes around the Q point, rather than an increase of electrons at Fermi level (EF) as observed in other similar systems. Thus, phonon plays a more beneficial role in the EPC of BTS cases, highlighting its significance as a medium in BCS superconductors. Moreover, we find KB2C2 exhibits interesting topological properties, spin antivortex, and Ising-type spin splitting. This is the first report of the coexistence of nontrivial topology and superconductivity with such a high Tc. Therefore, KB2C2 may offer promising sandwich structures to explore higher-Tc 2D superconductors, alongside present potential avenues for investigating fundamental quantum physics. © 2024, CC BY.

关键词： High temperature superconductors

AUTOAMG(θ): AN AUTO-TUNED AMG METHOD BASED ON DEEP LEARNING FOR STRONG THRESHOLD

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arXiv 2023年

作者： Zou, Haifeng Xu, Xiaowen Zhang, Chen-Song Mo, Zeyao Graduate School of China Academy of Engineering Physics China Academy of Engineering Physics China Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics China Academy of Mathematics and Systems Science Chinese Academy of Sciences China

Algebraic Multigrid (AMG) is one of the most used iterative algorithms for solving large sparse linear equations Ax = b. In AMG, the coarse grid is a key component that affects the efficiency of the algorithm, the construction of which relies on the strong threshold parameter θ. This parameter is generally chosen empirically, with a default value in many current AMG solvers of 0.25 for 2D problems and 0.5 for 3D problems. However, for many practical problems, the quality of the coarse grid and the efficiency of the AMG algorithm are sensitive to θ;the default value is rarely optimal, and sometimes is far from it. Therefore, how to choose a better θ is an important question. In this paper, we propose a deep learning based auto-tuning method, AutoAMG(θ) for multiscale sparse linear equations, which are widely used in practical problems. The method uses Graph Neural Networks (GNNs) to extract matrix features, and a Multilayer Perceptron (MLP) to build the mapping between matrix features and the optimal θ, which can adaptively output θ values for different matrices. Numerical experiments show that AutoAMG(θ) can achieve significant speedup compared to the default θ value. Copyright © 2023, The Authors. All rights reserved.

关键词： Linear equations

Fine-tune chiroptical activity in discrete chiral Au nanorods

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Nano Research 2022年第7期15卷 6574-6581页

作者： Guangchao Zheng Sulin Jiao Wei Zhang Shenli Wang Qinghua Zhang Lin Gu Weixiang Ye Junjun Li Xiaochen Ren Zhicheng Zhang Kwok-yin Wong School of Physics and Microelectronics Zhengzhou UniversityZhengzhou 450001China State Key Laboratory of Chemical Biology and Drug Discovery Department of Applied Biology and Chemical TechnologyThe Hong Kong Polytechnic UniversityKowloonHong KongChina Institute of Applied Physics and Computational Mathematics Beijing 100088China School of Food Science and Engineering Henan University of TechnologyZhengzhou 450001China Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China Department of Applied Physics School of ScienceHainan UniversityHaikou 570228China Tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of ChemistrySchool of ScienceTianjin University&Collaborative Innovation Center of Chemical Science and EngineeringTianjin 300072China

Accurate researches on the surface plasmon resonance(SPR)-based applications of chiral plasmonic metal nanoparticles(NPs)still remain a great ***,a series of chiral plasmonic metal NPs,e.g.,chiral Au nanorods(c-Au NRs),c-Au@Ag core–shell,and c-Au@TiO_(2) core–shell NRs,with different chiroptical activities have been *** circular dichroism(PCD)bands of c-Au NRs can be precisely tailored by tuning the longitudinal SPR(LSPR)and amount of Au NRs as ***,a shift of PCD bands within ultraviolet–visible–near infrared ray(UV–vis–NIR)region can also be achieved through the functionalization of a shell of another metal or ***,chirality transfer from c-Au core to Ag shell leads to new PCD bands at the near-UV *** tuning of PCD bands and chirality transfer are confirmed by our developed theoretical *** chiral Au NRs-based chiral plasmonic nanomaterials with tunable chiroptical activities will be helpful to understand the structure-direct PCD and to extend circularly polarized-based applications.

关键词： chiral Au nanorods(c-Au NRs) surface plasmon resonance optical activity chirality transfer

SCATTERING THEORY FOR THE DEFOCUSING 3D NLS IN THE EXTERIOR OF A STRICTLY CONVEX OBSTACLE

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arXiv 2024年

作者： Liu, Xuan Song, Yilin Zheng, Jiqiang School of Mathematics Hangzhou Normal University Hangzhou311121 China The Graduate School of China Academy of Engineering Physics Beijing100088 China Institute of Applied Physics and Computational Mathematics Beijing100088 China National Key Laboratory of Computational Physics Beijing100088 China

In this paper, we investigate the global well-posedness and scattering theory for the defocusing nonlinear Schrödinger equation iut + ∆Ωu = |u|αu in the exterior domain Ω of a smooth, compact and strictly convex obstacle in R3. It is conjectured that in Euclidean space, if the solution has a prior bound in the critical Sobolev space, that is, u ∈ L∞t (I;H‧xsc (R3)) with sc := 32 − α2 ∈ (0, 23 ), then u is global and scatters. In this paper, assuming that this conjecture holds, we prove that if u is a solution to the nonlinear Schrödinger equation in exterior domain Ω with Dirichlet boundary condition and satisfies u ∈ L∞t (I;H‧Dsc (Ω)) with sc ∈ ［2123 ）, then u is global and scatters. The proof of the main results relies on the concentration-compactness/rigidity argument of Kenig and Merle [Invent. Math. 166 (2006)]. The main difficulty is to construct minimal counterexamples when the scaling and translation invariance breakdown on Ω. To achieve this, two key ingredients are required. First, we adopt the approach of Killip, Visan, and Zhang [Amer. J. Math. 138 (2016)] to derive the linear profile decomposition for the linear propagator eit∆Ω in H‧ sc(Ω). The second ingredient is the embedding of the nonlinear profiles. More precisely, we need to demonstrate that nonlinear solutions in the limiting geometries, which exhibit global spacetime bounds, can be embedded back into Ω. Finally, to rule out the minimal counterexamples, we will establish long-time Strichartz estimates for the exterior domain NLS, along with spatially localized and frequency-localized Morawetz *** Codes 35Q55 Copyright © 2024, The Authors. All rights reserved.

关键词： Schrodinger equation

Physical properties of relativistic electron beam during long-range propagation in space plasma environment

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Chinese physics B 2021年第10期30卷 283-291页

作者： Bi-Xi Xue Jian-Hong Hao Qiang Zhao Fang Zhang Jie-Qing Fan Zhi-Wei Dong School of Electrical and Electronic Engineering Department North China Electric Power UniversityBeijing 102206China Institute of Applied Physics and Computational Mathematics Beijing 100094China

It is known that ion channel can effectively limit the radial expansion of an artificial electron beam during its longrange propagation in the space plasma *** prior studies discussed the focusing characteristics of the beam in the ion channel,but the establishment process and transient properties of the ion channel itself,which also plays a crucial role during the propagation of the relativistic electron beam in the plasma environment,were commonly *** this study,a series of two-dimensional(2D)particle-in-cell simulations is performed and an analytical model of ion channel oscillation is constructed according to the single-particle *** results showed that when the beam density is higher than the density of plasma environment,ion channel can be established and always continues to oscillate periodically over the entire *** factors,including the beam electron density,initial beam radius,and the plasma density can affect the oscillation properties of ion *** velocity of the beam oscillates synchronously with the ion channel and this phenomenon will finally develop into a two-stream instability which can seriously affect the effective transport for relativistic electron *** appropriate beam parameters based on various plasma environments may contribute to the improvement of the stability of ion ***,radial expansion of the beam can be limited by ion channel and a stable long-range propagation in terrestrial atmosphere may be achieved.

关键词： ion channel space plasma environment long-range propagation particle-in-cell(PIC)simulation

VAR-CLIP: Text-to-Image Generator with Visual Auto-Regressive Modeling

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arXiv 2024年

作者： Zhang, Qian Dai, Xiangzi Yang, Ninghua An, Xiang Feng, Ziyong Ren, Xingyu Institute of Applied Physics and Computational Mathematics China DeepGlint China Shanghai Jiao Tong University China

VAR is a new generation paradigm that employs’next-scale prediction’ as opposed to’next-token prediction’. This innovative transformation enables auto-regressive (AR) transformers to rapidly learn visual distributions and achieve robust generalization. However, the original VAR model is constrained to class-conditioned synthesis, relying solely on textual captions for guidance. In this paper, we introduce VAR-CLIP, a novel text-to-image model that integrates Visual Auto-Regressive techniques with the capabilities of CLIP. The VAR-CLIP framework encodes captions into text embeddings, which are then utilized as textual conditions for image generation. To facilitate training on extensive datasets, such as ImageNet, we have constructed a substantial image-text dataset leveraging BLIP2. Furthermore, we delve into the significance of word positioning within CLIP for the purpose of caption guidance. Extensive experiments confirm VAR-CLIP’s proficiency in generating fantasy images with high fidelity, textual congruence, and aesthetic excellence. Our project page are https://***/daixiangzi/VAR-CLIP Copyright © 2024, The Authors. All rights reserved.

关键词： Distribution transformers

Are there type-III multiferroics?

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arXiv 2025年

作者： Wang, Haojin Liu, Haitao Ye, Meng Li, Yuanchang Advanced Research Institute of Multidisciplinary Science Beijing Institute of Technology Beijing100081 China Institute of Applied Physics and Computational Mathematics Beijing100088 China National Key Laboratory of Computational Physics Beijing100088 China Graduate School of China Academy of Engineering Physics Beijing100193 China

Multiferroics are known to be classified into two types. However, type-I lacks sufficient magnetoelectric coupling and type-II lacks sufficient electric polarization, making both practically difficult. In this work, we explore the possibility of type-III multiferroics, where the origins of ferroelectricity and magnetism are highly intertwined but not causally related, with a combination of strong magnetoelectric coupling and large polarization. Our first-principles calculations predict that monolayer TiCdO4 is such a type-III ferroelectric-ferromagnetic multiferroics with both electronic and magnetic orders originating from competing electron populations on oxygen atoms. It shows an electric polarization of 50 µC/m2 while the maximum linear and quadratic magnetoelectric response are as high as 35000 ps/m and 1.59 × 10−14 s/A, respectively. Our study opens up new perspectives for the discovery and design of much-anticipated multiferroics that can be used for cross-modulation. © 2025, CC BY.

关键词： Ferroelectricity

Adaptive Multi-Resolution Method for 3D Reactive Flows with Level Set Front Capturing

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Communications in computational physics 2023年第3期33卷 849-883页

作者： Wenhua Ma Dongmi Luo Wenjun Ying Guoxi Ni Min Xiao Yibing Chen Institute of Applied Physics and Computational Mathematics Beijing 100094P.R.China College of Science China University of PetroleumBeijing 102249P.R.China School of Mathematical Sciences Shanghai Jiao Tong UniversityShanghai 200240P.R.China.

For compressible reactive flows with stiff source terms,a new block-based adaptive multi-resolution method coupled with the adaptive multi-resolution representation model for ZND detonation and a conservative front capturing method based on a level-set technique is *** simulating stiff reactive flows,underresolution in space and time can lead to incorrect propagation speeds of discontinuities,and numerical dissipation makes it impossible for traditional shock-capturing methods to locate the detonation *** solve these challenges,the proposed method leverages an adaptive multi-resolution representation model to separate the scales of the reaction from those of fluid dynamics,achieving both high-resolution solutions and high efficiency.A level set technique is used to capture the detonation front sharply and reduce errors due to the inaccurate prediction of detonation *** order to ensure conservation,a conservative modified finite volume scheme is implemented,and the front transition fluxes are calculated by considering a Riemann problem.A series of numerical examples of stiff detonation simulations are performed to illustrate that the present method can acquire the correct propagation speed and accurately capture the sharp detonation *** numerical results also validate the approach’s benefits and excellent performance.

关键词： Compressible reactive flows reactive Euler equations three-dimensional simulation adaptive multi-resolution level set method sharp front capturing.