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An effective method to calculate the electron impact excitation cross sections of helium from ground state to a final channel in the whole energy region

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Chinese physics B 2023年第11期32卷 194-200页

作者：孙瑞曾德灵金锐韩小英高翔李家明 Key Laboratory for Laser Plasmas Ministry of EducationSchool of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China Collaborative Innovation Center of IFSA Shanghai Jiao Tong UniversityShanghai 200240China Institute of Applied Physics and Computational Mathematics Beijing 100088China Institute of Electron&Electronic Measurement Technology Shanghai Institute of Measurement and Testing TechnologyShanghai 201203China Max-Planck-Institut fur Kernphysik Saupfercheckweg 169117 HeidelbergGerman Department of Physics and Center for Atomic and Molecular Nanosciences Tsinghua UniversityBeijing 100084China

The electron impact excitation(EIE) cross sections of an atom/ion in the whole energy region are needed in many research fields, such as astrophysics studies, inertial confinement fusion researches and so on. In the present work, an effective method to calculate the EIE cross sections of an atom/ion in the whole energy region is presented. We use the EIE cross sections of helium as an illustration example. The optical forbidden 1^(1)S–n^(1)S(n = 2–4) and optical allowed 1^(1)S–n^(1)P(n = 2–4) excitation cross sections are calculated in the whole energy region using the scheme that combines the partial wave R-matrix method and the first Born approximation. The calculated cross sections are in good agreement with the available experimental measurements. Based on these accurate cross sections of our calculation, we find that the ratios between the accurate cross sections and Born cross sections are nearly the same for different excitation final states in the same channel. According to this interesting property, a universal correction function is proposed and given to calculate the accurate EIE cross sections with the same computational efforts of the widely used Born cross sections,which should be very useful in the related application fields. The datasets presented in this paper are openly available at https://***/10.57760/sciencedb.j00113.00142.

关键词： the electron impact excitation cross sections correction function helium the partial wave R-matrix plus the first Born approximation method

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Multi-phase-field simulation of austenite peritectic solidification based on a ferrite grain

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Chinese physics B 2021年第1期30卷 572-577页

作者： Chao Yang Jing Wang Junsheng Wang Yu Liu Guomin Han Haifeng Song Houbing Huang School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China Advanced Research Institute of Multidisciplinary Science Beijing Institute of TechnologyBeijing 100081China Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Software Center for High Performance Numerical Simulation China Academy of Engineering PhysicsBeijing 100088China

A multi-phase-field model is implemented to investigate the peritectic solidification of Fe-C alloy. The nucleation mode of austenite is based on the local driving force, and two different thicknesses of the primary austenite on the surface of the ferrite equiaxed crystal grain are used as the initial conditions. The simulation shows the multiple interactions of ferrite, austenite, and liquid phases, and the effects of carbon diffusion, which presents the non-equilibrium dynamic process during Fe-C peritectic solidification at the mesoscopic scale. This work not only reveals the influence of the austenite nucleation position, but also clarifies the formation mechanism of liquid phase channels and molten pools. Therefore, the present study contributes to the understanding of the micro-morphology and micro-segregation evolution mechanisms of Fe-C alloy during peritectic solidification.

关键词： multi-phase-field simulation morphology evolution peritectic solidification carbon diffusion Fe-C alloy

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GLOBAL WELL-POSEDNESS FOR ROUGH SOLUTIONS OF DEFOCUSING CUBIC NLS ON THREE DIMENSIONAL COMPACT MANIFOLDS

arXiv

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arXiv 2024年

作者： Chen, Qionglei Song, Yilin Zheng, Jiqiang Institute of Applied Physics and Computational Mathematics Beijing100088 China National Key Laboratory of Computational Physics Beijing100088 China The Graduate School China Academy of Engineering Physics Beijing100088 China

In this article, we investigate the global well-posedness for cubic nonlinear Schrödinger equation(NLS) i∂tu + ∆gu = |u|2 u posed on the three dimensional compact manifolds (M, g) with initial data u0 ∈ Hs(M) where (Formula Presented) for Zoll manifold and (Formula Presented) for the product of spheres S2 × S1. We utilize the multilinear eigenfunction estimate on compact manifold to treat the interaction of different frequencies, which is more complicated compared to the case of flat torus [23] and waveguide manifold [47]. Moreover, combining with the I-method adapted to the non-periodic case, bilinear Strichartz estimates along with the scale-invariant Lp linear Strichartz estimates, we partially obtain the similar result of [47] on non-flat compact manifold setting. As a consequence, we obtain the polynomial bounds of the Hs norm of solution u. © 2024, CC BY.

关键词： Eigenvalues and eigenfunctions

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Characteristics of Cold Plasma Jet Initiated by Non-Contact and Contact Pulse Voltage 16

Characteristics of Cold Plasma Jet Initiated by Non-Contact ...

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16th IEEE International Scientific and Technical Conference Actual Problems of Electronic Instrument Engineering, APEIE 2023

作者： Gugin, Pavel P. Milakhina, Elena V. Zakrevsky, Dmitry E. Laboratory of Power Gas Laser Rzhanov Institute of Semiconductor Physics SB RAS Laboratory of Computational Aerodynamics Khristianovich Institute of Theoretical and Applied Mechanics SB RAS Novosibirsk Russia Department of Electronic Devices Novosibirsk State Technical University Laboratory of Power Gas Laser Rzhanov Institute of Semiconductor Physics SB RAS Laboratory of Computational Aerodynamics Khristianovich Institute of Theoretical and Applied Mechanics SB RAS Novosibirsk Russia

ISBN: (纸本)9798350330885

In the paper, the characteristics of a cold atmospheric plasma jet generated by non-contact and contact methods of initiating a gas discharge with a pulsed voltage are investigated. The parameters of current detectabled in the contact zone of the plasma jet touching the object, depending on the amplitude and duration of unipolar positive pulses for contact and non-contact initiation of the discharge, have been studied. The frequency of touching of the plasma jet current with the object under different durations of initiating voltage pulses and pulse repetition frequencies has been investigated. The spectral analysis of the plasma jet interaction zone with object has been carried out. The modes providing the highest intensity of OH radical emission were determined. The temperature increment in the cold plasma jet interaction zone with the object at different parameters of voltage and speed of gas pumped through the device has been investigated. Comparative research of the characteristics of cold plasma jets initiated by contact and non-contact excitation by unipolar positive pulses has been carried out. It is established that the amplitude of the current registered on the object surface is several times higher for the plasma jet initiated by contact excitation of the gas medium. It is shown that at non-contact method of discharge ignition by unipolar positive pulses the frequency of current touching the object of influence matches with the repetition frequency of voltage pulses. © 2023 IEEE.

关键词： Plasma jets

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DYNAMICS OF THE COMBINED NONLINEAR SCHRÖDINGER EQUATION WITH INVERSE-SQUARE POTENTIAL

arXiv

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arXiv 2024年

作者： Ma, Zuyu Song, Yilin Zheng, Jiqiang 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

We consider the long-time dynamics of focusing energy-critical Schrödinger equation perturbed by the H1/2 -critical nonlinearity and with inverse-square potential(CNLSa) in dimensions d ∈ {3, 4, 5} (Equation Presented), (t, x) ∈ R × Rd, (CNLSa) where La = −∆ + a|x|−2 and the energy is below and equal to the threshold ma, which is given by the ground state Wa satisfying (Equation Presented) Wa. When the energy is below the threshold, we utilize the concentration-compactness argument as well as the variatonal analysis to characterize the scattering and blow-up region. When the energy is equal to the threshold, we use the modulation analysis associated to the equation (CNLSa) to classify the dynamics of Ha1-solution. In both regimes of scattering results, we do not need the radial assumption in d = 4, 5. Our result generalize the scattering results of [31–33] and [3] in the setting of standard combined NLS. © 2024, CC BY.

关键词： Ground state

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A Simulation System of Space Object Images for Space Situation Awareness 15

A Simulation System of Space Object Images for Space Situati...

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15th International Congress on Image and Signal Processing, BioMedical Engineering and Informatics, CISP-BMEI 2022

作者： Wen, Gaojin Xu, Yun Liu, Changhai Zhou, Ziwei Beijing Institute of Space Mechanics and Electricity Beijing Engineering Research Center of Aerial Intelligent Remote Sensing Equipment Beijing China Institute of Applied Physics and Computational Mathematics Laboratory of Computational Physics Beijing China Troop of 63768 Xian China

ISBN: (数字)9781665488877

ISBN: (纸本)9781665488877

With the rapid development of space situational awareness technology, more and more space-based observation equipment has been launched into space to sense various objects residing in space. To test the capabilities of these observation devices, many space object image simulation system have been developed to produce the input data for the test. This paper presents a space target simulation system, which can simulate the images obtained by observing space target objects from different continuously changing perspectives under different solar illumination conditions. The system is mainly composed of perspective motion modeling module, scene rendering module and image post-processing module. Data transfer between modules is carried out in the form of files, mainly to facilitate the integration of various physically-based scene rendering methods. The quality of the simulated images produced by this system is very high, which can provide a good data foundation for the research of space-based observation equipment detection, space-based target detection, identification and analysis technology. © 2022 IEEE.

关键词： Data transfer

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A New Nonspherical Oxidation Model of Metal Particles

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Journal of Thermal Science 2023年第2期32卷 812-821页

作者： ZHAO Weijie WANG Yan CUI Yanling WANG Baorui MA Dongjun WANG Yue Innovation Academy for Light-duty Gas Turbine Chinese Academy of SciencesBeijing 100190China Key Laboratory of Advanced Energy and Power Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China Advanced Gas Turbine Laboratory Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Institute of Applied Physics and Computational Mathematics Beijing 100094China

This paper analyzes the oxidation law of metal particles and proposes a new oxidation reaction rate model,based on measurements of thermogravimetric-mass spectrometer(TG-MS),X-ray diffractometer(XRD)and scanning electron microscope(SEM).The model is named EBM(egg broken model)with a formula of exponential *** to the model,the aluminum particles do not react in a spherical shape,but crack and the melted metal inside flows out to form a new nonspherical surface and the reaction rate is still determined by the surface *** model is verified with heating rates of 5℃/min,10℃/min and 25℃/min,and with particle size of 1–2μm,8–9μm and 20–22μ*** models are based on spherical hypothesis and the new model gives a different physical illustration to explain oxidation progress of metal *** new model gives an exponential law,which fits the experimental data well,and it may be useful to understand oxidation mechanism of metal particles.

关键词： metal particles nonspherical oxidation model exponential law

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Magnetic ground state of monolayer CeI2: Occupation matrix control and DFT+U calculations

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Physical Review B 2024年第22期110卷 224421-224421页

作者： Yue-Fei Hou Shujing Li Xinlong Yang Wei Jiang Qiuhao Wang Fawei Zheng Zhen-Guo Fu Ping Zhang Institute of Applied Physics and Computational Mathematics Beijing 100088 China Graduate School China Academy of Engineering Physics Beijing 100088 China College of Mathematics and Physics Beijing University of Chemical Technology Beijing 100029 China School of Physics Beijing Institute of Technology Beijing 100081 China National Key Laboratory of Computational Physics Beijing 100088 China School of Physics and Physical Engineering Qufu Normal University Qufu 273165 China

The magnetic ground state is crucial for applications of two-dimension magnets because it determines the fundamental magnetic properties of the material, such as magnetic order, magnetic transition temperature, and low-energy excitation of the spin waves. However, simulations of the magnetism of local-electron systems are challenging due to the existence of metastable states. In this study, occupation matrix control and density functional theory plus Hubbard's U calculations are applied to investigate the magnetic ground state of monolayer CeI2. Following the predicted ferromagnetic (FM) order, the FM ground state and the FM metastable states are identified and found to have different values for the magnetic parameters. Based on the calculated magnetic parameters of the FM ground state, the Curie temperature is estimated to be 128 K for monolayer CeI2. When spin-orbit coupling (SOC) is considered, the FM ground state is further confirmed to contain both off-plane and in-plane components of magnetization. SOC is shown to be essential for reasonably describing not only magnetic anisotropy but also the local electronic orbital state of monolayer CeI2.

关键词： Magnetic anisotropy

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Well-posedness and dynamics of fractional Fitz Hugh-Nagumo systems on R^(N) driven by nonlinear noise

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Science China mathematics 2021年第11期64卷 2395-2436页

作者： Renhai Wang Boling Guo Bixiang Wang Institute of Applied Physics and Computational Mathematics Beijing 100088China Department of Mathematics New Mexico Institute of Mining and TechnologySocorroNM 87801USA

This article is concerned with the well-posedness as well as long-term dynamics of a wide class of non-autonomous,non-local,fractional,stochastic Fitz Hugh-Nagumo systems driven by nonlinear noise defined on the entire space *** well-posedness is proved for the systems with polynomial drift terms of arbitrary order as well as locally Lipschitz nonlinear diffusion terms by utilizing the pathwise and mean square uniform *** mean random dynamical system generated by the solution operators is proved to possess a unique weak pullback mean random attractor in a Bochner *** existence of invariant measures is also established for the autonomous systems with globally Lipschitz continuous diffusion *** idea of uniform tail-estimates of the solutions in the appropriate spaces is employed to derive the tightness of a family of probability distributions of the solutions in order to overcome the non-compactness of the standard Sobolev embeddings on RNas well as the lack of smoothing effect on one component of the *** results of this paper are new even when the fractional Laplacian is replaced by the standard Laplacian.

关键词： fractional Fitz Hugh-Nagumo system weak pullback mean random attractor invariant measure nonlinear noise unbounded domain

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Full quantum time-dependent simulations for the two-body breakups of H2Ar2+ and N2Ar2+

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Physical Review A 2022年第1期106卷 012814-012814页

作者： Xiaoqing Hu Congcong Jia Ting Xu Yong Wu Jianguo Wang Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China HEDPS Center of Applied Physics and Technology Peking University Beijing 10084 China

We developed a full quantum time-dependent wave-packet evolution method to simulate the multibody breakups of polyatomic molecular ions. The interaction picture theory was used to propagate the wave packet, where the effects of strong and long-range interactions are considered by basis functions and the weak and short-range interactions are included in the perturbation term. In this method, the Coulomb interactions, polycentric interactions, vibration-rotation coupling of molecular fragments, and the rotation-rotation coupling between molecular fragment and parent molecule are considered accurately. Using this method, we simulate the two-body breakups of H2Ar2+ and N2Ar2+. The simulated results show that the ultrafast rotation of the molecular fragment generally exists in the breakup of the polyatomic molecular ion. For H2Ar2+, H2+ can rotate from an initial broad distribution around 35∘ and 145∘ to a narrow distribution around 75∘ and 105∘ within 30 fs. For N2Ar2+, the initial sine-shaped angular distribution (j = 0) shrinks to a narrow range (90∘±20∘) within 120 fs and then spreads to an approximately random distribution within 300 fs. Such ultrafast rotations are dominated by the polycentric interaction between fragments and impacted by the vibration-rotation and rotation-rotation couplings.

关键词： Atomic & molecular clusters Atomic & molecular structure Ultrafast phenomena

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