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Unveiling phonon frequency-dependent mechanism of heat transport across stacking fault in silicon carbide

Chinese physics B 2023年第9期32卷 373-380页

作者：王甫孙彦东邹宇徐贲付宝勤 Key Laboratory of Radiation Physics and Technology of the Ministry of Education Institute of Nuclear Science and TechnologySichuan UniversityChengdu 610064China Graduate School China Academy of Engineering PhysicsBeijing 100193China

Stacking faults(SFs)are often present in silicon carbide(SiC)and affect its thermal and heat-transport ***,it is unclear how SFs influence thermal *** non-equilibrium molecular dynamics and lattice dynamics simulations,we studied phonon transport in SiC materials with an *** to perfect SiC materials,the SF can reduce thermal *** is caused by the additional interface thermal resistance(ITR)of SF,which is difficult to capture by the previous phenomenological *** analyzing the spectral heat flux,we find that SF reduces the contribution of low-frequency(7.5 THz-12 THz)phonons to the heat flux,which can be attributed to SF reducing the phonon lifetime and group velocity,especially in the low-frequency *** SF hinders phonon transport and results in an effective interface thermal resistance around the *** results provide insight into the microscopic mechanism of the effect of defects on heat transport and have guiding significance for the regulation of the thermal conductivity of materials.

关键词： silicon carbide stacking fault thermal conductivity interface thermal resistance phonon transport spectral heat flux

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Effect of laser focus in two-color synthesized waveform on generation of soft x-ray high harmonics

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Chinese physics B 2023年第1期32卷 319-326页

作者：陈炎波李保昌李胥红唐翔宇张弛金成 Department of Applied Physics Nanjing University of Science and TechnologyNanjing 210094China MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing Nanjing University of Science and TechnologyNanjing 210094China

Synthesis of multi-color laser pulses has been developed as a promising way to improve low conversion efficiency of high-order harmonic generation(HHG). Here we systematically study the effect of laser focus in a two-color waveform on generation of macroscopic HHG in soft x-rays. We find that the dependence of HHG yields on laser focus at low or high gas pressure is sensitive to the characteristics of single-atom harmonic response, in which “short”-or “long”-trajectory emissions can be selectively controlled by changing the waveform of two-color synthesized laser pulse. We uncover the phase-matching mechanism of HHG in the gas medium by examining the propagation of the two-color waveform and the evolution of time-frequency emissions of high-harmonic field. We further reveal that the nonlinear effects, such as geometric phase, atomic dispersion, and plasma defocusing, are responsible for modification of two-color waveform upon propagation. This work can be used to find better macroscopic conditions for generating soft x-ray HHG by employing two-color optimized waveforms.

关键词： high-order harmonic generation two-color waveform soft x-rays macroscopic propagation laser focus

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Ion and electron motions in the outer electron diffusion region of collisionless magnetic reconnection

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Earth and Planetary physics 2024年第3期8卷 472-478页

作者： Cong Chang QuanMing Lu San Lu Kai Huang RongSheng Wang Deep Space Exploration Laboratory School of Earth and Space SciencesUniversity of Science and Technology of ChinaHefei 230026China Chinese Academy of Sciences(CAS)Center for Excellence in Comparative Planetology CAS Key Laboratory of Geospace EnvironmentHefei 230026China Collaborative Innovation Center of Astronautical Science and Technology Harbin 150001China

Two-dimensional particle-in-cell simulations are performed to study the coupling between ion and electron motions in collisionless magnetic *** electron diffusion region(EDR),where the electron motions are demagnetized,is found to have a two-layer structure:an inner EDR near the reconnection site and an outer EDR that is elongated to nearly 10 ion inertial lengths in the outflow *** the inner EDR,the speed of the electron outflow increases when the electrons move away from the X *** the outer EDR,the speed of the electron outflow first increases and then decreases until the electrons reach the boundary of the outer *** the boundary of the outer EDR,the magnetic field piles up and forms a depolarization *** the perspective of the fluid,a force analysis on the formation of electron and ion outflows has also been *** the X line,the electrons are accelerated by the reconnection electric field in the out-of-plane *** the electrons move away from the X line,we find that the Lorentz force converts the direction of the accelerated electrons to the x direction,forming an electron *** electric field forces and electron gradient forces tend to drag the electron *** acceleration along the x direction is caused by the Lorentz force,whereas the pressure gradient force tends to decelerate the ion *** these two terms are important,their effects on ions are almost *** Hall electric field force does positive work on ions and is not *** ions are continuously accelerated,and the ion and electron outflow velocities are almost the same near the depolarization front.

关键词： collisionless magnetic reconnection electron diffusion region force analysis particle-in-cell simulation

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A refined Monte Carlo code for low-energy electron emission from gold material irradiated with sub-keV electrons

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Nuclear science and Techniques 2023年第4期34卷 79-92页

作者： Li-Heng Zhou Shui-Yan Cao Tao Sun Yun-Long Wang Jun Ma Department of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 211106China College of Physics MIIT Key Laboratory of Aerospace Information Materials and PhysicsNanjing University of Aeronautics and AstronauticsNanjing 211106China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230026China

Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.

关键词： Monte Carlo code Secondary electron emission Low-energy electrons

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Exploring Lifshitz transition and superconductivity in 3R-NbS_(2) under pressure

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Chinese physics B 2025年第3期34卷 161-166页

作者： Kun Chen Xindeng Lv Simin Li Yanping Huang Tian Cui Institute of High Pressure Physics School of Physical Science and TechnologyNingbo UniversityNingbo 315211China State Key Laboratory of Superhard Materials College of PhysicsJilin UniversityChangchun 130012China

The interplay between electronic topological phase transitions and superconductivity in the field of condensed matter physics has consistently captivated *** we have succeeded in modulating the Lifshitz transition by pressure and realized *** 25.7 GPa,superconductivity with a transition temperature of 1.9 K has been observed in 3R-NbS_(2).The Hall coefficient changes from negative to positive at 14 GPa,indicating a Lifshitz transition in 3R-NbS_(2),and the carrier concentration continues to increase with increasing pressure.X-ray diffraction results indicate that the appearance of superconductivity cannot be attributable to structural *** on theoretical calculations,the emergence of a new band is attributed to the Lifshitz transition and the new band coincides with the Fermi surface at the pressure of 30 *** findings provide new insights into the relationship between the Lifshitz transition and superconductivity.

关键词： high pressure superconductivity Lifshitz transition 3R-NbS_(2)

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Theoretical perspectives on the reduction of Pu(Ⅳ)and Np(Ⅵ)by methylhydrazine in HNO_(3)solution:Implications for Np/Pu separation

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Chinese Chemical Letters 2024年第7期35卷 306-312页

作者： Xiaobo Li Qunyan Wu Congzhi Wang Jianhui Lan Meng Zhang Weiqun Shi Fundamental Science on Nuclear Safety and Simulation Technology Laboratory College of Nuclear Science and TechnologyHarbin Engineering UniversityHarbin 150001China Laboratory of Nuclear Energy Chemistry Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

Effective adjustment and control of the oxidation state of plutonium(Pu)and neptunium(Np)is an indispensable component of Np/Pu separation in spent nuclear fuel *** hydrazine derivatives including methylhydrazine(CH_(3)N_(2)H_(3))effectively achieves the reduction of Np(Ⅵ)to Np(V)without reducing Pu(Ⅳ).Herein,we explored the reduction mechanisms of Pu(Ⅳ)and Np(Ⅵ)by CH_(3)N_(2)H_(3)in HNO_(3)solution using scalar-relativistic density functional *** elucidated the difference in the reduction mechanism between Np(Ⅵ)and Pu(Ⅳ)ions by CH_(3)N_(2)H_(3).The energy barrier for the reduction of[NpⅥO_(2)(H_(2)O)_(5)]^(2+)and[NpⅥO_(2)(NO_(3))(H_(2)O)_(3)]^(+)by CH_(3)N_(2)H_(3)is largely different due to the coordination of nitrate ***,the energy barrier of the reduction of[NpⅥO_(2)(H_(2)O)_(5)]^(2+)is apparently lower than that of[PuⅣ(NO_(3))_(2)(H_(2)O)_(7)]^(2+),which is in line with the experimental *** results of Mayer bond order and localized molecular orbitals clarify the structural evolution of the reaction *** of the spin density demonstrates that the first Np(Ⅵ)and Pu(Ⅳ)reduction belongs to the outer-sphere electron transfer and the second Np(Ⅵ)and Pu(Ⅳ)reduction is the hydrogen *** study explains theoretically why CH_(3)N_(2)H_(3)reduces Np(Ⅵ)but not Pu(Ⅳ),and helps to design promising reductants for the Np/Pu separation in spent nuclear fuel reprocessing.

关键词： Neptunium Plutonium Methylhydrazine Reduction mechanism Np/Pu separation

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Adsorption dynamics of double-stranded DNA on a graphene oxide surface with both large unoxidized and oxidized regions

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Chinese physics B 2023年第1期32卷 598-605页

作者：吴梦娇马慧姝方海平阳丽雷晓玲 College of Physics Science and Technology Guangxi Normal UniversityGuilin 541004China Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology Shanghai Institute of Applied PhysicsChinese Academy of SciencesShanghai 201800China Changzhou Vocational Institute of Mechatronic Technology Professional Basic DepartmentChangzhou 213164China School of Physics East China University of Science and TechnologyShanghai 200237China

The adsorption dynamics of double-stranded DNA(dsDNA)molecules on a graphene oxide(GO)surface are important for applications of DNA/GO functional structures in biosensors,biomedicine and materials *** this work,molecular dynamics simulations were used to examine the adsorption of different length dsDNA molecules(from 4 bp to24 bp)on the GO *** dsDNA molecules could be adsorbed on the GO surface through the terminal bases and stand on the GO *** short dsDNA(4 bp)molecules,the double-helix structure was partially or totally broken and the adsorption dynamics was affected by the structural fluctuation of short dsDNA and the distribution of the oxidized groups on the GO *** long dsDNA molecules(from 8 bp to 24 bp)adsorption is *** nonlinear fitting of the contact angle between the axis of the dsDNA molecule and the GO surface,we found that a dsDNA molecule adsorbed on a GO surface has the chance of orienting parallel to the GO surface if the length of the dsDNA molecule is longer than 54 *** attributed this behavior to the flexibility of dsDNA *** increasing length,the flexibility of dsDNA molecules also increases,and this increasing flexibility gives an adsorbed dsDNA molecule more chance of reaching the GO surface with the free *** work provides a whole picture of adsorption of dsDNA molecules on the GO surface and should be of benefit for the design of DNA/GO based biosensors.

关键词： double-strand DNA(dsDNA) molecular dynamics simulation adsorption dynamic graphene oxide

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Dynamic Event-Triggered Consensus Control for Input Constrained Multi-Agent Systems With a Designable Minimum Inter-Event Time

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IEEE/CAA Journal of Automatica Sinica 2024年第3期11卷 649-660页

作者： Meilin Li Yue Long Tieshan Li Hongjing Liang C.L.Philip Chen the School of Automation Engineering University of Electronic Science and Technology of ChinaChengdu 611731China IEEE the Yangtze Delta Region Institute University of Electronic Science and Technology of ChinaHuzhou 313000 the Laboratory of Electromagnetic Space Cognition and Intelligent Control Beijing 100089China the School of Computer Science and Engineering South China University of TechnologyGuangzhou 510006

This paper investigates the consensus control of multi-agent systems(MASs) with constrained input using the dynamic event-triggered mechanism(ETM).Consider the MASs with small-scale networks where a centralized dynamic ETM with global information of the MASs is first ***,a distributed dynamic ETM which only uses local information is developed for the MASs with large-scale *** is shown that the semi-global consensus of the MASs can be achieved by the designed bounded control protocol where the Zeno phenomenon is eliminated by a designable minimum inter-event *** addition,it is easier to find a trade-off between the convergence rate and the minimum inter-event time by an adjustable ***,the results are extended to regional consensus of the MASs with the bounded control *** simulations show the effectiveness of the proposed approach.

关键词： Constrained input designable minimum inter-event time directed communication topology dynamic event-triggered mechanism MASs consensus control

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Quantum State-Resolved Nonadiabatic Dynamics of the H+NaF→Na+HF Reaction

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Chinese physics Letters 2024年第3期41卷 152-160页

作者：毛叶陈航航杨紫江布仁巴雅尔陈茂笃 Key Laboratory of Materials Modification by Laser Electronand Ion Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024China School of Science Shenyang University of TechnologyShenyang 110870China

The H+NaF reaction is investigated at the quantum state-resolved level using the time-dependent wavepacket method based on a set of accurate diabatic potential energy *** structures in the total reaction probability i... 详细信息

关键词： complex. adiabatic quantum

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Aberration compensation design method of freeform reflection systems based on generalized aberration theory with series expansion

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Optics Express 2025年第10期33卷 20664-20681页

作者： Qian, Zhuang Ji, Huiru Fan, Rundong Tan, Hao Mo, Yan Ma, Donglin School of Optical and Electronic Information Wuhan National Laboratory of Optoelectronics Huazhong University of Science and Technology Wuhan430074 China National Gravitation Laboratory MOE Key Laboratory of Fundamental Physical Quantities Measurement School of Physics Huazhong University of Science and Technology Wuhan430074 China Shenzhen Huazhong University of Science and Technology Shenzhen518057 China

With the growing demand for high-performance, miniaturized, and lightweight optical systems, off-axis reflective configurations incorporating freeform surfaces have emerged as crucial solutions for reconciling imaging quality with system compactness. However, the intricate mathematical representations and non-rotational symmetry inherent in freeform surfaces present substantial challenges to conventional design methodologies, necessitating innovative direct design approaches. To address these limitations, this paper proposes an advanced aberration compensation method (ACM) rooted in generalized aberration theory (GAT) with series expansion, enabling balanced full-field performance. Distinct from the traditional coefficient minimization method (CMM) that independently minimizes aberration coefficients at individual orders, ACM strategically exploits cross-order aberration compensation through synergistic interactions between lower- and higher-order aberrations. This leads to enhanced full-field imaging performance and better adaptability to asymmetric field layouts. The method is demonstrated on two representative three-mirror anastigmat (TMA) systems: a field-offset zig-zag configuration and a compact circular layout with a small F-number. In both cases, ACM achieves more balanced aberration correction, improved MTF performance, and acceptable computation time increases (under 10%) compared to CMM. These results validate ACM as a promising tool for the efficient and accurate design of freeform optical systems in future advanced applications. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Aberrations

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