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Analytical solutions of equatorial geodesic motion in Kerr spacetime

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Chinese physics C 2024年第4期48卷 222-239页

作者：刘岩孙兵 department of physics Yantai UniversityYantai 264005China department of Basic Courses Beijing University of AgricultureBeijing 102206China CAS Key Laboratory of Theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China

The study of Kerr geodesics has a long history,particularly for those occurring within the equatorial plane,which are generally ***,when compared with the classification introduced by one of the authors[***.D 105,024075(2022)],it becomes apparent that certain classes of geodesics,such as trapped orbits,still lack analytical ***,in this study,we provide explicit analytical solutions for equatorial timelike geodesics in Kerr spacetime,including solutions of trapped orbits,which capture the characteristics of special geodesics,such as the positions and conserved quantities of circular,bound,and deflecting ***,we determine the precise location at which retrograde orbits undergo a transition from counter-rotating to prograde motion due to the strong gravitational effects near a rotating black ***,the trajectory remains prograde for orbits with negative energy despite the negative angular ***,we investigate the intriguing phenomenon of deflecting orbits exhibiting an increased number of revolutions around the black hole as the turning point approaches the turning point of the trapped ***,we find that only prograde marginal deflecting geodesics are capable of traversing through the *** summary,our findings present explicit solutions for equatorial timelike geodesics and offer insights into the dynamics of particle motion in the vicinity of a rotating black hole.

关键词： geodesic motion analytical solutions equatorial plane Kerr spacetime

Structure,ferroelectric,and enhanced fatigue properties of sol–gel-processed new Bi-based perovskite thin films of Bi(Cu_(1/2)Ti_(1/2))O_(3)–PbTiO_(3)

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Chinese physics B 2024年第5期33卷 608-615页

作者：宋伟宾席国强潘昭刘锦叶旭斌刘哲宏王潇单鹏飞张林兴鲁年鹏樊龙龙秦晓梅龙有文 department of physics Shanghai Normal UniversityShanghai 200234China Beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China institute for Advanced Materials Technology University of Science and Technology BeijingBeijing 100083China Songshan Lake Materials Laboratory Dongguan 523808China institute of High Energy physics Chinese Academy of SciencesBeijing 100049China

Bi-based perovskite ferroelectric thin films have wide applications in electronic devices due to their excellent ferroelectric *** Bi-based perovskite thin films Bi(Cu_(1/2)Ti_(1/2))O_(3)–PbTiO_(3)(BCT–PT) are deposited on Pt(111)/Ti/SiO_(2)/Si substrates in the present study by the traditional sol–gel *** structures and related ferroelectric and fatigue characteristics are studied *** BCT–PT thin films exhibit good crystallization within the phase-pure perovskite structure,besides,they have a predominant(100) orientation together with a dense and homogeneous *** remnant polarization(2P_(r)) values at 30 μC/cm^(2) and 16 μC/cm^(2) are observed in 0.1BCT–0.9PT and 0.2BCT–0.8PT thin films,*** intriguingly,although the polarization values are not so high,0.2BCT–0.8PT thin films show outstanding polarization fatigue properties,with a high switchable polarization of 93.6% of the starting values after 10^(8) cycles,indicating promising applications in ferroelectric memories.

关键词： ferroelectric thin films perovskite PbTiO_(3)-BiMeO_(3)

Ionizing terahertz waves with 260 MV/cm from scalable optical rectification

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Light(Science & Applications) 2024年第6期13卷 1075-1087页

作者： Hyeongmun Kim Chul Kang Dogeun Jang Yulan Roh Sang Hwa Lee Joong Wook Lee Jae Hee Sung Seong Ku Lee Ki-Yong Kim Advanced Photonics Research institute GISTGwangju61005Korea department of physics and Optoelectronics Convergence Research Center Chonnam National UniversityGwangju61186Korea Pohang Accelerator Laboratory POSTECHPohang37673Korea Center for Relativistic Laser Science Institute for Basic ScienceGwangju61005Korea institute for Research in Electronics and Applied physics Department of PhysicsUniversity of MarylandCollege ParkMaryland20742USA

Terahertz(THz)waves,known as non-ionizing radiation owing to their low photon energies,can actually ionize atoms and molecules when a sufficiently large number of THz photons are concentrated in time and ***,we demonstrate the generation of ionizing,multicycle,15-THz waves emitted from large-area lithium niobate crystals via phase-matched optical rectification of 150-terawatt laser pulses.A complete characterization of the generated THz waves in energy,pulse duration,and focal spot size shows that the field strength can reach up to 260 megavolts per *** particular,a single-shot THz interferometer is employed to measure the THz pulse duration and spectrum with complementary numerical *** intense THz pulses are irradiated onto various solid targets to demonstrate THz-induced tunneling ionization and plasma *** study also discusses the potential of nonperturbative THz-driven ionization in gases,which will open up new opportunities,including nonlinear and relativistic THz physics in plasma.

关键词： optical interferometer matched

Reconstructing coherent dynamics of bound states induced by strong attosecond XUV pulses

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Chinese Optics Letters 2024年第2期22卷 56-63页

作者：贾利娟刘明清王新强徐龙闫培光姜维超傅立斌 institute of Quantum Precision Measurement College of Physics and Optoelectronic EngineeringShenzhen UniversityShenzhen 518060China department of physics Xiamen UniversityXiamen 361005China Graduate School of China Academy of Engineering physics Beijing 100193China

We propose a scheme that utilizes weak-field-induced quantum beats to investigate the electronic coherences of atoms driven by a strong attosecond extreme ultraviolet(XUV)*** technique involves using a strong XUV pump pulse to excite and ionize atoms and a time-delayed weak short pulse to probe the photoelectron *** theoretical analysis demonstrates that the information regarding the bound states,initiated by the strong pump pulse,can be precisely reconstructed from the weak-field-induced quantum beat *** examine this scheme,we apply it to the attosecond XUV laser-induced ionization of hydrogen atoms by solving a three-dimensional time-dependent Schr?dinger *** work provides an essential reference for reconstructing the ultrafast dynamics of bound states induced by strong XUV attosecond pulses.

关键词： attosecond pulse bound-state dynamics quantum beats

Terahertz toroidal dipole metamaterial sensors for detection of aflatoxin B1

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Chinese physics B 2024年第3期33卷 672-676页

作者：徐建伟欧阳收剑段守鑫邹林儿叶丹妮杨思嘉邓晓华 department of physics School of Physics and Materials ScienceNanchang UniversityNanchang 330031China department of Measuring and Controlling Technology and Instrument Institute of Advanced ManufacturingNanchang UniversityNanchang 330031China institute of Space Science and Technology Nanchang UniversityNanchang 330031China

Terahertz metamaterial biosensors have attracted significant attention in the biological field due to their advantages of label-free,real-time and in situ *** this paper,a highly sensitive metamaterial sensor with semi-ring mirror symmetry based on toroidal dipole resonance is designed for a new metamaterial *** is shown that a refractive index sensitivity of 337.5 GHz per refractive index unit can be achieved under an analyte of saturated thickness near a 1.33 THz transmission *** biosensor samples where aflatoxin B1 is dropped on the metamaterial surface in our experiment,dip amplitudes of transmission varying from 0.1904 to 0.203 and 0.2093 are observed as aflatoxin B1 concentrations are altered from 0 to 0.001μg·ml-1 and to 0.01μg·ml-1,***,when aflatoxin B1 concentrations are 0.1μg·ml-1,1μg·ml-1,10μg·ml-1 and 100μg·ml-1,dip amplitudes of 0.2179,0.226,0.2384 and 0.2527 and dip redshifts of 10.1 GHz,20.1 GHz,27.7 GHz and 37.6 GHz are respectively *** results illustrate high-sensitivity,label-free detection of aflatoxin B1,enriching the applications of sensors in the terahertz domain.

关键词： terahertz metamaterial toroidal dipole aflatoxin B1

Design and fabrication of Nd-Fe-B magnet with excellent thermal stability

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Journal of Rare Earths 2024年第5期42卷 980-986,I0006页

作者： Rui Han Shengzhi Dong Dong Li Dongmin Zhang Hongsheng Chen Jiyuan Xu George CHadjipanayis Zhuolin Li Ying Zhang Wei Li Division of Functional Materials Research Central Iron and Steel Research InstituteBeijing100081China department of physics and Astronomy Sharp Lab University of DelawareNewarkDE19716USA Beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing100190China

A novel Nd-Fe-B type permanent magnet with excellent thermal stability was designed by Co replacing Fe in the main phase and the grain boundary *** remanence and coercivity temperature coefficient reach 0.058%/℃and 0.465%/℃in the te mperature range from 25 to 100℃,which are much lower than those of commercial Nd-Fe-B *** enhanced Curie temperature is obtained for the novel magnet due to the Co substitution,which significantly improves the operating *** microstructure result reveals that an amorphous phase exists in the intergranular grains which is probably responsible for the deterioration of intrinsic *** work can provide a reference for the design and optimization of components of sintered Nd-Fe-B magnets with excellent thermal stability.

关键词： Thermal stability Remanence temperature coefficient Operating temperature Atomic substitution Rare earths

Inward particle transport driven by biased endplate in a cylindrical magnetized plasma

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Plasma Science and Technology 2024年第3期26卷 126-130页

作者：盖跃徐田超肖池阶郭志彬王晓钢何任川杨肖易张祖煜袁瑞鑫 State Key Laboratory of Nuclear physics and Technology School of PhysicsPeking UniversityBeijing 100871People's Republic of China department of physics Harbin Institute of TechnologyHarbin 150001People's Republic of China

The inward particle transport is associated with the formation of peaked density profiles,which contributes to improve the fusion rate and the realization of steady-state *** active control of inward particle transport is considered as one of the most critical issues of magnetic confinement ***,it is realized preliminarily by adding a biased endplate in the Peking University Plasma Test(PPT)*** results reveal that the inward particle flux increases with the bias voltage of the *** is also found that the profile of radial electric field(Er)shear is flattened by the increased bias *** velocity fluctuations affect the inward particle more than density fluctuations,and the frequency of the dominant mode driving inward particle flux increases with the biased voltage applied to the *** experimental results in the PPT device provide a method to actively control the inward particle flux using a biased endplate and enrich the understanding of the relationship between E_(r)×B shear and turbulence transport.

关键词： inward particle transport biased endplate turbulent transport

Model of fractured medium and nondestructive control of composite materials

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Chinese Journal of Aeronautics 2024年第2期37卷 93-99页

作者： Vasily GOLUBEV Ilia NIKITIN Katerina BEKLEMYSHEVA department of Computers Science and Numerical Mathematics Moscow Institute of Physics and TechnologyDolgoprudny 141700Russia Mathematical Modeling and Management Department of InformatizationInstitute of Computer Aided Design RASMoscow 123056Russia

Non-destructive testing of composites is an important issue in the modern aircraft *** are susceptible to the barely visible impact damage which can affect the residual strength of the material and occurs both during production and *** continuum model for describing the damaged zone is *** slip theory relations used for a continuous distribution of slip planes are *** the initial stage,the isotropic background model is *** model allows the material slippage along the fractures based on the Coulomb friction law with the small viscous *** this regime,the govern system of equations becomes *** overcome this difficulty,the explicit-implicit grid-characteristic scheme is *** standard ultrasound diagnostic procedure of damaged composite materials is successfully *** with the trivial free-surface fracture model,different reactions on the compression and stretch waves are *** approach provided an effective way for the simulation of complex dynamic behavior of damage zones.

关键词： Non-destructive testing Composite materials Numerical modeling Continuum model Grid-characteristic method

Universal Machine Learning Kohn–Sham Hamiltonian for Materials

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Chinese physics Letters 2024年第7期41卷 95-110页

作者：钟阳于宏宇杨吉辉郭星宇向红军龚新高 Key Laboratory of Computational Physical Sciences(Ministry of Education) Institute of Computational Physical SciencesState Key Laboratory of Surface Physicsand Department of PhysicsFudan UniversityShanghai 200433China Shanghai Qi Zhi institute Shanghai 200030China

While density functional theory(DFT)serves as a prevalent computational approach in electronic structure calculations,its computational demands and scalability limitations ***,leveraging neural networks to parameterize the Kohn-Sham DFT Hamiltonian has emerged as a promising avenue for accelerating electronic structure *** advancements,challenges such as the necessity for computing extensive DFT training data to explore each new system and the complexity of establishing accurate machine learning models for multi-elemental materials still *** these hurdles,this study introduces a universal electronic Hamiltonian model trained on Hamiltonian matrices obtained from first-principles DFT calculations of nearly all crystal structures on the Materials *** demonstrate its generality in predicting electronic structures across the whole periodic table,including complex multi-elemental systems,solid-state electrolytes,Moir´e twisted bilayer heterostructure,and metal-organic ***,we utilize the universal model to conduct high-throughput calculations of electronic structures for crystals in GNoME datasets,identifying 3940 crystals with direct band gaps and 5109 crystals with flat *** offering a reliable efficient framework for computing electronic properties,this universal Hamiltonian model lays the groundwork for advancements in diverse fields,such as easily providing a huge data set of electronic structures and also making the materials design across the whole periodic table possible.

关键词： Hamiltonian utilize twisted