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Natural Frequency Identification Method for Substructures in Railway Bridges and Viaducts

Quarterly Report of RTRI (Railway Technical Research Institute) 2024年第1期65卷 28-35页

作者： Wada, Kazunori Sakai, Kimitoshi Structural Dynamics and Response Control Laboratory Center for Railway Earthquake Engineering Research Japan

We have proposed a method for identifying the natural frequency of single structures from data obtained by measuring the vibration of railway bridges and viaducts. With this method, the natural frequency of a single structure can be theoretically calculated using undamped natural frequencies and the natural modes of whole structures. The eigenvalue analysis shows that the natural frequency of a single structure can be identified by the proposed method. © 2024 Ken-yusha Inc.. All rights reserved.

关键词： Natural frequencies

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Enhancement of Quality Factor in Gain-Assisted Acoustic Resonance Systems

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Acta Mechanica Solida Sinica 2025年第1期38卷 25-32页

作者： Lei Zhang Linlin Geng Yonghui Zhang Youdong Duan Jinbo Yuan Xiaoming Zhou Key Laboratory of Dynamics and Control of Flight Vehicle of Ministry of Education School of Aerospace EngineeringBeijing Institute of TechnologyBeijing100081China

Damped acoustic systems have a limited quality factor due to intrinsic *** introducing gain elements,a method to enhance the quality factor of damped systems is proposed based on the concept of bound states in the continuum(BICs).The acoustic model under study is a two-port waveguide system installed with two side Helmholtz resonators connected by a coupling *** on the temporal coupled-mode theory,a Hamiltonian matrix with both intrinsic and radiation losses is used to characterize the resonance behavior of the coupled *** achieve a high quality factor,acoustic gain is introduced to compensate the intrinsic loss,leading the Hamiltonian parameters toward a quasi-BIC *** simulation demonstrates a gain-assisted and quasi-BIC-supported extremely high quality factor in damped acoustic *** concept is further utilized to design a sensor model for particle size *** enhanced sensing performance due to high quality factors is numerically *** findings suggest potential applications in acoustic sensing and detection devices.

关键词： Acoustic resonance Quality factor Bound states in the continum Coupled-mode theory

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Deployment dynamics and experiments of a tendon-actuated flexible manipulator

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Chinese Journal of Aeronautics 2025年第2期38卷 459-477页

作者： Benteng ZHANG Jialiang SUN Haiyan HU State Key Laboratory of Mechanics and Control for Aerospace Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China MOE Key Laboratory of Dynamics and Control of Flight Vehicle School of Aerospace EngineeringBeijing Institute of TechnologyBeijing 100081China

The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.

关键词： Flexible manipulator Tendon-actuated Dynamic modeling Deployment dynamics Ground experiments

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Determining origins of satellite breakup events in LEO region

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Astrodynamics 2023年第4期7卷 465-476页

作者： Yongjie Liu Yu Jiang Hengnian Li Zongbo Huyan Hongchao Wang State Key Laboratory of Astronautic Dynamics Xi'an Satellite Control CenterXi'an 710043China

Currently,a surge in the number of spacecraft and fragments is observed,leading to more frequent breakup events in low Earth orbits(LEOs).The causes of these events are being identified,and specific triggers,such as collisions or explosions,are being examined for their importance to space traffic *** propagation methods were employed to trace the origins of these types of breakup *** were conducted using the NASA standard breakup model,and satellite Hitomi’s breakup was ***-Leibler(KL)divergences,Euclidean 2-norms,and Jensen-Shannon(JS)divergences were computed to deduce potential types of breakups and the associated fragmentation *** the simulated case,a discrepancy of 22.12 s between the estimated and actual time was ***,the breakup of the Hitomi satellite was estimated to have occurred around UTC 1:49:26.4 on March 26,*** contrasts with the epoch provided by the Joint Space Operation Center,which was estimated to be at 1:42 UTC±11 *** the findings,it was suggested that the techniques introduced in the study can be effectively used to trace the origins of short-term breakup events and to deduce the types of collisions and fragmentation masses under certain conditions.

关键词： breakup collision explosion Kullback-Leibler(KL)divergence Jensen-Shannon(JS)divergence

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Analysis of the optimal target node to reduce seizure-like discharge in networks

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Chinese Physics B 2024年第5期33卷 712-720页

作者：闫璐瑶张红慧孙中奎 School of Mathematics and Statistics Northwestern Polytechnical UniversityXi'an 710129China MIIT Key Laboratory of Dynamics and Control of Complex Systems Xi'an 710129China

Network approaches have been widely accepted to guide surgical strategy and predict outcome for epilepsy *** study starts with a single oscillator to explore brain activity,using a phenomenological model capable of describing healthy and epileptic *** ictal number of seizures decreases or remains unchanged with increasing the speed of oscillator excitability and in each seizure,there is an increasing tendency for ictal duration with respect to the *** underlying reason is that the strong excitability speed is conducive to reduce transition behaviors between two attractor ***,the selection of the optimal removal node is estimated by an indicator proposed in this *** show that when the indicator is less than the threshold,removing the driving node is more possible to reduce seizures significantly,while the indicator exceeds the threshold,the epileptic node could be the removal ***,the driving node is such a potential target that stimulating it is obviously effective in suppressing seizure-like activity compared to other nodes,and the propensity of seizures can be reduced 60%with the increased stimulus *** results could provide new therapeutic ideas for epilepsy surgery and neuromodulation.

关键词： epilepsy driving node epileptic node seizure regulation

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Method for Updating Operational Regulation Standards Considering Seismic Risk of Railway Facilities

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Quarterly Report of RTRI (Railway Technical Research Institute) 2023年第1期64卷 37-42页

作者： Wada, Kazunori Sakai, Kimitoshi Toyooka, Akihiro Structural Dynamics and Response Control Laboratory Center for Railway Earthquake Engineering Research Japan

The regulation values of seismic intensity to suspend a train operation after earthquakes are determined empirically based on past disasters. Therefore, it is difficult to reflect the effects of seismic countermeasures in the operational regulation standards. To resume train operations as quickly as possible after earthquakes, this study proposes a method for updating the operational regulation standards based on risk analysis. In the proposed method, the seismic risk of each facility is evaluated and used to determine the regulation values for suspending train operations. Using this method, the effects of seismic countermeasures can be directly reflected in the operational regulation standards. © 2023 Ken-yusha Inc.. All rights reserved.

关键词： Earthquakes

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BGS Distribution Deformation in BOTDR Induced by Self-Phase Modulation

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Photonic Sensors 2025年第1期15卷 11-25页

作者： Haoting WU Wencun GUO Zixuan ZHONG Guolu YIN Tao LIU Tao ZHU State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China The Key Laboratory of Optoelectronic Technology&Systems(Ministry of Education) Chongqing UniversityChongqing 400044China

We report the numerical and experimental studies of the two-dimensional Brillouin gain spectrum(BGS)distribution deformation induced by the self-phase modulation in the Brillouin optical time domain reflectometry(BOTDR)with a 20.6 km sensing *** BGS distribution deformation is investigated by analyzing the evolution of the point spread function along the fiber in the two-dimensional model of the *** the simulation and experimental results,the specific deformation degree of the BGS distribution induced by the self-phase modulation is related to the pump pulse profile,pump pulse peak power,BGS demodulation method,and detected scattered light *** comprehensively analyzing the evolution of the point spread function induced by the self-phase modulation and using the image deconvolution,a typical BOTDR sensor with a 25 ns pump pulse reaches the 20 cm spatial resolution over the 20.6 km sensing fiber.

关键词： Optical time domain reflectometry Brillouin scattering self-phase modulation deconvolution

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Perturbed low-thrust geostationary orbit transfer guidance via polynomial costate estimation

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Chinese Journal of Aeronautics 2024年第3期37卷 181-193页

作者： Zhao LI Hengnian LI Fanghua JIANG Junfeng LI State Key Laboratory of Astronautic Dynamics Xi’an Satellite Control CenterXi’an 710043China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

This paper proposes an optimal,robust,and efficient guidance scheme for the perturbed minimum-time low-thrust transfer toward the geostationary *** Earth’s oblateness perturbation and shadow are taken into *** is difficult for a Lyapunov-based or trajectory-tracking guidance method to possess multiple characteristics at the same time,including high guidance optimality,robustness,and onboard computational *** this work,a concise relationship between the minimum-time transfer problem with orbital averaging and its optimal solution is identified,which reveals that the five averaged initial costates that dominate the optimal thrust direction can be approximately determined by only four initial modified equinoctial orbit elements after a coordinate *** on this relationship,the optimal averaged trajectories constituting the training dataset are randomly generated around a nominal averaged *** polynomial regression models are trained on the training dataset and are regarded as the costate *** the transfer,the spacecraft can obtain the real-time approximate optimal thrust direction by combining the costate estimations provided by the estimators with the current state at any ***,all these computations onboard are *** simulation results show that the proposed guidance scheme possesses extremely high guidance optimality,robustness,and onboard computational efficiency.

关键词： Low thrust Orbital transfer Trajectory optimization Guidance Indirect method Orbital averaging Machine learning Geostationary satellites

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Resistance law of a rod penetrating a multilayer granular raft

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Chinese Physics B 2023年第3期32卷 354-362页

作者：李宗霖田强胡海岩 MOE Key Laboratory of Dynamics and Control of Flight Vehicle School of Aerospace EngineeringBeijing Institute of TechnologyBeijing 100081China

This paper presents an experimental study on the resistance law of a rod vertically penetrating different kinds of multilayer granular rafts with a constant velocity so as to reveal the mechanical properties of the multilayer granular *** resistance was quasi-static under the chosen *** were conducted with different granular thicknesses,rod diameters and combinations of particles and *** study shows that the resistance–displacement relation of the rod has three smooth *** the first stage,the resistance rapidly *** the second stage,the resistance curve maintained an almost constant *** the third stage,the resistance smoothly changed with its slope continuously *** on the corresponding physical models for each stage,the study reveals the exponential dependence of the load-bearing capacity of the multilayer granular raft on its thickness,and clarifies the capillary effects on the resistance *** study extends the knowledge of the granular raft from monolayer to multilayer structure.

关键词： granular matter wet particles saturated particles capillary effects

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Fluid evolution and fragmentation characteristics under high pressure water jet impact on thermal rock

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International Journal of Mining Science and Technology 2025年第3期35卷 483-497页

作者： Jianming Shangguan Zhaolong Ge Qinglin Deng Yuhuai Cui Zhi Yao State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China School of Resources and Safety Engineering Chongqing UniversityChongqing 400044China

In the application of high-pressure water jet assisted breaking of deep underground rock engineering,the influence mechanism of rock temperature on the rock fragmentation process under jet action is still ***,the fluid evolution characteristics and rock fracture behavior during jet impingement were *** results indicate that the breaking process of high-temperature rock by jet impact can be divided into four stages:initial fluid-solid contact stage,intense thermal exchange stage,perforation and fracturing stage,and crack propagation and penetration *** the increase of rock temperature,the jet reflection angles and the time required for complete cooling of the impact surface significantly decrease,while the number of cracks and crack propagation rate significantly increase,and the rock breaking critical time is shortened by up to 34.5%.Based on numerical simulation results,it was found that the center temperature of granite at 400℃ rapidly decreased from 390 to 260℃ within 0.7 s under jet *** addition,a critical temperature and critical heat flux prediction model considering the staged breaking of hot rocks was *** findings provide valuable insights to guide the water jet technology assisted deep ground hot rock excavation project.

关键词： Fluid evolution Fragmentation characteristics Fracture process Water jet Thermal rock

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