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Triple collision orbits in the free-fall three-body system without binary collisions

CELESTIAL MECHANICS & DYNAMICAL ASTRONOMY 2021年第10期133卷 46-46页

作者： Li, Xiaoming Li, Xiaochen He, Linghui Liao, Shijun Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China South China Univ Technol Sch Civil Engn & Transportat Guangzhou 510641 Peoples R China Univ Sci & Technol China Dept Modern Mech Hefei 230026 Anhui Peoples R China Shanghai Jiao Tong Univ Ctr Adv Comp Sch Naval Architecture Ocean & Civil Engn Shanghai 200240 Peoples R China Shanghai Jiao Tong Univ Sch Phys & Astron Shanghai 200240 Peoples R China

We numerically investigate triple collision orbits of the free-fall three-body system which has no double collisions before three bodies collide. Triple collision is an important property of the three-body system. Tanikawa, Saito, Mikkola (Celest Mech Dyn Astron 131(6):24, 2019) obtained 11 triple collision orbits without double collision for the free-fall three-body problem. In this paper, we present 1658 triple collision orbits including the Lagrange's homothetic solution, 11 ones found by Tanikawa et al. (2019) and 1646 new triple collision orbits. The symbol sequences of these 1646 new triple collision orbits have digits that range between 1 and 120. With our high-precision results, numerical evidences of the asymptotic property of triple collision orbits are given.

关键词： Free-fall three-body problem Triple collision Symbol sequences

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A sparse self-estimated sensor-network for reconstructing moving vehicle forces

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SMART MATERIALS AND STRUCTURES 2019年第8期28卷 085009-085009页

作者： Pan, Chudong Liu, Huanlin Yu, Ling Guangzhou Univ Sch Civil Engn Guangzhou Guangdong Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China

Reconstructing moving vehicle forces from structural responses is an important inverse problem in bridge engineering. When a sensor-network is applied to moving force identification (MFI), a necessary task is to specify the contribution of different sensors at the first beginning. This paper proposes a novel method based on the sparse self-estimated sensor-network for estimating moving vehicle forces on bridges. Firstly, an over-completed dictionary is pre-defined to ensure a sparse representation of moving vehicle forces. Images corresponding to force atoms, i.e. structural responses caused by unit force components, are used to match the structural responses. As a self-estimated sensor-network, the signal features, noise energy and signal-to-noise ratio of each sensor can be self-estimated by combining sparse regularization and Bayesian information criterion. Then an improved L-2-norm regularization model, in which the cost function is defined by the weighted residuals of sensors, is proposed and applied to solve the MFI problem. Finally, both numerical and experimental examples are conducted to assess the accuracy and the feasibility of the proposed method. Illustrated results clearly show the robustness and applicability of the proposed method. Some related issues are discussed as well.

关键词： moving force identification sparse regularization self-estimated sensor-network structural health monitoring inverse problems

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Novel Dynamic Multiscale Model of Apparent Diffusion Permeability of Methane through Low-Permeability Coal Seams

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Energy & Fuels 2021年第9期35卷 7844-7857页

作者： Zhiqiang Li Jiansong Peng Lin Li Lingling Qi Wai Li MOE Engineering Center of Mine Disaster Prevention and Rescue Henan Polytechnic University Jiaozuo 454000 China Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization Henan Polytechnic University Jiaozuo 454000 China Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region (Henan Province) Henan Polytechnic University Jiaozuo 454000 China Henan Provincial Key Lab of Gas Geology and Control-Cultivation Base of Provincial and Ministry Joint State Key Henan Polytechnic University Jiaozuo 454000 China School of Engineering The University of Western Australia Crawley WA 6009 Australia

The low permeability of coal seams is a key factor restricting gas extraction. The multiscale pores in low-permeability coal make coal permeability present the multiscale characteristics. However, the conventional steady-state method cannot measure the multiscale permeability of low-permeability coal well. In this study, a unidirectional multiscale dynamic apparent diffusion model is proposed as an analytical model, and a multiscale dynamic apparent diffusion coefficient is defined. In addition, an experimental method for measuring low permeability from macroscale to microscale pores is provided. The experiments of gas desorption flow in the unidirectional, radial, and spherical directions were conducted to compare with each other. The research results show that (1) the apparent diffusion coefficient and apparent permeability decrease with time because of the multiscale pore structure in coal. (2) The multiscale dynamic apparent diffusion model can accurately describe the full-time process of the unidirectional gas desorption flow in coal. (3) The proposed model shows a broader applicability with a comparison to the current models.

关键词： Transport properties Coal Desorption Diffusion Permeability

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Experimental study on the energy absorption characteristics of viscoelastic damping layers

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IOP Conference Series: Earth and Environmental Science 2021年第2期861卷

作者： Xiancheng Mei Qian Sheng Zhen Cui Qingzi Luo Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China University of Chinese Academy of Sciences Beijing 100049 China School of Civil and Transportation Engineering Guangdong University of Technology Guangzhou 510006 MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou 510632

This work aims to further promote the research and development of flexible damping technology for the seismic damage control of underground engineering structures. On the basis of the understanding of the application of viscoelastic damping theory to the field of earthquake resistance of bridge buildings, impact tests on different rock damping layer– concrete specimens are conducted using the improved split Hopkinson pressure bar test system to analyze the energy absorption characteristics of the viscoelastic damping layers. A comparative analysis of the test results is also performed to differentiate the laws of energy absorption of the viscoelastic damping layer structure using different damping layer materials (rubber and silicone) and different damping layer shapes (honeycomb, corrugated, and cylindrical). Given damping layers with the same material and structure, the energy absorption laws of the structures with different damping layer thicknesses are compared and analyzed. The optimal thickness of the damping layers is also discussed. Results show that the incident energy absorbed by the damping layers of different materials increases by more than 10% relative to the control group (rock–concrete specimen). Such an increase indicates that the structures have superior energy absorption characteristics and that the rubber material can absorb more incident energy than the high-damping silicone as the damping layer. As for the damping layer shapes, the composite damping layer structure with a honeycomb shape achieves the best energy absorption among all structures. The comparison and analysis of the energy absorption effects when the damping layer thicknesses are 10, 20, and 25 mm reveal that a 20 mm-thick damping layer shows the best energy absorption effect. The current findings can provide theoretical foundation and data support for the application of composite damping layers to the seismic design of underground engineering structures.

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Damping of Particle-Reinforced Composites Due to Interfacial Sliding

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Acta Mechanica Solida Sinica 2018年第5期31卷 623-634页

作者： Linghui He Renhuai Liu CAS Key Laboratory of Mechanical Behavior and Design of Materials University of Science and Technology of China Hefei 230026 China MOE Key Lab of Disaster and Control in Engineering Institute of Applied Mechanics Jinan University Guangzhou 510632 China

Mechanical damping of composites reinforced by randomly distributed particles due to interfacial sliding is analyzed. The matrix is elastically isotropic, and the particles are assumed rigid and of identical radii. An auxiliary problem is solved at first for the steady-state response of an infinite matrix containing a single inclusion to a harmonic external load. The result is then used to derive the explicit expression of the specific damping capability of the composite by using Mori-Tanaka＇s mean-field method. Numerical results are given and discussed in detail. It is concluded that the overall damping of the composite depends on several factors, including volume fraction of particles, Poisson＇s ratio of matrix and a dimensionless parameter that incorporates the combined effects of particle size, matrix stiffness, interracial viscosity and vibration frequency. The result is expected to be helpful in tailoring the damping performance of particle-reinforced composites.

关键词： Particle-reinforced composite Damping Interracial sliding

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Study on the Sensitive Factors of Structural Nonlinear Damage Based on the Innovation Series

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INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY AND DYNAMICS 2020年第10期20卷

作者： Chen, Liujie Mei, Yahui Fu, Jiyang Ng, Ching Tai Cui, Zhen Guangzhou Univ Sch Civil Engn Guangzhou 51006 Guangdong Peoples R China MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Guangzhou Univ Tamkang Univ Joint Res Ctr Engn St Guangzhou 51006 Guangdong Peoples R China Univ Adelaide Sch Civil Environm & Min Engn Adelaide SA 5005 Australia Chinese Acad Sci Inst Rock & Soil Mech State Key Lab Geomech & Geotech Engn Wuhan 430071 Hubei Peoples R China

Constructing a damage-sensitive factor (DSF) is one of the key steps in structural damage detection. In this paper, innovation series extracted from the auto-regressive conditional heteroscedasticity (ARCH) model are proposed to construct a DSF, which is defined as the standard deviation of innovation (SDI). A three-story shear building structure is used to demonstrate and verify the performance of the proposed method, and the results are compared with the standard deviation of the residuals (SDR) based on an auto-regressive (AR) model. In the proposed method, the AR model is established using the acceleration responses obtained from the reference and test states. The residual series are then extracted for fitting the SDR. Subsequently, the ARCH model is constructed based on the residual series from the AR model, and a new DSF of SDI is defined. This study focuses on analyzing the accuracy of fitting AR model and ARCH model to vibration response data via the normal probability distribution, and identifying the characteristics of the residual and innovation series. The mean squared error (MSE) is used as the loss function to calculate the loss on residual and innovation series from the AR model and ARCH model, respectively. The results demonstrate that the SDR can be used for nonlinear damage detection. However, the proposed SDI can provide more accurate nonlinear damage identification and is robust to varying environmental condition and small damages. Thus, the innovation series developed based on ARCH model are promising for expressing and constructing nonlinear DSFs.

关键词： Nonlinear damage identification nonlinear damage-sensitive factor innovation series auto-regressive conditional heteroscedasticity

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Finite Element Analysis of Subsurface Damage of Optical Glass after Grinding

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Journal of Physics: Conference Series 2021年第2期1802卷

作者： Wei Su Wenhao Luo Xianshan Dong Renhuai Liu MOE Key lab of Disaster Forecast and Control in Engineering Guangzhou 510632 China Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou 510610 China School of Mechanics and Construction Engineering Jinan University Guangzhou 510632 China

The interaction between abrasive particles and optical element surface can result in various forms of subsurface damage while removing the material. In order to obtain the stress distribution during optical glass grinding, the finite element analysis of optical glass grinding is carried out by using ANSYS software. The stress distribution of optical glass was obtained by establishing the grinding model of consolidated abrasive and free abrasive. The simulation results show that different abrasives have different damage degrees to the glass surface, which provides a useful reference for improving the quality of optical material processing technology.

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Residual Stress Analysis of Laser Welding Between Output Needle and Helix

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Journal of Physics: Conference Series 2021年第2期1802卷

In order to obtain the welding stress of the output needle and helix, a finite element model is established and the mesh at the weld is refined to evaluate the welding residual stress. ANSYS parameter design language is used to simulate the motion load of welding heat source. Based on the exact calculation of the temperature field, the corresponding thermal units are converted into structural units to calculate the welding residual stress. Finally, the thermal stress distribution curve and residual stress distribution trend are obtained after post-treatment.

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Computer Transient Simulation for Dual In-Line Package through Finite Element Analysis and ANASYS Software

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Journal of Physics: Conference Series 2021年第1期2033卷

作者： Wei Su Wenhao Luo Xianshan Dong Si Chen Agam Tomar Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou China MOE Key lab of Disaster Forecast and Control in Engineering Guangzhou China School of Mechanics and Construction Engineering Jinan University Guangzhou China Faculty of Engineering and Mathematical Sciences University of Western Australia

The reliability of the DIP package is studied by numerical simulation. Firstly, the DIP package, fixture and metal steel are modeled. Based on this, variable thickness papers are laid on the sample. According to the experiment, corresponding excitation and boundary condition are set. Then, the transient analysis result of DIP package is obtained through numerical simulation. The results show the relation of different thickness papers and acceleration-time curve, which provides a beneficial reference for the optimization of DIP packing.

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Satellites of the Broucke-Hadjidemetriou-Hénon family of periodic unequal-mass three-body orbits

arXiv

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arXiv 2020年

作者： Li, Xiaoming Liao, Shijun MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China Department of Earth Atmospheric and Planetary Sciences Massachusetts Institute of Technology CambridgeMA02139 United States School of Physics and Astronomy Shanghai Jiaotong University Shanghai200240 China Center of Advanced Computing School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai200240 China

The Broucke-Hadjidemetriou-Hénon’s (BHH) orbits are a family of periodic orbits of the three-body system with the simplest topological free group word a, while the BHH satellites have free group words ak (k > 1), where k is the topological exponent. Janković and Dmitrašinović [Phy. Rev. Lett. 116, 064301 (2016)] reported 57 new BHH satellites with equal mass and found that at a fixed energy the relationship between the angular momentum (L) and the topologically rescaled period (T/k) is the same for both of the BHH orbits (k = 1) and the BHH satellites (k > 1). In this letter, we report 419,743 new BHH orbits (k = 1) and 179,253 new BHH satellites (k > 1) of the three-body system with unequal mass, which have never been reported, to the best of our knowledge. Among these newly-found 598,996 BBH orbits and satellites, about 33.5% (i.e., 200,686) are linearly stable and thus many among them might be observed in practice. Besides, we discover that, for the three-body system with unequal mass at a fixed energy, relationship between the angular momentum (L) and topologically rescaled period (T/k) of the BHH satellites (k > 1) is different from that of the BHH orbits (k = 1). Copyright © 2020, The Authors. All rights reserved.

关键词： Satellites

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