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Natural vibration and critical velocity of translating Timoshenko beam with non-homogeneous boundaries

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Applied Mathematics and Mechanics(English Edition) 2024年第9期45卷 1523-1538页

作者： Yanan LI Jieyu ding Hu ding Liqun CHEN Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy EngineeringShanghai Frontier Science Center of MechanoinformaticsSchool of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China School of Mathematics and Statistics Qingdao UniversityQingdao 266071Shandong ProvinceChina

In most practical engineering applications,the translating belt wraps around two fixed *** boundary conditions of the dynamic model are typically specified as simply supported or fixed *** this paper,non-homogeneous boundaries are introduced by the support *** the translating belt as the mechanical prototype,the vibration characteristics of translating Timoshenko beam models with nonhomogeneous boundaries are investigated for the first *** governing equations of Timoshenko beam are deduced by employing the generalized Hamilton's *** effects of parameters such as the radius of wheel and the length of belt on vibration characteristics including the equilibrium deformations,critical velocities,natural frequencies,and modes,are numerically calculated and *** numerical results indicate that the beam experiences deformation characterized by varying curvatures near the *** radii of the wheels play a pivotal role in determining the change in trend of the relative difference between two beam *** the results unearths that the relative difference in equilibrium deformations between the two beam models is more pronounced with smaller-sized *** the two wheels are of equal size,the critical velocities of both beam models reach their respective *** addition,the relative difference in natural frequencies between the two beam models exhibits nonlinear variation and can easily exceed 50%.Furthermore,as the axial velocities increase,the impact of non-homogeneous boundaries on modal shape of translating beam becomes more *** dealing with non-homogeneous boundaries is challenging,beam models with non-homogeneous boundaries are more sensitive to parameters,and the differences between the two types of beams undergo some interesting variations under the influence of non-homogeneous boundaries.

关键词： translating beam Timoshenko beam non-homogeneous boundary natural frequency critical velocity

Whittle’s Index Based Sensor Scheduling for Multiprocess Systems Under DoS Attacks

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Journal of Systems Science & Complexity 2024年第1期37卷 329-350页

作者： CAI Zai ding Kemi Shenzhen Key Laboratory of Control Theory and Intelligent Systems Southern University of Science and TechnologyShenzhen 518055China.

In this paper,the authors consider how to design defensive countermeasures against DoS attacks for remote state estimation of multiprocess *** each system,a sensor will measure its state and transmits the data packets through an unreliable channel which is vulnerable to be jammed by an *** limited communication bandwidth,only a subset of sensors are allowed for data transmission,and how to select the optimal one to maximize the accuracy of remote state estimation is the focus of the proposed *** authors first formulate this problem as a Markov decision process and investigate the existence of optimal ***,the authors demonstrate the piecewise monotonicity structure of optimal *** the difficulty of obtaining an optimal policy of large-scale problems,the authors develop a suboptimal heuristic policy based on the aforementioned policy structure and Whittle’s ***,a closed form of the indices is derived in order to reduce implementation complexity of proposed scheduling policy and numerical examples are provided to illustrate the proposed developed results.

关键词： DoS attacks Kalman filter remote state estimation Whittle’s index.

A vertical track nonlinear energy sink

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Applied Mathematics and Mechanics(English Edition) 2024年第6期45卷 931-946页

作者： Meng LI Hu ding Shanghai Key Laboratory of Mechanics in Energy Engineering School of Mechanics and Engineering ScienceShanghai Frontier Science Center of MechanoinformaticsShanghai UniversityShanghai 200444China

Eliminating the effects of gravity and designing nonlinear energy sinks(NESs)that suppress vibration in the vertical direction is a challenging task with numerous damping *** this paper,the dynamic design of a vertical track nonlinear energy sink(VTNES)with zero linear stiffness in the vertical direction is proposed and realized for the first *** motion differential equations of the VTNES coupled with a linear oscillator(LO)are *** the strong nonlinearity considered of the VTNES,the steady-state response of the system is analyzed with the harmonic balance method(HBM),and the accuracy of the HBM is verified *** this basis,the VTNES prototype is manufactured,and its nonlinear stiffness is *** damping effect and dynamic characteristics of the VTNES are studied theoretically and *** results show that the VTNES has better damping effects when strong modulation responses(SMRs)***,even for small-amplitude vibration,the VTNES also has a good vibration suppression *** sum up,in order to suppress the vertical vibration,an NES is designed and developed,which can suppress the vertical vibration within certain ranges of the resonance frequency and the vibration intensity.

关键词： track nonlinear energy sink(TNES) vertical direction gravity nonlinear stiffness harmonic balance method(HBM) vibration control

Deep structure of the Southeast Asian curved subduction system and its dynamic process

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Journal of Oceanology and Limnology 2024年第3期42卷 701-704页

作者： Weiwei ding Key Laboratory of Submarine Geoscience&Second Institute of Oceanography Ministry of Natural ResourcesHangzhou 310012China School of Oceanography Shanghai Jiao Tong UniversityShanghai 200030China

The deep structure,material circulation,and dynamic processes in the Southeast Asia have long been an elusive scientific puzzle due to the lack of systematic scientific observations and recognized theoretical *** on the deep seismic tomography using long-period natural earthquake data,in this study,the deep structure and material circulation of the curved subduction system in Southeast Asia was studied,and the dynamic processes since 100 million years ago was *** is pointed out that challenges still exist in the precise reconstruction of deep mantle structures of the study area,the influence of multi-stage subduction on deep material exchange and shallow magma activity,as well as the spatiotemporal evolution and coupling mechanism of multi-plate *** work should focus on high-resolution land-sea joint 3-D seismic tomography imaging of the curved subduction system in the Southeast Asia,combined with geochemical analysis and geodynamic modelling works.

关键词： curved subduction system deep structure material recycling dynamic process Southeast Asia

From London buses to activity trackers:A reflection of 70 years of physical activity research

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Journal of Sport and Health Science 2024年第6期13卷 736-738页

作者： ding ding Ulf Ekelund Prevention Research Collaboration Sydney School of Public HealthFaculty of Medicine and HealthThe University of SydneyCamperdownNSW 2006Australia Charles Perkins Centre The University of SydneyCamperdownNSW 2006Australia Department of Sports Medicine Norwegian School of Sports SciencesOslo 0806Norway Department of Chronic Diseases Norwegian Institute of Public HealthOslo 0213Norway

In 1953,Morris et al.^(1)published their ground-breaking findings among London bus drivers and conductors,linking physical activity to a major chronic disease for the first *** seminal paper marked the birth of a new field—physical activity epidemiology.^(1)Since then,the field has flourished,evidenced by mounting scientific publications.^(2)Our knowledge about the role of physical activity in disease prevention has expanded from coronary heart disease in Morris et al.’s^(1)initial study to dozens of additional diseases and conditions,such as diabetes,cancers,and dementia.^(3)More than 7 decades and thousands of publications later,we critically reflect on several aspects of the progress in physical activity epidemiology.

关键词： epidemiology prevention linking

Towards human-leveled vision systems

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Science China Technological Sciences 2024年第8期67卷 2331-2349页

作者： ding JianHao HUANG TieJun State Key Laboratory of Multimedia Information Processing School of Computer Science Peking University

The human visual system is a complex and interconnected network comprising billions of neurons. It plays an essential role in translating environmental light stimuli into information that guides and shapes human perception and action. Research on the visual system aims to uncover the underlying neural structure principles of human visual perception and their possible ***, there are two main approaches: biological system analysis and simulation, artificial intelligence models based on deep learning. Here we aim to discuss the two approaches to human-level vision systems. Deep learning has significantly impacted the field of vision with achievements in representation, modeling, and hardware design. However, there is still a significant gap between deep learning models and the human visual system in terms of scalability, transferability, and sustainability. The progress of the biological visual system can help fill the gap by further understanding the properties and functions of different components of the system. We take the efforts of reconstructing the retina as an example to illustrate that even if we are unable to replicate the visual system on a computer right now, we can still learn a lot by combining existing research outcomes in neuroscience. At the end of the paper, we suggest tracing back to gradually build visual systems from the computational counterpart of biological structures to achieve a human-level vision system in the future.

关键词： human-leveled vision system deep learning biological visual system

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New advances in the study of Tethyan Geodynamic System

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Science China Earth Sciences 2024年第3期67卷 874-878页

作者： Lin ding State Key Laboratory of Tibetan Plateau Earth System Science(LATPES) Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

Tethyan Ocean was initially proposed by Austrian geologist Eduard Suess in 1893. The study of the Tethyan evolution by European geologists has led to the development of modern geology, but not to the establishment of plate tectonics theory(Trümpy, 2001). With the progress in various studies, the concept of Tethys has evolved from a Mesozoic ocean into three long-term evolving oceans:Proto-Tethys, Paleo-Tethys, and Neo-Tethys (Figure 1), and their life cycles cover the entire Phanerozoic era (Wu et al., 2020).

关键词： geology Mesozoic ocean

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Equivalent linear model for seismic damage evaluation of single-degree-of-freedom systems representing reinforced concrete structures considering cyclic degradation behavior

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Earthquake Engineering and Engineering Vibration 2024年第3期23卷 637-648页

作者： Lulu Yan ding-Hao Yu Research Center for Geotechnical and Structural Engineering Technology of Liaoning Province Dalian UniversityDalian116622China State Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China

In this study,a novel equivalent damping ratio model that is suitable for reinforced concrete(RC)structures considering cyclic degradation behavior is developed,and a new equivalent linearization analysis method for implementing the proposed equivalent damping ratio model for use in seismic damage evaluation is *** this end,Ibarra’s peak-oriented model,which incorporates an energy-based degradation rule,is selected for representing hysteretic behavior of RC structure,and the optimized equivalent damping for predicting the maximum displacement response is presented by using the empirical method,in which the effect of cyclic degradation is ***,the relationship between the hysteretic energy dissipation of the inelastic system and the elastic strain energy of the equivalent linear system is established so that the proposed equivalent linear system can be directly integrated with the Park-Ang seismic model to implement seismic damage *** to the simplicity of the equivalent linearization method,the proposed method provides an efficient and reliable way of obtaining comprehensive insight into the seismic performance of RC *** verification demonstrates the validity of the proposed method.

关键词： degrading system equivalent linear system equivalent damping seismic damage RC structures

Catalysis by subsurface metal atoms in Al(001) through electron transfer

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National Science Review 2024年第4期11卷 12-13页

作者： Bo Sun ding Ma Beijing National Laboratory for Molecular Science New Cornerstone Science Laboratory College of Chemistry and Molecular Engineering Peking University

Heterogeneous catalysis plays a crucial role in the chemical industry, which has evolved from the investigation of chemisorption to an electronic structure[1]. Diverse strategies, such as alloying,doping, and confining, have been applied to enhance the catalytic properties of active sites through electronic modulation. The electron transfer between active sites and substrates profoundly influences catalytic activity [2].

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