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Development of a Three-Dimensional Multiscale Octree SBFEM for Viscoelastic Problems of Heterogeneous Materials

Computer Modeling in Engineering & Sciences 2024年第8期140卷 1831-1861页

作者： Xu Xu Xiaoteng Wang haitian yang Zhenjun yang Yiqian He State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDepartment of Engineering MechanicsDalian University of TechnologyDalian116024China Hubei Key Laboratory of Geotechnical and Structural Safety School of Civil EngineeringWuhan UniversityWuhan430072China Mechanik–Materialtheorie Ruhr-Universität BochumBochum44801Germany

The multiscale method provides an effective approach for the numerical analysis of heterogeneous viscoelastic materials by reducing the degree of freedoms(DOFs).A basic framework of the Multiscale Scaled Boundary Finite Element Method(MsSBFEM)was presented in our previous works,but those works only addressed two-dimensional *** order to solve more realistic problems,a three-dimensional MsSBFEM is further developed in this *** the proposed method,the octree SBFEM is used to deal with the three-dimensional calculation for numerical base functions to bridge small and large scales,the three-dimensional image-based analysis can be conveniently conducted in small-scale and coarse nodes can be flexibly adjusted to improve the computational ***,the Temporally Piecewise Adaptive Algorithm(TPAA)is used to maintain the computational accuracy of multiscale analysis by adaptive calculation in time *** results of numerical examples show that the proposed method can significantly reduce the DOFs for three-dimensional viscoelastic analysis with good *** instance,the DOFs can be reduced by 9021 times compared with Direct Numerical Simulation(DNS)with an average error of 1.87%in the third example,and it is very effective in dealing with three-dimensional complex microstructures directly based on images without any geometric modelling process.

关键词： Three-dimensionalmultiscale viscoelastic analysis numerical base functions octree SBFEM image-based analysis temporally piecewise adaptive algorithm

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Solving viscoelastic problems with cyclic symmetry via a precise algorithm and EFGM

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Acta Mechanica Sinica 2006年第2期22卷 170-176页

作者： Zhi Han haitian yang Ling Liu State Key Lab of Structural Analysis of Industrial Equipment Department of Engineering Mechanics Dalian University of Technology Dalian 116024 China

The paper combines a self-adaptive precise algorithm in the time domain with Meshless Element Free Galerkin Method （EFGM） for solving viscoelastic problems with rotationally periodic symmetry. By expanding variables at a discretized time interval, the variations of variables can be described more precisely, and iteration is not required for non-linear cases. A space-time domain coupled problem with initial and boundary values can be converted into a series of linear recursive boundary value problems, which are solved by a group theory based on EFGM. It has been proved that the coefficient matrix of the global EFG equation for a rotationally periodic system is block-circulant so long as a kind of symmetry-adapted reference coordinate system is adopted, and then a partitioning algorithm for facilitating parallel processing was proposed via a completely orthogonal group transformation. Therefore instead of solving the original system, only a series of independent small sub-problems need to be solved, leading to computational convenience and a higher computing efficiency. Numerical examples are given to illustrate the full advantages of the proposed algorithm.

关键词： EFGM Cyclic symmetry Precise algorithm Viscoelastic problem

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A Temporally Piecewise Adaptive Scaled Boundary Finite Element Method for Solving the Fuzzy Uncertain Viscoelastic Problems

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Acta Mechanica Solida Sinica 2018年第4期31卷 459-469页

作者： Qiwen Xue Jing Wang Yiqian He haitian yang Xiuyun Du School of civil and safety engineering Dalian Jiaotong University Dalian 116028 China State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics Dalian University of Technology DaIian 116024 China School of Physics and Electronic Technology Liaoning Normal University Dalian 116029 China

The numerical solutions for uncertain viscoelastic problems have important theo- retical and practical significance. The paper develops a new approach by combining the scaled boundary finite element method （SBFEM） and fuzzy arithmetic. For the viscoelastic problems with zero uncertainty, the SBFEM and the temporally piecewise adaptive algorithm is employed in the space domain and the time domain, respectively, in order to provide an accurate semi- analytical boundary-based approach and to ensure the accuracy of discretization in the time domain with different sizes of time step at the same time. The fuzzy arithmetic is used to address the uncertainty analysis of viscoelastic material parameters, and the transformation method is used for computation with the advantages of effectively avoiding overestimation and reducing the computational costs. Numerical examples are provided to test the performance of the proposed method. By comparing with the analytical solutions and the Monte Carlo method, satisfactory results are achieved.

关键词： Viscoelasticity Uncertainty Scaled boundary finite element Fuzzy arithmetic

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Impact of climate change and human activities on the spatiotemporal dynamics of surface water area in Gansu Province, China

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Journal of Arid Land 2024年第6期16卷 798-815页

作者： LU haitian ZHAO Ruifeng ZHAO Liu LIU Jiaxin LYU Binyang yang Xinyue College of Geography and Environmental Science Northwest Normal UniversityLanzhou 730070China Key Laboratory of Resource Environment and Sustainable Development of Oasis Gansu ProvinceLanzhou 730070China School of Geography Planning and Spatial SciencesUniversity of TasmaniaHobart TAS 7005Australia School of Chinese Language and Literature Xi'an International Studies UniversityXi'an 710128China Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen 518055China School of Design and Built Environment Curtin UniversityPerth 6102Australia

Understanding the dynamics of surface water area and their drivers is crucial for human survival and ecosystem stability in inland arid and semi-arid *** study took Gansu Province,China,a typical area with complex terrain and variable climate,as the research *** on Google Earth Engine,we used Landsat data and the Open-surface Water Detection Method with Enhanced Impurity Control method to monitor the spatiotemporal dynamics of surface water area in Gansu Province from 1985 to 2022,and quantitatively analyzed the main causes of regional differences in surface water *** findings revealed that surface water area in Gansu Province expanded by 406.88 km2 from 1985 to *** surface water area exhibited significant fluctuations,while permanent surface water area showed a steady ***,terrestrial water storage exhibited a trend of first decreasing and then increasing,correlated with the dynamics of surface water *** change and human activities jointly affected surface hydrological processes,with the impact of climate change being slightly higher than that of human ***,climate change affected the'source'of surface water to a greater extent,while human activities tended to affect the'destination'of surface *** of surface water resources faced by inland arid and semi-arid areas like Gansu Province are ***,we summarized the surface hydrology patterns typical in inland arid and semi-arid areas and tailored surface water'supply-demand'balance *** study not only sheds light on the dynamics of surface water area in Gansu Province,but also offers valuable insights for ecological protection and surface water resource management in inland arid and semi-arid areas facing water scarcity.

关键词： surface water area terrestrial water storage Open-surface Water Detection Method with Enhanced Impurity Control method Google Earth Engine climate change human activities inland arid and semi-arid areas

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Accelerated thermal ageing on performance of polypropylene-based semiconducting screen for high voltage direct current cable applications-Effect of antioxidants

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High Voltage 2024年第2期9卷 410-418页

作者： haitian Wang Yi Luo Mingyu Zhou Xintong Ren George Chen GEIRI BerlinGermany The Tony Davies High Voltage Laboratory University of SouthamptonSouthamptonUK

The potential of using eco-friendly thermoplastic polypropylene(PP)-based insulation for high voltage direct current(HVDC)cable has been widely investigated but much less work on the PP-based semiconducting screen(SC).Considering a long service life(>30 years)under high temperature and high electrical stress is required for typical HVDC cables,and investigations on the effect of antioxidant(AO)concentration and thermal oxidative sta-bility,mechanical,and electrical properties of PP-based SCs have been *** has been demonstrated that an appropriate combination and amounts of AOs are critical for achieving high thermal stability and maintaining the mechanical properties of SC after ageing in a harsh environment(150°C,with Cu,in air,7 days).Although higher amounts of space charges have been observed in SC/PP/SC samples with higher AO concentrations,the impact on space charge behaviours is less after ageing,suggesting that ageing(or operating at high temperature)leads to microstructure evolution in SC and can potentially mitigate space accumulation in PP-based insulating materials.

关键词： microstructure thermal high

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基于船基海冰参数现场测量的极区船舶结构冰激疲劳损伤分析

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中国造船 2023年第3期64卷 223-232页

作者：孙凯刘璐杨海天季顺迎大连理工大学工业装备结构分析国家重点实验室大连116024

论文建立了一种极区船舶结构冰激疲劳评估方法。基于极地科学考察船在北极现场的测量数据,分析得到海冰的统计特性;由冰厚和航速的联合概率分布,得到极区环境航行的典型工况。采用离散元方法建立船-冰作用模型,获取不同工况下船首局部... 详细信息

论文建立了一种极区船舶结构冰激疲劳评估方法。基于极地科学考察船在北极现场的测量数据,分析得到海冰的统计特性;由冰厚和航速的联合概率分布,得到极区环境航行的典型工况。采用离散元方法建立船-冰作用模型,获取不同工况下船首局部区域的冰载荷分布。将局部冰载荷施加在船首有限元模型的对应区域,采用插值方法计算热点区域应力幅值和循环次数。根据累积疲劳损伤理论,将各工况的疲劳损伤叠加,得到总损伤。为验证该方法的准确性,将船舶结构冰激疲劳寿命计算结果与英国劳氏船级社规范进行了对比分析。结果表明,该方法可很好地应用于极区船舶结构冰激疲劳设计。

关键词：极区船舶结构冰激疲劳极区航行工况离散元方法有限元方法

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平整冰和碎冰区单桩锥体风电基础结构冰载荷离散元分析

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应用力学学报 2022年第1期39卷 44-53页

作者：王祥刘璐杨海天季顺迎大连理工大学大连116024

在渤海和北黄海海域,冰载荷是影响风电基础结构振动响应及疲劳寿命的关键因素。对于单桩风电柔性结构而言,在水线处安装抗冰锥可有效降低冰载荷,保障海上风电安全运行。为分析海冰对锥体风电结构的冰载荷,基于扩展多面体离散元方法模拟... 详细信息

在渤海和北黄海海域,冰载荷是影响风电基础结构振动响应及疲劳寿命的关键因素。对于单桩风电柔性结构而言,在水线处安装抗冰锥可有效降低冰载荷,保障海上风电安全运行。为分析海冰对锥体风电结构的冰载荷,基于扩展多面体离散元方法模拟了平整冰和碎冰对锥体风电结构的作用过程,分析了不同锥径和海冰密集度下的锥体风电结构冰载荷及冰激结构振动响应。计算结果表明,锥体结构冰载荷具有显著的随机性和周期性,平整冰对锥体结构冰载荷要明显高于碎冰;平整冰对上锥体的冰载荷大于下锥体冰载荷,而碎冰对上锥的冰载荷却小于下锥体冰载荷;所提方法可有效模拟海冰对锥体风电结构的作用力。

关键词：离散元方法冰载荷锥体风电结构平整冰碎冰区

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Energy Identities of ADI-FDTD Method with Periodic Structure

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Applied Mathematics 2015年第2期6卷 265-273页

作者： Rengang Shi haitian yang Department of Applied Mathematics Dalian University of Technology Dalian China College of Science China University of Petroleum Qingdao China Department of Engineering Mechanics Dalian University of Technology Dalian China

In this paper, a new kind of energy identities for the Maxwell equations with periodic boundary conditions is proposed and then proved rigorously by the energy methods. By these identities, several modified energy identities of the ADI-FDTD scheme for the two dimensional (2D) Maxwell equations with the periodic boundary conditions are derived. Also by these identities it is proved that 2D-ADI-FDTD is approximately energy conserved and unconditionally stable in the discrete L2 and H1 norms. Experiments are provided and the numerical results confirm the theoretical analysis on stability and energy conservation.

关键词： Stability Energy Conservation ADI-FDTD Maxwell Equations

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Provenance of Upper Jurassic in North Yellow Sea Basin， Eastern North China Craton

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Journal of Earth Science 2024年

作者： haitian Yu Zhongjie Xu Rihui Cheng Duo Wan Dan Gao Zhen Zhang College of Earth Sciences Jilin University 2. Key Laboratory of Mineral Resources Evaluation in Northeast Asia Ministry of Natural Resources College of Palaeontology Shenyang Normal University Guangzhou Marine Geological Survey

Base on the detrital zircon U-Pb dating data， this paper discusses the provenance and constructs source-to-sink system of the Upper Jurassic in the North Yellow Sea Basin (NYSB)， Eastern North China Craton (ENCC). In addition， to avoid the bias of detrital zircon ages caused by variations in zircon fertility， we gather 1709 whole rock zirconium content values (ppm) from granitic rocks with different ages in the North China Craton (NCC). Base on mean Zr content of granitic rocks in each age， these granitic rocks can be divided into four groups: Group A consists of Jurassic， Group B consists of Paleozoic， Neo-Mesoproterozoic and Neoarchean， Group C consists of Early Cretaceous and Triassic， and Group D consists of Paleoproterozoic. This research assigns these groups zircon fertility factors (ZFF) of 1， 1.4， 1.8 and 2.2. The U-Pb age of detrital zircons from Late Jurassic sediments corrected by ZFF are statistically analyzed (K-S test， Similarity， Cross-correlation， Linkeness， Multidimensional scaling). And combining with palaeocurrent and palaeogeography， we construct two source-to-sink systems: 1) Jiaodong Uplift and Sulu Orogenic belt as the source area and the North Yellow Sea Basin as the sink area; 2) Liaodong Peninsula as the source area and the North Yellow Sea Basin as the sink area.

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Development and prospect of telemedicine

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Intelligent Medicine 2024年第1期4卷 1-9页

作者： Zhiyue Su Chengquan Li haitian Fu Liyang Wang Meilong Wu Xiaobin Feng University College London LondonWC1E 6BTUnited Kingdom School of Clinical Medicine Tsinghua UniversityBeijing 100084China Division of Hepatobiliary and Pancreas Surgery Department of General SurgeryShenzhen People’s Hospital(The Second Clinical Medical College of Jinan UniversityThe First Affiliated Hospital of Southern University of Science and Technology)ShenzhenGuangdong 518020China

With the continuous improvement and development of modern network information technology and the continuous improvement of people’s demands for health care,the traditional health care model has evolved,giving birth to a new telemedicine health care *** refers to the comprehensive application of information technology for medical information transmission and long-distance communication between different *** integrates medicine,computer technology,and communication technology for remote monitoring,diagnosis,consultation,case discussion,teaching,and surgery as well as a series of medical *** the continuous development of communication technology,telemedicine is also constantly *** a relatively novel technology,telemedicine is sought after by major *** the advancement of internet technology,digitization and informatization have been gradually applied in telemedicine,but due to various factors,telemedicine still has great *** paper summarized the development status of telemedicine;discussed in detail the development of telemedicine at home and abroad;reviewed the application of telemedicine as well as the feasibility and limitations of its promotion and development;and put forward an outlook for the future development of telemedicine.

关键词： Telemedicine Medical service Application development

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