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Applied Mathematics and Mechanics(English Edition) 2020年第4期41卷 551-566页

作者： W.T.ANG x.wang School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore Department of Mechanical Engineering National University of SingaporeSingapore 117575Singapore

A boundary integral method with radial basis function approximation is proposed for numerically solving an important class of boundary value problems governed by a system of thermoelastostatic equations with variable coe?cients. The equations describe the thermoelastic behaviors of nonhomogeneous anisotropic materials with properties that vary smoothly from point to point in space. No restriction is imposed on the spatial variations of the thermoelastic coe?cients as long as all the requirements of the laws of physics are satis?ed. To check the validity and accuracy of the proposed numerical method, some speci?c test problems with known solutions are solved.

关键词： elliptic partial differential equation variable coefficient boundary element method radial basis function anisotropic thermoelastostatics

A micromechanical model based on hypersingular integro-differential equations for analyzing micro-crazed interfaces between dissimilar elastic materials

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Applied Mathematics and Mechanics(English Edition) 2020年第2期41卷 193-206页

作者： x.wang W.T.ANG H.FAN School of Mechanical and Aerospace Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

The current work models a weak(soft) interface between two elastic materials as containing a periodic array of micro-crazes. The boundary conditions on the interfacial micro-crazes are formulated in terms of a system of hypersingular integro-differential equations with unknown functions given by the displacement jumps across opposite faces of the micro-crazes. Once the displacement jumps are obtained by approximately solving the integro-differential equations, the effective stiffness of the micro-crazed interface can be readily computed. The effective stiffness is an important quantity needed for expressing the interfacial conditions in the spring-like macro-model of soft interfaces. Specific case studies are conducted to gain physical insights into how the effective stiffness of the interface may be influenced by the details of the interfacial micro-crazes.

关键词： micromechanical modeling micro-crazed interface effective stiffness coefficient hypersingular integro-differential equation

3D bare-hand interactions enabling ubiquitous interactions with smart objects

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Advances in Manufacturing 2020年第2期8卷 133-143页

作者： S.K.Ong x.wang A.Y.C.Nee Department of Mechanical Engineering Faculty of EngineeringNational University of SingaporeSingapore

Ubiquitous augmented reality(UAR)implementation can benefit smart shop floor operations *** from a user's first-person view can support and provide the user with suitable and comprehensive information without him/her being distracted from ongoing tasks.A natural hand-based interaction interface,namely,a mobile bare-hand interface(MBHI),is proposed to assist a user in exploring and navigating a large amount of information for a task in the user's first-person *** integration of a smart shop floor and UAR-based MBHI is particularly challenging.A real shop floor environment is composed of challenging conditions for the implementation of UAR,e.g.,messy backgrounds and significant changes in illumination ***,the MBHI is required to provide precise and quick responses to minimize the dificulty of a user's *** this study,a wearable UAR system integrated with an MBH is proposed to augment the shop floor environment with smart information.A case study is implemented to demonstrate the practicality and effectiveness of the proposed UAR and MBHI system.

关键词： Augmented reality(AR) Mobile bare-hand interaction(MBH) Smart objects(SOs) Manufacturing shop-floor

Survey of the mechanisms of power take-off(PTO)devices of wave energy converters

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Acta Mechanica Sinica 2020年第3期36卷 644-658页

作者： Z.Liu R.Zhang H.xiao x.wang School of Engineering RMIT UniversityBundooraVIC 3083Australia

Ocean wave energy conversion as one of the renewable clean energy sources is attracting the research interests of many *** review introduces different types of power take-off(PTO)technology of wave energy *** novelty of this paper is to present advantages and disadvantages of the linear direct and indirect drive PTO devices for ocean wave energy *** designs and optimizations of PTO systems of ocean wave energy converters have been studied from reviewing the recently published *** novel mechanical designs of the PTO systems have been compared and investigated in order to increase the energy harvesting efficiency.

关键词： ocean wave energy

Structure modification and recovery of amorphous Fe_(73.5)Si_(13.5)B_9Nb_3Cu_1 magnetic ribbons after autoclave treatment:SAxS and thermodynamic analysis

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Journal of Materials Science & Technology 2019年第1期35卷 118-126页

作者： L.Y.Guo x.wang K.C.Shen K.B.Kim S.Lan x.L.wang W.M.wang Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of Education Shandong University Department of Nanotechnology and Advanced Materials Engineering Sejong University Herbert Gleiter Institute of Nanoscience School of Materials Science and Engineering Nanjing University of Science and Technology Department of Physics City University of Hong Kong

The structure, crystallization kinetics and magnetic property of as-quenched Fe_(73.5)Si_(13.5)B_9Nb_3Cu_1 amorphous ribbon(R0) as well as ribbons after autoclave treatment at 100°C and 150°C(R1 and R2) have been systematically studied by various techniques. With increasing autoclave treatment temperature,the measured structural, kinetic and magnetic parameters of samples increase firstly, i.e. R0 < R1; and then decrease or recover to the as-quenched sample, i.e. R2 < R1 or R2 ≈ R0. These results indicate that the SROs in R1 samples increased by transforming from fcc to bcc structure during the autoclave treatment and that the autoclave treatment can decrease the large radius(r_M) MRO(medium range order),but increase the small rMMRO. The measured structural, thermal and magnetic parameters of R2 sample have a tendency to recover toward as-quenched R0 sample. The thermal and magnetic parameters of samples after solely annealing treatment at higher temperature have no obvious recover *** uneven actions of pressure and temperature in autoclave treatment may be helpful for us to search a new method to improve the magnetic properties of Fe-based glasses.

关键词： SAxS (small-angle x-ray scattering) Fe-based glass Thermodynamic Magnetic ribbon DSC (differential scanning calorimetry)

A Boundary Condition-Implemented Immersed Boundary-Lattice Boltzmann Method and Its Application for Simulation of Flows Around a Circular Cylinder

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Advances in Applied Mathematics and Mechanics 2014年第6期6卷 811-829页

作者： x.wang C.Shu J.Wu L.M.Yang Department of Aerodynamics College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsYudao StreetNanjing 210016China Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260Singapore

A boundary condition-implemented immersed boundary-lattice Boltzmann method(IB-LBM)is presented in this *** present approach is an improvement to the conventional *** the conventional IB-LBM,the no-slip boundary condition is only approximately *** a result,there is flow penetration to the solid *** drawback of conventional IB-LBM is the use of Dirac delta function interpolation,which only has the first order of *** this work,the no-slip boundary condition is directly implemented,and used to correct the velocity at two adjacent mesh points from both sides of the boundary *** velocity correction is made through the second-order polynomial interpolation rather than the first-order delta function ***,the two drawbacks of conventional IB-LBM are removed in the present *** important contribution of this paper is to present a simple way to compute the hydrodynamic forces on the boundary from Newton’s second *** validate the proposed method,the two-dimensional vortex decaying problem and incompressible flow over a circular cylinder are *** shown in the present results,the flow penetration problem is eliminated,and the obtained results compare very well with available data in the literature.

关键词： Immersed boundary method lattice Boltzmann method velocity correction Lagrange interpolation no-slip boundary condition

Method of inter-turn fault detection for nextgeneration smart transformers based on deep learning algorithm

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High Voltage 2019年第4期4卷 282-291页

作者： Lian Duan Jun Hu Gen Zhao Kunjin Chen Shan x.wang Jinliang He Department of Electrical Engineering Tsinghua UniversityBeijingPeople's Republic of China Center for Magnetic Nanotechnology Stanford University450 Serra MallStanfordCA 94305USA

In this study,an inter-turn fault diagnosis method is proposed based on deep learning algorithm.12-channel data is obtained in MATLAB/Simulink as the time-domain monitoring signals and labelled with 16 different fault tags,including both primary and secondary voltage and current *** auto-encoder is presented to classify the fault type of the abundant and comprehensive fault *** overall waveforms compose a two-dimension data matrix and the auto-encoder is trained to extract the features in the multi-channel *** selected features are convoluted with the original data,generating a one-dimensional vector as the input to the softmax *** such as type,activation function and depth of auto-encoder,sparsity of sparse auto-encoder,number of features and pooling strategies are studied,which gives an intuitive process to train a proper learning *** overall recognition accuracy reaches 99.5%.Signal characteristics such as channel selection,time span of the input signal and signal sampling frequency are studied to find the best solution for the interturn fault detection of the three-phase *** proposed method under deep learning framework increases the accuracy and robustness in transformer fault diagnosis,indicating its potential and prospect in the next-generation smart transformers.

关键词： fault abundant smart

Analysis of Convolution Quadrature Applied to the Time-Domain Electric Field Integral Equation

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Communications in Computational Physics 2012年第2期11卷 383-399页

作者： Q.Chen P.Monk x.wang D.Weile Department ofMathematical Sciences University of DelawareNewarkDE 19716USA Department of Electrical and Computer Engineering University ofDelawareNewarkDE 19716USA

We show how to apply convolution quadrature(CQ)to approximate the time domain electric field integral equation(EFIE)for electromagnetic *** a suitable choice of CQ,we prove that the method is unconditionally stable and has the optimal order of ***,the resulting semi discrete EFIE is dispersive and dissipative,and we analyze this ***,we present numerical results supporting and extending our convergence analysis.

关键词： Electromagnetism scattering time-domain integral equation EFIE convolution quadrature multistep method

Laser ablation and structuring of CdZnTe with femtosecond laser pulses

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Journal of Materials Science & Technology 2020年第13期47卷 180-185页

作者： J.J.J.Nivas E.Allahyari A.Vecchione Q.Hao S.Amoruso x.wang Dipartimento di Fisica“Ettore Pancini” Universitàdi Napoli“Federico II”Via CintiaI-80126 NapoliItaly CNR-SPIN UOS NapoliVia CintiaI-80126 NapoliItaly CNR-SPIN UOS SalernoVia Giovanni Paolo II132I-84084 Fisciano(SA)Italy North China Research Institute of Electro-Optics Beijing 100015China School of Remote Sensing and Information Engineering Wuhan UniversityWuhan 430072China

We report an experimental investigation on laser ablation and associated surface structuring of CdZnTe by femtosecond Ti:Sa laser pulses(laser wavelengthλ≈800 nm,≈35 fs,10 Hz),in *** exploiting different static irradiation conditions,the fluence threshold and the incubation effect in CdZnTe are ***,surface treatment with a low laser fluence(laser pulse energy E≈5-10_μJ)and number of shots(5xpansion coefficients of Te inclusions and matrix during the sample heating and cooling processes ensuing femtosecond laser *** with a larger number of pulses(N≈500,1000)with higher pulse energies(E≈30-50μJ)results in the formation of welldefined laser-induced periodic surface structures(LIPSS)in the outskirts of the main crater,where the local fluence is well below the material ablation *** low spatial frequency and high spatial frequency LIPSS perpendicular to the laser polarization are found together and separately depending on the irradiation *** are ascribed to a process of progressive aggregation of randomly distributed nanoparticles produced during laser ablation of the deep crater in the region of the target irradiated by a fluence below the ablation threshold with many laser pulses.

关键词： Laser ablation Femtosecond laser surface processing CdZnTe Laser induced periodic surface structures Laser processing

Gradient Structured Copper by Rotationally Accelerated Shot Peening

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Journal of Materials Science & Technology 2017年第7期33卷 758-761页

作者： x.wang Y.S.Li Q.Z.ang Y.H.Zhao Y.T.Zhu Nano Structural Materials Center School of Materials Science and Engineering Nanjing University of Science and Technology Nanjing 210094 China School of Mechanical Engineering Nanjing University of Science and Technology Nanjing 210094 China Department of Materials Science and Engineering North Carolina State University Raleigh NC 27695 USA

A new technology-rotationally accelerated shot peening（RASP）, was developed to prepare gradient structured materials. By using centrifugal acceleration principle and large steel balls, the RASP technology can produce much higher impact energy compared to conventional shot peening. As a proof-of-concept demonstration, the RASP was utilized to refine the surface layer in pure copper（Cu） with an average grain size of 85 nm. The grain size increases largely from surface downwards the bulk, forming an800 ？m thick gradient-structured surface layer and consequently a micro-hardness gradient. The difference between the RASP technology and other established techniques in preparing gradient structured materials is discussed. The RASP technology exhibits a promoting future for large-scale manufacturing of gradient materials.

关键词： Microstructure Rotationally accelerated shot peening Gradient structure Hardness Copper