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Journal of Wuhan University of Technology(Materials Science) 2025年第1期 164-170页

作者：吴敏 cao Kailei XIAO Weirong YU Zetai 曹杰荣 DING Qingjun LI Jinhui China Railway Construction Corporation Harbour and Channel Engineering Bureau Group Co. LTD Construction Headquarters of Zhoushan Liuheng Bridge Phase Ⅱ Project China Railway Construction Bridge Engineering Bureau Group Co. LTD State Key Laboratory of Silicate Material for Architecture (Wuhan University of Technology) College of Materials Science and Engineering Wuhan Textile University

The paper presents experimental investigation results of crack pattern change in cement pastes caused by external sulfate attack （ESA）.To visualize the formation and development of cracks in cement pastes under ESA,an X-ray computed tomography （X-ray CT） was used,i e,the tomography system of Zeiss Xradia 510 *** results indicate that X-CT can monitor the development process and distribution characteristics of the internal cracks of cement pastes under ESA with attack *** addition,the C3A content in the cement significantly affects the damage mode of cement paste specimens during sulfate *** damage of ordinary Portland cement （OPC） pastes subjected to sulfate attack with high C3A content are severe,while the damage of sulfate resistant Portland cement （SRPC） pastes is much smaller than that of OPC ***,a quadratic function describes the correlation between the crack volume fraction and development depth for two cement pastes immermed in sulfate solution.

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Molecular Dynamics Simulations of the Effects of Surface Sinusoidal Nanostructures on Nanoscale Liquid Film Phase-Change

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Journal of Thermal Science 2020年第4期29卷 1076-1084页

作者： cao Qun CUI Zheng Institute of Thermal Science and Technology Shandong UniversityJinan 250061China

Nanostructures on heat transfer surfaces can enhance micro/nanoscale phase-change heat transfer processes. To understand the enhancement mechanisms provided by nanostructures, evaporation processes of nanoscale liquid films on periodic sinusoidal-shaped surfaces were investigated via molecular dynamics simulations. By changing the amplitudes(A) and periods(T) of the curves describing the sinusoidal shapes, which possess shapes similar to f(x)=h0+Asin(2πx/T), sinusoidal surfaces of different sizes were constructed. An unevaporated region always existed on the copper plate for all surfaces during phase-change processes. Moreover, we calculated the interfacial thermal resistances and the mismatches between the vibrational density of states of the solid and liquid for different surfaces. The results show that the argon temperature changes and evaporation rates during the phase-change process on sinusoidal surfaces are higher than those on flat surfaces, and these results increase with the increase in amplitudes and the decrease in periods within certain limits mainly because of the thermal resistance decrease at the solid-liquid interface. Furthermore, the corresponding mismatches between the vibrational density of states of the solid and liquid also decrease, which indicates that the existence of sinusoidal nanostructures enhances the heat transfer of the phase-change process.

关键词： molecular dynamics simulation sinusoidal surface phase-change interfacial thermal resistance nanoscale

Uniqueness Problem for Meromorphic Mappings in Several Complex Variables with Few Hyperplanes

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Acta Mathematica Sinica,English Series 2015年第8期31卷 1327-1338页

作者： Hong Zhe cao Ting Bin cao Department of Mathematics Nanchang University

The purpose of this article is to deal with uniqueness problem with truncated multiplicities for meromorphic mappings in several complex variables. We obtain a degeneracy theorem of meromorphic mappings without taking account of multiplicities of order 〉 k in counting functions and a uniqueness theorem for meromorphic mappings sharing 2n ＋ 2（n ≥ 2） hyperplanes in general position, which improve and extend some earlier work.

关键词： Uniqueness problem meromorphic mappings truncated multiplicities

Celebrate a decade of publishing:ten things in ten years

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Light(Science & Applications) 2022年第4期11卷 444-447页

作者： Jianlin cao Editor-in-Chief Light:Science&ApplicationsState Key Laboratory of Applied OpticsCIOMPCASNo.3888Dongnanhu RoadChangchunChina

It all started on 29th March,2012,the day Light:Science&Applications(LSA)was *** journal was established to promote research in all areas of optics and photonics,including basic,applied,and engineering research and applications,by publishing original articles,reviews,news&views,and perspectives of high quality,interest,and far-reaching *** back on that day,our optics and photonics community may hardly imagine how thrilled every founding member of LSA can be,to see the inaugural papers ***,ten years after its founding,LSA has evolved to be an essential and visible resource for our community.

关键词： founding optics hardly

Video-Driven 2D Character Animation

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Chinese Journal of Electronics 2021年第6期30卷 1038-1048页

作者： YIN Qinran cao Weiqun School of Information Science and Technology Beijing Forestry University Engineering Research Center for Forestry-oriented Intelligent Information Processing of National Forestry and Grassland Administration

Video-driven animation has always been a hot and challenging topic in the field of computer animation. We propose a method of mapping a sequence of human skeletal keypoints in a video onto a two-dimensional character to generate 2 D character animation. For a given two-dimensional character picture, we extract the motion of real human in video data, driving the character deformation. We analyze common two-dimensional human body movements, classify the basic posture of the human body, realize the recognition of skeleton posture based on back propagation network, capture human body motion by automatically tracking the position of the human skeleton keypoints coordinates in the video and redirect the motion data to a 2 D character. Compared with the traditional method, our work is less affected by video data illumination and background complexity. We calibrate human body motion in videos to a 2 D character according to the skeleton topology to avoid motion distortion caused by the difference in skeleton size and ratio. The experimental results show that the proposed algorithm can generate the motion of two-dimensional characters based on the motion of human characters in video data. The animation is natural and smooth, and the algorithm has strong robustness.

关键词： two-dimensional character picture motion distortion skeleton size video data illumination human characters video signal processing computer animation character deformation basic posture two-dimensional human body movements background complexity hot topic motion data video-driven animation computational geometry human skeleton keypoints skeleton topology skeleton posture human skeletal keypoints video-driven 2D character animation capture human body motion

Parametric Vibration Stability Analysis of a Pyramid Lattice Sandwich Plate Subjected to Pulsatile External Airflow

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Acta Mechanica Solida Sinica 2023年第1期36卷 95-104页

作者： Zhiwei cao Guo Yao School of Mechanical Engineering and Automation Northeastern UniversityShenyang 110819China

Lattice sandwich structures are broadly used in aerospace,navigation,and high-speed rail *** engineering practice,the airflow outside the vehicle or aircraft always exhibits the pulsatile property,which makes the elastic structural components and the external airflow a parametric excitation *** this paper,the parametric vibration stability analysis and dynamic characteristics of a lattice sandwich plate interacting with the pulsatile external airflow are *** equation of motion is derived using Hamilton’s principle and discretized using the assumed mode *** linear potential flow theory is applied to derive the perturbation aerodynamic *** stability of the system is analyzed using the Floquet theory and validated by numerical *** effects of design parameters of the lattice sandwich plate on the stability of the system are *** the simulations and discussions,some practical principles for the optimal design of lattice sandwich structures in the aerodynamic environment are proposed.

关键词： Lattice sandwich structures Pulsatile airflow Parametric excitation Floquet theory

Vibration-induced nanoscale friction modulation on piezoelectric materials

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Friction 2022年第10期10卷 1650-1659页

作者： Jiawei cao Qunyang LI Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua UniversityBeijing 100084China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

Mechanical vibration,as an alternative of application of solid/liquid lubricants,has been an effective means to modulate friction at the ***,atomic force microscopy(AFM)experiments and model simulations also suggest a similar vibration-induced friction reduction effect for nanoscale contact interfaces,although an additional external vibration source is typically needed to excite the ***,by introducing a piezoelectric thin film along the contact interface,we demonstrate that friction measured by a conductive AFM probe can be significantly reduced(more than 70%)when an alternating current(AC)voltage is *** real-time friction modulation is achieved owing to the localized nanoscale vibration originating from the intrinsic inverse piezoelectric effect,and is applicable for various material *** by analysis with the Prandtl–Tomlinson(P–T)friction model,our experimental results suggest that there exists an approximately linear correlation between the vibrational amplitude and the relative factor for perturbation of sliding energy *** work offers a viable strategy for realizing active friction modulation for small-scale interfaces without the need of additional vibration source or global excitation that may adversely impact device functionalities.

关键词： vibration friction modulation piezoelectric materials contact resonance Prandtl-Tomlinson(P-T)model

Effect of Rotor-stator Axial Gap on the Tip Seal Leakage Flow of a Steam Turbine

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Journal of Thermal Science 2021年第3期30卷 973-982页

作者： LI Pan cao Lihua School of Energy and Power Engineering Northeast Electric Power UniversityJilin 132012China

The tip leakage flow in different axial gaps is numerically investigated based on the Reynolds-Averaged Navier-Stokes equations and k-ω SST turbulent model using commercial CFD software ANSYS *** characteristics of vortexes in the flow field of tip seal and the distribution law of rotor tip leakage loss are analyzed under the change of axial *** results show that the flow field in the blade tip seal undergoes complex changes with the increase of axial *** are two opposite vortices in the seal cavity with small axial gap,namely,the large vortex in the cavity and the small vortex near the wall of the *** small vortex gradually disappears with the increase of the axial *** the axial gap is increased to a certain value,the reverse large vortex is formed in the cavity behind the low teeth of seal,and the leakage rate increases significantly;the steam flow angle and the mixing loss also show different *** on the traditional calculation formula of tip leakage rate,a more accurate calculation formula of tip leakage rate is constructed by introducing equivalent labyrinth seal teeth to consider the variation of axial gap.

关键词： steam turbine axial gap tip leakage labyrinth seal prediction formulation

Electromagnetic riveting technique and its applications

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Chinese Journal of Aeronautics 2020年第1期33卷 5-15页

作者： Zengqiang cao Yangjie ZUO School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China School of Aeronautics and Astronautics Sichuan UniversityChengdu 610065China

With the increasing applications of novel materials and structures in new-generation aircraft,conventional joining techniques in aircraft component assembly are greatly *** meet those challenges,the electromagnetic riveting(EMR)technique was developed as an advanced joining tool,which exhibits obvious advantages in the assembly of new-generation *** this paper,the riveting principle of EMR was analyzed,and its development history and status were presented in ***,equipment features of three typical EMR systems were ***,three important applications of EMR were covered,i.e.,composite structure riveting,titanium rivet and large-size aluminum rivet riveting,and interference fit bolt ***,a novel strengthening method for mechanical linking holes based on EMR was also presented,which can significantly improve the fatigue behaviors of mechanical ***,open questions in the EMR field were discussed,and some recommendations for future work were also *** paper can be useful for optimizing the joint designs of aircraft components and improving the level of aircraft maintenance.

关键词： Composite Electromagnetic riveting Hole strengthening Interference fit Titanium alloys

Neural-Network-Based Nonlinear Model Predictive Tracking Control of a Pneumatic Muscle Actuator-Driven Exoskeleton

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IEEE/CAA Journal of Automatica Sinica 2020年第6期7卷 1478-1488页

作者： Yu cao Jian Huang IEEE Key Laboratory of Image Processing and Intelligent Control School of Artificial Intelligence and AutomationHuazhong University of Science and TechnologyWuhan 430074China

Pneumatic muscle actuators(PMAs)are compliant and suitable for robotic devices that have been shown to be effective in assisting patients with neurologic injuries,such as strokes,spinal cord injuries,etc.,to accomplish rehabilitation ***,because PMAs have nonlinearities,hysteresis,and uncertainties,etc.,complex mechanisms are rarely involved in the study of PMA-driven robotic *** this paper,we use nonlinear model predictive control(NMPC)and an extension of the echo state network called an echo state Gaussian process(ESGP)to design a tracking controller for a PMA-driven lower limb *** dynamics of the system include the PMA actuation and mechanism of the leg orthoses;thus,the system is represented by two nonlinear uncertain *** facilitate the design of the controller,joint angles of leg orthoses are forecasted based on the universal approximation ability of the ESGP.A gradient descent algorithm is employed to solve the optimization problem and generate the control *** stability of the closed-loop system is guaranteed when the ESGP is capable of approximating system *** and experiments are conducted to verify the approximation ability of the ESGP and achieve gait pattern training with four healthy subjects.

关键词： Echo state Gaussian process model predictive control neural network pneumatic muscle actuators-driven exoskeleton