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Resonant frequencies of a piezoelectric drum transducer

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第9期10卷 1313-1319页

作者： Jiang-bo YUAN Tao XIE Xiao-biao SHAN Wei-shan CHEN State Key Laboratory of Advanced robot and system Harbin Institute of Technology Harbin 150001 China

This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric and metal material combined with the Rayleigh-Ritz method. The finite element method (FEM) was used to predict the excitation frequency of the drum transducer. To verify the theoretical analysis, the input impedance characteristic of the drum transducer was measured using an experimental method. The results obtained from theoretical analysis were in very good agreement with those from the FEM and experimental results. The effect of geometrical changes to the thick-walled steel ring of the drum transducer at the first resonance frequency is also described. The calculated results were found to be in good agreement with the FEM results. The results indicate that the first resonance frequency of the drum decreases with the increasing inner diameter of the thick-walled steel ring.

关键词： Piezoelectric Drum transducer Resonance frequency

Study on Blade Surface Flow around Wind Turbine by Using LDV Measurements

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Journal of Thermal Science 2015年第2期24卷 131-139页

作者： Tinnapob Phengpom Yasunari Kamada Takao Maeda Junsuke Murata Shogo Nishimura Tasuku Matsuno division of system Engineering Mie University division of Mechanical Engineering Mie University

This paper has attempted to study a mechanism of three-dimensional flow around a horizontal axis wind turbine(HAWT) rotor blade. An experimental study of the flow phenomenon in the vicinity of the wind turbine blade is a challenging endeavor. In this research, the HAWT model with 2.4 m diameter was tested in the large wind tunnel. The flow around the rotating blade surface was measured simultaneously for three velocity components, and two probes were used for the synchronized measurement of three-dimensional flow components. The local velocity was detected for the single seeding particle measured in the point where three pairs of laser beams intersected. Blade sections of interest in this study are composed of radial positions r/R = 0.3, 0.5 and 0.7. Optimum and low tip speed ratio flow characteristics were also compared. The velocity flow vector, skin friction coefficient and bound circulation were calculated from LDV measurements, and the experimental research showed reasonably and clearly the experimental results.

关键词： LDV measurement Sectional performance Wind turbine Boundary layer flow Span-wise flow

Transport mechanism in chemically reactive hybrid nanofluid flow containing gyrotactic micro-organisms over a curved oscillatory surface

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Applied Mathematics and Mechanics(English Edition) 2025年第1期46卷 177-192页

作者： M.NAVEED M.IMRAN T.ASGHAR Z.ABBAS Department of Mathematics Division of Science and TechnologyUniversity of Education Department of Mathematics The Islamia University of Bahawalpur

This paper examines the transport analysis, including both heat transfer and mass transfer, in hybrid nanofluid flow containing gyrotactic microorganisms towards a curved oscillatory surface. The influence of magnetic fields is also inspected in terms of their physical characteristics. To depict the phenomena of transport, modified versions of both Fick's and Fourier's laws are used. Additionally, the characteristics of both heterogeneous and homogeneous chemical reactions are also incorporated. Utilizing a curvilinear coordinate system, the flow problem is formulated as partial differential equations(PDEs)for momentum, concentration, microorganism field, and energy. An analytical solution to the obtained flow equations is achieved utilizing the homotopy analysis method(HAM).The effects of significant flow parameters on the pressure and microorganism fields, velocity, oscillation velocity, concentration, and temperature distributions are shown via graphs. Furthermore, the variations in skin friction, mass transfer rate, heat transfer rate, and local motile number due to different involved parameters are presented in tables and are analyzed in detail. Graphical results indicate that the curves of velocity and temperature fields are enhanced as the values of the solid volume fraction variables *** is also verified that the concentration rate field decreases as the values of the homogeneous reaction strength parameter and the radius of curvature parameter increase, and it increases with the Schmidt number and the heterogeneous reaction strength *** outcomes show a favorable response of the motile number to advanced values of the Peclet number, the Schmidt number, the microorganism difference parameter, and the bio-convective Lewis number.

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Novel Door-opening Method for Six-legged robots Based on Only Force Sensing

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Chinese Journal of Mechanical Engineering 2017年第5期30卷 1227-1238页

作者： Zhi-Jun Chen Feng Gao Yang Pan State Key Laboratory of Mechanical system and Vibration Shanghai Jiao Tong University Shanghai GQY robot Limited Company

Current door-opening methods are mainly developed on tracked, wheeled and biped robots by applying multi-DOF manipulators and vision systems. However, door-opening methods for six-legged robots are seldom studied, especially using 0-DOF tools to operate and only force sensing to detect. A novel door-opening method for six-legged robots is developed and imple- mented to the six-parallel-legged robot. The kinematic model of the six-parallel-legged robot is established and the model of measuring the positional relationship between the robot and the door is proposed. The measurement model is completely based on only force sensing. The real- time trajectory planning method and the control strategy are designed. The trajectory planning method allows the maximum angle between the sagittal axis of the robot body and the normal line of the door plane to be 45°. A 0-DOF tool mounted to the robot body is applied to operate. By integrating with the body, the tool has 6 DOFs and enough workspace to operate. The loose grasp achieved by the tool helps release the inner force in the tool. Experiments are carried out to validate the method. The results show that the method is effective and robust in opening doors wider than 1 m. This paper proposes a novel door-opening method for six-legged robots, which notably uses a O-DOF tool and only force sensing to detect and open the door.

关键词： Door-opening·Six-legged robots· Forcesensing · O-DOF tool

Implementation of Turbulent Mixing over a Stratocumulus-Topped Boundary Layer and Its Impact in a GCM

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Advances in Atmospheric Sciences 2009年第5期26卷 995-1004页

作者： Sun-Hee SHIN Kyung-Ja HA division of Earth Environmental system Pusan National University

The effect of a vertical diffusion scheme over a stratocumulus topped boundary layer （STBL） was investigated using the YONU AGCM （Yonsei University Atmospheric General Circulation Model）. To consider the impact of clouds on the turbulence production, the turbulence mixing term, driven by radiative cooling at the cloud top, is implemented as an extended non-local diffusion scheme. In the model with this new scheme, the STBL parameterization significantly influences the lower atmosphere over the tropical and subtropical regions. Consideration of the turbulent mixing within the cloud layer leads to continuous stratocumulus formation. The cloud-top radiative cooling tends to favor more rapid entrainment and produces top-down turbulent mixing. This cooling develops a mixed layer without initiation of deep convection by surface fluxes. Variations in thermodynamical and dynamical features are produced by planetary boundary layer （PBL） cloud development. The simulated stratocumulus induces more mixing of heat and moisture due to the cloud forcing. Over STBL regions, the lower boundary layer becomes warmer and drier. It also weakens vertical motion and zonal trade winds in the eastern Pacific, which indicates that stratocumulus cloud cover plays a role in weakening the Walker circulation; that is, cloud cover damps the tropical circulation.

关键词： stratocumulus topped boundary layer non-local diffusion scheme tropical circulation general circulation model

Oscillating Body Design for A 3-DOF Wave Energy Converter

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China Ocean Engineering 2018年第4期32卷 453-460页

作者： CHEN Wei-xing GAO Feng MENG Xiang-dun State Key Laboratory of Mechanical system and Vibration Shanghai Jiao Tong University Chejing robot Technology Co. Ltd.

Ocean wave energy converters(WECs) are obtaining more and more attentions in the world. So far, many types of converters have been invented. Oscillating body systems are a major class of WECs, which typically have one degree of freedom(DOF), and the power absorption efficiency is not quite satisfactory. In this paper, a 3-DOF WEC is proposed and a simplified frequency-domain dynamic model of the WEC depending on the linear potential theory is conducted. The performances of three geometries of the oscillating body including the cone, the cylinder and the hemisphere have been compared, and the results show that the hemisphere is more suitable for the 3-DOF ***, the relationship among the parameters of the hemisphere is established based on the equal natural frequencies of the heave and pitch(or roll) motions, and the results show that lowering the center of gravity leads to the better power absorption in the pitch(or roll) motion. In the end, the power matrixes of different sizes of the hemispheres under different irregular waves are obtained, which can give a size design reference for engineers.

关键词： WEC 3-DOF geometry dynamic parameters size design reference

Novel Mobility Formula for Parallel Mechanisms Expressed with Mobility of General Link Group

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Chinese Journal of Mechanical Engineering 2013年第6期26卷 1082-1090页

作者： ZHANG Yitong LU Wenjuan MU Dejun YANG Yandong ZHANG Lijie ZENG Daxing Key Laboratory of Parallel robot and Mechatronic system Yanshan University Key Laboratory of Advanced Forging & Stamping Technology and Science Yanshan University

The determination of virtual constraints is always one of the key and difficult problems in traditional mobility calculation. To make mobility calculation simple, considering avoiding virtual constraints, some new formulae have been presented, however these formulae can hardly intuitively reflect general link group＇s restrictions on output member and its influences on independence of output parameters, which is premise to the judgment of the properties of mobility. Towards the problem to reveal the intrinsic relationship between the degree of freedom（DOF） of a mechanism, the link group, and the dimension of output parameters, also to avoid determination of virtual constraint, based on the new concepts of the ＂DOF of general link group＂ and ＂node parameters＂, a new formula in the calculation of the mobility of mechanisms is presented that is expressed with DOFs of the general link groups and rank of motion parameters of base point of the output link. It is named GOM（mobility of groups and output parameter） formula. On the basis of new concepts of＂effective parameters＂ and ＂invalid parameters＂, a rule is put forward for solving the DOF of mechanisms with invalid parameters by GOM formula, that is, the base point parameters are the subset of effective parameters of link group. Thereafter, several examples are enumerated and the results coincide with the prototype data, which proves the validity of the proposed formula. Meanwhile, it is obtained that the necessary and sufficient condition for the judgment of output parameters independence is that each of the DOF of the link group is not less than zero. The proposed formula which is simple in calculation provides theoretical basis for the judgment of independence of output parameters and provides references for type synthesis of novel parallel mechanisms with independence requirements of their output parameters.

关键词： parallel mechanism degree of freedom general link group output parameters

Distributed Solving Linear Algebraic Equations with Switched Fractional Order Dynamics

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Journal of systems Science & Complexity 2023年第2期36卷 613-631页

作者： YU Wenqiang CHENG Songsong HE Shuping Anhui Engineering Laboratory of Human-robot Integration system and Intelligent Equipment School of Electrical Engineering and AutomationAnhui UniversityHefei 230601China

This paper proposes a novel distributed optimization algorithm with fractional order dynamics to solve linear algebraic ***,the authors proposed“Consensus+Projection”flow with fractional order dynamics,which has more design freedom and the potential to obtain a better convergent performance than that of conventional first order ***,the authors prove that the proposed algorithm is convergent under certain iteration order and ***,the authors develop iteration order switching scheme with initial condition design to improve the convergence performance of the proposed ***,the authors illustrate the effectiveness of the proposed method with several numerical examples.

关键词： Distributed optimization fractional order dynamics initial condition iteration order linear equations

Corrosion and optimum corrosion protection potential of friction stir welded 5083-O Al alloy for leisure ship

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中国有色金属学会会刊：英文版 2009年第4期19卷 898-903页

作者： Sung-Hyeon PARK Jong-Shin KIM Min-Su HAN Seong-Jong KIM division of Maritime Transportation system Mokpo Maritime University Korea Register of Shipping division of Marine Engineering Mokpo Maritime University

Electrochemical tests were undertaken to determine the optimum conditions in seawater for corrosion protection of friction stir-welded 5083-O Al *** trend observations show that the limiting potential that avoids the effects of hydrogen embrittlement is -1.6 V,corresponding to the crossover point between concentration polarization and activation ***,the optimum protection potential is between -1.5 and -0.7 V since the current density at these values is low in the potentiostatic *** a galvanic cell is formed in the seawater,the welds exhibit electrochemically stable *** parts in galvanic tests with various area ratios are stable and have excellent anticorrosion characteristics.

关键词：搅拌摩擦焊接保护电位海水腐蚀铝合金氧铝船舶休闲防腐