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Analysis of the Flow Rate Characteristics of Valveless Piezoelectric Pump with Fractal-like Y-shape Branching Tubes

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Chinese Journal of Mechanical Engineering 2014年第3期27卷 628-634页

作者： HUANG Jun ZHANG Jianhui WANG Shouyin LIU Weidong State Key laboratory of mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences

Microchannel heat sink with high heat transfer coefficients has been extensively investigated due to its wide application prospective in electronic cooling. However, this cooling system requires a separate pump to drive the fluid transfer, which is uneasy to minimize and reduces their reliability and applicability of the whole system. In order to avoid these problems, valveless piezoelectric pump with fractal-like Y-shape branching tubes is proposed. Fractal-like Y-shape branching tube used in microchannel heat sinks is exploited as no-moving-part valve of the valveless piezoelectric pump. In order to obtain flow characteristics of the pump, the relationship between tube structure and flow rate of the pump is studied. Specifically, the flow resistances of fractal-like Y-shape branching tubes and flow rate of the pump are analyzed by using fractal theory. Then, finite element software is employed to simulate the flow field of the tube, and the relationships between pressure drop and flow rate along merging and dividing flows are obtained. Finally, valveless piezoelectric pumps with fractal-like Y-shape branching tubes with different fractal dimensions of diameter distribution are fabricated, and flow rate experiment is conducted. The experimental results show that the flow rate of the pump increases with the rise of fractal dimension of the tube diameter. When fractal dimension is 3, the maximum flow rate of the valveless pump is 29.16 mL/min under 100 V peak to peak （13 Hz） power supply, which reveals the relationship between flow rate and fractal dimensions of tube diameter distribution. This paper investigates the flow characteristics of valveless piezoelectric pump with fractal-like Y-shape branching tubes, which provides certain references for valveless piezoelectric pump with fractal-like Y-shape branching tubes in application on electronic chip cooling.

关键词： piezoelectric pump valveless fractal-like Y-shape branching tube

Distribution of Measuring Points and Piezoelectric Actuators in Flutter Suppression

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Chinese Journal of Aeronautics 2002年第1期15卷 33-37页

作者：陈伟民管德李敏诸德超 Dept. of mechanics and Engineering Science Beijing University Beijing 100871 China Dept. of Flight Vehicle Design and applied mechanics Beijing University of Aeronautics and Astronautics Beijing 100083 China The State Key lab. of Nonlinear mechanics Institute of Mechanics of China Science Academy Beijing 100080 China

Single input/single output (SISO), single input/multi output(SIMO) multi input/ multi output (SIMO) control laws for activeflutter suppression are designed and realized wind tun- nel *** agreement between analytical and tested results isachieved. Based on these re- sults, the distribution of responsemeasuring points and piezoelectric actuators is investigated.

关键词： flutter wind tunnel piezoelectric

A Review of Ultrasonic Nano Manipulation Technology

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Journal of Harbin Institute of Technology(New Series) 2016年第1期23卷 1-9页

作者： Junhui Hu State Key lab of mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics

Nano manipulation technology has great potential applications in the assembly,measurement and fabrication of nano materials,actuating and high-sensitivity sensing of biological samples,manufacture of nano sensors,decontamination of air and water,etc. As an actuating technology which is far from being mature,the nano manipulation still faces lots of challenges in the device principles,design,scaling up,sample safety,*** ultrasonic nano manipulation, in which nanoscale objects are handled and actuated by controlled ultrasound,is an emerging technology to meet some of challenges in nano manipulations. The author's research team and other groups have proposed and realized a series of nano manipulation functions such as trapping,transfer, rotation and concentration since 2012, by controlled ultrasound. Compared with other nano manipulating techniques,the ultrasonic method has the merits such as very low temperature rise at the manipulation area,little selectivity to the material properties of manipulated samples,capability of being implemented on the substrates without MENS or NEMS structure,etc. This paper reviews the progresses in principles,functions,structures and characteristics of the ultrasonic devices for nano manipulations.

关键词： nano manipulation ultrasound acoustic streaming

Design of nanofluid-cooled heat sink using topology optimization

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Chinese Journal of Aeronautics 2021年第2期34卷 301-317页

作者： Bin ZHANG Jihong ZHU Gaoxiang XIANG Limin GAO Deparment of Engineering mechanics School of MechanicsCivil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China MIIT lab of Metal Addive Manufacturing and Innovative Design Northwvestern Polytechrical UniversilyXi'an 710072China School of Power and Energy Northwestern Polytechnical UniversityXi'an 710072China

The paper presented topology optimization of 2 D and 3 D Nanofluid-Cooled Heat Sink(NCHS). The flow and heat transfer problem in the NCHS was treated as a single-phase nanofluid based convective heat transfer model. The temperature-dependent fluid properties were taken into account in the model due to the strong temperature-dependent features of nanofluids. An average temperature minimum problem was studied subject to the fluid area and energy dissipation constraints by using the density method. In the method, the design variable is updated according to the gradient information obtained by an adjoint based sensitivity analysis process. The effects of the energy dissipation constraint, temperature-dependent fluid properties and nanofluid characteristics on optimal configurations of NCHS were numerically investigated with following ***, branched flow channels in the optimal configuration increased with the rise of the allowed energy dissipation. Secondly, temperature-dependent fluid properties were significant for obtaining the appropriate optimal results with best cooling performance. Thirdly, heat transfer performances of optimal configurations were enhanced by reducing the nanoparticle diameter or increasing the nanoparticle volume fraction. Fourthly, the optimal configuration for nanofluid had better cooling performance than that for its base fluid.

关键词： Forced convection Heat sinks Heat transfer Nanofluid Sensitivity analysis Topology optimization

Extraction of real modes and physical matrices from modal testing

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Earthquake Engineering and Engineering Vibration 2011年第2期10卷 219-227页

作者： Wang Tong Zhang Lingmi Tee Kong Fah MOE Key lab of Structural mechanics and Control for Aircraft Nanjing University of Aeronautics and Astronautics Nanjing 210016 China Department of Civil Engineering University of Greenwich United Kingdom

A technique to extract real modes from the identified complex modes is presented in this paper, which enables the normalized real mode shapes, modal masses, and full or reduced mass and stiffness matrices to be obtained. The theoretical derivation of the method is provided in detail. An 11-DOF vibration system is used to validate the algorithm, and to analyze the effects of the number of modes utilized and measurement DOFs on the extraction results. Finally, the method is used to extract real modes from both experimental modal analysis and operational modal analysis.

关键词： modal analysis complex mode real mode normalized mode shape modal mass

Base force element method of complementary energy principle for large rotation problems

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Acta Mechanica Sinica 2009年第4期25卷 507-515页

作者： Yijiang Peng Yinghua Liu FML Department of Engineering Mechanics Tsinghua University 100084 Beijing China Key lab of Urban Security and Disaster Engineering Beijing University of Technology 100124 Beijing China

Using the concept of the base forces, a new finite element method （base force element method, BFEM） based on the complementary energy principle is presented for accurate modeling of structures with large displacements and large rotations. First, the complementary energy of an element is described by taking the base forces as state variables, and is then separated into deformation and rotation parts for the case of large deformation. Second, the control equations of the BFEM based on the complementary energy principle are derived using the Lagrange multiplier method. Nonlinear procedure of the BFEM is then developed. Finally, several examples are analyzed to illustrate the reliability and accuracy of the BFEM.

关键词： Base force element method (BFEM) Complementary energy principle Lagrange multiplier method Geometrically nonlinear Large rotation

Independent continuous mapping for topological optimization of frame structures

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Acta Mechanica Sinica 2006年第6期22卷 611-619页

作者： Yunkang Sui Jiazheng Du Yingqiao Guo Department of mechanics Beijing University of Technology Beijing 100022 China lab. GMMS University of Reims Champagne-Ardenne BP1039 51687 Reims France

Based on the Independent Continuous Mapping method （ICM）, a topological optimization model with continuous topological variables is built by introducing three filter functions for element weight, element allowable stress and element stiffness, which transform the 0-1 type discrete topological variables into continuous topological variables between 0 and 1. Two methods for the filter functions are adopted to avoid the structural singularity and recover falsely deleted elements： the weak material element method and the tiny section element method. Three criteria （no structural singularity, no violated constraints and no change of structural weight） are introduced to judge iteration convergence. These criteria allow finding an appropriate threshold by adjusting a discount factor in the iteration procedure. To improve the efficiency, the original optimization model is transformed into a dual problem according to the dual theory and solved in its dual space. By using MSC/Nastran as the structural solver and MSC/Patran as the developing platform, a topological optimization software of frame structures is accomplished. Numerical examples show that the ICM method is very efficient for the topological optimization of frame structures.

关键词： Frame structures Topological optimization ICM method Filter functions Element elimination

Hardness Testing on Surface Layer of Material and Results Analyzing Contrastively

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Chinese Journal of Aeronautics 2002年第2期15卷 82-89页

作者：李敏张泰华甘翠华梁乃刚 State Key lab. of Nonlinear mechanics Institute of Mechanics CAS Beijing 100080 China

Several methods of microhardness and nanoindentation test on the surface layer of material are discussed in this paper. The characteristics and the testing range of several microhardness instruments are introduced. The emphasis of this paper is the differences in essence between microhardness and nanoindentation hardness. At last, using the FEA simulation and nanoindentation test, the quantitative relationship between Vicker microhardness and nanoindentation hardness is given.

关键词： microhardness nanoindentation finite element simulation

Study of Growth Mechanism of Lysozyme Crystal by Batch Crystallization Method

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Chinese Chemical Letters 2006年第1期17卷 101-104页

作者： Hai Liang CUI Yong YU Wan Chun CHEN Qi KANG National Microgravity lab Institute of Mechanics Chinese Academy of Science Beijing 100080 Institute of Physics Chinese Academy of Science Beijing 100080

The lysozyme crystals were made by batch crystallization method and the distribution of aggregate in solution were measured by dynamic light scattering. The results showed that the dimension of aggregate increased with the increase of the concentration of lysozyme and NaCl, lysozyme molecules aggregated gradually in solution and finally arrived at balance each other. The higher the concentrations of lysozyme and NaCl were, the faster the growth rate of （110） face was. The growth rates of lysozyme crystal were obtained by a Zeiss microscope, and the effective surface energy （a） of growing steps were calculated about 4.01×10^-8s J·cm^-2 according to the model of multiple two-dimensional nucleation mechanism.

关键词： Protein crystal growth rate dynamic light scattering lysozymc.