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A Lamb wave signal reconstruction method for high-resolution damage imaging

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Chinese Journal of Aeronautics 2019年第5期32卷 1087-1099页

作者： Xiaopeng WANG jian cai Zhiquan ZHOU State Key Lab of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics

In Lamb wave-based Structural Health Monitoring(SHM), a high-enough spatial resolution is highly required for Lamb wave signals to ensure the resolution and accuracy of damage detection. However, besides the dispersion characteristic, the signal spatial resolution is also largely restricted by the space duration of excitation waveforms, i.e., the Initial Spatial Resolution(ISR)for the signals before travelling. To resolve the problem of inferior signal spatial resolution of Lamb waves, a Lamb Wave Signal Reconstruction(LWSR) method is presented and applied for highresolution damage imaging in this paper. In LWSR, not only a new linearly-dispersive signal is reconstructed from an original Lamb wave signal, but also the group velocity at the central frequency is sufficiently decreased. Then, both dispersion compensation and ISR improvement can be realized to achieve a satisfying signal spatial resolution. After the frequency domain sensing model and spatial resolution of Lamb wave signals are firstly analyzed, the basic idea and numerical realization of LWSR are discussed. Numerical simulations are also implemented to preliminarily validate LWSR. Subsequently, LWSR-based high-resolution damage imaging is developed. An experiment of adjacent multiple damage identification is finally conducted to demonstrate the efficiency of LWSR and LWSR-based imaging methods.

关键词： Damage imaging Dispersion compensation High resolution Lamb waves Signal reconstruction

NONLINEAR NUMERICAL ANALYSIS OF A FLEXIBLE ROTOR EQUIPPED WITH SQUEEZE COUPLE STRESS FLUID FILM JOURNAL BEARINGS

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Acta Mechanica Solida Sinica 2007年第4期20卷 309-316页

作者： cai-Wan Chang-jian Her-Terng Yau Department of Mechanical and Automation Engineering I-Shou University Kaohsiung County 840 Taiwan China Department of Electrical Engineering Far-East College Tainan County 744 Taiwan China

This study performs a dynamic analysis of a rotor supported by two squeeze couple stress fluid film journal bearings with nonlinear suspension. The numerical results show that the stability of the system varies with the non-dimensional speed ratios and the dimensionless parameter l＊. It is found that the system is more stable with higher dimensionless parameter l＊. Thus it can conclude that the rotor-bearing system lubricated with the couple stress fluid is more stable than that with the conventional Newtonian fluid. The modeling results thus obtained by using the method proposed in this paper can be used to predict the stability of the rotor-bearing system and the undesirable behavior of the rotor and bearing center can be avoided.

关键词： couple stress fluid rotor-bearing system bifurcation chaos squeeze

Conformal Invariance of Higher-Order Lagrange Systems by Lie Point Transformation

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Chinese Physics Letters 2011年第11期28卷 8-11页

作者： HUANG Wei-Li cai jian-Le Department of Physics and Telecom Engineering Hunan City UniversityYiyang 413000 College of Science Hangzhou Normal UniversityHangzhou 310018

Conformal invariance and conserved quantities for a higher-order Lagrange system by Lie point transformation of groups are *** differential equation of motion for the higher-order Lagrange system is *** definition of conformal invariance for the system together with its determining equations and conformal factor are *** necessary and sufficient condition that the system’s conformal invariance would be Lie symmetry by the infinitesimal one-parameter point transformation group is *** conserved quantity of the system is derived using the structural equation satisfied by the gauge *** example of a higher-order mechanical system is offered to illustrate the application of the result.

关键词： function conformal system

New Features of the Coercivity in Exchange-Coupled Ni_(81)Fe_(19)/CoO Bilayers

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Chinese Physics Letters 2001年第12期18卷 1651-1654页

作者： cai jian-Wang LAI Wu-Yan State Key Laboratory of Magnetism Institute of Physics and Center for Condensed Matter PhysicsChinese Academy of SciencesBeijing 100080

The coercivity behaviour of the Nis1Fe19 film exchange-coupled with an antiferromagnetic CoO underlayer has been investigated systematically. It has been found that the coercivity is greatly enhanced not only in the easy axis direction but also in the hard axis direction when the temperature is below the Néel temperature of CoO. Also, the thickness dependence of coercivity at low temperature follows the scaling relation as 1/tNiFe with α=2.5 at the hard axis, which is quite in contrast with the case of the easy axis, i.e. α=1.5, predicted theoretically and verified experimentally previously. The increase of the temperature leads to the decrease of the coercivity at both the easy and hard axes, but the scaling relations are held except the narrow region just below the Néel temperature of CoO, at which the coercivity varies as 1/t NiFe with α=1.0 for both the easy and hard axes. Based upon Hoffmann's ripple theory and Malozemoff's random field model, a simple interpretation of the experiment findings is presented.

关键词： scaling narrow behaviour

Thermal Resistance Simulation for CoF Packages

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Tsinghua Science and Technology 2015年第3期20卷 277-284页

作者： Chuan Chen Qian Wang Xiaotian Meng Lin Tan jian Wang Chengqiang Cui jian cai the Institute of Microelectronics Tsinghua University Beijing 100084 China AKM Electronics Technology (Suzhou) Company Ltd. Suzhou 215000 China the Institute of Microelectronics and Tsinghua National Laboratory for Information Science and Technology Tsinghua University. Beijing 100084 China

Chip-on-Film （CoF） is a packaging technology that mounts Integrated Circuits （IC） chips directly on a flexible substrate surface. As both power and the number of pins in such packages increase, thermal conditions become more important. In this paper, the thermal resistance of CoF packages is studied using Ansys software to perform finite-element analysis. Because of circuit complexity, two equivalent methods-a length-weighted method and an image-recognition method--are proposed in place of an accurate model to get equivalent thermal conductivity of CoF package devices. In our experiments, the simulated value of thermal resistance based on the length-weighted method was 1.653 K/W, and the value based on the image-recognition method was 1.911 K/W. The real thermal resistance value of the CoF package device is 1.812 K/W. So the error between the real value measured by a tester and the simulated value based on the length-weighted method is 8.8%, and the error between the real value and the simulated value based on the image-recognition method is 5.5%. Hence, both methods can provide effective simulation results, and the image-recognition method is more accurate. In addition, we optimized the CoF package structure. From the simulation results, the drop in thermal resistance after the optimization is obvious.

关键词： Chip-on-Film (CoF) finite element analysis equivalent thermal conductivity

Phenomenological Studies on Internal Friction of Noncrystalline Materials in Structural Relaxation Processes

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Chinese Physics Letters 1998年第4期15卷 281-283页

作者： cai jian-le QIAO Chu-liang Department of Applied Physics Hunan UniversityChangsha 410082 Department of Physics Yiyang Teachers’CollegeYiyangHunan 413049

Based on not only the ideas of phenomenological investigations about the internal friction of crystalline materials but also the studies on the internal friction laws of noncrystalline materials during structural relaxation processes in recent years,the method of making relaxation cell is put *** the method,traditional mechanics parameter model and two-level model are unified,so phenomenological studies on the internal friction of noncrystalline materials during structural relaxation processes are made and a new relaxation law is formed.

关键词： friction relaxation Internal

Access to 3-alkylselenindoles by multicomponent reaction of indoles,selenium powder and unactivated alkyl halides under transition-metal-free conditions

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Chinese Chemical Letters 2022年第9期33卷 4303-4305页

作者： Huan Liu Zhong-jian cai Shun-Jun Ji Key Laboratory of Organic Synthesis of jiangsu Province College of ChemistryChemical Engineering and Materials Science&Collaborative Innovation Center of Suzhou Nano Science and TechnologySoochow UniversitySuzhou 215123China

Herein,we reported a convenient and efficient multicomponent reaction of indoles,selenium powder and unactivated alkyl *** protocol provides a practical,and facile approach for the synthesis of 3-alkylselenindole *** advantages of this strategy include mild and transition-metal-free conditions,broad functional group tolerance,the use of simple and easily accessible seleniium powder and alkyl halides as coupling *** importantly,the reaction proceeded smoothly with a large scale(>10 g,>90%yield),which further highlighted the potential application of this selenation strategy.

关键词： Selenium 3-Alkylselenindole Indole Selenization

Properties and Morphology of TiN Films Deposited by Atomic Layer Deposition

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Tsinghua Science and Technology 2014年第2期19卷 144-149页

作者： Siyi Xie jian cai Qian Wang Lu Wang Ziyu Liu the Institute of Microelectronics Tsinghua University the Institute of Microelectronics and Tsinghua National Laboratory for Information Science and Technology Tsinghua University

In this study, TiN films were deposited on SiO2 substrates by Atomic Layer Deposition （ALD） using TiCI4 and NH3 as precursors. Properties and morphology of the TiN films were characterized by different methods. Using Grazing Incidence X-Ray Diffraction （GIXRD）, TiN films demonstrated polycrystalline structure with （111） preferred orientation. Film thickness was measured by Spectroscopic Ellipsometry （SE） and a stable growth rate of 0.0178 nm/cycle was reached after 500 deposition cycles, which was consistent with the essence of ALD as a surface-saturated self-limiting reaction. Film resistivity measured by a four-point probe continuously decreased with increasing deposition cycles until it reached the minimum value of 300 μΩ.cm at 5000 deposition cycles with a thickness of 87.04 nm. The surface roughness and morphology of the TiN films at different deposition cycles ranging from 50 to 400 were analyzed by Atomic Force Microscopy （AFM）. The AFM results indicated that the initial film growth follows the Stranski-Krastanov mode.

关键词： atomic layer deposition titanium nitride morphology

Entanglement of Non-symmetric Two Atomic Qubits Induced by a Coherent State Field

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Communications in Theoretical Physics 2006年第1期45卷 67-70页

作者： LI Jun-Gang ZOU jian cai Jin-Fang SHAO Bin Department of Physics School of Science Beijing Institute of Technology Beijing 100081 China

The entanglement of two atomic qubits, which are coupled to a coherent state field with different couplings, is studied. The dynamical evolution of the concurrence, which measures the degree of the entanglement between the two qubits, is plotted versus the scaled time gt. It is found that the two qubits can be entangled by the coherent state field even when they are initially prepared in the most mixed state, and for very weak field, the most mixed state can be; more easily entangled than some pure states. It is also found that the entanglement between the qubits sensitively depends on the relative difference of the atomic couplings and the mean photon number of the field.

关键词： entanglement mixed state coherent state field