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Biomimetic Material Simulating Solar Spectrum Reflection Characteristics of Yellow Leaf

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Journal of Bionic Engineering 2018年第4期15卷 741-750页

作者： Kai Xu Yang Lin Xuezhong wei Hong Ye Department of Thermal Science and Energy Engineering University of Science and Technology of China Hefei 230027 China Beijing Institute of Space Launch Technology Beijing 100076 China

To counter the threat of hyperspectral detection, it is necessary to develop biomimetic materials to simulate the solar spectral re- flection characteristics of plant leaf accurately. Two kinds ofmembranaceous yellow biomimetic materials were prepared by dispersing the particles of chrome titanium yellow and iron oxide yellow as fillers in polyvinyl alcohol films respectively. Reflectance and transmittance of the biomimetic materials were measured, and absorption and scattering coefficients of the biomimetic materials were inverted with a four-flux model. Results indicate that the biomimetic material adopting chrome titanium yellow particles can simulate the solar spectrum reflection characteristics of yellow leaf because of the similar absorption and scattering characteristics. The biomimetic material adopting iron oxide yellow particles cannot simulate the spectrum reflection characteristics of yellow leaf near the wavelength of 900 nm due to the characteristic absorption of the iron oxide. When the volume fraction of the chrome titanium yellow particles is lower than 2.12%, the absorption and scattering coefficients both increase approximately linearly with the volume fraction, indicating that the particles can scatter radiation independently. Therefore, the reflectance of the biomimetic material can be regulated through linearly changing of the volume fraction of the chrome titanium yellow particles.

关键词： biomimetic material yellow leaf solar spectrum reflection four-flux model absorption coefficient scattering coefficient

Nonlinear Static and Dynamic Stiffness Characteristics of Support Hydraulic System of TBM

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Chinese Journal of Mechanical Engineering 2019年第6期32卷 26-34页

作者： Jianfeng Tao Junbo Lei Chengliang Liu wei Yuan School of mechanical engineering Shanghai Jiaotong UniversityShanghai 200240China School of Electronic Information Jiangsu University of Science and TechnologyZhenjiang 212003China

Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering *** the tunneling process,TBM have serious vibrations,which can damage some of its key *** support system,an important part of TBM,is one path through which vibrational energy from the cutter head is *** reduce the vibration of support systems of TBM during the excavation process,based on the structural features of the support hydraulic system,a nonlinear dynamical model of support hydraulic systems of TBM is *** influences of the component structure parameters and operating conditions parameters on the stiffness characteristics of the support hydraulic system are *** analysis results indicate that the static stiffness of the support hydraulic system consists of an increase stage,stable stage and decrease *** static stiffness value increases with an increase in the *** pre-compression length of the spring in the relief valve a ects the range of the stable stage of the static stiffness,and it does not a ect the static stiffness *** dynamic stiffness of the support hydraulic system consists of a U-shape and reverse *** bottom value of the U-shape increases with the amplitude and frequency of the external force acting on the cylinder body,however,the top value of the reverse U-shape remains *** study instructs how to design the support hydraulic system of TBM.

关键词： Tunnel boring machine Support hydraulic system Nonlinear model Static stiffness characteristics Dynamic stiffness characteristics

Novel Cascaded Z-Source Neutral Point Clamped Inverter

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Chinese Journal of Electronics 2016年第5期25卷 965-973页

作者： HE Yuyao LIU Hailong FENG wei LI Jie School of Marine Science and Technology Northwestern Polytechnical University

Z-source Neutral point clamped(NPC) inverter inherits the advantages of Z-source inverter, which can buck-boost energy and allow the shoot-through *** the same time, Z-source NPC inverter has high running efficiency and less harmonic content. Hence, it can be widely used in motor drives and fuel cell *** increasing the modulation index, one can only get smaller shoot through value in Z-source NPC inverter,therefore the output voltage of the inverter can not be boosted very high. In this paper, a novel cascaded Z-source neutral point clamped inverter is proposed by cascading two Z-source networks in series. An Alternative phase opposition disposition(APOD) carrier-based modulator is applied to control the proposed Z-source inverter. To confirm the operating principle of the new Z-source NPC inverter, a generic APOD carrier-based modulator for the cascaded Z-source NPC Inverter under Matlab/Sinmulink is built. The simulation results show that the boost factor has been increased from 1/(1- 2D) for the traditional Z source NPC inverter to 1/(1- 4D) for the proposed cascaded Z-source NPC inverter. A prototype of the cascaded Z-source NPC inverter has been set up. The experimental results verify that the new topology can increase the boost factor and expand the voltage regulation range of the inverter.

关键词： Cascaded network Z-source inverter Three-level Boost factor APOD

Direct numerical simulation of the viscoelastic channel flow using Giesekus model with variable parameters

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Journal of Hydrodynamics 2019年第2期31卷 326-332页

作者： wei-guo Gu Yu Li De-zhong Wang School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

The paper presents a direct numerical simulation(DNS)for the drag-reducing channel flow using the Giesekus model with variable *** is assumed that the relaxation time in the constitutive equation is varied depending on the local shear *** maximal drag reduction rate is obtained when variable parameters are applied in the Giesekus model at a high weissenberg *** Reynolds shear stress is reduced when the weissenberg number *** this case,the turbulence generation and transportation are further weakened and increasingly approach to the values in the experiments.

关键词： Viscoelastic fluid Giesekus model direct numerical simulation(DNS) Variable parameters

CRYSTALLIZATION AND MELTING OF POLY(ETHYLENE OXIDE)CONFINED IN NANOSTRUCTURED PARTICLES WITH CROSS-LINKED SHELLS OF POLYBUTADIENE

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Chinese Journal of Polymer Science 2005年第3期23卷 275-284页

作者： wei-pingGao YuBai 陈尔强 Qi-fengZhou DepartmentofPolymerScienceandEngineering CollegeofChemistryand~IolecularEngineeringPekingUniversityBeijing100871China

Small fixed aggregates of a poly(ethylene oxide)-block-polybutadiene diblock copolymer(PEO-b-PB)in THFsolution were obtained by adding a selective solvent for PB blocks,followed by cross-linking the PB *** of the nanostructured particles with a cross-linked shell were investigated by atomic force microscopy andtransmission electron *** average behaviors of the PEO crystallization and melting confined within thenanostructured particles were studied by using differential scanning calorimetry *** the deeply cross-linkedsample(SCL-1),the crystallization of the PEO blocks was fully *** individual nanoparticles only crystallized atvery low crystallization temperatures(T_cs),wherein the homogenous primary nucleation determined the overallcrystallization *** the lightly cross-linked sample(SCL-2),the confinement effect was T_c *** T_c(?)42℃,thecrystallization and melting behaviors of SCL-2 were similar to those of the pure PEO-b-PB diblock *** T_c>42℃,SCL-2 could form PEO lamellae thicker than those of the pure PEO-b-PB crystallized at the same T_c.

关键词： Diblock copolymer Aggregates Cross-linking Confined crystallization and melting.

A Micro-coupling for Micro Mechanical Systems

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Chinese Journal of Mechanical Engineering 2016年第3期29卷 571-578页

作者： LI wei ZHOU Zhixiong ZHANG Bi XIAO Yunya College of Mechanical and Vehicle Engineering Hunan University School of Engineering University of Connecticut

The error motions of micro mechanical systems, such as micro-spindles, increase with the increasing of the rotational speed, which not only decreases the rotational accuracy, but also promotes instability and limits the maximum operational speed. One effective way to deal with it is to use micro-flexible couplings between the drive and driven shafts so as to reduce error motions of the driven shaft. But the conventional couplings, such as diaphragm couplings, elastomeric couplings, bellows couplings, and grooved couplings, etc, cannot be directly used because of their large and complicated structures. This study presents a novel micro-coupling that consists of a flexible coupling and a shape memory alloy（SMA）-based clamp for micro mechanical systems. It is monolithic and can be directly machined from a shaft. The study performs design optimization and provides manufacturing considerations, including thermo-mechanical training of the SMA ring for the desired Two-Way-Shape-Memory effect（TWSMe）. A prototype micro-coupling and a prototype micro-spindle using the proposed coupling are fabricated and tested. The testing results show that the prototype micro-coupling can bear a torque of above 5 N · mm and an axial force of 8.5 N and be fitted with an SMA ring for clamping action at room temperature（15 ℃） and unclamping action below –5 ℃. At the same time, the prototype micro-coupling can work at a rotational speed of above 200 kr/min with the application to a high-speed precision micro-spindle. Moreover, the radial runout error of the artifact, as a substitute for the micro-tool, is less than 3 μm while that of turbine shaft is above 7 μm. It can be concluded that the micro-coupling successfully accommodates misalignment errors of the prototype micro-spindle. This research proposes a micro-coupling which is featured with an SMA ring, and it is designed to clamp two shafts, and has smooth transmission, simple assembly, compact structure, zero-maintenance and balanced motio

关键词： coupling clamp shape memory alloy thermo-mechanical training micro-spindle

Electroplastic Tensile Behavior of 5A90 Al–Li Alloys

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Acta Metallurgica Sinica(English Letters) 2014年第4期27卷 642-648页

作者： Pengchao Song Xifeng Li wei Ding Jun Chen Department of Plasticity Technology School of Materials Science and EngineeringShanghai Jiao Tong University

The electroplastic（EP） tensile properties of 5A90 Al–Li alloys compared with thermal tension were *** microstructural variation at different conditions was observed by SEM and *** current density significantly influences the elongation and the flow *** increasing current density,wider and deeper dimples on the fracture surfaces and less dislocation density and pile-ups in the EP tension samples were observed compared with roomtemperature and thermal tension,which indicates the plasticity improvement and flow stress *** EP effect（EPE） mainly results from a comprehensive function of Joule heating and pure *** them,Joule heating effect is perhaps a dominant factor.

关键词： 5A90 Al–Li alloys Electroplastic effect Tensile properties Microstructure

Simultaneous inversion of seismic scattering and absorption attenuation using coda energies

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Science China Earth Sciences 2024年第12期67卷 3939-3949页

作者： Jia wei Qiancheng LIU Ling CHEN Liang ZHAO State Key Laboratory of Lithospheric and Environmental Coevolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology Southern University of Science and TechnologyShenzhen 518055China

Simultaneous inversion of scattering and absorption attenuation is of great significance for investigating small-scale inhomogeneities and inelastic properties of the ***,applying this to complex geophysical issues is constrained by the costly computational requirements for simulations and inversions using existing *** coupling effects between the scattering and absorption coefficients cause parameter crosstalk artifacts in multi-parameter inversion,significantly increasing the nonlinearity of the inverse *** paper proposes a robust and effective simultaneous inversion method for scattering and absorption *** propagation of coda energy is modeled using the finite-element method based on the frequency-domain diffusion *** employ the truncated Gauss-Newton technique for the simultaneous estimation of scattering and absorption coefficients to decouple the two attenuation parameters during the inversion ***,the inversion may reach a local minimum if the energy frequency is inappropriate due to a phase mismatch between the simulated and measured *** mitigate this issue,we provide a frequency selection criterion that considers the substantial spectral shift of the energy density spectrum toward lower *** examples using synthetic and experimental data indicate that our method can significantly reduce computational complexity and suppress two-parameter crosstalk without requiring a precise initial attenuation model.

关键词： Scattering attenuation Absorption attenuation Simultaneous inversion Coda energy

DAMAGE DETECTION BASED ON OPTIMIZED INCOMPLETE MODE SHAPE AND FREQUENCY

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Acta Mechanica Solida Sinica 2015年第1期28卷 74-82页

作者： wei Chen Wenguang Zhao Huizhen Yang Xuquan Chen Hubei Key Laboratory of Control Structure Huazhong University of Science and Technology

For the purpose of structural health monitoring, a damage detection method combined with optimum sensor placement is proposed in this paper. The back sequential sensor placement （BSSP） algorithm is introduced to optimize the sensor locations with the aim of maximizing the 2-norm of information matrix, since the EI method is not suitable for optimum sensor placement based on eigenvector sensitivity analysis. Structural damage detection is carried out based on the respective advantages of mode shape and frequency. The optimized incomplete mode shapes yielded from the optimal sensor locations are used to localize structural damage. After the potential damage elements have been preliminarily identified, an iteration scheme is adopted to estimate the damage extent of the potential damage elements based on the changes in the frequency. The effectiveness of this method is demonstrated using a numerical example of a 31-bar truss structure.

关键词： structural damage detection optimum sensor placement sensitivity analysis information matrix