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Strain engineering in electrocatalysis:Strategies,characterization,and insights

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Nano Research 2024年第5期17卷 3603-3621页

作者： Qibo Deng Peng Xu Hassanien Gomaa Mohamed A.Shenashen Sherif A.El-Safty Cuihua An Li-Hua Shao Ning Hu School of Mechanical Engineering Hebei University of TechnologyTianjin 300401China Department of Chemistry Faculty of ScienceAl-Azhar University71524AssiutEgypt Department of Petrochemical Egyptian Petroleum Research Institute(EPRI)Nasr City11727CairoEgypt Center for Functional Materials National Institute for Materials Science(NIMS)1-2-1 SengenTsukubaIbaraki-ken305-0047Japan state key laboratory of Reliability and Intelligence Electrical Equipment Key Laboratory of Advanced Intelligent Protective Equipment TechnologyMinistry of Educationand School of Mechanical EngineeringHebei University of TechnologyTianjin 300401China National key laboratory of Strength and Structural Integrity Institute of Solid MechanicsSchool of Aeronautic Science and EngineeringBeihang UniversityBeijing100191China Advanced Equipment Research Institute Co. Ltd.of HEBUTTianjin 300401China

Strain engineering,as a cutting-edge method for modulating the electronic structure of catalysts,plays a crucial role in regulating the interaction between the catalytic surface and the adsorbed *** electrocatalytic performance is influenced by the electronic structure,which can be achieved by introducing the external forces or stresses to adjust interatomic spacing between surface *** challenges in strain engineering research lie in accurately understanding the mechanical impact of strain on *** paper first introduces the basic strategy for generating the strain,summarizes the different strain generation forms and their advantages and *** progress in researching the characterization means for the lattice strains and their applications in the field of electrocatalysis is also ***,the challenges of strain engineering are introduced,and an outlook on the future research directions is provided.

关键词： strain electrocatalysis characterization chemical reaction kinetics lattice mismatch

Machine learning optimization strategy of shaped charge liner structure based on jet penetration efficiency

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Defence Technology（防务技术） 2024年第9期39卷 23-41页

作者： Ziqi Zhao Tong Li Donglin Sheng Jian Chen Amin Yan Yan Chen Haiying Wang Xiaowei Chen Lanhong Dai state key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Future Technology University of Chinese Academy of SciencesBeijing 100049 China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China state key laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

Shaped charge liner(SCL)has been extensively applied in oil recovery and defense *** superior penetration capability through optimizing SCL structures presents a substantial challenge due to intricate rate-dependent processes involving detonation-driven liner collapse,high-speed jet stretching,and *** study introduces an innovative optimization strategy for SCL structures that employs jet penetration efficiency as the primary objective *** strategy combines experimentally validated finite element method with machine learning(FEM-ML).We propose a novel jet penetration efficiency index derived from enhanced cutoff velocity and shape characteristics of the jet via machine *** index effectively evaluates the jet penetration ***,a multi-model fusion based on a machine learning optimization method,called XGBOOST-MFO,is put forward to optimize SCL structure over a large input *** strategy's feasibility is demonstrated through the optimization of copper SCL implemented via the FEM-ML ***,this strategy is extended to optimize the structure of the recently emerging CrMnFeCoNi high-entropy alloy conical liners and hemispherical copper ***,the strategy can provide helpful guidance for the engineering design of SCL.

关键词： Jet penetration efficiency Shaped charge liner FEM-ML XGBOOST MFO High-entropy alloy

Tomographic PIV investigation of coherent structures in a turbulent boundary layer flow

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Acta Mechanica Sinica 2012年第3期28卷 572-582页

作者： Zhan-Qi Tang Nan Jiang Andreas Schroder Reinhard Geisler Department of mechanics Tianjin University300072 TianjinChina Tianjin key laboratory of Modern Engineering mechanics 300072 TianjinChina Institute of Aerodynamics and Flow Technology Department of Experimental MethodsBunsenstrasse 1037073 GiSttingenGermany

Tomographic particle image velocimetry was used to quantitatively visualize the three-dimensional co- herent structures in the logarithmic region of the turbulent boundary layer in a water tunnel. The Reynolds number based on momentum thickness is Reo = 2 460. The in- stantaneous velocity fields give evidence of hairpin vortices aligned in the streamwise direction forming very long zones of low speed fluid, which is flanked on either side by high- speed ones. Statistical support for the existence of hairpins is given by conditional averaged eddy within an increasing spanwise width as the distance from the wall increases, and the main vortex characteristic in different wall-normal re- gions can be reflected by comparing the proportion of ejec- tion and its contribution to Reynolds stress with that of sweep event. The pre-multiplied power spectra and two-point cor- relations indicate the presence of large-scale motions in the boundary layer, which are consistent with what have been termed very large scale motions （VLSMs）. The three dimen-sional spatial correlations of three components of veloc- ity further indicate that the elongated low-speed and high- speed regions will be accompanied by a counter-rotating roll modes, as the statistical imprint of hairpin packet structures, all of which together make up the characteristic of coherent structures in the logarithmic region of the turbulent boundary layer （TBL）.

关键词： Tomographic particle image velocimetry Tur-bulent boundary layer Coherent structures Hairpin vortex Very large scale motion

Second mode unstable disturbance measurement of hypersonic boundary layer on cone by wavelet transform

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Acta Mechanica Sinica 2011年第4期27卷 488-493页

作者： Jian Han.Nan Jiang.Yan Tian Department of Mathematics,Tianjin University,300072 Tianjin,China Department of mechanics,Tianjin University,300072 Tianjin,China Tianjin key laboratory of Modern Engineering mechanics,300072 Tianjin,China state key laboratory of nonlinear mechanics,Institute of mechanics,Chinese Academy of Sciences,100190 Beijing,China Department of Mathematics Tianjin University Tianjin China Department of mechanics Tianjin University Tianjin China Tianjin key laboratory of Modern Engineering mechanics Tianjin China state key laboratory of nonlinear mechanics Institute of Mechanics Chinese Academy of Sciences Beijing China

Experimental investigation of hypersonic boundary layer instability on a cone is performed at Mach number 6 in a hypersonic wind tunnel. Time series signals of instantaneous fluctuating surface-thermal-flux are measured by Pt-thin-film thermocouple temperature sensors mounted at 28 stations on the cone surface in the streamwise direction to investigate the development of the unstable disturbance. Wavelet transform is employed as a mathematical tool to obtain the multi-scale characteristics of fluctuating surfacethermal-flux both in the temporal and spectrum space. The conditional sampling algorithm using wavelet coefficient as an index is put forward to extract the unstable disturbance waveform from the fluctuating surface-thermal-flux *** generic waveform for the second mode unstable disturbance is obtained by a phase-averaging technique. The development of the unstable disturbance in the streamwise direction is assessed both in the temporal and spectrum space. Our study shows that the local unstable disturbance detection method based on wavelet transformation offers an alternative powerful tool in studying the hypersonic unstable mode of laminar-turbulent transition. It is demonstrated that, at hypersonic speeds, the dominant flow instability is the second mode, which governs the course of laminar-turbulent transition of sharp cone boundary layer.

关键词： Hypersonic boundary layer. Sharp cone Insta-bility Wavelet transform

TR PIV Experimental Investigation on Bypass Transition Induced by a Cylinder Wake

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Chinese Physics Letters 2011年第5期28卷 172-175页

作者： TANG Zhan-Qi JIANG Nan Department of mechanics Tianjin UniversityTianjin 300072 Tianjin key laboratory of Modern Engineering mechanics Tianjin UniversityTianjin 300372

The process of laminar to turbulent transition induced by a cylinder wake is studied by time-resolved(TR)particle image velocimetry(PIV)in a water *** combination of multi-scale local-averaged structure function analysis with criteria is used to identify the generation of secondary transverse vortex structure andto track its evolution along the *** the beginning of transition,with the decent of cylinder wake vortex,the secondary vortex structure is induced near the *** the secondary vortex moves dovnstream,it is induced to lift up by the wake vortex,meanwhile they are diffused and *** to the method of spatial conditional average,a low-speedhump is found in the near-wallregion along the bypass transition zone,accompanied by a low-speed region in the free stream occupied by the vake *** further downstream,the hump in the near-wall region becomes more and more *** the later stage of transition zone,hairpin vortex can be seen by conditional-averaged low-pass filtered *** hairpin head is almost vertical to the wall with an inclination angle of about 90°,which is attributed to the additional lift-up behavior induced by wake *** can be concluded that in the process of bypass transition,the wake vortex would not only induce the secondary vortex but also leaven its growth and evolution,resulting in the robust and rapidly growing hairpin vortex.

关键词： vortex cylinder averaged

Dynamics Evolution Investigation of Mack Mode Instability in a Hypersonic Boundary Layer by Bicoherence Spectrum Analysis

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Chinese Physics Letters 2012年第7期29卷 171-174页

作者： HAN Jian JIANG Nan Department of mechanics Tianjin UniversityTianjin 300072 Department of Mathematics Tianjin UniversityTianjin 300072 Tianjin key laboratory of Modern Engineering mechanics Tianjin 300072

The instability of a hypersonic boundary layer on a cone is investigated by bicoherence spectrum *** experiment is conducted at Mach number 6 in a hypersonic wind *** time series signals of instantaneous fluctuating surface-thermal-flux are measured by Pt-thin-film thermocouple temperature sensors mounted at 28 stations on the cone surface along streamwise direction to investigate the development of the unstable *** bicoherence spectrum analysis based on wavelet transform is employed to investigate the nonlinear interactions of the instability of Mack modes in hypersonic laminar boundary layer *** results show that wavelet bicoherence is a powerful tool in studying the unstable mode nonlinear interaction of hypersonic laminar-turbulent *** first mode instability gives rise to frequency shifts to higher unstable modes at the early stage of hypersonic laminar-turbulent *** modulations subsequently lead to the second mode instability *** second mode instability governs the last stage of instability and final breakdown to turbulence with multi-scale disturbances growth.

关键词： transition laminar turbulent

Polymorph selection in the crystallization of hard-core Yukawa system

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Science China Chemistry 2016年第3期59卷 316-323页

作者： Wenze Ouyang Zhiwei Sun Jun Zhong Hongwei Zhou Shenghua Xu key laboratory of Microgravity Institute of MechanicsChinese Academy of SciencesBeijing100190China School of Materials Engineering North China Institute of Aerospace EngineeringLangfang065000China Opening Fund of state key laboratory of nonlinear mechanics Institute of MechanicsChinese Academy of SciencesBeijing100190China

Colloid-colloid interactions in charge-stabilized dispersions can to The crystallization process and polymorph selection of hard-core some extent be represented by the hard-core Yukawa model. Yukawa model are studied by means of smart Monte Carlo simulations in the region of face-centered-cubic （fcc） phase. The contact value of bard-core Yukawa potential and the volume fraction of the colloids are fixed, while the Debye screening length can be varied. In the early stage of the crystallization, the precursors with relatively ordered liquid structure have been observed. Although the crystal structure of thermodynamically stable phase is fcc, the system crystallizes into a mixture of fcc and hexagonal close-packed （hcp） structures under small Debye screening length since the colloidal particles act as effective hard spheres. In the intermediate range of Debye screening length, the system crystallizes into a mixture of fcc, hcp, and body-centered-cubic （bcc）. The existence of metastable hcp and bcc structures can be interpreted as a manifestation of the Ostwald＇s step rule. Until the Debye screening length is large enough, the crystal structure obtained is almost a complete fcc suggesting the system eventually reaches to a thermodynamically stable state.

关键词： colloidal crystallization hard-core Yukawa model polymorph selection computer simulation

Dynamic mode decomposition of hairpin vortices generated by a hemisphere protuberance

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Science China(Physics,mechanics & Astronomy) 2012年第1期55卷 118-124页

作者： TANG ZhanQi JIANG Nan Department of mechanics Tianjin University Tianjin 300072 China Tianjin key laboratory of Modern Engineering mechanics Tianjin 300072 China

We present dynamic mode decomposition (DMD) for studying the hairpin vortices generated by hemisphere protuberance measured by two-dimensional (2D) time-resolved (TR) particle image velocimetry (PIV) in a water channel. The hairpins dynamic information is extracted by identifying their dominant frequencies and associated spatial structures. For this quasi-periodic data system, the resulting main Dynamic modes illustrate the different spatial structures associated with the wake vortex region and the near-wall region. By comparisons with proper orthogonal decomposition (POD), it can be concluded that the dynamic mode concentrates on a certain frequency component more effectively than the mode determined by POD. During the analysis, DMD has proven itself a robust and reliable algorithm to extract spatial-temporal coherent structures.

关键词： hairpin vortices hemisphere protuberance time-resolved particle image velocimetry dynamic mode decomposition proper orthogonal decomposition

MICROBRIDGE TESTING OF YOUNG'S MODULUS AND RESIDUAL STRESS OF NICKEL FILM ELECTROPLATED ON SILICON WAFER

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 247-254页

作者： Y.Zhou C.S.Yang J.A. Chen G.F. Ding L. Wang M.J Wang Y.M Zhang T.H Zhang key laboratory for Thin Film and Microfabrication of Ministry of Education Research Institute of Micro/Nanometer Science and Technology Shanghai Jiaotong University Shanghai 200030 China state key laboratory of nonlinear mechanics (LNM) Institute of Mechanics The Chinese Academy of Sciences Beijing 100080 China.

Microbridge testing is used to measure the Young's modulus and residual stresses of metallic *** film microbridges with widths of several hundred microns are fabricated by Microelectromechanical *** order to measure the mechanical properties of nickel film microbridges,special shaft structure is designed to solve the problem of getting the load--deflection curves of metal film microbridge by Nanoin--denter XP system with normal Berkovich *** analysis of the micro--bridge load--deflection curve is proposed to evaluate the Young's modulus and residual stress of the films *** calculated results based on the experimental measurements show that the average Young's modulus and residual stress are around 190GPa and 175MPa respectively,while the Young's modulus measured by Nano-hardness method on nickel film with silicon substrate is 186.8±7.34GPa.

关键词： nickel film microbridge MEMS mechanical property loadeflection measurement