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A radar-infrared compatible broadband absorbing surface:Design and analysis

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Chinese Physics B 2021年第7期30卷 605-612页

作者： Qing-Tao Yu Yuan-Song Zeng Guo-Jia Ma Aviation Key Laboratory of Science and technology on advanced Surface Engineering AVIC Manufacturing Technology InstituteBeijing 100024China

A radar-infrared compatible stealth surface is designed and *** modifying the radar absorbing material(RAM),the design can theoretically achieve radar-infrared compatibility and broadband radar absorption through surface patterns and structures.A transmission-line-based model(TLM)is developed to analyze the radar absorbing performance of the *** of the structure geometries is conducted aiming to maximize the-10 d B absorption bandwidth in 2–18 *** with optimized structure geometries exhibits a superior absorption bandwidth,more than twice the bandwidth of the original 1.5 mm RAM slab,while maintaining a relatively low infrared emissivity.

关键词： stealth infrared-radar compatible broadband absorbing patterned surface

Flow regimes of the immiscible liquids within a rectangular microchannel

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Acta Mechanica Sinica 2021年第10期37卷 1544-1556,I0003页

作者： Xiang Wang Yan Pang Yilin Ma Yanlin Ren Zhaomiao Liu College of Mechanical Engineering and Applied Electronics technology Faculty of Materials and ManufacturingBeijing University of TechnologyBeijing100124China Beijing Key Laboratory of advanced manufacturing technology Beijing University of TechnologyBeijing100124China

Flow regimes of two immiscible liquids at the cross junction within a rectangular microchannel are experimentally *** of the flow regimes including critical conditions and interfacial deformations are *** is found that the occurrence of the tubing regime is favored by increased viscosity of the dispersed phase or reduced cross-sectional aspect ratio,leading to the shrinkage of the flow rate range that could produce *** order to reveal the physical mechanism,the force analysis is carried out based on the tunnel structure formed between the interface and channel side walls within the rectangular *** reshaping stage and pinch-off stage are mainly driven by the interfacial tension,leading to far larger neck thinning rate compared to the superficial velocity of either *** filling stage and squeezing stage are dominated by the pressure drop across the dispersed tip while the role of the shear force becomes more important with increasing tunnel *** filling period is estimated as t2≈kHwn02/Qd with k=1.34 and the squeezing period is expressed as t3/Tc=0.3Cac−*** to the force analysis,the critical tip velocity under dripping scales with three key parameters,which can be expressed as(utip/U)*~QcLtip/wtunnel3.

关键词： Cross junction Flow regime Liquid interface Force analysis Rectangular microchannel

Enhanced mechanical properties and thermal shock resistance of Si_2BC_3N ceramics with SiC coated MWCNTs

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Journal of advanced Ceramics 2019年第1期8卷 121-132页

作者： Ning LIAO Dechang JIA Zhihua YANG Yu ZHOU Institute for advanced Ceramics School of Materials Science and EngineeringHarbin Institute of Technology Key Laboratory of advanced Structure-Function Integrated Materials and Green manufacturing technology Ministry of Industry and Information Technology

Bulk Si_2 BC_3 N ceramics were reinforced with SiC coated multi-walled carbon nanotubes(MWCNTs). The phase compositions, mechanical properties, and thermal shock resistance, as well as the oxidation resistance of the designed Si_2 BC_3 N ceramics were comparatively investigated. The results show that nano SiC coating can be formed on MWCNTs through pyrolyzing polysilazane, which improves the oxidation resistance of MWCNTs. A stronger chemical bonding is formed between the SiC coated MWCNTs and SiC particles, contributing to improved flexural strength(532.1 MPa) and fracture toughness(6.66 MPa m1/2). Besides, the 2 vol% SiC coated MWCNTs reinforced Si_2 BC_3 N ceramics maintains much higher residual strength(193.0 MPa) after thermal shock test at 1000 ℃.The enhanced properties should be attributed to:(1) the breaking of MWCNTs and the debonding between MWCNTs and SiC interfaces, which leads to more energy dissipation;(2) the rough surfaces of SiC coated MWCNTs increase the adhesion strength during the "pull out" of MWCNTs.

关键词： Si2BC3N ceramics SiC coated MWCNTs mechanical properties thermal shock resistance

Synthesis and high temperature thermoelectric transport properties of Si-based type-Ⅰ clathrates

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Chinese Physics B 2009年第7期18卷 3084-3089页

作者：邓书康唐新峰唐润生 Education Ministry Key Laboratory of Renewable Energy advanced Materials and manufacturing technology Yunnan Normal University State Key Laboratory of advanced technology for Materials Synthesis and Processing Wuhan University of Technology

N-type Si-based type-Ⅰ clathrates with different Ga content were synthesized by combining the solid-state reaction method,melting method and spark plasma sintering （SPS） *** effects of Ga composition on high temperature thermoelectric transport properties were *** results show that at room temperature,the carrier concentration decreases, while the carrier mobility increases slightly with increasing Ga *** Seebeck coefficient increases with increasing Ga content. Among all the samples,Ba7.93Ga17.13Si28.72exhibits higher Seebeck coefficient than the others and reaches -135μV·K^-1 at 1000 *** sample prepared by this method exhibits very high electrical conductivity,and reaches 1.95x 10^5 S·m^-1 for Ba8.01Ga16.61Si28.93 at room *** thermal conductivity of all samples is almost temperature independent in the temperature range of 300-1000 K,indicating the behaviour of a typical *** maximum ZT value of 0.75 is obtained at 1000 K for the compound Ba7.93Ga17.13Si28.72.

关键词： type-Ⅰ clathrate thermoelectric materials synthesis

Theoretical and experimental investigation on novel 2D maglev servo proportional valve

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Chinese Journal of Aeronautics 2021年第4期34卷 416-431页

作者： Bin MENG Hao XU Jian RUAN Sheng LI Key Laboratory of Special Purpose Equipment and advanced manufacturing technology Ministry of Education Zhejiang University of TechnologyHangzhou 310018China

This paper presents a novel two-dimensional maglev servo proportional cartridge valve(2 D maglev valve),where a contactless maglev coupling is introduced between electro-mechanical converter and valve body to realize functions of force transmission,spool position feedback and linear-rotary motion *** configuration can effectively reduce cost of both valve manufacturing and electro-mechanical converter,while still maintain features of 2 D valve such as null pilot leakage,high power-to-weight ratio and excellent anti-pollution ***,the characteristic equation of the valve is derived using linear theory,and the stability criterion is established for parameter *** influences of crucial structural parameters such as initial height of overlapping area,width of high-pressure and low-pressure holes,acting radius of magnetic force,pitch angle of maglev coupling,length of sensitive chamber and system pressure on the dynamic response are investigated based on AMESim numerical *** prototype valve is then designed and manufactured and a special test rig is *** no-load flow characteristic,load flow characteristic,leakage characteristic,amplitude and phase frequency characteristics and step response under different system pressures are *** experimental results are in a good agreement with the simulated *** an over-damped system,the prototype valve has excellent working stability,which can reach a no-load flow rate of 105.9 L/min with hysteresis of 3.51%,amplitude bandwidth of 28.7 Hz and phase bandwidth of 42.8 Hz under 21 *** research indicates that the 2 D maglev valve can be a potential solution of flow rate control valve for flight control surface system of civil aircraft with high pressure and large flow rate application.

关键词： Dynamic characteristic 2D valve Maglev coupling Servo proportional valve Stability criterion

Finite Element Simulations of Dynamic Fracture of Full-Scale Gas Transmission Pipelines

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Acta Mechanica Solida Sinica 2018年第3期31卷 357-368页

作者： Peishi Yu Jinjie Lv Junhua Zhao Jiangsu Key Laboratory of advanced Food manufacturing Equipment and technology School of Mechanical Engineering Jiangnan University

The dynamic crack growth in a full-scale gas pipeline of API X80 steel is analyzed using the finite element method with the cohesive zone model. Based on the simulation, it is revealed that for the moderate steady-state crack growth, the crack-tip-opening angle strongly depends on the crack growth speed. In addition, the threshold initial crack sizes under different internal pressures are analyzed, which show a significant three-dimensional effect due to the wall thickness of the pipeline. The presented model offers a feasible way to study some details of the dynamic fracture of full-scale pipelines when tests are difficult or expensive.

关键词： Dynamic fracture Finite element Full-scale pipeline Cohesive zone model

Single-atom Co-N_(4)catalytic sites anchored on N-doped ordered mesoporous carbon for excellent Zn-air batteries

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Journal of Materials Science & technology 2023年第8期139卷 224-231页

作者： Na Li Le Li Jiawei Xia Muhammad Arif Shilong Zhou Fengxiang Yin Guangyu He Haiqun Chen Key Laboratory of advanced Catalytic Materials and technology Advanced Catalysis and Green Manufacturing Collaborative Innovation CenterChangzhou UniversityChangzhou 213164China

Developing efficient transition metal-nitrogen-carbon(TM-N-C)catalysts with abundant accessible active sites has been in the limelight in recent years due to their exceptional application potential in Zn-air bat-teries(ZABs).Herein,we report the simple and environmentally-friendly fabrication of a single-atom Co electrocatalyst,Co-SA/N-C_(900),via in-suit pyrolysis of the co-precursor containing sucrose,dicyandiamide,and Co *** Co single atoms coordinated with adjacent N atoms are anchored on the doped ordered mesoporous carbon,generating the atomic Co-N_(4)***-SA/N-C_(900)displays high oxygen reduction reaction(ORR)activity with an onset potential of 0.96 V and a half-wave potential of 0.87 ***,the liquid ZAB with Co-SA/N-C_(900)catalyst exhibits exceptional discharge specific capacity of 706.38 mAh g^(-1),peak power density of 191.11 mW cm^(-2),and excellent stability at high current densities up to 100 mA cm^(-2),surpassing commercial Pt/*** to the density functional theory(DFT)study,the Co-N_(4)moi-ety with graphitic N dopants can decrease the rate-determining step(RDS)energy barrier and thus accel-erate the ORR *** study offers experimental and theoretical guidelines for the rational design of TM-N-C catalysts for practical implementation with notable ORR activity for application in ZABs.

关键词： Single-atom electrocatalyst Co-N_(4)active sites Oxygen reduction reaction Zn-air battery DFT study

Swelling of Spherical Polyelectrolyte Gels

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Chinese Journal of Polymer Science 2024年第9期42卷 1386-1392,I0009页

作者： Ming-Yu Duan Jia-Dong Chen Yi-Ming Liu Zhao-Feng Peng Guang Chen department of advanced manufacturing and Robotics College of EngineeringPeking UniversityBeijing 100871China

Polyelectrolyte(PE)gels,distinguished by their unique stimuli-responsive swelling behavior,serve as the basis of broad applications,such as artificial muscles and drug *** this work,we present a theoretical model to analyze the electrostatics and its contribution to the swelling behavior of PE gels in salt *** minimizing the free energy of PE gels,we obtain two distinct scaling regimes for the swelling ratio at equilibrium with respect to the salt *** compare our predictions for the swelling ratio with experimental measurements,which show excellent *** addition,we employ a finite element method to assess the applicability range of our theoretical model and *** anticipate that our model will also provide valuable insights into drug adsorption and release,deformation of red blood cells,4D printing and soft robotics,where the underlying mechanism of swelling remains enigmatic.

关键词： Gels Polyelectrolytes Swelling Stimuli-responsive Electrostatic interaction Cell model

Cubic hollow porous carbon with defective-edge Fe-N_(4) single-atom sites for high-performance Zn-air batteries

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Journal of Materials Science & technology 2024年第14期181卷 82-90页

作者： Shilong Zhou Chao Chen Jiawei Xia Le Li Xingyue Qian Fengxiang Yin Guohong Dai Guangyu He Qun Chen Haiqun Chen Key Laboratory of advanced Catalytic Materials and technology Advanced Catalysis and Green Manufacturing Collaborative Innovation CenterChangzhou UniversityChangzhou 213164China department of Chemistry and Chemical Engineering Jiangsu University of TechnologyChangzhou 213001China

Regulating the local coordination of Fe active center can further improve the oxygen reduction reaction(ORR)performance of Fe-N-C catalyst to meet the practical application requirements of zinc-air batteries(ZABs).Herein,carbon vacancies modified hollow porous catalysts(C-FeZ8@PDA-950)are constructed by microenvironment modulation,achieving the efficient utilization of active sites and optimization of elec-tronic *** functional theory(DFT)calculations confirm that the defective-edge Fe-N_(4) sites can weaken the adsorption free energy of OH^(∗),and hinder the dissolution of Fe center,significantly accel-erating the ORR process for *** rechargeable liquid ZABs equipped with C-FeZ8@PDA-950 display high specific capacity(819.95 mAh g Zn^(−1))and excellent long-cycling life(over 500 h).Furthermore,the relevant flexible all-solid-state ZABs also display outstanding folding performance under various bending *** work will provide insights into optimizing the electronic structure to improve electrocatalytic performance in the energy conversion and storage area.

关键词： Hollow porous catalyst ORR Defective-edge Fe-N_(4) sites Zn-air battery DFT calculations