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Highly active and durable La_(0.6) Ca_(0.4)(CrMnFeCo_(2)Ni)O_(3) high entropy perovskite oxide as electrocatalyst for oxygen evolution reaction in alkaline media

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Journal of Materials Science & Technology 2024年第1期168卷 71-78页

作者： xiaoqiang Ji Fan Yang Yunzhu du Jing Li Jianguo Li Qiaodan Hu Shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China

Oxygen evolution reaction(OER)is the imperative reaction for many energy storage and conversion devices such as recharge-able metal-air batteries and electrochemical water splitting[1].OER is a complex 4-electron process with sluggish kinetics and therefore requires electrocatalysts to overcome the high overpo-tential.Ruthenium oxide(RuO_(2))and iridium oxide(IrO_(2))catalysts can promote the OER process remarkably[2-4],however,their ex-tremely high cost,natural scarcity,and long-term instability con-strain their scale-up application in clean-energy technologies[5,6].It is crucial to develop inexpensive,highly efficient,and durable electrocatalysts for OER.

关键词： entropy alkaline perovskite

Inverse design of mechanical metamaterial achieving a prescribedconstitutive curve

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Theoretical & Applied Mechanics Letters 2024年第1期14卷 16-22页

作者： Zongliang du Tanghuai Bian xiaoqiang Ren Yibo Jia Shan Tang Tianchen Cui Xu Guo State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDepartment of Engineering MechanicsDalian University of TechnologyDalian 116023China Ningbo Institute of Dalian University of Technology Ningbo 315016China

Besides exhibiting excellent capabilities such as energy absorption,phase-transforming metamaterials offer a vast design space for achieving nonlinear constitutive relations.This is facilitated by switching between different patterns under deformation.However,the related inverse design problem is quite challenging,due to the lack of appropriate mathematical formulation and the convergence issue in the post-buckling analysis of intermediate designs.In this work,periodic unit cells are explicitly described by the moving morphable voids method and effectively analyzed by eliminating the degrees of freedom in void regions.Furthermore,by exploring the Pareto frontiers between error and cost,an inverse design formulation is proposed for unit cells.This formulation aims to achieve a prescribed constitutive curve and is validated through numerical examples and experimental results.The design approach presented here can be extended to the inverse design of other types of mechanical metamaterials with prescribed nonlinear effective properties.

关键词： MetamaterialPattern-transformationConstitutive curveInverse design

MOF-derived Zn-Co-Ni sulfides with hollow nanosword arrays for high-efficiency overall water and urea electrolysis

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Green Energy & Environment 2023年第3期8卷 798-811页

作者： xiaoqiang du Yangyang Ding Xiaoshuang Zhang School of Chemical Engineering and Technology North University of ChinaTaiyuan030051China School of Science North University of ChinaTaiyuan030051China

Water electrolysis is a promising technology to produce hydrogen but it was severely restricted by the slow oxygen evolution reaction(OER).Herein,we firstly reported an advanced electrocatalyst of MOF-derived hollow Zn-Co-Ni sulfides(ZnS@Co_(9)S_(8)@Ni_(3)S_(2)-1/2,abbreviated as ZCNS-1/2)nanosword arrays(NSAs)with remarkable hydrogen evolution reaction(HER),OER and corresponding water electrolysis performance.To reach a current density of 10 mA cm^(-2),the cell voltage of assembled ZCNS-1/2//ZCNS-1/2 for urea electrolysis(1.314 V)is 208 mV lower than that for water electrolysis(1.522 V)and stably catalyzed for over 15 h,substantially outperforming the most reported water and urea electrolysis electrocatalysts.Density functional theory calculations and experimental result clearly reveal that the properties of large electrochemical active surface area(ECSA)caused by hollow NSAs and fast charge transfer resulted from the Co_(9)S_(8)@Ni_(3)S_(2) heterostructure endow the ZCNS-1/2 electrode with an enhanced electrocatalytic performance.

关键词： Water electrolysis Urea electrolysis MOF Multi-metal sulfides Density functional theory

Solvent-free carbon sphere nanofluids towards intelligent lubrication regulation

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Friction 2024年第1期12卷 95-109页

作者： Sheng ZHANG Wen LI Xiaoliang MA xiaoqiang FAN Minhao ZHU Tribology Research Institute School of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu 610031China Key Laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China

By simply switching the electrical circuit installed on steel/steel contact,the tribological behaviors of nanofluids(NFs)can be regulated in real time,thereby achieving the desired performance of friction reduction and wear resistance.Herein,solvent-free carbon spherical nanofluids(C-NFs)were successfully prepared for intelligent lubrication regulation.C-NFs with excellent lubrication performance can immediately reduce the coefficient of friction(COF)despite applying a weak electric potential(1.5 V).Moreover,polyethylene glycol 400(PEG400)containing 5.0 wt%C-NFs remained responsive to electrical stimulation under the intermittent voltage application with an average coefficient of friction(ACOF)reduction of 20.8%over PEG400.Such intelligent lubrication regulation of C-NFs under an external electric field(EEF)mainly depends on the orderly arranged double-electric adsorption film of ion canopy-adsorbed carbon spheres(CSs).The intermittent electrical application can continuously reinforce the adsorption film and its durability for real-time controlling the sliding interfaces.Electrical-stimulation-responsive intelligent lubricants provide a new technical support for realizing intelligent stepless control of devices.

关键词： solvent-free carbon spherical nanofluids(C-NFs) intelligent lubrication regulation lubrication performance adsorption film

Improving the high cycle fatigue property of Ti6Al4V ELI alloy by optimizing the surface integrity through electric pulse combined with ultrasonic surface rolling process

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Journal of Materials Science & Technology 2024年第3期170卷 103-121页

作者： Pengfei Sun Shengguan Qu Chenfeng duan Xiongfeng Hu xiaoqiang Li National Engineering Research Center of Near-Net-Shape Forming for Metallic Materials South China University of TechnologyGuangzhou 510640China School of Mechanical and Automotive Engineering South China University of TechnologyGuangzhou 510640China

To improve the surface integrity and high cycle fatigue property of Ti6Al4V ELI alloy,the electric pulse has been introduced into the ultrasonic surface rolling process(USRP),which is called electric pulse-assisted ultrasonic surface rolling process(EUSRP).With the help of“electroplasticity”of the electric pulse,the thickness of the surface gradient deformation layer was about three times of the USRP specimens by adjusting the pulse current level.However,the surface hardness decreases due to the continuous effect of the pulse current and the“skin effect”during treatment.It is worth noting that the higher the applied pulse current,the more severe the softening.This paradox causes the fatigue performance of EUSRP specimens lower than that of USRP specimens.To break this paradox,the EUSRP treatment is followed by a USRP treatment.The EUSRP-2(with a pulse current of 200 A)+USRP specimens exhibit excellent surface hardness,a gradient deformation layer thickness of about 400μm,low surface roughness and high compressive residual compressive stress.Besides,the hardening mechanisms of the different surface strengthening specimens have been quantitatively analyzed in combination with microstructure analysis.The fatigue life of Ti6Al4V ELI alloy can be improved by about 25 times at 780 MPa using the EUSRP-2+USRP treatment,the main reason for the highest fatigue life is the deepest surface gradient layer and the deepest crack initiation site.The fatigue limit of the EUSRP-2+USRP specimens is not the highest because too much surface hardening causes compressive residual stress relaxation during cycling and the beneficial effect of compressive residual stress is eliminated.

关键词： Ti6Al4V ELI alloy Combined surface treatment Transmission electron microscopy Residual stress Fatigue performance

LLTH‑YOLOv5:A Real‑Time Traffic Sign Detection Algorithm for Low‑Light Scenes

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Automotive Innovation 2024年第1期7卷 121-137页

作者： xiaoqiang Sun Kuankuan Liu Long Chen Yingfeng Cai Hai Wang Automotive Engineering Research Institute Jiangsu UniversityZhenjiang 212013China School of Automotive and Traffic Engineering Jiangsu UniversityZhenjiang 212013China

Traffic sign detection is a crucial task for autonomous driving systems.However,the performance of deep learning-based algorithms for traffic sign detection is highly affected by the illumination conditions of scenarios.While existing algo-rithms demonstrate high accuracy in well-lit environments,they suffer from low accuracy in low-light scenarios.This paper proposes an end-to-end framework,LLTH-YOLOv5,specifically tailored for traffic sign detection in low-light scenarios,which enhances the input images to improve the detection performance.The proposed framework comproses two stages:the low-light enhancement stage and the object detection stage.In the low-light enhancement stage,a lightweight low-light enhancement network is designed,which uses multiple non-reference loss functions for parameter learning,and enhances the image by pixel-level adjustment of the input image with high-order curves.In the object detection stage,BIFPN is introduced to replace the PANet of YOLOv5,while designing a transformer-based detection head to improve the accuracy of small target detection.Moreover,GhostDarkNet53 is utilized based on Ghost module to replace the backbone network of YOLOv5,thereby improving the real-time performance of the model.The experimental results show that the proposed method significantly improves the accuracy of traffic sign detection in low-light scenarios,while satisfying the real-time requirements of autonomous driving.

关键词： Deep learning Traffic sign detection Low-light enhancement YOLOv5 Object detection

Wood use and forest management by Neolithic millet farmers at the Xinglong site,northern China

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Science China Earth Sciences 2024年第6期67卷 1910-1921页

作者： Hui SHEN Zhenwei QIU Keliang ZHAO Xinying ZHOU xiaoqiang LI Key Laboratory of Vertebrate Evolution and Human Origins Institute of Vertebrate Paleontology and PaleoanthropologyChinese Academy of SciencesBeijing 100044China National Museum of China Beijing 100006China University of Chinese Academy of Sciences Beijing 100049China

The origin and development of agriculture and its relationship with climate change are hotly debated topics among environmental archaeologists.In this study,we analyzed wood charcoal materials from the Neolithic Xinglong site in northern China in order to understand the woody vegetation around the site and how early millet farmers shaped local woodlands.Our results suggest that the area around the Xinglong sites during 8700-7000 yr BP was primarily woodlands,including Prunus sibirica shrubs,Ulmus and Acer forests,and Populus stands near waterways.From 8000 to 7000 yr BP,the warm and humid climate probably contributed to the expansion of Acer,Rhamnus,and Juniperus,and may have facilitated the development of early millet agriculture.Among these ancient wood fragments that we studied,the high percent of Prunus charcoal appears to indicate an abundance of fruit trees,which might have constituted the main component of local vegetation.Meanwhile,the wood taxa illustrate the existence of a variety of ecological habitats,and it is logical to assume that people made full use of the locally available wood resources.Notably,Populus and Ulmus were the dominant sources of fuel.The results of tree-ring curvature analyses indicate that people mainly collected trunks or large branches of Ulmus,Populus,Acer,and Juniperus timbers.We interpret the increasing use of Prunus twigs and the declining percentage of Prunus charcoal in the period between 8000-7000 yr BP as indicating that people started to protect and manage wild fruit trees.They may have started pruning to acquire more food resources as part of the cultural responses and adaptation strategies employed by these early millet cultivators.

关键词： Xinglong site Wood charcoal Wood use Woodland management

Hot Deformation Behavior and Microstructures Evolution of GNP-Reinforced Fine-Grained Mg Composites

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Acta Metallurgica Sinica(English Letters) 2024年第3期37卷 407-424页

作者： Hengrui Hu Jiayu Qin Yunpeng Zhu Jinhui Wang xiaoqiang Li Peipeng Jin Qinghai Provincial Key Laboratory of New Light Alloys Qinghai UniversityXining 810016China Qinghai Provincial Engineering Research Center of High Performance Light Metal Alloys and Forming Qinghai UniversityXining 810016China Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China School of Material Science and Engineering Lanzhou University of TechnologyLanzhou 730050China

Graphene nanoplates(GNPs)-reinforced magnesium matrix composites have been attracted great attention.However,knowledge is lack for the hot deformation behavior of GNP-reinforced magnesium(GNPs/Mg)composite.In this study,the fine-grained GNPs/Mg composite was fabricated by powder metallurgy process followed by extrusion.The hot deformation behavior,microstructure evolution and dynamic recrystallization(DRX)mechanism of fine-grained GNPs/Mg composite were investigated by hot compression test and electron back-scatter diffraction(EBSD).The hot compression tests of the composite were conducted at temperatures between 423 and 573 K with the strain rates from 0.001 to 1 s^(-1).The strain compensated power law equation was established to describe the hot deformation behavior of the composites.The stress exponent and activation energy of the composite are 7.76 and 83.23 kJ/mol,respectively,suggesting that the deformation mechanism is grain boundary slip controlled dislocation climb creep.The abnormally high stress exponent and activation energy are unattainable in the composite due to the fine grain size of the composites and the absence of Zener pinning and Orowan effects of GNPs reinforcement.The grain size increases with the decrease in Zener-Hollomn(Z)parameter,which can be well fitted by power-law relationship.With the increase in grain size and decrease in Z parameter,the geometrically necessary dislocation density decreases,which shows the approximately power-law relationship.A random and weak texture was formed after hot compression.The discontinuous dynamic recrystallization and continuous dynamic recrystallization mechanism dominated the DRX behavior at 473 K/0.001 s^(-1) and 573 K/0.001 s^(-1),respectively.

关键词： GNPs Mg composite Hot deformation behavior Constitutive equations Microstructure evolution Dynamic recrystallization

Flow characteristics of radial inflow in impeller rear cavity with baffle plate

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Chinese Journal of Aeronautics 2024年第2期37卷 270-282页

作者： Yang BAI Xiang LUO Dongdong LIU Zeyu WU xiaoqiang ZHANG Sipeng WANG Research Institute of Aero-Engine Beihang UniversityBeijing 100191China National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics Beihang UniversityBeijing 100191China School of Energy and Power Engineering Beihang UniversityBeijing 100191China

The research purpose of this paper is to explore the influence of the baffle plate on the airflow in the rear cavity of the centrifugal impeller and optimize the performance of the secondary air system’s air bleed section.In this paper,a comprehensive experimental study was carried out on the flow characteristics in the impeller rear cavity with baffle plate.The windage torque,flow structure and pressure drop between inlet and outlet were measured respectively.The experiment was carried out with the condition that the range of rotational Reynolds number was from 8.33×10^(5)to 22.2×10^(5)and the range of mass flow rate coefficient was from 0.92×10^(4)to 2.92×10^(4).The results show that the static cavity and the narrow stator-rotor cavity formed by the baffle plate effectively suppress the overall swirl coefficient in the cavity.Thus,the static pressure and total pressure drop in the rotor-stator cavity were reduced.The influence of the baffle plate on the windage torque of the rotary disk is related to the turbulence parameters.Under large turbulence parameters,the windage torque would be reduced with baffle plate,while under small turbulence parameters,the baffle plate would increase with baffle plate.In general,the baffle plate can improve the flow capacity and optimize the bleed air performance with proper structure and operation conditions.

关键词： Impeller rear cavity Baffle plate Flow structure Windage torque Pressure drop