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Experimental investigation of junction growth of rough contacts using X-ray computed tomography

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Friction 2024年第11期12卷 2519-2531页

作者： Runliang WANG jianhua liu Bo liu Duo JIA Xiaoyu DING School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China AECC Shenyang Engine Research Institution Shenyang 110000China

The real contact area(RCA)of randomly rough contacts has received a great deal of attention because it correlates strongly with friction,lubrication,sealing,and *** have revealed that the RCA associated with deterministic normal squeezing loads increases when tangential loads are also applied,in a phenomenon called junction ***,experimental investigations of the junction growth of randomly rough contacts are ***,we used X-ray computed tomography(CT)to measure junction growth when two aluminum alloy surfaces were in contact.A high-resolution experimental setup was used to apply loads and observe contact behaviors at a resolution of 4μ*** RCA and average contact gaps were computed using a three-dimensional(3D)geometric model constructed from gray CT images using the Otsu thresholding *** results showed that the RCA increased as the normal load *** RCA increased by 22.67%after a tangential load was applied(junction growth),and the average gap decreased by 14.01%after a tangential load was ***,X-ray CT accurately measured the junction growth as a novel quantitative method.

关键词： three-dimensional(3D)contact analyses real contact area(RCA),junction growth X-ray computed tomography(CT) assembly interfaces

Screening current in ultra-high-field non-insulated superconducting magnets

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Science China(Technological Sciences) 2024年第7期67卷 2255-2273页

作者： ZHOU BenZhe WANG Lei CHEN Yong WANG QiuLiang WANG KangShuai ZHANG ZiLi liu jianhua University of Chinese Academy of Sciences Beijing 100049China Institute of Electrical Engineering Chinese Academy of SciencesBeijing 100190China

Screening current is recognized as one of the critical elements limiting the progression of superconducting magnets toward achieving higher magnetic fields. Currently, most non-insulated(NI) superconducting magnets consider the magnet as insulated when addressing the issue of screening current. However, the bypass current in the NI magnet can modify the actual history of magnetization, so the screening current in NI magnet will be different from that in the insulated magnet. This paper presents a novel method based on the homogenized T-A formulation(T is the current vector potential, and A is the magnetic vector potential), which enables real-time simulation of both the bypass current behavior and the implications of screening current in NI superconducting magnets, even when these magnets contain tens of thousands of turns. We have developed a 32 T NI hybrid superconducting magnet and validated the effectiveness of this method through experiments. Employing this efficacious method,we conducted a comprehensive calculation of screening current in NI magnets, comparing them with insulated magnets in terms of screening current-induced stress(SCIS), screening current-induced field(SCIF), and losses. The results indicate that in the NI insert coils, the sequential excitation of background coils and insert coils induces a reverse screening current, resulting in slightly lower SCIF and SCIS compared to those in the insulated magnets. The method and results can contribute to the enhancement of magnet design and provide valuable insights for the development of ultra-high fields(UHF) NI magnets.

关键词： ultra-high-field superconducting magnet screening current REBCO coil NI coil stress loss

Aggregation-induced T_(1)/T_(2) contrast enhancement for magnetic resonance imaging-guided intraoperative surgery

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Science China Chemistry 2024年第6期67卷 2046-2055页

作者： Wenbo Sun Bin Yu Dianshuai Huang Chunhuan Jiang Wei Wang jianhua liu Zonghua Wang Lehui Lu State Key Laboratory of Electroanalytical Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun130022China College of Chemistry and Chemical Engineering Shandong Sino-Japanese Center for Collaborative Research of Carbon NanomaterialsQingdao Application Technology Innovation Center of Photoelectric Biosensing for Clinical Diagnosis and TreatmentQingdao UniversityQingdao266071China Department of Radiology Second Hospital of Jilin UniversityChangchun130041China

Magnetic resonance imaging(MRI)plays an important role in precision medicine that is hampered by the lack of contrast agents with high efficiency and the ability to translate diagnostic accuracy into therapeutic ***,we demonstrate a DNA-based MRI probe that overcomes previous single-mode enhancement and provides a mechanism of action for aggregationinduced dual-modal MRI signal enhancement.A facile method is developed to produce aggregated T_(1)/T_(2)dual-modal NaGdF_(4):Dy@PDA-DNA(PDA=polydopamine)MRI *** aggregated,this probe can further amplify MRI signal intensity and exhibit improved geometrical and positional stability in *** performance of the NaGdF_(4):Dy@PDA-DNA MRI probe toward MRI-guided preoperative planning and visualization-guided surgery is verified using an orthotopic tumor-bearing mouse *** result shows that the rapid metabolism of the degraded probe leads to the mitigation of long-term toxic ***,the developed high-performance MRI probe is of great significance for enhancing MRI diagnostic accuracy into precision medical therapeutic interventions.

关键词： MRI probe DNA aggregation-induced T_(1)/T_(2)contrast enhancement precision medicine degradable probe

Highly adaptive triboelectric tactile sensor on the foot of autonomous wall-climbing robots for detecting the adhesion state and avoiding the hazard

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Nano Research 2024年第7期17卷 6518-6526页

作者： Zhaoyang Wang jianhua liu Ziyu Wang Chang liu Qingyu Chen Chaofan Zhang Wenbo Zhang Jicang Si Xiu Xiao Peng Xu Minyi Xu Dalian Key Lab of Marine Micro/Nano Energy and Self-powered System Marine Engineering CollegeDalian Maritime UniversityDalian 116026China Information Science and Technology College Dalian Maritime UniversityDalian 116026China Navigation College Dalian Maritime UniversityDalian 116026China Intelligent Biomimetic Design Lab College of EngineeringPeking UniversityBeijing 100871China

Due to the excellent maneuverability and obstacle crossing of legged robots,it is possible for an autonomous legged wallclimbing robots to replace manual inspection of ship exterior ***,when the magnetic adsorption legged wallclimbing robot steps on the convex point or convex line of the wall,or even when the robot missteps,the robot is likely to detach from the ferromagnetic ***,this paper proposes a tactile sensor for the legged magnetic adsorption wall-climbing robot to detect the magnetic adsorption state and improve the safety of the autonomous crawling of the *** tactile sensor mainly comprises a three-dimensional(3D)-printed shell,a tactile slider,and three isometric sensing units,with an optimized *** experiment shows that the triboelectric tactile sensor can monitor the sliding depth of the tactile slider and control the light-emitting device(LED)signal *** addition,in the demonstration experiment of detecting the adsorption state of the robot's foot,the triboelectric tactile sensor has strong adaptability to various ferromagnetic wall ***,this study establishes a robot gait control system to verify the feedback control ability of the triboelectric tactile *** results show that the robot equipped with the triboelectric tactile sensor can recognize the dangerous area on the crawling wall and autonomously avoid the ***,the proposed triboelectric tactile sensor has great potential in realizing the tactile sensing ability of robots and enhancing the safety and intelligent inspection of ultra-large vessels.

关键词： legged wall-climbing robot ship inspection tactile perception triboelectric sensor

Bearing fault diagnosis based on a multiple-constraint modal-invariant graph convolutional fusion network

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High-Speed Railway 2024年第2期2卷 92-100页

作者： Zhongmei Wang Pengxuan Nie jianhua liu Jing He Haibo Wu Pengfei Guo College of Railway Transportation Hunan University of TechnologyZhuzhou 412007China Wuxi Maimurun Environmental Technology Co. LtdWuxi 214000China

Multisensor data fusionmethod can improve the accuracy of bearing fault diagnosis,in order to address the problems of single-sensor data types and the insufficient exploration of redundancy and complementarity between different modal data in most existing multisensor data fusion methods for bearing fault diagnosis,a bearing fault diagnosis method based on a Multiple-Constraint Modal-Invariant Graph Convolutional Fusion Network(MCMI-GCFN)is proposed in this ***,a Convolutional Autoencoder(CAE)and Squeeze-and-Excitation Block(SE block)are used to extract features of raw current and vibration ***,the model introduces source domain classifiers and domain discriminators to capture modal invariance between different modal data based on domain adversarial training,making use of the redundancy and complementarity between multimodal ***,the spatial aggregation property of Graph Convolutional Neural Networks(GCN)is utilized to capture the dependency relationship between current and vibration modes with similar time step features for accurately fusing contextual semantic ***,the validation is conducted on the public bearing damage current and vibration dataset from Paderborn *** experimental results showed that the delivered fusion method achieved a bearing fault diagnosis accuracy of 99.6%,which was about 9%–11.4%better than that with nonfusion methods.

关键词： Bearing fault diagnosis Data fusion Domain adversarial training GCN

Achievement of a high-performance 30-tesla metal-as-insulated user superconducting magnet

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Science China(Technological Sciences) 2024年第6期67卷 1974-1978页

作者： ZHOU BenZhe DAI YinMing ZHANG ZiLi liu Hui WANG YaoHui WANG Lei WANG Hui CHEN ShunZhong WANG KangShuai CHEN Yong liu jianhua WANG QiuLiang Institute of Electrical Engineering Chinese Academy of Sciences University of Chinese Academy of Sciences

Strong magnetic fields can be used to manipulate the states of matter and induce unique ***,they enable a thorough investigation of the intrinsic properties of matter through the application of the nuclear magnetic resonance(NMR)*** versatile nature of strong magnetic fields facilitates the discovery of novel phenomena and patterns.

关键词： effect NMR versatile

Synergistic PM_(2.5)and O_(3)control to address the emerging global PM_(2.5)-O_(3)compound pollution challenges

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Eco-Environment & Health 2024年第3期3卷 325-337页

作者： Chao He jianhua liu Yiqi Zhou Jingwei Zhou Lu Zhang Yifei Wang Lu liu Sha Peng College of Resources and Environment Yangtze UniversityWuhan 430100China Hubei Key Laboratory of Petroleum Geochemistry and Environment Yangtze UniversityWuhan 430100China School of Geography and Ocean Science Nanjing UniversityNanjing 210023China Hydrology and Environmental Hydraulics Group Wageningen University and ResearchWageningen 6700 HBthe Netherlands State Key Laboratory of Freshwater Ecology and Biotechnology Institute of HydrobiologyChinese Academy of SciencesWuhan 430072China State Key Joint Laboratory for Environmental Simulation and Pollution Control School of Environmental Sciences and EngineeringPeking UniversityBeijing 100871China State Key Laboratory of Pollution Control and Resource Reuse School of EnvironmentNanjing UniversityNanjing 210023China Collaborative Innovation Center for Emissions Trading System Co-constructed by the Province and Ministry Hubei University of EconomicsWuhan 430205China

In recent years,the issue of PM_(2.5)-O_(3)compound pollution has become a significant global environmental *** study examines the spatial and temporal patterns of global PM_(2.5)-O_(3)compound pollution and exposure risks,firstly at the global and urban scale,using spatial statistical regression,exposure risk assessment,and trend analyses based on the datasets of daily PM_(2.5)and surface O_(3)concentrations monitored in 120 cities around the world from 2019 to ***,on the basis of the common emission sources,spatial heterogeneity,interacting chemical mechanisms,and synergistic exposure risk levels between PM_(2.5)and O_(3)pollution,we proposed a synergistic PM_(2.5)-O_(3)control framework for the joint control of PM_(2.5)and *** results indicated that:(1)Nearly 50%of cities worldwide were affected by PM_(2.5)-O_(3)compound pollution,with China,South Korea,Japan,and India being the global hotspots for PM2.5-O3 compound pollution;(2)Cities with PM_(2.5)-O_(3)compound pollution have exposure risk levels dominated by ST t ST(Stabilization)and ST t HR(High Risk).Exposure risk levels of compound pollution in developing countries are significantly higher than those in developed countries,with unequal exposure characteristics;(3)The selected cities showed significant positive spatial correlations between PM_(2.5)and O_(3)concentrations,which were consistent with the spatial distribution of the precursors NOx and VOCs;(4)During the study period,52.5%of cities worldwide achieved synergistic reductions in annual average PM_(2.5)and O_(3)*** average PM_(2.5)concentration in these cities decreased by 13.97%,while the average O_(3)concentration decreased by 19.18%.This new solution offers the opportunity to construct intelligent and healthy cities in the upcoming low–carbon transition.

关键词： PM_(2.5)-O_(3)compound pollution Population exposure risk Spatial correlation Synergistic treatment potential

Multi-Body Dynamics Modeling of Heavy Goods Vehicle-Rail Interaction

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Open Journal of Applied Sciences 2024年第7期14卷 1715-1722页

作者： Lili liu jianhua liu Jihong Zuo College of Intelligent Control Hunan Railway Professional Technology College Zhuzhou China College of Transportation Engineering Hunan University of Technology Zhuzhou China

Based on the principle of vehicle-track coupling dynamics, SIMPACK multi-body dynamics software is used to establish a C80 wagon line-coupled multi-body dynamics model with 73 degrees of freedom. And the reasonableness of the line-coupled dynamics model is verified by using the maximum residual acceleration, the nonlinear critical speed of the wagon. The experimental results show that the established vehicle line coupling dynamics model meets the requirements of vehicle line coupling dynamics modeling.

关键词： Vehicle-Rail Coupling Dynamic Modeling Wheel-Rail Interaction Forces

空间溢出视角下风险投资对区域技术创新的影响研究

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当代经济科学 2024年第2期46卷 104-119页

作者：刘建华西安交通大学经济与金融学院陕西西安710061

以2005—2018年中国31个省份(不包含港澳台地区)的数据为研究样本,基于风险投资创新理论、区域创新理论以及空间集聚理论,从区域层面实证检验风险投资对技术创新的空间溢出效应,并结合风险投资活动的空间集聚分布特征,检验其对风险投资... 详细信息

以2005—2018年中国31个省份(不包含港澳台地区)的数据为研究样本,基于风险投资创新理论、区域创新理论以及空间集聚理论,从区域层面实证检验风险投资对技术创新的空间溢出效应,并结合风险投资活动的空间集聚分布特征,检验其对风险投资空间溢出效应的影响。研究发现,区域技术创新具有较强的空间相关性。风险投资对区域技术创新具有积极影响,且这种影响具有显著的空间溢出效应,即风险投资不仅会提升所处区域的技术创新,而且还会提升邻近区域的技术创新。该空间溢出效应受到空间集聚特征的调节,即相较于风险投资机构的空间集聚,创业企业的空间集聚更能强化风险投资对区域技术创新的空间溢出效应。因此,政府应创造更有吸引力的投资环境,鼓励风险资本向本地区集聚,完善知识产权保护政策,通过加强人才激励力度促进地区科研实力的提升。

关键词：风险投资区域技术创新空间溢出知识溢出空间集聚