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A Local Region Molecular Dynamics Simulation Method for Nanoscale Sliding Contacts

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Chinese Journal of Mechanical Engineering 2018年第5期31卷 119-126页

作者： Rui-Ting Tong Geng Liu tian-xiang Liu Shaanxi Engineering Laboratory for Transmissions and Controls Northwestern Polytechnical University Xi’an 710072 China Institute for Mechanics and Fluid Dynamics TU Bergakademie Freiberg Lampadiusstr. 4 09596 Freiberg Germany

Computational e ciency and accuracy always conflict with each other in molecular dynamics(MD) simulations. How to enhance the computational e ciency and keep accuracy at the same time is concerned by each corresponding researcher. However, most of the current studies focus on MD algorithms, and if the scale of MD model could be reduced, the algorithms would be more meaningful. A local region molecular dynamics(LRMD) simulation method which can meet these two factors concurrently in nanoscale sliding contacts is developed in this paper. Full MD simulation is used to simulate indentation process before sliding. A criterion called contribution of displacement is presented, which is used to determine the e ective local region in the MD model after indentation. By using the local region, nanoscale sliding contact between a rigid cylindrical tip and an elastic substrate is investigated. Two two?dimensional MD models are presented, and the friction forces from LRMD simulations agree well with that from full MD simulations, which testifies the e ectiveness of the LRMD simulation method for two?dimensional cases. A three?dimensional MD model for sliding contacts is developed then to show the validity of the LRMD simulation method further. Finally, a discussion is carried out by the principles of tribology. In the discussion, two two?dimensional full MD models are used to simulate the nanoscale sliding contact problems. The results indicate that original smaller model will induce higher equivalent scratching depth, and then results in higher friction forces, which will help to explain the mechanism how the LRMD simulation method works. This method can be used to reduce the scale of MD model in large scale simulations, and it will enhance the computational e ciency without losing accuracy during the simula?tion of nanoscale sliding contacts.

关键词： Local region molecular dynamics simulation Nanoscale Sliding contacts Contribution of displacement

Research,application and development of inorganic binder for casting process

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China Foundry 2024年第5期21卷 461-475页

作者： Xiao-long Gong Sheng-li Hu Zi-tian Fan State Key Laboratory of Materials Processing and Die&Mould Technology School of Materials Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

Inorganic binder used in casting process has the advantages of low odor,labor-friendly conditions,and relatively low cost,which is one of the main development directions for casting molding materials in the ***,compared to organic binders(such as resin binders),inorganic binders exhibit lower bonding strength and are more sensitive to environmental *** sensitivity poses challenges,particularly in the reclamation of used sand,thus limiting their broader *** this paper,the research and application status of inorganic binders(mainly silicate inorganic binders)and their curing methods are *** addition,the research and application of phosphate inorganic binders and 3D printing inorganic binders that are being developed are ***,a detailed comparative analysis is conducted on the challenging issue of“reclamation for used sand”in the application of inorganic ***,the development direction of inorganic binders is clarified.

关键词： inorganic binder silicate system phosphate system 3D printing used sand reclamation development trend

Effects of annealing temperature and cooling rate on microstructures of a novel titanium alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si manufactured by laser additive manufacturing

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Journal of Iron and Steel Research International 2018年第4期25卷 442-452页

作者： Guo-chao Li Xu Cheng xiang-jun tian National Engineering Laboratory of Additive Manufacturing for Large Metallic Components and Engineering Research Center of Ministry of Education on Laser Direct Manufacturing for Large Metallic Components School of Materials Science and Engineering Beihang University Beijing 100091 China

The microstructure changes of Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si alloy manufactured by laser additive manufacturing （LAM） are systematically investigated with statistical analysis of primary α phase （αp） and secondary α phase （αs） under different annealing conditions. Results indicate that, with the increase in holding temperature, the content of αp lamellas decreases with the increasing αs content, maintaining the total α phases concentration stabilized. The width of αp lamellas and the nominal specific surface area of α phase both exhibit positive correlation with the temperature, while the increment of αp and the widths of αs lamellas show an increase-decrease tendency. Besides, with the decrease in cooling rate, the total content of α and the width of αp lamellas increase, while the nominal specific surface area of α phase shows no significant change. The results indicate that, in the annealing process, the holding temperature determines the surplus and growth interfaces of % lamellas, and the cooling rate influences the nucleation quantity of c^s in unit time. During the cooling stage, the αp lamellas grow initially, and then, the nucleation and crab-like structure growth occur followed by those of the αs lamellas. The time intervals among them are influenced by cooling rate. The mechanism of microstructure formation of the LAMed titanium alloy during annealing stage was discussed, which would guide for the heat treatment method to achieve required microstructure.

关键词： Novel titanium alloy Annealing Microstructure statistics Holding temperature Cooling rate

Artificial muscles for wearable assistance and rehabilitation

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Frontiers of Information Technology & Electronic Engineering 2018年第11期19卷 1303-1315页

作者： tian-yun DONG xiang-liang ZHANG Tao LIU State Key Laboratory of Fluid Power and Mechatronic Systems School of Mechanical Engineering Zhejiang University Yunnan Key Laboratory of Computer Kunming University of Science and Technology

Traditional exoskeletons have made considerable contributions to people in terms of providing wearable assistance and rehabilitation. However, exoskeletons still have some disadvantages, such as being heavy, bulky, stiff, noisy, and having a fixed center of rotation that can be a burden on elders and patients with weakened muscles. Conversely, artificial muscles based on soft, smart materials possess the attributes of being lightweight, compact, highly flexible, and have mute actuation, for which they are considered to be the most similar to natural muscles. Among these materials, dielectric elastomer(DE) and polyvinyl chloride(PVC) gel exhibit considerable actuation strain, high actuation stress, high response speed, and long life span, which give them great potential for application in wearable assistance and rehabilitation. Unfortunately, there is very little research on the application of these two materials in these fields. In this review, we first introduce the working principles of the DE and PVC gel separately. Next, we summarize the DE materials and the preparation of PVC gel. Then, we review the electrodes and self-sensing systems of the two materials. Lastly, we present the initial applications of these two materials for wearable assistance and rehabilitation.

关键词： Artificial muscle Smart material Dielectric elastomers (DE) Polyvinyl chloride (PVC)gel Actuator Wearable assistance Rehabilitation

Flexible servo riveting system control strategy based on the RBF network and self-pierce riveting process

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Advances in Manufacturing 2023年第1期11卷 39-55页

作者： Yan Liu Qiu Tang Xin-Cheng tian long Cui Center for Robotics School of Control Science and EngineeringShandong UniversityJinan250061People’s Republic of China Engineering Research Center of Intelligent Unmanned System Ministry of EducationJinan250061People’s Republic of China

As more and more composite materials are used in lightweight vehicle white bodies,self-pierce riveting(SPR)technology has attracted great ***,the existing riveting tools still have the disadvantages of low efficiency and *** improve these disadvantages and the riveting qualification rate,this paper improves the control scheme of the existing riveting tools,and proposes a novel controller design approach of the flexible servo riveting system based on the RBF network and SPR ***,this paper briefly introduces the working principle and SPR procedure of the servo riveting *** a moving component force analysis is performed,which lays the foundation for the motion ***,the riveting quality inspection rules of traditional riveting tools are used for reference to plan the force-displacement curve *** control this process,the riveting force is fed back into the closed-loop control of the riveting tool and the riveting speed is computed based on the admittance control ***,this paper adopts the permanent magnet synchronous motor(PMSM)as the power of riveting tool,and proposes an integral sliding mode control approach based on the improved reaching law and the radial basis function(RBF)network friction compensation for the PMSM speed ***,the proposed control approach is simulated by Matlab,and is applied to the servo riveting system designed by our *** simulation and riveting results show the feasibility of the designed controller.

关键词： Lightweight vehicle body connection Self-pierce riveting(SPR)process Flexible servo riveting tool Riveting force planning and control

A zebrafish gene trap line expresses GFP recapturing expression pattern of foxj1b

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Journal of Genetics and Genomics 2009年第10期36卷 581-589页

作者： tian tian long Zhao Xinyi Zhao Min Zhang Anming Meng Protein Science Laboratory of Ministry of Education Department of Biological Sciences and Biotechnology Tsinghua University Beijing 100084 China State Key Laboratory of Biomembrane and Membrane Engineering Institute of Zoology Chinese Academy of Sciences Beijing 100101 China

Foxj1 has been found to play an important role in cilia formation and function in vertebrates. The zebrafish or Xenopus genome expresses two Foxjl genes, foxjlalFoxJ1 and foxjlb/FoxJ1.2. In this study, we have generated a zebrafish transgenic line T2BGSZIO by Tol2 transposon-based gene trapping approach. T2BGSZ10 transgenic fish carry an insertion of the transposon genome into the first intron of thefoxj1b locus. This insertion results in GFP expression in the forebrain, otic vesicles, floorplate, pronephric ducts and other domains during embryogenesis, which recaptures the expression pattern offoxj1b. Although normal expression offoxj1b is dramatically reduced, T2BGSZ10 homozygous embryos develop normally and grow to adulthood without detectable defects, which may be due to the incomplete interruption of foxjlb expression. Nevertheless, this transgenic line may serve as a useful model for dynamic observation of GFP-labeled tissues and organs and for isolation of GFP-labeled cells.

关键词： zebrafish transposon embryo transgenic foxj1

Effect of Nb on corrosion behavior of inner bottom plate of cargo oil tankers

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Journal of Iron and Steel Research International 2019年第6期26卷 611-620页

作者： xiang-yu Xu long tian Yun Zhou Ming-yu Sun Xue-min Wang Cheng-jia Shang R.D.K. Misra Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Beijing 100083 China tianjin long March Launch Vehicle Manufacturing Co. Ltd. Tianjin 300462 China Institute of Research of Iron and Steel (IRIS) Sha-steel Zhangjiagang 215625 Jiangsu China Center for Structural and Functional Materials Research and Innovation Department of Metallurgical and Materials Engineering University of Texas at El Paso El Paso TX 7996& USA

The effect of Nb on the corrosion resistance of steels in simulating an oil-corrosion environment was investigated by means of microstructure observation, electrochemical test, dissolved Nb content measurement and Nb segregation observation. The results show that the microstructure of the experimental steels is mainly ferrite with a little pearlite. The dissolved Nb contents of the experimental steels are 0.0235 and 0.0458 wt.%, respectively, while the undissolved Nb content is nearly the same. In addition to enhancing mechanical properties of the steel, dissolved Nb improves the corrosion resistance by enriching Nb in the rust layer. Nb oxides in the rust layer cause a decrease in the corrosion rate due to a decrease in the anodic reaction kinetics. The segregation of Nb at the grain boundaries suppresses the corrosion. Moreover, Nb is enriched at the bottom of the corrosion pit and prevents any further corrosion.

关键词： Low-alloy steel Acid corrosion Pitting corrosion Electrochemical impedance spectroscopy segregation

Interaction between hepatitis B virus and SARS-CoV-2 infections

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World Journal of Gastroenterology 2021年第9期27卷 782-793页

作者： tian-Dan xiang Xin Zheng Department of Infectious Diseases Union HospitalTongji Medical CollegeHuazhong University of Science and TechnologyWuhan 430022Hubei ProvinceChina

Coronavirus disease 2019(COVID-19)has become a global pandemic and garnered international *** causative pathogen of COVID-19 is severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),a novel,highly contagious *** studies have reported that liver injury is quite common in patients with *** B has a worldwide distribution as well as in *** present,hepatitis B virus(HBV)remains a leading cause of cirrhosis,liver failure,and hepatocellular *** both viruses challenge liver physiology,it raises questions as to how coinfection with HBV and SARS-CoV-2 affect disease progression and *** there an increased risk of COVID-19 in patients with HBV infection?In this review,we summarize the current reports of SARS-CoV-2 and HBV coinfection and elaborate the interaction of the two *** emphasis was placed on evaluating the impact of HBV infection on disease severity and clinical outcomes in patients with COVID-19 and discussing the potential mechanism behind this effect.

关键词： COVID-19 Hepatitis B virus Liver injury SARS-CoV-2 Coinfection Immune exhaustion

Influence of climatic warming in the Southern and Northern Hemi-sphere on the tropical cyclone over the western North Pacific Ocean

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第11期7卷 1923-1927页

作者： tian Rong-xiang WENG Huan-xin Department of Earth Science Zhejiang University Hangzhou 310027 China

Based on analyzing the surface air temperature series in the Southern and Northern Hemisphere and the tropical cyclone (TC) over the western North Pacific Ocean, the relationships between climatic warming and the frequency and intensity of tropical cyclone are investigated. The results showed that with the climatic warming in both hemispheres, the frequency of the tropical cyclone over the western North Pacific Ocean reduces and its intensity weakens simultaneously. A possible explanation might be that the cold air invasion from the Southern Hemisphere weakens due to global warming.

关键词： Climatic warming Southern and Northern Hemisphere Western North Pacific Ocean Tropical cyclone (TC)