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A mechanical model for the adhesive contact with local sliding induced by a tangential force

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Acta Mechanica Solida Sinica 2017年第4期30卷 369-373页

作者： Gan-Yun Huang Ji-Feng Yan department of Mechanics School of Mechanical EngineeringTianjin University

Adhesion has been demonstrated to play an important role in contact and friction between objects at small scales. While various models have been established for adhesive contact under normal forces, studies on the adhesive contact under tangential force have been far fewer, which if any, are mostly confined to the non-slipping situations. In the present work, a model has been proposed for adhesive contact with local sliding under tangential forces. Herein, the onset of local sliding in adhesive contact has been addressed by assuming the nucleation of dislocations. By analogy with the emission of dislocations at a crack tip, the critical tangential force for the onset of sliding has been determined, and its effect on the evolution of contact size has also been studied. Comparison with relevant experiments has verified the validity of the present model.

关键词： Adhesive contact Tangential force Local sliding Dislocation Contact size

Co-doping of hydroxyapatite with zinc and fluoride improves mechanical and biological properties of hydroxyapatite

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Progress in Natural Science:Materials International 2014年第4期24卷 340-349页

作者： Idil Uysal Feride Severcan Aysen Tezcaner Zafer Evis Middle east Technical university Department of Biomedical Engineering Middle east Technical university Department of Biological Sciences Middle east Technical university Department of Engineering Sciences

Hydroxyapatite(HA) co-doped with Zn2+ tand F- ions was synthesized by precipitation method for the first time in this *** spectroscopy revealed Zn2+ tand F ions incorporation into HA ***-doping of Zn2+ tand F- ions decreased unit cell volume of HA and decreased grain ***2+ tor 5 mol% F addition into HA significantly improved its *** was increased with Zn2+ taddition and further increase was detected with F ***2+ tand F co-doped samples had higher fracture toughness than pure ***2+ tincorporation to the structure resulted in an increase in cell proliferation and ALP activity of cells,and further increase was observed with 1 mol%F *** superior mechanical properties and biological response 2Zn1 F is a good candidate for biomedical applications.

关键词： Hydroxyapatite Co-doping Microstructure Microhardness Biocompatibility

Composite impact vector control based on Apollo descent guidance

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Chinese Journal of Aeronautics 2022年第7期35卷 67-74页

作者： Koray S.ERER Raziye TEKIN MKemal OZGOREN Tactical Missile Systems Roketsan Missiles Inc.Elmadağ06780Turkey department of mechanical engineering Middle East Technical UniversityÇankaya 06800Turkey

A new three-dimensional missile guidance law to control the impact vector against a stationary target is *** composite guidance law has two well-known components:Apollo descent guidance and trajectory shaping *** respectively linear and planar guidance laws are combined to achieve a specified impact *** main idea is to define an impact plane and to steer the missile onto this plane using Apollo descent guidance while concurrently performing trajectory shaping with reference to the impact *** resulting guidance law is expressed by a single equation in vector form,which is straightforward to *** it originates from an optimal formulation,the performance of the proposed technique is expected to be *** is confirmed by comparative simulation runs,which also involve the method known as generalized explicit guidance.

关键词： Impact angle Impact plane Impact vector Three-dimensional missile guidance Trajectory shaping

Styrene/Butadiene Copolymer Synthesized by Reactive Extrusion

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Chinese Journal of Polymer Science 2015年第8期33卷 1096-1103页

作者： Ji-ming Wang Bo Chen Sheng-jie Tang Dong Shan 郑安呐 Shanghai Key Laboratory of Advanced Polymeric Materials Key Laboratory for Ultrafine Materials of Ministry of EducationSchool of Materials Science and EngineeringEast China University of Science and Technology department of mechanical engineering University of Houston

In this study, we present a method to synthesize styrene-butadiene copolymer, using anionic polymerization in a co-rotating closely intermeshing twin-screw extruder. The weight content of polybutadiene in these copolymers was above 50% although in the past studies it had been possible to accomplish levels higher than 30%. ^1H-NMR and GPC show that the molecular structure of the two polymers is different due to different feeding method. In terms of the structure of the polymerized products, the mechanism of polymerization in the bulk polymerization is discussed. TEM and DMA show that two phases in the block copolymer are completely incompatible, leading to sharp phase separation, while the case is complicated in the copolymer through the mixture feeding. Traditionally, styrene-butadiene rubber is mainly synthesized by solution polymerization. Reactive extrusion in this paper provides a possibility to synthesize these products in an environmentally friendly way.

关键词： Reactive extrusion Styrene Butadiene Anionic polymerization.

Thermogravimetric kinetic analysis of Nannochloropsis oculata combustion in air atmosphere

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Frontiers in Energy 2015年第2期9卷 125-133页

作者： SUKARNI SUDJITO Nurkholis HAMIDI I.N.G. WARDANA Uun YANUHAR department of mechanical engineering Faculty of Engineering StateUniversity of Malang J1. Semarang 5 Malang 65145 East-JavaIndonesia department of mechanical engineering Faculty of EngineeringUniversity of Brawijaya J1. Mayjen Haryono 167 Malang 65145East-Java Indonesia Biotechnology Laboratory Department of Water Resources Manage-ment Faculty of Fisheries and Marine Sciences University ofBrawijaya J1. Veteran Malang 65145 East-Java Indonesia

The thermal behavior of Nannochloropsis oculata combustion in air atmosphere were investigated by performing experiments on STA PT1600 Thermal Analyzer at heating rates of 10℃/min, 40℃/min and 70℃/min and range of temperatures from room tempera- ture to 1200℃. The kinetic parameters were evaluated by using Kissinger and Ozawa methods. The result showed that Nannochloropsis oculata combustion occurred in five stages. Started with initial devolatilization, the main thermal decomposition and combustion process, transition stage, the combustion of char and the last stage was the slow burning reaction of residual char. In line with increasing heating rate, the mass loss rate increased as well, but it delayed the thermal decomposition processes toward higher temperatures. The average activation energy at the main thermal decomposition stage and the stage of char combustion were approximately 251 kJ/mol and 178 kJ/mol, respectively.

关键词： Nannochloropsis oculata combustion,kinetic parameters air atmosphere thermogravimetric

A comparative study on ApEn,SampEn and their fuzzy counterparts in a multiscale framework for feature extraction

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Journal of Zhejiang university-Science A(Applied Physics & engineering) 2010年第4期11卷 270-279页

作者： Guo-liang XIONG Long ZHANG He-sheng LIU Hui-jun ZOU Wei-zhong GUO School of Mechatronie engineering East China Jiaotong University Nanchang 330013 China School of mechanical engineering Shanghai Jiao Tong University Shanghai 200240 China department of Physics Shangrao Normal University Shangrao 334001 China

Feature extraction from vibration signals has been investigated extensively over the past decades as a key issue in machine condition monitoring and fault *** existing methods,however,assume a linear model of the underlying *** this study,the feasibility of devoting nonlinear dynamic parameters to characterizing bearing vibrations is ***,fuzzy sample entropy (FSampEn) is formulated by defining a fuzzy membership function with clear physical ***,inspired by the multiscale sample entropy (multiscale SampEn) which is originally proposed to quantify the complexity of physiological time series,we placed approximate entropy (ApEn),fuzzy approximate entropy (FApEn) and the proposed FSampEn into the same multiscale *** led to the developments of multiscale ApEn,multiscale FApEn and multiscale ***,all four multiscale entropies along with their single-scale counterparts were employed to extract discriminating features from bearing vibration signals,and their classification performance was evaluated using support vector machines (SVMs).Experimental results demonstrated that all four multiscale entropies outperformed single-scale ones,whilst multiscale FSampEn was superior to other multiscale methods,especially when analyzed signals were contaminated by heavy *** with statistical features in time domain also support the use of multiscale FSampEn.

关键词： Fault diagnosis Bearing Multiscale entropy Feature extraction Support vector machines (SVMs)

Enhancement effect of cumulative second-harmonic generation by closed propagation feature of circumferential guided waves

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Chinese Physics B 2020年第2期29卷 301-308页

作者： Guang-Jian Gao Ming-Xi Deng Ning Hu Yan-Xun Xiang department of Physics Army Logistics UniversityChongqing 401331China College of Aerospace engineering Chongqing UniversityChongqing 400044China School of mechanical and Power engineering East China University of Science and TechnologyShanghai 200237China

On the basis of second-order perturbation approximate and modal expansion approach,we investigate the enhancement effect of cumulative second-harmonic generation(SHG)of circumferential guided waves(CGWs)in a circular tube,which is inherently induced by the closed propagation feature of *** appropriate mode pair of primary-and double-frequency CGWs satisfying the phase velocity matching and nonzero energy flux is selected to ensure that the second harmonic generated by primary CGW propagation can accumulate along the *** a coherent superposition of multi-waves,a model of unidirectional CGW propagation is established for analyzing the enhancement effect of cumulative SHG of primary CGW mode *** theoretical analyses and numerical simulations performed directly demonstrate that the second harmonic generated does have a cumulative effect along the circumferential direction and the closed propagation feature of CGWs does enhance the magnitude of cumulative second harmonic *** applications of the enhancement effect of cumulative SHG of CGWs are considered and *** theoretical analysis and numerical simulation perspective presented here yield an insight previously unavailable into the physical mechanism of the enhancement effect of cumulative SHG by closed propagation feature of CGWs in a circular tube.

关键词： circumferential guided wave second-harmonic generation(SHG) enhancement effect of cumulative SHG closed propagation feature

Linkage Between European and east Asian Heatwaves on Synoptic Scales

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Journal of Tropical Meteorology 2024年第2期30卷 97-105页

作者：蔡奋颖刘彩红杨崧邓开强 KURTHS Jürgen School of Atmospheric Sciences Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)ZhuhaiGuangdong 519082 China department of Complexity Science Potsdam Institute for Climate Impact Research(PIK)Member of the Leibniz AssociationPotsdam 14473 Germany department of Water and Climate Risk Institute for Environmental StudiesVrije Universiteit AmsterdamAmsterdam 1087HV Netherlands Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen UniversityZhuhaiGuangdong 519082 China department of Physics Humboldt-Universität zu BerlinBerlin 12489 Germany

Concurrent extreme weather events in geographically distant areas potentially cause high-end risks for *** using network analysis,the present study managed to identify significant nearly-simultaneous occurrences of heatwaves between the grid cells in east Asia and eastern Europe,even though they are geographically far away from each *** further composite analysis,this study revealed that hot events first occurred in eastern Europe,typically with a time lag of3-4 days before the east Asian heatwave *** eastward propagating atmospheric wave train,known as the circumglobal teleconnection(CGT)pattern,bridged the sequent occurrences of extreme events in these two remote *** blockings,amplified by surface warming over eastern Europe,not only enhanced local heat extremes but also excited a CGT-like pattern characterized by alternative anomalies of high and low *** downstream anticyclones in the middle and upper troposphere reduced local cloud cover and increased downward solar radiation,thereby facilitating the formation of heatwaves over east *** half of east Asian heatwave events were preceded by eastern European heatwave events in the 10-day time range before east Asian heatwave *** investigation of heatwave teleconnection in the two distant regions exhibits strong potential to improve the prediction accuracy of east Asian heatwaves.

关键词： concurrent heatwaves eastern Europe east Asia circum-global teleconnection pattern

Lamellar aspect-ratio and thickness-dependent strength-ductility synergy in pure nickel during in-situ micro-tensile loading

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Journal of Materials Science & Technology 2023年第26期157卷 89-97页

作者： Zi-Meng Wang Yun-Fei Jia Kai-Shang Li Yong Zhang Jia-Dong Cai Xian-Cheng Zhang Hiroyuki Hirakata Shan-Tung Tu Key Laboratory of Pressure Systems and Safety Ministry of EducationSchool of Mechanical and Power EngineeringEast China University of Science and TechnologyShanghai 200237China department of mechanical engineering and Science Kyoto UniversityKyoto daigaku-katsuraNishikyo-kuKyoto 615-8540Japan

In order to overcome the trade-offbetween strength and ductility in traditional metallic materials,the gradient lamellar structure was fabricated through an ultrasound-aided deep rolling technique in pure Ni with high stacking fault energy after heat *** gradient lamellar Ni was successively di-vided into three ***-situ micro-tensile tests were performed in different regions to reveal the corresponding microscopic mechanical *** characterization techniques were adopted to explore the effects of microstructural parameters and defects on mechanical *** work demonstrates that the micro-tensile sample with small lamellar thickness and large aspect ratio possesses excellent strength and ductility when the loading direction is parallel to the long side of lamellar grain *** finding is helpful to the design of metallic material microstructure with superior com-prehensive *** one hand,the reason for high strength is that the strength increases with the decrease of lamellar thickness according to the Hall-Petch ***,initial dislocation density also participates in the strengthening *** the other hand,the deformation mechanisms include dislocation slip,grain rotation,and the effects of grain boundaries on dislocations,jointly contributing to good ductility.

关键词： Lamella In-situ micro-tensile test Strength-ductility synergy Aspect ratio Grain rotation