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High Strain Rate Superplasticity in a Micro-grained Al-Mg-Sc Alloy with Predominant High Angle Grain Boundaries

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Journal of.Materials Science & Technology 2012年第11期28卷 1025-1030页

作者： f. C. Liu Z.y. Ma f. C. Zhang Shenyang National Laboratory f.r Materials Science Institute of Metal Research Chinese Academy of SciencesShenyang 110016 China State Key Laboratory of.Metastable Materials Science and Technology Yanshan University Qinhuangdao 066004China

f.iction stir processing （f.P） was applied to extruded AI-Mg-Sc alloy to produce f.ne-grained microstructure with a grain size of.2.2μm. Electron backscatter dif.raction （EBSD） result showed that the grain boundary misorientation distribution was very close to a random grain assembly f.r randomly oriented cubes. Super- plastic investigations in the temperature range of.425-500 ℃ and strain rate range of.1x100^-2-1x10 s^-1 showed that a maximum elongation of.1500% was achieved at 475 ℃ and a high strain rate of.1x100^-2-1x10 s^-1. The f.P AI-Mg-Sc exhibited enhanced superplastic def.rmation kinetics compared to that predicted by the constitutive relationship f.r superplasticity in f.ne-grained aluminum alloys. The origin f.r enhanced superplas- tic def.rmation kinetics in the f.P alloy can be attributed to its high f.action of.high angle grain boundaries （HAGBs）. The analyses of.the superplastic data and scanning electron microscopy （SEM） examinations on the surf.ces of.def.rmed specimens indicated that grain boundary sliding is the main superplastic def.rmation mechanism f.r the f.P AI-Mg-Sc alloy.

关键词： Superplasticity f.iction stir processing Aluminum Microstructure f.iction stir welding

Propagation behavior of.elastic waves in one-dimensional piezoelectric/piezomagnetic phononic crystal with line def.cts

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Acta Mechanica Sinica 2014年第5期30卷 703-713页

作者： y.Pang f.-y.Jiao J.-X.Liu Department of.Engineering Mechanics Shijiazhuang Tie Dao University School of.Mathematics and Physics University of Science and Technology Beijing

Using a stif.ness matrix method, we in- vestigate the propagation behaviors of.elastic waves in one-dimensional （1D） piezoelectric/piezomagnetic （PE/PM） phononic crystals （PCs） with line def.cts by calculating energy ref.ection/transmittion coef.icients of.quasi-pressure and quasi-shear waves. Line def.cts are created by the re- placement of.PE or PM constituent layer. The def.ct modes existing in the f.rst gap are considered and the inf.uences on def.ct modes of.the material properties and volume f.action of.the def.ct layers, the type of.incident waves, the location of.def.ct layer and the number of.structural layers are discussed in detail. Numerical results indicate that def.ct modes are the most obvious when the def.ct layers are inserted in the middle of.the perf.ct PCs; the types of.incidence wave and material properties of.the def.ct layers have important ef.ects on the numbers, the location of.f.equencies and the peaks of.def.ct modes, and the def.ct modes are strongly de- pendent on volume f.action of.the def.ct layers. We hope this paper will be f.und usef.l f.r the design of.PE/PM acoustic f.lters or acoustic transducer with PCs structures.

关键词： 1D phononic crystal Piezoelectric/piezomag- netic. Elastic wave Line def.ct Stif.ness matrix method

An SBf.M-Based Model f.r Hydraulic f.acturing in Quasi-Brittle Materials

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Acta Mechanica Solida Sinica 2018年第4期31卷 416-432页

作者： f. yao Z.J. yang y.J. Hu College of.Civil Engineering and Architecture Zhejiang University Hangzhou 310058 China School of.Civil Engineering Shaoxing University Shaoxing 312000 China

A numerical model based on the scaled boundary f.nite element method is devel- oped to simulate the hydraulic f.acturing in concrete-like quasi-brittle materials using cohesive interf.ce elements. The shadow domain method developed previously （yang and Deeks in Eng f.act Mech 143（4）：333 354, 2007） is extended to consider crack-width-dependent hydraulic pres- sure and cohesive traction, so that the stress intensity f.ctors caused by both crack-f.ce f.rces are semi-analytically calculated separately in the same way. The crack propagation is determined by the criterion of.KI ≥ 0, and the propagation direction by the linear elastic f.acture mechanics criteria. Two examples of.concrete structures are modeled, and the results are in good agreement with the experimental data and others numerical results.

关键词： Scaled boundary f.nite element method Hydraulic f.acture Cohesive crackmodel Crack propagation

Leveraging ROTI map derived f.om Indonesian GNSS receiver network f.r advancing study of.Equatorial Plasma Bubble in Southeast/East Asia

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Earth and Planetary Physics 2025年第1期9卷 101-116页

作者： Prayitno Abadi Ihsan N.Muaf.ry Teguh N.Pratama Angga y.Putra Suraina Gatot H.Pramono Sidik T.Wibowo f.brylian f.Chabibi Umar A.Ahmad Wildan P.Tresna Asnawi Research Center f.r Climate and Atmosphere Indonesian National Research and Innovation Agency(BRIN)BandungIndonesia School of.Electrical Engineering Telkom UniversityBandungIndonesia Directorate of.Laboratory Management f.cilities and Science and Technology Park Indonesian National Research and Innovation Agency(BRIN)PontianakIndonesia Geophysics Laboratory Master Program in PhysicsUniversitas Gadjah Mada(UGM)YogyakartaIndonesia Research Center f.r Space Indonesian National Research and Innovation Agency(BRIN)BandungIndonesia Indonesian Geospatial Inf.rmation Agency(BIG) JakartaIndonesia Research Center f.r Photonics Indonesian National Research and Innovation Agency(BRIN)Tangerang SelatanIndonesia Department of.Earth and Planetary Sciences Hokkaido UniversitySapporoJapan

This paper highlights the crucial role of.Indonesia’s GNSS receiver network in advancing Equatorial Plasma Bubble(EPB)studies in Southeast and East Asia,as ionospheric irregularities within EPB can disrupt GNSS signals and degrade positioning *** by the Indonesian Geospatial Inf.rmation Agency(BIG),the Indonesia Continuously Operating Ref.rence Station(Ina-CORS)network comprises over 300 GNSS receivers spanning equatorial to southern low-latitude ***-CORS is uniquely situated to monitor EPB generation,zonal drif.,and dissipation across Southeast *** provide a practical tool f.r EPB research,by sharing two-dimensional rate of.Total Electron Content(TEC)change index(ROTI)derived f.om this *** generate ROTI maps with a 10-minute resolution,and samples f.om May 2024 are publicly available f.r f.rther scientif.c *** preliminary f.ndings f.om the ROTI maps of.Ina-CORS are ***,the Ina-CORS ROTI maps reveal that the irregularities within a broader EPB structure persist longer,increasing the potential f.r these irregularities to migrate f.rther ***,we demonstrate that combined ROTI maps f.om Ina-CORS and GNSS receivers in East Asia and Australia can be used to monitor the development of.ionospheric irregularities in Southeast and East *** have demonstrated the combined ROTI maps to capture the development of.ionospheric irregularities in the Southeast/East Asian sector during the G5 Geomagnetic Storm on May 11,*** observed simultaneous ionospheric irregularities in Japan and Australia,respectively propagating northwestward and southwestward,bef.re midnight,whereas Southeast Asia’s equatorial and low-latitude regions exhibited irregularities *** sharing ROTI maps f.om Indonesia and integrating them with regional GNSS networks,researchers can conduct comprehensive EPB studies,enhancing the understanding of.EPB behavior across Southeast and East Asia and contributing signif.cantly to ionosphe

关键词： Equatorial Plasma Bubble(EPB) GNSS receivers’network Indonesia Continuously Operating Ref.rence Station(Ina-CORS) ionospheric map Rate of.TEC change index(ROTI)map

ARTIf.CIAL NEURAL NETWORK MODEL Of.CONSTITUTIVE RELATIONSHIP f.R 2A70 ALUMINUM ALLOy

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Acta Metallurgica Sinica(English Letters) 2005年第6期18卷 719-723页

作者： f. Liu D.B. Shan y. Lu y. y. yang School of.Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

The hat def.rmation behavior of.2A70 aluminum alloy was investigated by means of.isothermal compression tests perf.rmed on a Gleeble-1500 thermal simulator over a wide range of.temperatures 360-480℃ with strain rates of.0.01-1s^-1 and the largest def.rmation of.60%, and the true stress of.the material was obtained under the above-mentioned conditions. The experimental results shows that 2A70 aluminum alloy is a kind of.aluminum alloy with the property of.dynamic recovery; its f.ow stress declines with the increase of.temperature, while its f.ow stress increases with the increase of.strain rates. On the basis of.experiments, the constitutive relationship of.the 2A70 aluminum alloy was constructed using a BP artif.cial neural network. Comparison of.the predicted values with the experimental data shows that the relative error of.the trained model is less than ±3% f.r the sampled data while it is less than ±6% f.r the nonsampled data. It is evident that the model constructed by BP ANN can accurately predict the f.ow stress of.the 2A70 alloy.

关键词： 2A70 aluminum alloy f.ow stress constitutive relationship,BP artif.cial neural network

Complete Maps f.r the Internal Oxidation of.Ideal Ternary Alloys f.rming Insoluble Oxides under High Oxidant Pressures

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中国腐蚀与防护学报 2009年第4期29卷 253-261页

作者： f. GESMUNDO S. WANG y. NIU State Key Laboratory f.r Corrosion and Protection Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 DICHEP Universita di Genova Fiera del Mare Pad. D 16129 Genova Italy

This paper presents an analysis of.the conditions of.stability of.the dif.erent f.rms of.internal oxidation of.ideal ternary A-B-C alloys,where A is the most noble and C the most reactive component, f.rming insoluble oxide and exposed to high pressures of.a single *** treatment,based on an extension to ternary alloys of.Wagner' s criterion f.r the transition f.om internal to external oxidation in binary alloys,allows to predict the existence of.three dif.erent f.rms of.internal *** f.ct,in addition to the most common kinds of.internal attack,involving the coupled internal oxidation of.B+C beneath external AO scales and the internal oxidation of.C beneath external BO scales,a third mode, involving the internal oxidation of.C beneath external scales composed of.mixtures of.AO+BO,becomes also possible under special conditions.A combination of.the boundary conditions f.r the existence of.these dif.erent types of.internal oxidation allows to predict three dif.erent kinds of.complete maps f.r the internal oxidation in these systems,one of.which involves only two modes,while the other two involve all the three possible modes of.internal oxidation.

关键词：镁合金氧化腐蚀金属

Analytical solutions of.unif.rm extended dislocations and tractions over a circular area in anisotropic magnetoelectroelastic bimaterials

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Acta Mechanica Sinica 2013年第1期29卷 73-84页

作者： y.-f. Zhao X.-C. Shang E. Pan Dept. of.Civil Engineering University of Akron Dept. of.Applied Mechanics University of Science and Technology

In this paper, we derive the analytical solutions in a three-dimensional anisotropic magnetoelectroelastic bimaterial space subject to unif.rm extended dislocations and tractions within a horizontal circular area. By virtue of.the Stroh f.rmalism and f.urier transf.rmation, the f.nal expression of.solutions in the physical domain contains only line integrals over [0, 2π] rather than inf.nite integrals. As the reduced cases, the half.space and homogeneous f.ll-space solutions can be directly derived f.om the present solutions. Also, in terms of.material domains, the present solutions can be reduced to the piezoelectric, piezomagnetic, purely elastic materials with dif.erent symmetries of.material prop- erty. To carry out numerical calculations, Gauss quadrature is adopted. In the numerical examples, the ef.ect of.dif.erent loading locations on the response at the interf.ce is analyzed. It is shown that, when the magnetic traction or electric dislocation is applied, the physical quantities on the interf.ce may not decrease monotonically as the loading area moves away f.om the interf.ce. The distributions of.dif.erent in-plane physical quantities on the upper and lower interf.ces under various extended horizontal loadings are compared and the dif.erences are discussed. The work presented in this paper can serve as benchmarks f.r f.ture numerical studies in related research f.elds.

关键词： Anisotropic bimaterial space. Magnetoelectroe- lastic Extended dislocations Extended tractions Circular loading Analytic solutions

Ef.ectiveness of.air cleaner on mitigating the transmission of.respiratory disease in a dental clinic environment

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Building Simulation 2024年第10期17卷 1789-1803页

作者： Gang yang yif.n Wang Ka Chung Chan kwok Wai Mui Thomas f.f.emmig SThomas Ng Christopher y.H.Chao Sau Chung f. Department of.Building Environment and Energy Engineering The Hong Kong Polytechnic UniversityHong KongChina f.culty of.Dentistry The University of Hong KongHong KongChina Department of.Architecture&Civil Engineering City University of Hong KongHong KongChina Department of.Mechanical Engineering The Hong Kong Polytechnic UniversityHong KongChina

In dental clinics with an open f.oor plan,the risk of.patient-to-patient transmission of.respiratory disease is a *** dental procedures large amounts of.bioaerosol are produced and patients cannot wear personal protective *** paper examines how to ef.ectively deploy air cleaner to reduce the inf.ction risk in dental clinics with an open f.oor *** locations of.air cleaners at various clean air delivery rates(CADRs)were *** dispersion of.bioaerosol was studied through numerical simulations,and risk assessment was perf.rmed by a dose-response *** f.ndings indicated that dental patients downstream of.the background ventilation have a higher inf.ction risk than those to the lef. and right of.an inf.cted patient(i.e.,the source).The lowest inf.ction risks f.r the adjacent patients were f.und when the air cleaner was place opposite to the dentists,i.e.,on the f.oor at low CADR levels of.2.2 m^(3)/min or on the bench at CADR levels of.4.4 m^(3)/min or *** results of.this study indicated that air cleaner can mitigate the risk of.patient-to-patient transmission of.SARS-CoV-2 in dental clinics with an open f.oor *** CADR levels determine the optimal placement of.air cleaners.

关键词： inf.ction risk air cleaner location dental clinic Cf. simulation respiratory disease

Ef.ect of.electric boundary conditions on crack propagation in f.rroelectric ceramics

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Acta Mechanica Sinica 2014年第2期30卷 153-160页

作者： f.-X. Li y.Sun R.K.N.D.Rajapakse State Key Laboratory f.r Turbulence and Complex Systems College of EngineeringPeking University f.culty of.Applied Sciences Simon Fraser University

In this paper, the ef.ect of.electric boundary conditions on Mode I crack propagation in f.rroelectric ceramics is studied by using both linear and nonlinear piezoelectric f.acture mechanics. In linear analysis, impermeable cracks under open circuit and short circuit are analyzed using the Stroh f.rmalism and a rescaling method. It is shown that the energy release rate in short circuit is larger than that in open circuit. In nonlinear analysis, permeable crack conditions are used and the nonlinear ef.ect of.domain switching near a crack tip is considered using an energy-based switching criterion proposed by Hwang et al.（Acta Metal. Mater.,1995）. In open circuit, a large depolarization f.eld induced by domain switching makes switching much more dif.cult than that in short circuit. Analysis shows that the energy release rate in short circuit is still larger than that in open circuit, and is also larger than the linear result. Consequently,whether using linear or nonlinear f.acture analysis, a crack is f.und easier to propagate in short circuit than in open circuit, which is consistent with the experimental observations of.Kounga Njiwa et al.（Eng. f.act. Mech., 2006）.

关键词： f.rroelectric ceramics Crack propagation En-ergy release rate Electric boundary conditions Domain switching