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Dynamic modeling of.preloaded size-dependent nano-crystalline nano-structures

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Applied mathematics and mechanics(English Edition) 2017年第12期38卷 1753-1772页

作者： f.EBRAHImI m.R.BARATI Department of.mechanical Engineering Faculty of EngineeringImam Khomeini International University Aerospace Engineering Department and Center of.Excellence in Computational Aerospace Amirkabir University of Technology

The vibration behavior of.size-dependent nano-crystalline nano-beams is investigated based on nonlocal, couple stress and surf.ce elasticity theories. A nano- crystalline nano-beam is composed of.three phases which are nano-grains, nano-voids, and interf.ce. Nano-voids or porosities inside the material have a stif.ness-sof.ening impact on the nano-beam. A Eringen＇s nonlocal elasticity theory is applied in the analysis of.nano-crystalline nano-beams f.r the f.rst time. Residual surf.ce stresses which are usually neglected in modeling nano-crystalline nano-beams are incorporated into nonlocal elasticity to better understand the physics of.the problem. Also, a modif.ed couple stress theory is used to capture rigid rotations of.grains. Applying a dif.erential transf.rm method （DTm） satisf.ing various boundary conditions, the governing equations obtained f.om the Hamilton＇s principle are solved. Reliability of.the proposed approach is verif.ed by comparing the obtained results with those provided in the literature. The ef.ects of.the nonlocal parameter, surf.ce ef.ect, couple stress, grain size, porosities, and interf.ce thickness on the vibration characteristics of.nano-crystalline nano-beams are explored.

关键词： surf.ce ef.ect f.ee vibration nano-crystalline nano-beam nonlocal elasticity modif.ed couple stress theory

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Acta mechanica Sinica 2020年第6期36卷 1294-1301,I0003页

作者： C.G.Chai A.G.Pi Q.m.Li f.L.Huang Institute of.Chemical materials China Academy of Engineering PhysicsMianyang621900China State Key Laboratory of.Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China School of.mechanical Aerospace and Civil EngineeringUniversity of ManchesterManchesterM139PLUK

Similarity can ref.ect common laws in the mechanism of.rigid-body *** this paper,the similarities in rigid-body penetration depth are demonstrated by three non-dimensional but physically meaningf.l quantities,i.e.,ρkinetic,I∗ln and N′*** three quantities represent the non-dimensional areal density of.projectile kinetic energy,the ef.ect of.nose geometry,and the f.iction at the interactive cross section between projectile and target *** is shown that experimental data of.rigid projectile penetration,f.om shallow to deep penetration,can be uniquely unif.ed by these three similarity quantities and their ***,f.r ogival nose projectiles,their penetration capacities are dominated byρkinetic,which is consisted by non-dimensional ef.ective length Lef. and non-dimensional quantity Dpn=ρpv20AY which has the same f.rm as Johnson’s damage *** the sacrif.ce of.minor theoretical accuracy,the non-dimensional penetration depth P/d can be understood as directly controlled by Dpn,enhanced by projectile ef.ective length Lef. under a multiplication relation,and optimized by projectile nose geometry in the f.rmation of.I∗ln.

关键词： Concrete target Deep penetration Similarity-Johnson's damage number

Band structure,f.rmi surf.ce,elastic,thermodynamic,and optical properties of.AlZr3,AlCu3,and AlCu2Zr:f.rst-principles study

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Chinese Physics B 2016年第8期25卷 103-112页

作者： Parvin R Parvin f.Ali m S Islam A K m A Department of.Physics Rajshahi University Rajshahi-6205 Bangladesh Department of.Physics Pabna University of Science and Technology Pabna 6600 Bangladesh International Islamic University Chittagong 154/A College Road Chittagong-4203 Bangladesh

The electronic properties（f.rmi surf.ce,band structure,and density of.states（DOS）） of.Al-based alloys Alm3（m=Zr and Cu） and AlCu2Zr are investigated using the f.rst-principles pseudopotential plane wave method within the generalized gradient approximation（GGA）.The structural parameters and elastic constants are evaluated and compared with other available ***,the pressure dependences of.mechanical properties of.the compounds are *** temperature dependence of.adiabatic bulk modulus,Debye temperature,specif.c heat,thermal expansion coef.icient,entropy,and internal energy are all obtained f.r the f.rst time through quasi-harmonic Debye model with phononic ef.ects f.r T = 0 K-100 *** parameters of.optical properties（dielectric f.nctions,ref.active index,extinction coef.icient,absorption spectrum,conductivity,energy-loss spectrum,and ref.ectivity） of.the compounds are calculated and discussed f.r the f.rst *** ref.ectivities of.the materials are quite high in the IR-visible-UV region up to ~ 15 eV,showing that they promise to be good coating materials to avoid solar *** of.the properties are also compared with those of.the Al-based Ni3 Al compound.

关键词： f.rst principle calculations f.rmi surf.ce elastic moduli entropy and internal energy optical properties

microstructural characteristics and second-phase particles in yttrium-bearing f.-10Ni-7mn martensitic steels

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Journal of.Rare Earths 2014年第4期32卷 326-333页

作者： f.f.rghani m.Nili-Ahmadabadi School of.metallurgy and materials Engineering College of EngineeringUniversity of Tehran Center of.Excellence f.r High Perf.rmance materials University of Tehran

In this study, the microstructure and second-phase particles in yttrium （0.05 wt.%and 0.8 wt.%） bearing f.-10Ni-7mn steels were characterized. The results of.X-ray analysis as well as scanning electron microscopy coupled with energy dispersive X-ray spectroscopy indicated the f.rmation of.（f., Ni, mn）17Y2 precipitates with hexagonal structure in a f.-10Ni-7mn-0.8Y （wt.%） alloy. Lattice parameters of.these precipitates were calculated as f.llows：a=0.8485 nm and c=0.8274 nm. f.rmation of.Y2O3 sub-micron particles was also conf.rmed in both yttrium bearing steels via electrolytic phase extraction method. The ef.ect of.these precipitates on the prior austenite grain size was investigated. The results revealed that these precipitates had an ef.ective role in controlling the prior austenite grain size.

关键词： f.-10Ni-7mn (wt.%) steel yttrium addition microstructure characterization second-phase particles grain growth rare earths

Cognition and the brain of.brood parasitic cowbirds

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Integrative Zoology 2019年第2期14卷 145-157页

作者： David f.SHERRY mélanie f.GUIGUENO Department of.Psychology Western University LondonOntario Department of.Natural Resource Sciences McGill UniversityMontrealQuebecCanada

Cowbirds are brood *** lay their eggs in the nests of.other species,which then incubate the cowbird eggs and raise the young *** and returning to heterospecif.c nests presents cowbirds with several cognitive *** some species,such as brown-headed cowbirds(molothrus ater),f.males but not males search f.r and remember the locations of.potential host *** describe recent research on sex dif.f.rences in cognition and the hippocampus associated with this sex dif.erence in search f.r host *** brown-headed cowbirds perf.rm better than males on some,but not all,tests of.spatial memory and f.males show a pattern of.adult hippocampal neurogenesis not f.und in males or in closely related non-parasitic *** of.the apparent specialization of.the hippocampus,brown-headed cowbirds may be a good model in which to examine spatial inf.rmation processing in the avian hippocampus and we also describe recent research on the spatial response properties of.brown-headed cowbird hippocampal neurons.

关键词： adult neurogenesis brood parasites cowbirds hippocampus sex dif.erences spatial memory

multimedia model of.atrazine in plant-soil-groundwater system with a f.gacity approach

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Journal of.Environmental Sciences 2001年第4期13卷 466-471页

作者： Ye, C.-m. Lei, Z.-f. Wang, X.-j. Gong, A.-j. Zheng, H.-h. Res. Cntr. Eco-Environmental Sci. Chinese Academy of Sciences Beijing 100085 China

The application of.atrazine in China during the last ten years has led to some environmental problems. In this paper, the multimedia model of.atrazine in soil-plant-groundwater system at Baiyangdian Lake area in Northern China was established using a f.gacity approach, and verif.ed with observed values. The model involved 7 environmental compartments which are air, groundwater, soil, corn roots, corn stem, corn leaf.and kernel of.corn. The results showed that the relative errors between calculated and observed values have a mean value of.24.7%, the highest value is 48% and the lowest value is 1.4%. All these values indicated that this multimedia model can be used to simulate the environmental f.te of.atrazine. Both the calculated and observed values of.concentrations of.atrazine in plant compartments are in the f.llowing order: in corn roots > in corn stem > in kernel of.corn > in corn leaf. it exhibited a good regularity. The prediction results indicated that concentrations of.atrazine in the groundwater and kernel of.corn will override the limitation of.3 μg/L and 0.05 mg/kg respectively.

关键词： Concentration (process) Error detection Groundwater Lakes Plants (botany) Soils

A new image watermarking f.amework based on levels-directions decomposition in contourlet representation

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Journal of.Central South University 2017年第3期24卷 521-532页

作者： m.f.Kazemi m.A.Pourmina A.H.mazinan Department of.Electrical and Computer Engineering Science and Research BranchIslamic Azad University(IAU)TehranIran Department of.Control Engineering Faculty of Electrical EngineeringSouth Tehran BranchIslamic Azad University(IAU)TehranIran

With the development of.digital inf.rmation technologies,robust watermarking f.amework is taken into real consideration as a challenging issue in the area of.image processing,due to the large applicabilities and its utilities in a number of.academic and real *** are a wide range of.solutions to provide image watermarking f.ameworks,while each one of.them is attempted to address an ef.icient and applicable *** reality,the traditional techniques do not have suf.icient merit to realize an accurate *** to the f.ct that the main idea behind the approach is organized based on contourlet representation,the only state-of.the-art materials that are investigated along with an integration of.the af.rementioned contourlet representation in line with watermarking f.amework are concentrated to be able to propose the novel and skilled *** a word,the main process of.the proposed robust watermarking f.amework is organized to deal with both new embedding and de-embedding processes in the area of.contourlet transf.rm to generate watermarked image and the corresponding extracted logo image with high *** f.ct,the motivation of.the approach is that the suggested complexity can be of.novelty,which consists of.the contourlet representation,the embedding and the corresponding de-embedding modules and the perf.rmance monitoring including an analysis of.the watermarked image as well as the extracted logo *** is also a scrambling module that is working in association with levels-directions decomposition in contourlet embedding mechanism,while a decision maker system is designed to deal with the appropriate number of.sub-bands to be embedded in the presence of.a series of.simulated *** required perf.rmance is tangibly considered through an integration of.the peak signal-to-noise ratio and the structural similarity indices that are related to watermarked *** the bit error rate and the normal correlation are considered that are

关键词： contourlet based watermarking f.amework levels-directions decomposition embedding process de-embedding process peak signal-to-noise ratio structural similarity indices normal correlation bit error rate

Level-direction decomposition analysis with a f.cus on image watermarking f.amework

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f.ontiers of.Inf.rmation Technology & Electronic Engineering 2016年第11期17卷 1199-1217页

作者： m.f.KAZEmI m.A.POURmINA A.H.mAZINAN Department of.Electrical and Computer Engineering Science and Research Branch Islamic Azad University Department of.Control Engineering Faculty of Electrical Engineering South Tehran Branch Islamic Azad University

This research addresses the new level-direction decomposition in the area of.image watermarking as the f.rther development of.investigations. The main process of.realizing a watermarking f.amework is to generate a watermarked image with a f.cus on contourlet embedding representation. The approach perf.rmance is evaluated through several indices including the peak signal-to-noise ratio and structural similarity, whereby a set of.attacks are carried out using a module of.simulated attacks. The obtained inf.rmation is analyzed through a set of.images, using dif.erent color models, to enable the calculation of.normal correlation. The module of.the inverse of.contourlet embedding representation is correspondingly employed to obtain the present watermarked image, as long as a number of.original images are applied to a scrambling module, to represent the inf.rmation in disorder. This allows us to evaluate the perf.rmance of.the proposed approach by analyzing a complicated system, where a decision making system is designed to f.nd the best level and the corresponding direction regarding contourlet embedding representation. The results are illustrated in appropriate level-direction decomposition. The key contribution lies in using a new integration of.a set of.subsystems, employed based upon the novel mechanism in contourlet embedding representation, in association with the decision making system. The presented approach is ef.icient compared with state-of.the-art approaches, under a number of.serious attacks. A number of.benchmarks are obtained and considered along with the proposed f.amework outcomes. The results support our ideas.

关键词： Level-direction decomposition analysis Watermarking f.amework Contourlet embedding representation Scrambling module Simulated attacks

Structure and properties of.brazed joints on dispersion-strengthened copper

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China Welding 2014年第3期23卷 31-36页

作者： S. V. maksymova V. f. Khorunov E. O. Paton Electric Welding Institute National Academy of Sciences of Ukraine Brazing

Development of.the technological process f.r brazing of.heat-resistant copper alloy strengthened with Al2O3 oxide particles is an important task of.f.brication of.high-temperature application structures. As mechanical properties of.the brazed joints directly depend on the structural f.ctor and morphological peculiarities of.the brazed seams, the latter are of.technological interest in terms of.making of.permanent joints. This study gives results of.X-ray spectral microanalysis of.the brazed joints on dispersion-strengthened copper alloy （ Gridcop Al-25 ） produced by using the Ti-Cu system adhesion-active brazing f.ller alloy, dif.erent heat sources and temperature-time parameters of.the brazing process. Shown are dif.erences in f.rmation of.structure of.the seams made by vacuum brazing using radiation and high-f.equency heating. Vacuum brazing with radiation heating provides the homogeneous seams with crystallisation of.the phases based on the CuTi and CuTi2 compounds in the f.rm of.discrete f.ceted particles 2 - 9μm in size against the background of.the copper matrix. Based on investigation of.structural peculiarities of.the brazed seams, the temperature-time conditions of.vacuum brazing with radiation heating were selected f.r manuf.cture of.specimens f.r mechanical tests. Analysis of.the results of.strength tests of.the butt brazed specimens proved the expediency of.preliminary heat treatment of.the base material, providing strength of.the joints at a level of.about 92% of.that of.the base material.

关键词： dispersion-strengthened copper alloy aluminium oxide Al2O3 vacuum brazing adhesion-active f.ller alloy,microstructure