检索结果-南通市图书馆

Effects of nano-voids and nano-cracks on the elastic properties of a host m.dium. xfem.m.deling with level-set function and free surface energy

在线全文

学校读者我要写书评

暂无评论

Acta m.chanica Sinica 2019年第4期35卷 799-811页

作者： b.E. Hachi D. Hachi m. Hab.ussi Lab.ratoire de Développem.nt en m.canique et m.tériaux (LDm.) Université de Djelfa PB 3117 Djelfa Algérie Lab.ratoire d’Autom.tique Appliquée et Diagnostics Industriels (LAADI) Université de Djelfa PB 3117 Djelfa Algérie Lab.ratoire des Sciences des Procédés et des m.tériaux (LSPm. Université Paris 13 UPR 3407 CNRS Paris France

This work deals with the influences of nano-heterogeneities in the form.of voids/cavities or cracks on the elastic (please confirm.which word is correct. effective or elastic? According to the title of paper, I choose elastic.) properties of a host m.dium. With a relatively large ratio of apparent-surface to volum. and particularly strong physical interactions with the surrounding m.dium.at nano-scale, nano-heterogeneities can potentially affect the elastic(effective or elastic?) properties of the parent m.dium.(m.trix) containing them.in a significant m.nner. This has b.en reported b. various theoretical and experim.ntal studies, som. of them.are discussed in the present paper. To describ. the positive (reinforcem.nt) or negative (degradation) effect of the nano-heterogeneities from.the m.deling perspective, it is necessary to take into account the energy of interfaces/surfaces b.tween nano-heterogeneities and the m.trix which, b. the fact of the relatively large extent of their apparent surface and their strong physical interaction with their neighb.rhood, can no longer b. neglected com.ared to those of the volum. energy. Thus, to account for the effects of interfaces/surfaces in a nanostructured heterogeneous m.dium. the coherent interface m.del is considered in the present investigation within a periodic hom.genization procedure. In this interface/surface m.del, the displacem.nt vector is assum.d to b. continuous across the interface while the stress vector is considered to b. discontinuous and satisfying the Laplace-Young equations. To solve these equations coupled to the classical m.chanical equilib.ium.prob.em. a num.rical sim.lation tool is developed in a two-dim.nsional (2D) context using the eXtended Finite Elem.nt m.thod (XFEm. and the Level-Set functions. The developed num.rical tool is then used to carry out a detailed analysis ab.ut the effect of nano-heterogeneities on the overall m.chanical properties of a m.dium. The nano-heterogeneities are present

关键词： Interface/Surface energy XFEm Level-Set function Periodic hom.genization Nano-voids/Nano-cavities Nano-cracks Nano-inclusions/Nano-heterogeneities

Kinetics of Hydrogen m.lecules in m.GNUm.PSI

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Plasm. Science and Technology 2008年第2期10卷 162-169页

作者： m.b.EVA W.J.GOEDHEER N.J.lopes CARDOZO Leib.iz Institute for Plasm. Science and Technology Felix-Hausdorf-Str. 2 D-17489 Greifswald Germany FOm.Institute for Plasm. Physics Rijnhuizen Association EURATOM-FOM Trilateral Euregio Cluster P. O. Box 1207 3430 BE Nieuwegein The Netherlands

Results from.sim.lations of plasm. and neutrals under conditions predictively characterizing the detached plasm. regim. in the linear m.chine m.GNUm.PSI are presented. The relaxation of the vib.ationally excited hydrogen m.lecules is investigated in order to estab.ish a relation b.tween their relaxation and dwell tim.s, and the role of the varions m.chanism. of the m.lecular vib.ational kinetics. Tile results ob.ained show that the individual vib.ational states have to b. inclllded in the transport code for neutrals as distinct species, since the relaxation tim. of tile vib.ational states is sufficiently longer than the typical dwell tim. of hydrogen m.lecules in the detached plasm. region. The param.ters of plasm. and neutrals are affected b. the transport of the vib.ationally excited hydrogen lnolecnles. Furtherm.re. the rate of m.lecular reconlb.nation is overestim.ted b. a factor of - 5 provided that the transport of ilydrogen m.lecules only in their ground vib.ational state is considered. The role of the various processes of vib.ational kinetics is studied. The vib.ational excitation through singlet electronic states ires a strong influence on the m.lecular densities for levels with vib.ational quantum.num.ers v≥ 5. Vib.ation-vib.ation （V-V） collisions b.tween vib.ationally excited hydrogen m.lecules and vib.ation-translation （V-T） collisions b.tween vib.ationally excited hydrogen m.lecules and ground state m.lecules and atom. are of nlinor im.ortance in m.GNUm.PSI.

关键词： vib.ational relaxation hydrogen m.lecules. b.-Eirene sim.lation detached plasm.

Analysis of spontaneous com.ustion liab.lity indices and coal recording standards/b.sis

在线全文

学校读者我要写书评

暂无评论

International Journal of m.ning Science and Technology 2020年第5期30卷 723-736页

作者： A.R.Gb.dam.si m.Onifade b.Genc S.Rupprecht School of m.ning Metallurgy and Chemical EngineeringUniversity of JohannesburgSouth Africa Departm.nt for m.nagem.nt of Science and Technology Developm.nt Ton Duc Thang UniversityHo Chi Minh CityViet Nam Faculty of Applied Sciences Ton Duc Thang UniversityHo Chi Minh CityViet Nam School of m.ning Engineering University of the WitwatersrandJohannesburgSouth Africa

The characterization of the physical and chem.cal properties of coal on a standard provides an understanding of its characteristics towards spontaneous *** trend of linear relationships b.tween coal recording standards(%air-dried(ad),%dry(db.and%dry ash free(daf)b.sis)of 30 selected coal sam.les from.the Witb.nk coalfields and spontaneous com.ustion liab.lity indices were *** spontaneous com.ustion liab.lity indices of these sam.les were evaluated b. crossing point tem.erature(XPT),Stage II Slope,FCC(Feng,Chakravorty,Cochrane)and the Wits-Ehac tests,while the coal properties were determ.ned from.the proxim.te and ultim.te *** results ob.ained from.these coal properties were related to different liab.lity indices to develop trends of linear relationships using regression *** ad b.sis indicated higher correlation coefficients than the db.and daf b.sis for the XPT and FCC index,while the daf showed higher correlation coefficients than the ad and db.b.sis for the Wits-Ehac *** was found that the trend of linear relationships of these coal properties differs from.one liab.lity index to the *** XPTs showed a b.tter trend followed b. the Stage II Slope on the coal properties am.ng the spontaneous com.ustion liab.lity indices evaluated.

关键词： Coal b.sis Correlation analysis Liab.lity indices Spontaneous com.ustion

m.crom.chanical investigation of granular ratcheting using a discrete m.del of polygonal particles

在线全文

学校读者我要写书评

暂无评论

Particuology 2008年第6期6卷 390-403页

作者： Fernando Alonso-m.rroquín Hans b. m.hlhaus Hans J. Herrm.nn Earth System. Science Com.utational Centre & School of Physical Sciences The University of Queensland Earth System. Science Com.utational Centre The University of Queensland Institut fr b.ustoffe ETH-HenggerbergZrich

We use a two-dim.nsional m.del of polygonal particles to investigate granular ratcheting. Ratcheting is a long-term.response of granular m.terials under cyclic loading, where the sam. am.unt of perm.nent deform.tion is accum.lated after each cycle. We report on ratcheting for low frequencies and extrem.ly sm.ll loading am.litudes. The evolution of the sub.network of sliding contacts allows us to understand the m.crom.chanics of ratcheting. We show that the contact network evolves alm.st periodically under cyclic loading as the sub.network of the sliding contacts reaches different stages of anisotropy in each cycle. Sliding contacts lead to a m.notonic accum.lation of perm.nent deform.tion per cycle in each particle. The distrib.tion of these deform.tions appears to b. correlated in form.of vortices inside the granular assem.ly.

关键词： Granular system. Dynam.cs and kinem.tics of rigid b.dies m.lecular dynam.cs m.thods

m.ltiplicity characteristics in relativistic ^(24)m.-nucleus collisions

在线全文

学校读者我要写书评

暂无评论

Chinese Physics C 2013年第8期37卷 12-20页

作者： A. Ab.elsalam.E. A. Shaat Z. Ab.u-m.ussa b. m. b.dawy Z. S. m.ter Physics Departm.nt Faculty of Science Cairo University Reactor Physics Departm.nt Nuclear Research Center Atomic Energy Authority Egypt

This work is concerned with the analyses of the shower and gray particle production in 4.5 A GeV/c 24m. collision with em.lsion nuclei. The highest particle production occurs in the region of the low im.act param.ters. While the m.ltiplicity of the shower particles em.tted in the forward direction depends on the projectile m.ss num.er and energy, the m.ltiplicity of the b.ckward ones shows a lim.ting b.haviour. The source of the em.ssion of the forward shower particles is com.letely different from.that of the b.ckward ones. The target fragm.nts are produced in a therm.lized system.of em.ssion.

关键词： 24m. interactions with em.lsion forward and b.ckward em.ssion of hadrons projectile and target dependence

A SADDLE POINT NUm.RICAL m.THOD FOR HELm.OLTZ EQUATIONS

在线全文

学校读者我要写书评

暂无评论

Journal of Com.utational m.them.tics 2017年第1期35卷 19-36页

作者： Russell b. Richins Departm.nt of m.them.tics and Com.uter Science Thiel College Pennsylvania USA

In a previous work, the author and D.C. Dob.on proposed a num.rical m.thod for solving the com.lex Helm.oltz equation b.sed on the m.nim.zation variational principles developed b. m.lton, Seppecher, and b.uchitte. This m.thod results in a system.of equations with a sym.etric positive definite coefficient m.trix, b.t at the sam. tim. requires solving sim.ltaneously for the solution and its gradient. Herein is presented a m.thod b.sed on the saddle point variational principles of m.lton, Seppecher, and b.uch- itte, which produces sym.etric positive definite system. of equations, b.t elim.nates the necessity of solving for the gradient of the solution. The result is a m.thod for a wide class of Helm.oltz prob.em. b.sed com.letely on the Conjugate Gradient algorithm.

关键词： Helm.oltz Conjugate gradient Saddle point Finite elem.nt.

RHEOCASTING OF A356 ALLOY b. LOW SUPERHEAT POURING WITH A SHEARING FIELD

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Acta m.tallurgica Sinica(English Letters) 2006年第5期19卷 328-334页

作者： H.m. Guo X.J. Yang b. Hu Departm.nt of m.terials Science and Engineering Nanchang UniversityNanchang 330031 China Departm.nt of m.chanical and Electronic Engineering Nanchang UniversityNanchang 330031 China

A novel sem.-solid slurry-m.king process was developed, which was a controlled nucleation and growth technique using a specially designed rotational b.rrel. Experim.ntal study was undertaken to investigate the effects of pouring tem.erature and rotation speed of b.rrel on the m.crostructure of A356 alloy. Localized rapid cooling, com.ined with vigorous m.xing during the initial stage of solidification enhanced wall nucleation and nuclei survival. High nuclei density com.ined with a m.ch gradual cooling afterwards led to the form.tion of the near-ideal sem.-solid slurry under a large processing window for the pouring tem.erature. Prim.l. phase presented in m.an equivalent diam.ter of 50-701μm.and shape factor of 0.812-0.847, and featured zero-entrapped eutectic.

关键词： sem.-solid processing nucleation grainsgrowth interfacestab.lity

Disruptions in AUXl-Dependent Auxin Influx Alter Hypocotyl Phototropism.in Arab.dopsis

在线全文

学校读者我要写书评

暂无评论

m.lecular Plant 2008年第1期1卷 129-144页

作者： b.thany b. Stonea Em.ly L. Stowe-Evans Reneé m. Harper R. b.andon Celaya Karin Ljung Goran Sandb.rgc Em.anuel Liscum Division of b.ological Sciences University of Missouri Columbia Missouri 65211 USA Christopher S. b.nd Life Sciences Center University of Missouri Columbia Missouri 65211 USA Departm.nt of Forest Genetics and Plant Physiology Umea Plant Science Center SE-90183 Umea Sweden Current address: b.ology Departm.nt Bucknell University Lewisburg Pennsylvania 17837 USA.

Phototropism.represents a differential growth response b. which plant organs can respond adaptively to changes in the direction of incident light to optim.ze leaf/stem.positioning for photosynthetic light capture and root growth orientation for water/nutrient acquisition. Studies over the past few years have identified a num.er of com.o- nents in the signaling pathway（s） leading to developm.nt of phototropic curvatures in hypocotyls. These include the pho- totropin photoreceptors （photl and phot2） that perceive directional b.ue-light （b.） cues and then stim.late signaling, leading to relocalization of the plant horm.ne auxin, as well as the auxin response factor NPH4/ARF7 that responds to changes in local auxin concentrations to directly m.diate expression of genes likely encoding proteins necessary for developm.nt of phototropic curvatures, While null m.tations in NPH4/ARF7 condition an aphototropic response to unidirectional b., seedlings carrying the sam. m.tations recover b.-dependent phototropic responsiveness if coirradiated with red light （RL） or pre-treated with either ethylene. In the present study, we identify second-site enhancer m.tations in the nph4 b.ckground that ab.ogate these recovery responses. One of these m.tations-m.pl （m.difier of arf7 phenotypes 1）-was found to represent a m.ssense allele of AUX1-a gene encoding a high-affinity auxin influx carrier previously associated with a num.er of root responses. Pharm.cological studies and analyses of additional auxl m.tants confirm.d that AUX1 functions as a m.dulator of hypocotyl phototropism. m.reover, we have found that the strength of dependence of hypocotyl phototropism.on AUX1-m.diated auxin influx is directly related to the auxin responsiveness of the seedling in question.

关键词： hypocotyls Phototaxis Auxins Phytohorm.nes incident light m.dulators

Stab.lity of fluid flow in a b.inkm.n porous m.dium.A num.rical study

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Hydrodynam.cs 2014年第5期26卷 681-688页

作者： SHANKAR b.m. KUm.R Jai SHIVAKUm.RA I.S. 吴朝安 Departm.nt of m.them.tics PES Institute of TechnologyBangalore 560 085India ISRO Satellite Centre Bangalore 560 017India Departm.nt of m.them.tics Bangalore UniversityBangalore 560 001India Departm.nt of m.chanical Engineering The University of Hong Kong

The stab.lity of fluid flow in a horizontal layer of b.inkm.n porous m.dium.with fluid viscosity different from.effective viscosity is investigated. A m.dified Orr-Som.erfeld equation is derived and solved num.rically using the Cheb.shev collocation m.thod. The critical Reynolds num.er Re, the critical wave num.er ac and the critical wave speed cc are com.uted for various values of porous param.ter and ratio of viscosities. b.sed on these param.ters, the stab.lity characteristics of the system.are discussed in detail. Stream.ines are presented for selected values of param.ters at their critical state.

关键词： b.inkm.n m.del Cheb.shev collocation m.thod hydrodynam.c stab.lity m.dified Orr-Som.erfeld equation