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The_electronic_properties_of_graphene

The electronic properties of grapheneA.H.Castro NetoDepartment of Physics,Boston University,590Commonwealth Avenue,Boston,Massachusetts02215,USAF.GuineaInstituto de Ciencia de Materiales de Madrid,CSIC,Cantoblanco,E-28049Madrid,SpainN.M.R.PeresCenter of Physics and Department of Physics,Universidade do Minho,P-4710-057,Braga,PortugalK.S.Novoselov and A.K.GeimDepartment of Physics and Astronomy,University of Manchester,Manchester,M139PL,United Kingdom͑Published14January2009͒This article reviews the basic theoretical aspects of graphene,a one-atom-thick allotrope of carbon, with unusual two-dimensional Dirac-like electronic excitations.The Dirac electrons can be controlled by application of external electric and magneticﬁelds,or by altering sample geometry and/or topology.The Dirac electrons behave in unusual ways in tunneling,conﬁnement,and the integer quantum Hall effect.The electronic properties of graphene stacks are discussed and vary with stacking order and number of layers.Edge͑surface͒states in graphene depend on the edge termination͑zigzag or armchair͒and affect the physical properties of nanoribbons.Different types of disorder modify the Dirac equation leading to unusual spectroscopic and transport properties.The effects of electron-electron and electron-phonon interactions in single layer and multilayer graphene are also presented.DOI:10.1103/RevModPhys.81.109PACS number͑s͒:81.05.Uw,73.20.Ϫr,03.65.Pm,82.45.MpCONTENTSI.Introduction110II.Elementary Electronic Properties of Graphene112A.Single layer:Tight-binding approach1121.Cyclotron mass1132.Density of states114B.Dirac fermions1141.Chiral tunneling and Klein paradox1152.Conﬁnement and Zitterbewegung117C.Bilayer graphene:Tight-binding approach118D.Epitaxial graphene119E.Graphene stacks1201.Electronic structure of bulk graphite121F.Surface states in graphene122G.Surface states in graphene stacks124H.The spectrum of graphene nanoribbons1241.Zigzag nanoribbons1252.Armchair nanoribbons126I.Dirac fermions in a magneticﬁeld126J.The anomalous integer quantum Hall effect128 K.Tight-binding model in a magneticﬁeld128 ndau levels in graphene stacks130 M.Diamagnetism130 N.Spin-orbit coupling131 III.Flexural Phonons,Elasticity,and Crumpling132 IV.Disorder in Graphene134A.Ripples135B.Topological lattice defects136C.Impurity states137D.Localized states near edges,cracks,and voids137E.Self-doping138F.Vector potential and gaugeﬁeld disorder1391.Gaugeﬁeld induced by curvature1402.Elastic strain1403.Random gaugeﬁelds141G.Coupling to magnetic impurities141H.Weak and strong localization142I.Transport near the Dirac point143J.Boltzmann equation description of dc transport indoped graphene144 K.Magnetotransport and universal conductivity1451.The full self-consistent Born approximation͑FSBA͒146 V.Many-Body Effects148A.Electron-phonon interactions148B.Electron-electron interactions1501.Screening in graphene stacks152C.Short-range interactions1521.Bilayer graphene:Exchange1532.Bilayer graphene:Short-range interactions154D.Interactions in high magneticﬁelds154VI.Conclusions154 Acknowledgments155 References155REVIEWS OF MODERN PHYSICS,VOLUME81,JANUARY–MARCH20090034-6861/2009/81͑1͒/109͑54͒©2009The American Physical Society109I.INTRODUCTIONCarbon is the materia prima for life and the basis of all organic chemistry.Because of the ﬂexibility of its bond-ing,carbon-based systems show an unlimited number of different structures with an equally large variety of physical properties.These physical properties are,in great part,the result of the dimensionality of these structures.Among systems with only carbon atoms,graphene—a two-dimensional ͑2D ͒allotrope of carbon—plays an important role since it is the basis for the understanding of the electronic properties in other allotropes.Graphene is made out of carbon atoms ar-ranged on a honeycomb structure made out of hexagons ͑see Fig.1͒,and can be thought of as composed of ben-zene rings stripped out from their hydrogen atoms ͑Pauling,1972͒.Fullerenes ͑Andreoni,2000͒are mol-ecules where carbon atoms are arranged spherically,and hence,from the physical point of view,are zero-dimensional objects with discrete energy states.Fullerenes can be obtained from graphene with the in-troduction of pentagons ͑that create positive curvature defects ͒,and hence,fullerenes can be thought as wrapped-up graphene.Carbon nanotubes ͑Saito et al.,1998;Charlier et al.,2007͒are obtained by rolling graphene along a given direction and reconnecting the carbon bonds.Hence carbon nanotubes have only hexa-gons and can be thought of as one-dimensional ͑1D ͒ob-jects.Graphite,a three dimensional ͑3D ͒allotrope of carbon,became widely known after the invention of the pencil in 1564͑Petroski,1989͒,and its usefulness as an instrument for writing comes from the fact that graphite is made out of stacks of graphene layers that are weakly coupled by van der Waals forces.Hence,when one presses a pencil against a sheet of paper,one is actually producing graphene stacks and,somewhere among them,there could be individual graphene layers.Al-though graphene is the mother for all these different allotropes and has been presumably produced every time someone writes with a pencil,it was only isolated 440years after its invention ͑Novoselov et al.,2004͒.The reason is that,ﬁrst,no one actually expected graphene to exist in the free state and,second,even with the ben-eﬁt of hindsight,no experimental tools existed to search for one-atom-thick ﬂakes among the pencil debris cov-ering macroscopic areas ͑Geim and MacDonald,2007͒.Graphene was eventually spotted due to the subtle op-tical effect it creates on top of a chosen SiO 2substrate ͑Novoselov et al.,2004͒that allows its observation with an ordinary optical microscope ͑Abergel et al.,2007;Blake et al.,2007;Casiraghi et al.,2007͒.Hence,graphene is relatively straightforward to make,but not so easy to ﬁnd.The structural ﬂexibility of graphene is reﬂected in its electronic properties.The sp 2hybridization between one s orbital and two p orbitals leads to a trigonal planar structure with a formation of a ␴bond between carbon atoms that are separated by 1.42Å.The ␴band is re-sponsible for the robustness of the lattice structure in all allotropes.Due to the Pauli principle,these bands have a ﬁlled shell and,hence,form a deep valence band.The unaffected p orbital,which is perpendicular to the pla-nar structure,can bind covalently with neighboring car-bon atoms,leading to the formation of a ␲band.Since each p orbital has one extra electron,the ␲band is half ﬁlled.Half-ﬁlled bands in transition elements have played an important role in the physics of strongly correlated systems since,due to their strong tight-binding charac-ter,the Coulomb energies are large,leading to strong collective effects,magnetism,and insulating behavior due to correlation gaps or Mottness ͑Phillips,2006͒.In fact,Linus Pauling proposed in the 1950s that,on the basis of the electronic properties of benzene,graphene should be a resonant valence bond ͑RVB ͒structure ͑Pauling,1972͒.RVB states have become popular in the literature of transition-metal oxides,and particularly in studies of cuprate-oxide superconductors ͑Maple,1998͒.This point of view should be contrasted with contempo-raneous band-structure studies of graphene ͑Wallace,1947͒that found it to be a semimetal with unusual lin-early dispersing electronic excitations called Dirac elec-trons.While most current experimental data in graphene support the band structure point of view,the role of electron-electron interactions in graphene is a subject of intense research.It was P .R.Wallace in 1946who ﬁrst wrote on the band structure of graphene and showed the unusual semimetallic behavior in this material ͑Wallace,1947͒.At that time,the thought of a purely 2D structure was not reality and Wallace’s studies of graphene served him as a starting point to study graphite,an important mate-rial for nuclear reactors in the post–World War II era.During the following years,the study of graphite culmi-nated with the Slonczewski-Weiss-McClure ͑SWM ͒band structure of graphite,which provided a description of the electronic properties in this material ͑McClure,1957;Slonczewski and Weiss,1958͒and was successful in de-scribing the experimental data ͑Boyle and Nozières 1958;McClure,1958;Spry and Scherer,1960;Soule et al.,1964;Williamson et al.,1965;Dillon et al.,1977͒.From 1957to 1968,the assignment of the electron and hole states within the SWM model were oppositetoFIG.1.͑Color online ͒Graphene ͑top left ͒is a honeycomb lattice of carbon atoms.Graphite ͑top right ͒can be viewed as a stack of graphene layers.Carbon nanotubes are rolled-up cylinders of graphene ͑bottom left ͒.Fullerenes ͑C 60͒are mol-ecules consisting of wrapped graphene by the introduction of pentagons on the hexagonal lattice.From Castro Neto et al.,2006a .110Castro Neto et al.:The electronic properties of grapheneRev.Mod.Phys.,V ol.81,No.1,January–March 2009what is accepted today.In1968,Schroeder et al.͑Schroeder et al.,1968͒established the currently ac-cepted location of electron and hole pockets͑McClure, 1971͒.The SWM model has been revisited in recent years because of its inability to describe the van der Waals–like interactions between graphene planes,a problem that requires the understanding of many-body effects that go beyond the band-structure description ͑Rydberg et al.,2003͒.These issues,however,do not arise in the context of a single graphene crystal but they show up when graphene layers are stacked on top of each other,as in the case,for instance,of the bilayer graphene.Stacking can change the electronic properties considerably and the layering structure can be used in order to control the electronic properties.One of the most interesting aspects of the graphene problem is that its low-energy excitations are massless, chiral,Dirac fermions.In neutral graphene,the chemical potential crosses exactly the Dirac point.This particular dispersion,that is only valid at low energies,mimics the physics of quantum electrodynamics͑QED͒for massless fermions except for the fact that in graphene the Dirac fermions move with a speed v F,which is300times smaller than the speed of light c.Hence,many of the unusual properties of QED can show up in graphene but at much smaller speeds͑Castro Neto et al.,2006a; Katsnelson et al.,2006;Katsnelson and Novoselov, 2007͒.Dirac fermions behave in unusual ways when compared to ordinary electrons if subjected to magnetic ﬁelds,leading to new physical phenomena͑Gusynin and Sharapov,2005;Peres,Guinea,and Castro Neto,2006a͒such as the anomalous integer quantum Hall effect ͑IQHE͒measured experimentally͑Novoselov,Geim, Morozov,et al.,2005a;Zhang et al.,2005͒.Besides being qualitatively different from the IQHE observed in Si and GaAlAs͑heterostructures͒devices͑Stone,1992͒, the IQHE in graphene can be observed at room tem-perature because of the large cyclotron energies for “relativistic”electrons͑Novoselov et al.,2007͒.In fact, the anomalous IQHE is the trademark of Dirac fermion behavior.Another interesting feature of Dirac fermions is their insensitivity to external electrostatic potentials due to the so-called Klein paradox,that is,the fact that Dirac fermions can be transmitted with probability1through a classically forbidden region͑Calogeracos and Dombey, 1999;Itzykson and Zuber,2006͒.In fact,Dirac fermions behave in an unusual way in the presence of conﬁning potentials,leading to the phenomenon of Zitter-bewegung,or jittery motion of the wave function͑Itzyk-son and Zuber,2006͒.In graphene,these electrostatic potentials can be easily generated by disorder.Since dis-order is unavoidable in any material,there has been a great deal of interest in trying to understand how disor-der affects the physics of electrons in graphene and its transport properties.In fact,under certain conditions, Dirac fermions are immune to localization effects ob-served in ordinary electrons͑Lee and Ramakrishnan, 1985͒and it has been established experimentally that electrons can propagate without scattering over large distances of the order of micrometers in graphene͑No-voselov et al.,2004͒.The sources of disorder in graphene are many and can vary from ordinary effects commonly found in semiconductors,such as ionized impurities in the Si substrate,to adatoms and various molecules ad-sorbed in the graphene surface,to more unusual defects such as ripples associated with the soft structure of graphene͑Meyer,Geim,Katsnelson,Novoselov,Booth, et al.,2007a͒.In fact,graphene is unique in the sense that it shares properties of soft membranes͑Nelson et al.,2004͒and at the same time it behaves in a metallic way,so that the Dirac fermions propagate on a locally curved space.Here analogies with problems of quantum gravity become apparent͑Fauser et al.,2007͒.The soft-ness of graphene is related with the fact that it has out-of-plane vibrational modes͑phonons͒that cannot be found in3D solids.Theseﬂexural modes,responsible for the bending properties of graphene,also account for the lack of long range structural order in soft mem-branes leading to the phenomenon of crumpling͑Nelson et al.,2004͒.Nevertheless,the presence of a substrate or scaffolds that hold graphene in place can stabilize a cer-tain degree of order in graphene but leaves behind the so-called ripples͑which can be viewed as frozenﬂexural modes͒.It was realized early on that graphene should also present unusual mesoscopic effects͑Peres,Castro Neto, and Guinea,2006a;Katsnelson,2007a͒.These effects have their origin in the boundary conditions required for the wave functions in mesoscopic samples with various types of edges graphene can have͑Nakada et al.,1996; Wakabayashi et al.,1999;Peres,Guinea,and Castro Neto,2006a;Akhmerov and Beenakker,2008͒.The most studied edges,zigzag and armchair,have drastically different electronic properties.Zigzag edges can sustain edge͑surface͒states and resonances that are not present in the armchair case.Moreover,when coupled to con-ducting leads,the boundary conditions for a graphene ribbon strongly affect its conductance,and the chiral Dirac nature of fermions in graphene can be used for applications where one can control the valleyﬂavor of the electrons besides its charge,the so-called valleytron-ics͑Rycerz et al.,2007͒.Furthermore,when supercon-ducting contacts are attached to graphene,they lead to the development of supercurrentﬂow and Andreev pro-cesses characteristic of the superconducting proximity effect͑Heersche et al.,2007͒.The fact that Cooper pairs can propagate so well in graphene attests to the robust electronic coherence in this material.In fact,quantum interference phenomena such as weak localization,uni-versal conductanceﬂuctuations͑Morozov et al.,2006͒, and the Aharonov-Bohm effect in graphene rings have already been observed experimentally͑Recher et al., 2007;Russo,2007͒.The ballistic electronic propagation in graphene can be used forﬁeld-effect devices such as p-n͑Cheianov and Fal’ko,2006;Cheianov,Fal’ko,and Altshuler,2007;Huard et al.,2007;Lemme et al.,2007; Tworzydlo et al.,2007;Williams et al.,2007;Fogler, Glazman,Novikov,et al.,2008;Zhang and Fogler,2008͒and p-n-p͑Ossipov et al.,2007͒junctions,and as“neu-111Castro Neto et al.:The electronic properties of graphene Rev.Mod.Phys.,V ol.81,No.1,January–March2009trino”billiards ͑Berry and Modragon,1987;Miao et al.,2007͒.It has also been suggested that Coulomb interac-tions are considerably enhanced in smaller geometries,such as graphene quantum dots ͑Milton Pereira et al.,2007͒,leading to unusual Coulomb blockade effects ͑Geim and Novoselov,2007͒and perhaps to magnetic phenomena such as the Kondo effect.The transport properties of graphene allow for their use in a plethora of applications ranging from single molecule detection ͑Schedin et al.,2007;Wehling et al.,2008͒to spin injec-tion ͑Cho et al.,2007;Hill et al.,2007;Ohishi et al.,2007;Tombros et al.,2007͒.Because of its unusual structural and electronic ﬂex-ibility,graphene can be tailored chemically and/or struc-turally in many different ways:deposition of metal at-oms ͑Calandra and Mauri,2007;Uchoa et al.,2008͒or molecules ͑Schedin et al.,2007;Leenaerts et al.,2008;Wehling et al.,2008͒on top;intercalation ͓as done in graphite intercalated compounds ͑Dresselhaus et al.,1983;Tanuma and Kamimura,1985;Dresselhaus and Dresselhaus,2002͔͒;incorporation of nitrogen and/or boron in its structure ͑Martins et al.,2007;Peres,Klironomos,Tsai,et al.,2007͓͒in analogy with what has been done in nanotubes ͑Stephan et al.,1994͔͒;and using different substrates that modify the electronic structure ͑Calizo et al.,2007;Giovannetti et al.,2007;Varchon et al.,2007;Zhou et al.,2007;Das et al.,2008;Faugeras et al.,2008͒.The control of graphene properties can be extended in new directions allowing for the creation of graphene-based systems with magnetic and supercon-ducting properties ͑Uchoa and Castro Neto,2007͒that are unique in their 2D properties.Although the graphene ﬁeld is still in its infancy,the scientiﬁc and technological possibilities of this new material seem to be unlimited.The understanding and control of this ma-terial’s properties can open doors for a new frontier in electronics.As the current status of the experiment and potential applications have recently been reviewed ͑Geim and Novoselov,2007͒,in this paper we concen-trate on the theory and more technical aspects of elec-tronic properties with this exciting new material.II.ELEMENTARY ELECTRONIC PROPERTIES OF GRAPHENEA.Single layer:Tight-binding approachGraphene is made out of carbon atoms arranged in hexagonal structure,as shown in Fig.2.The structure can be seen as a triangular lattice with a basis of two atoms per unit cell.The lattice vectors can be written asa 1=a 2͑3,ͱ3͒,a 2=a2͑3,−ͱ3͒,͑1͒where a Ϸ1.42Åis the carbon-carbon distance.Thereciprocal-lattice vectors are given byb 1=2␲3a͑1,ͱ3͒,b 2=2␲3a͑1,−ͱ3͒.͑2͒Of particular importance for the physics of graphene are the two points K and K Јat the corners of the graphene Brillouin zone ͑BZ ͒.These are named Dirac points for reasons that will become clear later.Their positions in momentum space are given byK =ͩ2␲3a ,2␲3ͱ3aͪ,K Ј=ͩ2␲3a ,−2␲3ͱ3aͪ.͑3͒The three nearest-neighbor vectors in real space are given by␦1=a 2͑1,ͱ3͒␦2=a 2͑1,−ͱ3͒␦3=−a ͑1,0͒͑4͒while the six second-nearest neighbors are located at ␦1Ј=±a 1,␦2Ј=±a 2,␦3Ј=±͑a 2−a 1͒.The tight-binding Hamiltonian for electrons in graphene considering that electrons can hop to both nearest-and next-nearest-neighbor atoms has the form ͑we use units such that ប=1͒H =−t͚͗i ,j ͘,␴͑a ␴,i †b ␴,j +H.c.͒−t Ј͚͗͗i ,j ͘͘,␴͑a ␴,i †a ␴,j +b ␴,i †b ␴,j +H.c.͒,͑5͒where a i ,␴͑a i ,␴†͒annihilates ͑creates ͒an electron with spin ␴͑␴=↑,↓͒on site R i on sublattice A ͑an equiva-lent deﬁnition is used for sublattice B ͒,t ͑Ϸ2.8eV ͒is the nearest-neighbor hopping energy ͑hopping between dif-ferent sublattices ͒,and t Јis the next nearest-neighbor hopping energy 1͑hopping in the same sublattice ͒.The energy bands derived from this Hamiltonian have the form ͑Wallace,1947͒E ±͑k ͒=±t ͱ3+f ͑k ͒−t Јf ͑k ͒,1The value of t Јis not well known but ab initio calculations ͑Reich et al.,2002͒ﬁnd 0.02t Շt ЈՇ0.2t depending on the tight-binding parametrization.These calculations also include the effect of a third-nearest-neighbors hopping,which has a value of around 0.07eV.A tight-binding ﬁt to cyclotron resonance experiments ͑Deacon et al.,2007͒ﬁnds t ЈϷ0.1eV.FIG.2.͑Color online ͒Honeycomb lattice and its Brillouin zone.Left:lattice structure of graphene,made out of two in-terpenetrating triangular lattices ͑a 1and a 2are the lattice unit vectors,and ␦i ,i =1,2,3are the nearest-neighbor vectors ͒.Right:corresponding Brillouin zone.The Dirac cones are lo-cated at the K and K Јpoints.112Castro Neto et al.:The electronic properties of grapheneRev.Mod.Phys.,V ol.81,No.1,January–March 2009f ͑k ͒=2cos ͑ͱ3k y a ͒+4cosͩͱ32k y a ͪcosͩ32k x a ͪ,͑6͒where the plus sign applies to the upper ͑␲*͒and the minus sign the lower ͑␲͒band.It is clear from Eq.͑6͒that the spectrum is symmetric around zero energy if t Ј=0.For ﬁnite values of t Ј,the electron-hole symmetry is broken and the ␲and ␲*bands become asymmetric.In Fig.3,we show the full band structure of graphene with both t and t Ј.In the same ﬁgure,we also show a zoom in of the band structure close to one of the Dirac points ͑at the K or K Јpoint in the BZ ͒.This dispersion can be obtained by expanding the full band structure,Eq.͑6͒,close to the K ͑or K Ј͒vector,Eq.͑3͒,as k =K +q ,with ͉q ͉Ӷ͉K ͉͑Wallace,1947͒,E ±͑q ͒Ϸ±vF ͉q ͉+O ͓͑q /K ͒2͔,͑7͒where q is the momentum measured relatively to the Dirac points and v F is the Fermi velocity,given by v F =3ta /2,with a value v F Ӎ1ϫ106m/s.This result was ﬁrst obtained by Wallace ͑1947͒.The most striking difference between this result and the usual case,⑀͑q ͒=q 2/͑2m ͒,where m is the electron mass,is that the Fermi velocity in Eq.͑7͒does not de-pend on the energy or momentum:in the usual case we have v =k /m =ͱ2E /m and hence the velocity changes substantially with energy.The expansion of the spectrum around the Dirac point including t Јup to second order in q /K is given byE ±͑q ͒Ӎ3t Ј±vF ͉q ͉−ͩ9t Јa 24±3ta 28sin ͑3␪q ͉͒ͪq ͉2,͑8͒where␪q =arctanͩq x q yͪ͑9͒is the angle in momentum space.Hence,the presence of t Јshifts in energy the position of the Dirac point and breaks electron-hole symmetry.Note that up to order ͑q /K ͒2the dispersion depends on the direction in mo-mentum space and has a threefold symmetry.This is the so-called trigonal warping of the electronic spectrum ͑Ando et al.,1998,Dresselhaus and Dresselhaus,2002͒.1.Cyclotron massThe energy dispersion ͑7͒resembles the energy of ul-trarelativistic particles;these particles are quantum me-chanically described by the massless Dirac equation ͑see Sec.II.B for more on this analogy ͒.An immediate con-sequence of this massless Dirac-like dispersion is a cy-clotron mass that depends on the electronic density as its square root ͑Novoselov,Geim,Morozov,et al.,2005;Zhang et al.,2005͒.The cyclotron mass is deﬁned,within the semiclassical approximation ͑Ashcroft and Mermin,1976͒,asm *=12␲ͫץA ͑E ͒ץEͬE =E F,͑10͒with A ͑E ͒the area in k space enclosed by the orbit andgiven byA ͑E ͒=␲q ͑E ͒2=␲E 2v F2.͑11͒Using Eq.͑11͒in Eq.͑10͒,one obtainsm *=E Fv F2=k Fv F.͑12͒The electronic density n is related to the Fermi momen-tum k F as k F2/␲=n ͑with contributions from the two Dirac points K and K Јand spin included ͒,which leads tom *=ͱ␲v Fͱn .͑13͒Fitting Eq.͑13͒to the experimental data ͑see Fig.4͒provides an estimation for the Fermi velocity andtheFIG.3.͑Color online ͒Electronic dispersion in the honeycomb lattice.Left:energy spectrum ͑in units of t ͒for ﬁnite values of t and t Ј,with t =2.7eV and t Ј=−0.2t .Right:zoom in of the energy bands close to one of the Diracpoints.FIG.4.͑Color online ͒Cyclotron mass of charge carriers in graphene as a function of their concentration n .Positive and negative n correspond to electrons and holes,respectively.Symbols are the experimental data extracted from the tem-perature dependence of the SdH oscillations;solid curves are the best ﬁt by Eq.͑13͒.m 0is the free-electron mass.Adapted from Novoselov,Geim,Morozov,et al.,2005.113Castro Neto et al.:The electronic properties of grapheneRev.Mod.Phys.,V ol.81,No.1,January–March 2009hopping parameter as v F Ϸ106ms −1and t Ϸ3eV,respec-tively.Experimental observation of the ͱn dependence on the cyclotron mass provides evidence for the exis-tence of massless Dirac quasiparticles in graphene ͑No-voselov,Geim,Morozov,et al.,2005;Zhang et al.,2005;Deacon et al.,2007;Jiang,Henriksen,Tung,et al.,2007͒—the usual parabolic ͑Schrödinger ͒dispersion im-plies a constant cyclotron mass.2.Density of statesThe density of states per unit cell,derived from Eq.͑5͒,is given in Fig.5for both t Ј=0and t Ј 0,showing in both cases semimetallic behavior ͑Wallace,1947;Bena and Kivelson,2005͒.For t Ј=0,it is possible to derive an analytical expression for the density of states per unit cell,which has the form ͑Hobson and Nierenberg,1953͒␳͑E ͒=4␲2͉E ͉t 21ͱZ 0F ͩ␲2,ͱZ 1Z 0ͪ,Z 0=Άͩ1+ͯE t ͯͪ2−͓͑E /t ͒2−1͔24,−t ഛE ഛt4ͯE t ͯ,−3t ഛE ഛ−t ∨t ഛE ഛ3t ,Z 1=Ά4ͯE t ͯ,−t ഛE ഛtͩ1+ͯE tͯͪ2−͓͑E /t ͒2−1͔24,−3t ഛE ഛ−t ∨t ഛE ഛ3t ,͑14͒where F ͑␲/2,x ͒is the complete elliptic integral of theﬁrst kind.Close to the Dirac point,the dispersion is ap-proximated by Eq.͑7͒and the density of states per unit cell is given by ͑with a degeneracy of 4included ͒␳͑E ͒=2A c ␲͉E ͉v F2,͑15͒where A c is the unit cell area given by A c =3ͱ3a 2/2.It is worth noting that the density of states for graphene is different from the density of states of carbon nanotubes ͑Saito et al.,1992a ,1992b ͒.The latter shows 1/ͱE singu-larities due to the 1D nature of their electronic spec-trum,which occurs due to the quantization of the mo-mentum in the direction perpendicular to the tube axis.From this perspective,graphene nanoribbons,which also have momentum quantization perpendicular to the ribbon length,have properties similar to carbon nano-tubes.B.Dirac fermionsWe consider the Hamiltonian ͑5͒with t Ј=0and theFourier transform of the electron operators,a n =1ͱN c͚ke −i k ·R na ͑k ͒,͑16͒where N c is the number of unit ing this transfor-mation,we write the ﬁeld a n as a sum of two terms,coming from expanding the Fourier sum around K Јand K .This produces an approximation for the representa-tion of the ﬁeld a n as a sum of two new ﬁelds,written asa n Ӎe −i K ·R n a 1,n +e −i K Ј·R n a 2,n ,b n Ӎe −i K ·R n b 1,n +e −i K Ј·R n b 2,n ,͑17͒ρ(ε)ε/tρ(ε)ε/tFIG.5.Density of states per unit cell as a function of energy ͑in units of t ͒computed from the energy dispersion ͑5͒,t Ј=0.2t ͑top ͒and t Ј=0͑bottom ͒.Also shown is a zoom-in of the density of states close to the neutrality point of one electron per site.For the case t Ј=0,the electron-hole nature of the spectrum is apparent and the density of states close to the neutrality point can be approximated by ␳͑⑀͒ϰ͉⑀͉.114Castro Neto et al.:The electronic properties of grapheneRev.Mod.Phys.,V ol.81,No.1,January–March 2009where the index i =1͑i =2͒refers to the K ͑K Ј͒point.These new ﬁelds,a i ,n and b i ,n ,are assumed to vary slowly over the unit cell.The procedure for deriving a theory that is valid close to the Dirac point con-sists in using this representation in the tight-binding Hamiltonian and expanding the opera-tors up to a linear order in ␦.In the derivation,one uses the fact that ͚␦e ±i K ·␦=͚␦e ±i K Ј·␦=0.After some straightforward algebra,we arrive at ͑Semenoff,1984͒H Ӎ−t͵dxdy ⌿ˆ1†͑r ͒ͫͩ3a ͑1−i ͱ3͒/4−3a ͑1+i ͱ3͒/4ͪץx +ͩ3a ͑−i −ͱ3͒/4−3a ͑i −ͱ3͒/4ͪץy ͬ⌿ˆ1͑r ͒+⌿ˆ2†͑r ͒ͫͩ3a ͑1+i ͱ3͒/4−3a ͑1−i ͱ3͒/4ͪץx +ͩ3a ͑i −ͱ3͒/4−3a ͑−i −ͱ3͒/4ͪץy ͬ⌿ˆ2͑r ͒=−i v F͵dxdy ͓⌿ˆ1†͑r ͒␴·ٌ⌿ˆ1͑r ͒+⌿ˆ2†͑r ͒␴*·ٌ⌿ˆ2͑r ͔͒,͑18͒with Pauli matrices ␴=͑␴x ,␴y ͒,␴*=͑␴x ,−␴y ͒,and ⌿ˆi†=͑a i †,b i †͒͑i =1,2͒.It is clear that the effective Hamil-tonian ͑18͒is made of two copies of the massless Dirac-like Hamiltonian,one holding for p around K and the other for p around K Ј.Note that,in ﬁrst quantized lan-guage,the two-component electron wave function ␺͑r ͒,close to the K point,obeys the 2D Dirac equation,−i v F ␴·ٌ␺͑r ͒=E ␺͑r ͒.͑19͒The wave function,in momentum space,for the mo-mentum around K has the form␺±,K ͑k ͒=1ͱ2ͩe −i ␪k /2±e i ␪k /2ͪ͑20͒for H K =v F ␴·k ,where the Ϯsigns correspond to the eigenenergies E =±v F k ,that is,for the ␲*and ␲bands,respectively,and ␪k is given by Eq.͑9͒.The wave func-tion for the momentum around K Јhas the form␺±,K Ј͑k ͒=1ͱ2ͩe i ␪k /2±e −i ␪k /2ͪ͑21͒for H K Ј=v F ␴*·k .Note that the wave functions at K and K Јare related by time-reversal symmetry:if we set the origin of coordinates in momentum space in the M point of the BZ ͑see Fig.2͒,time reversal becomes equivalent to a reﬂection along the k x axis,that is,͑k x ,k y ͒→͑k x ,−k y ͒.Also note that if the phase ␪is rotated by 2␲,the wave function changes sign indicating a phase of ␲͑in the literature this is commonly called a Berry’s phase ͒.This change of phase by ␲under rotation is char-acteristic of spinors.In fact,the wave function is a two-component spinor.A relevant quantity used to characterize the eigen-functions is their helicity deﬁned as the projection of the momentum operator along the ͑pseudo ͒spin direction.The quantum-mechanical operator for the helicity has the formhˆ=12␴·p ͉p ͉.͑22͒It is clear from the deﬁnition of h ˆthat the states ␺K͑r ͒and ␺K Ј͑r ͒are also eigenstates of h ˆ,h ˆ␺K ͑r ͒=±12␺K͑r ͒,͑23͒and an equivalent equation for ␺K Ј͑r ͒with inverted sign.Therefore,electrons ͑holes ͒have a positive ͑negative ͒helicity.Equation ͑23͒implies that ␴has its two eigen-values either in the direction of ͑⇑͒or against ͑⇓͒the momentum p .This property says that the states of the system close to the Dirac point have well deﬁned chiral-ity or helicity.Note that chirality is not deﬁned in regard to the real spin of the electron ͑that has not yet ap-peared in the problem ͒but to a pseudospin variable as-sociated with the two components of the wave function.The helicity values are good quantum numbers as long as the Hamiltonian ͑18͒is valid.Therefore,the existence of helicity quantum numbers holds only as an asymptotic property,which is well deﬁned close to the Dirac points K and K Ј.Either at larger energies or due to the presence of a ﬁnite t Ј,the helicity stops being a good quantum number.1.Chiral tunneling and Klein paradoxIn this section,we address the scattering of chiral elec-trons in two dimensions by a square barrier ͑Katsnelson et al.,2006;Katsnelson,2007b ͒.The one-dimensional scattering of chiral electrons was discussed earlier in the context on nanotubes ͑Ando et al.,1998;McEuen et al.,1999͒.We start by noting that by a gauge transformation the wave function ͑20͒can be written as115Castro Neto et al.:The electronic properties of grapheneRev.Mod.Phys.,V ol.81,No.1,January–March 2009。

Debye Length

n(r)
=
n e0
−
qφ(r) kT
In the quasi-nuetral situtaion, the number of ions ni and electrons ne are approximately equal, ni ≈ ne ≈ n0. However, the distribution of these diﬀerent kinds of particles are not necessarily unifrom in space in the quasineutral situtation, and so charge gradients and ﬁelds can still exist within the plasma.
∂φ E=−
∂x
⇒ σ = B e0 2 0 λD
⇒ B = σλD 20
⇒
φ(x)
=
σλD
e−
|x| λD
20
In position space, φ(x) decays exponentially away from the sheet of charge. The scale length of the exponential decay is λD. Hence the Debye length is the scale length to which a charge in the plasma is shielded.
ρ φ·E=
0
E = −∇φ ⇒ −∇2φ = ρ
0
ρ is the charge density, which must take into account all species of particle. Assuming the charge of the electrons and ions to be equal and opposite,

麻省理工学院微电子实验室简介

MITResearch in nano- and micro- scale technologies is in the departments of Material Sci. and Eng. And Computer Sci. or Chemical Eng.MIT’s major micro and nano centers are MTL(Microsystem Technology Laboratories) which provide microelectronics fabrication lab/research/index.html.MTL is home to several research centers, including:∙The Center for Integrated Circuits and Systems (CICS) serves to promote closer technical relation between MIT's Microsystems Technology Lab's (MTL) research and industry, initiate and fund new research in integrated circuits and systems, produce more students skilled in the same area, address important research issues relevant to industry, and solicit ideas for new research from industry.∙The Intelligent Transportation Research Center (ITRC) focuses on the key Intelligent Transportation Systems (ITS) technologies, including an integrated network of transportation information, automatic crash & incident detection, notification and response, advanced crashavoidance technology, advanced transportation monitoring and management, etc., in order toimprove the safety, security, efficiency, mobile access, and environment. There are two emphasis for research conduced in the center: the integration of component technology research andsystem design research, and the integration of technical possibilities and social needs.∙MEMS@MIT is a collection of faculty/staff/students working in the broad area of a Micro/nano systems and MEMS. This center was created to serve as a forum for collectingintellectually-synergistic but organizationally diverse groups of researchers at MIT. In addition, we have organized an industrial interaction mechanism to catalyze the transfer of knowledge to the larger MEMS community.The research:Chemical/Mechanical/Optical MEMS1. A MEMS Electrometer for Gas Sensing2. A Single-Gated CNT Field-Ionizer Array with Open Architecture3. A MEMS Quadrupole that Uses a Meso-scaled DRIE-patterned Spring Assembly System4. Digital Holographic Imaging of Micro-structured and Biological Objects5. Multi-Axis Electromagnetic Moving-Coil Microactuator6. Multiphase Transport Phenomena in Microfluidic Systems7. Microfluidic Synthesis and Surface Engineering of Colloidal Nanoparticles8. Microreactor Enabled Multistep Chemical Synthesis9. Integrated Microreactor System10. Crystallization in Microfluidic Systems11. Microreactors for Synthesis of Quantum Dots12. A Large Strain, Arrayable Piezoelectric Microcellular Actuator13. MEMS Pressure-sensor Arrays for Passive Underwater Navigation14. A Low Contact Resistance MEMS-Relay15. "Fast Three-Dimensional Electrokinetic Pumps for Microfluidics16. Carbon Nanotube - CMOS Chemical Sensor Integration17. An Energy Efficient Transceiver for Wireless Micro-Sensor Applications18. Combinatorial Sensing Arrays of Phthalocyanine-based Field-effect Transistors19. Nanoelectromechanical Switches and Memories20. Integrated Carbon Nanotube Sensors21. Organic Photovoltaics with External Antennas22. Integrated Optical-wavelength-dependent Switching and Tuning by Use of Titanium Nitride (TiN)MEMS Technology23. Four Dimensional Volume Holographic Imaging with Natural Illumination24. White Light QD-LEDs25. Organic Optoelectronic Devices Printed by the Molecular Jet Printe26. Design and Measurement of Thermo-optics on SiliconBioMEMS1. A Microfabricated Platform for Investigating Multicellular Organization in 3-D Microenvironments2. Microfluidic Hepatocyte Bioreactor3. Micromechanical Control of Cell-Cell Interaction4. A MEMS Drug Delivery Device for the Prevention of Hemorrhagic Shock5. Multiwell Cell Culture Plate Format with Integrated Microfluidic Perfusion System6. Characterization of Nanofilter Arrays for Biomolecule Separation7. Patterned Periodic Potential-energy Landscape for Fast Continuous-flow BiomoleculeSeparation8. Continuous-flow pI-based Sorting of Proteins and Peptides in a Microfluidic Chip Using DiffusionPotential9. Cell Stimulation, Lysis, and Separation in Microdevices10. Polymer-based Microbioreactors for High Throughput Bioprocessing11. Micro-fluidic Bioreactors for Studying Cell-Matrix Interactions12. A Nanoscanning Platform for Biological Assays13. Label-free Microelectronic PCR Quantification14. Vacuum-Packaged Suspended Microchannel Resonant Mass Sensor for BiomolecularDetection15. Microbial Growth in Parallel Integrated Bioreactor Arrays16. BioMEMS for Control of the Stem-cell Microenvironment17. Microfluidic/Dielectrophoretic Approaches to Selective Microorganism Concentration18. Microfabricated Approaches for Sorting Cells Using Complex Phenotypes19. A Continuous, Conductivity-Specific Micro-organism Separator20. Polymer Waveguides for Integrated BiosensorsEnabling Technology1. A Double-gated CNF Tip Array for Electron-impact Ionization and Field Ionization2. A Double-gated Silicon Tip, Electron-Impact Ionization Array3. A Single-Gated CNT Field-Ionizer Array with Open Architecture4. Aligning and Latching Nano-structured Membranes in 3D Micro-Structures5. Characterization and Modeling of Non-uniformities in DRIE6. Understanding Uniformity and Manufacturability in MEMS Embossing7. Atomic Force Microscopy with Inherent Disturbance Suppression for Nanostructure Imaging8. Vacuum-Sealing Technologies for Micro-chemical Reactors9. Direct Patterning of Organic Materials and Metals Using Micromachined Printheads10. MEMS Vacuum Pump11. Rapid and Shape-Controlled Growth of Aligned Carbon Nanotube Structures12. Prediction of Variation in Advanced Process Technology Nodes13. Parameterized Model Order Reduction of Nonlinear Circuits and MEMS14. Development of Specialized Basis Functions and Efficient Substrate Integration Techniques forElectromagnetic Analysis of Interconnect and RF Inductors15. A Quasi-convex Optimization Approach to Parameterized Model-order Reduction16. Amorphous Zinc-Oxide-Based Thin-film Transistors17. Magnetic Rings for Memory and Logic Devices18. Studies of Field Ionization Using PECVD-grown CNT Tips19. Growth of Carbon Nanotubes for Use in Origami Supercapacitors20. Self-Alignment of Folded, Thin-Membranes via Nanomagnet Attractive Forces21. Control System Design for the Nanostructured Origami™ 3D Nanofabrication Process22. Measuring Thermal and Thermoelectric Properties of Single Nanowires and Carbon Nanotubes23. Nanocomposites as Thermoelectric Materials24. CNT Assembly by Nanopelleting25. Templated Assembly by Selective Removal26. Building Three-dimensional Nanostructures via Membrane FoldingPower MEMS1. Hand-assembly of an Electrospray Thruster Electrode Using Microfabricated Clips2. A Fully Microfabricated Planar Array of Electrospray Ridge Emitters for Space PropulsionApplications3. Thermal Management in Devices for Portable Hydrogen Generation4. Autothermal Catalytic Micromembrane Devices for Portable High-Purity Hydrogen Generation5. Self-powered Wireless Monitoring System Using MEMS Piezoelectric Micro Power Generator6. An Integrated Multiwatt Permanent Magnet Turbine Generator7. Micro-scale Singlet Oxygen Generator for MEMS-based COIL Lasers8. A Thermophotovoltaic (TPV) MEMS Power Generator9. MEMS Vibration Harvesting for Wireless Sensors10. Fabrication and Structural Design of Ultra-thin MEMS Solid Oxide Fuel Cells11. Tomographic Interferometry for Detection of Nafion® Membrane Degradation in PEM Fuel Cells∙The Center for Integrated Photonic Systems (CIPS) mission is to create a meaningful vision of the future, a framework for understanding how technology, industry and business interact and evolve together in the future is required. Models provide us with a process for analyzing the many complex factors that shape this industry and the progress of related technologies.The materials processing center .Making matter meet human needsResearchThe Center brings together MIT faculty and research staff from diverse specialties to collaborate on interdisciplinary materials problems. Center research involves over 150 faculty, research staff, visiting scientists, and graduate and undergraduate students.MPC researchers cover the full range of advanced materials, processes, and technologies, including∙electronic materials∙batteries & fuel cells∙polymers∙advanced ceramics∙materials joining∙composites of all types∙photonics∙electrochemical processing ∙traditional metallurgy∙environmental degradation∙materials modeling- many scale ∙materials systems analysis∙nanostructured materials∙magnetic materials and processes ∙biomaterials∙materials economicsFaculty ProfilesA.I. AkinwandeFlat panel displays,Vacuum Microelectronics and its application to flat panel displays, RF power sources, and sensors. Wide bandgap semiconductors and applications to flat panel displays, UV emitters and RF power sourcesView current research abstracts (pdf)G. BarbastathisBiomedical design instrumentation; precision engineering robotics; volume holographic architectures for data storage, color-selective tomographic imaging, and super-resolving confocal microscopy; interferometric surface characterization; and adaptive micro-opto-mechanics. Optical MEMS.View current research abstracts (pdf)View group web siteM. BazantResearch focuses on transport phenomena in materials and engineering systems, especially diffusion coupled to fluid flow. My group is currently studying granular flow in pebble-bed nuclear reactors, nonlinear electrokinetic flows in microfludic devices, ion transport in thin-film lithium batteries, and advection-diffusion-limited aggregation.View current research abstracts (pdf)View group web siteS. BhatiaResearch focuses on applications of micro- and nanotechnology to tissue repair and regeneration. Emphasis on development of microfabrication tools to improve cellular therapies for liver disease, living cell arrays to study stem cell biology, and nanoparticles for cancer diagnosis and treatment.View current research abstracts (pdf)View group web siteD. BoningSemiconductor manufacturing. Modeling and control of chemical mechanical polishing. Variation modeling and reduction in fabrication processes, devices, and interconnects. Run by run and feedback control for quality and environment in semiconductor fabrication. Software systems for distributed and collaborative computer aided design and fabrication.View current research abstracts (pdf)View group web siteA.P. ChandrakasanDesign of digital integrated circuits and systems. Emphasis on the energy efficient implementation of distributed microsensor and signal processing systems. Protocols and Algorithms for Wireless Systems. Circuits techniques for deep sub-micron technologies.View current research abstracts (pdf)View group web siteG. ChenMicro- and nanoscale heat transfer and energy conversion with applications in thermoelectrics, photonics, and microelectronics; nano-mechanical devices and micro-electro-mechanical systems; radiation and electromagnetic metamaterials.View current research abstracts (pdf)View group web siteM. CulpepperResearch focuses on precision interfaces, precision manufacturing, design for manufacturing, applying precision principles as enabling technologies in multi-disciplinary product design: electronic test equipment, automotive systems, precision compliant mechanisms.View current research abstracts (pdf)View group web siteL. DanielResearch focuses on engineering design applications to drive research in simulation and optimization algorithms and software, design of microfabricated inductors.View current research abstracts (pdf)View group web siteP. DoyleUnderstanding the dynamics of single polymers and biomolecules under forces and fields; lab-on-chip separations, polymer rheology. DNA electrophoresis in microdevices. Superparamagnetic colloids. Brownian Dynamics simulations of complex molecules. Microheology of biopolymers.View current research abstracts (pdf)View group web siteA. EpsteinSmart engines, turbine heat transfer and aerodynamics, advanced diagnostic instrumentation, turbomachinery noise, environmental impact of aircraft.View current research abstracts (pdf)View group web siteD. FreemanBiological micromechanics, MEMS, light microscopy and computer microvision.View current research abstracts (pdf)牋牋牋牋牋牋牋牋牋牋牋?牋View group web siteM. GrayMicrofabricated devices for use in diagnostic medicine and biological research. Particle and fuid analysis of flowing media using absorbance and fluorescence techniques as a means for understanding cell or organism metabolism and phenotypic expression.View group web siteJ. HanBioMEMS, biomolecule analysis, micro/nanofluidics, micro-analysis systems.View current research abstracts (pdf)View group web siteJ. JacobsonDevelopment of processes for directly and continuously printing communication, computation, and displays onto arbitrary substrates. Electronic control of biomolecules.View group web siteK. JensenMicrofabrication and characterization of devices and systems for chemical synthesis and detection, hydrocarbon fuel conversion to electrical energy, bioprocessing and bioanalytics. Multiscale simulation of transport and reaction processes. Chemical vapor deposition of polymer, metal, and semiconductor thin films. Synthesis and characterization of quantum dot composite materials.View current research abstracts (pdf)View group web siteR. KarnikMicro- and nanofluidic systems. Application of transport phenomena in nanofluidics for flow control, separation, sensing. Microfluidic devices for studying chemical kinetics and nanoparticle synthesis.View group web siteS.G. KimSystems Design and Manufacturing, MEMS for optical beam steering, microphotonic packaging and active alignment, micro power generation, massive parallel positional assembly of nanostructures, and nano actuator array.View current research abstracts (pdf)View group web siteJ.H. LangAnalysis, design and control of electromechanical systems. Application to traditional electromagnetic actuators, micron scale actuators and sensors, and flexible structures.View current research abstracts (pdf)View group web siteC. LivermoreMicroElectroMechanical Systems (MEMS). Design and fabrication of high power microsystems. Nanoscale self-assembly and manufacturing.View current research abstracts (pdf)View group web siteS. ManalisApplication of micro- and nanofabrication technologies towards the development of novel methods for probing biological systems. Current projects focus on electrical and mechanical detection schemes for analyzing DNA, proteins, and cells.View current research abstracts (pdf)View group web siteD.J. PerreaultAnalysis, design, and control of cellular power converter architectures. DC/DC Converters fordual-voltage electrical systems. Electrical system transient investigation. Exploration of non-conventional electricity sources for motor vehicles.View group web siteM.A. SchmidtMicroElectroMechanical Systems (MEMS). Microfabrication technologies for integrated circuits, sensors, and actuators. Design of microsensor and microactuator systems.View current research abstracts (pdf)A. SlocumPrecision Engineering; Machine Design; Product Design.View current research abstracts (pdf)View group web siteC.V. ThompsonProcessing, structure, properties, performance, and reliability of thin films and structures for micro- and nano-devices and systems. Reliability and Interconnect.View current research abstracts (pdf)View group web siteT. ThorsenIntegrating microfluidic design and fabrication techniques, electronics and optics with biochemical applications. Optimizing channel dimensions, geometry, and layout to generate 3-D fluidic networks that are functional and scalable. Interface development to combine microfluidic technologies with pneumatic valves, MEMS-based detector systems, and software-based data acquisition and interpretation, creating devices for fundamental research and diagnostic applications.View current research abstracts (pdf)View group web siteH.L. TullerCharacterize and understand key electronic, microstructural, and optical properties of advanced ceramic materials. Fabrication andcharacterization of crystals, ceramics and glasses for electronic devices, lasers, electrochemical energy conversion, sensors and actuators.View current research abstracts (pdf)View group web siteJ. VoldmanBiological applications of microsystem technology. Engineering and use of microsystems for analysis and engineering of single cells. Physical and electrical cell manipulation. Design, modeling, microfabrication, and testing of microfluidic biological devices employing unconventional materials and fabrication processes. Electromechanics at the microscale.View current research abstracts (pdf)View group web siteE. N. WangDevelopment of MEMS/NEMS for: Biochemical sensing and detection; Thermal management of high power density and high performance systems; Diagnostics for biological systems and bio-functionality View group web siteB. WardlePower MEMS microyhydraulics, structural health monitoring, nanocomposites, damageresistance/tolerance of advanced composite materials, cost modeling in the structural design process, conversion of technology to value.View current research abstracts (pdf)View group web siteJ. WhiteTheoretical and practical aspects of numberical algorithms for problems in circuit, device, interconnect, packaging, and micromechanical system design; parallel numerical algorithms; interaction between numerical algorithms and computer architecture.View current research abstracts (pdf)View group web siteLaser-cooling brings large object near absolute zeroAnne Trafton, News OfficeApril 5, 2007Using a laser-cooling technique that could one day allow scientists to observe quantum behavior in large objects, MIT researchers have cooled a coin-sized object to within one degree of absolute zero.Fig.1Assistant professor Nergis Mavalvala, left, and Ph.D. student Thomas Corbitt are part of an international team that has devised a way to cool large objects to near absolute zero. Enlarge image (no JavaScript)Fig.Super-mirrorMIT researchers have developed a technique to cool this dime-sized mirror (small circle suspended in the center of large metal ring) to within one degree of absolute zero. Enlarge image (no JavaScript)Fig.2Assistant professor Nergis Mavalvala, right, and Ph.D. student Thomas Corbitt look over the laser system they use to cool a coin-sized mirror to within one degree of absolute zero. Enlarge image (no JavaScript)。

The jet in crossflowa_Kargra

The jet in crossflowa)Ann R. KaragozianCitation: Physics of Fluids (1994-present) 26, 101303 (2014); doi: 10.1063/1.4895900View online: /10.1063/1.4895900View Table of Contents: /content/aip/journal/pof2/26/10?ver=pdfcov Published by the AIP PublishingArticles you may be interested inA dynamical systems approach to the control of chaotic dynamics in a spatiotemporal jet flow Chaos 23, 033133 (2013); 10.1063/1.4820819Control of a jet-in-cross-flow by periodically oscillating tabsa)Phys. Fluids 24, 055107 (2012); 10.1063/1.4719150Stability of a jet in crossflowPhys. Fluids 23, 091113 (2011); 10.1063/1.3640011Transverse jet injection into a supersonic turbulent cross-flowPhys. Fluids 23, 046103 (2011); 10.1063/1.3570692Growth of kidney and antikidney vortices over a square jet in crossflowPhys. Fluids 18, 128102 (2006); 10.1063/1.2401624PHYSICS OF FLUIDS26,101303(2014)The jet in crossﬂow a)Ann R.Karagozian b)Mechanical and Aerospace Engineering Department,University of California,Los Angeles,California90095,USA(Received27June2014;accepted2September2014;published online23September2014)The jet in crossﬂow,or transverse jet,is aﬂowﬁeld that has relevance to a wide range ofenergy and propulsion systems.Over the years,our group’s studies on this canonicalﬂowﬁeld have focused on the dynamics of the vorticity associated with equidensityand variable density jets in crossﬂow,including the stability characteristics of the jet’supstream shear layer,as a means of explaining jet response to altered types of excita-tion.The jet’s upstream shear layer is demonstrated to exhibit convectively unstablebehavior at high jet-to-crossﬂow momentumﬂux ratios,transitioning to absolutelyunstable behavior at low momentumﬂux and/or density ratios,with attendant dif-ferences in shear layer vorticity evolution and rollup.These differences in stabilitycharacteristics are shown to have a signiﬁcant effect on how one optimally employsexternal excitation to control jet penetration and spread,depending on theﬂow regimeand speciﬁc engineering application.Yet recent unexpected observations on alteredtransverse jet structure under differentﬂow conditions introduce a host of unansweredquestions,primarily but not exclusively associated with the nature of molecular mix-ing,that make this canonicalﬂowﬁeld one that is of great interest for more extensiveexploration.C 2014AIP Publishing LLC.[/10.1063/1.4895900]I.INTRODUCTION AND BACKGROUNDJets injected perpendicularly into a cross-stream can be found in a range of technological systems.1,2The jet in crossﬂow(JICF)or transverse jet is utilized in dilution or primary air jet injection in gas turbine combustors,to accomplish mixture ratio and NOx control as well as turbine hot section cooling;inﬁlm cooling of turbine blades;in primary fuel injection in high speed air-breathing engines;and in thrust vector control for missiles and other high speed vehicles.Transverse jets are also found in environmental control systems,including control of efﬂuent from chimney and smokestack plumes as well as liquid efﬂuent dispersal in streams.Hence many variations on this canonicalﬂowﬁeld exist,2including gas injection into gas;liquid injection into a crossﬂow of liquid or gas;reactive fuel jets injected into a cross-stream of oxidizer;jetﬂuid injection that is either elevated orﬂush with respect to a surface;circular or rectangular jets of various aspect ratios;and gas or liquid injection into high speed crossﬂows of air,with bow shocks or other wave structures inﬂuencing jet behavior.The range ofﬂow conditions and applications of the transverse jet requires a thorough understanding of the structural,mixing,and,when relevant,reactiveﬂow characteristics in order to determine optimum operating conditions and control strategies.The interaction of the jet and crossﬂow creates a complex set ofﬂow structures and vortex systems,as shown for the round transverse jet withﬂush perpendicular injection in Figure1.The counter-rotating vortex pair(CVP)structure observed to dominate the jet cross-section3,4is generated in the nearﬁeld region of the jet and is thought to be associated with the evolution of vorticity in the jet’s shear layer5–8as well as pressure differences between the upstream and downstream regions of the jet.9,10In addition to the CVP,horseshoe vortices are observed to wrap around the jet column11 a)This paper was presented as an invited talk at the66th Annual Meeting of the APS Division of Fluid Dynamics,24–26 November2013,Pittsburgh,Pennsylvania,USA.b)ark@26,101303-11070-6631/2014/26(10)/101303/17/$30.00C 2014AIP Publishing LLCFIG.1.Schematic of the transverse jet,introducedﬂush with respect to the injection wall,including relevant vortical structures and orientation of coordinate axes.Shown are the counter-rotating vortex pair(CVP)as well as the jet’s upstream shear layer vortices,wake vortices,and horseshoe vortex structures.Adapted with permission from T.F.Fric and A.Roshko, J.Fluid Mech.279,1–47(1994).Copyright1994by Cambridge University Press.and can become unsteady at speciﬁcﬂow conditions.12Wake vortices forming on the lee side of theﬂush-injected JICF are another prominentﬂow feature and have been determined to contain wallboundary layerﬂuid which is drawn into the jet.13All of these vortical features play a role in thetransverse jet’s structure and mixing characteristics.14Among the important non-dimensional parameters associated with the transverse jet includethe jet-to-crossﬂow velocity ratio,R≡U j/U∞,the jet-to-crossﬂow density ratio,S≡ρj/ρ∞,thejet-to-crossﬂow momentumﬂux ratio,J≡SR2,and the jet Reynolds number,Re j≡U j D/νj,which is based on the jet exit diameter D and,most commonly,the bulk or mean jet velocity,U j.Typicalﬂowand operating conditions can vary quite widely for the JICF,depending on the speciﬁc application,even in the subsonic regime.For example,for applications involving dilution air jets and thrustvector control,the degree of jet penetration as well as molecular mixing of the jet with surroundingsis generally desired to be high.Since mixing and penetration have been correlated with each otherfor a range of JICF geometries,15the momentumﬂux ratio J for these applications tends to exceed25,and often involves J>100.In contrast,ﬁlm cooling to enable thermal protection of turbineblades involves arrays of jets injected perpendicularly from the blade surface into hot crossﬂow atrelatively low momentumﬂux ratios,often J<5or even J<1,to enable the jets to adhere to thesurface of the blades while cooling them,rather than penetrating deeply into the hot crossﬂow.16,17Yet turbine bladeﬁlm cooling jets can be subject to separation occurring over the trailing portion ofthe suction surface,and this is especially problematic at lower Reynolds numbers that are present inclasses of small gas turbine engines typically used or planned for use in high-altitude air vehicles.Infact,many of the features of the transverse jet,even those shown notionally in Fig.1,are dependenton the particularﬂow regime in terms of momentumﬂux ratio,Reynolds number,and density ratio,as well as speciﬁc injection geometry,as described below.Hence it has been of interest over severaldecades to be able to understand,predict,and control features of the jet in crossﬂow across a widerange ofﬂow conditions.A.Transverse jet vorticity generation and evolutionMany of the global features of the transverse jet can be understood and,to a limited extent,predicted on the basis of the dynamics of the CVP.The generation and evolution of these vorti-cal structures has been a matter of some debate and examination over the past several decades.Broadwell and Breidenthal18suggest that the CVP fundamentally arises from the impulse asso-ciated with the jet and thus is a global feature of the farﬁeld,in which the CVP is convecteddownstream by the crossﬂow.This concept,coupled with a simple nearﬁeld model for the deﬂec-tion of crossﬂow about the jet,enables vorticity-based,low-order models for the transverse jet toFIG.2.Interpretation of transverse jet shear layer evolution by Kelso,Lim,and Perry,7including(a)isometric view of the tilting of shear layer vortex rings and(b)reorientation of the shear layer vorticity,leading to folding of the vortex sheet and eventual formation of the CVP.Reprinted with permission from R.M.Kelso,T.T.Lim,and A.E.Perry,J.Fluid Mech.306, 111–144(1996).Copyright1996by Cambridge University Press.predict global trajectories andﬂame lengths reasonably well19,20at higher jet-to-crossﬂow velocity ratios(R≥4).Detailed experimental studies in the nearﬁeld of the JICF have suggested that the CVP is formed by the vortex sheet emanating from the jet nozzle or pipe.5–7,13The experiments of Kelso,Lim,and Perry7in both water and air suggest that periodic vortex ring rollup from the nozzle occurs for the round jet injectedﬂush into crossﬂow,similar to that which occurs in the free jet,yet superposed on this process is a re-orientation of this shear layer vorticity that is imposed by the crossﬂow,which leads to a folding of the cylindrical vortex sheet.The superposition of these two mechanisms is thought to result in a tilting of the upstream portion of the ring oriented with the mean curvature of the jet,and a tilting and folding of the downstream portion of the ring aligned with the direction of the jet.It is this tilting and folding which is thought to contribute to the circulation of the CVP, shown notionally in Fig.2.Kelso,Lim,and Perry7state that“the shear layer of the jet folds and rolls up very near to the pipe exit,leading to or contributing to the formation of the CVP,”as suggestedin theﬁgure.The relationship of the CVP to transverse jet mixing characteristics has also been of greatinterest over many decades.3,4Among the beneﬁts of using the jet in crossﬂow in many practicalenvironments is the enhancement of the entrainment of crossﬂow into the vicinity of the jet andthe associated enhancement of the molecular mixing of the twoﬂuids.Entrainment by a subsonictransverse jet orﬂame is typically seen to be much greater than that by a free jet or a buoyant turbulentjet.14,18,20,21For transverse jets in high speed airbreathing applications,e.g.,for fuel injection intohigh speed crossﬂow,the degree of penetration of the jet is of particular importance.22–24Rapidfuel penetration,mixing with crossﬂow,and ignition and sustainment of combustion processesare highly desirable,since high air speeds entering the combustion chamber(supersonic in thecase of a scramjet)require very rapid completion of the reaction process.25With respect to therelationship between the CVP and mixing enhancement,Smith and Mungal14suggest that,in lightof the evolving development of the CVP in the nearﬁeld of the jet,the enhanced mixing in thejet’s nearﬁeld corresponds to and likely results from the structural formation of the CVP rather thanits fully developed existence.Hence at many levels,the nature of the CVP and its initiation areimportant features of the transverse jet.B.Temporally forced jets in crossﬂowAmong the means by which control of transverse jets has been studied in recent years involvestemporal excitation of the jetﬂuid.Through such active excitation,control of vorticity generation maybe accomplished.Fundamental experiments on pulsed or acoustically driven transverse jets7,26–31suggest that,for certain excitation conditions,increased jet penetration into the crossﬂow and/orincreased spread and mixing may be achieved.Yet speciﬁc conditions yielding signiﬁcant jet responseto forcing vary rather widely among these different sets of experiments,which have been conductedin both liquids27,28and gases.26,29–31Some of these recent studies have focused on sinusoidal or sinusoidal-like excitation7,26,30andﬁnd improvement in transverse jet mixing when forcing is applied at speciﬁc values ofthe Strouhal number(based on forcing frequency f f,mean jet velocity,and jet oriﬁce diameter,St f≡f f D/U j).In some cases,e.g.,in the gas phase experiments in Narayanan,Barooah,and Cohen,30 the forcing frequency f f for maximized jet spread and mixing is equal to or greater than that associatedwith the unforced transverse jet’s shear layer instability,f o;in these experiments,the mean jet-to-crossﬂow velocity ratio R isﬁxed at6.Signiﬁcant jet response is achieved even when sinusoidaljet forcing,with a moderate peak-to-peak velocity excitation amplitude of about30%of the meanjet exit velocity,is employed.Enhancements of30%–46%in time-averaged entrainment,relativeto that for the unforced jet,are quantiﬁed via Mie scattering-basedﬂow visualization,30and theobserved vorticity dynamics are similar to those predicted in Direct Numerical Simulations(DNS)of a transverse jet operating at the sameﬂow conditions by Muldoon and Acharya.32Yet sinusoidal excitation of the transverse jet does not always produce such a response.Earlyexperimental research on controlled transverse jets at UCLA29,31,33focuses on acoustically forced,ﬂush round jets in crossﬂow with relatively low jet-to-crossﬂow velocity ratios,R=2.56and4.0,where the jet exit velocity is based on the measured centerline value.In contrast to the above-notedobservations30at R=6,experiments with forced sinusoidal excitation of the jet at R=2.56inM’Closkey et al.,29for example,show relatively little visual inﬂuence of forcing on jet behavior ascompared with unforced jet behavior.Even with very large amplitude excitation,exceeding75%ofthe mean jet velocity,and irrespective of the frequency of excitation,there is relatively little observedresponse of the transverse jet to temporal sine wave forcing.On the other hand,M’Closkey et al.29and Shapiro et al.31show that square-wave excitation ofthe jet at subharmonics of the fundamental(unforced)shear layer frequency,and with the same RMSof the velocity excitation as in sinusoidal forcing,yields signiﬁcant increases in the jet penetrationand spread.Feedforward or open loop control is employed to enable relatively precise temporalsquare wave excitation of the jetﬂuid.29Comparisons of jet response to these alternative modesof excitation,imaged via smoke visualization,are shown,for example,in Fig.3.Distinct,deeplypenetrating vortical structures are formed periodically in response to square-wave forcing,creatingmuch greater overall jet penetration and,for the relatively low duty cycle shown,a bifurcated jetFIG.3.Smoke visualization of the jet injected from aﬂush nozzle into crossﬂow at an average jet-to-crossﬂow velocity ratio of R=2.58,where U j=3.1m/s and U∞=1.2m/s.Results are shown for(a)the“unforced”jet,with an initial shear layer instability occurring at220Hz,(b)the jet forced with sine wave excitation at one-third the natural frequency,73.5Hz,and(c) the jet forced with square wave excitation at73.5Hz and a duty cycle of22%.For the forced conditions,a RMS amplitude of the velocity perturbations is matched between(b)and(c)at1.7m/s.Reprinted with permission from R.T.M’Closkey,J. King,L.Cortelezzi,and A.R.Karagozian,J.Fluid Mech.452,325–335(2002).Copyright2002by Cambridge University Press.structure;this contrasts the relatively minimal response seen when the transverse jet is forced with a sinusoidal excitation with the same RMS of the velocity disturbance,also shown in thisﬁgure.The conditions(forcing frequencies,duty cycles for square-wave excitation,amplitudes of excitation)leading to enhancement of jet penetration and spread indicate that speciﬁc values of the temporal pulse widthτcan provide optimal merger and penetration of vortical structures.31The time scales associated with this optimization appear to be nominally related to a“universal time scale”or non-dimensional stroke ratio L/D associated with coherent vortex ring formation,34which is observed to be optimized for L/D in the range3.6–4.5,where stroke length L is related to the velocity amplitude of square wave excitation,integrated over time.These observations for the transverse jet are also consistent with the ideas of Johari,35who suggests that transverse jet forcing with low duty cycles(α≡τ/T∼0.2)can lead to deeply penetrating transverse jets with distinct vortex rings. Experiments by Shapiro et al.31as well as DNS by Sau and Mahesh36of the transverse jet exposed to square wave-like excitation(i.e.,with imperfect but approximate square waves)suggest that,as long as the temporal waveform has a sharp upsweep for the delivery of sharp pulses of vorticity,and a relatively sharp downsweep to more clearly deﬁne the pulsewidth,imperfections in the waveform have very little effect on transverse jet behavior,and that such forcing can have a profound inﬂuence on jet behavior.It is noted that temporal square wave forcing has also been found to beneﬁt transverse jet heat transfer processes inﬁlm cooling applications,i.e.,at very low jet-to-crossﬂow momentumﬂux ratios,where enhanced jet penetration is not desirable.Pulsed transverse or“vortex generator”jets are observed16,17to improve cooling effectiveness at lower heat transfer coefﬁcients,to reduce blade suction surface boundary layer separation at low Reynolds numbers,and to require an order of magnitude reduction in mean massﬂow as compared with steady injection.II.TRANSVERSE JET INSTABILITIESA.Shear layer instabilities for equidensity and low density jets in crossﬂowThe difference between transverse jet response to sinusoidal excitation and to prescribed square wave excitation shown in Fig.3is quite striking,suggesting the importance of controlling nearﬁeld vorticity generation in order to inﬂuence overall jet behavior.But it has also been of interest to understand why,even with such large scale jet excitation as in Fig.3(b),jet response to sinusoidal excitation is rather minimal,in contrast to the observations of others such as Narayanan,Barooah, and Cohen,30for example.Recent explorations of the transverse jet’s shear layer instabilities have been pursued in part to explain the reasons for these differences in jet response.Extensive experimental explorations of the instabilities associated with the equidensity(S= 1)transverse jet’s nearﬁeld upstream shear layer37,38as well as the shear layer for the low density (S<1)jet in crossﬂow39have been pursued by our group.Flow conditions in the range1<R<∞for the equidensity jet in crossﬂow,and in the range2≤J≤41for the low density jet in crossﬂowFIG.4.Variable density transverse jet wind tunnel,and associated data acquisition and jet excitation apparatus.One additional tunnel section,of identical dimensions,was situated downstream of the test section shown.Reprinted with permission from D.R.Getsinger,C.Hendrickson,and A.R.Karagozian,Exp.Fluids53,783–801(2012).Copyright2012by Springer-Verlag. (with density ratios0.25≤S≤1.0)have been explored,for jet Reynolds numbers in the range 1800≤Re j≤3000.These detailed measurements indicate signiﬁcant differences in the nature of upstream shear layer instabilities for the JICF,depending on theﬂow regime.The low speed wind tunnel used for low density and equidensity transverse jet shear layer experiments is shown in Fig.4.Jetﬂuid is introduced through an injector situated at the bottom wall of the wind tunnel test section,issuing at room temperature into a crossﬂow of air.The tunnel test section is12cm×12cm in cross-section and30cm in length,with optical access windows(quartz)ﬁtted to the sides and top surfaces.Alternative jet nozzles,each with aﬁfth-order polynomial shape, an exit diameter of4mm,and producing a nearly top-hat velocity proﬁle at the exit plane in the absence of crossﬂow,have been explored in these studies.37The exit plane of one nozzle is situated ﬂush with respect to the tunnel wall and that of the other nozzle is extended by nearly four diameters from the tunnel wall,allowing gas injection outside of the wall boundary layer created by crossﬂow. Flush nozzles alone are studied in greater detail in later equidensity shear layer stability studies38and in low density JICF studies.39In general,the jetﬂuid is composed of varying proportions of nitrogen and helium to achieve the desired jet-to-crossﬂow density ratio.In these transverse jet shear layer studies,spectral measurements corresponding toﬂuctuations in the vertical velocity(z-component) are obtained using a single-component,boundary-layer type hotwire probe.The range of Reynolds numbers and momentumﬂux ratios J in these studies are such that,even at low jet-to-crossﬂow density ratios S,buoyancy effects are not important until at least20diameters downstream of injection,per approximate Richardson number scaling for low density jets.40Further details on the tunnel,injection system,and measurement procedures may be found in Megerian et al.,37Davitian et al.,38and Getsinger,Hendrickson,and Karagozian.39When the crossﬂow is successively increased for aﬁxed jet Reynolds number andﬁxed density ratio S in these experiments,the reduction in jet-to-crossﬂow velocity ratio R or momentumﬂux ratio J is observed to create signiﬁcant alterations in the shear layer instabilities at the upstream side of the jet.For the equidensity jet in crossﬂow,for example,as R or J is reduced from inﬁnity, the shear layer instabilities are observed to be strengthened,to be initiated closer to the jet oriﬁce, and to show evidence of successively weakening subharmonic instabilities.Sample results for the transition in the nature of the shear layer spectra for equidensityﬂush nozzle conditions are shown inSt s / D −90−80−70−60−50−40−30−200.10.30.50.70.9 1.1 1.3 1.5−100−80−60−40−20f o ^St d B s/D= .1s/D= 1.0s/D= 2.0s/D= 3.0s/D= 4.0s/D= 5.0s/D= 6.0St −90−80−70−60−50−40−30−200.10.30.50.70.9 1.1 1.3 1.5−100−80−60−40−20f o ^St d B s/D= .1s/D= 1.0s/D= 2.0s/D= 3.0s/D= 4.0s/D= 5.0St −90−80−70−60−50−40−30−200.10.30.50.70.9 1.1 1.3 1.5−100−80−60−40−20f o ^St d B s/D= .1s/D= 1.0s/D= 2.0s/D= 3.0(a)(b )(c)FIG.5.Shear layer instabilities for equidensity jets (S =1.0)emanating from a ﬂush nozzle at ﬁxed Re j =2000(based oncenterline jet velocity at the exit plane 37).Upper images:power spectra from hotwire response at various s /D locations alongthe jet’s upstream shear layer;lower images:spectra with a ﬁner spatial grid represented by spectral magnitude contours,with the magnitude colorbar (in dB)matched for each condition.Data are shown for (a)equidensity free jet (R →∞),(b)velocity ratio R =6.4,and (c)R =1.15,with initial oscillation frequency given in terms of Strouhal number St .Reprintedwith permission from S.Megerian,J.Davitian,L.S.de B.Alves,and A.R.Karagozian,J.Fluid Mech.593,93–129(207).Copyright 2007by Cambridge University Press.Fig.5for velocity ratios corresponding to the free jet (R →∞),the transverse jet at a relative highvelocity ratio (R =6.4),and the transverse jet at a velocity ratio below that at which a transition inspectral characteristics is observed (R =1.15),for a jet Reynolds number of 2000.Note that in theseearlier studies,37,38Re j and R are based on the jet’s centerline velocity at the exit plane rather thanthe mean velocity,the former being approximately 20%higher than the latter for the range of ﬂowconditions explored.Shown in the upper row of Fig.5are power spectra measured by the hotwireon a course spatial grid,with each line color representing a different s /D location.Spectral data fora ﬁner spatial grid represented by spectral magnitude contours,with the magnitude colorbar (in dB)matched for each condition,are shown in the lower row of this ﬁgure.Strouhal number St ≡f o D /U jis based on the frequency f o of the initial instability detected along the shear layer.As is typically observed for the free jet,41,42the early-developing shear-layer mode inFig.5(a)evolves along the layer to be taken over eventually by the “preferred mode”occurringfurther downstream.As R is reduced to 6.4via increasing the crossﬂow velocity magnitude,U ∞,ata ﬁxed jet Reynolds number,the instabilities are initiated closer to the jet exit,while the transversejet’s fundamental mode (as well as its higher harmonics)exhibits shifting to lower frequencies andsubsequent hopping to higher frequencies in multiple stages,before eventually being reduced inmagnitude farther downstream,where the subharmonic becomes dominant.Such frequency shift-ing/hopping behavior is a result of a shear layer tonal phenomenon,observed in both planar andaxisymmetric free jets by Hussain and Zaman.43The presence of the hotwire probe itself inﬂuencesthe transverse jet shear layer,resulting in feedback that serves to alter the shear layer’s fundamentalinstability frequency in a manner that is dependent on the distance between the probe and the jetexit.The impact of the shear layer tonal interactions with the hotwire is signiﬁcantly reduced asR is lowered,however.Such tonal interactions are not observed in our experiments for the free jet(either equidensity or low density),but are determined to occur for transverse jets emanating froma ﬂush circular nozzle,as in Fig.5,for a range of conditions where R >3.1.Thus the spectralcharacteristics represented in Fig.5(b)can be used as a spectral signature for the transverse jetat relatively high velocity ratios.As the crossﬂow velocity is increased for this equidensity case,however,so that R is reduced below around3.1,the oscillations are altered quite strikingly.Thefundamental shear layer mode continues to be initiated ever closer to the jet oriﬁce with decreasingR,but exhibits the same dominant,pure tone instability throughout the shear layer.An example of the spectral characteristics for these“low”velocity or momentumﬂux ratios is shown in Fig.5(c)forR=1.15.The frequency-shifting behavior is altogether eliminated below approximately R=3.1,and subharmonics are signiﬁcantly weakened,suggesting a reduction in vortex merger and pairingat lower R values.A similar transition in spectral characteristics is observed for the transverse jetproduced by the elevated nozzle,37but at a lower velocity ratio,R≈1.2based on jet centerlinevelocity.This difference in the critical value of R is found to result from the vertical coﬂow along theupstream edge of the elevated nozzle that increases in magnitude with increasing crossﬂow velocityU∞;coﬂow is known to stabilize a jet’s shear layer,as documented for purely coﬂowing jets.44Oncethe transverse jet emanating from the elevated nozzle has been turned sufﬁciently at low R,however,the spectral character becomes very similar to that for the jet emanating from theﬂush nozzle,asindicated in Fig.5(c).This signiﬁcantly altered behavior in the transverse jet as R is reduced below a critical value isconsistent with transition in the upstream shear-layer from being convectively unstable to becomingself-sustained or absolutely unstable.The presence of global instability in a number of differenttypes of shearﬂows is well known.45Suchﬂows include low density axisymmetric jets in quiescentsurroundings below a critical jet-to-surroundings density ratio,40,46countercurrent mixing layersabove a critical velocity difference,47,48and wakeﬂows above a critical Reynolds number.49,50The evidence for such a transition in the JICF shear layer includes phenomena that are exten-sively documented for the equidensity transverse jet37,38below a velocity ratio of R≈3.1andfor the low density jet in crossﬂow39for a momentumﬂux ratio J 10or with a density ratioS 0.4.These phenomena include:(1)clear changes in the spectral character of the shear-layer,with strong oscillations at narrow spectral peaks for global instability,representing pure tones withhigher harmonics,as seen in Fig.5(c);(2)a rather dramatic alteration in the value of the Strouhalnumber associated with the initial instability as the inﬂuencingﬂow parameter is brought into therange for globally unstableﬂow;(3)little spectral alteration of the globally unstableﬂow in responseto low to moderateﬂow excitation,in contrast to signiﬁcant spectral alteration of the convectivelyunstableﬂow during such excitation;(4)a rather abrupt increase in the amplitude of the distur-bance within and near the shear-layer as one approaches the criticalﬂow parameter,consistentwith the characteristics of the forced Landau equation;45,47and(5)a reduction in the energy trans-fer from fundamental to subharmonic frequencies along the shear-layer,and hence a reduction inthe strength of subharmonics and corresponding inhibition of the vortex pairing process after thetransition.For low density free jets,it is known that very strong external sinusoidal excitation can be usedto overcome the fundamental instability mode for globally unstable conditions,51,52resulting in a“lock-in”to the applied forcing frequency f f.A linear dependence of the critical amplitude abovewhich lock-in occurs on|f f−f0|is observed for the low density free jet by Juniper,Li,and Nichols,52 suggesting a Hopf bifurcation to a global mode in their helium jet.Such lock-in behavior is alsoobserved for both the equidensity transverse jet and the low density transverse jet.For example,Figure6shows this behavior for the low density tranvserse jet emanating from aﬂush nozzle39withjet-to-crossﬂow density ratio S=0.55.This particular density ratio S is above the transition valuefor the low density free jet documented for this Reynolds number(1800based on mean jet velocity);the jet-to-crossﬂow momentumﬂux ratio J needs to be less than approximately10to cause theshear layer to become globally unstable.Figure6(a)shows the variation in response of the J=5jetshear layer for successively increasing jet forcing amplitudes at frequency f f,which is greater thanthe natural,unforced shear layer frequency f o.Here,the forcing amplitude is quantiﬁed in termsof the normalized pressureﬂuctuation p created via the loudspeaker shown in Fig.4.In the caseshown,“lock-in”of the jet to f f is achieved between normalized forcing amplitudes of0.126and0.138.In a similar manner to the results of Juniper,Li,and Nichols,52many spectral peaks related toboth f o and f f are observed at lower forcing amplitudes,as the competition between the natural and。

非织造常用英语专业词汇

英汉非织造布专业词汇在此收集的大部分词汇是在翻译非织造布专业文献,特别是美国《非织造布工业》月刊中遇到的不太熟悉的词汇。

非织造布专业是一个跨行业的边缘学科,因此,有关文献涉及纺织、造纸、塑料、机械、电气、医学等领域。

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这些词汇有待专家确切定义。

Aabsorb吸收absorbent有吸收能力的absorbent core吸水芯材acquisition layer(卫生巾)集液层acrylicester emulsion丙烯酸酯乳液activated carbon活性碳activated charcoal filter活性碳过滤器adhesion tension附着强度adhesive粘接剂adult diapers成人失禁垫aerodynamic空气动力学的aesthetic fabric美观的布品aesthetics美学affordable买得起的affordability买力after treatment后处理ageing resistance耐老化性agriculture农业A I DS艾滋病air bridge空气桥air laid气流成网air porosity气孔率air through热风法all-in-one全合一aluminosilicate-based fiber 铝硅酸盐玻璃纤维angiography血管造影术anisotropy各向异性annual growth年增长率antiadherent film防粘膜anti-crease抗皱antistatic finish防静电处理APE(alkyl phenol ethoxylate)烷基酚乙氧基化物aperture网眼(布)appearance外观applicator涂胶机apparel服装apron围裙aqueous liquid水溶液aquarium filter养鱼缸过滤器area bonding面积粘合artificial leather substrate 人造革基布attenuation钝化,变细automation control自动化控制automobile carburetor汽车汽化器automobile interior汽车内装饰automotive headliner汽车车头衬里automotive carpet汽车用毯Bbaby diaper婴儿尿布baby wipe婴儿擦拭巾back sheet底衬bacteriaproof防菌bacteriophage噬菌体bale棉包barb(刺针)倒钩barrier阻挡层barrier-seal medical garment 密封阻挡层医用服装base cloth基布basis weight布品单位重量batt棉胎batteries电池组battery separator电池分隔层beater打浆机bedding床上用品,被褥betagauge测试仪beverage饮料bias斜线bib小儿围涎bicomponent fiber双组分纤维bilirubin胆红素birth rate出生率blanket毯子bleaching漂白bleachplant漂白厂blending混合bloodborne pathogen以血液为载体的病原菌blood spread血液散布blouse罩衫body cavities体腔bond area粘合面积bonded-face fabric面粘合布品bonded mat粘合纤维网bonded web粘合纤维网bonded yarn fabric纱线粘合布品bonding粘合bonding pattern粘合样式bonding pressure粘合压力bonding roll pattern粘合辊式样bonding temperature粘合温度bond point粘合点bottom layer(复合纤维)底层bottom line基线brand recognition品牌识别Breaking elongation断裂伸长Breaking strength断裂强度breaking stretchability断裂拉伸性breathability透气性Brownian movement布朗运动bulk松密度bulk melting system整体熔融系统burn烧痕burst strength撕裂强度Ccable wrap电缆包布calendering压光,轧制capillary force gradient毛管力梯度card梳理carded web梳理成网cardiovas cularsurgery心血管手术caregiver保育员carpet backing地毯基布carpet tile铺地地毯块CBR puncture(DIN54307)圆盘夹平面顶破压力试验穿刺CD(cross direction)布品(横向)cellulose acetate fiber醋酸纤维素纤维cellulose fiber纤维素纤维cellulose wadding纤维素填絮challenge挑战challenge tracer挑战示踪剂charring烧焦chemical binder化学粘合剂chemical bonding化学粘合chemical finishing化学后整理chemical resistance耐化学特性chemical stability化学稳定性chemical-to-fiber process化学成纤工艺child care保育clay粘土cleaning除杂cleanroom净化车间clinical experience临床经验clothlike仿棉布coastal protection work海岸防护工程coast line海岸线coated涂浆的coefficient of friction摩擦系数coherent bonded web粘接纤维网cohesive soil粘性土壤cold compress plaster base material冷压膏基材料collision碰撞coloration着色comfort舒适comforter盖被commercial wipe商用擦拭巾commitment of large capital expenditures大量资本开支投commodity商品compacting machine(打包)压实机comparative aesthetic property比较美学性competition竞争composite materia复合材料composite structure复合结构compressive force压缩力conductive shoe cover导电性鞋套conformable顺从consolidation凝固constituent fiber组成纤维contact anglemeter接触角测试仪containment遏制continuous filament长丝continuous travelling screen 连续移动筛网coordinated bedding set配套床上用品copolymer共聚物core芯材coreless无芯材的corrugated cardboard box瓦楞纸板箱cosmetic化妆品cost-effective有成本效益的cotton-rich富含棉花的(70%棉,30%涤纶)coverall连裤工作服cover factor覆盖系数cover gown遮挡罩衣coverstock(卫生巾、尿布)包布crease-resist finishing防皱整理creativity创造性crimp卷曲crimped bulking fiber卷曲膨松纤维criteria准则cross contamination交叉污染cross direction横向cross-laid webs交叉铺置纤网cross lapper交叉(折叠)铺网机cross-laying交叉铺网cross-laying process交叉铺网工艺crosslinked交联的cross-over重叠交叉cross section截面积cross-web profile纤网横向剖面crotch area裤裆,两腿交叉部位crystalline quartz fiber结晶石英纤维cystoscopy膀胱镜Dday care I.D.(儿童)日托标志degradation降解de-inked paper去除油墨的纸delta三角洲denier旦数(纤度单位)dental口腔科deposition沉积diagnostic procedure诊断过程dialysis drape透析帘diaper elastic尿布松紧带diaperless不戴尿布diaper machine尿布机diaper rash尿布皮疹die喷丝板die assembly模具diffusion扩散dimensional stability尺寸稳定性diminish递减dip bonding浸渍粘合法directional定向的direct polymer to web system 聚合物直接成网discard丢弃discharge排放discontinuous filament不连续丝disentanglement解缠disposable用即弃的disposable apparel用即弃服装disposable diaper用即弃尿布disposable masks and respirators用即弃面具和呼吸器dissipate消散,耗散diversity差异性down-web profile纵向纤网剖面drainage composite system 排水复合系统Drain sponge引流纱布drape(手术室里)消毒被单，消毒盖布drapery帐,帘drawing牵伸dressing sponge包扎纱布dry cleaning fastness耐干洗牢度dry feel滑爽感drying烘燥drylaid干法成网durability耐用性dust cage尘笼dyeing染色dynamics动态Eeasy pelf-opening(包装袋)方便开孔elasticated mob cap带松紧的帽子elastic bandage弹性绷带elastomeric properties弹胶性elastomeric thread弹力松紧带elastomeric web弹胶性纤网elderly population老年人口electrostatic laid静电法成网elongation to break断裂伸长embossing凹凸轧花embossing roller轧花辊筒emergency room急诊室endoscopic内窥镜的end product最终产品engraved roll雕刻辊environmental friendliness 与环境友好的EPA(US EnvironmentalProtection Agency)美国国家环境保护局ergodynamics人机动力学ergonomics人机工程学erodible易受冲蚀的erosion冲蚀European Pharmaco peas Standards欧洲药典标准exhume发掘expenditure消耗extruder挤出机extrusion挤出Ffabric advance per stroke每一针刺行程布品移动量fabric basis weight布品基本重量fabric filter media布品过滤介质fabric softener sheet含有织物软化剂的片材facewear面具,面罩fake fur人造毛皮fashion apparel流行时装fastening tape扣紧带fatal致命的fecal粪便feminine care妇女用品feminine hygiene妇女卫生巾feminine hygiene application 妇女卫生巾应用fenestration(耳科手术)开窗术fiber arrangement纤维排列fiber clump纤维束fiber crimp纤维卷曲fiber denier旦数(纤度单位)fiber density纤维密度fiber diameter纤维直径fiberfill web填丝纤网fiber fineness纤维细度fiber geometry纤维几何形状fiberglass mat玻璃纤维垫fiber orientation纤维取向fiberous filter media纤维状过滤介质fiber strength纤维强度fiber-to-fiber contact纤维间接触fiber-to-fiber frictional properties纤维间摩擦特性fiber-to-fiber fusion纤维间融合fiber tuft纤维簇fiber type纤维类型fiber web纤(维)网fibrillate原纤化fibrillation原纤化filament长丝filament area bonding长丝热熔粘接法filament sheet长丝片材fiscal year财政年度,会计年度flame retardancy阻燃性flame retardant chemicals阻燃化学品flame retardant finishing阻燃整理flammability可燃性flexibility柔韧性floorcovering地板覆盖材料floor personal一线工人fluffless diaper无短纤尿布fluff pulp绒毛浆fluidproof防液体渗漏foam-to-fabric process泡沫成布法folding eqiupment折叠设备Food service wipe食品专用擦拭巾Food soaker pad食品浸渍垫footwear鞋袜类fomaldehyde甲醛foster鼓励fray绽裂Full span moisture analyzer 全量程水分分析Full time nurse专职护士Functional fabric功能织物Functional group官能团functionality功能性furniture家具fusion融合GGamma gauge伽马射线仪gauze纱布geotextile土工布geotextile filter土工过滤材料glass microfiber玻璃微纤glass transition玻璃化转变glazed surface轧光表面glued-in浸胶式gown罩衣grab strength(ASTM D4632)抓样强力grade specification等级规格granular super absorbent polymer颗粒状超级吸水聚合物gravel砾石groin腹股沟GUI(graphical user inter face)图形用户接口Hhalf time半场hand feeling手感health care保健heat bonding热粘合heat conductivity热传导性heat setting bonding热定形粘合Heavy weight重型hepatitis virus肝炎病毒herbicides除锈剂heritage遗产,传统heterofil filament异质丝high density polyethylene高密度聚乙烯high-duty flow-throughdryer大型直通式烘燥机higher melting fiber高熔点纤维higher melting polymer高熔点聚合物highloft高膨松的highper formance高性能high pressure water jet高压水喷嘴hightech fiber高技术纤维high value-added高附加值的HIV(human immunodeficiency virus)艾滋病病毒home furnishings家具布horticulture园艺学hosiery袜类hot air drying热风烘燥hot calendering热轧光hot flue dryer热风烘燥机hot melt laminator热熔层压机hot melt system热熔系统hospital-acquired infectio n 医院得的传染病hospital sheet医院用床单household application家庭应用household items家庭用品housew rap家用毯子hybrid混杂物hydraulic entanglement水力缠结法hydraulic properties水力特性hydrogen-bond氢键hydrogen bonding氢键键合hydrophilic亲水的hydrophobic疏水的hyg ienic finishing卫生整理hyperbilirubinemia高胆红素血Iice replacement换冰image analysis software图像分析软件imbalance不平衡immobilization固定不动immunodeficiency免疫缺陷impair损害impregnated浸渍的impregnating bonding浸渍粘合法impregnation浸渍incision(手术)切口incont inence underpad失禁垫industrial dedusting工业除尘industrial tex tile产业用纺织品industr ial wipe工业用擦拭巾indwelling dev ice(手术)留置装置inertia惯量inertial impaction惯性碰撞infant婴幼儿infant diaper幼儿尿布infant training pant幼儿训练裤infection contro l goods控制传染用品infrared drying红外线烘燥infrared sensor红外传感器ingenuity精巧in redient配料inhospital patient days病人住院天数initial modulus初始模量innovation创新inpatient admission kit住院病人入院用品inplane flow面内滑动instability不稳定性integrated process组合工艺intensity强度interception交叉interfiber bonding force纤维间粘合力interfiber entanglement纤维间缠结interfiber fr iction纤维间摩擦interfolder中间折叠机interlining衬里interlocking(纤维)缠合intersperse分散,点缀intimate apparel内衣intr avenous catheter静脉导管intr insic properties固有特性investigation调查irregular不规则的irrigation灌溉irritation刺激(皮肤)发炎island in the sea matrix fiber 海岛式基质纤维isolated testing隔离试验isolation ward隔离病房isophthalic acid异肽酸isotactic全同立构isotropy各向同性Jjaundice黄疸judicious明智的,审慎的jumbo bag大袋子Llab co at实验室工作服labour intensive劳动密集型的laminated层压的laminate层压片材lap棉卷laparotomy剖腹术laparoscopy腹腔镜检查laser激光latex胶乳latex bonding胶乳粘合laydown铺网leading brand领先品牌leak proof防漏leg cuff裤腿翻边leg elastics(长统袜)袜口橡筋level wind匀整卷绕life cycle生命周期light stability光稳定性lightweight web轻质纤网linear low density polyethylene线性低密度聚乙烯lint fr ee不起绒lint residue棉绒残余liquid bar rier液体阻挡层liquid penetr at ion液体渗透liquid repellency液体排斥liquid wicking液体吸取longevity长寿lower melting polymer低熔点聚合物low Oformaldehyde低甲醛含量lucrative可赢利的lump团块Mmachine direction纵向magic towel(遇水变大的)魔术毛巾mandate命令manOmade f iber人造纤维mar ine clay海洋粘土mar ket penetration市场渗透率mar ket shar e市场份额mask面具,口罩mat lining垫衬材mattress褥垫MD(machine direct ion)(布品)纵向mechanical bonding机械粘合法mechanical drawing process 机械牵伸法mechanical finishing机械后整理mechanical needling机械针刺mechanical properties机械特性medical bandage医用绷带medical dressing医用绷带medical establishments医疗机构medical eyepad医用眼垫medical gauze医用纱布medical mask医用口罩medical nonwovens医用非织造布medical supplies医疗用品medical swab医用拖把medical wrap医用包布melding熔合meltblown熔喷法meltblown web熔喷纤网meltObonded web热熔粘合纤维网melter熔胶器melting point熔点menswear男服metering pump计量泵MFI(melt f low index)熔融流动指数microbreak细微断丝microdenier细旦microfiber微细纤维micro fine glass fiber微细玻纤microor ganism微生物microporous polyolefin membrane微孔聚烯烃薄膜microw ave absorbing product微波吸收制品microw ave moisture monitor 微波水分监视仪miction排尿migration泳移mob cap松紧帽modular equipment模块设备modulus模量moisture水分molycular by molycular examination逐个分子检验molecular weight distribution 分子量分布monofilament单丝monolit hic membrane单片薄膜monomer单体mor phology形态学mouldability可塑性multibonded binding多重粘合multi module application多头成形机multi national links多国网络MVTR(moistur e v apor transmission rate)湿气传透率Nnapping起绒nasal analysis嗅觉分析NBC(nuclear/biolog ical/ chemical)protective apparel核工业、生物工程、化工用防护服needlebonding针刺结合法needle felt针刺毡needlepunched针刺法needlepunching针刺needling bo nding针刺结合法NET(nonwovens engineering technology)非织造工程技术neurolo gical神经病学的niche领域Non Contact/Non Wear ultr asonic bonding无接触、无磨损超声波粘合nondirectional无定向的non irritating无刺激性的nonisotropic非各向同性non negotiable无商议余地的nonwoven fabr ic softener富含软化剂的非织造布片材nonwovens非织造布,无纺布Nonwovens Industry!非织造布工业nonwovens matr ix非织造布基体nonwovens towel非织造布毛巾nozzle喷嘴nursing home小型疗养院nylon尼龙Oopacity不透明odor嗅味offset抵消,补偿oil spill absorber溅油吸收材料one-step manufactur ing process一步法生产工艺opener开包机opening开松operating room手术室ophthalmic眼科的optical proper ties光特性order of mag nitude数量级orientation定向oriented web定向纤维网orthog onal相互垂直的orthopedic矫形术orthopedic padding矫形术用纱布块ostomy bag filter造口术袋形过滤器outdoor clothing户外服装outpatient门诊病人own-label mar ket采用自己商标的市场o xidat ion氧化作用Ppackaging包装pallet码垛盘pant diaper裤样尿布pants裤子panty shield裤裆垫布pantistocking连袜裤paper-like纸一样的手感papermaking造纸paper pulp纸浆,浆粕patient room utensil病房用具patter n roll雕花辊pediatric儿科performance性能pesticides杀虫剂PET(polyethylene ter ephthalate)聚对苯二甲酸乙二酯phosphorus-based flame r etardant磷基阻燃剂pillow case枕套pilot plant中试装置planar-isotropic平面各向同性plastic pellet塑料粒料point bond点粘合point bonding点粘合polybag塑料袋polyester涤纶polyethylene terephthalate 聚对苯二甲酸乙二酯polymer聚合物polymer-to-fabric process 聚合物成布工艺polypropylene聚丙烯polyurethane聚氨酯polyviny lalcohol fiber聚乙烯醇纤维poresize孔径po rosity孔隙度post-consum erwaste resin消费者用过的废树脂powder bonding粉末粘合poer-to-weight ratio功率-重量比PP(po lypropy lene)聚丙烯premature baby早产婴儿premoistened to welettes湿纸巾pressure drop压力降primary health care初级保健processability加工性能productivity生产率pro tecti ve apparel防护服puncture resi stance耐针刺Rradiant dryer辐射烘燥机railroad track absorbent matting铁轨减震垫randoen tangled web无定向缠结纤网random-laid web无定向纤网random shock无规电击random web无规纤网Rando w ebber兰多成网机rayon粘胶丝recovery复原regenerated fiber再生纤维reinforcement fabric(加厚)增强布品resiliency properties弹性resistance to tear propagation 抗扯裂传播retraction strength收缩强度retractive force收缩力reusables可重复使用的(布品)rheological characteristics流变特性robe长袍roll good卷材roofing屋面材料roofingm embrane屋面防水材料(油毡)roofing sheet屋面防水材料(油毡)Ssafety apparel安全服sandiwich structure夹层结构sanitary napkin卫生巾SAP(superabsorbent polymer)超级吸水聚合物saturating-bonding饱和浸渍粘合法saturation bonding饱和浸渍粘合scrubdress清洁工服装sealable可密封的sealing machine封口机seam strength密封强度self-bonding(纤网)自身粘合法sem i-durab le textile半耐用性纺织品share force剪切力sheath皮材sheet床单sheet integrity片材完整性shingle压合short cellulose fiber短纸浆纤维shot-free ceramic oxide fiber 无疵氧化陶瓷纤维shrinkage收缩率singeing烧毛skin friendly不伤皮肤的sku(stock keepi ng un its)库存单位slitti ng分切SMS(spunbond-meltblown-spunbond)纺粘-熔喷-纺粘复合工艺soft hand柔软手感softness柔软度soil retardant防污整理剂sonicvelocity声速Spandex氨纶spinneratte喷丝板spinning纺丝splice-free roll免切割布卷split film裂膜法sponge外科用纱布spray bonding喷洒粘合法spray spinning喷纺成形spunbond纺粘法spunbonds纺粘布制品spunbonded nonwovens纺粘法非织造布spunlaced纺络法spun web分丝成网squeezing roller压液辊stability稳定性staff appar el员工服staple fiber短纤维static shock静电电击steam sterilization pack蒸汽消毒组合装置step winding分步卷绕sterile无菌的,消毒的sterile wrap消毒包布stiff刚硬手感stiff structure刚性结构stitchbond缝编法stitchbonder缝编制品厂stitchbonding缝编stress strain curve应力应变关系曲线stretch拉伸strip tensile str ength带材抗张强度submicron fibr il亚微原纤维suede人造麂皮superabsorbent超级吸水材料supermarket chain超市连锁店surface abrasion resistance 表面耐磨性surface activeag ent表面活性剂surface energy表面能surgical drape手术帘surgical footw ear手术鞋袜surgical gown手术罩衣surgical headwear手术帽surgical mask手术口罩surgical table手术台surv ivability耐久性suspension悬浮swelling溶胀swimsuits游泳衣synthetic fiber合成纤维synthetic leat her合成Ttable cover台布tack定位缝合tactile触觉talc云母tea bag泡茶袋tear resistance抗撕裂性tear st rength撕裂强度temperature resistance耐温性tensile st reng th拉伸强度terephthalic acid对苯二酸tex tile like类纺织品therapeutic pr ocedure治疗过程thermal behav ior热力特性thermal bonded热粘合thermal calendering热轧法thermal insulation绝热thermoplastic热塑性thermoplastic elastomer合成橡胶thermoplastic r esin热塑性树脂thermoplastic matrix热塑性基体thickness厚度three dimensions三维through air热风法throughput产量toddler学步的儿童top sheet面材total randomization完全无规化toughness韧性traditional textile fabr ic传统纺织品training pants儿童训练裤transfer layer(卫生巾)液体转移层transpar ent透明的traverse w ind横动卷绕triboelectric property摩擦电特性tri folded sanitary napkin三折卫生巾tri lingual三种文字的trouble free无故障的twist ing加捻Uultrafine超细、超优ultra low formaldehy de超低甲醛含量ultrasonic bonding超声波粘合ultrasonic fabric sealing system超声波布品密封系统ultrasonic fusing超声波熔合ultra thin超薄ultravio let photot herapy紫外线疗法underpad垫子unifo rmity 均匀性unisex单一性别(专用)universal w ind万向卷绕unor iented无定向的unr av eling散开upholstery室内装饰urine尿UV light r esistance抗紫外线UV stabilized green fiber紫外线稳定的绿色纤维Vventuri feed tube文丘里喂入管versatility多样性,通用性vinyl acetate ethylene binder 醋酸乙烯酯粘接剂。

采暖通风与空气调节术语英汉对照b

feedback||反馈 feeding branch tlo radiator||散热器供热⽀管 fibrous dust||纤维性粉尘 fillter cylinder for sampling||滤筒采样管 fillter efficiency||过滤效率 fillter section||过滤段 filltration velocity||过滤速度 final resistance of filter||过滤器终阻⼒ fire damper||防⽕阀 fire prevention||防⽕ fire protection||防⽕ fire-resisting damper||防⽕阀 fittings||(通风〕配件 fixed set-point control||定值调节 fixed support||固定⽀架 fixed time temperature (humidity)||定时温（湿）度 flame combustion||热⼒燃烧 flash gas||闪发⽓体 flash steam||⼆次蒸汽 flexible duct||软管 flexible joint||柔性接头 float type steam trap||浮球式疏⽔器 float valve||浮球阀 floating control||⽆定位调节 flooded evaporator||满液式蒸发器 floor panel heating||地板辐射采暖 flow capacity of control valve||调节阀流通能⼒ flow characteristic of control valve||调节阀流量特性 foam dust separator||泡沫除尘器 follow-up control system||随动系统 forced ventilation||机械通风 forward flow zone||射流区 foul gas||不凝性⽓体 four-pipe water system||四管制⽔系统 fractional separation efficiency||分级除尘效率 free jet||⾃由射流 free sillica||游离⼆氧化硅 free silicon dioxide||游离⼆氧化硅 freon||氟利昂 frequency interval||频程 frequency of wind direction||风向频率 fresh air handling unit||新风机组 resh air requirement||新风量 friction factor||摩擦系数 friction loss||摩擦阻⼒ frictional resistance||摩擦阻⼒ fume||烟〔雾〕 fumehood||排风柜 fumes||烟⽓ G gas-fired infrared heating 煤⽓红外线辐射采暖 gas-fired unit heater 燃⽓热风器 gas purger 不凝性⽓体分离器 gate valve 闸阀 general air change 全⾯通风 general exhaust ventilation (GEV) 全⾯排风 general ventilation 全⾯通风 generator 发⽣器 global radiation||总辐射 grade efficiency||分级除尘效率 granular bed filter||颗粒层除尘器 granulometric distribution||粒径分布 gravel bed filter||颗粒层除尘器 gravity separator||沉降室 ground-level concentration||落地浓度 guide vane||导流板 H hair hygrometor||⽑发湿度计 hand pump||⼿摇泵 harmful gas andvapo||有害⽓体 harmful substance||有害物质 header||分⽔器、集⽔器（、） heat and moisture||热湿交换 transfer||热平衡 heat conduction coefficient||导热系数 heat conductivity||导热系数 heat distributing network||热 heat emitter||散热器 heat endurance||热稳定性 heat exchanger||换热器 heat flowmeter||热流计 heat flow rate||热流量 heat gain from lighting||设备散热量 heat gain from lighting||照明散热量 heat gain from occupant||⼈体散热量 heat insulating window||保温窗 heat(thermal)insuation||隔热 heat(thermal)lag||延迟时间 heat loss||耗热量 heat loss by infiltration||冷风渗透耗热量 heat-operated refrigerating system||热⼒制冷系统 heat-operated refrigetation||热⼒制冷 heat pipe||热管 heat pump||热泵 heat pump air conditioner||热泵式空⽓调节器 heat release||散热量 heat resistance||热阻 heat screen||隔热屏 heat shield||隔热屏 heat source||热源 heat storage||蓄热 heat storage capacity||蓄热特性 heat supply||供热 heat supply network||热 heat transfer||传热 heat transmission||传热 heat wheel||转轮式换热器 heated thermometer anemometer||热风速仪 heating||采暖、供热、加热（、、） heating appliance||采暖设备 heating coil||热盘管 heating coil section||加热段 heating equipment||采暖设备 heating load||热负荷 heating medium||热媒 heating medium parameter||热媒参数 heating pipeline||采暖管道 heating system||采暖系统 heavy work||重作业 high-frequency noise||⾼频噪声 high-pressure ho twater heating||⾼温热⽔采暖 high-pressure steam heating||⾼压蒸汽采暖 high temperature water heating||⾼温热⽔采暖 hood||局部排风罩 horizontal water-film syclonet||卧式旋风⽔膜除尘器 hot air heating||热风采暖 hot air heating system||热风采暖系统 hot shop||热车间 hot water boiler||热⽔锅炉 hot water heating||热⽔采暖 hot water system||热⽔采暖系统 hot water pipe||热⽔管 hot workshop||热车间 hourly cooling load||逐时冷负荷 hourly sol-air temperature||逐时综合温度 humidification||加湿 humidifier||加湿器 humididier section||加湿段 humidistat||恒湿器 humidity ratio||含湿量 hydraulic calculation||⽔⼒计算 hydraulic disordeer||⽔⼒失调 hydraulic dust removal||⽔⼒除尘 hydraulic resistance balance||阻⼒平衡 hydraulicity||⽔硬性 hydrophilic dust||亲⽔性粉尘 hydrophobic dust||疏⽔性粉尘 I impact dust collector||冲激式除尘器 impact tube||⽪托管 impedance muffler||阻抗复合消声器 inclined damper||斜插板阀 index circuit||最不利环路 indec of thermal inertia (valueD)||热惰性指标（D值） indirect heat exchanger||表⾯式换热器 indirect refrigerating sys||间接制冷系统 indoor air design conditions||室内在⽓计算参数 indoor air velocity||室内空⽓流速 indoor and outdoor design conditions||室内外计算参数 indoor reference for air temperature and relative humidity||室内温湿度基数 indoor temperature (humidity)||室内温（湿）度 induction air-conditioning system||诱导式空⽓调节系统 induction unit||诱导器 inductive ventilation||诱导通风 industral air conditioning||⼯艺性空⽓调节 industrial ventilation||⼯业通风 inertial dust separator||惯性除尘器 infiltration heat loss||冷风渗透耗热量 infrared humidifier||红外线加湿器 infrared radiant heater||红外线辐射器 inherent regulation of controlled plant||调节对象⾃平衡 initial concentration of dust||初始浓度 initial resistance of filter||过滤器初阻⼒ imput variable||输⼊量 insulating layer||保温层 integral enclosure||整体密闭罩 integral time||积分时间 interlock protection||联锁保护 intermittent dust removal||定期除灰 intermittent heating||间歇采暖 inversion layer||逆温层 inverted bucket type steam trap||倒吊桶式疏⽔器 irradiance||辐射照度 isoenthalpy||等焓线 isobume||等湿线 isolator||隔振器 isotherm||等温线 isothermal humidification||等温加湿 isothermal jet||等温射流 J jet||射流 jet axial velocity||射流轴⼼速度 jet divergence angle||射流扩散⾓ jet in a confined space||受限射流 K katathermometer||卡他温度计 L laboratory hood||排风柜 lag of controlled plant||调节对象滞后 large space enclosure||⼤容积密闭罩 latent heat||潜热 lateral exhaust at the edge of a bath||槽边排风罩 lateral hoodlength of pipe section||侧吸罩 length of pipe section||管段长度 light work||轻作业 limit deflection||极限压缩量 limit switch||限位开关 limiting velocity||极限流速 linear flow characteristic||线性流量特性 liquid-level gage||液位计 liquid receiver||贮液器 lithium bromide||溴化锂 lithium-bromide absorption-type refrigerating machine||溴化锂吸收式制冷机 lithium chloride resistance hygrometer||氯化锂电阻湿度计 load pattern||负荷特性 local air conditioning||局部区域空⽓调节 local air suppiy system||局部送风系统 local exhaustventilation (LEV)||局部排风 local exhaust system||局部排风系统 local heating||局部采暖 local relief||局部送风 local relief system||局部送风系统 local resistance||局部阻⼒ local solartime||地⽅太阳时 local ventilation||局部通风|| local izedairsupply for air-heating||集中送风采暖 local ized air control||就地控制 loop||环路 louver||百叶窗 low-frequencynoise||低频噪声 low-pressure steam heating||低压蒸汽采暖 lyophilic dust||亲⽔性粉尘 lyophobic dust||疏⽔性粉尘 M main ||总管、⼲管 main duct||通风〕总管、〔通风〕⼲管 main pipe||总管、⼲管 make-up water pump||补给⽔泵 manual control||⼿动控制 mass concentration||质量浓度 maximum allowable concentration (MAC)||容许浓度 maximum coefficient of heat transfer||传热系数 maximum depth of frozen ground||冻⼟深度 maximum sum of hourly colling load||逐时冷负荷综合值 mean annual temperature (humidity)||年平均温（湿）度 mean annual temperature (humidity)||⽇平均温（湿）度 mean daily temperature (humidity)||旬平均温（湿）度 mean dekad temperature (humidity)||⽉平均温度 mean monthly maximum temperature||⽉平均最低温度 mean monthly minimum temperature||⽉平均湿（湿）度 mean monthly temperature (humidity)||平均相对湿度 mean relative humidity||平均风速 emchanical air supply system||机械送风系统 mechanical and hydraulic||联合除尘 combined dust removal||机械式风速仪 mechanical anemometer||机械除尘 mechanical cleaning off dust||机械除尘 mechanical dust removal||机械排风系统 mechanical exhaust system||机械通风系统 mechanical ventilation||机械通风 media velocity||过滤速度 metal radiant panel||⾦属辐射板 metal radiant panel heating||⾦属辐射板采暖 micromanometer||微压计 micropunch plate muffler||微穿孔板消声器 mid-frequency noise||中频噪声 middle work||中作业 midfeed system||中分式系统 minimum fresh air requirmente||最⼩新风量 minimum resistance of heat transfer||最⼩传热阻 mist||雾 mixing box section||混合段 modular air handling unit||组合式空⽓调节机组 moist air||湿空⽓|| moisture excess||余湿 moisure gain||散湿量 moisture gain from appliance and equipment||设备散湿量|| moisturegain from occupant||⼈体散湿量 motorized valve||电动调节阀 motorized (pneumatic)||电（⽓）动两通阀 -way valvemotorized (pneumatic)-way valve||电（⽓）动三通阀 movable support||活动⽀架 muffler||消声器 muffler section||消声段 multi-operating mode automtic conversion||⼯况⾃动转换 multi-operating mode control system||多⼯况控制系统 multiclone||多管〔旋风〕除尘器 multicyclone||多管〔旋风〕除尘器 multishell condenser||组合式冷凝器N natural and mechanical combined ventilation||联合通风 natural attenuation quantity of noise||噪声⾃然衰减量 natural exhaust system||⾃然排风系统 natural freguency||固有频率 natural ventilation||⾃然通风 NC-curve[s]||噪声评价NC曲线 negative freedback||负反馈 neutral level||中和界 neutral pressure level||中和界 neutral zone||中和界 noise||噪声 noise control||噪声控制 noise criter ioncurve(s)||噪声评价NC曲线 noisc rating number||噪声评价NR曲线 noise reduction||消声 non azeotropic mixture refragerant||⾮共沸溶液制冷剂 non-commonsection||⾮共同段 non condensable gas ||不凝性⽓体 non condensable gas purger||不凝性⽓体分离器 non-isothermal jet||⾮等温射流 nonreturn valve||通风〕⽌回阀 normal coldest month||⽌回阀 normal coldest month||累年最冷⽉ normal coldest -month period||累年最冷三个⽉ normal hottest month||累年最热⽉（3） normal hottest month period||累年最热三个⽉ normal three summer months||累年最热三个⽉ normal three winter months||累年最冷三个⽉ normals||累年值 nozzle outlet air suppluy||喷⼝送风 number concentration||计数浓度 number of degree-day of heating period||采暖期度⽇数 O octave||倍频程 / octave||倍频程 octave band||倍频程 oil cooler||油冷却器 oill-fired unit heater||燃油热风器 one-and-two pipe combined heating system||单双管混合式采暖系统 one (single)-pipe circuit (cross-over) heating system||单管跨越式采暖系统 one(single)-pipe heating system||单管采暖系统 pne(single)-pipe loop circuit heating system||⽔平单管采暖系统 one(single)-pipe seriesloop heating system||单管顺序式采暖系统 one-third octave band||倍频程 on-of control||双位调节 open loop control||开环控制 open return||开式回⽔ open shell and tube condenser||⽴式壳管式冷凝器 open tank||开式⽔箱 operating pressure||⼯作压⼒ operating range||作⽤半径 opposed multiblade damper||对开式多叶阀 organized air supply||有组织进风 organized exhaust||有组织排风 organized natural ventilation||有组织⾃然通风 outdoor air design conditions||室外空⽓计算参数 outdoor ctitcal air temperature for heating||采暖室外临界温度 outdoor design dry-bulb temperature for summer air conlitioning||夏季空⽓调节室外计算⼲球温度 outdoor design hourly temperature for summer air conditioning||夏季空⽓调节室外计算逐时温度 outdoor design mean daily temperature for summer air conditioning||夏季空⽓调节室外计算⽇平均温度 outdoor design relative humidityu for summer ventilation||夏季通风室外计算相对湿度 outdoor design relative humidity for winter air conditioning||冬季空⽓调节室外计算相对湿度 outdoor design temperature ture for calculated envelope in winter冬季围护结构室外计算温度 outdoor design temperature ture for heating||采暖室外计算温度 outdoor design temperature for summer ventilation||夏季通风室外计算温度 outdoor design temperature for winter air conditioning||冬季空⽓调节室外计算温度 outdoor design temperature for winter vemtilation||冬季通风室外计算温度 outdoor designwet-bulb temperature for summer air conditioning夏季空⽓调节室外计算湿球温度 outdoor mean air temperature during heating period||采暖期室外平均温度 outdoor temperature(humidity)||室外温（湿）度 outlet air velocity||出⼝风速 out put variable||输出量 overall efficiency of separation||除尘效率 overall heat transmission coefficient||传热系数 ouvrflow pipe||溢流管 overheat steam||过热蒸汽 overlapping averages||滑动平均 overshoot||超调量 P packaged air conditioner||整体式空⽓调节器。

Measuring The Collective Flow With Jets

Measuring The Collective Flow With Jets
N´ estor Armesto, Carlos A. Salgado and Urs Achim Wiedemann
Department of Physics, CERN, Theory Division, CH-1211 Gen` eve 23, Switzerland (Dated: February 2, 2008) In nucleus–nucleus collisions, high-pT partons interact with a dense medium, which possesses strong collective ﬂow components. Here, we demonstrate that the resulting medium-induced gluon radiation does not depend solely on the energy density of the medium, but also on the collective ﬂow. Both components cannot be disentangled on the basis of leading hadron spectra, but the measurement of particle production associated to high-pT trigger particles, jet-like correlations and jets, allows for their independent characterization. In particular, we show that ﬂow eﬀects lead to a characteristic breaking of the rotational symmetry of the average jet energy and jet multiplicity distribution in the η × φ-plane. We argue that data on the medium-induced broadening of jet-like particle correlations in Au+Au collisions at RHIC provide a ﬁrst evidence for a signiﬁcant distortion of parton fragmentation due to the longitudinal collective ﬂow.

农药英语词汇

1) acaricide 杀螨剂6) acute toxicity 急性毒性7) adult 成虫8) affinity 亲和力17) aphid 蚜虫19) avirulence 无毒性20) baccine 疫苗21) bactericides 杀细菌剂37) chlorothalonil (daconil) 百菌清46) derosal 多菌灵51) diamondback moth 小菜蛾77) formulation 剂型78) fumigant 熏剂79) fungicides 杀真菌剂81) glycol 乙二醇82) granular pesticide 粒状农药83) herbicide 除草剂84) hibernate 越冬91) in vitro 体外92) in vivo 体内94) insecticide 杀虫剂105) larva 幼虫106) less-persistent pesticide 低残留农药107) life history 生活史108) low-toxic pesticide 低毒性农药116) methyl 甲基118) mildethane 托布津119) mist spryer 喷雾器125) nematicide 杀线虫剂143) pesticide 杀虫剂168) repellent 忌避剂，驱虫剂172) riskiest pesticide 高毒农药173) rodenticide 灭鼠剂176) selected insecticides 选择性杀虫剂189) tetrachloride 四氯化物190) virulence 毒力191) toxicity 毒性192) virus 病毒农药专业英语⑤蔬菜与谷物Vegetable and Grain (cereal)蔬菜与谷物1. Soybean 大豆2. Bean sprout 豆芽3. Bean 菜豆4. Pea 豌豆5. Onion 洋葱6. Garlic 大蒜7. Ginger 生姜8. Tomato 西红柿9. Potato 土豆sweet potato 红薯10. Cucumber 黄瓜11. Cabbage 包菜12. Rape (colza) 油菜13. Celery 芹菜14. Cauliflower 花椰菜15. Spinach 菠菜16. Mushroom 蘑菇17. Sugar beet 甜菜18. Pea nut (groundnuts) 花生19. Carrot 胡萝卜20. Radish 萝卜21. Green pepper 青椒22. Lettuce 莴苣, 生菜23. Chilies 红辣椒24. Eggplant 茄子25. corn 玉米26. Wax gourd (whit gourd) 冬瓜27. Watermelon 西瓜28. Pumpkin 南瓜29. Kaoliang (sorghum) 高粱30. Corn (maize) 玉米31. Rice (paddy) 水稻32. Wheat 小麦33. Barley 大麦34. Oat 燕麦35. Rye 黑麦36. Millet 小米，稷, 粟农药专业英语⑥经济作物Economic Plant 经济作物1. Tobacco 烟草2. Cotton 棉花3. Tea 茶树4. Sugar cane 甘蔗5. Cacao 可可豆6. Coffee 咖啡7. Panax 人参Ginseng 高丽参gen-seng 西洋参8. Jute 黄麻9. Flax 亚麻10. Hemp 大麻11. Sesame 芝麻12. Rose 玫瑰13. Palm 棕榈树14. Ornament 观赏植物15. Peppermint 薄荷16. Mulberry 桑树17. Sugar sweet 甜菜18. Wheat 小麦19. Rice (paddy) 水稻20. Rape 油菜21. Maize (corn) 玉米1) acaricide 杀螨剂2) acetate 醋酸盐,醋酸纤维素及其制成的产品3) acetyltransferase 乙酰基转移酶4) acidify 使酸化5) activator 催化剂,触媒剂6) acute toxicity 急性毒性7) adult 成虫8) affinity 亲和力9) aldehyde 醛10) alkaloid 生物碱11) amino 氨基的12) analysis of covariance 协方差分析13) analysis of variance 方差分析14) antibiotics 抗生素15) antifeedant 拒食16) antigen 抗原17) aphid 蚜虫18) arthropod 节肢动物19) avirulence 无毒性20) baccine 疫苗21) bactericides 杀细菌剂22) bioassay 生物测定23) biocontrol 生物防除24) biological control 生物防治25) biosynthesis 生物合成26) biotic pesticide 生物杀虫剂27) biotype 生物型28) botanical pesticide 植物源杀虫剂30) broad spectrum pesticide 广谱杀虫剂31) carbohydrate 碳水化合物32) carbonyl 羰基；碳酰33) carcinogenicity 致癌性34) causal agents 病原体35) chiller 冷却器36) chloroform 氯仿37) chlorothalonil (daconil) 百菌清38) chronic 慢性39) coagulation 凝结物40) concentration 浓度,浓缩41) constant temperature 恒温42) contact pesticide 触杀性农药43) cytokinin 细胞分裂素44) deactivation 灭活作用45) derivative 衍生物46) derosal 多菌灵47) desorption 解吸附作用48) detoxification 脱毒49) development rate 发育速度50) development zero 发育起点51) diamondback moth 小菜蛾52) diapause 滞育53) digenesis 世代交替54) disease-resistant cultivar 抗病品种55) disinfectant 消毒剂56) dissect 解剖57) disulfide 二硫化物(=disulphide)58) ecdysone 蜕皮激素59) economic threshold 经济阈值60) egg/ovum 卵61) electrophoresis 电泳62) endotoxin 内毒素63) entomology 昆虫学64) entomophagous insect 食虫昆虫65) enzyme 酶66) epidemiology 流行病学67) ethylene 乙烯68) exotic species 外来的物种69) fatal temperature 致死温度70) fauna 动物群,动物区系,动物志71) fecundity 生殖力，产卵力73) feign death 假死74) fermentation 发酵75) flammable 易燃的76) flavonod 类黄铜77) formulation 剂型78) fumigant 熏剂79) fungicides 杀真菌剂80) galactosyltransferase 乳化转移酶81) glycol 乙二醇82) granular pesticide 粒状农药83) herbicide 除草剂84) hibernate 越冬85) hormone 荷尔蒙,激素86) hydrocarbon 碳氢化合物87) hydrophilic 亲水的88) hydrophobic 疏水的89) hydroxyl 羟基90) hypochlorite 次氯酸盐91) in vitro 体外92) in vivo 体内93) inorganic 无机的94) insecticide 杀虫剂95) instar 龄，96) 龄期97) instar larvae 幼虫龄期98) integrated pest management IPM 有害生物综合防治99) interferon 干扰素100) ionization 离子化，电离102) isotope 同位素104) juvenile hormone mimic 仿生的保幼激素105) larva 幼虫106) less-persistent pesticide 低残留农药107) life history 生活史108) low-toxic pesticide 低毒性农药109) maggot 蛆110) malarial 毒气的111) male sterility 雄性不育113) median lethal dosage (LD50)致死中量114) median lethal concentration (LD50)致死中浓度115) metabolic 代谢作用的, 新陈代谢的116) methyl 甲基117) microbial 微生物的,由细菌引起的118) mildethane 托布津119) mist spryer 喷雾器120) molt 蜕皮121) mortality 死亡率122) moulting hormone antagonist 抗蜕皮激素123) mutase 变位酶124) mutation 突变125) nematicide 杀线虫剂126) nematode 线虫127) nicotine 烟碱128) nitrogen 氮129) non-contamination pesticide 无污染农药130) nontarget organism 非靶标生物132) normal saline 生理盐水133) nymph 若虫134) offspring 后代135) organic pesticide 有机农药136) organomercury pesticide 有机汞农药137) organophosphorus pesticide 有机磷农药138) parasitism 寄生139) pathogens 病原体(物)140) pathology 病理学141) peroxidase 过氧(化)物酶142) persistent pesticide 持久性农药;残留性农药143) pesticide 杀虫剂144) pesticide residue 农药残留145) pesticide tolerances 耐药性146) pest-resistant cultivar 抗虫品种147) petri dish 有盖培养皿148) pharmaceutical 制药学149) pheromone 信息素，外激素151) phosphatase 磷酸酶152) photosynthesis 光合作用153) phytohormone 植物生长素155) phytopathology 植物病理学157) phytotoxic 植物性毒素的159) polyethylene 聚乙烯160) population density 种群密度，虫口密度162) progeny 后裔163) pronotum 前胸背板164) pupa 蛹165) quarantine 检疫166) reductase 还原酶167) remnant 残留168) repellent 忌避剂，驱虫剂170) resistance 抗药性171) risk assessment 风险评估172) riskiest pesticide 高毒农药173) rodenticide 灭鼠剂174) secretion 分泌175) segregate 隔离176) selected insecticides 选择性杀虫剂177) semiochemicals 化学信息素178) sodium 钠179) solvent 溶解的，溶剂181) stochastic 随机的182) sublethal concentrations 亚致死浓度183) sublethal dose 亚致死中量184) sustainable agriculture 可持续农业185) synthase 合酶186) target organism 靶标生物188) terpenoid 萜类化合物189) tetrachloride 四氯化物190) virulence 毒力191) toxicity 毒性192) virus 病毒Pesticide Formulation 农药剂型1. Dust formulation 粉剂2. Wettable Powder (WP) 可湿粉剂3. Emulsifiable Cocentration (EC) 乳油4. Control release formulation 控制释放剂5. Slow release formulation 缓释剂型6. Capsule release formulation 胶囊释放剂7. Granule formulation 颗粒剂8. Smoke generator formulation 烟雾剂Aerosol formulation 气雾剂9. Soluble powder formulation 可溶性粉剂10. Fumigant formulation 熏蒸剂11. Multipurpose formulation 混合制剂12. Water flowable formulation 水悬剂13. Suspension concentrate formulation (SC) 悬浮剂14. Emulsion in Water formulation (EW) 水乳剂15. Suspend emulsion formulation (SE) 悬乳剂16. Micro emulsion formulation (ME) 微乳剂17. water dispersing granule (WDG) 水分散粒剂Dry flowable formulation 干胶悬剂18. water soluble granule (WSG) 水溶性粒剂②表面活性剂Adjuvant and Surfactant 表面活性剂1. Non-ioic surfactant 非离子表面火性剂2. Cationc surfactant (Anadionic) 阳离子表面活性剂3. Anionic surfactant 阴离子表面活性剂4. Wetting agent 润湿剂5. Suspending agent 悬浮剂6. Spreading agent (spreader) 分散剂7. Sticking agent (sticker) 粘着剂binding agent 胶粘合剂adhesive agent 粘合剂8. Stabilizing agent (stabilizer) 稳定剂9. Synergistic agent (synergist) 增效剂10. Flowable agent 流动剂11. Antidrift agent 抗飘剂12. Emulsifying agent 乳化剂13. Dispersing agent (disperser) 分散剂14. Defoaming agent 消泡剂15. Flocculation agent (flocculant) 聚凝剂16. Deflocculation agent (deflocculant) 抗聚凝剂17. Penetrating agent (penetrant) 渗透剂18. Antiseptic 防腐剂19. Thicker 增稠剂20. emulsifying agent 乳化剂21.phase inversion temperature 转型温度,简称PIT (反相)22.deemulsification 破乳23.deemulsifier 破乳剂③设备与仪器Instrument Ⅰ仪器Ⅰ（基础分析）1. Gas chromatography 气相色谱2. Liquid chromatography 液相色谱3. Electro microscope (scanning) 电子显微镜4. Electro probe 电极5. Heat weight balance 压力天平6. Hg extru meter 汞压力计7. Electronic balance 电子天平8. Surface tension meter (surface tensiometer) 表面张力仪9. Viscosimeter 黏度计10. Particle size counting analyzer 粒度仪Particle distribution analyzer 粒度分布仪11. Contact angle meter （忘了，呵呵！）12. Moisture content analyzer 水分测定仪Equipment and apparatus 设备与仪器1. Sand mill (bead mill) 砂磨机2. Colloid mill 胶体磨3. Homogenizer 均化器，高速搅拌器4. Disperser 扩散器5. Spray dryer 喷雾干燥器6. Atomizer 喷雾器7. Blender (twin shell blender) 搅拌机，掺和器8. Kneader 捏合机9. Granulator 造粒机10. Fluidized bed granulator 沸腾床11. Jet mill 气流粉碎机12. Super micro mill 超微粉碎机13. Packaging machine 包装机14. Cryostat for accelerated storage 恒温烘箱oven 烘箱(test facilities 0℃to 100℃)15. Raymond mill16. Refrigerating unit 冷冻机17. Transformer 变压器18. Boiler 锅炉19. Vacuum rotary dryer 真空旋转干燥机20. Electronic equipment (electricity, electric) 电子设备21. Pump 泵22. Biological treatment equipment 生物处理装置23. Incinerator equipment 焚烧炉24. Autoclave 高压灭菌器④稀释剂与填料Diluent carrier and filling (filler) 稀释剂与填料A．Solvent (aromatic compound or aliphatic compound) 溶剂1.Xylene 二甲苯2.Toluene 甲苯3.acetone 丙酮4.甲醇Methanol5.ethyl alcohol 乙醇B．Carrier and filling (filler) 载体与填料1.Talc 滑石粉2.Bentonile 皂粉3.Infusorial earth (kieselguhr, diatomaceous earth) 硅藻土4.Kaolinite 高岭土5.Active carbon 活性炭6.Silica gel 硅胶7.Maizena 玉米淀粉农药专业英语⑤蔬菜与谷物Vegetable and Grain (cereal)蔬菜与谷物1. Soybean 大豆2. Bean sprout 豆芽3. Bean 菜豆4. Pea 豌豆5. Onion 洋葱6. Garlic 大蒜7. Ginger 生姜8. Tomato 西红柿9. Potato 土豆sweet potato 红薯10. Cucumber 黄瓜11. Cabbage 包菜12. Rape (colza) 油菜13. Celery 芹菜14. Cauliflower 花椰菜15. Spinach 菠菜16. Mushroom 蘑菇17. Sugar beet 甜菜18. Pea nut (groundnuts) 花生19. Carrot 胡萝卜20. Radish 萝卜21. Green pepper 青椒22. Lettuce 莴苣, 生菜23. Chilies 红辣椒24. Eggplant 茄子25. corn 玉米26. Wax gourd (whit gourd) 冬瓜27. Watermelon 西瓜28. Pumpkin 南瓜29. Kaoliang (sorghum) 高粱30. Corn (maize) 玉米31. Rice (paddy) 水稻32. Wheat 小麦33. Barley 大麦34. Oat 燕麦35. Rye 黑麦36. Millet 小米，稷, 粟农药专业英语⑥经济作物Economic Plant 经济作物1. Tobacco 烟草2. Cotton 棉花3. Tea 茶树4. Sugar cane 甘蔗5. Cacao 可可豆6. Coffee 咖啡7. Panax 人参Ginseng 高丽参gen-seng 西洋参8. Jute 黄麻9. Flax 亚麻10. Hemp 大麻11. Sesame 芝麻12. Rose 玫瑰13. Palm 棕榈树14. Ornament 观赏植物15. Peppermint 薄荷16. Mulberry 桑树17. Sugar sweet 甜菜18. Wheat 小麦19. Rice (paddy) 水稻20. Rape 油菜21. Maize (corn) 玉米农药外贸专业英语⑦质检报告Analysis Certificate 分析报告Test Report 检验报告单Sample Name 样品名称Sample Source 样品来源或产地Sample Quantity 取样量Standard 样品名称Batch No. 批号Testing Date (Examine Date) 测试时间Analytical Results 分析结果Item 项目Result Note 结果记录A.I. Content (%) 有效成分质量分数Water content (%) 含水量pH Value (25℃) pH 值Viscosity (25℃mpas) 粘度.Stability 稳定性Gravity 比重Wettable time (Sec) 润湿时间Suspensibility (%)悬浮率Mean Particle Size (?m) 平均粒度Accelerated storage stability 低温稳定性Qualification (qualified) 合格Conclusion 结论Signature 签名Operator (Analyst) 操作者，检验者Checker 复核者Assessor 审核者。

(NEW)北京航空航天大学外国语学院211翻译硕士英语[专业硕士]历年考研真题及详解

9. If you _____ something, such as food or drink, you reduce its quality or make it weaker, for example by adding water to it.
A. adulterate B. moor C. vaccinate D. sue 【答案】A 【解析】句意：如果你往食物或饮品之类的东西里掺假，例如往里面兑水，就会降低它们的质量。adulterate掺杂。moor停泊；固定。 vaccinate注射疫苗。sue控告；起诉。
10. The orphanage is just one of her _____ causes. A. phonetic B. philanthropic C. prevalent D. lunatic 【答案】B 【解析】句意：这座孤儿院只是她的慈善事业之一。philanthropic仁慈的；慈善的。phonetic语音的。prevalent盛行的，流行的。lunatic精神
2010年北京航空航天大学211翻译硕士英语考研真题及详解
Part Ⅰ. Vocabulary (30 points) Directions: There are 30 incomplete sentences in this part. For each sentence there are four choices marked A, B, C and D. Choose the ONE answer that best completes the sentence. 1. The _____ is used by astrologers to help calculate the influence of the planets on people’s lives. A. zephyr B. zodiac C. zyme D. zest 【答案】B 【解析】句意：天文学家通过占星术中的黄道十二宫来计算星球对人类生活的影响。zodiac黄道十二宫（用于占星术）。zephyr和风，微风。zyme酶。zest热情；热心。

Fluent流体数值模拟软件中英对照

Aabort 异常中断, 中途失败, 夭折, 流产, 发育不全，中止计划[任务] accidentally 偶然地, 意外地accretion 增长activation energy 活化能active center 活性中心addition 增加adjacent 相邻的aerosol浮质(气体中的悬浮微粒,如烟,雾等), [化]气溶胶, 气雾剂, 烟雾剂Air flow circuits 气流循环ambient 周围的, 周围环境amines 胺amplitude 广阔, 丰富, 振幅, 物理学名词annular 环流的algebraic stress model(ASM) 代数应力模型algorithm 算法align 排列，使结盟, 使成一行alternately 轮流地analogy 模拟，效仿analytical solution 解析解anisotropic 各向异性的anthracite 无烟煤apparent 显然的, 外观上的，近似的approximation 近似arsenic 砷酸盐assembly 装配associate 联合，联系assume 假设assumption 假设atomization 雾化axial 轴向的Axisymmetry 轴对称的BBaffle 挡流板battlement 城垛式biography 经历bituminous coal 烟煤blow-off water 排污水blowing devices 鼓风(吹风)装置body force 体积力boiler plant 锅炉装置（车间）Boiling 沸腾Boltzmann 玻耳兹曼Bounded central differencing：有界中心差分格式Brownian rotation 布朗转动bulk 庞大的bulk density 堆积密度burner assembly 燃烧器组件burnout 燃尽Ccapability 性能，（实际）能力，容量，接受力carbon monoxide COcarbonate 碳酸盐carry-over loss 飞灰损失Cartesian 迪卡尔坐标的casing 箱，壳，套catalisis 催化channeled 有沟的，有缝的char 焦炭、炭circulation circuit 循环回路circumferential velocity 圆周速度clinkering 熔渣clipped 截尾的clipped Gaussian distribution 截尾高斯分布closure (模型的)封闭cloud of particles 颗粒云close proximity 距离很近cluster 颗粒团coal off-gas 煤的挥发气体coarse 粗糙的coarse grid 疏网格，粗网格Coatingcoaxial 同轴的coefficient of restitution 回弹系数；恢复系数coke 碳collision 碰撞competence 能力competing process 同时发生影响的competing-reactions submodel 平行反应子模型component 部分分量composition 成分computational expense 计算成本cone shape 圆锥体形状configuration 布置，构造confined flames 有界燃烧confirmation 证实, 确认, 批准Configuration 构造，外形conservation 守恒不灭conservation equation 守恒方程conserved scalars 守恒标量considerably 相当地consume 消耗contact angle 接触角contamination 污染contingency 偶然, 可能性, 意外事故, 可能发生的附带事件continuum 连续体Convection 对流converged 收敛的conveyer 输运机convolve 卷cooling duct 冷却管cooling wall 水冷壁coordinate transformation 坐标转换correlation 关联(式)correlation function 相关函数corrosion 腐蚀，锈coupling 联结, 接合, 耦合Cp：等压比热crack 裂缝，裂纹creep up （水）渗上来，蠕升critical 临界critically 精密地cross-correlation 互关联cumulative 累积的curtain wall 护墙，幕墙curve 曲线custom 习惯, 风俗, <动词单用>海关, (封建制度下)定期服劳役, 缴纳租税, 自定义, <偶用作>关税v.定制, 承接定做活的Cyan青色cyano 氰（基），深蓝，青色cyclone 旋风子，旋风，旋风筒cyclone separator 旋风分离器[除尘器]cylindrical 柱坐标的cylindrical coordinate 柱坐标Ddead zones 死区decompose 分解decouple 解藕的defy 使成为不可能Deforming：变形demography 统计Density：密度deposition 沉积derivative with respect to 对…的导数derivation 引出, 来历, 出处, (语言)语源, 词源design cycle 设计流程desposit 积灰，结垢deterministic approach 确定轨道模型deterministic 宿命的deviation 偏差devoid 缺乏devolatilization 析出挥发分，液化作用diffusion 扩散diffusivity 扩散系数digonal 二角(的), 对角的，二维的dilute 稀的diminish 减少direct numerical simulation 直接数值模拟discharge 释放discrete 离散的discrete phase 分散相, 不连续相discretization [数]离散化deselect 取消选定dispersion 弥散dissector 扩流锥dissociate thermally 热分解dissociation 分裂dissipation 消散, 分散, 挥霍, 浪费, 消遣, 放荡, 狂饮distribution of air 布风divide 除以dot line 虚线drag coefficient 牵引系数，阻力系数drag and drop 拖放drag force 曳力drift velocity 漂移速度driving force 驱[传, 主]动力droplet 液滴drum 锅筒dry-bottom-furnace 固态排渣炉dry-bottom 冷灰斗，固态排渣duct 管dump 渣坑dust-air mixture 一次风EEBU---Eddy break up 漩涡破碎模型eddy 涡旋effluent 废气，流出物elastic 弹性的electro-staic precipitators 静电除尘器emanate 散发, 发出, 发源，[罕]发散, 放射embrasure 喷口，枪眼emissivity [物]发射率empirical 经验的endothermic reaction 吸热反应enhance 增，涨enlarge 扩大ensemble 组，群，全体enthalpy 焓entity 实体entrain 携带，夹带entrained-bed 携带床Equation 方程equilibrate 保持平衡equilibrium 化学平衡ESCIMO-----Engulfment（卷吞）Stretching（拉伸）Coherence（粘附）Interdiffusion-interaction（相互扩散和化学反应）Moving-observer（运动观察者）exhaust 用尽, 耗尽, 抽完, 使精疲力尽排气排气装置用不完的, 不会枯竭的exit 出口，排气管exothermic reaction 放热反应expenditure 支出，经费expertise 经验explicitly 明白地, 明确地extinction 熄灭的extract 抽出，提取evaluation 评价，估计，赋值evaporation 蒸发(作用)Eulerian approach 欧拉法Ffacilitate 推动，促进factor 把…分解fast chemistry 快速化学反应fate 天数, 命运, 运气，注定, 送命，最终结果feasible 可行的，可能的feed pump 给水泵feedstock 填料Filling 倒水fine grid 密网格，细网格finite difference approximation 有限差分法flamelet 小火焰单元flame stability 火焰稳定性flow pattern 流型fluctuating velocity 脉动速度fluctuation 脉动，波动flue 烟道（气）flue duck 烟道fluoride 氟化物fold 夹层块forced-and-induced draft fan 鼓引风机forestall 防止Formulation:公式，函数fouling 沾污fraction 碎片部分，百分比fragmentation 破碎fuel-lean flamefuel-rich regions 富燃料区，浓燃料区fuse 熔化，熔融Ggas duct 烟道gas-tight 烟气密封gasification 气化(作用)gasifier 气化器Gauge 厚度，直径，测量仪表，估测。

BOSS RC-505 Loop Station商品说明书

For vocalists, vocal percussiFoonrisgtusi,taarnidsthsu, mbaanssbisetast,baonxdeWrositthhefrivpelainydeerspeonfdeelnetctloroonpict2r1aancddkisfaf,ectroheuenstRtitCcy-pi5ne0ss5trooufpmIenenpnsutstthFeSXi,dmpoplolurestudoseeidnrifciinantitteeedrfpaTercraefcowkrmiFtXhanfiocnretuipintodisvisveiibdfiiunlaigtleielrostoippscontrol
GRANULAR DELAY
Repeats a short portion of the input sound, giving it a buzzy character or producing the effect of playing a roll.
CHORUS REVERB
In this effect, a slightly detuned sound is added to the original sound to add depth and breadth.
DYNAMICS EQ ISOLATOR
Makes the volume more consistent, and produces a more evenly balanced low-frequency range.
Adjusts the tone as a equalizer.
Divides the audio input into three ranges (LO, MID, HI) and cuts the specified region. You can cut in synchronization with the tempo.

关于认识小动物的英语作文

When it comes to learning about small animals in English,there are various ways to approach the topic.Heres a detailed guide on how to write an essay on this subject, including vocabulary,sentence structures,and examples.Title:Exploring the World of Small AnimalsIntroduction:Begin your essay by introducing the topic and explaining why it is important to learn about small animals.You could mention their role in the ecosystem,their diversity,and the joy they bring to many people.In the vast tapestry of nature,small animals play a crucial role in maintaining the balance of ecosystems.From the tiniest insects to the smallest mammals,these creatures are not only fascinating to observe but also essential to the environment.Body Paragraph1:Types of Small AnimalsDiscuss the different types of small animals,such as insects,birds,reptiles,and mammals. Provide examples of each type and explain their characteristics.Insects,the most diverse group of animals on the planet,include butterflies,ants,and bees.They are known for their incredible variety of forms and colors.Birds,on the other hand,are characterized by their feathers,beaks,and the ability to fly.Small reptiles such as geckos and snakes are often admired for their unique scales and patterns.Mammals like mice,bats,and hedgehogs are warmblooded and often have fur,making them endearing to many.Body Paragraph2:Habitats and BehaviorsExplain where these small animals can be found and what their typical behaviors are. This could include their living environments,social behaviors,and feeding habits.Small animals inhabit a wide range of habitats,from the dense forests to the arid deserts. For instance,bats are often found in caves or hollow trees,where they roost during the day.In contrast,ants build complex colonies underground,demonstrating a highly organized social structure.The feeding habits of small animals are equally diverse,with some,like bees,being essential pollinators,while others,such as spiders,are predators. Body Paragraph3:Human Interaction and ConservationDiscuss the relationship between humans and small animals,including the benefits they provide and the challenges they face due to human activities.Human interaction with small animals can be both beneficial and detrimental.On one hand,animals like bees contribute significantly to agriculture by pollinating crops.On the other hand,habitat destruction and pollution pose serious threats to the survival of many small animal species.Conservation efforts are therefore essential to protect these creatures and the ecosystems they support.Conclusion:Summarize the main points of your essay and reiterate the importance of understanding and protecting small animals.In conclusion,small animals are an integral part of our natural world,offering a wealth of ecological services and a source of wonder for those who take the time to observe them. By learning more about these creatures,we can better appreciate their value and take necessary steps to ensure their continued existence in our everchanging world. Vocabulary List:Ecosystem:A community of living and nonliving things that interact with each other in a particular environment.Pollinators:Animals that help plants reproduce by transferring pollen from the male structures to the female structures of flowers.Habitat:The natural environment in which an organism lives.Warmblooded:Having a body temperature that is regulated independently of the environment.Conservation:The protection of plants,animals,and natural resources.Sentence Structures:Insects are known for their...Birds,characterized by...Reptiles,such as...Mammals,like...Human interaction with small animals can be...Remember to use descriptive language and varied sentence structures to make your essay engaging and informative.。

With its trun kN.完成短文Brown Bea

worked out.考研二 2010 阅读DirectionsRead the following text and decide whether each of the statements is true or false.Choose T if the statement is true or F it the statement is not true.Mark your answers on ANSWER SHEET1.(10 points)Copying Birds May Save Aircraft FuelBoth Boeing and Airbus have trumpeted the efficiency of their newest aircraft.The 787 and 350 respectively.Their clever designs and lightweight composites certainly make a difference.But a group of researchers at Stanford University,led by Ilan Kroo,has suggested that airlines could take a more naturalistic approach to cutting jet-fuel use and it would not require them to buy new aircraft.The answer,says Dr Kroo,lies with birds.Since191,scientists have known that birds flying in formation-a V-shape-expend less energy.The air flowing over a bird’s wings curls upwards behind the wingtips.a phenomenon known as upwash.Other birds flying in the upwash experience reduced drag,and spend less energy propelling themselves.Peter Lissaman,an aeronautics expert who was formerly at Caltech and the University of Southern California,has suggested that a formation of 25 birds might enjoy a range increase of 71%.When applied to aircraft,the principles are not substantially different.Dr Kroo and his team modeled what wouldhappen if three passenger jets departing from Los Angeles,San Francisco and I as Vegas were to assemble over Utah,assume an inverted V-formation occasionally change places so all could have a turn in the most favourable positions,and proceed to London.They found that the aircraft consumed as much as 15%less fuel(coupled with a reduction in carbon-dioxideoutput).Nitrogen-oxide emissions during the cruising portions of the flight fell by around a quarter.There are,of course,knots to be worked out.One consideration is safety,or at least the perception of it.Would passengers feel comfortable travelling in companion?Dr Kroo points out that the aircraft could be separated by several nautical miles,and would not be in the intimate groupings favoured by display teams like the Red Arrows,A passenger peering out of the window might not even see the other planes.Whether the separation distances involved would satisfy air-traffic-control regulations is another matter,although a working group at the International Civil Aviation Organisation has included the possibility of formation flying in a blueprint for new operational guidelines.It remains to be seen how weather conditions affect the air flows that make formation flight more efficient.In zones of increased turbulence,the planes’wakes will decay more quickly and the effect will diminish.Dr Kroo says this is one of the areas his team will investigate further.It might also be hardfor airlines to co-ordinate the departure times and destinations of passenger aircraft in a way that would allow them to gain from formation flight.Cargo aircraft,in contrast,might be easier to reschedule,as might routine military flight.As it happens,America’s armed forces are on the on case already.Earlier this year the country’s Defence Advanced Research Projects Agency announced plans to pay Boeing to investigate formation flight,though the programme has yet to begin.There are reports that some military aircraft flew in formation when they were low on fuel during the Second World War,but Dr Lissaman says they are unsubstantiated.“My father was an RAF pilot and my cousin the skipper of a Lancaster lost over Berlin,”he adds.So he should know.1.Findings of the Stanford University researchers will promote the sales of new Boeing and Airbus aircraft.2.The upwash experience may save propelling energy as well as reducing resistance.3.Formation flight is more comfortable because passengers can not see the other plans.4.The role that weather plays in formation flight has not yet been clearly defined.5.It has been documented that during World WarⅡ,America’s armed forces once tried formation flight to save fuel.答案：1.F2.T3.F .T 5.F。

第3章-振密、挤密分解

10
3）动力置换
动力置换可分为整体式或桩式动力置换二种，见下图。
整体式置换
桩式置换
11
2、设计计算
1）有效加固深度和单击夯击能
根据现场试夯或当地经验等确定有效加固深度。试验前也可采用修正的Menard公式估算：
H≈K(Wh/10)1/2
K在国内一般取0.34--0.8。
12
2）夯锤与落距
W *h称为单击夯击能，而整个场区的总夯击能（即锤重*落距*总夯击数）除以加固面积称为单位夯击能。单位夯击能应根据地基土类别、加固的深度、结构的类型、荷载的大小等综合考虑确定。
因夯坑过深而发生起锤困难。
14
遍数：夯击遍数应根据地基土的性质确定，采用点夯2－3遍，最后再以低能量满夯2遍。
2遍夯间应有一定的时间间隔。
5）垫层的铺设
垫层的铺设具有支承设备，便于施工的 “夯击能”得到扩散，同时也可加大地下水位与地表面的距离，有时也可控制施工标高。
15
6）间歇时间
其取决于加固土层中孔隙水压力的扩散。土性不同，间歇时间相差很大。对砂性土为2-4min，对粘性土为2-4周。
26
4、强夯置换碎石桩
强夯置换碎石桩: 利用强夯设备和技术制造的粗而短的“矮胖形”（碎石墩)。
施工机具包括重锤、机架和升降机等。一般为在夯点夯击一定深度的夯坑，用翻斗车向境内填满碎石或建筑垃圾等粗粒材料，再在原夯点夯击，将碎石击入坑底并挤向旁侧，形成新的夯坑，然后重复上述步骤，直到单击夯沉量达到设计要求为止，在地基中形成一碎石桩墩，该桩墩与桩间土共同工作形成复合地基。可以在软土中应用，这时，承裁力提高的幅度较大。
3、质量检验
依据《地基与基础工程施工与验收规范》（GBJ202-83）、《建筑地基处理技术规范》（JGJ792002）、《强夯地基技术规范》（YSJ209-92、YBJ2592）（冶金部、有色金属工业总公司）

企鹅英语作文

Penguins are fascinating creatures that inhabit the cold regions of the Earth, particularly the Antarctic.They are known for their distinctive appearance,social behavior,and unique adaptations to the harsh polar environment.Here is an essay on these charming birds,highlighting their characteristics and lifestyle.Introduction to PenguinsPenguins are a group of aquatic,flightless birds that are native to the Southern Hemisphere,especially Antarctica.They are easily recognizable by their black and white plumage,which serves as a form of camouflage in the water,helping them avoid predators.Physical CharacteristicsPenguins have a streamlined body shape that allows them to move efficiently through the water.Their wings have evolved into flippers,which they use for swimming.The most notable feature of penguins is their waddle,a distinctive walk that comes from the structure of their legs,which are set far back on their bodies to aid in swimming. Diversity of SpeciesThere are around18to20species of penguins,varying greatly in size and habitat.The Emperor Penguin,for instance,is the largest species,while the Little Penguin is the smallest.Each species has adapted to its specific environment,whether it be the icy waters of the Antarctic or the warmer climates of South America and Africa.Social BehaviorPenguins are highly social animals.They live in large groups called colonies,which can number in the thousands.These colonies are not just for breeding but also serve as a form of protection against predators.Penguins communicate with each other using a variety of calls,which are essential for maintaining social bonds within the group.Reproduction and ParentingPenguin reproduction is a remarkable process.Many species,like the Emperor Penguin, breed in the harshest conditions of the Antarctic winter.Males and females mate for life, and both parents share the responsibility of incubating the egg and caring for the chick.In some species,such as the Emperor Penguin,the male incubates the egg while the female goes to sea to feed.Adaptations to the EnvironmentPenguins have developed several adaptations to survive in their cold habitats.They have a thick layer of blubber under their skin,which provides insulation and energy reserves. Their feathers are densely packed and coated with a waterproof oil,allowing them to stay warm and dry in the water.Threats and ConservationPenguins face numerous threats,including climate change,which affects their habitats and food sources.Overfishing and pollution also pose significant risks.Conservation efforts are crucial to protect these species and their ecosystems.This includes monitoring populations,protecting habitats,and regulating fishing activities.ConclusionPenguins are not just endearing symbols of the Antarctic they are also important indicators of the health of our planets ecosystems.Their unique adaptations and social behaviors offer valuable insights into the resilience of life in extreme conditions.As we learn more about these remarkable birds,it becomes increasingly important to ensure their survival for future generations to appreciate and study.。

联合国危险品货物一览表英文

Packing
Special
instruction packing
provisions
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
0037 BOMBS, PHOTO-FLASH†
1.1F
NONE
P130
0038 BOMBS, PHOTO-FLASH†
1.1D
NONE
P130 LP101
PP67 L1
NONE
P140
0070 CUTTERS, CABLE,
1.4S
EXPLOSIVE†
NONE
P134 LP102
0072 CYCLOTRIMETHYLENE-
1.1D
TRINITRAMINE (CYCLONITE;
HEXOGEN; RDX), WETTED
with not less than 15% water, by
P130
204 NONE 204 NONE
NONE
P130 LP101
P130 LP101
P130 LP101
NONE
P130 LP101
274 NONE
P101
274 NONE
P101
NONE
P113
NONE
P113
PP67 L1
PP67 L1
PP67 L1
PP67 L1
PP67 L1
PP67 L1
(10)
(11)
- 179 -
UN
Name and description
Class Subsi- UN Special Limited Packagings and IBCs

稠密颗粒射流倾斜撞击颗粒膜特征

稠密颗粒射流倾斜撞击颗粒膜特征王悦;李伟锋;施浙杭;刘海峰;王辅臣【摘要】采用高速摄像仪对稠密颗粒射流倾斜撞击形成的类液体颗粒膜特征进行实验研究,考察了颗粒粒径、射流速度以及射流含固率等因素对颗粒膜形态及动态特征的影响.结果表明:随着颗粒粒径增大,稠密颗粒倾斜撞击流由颗粒膜向散射模式转变;随着射流速度增加,气固不稳定增强,射流流量出现脉动,正面与侧面分别表现为颗粒膜的非轴对称振荡和表面波纹结构;颗粒膜非轴对称振荡的振荡频率和振荡幅度随射流速度的增大而增大;表面波纹速度和波长沿传播方向增大,波纹间存在叠加现象.颗粒膜出现非轴对称振荡主要是因为喷嘴出口由气固不稳定性引起的射流流量脉动,射流流量脉动频率与撞击面振荡频率基本相当.【期刊名称】《物理学报》【年(卷),期】2018(067)010【总页数】10页(P121-130)【关键词】稠密颗粒射流;撞击流;颗粒膜;非轴对称振荡【作者】王悦;李伟锋;施浙杭;刘海峰;王辅臣【作者单位】华东理工大学, 煤气化及能源化工教育部重点实验室, 上海 200237;华东理工大学, 上海煤气化工程技术研究中心, 上海 200237;华东理工大学, 煤气化及能源化工教育部重点实验室, 上海 200237;华东理工大学, 上海煤气化工程技术研究中心, 上海 200237;华东理工大学, 上海煤气化工程技术研究中心, 上海200237;华东理工大学, 煤气化及能源化工教育部重点实验室, 上海 200237;华东理工大学, 上海煤气化工程技术研究中心, 上海 200237;华东理工大学, 煤气化及能源化工教育部重点实验室, 上海 200237;华东理工大学, 上海煤气化工程技术研究中心, 上海 200237【正文语种】中文1 引言自1961年前苏联科学家Elperin提出撞击流的概念之后,众多学者对其进行了大量的研究.因其独特的相间传递特性,气固两相撞击流已被广泛应用于干燥、气化、燃烧、混合[1−3]等工业过程中,得到了众多学者的关注和研究.因此对气固撞击流进行深入研究,考察各种因素对气固撞击流流动形态的影响以及揭示撞击区颗粒运动特征具有重要的学术意义以及工业前景.迄今为止,已有较多学者对稀疏气固撞击流进行了实验和模拟研究.刘红娟等[4]基于玻尔兹曼方法对稀疏气固两相撞击流中单颗粒运动行为进行了模拟.孙志刚等[5,6]采用高速摄像仪和PV6D型颗粒测速仪分别研究了单颗粒在撞击流中的运动特征和稀疏气固两相撞击流的流动特征.Xu等[7]应用基于颗粒流动力学的欧拉-欧拉方法模拟了气固平面撞击流,观察到了撞击面的周期性偏转振荡现象,研究发现喷嘴间距、初始射流雷诺数和颗粒粒径对振荡周期影响较大.一些学者还利用DSMC(direct simulation Monte Carlo method)模拟对稀疏气固撞击流进行了研究.Du等[8,9]通过改进的DSMC方法对稀疏气固撞击流进行了模拟,结果发现可将其分为三个区域:颗粒碰撞区、颗粒射流区以及颗粒散射区.Liu等[10]在考虑颗粒自身旋转和碰撞的前提下,采用基于三维的欧拉-拉格朗日方法的DSMC模拟对稀疏气固撞击流的流动特性进行了研究.但是与稀疏气固两相撞击流相比,稠密气固撞击流的相关研究非常有限.一些学者对稠密颗粒射流撞壁进行研究,发现稠密颗粒射流撞壁会形成类液体颗粒膜形态.Cheng等[11]通过实验研究发现:当稠密颗粒射流撞击有限尺寸壁面时,会形成仅有几个颗粒厚度的类液体颗粒膜,而随着颗粒射流内颗粒数量的减少,其撞击形态由颗粒膜转变为散射形态.Cheng等[12]还以颗粒流射流通过非圆形截面验证了颗粒膜的各向异性.Johnson和Gray[13]使用实验和数值模拟手段对稠密颗粒射流撞击倾斜平板进行了研究,发现撞击后会形成月桂形的“水跃”现象.Boudet等[14,15]研究了稠密颗粒射流撞击无限大壁面时颗粒膜波纹结构的产生和传播过程,发现颗粒膜上波纹的形成受到颗粒与平板之间摩擦力的影响.最近,本课题组也对稠密颗粒射流撞击圆形壁面进行了实验研究[16−18],发现稠密颗粒射流撞击壁面后会呈现颗粒膜与散射形态,其形态主要受D/d(D为喷嘴直径,d为颗粒粒径)与颗粒射流含固率的影响,同时在颗粒膜表面上可以观察到明显的波纹结构,形成表面波纹主要是因为颗粒射流在气固相互作用下变得不稳定.目前为止,仅有的对稠密颗粒撞击流的研究均为实验模拟.Huang等[19]在对撞壁流进行研究的基础上,采用离散单元法对两股对置稠密颗粒射流撞击进行了初步模拟.结果表明,稠密颗粒射流对置撞击后的运动形态与d/Djet(d为颗粒粒径,Djet为射流直径)、法向弹性系数和撞击间距有关.在特定的撞击间距下,两股颗粒射流对置撞击形成颗粒膜.Ge等[20]采用能量最小多尺度模型(EMMS)模拟了两股颗粒射流倾斜撞击,结果表明,在质量流量相同的情况下,撞击后颗粒会发生振荡.O’Rourke和Snider[21]采用基于MPPIC(multiphase-particle-in-cell)方法的修正BGK(Bhatnagar,Gross,and Krook)颗粒碰撞模型对稠密颗粒射流倾斜撞击进行数值模拟,发现当不考虑颗粒间的碰撞作用时,两股稠密颗粒射流倾斜撞击的流股相互交叉流过;考虑颗粒间碰撞阻尼作用时,两股颗粒射流发生弯曲;当同时考虑碰撞阻尼和各向异性作用时,撞击后的颗粒发生散射.Ellowitz[22]观察到稠密颗粒对置撞击表现出的类流体现象之后,为了研究二者相似的原因,采用离散单元法进行了模拟.结果表明,两股稠密颗粒射流撞击之后会产生驻点振荡现象,撞击形态与颗粒本身性质无关.值得注意的是,上述模拟结果尚无实验数据进行验证,因此非常有必要对稠密颗粒射流撞击进行实验研究.本文以华东理工大学多喷嘴对置式气化炉为研究背景,采用高速摄像仪和图像处理软件对稠密颗粒射流倾斜撞击过程进行了实验研究,考察了颗粒粒径、射流速度以及含固率等因素对类液体颗粒膜形态的影响.本文旨在揭示稠密颗粒射流倾斜撞击过程中类流体结构及其形成机理,为工业应用中广泛出现的稠密颗粒射流撞击流提供理论依据.2 实验方法2.1 实验装置及流程稠密颗粒射流倾斜撞击实验装置和流程如图1所示,实验在常温下进行,密闭储料罐内的玻璃微珠在钢瓶中高压空气的推动作用下,从两个间隔一定间距、呈一定角度的喷嘴中喷出,形成两股稠密颗粒射流,然后撞击形成稠密颗粒撞击流.通过调节储料罐内的空气压力可以改变喷嘴出口质量流量.如图1(a)和图1(b)所示,金属喷嘴出口直径D=3 mm,两喷嘴出口夹角2θ为60◦,撞击间距L/D=3(L为两喷嘴中心点直线距离).颗粒为玻璃微珠,密度ρp=2490 kg/m3,粒径Dp=82,122,184和246µm.实验中,采用FASTCAM APX-RS型高速摄像仪,在1300 W的卤素聚光灯的照射下,分别从侧面(yox平面)和正面(yoz平面)对颗粒撞击区的流场形态进行拍摄,拍摄的快门速度为1000 fps或3000 fps,曝光时间为1/8000 s,拍摄图片分辨率为1024×1024.定义喷嘴出口处颗粒射流含固率:其中u0为喷嘴出口截面平均速度(m/s);mp为喷嘴出口质量流量(kg/s);ρp为颗粒密度(kg/m3);A为喷嘴出口截面积(m2),可通过上述含固率的计算公式得到不同工况下稠密颗粒射流的含固率值.实验中对不同颗粒粒径含固率随颗粒射流速度的变化规律进行了测量,结果如图2所示.实验结果表明,相同颗粒射流速度下,稠密颗粒射流含固率随颗粒粒径的增大而减小.实验中采用PV6D型颗粒速度测量仪对稠密颗粒射流在喷嘴出口的截面平均速度(u0)进行测量,通过计算两通道信号互相关函数来测量颗粒运动速度.互相关函数曲线最大值处的延迟时间为τ,为被测稠密颗粒射流通过某一个固定距离l=2.1 mm 的时间,通过V=l/τ可得颗粒在这段距离内的平均运动速度,实验中测量次数不小于20次,测量误差小于5%.图1(b)为稠密颗粒射流倾斜撞击中颗粒膜上波纹传播过程的示意图.在正面示意图(yoz平面)中,通过跟踪单位时间内波峰的位移可得该位置处的波纹传播速度us;通过跟踪10个表面波纹的波峰经过同一位置处的时间,然后同一个数据点测量10次取平均值,则可得到表面波纹传播频率fs;颗粒膜在沿y轴正方向上两相邻波峰间的距离为波长λs.通过测量500张叠加的正面和侧面图片中颗粒膜形成的角度可分别得到正面扩展角(α)与侧面扩展角(β).在侧面示意图(yox 平面)中,定义某位置处波峰的x坐标值为颗粒膜振荡幅度Ab;颗粒膜非轴对称振荡频率fb的测量方法与表面波纹传播频率fs的测量方法相同.本文在处理实验数据时,同一数据点重复测量10次,10次测量结果的标准方差在图中用误差棒表示.图1 稠密颗粒射流倾斜撞击实验图 (a)流程图;(b)流场示意图Fig.1.Sketch of the experimental setup of dense granular impinging jets:(a)Flow chart;(b)flow diagram.图2 不同颗粒粒径含固率随射流速度的变化Fig.2. Solid content of different particle diameter varies with granular jet velocity.3 结果与讨论3.1 稠密颗粒射流倾斜撞击运动特征图3为不同颗粒粒径下稠密颗粒射流倾斜撞击的可视化图像.由图3可知,稠密颗粒射流倾斜撞击表现出两种形态:当颗粒粒径为82µm时,撞击后形成较平滑的颗粒膜形态,与液膜类似;当颗粒粒径为246µm时,撞击后的许多颗粒沿轴向(x方向)运动,呈现为散射形态.这是因为随着颗粒粒径的增大,颗粒射流含固率减小,单位体积内所含颗粒数目减少,颗粒运动自由程增加,颗粒间碰撞概率减小,颗粒膜形态消失[12]. 图4(a)—(c)与图4(d)—(f)分别为不同颗粒射流速度下的稠密颗粒射流倾斜撞击侧面与正面的可视化图像.从图4(a)—(c)可以看出,在颗粒射流速度较小时,颗粒撞击后呈现为竖直的颗粒膜形态,几乎稳定在与两射流垂直的平面内,不发生振荡.随着射流速度的增加,颗粒膜发生弯曲、摆动,呈现非轴对称振荡.如图4(d)—(f)所示,在颗粒膜表面上可以观察到明显的波纹结构,由撞击中心沿y轴正向发展.随着射流速度的增大,由于颗粒膜发生非轴对称振荡,均匀分布的细小波纹逐渐演变为波长增大的显著波纹.图3 稠密颗粒射流倾斜撞击流动模式可视化图像 (a),(e)水,u0=1.46m/s;(b),(f)Dp=82µm,u0=1.41 m/s,xp=0.32;(c),(g)Dp=122µm,u0=1.39m/s,xp=0.23;(d),(h)Dp=246µm,u0=1.64 m/s,xp=0.13Fig.3.Flow regimes of dense granular impinging jets:(a),(e)Water,u0=1.46m/s;(b),(f)Dp=82µm,u0=1.41 m/s,xp=0.32;(c),(g)Dp=122µm,u0=1.39m/s,xp=0.23;(d),(h)Dp=246µm,u0=1.64 m/s,xp=0.13.图4 稠密颗粒射流倾斜撞击振荡模式可视化图像(Dp=82µm) (a),(d)u0=1.41m/s,xp=0.33;(b),(e)u0=3.62 m/s,xp=0.25;(c),(f)u0=7.43m/s,xp=0.20Fig.4.Images of surface waves of dense granular impinging jets at Dp=82µm:(a),(d)u0=1.41 m/s,xp=0.33;(b),(e)u0=3.62m/s,xp=0.25;(c),(f)u0=7.43 m/s,xp=0.20.图5为稠密颗粒射流倾斜撞击颗粒膜正面与侧面扩展角的变化特征.结果显示,随着射流速度的增大,颗粒膜正面扩展角先增大后减小,而侧面扩展角一直增大.将图5与图4进行对比,可以发现,颗粒膜正面扩展角达到峰值时的速度与颗粒膜开始发生非轴对称振荡对应的速度基本一致.当颗粒膜发生非轴对称振荡时,颗粒除了具有沿竖直方向(yoz平面)的分速度之外,x方向也存在分速度,因此正面扩展角减小,侧面扩展角增大.从图5中还可以看出,在相同射流速度下,颗粒膜正面扩展角随颗粒粒径的减小而增大,侧面扩展角随颗粒粒径的变化不明显.这是因为随着颗粒粒径的增大,含固率降低,稠密颗粒射流撞击形态由颗粒膜逐渐向散射形态转变,颗粒也向x轴方向运动,颗粒变得分散,正面扩展角减小;对于侧面扩展角而言,改变颗粒粒径对其扩展角的影响不明显,说明射流速度对侧面扩展角的影响大于颗粒粒径对其的影响.图5 扩展角随射流速度变化特征 (a)正面扩展角;(b)侧面扩展角Fig.5.Variation of opening angles with velocities from the front view(a)and the side view(b).3.2 稠密颗粒射流倾斜撞击颗粒膜动态特征及影响因素从图4(a)—(c)中可以看出,颗粒膜非轴对称振荡由撞击点处产生,沿着y轴距离的增大,其振幅逐渐增大.在靠近撞击点处,颗粒膜振幅较小,统计困难;在距离撞击点较远处,颗粒膜上的颗粒发生散射,其振幅较难清晰分辨,统计误差较大,因此选取y/D=4作为特征位置对颗粒膜的非轴对称振荡进行表征.图6为稠密颗粒射流倾斜撞击颗粒膜侧面y/D=4处的非轴对称振荡频率和无量纲振荡幅度(Ab/D)随射流速度的变化特征.从图6中可以看出,随着射流速度的增加,颗粒膜振荡频率与无量纲振荡幅度均增大;随着颗粒粒径的增大,颗粒膜非轴对称振荡频率减小,无量纲振荡幅度增大;颗粒膜进行准周期的非轴对称振荡.图6 y/D=4处颗粒膜振荡频率和无量纲振荡幅度随射流速度变化特征(a)振荡频率;(b)无量纲振荡幅度Fig.6. Variation of oscillation amplitude and frequency with velocity at y/D=4:(a)Oscillation frequency;(b)non-dimensional oscillation amplitude.图7展示了颗粒膜表面波纹无量纲传播速度沿径向的变化特征.可以看出,稠密颗粒射流倾斜撞击表面波纹的无量纲传播速度沿y轴正向距离的增大而增大,并且颗粒膜表面波纹传播速度与射流速度之比(us/u0)在0.7—0.9之间.这是因为在此速度(u0>3.62 m/s)下,颗粒膜发生非轴对称振荡,所测得的表面波纹速度为颗粒流在y 方向的分速度,因此二者速度比小于1,而撞击后在重力的加速作用下,表面波纹速度沿y轴正向距离增大.钱文伟等[16]发现稠密颗粒射流撞壁实验中表面波纹速度与射流速度之比约为0.4,这是由于撞壁过程中颗粒间非弹性碰撞更加频繁,速度耗散较大,同时颗粒间基本无相互作用力,且波纹传播方向与重力方向垂直,因此随着径向距离的增大,表面波纹速度基本保持不变.黄国锋[23]发现液膜表面波纹的无因次传播速度在0.7—0.9之间,呈现逐渐减小的趋势.这是因为撞击之后液膜主要受到表面张力的影响,表面张力促使液膜收缩,阻碍波纹传播.图7 表面波纹无量纲速度沿y轴正向变化特征Fig.7.Variation of the non-dimensional velocity alongy direction.由图8(a)可以看出,稠密颗粒射流倾斜撞击产生的表面波纹频率随径向距离的增大而减小,相同位置处,射流速度越大,表面波纹频率越大.与射流速度相比,颗粒粒径对表面波纹频率的影响不显著.由图8(b)可知,颗粒膜表面波纹的波长随径向距离和射流速度的增大而增大.同时在颗粒膜表面波纹传播过程中观察到了颗粒膜波纹的叠加现象,并且波纹叠加现象在时间和空间位置上存在明显的偶然性和随机性,这与黄国锋等[24]发现的液膜上波纹的融合现象相似.颗粒膜上波纹的运动属于非稳态运动,波纹的运动速度存在瞬时波动性,这是导致波纹叠加的主要原因.如图9所示,该现象使得颗粒膜表面波纹频率随着径向距离的增大而减小,波长随着径向距离的增大而增大.图8 表面波纹频率及无量纲波长沿径向变化特征 (a)表面波纹频率;(b)无量纲波长Fig.8.Variation of the frequency and non-dimensional wavelength of surface waves along radial direction:(a)Frequency of surface waves;(b)non-dimensional wavelength of surface waves.图9 Dp=82µm,u0=3.87 m/s,xp=0.25时颗粒膜表面波纹叠加过程Fig.9.Merging process of surface waves at Dp=82µm,u0=3.87 m/s,xp=0.25.4 讨论实验中,在喷嘴出口观察到了明显的射流不稳定性现象,并且随着储料罐内空气压力的增大,颗粒射流速度增大,气固不稳定增强,射流不稳定性也增强.定义颗粒射流流量脉动频率fj为单位时间内喷嘴出口处颗粒射流由于不稳定性发生收缩或摆动的次数,如图10所示,将喷嘴出口射流流量脉动频率与y/D=4处颗粒膜非轴对称振荡频率进行对比,发现fb/fj大约为1,表明由气固不稳定性引起的喷嘴出口射流脉动是颗粒膜发生非轴对称振荡的关键因素.从图10中可以看出,随着射流速度的增大,气固不稳定性增强,射流脉动频率逐渐增大,因此颗粒膜发生非轴对称振荡的频率也增大.而在稠密颗粒射流撞击圆形壁面的实验研究中,认为颗粒膜上表面波纹的产生源于颗粒射流振荡不稳定性[18],其表面波纹频率主要受到射流不稳定频率的影响.由图8可知,颗粒膜表面波纹频率大于射流流量脉动频率,因为颗粒膜表面波纹既受喷嘴出口射流流量脉动的影响,也受到撞击不稳定性的影响[25].图10 Dp=82µm射流流量脉动频率与颗粒膜振荡频率的对比parison the pulsation frequency of the granular jet with oscillation frequency of the granular fi lm at Dp=82µm.5 结论采用高速摄像仪对稠密颗粒射流倾斜撞击过程进行了实验研究,刻画了稠密颗粒射流倾斜撞击的类流体颗粒膜现象,揭示了颗粒膜形成非轴对称振荡的原因.得到以下主要结论:1)稠密颗粒射流倾斜撞击主要呈现两种不同的形态,当颗粒粒径较小时,稠密颗粒射流倾斜撞击呈现类液体颗粒膜形态;随着颗粒粒径的增大,含固率减小,单位体积内所含颗粒数目减少,颗粒运动自由程增加,颗粒间碰撞概率减小,颗粒膜形态消失,形成散射形态;2)随着射流速度的增大,颗粒膜出现非轴对称振荡,颗粒膜表面出现波纹结构;颗粒膜的非轴对称振荡频率和振荡幅度随射流速度的增大而增大;当颗粒粒径与射流速度保持不变时,沿着传播方向的距离增大,表面波纹传播速度略微增大,且us/u0在0.7—0.9之间;因为波纹间存在叠加现象,沿着传播方向,其表面波纹波长增大,波纹频率降低;3)稠密颗粒射流撞击形成非轴对称振荡的主要因素是喷嘴出口由气固不稳定性引起的射流流量脉动,射流流量脉动频率与颗粒膜的非轴对称振荡频率基本相当,而颗粒膜表面波纹的形成原因较复杂,受到喷嘴出口射流流量脉动和撞击不稳定性的双重影响.参考文献[1]Wu Y 2001 Chem.Indus.Eng.Prog.11 8(in Chinese)[伍沅2002化工进展 11 8][2]Guo Q H,Yu G S,Wang F C,Wang Y F,Dai Z H 2017 XIAO Danfei 4 1(in Chinese)[郭庆华,于广锁,王辅臣,王奕飞,代正华2017氮肥与合成气4 1][3]Liang T,Bai J,Zhang L,Chang C,Fang S H,Han X L 2016Petrochem.Technol.3 360(in Chinese)[梁腾波,白净，张璐，常春，方书起，韩秀丽 2016石油化工 3 360][4]Liu H J,Zou C,Tian Z W,Zheng C G 2008 J.HuazhongUniv.Sci.Technol.(Natural Science Edition)5 106(in Chinese)[刘红娟,邹春,田智威,郑楚光2008华中科技大学学报:自然科学版5 106][5]Sun Z G,Li W F,Liu H F,Yu Z H 2009 Chem.Reaction Engineer.Technol.2 97(in Chinese)[孙志刚,李伟锋,刘海峰,于遵宏2009化学反应工程与工艺2 97] [6]Sun Z G 2009 Ph.D.Dissertation(Shanghai:East China University ofScience and Technology)(in Chinese)[孙志刚2009博士学位论文(上海:华东理工大学)][7]Xu H,Zhao H,Zheng C 2014 Chem.Eng.Process.Process Intensify 76 6[8]Du M,Hao Y L,Liu X D 2009 CIESC J.60 1950(in Chinese)[杜敏,郝英立,刘向东 2009化工学报 60 1950][9]Du M,Zhao C,Zhou B 2011 Chem.Eng.Sci.66 4922[10]Liu X,Chen Y,Chen Y 2014 Chem.Eng.Process.Process Intensify 79 14[11]Cheng X,Varas G,Citron D,Jaeger H M,Nagel S R 2007 Phys.Rev.Lett.99 188001[12]Cheng X,Gordillo L,Zhang W W,Jaeger H M,Nagel S R 2014 Phys.Rev.E 89 042201[13]Johnson C G,Gray J M N T 2011 J.Fluid Mech.675 87[14]Boudet J F,Amaroucheme Y,Bonnier B,Kellay H 2007 J.Fluid Mech.572 413[15]Boudet J F,Amaroucheme Y,Bonnier B,Kellay H 2005 Europhys.Lett.69 365[16]Qian W W,Li W F,Shi Z H,Liu H F,Wang F C 2016 Acta Phys.Sin.65 214501(in Chinese)[钱文伟,李伟锋,施浙杭,刘海峰,王辅臣2016物理学报 65 214501][17]Shi Z H,Li W F,Qian W W,Wang F C 2017 Chem.Eng.Sci.62 1[18]Shi Z H,Li W F,Liu H F,Wang F C 2017 AIChE J.63 3276[19]Huang Y J,Chan C K,Zamankhan P 2010 Phys.Rev.E 82 031307[20]Ge W,Chen F,Gao J 2007 Chem.Eng.Sci.62 3346[21]O’Rourke P J,Snider D M 2010 Chem.Eng.Sci.65 6014[22]Ellowitz J 2016 Phys.Rev.E 93 012907[23]Huang G F 2014 M.S.Dissertation(Shanghai:East China University of Science and Technology)(in Chinese)[黄国锋2014硕士学位论文(上海:华东理工大学)][24]Huang G F,Li W F,Tu G Y 2014 CIESC J.10 3789(in Chinese)[黄国峰,李伟锋,屠功毅 2014化工学报 10 3789][25]Li W F,Yao T L,Liu H F,Wang F C 2011 AIChE J.57 1434。

航空发动机专业英语词汇大全之欧阳历创编

航空发念头专业英语词汇年夜全，值得收藏！0129 航佳技术飞机维修砖家Part 1Para. 1gas turbine engine燃气涡轮发念头aircraft 飞机，遨游翱翔器（单复同形）power plant 发念头，动力装置appreciate 理解，意思到prior to 在…之前propulsion 推进reaction 反作用jet 喷气, 喷射, 喷气发念头designer 设计师initially 最初，开始时unsuitability 不适应性piston engine 活塞发念头airflow 空气流present 带来, 产生obstacle 障碍Para. 2patent 专利, 获得专利jet propulsionengine 喷气推进发念头athodyd 冲压式喷气发念头heat resistingmaterial 耐热资料develop 研究出，研制出in the secondplace 其次inefficient 效率底的ram jet, ramjet冲压式喷气发念头conception 构想, 设计，概念Para. 3grant 授予propulsive jet 推进喷射turbojet engine 涡轮喷气发念头turbojetturbopropellerengine涡轮螺桨发念头turbopropVickers Viscountaircraft 维克斯子爵式飞机be fitted with 配备term 术语, 称为, 叫做twinspool engine 双转子发念头triplespoolengine三转子发念头bypass engine 双涵道发念头ducted fan 涵道电扇发念头unducted fan (UDF)无涵道电扇发念头propfan 桨扇发念头inevitable 不成避免的, 必定的p.4propeller 螺旋桨basic principle 基来源根基理effect 产生propel 推进solely 单独, 只thrust 推力p.5popularly 普遍地, 一般地pulse jet 脉动式喷气发念头turbo/ram jet 涡轮冲压式喷气发念头turborocket 涡轮火箭p.6accelerate 加速acceleration 加速度apparatus 装置, 机器slipstream 滑流p.7momentum 动量issue 冒出to impart M to N 把M给与N revolve 旋转p.8whirl 旋转sprinkler 喷水器mechanism 机构by [in] virtue of 依靠hose 软管afford 提供carnival 狂欢节p.9definitely 确切地, 明确地assume 想象, 以为expel 排出, 驱逐propulsiveefficiency 推进效率Page 3p.10differ 不合convert 转换p.11thermodynamic 热动力的divergent 扩散diverge 扩散convergent 收敛converge收敛entry 进气段exit 排气管kinetic energy 动能air intake 空气进口diverging duct 扩散管道outlet duct 排气管missile 导弹target vehicle 靶机p.12intermittentcombustion 间断式燃烧aerodynamic 空气动力的involve 具有robust 结实的, 坚固的inlet valve 进气阀inject 喷入eject 喷出depression 降压, 减压exhaust 排气cycle 循环helicopter rotorpropulsion 直升飞机旋翼驱动器dispense with 省去, 无需resonate 共振resonating cycle 共振循环fuel consumption 燃油消耗equal 比得上performance 性能p.13decompose 分化p.14inherent 固有的draw 吸入p.15arrangement 结构simplicity 简单性subsequent 接下来的thermodynamic 热力的Page 7p.16disturbance 扰动bladetip 叶尖departure from 叛变p.17offset 抵消exceed 超出p.18Mach number 马赫数p.19variable intake 可变进口afterburning 加力燃烧variable nozzle 可调喷口conventional 惯例的afterburner 加力燃烧室inoperative 不工作的divert 使转向guide vane 导流叶片duct 管道，用管道输送sustained 继续的cruise 巡航mode 模式p.21multistageturbine 多级涡轮derive 获得，取得kerosene, kerosine煤油be in the orderof…达到…的量级spray 喷雾fuelrich mixture 富油混合物dilute 稀释surplus 剩余的p.22interceptor 截击机spacelauncher 航天发射器altitude 高度attitude 态度、姿态latitude 纬度longitude 经度accelerative 加速的duration 继续时间Part2Para.1working fluid 工作流体conversion 转换jet efflux 喷射气流Para.2fourstroke pistonengine 四冲程活塞发念头constant pressure 等压constant volume 等容induction 进气compression 压缩intermittent 间断的be involved in…与…有关charging 进气eliminate 消除idle stroke 空冲程Para.3peak 峰, 峰值fluctuate,fluctuating 摆荡, 起伏withstand,withstood 接受in excess of 超出employ 采取cylinder 汽缸high octane fuel 高辛烷值燃料low octane fuel 低辛烷值燃料fabricated 装配式的Para.4function 运行, 运转introduce,introducing 输入remainder 剩余部分discharge 排出Para.5,6turbine assembly 涡轮部件aircooled blade 气冷叶片consequently 随之而来的, 因此, 所以Para.7embody 体现be embodied in M 体现在M中be directlyproportional to…与…成正比be inversely proportional to…与…成正比Para.9trace 描绘show up 表示Para.10attain 达到, 实现conversely 相反地Para.11adiabatic 绝热的friction 摩擦conduction 传导turbulence 紊流Para.12propelling nozzle 推力喷管momentum 动量deceleration 减速Page 14Para.13effect 实现conversion 转换convert 转换sonic 音速的subsonic 亚音速的supersonic 超音速的encounter 遇到venturi 文氏管Para.14interference 干扰component failure 部件失效eddy 涡流turbulence 紊流Para.15frontal area 迎面面积straightthroughflow system 直流式系统reverse flowsystem 回流式系统subsequent 接下来的Para.17conventionally 惯例地percentage 部分，百分比duct 管道，用管道输送remainder 剩余物deliver 送，流to be conducive to…有利于…specific fuelconsumption 燃油消耗率Para.18design feature 设计特征bypass engine 双涵道发念头bypass ratio 涵道比twinspoolconfiguration 双转子结构propfan 桨扇发念头turbopropeller 涡轮螺桨发念头Para.19bypass airstream 外涵道气流overboard 向船外，排出ducted fan 涵道式电扇发念头aft fan 后电扇发念头Part 3Para.1centrifugal 离心的axial 轴流的couple 耦合，联接coupling 联轴器coupler联轴器shaft 轴Para.2centrifugal (flow)compressor 离心压气机impeller 叶轮diffuser 扩散器axial (flow)compressor 轴流压气机multistage unit 多级装置alternate 交替的rotor blade转子叶片stator vane 静子叶片diffuse 扩散boost 增压booster 增压器Para.3with regard to 关于robust 坚固，结实develop andmanufacture 设计与制造consume 消耗，使用attain 达到air flow 空气流量，空气流adoption 采取favour (Am. E favor) 喜爱，偏爱ruggedness坚固性rugged 坚固的outweigh 胜过，重于Fig. 31rotating guidevane 旋转导流叶片intake chute 进气斜道swirl vane 旋流叶片Para.5diffuser vane 扩散器叶片doubleentry impeller双面进气叶轮plenum chamber 稳流室Para.6induce 吸入radially 径向地intake duct 进气管initial swirl 预旋Para.7divergent nozzle 扩散排气管Para.8tip speed 叶尖速度Para.9maintain 坚持leakage 泄漏clearance 间隙Para.10construction 结构center around(about, at, in, on, round, upon)…以…为中心ball bearing 滚珠轴承roller bearing 滚柱轴承split 分隔detachment 拆开，别离forged 铸造的radially disposedvanes 径向排列的叶片in conjunctionwith…和…共同swept back 后掠Para.12attach 联接tangential 相切的inner edge 内缘in line with…与…一致buffeting impulse 扰流抖振脉冲Para. 13rotor assembly 转子部件airfoilsection 翼型截面mount 装置bearing 轴承incorporate 安有，装有in series 依次地design condition 设计状态incorporation 引入，采取variable statorvane 可调静子叶片succeeding stage下一级gradual reduction 逐渐减小annulus 环型stator casing 静子机匣maintain 坚持density 密度convergence 收敛taper，tapering 带斜度，带锥度arrangement 结构Para. 16multispoolcompressor 多转子压气机optimum 最佳（的），最优（的）flexibility 适应性，灵活性Para. 17handle 处理duct 管道，用管道输送exhaust system 排气系统propelling nozzle 推力喷管match 使匹配obsolete 已不必but 除…….之外Para. 18trend 趋势stage 阶段, 级undergo 接受split 分隔core 核心gas generator 燃气产生器optimumarrangement 最佳结构Para. 19induce 吸入，引入，引导sweep, swept 扫，猛推adjacent 相邻的translate 翻译，转换decelerate 减速serve 起……作用deflection 偏转straightener 整流器swirl 旋流diagrammatically 图示地accompany 陪伴progressive 不竭的，逐渐的Para. 20breakaway 别离stall 失速precede 在……前面Para. 21incidence 攻角tolerate 允许interstagebleed 级间放气intermediatestage 中间级Para. 22proportion 比例 pl. 尺寸, 年夜小coaxial 同轴的inner radius 内半径supercharge 增压akin 相似的Para.23to center around(round, on, upon, about, at, in)…以…为中心alignment 对中, 同心cylindrical 圆筒形的bolted axial joint轴向螺栓联接bolted center linejoint 中心线螺栓联接Para.24secure 固定assemble 装配weld 焊接periphery 边沿drum 鼓筒Para.25circumferential 周向的fixing 装置, 固定maintainability 维护性blisk 整体叶盘Para.26gradient 梯度balance out 抵消twist 扭angle of incidence攻角boundary layer 附面层, 鸿沟层stagnant 滞止的compensate for 赔偿camber 弯度extremity 端部endbend 端弯Para.27retaining ring 坚持环in segments 成组的shroud 叶冠Para.28dissimilar 不相似的, 不合的workable 可用的, 可运转的implement 实现, 执行, 完成retain 坚持Para.29impose upon…强加于…之上depart from 偏离intention 意图positive incidencestall 正攻角失速negative incidencestall 负攻角失速blading 叶栅sustain 接受得住surge 喘振instantaneous 即刻的expel 排出margin 欲度instability 不稳定性Para. 30provision 提供margin 欲度hydraulic 液压的pneumatic 气动的electronic 电子的Para. 31cost effective 本钱效益好的prevail 流行，胜利Para. 32rigid 刚性的clearance 间隙alloy 合金nickel based alloy镍基合金titanium 钛in preference to 优先于rigidity todensity ratio 刚度密度比Para. 33prime 主要的fatigue strength 疲劳强度notch 切口，开槽ingestion 吸气inferior 差的decline 下降rub 碰磨ignite 扑灭airworthiness 遨游翱翔性能hazard 危险Para. 34dominate 起支配作用Para. 35solid forging 实锻件chord 弦midspan 叶片中部snubber 减振器clapper 拍板fabricate 制造skin 蒙皮honeycomb 蜂窝Para. 36robust section 坚固截面ingestioncapability 吸气能力Part4Para.1fuel supply nozzle燃油喷嘴extensive 广泛的，年夜量的accomplish 完成Para.2range 规模CCentigrade orCelsiusturbine nozzle涡轮导向器Para.3consequent 随之产生的，结果的Para.4kerosene, cerosine煤油light, lit orlighted 扑灭blow, blew，blown 吹alight 燃烧的Para.5flame tube 火焰筒liner 衬筒meter, metering 调节配量Para.6snout 进气锥体downstream 下游，顺流swirl vane 旋流叶片perforated flare 带孔的喇叭管primary combustionzone 主燃区upstream上游，逆流promote 增进，引起recirculation 环流，回流Para.7secondary air hole二股气流孔toroidal vortex 喇叭口形涡流anchor, anchoring 锚，固定hasten 增进，加速droplet 小滴ignitiontemperature 燃点Para.8conical 锥形的intersect 相交turbulence 紊流break up, breakingup 割裂，破碎incoming 进来的Para.9nozzle guide vane 涡轮导向叶片amount to 占…比例, 达到progressively 逐渐地dilution zone 掺混区remainder 剩余物insulate M from N 使M与N隔离Para.10,11electric spark 电火花igniter plug 燃烧塞selfsustained 自持的Para.12airstream =airflowdistinct =different type injection 喷射，喷入ejection 喷射，喷出atomize 使雾化spray nozzle 喷嘴prevaporization 预蒸发Para.13vapor 蒸汽vaporize 蒸发vaporizer 蒸发器feed tube 供油管vaporizing tube 蒸发管atomizer flametube装有雾化喷嘴的火焰筒Para.14multiple(combustion) chamber 分担燃烧室tuboannular(combustion) chamber 环管燃烧室cannular(combustion) chamber 环管燃烧室annular(combustion) chamber 环形燃烧室Para.15F.g.46Para.16dispose 安插delivery 排气Para.17interconnect 互相连通propagate传播Para.18bridge a gapbetween填补空白，使连接起来evolutionary 成长，演变arrangement 结构overhaul 年夜修compactness 紧凑性Para.19contain 包含，装置be open to 与…相通Para.20elimination 消除propagation 传播Para.21virtually 实际上oxidize 氧化carbon monoxide 一氧化碳nontoxic 无毒的carbon dioxide 二氧化碳Para.22aerate, aerating 吹气，供气overrich pocket 过富区fuel vapour 燃油蒸汽carbon formation积碳形成Para.23incur 招致extinction 熄灭relight 重新扑灭perform,performing 完成，执行spray nozzleatomizer 喷嘴雾化器Para.25intensity 强度compact 紧凑的exceptionally 格外地，特别地Para.26calorific value 热值British thermalunit (BTU)英国热量单位=252卡expenditure 使用，消耗Para.27altitude cruise 高空巡航Para.29weak limit 贫油极限rich limit 富油极限extinguish 熄灭extinguisher 灭火器dive 爬升idle, idling 空载，慢速mixture strength 混合物浓度Para.30stability loop 稳定区Para.32emission 排放物pollutant污染物create 产生，形成legislatively 立法地hydrocarbon 碳氢化合物oxides of nitrogen氧化氮Para.34suppression 抑制desirable 合乎需要的conflict 冲突compromise 折中combustor 燃烧室substantially 实际上Para.35coating 涂层insulation 隔热，隔离Para.36corrosion 腐化creep failure 蠕变失效fatigue 疲劳Part5Para.1accessory,accessories 附件solely = onlyextract,extracting 提取to expose M to N 使M流露于NM is exposed to NPara.2torque 扭矩Para.3intermediate 中间的interpose 置于…之间to be derivedfrom…从…获得, 取自freepower turbine自由动力涡轮to be independentof…不受…的限制Para.4mean 平均的deflection 偏转in proportion to 按比例sectionalthickness 截面厚度disproportionately不相称地Para.5broadly 主要地aerofoil shape 翼型形状impulse turbine 冲击式涡轮reaction turbine 反作用式涡轮incorporate 采取cartridge starter 弹药筒式起念头air starter 空气起念头Para.7to force one’s wayinto 有力地冲入spin 旋转whirl 旋转Para.8to be governed by 取决于, 由…决定substantially 实际上, 年夜体上excessive 过分的residual 剩余的，剩余detrimental =harmfulstrut 支柱, 支杆Para.9twist, twisted 带扭向的stagger angle 斜罩角Para.10mean section 中间截面Para.12selfaligningcoupling 自动调节联轴器Para.15machined forging 机加锻件flange 法兰，装置边bolt 螺栓，用螺栓联结perimeter 周边，圆周to have provisionfor…为…作好准备attachment 联接, 装置Para.16heat conduction 热传导Para.17degree of reaction反力度Para.18fix 确定, 决定,trailing edge 排气边so as to (do) 为了prevent M (from)+ingPara.19attach联接, 装置fixing 联接have a bearing on …对…有影响rim speed 轮缘速度de Laval bulb root圆头叶根supersede 取代, 取代firtree fixing 纵树榫头联接involve 需要, 要求serration 榫齿stiffen 加劲, 固牢Para.20contraction 收缩shroud 叶冠fit 配备, 装置segment 部分, 片peripheral 外围的, 周边的abradable lining 易磨涂层A.C.C. activeclearance control shroudless blade 无冠叶片Para.21revolve 旋转extract 提取conventional 惯例的Para.22impractical 不实际的dual alloy disc 双金属轮盘blisk 整体叶轮cast 铸造bond 粘接Para.23match 匹配nozzle guide vane 涡轮导向叶片back pressure 反压surge 喘振choke 壅塞，阻塞Para.24obstacle 障碍impart to…给与tensile stress 拉应力limiting factor 限制因素Para.25endure 接受nickel alloy 镍合金ceramic coating 陶瓷涂层enhance 增强Para.26resistance 抵当，耐fatigue cracking 疲劳破坏Para.27ferritic 铁素体terrific 可怕的，极妙的austenitic 奥氏体alloying element 合金元素extend 延长fatigue resistance抗疲劳性powder metallurgy 粉末冶金Para.28in connection with关于，与…有关glowing redhot 赤热发光ounce 盎施=28.35 gbending load 弯曲载荷thermal shock 热冲击corrosion 腐化oxidization 氧化Para.29foregoing 前面的, 上述的it follows that 因此, 可见permissible 允许的metallurgist 冶金学家Para.30creep 蠕变finite useful life有限使用寿命failure 失效Para.31forge 铸造forging 锻件cast 铸造creep property 蠕变性能fatigue property 疲劳性能Para.32reveal 揭示, 显示a myriad of 无数crystal 晶体equiaxed 等轴的service life 使用寿命directionalsolidification 定向凝固useful creep life 有效蠕变寿命single crystalblade 单晶叶片substantially 实质上, 显著地Para.33reinforced ceramic加固陶瓷Para.34balancing 平衡operation 工序in view of 考虑到Part 6Para.1aero 航空的pass 排送resultant thrust 合成推力，总推力create 引起，产生contribute 提供absorb 吸收exert an influenceon…对…产生影响jet pipe 尾喷管propelling nozzle 推力喷管outlet nozzle 出口喷管Para.2distortion 扭曲, 变形cracking 产生裂纹Para.3thrust reverser 推力反向装置noise suppressor 消音器entail 需要, 要求low bypass engine低涵道比发念头mixer unit 掺混装置encourage 增进Para.4exhaust cone 排气锥hold 坚持residual whirl 剩余旋流strut 支板straighten 整流Para.5in relation to…对…来说choked 壅塞, 阻塞upstream totalpressure 上游总压pressure thrust 压力推力momentum 动量Para.6wastage 损失, 消耗with advantage 有效地convergentdivergentnozzle 收扩喷管recover 重新获得Para.7flared 扩张的restriction 限制progressively 逐渐地longitudinal 纵向的Para.9fixed area nozzle 固定面积喷口variable areanozzle 可变面积喷口offset 抵消Para.13nickel 镍titanium 钛ventilate,ventilating 通风lag, lagging 用隔热资料呵护insulating blanket隔热层fibrous 纤维状的stainless steel 不锈钢dimple 使起波纹acousticallyabsorbent material 吸声资料Para.14doublewallconstruction 双壁结构induce 引导ejector action 喷射器作用engine nacelle 发念头短舱Para.15streamline fairing流线型整流板欧阳历创编2021..02.09欧阳历创编2021..02.09。

jet aime

jet aimeJet Aime: The Ultimate Guide to Jet EnginesIntroduction:Jet Aime, also known as Jet Love, is a term used to describe the fascination and admiration people have for jet engines. These powerful machines have revolutionized the way we travel and play a vital role in various industries. In this comprehensive guide, we will explore the history, mechanics, and applications of jet engines, shedding light on the reasons behind the Jet Aime phenomenon.I. History of Jet Engines1. The Early Years: The first concepts and designs of jet engines were pioneered by scientists and engineers in the early 20th century. Notable figures such as Sir Frank Whittle and Hans von Ohain contributed to the development of these engines.2. World War II: Jet engines played a crucial role in aircraft during World War II, with Germany's Messerschmitt Me 262 becoming the first operational jet-powered fighter plane.3. Post-War Advancements: Following the war, improved engine designs were developed by countries worldwide. Theadvent of commercial air travel further accelerated the advancements in jet engine technology.II. How do Jet Engines Work?1. Basic Principles: Jet engines work on the principle of the conservation of momentum. Air is drawn into the engine, compressed, mixed with fuel, ignited, and expelled at high speeds to create thrust.2. Main Components: Jet engines consist of several key components, including the compressor, combustion chamber, turbine, and exhaust nozzle. Each component has a specific role in the engine's operation.3. Types of Jet Engines: There are different types of jet engines, including turbojet, turbofan, turboprop, and ramjet engines. Each type has unique characteristics and applications.III. Applications of Jet Engines1. Commercial Aviation: Jet engines power most commercial airliners, enabling faster, more efficient, and longer-distance travel. They have significantly reduced travel times and made air travel more accessible to the masses.2. Military Aviation: Fighter jets and military aircraft rely on jet engines for their high speed, maneuverability, and firepower.Jet engines have vastly improved military capabilities and provided strategic advantages in warfare.3. Space Exploration: Rockets and spacecraft also utilize jet engines, enabling them to break free from Earth's gravitational pull and enter space. Jet engines play a critical role in launching satellites, conducting space exploration missions, and enabling human space travel.IV. Advancements and Future of Jet Engines1. Fuel Efficiency: Modern jet engine designs aim to improve fuel efficiency and reduce carbon emissions. Efforts are being made to develop more efficient engines through advanced materials, design optimizations, and alternative fuels.2. Noise Reduction: Noise pollution from jet engines has been a concern, particularly in densely populated areas. Ongoing research and development aim to reduce noise levels through technological advancements and aerodynamic improvements.3. Hypersonic Flight: The future of jet engines lies in achieving hypersonic speeds, enabling extremely fast travel and revolutionizing air transportation. This technology could potentially reduce long-haul travel times significantly.Conclusion:Jet engines have undeniably transformed the world of travel and technology. The Jet Aime phenomenon reflects the awe-inspiring power, versatility, and ingenuity of these machines. As advancements continue to push the boundaries of what jet engines can achieve, it is certain that Jet Aime will persist and captivate the minds of enthusiasts worldwide.。

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PACS numbers: 45.70.-n, 45.70.Mg, 47.50.Tn
arXiv:0706.2027v1 [cond-mat or two particles strike a smooth wall at normal incidence, they rebound in the direction whence they came. Yet, as we show here, a dense stream of noncohesive particles hitting a target retains its integrity and deforms into a thin sheet with a shape resembling the structures created by an impinging water jet [1, 2]. Thus the collective behavior of many particles diﬀers qualitatively from that of the individual components. When can a jet of discrete particles be modeled as a liquid [3, 4, 5, 6] and how do the liquid patterns emerge out of individual particle scattering events from a target? Such questions, posed and investigated here with granular materials, have their counterpart in much more microscopic situations such as the quark-gluon plasma caused by relativistic high-energy collisions of gold ions, which also produces scattering patterns indicative of a liquid state (author?) [7, 8]. Our ﬁndings provide a macroscopic, purely classical example of how strong interactions, mediated by rapid collisions in a densely packed region, can give rise to liquid behavior. When a water stream hits a ﬂat target, it spreads symmetrically in the direction transverse to the impact and deforms into a thin sheet. For targets smaller than the stream diameter, the sheet forms a hollow bell-shaped structure that envelopes the target. Such ”water bells” were reported in 1883 by Savart [1] and have been systematically studied by Clanet [2]. By contrast, with the exception of several simulations and experiments on granular streams passing by solid obstacles at relatively low particle density and speed [9, 10, 11], little is known about the structures emerging from equivalent experiments using granular material rather than a liquid. Here, we examine a non-cohesive granular jet colliding with a target. For jets many particles wide, the impact produces granular sheets and cones similar to those seen for water with structures that depend on the ratio of the jet to the target diameter. In this regime, we conclude that the granular medium behaves as if it were a liquid with inﬁnite Weber number – that is, with zero surface ten-
Collective behavior in a granular jet: Emergence of a liquid with zero surface-tension
Xiang Cheng,1 German Varas,1, ∗ Daniel Citron,1 Heinrich M. Jaeger,1 and Sidney R. Nagel1
1
The James Franck Institute and Department of Physics, The University of Chicago, Chicago, IL 60637 (Dated: February 1, 2008) We perform the analog to the “water bell” experiment using non-cohesive granular material. When a jet of granular material, many particles wide, rebounds from a ﬁxed cylindrical target, it deforms into a sharply-deﬁned sheet or cone with a shape that mimics a liquid with zero surface tension. The particulate nature of granular material becomes apparent when the number of particles in the cross-section of the jet is decreased and the emerging sheets and cones broaden and gradually disintegrate into a broad spray. This experiment has its counterpart in the behavior of the quarkgluon plasma generated by collisions of gold ions at the Relativistic Heavy Ion Collider. There a high density of inter-particle collisions gives rise to collective behavior that has also been described as a liquid.
sion appropriate for a system of non-cohesive particles. The particulate nature of the material becomes apparent when the sheets and cones broaden and gradually disintegrate as the number of particles in the beam is decreased. We prepared our dense jets by packing granular material into a 40cm section of a glass launching tube of inner diameter DJet = 0.73cm (Fig.1a). The grains, which were compacted to a reproducible density by tapping, were mono-disperse spherical beads of glass (ρ = 2.5g/cm3) or copper (ρ = 8.2g/cm3) with diameters between d = 50µm and d = 2.1mm. Prior to ﬁlling the tube, we baked the beads in vacuum to minimize any residual adhesion between beads. Pressurized gas accelerated this granular plug into a jet which hits a target 2.5cm in front of, and collinear with, the tube. The jet velocity U0 could be varied between 1 and 16m/s. The impacts were ﬁlmed at 2000 frames/second with a Phantom V7.1 camera. Fig.1b and c show the side and front views respectively of a colliding jet. Since there are very few collisions inside it, the jet maintains its cylindrical shape before hitting the target, consistent with jets produced when a sphere impacts loosely packed powers [12, 13]. After hitting the target, the jet deforms into an extraordinarily thin symmetric granular sheet clearly resembling a spreading liquid. To investigate the similarities between granular and ordinary liquid jets, we ﬁrst keep the jet diameter, DJet , ﬁxed at values much larger than the particle diameter, d, and vary the target diameter, DT ar , as shown in Fig.1d. When DT ar is reduced, these planar sheets change into cones with opening angle, ψ0 < 90◦ . Fig.2 shows that ψ0 increases linearly with DT ar /DJet until ψ0 saturates at 90◦ above DT ar /DJet ∼ 2. Glass and copper beads produces essentially identical behavior. We can compare our results with those from Clanet [2] for water jets, who found that the opening angle, ψ , of the “water bell” depends on the Weber number 2 We = ρU0 DJet /σ , where U0 is the jet velocity and ρ the density and σ the surface tension of water. In the