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Halo properties in models with dynamical Dark Energy

Halo properties in models with dynamical Dark Energy
Halo properties in models with dynamical Dark Energy

a r X i v :a s t r o -p h /0303304v 1 13 M a r 2003

Halo properties in models with dynamical Dark Energy

A.Klypin

Astronomy Department,New Mexico State University,Box 30001,Department 4500,Las Cruces,NM

88003-0001

A.V.Macci`o ,R.Mainini &S.A.Bonometto

Physics Department G.Occhialini,Universit`a degli Studi di Milano–Bicocca,Piazza della Scienza 3,

I20126Milano (Italy)

I.N.F.N.,Via Celoria 16,I20133Milano (Italy)

ABSTRACT

We study properties of dark matter halos in a variety of models which include Dark En-ergy (DE).We consider both DE due to a scalar ?eld self–interacting through Ratra–Peebles or SUGRA potentials,and DE with constant negative w =p/ρ>?1.We ?nd that at redshift zero the nonlinear power spectrum of the dark matter,and the mass function of halos,practically do not depend on DE state equation and are almost indistinguishable from predictions of the ΛCDM model.This is consistent with the nonlinear analysis presented in the accompanying paper.It is also a welcome feature because ΛCDM models ?t a large variety of data.On the other hand,at high redshifts DE models show substantial di?erences from ΛCDM and substan-tial di?erences among themselves.Halo pro?les di?er even at z =0.DE halos are denser than ΛCDM in their central parts because the DE halos collapse earlier.Nevertheless,di?erences between the models are not so large.For example,the density at 10kpc of a DE ~1013M ⊙halo deviates from ΛCDM by not more than 50%.This,however,means that DE is not a way to ease the problem with cuspy dark matter pro?les.Addressing another cosmological problem -abundance of subhalos –we ?nd that the number of satellites of halos in various DE models does not change relative to the ΛCDM,when normalized to the same circular velocity of the parent halo.To summarize,the best way to ?nd which DE model ?ts the observed Universe is to look for evolution of halo properties.For example,the abundance of galaxy groups with mass larger than 1013h ?1M ⊙at z >~2can be used to discriminate between the models,and,thus,to constrain the nature of DE.

Subject headings:methods:analytical,numerical –galaxies:clusters –cosmology:theory –dark energy

1.Introduction

Mounting observational evidence for Dark En-ergy (Perlmutter et al.1999;Riess et al.1998;Tegmark,Zaldarriaga,&Hamilton 2001;Netter-?eld et al.2002;Pogosian,Bond,&Contaldi 2003;Efstathiou et al.2002;Percival et al.2002;Spergel et al 2003),which probably contributes ~70%of the critical density of the Universe,rises a number of questions regarding consequences for galaxy formation.Traditionally,DE is described

by the parameter w =p/ρcharacterizing its equa-tion of state.The ΛCDM model (w =?1)was extensively studied during the last decade.Mod-els with a constant negative w >?1were much less studied,let alone physically motivated models with variable w (Mainini,Macci`o ,&Bonometto 2003;Mainini et al.2003),for which no N–body simulation has been performed yet.Observations (Spergel et al 2003;Schuecker et al.2003)limit the present day value of w <~?0.8,though the limit has been derived for constant–w models only.

In the accompanying paper(Mainini et al. 2003)we describe procedures and give approx-imations for di?erent quantities encountered in the linear and nonlinear analyzes of?uctuations in models in which DE is produced by a self–interacting scalar?eld(dynamical DE).In this paper we use these approximations to perform N–body simulations of models with dynamical DE and to study di?erent properties of dark matter halos in such N?body simulations.For complete-ness we also study models with constant w=?0.6 and w=?0.8

Our main interest is in the models with varying w.These models use physically motivated poten-tials of scalar?eld and admit tracker solutions. We focus on the two most popular variants of dy-namical DE(Wetterich1988;Ratra&Peebles 1988;Wetterich1995).The?rst model was pro-posed by Ratra&Peebles(1988,RP hereafter). It produces rather slow evolution of w.The sec-ond model(Brax&Martin1999;Brax,Martin, &Riazuelo2000;Brax&Martin2000)is based on simple potentials in supergravity(SUGRA). It results in much faster evolving w.Hence,RP and SUGRA potentials cover a large spectrum of evolving w.These potentials are written as V(φ)=

Λ4+α

φα

exp(4πGφ2)SUGRA.(2)

HereΛis an energy scale,currently set in the range102–1010GeV,relevant for fundamental in-teraction physics.The potentials depend also on the exponentα.The parametersΛandαde-?ne the DE density parameter?DE.However, we prefer to useΛand?DE as independent pa-rameters.Figure10in Mainini et al.(2003)gives examples of w evolution for RP and SUGRA mod-els.The RP model considered in this paper has Λ=103GeV.At redshift z=0it has w=?0.5. The value of w gradually changes with the red-shift:at z=5it is close to?0.4.The SUGRA model has w=?0.85at z=0,but w drastically changes with redshift:w≈?0.4at z=5.Al-though the w interval spanned by the RP model covers values signi?cantly above-0.8(not favored by observations),this case is still important both as a limiting reference case and to emphasize that models with constant w and models with variable w produce di?erent results even if average values of w are not much di?erent.Constant w models have no physical motivation and can only be justi-?ed as toy models to explore the parameter space. The typical values of w observed in dynamical DE models,however,suggest to use w=?0.8and w=?0.6for the models with constant w.

2.Simulations

The Adaptive Re?nement Tree code(ART; Kravtsov,Klypin&Khokhlov1997)was used to run the simulations.The ART code starts with a uniform grid,which covers the whole computa-tional box.This grid de?nes the lowest(zeroth) level of resolution of the simulation.The stan-dard Particles-Mesh algorithms are used to com-pute density and gravitational potential on the zeroth-level mesh.The ART code reaches high force resolution by re?ning all high density regions using an automated re?nement algorithm.The re?nements are recursive:the re?ned regions can also be re?ned,each subsequent re?nement hav-ing half of the previous level’s cell size.This cre-ates a hierarchy of re?nement meshes of di?erent resolution,size,and geometry covering regions of interest.Because each individual cubic cell can be re?ned,the shape of the re?nement mesh can be arbitrary and match e?ectively the geometry of the region of interest.

The criterion for re?nement is the local density of particles:if the number of particles in a mesh cell(as estimated by the Cloud-In-Cell method) exceeds the level n thresh,the cell is split(“re?ned”) into8cells of the next re?nement level.The re-?nement threshold may depend on the re?nement level.The code uses the expansion parameter a as the time variable.During the integration,spa-tial re?nement is accompanied by temporal re?https://www.wendangku.net/doc/049462727.html,ly,each level of re?nement,l,is in-tegrated with its own time step?a l=?a0/2l, where?a0is the global time step of the zeroth re?nement level.This variable time stepping is very important for accuracy of the results.As the force resolution increases,more steps are needed to integrate the trajectories accurately.Extensive tests of the code and comparisons with other nu-merical N-body codes can be found in Kravtsov (1999)and Knebe et al.(2000).The code was modi?ed to handle DE of di?erent types.

Fig. 1.—The mass function of isolated halos in the

ΛCDM and RP models.The masses are found within virial radii.Results of all the rest of the models are in between these two models.At z =0there is no dif-ference between the mass functions.The dot-dashed curve shows ST prediction.At z =2the mass func-tions of w =?1models are above that of the ΛCDM.

A large number of simulations were performed.The simulations have di?erent sizes of computa-tional box,di?erent force and mass resolutions.Table 1lists parameters of all our simulations.This large set of simulations allows us to study properties of halos ranging from dwarf satellites to clusters of galaxies.All simulations were exten-sively studied.We ?nd that in all cases the results are bracketed by the ΛCDM and the RP models.Normally,di?erences between models are not very large.In order to avoid too crowded plots,in most of the presented plots we show only results of these two models.3.

Statistics of halos:power spectrum,mass and velocity functions

Figure 1shows the mass function for isolated halos in the RP and the ΛCDM models.The sim-ulations have the same initial phases and the same value σ8=0.75.Thus,the di?erences between models are only due to di?erent w (t ).Remark-ably,at z =0the mass functions are practically indistinguishable:a mass function has no

“mem-Fig.2.—The evolution of the number density of halos

with virial mass larger than 1013h ?1Mpc for di?erent models.The bottom and top symbols are for N ?body results in ΛCDM and in RP models.The curves show ST approximations.The dashed (dot-dashed)curve is for w =?0.6(SUGRA)models.There is hardly any di?erence between models at redshifts smaller than z =1.At higher z the number of halos in ΛCDM de-clines faster than for other models.

ory”of the past evolution.In this ?gure we show only two models,but all other models show the same results at z =0.The mass function is well ?tted by the approximation provided by Sheth &Tormen (ST,Sheth &Tormen 1999;Sheth,Mo &Tormen 2001;Sheth &Tormen 2002).

At higher redshifts the situation is quite dif-ferent:mass functions deviate substantially.Bot-tom panel in Figure 1clearly demonstrates this:the number of clusters with mass large than ≈3×1013h ?1M ⊙is almost ten times larger in the RP simulation.The di?erences depend on mass.They are larger for massive clusters and much smaller for less massive halos.For galaxy-size ha-los with mass ~1012h ?1M ⊙the di?erences are only ~20%,which will be di?cult to detect ob-servationally.

The dependence of halo abundance with red-shift is further illustrated in Figure 2,where we study halos with mass of a group of galaxies.There is almost no way to distinguish models at

Table1

Parameters of simulations

Modelσ8Box size Number of particles Mass resolution Force resolution

(h?1Mpc)(h?1M⊙)(h?1kpc) recent times z<1.But at z=2?3the dif-

ferences are quite signi?cant.We note that ob-

servational detection of group-size halos at high

redshifts is di?cult,but feasible.We know how

these objects should look like-almost the same as

nearby groups.A group at high redshift should be

more compact than a group at z=0and it should

consist of3-10Milky-Way size galaxies.Galaxies

are expected to be distorted by interactions.A

sample of few thousands galaxies can be used to

count the number of https://www.wendangku.net/doc/049462727.html,parison with the

number of groups at present moment seems to be

the way to discriminate between di?erent models

of DE.

For each halo we?nd the density pro?le and

estimate the maximum circular velocity V circ=

Fig.4.—Power spectrum of?uctuations of dark mat-ter for theΛCDM(full curves)and for the RP(dashed curves)models at di?erent redshifts.The dot-dashed curves show linear spectra for theΛCDM model.At high redshifts?uctuations in the RP model are larger than for theΛCDM model resulting in earlier collapse and in more dense halos.The di?erences in P(k)are the largest at z=2?3.

in the case of the mass function,the di?erences be-tween models are larger at high redshifts.At given redshift the di?erences are larger for massive ha-los.Still,the velocity function brings new results. Even at z=2the mass functions are very close for low mass halos with virial mass≈1012h?1M⊙. These halos have V circ≈200km/s.The velocity functions at that V circ are visibly di?erent:RP model has about1.5times more halos.The only way to explain this is to have more concentrated halos in RP model.In the next section we will explore this possibility in detail.

Figure4shows the evolution of the power spec-trum P(k)for?uctuations in the dark matter. The power spectrum basically follows the same pattern as the mass function:relatively large di?erences at high redshift,which become much smaller at z=0.At z=0the deviations remain only on small scales(k>

2).Fig.5.—Pro?le of the same halo simulated in di?er-ent models.The full curve is for theΛCDM model. The shot(long)dashed curve is for SUGRA(RP)mod-els.The halo has the virial mass5×1013h?1M⊙.For di?erent DE models the density pro?les are practically the same in the outer R>100h?1kpc region.Each pro?le is well approximated by the NFW pro?le.

4.Halo structure

We start our study of halo pro?les by making high resolution simulations of the same halo in dif-ferent models.The halo was initially identi?ed in a low resolution run.Short waves were added to the spectrum of initial perturbations and the halo was simulated again using≈2×105particles.In theΛCDM model the halo has virial mass5×1013h?1M⊙and virial radius730h?1kpc.It is ac-curately?tted by the NFW pro?le(Navarro,Frenk &White2002)with the concentration C vir=7.2. In the RP model the virial radius is680h?1kpc–visibly smaller than for theΛCDM halo.The RP halo also have larger maximum circular velocity as compared with theΛCDM halo.Figure5shows pro?les of the halo in theΛCDM,RP,and SUGRA models.In spite of the fact that the virial radii for all the models are di?erent,the density pro?les in the outer part of the halo R>100h?1kpc are prac-tically the same:from100h?1kpc to700h?1kpc the di?erences are less than10%.The halos di?er only in the central region R<100h?1kpc.The RP halo is clearly denser and more concentrated

than theΛCDM halo with the SUGRA halo being in between.This di?erence can be used to discrim-inate between the models.Yet,it will not be easy because the di?erences are relatively small:factor 1.5at10h?1kpc.

The RP has a smaller virial radius because the virial radius in the RP model is de?ned at larger overdensity(?vir,RP=149.8ρcr).This is the pre-diction of the top-hat model of halo collapse used to de?ne the virial mass(Mainini et al.2003). There is nothing wrong with it,but it complicates the comparison of density pro?les and concentra-tions in di?erent DE models.For example,a halo with exactly the same pro?le will have di?erent virial radii and,thus,di?erent concentrations in di?erent DE models.In order to make compari-

son of density pro?les less ambiguous,we decided to measure the halo concentration as the ratio of the radius at the overdensity of theΛCDM model (103times the critical density)to the characteris-tic(“core”)radius of the NFW pro?le.The e?ect of using the radius at the constant overdensity in-stead of the virial radius is relatively small.For typical RP halo with virial mass~1013h?1M⊙the virial radius is~15%smaller as compared with the constant overdensity radius.

We also study pro?les of hundreds of halos in simulations with lower resolution.Figure6 shows the dependence of halo concentration on the mass of halos in simulations with80h?1Mpc box withσ8=0.75.This plot shows the same tendency,which we found for the high-resolution halo:models with dynamical DE produce more concentrated halos.Figure7shows the distri-bution of halo concentrations for halos in mass range(5?10)×1013h?1M⊙.Halos with large deviations from NFW?ts(non-relaxed halos)are not used.The spread of concentrations in the ΛCDM model is about twice smaller than in Bul-lock et al.(2001).

Abundance of subhalos in theΛCDM model is a known problem(Klypin et al.1999;Moore et al.1999).It is interesting to?nd where dynamical DE models stand regarding the problem.Because ?uctuations in dynamical DE models collapse ear-lier than in theΛCDM model,one naively ex-pects that the number of subhalos is also larger. We study the number of subhalos in a high reso-lution halo.The halo is simulated in the RP and theΛCDM models.The halo with virial

mass Fig.6.—Dependence of concentration on halo mass. Halos for models with w=?1are all more concen-trated and,thus,are denser than the halos in the ΛCDM model.To avoid crowding we show statistical errors only for theΛCDM

model.

Fig.7.—Distribution of halo concentrations for ha-los in mass range(5?10)×1013h?1M⊙for di?erent models.Halos with large deviations from NFW?ts (non-relaxed halos)are not used.

2.4×1013h?1M⊙is resolved with particles of mass

Fig.8.—Abundance of subhalos in a halo with virial

mass M vir =2.4×1013h ?1M ⊙.When normalized to the circular velocity of the parent halo,the ve-locity function is the same for both the RP and the ΛCDM models and is well approximated by the power-law n (>V )∝V ?2.75.Vertical bars indicate the shot-noise errors.

1.3×108h ?1M ⊙.The maximum circular velocity of the halo in ΛCDM (RP)model is 522km/s (594km/s).The force resolution ≈1h ?1kpc al-lows us to resolve dwarf DM halos with circular velocity larger than 30km/s.For each (sub)halo we measure the density pro?le and estimate the value of the maximum circular velocity.

The number of subhalos in the RP halo is larger than in the ΛCDM halo:Inside the radius with the mean overdensity 103of the critical density there are 87satellites in the RP halo and 52satel-lites in the ΛCDM model.Thus,there are a factor of 1.7more satellites in the RP halo.Nevertheless,this large di?erence can be misleading because the circular velocity of the RP halo is larger by factor 1.14and halos with larger circular velocity have a tendency to have more satellites (Klypin et al.1999).In Figure 8we plot the number of satellites as the function of the ratio of the satellite velocity to the halo velocity.Di?erences between the mod-els are very small.It is also interesting to note that the velocity function of the subhalos is well approximated by the power-law n (>V )∝V ?2.75.

The slope of the power is the same as for subhalos of Milky Way-size halos (Klypin et al.1999).In other words,it indicates that the slope does not depend on the mass of halo and does not depend on the DE equation of state.5.

Discussion and conclusions

Models with the dynamical DE are in infant state.We do not know the nature of DE.Thus,a great arbitrariness exists on the choice of the equation of state w (t ).

At ?rst sight it seems that the situation is hope-less.This paper shows that this is not true:if we accept that w is close to -1at z =0,as many ob-servations suggest,and that w monotonically in-creases with redshift,dynamical models are useful and can produce de?nite predictions for proper-ties of halos and for galaxies hosted by the halos.Furthermore,the di?erences between rather ex-treme models of DE appear to be relatively small.In other words,one can make detailed predictions for properties of dark matter halos and for their clustering without knowing too many details of w evolution.Yet,the di?erences between models of DE exist and can be used to constrain the value and the evolution of w .In particular,distinguish-ing DE models by using only the value of w at the present time is clearly insu?cient.

The main tendency,which we ?nd in all DE models is that halos tend to collapse earlier.As the result,they are more concentrated and more dense in the inner parts.Nevertheless,di?erences are not so large.For example,the density at 10kpc of a ~1013M ⊙halo in a dynamical DE model deviates from ΛCDM not more than by 50%.This,however,means that DE is not a way to ease the problem with cuspy dark matter pro-?les.Nevertheless,the di?erences in halo pro?les can be exploited.Denser cluster pro?les in dy-namical DE models can be tested by both the weak (Bartelmann et al 2002)and especially by the strong gravitational lensing.Bartelmann et al (1998)and Meneghetti et al (2000)argue that the arclet statistics favors ΛCDM models when com-pared with the open CDM models.In this respect dynamical DE models are between the above two models.This problem deserves further investiga-tion.

We ?nd that the best way to ?nd which DE

model?ts the observed Universe best is to look for evolution of halo properties.For example,com-parison of low-and high-z(z>~2)abundances of galaxy groups with mass larger than1013h?1M⊙can be used to discriminate between models.Po-tentially,clustering of galaxies at redshifts2?3 can also be used for this.

In this paper we mostly pay attention to the group-size halos with mass~1013h?1M⊙at high redshifts as a probe for the DE.In the accompany-ing paper Mainini et al.(2003)we also argue that abundance of clusters at intermediate redshifts can be used as a test for DE models.Available cluster samples,unfortunately,still include too few clus-ters at intermediate and high redshift.

To directly investigate the cluster mass function at intermediate redshift with optical instruments, deep optical or near infrared data are used.Ex-ploiting this kind of data the Red–Sequence Clus-ter Survey(Gladders&Yee2000)and the Las Campanas Distant Cluster Survey(Nelson et al. 2002)were compiled.Taking carefully in to ac-count selections e?ects is rather hard and these samples include just tenth of objects.Selection e?ects are easier to handle for clusters detected in X–rays.The ROSAT data were used to com-pile a number of cluster catalogs(Ebeling et al. 1996,2000;de Grandi et al.1999).The most nu-merous sample of?ux limited clusters(REFLEX: Guzzo et al1999,Schuecker et al2003b)is based on the ROSAT observations.It includes426ob-jects with redshifts up to z~0.3.The XMM Survey(Pierre2000)will add another800clusters with redshifts up to z~1.Hopefully,follow–up optical programs will provide redshifts for the clusters in the catalogs.While designed for dif-ferent goals,REFLEX have been already used to constrain many cosmological parameters such as σ8,and,together with SNIa data,it provides im-portant constraints on the DE equation of state (Schuecker et al2003a).

The Suniaev-Zeldovich(SZ)e?ect(scattering of CMB photons by the hot intracluster gas)is even more promising for detection of high–z clus-ters(La Roque et al,2003;Weller et al2002, Hu2003).The shallow all-sky survey that the PLANCK experiment will produce will be sup-plemented by narrower surveys covering a smaller fraction of the sky,based on interferometric de-vices(OCRA:Browne et al2000;SZA:Carlstrom et al2000;AMIBA:Lo et al2000;AMI:Kneisel 2001).

These new cluster catalogs require more exten-sive and detailed theoretical modeling.Confronta-tion of new observational data with theoretical predictions will be able to discriminate between di?erent DE models.

In our analysis we also address another impor-tant issue:the abundance of subhalos.It is well known(Klypin et al.1999;Moore et al.1999) that in theΛCDM model the number of predicted dwarf dark matter satellites signi?cantly exceeds the observed number of satellite galaxies in the Local Group.There are di?erent possibilities to explain this excess.The most attractive explana-tion is related with the reionization of the Universe resulting in heating of gas in dwarf halos,which prevents them from becoming galaxies(Bullock, Kravtsov,&Weinberg2001,?;Somerville2002; Benson et al.2002).

We?nd that the number of satellites of halos,at z=0,in various DE models does not change rel-ative to theΛCDM,when normalized to the same circular velocity of parent halo.If the reionization of the Universe is the solution of the problem,then the DE models predict an earlier reionization of the Universe,because the earlier collapse of dwarf dark matter halos requires an earlier reionization to avoid too many satellites at redshift zero.The recent WMAP results(Kogut et al2003,Spergel et al2003),can be interpreted as giving a large opacity for CMB photonsτ?0.17±0.04.If true, this requires that the reionization occurred at a redshift z ri~13–20,which is too large for the standardΛCDM model(Gnedin2000).If the early reionization happens in theΛCDM model, it would predict too few satellites for the Local Group because too few dwarf halos collapse that early.Models with SUGRA DE seem to be in a better position to?t WMAP results and,at the same time,the observed number of satellites:in fact,in this model,halos collapse at higher red-shifts as compared with theΛCDM model. ACKNOWLEDGEMENTS

We thank INAF for allowing us the CPU time to perform some of the simulations used in this work at the CINECA consortium(grant cnami44a on the SGI Origin3800machine).

REFERENCES

Bartelmann M.,Huss A.,Carlberg J.,Jenkins A.

&Pearce F.1998,A&A330,1

Bartelmann M.,Perrotta F.&Baccigalupi C.

2002,A&A396,21

Benson,A.J.,Lacey,C.G.,Baugh,C.M.,Cole, S.,&Frenk,C.S.2002,MNRAS,333,156 Brat,P.&Martin,J.,1999,Phys.Lett.,B468,40 Brax,P.&Martin,J.,2000,Phys.Rev.D,61, 103502

Brax P.,Martin J.&Riazuelo A.,2000,Phys.Rev.

D,62,103505

Browne,I.W.,et al.in“Radio Telescopes”

(SPIEProc.vol41015)edited by H.R.Butcher (2000)

Bullock,J.S.,Kravtsov,A.V.,&Weinberg,D.H.

2000,ApJ,539,517

Bullock,J.S.,Kravtsov,A.V.,&Weinberg,D.H.

2001,ApJ,548,33

Bullock J.,Kolatt T.,Sigad Y.,Somerville R., Kravtsov A.,Klypin A.,Primack J.&Dekel

A.2001,MNRAS,321,559

Carlstrom J.E.,et al.,in Constructing the Uni-verse with Cluster of Galaxies,2000,edited by

F.Durret and

G.Gerbal.

de Grandi et al.,1999,ApJ,514,148

Ebeling H.,Voges W.,Bohringer H.,Edge A.C., Huchra J.P.,Briel U.G.,1996,MNRAS,281, 799

Ebeling H.,Edge A.C.,Allen S.W.,Crawford C.S., Fabian A.C.,Huchra J.P.,2000,MNRAS,318, 333

Efstathiou,G.et al.,2002,MNRAS,330,29 Gladders,M.D.&Yee,H.K.C.,2000,AJ,120, 2148

Gnedin,N.Y.2000,ApJ,535,530

Guzzo L.et al1999,The Messenger,95,27

Hu W.,astro-ph/0301416,Klypin A.,Gottloeber S.,Kravtsov A.&Khokhlov

A.(1999)ApJ516,530

Klypin,A.,Kravtsov,A.V.,Valenzuela,O.,& Prada,F.1999,ApJ,522,82

Kneissl,R.,et al.,MNRAS.2001,328,783

Kogut et al.,2003,astro–ph/0302213

Kravtsov A.,Klypin A.&Khokhlov A.,1997ApJ, 111,73K

La Roque S.J.et al.,2003,ApJ,583,559

Lo K.Y.,et al.,in New Cosmological Data and the values of the Fundamental Parameters,2000, edited by https://www.wendangku.net/doc/049462727.html,senby and A.Wilkinson.

Lokas,E.L.,2002,astro-ph/0112031

Mainini R.,Macci`o A.V.&Bonometto S.A.,2003, NewA8,172

Mainini R.,Macci`o A.V.,Bonometto S.A.,& Klypin,A.,2003

Meneghetti M.,Bolzonella M.,Bartelmann M., Moscardini L.&Tormen G.2000,MNRAS314, 338M

Moore,B.,Ghigna,S.,Governato,F.,Lake,G., Quinn,T.,Stadel,J.,&Tozzi,P.1999,ApJ, 524,L19

Navarro,J.F.,Frenk,C.S.&White S.D.M.,1997, ApJ,490,493

Nelson A.E.,Gonzalez A.H.,Zaritsky D.&Dal-canton J.J,2002,ApJ,566,103

Netter?eld,C.B.et al.2002,ApJ,571,604

Percival W.J.et al.,2002,astro-ph/0206256,MN-RAS(in press)

Perlmutter S.et al.,1999,ApJ,517,565

Pierre M.,2000,astro-ph/0011166

Pogosian,D.,Bond,J.R.,&Contaldi,C.2003, astro-ph/0301310

Ratra B.,Peebles P.J.E.,1988,Phys.Rev.D,37, 3406

Riess,A.G.et al.,1998,AJ,116,1009

Schuecker P.,Caldwell R.R.,Boehringer H., Collins C.A.&Guzzo L.,2003astro-ph/0211480,A&A(in press)

Schuecker P.,Bhringer H.,Collins C.A.&Guzzo L.,2003,A&A,398,867

Sheth R.K.,Mo H.J.&Tormen G.,2001,MNRAS, 323,1

Sheth R.K.&Tormen G.,1999,MNRAS,308,119 Sheth R.K.&Tormen G.,2002,MNRAS,329,61 Somerville,R.S.2002,ApJ,572,L23

Spergel et al.2003,astro–ph/0302209 Tegmark,M.,Zaldarriaga,M.,&Hamilton,A.J.

2001,Phys.Rev.D,63,43007

Weller,J.,Battye,R.&Kneissl,R.2002, Phys.Rev.Lett.,88,231301

Wetterich C.,1988,Nucl.Phys.B,302,668 Wetterich C.,1995A&A301,32

With的用法全解

With的用法全解 with结构是许多英语复合结构中最常用的一种。学好它对学好复合宾语结构、不定式复合结构、动名词复合结构和独立主格结构均能起很重要的作用。本文就此的构成、特点及用法等作一较全面阐述,以帮助同学们掌握这一重要的语法知识。 一、 with结构的构成 它是由介词with或without+复合结构构成,复合结构作介词with或without的复合宾语,复合宾语中第一部分宾语由名词或代词充当,第二部分补足语由形容词、副词、介词短语、动词不定式或分词充当,分词可以是现在分词,也可以是过去分词。With结构构成方式如下: 1. with或without-名词/代词+形容词; 2. with或without-名词/代词+副词; 3. with或without-名词/代词+介词短语; 4. with或without-名词/代词 +动词不定式; 5. with或without-名词/代词 +分词。 下面分别举例: 1、 She came into the room,with her nose red because of cold.(with+名词+形容词,作伴随状语)

2、 With the meal over , we all went home.(with+名词+副词,作时间状语) 3、The master was walking up and down with the ruler under his arm。(with+名词+介词短语,作伴随状语。) The teacher entered the classroom with a book in his hand. 4、He lay in the dark empty house,with not a man ,woman or child to say he was kind to me.(with+名词+不定式,作伴随状语)He could not finish it without me to help him.(without+代词 +不定式,作条件状语) 5、She fell asleep with the light burning.(with+名词+现在分词,作伴随状语) Without anything left in the with结构是许多英 语复合结构中最常用的一种。学好它对学好复合宾语结构、不定式复合结构、动名词复合结构和独立主格结构均能起很重要的作用。本文就此的构成、特点及用法等作一较全面阐述,以帮助同学们掌握这一重要的语法知识。 二、with结构的用法 with是介词,其意义颇多,一时难掌握。为帮助大家理清头绪,以教材中的句子为例,进行分类,并配以简单的解释。在句子中with结构多数充当状语,表示行为方式,伴随情况、时间、原因或条件(详见上述例句)。 1.带着,牵着…… (表动作特征)。如: Run with the kite like this.

五种计算机语言的特点与区别

php语言,PHP(PHP: Hypertext Preprocessor的缩写,中文名:“PHP:超文本预处理器”)是一种通用开源脚本语言。语法吸收了C语言、Java和Perl的特点,入门门槛较低,易于学习,使用广泛,主要适用于Web开发领域。 特性:PHP 独特的语法混合了C、Java、Perl 以及PHP 自创新的语法;PHP可以比CGI 或者Perl更快速的执行动态网页——动态页面方面,与其他的编程语言相比,PHP是将程序嵌入到HTML文档中去执行,执行效率比完全生成htmL标记的CGI要高许多,PHP具有非常强大的功能,所有的CGI的功能PHP都能实现;PHP支持几乎所有流行的数据库以及操作系统;最重要的是PHP可以用C、C++进行程序的扩展。 Java语言,Java是一种可以撰写跨平台应用软件的面向对象的程序设计语言,是由Sun Microsystems公司于1995年5月推出的Java程序设计语言和Java平台(即JavaSE, JavaEE, JavaME)的总称。 Java 技术具有卓越的通用性、高效性、平台移植性和安全性,广泛应用于个人PC、数据中心、游戏控制台、科学超级计算机、移动电话和互联网,同时拥有全球最大的开发者专业社群。在全球云计算和移动互联网的产业环境下,Java更具备了显著优势和广阔前景。 Java的优势,与传统程序不同,Sun 公司在推出Java 之际就将其作为一种开放的技术。全球数以万计的Java 开发公司被要求所设计的Java软件必须相互兼容。“Java 语言靠群体的力量而非公司的力量”是Sun公司的口号之一,并获得了广大软件开发商的认同。这与微软公司所倡导的注重精英和封闭式的模式完全不同。 Sun 公司对Java 编程语言的解释是:Java 编程语言是个简单、面向对象、分布式、解释性、健壮、安全与系统无关、可移植、高性能、多线程和动态的语言。 python语言,是一种面向对象、直译式计算机程序设计语言,Python语法简洁而清晰,具有丰富和强大的类库。它常被昵称为胶水语言,它能够很轻松的把用其他语言制作的各种模块(尤其是C/C++)轻松地联结在一起。 常见的一种应用情形是,使用python快速生成程序的原型(有时甚至是程序的最终界面),然后对其中有特别要求的部分,用更合适的语言改写。 Python是完全面向对象的语言。函数、模块、数字、字符串都是对象。并且完全支持继承、重载、派生、多继承,有益于增强源代码的复用性。 Python支持重载运算符和动态类型。相对于Lisp这种传统的函数式编程语言,Python对函数式设计只提供了有限的支持。有两个标准库(functools, itertools)提供了Haskell和Standard

with用法归纳

with用法归纳 (1)“用……”表示使用工具,手段等。例如: ①We can walk with our legs and feet. 我们用腿脚行走。 ②He writes with a pencil. 他用铅笔写。 (2)“和……在一起”,表示伴随。例如: ①Can you go to a movie with me? 你能和我一起去看电影'>电影吗? ②He often goes to the library with Jenny. 他常和詹妮一起去图书馆。 (3)“与……”。例如: I’d like to have a talk with you. 我很想和你说句话。 (4)“关于,对于”,表示一种关系或适应范围。例如: What’s wrong with your watch? 你的手表怎么了? (5)“带有,具有”。例如: ①He’s a tall kid with short hair. 他是个长着一头短发的高个子小孩。 ②They have no money with them. 他们没带钱。 (6)“在……方面”。例如: Kate helps me with my English. 凯特帮我学英语。 (7)“随着,与……同时”。例如: With these words, he left the room. 说完这些话,他离开了房间。 [解题过程] with结构也称为with复合结构。是由with+复合宾语组成。常在句中做状语,表示谓语动作发生的伴随情况、时间、原因、方式等。其构成有下列几种情形: 1.with+名词(或代词)+现在分词 此时,现在分词和前面的名词或代词是逻辑上的主谓关系。 例如:1)With prices going up so fast, we can't afford luxuries. 由于物价上涨很快,我们买不起高档商品。(原因状语) 2)With the crowds cheering, they drove to the palace. 在人群的欢呼声中,他们驱车来到皇宫。(伴随情况) 2.with+名词(或代词)+过去分词 此时,过去分词和前面的名词或代词是逻辑上的动宾关系。

摄像头接口分类及

摄像头接口分类及基础知识

一、Camera 工作原理介绍 1.结构 2.工作原理 外部光线穿过 lens 后,经过 color filter 滤波后照射到 Sensor 面上, Sensor 将从 le ns 上传导过来的光线转换为电信号,再通过内部的 AD 转换为数字信号。如果 Sensor 没有集成 DSP,则通过 DVP 的方式传输到 baseband,此时的数据格式是 RAW DATA。如果集成了 DS P, RAW DATA 数据经过 AWB、则 color matr ix、 lens shading、 gamma、 sharpness、 A E 和 de-noise 处理,后输出 YUV 或者 RGB 格式的数据。 最后会由 CPU 送到 framebuffer 中进行显示,这样我们就看到 camera 拍摄到的景象了。3. YUV 与 YCbCr . 一般来说,camera 主要是由lens 和 senso r IC 两部分组成,其中有的 sensor IC 集成了 DSP,有的没有集成,但也需要外部 DSP 处

理。细分的来讲,camera 设备由下边几部分构成: 1) lens(镜头)一般 camera 的镜头结构是有几片透镜组成,分有塑胶透镜(Plastic)和玻璃透镜(Glass) ,通常镜头结构有:1P,2 P,1G1P,1G3P,2G2P,4G 等。 2) sensor(图像传感器) Senor 是一种半导体芯片,有两种类型:CCD(Charge Coupled Device)即电荷耦合器件的缩写和 CMOS(Co mplementary Metal-Oxide Semiconductor)互补金属氧化物半导体。Sensor 将从 lens 上传导过来的光线转换为电信号,再通过内部的AD 转换为数字信号。由于 Sensor 的每个 pi xel 只能感光 R 光或者 B 光或者 G 光,因此每个像素此时存贮的是单色的,我们称之为 R AW DATA 数据。要想将每个像素的 RAW DATA 数据还原成三基色,就需要 ISP 来处理。 注:

真理的定义和特点以及谬误的区别

、真理的定义和特点以及谬误的区别 定义:真理是人们对客观事物及其规律的正确反映。 特点:1、真理具有客观性。真理的内容是客观的;检验真理的标准是客观的。 2、真理具有价值性。真理的价值性是指真理对人类实践活动的功能性,它揭示了客观真理具有能满足主体需要、对主体有用的属性。 9.资本循环和资本周转(资本循环的三个阶段三大职能,两大前提条件;资本周转的定义,影响周转的因素) 资本循环指产品资本从一定的形式出发,经过一系列形式的变化,又回到原来出发点的运动。产品资本在循环过程中要经历三个不同的阶段,于此相联系的是资本依次执行三种不同的职能: 第一个阶段是购买阶段,即生产资料与劳动力的购买阶段。它属于商品的流通过程,在这一阶段,产业资本执行的是货币资本的职能。 第二个阶段是生产阶段,即生产资料与劳动者相结合生产物质财富并使生产资本得以增值,执行的是生产资本的职能。 第三个阶段是售卖阶段,即商品资本向货币资本的转化阶段。在此阶段产业资本所执行的是商品资本的职能,通过商品买卖实现商品的价值,满足人们的需要。 资本循环必须具备两个基本前提条件: 一是产业资本的三种职能形式必须在空间上同时并存,也就是说,产业资本必须按照一定比例同时并存于货币资本、生产资本和商品资本三种形式中。 二是产业资本的三种职能形式必须在时间上继起,也就是说,产业资本循环的三种职能形式必须保持时间上的依次连续性。 资本周转是资本反复不断的循环运动所形成的周期性运动。 影响资本周转最重要的两个要素是:一是资本周转的时间;二是生产资本的固定资本和流动资本的构成。要加快资本周转的时间,获得更多的剩余价值,就要缩短资本周转时间,加快流动资本周转速度。 第五章 2.垄断条件下竞争的特点 竞争目的上,垄断竞争是获取高额利润,并不断巩固和扩大自己的垄断地位和统治权力;竞争手段上,垄断组织的竞争,除采取各种形式的经济手段外,还采取非经济手段,使经济变得更加复杂、更加激烈; 在竞争范围上,国际市场的竞争越来越激烈,不仅经济领域的竞争多种多样,而且还扩大到经济领域范围以外进行竞争。 总之,垄断条件下的竞争,不仅规模大、时间长、手段残酷、程度更加激烈,而且具有更大的破坏性。 3.金融寡头如何握有话语权 金融寡头在经济领域中的统治主要通过“参与制”实现。所谓参与制,即金融寡头通过掌握

独立主格with用法小全

独立主格篇 独立主格,首先它是一个“格”,而不是一个“句子”。在英语中任何一个句子都要有主谓结构,而在这个结构中,没有真正的主语和谓语动词,但又在逻辑上构成主谓或主表关系。独立主格结构主要用于描绘性文字中,其作用相当于一个状语从句,常用来表示时间、原因、条件、行为方式或伴随情况等。除名词/代词+名词、形容词、副词、非谓语动词及介词短语外,另有with或without短语可做独立主格,其中with可省略而without不可以。*注:独立主格结构一般放在句首,表示原因时还可放在句末;表伴随状况或补充说明时,相当于一个并列句,通常放于句末。 一、独立主格结构: 1. 名词/代词+形容词 He sat in the front row, his mouth half open. Close to the bank I saw deep pools, the water blue like the sky. 靠近岸时,我看见几汪深池塘,池水碧似蓝天。 2. 名词/代词+现在分词 Winter coming, it gets colder and colder. The rain having stopped, he went out for a walk.

The question having been settled, we wound up the meeting. 也可以The question settled, we wound up the meeting. 但含义稍有差异。前者强调了动作的先后。 We redoubled our efforts, each man working like two. 我们加倍努力,一个人干两个人的活。 3. 名词/代词+过去分词 The job finished, we went home. More time given, we should have done the job much better. *当表人体部位的词做逻辑主语时,不及物动词用现在分词,及物动词用过去分词。 He lay there, his teeth set, his hands clenched, his eyes looking straight up. 他躺在那儿,牙关紧闭,双拳紧握,两眼直视上方。 4. 名词/代词+不定式 We shall assemble at ten forty-five, the procession to start moving at precisely eleven. We divided the work, he to clean the windows and I to sweep the floor.

常用摄像机的分类

常用摄像机的分类 根据不同感光芯片划分 我们知道感光芯片是摄像机的核心部件,目前摄像机常用的感光芯片有ccd和cmos 两种: 1.ccd摄像机,ccd称为电荷耦合器件,ccd实际上只是一个把从图像半导体中出来的电子有组织地储存起来的方法。 2.cmos摄像机,cmos称为“互补金属氧化物半导体”,cmos实际上只是将晶体管放在硅块上的技术,没有更多的含义。 尽管ccd表示“电荷耦合器件”而cmos表示“互补金属氧化物半导体”,但是不论ccd或者cmos对于图像感应都没有用,真正感应的传感器称做“图像半导体”,ccd和cmos传感器实际使用的都是同一种传感器“图像半导体”,图像半导体是一个p n结合半导体,能够转换光线的光子爆炸结合处成为成比例数量的电子。电子的数量被计算信号的电压,光线进入图像半导体得越多,电子产生的也越多,从传感器输出的电压也越高。 因为人眼能看到1lux照度(满月的夜晚)以下的目标,ccd传感器通常能看到的照度范围在0.1~3lux,是cmos传感器感光度的3到10倍,所以目前一般ccd摄像机的图像质量要优于cmos摄像机。 cmos可以将光敏元件、放大器、a/d转换器、存储器、数字信号处理器和计算机接口控制电路集成在一块硅片上,具有结构简单、处理功能多、速度快、耗电低、成本低等特点。cmos摄像机存在成像质量差、像敏单元尺寸小、填充率低等问题,1989年后出现了“有源像敏单元”结构,不仅有光敏元件和像敏单元的寻址开关,而且还有信号放大和处理等电路,提高了光电灵敏度、减小了噪声,扩大了动态范围,使得一些参数与ccd摄像机相近,而在功能、功耗、尺寸和价格方面要优于ccd,逐步得到广泛的应用。cmos传感器可以做得非常大并有和ccd传感器同样的感光度,因此非常适用于特殊应用。cmos传感器不需要复杂的处理过程,直接将图像半导体产生的电子转变成电压信号,因此就非常快,这个优点使得cmos传感器对于高帧摄像机非常有用,高帧速度能达到400到100000帧/秒。 按输出图像信号格式划分 模拟摄像机 模拟摄像机所输出的信号形式为标准的模拟量视频信号,需要配专用的图像采集卡才能转化为计算机可以处理的数字信息。模拟摄像机一般用于电视摄像和监控领域,具有通

功能和特点的区别Excel的主要功能和特点

功能和特点的区别Excel的主要功能和特点 Excel的主要功能和特点 Excel电子表格是office系列办公软的-种,实现对日常生活、工作中的表格的数据处理。它通过友好的人机界面,方便易学的智能化操作方式,使用户轻松拥有实用美观个性十足的实时表格,是工作、生活中的得力助手。 一、Excel功能概述; 1、功能全面:几乎可以处理各种数据 2、操作方便:菜单、窗口、对话框、工具栏 3、丰富的数据处理函数 4、丰富的绘制图表功能:自动创建各种统计图表 5、丰富的自动化功能:自动更正、自动排序、自动筛选等 6、运算快速淮确: 7、方便的数据交换能力 8、新增的Web工具 二、电子数据表的特点Excel 电子数据表软工作于Windows平台,具有Windows环境软的所有优点。而在图形用户界面、表格处理、数据分析、图表制作和网络信息共享等方面具有更突出的特色。工.图形用户界面Excel 的图形用户界面是标准的Windows的窗口形式,有控制菜单、最大化、最小化按钮、标题栏、菜单栏等内容。其中的

菜单栏和工具栏使用尤为方便。菜单栏中列出了电子数据表软的众多功能,工具栏则进一步将常用命令分组,以工具按钮的形式列在菜单栏的下方。而且用户可以根据需要,重组菜单栏和工具栏。在它们之间进行复制或移动操作,向菜单栏添加工具栏按钮或是在工具栏上添加菜单命令,甚至定义用户自己专用的菜单和工具栏。当用户操作将鼠标指针停留在菜单或工具按钮时,菜单或按钮会以立体效果突出显示,并显示出有关的提示。而当用户操作为单击鼠标右键时,会根据用户指示的操作对象不同,自动弹出有关的快捷菜单,提供相应的最常用命令。为了方便用户使用工作表和建立公式,Excel 的图形用户界面还有编辑栏和工作表标签。. 2.表格处理 Excel的另-个突出的特点是采用表格方式管理数据,所有的数据、信息都以二维表格形式(工作表)管理,单元格中数据间的相互关系一目了然。从而使数据的处理和管理更直观、更方便、更易于理解。对于曰常工作中常用的表格处理操作,例如,增加行、删除列、合并单元格、表格转置等操作,在Excel中均只需询单地通过菜单或工具按钮即可完成。此外Excel还提供了数据和公式的自动填充,表格格式的自动套用,自动求和,自动计算,记忆式输入,选择列表,自动更正,拼写检查,审核,排序和筛选等众多功能,可以帮助用户快速高效地建立、编辑、编排和管理各种表格。

with用法小结

with用法小结 一、with表拥有某物 Mary married a man with a lot of money . 马莉嫁给了一个有着很多钱的男人。 I often dream of a big house with a nice garden . 我经常梦想有一个带花园的大房子。 The old man lived with a little dog on the lonely island . 这个老人和一条小狗住在荒岛上。 二、with表用某种工具或手段 I cut the apple with a sharp knife . 我用一把锋利的刀削平果。 Tom drew the picture with a pencil . 汤母用铅笔画画。 三、with表人与人之间的协同关系 make friends with sb talk with sb quarrel with sb struggle with sb fight with sb play with sb work with sb cooperate with sb I have been friends with Tom for ten years since we worked with each other, and I have never quarreled with him . 自从我们一起工作以来,我和汤姆已经是十年的朋友了,我们从没有吵过架。 四、with 表原因或理由 John was in bed with high fever . 约翰因发烧卧床。 He jumped up with joy . 他因高兴跳起来。 Father is often excited with wine . 父亲常因白酒变的兴奋。 五、with 表“带来”,或“带有,具有”,在…身上,在…身边之意

摄像机类型与功能

摄像机类型与功能 电视监控系统的前端设备主要包括了:摄像机、镜头、云台、防护罩、支架、控制解码器、射灯等; 1:摄像机的选择 如果监视目标照度不高,对监视图像清晰度要求较高时,宜选用黑白CCD摄像机; 如果要求彩色监视时,因考虑加辅助照明装置或选用彩色�;黑白自动转换的CCD摄像机,这种摄像机当监视目标照度不能满足彩色摄像机要求时自动转化黑白摄像。 1>彩色摄像机:适用于景物细部辨别,信息量一般是黑白摄像机的10倍 2>黑白摄像机:适用于管线不住地区及夜间无法安装照明设备的地区 2:摄像机功能和工作原理 1>分辨率:表示摄像机分配率图像细节的能力,通常用电视线TVL表示,黑白摄像机水平清晰度一般选择450TVL左右; (1)25万像素左右,彩色分辨率为330线、黑白分配率420线左右的低档型; (2)25~38万像素之间,彩色分配率为420线,黑白分配率在500线上下的中档型 (3)38万以上,彩色分配率大于或者等于480线、黑白分配率,570线以上的高分配率2>灵敏度:在镜头光圈大小一定的情况下,获取规定信号电平所需要的最低靶面照度。 (1)普通型:正常工作所需照度为1~31 ux (2)月光型:正常工作所需照度为 0.1 lux左右 (3)星光型:正常工作所需照度为0.01 lux以下 (4)红外照明型:原则上可以为零照度,采用红外光源成像 3>信噪比:视频信号电平与噪声平之比,衡量摄像机质量的重要指标; 信噪比越高,图像越干净,质量就越高,通常在45~55dB之间; 4>工作温度:-10~+50dB是绝大多数摄像机生产厂家的温度指标 5>电源电压:国外摄像机交流电压适应范围是198~264V抗电源电压变化能力较强,国内摄像机交流电压适应范围一般是200~240,抗电源电压变化能力较弱;

各类格式的特点区分

在用各类软件设计时相信大家肯定存在着这样的问题,各种各样的格式让大家很是迷惑。没关系,福利来了,这里就给大家介绍了各种格式的特点应用。 TIFF格式 标签图像文件格式(Tagged Image File Format,简写为TIFF) 是一种主要用来存储包括照片和艺术图在内的图像的文件格式。它最初由Aldus公司与微软公司一起为PostScript 打印开发.TIFF文件格式适用于在应用程序之间和计算机平台之间的交换文件,它的出现使得图像数据交换变得简单。 TIFF是最复杂的一种位图文件格式。TIFF是基于标记的文件格式,它广泛地应用于对图像质量要求较高的图像的存储与转换。由于它的结构灵活和包容性大,它已成为图像文件格式的一种标准,绝大多数图像系统都支持这种格式。用Photoshop 编辑的TIFF文件可以保存路径和图层。 应用广泛 (1)TIFF可以描述多种类型的图像;(2)TIFF拥有一系列的压缩方案可供选择;(3)TIFF 不依赖于具体的硬件;(4)TIFF是一种可移植的文件格式。 可扩展性 在TIFF 6.0中定义了许多扩展,它们允许TIFF提供以下通用功能:(1)几种主要的压缩方法;(2)多种色彩表示方法;(3)图像质量增强;(4)特殊图像效果;(5)文档的存储和检索帮助。 格式复杂 TIFF文件的复杂性给它的应用带来了一些问题。一方面,要写一种能够识别所有不同标记的软件非常困难。另一方面,一个TIFF文件可以包含多个图像,每个图像都有自己的IFD 和一系列标记,并且采用了多种压缩算法。这样也增加了程序设计的复杂度。 文档图像中的TIFF TIFF格式是文档图像和文档管理系统中的标准格式。在这种环境中它通常使用支持黑白(也称为二值或者单色)图像的CCITT Group IV 2D压缩。在大量生产的环境中,文档通常扫描成黑白图像(而不是彩色或者灰阶图像)以节约存储空间。A4大小200dpi(每英寸点数分辨率)扫描结果平均大小是30KB,而300dpi的扫描结果是50KB。300dpi比200dpi更

with的用法

with[wIT] prep.1.与…(在)一起,带着:Come with me. 跟我一起来吧。/ I went on holiday with my friend. 我跟我朋友一起去度假。/ Do you want to walk home with me? 你愿意和我一道走回家吗 2.(表带有或拥有)有…的,持有,随身带着:I have no money with me. 我没有带钱。/ He is a man with a hot temper. 他是一个脾气暴躁的人。/ We bought a house with a garden. 我们买了一座带花园的房子。/ China is a very large country with a long history. 中国是一个具有历史悠久的大国。3.(表方式、手段或工具)以,用:He caught the ball with his left hand. 他用左手接球。/ She wrote the letter with a pencil. 她用铅笔写那封信。4.(表材料或内容)以,用:Fill the glass with wine. 把杯子装满酒。/ The road is paved with stones. 这条路用石头铺砌。5.(表状态)在…的情况下,…地:He can read French with ease. 他能轻易地读法文。/ I finished my homework though with difficulty. 虽然有困难,我还是做完了功课。6.(表让步)尽管,虽然:With all his money, he is unhappy. 尽管他有钱,他并不快乐。/ With all his efforts, he lost the match. 虽然尽了全力,他还是输了那场比赛。7.(表条件)若是,如果:With your permission, I’ll go. 如蒙你同意我就去。8.(表原因或理由)因为,由于:He is tired with work. 他工作做累了。/ At the news we all jumped with joy. 听到这消息我们都高兴得跳了起来。9.(表时间)当…的时候,在…之后:With that remark, he left. 他说了那话就离开了。/ With daylight I hurried there to see what had happened. 天一亮我就去那儿看发生了什么事。10. (表同时或随同)与…一起,随着:The girl seemed to be growing prettier with each day. 那女孩好像长得一天比一天漂亮。11.(表伴随或附带情况)同时:I slept with the window open. 我开着窗户睡觉。/ Don’t speak with your mouth full. 不要满嘴巴食物说话。12.赞成,同意:I am with you there. 在那点上我同你意见一致。13.由…照看,交…管理,把…放在某处:I left a message for you with your secretary. 我给你留了个信儿交给你的秘书了。/ The keys are with reception. 钥匙放在接待处。14 (表连同或包含)连用,包含:The meal with wine came to £8 each. 那顿饭连酒每人8英镑。/ With preparation and marking a teacher works 12 hours a day. 一位老师连备课带批改作业每天工作12小时。15. (表对象或关系)对,关于,就…而言,对…来说:He is pleased with his new house. 他对他的新房子很满意。/ The teacher was very angry with him. 老师对他很生气。/ It’s the same with us students. 我们学生也是这样。16.(表对立或敌对)跟,以…为对手:The dog was fighting with the cat. 狗在同猫打架。/ He’s always arguing with his brother. 他老是跟他弟弟争论。17.(在祈使句中与副词连用):Away with him! 带他走!/ Off with your clothes! 脱掉衣服!/ Down with your money! 交出钱来! 【用法】1.表示方式、手段或工具等时(=以,用),注意不要受汉语意思的影响而用错搭配,如“用英语”习惯上用in English,而不是with English。2.与某些抽象名词连用时,其作用相当于一个副词:with care=carefully 认真地/ with kindness=kindly 亲切地/ with joy=joyfully 高兴地/ with anger=angrily 生气地/ with sorrow=sorrowfully 悲伤地/ with ease=easily 容易地/ with delight=delightedly 高兴地/ with great fluency =very fluently 很流利地3.表示条件时,根据情况可与虚拟语气连用:With more money I would be able to buy it. 要是钱多一点,我就买得起了。/ With better equipment, we could have finished the job even sooner. 要是设备好些,我们完成这项工作还要快些。4.比较with 和as:两者均可表示“随着”,但前者是介词,后者是连词:He will improve as he grows older. 随着年龄的增长,他会进步的。/ People’s ideas change with the change of the times. 时代变了,人们的观念也会变化。5.介词with和to 均可表示“对”,但各自的搭配不同,注意不要受汉语意思的影响而用错,如在kind, polite, rude, good, married等形容词后通常不接介词with而接to。6.复合结构“with+宾语+宾语补足语”是一个很有用的结构,它在句中主要用作状语,表示伴随、原因、时间、条件、方式等;其中的宾语补足语可以是名词、形容词、副词、现在分词、过去分词、不定式、介词短语等:I went out with the windows open. 我外出时没有关窗户。/ He stood before his teacher with his head down. 他低着头站在老师面前。/ He was lying on the bed with all his clothes on. 他和衣躺在床上。/ He died with his daughter yet a schoolgirl. 他去世时,女儿还是个小学生。/ The old man sat there with a basket beside her. 老人坐在那儿,身边放着一个篮子。/ He fell asleep with the lamp burning. 他没熄灯就睡着了。/ He sat there with his eyes closed. 他闭目坐在那儿。/ I can’t go out with all these clothes to wash. 要洗这些衣服,我无法出去了。这类结构也常用于名词后作定语:The boy with nothing on is her son. 没穿衣服的这个男孩子是她儿子。 (摘自《英语常用词多用途词典》金盾出版社) - 1 -

扫盲7--安防摄像头6mm与3mm镜头的差异

安防摄像头6mm与3mm镜头的差异 差异肯定是有的,具体如下: 摄像机镜头是视频监视系统的最关键设备,它的质量(指标)优劣直接影响摄像机的整机指标,因此,摄像机镜头的选择是否恰当既关系到系统质量,又关系到工程造价。 镜头相当于人眼的晶状体,如果没有晶状体,人眼看不到任何物体;如果没有镜头,那么摄像头所输出的图像就是白茫茫的一片,没有清晰的图像输出,这与我们家用摄像机和照相机的原理是一致的。当人眼的肌肉无法将晶状体拉伸至正常位置时,也就是人们常说的近视眼,眼前的景物就变得模糊不清;摄像头与镜头的配合也有类似现象,当图像变得不清楚时,可以调整摄像头的后焦点,改变CCD芯片与镜头基准面的距离(相当于调整人眼晶状体的位置),可以将模糊的图像变得清晰。由此可见,镜头在闭路监控系统中的作用是非常重要的。工程设计人员和施工人员都要经常与镜头打交道: 设计人员要根据物距、成像大小计算镜头焦距,施工人员经常进行现场调试,其中一部分就是把镜头调整到最佳状态。 1、镜头的分类 按外形功能分按尺寸大小分按光圈分按变焦类型分按焦距长矩分球面镜头1 ” 25mm自动光圈电动变焦长焦距镜头 非球面镜头手动变焦标准镜头 针孔镜头固定焦距xx 鱼眼镜头 (1)以镜头安装分类所有的摄象机镜头均是螺纹口的,CCD摄象机的镜头安装有两种工业标准,即C安装座和CS安装座。两者螺纹部分相同,但两者从镜头到感光表面的距离不同。

C安装座: 从镜头安装基准面到焦点的距离是 17.526mm。CS安装座: 特种C安装,此时应将摄象机前部的垫圈取下再安装镜头。其镜头安装基准面到焦点的距离是 12.5mm。如果要将一个C安装座镜头安装到一个CS安装座摄象机上时,则需要使用镜头转换器。 (2)以摄象机镜头规格分类摄象机镜头规格应视摄象机的CCD尺寸而定,两者应相对应。 即摄象机的CCD靶面大小为1/2英寸时,镜头应选1/2英寸。摄象机的CCD靶面大小为1/3英寸时,镜头应选1/3英寸。摄象机的CCD靶面大小为1/4英寸时,镜头应选1/4英寸。如果镜头尺寸与摄象机CCD靶面尺寸不一致时,观察角度将不符合设计要求,或者发生画面在焦点以外等问题。 (3)以镜头光圈分类镜头有手动光圈(manualiris)和自动光圈(autoiris)之分,配合摄象机使用,手动光圈镜头适合于亮度不变的应用场合,自动光圈镜头因亮度变更时其光圈亦作自动调整,故适用亮度变化的场合。自动光圈镜头有两类: 一类是将一个视频信号及电源从摄象机输送到透镜来控制镜头上的光圈,称为视频输入型,另一类则利用摄象机上的直流电压来直接控制光圈,称为DC 输入型。自动光圈镜头上的ALC(自动镜头控制)调整用于设定测光系统,可以整个画面的平均亮度,也可以画面中最亮部分(峰值)来设定基准信号强度,供给自动光圈调整使用。一般而言,ALC已在出厂时经过设定,可不作调整,但是对于拍摄景物中包含有一个亮度极高的目标时,明亮目标物之影像可能会造成"白电平削波"现象,而使得全部屏幕变成白色,此时可以调节ALC来变换画面。另外,自动光圈镜头装有光圈环,转动光圈环时,通过镜头的光通量会发生变化,光通量即光圈,一般用F表示,其取值为镜头焦距与镜头通光口径之比,即:

产品特性与过程特性的区别

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