Fokker-Planck models of NGC 6397 -- A. The modeling
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Fokker-Planck models of NGC 6397–A.The modeling 1G.A.Drukier Institute of Astronomy,University of Cambridge ABSTRACT This is the ?rst of two papers presenting a detailed examination of Fokker-Planck models for the globular cluster NGC 6397.I show that these models provide a good match to observations of the surface density pro?le,mass functions at three radii and the velocity dispersion pro?le.The constraint of requiring the best matches to the mass functions and surface density pro?les to occur simultaneously de?nes a surface in an initial parameter space consisting of the cluster concentration,mass,and limiting radius.I discuss various techniques for locating this surface and the dependence of the quality of the matches on the position of the model on the surface,the initial mass function and the retention rate of neutron stars.The quality of the matches are usually strongly related to the age of the models,but one initial mass function was found for which the quality of the matches are independent of time.Subject headings:globular clusters:individual:NGC 6397–stellar dynamics 1.Introduction This binary paper is a an outgrowth of previous studies of the dynamics of the globular cluster M71(Lee,Fahlman,&Richer 1991;Drukier,Fahlman,&Richer 1992,hereafter DFR).
In DFR we attempted to compare detailed Fokker-Planck models with observations of M71.The approach taken there was to use star counts to measure the surface density pro?le and mass function of the cluster and radial velocities to measure the velocity dispersion,and then try to ?nd a Fokker-Planck model to match the observations.For M71no matching model was found and the nature of the discrepancy suggested that additional physical processes were required in the modeling.One of the main lacks in the DFR models,and in all other detailed comparisons between Fokker-Planck models and observations of globular clusters,was the absence of any allowance for the e?ects of stellar evolution.The di?culties in the case of M71left open the
question of whether these Fokker-Planck models were relevant to the question of globular cluster evolution.
Studies previous to DFR had found models to match observations,but these were for more limited data sets and for clusters with power-law cusps(Grabhorn et al.1992).Considering this success,it seemed natural to pursue the question of relevance by?rst adding stellar evolution
e?ects to the model,and then conducting a detailed comparison with a large set of observations of a cusp cluster,in this case NGC6397.
Since,as will be demonstrated in these papers,matching models can be found,there are two perspectives that can be taken.One perspective is that of the numerical modeler who is concerned with the details of the modeling and the comparison procedure,the size of the initial parameter space,and questions of uniqueness.The second perspective is much more narrowly focused and is concerned with what the models tell us speci?cally about the current state of a?airs in NGC 6397.In order to prevent an entangled perspective I have decided to split the discussion of these two aspects into two separate papers.In this,the?rst,I will discuss the details of the models used,the?tting procedure and the general results of the modeling.In particular,I will discuss in some detail the e?ects on the models of changes in the initial parameters.Here the NGC6397 data will be treated as a guide to the interpretation of the models.In the second paper(Drukier 1994,Paper B)I will look at the results from the other angle by examining the details of the best matching models.The discussions in the two papers are necessarily intertwined and the second especially will refer back to results and diagrams in this paper.The reader might consider them to be an interacting binary.
As it stood in DFR,the Fokker-Planck code,which is descended from the orbit-averaged, isotropic Fokker-Planck code of Cohn(1980),had been extended to include a mass function,a tidal boundary following the formulation of Lee&Ostriker(1987),and a heating term based on the formation and evolution of binaries formed in three-body interactions(“three-body binaries”; Lee1987;Lee et al.1991).The models used here have been further extended by introducing the e?ects of stellar evolution.In DFR,the models started with the mass function as it would be after
a Hubble time of stellar evolution.That is,it contained a main sequence terminating at about
0.8M⊙and the degenerate remnants of the higher mass stars.In these models it was assumed that the initial model was at some stage after the massive stars have evolved and that the further evolution of the lower mass stars was unimportant.Such an approach is clearly inconsistent with models meant to follow the full evolution of a globular cluster.The models presented here remove this inconsistency by including stellar evolution and pushing the assumed starting time much earlier conceptually.The expulsion of the left-over gas from the star-formation process is neglected.The details are discussed in the next section.
What is left out of a model can be as important as what is included.These models assume spherical symmetry and an isotropic velocity dispersion.The tidal stripping is idealized by assuming that the tidal boundary is spherically symmetric with respect to the cluster center and
that the strength of the tidal?eld is constant.The constancy of the tidal?eld excludes both slow changes and tidal shocks.A globular cluster in our galaxy can certainly be expected to su?er tidal shocks from passages through the disk,passages near the bulge,and from giant molecular clouds within the disk.Weinberg(1994)has recently shown that shock heating can result in large amounts of mass loss for clusters such as NGC6397.Also excluded are all e?ects of binaries except for the few“virtual”three-body binaries used as the energy source.Gao et.al(1991) included an initial population of binaries as one component in their two-component Fokker-Planck models.These delay core collapse and leave the post-collapse clusters with fairly large core radii of between1%and4%their half-mass radii.
In many ways NGC6397is a useful foil to M71.Both lie at about the same distance from the galactic center and the galactic plane,but M71has the metallicity and kinematics of the disk globular cluster system while NGC6397belongs to the halo population.NGC6397is also more massive and more centrally concentrated than M71and is regarded as a post-core-collapse cluster.From isochrone?tting the age of NGC6397is16±2.5Gyr(Anthony-Twarog,Twarog,& Suntze?1992).As discussed in DFR,the dynamical status of M71,ie.whether it is in a pre-or post-collapse phase,is unclear since the models give contradictory indications.NGC6397,from its high central concentration,is highly evolved dynamically and thus is a good candidate for comparison.The star count data for NGC6397is that of Drukier et al.(1993)supplemented by the mass function from Fahlman et al.(1989).The velocity dispersion pro?le of Meylan&Mayor (1991)has also been used.
I will begin with the description of the numerical models paying special attention to the new feature of stellar evolution.Section3.will discuss the method used to compare the models with the observations.Since minimal post-facto scaling is possible with these models,the results depend only on the initial parameters and the age of the model.Section3.2.will de?ne the initial parameters used here and§3.3.will give an overview of the e?ect varying these has on the resulting model.In total,over1000models went into the results to be presented in this paper.They were used to re?ne the description of the e?ects of parameter variation on the resulting model?ts.I de?ne a model set by their initial mass function(IMF)and the choice of tidal radius(see§3.2.).
I will look?rst at the largest of these model sets,will expand the discussion to include model sets with di?erent tidal radii,and subsequently di?erent IMFs.I will conclude by discussing the implications of these?ndings for future comparisons.A more general conclusion appears at the end of Paper B.
2.Models
With the exception of the inclusion of the e?ects of stellar evolution,the code used here is basically the same as that discussed in DFR.Brie?y,I use the isotropic,orbit-averaged form of the
Fokker-Planck equation,where the distribution function is a function of energy and stellar mass. The clusters are assumed to be spherically symmetric.The coupled Fokker-Planck and Poisson equations are solved by the two step process discussed more fully in Cohn(1980).First the
di?usion coe?cients are calculated and the distribution function is advanced in time in accordance with the Fokker-Planck equation.At this point the potential and the distribution functions are no longer consistent,so the second step is to solve the Poisson equation subject to the constraint that the distribution function remains the same function of the adiabatic invariant q(E)in the notation of Cohn(1980).The solution of the Poisson equation is done iteratively.
In order to reverse core collapse,an energy source is required.Here,I estimate statistically the number of binaries formed in three-body encounters and the energy released by each such binary as it is hardened by interactions with the?eld stars.At any time there are only a few such binaries present in the cluster,which is why the treatment is statistical.The prescription for doing this is discussed in Lee et al.(1991)and DFR.Alternative sources of energy are from initial population of binaries,or from binaries formed by close encounters and subsequent dissipation of orbital energy via tides in their atmospheres.These processes are not included in the models presented here.
The tidal boundary is imposed in energy space by de?ning the tidal energy boundary as the potential at the radius enclosing a?xed mean density.This radius is referred to as the tidal radius r t.The distribution functions are reduced exponentially for energies beyond this boundary with the stripping rate dependent on the di?erence between the energy and the tidal-energy.The rate is given by the formula in Lee et al.(1991)based on the derivation of Lee&Ostriker(1987).Two modi?cations have been made here.The?rst is to remove the discontinuity in the?rst derivative of the tidal stripping rate with respect to energy.Since the distribution function is a function of energy and not the adiabatic invariant,the iterative solution of the Poisson equation requires that it be regridded in E to preserve the dependence on q(E).The regridding is done via a second-order Taylor expansion of the the distribution function in terms of the adiabatic invariant.The e?ect of the discontinuity in the stripping rate is to introduce discontinuities in the?rst derivative of the distribution function.These are then ampli?ed by the regridding procedure and can lead to a catastrophic failure of the Poisson equation solver.To reduce the chances for this,the stripping rate has been smoothed over the transition region using a cubic polynomial which is required to be continuous to the?rst derivative.This is described in Appendix A.
The second modi?cation concerns the timing of the tidal stripping phase with respect to the two stages of advancing the Fokker-Planck equation and updating the potential.Since we need both the density pro?le and the potential to de?ne the tidal boundary,the tidal stripping must be done after the potential is updated and is once again consistent with the distribution functions, but before proceeding with the next Fokker-Planck step.This was the method used by Lee& Ostriker(1987).The problem with this is that the stripping is done on the distribution functions and afterward the potential and densities are once again inconsistent with them.If the amount of tidal stripping is small,this is only a small inconsistency;but in the late stages of the model’s
evolution the mass becomes small and the tidal losses proportionately large.The mass decreases approximately linearly with time and since r t∝M1/3,˙r t∝M?2/3.In cases where the rate of decrease in r t is large it becomes necessary to?nd a self-consistent solution.To correct for this problem an iterative scheme for simultaneously doing the tidal stripping and solving the Poisson equation was used.This scheme is described in Appendix B.
In their Fokker-Planck model,Cherno?&Weinberg(1990)used a somewhat di?erent scheme for tidal stripping.They found that in the late stages they were unable to?nd a self-consistent solution to the Poisson equation and the tidal boundary condition.What I?nd using the iterative scheme is that a self-consistent solution was possible in these situations.The di?erence arises
in that the tidal boundary condition of Cherno?&Weinberg(1990)is equivalent to f(E)=0 for E>E t(as de?ned in Appendix A.)which is discontinuous at E=E t.The tidal stripping condition used here ensures continuity in f(E)and its?rst two derivatives.Thus,a self-consistent solution is still possible even with extreme rates of tidal mass loss.
The addition of the e?ects of stellar evolution is the main change in the code from DFR.The approach used here is much the same as that used in Cherno?&Weinberg(1990).Even without stellar evolution a mass spectrum is desirable.To introduce this a mass grid is employed,with the mass spectrum being broken into a series of bins,each with its own mass and distribution function.Each of these can be considered a mass species which is meant to represent a range of stars with similar mass.The initial mass for each mass species is taken to be the geometric mean of the masses at the bin boundaries.In order to account for stellar evolution,we simply allow the mass for each mass species to change with time.The simplest way to specify this is to adopt functions for the stellar lifetimes and?nal masses for stars of a given initial mass.I assume that the stars evolve instantaneously from their initial masses to their?nal masses without worrying about the details of stellar evolution.
To be more speci?c,let t(m i)be the lifetimes of stars with initial mass m i and let m f(m i)be their?nal masses.I assume that at time t(m i)a star with initial mass m i becomes a star with mass m f(m i).The initial mass function(IMF)is given by N(m i)dm i.This is often taken to be a power law
N(m)dm∝m?(x+1)dm.(1) When the mass spectral index(MSI),x,is de?ned this way,the Salpeter mass function has
x=1.35.For a bin j with boundaries m i j?1and m i j,m i j?1 M j= m i j m i j?1m i N(m i)dm i.(2) The initial mass of mass species j is taken to be m i j?1m i j and the initial number of stars in the bin is N j=M j/m f j=m f( m i j to The main e?ect of mass loss due to stellar evolution is to reduce the depth of the potential and indirectly“heat”the cluster.To remain in virial equilibrium in the shallower potential,the kinetic energy of the cluster stars must also be reduced.Due to the negative speci?c heat of self-gravitating systems,this results in a net expansion,especially in the core.The closer to the cluster center the mass loss takes place,the more e?ective is the heating and the stronger the expansion.If,as is done here,the model starts with the relative proportions of the various mass species the same at all radii,then the e?ectiveness of stellar evolution in causing the expansion will depend on the ratio of the stellar evolution time scale,t se,to the dynamical evolution time scale. If t se is long compared to,for example,the central relaxation time,then the most massive stars will have time to sink to the center of the cluster through dynamical friction before they evolve. Their evolution is then a more e?ective energy source.The practical e?ect of the stellar evolution mass loss is to expand the cluster and delay core collapse beyond the time expected without such mass loss.The length of the delay,if indeed the mass loss doesn’t destroy the cluster entirely,is strongly dependent on the IMF,m f(m i),t(m i),and the initial structure. Cherno?&Weinberg(1990)based their stellar lifetimes on the Miller&Scalo(1979) compilation for Population I stars.For m i<4.7M⊙the masses of their white dwarf remnants were based on the formula of Iben&Renzini(1983)withη=1/3.The intermediate mass stars(4.7 In terms of?nding a model to match NGC6397,the stellar lifetimes chosen by Cherno?& Weinberg(1990)are not useful because of the e?ects of metallicity on stellar lifetimes.What is needed are the lifetimes of stars of all masses for[F e/H]=?1.9appropriate to NGC6397. Stellar models of the appropriate metallicity are available for low-mass stars,but no such models have been published for masses above about0.95M⊙.The most extensive set of stellar evolution models are those by the Geneva Observatory group(Schaller et al.1992;Shaerer et al.1993a,b; Charbonnel et al.1993).These cover the mass range from0.8to120M⊙,but only extend to Z=0.001.For stars with the metallicity of NGC6397,models with Z=0.0002are required.To estimate these,the lifetimes until the end of He burning for stars of varying metallicity at constant mass were taken from the Geneva models.For Z≤0.008the lifetimes of stars with m>5M⊙is approximately constant with varying metallicity so the lifetimes for Z=0.001were adopted.For m<5M⊙the lifetimes were extrapolated to Z=0.0002by a polynomial?t to the lifetimes for Z≤0.008.For m<1.25M⊙the lifetime goes as m?3.5and lifetimes for stars with m<0.8M⊙have been extrapolated assuming this power law.As a consistency check,I compared these ages with ages derived from the models of VandenBerg(1992).For the[Fe/H]=?2.030models,the ages agree to within5%.The lifetimes are given in Table1. There are several options for the choice of m f(m i).First,for M>8M⊙I have assumed that the remnants are1.4M⊙neutron stars.The situation for the stars which become white dwarfs is more complicated.Figure3of Weidemann and Yuan(1989)shows over a dozen di?erent proposals and models for this relation with a wide range of properties.The e?ect of varying the m f(m i) relation is to change the total amount of mass lost from the cluster through stellar evolution and to change the rate at which the mass is lost.This is most important in the early stages.A higher mass loss rate and a larger total mass loss at the same rate results in a greater expansion of the cluster.The e?ect on the time of core-collapse is more complicated.While a large cumulative mass loss results in a more expanded cluster,the total mass is also smaller.This reduces the relaxation time and could cause a quicker collapse.For the models described here I have used the scheme of Wood(1992): m f(m i)=0.4e m i/8.(3) for0.5M⊙ All of the models I discuss in these papers have t(m i)based on Table1and m f(m i)using eq. (3)for the stars less massive than8M⊙and1.4M⊙for the more massive stars. 3.Finding a match Locating a matching model for a particular set of observations is not an easy task.The available parameter space is large and the e?ects on the resulting models of changing individual parameters are complex and non-linear.The interaction of the various parameters provide tradeo?s which can be played against each other to achieve the desired end,but can also lead to models with quite di?erent initial conditions leading to equally good matches.Experience does lead to some useful guidelines and these will be discussed in§3.3. https://www.wendangku.net/doc/955801044.html,parison procedure To tell how well a particular model matches the NGC6397,the results of the model must be compared with the observations.Once a set of initial parameters has been decided on,the model is run and its state is periodically saved.Of these data,I have taken those in the interval between10.5and19Gyr for further analysis.In terms of scaling,once the tidal boundary,the three-body reheating mechanism and stellar evolution have been included in the model there are no global scales left free for adjusting.Thus the comparison procedure is fairly straight forward. The data available for comparison with the models are the surface density pro?le(SDP)and two mass functions(MFs)from Drukier et al.(1993),the intermediate-distance mass-function from Fahlman et al.(1989)and the velocity dispersion pro?le from Meylan&Mayor(1991).I will follow the naming convention from Drukier et al.(1993)and refer to the three mass functions as the du Pont:if,FRST,and du Pont:out MFs in order of distance from the cluster center. Since the observations are based on the projected distribution of stars in the cluster,the?rst thing to do is to project the density distributions and velocity dispersions for each mass species in the model.I then simulated the observing procedure by integrating the projected pro?les over appropriate regions.For the mass functions,the projected densities for each unevolved mass species were integrated over rectangular regions with the same size and orientation and at the same radial position as the observed?elds.The widths of the mass bins were then used to convert the integrated counts into numbers per unit mass.The observed and model mass functions are not on the same grid,so the model mass function is interpolated to give values at the observed mean masses.Since the model MF is smooth this is not di?cult.Aχ2statistic is calculated for each of the three pairs of observed and model mass functions using the observational uncertainties as weights.The quality of the match is judged by the mean of the three mass functionχ2statistics,χ2MF. Sets of annuli were de?ned matching the observed radii and mean densities within the annuli were integrated from the model density pro?le.There is a slight inconsistency here in that many of the observed data points are from sections of annuli rather than full annuli.The mean ofχ2 from the two magnitude limited surface density pro?les,χ2SDP,was used as the?gure of merit for the SDP?ts. There are several issues to be addressed before proceeding with the comparison of the model and observed pro?les.First,the observed pro?le is for stars above the main-sequence turn-o?. This is because of the brightness of these stars and the high degree of crowding in the images of this concentrated cluster.Therefore,the mass bin to use for comparison is the one which is currently evolving.With the scheme used for implementing stellar evolution,the mass of the currently evolving bin is usually less than the mass of the stars at the turn-o?.Once the mass drops,the stars in the evolving mass species becomes less concentrated and the mass species is no longer suitable for comparison.Instead of the evolving species I have used the next less massive one.The interval between0.74and0.90M⊙has been divided into seven mass species to ensure that the mass discrepancy is small.2 The second issue relates to the widths of the mass bins and the range of masses in the observed surface density pro?les.Drukier et al.(1993)produced two surface density pro?les with di?erent magnitude limits.The shallower pro?le(I<14.)extends into the center of the cluster while the deeper pro?le(I<15.5)is limited to radii greater than20′′from the cluster center. Without detailed information on the mass-luminosity relationship for the observed stars it is very di?cult to measure the mass range observed.Therefore,one free scaling parameter was allowed for in comparing the model and observed surface density pro?les.When theχ2SDP statistic was calculated a single rescaling was also?t by minimizing theχ2for each of the two SDPs.The two pro?les were?t separately and the known o?set of a factor of3.09(Drukier et al.1993)was employed.The mean rescaling was adopted andχ2SDP calculated. Similar techniques could not be employed for the velocity dispersions since the observed velocities were not available.Rather,the projected velocity dispersion pro?le for the model was plotted together with the observed data points and used to con?rm that the time which best?t the surface density pro?le and the mass functions also matched the dynamical information. It should be kept in mind during the comparisons discussed below thatχ2MF andχ2SDP are independent estimators of the quality of?t.The optimal model will be one that minimizes both at the same time and which also gives a velocity dispersion pro?le consistent with the data of Meylan&Mayor(1991).The age of the model at the optimal time should also be the age of stars in the cluster.Given the large uncertainties in determinations of the absolute ages of globular clusters,this requirement will not be applied too strictly,but the age should be between13and18 Gyr.As will be seen,once a range of parameters giving good matches is found,locating the best of these becomes a?ne tuning problem.In general,I have not tried to?nd the best-matching age for any given model,but have just adopted the best of the model dumps.While the model could be rerun with?ner time resolution,the di?erences in the?ts are small enough to be unimportant given the quality of the data.The models shown in Paper B have been rerun this way at around the age of their best match. 3.2.Initial parameters The IMF I initially used was the same as IMF J in Drukier(1992)where,of the10tried,it provided the best?t to the observed NGC6397mass functions.In§4.2.I will discuss the e?ects of variations in the IMF.The mass gridding has been changed to allow for?ner gridding between 0.74and0.90M⊙as discussed above.The IMF is made up of two power-laws,one with mass spectral index1.5for m<0.4M⊙and the second with x=0.9for m>0.4M⊙.The relative scalings were set so that the mass function is continuous at0.4M⊙.I will refer to models made with this IMF and the set of stellar data in§2.as“U20”models. The models start as King(1966)models with all species having the same initial pro?le.The initial structure of the model is de?ned by four parameters.The?rst is the dimensionless central potential of the King model,W0.The strength of the tidal?eld is given by the initial tidal radius, r t and the initial limiting radius of the model is r l.A more useful way to parameterize this is to use the ratio r l/r t.If ratio is unity then the initial model?lls its tidal volume,but this need not be the case.If r l/r t<1.then the model has room to expand before su?ering substantial tidal losses.The models are taken to travel on a circular orbit so that the strength of the tidal?eld is constant.The treatment of tidal stripping is further limited by the assumptions of spherical symmetry and an isotropy velocity dispersion.The tidal radius,r t,is given in terms of a cluster with mass105M⊙.The initial mass,M0,completes the speci?cation of the model once r t is rescaled by M0 3 M c as a function of age.What I call a“well-?tting model”will be one where both these minima occur simultaneously.The minima inχ2SDP occur close to,but before,core collapse,so the time of core collapse is a useful marker.The minima inχ2MF cluster around a optimal mass(see§2.1. in Paper B)and can be thought of as occurring when the model mass reaches this value.In Fig.1 I showχ2MF andχ2SDP as a function of time for one model.The two minima are not aligned and it is desirable to change the parameters to bring them into alignment at,preferably,an age older than13Gyr.To achieve this the following rules came in handy for this data set:?Changing M0alone tends to move both the time of optimal mass and the time of core collapse by about the same amount. ?Changing W0alone tends to not a?ect the time of core collapse by very much,but does change the time of optimal mass. ?Increasing r l alone(ie.r l/r t)reduces the time of optimal mass and,to a lesser extent,the time of core collapse. The inter-relationship of these rules de?nes the parameter surface containing the good models. For other sets of observations and in other clusters di?erent relationships may apply.In each case, the sensitivity of the results to changes in the initial parameters need to be estimated.They can then be used to formulate similar rules applicable to those data. 4.Results 4.1.The Parameter Surface In order to pursue the idea of a lower-dimension surface de?ned by the well-?tting models I ran a grid of models in the three-dimensional space de?ned by W0,M0,and r l/r t.As I explain in Paper B,the optimal value for r t is around20pc,but there is a wide range of acceptable values.The well-?tting models found in the hunting stage had r t=18or19pc so it was more straight-forward to look for a surface with r t=18.5since points on the surface were already approximately known.I later ran model sets with r t=17,20,and21pc and will discuss them further below.For now,it su?ces to note that the choice of r t does not a?ect the results very strongly.The region covered was4.01 In Fig.1I showχ2MF andχ2SDP as a function of time for a typical model.Note that this is not what I have been calling a“well-?tting”model since the two minima are not coincident.De?ning the di?erence in the time of minima as?t≡(time in minimum inχ2MF)?(time of minimum in χ2SDP),the locus of well-?tting models is that region of parameter space where?t=0.As might be expected,the well-?tting models de?ne a surface in(W0,M0,r l/r t)space.Since only a fraction of the models in the grid happen to lie on this surface,I estimated the position of the surface by interpolating along the grid.I took all the pairs of models di?ering in only one parameter and with?t of opposite signs and used linear interpolation between them to?nd the third parameter. The same procedure for these models,together with the data from the models with?t=0,gave the age of the model,χ2MF,andχ2SDP on the?t=0surface.This surface is fairly smooth,but has some thickness(±0.4Gyr)due to the?nite time resolution in the model results(see.§5.). Figure2shows this surface of well-?tting models.The contours give the estimated value of r l/r t as a function of W0and M0.The squares indicate the positions of the estimates used in constructing the contours and the circled squares are models which had?t=0.Contouring algorithms generally require points on a regular grid,so for the contour diagrams I de?ned a grid in(W0,M0)and used bi-linear interpolation to estimate the desired datum at each grid point from the values at the three nearest data points.Any grid point which did not have three data points closer than3.5grid spacings were ignored.These ignored points are indicated by dots in Fig.2 and show the size of the interpolating grid.Features on this scale are artifacts of the contouring process.The contours are spaced by0.05in r l/r t with thicker contours every0.25.The value of r l/r t increases from lower-left to upper-right with the thick contour on the right side being r l/r t=1.Contours in this diagram were a very reliable guide in estimating the value of r l/r t as a function of the other two parameters. Figure3shows the age of the models on the?t=0surface.The contours are at1Gyr intervals with the thick lines indicating12and15Gyr.Models with ages less than10.5Gyr and greater than19Gyr have been excluded from these contour plots.The upper age limit de?nes the top-left edge of the contoured region,the lower limit,the lower-edge.Additional good models with higher concentrations probably exist,but some tests with W0=9models with this IMF indicate that these all core collapse very quickly.An extrapolation from Fig.2suggests that high-concentration models would also need to have values of r l/r t much larger than one,ie.we would have to assume that globular clusters start with sizes much larger than the tidal limit imposed at the galactocentric distance of their origin.This is not an unreasonable suggestion.For the high concentrations being considered(eg.W0>6),most of the mass is well within the initial tidal boundary.Further,contrary to the assumption here,real globular clusters travel on eccentric orbits and thus feel a time-varying tidal force.If a globular cluster moved closer to the center of the galaxy after its birth,then it would,in e?ect,be starting its evolution over?owing its tidal boundary.Such high W0models will not be discussed here. Figure4show similar contour plots for(a)χ2MF,(b)χ2SDP and(c)their mean.There are several features to note in these diagrams.First,there is a broad region in Fig.4a where the models match the observed mass functions.The?t improves with higher initial mass at a given initial concentration and the dependence on initial concentration is weak.The models with the lowest initial masses evolve fairly quickly and,if not already excluded for being younger than10 Gyr,would be excluded for giving a poor match to the MFs.The?ts to the mass functions are quite satisfactory in much of the parameter space. The match for the surface density pro?le is more problematic.A comparison of Fig.4b with Fig.3shows that the contours of constantχ2SDP are parallel to the contours of constant age. Further,χ2SDP increases with age and is less than two only for models younger than14Gyr. Figure4c shows the contours of constant(χ2SDP+χ2MF)/2which I use as an overall?gure of merit.This meanχ2is dominated byχ2SDP,but at young ages the increase inχ2MF becomes important.The result is a valley in the meanχ2contours where the best models lie.The lower boundary of the valley is truncated in the contour plot by the lower age cuto?in the models,but is readily apparent in the original numbers.This region is occupied by models with ages between 11and13Gyr. The dependencies ofχ2MF andχ2SDP on time implied in Fig.3and4a and b are shown more explicitly in Fig.5.This plotsχ2MF andχ2SDP against the age of the model for all the points de?ning the?t=0surface.Clearly,the best?tting models have an age of about12Gyr.If it is assumed that the U20IMF is correct,then these models would imply that NGC6397is12Gyr old. This age does contradict the age derived from isochrone?tting(16±2.5Gyr,Anthony-Twarog, Twarog,&Suntze?1992)and,if it were correct,would suggest a problem either with the stellar evolution models,or with these dynamical models.However,models run with other IMFs(see §4.2.)give either older ages,or no preferred age for NGC6397.In view of this,the safest thing to do is to reject the assumption that the U20IMF is correct. Why is there such a strong dependence on the?t of the SDP with time?As discussed in Cohn(1985)and Cherno?&Weinberg(1990)the central density pro?le for stars with mass m k in this sort of model will have a logarithmic slope ζk=?d lnρk m u +0.35 ,(5) where m u is the mass of the species dominating the core.Projection e?ects make the observed surface density?atter by one.Clearly,as the model ages the mass of the stars at the turn-o?decreases and it is these stars which are counted for the surface density pro?le.Given a core dominated by1.4M⊙neutron stars,theχ2SDP result requires that the turno?stars be more massive than0.83M⊙.The correlation ofχ2SDP with time is a re?ection of the dependence of turn-o?mass on the age of the model.The correlation would not be changed if a di?erent t(m i) relation were used.The only di?erence would be in the initial parameters needed to produce a well-?tting model of a desired age. When models are run with a di?erent choice of r t the same principle still applies.In Fig.6(a) to(c)I show contour plots of r l/r t,t and the meanχ2for a U20model set with r t=20pc.The parameter surface is very similar to that for r t=18.5pc,but the models are about1.6Gyr older at a given point on the surface.The lines of constantχ2SDP are shifted by a similar amount,but retain the same relationship to the age of the model.Figure6(d)to(f)shows a similar series of contour diagrams for r t=17pc.In this case the shift is in the opposite sense,with the models being about1.6Gyr younger than the r t=18.5pc models at a given place on the parameter surface.Again,theχ2SDP contours shift with the age contours. Column3in Fig.7show the time dependencies ofχ2SDP andχ2MF for four sets of models with IMF U20and r t as indicated in the right margin.The r t=18.5pc panel in this column is based on Fig.5.(The other of model sets shown in this?gure will be discussed in the next section.)The distribution of points with time is a result of the varying coverage of parameter space for each set of models.All four model sets display very similar temporal dependencies although the initial parameters giving rise to a point with a given age are di?erent for each model set. Since all the well-?tting models have much the same structure in terms of the mass and half-mass radius,it is not surprising that there is very little di?erence between them in terms of half-mass relaxation time.The number of elapsed half-mass relaxation times,τ≡ dt U10and X2model sets were also run with r t=20pc.Table2gives the mass fractions for the various mass components in each IMF.Note that the IMFs are the same in the NNS and U20 IMFs,but that the high mass stars leave no remnants. For the X2and NNS models no satisfactory matches were found.In all cases where the models had evolved through core collapse,minima inχ2SDP were seen both before and after core collapse,with a maximum at core collapse.In these models,the mass of the evolving stars is much closer to the mean mass in the core and therefor they show very steep surface density pro?les at the time of core collapse(see Fig.12in Paper B).The surface density drops o?more quickly than observed in the outer region covered by the mass functions.The segregation measure S r(m;du Pont:out,du Pont:if)(de?ned by eq.(2)in Drukier et al.1993as the logarithm of the ratio of the two mass functions)between the du Pont:if and du Pont:out mass functions is much larger than observed indicating that these models su?er too much mass segregation.Coincidences between local minima inχ2MF andχ2SDP occurred in both the collapsing and post-collapse phases.The collapsing models still have large core radii and gave quite poor matches to the surface density pro?le.For the X2models,the mass functions were matched better when r t=20pc was used, but there was no improvement to the match of the SDP.Post-core-collapse models have pro?les that match the observed SDP fairly well,but these are all older than18.5Gyr and the matches to the mass functions are very poor. Figure7summarizes the time dependence ofχ2MF andχ2SDP for the model sets with well-?tting models.The U30model set has much the same time dependency as do the U20 model sets.The best U30models lie at a somewhat younger age than do the U20models.This is understandable in terms of the argument given above since the U30models have a higher proportion of heavy remnants than do the U20models and the e?ective m u in equation(5)is higher.For the same observed slope at core collapse,the mass of the turn-o?stars must be higher and thus younger.The e?ect is small,but,given the even larger contradiction between the optimal age here,and the isochrone age of NGC6397,a higher number of neutron stars can be excluded. Panels(a)to(c)of Fig.8shows r l/r t,the meanχ2,and age of the models on the?t=0surface for the U30model set.The behavior is very similar to that of the U20model sets.Note that the shapes of the contoured regions are determined by the range of models runs.There certainly exist well-?tting models beyond these regions,I just haven’t looked for them. That the L05model set has a later time when the models best?t all the observations is not surprising given the comparison between the U20model sets and the U30model set.On the other hand,the dependence ofχ2MF on time is much stronger than for the U30and U20model sets.It is as strong,though in the opposite sense,as the dependence ofχ2SDP on time.The meanχ2is fairly constant with time,but at about14Gyr the trade-o?between the two is minimized.Panels (d)to(f)of Fig.8con?rms that the dependence of the meanχ2on time is much weaker than for the U20or U30models.There is a large basin of models with W0between4.5and6.0and M0between4×105and6×105M⊙which give matches of similar overall quality by trading o?betweenχ2MF andχ2SDP. The behavior of the U10models serves as a warning against extrapolation.For r t=18.5 neitherχ2shows any time dependence at all.Further,the meanχ2for this model set is the lowest of any.χ2SDP is at all times as low as that seen in any other model andχ2MF although globally higher than in some other cases,is no higher than its value at the time of minimum meanχ2in the other model sets.An additional model set was run with IMF U10and r t=20pc.In this model setχ2SDP is still approximately constant with time,andχ2MF now decreases with time;the minimum in the mean is at over18Gyr.The di?erence in the time dependence ofχ2MF between the r t=18.5pc and r t=20pc models is consistent with a trend to steeper slope inχ2MF vs.r t in the U20models.Panels(g)to(l)in Fig.8make clear the very weak time dependence of the mean χ2. To further investigate this problem,Fig.9presentsχ2for each of the three mass functions separately as a function of time for each of the model sets.To reduce the clutter in the diagram I have just plotted the best?tting straight line through each of the sets of estimates.Systematic trends are visible in the U20column for both the slopes and intercepts of theχ2lines and these trends are also present in the two U10model sets.The decrease inχ2for the du Pont:out MF with increasing r t is understandable as indicating that larger tidal radii are preferred in matching this region of the cluster.On the other hand,the?t to the du Pont:if MF gets worse as r t is increased. To expand on the points made at the end of§4.1.,the variation inτin any single model set is small and its value does not predict the size ofχ2MF.That the variation ofχ2MF is so small in the U10model with r t=18.5is a result of the tradeo?between the three mass functions.There is no correlation betweenτandχ2MF between data sets since the degree of mass segregation with both time and position also depends on the IMF and r t.The detailed reasons for these trends are unclear,but relate to the more general question of mass segregation.This matter warrants further study. For the U10model setsχ2SDP is constant for both of the magnitude limited SDPs and does not result from a tradeo?between them.Rather,the improved behavior can be understood in terms of eq.(5).For the U10model sets,the mean mass in the core at the time of best?t is about 1.0M⊙,while for the other IMFs it is about1.2M⊙.The observed slope of the central SDP is -0.9(Drukier et al.1993),givingζk=1.9.Taking m u to be the central mean mass,the mass for the observable stars which gives the best match to the SDP is0.8M⊙for the U10model sets and 1.0M⊙for the others.The rate of change dζk mass of the turn-o?stars at a given time,the discrepancy could suggest that there are problems with the stellar modeling.However,the existence of the U10models which do not show the strong time e?ect,shows that this is not the case and that model sets having their best models at the wrong age probably have the wrong IMF.A somewhat philosophical question remains.Is an IMF giving a model set without any age dependence(such as U10)to be preferred to one with an age-dependent quality-of-?t,but with a preferred age consistent with the isochrone age(such as L05)?If they are not to be preferred,then can we use the existence of a preferred age to learn anything about particular clusters? 4.3.Robustness Up until now the discussion of the matches between the models and the observations has been conducted at a level removed from the actual matches.In this section I will show two matches in order to bring some meaning to the values and di?erences inχ2.More such matches are shown in Paper B where the purpose is to extract information about NGC6397. I will begin with a model which has been selected for having the lowest meanχ2of the well-?tting models with ages between15and17Gyr.It is the third best of all the well-?tting models,and has a meanχ2only0.06larger than the best model.As well,it happens to have the lowestχ2SDP of all the well-?tting models.This model,designated t074,is a U10model,with W0=6.00,M0=4.5×105M⊙,r t=20.pc,and r l/r t=1.08.At the displayed time(Fig.10) its age is15.8Gyr,χ2MF=1.54,andχ2SDP=1.06.As might be expected,the?t to the SDP is quite good.The mass function matches are not as much of a success since many of the details in the observed MFs are not matched.Of more concern,the du Pont:out MF is systematically higher than the model MF at that radius.This is probably an e?ect of the choice of r t.The other concern is that the model velocity dispersion is systematically lower,although still consistent with,the observed velocity dispersion data.Overall,this is certainly an acceptable model and demonstrates the validity of the Fokker-Planck modeling. By way of comparison,in Fig.11I show the well-?tting model with an age between15and 17Gyr and with the lowestχ2MF.This is the model with the second best MF?t and is only0.02 worse inχ2MF than the best model.It is also has the fourth-highestχ2SDP.This model,designated GG057,is a U20model,with W0=5.35,M0=7.56×105M⊙,r t=18.5pc,and r l/r t=0.78. At the displayed time its age is17Gyr,χ2MF=1.06,andχ2SDP=3.16.The central part of the SDP is conspicuously poor.Model GG057also has more stars in the outer region than model t074.This is not a result of the rescaling of the model SDP(see§3.1.),but is a real e?ect.That this is so can be seen in the mass functions;their radial positions in the cluster are indicated by the vertical lines in the SDP panel.The MFs for the low-mass stars are almost identical for both models;the di?erences lie for stars more massive than about0.3M⊙.For all three MFs,model GG057has more of these stars than does model t074and the size of the di?erence increases with radius.The velocity data is matched very well. 5.Discussion I have run eleven sets of models in attempting to match a set of observations of the globular cluster NGC6397.For any given IMF and galactocentric distance(parameterized as a?ducial tidal radius r t)any two of the remaining parameters W0,M0,and r l/r t are independent;the requirement to match all the observations at the same time?xes the third.For most of the IMFs tested the quality of the match to the observations is time dependent with only a fairly narrow interval in which both the surface density pro?le and the mass functions are matched well.The size of the time dependencies is determined by the IMF and,to a lesser extent,by r t.In two model sets with one IMF,only a weak time dependence was seen.While this may still not be the optimal choice of IMF,as things stand the existence of preferred times in the other models cannot be used to constrain the age of NGC6397in the face of an IMF without a preferred age.What can be said is that the existence and quality of matching models can put limits on the existence and numbers of stars with masses outside the observed range.A small fraction of neutron stars is required,but not too many.As well,the existence of a very large number of low mass stars also appears unlikely.These,and other constraints relating speci?cally to NGC6397,are discussed in more detail in Paper B. The generalized rules discussed in§3.3.can be put on a?rmer footing using the results of the various model sets.The(W0,M0,r l/r t)surfaces are curved,but rough estimates can be made of the relationship between changes in the parameters and the times of best match to the SDP or the MFs.Series of models varying in only one parameter can be taken from the grids and used to estimate the variation in the times as a function of the parameters.For the eight models sets shown in Fig.7the slopes estimated this way are shown in Table3.These numbers are meant to be representative and suggest the range of variation possible with variations in the IMF.Changes in r l/r t are about three times more e?ective in changing the time of optimal mass than the time of core collapse.Changes in W0do not e?ect the time of core collapse all that much.The slopes can also be used to quantify the thickness of the surface.Since the models are checked intermittently even the well-?tting models may not have?t=0if they are rerun and checked more frequently. From my list of?t values,the most common one other than zero is0.4,suggesting that this is the typical time interval between data saves in the vicinity of well-?tting models.The?nal three columns of Table3give the variations in W0,M0,and r l/r t which change?t by0.4Gyr.A model with a single one of these parameters changed by the indicated amount should still be well-?tting. One thing that is clear from this work is the strong e?ect the IMF has on the quality of the model?ts.Additional data can only serve to further limit the range of initial parameters which match the observations.In retrospect,it may have been more fruitful to treat the three mass functions as independent constraints rather than to use the combined results.As a?rst attempt at such an extensive comparison,the more limited goal of matching the ensemble of mass functions simpli?ed the analysis of the results.The velocity data does not give as strong a constraint on individual models as does the SDP and the MFs.The model velocity pro?les are much the same for all well-?tting models in a model set.The velocities do provide a stronger limit on the IMF, but the present data set is not precise enough to make?rm statements. These models still do not include all the e?ects that are expected to a?ect globular clusters. One such e?ect is disk shocking.Weinberg(1994)has included this in his Fokker-Planck code and shown that in the inner part of the galaxy,clusters can lose substantial amounts of mass through disk shocking.This has much the same e?ect as stellar evolution mass loss,but takes place for the entire lifetime of the cluster not just the initial Gyr.The extra mass loss would allow for models with higher initial masses to reach core collapse at the present,but also requires high initial concentrations to prevent them from disrupting entirely.In Fig.2,only the models on the right edge of the diagram(those with W0>6.5)would survive based on Weinberg’s preliminary results.For more distant clusters the initial concentration can be lower. The techniques I have used here could certainly be extended to other clusters,provided su?ciently detailed sets of observation exists.Once an IMF which can give an good match to those observed has been found,and I have not addressed this question here,it should be fairly straightforward to locate the range of good models,assuming they exist.It is di?cult to give explicit rules,even those as rough as the ones given in§3.3.,which would apply in all cases,but a little experience with a given data set soon provides these.The surfaces of well-?tting models for the last model sets calculated were located much more quickly than the?rst ones.No hunting phase was required.One technique is to take a single cut,varying only one of W0,M0,or r l/r t. Once the?t=0point has been found,simple extrapolations along a regular grid,following the rules in§3.3.,quickly?nd additional extrapolations.After several intersection points have been located,estimates can be made of the shape of the surface.Farther-range extrapolations are often quite successful and only a minimum of non-useful models need to be run.Until this has been tested on other data sets,it is impossible to say how universally this will apply.For NGC6397,at least,these Fokker-Planck models have been quite successful in matching the observations.The information which can be extracted from these matches is the subject of the accompanying Paper B. Thanks go to R.Elson for suggesting the contour plots.This work was supported by NSERC of Canada and PPARC of the U.K. A.A smooth tidal boundary Assume that the cluster moves in a circular orbit at a distance R G from the center of the galaxy and that the mass of the galaxy within R G is M G.From Lee&Ostriker(1987)the tidal stripping is given by ?f(E,t) 3Gρt(A3) is the orbital periods of the cluster about the galaxy.The tidal-energy boundary E t is given by the potential at the radius which encloses a mean density equal to the tidal densityρt,a constant dependent on R G and the ratio of the initial mass of the cluster to M G.Note that the potential is de?ned to be positive here withφ→0as r→∞.C t is a dimensionless constant giving the overall rate of mass loss per orbital period and is taken to be unity.The discontinuity in the?rst derivative of the stripping rate is obvious in eq.(A2). Let β=1? E βforβ>0and is identically zero forβ<0.For the region|β|≤?, where?is small,I?nd a cubic polynomial which has the same values and?rst derivatives as b(β) atβ=±?.The required polynomial is b1(β)=√ 8 ? β? 2+5β 水平对置、后置后驱、低重心、前双横臂后多连杆、全铝合金车架、5门5座，你以为笔者说的是保时捷新车型吗？那笔者再补充多几个关键词好了，后置的水平对置双电刷电动机、0油耗、藏在地板下的笔记本电池组，同时拥有这些标签的，便是Tesla第二款车型Model S。Model S是五门五座纯电动豪华轿车，布局设计及车身体积与保时捷Panamera相当，并且是目前电动车续航里程的纪录保持者（480公里）。虽然现在纯电动在我国远未至于普及，但是在香港地区却是已经有Tesla的展厅，在该展厅内更是摆放了一台没有车身和内饰，只有整个底盘部分的Model S供人直观了解Model S的技术核心。 图：Tesla Model S。 图：拆除车壳之后，Model S的骨架一目了然。 图：这套是Model S的个性化定制系统，可以让买家选择自己喜爱的车身颜色、内饰配色和轮圈款式，然后预览一下效果。可以看到Model S共分为普通版、Sign at ure版和Performance版，后面两个型号标配的是中间的21寸轮圈，而普通版则是两边的19寸款式。Signature版是限量型号，在美国已全部售罄，香港也只有少量配额。 图：笔者也尝试一下拼出自己心目中的Model S，碳纤维饰条当然是最爱啦。 图：参观了一下工作车间，不少Roadster在等着检查保养呢，据代理介绍，不同于传统的汽车，电动车的保养项目要少很多，至少不用更换机油和火花塞嘛，换言之电动车的维护成本要比燃油汽车要低。 Tesla于2010年5月进军香港市场，并于翌年2011年9月成立服务中心。由于香港政府对新能源车的高度支持，香港的电动车市场发展比起大陆地区要好得多。例如Tesla的第一款车型Roadster（详见《无声的革命者——Tesla Roadster Sport 》），在香港获得豁免资格，让车主可以节省将近100万港元的税款。在这样的优惠政策之下，Tesla Roadster尽管净车价达100万港元，但50台的配额已经基本售罄。而Model S目前在香港已经开始接受报名预定，确定车型颜色和配置之后约两个月左右可以交车。 华为FireHunter6000系列沙箱产品 产品概述 高级持续性威胁（APT）常常以钓鱼邮件方式入侵低防御意识人群，以物联设备漏洞为切入点，潜伏到企业高价值数据资产区域，在传统防御手段未检测感知以前，窃取或破坏目标。APT攻击通常主要攻击涉及国计民生的基础设施，例如金融、能源、政府等，攻击的实施者会经过大量精心的准备和等待，利用0-Day漏洞、高级逃逸技术等多种技术组合成未知威胁恶意软件，它们可以绕过现有的基于特征检测的安全设备，非常难以防御。 华为FireHunter6000系列沙箱产品是华为公司推出的新一代高性能APT威胁检测系统，可以精确识别未知恶意文件渗透和C&C（命令与控制，Command & Control，简称C&C）恶意外联。通过直接还原网络流量并提取文件或依靠下一代防火墙提取的文件，在虚拟的环境内进行分析，实现对未知恶意文件的检测。凭借华为独有的ADE高级威胁检测引擎，华为FireHunter6000系列沙箱产品与下一代防火墙配合，对“灰度”流量实时检测、阻断和报告呈现，有效避免未知威胁攻击的迅速扩散和企业核心信息资产损失，特别适用于金融、政府机要部门、能源、高科技等关键用户。 产品特点 50+文件类型检测，全面识别未知恶意软件 ●全面的流量还原检测：具备业内领先的流量还原能 力，可以识别主流的文件传输协议如HTTP、SMTP、 POP3、IMAP、FTP、SMB等，从而确保识别通过 这些协议传输的恶意文件 ●支持主流文件类型检测：支持对主流的应用软件及 文档进行恶意代码检测，包括支持PE、PDF、Web、 Office、图像、脚本、SWF、COM等50+类型文 件的检测 4重纵深检测，准确性达99.5%以上 ●模拟多种软件运行环境和操作系统：模拟操作系统 和多种软件运行环境：提供PE、PDF、Web启发 式沙箱和虚拟执行环境沙箱。虚拟执行环境支持多 种Windows操作系统、浏览器及办公软件 ●动静结合检测：通过静态分析，包括代码片段分析、 文件格式异常、脚本恶意行为分析等，来缩小可疑 流量范围；通过指令流监控，识别文件、服务操作， 来进行动态分析，最后通过行为关联分析，判断定 性 ●高级抗逃逸：多种抗逃逸技术，防止恶意软件潜伏、 躲避虚拟机检测 秒级联动响应，快速拦截未知恶意软件 ●业内一流的性能：提供业内一流的沙箱分析能力， 同时支持通过横向扩容方式组成沙箱分析集群。 ●实时的处理能力：创造性的将对高级威胁的检测和 响应时间降到秒级，并通过与下一代防火墙配合实 现APT在线防御。 ●提供详细威胁报告，帮助运维、快速决策：详细展 示文件检测结果，包括文件检测结果、文件相关会 话信息、文件格式异常、文件行为异常、网络通讯 异常、虚拟执行环境信息、网络行为和主机行为等。 产品部署模式 ●与NGFW/NGIPS设备联动部署：NGFW/NGIPS 设备负责还原文件，并将需要检测的文件送到沙箱 进行检测。同时NGFW/NGIPS设备还支持SSL流 量解密，针对解密后的流量做文件还原，再送沙箱 检测。 ●单机独立部署：通过镜像的方式，先将流量镜像到 沙箱，沙箱进行流量还原，并对还原出的文件进行 检测。 特斯拉电动汽车动力电池管理系统解析 1. Tesla目前推出了两款电动汽车，Roadster和Model S，目前我收集到的Roadster 的资料较多，因此本回答重点分析的是Roadster的电池管理系统。 2. 电池管理系统（Battery Management System, BMS）的主要任务是保证电池组工作在安全区间内，提供车辆控制所需的必需信息，在出现异常时及时响应处理，并根据环境温度、电池状态及车辆需求等决定电池的充放电功率等。BMS的主要功能有电池参数监测、电池状态估计、在线故障诊断、充电控制、自动均衡、热管理等。我的主要研究方向是电池的热管理系统，因此本回答分析的是电池热管理系统 (Battery Thermal Management System, BTMS). 1. 热管理系统的重要性 电池的热相关问题是决定其使用性能、安全性、寿命及使用成本的关键因素。首先，锂离子电池的温度水平直接影响其使用中的能量与功率性能。温度较低时，电池的可用容量将迅速发生衰减，在过低温度下（如低于0°C）对电池进行充电，则可能引发瞬间的电压过充现象，造成内部析锂并进而引发短路。其次，锂离子电池的热相关问题直接影响电池的安全性。生产制造环节的缺陷或使用过程中的不当操作等可能造成电池局部过热，并进而引起连锁放热反应，最终造成冒烟、起火甚至爆炸等严重的热失控事件，威胁到车辆驾乘人员的生命安全。另外，锂离子电池的工作或存放温度影响其使用寿命。电池的适宜温度约在10~30°C之间，过高或过低的温度都将引起电池寿命的较快衰减。动力电池的大型化使得其表面积与体积之比相对减小，电池内部热量不易散出，更可能出现内部温度不均、局部温升过高等问题，从而进一步加速电池衰减，缩短电池寿命，增加用户的总拥有成本。 电池热管理系统是应对电池的热相关问题，保证动力电池使用性能、安全性和寿命的关键技术之一。热管理系统的主要功能包括：1）在电池温度较高时进行有效散热，防止产生热失控事故；2）在电池温度较低时进行预热，提升电池温度，确保低温下的充电、放电性能和安全性；3）减小电池组内的温度差异，抑制局部热区的形成，防止高温位置处电池过快衰减，降低电池组整体寿命。 2. Tesla Roadster的电池热管理系统 Tesla Motors公司的Roadster纯电动汽车采用了液冷式电池热管理系统。车载电池组由6831节18650型锂离子电池组成，其中每69节并联为一组（brick），再将9组串联为一层（sheet），最后串联堆叠11层构成。电池热管理系统的冷却液为50%水与50%乙二醇混合物。 WPS Office 2007 中国人自己的办公软件 Wps是(Word Processing System)的缩 写，中文意思是字处理系统。是由求伯君一手创办起来，后来成为国产软件的旗帜。 Wps经历了从dos时代的wps到现在windows下的wps. 1.WPS Office专业版31M，个人版16M，以Microsoft Office几十分之一的体 积,实现了与Microsoft Office的深度双向兼容,包括界面、使用习惯和二次开发； 2.5秒钟将Word、WPS文档输出为PDF格式； 3.各类斜线表头，无论文字多少，不跑版，不变形，真正符合中文需要； 4.阿拉伯数字自动转换为人民币大写，同时自动添加货币单位； 5.无论文档长短，瞬间可转化为中文稿纸格式，连标点符号都严格符合中文行 文规范； 6.套打隐藏文字功能，将要填写的内容直接打印在各类固定格式上； 7.文档标签，只需一点，即可实现多个文档间的便捷切换; 8.严格符合中文标准和习惯的项目符号，无需另外设置; 9.编辑栏智能收缩:编辑栏内容再长，也不会遮盖单元格内容了; 10.允许文本框内的文字绕排外部对象适合经常需要进行图文排版等复杂长文 档编辑的用户; 11.反片打印;适合有印刷出片需求的用户; 12.WPS表格支持缩放打印功能，表格能够按各类打印纸型自由缩放; 13.WPS文字独有文字工具瞬间全篇文档职能排版; 14.增加了书签和关闭按钮的文档结构图：阅读长文档更方便，可随时记下阅读 心得; 金山公司联系方式: Wps office 2007 中国人自己的办公软件 二十载风雨艰辛路回顾WPS发展全记录 1993年，金山推出了它的第一代产品： WPS1.0forWindow 1998年8月金山又推出了它的新的产品：WPS2000 2001年的5月，金山又推：WPSOffice 2001年9月23日，WPSOffice蒙文版发布 2002年6月出了：WPSOffice2002 2003年的8月，又一款新的金山出来了，它就是： WPSOffice2003 2004年6月研发代号为kingstorm的WPSOffice飓风版发 布了 WPS Office 2005：决胜巅峰之作 2007年8月30日期待已久的Wps Office2007正式发布 Tesla Model S 特斯拉Model S是一款纯电动车型，外观造型方面，该车定位一款四门Coupe车型，动感的车身线条使人过目不忘。此外在前脸造型方面，该车也采用了自己的设计语言。另值得一提的是，特斯拉Model S的镀铬门把手在触摸之后可以自动弹出，充满科技感的设计从拉开车门时便开始体现。该车在2011年年中正式进入量产阶段，预计在2012年年内将有5000台量产车投放市场。 目录 1概述 2售价 3内饰 4动力 5车型 6技术规格 7性能表现 8荣誉 9对比测试 10车型参数 1概述 Tesla Model S是一款由Tesla汽车公司制造的全尺寸高性能电动轿车，预计于2012年年中投入销售，而它的竞争对手则直指宝马5系。该款车的设计者Franz von Holzhausen，曾在马自达北美分公司担任设计师。在Tesla汽车公司中，Model S拥有独一无二的底盘、车身、发动机以及能量储备系统。Model S的第一次亮相是在2009年四月的一期《大卫深夜秀》节目中 4 Tesla Model S 。 2售价 Model S的电池规格分为三种，分别可以驱动车辆行驶260公里、370公里和480公里。而配备这三种电池的Model S的售价则分别为57400美元、67400美元和77400美元。下线的首批1000辆签名款车型将配有可以行驶480公里的蓄电池。尽管官方尚未公布该签名款车型的具体售价，但据推测，价格将会保持在50000美元左右。 Tesla汽车公司称其将会对市场出租可以提供480公里行驶距离的电池。而从Model S中取得的收益将为第三代汽车的发展提供资金保障。 3内饰 基于4P-4C-4R理论的特斯拉电动汽车品牌营销策略探究 兰州大学管理学院：鲍瑞雪指导老师：苏云【摘要】：特斯拉汽车作为新兴的电动汽车品牌，其发展速度是十分惊人的，尤其是自2014年进入中国市场后更是在中国新能源汽车业引起巨大的轰动，其成功模式值得深思，其中特斯拉汽车公司的营销策略，不仅根据目标市场进行分析，还结合了自身的实际情况，通过对多种营销策略的综合利用，最终实现了成功，促进了企业的持续发展。本文基于营销学4P-4C-4R理论对特斯拉汽车公司的营销策略进行深入分析，研究表明特斯拉从顾客角度出发，采取4P、4C、4R相结合的营销策略。4P是战术，4C是战略，应用4C、4R来思考， 4P角度来行动。 【关键词】： 4P 4C 4R 品牌营销策略特斯拉电动汽车 一、研究背景 当前，美国电动汽车企业特斯拉公司已经成为世界电动汽车界的一匹黑马。特斯拉公司成立于2003年，不同于其它新能源汽车企业，它主要从事电动跑车等高端电动汽车的设计、制造和销售。成立仅仅10年，特斯拉就已经开始在新能源汽车企业和高端汽车企业中崭露头角。作为新兴电动汽车品牌，特斯拉汽车的成功不是偶然的，这与其注重品牌营销策略密不可分。特斯拉汽车公司不仅对目标市场进行具体细分，结合自身实际进行有特色的精准的定位，还充分利用名人效应，提升品牌形象，并借助已有成功模式，寻求找到符合自身发展的途径，出一条饱含自己特色的品牌营销之路。 二、理论依据及文献综述 （一）理论依据 本文以经典的营销学理论4P-4C-4R理论为理论依据，着力探究4P-4C-4R 理论与特斯拉电动汽车营销策略之间的内在联系，分析特斯拉电动汽车品牌营销策略的经典之处。 1、4P营销理论 4P营销理论被归结为四个基本策略的组合，即产品（Product）、价格（Price）、渠道（Place）、促销（Promotion）。该理论注重产品开发的功能，要求产品有独特的卖点，把产品的功能诉求放在第一位。在价格策略方面，企业应当根据不 详解特斯拉Model S 1、Model S的核心技术是什么？ 核心技术是软件，主要包括电池管理软件，电机以及车载设备的电控技术。最重要的是电池控制技术。 Model S的加速性能，续航里程、操控性能的基础都是电池控制技术，没有电池控制技术，一切都就没有了。 2、Model S的电池控制技术有什么特色？ 顶配的Model S使用了接近7000块松下NCR 18650 3100mah电池，对电池两次分组，做串并联。设置传感器，感知每块电池的工作状态和温度情况，由电池控制系统进行控制。防止出现过热短路温度差异等危险情况。 在日常使用中，保证电池在大电流冲放电下的安全性。 其他厂商都采用大电池，最多只有几百块，也没有精确到每块电池的控制系统。 3、为什么要搞这么复杂的电池控制系统？ 为了能够使用高性能的18650钴锂电池。高性能电池带来高性能车。因为18650钴锂电池的高危性，没有一套靠谱的系统，安全性就不能保证。这也是大多数厂商无论电力车，插电车，混合动力车都不太敢用钴锂电池，特别是大容量钴锂电池的原因。 松下NCR 18650 3100mah，除了测试一致性最好，充放电次数多，安全性相对较好以外，最重要的是能量大，重量轻，价格也不高。 由于能量大，重量轻，在轿车2吨以内的车重限制下，可以塞进去更多的电池，从而保证更长的续航里程。因为电池输出电流有限制，电池越多，输出电流越大，功率越大，可以使用的电机功率也就越大。电机功率越大，相当于发动机功率大，车就有更快的加速性能，而且可以保持较长的一段时间。 4、作为一辆车，Model S有哪些优点？这些优点是电动车带来的吗？ 作为一辆车，Model S主要具有以下几个优点 （1）起步加速快，顶配版本0-100公里加速4秒多，能战宝马M5 TESLA 硅谷工程师、资深车迷、创业家马丁·艾伯哈德（Martin Eberhard）在寻找创业项目时发现，美国很多停放丰田混合动力汽车普锐斯的私家车道上经常还会出现些超级跑车的身影。他认为，这些人不是为了省油才买普锐斯，普锐斯只是这群人表达对环境问题的方式。于是，他有了将跑车和新能源结合的想法，而客户群就是这群有环保意识的高收入人士和社会名流。 2003年7月1日，马丁·艾伯哈德与长期商业伙伴马克·塔彭宁（Marc Tarpenning）合伙成立特斯拉（TESLA）汽车公司，并将总部设在美国加州的硅谷地区。成立后，特斯拉开始寻找高效电动跑车所需投资和材料。 由于马丁·艾伯哈德毫无这方面的制造经验，最终找到AC Propulsion公司。当时，对AC Propulsion公司电动汽车技术产生兴趣的还有艾龙·穆思科（Elon Musk）。在AC Propulsion公司CEO汤姆·盖奇（Tom Gage）的引见下，穆思科认识了艾伯哈德的团队。2004年2月会面之后，穆思科向TESLA投资630万美元，但条件是出任公司董事长、拥有所有事务的最终决定权，而艾伯哈德作为创始人任TESLA的CEO。 在有了技术方案、启动资金后，TESLA开始开发高端电动汽车，他们选择英国莲花汽车的Elise作为开发的基础。没有别的原因，只是因为莲花是唯一一家把TESLA放在眼里的跑车生产商。 艾伯哈德和穆思科的共同点是对技术的热情。但是，作为投资人，穆思科拥有绝对的话语权，随着项目的不断推进，TESLA开始尝到“重技术研发轻生产规划、重性能提升轻成本控制”的苦果。2007年6月，离预定投产日期8月27日仅剩下两个月时，TESLA还没有向零部件供应商提供Roadster的技术规格，核心的部件变速箱更是没能研制出来。另一方面，TESLA在两个月前的融资中向投资人宣称制造Roadster的成本为6.5万美元，而此时成本分析报告明确指出Roadster最初50辆的平均成本将超过10万美元。 生意就是生意，尤其硅谷这样的世界级IT产业中心，每天都在发生一些令人意想不到的事情。投资人穆思科以公司创始人艾伯哈德产品开发进度拖延、成本超支为由撤销其 版权所有 ? 华为技术有限公司 2017。 保留一切权利。 无担保声明在本手册中以及本手册描述的产品中，出现的其他商标、产品名称、服务名称以及公司名称，由其各自的所有人 拥有。 商标声明 非经华为技术有限公司书面同意，任何单位和个人不得擅自摘抄、复制本手册内容的部分或全部，并不得以任 何形式传播。 本手册内容均“如是”提供，不构成任何形式的承诺。除非适法要求，华为技术有限公司对本手册所有内容不提供任何明示或暗示的保证。在法律允许的范围内，华为技术有限公司在任何情况下，都不对因使用本手册相关内容而产生的任何特殊的、附带的、间接的、继发性的损害进行赔偿，也不对任何利润、数据、商誉或预期节约的损失进行赔偿。华为数字银行服务解决方案华为技术有限公司 目录 CONTENTS 02生态合作17 0319成功案例 0105 07 09 11 13 15 解决方案概览03 咨询服务规划设计与验证集成实施运维支持服务优化提升服务金融行业人才培养服务1.11.21.31.41.51.6 方案价值 华为拥有业界领先的ICT技术和丰富的银行业项目实践经 验，为商业银行客户提供全方位的银行ICT基础设施平台建 设及使能服务。 自主可控 快速部署高效运营数字银行服务解决方案概览 01华为基于银行数字化转型的最佳实践，秉承 “助力商业银行提升业务创新效率、降低IT运 营成本”的服务理念，提供集咨询服务、规划 设计、集成实施、运维支持、优化提升、人才 培养于一体的全方位银行ICT服务解决方案，帮 助银行客户构筑自主可控、安全合规、敏捷高 效、弹性伸缩的数字银行ICT基础设施平台，提 升客户IT运营水平。概述 前瞻的顶层设计和开放包容的技术架构最大程度保护银行的IT投资SmartNOS、运维使能、专业人才培养服务，助力银行IT卓越运营 模块化的产品设计，遍布全球的交付专家，以及便捷的集成验证服务，全面满足银行业务敏捷需求 华为技术有限公司 0102 ? 接入终端及业务多样化，需要融合承载的园区网络 传统企业园区网络，有线、Wi-Fi 及IoT 三种业务，各自独立规划部署，独立管理，网络总体建设成本高，相应的网络管理运维工作量也成倍增加。 ? 人力成本快速攀升，网络自动化部署成为普遍需求 传统的手工配置需要逐台设备配置，时间长效率低；以IP 地址为核心的用户策略配置复杂，也无法适应终端移动化的发展趋势；新业务上线需要新增专用业务网络，并且逐台设备配置，周期长，成本高。 ? 无法随时随地感知Wi-Fi 用户体验，成为网络运维最大挑战 传统运维模式下，采集周期较长（5分钟左右），有可能错过故障发生时间，业务无法实时监控；故障发生后更多是依赖专业人员的运维经验判定业务故障原因，故障无法快速定位；网络指标劣化后，由IT 人员借助网管评估网络状况，做出针对性的优化策略并部署，网络无法实现自主优化。 ? 园区网络的安全威胁持续更长，防范更难，损失更大 随着物联网等新业务形态的发展，接入终端数量大幅攀升，带来了新的安全和隐私问题。同时，网络安全问题带来的网络故障同样提升了企业的IT 成本，Gartner 报告显示，80%的亚洲企业处在“救火式”的企业运维状态；部分企业甚至会将每年三分之一的IT 成本，用于网络排障。 随 着人类对数字世界的探索不断取得突破，一场波澜壮阔的数字化变革正在各行各业发生，催生了许多新的商业模式。同时，人工智能、增强现实、虚拟现实、机器人、物联网和云计算等新 技术正加速各行业数字化转型与升级，进入“+智能”时代。人类社会迈向“万物感知、万物互联、万物智能”的智能社会的趋势无可阻挡。 数字化转型也对企业的可持续发展产生了巨大影响。IDC 的报告显示，未来3～5年，每个行业排名前20位的企业和组织中将有三分之一被数字化所颠覆，“任何组织唯有数字化才能不掉队”，数字化转型大赛已拉开帷幕。对企业来说，无论是面对同业的激烈竞争，还是随时接受“跨界入侵者”的挑战，数字化都是当前最重要的武器之一。数字化转型已成为企业可持续性发展的重要保障，能让企业走得更快更远。 数字世界的繁荣是建立在ICT 网络之上的。有了无处不在的基础网络，用户才可以通过各种接入方式接入多种多样的数字应用。除满足内部办公数字化的需求之外，越来越多的企业要求网络成为行政、财务、营销、人力、销售和供应链等部门业务原始数据的抓取者、传递者和分析者，企业的智能办公、商超的大数据精准营销等数字化方案都需要依托网络才能完成。 企业园区网络作为企业数字化转型的基石，随着BYOD 移动办公、云计算、SDN 软件定义网络、物联网、人工智能以及大数据等概念的持续升温，新技术、新应用层出不穷，这些应用和业务进入企业园区，传统园区网络面临诸多挑战。 交通 + 智能，最懂你的路 医疗 + 智能，最懂您的痛 各行业进入“+智能”时代 制造 + 智能，最懂您所需 1. Tesla目前推出了两款电动汽车，Roadster和Model S，目前我收集到的Roadster的资料较多，因此本回答重点分析的是Roadster的电池管理系统。 2. 电池管理系统（Battery Management System, BMS）的主要任务是保证电池组工作在安全区间内，提供车辆控制所需的必需信息，在出现异常时及时响应处理，并根据环境温度、电池状态及车辆需求等决定电池的充放电功率等。BMS的主要功能有电池参数监测、电池状态估计、在线故障诊断、充电控制、自动均衡、热管理等。我的主要研究方向是电池的热管理系统，因此本回答分析的是电池热管理系统 (Battery Thermal Management System, BTMS). 1. 热管理系统的重要性 电池的热相关问题是决定其使用性能、安全性、寿命及使用成本的关键因素。首先，锂离子电池的温度水平直接影响其使用中的能量与功率性能。温度较低时，电池的可用容量将迅速发生衰减，在过低温度下（如低于0°C）对电池进行充电，则可能引发瞬间的电压过充现象，造成内部析锂并进而引发短路。其次，锂离子电池的热相关问题直接影响电池的安全性。生产制造环节的缺陷或使用过程中的不当操作等可能造成电池局部过热，并进而引起连锁放热反应，最终造成冒烟、起火甚至爆炸等严重的热失控事件，威胁到车辆驾乘人员的生命安全。另外，锂离子电池的工作或存放温度影响其使用寿命。电池的适宜温度约在10~30°C 之间，过高或过低的温度都将引起电池寿命的较快衰减。动力电池的大型化使得其表面积与体积之比相对减小，电池内部热量不易散出，更可能出现内部温度不均、局部温升过高等问题，从而进一步加速电池衰减，缩短电池寿命，增加用户的总拥有成本。 电池热管理系统是应对电池的热相关问题，保证动力电池使用性能、安全性和寿命的关键技术之一。热管理系统的主要功能包括：1）在电池温度较高时进行有效散热，防止产生热失控事故；2）在电池温度较低时进行预热，提升电池温度，确保低温下的充电、放电性能和安全性；3）减小电池组内的温度差异，抑制局部热区的形成，防止高温位置处电池过快衰减，降低电池组整体寿命。 2. Tesla Roadster的电池热管理系统 Tesla Motors公司的Roadster纯电动汽车采用了液冷式电池热管理系统。车载电池组由6831节18650型锂离子电池组成，其中每69节并联为一组（brick），再将9组串联为一层（sheet），最后串联堆叠11层构成。电池热管理系统的冷却液为50%水与50%乙二醇混合物。 图 1.(a)是一层（sheet）内部的热管理系统。冷却管道曲折布置在电池间，冷却液在管道内部流动，带走电池产生的热量。图 1.(b)是冷却管道的结构示意图。冷却管道内部被分成四个孔道，如图 1.(c)所示。为了防止冷却液流动过程中温度逐渐升高，使末端散热能力不佳，热管理系统采用了双向流动的流场设计，冷却管道的两个端部既是进液口，也是出液口，如图 1(d)所示。电池之间及电池和管道间填充电绝缘但导热性能良好的材料（如Stycast 2850/ct），作用是：1)将电池与散热管道间的接触形式从线接触转变为面接触；2)有利于提高单体电池间的温度均一度；3)有利于提高电池包的整体热容，从而降低整体平均温度。 Tesla Model S电池组设计全面解析 对Tesla来说最近可谓是祸不单行；连续发生了3起起火事故，市值狂跌40亿，刚刚又有3名工人受伤送医。Elon Musk就一直忙着到处“灭火”，时而还跟公开表不对Tesla“不感冒”的乔治·克鲁尼隔空喊话。在经历了首次盈利、电池更换技术·穿越美国、水陆两栖车等头条新闻后，Elon Musk最近总以各种负面消息重返头条。这位"钢铁侠。CE0在201 3年真是遭遇各种大起大落。 其中最为人关注的莫过于Model S的起火事故，而在起火事故中最核心的问题就是电池技术。可以说，牵动Tesla股价起起落落的核心元素就是其电池技术，这也是投资者最关心的问题。在美国发生的两起火事故有着相似的情节Model S 撞击到金属物体后，导致电池起火，但火势都被很好地控制在车头部分。在墨西哥的事故中，主要的燃烧体也是电池；而且在3起事故中，如何把着火的电池扑灭对消防员来说都是个难题。 这让很多人产生一个疑问：Model S的电池就这么不禁撞吗?在之前的一篇文章中，我跟大家简单讨论了一下这个问题，但只是停留在表面。读者普遍了解的是，Model S的电池位于车辆底部，采用的是松下提供的18650钴酸锂电池，整个电池组包含约8000块电池单元；钴酸锂电池能量密度大，但稳定性较差，为此Tesla研发了3级电源管理体系来确保电池组正常运作。现在，我们找到了Tesla的一份电池技术专利，借此来透彻地了解下Model S电池的结构设计和技术特征。 电池的布局与形体 FIG3 如专利图所示，Model S的电池组位于车辆的底盘，与轮距同宽，长度略短于轴距。电池组的实际物理尺寸是：长2.7m，宽1.5m，厚度为0.1 m至0.1 8m。其中0.1 8m较厚的部分是由于2个电池模块叠加而成。这个物理尺寸指的是电池组整体的大小，包括上下、左右、前后的包裹面板。这个电池组的结构是一个通用设计，除了18650电池外，其他符合条件的电池也可以安装。此外，电池组采用密封设计，与空气隔绝，大部分用料为铝或铝合金。可以说，电池不仅是一个能源中心，同时也是Model S底盘的一部分，其坚固的外壳能对车辆起到很好的支撑作用。 由于与轮距等宽，电池组的两侧分别与车辆两侧的车门槛板对接，用螺丝固定。电池组的横断面低于车门槛板。从正面看，相当于车门槛板"挂着。电池组。其连接部分如下图所示。 FIG, 4 特斯拉Model S 特斯拉Model S并非小尺寸、动力不足的短程汽车——这是某些人对电动车的预期。作为特斯拉三款电动车中体积最大的车型，根据美国环保署认证，这款快捷、迷人的运动型轿车一次充电能够行驶265英里(426公里)，不过特斯拉声称可以达到300英里。不管哪种情况，这肯定是电动车行业的新高。Model S Performance版本的入门级价格为94,900美元，我测试的版本价格为101,600美元(按照美国联邦税收抵免，可以在此基础上扣减7,500美元)。 在一次开放驾驶上，这款特斯拉汽车硕大的85千瓦时电池的确可以至少行驶426公里。电流来自于车底的电池组，里面有大约7,000颗松下锂电池，重量约为590公斤(1,300磅). 试驾的第二天是前往威斯康辛州，在行驶了320公里后电几乎用光，不过其中包括了在芝加哥的一场交通拥堵中无奈爬行的两个小时。这天的测试充满野心，更多是针对性能而非行驶里程，包括这款特斯拉汽车迅速地用4.4秒时间从0加速到时速97公里(0至60英里每小时)，此外测试达到的最高时速为210公里。 我有没有提到，在0到时速100英里的加速时间方面，这款310千瓦(416马力)的特斯拉汽车将击败威力巨大、使用汽油的413千瓦(554马力)宝马M5？部分原因在于这款特斯拉汽车的同步交流电发动机能够即时提供600牛·米(443英尺磅)的扭矩。像电灯开关一样轻点特斯拉的油门，最大的扭矩已经准备就绪，一分钟内能够实现从0到5,100转。后悬挂、液冷式发动机可以保持1.6万转每分钟，通过一个单速变速箱将动力传导至后轮。 它就像一头冷酷的猛兽，在出奇安静之中让内燃机这个猎物消失于无形——安静到何种程度呢？来自轮胎和风阻的声音比在其他大部分豪华车中感受到的更加明显。安装于车底的电池让特斯拉获得与很多超级车相当的重心，这非常有利于稳定操控。Model S经过弯道的时候也能很好地保持贴地感。 尽管这款特斯拉汽车看起来并不笨重，但其重量达到2,108公斤；随着速度和重力的提升，这些多余的重量表露无遗。加大油门后，沉重的尾部会产生震动。在操控手感的愉悦性方面，特斯拉无法与宝马相提并论，甚至连马自达都赶不上。 美妙的试驾体验在你进入车内之前就开始了，你靠近汽车时，可伸缩的车门把手自动弹出。接着看到的是特斯拉标志性的驾驶室特色内容，一个43厘米(17英寸)电容触摸屏，看起来就像一对相互配合的iPad. 在其用铝合金加强的底盘和车身内，Model S可以容纳5人。一个可爱但是奇怪的按钮可以在车门位置增加脸朝车后的儿童座椅，从而实现最多承载7人。将第二排座椅向下折，可以扩展后座载货空间，可用于家得宝(Home Depot)采购之旅。由于引擎盖下面没有发动机，这些空间可以作为有用的前置行李箱，特斯拉将其称为“前备箱”(“frunk”)，就像保时捷911一样。 华为智慧城市解决方案 价值主张解决方案关键技术成功案例开放合作0305212537 C O N T E N 目录 人类创造出高度的城市文明，高度的城市文明吸引更多的人涌进城市。城市给生活其中的人们创 造无限机会，同时也承受着新生问题带来的巨大压力。治安问题日益突出，教育和医疗资源日渐不足；道路交通越来越拥堵，污染治理成本越来越高昂；能源的单位产出率不断下降，食品安全问题屡见报端。城市建设与发展面临着前所未有的挑战。 信息和通信技术的进步，支撑着城市的建设由工业型向智慧型的发展：网络技术尤其是4G 移动宽带技术的发展，为无处不在的连接提供可能；云计算技术为数据的共享、整合、数据挖掘和分析提供可能；统一通信与协作为跨部门的相互协同提供技术支撑，提高城市管理和应急能动效率。 华为，基于20多年的信息技术积累，打造智慧城市信息高速公路，并在此基础之上，提供智慧政务、平安城市、智慧医疗、智慧教育、智能交通、智能电网、智慧园区、智慧旅游等解决方案，为智慧城市建 设贡献力量。华为智慧城市价值主张 03 华为智慧城市解决方案 https://www.wendangku.net/doc/955801044.html, 打造信息高速公路 倾力助建智慧城市 ?信息高度共享，连接部门孤岛，让信息整合增值 ?带宽无处不在，弥平网络鸿沟，让信息随处畅享 ?业务敏捷灵动，便利应用部署，让服务近在指端 ?安全固若金汤，消除安全隐患，让信息绿色可信 信息高速公路 的四个特征04 价值主张 https://www.wendangku.net/doc/955801044.html, 05 华为智慧城市解决方案 以世界领先的信息与通信技术 构建智慧城市基石 https://www.wendangku.net/doc/955801044.html, 目录 一、特斯拉简介 (3) 二、特斯拉纯电动车主要功能特点 (3) （一）Model S 主要特点 (3) （二）Model X 主要特点 (9) （三）Model 3 主要特点 (12) 三、特斯拉的电池技术 (13) （一）特斯拉动力电池简介 (13) （二）85kwh电池板的拆解分析 (14) （三）单体电池的能量密度 (20) （四）电量的衰减性能 (22) （五）电池检测实验室：从源头保证锂电池单体一致性 (24) （六）动力电池系统PACK技术 (25) （七）电池管理系统（BMS） (27) 四、特斯拉的充电技术 (35) （一）家用充电桩 (35) （二）超级充电桩 (37) （三）目的地充电桩 (38) （四）计划使用太阳能为超级充电站供电 (38) 五、电机及电控的主要技术 (38) （一）感应电机与永磁电机的对比 (39) （二）Model S采用三相交流感应电机 (40) （三）双电机可以有效减少高速时的效率降低，并延长续航能力 (41) （四）电机的结构改进提效并易于自动化 (41) （五）逆变器采用分散塑封IGBT，实现低散热要求 (43) 六、车身的主要技术 (46) （一）全铝车身 (46) （二）Model X的双铰链鹰翼门 (47) 七、安全方面的主要技术 (48) （一）车身的安全设计 (49) （二）电池的安全性 (50) （三）信息安全技术 (51) 八、智能化技术 (51) （一）空中升级 (51) （二）远程诊断 (52) （三）自动求助 (52) （四）交互关系 (52) 特斯拉纯电动车的核心技术分析 一、特斯拉简介 特斯拉(Tesla)，是一家美国电动车及能源公司，产销电动车、太阳能板、及储能设备。总部位于美国加利福尼亚州硅谷帕洛阿尔托（Palo Alto）。 特斯拉第一款汽车产品Roadster发布于2008年，为一款两门运动型跑车。2012年，特斯拉发布了其第二款汽车产品——Model S，一款四门纯电动豪华轿跑车；第三款汽车产品为Model X，豪华纯电动SUV ，于2015年9月开始交付。特斯拉的下一款汽车为Model 3，首次公开于2016年3月，并将于2017年末开始交付。 2016年11月17日特斯拉电动车收购美国太阳能发电系统供应商SolarCity，使得特斯拉转型成为全球唯一垂直整合的能源公司，向客户提供包括Powerwall能源墙、太阳能屋顶等端到端的清洁能源产品。2017年2月1日，特斯拉汽车公司（Tesla Motors Inc．）正式改名为特斯拉（Tesla Inc．）。这意味着汽车不再是特斯拉的唯一业务。 二、特斯拉纯电动车主要功能特点 （一）Model S 主要特点 得益于特斯拉独特的纯电动动力总成，Model S 的性能表现十分出色，0-100公里/小时加速最快仅需2.7 秒。通过Autopilot 自动辅助驾驶（选装），Model S 还可以使高速公路驾驶更为安全且轻松，让你更好的享受驾驶乐趣。 深度揭秘特斯拉Model S底盘：电池组/电机/四驱 特斯拉的第一代产品Roadster，用的是莲花Elise的底盘。这台车当时卖了2000多台。现在，这个经典的跑车底盘又被底特律电动车（Detroit Electric）拿来做另外一款“Roadster”了。 2012年，特斯拉发布Model S。底盘结构由特斯拉自主研发，并为其今后的车系奠定了基础。与燃油汽车不同，特斯拉一个底盘就可以涵盖所有级别的车型。比如将于2017年上市的Model 3，其底盘是在Model S的基础上缩短了轴距而已。 本期，我们来彻底解构下特斯拉Model S的底盘结构。共分为三部分来讲：电池组、电机，以及四驱。先从电池组说起。 特斯拉的电池，是特斯拉的核心专利技术之一，可以说是整台Model S最核心的一个零件。特斯拉一共拥有249项专利，其中有104项是跟电池有关的。与很多采用几个大的电池单元成电池组的布局不同，特斯拉采用的是与笔记本一样的电池。整台Model S的整备质量为2108kg（2.1吨），其中电池组的重量就占了600kg（0.6吨）。作为一辆D级豪华车，特斯拉Model S并没有超重。这在很大程度上得益于Model S的全铝车身。 由于电池组横贯于位于车辆底部，这使得Model S的重心得以降低，平衡了配重，从而提升了操控性。根据官方数据，Model S的前后配重比为48：52。 在Model S刚上市时，按照电池划分共有3款型号，分别是85kWh、60kWh，以及40kWh。2013年，由于40kWh车型销量惨淡，特斯拉决定停止销售。不久前，特斯拉又推出了70Kwh车型，来取代之前的60kWh版本。 值得一提的是，当年60kWh的车型与40kWh的车型，电池组其实是一样的；两者的区别在于，特斯拉将40kWh的电池进行了软件限制，从而在一个可容纳60kWh电量的电池组中，只有40kWh的电量可用。 而85kWh电池与60kWh电池的区别，主要是电池组中装配的电池单元数量。85kWh的电池组电压为400V，由一共16个电池包组成，每个电池包装配了444颗电池单元，所以这个电池组一共有7104颗电池组成。60kWh，则是由14个电池包，共计6216颗电池单元组成。这里所说的电池单元，是由松下提供的 NCR-18650A型电池。 18650是可充电锂离子电池的一种型号，它的命名来源于这种电池的尺寸 --18mm*65mm，但由于还要加入保护电路，所以电池的实际尺寸要略微大几零点几毫米。18650电池的主要用途，是笔记本电脑的电池，它有很多生产厂商；而特斯拉则选用了松下提供的18650电池，但要注意特斯拉使用的电池与笔记本中的电池还是有差别。18650只是一个统称。 特斯拉电动车2013全球销量 ————————————————————————————————作者：————————————————————————————————日期： 特斯拉的2013年：利润超1亿美元售车2.25万辆 2014年02月20日来源：第一电动网 特斯拉（NASDAQ:TSLA）将2013年一季度创出的盈利“奇迹”延续到了全年。按照特斯拉一贯采纳的非通用会计准则（Non-GAAP），特斯拉2013年赚得超过1亿美元的利润。特斯拉的电动汽车销量也大为增长，达到了约2.25万辆。 近日，特斯拉发布财务数据称，根据GAAP准则，即不计入股权奖励支出及其他一次性项目，特斯拉2013年营业收入为20.13496亿美元，对比2012年的4.13256亿美元，同比增长387.2%。而按照非GAAP准则，特斯拉2013年营业收入为24.77662亿美元，对比2012年的4.13256亿美元，同比增长499.5%。 根据GAAP准则，特斯拉去年亏损额为7401.4万美元，2012年则为39621.3万美元，同比削减81.3%。按照非GAAP准则，特斯拉去年实现利润10356.3万美元，2012年亏损34421.4万美元。 特斯拉汽车于美国时间本周三下午发布了2013年的致股东邮件。邮件显示，第四季度，特斯拉创纪录地销售了6892辆电动汽车，全年销量22477辆。 未来，特斯拉还计划在美国发展超级充电站网络和服务中心，推动汽车销售。此外特斯拉还预计，欧洲和中国市场将带来巨大销量。2014年的汽车总销量将达到3.5万辆，比今年的22477辆高55%。 彩页（电子版）设计要求（讨论稿） 为直观反映、全面呈现翱翔学员的研究性学习成果（小论文或小发明），根据《北京青少年科技创新学院?翱翔计划?学员研究性学习评价工作方案》要求，学员应依据成果内容，独立设计完成彩页（电子版），具体要求如下： 一、彩页设计原则 1．整体性，包括色调统一，主题突出，信息传达明确等； 2．真实性，包括如实呈现成果内容，体现研究过程的真实性等； 3．创新性，包括设计新颖，视觉效果突出等； 4．艺术性，包括编排美观，色彩鲜明，图文并茂，布局合理等。 二、彩页内容要求 彩页内容包括彩页题目、基础信息和成果内容3个方面。 （一）彩页题目 彩页题目即为研究性学习成果（小论文或小发明）的题目。 （二）基础信息 1．包括学员姓名、所在学科领域、所在学校、基地学校、高校或科研院所实验室的全称，以及相关指导教师等信息。 2．需含学员正面、免冠一寸近照一张。 若成果为合作项目，应在学员姓名，及其对应的所在学校、所在学校指导教师及学员照片左（右）上角标明相同的上角标。 （三）成果内容 应以清晰、简洁的语言，科学、合理的构图，严谨、简明的表格，生动、丰富的图片（至少含一张清晰的图片）呈现成果的内容、意义和价值。 一般包括选题价值、材料与方法、结果与分析、讨论、结论等，要保证内容的真实、可靠，体现学员成果（小论文或小发明）的客观水平。 三、彩页设计规格 1．彩页为竖版：长28.5cm（29.7cm），宽21cm（A4纸大小）；文件格式： pds或tiff；分辨率：300dpi。 2．页边距：上2.5-3cm，下2cm，左右2cm。 3．成果内容按各层级安排好字体、字号和格式。其中，彩页题目字体不限，字号为二号字，基础信息部分字体为宋体五号字，成果内容部分字体在五号字和四号字之间。 成果内容编排可一栏或分栏，以美观、便于阅读为宜。并选择对称或均衡的构图方式， ChannelMaster 型H-ADCP 高质量水平声学多普勒流速剖面仪 ChannelMaster 型水平声学多普勒流速剖面仪（简称CM型H-ADCP）是RDI公司新一代ADCP产品。它结构紧凑、标准配置高、功能强、适用范围广。 ChannelMaster 型H-ADCP主要特点： ? 采用RDI公司宽带专利技术。 ? 高精度、高空间和时间分辨率。可以使用较小的单元、在较短的采样时间步长内获得精确的流速数据。 ? 对于很难测验的低流速和非恒定流也能获得高质量测验数据。 ? 标准配置1－128 个可选单元、0.1－10 m 可选单元长度、1－300 m剖面范围（取决于系统频率）。可以得到更多的流速数据，具有很大的灵活性。 ? 标准配置超声波水位计和压力式水位计。 ? 标准配置倾斜计。倾斜计对于调整H-ADCP安装支架和监测安装支架的倾斜变化从而保证测验数据质量具有重要的作用。? 标准配置不锈钢安装底座，使H-ADCP安装十分方便。 在二十多年的发展历程中，RDI公司始终位于ADCP技术的世界领先地位。RDI公司已通过 ISO9001 国际质量体系认证。 左上：300kHz H-ADCP；右上：300kHz H-ADCP/不锈钢底座左下：600kHz H-ADCP；右下：1200kHz H-ADCP 2003年4月初稿 ChannelMaster 型H-ADCP技术指标 Corporate Headquarters: RD Instruments (USA) 9855 Businesspark Avenue San Diego, CA 92131-1101 USA Tel +1-858-693-1178 Fax +1858-695-1459 E-mail: sales@https://www.wendangku.net/doc/955801044.html, https://www.wendangku.net/doc/955801044.html, 2003年4月初稿Tesla Model S底盘全透视..
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