a r X i v :a s t r o -p h /9902176v 1 11 F e
b 1999
A&A manuscript no.
(will be inserted by hand later)
ASTRONOMY
AND
ASTROPHYSICS
1.Introduction
The Hubble Space Telescope (HST)allows the derivation of color magnitude diagrams (CMDs)of Galactic globular clus-ters (GCs)which extend to almost the faintest visible stars,just above the hydrogen-burning limit for the nearest clusters (King et al.1998).These CMDs can be used to extract luminosity
2Piotto and Zoccali Table1.Data Set
M22HST30-9-1995F606W1100
””F606W1200×3
””F814W1100
””F814W1200×3
DUTCH15-4-1997V45
””V1500
””I45
””I1500
M55HST4-11-1995F606W1100
””F606W1200×5
””F814W1100
””F814W1200×5
DUTCH15-4-1997V45
””V1500
””I45
””I1500
M10HST10-10-1995F606W1100
””F606W1200×9
””F814W1100
””F814W1200×9
JKT30-5-1997V15
””V45
””V1500
””I15
””I45
””I1500
HST LFs of M10,M22,and M553
magnitudes was performed by comparison with the stars in the overlapping HST?elds.We?rst adopted the color term ob-tained for the same telescopes during the previous nights in the same run(Rosenberg et al.1999).The zero points have been calculated by comparing all the non-saturated stars in the WFPC2chips that were also measured in the ground-based im-ages.The uncertainties in the V zero points are0.004,0.035, and0.015magnitudes(the errors refer to the errors on the mean differences)for M10,M22,and M55,respectively.The errors in the(V?I)colors are0.006,0.055,and0.025,re-spectively.The zero point uncertainties for M22are noticeably larger than for the other two clusters.This fact is due to the smaller overlap in magnitude between the
ground-based and the HST photometries,as can be seen in Fig.2.The calibra-tion of the M22and M55CMDs has been further checked by comparing these diagrams with other independently calibrated V vs.(V?I)ground-based CMDs kindly provided by Alfred Rosenberg(Rosenberg et al.1999).The two sets of data are consistent within the uncertainties given above.
Shorter-exposure HST images(or longer-exposure ground-based frames)are desirable for a smoother overlap of the two data sets.Note that this problem does not affect the LF pre-sented in Section4.Indeed,a zero point error of a few hundreds
of a magnitude is perfectly acceptable for a LF with magnitude bins of0.5mag.
2.3.Arti?cial star tests
Particular attention was devoted to estimating the complete-ness of our samples.The completeness corrections have been determined by standard arti?cial-star experiments on both the HST and ground-based data.For each cluster,we performed ten independent experiments for the HST images and?ve for the ground-based ones.In order to optimize the cpu time,in our experiments we tried to add the largest possible number of arti?cial stars in a single test,without arti?cially increasing the crowding of the original?eld.The arti?cial stars have been added in a spatial grid such that the separation of the centers in each star pair was two PSF radii plus one pixel.The position of each star is?xed within the grid.However,the grid was ran-domly moved on the frame in each different experiment.We veri?ed that in this way we were not creating over-crowding by running an experiment with half the number of arti?cial stars. The?nding algorithm adopted to identify and measure the arti-?cial stars was the same used for the photometry of the original images.The arti?cial stars were added on each single V and I frame.For each arti?cial star test,the frame to frame coordinate transformations(as calculated from the original photometry) have been used to ensure that the arti?cial stars were added ex-actly in the same position in each frame.We started by adding stars in one V frame at random magnitudes;the corresponding I magnitude for each star was obtained using the?ducial line of the instrumental CMD.Finally,in each band,we scaled the magnitudes according to the frame to frame magnitude offset as calculated from the original photometry.The frames obtained in this way were stacked together in order to perform star?https://www.doczj.com/doc/ae1647909.html,posite CMD for6986stars in M10.The ground-based data are from the JKT telescope.
ing and obtain the most complete star list.The latter was used to reduce the single frames simultaneously with ALLFRAME, following all the steps and using the same parameters as on the original images.
In order to take into account the effect of the migration of stars toward brighter magnitudes in the LF(Stetson&Harris 1988),we corrected for completeness using the matrix method described in Drukier et al.(1988).
In the LFs presented here,we include only points for which the completeness?gures were50%or higher,so that none of the counts have been corrected by more than a factor of2.
A comparison between the added magnitudes and the mea-sured magnitudes allows also a realistic estimate of the pho-tometric errorσpho(de?ned as the standard deviation of the differences between the magnitudes added and those found)as a function of magnitude.We use this information in different places in what follows.
3.The color-magnitude diagrams
The CMDs derived from the photometry discussed in the previ-ous Section are presented in Figs.1,2,and3.The upper part of the CMDs comes from the ground-based data,while the lower part is from the three WF cameras of the WFPC2.In the case of M22,the CMD for magnitudes fainter than V=19.8comes from the WF2only:the differential reddening of this cluster(Peter-son and Cudworth1994)makes the sequence much broader than expected from the photometric errors.The MS of M22 from the three WF cameras is shown in Fig.4.In Table2the
4Piotto and
Zoccali
https://www.doczj.com/doc/ae1647909.html,posite CMD of5385stars in M22.The ground-based data are from the ESO-Dutch telescope.For the HST data only the stars in the WF2?eld are shown.
Table2.
20.50.0680.0360.058
21.50.0690.0450.052
22.50.0720.0520.048
23.50.0810.0710.039
24.50.0930.0790.049
25.50.1000.0860.051
σ2MS?σ2
(V?I) = 0.05magnitudes.This value must be considered as an upper limit for the differential reddening in this region.
The ground-based and the HST?elds are partially overlap-ping,with the ground-based images always covering a larger portion of the cluster.A detailed discussion of these CMDs will appear elsewhere.Here it suf?ce to note that we measured stars from the tip of the giant brach to a limiting magnitude V～28.
A white dwarf cooling sequence is clearly seen in all diagrams (but it will be discussed elsewhere).For the?rst time,we have a complete picture of a simple stellar population about15
Gyr https://www.doczj.com/doc/ae1647909.html,posite CMD of8121stars in M55.The ground-based data are from the ESO-Danish telescope.
after its birth,from close to the hydrogen-burning limit to the ?nal stages of its evolution along the white dwarf sequence. These diagrams can be used for a?ne tuning of the stellar evo-lution and population synthesis models(Brocato et al.
1996). Fig.4.CMD of13359stars from the three WF?elds of M22. The large dispersion of the MS is interpreted in terms of a dif-ferential reddening of～0.05magnitudes in(V?I)
.
HST LFs of M10,M22,and M55
5 https://www.doczj.com/doc/ae1647909.html,parison between the observed CMD of M10and the
models by the Lyon group(left panel),and the Teramo group
(right panel)for[M/H]=?1.3(solid line)and[M/H]=?1.5
(dashed line).The open circles represent the MS ridgeline.
Contamination by foreground/background stars is small for
M10,as expected from its galactic latitute(b=23?),though a
few background stars(likely from the outskirts of the Galac-
tic bulge)are present.Despite the fact that M55has the same
latitude as M10,a
signi?cantly larger fraction of?eld stars is
visible in the CMD of Fig.3.Some of these stars are likely
bulge members,but the prominent sequence blueward of the
MS of M55must be associated with the MS and TO of the stars
in the Sagittarius dwarf spheroidal galaxy(Mateo et al.1996,
Fahlman et al.1996).M22is the most contaminated cluster.
Both Galactic disk and Galactic bulge stars are clearly seen in
the CMDs of Figs.2and4.
Deep CMDs also contain information on the low-mass con-
tent of the clusters.This information can be extracted from our
data only after we have a reliable transformation from lumi-
nosities to masses.Unfortunately,such a transformation re-
mains uncertain for low-metallicity,low-mass stars.Almost
nothing is known from the empirical point of view,and differ-
ent calculations of stellar models yield different masses,par-
ticularly for the lowest-mass stars(King et al.1998),and dif-
ferent overall trends(slopes)for the mass-luminosity relations
(MLRs).
As already found for NGC6397(King et al.1998)and the
other three metal-poor clusters studied by PCK(cf.their Fig.3),
among the existing models we?nd that those by the group in
Lyon(Baraffe et al.1997)and by the group in Teramo(Cas-
sisi et al.1998,in preparation)best reproduce the observed
sequences of M10,M22,and M55.[Note that Cassisi et al.’s
(1998)models below0.5m⊙(M V～8.1)are the same models
as in Alexander et al.(1997).]The level of agreement between
the models and the observed data can be fully appreciated in
Figs.5,6,and7.In these?gures the open circles represent the
MS ridgeline,obtained by using a mode-?nding algorithm and
https://www.doczj.com/doc/ae1647909.html,parison between the observed CMD of M22and the
models by the Lyon group(left panel),and the Teramo group
(right panel)for[M/H]=?1.5(dashed line)and[M/H]=
?2.0(solid line).The open circles represent the MS ridgeline.
https://www.doczj.com/doc/ae1647909.html,parison between the observed CMD of M55and the
models by the Lyon group(left panel),and the Teramo group
(right panel)for[M/H]=?1.5(dashed line)and[M/H]=
?2.0(solid line).The open circles represent the MS ridgeline.
a kappa-sigma iteration in order to minimize the?eld star con-
tamination.The dotted line represents the V magnitude limit
of the LFs presented in the following Section4;the data be-
low this magnitude limit are not used in the present paper.The
dashed line shows the isochrone corresponding to the metallic-
ity which best matches the Zinn and West(1984)[Fe/H](iron)
content,scaled to the appropriate metallicity[M/H]assuming
[O/Fe]=0.35(Ryan and Norris1991),and using the relation by
Salaris,Chief?,and Straniero(1993).According to Table3,we
used the models for[M/H]=?1.5for M22and M55,and the
models for[M/H]=?1.3for M10.For comparison reasons,
6Piotto and Zoccali Table3.Adopted Parameters
M10Baraffe et al.14.200.29-1.3
Cassisi et al.14.250.23-1.3
M22Baraffe et al.13.700.37-1.5
Cassisi et al.13.710.31-1.54
M55Baraffe et al.13.900.14-1.5
Cassisi et al.14.150.10-1.54
HST LFs of M10,M22,and M55
7 Fig.8.The V(lower panel)and I(upper panel)ground-based
(open
circles)and HST(?lled circles)LFs of M10from the
CMD of Fig.1.The ground-based LFs have been scaled to the
HST area.The arrows indicate the TO position.The error bars
are plotted only when they exceed the symbol size.
the HST LF,particularly at the lower end;this might be due
to a mass-segregation effect.In Fig.9the open triangles show
the LF obtained by De Marchi and Paresce(1997)from the
same HST data.Despite the fact that the photometry has been
obtained in a completely independent way,and using rather dif-
ferent reduction procedures,it is comfortable to see that there
is perfect agreement between the two LFs down to I=23.25,
where the completeness is only56%(cf.Table5).We have
already commented how,below I～23.5,the incompleteness
and,most importantly,the dif?culties in the?eld-star contam-
ination estimates make the LF rather uncertain,and we prefer
to avoid presenting data that are too uncertain.
As was discussed in Section1,all three clusters have com-
parable metallicities(within～0.3dex).This fact allows to
compare directly their LFs,without having to pass through the
uncertain MLRs.Similarities or differences among the LFs of
the three clusters re?ect directly similarities or differences in
their MFs.In addition,the HST?elds where the LF was mea-
sured for M10,M22,and M55are all located very close to the
half-mass radius(r obs/r h=1.1for M55,r obs/r h=1.4for M10,
and r obs/r h=1.8for M22).This is a particularly fortunate case,
as Vesperini and Heggie(1997),among others,have shown that
the LF observed close to the half-mass radius in a King model
(i.e.,not collapsed)cluster,is close to the global(present day)
LF.In other words,as a?rst approximation,our LFs do not
need any mass-segregation correction.
Fig.9.The V(lower panel)and I(upper panel)ground-based
(open circles)and HST(?lled circles)LFs of M22from the
CMD of Fig.2.The ground-based LFs have been scaled to
the HST area.The arrows indicate the TO position.The er-
ror bars are plotted only when they exceed the symbol size.
The open triangles show the LF obtained by De Marchi and
Paresce(1997)from the same HST data.
The comparison is shown in Fig.11(V LFs)and Fig.12
(I LFs).The adopted apparent distance moduli and reddenings
are given in Table3(Baraffe et al.rows).In the absence of
a means of normalizing the three LFs to a global cluster pa-
rameter,arbitrary constants determine the vertical positioning
of the individual LFs.We have chosen these constants exactly
as described in PCK.Brie?y,vertical shift of the M10,M22,
and M55LFs were made to bring them into alignment,ac-
cording to a least-square algorithm,in the magnitude intervals
4.0 5.5.The overall trend of the LFs in Fig.11and Fig.12is similar,with a steep rise up to M V～10(M I～8.5),followed by a drop to the limiting magni- tude of the present investigation.Indeed,both the V and I LFs for M10reach their maximum at magnitudes～0.5fainter than in M55and M22.This is qualitatively consistent with the fact that M10is slightly more metal rich than the other two clusters (D’Antona and Mazzitelli,1995). Despite the fact that the overall shape of the LF of M10is similar to the others,a close inspection of Figs.11and12re- veals that it is signi?cantly steeper than the other two LFs.This difference can hardly be due to any internal dynamical evolu- tion,if we consider that the three clusters have similar internal structures.Even if we did not fully trust the dynamical models (both King-Michie models and N-body simulations,Vesperini 8Piotto and Zoccali Fig.10.The V(lower panel)and I(upper panel)ground-based and HST(?lled circles)LFs of M55from the CMD of Fig.3. The ground-based LFs are from Zaggia et al.(1997,?lled tri-angles)and Mandushev et al.(1996,open circles).The LF from Zaggia et al.have been normalized to the HST area,while the Mandushev et al.LF has been scaled to the total counts in the common magnitude range.The arrows indicate the TO position.The error bars are plotted only when exceeding the symbol size. Table4.M10Luminosity Function 18.2591116.7544 18.75162017.2569 19.25212717.751120 19.75253218.251630 20.25534618.754134 20.75726819.257564 21.25879419.759898 21.75897820.25115115 22.25796820.7510199 22.7510811021.25149157 23.2511612421.75179202 23.7516318722.25222255 24.2518822022.75250323 24.7520326023.25180243 25.2517523023.75141195 25.7512616724.25104150 26.2510216124.754686 26.755575 27.254580 27.751934 HST LFs of M10,M22,and M559 Table5.M22Luminosity Function 15.256613.9455 15.755514.4655 16.258814.9977 16.75101015.5488 17.25292916.172222 17.75404816.694436 18.25516517.166551 18.75598317.638158 19.25768218.25105104 19.75898918.75127128 20.2512010619.25119130 20.7511110819.75123145 21.2514113720.25144175 21.7514914420.75197264 22.2518519521.25292395 22.7521524921.75272427 23.2524429522.25237397 23.7524530122.75189325 24.2519727623.25140251 24.75164243 25.25125181 25.75121226 26.2577146 V N N corr I N N corr and Heggie1997),which predict that our local LFs for M10, M22,and M55closely resemble the global ones,it is notewor-thy that the M10?eld is at an intermediate position in terms of half-light radius r h,between the M55and the M22?elds. Therefore,the differences in LF slopes cannot be due to mass segregation. 5.The mass functions The LFs can be transformed into MFs using a MLR.As em-phasized in Section3,such transformations are still uncertain for low-mass,low-metallicity stars,and we must rely on the models almost entirely.It is somehow reassuring that not only at least two of the existing models are able to reproduce the ob-Fig.13.The MFs of M10,M22,and M55from the I LFs and from different theoretical MLRs are compared.For reasons of clarity the MFs are arbitrarily shifted on the vertical axis. https://www.doczj.com/doc/ae1647909.html,parison of the MFs of M10,M22,and M55from the V and I LFs and from the Teramo MLRs.For reasons of clarity the MFs are arbitrarily shifted on the vertical axis. 10Piotto and Zoccali served diagrams,but also the distance moduli and reddenings that result from the ?t are in agreement,within the errors,with the values in the literature.This does not mean that the models by the Lyon and the Teramo groups used in Section 3are the correct ones.They are simply the best ones presently available,and we will use both of them to gather some information on the general shape of the MFs of M10,M15,and M22.The caution-ary remarks on the absence of empirical MLR data should still be heeded.For the sake of comparison,and in order to give an idea of the possible range of uncertainty,we will also use the MLR of the Roma group (D’Antona and Mazzitelli 1995).In Fig.13we compare the MFs derived from the I LFs of M10,M22,and M55from the TO down to ～0.11m ⊙.An arbi-trary vertical shift is applied for reasons of clarity.The adopted distance moduli,reddenings,and metallicities for the MFs ob-tained using the Lyon and Teramo models are in Table 3.For the Roma model we adopted the values in Djorgovski (1993)and used the isochrone corresponding to 10Gyr. The MFs obtained using the Lyon and Teramo models track one other closely for m <0.6m ⊙.The small differences for higher masses might be due,at least in part,to the difference in the adopted ages.The MFs from the Roma models are system-atically steeper,as already noted in PCK.Fig.14compares the MFs obtained from the V and I LFs,using the Teramo mod-els.In all cases,the two MFs are very similar,despite the fact that the two LFs have been independently obtained.This result is also reassuring on the theoretical side,showing the internal consistency of the models. In all cases,there is a hint of ?attening at the low-mass end,but no sign of a drop-off. As the transformation from the LF to the MF is the weakest part of the present analysis,we prefer not to comment further on the detailed structure of the MF.We note only that the slopes of the MFs below 0.5m ⊙,using any existing MLRs,are shal-lower than the x =1slope (x =1.35for the Salpeter MF in this notation)for which the integration of the total mass down to m =0would diverge. https://www.doczj.com/doc/ae1647909.html,parison with other clusters It is interesting to compare the LFs in Fig.11and 12with the LFs of other GCs with similar metallicity.The only other homogeneous set of V and I LFs extending from the TO to m <0.15m ⊙has been collected by PCK for M15,M30,M92,and NGC 6397.In addition,Ferraro et al.(1997)have published an I LF for NGC 6752.There are two other clusters,which have a metallicity comparable to M22and M10,and for which deep HST LFs have been published:ωCen (Elson,Gilmore,and Santiago 1995)and M3(Marconi et al.1998).In both cases,saturation of the brightest stars does not allow to extend the LFs to the TO and we will omit them in the present comparison.As discussed in King et al.(1995)and PCK,at the inter-mediate radius at which M15,M30,M92,and NGC 6397were observed,their LFs are fortuitously close to the global ones,with differences that nowhere exceed a few tenths in the log- Fig.15.The theoretical LFs from the Baraffe et al.(1997)models for a power law MF with slope x=-0.3and metallic-ities as shown in the labels are compared with the V LFs on M15,M30,M92,and NGC 6397.In the metallicity interval covered by the clusters in our sample,the theoretical LFs look quite similar. arithm (PCK),with the local LFs being always steeper than the global ones.So,a comparison of these LFs with the LFs of M10,M22,and M55should be only marginally affected by mass segregation effects.Unfortunately,no detailed dynami-cal model for NGC 6752is available at the moment.We ran a multi-mass King-Michie model on this cluster (cf.Section 7).We ?nd that the locally observed LFs of NGC 6752is signi?-cantly ?atter than the global one. The metallicity of the three clusters presented in this paper is slightly higher than that of the clusters in PCK.We need to investigate the effect of this metallicity spread on the LFs.In Fig.15the theoretical LFs for a power law MF with a slope x=0.3and three different metallicities are plotted together with the V LFs of the four clusters in PCK used as reference.The three theoretical LFs are quite similar in the metallicity interval which span the entire metallicity range of the clusters discussed in the following. Figs.17and 16compare the V and I LFs of M10,M22,and M55with the LFs of all the clusters with [Fe/H] HST LFs of M10,M22,and M55 11 Fig.16.As in Fig. 17,but for the I LFs.The I LF of NGC 6397is from King et al.(1998).The LF of NGC 6752is from Fer-raro et al.(1997).As in Fig.17,note the spread in slope.the fact that the general trend of these LFs is similar,their slope is different.These differences are much larger than expected from the error bars (Figs.11and 12)and from the cluster metal-licity differences (Fig.15),i.e.imply different (local)MFs.In view of the small expected correction for the mass segregation above discussed,this also imply different global present day MFs. Had we chosen to align the LFs at the faint end instead of the bright end,the result would have been the same,as shown in Fig.18.This ?gure explicitly shows that the differences among the GC LFs become apparent only when they are extended to the TO.7.Discussion The differences among the LFs noted in the previous Section suggest differences among the observed MFs.They mainly im-ply that the ratio of the low mass to high mass stars differs from cluster to cluster.It is interesting to further comment on the possible origin of these differences.There are two possibil-ities: –The differences are primordial,i.e.the Galactic GCs are born with different IMFs; –The differences are a consequence of the dynamical evo-lution,both internal (energy equipartition,evaporation),or externally induced by the gravitational potential of our Ga-laxy. Fig.17.The V and I LFs of M10,M22,and M55are compared with the LFs of all the clusters with [Fe/H] Of course,it is not possible to test the ?rst hypothesis di-rectly,and a combination of the above two possibilities cannot be excluded.PCK,relying on the presently available models for M15,M30,M92,and NGC 6397,and on the Galactic orbits of some of these clusters,propose that the different shape of the LF of NGC 6397with respect to the other three arises from the interaction of this cluster with the Galaxy.It is a consequence of the frequent tidal shocks experienced by NGC 6397along its orbit. At the time we are writing this paper,the number of clusters at our disposal is more than doubled,though it is still too small for any detailed analysis.As discussed in the previous Section,among the GCs with deep HST LFs,there are 8clusters with a LF extending from the TO to somewhat above 0.1m ⊙.As a sort of exercise,we can try to look for possible dependences of the overall shape of the MFs on the observable parameters which characterize the GGC population. This analysis can be done if we can:–Correct for mass segregation effects (though these have been anticipated to be small,with the only exception of NGC 6752); –Parametrize in some way the MF shape. 12Piotto and Zoccali Fig.18.As in Fig.16,but with a different normalization inter-val. In view of the still relatively small sample of objects,we have chosen a very simple approach.We have limited our anal-ysis to the 3clusters presented in this paper,the four objects of PCK,and NGC 6752(Ferraro et al.1997).The other three ob-jects with deep HST LFs have not been considered as their LFs are not complete,lacking the brightest part (from ～0.5m ⊙to the TO). First of all,the LFs have been trasformed into MFs using Baraffe et al.’s (1997)MLRs for the appropriate metallicity and using the distance modulus which best ?ts the CMDs (cf.pre-vious Sections). Second,we run a King-Michie model in order to have a ?rst approximation correction for the mass segregation ef-fects.We used the code kindly provided by Jay Anderson and described in Anderson (1998),which is based on the Gunn and Grif?n (1979)formulation of the multimass King–Michie model.These models have a lowered-Maxwellian distribution function,which approximate the steady-state solution of the Fokker–Planck equation (King 1965).In the case of the post–core–collapse (Djorgovski and King 1986)clusters these mod-els do not incorporate important physical effects,most impor-tantly,the deviation from a Maxwellian distribution function in the collapsed core (Cohn 1980).However,they are the simplest models that can predict the radial variation of the MF due to en-ergy equipartition,and rather realistically,as shown by King et al.(1995)and Sosin (1997,see also King 1996).On the other side,as shown by Murphy et al.(1997)for M15,mass segre-gation prediction of King-Michie models are not very different from what found with more sophisticated Fokker–Planck mod-els. For NGC 6397we used the same model parameters ob-tained by King et al.(1995),for M15the parameters by Sosin and King (1997),and for M30the parameters by Sosin (1997).For M92,we used the model parameters by Anderson (1998).The details of the models for the other clusters will be de-scribed elsewhere.We essentially followed the same procedure described in Sosin (1997).Brie?y,we calculated the model by ?rst choosing the core and tidal radii given by Trager,King and Djorgovski (1995).We then de?ned 17mass groups,whose number of stars and averaged masses were constrained to agree with the observed MF at the distance from the cluster center of the observed ?eld.We then added a group of 0.55m ⊙white dwarfs chosen (somewhat arbitrarely)to contain 20%of the cluster mass.Finally,we added 1.4m ⊙dark remnants and ad-justed their mass fraction (usually around 1.5%)to make the radial pro?le of the stars in the brightest bin agree with the sur-face density pro?le of Trager et al.(1995). One of the outputs of the models are the global MFs for each cluster.In our model,the NGC 6752?eld is located in a position strongly affected by mass segregation.In view of the large correction we should apply to its local MF in order to have the global one,the further uncertainties in the model due to the post–core–collapse status of this cluster,and the strong deviation from a power law of its MF (likely a further effect of the mass segregation),we will not include NGC 6752in the following analysis. We ?tted the global MFs of the remaining seven clusters with a power law ξ(m )=ξ0m ?(1+x ),and used the index x as a parameter indicating the ratio of low mass to high mass stars.The power law has proven to ?t reasonably well all the seven global MFs.In view of the uncertainties associated to the MLR and to the model itself,any more sophisticated analysis is not justi?ed. The slopes of the global present day MFs for m <0.7m ⊙for the clusters in our sample are plotted in Fig.19against the half mass relaxation time (T rh ),the position within the Galaxy (the galactocentric distance R GC and the distance from the disk Z )and the destruction rates ν(in units of inverse Hubble time)as calculated by Gnedin and Ostriker (1997).The error bars show the formal error of the ?t,and do not include the error in the MLR and the error associated to the mass segregation cor-rection.The full circles show the slope of the global MF,while the open circles refer to the slopes of the original (local )MF.As already anticipated,the corrections for mass segregation are in general small.The discussion which follows applies to both the global and local MFs. The slopes have a large dispersion,showing that the present day global MFs signi?cantly differ from cluster to cluster. Clusters with larger ν(and smaller T rh )tend to have ?atter MFs,suggesting that the observed differences in the MF slopes might be related to the cluster dynamical evolution.There is also an indication of a trend with the distance from the Galac-tic center which resembles a similar dependency suggested by Djorgovski,Piotto and Capaccioli (1993),and which has HST LFs of M10,M22,and M55 13 Fig.19.Univariate correlations of the slopes of the global (full dots )and local (open circles )MFs with the distance from the Galactic center R GC ,from the Galactic plane Z ,the half mass relaxation time (T rh ),the destruction rate ν,and the metallicity [M/H],calculated as in Section 3,assuming [O/Fe]=0.3.The MFs have been ?tted with a power law in the mass interval m <0.7m ⊙.The error bars represent the standard deviation of the slope of the straight line ?tted to the data in the Log-Log plane.Note the large dispersion of the data.Clusters with smaller T rh and νhave ?atter MFs.been interpreted in terms of evidences of a dynamical evolu-tion (Capaccioli,Piotto and Stiavelli 1993).Also a dependency on metallicity cannot be excluded,as shown in Fig.19.How-ever,the uncertainty associated to the various transformations from the local LFs to the global MFs,and the small number of points do not allow to assess the signi?cance of any of these trends. Another interesting feature from the slopes in Fig.19is their low value.For m <0.7m ⊙the MFs never exceed a slope x =0.3,ranging in the interval ?0.5 and ?eld stars.A slope x =0.3is also proposed by Kroupa,Tout,and Gilmore (1993)and Kroupa 1995for the ?eld stars.More recently,Gould,Bahcall,and Flynn (1996)?nd a smaller x =?0.1for m <0.6m ⊙,though this value is uncertain because it is based on a small number of stars.Still,the Galactic cluster and ?eld star MF slopes seem to represent an upper limit to the GC present day MF slopes. This result implies that either the IMF of some GCs was ?atter than the ?eld MF,or the present day MFs in GCs do not represent the IMF(s),at least for some of the clusters in this sample.This could imply an evolution of the GC MF with time,with a tendency to ?atten.This might be another evidence of the presence of dynamical evolution effects as predicted by the theoretical models (Chernoff and Weinberg 1990,Vesperini and Heggie 1997)and invoked by Capaccioli et al.(1993)and PCK in order to explain the observed GC MFs. 14Piotto and Zoccali Another consequence of the?atness of the MF is that the contribution to the total cluster mass by very-low-mass stars and brown dwarfs is likely to be negligible.Of course,the frac-tion of mass in form of brown dwarfs depends on(1)the MF slope in the corresponding mass interval and(2)the lower limit we assume for the brown dwarf masses(m low).As a working hypothesis,we might assume that we can extrapolate the MF power law which represents as a?rst approximation the GC present day MF for0.1 Acknowledgements.We are deeply grateful to Peter Stetson for pro-viding us the mask?les for vignetting and pixel area correction for WFPC2,and the PSF?les,and for providing the most up-to-date versions of his programs.We thank also Jay Anderson for making available his multimass King-Michie code.We are particularly in-debted to Ivan King who carefully read the manuscript and persua-sively pushed us to make the mass segregation corrections and the comparisons of the last Section.This work has been supported by the Agenzia Spaziale Italiana and the Ministero della Ricerca Scienti?ca e Tecnologica. 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HILTI化学锚栓-HVU承载力计算（喜利得CC法） 1 化学锚栓抗拉性能计算 单根锚栓抗拉承载力设计值取下列两者中的最小值： N Rd,c ：混凝土边缘破坏承载力 N Rd,s ：钢材破坏承载力 1.1 N Rd,c —— 混凝土锥体破坏抗拉承载力设计值计算 计算公式：N Rd,c =N Rd,c0×f B,N×f T×f A,N×f R,N 公式中：N Rd,c0 —— 混凝土锥体破坏的抗拉承载力设计值，通过标准值N Rk,c0由公式N Rk,c0 /γMc,N,得到，其中分项安全系数γMc,N 取 1.8， N Rd,c0按表L.1.1.1确定。 表L.1.1.1 混凝土锥体破坏的抗拉承载力设计值及标准埋置深度 锚栓规格 M8 M10 M12 M16 M20 N Rd,c0 (kN) 12.4 16.6 23.8 34.7 62.9 h nom (mm)1）80 90 110 125 170 注：1）h nom 为标准埋置深度 公式中：f B,N ——混凝土强度影响系数，不同标号混凝土系数按表L.1.1.2确定。 表L.1.1.2混凝土强度影响系数 混凝土强度等级立方体抗压强度 f B,N f ck,cube(N/mm2) C20 20 0.94 C25 25 1.0 C30 30 1.05 C40 40 1.12 C45 45 1.20 C50 50 1.25 C55 55 1.30 C60 60 1.35 注：f B,N 也可按公式计算： f B,N =1+(f ck,cube -25 ) / 80 限制条件： 20 N/mm2≤f ck,cube ≤ 60 N/mm2 公式中：f T ——埋置深度影响系数，可按公式计算： f T = h act / h nom 实际埋深限制h act： h nom≤h act≤2.0×h nom 公式中：f A,N ——锚栓间距影响系数，按表L.1.1.3确定。 表L.1.1.3锚栓间距影响系数 锚栓间距 锚栓规格 s(mm) M8 M10 M12 M16 M20 40 0.63 45 0.64 0.63 50 0.66 0.64 55 0.67 0.65 0.63 60 0.69 0.67 0.64 65 0.70 0.68 0.65 0.63 70 0.72 0.69 0.66 0.64 80 0.75 0.72 0.68 0.66 90 0.78 0.75 0.70 0.68 0.63 100 0.81 0.78 0.73 0.70 0.65 120 0.88 0.83 0.77 0.74 0.68 140 0.94 0.89 0.82 0.78 0.71 160 1.00 0.94 0.86 0.82 0.74 180 1.00 0.91 0.86 0.76 200 0.95 0.90 0.79 220 1.00 0.94 0.82 250 1.00 0.87 280 0.91 310 0.96 340 1.00 注：f A,N 也可按公式计算： f A,N =0.5 + s / 4 h nom 化学锚栓间距限制条件： s min ≤ s ≤ s cr,N s min = 0.5 h nom s cr,N = 2.0 h nom 液压传动装置的安装 本文的主要内容： ○液压元件安装的注意事项 ○油管安装的注意事项 ○空载试运转空载试运转的一般步骤 ○试运转时应注意的安全事项 1、安装注意事项 一般来说，在出厂之前，液压传动装置的各种液压元件和管道均已基本安装完毕，安装部门不需要再逐件安装。只是有些大型设备在出厂时，部件之间的油路管道被拆卸开，个别液压元件尚未安装，需要在安裝设备时重新进行安装。液压元件和油管安装的注意事项如下： (1)液压元件安装的注意事项 1)安装前，应用煤油对液压元件进行清洗，并进行压力和密封试验，合格后才能安装；对各种控制仪表（如压力表、压力继电器等）应进行校验，以免不准确而造成事故。 2)液压泵传动要求较高的同轴度，即使采用弹性联轴器，安装时也要保证尽量同轴。一般要保证同轴度误差在0.1mm以下，倾角不得大于1°。 3)液压泵和阀门的进出口必须正确连接，液压泵的旋转方向一般在泵上均已标明，不得反接。 4)液压缸安装应牢固可靠：为了防止热膨胀的影响，在行程长和工作温度高的场合下，液压缸的一端要保证浮动。 5)对于移动液压缸的中心线，应与负载作用中心线同轴；否则， 会引起侧向力，而侧向力易使密封件磨损、活塞损坏；对于移动物体的液压缸，安装时应使液压缸和移动物体保持平行。 6)液压元件的各连接处应密封好：低压系统的密封圈不要装得太紧，以免阻力过大；金属密封圈重新安装前，应经退火变软才能安装，否则起不到可靠的密封作用。 7)用法兰连接的阀件，应均匀地拧紧各个螺钉，以免螺钉受力不均而造成密封不严。 (2)油管安装的注意事项 1)当液压设备出厂后，由于存放时间长或保管不善引起油管锈蚀时，应先用20%的硫酸或盐酸溶液进行酸洗，再用10%的苏打水中和，然后用温水清洗、干燥、涂油并试压，才能安装。 2)泵的吸油高度一般不得超过500mm，以免造成吸油困难。 3）一般应在吸油管上装滤油器，滤网采用网号0154～0071，通过面积应为油管的两倍以上。 4）吸油管与泵相连接的螺纹或法兰接合面处应严格密封，不得漏气。 5）回油管应伸到油箱面以下，以防飞溅引起气泡。回油管不能直接接到泵的入口，一定要通过油箱，否则油温将很快升高。 6）部件之间的软管安装，应按说明书规定对号接管，不能扭转和相互摩擦，并且在长度上要留有适当余量，以使它安装后较为松弛。 2.试运转 第1章绪论 1．1 大型矿用电动轮自卸车的现状及发展 自1963年由美国Unit-Rig公司G.E公司合作研制出世界上第一台装载质量问77t矿用电动轮自卸车以来，经过多年的不断完善和大量新技术、新材料、新工艺的采用，重型矿用电动轮自卸车作为汽车中的新品种已发展成熟，已经有108t、154t、170t、280t等多个系列。它是目前过内外大型露天矿普通采用的高效运输设备，已占有大份额市场。国内矿用电动轮自卸车在我国大型露天矿山的使用始于70年代中期，使用单位主要分布在煤炭、冶金等行业，其装载质量主要为108t和154t两种。国外生产重型矿用自卸车的主要厂家有：小松矿用设备公司、尤克里德-日产公司、卡特彼勒、利勃海尔公司等，其共同特点是：车型全系列、部件专业化、有完整的配套体系。我国重型矿用电动轮自卸车的生产厂商主要有三家：湘潭电机厂、本溪重型汽车厂和常州冶金机械厂。湘潭电机厂生产的自卸车经过不断改进和完善，吸收国外技术的基础上已经形成了几个系列，辽宁本溪重型汽车厂由于多种原因现已停产，江苏常州冶金机械厂主要与美国Unit-Rig公司合作生产Mark-36型154t矿用电动轮自卸车。 目前重型矿用电动轮自卸车驱动的传动方式都是采用交-直流传动，由柴油机带动发电机发出三相中频交流电，经外部整流装置整流变成直流电后输往汽车后桥两侧的直流牵引电机，以驱动汽车行驶。举升和转向采用液压系统，有两种形式：常流式和常压式，转向系统均采用动力转向，举升系统才采用侧置式双缸三级双作用油缸外置于车架两侧。电传动系统是由发电机、牵引电机、和电控制三大部分组成，其主要满足恒功控制的要求。驱动形式通常都采用4×2后轴驱动。 重型矿用电动轮自卸车的发展趋势主要是三点： 1. 大型化。促使矿用电动轮自卸车朝大型化方向发展的动因主要有两个：一是大型露天矿山开采的需要，二是大型机械传动自卸车的发展。随着大型矿山的发展和开采运输量的增大，为了提高运输效率、降低成本，许多大型矿山都倾向于采用大吨位矿用自卸车，这促使许多制造厂家相继研制开发出大吨位矿用电动轮自卸车一满足矿山用户的需要。高速发展的电子技术、控制技术和新型电子元器件的出现、大功率车用柴油机的问世、高负荷大型轮胎材料的研制成功及相关技术的解决和发展又为矿用电动轮自卸车的大型化铺平了道路。因此，矿用电动轮自卸车的大型化已经成为许多制造厂家为开拓市场吸引更多客户而普遍采用的一种竞争策略。 2．计算机控制和大量新的电控元器件的使用。80年代中后期开始，计算机控制技术已经逐步用于矿用电动轮自卸车的车速自动调节、柴油机燃油喷射及整车的故障分析诊断等领域。随着计算机技术、通信技术、传感器技术等的进一步发展，计算机控制技术将在矿用电动轮自卸车的许多方面得到应用，从而减轻驾驶员和矿山维护人员的劳动强度，提高电动轮自卸车的自动化程度和劳动生产率，使其性能和工作可靠性将得到进一步的提高。随着交流变频调速技术的发展和大功率逆变器的问世，重型矿用电动轮自卸车已开始采用交-交传动。 3．整车性能和工作可靠性进一步提高。目前国内外许多厂家已将大量先进的设计方法和成熟的分析软件应用在矿用电动轮自卸车的前后桥悬架系统、车 一、填空题（每空1分，共20分） 1.液压传动是以（压力）能来传递和转换能量的。 2.、液压传动装置由（动力元件）、（执行元件）、（控制元件）、（辅 助元件）和（工作介质）五部分组成，其中（动力元件）和（执行元件）为能量转换装置。 3.液体在管中流动时，存在（层流）和（紊流）两种流动状态。液体的流 动状态可用（雷诺数）来判定。 4.液压系统中的压力,即常说的表压力，指的是（相对压力）压力。 5.在液压系统中，由于某一元件的工作状态突变引起油压急剧上升,在一瞬 间突然产生很高的压力峰值，同时发生急剧的压力升降交替的阻尼波动过程称为（液压冲击）。 6.单作用叶片泵转子每转一周，完成吸、排油各（1）次，同一转速的情况 下，改变它的（偏心距）可以改变其排量。 7.三位换向阀处于中间位置时，其油口P、A、B、T间的通路有各种不同 的联结形式，以适应各种不同的工作要求，将这种位置时的内部通路形式称为三位换向阀的（中位机能）。 8.压力阀的共同特点是利用（液体压力）和（弹簧弹力）相平衡的原理来 进行工作的。 9.顺序阀是利用油路中压力的变化控制阀口（启闭），以实现执行元件顺 序动作的液压元件。 10.一般的气源装置主要由空气压缩机、冷却器、储气罐、干燥器和（油水 分离器）等组成。 二、选择题（请在所选择正确答案的序号前面划√或将正确答案的序号填入 问题的空格内）（每选择一个正确答案1分，共10分） 1．流量连续性方程是（ C ）在流体力学中的表达形式，而伯努利方程是（ A ）在流体力学中的表达形式。 A能量守恒定律； B动量定理； C质量守恒定律； D 其他；2．液压系统的最大工作压力为10MPa，安全阀的调定压力应为（ C ） A)等于10MPa；B)小于10MPa；C)大于10MPa 3．（ A ）叶片泵运转时，存在不平衡的径向力；（ B ）叶片泵运转时，不平衡径向力相抵消，受力情况较好。 A 单作用；B、双作用 4. 一水平放置的双杆液压缸，采用三位四通电磁换向阀，要求阀处于中位 时，液压泵卸荷，液压缸浮动，其中位机能应选用（ H ）；要求阀 处于中位时，液压泵卸荷，且液压缸闭锁不动，其中位机能应选用 （ M ）。 A. O型 B. M型 C 、 Y型 D. H型 5．（ B ）在常态时，阀口是常开的，进、出油口相通；（ A ）、 （ C ）在常态状态时，阀口是常闭的，进、出油口不通。 A) 溢流阀；B)减压阀；C)顺序阀 静液压传动工程机械的制动系统(2005/11/21 10:44)标签： 目录：技术应用 浏览字体：大中小 摘要国内外研制和应用静液压传动的工程机械越来越多，本文简要介绍了其制动系统的特点、类型，分析了不同工况下制动系统的作用以及不同制动系统的应用范围。 关键词：静液压传动工程机械制动系统 根据技术要求及通行安全，采用静液压传动的工程机械与常规机械一样，需要具备行走制动、停车制动和应急制动等3套制动系统。它们的操纵装置必须是彼此独立的。 1 行车制动系统 行车制动系统应能在所以运行状态下发挥作用。它首先用以使运动中的车辆减速，继而在必要时使车辆完全停止运动处于静止状态。对行走制动系统的要求是：第一，在车辆运动的整个速度范围内均能产生足够的制动阻力，使车辆减速直至停车；第二，具有足够的耗能或贮能容量来吸收车辆的动能；第三，行走制动装置的作用必须是渐进的；第四，行走制动系统的操纵功能必须是独立的，不应受其它正常操纵机构的影响，不能在离合器分离或变速器空档时丧失制动能力。从原则上说，凡是能完全满足上述要求的装置，均可用于行走制动系统。行走制动是使用最频繁的制动装置，一般称为主制动系统。 现代工程机械行走制动系统除普遍采用带有较大容量的制动盘、鼓等摩擦式机械制动器作为主执行元件外，也越来越多地利用发动机排气节流、电涡流、液涡流等作为辅助的吸能装置。后几种装置的优点是本身没有产生磨损的元件，能更好地控制减速力（矩），从而减少主制动元件（刹车盘、片等）的磨损和延长其使用寿命。但它们的制动力都与行走速度有关，一般无法独立使车辆完全停止，只能作为辅助制动装置（缓速装置）来使用。 静液压传动系统由连接在一个闭式回路中的液压泵和液压马达构成。对这种传动装置所选用的泵和马达，除了有与一般液压元件相同的高功率密度、高效率、长寿命等性能要求外，还要求两者均能在逆向工况下运行，即在必要时马达可作为泵运行，泵可成为马达运行，使整个系统具备双向传输功率或能量的能力。这样当泵的输出流量大于马达在某一转速下需要的流量时，多余的流量就使马达驱动车辆加速，而加速力的反作用力通过马达使入口压力升高，液压能转化为车辆的动能增量；反之，如调节变量泵的排量使其通过流量不敷于马达的需求时，马达出口阻力增大，在马达轴上建立起反向扭矩阻止车辆行驶，车辆动能将通过车轮反过来的驱动马达使其在泵的工况下运行，并在马达出油口建立起压力，迫使泵按马达工况拖动发动机运转，车辆的动能将转化为热能由发动机和液压系统中的冷却器吸收并耗散掉。由于静液压传动系统产生的阻力（矩）原则上只取决于系统压力和马达排量而与行走速度无关，所以这种系统既能象上述“缓速器”那样使车辆减速，又能使其完全停止运动，不仅能满足行走制动全部功能要求，而且在制动过程中没有元件磨损且可控性良好。因此，静液压传动系统本身完全可以作为行走制动装置使用。装有静液压传动系统的车辆一般无须另行配置机械制动器，但系统中不能有驾驶员可随意操纵的使功率流中断的装置（如液压系统中的短路阀、马达与驱动之间的离合器或机械换挡装置等）。 在许多工业发达国家中，允许静液压传动装置作为行走制动系统使用已为相关安全法规所确认。例如，1987年4月1日起生效的德国交通工具及设备和自行式机械“静液压传动装置可以作为行车制动器使用，前提是这一驱动系统中不含有短路阀，或只装有驾驶员无法直接操纵的短路阀（例如将短路阀的操纵手柄装于机罩下面）。” 人们常回担心静液压传管路爆破或元件损坏后会丧失制动能力，但在显得技术条件下，出现这种风险的概率不会大于传统行走制动器的概率。 2 停车制动系统 停车制动系统用来使车辆保持静止状态。从原则上说，它可以采用任一种具有足够锁定能力 第一章绪论 第一节液压传动发展概况 自18世纪末英国制成世界上第一台水压机算起，液压传动技术已有二三百年的历史。直到20世纪30年代它才较普遍地用于起重机、机床及工程机械。在第二次世界大战期间，由于战争需要，出现了由响应迅速、精度高的液压控制机构所装备的各种军事武器。第二次世界大战结束后，战后液压技术迅速转向民用工业，液压技术不断应用于各种自动机及自动生产线。 本世纪60年代以后，液压技术随着原子能、空间技术、计算机技术的发展而迅速发展。因此，液压传动真正的发展也只是近三四十年的事。当前液压技术正向迅速、高压、大功率、高效、低噪声、经久耐用、高度集成化的方向发展。同时，新型液压元件和液压系统的计算机辅助设计(CAD)、计算机辅助测试(CAT)、计算机直接控制(CDC)、机电一体化技术、可靠性技术等方面也是当前液压传动及控制技术发展和研究的方向。 我国的液压技术最初应用于机床和锻压设备上，后来又用于拖拉机和工程机械。现在，我国的液压元件随着从国外引进一些液压元件、生产技术以及进行自行设计，现已形成了系列，并在各种机械设备上得到了广泛的使用。 机械的传动方式 一切机械都有其相应的传动机构借助于它达到对动力的传递和控制的目的。 机械传动——通过齿轮、齿条、蜗轮、蜗杆等机件直接把动力传送到执行机构 的传递方式。 电气传动——利用电力设备，通过调节电参数来传递或控制动力的传动方式 液压传动——利用液体静压 力传递动力 液体传动 液力传动——利用液体静流 动动能传递动力 流体传动 气压传动 气体传动 气力传动 第二节液压传动的工作原理及其组成 一、液压传动的工作原理 液压传动的工作原理，可以用一个液压千斤顶的工作原理来说明。 2017第四章血液分析仪及其临床应用 一、A1 1、下列哪种疾病滑膜积液的黏稠度增高 A、甲状腺功能减退 B、系统性红斑狼疮 C、腱鞘囊肿 D、骨关节炎引起的黏液囊肿 E、以上都是 2、通常在痛风患者的滑膜积液中可找到哪种结晶 A、尿酸盐 B、焦磷酸钙 C、磷灰石 D、脂类 E、草酸钙 3、正常关节腔积液中可见下列细胞，但除外的是 A、红细胞 B、单核-巨噬细胞 C、淋巴细胞 D、中性粒细胞 E、软骨细胞 4、白细胞直方图中淋巴细胞左侧区域异常，最不可能的原因是 A、血小板聚集 B、巨大血小板 C、异型淋巴细胞 D、脂类颗粒 E、有核红细胞 5、血小板直方图右侧呈脱尾状，MCV低于正常，最有可能的是 A、血小板聚集 B、红细胞碎片 C、大血小板增多 D、小红细胞干扰 E、小血小板增多 6、正常红细胞直方图中，大红细胞和网织红细胞分布于 A、50～125fl B、125～200fl C、36～360fl D、50～200fl E、35～95fl 7、白细胞稀释液不能破坏的细胞是 A、小红细胞 B、大红细胞 C、网织红细胞 D、有核红细胞 E、正常成熟红细胞 8、三分群白细胞直方图上，中间细胞区不包括哪类细胞 A、嗜碱性粒细胞 B、嗜酸性粒细胞 C、中性粒细胞 D、单核细胞 E、幼稚细胞 9、在白细胞直方图中，单个核细胞峰与中性粒细胞峰之间区域异常，可能是 A、单核细胞增多 B、中性粒细胞增多 C、淋巴细胞增多 D、异常细胞亚群 E、未溶解的红细胞 10、在白细胞直方图中，淋巴细胞峰右移与单个核细胞峰左侧相连并抬高，可能是 A、有核红细胞 B、蛋白质颗粒 C、脂质颗粒 D、异形淋巴细胞 E、中性粒细胞增多 11、在白细胞直方图中，淋巴细胞峰左侧区域异常，可能是 A、异常淋巴细胞 B、中性粒细胞增多 C、嗜酸性粒细胞增多 D、巨大血小板 E、浆细胞 12、在电阻抗型血液分析仪中，哪项与脉冲振幅成正比 A、细胞的数量 B、细胞的体积 C、细胞的比密 D、细胞的移动速度 E、以上都不是 13、精密度是指 A、对同一样品重复进行检测时所有结果的符合程度 B、样品的检测值与真值的符合程度 液压与气压传动》习题解答 第 1 章液压传动概述 1、何谓液压传动？液压传动有哪两个工作特性？答：液压传动是以液体为工作介质，把 原动机的机械能转化为液体的压力 能，通过控制元件将具有压力能的液体送到执行机构，由执行机构驱动负载实现所需的运动和动力，把液体的压力能再转变为工作机构所需的机械能，也就是说利用受压液体来传递运动和动力。液压传动的工作特性是液压系统的工作压力取决于负载，液压缸的运动速度取决于流量。 2、液压传动系统有哪些主要组成部分？各部分的功用是什么？ 答：⑴动力装置：泵，将机械能转换成液体压力能的装置。⑵执行装置：缸或马达，将液体压力能转换成机械能的装置。⑶控制装置：阀，对液体的压力、流量和流动方向进行控制和调节的装置。⑷辅助装置：对工作介质起到容纳、净化、润滑、消声和实现元件间连接等作用的装置。⑸传动介质：液压油，传递能量。 3、液压传动与机械传动、电气传动相比有哪些优缺点？ 答：液压传动的优点：⑴输出力大，定位精度高、传动平稳，使用寿命长。⑵容易实现无级调速，调速方便且调速范围大。⑶容易实现过载保护和自动控制。⑷机构简化和操作简单。 液压传动的缺点：⑴传动效率低，对温度变化敏感，实现定比传动困难。⑵出现故障不易诊断。⑶液压元件制造精度高，⑷油液易泄漏。 第2章液压传动的基础知识 1、选用液压油有哪些基本要求？为保证液压系统正常运行，选用液压油要考虑哪些方面？ 答：选用液压油的基本要求：⑴粘温特性好，压缩性要小。⑵润滑性能好，防锈、耐腐蚀性能好。⑶抗泡沫、抗乳化性好。⑷抗燃性能好。选用液压油 时考虑以下几个方面，⑴按工作机的类型选用。⑵按液压泵的类型选用。⑶按液压系统工作压力选用。⑷考虑液压系统的环境温度。⑸考虑液压系统的运动速度。⑹选择合适的液压油品种。 2、油液污染有何危害？应采取哪些措施防止油液污染？ 答：液压系统中污染物主要有固体颗粒、水、空气、化学物质、微生物等杂物。其中固体颗粒性污垢是引起污染危害的主要原因。1）固体颗粒会使滑动 部分磨损加剧、卡死和堵塞，缩短元件的使用寿命；产生振动和噪声。2）水的 侵入加速了液压油的氧化，并且和添加剂一起作用，产生粘性胶质，使滤芯堵塞。3）空气的混入能降低油液的体积弹性模量，引起气蚀，降低其润滑性能。4）微生物的生成使油液变质，降低润滑性能，加速元件腐蚀。 污染控制贯穿于液压系统的设计、制造、安装、使用、维修等各个环节。在实际工作中污染控制主要有以下措施：1）油液使用前保持清洁。2）合理选用液压元件和密封元件，减少污染物侵入的途径。3）液压系统在装配后、运行前 保持清洁。4）注意液压油在工作中保持清洁。5）系统中使用的液压油应定期检查、补充、更换。6）控制液压油的工作温度，防止过高油温造成油液氧化变质。 3、什么是液压油的粘性和粘温特性？为什么在选择液压油时，应将油液的粘度作为主要的性能指标？ 答：液体流动时分子间相互牵制的力称为液体的内摩擦力或粘滞力，而液体流动时呈现阻碍液体分子之间相对运动的这种性质称为液体的粘性。粘温特性：液体粘度随温度变化的性质称为液体的粘温特性。粘度是液体流动时阻力的度量，它是衡量粘性大小的指 静液压驱动在装载机上的应用 1.静液压系统构成与特点。 静液压传动系统HST(Hydraulic Static Transmission) 是指由液压泵、液压马达，补油泵和控制元件(液压阀)组成的闭式回路,辅以调节控制装置等组成的一种无级变速传动系统,有传动比连续、传递动力平稳、操纵方便等特点。静液压传动装置是以液压泵和液压马达为主组成,附加各种变量控制单元和传动元件(减速器或变速箱) ,成为一种无级变速的传动装置。它与纯机械传动和液力机械传动相比,具有高效区宽、布局灵活、无级变速、换向方便、控制方式多样和功率利用合理等众多优点。工程机械合理运用静液压传动装置,则能改善机器性能,提高生产效率,节省能量消耗,使机器的品质上升到一个新的 阶段。 静液压传动的四种基本形式组合： 根据静液压传动中排量是否可调可以分为4种系统组合方式：定量泵-定量马达，定量泵-变量马达，变量泵-定量马达，和变量泵-变量马达。 图二：静液压系统原件构成 3.静液压传动与传统的液力机械传动相比,具有以下优点: (1) 可以实现无级变速,换向方便; (2) 当发动机在任一调度转速下工作,传动系统都能发挥出较大的牵引力; (3) 传动系统能在很宽的输出转速范围内保持较高的效率; (4) 行走功率和作业装置功率可以合理匹配,使发动机功率充分利用; (5) 液压泵和液压马达位置布置比较灵活,有条件使发动机采用横向布置,缩短了装载机的纵向长度,改善了司机的视野; (6) 液压泵和液压马达都可采用电比例变量控制,考虑到微机技术的飞速发展,使二者很好的结合,实现智能化控制; (7) 据有关资料介绍,与液力机械传动相比,装载机作业率可以提高30 % ,燃油消耗可降低25 %。 轮式装载机行走驱动负荷变化较大,它的静液压传动装置都由变量泵和变量马达组成闭式回路。而液压泵的变量控制方式为与转速有关的液压控制。这种变量方式使装载机具有变矩器的功能,并有以下几个特点: (1) 它的控制泵与发动机直接相连变量机构中没有控制伐,当发动机转速发生变化时,控制泵输出流量随之变化,这样由于通过控制内节流处的流量发生变化,导致节流前后压差的变化,而造成控制压力的变化。转速提高—控制压力增大—排量变大; (2) 当行走驱动系统工作压力升高,引起发动机转速下降时,此时控制压力 下降,使泵的排量减少,此时泵的输入扭矩和发动机转速重新恢复到设定值; (3) 控制阀与发动机的油门控制杆联动,当发动机的油门加大,则控制阀内 的节流开度也加大,可以获得不同驱动转速下的控制曲线,这些控制曲线是相互平行的。一旦工况发生变化,使转速变化值尽可能地小; (4) 可以在发动机转速调定的情况下,改变控制阀内节流开度的大小,从而增、减控制压力,来调整行驶速度。 血液分析仪及其临床应用题库1-2-10 问题： [单选,A2型题,A1A2型题]关于血液分析仪VCS原理的叙述，正确的是（） A.V：体积 B.C：细胞 C.S：过氧化物酶 D.仅显示两种细胞散点图 E.以上都正确 在血液分析仪VCS原理中，V代表体积、C代表电导、S代表光散射。根据VCS原理，显示3种细胞散点图：DF1体积和散射光、DF2体积和电导、DF3体积和电导，但只显示嗜碱性粒细胞群。 问题： [单选,A2型题,A1A2型题]血小板直方图右侧呈脱尾状，MCV低于正常，最有可能的是（） A.血小板聚集 B.大血小板增多 C.小红细胞干扰 D.红细胞碎片 E.小血小板增多 血小板直方图右侧呈脱尾状说明引起脱尾细胞的体积比正常的血小板大，但MCV低于正常说明有小红细胞的存在。 问题： [单选,A2型题,A1A2型题]三分群白细胞直方图上，中间细胞区不包括哪类细胞（） A.单核细胞 B.嗜酸性粒细胞 C.嗜碱性粒细胞 D.中性粒细胞 E.幼稚细胞 根据不同体积的白细胞通过传感器时，脉冲大小不同，将白细胞分成三群，即小细胞群淋巴细胞为主、中间细胞群包括单核细胞、嗜酸性粒细胞、嗜碱性粒细胞、幼稚细胞及原始细胞等和大细胞群中性粒细胞为主。 (天津11选5 https://www.doczj.com/doc/ae1647909.html,) 问题： [单选,A2型题,A1A2型题]现代血液自动分析仪的英文缩写是（） A.AHA B.BCC C.HAA D.CBC E.BAC 现代血液自动分析仪的英文是automatichemalogicanalysiser，故缩写为AHA。 第1章思考题和习题解 1.1 液体传动有哪两种形式？它们的主要区别是什么？ 答：用液体作为工作介质来进行能量传递的传动方式被称之为液体传动。按照其工作原理的不同，液体传动又可分为液压传动和液力传动，其中液压传动是利用在密封容器内液体的压力能来传递动力的；而液力传动则的利用液体流动的动能来传递动力的。 1.2 什么叫液压传动？液压传动所用的工作介质是什么？ 答：利用液体的压力能来传递动力的传动方式被称之为液压传动。液压传动所用的工作介质是液体。 1.3 液压传动系统由哪几部分组成？各组成部分的作用是什么？ 答：（1）动力装置：动力装置是指能将原动机的机械能转换成为液压能的装置，它是液压系统的动力源。 （2）控制调节装置：其作用是用来控制和调节工作介质的流动方向、压力和流量，以保证执行元件和工作机构的工作要求。 （3）执行装置：是将液压能转换为机械能的装置，其作用是在工作介质的推动下输出力和速度（或转矩和转速），输出一定的功率以驱动工作机构做功。 （4）辅助装置：在液压系统中，除以上装置外的其它元器件都被称为辅助装置，如油箱、过滤器、蓄能器、冷却器、管件、管接头以及各种信号转换器等。它们是一些对完成主运动起辅助作用的元件，在系统中是必不可少的，对保证系统正常工作有着重要的作用。 （5）工作介质：工作介质指用来传递能量的液体，在液压系统中通常使用液压油液作为工作介质。 1.4 液压传动的主要优缺点是什么？ 答：优点：（1）与电动机相比，在同等体积下，液压装置能产生出更大的动力，也就是说，在同等功率下，液压装置的体积小、重量轻、结构紧凑，即：它具有大的功率密度或力密度，力密度在这里指工作压力。 （2）液压传动容易做到对速度的无级调节，而且调速范围大，并且对速度的调节还可以在工作过程中进行。 （3）液压传动工作平稳，换向冲击小，便于实现频繁换向。 （4）液压传动易于实现过载保护，能实现自润滑，使用寿命长。 化学锚栓使用方法图示文档编制序号：[KKIDT-LLE0828-LLETD298-POI08] 化学锚栓的使用方法,化学锚栓的安装方法 化学锚栓作为一套锚固件,由化学胶管和螺杆以及垫片与螺母组成。是通过特制的化学粘接剂，将螺杆胶结固定于砼基材钻孔中，以实现对固定件锚固的复合件。也叫化学膨胀螺栓,一种是机械膨胀原理的膨胀螺栓，钻孔-敲入螺杆-拧紧螺母（涨套撑开）-螺杆紧固；另一种就是靠粘结固定螺杆的化学锚栓；有两种形式。一种是国产的玻璃管形式，一种是喜利得式的药剂包； 化学锚栓使用方法： 1.根据工程设计要求，在基材（如混凝土）中相应位置钻孔，孔径、孔深及螺栓直径应由专业技术人员或现场试验确定。 2.用冲击钻或水钻钻孔。 3.用专用气筒、毛刷或压缩空气机清理钻孔中的灰尘，建议重复进行不少于3次，孔内不应有灰尘与明水。 4.保证螺栓表面洁净、干燥、无油圬。 5.确认玻璃管锚固包无外观破损、药剂凝固等异常现象，将其圆头朝内放入锚固孔并推至孔底。 6.使用电钻及专用安装夹具，将螺杆强力旋转插入直至孔底，不应采用冲击方式。 7.当旋至孔底或螺栓上标志位置时，立刻停止旋转，取下安装夹具，凝胶后至完全固化前避免扰动。超时旋转导致胶液流失，影响锚固力。（旋转时间不应超过30秒，转速 不应低于300转/分，不大于750转/分，螺栓推进速度约为2cm/秒，不允许采用冲击方式。） 化学锚栓如何安装,化学锚栓的安装方法 1、钻孔：先根据设计要求，按图纸间距、边距定好位置，在基层上钻孔，孔径、孔深必须满足设计要求。 2、清孔：用空气压力吹管等工具将孔内浮灰及尘土清除，保持孔内清洁。 3、置入药剂管：将药剂管插入洁净的孔中，插入时树脂在手温条件下能象蜂蜜一样流动时，方可使用胶管。 4、钻入锚栓：用电钻旋入螺杆直至药剂流出为止。电钻一般使用冲击钻或手钻，钻速为750转/分。这时锚栓旋入，药剂管将破碎，树脂、固化剂和石英颗粒混合，并填充锚栓与孔壁之间的空隙。同时，锚栓也可以插入湿孔，但水必须排出钻孔，凝胶过程及硬化过程的等待时间必须加倍。 5、凝胶过程：保持安装工具不动，化学反应时间见详细资料。 6、硬化过程：取下安装工具静待药剂硬化，化学反应时间见详细资料。 7、固定物体：待药剂完全硬化后，加上垫圈及六角螺母将物体固定便可。 化学锚栓型号主要是就M8*110，M10*130，M12*160，M16*190，M20*260， M24*300，M30*380，M33*420几种。 常见型号表: 尺寸说明:例如：M10*130MM(螺纹直径*总长） 推土机静液压传动装置的参数匹配与控制 王永奇1,单新周2 (11长安大学工程机械学院,陕西西安710064;21湖南交通职业技术学院,湖南长沙410004) [摘 要]研究了推土机静液压传动系统参数的匹配条件、原则和控制方法,分析了发动机、泵和马达组成的负荷驱动系统各环节的参数匹配和控制目标函数,并提出推土机行驶驱动液压系统的工作匹配压力、控 制原理、系统控制和配置方案,这对于其它静压驱动机型也有参考意义。 [关键词]全液压推土机;静液压传动;传动装置;合理匹配;控制原理 [中图分类号]TU62315 [文献标识码]A [文章编号]100121366(2003)1020034203 Parameter matching and controlling of static hydraulic driving device in bulldozers WANG Y ong2qi1,SH AN X in2zhou2 (11Chang′an University,Xi′an710064,China; 21Hunan vocational and Technical College of Communication,Changsha410004,China) Abstract:This paper describes the study of matching condition and principle and controlling method of static hydraulic driving device in bulldozers,and analysis of parameter matching and controlling object function in each tache of load drive system composed by engine and pump and motor,and it puts forward work matching pressure, controlling principle,system controlling and configure precept of steam drive hydraulic system in bulldozers,it also makes a reference to other static hydraulic driving construction machinery. K ey w ords:fully hydraulic bulldozers;static hydraulic drive;driving device;reasonable matching;controlling principle. ①目前,静液压传动与智能控制技术在国外中小功率推土机传动系统中已得到应用和发展,而我国在推土机智能化方面的研究刚刚起步,理论研究基本处于空白状态。推土机智能化的核心技术是发动机、泵和马达组成的传动系统参数的合理匹配、控制方式和原理,该系统参数的合理匹配和微电子控制可提高推土机的生产率和降低燃油消耗,减轻司机操作强度。 1 静液压传动合理匹配条件 1)由发动机最大扭矩工况所决定的牵引力和液压系统最高匹配压力所对应的最大牵引力应小于等于由土壤附着条件决定的附着力。 2)发动机最小油耗工况和液压系统额定压力工况应与行走机构之间最大生产率工况相一致,即发动机最小油耗工况和液压系统额定压力所决定的牵引力应等于行走机构滑转率所决定的牵引力,以保证最大的作业生产率。 3)平均最大工作阻力应等于机器的额定有效牵引力。 2 匹配原则与方法 由于液压传动系统、发动机和外负载之间存在着相互影响、相互制约的关系,因此在进行泵和马达参数之间的匹配时,首先应结合发动机性能和外负载特性来考虑,即液压参数的匹配首先应保证发动机—液压系统—外负载有最佳的动力性、经济性和生产率;其次应保证各液压元件有满意的工作寿命和可靠性。影响液压元件工作寿命的不可靠因素主要有:负荷特性(可采用降额匹配和加蓄能器的方法来解决)、元件的使用参数即工作压力、转速及其负荷的匹配状态。 ①[收稿日期]2003205222 [作者简介]王永奇(1969-),男,傣族,博士,研究方向工程机械机电一体化. 设计研究血液分析仪及其临床应用题库1-1-8
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