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Can Supermassive Black Holes Form in Metal-Enriched High-Redshift Protogalaxies ?K.Omukai 1,R.Schneider 2and Z.Haiman 3ABSTRACT Primordial gas in protogalactic dark matter (DM)halos with virial temper-atures T vir ～>104K begins to cool and condense via atomic hydrogen.Provided this gas is irradiated by a strong ultraviolet (UV)?ux and remains free of H 2and other molecules,it has been proposed that the halo with T vir ～104K may avoid fragmentation,and lead to the rapid formation of a supermassive black hole (SMBH)as massive as M ≈105?106M ⊙.This “head–start”would help explain the presence of SMBHs with inferred masses of several ×109M ⊙,powering the bright quasars discovered in the Sloan Digital Sky Survey at redshift z ～>6.However,high–redshift DM halos with T vir ～104K are likely already enriched with at least trace amounts of metals and dust produced by prior star–formation in their progenitors.Here we study the thermal and chemical evolution of low–metallicity gas exposed to extremely strong UV radiation ?elds.Our results,obtained in one–zone models,suggest that gas fragmentation is inevitable above a critical metallicity,whose value is between Z cr ≈3×10?4Z ⊙(in the absence of dust)and as low as Z cr ≈5×10?6Z ⊙(with a dust-to-gas mass ratio of about 0.01Z/Z ⊙).We propose that when the metallicity exceeds these critical values,dense clusters of low–mass stars may form at the halo nucleus.Relatively mas-sive stars in such a cluster can then rapidly coalesce into a single more massive object,which may produce an intermediate–mass BH remnant with a mass up to M ～<102?103M ⊙.
Subject headings:cosmology:theory —galaxies:formation —stars:formation
1.Introduction
The discovery of bright quasars at redshifts z～>6in the Sloan Digital Sky Survey (SDSS)implies that BHs as massive as several×109M⊙were already assembled when the age of the universe was less than≈1Gyr(see the recent review by Fan2006).The BH masses are inferred from the quasars’luminosities,assuming these sources shine near their Eddington limit.Strong gravitational lensing or beaming could,in principle,mean that the inferred BH masses are overestimated;however,there is no obvious sign of either e?ect in the images and spectra of these quasars(Willott et al.2003;Richards et al.2004).Indeed, their relatively“normal”line–to–continuum ratio,consistent with those in lower–redshift quasars,makes it unlikely that the apparent?ux of these sources was signi?cantly boosted by beaming(Haiman&Cen2002).Likewise,the lack of a second detectable image on Hubble Space Telescope images(Richards et al.2004)essentially rules out the hypothesis that most of the sources experienced strong magni?cation by lensing(Comerford et al.2002;Keeton et al.2005).
Relatively little time is available for the growth of several×109M⊙SMBHs prior to z～6,and their seed BHs must be present as early as z～10(e.g.Haiman&Loeb 2001).As the SMBHs grow from high–redshift seed BHs by accretion,they are expected to encounter frequent mergers.A coalescing BH binary experiences a strong recoil due to gravitational waves(GWs)emitted during the?nal stages of their merger.The typical recoil speed is expected to be v recoil～>100km s?1(and may be as large as4,000km s?1for special BH spin con?gurations;see,e.g.Campanelli et al.2007and references therein),signi?cantly exceeding the escape velocity(～<10km s?1)from typical DM halos that exist at z～10.As a result,SMBHs are often ejected from their host halos at high redshift.The repeated loss of the growing seeds makes it especially challenging to account for the several×109M⊙SMBHs at z～>6without at least a brief phase of super–Eddington accretion,or some equivalent “head–start”(Haiman2004;Yoo&Miralda-Escud′e2005;Shapiro2005;Volonteri&Rees 2006).
There have been several recent proposals that such a“head–start”may occur in metal–free gas in high–redshift DM halos with virial temperatures exceeding T vir～>104K,leading to the rapid formation of SMBHs with a mass of M≈105?106M⊙.As primordial gas falls into these halos,it initially cools via the emission of hydrogen Lyαphotons.Provided the gas is free of H2molecules,its temperature will remain near T vir～104K.Bromm&Loeb(2003, hereafter BL03)performed hydrodynamical simulations of a metal–and H2–free halo,with a mass of～108M⊙collapsing at z～10,corresponding to a2σGaussian overdensity and to T vir～104K.Under these conditions,which may apply to some dwarf galaxies collapsing close to the epoch of reionization,the primordial gas is marginally able to collapse and remains
nearly isothermal.BL03found that during the evolution,fragmentation of the gas cloud
is very ine?cient,leading at most to binary formation even with some degree of rotation.
Thus,a super–massive star is expected to form,and evolve into a SMBH with a mass as
high as M≈105?106M⊙.Oh&Haiman(2002)and Lodato&Natarajan(2006)have also showed that if H2formation is inhibited,a primordial-gas disk is stable to fragmentation and
a single massive object is formed in accordance with BL03’s conclusion.Volonteri&Rees
(2005)arrived at similar conclusions,by considering Bondi accretion onto a stellar seed BH,
which can signi?cantly exceed the Eddington rate at the gas density and temperature in a
similar halo.Finally,Begelman et al.(2006)and Spaans&Silk(2006)proposed di?erent
mechanisms to form similarly massive BHs by the direct collapse of primordial,atomic gas.
For reference,we note that the total(DM+gas)mass of halos with T vir=(1?5)×104K at
z=10is M tot≈108?9M⊙,so that such SMBHs would represent≈0.2?20%of the gas mass in these halos.We also note that in the WMAP5cosmology,the age of the universe at z=10and z=6.5is～0.5Gyr and～0.9Gyr,respectively.At the e–folding time–scale of4×107years(assuming Eddington accretion,and a radiative e?ciency of10%;see,e.g., Haiman&Loeb2001),a seed BH of M≈105M⊙at z～10could easily grow to a super massive BH of M≈2×109M⊙at z～6.5,if fed uninterruptedly.
A crucial assumption in all of the above proposals is that H2molecules cannot form as the gas cools and condenses in the DM halo.This assumption can be justi?ed in the presence of a su?ciently strong far ultraviolet(FUV)radiation,so that molecular hydrogen(or the intermediary H?necessary to form H2)is photodissociated.The relevant criterion is that the photodissociation timescale is shorter than the H2–formation timescale;since generically, t diss∝J and t form∝ρ,the condition t diss=t form yields a critical?ux J∝ρ.In DM halos with T vir～<104K,whose gas can not cool in the absence of H2,the densities remain low and H2can be dissociated even when background?ux is as low as J?21～10?2(e.g.Haiman, Rees&Loeb1997;Mesinger et al.2006;here J?21is the?ux just below13.6eV,in the usual units of10?21erg cm?2sr?1s?1Hz?1).However,if a gas cloud is massive enough and has a virial temperature higher than≈8000K,it is able to cool and start its collapse via atomic hydrogen Ly-αcooling.Even if the FUV?eld is initially above the critical value,molecular hydrogen can form,and dominate the gas cooling at a later stage during the collapse(Oh& Haiman2002);the H2–formation rate is furthermore strongly boosted by the large out–of–equilibrium abundance of free electrons in the collisionally ionized gas in these halos(Shapiro &Kang1987;Susa et al.1998;Oh&Haiman2002).The critical?ux required to keep the gas H2–free as it collapses by several orders of magnitude therefore increases signi?cantly; for halos with T vir～104K the value has been found to be J?21≈103?105,depending on the assumed spectral shape(Omukai2001,hereafter O2001;BL03).In halos exposed to such extremely intense UV?elds,the gas cloud is still able to collapse only via atomic hydrogen
line cooling,namely Lyαand H?free–bound(f-b)emission(O2001).
One possible source of such an intense UV?eld is the intergalactic UV background just before the epoch of cosmic reionization(BL03).The ionizing photon?ux J+21can be evaluated from the number density of hydrogen atoms in the intergalactic medium(IGM) and the average number of photons needed to ionize a hydrogen atom Nγ,which,in general, is>1,owing to recombinations in an inhomogeneous https://www.doczj.com/doc/5317140203.html,ing the escape fraction of ionizing radiation f esc,the?ux J?21just below the Lyman limit is given by
J?21=J+21
f esc
hc
m H?4×103
Nγ0.01 ?1 1+z
In the present paper,our goal is to answer the following question:can cooling and fragmentation be avoided in metal–enriched T vir～>104K halos,irradiated by a strong FUV ?ux?If so,this would suggest that supermassive black holes may form,similar to the metal–free case,in the more likely case of metal–enriched high–redshift protogalaxies.To investigate this possibility,we here study the thermal and chemical evolution of low–metallicity gas, exposed to extremely strong UV radiation?elds.We will evaluate the critical metallicity, above which fragmentation becomes unavoidable in the presence of a strong FUV?ux.
In§2,we describe our one–zone modeling procedure.Our results are presented and discussed in§3,?rst for the metal–free(§3.1),and then for the metal–enriched case(§3.2). The fragmentation and subsequent evolution of the metal–enriched clouds are then discussed in§3.3and3.4,respectively.In§4,we summarize our results and o?er our conclusions.
2.Model
2.1.Basics
We use the one–zone model described in Omukai(2001)to follow the gravitational collapse of gas clouds.The model includes a detailed description of gas–phase chemistry and radiative processes,and the e?ect of dark matter on the dynamics in a simpli?ed fashion.In addition,in the present version of the model we have implemented the contribution of metal lines and dust to gas cooling.
In what follows,all physical quantities are evaluated at the center of the cloud.The gas density increases as
dρgas
t col
.(2) where the collapse timescale,t col,is taken to be equal to the free-fall time,
t col=t?≡ 32Gρ,(3) andρis the sum of the gas and dark matter density.The dark matter density follows the evolution of a top–hat overdensity,
ρDM=9π2
1?cosθ 3?DMρcrit(4)
with
1+z=(1+z ta) θ?sinθ
(e.g.,Chapter8.2of Padmanabhan1993),where the turn-around and the virialization cor-
respond toθ=πand2π,respectively.Although,strictly speaking,this is correct only in
the Einstein-de Sitter universe(?0=1),it does not cause a signi?cant error in the high-z
universe(z 10)we consider.
The initial epoch of calculation is taken at the turn–around at redshift z ta=17.From
equation5,the virialization and turn-around redshifts have the relation1+z vir=2?2/3(1+
z ta);thus z vir?10.In our calculation,the dark matter density is kept constant after reaching its virialization value8ρDM(z ta).The initial values of the gas number density,temperature,
ionization degree,and H2fraction have been assumed to be n H=4.5×10?3cm?3,T=21K,
y(e)=3.7×10?4and y(H2)=2×10?6,respectively,to re?ect conditions at the turn–around
at z ta=17.Some runs with initial temperature ten times higher(210K)are also performed
to con?rm independence of our main results from the initial temperature.The cosmological
parameters are?DM=0.24,?b=0.04,and h=0.7.
Our calculation does not include the virialization shock.Owing to fast cooling by Lyα
emission,the central region whose evolution we intend to follow does not experience the
virialization shock in the spherically symmetric case(Birnboim&Dekel2003).In more real-
istic calculations,the outer regions can experience shocks and the temperature and electron
fraction become higher than in our case.In addition,recent numerical calculations(e.g.
Kereˇs et al.2005)show that low-mass galaxies,especially at high-redshifts,obtain their gas
through accretion predominantly along the large-scale?laments.Three-dimensional e?ects
such as asymmetric accretion might a?ect the evolution at low densities.However,since we
are considering halos with T vir?104K,which can marginally collapse by Lyαcooling,the shock is not strong:the temperature increase is modest and the electron fraction reaches at most 10?2(see Figures5a and5c in BL03).This additional electrons alter the early evolution for the J=0case.However,in the irradiated clouds,where H2formation is suppressed,during the collapse by the Lyαcooling recombination proceeds until the free electron fraction reaches x e?1.2×10?3n?1/2H,the value set by the balance between the recombination and the collapse time t rec～t col at8000K.Thus,our results for molecule formation and cooling are hardly a?ected.
We adopt t?as the collapse time scale just because it has been widely used in other
studies(e.g.,Palla et al.1983).Note that the free–fall time(3)is the time for density of an
initially static cloud to reach in?nity,while the dynamical timescale t col=ρ/(dρ/dt)in the
free–fall collapse is
t col,?=
1
24πGρ
(6)
in the limit where the density has become su?ciently larger than the initial value.Thus the rate we adopted(3)is3π/2=4.7times slower collapse than the genuine free–fall one.In
fact,pressure gradients oppose gravity and the collapse becomes slower than the free–fall one within a factor of a few(e.g.,Foster&Chevalier1993).Adoption of t?as the e–folding time for density increase mimics the pressure e?ect.The assumption of nearly free-fall collapse is invalidated,and the collapse is slowed down,once the cloud becomes optically thick to continuum radiation.However,our result on the thermal evolution is not altered:with little radiative cooling,the temperature is now determined by the adiabatic compression and the chemical cooling by dissociation and ionization,both of which are independent of the collapse timescale.Moreover,the evolution after the cloud becomes optically thick is not relevant to our argument on fragmentation,which occurs at much lower density,in the optically thin regime.
The overall size of the collapsing gas cloud(or of the roughly uniform density central region)determines its optical depth,and is therefore important for its thermal evolution. Here we assume the size equals the Jeans length,
λJ= Gρgasμm H,(7)
where T gas is the gas temperature,μis the mean molecular weight.Similarly,its mass is given by the Jeans mass
M J=ρgasλ3J.(8) Speci?cally,we assume that the radius of the cloud is R c=λJ/2and the optical depth is
τν=κνR c=κν λJ
dt =?p
d
ρgas ?Λnet γad?1
kT gas
continuum emission,as well as emission by H and H2lines,and chemical heating/cooling, the net cooling rate includes emission by C and O?ne–structure linesΛmetal,by dust grains Λgr,and heating by photoelectric emission of dust grainsΓpe.Cooling by?ne–structure lines of[CII]and[OI]is included as in Omukai(2000).Dust processes are described below in §2.2.
Primordial–gas chemical reactions are solved for the nine species of H,H2,e,H+,H+2, H?,He,He+,and He++.We do not explicitly include the chemical reactions involving metals. Instead,all the carbon and oxygen is assumed to be in the form of CII and OI,respectively. Having a lower ionization energy(11.26eV)than hydrogen,carbon remains in the form of CII in the atomic medium owing to photoionization by the background radiation.We maintained this assumption even in J=0runs,although carbon is expected to recombine and become neutral in these cases.The cooling rates by CII and CI?ne–structure lines are within a factor of?2di?erence for T 30K,and therefore this assumption does not signi?cantly a?ect the results.On the other hand,the ionization potential of oxygen (13.61eV)is very similar to that of hydrogen(13.60eV)and the charge exchange reaction
O++H?H++O,(12) keeps its ionization degree equal to that of hydrogen.In fact,the coe?cient of the rightward
yr. reaction being6.8×10?10cm3/sec,these reactions reach equilibrium only in～50n?1
H In a cold( a few100K)and dense( 103?4cm?3)environment,molecular coolants such as CO and H2O may become important(Omukai et al.2005).Since we are interested here in metal e?ects on warm( a few1000K)atomic clouds,we neglect the contribution to cooling of metals in molecules.This simpli?cation does not a?ect the early evolution of gas clouds,when the e?ects of metals induce a deviation from the primordial evolutionary track at several1000K.It is true that it may alter the predicted thermal behavior at later stages, when the gas has cooled signi?cantly( 1000K).However,even in such cold environments, the error in the temperature caused by neglect of metal molecular coolants is very small(see Figure10of Omukai et al.2005)and the thermal evolution is well reproduced when only dust processes and?ne–structure line cooling of C and O are considered.
2.2.Dust Processes
Dust in the local interstellar medium(ISM)originates mainly from the asymptotic giant–branch(AGB)stars,whose age is 1Gyr,longer than the Hubble time at z 6.At higher redshifts,supernovae(SNe)are considered to be the major dust factories.Indeed, the observed extinction law of high–z quasars and gamma–ray bursts can be well reproduced
by this scenario(Maiolino et al.2004,Stratta et al.2007).Dust grains produced in SN ejecta are more e?ective in cooling and H2formation because of their smaller size and larger area per unit mass(Schneider et al.2006).However,their composition and size distribution are still a?ected by many uncertainties,such as the degree of mixing in the ejecta and the e?ciency of grain condensation and their destruction by the reverse shock(Nozawa et al. 2007,Bianchi&Schneider2007).
To be conservative,in this work the properties of dust,such as grain composition and size distribution,are assumed to be similar to those in the solar neighborhood and its amount is reduced in proportion to the assumed metallicity of the gas clouds.Speci?cally,we adopt the dust opacity model developed by Semenov et al.(2003).This model partly follows the scheme proposed by Pollack et al.(1994),which was used in Omukai et al.(2005),assuming the same dust composition,size distribution and evaporation temperatures,but uses a new set of dust optical constants.Overall,the opacity curves of the two models are in good agreement,the largest di?erence being at most a factor of two(see Semenov et al.2003 for a thorough discussion).The main dust constituents include amorphous pyroxene([Fe, Mg]SiO3),olivine([Fe,Mg]2SiO4),volatile and refractory organics,amorphous water ice, troilite(FeS)and iron.The grains are assumed to follow a size distribution modi?ed from that by Mathis,Rumpl,&Nordsieck(1977)with the inclusion of large(0.5-5)μm grains.
At each density and gas temperature,the dust is assumed to be in thermal equilibrium, and its temperature T gr,which is followed separately from the gas temperature,is determined by the energy balance equation
4π κa,νBν(T gr)dν=Λgas→dust+4π κa,νJ inνdν.(13) HereΛgas→dust is the energy transfer rate per unit mass from gas to dust due to gas–dust collisions,which we take from Hollenbach&McKee(1979),κa,νis the absorption opacity of dust,and J inνis the mean intensity of the radiation?eld inside the cloud.Note that Λgas→dust also represents the net cooling rate of the gas,caused by the presence of dust grains at temperature T gr.We model the external radiation?eld assuming a diluted thermal spectrum(i.e.a blackbody spectrum,scaled by an overall constant representing a mean geometrical dilution).Its shape is then fully described by only two free parameters,J21,the mean intensity at the Lyman limit(νH)and T?,the color temperature,
(T?)]erg cm?2sr?1s?1Hz?1.(14) J exν=J2110?21[Bν(T?)/Bν
H
In the following,we will consider two possible values for the radiation color temperature,T?= 104K and105K,representing“standard”Population II stars and very massive Population III stars,respectively.Given the mean intensity of the external radiation?eld J exν,the?eld
inside the gas cloud is obtained as(see O2001),
J inν=
J exν+ξνxνS a,ν
[1+4×10?3(G0T1/2/n(e))0.73]+
3.7×10?2(T/10?4)0.7
1+4.0×10?2(T+T gr)1/2+2.0×10?3T+8.0×10?6T2
(21) where
f a=[1+exp(7.5×102(1/75?1/T gr))]?1.(22)
3.Results
In what follows,we will?rst discuss the results obtained for the thermal evolution of metal–free gas clouds,and then describe the e?ects induced by the presence of metals and dust grains.
3.1.Metal–free Clouds
The thermal evolution of metal–free clouds irradiated by a FUV radiation background
is expected to change with radiation temperature T?and intensity J21.The models with
a radiation temperature of T?=104K(105K)are shown in Figure1(2,respectively)for
di?erent values of intensity J21.
Initially,i.e.at low densities,the temperature increases adiabatically,because there is
not enough H2to activate cooling.In the no radiation case,when the density is～1cm?3
and the temperature is～1000K,su?cient H2is formed and,as a result,the temperature
decreases.It is to be noted that the relatively low temperature where this condition is met
does not contradict previous results(BL03).In fact,the predicted temperature of each?uid
element in the simulation of BL03shows a large scatter at low densities.This scatter re?ects
the radial temperature gradient,and the central value,which we calculate here,corresponds
to the lower boundary of the scattered points and it is in agreement with our result.We
expect that the central temperature of the gas cloud does not reach the virial temperature
of the host dark matter halo since the innermost region starts to cool and collapse during
the adiabatic compression and does not experience the virialization shock.
As the external radiation intensity J21increases,the onset of H2cooling is delayed
because higher densities and temperatures are required for H2formation to compensate for
the photodissociation.If the UV intensity is below a threshold value,J21,thr,which we?nd
to be in the range102?103for T?=104K and(1?3)×105for T?=105K,there is always a density at which H2cooling starts to become e?ective.The temperature then decreases
and eventually reaches the no–radiation evolutionary track,along which it evolves thereafter.
On the other hand,if the radiation is stronger than the threshold value,H2cooling never
becomes important.In this case,atomic hydrogen cooling by H excitation(for 107cm?3)
and H?free-bound(f-b)emission(for 107cm?3),are the main cooling channels(see Figure
3).
In Figure1,runs with higher initial temperature(210K)are also shown(dotted lines).
During the initial adiabatic phase,the temperature at a given density is proportional to its
initial value,and thus higher in runs with higher initial temperature.However,after the
onset of e?cient radiative cooling,these initially di?erent thermal evolutionary tracks soon
converge.At higher densities,the results are independent of the initial temperature(see
Figure1).
As it can be inferred from Figs.1and2,we?nd that the threshold value,J21,thr,is
lower for a radiation temperature of T?=104K than for T?=105K.Thus,for comparable
radiation intensities,J21,the lower T?radiation has a stronger impact on the cloud evolution.
To understand why this is the case,in Figure4we show the H2and H?photodissociation rates,for the same intensity J21=1.The dilution factor W,de?ned by Jν≡W Bν(T?), which was used in Omukai&Yoshii(2003),is also shown for reference.As the?gure shows, the H?photodissociation rate decreases steeply with T?,while the H2photodissociation rate remains nearly constant.The H2and H?photodissociation rate coe?cients are
k H
=1.4×109Jν(12.4eV)(23)
2ph
in the unattenuated case and
k H?ph= 0.755eV4πJν
Since the compressional heating rate
?p dρ
gas =
p
β?1.(30)
Both the H line and H?f-b emissions are very sensitive to temperature,and thusβ>1.For those collisional processes,α=2for?xed chemical abundances.With chemical evolution, it deviates from2,but remains>3/2.Therefore,the exponent in equation(30)is negative for the atomic-cooling track as long as the cloud is optically thin:the temperature decreases with density as observed in Figures1and2.On the other hand,on the molecular-cooling track,α=1for densities higher than the critical value for the LTE.Thus,the temperature increases with density for n H 104cm?3.
The existence of a threshold UV background and the discontinuity of thermal evolution at this value are due to the presence of non-local thermodynamic equilibrium(non-LTE)to LTE transition of H2ro–vibrational level population at～104cm?3.When the gas density is higher than this value,the cooling rate saturates and more H2is needed to compensate for compressional heating.In addition,after the LTE is reached,collisional dissociation rate is enhanced owing to a large H2level population in the excited levels.Thus,if a strong FUV radiation delays H2formation and cooling until the critical density for LTE is reached,a fraction of the remaining H2is collisionally dissociated.Thus the gas cloud is no longer able to cool by H2even at a later phase of the evolution.On the other hand,if the UV background is slightly smaller than the threshold,the cloud begins to cool by H2and the temperature begins to fall before the collisional dissociation e?ect becomes signi?cant(see Figure5b in Omukai2001for cooling rates by each process in such a case).The lower temperature allows further H2formation and resultant cooling.The cooling proceeds in this accerelated fashion and the temperature eventually reaches the molecular cooling track.This is the origin of the dichotomy between the atomic and molecular cooling tracks.To summarize,the main e?ect of the FUV radiation is to photodissociate H2directly and to decrease the H2formation rate through photodissociating H?.If these two processes inhibit H2formation and cooling until the critical density for LTE is reached,the gas remains warm( several thousands K) and H2is collisionally dissociated at higher densities.Thus the high density evolution is not a?ected by the presence of the FUV?eld and depends only on the temperature at the H2 critical density.
3.2.Metallicity E?ects on Irradiated Clouds
In this section,we show the e?ects induced by the presence of metals and dust grains on the thermal evolution of gas clouds irradiated by a FUV?eld with a mean intensity larger than J21,thr.In what follows,the total metallicity is expressed relative to the solar value, as[M/H]≡log(Z/Z⊙).Unless speci?ed otherwise,the fractions of metals in the gas phase and in dust grains are assumed to be the same as in the interstellar medium(ISM)of the Galaxy.Speci?cally,the number fractions of C and O nuclei in the gas phase with respect to H nuclei are y C,gas=0.927×10?4Z/Z⊙and y O,gas=3.568×10?4Z/Z⊙.The mass fraction of dust grains relative to the mass in gas is0.939×10?2Z/Z⊙below the ice-vaporization temperature(T gr 100K).
In Figure5we present the thermal evolution of clouds with metallicity in the range ?6≤[M/H]≤?3irradiated by extremely strong FUV radiation?elds.The parameters of the radiation?elds are(a)T?=104K,J21=103and(b)T?=105K,J21=3×105, respectively.Under these conditions,the clouds would collapse only via atomic cooling in the absence of metals or dust grains(see Figs.1and2).For a metallicity as low as [M/H] ?6,the predicted thermal evolution follows the metal–free track.In both panels of Figure5,deviations from the metal–free tracks start to appear at a density～1011cm?3 when the metallicity is[M/H]??5.3.For the sake of comparison,thin lines show the expected evolution in the absence of radiation for the same initial values of metallicity. At metallicity[M/H]=?5.3,although the temperature drops and eventually reaches the molecular-cooling track at～1016cm?3,this arrival is after the minimum in the molecular cooling at～1014cm?3.With a slightly higer metallicity of[M/H]=?5,this arrival takes place at～1011?12cm?3,and the temperature subsequently decreases to the minimum in the no-radiation case.For higher metallicities,the temperature drop occurs at lower density and the temperature minima becomes lower.In Figure6we show the cooling and heating rates contributed by each process during the evolution of the cloud with T?=104K,J21=103 and[M/H]=-5.Up to1010cm?3,cooling is dominated by the H line emission(denoted as “H”in the Figure; 107cm?3)and H?f-b emission(“H?f-b”; 107cm?3),and the cloud collapses along the atomic cooling track(see Fig.5a).However,at a density～1010cm?3, cooling by the dust grain(“grain”)becomes dominant and causes the sudden temperature drop.Now the temperature is lower than that in the atomic cooling track,the H2collisional dissociation rate is also reduced,which causes a high equilibrium value of the H2fraction. As a result of H2cooling,the temperature decreases further,although this e?ect is almost completely balanced by heating due to H2formation(“H2form”).Note that?ne-structure line cooling(“CII,OI”)is not important at such low metallicities(see the discussion below). Eventually,the thermal evolutionary tracks reach those of the corresponding metallicity in the no–radiation case(shown as thin curves in Fig.5)and evolve along them thereafter.
We also run models with an external UV?eld with parameters T?=104K,J21=104,
which is10times stronger than that considered in Fig.5(a)and we found that the critical
value of the metallicity at which deviations from the metal–free evolution appear,Z cr～5×10?6Z⊙does not depend on the intensity of the FUV radiation as long as J21>J21,thr.
Furthermore,for the same value of the metallicity,the evolutionary tracks at high densities
( 104cm?3)are independent of the type of external radiation,as can be seen comparing the
results in panels(a)and(b)of Figure5.In fact,once the evolution has reached the density
at which molecular and atomic cooling tracks bifurcate( 104cm?3),collisional processes
rather than radiative ones dominate the energy balance(see also§3.1).
It is interesting to stress that the physical processes responsible for the origin of a critical
metallicity and its numerical value are the same as those found in the absence of FUV
radiation(Schneider et al.2003;Omukai et al.2005).This is because despite the higher gas
temperatures induced by the presence of a strong FUV?eld(several thousands of degrees),
the dust temperature remains at a few tens of degrees until the energy transfer rate from gas
to dust by collisions become important and the dust and gas temperatures approach each
other(with the associated gas cooling).Nevertheless,the ultimate fate of protogalaxies at
low metallicity can be signi?cantly a?ected by the presence of the UV?ux(see discussion in
§3.4below).In Figure7,the evolution of dust and gas temperatures is shown for the lowest metallicity tracks presented in Figure5(a).The disappearance of the dust temperature curve for[M/H]=?6at a density of～1014cm?3is due to complete vaporization of grains,which occurs at?1300K.At dust temperatures higher than this value,grains are no longer present in the cloud.Other smaller discontinuities in the dust temperature also re?ect vaporization of some dust compounds.For example,those at?130K(at～109cm?3for[M/H]=?6 and-5;at～1011cm?3for[M/H]=?4)are due to vaporization of water ice.This?gure indeed shows that despite the high gas temperature,the dust temperature remains low at a few10K,which allows survival of grains until very high densities.
As discussed above,OI and CII line emission contributes negligibly to gas cooling in
the metallicity and density range where the e?ects of dust grains start to become relevant
(Z cr～5×10?6Z⊙,n H～1010cm?3).Metal–line cooling causes a deviation from the metal–free atomic track only when the metallicity reaches[M/H]～?3.In this case,since the temperature track converges to the J=0track before the dust–cooling phase,two tem-perature minima appear at105cm?3and1010cm?3(see Fig.5a,b).In the absence of dust grains,a higher fraction of metals is required to cool the gas at a rate such that the thermal evolution deviates from the atomic cooling metal–free tracks.To demonstrate this,we have performed a numerical experiment where we have suppressed the contribution of dust grains to the energy balance of the collapsing clouds.The results for models with radiation?eld parameters of(T?=104K,J21=103)are shown in Figure8.When the metallicity is
below[M/H]??3.5,the temperature evolution is exactly the same as the metal-free one (shown by the2×10?4Z⊙track in the Figure).For higher metallicity,?ne-structure line cooling becomes dominant when n H 104cm?3and the temperature drops abruptly by more than two orders of magnitude.Therefore we?nd that the critical metallicity[M/H]??3.5 (?3×10?4Z⊙)required to modify the thermal evolution is almost two orders of magnitude higher than in models with dust.This level of metallicity is approximately the same as the value at which metal cooling rate exceeds the H2cooling rate in clouds which are already col-lapsing by molecular cooling(Bromm&Loeb2003b,Santoro&Shull2006;Frebel,Johnson &Bromm2007).
3.3.Fragmentation Properties
The thermal properties of star–forming clouds have an important in?uence on how they fragment into stars(Larson2005).There is observational evidence that proto–stellar cores have a mass spectrum which resemble the stellar initial mass function(IMF),indicating that cloud fragmentation must be responsible for setting some fundamental properties of the star formation process(e.g.,Motte,Andre,&Neri1998;Lada et al.2007;for the recent reviews, see Bonnell,Larson&Zinnecker2006and Elmegreen2008).
Roughly speaking,fragmentation occurs e?ciently when the e?ective adiabatic index γ≡?ln p/?lnρ 1,i.e.,during the temperature drops,and almost stops when isothermality breaks(γ 1)as also shown by the simulations of Li,Klessen&Mac Low(2003).Thus, consistent with Schneider et al.(2002,2003,2006)we can adopt the density at which the equation of state?rst becomes softer thanγ≈1to identify the preferred mass scale of the initial fragments(Inutsuka&Miyama1997,Jappsen et al.2005).The fragment mass is given roughly by the Jeans mass(or Bonnor–Ebert mass)at this epoch,
M frag=M J(n frag,T frag)∝T3/2
frag n?1/2
frag
.(31)
In the absence of an external FUV radiation?eld,the temperature of metal–free clouds decreases with density in the range1cm?3 n H 104cm?3and increases at higher densities, after the major coolant H2has reached the LTE.Dense cores form around this density with typical masses of103M⊙,which is close to the Bonnor–Ebert mass at this thermal state (Bromm,Coppi,&Larson1999,2002;Abel,Bryan,&Norman2002).As the metallicity increases to Z cr=10?6Z⊙,dust–induced fragmentation leads to solar or sub–solar fragments (Schneider et al.2006),making a fundamental transition in the characteristic mass scales of proto–stellar cores.
It is important to stress that the presence of a temperature dip in the thermal evolution, and the softening of the equation of stateγ<1,imply only the possibility of fragmentation. For example,fragmentation depends also on the initial conditions,and requires the existence of su?ciently large initial density perturbations.In the?rst cosmological objects,which are barely able to cool and collapse,fragmentation can be less e?cient.Still,self–gravitating cores of mass comparable with that predicted by the above criterion are observed to form in high–resolution3D simulations(Abel,Bryan,&Norman2002,Yoshida et al.2006).Even for turbulent molecular clouds of solar metallicity,3D simulations show that fragmentation is e?cient whenγ≈0.7and it is suppressed afterγincreases to≈1.1(Jappsen et al.2005).
The evolution with density of the e?ective adiabatic index,γ,is presented in Figure9for clouds with initial metallicities[M/H]=?∞,-6,-5.3,-5,-4,and-3,irradiated by a?eld with parameters T?=104K and J?=103,whose temperature evolution is shown in Fig.5a.The application of the above arguments to predict the typical fragment mass from the thermal evolution of the clouds is not straightforward because,along the metal–free atomic cooling tracks and over a broad density range101?16cm?3,the e?ective adiabatic index remainsγ?1,although slightly below unity(0.95-1;see Fig.9,top panel).If we adoptγfrag=1as the threshold value of the e?ective adiabatic index for fragmentation,in this case fragmentation would be expected to occur up to densities of～1016cm?3,leading to solar–mass fragments, as discussed by O2001and Omukai&Yoshii(2003).In contrast,the numerical simulations by BL03show that down to the highest density reached by the simulations( 109cm?3) fragmentation is very ine?cient.Even with some degree of rotation,the cloud fragments at most into two pieces,resulting in a binary system.Although fragmentation might occur at higher densities,in BL03’s calculations neither e?cient fragmentation leading to the formation of a star cluster,nor the growth of elongation of the clouds is observed.We speculate that this result is due to the following reasons.The objects considered by BL03 are those only marginally able to collapse by atomic cooling,and thus are initially close to the hydrostatic equilibrium.During this initial epoch,the Jeans mass is large,and density and velocity perturbations are erased by pressure forces.In addition to this little initial seed perturbation,sinceγis only slightly below unity,the growth of perturbation would be very slow.Thus the perturbation might not grow enough to cause fragmentation.
Note however that,although we?nd that along the atomic cooling tracks H?cooling is the dominant cooling agent at high densities, 107cm?3,this process is not considered in the simulation of BL03,which implements only H Lyαcooling.To check whether this omission might cause the lack of fragmentation,we have followed the evolution of a metal–free cloud under the in?uence of an external FUV radiation?eld with T?=104K and J21=103but turning o?the H?cooling by hand.The result is shown in Figure10.With no H?cooling,the cloud follows a slightly higher temperature track when the density is
107cm?3.However,below～1012cm?3,the di?erence is small and it has a weak e?ect on the cloud dynamics.Therefore the inclusion of H?cooling would not a?ect the results of BL03’s simulation,which is limited to densities<109cm?3.
On the basis of these considerations,we assume that for metal–free clouds irradiated by a strong FUV background,fragmentation does not occur during the atomic–cooling phase, whereγ?1,and it occurs only when the temperature drops more rapidly,whereγ<γfrag< 1,by molecular cooling,that is when Jν In the metal–enriched,irradiated clouds we studied,the temperature dip due to dust cooling occurs at very high densities,1010cm?3,deep in the interior of the collapsing clouds, where pre–existing density perturbations might also be erased by pressure forces.However, in this regime we?ndγ 0.5as shown in Figure9;fragmentation has also been con?rmed to occur in two independent hydrodynamic simulations of collapsing clouds not irradiated by external FUV?elds(Tsuribe&Omukai2006,Clark,Glover,&Klessen2008).Therefore, we expect that for metallicities[M/H] ?5,when the thermal evolutionary tracks shown in Figure5suddenly deviate from the atomic–cooling track,in other words,whenγfalls su?ciently below unity(Figure9),the clouds begin a vigorous fragmentation,which then lasts until the temperature increases again.The value ofγfrag to cause fragmentation is uncertain as discussed above,but likely to be slightly below unity.In the following,for the sake of de?niteness,adoptγfrag=0.8as the?ducial value below which fragmentation is triggered(the lower horizontal lines in Fig.9),and use it to de?ne the properties of the fragments.This choice refrects the fact that forγ=0.7e?cient fragmentation has been observed to occur in the numerical simulations of Jappsen et al.(2005).In all cases,once molecular cooling becomes e?cient,γsoon falls below 0.5(Fig.9).Varying the threshold valueγfrag,say,by～0.1,leads to fragmentation densities whose di?erences are within an order of magnitude.For example,when[M/H]=?4fragmentation begins at log n H(cm?3)= 7.5,8,and8.3forγfrag=0.7,0.8,and0.9,respectively.We assume that fragmentation stops whenγexceeds unity again.For[M/H]=?4,this occurs at n H～1013cm?3. The mass scale of the?nal fragments is given by the Jeans mass at the temperature minimum,i.e.,whenγexceeds unity.When the initial metallicity is[M/H]??5,the tem-perature minimum corresponds to300K at n H=1014cm?3,and thus the typical fragment mass is0.1M⊙.As the metallicity increases,both the density and temperature at the frag-mentation scale decrease,being(1013cm?3,150K)for[M/H]??4,and(1011cm?3,30K)for [M/H]??3.However,the corresponding fragment mass scale remains～0.1M⊙,because the variations of density and temperature almost cancel out(see eq.31).In some cases,e.g. [M/H]～?3gas in a J21>J21,thr?eld,two fragmentation epochs(log n H=3.5?5.1and 8.5?10.7for[M/H]=?3)appear,which corresponds to two dips in the temperature(or γ)evolutionary track.The outcome of this kind of track is not clear without any numerical work studying their e?ect.Here,we speculate that the?rst dip produces clumps as a result of the fragmentation of clouds.Then the clumps fragments again into cores owing to the second dip. In the absence of dust,the temperature minimum appears at a lower density,n H～105cm?3,and higher metallicity[M/H]??3.5(see Fig.8).Therefore,the corresponding fragment mass remains as high as10?100M⊙and the formation of sub–solar mass fragments is not possible in this case.This property of pre–stellar clouds enriched only by gas–phase metals has been already proven to hold in the absence of external FUV?elds(Schneider et al.2006). To summarize,our results show that in the presence of a su?ciently strong FUV radia-tion?eld the collapse of metal–free clouds by molecular cooling is inhibited and it can proceed only via atomic cooling.Under these conditions,cloud fragmentation is highly ine?cient, leading at most to the formation of a binary system.The typical mass of pre–stellar clouds is therefore105?6M⊙and the formation of a super massive star,seed of a super massive black hole,is the likely outcome of the evolution(BL03).However,this scenario is altered as soon as trace amounts of metals and dust grains are present in the collapsing clouds:dust cooling leads to fragmentation of the clouds into sub–clumps with mass as low as～0.1M⊙already at a?oor metallicity of Z cr～5×10?6Z⊙.This conclusion holds independently of the intensity and spectrum of the FUV radiation?eld.In the absence of dust,an enrichment level of Z cr～3×10?4Z⊙is required for OI and CII line cooling to fragment the cloud;the fragments in this case are predicted to be relatively more massive,～10?100M⊙. 3.4.Dynamical Interactions and Accretion Since dust–induced fragmentation takes place at high densities,a dense proto–stellar cluster is expected to form(Omukai et al.2005,Schneider et al.2006,Clark et al.2008).As an example,when the initial metallicity of the collapsing cloud is[M/H]=?5,the sudden temperature drop,whereγ<γfrag=0.8,begins at T drop～3500K and n drop?1010.5cm?3. At this stage,the size and mass of the cooling region,or proto–cluster,are given by the corresponding Jeans length,λJ?4×10?3pc,and mass M cl?70M⊙.When a di?erent threshold valueγfrag is adopted,these quantities change,e.g.,toλJ?3×10?3pc,and M cl?40M⊙forγfrag=0.7(0.9,respectively).In the following order of magnitude estimation,we useλJ～1×10?2pc and M cl～100M⊙as typical values.After virialization,the proto–stellar cluster has a size half of this.Since each ultimate fragment has a typical mass of M frag～0.1M⊙,which is set by the Jeans mass at the end of the fragmentation process (n H～1014cm?3),we expect that up to N?～M cl/M frag～1000low–mass star can be formed and con?ned into a small region of size～0.01pc.The di?erence between the formation epochs of each protostar is of the order of the free–fall time of the proto–cluster gas.Since the cluster begins to form in a dense cloud with density～1010cm?3,protostar formation is synchronized on a timescale of～300yrs. The fate of dense,compact star clusters has been discussed extensively in the literature (see,e.g.Rasio et al.2004for a recent review,focusing on the possibility of intermediate BH, IMBH,formation through a runaway collapse that is relevant in our case).It is important to stress that,even assuming a star formation e?ciency of order unity(which seems likely when the density exceeds 104cm?3;Alves,Lombardi&Lada2007),the stellar IMF will be strongly a?ected by gravitational interactions,collisions and mergers.In fact,observed properties of present–day star forming regions,as well as numerical simulations,suggest that gravitational fragmentation is probably responsible for setting a characteristic stellar mass but the full mass–spectrum and the Salpeter–like slope of the IMF are most likely formed through continued accretion and dynamical interactions in a clustered environment (see Bonnell et al.2006and references therein).Furthermore,in young and compact star clusters supermassive stars may form through repeated collisions(e.g.Portegies Zwart et al. 1999,2004;Ebisuzaki et al.2001). We can therefore ask,what is the expected fate of the dense star cluster forming in our clouds?The evolution of a star cluster with half–mass radius R cl and mass M cl proceeds on the dynamical friction timescale(Binney&Tremaine1987), t fric?1.2×1050.01pc 2 R cl102M⊙ 1/2 m? Blackboard平台在网络课程中的应用研究 【摘要】Blackboard网络教学平台作为传统课程的辅助机制，为学生创设了互动的教学环境，提升了学习的自主性。课程模块可分为课程学习模块、协作交流模块、学习评价模块等。环环相扣的模块可以提高学生的课程参与度。Blackboard平台可以与慕课融合与互补，实现以学生为中心的教学，促进学生的发展，激发学习的热情，使学习过程得到及时反馈，为教育带来新机遇。 【关键词】网络课程；Blackboard平台；MOOCs 【中图分类号】G645 【文献标识码】A 【文章编号】10018794（2015）09005704 网络课程可以使教学有效地突破时空限制，加强学生和教师之间交流的主动性、及时性。当前，处于实际应用阶段的网络课程教育，研究重点已不再是“为什么要开展网络课程教育”的理论探讨，而是“如何建设好网络课程资源”、“如何让学生更高效地使用网络课程”的实施问题。利用网络课程的形式对高校学生进行教学，既能够为学生构建个别化学习环境，提升学习效率，使学生针对自身的情况进行网络课程的学习，又将传统的单向灌输式教学变为多元互助教学，使高校艺术课程不再局限于理论，而是更加艺术地体现出理 论与实践相结合的特性。本文以《电子音乐制作》课程与信息网络相结合的教学实践为例，给教师提供丰富的教学手段的同时，也给学生学习理论知识与艺术作品的创作带来了便捷、丰富、高效的途径。[1] 一、Blackboard在网络课程中的作用分析 Blackboard平台（简称Blackboard或Bb，全称Blackboard Learning System TM）是专门用于加强网络教学、辅助课堂教学并提供教师与学生之间、学生与学生之间交流、互动的网络公共教学平台。全球目前有5 200多个用户，其中包括著名的哈佛大学、斯坦福大学、普林斯顿大学等。2003年，北京赛尔毕博公司将Blackboard公共教学平台引入国内，至今，全国大约已有240个用户。随着网络技术和信息技术的发展，国内越来越多的高校使用Blackboard进行辅助教学，如北京大学、中山大学、香港大学、中国传媒大学、武汉大学、北京师范大学、湖南师范大学等。[2] 由于传统课堂教学的局限性，存在很多不尽如人意的地方。课堂上的大部分时间是教师主导地传授知识，没有充分的时间进行师生之间以及生生之间的交流与探讨。课堂时间有限，许多学生对教师展示的作品无法深入分析与鉴赏，限制了审美力的提升。学生被动地思考教师提出的问题，被动地完成教师布置的任务，被动地分析教师展示的作品，缺乏主动学习思考的意识，缺乏动手设计作品的经验。例如，《电 第一部分 项目总体规划 人类社会进入二十一世纪，信息技术已渗透到经济发展和社会生活的各个方面，人们的生产方式、生活方式以及学习方式正在发生深刻的变化，全民教育、优质教育、个性化学习和终身学习已成为信息时代教育发展的重要特征。面对日趋激烈的国力竞争，世界各国普遍关注教育信息化在提高国民素质和增强国家创新能力方面的重要作用。《国家中长期教育改革和发展规划纲要（2010-2020年）》（以下简称《教育规划纲要》）明确指出：“信息技术对教育发展具有革命性影响，必须予以高度重视”。 1. 项目建设背景 我国教育改革和发展正面临着前所未有的机遇和挑战。以教育信息化带动教育现代化，破解制约我国教育发展的难题，促进教育的创新与变革，是加快从教育大国向教育强国迈进的重大战略抉择。教育信息化充分发挥现代信息技术优势，注重信息技术与教育的全面深度融合，在促进教育公平和实现优质教育资源广泛共享、提高教育质量和建设学习型社会、推动教育理念变革和培养具有国际竞争力的创新人才等方面具有独特的重要作用，是实现我国教育现代化宏伟目标不可或缺的动力与支撑。 2. 项目建设目标 充分利用现代信息技术，以“课程教学”为核心，针对课程教学过程的需求构建基于校园网或城域网上的“数字化教学系统”，满足随时、随地、个性化教与学的需求。“数字化教学系统”建设容包括一个教学服务支撑平台（即学校或区域教育云）、两个基于教育云的教学应用客户端（即教师工作台和学生电子书包）和每个教室的无线网覆盖。 2.1 构建学校或区域教育云 教育云是基于网络和云计算技术构建的网络教学应用服务平台，为实施数字化教学、网络协同教研和课程同步辅导的需要提供包括资源和应用在的一体化教学支撑系统。教育云建设容包括服务器平台、网络平台、教学资源平台和数字化网络教学服务平台等软硬件系统的建设。教育云必须支持面向教师的教学、学生的学习辅导以及支持师生互动和生生互动。2.2 配置教师工作台 包括教师笔记本和教学应用软件系统，将课程资源与教师的教学要求紧密结合，支持教师对资源、资源管理、教学备课和互动授课等应用的需求满足。 2.3 配置学生电子书包 包括学生学习终端及支持学生进行课程学习需求的学习应用软件系统。 3. 项目应用目标 3.1 推进信息技术与学科教学的融合 应用智能化教学环境，提供优质数字教育资源和软件工具，利用信息技术开展启发式、探究式、讨论式、参与式教学，鼓励发展性评价，探索建立以学习者为中心的教学新模式，倡导网络校际协作学习，提高信息化教学水平。逐步普及专家引领的网络教研，提高教师网络学习的针对性和有效性，促进教师专业化发展。 3.2 培养学生信息化环境下的学习能力 适应信息化和国际化的要求，完善信息技术教育，开展多种方式的信息技术应用活动，创设绿色、安全、文明的应用环境。鼓励学生利用信息手段主动学习、自主学习、合作学习； Blackboard平台功能简介 一、Blackboard教育软件基本情况 ◆网络教学（e-Learning）是目前全球教学改革的潮流； ◆Blackboard Academic Suite TM 教育软件，简称Blackboard，是美国Blackboard 公司开发的网络教学平台； ◆Blackboard平台是一个能给教师带来无限应用、交流、创新的平台，在全球有3700 多所高校利用它开展网络应用； ◆它为200多所中国高校提供产品和服务，涉及高等教育、基础教育、职业教育以及 企业培训； ◆Blackboard教育软件以“教学”、“联系”、“分享”为核心目标，提供一套综合、完 整、优化的解决方案。 1.1 Blackboard平台构建目标 1.2 Blackboard平台用户与课程关系示意图 1.3 Blackboard平台系统结构图 二、Blackboard教育软件主要功能 2.1 Blackboard教学平台 2.1.1 课程重复使用 ◆复制课程内容 ◆循环使用课程 ◆将课程存档 2.1.2 学习单元 ◆支持教师创建有序的课程内容，控制学生按顺序进行学习; ◆能够保存学生在学习单元中的进度位置，便于学生以后继续学习。 2.1.3 选择性发布 ◆支持教师根据课程内容和活动定制教学路径，如先学什么再学什么，哪些用户学什 么等； ◆系统根据教学路径中设定的条件有选择地将内容发布给学生。 2.1.4 反抄袭工具 ◆四个对比检测库：互联网欧美硕博论文数据库全球参考数据库 院校自己的数据库 ◆提供原创性报告 ◆与成绩中心相连通，可直接给论文打分 ◆促使学生进行思考 2.1.5 预警系统 ◆当学生未能达到教师设定的标准时，系统自动向学生发出警示 ◆可创建多种规则 2.1.6 测验和调查 ◆17种可选择的题型 ◆可设置是否允许多次尝试 ◆可进行时间控制 2.1.7 成绩中心 ◆直接编辑成绩 ◆添加外部成绩 ◆加权计算成绩 ◆智能视图 ◆生成成绩报告 ◆发送成绩报告 2.1.8 学业表现统计 ◆及时了解学生的学习情况 ◆学生参与网络学习的数据 ◆学生各个课程内容的学习情况 2.1.9 支持协作活动的平台 ◆讨论板 ◆邮件、消息 ◆虚拟课堂、聊天室 ◆工作流程流程化的协作活动管理可查看流程进展情况 2.1.10 自评与互评 ◆促进学生更好地理解评分标准 ◆促进学生之间的建设性反馈 ◆完全客观的反馈（可选匿名评估） Blackboard在线教学管理系统 Blackboard是一个由美国Blackboard公司开发的数位教学平台，被广泛认为是业界领先的课程主导型管理系统。数位教学意指数字化教学，老师和学生可以在多媒体、网络组成的平台内进行各种课程方面的交流。Blackboard在线教学管理系统，正是以课程为中心集成网络“教”“学”的环境。教师可以在平台上开设网络课程，学习者可以自主选择要学习的课程并自主进行课程内容学习。不同学习者之间以及教师和学习者之间可以根据教、学的需要进行讨论、交流。“Blackboard”为教师、学生提供了强大的施教和学习的网上虚拟环境，成为师生沟通的桥梁。 欧桥国际学院（ObridgeAcademy）就是采用最领先的在线教育管理系统–“Blackboard Learning System” 平台以课程为核心，每一个课程都具备以下4个独立的功能模块： ●教学组织管理–方便地发布和管理教学内容、组织教学活动 ●交流互动工具–支持异步和同步的交流协作 ●考核管理功能–自测、测验、考试、调查和成绩统计管理 ●管理统计功能–课程以及平台的管理和统计 登陆平台的三类身份：系统管理员、教师、学生。 系统管理员：个性化定制平台界面风格、功能；根据学校的根据实际情况设定、添加、管理用户；统计并管理整个平台的使用情况；为其他校园信息化的应用系 统提供服务和接口等。 教师：管理教学、编辑组织教学内容、在线考试、批改作业、组织在线答疑、统计分析学生学习情况等。 学生：选修课程、安排学习计划、查看课程内容、提交作业、参加在线测试、查看学习成绩、协作学习和交流、参与学校社团交流等。 Blackboard教学管理平台是目前市场上唯一支持百万级用户的教学平台，能使学校更好地进行课业交流，达到自主学习、教学相长的目的。使任何教师、学生和研究者都可以随时随地浏览内容、获取资源、评估教学效果、实现彼此的协作。可帮助教师在线授课、测验、检查作业,学生可以通过各种论坛区与师生交流，巩固学习效果，增进学习兴趣。Blackboard界面直观，工具简单易用，对技术人员依赖程度低。通过与世界最大的网络教学平台提供商Blackboard的合作，还可以为学校提供更多的与国际上其他学校交流的机会。 blackbaord教学平台简单易用、本地化功能强，将多媒体的网络学习资源、网上学习社区以及网络技术结合于一体，形成一种全新的网络学习环境。汇集了大量的数据、档案资料、兴趣讨论组、新闻组等学习资源，形成了一个高度集成的资源库，轻松实现了信息资源的交流与共享。 在中国，blackbaord已成功地为北京师范大学，华南师范大学，中山大学，南京大学等学校用户构建了网络教学平台。 Blackboard 网络学习平台在课堂教学中的设计 Designing and Application of Web-based Course Platform Blackboard in Classroom Teaching: A Case Study in Second Language Acquisition//Su Baohua, Luo Xiaoying It is designed to develop the application of web-based course platform in the classroom teaching. The process of teaching and learning are united closely on the platform. In an effective way it shows the importance the bilingual teaching and increases the students ' active learning, which also expands the students ' learning domain s. Author 's address College of Chinese Language and Culture of Jinan University, Guangzhou, China 510610 1课程简介第二语言习得理论为暨南大学华文学院应用语言学系对外汉语专业以及华文教育系华文教育专业的本科专业必修课。这门课程开设的目的是帮助学生掌握一些基本的第二语言习得理论及研究方法。因此，结合Blackboard 网络学习平台（以下简称BB平台）为他们今后的对外汉语教学实践或进一步的研究工作做准备，具有非常重要的意义。 2实验教学单元 下面是第二语言习得理论课程的主要教学内容。 一、信息化建设的意义 信息化建设是学校建设重要组成部分，是一项基础性、长期性和经常性的重要工作，其建设水平是学校整体办学水平、学校形象和地位的重要标志。而数字化校园建设更是提升办学实力，加强内涵建设的重要内容，也是实现优质教育资源共享、共用，促进职业教育共同发展的有力举措。为了加速学校信息化进程，进一步提升我校信息化教学水平，为此我校决定制定用“数字化校园”提升学校信息化教学水平项目建设计划。 数字化校园建设的需求论证 职教新干线是由国家教育部、科技部共同组建的共享型网络学习平台，是创新教育、改革学习方法、提高教学质量的重要平台。职教新干线作为职教资源的“航母”，已于2009年在湖南省全面启动，湖南省教育厅还于2010年4月23日下发了《以职教新干线为引领，打造网上湖南职业教育》的通知。湖南省的职教新干线是由省教育厅主管、省教科院职成所承办的湖南职业教育网站，是以个人空间为基础，基于实名制、开放的网络学习互动交流平台。由省教科院职成所为全省国家级重点中等职业学校、省级示范性中职学校及县级职教中心牵头学校统一注册机构空间（示范性中职学校同时又是示范性县级职教中心牵头学校的只注册一个空 间），并在职教新干线网站首页建立一个提供在线咨询服务的工作空间。要求各单位组织专门力量，按照申请注册机构空间——制定栏目方案——开展网页主体设计的顺序，仿照职教新干线模式进行建设，并明确一名负责人，负责本单位空间建设工作。 我校是首批重点国家级中等职业学校、省级示范性中职学校，早在2000年就着手校园网的建设，并于2010年进行全面升级改造，建成千兆主干、百兆桌面的数字化校园，配备了较为完善的校园信息管理系统。目前，以职教新干线为引领，通过应用带动，建设覆盖全校的网络学习交流互动平台已有基础。为加强我校职业教育信息化建设，实现优质职教资源共享、共用，我们将充分利用职教新干线，加速学校信息化进程，进一步提升我校信息化教学水平。为此特制定利用“职教新干线”提升学校信息化教学水平项目建设计划。 (一)、必要性 1、数字化校园是指挖掘先进的管理理念，以数字化信息和网络为基础，应用先进的信息化手段将信息技术融于教育的各个环节，通过全校所有部门的信息编码统一，使学校的所有信息能够实时自动的互连互通，资源得到充分的共享和利用，将学校内部相对独立分散的网络应用系统，进行了 广东金融学院 Blackboard教学平台使用手册 （学生版V1.0） 校园网络中心编写 2010年10月 （一）平台基本操作 (3) （二）查看课程 (5) （三）提交作业及查看成绩 (7) （四）测验及查看成绩 (13) （五）论坛讨论 (18) （一）平台基本操作 1．登陆及退出 BB平台 网址：https://www.doczj.com/doc/5317140203.html, 用户名：学生学号 密码：初始密码与用户名相同（学生登陆平台后可以修改初始密码，修改方法见“2.修改密码”）为了保证帐户安全，请同学们在离开平台时，点页面上方的“注销”按钮安全退出平台后再关闭浏览器窗口，如图1。 图 1 2．修改密码 学生登陆平台后可以修改初始密码；若忘记密码，只能申请由系统管理员进行重设密码。 ?登陆 BB平台后，点击“我的首页”选项卡左边“工具”栏中的“个人信息”按钮，如图2。 图 2 ?在“个人信息”页面，点击“更改密码”，如图3。 图 3 ?输入新密码后点击“提交”，如图4，新密码要求为 5-8位数字、字母或下划线的组合。 图 4 注意：修改密码后，新密码请同学自行保管， BB系统不能查询，只能帮助同学重设密码。 （二）查看课程 1．登陆 BB平台后，点击“我的课程”选项卡，“课程列表”中列出学生选修的课程名称，点击某一门课程，如图6。 图 6 2．进入课程后，左边为课程菜单列表，右边默认显示“通知”内容，学生可及时查看教师发布的通知，如图7。 图 7 3．点击左边课程菜单中的“教学大纲”，即可在右边页面中查看教师上 传的教学大纲，如图8。 图 8 4．点击教师上传的教学大纲文件，在弹出的对话框中点击“打开”，如图9，将在当前页面显示教学大纲的内容，若点击“保存”可将教学大纲文件下载至本地计算机。 图 9 5．同理，点击课程菜单中的“教学进度”，可查看课程的教学进度表；点击课程菜单中的“课程文档”，可查看教师上传的课件；点击课程菜单中的“教师信息”，可查看任课教师的基本信息和答疑时间等。 数字化资源平台建设 随着计算机网络技术的发展，互联网的普及，教育也进入了网络的新时代，信息技术在教学中的应用也快速发展，信息化教学成为教育发展的新趋势。而数字化教学资源共享平台是实施信息化教学的基础，因此各学校开始重视数字化教学资源平台的建设，利用信息技术促进教学质量与效率的提高。下面结合本人的工作经历，分析如何进行数字化资源平台建设。 一、数字化教学资源共享平台构建体系 数字化教学资源共享平台是指在教育领域全面深入地运用现代信息技术来促进教育改革和教育发展，实现教育资源共建、共享，促使教学资源的统一管理，最终实现信息化教学的一个综合信息管理系统。它具有数字化、网络化、智能化和多媒体化的特点。现有大部分平台开发遵循教学性、科学性、开放性、应用性、层次性和经济性原则，基于SAN网络存储架构、TRS跨数据库检索技术和统一身份认证的门户网站的导航三层技术在校园局域网的基础上对数字化教学资源进行高度整合，从而实现校内资源的有效聚集与广泛共享、教学资源的个性化服务、确保查询速度、保护知识产权及资源的交互式应用。 而我校是一所中职学校，从资金到技术都没有这个实力，校园网的安全性较差，因此设了两台服务器，把校园网站等对外网的信息放到一个服务器上，把数字化资源平台和信息管理系统等放到另一个服务器上不对外网开放，这样不用怎么考虑外网的入浸。 二、注重技能培养需求开发优质资源 现代教育技术的发展对教育产生了全面、深刻的影响,不仅改革了教学模式和教学方法，还为我们呈现了一个教育现代化的宏伟蓝图。如何运用教育规律，利用现代教育技术手段，进行数字化资源建设已成为必然趋势。不同层次，不同类型的人才培养,需要适合其自身特点的教育信息化资源。以培养应用型人才为主，进行数字化资源建设也应注重对学生动手能力的培养，资源的构成可以以技术应用型媒体资源为主，同时注重理论与研究型媒体资源的开发。以计算机应用技术专业为例，在专业资源库建设前期，经过充分调研后，结合该专业人才培养方案，我们将应用案例的收集与开发及相关工具的使用作为该专业数字化资源建设的重点，同时做好相关技术素材的整理与制作工作。 内容与技术是数字化资源建设从不同角度划分的两个层面,内容表示该资源要呈现的信息内涵,技术指具体资源用何种媒体、什么样的方式来呈现。一般专业教师，对自身涉及到的专业比较了解，在数字化资源建设过程中制作一些PPT 课件还可以，但是要进行一些深层次数字化媒体资源的开发往往就无能为力了。学校在进行数字化资源整体规划中，要明确哪些是重点资源，对于这些资源可以按课程或专业列子项目成立开发小组，小组成员应由专业教师、IT方面或艺术方面的教师组成,专业教师负责具体资源的内容设计和脚本编写，然后由IT方面的教师选择合适的媒体形式并实现。 数字化教学资源的设计涉及到教育学理论、心理学理论、学习理论、教学设计、美学等多方面的知识,并非一个简单的过程。如何综合运用相关理论设计出 Blackboard网络教学平台介绍 互联互动的网络学习环境 Blackboard致力于帮助院校打造一个真正的互联互动的网络学习环境（Networked Learning Environment，简称NLe），以实现互联网为教育带来的强大力量。在这个环境中，任何教师、学生和研究者都可以在任何方便的时间浏览内容、获取资源、评估教学效果、实现彼此的协作。 为实现NLe，Blackboard提供Blackboard教育软件（Blackboard Academic Suite?）以及与之配套的解决方案，为院校互联互动的网络学习环境提供专业技术支撑、赋予强大力量。 Blackboard教育软件是Blackboard公司基于NLe的理念精髓，体察全球各类院校的实际需求，并融入其在e-Learning行业多年的经验推出的全新力作。Blackboard教育软件提供了一套综合完整的解决方案，最大限度地优化和增强了此系列中每个独立产品的应用。该软件系列由以下3个平台组成：Blackboard教学管理平台、Blackboard门户社区平台、Blackboard资源管理平台 这3个平台涵盖院校教学信息化涉及的各个层面的需求：教学流程管理与监控、内容建设与共享、信息管理与发布、应用系统整合等。系列产品以“教学”、“联系”、“分享”为核心目标，为教育机构提供了丰富完善的工具和无限广阔的空间。 Blackboard教学管理平台（Blackboard Learning System?）是行业领先的软件应用，用于加强虚拟学习环境、补充课堂教学和提供远程教学平台。Blackboard教学管理平台拥有一套强大的核心功能，使教师可以有效的管理课程、制作内容、生成作业和加强协作，从而协助学校达到与教学、交流和评价有关的重要目标。这些关键的功能包括： 课程管理： 用于管理课程网站或者其主要组成部分。课程管理功能有效的创建和设置课程（课程创建向导，课程模板），同时提供学期间的课程转移工具（课程复制，课程循环使用）和文档工具（课程导入/导出，课程文档，课程备份）。 课程内容制作： 直观的文本编辑器提供丰富的文本编辑界面，包括WYSIWYG（所见即所得）和拼写检查，用来创建有效的学习内容。快速编辑功能使教师可以在学生课程内容界面和教师课程界面间迅速切换。教师还可以导入由外部制作工具生成的电子学习内容，如Macromedia Dreamweaver , Microsoft Frontpage, 或任何和SCORM配套的制作工具。 选择性内容发布： 教师可以根据课程内容和活动定制教学路径。内容项目、讨论、测验、作业或其他教学活动可以根据一系列的标准有选择的发布给学生。这些标准包括：日期/时间，用户名，用户组，机构角色，某一次考试或作业的成绩，或者该用户是否预习了下一内容单元。 课程大纲编辑器： 教师可以容易地创建课程大纲。他们可以上传已有的大纲，或者用内置的大纲制作功能设计和开发自己的课程大纲和课程计划。 学习单元： 教师可以创建有序的课程，控制学生是否必须根据该顺序学习所有的课程单元，或者允许学生从内容目录中选择单个的课程进行学习。学生可以保存他们在课程单元中的进度位置，以便以后从该位置继续。在线教材内容（出版商的课程包）： 所有全球大的教育出版商都开发了Blackboard适用的课程内容资料，以补充他们相应的课程教科书。课程内容包括多媒体资料、测试、题库和教材以外的附加资源的链接，比如交互式学习应用。课程包一旦下载到课程网站中，就可以进行用户化定制。 教学工具： 支持特定教学活动的多种工具，比如术语表（生成可分享可定制的词汇列表）；电子记事本（网络笔记本，学生在学习课程资料时可以在线记笔记）；教员信息（详细的联系信息和教员及助教的办公时间）。个人信息管理： 日历用来管理和浏览教师安排的课程事件和个人以及学院的事件。任务工具方便教师给学生（个人或小组）分配任务以及截止日期，并观察他们的完成进度。Blackboard短信用类似email的方式在课程内部通信，不必使用外部的email系统或地址。 讨论区： Blackboard教学系统（Blackboard Learning System?） 产品功能简述 2005-5-8 授课、交流和测验 Blackboard Learning System?是行业领先的软件应用，用于加强虚拟学习环境、补充课堂教学和提供远程教学的平台。Blackboard Learning System?拥有一套强大的核心功能，使教师可以有效的管理课程、制作内容、生成作业和加强协作，从而协助学校达到与授课、交流和测验有关的重要目标。这些关键的功能包括： 课程管理： 用于管理课程网站或者其主要组成部分。课程管理功能有效的创建和设置课程（课程创建向导，课程模板），同时提供学期间的课程转移工具（课程复制，课程循环使用）和文档工具（课程导入/导出，课程存档，课程备份）。 课程内容制作： 直观的文本编辑器提供丰富的文本编辑界面，包括WYSIWYG（所见即所得）和拼写检查，用来创建有效的学习内容。快速编辑功能使教师可以在学生课程内容界面和教师课程界面间迅速切换。教师还可以导入由外部制作工具生成的电子学习内容，如Macromedia? Dreamweaver ? ,Microsoft? Frontpage?, 或任何和SCORM 配套的制作工具。 选择性内容发布： 教师可以根据课程内容和活动定制教学路径。内容项目、讨论、测验、作业或其他教学活动可以根据一系列的标准有选择的发布给学生。这些标准包括：日期/时间，用户名，用户组，机构角色，某一次考试或作业的成绩，或者该用户是否预习了下一内容单元。 课程大纲编辑器： 教师可以容易地创建课程大纲。他们可以上传已有的大纲，或者用内置的大纲制作功能设计和开发自己的课程大纲和课程计划。 学习单元： 教师可以创建有序的课程，控制学生是否必须根据该顺序学习所有的课程单元，或者允许学生从内容目录中选择单个的课程进行学习。学生可以保存他们在课程单元中的进度位置，以便以后从该位置继续。 在线教材内容（出版商的课程包）： 所有全球大的教育出版商都开发了Blackboard适用的课程内容资料，以补充他们相应的课程教科书。课程内容包括多媒体资料、测试、题库和教材以外的附加资源的链接，比如交互式学习应用。课程包一旦下载到课程网站中，就可以进行用户化定制。 教学工具： 支持特定教学活动的多种工具，比如术语表（生成可分享可定制的词汇列表）；电子记事本（网络笔记本，学生在学习课程资料时可以在线记笔记）；教员信息（详细的联系信息和教员及助教的办公时间）。 个人信息管理： 日历用来管理和浏览教师安排的课程事件和个人以及学院的事件。任务工具方便教师给学生（个人或小组）分配任务以及截止日期，并观察他们的完成进度。Blackboard短信用类似email的方式在课程内部通信，不必使用外部的email 系统或地址。 讨论区： 讨论区支持多话题的异步讨论。教师可以围绕不同的主题设置多个论坛，并嵌入合适的内容区或课程中。教师可以决定学生是否能够修改、删除、匿名留言和粘 数字化校园建设方案预算 一、建设基础 学院在2006年完成校园网一期基础设施建设，目前已建成主干千兆、百兆到桌面技术先进、高速、稳定、安全的校园网络。网络核心采用万兆路由核心交换机，现有9台专业服务器，安装了教务管理软件、学生管理软件、图书管理等软件。实现了教务管理、学生管理、图书管理、财务资产管理等功能，校园网已覆盖整个校园。 二、建设目标 数字化校园主要建设目标：完善校园网基础设施建设，构建技术先进、扩展性强、安全可靠、高速畅通、覆盖全校的校园网络环境。建立公共信息系统基础平台，提供先进数字化管理手段，提高管理效率；建立功能齐全的教学管理平台；配合“工学结合”教学模式，建设内容丰富的教学资源库，实现教学资源共享；提高全校师生信息素养，为培养高技能应用性人才和服务社会搭建公共服务平台。 三、建设内容 （一）教学方面 1、教学管理及教学资源共享平台建设 采取购买与自行开发相结合的方式，在现有教务管理平台基础上，引进教学管理信息系统，实现教学数据统一管理，2008年底综合教学管理平台建立后，实现教学动态管理，教学管理信息数字化。建立教学资源共享平台，建设重点专业优质核心课程教学资源库，将 中央财政重点支持专业的优质核心课程的教学资源在网上公开，实现优质资源共享。2009年建成学生自主学习环境，实现网上授课、网上辅导、网上答疑、网上批改作业功能，为“工学结合”教学模式在学院实施提供技术保证。 2、数字化图书馆建设 根据学院“十一五”发展规划，继续加强电子图书、文献资源库建设，全面升级图书馆现有硬件设备。新建一个80座电子阅览室；增加馆藏电子图书60万册；增加电子期刊30万册。通过建设，把图书馆建成全省同类院校一流水平的数字化图书馆。 3、公共资源服务平台建设 在现有9个多媒体教室基础上，新增2间48座语音教室，同时改造升级现有计算机教室2间，满足学院现代化教学要求，保证新增或改建后的教室能够达到国内同类院校先进标准。 4、多媒体应用平台建设 学院现有电子阅览室和办公用计算机很难满足一些包括图形图像制作处理、计算机软件等专业教师制作多媒体课件需求，拟购置10台高配计算机设备，以满足学院教学用多媒体课件制作要求。通过引进先进精品课录播系统，实现精品课程录制、编辑全过程自动化处理。 5、数据资源共享平台建设 学院现有教学资源库还不够完善，容量仅为400G，远远满足不了在校生网上自主学习需要，拟通过对现有FTP服务器进行硬件升级 2010年第8期(下半月)软件导刊·教育技术 Blackboard 教学平台在《教学系统设计》 课程中的应用 王 辉 （西南大学西南民族教育与心理研究中心，重庆400715） 摘 要：鉴于Blackboard 网络教学平台在课程设计方面的优势，对《教学系统设计课程》通过该平台设计出高质 量的课程，能够促进学生对《教学系统设计》课程知识点的理解和掌握。阐述《教学系统设计》课程在Blackboard 网络教学平台的构建情况，以及构建教学系统设计课程网络教学平台的意义。 关键词：Blackboard ；教学平台；网络课程中图分类号：G434 文献标识码：A 文章编号：1672-7800（2010）08－0094－02 收稿日期:2010－06－17 作者简介:王辉（1985-），男，河南淮阳人，西南大学西南民族教育与心理研究中心硕士研究生，研究方向为新媒体与未来教育。 1Blackboard 网络教学平台简介 Blackboard 网络教学平台是由赛尔网络与美国毕博 （Blackboard ）公司共同开发的一种集声音、图像和文字于一体，专门用于加强虚拟学习环境、补充课堂教学并提供互动、交流的网络教学平台。它拥有一套强大的核心功能，是行业内领先的应用软件，可用于加强虚拟学习环境、补充课堂教学和提供远程教学的平台，使教师可以有效地管理课程、制作内容、生成作业和加强协作，从而协助学校达到与教学、交流和评价有关的重要目标。用户登录后可进入各自的控制面板界面，对自己所用的界面的功能模块进行配置。同时，教师和学生能够突破时间、地点的限制，通过控制面板对平台进行操作，教师也可以对平台内容进行组织管理。学生可以在线获取各种信息、学习资料，进行在线学习、考试等活动。目前我院投入使用的Black - board 平台主要包括5个主要的功能模块：①教学内容区模块。 它是教学平台的核心组成部分，主要供教师发布和管理教学资源以及作业的布置。包括课程信息、教学信息、课后作业、教学效果、课程特色、测试评价、政策支持和师生互动等内容。②课程工具模块。该模块为课程教学提供了多样化的工具，主要包括课程通知、课程日程表、职员信息、任务、发送电子邮件、讨论板、协作、数字收发箱、词汇表管理器、消息等。这些在线交流功能，可同时为用户提供讨论区的异步和虚拟教室的同步等交流工具，从而增强学习效果。③课程选项模块。主要用于管理课程网站或其主要组成部分，设置课程的显示界面、课程内容的重复使用以及课程资源的管理进行操作，主要包括管理课程菜单、课程设计、管理工具、循环使用课程、导入数据包、导出课程等。④用户管理模块。主要包括可对本课程的学生用户进 行注册或删除，并可设置学习小组以便进行小组讨论和其他类型的小组活动。包括列出/修改用户、注册用户、从课程中删除用户、管理小组等。⑤测试模块。主要由测试管理器、调查管理器、题库管理器、课程统计、成绩中心和成绩指示板组成，主要进行测试题库管理和成绩和数据统计管理。测验和调查主要用于教师开展在线的、自动评分的测验和调查。通过课程统计、成绩中心可以进行成绩和数据统计管理［1］。 2教学系统设计课程网络教学平台的构建 依据Blackboard 教学管理平台，对《教学系统设计》课程进 行系统设计，可以将该课程的教学资源不仅实施再生而且还可以进行延续使用也即是今年能使用，明年可以通过改进可以继续使用。该教学系统设计课程教授的对象是教育技术学专业的大三本科生。Blackboard 网络教学平台在教学中起到辅助学习的作用。在课程有限的情况下，教师可以通过Blackboard 平台进行课程设计，将每次课堂讲授的内容，教学电子材料（PPT 等课件）、课后作业、设计练习、期中考试、网上讨论等，对学习内容进行强化练习，最终能够根据学生的反馈和对学生的学习进行评价并对其进行综合分析，能够进一步对接下来的课程内容进行有针对性的设计。对于本课程，进行了教学内容设计、交互设计、课程管理设计以及评价设计。 对于Blackboard 网络平台为我们提供了14余种教学内容模块，本课程使用了其中的13种模块（图1）。 2.1教学内容设计 教学内容主要展示教师讲授的课程内容以及相关的辅助 教学材料。学生可以通过该Blackboard 网络教学平台在任何时候都能够进行自学、演练等。 资源建设 94 数字化教学资源建设方 案 Company number：【WTUT-WT88Y-W8BBGB-BWYTT-19998】 安徽金寨职业学校 机电技术应用专业 数字化教学资源库建设方案 一、成立教学资源与信息化建设领导小组，将专业教学目标、专业教学标准、专业优质核心课程体系、实验实训指导、学习评价等整合处理，通过校园网络等实现课程资源网络化、信息化，建立具有四个功能、三大服务的共享型教学资源库。 二、推行“模块教学”、“情境教学”、“仿真教学”等教学模式改革。优化创新教学内容，提高信息化教学水平，广泛采用多媒体辅助教学手段，推动专业应用软件在教学中的应用，建设优质教材和特色学习资料，建设跨越围墙、跨越课堂、跨越时间的新型数字化立体教学资源库，按照一体化教学、一体化评价的要求，整合相关教学资源建立电子教案库、实训案例库、教学录像、相关图片、实物模型、试题库等组成机电技术应用专业的教学资源库，将多媒体技术最大可能的植入专业教学活动之中，利用教学软件、教学课件、多媒体教学平台、试题库、课程录像等多种媒体形式组成的机电专业教学资源库系统。 三、依托数字化校园建设，以创建精品资源为核心，组织建设多媒体教学课件，多媒体教学素材（含辅助教学软件、课程录像），教学案例，电子教案及电子教材，学生自主学习资料汇编（含考证题库）等，建立信息共享和自主学习平台上的立体化教学资源库，实现全校师生的网络教学资源的共享与应用。2016年初步建立并校内开放，2017年基本完成并对社会有限开放。为学生提供一个性能稳定、功能强大的自主学习平台；促进主动式、协作式、研究型、自主型学习，形成开放、高效的新型教学模式。立体化教学资源库组成如下图所示： BB教学平台操作指南（学生版） 平台简介 Blackboard教学平台是国际领先的教学平台及服务提供商专门为教育机构开发研制的软件平台, 以“教学”、“联系”、“分享”为核心目标，提供一套综合、完整、优化的解决方案。Blackboard教学平台是以课程为中心集成网络“教”、“学”的网络教学环境。教师可以在平台上开设网络课程，学习者可以在教师的引导下，自主选择要学习的课程内容。不同学生之间，以及教师和学生之间可以根据“教和学”的需要进行讨论、交流。 开始使用 1、登录Blackboard教学平台 1）启动浏览器； 2）在地址栏处输入：https://www.doczj.com/doc/5317140203.html,/，然后按下键盘上的回车键Enter。出现教学平台首页 3）学生用户登录教学平台的用户名为本人学号，初始密码与用户名相同 4) 在用户名输入框输入用户名如2010XXXXXXXX。 5) 在密码输入框中输入密码； 6) 单击登录按钮。 初步了解教学平台 ——认识我的主页 登录Blackboard 教学平台后页面上部会有一系列的选项卡,点击不同的选项，可见不同的内容，了解一个选项卡下的内容，对您能够尽快使用该教学平台将有很大帮助。 1．我的主页 登录Blackboard 教学平台后，首先看到的应是默认的选项卡“我的主页”，在此选项卡下用户可以看到自己可用的工具，自己学习的课程，系统及相关课程最新的通知，以及系统提供的日程表及快速指南等模块 2．认识选项卡 是平台内划分不同区域的标识。位于 Blackboard 教学平台的左上方。作为学生用户可以看到的选项卡有：我的主页，课程、院系工具 ● 我的主页：汇集了教师用户所教授和参与的课程信息以及可以使用的一些工具。 ● 课程：汇集了我校Blackboard 教学平台现有的所有在线课程。 高校数字化校园建设方案一、数字化校园建设目标通过数字化校园项目建设，构造能够满足数字化校园应用长期持续发展的应用框架，通过这一稳定、可扩展的应用框架为应用系统建设提供良好的支撑和服务。该应用框架将充分支持于学校的应用需求和未来发展，同时考虑到系统的总体拥有成本，必须采用先进的理念和思路，辅以成熟的、主流的、符合未来发展趋势的技术, 运用现代系统工程和项目管理规范标准，科学合理的进行建设。 建成完整统一、技术先进，覆盖全面、应用深入，咼效稳定、安全可靠的数字化校园，消除信息孤岛和应用孤岛，建立校级统一信息系统，实现部门间流程通畅，可平滑过渡到新一代技术，对校园的各项服务管理工作和广大教职工提供无所不在的一站式服务。提高工作效率，提高管理效率，提高决策效率，提高信息利用率, 提高核心竞争力，总体水平达到国内一流，满足教学、科研和管理工作的需要。具体目标就是实现“六个数字化”和“一站式服务”：1、环境数字化构建结构合理、使用方便、高速稳定、安全保密的基础网络。在此基础上，建立咼标准的数据共享中心和统身份认证及授权中心（Ucenter泛学校，统一门户平台以及集成应用软件平台，为实现更科学合理的高校数字化环境打下坚实的基础。 2、管理数字化构建覆盖全校工作流程的、协同的管理信息体系，通过管理信息的同步与共享，畅通学校的信息流，实现管理的科学化、自动化、精细化，突出以人为本的理念，提高管理效率，降低管理成本。 3、教学数字化构建综合教学管理的数字化环境，科学统一的配置教学资源，提高教师、教室、实训室等教学资源的利用率, 改革教学模式、手段与方法，丰富教学资源，提高教学效率与质量。 4、产学研数字化构建数字化产学研信息平台，为产学研工作者提供快捷、全面、权威的信息资源，实现教学、科研和实训一 体化，提供开放、协同、高效的数字化产学研环境，促进知识的产生、传播与管理。 5、学习数字化构建先进实用的网络教学平台，整合、丰富数字 数字化校园应用平台建设方案 承担部门：网络中心 领导小组组长：夏连学 成员：张瑞春宋全有马战宝党海宽 吴运友徐普民 数字化校园应用平台建设是以网络平台和共享型教学资源管理服务平台建设及其功能开发为基础，在网络技术、多媒体技术上建立起来的对教学资源、科研信息、综合管理、技术服务、生活服务等校园信息的收集、处理、整合、存储、制作、传输和应用，使数字资源得到充分优化利用的一种数字化虚拟教育环境。通过实现从环境（包括设备、教室等）、资源（如图书、讲义、课件等）到应用（包括教、学、管理、服务、办公等）的全部数字化，在传统校园基础上构建一个数字空间，以拓展现实校园的时间和空间维度，提升传统校园的运行效率，扩展传统校园的业务功能，最终实现教育过程的全面信息化，从而达到提高教学管理水平和效率的目的。 数字化校园应用平台建设包括：校园网络基础平台建设、共享型教学资源管理服务平台建设两个部分。 一、校园网络基础平台建设方案 （一）建设内容 校园网络基础平台分为“网络基础”、“网络中心机房系统”两个模块，建设内容及经费来源见表1。 表1 建设内容及经费来源 1、网络基础建设：在学院现有千兆以太网、主干网速率1000兆、桌面终 端100兆的基础上，提高校园网基础设施水平，构建万兆（10G）带宽的主干网络，做到技术先进、应用广泛、性能稳定；构建安全系统，形成一个包括认证、监测、追踪、加密、记录、路由管理、防火墙在内的安全管理系统，建设一个安全可靠的局域网。完成学生宿舍楼的光纤、双绞线等线路的布线以及交换机、学生宿舍分中心机房设备的安装和调试工作；艺术中心、图书馆、广场等公共场所采用有线网和无线网相结合，覆盖校园的每个角落。 逐步建立和完善校园网络安全体系，完善校园网络管理系统，升级校园网交换机，确保校园网中的所有交换机均能支持网络管理，支持802.1x身份认证。保证可以向第二代互联网平滑过渡。 2、网络中心机房系统：为提高校园网络的可靠性，对我院网络中心机房设备进行改造，主干采用交换机2台冗余，有条件的情况下，采用3台设备组成环状冗余网络。 依据学院建筑布局，对机房环境、供电系统、光纤连接、机柜及布线系统进行改造。使中心机房具有独立的UPS配电室，具备恒温、防静电、防雷功能。 拟购代表性仪器设备建设经费预算见表2。 表2 拟购代表性仪器设备建设经费预算 校园网络基础平台建设项目进度见表3 第一部分：平台使用说明 (2) （一）平台简介 (2) （二）适用对象 (2) （三）教师需做的准备工作（必要操作） (2) （四）教师使用BB 平台流程图 (3) 第二部分：平台入门操作 (4) （一）平台入口与登陆平台（必要操作） (4) （二）认识平台 (4) （三）修改密码（可选操作） (5) （四）定制个人首页界面（可选操作） (6) （五）进入教授的课程（必要操作） (7) 第三部分：课程建设 (8) （一）课程结构设计（必要操作） (8) （二）添加课程内容（必要操作） (10) ●教学大纲（必要操作） (10) ●授课讲义（必要操作） (11) ●网络课件（可选操作） (11) ●精品课程网站（可选操作） (11) ●课外补充材料（可选操作） (11) ●随堂测验（可选操作） (11) ●课后作业（必要操作） (14) （三）课程存档和导入以及循环使用（有重复班的必要操作） (15) ●课程存档 (16) ●在新课程中导入课程文档 (16) ●课程循环 (17) 第四部分：互动教学 (18) （一）更新教师信息（必要操作） (18) （二）课程通知（必要操作） (19) （三）课程讨论板（可选操作） (20) （四）设定助教（可选操作） (23) （五）管理学习小组（可选操作） (24) 第五部分：学习跟踪与教学评价 (25) （一）学习跟踪；（必要操作） (25) （二）作业批改；（必要操作） (26) （三）试卷批改；（可选操作） (31) （四）教学评价；（可选操作） (32) 第六部分：常见问题及如何获得帮助 (34) （一）温馨提示 (34) （二）常见问题 (34) （三）如何获得帮助 (36)Blackboard平台在网络课程中的应用研究
数字化教学解决方案
Blackboard平台功能简介
Blackboard在线教学管理系统
Blackboard网络学习平台在课堂教学中的设计
数字化网络平台
Blackboard教学平台使用手册(学生版V1.0)
数字化资源平台建设
Blackboard网络教学平台介绍
Blackboard教学系统
数字化校园建设方案预算
Blackboard教学平台在_教学系统设计_课程中的应用
数字化教学资源建设方案
BB教学平台操作指南(学生用户版)
高校数字化校园建设方案
数字化校园应用平台建设方案
blackboard操作指南
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