Energy transfer processes in Er3+-doped and Er3+,Pr3+-codoped ZBLAN glasses
Energy transfer processes in Er3?-doped and Er3?,Pr3?-codoped ZBLAN glasses
P.S.Golding,S.D.Jackson,T.A.King,and M.Pollnau*
Laser Photonics Group,Schuster Laboratory,Department of Physics and Astronomy,University of Manchester,
Manchester M139PL,United Kingdom
?Received26October1999;revised manuscript received10February2000?
We present a detailed characterization of energy transfer processes in Er3?-doped and Er3?,Pr3?-codoped
ZBLAN bulk glasses.For several Er3??0.25–8.75mol%?and Pr3??0.25–1.55mol%?concentrations,we
investigate energy transfer upconversion?ETU?and cross relaxation in Er3?as well as energy transfer?ET?
from Er3?to the Pr3?codopant.The measured parameters of ETU from the Er3?4I13/2and4I11/2levels are
comparable to those of LiYF4:Er3?.ETU from4I13/2,in particular,possesses a factor of3larger probability
than ETU from4I11/2.The parameters of ET from the Er3?4I13/2and4I11/2levels to the Pr3?codopant are
larger than the corresponding ETU parameters.ET effectively quenches the4I13/2intrinsic lifetime of9ms
down to20?s for the highest Er3?and Pr3?concentrations investigated,and is more ef?cient than ET from
4I
11/2
,because the corresponding absorption transition in Pr3?has a large oscillator strength and back transfer is inhibited by fast multiphonon relaxation from the corresponding Pr3?level.In both cases,the ET parameters
depend on Er3?concentration in a similar way as the ETU parameters but depend only weakly on Pr3?
concentration.This shows that energy migration within the Er3?4I13/2and4I11/2levels is fast.The presented
results are important for the choice of the appropriate operational regime of the erbium3-?m?ber laser.
I.INTRODUCTION
After the?rst successful descriptions of energy transfer
processes by Fo¨rster1and Dexter,2strong interest in the spec-
troscopic investigation of these processes has proceeded.
One possible manifestation of an energy transfer process is
the occurrence of visible luminescence from a sample after
infrared excitation and the subsequent energy transfer upcon-
version?ETU?to the emitting state.3–5The in?uences of en-
ergy transfer processes affect the performance of many rare-
earth-doped solid-state lasers.For instance,these processes
can be a source of loss if originating in the upper laser
level.6,7However,these processes can be bene?cial,e.g.,for
sensitizing the lasing ion by energy transfer?ET?from a
codopant,8,9for quenching the lower laser level by ET to a
codopant,10,11or for ETU of the pump excitation to a high-
lying upper laser level.12,13A quantitative understanding of
the relevant energy transfer processes is,therefore,required
for optimizing the corresponding laser system.
The erbium3-?m laser which is of interest for medical
applications14–16is based on a simple four-level laser
scheme,see Fig.1.Since the4I13/2lower laser level is meta-
stable,however,signi?cant excitation is accumulated in this
level and,due to the CW threshold condition,also in the
4I
11/2upper laser level.Owing to the equal energetic spacing
of several multiplet-to-multiplet transitions,energy transfer processes occur from these levels.An important process is ETU from4I13/2,which recycles energy from the lower to the upper laser level.Based on this process,the3-?m crystal laser is operated CW even for unfavorable lifetime ratios of the laser levels17and output powers exceeding1W have been obtained.18,19Energy recycling by way of ETU from the4I13/2level enhances the limit of the slope ef?ciency to twice the Stokes ef?ciency.20,21On the other hand,lifetime quenching of the lower laser level by ET to a codopant ion such as Pr3??see Fig.1?limits the slope ef?ciency10to val-ues below the Stokes limit.
ZBLAN glass?ber also serves as a useful host for Er3?ions for an ef?cient3-?m laser,providing,as a result of its geometry,a high-brightness laser beam and greatly reduced thermal effects.The operation of the Er3?-doped ZBLAN ?ber laser is often limited,however,by ground-state bleach-ing with the consequence of undesired excited-state absorp-tion?ESA?from the4I13/2and4I11/2laser levels.22–24Under intense pumping,ESA can be exploited in cascade-lasing regimes,25,26but under pump excitation with
low-brightness
FIG. 1.Partial energy level diagram of Er3?and Pr3?in ZBLAN glass indicating the simple four-level scheme of the erbium 3-?m laser?left-hand side?,ETU and CR processes from the Er3?4I13/2,4I11/2,and4S3/2/2H11/2levels,as well as ET processes from Er3?to Pr3?.
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diode lasers the limitation can only be overcome by either of two different operational regimes:quenching of the4I13/2 lifetime by ET to a Pr3?codopant or energy recycling from
4I
13/2by ETU?Fig.1?.The former regime has recently been
shown to be applicable27and output powers at3?m ap-proaching1W?Ref.28?or even2W?Ref.29?have been achieved in double-clad geometries.30Lasers based on singly erbium-doped ZBLAN?bers and bulk glasses have also been demonstrated.31,32It has been an open question in which of these two regimes the?ber laser can be operated more ef?ciently.
In order to prepare the spectroscopic ground for an an-swer to this question,we have measured the intrinsic life-times of the Er3?4I13/2,4I11/2and4S3/2/2H11/2levels and investigated the major energy transfer processes such as ETU from the Er3?4I13/2and4I11/2laser levels,ET from these levels to the corresponding levels of a Pr3?codopant,and cross relaxation?CR?from the thermally-coupled
Er3?4S3/2/2H11/2levels.The macroscopic energy transfer parameters of all these processes are derived and their de-pendence on Er3?and Pr3?concentrations is investigated. Consequences for the choice of the appropriate operational regime of the erbium3-?m?ber laser are established.
II.EXPERIMENT
Lifetimes as well as the parameters of ETU,CR,and ET for Er3?-doped and Er3?,Pr3?-codoped in ZBLAN bulk glasses?Le Verre Fluore′,France?were determined by mea-suring luminescence decay from the4I13/2,4I11/2levels and the thermally coupled4S3/2/2H11/2levels to the4I15/2ground state following direct excitation of these levels at532,979, and1510nm,respectively.The samples studied in this in-vestigation comprised of four Er3?-doped samples of con-centrations0.25,1.25,5,and8.75mol%,and six Er3?, Pr3?-codoped samples:Er3?8.75mol%,Pr3?0.25,0.5,and 1.25mol%,and Er3?5mol%,Pr3?0.25,0.5,and1.55mol% (1mol%?1.6?1020cm?3?.Each sample had dimensions of 10?10?5mm3and was polished on all faces.
The excitation source for the spectroscopic measurements was an in-house KTP optical parametric oscillator?OPO?pumped by a frequency-doubled,10Hz,Q-switched laser ?Spectron SL802G?at532nm.The OPO consisted of a two-crystal,walk-off-compensated cavity33?see Fig.2?.A signal tuning range of770to980nm with the associated idler wavelength of1700to1160nm was attainable.Two mirror sets were used;one that was highly transmitting at the idler wavelength of1500nm and highly re?ecting at the signal wavelength of824nm,and a second with a high transmis-sion at980nm and a high re?ection at1160nm.This source provided pump light which was tunable across the absorption regions of the4I13/2and4I11/2levels,with maximum output energies of1mJ and a pulse length of approximately6ns that allowed each level to be excited in a time scale signi?-cantly shorter than its lifetime.Furthermore,since each level could be directly excited,it was possible to determine life-times systematically allowing a simple and accurate method for determining the temporally-resolved spectroscopic char-acteristics of each sample.Since the bandwidth of the OPO was approximately5nm,the majority of the inhomogeneous bandwidth was excited and hence the emission from most Er3?sites was measured.
To excite the4I13/2level,a center wavelength of the pump of1510nm was selected.For the4I11/2level a center wavelength of the pump of979nm was used,because ground-state absorption?GSA?was suf?ciently high,but ESA was signi?cantly less than GSA due to the relatively small excitation density and the small ESA cross-section at this wavelength.23The lifetime of the thermally coupled 4S
3/2
/2H11/2levels was measured after direct excitation by the second harmonic of the Q-switched Nd:YAG laser at532 nm.
The pump beam was focused by an8-cm lens and sent through a200-?m pinhole to give a known excitation vol-ume with a relatively homogeneously excited cross section and directed through the sample close to one of its surfaces, see Fig.2.Luminescence was then detected from the surface closest to the excitation path to ensure that reabsorption ef-fects did not affect the decay-time data.The luminescence from the samples was imaged onto the entrance slit of a30 cm monochromater,and the resulting signal was detected using a InGaAs photodiode?Hamamatsu G5746-01?to de-tect the4I13/2luminescence at1560nm and a silicon photo-diode?IPL10530DAL?to detect the1010nm(4I11/2)and 550nm(4S3/2)luminescences.The overall bandwidth of the detected luminescence was measured to be approximately4 nm.Signals were averaged over512shots with use of a Hewlett-Packard54522A digital storage oscilloscope.Decay curves were measured for different pump energies incident on the crystal surface,and the transmitted pump energies were recorded.
III.RESULTS
A.Cross relaxation in Er3?-doped ZBLAN
We?rst investigate the luminescent decay from the 4S
3/2
/2H11/2levels,because the result is important for the determination of the parameter of the ETU process from the 4I
11/2
level?see later?.The4S3/2level is in thermal equilib-rium with the2H11/2level,therefore,after excitation,the population relaxes to the Boltzmann distribution within the two levels.At high Er3?concentrations,the luminescent
life-FIG. 2.Experimental setup for the measurement of the temporally-and spectroscopically-resolved luminescence from the ZBLAN:Er3?and ZBLAN:Er3?:Pr3?glass samples.
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time of these levels is shortened as a result of the CR pro-cesses (2H 11/2,4I 15/2)→(4I 9/2,4I 13/2)and (2H 11/2,4I 15/2)→(413/2,4I 9/2).The effect of the Er 3?concentration upon the luminescent lifetime of the 4S 3/2/2H 11/2levels is shown in Fig.3.The observed luminescence from the 4S 3/2/2H 11/2levels shows a dramatic reduction in lifetime with a value of 518?6?s for an Er 3?concentration of 0.25mol%(4?1019cm ?3?falling to 21?1?s for an Er 3?concentration of 8.75mol%(1.4?1021cm ?3?.Extrapolation of the curve toward zero Er 3?concentration provides an intrinsic lifetime of 586?s,in good agreement with Ref.34which states a lifetime of 570?s.
The rate of the CR process,R CR ,can be described by
R CR ?W CR N ?4S 3/2?N ?4I 15/2?,
?1?
where W CR is the macroscopic CR parameter,N (4S 3/2)is the population density of the 4S 3/2/2H 11/2levels,and N (4I 15/2)is the population density of the 4I 15/2ground state.In our ex-periment,the ground-state bleaching and excitation of the 4
S 3/2/2H 11/2levels is small.It follows that the ground-state population density can be approximated by the Er 3?concen-tration N ?Er ?in the sample,the rate R CR increases linearly with pump power and excitation in the 4S 3/2/2H 11/2levels,and the resulting effective luminescent lifetime ?eff (4S 3/2)can be described as follows:
1/?eff ?4S 3/2??1/??4S 3/2??W CR N ?Er ?,
?2?
where ?(4S 3/2)is the intrinsic lifetime of the 4S 3/2/2H 11/2levels.The CR parameters determined from the measured lifetime quenching are given in Table I and Fig.4.
B.Energy transfer upconversion in Er 3?-doped ZBLAN
The luminescent decay measured from the 4I 11/2and 4
I 13/2levels of Er 3?can be considered as being composed of two separate parts.As can be seen in Fig.5?a ?,a fast nonex-ponential section is observed at the beginning of the decay that contains a strong contribution from fast ion–ion interac-tions.For a given sample,the magnitude of the ETU-induced part of the decay increases with increasing initial excitation density N 0of the corresponding excited level.This fast de-cay is followed by a slower exponential decay that results solely from the intrinsic decay rate of the level ?i.e.,the decay rate of an isolated ion ?and is independent of the initial pump excitation.To determine the lifetime of the excited levels a linear ?t is applied to the last portion of the ln(I /I 0)graph,with care taken not to include the part of the decay that involves ion–ion interaction.
Figure 3shows the measured luminescent lifetimes of the 4
I 13/2and 4I 11/2levels.The 4I 11/2level has a shorter lifetime than the 4I 13/2level,commensurate with a previous investigation.34For the lowest doped samples,lifetimes of 6.9?0.1ms and 9.0?0.2ms,respectively,were measured.On increasing the Er 3?concentration,the 4I 11/2lifetime is seen to increase and the 4I 13/2lifetime to decrease.Other authors studying Er 3?-doped ?uorozirconate glass have ob-served small ?uctuations in these lifetimes over a concentra-tion range of 0.8to 18mol%.35This variation may be caused by a slight change in the maximum phonon energies with glass composition,which will affect the multiphonon decay rates,or an energy transfer process to the host material.
36
FIG. 3.Intrinsic lifetimes of the 4I 13/2?squares ?and 4I 11/2?circles ?levels as well as the effective lifetime of the 4S 3/2/2H 11/2levels ?triangles ?in ZBLAN:Er 3?for different Er 3?concentrations.
TABLE I.Values of the measured ETU,CR,and ET parameters (10?17cm 3s ?1)for the different inves-tigated Er 3?and Pr 3?concentrations (1020cm ?3).
Er 3?conc.Pr 3?conc.
ETU 4I 13/2
ETU 4I 11/2
CR 4S 3/2ET 4I 13/2
ET 4I 11/2
0.400.620 1.30.20.68
0 2.8
1.0
2.4
0.49.00.90.810.6 1.02.513.2
1.0
14
0 6.7
1.9
3.3
0.416.8 2.10.817.2 2.02.0
20.5
2.2FIG.4.Macroscopic parameters ?solid symbols ?of ETU from Er 3?4
I 13/2and 4I 11/2as well as CR from Er 3?4S 3/2/2H 11/2vs.Er 3?concentration.Also shown are the macroscopic parameters ?open symbols ?of ET from Er 3?4I 13/2and 4I 11/2to the Pr 3?codopant for a Pr 3?concentration of 8?1019cm ?3.
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ETU parameters were calculated according to a previ-ously published method,37as follows.If N represents the time-dependent population density of the excited 4I 13/2level,then the rate equation for N is given by
dN dt ??N
?
?2W ETU N 2,?3?
where ?is its intrinsic lifetime,and W ETU is the macroscopic
ETU parameter relating to the process (4I 13/2,4I 13/2)→(4I 15/2,4I 9/2).With N (t ?0)?N 0,integration yields 38
N ?t ??
N 0exp ??t /??
1?2W ETU N 0??1?exp ??t /???
,
?4?
or
?N 0/N ?t ??exp ??t /???1?2W ETU N 0??1?exp ??t /???.
?5?
A plot of ?N 0/N (t )?exp(?t /?)?1vs.?1?exp(?t /?)?will,therefore,give a gradient of 2W ETU N 0?.This is only correct as long as the decay can be described by Eq.?3?,i.e.,in the ?rst temporal part of the decay when only the directly-pumped level is signi?cantly excited and processes involving other excited levels,especially those processes which re-populate the level under investigation,are negligible.After a
certain time,the curves plotted in this way will deviate from the linear behavior according to Eq.?5?because of the in-creasing in?uence of those processes.By using only the data in the ?rst temporal part of the decay we can avoid this complication.37If we considered the complete decay curve,a more complex rate–equation system of ZBLAN:Er 3?with a corresponding number of parameters,parameter values,and error margins would have to be taken into account.Most notably,the evaluation of a transfer parameter would depend on the other transfer parameters,which are themselves sub-ject to the investigation.Such a method would be less precise than the one chosen here.
A plot of the data of Fig.5?a ?in a ?N 0/N (t )?exp(?t /?)?1vs.?1?exp(?t /?)?representation for different pump en-ergies,in this case for the decay from the 4I 13/2level in ZBLAN:8.75mol%Er 3?,is shown in Fig.5?b ?,where N 0/N (t )is the luminescence signal at the beginning of the decay ratioed to the signal at time t ,and ?is taken to be the lifetime of the lowest doped sample.A straight-line ?t to the initial linear part of the resulting graph gives a gradient equal to 2W ETU N 0?.N 0is calculated by knowing the absorbed photon density,i.e.,the energy absorbed within a pulse,the excited volume determined by the pinhole and the thickness of the sample,and the pump–photon energy.
ETU from the 4I 13/2level populates the 4I 9/2level from where most of the excitation decays by fast multiphonon relaxation to the metastable 4I 11/2level.Repopulation of the 4
I 13/2level from 4I 11/2occurs at a time scale which is large compared to the time scale used for extracting the ETU pa-rameters;see Fig.5?a ?.Direct back transfer from the 4I 9/2level by the CR process (4I 9/2,4I 15/2)→(4I 13/2,4I 13/2)has a relatively small in?uence because of the relatively short life-time of the 4I 9/2level ?calculated from Ref.36to be ?20?s ?as a result of relatively fast nonradiative relaxation from this level to the 4I 11/2level.Investigations in LiYF 4:Er 3?have established 37that the direct back transfer changes the parameter of ETU from 4I 13/2by less than 10%for the dop-ant concentrations of interest in the present article.This de-viation is in the order of the error margin of the ETU param-eter and is,therefore,neglected in our evaluation.The parameters of ETU from 4I 13/2are,therefore,derived from Fig.5?b ?by assuming a slope of 2W ETU N 0?,as suggested by Eq.?5?.
The situation is different for the luminescent decay curve and ETU process,(4I 11/2,4I 11/2)→(4I 15/2,4F 7/2),from the 4
I 11/2level.ETU from this level populates the 4F 7/2level from where the excitation relaxes by fast multiphonon decay to the 4S 3/2/2H 11/2levels.At a low dopant concentration,these levels decay mostly radiatively to the 4I 15/2and 4I 13/2levels,i.e.,there is no signi?cant back transfer to 4I 11/2within the time scale relevant for the determination of the parameter of ETU from 4I 11/2.At a higher dopant concen-tration,however,CR from the 4S 3/2/2H 11/2levels discussed above,leads to a fast back transfer into the 4I 9/2level and further into the 4I 11/2level by multiphonon relaxation.If the effective lifetime of the 4S 3/2/2H 11/2levels is short,most of the upconverted excitation is transferred back to 4I 11/2within the relevant time scale.The result is that only one excitation is removed from the 4I 11/2level by each ETU process and the factor of 2in Eq.?3?reduces to a factor of 1.For inter-mediate dopant concentrations,CR and luminescent
decay
FIG.5.?a ?Example of the measured ?and normalized ?lum-inescence-decay characteristic from the Er 3?4I 13/2level at a wave-length of 1560nm in ZBLAN:8.75mol%Er 3?for different exci-tation densities.Indicated are the portions of the measured lumines-cence characteristic that were used for the determination of the ETU parameters and the intrinsic lifetimes.?b ?Linearization of the decay curves of ?a ?with respect to the ETU parameters W .Indicated are the slopes that lead to the determination of the ETU parameters.This method is taken from Ref.37.N 0is the initial excitation den-sity at t ?0ms.
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ENERGY TRANSFER PROCESSES IN Er 3?-DOPED AND ...
compete for the depletion of the4S3/2/2H11/2levels.We can de?ne a branching ratio,?,for the part that decays by CR,
??
W CR N?4S3/2?N?Er?
N?4S3/2?/??4S3/2??W CR N?4S3/2?N?Er?
?1??eff?4S3/2?
??4S3/2?.?6?
It follows that Eq.?3?changes to
dN?4I11/2?
dt ??
N?4I11/2?
??4I11/2???2???W ETU N2?4I11/2?.?7?
The initial slope which is derived from Eq.?5?and indicated in Fig.5?b?then reduces to?1??eff(4S3/2)/?(4S3/2)?W ETU N0?.The parameters of ETU from the4I11/2
level are evaluated from the data of Fig.5?b?by assuming this slope and using the effective lifetimes of the
4S
3/2/2H11/2levels of Fig.3and the intrinsic lifetime of586
?s.
Equation?7?holds true for1/?eff(4S3/2)?1/?(4I11/2)?W ETU N2(4I11/2),i.e.,for situations where the back transfer is immediate with respect to the depletion of the4I11/2level. This is the case for the highly Er3?-doped samples investi-gated.For the lowest dopant concentration for which ETU is investigated,this approximation is not valid,but since for this concentration?eff(4S3/2)approaches?(4S3/2),it follows that?vanishes and Eq.?7?reduces to Eq.?3?.
Without considering back transfer the derived ETU pa-rameter would be correct only for a low dopant concentra-tion,but would be a factor of2too small for a high dopant https://www.wendangku.net/doc/3b8018795.html,ing the parameters of ZBLAN:Er3?and a
prede?ned ETU parameter,we have solved an extended rate–equation system?see,e.g.,Ref.27?numerically and generated luminescent decay curves with and without con-sidering the in?uence of back transfer by CR.This method con?rmed that the consideration of back transfer as in Eqs.?6?and?7?leads to a much higher precision in the evaluation of the parameter of ETU from4I11/2.
The ETU parameters for the4I11/2and4I13/2levels cal-culated in the different ways described above are given in Table I and Fig.4for several Er3?concentrations.It can be seen that the probability of ETU from the4I13/2level is higher by approximately a factor of3times that of the4I11/2 level.The ETU parameters increase with increasing Er3?concentration.
C.Energy transfer in Er3?,Pr3?-codoped ZBLAN
The luminescent decay curves after excitation with the OPO source for the Er3?,Pr3?-codoped samples were ob-tained in a similar manner to the Er3?-doped samples.Figure 6?a?shows the in?uence of the Pr3?codopant on the Er3?4I13/2and4I11/2lifetimes.A signi?cant reduction in the lifetime of the4I13/2level is observed following the addition of a small amount of Pr3?,while the lifetime of4I11/2level is affected to a lesser degree.
Using the same analysis as for the4S3/2/2H11/2lumines-cent decay described above,a rate for the ET process,R ET, can be described by
R ET?W ET N?Er*?N?3H4?,?8?where W ET is the macroscopic ET parameter,N(Er*),is the excited-state population density of a given Er3?level,and N(3H4)is the population density of the3H4ground state of Pr3?.Assuming negligible excitation of the Pr3?ions,the resulting luminescent decay from the Er3?levels can be de-scribed as follows:
1/?eff?Er*??1/??Er*??W ET N?Pr?,?9?where?eff(Er*)is the effective lifetime of the excited level of Er3?in which ET is observed,?(Er*)is the intrinsic lifetime of the same level,and N?Pr?is the Pr3?concentra-tion in the https://www.wendangku.net/doc/3b8018795.html,ing Eq.?9?,the ET parameters W ET have been calculated for the samples under investigation,see Table I and Fig.6?b?.The degree of ET to Pr3?is found to be much higher for the4I13/2than for the4I11/2level of Er3?.
IV.DISCUSSION
A.Relative strengths of transfer parameters
We?rst compare the strengths of the investigated ETU, CR,and ET parameters relative to each other in a simpli?ed model.For the most common energy transfer mechanism of electric-dipole–electric-dipole interaction,the values for the transfer parameters are proportional to the product of the oscillator strengths of the corresponding emission and
ab-FIG.6.?a?Measured lifetimes and?b?macroscopic parameters of ET from the Er3?4I13/2and4I11/2levels to the Pr3?codopant,as a function of Pr3?concentration and for two different Er3?concen-trations.
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sorption transitions.2,4Table II lists the oscillator strengths for the Er 3?and Pr 3?transitions 39that are relevant for the transfer processes investigated experimentally in Secs.II and III.
For the ETU process (4I 13/2,4I 13/2)→(4I 15/2,4I 9/2),the product of the oscillator strengths (4I 15/2?4I 13/2)?(4I 13/2?4I 9/2)of Table II is 4500?1016,which is higher than the product of 1963?1016for the ETU process (4I 11/2,4I 11/2)→(4I 15/2,4F 7/2),in qualitative agreement with the experimental results for the ETU parameters W of Fig.4.The ET process (4I 13/2,3H 4)→(4I 15/2,3F 3)is larger than the ET process (4I 11/2,3H 4)→(4I 15/2,1G 4),because the oscillator-strength product (4I 15/2?4I 13/2)?(3H 4?3F 3)of 84000?1016is signi?cantly larger than the product (4I 15/2?4I 11/2)?(3H 4?1G 4)of 924?1016.The same result is found experimentally when comparing the ET parameters of Table I or Fig.6?b ?.This explains the large difference in the lifetime quenching of the Er 3?4I 13/2and 4I 11/2levels by the Pr 3?codopant ?Fig.6?a ??.
For the calculation of the oscillator-strength product of the CR processes (2H 11/2,4I 15/2)→(4I 9/2,4I 13/2)and (2H 11/2,4I 15/2)→(4I 13/2,4I 9/2),the following considerations are made.First,the product is the sum of the oscillator-strength products of the two individual processes.Second,the Stark components of the 2H 11/2level have a combined room-temperature Boltzmann population of typically 10%of the thermally coupled 4S 3/2/2H 11/2levels.Third,also CR from 4S 3/2may occur.Since this process requires the absorp-tion of one phonon,i.e.,it is an energetically-endothermic process,its probability is typically an order-of-magnitude smaller 4than for a process with a direct spectral overlap of its emission and absorption lines or an exothermic process which leads to the emission of one phonon.In this way,we ?nd with the data of Table II that the overall CR process has a combined oscillator-strength product of 2133?1016.
In Table III,the relative strengths of the ?ve investigated ETU,CR,and ET parameters are compared to each other with respect to their experimental values ?W parameters of Table I ?and the above oscillator-strength products ?obtained from the data of Table II ?.Experimentally as well as in the
simpli?ed model,transfer processes from the Er 3?4I 13/2level are the strongest processes whereas processes originat-ing in the Er 3?4I 11/2level are relatively weak.
We ?nd,however,that there is not a total qualitative agreement between the experimental data and the simpli?ed model concerning the ordering of the process strengths.The ETU and ET processes from 4I 11/2do not have the same ordering in the experiment and the model.This may be due to the fact that the value of the 4I 11/2?4F 7/2transition is different from the assumption made in Table II.Another pos-sible reason might be that,in addition to the dependence on their oscillator-strength products,the transfer parameters also depend on the overlap integral of the corresponding absorp-tion and emission lines.2However,the in?uence of the inte-gral seems to be rather weak,because the possible assistance of phonons may smoothen the overlap.4
In general,the comparison in Table III shows that the product of the oscillator strengths of the emission and ab-sorption transitions involved in an energy transfer process gives a reasonable indication of its strength which is ex-pressed by its macroscopic transfer parameter W .
https://www.wendangku.net/doc/3b8018795.html,parison with LiYF 4:Er 3?
Recently,the same method as applied here was used to measure the parameters of ETU from the Er 3?4I 13/2and 4
I 11/2levels in LiYF 4?Ref.37?for different dopant concen-trations of 5,10,15,20,30,and 32at.%,and curves were ?tted to derive equations for the concentration dependence of the ETU parameters.We compare here the values of these ETU parameters in LiYF 4and ZBLAN for an Er 3?concen-tration of 8?1020cm ?3(?5.8at.%in LiYF 4or 5mol%in ZBLAN ?.Since the rate–equation sets used in the two pub-lications are slightly different from each other,the data for the ETU parameters ?of Ref.37have to be divided by two to compare to our W parameters.
In general,it is found that the values of the ETU param-eters are of the same order-of-magnitude in LiYF 4and ZBLAN.In particular,for ETU from 4I 13/2,the data of Ref.37provide a value of W ETU ?1.7?10?17cm 3/s in LiYF 4,which is approximately half of the value of W ETU ?2.8?10?17cm 3/s in ZBLAN ?Table I ?.For ETU from 4I 11/2,the situation is reversed.In LiYF 4a value of W ETU ?1.6?10?17cm 3/s is derived,whereas the value in ZBLAN,W ETU ?1.0?10?17cm 3/s ?Table I ?,is almost a factor of 2smaller.
For the operation of the Er 3?3-?m laser ?Fig.1?,the above comparison provides the following result:At the Er 3?
TABLE II.Oscillator strengths ?108?for electric–dipole transi-tions of Er 3?and Pr 3?from Ref.39.The value of the 4I 11/2?4F 7/2transition which is denoted by an asterisk is not given in Ref.39.From a comparison with LiYF 4?Ref.40?,it is assumed here to have the same values as the 4I 15/2?4I 11/2transition.
Ion Transition YLF Oscillator Strength
Er 3?
4
I 15/2?4I 13/2135.81004
I 15/2?4I 11/2126.7444
I 15/2?4I 9/254.3334
I 13/2?4I 9/248.5454
I 13/2?4S 3/2474.2424
I 13/2?2H 11/258.2304
I 11/2?4F 7/2129.644*4
I 9/2?4S 3/252.1344
I 9/2?2H 11/243.8
95Pr 3?
3
H 4?3F 38403
H 4?1G 4
21
TABLE III.Relative strengths of the ETU,CR,and ET param-eters ?decreasing from top to bottom ?.Left-hand side:ordering of the W parameters of Table I;right-hand side:ordering of the oscillator-strength products obtained from the data of Table II.
No.
Measured Calculated 1ET from 4I 13/2ET from 4I 13/22ETU from 4I 13/2ETU from 4I 13/23CR from 4S 3/2/2H 11/2
CR from 4S 3/2/2H 11/2
4ET from 4I 11/2ETU from 4I 11/25
ETU from 4I 11/2
ET from 4I 11/2
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ENERGY TRANSFER PROCESSES IN Er 3?-DOPED AND ...
concentrations investigated here,the ratio of the probabilities of ETU from the4I13/2lower laser level,which recycles energy to the4I11/2upper laser level,vs.ETU from the4I11/2 upper laser level,which depletes inversion,is more favorable for ZBLAN compared to LiYF4.The highest slope ef?ciency of the laser system is obtained at the Er3?concentration at which the ratio of the probabilities of these ETU processes is largest.20This optimum Er3?concentration is probably smaller in ZBLAN than the optimum concentration of2?1021cm?3(?15at.%)in LiYF4?Refs.18,37?.
C.Concentration dependence
The parameters of ETU and ET from the4I13/2and4I11/2 levels as well as CR from the4S3/2/2H11/2levels increase with increasing Er3?concentration.The slopes in double-logarithmic representation are close to linear in all the?ve cases?Fig.4?.In contrast,the parameters of ET from the Er3?4I13/2and4I11/2levels to the Pr3?codopant are almost insensitive to Pr3?concentration?Fig.6?b??,i.e.,the param-eters of the ET processes depend linearly on donor concen-tration but are almost independent of acceptor concentration. If the same dependence on donor and acceptor concentra-tions that is found for the ET processes holds true for Er3?–Er3?transfer processes such as ETU and CR,then the experimentally-observed linear dependence of these pro-cesses on Er3?concentration?Fig.4?is indeed expected, because Er3?acts simultaneously as donor and acceptor in these cases.Thus,all the investigated transfer processes ex-hibit the same dependence on donor and acceptor concentra-tions.
A comprehensive study on migration-accelerated ET in rare-earth-doped glasses was performed in Ref.41.The ma-jor conclusion of this study was that ET in glasses,in con-trast to ET in crystalline host materials,cannot be described by migration-accelerated quenching theories such as the dif-fusion model42or the jump model.42The most notable devia-tion of the experimental?ndings from theoretical predictions was the unusual increase of the transfer parameter with do-nor concentration which,in the case of glasses,typically fol-lows a square-law dependence in the static-quenching regime which saturates to a linear dependence in the kinetic,i.e.,the migration-accelerated regime.
If we want to compare our results?ion densities treated in units of cm?3?to the results of Ref.41and references therein ?ion densities treated in units of1?,then we have to translate
our W parameters?given in units of cm3s?1?to the transfer parameters of Ref.41?given in units of s?1?.This is done by multiplying the W parameter of a speci?c transfer process with the concentration of acceptor ions in the sample under investigation.For the ETU and CR processes,the W param-eters are multiplied by the Er3?concentration.It follows that the dependence on Er3?concentration translates from linear ?as observed in our experiments;Fig.4?to quadratic in the unit system of Ref.41.For the ET processes,the W param-eters are multiplied by the Pr3?concentration.The depen-dence on Er3?concentration remains linear whereas the de-pendence on Pr3?concentration translates from independent to linear in the unit system of Ref.41.Again,all the inves-tigated transfer processes exhibit the same dependence on donor and acceptor concentrations,because we have only transformed the unit system.
When comparing the translated dependence of the transfer parameters on donor concentration with the results of Ref. 41,we?nd that the linear dependence corresponds to the migration-accelerated regime where the dependence of the transfer parameter on donor concentration saturates.In those glasses investigated in Ref.41,this regime was observed for donor concentration above1020–1021cm?3,depending on glass composition.Our samples have donor concentrations of2–14?1020cm?3.In the case of ET to Pr3?,the acceptor concentrations of0.4–2.5?1020cm?3are also in the range typically used in Ref.41,whereas in the case of ETU and CR within Er3?,the acceptor concentrations are higher in our samples.
A possible reason for migration-accelerated transfer is the occurrence of active-ion clusters.Such clusters have been reported,e.g.,for silica glasses.43–45Although the?ndings concerning the dependence of the transfer parameters on do-nor concentration in glasses are in agreement with the as-sumption that active-ion clusters occur in glass hosts,41the conclusion was drawn in Ref.41that clustering cannot be an explanation for the observed behavior.The reason for this conclusion was that similar results were found for all the glasses under investigation,despite the fact that these com-positions were known to exhibit different degrees of segre-gation.For a comparison,fast energy migration between Er3?ions was found to be present at dopant concentrations as small as3.36?1019cm?3(?1at.%)in the crystalline ma-terial Cs3Lu2Br9:Er3??Ref.46?,although there is currently no reason to assume that clustering of Er3?ions occurs in this material.
The present data and the comparison with the results of other publications do not support the assumption that active-ion clusters are present in ZBLAN glass.The strong quench-ing of the Er3?4I13/2lifetime by the Pr3?codopant can be explained by the large oscillator strength of the correspond-ing Pr3?absorption transition.Also the comparison with transfer processes in LiYF4:Er3?does not reveal signi?cantly-enhanced transfer parameters in ZBLAN:Er3?. The comparison with migration-accelerated transfer in other glasses and a crystalline material shows that this phenom-enon is typically observed at the dopant concentrations under investigation and is not necessarily related to the occurrence of active-ion clustering.However,the presence of active-ion clusters cannot be excluded by the investigations of this ar-ticle.
V.CONCLUSIONS
In the ZBLAN glass host,we have measured the intrinsic lifetimes of the Er3?4I13/2,4I11/2,and4S3/2/2H11/2levels as well as the parameters of ETU from4I13/2and4I11/2,ET from these levels to the Pr3?3F3and1G4levels,respec-tively,and CR from the thermally-coupled Er3?4S3/2/2H11/2 levels.The results show that ETU is as ef?cient in ZBLAN glass as in LiYF4.Due to the higher oscillator strengths of the corresponding emission and absorption transitions,ETU and ET processes originating in the4I13/2level have gener-ally a higher probability than those from the4I11/2levels.
862PRB62
GOLDING,JACKSON,KING AND POLLNAU
The concentration dependence of the transfer parameters in-dicate that,at the dopant concentrations under investigation, transfer processes occur in the migration-accelerated regime. From the presented data,the presence of Er3?ion clusters in ZBLAN cannot be excluded.
The lifetimes as well as the parameters of ETU,CR,and ET have been determined over a range of Er3?and Pr3?concentrations applicable to the design of double-clad diode-pumped Er3?3-?m?ber lasers operating on the4I11/2→4I13/2transition.27–29,31The consequences of our results
for the operation of the Er3??ber laser are as follows. Codoping the system with Pr3?is the preferred technique for a diode-pumped3-?m?ber laser when high Er3?concentra-tions for ef?cient ETU from the lower laser level are unavail-able.Relatively small amounts of Pr3?rapidly deplete the lower laser level while having a much lesser effect on the upper laser level.This allows the system to operate as a simple four-level laser with short lower and longer upper-state lifetimes.47
For Er3?concentrations up to8.75mol%used in this investigation,ETU has approximately a factor of3larger probability for the lower laser level as compared to the upper laser level.These values are more favorable than those of LiYF4:Er3?,i.e.,ef?cient ETU from the lower laser level can be achieved in ZBLAN without signi?cantly quenching the upper laser level.With the future availability of highly Er3?-doped?bers,ETU from the lower laser level can up-convert ions back to the upper laser level.This energy recy-cling regime with its inherent enhancement of the slope ef-?ciency by a factor of two will,thus,be an attractive alternative to Pr3?codoping at higher dopant concentrations.
ACKNOWLEDGMENTS
This work was?nancially supported by Engineering and Physical Sciences Research Council.M.Pollnau is indebted to Hans-Ulrich Gu¨del from the Department of Chemistry and Biochemistry,University of Bern,Switzerland,for his sup-port.
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能量的转化和转移-初中物理知识点习题集
能量的转化和转移（北京习题集）（教师版） 一．选择题（共5小题） 1．（2016秋?昌平区期末）下列说法中不正确的是 A ．发电机工作时，将机械能转化为电能 B ．电风扇工作时，扇叶的机械能是由电能转化的 C ．在被阳光照射时，太阳能电池将太阳能转化为电能 D ．干电池给小灯泡供电时，干电池将电能转化为化学能 2．（2016秋?西城区校级期中）下列生活实例中，只有能量的转化而没有能量的转移的是 A ．利用煤气灶将冷水烧热 B ．汽车行驶一段路程后，轮胎会发热 C ．太阳能水箱中的水被晒热了 D ．把冰块放在果汁里，饮用时感觉很凉快 3．（2015秋?东城区校级期中）在能的转化过程中，下列叙述不正确的是 A ．木柴燃烧过程中是化学能转化为内能 B ．发电机工作时是机械能转化为电能 C ．电源是将其它形式的能转化为电能的装置 D ．干电池使用时，是把电能转化为化学能 4．（2014秋?北京校级月考）下列现象中，只有能的转移而不发生能的转化的过程是 A ．水蒸气会把壶盖顶起来 B ．洗衣机工作 C ．用锤子打铁件，铁件发热 D ．冬天用手摸户外的东西时感到冷 5．（2011秋?西城区校级月考）下列过程中，机械能转化为内能的是 A ．锯木头，经过一段时间后，锯条和木头都发热 B ．锅里的水沸腾时，水蒸气把锅盖顶起 C ．神州号飞船点火后，腾空而起 D ．礼花弹在节日的夜空中绽开 二．多选题（共1小题） 6．（2008?宣武区二模）在以下事例中，机械能转化为内能的是 ()()()() ()()
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第三方支付介绍及国内第三方支付平台比较分析
第三方支付介绍及国内第三方支付平台比较分析 摘要 第三方支付是我国电子商务支付领域发展的重要力量，在解决网络信用方面有重要保障作用。本文先介绍第三方支付系统流程、特点、功能，然后对目前国内四大支付平台的发展情况进行比较分析，可以从中看出第三方支付的发展规律及其存在的问题，从而才能够采取有效应对措施推动我国电子支付的健康有序的可持续发展。文章主要分为七个部分：第一部分，对第三方支付系统及发展现状的概述；第二、三、四部分，分别介绍第三方支付的交易流程、特点、功能及作用，第五部分通过对国内四大第三方支付平台的详细分析得出分析结论；第六部分，对国内第三方支付企业存在的问题进行了探讨及提出对我国第三方支付平台建设的对策建议;第七部分总结。 关键词:网上支付、第三方支付、分析 一、第三方支付概述及发展现状 （一）第三方支付概述 “第三方支付”是指一些和国内外银行签约、具备一定实力和信誉保障的第三方独立机构提供的交易支持平台。在通过第三方支付平台的电子商务交易中，买方选购商品后，使用第三方平台进行货款支付，由第三方通知卖家货款到达，进行发货；买方检验签收物品后，通过第三方支付平台确认收货，可以付款给卖家。第三方平台再将款项转至卖家账户。 第三方支付平台与国内知名物流企业紧密合作，使网络交易的安全性更加坚固，进一步防止了交易中可能出现的欺诈行为，提高了第三方支付平台的运作效率。第三方支付平台正好抓住互联网购物中消费者希望少花钱的心理，在用户交易过程中不收取任何费用，利用这种会员免费服务集聚了大量人气，提升了整体用户数量，为企业带来了更丰厚的收入。（二）国内第三方支付发展现状 下图1是艾瑞咨询对2013年第二季度国内支付市场份额的统计数据。2013Q2中国第三
输电线微风振动分析方法能量平衡法的改进研究
第26卷增刊I V ol.26 Sup. I 工 程 力 学 2009年 6 月 June 2009 ENGINEERING MECHANICS 176 ——————————————— 收稿日期：2008-03-04；修改日期：2008-11-21 基金项目：国家自然科学基金项目(50878093) 作者简介：李 黎(1956―)，女，上海人，教授，学士，副院长，从事结构抗震抗风与振动控制研究(E-mail: lili2431@https://www.wendangku.net/doc/3b8018795.html,)； *叶志雄(1981―)，男，湖北人，博士生，从事结构振动控制研究(E-mail: yesui5685@https://www.wendangku.net/doc/3b8018795.html,)； 孔德怡(1982―)，男，河南人，博士生，从事结构抗震抗风研究(E-mail: kongdy@https://www.wendangku.net/doc/3b8018795.html,). 文章编号：1000-4750(2009)Sup.I-0176-05 输电线微风振动分析方法能量平衡法的改进研究 李 黎1,2，*叶志雄1,2，孔德怡1,2 (1. 华中科技大学土木工程与力学学院，湖北，武汉430074；2. 华中科技大学控制结构湖北省重点实验室，湖北，武汉 430074) 摘 要：针对输电线微风振动传统计算方法能量平衡法计算误差较大的特点，分别从风能输入功率、输电线自阻尼功率、防振锤消耗功率、输电线-防振锤耦合体系的振动求解等方面，对能量平衡法进行了改进，使能量平衡法可以考虑更多的影响因素以提高求解精度。基于改进后能量平衡法编制了计算机辅助计算程序，并以特高压汉江大跨越地线的微风振动防振计算为例，说明了改进后的能量平衡法在特高压输电线微风振动防振设计中的应用。 关键词：微风振动；能量平衡法；防振锤；风能输入功率；导线自阻尼 中图分类号：TM752; TU311.3 文献标识码：A IMPROVEMENT OF ENERGY BALANCE METHOD AND ANALYSIS OF AEOLIAN VIBRATION ON UHV TRANSMISSION LINES LI Li 1,2 , *YE Zhi-xiong 1,2 , KONG De-yi 1,2 (1. School of Civil Engineering & Mechanics, Huazhong University of Science & Technology, Wuhan, Hubei 430074, China; 2. Hubei Key Laboratory of Control Structure, Huazhong University of Science & Technology, Wuhan, Hubei 430074, China) Abstract: The aeolian vibration of an overhead line is analyzed most commonly by applying the energy balance method, but the result of this method has big errors. In order to improve the solving precision of the method, the improvement of power inputted from wind, the conductor self-damping, the power dissipated by dampers and the solution for the nonlinear vibration of power line-damper coupling system were reported in the paper. Then the computer program is developed by applying MATLAB based on an improved energy balance method, and Ultra-high Voltage (UHV) Han-River Large Crossing Ground Wires were analyzed. The results show that the algorithm is very efficient. Therefore, the improved method can be applied to the design of UHV transmission lines. Key words: aeolian vibration; energy balance method; stockbridge dampers; wind power input; conductor self-damping 微风振动是输电线风致振动中的一种危害极大时常性振动。目前，对输电线微风振动的防振计算，国内外普遍采用能量平衡法[1 ―2] 。该方法是基 于风输入给输电线的能量与输电线-防振器系统消耗能量相等的原则计算输电线平衡振幅，继而求解输电线微风振动强度。由于风能输入和输电线自阻尼的不确定性，用能量平衡法求解的导线振幅存在一定误差，其精度很大程度上由实验精度决定。国 际大电网会议(CIGRE)1998年发表文章[3]对该法的精度进行了探讨，指出用能量平衡法求解的导线振幅的误差最大达到40%。近年来国外学者对如何更好、更精确的使用能量平衡法的研究已经取得较多的成果。Lu [4]用阻抗矩阵转换结合强迫振动分析理论，把输电线等效成小刚度梁来分析输电线-防振锤体系的微风振动情况，具有较高的精度和效率，并且开发出了微风振动分析设计商用软件。而国内工
初中物理能量的转化和守恒教案
《能量的转化和守恒》教案 一、教学目标： 1、知道各种形式的能是可以相互转化的。 2、知道在转化的过程中，能量的总量是保持不变的。 3、列举出日常生活中能量守恒的实例。 4、有用能量守恒的观点分析物理现象的意识。 教学重点：能的转化和守恒定律，强调能的转化和守恒定律是自然科学中最基本定律。 教学难点：运用能的转化和守恒原理计算一些物理习题；运用能的转化和守恒定律对具体的自然现象进行分析，说明能是怎样转化的。 二、资料准备：教材分析： 教材从能量的转化与守恒中，列举出生活中的能量守恒实例来加强教学。 三、教学过程： 环节一：引入新课 我们知道物体的动能和热能，是由物体的机械能运动情况决定的能量，内能跟物体内部分子的热运动和分子间的相互作用情况有关。物体内部分子的热运动，物体的机械运动都是物质运动的形式，由于运动形式不同，与之相联系的能量也不相同。 环节二：进行新课 的事例，说明各种形式的能的转化和转移）。在热传递过程中，高温物体的内能转移到低温物体。运动的甲钢球碰击静止的乙钢球，甲球的机械能转移到乙球。在这种转移的过程中能量形式没有变。 在自然界中能量的转化也是普遍存在的。小朋友滑滑梯，由于摩擦而使机械能转化为内能；在气体膨胀做功的现象中，内能转化为机械能；在水力发电中，水的机械能转化为电能；在火力发电厂，燃料燃烧释放的化学能，转化成电能；在核电站，核能转化为电能；电流通过电热器时，电能转化为内能；电流通过电动机，电能转化为机械能。有关能量转化的事例同学们一定能举出许多，课本图2-17中画出了一些农常用的生活、生产设备。请同学分析在使用图中设备时能量的转化。 (3)在能量转化和转移的过程中，能的总量保持不变。大量事实证明，在普遍存在的能量的转化和转移过程中，消耗多少某种形式的能量，就得到多少其他形式的能量。如在热传递过程中，高温物体放出多少热量（减少多少内能），低温物体就吸收多少热量（增加多少内能）；克服摩擦力做了多少功，就有多少机械能转化为能量，但能量的总量不变。就是说某物体损失的能量等于几个物体得到几个物体得到的能量的总和。例如，把烧热的金属块，投到冷水中，冷水，盛水的容器以及周围的空气等，都要吸收热量，它们所吸收的热量总和跟金属块放出的热量相等。再如水电站里，水从高处流下，损失了机械能，一方面由于推动发电机转动而转化为电能，一方面水跟水轮机、管道摩擦而转化为内能。那么水的机械能的损失等于产生的电能和内能的总和。 以上规律是人类经过长期的实践探索，直到19世纪，才确立了这个自然界最普遍的定律棗能量的转化守恒定律。通常把它表述为： 能量既不会消灭，也不会创生，它只会从一种形式转化为其他形式，或者从一个物体转移
能源平衡计算及统计分析标准及考核办法
能源平衡计算及统计分析标准及考核办法 企业能源平衡是以企业为考察体系进行的能源平衡，包括企业各种能源输入与支出的平衡，消耗及有效利用能源及各项损失之间的数量平衡，以及与之相关的技术经济分析。其目的在于掌握企业的耗能情况，分析企业的用能水平，查找节能潜力和明确节能方向，为改进企业的能源管理，实行节能技术改造，从而为提高企业的能源利用率提供科学依据。 1 内容与要求 1.1 能源平衡计算及统计分析的内容 1.1.1 能源平衡计算是反映一个企业在统计期内所消耗的各类能源总量及其组成结构。包括购入能源、库存变化；二次能源、利用余热余能；外销能源、企业自耗能源(燃料及动力)等信息。 l.1.2 能源平衡反映了企业主要产品品种耗能情况。 1.1.3 能源平衡反映了企业二次能源转换及其消耗水平。包括企业自产燃料、动力所消耗的燃料、动力。 1.1.4 能源消耗品种按企业统计习惯分为两大类。第一类为燃料，包括：原煤、洗精煤、冶金焦、重油、焦油、汽油、柴油、高炉煤气、焦炉煤气、转炉煤气；第二类为动力，包括：电力、蒸汽、氧气、氮气、压缩空气、鼓风、深井水、循环水、净化水等。 1.1.5 根据能源平衡计算，对各种耗能指标进行统计分析，找出末完成指标的原因，并提出解决问题的办法。 1.2 能源平衡计算及统计分析的要求
1.2.1 产品产量必须以统计期内生产处的统计数据为准。 1.2.2 产品产量必须是指同类型各种产品产量的总和。生产同类产品可直接计算合计产量，如钢产量。生产不同规格产品，但生产工艺相近的产品产量也可直接相加。 1.2.3 生产不同类型的多种产品，各种能耗不宜直接相加，应选择一种主要产品，做为计算综合能耗的产量。 1.2.4 分品种能耗必须是统计期内，各厂实际消耗的各种能源实物量及相应的标准煤量。 1.2.5 总能耗量必须是各单位实际消耗的能源量折算标准煤量与回收并外供能量折算标准煤量之差。 1.2.6 各种能源折算标准煤系数，均以公司能源主管部门计算确定的折算系数为准。各生产厂在计算各种能源消耗量时均要采用公司规定的统一折算系数。 l.2.7 吨钢综合能耗是综合反映一个单位能源消耗总水平的指标，其含义是单位钢产量(产值)所消耗的能源量。 1.2.8 工序能耗是工序的总能耗与该工序同期产品产量之比，是衡量该工序(车间)能耗高低的技术经济指标。 1.2.9 工序能耗是按产品分工序进行计算的能源消耗水平。如炼铁厂分炼铁工序、烧结工序等。 1.2.10 各种能源消耗定额，以统计期内能源实物消耗量与该统计期内产量之比。 1.3 其它
苏科初中物理九下《18.4能量转化的基本规律》word教案 (3)
四、能量转化的基本规律 学习要求 1．知道能量守恒定律。能举出日常生活中能量守恒的实例。有用能量转化与守恒的分析物理现象的意识。 2.初步了解在现实生活中能量的转化与转移有一定的方向性。 3.讨论和分析两个具体的永动机设计方案，说明永动机是不可能的。 学习指导 1．能量守恒定律：能量既不会凭空消灭，也不会凭空产生，它只会从一种形式转化为另一种形式，或者从一个物体转移到另一个物体，而在转化或转移的过程中，其总量保持不变。能量守恒定律是自然界最普遍、最重要的基本定律之一。一切有能量转化或转移的场合，大到宇宙、小到原子核内部，也不论是生物、化学还是物理、地质现象，都遵守能量守恒定律。自然界中能的总量保持不变，但是对于某一物体可能改变。 2．能量转化和转移的方向性：热量只能从高温物体转移到低温物体，不能相反，具有方向性，否则就要消耗其他的能。不是什么能源都可以利用，能源的利用是有条件的，也是有代价的，有的东西能成为能源，有的则不能。虽然能量在转化和转移的过程中是守恒的，但具有方向性，因此我们一定要节约能源。 典型范例 例题市场经济的今天，一些厂商一改过去“酒香不怕巷子深”的做法，纷纷对产品进行广告宣传。可是有些厂商在广告上弄虚作假，夸大其词，欺骗消费者。如某品牌电热水器这样写道：“我厂电热水器功率只有55W，烧开一瓶水只需5min，节钱省电，最适合普通家庭使用。”这则广告可信吗？ 精析：电热水器烧开水，是电能转化为热能被水吸收的过程。方法一：根据题意求出电热水器所产生的热能，再利用热量公式，算出这些热量能够烧开多少质量的水，与事实进行比较，判断信息是否可信；方法二：先求出电热电热水器所产生的热能，再估算出烧开一瓶水所需要的热量，两者进行比较，判断信息是否可信，判断的依据是能量守恒定律。 全解：方法一：电热水器产生的热能为W=Pt=55W×5×60s=1.65×104J。 假设一般情况下烧开水是把水从20℃加热到100℃，则这些热量可以烧开的水的质量m＝ Q c△t ＝ W c△t ＝ 1.65×104J 4.2×103J/（kg·℃×（100℃-20℃）） ＝0.049kg。
无线电波的发射与接收
第一章无线电波的发射与接收 我们在物理学的学习中知道，通有交流电的导线，会在它周围产生变化的磁场，变化的磁场又能在它周围引起变化的电场，而变化的电场还将在它周围更远的空间引起变化的磁场。这种不断交替变化，由近及远传播的电磁场就叫电磁波。无线电技术中使用的电磁波叫无线电波。 无线电广播、电视广播都是利用无线电波进行传播信号的。现代通讯离不开无线电波。本章将介绍无线电波的波长、频率、波段划分，以及它的发射与接收。 第一节无线电波的波长、频率与波段划分 一、无线电波波段的划分 表1-1无线电波波段的划分 理论和实验都可以证明，无线电波在真空中的传播速度跟实验测得的光速相等，即 C=3.0×108m/s 无线电波在一个振荡周期T内传播的距离叫做波长。波长、频率和无线电波传播速度c的关系为 λ=c/f
式中：λ一无线电波的波长，单位m ； c 一无线电波的传播速度，单位m/s; f 一无线电波的频率，单位H Z 无线电波的波长从不到一毫米到几十千米（频率范围由几十千赫到几十万兆赫）。通常根据波长〔频率）把无线电波划分成几个波段，如表1-1所示。 二、无线电波的传播 无线电波是横波，即电场和磁场的方向都跟波的传播方向垂直。在无线电波中各 处 的电场强度和磁感应强度的方向也总是互相垂直的，如图1-1所示。不同波长的电磁波，传播特性不相同；其传播方式大致可分为地波、天波和空间波三种形式。 (一）地波 沿地球表面空间向外传播的无线电波叫地波，如图1-2(a)所示。波具有衍射特性，当无线电波的波长大于或相当于山坡、建筑物等障碍物的尺寸时，它可以绕过障碍物继续向前传播。 地球是导体，地波沿地面传播时，地球表面因电磁感应而产生感应电流，因此要消耗能量，并且能量损耗随频率升高而增大。考虑到能量损失，只有中、长波才利用地波方式传播。由于地波传播稳定可靠，在超远 程无线电通讯和导航等方面多采用中长波。 图1-1无线电波传播示意图 (二)天波 依靠电离层的反射作用传播的无线电波叫做天波，如图1-2(b 〕所示。在地球表面的大气层中，大约在60km 到400km 的范围内，由于太阳光的照射，气体分子分解为带正电的离子和自由电子，这就是电离层。电离层一方面可以反射无线电波，反射本领随频率增大而减小。实践表明，波长短于10m 的微波会穿过电离层飞向宇宙，它只能反射短波或波长更长的无线电波。电离层另一方面要吸收无线电波，吸收本领随频率减小而增大，中波和中短波一部分被吸收，因此，只有短波多采用天波方式传播。 天波传播受外界影响较大，它与电离层强度、太阳辐射强度等多种因素有关，.由于这些原因，收音机夜晚收到的电台比白天多， (三）空间波 沿直线传播的无线电波叫做空间波，它包括由发射点直接到达接收点的直射波和经地面反射到接收点的反射波，如图1-2(C 〉所示。
(九年级物理)能量(能量的转移和转化)
能量（能量的转移和转化） 【复习要点】： 要点（40）：了解能量及其存在的不同形式，描述各种能量和生产生活的联系； 例题1：关于信息和能源，下列说法正确的是（） A．电风扇工作时，电能主要转化为内能 B．目前的核电站是利用核裂变释放的核能工作的 C．煤、石油、风能、天然气等都是不可再生能源 D．能量在转移、转化过程中总是守恒的，我们无需节约能源 要点（41）：通过实验，认识能量可以从一个物体转移到另一个物体，不同形式的能量可以互相转化； 例题2：随着智能手机的普及，人们的聊天方式也不断推陈出新，由于智能手机的待机时间很短，因此需要经常充电，当给电池充电时是将能转化成能．当手机正常使用时是将能转化成。将微风扇通电时它可以转动，这是将能转化成能，如果转动微风扇的风叶，还可以使与风扇插头相连的二极管发光，这是将 能转化成能。 要点（42）：结合实例，认识功的概念。知道做功的过程就是能量转化或转 移的过程； 例题3：如图，在空气压缩引火仪玻璃筒的底部放一小撮干燥的棉絮，用力 将活塞迅速向下压，棉絮燃烧起来。此实验得到的结论是：对（选 填“棉絮”或“筒内气体”）做功，它的内能会增加，其能量转化情况与 单缸四冲程汽油机的冲程相同，若汽油机的转速是2400r/min，则此汽油机每秒对外做功次。
要点（43）：知道动能、势能和机械能。通过实验，了解动能和势能的相互转化。举例说明机械能和其它形式能量的相互转化。 例题4：如图所示是演示点火爆炸的实验装置．按动电火花发生器的按钮，点燃盒内酒精，盒盖被打出去．在汽油机工作的四个冲程中，与此能量转化相同的冲程示意图是（） 【反馈练习】： 1．以下说法正确的是（） A．太阳能和核能都属于可再生能源 B．发光二极管主要使用的材料是超导体 C．热量不能自发地从低温物体传递给高温物体，说明能量转移具有方向性， D．飞 机的 机翼 做成 上面 凸起，下面平直．是因为流过机翼上方的空气流速大，压强大。 2．周末小明骑自行车去傅家边游玩．自行车下坡的过程中，为了减小车速，他捏紧车闸，这是通过的方法增大摩擦，此时刹车皮会发热，这是通过
滨州市邹平县初中物理九年级全册14.3能量的转化和守恒练习题
滨州市邹平县初中物理九年级全册14.3能量的转化和守恒练习题 姓名:________ 班级:________ 成绩:________ 一、练习题 (共12题；共25分) 1. （2分）某品牌手机充电宝，上面标有电压为5V，容量为12000mA?h，它充满电后，可以储存的电能是________J，在充电过程中，将电能转化为________能储存． 2. （2分）大量事实证明“永动机”是不可能存在的，因为它违背了________定律。热机的效率总是会________1．（填“大于”“小于”或“等于”） 3. （2分）木材燃烧是将化学能转化为________能，这一过程能量的总量将________（填变大、变小或不变）． 4. （3分） 2017年1月5日19时45分，西昌卫星发射中心用长征三号运载火箭，成功发射两颗北斗三号全球组网卫星。预计到22018年底，将有18颗北斗卫星发射升空，服务区覆盖“一带一路”沿线国家及周边国家，长征三号乙运载火箭起飞过程中燃料燃烧释放的内能将转化为火箭的________能，加速上升过程中受到________（选填“平衡力”或“非平衡力”）作用，北斗卫星与地面之间通过________传递信息。 5. （2分）(2020·绵阳模拟) 如图甲所示，小明在吹气球时，被吹大了的气球没能用手握住，呼啸着飞了出去，若他及时捡拾起气球，将会感觉到它喷气的嘴部温度和原来相比________（选填“变高”、“变低”或“没有变化”），发生的能量转化与汽油机的________冲程的能量转化是一致的。 6. （2分）关于热机中的能量转化关系，下列说法中正确的是（） A . 热机是将机械能转化为内能的机器 B . 热机是将内能转化为机械能的机器 C . 热机是将燃料的化学能转化为机械能的机器 D . 热机是利用化学能来做功，它是将化学能转化为内能 7. （2分） (2017九上·广州月考) 如图所示，在一个配有活塞的厚壁玻璃筒里放一小团硒化棉布，用力把活塞迅速下压，棉花就会立即燃烧．根据该实验现象，下列结论正确的是（）
能量分析法
2. 5. 1 能量分析法 此法的特点：仅依据热力学第一定律（即只从能量的数量出发）分析揭示装置或设备在能量的数量上的转换、传递、利用和损失的情况。故此法被许多人称为“第一定律分析法”。其主要计算：对装置或设备进行“能量平衡”（一般又称“热平衡”）计算。故此法又称为“能量平衡法”（或“热平衡法”）。其主要热力学指标为“能效率”（或“热效率”），其定义为： （ 2-6 ）故此方法又常称为“能效率法”。 2. 5. 2 分析法 此法的本质：结合热力学第一定律和第二定律（以第二定律为主），即从能量的数量和质量相结合的角度出发分析揭示装置或设备在能量中的（有效能）的转换、传递、利用和损失的情况。故又被许多人称为“第二定分析法”。其主要计算：对装置或设备进行平衡计算。故又称为“平衡法”。其主要热力学指标为“效率”，其定义为： （ 2-7 ） 故此法又称为“效率法”。 2. 5. 3 能量分析法和分析法的比较 因为能量分析法是依据不同质的能量在数量上的平衡，只考虑了量的利用和量的直接“外部损失”，在计算投入装置或设备的总能量中，有多少被利用（收益），有多少直接转移到环境中损失掉，比较直观和容易理解。例如，若某锅炉的热效率为何 90% ，则在投入（消耗）的燃料燃烧发出热量的总能量中，有偿使用 90% 能量（热能）传给水蒸汽被利用（收益），10% 能量（热能）通过排烟．散热等直接损失到环境中。又如一个蒸汽动力发电厂，若其总效率为 40% ，则在投入燃料发热量的总能量中，有 40% 能量（热能）转变为机械能（最后变为电能）输出被利用（或收益），而 60% 的能量（热能）在锅炉、汽轮机、冷凝器、换热器、管道等设备通过各种途径散失到环境中造成损失。而且也确为节约能量指明了一定的方向，例如回收余、废热、减少工质或物料的泄漏．加强保温等措施
九年级物理能量的转化与守恒练习题
九年级物理能量的转化与守恒练习题 基础知识训练 1．从能的转化和守恒的观点来看，用热传递来改变物体的内能，实际上是的过程，用做功方法来改变物体的内能，实际上是的过程． 2．英国物理学家法拉第经过10年不懈努力，终于在1831年发现了现象，导致发电机的发明，实现了电能的大规模生产。我国兴建的长江三峡发电机组，是通过能转化为电能。福州市即将兴建的垃圾焚烧电厂，是将垃圾焚烧后获得的能。最终转化为电能。 3．当水壶中的水烧开时，壶盖会被顶起，从能量转化的观点看，这是水蒸气的_________能转化为壶盖的能。 4．能量转化与守恒是自然界的基本规律之一，下列过程中机械能转化为电能的 是（）A．干电池放电B．给蓄电池充电 C．风力发电D．电动机带动水泵抽水 5．下列现象中，利用内能做功的是（） A．冬天在户外时两手相搓一会儿就暖和B．车刀在砂轮的高速磨擦之下溅出火花 C．在烈日之下柏油路面被晒熔化了D．火箭在“熊熊烈火”的喷射中冲天而起 6．下列说法中错误的是（） A．能的转化和守恒定律只适用于物体内能的变化 B．只要有能的转化和转移，就一定遵从能量守恒定律 C．能的转化和守恒定律是人们认识自然和利用自然的有力武器 D．任何一种形式的能在转化为其他形式的能的过程中，消耗多少某种形式的能量，就能得到多少其他形式的能量，而能的总量是保持不变 7．我区大力发展火力发电，火电厂进的是“煤”，出的是“电”，在这个过程中能量的转化是（） A．机械能→内能→化学→能电能B．化学能→内能→机械能→电能C．化学能→重力势能→动能→电能D．内能→化学能→机械能→电能综合提高训练 1．指出下列现象中能量的转化和转移情况． （1）气体膨胀做功． （2）植物进行光合作用． （3）燃料燃烧． （4）风吹动帆船前进． 2．如图15-14所示，在试管内装一些水，用软木塞塞住，用 酒精灯加热试管使水沸腾，水蒸气会把软木塞冲出．在水蒸
能源平衡分析
企业能量平衡统计方法——中华人民共和国国家标准 ［作者：佚名来源：0000 更新时间：2008-5-9］ 中华人民共和国国家标准 企业能量平衡统计方法 Statistical method of energy balance in enterprises GB/T 16614-1996 _______________________________________________________________________________ 1 范围 本标准规定了企业能量平衡统计方法的基本原则。 本标准适用于确定的能源统计系统、指标与方法。 2 引用标准 GB2586-91 热量单位、符号与换算 GB/T2589-90 综合能耗计算通则 GB/T3484-93 企业能量平衡通则 GB/3101-93 有关量、单位和符号的一般原则 GB/T13234-91 企业节能量计算方法 3 企业能耗统计系统 企业能耗统计系统根据能量流动过程划分为能源购入贮存、加工转换、输送分配和最终使用四个环节，其系统简图如图1，每一个环节中可分为若干用能单元。 4 企业能源统计范围 企业能源统计，应包括一次能源、二次能源和耗能工质所消耗的能源。 5 企业能源统计方法 5.1 企业能源供入量统计 为进行企业能量平衡分析与评价，首先应做企业能源供入量的统计，并折算出它们的等价值和当量值。其等价值用以反映国家对企业供入的能源资源量；当量值用于企业能量平衡，分析企业用能过程，不可混合使用等价值和当量值。 5.1.1 等价值和当量值的折算应符合GB/T2589的规定。 5.1.2 企业能源供入量统计应包括：各类能源购入量、库存增减量、亏损量、外供量、供入量等。
无线电波的传播特性修订版
无线电波的传播特性 Document number：PBGCG-0857-BTDO-0089-PTT1998
无线电波的传播特性 无线电通信就是不用导线，而利用电磁波振荡在空中传递信号，天线就是波源。电磁波中的电磁场随着时间而变化，从而把辐射的能量传播至远方。 在莫尔斯和贝尔先后发明了有线电报和电话之后，很多科学家对电磁现象大量研究。直到1831年，在英国，法拉弟首先发现了电磁感应现象，并且预言：电与磁的传播是和光一样的一种波。 英国科学家麦克斯韦从1850年就开始对法拉弟提出的课题展开研究。他总结了前人的研究成果，用数学方法对法拉弟的电磁场思想做了严格的论证，并在1864年做出“电与磁的交替转化过程，是一种波的传播形式，是一种光波”的论断，他称这种波为电磁波。 在麦克斯韦首先提出电磁理论后，又过了24年，才由德国伟大的物理学家赫兹通过实验证实了麦氏理论的正确。赫兹设计了一个能够接收电火花的装置，结构极简单。把一根导线弯成圆形，使两端之间仅留一微小的间隙，称它为“共振子”。“共振子”为什么也有火花发生呢赫兹认为，这一定是电振荡以电磁波形式通过空间传播过去的。赫兹于1888年公布了自己的实验结果，证实了电磁波的存在。 赫兹的实验成果震惊了世界，许多科学家继续开展对电磁波的研究。1890年，法国物理学家布朗利发现，将金属粉末即紧缩成块，但是它的电阻减小了，使电流容易通过。这种装有金属粉未的玻璃管被称为“布朗利管”，又称“粉末检波器”，它接收电磁波的灵敏度比赫兹的“共振子”要高得多。 1894年，20岁的意大利青年马可尼从杂志上读到悼念赫兹的文章和他生前的感人事迹，受到极大启发：“如果利用赫兹发现的电磁波，不需要导线也可以实现远距离通信了”。马可尼为自己的大胆设想所激动下宏愿，决心开拓无线电通信事业，把赫兹的研究成果付诸实际应用。在家人的支持下，马可尼就在自己家中进行实验，他用赫兹的火花放电器作发射机，用布朗利的金属粉未检波器作接收机经过一个多月的努力，终于完成了电磁波的发送和接收实验，并在实
初二物理复习知识点：能量的转化和守恒
初二物理复习知识点：能量的转化和守恒 在一定的条件下，各种形式的能量可以相互转化;摩擦生热，机械能转化为内能;发电机发电，机械能转化为电能;电动机工作，电能转化为机械能;植物的光合作用，光能转化为化学能;燃料燃烧，化学能转化为内能。 能量守恒定律：能量既不会消灭，也不会创生，它只会从一种形式转化为其他形式，或者从一个物体转移到另一个物体，而在转化和转移过程中，能量的总量保持不变能量的转化和守恒练习题 能量既不会______，也不会______，它只会从一种形式______为其他形式，或者从一个物体______到另一个物体，而在转化和转移过程中，______的总量保持不变.这就是能量守恒定律. 克服摩擦或压缩气体做功时，消耗______能，使______能转化为______能，而且消耗多少______能，就得到多少______能，在这个过程中，能量的总量______. “和平”号空间站完成使命后，安全坠入南太平洋海域，当“和平”号进入稠密大气层时，燃起了熊熊大火，这是将______能转化为______能，在“和平”号坠入南太平洋的过程中，它的______能增加，______能减少，而能的总量______. 自然界中各种不同形式的能量都可以相互转化，电动机
可以把______能转化为______能;太阳能电池把______能转化为______能;植物的光合作用可以把______能转化为______能，燃料燃烧时发热，将______能转化为______能. 秋千荡起来，如果不继续用力会越荡越低，甚至停止;皮球落地后，每次弹起的高度都会比原来低.在这两个过程中，机械能______了，转化成了______能.机械能是否守恒______，能的总量是否守恒______.
无线电波传播模型与覆盖预测
无线电波传播模型 与 覆盖预测 河北全通通信有限责任公司 工程部网络服务组 二0 0二年四月二十日
第一节无线传播理论 1.1 无线传播基本原理 在规划和建设一个移动通信网时，从频段的确定、频率分配、无线电波的覆盖范围、计算通信概率及系统间的电磁干扰，直到最终确定无线设备的参数，都必须依靠对电波传播特性的研究、了解和据此进行的场强预测。它是进行系统工程设计与研究频谱有效利用、电磁兼容性等课题所必须了解和掌握的基本理论。 众所周知，无线电波可通过多种方式从发射天线传播到接收天线：直达波或自由空间波、地波或表面波、对流层反射波、电离层波。如图1-1所示。就电波传播而言，发射机同接收机间最简单的方式是自由空间传播。自由空间指该区域是各向同性（沿各个轴特性一样）且同类（均匀结构）。自由空间波的其他名字有直达波或视距波。如图1-1（a），直达波沿直线传播，所以可用于卫星和外部空间通信。另外，这个定义也可用于陆上视距传播（两个微波塔之间），见图1-1（b）。 第二种方式是地波或表面波。地波传播可看作是三种情况的综合，即直达波、反射波和表面波。表面波沿地球表面传播。从发射天线发出的一些能量直接到达接收机；有些能量经从地球表面反射后到达接收机；有些通过表面波到达接收机。表面波在地表面上传播，由于地面不是理想的，有些能量被地面吸收。当能量进入地面，它建立地面电流。这三种的表面波见图1-1（c）。第三种方式即对流层反射波产生于对流层，对流层是异类介质，由于天气情况而随时间变化。它的反射系数随高度增加而减少。这种缓慢变化的反射系数使电波弯曲。如图1-1（d）所示。对流层方式应用于波长小于10米（即频率大于30MHz）的无线通信中。第四种方式是经电离层反射传播。当电波波长小于1米（频率大于300MHz）时，电离层是反射体。从电离层反射的电波可能有一个或多个跳跃，见图1-1（e）。这种传播用于长距离通信。除了反射，由于折射率的不均匀，电离层可产生电波散射。另外，电离层中的流星也能散射电波。同对流层一样，电离层也具有连续波动的特性，在这种波动上是随机的快速波动。蜂窝系统的无线传播利用了第二种电波传播方式。这一点将在后文中论述。 在设计蜂窝系统时研究传播有两个原因。第一，它对于计算覆盖不同小区的场强提供必要的工具。因为在大多数情况下覆盖区域从几百米到几十公里，地波传播可以在这种情况下应用。第二，它可计算邻信道和同信道干扰。 预测场强有两种方法。第一种纯理论方法，适用于分离的物体，如山和其他固体物体。但这种预测忽略了地球的不规则性。第二种基于在各种环境的测量，包括不规则地形及人为障碍，尤其是在移动通信中普遍存在的较高的频率和较低的移动天线。第三种方法是结合上述两种方法的改进模型，基于测量和使用折射定律考虑山和其他障碍物的影响。在蜂窝系统中，至少有两种传播模型，第一种是FCC建议的模型。第二种设计模型由Okumura提供，覆盖边
第三方支付平台
第三方支付平台 D 实验三关于第三方支付平台(2学时) 1、现在第三方支付平台的格局如何以及各自所占有的市场情况是多少, 2、请同学上网查询目前主要的第三方支付平台有哪些?大的网上商城采用的有哪些?(列表说明) 网上商快钱易宝支付宝 Paypal 财付通首信易城 淘宝 ? 易趣 ? 当当网 ? ? ? ? 卓越网银行卡 支付 拍拍网 ? 你认为哪几家第三方支付平台最有生命力,会长期生存下去? 我觉得易宝的生命力比较强，会长期生存下去。 (1)如果消费者可以享受到:安全的在线支付，方便的电话支付，免费的会员服务，为您的手机充植，精彩活动积分奖励。 (2)可以为商户提供:网上、电话、汇款，多种收款方式，支持外卡，让你您的生意做到全球，7*24小时客服，技术支持快速反应，接入更简单，交易更安全， 结算更及时～ (3)功能有:会员登录安全设置:通过验证图片、提示问题、常用机校验等手段实现的双向安全验证机制，确保用户在任意场所登录易宝网站时的安全。 快捷查单服务:消费者通过此项服务可以方便快捷的查到自己选择YeePay易宝支付的网上购物订单～商户通过接入“快捷查单”功能，为客户提供贴心增值服务，提升服务品质和形象～ 自主接入服务:商户可通过自助方式网上注册并使用易宝在线支付服务，不仅 可以在线收款，而且还能登录商户系统进行定单管理和交易结算。依托易宝强大平台，确保安全交易，并享受7*24小时客户服务及快捷查单等增值服务。 3、第三方支付牌照的颁发会对现行的网络支付以及银联会产生什么样的影响,
易观国际分析认为，牌照发放后，获得牌照的企业将可接入超级网银，第三方支付企业以提高企业资金周转效率的定制化解决方案，将会逐步向传统企业进行渗透，也将出现从单一产业链的支付服务向跨产业链的融合转移的趋势。支付企业通过整合各种支付产品，为企业进行深度定制化服务，加快资金周转效率，而保险、基金等行业将是一个新的蓝海市场。 一旦涉及到钱，那么这个庞大的支付产业必定摆脱不了银行的介入。在《支付机构客户备付金存管暂行办法(06.02会议征求意见稿)》出台前，仅有支付宝等少数国内第三方支付公司委托银行每月对客户的交易保证金做托管审计，其他公司则会依托三四家银行提供备付金托管与清算服务。而随着今年5月26日首批支付牌照正式发放，一场第三方支付公司挑 选客户备付金存管行与回流备付金的“战斗”悄然开启。 根据之前提到的艾瑞公布的第一季度中国第三方网上支付的交易规模达到3650亿元这个数据，如果按5%交易金额被沉淀计算，仅在网上支付领域近180亿元资金将回流银行存款。业内人士表示，获得第三方支付备付金存管资格对商业银行中间业务收入、存款规模等都会带来有利影响，而在一些支付公司涉足预付卡业务之后，银行也将获得更多沉淀资金。 各第三方支付早已“明刀明枪”激战，备付金存管这“粮草”又怎会毫无准备。日前，支付宝正式宣布选择工商银行作为其备付金存管银行;本月初，建设银行与深圳华夏通宝商务有限公司签署战略合作协议，华夏通宝将选择建行作为主要的结算银行;7月上旬，浦发银行也与首批获得第三方支付牌照的上海付费通信息服务有限公司签署了战略合作协议，成为付费通的备付金托管银行;快钱公司日前也宣布与八家银行分别签署战略合作协议。 目前，《非金融机构支付业务许可证》已经颁发，首批获得支付牌照的公司包括消费者熟知的支付宝、快钱、财付通、银联商务等27家第三方支付公司。
直接能量平衡
编者导读：本文以某电厂 2 ×300MW 机组DEB 设计和运行情况为背景，阐述并分析了采用直接能量平衡策略的技术原理、工程实现、过程实际响应以及运行效果。结果表明：DEB 协调控制策略的控制目标直接、明确活，而且具有适应性强、稳定性好等特点。 0 前言大型火力发电机组由于机组容量大、运行参数高，若运行操作不当将对机组本身甚至电网的安全带来很大的危害，故对自动控制的要求和依赖越来越高。发电机组自动控制的最终目标是安全快速地满足电网的负荷需求并保证电力品质，由于组成火力发电机组的锅炉和汽轮机对负荷响应特性的差异很大，所以在设计机组级控制时必须充分考虑这两个对象的不同特性，使锅炉和汽轮机协调地运转，以机组实际最大能力来满足电网的要求。 协调控制系统CCS （Coordinated Control System ）的任务是协调锅炉和汽轮机两个不同的工艺系统共同来满足电力负荷需求。因此，协调控制系统的设计应将锅炉和汽轮机作为一个整体来考虑，使机组在实际能力下，能最大限度地满足电网要求的发电数量（功率）和质量（频率），确保发电机组安全、稳定、经济地运行，这是协调控制的基本要求。协调控制系统在理论上可以有许多方法来实现，但对于一个特定的发电机组来说，当主设备和工艺系该选择一种最适合该机组特定条件的技术方案作为控制系统设计的基本策略。随着分散控制系统（DCS ）熟，为火电机组实现复杂的协调控制创造了技术和物质的基础。本文阐述的是DEB 直接能量平衡控制系统制策略以及机组在协调控制方式下的实际负荷响应情况，采用的系统硬件是MAX1000 分散控制系统。 1 DEB 原理分析[1] 直接能量平衡（Direct Energy Balance ；DEB ）协调控制系统是由美国原Leeds & Northrup 公司创立的美国metsoMAX 公司继承此项技术，上海自动化仪表股份有限公司通过技术引进获得使用许可）。其著名的表式中P TS 为机前压力设定值；P 1 为汽机一级压力；P T 为机前压力；P D 为汽包压力；C b 为锅炉蓄热左边是汽机的能量需求信号，等式的右边是锅炉的热量信号。 DEB 实质上是以锅炉跟随为基础的协调控制，汽机侧控制功率，同时以汽机的能量需求作为锅炉负荷指令炉的热量信号相平衡，而满足这种平衡的控制手段是调节输入锅炉的燃料量，因此在燃料调节器入口代表燃料