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Mathematical Modeling of the Hot Strip Rolling of Microalloyed Nb,Multiply-Alloyed Cr-Mo,and Plain C-Mn Steels FULVIO SICILIANO,Jr.and JOHN J.JONASIndustrial mill logs from seven different hot strip mills(HSMs)were analyzed in order to calculatethe mean flow stresses(MFSs)developed in each stand.The schedules were typical of the processingof microalloyed Nb,multiply-alloyed Cr-Mo,and plain C-Mn steels.The calculations,based on theSims analysis,take into account work roll flattening,redundant strain,and the forward slip ratio.Themeasured stresses are then compared to the predictions of a model based on an improved MisakaMFS equation,in which solute effects,strain accumulation,and the kinetics of static recrystallization(SRX)and metadynamic recrystallization(MDRX)are fully accounted for.Good agreement betweenthe measured and predicted MFSs is obtained over the whole range of rolling temperatures.Theevolution of grain size and the fractional softening are also predicted by the model during all stagesof strip rolling.Special attention was paid to the Nb steels,in which the occurrence of Nb(C,N)precipitation strongly influences the rolling behavior,preventing softening between passes.The presentstudy leads to the conclusion that Mn addition retards the strain-induced precipitation of Nb;bycontrast,Si addition has an accelerating effect.The critical strain for the onset of dynamic recrystalliza-tion(DRX)in Nb steels is derived,and it is shown that the critical strain/peak strain ratio decreaseswith increasing Nb content;furthermore,Mn and Si have marginal but opposite effects.It is demon-strated that DRX followed by MDRX occurs under most conditions of hot strip rolling;during theinitial passes,it is due to high strains,low strain rates,and high temperatures,and,in the final passes,it is a consequence of strain accumulation.I.INTRODUCTION been achieved.The goal of the present research was,there-fore,to characterize strip rolling in terms of softening mecha-T HE metallurgical features of plate rolling are now nism,strain accumulation,grain size,and precipitation.Also,largely understood.[1–10]The long interpass times allow com-the rolling behavior of microalloyed Nb,plain C-Mn,andsome Cr-Mo grades will be considered and compared. plete static recrystallization(SRX)to take place if the steelAnother important point that arose from this study is that is being rolled above the interpass recrystallization stopthe levels of Mn and Si present in the steel appear to influence temperature(T nr),i.e.,in the absence of carbonitride precipi-the precipitation behavior during strip rolling.The occur-tation.Plate rolling below T nr leads to austenite pancaking,rence of precipitation changes the rolling load and must, because strain-induced precipitation prevents any furthertherefore,be accurately predicted.SRX from occurring.By contrast,during the very shortHodgson[15]has carried out an excellent analysis of the interpass times involved in rod rolling,neither SRX nordifferent types of mathematical models and has supplied a precipitation can take place,[11–14]and,in contrast to platelist of the advantages associated with the application of a rolling,the strain accumulation that takes place leads toparticular model to a given practical situation.According dynamic recrystallization(DRX)followed by metadynamicto this author,the main advantages are(1)a reduction in recrystallization(MDRX).Thus,the metallurgical character-the number of mill trials,(2)an evaluation of hardware istics of plate rolling,on the one hand,and of rod rolling,modifications,(3)the prediction of variables that cannot on the other hand,are now fairly clear.be measured,(4)an estimation of the effect of interactions, From the point of view of interpass time,strip rolling(5)the potential for performance enhancement,and(6) falls between the two processes discussed previously.Duringinexpensive research costs.the initial passes,when the interpass times are still relativelyThe applicability of any model must be intensively tested long,the metallurgical behavior is similar to plate rolling.in advance,preferably with industrial data.That is the As the interpass intervals become shorter,the characteristicsapproach that was employed here.After an improved accu-approach those of rod rolling.Because the classification of racy in predicting the operational parameters has been dem-strip rolling as being like plate rolling,on the one hand,or onstrated,the model can then be applied to production. like rod rolling,on the other,depends on chemistry and The analysis of mean flow stress(MFS)behavior as a rolling schedule as well as pass number,a relatively simple function of inverse absolute temperature permits identifica-and generally accepted analysis of this process has not yet tion of the main microstructural changes taking place duringrolling.These include SRX,DRX followed by MDRX,strainaccumulation,and phase transformation.Figure1illustratesthese phenomena schematically in the form of an MFS vs FULVIO SICILIANO,Jr.,Research Associate,and JOHN J.JONAS,1/T curve for a hypothetical five-pass schedule.Beginning Professor,are with the Department of Metallurgical Engineering,McGillat the first pass(on the left-hand,or high-temperature side), University,Montreal,PQ,Canada H3A2B2.Manuscript submitted March22,1999.there is a low-slope region,within which SRX occurs.The(a )Fig.1—Schematic representation of the evolution of MFS as a function of the inverse absolute temperature.Each characteristic slope is associated with a distinct metallurgical phenomenon.high temperature permits full softening to take place during the interpass interval.After pass 2,the lower temperature does not permit full softening,leading to strain accumula-tion.This accumulation then leads to the onset of DRX (as long as there is no precipitation),which is followed by MDRX between passes 3and 4.The analysis of MFS curves as described previously was first proposed by Boratto et al.[1]for determination of the (b )three critical temperatures of steel rolling (Ar3,Ar1,and Tnr ).[2,3,4]This technique has also been used to deduce that DRX occurs in seamless tube rolling [16,17]as well as in hot strip mills (HSMs).[18,19]Sarmento and Evans [19]came to similar conclusions in their analysis of industrial data from two HSMs.The main types of controlled rolling considered here are listed in the following paragraphs.Recrystallization-Controlled Rolling .In the schedules considered subsequently,as long as strip rolling is carried out above T nr ,SRX is considered to take place.Conversely,below T nr ,there is strain accumulation.Conventional-Controlled Rolling .Here,finishing is employed to flatten or “pancake”the austenite grains at temperatures below T nr .In this case,the particle pinning (c )resulting from the precipitation of Nb(C,N)retards or even Fig.2—Temperature-time diagrams comparing three rolling approaches:prevents the occurrence of recrystallization.In the absence (a )recrystallization controlled rolling,(b )conventional controlled rolling,of precipitation,as long as rolling is carried out below T nr and (c )dynamic recrystallization controlled rolling.for static recrystallization,the strain accumulation that takes place can trigger DRX followed by MDRX,leading to rapid softening between passes.In terms of mathematical model-ing,if there is no precipitation and the accumulated strain exceeds the critical strain,DRX is initiated,often causing caused by DRX when high strain rates are employed and large strains are applied (this corresponds to single-peak full and fast softening.This is usually associated with unpre-dictable load drops in the final passes.[20]behavior in the stress-strain curve).Circumstantial evidence for the occurrence of DRX in seamless tube rolling [16,17]and Dynamic Recrystallization-Controlled Rolling .This type of process consists of inducing DRX in one or more passes HSMs [18,19,21,22]can be found in the literature.Figure 2illustrates schematically the three different rolling during the rolling schedule.This can be done either by applying large single strains to the material or via strain paradigms described previously for a hypothetical five-pass schedule.The conditions associated with each type of rolling accumulation.Both methods allow the total strain to exceed the critical strain for the initiation of DRX.Some of the are displayed in Table I.Knowledge of the rolling parameters and process limitations associated with each method makesbenefits of this approach involve the intense grain refinementTable I.Mechanistic Conditions Pertaining to the Three Controlled Rolling TechniquesRole of Relation betweenType of T Range with Strain-Induced Precipitation andProcess Respect to T nr Precipitation RecrystallizationRCR above absence required SRX before precipitationCCR below presence required precipitation before SRX or DRX DRCR below absence required no SRX;DRX before precipitation possible the design of rolling schedules to fit the needs and B.Analysis of Mill Log Dataconstraints of each case.Logged data were collected from the following fiveHSMs:Dofasco seven-stand HSM(Hamilton,Canada), II EXPERIMENTAL PROCEDURE Algoma six-stand–2.69-m-wide HSM(Sault Ste.Marie,Canada),Sumitomo seven-stand HSM(Kashima,Japan), The present work combines the use of models developedSumitomo seven-stand HSM(Wakayama,Japan),and BHP from hot torsion test data and from the analysis of industrialsix-stand HSM(Port Kembla,Australia).Data from two mill logs.other HSMs were taken from the literature.[19]One is fromthe Usiminas six-stand HSM in Brazil,and the other is an A.Materials unidentified seven-stand HSM referred to here as“Davy.”Some1300logs were made available for analysis,of Various materials were tested and were divided into threewhich about300were examined in detail.The data that groups:microalloyed Nb(group A),multiply alloyed Cr-were employed consisted of interstand distances,work roll Mo(group B),and plain C-Mn(group C)steels.Tables IIdiameters,and pyrometer locations.For each strip,the fol-and III list the grades studied here.In group A(Table II),lowing data were used:chemical composition,strip width, some steels have low Si contents,with the same base compo-strip thicknesses before and after all passes(H and h,respec-sition(e.g.,AD5and AD6and AD7and AD8).Other typestively),work roll rotational speeds,roll forces,and tempera-have different Mn contents,with the same base compositiontures(mean values)for each pass,according to a model or (e.g.,AD9and AD10and AD2,AD3,and AD4).Theseto entry and exit temperatures.grades are used to study the influences of Mn and Si on theThe previous parameters were then employed to calculate precipitation of Nb(C,N)and on the critical strain/peakthe true strains,strain rates,interpass times,and MFSs, strain ratio.Table III gives the chemical compositions ofaccording to the Sims formulation.[4,23]The corrections for some of the multiply alloyed Cr-Mo and plain C-Mn gradesroll flattening,[24,25]redundant strain,and forward slip studied here.The steels used for the torsion tests are markedwith“TT.”between roll and strip[25]were taken into account in theseTable II.Chemical Compositions of the Niobium Steels Investigated(Group A)Steel Plant C Mn Si Nb Ti N*Al P S AA1TT Algoma0.050.350.0100.035—0.0040.0430.0080.006 AA2Algoma0.050.700.1000.053—0.0050.0450.0070.004 AA3Algoma0.060.700.1100.058—0.0050.0450.0080.004 AS1TT Sumitomo0.07 1.120.0500.0230.0160.0000.0290.0190.002 AS2TT Sumitomo0.09 1.330.0600.0360.0160.0030.0190.0170.020 AB BHP0.11 1.050.0100.031—0.0030.0400.0120.012 AD1Dofasco0.060.650.2250.020—0.0040.0350.0080.005 AD2Dofasco0.140.650.2250.020—0.0040.0350.0080.005 AD3Dofasco0.120.850.2250.020—0.0040.0350.0080.005 AD4Dofasco0.12 1.000.2250.020—0.0040.0350.0080.005 AD5Dofasco0.060.650.1150.030—0.0040.0350.0080.005 AD6Dofasco0.060.650.0100.030—0.0040.0350.0080.005 AD7Dofasco0.060.650.1150.045—0.0040.0350.0080.005 AD8Dofasco0.060.650.0100.045—0.0040.0350.0080.005 AD9Dofasco0.060.450.0100.008—0.0040.0350.0080.005 AD10Dofasco0.060.650.0100.008—0.0040.0350.0080.005 AD11Dofasco0.06 1.250.3250.0750.0240.0040.0350.0080.005 AD12Dofasco0.06 1.250.3250.080—0.0040.0350.0080.005 AM1“Davy”0.060.700.0700.050—0.0040.0510.0180.013 AM2“Davy”0.050.450.0200.020—0.0050.0470.0140.008 AU Usiminas0.110.540.0020.018—0.0040.0570.0140.008 *For the Dofasco grades,a mean value of40ppm N is listed here.The actual values are taken into account in the spreadsheets.Table III.Chemical Compositions of the Multiply-Alloyed and Plain C-Mn SteelsGroup Steel Plant C Mn Si Nb Ti Cr Mo V Ni N Al P S B BCM Sumitomo 0.280.520.220——0.830.15——0.0050.0260.0160.004BCMV Sumitomo 0.410.630.280—0.015 1.380.600.270.020.0060.0460.0130.001BCMVN Sumitomo 0.470.660.1700.0160.0160.980.970.120.460.0040.0420.0160.004CCA TT Algoma 0.030.270.010——————0.0040.0420.0080.010CS1TT Sumitomo 0.10 1.080.060——————0.0030.0200.0170.003CS2Sumitomo 0.450.760.210——————0.0050.0040.0170.004CD Dofasco 0.060.270.000——————0.0040.0350.0070.005CM “Davy”0.030.240.020——————0.0040.0420.0090.006CUUsiminas0.050.240.002——————0.0040.0300.0160.010calculations and were organized using MICROSOFT [1];here,the MFS (␴M )is a function of the strain,strain rate,temperature,and carbon content in weight percent.EXCEL*spreadsheet software.Some typical spreadsheet*MICROSOFT and EXCEL are trademarks of the Microsoft Corpora-␴M ϭexp ΂0.126Ϫ1.75C ϩ0.594C 2[1]tion,Redmond,WA.inputs and outputs are shown in Table IV .The same spread-sheet was used for the microalloyed Nb,multiply alloyed ϩ2851ϩ2968C Ϫ1120C 2T΃␧0.21␧˙0.13Cr-Mo,and plain C-Mn grades;this is because it does not consider microstructure but only mechanical parameters.According to the present method,the Sims formulation is employed to calculate and plot the MFS vs 1000/T for several bars.Because strip rolling reductions are applied at III.THE SUBMODELS APPLIED TO HOTSTRIP ROLLING various strains and strain rates,all the derived MFSs are“normalized”to ␧ϭ0.4and ␧˙ϭ5s Ϫ1.[27,28]An example of this approach for grade D5is illustrated A.The MFS Modelin Figure 3.It can be seen that Misaka’s equation overpre-dicts the MFSs obtained from the mill logs for this 0.03pct Improvement of the Misaka equationMisaka’s equation [26]has often been employed to specify Nb steel.On the other hand,it underpredicts the MFSs for some higher Nb grades.[28]The trend of the Misaka equation the MFS for C-Mn steels during hot strip rolling.It will be used here as the basis for a modified equation that takes fits the mill log values reasonably well in the region where the slope is quite shallow (i.e.,at low 1/T or high T values).into account the effects of different alloying elements,such as Mn,Nb,and Ti.The Misaka equation is displayed in Eq.This indicates that full SRX is occurring between the passesTable IV .Example of the Spreadsheet Calculations Carried Out Using the Mill DataInputs:Data from mill logsRoll Radius Roll Speed Width Gage TemperatureRoll Force Pass (mm)(rpm)(mm)(mm)(ЊC)(Tonne)————30.60——F139433.9126417.339872157F239154.5126410.799512223F338179.212647.429152116F4365119.01264 5.109071691F5363147.11264 3.908961357F6376167.21264 3.148841264F7378172.012642.618721627Outputs Hitchcock Forward Nominal Total Strain Rate Interpass 1000/T Sims MFS Pass R Ј(mm)Slip Factor Strain Strain*(s Ϫ1)Time (s)(K Ϫ1)(MPa)F1403 1.100.660.7512.9 3.480.79116F2412 1.090.550.6125.2 2.140.82151F3416 1.080.430.4841.3 1.480.84179F4402 1.080.430.4772.7 1.010.85151F5428 1.060.310.3494.20.790.86178F6472 1.050.250.271150.630.86185F75611.040.210.23131—0.87250*Includes the redundant strain.effects of the other elements are considered to be linear over their concentration intervals.**Comparison of Tables II and III indicates that the Eq.[2](group A)steels (Table II)have only half the average Si levels (about 0.11)compared to the Eq.[4](group B)steels of Table III (about 0.22pct Si).At the time this analysis was carried out,no account was taken of the Si levels on the MFS and,therefore,on the rolling load.In retrospect,however,this would have been desirable,as it appears from a study of the previous relations that the introduction of such a term may have permitted the use of a single set of coefficients.B.Modeling of Grain Size and Fractional SofteningDuring a particular pass of a rolling schedule,the sum ofFig.3—Comparison of Misaka’s equation and the present equation (MFS*)the retained and applied strains will determine which soften-based on chemical composition and fitted to the mill (Sims)data in the ing mechanism (SRX or DRX ϩMDRX)will operate.SRX region.Here,the mill data for grade AD5(0.03pct Nb)are corrected Depending on the type of softening,different equations are to a constant strain of 0.4and a constant strain rate of 5s Ϫ1.then employed to specify the grain size and fractional soften-ing.In this section,a method is described that can be used to follow the microstructural evolution during multipass roll-in this region.A solution-strengthening factor can,therefore,ing.For now,no attention is paid to the exact onset of DRX,be added that allows Misaka’s equation to fit all grades.For and the critical strain is simply taken as a fixed fraction of compositions AS1,AS2,and AB,for example,a correction the peak strain.The example given subsequently involves for solute strengthening due to the high Mn content (1.12,modeling microstructural evolution in a plain C-Mn grade,1.33,and 1.08,respectively),allows Misaka’s equation to and the critical strain is considered to be 0.8␧p .The onset fit the mill values.[28]Another correction is still required for of DRX in Nb steels is discussed in the next section,IIIC.the occurrence of strain accumulation and DRX,which leads During rolling,the temperature decreases continuously.to departures from Misaka-type behavior at high values of Thus,the temperature adopted for each interpass interval 1/T (i.e.,low T ).For this purpose,the model by Yada and is taken as the average of the prior and subsequent pass Senuma [29,30,31]was adapted and tested.[25,27,29]This pro-temperatures.This assumption is employed because the pres-duced the following final MFS equation:ent equations were derived for isothermal conditions and the interpass times are short enough to allow the use of a MFS ϩNbϭ(MFS Misaka (0.768ϩ0.51Nb ϩ0.137Mn [2]single temperature value.In the present work,the recrystallization and grain-size ϩ4.217Ti))ϫ(1ϪX dyn )ϩK ␴ss X dynrelations described subsequently were incorporated into the Here,X dyn is the softening attributable to DRX,␴ss is theMICROSOFT EXCEL spreadsheet software,as shown in steady-state stress,and K ϭ1.14is a parameter that converts more detail in Section IV .The submodels involved here flow stress to MFS.were assembled by following a method developed for rod Equation [2]is valid over the following concentration rolling.[11]The recrystallization kinetics equations used here ranges:0.020to 0.080pct Nb,0.35to 1.33pct Mn,and 0are adaptations of the Avrami–Johnson–Mehl–Kolmogorov to 0.024pct Ti.This approach has been used successfully equation,with parameters that were selected to fit the mill to calculate the MFSs in plain C-Mn [25,27]as well as in Cr-data.Mo steels,[27,32]and the respective equations are displayed 1.Softening between passesin Eqs.[3]and [4],respectivelyA softening model uses parameters such as strain,strain MFS ϩC-Mn ϭ(MFS Misaka (0.768ϩ0.137Mn))[3]rate,initial grain size,and temperature to decide upon the mechanism and calculate the extent of softening.In an HSM,ϫ(1ϪX dyn )ϩK ␴ss X dynthe softening between passes can be calculated with the aid of an MFS equation and temperature corrections.In the The Mn concentrations studied ranged from 0.27to 1.08present work,the microstructural evolution equations were pct.For the multiply alloyed steels,the following relation tested directly using the spreadsheet for the three groups of is applicable:[27,32]steels.The t 0.5equation selected for each group is shown in MFS ϩCr-Moϭ(MFS Misaka (0.835ϩ0.51Nb ϩ0.098Mn Table V .Note that Eq.[6]is the only one available for the DRX ϩ0.128Cr 0.8ϩ0.144Mo 0.3ϩ0.175V [4]kinetics of Nb steels.A similar expression is employed for ϩ0.01Ni))ϫ(1ϪX dyn )ϩK ␴ss X dynthe multiply alloyed grades,as derived in a recent study.[32]For the C-Mn steels,several equations are available;how-Equation [4]is considered to apply to the following composi-ever,the one developed by Hodgson et al.[33,36]provided the tion ranges:0.52to 0.66pct Mn,0to 0.08pct Nb,0.83tobest fit to the mill logs.1.38pct Cr,0to 0.46pct Ni,0.15to 0.97pct Mo,and 0to 0.27pct V .Due to the high maximum concentrations of Cr2.Strain accumulation between passesPartial recrystallization between passes results in retained and Mo,the solution effects approached “saturation;”this is why exponents are employed in this expression.Thestrain,which must be added to the strain applied in theTable V .Equations Describing the Softening KineticsGroup Type EquationReferenceASRX t SRX 0.5ϭ(Ϫ5.24ϩ550[Nb])ϫ10Ϫ18␧(Ϫ4.0ϩ77[Nb])d 20exp (330,000/R T )[5]33DRXt MDRX 0.5ϭ4.42ϫ10Ϫ7␧˙(Ϫ0.59)exp (153,000/R T )[6]34,35B SRX32t 0.5ϭ1.57ϫ10Ϫ14иd 20и␧Ϫ2.9exp ΂271,000R T ΃[7]DRX32t 0.5ϭ1.84ϫͫ␧˙иexp ΂330,000R T΃ͬϪ0.86exp΂271,000R T΃[8]C SRX32,36t SRX0.5ϭ2.3ϫ10Ϫ15␧Ϫ2.5d 20exp΂230,000R T ΃[9]DRX14t MDRX 0.5ϭ0.4΂␧˙иexp ΂300,000R T΃΃Ϫ0.8exp΂240,000R T΃[10]subsequent stand.The accumulated strain in pass i (i Ͼ1)is small,d 0i ϩ1will be close to the original grain size,d 0i ;in the latter case,the grains only change their shapes because then becomes [37]of the applied strain.[11]␧a i ϭ␧i ϩK acc (1ϪX i Ϫ1)␧i Ϫ1[11]b.Grain growth after recrystallizationwhere X is the fractional softening and K acc is a constant.After complete recrystallization,the microstructure is sub-The value of K acc was reported in the literature as falling jected to grain growth;this is driven by the decrease in free between 0.5and 1.[11,37]The parameter K acc can be related energy associated with the grain boundaries.For the group to the rate of recovery.High rates of recovery result in less A and B steels,one single equation (Eq.[19])was employed accumulated strain.This is clear from the work of Gibbs et to describe grain growth:al.,[37]where longer interpass times led to K acc ϭ0.5and shorter interpass times (less recovery)to K acc ϭ1.In the present hot strip model,the K acc constant is assumed to be d 4.5ϭd 4.50ϩ4.1ϫ1023ϫt ip[19]1and the accumulated strain is used in all the calculations.The latter is considered to represent the average strain pres-ϫexp (Ϫ435,000/R T )ent within the material.3.Grain-size evolutionAlthough the previous equation was derived for Nb steels,a.Recrystallized grain sizeit is used here to describe grain growth in the multiply This calculation simply takes into account the initial grain alloyed steels as well.This is due to the lack of an equation size,strain,and/or strain rate.The grain size after SRX is for the multiply alloyed grades,and because the alloying well known to be strongly dependent on the prior strain and elements present in the group B grades make it more rea-only depends on the strain rate to a minor extent.On the other sonable to adopt an equation derived for Nb steels than hand,the grain sizes after MDRX are strongly dependent on one derived for C-Mn grades.The grain-growth kinetics the strain rate.[14,15,34–36,38–41]The equations used here are in Nb and multiply alloyed steels are,of course,expected listed in Table VI.to be slower than in plain C-Mn compositions due to solute The grain size pertaining to the entrance of a given pass drag.For the group C (C-Mn)steels,however,a group of is considered to be the “initial”grain size (d 0).Note that equations is available to describe grain growth.The the equations used to model the recrystallized grain sizes method used here was proposed by Hodgson et al.[11,36,44]for the steels pertaining to groups A and B are the same;and is a “pragmatic”one,based on both laboratory [44]and this is due to the lack of appropriate equations for the multi-industrial [11]observations.ply alloyed steels.It should be noted that there is a large difference between In the case of incomplete recrystallization,the initial grain the rate of growth during the first second of the interpass size for the following pass (d 0i ϩ1)can be calculated using interval and the remaining time.This difference may arise the following relation,[11,33,43]which specifies a kind of because of the large driving force for grain growth present “average”derived from the freshly formed and original in the initially fine-grained structure.Another possible effect grain sizes:concerns the presence of “deformation”vacancies immedi-ately after rolling,which could accelerate growth.[45]This d 0i ϩ1ϭd rex i ϫX 4/3i ϩd 0i (1ϪX i )2[18]transition was handled by adopting different grain-growth exponents for each stage [11]and by using the following With this formulation,when X i is close to 1,the initial grainsize for the following pass is d rex i .On the other hand,if X iequations.Table VI.Equations Describing the Recrystallized Grain SizeGroup Type Equation Ref.A SRX d SRXϭ1.1иd0.670и␧Ϫ0.67[12]42DRX34d MDRXϭ1370ϫ␧Ϫ0.13exp΂Ϫ45,000R T΃[13]B SRX d SRXϭ1.1иd0.670и␧Ϫ0.67[14]41DRX35d MDRXϭ1370ϫ␧Ϫ0.13exp΂Ϫ45,000R T΃[15]C SRX33,36d SRXϭ343иd0.40и␧Ϫ0.5exp΂Ϫ45,000R T΃[16]DRX33,36d MDRXϭ2.6ϫ104и΂␧˙иexp΂300,000R T΃΃Ϫ0.23[17]SRX,t ipϽ1s[20]Eq.[3],based on the Misaka equation.The observed andpredicted MFSs are compared in Table VIII,where the differ-ences between the three sets of MFSs are also shown(in d2ϭd2SRXϩ4.0ϫ107(t ipϪ4.32t0.5)exp΂Ϫ113,000R T΃percentage).The“basic”version of the prediction spreadsheet MDRX,t ipϽ1s[21]described previously,allowing for strain accumulation andDRXϩMDRX,is considered to be fully applicable to the d2ϭd2MDRXϩ1.2ϫ107(t ipϪ2.65t0.5)exp΂Ϫ113,000R T΃group C(C-Mn)grades.However,for Nb steels,the criticalstrain for the initiation of DRX must be accurately known,and agreement regarding this quantity is lacking in the litera-SRX,t ipϾ1s[22]ture.The actual precipitation start time during hot strip roll-ing is also an unknown quantity.In the next two sections d7ϭd7SRXϩ1.5ϫ1027(t ipϪ4.32t0.5)exp΂Ϫ400,000R T΃(C and D),some improved methods for the estimation ofthese two parameters will,therefore,be proposed anddescribed for the Nb grades.MDRX,t ipϾ1s[23]d7ϭd7MDRXϩ8.2ϫ1025(t ipϪ2.65t0.5)exp΂Ϫ400,000R T΃ C.Critical Strain for the Initiation of DRX4.Design of the microstructural-predictionThe critical strain for the onset of DRX is an important spreadsheet parameter employed in the mathematical modeling of micro-The previous equations describing the microstructuralstructural evolution and of rolling load.Knowledge of the events can now be organized into a spreadsheet.Basically,critical strain for the initiation of DRX is a requirement for the spreadsheet parameters displayed in Table VII are usedprediction of the operating softening mechanisms in hot as input data to simulate the microstructural changes taking working processes.place during hot rolling,in a pass-by-pass analysis.TheFor the present purpose,it is useful to express the critical starting grain size(after roughing and before strip rolling)strain for the initiation of DRX(␧c)as a function of the is adopted as100␮m for the C-Mn grades and as80␮mpeak strain(␧p),as determined from a stress-strain curve. for the others.The subsequent grain sizes are calculated This is because several equations are available to specify after recrystallization and grain growth,and the results con-the peak strain as a function of initial grain size,temperature, stitute the input data for the next pass.Both the accumulated and strain rate for Nb steels.The␧c/␧p ratio often lies strain as well as the redundant strain are employed through-between0.67and0.86[46]and is generally considered to be out the calculations.Some typical inputs and outputs of the0.8for plain C-Mn steels.Previous workers have reportedvalues for Nb steels as low as0.65.[34]The effects of Nb, microstructural-evolution spreadsheet are given in Table VII.The following example uses data from the Dofasco HSM,Mn,and Si were taken into account in a recent investiga-grade CD.tion,[47]and a fit was found for the␧c/␧p ratio.The method In C-Mn steels,mechanisms such as carbonitride precipi-used was to test several possible values of␧c/␧p and then tation followed by strain accumulation do not take place,soto select the ratio that provides the best fit to the Sims MFS only SRX as well as DRXϩMDRX effects are considered curve.This procedure,thus,specifies the conditions underwhich DRX will occur.Over100mill logs were tested in here.The observed MFS is calculated using the Sims formu-lation(from the mill data).Then,predictions are made using this way using the grades listed in Table I.The resulting。

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Throughout the paper, the term "intensity of seed attack" is used to mean the proportion of seeds that have bruchid egg(s) on them, regardless of the fate of the developing insect(s). Thus, intensity is only an estimate of the number of seeds preyed upon by bruchids. Moreover, even those seeds in which bruchids have finished development may still germinate if the larvae have not eaten the embryo or most of the cotyledons (Lamprey et al. 1974), even though they will probably not produce a viable seedling.
Post-dispersal seed predation stu animals may modify the probability
* Present address andaddressfor offprint requests: Estaci6n Bioldgica de Dofiana, Apartado 1056, E-41080 Sevilla, Spain
Study site
The experiments were conducted in Santa Rosa National Park, Guanacaste province, in northwestern Costa Rica, during the dry seasons (January-May) of 1987 and 1988. Santa Rosa consists of about 10 800 ha of secondary deciduous forest, with small patches of semievergreen oak forest, and large artificial pastures or savannas on an upland plateau (at 300-350 m elevation). The savannas are dominated by Hyparrhenia rufa (Mees.), a grass introduced from Africa in the 1940 s. Clumps of Acacia farnesiana are abundant in these artificial grasslands. The climate and vegetation of the area are described in Hartshorn (1983).

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Damping Characteristics of Chlorobutyl Rubber/ Poly(ethyl acrylate)/Piezoelectric Ceramic/Carbon Black CompositesZhiyuan Liu,Yanyan Wang,Guangsu Huang,Jinrong WuCollege of Polymer Science and Engineering,State Key Laboratory of Polymer Material Engineering, Sichuan University,Chengdu610065,ChinaReceived7March2007;accepted28July2007DOI10.1002/app.27141Published online7March2008in Wiley InterScience().ABSTRACT:In this study,a new kind of damping com-posite consisting of chlorobutyl rubber,poly(ethyl acry-late),piezoelectric ceramic(PZT),and carbon black(CB) was prepared,and some efforts were made to characterize the damping behavior and explore the damping mecha-nism.The damping behaviors of the composites were mainly decided by the contents of CB and PZT.When an external vibration was exerted on the composites,the me-chanical energy of vibration was transformed into electric energy by PZT;if the resistance was adjusted to a suitable range by the variation of the CB content,the composites could behave as semiconductors:the electric energy could not be transferred to the surface of the material but rather was dissipated as thermal energy.For this system,when the contents of CB and PZT were between10and30vol %,respectively,the volume resistivity was between105 and109.5O cm,and a good damping performance could be achieved.On the basis of the results,a theoretical model is proposed to explain the damping performance of the composites.Ó2008Wiley Periodicals,Inc.J Appl Polym Sci 108:3670–3676,2008Key words:composites;elastomers;ﬁllers;functionaliza-tion of polymers;matrixINTRODUCTIONThe control of vibration and noise pollution has become an urgent task in modern society.For this purpose,developing a new style of damping mate-rial and researching the damping mechanism are strongly required.Currently,polymers are often used as damping materials because of their visco-elasticity,but they also have some disadvantages. First of all,the damping range of homopolymers is generally20–308C because of their narrow glass-tran-sition region,which is not broad enough for practi-cal applications.Second,damping materials derived from polymers often exhibit a strong dependence on the temperature or frequency,and they hardly keep an even damping property in their functional area.A lot of methods,such as polymer blends,interpene-trating networks,and copolymers,1–5have been suc-cessfully developed to broaden the effective damp-ing range of polymers and to modify the depend-ence of damping behaviors on the temperature and frequency.However,there are few results yet that can broaden the transition peaks and at the same time retain a high loss factor.Recently,some studies have been carried out on piezoelectric composite materials6–12and on organic hybrids consisting of polymers and small molecules.13,14As far as organic hybrids are concerned,the weakness of the intermo-lecular hydrogen bond can easily lead to phase sepa-ration during the application process,which limits their usage in long-term service,whereas piezoelec-tric composite materials do not have such a disad-vantage.Piezoelectric ceramic(PZT)is a kind of material that has the ability to transform vibration and noise into electric energy.If PZT is pressed or pulled in a speciﬁc direction,a positive electrical charge or a negative one,respectively,will appear on the surfa-ces,and the electrical charge density has a propor-tional relationship with the stress intensity;this is called the piezoelectric effect.However,the hard and crisp properties of PZT limit its applications. Fortunately,Newnham et al.15in1978put forward a novel idea for a piezoelectric composite.According to the approach,PZT andﬂexible polymers are mixed with each other by certain combination meth-ods to obtain a piezoelectric composite with a certain mass ratio and a certain space distribution to take advantage of the two kinds of materials,which com-pensate each other and have good synthesis proper-ties.As a new kind of damping material,a piezo-electric composite overcomes the weakness that properties of polymers heavily depend on the tem-perature and frequency and avoids the disadvantage that PZT is hard,frail,and not easily processed,pre-serving the advantages of the two materials.Correspondence to:G.Huang(polymer410@). Journal of Applied Polymer Science,Vol.108,3670–3676(2008)Research on the relation between the damping prop-erty and electric resistance shows that a certainmatched electric resistance is necessary for a piezo-electric composite to have a high damping prop-erty.16Therefore,it is possible to control the damp-ing property of piezoelectric composites by changes in the quantity of carbon black(CB).17,18In our previous study,19poly(ethyl acrylate)(PEA)was used to successfully broaden the effective damp-ing region of chlorobutyl rubber(CIIR)to the room-temperature region,but it was found that the loss fac-tor of CIIR/PEA blends was not high enough and,moreover,its dependence on temperature(or fre-quency)was not completely overcome either.In this work,to enhance the damping property of CIIR/PEAblends,PZT and CB were added to prepare CIIR/PEA/PZT/CB composites,and the effect of the PZTand CB contents on the damping property of piezo-electric composites was studied intensively.EXPERIMENTALMaterials and preparationCIIR(Exxon1068),with a Mooney viscosity andchlorination concentration of ML114(1258C)545–55and 1.1–1.3wt%,respectively,was produced byU.S.Exxon Co.(Supplied by Exxonmobil ChemicalServices Co.,Ltd.,Shanghai,China)PZT was sup-plied by Shandong Guoteng Functional Ceramic Co.,Ltd.(Dongying,Shandong,China).PEA was synthe-sized by emulsion polymerization with a K2S2O8–FeSO4redox initiator system at a temperature of25 628C.When the reaction wasﬁnished,PEA was obtained by the breaking of the emulsion,coacerva-tion,and drying.Phenol–formaldehyde resin(PR201),which was used as the cocuring agent of CIIR and PEA,was offered by Chongqing Resin Plant of China(Chongqing,China).Other chemicals, such as ZnO,MgO,CB,and stearic acid,were com-mercially available.PZT with alcohol was lapped in a ball mill to beshattered for48h and then was cooled and kept atroom temperature for24h.After most of the alcoholspontaneously vaporized,PZT was sieved through a net of400eyes,and this was followed by vacuum drying.PEA was blended with CIIR in a ratio of30/ 70(wt%)by a twin-roll mill for20min at1608C. After cooling,PZT,CB,PR201,and other accelerating agents were added at room temperature.The resulting blends were then vulcanized at1608C under a pres-sure of10MPa for20min.The vulcanized sheets were directly cut into certain pieces for the analysis. Electric resistance testFor the high-electric-resistance sample,the electricresistance was measured with a model ZC36megger (Shanghai Precise Scientiﬁc Instrument Co.,Shang-hai,China).For the low-electric-resistance sample, the four-electrode test method was adopted accord-ing to the American National Test Standards. Vibration analysisThe vibration performance of the composites was an-alyzed with a model3652dynamic signal analyzer (Hewlett–Packard Co.,USA)as follows:1.The vulcanized sheets were cut into6035033mm3samples,which were thenﬁxed at one end to an iron stand,and theﬁxed-frequency knock was exerted through the running of an electric engine.Through a sensor on the dynamic signal analyzer,the vibration decay time of the composites was recorded after the removal of the external force.2.The vulcanized sheets were cut into6031633mm3samples.Both ends of the samples were ﬁxed on self-made tongs,and a cork ball with a radius of5mm was allowed to fall freely from 1m high down to the middle of the samples;then,the vibration decay time of the samples was measured by a sensor after the cork ball was removed.RESULTS AND DISCUSSIONInﬂuence of PZT on the damping property of the compositesThe piezoelectric composite is a new kind of damp-ing material,whose damping function mainly origi-nates from three parts:the viscoelastic damping of the polymer(a),the friction damping between the polymer andﬁllers orﬁllers themselves(b),and the piezoelectric damping of PZT(g).As for g,there are two steps of the energy dissipation process,which are shown as follows:Mechanical energyÀ!PZT Electric energyÀÀÀÀÀÀÀÀÀÀÀÀÀ!PowerÀwasting unitThermal energyTherefore,the damping property of piezoelectric composites initially depends on the conversion between the mechanical energy and electric energy. Figures1and2show the vibration attenuation of the composites with PZT contents of0and30vol%, respectively,under the condition of the cork ball bumping.From a comparison of Figures1and2,it is evident that with the10vol%content of CB unchanged,the vibration attenuation time of theCIIR/PEA/PZT/CB COMPOSITES3671Journal of Applied Polymer Science DOI10.1002/appsample with 30vol %PZT was shorter than that of the other sample without PZT.Therefore,adding the proper amount of PZT can decrease the vibration attenuation time and improve the damping property of piezoelectric composites.Figures 3and 4show the inﬂuence of the PZT content on the attenuation time of the composites knocked at a certain frequency and with a cork ball,respectively.It can be observed in both Figures 3and 4that with increasing PZT,the attenuation time of the composites shows a trend of descending ini-tially but rising subsequently and exhibits a mini-mum at a PZT content of 30vol %.The reason can be expressed as follows:as the content of PZT increases,PZT and CB will match better and better,and g and b rise,although a decreases,and D a is smaller than D b 1D g .Consequently,the integrated damping (a 1b 1g )goes up,and at the point of30vol %PZT,the piezoelectric composite attains the highest value.With the content of PZT further grow-ing,b keeps on going up;however,because the con-tent of CB is constant,the increase of g is limited,whereas a descends much at the same time.In other words,D a is much bigger than D b 1D g .As a result,a 1b 1g drops,whereas the attenuation time increases.On the other hand,too much PZT will result in excessive cost (because of its high price)and a reduction of the mechanical properties of pie-zoelectric composites because the material becomes too hard and crisp.Therefore,30vol %PZT is very condign.In addition,the PZT particles also have a certain inﬂuence on the volume resistivity of the composites,as shown in Figure 5.Under the same condition of 10vol %CB,with an increase in PZT,thevolumeFigure 1Attenuation time of the sample with 10vol %CB and withoutPZT.Figure 2Attenuation time of the sample with 10vol %CB and 30vol %PZT.Figure 3Inﬂuence of the PZT content on the damping time of composites with 10vol %CB under a knocking frequency of 50Hz.Figure 4Inﬂuence of the PZT content on the damping time of composites with 10vol %CB during knocking with a cork ball.3672LIU ET AL.Journal of Applied Polymer Science DOI 10.1002/appresistivity of the composites goes down.However,the trend of the volume resistivity,which decreases lentamente with increasing PZT,is different from that with increasing CB (as shown later in Fig.10).This is because PZT is a kind of semiconductor,and its conduction property is better than that of a rub-ber matrix but poorer than that of CB.Inﬂuence of CB on the damping property of the compositesAs mentioned previously,the second step of energy dissipation in the piezoelectric composite is the elec-tric energy/thermal energy conversion,for which CB,as a primary electric ﬁller in the composite whose dosage is directly related to the conductivityand conversion of electric power,is one of the most important factors that affect the damping property.Figures 6and 7show the vibration attenuation of the composites with CB contents of 0and 15vol %,respectively,under the condition of the cork ball bumping.From a comparison of Figures 6and 7,it can be seen that with 40vol %PZT kept constant,the vibration attenuation time of the sample with 15vol %CB is evidently shorter than that of the sample without CB.Therefore,it is clear that adding an opportune content of CB can decrease the vibration attenuation time of the piezoelectric composite and improve its damping property.Figures 8and 9indi-cate the inﬂuence of the CB content on the attenua-tion time of the samples knocked with a certain fre-quency or a cork ball.With increasing CB,theFigure 5Change of the volume resistivity (R v )of piezo-electric composites with the PZT content varying from 0to 60vol %and with CB remaining at 10vol%.Figure 6Attenuation time of a sample with 40vol %PZT and withoutCB.Figure 7Attenuation time of a sample with 40vol %PZT and 15vol %CB.Figure 8Inﬂuence of the CB content on the attenuation time of composites with 40vol %PZT under a knocking frequency of 50Hz.CIIR/PEA/PZT/CB COMPOSITES 3673Journal of Applied Polymer Science DOI 10.1002/appattenuation time decreases ﬁrst but rises afterward,and a minimum valley around 10vol %CB can be observed.When the CB and PZT particles are mixed together in the matrix,they are made of small loops;only when the volume resistivity of the composite is appropriate can every small loop become a power-wasting unit,and so it can function as the conver-sion unit from electric energy to thermal energy.Therefore,for these systems,with 10vol %CB,CB and PZT particles get in touch with each other and form conducting electric networks with appropriate electric resistance,by which the electric energy can be converted to thermal energy.To understand the effect of the CB content on the attenuation time of piezoelectric composites,the rela-tion between the CB content and electrical resistivity has been investigated,as shown in Figure 10.It is obvious that the electrical resistivity displays a declining trend with increasing CB.At the begin-ning,because the content of CB is small,its particles are scattered in the composite,and the electric net-work does not form yet;thus,the piezoelectric com-posite is in the situation of an opening circuit,and the volume resistivity is relatively high and shows a slight decrement with increasing CB loading.When the CB content goes up to 5vol %,the volume resis-tivity decreases slowly;at a certain time when CB reaches one certain critical density (10vol %or so),ﬁllers form electric networks at the moment,and the mass resistivity goes down rapidly.When the con-tent of CB varies from 5to 15vol %,ﬁller particles come into contact with one another,and they induce the galvanic circle ultimately.Beyond 15vol %CB,although the density of electric networks becomesbigger,a further increase in CB can raise the conduc-tivity only slightly for it exceeds the threshold.Therefore,the electric resistivity can be controlled through changes in the volume content of CB,which is a valid method to raise the power-wasting ability and the damping property.If R denotes the electric resistance of the compos-ite,C denotes the capacitance of PZT,and x denotes the vibration frequency,then R 51/x C is the best matching condition for the composite.Connecting Figures 8–10,we can see that when the content of the CB is between 5and 15vol %,the vibration attenuation time is shorter.Under this circumstance,the value of the logarithm of the volume resistivity is 2.5–9.5,so the matching mass resistivity of the composite is 102.5–109.5O cm.This scope,including the critical point of varying mass resistivity,is the most changeful district.Theoretical model for the piezoelectric composites To gain insight into the damping mechanism of pie-zoelectric composites,a theoretical model is brought forward according to the experimental results.As the scheme of Figure 11shows,when a sample is subjected to ﬁxed-frequency knock,the combination damping property (a 1b 1g )of the material climbs up to a maximum but slides down along with CB increasing.If a composite does not contain CB,only a and a small amount of b contribute to the damping func-tion (from PZT,ZnO,etc.).PZT in the composite can transform mechanical energy into electric powerbutFigure 9Inﬂuence of the CB content on the attenuation time of composites with 40vol %PZT during knocking with a corkball.Figure 10Change of the volume resistivity (R v )of piezo-electric composites with the CB content varying from 0to 30vol %and with PZT remaining at 40vol %.3674LIU ET AL.Journal of Applied Polymer Science DOI 10.1002/appcannot implement the conversion between electric power and heat energy because it lacks the function of a conductive body;consequently,the system has no g .When the CB density is lower than 5vol %,the matrix and ﬁllers cannot contact each other well,and this leads to its poor conductance,as shown in Figure 12(a).Under this circumstance,the piezoelec-tric composite behaves like an open circuit,so electric energy also cannot be transported into the matrix and thus cannot be converted into the thermal energy well;as a result,it can be saved only in the PZT par-ticles,which obstruct the conversion between electric energy and thermal energy.Hence,as the CB content varies from 0to 5vol %,a goes down gradually,b goes up,and g can be neglected.As a result,an increasing trend of a 1b 1g can be observed.As CB rises above 5vol %,the ﬁller particles grad-ually get in touch with each other,leading to the for-mation of the electric networks,as shown in Figure 12(b).Like metallic networks,these electric networks run through the whole polymer matrix and become electric routes to conduct electric energy.At the same time,because of the large electric resistance of the material,the energy cannot be conducted to the surface directly but rather is converted to thermalenergy in the composite.Thus,a and b show the same tendency as the former stage,but g is greatly enhanced.With a further increase in CB,ﬁller particles come into intimate contact with one another,and the elec-tric network becomes more and more compact,as shown in Figure 12(c);this makes the electric resist-ance of the composite become smaller and smaller.Therefore,a short circuit in the piezoelectric compos-ite gradually is formed (>15vol %CB),which can conduct electric energy to the composite surface quickly,it being equal to connect the ground,at which the electric energy cannot be converted into the thermal energy;as a result,g decreases greatly.At the same time,a goes down and b goes up.As a result,a 1b 1g is depressed from the maximum.In a word,by the variation of the CB content,the composite can transform from an open circuit to a loop circuit to a short circuit;and within the scope of the loop circuit,the piezoelectric composite can carry out the conversion of mechanical energy to electric energy to thermal energy.CONCLUSIONSIn this work (for purpose of damping applications),CIIR/PEA/PZT/CB composites were prepared.The results from research on the properties of the com-posites show that the damping behavior of the com-posites strongly depends on the contents of CB and PZT,and when the contents of CB and PZT are between 10and 30vol %,the volume resistivity of the materials is between 105and 109.5O cm,and a good damping performance can be achieved.There-fore,by the adjustment of the electrical resistance to a suitable range by the variation of the CB content,the composites can behave as semiconductors,in which the electric energy is not transferred to the surface of the material but rather is dissipated as thermal energy.According to the results,a theoreti-cal model based on an open circuit to a loop circuit to a short circuit has been proposed to explain the damping performance of the composites.References1.Min,B.G.;Stachurski,Z.H.;Hodgkin,J.H.;Heath,G.R.Polymer 1993,34,3620.2.Fay,J.J.;Murphy,C.J.;Thomas,D.A.;Sperling,L.H.Polym Eng Sci 1991,31,1731.3.Foster,J.N.;Sperling,L.H.J Appl Polym Sci 1987,33,2637.4.Hourston,D.J.;Aughes,I.D.J Appl Polym Sci 1977,21,3487.5.Chang,M.C.O.;Thomas,D.A.;Sperling,L.H.J Polym Sci Part B:Polym Phys 1988,26,1627.6.Uchino,K.;Ishii,T.Jpn Ceram Soc Scholarly Pap Mag 1988,96,863.7.Sumita,M.;Gohda,H.;Asia,S.;Miyasaka,K.;Fukuda,A.;Suzuki,Y.;Utino,K.Macromol Rapid Commun 1991,12,657.Figure 12Schematic representations of the circuit models:(a)open circuit,(b)loop circuit,and (c)shortcircuit.Figure 11Schematic representation of the effect of CB on the volume resistivity and damping performance of the composites.CIIR/PEA/PZT/CB COMPOSITES 3675Journal of Applied Polymer Science DOI 10.1002/app8.Sumita,M.Shinsozai1993,4,66.9.Asai,S.;Nakashima,M.;Sumita,M.;Kaneko,H.;Kaneko,I.;Ohhira,Y.;Hori,M.J Mater Sci Jpn1997,34,244.10.Sumita,M.Koubunshi1997,46,116.11.Sumita,M.Funct Mater1995,15,12.12.Akasaka,S.;Sumita,M.;Date,M.;Tokushima,T.Meet PolymMater Forum Text Soc Polym Sci Jpn1997,6,165.13.Wu,C.Y.;Qian,S.Y.;Wu,C.F.J Funct Polym2005,4,586.14.Zhou,X.Q.;Wu,C.F.Chin J Nonferrous Met2004,2,232.15.Newnham,R.E.;Schembeim,J.I.;Lee,J.W.J Intell MaterSyst Struct1993,7,289.16.Hagood,N.W.;Flotow,A.von.J Sound Vibr1991,146,243.17.Sumita,M.;Gohda,H.;Asai,S.;Miyasaka,K.;Furuta, A.;Suzuki,Y.;Uchino,K.Macromol Rapid Commun1991,12, 657.18.Hori,M.;Aoki,T.;Ohira,Y.;Yano,pos A2001,32,287.19.He,X.R.;Huang,G.S.;Wang,J.H.China Synth Rubber Ind2005,28,44.3676LIU ET AL. Journal of Applied Polymer Science DOI10.1002/app。

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新世纪研究生公共英语教材阅读A学生用书第二版-Unit9-14选词填空-无答

新世纪研究生公共英语教材阅读A学生用书第二版-Unit9-14选词填空-无答研究生阅读实战技巧研究生英语是考研的重点科目之一，阅读理解是其中重要的一部分。

为了帮助研究生考生提高英语阅读水平，新世纪研究生公共英语教材阅读A学生用书第二版-Unit9-14选词填空的练习非常有助于提高学生的阅读理解能力。

本文将从理解选词填空的策略、解题技巧以及日常练习方法等方面详细分析，为学生们提供实用的阅读实战技巧。

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在文章中，选项往往会与上下文的特定信息相对应，学生们可以通过查找上文或下文中与选项相关的内容来判断选项的适配度。

解题技巧二是注意排除法。

当学生们无法确定答案时，可以通过排除一些明显不相关的选项来缩小范围，从而提高答案的准确性。

这些解题技巧能够帮助学生们更有效地解决选词填空题。

此外，在日常学习中，学生们需要进行系统的练习以提高阅读理解能力。

首先，学生们可以积极阅读英文文章，扩充词汇量和阅读速度。

阅读时，学生们应该学会用一定的节奏阅读，避免对每个单词都进行深度解读。

其次，学生们可以进行针对性的练习，通过选词填空的练习题来提高解题速度和准确性。

这些练习能够帮助学生们熟悉题型并掌握解题技巧。

此外，学生们还可以参加一些英语阅读理解的模拟考试，通过模拟考试可以让学生们对自己的考试准备情况进行评估并找到不足之处。

总之，通过掌握选词填空题的策略和解题技巧，以及进行系统的练习，研究生们可以有效地提高英语阅读理解能力，更好地应对考研。

新世纪研究生公共英语教材阅读A学生用书第二版-Unit9-14选词填空的练习是一个很好的方式，帮助学生们熟悉题型并提高解题能力。

fulltext

J Cancer Res Clin Oncol (2009) 135:1777–1782DOI 10.1007/s00432-009-0624-2ORIGINAL PAPERGambogic acid reduced bcl-2 expression via p53 in human breast MCF-7 cancer cellsHongyan Gu · Shuyun Rao · Jie Zhao · Jia Wang ·Rong Mu · Jingjing Rong · Lei Tao · Qi Qi ·Qidong You · Qinglong GuoReceived: 2 February 2009 / Accepted: 8 June 2009 / Published online: 7 July 2009© Springer-Verlag 2009AbstractPurpose In this study, we investigated the correlation between p53 and bcl-2 in gambogic acid (GA)-induced apoptosis.Method MTT assay was employed to evaluate MCF-7 cell viability after GA treatment. Cell morphological changes were observed follow-up under the inverted micro-scope after GA withdrawal. To observe the cell apoptosis, DAPI staining was used. Meanwhile, p53 small interfering RNA (si-RNA) was adopted to knock p53 down. All expressions of p53 and bcl-2 were evaluated by Western blot analysis.Results MTT assay showed that GA inhibited MCF-7 cell growth e V ectively in a time-dependent manner. With 0.5h GA treatment, p53 was signi W cantly increased, whereas bcl-2 was reduced potently with 6h GA treatment. After GA withdrawal, p53 expressions were maintained in high levels. Furthermore, bcl-2 decreasing was attenuated after co-treatment with PFT alpha, a p53 transcription blocker. Same result was observed after p53 knock-down by p53 si-RNA.Conclusions Gambogic acid induced human breast cancer cells MCF-7 apoptosis by reducing bcl-2 expression via p53.Keywords Gambogic acid · P53 · Bcl-2 · Growth IntroductionWild type p53 (Wtp53), a critical tumor suppressor, has been found to modulate lots of biological processes includ-ing DNA repair, apoptosis, cell cycle, angiogenesis and mobility, autophagy, and glycolysis (Gu and Guo 2007). Di V erent stress signals, such as DNA damage, hypoxia, heat shock, and activation of oncogene increase the p53 sta-bility (Michael and Oren 2003; Tomita et al. 2006). As a transcriptional promoter, p53 a V ects transcription of a vari-ety of genes transcription including bcl-2, bax, p21WAF/ CIP1, and gadd45 and thereby results in apoptosis or cell cycle arrest (Gu and Guo 2007; Tomita et al. 2006).Gambogic acid (GA, C38H44O8, Fig.1a) is one of the active components that secreted from garcinia hanburryi hool.f., which mainly grows in South China, Cambodia, Vietnam, and Thailand (Yang et al. 1994). High purity of GA was obtained (¸98%) using a novel method (Liu et al. 2004a). Previously our lab and other groups showed that GA inhibited tremendous cancer growth including mice H22, EC and S180 cancer (Gu et al. 2008a, b), human hepa-tocarcinoma, gastric carcinoma, lung carcinoma (Wu et al. 2004; Zhao et al. 2004). Recently, a lot of data supported that GA mediates some crucial steps in carcinogenesis. YuElectronic supplementary material The online version of this article (doi:10.1007/s00432-009-0624-2) contains supplementary material, which is available to authorized users.H. Gu · S. Rao · J. Zhao · J. Wang · R. Mu · J. Rong · L. Tao · Q. Qi · Q. You (&) · Q. Guo (&)Jiangsu Key Laboratory of Carcinogenesis and Intervention, China Pharmaceutical University, P.O. Box 209,24 Tongjia Xiang, 210009 Nanjing, Jiangsu, Chinae-mail: anticancer_drug@H. GuBeijing Shijitan Hospital, 100038 Beijing, ChinaS. RaoDepartment of Molecular and Cellular Pharmacology, University of Miami School of Medicine,1600 NW, 10th Ave, Miami, FL 33136, USAshowed that GA arrested cancer cell growth in G2/M phase through disturbing phosphorylation of CDC2/p34 (Yu et al.2007). Zhao reported that GA inhibited telomerase activi-ties through repressing hTERT post-transcriptions (Zhao et al. 2008). GA was also shown to suppress angiogenesis through acting on human umbilical vein endothelial cell receptor (Lu et al. 2007) and inhibited cancer cell growth by repressing human topoisomerase II alpha activity (Qin et al. 2007). Furthermore, GA triggered mitochondrial dependent- and independent-apoptosis pathways by combi-nation with transferrin as its receptor (Kasibhatla et al.2005; Pandey et al. 2007). Apparently, GA inhibits tumor cell growth via a multi-mechanism manner.Our group observed lower toxicity of GA on the normal cells than that in the cancer cells (Guo et al. 2006; Yang et al. 2007). Currently, GA has been evidenced as a potent p53 inducer to trigger cancer cell apoptosis (Gu et al.2008a , b ). As Zhai D et al studied, GA was an inhibitor of the anti-apoptotic Bcl-2 family proteins (Zhai et al. 2008).So, in this report, we focused on studying the correlation between p53 and bcl-2 in apoptosis induced by GA.Materials and methods ReagentsThe gamboge resin (lot# 20000526) of G. hanburyi, was purchased from Jiangsu Provincial Medicinal Materials Company, China. GA was then isolated and puri W ed according to the established methods (Zhang et al. 2004).The purity of GA used in all experiments was achieved more than 95% (Liu et al. 2003). GA was solubilized in dimethylsulfoxide (DMSO) to a W nal stock concentration of 10mM and stored at ¡20°C. Pi W thrin-alpha (PFT-alpha, p53 transcriptional inhibitor) from Sigma-Aldrich Inc. (St. Louis, MO) was prepared according to the manufacture instructions. P53 si-RNA and its control were purchased from Santa Cruz Biotechnology Inc.(Santa Cruz, CA). All the agents used above were diluted in the corresponding culture medium to the destinedconcentration before used. DMSO was used as a solvent control.Cell lines and cultureHuman breast cancer MCF-7 cells containing wtp53expressions were obtained from cell bank of Shanghai insti-tute of Biochemistry and Cell Biology. Cells were cultured in the RPMI 1640 medium (Gibco, Grand Island, NY) sup-plemented with 10% heat-inactivated fetal bovine serum (FBS, by Sijiqing Company Ltd., Hangzhou, China) and sodium bicarbonate (2.2%, w/v) and incubated in a stable environment with 5% CO 2 at 37°C in a humidi W ed incuba-tor (310/Thermo, Forma Scienti W c Inc., Marietta, OH).Cell viability assaysCells viabilities were measured by colorimetric assay using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazol-iumbro-mide (MTT) (Roche Ltd., Nutley, NJ). The method was performed as previous description (Wu et al. 2004). MCF-7cells were administered to GA for indicated time. After incubation for 48h, absorbance (A ) was measured at 570nm. Survival ratio (%) was calculated following the equation: Survival ratio (%)=(A treatment /A control )£100%.Cell morphological assessmentExponentially growth cells were dispersed to prepare the 1£106 per ml cell suspension. After treatment with GA for 6h, cells were observed under the inverted microscope (Olympus, Japan).DAPI stainingCancer cells were inoculated onto glass coverslips in a six-well plate. Twenty-four hours later, cells were treated with GA for 6h. After washing three times with PBS, the cells were W xed in 4% formaldehyde for 30min, permeabilized with 3% Triton X-100 for 30min. Nucleus was then stained by 4Ј, 6-diamidino-2- phenylindole (DAPI, Sigma),Fig.1a The molecular struc-ture of GA. b GA inhibited MCF-7 cell growth potently in a time dependent-manner. MTT assay was performed as shown in Materials and methods . Data were plotted as mean §SE (n =3)mounted by neutral gum, and examined under the X uores-cent inverted microscope. Apoptosis cells were counted during 100 of cells per region. Normally W ve regions were counted respectively and average apoptosis cells were calculated. Apoptosis rate was obtained following the equation: Apoptosis rate (%)=Average apoptosis cells/ 100£100%.P53 si-RNA transfectionP53 si-RNA and control si-RNA were purchased from Santa Cruz Biotechnology Inc. Transient transfection was performed by manufacture’s instructions of lipofectamine 2000TM reagent (Invitrogen, San Diego, CA). After that, GA was treated and lysates were prepared. Western blot analysis was performed as below.Western blotWestern blot assay was performed mainly as previous description (Yu et al. 2007) with anti-p53 (Ab-6) monoclo-nal (Calbiochem, La Jolla, CA), anti-bcl-2 (Santa Cruz, CA) and beta-actin monoclonal antibodies (Santa Cruz, CA) followed by IRDye TM800 conjugated with anti-mouse IgG antibody (LI-COR Biosciences, Lincoln, Nebraska) incubation and visualized by odyssey infrared imaging sys-tem (LI-COR Biosciences, Lincoln, Nebraska).Statistical analysisAll data were expressed as means§SD or means§SE (Cumming et al. 2007) and statistically compared by one-way ANOVA. Triplicate experiments were performed in a parallel manner.ResultsGA inhibited cancer cell growth e V ectivelyBased on the previous IC50 of GA on MCF-7 cells (Gu et al. 2008a, b), we used 4 M GA for these studies. MCF-7 cells were treated with 4 M GA for indicated period and results were shown in Fig.1b. GA inhibited MCF-7 cell growth at 48h, achieved its maximum e V ect at 72h with a time-dependent manner.GA inhibited cell growth irreversiblyTo demonstrate that whether cell growth will be recovered after GA withdrawal, cells were treated with 4 M GA for 6h and replaced with fresh culture medium. Cell growth was then observed at 0.5, 3, 6, 12, 24, and 48h after GA withdrawal. As shown in Fig.2a, cell growth was repressed in response to 6h GA treatment. Six hours after GA with-drawal, cells were observed to turn round and X oat gradu-ally. Twenty-four hours later, most of cells died, which suggested that cell growth inhibition caused by GA was irreversible.High levels of p53 were maintained up to 6hafter GA withdrawalIn this study we also evaluated p53 expressions after GA withdrawal. Cells were treated with 4 M of GA for 6h and then supernatant was replaced with fresh culture medium. As shown in Fig.2b, GA increased p53 expres-sion levels and this increased p53 expression was main-tained even after GA withdrawal at 6h. Twelve hours later, p53 protein degradation was observed which may due to the cell death as shown in Fig.2a. All the results strongly indicated that GA signi W cantly increased p53 expressions irreversibly.P53 played a key role in GA-triggered apoptosisAfter MCF-7 cells were transfected with p53 si-RNA or control si-RNA, GA was treated for 6h and then DAPI staining was performed. As shown in Fig.3a, in the mock group, nuclei was condensed and presented strong blue staining after GA treatment under the X uorescent inverted microscope, suggesting apoptosis occurrence. In contrast, reduced blue staining was observed in the nuclei after p53 was knocked down by si-RNA. Correspondingly, we counted apoptosis cells in 100 cells among W ve areas under the inverted microscope and calculated the average apopto-sis rate (%). As shown in Fig.3b, after p53 was knocked down, the numbers of apoptosis cells that induced by GA were dramatically decreased compared to that in the mock group (10.2 vs. 29.6%), implying the key role of p53 in GA-stressed apoptosis in MCF-7 cells.GA inhibited bcl-2 expression via p53 enhancement Since GA-trigged apoptosis is tightly associated with bcl-2 related mitochondria-dependent apoptosis pathway, we fur-ther study the connection between p53 and bcl-2 after GA treatment. MCF-7 cells were exposed to 4 M of GA for indicated period and the expression levels of p53 and bcl-2 were evaluated. As shown in Fig.4a, p53 expression was up-regulated as early as 0.5h after GA treatment, whereas repression of bcl-2 was not able to be detected until 6h, which suggested that bcl-2 alteration occurred after p53 up-regulation.Moreover, to con W rm the results obtained above, p53 expression was inhibited by 10 M of PFT alpha, a p53Fig.2a E V ect of GA onMCF-7 cell growth after GA withdrawal. After administered to cells for 6h, GA was taken away and fresh culture medium was supplied. Cell growth was then detected at 0.5, 3, 6, 12, 24, and 48h under the inverted microscope. b E V ect of GA on p53 expression after GA with-drawal. After 6h treatment, GA was taken away and fresh culture medium was supplied. P53 expression was detected at 0, 6, 12, and 24h by Western blot assayFig.3E V ect of GA on cellapoptosis with p53 knockdown by si-RNA. a Cells with DAPI staining was observed under the X uorescent inverted microscope.b Apoptosis rate that calculated according to the formula described in Materials and methodsblocker (Liu et al. 2004b), or p53 si-RNA. As shown in Fig.4b, c, we failed to observe the bcl-2 reduction after GA treatment. All these results demonstrated that bcl-2 down-regulation resulted from p53 enhancement induced by GA. DiscussionGambogic acid is known as an anticancer compound since it was characterized to be an apoptosis inducer. Induction of mitochondrial-dependent and -independent apoptosis path-way by GA had been evidenced before (Pandey et al. 2007; Zhao et al. 2004). As a broad-spectrum repressor of cancer cell growth, GA inhibited MCF-7 cell growth in a time- and concentration-dependent manner (Gu et al. 2008a, b). In this study, we demonstrated that GA induced human breast can-cer cells MCF-7 apoptosis by reducing bcl-2 expression via p53 and highlighted the importance of p53 in GA induced cell apoptosis. Since the 50% inhibiting concentration (IC50) of GA to MCF-7 cells was approximately 4 M (Gu et al. 2008a, b) and this concentration of GA caused less cell death but was su Y cient to enhance p53 expression (see Fig. S1 in Electronic Supplementary Material) compared to the higher concentration such as 8 M, we decided to use 4 M GA as the optimal experimental condition.Currently, Zhai et al had shown that GA inhibited bcl-2 family members by competing for BH3 binding (Zhai et al. 2008) and induced cell apoptosis by repressing bcl-2 expression (Liu et al. 2005; Zhao et al. 2004). As is well known, in mitochondria-dependent apoptosis pathway,decreased bcl-2 expression correlates with cytochrome c release and then results in an apoptosis cascade reaction (Smith et al. 2008). Here we found that GA inhibited bcl-2 expression via increasing p53 which was supported by the results that GA modulated p53 before bcl-2 and bcl-2 repression was attenuated dramatically when GA was blocked by PFT alpha or by p53 si-RNA.As an apoptosis inducer, p53 caused cell growth arrest, apoptosis, and senescence in response to various types of stimuli (Li et al. 2003). Recently it was reported that p53 was associated with cancer cell metastasis, metabolism, and small G protein signal transduction (Xia and Land 2007; Roger et al. 2006). Without doubt, p53 has been regarded as a comprehensive and valuable target in cancer research. Consistent with our previous studies, we observed that GA up-regulated p53 expression potently and this high expres-sion level of p53 was maintained within 6 hours even after GA withdrawal, indicating the long-lasting e V ect of GA. Besides triggering intrinsic apoptotic pathway, GA could activate extrinsic apoptotic pathway by inhibition of NF B (Pandey et al. 2007). Stathmin 1 (STMN1) was also found currently as the key target of GA by the proteomic approach (Wang et al. 2009). In present study, we found that in MCF-7 cells, GA as an e Y cient apoptosis inducer, repressed bcl-2 expression via increasing p53. Now GA is tested in the sec-ond clinical trial in China. Hopefully, we will have it as a new anti-cancer drug in clinic and bene W t cancer patients. Acknowledgments We thank Professor Zhijie Chang for helpful comments and technical suggestions and Dr. Feng Feng for gambogic acid puri W cation. This work was supported by the Natural ScienceFig.4Western blot assay to show the correlation between p53 andbcl-2 with GA treatment. The methods of Western blot assay were performed as described in Materials and methods. Cell lysates were prepared and p53, bcl-2 protein expressions were analyzed by Western blot assay with anti-p53 (Ab-6) and anti-bcl-2 antibodies. a MCF-7cells were treated with either vehicle or 4 M GA for 0.5, 3, 6, 12, and 24h. b MCF-7 cells were co-treated with 4 M GA and 10 M PFT-alpha for 6h. c P53 si-RNA or control si-RNA was transfected into MCF-7 cells and 4 M GA was administered for corresponding periodsFoundation of China (No. 30472044), the Natural Science Foundation of Jiangsu Province, China (No. BK2005096), Service Center for Phar-macodynamics Research and Evaluation of Jiangsu Province.Con X ict of interest statement We declare that we have no con X ict of interest.ReferencesCumming G, Fidler F, Vaux DL (2007) Error bars in experimental biology. J Cell Biol 177:7–11. doi:10.1083/jcb.200611141Gu H, Guo Q (2007) The advanced developments of P53. J Int Oncol 34(11):801–803Gu H, Wang X, Rao S, Wang J, Zhao J, Ren FL et al (2008a) Gambo-gic acid mediates apoptosis as a P53 inducer through down-regu-lation of Mdm2 in wild-type P53-expressing cancer cells. Mol Cancer Ther 7:3298–3305. doi:10.1158/1535-7163.MCT-08-0212 Gu H, You Q, Liu W, Yang Y, Zhao L, Qi Q et al (2008b) Gambogic acid induced tumor cell apoptosis by T lymphocyte activation in H22 transplanted mice. Int Immunopharmacol 8:1493–1502.doi:10.1016/j.intimp.2008.05.013Guo Q, Qi Q, You Q, Gu H, Zhao L, Wu Z (2006) Toxicological stud-ies of gambogic acid and its potential targets in experimental ani-mals. Basic Clin Pharmacol Toxicol 99:178–184. doi:10.1111/ j.1742-7843.2006.pto_485.xKasibhatla S, Jessen KA, Maliartchouk S, Wang JY, English NM, Drewe J et al (2005) A role for transferrin receptor in triggering apoptosis when targeted with gambogic acid. Proc Natl Acad Sci USA 102:12095–12100. doi:10.1073/pnas.0406731102Li M, Brooks CL, Wu-Baer F, Chen D, Baer R, Gu W (2003) Mono-versus polyubiquitination: di V erential control of P53 fate by Mdm2. Science 302:1972–1975. doi:10.1126/science.1091362 Liu WY, Feng F, You QD, Zhang ZH (2003) The assessment of gam-bogic acid content in total gambogic acid by Rp-Hplc assay. Chin Tradit Herbal Drugs 34:706–707Liu W, Feng F, You Q, Zhang ZX (2004a) The improvement on con-tents measurement of gambogic acid injection. Traditional Patent Medicine 26:add 8–9Liu X, Chua CC, Gao J, Chen Z, Landy CL, Hamdy R et al (2004b) Pi W thrin-alpha protects against doxorubicin-induced apoptosis and acute cardiotoxicity in mice. Am J Physiol Heart Circ Physiol 286:H933–H939. doi:10.1152/ajpheart.00759.2003Liu W, Guo QL, You QD, Zhao L, Gu HY, Yuan ST (2005) Anticancere V ect and apoptosis induction of gambogic acid in human gastriccancer line Bgc-823. World J Gastroenterol 11:3655–3659Lu N, Yang Y, You QD, Ling Y, Gao Y, Gu HY et al (2007) Gambogic acid inhibits angiogenesis through suppressing vascular endothe-lial growth factor-induced tyrosine phosphorylation of Kdr/Flk-1.Cancer Lett 258:80–89. doi:10.1016/j.canlet.2007.08.015 Michael D, Oren M (2003) The P53-Mdm2 module and the ubiquitin system. Semin Cancer Biol 13:49–58. doi:10.1016/S1044-579X(02)00099-8Pandey MK, Sung B, Ahn KS, Kunnumakkara AB, Chaturvedi MM, Aggarwal BB (2007) Gambogic acid, a novel ligand for transferrinreceptor, potentiates Tnf-induced apoptosis through modulation of the nuclear factor-kappab signaling pathway. Blood 110:3517–3525. doi:10.1182/blood-2007-03-079616Qin Y, Meng L, Hu C, Duan W, Zuo Z, Lin L et al (2007) Gambogic acid inhibits the catalytic activity of human topoisomerase iialpha by binding to its atpase domain. Mol Cancer Ther 6:2429–2440.doi:10.1158/1535-7163.MCT-07-0147Roger L, Gadea G, Roux P (2006) Control of cell migration: a tumour suppressor function for P53? Biol Cell 98:141–152. doi:10.1042/ BC20050058Smith DJ, Ng H, Kluck RM, Nagley P (2008) The mitochondrial gate-way to cell death. IUBMB Life 60:383–389. doi:10.1002/iub.44 Tomita Y, Marchenko N, Erster S, Nemajerova A, Dehner A, Klein C et al (2006) Wt P53, but not tumor-derived mutants, bind to Bcl2 via the DNA binding domain and induce mitochondrial permeabi-lization. J Biol Chem 281:8600–8606. doi:10.1074/jbc.M50761 1200Wang X, Chen Y, Han QB, Chan CY, Wang H, Liu Z et al (2009) Pro-teomic identi W cation of molecular targets of gambogic acid: role of stathmin in hepatocellular carcinoma. Proteomics 9:242–253.doi:10.1002/pmic.200800155Wu ZQ, Guo QL, You QD, Zhao L, Gu HY (2004) Gambogic acid inhibits proliferation of human lung carcinoma Spc-A1 cells in vivo and in vitro and represses telomerase activity and telomerase reverse transcriptase Mrna expression in the cells. Biol Pharm Bull 27:1769–1774. doi:10.1248/bpb.27.1769Xia M, Land H (2007) Tumor suppressor P53 restricts ras stimulation of rhoa and cancer cell motility. Nat Struct Mol Biol 14:215–223.doi:10.1038/nsmb1208Yang QZ, Jia SJ, Li DH (1994) The neoteric study of chinese tradi-tional drug, gamboge. Chin J Clin Oncol 21:464–465Yang Y, Yang L, You QD, Nie FF, Gu HY, Zhao L et al (2007) Di V er-ential apoptotic induction of gambogic acid, a novel anticancer natural product, on hepatoma cells and normal hepatocytes. Can-cer Lett 256:259–266. doi:10.1016/j.canlet.2007.06.014Yu J, Guo QL, You QD, Zhao L, Gu HY, Yang Y et al (2007) Gambo-gic acid-induced G2/M phase cell-cycle arrest via disturbing Cdk7-mediated phosphorylation of Cdc2/P34 in human gastric carcinoma Bgc-823 cells. Carcinogenesis 28:632–638.doi:10.1093/carcin/bgl168Zhai D, Jin C, Shiau CW, Kitada S, Satterthwait AC, Reed JC (2008) Gambogic acid is an antagonist of antiapoptotic Bcl-2 family proteins. Mol Cancer Ther 7:1639–1646. doi:10.1158/1535-7163.MCT-07-2373Zhang HZ, Kasibhatla S, Wang Y, Herich J, Guastella J, Tseng B et al (2004) Discovery, characterization and Sar of gambogic acid as a potent apoptosis inducer by a Hts assay. Bioorg Med Chem 12:309–317. doi:10.1016/j.bmc.2003.11.013Zhao L, Guo QL, You QD, Wu ZQ, Gu HY (2004) Gambogic acid induces apoptosis and regulates expressions of Bax and Bcl-2 protein in human gastric carcinoma Mgc-803 cells. Biol Pharm Bull 27:998–1003. doi:10.1248/bpb.27.998Zhao Q, Yang Y, Yu J, You QD, Zeng S, Gu HY et al (2008) Posttran-scriptional regulation of the telomerase Htert by gambogic acid in human gastric carcinoma 823 cells. Cancer Lett 262:223–231.doi:10.1016/j.canlet.2007.12.002。

navcat mysql fulltext 用法

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SELECT * FROM your_table WHERE MATCH(content)AGAINST('search_term') LIMIT 10;5.排除特定词：可以使用-符号排除包含特定词的行。

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中国农业科学院图书馆 ——农业图书馆中国医学科学院图书馆 ——医学图书馆
NSTL
NSTL
NSTL
NSTL
理
工
农
医
NSTL的网络文献全文提供服务

电子图书与传统书籍

相同的特点： 1、包含一定的信息量，如有一定的文字量、彩页； 2、编排按照传统书籍的格式以适应读者的阅读习惯； 3、通过被阅读而传递信息等等。
电子图书与传统书籍

不同的特点： 1、必须通过一定的设备读取并通过屏幕显示出来； 2、具备图文声像结合的优点； 3、可检索，可复制； 4、有更高的性价比； 5、有更多样的发行渠道等等。
文献全文获取方法

利用图书馆馆藏获取印刷版全文利用图书馆馆藏全文数据库等电子资源获取全文利用免费网络期刊和图书获取全文直接向作者索取全文借助图书馆文献资源共享获取全文通过网络文献传递服务获取全文
一、利用图书馆馆藏获取全文

利用图书馆的馆藏目录检索图书馆收藏的纸本文献，可以借阅复制。利用图书馆的电子资源，直接获取所需的文献全文。如：中国学术期刊全文数据库（中国期刊网）、中文科技期刊数据库、万方数字化期刊
ScienceDirect、 Wiley InterScience ProQuest、EBSCO、 OVID、 Nature 、
SpringerLINK 等
二、通过文献资源共享获取全文

图书馆文献资源共享是指图书馆利用各自的馆藏文献资源为其他图书馆的读者提供服务通过图书馆馆藏联合目录或相应的联合馆藏检索系统，检索需要的文献在其他图书馆的收藏情况。

三、利用免费网络期刊获取全文

可以利用因特网免费书刊目录或直接提供免费书刊的网站，查询自己所需的文献是否可以免费获取。或者登陆免费的网站如： Free Medical Journals Site HighWire Press
书生电子图书练习：
1、检索许乙凯《现代CT与MRI诊断技术》 2、阅读《神秘的海》 3、使用选择工具、抓屏、OCR 4、在阅读图书的时候，制作电子书签、利用收藏夹收藏你近期需要阅读的若干本书生电子书。
全文获取
检索得到的文献信息（文摘、题录），需要阅读文献全文，去哪里找？
检
索
文献全文获取

网址：
全国性的唯一的人文社会科学外文期刊保障体系。
文献传递专题检索馆际互借国际互借
国家科技图书文献中心 NSTL
National Science & Technology Library
பைடு நூலகம்
网址：

《铁凝文集》
数字图书馆中的电子图书

超星数字图书馆书生之家数字图书馆方正数字图书（Apabi，阿帕比）
方正（Apabi）电子图书

2003年以后出版的新书占70％，
电子图书的优势：

方便信息检索。存储介质相较传统书籍而言容量更大。成本更低。内容更丰富。更具系统性。
《英国人名词典》（Dictionary of National Biography）
印刷版： 60卷

61440页总厚度近3.5米重达125公斤
/ oxforddnb/info/online/
联合目录
文献检索与原文提供
在NSTL申请全文流程

注册、预付费检索或通过期刊分类目次浏览（免费）选择数据库限定检索年限选择检索字段输入检索词
在检索结果中选择需要的文献订购全文（注册用户—收费）选择投递方式确认下订单

小结：

电子图书和数字图书馆书生数字图书馆超星数字图书馆全文获取途径利用联合目录查其他图书馆收藏的文献利用NSTL网上检索订购理工农医文献全文利用CASHL获取人文社会科学文献全文

超星数字图书馆使用（二）

分类检索：图书按《中国图书馆分类法》分类，点击某一类目，显示相应类下的图书信息，点击书名超链接，阅读图书。快速检索：字段有 “书名”、“作者” 、“主题词” ，默认字段为“书名”。高级检索：对多个字段和关键词进行组合检索。
选择阅读方式
IE阅读
阅览器阅读
分类检索：
医药卫生—口腔科学—口腔内科学—口腔粘膜病
二次检索
书生之家关键词检索
检索包括以下几种途径：
图书名称出版机构作者丛书名称 ISBN（国际标准书号）主题提要
组合检索：检索项之间的 “或”、“与” 的逻辑关系进行组合检索
书生之家阅读器的使用

书签：设置、利用通过创建电子书签，进行阅读管理。收藏夹将阅读过的电子书链接保存到收藏夹中图书内容的拾取、复制利用选择工具、抓屏、OCR
书生数字图书馆
书生之家数字图书馆使用

分类检索二次检索关键词检索阅读器的使用
书生之家分类检索

利用书生之家检索主页上的图书分类类目表逐级深入浏览。点击主页左边的分类目次，系统便会在右边列表显示相关类别的图书书目信息。分类目次提供四级详细分类。打开所需的子类，在图书列表中，单击“全文”，即可阅读您所需要的图书。
中文电子图书网站

榕树下
上海榕树下计算机有限公司的中文原创作品网站，作品有短篇小说、散文、诗歌。网站包括线下出版的图书和精心制作的网络杂志。

我爱e书
图书总数超过1万本，有原创，有转载，其中很多网友制作的电子书；一定时间段内的某类图书有光盘；网站设有学习、制作、交流 E书的论坛。
Jurge S, Kuffer R, Scully C, Porter SR. Mucosal disease series. Number VI. Recurrent aphthous stomatitis. Oral Dis. 2006 Jan;12(1):1-21. Review. Deane EE, Woo NY. Life-Sci 2003,72(7):805-18
全文获取步骤
图书馆资源
免费网络资源其它图书馆
联合目录全文传递服务机构求助作者
查找文献全文实例：

【标题】先天性急性巨核细胞白血病1例【著者】窦心灵; 朱建敏; 何贵山; 夏家敏【著者单位】酒泉市人民医院 735000 【出处】中国小儿血液 2005.02.17; 10(1): 31-32

网址：
CALIS的宗旨是整合高校丰富的文献资源和人力资源起来，实现信息资源共建、共知、共享。 CALIS馆际互借与文献传递网面向读者或文献服务机构文献传递服务。

中国高校人文社会科学文献中心 CASHL China Academic Humanities and Social Sciences Library
四、利用网络文献传递服务
获取全文

信息服务机构或图书馆利用因特网向用户提供文献传递服务通过网络进行文献检索获得有关的文献信息，同时获取馆藏信息，使文献检索与文献提供两个过程紧密结合
五、直接向作者索取全文

在数据库检索结果中，作者的Email地址通常附在作者所在单位地址的后面。如查到的文献较早或没有附带Email 地址，可通过著者途径检索该作者近年来发表或与他人合著的文献，从而找到联系方式。在网上查询作者个人主页或其单位的网站以获取其Email地址。

/lm/
联合目录
500多家成员馆包括：公共图书馆高校图书馆科学院系统图书馆国防所属各单位图书馆公司和科研院所图书馆等
联合目录
仅限于中科院系统
联合目录
联合目录
联合目录
文献传递服务机构--订购全文

电子图书的不足之处：
（1）改变了阅读习惯，有些人不适应；（2）各家出版社（公司）出版的电子图书格式不同，需要不同的阅读器；（3）知识产权保护不力；
（4）图书数量少。
几种电子图书的文件格式

超星公司的PDG格式，阅读器为SSReader 书生公司的SEP、IFR、GD格式，阅读器为 Sursen Reader。维普公司的PDF格式，用Adobe Acrobat Reader阅读。清华同方的CAJ格式，阅读器为CAJViewer 。
电子图书与全文获取