Tài liệu HTML and Web Design Secrets P2 docx

... Toolbox29ࡗࡗࡗSecret #16: Audio and Video PlayersAudio players are necessary for Web designers who are both working with audio and video as well as visiting Web sites where forms of audio and video are in ... “Skencil.’’Figure 1-17:Using Mayura Draw for vector-based design. tip Web designers and developers using Linux platform and open sourcesoftware for designing graphics should check out LinuxArtist.Org, ... is an HTML tag stripper. Utilitiesof this type let you take an HTML or related Web document and strip all the codeout of it, leaving you with just the text.In some cases, commercial Web design...

... signif-icantly reducing bandwidth and increasing revenue.Most likely you are a person who is working on public or private Web sites and issomewhat experienced with HTML and Web graphic design and are interested ... forself-expression via Weblogs, social networks, and special interest groups.250 HTML and Web Design Secrets looks into the detailed work required to createsuccessful Web sites and provides extremely ... BookFocusing on theory, standards, and rigid practices is, in a word, dry. 250 HTML and Web Design Secrets takes a fresh and fun approach, providing insider techniquesthat will help designers get the...

... the lining material and the drum, p represents the pressure betweenthe drum and the lining, and w represents the width of the band. Uponsimplifying equations (1-1) and (1-2) and remembering that ... the element ofband length approaches zero, sin(du/2) approaches du/2, cos(du/2)FIGURE2 Quantities and geometry used in the derivation of the band-brake design relations.Band Brakes 19Copyright ... Inc.Sincereinforcementofthebandnearitsleadingenddependsontheforcedecayasafunctionofanglealongtheband,itmaybeofinteresttodisplayhowFdecreaseswithf,measuredfromtheleadingendoftheband.TodothiswesimplyreplaceF2withFandreplaceawithfinequation(1-7)toobtainFF1¼eÀAff¼aÀuð1-12ÞForabrakebandextendingoveranangleffromF1.T¼ðF1ÀFÞr¼F1r1ÀFF1¼F1rð1ÀeÀAfÞð1-13ÞThusthedecayofthebandforcefromitsmaximumattheleadingendofthebandmaybefoundfromFigure3usingthescalesshownontheright-handordinateandassociatingtheabscissawithf.Itisbecauseofthelowcoefficientoffrictionforwetfrictionmaterialthatthebrakebandsinanautomatictransmissionarerelativelythickandcurvedtofitthedrumwithonlyasmallclearance.Thethicknessisrequiredtosupportthelargebandforcenecessarytodeliverarelativelylargetorquewhenoperatingatlowefficiencyandthesmallclearanceisnecessarytominimizetherequiredactivationforcetobendthebandandliningtothedrumradius.II.APPLICATIONInthissectionweconsiderthedesignofabandbraketoexertatorqueof9800.0N-msubjecttotheconditionsthatthedrumwidthbenogreaterthan100mmandthatthedrumdiameterbenogreaterthan750mm.Tocompletethedesignweshouldalsospecifythenecessarylinkstrengthforasafetyfactorof3.5whenusingasteelthathasaworkingstressof410MPa.Othermechanismsrequirethattheangleofwrapnotexceed290j.Liningtemper-atureisnotexpectedtoriseabove300jF(148jC)duringthemostsevereconditions.Selectaliningmaterialthatcansustainamaximumpressureof1.10MPa.ReturntoChapter1tofindthattheliningrepresentedbyFigure4isoneofseveralthatisflexibleenoughforusein abandbrakeandhasthelimitingtemperatureand pressurecapability.Thus,useA=0.4 andequation (1-10) tofind that at the maximum radius the band width should be given bywðrÞ¼Tpmaxr2ð1ÀeÀAaÞð2-1ÞChapter...

... rsinacosRrcosðhÞÀ h0Chapter 4825Dry and Wet Disk Brakes and ClutchesThis chapter on disk brakes and clutches will consider annular contact diskclutches and both caliper and annular contact disk brakes, ... Continued.Dry and Wet Disk Brakes and Clutches 85Evaluation of these integrals is easiest for brake pads with radial and circular boundaries, as in Figure 4, for which equation (1-4) and (1-5) may ... Toledo, OH.)Dry and Wet Disk Brakes and Clutches 97the radius such that the pressure can become constant. Whenever the pressureis uniform, equations (1-5) and (1-4) hold and may be easily...

... Inc.Thislinkforceandtheactivatingmomentbothactonthesecondaryshoe,sothattheforceandmomentequationsofequilibriumforthesecond-aryshoebecomeFr2¼ÀrwZf2f1pcosfdfþArwZf1f2psinfdfþFlsinf2þh2ð5-7ÞFu2¼ÀrwZf2f1psinfdfþArwZf2f1pcosfdfþFlcosf2þh2ð5-8Þwhere2histheanglesubtendedbytheadjustinglink.Next,Ma2¼Mp2þMf2À2RFlsinf22sinf22þh2ð5-9ÞwhereMp2andMf2areagaingivenbyequations(5.1 )and( 5.2)intermsofthepressuredistributiononthesecondaryshoe.TorqueforeithershoemaybecalculatedfromT¼ArwZf2f1pdfð5-10ÞEventhoughtheseequationsdonotuniquelydeterminethepressuredistributionoverthebrakelining,theyarestillofusebecausetheyallowthedesignengineertocomparetheeffectsofdifferentrealisticpressuredistribu-tionandtodesigndrumsandshoeswhoserigiditywillinduceparticularpressuredistributionsovertheprimaryandsecondaryshoes.Thefirstofthetwopressuredistributionsconsideredisasynthesisof(1)thesinusoidaldistributionassociatedwithanondeformingdrumandshoe,generallyassociatedwithalightlyloadedbrake ,and( 2)theforcepeaksthatoccurattheendsofload-bearingmembersincontact.Thesecondofthetwoisasysthesisof(1)theconstantdistributionsaidtobeassociatedwithmoreheavilyloadedbrakes ,and( 2)thepreviouslynotedforcepeaks.Thusthepressuredistributionswillberepresentedeitherbypp0¼eÀc1c=f0ðÞcoscf0kc2þc3c¼fÀf1ð5-11Þorbypp0¼eÀc1c=f0ðÞcoscf0kc2þc3sincþf1ðÞð5-12Þfortheprimaryshoes,wherethepeakpressureoneachshoeoccursattheheelbecauseitspivotcannotsustainaradialforceintheoutwarddirection.TheserelationsproducethepressuredistributionsshowninFigures1 4and1 5forthe ... brake life, heatdissipation, fading, and braking torque capability.III. DESIGN OF DUAL-ANCHOR TWIN-SHOE DRUMBRAKESFor both external and internal shoes and for either direction of rotation ... Inc.rotatesawayfromthepivot,self-lockingcanbeavoidedifMf/MpisalwaysgreaterthanÀ1.Similarcriteriaholdforinternalbrakesexceptthatthedirectionsofrotationarereversedforthesamealgebraicsigns.Sincemostbrakesaredesignedforrotationinbothdirections,itisgenerallyconvenienttocombinethesecriteriaintoasinglecriterion,whichisthatself-lockingofbothinternalandexternaldrumbrakesmaybeavoidedifÀ1VMfMpVþ1ð3-3ÞSelectionofshoeanddrumanglesanddimensionsinaccordancewiththiscriterionmaybeaidedbyconstructionofdesigncurvessuchasillustratedinFigures 7and8 ,inwhichtheratioMf/AMpisplottedagainstanglef2forselectedvaluesofthecoefficientoffriction.ExternalshoesarecharacterizedbyR/rratiosgreaterthanunityandinternalshoesbyr/Rratioslessthanunity.TheratioMf/AMphasbeenplottedinsteadofMf/MpinFigures 7and8 because...

... 4LinearlyActingExternalandInternalDrumBrakesLinearlyactingdrumbrakesarethosefittedwithshoeswhich,whenacti-vated,approachthedrumbymovingparalleltoaradiusthroughthecen-teroftheshoe.TypicallinearlyactingdrumbrakesareillustratedinFigures1–3.Analysisoflinearlyactingbrakesincludesthoseinwhichthecentrallypivotedshoesareattachedtopivotedlevers,asinFigure1.Includingbrakesofthisdesignwithinthecategoryoflinearlyactingbrakesisjustifiediftheyaredesignedsothattheappliedforcesontheshoesandliningsactalongtheradiioftheshaftsthattheygripwhenthebrakesareapplied.Brakesofthistypemayacteitheruponbrakedrumsordirectlyuponrotatingshaftsandaresuitableforuseinheavy-dutyapplications,suchasfoundinminingandconstructionequipmentandinmaterials-handlingmachinery.Internallinearlyactingdrumbrakes,suchasusedontrucksinEurope,maybedesignedasinFigure2.Eitherpneumaticorhydrauliccylindersorcams ... Inc.Letusdefinetheefficiencyofabrakeastheratioofthetorqueprovidedbythebraketothetorquethatcouldbehadbyapplyingtheforcedirectlytothedrum,orshaft.Accordingtothisdefinition,theefficiencybecomesTFsr¼Apmaxr2wðsinu2Àsinu1Þð1=2Þpmaxr2wðf0þsinf0Þ¼2Asinu2Àsinu1f0þsinf0ð1-10ÞUponsubstitutingforu1andu2inequation(1-8)andrecallingequations(1-6) and( 1-7)wefindthatTFsr¼4Asinðf0=2Þf0þsinf0¼ARrð1-11Þwheretheright-handsidehasalreadybeenplottedinFigure5.Fromthatfigurewefindthatalthoughmaximumefficiencymaybeachievedonlyifeachshoeandliningextendoverhalfofthedrum,orshaft,relativelylittleefficiencyislostiftheliningextendsoveronly160jinsteadof180j.This,togetherwiththenearimpossibilityofmaintaininggoodcontactbetweentheliningandthedrumneartheendsofashoesubtending180jatthecenterofthedrum,accountsfortheangulardimensionsofthebrakeliningsshowninFigure1.Finally,itfollowsfromequation(1-11)thatiftheshoeissymmetricallypivotedandifequation(1-7)holds,theappliedtorqueisgivenbyT¼ARFsð1-12ÞII.BRAKINGTORQUEANDMOMENTSFORSYMMETRICALLYSUPPORTEDINTERNALSHOESPressurepandbrakingtorqueareagaingivenbyequations(1-2 )and( 1-4),respectively,foraninternalshoemovedagainstarotatingdrumalongalineparalleltoitsaxisofsymmetry,lineOB,inFigure6.Inthefollowinganalysisit ... Inc.Letusdefinetheefficiencyofabrakeastheratioofthetorqueprovidedbythebraketothetorquethatcouldbehadbyapplyingtheforcedirectlytothedrum,orshaft.Accordingtothisdefinition,theefficiencybecomesTFsr¼Apmaxr2wðsinu2Àsinu1Þð1=2Þpmaxr2wðf0þsinf0Þ¼2Asinu2Àsinu1f0þsinf0ð1-10ÞUponsubstitutingforu1andu2inequation(1-8)andrecallingequations(1-6) and( 1-7)wefindthatTFsr¼4Asinðf0=2Þf0þsinf0¼ARrð1-11Þwheretheright-handsidehasalreadybeenplottedinFigure5.Fromthatfigurewefindthatalthoughmaximumefficiencymaybeachievedonlyifeachshoeandliningextendoverhalfofthedrum,orshaft,relativelylittleefficiencyislostiftheliningextendsoveronly160jinsteadof180j.This,togetherwiththenearimpossibilityofmaintaininggoodcontactbetweentheliningandthedrumneartheendsofashoesubtending180jatthecenterofthedrum,accountsfortheangulardimensionsofthebrakeliningsshowninFigure1.Finally,itfollowsfromequation(1-11)thatiftheshoeissymmetricallypivotedandifequation(1-7)holds,theappliedtorqueisgivenbyT¼ARFsð1-12ÞII.BRAKINGTORQUEANDMOMENTSFORSYMMETRICALLYSUPPORTEDINTERNALSHOESPressurepandbrakingtorqueareagaingivenbyequations(1-2 )and( 1-4),respectively,foraninternalshoemovedagainstarotatingdrumalongalineparalleltoitsaxisofsymmetry,lineOB,inFigure6.Inthefollowinganalysisit...

... MI.)Dry and Wet Disk Brakes and Clutches 87Copyright © 2004 Marcel Dekker, Inc.Evaluationoftheseintegralsiseasiestforbrakepadswithradialandcircularboundaries,asinFigure4,forwhichequation(1-4 )and( 1-5)maybewrittenusingadummyvariablefasF¼pmaxriZA1rda¼pmaxriZr0riZu0dfdrð1-6Þ¼pmaxriuðr0ÀriÞ and T¼ApmaxriZAda¼ApmaxriZrorirdrZu0dfð1-7Þ¼Apmaxriu2r2oÀr2iÀÁFromequation(1-7)wefindthatforthepressuredistributiongivenbyrela-tion(1-3)thetorquemaybeeasilycalculatedforanybrakepadwhoseareaisFIGURE2Combinationdiskbrakeanddiskclutch,bothdry.(CourtesyofMinsterMachine ... Inc.Evaluationoftheseintegralsiseasiestforbrakepadswithradialandcircularboundaries,asinFigure4,forwhichequation(1-4 )and( 1-5)maybewrittenusingadummyvariablefasF¼pmaxriZA1rda¼pmaxriZr0riZu0dfdrð1-6Þ¼pmaxriuðr0ÀriÞ and T¼ApmaxriZAda¼ApmaxriZrorirdrZu0dfð1-7Þ¼Apmaxriu2r2oÀr2iÀÁFromequation(1-7)wefindthatforthepressuredistributiongivenbyrela-tion(1-3)thetorquemaybeeasilycalculatedforanybrakepadwhoseareaisFIGURE2Combinationdiskbrakeanddiskclutch,bothdry.(CourtesyofMinsterMachine Co., Minster, OH.)Chapter 586Copyright © 2004 Marcel Dekker, Inc.5DryandWetDiskBrakesandClutchesThischapterondiskbrakesandclutcheswillconsiderannularcontactdiskclutchesandbothcaliperandannularcontactdiskbrakes,asillustratedinFigures1,2 ,and3 .Caliper ... Inc.5DryandWetDiskBrakesandClutchesThischapterondiskbrakesandclutcheswillconsiderannularcontactdiskclutchesandbothcaliperandannularcontactdiskbrakes,asillustratedinFigures1,2 ,and3 .Caliper disk brakes, as shown in Figure 1, are used on aircraft, auto-motive, industrial, and mining equipment....

... Inc.II.FOLDEDCONEBRAKEPrototypeconebrakeshavebeendesignedandtestedforarangeofvehiclesizes,fromtractorsandtrailerstosubcompactautomobiles[1].Boththelargeandsmallsizesusedafoldedconedesign,asillustratedinFigures 5and6 ,eachwitha=27j.Althoughtheconebrakehasfewerpartsthandrumbrakes,thisadvantagemustbebalancedagainstthedisadvantageofrequiringanoutboardwheelbearing.Analysisofthefoldedconebrakewithasectorshoe,showninFigure5,toobtaindesignformulasforthetorquecapabilityandtherequiredactiva-tionforceisquitesimilartothatusedforsimpleconebrakesandclutches.SincethebrakesillustratedinFigures 5and6 useasectorpad,webegintheanalysisbyobservingfromFigure7(a)thatanelementofareaontheconicalsurfacemaybewrittenasda¼rdudrsinað2-1ÞFIGURE4DesignregionsintheA,aplaneforconeclutches/brakes.Cone ... Inc.comparisonofthethreefigures,theminimumdescribedbyequation(1-16)andplottedinFigure4isqualitativelyevidentinFigures 3and4 .It is Figure 4 that is directly useful in the design of cone brakes and clutches, because we find from equation (1-19) that the regions to the left ofthe solid curve (regions 2 and ... Inc.II.FOLDEDCONEBRAKEPrototypeconebrakeshavebeendesignedandtestedforarangeofvehiclesizes,fromtractorsandtrailerstosubcompactautomobiles[1].Boththelargeandsmallsizesusedafoldedconedesign,asillustratedinFigures 5and6 ,eachwitha=27j.Althoughtheconebrakehasfewerpartsthandrumbrakes,thisadvantagemustbebalancedagainstthedisadvantageofrequiringanoutboardwheelbearing.Analysisofthefoldedconebrakewithasectorshoe,showninFigure5,toobtaindesignformulasforthetorquecapabilityandtherequiredactiva-tionforceisquitesimilartothatusedforsimpleconebrakesandclutches.SincethebrakesillustratedinFigures 5and6 useasectorpad,webegintheanalysisbyobservingfromFigure7(a)thatanelementofareaontheconicalsurfacemaybewrittenasda¼rdudrsinað2-1ÞFIGURE4DesignregionsintheA,aplaneforconeclutches/brakes.Cone...

... They are often designed in the laboratory by acombination of theory and trial and error because our present theory is notadequate to handle small geometric effects on the electric and magnetic ... Inc.OMandtheIM.ThebrakeconfigurationdiffersfromtheclutchonlyinthattheIMisrigidlyattachedtothebrakeframe.AnelectromagneticcoiloutsidetheOMandconcentricwithitisusedtoactivatethebrakeorclutch.WhenthecoilinenergizedbypassingcurrentthroughitamagneticfieldisestablishedwhichcausestheparticlestobridgethegapbetweentheIMandtheOMandformlinksbetweenthetwo,asrepresentedinFigure6(b).Theselinksarealongthemagneticlinesofforce,whicharemadenearlyperpendiculartotheOMbytheconfigurationoftheOMandthecoilhousing,asshowninFigures 6and7 .BoththeshearandtensilestressesintheselinksresistrelativemotionbetweentheIMandtheOMandsotransmittorqueforthebrake/clutch.TheseshearandtensilestressesdevelopedaredependentonthecoilcurrentFIGURE4Hysteresisbrakewitha8-lb-ftcapacity.(CourtesyofMagneticPowerSystems, ... P and magnetization vector M are defined byP ¼ D À eoE and B ¼ AoH þ M þ MoðÞ ð1-4Þbecause both P and M vanish in free space. The last two of equations (1-2) arereplaced byD ¼ eE and...

... Inc.theannularcaliperandannulardiskbegivenbyequation.Accordingly,eval-uatetheformulasT¼pmaxwr2oð1ÀeÀAfÞð8-7Þforabandbrake,T¼2Apmaxwr2osinfo2ð8-8Þforeithertwoopposinginternalorexternallinearlyactingbrakeshoes,T¼2Apmaxr3o3ffiffiffi3pfoð8-9Þfortwoopposingdiscbrakepads,eachsubtendingangleBo ,and T¼4kApmaxr3o3ffiffiffi3pð8-10ÞfortwocompleteannularpadsinwhichBo=2kinequation(8-9).WeshallalsoconsideranexternalpivoteddrumbrakewithaleadingandtrailingshoethatmaybeevaluatedbyinvokingtheprogramusedinChapter3.Inallofthesecalculationsassumeafrictioncoefficientof0.3 ,and setthewidthfortheband,thelinearlyactingdrumbrake,andtheexternallypivotedbraketo5cm.Limitthemaximumliningpressureforthebandbrakeandfortheexternallypivotedbraketo2.0MPa,andlimitthepressurefortheotherliningsto3.0MPa,whichmaybeeitherformedorsolid.Liningpressurefortheexternallypivotedbrakewastakentobe2.0MPa,merelyforcomparisonwiththebandbrake.Figure11(a)showsthetorquecapacityinnewton-metersasafunctionofangleBsubtendedbyeachshoeforadrumdiameterof300mm,andFigure11(b)showsthetorquecapacityinnewton-metersforband,linearlyacting,caliper,andannularbrakesasafunctionofthedrumordiscdiameterinmillimeters.AlthoughthelinearlyactingdrumbrakeisclearlymoreeffectivethantheotherbrakesshowninFigure11(b),itandalloftheotherthreebrakesinthatfigurerequiremorehardwarethandoesthebandbrake.Therefore,selectthebandbrake,becauseitcanprovidethenecessarytorquecapabilitywithmechanicalsimplicity.Externaldual-shoedrumbrakesarethenextsimplest.Increasingthemaximumliningpressureto3.0MPaforanexternallypivoteddual-shoebrakeallowsthedrumdiametertobereducedto170mmandtheradialdistancetotheshoepivottobereducedto100mm,fromthe150mmas-sociatedwithFigure11(a),togetatorquevs.anglecurvesimilarinshapeandmagnitudetothatinFigure11(a).Thus,eitheranexternallypivotedChapter8174Copyright ... inertia Ii, n weights Wˆi and theirelevation changes, and including nonzero values of velocity vi, and angularrotation Ni.III. BRAKING AND CLUTCHING TIME AND TORQUEWork done by a brake ... !¼6:344lb-ftð6-6Þ¼76:130lb-in:whereni=1/5.488fortheendrollersandni=1/1.254fortheintermediaterollers.Ifthebrakehadbeenmountedoneitheroftheendrollershafts,equation(6-6)wouldhavebeenreplacedbyT¼4:1140:1553"2ð0:0759Þþ20ð0:000556Þð4:375Þ2þ23032:24:375122#¼34:811lb-ftð6-7Þandthebrakingtorquerequirementwouldhavebeenn=5.488timeslargerthanthatfoundbyequation(6-6).Thiscomparisonisanexampleofthegen-eralrulethatthebrakeshouldusuallybeplacedinthefastershaft.VII.EXAMPLE3:ROTARYKILNThecurvesinFigure6clearlyimplythatefficientuseofaclutchbyreducingthepowerlossduetoheatgeneration,alongwithwear,requiresthatthespeedsofitsinputandoutputshaftsshouldbenearlyequal.Accordingly,dependinguponthepowersource(electricorhydraulicmotor,turbine,orinternalcombustionengine),aclutchmaybeusedtochangegearratios,tochangefromonepowersourcetoanotherwhenthespeedsarenearlyequal,ortodisconnectthepowersourcebeforebraking.Thisexamplewillconsideraloadthatisessentiallyrotationalinordertoconcentrateonclutchandbrakeselectionwhendynamictorqueandbrakeheatingcurvesareavailable.Bothclutchandbrakeanalyseswilldisplaysomeofthecalculationinvolvedwhenthespeedsoftheinputandoutputshaftsarenotalmostequal.Arotarykilnistobedrivenbya15-hpthree-phasemotoroperatingat870rpmandratedtodeliveratorqueof240lb-ftwithaKfactor(overloadfactorforstarting)of2.64.Themotor,clutch,geartrainwitha28.4speed-reductionratio,androtarykilnarearrangedasshowninFigure7.Theoveralldamping...