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简介：BasedonthecontinuityofthederivativesoftheNon-UniformRationalB-Splines(NURBS)curveandtheJaumannstrainmeasure,thepresentpaperadoptedthepositioncoordinatesofthecontrolpointsasthedegreesoffreedomanddevelopedaplanarrotation-freeEuler-Bernoullibeamelementforisogeometricanalysis,wherethederivativesofthefieldvariableswithrespecttothearc-lengthwereexpressedasthesumoftheweightedsumofthepositioncoordinatesofthecontrolpoints,andtheNURBSbasisfunctionswereusedastheweightfunctions.Furthermore,theconceptofbendingstripwasusedtoinvolvetherigidconnectionbetweenmultiplepatches.Severaltypicalexampleswithgeometricnonlinearitieswereusedtodemonstratetheaccuracyandeffectivenessoftheproposedalgorithm.Thepresentedformulationfullyaccountsforthegeometricnonlinearitiesandcanbeusedtostudythesnap-throughandsnap-backphenomenaofflexiblebeams.

简介：Purpose:Thepurposeofthisstudywastocomparethecoordinationbetweenthetrunkandthepelvisduringasustainedasymmetricrepetitiveliftingtaskbetweenagroupwithahistoryoflowbackpain(LBP;HBP)andagroupwithnohistoryofLBP(NBP).Methods:Volunteerslifteda11-kgboxfromankleheightinfronttoashelf45°off-centeratwaistheight,andloweredittothestartpositionat12cycles/minfor10min.Liftingsidewasalternatedduringthetrial.Continuousrelativephasewasusedtocalculatecoordinationbetweenthepelvisandtrunkrotationatthebeginning(Min1),middle(Min5),andendofthebout(Min9).Results:Whiletherewerenomaineffectsforgroup,asignificantinteractionbetweentimeandgroupindicatedthat,inthefrontalplane,theNBPgroupcoordinationwasmoreanti-phasetowardtheendofthebout,withnosuchdifferencesfortheHBPgroup.Analysisofsagittal-axial(bendandtwist)coordinationrevealedtheHBPgroupcoordinationwasmorein-phaseattheendoftheboutovertheentirecycleandfortheliftingphasealone,withnosuchdifferencesfortheNBPgroup.Conclusion:DifferencesbetweengroupsdemonstrateresidualconsequencesofLBPinanoccupationalscenario,eventhoughtheHBPgroupwaspain-freefor>6monthspriortodatacollection.Morein-phasecoordinationintheHBPgroupmayrepresentacoordinationpatternanalogousto'guardedgait'whichhasbeenobservedinotherstudies,andmaylendinsightastowhytheseindividualsareatincreasedriskforre-injury.