基本信息
| 标准名称： | 电磁高真空阀 型式与基本参数 |
| 替代情况： | 被JB/T 4080-1991代替 |
| 发布日期： | |
| 实施日期： | 1994-06-01 |
| 首发日期： | |
| 作废日期： | |
| 出版日期： | |
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前言
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引用标准
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所属分类： 机械 金属切削机床 插 拉 刨 锯床
【英文标准名称】:StandardGuideforComputedTomography(CT)Imaging
【原文标准名称】:计算机断层摄影(CT)成像的标准指南
【标准号】:ASTME1441-2000(2005)
【标准状态】:现行
【国别】:
【发布日期】:2000
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:E07.01
【标准类型】:(Guide)
【标准水平】:()
【中文主题词】:计算机断层摄影;导则;图例;信息处理
【英文主题词】:computedtomography(CT);contrast;contrast-detail-dose(CDD);detectability;imaging;modulationtransferfunction(MTF);nondestructiveevaluation(NDE);pointspreadfunction(PSF);reconstruction;resolution;scan;X-rayattenuation
【摘要】:1.1Computedtomography(CT)isaradiographicmethodthatprovidesanidealexaminationtechniquewhenevertheprimarygoalistolocateandsizeplanarandvolumetricdetailinthreedimensions.BecauseoftherelativelygoodpenetrabilityofX-rays,aswellasthesensitivityofabsorptioncrosssectionstoatomicchemistry,CTpermitsthenondestructivephysicaland,toalimitedextent,chemicalcharacterizationoftheinternalstructureofmaterials.Also,sincethemethodisX-raybased,itappliesequallywelltometallicandnon-metallicspecimens,solidandfibrousmaterials,andsmoothandirregularlysurfacedobjects.Whenusedinconjunctionwithothernondestructiveevaluation(NDE)methods,suchasultrasound,CTdatacanprovideevaluationsofmaterialintegritythatcannotcurrentlybeprovidednondestructivelybyanyothermeans.1.2ThisguideisintendedtosatisfytwogeneralneedsforusersofindustrialCTequipment:(1)theneedforatutorialguideaddressingthegeneralprinciplesofX-rayCTastheyapplytoindustrialimaging;and(2)theneedforaconsistentsetofCTperformanceparameterdefinitions,includinghowtheseperformanceparametersrelatetoCTsystemspecifications.Potentialusersandbuyers,aswellasexperiencedCTinspectors,willfindthisguideausefulsourceofinformationfordeterminingthesuitabilityofCTforparticularexaminationproblems,forpredictingCTsystemperformanceinnewsituations,andfordevelopingandprescribingnewscanprocedures.1.3ThisguidedoesnotspecifytestobjectsandtestproceduresforcomparingtherelativeperformanceofdifferentCTsystems;nordoesittreatCTinspectiontechniques,suchasthebestselectionofscanparameters,thepreferredimplementationofscanprocedures,theanalysisofimagedatatoextractdensitometricinformation,ortheestablishmentofaccept/rejectcriteriaforanewobject.1.4Standardpracticesandmethodsarenotwithinthepurviewofthisguide.Thereaderisadvised,however,thatexaminationpracticesaregenerallypartandapplicationspecific,andindustrialCTusageisnewenoughthatinmanyinstancesaconsensushasnotyetemerged.ThesituationiscomplicatedfurtherbythefactthatCTsystemhardwareandperformancecapabilitiesarestillundergoingsignificantevolutionandimprovement.Consequently,anattempttoaddressgenericexaminationproceduresiseschewedinfavorofprovidingathoroughtreatmentoftheprinciplesbywhichexaminationmethodscanbedevelopedorexistingonesrevised.1.5TheprincipaladvantageofCTisthatitnondestructivelyprovidesquantitativedensitometric(thatis,densityandgeometry)imagesofthincrosssectionsthroughanobject.Becauseoftheabsenceofstructuralnoisefromdetailoutsidethethinplaneofinspection,imagesaremucheasiertointerpretthanconventionalradiographicdata.Thenewusercanlearnquickly(oftenuponfirstexposuretothetechnology)toreadCTdatabecausetheimagescorrespondmorecloselytothewaythehumanmindvisualizesthree-dimensionalstructuresthanconventionalprojectionradiography.Further,becauseCTimagesaredigital,theymaybeenhanced,analyzed,compressed,archived,inputasdataintoperformancecalculations,comparedwithdigitaldatafromotherNDEmodalities,ortransmittedtootherlocationsforremoteviewing.Additionally,CTimagesexhibitenhancedcontrastdiscriminationovercompactareaslargerthan20to25pixels.Thiscapabilityhasnoclassicalanalog.Contrastdiscriminationofbetterthan0.1%atthree-sigmaconfidencelevelsoverareasassmallasone-fifthofonepercentthesizeoftheobjectofinterestarecommon.1.6Withpropercalibration,dimensionalinspectionsandabsolutedensitydeterminationscanalsobemadeveryaccurately.Dimensionally,virtuallyallCTsystemsprovideapixelresolutionofrough......
【中国标准分类号】:L81;C43
【国际标准分类号】:35_240_80
【页数】:33P.;A4
【正文语种】: