【英文标准名称】:Cablenetworksfortelevisionsignals,soundsignalsandinteractiveservices-Headendequipment
【原文标准名称】:电视信号、声音信号和交互式设备用电缆网络.数据转发器设备
【标准号】:BSEN60728-5-2008
【标准状态】:现行
【国别】:英国
【发布日期】:2008-07-31
【实施或试行日期】:2008-07-31
【发布单位】:英国标准学会(GB-BSI)
【起草单位】:BSI
【标准类型】:()
【标准水平】:()
【中文主题词】:音频信号;宽带系统;广播工程;广播信号;广播;电缆配线箱;电缆分布系统;电缆电视;电缆网络;公共天线电视;同轴电缆;分布系统;电磁兼容性;EMC;交互式的;互相调制;测量;测量技术;噪音宽带;噪声测量;性能;额定值;信号;声音广播;声传输;规范(验收);电视;电视广播;电视接收;电视技术;终端站;传输;传输技术;电视信号;宽频带传输
【英文主题词】:Audiosignals;Broadbandsystems;Broadcastengineering;Broadcastsignals;Broadcasting;Cabledistributioncubicles;Cabledistributionsystems;Cabletelevision;Cablednetworks;Central-antennatelevision;Coaxialcables;Distributionsystems;Electromagneticcompatibility;EMC;Interactive;Intermodulation;Measurement;Measuringtechniques;Noisebandwidths;Noisemeasurements;Properties;Ratings;Signals;Soundbroadcasting;Soundtransmission;Specification(approval);Television;Televisionbroadcasting;Televisionreception;Televisiontechnology;Terminalstations;Transmission;Transmissiontechnique;Visionsignals;Widebandtransmission
【摘要】:
【中国标准分类号】:M61
【国际标准分类号】:33_060_40
【页数】:94P;A4
【正文语种】:英语


【英文标准名称】:StandardTestMethodforSilicainWater
【原文标准名称】:水中二氧化硅的标准试验方法
【标准号】:ASTMD859-2005
【标准状态】:现行
【国别】:
【发布日期】:2005
【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】:D19.05
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:试验;含量测定;硅;水
【英文主题词】:colorimetric;silicawater
【摘要】:Siliconcomprisesabout28%ofthelithosphereandis,nexttooxygen,themostabundantelement.Itisfoundastheoxideincrystallineforms,asinquartz;combinedwithotheroxidesandmetalsinavarietyofsilicates;andinamorphousforms.Siliconisthemostabundantelementinigneousrocksandisthecharacteristicelementofallimportantrocksexceptthecarbonates.Itistheskeletalmaterialofdiatomsbutisnotknowntoplayasignificantroleinthestructureofprocessesofhigherlifeforms.Silicaisonlyslightlysolubleinwater.Thepresenceofmostsilicainnaturalwaterscomesfromthegradualdegradationofsilica-containingminerals.Thetypeandcompositionofthesilica-containingmineralsincontactwiththewaterandthepHofthewateraretheprimaryfactorscontrollingboththesolubilityandtheformofsilicaintheresultingsolution.Silicamayexistinsuspendedparticles,asacolloid,orinsolution.Itmaybemonomericorpolymeric.Insolutionitcanexistassilicicacidorsilicateion,dependinguponpH.Thesilicacontentofnaturalwatersiscommonlyinthe5to25mg/Lrange,althoughconcentrationsover100mg/Loccurinsomeareas.Silicaconcentrationisanimportantconsiderationinsomeindustrialinstallationssuchassteamgenerationandcoolingwatersystems.Undercertainconditions,silicaformstroublesomesilicaandsilicatescales,particularlyonhigh-pressuresteamturbineblades.Incoolingwatersystems,silicaformsdepositswhensolubilitylimitsareexceeded.Incontrast,silicamaybeaddedasatreatmentchemicalinsomesystems,forexample,incorrosioncontrol.Silicaremovaliscommonlyaccomplishedbyionexchange,distillation,reverseosmosis,orbyprecipitation,usuallywithmagnesiumcompoundsinahotorcoldlimesofteningprocess.1.1Thistestmethodcoversthedeterminationofsilicainwaterandwastewater;however,theanalystshouldrecognizethattheprecisionandaccuracystatementsforreagentwatersolutionsmaynotapplytowatersofdifferentmatrices.1.2Thistestmethodisacolorimetricmethodthatdeterminesmolybdate-reactivesilica.Itisapplicabletomostwaters,butsomewatersmayrequirefiltrationanddilutiontoremoveinterferencesfromcolorandturbidity.Thistestmethodisusefulforconcentrationsaslowas20[u]g/L.1.3Thistestmethodcoversthephotometricdeterminationofmolybdate-reactivesilicainwater.Duetothecomplexityofsilicachemistry,theformofsilicameasuredisdefinedbytheanalyticalmethodasmolybdate-reactivesilica.Thoseformsofsilicathataremolybdate-reactiveincludedissolvedsimplesilicates,monomericsilicaandsilicicacid,andanundeterminedfractionofpolymericsilica.1.4Theusefulrangeofthistestmethodisfrom20to1000[u]g/Latthehigherwavelength(815nm)and0.1to5mg/Latthelowerwavelength(640nm).Itisparticularlyapplicabletotreatedindustrialwaters.Itmaybeappliedtonaturalwatersandwastewatersfollowingfiltrationordilution,orboth.Forseawaterorbrines,thistestmethodisapplicableonlyifmatchedmatrixstandardsorstandardadditiontechniquesareemployed.1.5Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.Note1--Formanynaturalwaters,ameasurementofmolybdate-reactivesilicabythistestmethodprovidesacloseapproximationoftotalsilica,and,inpractice,thecolorimetricmethodisfrequentlysubstitutedforothermoretime-consumingtechniques.Thisisacceptablewhen,asfrequentlyoccurs,themolybdate-reactivesilicaisinthe