简介:HEMINGWAY’sstory,“HillsLikeWhiteElephants”,isaboutlovingrelationshipsbetweenanAmericanmanandagirl.Aslovers,theyarein-timate,withthegirlinthestateofpregnancy.Thestoryistoldfromtheobjectivepointofview.Ittakesplaceduringa40-minutewaitbetweentrains.Whatliesbehindthemisindicatedbythelabelsontheirbags.Whatliesaheadofthemimpliesentireforceanddir-ectionofthestory.Itisatthestationthatadecisionwillbemadethat
简介:Inthispaper,anelectricalresistancetomography(ERT)imagingmethodisusedasaclassifier,andthentheDempster-Shafer’sevidencetheorywithfuzzyclusteringisintegratedtoimprovetheERTimagequality.Thefuzzyclusteringisappliedtodeterminingthekeymassfunction,anddealingwiththeuncertain,incompleteandinconsistentmeasuredimagingdatainERT.Theproposedmethodwasappliedtoimageswiththesameinvestigatedobjectundereighttypicalcurrentdrivepatterns.ExperimentswereperformedonagroupofsimulationsusingCOMSOLMultiphysicstoolandmeasurementswithapieceofporcinelungandapairofporcinekidneysastestmaterials.Comparedwithanysingledrivepattern,theproposedmethodcanprovideimageswithaspatialresolutionofabout10%higher,whilethetimeresolutionwasalmostthesame.
简介:利用化学多元醇法合成Gd2O3:Tb^3+纳米粒子,通过对NaOH的加入速率的控制,能将纳米粒子的直径从1-2nm能增大到4nm。利用透射电子显微镜,紫外分光光度计对Gd2O3:Tb^3+纳米粒子的形貌和尺寸、发光进行表征分析。结果表明:分多次加入NaOH比一次性加入NaOH能获得更大尺寸的Gd2O3:Tb^3+纳米粒子。
简介:BaFe12O19fiberswaspreparedviaanaqueoussol-gelprocessusingFe(OH)(HCOO)2synthesizedinlaboratoryandBa(CH3COO)2astheoriginalmaterialsandcitrateasthechelate.Therheologicalbehaviourofspinnablesolwascharacterizedonrheometer,andthedevelopmentofgelfiberstobariumferritefiberswasstudiedbyIR,TGandXRD.MorphologyobservationofthefiberswasgivenonSEM,andthediameteroftheobtainedfiberswasbetween5and10μmcorrespondingtodifferentadditives.Theadditivesaffectedthesurfacetensionoftheprecursorsolwhichhadcloserelationtothemicrostructureoffibers.Sucroseandhydroxyethyliccellulosecouldimprovethesurfacetensionwhilediethanolamineandhexadecylaminereducethatoftheprecursorsol.Andusingdiethanolamineorhexadecylamineasanadditive,well-structuredBaFe12O19fiberscouldbeobtained.
简介:用正丁醇和柠檬酸为原料,WO3/MOO3/SiO2为催化剂催化合成柠檬酸三丁酯。通过考察醇与酸的物质的量比,反应温度和反应时间,催化剂用量和溶剂用量对酯化反应的影响。确定合成柠檬酸三丁酯的最佳反应条件为n(正丁醇)/n(柠檬酸)=4.5,催化剂用量为反应物柠檬酸质量的6%,反应温度130—140℃,反应时间3.5h,酯化率最高达98.5%,产率最高迭94.3%。WO3/MOO3/SiO2催化剂可重复使用,其催化活性基本不变。实验对合成的产品进行了红外光谱分析及折光率的测定,与文献值相符。