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Coping with methods for delineating emerging fields: Nanoscience and nanotechnology as a case study

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Proper field delineation plays an important role in scientometric studies, although it is a tough task. Based on an emerging and interdisciplinary field nanoscience and nanotechnology-this paper highlights the problem of field delineation. First we
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   JournalofInformetrics13   (2019)100976 Contents lists available at ScienceDirect  Journal   of    Informetrics  journal homepage: www.elsevier.com/locate/joi Regular   article Coping   with   methods   for   delineating   emerging   fields:Nanoscience   and   nanotechnology   as   acase   study Teresa   Mu˜noz-Écija a ,   Benjamín   Vargas-Quesada a , b ,ZaidaChinchilla   Rodríguez c , ∗ a DepartmentofInformationandCommunication,Facultyof    CommunicationandDocumentation,Universityof    Granada,CampusdeCartujas/n,18071Granada,Spain b SCImagoResearchGroup,Granada,Spain c CSIC,InstituteofPublicGoodsand   Policies(IPP),Albasanz26-28,28037Madrid,Spain a   r   ti   c   le   i   n   f   o  Articlehistory: Received20December2018Receivedinrevisedform12August2019Accepted5September2019 Keywords: FielddelineationScienceclassificationResearchtopicsBibliometricsScientometrics ab   s   t   ra   ct Proper   fielddelineation   plays   an   important   role   inscientometric   studies,   although   itisa   toughtask.Basedonanemerging   and   interdisciplinary   fieldnanoscience   andnanotechnology–   this   paperhighlights   the   problemof    field   delineation.First   wereviewthe   related   literature.   Then,threedifferent   approaches   todelineateafieldof    knowledgewere   appliedat   three   different   levelsof    aggregation:   subject   category,   publication   level,and    journallevel.   Expert   opinioninterviews   servedtoassess   thedata,   andprecision   andrecall   of    each   approachwere   calculated   for   comparison.   Our   findingsconfirm   thatfielddelineationisa   complicatedissueatboth   the   quantitativeandthequalitative   level,   evenwhenexpertsvalidateresults.©   2019   Elsevier   Ltd.   Allrights   reserved. 1.Introduction Fielddelineation, 1 whichconsistsof    assigningjournalsorpublicationstofields,tendstobethefirststageundertakeninbibliometricorscientometricstudiesoffields(Zhao,2009).Properfielddelineationisimportantforresearcherswhostudy thestructureanddynamicsof    afield,anditisfundamentalforinformationretrievalintheresearchareasofbibliometricsandscientometrics.Itisalsoneededwhendesigningreliableandsolidtoolsforrankingsanddomainanalysis,highlyvaluableinsciencepolicydesignandscienceevaluationprocesses(Gómez-Nú˜nez,Batagelj,Vargas-Quesada,Moya-Anegón, &Chinchilla-Rodríguez,2014).Indeed,therelevanceofsuchstudieswilldependonthequalityof    theirdelineation.Specificchallengeslieintheprocessof    delineatingemergingand/orinterdisciplinaryfields,forexample,in   theretrievalof    relevantdatawithhighprecisionandheftyrecall,andtheconstructionof    a   corejournalorpublicationsettocomprisea   field(Milanez,Noyons,&deFaria,2016).Likewise,delineatingscientificfieldsbeforedevelopingdisciplinarysubjectclassificationschemesmay   involveempiricalandpragmatictechniques,orotherautomatedproceduresbasedonstatisticsandcomputerizedmethods.However,thehierarchyofsciences,whereconsensuswithinscientificcommunityof    afieldcanbeeasilyreachedatthecorelevel(wheretheoriesormethodsarefullyaccepted),butnotattheresearchfrontierlevel(wheretheresearchisconducted)(Cole,1983), ∗ Correspondingauthor. E-mailaddresses: teiki@correo.ugr.es(T.Mu˜noz-Écija),benjamin@ugr.es(B.Vargas-Quesada),zaida.chinchilla@csic.es(Z.   ChinchillaRodríguez). 1 The   termsfielddelineation,subjectclassification,subjectcategorydelineation,subjectdelineation,thematicdelineation,anddisciplinedelineationare   usedinterchangeablythroughoutthis   text.https://doi.org/10.1016/j.joi.2019.1009761751-1577/©2019ElsevierLtd.Allrightsreserved.  2  T.Mu˜noz-Écijaetal./     Journalof    Informetrics13   (2019)100976 providesaframeworktounderstandthediversityofa   disciplinesinceitreflectsthelevelofscholarlyconsensusandshowsnatural-socialdichotomies(Fanelli&Glänzel,2013).Thisconsensuscaninvolvenotonlycognitiveaspectsorcomplexityof  asubjectmatter,butalsosociologicalaspects.Therefore,thedefinitionof    a   fieldderivesfromitsscientificcontentaswellasfromtheassociationandinteraction(social,professionalorbypublishing)of    itsresearchers.Alackof    cohesionin   a   fieldcanbeconsideredasafactorto   detectanemergingfield(Casadevall&Fang,2015).Severalmethodsmay   beusedto   delineatefields.Subject-classificationschemes,madeup   mainlyofscientificjournals,areoneinformationretrievalstrategythatcanhelptocollectarelevantdocumentsetforfielddelineation.Thisistheclassificationsystemusedbythetoptwomultidisciplinarybibliographicaldatabases,ScopusandWeb   ofScience(WoS).Theyassignscientificjournalsto   categoriestakingintoaccountjournaltitleandscope,aswellasjournalcitationanalysis.Althoughsubject-classificationschemesmay   definea   broadfield,thistypeofdelineationencounterslimitationsregardingthelevelofdetail,multidisciplinaryjournals,andinterdisciplinaryresearchpublishedinavarietyof     journals,defyingdisciplinaryboundaries(Zhao,2009);in   suchcases,theretrieveddocumentsetcontainsconsiderablenoiseaffectingbothprecisionandrecall(Glänzel,2015).Inorderto   offsettheselimitations,analternativemethodmaybeusedtodelineatebyassigningnotonlyjournalsbutalsopublicationstocategories(Glänzel&Schubert,2003).Themostcommoninformationretrievalarchetypeusedforfielddelineationentailsthetranslationof    aninformationneedintoaqueryora   setofqueries.Theapplicationofcomplexsearchstrategiesbasedonlexicalterms(keywordsandphrases)ismostwidelyusedtocollecta   documentsetrelatedtoa   field/domain,especiallyinemergingandinterdisciplinaryfields,becauseitcaneffectivelycovermostaspectsofthefield(Glänzel,2015).Thismethodhasbeenprogressivelyfine- tuned,andcannowbeconsidereda   hybridlexical-citationmethod.At   theseminallevel,itmay   beusedtoappraisea   fieldof literature,orcorejournalpublications,throughretrievalbylexicalqueries.Theinitialseedsetis   thenextendedbycitationanalysisamongpublicationsusingdifferentparameters.However,thisprocessbecomesproblematicwhen,forinstance,theuseofcommontermsbearsanegativeinfluenceonprecisionyeta   positiveoneonrecall.Totalrecallcanalsobeaffectedbecausethebordersof    fieldsaresometimesdifficulttodefine;andthehelpof    expertsin   thefieldtodesignlexicalqueriescanproduceaspecializationbias,leadingto   a   skewedandsuperficialoverviewofthefield/domain(Zitt,2015).Extensiveresearchhasshownthatclusteringanalysisisavaluableandpopularmethodapplicableatjournalandpublica-tionlevel,ina   widevarietyof    scientificfields(Bassecoulard,Lelu,&Zitt,2007;Gómez-Nú ˜nezetal.,2014;Zitt&Bassecoulard,2006).Boyack&Klavans(2010,2013)usehybridmethodsthatcombinedifferenttypesofcitationrelationsandconclude thattheapproachgeneratesaccurateclusters.Morerecentattentionhasfocusedontheuseof    multidisciplinaryclassificationsystemsatthepublicationlevel,asestablishedbyWaltmanandvanEck(2012).   ItisbasedondirectcitationrelationsbetweenpublicationsfromWoS   andclustersthemintoresearchareasorganizedinathree-levelhierarchicalstructure.Delineatingatthepublicationlevelmoreaccuratelymatchesthecurrentstructureof    scientificresearchina   field.Accordingly,theclassificationsystemof    publicationscouldhelpdefineajournallevelsystem,butitmightproveproblematictheotherwayaround.Fielddelineationatthelevelofpublicationisonepossiblesolutionwhenfacingthelimitationsinvolvedin   classificationatthelevelofjournal.Inthesameline,KlavansandBoyack(2017)introduceadetailedclassificationsystematthetopiclevelwitharound 100,000topicsthathavebeenappliedinScopus.TheScopusdocumentssetis   dividedintotopicsbytheclusteringofdirectcitationlinks.Then,a   measuretorankthetopicprominenceinscienceisappliedtoidentifythosetopicsthatrevealsupplyanddemandinthesciencesystems.Fielddelineationatthistopiclevelofferstheadvantageof    predictingifa   topicwillgrowordecline,anditscontributiontothedynamicsofthescience,in   termsof    thefundingreceived.Recentresearchhascompareddifferentjournalandpublicationclassificationsystems(Shuetal.,2019).Theseauthors claimthenecessityof    developingrobustandaccuratepublicationandjournalclassificationsystems.Anincreasein   thenumbersubjectsincludedin   a   publicationjournalclassificationsystemhasaneffectintheaccuracyandcanreducethemisclassificationof    papers.Thesameeffectisproducedin   a    journalclassificationsystemwhenitincludesbroadorhigh-leveldisciplinesinsteadofmanydisciplines.Nowadays,nanoscienceandnanotechnology(henceforthNST)is   anareaholdingvasttechnologicalandsocialpotentialforthecommunity,presentingadvancementsforindustry,health,theenvironment,andsecurity.It   thereforeattractsgreatpolicyinterest.Thus,NSThasbeenincludedasa   strategicareawithaninnovativeandeconomicpotentialinmanyresearchanddevelopmentplans,evenworldwide,liketheEUResearchandInnovationProgrammeknownasHorizon2020, 2 theNationalScienceFoundation 3 andtheNationalNanotechnologyInitiative. 4 PreviouseffortshavedelineatedNSTfromdiffer-entperspectives(Arora,Porter,Youtie,&   Shapira,2013;Arora,Youtie,Carley,Porter,&Shapira,2014;Grieneisen&Zhang, 2011;Leydesdorff&   Zhou,2007;Mogoutov&Kahane,2007;Zitt&Bassecoulard,2006),buttodatenocomparisonofthesemethodshasbeenperformed.Thecurrentstudycomparesthreedifferentapproachestodelineatetheemergingfieldof    NST,sheddingnewlightonthekeyproblemsthatunderlieemergingfielddelineation. 2 ec.europa.eu/programmes/horizon2020/en/what-horizon-2020. 3 www.nsf.gov. 4 www.nano.gov.  T.Mu˜noz-Écijaetal./     JournalofInformetrics13(2019)100976  3 1.1.Delineationofnanoscienceandnanotechnology Nanoscienceandnanotechnologyconstitutesaninterdisciplinaryandemergingdomainthatembracesphysics,chem-istry,materialsscience,engineering,andmore.Sincethe1990s,manyworkshaveattemptedtodelineateNSTbyusingdifferentperspectives,e.g.,thematicdelineationorbibliometrictechniques.VariouslexicalquerieshavebeenproposedforgatheringthedatasettostudyNST,including:1)Theprefix nano ,toharvestallpublicationsthatincludeitwithintheirtitle(Dunn&Whatmore,2002;Meyer,Persson,& Power,2001;Tolles,2001); 2)   Acombinationof    nano prefixandrepresentativekeywordsof    NST,excludingthosetermsthatincludethe nano prefixbuthavenothingtodowithNST(Glänzeletal.,   2003;Mogoutov&Kahane,2007;Noyonsetal.,2003;Porter,Youtie,Shapira,&Schoeneck,2008).Thedrawbackofsearchingbasedonthe nano *prefixaloneisthatpublicationswithouta   prefixarenotretrieved(forinstance,biotechnologypublications).Inaddition,someNSTkeywordssuchasfullerenesorgrapheneareexcluded.Thesecondsearchstrategyis   supportedbyexperts’opiniontoincludeorexcludekeywords,yetittendstowardbias,becausetheexpertsmay   includekeywordsassociatedwiththeirparticularfieldof    knowledge(Huang,Notten,&Rasters,2011).Anearlyworkproposinga   lexicalqueryto   studyNSTis   thatbyBraun,Schubert,andZsindely(1997).   Theseauthorsharvestedarticleswiththeprefix nano from1986to1995in   ordertoanalyzethegrowthofnanotechnology.Someyearslater,Kostoff,Koytcheff,andLau(2006)studiedNSTtoidentifyitsthematicstructure.TheyrecreatedthegenealogyofNSTin termsofthemostimportantworksbehindthedevelopmentof    NSTbasedontheassumptionthat   theywouldbehighlycited.ZittandBassecoulard(2006)delineateNSTliteraturebycombininglexicalqueriesandcitationanalysis,additionallyusingasetofparameterstohighlightrelevanceandreducenoise.Aworldwideviewof    thetechnicalstructureandinfrastructureofscientificproductioninNSTdrawnupbyKostoff,Koytcheff,andLau(2007)introducedustothemostproductiveand highlyimpactingcountries.Oneimportantfindingtwodecadesagois   thatjournalsfocusingonphysicspublishedthegreatestnumberof    NSTpub-lications,followedbyinterdisciplinaryjournals(Meyer&Persson,1998).Thesearchinvolvedarticleswiththeprefix nano in   theirtitlesbetween1991and1996retrievedfromtheScienceCitationIndex,distributingthemaccordingto   thejournalclassificationschemeproposedbyHicksandKatz(1996).Schummer(2004)rana   co-authoranalysisofover600articlespublishedin   nano  journalsin   2002and2003.TheresultsshowedthatmostNSTjournalsincludepublicationsbyauthorswithjustonedisciplinaryaffiliation,especiallybyphysicists.Hefurthermoreexploredthespeedatwhichthescientistsandengineersfromdifferentdisciplines,institutionsandcountriestakepartinNSTresearch,andwhetherthedevelopmentofNSTinvolvesnewmeansorlevelsof    multiandinterdisciplinaryresearch,orinstitutionalandgeographicalcollaborationpatterns.Resultsindicatedthattherearenoparticularpatternsorstablelevelsofmulti-or   interdisciplinaryresearch—whileinteractionexists,itshareslittlemorethantheprefix nano .Bassecoulardetal.(2007)lookedintoNSTasa   multidisciplinaryfieldofknowledgebymeansof    aclassificationof publicationsinthematicclustersconnectedbythesimilarityoftheirreferences.Witha   NSTdatasetfrom1999to2003,theyevidenceda   moderatelevelof    multidisciplinarity,thoughjusta   fewpublicationsin   physicsandchemistrywereattherootofthatmultidisciplinarity.TheNSTjournalswiththe nano prefixin   theirtitlesincludedin   theJournalCitationReportsfrom25countrieswerestudiedbyAndrievskiandKlyuchareva(2011).   Newjournalsin   NSTwerefoundtocomefromfieldssuch   asnanobiology,nanomedicine,nanobiomedicine,andnanobiotechnology,whereasthebulkof    scientificproductioninNSTwaspublishedinclassicnatural-scienceandengineeringjournals.Huangetal.(2011)conducteda   reviewof    thenanotechnologyliteraturethathadanalyzedpublicationsandpatents.Theyidentifiedprosandconsof    thedifferentsearchstrategiescarriedoutfornanotechnologydelineation:keywordqueriesandalltheirimprovements,citationanalyses,andtheuseofacorejournalsetto   identifyarticles.Asmostof    thesearchstrategiesfornanotechnologydelineationshareda   corekeywordset,theresultsobtainedintermsof    mainareasandjournalsinnanotechnologyprovedsimilar.Theirlexicalqueriesweredesignedin   viewofthesearchstrategysuggestedbyGlänzeletal.(2003).Theothersearchstrategywasbasedontheuseofthetop10journalsin   nanotechnology;however,itdidnotprovideasoliddelineationbecausemanynanotechnologypapersarepublishedinmultidisciplinaryjournals.Anumberofattemptsto   improvekeywordqueriesfortheretrievalofNSTpublications(Kostoff,Koytcheffetal.,   2006;Kostoff,Murday,Lau,&Tolles,2006;Mogoutov&Kahane,2007;Maghrebi,Abbasi,Amiri,Monsefi,&Harati,2011;Zucker, Darby,Furner,Liu,&Ma,   2007)relyona   datasetharvestedusinganinitialkeywordsearchstrategyandaselectionof keywordsbasedontherelevanceofthoseterms.Ontheonehand,Maghrebietal.(2011)usedkeywordqueriesproposedbyWarris(2004)tostudyprecisionandrecallof  thekeywordsbyanalyzingthearticlesof    2008in   WoS.Ontheotherhand,thecombinationof    keywordqueriesandcitationanalysisusedto   delineateNSTcanbeseenasa   highlyeffectiveapproach,sinceitincreasesprecisionandrecall,reducingthenoiseofinformationretrieval(Zitt   &Bassecoulard,2006).Althoughkeywordqueriesarestillused,subjectivityis   reducedbecauseexpertconsultationisnotnecessarilyrequired(Huangetal.,   2011).AnothersearchstrategydescribedintheliteratureonNSTdelineationinvolvestheuseof    corejournals.LeydesdorffandZhou(2007)identifieda   setof    10relevantjournalsinNSTusingbetweennesscentralityasa   measureof    theinterdisciplinary  4  T.Mu˜noz-Écijaetal./     Journalof    Informetrics13   (2019)100976 ofscientificjournals,withvisualizationtechniquesbasedoncitationanalysisof     journaltitles.Inaddition,theyanalyzednanotechnologypatentsfromtheU.S.PatentandTradeOffice(USPTO)to   determinewhetherthepatentscontainreferencestonon-patentliterature.Suchreferenceswerefoundto   betoogeneraltodefinea   setofkeyjournals,andNSTappearedtoarisefromtheinterrelationbetweenphysicsandchemistry.Thedrawbackof    thismethod,asopposedto   retrievalbasedonkeywordqueriesandcitationanalyses,is   thatonlyasmallportionof    theNSTliterature(thematiccorpus)is   covered.Detailedexaminationandupdateof    thenanosearchstrategybyWangetal.(2019)reportedthatthedynamismof  nanotechnologyforcestoconstantlyreviewitsterminologyto   conductaccurateanalysesof    thefieldanddetectemergingnanoresearchterms.Theysuggestedaproceduretoharvesta   propernanodatasetthatcombinednanodocumentsretrievedbylexicalqueriesandnanodocumentsretrievedbyNSTWoS   subjectcategory.Theoutcomesevidencethat   manyof    thenanoresearchis   notcoveredbytheNSTWoS   subjectcategory.Thepresentcontributionstemsfromasearchstrategycombiningseveralapproachespreviouslydescribedfortherecov-eryofNSTdocuments,launchedin   theScopusdatabase.OurobjectivewastoderiveaNSTjournalclassificationintheSCImagoJournalandCountryRank(SJR)andintheSCImagoInstitutionsRankings(SIR)portalsbasedontheScopusdata.AllNSTarticles,conferencepapers,andreviewscontainedin   Scopuswererecoveredfortheyear2010.Subsequently,a   citationanalysisofthemostcitedjournalswascarriedoutbasedonthereferencesof    theanalyzeddocuments.The    journalsthatreflectedover1%oftotalcitationwereselected(A),excludingmultidisciplinaryjournals.Inordertoidentifythejournalsthatcontainedtheprefix nano inthetitlecoveredin   Scopus,anothersearchwas   launchedinthedatabase,takingonlythose journalswitha   nano prefixthat   hadreceivedatleastonecitationin2010(B).ThesumofjournalsetsAandBdeterminedtheNSTcorejournals(Mu˜noz-Écija,Vargas-Quesada,Chinchilla-Rodríguez,Gómez-Nú˜nez,&Moya-Anegón,2013). 2.Objectives Theoverallmotivationbehindthisstudywasto   keepworkingonoptimizingandupdatingtheNSTjournalclassificationintheframeworkoftheSCImagoJournal&CountryRankportal.Asthereisnouniqueandinfalliblemeansoffielddelineation,thepresentpaperseekstohighlightcertainissuesinvolvedindelineatingemergingfields,usingNSTasa   studycase.Ourmainaimisnottooffera   newmethodorsolution,buttoexploreandcomparethreeapproachessoastoshowhowfielddelineationvariesunderthedifferentmethods,andaspireto   thefollowingspecificobjectives: •  Toupdatetheliteraturereviewof    fielddelineationin   NST; •  TounifysearchstrategieswhenharvestingtheNSTcollection; •  Tosetupaframeworkforcomparingandcombiningapproachesatthejournallevelthroughaseven-stepprocedure; •  Tousetwodistinctvaluedatasources,ScopusandWoS,todelineateanemergingfield; •  ToincludevalidationbyexpertsintheNSTfield. 3.Materialandmethod Twodifferentdatabaseswereusedtoharvestthedataset:ScopusandWoS   CoreCollection(SCI-Expanded,SSCI,andA&HCIindexes).Thesetwodatabasesarewidelyheldto   bethemostformaldatasourcesintermsofpublicationsbecausetheycoverahugejournalcollection,andtheystorepublicationactivitiesincludingvariousreliableindicators(Park,Yoon,&Leydesdorff,2016).Moreover,twoseparateclassificationjournalsystemswereemployedtoobtainjournallists:JournalCitationReports(JCR)andSCImagoJournal&CountryRank(SJR)intheir2015and2016versions.Thetimeperiodchosenwas2008–2015becauseitmarkeda   certainstabilityin   NSTscientificoutput(Mu˜noz-Écija,Vargas-Quesada,&Chinchilla-Rodríguez,2017).Inanalyzingthesedatasets,threealternativeapproacheswereapplied:1)atcategorylevel(  A 1 );2)atpublicationlevel(  A2 );and3)atjournallevel(  A3 ).  3.1.Approach1:Delineationatcategorylevel(A 1 ) To   date,WoS   is   theonlymultidisciplinarydatabasethatincludesNSTasa   subjectcategory.AssignationofjournalstosubjectcategoriesinWoS   is   theresultof    aheuristicmethodbasedoncitationdata,longregardedasperhaps “thebestway”  todelineatefieldsinjournalterms(Pudovkin&Garfield,2002).Underthisapproach,88journalscontainedintheWoS NSTsubjectcategorywereselected.To   doso,thissubjectcategoryintheJCRScienceEdition2015and2016werechosen(Appendix1a).BecauseScopusdoesnotincludethesubjectcategoryNSTamongtheirsubjectareas,fielddelineationforNSTwasdrawnin   theSCImagoJournalandCountryRankportalusingsubjectclassificationin   conjunctionwithcitation-andquery-basedapproaches(Mu˜noz-Écijaetal.,   2013).Atotalof86journalscontainedinSJRintheyears2015and2016wereselectedforusedinapproachA3,excludingceased/discontinuedjournals(Appendix1b).  3.2.Approach2:Delineationatpublicationlevelusingmicro-levelfields(A2) Thissecondapproachwasappliedforfielddelineationintermsof    publicationsasdescribedinWaltmanandvanEck(2012).ThisclassificationsystemisusedbytheCentreforScienceandTechnology(CWTS)PublicationLevelClassification  T.Mu˜noz-Écijaetal./     JournalofInformetrics13(2019)100976  5  Table   1 DataretrievedbyApproach3(A3).DatabasePeriodDocumenttypeNumberofpublicationsScopus2008–2015All   902,082WoS   2008–2015All   711,464 System,thatcomprisesmorethan4000categories,alsoknownasmicro-levelfields.Thesearchstrategyreliedonthein-houseversionofWoS   fromtheCWTSof    LeidenUniversity(Appendix2)toobtainaninitialNSTdataset.ThestrategyevolvesfromoneusedearliertoconstructtheNSTcategoryinSJRandSIRportals(Mu˜noz-Écijaetal.,2013),basedonlexicalqueriescombiningthe nano prefixandalist   of    keywordsrelatedto nano bymeansofBooleanoperators.All   thekeywordsqueriesweredesignedtakingintoaccountlexicalqueriesreportedelsewhere(Aroraetal.,2013;Grieneisen&Zhang,2011;Kostoff, Koytcheffetal.,2006;Maghrebietal.,   2011).FortheperiodcoveredbytheCWTSclassification,2000–2016,thenumberof articlesandreviewsretrievedamountedto   1,005,801.Thistotalof1,005,801publicationswasspreadoutintomicro-levelfieldsthat   includedatleastonepublicationfromtheNSTpublicationset2008–2015.Thesepublicationswerelocatedat3433micro-levelfields.Thepercentageofoverlappedpublicationswascalculatedbydividingthenumberof    matchedpublicationspermicro-levelfieldbythetotalnumberof publicationsineachmicro-levelfield.We   believethattheoccurrenceof    publicationinrelevantmicro-fieldsthatcometorepresentafieldcanberegardedasa   publicationoverlaphavingaminimumfrequencyof    60%ineachcluster.Consequently,onlymicro-levelfieldswithathresholdequalto   or   greaterthan0.6of    overlappedpublicationwereselected.Afterwards,thenumberofpublicationsperjournalcoveringthe35-selectedmicro-clusterwerecalculated(3851journalsand332,739publicationsintotal),aswasthetotalnumberof    publicationsperjournalintheWoS   collectionforthesametimeperiod.Thepercentageof    publicationsperjournalis   thusapproximatedbydividingthetwovalues.Journalsoverthe0.2thresholdofpublicationperjournalandover50publicationswereextracted.Alistof    78journalswasmade,buttwoturnedouttobethesamejournalthathadchangeditsname.Also,one“ceased”journalwas   identifiedusingthisapproach.Thefinalnumberofjournalswastherefore76.  3.3.Approach3:   Delineationatjournallevel(A3)/Lexicalquery Thisapproachbuildsona   previouswork(Mu˜noz-Écijaetal.,2013),butimprovesuponthedesignforanoptimallexicalquerytoharvesttheNSTdatasetandimplementsastatisticalmethodtoestimateunknownparameters.  3.3.1.Step1.Searchinglexicalquery Fig.1   showsa   sequenceofstepsatthejournallevel.ItstartswithretrievingthedatasetfromScopusandWoS   databasesbyapplyingtheNSTsearchstrategy(Appendix2).Alldocumenttypespublishedfrom2008to   2015wereconsideredforbothdatabases(Table1).  3.3.2.Step2.Citationanalysis We   determinethesetof    citedjournalsinNSTpublicationsretrievedineachdatabase.Beforethat,themultidisciplinarycitedjournalsincludedintheMultidisciplinarysubjectcategoryof     JCRwereremoved,alongwiththosein   theGeneralsubjectcategoryofSJR.Thisstepwasbasedontheassumptionthatmultidisciplinaryjournalspublisharticlesofmanydifferentfieldsandcannotbeconsideredasjournalspertainingto   aspecificfieldof    knowledge(Narin,1976).Themultidisciplinarity ofjournalsmightalsobestudiedasanindicatorin   the citing  dimensionratherthaninthe cited one(Leydesdorff,2007).  3.3.3.Step3.Elbowcriterionwiththresholdkink Aftercalculatingthepercentageofcitationforeachcitedjournal,theelbowcriterionwas   usedtochoosethemostrepresentativejournals.To   formalizethevisualprocedureof    anelbowcriterion,weemployastatisticalprocedurethatisextensivelyusedineconomicsandrelatedfields.Inparticular,weestimatea   thresholdmodelwithakinkandtwo   straightlinesconnectedatthiskink,basedonapplyingthemethodknownasOrdinaryLeastSquares(OLS)thatminimizesthedistanceofpointsto   a   fittedlinebyminimizingthesquareddistancetoeachline.Foreachsubsection,werelatedifferentvaluesofthevariablex   (mostcitedjournals)tothevariabley(percentageofcitation)anddetermineparameters a   and b bytheOLStechnique,whichleadstoa   straightline(Greene,2012),where:  y = ax + ba   = n (   x i  y i )   − (   x i )(   y i ) n   x 2 i  − (   x i ) 2 b   = (   y i )   − a (   x i ) n

ARTI 29-INSOMNIE

Oct 13, 2019
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