JOURNAL OF URBAN TECHNOLOGY7 Period11992-2006 ，Period22007-20091 Period3(2010-2012 385 356 350 315 280 : 27H 245 213 210 175 140 LIO7 1sn3nV St 9:E0e [AlSJaAlun Suojoelf leyaueys] 105 70 59 33 35 24-25 2522 9 0200 030 8 Ab Bo Ch Ed Ar Co Gr:Ab Bo Ch Ed Ar Co Gr:Ab Bo Ch Ed Ar Co Gr Ab Abstract Bo Book Ch Book chapter Ed Editorial: Ar Journal article;Co Conference paper,Gr Grey literature Figure 1.Source documents by type and period of publication often contain errors,which can lead to significant variations in the results of their analysis (Adam,2002),all citations were tested for correctness and completeness,so as to guaran- tee the highest degree of data reliability.Altogether,a total of 22,137 citations were col- 花o P lected(957 to source documents and 21,180 to non-source documents),and they were used to build a frequency table showing each cited publication,together with the number of times it had been cited.This made it possible to determine that the total number of cited references was 17,574.Only citations to source documents were con- sidered during the analysis. The First Two Decades of Smart-City Research A New and Fast Growing Research Area The analysis shows that smart city-research established itself as a new area of scientific enquiry in 2009,and since then,it has been fast-growing,arousing strong interest from an expanding scientific community of researchers.This growth is particularly evident when observing the rise in the production of source documents(See Figure 3),which has continued to increase over time,together with the number of researchers involved
often contain errors, which can lead to significant variations in the results of their analysis (Adam, 2002), all citations were tested for correctness and completeness, so as to guarantee the highest degree of data reliability. Altogether, a total of 22,137 citations were collected (957 to source documents and 21,180 to non-source documents), and they were used to build a frequency table showing each cited publication, together with the number of times it had been cited. This made it possible to determine that the total number of cited references was 17,574. Only citations to source documents were considered during the analysis. The First Two Decades of Smart-City Research A New and Fast Growing Research Area The analysis shows that smart city-research established itself as a new area of scientific enquiry in 2009, and since then, it has been fast-growing, arousing strong interest from an expanding scientific community of researchers. This growth is particularly evident when observing the rise in the production of source documents (See Figure 3), which has continued to increase over time, together with the number of researchers involved Figure 1. Source documents by type and period of publication JOURNAL OF URBAN TECHNOLOGY 7 Downloaded by [Shanghai Jiaotong University] at 03:36 25 August 2017
8©L.MORA ET AL Africa (19)America(133),Asia (188),Australia (35).Europe (404) 275 250 237 225 200 175 150 137 125 100 83 LI07 1sn3nV St 9:E0e [ASJaAlun Suojoelf leyueys]Kq papeojuMod 75 53 50 33 26 25 25 25 16 10 15 0 uEdoBu EdGotBu EdGoBuEdo Ed ot B Research and Business;E Research and Education; G Research and Government O Other Figure 2.Organizations by type and location in their development(See Figure 4).Initially,this research area was very small,with only 19 source documents published during the first 10 years of research.Over the following eight years,from the beginning of 2002 to the end of 2009,production increased slightly. During this period 132 documents were published,about 17 per year.The period between 2010 and 2012,instead,was characterized by a tremendous growth in the number of pub- lications.More than 900 new source documents were produced in three years,and they represent approximately 86 percent of the smart-city literature developed during the first two decades of research. Fragmentation of Knowledge All branches of knowledge are composed of large groups of interconnected publications, and their structure can be represented through the use of complex mapping techniques, allowing the scientific community involved in their production to easily grasp "the big picture"(Moya-Anegon et al.,2004):"a spatial representation of the relationship among [...individual papers as reflected in some formal,strictly quantifiable properties of scientific literature at a given time"(De Bellis,2009:142).Citations are the elements that
in their development (See Figure 4). Initially, this research area was very small, with only 19 source documents published during the first 10 years of research. Over the following eight years, from the beginning of 2002 to the end of 2009, production increased slightly. During this period 132 documents were published, about 17 per year. The period between 2010 and 2012, instead, was characterized by a tremendous growth in the number of publications. More than 900 new source documents were produced in three years, and they represent approximately 86 percent of the smart-city literature developed during the first two decades of research. Fragmentation of Knowledge All branches of knowledge are composed of large groups of interconnected publications, and their structure can be represented through the use of complex mapping techniques, allowing the scientific community involved in their production to easily grasp “the big picture” (Moya-Anegon et al., 2004): “a spatial representation of the relationship among […] individual papers as reflected in some formal, strictly quantifiable properties of scientific literature at a given time” (De Bellis, 2009: 142). Citations are the elements that Figure 2. Organizations by type and location 8 L. MORA ET AL. Downloaded by [Shanghai Jiaotong University] at 03:36 25 August 2017
JOURNAL OF URBAN TECHNOLOGY 9 1100 1000 1source documents which belong to the smart city research field 900 %produced un the period 19922009 percentage of source documents 800 5%produced in the perod 2010-2012 percentage of source documents 700 600 500 400 LIOZ isnanV st 96:E0 e [AlIsJaalun 300 200 100 0- TT 含昌香台驾含器器号是尾第葛美号爱司美 Figure 3.Cumulative growth in the number of source documents uoloef eyueyS] create the connections between publications.They represent"a type of symbolic currency that signals intellectual influences"and serve as an indicator by which the influence and impact of any scientific document can be assessed (Jacobsen et al.,2013:226).By using citations,researchers can incorporate intellectual work from other research into their own studies (Garfield,1970;Small 1973,1978),and collaborate in the construction of 花o P the intellectual structure of their field of investigation. The use of these techniques made it possible to visualize the overall intellectual struc- ture that results from the first 20 years of research in the field of smart cities.The structure is illustrated in Figure 5,and is represented by a network of undirected and unweighted links in which the 1,067 source documents are nodes and the 957 citations referring to them are the connecting elements.This graph has been obtained using the Fruchter- man-Reingold layout algorithm provided by the open-source software Gephi(Fruchter- man and Reingold,1991).Within the graph,the source documents are represented by a circle with a diameter proportional to the number of citations they have received.There- fore,the larger the circle,the greater number of citations.In addition,source documents with at least one citation are shown in blue,whereas those without citations are gray. By observing the organization of the nodes,it becomes evident that fragmentation and divergence are the main features of this structure,and they result from the absence of con- nections between the source documents.This means that the impressive growth of avail- able scientific literature observed in the last three years of the second decade goes hand in
create the connections between publications. They represent “a type of symbolic currency that signals intellectual influences” and serve as an indicator by which the influence and impact of any scientific document can be assessed (Jacobsen et al., 2013: 226). By using citations, researchers can incorporate intellectual work from other research into their own studies (Garfield, 1970; Small 1973, 1978), and collaborate in the construction of the intellectual structure of their field of investigation. The use of these techniques made it possible to visualize the overall intellectual structure that results from the first 20 years of research in the field of smart cities. The structure is illustrated in Figure 5, and is represented by a network of undirected and unweighted links in which the 1,067 source documents are nodes and the 957 citations referring to them are the connecting elements. This graph has been obtained using the Fruchterman-Reingold layout algorithm provided by the open-source software Gephi (Fruchterman and Reingold, 1991). Within the graph, the source documents are represented by a circle with a diameter proportional to the number of citations they have received. Therefore, the larger the circle, the greater number of citations. In addition, source documents with at least one citation are shown in blue, whereas those without citations are gray. By observing the organization of the nodes, it becomes evident that fragmentation and divergence are the main features of this structure, and they result from the absence of connections between the source documents. This means that the impressive growth of available scientific literature observed in the last three years of the second decade goes hand in Figure 3. Cumulative growth in the number of source documents JOURNAL OF URBAN TECHNOLOGY 9 Downloaded by [Shanghai Jiaotong University] at 03:36 25 August 2017
10© L.MORA ET AL 2750 2500 2584authors involved in the F production of source documents 2250 %towork bewteen 1992 and 2009 percentage of authors who started 2000 88.89%68 petween2609and202 percentage of authors who started 1750 1500 1250 1000 750 LI07 1sn3nV St 9:E0e [ASJaAlun SuoloeIf leyueys]Kq papeojumod 500 250 0-一 Figure 4.Cumulative growth in the number of authors involved in the production of source documents hand with the lack of cohesion between the researchers involved in their production.As a result,the intellectual structure of the smart-city research area is divided into a multitude of unconnected publications.The central core of the network,indeed,is compact and well- 40 ●NODE TY1- ●oont3 oa Figure 5.Knowledge structure of the smart-city research field
hand with the lack of cohesion between the researchers involved in their production. As a result, the intellectual structure of the smart-city research area is divided into a multitude of unconnected publications. The central core of the network, indeed, is compact and wellFigure 4. Cumulative growth in the number of authors involved in the production of source documents Figure 5. Knowledge structure of the smart-city research field 10 L. MORA ET AL. Downloaded by [Shanghai Jiaotong University] at 03:36 25 August 2017