Bibliometric Analysis of Thermodynamic Research: A Science Citation Index Expanded-Based Analysis

© 2012 Fu and Ho, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Bibliometric Analysis of Thermodynamic Research: A Science Citation Index Expanded-Based Analysis

Finally, the journal articles (41,245) were extracted from the 50,865 documents for subsequent analyses.

Analyzing structure
The analyzing aspects were divided into five sections from different angles.To be specific, the analytic structure of analytic structure of bibliometric analysis of thermodynamic research is presented in Fig. 2. The first section dealt with the basic information covering the distribution of languages and annual production.The second section revealed the performance of productive journals and Web of Science categories.Then national contributors countries and institutional contributors institutions were analyzed in the following third and fourth sections.Finally, recent research emphases and trends were examined by the frequency of author keywords.Web of Science SCI-Expanded Topic = "thermodynamic" or "thermodynamics" or "free energy change" or "enthalpy change" or "entropy change" Lemmatization = off Year published = 1991-2010 157140 documents "thermodynamic", "thermodynamics", "free energy change", "enthalpy change", and "entropy change" in front page (title, abstract, and author keywords)

documents
Document type= article

Indicators and acronyms
The indicators displayed in Fig. 2 for detail analysis are explained in Table 1.As for the section of national and institutional contributors, some newly indicators (CP, SP, FP, and RP) were employed to evaluate the performance of countries/territories and institutions.The institutions' and countries/territories' contributions were identified by the appearance of at least one author in the publications.Collaboration type was determined by the addresses of the authors.The articles were classified by four types for country/territory and institution.(1) The term "single country article" was assigned if the researchers' addresses were from the same country.The term "single institution article" was assigned if the researchers' addresses were from the same institution.(2) The term "internationally collaborative article" was designated to those articles that were coauthored by researchers from multiple countries.The term "inter-institutionally collaborative article" was assigned if authors were from different institution.
(3) The term "first author article" was assigned if the first author was from the country/territory or institution for analysis.(4) The term "corresponding author article" was assigned if the corresponding author was from the country/territory or institution for analysis.In addition, the acronyms used in the following analysis were listed in   German (146).Some other languages that were less used were as follows: Spanish, Portuguese, Polish, Czech, Korean, Ukrainian, Croatian, Hungarian, Slovak, Serbo-Croatian, and Romanian.The high proportion of English also appears in other research areas, such as 94% of desalination research (Tanaka & Ho, 2011), and 93% in acupuncture research (Han & Ho, 2011).Non-English language publications considerably dilute the the measured impact of published articles (van Raan, 2005).and Russian Journal of Physical Chemistry (1999Chemistry ( -2006)).Articles published in this journal concern chemical thermodynamics and thermochemistry (http://www.maik.ru/cgiperl/journal.pl?name=physcha&page=main) which is closely related to the topic of this study.

Web of Science categories
As for category analysis, excluding the 84 articles without subject category information, the remained 41,161 articles were analyzed.The most common category was physical chemistry (10,295; 25%), followed distantly by other categories.A half of the above top 20 journals are assigned to the category of physical chemistry.Within the total 150 Web of Science categories, 92 categories (61%) published articles less than 100 articles; 40 categories (27%) published 101-1000 articles; 12 categories (8.0%) published 1,001-3,000 articles; only six categories (4.0%) published more than 3,000 articles.The six core categories including physical chemistry, multidisciplinary materials science, multidisciplinary chemistry, metallurgy & metallurgical engineering, chemical engineering, and biochemistry & molecular biology, took the majority of the total articles with a great percentage of 55%.As illustrated in Fig. 5, these categories showed greater growth rates in recent years than those in 1990s.These trends were similar to the above trends of annual total publication outputs.

Global geographical distribution
Excluding 263 articles without any author address information on the Web of Science, the 40,982 articles originated from 128 countries.Articles originating from England, Scotland, Northern Ireland, and Wales were reclassified as being from the United Kingdom (UK) (Chiu & Ho, 2005).Articles from Hong Kong were included in the ones from China.The geographical global distribution of thermodynamic research is shown in Fig. 6.According to their production, the 128 countries were divided into five parts.Particularly, 81 countries (63%) belonged to the first part of 1-100 articles; 36 countries (28%) belonged to the second part of 101-1,000 articles; seven countries (Japan, France, India, Italy, UK, Spain, and Canada) belonged to the third part of 1,001-3,000 articles; three countries (China, Russia, and Germany) belonged to the fourth part of 3,001-5,000 articles; and only one country (USA) which totally published 9,161 articles, belonged to the fifth part of 5,001-10,000 articles.Although there were only 11 countries which published more than 1,000 articles, these 11 countries produced 77% articles.The majority of articles originated from a small number of particular countries.Furthermore, five continents contributed to the thermodynamics research differently.Europe with 42 countries published the most articles 22,969 (56%); Asia with 42 countries published the second most articles 13,163 (32%); and America with sixteen countries published the third most articles 12,333 (30%).Africa, and Oceania two continents made much less contributions, and the quantity of them were 933 (2.3%), and 667 (1.6%), respectively.It is noticeable that Europe is taking the leading position of thermodynamic research.Asia was seeing a striking increase to catch up with Europe in terms of scientific output (Friedberg, 2000;von Bubnoff, 2005).

Characteristics of top 20 countries/territories
With respect to international collaboration, 33,234 (81%) were independent publications and 7,748 (19%) were internationally collaborative publications.The collaboration rate was a little greater than that of other areas, such as 14% biosorption technology for water treatment (Ho, 2008), 16% of desalination research (Tanaka & Ho, 2011), 16% of solid waste research (Fu et al., 2010), and 14% of acupuncture research (Han & Ho, 2011).Table 4 shows the characteristics of the top 20 productive countries.The eight major industrialized countries G8, ranked in the top 11 in Table 4, had 59% over the investigation period.Similarly, the seven major industrialized countries G7 the USA, Germany, the UK, Japan, France, Canada, and Italy accounted for a significant proportion exited in many researches (Li et al., 2009;He, 2009;Fu et al., 2010;Wang et al., 2010).The USA dominated, ranking 1 st in independent and collaborative articles, as well as first author and corresponding author articles.Total 1,421 contributing institutions (13%) were affiliated with USA, followed by China (824 institutions, 7.7%), and Russia (792 institutions, 6.5%).The 2 nd position China, the 7 th position India, and the 19 th position Iran had low percentages of collaboration less than 20%.It was not coincident that China emerged as a leading nation in science production (Zhou & Leydesdorff, 2006;Zhou & Leydesdorff, 2008).In most fields, the USA had the quantity (number of papers) lead, although the China has made dramatic strides to overtake the USA, except the biomedical field and some aspects of environmental science (Kostoff, 2008).Besides, the 9 th position UK, the 13 th position Netherlands, the 16 th position Switzerland, and the 20 th position Australia had high cooperation rates no less than 50%.It was also reported that international collaboration in both within and outside the European Communities played an increasing role for European scientific literature (Narin et al., 1991;Glänzel, 1999).South Korea and Iran had higher rankings in terms of FP and RP than that of TP, while Netherlands and Sweden had lower rankings in terms of FP and RP.Moreover, from the above languages analysis, except English, the popular languages (Russian, Chinese, French, Japanese, and German) were just the mother tongue of the top five countries China, Russia, Germany, Japan, and France except the USA.The excellent performance of these countries was consistent with the results of language analysis.

Comparison of top six countries
The comparison of top six countries with the most articles in 2010 is illustrated in Fig. 7.The USA hold the trump card based on the total number of articles in the study period, but did not have the highest growth rate.China which was ranked 1 st according to the 2010 production had the highest growth rate of 32 articles per year, and surpassed the USA in 2009, following distantly by other countries.USA, India, and Russia had the lower growth rate of 10 -13 articles per year.The following Germany and France had the growth rate of 6.3 and 5.9 articles per year.Particularly, Russia experienced a sharply increase in the first three year from 6 articles in 1991 to 174 articles in 1993, may due to its large fund for recovery of the politic reason (Goodman, 1993;Webb, 1994).The Russian annual output grew from 1980 to 1990, but fell after the dissolution of the USSR in late 1991; from 1994 there has been an inconsistent partial recovery, and by 2000 the annual output had approximately regained its 1980 value (Wilson & Markusova, 2004).It seems that the recovery time of Russian thermodynamic research was shorter..9 in 2010.Both countries indicated declines as for annual CPPs, which can be attributed to that it needs time to accumulate their citations (Picknett & Davis, 1999).The outstanding performance of China's CPP in 1993 might be owned to the two highly cited articles of a series by the same authors.They were "thermodynamics of molecular recognition by cyclodextrins. 1. calorimetric titration of inclusion complexation of naphthalenesulfonates with -, -, and -cyclodextrin: enthalpy entropy compensation" (Inoue et al., 1993a) with 344 citations and "thermodynamics of molecular recognition by cyclodextrins.calorimetric titration of inclusion complexation with modified -cyclodextrins.enthalpy-entropy compensation in host-guest complexation: from ionophore to cyclodextrin and cyclophane" (Inoue et al., 1993b) with 198 citations, respectively.Furthermore, the most frequently cited article was "a modified UNIFAC model.2. present parameter matrix and results for different thermodynamic properties" (Gmehling et al., 1993) with 727 citations.
Although this article was published by authors from Germany only, it was also assigned to China according to its address record from Web of Science, because one of the authors had permanent address of China.It is a bias of address information for articles from Web of Science.China's CPP in 1993 were still high (CPP = 20) without these highest citations articles.
Likewise, the well performance of the USA's CPP in 1991 can be ascribed to the top cited article "protein folding and association: insights from the interfacial and thermodynamic properties of hydrocarbons" which was published in 1991 (Nicholls et al., 1991) and received 4,999 citations.Most scientific publications from China have a lower citation impact than the world average and have a lower citation rate than expected (Glänzel et al., 2002).It is suggested that China's science needs to move from the "quantitative expansion" phase in nowadays to a "rising quality" phase (Jin & Rousseau, 2005).In general, China showed a high growth rate in recent years and dominant now in annual production, but still needs to make efforts on increasing their citations in thermodynamics.

Characteristics of top 20 institutions
After examining the national contributors, the characteristics of institutional contributors institutions were identified.Of 40,982 articles from 10,696 institutions in 128 countries, 16,628 (41%) were inter-institutionally collaborative publications, and 24,354 (59%) were independent publications.The percentage of collaboration among institutions was much higher than that among countries (19%).The inter-institutional collaboration rate was usually greater than international collaboration rates (Fu et al., 2010;Han & Ho, 2011;Li et al., 2011;Tanaka &Ho, 2011).The number of articles of institutions was smaller than the country, and it was reported that the collaboration was more likely to happen when the size of actors was small (Narin et al., 1991).Nevertheless, the inter-institutional collaboration rate (41%) of thermodynamic research was observed to be lower than that of many other fields, such as 62% of global climate change (Li et al., 2011), 53% in atmospheric simulation (Li et al., 2009), 44% in solid waste research (Fu et al., 2010), and 53% of acupuncture research (Han &Ho, 2011).Four institutions in the USA and Japan, three in China, two each in Russia, and one each in Sweden, Ukraine, UK, India, France, and Italy were ranked in the top 20 productive institutions (16%) as shown in Table 5.It is worth noting that the Russian Academy of Sciences ranked 1 st and Chinese Academy of Sciences ranked 2 nd are both integrated research centers and made up of many relatively independent institutions distributed throughout their country.At present, the publications of these institutions were pooled as one heading, and publications divided into branches would result in different rankings.A bias appeared because national research institutions might have many branches in different cities, for example the CAS (Li et al., 2009), the RAS (Li et al., 2009), and Indian Institute of Technology (Tanaka & Ho, 2011).RAS founded the most productive thermodynamic journal of Russian Journal of Physical Chemistry A. In particular, 228 articles (28%) were contributed by RAS, and 117 articles (14%) were contributed by Moscow Lomonosov State University in Russia based on the total articles (817 articles with author information) of Russian Journal of Physical Chemistry A during 1991-2010.With the exception of these two institutions, the most productive institution is Moscow Lomonosov State University in Russia (425; 1.0%), followed by Tohoku University in Japan (335; 0.82%), and Centre National de la Recherche Scientifique in France (313; 0.76%).However, a bias would appear in the analysis of institutions which was used by different names in their publications.It is strongly recommended that an "international identity number" for all institutions when authors published their paper with an institution as affiliation in a Web of Science-listed journal (Chiu &Ho, 2007).
More independent institutions might lead to more first author articles and corresponding author articles or vice versa.Some institutions which had low collaboration rates no more than 40% usually had a higher rank in FP and RP.For example, the 12 th place Indian Institute of Technology in India with the low collaboration rate of 33% ranked 6 th in FP and 8 th in RP; the 15 th position Massachusetts Institute of Technology in USA with the low collaboration rate of 40% ranked 10 th in FP and 11 th in RP; the 19 th position National Academy of Sciences of Ukraine in Ukraine with the low collaboration rate of 31% ranked 12 th in FP and 9 th in RP.On the other hand, some institutions which had high collaboration rates more than 70% were ranked lower in the rankings of FP and RP.For example, the 5 th position Centre National de la Recherche Scientifique in France with the high collaboration rate of 73% ranked 11 th in FP and 13 th in RP; the 18 th position National Research Council in Italy with the high collaboration rate of 87% ranked 52 th in FP and 58 th in RP.
Thermodynamics -Fundamentals and Its Application in Science 534

Comparison of top seven institutions
To identify the growth trends of active institutions in recent years, the trends of top seven productive institutions with most articles in 2010 are shown in Fig. 9.The most productive institution -RAS had an overwhelming majority in the total articles, and CAS was just down by three articles in 2010, following distantly by the other institutions.CAS as the China's highest academic institution in natural sciences played an active role in terms of scientific outputs in recent years as the exponentially growth scientific production in China (Li et al., 2009;Fu et al., 2010;Tanaka &Ho, 2011;Fu et al., 2011;Li et al., 2011).Although three universities in China including Central South University, Naval University of Engineering, and SiChuan University just ranked 10 th , 39 th , and 43 rd of total articles from 1991 to 2010, but they had high rankings (3 rd , 4 th , and 7 th ) with respect to the number of articles in 2010.The growth rates of the top institutions differed from each other.Particularly, based on the last decade (2001-2010), CAS showed the highest growth rate of 7.2 articles per year; CSU and NUE showed the growth rate of 4 -5 articles per year.The other four institutions, RAS, Moscow Lomonosov State University, University of Science and Technology Beijing, and SiChuan University showed the growth rate of 1 -2 articles per year.About 14% percent articles in RAS were published in Russian Journal of Physical Chemistry A which was founded by RAS.It was interesting that the top three institutions (CAS, CSU, and NUE) with the greatest growth rates were all in China.CSU was established in 2000 by merging three separate universities: Hunan Medical University, Changsha Railway University, and Central South University of technology, and was involved in "985 Project" and "211 Project" which were supported by Chinese government to promote the development and reputation of the Chinese higher education system (http://iecd.csu.edu.cn/en-US/ColumnS.aspx?cid=12).Moreover, CSU hold one SCI journal named Transactions of Nonferrous Metals Society of China which published 11% thermodynamic related articles of CSU in the study period.Another institution, NUE ranks as a military university of higher learning subjected to the leadership of the Central Military Commission and the Party Committee of the PLA Navy, and is listed as one of the five comprehensive universities in the armed forces and the army "2110 project" that enjoys the priority in development.It falls into the category of key national university specializing in engineering (http://english.chinamil.com.cn/site2/special-reports/2007-06/21/content_853791.htm).

Research emphases and trends
Bibliometric analysis of author keywords has been only observed in recent years (Chiu &Ho, 2007;Wang et al., 2010;Li et al., 2011).It tried to find the research emphases and trends by quantitatively analyzing the frequency of author keywords.Excluding some articles without author keywords information, 23,458 articles (57%) with records of author keywords in the SCI-Expanded database were analyzed.There were 45,182 author keywords listed by authors, 43,930 (97%) keywords were used no more than ten times, which indicated that thermodynamic research involved diverse scientific literature and a wide disparity in research focuses (Chuang et al., 2007).Only 74 (0.16%) author keywords were used no less than 100 times, suggesting that the mainstream research in thermodynamics was considered to focus on a small field.Four five-year intervals (1991-1995, 1996-2000, 2001-2005, and 2006-2010) were employed to obtain the trends of these author keywords as well as minimize the year-to-year fluctuations.The top 30 author keywords (accounting for 37% of the total articles) in the latest interval 2006-2010 are listed in Table 6.
Except the author keywords "thermodynamics", "thermodynamic properties", "thermodynamic parameters", and "thermodynamic" related to searching keywords, the three most frequently used author keywords were "kinetics" (883; 3.8%), "adsorption" (736; 3.1%), and "phase diagram" (545; 2.3%)."Thermodynamics" and "kinetics" were related to one another in ways, and were both commonly used to describe process (Kocks et al., 1975;Astumian, 1997;Ho & Ofomaja, 2005)."Adsorption" was a widely applied process, for example in environmental science (Wang et al., 2010;Wang et al., 2011;Chuang et al., 2011).The term "phase diagram" is a type of chart used to obtaining thermodynamic data at equilibrium (Kleppa, 1952;Svirbely, 1954).In particular, there were also some emerging hotspots in thermodynamics recently.Some author keywords including the 3 rd "adsorption", the 9 th "thermodynamic modeling", the 14 th "CALPHAD", the 17 th "thermodynamic property", the 18 th "density functional theory", the 19 th "isothermal titration calorimetry", the 20 th "thermodynamic stability", the 21 st "isotherm", the 25 th "free energy", the 27 th "biosorption", and the 28 th "AB initio calculations" in the list showed the increasing trends during the study period.It is noticeable that "CALPHAD", "biosorption", and "AB initio calculations" increased rapidly from zero articles in 1991-1995 into the top 30 rankings in 2006-2010."CALPHAD" was firstly used as the author keyword of the article entitled "compilation of 'CALPHAD' formation enthalpy data -Binary intermetallic compounds in the COST507 Gibbsian database" in 1998 (Fries & Jantzen, 1998).However, "CALPHAD method" had been used as the author keyword of the article titled "thermodynamic study on the Ag-Sb-Sn system" in 1996 (Oh et al., 1996).The first article which employed "biosorption" as author keyword was titled "determination of the equilibrium, kinetic and thermodynamic parameters of the batch biosorption of nickel(II) ions onto Chlorella vulgaris" in Process Biochemistry in 2002 (Aksu, 2002)."Biosorption" as a process for water treatment received increasing attention in recent years (Ho, 2008).As for "AB initio calculations", it was originally utilized as author keywords of the article "an AB initio study of structures and energetics of copper sulfide clusters" in 1996 (Dehnen et al., 1996).Similarly, "density functional theory", "isothermal titration calorimetry", and "isotherm" grew fast from the 1288 th (only one article) in 1991-1995 to 18 th , 19 th , and 21 st in 2006-2010.The article targeting at "density functional theory" could be found in 1994 and it was entitled "density-functional theory as thermodynamics" (Nagy & Parr, 1994).Thermodynamical interpretation of the density functional theory for an electronic ground state was developed (Nagy & Parr, 1994).The following article which utilized "density functional theory" as author keyword was published in 1999.For the phrase "isothermal titration calorimetry", the article which used it as author keyword appeared in 1995, and it was titled "comparative thermodynamic analyses of the Fv, Fab* and Fab fragments of anti-dansyl mouse monoclonal-antibody" (Shimba, 1995).However, it should be noticed that there was a bias that all these analysis were based on the data (57%) with author keywords information from SCI-Expanded.

Conclusion
Except the dominant language English, Russian, Chinese, French, Japanese and German were the most common languages.Above all, the growth process of annual thermodynamic scientific outputs can be divided into two stages, and the annual growth rate of the second stage 2004-2010 was four times of that in the first stage 1991-2003.Secondly, Russian Journal of Physical Chemistry was the most productive journal, and then Journal of Alloys and Compounds and Journal of Chemical Physics.The most common category was found to be physical chemistry.Thirdly, the global geographic distribution discovered that Europe took the leading position, following by Asia, America, Africa and Oceania.In particular, the eight major industrialized countries (G8: Canada, France, Germany, Italy, Japan, Russia, the UK, and USA) played a prominent role with more than a half contribution, especially the USA.

Figure 1 .
Figure 1.Data collection process for searching thermodynamic related research

Figure 2 .
Figure 2. Analytic structure of bibliometric analysis of thermodynamic research

Figure 3 .
Figure 3.The growth trend of articles in thermodynamic research ; and seven sources (0.28%) contained more than 600 articles, accounting for 11 percent of the total articles.The trends of the annual publication outputs of the top core seven journals are displayed in Fig. 4. The curves of these seven journals (Russian Journal of Physical Chemistry A, Journal of Alloys and Compounds, Physical Review B, Journal of Chemical Physics, Journal of Chemical Thermodynamics, and Thermochimica Acta Biochemistry) had been interlacing in the study period.However, after 2008, Journal of Alloys and Compounds which published 108 articles in 2009 and 70 articles in 2010 showed its domination in the thermodynamic field.

Figure 4 .
Figure 4.The trends of top seven journals with more than 600 articles

Figure 5 .
Figure 5.The trends of top seven Web of Science categories with more than 3000 articles

Figure 6 .
Figure 6.Global geographical distribution of thermodynamics research outputs

Figure 7 .
Figure 7. Trends of top six countries with most articles in 2010

Figure 8 .
Figure 8.Comparison of USA and China by number of articles and citations per publication

Figure 9 .
Figure 9. Trends of top seven institutions with most articles in 2010

Table 2 .
AbbreviationIndicators TP Number of scientific publications by the analyzed unit (document type, language, year, journal, Web of Science category, country/territory, institution, or author keyword) % Number of papers of an actor (document type, language, journal, country/territory, institution, or author keyword) as a share of the

Table 1 .
Explanation of the abbreviations used in subsequent analysis

Table 2 .
Introduction of the acronyms used in subsequent analysis

Table 3 .
Characteristics of top 20 journals with the most articles in thermodynamics

. Journals and Web of Science categories
Bibliometric Analysis of Thermodynamic Research: A Science Citation Index Expanded-Based Analysis 529 IN: Number of institutions.

Table 4 .
Characteristics of the top 20 productive countries/territories