Bibliometric Analysis of Lead-acid batteries Publications : Trends and Characteristics

The scientific productivity of lead-acid batteries related research among researchers, countries, institutions, journals, and subject area’s was investigated by a bibliometric analysis of lead-acid batteries research from 1980 to 2014. The search includes the Web of Knowledge and SCOPUS databases with the word lead-acid batteries in the title. From Web of Knowledge 2102 documents were obtained, whereas a total of 4685 documents were obtained from SCOPUS. More than 58 % of the documents are research articles, mostly (more than 92%) written in English, about 20 % produced in the United States and 20% produced by Chinese researchers. The study reveals the most productive institutions and authors. Most prolific author is Detchko Pavlov from Bulgarian Academy of Sciences, who account for 1 % of the published articles. Journal of Power Sources is the main journal most used for leadacid batteries research publications (more than 32% in WoS and more than 20% in SCOPUS). According to this results it can be concluded that there is an important gap identified between developed and developing countries in the volume of scientific papers. About the 30% of the papers have been published by the 10 most developed countries excluded Taiwan.


INTRODUCTION
Lead-acid batteries research is an important scientific area.These batteries have applications in energy storage, emergency power, and electric and hybrid vehicles (including off-road vehicles), in telephone systems, power tools, communication devices, emergency lighting systems, and as the power source for mining and material-handling equipment. 1,2The wide use of the lead-acid battery in many designs, sizes, and system voltages is accounted for by the low price and the ease of manufacture on a local geographic basis of this battery system.The lead-acid battery is almost always the least expensive storage battery for any application, while still providing good performance and life characteristics. 3e main objective of this paper is to apply the bibliometric analysis to the Lead-acid batteries papers published in scientific journals with the aim of identifying tendencies, gaps and characteristics in comparing scientific production of some developed countries.These results are expected to be a contribution towards the support of new developments in this area.
The scientific literature was analyzed with emphasis on: papers-temporal trends, document type, language, most frequent subject areas, and most relevant papers from citation indicators; researchers: most productive and most frequent institutions of residence and countries; journals: core journals, and impact factors.
Evaluative bibliometrics, as a subfield of quantitative science and technology studies, can be used to: • Identify the infrastructure (authors, journals, institutions) of a technical domain; • Identify experts for innovation-enhancing technical workshops and review panels; • Develop site visitation strategies for assessment of prolific organizations globally; • Identify impacts (literature citations) of individuals, research units, organizations, and countries. 4,5search Objectives To achieve the aim the following objectives must be fulfilled: • To find out the year-wise distribution.
• To analyze the authorship pattern.
• To analyze the country productivity.
• To categorize document types.
• To examine subject areas.
• To verify Bradford distribution.

Methodology and Sources
The bibliographic search covered papers published during 1980-2014.The search was performed using the two Data bases (DB) -SCI, ( We accessed the WoS and SCOPUS until 2014, in order to find out where research in lead-acid batteries has been done.We accessed data on documents with the word lead-acid batteries in the title and in the abstract of the papers.All records were retrieved for each database and were systematized; then the data sets were validated and normalized, and a quantitative analysis for each category was done: document, author, affiliation (institution), country, journal, subject area.
The 10 most cited papers from two data bases were identified.Impact Factors (IF) were obtained from Journal Citation Report 2014, and core journals were identified with Bradford`s method 6,7 A total of 5947 records were retrieved up to August 30, 2015.

Descriptive analysis of lead acid batteries papers by year of publication
The total number of lead-acid batteries publications was 2102 in the WoS.
The trend analysis from 1980 to 2014 indicates a clear increase of the number of lead-acid batteries papers published: from 8 papers in 1980 to 114 in 2014 (14 times increase) (Figure 1).Nevertheless, when comparing this trend with the total articles in the database it is clear a slight relative increase, that is, from 1.56 in 1991 to 2.51 in 2014.
The SCOPUS database is also analyzed by identifying the number of publications under the subheading lead-acid batteries (see Figure 1).In the 30-year period, there are a total of 4685 publications.We observe an increase of 13 times of the number of publications from 1980 till 2014.
From these data we can infer a first conclusion indicating that, there is increase in the total number of articles per year over the 30 years in the two data bases.
The increase in the period 2000-2014 is obvious.For this reason we analyzed in detail only the data from this 15 years period.

Author frequency results
More than 500 author names in each DB were found.Table 1 shows the 26 most prolific authors, each with more than 9 published articles in WoS and more 11 published articles in SCOPUS and jointly accounting for 20% of all the papers.
In WoS 9 of each 18 authors are from Europe, 8 from Asia and 1 from North America.On the contrary, in the SCOPUS database, the authors from Asia and from Europe are equal number -9.In two DB the most prolific author is Dechko Pavlov from Bulgaria.This is another strong indication of the priority given to lead-acid batteries activities in the countries from Europe and Asia.

Countries producing most lead-acid batteries papers
The 10 countries with the highest number of publications are shown in Table2.It is reasonable that the USA is the country most represented in WoS (11.5%).After USA the most productive country with 9.3 % of publications is People Republic of China.Countries with more or less each one with about 3% of the total were Taiwan, Spain, France and England.Jointly, India, Japan and Iran account for 10 % of the publications.
The analysis of the number of articles by country in Scopus indicates that the most productive country is People Republic of China with 20,5% of all publications.People Republic of China is followed by USA with15.8% of all publications.Germany and Japan have about 300 publications.
The concentration of publications in few developed countries is even more evident in two databases where only two countries (USA and People Republic of China) are leaders.This is a clear hint, in our opinion, not only of the different cultural and economic situations that influence the production of scientific knowledge but also of the different interests, incentives and opportunities that authors encounter when producing and publishing leadacid papers.

Institutions producing most lead-acid batteries papers
There are more than 500 different institutions, such as universities, research Institutes and corporations.The 23 most highly represented are shown in Table 3.The most productive institution according DB WoS is the Bulgarian Academy of Sciences (31 papers).The Harbin Institute of Technology with 60 total number of papers, and Tsinghai University from PR of China with 46 publications are leaders according DB SCOPUS.Taking together all the institutions by country the Asian institutions account about 50% of all published papers.

Journals containing most lead-acid batteries papers
16 of the journals in WoS published 31 % of the articles about lead-acid batteries (Table 4).Sixteen of the journals have 42,5% of the published articles in SCOPUS.Journal of Power Sources is the leader among the journals with the highest number of publications (20% of the total in DB WoS and 13% of the total publications in DB SCOPUS).
Journal of Power Sources and Journal of Electrochemical Society have the highest impact (respectively 6.217 and 3.266).
The journal article is the single most common form of publication.Our sample for 2001 to 2014 includes 2102 articles in WoS.Of these, 410 articles have been published in 1 source title.Three zones constitute the most specific subdivisions of these data for which the Bradford hypothesis is not valid.The nucleus of journals (zone 1) consists of 1 journal in Wos, followed by 66 titles (zones 2), 217 titles (zone 3).The ratio of source title number among these 3 zones in WoS is 1:64:279 which isn't quite close to 1:a:a 2 .This may be due to the widespread nature of lead-acid batteries articles in a vast number of source titles.
Hawkins 8 suggests that the droop might be due to the dispersion of the literature on the subject under study.This finding corresponds to the large number of journals in zone 3. Table 5 also lists the cumulative number of articles and the percentage of each zone.The 67 journals in the 1st and 2nd zones cover 74% of literature, and the 1 journal in the 1st zone cover 32.5 % of the literature.This finding implies that, while 32 % of the literature is concentrated in only the one journal, the remaining 68 % is scattered in 283 journals, showing remarkable scattering of lead-acid batteries literature.The final droop portion reveals that the lead-acid batteries literature has been extensively spread to many different journals.The scattering of information poses a problem in the complete retrieval of relevant information.

Language of publications
It is also important to note the language of publications.Table 6 shows the number of publications in different languages.English was found to be the predominant language and out of a total of records,.1233 articles (97.7%) in WoS and 4310 (92%) articles in SCOPUS are in English.Since WoS is a US based database, some bias for English language may have inadvertently crept in the records.Also, since English is the official scientific language in many countries; it leads to its wide usage in dissemination of scientific data and proceedings.This observation matches with other scientific publications where information is available largely in English.Moreover, English is the official language for most international conferences.
Only 8 % of the articles in SCOPUS are not in English.
The most common non-English language is Chinese, which constitutes 6 % of the total.

Publication type
For convenience, all documents have been placed in five categories in WoS i.e. journal articles, proceedings papers, reviews, editorial materials and meeting abstracts.
In SCOPUS all documents are distributed in seven categories -journal articles, proceedings papers, reviews,

Subject areas analysis
Analysis by subject areas has disclosed that all original articles in lead-acid batteries researches are published

Citation analysis
Some of the many possible uses of citations are bookmarks, intellectual heritage, impact tracker and self-serving purposes.The main function of the applicability of citation analysis is to show the impact or quality measure. 9 the time of this study, there have been 12033 total number of citations in WoS and 10436 total number of citations in SCOPUS published during 2001-2014.
Citations through the years have been shown in Figure 4.
It is clearly seen that there has been almost continuous growth in the number of citations through the years, with the rapid growth started from 2003.
The continuous growth in citations numbers through the years is partly because citations accumulate by years, and within each year, citations include not only current articles but also previous ones which may date back to a few years or even many more years ago.However, the continuous and rapid growth in citations since 2003 is also partly attributed to the continuous and rapid growth of the original articles from 2000.The delay of years is because citations are always one or two years behind the original publications.On the other hand, the continuously increasing number of citations also indicates that the general impact of the original articles in lead-acid batteries research has been increasing gradually.It is interesting to note that some of the most cited articles treat more general questions.For example the articles N= 1 and N= 6 from table 9 treat mathematical models.Article N= 4 from table 9 is dedicated to rechargeable lithium batteries.As well the number of the most cited articles, examined the structure of active materials is small.

CONCLUSION
One of the main conclusions of the empirical analysis of lead acid batteries publications is the important gap identified between developed and developing countries in the volume of scientific papers.About the 33% of the papers have been published by the 10 most developed countries excluded Spain and Taiwan.
The results are summarized as follows: 1.The lead-acid batteries literature from 1980 to 2014 grew practically exponentially.2. The single most common form of publication covered in two data bases is the journal article, which contributes more than 58 % of the total literature.3. The United States of America is the predominant publishing country in WoS in the lead-acid batteries literature (about 12 % of papers).People Republic of China is the most prolific country in SCOPUS with 20.5% of all papers.English is the most common language.English articles constitute more than 92 % of the total.4. The subject areas are diverse.The areas that look into lead acid batteries are energy, engineering, chemistry, material sciences, energy fuels.5.The analysis of the core journals indicates that the more productive is Journal of Power Sources. 6.According Bradford law of information distribution we established that only 1 journal consist the 1st zone and cover 30% of the literature.The remaining 70% of articles is scattered in 284 journals.
This report represents the effort to explore the global scientific production employing Lead acid batteries.It provides quantitative information about the growth of Lead acid batteries research and qualifiers, a ranking of the most successful authors, institutions, countries, journals, topics and temporal trends.

Figure 2 :
Figure 2: The most used subject areas in lead acid batteries, WoS DB

Figure 3 :Figure 4 :
Figure 3: The most used subject areas in lead acid batteries, SCOPUS DB

Figures 2 and 3
Figures 2 and 3 illustrate the focus on original subject areas of the articles in lead-acid batteries research, which are defined as that each of these subject areas has included at least 5 % original articles.It is seen that the top 6 subject areas according WeS are: Energy fuels, Electrochemistry, Engineering, Materials sciences, Automatic Control systems and Telecommunications, which have published most original articles.In SCOPUS the

Table 3 : The most prolific institutions in lead-acid batteries
Figure1: Growth of publications in lead-acid batteries during 1980-2010, WoS and SCOPUS DB

Table 8
and 9 show the most cited articles in WoS and SCOPUS DB.Only five of the top cited articles in two DB are the same.Not surprisingly, the highest ranked journals also have the most cited article is J.of Power Sources.Tables show that the most cited country among the top 10 articles is USA.