Comparison of the effect of mean-based method and z-score for field normalization of citations at the level of Web of Science subject categories

Field normalization is a necessary step in a fair cross-field comparison of citation impact. In practice, mean-based method (m-score) is the most popular method for field normalization. However, considering that mean-based method only utilizes the central tendency of citation distribution in the normalization procedure and dispersion is also a significant characteristic, an open and important issue is whether alternative normalization methods which take both central tendency and variability into account perform better than mean-based method. With the aim of collapsing citation distributions of different fields into a universal distribution, this study compares the normalization effect of m-score and z-score based on 236 Web of Science (WoS) subject categories. The results show that both m-score and z-score have remarkable normalization effect as compared with raw citations, but neither of them can realize the ideal goal of “universality of citation distributions”. The results also suggest that m-score is generally preferable to z-score. The essential cause that m-score has an edge over z-score as a whole has a direct relationship with the characteristics of skewed citation distributions in which case m-score is more applicable than z-score.     

Citation regression analysis of computer science publications in different ranking categories and subfields

A number of bibliometric studies point out that the role of conference publications in computer science differs from that in other traditional fields. Thus, it is interesting to identify the relative status of journal and conference publications in different subfields of computer science based on the citation rates categorised by the China Computer Federation (CCF) classifications and venue types. In this research, we construct a dataset containing over 100,000 papers recommended by the CCF catalogue and their citation information. We also investigate some other factors that often influence a paper’s citation rate. An experimental study shows that the relative status of journals and conferences varies greatly in different subfields of computer science, and the impact of different publication levels varies according to the citation rate. We also verify that the classification of a publication, number of authors, maximum h-index of all authors of a paper, and average number of papers published by a publication have different effects on the citation rate, although the citation rate may have a different degree of correlation with these factors.     

Top-down decomposition of the Journal Citation Reportof the Social Science Citation Index: Graph- and factor-analytical approaches

The aggregated journal-journal citation matrix of the Journal Citation Report 2001of the Social Science Citation Indexis analyzed as a single domain in terms of both its eigenvectors and the bi-connected components contained in it. The traditional disciplines (e.g., economics, psychology, or political science) can be retrieved using both methods. These main disciplines do interact marginally. The space between them is occupied by a large number of small clusters of journals indicating specialties that gravitate among the major disciplines. These specialties operate in a mode different from that of the disciplines. For example, the impact factors are low on average and the developments remain volatile. Factor analysis enables us to study how the smaller bi-connected components are related to the larger ones. Factor analysis also highlights methodological differences among groups which may be theoretically connected in a single bi-component. This revised version was published online in June 2006 with corrections to the Cover Date.     

Sources of Google Scholar citations outside the Science Citation Index: A comparison between four science disciplines

For practical reasons, bibliographic databases can only contain a subset of the scientific literature. The ISI citation databases are designed to cover the highest impact scientific research journals as well as a few other sources chosen by the Institute for Scientific Information (ISI). Google Scholar also contains citation information, but includes a less quality controlled collection of publications from different types of web documents. We define Google Scholar unique citations as those retrieved by Google Scholar which are not in the ISI database. We took a sample of 882 articles from 39 open access ISI-indexed journals in 2001 from biology, chemistry, physics and computing and classified the type, language, publication year and accessibility of the Google Scholar unique citing sources. The majority of Google Scholar unique citations (70%) were from full-text sources and there were large disciplinary differences between types of citing documents, suggesting that a wide range of non-ISI citing sources, especially from non-journal documents, are accessible by Google Scholar. This might be considered to be an advantage of Google Scholar, since it could be useful for citation tracking in a wider range of open access scholarly documents and to give a broader type of citation impact. An important corollary from our study is that Google Scholar’s wider coverage of Open Access (OA) web documents is likely to give a boost to the impact of OA research and the OA movement.     

Representation of journals from five neighboring European countries in the Journal Citation Reports

This study explores the representation of scientific journals from Italy, Hungary, Slovenia, Croatia, and Serbia and Montenegro in the Thomson Scientific’s 2005 Journal Citation Reports (JCR). The number of journals covered by JCR was analyzed in relation to scientific productivity of selected countries and the size of their economies, and no apparent relationship between these factors was found. Our findings suggest that other factors, including the quality of individual journals, may influence how many journals a country will have in the JCR.     

The effect of citations on the significance of decimal places in the computation of journal impact factors

Journal impact factors (JIF) are computed by Thomson Reuters to three decimal places. Some authors have cast doubt on the validity of the third decimal place in JIFs. In this paper I present a new approach to evaluate the significance of decimal places in JIFs. To do so, two modified JIFs were computed by adding or removing one citation to the number used by Thomson Reuters to compute the JIF for journals listed in the 2008 Journal Citation Report. The rationale is that one citation is the minimum amount of impact that can be observed and analyzed. Next, the modified JIFs were compared with the original JIF to identify the decimal place that changed as consequence of adding or removing one citation. The results suggest that for about two-third of journals, the number of places used by Thomson Reuters to compute JIFs can be considered appropriate for the most part.     

Reassessing the N-rays reference network: The role of self citations and negative citations

In his article networks of Scientific Papers,Price argued that the N-rays reference network exhibits characteristics one would expect for a cumulative and rapidly developing research area. Although subsequent researchers have questioned Price's characterization of the N-rays network, there have been no replications of Price's work for either the N-rays literature or for any other literature. We reexamine the N-rays reference network, this time distinguishing negative citations and self citations from other citations. Although previous studies of negative and self citations show they are relatively infrequent in scientific literatures, we find that both are very prominent in the N-rays literature. In addition, we show that self citations comprise most of the recency effect observed in the N-rays reference network, and that the high level of self citations in the N-rays literature results primarily from the character of the journal that published the majority of the N-rays papers. Our findings therefore support those who have been skeptical about Price's claim that the N-rays reference graph exemplifies basic characteristics of the structure of scientific literatures.     

Increasing the between-year stability of the impact factor in the Science Citation Index

The critical evaluation of scientific productivity during, last years has been done with the help of the Journal Citation Reports ranks of journals. The relative performance of each journal was derived from a simple calculation called Impact Factor. Such measure has been widely criticized by scientometricians, but alternative proposals were nerver adopted due perhaps to their complexity, but also to economic limitations. For the informetric purposes this situation has led to a worrying lack of standardization and, worst of all, makes useless many studies for comparative purposes. In order to enhance the comparative value of the impact factor we develop a new easy method that increases the time period used for its calculation. Such new index has advantages over the old one.     

The SCI Journal Citation Reports: A potential tool for studying journals?

In this paper, we analysed six indicators of the SCI Journal Citation Reports (JCR) over a 19-year period: number of total citations, number of citations to the two previous years, number of source items, impact factor, immediacy index and cited half-life. The JCR seems to have become more or less an authority for evaluating scientific and technical journals, essentially through its impact factor. However it is difficult to find one's way about in the impressive mass of quantitative data that JCR provides each year. We proposed the box plot method to aggregate the values of each indicator so as to obtain, at a glance, portrayals of the JCR population from 1974 to 1993. These images reflected the distribution of the journals into 4 groups designated low, central, high and extreme. The limits of the groups became a reference system with which, for example, it was rapidly possible to situate visually a given journal within the overall JCR population. Moreover, the box plot method, which gives a zoom effect, made it possible to visualize a large sub-population of the JCR usually overshadowed by the journals at the top of the rankings. These top level journals implicitly play the role of reference in evaluation processes. This often incites categorical judgements when the journals to be evaluated are not part of the top level. Our «rereading» of the JCR, which presented the JCR product differently, made it possible to qualify these judgements and bring a new light on journals.     

The effect of the additional biasing on the switching process in pseudo spin-valve structure

The magnetization reversal of the free layer was studied in a pseudo spin-valve Gd-Co/Cu/Co structure prepared by thermal evaporation. The uniaxial magnetic anisotropy in a plane of the film was induced by applying the magnetic field during deposition. The angular dependence of the free Co layer coercivity was observed to be consistent with the Stoner-Wohlfarth rotation model. The switching field of this Co layer was found to be dependent on an additional constant magnetic field, oriented perpendicular to the anisotropy axis in a plane of the multilayered structure. This dependence confirms the possibility of additional regulations of the sensitivity of the spin-valve structure by the application of an appropriate bias field and could be useful for sensor applications.     

Succinct effect or informative effect: the relationship between title length and the number of citations

Previous studies produced mixed results with respect to the correlation between title length and number of citations. This research aims to provide a new explanation for this controversy by examining one of the largest pools of papers to date, containing over 300,000 economics papers spanning a much longer time period (1956–2012). The results show that correlation between title length and the number of citations is negative between 1956 and 2000, but becomes positive after 2000, when online searches became the predominant method for literature retrieval. Moreover, heterogeneity analyses show that longer titles are especially crucial for papers with relatively lower influence, which researchers can typically only access using online searches.     

The apparent additional mass effect and waves in poroelastic layered media

The effect of the apparent additional mass of fluid in case of propagation of elastic waves in porous saturated media is considered. There are various points of view about this term. Some authors suggest to consider this term equal to zero, and the others nonzero. Here, the type of wave motion is established in which nonzero apparent additional masses lead to essential effect on some frequences.     

The frequency distribution of legal decision citations in the German jurisdiction

This investigation has three aims: 1. To direct the attention of scientometrics to the widespread use of citation indexes by practising lawyers. The analysis of this practice is of special value for comparative studies in scientometrics and informetrics. 2. To examine the frequency distribution of legal decision citations in the German jurisdiction. 3. To test whether these frequency distributions depend exclusively on the density of citations between documents of a database, as stated by D. Price.

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Résumé One can find the characteristic distribution regularities of information science in a communication system with similarities, but also great differences to scientific communication systems. The inverse power law of scientific productivity of Lotka is — in congruence with a contention ofPrice — true for the informatory productivity of legal decisions of some areas of law, if the reception of decisions is measured by the frequency of citations. The slopes of the curves vary with the areas of law (in my investigations roughly between 2.5 and 3.0), and the concentration processes exhibit different velocities. Lotka's formula is not applicable in every case: there seem to be areas of law with a stronger concentration of lower citation scores than permitted by the formula. The slope of the curve in some cases seems to be correlated — asPrice assumed — with the citation density of a database. Here again the income-tax law does not fit to the picture, as in the case of the Lotka law, too.

     

The effect of document types and sizes on the scaling relationship between citations and co-authorship patterns in management journals

The aim of this paper is to explore the power-law relationship between citation-based performance (CBP) and co-authorship patterns for papers in management journals by analyzing its behavior according to the type of documents (articles and reviews) and the number of pages of documents. We analyzed 36,241 papers that received 239,172 citations. The scaling exponent of CBP for article papers was larger than for reviews. Citations to articles increased 2^1.67 or 3.18 times each time the number of article papers published in a year in management journals doubled. The citations to reviews increased 2^1.29 or 2.45 times each time the number of reviews published in a year in management journals doubled. The scaling exponent for the power-law relationship of citation-based performance according to number of pages of papers was 1.44 ± 0.05 for articles and 1.25 ± 0.05 for reviews. The citations to articles increased faster than citation to reviews. The scaling exponent for the power-law of citation-based performance to co-authored articles was higher than single-authored articles. For reviews the scaling exponent was the same for the relationship between citation based performance and the number of reviews. Citations increased faster in single authored reviews than co-authored reviews.     

Indicators of structural change in the dynamics of science: Entropy statistics of the SCI Journal Citation Reports

Scientometrics - Can change in citation patterns among journals be used as an indicator of structural change in the organization of the sciences? Aggregated journal-journal citations for 1999 are...     

The distribution of reference citations in two agricultural journals

The average numbers of references cited in papers published inN. Z. Journal of Experimental Agriculture (JEA) andN. Z. Journal of Agricultural Research (JAR) are compared. The papers inJAR have a greater number of references per paper than doJEA papers, probably becauseJAR papers are longer.ForJEA papers there is a steady increase in the average number of references per paper as the number of authors per paper increases. ForJAR there is no such steady increase but there is a marked increase in the average number of references per paper for 3- and 4+-author papers.There is a clear difference betweenJEA andJAR papers in the distribution of references between the different sections of the text. ForJEA papers 49% of references are cited in the Introduction and 52% are cited in the Results & Discussion sections. ForJAR the figures are 38% and 65% respectively.It is suggested that the distribution of cited references in the different sections of the text may be an indicator of the appliedness of a paper or of a journal.     

The use of citations matrices to group journals

A method of grouping journals within a wide discipline area into clusters is proposed, based on a algorithm that attempts to re-order a citations matrix so that it is block diagonal, or block recursive. The algorithm is based on a penalty function which allows one to account for the level of citation, not just the distribution of citations between journals. A case study involving eight economics journals is presented which illustrates the principles involved, but which also highlights the computational problems associated with extending the analysis to larger numbers of journals.The permission of the Institute for Scientific Information to access data from theSocial Science Citations Index ^® is gratefully acknowledged, as are the comments of a reviewer, who brought additional literature to my attention.