Citation and impact factor distributions of scientific journals published in individual countries

The distributions of citations L, two- (IF2) and five-year impact factors (IF5), and citation half-lives λ of journals published in different selected countries are analyzed using Langmuir-type relation: y_n = y₀ {1 ? αKn/(1 + Kn)}, where y_n denotes L_n, IF2_n or IF5_n of n-ranked journal, y₀ is the value of y_n when journal rank n = 0, α is an empirical effectiveness parameter, and K is the Langmuir constant. It was found that: (1) the general features of the distribution of L_n, IF2_n or IF5_n of the journals published in different individual countries are similar to the results obtained before by the author from the analysis of the citation distribution data of papers of individual authors (K. Sangwal, Journal of Informetrics 7 (2013) 36–49), (2) in contrast to the theoretically expected value of the effectiveness parameter α = 1, the calculated values of α > 1 for journals published in different countries, (3) the trends of the distribution of cited half-lives λ_n of journals differ from those of L_n, IF2_n and IF5_n data for different countries, and show one, two or three linear regions, the longest linear regions with low slopes are observed in the case of countries publishing relatively high number of journals, and (4) the product of the Langmuir constant K and the number N of journals for the processes of citations and two- and five-year impact factors of journals published in different countries is constant for a process. The results suggest that: (1) the values of α > 1 are associated with a process that retards the generation of items (i.e. citations or impact factors), the difference (α ? 1) being related to the dissemination of contents of the journals published by a country, and (2) the constancy of KN is related to the publication potential of a country.     

Comparison of different mathematical functions for the analysis of citation distribution of papers of individual authors

The citation distribution of papers of selected individual authors was analyzed using five mathematical functions: power-law, stretched exponential, logarithmic, binomial and Langmuir-type. The former two functions have previously been proposed in the literature whereas the remaining three are novel and are derived following the concepts of growth kinetics of crystals in the presence of additives which act as inhibitors of growth. Analysis of the data of citation distribution of papers of the authors revealed that the value of the goodness-of-the-fit parameter R² was the highest for the empirical binomial relation, it was high and comparable for stretched exponential and Langmuir-type functions, relatively low for power law but it was the lowest for the logarithmic function. In the Langmuir-type function a parameter K, defined as Langmuir constant, characterizing the citation behavior of the authors has been identified. Based on the Langmuir-type function an expression for cumulative citations L relating the extrapolated value of citations l₀ corresponding to rank n = 0 for an author and his/her constant K and the number N of paper receiving citation l ≥ 1 is also proposed.     

A mathematical characterization of the Hirsch-index by means of minimal increments

The minimum configuration to have a h-index equal to h is h papers each having h citations, hence h² citations in total. To increase the h-index to h + 1 we minimally need (h + 1)² citations, an increment of I₁(h) = 2h + 1. The latter number increases with 2 per unit increase of h. This increment of the second order is denoted I₂(h) = 2.If we define I₁ and I₂ for a general Hirsch configuration (say n papers each having f(n) citations) we calculate I₁(f) and I₂(f) similarly as for the h-index. We characterize all functions f for which I₂(f) = 2 and show that this can be obtained for functions f(n) different from the h-index. We show that f(n) = n (i.e. the h-index) if and only if I₂(f) = 2, f(1) = 1 and f(2) = 2.We give a similar characterization for the threshold index (where n papers have a constant number C of citations). Here we deal with second order increments I₂(f) = 0.     

A refinement of Egghe's increment studies

In this contribution we show how results obtained in a series of papers by Egghe can be refined in the sense that we need fewer additional conditions. In these articles Egghe considered a general h-type index which has a value n if n is the largest natural number such that the first n publications (ranked according to the number of received citations) have received at least f(n) citations, with f(n) any increasing function defined on the strictly positive numbers. His results deal with increments I₂ and I₁ defined by: I₂(n) = I₁(n + 1) − I₁(n) where I₁(n) = (n + 1)f(n + 1) − nf(n). Our results differ from Egghe's because we also consider I_k(0), k = 1,2. We, moreover, provide a non-recursive definition of the increment functions I_k(n).     

Convergent validity of bibliometric Google Scholar data in the field of chemistry—Citation counts for papers that were accepted by Angewandte Chemie International Edition or rejected but published elsewhere,using Google Scholar,Science Citation Index,Scopus, and Chemical Abstracts

Examining a comprehensive set of papers (n = 1837) that were accepted for publication by the journal Angewandte Chemie International Edition (one of the prime chemistry journals in the world) or rejected by the journal but then published elsewhere, this study tested the extent to which the use of the freely available database Google Scholar (GS) can be expected to yield valid citation counts in the field of chemistry. Analyses of citations for the set of papers returned by three fee-based databases – Science Citation Index, Scopus, and Chemical Abstracts – were compared to the analysis of citations found using GS data. Whereas the analyses using citations returned by the three fee-based databases show very similar results, the results of the analysis using GS citation data differed greatly from the findings using citations from the fee-based databases. Our study therefore supports, on the one hand, the convergent validity of citation analyses based on data from the fee-based databases and, on the other hand, the lack of convergent validity of the citation analysis based on the GS data.     

Comparative rank assessment of journal articles

To take into account the impact of the different bibliometric features of scientific fields and different size of both the publication set evaluated and the set used as reference standard, two new impact indicators are introduced. The Percentage Rank Position (PRP) indicator relates the ordinal rank position of the article assessed to the total number of papers in the publishing journal. The publications in the publishing journal are ranked by the decreasing citation frequency. The Relative Elite Rate (RER) indicator relates the number of citations obtained by the article assessed to the mean citation rate of the papers in the elite set of the publishing journal. The indices can be preferably calculated from the data of the publications in the elite set of journal papers of individuals, teams, institutes or countries. The number of papers in the elite set is calculated by the equation: P(π_v) = (10 log P) ? 10, where P is the total number of papers. The mean of the PRP and RER indicators of the journal papers assessed may be applied for comparing the eminence of publication sets across fields.     

The problem of citation impact assessments for recent publication years in institutional evaluations

Bibliometrics has become an indispensable tool in the evaluation of institutions (in the natural and life sciences). An evaluation report without bibliometric data has become a rarity. However, evaluations are often required to measure the citation impact of publications in very recent years in particular. As a citation analysis is only meaningful for publications for which a citation window of at least three years is guaranteed, very recent years cannot (should not) be included in the analysis. This study presents various options for dealing with this problem in statistical analysis. The publications from two universities from 2000 to 2011 are used as a sample dataset (n = 2652, univ 1 = 1484 and univ 2 = 1168). One option is to show the citation impact data (percentiles) in a graphic and to use a line for percentiles regressed on ‘distant’ publication years (with confidence interval) showing the trend for the ‘very recent’ publication years. Another way of dealing with the problem is to work with the concept of samples and populations. The third option (very related to the second) is the application of the counterfactual concept of causality.     

The citation speed index: A useful bibliometric indicator to add to the h index

The scientific impact of a publication can be determined not only based on the number of times it is cited but also based on the citation speed with which its content is noted by the scientific community. Here we present the citation speed index as a meaningful complement to the h index: whereas for the calculation of the h index the impact of publications is based on number of citations, for the calculation of the speed index it is the number of months that have elapsed since the first citation, the citation speed with which the results of publications find reception in the scientific community. The speed index is defined as follows: a group of papers has the index s if for s of its N_p papers the first citation was at least s months ago, and for the other (N_p ? s) papers the first citation was ≤s months ago.     

A case study of the arbitrariness of the h-index and the highly-cited-publications indicator

The arbitrariness of the h-index becomes evident, when one requires q × h instead of h citations as the threshold for the definition of the index, thus changing the size of the core of the most influential publications of a dataset. I analyze the citation records of 26 physicists in order to determine how much the prefactor q influences the ranking. Likewise, the arbitrariness of the highly-cited-publications indicator is due to the threshold value, given either as an absolute number of citations or as a percentage of highly cited papers. The analysis of the 26 citation records shows that the changes in the rankings in dependence on these thresholds are rather large and comparable with the respective changes for the h-index.     

Real and rational variants of the h-index and the g-index

The definitions of the rational and real-valued variants of the h-index and g-index are reviewed. It is shown how they can be obtained both graphically and by calculation. Formulae are derived expressing the exact relations between the h-variants and between the g-variants. Subsequently these relations are examined. In a citation context the real h-index is often, but not always, smaller than the rational h-index. It is also shown that the relation between the real and the rational g-index depends on the number of citations of the article ranked g + 1. Maximum differences between h, h_r and h_rat on the one hand and between g, g_r and g_rat on the other are determined.     

Growth of journals,articles and authors in malaria research

In the present study we have tried to trace the growth of malaria research at Global Level and the distribution of articles in various journals for the period 1955–2005. The data have been extracted from a database, which has been developed in-house from MEDLINE, SCI, TDB, Ovid Heath Information and Indian Science Abstracts. Study indicates that the exponential model fits the data on journals, articles and authors. The R² value for the trend for journals, articles, and authors are 0.9502, 0.9475, and 0.9651, respectively. The growth rates for journals, articles and authors are 5.31%, 7.38%, and 10.06%, respectively. The linear multiple regression equation that Articles = ?39.2771 + 3.61719*journals + 0.085882*Authors (R² = 99.16%) is most meaningful and it may be used to estimate the articles for given numbers of journals and authors.     

An exploratory usability evaluation of Colorado State University Libraries' digital collections and the Western Waters Digital Library Web sites

In an exploratory study, participants (n = 18) completed 11 usability tasks to assess ease of use of two Web sites, and then a Web site perception questionnaire for each. Participants rated both Web sites positively, but 25% and 36% could not complete all tasks; doing so required more than a minute to complete.     

Efficiency,unused capacity and transmission power as indicators of the Triple Helix of university–industry–government relationships

In this paper, we show that an information source composed with n random variables may be split into 2ⁿ or 2ⁿ − 1 “states”; therefore, one could compute the maximum entropy of the source. We derive the efficiency and the unused capacity of an information source. We demonstrate that in more than two dimensions, the transmission's variability depends on the system configuration; thus, we determine the upper and the lower bounds to the mutual information and propose the transmission power as an indicator of the Triple Helix of university–industry–government relationships. The transmission power is defined as the fraction of the total ‘configurational information’ produced in a system; it appears like the efficiency of the transmission and may be interpreted as the strength of the variables dependency, the strength of the synergy between the system's variable or the strength of information flow within the system.     

Regularity in the time-dependent distribution of the percentage of never-cited papers: An empirical pilot study based on the six journals

The non-citation rate refers to the proportion of papers that do not attract any citation over a period of time following their publication. After reviewing all the related papers in Web of Science, Google Scholar and Scopus database, we find the current literature on citation distribution gives more focus on the distribution of the percentages and citations of papers receiving at least one citation, while there are fewer studies on the time-dependent patterns of the percentage of never-cited papers, on what distribution model can fit their time-dependent patterns, as well as on the factors influencing the non-citation rate. Here, we perform an empirical pilot analysis to the time-dependent distribution of the percentages of never-cited papers in a series of different, consecutive citation time windows following their publication in our selected six sample journals, and study the influence of paper length on the chance of papers’ getting cited. Through the above analysis, the following general conclusions are drawn: (1) a three-parameter negative exponential model can well fit time-dependent distribution curve of the percentages of never-cited papers; (2) in the initial citation time window, the percentage of never-cited papers in each journal is very high. However, as the citation time window becomes wider and wider, the percentage of never-cited papers begins to drop rapidly at first, and then drop more slowly, and the total degree of decline for most of journals is very large; (3) when applying the wider citation time windows, the percentage of never-cited papers for each journal begins to approach a stable value, and after that value, there will be very few changes in these stable percentages, unless we meet a large amount of “Sleeping Beauties” type papers; (4) the length of an paper has a great influence on whether it will be cited or not.     

Where are citations located in the body of scientific articles? A study of the distributions of citation locations

We address issues concerning what one may learn from how citation instances are distributed in scientific articles. We visualize and analyze patterns of citation distributions in the full text of 350 articles published in the Journal of Informetrics. In particular, we visualize and analyze the distributions of citations in articles that are organized in a commonly seen four-section structure, namely, introduction, method, results, and conclusions (IMRC). We examine the locations of citations to the groundbreaking h-index paper by Hirsch in 2005 and how patterns associated with citation locations evolve over time. The results show that citations are highly concentrated in the first section of an article. The density of citations in the first section is about three times higher than that in subsequent sections. The distributions of citations to highly cited papers are even more uneven.     

Copyright Awareness,Partnerships, and Training Issues in Academic Libraries

This article reports on the results of a national survey of academic librarians and library staff (N = 226) in the United States about their awareness of various copyright policies, partnerships with campus groups to address copyright issues, and training needs. A majority of the survey respondents reported that they have answered copyright-related questions in the workplace, yet only 49% (n = 98) of the respondents perceived they were prepared to provide copyright information to library users. Awareness of various copyright policies among librarians and staff members varied, including a reported minimal awareness of the T.E.A.C.H. Act. In addition, survey respondents expressed the desire for more copyright-related training. In light of these findings, the present study extends the existing literature and offers recommendations to help better prepare a “copyright confident” or “copyright responsive” academic library workforce.     

Including cited non-source items in a large-scale map of science: What difference does it make?

Cited non-source documents such as articles from regional journals, conference papers, books and book chapters, working papers and reports have begun to attract more attention in the literature. Most of this attention has been directed at understanding the effects of including non-source items in research evaluation. In contrast, little work has been done to examine the effects of including non-source items on science maps and on the structure of science as reflected by those maps. In this study we compare two direct citation maps of a 16-year set of Scopus documents – one that includes only source documents, and one that includes non-source documents along with the source documents. In addition to more than doubling the contents of the map, from 19 M to 43 M documents, the inclusion of non-source items strongly augments the social sciences relative to the natural sciences and medicine and makes their position in the map more central. Books are also found to play a significant role in the map, and are much more highly cited on average than articles.     

Paper-patent citation linkages as early signs for predicting delayed recognized knowledge: Macro and micro evidence

In this study, we investigate the extent to which patent citations to papers can serve as early signs for predicting delayed recognized knowledge in science using a comparative study with a control group, i.e., instant recognition papers. We identify the two opposite groups of papers by the Bcp measure, a parameter-free index for identifying papers which were recognized with delay. We provide a macro (Science/Nature papers dataset) and micro (a case chosen from the dataset) evidence on paper-patent citation linkages as early signs for predicting delayed recognized knowledge in science. It appears that papers with delayed recognition show a stronger and longer technical impact than instant recognition papers. We provide indication that in the more recent years papers with delayed recognition are awakened more often and earlier by a patent rather than by a scientific paper (also called “prince”). We also found that patent citations seem to play an important role to avoid instant recognition papers to level off or to become a so called “flash in the pan”, i.e., instant recognition. It also appears that the sleeping beauties may firstly encounter negative citations and then patent citations and finally get widely recognized. In contrast to the two focused fields (biology and chemistry) for instant recognition papers, delayed recognition papers are rather evenly distributed in biology, chemistry, psychology, geology, materials science, and physics. We discovered several pairs of “science sleeping”-“technology inducing”, such as “biology-biotechnology/pharmaceuticals”, “chemistry-chemical engineering”, as well as some trans-fields science-technology interactions, such as “psychology - computer technology/control technology/audio-visual technology”, “physics - computer technology”, and “mathematics-computer technology”. We propose in further research to discover the potential ahead of time and transformative research by using citation delay analysis, patent & NPL analysis, and citation context analysis.     

Quantitative evaluation of alternative field normalization procedures

Wide differences in publication and citation practices make impossible the direct comparison of raw citation counts across scientific disciplines. Recent research has studied new and traditional normalization procedures aimed at suppressing as much as possible these disproportions in citation numbers among scientific domains. Using the recently introduced IDCP (Inequality due to Differences in Citation Practices) method, this paper rigorously tests the performance of six cited-side normalization procedures based on the Thomson Reuters classification system consisting of 172 sub-fields. We use six yearly datasets from 1980 to 2004, with widely varying citation windows from the publication year to May 2011. The main findings are the following three. Firstly, as observed in previous research, within each year the shapes of sub-field citation distributions are strikingly similar. This paves the way for several normalization procedures to perform reasonably well in reducing the effect on citation inequality of differences in citation practices. Secondly, independently of the year of publication and the length of the citation window, the effect of such differences represents about 13% of total citation inequality. Thirdly, a recently introduced two-parameter normalization scheme outperforms the other normalization procedures over the entire period, reducing citation disproportions to a level very close to the minimum achievable given the data and the classification system. However, the traditional procedure of using sub-field mean citations as normalization factors yields also good results.