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1.
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 Ik(0), k = 1,2. We, moreover, provide a non-recursive definition of the increment functions Ik(n).  相似文献   

2.
The distribution of cumulative citations L and contributed citations Lf to individual multiauthored papers published by selected authors working in different scientific disciplines is analyzed and discussed using Langmuir-type function: yn = y0[1 − αKn/(1 + Kn)], where yn denotes the total number of normalized cumulative citations ln* and normalized contributed citations lnf* received by individual papers of rank n, y0 is the maximum value of yn when n = 0, α ≥ 1 is an effectiveness parameter, and K is the Langmuir constant related to the dimensionless differential energy Q = ln(KNc), with Nc as the number of papers receiving citations. Relationships between the values of the Langmuir constant K of the distribution function, the number Nc of papers of an individual author receiving citations and the effectiveness parameter α of this function, obtained from analysis of the data of rank-size distributions of the authors, are investigated. It was found that: (1) the quantity KNc obtained from the real citation distribution of papers of various authors working in different disciplines is inversely proportional to (α − 1) with a proportional constant (KNc)0 < 1, (2) the relation KNc = (KNc)0/(α − 1) also holds for the citation distribution of journals published in countries of two different groups, investigated earlier (Sangwal, K. (2013). Journal of Informetrics, 7, 487–504), and (3) deviations of the real citation distribution from curves predicted by the Langmuir-type function are associated with changing activity of sources of generation of items (citations).  相似文献   

3.
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, hr and hrat on the one hand and between g, gr and grat on the other are determined.  相似文献   

4.
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.  相似文献   

5.
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: yn = y0 {1 ? αKn/(1 + Kn)}, where yn denotes Ln, IF2n or IF5n of n-ranked journal, y0 is the value of yn 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 Ln, IF2n or IF5n 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 λn of journals differ from those of Ln, IF2n and IF5n 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.  相似文献   

6.
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(πv) = (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.  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
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 Np papers the first citation was at least s months ago, and for the other (Np ? s) papers the first citation was ≤s months ago.  相似文献   

10.
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.  相似文献   

11.
The definition of the g-index is as arbitrary as that of the h-index, because the threshold number g2 of citations to the g most cited papers can be modified by a prefactor at one's discretion, thus taking into account more or less of the highly cited publications within a dataset. In a case study I investigate the citation records of 26 physicists and show that the prefactor influences the ranking in terms of the generalized g-index less than for the generalized h-index. I propose specifically a prefactor of 2 for the g-index, because then the resulting values are of the same order of magnitude as for the common h-index. In this way one can avoid the disadvantage of the original g-index, namely that the values are usually substantially larger than for the h-index and thus the precision problem is substantially larger; while the advantages of the g-index over the h-index are kept. Like for the generalized h-index, also for the generalized g-index different prefactors might be more useful for investigations which concentrate only on top scientists with high citation frequencies or on junior researchers with small numbers of citations.  相似文献   

12.
The following seniority-independent Hirsch-type index has been defined. A scientist has index hpd if hpd of his/her papers have at least hpd citations per decade each, and his/her other papers have less than hpd + 1 citations per decade each. In contrast with the original h-index, which steadily increases in time, hpd of a mature scientist is nearly constant over many years, and hpd of an inactive scientist slowly declines. Therefore hpd is suitable to compare the scientific output of scientists in different ages.  相似文献   

13.
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14.
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.  相似文献   

15.
In the present work we introduce a modification of the h-index for multi-authored papers with contribution based author name ranking. The modified h-index is denoted by hmc-index. It employs the framework of the hm-index, which in turn is a straightforward modification of the Hirsch index, proposed by Schreiber. To retain the merit of requiring no additional rearrangement of papers in the hm-index and in order to overcome its shortage of benefiting secondary authors at the expense of primary authors, hmc-index uses combined credit allocation (CCA) to replace fractionalized counting in the hm-index. The hm-index is a special form of hmc-index and fits for papers with equally important authors or alphabetically ordered authorship. There is a possibility of an author of lower contribution to the whole scientific community obtaining a higher hmc-index. Rational hmc-index, denoted by hmcr-index, can avoid it. A fictitious example as a model case and two empirical cases are analyzed. The correlations of the hmcr-index with the h-index and its several variants considering multiple co-authorship are inspected with 30 researchers’ citation data. The results show that the hmcr-index is more reasonable for authors with different contributions. A researcher playing more important roles in significant work will obtain higher hmcr-index.  相似文献   

16.
This study describes the meaning of and the formula for S-index, which is a novel evaluation index based on the number of citations of each article in a particular journal and the rank of the article according to the number of citations. This study compares S-index with Impact Factor (IF), which is the most well-known evaluation index, using the Korea Citation Index data. It is shown that S-index is positively correlated with the number of articles published in a journal. Tapered h-index (hT-index), which is based on all articles of a journal like S-index, is compared with S-index. It is shown that there is a very strong positive correlation between S-index and hT-index. Although S-index is similar to hT-index, S-index has a slightly better differentiating power and ranks the journal with evenly cited articles higher.  相似文献   

17.
We show that the h-index, g-index, ψ-index, and p-index, are related through the inequalities: h ≤ p ≤ g ≤ ψ. Moreover, this relation is proved theoretically in the mathematical framework of Lotkaian informetrics and is verified empirically by using two datasets from the Web of Science in the fields of electrochemistry and gerontology. For quantifying their relations, we estimate the g-index, ψ-index, and their cores and ratios of cores via a second-order Taylor series when the e-index, h-index, and C1 (the maximum number of citations received by a paper) are known. Then we find for the two empirical cases, that ratios of cores and average citations are approximately stable. Compared with the g-index, the offset-ability of the h-index decreases by 20% but the average citations increase by 20%. A similar observation holds for the comparison of the g-index and ψ-index. To explore the possible applications of cores of different indices, we apply them to extract the core structure of a network. The h-core is the most efficient, while the ψ-core includes more nodes with high betweenness.  相似文献   

18.
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.  相似文献   

19.
In order to take multiple co-authorship appropriately into account, a straightforward modification of the Hirsch index was recently proposed. Fractionalised counting of the papers yields an appropriate measure which is called the hm-index. The effect of this procedure is compared in the present work with other variants of the h-index and found to be superior to the fractionalised counting of citations and to the normalization of the h-index with the average number of authors in the h-core. Three fictitious examples for model cases and one empirical case are analysed.  相似文献   

20.
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.  相似文献   

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