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Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Publications

Mostrando recursos 1 - 20 de 478

  1. Comparative study of four impact measures and qualitative conclusions

    Egghe, L.
    We present a study of four impact measures: the h-index, the g-index, the R-index and the j-index. The g-index satisfies the transfer principle, the j-index satisfies the opposite transfer principle while the h- and R-indices do not satisfy any of these principles. We study general inequalities between these measures and also determine their maximal and minimal values, given a fixed total number of citations.

  2. Metadata quality evaluation of a repository based on a sample technique

    Goovaerts, Marc; Leinders, Dirk
    In this paper, we evaluate the quality of the metadata of an OAI-compliant repository based on the completeness metric proposed by X. Ochoa and E. Duval. This study focuses on the completeness of the metadata records as defined by M.A. Sicilia et al, where machine-understandability is a mandatory requirement for completeness. The goal is to use the completeness metric as a tool for harvesters and repository managers to evaluate easily the quality of the metadata of a repository. We focus on the metadata used by the communities of agriculture, aquaculture and environment from the VOA3R project. The OceanDocs repository serves...

  3. Dynamical aspects of Information Production Processes

    Egghe, L.
    In this paper and talk we present a short proof of a theorem of Naranan stating that if sources grow exponentially and if items in sources also grow exponentially, then the system is Lotkaian, i.e. its size-frequency function is the law of Lotka. We apply this technique to the case of power law growth of sources and of items in sources and determine the size- and rank frequency functions in this case. These functions have a greater variety of shapes than in the classical Naranan case and we give practical examples. We also show that, in this context, the law...

  4. On the correction of the h-index for career length

    Egghe, L.
    We describe mathematically the age-independent version of the h-index, defined by Abt (Scientometrics 91(3), 863-868, 2012) and explain when this indicator is constant with age. We compare this index with the one where not the h-index is divided by career length but where all citation numbers are divided by career length and where we then calculate the new h-index. Both mathematical models are compared. A variant of this second method is by calculating the h-index of the citation data, divided by article age. Examples are given.

  5. Letter to the Editor. Note on a possible decomposition of the h-index

    Egghe, L.
    Informetrics

  6. Theoretical evidence for empirical findings of A. Pulgarin on Lotka's law

    Egghe, L.
    In [A. Pulgarin. Dependence of Lotka’s law parameters on the scientific area. Malaysian Journal of Library and Information Science 17(1), 41-50, 2012] the author finds negative correlations between the average number of papers per author and the Lotka exponent and the Lotka constant as well as positive correlations between the latter two parameters. He also finds lower values for the latter two parameters in fields or countries with highly concentrated productions (e.g. where there is heavy growth). In the present paper these findings are proved mathematically, based on earlier results on Lotka's law proved by this author.

  7. The functional relation between the impact factor and the uncitedness factor revisited

    Egghe, L.
    We give a heuristic proof of the relation between the impact factor (IF) and the uncitedness factor (U), the fraction of the papers that are uncited: U = 1/1+IF . This generalizes the proof of Hsu and Huang [Physica A 391, 2129-2134, 2012] who obtain the same result but based on the assumption of the validity of the Matthew-effect. This new informetric function opens the discusion on universal informetric laws, distribution dependent laws and parameter dependent laws of which examples from the informetrics literature are given.

  8. Measuring co-authors' contribution to an article's visibility

    Egghe, L.; Guns, R.; Rousseau, R.
    The visibility of an article depends to a large extent on its authors. We study the question how each co-author's relative contribution to the visibility of the article can be determined and quantified using an indicator, referring to such an indicator as a CAV-indicator. A two-step procedure is elaborated, whereby one first chooses an indicator (e.g. total number of citations, h-index,...) and subsequently one of two possible approaches. The case where the indicator is an h-type index is elaborated in a Lotkaian framework. Different examples illustrate the procedure and the choices involved in determining a CAV-indicator.

  9. Theoretical justification of the central area indices and the central interval indices

    Egghe, L.
    The central area indices and the central interval indices, as introduced in Dorta-González, Scientometrics 88(3), 729-745, 2011, are studied from a theoretical point of view. They are defined in order to yield higher impact values of "selective" authors (i.e. authors with concentrated number of citations over their publications). We show that this property is not valid for every citation distribution. However,if Zipf's law is adopted for the citation distribution, we can show that the central area indices and the central interval indices have indeed higher values for more selective authors.

  10. Theory of the topical coverage of multiple databases

    Egghe, L.
    We present a model that describes which fraction of the literature on a certain topic we will find when we use n(n=1,2,...)databases. It is a generalization of the theory of discovering usability problems. We prove that, in all practical cases, this fraction is a concave function of n, the number of used databases, hereby explaining some graphs that exist in the literature. We also study limiting features of this fraction for n very high and we characterize the case that we find all literature on a certain topic for n high enough.

  11. Fallout and Miss in journal peer review

    Egghe, L.; Bornmann, L.
    Purpose: We further exploit the analogy between journal peer review and information retrieval. In this way we want to quantify some imperfections of journal peer review. Design/methodology/approach: We define fallout rate and missing rate in order to describe quantitavely the weak papers that were accepted and the strong papers that we missed, respectively. To assess the quality of manuscripts we use bibliometric measures. Findings: Fallout rate and missing rate are put in relation with the hitting rate and success rate. Conclusions are drawn on what friction of weak papers will be accepted in order to have a certain fraction of...

  12. Theoretical evidence for empirical findings of A. Pulgarin on Lotka's law

    Egghe, L.
    In [A.Pulgarin. Dependence of Lotka's law parameters on the scientific area. Malaysian Journal of Library and Information Science 17(1), 41-50, 2012] the author finds negative correlations between the average number of papers per author and the Lotka exponent and the Lotka constant as well as positive correlations between the latter two parameters. He also finds lower values for the latter two parameters in fields or countries with highly concentrated productions(e.g. where there is heavy growth). In the present paper these findings are proved mathematically, based on earlier results on Lotka's law proved by this author.

  13. A rationale for the relation between the citer h-index and the classical h-index of a researcher

    Egghe, L.
    The citer h-index of a researcher (introduced by Ajiferuke and Wolfram) was found to have a strong linear relationship with the h-index of this researcher. This finding of Franceschini, Maisano, Perotti and Proto also revealed, experimentally, that the slope of this straight line (passing through the origin) is strictly larger than one. In this paper we present a rationale for this empirical result of this author on the relation between the h-index before and after a transformation of the citation data.

  14. Applications of the generalized law of Benford to informetric data

    Egghe, L.; Guns, R.
    In a previous work (Egghe, 2011), the first author showed that Benford's law (describing the logarithmic distribution of the numbers 1, 2,..., 9 as first digits of data in decimal form) is related to the classical law of Zipf with exponent 1. The work of Campanario and Coslado (2011), however, shows that Benford's law does not always fit practical data in a statistical sense. In this article, we use a generalization of Benford's law related to the general law of Zipf with exponent ?????>???0. Using data from Campanario and Coslado, we apply nonlinear least squares to determine the optimal ??...

  15. Thoughts on uncitedness: Nobel laureates and Field medalists as case studies

    Egghe, Leo; Guns, Raf; Rousseau, Ronald
    Contrary to what one might expect, Nobel laureates and Fields medalists have a rather large fraction (10% or more) of uncited publications. This is the case for (in total) 75 examined researchers from the fields of mathematics (Fields medalists), physics, chemistry, and physiology or medicine (Nobel laureates). We study several indicators for these researchers, including the h-index, total number of publications, average number of citations per publication, the number (and fraction) of uncited publications, and their interrelations. The most remarkable result is a positive correlation between the h-index and the number of uncited articles. We also present a Lotkaian model,...

  16. Five years "Journal of Informetrics"

    Egghe, Leo
    End of 2011, the Journal of Informetrics (Elsevier) existed five years. We overview its scope, published articles (topics, co-authorship, authors’ countries), editorial decisions, editorial and production times, impact factor and article downloads aspects. Finally we present a local citation environment map of JOI.

  17. Study of the rank- and size-frequency functions in case of power law growth of sources and items and proof of Heaps' law

    Egghe, Leo
    Supposing that the number of sources and the number of items in sources grow in time according to power laws, we present explicit formulae for the size- and rank-frequency functions in such systems. Size-frequency functions can decrease or increase while rank-frequency functions only decrease. The latter can be convex, concave, S-shaped (first convex, then concave) or reverse S-shaped (first concave, then convex). We also prove that, in such systems, Heaps’ law on the relation between the number of sources and items is valid.

  18. The single publication H-index and the indirect H-index of a researcher

    Egghe, Leo
    The single publication H-index, introduced by A. Schubert in 2009 can be applied on all articles in the Hirsch-core of a researcher. In this way one can define the ‘‘indirect H-index’’ of a researcher.

  19. Remarks on the paper of A. De Visscher "What does the g-index really measure?"

    Egghe, Leo
    This paper presents a different view on properties of impact measures than given in the paper of De Visscher. We argue that a good impact measure should prefer concentrated (unequal) situations of citations per paper rather than situations where citations are more equally spread out over papers. We also present theoretical evidence that the g-index and the R-index can be close to the square root of the total number of citations, while this is not the case for the A-index. Here we confirm an assertion of De Visscher.

  20. A disadvantage of h-type indices for comparing the citation impact of two researchers

    EGGHE, Leo
    We show that the rank frequency functions of two researchers usually intersect. As a consequence of this, different h-type indices can conclude on different impact judgements of the two researchers. Also in this paper a new indicator is proposed: the average number of citations per paper in the papers whose ranks are smaller than or equal to the intersection point of their two rank frequency functions. The theoretical derivations are illustrated using an empirical example.

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