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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.


Mostrando recursos 1 - 20 de 204

  1. Comments on the paper of J. M. Campanario: The effect of citations on the significance of decimal places in the computation of journal impact factors

    EGGHE, Leo
    We give mathematical explanations of some empirical results obtained by Campanario in Scientometrics 99(2):289-298, (2014).

  2. A new method for information retrieval, based on the theory of relative concentration

    Egghe, Leo
    This paper introduces a new method for information retrieval of documents that are represented by a vector. The novelty of the algorithm lies in the fact that no (generalized) p-norms are used as a matching function between the query and the document (as is done e.g. by Salton and others) but a function that measures the relative dispersion of the terms between a document and a query. This function originates from an earlier paper of the author where a good measure of relative concentration was introduced, used in informetrics to measure the degree of specialization of a journal w.r.t. the...

  3. Informetrics 89/90. Proceedings of the second international Conference on Bibliometrics, Scientometrics and Informetrics London

  4. A note on different Bradford multipliers

    EGGHE, Leo
    In this note we show that the multiplier k that appears in the law of Bradford is not the average production of articles per author nor the average number p of articles per journal, contradicting some earlier statements of Goffman and Warren and of Yablonsky. We remark however that the Bradford multiplier might be close to p in a lot of cases, being merely a coincidence of the special functional relation between ~1 and k which we develop in full detail. We finally show that K = kplA (p = number of Bradford groups, A = total numbers of articles) is a universal constant for the bibliography. Furthermore, K is...

  5. The duality of informetric systems with applications to the empirical laws

    EGGHE, Leo
    Informetric systems are formalized in order to make them suitable for mathematical dual analysis: the duality of sources vs. items (sources being the objects that produce while the items are the objects that are produced). The special place of empirical laws, such as those of Bradford, Leimkuhler. Mandelbrot and Lotka, in this framework is indicated. The paper closes with a section on some of the fundamental problems in informetric systems: higher dimensions, time dependence and fractal aspects.

  6. Applications of the theory of Bradford???s law to the calculation of Leimkuhler???s law and to the completion of bibliographies

    EGGHE, Leo
    In a previous article (L. Egghe, JASIS 37(4); p. 246-255, 1966) we further developed the theory of Bradford???s law by deriving a theoretical formula for the Bradford multiplier and for the number of items, produced by the most productive source in every Bradford group. In this article we apply these results to some classical bibliographies, for which we determine the underlying law of Leimkuhler and also different Bradford groupings. We also extend the above mentioned theory in order to be ap plicable to incomplete bibliographies (s.a. citation tables or bibliographies truncated before the Groos droop). Finally this extension also has an application in determining...

  7. Concentratie en diversiteit in de bibliometrie.

    EGGHE, Leo

  8. A Good Normalized Impact and Concentration Measure

    EGGHE, Leo
    It is shown that a normalized version of the g-index is a good normalized impact and concentration measure. A proposal for such a measure by Bartolucci is improved.

  9. Informetric Explanation of Some Leiden Ranking Graphs

    EGGHE, Leo
    The S-shaped functional relation between the mean citation score and the proportion of top 10% publications for the 500 Leiden Ranking universities is explained using results of the shifted Lotka function. Also the concave or convex relation between the proportion of top 100??% publications, for different fractions ??, is explained using the obtained new informetric model.

  10. Impact coverage of the success-index

    EGGHE, Leo
    We show mathematically that the success-index can be any of the following impact indices, dependent on the value of the threshold used in the definition of the success-index: Hirsch-index (h-index), g-index, generalized Wu- and Kosmulski-indices, the average.

  11. A basic indicator for relative contributions and a remarkable difference between a ratio of averages and an average of ratios

    EGGHE, Leo; ROUSSEAU, Ronald
    This article has been inspired by the activity index and problems in its proper understanding. It studies a basic relative contribution index which is placed in the context of countries??? publication contributions. Two versions are proposed: one being an average of ratios (AoR) and the other one a ratio of averages (RoA). A Lotkaian-Zipfian framework is used to model the two versions of the proposed indicator. A remarkable difference between the two approaches (RoA vs. AoR) is found when determining the fraction of units (countries) that have a value larger than one. This observation contributes to the understanding of the...

  12. Comments on "year-based h-type indicators"

    EGGHE, Leo

  13. Theory and practice of the shifted Lotka function

    EGGHE, Leo; ROUSSEAU, Ronald
    One of the major drawbacks of the classical Lotka function is that arguments only start from the value 1. However, in many applications one may want to start from the value 0, e.g. when including zero received citations. In this article we consider the shifted Lotka function, which includes the case of zero items. Basic results for the total number of sources, the total number of items and the average number of items per source are given in this framework. Next we give the rank-frequency function (Zipf-type function) corresponding to the shifted Lotka function and prove their exact relation. The...

  14. A new explanation of some Leiden Ranking graphs using exponential functions

    EGGHE, Leo
    A new explanation, using exponential functions, is given for the S-shaped functional relation between the mean citation score and the proportion of top 10% (and other percentages) publications for the 500 Leiden Ranking universities. With this new model we again obtain an explanation for the concave or convex relation between the proportion of top 100??% publications, for different fractions of ??.

  15. Comments on the article "Relative h-index to compare the scientific performance of researchers" by L.A.S. Dias

    EGGHE, Leo
    The relative h-index, proposed by L.A.S. Dias, is not useful to compare the scientific performance of researchers. This is shown by examples. More adequate alternatives include the g-index and the R-index.

  16. Mathematical characterizations of the Wu- and Hirsch-indices using two types of minimal increments.

    EGGHE, Leo

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

    EGGHE, Leo
    The minimum configuration to have a h-index equal to h is h papers each having h citations, hence h(2) citations in total. To increase the h-index to h + 1 we minimally need (h + 1)(2) citations, an increment of I-1(h) = 2h + 1. The latter number increases with 2 per unit increase of h. This increment of the second order is denoted I-2(h) =2. If we define I-1 and I-2 for a general Hirsch configuration (say n papers each having f(n) citations) we calculate I-1(f) and I-2(f) similarly as for the h-index. We characterize all functions f for...

  18. The Hirsch index of a shifted Lotka function and its relation with the impact factor

    EGGHE, Leo; ROUSSEAU, Ronald
    Based on earlier results about the shifted Lotka function, we prove an implicit functional relation between the Hirsch index (h-index) and the total number of sources (T). It is shown that the corresponding function, h(T), is concavely increasing. Next, we construct an implicit relation between the h-index and the impact factor IF (an average number of items per source). The corresponding function h(IF) is increasing and we show that if the parameter C in the numerator of the shifted Lotka function is high, then the relation between the h-index and the impact factor is almost linear.

  19. 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.

  20. 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...

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