Loet Leydesdorff

  1. Global Maps of Science based on the new Web-of-Science Categories.

    Authors: Loet Leydesdorff, Ismael Rafols, Stephen Carley
    Subjects: Digital Libraries
    Abstract

    In August 2011, Thomson Reuters launched version 5 of the Science and Social
    Science Citation Index in the Web of Science (WoS). Among other things, the 222
    ISI Subject Categories (SCs) for these two databases in version 4 of WoS were
    renamed and extended to 225 WoS Categories (WCs). A new set of 151 Subject
    Categories (SCs) was added, but at a higher level of aggregation.

  2. Citation impact of papers published from six prolific countries: A national comparison based on InCites data.

    Authors: Lutz Bornmann, Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    Using the InCites tool of Thomson Reuters, this study compares normalized
    citation impact values calculated for China, Japan, France, Germany, United
    States, and the UK throughout the time period from 1981 to 2010. The citation
    impact values are normalized to four subject areas: natural sciences;
    engineering and technology; medical and health sciences; and agricultural
    sciences. The results show an increasing trend in citation impact values for
    France, the UK and especially for Germany across the last thirty years in all
    subject areas.

  3. How journal rankings can suppress interdisciplinary research. A comparison between Innovation Studies and Business & Management.

    Authors: Loet Leydesdorff, Ismael Rafols, Alice O'Hare, Paul Nightingale, Andy Stirling
    Subjects: Digital Libraries
    Abstract

    This study provides quantitative evidence on how the use of journal rankings
    can disadvantage interdisciplinary research in research evaluations. Using
    publication and citation data, it compares the degree of interdisciplinarity
    and the research performance of a number of Innovation Studies units with that
    of leading Business & Management schools in the UK.

  4. Accounting for the Uncertainty in the Evaluation of Percentile Ranks.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    In a recent paper entitled "Inconsistencies of Recently Proposed Citation
    Impact Indicators and how to Avoid Them," Schreiber (2012, at arXiv:1202.3861)
    proposed (i) a method to assess tied ranks consistently and (ii) fractional
    attribution to percentile ranks in the case of relatively small samples (e.g.,
    for n < 100). Schreiber's solution to the problem of how to handle tied ranks
    is convincing, in my opinion (cf. Pudovkin & Garfield, 2009).

  5. An Evaluation of Impacts in "Nanoscience & nanotechnology:" Steps towards standards for citation analysis.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    One is inclined to conceptualize impact in terms of citations per
    publication, and thus as an average. However, citation distributions are
    skewed, and the average has the disadvantage that the number of publications is
    used in the denominator. Using hundred percentiles, one can integrate the
    normalized citation curve and develop an indicator that can be compared across
    document sets because percentile ranks are defined at the article level.

  6. A Rejoinder on Energy versus Impact Indicators.

    Authors: Loet Leydesdorff, Tobias Opthof
    Subjects: Digital Libraries
    Abstract

    Citation distributions are so skewed that using the mean or any other central
    tendency measure is ill-advised. Unlike G. Prathap's scalar measures (Energy,
    Exergy, and Entropy or EEE), the Integrated Impact Indicator (I3) is based on
    non-parametric statistics using the (100) percentiles of the distribution.
    Observed values can be tested against expected ones; impact can be qualified at
    the article level and then aggregated.

  7. Interactive Overlays: A New Method for Generating Global Journal Maps from Web-of-Science Data.

    Authors: Loet Leydesdorff, Ismael Rafols
    Subjects: Digital Libraries
    Abstract

    Recent advances in methods and techniques enable us to develop an interactive
    overlay to the global map of science based on aggregated citation relations
    among the 9,162 journals contained in the Science Citation Index and Social
    Science Citation Index 2009 combined. The resulting mapping is provided by
    VOSViewer. We first discuss the pros and cons of the various options: cited
    versus citing, multidimensional scaling versus spring-embedded algorithms,
    VOSViewer versus Gephi, and the various clustering algorithms and similarity
    criteria.

  8. Publish or Patent: Bibliometric evidence for empirical trade-offs in national funding strategies.

    Authors: Loet Leydesdorff, Robert D. Shelton
    Subjects: Digital Libraries
    Abstract

    Multivariate linear regression models suggest a trade-off in allocations of
    national R&D investments. Government funding, and spending in the higher
    education sector, seem to encourage publications, whereas other components such
    as industrial funding, and spending in the business sector, encourage
    patenting. Our results help explain why the US trails the EU in publications,
    because of its focus on industrial funding - some 70% of its total R&D
    investment. Conversely, it also helps explain why the EU trails the US in
    patenting.

  9. Non-consistency, non-cited items, and the impact factor: A consequence of the arithmetic.

    Authors: Loet Leydesdorff, Ronald Rousseau
    Subjects: Digital Libraries
    Abstract

    We discuss the "rate of averages" versus the "average of rates" in the case
    of the impact factor. Synchronous as well as diachronous journal impact factors
    are sensitive to adding non-cited articles (to the denominator). This is a
    consequence of basic properties of elementary arithmetic. Our findings provide
    a rationale for not taking uncitable publications into account in impact factor
    calculations, at least if these items are truly uncitable, that is, are never
    cited.

  10. Normalizing the measurement of citation performance: Principles for comparing sets of documents.

    Authors: Lutz Bornmann, Loet Leydesdorff, Tobias Opthof, R&#xfc;diger Mutz
    Subjects: Digital Libraries
    Abstract

    Using citation analysis, sets of documents can be compared as independent
    samples; for example, in terms of average citation counts using potentially
    different reference sets. From this perspective, the size of samples matters
    only for the identification of significant differences and estimating margins
    of error. Using the percentile rank approach, differences among citation
    distributions can be studied non-parametrically and in a single scheme.
    Comparison among the sets clarifies that the different sizes of samples affect
    the weighing of the probabilities and therefore the rankings.

  11. What the Cited and Citing Environments Reveal of_Advances in Atmospheric Sciences?.

    Authors: Loet Leydesdorff, Shie Aolan
    Subjects: Digital Libraries
    Abstract

    The networking ability of journals reflects their academic influence among
    peer journals. This paper analyzes the cited and citing environments of the
    journal--Advances in Atmospheric Sciences--using methods from social network
    analysis. The journal has been actively participating in the international
    journal environment, but one has a tendency to cite papers published in
    international journals. Advances in Atmospheric Sciences is intensely
    interrelated with international peer journals in terms of similar citing
    pattern.

  12. How Do Emerging Technologies Conquer the World? An Exploration of Patterns of Diffusion and Network Formation.

    Authors: Loet Leydesdorff, Ismael Rafols
    Subjects: Digital Libraries
    Abstract

    Grasping the fruits of "emerging technologies" is an objective of many
    government priority programs in a knowledge-based and globalizing economy. We
    use the publication records (in the Science Citation Index) of two emerging
    technologies to study the mechanisms of diffusion in the case of two innovation
    trajectories: small interference RNA (siRNA) and nano-crystalline solar cells
    (NCSC). Methods for analyzing and visualizing geographical and cognitive
    diffusion are specified as indicators of different dynamics.

  13. Remaining problems with the "New Crown Indicator" (MNCS) of the CWTS.

    Authors: Loet Leydesdorff, Tobias Opthof
    Subjects: Digital Libraries
    Abstract

    In their article, entitled "Towards a new crown indicator: some theoretical
    considerations," Waltman et al.

  14. The Development of the Journal Environment of Leonardo.

    Authors: Loet Leydesdorff, Alkim Almila Akdag Salah
    Subjects: Digital Libraries
    Abstract

    We present animations based on the aggregated journal-journal citations of
    Leonardo during the period 1974-2008. Leonardo is mainly cited by journals
    outside the arts domain for cultural reasons, for example, in neuropsychology
    and physics. Articles in Leonardo itself cite a large number of journals, but
    with a focus on the arts. Animations at this level of aggregation enable us to
    show the history of the journal from a network perspective.

  15. Eugene Garfield and Algorithmic Historiography: Co-Words, Co-Authors, and Journal Names.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    Algorithmic historiography was proposed by Eugene Garfield in collaboration
    with Irving Sher in the 1960s, but further developed only recently into
    HistCite^{TM} with Alexander Pudovkin. As in history writing, HistCite^{TM}
    reconstructs by drawing intellectual lineages. In addition to cited references,
    however, documents can be attributed a multitude of other variables such as
    title words, keywords, journal names, author names, and even full texts.

  16. What Can Heterogeneity Add to the Scientometric Map? Steps towards algorithmic historiography.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    The Actor Network represents heterogeneous entities as actants (Callon et
    al., 1983; 1986). Although computer programs for the visualization of social
    networks increasingly allow us to represent heterogeneity in a network using
    different shapes and colors for the visualization, hitherto this possibility
    has scarcely been exploited (Mogoutov et al., 2008). In this contribution to
    the Festschrift, I study the question of what heterogeneity can add
    specifically to the visualization of a network.

  17. Scientometrics and Communication Theory: Towards Theoretically Informed Indicators.

    Authors: Loet Leydesdorff, Peter van den Besselaar
    Subjects: Digital Libraries
    Abstract

    A theory of citations should not consider cited and/or citing agents as its
    sole subject of study. One is able to study also the dynamics in the networks
    of communications. While communicating agents (e.g., authors, laboratories,
    journals) can be made comparable in terms of their publication and citation
    counts, one would expect the communication networks not to be homogeneous. The
    latent structures of the network indicate different codifications that span a
    space of possible 'translations'. The various subdynamics can be hypothesized
    from an evolutionary perspective.

  18. Implicit media frames: Automated analysis of public debate on artificial sweeteners.

    Authors: Loet Leydesdorff, Iina Hellsten, James Dawson
    Subjects: Information Retrieval
    Abstract

    The framing of issues in the mass media plays a crucial role in the public
    understanding of science and technology. This article contributes to research
    concerned with diachronic analysis of media frames by making an analytical
    distinction between implicit and explicit media frames, and by introducing an
    automated method for analysing diachronic changes of implicit frames. In
    particular, we apply a semantic maps method to a case study on the newspaper
    debate about artificial sweeteners, published in The New York Times (NYT)
    between 1980 and 2006.

  19. Distributed scientific communication in the European information society: Some cases of "Mode 2" fields of research.

    Authors: Loet Leydesdorff, Peter van den Besselaar, Gaston Heimeriks
    Subjects: Information Retrieval
    Abstract

    Can self-organization of scientific communication be specified by using
    literature-based indicators? In this study, we explore this question by
    applying entropy measures to typical "Mode-2" fields of knowledge production.
    We hypothesized these scientific systems to be developing from a
    self-organization of the interaction between cognitive and institutional
    levels: European subsidized research programs aim at creating an institutional
    network, while a cognitive reorganization is continuously ongoing at the
    scientific field level.

  20. Quality Control and Validation Boundaries in a Triple Helix of University-Industry-Government: 'Mode 2' and the Future of University Research.

    Authors: Loet Leydesdorff, Yuko Fujigaki
    Subjects: Computers and Society
    Abstract

    How is quality control organized in the new "Mode 2" of the production of
    scientific knowledge? When institutional boundaries are increasingly blurred in
    a Triple Helix of University-Industry-Government relations, criteria for
    quality control in the production of scientific knowledge can be expected to
    change at the interfaces. The categorization in terms of two modes of knowledge
    production was introduced by Gibbons et al. (1994) in order to describe changes
    in the networks of scientific communications (funding patterns, research
    configurations, styles of knowledge management, etc.).

  21. Knowledge-Based Innovation Systems and the Model of a Triple Helix of University-Industry-Government Relations.

    Authors: Loet Leydesdorff
    Subjects: Computers and Society
    Abstract

    The (neo-)evolutionary model of a Triple Helix of
    University-Industry-Government Relations focuses on the overlay of
    expectations, communications, and interactions that potentially feed back on
    the institutional arrangements among the carrying agencies. From this
    perspective, the evolutionary perspective in economics can be complemented with
    the reflexive turn from sociology. The combination provides a richer
    understanding of how knowledge-based systems of innovation are shaped and
    reconstructed.

  22. Redundancy in Systems which Entertain a Model of Themselves: Interaction Information and the Self-organization of Anticipation.

    Authors: Loet Leydesdorff
    Subjects: Information Retrieval
    Abstract

    Mutual information among three or more dimensions (mu-star = - Q) has been
    considered as interaction information. However, Krippendorff (2009a, 2009b) has
    shown that this measure cannot be interpreted as a unique property of the
    interactions and has proposed an alternative measure of interaction information
    based on iterative approximation of maximum entropies. Q can then be considered
    as a measure of the difference between interaction information and redundancy
    generated in a model entertained by an observer.

  23. Science overlay maps: a new tool for research policy and library management.

    Authors: Loet Leydesdorff, Ismael Rafols, Alan L. Porter
    Subjects: Digital Libraries
    Abstract

    We present a novel approach to visually locate bodies of research within the
    sciences, both at each moment of time and dynamically. This article describes
    how this approach fits with other efforts to locally and globally map
    scientific outputs. We then show how these science overlay maps help benchmark,
    explore collaborations, and track temporal changes, using examples of
    universities, corporations, funding agencies, and research topics.

  24. Maps on the basis of the Arts & Humanities Citation Index: The journals Leonardo and Art Journal versus "Digital Humanities" as a topic.

    Authors: Loet Leydesdorff, Alkim Almila Akdag Salah
    Subjects: Digital Libraries
    Abstract

    The possibilities of using the Arts & Humanities Citation Index (A&HCI) for
    journal mapping have not been sufficiently recognized because of the absence of
    a Journal Citations Report (JCR) for this database.

  25. 'Interaction' versus 'action' in Luhmann's sociology of communication.

    Authors: Loet Leydesdorff
    Subjects: Computers and Society
    Abstract

    Both 'actions' and 'interactions' can be considered as micro-operations that
    can be aggregated from a systemic perspective. Whereas actions operate
    historically, interactions provide the events retrospectively with meaning.
    Luhmann's sociology of communication systems adds to the approach of symbolic
    interactionism the question of what global dimensions of communication mean for
    local interactions.

  26. The Mutual Information of University-Industry-Government Relations: An Indicator of the Triple Helix Dynamics.

    Authors: Loet Leydesdorff
    Subjects: Computers and Society
    Abstract

    University-industry-government relations provide a networked infrastructure
    for knowledge-based innovation systems. This infrastructure organizes the
    dynamic fluxes locally and the knowledge base remains emergent given these
    conditions. Whereas the relations between the institutions can be measured as
    variables, the interacting fluxes generate a probabilistic entropy. The mutual
    information among the three institutional dimensions provides us with an
    indicator of this entropy. When this indicator is negative, self-organization
    can be expected.

  27. Measuring the Knowledge Base: A Program of Innovation Studies.

    Authors: Loet Leydesdorff, Andrea Scharnhorst
    Subjects: Computers and Society
    Abstract

    Organized knowledge production can then be considered as the codification of
    communication. Communications leave traces that can be studied as indicators.
    Institutions can be considered as retention mechanisms functional for the
    reproduction of ever more complex, that is, scientific and knowledge-based,
    communications. The focus on communication enables us to operationalize the
    research questions in terms of indicators by using the mathematical theory of
    communication.

  28. The Construction and Globalization of the Knowledge Base in Inter-human Communication Systems.

    Authors: Loet Leydesdorff
    Subjects: Computers and Society
    Abstract

    The relationship between the "knowledge base" and the "globalization" of
    communication systems is discussed from the perspective of communication
    theory. I argue that inter-human communication takes place at two levels. At
    the first level information is exchanged and provided with meaning and at the
    second level meaning can reflexively be communicated. Human language can be
    considered as the evolutionary achievement which enables us to use these two
    channels of communication simultaneously.

  29. A study of seismology as a dynamic, distributed area of scientific research.

    Authors: Loet Leydesdorff, Caroline S. Wagner
    Subjects: Digital Libraries
    Abstract

    Seismology has several features that suggest it is a highly internationalized
    field: the subject matter is global, the tools used to analyse seismic waves
    are dependent upon information technologies, and governments are interested in
    funding cooperative research. We explore whether an emerging field like
    seismology has a more internationalised structure than the older, related field
    of geophysics. Using aggregated journal-journal citations, we first show that,
    within the citing environment, seismology emerged from within geophysics as its
    own field in the 1990s.

  30. Communication and Knowledge: How is the knowledge base of an economy constructed?.

    Authors: Loet Leydesdorff
    Subjects: Computers and Society
    Abstract

    The competitive advantages in a knowledge-based economy can no longer be
    attributed to single nodes in the network. Political economies are increasingly
    reshaped by knowledge-based developments that upset market equilibria and
    institutional arrangements. The network coordinates the subdynamics of (i)
    wealth production, (ii) organized novelty production, and (iii) private
    appropriation versus public control. The interaction terms generate a complex
    dynamics which cannot be expected to contain central coordination.

  31. Giddens' "structuration," Luhmann's "self-organization," and the operationalization of the dynamics of meaning.

    Authors: Loet Leydesdorff
    Subjects: Computers and Society
    Abstract

    Luhmann's social systems theory and Giddens' structuration theory of action
    share an emphasis on reflexivity, but focus on meaning along a divide between
    inter-human communication and intentful action as two different systems of
    reference. Recombining these two theories, simulations of interaction,
    organization, and self-organization of intentional communication can be
    distinguished by using algorithms from the computation of anticipatory systems.
    The self-organizing and organizing layers remain rooted in the double
    contingency of the human encounter which provides the variation.

  32. Similarity Measures, Author Cocitation Analysis, and Information Theory.

    Authors: Loet Leydesdorff
    Subjects: Information Retrieval
    Abstract

    The use of Pearson's correlation coefficient in Author Cocitation Analysis
    was compared with Salton's cosine measure in a number of recent contributions.
    Unlike the Pearson correlation, the cosine is insensitive to the number of
    zeros. However, one has the option of applying a logarithmic transformation in
    correlation analysis. Information calculus is based on both the logarithmic
    transformation and provides a non-parametric statistics. Using this methodology
    one can cluster a document set in a precise way and express the differences in
    terms of bits of information.

  33. An Indicator of Research Front Activity: Measuring Intellectual Organization as Uncertainty Reduction in Document Sets.

    Authors: Loet Leydesdorff, Diana Lucio-Arias
    Subjects: Digital Libraries
    Abstract

    When using scientific literature to model scholarly discourse, a research
    specialty can be operationalized as an evolving set of related documents. Each
    publication can be expected to contribute to the further development of the
    specialty at the research front.

  34. Measuring the Meaning of Words in Contexts: An automated analysis of controversies about Monarch butterflies, Frankenfoods, and stem cells.

    Authors: Loet Leydesdorff, Iina Hellsten
    Subjects: Computation and Language (Computational Linguistics and Natural Language and Speech Processing)
    Abstract

    Co-words have been considered as carriers of meaning across different domains
    in studies of science, technology, and society. Words and co-words, however,
    obtain meaning in sentences, and sentences obtain meaning in their contexts of
    use. At the science/society interface, words can be expected to have different
    meanings: the codes of communication that provide meaning to words differ on
    the varying sides of the interface. Furthermore, meanings and interfaces may
    change over time.

  35. Can Scientific Journals be Classified in terms of Aggregated Journal-Journal Citation Relations using the Journal Citation Reports?.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    The aggregated citation relations among journals included in the Science
    Citation Index provide us with a huge matrix which can be analyzed in various
    ways. Using principal component analysis or factor analysis, the factor scores
    can be used as indicators of the position of the cited journals in the citing
    dimensions of the database. Unrotated factor scores are exact, and the
    extraction of principal components can be made stepwise since the principal
    components are independent. Rotation may be needed for the designation, but in
    the rotated solution a model is assumed.

  36. Co-occurrence Matrices and their Applications in Information Science: Extending ACA to the Web Environment.

    Authors: Loet Leydesdorff, Liwen Vaughan
    Subjects: Information Retrieval
    Abstract

    Co-occurrence matrices, such as co-citation, co-word, and co-link matrices,
    have been used widely in the information sciences. However, confusion and
    controversy have hindered the proper statistical analysis of this data. The
    underlying problem, in our opinion, involved understanding the nature of
    various types of matrices. This paper discusses the difference between a
    symmetrical co-citation matrix and an asymmetrical citation matrix as well as
    the appropriate statistical techniques that can be applied to each of these
    matrices, respectively.

  37. Multiple Presents: How Search Engines Re-write the Past.

    Authors: Loet Leydesdorff, Iina Hellsten, Paul Wouters
    Subjects: Information Retrieval
    Abstract

    Internet search engines function in a present which changes continuously. The
    search engines update their indices regularly, overwriting Web pages with newer
    ones, adding new pages to the index, and losing older ones. Some search engines
    can be used to search for information at the internet for specific periods of
    time. However, these 'date stamps' are not determined by the first occurrence
    of the pages in the Web, but by the last date at which a page was updated or a
    new page was added, and the search engine's crawler updated this change in the
    database.

  38. The Import and Export of Cognitive Science.

    Authors: Loet Leydesdorff, Rob Goldstone
    Subjects: Digital Libraries
    Abstract

    From its inception, a large part of the motivation for Cognitive Science has
    been the need for an interdisciplinary journal for the study of minds and
    intelligent systems. One threat to the interdisciplinarity of Cognitive
    Science, both the field and journal, is that it may become, or already be, too
    dominated by psychologists. In 2005, psychology was a keyword for 51% of
    submissions, followed distantly by linguistics (17%), artificial intelligence
    (13%), neuroscience (10%), computer science (9%), and philosophy (8%).

  39. A Meta-evaluation of Scientific Research Proposals: Different Ways of Comparing Rejected to Awarded Applications.

    Authors: Lutz Bornmann, Loet Leydesdorff, Peter van den Besselaar
    Subjects: Computers and Society
    Abstract

    Combining different data sets with information on grant and fellowship
    applications submitted to two renowned funding agencies, we are able to compare
    their funding decisions (award and rejection) with scientometric performance
    indicators across two fields of science (life sciences and social sciences).
    The data sets involve 671 applications in social sciences and 668 applications
    in life sciences. In both fields, awarded applicants perform on average better
    than all rejected applicants.

  40. Visualization of the Citation Impact Environments of Scientific Journals: An online mapping exercise.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    Aggregated journal-journal citation networks based on the Journal Citation
    Reports 2004 of the Science Citation Index (5968 journals) and the Social
    Science Citation Index (1712 journals) are made accessible from the perspective
    of any of these journals. The user is thus able to analyze the citation
    environment in terms of links and graphs. Furthermore, the local impact of a
    journal is defined as its share of the total citations in the specific
    journal's citation environments; the vertical size of the nodes is varied
    proportionally to this citation impact.

  41. Citation Environment of Angewandte Chemie.

    Authors: Lutz Bornmann, Loet Leydesdorff, Werner Marx
    Subjects: Digital Libraries
    Abstract

    Recently, aggregated journal-journal citation networks were made accessible
    from the perspective of each journal included in the Science Citation Index see
    (this http URL). The local matrices can be used to inspect the
    relevant citation environment of a journal using statistical analysis and
    visualization techniques from social network analysis. The inspection gives an
    answer to the question what the local impact of this and other journals in the
    environment is. In this study the citation environment of Angewandte Chemie was
    analysed.

  42. Environment and Planning B as a Journal: The interdisciplinarity of its environment and the citation impact.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    The citation impact of Environment and Planning B can be visualized using its
    citation relations with journals in its environment as the links of a network.
    The size of the nodes is varied in correspondence to the relative citation
    impact in this environment. Additionally, one can correct for the effect of
    within-journal "self"-citations. The network can be partitioned and clustered
    using algorithms from social network analysis.

  43. Indicators of Structural Change in the Dynamics of Science: Entropy Statistics of the SCI Journal Citation Reports.

    Authors: Loet Leydesdorff
    Subjects: Digital Libraries
    Abstract

    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 compared with similar data in the
    Journal Citation Reports 1998 of the Science Citation Index. In addition to
    indicating local change, probabilistic entropy measures enable us to analyze
    changes in distributions at different levels of aggregation. The results of
    various statistics are discussed and compared by elaborating the
    journal-journal mappings.

  44. A Comparison between the China Scientific and Technical Papers and Citations Database and the Science Citation Index in terms of journal hierarchies and inter-journal citation relations.

    Authors: Loet Leydesdorff, Ping Zhou
    Subjects: Digital Libraries
    Abstract

    The journal structure in the China Scientific and Technical Papers and
    Citations Database (CSTPCD) is analysed from three perspectives: the database
    level, the specialty level and the institutional level (i.e., university
    journals versus journals issued by the Chinese Academy of Sciences). The
    results are compared with those for (Chinese) journals included in the Science
    Citation Index. The frequency of journal-journal citation relations in the
    CSTPCD is an order of magnitude lower than in the SCI.

  45. The Citation Impacts and Citation Environments of Chinese Journals in Mathematics.

    Authors: Loet Leydesdorff, Ping Zhou
    Subjects: Digital Libraries
    Abstract

    Based on the citation data of journals covered by the China Scientific and
    Technical Papers and Citations Database (CSTPCD), we obtained aggregated
    journal-journal citation environments by applying routines developed
    specifically for this purpose. Local citation impact of journals is defined as
    the share of the total citations in a local citation environment, which is
    expressed as a ratio and can be visualized by the size of the nodes.

  46. Journals as constituents of scientific discourse: economic heterodoxy.

    Authors: Loet Leydesdorff, Wilfred Dolfsma
    Subjects: Digital Libraries
    Abstract

    Purpose: to provide a view and analysis of the immediate field of journals
    which surround a number of key heterodox economics journals.
    Design/methodology/approach: Using citation data from the Science and Social
    Science Citation Index, the individual and collective networks of a number of
    journals in this field are analyzed. Findings: The size and shape of the
    citation networks of journals can differ substantially, even if in a broadly
    similar category.

  47. Knowledge linkage structures in communication studies using citation analysis among communication journals.

    Authors: Loet Leydesdorff, Han Park
    Subjects: Digital Libraries
    Abstract

    This research analyzes a "who cites whom" matrix in terms of aggregated,
    journal-journal citations to determine the location of communication studies on
    the academic spectrum. Using the Journal of Communication as the seed journal,
    the 2006 data in the Journal Citation Reports are used to map communication
    studies. The results show that social and experimental psychology journals are
    the most frequently used sources of information in this field.

  48. The Dynamics of Exchanges and References among Scientific Texts, and the Autopoiesis of Discursive Knowledge.

    Authors: Loet Leydesdorff, Diana Lucio-Arias
    Subjects: Computers and Society
    Abstract

    Discursive knowledge emerges as codification in flows of communication. The
    flows of communication are constrained and enabled by networks of
    communications as their historical manifestations at each moment of time. New
    publications modify the existing networks by changing the distributions of
    attributes and relations in document sets, while the networks are
    self-referentially updated along trajectories. Codification operates
    reflexively: the network structures are reconstructed from the perspective of
    hindsight.

  49. Retrieval of very large numbers of items in the Web of Science: an exercise to develop accurate search strategies.

    Authors: Loet Leydesdorff, Ricardo Arencibia-Jorge, Zaida Chinchilla-Rodriguez, Ronald Rousseau, Soren W. Paris
    Subjects: Digital Libraries
    Abstract

    The current communication presents a simple exercise with the aim of solving
    a singular problem: the retrieval of extremely large amounts of items in the
    Web of Science interface. As it is known, Web of Science interface allows a
    user to obtain at most 100,000 items from a single query. But what about
    queries that achieve a result of more than 100,000 items? The exercise
    developed one possible way to achieve this objective. The case study is the
    retrieval of the entire scientific production from the United States in a
    specific year.

  50. The relation between Pearson's correlation coefficient r and Salton's cosine measure.

    Authors: Leo Egghe, Loet Leydesdorff
    Subjects: Information Retrieval
    Abstract

    The relation between Pearson's correlation coefficient and Salton's cosine
    measure is revealed based on the different possible values of the division of
    the L1-norm and the L2-norm of a vector. These different values yield a sheaf
    of increasingly straight lines which form together a cloud of points, being the
    investigated relation. The theoretical results are tested against the author
    co-citation relations among 24 informetricians for whom two matrices can be
    constructed, based on co-citations: the asymmetric occurrence matrix and the
    symmetric co-citation matrix.

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