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  • × author_ss:"Leydesdorff, L."
  • × year_i:[2000 TO 2010}
  1. Leydesdorff, L.: Can networks of journal-journal citations be used as indicators of change in the social sciences? (2003) 0.00 
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    Abstract
    Aggregated journal-journal citations can be used for mapping the intellectual organization of the sciences in terms of specialties because the latter can be considered as interreading communities. Can the journal-journal citations also be used as early indicators of change by comparing the files for two subsequent years? Probabilistic entropy measures enable us to analyze changes in large datasets at different levels of aggregation and in considerable detail. Compares Journal Citation Reports of the Social Science Citation Index for 1999 with similar data for 1998 and analyzes the differences using these measures. Compares the various indicators with similar developments in the Science Citation Index. Specialty formation seems a more important mechanism in the development of the social sciences than in the natural and life sciences, but the developments in the social sciences are volatile. The use of aggregate statistics based on the Science Citation Index is ill-advised in the case of the social sciences because of structural differences in the underlying dynamics.
    Date
    6.11.2005 19:02:22
    Source
    Journal of documentation. 59(2003) no.1, S.84-104
  2. Leydesdorff, L.; Sun, Y.: National and international dimensions of the Triple Helix in Japan : university-industry-government versus international coauthorship relations (2009) 0.00 
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    Abstract
    International co-authorship relations and university-industry-government (Triple Helix) relations have hitherto been studied separately. Using Japanese publication data for the 1981-2004 period, we were able to study both kinds of relations in a single design. In the Japanese file, 1,277,030 articles with at least one Japanese address were attributed to the three sectors, and we know additionally whether these papers were coauthored internationally. Using the mutual information in three and four dimensions, respectively, we show that the Japanese Triple-Helix system has been continuously eroded at the national level. However, since the mid-1990s, international coauthorship relations have contributed to a reduction of the uncertainty at the national level. In other words, the national publication system of Japan has developed a capacity to retain surplus value generated internationally. In a final section, we compare these results with an analysis based on similar data for Canada. A relative uncoupling of national university-industry-government relations because of international collaborations is indicated in both countries.
    Date
    22. 3.2009 19:07:20
    Source
    Journal of the American Society for Information Science and Technology. 60(2009) no.4, S.778-788
  3. Leydesdorff, L.: ¬The construction and globalization of the knowledge base in inter-human communication systems (2003) 0.00 
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    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. Providing meaning with hindsight is a recursive operation: a meaning that makes a difference can be considered as knowledge. If the production of knowledge is socially organized, the perspective of hindsight can further be codified. This adds globalization to the historically stabilized patterns of communications. Globalization can be expected to transform the communications in an evolutionary mode. However, the self-organization of a knowledge-based society remains an expectation with the status of a hypothesis.
    Date
    22. 5.2003 19:48:04
    Source
    Canadian Journal of Communication 28(2003), H.3, S. -
  4. Leydesdorff, L.: Dynamic and evolutionary updates of classificatory schemes in scientific journal structures (2002) 0.00 
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    Abstract
    Can the inclusion of new journals in the Science Citation Index be used for the indication of structural change in the database, and how can this change be compared with reorganizations of reiations among previously included journals? Change in the number of journals (n) is distinguished from change in the number of journal categories (m). Although the number of journals can be considered as a given at each moment in time, the number of journal categories is based an a reconstruction that is time-stamped ex post. The reflexive reconstruction is in need of an update when new information becomes available in a next year. Implications of this shift towards an evolutionary perspective are specified.
    Source
    Journal of the American Society for Information Science and technology. 53(2002) no.12, S.987-994
  5. Leydesdorff, L.: Similarity measures, author cocitation Analysis, and information theory (2005) 0.00 
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    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 caiculus is based an 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. The algorithm is explained and used an the data set, which was made the subject of this discussion.
    Source
    Journal of the American Society for Information Science and Technology. 56(2005) no.7, S.769-772
  6. Leydesdorff, L.: Can scientific journals be classified in terms of aggregated journal-journal citation relations using the Journal Citation Reports? (2006) 0.00 
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    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. By using principal component analysis or factor analysis, the factor scores can be employed 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 because the principal components are independent. Rotation may be needed for the designation, but in the rotated solution a model is assumed. This assumption can be legitimated on pragmatic or theoretical grounds. Because the resulting outcomes remain sensitive to the assumptions in the model, an unambiguous classification is no longer possible in this case. However, the factor-analytic solutions allow us to test classifications against the structures contained in the database; in this article the process will be demonstrated for the delineation of a set of biochemistry journals.
    Source
    Journal of the American Society for Information Science and Technology. 57(2006) no.5, S.601-613
  7. Leydesdorff, L.; Bihui, J.: Mapping the Chinese Science Citation Database in terms of aggregated journal-journal citation relations (2005) 0.00 
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    Abstract
    Methods developed for mapping the journal structure contained in aggregated journal-journal citations in the Science Citation Index (SCI; Thomson ISI, 2002) are applied to the Chinese Science Citation Database of the Chinese Academy of Sciences. This database covered 991 journals in 2001, of which only 37 originally had English titles; only 31 of which were covered by the SCI. Using factor-analytical and graph-analytical techniques, the authors show that the journal relations are dually structured. The main structure is the intellectual organization of the journals in journal groups (as in the international SCI), but the university-based journals provide an institutional layer that orients this structure towards practical ends (e.g., agriculture). This mechanism of integration is further distinguished from the role of general science journals. The Chinese Science Citation Database thus exhibits the characteristics of "Mode 2" or transdisciplinary science in the production of scientific knowledge more than its Western counterpart does. The contexts of application lead to correlation among the components.
    Source
    Journal of the American Society for Information Science and Technology. 56(2005) no.14, S.1469-1479
  8. Leydesdorff, L.; Zhou, P.: Co-word analysis using the Chinese character set (2008) 0.00 
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    Abstract
    Until recently, Chinese texts could not be studied using co-word analysis because the words are not separated by spaces in Chinese (and Japanese). A word can be composed of one or more characters. The online availability of programs that separate Chinese texts makes it possible to analyze them using semantic maps. Chinese characters contain not only information but also meaning. This may enhance the readability of semantic maps. In this study, we analyze 58 words which occur 10 or more times in the 1,652 journal titles of the China Scientific and Technical Papers and Citations Database. The word-occurrence matrix is visualized and factor-analyzed.
    Source
    Journal of the American Society for Information Science and Technology. 59(2008) no.9, S.1528-1530
  9. Leydesdorff, L.: Clusters and maps of science journals based on bi-connected graphs in Journal Citation Reports (2004) 0.00 
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    Abstract
    The aggregated journal-journal citation matrix derived from Journal Citation Reports 2001 can be decomposed into a unique subject classification using the graph-analytical algorithm of bi-connected components. This technique was recently incorporated in software tools for social network analysis. The matrix can be assessed in terms of its decomposability using articulation points which indicate overlap between the components. The articulation points of this set did not exhibit a next-order network of "general science" journals. However, the clusters differ in size and in terms of the internal density of their relations. A full classification of the journals is provided in the Appendix. The clusters can also be extracted and mapped for the visualization.
    Source
    Journal of documentation. 60(2004) no.4, S.371-427
  10. Zhou, P.; Leydesdorff, L.: ¬A comparison between the China Scientific and Technical Papers and Citations Database and the Science Citation Index in terms of journal hierarchies and interjournal citation relations (2007) 0.00 
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    Abstract
    The journal structure in the China Scientific and Technical Papers and Citations Database (CSTPCD) is analyzed from three perspectives: the database level, the specialty level, and the institutional level (i.e., university journals vs. journals issued by the Chinese Academy of Sciences). The results are compared with those for (Chinese) journals included in the Science Citation Index (SCI). The frequency of journal-journal citation relations in the CSTPCD is an order of magnitude lower than in the SCI. Chinese journals, especially high-quality journals, prefer to cite international journals rather than domestic ones; however, Chinese journals do not get an equivalent reception from their international counterparts. The international visibility of Chinese journals is low, but varies among fields of science. Journals of the Chinese Academy of Sciences have a better reception in the international scientific community than university journals.
    Source
    Journal of the American Society for Information Science and Technology. 58(2007) no.2, S.223-236
  11. Leydesdorff, L.; Schank, T.: Dynamic animations of journal maps : indicators of structural changes and interdisciplinary developments (2008) 0.00 
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    Abstract
    The dynamic analysis of structural change in the organization of the sciences requires, methodologically, the integration of multivariate and time-series analysis. Structural change - for instance, interdisciplinary development - is often an objective of government interventions. Recent developments in multidimensional scaling (MDS) enable us to distinguish the stress originating in each time-slice from the stress originating from the sequencing of time-slices, and thus to locally optimize the trade-offs between these two sources of variance in the animation. Furthermore, visualization programs like Pajek and Visone allow us to show not only the positions of the nodes, but also their relational attributes such as betweenness centrality. Betweenness centrality in the vector space can be considered as an indicator of interdisciplinarity. Using this indicator, the dynamics of the citation-impact environments of the journals Cognitive Science, Social Networks, and Nanotechnology are animated and assessed in terms of interdisciplinarity among the disciplines involved.
    Source
    Journal of the American Society for Information Science and Technology. 59(2008) no.11, S.1810-1818
  12. Leydesdorff, L.: Betweenness centrality as an indicator of the interdisciplinarity of scientific journals (2007) 0.00 
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    Abstract
    In addition to science citation indicators of journals like impact and immediacy, social network analysis provides a set of centrality measures like degree, betweenness, and closeness centrality. These measures are first analyzed for the entire set of 7,379 journals included in the Journal Citation Reports of the Science Citation Index and the Social Sciences Citation Index 2004 (Thomson ISI, Philadelphia, PA), and then also in relation to local citation environments that can be considered as proxies of specialties and disciplines. Betweenness centrality is shown to be an indicator of the interdisciplinarity of journals, but only in local citation environments and after normalization; otherwise, the influence of degree centrality (size) overshadows the betweenness-centrality measure. The indicator is applied to a variety of citation environments, including policy-relevant ones like biotechnology and nanotechnology. The values of the indicator remain sensitive to the delineations of the set because of the indicator's local character. Maps showing interdisciplinarity of journals in terms of betweenness centrality can be drawn using information about journal citation environments, which is available online.
    Source
    Journal of the American Society for Information Science and Technology. 58(2007) no.9, S.1303-1319
  13. Leydesdorff, L.: On the normalization and visualization of author co-citation data : Salton's Cosine versus the Jaccard index (2008) 0.00 
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    Abstract
    The debate about which similarity measure one should use for the normalization in the case of Author Co-citation Analysis (ACA) is further complicated when one distinguishes between the symmetrical co-citation - or, more generally, co-occurrence - matrix and the underlying asymmetrical citation - occurrence - matrix. In the Web environment, the approach of retrieving original citation data is often not feasible. In that case, one should use the Jaccard index, but preferentially after adding the number of total citations (i.e., occurrences) on the main diagonal. Unlike Salton's cosine and the Pearson correlation, the Jaccard index abstracts from the shape of the distributions and focuses only on the intersection and the sum of the two sets. Since the correlations in the co-occurrence matrix may be spurious, this property of the Jaccard index can be considered as an advantage in this case.
    Source
    Journal of the American Society for Information Science and Technology. 59(2008) no.1, S.77-85
  14. Leydesdorff, L.; Probst, C.: ¬The delineation of an interdisciplinary specialty in terms of a journal set : the case of communication studies (2009) 0.00 
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    Abstract
    A journal set in an interdisciplinary or newly developing area can be determined by including the journals classified under the most relevant ISI Subject Categories into a journal-journal citation matrix. Despite the fuzzy character of borders, factor analysis of the citation patterns enables us to delineate the specific set by discarding the noise. This methodology is illustrated using communication studies as a hybrid development between political science and social psychology. The development can be visualized using animations which support the claim that a specific journal set in communication studies is increasingly developing, notably in the being cited patterns. The resulting set of 28 journals in communication studies is smaller and more focused than the 45 journals classified by the ISI Subject Categories as Communication. The proposed method is tested for its robustness by extending the relevant environments to sets including many more journals.
    Source
    Journal of the American Society for Information Science and Technology. 60(2009) no.8, S.1709-1718
  15. Leydesdorff, L.; Vaughan, L.: Co-occurrence matrices and their applications in information science : extending ACA to the Web environment (2006) 0.00 
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    Abstract
    Co-occurrence matrices, such as cocitation, coword, and colink matrices, have been used widely in the information sciences. However, confusion and controversy have hindered the proper statistical analysis of these data. The underlying problem, in our opinion, involved understanding the nature of various types of matrices. This article discusses the difference between a symmetrical cocitation matrix and an asymmetrical citation matrix as well as the appropriate statistical techniques that can be applied to each of these matrices, respectively. Similarity measures (such as the Pearson correlation coefficient or the cosine) should not be applied to the symmetrical cocitation matrix but can be applied to the asymmetrical citation matrix to derive the proximity matrix. The argument is illustrated with examples. The study then extends the application of co-occurrence matrices to the Web environment, in which the nature of the available data and thus data collection methods are different from those of traditional databases such as the Science Citation Index. A set of data collected with the Google Scholar search engine is analyzed by using both the traditional methods of multivariate analysis and the new visualization software Pajek, which is based on social network analysis and graph theory.
    Source
    Journal of the American Society for Information Science and Technology. 57(2006) no.12, S.1616-1628
  16. Leydesdorff, L.: ¬The university-industry knowledge relationship : analyzing patents and the science base of technologies (2004) 0.00 
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    Abstract
    Via the Internet, information scientists can obtain costfree access to large databases in the "hidden" or "deep Web." These databases are often structured far more than the Internet domains themselves. The patent database of the U.S. Patent and Trade Office is used in this study to examine the science base of patents in terms of the literature references in these patents. Universitybased patents at the global level are compared with results when using the national economy of the Netherlands as a system of reference. Methods for accessing the online databases and for the visualization of the results are specified. The conclusion is that "biotechnology" has historically generated a model for theorizing about university-industry relations that cannot easily be generalized to other sectors and disciplines.
    Source
    Journal of the American Society for Information Science and Technology. 55(2004) no.11, S.991-1001
  17. Leydesdorff, L.: Patent classifications as indicators of intellectual organization (2008) 0.00 
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    Abstract
    Using the 138,751 patents filed in 2006 under the Patent Cooperation Treaty, co-classification analysis is pursued on the basis of three- and four-digit codes in the International Patent Classification (IPC, 8th ed.). The co-classifications among the patents enable us to analyze and visualize the relations among technologies at different levels of aggregation. The hypothesis that classifications might be considered as the organizers of patents into classes, and therefore that co-classification patterns - more than co-citation patterns - might be useful for mapping, is not corroborated. The classifications hang weakly together, even at the four-digit level; at the country level, more specificity can be made visible. However, countries are not the appropriate units of analysis because patent portfolios are largely similar in many advanced countries in terms of the classes attributed. Instead of classes, one may wish to explore the mapping of title words as a better approach to visualize the intellectual organization of patents.
    Source
    Journal of the American Society for Information Science and Technology. 59(2008) no.10, S.1582-1597
  18. Leydesdorff, L.: ¬A sociological theory of communication : the self-organization of the knowledge-based society (2001) 0.00 
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    Footnote
    Rez. in: JASIST 53(2002) no.1, S.61-62 (E.G. Ackermann): "This brief summary cannot do justice to the intellectual depth, philosophical richness of the theoretical models, and their implications presented by Leydesdorff in his book. Next to this, the caveats presented earlier in this review are relatively minor. For all that, this book is not an "easy" read, nor is it for the theoretically or philosophically faint of heart. The content is certainly accessible to those with the interest and the stamina to see it through to the end, and would repay those who reread it with further insight and understanding. This book is recommended especially for the reader who is looking for a well-developed, general sociological theory of communication with a strong philosophical basis upon which to build a postmodern, deconstructionist research methodology"
    Pages
    351 S
  19. Leydesdorff, L.; Bensman, S.: Classification and Powerlaws : the logarithmic transformation (2006) 0.00 
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    Abstract
    Logarithmic transformation of the data has been recommended by the literature in the case of highly skewed distributions such as those commonly found in information science. The purpose of the transformation is to make the data conform to the lognormal law of error for inferential purposes. How does this transformation affect the analysis? We factor analyze and visualize the citation environment of the Journal of the American Chemical Society (JACS) before and after a logarithmic transformation. The transformation strongly reduces the variance necessary for classificatory purposes and therefore is counterproductive to the purposes of the descriptive statistics. We recommend against the logarithmic transformation when sets cannot be defined unambiguously. The intellectual organization of the sciences is reflected in the curvilinear parts of the citation distributions while negative powerlaws fit excellently to the tails of the distributions.
    Source
    Journal of the American Society for Information Science and Technology. 57(2006) no.11, S.1470-1486
  20. Leydesdorff, L.; Heimeriks, G.: ¬The self-organization of the European information society : the case of "biotechnology" (2001) 0.00 
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    Abstract
    Fields of technoscience like biotechnology develop in a network mode: disciplinary insights from different backgrounds are recombined as competing innovation systems are continuously reshaped. The ongoing process of integration at the European level generates an additional network of transnational collaborations. Using the title words of scientific publications in five core journals of biotechnology, multivariate analysis is used to distinguish between the intellectual organization of the publications in terms of title words and the institutional network in terms of addresses of documents. The interaction among the representation of intellectual space in terms of words and co-words, and the potentially European network system is compared with the document sets with American and Japanese addresses. The European system can also be decomposed in terms of the contributions of member states. Whereas a European vocabulary can be made visible at the global level, this communality disappears by this decomposition. The network effect at the European level can be considered as institutional more than cognitive
    Footnote
    Vgl. auch die Stellungnahme von P. van den Besselaar: Empirical evidence of self-organization? in: JASIST 54(2003) no.1, S.87-90.
    Source
    Journal of the American Society for Information Science and technology. 52(2001) no.14, S.1262-1274

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