Search

In this investigation we study a family of networks, called spiders, which covers a range of networks going from chains to complete graphs. These spiders are characterized by three parameters: the number of nodes in the core, the number of legs at each core node, and the length of these legs. Keeping two of the three parameters constant we investigate if spiders are small worlds in the sense recently defined by Egghe.

We investigate the relation between degree sequences of trees and the majorization order using the Muirhead theorem. In this way, we prove a theorem that provides a necessary and sufficient condition for delta sequences of trees to be comparable in the majorization order. Although our investigation is largely theoretical, our study contributes to a better knowledge of trees as an important data structure. We point out that this study is among the few combining Lorenz curves and majorization on the one hand, and degree sequences of networks on the other., Comment: 17 pages

In previous work, we introduced the notion of an impact bundle, showing how e.g., the h-index and the g-index can lead to such a bundle. Here we extend the set of impact bundles by a new impact bundle, based on the Zhang e-index. It is, moreover, shown that some other plausible definitions do not lead to an impact bundle.

The concept of impact is one of the most important concepts in informetrics. It is here studied mathematically. We first fix a topic for which we want to find influential objects such as authors or journals, and their production, such as publications generating citations. These objects are then said to have a certain degree of impact. We work on three levels. On the first level, we need a measure for these objects, represented by their rank-frequency function, describing the number of items per source (ranked in decreasing order of the number of items): an impact measure. These measures focus on the production of the most productive sources. The h-index is one example. In paper II we study a formal definition of impact measures based on these left-hand sides of the source-item rank-frequency functions representing these objects. The second level of impact investigation is using impact bundles (or sheaves) as in paper III. As an illustration, we mention that the h-index of a function Z is defined as x for which Z(x) = x, i.e., the abscissa of the intersection of the graph of Z with the line y = x. The h-bundle is defined in the same way but now the line y = x is replaced by an increasing line through the origin: y = $\theta$.x, $\theta$ > 0. So, we have a bundle of impact measures which is more powerful to measure the impact of an object Z. Impact bundles are characterized in paper III. A third level of impact investigations involves the non-normalized form of the Lorenz curve. In papers IV and V we study global impact measures as measures that respect the non-normalized Lorenz order between the rank-frequency functions representing objects Z. We say that object Z has more impact than object Y if Y is smaller than Z in the sense of the non-normalized Lorenz order. This is the highest level of impact treatment: a mathematical definition of the concept itself., Comment: Bundle of 5 related papers

We extend the discrete majorization theory by working with non-normalized Lorenz curves. Then we prove two generalizations of the Muirhead theorem. These not only use elementary transfers but also local increases. Together these operations are described as elementary impact increases. The first generalization shows that if an array X is dominated, in the generalized sense, by an array Y then Y can be derived from X by a finite number of elementary impact increases and this in such a way that each step transforms an array into a new one which is strictly larger in the generalized majorization sense. The other one shows that if the dominating array, Y, is ordered decreasingly then elementary impact increases starting from the dominated array, X, lead to the dominating one. Here each step transforms an array to a new one for which the decreasingly ordered version dominates the previous one and is dominated by Y., Comment: 11 pages

In this feasibility study, the impact of academic research from social sciences and humanities on technological innovation is explored through a study of citations patterns of journal articles in patents. Specifically we focus on citations of journals from the field of environmental economics in patents included in an American patent database (USPTO). Three decades of patents have led to a small set of journal articles (85) that are being cited from the field of environmental economics. While this route of measuring how academic research is validated through its role in stimulating technological progress may be rather limited (based on this first exploration), it may still point to a valuable and interesting topic for further research., Comment: 10 pages, 4 tables

In a previous article (Rahman, Guns, Rousseau, and Engels, 2015) we described several approaches to determine the cognitive distance between two units. One of these approaches was based on what we called barycenters in N dimensions. The present note corrects this terminology and introduces the more adequate term 'similarity-adapted publication vectors'. Furthermore, we correct an error in normalization and explain the importance of scale invariance in determining cognitive distance. We also consider weighted cosine similarity as an alternative approach to determine cognitive (dis)similarity. Overall, we find that the three approaches (distance between barycenters, distance between similarity-adapted publication vectors, and weighted cosine similarity) yield very similar results., Comment: 15 pages, 3 figures

In this paper, we try to answer two questions about any given scientific discipline: First, how important is each subfield and second, how does a specific subfield influence other subfields? We modify the well-known open-system Leontief Input-Output Analysis in economics into a closed-system analysis focusing on eigenvalues and eigenvectors and the effects of removing one subfield. We apply this method to the subfields of physics. This analysis has yielded some promising results for identifying important subfields (for example the field of statistical physics has large influence while it is not among the largest subfields) and describing their influences on each other (for example the subfield of mechanical control of atoms is not among the largest subfields cited by quantum mechanics, but our analysis suggests that these fields are strongly connected). This method is potentially applicable to more general systems that have input-output relations among their elements., Comment: 22 pages, 13 figures

Synthetic biology is one of the battlefields where the main countries fight for the supremacy in science. The word synthetic biology hides a big world, ready to be explored by interdisciplinary research collaborations. The purpose of this investigation is to reveal the what, where, when of the current situation in this emerging field. A keyword search string for the field was constructed and applied in the Web of Science and in the Derwent Innovations Index. In particular, we calculated year based h-type indices for high-frequent keywords., Comment: 8 pages