125,128 research outputs found
Applying the possibilistic C-means algorithm in kernel-induced spaces
No full textIn this paper, we study a kernel extension of the classic possibilistic c-means. In the proposed extension, we implicitly map input patterns into a possibly high-dimensional space by means of positive semidefinite kernels. In this new space, we model the mapped data by means of the possibilistic clustering algorithm. We study in more detail the special case where we model the mapped data using a single cluster only, since it turns out to have many interesting properties. The modeled memberships in kernel-induced spaces yield a modeling of generic shapes in the input space. We analyze in detail the connections to one-class support vector machines and kernel density estimation, thus, suggesting that the proposed algorithm can be used in many scenarios of unsupervised learning. In the experimental part, we analyze the stability and the accuracy of the proposed algorithm on some synthetic and real datasets. The results show high stability and good performances in terms of accuracy
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dealing with non-metric dissimilarities in fuzzy central clustering algorithms
No full textClustering is the problem of grouping objects on the basis of a similarity measure among them. Relational clustering methods can be employed when a feature-based representation of the objects is not available, and their description is given in terms of pairwise (dis)similarities. This paper focuses on the relational duals of fuzzy central clustering algorithms, and their application in situations when patterns are represented by means of non-metric pairwise dissimilarities. Symmetrization and shift operations have been proposed to transform the dissimilarities among patterns from non-metric to metric. In this paper, we analyze how four popular fuzzy central clustering algorithms are affected by such transformations. The main contributions include the lack of invariance to shift operations, as well as the invariance to symmetrization. Moreover, we highlight the connections between relational duals of central clustering algorithms and central clustering algorithms in kernel-induced spaces. One among the presented algorithms has never been proposed for non-metric relational clustering, and turns out to be very robust to shift operations. (C) 2008 Elsevier Inc. All rights reserved
Large-eddy simulation for aerodynamic noise from high-lift device
No full textThree dimensional time-accurate simulations on a leading-edge slat and wing combination were carried out by using a large-eddy simulation model (LES). To reduce the cost of LES simulations in terms of grid size/resolution, a transverse boundary condition of a symmetry type was imposed at the sides of the model whilst keeping the slat spanwise extent to 18% of the main element's chord. The cove region was decomposed into three zones in which the grid was generated separately. The model predicts the unsteady dynamics of the slat's flow field, and also those features of the flow that are related to the noise generation. Fluctuating properties of the flow were captured and analyzed for the aeroacoustic predictions. Special attention was paid to the pressure fluctuations (aerodynamic and acoustic pressures) inside the cove and over the slat surface, where the noise sources were initially based on. For the aeroacoustic computations the model based on Ffowcs-Williams and Hawkings analogy has been used in conjunction with the LES solver. Copyright © 2009 by B. Rakhshani and A. Filippone
Pragmatic Case Studies as a Source of Unity in Applied Psychology
No full textTo unify or not to unify applied psychology: that is the question. In this article we review pendulum swings in the historical efforts to answer this question—from a comprehensive, positivist, “top-down,” deductive yes between the 1930s and the early 60s, to a postmodern no since then. A rationale and proposal for a limited, “bottom-up,” inductive yes in applied psychology is then presented, employing a case-based paradigm that integrates both positivist and postmodern themes and components. This paradigm is labeled “pragmatic psychology” and, its specific use of case studies, the “Pragmatic Case Study Method” (“PCS Method”). We call for the creation of peer-reviewed journal-databases of pragmatic case studies as a foundational source of unifying applied knowledge in our discipline. As one example, the potential of the PCS Method for unifying different angles of theoretical regard is illustrated in an area of applied psychology, psychotherapy, via the case of Mrs. B. The article then turns to the broader historical and epistemological arguments for the unifying nature of the PCS Method in both applied and basic psychology.Peer reviewe
Large-eddy simulation for aerodynamic noise from high-lift device
No full textThree dimensional time-accurate simulations on a leading-edge slat and wing combination were carried out by using a large-eddy simulation model (LES). To reduce the cost of LES simulations in terms of grid size/resolution, a transverse boundary condition of a symmetry type was imposed at the sides of the model whilst keeping the slat spanwise extent to 18% of the main element's chord. The cove region was decomposed into three zones in which the grid was generated separately. The model predicts the unsteady dynamics of the slat's flow field, and also those features of the flow that are related to the noise generation. Fluctuating properties of the flow were captured and analyzed for the aeroacoustic predictions. Special attention was paid to the pressure fluctuations (aerodynamic and acoustic pressures) inside the cove and over the slat surface, where the noise sources were initially based on. For the aeroacoustic computations the model based on Ffowcs-Williams and Hawkings analogy has been used in conjunction with the LES solver. Copyright © 2009 by B. Rakhshani and A. Filippone
Dr. Edwin Wright Collection: Author Unknown
No full textNotes - The author relates several short stories about his neighbours including Alex McDonell, homesteading and life around Meanook and Athabasca (1 page
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Nitrogen passivation by atomic hydrogen in GaAsyN1-y and InxGa1-xAsyN1-y alloys
No full textPrevious theoretical studies on N-H complexes in GaAsN have been extended here to new di-hydrogen complex configurations and to N-H complexes in the In0.25Ga0.75As0.97N0.03 alloy. Moreover, a deeper analysis has been performed on the structure, formation energies, chemical bonding and electronic properties of old and new N-H complexes in the above alloys. On the ground of the achieved results, the existence of a novel di-hydrogen complex is predicted that is characterized by a C-2v symmetry and peculiar vibrational properties. Complexes with this symmetry are not stable in N-free GaAs. Further, we propose a sound model for the N passivation founded on the characteristics of the electronic states and the local atomic relaxations induced by the N-H complexes. This model explains why the N passivation is not achieved in the case of monohydrogen complexes and realized through the formation of the N-H-2(*) dihydrogen complexes. Finally, it is suggested that different N-H complexes (and different vibrational spectra) should be observed in hydrogenated p-type and n-type N-containing alloys
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