105,670 research outputs found
Study of the structural, optical and electrical properties of extended defects in GaN
No full textIn questo progetto si vuole studiare l’attività di ricombinazione dei difetti estesi (dislocazioni, bordi di grano, inversion domain) in GaN attraverso metodi di caratterizzazione strutturale (TEM ad alta risoluzione, olografia elettronica) e spettroscopica (DLTS DeepLevelTransientSpectroscopy, Persistent PhotoCurrent, fotoconducibilità). Finalità del progetto di ricerca è da un lato comprendere la relazione tra struttura atomica e attività opto-elettronica delle dislocazioni e dall’altro analizzare l’influsso delle condizioni di crescita, del drogaggio e della struttura del nucleo delle dislocazioni sulle proprietà ottiche ed elettriche
A Comparative Evaluation of a New Unsupervised Sentence Boundary Detection Approach on Documents in English and Portuguese
No full textIn this paper, we describe a new unsupervised sentence boundary detection system and present a comparative study evaluating its performance against dierent systems found in the literature that have been used to perform the task of automatic text segmentation into sentences for English and Portuguese documents. The results achieved by this new approach were as good as those of the previous systems, especially considering that the method does not require any additional training resources
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
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
Beiträge zum Quartär der nördlichen Rheinlande
No full textDie Niederrheinische Bucht und die rahmenden Gebirgsregionen der Nordeifel zählen zu den klassischen Gebieten der Quartärforschung. Durch die Untersuchungen seitens des Lehrstuhls für Eiszeitenforschung der Universität Köln unter K. Brunnacker sind die stratigraphischen, sedimentologischen, bodenkundlichen und geomorphologischen Entwicklungen im großen und ganzen weitgehend bekannt. Im Zusammenhang mit Quartärforschungen des Geographischen Instituts und des Instituts für Bodenkunde der Universität Bonn ergaben sich jedoch weitere Fragen, die bisher nicht oder unbefriedigend gelöst waren. über einige Ergebnisse berichtet der vorliegende Band.
Das Problem der Tertiär/Pleistozängrenze wird in Verbindung mit einem Wandel der Morphogenese in den Beiträgen von H. Strunk und H. Zepp erneut aufgegriffen. Eine Umdatierung der Erftterrassen (H. Zepp) scheint erforderlich zu werden, denn die Talbildung war im Altpleistozän bereits an der oberen Erft größtenteils abgeschlossen. Die im Jungtertiär und Altpleistozän gebildeten Reliefformen betrachtet H. Strunk am Eifelnordrand und zeigt, daß Hauptterrassen-Rheinschotter und Eifelschotterfächer verschiedenes altpleistozänes Alter haben, jedoch jünger als die Fußflächen sind; auch H. Strunk stellt fest, daß seit dem Altpleistozän die Taleintiefung äußerst gering ist. Der Beitrag von K. Heine gibt eine Erklärung für den Widerspruch zwischen den Formen, Sedimenten und glaziotektonischen Verhältnissen der Louisendorfer Sanderfläche aufgrund einer Rekonstruktion der Bewegungen des saalezeitlichen Eisrandes. H. Siebertz untersucht die äolischen Sedimente im gleichen Raum und kann differenzierte Vorstellungen über die paläogeographischen Bedingungen zur Zeit der Bildung der äolischen Deckschichten auf dem Niederrheinischen Höhenzug entwickeln. Die Arbeiten von Urban, Schröder & Leßmann erfassen die holozänen Bildungen des unteren Niederrheingebietes interdisziplinär; die Vegetations- und Bodenentwicklung wird mit dem Siedlungsgang verknüpft; die räumliche Verteilung der Bodentypen richtet sich nach der Dauer der Bodenentwicklung auf spätpleistozänen bis altholozänen, mittelholozänen und jungholozänen Rheinsedimenten.
Die hier zusammengestellten Aufsätze sollen zur besseren Kenntnis der nördlichen Rheinlande im Quartär beitragen. Die Autoren würden sich freuen, wenn sie als Diskussionsbeiträge Beachtung fänden. Unsere Vorstellungen über die plio/pleistozäne Talentwicklung in der Nordeifel sollten nicht aus der intensiven Mittelrhein-Terrassenforschung abgeleitet werden (Beiträge H. Strunk und H. Zepp). Einzelprofile und regional eng begrenzte Detailstudien sollten nicht sofort zur weiteren Differenzierung der Quartärstratigraphie führen (Beitrag K. Heine). Die Forschungen über die pleistozänen äolischen Bildungen („Nördliche Lößgrenze“ ) sollten nicht nur zur stratigraphischen, sondern auch zur paläogeographischen Diskussion in der Lößforschung anregen (Beitrag H. Siebertz). Schließlich sollten holozäne Rekonstruktionen der großen Talauen (Beitrag Urban, Schröder, Leßmann) zum besseren Verständnis und zur besseren Nutzung unserer natürlichen Umwelt führen
The energy-critical nonlinear Schrodinger equation on a product of spheres
No full textHerr S, Strunk N. The energy-critical nonlinear Schrodinger equation on a product of spheres. Mathematical Research Letters. 2015;22(3):741-761.Let (M, g) be a compact smooth 3-dimensional Riemannian manifold without boundary. It is proved that the energy-critical nonlinear Schrodinger equation is globally well-posed for small initial data in H-1(M), provided that a certain tri-linear estimate for free solutions holds true. This estimate is known to hold true on the sphere and tori in 3d and verified here in the case S x S-2. The necessity of a weak form of this tri-linear estimate is also 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
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Obstetric litigation is asphyxiating our maternity services
No full textCopyright © 2006 The American College of Obstetricians and GynecologistsObstetric care in the United States, as judged by maternal mortality, neonatal mortality, stillbirth rates, or any other metric, has never been better. Despite this, litigation over "bad outcomes" is threatening the specialty, not only now, but into the future. Despite damage to our specialty, the injured party often benefits little, if at all, from the process. Potential solutions include an emphasis on evidence-based medicine, a qualification and review process for medical experts, and a more rational and fair health court system.Hankins, Gary D. V.; MacLennan, Alastair H.; Speer, Michael E.; Strunk, Albert JD; Nelson, Kari
Contribution of Information and Communication Technology (ICT) in Country’S H-Index
No full textThe aim of this study is to examine the effect of Information and Communication Technology (ICT) development on country’s scientific ranking as measured by H-index. Moreover, this study applies ICT development sub-indices including ICT Use, ICT Access and ICT skill to find the distinct effect of these sub-indices on country’s H-index. To this purpose, required data for the panel of 14 Middle East countries over the period 1995 to 2009 is collected. Findings of the current study show that ICT development increases the H-index of the sample countries. The results also indicate that ICT Use and ICT Skill sub-indices positively contribute to higher H-index but the effect of ICT access on country’s H-index is not clear
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