1,720,970 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A quantum logic-based query processing approach for extending relational query languages
Full text linkEvaluating a traditional database query against a data tuple returns a true on match and a false on mismatch. Unfortunately, there are many application scenarios where such an evaluation is not possible or does not adequately meet users needs. A further problematic application area is text retrieval where in general finding a complete match is impossible. Thus, there is a need for incorporating impreciseness and proximity into a logic-based query language: Objects fulfill such a similarity condition to a certain degree which is expressed by a result value out of the interval [0, 1]. In this work we will sketch a quantum logic-based approach, which provides the combination of classical Boolean predicates and similarity conditions into one integrating formalism
Effiziente und flexible Konstruktion von Abstammungsformeln für probabilistische Datenbanken
Full text linkIn contrast to traditional data applications, many real-world scenarios nowadays depend on managing and querying huge volumes of uncertain and incomplete data. This new type of applications emerge, for example, when we integrate data from various sources, analyse social/biological/chemical networks or conduct privacy-preserving data mining.
A very promising concept addressing this new kind of probabilistic data applications has been proposed in the form of probabilistic databases. Here, a tuple only belongs to its table or query answer with a specific likelihood. That probability expresses the uncertainty about the given data or the confidence in the answer. The most challenging task for probabilistic databases is query evaluation. In fact, there are even simple relational queries for which determining the occurrence probability of a single answer tuple is hard for #P.
Lineage formulas constitute the central concept under investigation in this work. In short, the mechanism behind lineage formulas facilitates the representation and evaluation of events of the probability space, which is defined by a probabilistic database. On the basis of lineage formulas, we devise a framework that is designed as a combination of a relational database layer and an additional probabilistic query engine.
In particular, the following three aspects are studied:
(i) an efficient construction of lineage formulas,
(ii) an orthogonal combination of lineage optimization techniques, which are performed within the relational database layer and the probabilistic query engine, and
(iii) effective and compact data structures to represent lineage formulas within a probabilistic query engine.
The developed framework provides a novel lineage construction method that is able to construct nested lineage formulas, to avoid large tuple sets within the relational database layer tuples, and to provide full relational algebra support. In addition, the proposed system completely resolves the conflict between the contradicting query plans optimized for the relational database layer and the probabilistic query engine.Probabilistische Datenbanken standen in den letzten Jahren im Fokus intensiver Forschungsaktivitäten. Dies wurde durch eine Vielzahl von Anwendungsszenarien motiviert, in denen eine effiziente Verwaltung von großen, unsicheren Datenbeständen unabdingbar ist. Typische Anwendungsgebiete lassen sich leicht in den Bereichen der Datenextraktion und -integration, der wissenschaftlichen Datenauswertung und der Analyse von sensorischen und sozialen Netzwerken finden.
In einer probabilistischen Datenbank wird jedes Datentupel mit einer Eintrittswahrscheinlichkeit annotiert. Diese verdeutlicht, mit welcher Wahrscheinlichkeit das jeweilige Tupel zu einer bestimmten Datentabelle bzw. zu einem berechneten Anfrageergebnis gehört. Für probabilistische Datenbanken ist die Berechnung der Eintrittswahrscheinlichkeit für ein Ergebnistupel die größte Herausforderung, da dieses Problem in der Komplexitätsklasse #P liegt. Diese Klasse beinhaltet alle Probleme, die mindestens so schwer sind wie das Zählen aller erfüllenden Modelle einer aussagenlogischen Formel. Es gilt NP ⊆ #P.
Traditionell werden Auswertungsverfahren für probabilistische Datenbanken in intensionale und extensionale Ansätze unterteilt. Intensionale Ansätze greifen auf die Konstruktion und Auswertung von Abstammungsformeln zurück. Auf der Basis von Abstammungsformeln, die das zentrale Untersuchungsobjekt dieser Arbeit darstellen, können Ereignisse des Wahrscheinlichkeitsraumes einer probabilistischen Datenbank repräsentiert werden.
In der vorliegenden Dissertation wird ein System entworfen, welches als Kombination einer relationalen Datenbank-Schicht und einer zusätzlichen probabilistischen Auswertungskomponente konzipiert ist. Hierbei werden folgende drei Hauptaspekte untersucht:
(i) die effiziente Konstruktion von Abstammungsformeln,
(ii) die orthogonale Kombination von Optimierungstechniken und
(iii) die Entwicklung von effektiven und kompakten Datenstrukturen für die Kodierung von Abstammungsformeln für die probabilistische Auswertungskomponente.
Die entwickelten Techniken ermöglichen die schnelle Generierung von geschachtelten Abstammungsformeln, die Vermeidung von großen Tupel-Mengen innerhalb der relationen Datenbank-Schicht und die Unterstützung aller relationalen Anfrage-Operatoren
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Investigating accuracy and precision of ionoacoustics for range determination of ion beams in water
No full textDispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Optimierung und Kalibrierung der "Top-of-Fringe"-Stabilisierung einer Laserdiode auf einem Methan-Absorptionstrog bei 6077 cm-1 mithilfe eines selbst-referenzierten, optischen Frequenzkammes
No full textMithilfe frequenzmodulierter Absorptionsspektroskopie wird Methan bei 6077 cm-1 untersucht. Ziel ist es, gute Werte für die Stabilisierung eines Referenzsystems zu ermitteln. Dazu wird einerseits eine Laserdiode hoch- und tieffrequent moduliert und der Laserstrahl durch eine Multipasszelle mit reinem Methan geleitet und das Fehlersignal aufgezeichnet. Andererseits mithilfe eines schnellen Photodetektors das Schwebungssignal dieser modulierten Laserdiode mit einer Referenzdiode gemessen. Zur Stabilisierung der Referenzdiode wird ein optischen, selbstreferenzierten frequenzkammes verwendet. Es wird die Steigung der Fehlersignalsfunktion am Nulldurchgang und unter Verwendung der genauen Stabilisierung der Referenzdiode die Lage des Nulldurchganges für verschiedene Drücke des Methans und verschiedene Werte der hochfrequenten Modulation errechnet. Es zeigt sich für jeden Druck ein anderes deutliches Maximum, jedoch bei keinem Druck ein besonders hoher Wert der Steigung am Nulldurchgang. Die Messung der Lage des Nulldurchganges zeigt ein merkwürdige Sprungverhalten, welches im Rahmen dieser Arbeit nicht abschliessend erklärt werden konnte. Weitere Messungen mit Mischungen von Methan und Kohlendioxid in der Gaszelle zur Untersuchung komplexerer Einflüsse der beiden Gase aufeinander werden folgen
- …
