Das MINERVA-Projekt: Datenbankselektion für Peer-to-Peer-Websuche     

Matthias Bender  Sebastian Michel  Gerhard Weikum und Christian Zimmer 《Informatik - Forschung und Entwicklung》2005,20(3):152-166

Zusammenfassung In diesem Artikel wird MINERVA pr?sentiert, eine prototypische Implementierung einer verteilten Suchmaschine basierend auf einer Peer-to-Peer (P2P)-Architektur. MINERVA setzt auf die in der P2P-Welt verbreitete Technik verteilter Hash-Tabellen auf und benutzt diese zum Aufbau eines verteilten Verzeichnisses. Peers in unserem Ansatz entsprechen v?llig autonomen Benutzern mit ihren lokalen Suchm"oglichkeiten, die bereit sind, ihr lokales Wissen und ihre lokalen Suchm?glichkeiten im Rahmen einer Kollaboration zur Verfügung zu stellen. Wir formalisieren unsere Systemarchitektur und beschreiben das zentrale Problem einer effizienten Suche nach vielversprechenden Peers für eine konkrete Anfrage innerhalb des Verbundes. Wir greifen dabei auf existierende Methoden zurück and passen diese an unseren Systemkontext an. Wir pr?sentieren Experimente auf realen Daten, die verschiedene dieser Ans?tze vergleichen. Diese Experimente zeigen, dass die Qualit?t der Ans?tze variiert und untermauern damit die Wichtigkeit und den Einfluss einer leistungsstarken Methode zur Auswahl guter Datenbanken. Unsere Experimente deuten an, dass eine geringe Anzahl sorgf?ltig ausgew?hlter Datenbanken typischerweise bereits einen Gro?teil aller relevanten Ergebnisse des Gesamtsystems liefert.

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This paper presents the MINERVA project that protoypes a distributed search engine based on P2P techniques. MINERVA is layered on top of a Chord-style overlay network and uses a powerful crawling, indexing, and search engine on every autonomous peer. We formalize our system model and identify the problem of efficiently selecting promising peers for a query as a pivotal issue. We revisit existing approaches to the database selection problem and adapt them to our system environment. Measurements are performed to compare different selection strategies using real-world data. The experiments show significant performance differences between the strategies and prove the importance of a judicious peer selection strategy. The experiments also present first evidence that a small number of carefully selected peers already provide the vast majority of all relevant results.

CR Subject Classification H.4,H.3.3,H3.4  相似文献   

Das MINERVA-Projekt: Datenbankselektion für Peer-to-Peer-Websuche     

Matthias Bender  Sebastian Michel  Gerhard Weikum  Christian Zimmer 《Informatik - Forschung und Entwicklung》2005,12(5):152-166

In diesem Artikel wird MINERVA pr?sentiert, eine prototypische Implementierung einer verteilten Suchmaschine basierend auf einer Peer-to-Peer (P2P)-Architektur. MINERVA setzt auf die in der P2P-Welt verbreitete Technik verteilter Hash-Tabellen auf und benutzt diese zum Aufbau eines verteilten Verzeichnisses. Peers in unserem Ansatz entsprechen v?llig autonomen Benutzern mit ihren lokalen Suchm"oglichkeiten, die bereit sind, ihr lokales Wissen und ihre lokalen Suchm?glichkeiten im Rahmen einer Kollaboration zur Verfügung zu stellen. Wir formalisieren unsere Systemarchitektur und beschreiben das zentrale Problem einer effizienten Suche nach vielversprechenden Peers für eine konkrete Anfrage innerhalb des Verbundes. Wir greifen dabei auf existierende Methoden zurück and passen diese an unseren Systemkontext an. Wir pr?sentieren Experimente auf realen Daten, die verschiedene dieser Ans?tze vergleichen. Diese Experimente zeigen, dass die Qualit?t der Ans?tze variiert und untermauern damit die Wichtigkeit und den Einfluss einer leistungsstarken Methode zur Auswahl guter Datenbanken. Unsere Experimente deuten an, dass eine geringe Anzahl sorgf?ltig ausgew?hlter Datenbanken typischerweise bereits einen Gro?teil aller relevanten Ergebnisse des Gesamtsystems liefert.  相似文献   

Selective search, sectoral patterns, and the impact on product innovation performance     

Christian Köhler 《Research Policy》2012,41(8):1344-1356

The shift toward more open and interconnected innovation activities has been a major topic in recent academic and practitioner discussions. Firms must connect their in-house R&D activities with external partners, such as leading customers or universities, to increase the effectiveness of their innovation activities. Hence, management needs to define where to search for valuable knowledge in its environment. In this paper we argue that knowledge search has to reflect the heterogeneity of various knowledge sources with regard to the knowledge they can provide and how these sources can be activated. We hypothesize that search strategies driven by science, suppliers and the product market will contribute differently to innovation success with new-to-market versus imitated products. Moreover, we explore the effect of these types of knowledge search within different sectoral patterns of innovation. Our empirical analysis rests on a sample of almost 5000 firms from five Western European countries. The results support our hypotheses and highlight the potentials and shortcomings of different types of knowledge search.  相似文献   

Institutional Struggles for Recognition in the Academic Field: The Case of University Departments in German Chemistry     

Richard Münch  Christian Baier 《Minerva》2012,50(1):97-126

This paper demonstrates how the application of New Public Management (NPM) and the accompanying rise of academic capitalism in allocating research funds in the German academic field have interacted with a change from federal pluralism to a more stratified system of universities and departments. From this change, a tendency to build cartel-like structures of allocating symbolic capital resulting in oligopolistic structures of appropriating research funds has emerged. This macro level structure is complemented by the strengthening of the traditional oligarchic structures of research, carried out by an increasing number of assistants under the direction of a professor on the meso level. The outcome of this institutional setting is a significant gap between the appropriation of research funds according to the allocation of symbolic capital and the production of knowledge in publications. The application of NPM therefore needs to be explained more as a result of the normative pressure of a globally established model of “rational” administration, and less as a result of its functional effectiveness. This is demonstrated by an empirical analysis with simple and multiple regressions using data on the allocation of research grants and publication records of German chemistry departments.  相似文献   

Transferwirkungen künstlerischer Tätigkeiten. Ihre kritische Kommentierung durch eine umfassende Theorie ästhetischer Bildung     

Christian Rittelmeyer 《Zeitschrift für Erziehungswissenschaft》2013,16(3):217-231

Transfer research examines how artistic activities can have an impact outside of the realm of art itself. The article concludes that this research can be carried out in a meaningful way, only within the framework of a comprehensive theory of aesthetic education. This theory would encompass the structural analysis of artistic activity, as well as biographical reports about artistic experiences. The elucidation of the concepts or themes relevant to the theory would include the notion of aesthetic experience, the understanding of immediate, aesthetic experiences, the analysis of artistic processes, and the outcomes of scientifically evaluated applications of aesthetic education.  相似文献   

Approaches for Effective Vocationalisation of Secondary School Agriculture in Nigeria: The Views of Agricultural Science Teachers in Delta State,Nigeria     

Dr Canice N. Ikeoji  Christian C. Agwubike 《The Journal of Agricultural Education and Extension》2013,19(3):213-222

Abstract

This paper describes a random sample of serving agricultural science teachers in Delta State, Nigeria, as a background to understanding their views on four selected approaches for effective vocationalisation of secondary school agriculture. These approaches were used to develop a 23-item questionnaire based on current literature. A five-point Likert-type scale was used to determine how well the views of the respondents corresponded with the items in the questionnaire. Results showed, among others, that the average teaching experience of the 322 sampled teachers was 12.9 years; 50.6 % of the respondents were BSc(Ed) degree holders; 38.8% had Nigerian Certificate in Education (NCE), while 10.6% were Higher National Diploma (HND) holders. The respondents agreed that the identified approaches were necessary for effective vocationalisation of secondary school agriculture. The paper therefore recommends that the identified approaches should be pursued by the Nigerian government to ensure that vocational agriculture in secondary schools achieves the goals of the National Policy on Education.  相似文献   

Robots Teaching Other Little Robots: Neoliberalism,CCSS, and Teacher Professionalism     

Jason L. Endacott  Ginney P. Wright  Christian Z. Goering  Vicki S. Collet  George S. Denny  Jennifer Jennings Davis 《Review of Education, Pedagogy & Cultural Studies》2013,35(5):414-437

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What do we see out of the corner of our eye? The role of visual pivots and gaze anchors in sport     

Christian Vater  Andrew Mark Williams  Ernst-Joachim Hossner 《International review of sport and exercise psychology》2020,13(1):81-103

ABSTRACT

The role and importance of peripheral vision have been discussed across various sports. Yet, its functionality remains unclear and the terms employed in the literature to characterize the use of peripheral vision are not well defined. We present a review of 29 studies focusing on the use of peripheral vision in sports. We focus on the methodological approaches employed to study its use and identify the mechanisms that may underlie the effective use of peripheral vision in sport. We define key differences between ‘gaze anchors’ and ‘visual pivots’ and introduce the concept of a ‘foveal spot’. All three gaze behaviors, while being characterized by a consistent, dynamically adjustable gaze location, have different functionalities. A gaze anchor is a cue-optimized position used for the monitoring of peripheral cues and avoiding the negative consequences of saccades (i.e. information suppression), especially under time pressure. A visual pivot is a distance-optimized location between relevant cues which allows athletes to optimally initiate saccades to those cues, especially if the costs of eye-movements are low. A foveal spot is primarily used for information processing via the fovea. Finally, we highlight suggestions for future research to improve our understanding of the functional differences between these gaze behaviors.  相似文献   

A conjoint experiment of how design features affect evaluations of participatory platforms     

Henrik Serup Christensen 《Government Information Quarterly》2021,38(1):101538

Online participatory platforms are introduced to boost citizen involvement in political decision-making. However, the design features of these platforms vary considerably, and these are likely to affect how prospective users evaluate the usefulness of these platforms. Previous studies explored how prevalent different design features are and how they affect the success of platforms in terms of impact, but the attitudes of prospective users remain unclear. Since these evaluations affect the prospects for launching successful participatory platforms, it is imperative to assess what citizens want from such digital possibilities for participation. This study uses a conjoint experiment (n = 1048) conducted in Finland that explore the impact of seven design features: Discussion possibilities; Interaction with politicians and experts; Information availability, Aim of participation; Identity verification; Anonymous participation and Accessibility. Furthermore, it is examined whether the effects differ across use of ICTs measured by generation, time online and prior use of participatory platforms. The results suggest that most design features have clear effects on evaluations, and that deliberative features have the strongest effects. Furthermore, the effects are relatively stable across prior use although the less experienced put a stronger emphasis on verification.  相似文献   

Are quiz-games an effective revision tool in Anatomical Sciences for Higher Education and what do students think of them?     

Kate Wilkinson  George Dafoulas  Hemda Garelick  Christian Huyck 《British journal of educational technology : journal of the Council for Educational Technology》2020,51(3):761-777

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