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   

The indexing of periodicals     

Hans H. Wellisch 《Learned Publishing》1992,5(1):13-18

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Entrepreneurship: Exploring the knowledge base   总被引：1，自引：0，他引：1  

Hans Landström  Gouya Harirchi 《Research Policy》2012,41(7):1154-1181

Entrepreneurship research has a long tradition and since the 1980s the field has grown significantly. In this study we identify the ‘knowledge producers’ who have shaped the field over time and their core entrepreneurship research works. A unique database consisting of all references in twelve entrepreneurship ‘handbooks’ (or state-of-the-art books) has been developed. The chapters in these handbooks were written by experts within the field, and it can be assumed that the most frequently cited references represent ‘core knowledge’ with relevance to entrepreneurship research.From our analysis, it appears that entrepreneurship is a rather changeable field of research, closely linked to disciplines such as ‘management studies’ and ‘economics’. Over time, the field has become more formalized with its own core knowledge, research specialities and an increasing number of ‘insider works’. However, it is still based on some fairly old theoretical frameworks imported from mainstream disciplines, although during the last decade we have seen the emergence of a number of new field-specific concepts and theories. We argue that to successfully develop entrepreneurship research in the future, we need to relate new research opportunities to earlier knowledge within the field, which calls for a stronger ‘knowledge-based’ focus. We would also like to see greater integration between the fields of entrepreneurship and innovation studies in the future.  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   

Creativity, trust and systematic processes in product development     

Anna Brattström  Hans Löfsten 《Research Policy》2012,41(4):743-755

This paper addresses the challenge of striking a balance between, on one hand, mitigating uncertainty through the existence of systematic processes and structures and, on the other, stimulating creativity through allowable variation in work processes and structures. Both objectives are fundamental aspects of product development work. Our main finding is that both objectives can be achieved simultaneously. We introduce trust as a mediating variable. We show first, that being systematic in the processes for obtaining information and applying explicit organizational rules and structures in product development work creates an atmosphere of trust in the organization. Second, we show that trust increases creativity. The paper contributes to an understanding of how and why trust is important in product development organizations and of how trust can be actively managed. Above all, the paper contributes to the understanding of how uncertainty and creativity should be managed in organizations conducting product development.  相似文献   

Characterizing the mechanical parameters of forward and backward falls as experienced in snowboarding     

Schmitt KU  Wider D  Michel FI  Brügger O  Gerber H  Denoth J 《Sports biomechanics / International Society of Biomechanics in Sports》2012,11(1):57-72

Wrist injuries are frequently observed after falls in snowboarding. In this study, laboratory experiments mimicking forward and backward falls were analysed. In six different falling scenarios, participants self-initiated falls from a static initial position. Eighteen volunteers conducted a total of 741 trials. Measurements were taken for basic parameters describing the kinematics as well as the biomechanical loading during impact, such as impact force, impact acceleration, and velocity. The effective mass affecting the wrist in a fall also was determined. The elbow angle at impact showed a more extended arm in backward falls compared to forward falls, whereas the wrist angle at impact remained similar in forward and backward falls. The study results suggest a new performance standard for wrist guards, indicating the following parameters to characterize an impact: an effective mass acting on one wrist of 3-5 kg, an impact angle of 75 degrees of the forearm relative to the ground, and an impact velocity of 3 m/s.  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   

Competence in nursing informatics among nursing students and staff at a nursing institute in Sweden     

Ragneskog H  Gerdner L 《Health information and libraries journal》2006,23(2):126-132

BACKGROUND: Information technology (IT) has slowly been implemented in many health-care organizations (i.e. hospitals). The use of computers has advanced to home care and long-term facilities. Consequently, it is important that nurses are able to demonstrate competence and feel confident in the use of IT. Yet, research has reported that nursing students have varying degrees of competence and experience with IT. AIMS: The purpose of this study was to ascertain nursing students' and nursing educators' self-reported attitudes, skills and experiences using IT. METHODS: Data were collected through a written survey distributed and completed by 247 nursing students (45 of whom were registered nurses who participated in extension courses) and 52 staff members from the nursing faculty at a university in Sweden. RESULTS: Two-thirds of the students and 92% of the nursing educators had access to the Internet from their homes. Of the students, 71% identified their IT skills as being sufficient for their current or future work as a registered nurse. Nurse educators were less confident in the students' ability, reporting that only 29% of nursing students had sufficient IT skills. Comparatively, 48% of the nursing educators believed that they themselves had sufficient IT skills for their role as a nurse educator. CONCLUSIONS: It is important that nursing students have basic IT skills and are familiar with e-mail, word-processing and various databases on the World Wide Web. Findings indicate that participants had a deficit in these skills, suggesting the need to integrate IT into the nursing curriculum.  相似文献   

The funding of fachhochschulen in Austria     

Hans Pechar 《Tertiary Education and Management》2013,19(2):165-172

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