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

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     

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

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.     

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

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.     

Fault reconstruction using a LPV sliding mode observer for a class of LPV systems

This paper proposes a new sliding mode observer for fault reconstruction, applicable for a class of linear parameter varying (LPV) systems. Observer schemes for actuator and sensor fault reconstruction are presented. For the actuator fault reconstruction scheme, a virtual system comprising the system matrix and a fixed input distribution matrix is used for the design of the observer. The fixed input distribution matrix is instrumental in simplifying the synthesis procedure to create the observer gains to ensure a stable closed-loop reduced order sliding motion. The ‘output error injection signals’ from the observer are used as the basis for reconstructing the fault signals. For the sensor fault observer design, augmenting the LPV system with a filtered version of the faulty measurements allows the sensor fault reconstruction problem to be posed as an actuator fault reconstruction scenario. Simulation tests based on a high-fidelity nonlinear model of a transport aircraft have been used to demonstrate the proposed actuator and sensor FDI schemes. The simulation results show their efficacy.     

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

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.     

Generation of virtual models of cultural heritage

Different techniques and tools currently exist to generate three-dimensional models of small elements, buildings and cities. Apart from being easier to interpret than two-dimensional drawings, these models facilitate data necessary for reconstruction projects, preservation or rehabilitation of the architectural or archaeological heritage. Traditional surveying only enables us to obtain discrete information of the characteristic lines that define each surface, edge, slope change etc. whereas work with massive capture techniques allows us to obtain continuous points of the surfaces. Photogrammetry or laser scanning combined with conventional photography provides information of the building in addition to its geometry. We carried out a review of the different techniques showing the advantages and disadvantages of each technique as well as the information that can be obtained by applying these techniques to the survey of the great Gate of Antioch in the town of Aleppo, declared a World Heritage Site by UNESCO in 1986, in Syria.     

Hirsch-type characteristics of the tail of distributions. The generalised h-index

In this paper a generalisation of the h-index and g-index is given on the basis of non-negative real-valued functionals defined on subspaces of the vector space generated by the ordered samples. Several Hirsch-type measures are defined and their basic properties are analysed. Empirical properties are illustrated using examples from the micro- and meso-level. Among these measures, the h-index proved the most, the arithmetic and geometric g-indices, the least robust measures. The μ-index and the harmonic g-index provide more balanced results and are still robust enough.     

Is Education Getting Lost in University Mergers?

Mergers are common phenomena in higher education institutions. Improving educational quality is typically one of the stated goals of university mergers. Yet, little information exists about how merging institutions approach this goal. This paper presents results from a study of planning documents created prior to four mergers in the Finnish higher education system. These documents show that there was little concrete attention given to the educational issues related to the mergers. Most attention was placed on administrative issues and issues related to research. When educational issues were mentioned, it was almost always in the form of vague goals with few details provided about how the goals were to be reached. We conclude that this lack of attention to the educational aspect of mergers is a significant weakness of the planning process in these mergers.     

Training and psychosocial patterns during the early development of Portuguese national team athletes

This study explored the early development of expert athletes compared to a group of athletes that did not achieve an expert level of performance despite being involved in youth events with their national squads. In particular, the activities, training patterns, and psychosocial influences that characterized their paths in competitive sports were examined. Male and female participants (N?=?42) from different sports were interviewed. Overall, athletes showed several commonalities. However, experts were selected to national squads later and also started thinking about investing in becoming elite athletes later. Non-experts revealed more parental pressure and less individual training with coaches.     

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

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.