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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.
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
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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
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Cultural and linguistic diversity in early childhood teacher preparation: The impact of contextual characteristics on coursework and practica 总被引：1，自引：0，他引：1
Chih-Ing Lim Kelly L. Maxwell Harriet Able-Boone Catherine R. Zimmer 《Early childhood research quarterly》2009
The population of children in early childhood settings is becoming increasingly culturally and linguistically diverse, and these changes in demographics have warranted teachers becoming more culturally responsive and better prepared to work with diverse young children and families. Teacher preparation programs across the nation have responded differently to this critical issue, in part because of the different contexts in which they exist. Analyses were conducted using data from the National Prekindergarten Center’s (NPC) National Study of Early Childhood Teacher Preparation Programs and the National Center for Educational Statistics (NCES) Integrated Post-Secondary Education Dataset (IPEDS). Geographical, program, and institutional characteristics were analyzed from a sample of 416 Bachelor’s degree programs to determine how these variables were associated with the amount of diversity content and experience required in teacher preparation programs. Results indicated that the presence of non-White full-time faculty was positively related to more required coursework focused on working with children and families from culturally diverse backgrounds, while degree of urbanization, governance of institutions, and National Council for Accreditation of Teacher Education accreditation were associated with required coursework focused on working with bilingual children and English language learners. The percentage of the non-Hispanic White population in a state and geographic region were both associated with practica requirements focused on working with bilingual children and English language learners. Implications and recommendations for policy, future research, and early childhood teacher preparation are discussed. 相似文献
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在中国文化背景下,用筷子进餐是一项重要的生活技能,同时也能促进幼儿精细动作的发展与脑的发育.对浙江省82所幼儿园及186位幼儿园教师就幼儿用筷现状及教师对幼儿用筷观念所作的调查表明,幼儿园对引导幼儿用筷的关注度较低,仅14.6％的幼儿园要求幼儿用筷进餐,其中75％的幼儿是从大班上学期开始学习用筷子的;教师不愿意教幼儿用筷或不愿意让幼儿用筷主要是出于对筷子的安全性和使用难度等问题的考虑.幼儿园如果安排用筷教学和幼儿用筷实践活动,宜从中班上学期(约4岁)开始,同时要强调家园合作,创设适宜的环境,对幼儿进行安全教育,以促使他们安全用筷,逐步熟练用筷. 相似文献
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Using the neo-classical justifications for government support of the arts that Dick Netzer discussed in The Subsidized Muse as a starting point, the article contends that market failure is not an useful concept to understand and explain cultural policies and the degree of government involvement, particularly when viewed from a comparative perspective. The basic fault is that historical- institutional arrangements and the role of non-state actors in the formation of cultural policies are not taken into account. Discussing some aspects of the institutional framework in the development of French, Swedish and U.S. cultural policies, the article concludes with a call for the use of neo-institutionalist perspectives in analyzing government intervention in the arts field. 相似文献
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While a growing body of literature on education production looks at the impact school inputs have on academic achievement, virtually no research is examining the impact capital is having on academic achievement. In this study, we take an initial step towards that end. By using school districts' level of bond indebtedness as a proxy for capital, we find evidence that capital stock does affect academic achievement. In light of these findings along with the general lack of research on capital inputs, we conclude that capital expenditures should be given greater attention in future research. 相似文献
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ABSTRACTIn this article, we reflect on the contributions of the social sciences to the field of adapted physical activity by examining the theories and methods that have been adopted from the social science disciplines. To broaden our perspective on adapted physical activity and provide new avenues for theoretical and empirical exploration, we discuss and evaluate broad ideas/tensions arising from the social science literature—the individual versus social/ecological, and social science of adapted physical activity versus social science in adapted physical activity. We intentionally focus discussion on the application of specific lines of inquiry in the social sciences that have not yet emerged (or have done so only in limited applications) in the field of adapted physical activity. Such untapped areas of scholarship in the social sciences can lead to broader understanding, innovations, and new lines of inquiry when applied to an adapted physical activity context. 相似文献