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1.
Measuring Search Engine Quality   总被引:12,自引:3,他引:9  
The effectiveness of twenty public search engines is evaluated using TREC-inspired methods and a set of 54 queries taken from real Web search logs. The World Wide Web is taken as the test collection and a combination of crawler and text retrieval system is evaluated. The engines are compared on a range of measures derivable from binary relevance judgments of the first seven live results returned. Statistical testing reveals a significant difference between engines and high intercorrelations between measures. Surprisingly, given the dynamic nature of the Web and the time elapsed, there is also a high correlation between results of this study and a previous study by Gordon and Pathak. For nearly all engines, there is a gradual decline in precision at increasing cutoff after some initial fluctuation. Performance of the engines as a group is found to be inferior to the group of participants in the TREC-8 Large Web task, although the best engines approach the median of those systems. Shortcomings of current Web search evaluation methodology are identified and recommendations are made for future improvements. In particular, the present study and its predecessors deal with queries which are assumed to derive from a need to find a selection of documents relevant to a topic. By contrast, real Web search reflects a range of other information need types which require different judging and different measures.  相似文献   
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This small-scale research study looks at the PSHE/Citizenship framework and the opportunities for student teachers to understand and experience within school the relationship between values, personal and social development and learning. A questionnaire was given to two sets of student teachers on their final school-based placements. The research suggests that there needs to be greater recognition of the centrality of multi-cultural awareness and understanding within the political literacy section of the PSHE/Citizenship framework. This is the counterpart to a previous study of the opportunities for values education within the university-based elements of Primary Initial Teacher Education ( Mead, 2003 ).  相似文献   
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Public libraries tend to be taken for granted. They can be found in nearly every community and are used by a substantial proportion of the population, particularly the young and the old. Yet the public library service, as it is today, is a relatively recent phenomenon. Despite their origins in the mid-19th century, the widespread network of public libraries is largely the product of the post-war welfare state. The demand for the service grew rapidly during the war and in the immediate post-war period. Provision to meet the demand was constrained initially by the competing demands for reconstruction, but by 1960 the service was ready to expand. The growth was consolidated by the 1964 Public Libraries and Museums Act and was given further emphasis by the 1962 Bourdillon standards (Ministry of Education, 1962). The Act and the standards provided the impetus for what might be described as the golden age of public libraries. This brief period was brought to an abrupt end by the economic crises of the mid-1970s and the subsequent downward pressure on public expenditure. The service managed to hold its own during the late 1970s and early 1980s but since then it has been in decline, with the rate of decline accelerating during the 1990s as new requirements and increasing costs stretched diminishing resources even further, to the point where the overall level of provision now falls well short of the basic standards that were considered to be essential in the early 1960s.  相似文献   
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When searching for health information, results quality can be judged against available scientific evidence: Do search engines return advice consistent with evidence based medicine? We compared the performance of domain-specific health and depression search engines against a general-purpose engine (Google) on both relevance of results and quality of advice. Over 101 queries, to which the term ‘depression’ was added if not already present, Google returned more relevant results than those of the domain-specific engines. However, over the 50 treatment-related queries, Google returned 70 pages recommending for or against a well studied treatment, of which 19 strongly disagreed with the scientific evidence. A domain-specific index of 4 sites selected by domain experts was only wrong in 5 of 50 recommendations. Analysis suggests a tension between relevance and quality. Indexing more pages can give a greater number of relevant results, but selective inclusion can give better quality.  相似文献   
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Der gleichzeitige Betrieb mehrerer Gast-Betriebssysteme auf einem einzigen physischen Rechner unter einem Host-Betriebssystem ist eine leistungsfähige moderne Entwicklung. Bekannte Beispiele sind VMware für die IA32-Architektur sowie das Betriebssystem z/VM und die PR/SM-LPAR Einrichtungen der zSeries-Architektur. Die Nutzung eines Betriebssystems als Gast bedingt einen Leistungsverlust. Die als Partitionierung bezeichnete Zuordnung von Systemressourcen zu den einzelnen Gast-Betriebssysteme ist schwierig, wenn eine dynamische Anpassung an sich ändernde Lastprofile erforderlich ist. Diese Probleme lassen sich mittels Erweiterungen der Hardwarearchitektur adressieren, sowie durch Softwarestrukturen, welche diese Erweiterungen nutzen. Die Erweiterungen der Hardwarearchitektur gehen über das hinaus, was auf heutigen Rechnerarchitekturen wie IA32 oder Mips verfügbar ist. Der vorliegende Beitrag erläutert den optimalen Betrieb von Gast-Betriebssystemen und die begleitenden Partitionierungsmöglichkeiten auf der zSeries-Plattform und beschreibt die zusätzlichen Hardware- und Software-Einrichtungen, welche dies ermöglichen.  相似文献   
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ABSTRACT

Libraries worldwide have had to re-think their purpose and adapt to changing community needs and expectations. They are no longer simply repositories for old books. Rather, they are vital components of a community’s social and economic infrastructure that connects communities and fosters creativity and innovation. This paper explores the changing role of libraries—and public value organizations more broadly—in creating positive social, economic, and environmental outcomes for individuals and communities.  相似文献   
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Reports about political scandals have increased lately. Yet the general impact of news visuals and the specific role of lightness and darkness cues in images of scandalized politicians remain unclear. With the help of an experiment, the present pilot study examined the influence of candidate images and the effects of particular image backgrounds (light versus dark). While the foreground of the image depicting a politician involved in a scandal remained unchanged, the background was systematically altered. The results revealed that a light background had a positive effect on recipients’ attitudes toward the politician. In contrast, participants exposed to a dark image background demanded a more severe punishment for the politician.  相似文献   
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