著者

Watanabe Yousuke Kitagawa Hiroyuki

出版者

Elsevier B.V.

雑誌

Information systems (ISSN:03064379)

巻号頁・発行日

vol.35, no.1, pp.94-110, 2010-01

被引用文献数

4 7

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With the increasing demands for advanced use of streaming data, efficient execution of continuous queries is an important research issue. This paper focuses on event-driven continuous queries that are activated by foreign events such as data arrival and the progression of time. Existing approaches to multiple continuous query optimization decide the optimal query plan by extracting common subexpressions from the given queries. Event-driven queries containing the common subexpressions may produce many common intermediate results when they are activated within a small interval, but may produce only disjoint data when activated at completely different timings.This paper proposes an efficient data stream processing scheme for multiple event-driven continuous queries. In the proposed approach, we introduce query result caching to achieve a flexible way to share common operators among queries activated by unpredictable events. When a query is activated, an intermediate result generated for the query is stored into the cache area if it is expected to be reused by other queries. When other queries including the same operator are activated, they reuse the cached result if the cache includes reusable data. Efficiency of the proposed scheme is validated by intensive experimental evaluations.

著者

北川 浩之 Kitagawa Hiroyuki

出版者

名古屋大学年代測定資料研究センター

雑誌

名古屋大学加速器質量分析計業績報告書

巻号頁・発行日

vol.24, pp.56-61, 2013-03

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Radiocarbon (14C) provides a way to date material that contains carbon with an age up to 50,000 years and is also an important tracer of the global carbon cycle. To obtain the calendar year, radiocarbon age is calibrated using radiocarbon calibration dataset such as IntCal09. However there is still uncertainty in the available radiocarbon calibration dataset prior to 12.5 thousand years before the present. Recently,the radiocarbon calibration dataset from the annual laminated (varve) sediments of Lake Suigetsu, Japan (35°35'N, 135°53'E), have been updated by more than 800 14C analyses of terrestrial materials which provide a comprehensive record of atmospheric (or terrestrial) radiocarbon to the present limit of the 14C method (Bronk Ramsey et al., 2013).炭素14年代測定法は、過去5万年間の年代決l定には無くてはならない年代測定法である。しかし、炭素14年代は暦年代とは一致しなく、炭素14年代から暦年代を推定するには炭素14年代キャリブレーションデータセットを用いた較正が必要である。過去12500年間の炭素14年代キャリブレーションセットは、年輪年代学の手法で年代決定された木材の高精度炭素14年代測定によって求められている。それ以前は、海洋試料の高精度炭素14年代測定結果に海洋のリザーバ効果の補正が行われデータから推定され、不確かさが残されていた。水月湖年縞堆積物の研究で、海洋のリザーバ効果の補正が必要がなくなり、考古学試料などの陸域試料に適用できる炭素14年代キャリブレーションデータセットが、炭素14年代測定法が適用できる全期間について求められた。

著者

TAKAHASHII Tsubasa KITAGAWA Hiroyuki WATANABE Keita

出版者

電子情報通信学会

雑誌

IEICE transactions on information and systems (ISSN:09168532)

巻号頁・発行日

vol.E93.D, no.6, pp.1403-1413, 2010-06

被引用文献数

1 2

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Social bookmarking services have recently made it possible for us to register and share our own bookmarks on the web and are attracting attention. The services let us get structured data: (URL, Username, Timestamp, Tag Set). And these data represent user interest in web pages. The number of bookmarks is a barometer of web page value. Some web pages have many bookmarks, but most of those bookmarks may have been posted far in the past. Therefore, even if a web page has many bookmarks, their value is not guaranteed. If most of the bookmarks are very old, the page may be obsolete. In this paper, by focusing on the timestamp sequence of social bookmarkings on web pages, we model their activation levels representing current values. Further, we improve our previously proposed ranking method for web search by introducing the activation level concept. Finally, through experiments, we show effectiveness of the proposed ranking method.