論文 - 吉廣　卓哉

Single backup table schemes for shortest-path routing

Hiro Ito, Kazuo Iwama, Yasuo Okabe, Takuya Yoshihiro

Theoretical Computer Science   333 ( 3 ) 347 - 353   2005年03月  [査読有り]

　概要を見る

We introduce a new recovery scheme that needs only one extra backup routing table for networks employing shortest-path routing. By precomputing this backup table, the network recovers from any single link failure immediately after the failure occurs. To compute the backup routing table for this scheme, we use an almost linear time algorithm to solve the {r,v}-problem, which is a variation of the best swap problem presented by Nardelli et al. We further show that the same solution can be computed in exactly linear time if the underlying graph is unweighted. © 2004 Elsevier B.V. All rights reserved.

DOI

花園村遠隔看護システムの構築

宮本 浩伸, 岡本 裕宇, 小脇 亮平, 吉廣 卓哉, 堀内 恵美子, 中川 優

情報知識学会誌 ( 情報知識学会 )  14 ( 2 ) 57 - 60   2004年

　概要を見る

We developed a remote aged care system for Hanazono village which is one of the typical underpopulated villages in Japan. In many of such depopulated villages, there is the problem that the number of visiting nurses who provide aged care services is not enough. As a result, visiting nurses can visit aged people not so often (it might be once a week or so), and hence aged people is easy to lose their health. To improve this situation, our system helps visiting nurses get hold of the health condition of aged people by showing the information of their daily health condition which is input everyday by aged people at their own houses. Here, to make a easy input operation even for aged people, we use L-mode terminals at each house and design easy-to-operate Web pages which are accessed by the terminal. We further performed a test operation of our system in Hanazono village and confirmed the effectiveness of our system.

DOI

Avoiding Routing Loops on the Internet

Hiro Ito, Kazuo Iwama, Yasuo Okabe, Takuya Yoshihiro

Theory of Computing Systems   36 ( 6 ) 597 - 609   2003年11月  [査読有り]

　概要を見る

Suppose that some particular link in the Internet is currently congested. A natural solution is to try to make packets bypass that link. This can be done by increasing the cost of that link intentionally, say from a1 to a2, since the Internet uses shortest-path routing. Unfortunately, however, this often causes temporary loops for packet traveling, called routing loops. In this paper we show that routing loops can be avoided by increasing the cost of the link not directly from a1 to a2 but through an intermediate value, a3, i.e., from a1 to a 3 and then to a2. We may need several intermediate values. We show that in this case the greedy strategy, namely, raising the cost as much as possible in each step, is optimal.

DOI

Polynomial-Time Computable Backup Tables for Shortest-Path Routing

ITO H. (担当区分： 筆頭著者,　責任著者 )

Carleton Scientific Proc. SIROCC 2003     163 - 177   2003年

Avoiding Routing Loops on the Internet

Hiro Ito, Kazuo Iwama, Yasuo Okabe, Takuya Yoshihiro (担当区分： 筆頭著者,　責任著者 )

Carleton Scientific Proc. of SIROCCO 2002     197 - 210   2002年

Stateless Autoconfiguration of IPv6 Site-Local Addresses.

Takuya YOSHIHIRO, Masayuki SHIMADA, Yasuo OKABE, Kazuo IWAMA

IASTED Proc. of CCN 2002     299 - 304   2002年

遠隔教育のための柔軟な講義検索手法

片山 薫, 香川 修見, 神谷 泰宏, 對馬 英樹, 吉廣 卓哉, 上林彌彦

情報処理学会論文誌 ( 一般社団法人情報処理学会 )  39 ( 10 ) 2837 - 2845   1998年10月

　概要を見る

遠隔講義システムにおいて，記録された講義の検索をサポートすることは重要である．それによって学生が講義の必要な部分だけを復習したり，教師が過去の講義をより簡単に再利用したりすることができる．講義はマルチメディア教材を作成する過程であると見ることができるが，一般にマルチメディアデータの検索は困難である．画像認識技術や音声認識技術を利用して信頼性の高い索引を生成することはまだ容易ではない．我々はこれらの直接的なアプローチとは異なり，マルチメディアデータが作成される過程（講義）で同期をとって結び付けられる，より検索しやすいデータ〔スライドに含まれるテキスト，ペンやポインタ，キーボードなどの入力装置からのイベント情報（動作履歴と呼ぶ）など〕を利用する．これまでの講義システムでは，講義のビデオを結び付けられたスライド（教材）やノートの単位でしか検索することができなかった．我々のシステムでは，テキストデータに対する文字列検索や動作履歴の検索，ビデオの早送りや巻き戻しなど，これら多様なデータのそれぞれに検索機能を提供しそれを組み合わせることによってより柔軟な検索機能を実現する．また，講義中の雑談部分を検索したり，教材をスライドより詳細なブロック（教材の意味的な単位）の単位で検索できるようにするためのユーザインタフェースも提供する．Support of searching recorded lectures is important in distance education systems because students review parts of lectures they need and teachers reuse their past lectures easily.We view lecturing as a process of making multimedia teaching materials.It is difficult to search multimedia data in general.Although automatic scene analysis and speech recognition are very popular among researchers,it is still not easy to form reliable index.Our approach is different from these ways of searching multimedia data directly.We use information which are connected to continuous media such as video and audio with synchronous constraints during lectures,that is,texts contained in slides,sequences of events of pens and pointers(called Action History) and so on.In conventional systems search of lectures is supported only in a unit of slides or annotations.Our system provides a flexible search mechanism by combining search functions for various recorded information,for example,string for texts,a search function for action histories,fast forward and rewind of video and so on.User interfaces are also provided to enable users to search lectures for idle talk or search them in a unit of blocks which are semantic units of slided.