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第7回

日 時 : 1月28日(水) 13:30〜15:00

講演者 : Michael Zock 氏 (Limsi-CNRS, Orsay/France)

場 所 : W 1008 号室

題 目 : 『Electronic Dictionaries for Men, Machines or for Both?』

要旨:

Dictionaries are a vital component of any natural language processing system (natural or artificial). In their modern form, the electronic dictionary, they have a tremendous potential, provided that they are built in a way that allows for use not only by experts or machines, but also by ordinary language users. Unfortunately, despite the enormous interest in electronic dictionaries in general and thesaurus-like semantic networks (Wordnet) in particular, little attention has been paid to the language USER. And yet, a lexical database is worthless if the data is not (easily) accessible.

There are many possibilites to make a dictionary useful for people in their daily tasks of processing or learning a language. In many cases it would require relatively little effort to make a lexical knowledge base accessible to the language user. For example, a dictionary fully interfaced with a wordprocessor would allow for active reading. In such an environment, clicking on a word would reveal its translation, its definition, its usage (in the current context), the idioms it controls, grammatical information, its spoken form, etc. For the language producer it would be definitely useful to have a tool assisting him in finding or in generating the needed inflected form. Words should be accessible on the basis of meaning, (i.e. lexically or conceptually related words), linguistic form (sound, spelling) and perhaps even the surrounding context.

It is true that there are tools for some of these types of operations, yet, typically, existing electronic tools allow only one or a few of these options. It would be nice to have a single tool that allows many different kinds of operations, using the same dictionary. The question of integrating the different kinds of lexical search should be the focus for psycholinguistic as well as cognitive ergonomic research.

The goal of this talk is to explore ways of enhancing electronic dictionaries by adding specific functionality (i.e. cross lingual/intra lingual lexical search) and to discuss the problems that have to be solved in order to build them. For example, if electronic dictionaries were built like mental dictionaries (associative networks, akin to Wordnet, but with many more relations), they could assist people in finding new ideas (brainstorming) or the word on the tip of their tongue/pen. Within this framework, word access amounts to entering the network at a node and to following the links from the source node (the first word that comes to your mind) to the target word (the one you are looking for).

Interesting questions that arise in this practical scenario are: What are the links or associations between words? Can we reasonably encode (all or some of) them into a dictionary? Where to look for in order to get a list of associations (Mel'cuk's work)? Should we allow for adding private information (personal associations)? Is it possible to extract this kind of information automatically by parsing an encyclopedia or large amounts of text?

In sum, it seems that builders of electronic dictionaries are sitting on a gold mine that they still largely ignore how to explore andexploit. Yet, there is good reason to believe that there is a market for products integrating more advanced ways of accessing lexical information.

第6回

日 時 : 1月7日(水) 13:30〜15:00

講演者 : 光来 健一 氏 (東京工業大学)

場 所 : W 1008 号室

題 目 : パーソナルネットワーク:情報の流れを制御可能なVPN

要旨:

近年、仮想プライベートネットワーク(VPN)が企業間のみならず、個人レベルでも使われるようになってきており、その結果、ユーザが複数のVPNを同時に扱う状況が増えている。しかしながら、従来のVPNではネットワークの使い分けはユーザに任されており、VPN間での機密情報の流れをシステムが制御することは難しかった。本発表ではVPNについて解説した後、情報の流れを制御できるようにVPNを拡張したパーソナルネットワークについて述べる。さらに、その応用についても述べる。

第5回

日 時 : 11月12日(水) 13:30〜15:00

講演者 : 武田 朗子 氏 (東京工業大学)

場 所 : W 1008 号室

題 目 : 『条件付き線形不等式系の全解列挙に対する並列計算アルゴリズム』

要旨:

1995年にPolyhedral Homotopy法が提案されて以来,多項式方程式系の全根列挙問題に関する研究は飛躍的に進歩した.

Polyhedral Homotopy法は従来のHomotopy法に比べて計算量が少なく済むという素晴らしい性質を持つ反面,Homotopy法に必要な"初期補助方程式系"を形成するために「条件付き線形不等式系の全解列挙」という新たな問題が生じる.現在,多項式方程式系の全根列挙に必要な計算時間の約3分の1が,この組合せ問題を解くことに費されており,この部分の高速化が望まれている.

本発表では,条件付き線形不等式系の全解列挙問題に対して,線形計画問題の解法であるシンプレックス法,および,双対理論を使ったアルゴリズムを提案する.また,本アルゴリズムに対して効率の良い並列計算処理が可能であり,その結果,今まで解けなかった規模の問題まで扱えるようになった.

第4回

日 時 : 10月8日(水) 13:30〜15:00

講演者 : Dening Li 氏 (West Virginia University)

場 所 : W 1008 号室

題目: Conical Shock Waves in Supersonic Flow

要旨:

Shock wave formation is one of the most fascinating phenomena in gas-dynamics and has been the focus of many research efforts. Indeed,``shock wave" appears in many other fields when the main event travels faster than its signal.

The governing equations of gas-dynamics is Euler system of conservation laws. Shock wave are described as the solution of Euler system which is piece-wise smooth with jump discontinuity along the shock front.

Various simplifications are introduced to study shock waves under different situations. They include dimension reduction, linearization, and thermo-dynamical simplification of isentropic or polytropic gas.

The rigorous mathematical analysis of stability and existence of shock wave have been developed for multi-dimensional case only since 1980s. Oblique or conical shock waves are generated when a projectile with sharp head flying supersonically in the air. They are genuine multi-dimensional phenomena.

The progress in the last few years in the study of conical shock waves will be introduced, both for a simplified isentropic irrotational model and for Euler system. In particular, the sufficient and necessary condition for the linear stability of such shock waves for non-symmetrical projectile and non-uniform incoming supersonic flow are obtained and their physical meaning analyzed. The existence of such shock waves are established for several different non-symmetrical conical cases.

第3回

日 時 : 7月24日(木) 13:30〜15:00

講演者 : 脇田 建 氏 (東京工業大学)

場 所 : W 1008 号室

題目: スパムーーーメイルにまつわる迷惑な話

要旨:

三ヶ月間に届いたメイルのうち、職務に関連するものが5,000通、迷惑メイルが4,500 通。面倒を感じながらも、なんとか許容する毎日。

「みんな困っているんです」

事務官のそのひとことで、迷惑メイルとの戦いが始まりました。

迷惑メイルに対処するには、メイルをユーザの嗜好に合わせて、受信したメイルから迷惑メイルを効率かつ簡易な方法で分別することが大切です。談話会で紹介するアルゴリズムは、ユーザに届いた通常メイルと迷惑メイルのサンプルを解析し、その中の語彙の出現頻度から通常メイルと迷惑メイルを特長づけ、それによりそれ以後の受信メイルを仕分けます。

談話会では、文書を仕分けるアルゴリズム、過去10日間の試用から得られる(であろう)成果、専攻にインストールしたソフトウェアの設定と利用の方法などについてお話しします。

わたし自身が専門家ではないので、どなたさまにも易しい話になります。

第2回

日 時 : 7月23日(水) 13:30〜15:00

講演者 : Guenther Walther 氏 (Stanford Univ.)

場 所 : W 1008 号室

題目: Oscillation Analysis for the Mixture Complexity

要旨:

The problem under consideration is to determine the number of components in a location mixture, in the case where one does not want to make parametric assumptions on the component distribution. It turns out that whenever mode- or bumphunting works, it is as well possible to do a much more sensitive analysis that can resolve mixtures that are unimodal (say). Further, a simple criterion can be derived for this analysis. Moreover, this more sensitive analysis comes without penalty in simpler situations: Even if one knew a priori that the mixture were multimodal and hence detectable by mode-hunting, the refined analysis will detect it essentially as well as any mode-hunting procedure possibly could. I will explain this heuristically and also give a precise theoretical result.

第1回

日 時 : 5月28日(水) 13:30〜15:00

講演者 : Reha Husnu Tutuncu 氏 (Carnegie Mellon Univ.)

場 所 : W 1008 号室

題 目 : Returns-Based Estimation of Sector Allocations in Mutual Funds

要 約 :

Mutual fund managers have a tactical interest in knowing the structure of their peers' equity portfolios--especially the allocation of funds in different sectors. The data available on sector allocations of mutual funds is often old or expensive. We formulate this problem as an inverse problem and apply Sharpe's return-based style analysis approach as well as a few of its variants to estimate sector weights of mutual funds in a timely, accurate fashion using daily returns data. Our models result in convex quadratic programming problems that are efficiently solved using interior-point methods.