## Section: Other Grants and Activities

### Bilateral actions

#### PAI STAR South Corea collaboration

Participants : Laurent Busé, André Galligo, Gang Xu, Evelyne Hubert, Angelos Mantzaflaris, Bernard Mourrain.

The objective of this collaboration is to conduct research in algebraic techniques for solving geometric modeling problems. More specially, we are interested in developing efficient and robust methods to solve non-linear constraints which appear in geometric computation. These methods will be used in applications such as shape design and reconstruction, for solving interpolation or approximation problems. A typical area in which we will apply our methods is ship design. Experimentation and validation will lead to open source software implementation.

Collaborators from Seoul National University: Park Sung Ha, Tae-Wan Kim, Sharma Rajiv, Hur Seok.

A. Galligo and B. Mourrain visited Seoul National University (July 27 - Aug. 2).

#### ECOS-Sud collaboration

Participants : Jérôme Brachat, Laurent Busé, Mohamed Elkadi, André Galligo, Bernard Mourrain.

The first objective of this collaboration with the team of A. Dickenstein at the University of Buenos Aires, Argentina is the development of effective methods for geometric modeling, with a special focus on singularity and numerical stability problems. This includes intersection problems for curves or surfaces, change of representations such as implicitization via syzygies and moving planes, polytopes analysis and Puiseux expansions. A second objective is the development of open tools dedicated to such problems which could be shared by the different groups working on this topic.

This year we had the visit of N. Botbol (Ph.D. student), May 15 - June 14, A. Dickenstein (Professor), June 1-15. J. Brachat (Ph.D. student), gave a visit to Buenos Aires, November 23 – December 17.