Benjamin Gras

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It is shown that the shortest-grammar problem remains NP-complete if the alphabet is fixed and has a size of at least 24 (which settles an open question). On the other hand, this problem can be solved in polynomial-time, if the number of nonterminals is bounded, which is shown by encoding the problem as a problem on graphs with interval structure.(More)
The collaborative filtering (CF) approach in recommender systems assumes that users' preferences are consistent among users. Although accurate, this approach fails on some users. We presume that some of these users belong to a small community of users who have unusual preferences, such users are not compliant with the CF underlying assumption. They are(More)
An interband cascade laser (ICL) operating at 3.7 μm has been used to perform multimode absorption spectroscopy, MUMAS, at scan rates up to 10 kHz. Line widths of individual modes in the range 10-80 MHz were derived from isolated lines in the MUMAS signatures of HCl. MUMAS data for methane covering a spectral range of 30 nm yielded a detection level of 30(More)
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