Florence Levé | Université de Picardie Jules Verne (original) (raw)
Papers by Florence Levé
Musical co-creativity aims at making humans and computers collaborate to compose music. As an MIR... more Musical co-creativity aims at making humans and computers collaborate to compose music. As an MIR team in computational musicology, we experimented with co-creativity when writing our entry to the "AI Song Contest 2020". Artificial intelligence was used to generate the song's structure, harmony, lyrics, and hook melody independently and as a basis for human composition. It was a challenge from both the creative and the technical point of view: in a very short time-frame, the team had to adapt its own simple models, or experiment with existing ones, to a related yet still unfamiliar task, music generation through AI. The song we propose is called "I Keep Counting". We openly detail the process of songwriting, arrangement, and production. This experience raised many questions on the relationship between creativity and machine, both in music analysis and generation, and on the role AI could play to assist a composer in their work. We experimented with AI as automation, mechanizing some parts of the composition, and especially AI as suggestion to foster the composer's creativity, thanks to surprising lyrics, uncommon successions of sections and unexpected chord progressions. Working with this material was thus a stimulus for human creativity.
Bulletin of the European Association for Theoretical Computer Science, 2004
We answer some questions about infinite quasiperiodic words asked by Marcus in Bulletin 82 of the... more We answer some questions about infinite quasiperiodic words asked by Marcus in Bulletin 82 of the European Assocation of Theoretical Computer Science.
Lecture Notes in Computer Science
Starting from any configuration, a snap-stabilizing algorithm guarantees that the system always b... more Starting from any configuration, a snap-stabilizing algorithm guarantees that the system always behaves according to its specification while a self-stabilizing algorithm only guarantees that the system will behave according to its specification in a finite time. So, a snap-stabilizing algorithm is a time optimal self-stabilizing algorithm (because it stabilizes in 0 rounds). That means that even the first attempt of using a snap-stabilizing algorithm by any user (human or algorithm) will produce a correct execution. This is a very desirable property, especially in the case of systems that are prone to transient faults. So the problem of the existence of snap-stabilizing solutions in the message passing model is a very crucial question from a practical point of view.
Weakly and strongly quasiperiodic morphisms are tools introduced to study quasiperiodic words. Fo... more Weakly and strongly quasiperiodic morphisms are tools introduced to study quasiperiodic words. Formally they map respectively at least one or any non-quasiperiodic word to a quasiperiodic word. Considering them both on finite and infinite words, we get four families of morphisms between which we study relations. We provide algorithms to decide whether a morphism is strongly quasiperiodic on finite words or on infinite words.
We characterize all quasiperiodic Sturmian words: a Sturmian word is not quasiperiodic if and onl... more We characterize all quasiperiodic Sturmian words: a Sturmian word is not quasiperiodic if and only if it is a Lyndon word. Moreover, we study links between Sturmian morphisms and quasiperiodicity.
Fugues alternate between instances of the subject and of other patterns, such as the counter-subj... more Fugues alternate between instances of the subject and of other patterns, such as the counter-subject, and modulatory sections called episodes. The episodes play an important role in the overall design of a fugue: detecting them may help the analysis of the fugue, in complement to a subject and a counter-subject detection. We propose an algorithm to retrieve episodes in the fugues of the first book of Bach’s Well-Tempered Clavier, starting from a symbolic score which is already track-separated. The algorithm does not use any information on subject or counter-subject occurrences, but tries to detect partial harmonic sequences, that is similar pitch contour in at least two voices. For this, it uses a substitution function considering “quantized partially overlapping intervals ” [14] and a strict length matching for all notes, except for the first and the last one. On half of the tested fugues, the algorithm has correct or good results, enabling to sketch the design of the fugue. 1.
The factor complexity function C w (n) of a finite or infinite word w counts the number of distin... more The factor complexity function C w (n) of a finite or infinite word w counts the number of distinct factors of w of length n for each n ≥ 0. A finite word w of length |w| is said to be trapezoidal if the graph of its factor complexity C w (n) as a function of n (for 0 ≤ n ≤ |w|) is that of a regular trapezoid (or possibly an isosceles triangle); that is, C w (n) increases by 1 with each n on some interval of length r, then C w (n) is constant on some interval of length s, and finally C w (n) decreases by 1 with each n on an interval of the same length r. Necessarily C w (1) = 2 (since there is one factor of length 0, namely the empty word), so any trapezoidal word is on a binary alphabet. Trapezoidal words were first introduced by de Luca (1999) when studying the behaviour of the factor complexity of finite Sturmian words, i.e., factors of infinite "cutting sequences", obtained by coding the sequence of cuts in an integer lattice over the positive quadrant of R 2 made by a line of irrational slope. Every finite Sturmian word is trapezoidal, but not conversely. However, both families of words (trapezoidal and Sturmian) are special classes of socalled rich words (also known as full words)-a wider family of finite and infinite words characterized by containing the maximal number of palindromes-studied in depth by the first author and others in 2009. In this paper, we introduce a natural generalization of trapezoidal words over an arbitrary finite alphabet A, called generalized trapezoidal words (or GT-words for short). In particular, we study combinatorial and structural properties of this new class of words, and we show that, unlike the binary case, not all GT-words are rich in palindromes when |A| ≥ 3, but we can describe all those that are rich.
Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmi... more Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmian word is non-quasiperiodic if and only if it is an infinite Lyndon word. Here we extend this study to episturmian words (a natural generalization of Sturmian words) by describing all the quasiperiods of an episturmian word, which yields a characterization of quasiperiodic episturmian words in terms of their directive words. Even further, we establish a complete characterization of all episturmian words that are Lyndon words. Our main results show that, unlike the Sturmian case, there is a much wider class of episturmian words that are non-quasiperiodic, besides those that are infinite Lyndon words. Our key tools are morphisms and directive words, in particular normalized directive words, which we introduced in an earlier paper. Also of importance is the use of return words to characterize quasiperiodic episturmian words, since such a method could be useful in other contexts.
Cadences, as breaths in music, are felt by the listener or studied by the theorist by combining h... more Cadences, as breaths in music, are felt by the listener or studied by the theorist by combining harmony, melody, texture and possibly other musical aspects. We formalize and discuss the significance of 44 cadential features, correlated with the occurrence of cadences in scores. These features describe properties at the arrival beat of a cadence and its surroundings, but also at other onsets heuristically identified to pinpoint chords preparing the cadence. The representation of each beat of the score as a vector of cadential features makes it possible to reformulate cadence detection as a classification task. An SVM classifier was run on two corpora from Bach and Haydn totaling 162 perfect authentic cadences and 70 half cadences. In these corpora, the classifier correctly identified more than 75% of perfect authentic cadences and 50% of half cadences, with low false positive rates. The experiment results are consistent with common knowledge that classification is more complex for ha...
Voice and stream segmentation algorithms group notes from polyphonic data into relevant units, pr... more Voice and stream segmentation algorithms group notes from polyphonic data into relevant units, providing a better understanding of a musical score. Voice segmentation algorithms usually extract voices from the beginning to the end of the piece, whereas stream segmentation algorithms identify smaller segments. In both cases, the goal can be to obtain mostly monophonic units, but streams with poly-phonic data are also relevant. These algorithms usually cluster contiguous notes with close pitches. We propose an independent evaluation of four of these algorithms (Tem-perley, Chew and Wu, Ishigaki et al., and Rafailidis et al.) using several evaluation metrics. We benchmark the algorithms on a corpus containing the 48 fugues of Well-Tempered Clavier by J. S. Bach as well as 97 files of popular music containing actual polyphonic information. We discuss how to compare together voice and stream segmen-tation algorithms, and discuss their strengths and weaknesses.
We focus on the rhythmic component of symbolic music similarity, proposing several ways to extrac... more We focus on the rhythmic component of symbolic music similarity, proposing several ways to extract a monophonic rhythmic signature from a symbolic poly- phonic score. To go beyond the simple extraction of all time intervals between onsets (noteson extraction), we select notes according to their length (short and long extractions) or their intensities (intensity+/− extractions). Once the rhythm is extracted, we use dynamic programming to compare several sequences. We report results of analysis on the size of rhythm patterns that are specific to a unique piece, as well as experiments on similarity queries (ragtime music and Bach chorale variations). These results show that long and intensity+ extractions are often good choices for rhythm extraction. Our conclusions are that, even from polyphonic symbolic music, rhythm alone can be enough to identify a piece or to perform pertinent music similarity queries, especially when using wise rhythm extractions.
La forme sonate, bien que ce nom lui ait ete donne a posteriori, etait tres prisee de la periode ... more La forme sonate, bien que ce nom lui ait ete donne a posteriori, etait tres prisee de la periode classique jusqu'a la fin de la periode romantique. Une piece de cette forme est composee de trois parties complementaires, une exposition, un developpement et une reexposition. Nous defendons l'idee que l'etude des formes sonates est un defi interessant pour la musicologie computationnelle. Nous proposons aussi quelques premieres experiences sur l'analyse informatique de ce type de partitions. Sur un corpus de premiers mouvements de quatuor a cordes, nous arrivons a localiser approximativement le couple exposition/reexposition dans la majorite des cas.
Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturm... more Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing a common episturmian word. As a consequence, we characterize episturmian words having a unique directive word.
Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturm... more Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing a common episturmian word. As a consequence, we characterize episturmian words having a unique directive word.
Separating a polyphonic symbolic score into monophonic voices or streams helps to understand the ... more Separating a polyphonic symbolic score into monophonic voices or streams helps to understand the music and may simplify further pattern matching. One of the best ways to compute this separation, as proposed by Chew and Wu in 2005, is to first identify contigs that are portions of the music score with a constant number of voices, then to progressively connect these contigs. This raises two questions: Which contigs should be connected first? And, how should these two contigs be connected? Here we propose to answer simultaneously these two questions by consid- ering a set of musical features that measures the quality of any connection. The coefficients weighting the features are optimized through a genetic algorithm. We benchmark the resulting connection policy on corpora containing fugues of the Well-Tempered Clavier by J. S. Bach as well as on string quartets, and we compare it against previously proposed policies. The contig connection is improved, particularly when one takes into a...
Can a computer understand musical forms? Musical forms describe how a piece of music is structure... more Can a computer understand musical forms? Musical forms describe how a piece of music is structured. They explain how the sections work together through repetition, contrast, and variation: repetition brings unity, and variation brings interest. Learning how to hear, to analyse, to play, or even to write music in various forms is part of music education. In this chapter, we briefly review some theories of musical form, and discuss the challenges of computational analysis of musical form. We discuss two sets of problems, segmentation and form analysis. We present studies in music information retrieval (MIR) related to both problems. Thinking about codification and automatic analysis of musical forms will help the development of better MIR algorithms.
1. A Brief Look at 20 Years of ISMIR Evolution From the International Symposium on Music Informat... more 1. A Brief Look at 20 Years of ISMIR Evolution From the International Symposium on Music Information Retrieval (ISMIR) held in Plymouth, Massachusetts USA, in October 2000 to the International Society for Music Information Retrieval Conference held in Delft, The Netherlands, in November 2019, twenty annual meetings took place that have allowed MIR researchers to meet, present and exchange their ideas leading today to an MIR community and identity for more than 2000 researchers (according to the number of subscriptions to the mailing list). Not only the acronym meaning changed from symposium to conference, but also the size of its yearly conference from less than 100 researchers to more than 500. Due to ISMIR’s single track conference nature the number of accepted papers has been constant at around 100 since 2004 (solid line in Figure 1), but the number of submitted papers is now at a level of about 250 (dashed line in Figure 1). This gives an acceptance rate of about 40% at the mome...
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Musical co-creativity aims at making humans and computers collaborate to compose music. As an MIR... more Musical co-creativity aims at making humans and computers collaborate to compose music. As an MIR team in computational musicology, we experimented with co-creativity when writing our entry to the "AI Song Contest 2020". Artificial intelligence was used to generate the song's structure, harmony, lyrics, and hook melody independently and as a basis for human composition. It was a challenge from both the creative and the technical point of view: in a very short time-frame, the team had to adapt its own simple models, or experiment with existing ones, to a related yet still unfamiliar task, music generation through AI. The song we propose is called "I Keep Counting". We openly detail the process of songwriting, arrangement, and production. This experience raised many questions on the relationship between creativity and machine, both in music analysis and generation, and on the role AI could play to assist a composer in their work. We experimented with AI as automation, mechanizing some parts of the composition, and especially AI as suggestion to foster the composer's creativity, thanks to surprising lyrics, uncommon successions of sections and unexpected chord progressions. Working with this material was thus a stimulus for human creativity.
Bulletin of the European Association for Theoretical Computer Science, 2004
We answer some questions about infinite quasiperiodic words asked by Marcus in Bulletin 82 of the... more We answer some questions about infinite quasiperiodic words asked by Marcus in Bulletin 82 of the European Assocation of Theoretical Computer Science.
Lecture Notes in Computer Science
Starting from any configuration, a snap-stabilizing algorithm guarantees that the system always b... more Starting from any configuration, a snap-stabilizing algorithm guarantees that the system always behaves according to its specification while a self-stabilizing algorithm only guarantees that the system will behave according to its specification in a finite time. So, a snap-stabilizing algorithm is a time optimal self-stabilizing algorithm (because it stabilizes in 0 rounds). That means that even the first attempt of using a snap-stabilizing algorithm by any user (human or algorithm) will produce a correct execution. This is a very desirable property, especially in the case of systems that are prone to transient faults. So the problem of the existence of snap-stabilizing solutions in the message passing model is a very crucial question from a practical point of view.
Weakly and strongly quasiperiodic morphisms are tools introduced to study quasiperiodic words. Fo... more Weakly and strongly quasiperiodic morphisms are tools introduced to study quasiperiodic words. Formally they map respectively at least one or any non-quasiperiodic word to a quasiperiodic word. Considering them both on finite and infinite words, we get four families of morphisms between which we study relations. We provide algorithms to decide whether a morphism is strongly quasiperiodic on finite words or on infinite words.
We characterize all quasiperiodic Sturmian words: a Sturmian word is not quasiperiodic if and onl... more We characterize all quasiperiodic Sturmian words: a Sturmian word is not quasiperiodic if and only if it is a Lyndon word. Moreover, we study links between Sturmian morphisms and quasiperiodicity.
Fugues alternate between instances of the subject and of other patterns, such as the counter-subj... more Fugues alternate between instances of the subject and of other patterns, such as the counter-subject, and modulatory sections called episodes. The episodes play an important role in the overall design of a fugue: detecting them may help the analysis of the fugue, in complement to a subject and a counter-subject detection. We propose an algorithm to retrieve episodes in the fugues of the first book of Bach’s Well-Tempered Clavier, starting from a symbolic score which is already track-separated. The algorithm does not use any information on subject or counter-subject occurrences, but tries to detect partial harmonic sequences, that is similar pitch contour in at least two voices. For this, it uses a substitution function considering “quantized partially overlapping intervals ” [14] and a strict length matching for all notes, except for the first and the last one. On half of the tested fugues, the algorithm has correct or good results, enabling to sketch the design of the fugue. 1.
The factor complexity function C w (n) of a finite or infinite word w counts the number of distin... more The factor complexity function C w (n) of a finite or infinite word w counts the number of distinct factors of w of length n for each n ≥ 0. A finite word w of length |w| is said to be trapezoidal if the graph of its factor complexity C w (n) as a function of n (for 0 ≤ n ≤ |w|) is that of a regular trapezoid (or possibly an isosceles triangle); that is, C w (n) increases by 1 with each n on some interval of length r, then C w (n) is constant on some interval of length s, and finally C w (n) decreases by 1 with each n on an interval of the same length r. Necessarily C w (1) = 2 (since there is one factor of length 0, namely the empty word), so any trapezoidal word is on a binary alphabet. Trapezoidal words were first introduced by de Luca (1999) when studying the behaviour of the factor complexity of finite Sturmian words, i.e., factors of infinite "cutting sequences", obtained by coding the sequence of cuts in an integer lattice over the positive quadrant of R 2 made by a line of irrational slope. Every finite Sturmian word is trapezoidal, but not conversely. However, both families of words (trapezoidal and Sturmian) are special classes of socalled rich words (also known as full words)-a wider family of finite and infinite words characterized by containing the maximal number of palindromes-studied in depth by the first author and others in 2009. In this paper, we introduce a natural generalization of trapezoidal words over an arbitrary finite alphabet A, called generalized trapezoidal words (or GT-words for short). In particular, we study combinatorial and structural properties of this new class of words, and we show that, unlike the binary case, not all GT-words are rich in palindromes when |A| ≥ 3, but we can describe all those that are rich.
Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmi... more Recently the second two authors characterized quasiperiodic Sturmian words, proving that a Sturmian word is non-quasiperiodic if and only if it is an infinite Lyndon word. Here we extend this study to episturmian words (a natural generalization of Sturmian words) by describing all the quasiperiods of an episturmian word, which yields a characterization of quasiperiodic episturmian words in terms of their directive words. Even further, we establish a complete characterization of all episturmian words that are Lyndon words. Our main results show that, unlike the Sturmian case, there is a much wider class of episturmian words that are non-quasiperiodic, besides those that are infinite Lyndon words. Our key tools are morphisms and directive words, in particular normalized directive words, which we introduced in an earlier paper. Also of importance is the use of return words to characterize quasiperiodic episturmian words, since such a method could be useful in other contexts.
Cadences, as breaths in music, are felt by the listener or studied by the theorist by combining h... more Cadences, as breaths in music, are felt by the listener or studied by the theorist by combining harmony, melody, texture and possibly other musical aspects. We formalize and discuss the significance of 44 cadential features, correlated with the occurrence of cadences in scores. These features describe properties at the arrival beat of a cadence and its surroundings, but also at other onsets heuristically identified to pinpoint chords preparing the cadence. The representation of each beat of the score as a vector of cadential features makes it possible to reformulate cadence detection as a classification task. An SVM classifier was run on two corpora from Bach and Haydn totaling 162 perfect authentic cadences and 70 half cadences. In these corpora, the classifier correctly identified more than 75% of perfect authentic cadences and 50% of half cadences, with low false positive rates. The experiment results are consistent with common knowledge that classification is more complex for ha...
Voice and stream segmentation algorithms group notes from polyphonic data into relevant units, pr... more Voice and stream segmentation algorithms group notes from polyphonic data into relevant units, providing a better understanding of a musical score. Voice segmentation algorithms usually extract voices from the beginning to the end of the piece, whereas stream segmentation algorithms identify smaller segments. In both cases, the goal can be to obtain mostly monophonic units, but streams with poly-phonic data are also relevant. These algorithms usually cluster contiguous notes with close pitches. We propose an independent evaluation of four of these algorithms (Tem-perley, Chew and Wu, Ishigaki et al., and Rafailidis et al.) using several evaluation metrics. We benchmark the algorithms on a corpus containing the 48 fugues of Well-Tempered Clavier by J. S. Bach as well as 97 files of popular music containing actual polyphonic information. We discuss how to compare together voice and stream segmen-tation algorithms, and discuss their strengths and weaknesses.
We focus on the rhythmic component of symbolic music similarity, proposing several ways to extrac... more We focus on the rhythmic component of symbolic music similarity, proposing several ways to extract a monophonic rhythmic signature from a symbolic poly- phonic score. To go beyond the simple extraction of all time intervals between onsets (noteson extraction), we select notes according to their length (short and long extractions) or their intensities (intensity+/− extractions). Once the rhythm is extracted, we use dynamic programming to compare several sequences. We report results of analysis on the size of rhythm patterns that are specific to a unique piece, as well as experiments on similarity queries (ragtime music and Bach chorale variations). These results show that long and intensity+ extractions are often good choices for rhythm extraction. Our conclusions are that, even from polyphonic symbolic music, rhythm alone can be enough to identify a piece or to perform pertinent music similarity queries, especially when using wise rhythm extractions.
La forme sonate, bien que ce nom lui ait ete donne a posteriori, etait tres prisee de la periode ... more La forme sonate, bien que ce nom lui ait ete donne a posteriori, etait tres prisee de la periode classique jusqu'a la fin de la periode romantique. Une piece de cette forme est composee de trois parties complementaires, une exposition, un developpement et une reexposition. Nous defendons l'idee que l'etude des formes sonates est un defi interessant pour la musicologie computationnelle. Nous proposons aussi quelques premieres experiences sur l'analyse informatique de ce type de partitions. Sur un corpus de premiers mouvements de quatuor a cordes, nous arrivons a localiser approximativement le couple exposition/reexposition dans la majorite des cas.
Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturm... more Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing a common episturmian word. As a consequence, we characterize episturmian words having a unique directive word.
Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturm... more Episturmian morphisms constitute a powerful tool to study episturmian words. Indeed, any episturmian word can be infinitely decomposed over the set of pure episturmian morphisms. Thus, an episturmian word can be defined by one of its morphic decompositions or, equivalently, by a certain directive word. Here we characterize pairs of words directing a common episturmian word. As a consequence, we characterize episturmian words having a unique directive word.
Separating a polyphonic symbolic score into monophonic voices or streams helps to understand the ... more Separating a polyphonic symbolic score into monophonic voices or streams helps to understand the music and may simplify further pattern matching. One of the best ways to compute this separation, as proposed by Chew and Wu in 2005, is to first identify contigs that are portions of the music score with a constant number of voices, then to progressively connect these contigs. This raises two questions: Which contigs should be connected first? And, how should these two contigs be connected? Here we propose to answer simultaneously these two questions by consid- ering a set of musical features that measures the quality of any connection. The coefficients weighting the features are optimized through a genetic algorithm. We benchmark the resulting connection policy on corpora containing fugues of the Well-Tempered Clavier by J. S. Bach as well as on string quartets, and we compare it against previously proposed policies. The contig connection is improved, particularly when one takes into a...
Can a computer understand musical forms? Musical forms describe how a piece of music is structure... more Can a computer understand musical forms? Musical forms describe how a piece of music is structured. They explain how the sections work together through repetition, contrast, and variation: repetition brings unity, and variation brings interest. Learning how to hear, to analyse, to play, or even to write music in various forms is part of music education. In this chapter, we briefly review some theories of musical form, and discuss the challenges of computational analysis of musical form. We discuss two sets of problems, segmentation and form analysis. We present studies in music information retrieval (MIR) related to both problems. Thinking about codification and automatic analysis of musical forms will help the development of better MIR algorithms.
1. A Brief Look at 20 Years of ISMIR Evolution From the International Symposium on Music Informat... more 1. A Brief Look at 20 Years of ISMIR Evolution From the International Symposium on Music Information Retrieval (ISMIR) held in Plymouth, Massachusetts USA, in October 2000 to the International Society for Music Information Retrieval Conference held in Delft, The Netherlands, in November 2019, twenty annual meetings took place that have allowed MIR researchers to meet, present and exchange their ideas leading today to an MIR community and identity for more than 2000 researchers (according to the number of subscriptions to the mailing list). Not only the acronym meaning changed from symposium to conference, but also the size of its yearly conference from less than 100 researchers to more than 500. Due to ISMIR’s single track conference nature the number of accepted papers has been constant at around 100 since 2004 (solid line in Figure 1), but the number of submitted papers is now at a level of about 250 (dashed line in Figure 1). This gives an acceptance rate of about 40% at the mome...
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.