Modifying the Symbolic Aggregate Approximation Method to Capture Segment Trend Information

The Symbolic Aggregate approXimation (SAX) is a very popular symbolic dimensionality reduction technique of time series data, as it has several advantages over other dimensionality reduction techniques. One of its major advantages is its efficiency, as it uses precomputed distances. The other main advantage is that in SAX the distance measure defined on the reduced space lower bounds the distance measure defined on the original space. This enables SAX to return exact results in query-by-content tasks. Yet SAX has an inherent drawback, which is its inability to capture segment trend information. Several researchers have attempted to enhance SAX by proposing modifications to include trend information. However, this comes at the expense of giving up on one or more of the advantages of SAX. In this paper we investigate three modifications of SAX to add trend capturing ability to it. These modifications retain the same features of SAX in terms of simplicity, efficiency, as well as the exact results it returns. They are simple procedures based on a different segmentation of the time series than that used in classic-SAX. We test the performance of these three modifications on 45 time series datasets of different sizes, dimensions, and nature, on a classification task and we compare it to that of classic-SAX. The results we obtained show that one of these modifications manages to outperform classic-SAX and that another one slightly gives better results than classic-SAX.Comment: International Conference on Modeling Decisions for Artificial Intelligence - MDAI 2020: Modeling Decisions for Artificial Intelligence pp 230-23

Microstructure and magnetocaloric effect of melt-spun Ni52Mn26Ga22 ribbon

"Microstructural features and magnetocaloric properties of Ni52Mn26Ga22 melt-spun ribbons were studied. Results show that there are four types of differently oriented variants of seven-layered modulated (7M) martensite at room temperature, being twin-related one another and clustered in colonies. Due to the coupled magnetic and structural transformations between parent austenite and 7M martensite, the melt-spun ribbons exhibit a significant magnetocaloric effect. At an applied magnetic field of 5 T, an absolute maximum value of the isothermal magnetic entropy change of 11.4 J kg(-1) K-1 is achieved with negligible hysteresis losses.

Routine Modeling with Time Series Metric Learning

version éditeur : https://rd.springer.com/chapter/10.1007/978-3-030-30484-3_47International audienceTraditionally, the automatic recognition of human activities is performed with supervised learning algorithms on limited sets of specific activities. This work proposes to recognize recurrent activity patterns, called routines, instead of precisely defined activities. The modeling of routines is defined as a metric learning problem, and an architecture, called SS2S, based on sequence-to-sequence models is proposed to learn a distance between time series. This approach only relies on inertial data and is thus non intrusive and preserves privacy. Experimental results show that a clustering algorithm provided with the learned distance is able to recover daily routines

Vocal fold vibratory patterns in tense versus lax phonation contrasts

This study explores the vocal fold contact patterns of one type of phonation contrast--the tense vs lax phonation contrasts of three Yi (Loloish) languages. These contrasts are interesting because neither phonation category is very different from modal voice, and because both phonations are largely independent of the languages' tonal contrasts. Electroglottographic (EGG) recordings were made in the field, and traditional EGG measures were derived. These showed many small but significant differences between the phonations, with tense phonation having greater contact quotients and briefer but slower changes in contact. Functional data analysis was then applied to entire EGG pulse shapes. The resulting first principal component was found to be mostly strongly related to the phonation contrasts, and correlated with almost all the traditional EGG measures. Unlike the traditional measures, however, this component also seems to capture differences in abruptness of contact. Furthermore, previously collected perceptual responses from native speakers of one of the languages correlated better with this component than with any other EGG measure or any acoustic measure. The differences between these tense and lax phonations are not large, but apparently they are consistent enough, and perceptually robust enough, to support this linguistic contrast

Determination of the odd part of the texture function

By calculating the series expansion of the orientation distribution function (O.D.F.) from experimental pole-figures, previously only the even part (l even) could be considered, since the pole-figures are necessarily centro-symmetric. When the condition of non-negativity of the O.D.F. is taken into account, particularly in the null-domains in which the O.D.F. is zero, it is also possible to determine the odd part of the development by means of an approximation method. From individual orientation measurements, it is also possible to determine the even and odd parts of the O.D.F.Lors du calcul du développement en série de la fonction de distribution des orientations (F.D.O.) à partir de figures de pôles expérimentales, seule la partie paire (rangs l pair) a pu être considérée à ce jour, puisque les figures de pôles sont nécessairement centro-symétriques. Si l'on tient compte de la condition de non-négativité de la F.D.O., et ce plus particulièrement dans les domaines nuls dans lesquels la F.D.O. prend la valeur zéro, il est également possible de déterminer la partie impaire du développement par une méthode d'approximation. A partir de mesures d'orientations individuelles, il est également possible de déterminer les parties paires et impaires de la F.D.O

Description of the texture by distribution functions on the space of orthogonal transformations. Implications on the inversion centre

In the most general case the orientation distribution function (texture) is a function on the space of orthogonal transformations which splits into a couple of functions on the space of rotations. In the case of non-enantiomorphic crystal symmetry groups only one of these functions is independent. Sample symmetry (especially centrosymmetry) can be achieved in a trivial and a non-trivial way. The first one leads to relations between individual functional values the latter one to integral relations.Dans le cas le plus général, la fonction de distribution des orientations (texture) est une fonction sur l'espace des transformations orthogonales, qui se scinde en un couple de fonctions sur l'espace des rotations. Dans le cas de groupes de symétrie cristalline non énantiomorphes, une seule de ces fonctions est indépendante. La symétrie d'échantillon (notamment la centro-symétrie) peut être réalisée d'une façon triviale et d'une façon non-triviale. La première conduit à des relations entre des valeurs individuelles de fonction, la seconde à des relations intégrales

An inversion formula expressing the texture function in terms of angular distribution functions

The determination of the orientation distribution function of crystallites in a polycrystalline material from experimental pole figures leads to an integral equation which is usually solved by a series expansion method. Recently S. Matthies [4] has proposed, without proof, an inversion formula which is not based on series expansion. Such a direct formula is being deduced by efficient group theoretical methods. The solution can further be expressed in terms of the angular distribution function Why(cos θ) which had been introduced earlier [3]. Both methods are being compared with regard to the obtainable experimental data and the required computational efforts.La détermination de la fonction de distribution des orientations de cristallites dans un matériau polycristallin à partir de figures de pôles expérimentales conduit à une équation intégrale qui est généralement résolue par une méthode de développement en série. Récemment S. Matthies [4] a proposé, sans démonstration, une formule d'inversion qui n'est pas basée sur un développement en série. Une telle formule directe est déduite par des méthodes efficaces de théorie des groupes. La solution peut être ultérieurement exprimée au moyen de la fonction de distribution angulaire Why(cos θ) qui avait été introduite précédemment [3]. Les deux méthodes sont comparées pour ce qui conceme les données expérimentales accessibles et l'effort de calcul numérique requis

Texture analysis of silicon with an heterogeneous morphology used for the photovoltaic conversion by neutron diffraction

Polycrystalline silicon ingots, obtained by rapid solidification according to Bridgman method without seed crystal, are studied. The texture in the bulk, determined using the transmission neutron diffraction, is characterized from the direct pole figures plotted for the four families of the low indices lattice planes (400), (220), (111) and (113). An accurate exploring mode has been defined for this heterogeneous material. The use of smoothing computer programs on the pole densities is necessary to calculate the Orientation Distribution Function (O.D.F.) by spherical harmonics analysis.L'étude a porté sur un matériau polycristallin massif obtenu par refroidissement rapide dans un gradient thermique selon le procédé de Bridgman sans germe. La texture en volume, étudiée par diffraction neutronique en transmission, est caractérisée à partir des figures de pôles directes relatives aux quatre families de plans cristallographiques : (400 ), (220 ), (111 ) et (113 ). Un mode d'exploration précis a été défini pour ce matériau hétérogène. Le calcul de la Fonction de Distribution des Orientations Cristallines ne peut se faire qu'après utilisation d'une technique de lissage des densités de pôles