The Be star content of young open clusters

We present a photometric survey aimed to characterize the Be star population of young open clusters. It is found that in these clusters early-type Be stars are more frequent than in the galactic field, and late-type Be stars are scarce or inexistent. We interpret this result as evidence for an evolutionary enhancement of the Be phenomenon towards the end of the main sequence lifetime.Comment: 6 pages, to be published in ASP Conference Series "Interplay between periodic, cyclic and stochastic variability in selected areas of the H-R diagram", C. Sterken, E

Analysis of prepositions: near and away from Frames of reference.

XXII Jornades de Foment de la Investigació de la Facultat de Ciències Humanes i Socials (Any 2017)Traditional strategies and procedures to learn a foreign language include the study of rules of grammar and doing exercises such as filling the gaps, repetition of words, drills, memorization of irregular verbs and sentences which may express usual expressions of everyday life. Even if the array of exercises is adequate, polysemy in prepositions causes difficulties in choosing the proper preposition conveying the meaning required by different contexts. Two prepositions of the horizontal axis (near and away from) are taken into consideration in this paper. Approaching the problem from the theory of polysemy and understanding, the use of these prepositions is explored along the dimensions of function, topology – which is the study of physical space–, and force dynamics – introduced in studies such as Navarro (1998)–, as well as the notion of frame of reference (Levinson, 2004). Then, the different senses and uses of these prepositions of the horizontal axis are systematized, explained and examples are used to illustrate the difficulties in learning a language and the doubts which students may have in some situations

Application-tailored Linear Algebra Algorithms: A search-based Approach

In this paper, we tackle the problem of automatically generating algorithms for linear algebra operations by taking advantage of problem-specific knowledge. In most situations, users possess much more information about the problem at hand than what current libraries and computing environments accept; evidence shows that if properly exploited, such information leads to uncommon/unexpected speedups. We introduce a knowledge-aware linear algebra compiler that allows users to input matrix equations together with properties about the operands and the problem itself; for instance, they can specify that the equation is part of a sequence, and how successive instances are related to one another. The compiler exploits all this information to guide the generation of algorithms, to limit the size of the search space, and to avoid redundant computations. We applied the compiler to equations arising as part of sensitivity and genome studies; the algorithms produced exhibit, respectively, 100- and 1000-fold speedups

Computing Petaflops over Terabytes of Data: The Case of Genome-Wide Association Studies

In many scientific and engineering applications, one has to solve not one but a sequence of instances of the same problem. Often times, the problems in the sequence are linked in a way that allows intermediate results to be reused. A characteristic example for this class of applications is given by the Genome-Wide Association Studies (GWAS), a widely spread tool in computational biology. GWAS entails the solution of up to trillions ($10^{12}$) of correlated generalized least-squares problems, posing a daunting challenge: the performance of petaflops ($10^{15}$ floating-point operations) over terabytes of data. In this paper, we design an algorithm for performing GWAS on multi-core architectures. This is accomplished in three steps. First, we show how to exploit the relation among successive problems, thus reducing the overall computational complexity. Then, through an analysis of the required data transfers, we identify how to eliminate any overhead due to input/output operations. Finally, we study how to decompose computation into tasks to be distributed among the available cores, to attain high performance and scalability. With our algorithm, a GWAS that currently requires the use of a supercomputer may now be performed in matter of hours on a single multi-core node. The discussion centers around the methodology to develop the algorithm rather than the specific application. We believe the paper contributes valuable guidelines of general applicability for computational scientists on how to develop and optimize numerical algorithms

Computer vision techniques to improve micromobility safety

L'ús de vehicles de micromobilitat, concretament de patinets elèctrics o bicicletes, ha experimentat un auge a les àrees metropolitanes. Aquests vehicles comparteixen el carril amb vianants, cotxes i altres usuaris. La seguretat és imprescindible per a tots ells. Les tècniques de visió per computador com la detecció d'objectes, el seguiment d'objectes i la classificació del tipus de carril poden marcar una gran diferència i prevenir accidents. Aquest projecte proposa una xarxa neuronal multitasca que integra els models d'última generació YOLOv5, YOLOv7 i StrongSORT, entrenada per detectar i fer el seguiment d'objectes de la carretera i classificar el tipus de carril en temps real. L'aparell encarregat d'aquestes prediccions és un telèfon mòbil acoblat al vehicle; per tant, el model es quantifica i es poda per reduir els requisits de càlcul.El uso de vehículos de micromovilidad, concretamente patinetes eléctricos o bicicletas, ha experimentado un auge en las áreas metropolitanas. Estos vehículos comparten el carril con peatones, automóviles y otros usuarios. La seguridad es imprescindible para todos ellos. Las técnicas de visión por computadora, como la detección de objetos, el seguimiento de objetos y la clasificación del tipo de carril, pueden marcar una gran diferencia y evitar accidentes. Este proyecto propone una red neuronal multitarea que integra los modelos de última generación YOLOv5, YOLOv7 y StrongSORT, entrenada para detectar y rastrear objetos en la carretera y clasificar el tipo de carril en tiempo real. El dispositivo encargado de estas predicciones es un teléfono móvil acoplado al vehículo; por lo tanto, el modelo se cuantifica y se poda para reducir los requisitos de cálculo.The use of micromobility vehicles, namely electric scooters or bicycles, has experienced an upsurge in metropolitan areas. These vehicles share the lane with pedestrians, cars, and other users. Safety is a must for all of them. Computer vision techniques such as object detection, object tracking, and lane-type classification can make a huge difference and prevent crashes. This project proposes a multitask neural network integrating the state-of-the-art models YOLOv5, YOLOv7, and StrongSORT, trained to detect and track road objects and classify the lane type in real-time. The device in charge of these predictions is a mobile phone attached to the vehicle; therefore, the model is quantized and pruned to reduce computation requirements

A slitless spectroscopic survey for Halpha emission-line objects in SMC clusters

This paper checks on the roles of metallicity and evolutionary age in the appearance of the so-called Be phenomenon. Slitless CCD spectra were obtained covering the bulk of the Small Magellanic Cloud. For Halpha line emission twice as strong as the ambient continuum, the survey is complete to spectral type B2/B3 on the main sequence. About 8120 spectra of 4437 stars were searched for emission lines in 84 open clusters. 370 emission-line stars were found, among them at least 231 near the main sequence. For 176 of them, photometry could be found in the OGLE database. For comparison with a higher-metallicity environment, the Galactic sample of the photometric Halpha survey by McSwain & Gies (2005) was used. Among early spectral sub-types, Be stars are more frequent by a factor 3-5 in the SMC than in the Galaxy. The distribution with spectral type is similar in both galaxies, i.e. not strongly dependent on metallicity. The fraction of Be stars does not seem to vary with local star density. The Be phenomenon mainly sets in towards the end of the main-sequence evolution (this trend may be more pronounced in the SMC); but some Be stars already form with Be-star characteristics. In all probability, the fractional critical angular rotation rate, \omc, is one of the main parameters governing the occurrence of the Be phenomenon. If the Be character is only acquired during the course of evolution, the key circumstance is the evolution of \omc, which not only is dependent on metallicity but differently so for different mass ranges.Comment: Accepted by A&A, language correction not yet done. Short version of the abstrac

The WFI Halpha spectroscopic survey of the Magellanic Clouds: Be stars in SMC open clusters

At low metallicity, B-type stars show lower loss of mass and, therefore, angular momentum so that it is expected that there are more Be stars in the Magellanic Clouds than in the Milky Way. However, till now, searches for Be stars were only performed in a very small number of open clusters in the Magellanic Clouds. Using the ESO/WFI in its slitless spectroscopic mode, we performed a Halpha survey of the Large and Small Magellanic Cloud. Eight million low-resolution spectra centered on Halpha were obtained. For their automatic analysis, we developed the ALBUM code. Here, we present the observations, the method to exploit the data and first results for 84 open clusters in the SMC. In particular, cross-correlating our catalogs with OGLE positional and photometric data, we classified more than 4000 stars and were able to find the B and Be stars in them. We show the evolution of the rates of Be stars as functions of area density, metallicity, spectral type, and age.Comment: talk at IAUS25

Micro-modeling of stack bond masonry in compression using a plasticity law

A set of experimental tests to determine the compressive strength of masonry stack prisms has been numerically simulated using a combined plasticity-smeared crack constitutive law employed in three-dimensional analysis