Layer Selection in Progressive Transmission of Motion-Compensated JPEG2000 Video

MCJ2K (Motion-Compensated JPEG2000) is a video codec based on MCTF (Motion- Compensated Temporal Filtering) and J2K (JPEG2000). MCTF analyzes a sequence of images, generating a collection of temporal sub-bands, which are compressed with J2K. The R/D (Rate-Distortion) performance in MCJ2K is better than the MJ2K (Motion JPEG2000) extension, especially if there is a high level of temporal redundancy. MCJ2K codestreams can be served by standard JPIP (J2K Interactive Protocol) servers, thanks to the use of only J2K standard file formats. In bandwidth-constrained scenarios, an important issue in MCJ2K is determining the amount of data of each temporal sub-band that must be transmitted to maximize the quality of the reconstructions at the client side. To solve this problem, we have proposed two rate-allocation algorithms which provide reconstructions that are progressive in quality. The first, OSLA (Optimized Sub-band Layers Allocation), determines the best progression of quality layers, but is computationally expensive. The second, ESLA (Estimated-Slope sub-band Layers Allocation), is sub-optimal in most cases, but much faster and more convenient for real-time streaming scenarios. An experimental comparison shows that even when a straightforward motion compensation scheme is used, the R/D performance of MCJ2K competitive is compared not only to MJ2K, but also with respect to other standard scalable video codecs

Perspectives towards oral corrective feedback of students from a ba in foreign language teaching

Esta investigación cualitativa se realizó en una universidad privada del oriente antioqueño. El objetivo de este estudio fue describir las percepciones de los estudiantes de tercer semestre de la Licenciatura en Lengua Extranjera de un curso de inglés en 2021 sobre la retroalimentación correctiva oral (OCF) proporcionada por el profesor de inglés sobre su producción oral (OP) en el salón de clases de ingles como lengua extranjera. Los datos se obtuvieron mediante un cuestionario que se aplicó de forma remota a los participantes. Fueron once estudiantes los que participaron totalmente en esta investigación. Los hallazgos mostraron que para los estudiantes el hecho de ser corregidos oralmente no fue un problema y además manifestaron que les gusta. Además, consideraron al OCF como parte fundamental de su proceso de aprendizaje de idiomas. Además, los participantes señalaron que prefieren ser corregidos de inmediato en lugar de retrasar la OCF cuando cometen un error. También recomendamos al final de esta investigación, considerar las perspectivas de los estudiantes debido a su papel principal en el proceso de aprendizaje.This qualitative research was carried out at a private university in Eastern Antioquia. The objective of this study was to describe the perceptions of third-semester students from a BA in Foreign Language from an English course in 2021 about the oral corrective feedback (OCF) provided by the English teacher about their oral production (OP) in the EFL classroom. The data was obtained through a questionnaire that was applied remotely to the participants. They were eleven students who participated totally in this research. The findings showed that for students the fact of being orally corrected was not a problem and also manifested that they like it. In addition, they considered the OCF as a fundamental part of their language learning process. Moreover, the participants pointed out that they prefer to be corrected immediately instead of delayed OCF when they make a mistake. We also recommended at the end of this research, to consider students' perspectives due to their main role in the learning process

Autonomus Motivation as a Mediator Between an Empowering Climate and Enjoyment in MAle Volleyball Players

The objective of this work was to analyze a mediation model concerning the perception ofan empowering climate generated by a coach and enjoyment through the autonomous motivation ofathletes. The sample consisted of 71 elite male volleyball players from six countries. The age rangewas 14 to 18 years (M=16.5, SD=0.96). The relationships between the perception of an empoweringclimate, autonomous motivation, and enjoyment were positive and significant. The mediation modelshowed that autonomous motivation acts as a mediator in the relationship between the perception ofan empowering climate generated by the coach and the enjoyment reported by the athletes

Paving the way to collaborative context-aware mobile applications: a case study on preventing worsening of allergy symptoms

En los últimos años, la evolución de los teléfonos inteligentes y sus aplicaciones de software ha crecido exponencialmente; junto con el avance del Internet de las Cosas y las ciudades inteligentes, ha generado una gran demanda de servicios y aplicaciones en estos dominios. Aunque la amplia gama de aplicaciones móviles es incuestionable, los ciudadanos ya exigen que las aplicaciones se adapten a sus necesidades y situaciones específicas en tiempo real, es decir, que sean conscientes del contexto. Sin embargo, las aplicaciones móviles conscientes del contexto a menudo son muy limitadas y pierden la oportunidad de beneficiarse de la retroalimentación proporcionada por la colaboración ciudadana. Para llenar este vacío, este documento propone una arquitectura de software y una aplicación móvil colaborativas y conscientes del contexto. En particular, los hemos implementado en el ámbito de la e-salud, más específicamente en el área de las alergias estacionales, que causan que las personas alérgicas experimenten síntomas molestos que podrían evitarse si tuvieran acceso a información sobre el polen en tiempo real. Además, también se beneficiarán de la colaboración ciudadana a través del conocimiento de los síntomas que otras personas alérgicas con la misma alergia y en la misma ubicación están experimentando. Para ello, los usuarios podrán proporcionar sus síntomas en cualquier momento a través de su aplicación móvil y la arquitectura propuesta procesará constantemente esa información en tiempo real, enviando notificaciones a los usuarios tan pronto como se vea que los síntomas reportados superan un cierto umbral. Se han probado el rendimiento de la arquitectura, el consumo de recursos de la aplicación y una encuesta de satisfacción sobre la usabilidad y utilidad de la aplicación; todos los resultados han sido completamente satisfactorios.In recent years, the evolution of smartphones and their software applications has grown exponentially; together with the advance of the Internet of Things and smart cities, it has raised huge demand for services and applications in these domains. Although the wide range of mobile applications is unquestionable, citizens already demand that applications adapt to their specific needs and situations in real time, that is, that they are context-aware. However, context-aware mobile applications are often very limited and miss out on the opportunity of benefiting from feedback provided by citizen collaboration. In order to fill this gap, this paper proposes a context-aware and collaborative software architecture and mobile application. In particular, we have implemented them in the scope of e-health, more specifically in the area of seasonal allergies, which cause allergic people to experience annoying symptoms that could be avoided by having access to pollen information in real time. Furthermore, they will also benefit from citizen collaboration through the knowledge of the symptoms other allergic people with the same allergy and in the same location are experiencing. To this end, users will be able to provide their symptoms at any time through their mobile application and the proposed architecture will constantly process that information in real time, sending notifications to users as soon as reported symptoms are seen to exceed a certain threshold. The architecture’s perfor mance, the application’s resource consumption and a satisfaction survey of the app’s usability and usefulness have been tested; all results have been fully satisfactoryThis work was supported by the Spanish Ministry of Science and Innovation and the European Union FEDER Funds [grant numbers RTI2018-093608-B-C33, RED2018-102654-T

Melting of crystals of polarization vortices and chiral phase transitions in oxide superlattices

We study the equilibrium arrangements of polarization vortices in (PbTiO3 )n/(SrTiO3 )n superlattices by means of second-principles simulations. We find that, at low temperatures, polarization vortices organize in a regular arrangement in which clockwise and counterclockwise vortices alternate positions, leading to a crystal-like structure with well-defined handedness. This chiral crystal melts at a critical temperature TM into a chiral liquid where long-range order is lost but handedness is preserved. At even higher temperatures TC, a second pase transition occurs at which the chiral liquid of polarization vortices loses its handedness. Both phase transitions can be readily identified by the adequate choices of order parameters.F.G.-O., P.G.-F., and J.J. acknowledge financial support from Grant No. PGC2018-096955-B-C41 funded by MCIN/AEI/10.13039/501100011033 and by ERDF “A way of making Europe,” by the European Union. J.M.L. was funded by Grant No. FIS2016-74957-P MCIN/AEI/10.13039/501100011033/ and ERDF “A way of making Europe” by the European Union. F.G.-O. acknowledges financial support from Grant No. FPU18/04661 funded by MCIN/AEI/10.13039/501100011033. We thankfully acknowledge computing time at Altamira supercomputer and the technical support provided by the Instituto de Física de Cantabria (IFCA) and Universidad de Cantabria (UC). We also thank J. Á. Herrero for his valuable assistance with the supercomputing environment HPC/HTC cluster Calderon, supported by datacenter 3Mares from Universidad de Cantabri

Berezinskii-Kosterlitz-Thouless phases in ultrathin PbTiO3/SrTiO3 superlattices

We study the emergence of Berezinskii-Kosterlitz-Thouless (BKT) phases in (PbTiO3 )3/(SrTiO3 )3 superlattices by means of second-principles simulations. Between a tensile epitaxial strain of _ = 0.25?1%, the local dipole moments within the superlattices are confined to the film-plane, and thus the polarization can be effectively considered as two-dimensional. The analysis of the decay of the dipole-dipole correlation with the distance, together with the study of the density of defects and its distribution as a function of temperature, supports the existence of a BKT phase in a range of temperature mediating the ordered ferroelectric (stable at low T ), and the disordered paraelectric phase that appears beyond a critical temperature TBKT. This BKT phase is characterized by quasi-long-range order (whose signature is a power-law decay of the correlations with the distance), and the emergence of tightly bound vortex-antivortex pairs whose density is determined by a thermal activation process. The proposed PbTiO3/SrTiO3 superlattice model and the imposed mechanical boundary conditions are both experimentally feasible, making it susceptible for an experimental observation of these new topological phases in ferroelectric materials.F.G.-O., P.G.-F., and J.J. acknowledge financial support from Grant No. PGC2018-096955-B-C41 funded by MCIN/AEI/10.13039/501100011033 and by ERDF “A way of making Europe” by the European Union. F.G.-O. acknowledges financial support from Grant No. FPU18/04661 funded by MCIN/AEI/10.13039/501100011033

Kittel law and domain formation mechanism in PbTiO₃/SrTiO₃ superlattices

We report second-principles simulations on the structural and energetic properties of domains in (PbTiO₃)n/(SrTiO₃)n superlattices. For the explored layer thickness (n ranging between 8 and 16 unit cells) and lateral sizes of the domains, the most stable configuration corresponds to polar domains separated by a sequence of counter-rotating vortices (clockwise/counterclockwise) perpendicular to the stacking direction and acting as domain walls. The balance between the domain wall energy and the electrostatic energy yields to an optimal domain period ω that is proportional to the square root of the thickness of the PbTiO₃ layer, following the Kittel law. For a given lateral size of the simulation box, suboptimal domain structures (with a width larger than the one predicted by the Kittel law) can be obtained in a metastable form. However, at finite temperature, molecular dynamics simulations show the spontaneous change of periodicity, which implies the formation of new domains whose generation is initiated by the nucleation of vortices and antivortices at the interface between the SrTiO₃ and the PbTiO₃ layers. The vortices progressively elongate and eventually annihilate with the antivortices yielding the formation of new domains to comply with the Kittel law via defect recombination.F.G.-O., P.G.-F., and J.J. acknowledge financial support from Grant No. PGC2018-096955-B-C41 funded by MCIN/AEI/10.13039/501100011033 and by ERDF "A way of making Europe" by the European Union. F.G.-O. acknowledges financial support from Grant No. FPU18/04661 funded by MCIN/AEI/ 10.13039/501100011033. J.M.L. was supported by Grant No. PID2021-125543NB-I00 funded by MCIN/AEI/10.13039/501100011033/ and by ERDF "A way of making Europe" by the European Union. H.A. and J.I. were funded by the Luxembourg National Research Fund through Grant No. C21/MS/15799044/FERRODYNAMICS

3GPP QoS-based scheduling framework for LTE

This paper proposes the design of a scheduling framework for the downlink of the Long Term Evolution (LTE) system with the objective of meeting the Quality of Service (QoS) requirements as defined by the QoS architecture of the 3G Partnership Project (3GPP) specifications. We carry out a thorough review of 3GPP specifications analyzing the requirements of the 3GPP QoS architecture. LTE bearers may be associated with a Guaranteed Bit Rate (i.e., GBR bearers) or not (i.e., non-GBR bearers). Additionally, the specifications establish a Packet Delay Budget (PDB) to limit the maximum packet transfer delay. To achieve our goal, we design a channel-aware service discipline for GBR bearers which is able to fulfill not only the GBR but also the PDB. Additionally, we also design an algorithm for prioritizing GBR and non-GBR bearers from different QoS Class Identifiers (QCIs) following 3GPP QoS rules. We compare the proposed framework with two reference schedulers by means of network-level simulations. The results will show the ability of the proposed framework to address the QoS requirements from 3GPP specifications while providing an interesting performance from a spectral efficiency viewpoint.This work is partially supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (project TIN2013-46223-P)