El efecto escuela: más allá del aula

La presente investigación tiene como objetivo destacar la importancia de los aspectos ligados a la escuela que están fuera del aula, como lo son las prácticas de los directivos, los recursos con los que cuenta la escuela, su autonomía o la vulnerabilidad de los estudiantes. Mediante un análisis cuantitativo de fuentes secundarias, se ha tomado una muestra de 2882 escuelas básicas vulnerables a lo largo del país, las cuales han postulado a la Subvención Escolar Preferencial (SEP) y han presentado diagnósticos sobre sus aspectos institucionales, y cuyos planes de mejoramiento fueron aprobados a Septiembre del 2009. Además son escuelas que presentan resultados SIMCE en las bases de datos públicas. Se realizó un análisis de regresiones lineales múltiples para tener una mirada comparativa de las variables que influyen en los resultados de aprendizaje. Los resultados muestran que existe una relación importante de las prácticas de los directivos en los resultados de aprendizaje de los alumnos, influencia que es mayor incluso al de las habilidades con que cuentan los docentes. También se muestra que la cantidad de recursos con los que cuenta el establecimiento no tienen una influencia estadísticamente significativa al considerarse junto con las prácticas directivas. Los resultados podrían dar pistas sobre en qué debieran enfocarse los recursos de la Subvención Escolar Preferencial y de otras políticas públicas en Chile u otros países de Latinoaméric

Approximations of the aggregated interference statistics for outage analysis in massive MTC

This paper presents several analytic closed-form approximations of the aggregated interference statistics within the framework of uplink massive machine-type-communications (mMTC), taking into account the random activity of the sensors. Given its discrete nature and the large number of devices involved, a continuous approximation based on the Gram–Charlier series expansion of a truncated Gaussian kernel is proposed. We use this approximation to derive an analytic closed-form expression for the outage probability, corresponding to the event of the signal-to-interference-and-noise ratio being below a detection threshold. This metric is useful since it can be used for evaluating the performance of mMTC systems. We analyze, as an illustrative application of the previous approximation, a scenario with several multi-antenna collector nodes, each equipped with a set of predefined spatial beams. We consider two setups, namely single- and multiple-resource, in reference to the number of resources that are allocated to each beam. A graph-based approach that minimizes the average outage probability, and that is based on the statistics approximation, is used as allocation strategy. Finally, we describe an access protocol where the resource identifiers are broadcast (distributed) through the beams. Numerical simulations prove the accuracy of the approximations and the benefits of the allocation strategy.Peer ReviewedPostprint (published version

Stochastic resource allocation with a backhaul constraint for the uplink

We propose a novel stochastic radio resource alloca- tion strategy for the uplink that achieves long-term fairness in terms of similar bitrates considering backhaul and air-interface capacity limitations. We focus on a single cell scenario based on WCDMA technology. We propose to use a maximin criteria to introduce fairness among the different users’ throughputs. An stochastic approximation is implemented to obtain an online algorithm where the Lagrange multipliers are estimated at each scheduling period. Our results show that the proposed scheme achieves higher fairness among the users and, in some cases, a higher sum-rate compared with the well-known proportional fair scheduler.Postprint (author's final draft

Pricing intraday dynamics across EUAS and CERS markets

The relative contribution of European Union Allowances (EUAs) and Certified Emission Reductions (CERs) to the price discovery of their common true value has been empirically studied using daily data with inconclusive results. In this paper, we study the short-run and long-run price dynamics between EUAs and CERs future contracts using intraday data. We report a bidirectional feedback causality relationship both in the short-run and in the long-run, with the EUA's market being the leader

Closed-form capacity bounds for downlink and uplink decoupling

©2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Downlink (DL) and uplink (UL) decoupling (DUDe) is a new architectural paradigm where DL and UL are not constrained to be associated to the same base station (BS). Thus, a user having access to multiple BSs within a dense cellular network can receive the DL traffic from one BS and send its UL traffic through another. Building upon this architectural paradigm, the present paper provides tight analytical bounds in closed form for the UL ergodic capacity that depend solely on the density of the infrastructure. The devised bounds account for the backbone network congestion and the synchronization of the acknowledgments of the decoupled channels. The proposed bounds are compared against extensive numerical simulations demonstrating the tractability and accuracy of the expressions.Peer ReviewedPostprint (author's final draft

Stochastic Geometry Analysis and Design of Wireless Powered MTC Networks

Machine-type-communications (MTC) are being crucial in the development of next generation mobile networks. Given that MTC devices are usually battery constrained, wireless power transfer (WPT) and energy harvesting (EH) have emerged as feasible options to enlarge the lifetime of the devices, leading to wireless powered networks. In that sense, we consider a setup where groups of sensors are served by a base station (BS), which is responsible for the WPT. Additionally, EH is used to collect energy from the wireless signals transmitted by other sensors. To characterize the energy obtained from both procedures, we model the sporadic activity of sensors as Bernoulli random variables and their positions with repulsive Mat\'ern cluster processes. This way, the random activity and spatial distribution of sensors are introduced in the analysis of the energy statistics. This analysis can be useful for system design aspects such as energy allocation schemes or optimization of idle-active periods, among others. As an example of use of the developed analysis, we include the design of a WPT scheme under a proportional fair policy.Comment: This work has been accepted at the 2020 21st IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC 2020). Copyright held by IEE

A stochastic approach for resource allocation with backhaul and energy harvesting constraints

We propose a novel stochastic radio-resource-allocation strategy that achieves long-term fairness considering backhaul and air-interface capacity limitations. The base station (BS) is powered only with a finite battery that is recharged by an energy harvester. The energy harvesting is also taken into account in the proposed resource-allocation strategy. The constrained scenario is often found in remote rural areas where the backhaul connection is limited, and the BSs are fed with solar panels of reduced size. Our results show that the proposed scheme achieves higher fairness among the users and provides greater worst user rate and sum rate if an average backhaul constraint is considered.Peer ReviewedPostprint (published version

El miedo al crimen en la ciudad de Murcia. ¿Influye el consumo de medios de comunicación en la percepción de inseguridad?

Existen estudios que relacionan el consumo de información en medios de comunicación con el miedo al crimen y el riesgo que percibe la población de convertirse en víctima de un delito. Estas investigaciones demuestran la importancia de estudiar la relación entre el miedo al delito, la percepción subjetiva del riesgo en convertirse en víctima y la influencia que puede tener la exposición a noticias vinculadas con el crimen para paliar el crecimiento del miedo en la población. Hasta la fecha no se han realizado estudios específicos en torno al concepto del miedo al crimen y su relación con el consumo de información en los medios de comunicación en la ciudad de Murcia, motivo que inspiró la investigación en torno a estas variables, pero, ¿realmente influye esta exposición mediática en el miedo al crimen? El objetivo de este trabajo de investigación es el de analizar si realmente influye el consumo de información relacionada con el crimen en la sensación de miedo al crimen y en la percepción subjetiva de convertirse en víctima de un delito; para ello se ha llevado a cabo una investigación en la que han participado 133 personas, 68 mujeres y 65 hombres, todos mayores de edad y residentes en la ciudad de Murcia: Los resultados obtenidos, indican una correlación positiva de r=0,31 en cuanto el miedo al crimen y su exposición mediática y una correlación positiva de r=0,38 en la percepción subjetiva de ser víctima de un delito con respecto a la exposición mediática, además, a ojos de la muestra los delitos con mayor repercusión mediática no son los que ocupan los índices superiores con respecto a la estadística oficial de la Secretaría de Estado de Seguridad. Conclusiones: Los resultados obtenidos concuerdan con las investigaciones anteriores que afirmaban que los delitos con mayor repercusión mediática son aquellos más graves, y que la relación existente entre el consumo de información relacionada con el crimen, la sensación de miedo al delito y a la percepción subjetiva de ser víctima de un delito es moderada. El delito que la muestra percibe como más probable que pueda convertirse en víctima coincide con los datos oficiales de la Secretaría de Estado de Seguridad.There are studies that relate the consumption of information in the media with the fear of crime and the risk that the population perceives of becoming a victim of a crime. These investigations demonstrate the importance of studying the relationship between fear of crime, subjective insecurity and the influence that exposure to crime-related news can have in mitigating the growth of fear in the population. To date, no specific studies have been carried out on the concept of fear of crime and its relationship with the consumption of information in the media in the city of Murcia, the reason that inspired the research on these variables, but, ¿ Does this media exposure really influence the fear of crime? The objective of this research work is to analyze whether the consumption of information related to crime really influences the feeling of fear of crime and the subjective perception of becoming a victim of a crime; For this, an investigation has been carried out in which 133 people have participated, 68 women and 65 men, all of legal age and residents of the city of Murcia. The results obtained indicate a positive correlation of r=0.31 in terms of fear of crime and its media exposure and a positive correlation of r=0.38 in the subjective perception of being a victim of a crime with respect to media exposure. In addition, in the eyes of the sample, the crimes with the greatest media impact are not those that occupy the highest rates with respect to the official statistics of the Secretary of State for Security. Conclusions: The results obtained are consistent with previous research that stated that the crimes with the greatest media impact are the most serious, and that the relationship between the consumption of information related to crime, the feeling of fear of crime and the subjective perception of being victim of a crime is moderate. The crime that the sample perceives as most likely to become a victim coincides with the official data from the Secretary of State for Security

Effect of correlated building blockages on the ergodic capacity of mmWave systems in urban scenarios

The millimeter waves (mmWave) bands, considered to support the forthcoming generation of mobile communications technologies, have a well-known vulnerability to blockages. Recentworks in the literature analyze the blockage probability considering independence or correlation among the blocking elements of the different links. In this letter, we characterize the effect of blockages and their correlation on the ergodic capacity. We carry out the analysis for urban scenarios, where the considered blocking elements are buildings that are primarily parallel to the streets.We also present numerical simulations based on actual building features of the city of Chicago to validate the obtained expressions.This work was supported by Agencia Estatal De Investigación, Ministerio De Ciencia e Innovación, MCIN / AEI / 10.13039/501100011033 through the Project ROUTE56 - PID2019-104945GB-I00.Peer ReviewedPostprint (author's final draft

Relationship between resolution and accuracy of four intraoral scanners in complete-arch impressions

The scanner does not measure the dental surface continually. Instead, it generates a point cloud, and these points are then joined to form the scanned object. This approximation will depend on the number of points generated (resolution), which can lead to low accuracy (trueness and precision) when fewer points are obtained. The purpose of this study is to determine the resolution of four intraoral digital imaging systems and to demonstrate the relationship between accuracy and resolution of the intraoral scanner in impressions of a complete dental arch. A master cast of the complete maxillary arch was prepared with different dental preparations. Using four digital impression systems, the cast was scanned inside of a black methacrylate box, obtaining a total of 40 digital impressions from each scanner. The resolution was obtained by dividing the number of points of each digital impression by the total surface area of the cast. Accuracy was evaluated using a three-dimensional measurement software, using the ?best alignment? method of the casts with a highly faithful reference model obtained from an industrial scanner. Pearson correlation was used for statistical analysis of the data. Of the intraoral scanners, Omnicam is the system with the best resolution, with 79.82 points per mm2, followed by True Definition with 54.68 points per mm2, Trios with 41.21 points per mm2, and iTero with 34.20 points per mm2. However, the study found no relationship between resolution and accuracy of the study digital impression systems (P >0.05), except for Omnicam and its precision. The resolution of the digital impression systems has no relationship with the accuracy they achieve in the impression of a complete dental arch. The study found that the Omnicam scanner is the system that obtains the best resolution, and that as the resolution increases, its precision increases