Abstract Northern Baja California (NBC) is characterized by two subregions: Peninsular Ranges of Baja California (PRBC) and Mexicali Valley (MV). In NBC, there are cities whose population could benefit from the operation of an Early Earthquake Warning System (EEWS). To implement an EEWS in NBC, which allows issuing notifications to warn people about the arrival of seismic waves generated by relevant earthquakes in NBC, we evaluated the capacity of response of the CICESE Seismological Network (CSN). The seismic signals from stations of this network are sent to the processing center, located at CICESE, using different transmission media. Commercial and cellular Internet modem transmissions with low latency times (< 2 s) stand out. We evaluated the performance of the CSN using the SeisComP3 acquisition and detection system in combination with the Virtual Seismologist (VS) method. This evaluation began in April 2017 and resulted in more than 5,000 earthquakes (2.0 ≤ M ≤ 5.0) recorded and processed with SeisComP3/VS. Based on the current geographical coverage of the network and the area of occurrence of a relevant earthquake, the EEWS could notify the population up to 20 seconds in advance. There is good coverage for earthquakes occurring in the VM, and notifications can be sent to cities such as Ensenada and Tijuana but not to Mexicali. For PRBC earthquakes, it is impossible to issue a prior notice to any of the towns mentioned due to insufficient station coverage. However, we consider the implementation of an EEWS for NBC feasible if the geographical coverage of the CSN stations is improved and transmission schemes with low latency times are used.

Resumen El norte de Baja California (NBC) está caracterizado por dos subregiones las Sierras Peninsulares de Baja California (SPBC) y el Valle de Mexicali (VM). En el NBC existen ciudades en las que su población pudiera beneficiarse del funcionamiento de un Sistema de Alerta Sísmica Temprana (SAST). Con el propósito de implementar un SAST, que permita emitir notificaciones previas al arribo de las ondas sísmicas generadas por la ocurrencia de algún sismo relevante en el NBC, evaluamos la capacidad de respuesta de la Red Sismológica del CICESE (RSC). Las señales sísmicas de las estaciones de esta red se envían al centro de procesamiento ubicado en el CICESE usando distintos medios de transmisión. De éstos, destacan las transmisiones por módem de Internet por módem telefónico y celular con tiempos de latencia bajos (< 2 s). La evaluación de la RSC la hicimos vía el sistema de adquisición y detección SeisComP3 y el método Virtual Seismologist (VS). Esta evaluación inició en abril de 2017 y dio como resultado un catálogo de más de 5,000 sismos (1.0 ≤ M ≤ 5.7) registrados y procesados con SeisComP3/VS. Con la cobertura geográfica actual de la red y dependiendo de la zona de ocurrencia del sismo, puede notificarse a la población con una anticipación de hasta 20 segundos (M ≈ 4). Para sismos ocurridos en el VM, existe una buena cobertura y pueden enviarse notificaciones a ciudades como Ensenada y Tijuana; no así para la ciudad de Mexicali. Para sismos de las SPBC, el envío de notificación dependerá de la ubicación del evento ya que la cobertura en las SPBC no es la requerida y además los enlaces de transmisión, presentan una alta latencia. No obstante, consideramos factible la implementación de un SAST para el NBC, si se mejora la cobertura geográfica de las estaciones de la RSC y se usan esquemas de transmisión con tiempos de latencia bajos.

Resumen (analítico) Este artículo sistematiza una propuesta metodológica denominada emojilogía, la cual se enfoca en el desarrollo de procesos de investigación-acción participativa con y desde el estudiantado. En primer lugar, se aborda la «caja de herramientas» teórico-epistemológica que permite repensar al colectivo estudiantil como agentes sociales válidos para generar procesos de transformación escolar. Luego, se profundiza sobre el procedimiento que involucra la propuesta, dando cuenta de la preparación grupal para iniciar el trabajo, la co-construcción de consignas de exploración, la producción de narrativas desde el uso de emojis y la consolidación de espacios de diálogo con el resto de la comunidad educativa. Se concluyen los beneficios y limitaciones de la metodología, vinculados al rol del conflicto como un medio para suscitar transformaciones, pero también como barrera por la generación de resistencias institucionales.

Abstract (analytical) This article systematizes a methodological proposal called Emojiology, which focuses on the development of participatory action research processes with and from students. The proposal begins with a theoretical-epistemological «toolbox» that reconsiders students as valid social agents who can trigger school transformation processes. The details of the proposal are then discussed in an indepth manner, highlighting the preparatory actions required to start working with the group, the co-construction of slogans to guide the research, the production of narratives through the use of emojis and the consolidation of spaces for dialogue with the rest of the educational community. The authors conclude the article by highlighting the benefits and limitations of the methodology in relation to the role of conflict to trigger transformations, but also as a barrier that can generate institutional resistance.

Resumo (analítico) Este artigo sistematiza uma proposta metodológica chamada Emojilogia, que se centra no desenvolvimento de processos de investigação de acção participativa com e a partir do corpo estudantil. Em primeiro lugar, é abordada a «caixa de ferramentas» teórico-epistemológica que nos permite repensar o colectivo estudantil como agentes sociais válidos para desencadear processos de transformação escolar. Depois, aprofundamos o procedimento envolvido na proposta, dando conta da preparação do grupo para iniciar o trabalho, da co-construção de slogans de exploração, da produção de narrativas a partir do uso de emojis e da consolidação de espaços de diálogo com o resto da comunidade educativa. Concluímos os benefícios e limitações da metodologia ligada ao papel do conflito como meio de desencadear transformações, mas também como uma barreira para gerar resistência institucional.

This work analyzes the effect of Cu additions on the microstructure of quaternary alloys Al-6Si-7Mg-xCu (x= 3, 5 and 7 wt.%) produced by conventional metallurgy. Microstructural modifications were studied using Optical Microscopy (OM), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM), focusing on second phases identification and quantification. Conventional image analyses were developed measuring the total percentage of second phases, and individually for each phase determining its equivalent diameter, shape factor, roundness and aspect ratio; while fractal analyses were carried out complementarily through fractal dimension measurements for the whole microstructure and for individual phases. Compression tests were also carried out. SEM and XRD results revealed that second phases were eutectic Si, Mg2Si, Al2Cu and Al5Cu2Mg8Si6 (Q). The increase in Cu content led to higher quantities of these phases, mainly Al2Cu, which was barely present for the alloy with the lowest Cu content. Morphologies of second phases depended on Cu content, being present as eutectic, block like, finely dispersed or primary particles. The combination of conventional and fractal parameters provided a useful tool for comparatively analyze microstructural modifications and second phases features. It was also found that the compressive behavior of the alloys depended on the resulting microstructures.

An approach following the null-matrix, Ti/Zr ratio of 2.08, for neutron diffraction was used to calculate the glass formation in Cu-Ti-(Hf,Zr) alloys. The Cu55Zr14.6Ti30.4, Cu61.48Hf18.52Zr6.48Ti13.52, Cu58.1Hf16.9Zr8.1Ti16.9 and Cu52.46Hf14.2Zr10.8Ti22.54 compositions (at. %), were calculated and prepared by argon arc melting. Copper die suction casting was employed to produce conical shaped samples with diameters decreasing from 8 mm to 1 mm. X-ray diffraction and Neutron Diffraction were used to characterize the alloys with the aim of obtaining the critical glassy diameter, dc, of the alloys. The results showed the composition with the biggest dc was the Cu61.48Hf18.52Zr6.48Ti13.52 alloy, with dc = 6 mm. Thermal parameters were obtained by differential scanning calorimetry and the maximum values for glass transition temperature, Tg, (747 K), crystallization temperature, Tx, (772 K), solidus temperature, Tm, (1152 K) and liquidus temperature, Tl, (1230 K) corresponded to the Cu61.48Hf18.52Zr6.48Ti13.52 composition. The results also showed that the parameters obtained from thermal analysis did not correlate with the GFA obtained. However, a good correlation of GFA and dc was found by means of the topological model, where the highest % packing efficiency (53.57 %) was found for the Cu61.48Hf18.52Zr6.48Ti13.52 alloy, which also showed the highest dc value with 6 mm.

This paper presents an experience of counseling in a group of schools from the Metropolitan Region of Chile for the design and implementation of an inclusive development plan, based on the proposal of the Index for Inclusion. This plan sought to identify and address barriers to inclusion, detected by the collective with the support of an external consultant called critical friend. The article points out in the understanding of this role, as an important piece of a collaborative counseling strategy. This study use a case study design with qualitative analysis, in order to identify the several positions and strategies deployed by these advisors, based on the identification of two central axes: control/autonomy and reflexive/instrumental focuses. The results problematize about the conditions, implications and challenges for collaborative counseling work, from an inclusive approach in the context of municipal education in Chile.

Este trabajo recoge una experiencia de asesoramiento realizada a un conjunto de escuelas de la Región Metropolitana de Chile, para el diseño e implementación de un plan de desarrollo inclusivo, a partir de la propuesta de la Guía para la Inclusión Educativa. Dicho plan buscó identificar y abordar barreras a la inclusión, detectadas por el colectivo y con el apoyo de un asesor externo denominado amigo crítico. El artículo puntualiza en la comprensión de este rol, como pieza importante de una estrategia de asesoramiento colaborativo. Por medio de un estudio de casos y un análisis cualitativo, se caracterizan los diversos posicionamientos y estrategias desplegadas por estos asesores, a partir de la identificación de dos ejes centrales: el del control/autonomía y según los focos reflexivo/instrumental. Los resultados permiten problematizar respecto de las condiciones, implicancias y desafíos para el trabajo de asesoramiento colaborativo, desde un enfoque inclusivo, en el contexto de la educación municipal.

The present work shows the fractal analysis for the microstructure of Al-6Si-3Cu-xMg (x = 0.59, 3.80 and 6.78 wt.%) alloys, solution heat treated at 480 °C for times ranging from 4 to 72 h. Microstructural changes were examined using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM), and quantified by measuring conventional characteristics of second phases. The fractal analysis of the microstructures was also carried out using fractal dimension (Df). Results shown important variations in the microstructure when Mg content is increased, being the eutectic Al-Si and Cu-rich phases the predominant phases for the alloys with low Mg content, while for higher Mg contents predominant phases were Mg2Si and Cu-rich phases. The analysis of Df showed that this parameter could be used in order to compare the microstructural solution response of the Al alloys. Besides, it was possible to correlate the fractal dimension with the shape factor of the second phases, mainly for the alloys with only one second phase remaining after heat treatment.

Abstract: In this study, Al-Ni alloy ribbons in hypoeutectic, euctectic and hypereutectic compositions were obtained by melt spinning. The microstructural changes of the samples, from the as-cast to rapid solidification processes at different Cu wheel tangential velocities were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The rapid solidification caused morphological transformation of the Al-Al3Ni microstructure from acicular in the as-cast condition to globular in the melt spun ribbons and the growth of the metastable Al9Ni2 intermetallic compound, which acted as reinforcing particles. Due to the increment of the Ni content and the presence of these intermetallic compounds, with size of ~5nm, distributed in the aluminum matrix, the hardness of the alloys significantly increased from the hypoeutectic (90 VHN) to the hypereutectic (205VHN) composition.

Resumen: En este estudio, cintas de la aleación Al-Ni en las composiciones hipoeutéctica, eutéctica e hipereutéctica fueron obtenidas por la técnica de "melt spinning". Los cambios microestructurales, desde la colada hasta las cintas solidificadas rápidamente a distintas velocidades de solidificación, fueron caracterizados por difracción de Rayos X, microscopía electrónica de barrido y microscopia electrónica de transmisión. La solidificación rápida causó una transformación morfológica de la microestructura Al-Al3Ni acicular en la muestras de colada a una morfología globular en la cintas solidificadas rápidamente y el crecimiento del compuesto intermetálico metaestable Al9Ni2, el cual actuó como partícula reforzadora. Debido al incremento del contenido de Ni y la presencia de estos compuestos intermetálicos, con tamaño de ~5nm, distribuidos en la matriz de aluminio, la dureza de la aleaciones aumentó significativamente de la composición hipoeutéctica (90VHN) a la hipereutéctica (205VHN).

Abstract: This paper presents the soft magnetic properties of the Fe-, Ni-, Coand Fe-Co-Ni polymer composites. The composites were obtained with Fe, Ni and Co powders (99.9% purity) with particle sizes of 150, 10 and 2 mm, respectively. Ring-shaped samples were obtained using uniaxial compaction at 91 MPa. The Fe-Co-Ni-polymer composite has the highest value of the magnetic permeability (μ=54) at 107 Hz and saturation magnetization (Ms=10000 Am2Kg-1) higher than the Ni-polymer composite (4100 Am2Kg-1).

Resumen: Este documento presenta las propiedades magnéticas suaves de los compositos Fe-polímero, Ni-polímero, Co-polímero y Fe-Ni-Co-polímero. Los compositos fueron obtenidos con polvos de Fe, Ni y Co (pureza 99.9%) con tamaños de partícula de 150, 10 and 2 mm, respectivamente. Muestras con forma anillada fueron obtenidas usando compactación uniaxial a 91 MPa. El composito Fe-Ni-Co-polímero tiene valores altos de permeabilidad magnética (μ=54) a 107 Hz y magnetización de saturación (Ms=16000 Am2Kg-1) mayor que el composito Ni-polímero (4100 Am2Kg-1).

This work presents a review of computational models that use the Finite Elements Method (FEM) for the study of composite materials mechanical behavior, focusing the analysis in materials reinforced by particles or fibers. Bibliographic analysis shows that using FEM it is possible to successfully estimate the effect on the composites mechanical properties, of parameters such as the reinforcement type, volumetric fraction, orientation, aspect ratio and size. This review showed that the most studied property is Young´s modulus, as well as the models that favor the geometry decrease using the computational advantages. Future work that needs attention is addressed.

En este trabajo se presenta una revisión bibliográfica de modelos computacionales que utilizan el Método de los Elementos Finitos (MEF) para el estudio del comportamiento mecánico de los materiales compuestos, enfocándose el análisis en materiales reforzados por partículas o fibras. El análisis realizado muestra que el MEF permite estimar, de manera efectiva, la influencia sobre las propiedades mecánicas de los materiales compuestos, de factores como el reforzante, su fracción volumétrica, orientación, relación de aspecto y tamaño. Esta revisión mostró que la propiedad más estudiada es el módulo de Young, así como los modelos que favorecen la disminución de la geometría utilizando las ventajas computacionales. Se destaca el trabajo futuro que requiere atención.

The solidification behavior of the Al-12.6% Si (A1), the hypereutectic Al-20%Si (A2) and the Al-20%Si-1.5% Fe-0.5%Mn (A3) (in wt. (%)) alloys, at different cooling rates is reported and discussed. The cooling rates ranged between 0.93 °C/s and 190 °C/s when cast in sand and copper wedge-shaped molds, respectively. A spheroidization heat treatment was carried out to the alloys in the as-cast condition at 540 °C for 11 hours and quench in water with a subsequent heat treatment at 170 °C for 5 hours with the purpose of improving the mechanical properties. The samples were characterized by optical microscopy, scanning electron microscopy and mechanically by tensile test, in order to evaluate the response of the heat treatment on the different starting microstructures and mechanical properties. It was found that alloys cooled at rates greater than 10.8 °C/s had a smaller particle size and better distribution, also showed a greater response to spheroidization heat treatment of all silicon (Si) phases. The spheroidization heat treatment caused an increase in the ultimate tensile stress (UTS) and elongation when compared with the alloys in the as-cast condition. The highest UTS value of 174 MPa was obtained for the (A1) alloy.