Covering functors without groups

Coverings in the representation theory of algebras were introduced for the Auslander-Reiten quiver of a representation finite algebra by Riedtmann and later for finite dimensional algebras by Bongartz and Gabriel, R. Martinez-Villa and de la Pe\~na. The best understood class covering functors is that of Galois covering functors F: A -> B determined by the action of a group of automorphisms of A. In this work we introduce the balanced covering functors which include the Galois class and for which classical Galois covering-type results still hold. For instance, if F:A -> B is a balanced covering functor, where A and B are linear categories over an algebraically closed field, and B is tame, then A is tame.Comment: Some improvements have been made; in particular, the proof of Theorem 2 has been restructured and clarifie

Cubist Algebras

We construct algebras from rhombohedral tilings of Euclidean space obtained as projections of certain cubical complexes. We show that these `Cubist algebras' satisfy strong homological properties, such as Koszulity and quasi-heredity, reflecting the combinatorics of the tilings. We construct derived equivalences between Cubist algebras associated to local mutations in tilings. We recover as a special case the Rhombal algebras of Michael Peach and make a precise connection to weight 2 blocks of symmetric groups

Reading competition and the use of new technologies of information and communication

El siguiente artículo investigativo presenta los resultados derivados del estudio “Incidencia del uso de las Tecnologías de la Información y la Comunicación, en el desarrollo de la competencia lectora en estudiantes de 3° grado de Básica Primaria”. Se plantea la situación actual del acceso a las TIC y la calidad educativa en Colombia, específicamente la relativa al departamento del Atlántico, y a las diversas problemáticas del municipio de Malambo, señalando aquellas asociadas a la educación. El análisis desarrollado fue trabajado desde las teorías del interaccionismo simbólico de Herbert Blumer y George Mead y la Teoría del Constructivismo de Lev Vygotsky. Se desarrolló bajo la metodología del paradigma empírico analítico, es una investigación de corte cuantitativo, alcance explicativo, con un diseño cuasi-experimental. Se realizó con un grupo de trabajo y medidas pretest-postest. El análisis de los resultados permite evidenciar que la exposición a las TIC fortalece los procesos asociados con la Competencia Lectora y se resalta la necesidad de implementar las TIC en el evento pedagógico, con el fin de implementar herramientas que le permitan al estudiante mejorar sus competencias lectoras y hacer frente a las exigencias de la contemporaneidad.Abstract: The following article presents the results derived from the study “Incidence of the usage of information technology in the development of reading competency among third graders in primary school”. The current access to ICT and the education quality in Colombia is posed, specifically the one related education in the department of the Atlantic and the diverse problematic in the municipal of Malabo, pointing out those associated to education. The developed analysis was worked from Herbert Blumer and George Mead´s Symbolic Interactionism Theory and Lev Vygotsy constructivism Theory. It was developed under the method of Empirical Analytical Paradigm; it’s a quantitative research, with an explanatory scope and a quasi-experimental design. It was performed with a workgroup and pretest- postest measures. The analysis of the results show that the exposure to ICT strengths the processes associated with the reading competences and highlights the need to implement the ICT in the pedagogical event, with the means to implement tools that allow the students to improve their reading competencies and cope with the demands of the contemporary times

Transport and Combustion of Firebrands. Final Report of Grants FG-SP-114 and FG-SP-146 Vol. II

A theoretical and experimental study has been carried out on the combustion properties and flight paths of firebrands when they are carried upwards by convective currents and then forwards by the winds. The study has shown that the flight paths of firebrands can be fall decreases continuously as the firebrand burns. Several types of wind tunnels have been developed especially designed to study combustion of firebrands at their final velocity of fall. The study has also show that combustion of firebrands at constant wind speed. The influence of the initial size and initial shape of the firebrands, kind of wood and initial moisture content has been studied, as well as the influence of several types convection columns configurations. Results of these studies enable the calculation of the maximum range of possible fire spread by firebrands of given initial characteristics, once the convective currents above the fire are known as vell as the horizontal wind conditions

Optical Impact of Corneal Clearance in Healthy Eyes Fitted with Scleral Contact Lenses: A Pilot Study

This pilot study was conducted to evaluate the effect on refraction and optical quality of the increase in the corneal clearance after fitting a specific model of scleral contact lens (ScCL) in healthy subjects. A total of 15 eyes from 15 subjects were enrolled in the study, with evaluation of refraction, ocular aberrations and central corneal clearance with the same model of ScCL (ICD Toric, Paragon Vision Science, Gilbert, AZ, USA), but using 3 different sagittal heights: 4200, 4500 and 4800 µm. Mean values of corneal clearance for each ScCL fitted were 418.1 ± 112.1, 706.5 ± 120.3 and 989.9 ± 117.0 µm, respectively. Significant changes were detected in the spherical equivalent and high-order aberrations, especially coma and spherical aberration, when fitting ScCLs of increasing sagittal heights compared to the pre-fitting values. In conclusion, the increase in central corneal clearance when fitting ScCLs affects refraction, leading to a more myopic refractive error, and inducing an increase in different ocular HOAs. This should be considered when fitting ScCLs, especially multifocal designs.The author David P Piñero has been supported by the Ministry of Economy, Industry and Competitiveness of Spain within the program Ramón y Cajal, RYC-2016-20471

Cements based on kaolinite waste

The cement industry involves high-energy consumption that generates high CO2 emissions into the atmosphere. Environmental concerns can be addressed by replacing parts of Portland cement clinkers with pozzolanic materials in mortars and concrete. Slag, fly ash and silica fume are materials considered for the planned replacement. Research studies on clay minerals, such as kaolinite, are being followed with special attention by the scientific community and the cement industry. It is well known that these minerals require an activation process to transform kaolinite (K) into metakaolinite (MK). MK is an amorphous material from the transformation of K with high pozzolanic activity, which is its capacity to react with the portlandite released during the hydration of Portland cement, generating compounds such as C–S–H gels and some aluminum-phase hydrates. One of the MK production methods is heat treatment controlled by kaolinite at temperatures in the range of 600–900°C. Different residues have been used (coal mining, paper sludge and waste from a drinking water treatment plant) activated at 600°C for 2h to elaborate blended cements. Due to their good behaviour as future eco-efficient additions, this research is a study by x-ray fluorescence (XRF), x-ray diffraction (XRD) and scanning electron microscopy (SEM) of their influence on the performances of blended cement mixtures (binary and ternary one), with substitutions of pozzolan ratio at 28 days of hydration. The porosity of pozzolanic cements decreases because of the formation of hydrated phases during pozzolanic reaction.the Spanish Ministry of the Economy and Competitiveness under coordinated projects BIA2015-65558C3-1-2-3R (MINECO/FEDER

Control de área amplia en sistemas de potencia considerando criterios de robustez para diferentes escenarios de generación

Este trabajo de grado se basa en el uso de medidas provenientes de unidades sincrofasoriales. Las medidas tomadas de estas unidades son usadas como señales de entrada para un sistema se control basado en realimentación de la salida. Los estados son medidas de frecuencia angular, angulo del par del rotor , y potencia mecánica de la turbina pm. La solución que se encuentra por medio del algoritmo de cúmulo de partículas permite mejorar la estabilidad del sistema. Al desplazar la parte real de los valores propios hacia la parte negativa, el tiempo de establecimiento de la señal es menor; la señal se hace estable cuando sigue una referencia. El análisis de estabilidad de pequeña señal se realizó para cuatro sistemas de prueba y para el caso de demanda máxima. Para el caso mencionado se obtuvo la mejora de los valores propios de los sistemas de prueba y la solución de la ecuación diferencial