Tres algoritmos para la construcción de figuras imposibles

Las Figuras Imposibles (FI) hacen parte del lenguaje visual. Este documento describe tres formas para construir FI hechas de secciones de prismas de base cuadrada (barras) que se unen formando ángulos rectos. Las FI generadas con las barras son divididas en tres grupos: FI con barras que no están cruzadas, FI con barras cruzadas y FI con un punto de vista simultáneo. Presentamos las características base de las FI desde la matemática haciendo uso de la teoría de grafos, la proyección isométrica y las teselaciones, además incluimos algunos links que permiten al lector interesado, descargar un software gratuito llamado “Imposible Puzzle 1.10” para explorar la realización de FI

Peer edition as a means for fostering EFL short story writing in a local private school an action research.

Este estudio de investigación-acción llevado a cabo con estudiantes de inglés de grado noveno en un colegio privado mixto ubicado en la ciudad de Bogotá, Colombia tuvo como objetivo entender el rol de la edición por pares En la construcción de historias cortas como tareas escritas en inglés. La importancia de esta propuesta radica en el fomentar que los estudiantes tomen control de sus procesos de alfabetización en inglés como lengua extranjera a través de la edición de sus propios productos escritos a través de la edición por pares. Los instrumentos de recolección de datos que se utilizaron para este propósito fueron artefactos, grabaciones de audio, notas de campo y un cuestionario de pregunta abierta. Los datos fueron recogidos durante diez clases del segundo semestre del año escolar a través de una intervención pedagógica siguiendo el modelo institucional del colegio: inducción, aprendizaje individual, aprendizaje grupal y evaluación. Los hallazgos revelaron que, a pesar de no haber mostrado un progreso sustancial en sus procesos de escritura en inglés, los participantes desarrollaron sus propias estrategias para llevar a cabo la práctica de edición por pares. En estas prácticas, también se evidenció una co-construcción de conocimiento en la cual los participantes se sintieron cómodos en clases que no fueron centradas en el profesor. Por lo tanto, la cooperación y la construcción de conocimiento entre los participantes revelaron relaciones de poder de experticia.Magister en Enseñanza de Lenguas ExtranjerasMaestríaThis action research study conducted with EFL ninth grade students at a coeducational private school located in the city of Bogotá, Colombia, aimed to understand the role of peer edition within EFL short story writing tasks construction. The importance of this proposal radiates in the encouragement on students to take control of their EFL literacy processes by editing their own written products through peer edition. The data collection instruments used for this purpose were artifacts, audio recordings, field notes and an open-ended questionnaire. The data was collected during 10 sessions along the second semester of the school year, through a pedagogical intervention following the school´s instructional model: induction, individual learning, group learning and evaluation. The findings exposed that, despite not showing a substantial progress in their EFL writing processes, the participants developed strategies to carry out the Peer Edition practices. In these practices, they also evidenced a co-construction of knowledge where they felt comfortable in a classroom which was not teacher-centered. Hence, cooperation and building of knowledge among partners revealed expert power relations

Capturing coevolutionary signals in repeat proteins

The analysis of correlations of amino acid occurrences in globular proteins has led to the development of statistical tools that can identify native contacts -- portions of the chains that come to close distance in folded structural ensembles. Here we introduce a statistical coupling analysis for repeat proteins -- natural systems for which the identification of domains remains challenging. We show that the inherent translational symmetry of repeat protein sequences introduces a strong bias in the pair correlations at precisely the length scale of the repeat-unit. Equalizing for this bias reveals true co-evolutionary signals from which local native-contacts can be identified. Importantly, parameter values obtained for all other interactions are not significantly affected by the equalization. We quantify the robustness of the procedure and assign confidence levels to the interactions, identifying the minimum number of sequences needed to extract evolutionary information in several repeat protein families. The overall procedure can be used to reconstruct the interactions at long distances, identifying the characteristics of the strongest couplings in each family, and can be applied to any system that appears translationally symmetric

Multifield-based modeling of material failure in high performance reinforced cementitious composites

Cementitious materials such as mortar or concrete are brittle and have an inherent weakness in resisting tensile stresses. The addition of discontinuous fibers to such matrices leads to a dramatic improvement in their toughness and remedies their deficiencies. It is generally agreed that the fibers contribute primarily to the post-cracking response of the composite by bridging the cracks and providing resistance to crack opening. On the other hand, the multifield theory is a mathematical tool able to describe materials which contain a complex substructure. This substructure is endowed with its own properties and it interacts with the macrostructure and influences drastically its behavior. Under this mathematical framework, materials such as cement composites can be seen as a continuum with a microstructure. Therefore, the whole continuum damage mechanics theory, incorporating a new microstructure, is still applicable. A formulation, initially based on the theory of continua with microstructure Capriz, has been developed to model the mechanical behavior of the high perfor-mance fiber cement composites with arbitrarily oriented fibers. This formulation approaches a continuum with microstructure, in which the microstructure takes into account the fiber-matrix interface bond/slip processes, which have been recognized for several authors as the principal mechanism increasing the ductility of the quasi-brittle cement response. In fact, the interfaces between the fiber and the matrix become a limiting factor in improving mechanical properties such as the tensile strength. Particularly, in short fiber composites is desired to have a strong interface to transfer effectively load from the matrix to the fiber. However, a strong interface will make difficult to relieve fiber stress concentration in front of the approaching crack. According to Naaman, in order to develop a better mechanical bond between the fiber and the matrix, the fiber should be modified along its length by roughening its surface or by inducing mechanical defor-mations. Thus, the premise of the model is to take into account this process considering a micro field that represents the slipping fiber-cement displacement. The conjugate generalized stress to the gradient of this micro-field verifies a balance equation and has a physical meaning. This contribution includes the computational modeling aspects of the high fiber rein-forced cement composites (HFRCC) model. To simulate the composite material, a finite element discretization is used to solve the set of equations given by the multifield approach for this particular case. A two field discretization: the standard macroscopic and the micro-scopic displacements, is proposed through a mixed finite element methodology. Furthermore, a splitting procedure for uncoupling both fields is proposed, which provides a more convenient numerical treatment of the discrete equation system. The initiation of failure in HPFRCC at the constitutive level identified as the onset of strain localization depends on the mechanical properties of the all compounds and not only on the matrix ones. As localization criteria is considered the bifurcation analysis in combination with the localized strain injection technique presented by Oliver et al. It consists of injecting a specific localization mode during the localization stage, via mixed finite element formulations, to the path of elements that are going to capture the cracks, and, in this way, the spurious mesh orientation dependence is removed. Model validation was performed using a selected set of experiments that proves the via-bility of this approach. The numerical examples of the proposed formulation illustrated two relevant aspects, namely: 1) the role of the bonding mechanism in the strain hardening be-havior after cracking in the HPFRCC and 2) the role that plays the finite element formulation in capturing the displacement localization in the localization stage

Automatic Lesser Kestrel’s Gender Identification using Video Processing

Traditionally, animal surveillance is a common task for biologists. However, this task is often accompanied by the inspection of huge amounts of video. In this sense, this paper proposes an automatic video processing algorithm to identify the gender of a kestrel species. It is based on optical flow and texture analysis. This algorithm makes it possible to identify the important information and therefore, minimizing the analysis time for biologists. Finally, to validate this algorithm, it has been tested against a set of videos, getting good classification results.Junta de Andalucía P10-TIC-570

Pensamiento algebraico: contraste entre resoluciones de distintos niveles académicos, una tarea de generalización de patrones

El estudio aborda el análisis de la aplicación de una actividad sobre generalización de patrones realizada a dos estudiantes de diferentes niveles académicos, en la cual un estudiante no ha tenido ningún acercamiento al álgebra escolar y el otro pertenece a la Licenciatura en Educación Básica con Énfasis en Matemáticas (LEBEM), con el objetivo de reconocer que aspectos del pensamiento algebraico emergen en la resolución de dicha actividad y además, contrastar los diferentes resultados obtenidos en ambos casos, en términos de abordaje de la tarea y solución a ella, encontrando que al comprender el álgebra desde lo puramente simbólico se pueden generar obstáculos en el desarrollo de este tipo de actividades, dado que el pensamiento de alguna manera se condiciona a buscar una expresión netamente literal

mTOSSIM: A simulator that estimates battery lifetime in wireless sensor networks

Knowledge of the battery lifetime of the wireless sensor network is important for many situations, such as in evaluation of the location of nodes or the estimation of the connectivity, along time, between devices. However, experimental evaluation is a very time-consuming task. It depends on many factors, such as the use of the radio transceiver or the distance between nodes. Simulations reduce considerably this time. They allow the evaluation of the network behavior before its deployment. This article presents a simulation tool which helps developers to obtain information about battery state. This simulator extends the well-known TOSSIM simulator. Therefore it is possible to evaluate TinyOS applications using an accurate model of the battery consumption and its relation to the radio power transmission. Although an specific indoor scenario is used in testing of simulation, the simulator is not limited to this environment. It is possible to work in outdoor scenarios too. Experimental results validate the proposed model.Junta de Andalucía P07-TIC-02476Junta de Andalucía TIC-570

LIS: Localization based on an intelligent distributed fuzzy system applied to a WSN

The localization of the sensor nodes is a fundamental problem in wireless sensor networks. There are a lot of different kinds of solutions in the literature. Some of them use external devices like GPS, while others use special hardware or implicit parameters in wireless communications. In applications like wildlife localization in a natural environment, where the power available and the weight are big restrictions, the use of hungry energy devices like GPS or hardware that add extra weight like mobile directional antenna is not a good solution. Due to these reasons it would be better to use the localization’s implicit characteristics in communications, such as connectivity, number of hops or RSSI. The measurement related to these parameters are currently integrated in most radio devices. These measurement techniques are based on the beacons’ transmissions between the devices. In the current study, a novel tracking distributed method, called LIS, for localization of the sensor nodes using moving devices in a network of static nodes, which have no additional hardware requirements is proposed. The position is obtained with the combination of two algorithms; one based on a local node using a fuzzy system to obtain a partial solution and the other based on a centralized method which merges all the partial solutions. The centralized algorithm is based on the calculation of the centroid of the partial solutions. Advantages of using fuzzy system versus the classical Centroid Localization (CL) algorithm without fuzzy preprocessing are compared with an ad hoc simulator made for testing localization algorithms. With this simulator, it is demonstrated that the proposed method obtains less localization errors and better accuracy than the centroid algorithm.Junta de Andalucía P07-TIC-0247

Locating sensors with fuzzy logic algorithms

In a system formed by hundreds of sensors deployed in a huge area it is important to know the position where every sensor is. This information can be obtained using several methods. However, if the number of sensors is high and the deployment is based on ad-hoc manner, some auto-locating techniques must be implemented. In this paper we describe a novel algorithm based on fuzzy logic with the objective of estimating the location of sensors according to the knowledge of the position of some reference nodes. This algorithm, called LIS (Localization based on Intelligent Sensors) is executed distributively along a wireless sensor network formed by hundreds of nodes, covering a huge area. The evaluation of LIS is led by simulation tests. The result obtained shows that LIS is a promising method that can easily solve the problem of knowing where the sensors are located.Junta de Andalucía P07-TIC-0247