Structural Changes in Data Communication in Wireless Sensor Networks

Wireless sensor networks are an important technology for making distributed autonomous measures in hostile or inaccessible environments. Among the challenges they pose, the way data travel among them is a relevant issue since their structure is quite dynamic. The operational topology of such devices can often be described by complex networks. In this work, we assess the variation of measures commonly employed in the complex networks literature applied to wireless sensor networks. Four data communication strategies were considered: geometric, random, small-world, and scale-free models, along with the shortest path length measure. The sensitivity of this measure was analyzed with respect to the following perturbations: insertion and removal of nodes in the geometric strategy; and insertion, removal and rewiring of links in the other models. The assessment was performed using the normalized Kullback-Leibler divergence and Hellinger distance quantifiers, both deriving from the Information Theory framework. The results reveal that the shortest path length is sensitive to perturbations.Comment: 12 pages, 4 figures, Central European Journal of Physic

Resolución por Skype de una tarea de visualización cooperativa por una pareja de estudiantes de talento

En este trabajo analizamos la transmisión de información entre dos estudiantes de alta capacidad matemática mientras resuelven, a través de videoconferencia, una tarea cooperativa de visualización. Las categorías que más afloraron en el análisis del discurso fueron informar, demandar información, sugerir, parafrasear y confirmar. Los indicadores que más manifestaron fueron validación, ampliación y paráfrasis. Los estudiantes manifestaron características del talento matemático como un alto compromiso con la tarea, a pesar de su dificultad, y buena capacidad para organizar los datos y para desarrollar estrategias eficientes de resolución

Estrategias didácticas para la construcción de conocimientos estadísticos

En este trabajo de investigación se presenta una guía de aprendizaje construida para utilizar una diversidad de herramientas tecnológicas y matemáticas como parte de una estrategia didáctica, estructurada en función de las necesidades de los estudiantes, donde se cuenta con una variedad de problemas contextuales y factibles, considerando una sociedad en crisis y cuya repercusión se proyecta en el proceso educativo. En la aplicación de ésta, se puede apreciar el hecho de la intencionalidad para utilizar las herramientas, las construcciones de conceptos estadísticos, la motivación del trabajo en equipo y los argumentos presentados por los estudiantes para dar significado a la media aritmética y la noción de variabilidad; como logran darle sentido a la toma de decisiones en forma empírica, basados en los efectos que presenta la inestabilidad de los datos

Reaching millikelvin resolution in Raman distributed temperature sensing using image processing

Image processing is proposed and experimentally demonstrated to improve the capabilities of Raman distributed optical fibre sensors. The here reported technique consists in stacking consecutive one-dimensional Raman Stokes and anti-Stokes traces in two-dimensional data arrays (one for each Raman component), which are then processed by an image denoising algorithm. Owing to the high level of correlation between consecutive measurements in conventional Raman sensing, it is experimentally demonstrated that this newly-proposed two-dimensional denoising approach provides a significant signal-to-noise ratio improvement, which in this case reaches 13.6 dB with no hardware modification to the conventional set-up. Experimental results demonstrate Raman distributed sensing with a remarkably enhanced temperature resolution of 4 mK at 9 km distance, which is obtained with 2 m spatial resolution and a short acquisition time of 35 s

Intensifying the response of distributed optical fibre sensors using 2D and 3D image restoration

Distributed optical fibre sensors possess the unique capability of measuring the spatial and temporal map of environmental quantities that can be of great interest for several field applications. Although existing methods for performance enhancement have enabled important progresses in the field, they do not take full advantage of all information present in the measured data, still giving room for substantial improvement over the state-of-the-art. Here we propose and experimentally demonstrate an approach for performance enhancement that exploits the high level of similitude and redundancy contained on the multidimensional information measured by distributed fibre sensors. Exploiting conventional image and video processing, an unprecedented boost in signal-to-noise ratio and measurement contrast is experimentally demonstrated. The method can be applied to any white-noise-limited distributed fibre sensor and can remarkably provide a 100-fold improvement in the sensor performance with no hardware modification

Estudo Dos Mecanismos De Funcionamento Do Algoritmo De Evolução Diferencial

This work presents theoretical considerations and experimental studies on the working mechanisms of the differential evolution (DE) algorithm for nonlinear optimization. A constant relationship between the covariance matrix of the population at a given iteration of the algorithm, and the corresponding covariance matrix of the probability distribution for the differential mutation operator, represented by the set of all possible mutation vectors, is obtained. This relationship is then employed for analyzing the adaptive behavior of the differential evolution algorithm

Mechanical properties of concrete using recycled aggregates obtained from old paving stones

Nowadays, construction, maintenance, reparation, rehabilitation, retrofitting, and demolition from infrastructure and buildings generate large amounts of urban waste, which usually are inadequately disposed due to high costs and technical limitations. On the other hand, the increasing demand for natural aggregates for concrete production seriously affects mountains and rivers as they are the source of these nonrenewable goods. Consequently, the recycling of aggregates for concrete is gaining attention worldwide as an alternative to reduce the environmental impacts caused by the extraction of nonrenewable goods and disposal of construction and demolition waste (C&DW). Therefore, this article describes the effect on the mechanical properties of new concrete using recycled aggregates obtained from old paving stones. Results show that replacing 50% by weight of the fine and coarse aggregate fractions in concrete with recycled aggregate does not meaningfully affect its mechanical behavior, making the use of recycled aggregates in new precast paving stones possible. Therefore, the latter can reduce environmental impacts and costs for developing infrastructure and building projects