Facultad Regional Buenos Aires

Permanent URI for this communityhttp://48.217.138.120/handle/20.500.12272/6

Browse

Author: search.filters.author.Rey, Andrea

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    DIFERENCIACIÓN DE SEÑALES CAÓTICAS Y ALEATORIAS MEDIANTE CARACTERÍSTICAS GEOMÉTRICAS
    (ASAMACI - Asociación Argentina de Mecánica Aplicada, Computacional e Industrial, 2023-03-25) García Blesa, Hernán Manuel; Legnani, Walter; Rey, Andrea
    Resumen: En este trabajo, proponemos un modelo basado en la construcción de un espacio de caracterı́sticas utilizando descriptores geométricos innovadores, para identificar diferentes tipos de señales discretas 1D. Calculamos dichas caracterı́sticas mediante el método de barrido con una dimensión de encastre (embedding, en inglés), técnica ampliamente utilizada en aplicaciones de Teorı́a de la Información. Proponemos tres caracterı́sticas: amplitud, ángulo de Zenit y factor de forma. A partir de las mismas, asociamos una terna a cada segmento de cada una de las señales de un grupo dado. Luego, reducimos el número de ternas concatenando la información repetida. El cardinal de este nuevo conjunto de ternas define la variable utilizada para la distinción de señales. Aplicamos la propuesta en un conjunto de señales sintéticas aleatorias y caóticas obteniendo muy buenos resultados para distinguir ambos tipos de señales.
  • Thumbnail Image
    Item
    Mathematical and informational tools for classifying blood glucose signals - a pilot study
    (2023-07-20) Amadio, Ariel; Rey, Andrea; Legnani, Walter; García Blesa, Manuel; Bonini, Cristian; Otero, Dino
    A survey campaign was carried out on the dynamics of blood glucose measured through interstitial sensors of relative recent diffusion in the market. These sensors generated time series that were labeled according to medical diagnosis in diabetics and non-diabetics, and that constituted the data core of the classification models. Based on the calculation of the distribution of ordinal patterns of the time series, the corresponding points in the entropycomplexity causal plane were located. Moreover, the transition matrices of these ordinal patterns (OPTMs) were calculated in order to find the proximity using the Manhattan distance of every OPTM with respect to the mean of each group, associating the corresponding signal to each class. On the other hand, the Frobenius norm of every OPTM and the norm of its stationary vector were computed given different values for the considered classes. The effect of repeated values in a signal was also analyzed. Notable differences were obtained in the properties of the OPTMs of each class. In another sense, it is shown that diabetes is a disease that reduces the entropy of the temporal evolution of blood glucose in well-defined time periods, and presents values of complexity significantly higher than those obtained in subjects without diabetes. The selected alternatives coincide in detecting patients positively diagnosed with type II diabetes mellitus. The calculations on the OPTMs show the correlation among patterns of the signals. At the same time, in the entropy-complexity plane, the considered groups were located in well-defined regions showing the differentiating power of these information measures, and indicating variations in the dynamics of the biological system when diabetes is present. With the four mathematical tools selected and the dynamical characterization given by the causal plane, it was possible to define an index that clearly differentiates the classes under study.
  • Thumbnail Image
    Item
    An alternative computation of the entropy of 1D signals based on geometric properties
    (2022-09-01) Bonini, Cristian; Rey, Andrea; Otero, Dino; Amadio, Ariel; García Blesa, Manuel; Legnani, Walter
    The objective of this work is to present a novel methodology based on the computation of a couple of geometric characteristics of the position of the data points in 1D signal to propose an alternative estimation of signal entropy. The conditions to be fulfilled by the signal are minimal; only those necessary to meet the sampling theorem requirement are enough. This work shows some examples in which the proposed methodology can distinguish among signals that cannot be differentiated by other in-use alternatives. Additionally an original example where the usual ordinal pattern algorithm to compute entropy is not applicable, is presented and analyzed. The proposal developed through this work carries some advantages over other alternatives and constitutes a true advancement in the pathway to compute the distribution function of the sequential points of 1D signals later used to compute the entropy of the signal.
  • Thumbnail Image
    Item
    Clasificación de señales de ECG arrítmicas en el espacio de características entropía- complejidad-tiempo de retraso de embebido
    (2022-10-01) Martínez Coq, Pablo; Rey, Andrea; Legnani, Walter
    La muerte súbita es consecuencia final de una arritmia severa. Así, la detección precoz de las arritmias es relevante. Se propone calcular para cada señal de ECG, el tiempo de retraso de embebido individualizado, la entropía de permutación y la complejidad estadística formando un espacio tridimensional de características, utilizado para entrenar un clasificador basado en la técnica de Random Forest. Los valores obtenidos de los parámetros de calidad de la clasificación son muy satisfactorios, permitiendo discriminar entre grupos de pacientes con ECG arrítmicos o con ritmos normales, presentando así una metodología prometedora en la definición de nuevos marcadores para la detección de patologías cardiovasculares.
  • Thumbnail Image
    Item
    Estudio del crecimiento de una región de interés en una imagen usando medidas de grafos
    (2021-10-01) Rey, Andrea; Caballero, Gisela; Arce, Andrea
    Graph theory provides a set of resources and tools for the representation and solution of problems arisen in several areas. In image analysis, each pixel is considered as the vertex of a graph, assigning a weight to each edge that describes certain relationship, such as the similarity of gray levels. In this work, measures of the graph associated to an image are computed, with the aim of analyzing the growth of a region of interest through time. Experiments are designed for different expansion schemes, both controlled and random. The results obtained show a strong correlation for some measures.