Marco Alzate - Academia.edu (original) (raw)

Papers by Marco Alzate

2007 IEEE Symposium on Computers and Communications, 2007

Page 1. End-to-End Mean Bandwidth Estimation as a Function of Packet Length in Mobile Ad Hoc Netw... more Page 1. End-to-End Mean Bandwidth Estimation as a Function of Packet Length in Mobile Ad Hoc Networks Marco A. Alzate Universidad de los Andes m-alzate@uniandes.edu.co María P. Salamanca Universidad de los Andes m-salama@uniandes.edu.co ...

Journal of Network and Computer Applications, 2011

2010 IEEE Latin-American Conference on Communications, 2010

The interest on firefly approaches to the problem of synchronizing the nodes of a wireless ad hoc... more The interest on firefly approaches to the problem of synchronizing the nodes of a wireless ad hoc communication network is rising, because of its efficiency and efficacy. In this paper we show that it is enough to have an indirect interaction among nodes, either spatially (through multi-hop paths), or temporally (through mobility) to achieve synchronism among them. As the interactions among nodes increases, global synchronization emerges faster.

Cognitive agents have the ability to perceive their environment and act on it according to models... more Cognitive agents have the ability to perceive their environment and act on it according to models of reality built through memory, intelligence and language. Interacting cognitive agents interchange information about their models in order to build a collective knowledge of their reality (social learning). In this paper we use this distributed cognitive system paradigm to solve a segmentation problem in image processing from the complex systems engineering approach. We build a cognitive cellular automata where each pixel in the image is a cognitive agent. Social learning is achieved by stigmergic and direct communication among agents. Our results outperform typical segmentation methodologies for granular material. Our social cognitive learning metaphor exemplifies a complex systems engineering approach for more general applications.

Engineering Transactions, 2021

Particle size distribution of aggregate in asphalt pavements is used for determining important ch... more Particle size distribution of aggregate in asphalt pavements is used for determining important characteristics like stiffness, durability, fatigue resistance, etc. Unfortunately, measuring this distribution requires a sieving process that cannot be done directly on the already mixed pavement. The use of digital image processing could facilitate this measurement, for which it is important to classify aggregate from asphalt in the image. This classification is difficult even for humans and much more for classical image segmentation algorithms. In this paper, an expert committee approach was used, including classical adaptive Otsu, k-means vector quantization over a set of 8 principal components obtained from 26 features, and a Gaussian mixture model whose parameters are estimated through the expectation-maximization algorithm. A novel cellular automata approach is used to coordinate these expert opinions. Finally, a simple heuristic is used to reduce sub- and over-segmentation. The se...

$Research paper thumbnail of Generation of Simulated Fractal and Multifractal Traffic$

We create software tools for the generation of sample traces of self-similar traffic as fractiona... more We create software tools for the generation of sample traces of self-similar traffic as fractional Brownian motion, using Mathcad. These methods have been widely used in simulation studies, but they present the difficulty of generating negative samples. So we also introduce a very efficient technique for the generation of multifractal traffic by means of wavelet synthesis, which posses the property of positiveness.

Revista Facultad De Ingenieria-universidad De Antioquia, 2012

For management purposes, it is very important to estimate the available bandwidth for each link i... more For management purposes, it is very important to estimate the available bandwidth for each link in a MANET, in an accurate, timely and efficient way. In this paper we show analytical results on the probability distribution function of the bandwidth of a link in a MANET based on IEEE 802.11, that take into account transmission errors. We also show some analytical results on the fraction of time the channel is available for a given virtual link, so the effects of other transmitting nodes can also be taken into account. Together, these results can be usefully exploited in an efficient, accurate and distributed available bandwidth estimation mechanism.

ArXiv, 2020

With artificial intelligence systems becoming ubiquitous in our society, its designers will soon ... more With artificial intelligence systems becoming ubiquitous in our society, its designers will soon have to start to consider its social dimension, as many of these systems will have to interact among them to work efficiently. With this in mind, we propose a decentralized deep reinforcement learning algorithm for the design of cooperative multi-agent systems. The algorithm is based on the hypothesis that highly correlated actions are a feature of cooperative systems, and hence, we propose the insertion of an auxiliary objective of maximization of the mutual information between the actions of agents in the learning problem. Our system is applied to a social dilemma, a problem whose optimal solution requires that agents cooperate to maximize a macroscopic performance function despite the divergent individual objectives of each agent. By comparing the performance of the proposed system to a system without the auxiliary objective, we conclude that the maximization of mutual information amo...

In this paper we estimate the end-to-end capacity and available bandwidth of a path between a pai... more In this paper we estimate the end-to-end capacity and available bandwidth of a path between a pair of nodes in an IEEE 802.11b ad hoc network using dispersion traces between packet pairs of different lengths. The pairs of packets that suffer the minimum delay are used to estimate the maximum achievable transmission rate as a function of packet length, for any packet length, while the variability of the dispersions is used to estimate the fraction of that capacity that is available for data transmission. To model the dependence of the variability of the dispersion traces on the true fraction of available capacity, we use a neuro-fuzzy estimator trained on data collected from a large set of real and simulated scenarios. The system is shown to provide accurate estimates (within 15% of accuracy 80% of the time on the test data), to be efficient in the use of communication resources (transmits 48 kbps during the test), and to present low computational cost (about 500 floating point opera...

Physical review. E, 2019

An alternative way to study the rules of life-like cellular automata is presented. The proposed p... more An alternative way to study the rules of life-like cellular automata is presented. The proposed perspective studies some multifractal and informational properties of Boolean functions behind these rules. Results from this approach challenge the traditional argument about the simplicity of Lifelike rules.

Revista de la Universidad Industrial de Santander. Salud

Introducción: El diagnóstico del estado eritrocitario en frotis de sangre periférica es un proces... more Introducción: El diagnóstico del estado eritrocitario en frotis de sangre periférica es un proceso realizado normalmente de forma manual a partir de observación microscópica, lo cual implica una considerable inversión de tiempo y recursos, además de posibles problemas de subjetividad y dificultad en la reproducibilidad del diagnóstico. Objetivo: Desarrollar una aplicación que permita la clasificación automática de glóbulos rojos en frotis de sangre periférica, de utilidad como herramienta de ayuda diagnóstica. Metodología: Se usaron técnicas de procesamiento de imágenes para segmentar los eritrocitos en las fotografías microscópicas y medir en ellos área, perímetro, solidez, circularidad, excentricidad, textura y dimensión box-counting. Se usó una red neuronal artificial para clasificar los eritrocitos según sus características en siete clases, incluyendo normalidad y seis alteraciones patológicas. La red se entrenó de acuerdo con la clasificación de 262 eritrocitos realizada por un hematólogo experto. Los desarrollos se hicieron en matlab ® , una poderosa plataforma de computación científica. Resultados: La red escogida alcanza el 97.3% de aciertos en los datos de validación. Las equivocaciones en la red corresponden a células de dudosa clasificación aún para un experto, por presentar características correspondientes a varias clasificaciones patológicas. Conclusiones: La aplicación desarrollada clasifica de manera rápida y acertada los diferentes tipos de glóbulos rojos presentes en una muestra microscópica de frotis de sangre periférica, siendo de utilidad como herramienta de apoyo diagnóstico.

Ingeniare. Revista chilena de ingeniería, 2016

El cáncer cervical puede ser curado si se detecta y trata oportunamente, para ello la prueba Pap ... more El cáncer cervical puede ser curado si se detecta y trata oportunamente, para ello la prueba Pap ha sido fundamental. En este contexto, una ayuda tecnológica puede reducir la naturaleza subjetiva del diagnóstico, pero existen dificultades en su construcción. Aquí abordamos dos de ellas: la identificación del citoplasma y el núcleo de cada célula, y la determinación de un conjunto de características relevantes para la detección de lesiones neoplásicas. En este artículo presentamos dos aportes. Primero se propone un método interactivo de segmentación basado en procesamiento morfológico multiespectral en el que las imperfecciones más engañosas de las imágenes son eliminadas con una interacción simple del analista. Segundo, se hace un análisis de la relevancia de algunas variables que caracterizan los tamaños relativos del núcleo y el citoplasma, sus formas, sus texturas y la rugosidad de sus bordes. El análisis se basa en las medidas de desempeño de un detector que utiliza extracción de características mediante análisis de componentes principales (PCA) y separación de células normales y lesionadas mediante una máquina de vectores de soporte (SVM). Encontramos que una mínima interacción con el médico permite obtener segmentaciones mucho más precisas y confiables. De otro lado, encontramos que las características más relevantes para detección de lesiones neoplásicas son los tamaños relativos del núcleo y del citoplasma y sus formas, mientras que otras características, como la textura y la rugosidad, son menos relevantes.

Revista Facultad De Ingenieria, Jul 31, 2012

Tecnura Tecnologia Y Cultura Afirmando El Conocimiento, 2011

Clasificación del artículo: Reflexión (Conciencias) Fecha de recepción: 19 de mayo de 2011 Fecha ... more Clasificación del artículo: Reflexión (Conciencias) Fecha de recepción: 19 de mayo de 2011 Fecha de aceptación: 29 de agosto de 2011 Palabras clave: Ancho de banda disponible, control de admisión, estimación, redes móviles AD HOC.

Cooperation among nodes is fundamental for the operation of mobile ad hoc networks (MANETs). Howe... more Cooperation among nodes is fundamental for the operation of mobile ad hoc networks (MANETs). However, in these networks there could be selfish nodes that use resources from other nodes to send their packets but do not offer their resources to forward packets for other nodes. Several trust models have been proposed as mechanisms to incentive cooperation in MANETs. Some of them are based on game theory concepts. Among game theoretic trust models, those that make nodes' strategies evolve genetically have shown promising results for cooperation improvement. However, current approaches propose a highly centralized genetic evolution so they cannot properly adapt to fast changing conditions. In this paper, we propose a game theoretic trust model that uses a bacterial-like algorithm to let the nodes quickly learn the appropriate cooperation behavior. Our model is completely distributed and achieves good cooperation values in a small fraction of the time compared with centralized algorithms.

Revista Facultad de Ingeniería

Mobile Ad-Hoc Networks: Protocol Design, 2011

Lecture Notes in Computer Science, 2007

Cross-traffic data rate over the tight link of a path can be estimated using different active pro... more Cross-traffic data rate over the tight link of a path can be estimated using different active probing packet dispersion techniques. Many of these techniques send large amounts of probing traffic but use just a tiny fraction of the measurements to estimate the long-run cross-traffic average. In this paper, we are interested in short-term cross-traffic estimation using bandwidth efficient techniques when the cross-traffic exhibits high variability. High variability increases the cross-correlation coefficient between cross-traffic and dispersion measurements on a wide range of utilization factors and over a long range of measurement time scales. This correlation is exploited with an appropriate statistical inference procedure based on a simple heuristically modified neuro-fuzzy estimator that achieves high accuracy, low computational cost, and very low transmission overhead. The design process led to a very simple architecture, ensuring good generalization properties. Simulation experiments show that, if the variability comes from a complex correlation structure, a single estimator can be used over a long range of utilization factors and measurement periods with no additional training.