Alternative approach to community detection in networks

The problem of community detection is relevant in many disciplines of science and modularity optimization is the widely accepted method for this purpose. It has recently been shown that this approach presents a resolution limit by which it is not possible to detect communities with sizes smaller than a threshold which depends on the network size. Moreover, it might happen that the communities resulting from such an approach do not satisfy the usual qualitative definition of commune, i.e., nodes in a commune are more connected among themselves than to nodes outside the commune. In this article we introduce a new method for community detection in complex networks. We define new merit factors based on the weak and strong community definitions formulated by Radicchi et al (Proc. Nat. Acad. Sci. USA 101, 2658-2663 (2004)) and we show that this local definitions avoid the resolution limit problem found in the modularity optimization approach.Comment: 17 pages, 6 figure

Traitement statistique de donnees palynologiques de l'Holocene du lac Tanma (Senegal)

Le traitement statistique de données pa l ynologiques de 1 ' Ho l ocene du Lac Tanma situé a u Sénégal, a u Nord de Dakar , a u moyen de 1' analyse canonique permet de préciser le schéma clima tique ex posé antérieuremcnt . Il est notamment mis en évidence une pulsation positive de la pluviosi té ca . 6000 BP .El procesamiento de datos palinológicos del Ho l oceno de l l ago Tanma situado al norte de Dakar en Senegal por medio de un anál i s i s canónico ha permitido precisar la in terpretación climá tica anteriormente propuesta , y parti cularmente , poner de manifiesto una pulsación positi va de la l l uvia c a . 6000 BP

Memory effects induce structure in social networks with activity-driven agents

Activity-driven modeling has been recently proposed as an alternative growth mechanism for time varying networks, displaying power-law degree distribution in time-aggregated representation. This approach assumes memoryless agents developing random connections, thus leading to random networks that fail to reproduce two-nodes degree correlations and the high clustering coefficient widely observed in real social networks. In this work we introduce these missing topological features by accounting for memory effects on the dynamic evolution of time-aggregated networks. To this end, we propose an activity-driven network growth model including a triadic-closure step as main connectivity mechanism. We show that this mechanism provides some of the fundamental topological features expected for social networks. We derive analytical results and perform extensive numerical simulations in regimes with and without population growth. Finally, we present two cases of study, one comprising face-to-face encounters in a closed gathering, while the other one from an online social friendship network.Comment: 19 pages, 12 figures, Major changes. Re-written wor

El estudio de la Geografía electoral, el lugar como ámbito de la gestión pública local

Ponderar los conceptos global y local puede parecer una dicotomía. En nuestro concepto no lo es a partir de haber establecido una categoría de pensamiento: la globalización semeja una compleja totalidad de hechos. Esa complejidad se ejerce en un espacio en el que están todos los lugares, concretando en el lugar ese espacio que nos es común aunque nunca lo visualicemos completamente y lo comprendamos en su totalidad. Hay quienes sostienen que "la globalización es un paradigma para la comprensión de los diferentes aspectos de la realidad contemporánea" (Santos, 1996:131). Pensemos en ella puntualizada en el espacio geográfico, con la idea de dinámica vertebrándolo, a la vez que se integra con objetos y acciones, en permanente transformación, y que con el agregado de la velocidad con que discurre la información, la dinámica es mayor. Y aparece otra aparente dicotomía: globalización / fragmentación. Aparente porque ningún espacio escapa a ambas condiciones interrelacionadas dado que la primera aporta la unidad propia del todo y la segunda la diversidad propia de los lugares. Nuestro interés se centra en los nuevos escenarios de producción social, dejando de lado la consideración de la fragmentación como correlato de la globalización habida cuenta que muchas veces la relación entre ambas elude las mediaciones institucionales y juridisccionales. De acuerdo a Arocena (1995), no consideramos como local aquello que responde a criterios cerrados de tipo localistas ni autárquicos, sino que por el contrario no se considera lo local (particular) sin pensar en lo global (universal). Cuando se asocia lo local a lo territorial, el concepto de "local" debe ser construído para poder establecer la relativa limitación de un espacio local y su global correspondiente. Estos conceptos abordados desde la Geografía, tienen en la escala el elemento clave, que los define como tal. Lo local nos remite a una lógica territorial horizontal, respondiendo a una autonomía de la decisión, con relación a la gestión, que en estudios electorales es totalmente comprobable. No constituye un recorte que excluya las escalas nacionales ni globales, sino que la diferencia se establece en el grado de compromiso que existe con los hechos locales. Un proceso electoral en Argentina involucra cuatrianualmente a tres escalas: nacional, provincial y municipal (global, intermedia y local ). Una focalización del análisis nos ha permitido comprobar las diferencias de evaluación a la hora de elegir por el sufragio, ponderando en la escala local elementos que no se valoran en las otras. Las tres escalas son ámbito de gestión pública.Evento también conocido bajo el nombre de "II Jornadas Platenses de Geografía"Facultad de Humanidades y Ciencias de la Educació

Decentralization, self-management, local management: A case study of a town hall of La Pampa, Argentina

Los municipios, en los últimos veinticinco años, han cambiado sus roles. En la actualidad, los gobernantes locales asumen formas de gestionar que atienden a las crecientes demandas sociales de sus vecinos, redefiniendo las políticas públicas municipales. Parte de la tarea de gestión es el ordenamiento territorial como estrategia para orientar la distribución espacial del desarrollo, de acuerdo con los recursos disponibles, con el mejor uso que a los mismos se da en términos sociales, económicos y ambientales. Concretarlo implica cambios cualitativos importantes, adecuaciones en la gestión político-administrativa. En Victorica, La Pampa, la autogestión se perfila como una de las características más sobresalientes. La dinámica gestión de su territorio es ejemplo para otros municipios que intentan imitar el estilo. Los actores sociales son la clave del cambio.In the last twenty-five years, Town Halls have changed their role. At present, local governors undertake managing policies that tend to assist the increasing social demands of the citizens by redefining the municipal public policies. Part of the managing tasks is the territorial arrangement as a strategy to organize the spatial developmental distribution with the available resources as well as their better use considering the social, economic and environmental aspects. To make this true implies important qualitative changes and adjustments of the political/administrative policies. In Victorica, La Pampa, self-management is turning to be one of the most outstanding policy. The dynamic management of the territory is an example for other Town Halls willing to imitate this management approach. The social actors are the key to the change.Departamento de Geografí

Végétations du quartenaire récent de Provence : histoire d'une biodiversité climatique et d'une homogénéisation anthropique.

Etude de l'histoire de la végétation au cours des siècles en Provence pour poser la question : doit-on aboutir à un conservatisme étroit ou aider au développement humain et social en entretenant un changement équilibré de notre biosystème

Experimental Analysis of IoT Networks Based on LoRa/LoRaWAN under Indoor and Outdoor EnvirMedusonments: Performance and Limitations

Nowadays, Internet of Things (IoT) has multiple applications in different fields. This concept allows physical devices to connect to the internet in order to establish a strong infrastructure that facilitates many device control and monitoring tasks. Low Power Wide Area (LPWA) communication protocols become widely used for IoT networks because of their low power consumption and the broad range communication. LPWA enables devices to transmit small amounts of data in a long distance. Among LPWA protocols, LoRa technology gained a lot of interest recently from the research community and many companies. LoRa is a long range and low power wireless communication technology regulated by the LoRaWAN standard. It can be o good candidate to deploy node network where long distance and extended battery life is required. A LoRaWAN architecture is deployed in a star-of-stars topology and based on a systematic evaluation of a long-term operation of the network monitoring. This works describes experimental results of testing LoRa in indoor and outdoor environments to understand how it works, evaluate its performance, and limitations. As expected, results show that LoRa performs better outdoor. It is also interesting to note that elevating the gateway in order to have a free line of sight with the IoT node, or close to it, increases the signal quality received by the end-node devices, and consequently, longer distances can be achieved

Food Tray Sealing Fault Detection in Multi-Spectral Images Using Data Fusion and Deep Learning Techniques

A correct food tray sealing is required to preserve food properties and safety for consumers. Traditional food packaging inspections are made by human operators to detect seal defects. Recent advances in the field of food inspection have been related to the use of hyperspectral imaging technology and automated vision-based inspection systems. A deep learning-based approach for food tray sealing fault detection using hyperspectral images is described. Several pixel-based image fusion methods are proposed to obtain 2D images from the 3D hyperspectral image datacube, which feeds the deep learning (DL) algorithms. Instead of considering all spectral bands in region of interest around a contaminated or faulty seal area, only relevant bands are selected using data fusion. These techniques greatly improve the computation time while maintaining a high classification ratio, showing that the fused image contains enough information for checking a food tray sealing state (faulty or normal), avoiding feeding a large image datacube to the DL algorithms. Additionally, the proposed DL algorithms do not require any prior handcraft approach, i.e., no manual tuning of the parameters in the algorithms are required since the training process adjusts the algorithm. The experimental results, validated using an industrial dataset for food trays, along with different deep learning methods, demonstrate the effectiveness of the proposed approach. In the studied dataset, an accuracy of 88.7%, 88.3%, 89.3%, and 90.1% was achieved for Deep Belief Network (DBN), Extreme Learning Machine (ELM), Stacked Auto Encoder (SAE), and Convolutional Neural Network (CNN), respectively