UPCommons: global access to Universitat Politècnica de Catalunya (UPC) knowledge

Programa de mà lliurat en la presentació del pòster 'UPCommons', exposat al primer COMMUNIA Workshop on Technology and the Public Domain, celebrat a Torí (Itàlia) el 18 de gener de 2008.

Informe d'Autors UOC a ISI Web of Knowledge. Maig 2014

UOC

Self-Organising Maps and Correlation Analysis as a Tool to Explore Patterns in Excitation-Emission Matrix Data Sets and to Discriminate Dissolved Organic Matter Fluorescence Components

Dissolved organic matter (DOM) is a complex mixture of organic compounds, ubiquitous in marine and freshwater systems. Fluorescence spectroscopy, by means of Excitation-Emission Matrices (EEM), has become an indispensable tool to study DOM sources, transport and fate in aquatic ecosystems. However the statistical treatment of large and heterogeneous EEM data sets still represents an important challenge for biogeochemists. Recently, Self-Organising Maps (SOM) has been proposed as a tool to explore patterns in large EEM data sets. SOM is a pattern recognition method which clusterizes and reduces the dimensionality of input EEMs without relying on any assumption about the data structure. In this paper, we show how SOM, coupled with a correlation analysis of the component planes, can be used both to explore patterns among samples, as well as to identify individual fluorescence components. We analysed a large and heterogeneous EEM data set, including samples from a river catchment collected under a range of hydrological conditions, along a 60-km downstream gradient, and under the influence of different degrees of anthropogenic impact. According to our results, chemical industry effluents appeared to have unique and distinctive spectral characteristics. On the other hand, river samples collected under flash flood conditions showed homogeneous EEM shapes. The correlation analysis of the component planes suggested the presence of four fluorescence components, consistent with DOM components previously described in the literature. A remarkable strength of this methodology was that outlier samples appeared naturally integrated in the analysis. We conclude that SOM coupled with a correlation analysis procedure is a promising tool for studying large and heterogeneous EEM data sets.

Fishery of the Goliath grouper, Epinephelus itajara (Teleostei: Epinephelidae) based on local ecological knowledge and fishery records in Yucatan, Mexico

The Goliath grouper, Epinephelus itajara, a large-bodied (similar to 2.5 m TL, > 400 kg) and critically endangered fish (Epinephelidae), is highly Vulnerable to overfishing. Although protected from fishing in many countries, its exploitation in Mexico is unregulated; a situation that puts its populations at risk. Fishery records of E. itajara are scarce, which prevents determination of its fishery status. This work aimed to elucidate the E itajara fishery in the northern Yucatan Peninsula by 1) analyzing available catch records and 2) interviewing veteran fishermen (local ecological knowledge) from two traditional landing sites: Dzilam de Bravo and Puerto Progreso. Historic fishery records from two fishing cooperatives were analyzed in order to elucidate the current situation and offer viable alternatives for conservation and management. Catches have decreased severely. Local knowledge obtained from fishermen represented a very important source of information for reconstructing the fisheries history of this species. Conservation measures that incorporate regional and international regulations on critically endangered fish species are suggested

Fer mapes per conèixer la Història: aportacions de la cartografia a l'estudi de l'Alta Edat Mitjana

To make maps to know history: contributions from the cartography to the study of the early middle ages. The accomplishment of maps can allow us to know many aspects that documents written do not allow us to have knowledge. This paper focuses on the boundaries of the townships or the parishes, on the routes and ways, and on the place names or on the invocations of the churches, in order to get to know like it was the territory in the early medieval centuries. One reaches the conclusion that often the limits, the ways and the settlements were created at early middle ages. This study allows to raise the ruptures and the continuities that took place throughout these centuries in the settlement.

Clustering of grape yield maps to delineate site-specific management zones

Zonal management in vineyards requires the prior delineation of stable yield zones within the parcel. Among the different methodologies used for zone delineation, cluster analysis of yield data from several years is one of the possibilities cited in scientific literature. However, there exist reasonable doubts concerning the cluster algorithm to be used and the number of zones that have to be delineated within a field. In this paper two different cluster algorithms have been compared (k-means and fuzzy c-means) using the grape yield data corresponding to three successive years (2002, 2003 and 2004), for a ‘Pinot Noir’ vineyard parcel. Final choice of the most recommendable algorithm has been linked to obtaining a stable pattern of spatial yield distribution and to allowing for the delineation of compact and average sized areas. The general recommendation is to use reclassified maps of two clusters or yield classes (low yield zone and high yield zone) and, consequently, the site-specific vineyard management should be based on the prior delineation of just two different zones or sub-parcels. The two tested algorithms are good options for this purpose. However, the fuzzy c-means algorithm allows for a better zoning of the parcel, forming more compact areas and with more equilibrated zonal differences over time.

Análisis del discurso colaborativo en el entorno Knowledge Forum: categorización de los mensajes

El objetivo de esta investigación es conocer la tipología de aportaciones, que se producen en el entorno virtual colaborativo Knowledge Forum y comprobar si está teniendo lugar un aprendizaje colaborativo a través del ordenador (CSCL). Las contribuciones a los diferentes 30 foros han sido analizados y categorizados usando un esquema de codificación en base a las scaffolds o andamiajes que dicho entorno proporciona. Los resultados muestran que en conjunto los 308 estudiantes universitarios aportan nueva información y opinan, pero hay escasez de mensajes con diferentes opiniones que lleven a la discusión y a intercambios de puntos de vista distintos.

Analysing knowledge building: usages, achievements and limits of forums at university

This paper aims to explore asynchronous communication in computer supported collaborative learning (CSCL). Thirty virtual forums are analysed in both a quantitative and a qualitative way. Quantitatively, the number of messages written, message threads and original and answer messages are counted. Qualitatively, the content of the notes is analysed, cataloguing these into two different levels: on the one hand, as a set of knowledge building process categories, and on the other hand, following the scaffolds that Knowledge Forum offers. The results show that both an exchange of information and a collaborative work take place. Nevertheless, the construction of knowledge is superficial.

Evaluation of the Development of Metacognitive Knowledge Supported by the KnowCat System

The aim of this study was to examine the development of the metacognitive knowledge of a group of higher education students who participated actively in an experiment based on a Computer Supported Collaborative Learning environment called KnowCat. Eighteen university students participated in a 12-month learning project during which the KnowCat learning environment was used to support scaffolding process among equals during problem-solving tasks. After using KnowCat, the students were interviewed over their work in this shared workspace. Qualitative analysis revealed that the educational application of KnowCat can favour and improve the development of metacognitive knowledge.

Using vegetation to characterize the avalanche to Canal del Roc Roig, Vall de Núria (Eastern Pyrenees, Spain)

Avalanche hazard maps of high accuracy are difficult to produce. For land-use planning and management purposes, a good knowledge of extreme run-out zones and frequencies of avalanches is required. In the present work, vegetation recognition (especially focused on Pinus uncinata trees) and dendrochronological techniques are used to characterize avalanches that have occurred in historical times, helping to determine both the extent of large or extreme avalanches and their occurrence in time. Vegetation was studied at the Canal del Roc Roig (eastern Pyrenees, Spain) avalanche path. The avalanches descending this path affect the railway that reaches the Vall de Núria resort and the run-up to the opposite slope. During winter 1996, two important avalanches affecting this path were well documented. These are compared with the results of the vegetation study, consisting of an inventory of flora, the recording of vegetation damages along eight transverse profiles at different altitudes on the path and a dendrochronological sampling campaign. The data obtained contributed to a characterization of the predominant snow accumulation in the starting zone, the 1996 avalanches and the range of frequencies of large avalanches. Also, traces of avalanches that increase the path mapped in the avalanche paths map published by the Institut Cartogràfic de Catalunya in 2000 were identified, improving the initial existing information.

Using vegetation to characterize the avalanche to Canal del Roc Roig, Vall de Núria (Eastern Pyrenees, Spain)

Avalanche hazard maps of high accuracy are difficult to produce. For land-use planning and management purposes, a good knowledge of extreme run-out zones and frequencies of avalanches is required. In the present work, vegetation recognition (especially focused on Pinus uncinata trees) and dendrochronological techniques are used to characterize avalanches that have occurred in historical times, helping to determine both the extent of large or extreme avalanches and their occurrence in time. Vegetation was studied at the Canal del Roc Roig (eastern Pyrenees, Spain) avalanche path. The avalanches descending this path affect the railway that reaches the Vall de Núria resort and the run-up to the opposite slope. During winter 1996, two important avalanches affecting this path were well documented. These are compared with the results of the vegetation study, consisting of an inventory of flora, the recording of vegetation damages along eight transverse profiles at different altitudes on the path and a dendrochronological sampling campaign. The data obtained contributed to a characterization of the predominant snow accumulation in the starting zone, the 1996 avalanches and the range of frequencies of large avalanches. Also, traces of avalanches that increase the path mapped in the avalanche paths map published by the Institut Cartogràfic de Catalunya in 2000 were identified, improving the initial existing information.

Informe d'Autors UOC a ISI Web of Knowledge. Juny 2014

UOC

Informe d'Autors UOC a ISI Web of Knowledge. Juliol 2014

UOC

A note on the periodic orbits and topological entropy of graph maps

This paper deals with the relationship between the periodic orbits of continuous maps on graphs and the topological entropy of the map. We show that the topological entropy of a graph map can be approximated by the entropy of its periodic orbits.

A parameterization method for the computation of invariant tori and their whiskers in quasi-periodic maps: explorations and mechanisms for the breakdown of hyperbolicity

In two previous papers [J. Differential Equations, 228 (2006), pp. 530 579; Discrete Contin. Dyn. Syst. Ser. B, 6 (2006), pp. 1261 1300] we have developed fast algorithms for the computations of invariant tori in quasi‐periodic systems and developed theorems that assess their accuracy. In this paper, we study the results of implementing these algorithms and study their performance in actual implementations. More importantly, we note that, due to the speed of the algorithms and the theoretical developments about their reliability, we can compute with confidence invariant objects close to the breakdown of their hyperbolicity properties. This allows us to identify a mechanism of loss of hyperbolicity and measure some of its quantitative regularities. We find that some systems lose hyperbolicity because the stable and unstable bundles approach each other but the Lyapunov multipliers remain away from 1. We find empirically that, close to the breakdown, the distances between the invariant bundles and the Lyapunov multipliers which are natural measures of hyperbolicity depend on the parameters, with power laws with universal exponents. We also observe that, even if the rigorous justifications in [J. Differential Equations, 228 (2006), pp. 530-579] are developed only for hyperbolic tori, the algorithms work also for elliptic tori in Hamiltonian systems. We can continue these tori and also compute some bifurcations at resonance which may lead to the existence of hyperbolic tori with nonorientable bundles. We compute manifolds tangent to nonorientable bundles.