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Emergence of Consensus in a Multi-Robot Network: From Abstract Models to Empirical Validation
No full textConsensus dynamics in decentralised multiagent systems are subject to intense studies, and several different models have been proposed and analyzed. Among these, the naming game stands out for its simplicity and applicability to a wide range of phenomena and applications, from semiotics to engineering. Despite the wide range of studies available, the implementation of theoretical models in real distributed systems is not always straightforward, as the physical platform imposes several constraints that may have a bearing on the consensus dynamics. In this letter, we investigate the effects of an implementation of the naming game for the kilobot robotic platform, in which we consider concurrent execution of games and physical interferences. Consensus dynamics are analyzed in the light of the continuously evolving communication network created by the robots, highlighting how the different regimes crucially depend on the robot density and on their ability to spread widely in the experimental arena. We find that physical interferences reduce the benefits resulting from robot mobility in terms of consensus time, but also result in lower cognitive load for individual agents
Research of R.A. Vollenweider in the Istituto Italiano di Idrobiologia as a contribute to the development of watershed phosphorus load - lake trophic state models
No full textRichard A. Vollenweider (Z?rich, 1922?Burlington, 2007) developed one of the first and probably the most used predictive model of lake eutrophication, relating nutrient loading to the biological response. In this presentation, we follow his early career to identify the cultural environment that allow him to develop his model. After getting his Ph. D. in Biology in the University of Z?rich (1951), he spent several years studying the limnology of Italian lakes at the Istituto Italiano di Idrobiologia Dott. Marco De Marchi in Verbania Pallanza (now the Institute of Ecosystem Study of the National Research Council of Italy), where he was awarded a study grant from 1954 to 1955, later being engaged as a contract researcher from 1959 to 1966. He considered very different aspects of limnological research, such as the regional hydrochemistry of subalpine lakes in relation to the geo-lithology of the watersheds, the mixing pattern of the deep lakes of the area (lakes Maggiore, Como, Lugano), the impact of River Toce flood events on the distribution and sedimentation of particulate matter in Lake Maggiore, phytoplankton primary production measured using the light and dark bottle technique and, later, with the C-14 method of Steemann-Nielsen. Primary production of the two lakes Maggiore and Mergozzo were compared, and experiments of nutrient enrichment of water performed. Other studies, all of them important from a limnological standpoint, involved a diverse range of topics; for example, laboratory experiments on the vitamin B12 requirements of Fragilaria crotonensis and composition of new media for algal cultures. These activities were performed in strict contact and agreement with Italian researchers, such as the director of the Institute Vittorio Tonolli, Oscar Ravera, Carlo Saraceni, Luigi Provasoli, and with foreign limnologist, frequently present in the Institute. The high quality and number of his publications testify to his tireless activity; 11 of them were published in the Memorie dell?Istituto Italiano di Idrobiologia (since 1999 published under the title of Journal of Limnology). In 1996 he got from the Organization for the Economic Cooperation and Development (OECD) a contract for the study of the causes of freshwater eutrophication. In this task he used all the experience he had accumulated and conspicuous available literature to produce in 1968 a work, where the role of phosphorus in determining the increase of lake trophic status was recognized and a preliminary predictive model linking phosphorus load to the lake trophy was proposed. This approach was fertile of developments and signed a remarkable progress in the freshwater studies and management. The presentation will discuss the different aspects which determined the approach of R.A. Vollenweider to this topic, considering the status of research on the theme, and his personal experiences, based on the papers he produced and on documents of the historical archive of the Institute
Alien species among Chironomids: a new topic on which direct our interest
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On the dynamics of a generalized predator-prey system with Z-type control.
No full textWe apply the Z-control approach to a generalized predator-prey system and consider the specific case of indirect control of the prey population. We derive the associated Z-controlled model and investigate its properties from the point of view of the dynamical systems theory. The key role of the design parameter ?for the successful application of the method is stressed and related to specific dynamical properties of the Z-controlled model. Critical values of the design parameter are also found, delimiting the ?-range for the effectiveness of the Z-method. Analytical results are then numerically validated by the means of two ecological models: the classical Lotka-Volterra model and a model related to a case study of the wolf- wild boar dynamics in the Alta Murgia National Park. Investigations on these models also highlight how the Z-control method acts in respect to different dynamical regimes of the uncontrolled mode
A comprehensive open package format for preservation and distribution of geospatial data and metadata
No full textThe complexities of the intricate geospatial resources and formats make preservation and distribution of GIS data difficult even among experts. The proliferation of, for instance, KML, Internet map services, etc, reflects the need for sharing geodata but a comprehensive solution when having to deal with data and metadata of a certain complexity is not currently provided. Original geospatial data is usually divided into several parts to record its different aspects (spatial and thematic features, etc), plus additional files containing, metadata, symbolization specifications and tables, etc; these parts are encoded in different formats, both standard and proprietary. To simplify data access, software providers encourage the use of an additional element that we call generically "map project", and this contains links to other parts (local or remote). Consequently, in order to distribute the data and metadata refereed by the map in a complete way, or to apply the Open Archival Information System (OAIS) standard to preserve it for the future, we need to face the multipart problem. This paper proposes a package allowing the distribution of real (comprehensive although diverse and complex) GIS data over the Internet and for data preservation. This proposal, complemented with the right tools, hides but keeps the multipart structure, so providing a simpler but professional user experience. Several packaging strategies are reviewed in the paper, and a solution based on ISO 29500-2 standard is chosen. The solution also considers the adoption of the recent Open Geospatial Consortium Web Services common standard (OGC OWS) context document as map part, and as a way for also combining data files with geospatial services. Finally, and by using adequate strategies, different GIS implementations can use several parts of the package and ignore the rest: a philosophy that has proven useful (e.g. in TIFF)
Effect of protection level in the hydroperiod of water bodies on Do?ana\u27s Aeolian sands
No full textMediterranean temporary ponds on Do?ana\u27s aeolian sands form an extensive system of small dynamic water bodies, dependent on precipitation and groundwater, of considerable importance for biodiversity conservation. Different areas of the aeolian sands have received different levels of environmental protection since 1969, and this has influenced the degree of conservation and the flooding dynamic of these temporary surface waters. We use the Landsat series of satellite images from 1985 to 2014 to study the temporal dynamic of small temporary water bodies on the aeolian sands in relation to the protection level and to distance to water abstraction pressures from agriculture and residential areas. The results show that even with small and ephemeral water bodies optical remote sensing time-series are an effective way to study their flooding temporal dynamics. The protected areas of the aeolian sands hold a better preserved system of temporary ponds, with a flooding dynamic that fluctuates with precipitation. The unprotected area shows an increase in mean hydroperiod duration, and surface flooded, and a decline in hydroperiod variability. This seems to be due to the creation of irrigation ponds and the artificialization of the flooding regime of the natural temporary ponds, that either receive excess irrigation water or dry-up due to the lowering of the groundwater table level. Although a decline in hydroperiod duration of temporary ponds is seen as negative to the system, an increase in hydroperiod of surface waters due to artificialization, or a decline in variability cannot be considered as positive compensatory effects
Indagini sull\u27evoluzione del popolamento zooplanctonico: confronto con i dati pregressi anche alla luce delle mutate condizioni meteo-climatiche
No full textNot availableRicerche sull\u27evoluzione del Lago Maggiore. Aspetti limnologici. Programma triennale 2013-2015. Campagna 2015 e rapporto triennale 2013-2015. Indagini sull\u27evoluzione del popolamento zooplanctonico: confronto con i dati pregressi anche alla luce delle mutate condizioni meteo-climatich
Indagini su DDT e sostanze pericolose nell\u27ecosistema del Lago Maggiore. Programma 2013-2015. Rapporto annuale 2015 e finale 2013-2015. Conclusioni
No full textNot availableConclusioni del volume "Indagini su DDT e sostanze pericolose nell\u27ecosistema del Lago Maggiore. Programma 2013-2015. Rapporto annuale 2015 e finale 2013-2015"
Contaminanti nel comparto ittico. Introduzione
No full textNot availableIndagini su DDT e sostanze pericolose nell\u27ecosistema del Lago Maggiore. Programma 2013-2015. Rapporto annuale 2015 e finale 2013-2015 - Contaminanti comparto ittico - introduzion
Arrive, survive and thrive: essential stages in the re-colonization and recovery of zooplankton in urban lakes in Sudbury, Canada
Get PDFThe recovery of lakes from severe, historical acid and metal pollution requires that colonists of extirpated species arrive, survive and subsequently thrive. We employed 40 year records from weekly to monthly crustacean zooplankton samples from Middle and Clearwater lakes near Sudbury, Canada, to identify the main mechanistic bottlenecks in this recovery process. While both lakes now have circum-neutral pH, acidity decreased more rapidly in Middle Lake because of past liming interventions, while Clearwater Lake, being larger and supporting more housing, likely receives more zooplankton colonists than Middle Lake. Community richness increased much faster in Middle Lake than in Clearwater Lake, at 1.6 vs 0.9 species decade-1, respectively. Richness has recovered in Middle Lake, when assessed against a target of 9-16 species collection-1 determined from regional reference lakes, but it has not yet recovered in Clearwater Lake. Species accumulation curves and a metric of annual persistence show that this difference is a product not of greater rates of species introduction into Middle Lake, but rather to their greater annual persistence once introduced. Greater annual persistence was associated with better habitat quality (i.e., lower acid and metal toxicity) in Middle Lake, particularly early in the record, and lower planktivore abundance, more recently. These results support a growing consensus that ecological recovery of zooplankton from acidification and metal pollution does not depend strongly on propagule introduction rates which are adequate, but rather on propagule persistence, in lake-rich, suburban landscapes such as those near Sudbury