523 research outputs found
Training a Convolutional Neural Network for Appearance-Invariant Place Recognition
Place recognition is one of the most challenging problems in computer vision,
and has become a key part in mobile robotics and autonomous driving
applications for performing loop closure in visual SLAM systems. Moreover, the
difficulty of recognizing a revisited location increases with appearance
changes caused, for instance, by weather or illumination variations, which
hinders the long-term application of such algorithms in real environments. In
this paper we present a convolutional neural network (CNN), trained for the
first time with the purpose of recognizing revisited locations under severe
appearance changes, which maps images to a low dimensional space where
Euclidean distances represent place dissimilarity. In order for the network to
learn the desired invariances, we train it with triplets of images selected
from datasets which present a challenging variability in visual appearance. The
triplets are selected in such way that two samples are from the same location
and the third one is taken from a different place. We validate our system
through extensive experimentation, where we demonstrate better performance than
state-of-art algorithms in a number of popular datasets
Floating millenial chronologies of Pinus in the Sierra de Gredos (Spain)
This research has been carried out by some members of the “History and Dynamics of the Vegetal Landscape” Research Group of the Technical University of Madrid (Spain). The team has been working on the flora, vegetation and dendrochronology of the Sierra de Gredos (Ávila, Spain) for the last 20 years. Recently, we have implemented a new research field focused on the study of megafossils. All this data set has allowed us to develop an interpretation of the dynamics of mountain pine forests in this region
The past distribution of pinus nigra arnold in northern iberia. Contribution from its macroremains.
The presence of Pinus nigra in central Spain, where its natural populations are very rare, has led to different interpretations of the current vegetation dynamics. Complementary to the available palynological evidence, macroremains provide local information of high taxonomic resolution that helps to reconstruct the palaeobiogeography of a given species. Here we present new macrofossil data from Tubilla del Lago, a small palaeolake located at the eastern part of the northern Iberian Meseta. We identified 17 wood samples and 71 cones on the basis of their wood anatomy and morphology, respectively. S ome of the fossil samples were radiocarbon dated (~4.230-3210 years cal BP). The results demonstrate the Holocene presence of P. nigra in the study area, where it is currently extinct. This evidence, together with other published palaeobotanical studies, indicates that the forests dominated by P. nigra must have had a larger importance on the landscape prior to the anthropogenic influence on the northern Iberian Meseta
Genetic and Swarm Algorithms for Optimizing the Control of Building HVAC Systems Using Real Data: A Comparative Study.
Buildings consume a considerable amount of electrical energy, the Heating, Ventilation,
and Air Conditioning (HVAC) system being the most demanding. Saving energy and maintaining
comfort still challenge scientists as they conflict. The control of HVAC systems can be improved by
modeling their behavior, which is nonlinear, complex, and dynamic and works in uncertain contexts.
Scientific literature shows that Soft Computing techniques require fewer computing resources
but at the expense of some controlled accuracy loss. Metaheuristics-search-based algorithms show
positive results, although further research will be necessary to resolve new challenging multi-objective
optimization problems. This article compares the performance of selected genetic and swarmintelligence-
based algorithms with the aim of discerning their capabilities in the field of smart buildings.
MOGA, NSGA-II/III, OMOPSO, SMPSO, and Random Search, as benchmarking, are compared
in hypervolume, generational distance, ε-indicator, and execution time. Real data from the Building
Management System of Teatro Real de Madrid have been used to train a data model used for the
multiple objective calculations. The novelty brought by the analysis of the different proposed dynamic
optimization algorithms in the transient time of an HVAC system also includes the addition,
to the conventional optimization objectives of comfort and energy efficiency, of the coefficient of
performance, and of the rate of change in ambient temperature, aiming to extend the equipment
lifecycle and minimize the overshooting effect when passing to the steady state. The optimization
works impressively well in energy savings, although the results must be balanced with other real
considerations, such as realistic constraints on chillers’ operational capacity. The intuitive visualization
of the performance of the two families of algorithms in a real multi-HVAC system increases
the novelty of this proposal.post-print888 K
Taxonomic composition of the Holocene forests of the northern of Spain, as determined from their macroremains
Eight sites distributed over a distance of some 400 km of the Cantabrian coast (northern Spain) provided 153 wood, 50 fruit and over 350 leaf remains belonging to the area’s Holocene forests. The high taxonomic precision with which these macroremains were identified (in many cases at the species level), plus the accurate information available regarding the original growth locations of these plants, provide new geobotanical insights into the history of northern Spain’s Atlantic forests. Radiocarbon dating of the wood samples showed the collected material to have lived between 8550 and 800 cal. BP. Analysis of the macroremains showed the deciduous mixed forests of the Holocene to contain a majority of Quercus robur and Corylus avellana, accompanied by Acer pseudoplatanus, Ulmus minor, Castanea sp., and hygro-thermophilous taxa (Arbutus, Laurus and Vitis vinifera). The remains of hygrophilous communities, dominated by Salix atrocinerea, Alnus glutinosa and Fraxinus sp., show these to have expanded during the Holocene. The absence of conifer macroremains is interpreted as reflecting the disappearance of Würmian conifer populations at the beginning of the Holocene. The different taxa (eg, Ilex spp. and V. vinifera) that survived the last glaciation in the refugia offered by Spain’s northern coast persisted in the same areas during the Holocene. A leaf sample of Ulmus minor dating to 3950 ± 120 cal. BP reveals for the first time the natural occurrence of this species on the northern coast of Spai
The value of leaf cuticle characteristics in the identification and classification of Iberian Mediterranean members of the genus Pinus
This study reports the value of leaf cuticle characteristics in the identification and classification of Iberian Mediterranean species of the genus Pinus (P. nigra subsp. salzmannii, P. pinaster, P. pinea and P. halepensis), with the aim of using these characters to identify isolated cuticles and stomata in palynology slides. Preparations were made of the cuticles of pine needles belonging to one natural Iberian population of each of the above species. A number of epidermal morphological characteristics were then recorded with the aim of distinguishing these species from one another. The structure of the stomatal complex (the shape and arrangement of the subsidiary cells) was different in each species. The aperture of the epistomatal chamber was significantly smaller in P. pinea than in the other species examined, and the variables recorded for the thickening of the guard cells provided relationships that clearly distinguished all four taxa. The width and length of the stomata and the upper woody lamellae, the central distance between the external limits of the medial lamellae borders and the length of the stem were the most useful variables in this respect. The present results contribute to the ongoing discussion regarding the taxonomic classification of the members of Pinus, and provide valuable clues for the identification of Iberian Mediterranean pine species from small pine needle fragments or isolated stomata. After validation of the present results for multiple populations, these results could also be used to help identify fossil leaf macroremains and the scattered/ isolated stomata commonly observed in palaeopalynological samples
Nuances matter: How fossil woody remains changed the interpretation of the vegetation in Iberia
Ejemplos de cómo los macrorrestos ayudan a mejorar la interpretación del paisaje vegetal de la península Ibéric
Lesson from the habitat suitability models to evaluate the environmental of Pinus nigra Arnold and Pinus sylvesris L. in the Iberian Peninsula
PREDICT POTENTIAL DISTRIBUTION. Spatial and temporal evolution of the species under different climate scenarios. Generation of habitat suitability models (HSM) high degree of uncertainty and limitations. The importance of their validation has been stressed. In this work we discuss the present potential distribution of P. sylvestris and P. nigra in the Iberian Peninsula by using MaxEnt, and evaluate the influence of the different environmental variables. Our intention is to select a set of environmental variables that explains better their current distribution, to achieve the most accurate and reliable models. Then we project them to the past climatic conditions (21 to 0 kyrs BP), to evaluate the outputs with existing palaeo-ecological data
Macrorremains evidence of anthropogenic recession of Pinus nigra Aiton in Northern Spain
The natural forest landscape of the Duero Basin in Spain¿s Northern Meseta is now reduced to small masses, its demise largely owed to the intense agricultural and stock-raising use made of its lands. The composition of the scant natural masses suggests that formations dominated by broadleaved species once occupied a much greater area. This idea has led to the believe that pine trees have few place within the natural dynamics of this area (Carrión and Fernández, 2009). However, P. pinaster Aiton and P.pinea L. on low-land sandy areas, P. sylvestris L. and P.uncinata Ramond ex DC on mountain high areas have been demonstrated to have played an important role during the Holocene (Franco et al., 2005; Rubiales et al., 2010). The abundant plant remains and moulds of pine wood and cones found on Northern Meseta peat bogs and travertines, now demonstrate its presence on mid-lands during the Quaternary until the last millenni
The long-term evolution of the Cantabrian landscapes and its possible role in the cappercaillie drama
Within the Iberian Peninsula, at the south-western boundary of its distribution area, the capercaillie is restricted to the Cantabrian and the Pyrenean Mountains. Cantabrian capercaillie Tetrao urogallus cantabricus has undergone a dramatic decline during the last three decades, as reported in the last Iberian Survey (Robles et al. 2006) and in previous issues of Grouse News (Bafiuelos et al., 2004, 2008). As a consequence, it is currently the only subspecies of capercaillie critically threatened worldwide. Although considerable efforts have been made to understand the reasons of this decline, the long-term ecology of this subspecies has received little attention, due probably to the absence of data in the palaeozoological records. Nevertheless, palaeoecological information based on their habitats can provide a useful insight that in the case of the Cantabrian Mountains offers a large body of data that covers the forest history of the last thousands of years
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