Search results for "spatio-temporal"
showing 10 items of 119 documents
Thermalization and condensation in an incoherently pumped passive optical cavity
2011
International audience; We study theoretically and numerically the condensation and the thermalization of classical optical waves in an incoherently pumped passive Kerr cavity. We show that the dynamics of the cavity exhibits a turbulent behavior that can be described by the wave turbulence theory. A mean-field kinetic equation is derived, which reveals that, in its high finesse regime, the cavity behaves essentially as a conservative Hamiltonian system. In particular, the intracavity turbulent field is shown to relax adiabatically toward a thermodynamic equilibrium state of energy equipartition. As a consequence of this effect of wave thermalization, the incoherent optical field undergoes …
Sensor Fusion Combining 3-D and 2-D for Depth Data Enhancement
2012
Time-of-Flight (ToF) cameras are known to be cost-efficient 3-D sensing systems capable of providing full scene depth information at a high frame rate. Among many other advantages, ToF cameras are able to provide distance information regardless of the illumination conditions and with no texture dependency, which makes them very suitable for computer vision and robotic applications where reliable distance measurements are required. However, the resolution of the given depth maps is far below the resolution given by standard 2-D video cameras which, indeed, restricts the use of ToF cameras in real applications such as those for safety and surveillance. In this thesis, we therefore investigate…
Représenter les dynamiques urbaines de Tours antique et médiéval
2012
ToToPI, for Topography of Tours Pre-Industrial, is a GIS for studying of the city of Tours (France) in large time span. The aim of this paper is to explain how GIS is used for historical data processing to understand time-space dynamics. The proposed principle for understanding the urban dynamic is based on considering the town as a set of complex objects, taking a systemic approach. The town system used to study the urban fabric over large time spans is composed of three sub-systems relating to historical objects from the level of the excavation to that of the former urban space: function (social use), space (location, surface area and morphology) and time (dating, duration and chronology)…
Walking tourism in Malaga: a pilot survey to explore tourism behaviours with a GPS approach
2018
Walking tourism in urban destinations can be defined as a sequence of day visits and/or a sequence of walking tours. In this work, GPS tracking data on spatio-temporal behaviour of walking tourists in Malaga are reported as case study. Malaga is a booming tourist destination characterized by a city centre, particularly suitable for a pedestrian visit. From 22nd January to 19th March 2018 for a total period of 41 days, a survey was carried out with a specific protocol: 103 interviews were conducted and 101 GPS valid tracks were collected. Walking tourists were systematically sampled, starting from the population of all tourists staying in the surveying day at some selected hotels in the city…
Temporal incoherent solitons supported by a defocusing nonlinearity with anomalous dispersion
2012
http://pra.aps.org/; International audience; We study temporal incoherent solitons in noninstantaneous response nonlinear media. Contrarily to the usual temporal soliton, which is known to require a focusing nonlinearity with anomalous dispersion, we show that a highly noninstantaneous nonlinear response leads to incoherent soliton structures which require the inverted situation: In the focusing regime (and anomalous dispersion) the incoherent wave packet experiences an unlimited spreading, whereas in the defocusing regime (still with anomalous dispersion) the incoherent wave packet exhibits a self-trapping. These counterintuitive results are explained in detail by a long-range Vlasov formu…
Using Semantic Web Technologies to Follow the Evolution of Entities in Time and Space
2013
International audience; In this paper we present the "continuum model". Our work follows a "perdurantism" approach and is designed to handle dynamic phenomena extending the 4D-fluent with the use of semantic web technologies. In our approach we represent dynamic entities as constituted by timeslices each with semantic, geometric, temporal and identity components. Our model is able to link the diverse representations of an entity and allows the inference of qualitative information from quantitative one. The inference results are later added to the ontology in order to improve knowledge about the phenomenon. The model has been implemented using OWL and SWRL. Our preliminary results are promis…
Representing and Reasoning for Spatiotemporal Ontology Integration
2004
International audience; The World-Wide Web hosts many autonomous and heterogeneous information sources. In the near future each source may be described by its own ontology. The distributed nature of ontology development will lead to a large number of local ontologies covering overlapping domains. Ontology integration will then become an essential capability for effective interoperability and information sharing. Integration is known to be a hard problem, whose complexity increases particularly in the presence of spatiotemporal information. Space and time entail additional problems such as the heterogeneity of granularity used in representing spatial and temporal features. Spatio-temporal ob…
Multidimensional Land Cover Change Analysis using Vector Change and Land Cover Taxonomies
2015
International audience; Around the world, land cover changes occur due to natural and anthropogenic factors. In many cases, the consequences of anthropogenic interventions are unexpected. In order for scientists and policy makers to identify land cover change processes of interest, it is necessary suitable tools for early and efficient analysis of land cover data. In our research, we present a data model that makes use of semantic web technologies to manage a hierarchical structure of land cover types. Using this approach, it is possible to manage the land cover information at different levels of abstraction. In our research, we use a Change Vector Analysis approach to represent the land co…
The spatio-temporal semantics from a perdurantism perspective
2013
International audience; In this paper we present the "continuum model". Our work follows a "perdurantism" approach and is designed to handle dynamic phenomena extending the 4D-fluent with the use of semantic web technologies. In our approach we represent dynamic entities as constituted by time slices each with semantic, geometric and temporal components. Our model is able to link the diverse representations of an entity and allows the inference of qualitative information from quantitative one. The inference results are later added to the ontology in order to enhance the knowledge base. The model has been implemented using OWL and SWRL. Our preliminary results are promising and we plan to fu…
Past and future spatio-temporal variability of rainfall of the Bani catchment in West Africa.
2011
6 pages; International audience; Since 1970, on the Bani, main tributary of the upper Niger, annual discharges have decreased by 69% while annual rainfall has decreased only by 15% to 25% over the catchment. Among the possible causes for this very strong discharge decrease changes of precipitation patterns must be explored. Four different methods of spatial interpolation of rainfall fields were compared on intra-seasonal indices (number of dry days, the dry spells, EDI, SPI, etc.) for the period 1950-2006. This study was also conducted on simulated pluviometric data generated by a regional climatic model (WRF) for the 2032-2041 period. The pluviometric deficit is explained by a conjunction …