Search results for "Temporal"
showing 10 items of 1095 documents
Classification of spatio-temporal point pattern in the presence of clutter using K-th nearest neighbour distances
2019
In a point process spatio-temporal framework, we consider the problem of features detection in the presence of clutters. We extend the methodology of Byers and Raftery (1998) to the spatio-temporal context by considering the properties of the K-th nearest-neighbour distances. We make use of the spatio-temporal distance based on the Euclidean norm where the temporal term is properly weighted. We show the form of the probability distributions of such K-th nearest-neighbour distance. A mixture distribution, whose parameters are estimated with an EM algorithm, is used to classify points into clutters or features. We assess the performance of the proposed approach with a simulation study, togeth…
Dynamic Community Discovery Method Based on Phylogenetic Planted Partition in Temporal Networks
2022
As most of the community discovery methods are researched by static thought, some community discovery algorithms cannot represent the whole dynamic network change process efficiently. This paper proposes a novel dynamic community discovery method (Phylogenetic Planted Partition Model, PPPM) for phylogenetic evolution. Firstly, the time dimension is introduced into the typical migration partition model, and all states are treated as variables, and the observation equation is constructed. Secondly, this paper takes the observation equation of the whole dynamic social network as the constraint between variables and the error function. Then, the quadratic form of the error function is minimized…
[ 18 F]Fluoroethylflumazenil: a novel tracer for PET imaging of human benzodiazepine receptors
2001
5-(2'-[18F]Fluoroethyl)flumazenil ([18F]FEF) is a fluorine-18 labelled positron emission tomography (PET) tracer for central benzodiazepine receptors. Compared with the established [11C]flumazenil, it has the advantage of the longer half-life of the fluorine-18 label. After optimisation of its synthesis and determination of its in vitro receptor affinities, we performed first PET studies in humans. PET studies in seven healthy human volunteers were performed on a Siemens ECAT EXACT whole-body scanner after injection of 100-280 MBq [L8F]FEF. In two subjects, a second PET scan was conducted after pretreatment with unlabelled flumazenil (1 mg or 2.5 mg i.v., 3 min before tracer injection). A t…
A pre-processing and network analysis of GPS tracking data
2020
Global Positioning System (GPS) devices afford the opportunity to collect accurate data on unit movements from temporal and spatial perspectives. With a special focus on GPS technology in travel surveys, this paper proposes: (1) two algorithms for the pre-processing of GPS data in order to deal with outlier identification and missing data imputation; (2) a clustering approach to recover the main points of interest from GPS trajectories; and (3) a weighted-directed network, which incorporates the most relevant characteristics of the GPS trajectories at an aggregate level. A simulation study shows the goodness-of-fit of the imputation data algorithm and the robustness of the clustering algori…
Applied Intertemporal Optimization
2009
This textbook provides all tools required to easily solve intertemporal optimization problems in economics, finance, business administration and related disciplines. The focus of this textbook is on 'learning through examples' and gives a very quick access to all methods required by an undergraduate student, a PhD student and an experienced researcher who wants to explore new fields or confirm existing knowledge. Given that discrete and continuous time problems are given equal attention, insights gained in one area can be used for learning solutions methods more quickly in other contexts. This step-by-step approach is especially useful for the transition from deterministic to stochastic wor…
Temporal drivers of liking
2013
Abstract Generally liking is measured overall but is likely to vary over the food intake, like sensory perception. Replacing the attributes in Temporal Dominance of Sensations (TDS) by the categories of a usual ordinal liking scale makes it possible to monitor liking changes while eating a product (Sudre et al., 2012). This methodology allows for a better understanding of the influence of temporal dominance of sensations on liking and liking evolution over the time of product intake. Thus, it is possible to associate hedonic temporal data and descriptive temporal data (TDS profiles), which would identify drivers of liking, that is attributes which, when cited as dominant, would lead to a de…
Modelización de la función de covarianza en procesos espacio-temporales : análisis y aplicaciones
2008
Desde sus orígenes durante la segunda mitad del siglo XX hasta la actualidad ha quedado suficientemente demostrada la validez de las técnicas geoestadísticas para el estudio de todo tipo de procesos naturales que se manifiestan sobre localizaciones espaciales. Durante los últimos años del siglo pasado y principios de este se observa en la literatura especializada una creciente demanda de técnicas estadísticas espacio-temporales que generalicen los procedimientos meramente espaciales para fenómenos espaciales de los que se conoce su evolución temporal. Es especialmente reseñable las numerosas aportaciones realizadas por los investigadores para la construcción de funciones de covarianza espac…
Functional principal component analysis for multivariate multidimensional environmental data
2015
Data with spatio-temporal structure can arise in many contexts, therefore a considerable interest in modelling these data has been generated, but the complexity of spatio-temporal models, together with the size of the dataset, results in a challenging task. The modelization is even more complex in presence of multivariate data. Since some modelling problems are more natural to think through in functional terms, even if only a finite number of observations is available, treating the data as functional can be useful (Berrendero et al. in Comput Stat Data Anal 55:2619–2634, 2011). Although in Ramsay and Silverman (Functional data analysis, 2nd edn. Springer, New York, 2005) the case of multiva…
Spatio-Temporal Analysis of Constitutive Exocytosis in Epithelial Cells
2006
Exocytosis is an essential cellular trafficking process integral to the proper distribution and function of a plethora of molecules, including transporters, receptors, and enzymes. Moreover, incorrect protein targeting can lead to pathological conditions. Recently, the application of evanescent wave microscopy has allowed us to image the final steps of exocytosis. However, spatio-temporal analysis of fusion of constitutive vesicular traffic with the plasma membrane has not been systematically performed. Also, the spatial sites and times of vesicle fusion have not yet been analyzed together. In addition, more formal tests are required in testing biological hypotheses, rather than visual insp…
Using genetic markers to unravel the origin of birds converging towards pre-migratory sites
2018
AbstractIdentifying patterns of individual movements in spatial and temporal scales can provide valuable insight into the structure of populations and the dynamics of communities and ecosystems. Especially for migrating birds, that can face a variety of unfavorable conditions along their journey, resolving movements of individuals across their annual cycle is necessary in order to design better targeted conservation strategies. Here, we studied the movements of a small migratory falcon, the Lesser Kestrel (Falco naumanni), by genetically assigning feathers from individuals of unknown origin that concentrate in large roosts during the pre-migratory period. Our findings suggest that birds fro…