Search results for "kr"

UBVRI photometry of NGC 2422

2003

We present UBVRI photometry of the open cluster NGC 2422 (age~10^8^yr) down to a limiting magnitude V=~19. These data are used to derive the Luminosity and Mass Functions and to study the cluster spatial distribution. By considering the color-magnitude diagram data and adopting a representative cluster main sequence, we obtained a list of candidate cluster members based on a photometric criterion. Cone search capability for table J/A+A/404/927/table4 (Astrometric/photometric catalog of candidate members of the open cluster NGC 2422)

Medicīna (Latvijas Universitātes Raksti; 812 sēj.)  

2016

Jaunlatviešu pedagoģiskais devums vēsturiskā un mūsdienu skatījumā

2018

Maģistra darba mērķis ir izpētīt jaunlatviešu pedagoģiskās idejas un noskaidrot to aktualitāti mūsdienu pirmsskolas pedagoģiskā procesā Latvijā, meklējot atbildi uz jautājumu: kādas ir jaunlatviešu pedagoģiskās atziņas, kuras ir nozīmīgas mūsdienu pirmsskolas pedagoģiskā procesā. Pētījuma bāzi veido Ausekļa autordarbs “Paidagoģiskā gadagrāmata”, Ata Kronvalda kopotie raksti un runas, Krišjāņa Valdemāra raksti, darbi par Ausekli, Krišjāni Valdemāru un Ati Kronvaldu, VISC pirmsskolas izglītības mācību satura programma. Darba teorētiskajā daļā sniegts ieskats politiskā, ekonomiskā un sociālā situācijā Latvijā 19. gadsimtā, izvēlēto jaunlatviešu dzīves gājumā, viņu personības veidošanos ietekmē…

Improving spatial temperature estimates by resort to time autoregressive processes

2012

Temperature estimation methods usually involve regression followed by kriging of residuals (residual kriging). Despite the performance of such models, there is invariably a residual which is not necessarily unpredictable because it may still be correlated in time. We set out to analyse such residuals through resort to autoregressive processes. It is shown that the optimal period varies depending on whether it is identified by functions of the form resd = f(resd−1, resd−2, ..., resd−p) or by partial correlations. Autoregressive processes significantly improve estimates, which are evaluated by cross-validations. Finally, the two following points are discussed: (1) the assumptions of the autor…

Temperature interpolation by local information ; the example of France

2010

International audience; Methods of interpolation, whether based on regressions or on kriging, are global methods in which all the available data for a given study area are used. But the quality of results is affected when the study area is spatially very heterogeneous. To overcome this difficulty, a method of local interpolation is proposed and tested here with temperature in France. Starting from a set of weather stations spread across the country and digitized as 250 m-sided cells, the method consists in modelling local spatial variations in temperature by considering each point of the grid and the n weather stations that are its nearest neighbours. The procedure entails a series of steps…

Gaussian Process Sensitivity Analysis for Oceanic Chlorophyll Estimation

2017

Source at https://doi.org/10.1109/JSTARS.2016.2641583. Gaussian process regression (GPR) has experienced tremendous success in biophysical parameter retrieval in the past years. The GPR provides a full posterior predictive distribution so one can derive mean and variance predictive estimates, i.e., point-wise predictions and associated confidence intervals. GPR typically uses translation invariant covariances that make the prediction function very flexible and nonlinear. This, however, makes the relative relevance of the input features hardly accessible, unlike in linear prediction models. In this paper, we introduce the sensitivity analysis of the GPR predictive mean and variance functions…

Spatiotemporal modeling and prediction of solar radiation

2003

[1] The radiation budget in the Earth-atmosphere system is what drives Earth's climate, and thus measurements of this balance are needed to improve our knowledge of Earth's climate and climate change. In the present paper we focus on the analysis of the surface shortwave radiation budget (SSRB), which is the amount of energy in the solar region of the electromagnetic spectrum (0.2–4.0 μm) absorbed at the surface. The SSRB has to be modeled from the surface to the top of the atmosphere, jointly with information about the state of the atmosphere and the surface. These data come from satellites orbiting the Earth and are often missing or disturbed. Its interest is not only at global scales; ra…

Seasonal precipitation interpolation at the Valencia region with multivariate methods using geographic and topographic information

2009

The spatial pattern of precipitation is a complex variable that strongly depends on other geographic and topographic factors. As precipitation is usually known only at certain locations, interpolation procedures are needed in order to predict this variable in other regions. The use of multivariate interpolation methods is usually preferred, as secondary variables—generally derived using GIS tools—correlated with precipitation can be included. In this paper, a comparative study on different univariate and multivariate interpolation methodologies is presented. Our study area is centred in the region of Valencia, located to the eastern Spanish Mediterranean coast. The followed methodology can …

RADIONUCLIDE CONCENTRATIONS IN AIR PARTICULATE AT PALERMO (ITALY) FOLLOWING FUKUSHIMA ACCIDENT

2012

Following the Fukushima accident, a series of samplings were carried out with a daily frequency to detect the arrival of radioactive contamination in air at Palermo (Italy) and to follow its evolution during the time. Air particulate collection was performed by suction of atmospheric air through cellulose filter paper by means of a high-volume air sampler (∼15 000 m(3) d(-1)). Spectrometric analysis of the filters highlights the presence of (131)I, (134)Cs, (137)Cs and, only for a few samples, traces of (132)Te-(132)I and (136)Cs. Maximum airborne concentrations were 883 μBq m(-3) for (131)I (only particulate), 81 μBq m(-3) for (137)Cs and 70 μBq m(-3) for (134)Cs. From a dose to population…

First-principles nonequilibrium Green's-function approach to transient photoabsorption: Application to atoms

2015

We put forward a first-principle NonEquilibrium Green's Function (NEGF) approach to calculate the transient photoabsorption spectrum of optically thin samples. The method can deal with pump fields of arbitrary strength, frequency and duration as well as for overlapping and nonoverlapping pump and probe pulses. The electron-electron repulsion is accounted for by the correlation self-energy, and the resulting numerical scheme deals with matrices that scale quadratically with the system size. Two recent experiments, the first on helium and the second on krypton, are addressed. For the first experiment we explain the bending of the Autler-Townes absorption peaks with increasing the pump-probe d…