A case study on the optimization of Posidonia oceanica density interpolation, using a data set from a large meadow at Porto Conte Bay (NW Sardinia, Italy), is presented. Ordinary point kriging, cokriging and a weighted average based on inverse square distance were used to interpolate density data measured in 36 sampling stations. The results obtained from different methods were then compared by means of a leave‐one‐out cross‐validation procedure. The scale at which interpolation was carried out was defined on the basis of the Hausdorff dimension of the variogram. Optimizing spatial scale and data points search strategy allowed obtaining more accurate density estimates independently of the interpolation method. 相似文献
Proposed to both the French and the European Space Agency as one possible small mission, SPICE is a project for a dedicated small satellite for a near-IR spectroscopic all-sky survey. The instrument would cover the spectral range 1.8 - 3.6µm, possibly extended to 1.8 - 7µm, at a resolution of 100, with pixels of 1 arc-min. The excellent sensitivity (0.02 MJy sr-1) results from: i) the quasi-zero level of background due to the efficient passive cooling of the whole experiment; ii) the use of large format arrays; iii) the non-stop observing mode (drift-scanning). The spectral domain, complementing the one of ISO, partially opaque from the ground, is specially rich in spectral features tracing stars and all components of the Interstellar Medium (molecular, atomic and ionized gas, dust). With a cooling below 80 K of the focal instrument, then it becomes possible to consider doubling the spectral domain and to cover the whole 1.8 - 7µm range. 相似文献
The evolutionary status of hydrogen-poor stars is analyzed.Photoelectric observations of six objects are reported as a first step of a long-term project devoted to search for variability of a large sample of hydrogen-poor stars.The observed stars show phenomena of microvariability with an amplitude of the order of 0m. 1 or less.Two extreme helium stars have been examined: a period in the range of 0d.162-0d.164 has been found for BD+ 1002179, andP=0d.1079962 for BD+1303324.The mass-losing O subdwarf (sdO) BD+370 443 presents short-term fluctuations with a time-scale of several minutes and long-term variations on a scale of months. The standard sdO BD+750325 is probably non-variable, although light variations of very small amplitude (m0.03) with a time-scale of about 1 hr might be present. The high gravity sdO BD+2504655, which is very close to the white dwarf stage, also presents variability on a time-scale of about 13 minutes, and might be an analog of the recently discovered pulsating sdO, or hot white dwarf, PG 1159-035.The variability of the intermediate helium star HD 37776 is finally confirmed. 相似文献
A 6.8-magnitude earthquake that occurred on January 24, 2020, has been effective in Turkey’s eastern regions. The earthquake, with recorded peak ground acceleration (PGA) value of 0.292 g, caused the destruction or heavy damage of buildings, especially in the city center of Elaz?? province. The purpose of this paper was to share the results of detailed investigation in the earthquake-stricken area. Additionally, the causes of damages and failures observed in the buildings were compared to those that had occurred in previous earthquakes in Turkey. In this study, the damages observed in especially RC buildings as well as in masonry and rural buildings were summarized, the lessons learned were evaluated, and the results were interpreted with reference to Turkish earthquake codes. In the study, it was particularly emphasized why the building stock underwent such damage even though the buildings were exposed to earthquake acceleration well below the design acceleration values.
Summary A principal component analysis (PCA) based on a network including 179 pluviometric gauges is attempted in order to describe the main patterns governing precipitation in Catalonia (NE Spain). This PCA procedure is applied to the interstation covariance matrix and component loadings are then deduced from it and extensively interpreted. PCA results are used immediately after in a Davis and Kalkstein clustering process, leading to a rainfall division. The homogeneity of the different groups obtained is tested by means of the analysis of their spatial and temporal within-group variances.With 8 Figures 相似文献
Résumé Ce texte a pour but d'analyser la notion d'échelle, ou de niveau d'hétérogénéité, d'un phénomène géologique, à l'aide d'outils de morphologie mathématique tels que la «fonction intrinsèque» de la théorie des variables régionalisées de G. Matheron. Une première étude expérimentale montre comment les structures s'emboitent les unes dans les autres dans un dépôt sédimentaire comme le gisement de fer de Lorraine. Puis, en formulant théoriquement ces imbrications de structures, on montre comment les deux types de fonctions intrinsèques observés couramment, le type transitif et le type de wijsien se relient l'un à l'autre. Mais la morphologie mathématique ne peut pas dire pourquoi des structures gigognes en progression géométrique existent.
The objective of this paper is to analyze the concept of scale in a geological set. The mathematical tool used here is the intrinsic function of the regionalized variables' theory of G. Matheron. A first experimental step shows how the structures observed in the sedimentary ore deposit of Lorraine fit into one another. The next part describe theoretically this phenomenon. The theoretical models allow to synthesize the two types of usual intrinsic functions, type transitif and de wijsien. But mathematical morphology appears to be unable to explain why these structures exist.
Summary Catalonian daily precipitation patterns were obtained by means of S-mode Principal Component Analysis (PCA) applied to subsets
built up according to synoptic surface airflow. Daily data from November to April 1990–1994 from 45 raingauge sites in Catalonia
without missing data were used. Eight circulation classes for days in this period were considered. A Precipitation Activity
Index (PAI) was calculated for each station and class, leading to the determination of the highest activity regions for each
subset. In addition, we determined which circulation type produced most precipitation at each station of the network. Separate
PCAs were performed for each of the eight classes considered and the first four Varimax rotated solutions were interpreted
for each circulation type. The physical meaning of the rest of the factors were omitted as they were associated with local
behaviour. Finally, some concluding remarks on the cyclogenic properties of the Western Mediterranean Basin and the diversity
of the extracted patterns are presented and supported by the authors experience in forecasting in Catalonia.
Received February, 11, 1997 Revised May 23, 1997 相似文献
Summary Daily pluviometric records of 43 meteorological stations across the Iberian Peninsula have permitted a detailed analysis of
dry spell patterns for the period 1951–2000 by distinguishing daily amount thresholds of 0.1, 1.0, 5.0 and 10.0 mm/day. The
analyses are based on three annual series, namely the number of dry spells, N, the average dry spell length, L, and the extreme dry spell length, Lmax. First, the statistical significance of local trends for the annual series of N, L and Lmax has been investigated by means of the Mann-Kendall test and significant field trends have been established by means of Monte
Carlo simulations. Clear signs of negative field trends are detected for N (1.0 and 10.0 mm/day) and L (0.1 mm/day). Second, the Weibull model fits well the empirical distributions of dry spell lengths for all the rain gauges,
whatever the daily amount threshold, with a well ranged spatial distribution of their parameters u and k. On the basis of the Weibull distribution, return period maps for 2, 5, 10, 25 and 50 years have been obtained for dry spell
lengths with respect to the four daily threshold levels. While for 0.1 and 1.0 mm/day the longest dry spells are expected
at the south of the Iberian Peninsula, for 5.0 and 10.0 mm/day they are mostly detected at the southeast. Finally, the elapsed
time between consecutive dry spells has been analysed by considering the same rain amount thresholds and different dry spell
lengths at increasing intervals of 10 days. This analysis makes evident a significant negative field trend of the elapsed
time between consecutive dry spells of lengths ranging from 10 to 20 days for daily amount thresholds of 1.0, 5.0 and 10.0 mm/day.
Authors’ addresses: X. Lana, C. Serra, Departament de Física i Enginyeria Nuclear, ETSEIB, Universitat Politècnica de Catalunya,
Av. Diagonal 647 planta 11, 08028 Barcelona, Spain; M. D. Marínez, Departament de Física Aplicada, Universitat Politècnica
de Catalunya, 08028 Barcelona, Spain; A. Burgue?o, Departament de Meteorologia i Astronomia, Universitat de Barcelona, 08028
Barcelona, Spain; J. Martín-Vide, L. Gómez, Grup de Climatologia, Universitat de Barcelona, 08028 Barcelona, Spain. 相似文献