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1.
In this paper a semiparametric approach is introduced to decompose an ARFIMA model in the long memory and short memory unobserved components. The procedure is based on the DECOMEL method which produces a statistical decomposition by minimizing the Euclidean distance between the spectrum of the aggregated series and the sum of the parametric spectra of the components. The extension to long memory stationary models is achieved defining an approximate model where the fractional operator is replaced by the ratio of two polynomials of order one. The feasibility and performance of the proposed procedure are discussed through a case study. 相似文献
2.
Estimation of residual fluxes in estuarine cross sections is a very important procedure to establish, among others aspects, residence time of contaminants, circulation pattern, and sediment transport dynamics. However, the analytical procedure to obtain such values is not trivial and is presented in detail, demonstrating the importance of the grid-cell area as a weighting element in the calculation of spatial averages. The procedure is tested with four different grid designs and it is shown that grids with proportional columns and rows are the only ones that do not introduce statistical noise in the estimation of the residual fluxes. The four designs are also tested with data from a cross section of the Bahía Blanca Estuary (Argentina), results again show that the proportional columns and rows grid provide the best approach in calculating residual fluxes. 相似文献
3.
Allessandro Piccolo Riccardo Spaccini Rolf Nieder Joerg Richter 《Climatic change》2004,67(2-3):329-343
In a long-term (one year) experiment, a sandy Podzol and a silty-loamy Loess soil were treated with labile (polysaccharides, AG) and stable (mature compost, CMP, and two humic acids from compost, HAC, and lignite, HAL) organic matter and the organic carbon (OC) lost by mineralization was periodically evaluated. The stable materials alone induced a significant reduction of OC losses in Podzol CMP <, HAL, <, HAC, Control), whereas the same treatments, except for CMP, produced an OC loss larger than control in Loess. This was attributed to the diverse textural and physical status of the two soils. The added stable organic matter became protected in the Podzol soil within the aggregates formed by the interaction with the coarse inorganic phase, while it was more easily decomposed in the Loess soils due to the strength of the native humic-clay complexes. In both soils, when the stable organic materials were mixed with polysaccharides (AG), the OC losses from this labile fraction were significantly reduced, being CMP more OC sequestering than HAC and HAL, in the order. These results confirmed that labile organic matter in soils can be protected from biodegradation by repartition into the hydrophobic domains of the stable, humified organic matter. This study suggests that mature compost and humic acids may usefully integrate management practices aimed to sequester organic carbon in soils. 相似文献
4.
We studied the physicochemical and molecular changes of compost during its maturation within 60, 90, and 150 days after the composting process. Moreover, the changes were also studied in compost residues after sequential removal of lipidic compounds. Infrared DRIFT spectrometry and 13C‐CPMAS‐NMR spectroscopy indicate that the molecular composition of compost changes dramatically during the stabilization period. The most decomposable components, mainly represented by bioavailable lipidic and peptidic structures, were progressively mineralized passing from 60 days to longer periods of compost stabilization. At increasing maturity stages, the composition of organic matter underwent a progressive enrichment in stable hydrophobic and ligno‐cellulosic material. The sequential extraction of lipidic compounds allowed an improved characterization of substrates and confirmed the outlined progressive transformation of compost. Compost may well be chosen on the basis of selected characteristics for environmental applications. 相似文献
5.
Guillermo R. Angeles Gerardo M. E. Perillo M. Cintia Piccolo Jorge O. Pierini 《Geomorphology》2004,57(3-4):263-274
The fractal dimension (D) was estimated for nine tidal channels depicted in thematic mapper (TM) Landsat-5 imagery to derive information about the degree of geomorphological control on a tidal channel network characteristic of the Bahía Blanca Estuary (Argentina). Two methods, box counting and contiguity, were used to estimate fractal dimensions for each tidal channel. All channels produced D values close to 1, meaning that they are self-affine fractal features. However, these fractal dimensions do not represent the meandering pattern complexity characteristic of the tidal channels analysed. Although both methods allowed for estimation of D, the contiguity method showed that three of the channels actually are not fractal but have sinusoidal characteristics, a condition that was not detected by the former method. 相似文献
6.
Zunino Josefina Alfonso María Belén Vitale Alejandro José Piccolo María Cintia 《Water Resources》2021,48(4):614-623
Water Resources - With conventional monitoring at low-frequency, biological responses to weather-related events are missed. In this paper, we examine the chlorophyll-a concentrations in a shallow... 相似文献
7.
Paula D. Pratolongo Gerardo M.E. Perillo M. Cintia Piccolo 《Estuarine, Coastal and Shelf Science》2010
This study was carried out at the Bahía Blanca Estuary, Argentina, at the seaward edge of a saltmarsh. The saltmarsh-mudflat boundary in the study area shows sediment deposits at a higher elevation immediately seaward of the saltmarsh edge. We compared field determinations of water velocity, bed shear stress, wind wave conditions and variations of the bed elevation in the mudflat and within the Spartina alterniflora canopy at the seaward edge of a saltmarsh, and we evaluated the relative role of vegetation in the observed morphology. A mud deposition event that raised bed elevation in more than 5 cm occurred during the study period, with TSS concentrations > 500 mg l−1, but simultaneous measurements performed on the bed levels confirmed that the sediments deposited did not originate from local resuspension within the edge of the canopy. In similar tidal cycles in terms of local wave activity and bed shear stresses at the sampling site, deposition occurred only with winds aligned with the azimuth of the Canal Principal, reaching a maximum fetch of more than 20 km in front of the sampling site. 相似文献
8.
A. Merlotto G. R. Bértola F. I. Isla L. C. Cortizo M. C. Piccolo 《Environmental Earth Sciences》2014,71(3):1213-1225
The short and medium-term coastal evolution of Necochea Municipality, Buenos Aires province (Argentina) was studied. The medium-term evolution study was based on aerial photographs from 1967 and 1984, and satellite images from 2004, using the dune or cliff toe as coastline indicator. The short-term evolution was studied from February 2006 to December 2009 by means of seasonal beach profiles and sediment sampling. Results showed that in the medium-term at Necochea, the coastline has remained stable or has advanced. Whereas in the short-term, the analysis has evidenced incipient erosion processes. On the other hand, at Quequén the retreat of the coastline and the negative sedimentary balances (medium and short-term) are clearly indicating an accentuated erosion process. The different degrees of coastal erosion are related in part to beach vulnerability to wave storms but mainly to anthropogenic actions, which have affected the beach sediment supply. These results evidence the necessity to develop a coastal management programme. 相似文献
9.
A two-dimensional planetary boundary-layer model is employed to simulate numerically observed temperature and humidity profiles of an airflow over the Argentine continental shelf. Predicted profiles satisfactorily agree with observed ones which are characterized by a stable boundary layer. 相似文献
10.