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101.
Vicente de P. Rodrigues da Silva Adelgicio F. Belo Filho Vijay P. Singh Rafaela S. Rodrigues Almeida Bernardo B. da Silva Inajá F. de Sousa 《水文科学杂志》2017,62(7):1029-1038
Using the Shannon entropy, the space–time variability of rainfall and streamflow was assessed for daily rainfall and streamflow data for a 10-year period from 189 stations in the northeastern region of Brazil. Mean values of marginal entropy were computed for all observation stations and entropy maps were then constructed for delineating annual and seasonal characteristics of rainfall and streamflow. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy as well as relative entropy for two sample stations. The marginal entropy values of rainfall and streamflow were higher for locations and periods with the highest amounts of rainfall. The entropy values were higher where rainfall was higher. This was because the probability distributions of rainfall and the resulting streamflow were more uniform and less skewed. The Shannon entropy produced spatial patterns which led to a better understanding of rainfall and streamflow characteristics throughout the northeastern region of Brazil. The total relative entropy indicated that rainfall and streamflow carried the same information content at annual and rainy season time scales. 相似文献
102.
Constantin Mildner Filippo Broggini Carlos Alberto da Costa Filho Johan O.A. Robertsson 《Geophysical Prospecting》2019,67(8):2085-2103
Imaging a target zone below a salt body can be challenging because large velocity contrasts in the overburden between the salt and surrounding sediments generate internal multiples, which interfere with primary reflections from the target level in the imaging process. This can lead to an erroneous interpretation of reflections in the sub-salt area if multiples are misinterpreted as primaries. The Marchenko redatuming method may enable imaging of the sub-salt target area where the effect of the multiply-scattering overburden is removed. This is achieved by creating a redatumed reflection response where virtual sources and receivers are located below the overburden using a macromodel of the velocity field and the surface reflection data. The accuracy of the redatumed data and the associated internal multiple removal, however, depends on the accurate knowledge of the source wavelet of the acquired reflection data. For the first time, we propose a method which can accurately and reliably correct the amplitudes of the reflection response in field data as required by the Marchenko method. Our method operates by iteratively and automatically updating the source function so as to cancel the most artefact energy in the focusing functions, which are also generated by the Marchenko method. We demonstrate the method on a synthetic dataset and successfully apply it to a field dataset acquired in a deep-water salt environment in the Gulf of Mexico. After the successful source wavelet estimation for the field dataset, we create sub-salt target-oriented images with Marchenko redatumed data. Marchenko images using the proposed source wavelet estimation show clear improvements, such as increased continuity of reflectors, compared to surface-based images and to conventional Marchenko images computed without the inverted source wavelet. Our improvements are corroborated by evidence in the literature and our own synthetic results. 相似文献
103.
Carlos José Freire Machado Maria Marlúcia Freitas Santiago Luiz Alberto Ribeiro Mendonça Horst Frischkorn Josué Mendes Filho 《Aquatic Geochemistry》2007,13(2):187-196
Flow modeling and hydrogeochemical inversion calculations were performed on the aquifer systems of the Crato-Juazeiro Graben
in the Araripe Sedimentary Basin of the Cariri Valley, Northeast Brazil, in order to assess aquifer interconnections through
an aquitard of the Araripe Plateau. Steady state hydraulic head numeric calculations with the finite difference method used
Modflow software with hydrologically based boundary conditions and a piezometric surface as initial condition. Hydrogeochemical
inversion with PHREEQC was performed for two water samples representing typical initial and final waters along the flow path.
Flow simulation shows that approximately 20% of all recharge water from the superior aquifer system passes through the Santana
aquitard reaching the middle aquifer system. Quantification of mineral dissolution/precipitation processes, ion exchange and
microbiological redox reactions taking place in the aquifer systems also indicates hydraulic interconnection of the superior
and middle aquifer systems through the Santana aquitard. 相似文献
104.
105.
João A. Lorenzzetti Jose L. Stech Wilson L. Mello Filho Arcilan T. Assireu 《Continental Shelf Research》2009
A data set of 199 sea surface temperature maps derived from the Advanced Very High Resolution Radiometer for the period 2000–2002 was processed to derive the position of the surface inshore thermal front of the Brazil Current (BCIF) in the SE Brazilian coastal and oceanic area. After the derivation of the position of the BC front for each image, the ensemble of digital frontal vectors was processed using the algorithm of frontal density (FD). For each 5′×5′ cell in the domain the calculated FD provided an index expressing the presence and persistence of the front in the area or the probability of finding the front in the region. In the paper we present the results of the FD analysis to get a better view of the space and time variability of the BC front in the region. The highest values of FD were in general observed close to or at the shelf break zone (between 200 and 1000 m isobaths). From 20°S to 23°S there is a tendency of BCIF to be positioned over the outer shelf, inshore of the 200 m isobaths. SE of Cape Sao Tome and S of Cape Frio it was observed a bimodal spatial distribution of highest FD caused by the presence of two semi-permanent frontal eddies. After moving offshore near Cape Frio, the BCIF tends to return to the shelf break zone south of 24°S probably due to a potential vorticity conservation mechanism. The position of the highest FD values calculated for different seasons confirms previous studies in that BCIF is closer to the coast during the summer and furthest offshore in the winter. Statistical analysis of the SST data gave for the BCIF an average SST gradient of 0.31°C km−1 with a standard deviation of 0.15°C km−1. A mean frontal width of 6 km was inferred from the average SST gradient and typical temperatures near the front at both sides, at outer shelf and in the BC itself. A Weibull probability density function can be fitted to describe the BCIF SST gradients with scale factor c=0.3460°C km−1 and shape factor k=2.1737. The BCIF SST gradient showed a seasonal variability with the smallest gradients in summer (~0.24 °C km−1) and the highest in autumn (~0.33 °C km−1). Using a three harmonic Fourier fit for the SST field near the BCIF, at the outer shelf and at interior of BC, it was possible to derive an analytical model for the time variability of the SST gradient of BCIF. 相似文献
106.
Application of Laser‐Induced Breakdown Spectroscopy and Hyperspectral Images for Direct Evaluation of Chemical Elemental Profiles of Coprolites
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Marco Aurélio Sperança Francisco Wendel Batista de Aquino Marcelo Adorna Fernandes Alejandro Lopez‐Castillo Renato Lajarim Carneiro Edenir Rodrigues Pereira‐Filho 《Geostandards and Geoanalytical Research》2017,41(2):273-282
This study demonstrates the application of laser‐induced breakdown spectroscopy (LIBS) and hyperspectral imaging to the investigation of coprolite and fossil samples. Solid samples from the Permian (seven coprolites and one fossil), Cretaceous (one coprolite) and Oligo‐Miocene (two coprolites) periods were directly analysed, and emission spectra from 186 to 1042 nm were obtained in several areas covering coprolite/fossil and rock material. Initial exploratory analyses were performed using principal component analysis with the data set normalised by the norm (Euclidean norm = 1). After identification and selection of emission lines of eleven elements (Al, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, P and Si), the signals were normalised again by the relative intensity of the selected element. Phosphorus was identified mainly in the coprolites, while K and Na were primarily found in the rock material. In several cases, there was a positive correlation between Ca and P. A sample from the Oligo‐Miocene series was also analysed using inductively coupled plasma‐optical emission spectrometry (ICP‐OES) (rock and coprolites were analysed separately). Based on the quantitative results from ICP‐OES, it was confirmed that the tendency was the same as that observed with the results obtained from LIBS directly in the solid sample. 相似文献
107.
G. Gioia G. Lacorata E. P. Marques Filho A. Mazzino U. Rizza 《Boundary-Layer Meteorology》2004,113(2):187-199
Relative dispersion in a neutrally stratified planetary boundary layer (PBL) is investigated by means of large-eddy simulations (LES). Despite the small extension of the inertial range of scales in the simulated PBL, our Lagrangian statistics turn out to be compatible with the Richardson t3 law for the average of square particle separation, where t is time. This emerges from the application of non-standard methods of analysis through which a precise measure of the Richardson constant was also possible. Its value is estimated as C2 0.5, in close agreement with recent experiments and three-dimensional direct numerical simulations. 相似文献
108.
A.G. Borrego C.V. Araujo A. Balke B. Cardott A.C. Cook P. David D. Flores M. Hmor-Vid W. Hiltmann W. Kalkreuth J. Koch C.J. Kommeren J. Kus B. Ligouis M. Marques J.G. Mendona Filho M. Misz L. Oliveira W. Pickel K. Reimer P. Ranasinghe I. Surez-Ruiz A. Vieth 《International Journal of Coal Geology》2006,68(3-4):151-170
The development of a qualifying system for reflectance analysis has been the scope of a working group within the International Committee for Coal and Organic Petrology (ICCP) since 1999, when J. Koch presented a system to qualify vitrinite particles according to their size, proximity to bright components and homogeneity of the surface. After some years of work aimed at improving the classification system using photomicrographs, it was decided to run a round robin exercise on microscopy samples. The classification system tested consists of three qualifiers ranging from excellent to low quality vitrinites with an additional option for unsuitable vitrinites. This paper reports on the results obtained by 22 analysts who were asked to measure random reflectance readings on vitrinite particles assigning to each reading a qualifier. Four samples containing different organic matter types and a variety of vitrinite occurrences have been analysed. Results indicated that the reflectance of particles classified as excellent, good or poor compared to the total average reflectance did not show trends to be systematically lower or higher for the four samples analysed. The differences in reflectance between the qualifiers for any given sample were lower than the scatter of vitrinite reflectance among participants. Overall, satisfactory results were obtained in determining the reflectance of vitrinite in the four samples analysed. This was so for samples having abundant and easy to identify vitrinites (higher plant-derived organic matter) as well as for samples with scarce and difficult to identify particles (samples with dominant marine-derived organic matter). The highest discrepancies were found for the organic-rich oil shales where the selection of the vitrinite population to measure proved to be particularly difficult. Special instructions should be provided for the analysis of this sort of samples. The certainty of identification of the vitrinite associated with the vitrinite reflectance values reported has been assessed through a reliability index which takes into account the number of readings and the coefficient of variation. The same statistical approach as that followed in the ICCP vitrinite reflectance accreditation program for single seam coals has been used for data evaluation. The results indicated low to medium dispersion for 17 out of 22 participants. This, combined with data from other sets of comparative analyses over a long period, is considered an encouraging result for the establishment of an accreditation program on vitrinite reflectance measurements in dispersed organic matter. 相似文献
109.
Cabral Victor Carvalho Reis Fábio Augusto Gomes Vieira D’Affonseca Fernando Mazo Lucía Ana dos Santos Corrêa Claudia Vanessa Veloso Vinicius Gramani Marcelo Fischer Ogura Agostinho Tadashi Lazaretti Andrea Fregolente Vemado Felipe Pereira Filho Augusto José dos Santos Claudia Cristina Lopes Eymar Silva Sampaio Rabaco Lis Maria Reoni do Carmo Giordano Lucilia Zarfl Christiane 《Natural Hazards》2021,108(3):3021-3043
Natural Hazards - Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies,... 相似文献
110.
Ludmila de Freitas Marcílio Vieira Martins Filho José Carlos Casagrande Ivanildo Amorim de Oliveira Luiz Gabriel da Silva 《Environmental Earth Sciences》2018,77(18):642
The evaluation of soil quality is an important tool for degradation monitoring and sustainable management implementation. The objective of this study was to measure physical and chemical soil properties to set soil quality and validate a model of soil quality indicator in latosols (oxisols) under sugarcane cropping and native forest. The study was carried out in the cities of Araras, Santa Ernestina, and Guariba in São Paulo State, Brazil. We collected 24 samples of disturbed and undisturbed soil at 0.0–0.10 m layer from three areas grown with sugarcane and neighboring locations under native woodland. We assessed the following soil properties: (a) chemical—pH in CaCl2, organic matter (OM), phosphorus (P), potassium (K+), calcium (Ca2+), magnesium (Mg2+), potential acidity (H?+?Al), aluminum (Al3+), and sulfur (S); (b) physical—macro- and microporosity, soil bulk density (Ds), aggregate stability, mean weight diameter (MWD), rill (Kr) and interrill (Ki) global erodibility, shear stress (τc), and magnetic susceptibility (MS). Data underwent multivariate statistics to identify the properties that denote soil quality and to set their weights within the functions of soil quality indicator (SQI). This study showed that the multivariate analysis was efficient in determining which physical and chemical properties were most sensitive, of which we can mention total sand, MS, clay, microporosity, Mg, Ca, pH, and OM. We can therefore conclude that the quality indicators of soils grown with sugarcane were lower than those under forest were, showing the need for adoption of conservation management practices. 相似文献