Uncertainty quantification in numerical simulation of particle-laden flows     

Gabriel M. Guerra  Souleymane Zio  Jose J. Camata  Jonas Dias  Renato N. Elias  Marta Mattoso  Paulo L. B. Paraizo  Alvaro L. G. A. Coutinho  Fernando A. Rochinha 《Computational Geosciences》2016,20(1):265-281

Numerical models can help to push forward the knowledge about complex dynamic physical systems. Modern approaches employ detailed mathematical models, taking into consideration inherent uncertainties on input parameters (phenomenological parameters or boundary and initial conditions, among others). Particle-laden flows are complex physical systems found in nature, generated due to the (possible small) spatial variation on the fluid density promoted by the carried particles. They are one of the main mechanisms responsible for the deposition of sediments on the seabed. A detailed understanding of particle-laden flows, often referred to as turbidity currents, helps geologists to understand the mechanisms that give rise to reservoirs, strategic in oil exploration. Uncertainty quantification (UQ) provides a rational framework to assist in this task, by combining sophisticated computational models with a probabilistic perspective in order to deepen the knowledge about the physics of the problem and to access the reliability of the results obtained with numerical simulations. This work presents a stochastic analysis of sediment deposition resulting from a turbidity current considering uncertainties on the initial sediment concentrations and particles settling velocities. The statistical moments of the deposition mapping, like other important features of the currents, are approximated by a Sparse Grid Stochastic Collocation method that employ a parallel flow solver for the solution of the deterministic problems associated to the grid points. The whole procedure is supported and steered by a scientific workflow management engine designed for high performance computer applications.  相似文献   

Quantitative risk assessment of slope hazards along a section of railway in the Canadian Cordillera—a methodology considering the uncertainty in the results   总被引：1，自引：0，他引：1  

Renato Macciotta  C. Derek Martin  Norbert R. Morgenstern  David M. Cruden 《Landslides》2016,13(1):115-127

Railway alignments through the Canadian Cordillera are constantly exposed to slope instabilities. Proactive mitigation strategies have been in place for a few decades now, and instability record keeping has been recognized as an important aspect of them. Such a proactive strategy has enhanced the industry’s capacity to manage slope risks, and some sections have been recognized as critical due to the frequency of instabilities. At these locations, quantification of the risks becomes necessary. Risk analysis requires knowledge of some variables for which statistical data are scarce or not available, and elicitation of subjective probabilities is needed. A limitation of such approaches lies in the uncertainty associated to those elicited probabilities. In this paper, a quantitative risk analysis is presented for a section of railway across the Canadian Cordillera. The analysis focused on the risk to life of the freight train crews working along this section. Upper and lower bounds were elicited to cope with the uncertainties associated with this approach. A Monte Carlo simulation technique was then applied to obtain the probability distribution of the estimated risks. The risk probability distribution suggests that the risk to life of the crews is below previously published evaluation criteria and within acceptable levels. The risk assessment approach proposed focuses on providing a measure of the uncertainty associated with the estimated risk and is capable of handling distributions that cover more than two orders of magnitude.  相似文献   

Cr and Zn biosorption by <Emphasis Type="Italic">Aspergillus niger</Emphasis>     

Maria do Socorro Vale  Ronaldo Ferreira do Nascimento  Renato Carrhá Leitão  Sandra Tédde Santaella 《Environmental Earth Sciences》2016,75(6):462

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A conceptual framework for the integral management of marine protected areas     

Celia Ojeda-Martínez  Francisca Giménez Casalduero  Just T. Bayle-Sempere  Carmen Barbera Cebrián  Carlos Valle  Jose Luis Sanchez-Lizaso  Aitor Forcada  Pablo Sanchez-Jerez  Pablo Martín-Sosa  Jesús M. Falcón  Fuensanta Salas  Mariagrazia Graziano  Renato Chemello  Ben Stobart  Pedro Cartagena  Angel Pérez-Ruzafa  Fréderic Vandeperre  Elisabeth Rochel  Serge Planes  Alberto Brito 《Ocean & Coastal Management》2009,52(2):89-101

A general conceptual framework for the management of marine protected areas (MPAs) was developed. The driver-pressure-state-impacts-response (DPSIR) framework was used to determine the elements affecting MPAs. The developed evaluation framework helped to select an appropriate suite of indicators to support an ecosystem approach, an assessment of the MPAs functioning and policy decisions. Gaps derived from the management and policy responses in the MPAs were also outlined. It was concluded that the DPSIR framework can help to simplify the complexity of MPA management. This document is a tool for policy makers, scientists and general public on the relevance of indicators to monitor changes and MPAs management.  相似文献   

Neoproterozoic glacial dynamics revealed by provenance of diamictites of the Bebedouro Formation, São Francisco Craton, Central Eastern Brazil     

Felipe Torres Figueiredo  Renato Paes de Almeida  Eric Tohver  Marly Babinski  Dunyi Liu  Christopher Mark Fanning 《地学学报》2009,21(5):375-385

One of the main questions on Neoproterozoic geology regards the extent and dynamics of the glacial systems that are recorded in all continents. We present evidence for short transport distances and localized sediment sources for the Bebedouro Formation, which records Neoproterozoic glaciomarine sedimentation in the central-eastern São Francisco Craton (SFC), Brazil. New data are presented on clast composition, based on point counting in thin section and SHRIMP dating of pebbles and detrital zircon. Cluster analysis of clast compositional data revealed a pronounced spatial variability of clast composition on diamictite indicating the presence of individual glaciers or ice streams feeding the basin. Detrital zircon ages reveal distinct populations of Archean and Palaeoproterozoic age. The youngest detrital zircon dated at 874 ± 9 Ma constrains the maximum depositional age of these diamictites. We interpret the provenance of the glacial diamictites to be restricted to sources inside the SFC, suggesting deposition in an environment similar to ice streams from modern, high latitude glaciers.  相似文献   

An integrated model simulating the initiation and motion of earthquake and rain induced rapid landslides and its application to the 2006 Leyte landslide   总被引：10，自引：7，他引：3  

Kyoji?SassaEmail author  Osamu?Nagai  Renato?Solidum  Yoichi?Yamazaki  Hidemasa?Ohta 《Landslides》2010,7(3):219-236

A gigantic rapid landslide claiming over 1,000 fatalities was triggered by rainfalls and a small nearby earthquake in the Leyte Island, Philippines in 2006. The disaster presented the necessity of a new modeling technology for disaster risk preparedness which simulates initiation and motion. This paper presents a new computer simulation integrating the initiation process triggered by rainfalls and/or earthquakes and the development process to a rapid motion due to strength reduction and the entrainment of deposits in the runout path. This simulation model LS-RAPID was developed from the geotechnical model for the motion of landslides (Sassa 1988) and its improved simulation model (Sassa et al. 2004b) and new knowledge obtained from a new dynamic loading ring shear apparatus (Sassa et al. 2004a). The examination of performance of each process in a simple imaginary slope addressed that the simulation model well simulated the process of progressive failure, and development to a rapid landslide. The initiation process was compared to conventional limit equilibrium stability analyses by changing pore pressure ratio. The simulation model started to move in a smaller pore pressure ratio than the limit equilibrium stability analyses because of progressive failure. However, when a larger shear deformation is set as the threshold for the start of strength reduction, the onset of landslide motion by the simulation agrees with the cases where the factor of safety estimated by the limit equilibrium stability analyses equals to a unity. The field investigation and the undrained dynamic loading ring shear tests on the 2006 Leyte landslide suggested that this landslide was triggered by the combined effect of pore water pressure due to rains and a very small earthquake. The application of this simulation model could well reproduce the initiation and the rapid long runout motion of the Leyte landslide.  相似文献   

The Colônia structure,São Paulo,Brazil     

Claudio RICCOMINI  Alvaro P. CRÓSTA  Renato L. PRADO  Marie‐Pierre LEDRU  Bruno J. TURCQ  Lucy G. SANT’ANNA  José A. FERRARI  W. Uwe REIMOLD 《Meteoritics & planetary science》2011,46(11):1630-1639

Abstract– The near‐circular Colônia structure, located in the southern suburbs of the mega‐city of São Paulo, Brazil, has attracted the attention of geoscientists for several decades due to its anomalous character and the complete absence of any plausible endogenous geologic explanation for its formation. Origin by impact cratering has been suggested repeatedly since the 1960s, but no direct evidence for this has been presented to date. New seismic data have been recently acquired at Colônia, providing new insights into the characteristics and possible layering of infill of the structure, as well as into the depth to the underlying basement. We review the current knowledge about the Colônia structure, present the new seismic data, and discuss the existing—as yet still indirect—evidence for a possible origin by an impact. The new data suggest the existence of a sedimentary fill of approximately 275 m thickness and also the presence of two intermediate zones between sediment and basement: an upper zone that is approximately 65 m thick and can be interpreted as a possible crater‐fill breccia, whereas the other zone possibly represents fractured/brecciated basement, with a thickness of approximately 50 m. Although this depth to basement seems to be inconsistent with the expected geometry of a simple, bowl‐shape impact structure of such diameter, there are a number of still unconstrained parameters that could explain this, such as projectile nature, size and velocity, impact angle, and particularly the current erosion depth.  相似文献   

Sterols as markers of sewage contamination in a tropical urban estuary (Guanabara Bay, Brazil): space–time variations     

Renato S. Carreira  Angela L. R. Wagener  James W. Readman 《Estuarine, Coastal and Shelf Science》2004,60(4):64

Guanabara Bay, located adjacent to Rio de Janeiro in Brazil, is highly contaminated by substances derived from domestic and industrial effluents as well as from agricultural runoff. In the present work, sedimentary coprostanol and other faecal sterols were used to investigate historical trends in sewage contamination. Sediment cores were collected from eight different (and characterized) locations in the bay and were sectioned into dated segments. Organic carbon was determined by dry combustion and sterols were separated and quantified by GC/MS. The space-distribution of organic carbon and faecal sterol concentrations generally coincided with the presence of known pollution sources. Concentrations of coprostanol as high as 40 μg g⁻¹ were found, indicating areas of severe sewage contamination. Faecal sterol ratios, commonly used as tools to investigate contamination in temperate environments, however, were found to have limited applicability to this tropical estuarine system, probably due to the influence of intensive primary production and microbial processes.  相似文献   

Organic matter assimilation and selective feeding by holothurians in the deep sea: some observations and comments     

Michael L. Ginger  David S. M. Billett  Karen L. Mackenzie  Konstandinos Kiriakoulakis  Renato R. Neto  Daniel K. Boardman  Vera L. C. S. Santos  Ian M. Horsfall  George A. Wolff   《Progress in Oceanography》2001,50(1-4)

The selective feeding behaviour and assimilation efficiencies of deep-sea holothurians were investigated in order to assess their impact on carbon and nitrogen remineralisation on the Porcupine Abyssal Plain (PAP; 49°N 16°W, 4850 m water depth). Unfortunately, reliable determination of organic matter in the gut contents of the organisms proved to be difficult, because of the lysis of cells associated with the death of the animals on recovery. This was expressed in high levels of free fatty acids in the gut contents of Oneirophanta mutabilis, which we ascribe to unregulated lipolysis of phospholipids and triacylglycerides. It was not possible to estimate accurately the contribution that such material made to the gut contents, but based on the distributions of sterols in the gut sediments, it is likely to have been substantial. Therefore, all assimilation efficiencies calculated for holothurians in the deep sea should be treated with caution.Fortuitously, a bloom of holothurians that feed on the sediment surface (namely Amperima rosea and Ellipinion molle) during the period of study provided an opportunity indirectly to assess the impact of megafauna on organic matter cycling at the PAP. Observations suggest that the depletion of phytosterols from the surficial sediments between July and October 1997 resulted from the selective uptake of fresh phytodetritus by the blooming species. Deep-sea holothurians do not biosynthesise sterols de novo and an estimate of the sterol required by the increased population of A. rosea and E. molle is equivalent to the sterol flux to the seafloor during the spring/summer of 1997. The implications are dramatic. Firstly, these and other megafauna apparently turned over and selectively removed phytosterols from the freshly arrived phytodetritus and the surficial sediment (0–5 mm) at the PAP in less than four months. Secondly, their action impacted the food resource available to other organisms. Finally, as phytosterols are expensive to biosynthesise and are apparently an important resource for holothurians, we speculate that the supply of these compounds to the sedimentary community may be one important control on their population in the abyssal ocean.  相似文献   

Ammothea hilgendorfi (Böhm, 1879), an Adventitious Pycnogonid new for the Mediterranean Sea     

Franz  Krapp Renato Sconfietti 《Marine Ecology》1983,4(2):123-132

Abstract. The authors demonstrate the probable immigration and stable settling of the pycnogonid Ammothea hilgendorfi (B öhm , 1879) at one station in the lagoon of Venice. The species is widely distributed naturally on both sides of the Pacific Ocean and has probably immigrated on ship hulls through the Suez Canal to the Mediterranean. Two more cases (the pycnogonid Anoplodactylus portus and the amphipod Elasmopus pectenicrus ) of adventitious species in this sea are compared.  相似文献