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51.
Zooplankton volume trends off Peru between 1964 and 2001 总被引:5,自引:0,他引:5
Ayon Patricia; Purca Sara; Guevara-Carrasco Renato 《ICES Journal of Marine Science》2004,61(4):478-484
52.
Roberto A. T. Gomes Renato F. Guimarães Osmar A. Carvalho Jr. Nelson F. Fernandes Eurípedes A. Vargas Jr. Éder S. Martins 《Natural Hazards》2008,45(2):197-209
In tropical areas, mass movements are common phenomena, especially during periods of heavy rainfall, which frequently take
place in the summer season. These phenomena have caused loss of life and serious damage to infrastructure and properties.
The most prominent of these phenomena are landslides that can produce debris flows. Thus, this article aims at determining
affected areas using a model to predict landslide prone areas (SHALSTAB) combined with an empirical model designed to define
the debris flow travel distance and area of deposition. The methodology of this work consists of the following steps: (a)
elaboration of a digital elevation model (DEM), (b) application of the deterministic SHALSTAB model to locate the landslide
prone areas, (c) identification of the debris flow travel distance and area of deposition, and (d) mapping of the affected
areas (landslides and debris flows). This work was developed in an area in which many mass movements occurred after intense
rainfall during the summer season (February 1996) in the state of Rio de Janeiro, southeast Brazil. All of the scars produced
by that event were mapped, allowing for validation of the applied models. The model results show that the mapped landslide
locations can adequately be simulated by the model. 相似文献
53.
Renato Macciotta C. Derek Martin Norbert R. Morgenstern David M. Cruden 《Landslides》2016,13(4):765-785
The benefits of quantitative risk assessments for landslide management have been discussed and illustrated in several publications. However, there still are some challenges in its application for low-probability, high-magnitude events. These challenges are associated with the difficulties in populating our models for risk calculations, which largely require the input of expert opinion. This paper presents a quantitative risk assessment to a very slow moving rock slope within a dam reservoir in the Province of British Columbia, Canada. The assessment is focused on the risk to the population in the vicinity of the dam and the populated areas downstream. Expert opinions quantified the slope failure probabilities in the order of 10?3 to 10?1 per year for the smallest failure scenario considered and less than 10?6 for a failure of the entire slope. However, these estimations are associated with high levels of uncertainty. Our approach starts with the calculation and assessment of the magnitude and probability of the potential slope failure consequences, minimizing the uncertainties associated with estimated slope failure probabilities. Then, these consequences and failure probabilities are combined to obtain a measure of risk. The uncertainty associated with the slope failure probabilities is managed by the estimation of plausible ranges for these. The calculated risk levels are then presented as ranges of values and assessed against adopted evaluation criteria. The consequence and risk assessment of the rock slope suggest that the risk to the population exposed in the vicinity of the dam and populated areas downstream is under adequate control. The probability of large consequence scenarios is extremely low, in the order of 10?7 chance of an event causing more than 100 fatalities. We propose an observational technique to assess changes in risk levels and decide when to update the risk management approach or deploy emergency measures. The technique is focused on the detection of changes in the slope deformation patterns that would indicate an increase in the potential failure volumes or an imminent failure. It can be considered an extension to the current early warning system in place, easy to implement and enhanced with the strength of the comprehensive analysis required for a quantitative risk assessment. 相似文献
54.
55.
Liliane Janikian Renato Paes de Almeida Antonio Romalino Santos Fragoso-Cesar Veridiana Teixeira de Souza Martins Elton Luiz Dantas Eric Tohver Ian McReath Manoel Souza D'Agrella-Filho 《Gondwana Research》2012,21(2-3):466-482
During the Ediacaran, southern Brazil was the site of multiple episodes of volcanism and sedimentation, which are best preserved in the 3000 km2 Camaquã Basin. The interlayered sedimentary and volcanic rocks record tectonic events and paleoenvironmental changes in a more than 10 km-thick succession. In this contribution, we report new U–Pb and Sm–Nd geochronological constraints for the 605 to 580 Ma Bom Jardim Group, the 570 Ma Acampamento Velho Formation, and a newly-recognized 544 Ma volcanism. Depositional patterns of these units reveal the transition from a restricted, fault-bounded basin into a wide, shallow basin. The expansion of the basin and diminished subsidence rates are demonstrated by increasing areal distribution and compressed isopachs and increasing onlap of sediments onto the basement to the west. The Sm–Nd isotopic composition of the volcanic rocks indicates mixed sources, including crustal rocks from the adjacent basement. Both Neoproterozoic and Paleoproterozoic sources are indicated for the western part of the basin, whereas only the older Paleoproterozoic signature can be discerned in the eastern part of the basin. 相似文献
56.
By means of multi-temporal analysis of satellite images and statistical algorithms, the amount of pyroclastic material deposited
on Lascar volcano walls after the gravitational collapse of the eruptive column caused by the eruption that occurred on April
the 19th and the 20th in 1993 was determined and quantified. For this analysis, scenes corresponding to Landsat 4 TM in 1989
and Landsat 7 ETM+ in 2001 were used. By careful selection methods such as combination of bands, unsupervised classification,
and the Karhunen–Loève transform, detailed analysis of zones of change that correspond to pyroclastic deposits were made.
This analysis was complemented with in situ data in order to correct and calibrate the satellite images to identify zones
of 1993s eruption pyroclastic deposits. Using Kittler’s and other thresholding algorithms, a search was performed for a proper
threshold to binarize the images to determine the surface area covered by the eruptive process. Matlab™ software was used
both for general programming and for digital image processing. 相似文献
57.
Renato De Santis 《Monthly notices of the Royal Astronomical Society》2001,326(1):397-402
In this paper, by assuming the equilibrium temperatures of RRab Lyrae variables defined by Carney, Storm & Jones as correct we show that temperatures derived from ( B − V ) colour (mean colour over the pulsational cycle calculated on the magnitude scale) transformations by Bessel, Castelli & Plez are consistent with the Carney et al. equilibrium temperatures within a probable error of δ log T e =±0.003 . As a consequence, it is shown that the pulsational temperature scale temperature–period–blue amplitude [ T eff = f ( P , A B )] relation provided by De Santis, who studied the ( B − V ) colour of about 70 stars of Lub's sample, is a suitable relation, being reddening- and metallicity-free, to calculate equilibrium temperatures for RRab variables. This relation is independent of variable mass and luminosity within a large range of period-shift from the mean period–amplitude relation valid for Lub's sample of variables. On the contrary, it is also shown that a temperature–amplitude–metallicity relation is strictly dependent on the period–amplitude relation of the sample used for calibrating it: we prove that this means it is dependent on both the mass and luminosity variations of variables. 相似文献
58.
Marco Mazzotti Renato Baciocchi Michael J. Desmond Robert H. Socolow 《Climatic change》2013,118(1):119-135
Direct Air Capture (DAC) of CO2 with chemicals, recently assessed in a dedicated study by the American Physical Society (APS), is further investigated with the aim of optimizing the design of the front-end section of its benchmark two-loop hydroxide-carbonate system. Two new correlations are developed that relate mass transfer and pressure drop to the air and liquid flow velocities in the countercurrent packed absorption column. These relationships enable an optimization to be performed over the parameters of the air contactor, specifically the velocities of air and liquid sorbent and the fraction of CO2 captured. Three structured Sulzer packings are considered: Mellapak-250Y, Mellapak-500Y, and Mellapak-CC. These differ in cost and pressure drop per unit length; Mellapak-CC is new and specifically designed for CO2 capture. Scaling laws are developed to estimate the costs of the alternative DAC systems relative to the APS benchmark, for plants capturing 1 Mt of CO2 per year from ambient air at 500 ppm CO2 concentration. The optimized avoided cost hardly differs across the three packing materials, ranging from $518/tCO2 for M-CC to $568/tCO2 for M-250Y. The $610/tCO2 avoided cost for the APS-DAC design used M-250 Y but was not optimized; thus, optimization with the same packing lowered the avoided cost of the APS system by 7 % and improved packing lowered the avoided cost by a further 9 % The overall optimization exercise confirms that capture from air with the APS benchmark system or systems with comparable avoided costs is not a competitive mitigation strategy as long as the energy system contains high-carbon power, since implementation of Carbon Capture and Storage, substitution with low-carbon power and end-use efficiency will offer lower avoided-cost strategies. 相似文献
59.
Talitha L. F. Costa Michelle P. Araújo Bastiaan A. Knoppers Renato S. Carreira 《Aquatic Geochemistry》2011,17(1):1-19
In the present work, we evaluated the origin of organic matter in the tropical estuarine-lagoon system of Mundaú–Manguaba,
NE Brazil, by considering the bulk (organic carbon and chlorophyll-a) and lipidic (n-alcohols and sterols) composition of suspended particles. Water samples were collected in August 2006 from
24 stations covering the salinity gradient from the rivers down to the sea outlet. Chlorophyll-a (Chl-a) varied from 22.7 to 134.1 μg L−1 in the lagoons, indicating eutrophic to hypertrophic conditions at the time of sampling. The high correlation between Chl-a and phytol together with the molar C:N ratio indicated the presence of fresh and recently produced autochthonous particulate
organic matter throughout the system, except for the river samples. The elevated concentrations of short-chain n-alcohols
and phytosterols, mainly 24-methylcholesta-5,24(28)-dien-3β-ol, also corroborated the predominance of autochthonous organic
matter in the lagoons but were generated by distinct sources: cianobacteria in the freshwater Manguaba lagoon and diatoms
in the brackish Mundaú lagoon compartments. Input of terrestrial organic matter was only detected in the rivers themselves
or at the upper river–lagoon interfaces. Coprostanol indicated contamination by sewage in Mundaú lagoon and in some rivers,
but at lower levels when compared to other Brazilian coastal lagoons and estuaries. 相似文献
60.
3D-electrical resistivity tomography monitoring of salt transport in homogeneous and layered soil samples 总被引:1,自引:1,他引:0
Cesare Comina Renato Maria Cosentini Gabriele Della Vecchia Sebastiano Foti Guido Musso 《Acta Geotechnica》2011,6(4):195-203
Monitoring transport of dissolved substances in soil deposits is particularly relevant where safety is concerned, as in the
case of geo-environmental barriers. Geophysical methods are very appealing, since they cover a wide domain, localising possible
preferential flow paths and providing reliable links between geophysical quantities and hydrological variables. This paper
describes a 3D laboratory application of electrical resistivity tomography (ERT) used to monitor solute transport processes.
Dissolution and transport tests on both homogeneous and heterogeneous samples were conducted in an instrumented oedometer
cell. ERT was used to create maps of electrical conductivity of the monitored domain at different time intervals and to estimate
concentration variations within the interstitial fluid. Comparisons with finite element simulations of the transport processes
were performed to check the consistency of the results. Tests confirmed that the technique can monitor salt transport, infer
the hydro-chemical behaviour of heterogeneous geomaterials and evaluate the performances of clay barriers. 相似文献