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Marcelo F. L. Souza Bjrn Kjerfve Bastiaan Knoppers Weber F. Landim de Souza Raimundo N. Damasceno 《Estuarine, Coastal and Shelf Science》2003,57(5-6):843-858
Lagoa de Araruama in the state of Rio de Janeiro, Brazil, is a hypersaline lagoon with salinity varying spatially from 45 to 56. We collected water samples during monthly cruises throughout the lagoon, and along the streams feeding the system, from April 1991 to March 1992. Nutrients and other water quality parameters exhibited great spatial and temporal variations. Mass balance calculations indicate large amounts of anthropogenic nutrient inputs. The data indicate that the lagoon currently is oligotrophic but is in a state of transition to become a mesotrophic system. Molar dissolved inorganic nitrogen:dissolved inorganic phosphorus (DIN/DIP) varied between 2.2:1 and 659:1 with a volume-weighted average of 22:1. The high DIN/DIP ratio contrasts with that found in nearby lagoons, suggesting that phytoplankton primary production is limited by phosphorus in Lagoa de Araruama. The major loss of DIP is apparently driven by biological assimilation and diagenic reactions in the sediments. Calculations indicate that the lagoon is slightly net autotrophic at +0.9 mol C m−2 yr−1. This suggests that the biomass of the primary producers is restricted by phosphorus availability. Phosphorus retention in the sediment and the hypersaline state of the lagoon prevent changes in autotrophic communities and the formation of eutrophic conditions. 相似文献
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de Rezende Igor Marasini Prietto Pedro Domingos Marques Thomé Antônio Dalla Rosa Francisco 《Geotechnical and Geological Engineering》2022,40(4):1997-2008
Geotechnical and Geological Engineering - New sustainable ground improvement techniques have been recently required for applications in onshore and offshore geotechnical structures. The... 相似文献
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Romeu Silva Vicente Hugo Rodrigues Humberto Varum Aníbal Costa Jos António Raimundo Mendes da Silva 《地震工程与工程振动(英文版)》2012,11(1):23-34
This paper discusses the issue of performance requirements and construction criteria for masonry enclosure and infill walls.Vertical building enclosures in European countries are very often constituted by non-load-bearing masonry walls, using horizontally perforated clay bricks.These walls are generally supported and confined by a reinforced concrete frame structure of columns and beams/slabs.Since these walls are commonly considered to be nonstructural elements and their influence on the structural response is ignored,their consideration in the design of structures as well as their connection to the adjacent structural elements is frequently negligent or insufficiently detailed.As a consequence,nonstructural elements,as for wall enclosures,are relatively sensitive to drift and acceleration demands when buildings are subjected to seismic actions. Many international standards and technical documents stress the need for design acceptability criteria for nonstructural elements,however they do not specifically indicate how to prevent collapse and severe cracking,and how to enhance the overall stability in the case of moderate to high seismic loading.Furthermore,a review of appropriate measures to improve enclosure wall performance and both in-plane and out-of-plane integrity under seismic actions is addressed. 相似文献
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F. J. García Navarro J. A. Amorós Ortiz-Villajos C. J. Sánchez Jiménez S. Bravo Martín-Consuegra E. Márquez Cubero Raimundo Jiménez Ballesta 《Environmental Earth Sciences》2009,59(3):603-611
The study described here involved evaluating the effects that the application of one by-product (sugar foam waste) has upon
red soils in the region of La Mancha (Central Spain). In view of the fact that this is a location where this type of soil
abounds, this technique has been a common practice for many years. The principal goal was to investigate the impact of this
approach on some of the soil properties and, secondly, on its level of fertility. As a result, this represents an investigation
into the effects that this type of waste has on some soil quality parameters. The results showed that, after the addition
of by-products over 25 years, sugar foam waste is of agricultural interest mainly due to the increase in organic matter concentration
(about 2%) and, to a lesser extent, by increases in calcium carbonate (more than 30%) and P (four times more). The soil pH
was also found to increase slightly (1.4), while the electrical conductivity almost did not change. The properties associated
with these pedological qualities therefore had a positive effect by improving nutrient availability. As a result, foams arising
from sugar industries have a positive effect on soil quality and the application of such foams to soils is beneficial since
the need to dispose this residue is also removed. 相似文献
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We tested two approaches to forecast species distributions while balancing the impact of climate change against the inertia promoted by other influential factors that have been forecast as not changing. Given that mountain species are presumed to be more at risk due to climate warming, we selected an amphibian, a reptile, a bird, and a mammal species present in the Spanish mountains, to model their distributional response to climate change during this century. The climatic forecasts were made according to the general circulation models CGCM2 and ECHAM4 and to the A2 and B2 emission scenarios. We modelled the response of the species to spatial, topographic, human, and climatic variables separately. In our first approach, we compared each of these single-factor models using the Akaike Information Criterion, and produced a combined model weighting each factor (spatial, topographic, human, and climatic) according to Akaike weights. This procedure overestimated the best model, and the other factors were neglected in the combined model output. In our second approach, we produced a combined model using stepwise selection of the variables previously selected within each factor. In this way every factor was effectively represented in the combined explanatory model of the distributional response of the species to environmental conditions. This enabled the construction of models that combined climate with the other explanatory factors, to be later extrapolated to the future by replacing current climatic and human values with those expected from each emission and socio-economic scenario, while preserving spatial and topographic variables in the model. 相似文献
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Shear effects on hollow section piers under seismic actions: experimental and numerical analysis 总被引：1，自引：0，他引：1
Raimundo Delgado Pedro Delgado Nelson Vila Pouca António Arêde Patrício Rocha Aníbal Costa 《Bulletin of Earthquake Engineering》2009,7(2):377-389
Shear effects are often a very important issue on the seismic behaviour of piers, particularly for hollow section bridge piers.
In fact, for this type of piers the cyclic response is similar to that of a structural wall in which both the transverse reinforcement
ratio and the detailing can play an important role on its performance, even likely to be determinant in terms of the failure
mechanism. On the other hand, codes and design guidelines are usually very conservative concerning shear capacity in order
to avoid any shear failure mechanism likely to trigger well known catastrophic consequences. Therefore, research studies on
this topic are still needed for a better understanding of pier cyclic shear response and also for improvement of the performance
under seismic actions. Pursuing this general objective, this paper partially reports on an experimental/numerical campaign
carried out on 1:4 reduced scale bridge piers in order to highlight and investigate shear-type problems. Within the scope
of this paper, two specimens types were selected having equal rectangular hollow section (900 × 450 mm2, 75 mm thick) but different transverse reinforcement detailing, namely one with a single stirrup per wall (representative
of typical bridge construction without seismic design requirements) and another with multiple stirrups, according to Eurocode
8 provisions. Numerical simulations of the experimental results were also conducted aiming at contributing for complete and
consistent interpretations of experimental results. Detailed modelling was performed allowing for realistic simulations of
the non linear behaviour, particularly suitable when a significant shear component is involved. Therefore, the numerical strategy
was based on a detailed 3D FEM discretization using a two-scalar variable damage model for the concrete constitutive law and
a suitable cyclic behaviour law for steel bars represented by truss elements. Results have shown that shear deformation and
failure modes are well simulated, while providing detailed insight concerning concrete damage pattern and distribution of
yielding on the transverse and longitudinal reinforcement. 相似文献
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Raimundo Jiménez Ballesta Paz Conde Bueno Juan A. Martin Rubi Rosario Garcia Giménez 《Central European Journal of Geosciences》2010,2(4):441-454
To evaluate trace element soil contamination, geochemical baseline contents and reference values need to be established. Pedo-geochemical baseline levels of trace elements in 72 soil samples of 24 soil profiles from the Mediterranean, Castilla La Mancha, are assessed and soil quality reference values are calculated. Reference value contents (in mg kg?1) were: Sc 50.8; V 123.2; Cr 113.4; Co 20.8; Ni 42.6; Cu 27.0; Zn 86.5; Ga 26.7; Ge 1.3; As 16.7; Se 1.4; Br 20.1; Rb 234.7; Sr 1868.4; Y 38.3; Zr 413.1; Nb 18.7; Mo 2.0; Ag 7.8; Cd 4.4; Sn 8.7; Sb 5.7; I 25.4; Cs 14.2; Ba 1049.3; La 348.4; Ce 97.9; Nd 40.1; Sm 10.7; Yb 4.2; Hf 10.0; Ta 4.0; W 5.5; Tl 2.3; Pb 44.2; Bi 2.2; Th 21.6; U 10.3. The contents obtained for some elements are below or close to the detection limit: Co, Ge, Se, Mo, Ag, Cd, Sb, Yb, Hf, Ta, W, Tl and Bi. The element content ranges (the maximum value minus the minimum value) are: Sc 55.0, V 196.0, Cr 346.0, Co 64.4, Ni 188.7, Cu 49.5, Zn 102.3, Ga 28.7, Ge 1.5, As 26.4, Se 0.9, Br 33.0 Rb 432.7, Sr 3372.6, Y 39.8, Zr 523.2, Nb 59.7, Mo 3.9, Ag 10.1, Cd 1.8, Sn 75.2, Sb 9.9, I 68.0, Cs 17.6, Ba 1394.9, La 51.3, Ce 93.5, Nd 52.5, Sm 11.2, Yb 4.2, Hf 11.3, Ta 6.3, W 5.2, Tl 2.1, Pb 96.4, Bi 3.0, Th 24.4, U 16.4 (in mg kg?1). The spatial distribution of the elements was affected mainly by the nature of the bedrock and by pedological processes. The upper limit of expected background variation for each trace element in the soil is documented, as is its range as a criterion for evaluating which sites may require decontamination. 相似文献