Uplift Capacity Prediction of Continuous Helix Piles in Cohesionless Soils Using Cone Penetrometer Tests     

Nait-Rabah  Ouahcène  Medjigbodo  Gildas  Salhi  Lakhdar  Roos  Christophe  Dias  Daniel 《Geotechnical and Geological Engineering》2021,39(7):4933-4946

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Horizontal patterns of water temperature and salinity in an estuarine tidal channel: Ria de Aveiro     

Nuno Vaz  João Miguel Dias  Paulo Leitão  Inês Martins 《Ocean Dynamics》2005,55(5-6):416-429

This work presents results from two complementary and interconnected approaches to study water temperature and salinity patterns in an estuarine tidal channel. This channel is one of the four main branches of the Ria de Aveiro, a shallow lagoon located in the Northwest coast of the Iberian Peninsula. Longitudinal and cross-sectional fields of water temperature and salinity were determined by spatial interpolation of field measurements. A numerical model (Mohid) was used in a 2D depth-integrated mode in order to compute water temperature and salinity patterns. The main purpose of this work was to determine the horizontal patterns of water temperature and salinity in the study area, evaluating the effects of the main forcing factors. The field results were depth-integrated and compared to numerical model results. These results obtained using extreme tidal and river runoff forcing, are also presented. The field results reveal that, when the river flow is weak, the tidal intrusion is the main forcing mechanism, generating saline and thermal fronts which migrate with the neap/spring tidal cycle. When the river flow increases, the influence of the freshwater extends almost as far as the mouth of the lagoon and vertical stratification is established. Results of numerical modelling reveal that the implemented model reproduces quite well the observed horizontal patterns. The model was also used to study the hydrology of the study area under extreme forcing conditions. When the model is forced with a low river flow (1 m³ s⁻¹) the results confirm that the hydrology is tidally dominated. When the model is forced with a high river flow (1,000 m³ s⁻¹) the hydrology is dominated by freshwater, as would be expected in such an area.  相似文献   

River breeze circulation in eastern Amazonia: observations and modelling results     

M. A. F. Silva Dias  P. L. Silva Dias  M. Longo  D. R. Fitzjarrald  A. S. Denning 《Theoretical and Applied Climatology》2004,78(1-3):111-121

Summary The CIRSAN/LBA field campaign was conducted close to two major rivers of the Amazon Basin, the Tapajós and the Amazon. The observations indicate that during weak trade wind episodes the Tapajós River breeze actually induces a westerly flow at the eastern margin with an associated line of shallow cumulus. The atmospheric circulation induced by the river has been interpreted with the help of a high resolution numerical simulation. A single cell forms during late morning over the Tapajós River and evolves into the afternoon with ascending motion in the eastern margin and a descending branch in the western margin suppressing cloud formation. During the night, convergence is seen along the centre of the River Tapajós. The implications of the particular geometry of the river with respect to the trade winds for the generalization of the surface measurements of turbulent fluxes of heat, moisture and CO₂ in the Tapajós eastern margin of the Amazon Basin as a whole are discussed.  相似文献   

Determination of O3-, CO- and PM10-transport in the metropolitan area of São Paulo, Brazil through synoptic-scale analysis of back trajectories     

O. R. Sánchez-Ccoyllo  P. L. Silva Dias  M. de Fátima Andrade  S. R. Freitas 《Meteorology and Atmospheric Physics》2006,92(1-2):83-93

Summary This study is aimed to qualitatively analyze the impact of remote sources on air pollution in the Metropolitan Area of S?o Paulo (MASP). Air-mass back trajectories from June to August of 1999 were calculated using a three-dimensional kinematic trajectory model and grouped into trajectory clusters. Correlations of individual trajectory clusters with O₃, CO and PM₁₀ concentrations were determined. In this model, trajectories were obtained using the means of the three wind velocity components (U, V and W). The three-dimensional wind field was derived from the Regional Atmospheric Modeling System, and downscaling was employed. Coarse and fine nested grids (64-km and 16-km horizontal resolution, respectively) were used. Every 12 h (at 00 and 12 UTC), a back-trajectory ensemble, using the 64-km grid, was calculated for five defined endpoints at intervals of 0.5° N, S, E and W of the MASP (λ = 23° 33′S, ϕ = 46° 45′W), that last endpoint being centered in the MASP. To analyze cluster trajectories, the five trajectory ensembles from each day were allocated into one of four clusters (northeast, southeast, southwest or northwest quadrant) based on the origin of the trajectory over 4 days. Days on which all five trajectories originated from the same quadrant were classified as “core” days. Core day concentrations of CO, O₃ and PM₁₀ during the study period were evaluated. The results show that, during the study period, air-mass back trajectories in the MASP originated from all four quadrants: northeast (32%), southeast (12%), southwest (19%) and northwest (37%). Our analysis of back-trajectory clusters in the MASP suggests a transport to ambient air of O₃ precursors and O₃ from the northeast region, which is associated with agricultural activities involving biomass burning.  相似文献   

Motional induction voltage measurements in estuarine environments: the Ria de Aveiro Lagoon (Portugal)     

Rita Nolasco  António Soares  João M. Dias  Fernando A. Monteiro Santos  N. A. Palshin  Patricia Represas  Nuno Vaz 《Geophysical Journal International》2006,166(1):126-134

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Singular spectrum analysis and forecasting of hydrological time series     

C.A.F. Marques  J.A. Ferreira  A. Rocha  J.M. Castanheira  P. Melo-Gonçalves  N. Vaz  J.M. Dias 《Physics and Chemistry of the Earth》2006,31(18):1172-1179

The singular spectrum analysis (SSA) technique is applied to some hydrological univariate time series to assess its ability to uncover important information from those series, and also its forecast skill. The SSA is carried out on annual precipitation, monthly runoff, and hourly water temperature time series. Information is obtained by extracting important components or, when possible, the whole signal from the time series. The extracted components are then subject to forecast by the SSA algorithm. It is illustrated the SSA ability to extract a slowly varying component (i.e. the trend) from the precipitation time series, the trend and oscillatory components from the runoff time series, and the whole signal from the water temperature time series. The SSA was also able to accurately forecast the extracted components of these time series.  相似文献   

Input of geophysics to understand hydrogeology towards the assessment of geoenvironmental conditions in Beira city,Mozambique     

E. C. Ramalho  J. Fernandes  E. Daudi  L. Quental  R. Dias  J. T. Oliveira  M. J. Batista  G. Cune  U. Ussene  D. Milisse  G. Balate  V. Manhiça 《Environmental Earth Sciences》2018,77(1):15

As the fourth largest city in Mozambique, and located right beside the Indian Ocean, Beira faces sanitary and environmental problems that are a strong concern to the local and national authorities. One of the major problems that Beira city has to deal with is the existence of undrinkable groundwater in many dug-wells that supply a large amount of the city population. The cooperation project among Direcção Nacional de Geologia of Mozambique, the Laboratório Nacional de Energia e Geologia of Portugal and the Instituto de Apoio ao Desenvolvimento Português that took place from 2007 to 2011 has as one of its main goals the production of the Geological and Geoenvironmental Maps of Beira at scale 1:50,000, intending to create a tool to support the implementation of governmental policies regarding sustainable groundwater and natural resources exploitations, land management and environmental protection. These goals were achieved through the identification, characterization and mapping of the different geological units and the evaluation of the city environmental problems regarding water and soil contamination in urban areas, involving the use of several methodologies that were subsequently integrated and jointly interpreted. These comprised remote sensing techniques, hydrogeology analysis and evaluation and the use of geochemistry and electrical geophysical methods. This work emphasizes the input of geophysical and hydrogeological methods to assess the geoenvironmental conditions of Beira, namely those related with the prediction of occurrence of saline and brackish water in the shallow dug-wells that supply a large amount of Beira populations, especially in the crowded suburbs. Several geophysical surveys using electrical and electromagnetic methods were conducted and interpreted regarding the evaluation of the several hypotheses that were stood for this feature. Results are related with hydrogeological conditions and organic and inorganic hydrochemical analysis. Considering these facts, this study was an important input for mapping areas with saline and brackish water imprisoned in the subsurface geological formations, using a wider set of methodologies that were integrated in these results.  相似文献   

Protective effect of phospholipid hydroperoxide glutathione peroxidase (PHGPx) against lipid peroxidation in mussels Perna perna exposed to different metals   总被引：2，自引：0，他引：2  

de Almeida EA  Miyamoto S  Bainy AC  de Medeiros MH  Di Mascio P 《Marine pollution bulletin》2004,49(5-6):386-392

Levels of antioxidant defenses and lipid peroxidation were evaluated in mussels exposed to lead (200 mg/l), iron (500 microg/l), cadmium (200 microg/l) and copper (40 microg/l), for 12, 24, 72 and 120 h. Glutathione S-transferase (GST) activity was unchanged with all treatments. Catalase (CAT) increased after 120 h of exposure to all metals. Mussels exposed to Cd for 12 h, and to Cu and Fe for 120 h had increased lipid peroxidation, which might be associated to decreased levels of reduced glutathione (GSH) and glutathione peroxidase (GPx) activity. Pb exposure caused GSH depletion after 12 h and increased GPx activity after 120 h. Negative correlations were observed between the enzyme phospholipid hydroperoxide glutathione peroxidase (PHGPx) and malonaldehyde (MDA) levels after Fe and Cu exposure, indicating a protective role of PHGPx against lipid peroxidation, and suggesting the use of this enzyme as a new potential biomarker of toxicity associated with contaminant exposure in mussels.  相似文献   

A comparison of direct macrofaunal mortality using three types of clam dredges     

Gaspar  M.B; Leitao  F; Santos  M.N; Chicharo  L; Dias  M.D; Chicharo  A; Monteiro  C.C 《ICES Journal of Marine Science》2003,60(4):733-742

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Z-Less stratification under stable conditions   总被引：2，自引：2，他引：0  

Nelson L. Dias  Wilfried Brutsaert  Marvin L. Wesely 《Boundary-Layer Meteorology》1995,75(1-2):175-187

Turbulent fluctuations were measured at a height of 2.5 m in stable conditions over grass to investigate the variability of the second- and third-order moments involving temperature, humidity and vertical wind velocity. With the exception of the normalized second moment of temperature, very little variation of the normalized moments was found with changes in the dimensionless stability parameter =z/L, whereL is the Obukhov stability length. Such limited variation is expected for stable conditions, and the normalized second moment of temperature might have been affected by nonstationary conditions. In addition, the variability of the normalized moments was lessened by computing the turbulence statistics over 56 min, instead of 26 min. Values of third-order moments involving the vertical velocity were all close to zero.  相似文献