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11.
During the SABLES2006 (Stable Atmospheric Boundary Layer Experiment in Spain 2006) field campaign, a gravity-wave episode
was observed on the night of July 11 by the microbarometers deployed at the surface and on the 100-m tower. The high-amplitude,
low-frequency periodic pressure fluctuations were very well correlated with the wind speed and direction. Data from neighbouring
automatic stations showed that the gravity wave was not local, but long-lived and mesoscale. The propagation of the wave over
the experimental site had significant effects on the structure of the weakly-stratified nocturnal boundary layer that developed
that night: the stability increased, turbulent vertical motions were suppressed, the nocturnal low-level jet was disrupted,
and periodic temperature fluctuations of amplitude up to 3–4 K were observed. In this work we analyse the different available
data sources (tower data, RASS-SODAR, microbarometric, satellite imagery, automatic stations) to describe the phenomena in
depth and to find a suitable explanation for the generation and propagation of the wave. The linear wave theory explains remarkably
well most of the observations, and the wave parameters could be estimated by applying a wavelet-based technique to surface
microbarometric measurements. We also analyse the vertical structure of the wave and find wave ducting conditions above the
surface. Finally, by means of the multi-resolution flux decomposition, we analyse in detail the changes in vertical turbulent
fluxes and the spectra of turbulent motions produced by the interaction between the gravity wave and the local flow. 相似文献
12.
Pedro T.P. Viana 《Astrophysics and Space Science》2004,290(1-2):149-158
Clusters of galaxies are the most massive virialized structures in the Universe. Given that the mass function of large-scale structures decreases exponentially at the high-mass end, galaxy clusters are a sensitive probe of its normalization and redshift evolution, and hence of the cosmological parameters that most influence it. It will be discussed to what extent these cosmological parameters, namely the present amplitude of density perturbations, the matter density and a possible cosmological constant, can be constrained using observational data on the present and past abundance of galaxy clusters. Results will be presented based on the available data, as well as expected constraints from the X-ray Cluster Survey (XCS). 相似文献
13.
The Portuguese coast has been affected several times in the past by strong earthquakes that generated tsunamis severely damaging the city of Lisbon.
The most significant event known was the Lisbon earthquake of 1 November 1755. It is generally assumed that the location of this event was the Gorringe Bank region in the North Atlantic. This ridge, located 200 km south-west of the Portuguese shore, was also the location of the 28 February 1969 magnitude Ms = 7.9 earthquake (Fukao, 1973), that generated a tsunami of small amplitude clearly recorded at the tidal stations of the Portuguese south and south-west coasts.
The need to reduce the social and economic impact of an event of this type, greatly amplified by the urban concentration of coastal areas, led to the research project 'Destructive Earthquakes and Tsunami Warning System in SW Portugal'. This project, sponsored by the European Economic Community and the public Portuguese research funding agencies, has been conducted by the Geophysical Centre of the University of Lisbon, since April 1988.
The main targets of the project are:•the installation of a pilot warning system against tsunamis, based on two ocean bottom stations, comprising a 3 component seismometer and a bottom mounted pressure sensor, linked by cable to a surface buoy. This buoy is equipped with a data acquisition and data transmission system. Seismic and water level data will be collected on an almost real-time basis and will be transmitted to Lisbon via satellite;
•the refinement of existing geological models, in order to clarify the genesis of the bank and the seismic activity in this area;
•the installation of an adequate network of seismic monitoring stations in order to better locate off shore earthquakes (Fig. 1);
•the evaluation of seismic and tsunami risk around the Iberian Peninsula. 相似文献
The most significant event known was the Lisbon earthquake of 1 November 1755. It is generally assumed that the location of this event was the Gorringe Bank region in the North Atlantic. This ridge, located 200 km south-west of the Portuguese shore, was also the location of the 28 February 1969 magnitude M
The need to reduce the social and economic impact of an event of this type, greatly amplified by the urban concentration of coastal areas, led to the research project 'Destructive Earthquakes and Tsunami Warning System in SW Portugal'. This project, sponsored by the European Economic Community and the public Portuguese research funding agencies, has been conducted by the Geophysical Centre of the University of Lisbon, since April 1988.
The main targets of the project are:•the installation of a pilot warning system against tsunamis, based on two ocean bottom stations, comprising a 3 component seismometer and a bottom mounted pressure sensor, linked by cable to a surface buoy. This buoy is equipped with a data acquisition and data transmission system. Seismic and water level data will be collected on an almost real-time basis and will be transmitted to Lisbon via satellite;
•the refinement of existing geological models, in order to clarify the genesis of the bank and the seismic activity in this area;
•the installation of an adequate network of seismic monitoring stations in order to better locate off shore earthquakes (Fig. 1);
•the evaluation of seismic and tsunami risk around the Iberian Peninsula. 相似文献
14.
Lai C. G. Bozzoni F. Conca D. Famà A. Özcebe A. G. Zuccolo E. Meisina C. Bonì R. Bordoni M. Cosentini R. M. Martelli L. Poggi V. Viana da Fonseca A. Ferreira C. Rios S. Cordeiro D. Ramos C. Molina-Gómez F. Coelho C. Logar J. Maček M. Oblak A. Ozcep F. Bozbey I. Oztoprak S. Sargin S. Aysal N. Oser C. Kelesoglu M. K. 《Bulletin of Earthquake Engineering》2021,19(10):4013-4057
Bulletin of Earthquake Engineering - Microzonation for earthquake-induced liquefaction hazard is the subdivision of a territory at a municipal or submunicipal scale in areas characterized by the... 相似文献
15.
Millen Maxim Viana da Fonseca Antonio Quintero Julieth Ferreira Cristiana Oztoprak Sadik Oser Cihan Bozbey Ilknur Aysal Namik Kosič Mirko Logar Janko 《Bulletin of Earthquake Engineering》2021,19(10):3987-4012
The seismic behaviour of a building on a liquefiable deposit is a complex interaction which involves quantifying both shaking induced damage and permanent ground deformation-related damage. In this paper the key parameters that influence both surface shaking and foundation settlements have been identified as the depth, thickness and liquefaction resistance of an equivalent liquefiable layer. These parameters can be used to develop an ‘equivalent soil profile’ that is analogous to the equivalent single degree-of-freedom that reduces the complexity of the dynamic response of a building into comparable and easily understood quantities. The equivalent soil profile is quantified independent of the seismic hazard, making it compatible with performance based design and assessment frameworks such that the building and soil profile can be directly assessed at different levels of seismic hazard. Several numerical studies are presented that demonstrate the influence of these key parameters on the ground surface shaking and foundation settlement. A set of criteria are proposed for classifying soil profiles into 22 different soil classes for regional loss assessment. An algorithm was developed for automatically fitting the equivalent soil profile to a cone penetration test trace and issues with the fitting are discussed. Field reconnaissance was undertaken to collect additional data to support existing datasets on the performance of buildings in Adapazari, during the 1999 Kocaeli, Turkey, earthquake (Mw = 7.4). The field case history data was used to investigate the correlation between the depth, thickness and liquefaction resistance of an equivalent liquefiable layer, on the extent of foundation permanent deformation. The case history data showed that in general a shallow, thick and weak liquefiable layer near the surface results in significant settlement but a lack of data for buildings on non-liquefiable deposits and the additional complexities involved with real buildings and soil deposits, meant that the trends observed in the idealised numerical models could not identified in the field case history data set.
相似文献16.
Fluvial carbon export and CO2 efflux in representative nested headwater catchments of the eastern La Plata River Basin 
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下载免费PDF全文 Mino Viana Sorribas David da Motta Marques Nilza Maria dos Reis Castro Fernando Mainardi Fan 《水文研究》2017,31(5):995-1006
This study involved a baseline evaluation of fluvial carbon export and degas rates in three nested rural catchments (1 to 80 km2) in Taboão, a representative experimental catchment of the Upper Uruguay River Basin. Analyses of the carbon content in stream waters and the catchment carbon yield were based on 4‐year monthly in situ data and statistical modeling using the United States Geological Survey load estimator model. We also estimated p CO2 and degas fluxes using carbonate equilibrium and gas‐exchange formulas. Our results indicated that the water was consistently p CO2 saturated (~90% of the cases) and that the steep terrain favors high gas evasion rates. The mean calculated fluvial export was 5.4 tC·km?2·year?1 with inorganic carbon dominating (dissolved inorganic carbon:dissolved organic carbon ratio >4), and degas rates (~40 tC km?2·year?1) were nearly sevenfold higher than the downstream export. The homogeneous land use in this nested catchment system results in similar water‐quality characteristics, and therefore, export rates are expected to be closely related to the rainfall–runoff relationships at each scale. Although the sampling campaigns did not fully reproduce storm‐event conditions and related effects such as flushing or dilution of in‐stream carbon, our results indicated a potential link between dissolved inorganic carbon and slower hydrological pathways related to subsurface water storage and movement. 相似文献
17.
On the shearing behaviour of an artificially cemented soil 总被引：2，自引：1，他引：1
Ground improvement by cementation is a technique widely used because of the easiness of application and relatively low cost. To date, however, there is no global understanding of the behaviour of artificially cemented soil with respect to its dosage, so that in practice methodologies still rely on previous used scenarios rather than scientific facts. This paper presents results of low-to-high-pressure triaxial tests performed on pure and cemented specimens of decomposed granite where the dosage was controlled, chosen as a function of the ratio of porosity to volumetric cement content or adjusted porosity/cement index. The behaviour of the cemented soil was analysed in terms of peak strength and failure envelopes, stress dilatancy and state boundary surfaces, on which the influence of the porosity/cement index was examined. 相似文献
18.
19.
Pedro P. Avelino Pedro T. P. Viana 《Monthly notices of the Royal Astronomical Society》2000,314(2):354-358
The cloud-in-cloud problem is studied in the context of the extension to non-Gaussian density fields of the PS approach for the calculation of the mass function. As an example of a non-Gaussian probability distribution function (PDF), we consider the chi-square distribution with various degrees of freedom. We generate density fields in cubic boxes with periodic boundary conditions, and then determine the number of points considered collapsed at each scale through a hierarchy of smoothing windows. We find that the mass function we obtain differs from that predicted using the extended PS formalism, particularly for low values of σ and for those PDFs that differ most from a Gaussian. 相似文献
20.
Marcelo Leandro BUENO Vanessa Leite REZENDE Luiza Fonseca A.DE PAULA Joo Augusto Alves MEIRA-NETO José Roberto Rodrigues PINTO Andreza Viana NERI Vanessa PONTARA 《山地科学学报》2021,(5):1192-1207
The campo rupestre sensu lato is a vegetation type that occurs in South American mountains, supports a distinctive flora characterized by high rates of endemism, high herbaceous species richness and often-neglected but also species-rich of the arboreal stratum. We aimed to investigate how environmental factors and elevation are associated with the distribution and diversity of woody species in different rupestrian vegetation types across South America. Using a database of 2,049 woody species from 185 sites across four vegetation types within the campo rupestre, we assessed how the vegetation types were grouped according to their floristic composition and number of shared indicator species, as well as by using different beta diversity indices. The most important variables from a set of 27 variables(e.g. altitude, geo-edaphic and climatic) explaining species distribution were identified using redundancy analysis(RDA) and variation partitioning methods. The distribution of vegetation types was related to both environmental and spatial fractions, with a set of 17 variables retained(e.g. rockiness, grass cover and temperature seasonality as the most important variables). There was an association between the floristic composition of each vegetation type and the elevation range. Although the identified vegetation types are floristically related, they are distinguished by exclusive and habitat-specialist woody species. This uniqueness of vegetation types should be considered in terms of complementarity for the conservation of campos rupestres. 相似文献