Structural behaviour and design criteria of under‐deck cable‐stayed bridges subjected to seismic action     

Alfredo Camara  Ana M. Ruiz‐Teran  Peter J. Stafford 《地震工程与结构动力学》2013,42(6):891-912

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SIDRA instrument for measurements of particle fluxes at satellite altitudes. Laboratory prototype     

O. V. Dudnik  M. Prieto  E. V. Kurbatov  S. Sanchez  T. G. Timakova  A. V. Spassky  V. N. Dubina  P. Parra 《Solar System Research》2013,47(1):58-65

The design concept and first set of results are presented for electronic modules of a laboratory prototype of the small-size satellite instrument SIDRA intended for measurements of charged particle fluxes in outer space. The working prototype consists of a detector assembly based on high-purity silicon and fast scintillation detectors, modules of analogue and digital processing, and a secondary power supply module. The first results are discussed of a Monte-Carlo simulation of the instrument with the use of the GEANT4 toolkit and of measurements of the main parameters of charge-sensitive pre-amplifiers, shapers, and peak detectors. Results of calibration measurements with the use of radioactive sources and beams of accelerated charged particles are presented.  相似文献   

Tidal and Groundwater Fluxes to a Shallow, Microtidal Estuary: Constraining Inputs Through Field Observations and Hydrodynamic Modeling     

Neil K. Ganju  Melanie Hayn  Shih-Nan Chen  Robert W. Howarth  Patrick J. Dickhudt  Alfredo L. Aretxabaleta  Roxanne Marino 《Estuaries and Coasts》2012,35(5):1285-1298

Increased nutrient loading to estuaries has led to eutrophication, degraded water quality, and ecological transformations. Quantifying nutrient loads in systems with significant groundwater input can be difficult due to the challenge of measuring groundwater fluxes. We quantified tidal and freshwater fluxes over an 8-week period at the entrance of West Falmouth Harbor, Massachusetts, a eutrophic, groundwater-fed estuary. Fluxes were estimated from velocity and salinity measurements and a total exchange flow (TEF) methodology. Intermittent cross-sectional measurements of velocity and salinity were used to convert point measurements to cross-sectionally averaged values over the entire deployment (index relationships). The estimated mean freshwater flux (0.19?m³/s) for the 8-week period was mainly due to groundwater input (0.21?m³/s) with contributions from precipitation to the estuary surface (0.026?m³/s) and removal by evaporation (0.048?m³/s). Spring?Cneap variations in freshwater export that appeared in shorter-term averages were mostly artifacts of the index relationships. Hydrodynamic modeling with steady groundwater input demonstrated that while the TEF methodology resolves the freshwater flux signal, calibration of the index?Csalinity relationships during spring tide conditions only was responsible for most of the spring?Cneap signal. The mean freshwater flux over the entire period estimated from the combination of the index-velocity, index?Csalinity, and TEF calculations were consistent with the model, suggesting that this methodology is a reliable way of estimating freshwater fluxes in the estuary over timescales greater than the spring?Cneap cycle. Combining this type of field campaign with hydrodynamic modeling provides guidance for estimating both magnitude of groundwater input and estuarine storage of freshwater and sets the stage for robust estimation of the nutrient load in groundwater.  相似文献   

Geodetic and Structural Research in La Palma, Canary Islands, Spain: 1992–2007 Results     

J. F. Prieto  P. J. González  A. Seco  G. Rodríguez-Velasco  L. Tunini  P. A. Perlock  A. Arjona  A. Aparicio  A. G. Camacho  J. B. Rundle  K. F. Tiampo  J. L. G. Pallero  S. Pospiech  J. Fernández 《Pure and Applied Geophysics》2009,166(8-9):1461-1484

We review the results of the geodetic and structural studies carried out on La Palma Island using geodetic and geophysical data during the period 1992–2007. InSAR and GPS observation techniques were applied to study the existence of deformation on the island and gravity observations were carried out for structural studies. Gravity data were inverted using a nonlinear three-dimensional gravity inversion approach to obtain the geometry of the anomalous bodies constructed in a random growth process with respect to an exponentially stratified background. The main structural feature is a large central body (under the Caldera de Taburiente) with high density, which was interpreted as the Pliocene-age uplifted seamount and a relatively dense intrusive plutonic complex/magma body. The Cumbre Vieja series is characterized by elongated minima distributed according to the rift structure. InSAR results show a clear subsidence located on the Teneguía volcano, where the last eruption took place in 1971. A thermal source is the most probable origin for this deformation. A GPS network composed of 26 stations covering the total island surface was set up. Vertical displacements determined comparing the GPS coordinates obtained in 2007 with coordinates determined in 1994 are consistent with the InSAR results obtained in the southern part of the island. This is not the case for the northern part. From the comparison of 2006 and 2007 coordinates it is clear that more time is needed to obtain significant displacements, but observed trends are also consistent with InSAR results. All the observed significant displacements are in stations located outside of the large high-density central body.  相似文献   

Short‐Term Stabilization of Organic Matter in Physically,Chemically, and Biochemically Protected Pools in Soils Amended with Municipal Wastes          下载免费PDF全文

José M. Fernández  Esther G. López‐de‐Sá  Alfredo Polo  César Plaza 《洁净——土壤、空气、水》2014,42(4):487-493

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Fingerprint of tropical climate variability and sea level in sediments of the Cariaco Basin during the last glacial period     

Gaudenz Deplazes  Anna Nele Meckler  Larry C. Peterson  Yvonne Hamann  Beat Aeschlimann  Detlef Günther  Alfredo Martínez‐García  Gerald H. Haug 《Sedimentology》2019,66(5):1967-1988

High‐resolution palaeorecords of climate are critical to improving current understanding of climate variability, its sensitivity and impact on the environment in the past and in the future. Sediments from the Cariaco Basin off the coast of Venezuela have proven to be sensitive recorders of tropical palaeoclimate variability down to an annual scale. However, the fingerprint of climate and sea level in the sediments of the last glacial period is still not completely understood. In this study, lamination analysis of sediments from the Cariaco Basin is extended to the last glacial period. Detailed sedimentological and geochemical analysis (laser ablation–inductively coupled plasma–mass spectrometry) reveals couplets of light‐coloured, terrigenous‐rich and dark‐coloured, biogenic opal‐rich laminae, which are interpreted to reflect the seasonal migration of the Intertropical Convergence Zone. In addition, a previously undescribed, nearly pure terrigenous lamina type is observed, which is referred to hereafter as a ‘C‐layer’. The C‐layers in the sedimentary sequence are interpreted as flood layers that originate from local rivers. The occurrence of these C‐layers is investigated for two core locations in the Cariaco Basin over the last 110 kyr by continuous X‐ray fluorescence scanning. Dansgaard–Oeschger oscillations are most clearly traced by proxies reflecting productivity and marine organic matter content of the sediment. In contrast, the abundance of terrigenous material differs at times between the two sites. On an interglacial to glacial timescale, the ability to record events causing C‐layers is likely to be influenced by changes in sea level and source proximity. On a millennial scale, both sediment cores contain more C‐layers during warmer interstadials compared with colder stadials during Marine Isotope Stage 3. This finding implies that interstadials were not only wetter than stadials, but probably also characterized by increased rainfall variability, leading to an enhanced frequency of flooding events in the hinterland of the Cariaco Basin.  相似文献   

Subantarctic macrotidal flats, cheniers and beaches in San Sebastian Bay, Tierra Del Fuego, Argentina   总被引：6，自引：0，他引：6  

Federico Vilas  Alfredo Arche  Marcelo Ferrero  Federico Isla 《Marine Geology》1999,160(3-4):301-326

San Sebastian Bay is a large, semicircular coastal embayment situated on the Atlantic coast of Tierra del Fuego, Argentina. It is a high-energy, subantarctic environment with a tidal range of 10.4 m, influenced by large waves of Atlantic and local origin and swept by constant, strong westerly winds. A 17 km long gravel spit protects the Northern part of the Bay giving rise to a gradient in sedimentary processes. From south to north, are seven distinct sedimentary environments. Coastal sedimentation started at least 5200 years before present (BP) and a rapid progradation related to a relative sea-level drop has infilled about 6 kilometres of the Bay with a sedimentary sequence 10–11 m thick. 14-C dating of unabraded shells in the Chenier ridges of the relict part of the complex allows for a precise reconstruction of the stages of the progradation, that has slowed from 2.35 m/year at 5000 years BP to 0.6 m/year at present. The possible causes of the sea-level drop are discussed.  相似文献   

Three-dimensional nonlinear random wave groups in intermediate water depth     

Felice Arena  Alfredo Ascanelli  Vincenzo Nava  Diego Pavone  Alessandra Romolo 《Coastal Engineering》2008,55(12):1052-1061

High waves at ocean occur during a complex space–time evolution of wave groups. In this paper the nonlinear structure of three-dimensional sea wave groups at intermediate water depth is investigated. To this purpose, the Boccotti's Quasi-Determinism theory is firstly applied to describe the linear wave groups when a given exceptionally high crest occurs. Then, the second-order correction to the linear solution is derived for the general condition of three-dimensional wave groups, at a finite water depth. Several numerical applications, finally, have been carried out in order to show how both the spectral bandwidth and the directional spreading modify the nonlinear high waves at different water depth.  相似文献   

Near-infrared spectroscopy of nearby Seyfert galaxies – II. Molecular content and coronal emission     

J. Reunanen  J. K. Kotilainen  M. A. Prieto 《Monthly notices of the Royal Astronomical Society》2003,343(1):192-208

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Structure and Dynamics of NGC 1300     

J.A.L. Aguerri  M. Prieto  A.M. Varela  C. Muñoz-Tuñón 《Astrophysics and Space Science》2001,276(2-4):611-618

The isophotal profiles and colour maps of a sample of 12 spiral galaxies allowed us to analyse the different structural components that compose them. These components were parameterized by performing a decomposition of the galaxy brightness profiles. Inferring the geometry for each component, we have obtained the spatial mass distribution and the gravitational potential for each object. Here we present the detailed analysis for one of the galaxies in the sample, the barred galaxy NGC 1300. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献