Transient kinematic pile bending in two-layer soil     

Stefania Sica  George Mylonakis  Armando Lucio Simonelli 《Soil Dynamics and Earthquake Engineering》2011

The dynamic response of piles to seismic loading is explored by means of an extensive parametric study based on a properly calibrated Beam-on-Dynamic-Winkler-Foundation (BDWF) model. The investigated problem consists of a single vertical cylindrical pile, modelled as an Euler–Bernoulli beam, embedded in a subsoil consisting of two homogeneous viscoelastic layers of sharply different stiffness resting on a rigid stratum. The system is subjected to vertically propagating seismic S waves, in the form of a transient motion imposed on rock outcrop. Several accelerograms recorded in Italy are employed as input motions in the numerical analyses. The paper highlights the severity of kinematic pile bending in the vicinity of the interface separating the two soil layers. In addition to factors already investigated such as layer stiffness contrast, relative soil–pile stiffness, interface depth and intensity of ground excitation, the paper focuses on additional important factors, notably soil material damping, stiffness of Winkler springs and frequency content of earthquake excitation. Existing predictive equations for assessing kinematic pile bending at soil layer interfaces are revisited and new regression analyses are performed. A synthesis of findings in terms of a set of simple equations is provided. The use of these equations is discussed through examples.  相似文献   

Facies Recognition Using Multifractal Hurst Analysis: Applications to Well-Log Data     

Eliseo Hernandez-Martinez  Teresa Perez-Muñoz  Jorge X. Velasco-Hernandez  Armando Altamira-Areyan  Luis Velasquillo-Martinez 《Mathematical Geosciences》2013,45(4):471-486

Well-log (radioactivity, density and resistivity) analysis constitutes a standard approach for inferring lithology from wells. However, due to inherent complexity of the signals (such as highly heterogeneous deep-water sedimentary sequences) lithology recognition is not straightforward. We used a rescaled range analysis, calibrated with cores, to recognize lithological patterns from signal recorded along wireline logs. The detected intervals coincide with zones of visual electro-facies associations proposed by geologist well-log interpreters. In addition, we propose a rescaled range multifractal analysis to identify ranges of well-log signal complexities, which could be related to sedimentary process variations at specific stratigraphic order cycles.  相似文献   

Macrobenthos and multi-molecular markers as indicators of environmental contamination in a South American port (Mar del Plata,Southwest Atlantic)     

Mariano J. Albano  Paulo da Cunha Lana  Claudia Bremec  Rodolfo Elías  César C. Martins  Natalia Venturini  Pablo Muniz  Silvia Rivero  Eduardo A. Vallarino  Sandra Obenat 《Marine pollution bulletin》2013

We evaluated benthic habitat quality along a presumed contamination gradient in the Mar del Plata port (Southwestern Atlantic) by coupling biological and chemical proxies in a multidisciplinary approach. Organic matter and photosynthetic pigment contents were higher in silty-clay bottoms of the inner port sites. Levels of all fecal steroids decreased from the inner sites to the port inlet. High concentrations of coprostanol in the inner sites seemed to derive from a permanent population of sea lions rather than from sewage outfalls due to coprostanol/epicoprostanol ratio (IV) values <2.5. PAHs levels were also higher in the inner sector, related to both biomass combustion and petroleum combustion associated to local marine traffic. High disturbance and low ecological status were reflected in low benthic diversity and high AMBI values in the inner sites.  相似文献   

Optical dating of clastic deposits generated by an extreme marine coastal flood: The 1755 tsunami deposits in the Algarve (Portugal)     

P.P. Cunha  J.P. Buylaert  A.S. Murray  C. Andrade  M.C. Freitas  F. Fatela  J.M. Munhá  A.A. Martins  S. Sugisaki 《Quaternary Geochronology》2010,5(2-3):329-335

Identification of past tsunamis is important for risk assessment and management of coastal areas. Obtaining accurate and precise ages of sediments originating from such extreme marine coastal floods is crucial for a reliable estimation of the recurrence interval of these often devastating events. We present here the results of quartz optical dating and ¹⁴C dating of two sites (Boca do Rio and Martinhal) on the Algarve coast (southern Portugal). These sites contain deposits of the great tsunami of November 1, 1755. The sections were described using sedimentological techniques; at both sites tsunami-laid sands and gravels were identified, intercalated between estuarine muds. Quartz luminescence ages from these sedimentary successions were derived using standard SAR-OSL dating using multi-grain sub-samples. A multiple sampling strategy was employed with several samples taken from the AD 1755 tsunami deposit and from the sediments bracketing the tsunami layer. Our SAR-OSL protocol was shown to be appropriate using dose recovery measurements (measured/given dose ratio of 1.004 ± 0.007, n = 165). The several OSL ages from the 1755 tsunamigenic deposits are internally reproducible but yield age overestimates of between 20 and 125% (60–310 years respectively); this is in agreement with values reported in the literature for similar deposits. The age overestimation of the tsunami-laid sands is presumably due to the rapid erosion and deposition of older sediments, with insufficient light exposure for complete bleaching during the tsunami event itself. The absence of significant bleaching during the tsunami is also suggested by the shape of the dose distributions based on sub-samples made up of only about 100 grains. Analysis of the distributions with the minimum-age model seems to yield the expected age for two of the three distributions. It is important to note that age offsets of a few tens of years to a few hundred years rapidly become insignificant when dating older (>1 to few ka) tsunami layers.  相似文献   

Stakeholder perceptions of the northern Gulf of Mexico grouper and tilefish individual fishing quota program     

Britni N. TokotchChristopher F. Meindl  Armando HoareMichael E. Jepson 《Marine Policy》2012,36(1):34-41

The Gulf of Mexico Fishery Management Council determined that previous management of the grouper and tilefish fisheries in the northern Gulf of Mexico were not meeting management goals, and developed a catch shares program using individual fishing quotas (IFQs) beginning in January 2010 in order to more effectively manage these fisheries. An IFQ is a management method in which individual fishers and corporations are allocated the right to harvest a percentage of a fishery's total allowable catch, thus specifying how much of a particular species each fisher can harvest. This study makes use of a mail out survey to document the perceptions of fishers, seafood wholesalers, fisheries managers, and academics with an interest in the (northern) Gulf of Mexico grouper and tilefish IFQ program. While fishers, seafood dealers, fisheries managers, and academics all acknowledge that the IFQ program will create some problems, commercial fishers and dealers were far more skeptical of the alleged benefits of IFQs. Moreover, larger commercial operators were more inclined to agree with managers and academics that the IFQ program will produce several benefits for their operations and the fisheries. Some smaller operators believe that they will be driven to ignore the new rules or be forced out of business. In the future, the Gulf Council might do two things: put a bit more effort into making fishers aware of the potential benefits of IFQs, and develop alternatives with more flexibility perhaps working more closely with communities of fishers, who prize their independent way of life above all else.  相似文献   

Geochemical Assessment of a Subtropical Reservoir: A Case Study in Curitiba,Southern Brazil     

Ricardo Henrique Moreton Godoi  Patricia Y. Hirata  Andre V. L. Bitterncourt  Ana F. L. Godoi  Miguel Jafelicci Jr  Francisco J. dos Santos  Rafael Bini  Liuz F. Zara  Cynara L. N. Cunha  Ana P. K Soares  Eduardo F. Gobbi  Sanja Potgieter‐Vermaak  José E. F. C. Gardolinski  José M. Reis Neto  Giuliana Gatto Rotondo  Rene van Grieken 《洁净——土壤、空气、水》2012,40(4):364-372

Suspended particles and dissolved substances in water provide reactive surfaces, influence metabolic activity and contribute to the net sediment deposition. It therefore plays an important part in the ecology and quality of the water mass. The water quality in reservoirs is crucial and it is naturally maintained by flushing and sedimentation, which continuously remove phosphorus from the water. In some reservoirs, however, these removal processes are countered by recycling of ions which could play a key role to start and/or maintain the eutrophic state. The combination of macro‐, trace‐ and microanalysis techniques can be useful to trace pollution sources through a chemical fingerprint, whether be during an acute environmental disaster or a long‐term release of pollutants. The water quality and total metal content of reservoir sediments were assessed in a reservoir, situated in the capital of the Paraná State, in the South‐Eastern part of Brazil. The goal of this paper was to determine the metal presence in the sediment and metal and ionic speciation in the Green River reservoir water. Water and bed sediment samples, collected from various sites during 2008 and 2009, were investigated using XRF, ICP‐OES, ICP‐MS, XRD and zeta potential measurements. Based on the results, the heavy metal concentration and chemical composition of the suspended matter in the water samples, as well as the sediment's chemical composition will be discussed.  相似文献   

Absorption and fluorescence properties of rainwater during the cold season at a town in Western Portugal   总被引：1，自引：0，他引：1  

Patrícia S. M. Santos  Regina M. B. O. Duarte  Armando C. Duarte 《Journal of Atmospheric Chemistry》2009,62(1):45-57

This study aims at evaluating the variability of the optical properties of chromophoric dissolved organic matter (CDOM) of rainwater during the cold season, specifically between Autumn and Winter periods. The spectroscopic characteristics of rainwater samples collected at a town (Aveiro) in western Portugal were assessed by UV-Vis absorbance and three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopies. Rainwater samples showed similar characteristics to those of natural humic substances when analysed by UV-Vis absorbance spectroscopy, but a significant difference was observed in the volume weight average (VWA) of absorbances between Autumn and Winter. In general, the EEM fluorescence spectra of the Autumn and Winter samples disclosed the presence of six fluorophores with different VWA specific fluorescence intensities: three humic-like (λ _excitation/λ _emission ≈ 230/415 nm; 290/415 nm; and 340/415 nm) and three protein-like (λ _excitation/λ _emission ≈ 230/350 nm; 280/340 nm; and 225/300 nm), but one of the humic-like peaks (≈340/415 nm) does not always appear in the EEM fluorescence spectra of the Winter samples. During the cold season, chromophoric compounds are important constituents of rainwater dissolved organic matter and the presence of these highly absorbing and fluorescing compounds may exert a determining effect in atmospheric absorption of solar radiation.  相似文献   

A reply to “Does temperature contain a stochastic trend? Evaluating conflicting statistical results” by R. K. Kaufmann et al     

Francisco Estrada  Carlos Gay  Armando Sánchez 《Climatic change》2010,101(3-4):407-414

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Management of non-structural measures in the prevention of flash floods: a case study in the city of Duque de Caxias,state of Rio de Janeiro,Brazil     

Priscila da Cunha Luz Barcellos  Marcello Silva da Costa  Marcio Cataldi  Carlos Alberto Pereira Soares 《Natural Hazards》2017,89(1):313-330

In the last years, natural hazards related to flash floods have caused serious damage and losses to the population of the state of Rio de Janeiro. This research discusses the importance of implementing a methodology for the prevention of flash floods, by comparing the methods applied since 2013 in the city of Duque de Caxias, in the Baixada Fluminense region of the state of Rio de Janeiro, Brazil, and the major prevention actions suggested by the Flash Flood Early Warning System Reference Guide from the National Oceanic and Atmospheric Administration, questioning civil defense professionals about the importance of each method to vulnerable communities. Even without the occurrence of an extreme event that proves the effectiveness of the method between 2014 and 2016, the population will certainly be better prepared to face the risks of disasters in the city in the future. In addition, the study also underscores an approach of approximation between academic studies and operational activities, which is still very incipient in Brazil.  相似文献   

Point defects and pre-dose requirements for sensitization of the 300°C TL peak in natural quartz     

Pedro L. Guzzo  Helen J. Khoury  Milena R. Miranda  Sandra B. Barreto  Armando H. Shinohara 《Physics and Chemistry of Minerals》2009,36(2):75-85

This paper discusses the structural features required to stimulate a strong thermoluminescence (TL) glow peak near 300°C in clear natural quartz. For that reason, fresh TL data taken from several specimens prepared from five single crystals with known impurity content are shown. The TL emission was measured with a test dose of 10 mGy of γ-rays in the readout intervals 50–160 and 160–320°C. The readings were carried out prior and after the administration of a pre-dose of 175 kGy of γ-rays followed by heat-treatments at 400°C. For each single specimen, the OH content and the population of inclusions were evaluated by infrared spectroscopy and optical microscopy, respectively. The darkening induced by high γ dose was evaluated by optical spectroscopy. It was observed that the absorption at 475 nm and TL responses decrease with increase of the OH. It was shown that both smoky darkening and TL signals were better explained in terms of Li/Al and Li/OH content ratios rather than the absolute values of aluminum and alkali concentrations. The sensitization with high γ dose and heating is essential to create and stabilize a class of defects sites with Li⁺ ions dislodged from [AlO₄/Li]⁰ and Li-dependent OH centers. It is suggested that the defect sites formed with Li⁺ act as electron traps during test dose irradiation, whereas electron-hole recombination occurs essentially at [AlO₄]⁰ centers during the TL output near 300°C.  相似文献