Evaluation of pile foundation response to lateral spreading   总被引：7，自引：0，他引：7  

Tarek Abdoun  Ricardo Dobry 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):1051-1058

The effects of liquefaction on deep foundations are very damaging and costly, and they keep recurring in many earthquakes. The first part of the paper reviews the field experience of deep foundations affected by liquefaction during earthquakes in the last few decades, as well as the main lessons learned. The second part of the paper presents results of physical modeling of deep foundations in the presence of liquefaction conducted by the authors and others at the 100g-ton RPI centrifuge. In the last decade centrifuge modeling has been identified as a key tool to identify and quantify mechanisms, calibrate analyses and evaluate retrofitting strategies for pile foundations. Results are presented of centrifuge models of instrumented pile foundations subjected to lateral spreading, including single pile and pile groups, 2- and 3-layer soil profiles, mass and stiffening elements above ground to incorporate the effect of the superstructure, and evaluation of proposed retrofitting strategies. Interpretations of these centrifuge experiments and their relation to field observations and soil properties.  相似文献   

Evaluation of sampling devices for the determination of polycyclic aromatic hydrocarbons in surface microlayer coastal waters     

Guitart C  García-Flor N  Dachs J  Bayona JM  Albaigés J 《Marine pollution bulletin》2004,48(9-10):961-968

The sea surface microlayer (SML) may play an important role on the transport and fate of persistent organic pollutants in the marine environment. In order to evaluate the appropriateness of a number of sampling devices for the analysis of 14 parent polycyclic aromatic hydrocarbons (3-5 aromatic rings), marine SML waters were sampled using a glass plate, a rotating drum/roller, a metal screen and a surface slick sampler. The underlying waters were also sampled for the determination of the corresponding enrichment factors (EF = [C](microlayer)/[C](underlying water)). The EFs were phase dependent, ranging from 1 to 3 for the dissolved phase and between 4 and 7 for the particulate phase. In order to better assess the performance of the different sampling methods, in terms of phase partitioning, the truly dissolved and colloidal phases were also estimated. Generally, no significant differences were found for the enrichment factors provided by the different methods, due to the observed large variability in concentrations that can be attributed to small-scale coastal processes. However, the metal screen is recommended as the most efficient sampling method for the study of PAHs taking into account the amount of water collected versus time.  相似文献   

Evolution of the Fine Structure of Magnetic Fields in the Quiet Sun: Observations from Sunrise/IMaX and Extrapolations     

T. Wiegelmann  S. K. Solanki  J. M. Borrero  H. Peter  P. Barthol  A. Gandorfer  V. Martínez Pillet  W. Schmidt  M. Knölker 《Solar physics》2013,283(2):253-272

Observations with the balloon-borne Sunrise/Imaging Magnetograph eXperiment (IMaX) provide high spatial resolution (roughly 100 km at disk center) measurements of the magnetic field in the photosphere of the quiet Sun. To investigate the magnetic structure of the chromosphere and corona, we extrapolate these photospheric measurements into the upper solar atmosphere and analyze a 22-minute long time series with a cadence of 33 seconds. Using the extrapolated magnetic-field lines as tracer, we investigate temporal evolution of the magnetic connectivity in the quiet Sun’s atmosphere. The majority of magnetic loops are asymmetric in the sense that the photospheric field strength at the loop foot points is very different. We find that the magnetic connectivity of the loops changes rapidly with a typical connection recycling time of about 3±1 minutes in the upper solar atmosphere and 12±4 minutes in the photosphere. This is considerably shorter than previously found. Nonetheless, our estimate of the energy released by the associated magnetic-reconnection processes is not likely to be the sole source for heating the chromosphere and corona in the quiet Sun.  相似文献   

Periodic orbits in the restricted four-body problem with two equal masses     

Jaime Burgos-García  Joaquín Delgado 《Astrophysics and Space Science》2013,345(2):247-263

The restricted (equilateral) four-body problem consists of three bodies of masses m ₁, m ₂ and m ₃ (called primaries) lying in a Lagrangian configuration of the three-body problem i.e., they remain fixed at the apices of an equilateral triangle in a rotating coordinate system. A massless fourth body moves under the Newtonian gravitation law due to the three primaries; as in the restricted three-body problem (R3BP), the fourth mass does not affect the motion of the three primaries. In this paper we explore symmetric periodic orbits of the restricted four-body problem (R4BP) for the case of two equal masses where they satisfy approximately the Routh’s critical value. We will classify them in nine families of periodic orbits. We offer an exhaustive study of each family and the stability of each of them.  相似文献   

A frequency criterion for optimal node selection in smoothing with cubic splines     

Jörg Schleicher  Ricardo Biloti 《Geophysical Prospecting》2008,56(2):229-237

When smoothing a function with high‐frequency noise by means of optimal cubic splines, it is often not clear how to choose the number of nodes. The more nodes are used, the closer the smoothed function will follow the noisy one. In this work, we show that more nodes mean a better approximation of Fourier coefficients for higher frequencies. Thus, the number of nodes can be determined by specifying a frequency up to which all Fourier coefficients must be preserved and increasing the number of nodes until this criterion is met. A comparison of the corresponding smoothing results with those obtained by filtering using moving average and moving median filters of corresponding length and a low pass with corresponding high‐cut frequency shows that optimal cubic splines yield better results as they preserve not only the desired low‐frequency band but also important high‐frequency characteristics.  相似文献   

Temporal and spatial changes of total and labile metal concentration in the surface sediments of the Vigo Ria (NW Iberian Peninsula): influence of anthropogenic sources     

Prego R  Filgueiras AV  Santos-Echeandía J 《Marine pollution bulletin》2008,56(5):1031-1042

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Towards an operational system for oil-spill forecast over Spanish waters: initial developments and implementation test     

Sotillo MG  Fanjul EA  Castanedo S  Abascal AJ  Menendez J  Emelianov M  Olivella R  García-Ladona E  Ruiz-Villarreal M  Conde J  Gómez M  Conde P  Gutierrez AD  Medina R 《Marine pollution bulletin》2008,56(4):686-703

The ESEOO Project, launched after the Prestige crisis, has boosted operational oceanography capacities in Spain, creating new operational oceanographic services and increasing synergies between these new operational tools and already existing systems. In consequence, the present preparedness to face an oil-spill crisis is enhanced, significantly improving the operational response regarding ocean, meteorological and oil-spill monitoring and forecasting. A key aspect of this progress has been the agreement between the scientific community and the Spanish Search and Rescue Institution (SASEMAR), significantly favoured within the ESEOO framework. Important achievements of this collaboration are: (1) the design of protocols that at the crisis time provide operational state-of-the-art information, derived from both forecasting and observing systems; (2) the establishment, in case of oil-spill crisis, of a new specialized unit, named USyP, to monitor and forecast the marine oceanographic situation, providing the required met-ocean and oil-spill information for the crisis managers. The oil-spill crisis scenario simulated during the international search and rescue Exercise "Gijón-2006", organized by SASEMAR, represented an excellent opportunity to test the capabilities and the effectiveness of this USyP unit, as well as the protocols established to analyze and transfer information. The results presented in this work illustrate the effectiveness of the operational approach, and constitute an encouraging and improved base to face oil-spill crisis.  相似文献   

Effects of the 'Prestige' oil spill on macroalgal assemblages: large-scale comparison     

Lobón CM  Fernández C  Arrontes J  Rico JM  Acuña JL  Anadón R  Monteoliva JA 《Marine pollution bulletin》2008,56(6):1192-1200

An assessment of the effects of the 'Prestige' oil spill on intertidal, macroalgal assemblages was carried out comparing abundance data obtained before and after the spill. Four zones in the North and Northwest coast of Spain were sampled, one of them located at the immediate vicinity of the spill, the zone most heavily oiled. Macroalgal assemblages had similar structure between years. Neither critical decrease in abundance of the dominant macroalgae, nor increase in opportunistic species were found. Some differences in abundance were observed, but they did not show any pattern, being more likely the result of the natural variability of the assemblage. Extensive, but not intense fuel deposition on the shores and a limited use of aggressive cleanup methods are suggested as possible causes for the lack of the effects in these assemblages after the 'Prestige' oil spill.  相似文献   

Organochlorine pesticide levels in loggerhead turtles (Caretta caretta) stranded in the Canary Islands, Spain     

Monagas P  Orós J  Araña J  González-Díaz OM 《Marine pollution bulletin》2008,56(11):1949-1952

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Spatial distribution of sedimentary linear alkylbenzenes and faecal steroids of Santos Bay and adjoining continental shelf, SW Atlantic, Brazil: origin and fate of sewage contamination in the shallow coastal environment   总被引：1，自引：0，他引：1  

Martins CC  Ferreira JA  Taniguchi S  Mahiques MM  Bícego MC  Montone RC 《Marine pollution bulletin》2008,56(7):1359-1363

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