Green water overtopping analyzed with a SPH model   总被引：3，自引：0，他引：3  

M. Gmez-Gesteira  D. Cerqueiro  C. Crespo  R.A. Dalrymple 《Ocean Engineering》2005,32(2):651-238

Wave overtopping on the decks of offshore platforms and ships can cause severe damage due to the high forces generated by the water. This phenomenon is analyzed within the framework of the Smoothed Particle Hydrodynamics (SPH) method. The presence of a fixed horizontal deck above the mean water level modifies strongly the wave kinematics. In particular, the flow in the wave crest is split into two, showing a different behavior above and below the deck. Numerical results generated by the SPH method are compared to laboratory experiments. The formation of a jet in the rear of the deck after overtopping is observed under extreme conditions.  相似文献   

Monitoring the status of a mechanical cable while in operation by means of the acoustic emission method     

Patricio A.A. Laura  James R. Matthews 《Ocean Engineering》1985,12(3):211-219

The mechanical cable is an essential element in towing operations, remote control of equipment, salvage operations, civil engineering applications, etc.Failure of these cables can result in loss of life and loss of equipment worth hundreds of thousands of dollars. Obviously then, sensors that can indicate the condition of these cables so that the risk to their continued use and their remaining safe life can be determined when in operation are very important from the point of view of commercial and military interest.This paper presents a brief review of research into failure mechanisms of various cables and the acoustic emission signatures of the various cables under simulated loading. The development of a specific operational monitor for a towed cable system is also given.  相似文献   

Advances in lithium analysis in solids by means of laser-induced breakdown spectroscopy: an exploratory study     

Cécile Fabre  Marie-Christine BoironJean Dubessy  Aliouka ChabironBernard Charoy  Tomas Martin Crespo 《Geochimica et cosmochimica acta》2002,66(8):1401-1407

Lithium is an important geochemical tracer for fluids or solids. However, because the electron microprobe cannot detect Li, variations of Li abundance at the micrometric scale are most often estimated from bulk analyses. In this study, the Li intense emission line at 670.706 nm in optical emission spectroscopy was used to perfect the analysis of Li at the micrometric scale by means of laser-induced breakdown spectroscopy (LIBS). To estimate lithium content for different geological materials, LIBS calibration of the emission line at 670.706 nm was achieved by use of synthetic glasses and natural minerals. The detection limit for this method is ∼5 ppm Li. Three applications to geological materials show the potential of LIBS for lithium determination, namely for Li-bearing minerals, melt inclusions, quartz, and associated fluid inclusions.For spodumene and petalite from granite pegmatite dikes (Portugal), the Li₂O concentrations are 7.6 ± 1.6 wt% and 6.3 ± 1.3 wt%, respectively, by use of LIBS. These values agree with ion microprobe analyses, bulk analyses, or both. For eucryptite crystals, the Li concentrations are scattered because grain size is smaller than the LIBS spatial resolution (6 to 8 μm). Lithium concentrations of melt inclusions from the Streltsovka U deposit (Siberia) are in the range of 2 to 6.2 wt% (Li₂O) for Li-rich daughter minerals. Lithium estimations on silicate glasses display values between 90 and 400 ppm.Lithium was also analyzed as a trace element in quartz. Transverse profiles were performed in hydrothermal barren quartz veins from the Spanish Central System (Sierra de Guadarrama). The highest Li concentrations (250 to 370 ppm) were found in specific growth bands in conjunction with the observed variation in optical cathodoluminescence intensity. Considering the fluid inclusion analysis, the source of fluid responsible to the Li enrichment in quartz is probably high-salinity fluids derived from sedimentary basins.  相似文献   

Glacial flood pulse effects on benthic fauna in equatorial high‐Andean streams          下载免费PDF全文

Sophie Cauvy‐Fraunié  Patricio Andino  Rodrigo Espinosa  Roger Calvez  Fabien Anthelme  Dean Jacobsen  Olivier Dangles 《水文研究》2014,28(6):3008-3017

Equatorial glacier‐fed streams present unique hydraulic patterns when compared to glacier‐fed observed in temperate regions as the main variability in discharge occurs on a daily basis. To assess how benthic fauna respond to these specific hydraulic conditions, we investigated the relationships between flow regime, hydraulic conditions (boundary Reynolds number, Re*), and macroinvertebrate communities (taxon richness and abundance) in a tropical glacier‐fed stream located in the high Ecuadorian Andes (> 4000 m). Both physical and biotic variables were measured under four discharge conditions (base‐flow and glacial flood pulses of various intensities), at 30 random points, in two sites whose hydraulic conditions were representative to those found in other streams of the study catchment. While daily glacial flood pulses significantly increased hydraulic stress in the benthic habitats (appearance of Re* > 2000), low stress areas still persisted even during extreme flood events (Re* < 500). In contrast to previous research in temperate glacier‐fed streams, taxon richness and abundance were not significantly affected by changes in hydraulic conditions induced by daily glacial flood pulses. However, we found that a few rare taxa, in particular rare ones, preferentially occurred in highly stressed hydraulic habitats. Monte‐Carlo simulations of benthic communities under glacial flood reduction scenarios predicted that taxon richness would be significantly reduced by the loss of high hydraulic stress habitats following glacier shrinking. This pioneer study on the relationship between hydraulic conditions and benthic diversity in an equatorial glacial stream evidenced unknown effects of climate change on singular yet endangered aquatic systems. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Difference of Ti,Zr, Y and P content in calc-alkaline andesites from island arcs and continental margin (Central Andes)     

Carlos M. Palacios  Nelson S. Guerra  Patricio B. Campano 《International Journal of Earth Sciences》1983,72(2):733-738

Ti, Zr, Y and P, known to be chemically immobile elements during alteration and metamorphism, have been ploted in a set of diagrams in order to discriminative between calc-alkaline andesites from island arcs and continental margin. This method may be an appropiate procedure to help in the discrimination between ancient volcanics of both groups.  相似文献   

Discussion of “A simple method to determine breaker height and depth for different deepwater wave height/length ratios and sea floor slopes”, by J.P. Le Roux [Coastal Engineering 54 (2007) 271–277]     

Merrick C. Haller  Patricio A. Catalán 《Coastal Engineering》2008

In the recent paper by J.P. Le Roux [Coastal Engineering 54 (2007) 271–277], the author provides a simplified approach to calculating the depth, length, and height of waves at the onset of depth-induced breaking (i.e. at the breaker line). However, the proposed methodology and the comparisons to other methods suffer from a large number of inconsistencies and basic calculation errors. In addition, there are a number of erroneous physical interpretations and many of the conclusions are based on erroneous data. The remaining conclusions are either not new or based on circular logic, such as to render them moot. In the following, we will not attempt to point out all the errors or inconsistencies that we found, instead we focus on major points of contention.  相似文献   

Optical archival spectra of blazar candidates of uncertain type in the 3rd Fermi Large Area Telescope Catalog     

N. Álvarez Crespo  F. Massaro  R. D’Abrusco  M. Landoni  N. Masetti  V. Chavushyan  E. Jiménez-Bailón  F. La Franca  D. Milisavljevic  A. Paggi  V. Patiño-Álvarez  F. Ricci  Howard A. Smith 《Astrophysics and Space Science》2016,361(9):316

  相似文献   

The Use of Geographically Weighted Regression for Spatial Prediction: An Evaluation of Models Using Simulated Data Sets   总被引：5，自引：0，他引：5  

P. Harris  A. S. Fotheringham  R. Crespo  M. Charlton 《Mathematical Geosciences》2010,42(6):657-680

Increasingly, the geographically weighted regression (GWR) model is being used for spatial prediction rather than for inference. Our study compares GWR as a predictor to (a) its global counterpart of multiple linear regression (MLR); (b) traditional geostatistical models such as ordinary kriging (OK) and universal kriging (UK), with MLR as a mean component; and (c) hybrids, where kriging models are specified with GWR as a mean component. For this purpose, we test the performance of each model on data simulated with differing levels of spatial heterogeneity (with respect to data relationships in the mean process) and spatial autocorrelation (in the residual process). Our results demonstrate that kriging (in a UK form) should be the preferred predictor, reflecting its optimal statistical properties. However the GWR-kriging hybrids perform with merit and, as such, a predictor of this form may provide a worthy alternative to UK for particular (non-stationary relationship) situations when UK models cannot be reliably calibrated. GWR predictors tend to perform more poorly than their more complex GWR-kriging counterparts, but both GWR-based models are useful in that they provide extra information on the spatial processes generating the data that are being predicted.  相似文献   

Resurfacing history of Europa from pole-to-pole geological mapping     

Patricio H. Figueredo  Ronald Greeley 《Icarus》2004,167(2):287-312

We produced geologic maps from two regional mosaics of Galileo images across the leading and trailing hemispheres of Europa in order to investigate the temporal distribution of units in the visible geologic record. Five principal terrain types were identified (plains, bands, ridges, chaos, and crater materials), which are interpreted to result from (1) tectonic fracturing and lineament building, (2) cryovolcanic reworking of surface units, with possible emplacement of sub-surface materials, and (3) impact cratering. The geologic histories of both mapped areas are essentially similar and reflect some common trends: Tectonic resurfacing dominates the early geologic record with the formation of background plains by intricate superposition of lineaments, the opening of wide bands with infilling of inter-plate gaps, and the buildup of ridges and ridge complexes along prominent fractures in the ice. It also appears that lineaments are narrower and more widely spaced with time. The lack of impact craters overprinted by lineaments indicate that the degree of tectonic resurfacing decreased rapidly after ridged plains formation. In contrast, the degree of cryovolcanic resurfacing appears to increase with time, as chaos formation dominates the later parts of the geologic record. These trends, and the transition from tectonic- to cryovolcanic-dominated resurfacing could be attributed to the gradual thickening of Europa's cryosphere during the visible geologic history, that comprises the last 2% or 30-80 Myr of Europa's history: An originally thin, brittle ice shell could be pervasively fractured or melted through by tidal and endogenic processes; the degree of fracturing and plate displacements decreased with time in a thickening shell, and lineaments became narrower and more widely spaced; formation of chaos regions could have occurred where the thickness threshold for solid-state convection was exceeded, and can be aided by preferential tidal heating of more ductile ice. In a long-term context it is not clear at this point whether this inferred thickening trend would reflect a drastic change in the thermal evolution of the satellite, or cyclic or irregular episodes of tectonic and cryovolcanic activity.  相似文献   

Do mixing models with different input requirement yield similar streamflow source contributions? Case study: A tropical montane catchment     

Jorge Ramón  Alicia Correa  Edison Timbe  Giovanny M. Mosquera  Enma Mora  Patricio Crespo 《水文研究》2021,35(6):e14209

Hydrogeochemical based mixing models have been successfully used to investigate the composition and source identification of streamflow. The applicability of these models is limited due to the high costs associated with data collection and the hydrogeochemical analysis of water samples. Fortunately, a variety of mixing models exist, requiting different amount of data as input, and in data scarce regions it is likely that preference will be given to models with the lowest requirement of input data. An unanswered question is if models with high or low input requirement are equally accurate. To this end, the performance of two mixing models with different input requirement, the mixing model analysis (MMA) and the end-member mixing analysis (EMMA), were verified on a tropical montane headwater catchment (21.7 km²) in the Ecuadorian Andes. Nineteen hydrogeochemical tracers were measured on water samples collected weekly during 3 years in streamflow and eight potential water sources or end-members (precipitation, lake water, soil water from different horizons and springs). Results based on 6 conservative tracers, revealed that EMMA (using all tracers) and MMA (using pair-combinations out of the 6 conservative ones), identified the same end-members: rainfall, soil water and spring water., as well as, similar contribution fractions to streamflow from rainfall 21.9% and 21.4%, soil water 52.7% and 52.3%, and spring water 26.1% and 28.7%, respectively. Our findings show that a hydrogeochemical mixing model requiring a few tracers can provide similar outcomes than models demanding more tracers as input data. This underlines the value of a preliminary detailed hydrogeochemical characterization as basis to derive the most cost-efficient monitoring strategy.  相似文献