Oil spill fishery impact assessment model: Sensitivity to spill location and timing     

Malcolm L. Spaulding  Mark Reed  Eric Anderson  Tatsusaburo Isaji  J.Craig Swanson  Saul B. Saila  Ernesto Lorda  Henry Walker 《Estuarine, Coastal and Shelf Science》1985,20(1):41-53

An oil spill fishery impact assessment model system has been applied to the Georges Bank-Gulf of Maine region to assess the sensitivity of probable impact on several key fisheries to spill location and timing. Simulations of the impact on the fishery of tanker spills (20 million gallons released over 5 days), at two separate locations for each season of the year, and blowout spills (68 million gallons released over 30 days) at one location, with monthly releases and at six other locations with seasonal spills have been studied. Atlantic cod has been employed as the principal fish species throughout the simulations. Impacts on Atlantic herring and haddock have also been investigated for selected cases. All spill sites are located on Georges Bank with the majority in the general region of OCS leasing activity.The results of these simulations suggest a complex interaction among spill location and timing, the spatial and temporal distribution of spawning, the population dynamics of the species under study, and the hydrodynamics of the area. For the species studied, spills occurring during the winter and spring have the largest impact with cod being the most heavily impacted followed by haddock and herring. In all cases, the maximum cumulative loss to the fishery of a one time spill event never exceeded 25% of the annual catch with the exact value depending on the number of ichthyoplankton impacted by the spill and the compensatory dynamics of the population.  相似文献   

Determination of the spinel group end-members based on electron microprobe analyses     

Gabriela R. Ferracutti  M. Florencia Gargiulo  M. Luján Ganuza  Ernesto A. Bjerg  Silvia M. Castro 《Mineralogy and Petrology》2015,109(2):153-160

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Seismic Bearing Capacity of Strip Footings Located Close to the Crest of Geosynthetic Reinforced Soil Structures     

Ernesto Ausilio 《Geotechnical and Geological Engineering》2014,32(4):885-899

This paper investigates the performance of geo-reinforced soil structures subjected to loading applied to strip footings positioned close to a slope crest. The kinematic theorem of limit analysis, which is based on the upper bound theory of plasticity, is applied for evaluating the ultimate bearing capacity within the framework of pseudo-static approach to account for earthquake effects. The mechanism considered in this analysis is a logarithmic spiral failure surface, which is assumed to start at the edge of the loaded area far from the slope, consistent with the observed failure mechanisms shown in the experimental tests reported in the literature. A parametric study is then carried out to investigate the influence of various parameters including the geosynthetic configuration, backfill soil friction angle, footing distances from the crest of the slope, slope angles and horizontal seismic coefficients. Attention is paid to the failure mechanism because its maximum depth is the depth at least to which the reinforcements must be placed. Results of the analyses are presented in the form of non-dimensional design charts for practical use. Finally, a simple procedure based on the assessment of earthquake-induced permanent displacements is shown for the design of footing resting on reinforced slopes subjected to earthquake.  相似文献   

Timing and rate of granulite facies metamorphism and cooling from multi-mineral chronology on migmatitic gneisses,Sierras de La Huerta and Valle Fértil,NW Argentina     

Florian Gallien  Aberra Mogessie  Ernesto Bjerg  Sergio Delpino  Brigida Castro de Machuca  Martin Thöni  Urs Klötzli 《Lithos》2010,114(1-2):229-252

Migmatitic paragneisses of the Valle Fértil–La Huerta Ranges at the Western margin of the Sierras Pampeanas are composed of garnet–cordierite–plagioclase–biotite–quartz-bearing units that experienced peak metamorphic conditions of ca. 800 °C at 6–7 kbar. Based on petrological studies, pseudosection modeling and petrographic observations, an anticlockwise P–T path with a small pressure increment is proposed. Rare earth element LA-ICP-MS patterns acquired from rutile bearing garnets suggest a single stage of garnet growth at high-T at pressures above the ilmenite–rutile transition. U–Pb dating of zircon rims from the migmatites indicates two distinct metamorphic U–Pb ages of 525 ± 9 Ma and 478 ± 9 Ma. The older age is suggested to record an amphibolite facies event of the Pampean orogeny. The younger metamorphic age is contemporary with igneous zircons from metatonalites and pegmatites that yield 478 ± 4 Ma. We suggest that the prograde high-T metamorphic Famatinian event is associated with the emplacement of large magmatic bodies in which large-scale magmatic activity gave rise to an increased geothermal gradient of about 35 °C/km. Sm–Nd garnet ages of 447 ± 3 Ma indicate a time span of around 30 Ma for which temperatures above the garnet closure temperature prevailed. Using U–Pb, Sm–Nd and Rb–Sr isotope systems, a cooling rate of 3 to 6 °C/Myr is inferred.  相似文献   

Scaling properties and spatial organization of snow depth fields in sub‐alpine forest and alpine tundra     

Ernesto Trujillo  Jorge A. Ramírez  Kelly J. Elder 《水文研究》2009,23(11):1575-1590

This paper reports on a study analysing the spatial distribution functions, the correlation structures, and the power spectral densities of high‐resolution LIDAR snow depths (～1 m) in two adjacent 500 m × 500 m areas in the Colorado Rocky Mountains, one a sub‐alpine forest the other an alpine tundra. It is shown how and why differences in the controlling physical processes induced by variations in vegetation cover and wind patterns lead to the observed differences in spatial organization between the snow depth fields of these environments. In the sub‐alpine forest area, the mean of snow depth increases with elevation, while its standard deviation remains uniform. In the tundra subarea, the mean of snow depth decreases with elevation, while its standard deviation varies over a wide range. The two‐dimensional correlations of snow depth in the forested area indicate little spatial memory and isotropic conditions, while in the tundra they indicate a marked directional bias that is consistent with the predominant wind directions and the location of topographic ridges and depressions. The power spectral densities exhibit a power law behaviour in two frequency intervals separated by a break located at a scale of around 12 m in the forested subarea, and 65 m in the tundra subarea. The spectral exponents obtained indicate that the snow depth fields are highly variable over scales larger than the scale break, while highly correlated below. Based on the observations and on synthetic snow depth fields generated with one‐ and two‐dimensional spectral techniques, it is shown that the scale at which the break occurs increases with the separation distance between snow depth maxima. In addition, the breaks in the forested area coincide with those of the corresponding vegetation height field, while in the tundra subarea they are displaced towards larger scales than those observed in the corresponding vegetation height field. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Motions close to escapes in the rhomboidal four body problem     

Ernesto A. Lacomba  Ernesto Pérez-Chavela 《Celestial Mechanics and Dynamical Astronomy》1993,57(3):411-437

In this work we study escape and capture orbits in the planar rhomboidal 4-body problem in a level of constant negative energy. There are only two different values of the masses here. By using numerical analysis, we show certain transversal intersections of the invariant manifolds of parabolic orbits. We then introduce Symbolic Dynamics when the mass ratio is small, and when it is close to one. In the first case the escapes or captures predominate in the direction of one of the diagonals of the rhombus, while in the second case we find solutions escaping or being captured in the direction of both possible diagonals.  相似文献   

The Anisotropic Schwarzschild-Type Problem, Main Features     

Vasile Mioc  Ernesto Pérez-Chavela  Magda Stavinschi 《Celestial Mechanics and Dynamical Astronomy》2003,86(1):81-106

The two-body problem associated to an anisotropic Schwarzschild-type field is being tackled. Both the motion equations and the energy integral are regularized via McGehee-type transformations. The regular vector field exhibits nice symmetries that form a commutative group endowed with an idempotent structure. The physically fictitious flows on the collision and infinity manifolds, as well as the local flows in the neighbourhood of these manifolds, are fully described. Homothetic, spiral, and oscillatory orbits are pointed out. Some features of the global flow are depicted for all possible levels of energy. For the negative-energy case, few things have been done. The positive-energy global flow does not have zero-velocity curves; every orbit is of the type ejection – escape or capture – collision. In the zero-energy case, the collision and infinity manifolds have a very similar structure. The existence of eight trajectories that connect the equilibria on these manifolds is proved. The projectability of the zero-energy global flow completes the full understanding of the problem in this case.  相似文献   

Gravitational microlensing of γ-ray blazars     

Diego F. Torres  Gustavo E. Romero  Ernesto F. Eiroa  Joachim Wambsganss  Martín E. Pessah 《Monthly notices of the Royal Astronomical Society》2003,339(2):335-352

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The complete SRSS modal combination rule     

Ernesto Heredia‐Zavoni 《地震工程与结构动力学》2011,40(11):1181-1196

The complete Square‐Root‐of‐Sum‐of‐Squares (c‐SRSS) modal combination rule is presented. It expresses the structural response in terms of uncoupled SDOF modal responses, yet accounting fully for modal response variances and cross‐covariances. Thus, it is an improvement over the classical SRSS rule which neglects contributions from modal cross‐covariances. In the c‐SRSS rule the spectral moments of the structural response are expressed rigorously in terms of the spectral moments of uncoupled modal responses and of some coefficients that can be computed straightforwardly as a function of modal frequencies and damping, without involving the computation of cross‐correlation coefficients between modal responses. An example shows an application of the c‐SRSS rule for structural systems with well separated and closely spaced modal frequencies, subjected to wide‐band and narrow‐band excitations. Comparisons with response calculations using the SRSS and the Complete Quadratic Combination rules are given and discussed in detail. Based on the c‐SRSS rule a response spectrum formulation is introduced to estimate the maximum structural response. An example considering a narrow‐band excitation from the great Mexico earthquake of September 19, 1985, is given and the accuracy of the response spectrum formulation is examined. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

An Analytical Model for Hydraulic Fracturing in Shallow Bedrock Formations     

José Sérgio dos Santos  Thomas Paul Ballestero  Ernesto da Silva Pitombeira 《Ground water》2011,49(3):415-425

A theoretical method is proposed to estimate post‐fracturing fracture size and transmissivity, and as a test of the methodology, data collected from two wells were used for verification. This method can be employed before hydrofracturing in order to obtain estimates of the potential hydraulic benefits of hydraulic fracturing. Five different pumping test analysis methods were used to evaluate the well hydraulic data. The most effective methods were the Papadopulos‐Cooper model (1967), which includes wellbore storage effects, and the Gringarten‐Ramey model (1974), known as the single horizontal fracture model. The hydraulic parameters resulting from fitting these models to the field data revealed that as a result of hydraulic fracturing, the transmissivity increased more than 46 times in one well and increased 285 times in the other well. The model developed by dos Santos (2008) , which considers horizontal radial fracture propagation from the hydraulically fractured well, was used to estimate potential fracture geometry after hydrofracturing. For the two studied wells, their fractures could have propagated to distances of almost 175 m or more and developed maximum apertures of about 2.20 mm and hydraulic apertures close to 0.30 mm. Fracturing at this site appears to have expanded and propagated existing fractures and not created new fractures. Hydraulic apertures calculated from pumping test analyses closely matched the results obtained from the hydraulic fracturing model. As a result of this model, post‐fracturing geometry and resulting post‐fracturing well yield can be estimated before the actual hydrofracturing.  相似文献