Note on the intensity of encountered waves     

Igor Rychlik  Sofia Aberg  Ross Leadbetter 《Ocean Engineering》2007,34(11-12):1561-1568

An apparent wave is a part of the sea record observed between two successive upcrossings of the still water level. Integral formulas are given for intensities of encountered waves that overtake a ship sailing in directional sea with constant velocity. The formulas can be evaluated exactly in the case when the directional spectrum is known and the sea is assumed to be Gaussian, i.e. is a sum of noninteracting sinusoidal waves.  相似文献   

Temporal Variations of Nutrients, ­Chlorophyll a and Particulate Matter in Three Coastal Lagoons of Amvrakikos Gulf (Ionian Sea, Greece)     

Konstantinos A. Kormas  Artemis Nicolaidou  & Sofia Reizopoulou 《Marine Ecology》2001,22(3):201-213

Abstract. The temporal variations of nutrients, chlorophyll a (chl a ), suspended particulate matter (SPM) and particulate organic carbon (POC) were measured over 12 months in three shallow coastal brackish water lagoons of the Amvrakikos Gulf, Ionian Sea. Two of the lagoons, Tsoukalio and Rodia, are interconnected but separated from Logarou by a narrow strip of land. Logarou has a better water exchange with the sea as indicated by the higher salinity and dissolved oxygen concentrations and the smaller variation of the above-mentioned parameters. Nitrate concentrations were largely the same in the three lagoons and higher than in the Amvrakikos Gulf. Phosphate concentrations in Logarou exceeded by far those of Tsoukalio/Rodia; the increased phosphate levels recorded in January caused an extended phytoplankton bloom with chl a concentrations higher than in the other two lagoons. Chl a in Tsoukalio was positively correlated with nitrate whereas in the most shallow lagoon, Logarou, it showed a positive correlation with light winds (force 4 and lower), probably caused by resuspension from the sediment. Increased phytoplankton biomass in Logarou coupled with the better water exchange may be related to the higher fish production in this lagoon.  相似文献   

Forced imbibition into a limestone: measuring P‐wave velocity and water saturation dependence on injection rate     

Sofia Lopes  Maxim Lebedev  Tobias M. Müller  Michael B. Clennell  Boris Gurevich 《Geophysical Prospecting》2014,62(5):1126-1142

Quantitative interpretation of time‐lapse seismic data requires knowledge of the relationship between elastic wave velocities and fluid saturation. This relationship is not unique but depends on the spatial distribution of the fluid in the pore‐space of the rock. In turn, the fluid distribution depends on the injection rate. To study this dependency, forced imbibition experiments with variable injection rates have been performed on an air‐dry limestone sample. Water was injected into a cylindrical sample and was monitored by X‐Ray Computed Tomography and ultrasonic time‐of‐flight measurements across the sample. The measurements show that the P‐wave velocity decreases well before the saturation front approaches the ultrasonic raypath. This decrease is followed by an increase as the saturation front crosses the raypath. The observed patterns of the acoustic response and water saturation as functions of the injection rate are consistent with previous observations on sandstone. The results confirm that the injection rate has significant influence on fluid distribution and the corresponding acoustic response. The complexity of the acoustic response —‐ that is not monotonic with changes in saturation, and which at the same saturation varies between hydrostatic conditions and states of dynamic fluid flow – may have implications for the interpretation of time‐lapse seismic responses.  相似文献   

Strength,deformation capacity and failure modes of RC walls under cyclic loading   总被引：1，自引：1，他引：0  

Sofia Grammatikou  Dionysis Biskinis  Michael N. Fardis 《Bulletin of Earthquake Engineering》2015,13(11):3277-3300

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Metrics for quantifying anthropogenic impacts on geomorphology: road networks          下载免费PDF全文

Giulia Sofia  Francesco Marinello  Paolo Tarolli 《地球表面变化过程与地形》2016,41(2):240-255

This work tests the capability of a recently published topographic index, the Slope Local Length of Auto‐correlation (SLLAC), to portrait and delineate anthropogenic geomorphologies. The patterns of the anthropogenic pressure are defined considering the road network density and the Urban Complexity Index (UCI). First, the research investigates the changes in the SLLAC in two derived parameters (average SLLAC and the SLLAC surface peak curvature – Spc – per km²) connected to the increasing of the anthropogenic structures. Next, natural and anthropogenic landscapes are clustered and classified. The results show that there is a direct correlation between the road network density and the UCI, and the mean SLLAC per km². However, the Spc is inversely correlated with the anthropogenic pressure (network density and urban complexity). This shows that the surface morphology (slope) of regions presenting anthropogenic structures tends to be well organized (low Spc) and, in general, self‐similar at a long distance (higher average SLLAC). The results of the clustering approach show that the procedure can correctly depict anthropogenic landscapes having a road network density greater than about 3 km/km², also in areas covered by vegetation. This latter result is promising for the use of such a procedure in regions that cannot be seen directly from orthophotos or satellite images. The proposed method can actively capture the alteration produced by road networks on surface morphology identifying different signatures of urban development: exploration and densification networks that are responsible for increasing the local density of the network and expanding the network into new areas, respectively. The effects of this alteration on surface processes could be significant for future research, creating new questions about differences due to human or landscape forcing on Earth surface processes. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Energy dissipation models for RC members and structures     

Sofia Grammatikou  Michael N. Fardis  Dionysis Biskinis 《地震工程与结构动力学》2019,48(3):287-305

The unloading parameters of hysteretic models for RC members are given in terms of their shear-span-to-depth ratio and the viscous damping used to model other energy dissipation sources. They reflect the energy dissipation in full post-yield load cycles in 534 tests of rectangular or circular members. Pre-yield hysteretic energy dissipation—ignored if the model is elastic till yielding—amounts in the tests to a mean viscous damping around 8.5% and can be considered in nonlinear response-history analysis through a new model which combines constant elastic stiffness in virgin loading with hysteretic energy dissipation both before and after yielding. Models with linear behavior till yielding and hysteretic energy dissipation only after it come closer to the results of the new model if viscous damping is 5%.  相似文献   

Drainage network detection and assessment of network storage capacity in agrarian landscape     

Federico Cazorzi  Giancarlo Dalla Fontana  Alberto De Luca  Giulia Sofia  Paolo Tarolli 《水文研究》2013,27(4):541-553

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Fish assemblages of small estuaries of the Portuguese coast: A functional approach   总被引：1，自引：0，他引：1  

Inês Cardoso  Susana França  Miguel Pessanha Pais  Sofia Henriques  Luis Cancela da Fonseca  Henrique N. Cabral 《Estuarine, Coastal and Shelf Science》2011

The importance of estuaries for coastal environments is widely acknowledged but their role, structure and ecological status have been the focus of recent scientific efforts mainly concerning large estuarine areas. In this work we used fish assemblages to establish, for the first time, the functional and ecological role of five small estuarine systems along the Portuguese south and southwest coasts. Our results showed that, at a functional approach, fish communities did not differ between estuaries, and that all systems presented a seasonal pattern in diversity values, ecological and feeding guilds. These small estuaries contribute to the support of coastal fish populations by providing temporary habitats to the critical life stages of marine species, shelter and feeding grounds, and should be considered in an ecological and conservation perspective.  相似文献   

Solar variability and climate     

Sabatino Sofia  Peter Fox 《Climatic change》1994,27(3):249-257

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Chronology of the sedimentary processes during the postglacial sea level rise in two estuaries of the Algarve coast,Southern Portugal     

T. Boski  S. Camacho  D. Moura  W. Fletcher  A. Wilamowski  C. Veiga-Pires  V. Correia  C. Loureiro  P. Santana 《Estuarine, Coastal and Shelf Science》2008

Four profiles of estuarine sediments obtained from boreholes drilled in the Algarve, Southern Portugal were studied in order to reconstruct the process of sediment accumulation driven by the postglacial sea level rise. In addition to the sedimentological analysis, the Foraminifera Index of Marine Influence (FIMI) permitted assessment of the nature and organization of sedimentary facies in the Beliche–Guadiana and Gilão–Almargem estuaries. The Beliche–Guadiana CM5 and Almargem G2 profiles accumulated in a sheltered environment, with the former presenting an almost continuous record of the sea level rise since ca 13?000 cal yr BP. The G1 and G3 profiles from the Gilão–Almargem area represent a more discontinuous record of the last 8000 years, which accumulated in the more dynamic environment of an outer estuary. The integration of all radiocarbon ages of dated levels, led to an estimate of sediment accumulation rates. Assuming a constant position of the sediment surface with respect to the tidal range and a negligible compaction of sediment, the sea level rose at the rate of 7 mm yr⁻¹ in the period from 13?000 to 7500 cal yr BP. This process slowed down to ca 0.9 mm yr⁻¹ from 7500 cal yr BP until the present. The marked historical change in the rate of sediment accumulation in these estuaries also occurred with the accumulation of organic matter and is, therefore, important data for global biogeochemical models of carbon. The main obstacle to obtain higher temporal resolution of the sedimentary processes was the intense anaerobic respiration of organic matter via sulphate reduction, which did not allow any accumulation of peat and, furthermore, led to erasure of the palaeontological record by acid formed from the subsequent oxidation of sulphides.  相似文献