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Andrea Blašković Paolo Fastelli Hrvoje Čižmek Cristiana Guerranti Monia Renzi 《Marine pollution bulletin》2017,114(1):583-586
This paper reports baseline levels of litter (macro, meso and microplastics) in sediments collected from different areas of the Croatian MPA of the Natural Park of Tela??ica bay (Adriatic Sea, GSA n. 17). The distribution of total abundance according to size, for all analysed locations evidences that microplastics are the dominant fraction concerning item's numbers. In all analysed samples no macroplastics were found, while microplastics are 88.71% and mesoplastics are 11.29% of the total. 相似文献
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Cristiana Dumitrache Diana Rodica Constantin Marilena Mierla Constantin Oprea 《Earth, Moon, and Planets》2009,104(1-4):69-71
A complex filament composed by a main body a polar filament and a tail—a small filament situated between active regions, was observed between 6 and 14 January 2001. A decaying active region plays the role of attractor for this filament. We have studied the dynamics of the filament which disappeared in a spectacular CME, produced after a helical up-awarded movement of plasma in the filaments loops. 相似文献
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The study of the interaction of mud-flows with obstacles is important to define inundation zones in urban areas and to design the possible structural countermeasures. The paper numerically investigates the impact of a mud-flow on rigid obstacles to evaluate the force acting on them using two different depth-integrated theoretical models, Single-Phase Model(SPM) and Two-Phase Model(TPM), to compare their performance and limits. In the first one the water-sediment mixture is represented as a homogeneous continuum described by a shearthinning power-law rheology. Alternatively, the twophase model proposed by Di Cristo et al in 2016 is used, which separately accounts for the liquid and solid phases. The considered test cases are represented by a 1D landslide flowing on a steep slope impacting on a rigid wall and a 2D mud dam-break flowing on a horizontal bottom in presence of single and multiple rigid obstacles. In the 1D test case, characterized by a very steep slope, the Two-Phase Model predicts the separation between the two phases with a significant longitudinal variation of the solid concentration. In this case the results indicate appreciable differences between the two models in the estimation of both the wave celerity and the magnitude of the impact, with an overestimation of the peak force when using the Single-Phase Model. In the 2D test-cases, where the liquid and solid phases remain mixed, even if the flow fields predicted by the two models present some differences, the essential features of the interaction with the obstacles, along with the maximum impact force, are comparable. 相似文献
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Millen Maxim Viana da Fonseca Antonio Quintero Julieth Ferreira Cristiana Oztoprak Sadik Oser Cihan Bozbey Ilknur Aysal Namik Kosič Mirko Logar Janko 《Bulletin of Earthquake Engineering》2021,19(10):3987-4012
The seismic behaviour of a building on a liquefiable deposit is a complex interaction which involves quantifying both shaking induced damage and permanent ground deformation-related damage. In this paper the key parameters that influence both surface shaking and foundation settlements have been identified as the depth, thickness and liquefaction resistance of an equivalent liquefiable layer. These parameters can be used to develop an ‘equivalent soil profile’ that is analogous to the equivalent single degree-of-freedom that reduces the complexity of the dynamic response of a building into comparable and easily understood quantities. The equivalent soil profile is quantified independent of the seismic hazard, making it compatible with performance based design and assessment frameworks such that the building and soil profile can be directly assessed at different levels of seismic hazard. Several numerical studies are presented that demonstrate the influence of these key parameters on the ground surface shaking and foundation settlement. A set of criteria are proposed for classifying soil profiles into 22 different soil classes for regional loss assessment. An algorithm was developed for automatically fitting the equivalent soil profile to a cone penetration test trace and issues with the fitting are discussed. Field reconnaissance was undertaken to collect additional data to support existing datasets on the performance of buildings in Adapazari, during the 1999 Kocaeli, Turkey, earthquake (Mw = 7.4). The field case history data was used to investigate the correlation between the depth, thickness and liquefaction resistance of an equivalent liquefiable layer, on the extent of foundation permanent deformation. The case history data showed that in general a shallow, thick and weak liquefiable layer near the surface results in significant settlement but a lack of data for buildings on non-liquefiable deposits and the additional complexities involved with real buildings and soil deposits, meant that the trends observed in the idealised numerical models could not identified in the field case history data set.
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In the present paper, an analytical expression of the Green’s function of linearized Saint-Venant equations (LSVEs) for shallow
water waves is provided and applied to analyse the propagation of a perturbation superposed to a uniform flow. Independently
of the kinematic character of the base flow, i.e., subcritical or supercritical uniform flow, the effects of a non-uniform vertical velocity profile and a non-constant resistance
coefficient are accounted for. The use of the Darcy-Weisbach friction law allows a unified treatment of both laminar and turbulent
conditions. The influence on the wave evolution of the wall roughness and the fluid viscosity are finally discussed, showing
that in turbulent regime the assumption of constant friction coefficient may lead to an underestimation of both amplification
and damping factors on the wave fronts, especially at low Reynolds numbers. This conclusion has to be accounted for, particularly
in describing hyper-concentrated suspensions or other kinds of Newtonian mixtures, for which the high values of the kinematic
viscosity may lead to relatively low Reynolds numbers. 相似文献
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Carlo Baroni Francesco Fasano Giovanna Giorgetti Maria Cristina Salvatore Cristiana Ribecai 《Global and Planetary Change》2008,60(3-4):457-470
The relationship between the Ricker Hills Tillite (RHT), which represents the northernmost outcrop of lithified continental glacial deposits in Victoria Land, is discussed with respect to the glacial landscape assemblage of the Ricker Hills, a nunatak at the internal border of the Transantarctic Mountains. A warm-based ice sheet deposited the tillite and induced syn- to post-depositional glacial deformation under wet conditions both of the tillite and of the bedrock. The thickness of the ice sheet on the nunatak is estimated to have been 600 m, at most. The area had been deeply eroded before deposition of the RHT as documented by the low elevation of tillite outcrops located in overdeepened depressions of the nunatak. Micropaleontological analysis evidences only the presence of Permian to Jurassic palynomorphs. X-ray diffraction and SEM–EDS analyses of clay minerals in the RHT indicate continental chemical weathering under wet conditions after the RHT deposition. As documented by clay mineral assemblage variation in CRP drillholes, the progressive cooling of the Antarctic continent allowed chemical weathering in “warm” conditions until the Late Oligocene period in southern Victoria Land, leading to a chronological constrain for RHT deposition. Conservatively estimating the sea level to have been between the tillite outcrops and the erosional trimline limiting horns in the Ricker Hills, at the time of RHT deposition, we suggest that the maximum uplift of the area would not have exceeded 900–1500 m since at least Late Oligocene. 相似文献
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Simulating the diurnal cycle of rainfall in global climate models: resolution versus parameterization 总被引：1，自引：1，他引：0
Paul A. Dirmeyer Benjamin A. Cash James L. Kinter III Thomas Jung Lawrence Marx Masaki Satoh Cristiana Stan Hirofumi Tomita Peter Towers Nils Wedi Deepthi Achuthavarier Jennifer M. Adams Eric L. Altshuler Bohua Huang Emilia K. Jin Julia Manganello 《Climate Dynamics》2012,39(1-2):399-418
The effects of horizontal resolution and the treatment of convection on simulation of the diurnal cycle of precipitation during boreal summer are analyzed in several innovative weather and climate model integrations. The simulations include: season-long integrations of the Non-hydrostatic Icosahedral Atmospheric Model (NICAM) with explicit clouds and convection; year-long integrations of the operational Integrated Forecast System (IFS) from the European Centre for Medium-range Weather Forecasts at three resolutions (125, 39 and 16 km); seasonal simulations of the same model at 10 km resolution; and seasonal simulations of the National Center for Atmospheric Research (NCAR) low-resolution climate model with and without an embedded two-dimensional cloud-resolving model in each grid box. NICAM with explicit convection simulates best the phase of the diurnal cycle, as well as many regional features such as rainfall triggered by advancing sea breezes or high topography. However, NICAM greatly overestimates mean rainfall and the magnitude of the diurnal cycle. Introduction of an embedded cloud model within the NCAR model significantly improves global statistics of the seasonal mean and diurnal cycle of rainfall, as well as many regional features. However, errors often remain larger than for the other higher-resolution models. Increasing resolution alone has little impact on the timing of daily rainfall in IFS with parameterized convection, yet the amplitude of the diurnal cycle does improve along with the representation of mean rainfall. Variations during the day in atmospheric prognostic fields appear quite similar among models, suggesting that the distinctive treatments of model physics account for the differences in representing the diurnal cycle of precipitation. 相似文献
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This study provides new information on the evolution of the Tiber delta during the late Holocene, and describes the record of sedimentation in the Port of Claudius and Trajan. The Tiber flowed into the Tyrrhenian Sea in the area of the Port of Claudius and Trajan between the 8th and 5th centuries B.C. The harbor basins excavated by the Romans during the 1st and 2nd centuries A.D. were filled with sediments containing saltwater fauna, then brackish‐water fauna, and finally by alluvial and marsh deposits. The Port of Claudius and Trajan was silted in as a consequence of episodes of alluviation that correlate with environmental events, possibly triggered by global climate changes. © 2009 Wiley Periodicals, Inc. 相似文献