Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework   总被引：1，自引：1，他引：0  

Vincenzo Marco Gatto  Bram Christiaan van Prooijen  Zheng Bing Wang 《Ocean Dynamics》2017,67(11):1385-1406

Net sediment transport in tidal basins is a subtle imbalance between large fluxes produced by the flood/ebb alternation. The imbalance arises from several mechanisms of suspended transport. Lag effects and tidal asymmetries are regarded as dominant, but defined in different frames of reference (Lagrangian and Eulerian, respectively). A quantitative ranking of their effectiveness is therefore missing. Furthermore, although wind waves are recognized as crucial for tidal flats’ morphodynamics, a systematic analysis of the interaction with tidal mechanisms has not been carried out so far. We review the tide-induced barotropic mechanisms and discuss the shortcomings of their current classification for numerical process-based models. Hence, we conceive a unified Eulerian framework accounting for wave-induced resuspension. A new methodology is proposed to decompose the sediment fluxes accordingly, which is applicable without needing (semi-) analytical approximations. The approach is tested with a one-dimensional model of the Vlie basin, Wadden Sea (The Netherlands). Results show that lag-driven transport is dominant for the finer fractions (silt and mud). In absence of waves, net sediment fluxes are landward and spatial (advective) lag effects are dominant. In presence of waves, sediment can be exported from the tidal flats and temporal (local) lag effects are dominant. Conversely, sand transport is dominated by the asymmetry of peak ebb/flood velocities. We show that the direction of lag-driven transport can be estimated by the gradient of hydrodynamic energy. In agreement with previous studies, our results support the conceptualization of tidal flats’ equilibrium as a simplified balance between tidal mechanisms and wave resuspension.  相似文献   

A multi‐performance design method for seismic upgrading of existing RC frames by BRBs          下载免费PDF全文

Francesca Barbagallo  Melina Bosco  Edoardo M. Marino  Pier Paolo Rossi  Paola R. Stramondo 《地震工程与结构动力学》2017,46(7):1099-1119

In the world, many existing buildings with RC framed structure were designed according to old seismic standards and present structural deficiencies. Buckling Restrained Braces (BRBs) can be effective for seismic upgrading of these structures, as pointed out by many studies. Nevertheless, Eurocode 8 (EC8) does not provide any rules for design of BRBs. This lack represents a big obstacle for application of this seismic upgrading technique in Europe. For this reason, a method for the design of seismic upgrading interventions by BRBs is proposed in this paper. The method is obtained as the best between two variants developed, investigated and compared in this paper. Based on a numerical investigation, the parameters that control the design method are calibrated to ensure the fulfillment of the Near Collapse performance objective stipulated in EC8. Finally, the capability of the proposed design method in fulfilling also performance objectives not explicitly considered in design is investigated. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Quantum gravity with THESEUS     

Burderi  L.  Sanna  A.  Di Salvo  T.  Riggio  A.  Iaria  R.  Gambino  A. F.  Manca  A.  Anitra  A.  Mazzola  S. M.  Marino  A. 《Experimental Astronomy》2021,52(3):439-452

Experimental Astronomy - In this paper we explore the possibility to search for a dispersion law for light propagation in vacuo with a sample of Gamma-Ray Bursts detected by the THESEUS satellite....  相似文献   

Variability in the Hydrographic and Biological Features of the Gulf of Naples   总被引：3，自引：0，他引：3  

Carrada  G.C.  Hopkins  T.S.  Bonaduce  G.  Ianora  A.  Marino  D.  Modigh  M.  Ribera  D'Alcalà M. Scotto  di Carlo B. 《Marine Ecology》1980,1(2):105-120

Abstract. Recent observations of physico-chemical and biological parameters in the Gulf of Naples are summarized. The water masses present within the Gulf during the various periods of the year are described. The temporal and spatial distribution of surface nutrients (N-NO₃, P-PO₄, Si-SiO₄) and chlorophyll a are reported and the areas exposed to local eutrophication are identified. Biweekly sampling at a reference station has permitted us also to identify both phytoplankton and zooplankton seasonal cycles. The morphology of the basin and the uneven land runoff distribution are interpreted as causal to the variability of chemico-physical parameters and of the associated biological communities, giving rise to two subsystems (coastal and "open water") within the Gulf.  相似文献   

Summer Phytoplankton Physiognomy in Coastal Waters of the Gulf of Naples     

Adriana  Zingone  Marina  Montresor Donato  Marino 《Marine Ecology》1990,11(2):157-172

Abstract. Thirteen sampling cruises were conducted at weekly intervals in the inner part of the Gulf of Naples in the summer of 1983 to investigate the effects of excess nutrient inputs on phytoplankton communities. High surface phytoplankton concentrations (up to 1.15 ×10⁸ cells 1^-1) were recorded, particularly near Naples harbour and along the eastern coast, two locations that receive most of the area's sewage and industrial discharge. Phytoplankton populations were generally dominated by small species, mainly diatoms, which were associated with small phytoflagcllatcs. Species diversity values were relatively high (H'≤ 3.62) in most samples. Throughout the sampling period a high spatial and temporal variability for phytoplankton abundances and species composition was observed.  相似文献   

A unified approach for the design of high ductility steel frames with concentric braces in the framework of Eurocode 8          下载免费PDF全文

Edoardo M. Marino 《地震工程与结构动力学》2014,43(1):97-118

Eurocode 8 (EC8) stipulates design methods for frames with diagonal braces and for chevron braced frames, which differ as regards the numerical model adopted, the value of the behavior factor q and the estimation of the lateral strength provided by braces. Instead, in this paper, the use of the same design method is suggested for both types of concentrically braced frames. The design method is a generalization of the one proposed for chevron braced frames in a previous study. A numerical investigation is conducted to assess the reliability of this design method. A set of concentrically braced frames is designed according to the EC8 and proposed design methods. The seismic response of these frames is determined by nonlinear dynamic analysis. Finally, it is demonstrated that the proposed design method is equivalent to those provided by EC8, because it can ensure the same level of structural safety which would be expected when using EC8. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Water-table and discharge changes associated with the 2016–2017 seismic sequence in central Italy: hydrogeological data and a conceptual model for fractured carbonate aquifers     

Petitta  Marco  Mastrorillo  Lucia  Preziosi  Elisabetta  Banzato  Francesca  Barberio  Marino Domenico  Billi  Andrea  Cambi  Costanza  De Luca  Gaetano  Di Carlo  Giuseppe  Di Curzio  Diego  Di Salvo  Cristina  Nanni  Torquato  Palpacelli  Stefano  Rusi  Sergio  Saroli  Michele  Tallini  Marco  Tazioli  Alberto  Valigi  Daniela  Vivalda  Paola  Doglioni  Carlo 《Hydrogeology Journal》2018,26(4):1009-1026

A seismic sequence in central Italy from August 2016 to January 2017 affected groundwater dynamics in fractured carbonate aquifers. Changes in spring discharge, water-table position, and streamflow were recorded for several months following nine Mw 5.0–6.5 seismic events. Data from 22 measurement sites, located within 100 km of the epicentral zones, were analyzed. The intensity of the induced changes were correlated with seismic magnitude and distance to epicenters. The additional post-seismic discharge from rivers and springs was found to be higher than 9 m³/s, totaling more than 0.1 km³ of groundwater release over 6 months. This huge and unexpected contribution increased streamflow in narrow mountainous valleys to previously unmeasured peak values. Analogously to the L’Aquila 2009 post-earthquake phenomenon, these hydrogeological changes might reflect an increase of bulk hydraulic conductivity at the aquifer scale, which would increase hydraulic heads in the discharge zones and lower them in some recharge areas. The observed changes may also be partly due to other mechanisms, such as shaking and/or squeezing effects related to intense subsidence in the core of the affected area, where effects had maximum extent, or breaching of hydraulic barriers.

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Exchange of Nitrogen and Phosphorus Between a Shallow Lagoon and Coastal Waters     

Melanie Hayn  Robert Howarth  Roxanne Marino  Neil Ganju  Peter Berg  Kenneth H. Foreman  Anne E. Giblin  Karen McGlathery 《Estuaries and Coasts》2014,37(1):63-73

West Falmouth Harbor, a shallow lagoon on Cape Cod, has experienced a threefold increase in nitrogen load since the mid- to late 1990s due to input from a groundwater plume contaminated by a municipal wastewater treatment plant. We measured the exchange of nitrogen and phosphorus between the harbor and the coastal waters of Buzzards Bay over several years when the harbor was experiencing this elevated nitrogen load. During summer months, the harbor not only retained the entire watershed nitrogen load but also had a net import of nitrogen from Buzzards Bay. During the spring and fall, the harbor had a net export of nitrogen to Buzzards Bay. We did not measure the export in winter, but assuming the winter net export was less than 112 % of the load, the harbor exported less than half of the watershed nitrogen load on an annual basis. For phosphorus, the harbor had a net import from coastal waters in the spring and summer months and a net export in the fall. Despite the large increase in nitrogen load to the harbor, the summertime import of phosphorus from Buzzards Bay was sufficient to maintain nitrogen limitation of primary productivity during the summer. Our findings illustrate that shallow systems dominated by benthic producers have the potential to retain large terrestrial nitrogen loads when there is sufficient supply of phosphorus from exchange with coastal waters.  相似文献