The importance of wind forcing in fjord wave modelling     

Christakos  Konstantinos  Furevik  Birgitte R.  Aarnes  Ole Johan  Breivik  Øyvind  Tuomi  Laura  Byrkjedal  Øyvind 《Ocean Dynamics》2020,70(1):57-75

Ocean Dynamics - Accurate predictions of surface ocean waves in coastal areas are important for a number of marine activities. In complex coastlines with islands and fjords, the quality of wind...  相似文献   

Buckling of circular, annular plates of non-uniform thickness     

P.A.A. Laura  R.H. Gutierrez  V. Sonzogni  S. Idelsohn 《Ocean Engineering》1997,24(1):51-61

This paper deals with the solution of the title problem in the case where the outer boundary is subjected to uniform, hydrostatic pressure while the inner edge of the plate is free. It is assumed that the plate thickness varies (a) in a discontinuous fashion and (b) linearly.An approximate approach is proposed using polynomial coordinate functions which identically satisfy the boundary conditions at the outer edge, only. The eigenvalues are determined using the optimized Rayleigh-Ritz method and good engineering agreement is shown to exist with buckling parameters obtained by means of a finite element code.  相似文献   

A GIS method to identify flat surfaces and restore relict fluvial long-profiles from terrace remnants gives new clues on how large basins respond to endorheic–exorheic transitions (Duero basin,Iberian Peninsula)     

Laura Rodríguez-Rodríguez  Loreto Antón  Raimon Pallàs  Daniel García-Castellanos  Ivone Jiménez-Munt  Candela Pastor-Martín 《地球表面变化过程与地形》2020,45(4):1013-1027

Fluvial terraces are used as geomorphic indicators for deciphering long-term landscape evolution. Knowing the distribution of fluvial terraces is essential for establishing former river profiles and their tectonic significance, for studying climate-modulated processes of terrace development, or for defining fluvial network adjustments in response to sudden base-level changes like those produced by fluvial captures. Multiple methods for automatic map production have been proposed based on the comparison of morphometric indices with those of the modern river course. Here we propose an alternative method to identify flat surfaces and scarps separating them from digital elevation models without setting comparisons with a modern river course and thus fully applicable to study flat landforms whatever their origin. Its application to the low-relief landscape of the Cenozoic Duero basin has allowed the improvement of previous geomorphological maps and the analysis of fluvial network adjustments in response to a sudden base-level fall after the opening of the Neogene endorheic basin towards the Atlantic Ocean. Reconstructed terrace long-profiles suggest an initial episode of fast vertical incision followed by a period of repeated planation–aggradation–incision with the formation of 14 to 13 unpaired terrace levels. Changes observed in the pattern of terrace profiles are discussed with regard to changes in regional tectonics and base-level variations. © 2019 John Wiley & Sons, Ltd.  相似文献   

Event-scale pebble mobility observed by RFID tracking in a pre-Alpine stream: a field laboratory     

Vladislav Ivanov  Alessio Radice  Monica Papini  Laura Longoni 《地球表面变化过程与地形》2020,45(3):535-547

Understanding coarse sediment transport is crucial for the prediction of sediment migration and the consequent development of fluvial morphologies. In this study, cobble displacements in a pre-Alpine creek have been recorded by means of radio frequency identification (RFID). Pebble monitoring has been systematically performed after each rainfall event with moderate precipitation, in order to exclude the superimposition of sediment displacements induced by triggering factors acting at different times. The analysis of the collected data was carried out through the application of both a principal component analysis and the Buckingham Π theorem. The experimental trends were interpreted considering the ratio of mobile pebbles, the pebbles' displacement and virtual velocity as the dependent variables. These quantities mostly depend on the event peak discharge, with a nonlinear increase of the travelled distance and a growth of up to two orders of magnitude of the virtual velocity (for an approximately 10× increase in peak discharge). An inverse dependency of the virtual velocity on the event duration was also observed. A comparison of the results obtained with those from laboratory investigations of bedload transport mechanics evidenced the differences in parametric trends associated with sediment mobility in the two environments. This contrast brings forward the combination of multiple drivers of sediment mobility, such as local morphology, sediment dimensions and flow unsteadiness, warranting a further in-depth investigation. Representation of results in a dimensionless form is suggested as a good practice to analyse data from case studies characterized by different scales. © 2019 John Wiley & Sons, Ltd.  相似文献   

Resisting Corporate Multiculturalism: Mapping Faculty Initiatives and Institutional‐Student Harassment in the Classroom     

Heidi J. Nast  Laura Pulido 《The Professional geographer》2000,52(4):722-737

This paper argues that calls for multicultural curricula in universities across the US can be met with strategic curricular interventions that radically confront gendered racisms across regional, national, and international racial formations. Faculty who risk making such interventions should plan for student and institutional resistances. Intersecting consumer and corporate interests desire universities to be socially nonconflictual and economical places of leisure and entertainment, not sites of critical intervention. Accordingly, we theorize how and why faculty committed to oppositional multiculturalism might be cast as transgressive. In so doing, we pay particular attention to how identity politics are quadrangulated through embodiment, performance, time, and place. We additionally discuss ways for systematically working against the grain of gendered racisms and for supporting those who are teaching multiculturalism (critically) or seen to embody it. Working against the grain is particularly important as we enter the 21st century, given the increasing diversification of faculty and student bodies in universities across the US and the attendant risks “diverse” persons take, risks generally not experienced or acknowledged by White Americans.  相似文献   

Unsteady thermoelastic analysis of a circular disk with a hot central core and subjected to adiabatic conditions     

Carlos A. Rossit  Patricio A. A. Laura 《Ocean Engineering》2000,27(4)

The unsteady thermoelastic analysis of a cooling circular disk or cylinder which is originally at uniform temperature is a classical problem of the theory of thermal stresses. More recent studies consider the case of composite structural configurations. The present paper deals with a situation which, apparently, has not been previously considered: unsteady thermal stresses caused by the presence of a hot, central nucleus. The temperature field is obtained in terms of a Fourier–Bessel expansion and then, radial and tangential stresses are evaluated analytically. The problem is of basic interest in mechanical and naval engineering systems.  相似文献   

Winchcombe: An example of rapid terrestrial alteration of a CM chondrite     

Laura E. Jenkins  Martin R. Lee  Luke Daly  Ashley J. King  Cameron J. Floyd  Pierre-Etienne Martin  Natasha V. Almeida  Matthew J. Genge 《Meteoritics & planetary science》2024,59(5):988-1005

Winchcombe is a CM chondrite that fell in England on February 28, 2021. Its rapid retrieval was well characterized. Within two polished sections of Winchcombe, terrestrial phases were observed. Calcite and calcium sulfates were found in a sample recovered from a field on March 6, 2021, and halite was observed on a sample months after its recovery from a driveway on March 2, 2021. These terrestrial phases were characterized by scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. Calcite veins crosscut the fusion crust and therefore postdate it. The calcite likely precipitated in the damp environment (sheep field) where the meteorite lay for six days prior to its retrieval. The sulfates occur on the edges of the sample and were identified as three minerals: gypsum, bassanite, and anhydrite. Given that the sulfates occur only on the sample's edges, including on top of the fusion crust, they formed after Winchcombe fell. Sulfate precipitation is attributed to the damp fall environment, likely resulted from sulfide-derived H₂S reacting with calcite within the meteorite. Halite occurs as euhedral crystals only on the surface of a polished section and exclusively in areas relatively enriched in sodium. It was likely produced by the interaction of the polished rock slice with the humid laboratory air over a period of months. The sulfates, fusion crust calcite, and halite all post-date Winchcombe's entry into the Earth's atmosphere and showcase how rapidly meteorite falls can be terrestrially altered.  相似文献   

Modeling alternative paths of chemical evolution of Na-HCO3-type groundwater near Oak Ridge, Tennessee, USA   总被引：2，自引：0，他引：2  

Laura E. Toran  James A. Saunders 《Hydrogeology Journal》1999,7(4):355-364

 This paper demonstrates that both cation exchange, a commonly invoked mechanism, and silicate hydrolysis, which is less commonly considered, can produce Na-HCO₃-type water in sedimentary rocks. Evolution of Na-HCO₃ groundwater beneath the Oak Ridge Reservation, Tennessee, USA, was studied by comparing observed end-member groundwater composition from multiport samplers to compositions generated by reaction-path geochemical models. Observed groundwater compositions could be reproduced by either the silicate-hydrolysis model or the cation-exchange model. Secondary minerals precipitated in the silicate-hydrolysis model are similar to those present along fractures in the shale and carbonate host rocks, and observed molar Sr²⁺/Ca²⁺ ratios more closely resemble evolution from shale weathering. Both mechanisms should be considered to understand the evolution of Na-HCO₃ groundwater. Received, April 1998 · Revised, January 1999 · Accepted, March 1999  相似文献   

Measurements of the Henry's Law Coefficients of 2-Methyl-3-buten-2-ol, Methacrolein, and Methylvinyl Ketone   总被引：1，自引：0，他引：1  

Laura T. Iraci  Bradly M. Baker  Geoffrey S. Tyndall  John J. Orlando 《Journal of Atmospheric Chemistry》1999,33(3):321-330

Using an equilibrium headspace technique, Henry's law coefficients were measured for methacrolein (H = 6.5 ± 0.7 M atm-1) and methylvinyl ketone (41 ± 7.0 M atm-1) in water at 25 °C. In addition, 2-methyl-3-buten-2-ol was studied at 30 °C in water and in an aqueous ionic solution representative of plant tissue. Similar values were found in deionized water (65 ± 3.5 M atm-1) and in a 0.05 mol kg-1 Ca2+, K+, NO3-, SO42- solution (62 ± 0.8 M atm-1). These Henry's Law coefficients are too small to allow for significant partitioning of methacrolein, methylvinyl ketone or methylbutenol into cloud water under equilibrium conditions.  相似文献   

Numerical experiments on the Rayleigh-Ritz method when applied to doubly connected plates in the case of free edge holes     

P. A. A. Laura  D. R. Avalos  H. A. Larrondo  R. E. Rossi 《Ocean Engineering》1998,25(7)

Numerical experiments are performed on the determination of the fundamental frequency of transverse vibration of simply supported rectangular plates having rectangular holes with free edges. This constitutes a rather common technological situation since holes are present in plates or slabs due to operational conditions, namely passage of conduits or ducts, electric conductors, etc., Satisfying exactly the governing natural boundary conditions at the hole edges is practically an impossible task. This study reviews numerical experiments where the displacement function is expanded into a double Fourier series which constitutes the exact solution when the plate is simply connected. Satisfactory convergence is achieved when the plate is doubly connected.  相似文献