2,076 research outputs found
Spoken Thesaurus: Sorrow
The Hindi Thesaurus addresses such questions in a series of lively, unscripted Hindi-medium conversations about groups of words of related meaning. Concentrating on selected mainstream words and phrases, we help you to broaden your active vocabulary by encountering styles of language appropriate for everyday speech. The conversations are between Rupert Snell (Hindi teacher and perpetual Hindi learner) and Neha Ladha (mother-tongue speaker of Hindi). Glossaries for each podcast can be read online or downloaded in PDF format. (Length: 7:49)Asian Studie
Statistical characterization of spatio-temporal sediment dynamics in the Venice lagoon
Characterizing the dynamics of suspended sediment is crucial when investigating the long-term evolution of tidal landscapes. Here we apply a widely tested mathematical model which describes the dynamics of cohesive and noncohesive sediments, driven by the combined effect of tidal currents and wind waves, using 1 year long time series of observed water levels and wind data from the Venice lagoon. The spatiotemporal evolution of the computed suspended sediment concentration (SSC) is analyzed on the basis of the \u201cpeak over threshold\u201d theory. Our analysis suggests that events characterized by high SSC can be modeled as a marked Poisson process over most of the lagoon. The interarrival time between two consecutive over threshold events, the intensity of peak excesses, and the duration are found to be exponentially distributed random variables over most of tidal flats. Our study suggests that intensity and duration of over threshold events are temporally correlated, while almost no correlation exists between interarrival times and both durations and intensities. The benthic vegetation colonizing the central
southern part of the Venice lagoon is found to exert a crucial role on sediment dynamics: vegetation locally decreases the frequency of significant resuspension events by affecting patiotemporal patterns of SSCs also in adjacent areas. Spatial patterns of the mean interarrival of over threshold SSC events are found to be less heterogeneous than the corresponding patterns of mean interarrivals of over threshold bottom shear stress events because of the role of advection/dispersion processes in mixing suspended sediments within the lagoon. Implications for long-term morphodynamic modeling of tidal environments are discussed
Field migration rates of tidal meanders recapitulate fluvial morphodynamics
The majority of tidal channels display marked meandering features.
Despite their importance in oil-reservoir formation and
tidal landscape morphology, questions remain on whether tidalmeander
dynamics could be understood in terms of fluvial processes
and theory. Key differences suggest otherwise, like the
periodic reversal of landscape-forming tidal flows and the widely
accepted empirical notion that tidal meanders are stable landscape
features, in stark contrast with their migrating fluvial counterparts.
On the contrary, here we show that, once properly
normalized, observed migration rates of tidal and fluvial meanders
are remarkably similar. Key to normalization is the role of
tidal channel width that responds to the strong spatial gradients
of landscape-forming flow rates and tidal prisms. We find that
migration dynamics of tidal meanders agree with nonlinear theories
for river meander evolution. Our results challenge the conventional
view of tidal channels as stable landscape features and
suggest that meandering tidal channels recapitulate many fluvial
counterparts owing to large gradients of tidal prisms across meander
wavelengths
Virtual water controlled demographic growth of nations
Population growth is in general constrained by food production, which in turn
depends on the access to water resources. At a country level, some populations
use more water than they control because of their ability to import food and
the virtual water required for its production. Here, we investigate the
dependence of demographic growth on available water resources for exporting and
importing nations. By quantifying the carrying capacity of nations based on
calculations of the virtual water available through the food trade network, we
point to the existence of a global water unbalance. We suggest that current
export rates will not be maintained and consequently we question the long-run
sustainability of the food trade system as a whole. Water rich regions are
likely to soon reduce the amount of virtual water they export, thus leaving
import-dependent regions without enough water to sustain their populations. We
also investigate the potential impact of possible scenarios that might mitigate
these effects through (1) cooperative interactions among nations whereby water
rich countries maintain a tiny fraction of their food production available for
export; (2) changes in consumption patterns; and (3) a positive feedback
between demographic growth and technological innovations. We find that these
strategies may indeed reduce the vulnerability of water-controlled societies.Comment: 11 pages, 3 figure
Using SAS functions and high resolution isotope data to unravel travel time distributions in headwater catchments
Acknowledgments. We are grateful to the European Research Council (ERC) VeWa project (GA335910) and NERC/JIP SIWA project (NE/MO19896/1) for funding. A.R. acknowledges the financial support from the ENAC school at EPFL. C.B. acknowledges support from the University of Costa Rica (project 217-B4-239 and the Isotope Network for Tropical Ecosystem Studies (ISONet)). Data to support this study are provided by the Northern Rivers Institute, University of Aberdeen and are available by the authors. The authors wish to thank Ype van der Velde, Arash Massoudieh, Jean-Raynald de Dreuzy and an anonymous referee for the useful review comments.Peer reviewedPublisher PD
Sonic Hyperbolic Phase Transitions and Chapman-Jouguet Detonations
AbstractWe prove that the Cauchy problem for an nĂn system of strictly hyperbolic conservation laws in one space dimension admits a weak global solution also in presence of sonic phase boundaries. Applications to ChapmanâJouguet detonations, liquidâvapor transitions and elastodynamics are considered
On the O'Brien-Jarrett-Marchi law
The relationship between the total water volume entering a lagoon during a characteristic tidal cycle (i.e., the prism) and the size of its inlet is well established empirically since the classic work of O'Brien and Jarrett widely cited in the geomorphic and hydrodynamic literature. Less known is a rather deep theoretical explanation proposed by Marchi. This paper reviews the empirical and theoretical evidence on which the relation is based, setting the various theoretical approaches so far pursued within the general framework ensured by Marchi's theoretical treatment of the problem. We conclude that the depth of the empirical and theoretical validations and the breadth and the importance of its implications suggest that the O'Brien-Jarrett-Marchi law relating the minimum inlet cross-sectional area and the tidal prism flowing through it may be referred to thereinafte
Models of Fractal River Basins
Two distinct models for self-similar and self-affine river basins are
numerically investigated. They yield fractal aggregation patterns following
non-trivial power laws in experimentally relevant distributions. Previous
numerical estimates on the critical exponents, when existing, are confirmed and
superseded. A physical motivation for both models in the present framework is
also discussed.Comment: 16 pages, latex, 9 figures included using uufiles command (for any
problem: [email protected]), to be publishes in J. Stat. Phys. (1998
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