29 research outputs found
Numerical modelling of the effect of the hydro-kinetic turbines on the transport of sediments - Application to the Rhone site
Confirmation of beach accretion by grain-size trend analysis: Camposoto beach, Cádiz, SW Spain
An application of the grain size trend analysis
(GSTA) is used in an exploratory approach to characterize
sediment transport on Camposoto beach (Cádiz, SW Spain).
In May 2009 the mesotidal beach showed a well-developed
swash bar on the upper foreshore, which was associated
with fair-weather conditions prevailing just before and during
the field survey. The results were tested by means of an
autocorrelation statistical test (index I of Moran). Two sedimentological
trends were recognized, i.e. development towards
finer, better sorted and more negatively skewed
sediment (FB–), and towards finer, better sorted and less
negatively or more positively skewed sediment (FB+). Both
vector fields were compared with results obtained from
more classical approaches (sand tracers, microtopography
and current measurements). This revealed that both trends
can be considered as realistic, the FB+ trend being identified
for the first time in a beach environment. The data demonstrate
that, on the well-developed swash bar, sediment
transported onshore becomes both finer and better sorted
towards the coast. On the lower foreshore, which exhibits a
steeper slope produced by breaking waves, the higherenergy
processes winnow out finer particles and thereby
produce negatively skewed grain-size distributions. The upper
foreshore, which has a flatter and smoother slope, is
controlled by lower-energy swash-backwash and overwash
processes. As a result, the skewness of the grain-size distributions
evolves towards less negative or more positive
values. The skewness parameter appears to be distributed
as a function of the beach slope and, thus, reflects variations
in hydrodynamic energy. This has novel implications for
coastal management
Rejuvenation of metallic glasses by non-affine thermal strain.
When a spatially uniform temperature change is imposed on a solid with more than one phase, or on a polycrystal of a single, non-cubic phase (showing anisotropic expansion-contraction), the resulting thermal strain is inhomogeneous (non-affine). Thermal cycling induces internal stresses, leading to structural and property changes that are usually deleterious. Glasses are the solids that form on cooling a liquid if crystallization is avoided--they might be considered the ultimate, uniform solids, without the microstructural features and defects associated with polycrystals. Here we explore the effects of cryogenic thermal cycling on glasses, specifically metallic glasses. We show that, contrary to the null effect expected from uniformity, thermal cycling induces rejuvenation, reaching less relaxed states of higher energy. We interpret these findings in the context that the dynamics in liquids become heterogeneous on cooling towards the glass transition, and that there may be consequent heterogeneities in the resulting glasses. For example, the vibrational dynamics of glassy silica at long wavelengths are those of an elastic continuum, but at wavelengths less than approximately three nanometres the vibrational dynamics are similar to those of a polycrystal with anisotropic grains. Thermal cycling of metallic glasses is easily applied, and gives improvements in compressive plasticity. The fact that such effects can be achieved is attributed to intrinsic non-uniformity of the glass structure, giving a non-uniform coefficient of thermal expansion. While metallic glasses may be particularly suitable for thermal cycling, the non-affine nature of strains in glasses in general deserves further study, whether they are induced by applied stresses or by temperature change.This research was supported by the World Premier International Research Center Initiative (WPI), MEXT, Japan, by NSF China and MOST 973 China, and by the Engineering and the Engineering and Physical Sciences Research Council, UK (Materials World Network project). Y.H.S. acknowledges support from a China Scholarship Council (CSC) scholarship.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nature1467
Essential Nutrients for Bone Health and a Review of their Availability in the Average North American Diet
Osteoporosis and low bone mineral density affect millions of Americans. The majority of adults in North America have insufficient intake of vitamin D and calcium along with inadequate exercise. Physicians are aware that vitamin D, calcium and exercise are essential for maintenance of bone health. Physicians are less likely to be aware that dietary insufficiencies of magnesium, silicon, Vitamin K, and boron are also widely prevalent, and each of these essential nutrients is an important contributor to bone health. In addition, specific nutritional factors may improve calcium metabolism and bone formation. It is the authors’ opinion that nutritional supplements should attempt to provide ample, but not excessive, amounts of factors that are frequently insufficient in the typical American diet
Numerical modelling of the effect of the hydro-kinetic turbines on the transport of sediments - Application to the Rhone site
Self healing glassy coating for high temperature application | Matériaux vitreux auto-cicatrisants pour application à haute température, élaborés sous forme de couches minces
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«Matériaux vitreux auto-cicatrisants pour applications haute températures»
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