Eutrophication is one of the most common causes of water quality impairment of inland and marine waters. Its best-known manifestations are toxic cyanobacteria blooms in lakes and waterways and proliferations of green macro algae in coastal areas. The term eutrophication is used by both the scientific community and public policy-makers, and therefore has a myriad of definitions. The introduction by the public authorities of regulations to limit eutrophication is a source of tension and debate on the activities identified as contributing or having contributed decisively to these phenomena. Debates on the identification of the driving factors and risk levels of eutrophication, seeking to guide public policies, have led the ministries in charge of the environment and agriculture to ask for a joint scientific appraisal to be conducted on the subject. Four French research institutes were mandated to produce a critical scientific analysis on the latest knowledge of the causes, mechanisms, consequences and predictability of eutrophication phenomena. This paper provides the methodology and the main findings of this two years exercise involving 40 scientific experts.
Finite-element calculations are used to study strain fields in vertically aligned InAs islands in GaAs. Such strain fields are found to be quite different from those of uncovered islands and nearly insensitive to the position of the island in the stacking. The driving force for vertically self-organized growth is known to be the interacting strain fields induced by the islands. The calculation of strain fields by the finite-element method makes it possible to model the correlations between adjacent InAs layers. A kinetic approach based on the effect of strain on surface diffusion is first proposed. A thermodynamic model is then analyzed to predict local island nucleation probabilities. Pairing probabilities of correlation between stacked islands, first calculated in the case of the InAs/GaAs system, are extended to the case of III-V semiconductors with a cubic crystalline structure. They are shown to be essentially dependent both on the ratio between the spacer layer thickness and the island height and on the lattice mismatch between islands and spacer layers.
ElsevierSerrano Cruz, JR.; Olmeda González, PC.; Tiseira Izaguirre, AO.; García-Cuevas González, LM.; Lefebvre, A. (2013) AbstractThe aim of the present work is to show an approximation, through an experimental an theoretical study, to quantify the mechanical losses in a turbocharging system. These are linked to the dynamics in the turbo shaft bearings, both axial and radial. Theoretical and experimental methodologies are presented in order to develop a mechanical losses model. The experimental work consists on a measurement campaign in quasi-adiabatic operating conditions, while in the theoretical part, a mathematical model is developed taking into account the radial and axial bearings. The model uses some assumptions in order to solve the Navier-Stokes equations, leading to a simplified model which includes viscosity and the Reynolds number of the oil film formed on the bearings. The proposed model has shown a good agreement with the experimental data.
Residual stresses and clamped thermal expansion in LiNbO3 and LiTaO3 thin films Appl. Phys. Lett. 101, 122902 (2012) Tribological properties of nanocrystalline diamond films deposited by hot filament chemical vapor deposition AIP Advances 2, 032164 (2012) The combined effect of surface roughness and internal stresses on nanoindentation tests of polysilicon thin films J. Appl. Phys. 112, 044512 (2012) Mechanism for atmosphere dependence of laser damage morphology in HfO2/SiO2 high reflective films Finite element ͑FE͒ analysis and transmission electron microscopy ͑TEM͒ observations have been used to model stress relaxation in InAs quantum dots deposited on ͑001͒ GaAs. TEM observations show that these islands are coherently strained and the corresponding strain contrast is simulated using the dynamical electron diffraction contrast theory. The dot strain fields used for the TEM contrast simulations are deduced from FE calculations. These calculations show that elastic stress relaxation mainly occurs at the crest of the island and that the underlying substrate is under tension. That experimental TEM images and simulated images should match shows that the FE method of determination of the dot strain fields is valid ͑even in the case of microscopic objects͒, and that the shape of islands can be specified.
Nowadays turbocharging the internal combustion engine has become a key point in the reduction on pollutant emissions and the improvement on engine performance. The matching between the turbocharger and the engine is vital due to the highly unsteady flow the turbocharger works with. In the present paper the importance of the heat transfer phenomena inside small automotive turbochargers will be analyzed. This phenomenon will be studied from the point of view of both the turbine and the compressor in one-dimensional modelling. The goodness of the model will be demonstrated predicting turbine and compressor outlet temperatures. An accurate prediction of these parameters will be key designing the intercooler and the after treatment devices. A series of tests in a gas stand with steady and pulsating hot flow in the turbine side will be modeled to show the good agreement in turbocharger enthalpies prediction.
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