Combien coûte l’électricité produite par le photovoltaïque (PV) en Suisse ?: situation, analyse des coûts détaillée et comparaison avec l’Allemagne

Le but de ce travail est d’évaluer la rentabilité et le potentiel des installations photovoltaïques afin de voir si cette technologie peut remplacer le nucléaire en Suisse. Après avoir présenté les concepts de bases relatifs à l’énergie électrique d’origine solaire, j’ai détaillé la situation suisse et introduit brièvement la situation allemande afin d’observer les différences entre les deux pays. Les alternatives aux nucléaires ainsi que leurs potentiels en Suisse ont également été exposés. Par la suite, l’évolution des coûts du photovoltaïque a été analysée afin de pouvoir procéder aux calculs relatifs au rendement de différentes installations. Enfin, j’ai étudié l’impact du développement de l’énergie photovoltaïque sur l’offre d’électricité et les défis en découlant. La recherche documentaire a été privilégiée pour la rédaction de ce rapport. Des précisions ont été demandées à des spécialistes en fonction des besoins. La sortie du nucléaire est un défi majeur pour le secteur énergétique suisse. Son remplacement par des énergies renouvelables est possible mais requiert des changements à plusieurs niveaux. Par ailleurs, la baisse du coût du photovoltaïque rend cette technologie plus accessible. Son utilisation est également encouragée par la rétribution à prix coûtant du courant injecté et par la rétribution unique, même si cette dernière est pour l’instant moins avantageuse en raison du faible prix de l’électricité. Le potentiel de l’énergie solaire est réel mais son développement dépend de la volonté des politiciens en ce qui concerne la rénovation des réseaux de distribution, l’augmentation des capacités de stockage et la promotion de ce moyen de production à l’aide d’incitations

KINEMATIC AND DYNAMIC COUPLED MEASUREMENTS IN TETHERED FRONT CRAWL SWIMMING

Force measurements of athletes in aquatic environments are difficult to perform. Competitive swimming has been confronted with this problem for many years. Tethered swimming is a means used to measure propulsive forces (Martin, Yeater & White, 1981). According to Filho and Denadai (2008), this method is often used to measure the performance level of swimmers and also as a training resource. Its validity has been shown on numerous occasions, notably in its good correlation between swimming velocity, stroke frequency and the measured forces (Yeater, Martin, White & Gilson, 1981; Morouço, Keskinen, Vilas-Boas & Fernandes, 2011). This method has good test–retest reliability (Kjendlie & Thorsvald, 2006), and it provides muscle activity patterns very similar to those displayed in free swimming (Bollens, Annemans, Vaes, & Clarys, 1988). Even if there are questions about the swimming technique used in the tethered swimming compared to the free swimming, this method is important to know the forces created by the stroke technique, especially by the arms. It seems also interesting to measure the forces in the three characteristic paces (long distance, middle distance and sprint). This kinematic and dynamic coupled method is transferable in training pool, and then it could be an everyday tool for swimmers and coaches to measure and to improve the technical swimmers

HYDRODYNAMIC ANGLES, ORIENTATION AND VELOCITY OF THE HAND IN FRONT CRAWL SWIMMING

The hydrodynamic parameters of the hand (angle of attack, sweepback, velocity and orientation) play an important role in the generation of the resultant forces. These parameters were measured throughout an aquatic stroke to study the possible modifications caused by a variation of the swimming pace. Seventeen competitive swimmers swam at the long distance, middle distance and sprint paces. Parameters were calculated from the trajectory of seven markers on the hand measured with an optoelectronic system. Results showed that sweepback and angle of attack, and orientation of the hand do not vary significantly depending to the pace. Only the velocity of the hand increases when the pace increases, but only during the less propulsive phases. The increase of pace is then explained by the swimmer's capacity to maintain propulsive phases rather than increasing the force generation within each cycle

Snow Processes in Mountain Forests: Interception Modeling for Coarse-Scale Applications

Snow interception by the forest canopy controls the spatial heterogeneity of subcanopy snow accumulation leading to significant differences between forested and nonforested areas at a variety of scales. Snow intercepted by the forest canopy can also drastically change the surface albedo. As such, accurately modeling snow interception is of importance for various model applications such as hydrological, weather, and climate predictions. Due to difficulties in the direct measurements of snow interception, previous empirical snow interception models were developed at just the point scale. The lack of spatially extensive data sets has hindered the validation of snow interception models in different snow climates, forest types, and at various spatial scales and has reduced the accurate representation of snow interception in coarse-scale models. We present two novel empirical models for the spatial mean and one for the standard deviation of snow interception derived from an extensive snow interception data set collected in an evergreen coniferous forest in the Swiss Alps. Besides open-site snowfall, subgrid model input parameters include the standard deviation of the DSM (digital surface model) and/or the sky view factor, both of which can be easily precomputed. Validation of both models was performed with snow interception data sets acquired in geographically different locations under disparate weather conditions. Snow interception data sets from the Rocky Mountains, US, and the French Alps compared well to the modeled snow interception with a normalized root mean square error (NRMSE) for the spatial mean of ≤10 % for both models and NRMSE of the standard deviation of ≤13 %. Compared to a previous model for the spatial mean interception of snow water equivalent, the presented models show improved model performances. Our results indicate that the proposed snow interception models can be applied in coarse land surface model grid cells provided that a sufficiently fine-scale DSM is available to derive subgrid forest parameters

Difficulties with Recovering The Masses of Supermassive Black Holes from Stellar Kinematical Data

We investigate the ability of three-integral, axisymmetric, orbit-based modeling algorithms to recover the parameters defining the gravitational potential (M/L ratio and black hole mass Mh) in spheroidal stellar systems using stellar kinematical data. We show that the potential estimation problem is generically under-determined when applied to long-slit kinematical data of the kind used in most black hole mass determinations to date. A range of parameters (M/L, Mh) can provide equally good fits to the data, making it impossible to assign best-fit values. We illustrate the indeterminacy using a variety of data sets derived from realistic models as well as published observations of the galaxy M32. In the case of M32, our reanalysis demonstrates that data published prior to 2000 are equally consistent with Mh in the range 1.5x10^6-5x10^6 solar masses, with no preferred value in that range. While the HST/STIS data for this galaxy may overcome the degeneracy in Mh, HST data for most galaxies do not resolve the black hole's sphere of influence and in these galaxies the degree of degeneracy allowed by the data may be substantial. We investigate the effect on the degeneracy of enforcing smoothness (regularization) constraints. However we find no indication that the true potential can be recovered simply by enforcing smoothness. For a given smoothing level, all solutions in the minimum-chisquare valley exhibit similar levels of noise. These experiments affirm that the indeterminacy is real and not an artifact associated with non-smooth solutions. (Abridged)Comment: Accepted for publication in The Astrophysical Journal. Changes include discussion of regularizatio

Antimicrobial Drug Use and Methicillin-resistant Staphylococcus aureus, Aberdeen, 1996–2000

Relationships between antimicrobial use and MRSA prevalence are analyzed in Aberdeen, Scotland

Debating the Sources and Prospects of European Integration

LetterOutput Type: Lette