Storm detectors. Tests and application

International audienceThe storm detector standard is now published at European level and is also introduced in the IEC program of work. However, this standard is only a first document that even if very important will not be enough to apply safely the storm detectors in field. First regarding application, it is assumed in the standard that a setting process will be possible for any device installed but in practice, for many industrial applications, this procedure will be very weak and the device should be able to meet the industry requirements in a very short time to be efficient and thus settings procedure should be very straight forward. Second regarding long term withstand, it is very important that the device be reliable and thus tested

Microbial bioanodes with high salinity tolerance for microbial fuel cells and microbial electrolysis cells

Increasing the conductivity of the electrolytes used in microbial electrochemical systems is an essential prerequisite to the large-scale success of these technologies. Microbial bioanodes formed from a salt marsh inoculum under constant acetate feeding generated up to 85 A·m-² in media containing 776 mM NaCl (45 g·L-¹, 1.5 times the salinity of seawater). These values were the highest salinities accepted by a microbial anode so far and the highest current densities reported with felt graphite electrodes

High-contrast Ultrabroadband Frontend Source for High Intensity Few-Cycle Lasers

An ultrabroadband seed source for high-power, high-contrast OPCPA systems at 800 nm is presented. The source is based on post compression in a hollow-core fiber followed by crossed polarized waves (XPW) filtering and is capable of delivering 80$\mu$J, 5fs, CEP-stable (0.3rad RMS) pulses with excellent spectral and temporal qualit

Optimal policy of water extraction of coastal lagoon under state constraints

International audienceIn many natural environments, water resources are not directly usable because their quality does not fulfill the drinking water norms, and therefore treatment or control needs to be applied. It could also happen that the quality of these resource is temporarily acceptable but impacted by its extraction. This is typically the case of coastal lagoons that communicate with the sea. Depending on the level of water in the lagoon, the communication with the sea increases its salt concentration and then one may want to maximize the water pumping within giving bound on the salt concentration, and preserving water volume in the lagoon for its sustainability. In this work, we model the problem as a non-autonomous optimal control problem under state constraints, distinguising two seasons (dry and humid) in the year. The state of the system describes the salt and volume concentration of a coastal lagoon connected to the sea, and the constraints represent bounds on the salt concentration and water volume of the lagoon. The control variable is the output flow rate from the lagoon and the objective the maximization of the total water extracted during one year. Instead of deriving necessary conditions of optimal control under state constraints (i.e. Maximum Principle under state constraints), we first characterize the viability kernel over the year period, that is the set of initial conditions for which there exists a (time-varying) control such that the corresponding trajectory satisfies the constraints over one year. Then, we study the optimal control within this set, expliciting for any initial condition an optimal control policy, as a state feedback, maximizing the pumped water over one year. This problem has been motivated by the case study of the Tunquen lagoon in Chile, but the modelling approach and the methodolgy could be extended to similar situations

Applicability of the bulk-transfer approach to estimate evapotranspiration from boreal peatlands

In northern landscapes, peatlands are widespread and their hydrological processes are complex. Furthermore, they are typically remote, limiting the amount and accuracy of in situ measurements. This is especially the case for evapotranspiration ET, which strongly influences watershed hydrology. The objective of this paper is to demonstrate the validity of the bulk-transfer approach to estimate ET over boreal peatlands. The simplicity of the model relies on four assumptions: (i) near-neutral atmospheric conditions; (ii) wet surface; (iii) constant momentum roughness length depending on vegetation height; and (iv) constant water vapor roughness length, with the last two assumptions implying a constant water vapor transfer coefficient CE. Using eddy covariance data from three Canadian peatlands—Necopastic (James Bay, Québec), Mer Bleue (Ottawa, Ontario), and Western Peatland (Athabasca, Alberta)—this paper shows that these sites are characterized by frequent occurrences of near-neutral atmospheric conditions, especially the Necopastic site, with nearly 76% of the 30-min data segments occurring under near-neutral stratification. The analysis suggests these near-neutral conditions occur as a result of strong mechanical turbulence and weak buoyancy effects. The bulk-transfer approach gives promising results for 30-min and daily ET in terms of mean error and correlation, with performances similar to the Penman equation, without requiring net radiation data. The accuracy of the approach is likely related to the number of near-neutral periods and the elevated position of the water table, which backs up the wet surface assumption

Voronoi Growth Model of Sheet Nacre.

The aim of this work was to study the tiling mode of nacre tablets in the 'brick and mortar' array of sheet nacre. For that purpose, incipient shell nacre (Pinctada margaritifera) was analysed by electron microscopy (SEM) and Raman spectroscopy. Experimental observations pointed out the key role of the stairs-like growing front in sheet-like nacre not only for its long range ordering but also as controlling the hierarchy of local mechanisms. A morphogenesis sequence is proposed taking into account the dynamics of the environment. First, the mantel cells are organised to synthesise and discharge alternatively the extrapallial fluid as batches. Because of the stairs-like feature of the growth front, the extrapallial fluid organizes as successive 'biological films', each of them delayed from the underlying one by 10 to 15µm. Each film is a compartment to prefigure a nacre layer. Then, after individualisation, this film undergoes nucleation and crystallisation of tablets. Finally, the biological film transforms progressively as mature nacre following self assembly mechanisms. The resulting tablets have a shape which responds to a Voronoi growth model, this is shown for the first time: aggregation at the same speed in all directions around single growth centers. This is an efficient model to understand the growth mechanism and rationalise all the experimental observations we have obtained