Extraction of Finite Element Basis Functions From the Cellular Topology of Meshes

This paper is devoted to the presentation of a simple but powerful topological approach for the computation of basis functions involved in the expression of finite element interpolants. It deals with the so-called nodal and edge elements but similar considerations can be made for the construction of facet ones. All standard cells are treated including pyramids.     

Mechanical behavior of axially magnetized permanent-magnet gears

We studied permanent-magnet (PM) gears with axially magnetized permanent magnets and a plane air gap in terms of mechanical behavior. We determined the torque and forces exerted between the two rotors of these devices, using a seminumerical method based on the calculation of the forces between the magnets of the rotors. The study deals with the general behavior of such devices and presents some very interesting configurations for their mechanical stability     

Stress and plastic deformation of MEA in running fuel cell

Numerical modelling of mechanical stresses in running fuel cell is provided. The evolution of stresses and plastic deformations in the membrane has been obtained during the turn-on phase. The operating conditions have been taken into account by imposing the heating sources and the humidity field. The results have been presented on two scales: the global scale reflects the stress evolution in the entire fuel cell and the local one corresponds to the tooth/channel structure. It has been shown that the stresses are strongly heterogeneous on the both scales and time dependent. From the mechanical point of view, the most sensible zone is under the GDL/seal joint interface. In the running fuel cell the heterogeneity decreases while it rises in the fuel cell just after the assembly. The stresses reach the maximum values during the humidification step, the magnitude of these stresses is sufficient for initiation of the plastic deformations in the Nafion membrane.     

PWR steam generator R&D in France: thermal-hydraulic and vibratory aspects

Concomitant with the launching of the French pressurized water reactor (PWR) nuclear power program, a large research and development (R&D) effort was initiated, devoted to the steam generators (SGs). This program, managed cooperatively by Framatome, the SG designer and manufacturer; Electricité de France (EDF), the French electrical utility; and the Commissariat à l'Energie Atomique (CEA), the French Atomic Energy Commission, primarily responsible for nuclear research; was focused on four main objectives:

1. (1) To obtain a better understanding of the physical phenomena existing in these steam generators and leading to SG performance alterations or operating life reductions.

2. (2) To test and validate improved design solutions for the model 51 Framatome steam generator, which was the first one designed under Westinghouse license.

3. (3) To test and validate new Framatome SG designs.

4. (4) To test and validate new, high-performance design tools.

This vast R&D program covers the following theses:

• - SG thermal-hydraulics,

• - SG tube vibration and wear,

• - SG materials (production, corrosion, etc.),

• - Primary and secondary fluid chemistry,

• - SG technology (manufacturing processes, NDT, etc.),

• - SG in-service inspection, and

• - SG maintenance.

These themes are too numerous to be dealt with in a single article. Consequently, the present article will focus on only the first two themes.     

Characterization by solid-state NMR and selective dissolution techniques of anhydrous and hydrated CEM V cement pastes

The long term behaviour of cement based materials is strongly dependent on the paste microstructure and also on the internal chemistry. A CEM V blended cement containing pulverised fly ash (PFA) and blastfurnace slag (BFS) has been studied in order to understand hydration processes which influence the paste microstructure. Solid-state NMR spectroscopy with complementary X-ray diffraction analysis and selective dissolution techniques have been used for the characterization of the various phases (C₃S, C₂S, C₃A and C₄AF) of the clinker and additives and then for estimation of the degree of hydration of these same phases. Their quantification after simulation of experimental ²⁹Si and ²⁷Al MAS NMR spectra has allowed us to follow the hydration of recent (28 days) and old (10 years) samples that constitutes a basis of experimental data for the prediction of hydration model.     

Proton-conducting ionic liquid-based Proton Exchange Membrane Fuel Cell membranes: The key role of ionomer-ionic liquid interaction

The paper deals with the synthesis and characterisation of proton-conducting ionic liquids (PCILs) and their polymer electrolytes obtained by blending modified Nafion membranes with different concentrations of PCILs. The PCILs are obtained by the neutralization of triethylamine with different organic acids. The first part of the paper studies the influence of acidity and acid structure on PCIL thermal and electrochemical performance, while the second part examines membrane conductivity and reveals it to depend more on PCIL structure than on its intrinsic conductivity. At 130 °C, conductivities exceeding 10 mS cm⁻¹ were obtained in fully anhydrous conditions.     

Josephson Coupling in Junctions Made of Monolayer Graphene Grown on SiC

Chemical vapor deposition has proved to be successful in producing graphene samples on silicon carbide (SiC) homogeneous at the centimeter scale in terms of Hall conductance quantization. Here, we report on the realization of co-planar diffusive Al/ monolayer graphene/ Al junctions on the same graphene sheet, with separations between the electrodes down to 200 nm. Robust Josephson coupling has been measured for separations not larger than 300 nm. Transport properties are reproducible on different junctions and indicate that graphene on SiC substrates is a concrete candidate to provide scalability of hybrid Josephson graphene/superconductor devices.     

A correlation between crystal structure and catalytic activity in the solid solutions CdMoxW1−xO4

Two CdMo_xW_1−xO₄ solid solutions with the scheelite and the wolframite structures were synthesised via different techniques and their structures were determined from powder refinements. The limit of the reciprocal solubility of Mo in CdWO₄ has been checked. Several compositions of the solid solutions have been tested in the catalytic mild oxidation of propane or propene and relations between the structures and the catalytic activity are proposed.     

Norovirus contamination on French marketed oysters

Contaminated shellfish have been implicated in gastroenteritis outbreaks in different countries. As no regulation has been set up yet regarding viral contamination of food, very few data are available on the prevalence of contaminated products on the market. This study presents data obtained from oysters collected on the French market in one producing area over a 16 month period of time. Noroviruses were detected in 9% of samples with a seasonal impact and influence of climatic events. Contamination levels were low and, surprisingly, oysters sampled directly from the producer were found to have less contamination than oysters from supermarkets.