Effects of polypyrrole modified electrode functionalization on potentiometric pH responses

Two functionalized polypyrrole films, poly(11-N-pyrrolylundecanoic) acid and poly(N-undecylpyrrole), were used as sensitive layers for pH sensors. The functionalized pyrrole monomers were first synthesized before carrying out their electropolymerization onto non-oxidizable electrodes. The deposits were characterized by SEM imaging, XPS and PM-IRRAS to study surface structure and composition. Poly(11-N-pyrrolylundecanoic) acid coating yielded very promising results as sensitive layer in pH sensors. Indeed, the potentiometric responses from pH 4.0 to 9.0 appeared linear, reversible, stable in time over a period of 1 month and highly selective for H⁺ ions. This behavior was attributed to carboxylic acid groups which are sensitive to proton concentration changes. This was confirmed by the fact that poly(N-undecylpyrrole) film led to potentiometric responses being pH dependent only from pH 6.0 to 9.0 with low sensitivity. Poly(11-N-pyrrolylundecanoic) acid is thus promoted to be used as sensitive layer in pH sensors.     

Adaptation of the near-field acoustic sensor to the measurement of the media properties

In this work, the geometry of the near-field acoustic (NFA) sensor has been modified and adapted to the media properties to be characterized. The NFA method consists in studying the alterations of resonance curve of a horn whose tip, the probe, is immersed in the medium to be characterized. The sensor design has been changed by variation of cylinders lengths and their sections ratio. So sensitivity in the measuring of the liquids properties as well as in the characterization of the cement setting has been increased.     

Study of PEMFC ionomers through model molecules mimicking the ionomer repeat units

The thermal and electrochemical behaviours of PEMFC ionomers based on an aromatic backbone i.e., sulfonated polysulfones, sulfonated polyetheretherketones and sulfonated polybenzimidazoles, were investigated through their model molecules. Thermal degradation was characterized by weight losses and allowed inferring ionomer thermal degradations by chain breakings that cannot be detected by thermogravimetric analysis. In addition, cyclic voltammetry was used to characterize the electroactivity of some ionomers, related to their backbone and their ionic moieties. The use of model molecules is thus a useful tool for assessing both the thermal and electrochemical stability of ionomers. Lastly, due to the high concentrations used in liquid electrolytes as compared with an electrode/membrane interface it may be considered as an electrochemical aging test.     

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.     

Miniemulsion polymerization for synthesis of structured clay/polymer nanocomposites: Short review and recent advances

This review intends to present different aspects concerning clay/polymer nanocomposites produced by heterophase polymerization in aqueous media. This paper highlights the ability of miniemulsion polymerization to produce clay/polymer nanoparticles with tailored nanostructures. Indeed, this polymerization route enables the synthesis of composite nanoparticles with the clay platelets located either on the surface of the polymer particle or embedded inside the polymer particle. A focus is given on the influence of these nanostructures on the properties of the final material through a direct comparison of the composites obtained after water evaporation from these structured nanoparticles. Indeed, the film obtained from the film forming process of these nanoparticles present significantly different nanostructures and exhibit totally different mechanical behaviours and water uptakes. By comparing experimental results and modeling approaches, it is demonstrated that their properties are clearly related to the clay dispersion and contacts. It is also evidenced that the main drawback of miniemulsion from the coating application point of view, is the large water uptake promoted by the surfactant presence whose localization is strongly influenced by nanostructuration. This stresses the need for the further development of surfactant free miniemulsion polymerization using advantageously the clay presence to stabilize the emulsion.     

Study of the Mechanical Properties of Fibers Extracted from Tunisian Agave americana L.

Agave americana L. fibers, the most abundant variety in Tunisia, have a quite important textile potential. This potential is demonstrated by studying the extraction of these fibers from leaves, their physical properties such us fineness or density and their mechanical behavior in tensile tests. In this work, results of a mechanical behavior study of fibers extracted from the Agave americana L. plant are presented. These results deal with the principal and mechanical characteristics of these fibers which are the strain at break, the elasticity modulus and the rupture facture. These results permitted to situate these fibers, compared to the other textile fibers, as materials that can be used in technical applications such as reinforcing composites or geotextile. In order to understand the mechanical properties of these fibers, a correlation study between the properties already cited and the fine structure was done. The obtained results showed that the mechanical properties of Agave americana L. fibers are closely related to the individual fibers deformations and to the natural matrix (lignin and gums) that are linked to these elementary fibers.     

Topological Modeling of a One Stage Spur Gear Transmission

Finding a basis of unification for the modeling of mechatronic systems is the search subject of several works.This paper is a part of a general research designed to the application of topology as a new approach for the modeling of mechatronic systems.Particularly,the modeling of a one stage spur gear transmission using a topological approach is tackled.This approach is based on the concepts of topological collections and transformations and implemented using the MGS（modeling of general systems）language.The topological collections are used to specify the interconnection laws of the one stage spur gear transmission and the transformations are used to specify the local behavior laws of its different components.In order to validate this approach,simulation results are presented and compared with those obtained with MODELICA language using Dymola solver.Since good results are achieved,this approach might be used as a basis of unification for the modeling of mechatronic systems.     

Using Linked Micromap Plots to Characterize Omernik Ecoregions

The paper introduces linked micromap (LM) plots for presenting environmental summaries. The LM template includes parallel sequences of micromap, label, and statistical summary graphics panels with attention paid to perceptual grouping, sorting and linking of the summary components. The applications show LM plots for Omernik Level II Ecoregions. The summarized United States continental data includes USGS digital elevation, 30-year normal precipitation and temperature, and 8 million AVHRR pixels classified into 159 types of land cover. One LM plot uses a line-height glyph to represent all 159 land cover percentages per ecoregion. LM plots represent new visualization methodology that is useful in the data and knowledge based pattern representation and knowledge discovery process. The LM plots focus on providing an orienting overview. The overview provides a starting place for subsequent drilling down to what could otherwise be viewed as an overwhelming mass of data. The overview also provides a starting place to learn about the intellectual structure that lies behind the notion of ecoregions and begins to connect this abstract structure to quantitative methods.     

Effect of W/C and superplasticizer type on rheological parameters of SCC repair mortar for gravitational or light pressure injection

The influence of pressure on the yield stress and plastic viscosity of SCC repair mortars was investigated using an adapted Marsh cone with cylindrical shear paddles. Twelve mortars proportioned with water over cement ratios from 0.45 to 0.55 and either Polycarboxylate ether (PCE), polyacrylate (PA) or polynaphtalene sulfonate (PNS) high-range water-reducing admixture (HRWRA) were prepared. Test results show that the exerted pressure, W/C and HRWRA type strongly influence the rheological response: the yield stress is mainly affected by HRWRA residual concentration, except for PCE mortars where sulfate ion concentration can play an important role. Plastic viscosity is mainly affected by solid friction between particles, the latter is influenced by HRWRA dosage and W/C. PA appears to be the most accurate HRWRA for light pressure injection, with less sensitivity to changes in pressure or W/C than PNS or PCE superplasticizers.