We present a new approach for the realisation of a molecular photo-switch, based on photochrochromic oligothiophene-substituted chromenes. When optically excited, these compounds undergo a structural change passing from a neutral state (closed form) to a strongly polarized one (open form). This photochromic process is accompanied by a deep changes in the electrical characterisation.

A systematic investigation on growth and sensor characteristics of SnO2 thin films of different orientations is reported for the first time. Thin films were grown by pulsed laser (KrF; λ = 248 nm) ablation technique under in-situ conditions. Films deposited at 525 °C on (1102) sapphire were predominantly (101) orientated whereas those deposited on (100) LaAlO3 were highly a-axis orientated. Sensors made of predominantly (101) oriented films exhibited more than two orders magnitude change in resistance even for 100 ppm of H2 in air at 310 °C. The response and retracing times of the sensor were remarkably short respectively 30 and 200 s. Sensors made of a-axis oriented films also exhibited similar sensitivity and response time for the same quantity of both H2 and LPG. However, the retrace time was very long typically about 20 min. Atomic force microscopic (AFM) investigation reveals that the films are highly granular with an average size of about 100–150 nm which is ten times larger than the critical size of 6 nm, a criterion required for high sensitivity. (The Debye length of ${\rm SnO}_2 \cong 3.07$ nm at 293 K and the critical grain size is therefore 2 × Debye length, which is 6 nm.)

The objective of this paper is to explore the possibility to use composites polyester/titanates (M2+Ti4+O$_3^{2-}$ with M = Ba2+, Sr2+, Ca2+, Mg2+) to get a miniature high- frequency components, and the proposal of signal processing allowing to minimize the different errors particular to the temporal spectroscopy in matched line for two spaces (time, frequency), and the establishment of an expression that determines directly the permittivity without having to make the inverse resolution transcendent equations related to the propagation. Analysis of results obtained by this signal processing, confirms the validity of Bottreau's modeling law, in low frequency according to the volume fraction and the spectral viewpoint, which allows to anticipate the composition of materials to be used to reply to electromagnetic predefined characteristics.

Thermally stimulated current measurements have been performed on polycrystalline layers of lead iodide grown from solution. Several TSC peaks or bands have been observed at temperatures of 100 K, 195–220 K, 230–240 K and 270–300 K. Comparison with PbI2 single crystal shows that the polycrystalline structure of the material introduces additional defects. In contrast the defect currently found in single crystal and attributed to the lead vacancy has not been clearly evidenced in the polycrystalline layers. The position and relative intensity of the peaks can be modified by Ag doping and thermal annealing. On the other hand, only small differences resulting from the anisotropy of the material have been observed depending on the orientation of the electric field with regards to the grains orientation.

The complementarity between 57Fe Mössbauer spectrometry and classical methods of powder characterizations is pointed out for determining the formula of metal-ferrite composites (Fe$_p^0$Co$_{1-p}^0$)a(CoxFe$_{3-x-t}$$\square_t$O4). It is shown that X-ray diffraction is essential to determine the composition of the metal, while TG measurements in air give an approximate value for the metal ratio. In-field spectrometry is expected as the most suitable tool to determine the Fe sites occupancy, although the complex hyperfine structure might originate some misfits. The composites formulae were therefore determined by selecting the set of refined Mössbauer parameters that were in best agreement with the TG measurements. Magnetic measurements prove the validity of such an approach.

The paper presents two large-scale observations of magnetic treatment of industrial water, aimed at investigating changes in the formation of deposits. First, a four-month experiment is described with two identical 25 kW heat exchangers, where in one case the inlet water was treated by a magneto-hydrodynamic method. Deposits recovered from both exchangers were analyzed chemically, by X-ray diffraction, infrared spectroscopy and PIXE. The amount of deposit for untreated water, composed mostly of calcite, increased exponentially with temperature reaching 20 g/m of tube at the warm end of the heat exchanger. The mass of the deposit for magnetically treated water did not depend on temperature and was only ca. 0.5 g/m of tube. It was composed of mainly noncrystalline silica-rich material. Further results were obtained from the practical installation at three blocks of a 1 GW power plant. The soft, amorphous deposit for magnetically treated water had a specific surface area of 80 m2/g and an infrared spectrum similar to that of a silicate hydrogel. Therefore, it appeared that, as a result of the passage through the magnetic device, crystallization of carbonates in water was blocked due to initiation of another, competitive process. This process is the activation of the colloidal silica, which will adsorb calcium, magnesium or other metal ions and then precipitate from the solution as the coagulated agglomerate. The most probable mechanism responsible for silica activation is a Lorentz-force induced deformation of the diffuse layer leading to the increased counterion concentration in the adsorption layer of the negatively charged silica.

The transport of non-equilibrium gases in the flow regime of slightly rarefied gas dynamics within a plane channel bounded by two parallel slabs is addressed. Hydrodynamic derivation of the entrainment of rarefied gases induced by a surface acoustic wave (SAW) along the walls in a confined parallel-plane microchannel is conducted by considering the nonlinear coupling between the interface and the velocity-slip. Both no-slip and slip flow results are obtained with the former ones matched with the previous approach. The critical reflux values associated with the product of the second order pressure-gradient and the Reynolds number decrease as the Knudsen number increases from zero to 0.1. We found when the Reynolds number is larger the surface wave-modulation effect (due to the wave number) to the flow field is significant which represents the strong coupling between the boundary and the flow-inertia term. Meanwhile, the (perturbed) mean flow induced by SAW along the walls of a 2D microchannel is proportional to the square of the wave-amplitude ratio which has been qualitatively confirmed by previous approaches.

This paper describes an optical investigation technique for visualizing the cross section of a vertical air stream flowing downward on a wet horizontal tube with moving liquid film. This method which associates the laser induced fluorescence and laser tomography techniques, uses Mie scattering tracers and fluorescent dye for marking the air and liquid flows, respectively. It allows us to visualize the air and liquid flows independently or simultaneously, and to measure the air flow separation angle. Results are compared with values obtained for a dry tube by the present and of other authors.

For thermal analysis, power module packages can often be considered as plane multilayered systems for which it has been demonstrated that appropriate Fourier transforms associated with the two-port network theory permit to develop very efficient solutions of the static or the time dependent 3D heat flow equation. However, in practice, the thermal resistances of soldered or pasted interfaces are most often not well known. Most of these parameters are theoretically unpredictable, therefore it is of highest interest to develop an experimental procedure intended for an adequate characterization of the 3D thermal behaviour of the cooling substrates. A two-port network theoretical basis for experimental characterization of the thermal behaviour of multilayered substrates (96% Alumina, AU4G, IMS), which are classically used for power module packaging, is presented. In spite of some difficulties in setting perfectly the boundary conditions for temperature and heat fluxes, the experimental results demonstrate the validity of the characterization method, and the soughted parameters can be measured for wide ranges of spatial pulsation. Suggested improvements of the existing experimental set can give rise to an industrial measurement set intended for thermal characterization of power module packages.