The microcrack distribution in a low porous granite exposed to weathering after quarrying was investigated in order to detect its microstructural evolution. Two blocks (A and B) were taken in the same granite body from two quarry faces respectively exposed during a few weeks and twenty years. Porosimetry by injection of carbon-14-methylmethacrylate (14C-MMA) was used for analysing the porous medium. Measurements of optical densities of autoradiographs provided data for the localization and the quantification of porosity. Results are compared with those obtained by mercury porosimetry. Average porosity of sample A was found to be 0.37 ± 0.03% whereas average porosity in sample B reaches 1.07 ± 0.45%. Most of the porosity increase may be explained by the opening of grain boundaries.

We have tried to understand the role of cellular tone (or internal tension mediated by actin filaments) and interactions with the microenvironment on cellular stiffness. For this purpose, we compared the apparent elasticity modulus of a 30-element tensegrity structure with cytoskeleton stiffness measured in subconfluent and confluent adherent cells by magnetocytometry, assessing the effect of changing cellular tone by treatment with cytochalasin D. Intracellular and extracellular mechanical interactions were analyzed on the basis of the non-dimensional relationships between the apparent elasticity modulus of the tensegrity structure normalized by Young's modulus of the elastic element versus: (i) element size, (ii) internal tension, and (iii) number of spatially fixed nodes, for small deformation conditions. Theoretical results and rigidity measurements in adherent cells consistently showed that higher cellular tone and stronger interdependencies with cellular environment tend to increase cytoskeleton stiffness. Visualization of the actin lattice before and after depolymerization by cytochalasin D tended to confirm the geometrical and mechanical assumptions supported by analysis of the present model.

In this paper we present the results of modeling concerning current-voltage (V < 0) characteristics of metal/ultra-thin oxide/semiconductor structures, where the oxide thickness varies from 45 Åto 80 Å. We analyze the theoretical influence of the temperature and Schottky effect, on the Fowler-Nordheim (FN) conduction. The results obtained show that these influences depend on the electric field in the oxide and the potential barrier at the metal/oxide interface. At the ambient temperature, the influence on this potential barrier is lower than 1.5% . However, it can reach 45% on the pre-exponential coefficient (K1). It is therefore necessary to consider in the FN classical conduction expression a correction term that takes account of the temperature and Schottky effects. These results are validated experimentally by modeling at high field, the current-voltage characteristics of the realized structures. At low field, we have determined the excess current [3], which is due to defects localized in the oxide layer, according to the structure area and the oxide thickness. By modeling this excess current, we show that it is of FN type, and deduct that the effective defect barrier depends little on the structure area and the oxide thickness. By taking into account the effective barrier value and the corrective factors due to the temperature and Schottky effect, we determine the defect effective area and show that it is related to the breakdown field of the structures: when the defect effective area increases, the breakdown field decreases.

EELS (electron energy loss spectrometry) in the transmission electron microscope (TEM) was used to determine the composition of a nanocrystalline magnetic specimen. The relative amounts of the hard magnetic phase Nd2Fe14B and the soft magnetic phase Fe3B at the point of measurement was measured by standard EELS quantification. In order to determine the structure of Fe3B present, the fine structure of the boron K-ionisation edge was analysed. Comparison of the experimental spectra with simulations of the fine structures based on the TELNES extension of the WIEN97 program package, a full potential linearised augmented plane wave approach to the calculation of electronic structure in crystals, shows that the tetragonal form of Fe3B is predominant.

An experimental investigation of hysteretic switching in antiferroelectric liquid crystals has been carried out. It is shown that in switching from the antiferroelectric state to the ferroelectric state there exists both a heterogeneous process involving the growth of finger-like domains and a homogeneous process in which the whole cell uniformly switches. At high field slew rates the homogeneous process dominates. However, ferroelectric to antiferroelectric switching involves only a heterogeneous process. A simple analytic model is then used to describe the experimental results and thus understand the competition between homogeneous and heterogeneous switching.

Our purpose is to build an inverse method which best fits a model of artery flow and experimental measurements (we assume that we are able to measure the displacement of the artery as a function of time at three stations). Having no clinical data, we simulate these measurements with the numerical computations from a "boundary layer" code. First, we revisit the system of Ling and Atabek of boundary layer type for the transmission of a pressure pulse in the arterial system for the case of an elastic wall (but we solve it without any simplification in the $u\partial u/\partial x$ term). Then, using a method analogous to the well known Von Kármán-Pohlhausen method from aeronautics but transposed here for a pulsatile flow, we build a system of three coupled non-linear partial differential equations depending only on time and axial co-ordinate. This system governs the dynamics of internal artery radius, centre velocity and a quantity related to the presence of viscous effects. These two methods give nearly the same numerical results. Second, we construct an inverse method: the aim is to find for the simple integral model, the physical parameters to put in the "boundary layer" code (simulating clinical data). This is done by varying in the integral model the viscosity and elasticity in order to fit best with the data. To achieve this in a rational way, we have to minimise a cost function, which involves the computation of the adjoint system of the integral method. The good set of parameters (i.e. viscosity, and two coefficients of a wall law) is effectively found again. It opens the perspective for application in real clinical cases of this new non-invasive method for evaluating the viscosity of the flow and elasticity of the wall.

Temperature is an important parameter for industrial process control. With the usual methods we obtain only an invasive or superficial information about temperature. Microwave radiometry is a non-invasive way to determine the temperature within dissipative body. This paper presents the design of a new radiometer. With this system, the radiometric temperature is independent of the reflection coefficient of the sensor. A simplified calibration takes into account insertion losses of the microwave elements and the frequency bandwidth has been greatly reduced to eliminate the unwanted electromagnetic noise.

This paper mainly deals with the design of an advanced control law for induction motors and its real-time implementation on an experimental test benchmark. First, relationship between the classical field oriented control (FOC) and non linear linearizing control laws is studied. It is shown that both control laws are similar. Classical non linear linearizing control improves the performances but not in a spectacular way when the observer and the controller are designed independently. A new non linear observer based control law is designed, which is shown to be globally stable and is implemented on an experimental test-bench. The control algorithm is studied and applied in many configurations (various set-points, flux and speed profiles and torque disturbances) and is shown to be very efficient.

This article presents an application of a speckle interferometry technique with video doubling, called "shearography". This technique can be used for near real time imaging of Lamb waves in continuous or burst modes, revealing the presence of delaminations in a carbon epoxy plate. The amplitude of the displacements is measured with a typical uncertainty of the order of 1 nm. The nominal Lamb wave can be suppressed from the shearographic image by optical filtering, to show only the wave interaction with any defects that may exist in the plate. This method is especially advantageous for non-destructive testing.

The linear stability analysis of a Newtonian fluid between two coaxial vertical cylinders with a radial temperature gradient shows the existence of thermal and hydrodynamic axisymmetric oscillatory modes. The critical parameters depend on the nature of the fluid and on the radius ratio of the cylinders. The two modes have the same threshold on a line of the codimension 2 points in a plane spanned by the radius ratio and Prandtl number.

The study concerns remote controlled sensors, associating micro-mechanical and microwave data communication functions. A radio link can be used to transmit information from the sensor as well as to provide internal power supply. Applications include Wireless Sensor Networks projects. An important operation is performed through a passive microwave frequency shifter used for retransmission. Two structures of this frequency shifter using silicon membrane micro-mechanical capacitors are described, with further details concerning the optimisation of the dimensions using electro-mechanical modellisation, the problems in technological silicon implantation, and some first experimental results.

The characteristics of the various modes of acoustic waves (velocity, attenuation, efficiency) radiated towards the focused sensor of an acoustic microscope are related to the acoustic properties of the coupling fluid. The aqueous solutions of electrolytes are suitable as coupling fluids because their acoustic properties can be adjusted owing to the choice of the nature and of the concentration of the dissolved ions. By adjusting the properties of the couplant, the performances of the sensors of the acoustic microscopes can be extended. The image contrasts and the accuracy of measurements of the acoustic waves velocity are improved, the radiation of the chosen modes are enhanced and very high frequencies can be used.