In Situ Treatment of Thermal RF Plasma Processed Nanopowders to Control their Agglomeration and Dispersability

Titanium carbonitride nanoparticles have been produced in an inductively coupled thermal plasma and subsequently modified using a surfactant that has been deposited in situ on their surface in-flight. The surfactant was injected in the reactor while the nanoparticles are still dispersed in the gas phase, allowing the coating of primary particles instead of the corresponding agglomerates. In contrast to naked TiCN nanoparticles, the surfactant coated particles could be readily dispersed in water with a short ultrasonic treatment and built up no large agglomerates as proved by Photon Correlation Spectroscopy measurements. The investigated surfactants seem, however, to undergo a chemical modification and/or a thermal degradation at the surface of the TiCN nanoparticle

On the Accessibility and Controllability of Statistical Linearization for Stochastic Control: Algebraic Rank Conditions and their Genericity

Statistical linearization has recently seen a particular surge of interest as a numerically cheap method for robust control of stochastic differential equations. Although it has already been successfully applied to control complex stochastic systems, accessibility and controllability properties of statistical linearization, which are key to make the robust control problem well-posed, have not been investigated yet. In this paper, we bridge this gap by providing sufficient conditions for the accessibility and controllability of statistical linearization. Specifically, we establish simple sufficient algebraic conditions for the accessibility and controllability of statistical linearization, which involve the rank of the Lie algebra generated by the drift only. In addition, we show these latter algebraic conditions are essentially sharp, by means of a counterexample, and that they are generic with respect to the drift and the initial condition.Comment: 23 page

El paisaje laforguiano: hacia una lectura cognitiva del pensamiento neurótico especializado

The main aims of this paper are to highlight the functions of one of the main leitmotivs of Laforgue's poetry: the landscape. Both visual and musical, the poetic landscape will be analysed thanks to the novel tools of the cognitive sciences. It is convenient to evidence that it expresses a range of perceptions and emotions that give rise to ryhtmic constructions and murky symbols. The landscape externalizes and metaphorises, in its structure, the functionning and consequences of the neurotic disorder in the subject's perception of his environment and of himself in space, considering emotion and homeostasis, as if it was a second skin that would somatise any erroneous movement of thinking.El presente trabajo tiene como principales objetivos destacar las funciones de uno de los principales leitmotivs de la poesía laforguiana: el paisaje. Tanto visual como musical, el paisaje poético se analizará gracias a las herramientas novedosas que son las ciencias cognitivas. Cabe decir que se expresan en él un abanico de percepciones y emociones que dan lugar a construcciones rítmicas y símbolos turbios. El paisaje exterioriza y metaforiza, en su estructura, el funcionamiento y las consecuencias del trastorno neurótico en la percepción que el sujeto tiene de su entorno y de sí mismo en el espacio, considerando la emoción y la homeostasis, como si fuese una segunda piel que somatizaría cualquier movimiento erróneo del pensamiento

Controlled Synthesis of β-SiC Nanopowders with Variable Stoichiometry Using Inductively Coupled Plasma

In the growing field of nanomaterials, SiC nanoparticles arouse interest for numerous applications. The inductively coupled plasma (ICP) technique allows obtaining large amount of SiC nanopowders from cheap coarse SiC powders. In this paper, the effects on the SiC structure of the process pressure, the plasma gas composition, and the precursor nature are addressed. The powders were characterized by X-ray diffraction (XRD), Raman and fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and high resolution electron microscopy (HREM), chemical analyses, BET and photon correlation spectroscopy (PCS) measurements. Whatever the precursor (α- or β-SiC), the nanoparticles were crystallised in the cubic β-SiC phase, with average sizes in the 20-40nm range. Few residual grains of precursor were observed, and the decarburization due to the reductive Ar-H2 plasma lead to the appearance of Si nanograins. The stoichiometry of the final product was found to be controllable by the process pressure and the addition of methan

New robust observables on Rayleigh waves affected by an underground cavity: from numerical to experimental modelling

International audienceThe investigation and monitoring of shallow hazards due to the presence of underground cavities remain a challenge for geophysical approaches. Thus, seismic surface waves have been tested in several recent research projects in order to detect and localize voids as well as to determine their geometries. Among these works, numerous numerical studies have proved the feasibility of Rayleigh waves to detect cavities. However, most imagery processes adapted to R waves are faced with difficulties when applying them to real data. This limitation points to a major problem: the interactions between Rayleigh waves and a cavity are complex, particularly in the case of dispersing and attenuating surrounding media. Here, a combined approach based on numerical and experimental data obtained in a reduced-scale measurement bench is conducted to better understand the seismic wave propagation phenomena involved in the presence of a cavity and define robust observables that can be used in field measurements. The observables bearing the cavity signature are studied qualitatively and quantitatively on numerical and experimental recordings. The latter take into account all the propagation phenomena involved. The observations are carried out on the vertical and horizontal component of the Rayleigh wave displacement. The selected observables are studied depending on non-dimensional cavity's parameters versus the frequency, that is the wavelength-to-size ratio and the wavelength-to-depth ratio. The effects of the cavity's parameters on the observables show particularities as a function of these components, such as a higher rate of the amplitude on the horizontal component as well as a perturbation of the direct seismic surface wave amplitude above the cavity, also higher on the horizontal component. This latter feature is particularly visible on the variation of the elliptical particle motion recorded at the surface. It can be linked to the mode conversions that occur in the vicinity of the cavity and which predominate on the horizontal component when the signal is normalized

High resolution quantitative seismic imaging of a strike-slip fault with small vertical o set in clay-rocks from underground galleries. Experimental Platform of Tournemire, France.

Imaging tectonic faults with small vertical offsets in argilittes (clay-rock) using geophysical methods is challenging. In the context of deep radioactive waste disposals, the presence of such faults has to be assessed since they can modify the rock confining properties. In the Tournemire Experimental Platform (TEP, France), fault zones with small vertical offsets and complex shape have been identified from underground works. However, 3D high-resolution surface seismic methods have shown limitations in this context that led us to consider the detection and characterization of the faults directly from underground works. We investigate here the potential of seismic full waveform inversion (FWI) applied in a transmission configuration to image the clay-rock medium in a horizontal plane between galleries, and compare it with first-arrival traveltime tomography (FATT). Our objective is to characterize seismic velocities of a block of argilittes crossed by a subvertical fault zone with a small vertical offset. The specific measurement configuration allows us to neglect the influence of the galleries on the wave propagation and to simplify the problem by considering a 2D isotropic horizontal imaging domain. Our FWI scheme relies on a robust adaptation of early-arrival waveform tomography. The results obtained with FATT and FWI are in accordance and both correlate with the geological observations from the gallery walls and boreholes. We show that even though various simplifications are done in the inversion scheme and only a part of the data is used, FWI allows to get higher resolution images than FATT, and is especially less sensitive to the incomplete illumination as it uses also diffracted energy. The results provided in this study highlight the complexity of the fault zone, showing a complex interaction of the main fault system with a secondary system composed of decimetric fractures associated with the presence of water

Aerosol emission monitoring in the production of silicon carbide nanoparticles by induction plasma synthesis

In this study, the synthesis of silicon carbide (SiC) nanoparticles in a prototype inductively coupled thermal plasma reactor and other supporting processes, such as the handling of precursor material, the collection of nanoparticles, and the cleaning of equipment, were monitored for particle emissions and potential worker exposure. The purpose of this study was to evaluate the effectiveness of engineering controls and best practice guidelines developed for the production and handling of nanoparticles, identify processes which result in a nanoparticle release, characterize these releases, and suggest possible administrative or engineering controls which may eliminate or control the exposure source. No particle release was detected during the synthesis and collection of SiC nanoparticles and the cleaning of the reactor. This was attributed to most of these processes occurring in closed systems operated at slight underpressure. Other tasks occurring in more open spaces, such as the disconnection of a filter assembly from the reactor system and the use of compressed air for the cleaning of filters where synthesized SiC nanoparticles were collected, resulted in releases of submicrometer particles with a mode size of ~170-180nm. Observation of filter samples under scanning electron microscope confirmed that the particles were agglomerates of SiC nanoparticle