Systematic error correction of a 3D laser scanning measurement device

Non-contact measurement techniques using laser scanning have the advantage of fast acquiring large numbers of points. However, compared to their contact-based counterparts, these techniques are known to be less accurate. The work presented in this paper aims at improving the accuracy of these techniques through an error correction procedure based on an experimental process that concerns mechanical parts. The influence of the three parameters, defining the relative position and the orientation between the sensor and the surface, is studied. The process used to build an experimental global model of error is presented and applied to a typical part composed of planes or skewed surface. The systematic errors have been reduced by half in comparison to the reference values, while the random errors have slightly increased. This phenomenon is due to the fact that the errors correction model does not take into account the local response of the laser sensor. A second model, taking into account the local defect, has been developed. Its application to an example of inspection of a mechanical part shows an improvement of the results of the correction.     

An attempt to reduce the membrane effects in Richtmyer–Meshkov instability shock tube experiments

A new device has been developed to reduce the effects of the initial materialization of the gaseous interface in the context of horizontal shock tube experiments for the Richtmyer–Meshkov instability study. The thin nitrocellulosic membrane deposited on a stereolithographed grid support woven with thin wires is destroyed by thermal effect, through a powerful electrical pulse, just before the arrival of the incident shock wave. We present a first attempt realized in the light/heavy gas configuration (air/SF₆) and compared with the experiments carried out without destruction. We show that the present device allows to reduce the influence of the membrane on the instability development.      

Investigation of the particle-laden airflow generated by a pseudo-machining operation

A test rig recreating a typical machining induced gas–solid flow is used to investigate the behaviour of the emitted pollutant particles and their effect upon the airflow around the machine tool. The flow is driven by a rotating cylinder and a tangential jet of inertial solid particles. Experimental data concerning both particle flow and air flow are collected by means of phase Doppler particle analyser (PDPA) and particle image velocimetry (PIV). After describing the specific treatments used to discriminate the two phases, complete results are provided and discussed. Additionally, with the main objective being to optimize the design of pollutant capture devices for machining systems, tentative numerical simulations are carried out and compared to experimental data. For the one-phase case (air flow without particles), good agreement between simulations and experiments is found and the superiority of a wall-function based large eddy simulation (LES) over realizable k–ε$k''–''\epsilon$ modelling is highlighted. For two-phase cases, combination of LES and Lagrangian tracking with two-way coupling leads to simulation results that are reasonably accurate considering the low degree of modelling and the empiricism involved. Particle-to-particle collisions, disregarded in simulations, appear to be a predominant phenomenon in the jet source region, thus partly explaining some discrepancies observed between simulations and experiments.     

Revisiting the reduction of indoles by hydroboranes: A combined experimental and computational study

A combined experimental and density functional computational study was used to probe the mechanism for the reduction of indoles using simple borane BH₃·DMS (DMS?=?dimethyl sulfide). Experimental and computational studies all steer to the formation of the reduced species 1-BH₂-indolines as the resting state for this reaction, as opposed to the historically presumed formation of the unreduced 1-BH₂-indoles, before the addition of a proton source to form the final product indolines. Furthermore, it was observed that molecular H₂ was generated and consumed in the reaction. Computations put forward hydroboration followed by protodeborylation as the very reasonable mechanistic route for the formation of experimentally observed major intermediate 1-BH₂ indolines. For the H₂ consumption in the reaction, computations suggest the frustrated Lewis pair-type heterolytic splitting of H₂ by a bis(3-indolinyl)borane intermediate.     

Oxygen-vacancy ordering in the YBa2Cu3Oz basal plane studied by the cluster variation method

The cluster variation method is used to calculate a phase diagram for a two-dimensional Ising model representing the Cu₂O plane of the high-T _c superconductor YBa₂Cu₃O_z. Both first (V ₁ and second-neighbor (V ₂) interactions are considered, withV ₂/V ₁= –1/2; At high temperatures, the transition from the disordered (tetragonal) to the ordered (orthorhombic) phase is second-order. A tricritical point is found below which phase separation occurs. Fractional site occupancy and second-neighbor pair correlations are calculated as a function of temperature. The relevance of the model to the thermodynamics of ordering in the high-T _c compound is discussed.     

Plasma modelisation and control for laser dismantling

Laser dismantling has been investigated for many years in several laboratories including the Photonics Systems Laboratory. However, until recently, material processing with high-power laser beams was not seriously considered as an acceptable alternative for nuclear power plant dismantling. Our laser dismantling approach associates optical technologies and target plasma modelization and control. In previous papers, we have reported on innovative digital diffractive engineering used for adapted light concentration. In this paper we introduce the plasma modelisation and control for which laser cutting at long distance without assist gas is now possible. We discuss the basic model that we have taken into account and we describe the mechanisms of laser material interaction with plasma formation that we have to deal with to optimise a laser dismantling process. We conclude with a discussion of optimized laser parameters to be used for efficient laser dismantling.     

Scaling limit of some critical models

In this paper we consider massless systems which are strong perturbations of the massless lattice free field. Under quite general assumptions on the potential, we prove that the continuum (scaling) limit of these systems is Gaussian.