The use of PDE centres in the local RBF Hermitian method for 3D convective-diffusion problems

In this work an extension is proposed to the Local Hermitian Interpolation (LHI) method; a meshless numerical method based on interpolation with small and heavily overlapping radial basis function (RBF) systems. This extension to the LHI method uses interpolation functions which themselves satisfy the partial differential equation (PDE) to be solved. In this way, a much improved reconstruction of partial derivatives can be obtained, resulting in significantly improved accuracy in many cases.     

On the role of the liquid flow characteristics on low-Weber-number atomization processes

At low Weber numbers, the aerodynamic forces due to the interaction between gas and liquid do not influence liquid atomization processes. In these situations, atomization processes depend on issuing liquid flow characteristics only. According to the literature, the atomization efficiency is best when the issuing liquid flow shows a high turbulence level. Some injectors are based on this concept and promote the production of turbulence by imposing deflection of the flow inside the nozzle. However, many studies indicate that the level of turbulence does not solely control the atomization efficiency. By conducting a numerical and experimental study on the behavior of cavity nozzles, it is found that internal flow deflection to produce turbulence also produces a non-axial flow component at the nozzle exit whose effect on the atomization process is of paramount importance. Indeed, the results show that the surface energy produced during the atomization process is linearly dependent on the sum of the turbulent kinetic energy and the non-axial kinetic energy at the nozzle exit. This sum represents the energy available for the atomization process, and the influence of the injection pressure as well as of the nozzle geometry on this energy is investigated.     

A technical study on the Spraytec performances: influence of multiple light scattering and multi-modal drop-size distribution measurements

The present paper reports an experimental investigation on the performance of the Spraytec, the recent particle sizer commercialized by Malvern Instruments, Malvern, UK. As with the previous Malvern particle sizers, the Spraytec provides a volume-based drop-size distribution from the analysis of a diffraction pattern resulting from the interaction between a spray and a laser beam. This work focuses on the behavior of the Spraytec in two different situations. First, the influence of multiple scattering caused by the measurement of large and spatially inhomogeneous sprays is investigated. Second, a test of multi-modal drop-size distribution measurement is conducted. Contrary to the previous Malvern instrument, Spraytec's mathematical inversion procedure includes a patented multiple-scattering algorithm that allows measurements of very high concentrated sprays. This algorithm is tested here for large and inhomogeneous sprays for which multiple light scattering affects the measurement. The results show that the Spraytec algorithm cannot satisfactorily correct the measurements in this specific situation. It was also observed that the use of this algorithm is prohibited in the absence of multiple light scattering. In the second part of the study, a test of multi-modal drop-size distribution measurement is conducted. For the investigated situations it was found that the Malvern Spraytec is reliable in measuring such spray drop-size distributions.     

Nano-structured cellulose nanocrystals-xyloglucan multilayered films for the detection of cellulase activity

Multilayered cellulose nanocrystals-xyloglucan (CN-XG) films were assembled by spincoating at two CN concentrations inducing different structural colourations. Internal structure of both films was probed by neutron reflectometry (NR) revealing different thicknesses and architectures. The impact of film structure on degradation process by cellulases was revealed by a change in colours of the films, as CN and XG are both sensitive to cellulolytic enzymes.     

A lightweight balloon-borne laser diode sensor for the in-situ measurement of CO2 at 2.68 micron in the upper troposphere and the lower stratosphere

We report the development of a laser sonde operated under stratospheric balloons and devoted to the in-situ measurement of carbon dioxide in the upper troposphere and the lower stratosphere. In the 2.68 micron region, strong CO₂ transitions are suitable for the in-situ monitoring of carbon dioxide, which gives ∼10% absorption depth and, moreover, antimonide laser diodes are nowadays available that show relevant spectral properties for absorption spectroscopy. The light-weight sensor is based on 50-cm single path configuration and is operated open to the atmosphere. We provide details of the design of the instrument and data processing. The performance and the stability of the instrument were evaluated with the Allan variance technique. The spectrometer was test-flown in the Arctic stratosphere from Kiruna, Sweden and we report preliminary flight results.     

Influence of the film‐forming process on the nanostructuration of Pebax®/1‐ethyl‐3‐methylimidazolium triflate ionic liquid: Consequences on the thermal,mechanical, gas,and water transport properties

1‐Ethyl‐3‐methylimidazolium triflate ionic liquid (IL) was incorporated in Pebax® MV 3000 copolymer through solvent cast (SC) or melt blending (MB) for composition from 0 to 30 wt % IL. The morphology was investigated by small angle neutron scattering, transmission electron microscopy, and differential scanning calorimetry. The SC copolymer film exhibited a lower mean correlation distance (D = 87 Å) and smoother transition between the rigid and soft phases in comparison with the MB film (D = 103 Å). By dissolving in the copolymer soft phase, IL acted as a plasticizer, impeded soft segments crystallization and led to linear increase of D. The differences observed in morphology as a function of the film process impacted the mechanical and gas transport properties: below 20 wt % IL, all SC films sustained thermomechanical properties up to 120 °C and exhibited lower permeability than MB films. IL adding made permeability decrease up to 60%, depending on the gas nature and IL amount. Hydration of the films was investigated by sorption and SANS analyses. The impact of water uptake on swelling was similar for all membranes whereas water diffusion depended on the film morphologies and IL amount. Interesting mechanical and transport properties were obtained for IL content up to 20 wt %. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 778–788     

Charge stoichiometry inside polyelectrolyte-protein complexes: a direct SANS measurement for the PSSNa-lysozyme system

We study by small angle neutron scattering and UV titration how the ratio of negative to positive charges, [-]/[+](intro), acts on the structure of complexes formed by short negatively charged polyelectrolyte chains (PSS) and globular positively charged proteins (lysozyme). The range of [-]/[+](intro) lies between 0.65 and 3.33. In all ratios, dense primary complexes are formed with radii around 10 nm. The species composition and the water content of the primary complexes are precisely obtained by the systematic use of the contrast matching of (deuterated) polymer or protein in SANS, yielding the compactness and the inner charge ratio [-]/[+](inner). The primary complexes have (i) an inner charge ratio [-]/[+](inner) close to 1 whatever [-]/[+](intro), (ii) a high total volume fraction (0.25-0.4), (iii) a constant radius (75 A) for [-]/[+](intro) 1, and (iv) a shell of PSS chains when [-]/[+](intro) > 1. Moreover, UV titration shows that there are free proteins if [-]/[+](introduced) < 1 and free PSS chains if [-]/[+](intro) is largely superior to 1. Hence, we observe that the primary complexes reach a finite size, controlled by electrostatic repulsion, and then aggregate at a higher scale with a fractal dimension of 2.1 characteristic of reaction-limited colloidal aggregation.     

Chemical vapor deposition and electric characterization of perovskite oxides LaMO3 (M=Co, Fe, Cr and Mn) thin films

Oxides with a perovskite structure are important functional materials often used for the development of modern devices. In view of extending their applicability, it is necessary to efficiently control their growth as thin films using technologically relevant synthesis methods. Pulsed spray evaporation CVD was used to grow several perovskite-type oxides on planar silicon substrates at temperatures ranging from 500 to 700 °C. The optimization of the process control parameters allows the attainment of the perovskite structure as a single phase. The electrical characterization using the temperature-dependent conductivity and thermopower indicates the p-type conduction of the grown films and shows a decreasing concentration of the charge carrier, mobility and band gap energy in the sequence LaCoO₃>LaMnO₃>LaCrO₃>LaFeO₃. The investigation of the electric properties of the obtained perovskite thin films shows the versatility of CVD as a method for the development of innovative devices.     

Laser spectroscopic monitoring of gas emission and measurements of the C/C isotope ratio in CO2 from a wood-based combustion

We report on the application of a compact and field-deployable instrument, based on a continuous-wave fiber-coupled Telecom external cavity diode laser, to measure the ¹³C/¹²C isotope ratio in CO₂ from a wood-based combustion. Carbon dioxide, the most important greenhouse gas, is a major product of combustion. The measurements of the ¹³C/¹²C isotopic ratio in CO₂ from combustion emission permit one to identify the CO₂ source and to study the temporal and spatial variations of pollution in the atmosphere. The average value of the ¹³CO₂/¹²CO₂ ratio is found to be (1.1011±0.0024)%. The corresponding δ-value relative to PDB standard is (−20.17±2.14)‰, which is in good agreement with the typical value of (−25±2)‰ for wood. Simultaneous monitoring of multiple species from gas emission has been performed using direct-absorption spectroscopy. The concentrations of C₂H₂, CO, CO₂ and H₂O were determined on the basis of integrated absorbance measured by least-squares fitting a Voigt lineshape to experimental absorption spectra.