Etude de l'influence du mode d'anodisation sur la cinétique de croissance des films d'alumine en milieu acide sulfurique

The kinetics of growth of Al₂O₃ oxide films made by anode oxidation of ALuminium 1050A with two anodization techniques has been investigatedan compared. The first technique is the classical method based on continuous tension during the complete electrlysis duration, and the second one is the modern method ofpulsed tensions, whcih consists of periodically imposing to the material two anodc tensions E₁ and E₂ (E₁ > E₂) during time T₁ and T₂ until the end on anodization. We have shown that the second technique allows the fabrication of films more rapidly for the same electrolysis duraton. Energy and electrolysis time are saved, making it attractive from an economical viewpoint. This advantage arises from the positive effect of excess heat disiption gathered during the imposition of tension, E₁, when E₂ is imposed thereafter (recovery effect). The logging of in situ transient responses in the case of pulsed anodization is a significant asset to explain the growth film kinetics obtained with this method.     

Optimal Sizing of a DBD Ozone Generator Using Response Surface Modeling

Dielectric barrier discharge (DBD) reactors used as ozone generators are well known today and widely used for water treatment and air disinfection. The purpose of this article is to propose an experimental procedure based on the response surface modeling in order to optimize the geometrical dimensions of the cylindrical shape ozone generator, i.e., the discharge gap and the electrodes length. Because an effective ozone generator is expected to give high ozone concentration with a minimum of power requirements, the applied high voltage was associated with the geometrical parameters to carry out a composite centered faces design. Obtained results indicate that for an efficient ozone generator, length of the electrodes needs to be optimized while the discharge gap should be minimized.     

Mono‐, Di‐ and Tetra‐Cationic Surfactants as Carbon Steel Corrosion Inhibitors

Corrosion inhibition of three new synthesized cationic surfactants, N‐(2‐(((Z)‐4‐(pyridin‐4‐yl)but‐3‐en‐1‐yl)amino)ethyl)‐N‐(2‐((E)‐(pyridin‐4‐ylmethylene)amino)ethyl)dodecan‐1‐aminium bromide I(4N), N¹,N²‐didodecyl‐N¹‐((Z)‐4‐(pyridin‐4‐yl)but‐3‐en‐1‐yl)‐N²‐(2‐((E)‐(pyridin‐4‐ylmethylene)amino)ethyl)ethane‐1,2‐diaminium bromide II(4N) and 1‐dodecyl‐4‐((E)‐((2‐(dodecyl(2‐(dodecyl((Z)‐4‐(1‐dodecylpyridin‐1‐ium‐4‐yl)but‐3‐en‐1‐yl)ammonio)ethyl)ammonio)ethyl)imino)methyl)pyridin‐1‐ium bromide IV(4N) on carbon steel was investigated by weight loss, electrochemical impedance spectroscopy and polarization measurements. Results show that the synthesized cationic surfactants inhibit corrosion of carbon steel in 1 M HCl. The inhibitive action occurs by virtue of adsorption on the metal surface following a Langmuir adsorption isotherm model. Polarization curves reveal that the investigated cationic surfactants can be classified as mixed inhibitor types. The variations in the corrosion inhibition efficiency between three cationic surfactants are correlated with their chemical structures, with more hydrophobic surfactants yielding higher inhibition efficiency.     

Prediction-based Deadbeat Control for Grid-connected Inverter with L-filter and LCL-filter

Abstract—In this article, an improved deadbeat control algorithm suitable for digital signal processor-based circuit implementation is proposed. The control algorithm allows the derivation of a nearly sine wave output current with a fixed switching frequency of a current-controlled voltage source inverter. Two low-pass output filters configurations are considered in this study: a simple inductance filter and an LCL-filter. By taking advantage of prior knowledge of the state variables’ shape, the improved deadbeat control algorithm is based on a simple prediction model to derive the expected duty cycle needed to switch on and off the power switches. The control study of the grid-connected inverter with L and LCL output filters has been considered using a co-simulation approach with (Powersim Inc., Rockville, Maryland, USA) and MATLAB software (The MathWorks, Natick, Massachusetts, USA). The obtained results show the improvement of both shape quality and tracking accuracy of the output current quantified by low ripple content and a nearly unity power factor.     

Dyeing of cationised cotton with acid dyes

The production of cationised cotton fabrics, via Sandene 8425, 1, 1-dimethyl-3-hydroxy azetidinium chloride and 1, 1-diethyl-3-hydroxy azetidinium chloride, greatly enhances the exhaustion and fixation of acid dyes. This paper shows that these dyes can be used in the absence of salt in a neutral medium. Wash fastness, light fastness and other properties were studied.     

Characterisation of 4043 aluminium alloy deposits obtained by wire and arc additive manufacturing using a Cold Metal Transfer process

ABSTRACT

4043 aluminium deposits were elaborated using a 3D print device equipped with a Cold Metal Transfer welding source. Two sets of process parameters leading to different average powers were compared in order to establish the relations between the powers and energies produced and the geometrical characteristics of the deposits. The effects of the travel speed and layer superposition on the transfer mechanisms as well as on the geometrical characteristics of the deposits were discussed for both sets of parameters. Finally, the formed microstructures were analysed and the porosity defects were quantified and discussed with regard to the heat input characteristics and the solidification conditions.     

Preimplantation hormonal differences between the conception and non-conception menstrual cycles of 32 normal women

We compared daily urinary concentrations of oestrogen and progesterone metabolites in paired menstrual cycles (conception and non-conception) from 32 women. Volunteers with no known fertility problems were enrolled in the study at the time they began trying to become pregnant. They collected first-morning urine specimens and kept daily records of menstrual bleeding and sexual intercourse for 6 months or until they became clinically pregnant. Intercourse in non-conception cycles was close to the time of ovulation so that failure to conceive was caused by factors other than poorly timed intercourse. Compared with non-conception cycles, conception cycles had a steeper early luteal rise in progesterone and higher mid-luteal oestrogen and progesterone concentrations. These hormonal characteristics may be markers of better quality cycles, but because all these differences were in the luteal phase, we cannot rule out the possibility that the preimplantation embryo had stimulated early increases in steroid production. We propose an analysis strategy that could help support or refute the importance of preimplantation embryonic signalling, but our small sample size limits our own conclusions about this mechanism.     

The addition of reactive compounds to nonreactive dyebaths. Part 5-procedure for obtaining reactive dyeings on cotton

An easy procedure for the preparation of solutions containing certain types of reactive dye and their subsequent application on cotton is described. This procedure takes advantage of the expected high reactivity of these dyes, which have adjacent hydroxy and amino groups in the molecule, and strives to evade the problems usually associated with the preparation and application of such dyes in the solid form. Several factors that affect the colour strength of reactive dyeings thus obtained are investigated. Possible disadvantages when applying this procedure are discussed.