Hydroisomerization of n-heptane and dehydration of 2-propanol on bulk and supported WO2(Hx)ac on TiO2

Characterization by XPS–UPS and XRD of commercial bulk WO₂ enabled us to identify the presence of four to five layers of WO₃ on the sample surface with an equal amount of W⁵⁺, possibly W₂₀O₅₈ in the interface. The presence of these WO₃ and W₂₀O₅₈ on the WO₂ surface were not detected by XRD. Exposure of commercial bulk WO₂ to hydrogen at temperatures higher than 673 K results in the reduction of surface WO₃ to WO₂ and the formation of the bifunctional WO₂(H_x)_ac phase on its surface. A complete conversion of surface WO₃ to WO₂(H_x)_ac has been obtained following the exposure of the sample to hydrogen for at least 6 h at 773 K. A conversion of 52% of n-heptane at 573 K reaction temperature and a selectivity of 90% in isomerization products, mainly 2,3-MH and multibranched molecules were obtained. The isomerization products distribution is in agreement with the statistical and thermodynamic equilibrium of the methyl-shift mechanism. The stability of the active WO₂(H_x)_ac phase has been tested under prolonged exposure to hydrogen and the reaction mixture. Similar results were obtained in the case of bulk WO₃ and WO₃/TiO₂ systems. Dehydration and dehydrogenation of 2-propanol were studied on these systems at 393 K reaction temperature.     

Self-assembly and characterization of layered double hydroxide/DNA hybrids

The purpose of this study was to control the fabrication of new labile supramolecular assemblies by formulating associations of DNA molecules with inorganic layered double hydroxides (LDHs). The results show that LDH/DNA hybrids synthesized by a coprecipitation route involving the in situ formation of LDHs around DNA molecules acting as templates were characterized by a lamellar organization, with DNA molecules sandwiched between hydroxide layers, exhibiting a regular spacing of 1.96 nm. Our results indicate that labile complexes resulting from the association of nucleic acids and inorganic materials can be obtained not only by anion exchange but also by a direct self-assembly route.     

Influence of machining parameters and new nano-coated tool on drilling performance of CFRP/Aluminium sandwich

Drilling and fastening of hybrid materials in one-shot operation reduces cycle time of assembly of aerospace structures. One of the most common problems encountered in automatic drilling and riveting of multimaterial is that the continuous chips curl up on the body of the tool. Drilling of carbon fiber reinforced plastic (CFRP) is manageable, but when the minute drill hits the aluminium (Al) or titanium (Ti), the hot and continuous chips produced during machining considerably damage the CFRP hole. This study aims to solve this problem by employing nano-coated drills on multimaterial made of CFRP and aluminium alloy. The influence of cutting parameters on the quality of the holes, chip formation and tool wear were also analyzed. Two types of tungsten carbide drills were used for the present study, one with nano-coating and the other, without nano coating. The experimental results indicated that the shape and the size of the chips are strongly influenced by feed rate. The thrust force generated during drilling of the composite plate with coated drills was 10–15% lesser when compared to that generated during drilling with uncoated drills; similarly, the thrust force in the aluminium alloy was 50% lesser with coated drills when compared to thrust force generated without coated drills. Thus, the use of nano-coated drills significantly reduced the surface roughness and thrust force when compared with uncoated tools.     

Étude de l'influence de l'évaporation d'un bac d'eau sur les transferts dans un canal corrugué

The authors present a numerical and experimental study on heat and mass transfers by forced convection in a channel with a sinusoidal protuberance and by natural convection in a reservoir full of water. The numerical study has been carried out for Reynolds numbers in a range of 35 to 350, several densities of heat flux and protuberance amplitude range of 0.005 to 0.02 m. Results show that the vapour diffusion in the air modifies the stream function profiles which become convex over the free surface of the water. In addition, the evaporation reduces the perturbation caused by the protuberance and increases the heat transfer rate in the channel. The visualisation of the flow, using smoke, an argon laser and a videocamera, shows the complexity of the interaction between the flow of vapour caused by the evaporation, the flow in the channel and the heat losses across the lateral walls. Theoretical and experimental results are in good qualitative agreement.     

Assessment of olive pomace wastes as flame retardants

Olive pomace (OP) is a lignocellulosic waste from olive oil industry. In order to valorize these wastes as flame retardant (FR) fillers into polymers, OP residues are milled and screened into three different fractions. Two strategies are then investigated. The first one is to modify OP particles by phosphorus molecules using radiation grafting as already done successfully with flax. Nevertheless, pyrolysis combustion flow calorimetry analyses show that the introduction of phosphorus does not promote charring of OP and flame retardancy is not significantly improved whichever the considered fraction. The second strategy is to replace pentaerythritol by OP as char source into well-known FR systems based on ammonium polyphosphate. The incorporation of such system into ethylene-vinyl acetate copolymer leads to satisfying FR performances according to cone calorimeter tests. Moreover, the presence of high amount of extractives into OP such as oleic acid does not appear detrimental. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47715.     

Simulation of the forming of mash seam welded sheets

The paper presents results on the optimization of the process of mash seam welding for improving the formability of the joined sheet metal semi-products. An integrated concept including the welding, smoothing and heat treatment of mash welded sheets has been developed. As an example, fatigue tests and the simulation of the forming behaviour of a mash seam welded tensile specimen simulated by the finite element method (FEM) is discussed. The determination of the material properties of the seam which, so far, have been determined experimentally is thus considerably simplified.     

Secure IoT solution for wearable health care applications,case study Electric Imp development platform

Internet expansion affects currently diverse entities on the physical world and daily life. The democratization of the technology called Internet of Things (IoT) brings back many problems associated with the security of the transmitted data, autonomy, and ease of use, with the central constraint of gathering momentum. The use of an embedded development platform for IoT operating through Wi‐Fi and cloud technology is in our case the solution that fits the internet model objects for wearable health care application. This work involves the study and implementation of wearable IoT secure solution dedicated to health care devoted to old and dependent people. The proposed hardware, powered by solar cells, operate through smart sleep and wake up events. The relevant part of the developed IoT operating software exploits the multiagent behavior. Case study, based on the exploitation of the Electric Imp platform, is proposed.     

Improving asynchronous motor speed and flux loop control by using hybrid fuzzy-SMC controllers

This paper presents a new method combining sliding mode control (SMC) and fuzzy logic control (FLC) to enhance the robustness and performance for a class of non-linear control systems. This fuzzy sliding mode control (FSMC) is developed for application in the area for controlling the speed and flux loops of asynchronous motors. The proposed control law can solve those problems associated with the conventional control by sliding mode control, such as high current, flux and torque chattering, variable switching frequency and variation of parameters, in which a robust fuzzy logic controller replaces the discontinuous part of the classical sliding mode control law. Simulation results of the proposed FSMC technique on the speed and flux rotor controllers present good dynamic and steady-state performances compared to the classical SMC in terms of reduction of the torque chattering, quick dynamic torque response and robustness to disturbance and variation of parameters.