New methods for the fast simulations of the extrusion process of hot metals

Being able to find alternatives to the costly and time-consuming trial and error current practice in die design based on know-how acquired by practitioners throughout years is of primary importance in the aluminum extrusion industry. In this paper, two programs aimed at helping extruders in estimating the performance and feasibility of processes and simulating in details the flow of material in the press, are presented. Although they have been used so far for aluminum alloys, they could also be applied to other extrusion applications like that of other metals and polymers for instance. Together with a process simulator, which enables one to obtain a fast estimate of the extrusion process performances and computer-aided production of aluminum extrudates, a three-dimensional software dedicated to the design of dies with complicated shapes is also described.     

Mesomorphism of dialkylterthiophene homologues

New dialkylterthiophene liquid crystalline compounds were synthesised and characterised using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarized optical microscopy (POM). Upon cooling from the isotropic state to the crystalline phase, these dialkylterthiophenes present different types of smectic mesophases. For the highest ordered smectic phase, XRD analyses have revealed a molecular organisation within the smectic layers and the key structural parameters are determined by molecular modelling simulations. The structural properties of these smectic phases are discussed in relation to the alkyl chain length.     

An analytical model of an elementary elliptical cell forming an alveolar elastic material under plane stress

This paper analyzes the static behavior of alveoled materials that is about to be developed for dynamic optimization of structural panels. It deals precisely with materials made of elliptical thin cells, filled with polymer material. The main contribution of the paper consists in elaborating an analytical approach describing the material. The considered problem represents an unidirectional stress, the goal being to calculate the elastic energy and strain globally obtained in the material. The wall of the elementary cell is represented in accordance with the classical BRESSE’s theory of thin beams, with specific adaptation for elliptical shape. The polymer material filling the cell is modelized with ABSI’s method of equivalence, which allows a direct approximation of various continuous media by equivalent spring segments. This method is presented and discussed for the present configuration, with its specific adaptation. The final result obtained by these analytical approaches is then compared to results from a finite element model. In spite of local differences between the analytical results and numerical computation, it appears clearly that the precision obtained by the proposed analytical approach is better than 95%, which is sufficient for this kind of material. Thus, the proposed analytical calculation and methodology allows robust and quick determination of material characteristics for elementary cells of such alveoled materials. The resulting laws can then be introduced into global models of a grid of cells.     

Application of multisine impedance spectroscopy, FE-AES and FE-SEM to study the early stages of copper corrosion

During the first 24 h of immersion of a pure copper surface in a NaCl containing solution, this surface is in constant evolution. The reactions going on the surface are still not known; discrepancies are found between different published studies. This study resolves these discrepancies using broadband impedance spectroscopy, field emission Auger spectroscopy and field emission electron microscopy. The surface evolution was studied using time series of impedance spectra. Also the experimental variables convection and electrolyte concentration were varied. Parameter evolutions were obtained by fitting the obtained impedance spectra to an equivalent circuit. Combining the calculated parameter values and their evolution with the spectroscopic data led to the identification or replacement of the elements present in the very general equivalent circuit found in the literature: a double layer, two circuit films in parallel and mass transfer.     

Evidence of sidewall covalent functionalization of single-walled carbon nanotubes and its advantages for composite processing

Single-walled carbon nanotubes (SWCNTs) were functionalized in a three-step procedure. The first step is a radical reaction creating a covalent bond between the carbon nanotube surface and grafted p-methoxyphenyl functional groups. In a second step, a deprotection of the methoxy functions generates free alcohol groups and in the final step an esterification is done in order to install a double bond for further polymerization. Evidence that functionalization has actually occurred on the SWCNT sidewalls is furnished through investigations involving several complementary techniques (visual dispersion tests, transmission electron microscopy, thermal gravimetric analysis and adsorption volumetry). We show that surface properties of SWCNTs are changed throughout the chemical treatments and that the obtained level of functionalization is low. Incorporation of functionalized SWCNTs in a polymer (poly(methyl methacrylate)) matrix was done through an in situ polymerization process. Observations of the obtained composites using scanning and transmission electron microscopy illustrate that interactions between the SWCNT surface and the polymer matrix are improved.     

Model of Water Application under Pivot Sprinkler. I: Theoretical Grounds

A model describing the application pattern produced by a single sprinkler is proposed. Based on calibrated statistical distributions and free from any ballistic consideration, this model uses a mixture of beta probability distributions in which parameters are first estimated with water application data measured in zero wind condition. Data measured in field conditions are then used to assess the wind effect on the shift of the center of gravity of the irrigated area, on the range of the sprinkler in various directions, and on the values of the beta distributions' parameters. The computation of the water application amounts at any point of the irrigated area is finally resolved in the use of a single equation, which can be easily implemented in a software package to simulate application patterns under a series of sprinklers attached to a center pivot or moving lateral irrigation machine.     

Effects of High Hydrostatic Pressure Processing on Hen Egg Compounds and Egg Products

High hydrostatic pressure (HHP), used alone or with other processes, is an emerging technology increasingly used in the food industry to improve microbial safety, and the functionality and bioactive properties of food products. HHP provides a way to reduce energy requirements for food processing and may contribute to improved energy efficiency in the food industry. Hen egg is used by the food industry to formulate many food products. To improve the microbiological safety of egg and egg‐derived products, HHP processing is an attractive alternative to heat‐ pasteurization and a potential technology. However, HHP treatment induces structural modifications of egg components (such as proteins) which could positively or negatively affect the physicochemical and functional properties of egg‐derived products. Improving our knowledge regarding the potential of HHP in the egg industry will add value to the final food products and increase profitability for egg producers and the food industry.     

Best practices for comparing optimization algorithms

Comparing, or benchmarking, of optimization algorithms is a complicated task that involves many subtle considerations to yield a fair and unbiased evaluation. In this paper, we systematically review the benchmarking process of optimization algorithms, and discuss the challenges of fair comparison. We provide suggestions for each step of the comparison process and highlight the pitfalls to avoid when evaluating the performance of optimization algorithms. We also discuss various methods of reporting the benchmarking results. Finally, some suggestions for future research are presented to improve the current benchmarking process.