Effect of Thermomechanical Fatigue on Precipitation Microstructure in Two Precipitation-Hardened Cast Aluminum Alloys

Thermal loading induces modifications of the precipitation microstructure of Al–Si–Cu–Mg alloys. This study focuses on the effect of deformation on precipitation microstructure during thermomechanical loadings. Several specimens were thermomechanically cycled while others were exposed to the same thermal cycles without any mechanical loading. The nature and morphological characteristics of the precipitation microstructure of the thermomechanically cycled specimens are compared to those of the thermally aged ones, using transmission electron microscopy (TEM), in order to assess the effect of deformation on the precipitation microstructure and especially on the kinetics of precipitate growth. The absence of any significant effect of superimposed straining during thermal cycling is discussed. Implications for the prevision of yield strength degradation during service operation are briefly presented.

     

Mice Lacking Gpr179 with Complete Congenital Stationary Night Blindness Are a Good Model for Myopia

Mutations in GPR179 are one of the most common causes of autosomal recessive complete congenital stationary night blindness (cCSNB). This retinal disease is characterized in patients by impaired dim and night vision, associated with other ocular symptoms, including high myopia. cCSNB is caused by a complete loss of signal transmission from photoreceptors to ON-bipolar cells. In this study, we hypothesized that the lack of Gpr179 and the subsequent impaired ON-pathway could lead to myopic features in a mouse model of cCSNB. Using ultra performance liquid chromatography, we show that adult Gpr179^−/− mice have a significant decrease in both retinal dopamine and 3,4-dihydroxyphenylacetic acid, compared to Gpr179^+/+ mice. This alteration of the dopaminergic system is thought to be correlated with an increased susceptibility to lens-induced myopia but does not affect the natural refractive development. Altogether, our data added a novel myopia model, which could be used to identify therapeutic interventions.     

High-Throughput Strategies for the Design,Discovery, and Analysis of Bismuth-Based Photocatalysts

Bismuth-based nanostructures (BBNs) have attracted extensive research attention due to their tremendous development in the fields of photocatalysis and electro-catalysis. BBNs are considered potential photocatalysts because of their easily tuned electronic properties by changing their chemical composition, surface morphology, crystal structure, and band energies. However, their photocatalytic performance is not satisfactory yet, which limits their use in practical applications. To date, the charge carrier behavior of surface-engineered bismuth-based nanostructured photocatalysts has been under study to harness abundant solar energy for pollutant degradation and water splitting. Therefore, in this review, photocatalytic concepts and surface engineering for improving charge transport and the separation of available photocatalysts are first introduced. Afterward, the different strategies mainly implemented for the improvement of the photocatalytic activity are considered, including different synthetic approaches, the engineering of nanostructures, the influence of phase structure, and the active species produced from heterojunctions. Photocatalytic enhancement via the surface plasmon resonance effect is also examined and the photocatalytic performance of the bismuth-based photocatalytic mechanism is elucidated and discussed in detail, considering the different semiconductor junctions. Based on recent reports, current challenges and future directions for designing and developing bismuth-based nanostructured photocatalysts for enhanced photoactivity and stability are summarized.     

Making Progress Towards « Green » Propellants – Part III

Stabilisers are an integral part of a propellant composition. They are essential for ensuring the chemical stability of nitrate-ester based propellants, preventing oxidation, chain scission and uncontrolled heat generation. Progress is being made, especially in Europe, with REACh legislation (1907/2006) to use more environmentally-friendly compounds. New stabilisers with a greener environmental profile and producing less toxic daughter products have been investigated by several groups, and several compounds demonstrated even better performances – more chemical stability and therefore longer shelf lives than formulations with the currently-used stabilisers. Additionally, the good efficiencies and lower toxicities of the daughter products of the “green” stabilisers are also evaluated. This paper is a continuation of our previous work and demonstrates that for industrially-manufactured propellants, that the tests performed by four different entities validate the stability and compatibility of the propellants, investigated previously on a laboratory scale, providing the community with safer formulations for the environment and health.     

BCI competition III: dataset II- ensemble of SVMs for BCI P300 speller

Brain-computer interface P300 speller aims at helping patients unable to activate muscles to spell words by means of their brain signal activities. Associated to this BCI paradigm, there is the problem of classifying electroencephalogram signals related to responses to some visual stimuli. This paper addresses the problem of signal responses variability within a single subject in such brain-computer interface. We propose a method that copes with such variabilities through an ensemble of classifiers approach. Each classifier is composed of a linear support vector machine trained on a small part of the available data and for which a channel selection procedure has been performed. Performances of our algorithm have been evaluated on dataset II of the BCI Competition III and has yielded the best performance of the competition.     

The structure of shock and interphase layers for a heat conducting Maxwellian rate-type approach to solid–solid phase transitions

One continues the qualitative analysis started in Part I (F?ciu and Molinari in Acta Mech) concerning the thermomechanical characteristics of a steady, structured moving phase boundary in a shape memory alloy (SMA) by a quantitative investigation. The internal structure of these interphase layers is governed by a Maxwellian rate-type constitutive equation coupled or not with the Fourier heat conduction law. We consider as equilibrium stress–strain–temperature response function for the Maxwellian model an explicit piecewise linear thermoelastic relation for an SMA bar which can exist in the austenite phase A and in two variants of martensite M ^±. Its thermal properties are built in agreement with experimental results on NiTi. This equilibrium relation has the atypical property that not only the derivative of the stress response function with respect to the strain changes its sign, but also the derivative with respect to the temperature. Considerable temperature variation is generated by impact-induced phase transformations due to the large amount of latent heat released (absorbed) inside the transition layer. One gets strong heating (cooling) across a compressive A→ M ^? (expansive M ^? → A) propagating interphase layer. A significant lower (larger) temperature than that at the front and Hugoniot back state is obtained inside an impact-induced M ⁺→ M ^? (M ^?→ M ⁺) interphase layer. The experimental finding of this phenomenon of temperature undershoot (overshoot) could be a valuable indication for the existence of an interphase layer.     

Fuzzy Online Auto-Tuning for an Industrial PID Controller

This paper presents a fuzzy tuning system for real-time industrial PID （proportional-integral-derivative） controllers. The algorithm set the proportional gain, integral time and derivative time of a classical PID structure according to the set point, error and error derivative of the process, respectively. The tuning of the PID controller is based on a fuzzy inference machine. The set of rules of the fuzzy inference machine was obtained by experts engineering. The system is tested in an austempering process but can be applied in any industrial plant. Besides, an analysis between the response of the process with a PID controller and the system of fuzzy auto-tuning for P1D proposed was made.     

Characterisation of hydrodynamics induced by air injection related to membrane fouling behaviour

The study focuses on fine bubble and spherical cap bubble injection in case of outside/in fibres immersed in a tank. The objectives are to quantify liquid circulations and shear stresses along the membrane and to understand their effects on the fouling resistance. Thus, both filtration experiments and hydrodynamic characterisation were performed in the same aeration conditions. Only particle cake deposit was studied as fouling mode and the hydrodynamics was characterized experimentally by 2-phase flow particle image velocimetry (PIV) and numerically with the CFD code FLUENT. Results presented in this paper are limited to tight hollow-fibres to well understand hydrodynamics without fibre motion. One important result is that mean values of wall shear stress are very low (maximum 0.25 Pa) eliminating the wall shear stress as a mechanism able to explain filtration performances for a non-confined aeration without fibre displacement. In addition, an analysis has been conducted in terms of horizontal liquid flow toward the membrane. The quantification of this flow allowed to conclude that i) for a given local bubble flow rate, there is no influence of the kind of aeration on this horizontal flow rate; and ii) the filtration performances can be correlated with this horizontal flow. The reason might be an over concentration of particles near the membrane surface induced by this flow.     

Modelling of axis feed consumed energy for sustainable manufacturing

The accurate evaluation of electrical energy demanded by a CNC toolpath during a machining process is essential to determine its efficiency. Actually, the dynamic behavior of cutting forces seems to be neglected by investigators despite its influence on the consumed cutting energy during a face milling operation. This paper aims to investigate the effect of dynamic behavior of the machining system in order to take into account the dynamic response of the cutting forces on the axis feed power prediction. A dynamic cutting power model is developed in order to predict the consumed cutting energy. A parametric study is performed in order to show the impact of cutting conditions on the consumed energy values. The numerical results are compared to experimental ones.