Composite material identification as micropolar continua via an optimization approach

A strategy based on material homogenization and heuristic optimization for the structural identification of composite materials is proposed. The objective is the identification of the constitutive properties of a micropolar continuum model employed to describe the mechanical behaviour of a composite material made of rigid blocks and thin elastic interfaces. The micropolar theory (Cosserat) has been proved to be capable of properly accounting for the particles arrangements as well as their size and orientation. The constitutive parameters of the composite materials, characterized by different textures and dimensions of the rigid blocks, are identified through a homogenization procedure. Thus, the identification is repeated exploiting the static or modal response of the composite materials and using the Differential Evolution algorithm. The benchmark structures assumed as target are represented by discrete models implemented in ABAQUS where the blocks and the elastic interfaces are modelled by rigid bodies and elastic interfaces, respectively. The obtained results show that proposed strategies provide accurate results paving the way to the experimental validation and in field applications

Super hygroscopic non-stoichiometric cerium oxide particles as electrode component for PEM fuel cells

The design of highly efficient promoters for the oxygen reduction reaction (ORR) is an important challenge in the large-scale distribution of proton exchange membrane (PEM) fuel cells. Hygroscopic cerium oxide (CeO2) is here proposed as co-catalyst in combination with Pt. Physical chemical characterizations, by means of X-ray diffraction, vibrational spectroscopy, morphological and thermal analyses, were carried out, demonstrating high water affinity of the synthesized CeO2 nanoparticles. Composite catalysts (i. e., Pt : CeO2 1 : 0.5 and 1 : 1 wt:wt), were studied by either rotating disk electrode (RDE) and fuel cell tests performed at 80 °C and 110 °C. Interestingly, the cell adopting the Pt : CeO2 1 : 0.5 catalyst enabled the achievement of high power densities reaching ∼80 and ∼35 mW cm−2 under low relative humidity and high temperatures. This result demonstrates that tuning material surface properties (e. g. oxygen vacancies) could significantly boost the electrochemical performance of cathodes as a combined result of optimized water retention and improved ORR kinetic

Towards a More Sustainable Photocatalyzed α-Arylation of Amines: Green Solvents, Catalyst Recycling and Low Loading

A more sustainable and efficient protocol for the photocatalytic α-amino arylation promoted by fac-Ir(ppy)3 was developed. Three noteworthy results were achieved: i) the replacement of toxic medium DMA with the greener solvents NBP and NHP, and the concurrent improvement of the process efficiency by lowering both the amine and the base amount; ii) the development of a recycling protocol for both the sustainable solvent NHP and the commercially available costly photocatalyst fac-Ir(ppy)3, achieving environmental and economic benefits. This approach to the photocatalyst recovery avoids very demanding catalyst structural modifications; iii) the protocol in green solvents proved to be scalable up to 10 mmol of limiting reagent, maintaining excellent performance also lowering the photocatalyst loading down to 0.05 mol%. This is the first example of photocatalytic α-arylation of amines promoted by such a low amount of catalyst. Lastly, the versatility of this approach was demonstrated by extending the use of the green solvent NBP to another photoredox process

Synthesis of Some New 3-Pyrrolidinylquinoline Derivatives via 1,3-Dipolar Cycloaddition of Stabilized Azomethine Ylides to Quinolinyl α,β- Unsaturated Ketones

International audienceN-Metallated azomethine ylide generated from methyl (E)-N-benzylideneglycinate, LiBr and triethylamine underwent cycloaddition to quinolyl α,β- unsaturated ketones with excellent diastereoselectivity to afford new functionalised 3-pyrrolidinylquinoline derivatives

ENHANCEMENT OF MODE I FRACTURE TOUGHNESS OF ADHESIVELY BONDED SECONDARY JOINTS USING LAYUP PATTERNING OF CFRP

This work aims to analyse the influence of the CFRP layup patterning on the crack path of composite bonded joints and evaluate its effect on the mode I fracture toughness. An experimental program has been performed using Double Cantilever Beam tests with three different CFRP layup patterning and two adhesives. In addition, a finite element analysis was also implemented to further identify different damage mechanisms during the tests. The outcome shows that different substrate CFRP layup patterning results in distinct crack onsets and propagation paths during the tests, also influenced by the type of adhesive used. Furthermore, an enhancement of around 25% in the joint's onset fracture toughness was observed with the layup patterning compared to a reference joint (with unidirectional layup). Thus, the substrate's patterning morphology seems to be a promising method to increase the mode I fracture toughness of the studied secondary joints

Chemodivergent Photocatalytic Synthesis of Dihydrofurans and β,γ-Unsaturated Ketones

A synthetic procedure, catalysed by Ir(ppy)3 under visible-light irradiation, for the chemodivergent synthesis of 2,3-dihydrofurans (3) or β,γ-unsaturated ketones (7) starting from α-halo ketones (1) and alkenes (2) has been developed. The mild reaction conditions and the redox-neutral nature of the process make it particularly sustainable avoiding the use of both sacrificial reactants and stoichiometric strong oxidants. Careful experimental investigations, supported by DFT calculations, allowed to disclose in details a possible mechanistic pathway and to direct the synthesis chemodivergently either toward 3 or 7, depending not only on the nature of the substrates, but also on the choice of the experimental conditions. (Figure presented.)

Status and performances of the FAZIA project

FAZIA is designed for detailed studies of the isospin degree of freedom, extending to the limits the isotopic identification of charged products from nuclear collisions when using silicon detectors and CsI(Tl) scintillators. We show that the FAZIA telescopes give isotopic identification up to Z$\sim$25 with a $\Delta$E-E technique. Digital Pulse Shape Analysis makes possible elemental identification up to Z=55 and isotopic identification for Z=1-10 when using the response of a single silicon detector. The project is now in the phase of building a demonstrator comprising about 200 telescopes

Analysis of fullerenes in soils samples collected in The Netherlands

Fullerenes are carbon based nanoparticles that may enter the environment as a consequence of both natural processes and human activities. Although little is known about the presence of these chemicals in the environment, recent studies suggested that soil may act as a sink. The aim of the present work was to investigate the presence of fullerenes in soils collected in The Netherlands. Samples (n = 91) were taken from 6 locations and analyzed using a new developed LC-QTOF-MS method. The locations included highly trafficked and industrialized as well as urban and natural areas. In general, C60 was the most abundant fullerene found in the environment, detected in almost a half of the samples and at concentrations in the range of ng/kg. Other fullerenes such as C70 and an unknown structure containing a C60 cage were detected to a lower extent. The highest concentrations were found in the proximity of combustion sites such as a coal power plant and an incinerator, suggesting that the nanoparticles were unintentionally produced during combustions processes and reached the soil through atmospheric deposition. Consistent with other recent studies, these results show that fullerenes are widely present in the environment and that the main route for their entrance may be due to human activities. These data will be helpful in the understanding of the distribution of fullerenes in the environment and for the study of their behavior and fate in soil.</p

All functions are (locally) ss-harmonic (up to a small error) - and applications

The classical and the fractional Laplacians exhibit a number of similarities, but also some rather striking, and sometimes surprising, structural differences. A quite important example of these differences is that any function (regardless of its shape) can be locally approximated by functions with locally vanishing fractional Laplacian, as it was recently proved by Serena Dipierro, Ovidiu Savin and myself. This informal note is an exposition of this result and of some of its consequences

Memristive neural network for on-line learning and tracking with brain-inspired spike timing dependent plasticity

Brain-inspired computation can revolutionize information technology by introducing machines capable of recognizing patterns (images, speech, video) and interacting with the external world in a cognitive, humanlike way. Achieving this goal requires first to gain a detailed understanding of the brain operation, and second to identify a scalable microelectronic technology capable of reproducing some of the inherent functions of the human brain, such as the high synaptic connectivity (~104) and the peculiar time-dependent synaptic plasticity. Here we demonstrate unsupervised learning and tracking in a spiking neural network with memristive synapses, where synaptic weights are updated via brain-inspired spike timing dependent plasticity (STDP). The synaptic conductance is updated by the local time-dependent superposition of pre-and post-synaptic spikes within a hybrid one-transistor/one-resistor (1T1R) memristive synapse. Only 2 synaptic states, namely the low resistance state (LRS) and the high resistance state (HRS), are sufficient to learn and recognize patterns. Unsupervised learning of a static pattern and tracking of a dynamic pattern of up to 4 Ã\u97 4 pixels are demonstrated, paving the way for intelligent hardware technology with up-scaled memristive neural networks