ELEMENTARY MECHANICS OF THE MITRAL VALVE

We illustrate a bare-bones mathematical model that is able to account for the elementary mechanics of the mitral valve when the leaflets of the valve close under the systolic pressure. The mechanical model exploits the aspect ratio of the valve leaflets that are represented as inextensible rods, subject to the blood pressure, with one fixed endpoint (on the endocardium) and an attached wire anchored to the papillary muscle. Force and torque balance equations are obtained exploiting the principle of virtual work, where the first contact point between rods is identified by the Weierstrass-Erdmann condition of variational nature. The chordae tendineae are modeled as a force applied to the free endpoint of the flaps. Different possible boundary conditions are investigated at the mitral annulus, and, by an asymptotic analysis, we demonstrate that in the pressure regime of interest generic boundary conditions generate a tensional boundary layer. Conversely, a specific choice of the boundary condition inhibits the generation of high tensional gradients in a small layer

Evaluation of the mechanical properties of cements with fillers derived from the CO2 reduction of cement plants

This work introduces a novel method for the development of CO2 recovery systems derived from the production process of cement in order to obtain CaCO3 nanofiller in cement-based composites. Research was carried out in collaboration between the Department of Applied Science and Technology (DISAT) and the Department of Structural, Construction and Geotechnical Engineering (DISEG) of Politecnico di Torino. The objective of this method was dual. Firstly, it aimed to obtain a precipitated calcium carbonate - nanoCaCO3 - with a high degree of purity. Secondly, it aimed to optimize the characteristics of these nanoparticles e.g. additional percentages, morphology, particle size distribution or crystal phase, according to their use in cement-based composites. The synthesized nanoCaCO3 particles were subsequently added into the cementitious composites in different percentages according to the weight of the cement, in order to understand their behaviour within the cement matrix. The mechanical properties were also evaluated, both at 7 and 28 days, through three point bending and compression tests. The results of the mechanical tests showed a promising improvement in strength and toughness. This study is a first step towards developing a CO2 circular economy

Nano CaCO3 particles in cement mortars towards developing a circular economy in the cement industry

This paper calls into question the effects of incorporating nano calcium carbonate (CaCO3) particles in cement mortars, as they are interesting additive materials already successfully tested as cement nanofiller. These nanoparticles could potentially be prepared through the carbonation route using CO2 from combustion gases from the cement industry. This could enable a circular-economy approach for carbon capture and its re-use within the cement industry, in a sustainable and synergistic manner. In this study, part of the cement content was substituted with commercial nano CaCO3 particles to investigate their effects on the flexural and compressive strength of the resulting cement mortars, after curing for 7 and 28 days. Decreasing the cement content could lead to a reduction in the carbon footprint of cement, which is responsible for approximately 8% of global carbon dioxide emissions. Preliminary results using synthesized CaCO3 particles as nanofillers showed that, after 7 days of curing, mechanical properties of cement mortars improved. This indicates that hydration reaction was accelerated since CaCO3 acts as seeding for this reaction. By contrast, after 28 days of curing, no major improvement was observed. A higher content of calcium carbonate nanoparticles may have reduced the filler effect of these particles due to aggregation phenomena. In the present work, the effects of commercial nano CaCO3 particles on cement hydration were investigated. Mechanical tests showed promising results both after 7 and 28 days of curing. This could lead to the reduction of the carbon footprint of cement manufacturing and produce increasingly better performing building materials. Thus, the development of a circular economy in the cement industry could be achieved

Aftertreatment technologies for diesel engines: An overview of the combined systems

The abatement of the pollutants deriving from diesel engines in the vehicle sector still represents an interesting scientific and technological challenge due to increasingly limiting regulations. Meeting the stringent limits of NOx and soot emissions requires a catalytic system with great complexity, size of units, and number of units, as well as increased fuel consumption. Thus, an aftertreatment device for a diesel vehicle requires the use of an integrated catalyst technology for a reduction in the individual emissions of exhaust gas. The representative technologies devoted to the reduction of NOx under lean‐burn operation conditions are selective catalytic reduction (SCR) and the lean NOx trap (LNT), while soot removal is mainly performed by filters (DPF). These devices are normally used in sequence, or a combination of them has been proposed to overcome the drawbacks of the individual devices. This review summarizes the current state of NOx and soot abatement strategies. The main focus of this review is on combined technologies for NOx removal (i.e., LNT–SCR) and for the simultaneous removal of NOx and soot, like SCR‐on‐Filter (SCRoF), in series LNT/DPF and SCR/DPF, and LNT/DPF and SCR/DPF hybrid systems

Electrical Tree Growth in EVA-Layered Silicate Nanocomposites

none5noneF. Guastavino; A. Dardano; G. C. Montanari; F. Deorsola; L. TestaF. Guastavino; A. Dardano; G. C. Montanari; F. Deorsola; L. Test

Effect of water adsorption on the dielectric properties of polymer nanocomposites

none7In this paper, the effect of the water absorbed by inorganic nanofillers (e.g. during the manufacturing process prior to the extrusion) on the electrical properties of a thermoplastic polymer based nanocomposite is studied. Particularly, it is shown how the absorption of water by the nanofiller can affect significantly the nanocomposite electrical properties. Two nanofillers, i.e. fluorohectorite and bohemite, with two different levels of water content, were used to study the effects on electrical properties, in particular space charge accumulation, electric strength and conduction current.noneD. Fabiani; G. C. Montanari; L. Testa; R. Schifani; F. Guastavino; F. Bellucci; F. DeorsolaD. Fabiani; G. C. Montanari; L. Testa; R. Schifani; F. Guastavino; F. Bellucci; F. Deorsol