Corrosion behavior in artificial seawater of thermal-sprayed WC-CoCr coatings on mild steel by electrochemical impedance spectroscopy

The corrosion behavior in artificial seawater of different as-sprayed ceramic-metallic (cermet) coatings applied on low-alloy steel was studied. Five conditions, associated to modifications of the composition of the powder or deposition parameters were evaluated. The degradation mechanisms were studied during extended immersion tests using conventional electrochemical measurement and electrochemical impedance spectroscopy. The extended immersion tests reveal that these as-thermal-sprayed coatings present a cathodic behavior compared with steel. During the first hours of immersion, the electrolyte infiltrates the defects of the coatings, which then result to the local degradation of the substrate accelerated by the galvanic coupling with the cermet coating. Optical observations and Raman analyses reveal the formation of calcium carbonates like aragonite on the cermet surface, very close to the appearance of local anodic sites. The cross-sectioned views reveal the infiltration of the corrosive solution, and the depth penetration of the degradation of steel substrate probably due to the acidification of the anodic sites.     

Analysis of steady combustion processes in a recombination reaction

In the present paper, the combustion processes, represented by steady deflagration or detonation waves, are studied for a set of balance laws in the framework of Navier–Stokes reactive equations related to a diatomic recombination reaction. Moreover, a systematic analysis of the combustion solutions is carried out, investigating the influence of all the physical parameters present in the hydrodynamical equations: the Mach number of the gas mixture in the unburned state, the chemical link energy of the diatomic molecule and the activation energy of the reaction. Results are discussed according to several numerical experiments.     

Weakly non-linear high frequency waves for a first order quasi-linear system involving source-like terms

Making use of the method of asymptotic expansion of multiple scales, a study of weakly non-linear, high frequency waves, through “homogeneous” media characterized by dissipative or dispersive hyperbolic systems of partial differential equations, is proposed. Within the present theoretical framework, asymptotic waves in a heat-conducting fluid are considered.     

Sopra i sistemi lineari di integrali semplici di prima specie con periodi ridotti sopra una varietà di Picard

AdAlexander Ostrowski nel suo 60^mo compleannoDie Durchsicht der Korrekturen hat freundlicherweise Herr Dr. M.Rosati, Rom Übernommen. (Anm. d. Red.)Il Prof. F.Conforto è deceduto a Roma il giorno 24 febbraio 1954.     

Sub-shock formation in Grad 10-moment equations for a binary gas mixture

The shock structure problem for Grad 10-moment equations for an inert binary mixture is investigated: necessary conditions for the formation of sub-shocks in fields of only one gas or of both components are rigorously obtained, and a detailed comparison with the shock-wave structure of its principal sub-system (deduced assuming vanishing viscous stress tensors) and of the equilibrium Euler sub-system is performed. Some numerical simulations for a mixture of argon and helium are presented.     

A high-statistics determination of the Λ mean lifetime

Recent determinations of the mean lifetime of the Λ hyperon have given values significantly greater than the previously accepted world average. Using 34 000 Λ → pπ^? decays in the CERN 2m. hydrogen bubble chamber, we have measured the Λ lifetime to be (2.611 ± 0.020) × 10^?10sec.     

Shock structure and multiple sub-shocks in binary mixtures of Eulerian fluids

The problem of sub-shock formation within a shock structure solution of hyperbolic systems of balance laws is investigated for a binary mixture of multi-temperature Eulerian fluids. The main purpose of this work is the analysis of the ranges of Mach numbers characterizing shock-structure solutions with different features, continuous or not, and to show the existence of ranges, below the maximum unperturbed characteristic velocity, for which each constituent of the mixture may develop a sub-shock within a smooth shock structure profile. The theoretical results are supported by numerical calculations.