Thermal energy balance in laser welding processes of austenitic stainless steels

Deep penetration weldings with a 2kW CO₂ laser were performed on different austenitic stainless steels in a wide range of thicknesses for two different assistant gases.The energy actually transferred to the samples to perform the welding process was calculated in terms of the LSM model for the different steels examined. Then, the trends of the efficiencies versus the thickness of the samples welded were plotted. These curves have a maximum which corresponds to an execution speed value which is approximately the same for all the different steels and is, moreover, equal to the heat propagation speed inside the material.Furthermore, a semi-empirical rule which takes into account both the thermophysical properties of the steel and the laser power is suggested for evaluating the trend of the weld width with respect to the process speed.     

Exclusive nuclear response to an electromagnetic probe

The nuclear response is studied in exclusive processes such as one- and two-nucleon knockout by an electromagnetic probe. The theoretical framework is the one-photon exchange approximation. The special role of the different theoretical ingredients is discussed with particular reference to nucleon-nucleon correlations, final-state interactions and reaction mechanism. An extension to high energy and momentum transfer is also considered where precursor phenomena connected with colour transparency may occur.Lectures given at the Indian-Summer School on Electron Scattering from Nucleons and Nuclei, Prague (The Czech Republic), September 1994.     

Asymmetric Poincaré inequalities and solvability of capillarity problems

In this paper we first establish an asymmetric version of the Poincaré inequality in the space of bounded variation functions, and then, basically relying on this result, we discuss the existence, the non-existence and the multiplicity of bounded variation solutions of a class of capillarity problems with asymmetric perturbations.     

Synthesis of Iron Oxide Nanoparticles in Listeria innocua Dps (DNA‐Binding Protein from Starved Cells): A Study with the Wild‐Type Protein and a Catalytic Centre Mutant

A comparative analysis of the magnetic properties of iron oxide nanoparticles grown in the cavity of the DNA‐binding protein from starved cells of the bacterium Listeria innocua, LiDps, and of its triple‐mutant lacking the catalytic ferroxidase centre, LiDps‐tm, is presented. TEM images and static and dynamic magnetic and electron magnetic resonance (EMR) measurements reveal that, under the applied preparation conditions, namely alkaline pH, high temperature (65 °C), exclusion of oxygen, and the presence of hydrogen peroxide, maghemite and/or magnetite nanoparticles with an average diameter of about 3 nm are mineralised inside the cavities of both LiDps and LiDps‐tm. The magnetic nanoparticles (MNPs) thus formed show similar magnetic properties, with superparamagnetic behaviour above 4.5 K and a large magnetic anisotropy. Interestingly, in the EMR spectra an absorption at half‐field is observed, which can be considered as a manifestation of the quantum behaviour of the MNPs. These results indicate that Dps proteins can be advantageously used for the production of nanomagnets at the interface between molecular clusters and traditional MNPs and that the presence of the ferroxidase centre, though increasing the efficiency of nanoparticle formation, does not affect the nature and fine structure of the MNPs. Importantly, the self‐organisation of MNP‐containing Dps on HRTEM grids suggests that Dps‐enclosed MNPs can be deposited on surfaces in an ordered fashion.     

Highly selective vapochromic fluorescence of polycarbonate films Doped with an ICT‐Based solvatochromic probe

The vapochromic properties of a fluorescent 3‐[2‐(4‐nitrophenyl) ethenyl]‐1‐(2‐ethylhexyl)‐2‐methylindole (NPEMI‐E) characterized by intramolecular charge transfer (ICT) character, dispersed in polycarbonate (PC) films is reported. NPEMI‐E solvatochromism is investigated by means of experimental and computational methods. Fluorescent PC films containing 0.1 wt % of NPEMI‐E are prepared and exposed to saturated atmospheres of different volatile organic compounds (VOCs). NPEMI‐E/PC films show remarkable and reversible vapochromism when exposed to VOCs with high polarity index and favorable interaction with PC matrix such as CHCl₃. Only minor variations in the emission wavelength are actually recorded for all other classes of VOCs investigated. The hue parameter is also used for the effective extraction of spectral information from digital color images without the need for wavelength discriminators. Overall, the present results support the use of NPEMI‐E/PC films for the cost‐effective detection of CHCl₃ vapors. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1171–1180     

Detailing Losses in the <Emphasis Type="Italic">M</Emphasis>/<Emphasis Type="Italic">M</Emphasis>/1/1 Transient Loss System

This paper is aimed at investigating the transient losses in the M/M/1/1 Erlang loss system. We evaluate the explicit form of the probability distribution of the number of losses in the time interval [0, t) and provide two alternative representations: one based on the iterated derivatives of hyperbolic sinus and cosine and the other on the spherical modified Bessel function of the second kind. The mathematical structures of the transient loss rate and of the transient probability of losing all customers are described and several analytical properties are derived.     

Electron-nucleon interaction in quasi-free scattering: (I). Non-relativistic Hamiltonian through second order

In the frame of a program aiming at examining the approximations involved in the theoretical treatment of (e, e′p) reactions, the electron-nucleon interaction producing the knock-out mechanism is considered in the non-relativistic approach of McVoy and Van Hove and compared with the relativistic one based on the one-photon-exchange Feynman graph. In this paper the non-relativistic Hamiltonian through second order in the nucleon recoil velocity is adopted; in the next paper higher order terms are included. The two approaches appear equivalent as far as the usual DWIA cross section is concerned, where a factorization occurs between the electron-nucleon cross section and the nucleon momentum distribution. However the unfactorized DWIA cross section behaves differently. This is attributed to a different off-shell behaviour of the two scattering amplitudes.     

Optimality principles and uniqueness for Bellman equations of unbounded control problems with discontinuous running cost

We study viscosity solutions of Hamilton-Jacobi equations that arise in optimal control problems with unbounded controls and discontinuous Lagrangian. In our assumptions, the comparison principle will not hold, in general. We prove optimality principles that extend the scope of the results of [23] under very general assumptions, allowing unbounded controls. In particular, our results apply to calculus of variations problems under Tonelli type coercivity conditions. Optimality principles can be applied to obtain necessary and sufficient conditions for uniqueness in boundary value problems, and to characterize minimal and maximal solutions when uniqueness fails. We give examples of applications of our results in this direction.     

Lyapunov Functions for Infinite-Dimensional Systems

We study Lyapunov functions for infinite-dimensional dynamical systems governed by general maximal monotone operators. We obtain a characterization of Lyapunov pairs by means of the associated Hamilton-Jacobi partial differential equations, whose solutions are meant in the viscosity sense, as evolved in works of Tataru and Crandall-Lions. Our approach also leads to a new sufficient condition for Lyapunov pairs, generalizing a classical result of Pazy.     

Stationary extended kinetic theory for a gas of hard spheres

Summary Analytical and numerical results for the stationary, spatially homogeneous distribution function of a gas of ?hard-sphere? particles are reported. Both removal and scattering effects are accounted for. In the case of only removal, comparison is also made with results obtained in the frame of alternative models proposed for approximating the exact ?hard-sphere? model.