Finite-difference and finite-volume methods for nonlinear standing ultrasonic waves in fluid media

In the framework of the application of high-power ultrasonics in industrial processing in fluid media, the mathematical prediction of the acoustical parameters inside resonators should improve the development of practical systems. This can be achieved by the use of numerical tools able to treat the nonlinear acoustics involved in these phenomena. In particular, effects like nonlinear distortion and nonlinear attenuation are fundamental in applications. In this paper, three one-dimensional numerical models in the time domain for calculating the nonlinear acoustic field inside a one-dimensional resonant cavity are presented and compared. They are based on the finite-difference and the finite-volume methods. These different algorithms solve the differential equations, from the linear up to the strongly nonlinear case (including weak shock). Some physical results obtained from the modelling of ultrasonic waves and a comparison of the efficiency of the different algorithms are presented.     

Analysis of plume deflection in the silicon laser ablation process

Changes in target surface morphology and ablation plume direction have been experimentally observed during the initial stages of the silicon laser ablation process. A relationship between both phenomena can be observed upon analysing the temperature field induced by the laser beam in a rough surface material. Theoretical studies on the deflection of the ablation plume are presented. These analyses are based on the hypothesis that particles that reach evaporation temperature will exit normally to the target surface with a velocity that is proportional to the surface temperature and the amount of the ablated material. Numerical solutions and experimental results of laser ablation process of silicon targets are found to agree with theoretical studies. PACS 42.25.Lc; 79.20.Dc; 02.70.Dc     

Analysis of excimer laser annealing of amorphous SiGe on La2O3//Si structures

The reduction of complementary metal oxide semiconductor dimensions through transistor scaling is in part limited by the SiO₂ dielectric layer thickness. Among the materials evaluated as alternative gate dielectrics one of the leading candidate is La₂O₃ due to its high permittivity and thermodynamic stability. However, during device processing, thermal annealing can promote deleterious interactions between the silicon substrate and the high-k dielectric degrading the desired oxide insulating properties.The possibility to grow poly-SiGe on top of La₂O₃//Si by laser assisted techniques therefore seems to be very attractive. Low thermal budget techniques such as pulsed laser deposition and crystallization can be a good choice to reduce possible interface modifications due to their localized and limited thermal effect.In this work the laser annealing by ArF excimer laser irradiation of amorphous SiGe grown on La₂O₃//Si has been analysed theoretically by a numerical model based on the heat conduction differential equation with the aim to control possible modifications at the La₂O₃//Si interface. Simulations have been carried out using different laser energy densities (0.26-0.58 J/cm²), different La₂O₃ film thickness (5-20 nm) and a 50 nm, 30 nm thick amorphous SiGe layer. The temperature distributions have been studied in both the two films and substrate, the melting depth and interfaces temperature have been evaluated. The fluences ranges for which the interfaces start to melt have been calculated for the different configurations.Thermal profiles and interfaces melting point have shown to be sensitive to the thickness of the La₂O₃ film, the thicker the film the lower the temperature at Si interface.Good agreement between theoretical and preliminary experimental data has been found.According to our results the oxide degradation is not expected during the laser crystallization of amorphous Si_0.7Ge_0.3 for the examined ranges of film thickness and fluences.     

Nouveau dosage volumétrique du cuivre au moyen du dichromate

A method for the determination of copper by cuprous thiocyanate is described. This is effected by reacting with ferric sulphate: 3CuCNS +2Fe(S0₄)₃→Fe(CNS)₃ + 3FeSO₄ + 3CuSO₄The determination of Fe′ with dichromate in presence of thiocyanate by means of mercuric sulphate or nitrate was first investigated, and when this had been established, the Fe′ produced according to the above reaction (and which is stoichiometrically equivalent to the amount of copper present), was determined. Very satisfactory results were obtained.     

Geometric interpolation in symmetrically-normed ideals

The aim of this work is to apply the complex interpolation method to norms of n-tuples of operators in a symmetrically-normed ideal J_?⊆B(H) defined by a ? symmetric norming function (s.n.f.). The norms considered define Finsler metrics in a certain manifold of positive operators, and can be regarded as weighted ?-norms, the weight being a positive invertible operator.     

Analysis of the magnetoresistance contributions in a nanocrystallized Cr-doped FINEMET alloy

The magnetoresistance (MR) was measured at 200, 250 and 300 K in magnetic fields up to B=12 T for a nanocrystallized Fe_63.5Cr₁₀Nb₃Cu₁Si_13.5B₉ alloy. Both the longitudinal (LMR) and transverse (TMR) component of the magnetoresistance decreased from B=0 to about 0.1 T. This could be ascribed to a giant MR (GMR) effect due to spin-dependent scattering of conduction electrons along their path between two Fe-Si nanograins via the non-magnetic matrix. Such a scattering may occur if the nanograin moments are not or only weakly coupled in the absence of a strong exchange coupling (due to the high Cr content in the matrix) and/or only weak dipole-dipole coupling is present (due to sufficiently large separations between the nanograins). For larger fields, the GMR saturated and a slightly nonlinear increase in MR with B was observed due to a contribution by the residual amorphous matrix. The anisotropic MR effect (AMR≡LMR−TMR) was negative for all fields and temperatures investigated. By measuring the MR of melt-quenched Fe_100−xSi_x solid solutions with x=15, 18, 20, 25 and 28, the observed AMR could be identified as originating from the Fe-Si nanograins having a D0₃ structure.     

A MIP formulation for the minmax regret total completion time in scheduling with unrelated parallel machines

The paper proposes a Mixed Integer Programming (MIP) formulation of the scheduling problem with total flow criterion on a set of parallel unrelated machines under an uncertainty context about the processing times. To model the problem we assume that lower and upper bounds are known for each processing time. In this context we consider an optimal minmax regret schedule as a suitable approximation to the optimal schedule under an arbitrary choice of the possible processing times.     

Normal operators and inequalities in norm ideals

In this work we characterize normal invertible operators via inequalities with unitarily invariant norm of elementary operators.