A new and simple process for the selective emitter realization was developed on multicrystalline silicon wafers. This material is in competition with single-crystal silicon since it is able to lead to similar performances with a reduction in the cost of solar cell realization.This work is centred on the study of emitter area of a photovoltaic cell and the possibilities to obtain a selective emitter in only one step while avoiding the use of chemicals.This would make substantial economies on the rejections treatment which became a capital environmental factor. A structure with selective emitter consists of a heavy doping under the metallic contacts, leaving weak the surface concentration between the grid lines.This allows a good surface passivation while keeping a good contact resistance for screen printed lines.The advantages of such a structure could be observed by quantum efficiency measurements yield where the benefit appears in the UV-VIS range of the solar spectrum.

This paper presents and discusses some numerical approaches for the simulation of induction machine behaviour under no-load conditions. All the approaches are based on the finite element solution of the electromagnetic field problem, including physical models of magnetic material and interaction with external circuits. The computed flux distributions enable the prediction of magnetic and additional losses, whose accuracy is discussed also in the light of the complexity of the used numerical technique.

In this paper, the Finite Integration Technique and an approach to solve simultaneously the magnetic and electric circuit equations is presented in magnetostatic case. The developments of the FIT will be compared with those used for the Finite Element Method. As example of application an iron core coil is studied and the results of both approaches are compared.

We have investigated the influence of the steric properties of conducting particles in a nonconducting host matrix on the conductivity threshold of the material, i.e., the minimum volume fraction of conducting phase for the whole sample to become conducting. A statistical, numerical method is used in which the particles are randomly put, one by one, into the nonconducting host and the conducting path is searched. The particles are allowed to penetrate each other to some extent. Three different types of particle shapes are considered: spherical, cylindrical with rounded ends and asymmetric cuboids with rounded surfaces. We have found that in addition to the anisotropy in the particles' dimensions, the angular distribution of the particles' long axes plays a dominant role in the calculations of the conductivity percolation threshold.

Fe $_{1-x}$ Crx thin films on Si and fused-SiO2 substrates were prepared using ion-beam sputtering deposition. Films with x = 0.69 and x = 0.49 were characterised by X-ray diffraction and conversion electron Mössbauer spectroscopy experiments, and concurrently the elastic and plastic behaviours were investigated through indentation tests. For x = 0.69, the paramagnetic bcc structure is observed, while the indentation modulus and hardness values are found to be 160 and 8.7 GPa, respectively. For x = 0.49, a strongly $\langle 200\rangle$ -textured paramagnetic phase is evidenced, having the A15 structure. Mössbauer measurements also allowed the site occupancy to be determined. The structural change from bcc to A15 phase yields a 50% increase in hardness, while the indentation modulus remains unchanged. This particular behaviour is discussed in terms of distances between near neighbours and Burgers vector length in both bcc and A15 structures. The results obtained here provide motivation to pursue the present study through wear experiments.

Cathode-directed sparks engrave in a specially prepared, originally low-conducting nonlinear silver-based material beyond a critical electric power input highly structured discharge patterns which exhibit an anomalous potential distribution consisting of an electrical double layer in series with a region of high electrical conductivity.

In this paper the measurements of the dynamic breakdownvoltages U b for linearly rising pulses in nitrogen at lowpressure are presented. The measurements were carried out for therates of voltage rise k up to $300\, {\rm V\,s}^{-1}$ . Dependence of thebreakdown voltages, delay times and electron yields on the rate ofrise were obtained experimentally and theoretically under different conditions. It was found thatthe overvoltage $\overline {\Delta U_b}$ and the mean effectiveelectron yield $\overline {YP}$ is proportional to $\sqrt k$ (Yis a number of generated electrons in the interelectrode space persecond and P the breakdown probability), while the statisticaltime delay $\overline t_s$ is proportional to $1/\sqrt k$ . In thesecond part, the experimental breakdown voltage distributions wereobtained, fitted by theoretical distributions and some breakdownparameters relevant to experimental conditions were determined.Based on the approximate analytical and numerical models, thedependence of the effective secondary electron yield γ onthe overvoltage and on the rate of voltage rise were derived fromthese measurements. It was found that γ varies linearlywith the overvoltage for a constant k, and the slope of γis proportional to  $\sqrt k$ .

In power electronics, magnetic components, such as inductors or transformers, are one of the main device which raise problems. Reliability for a large proportion depends on thermal stresses which are not easy to model nowadays. Moreover, both electrical and magnetic characteristics of magnetic components strongly depend on the temperature. In this case, it is very important to determine operating temperatures of such devices, in order to model correctly the magnetic components.This paper describes a thermal measurement equipment suitable for thermal characterization of magnetic components used in power electronics. Such equipment is essential for developing thermal models. The final aim is to define easy to use thermal models which are able to provide magnetic component operating temperatures for both transient and steady state conditions versus copper and core losses.The described thermal equipment in this paper is a powerful and original tool for magnetic component thermal characterization, because without any device modification, this equipment is able to measure operating magnetic component temperatures in both static and dynamic modes of testing. Temperatures are measured with an accuracy of 2 °C or better. Such accuracy is sufficient for determining steady-state thermal resistance with few temperature points.

The physical interactions of a growing tumor mass with the host tissue (boundaryconditions) play an important role in the dynamics of the tumor andtheir comprehension is essential for designing new therapeutic tools andmethods against cancer. Starting from experiments and biologicalinformation, we focus here on the analysis of the effects of the couplingbetween the host's mechanical properties and some relevant cellular processesinvolved in the growth of multicellular tumor spheroids. The physical-mathematical modelproposed here to describe such a coupling and the respective numerical simulations, after validation through a quantitative comparison withexperimental data, will be applied to support biological hypothesespreviously formulated and to propose new themes of investigation.