We present results on the room temperature mechanical quality factor of single crystal calcium fluoride (CaF2) grown by the Bridgman-Stockbarger method. Resonant mode Q-factors are measured in the frequency range 20 to 76 kHz using tungsten wire loop suspensions. In spite of indications of only moderate crystal purity, we observed 6 modes with Q-factor > 107, and one with $Q = 4.5 \times 10 ^{7}$, more than an order of magnitude higher than previously reported results.

The influence of pressure and temperature on continuum emission efficacy in a high pressure argon-mercury plasma for lighting applications are investigated. Extreme high temperature (EHT) lamps are introduced.

Nanowires of antimony (Sb) with diameters ranging from 90 down to 20 nm have been synthesized by electrodeposition within nanoporous polycarbonate membrane. The salient point of the present work is the detailed examination of each wire individually giving evidence of their good quality. The growth morphology, crystalline quality as well as chemical composition of individual nanowires were carried out by combination of various transmission electron microscopy (TEM) techniques. They are single crystals and have homogeneous cylindrical shape. However, a distribution of wire diameters and a roughness of few nanometers on the wire surface have been observed. Chemical analyses using electron energy loss spectroscopy (EELS) confirmed the purity of electrodeposited Sb nanowires, but revealed the existence of an oxidized layer (≤2 nm in width) surrounding the wires.

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.

This article reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With a reactant gas mixture of 530 ppm NO, 650 ppm C2H4, 5.8% O2 in N2, GHSV = 12 000 h-1 and input discharge energy density of 155 J L-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma-catalytic (in the POC reactor) NOx conversion percentages are 39%, 1.5% and 79%, respectively. A moderate plasma enhancement of NOx reduction by C2H4 was also observed in a two-stage plasma-followed-by-catalyst (PFC) reactor consisting of a discharge stage filled by fused silica pellets and a Cu-ZSM-5 catalyst stage.

The physical interactions of a growing tumor mass with the host tissue (boundary conditions) play an important role in the dynamics of the tumor and their comprehension is essential for designing new therapeutic tools and methods against cancer. Starting from experiments and biological information, we focus here on the analysis of the effects of the coupling between the host's mechanical properties and some relevant cellular processes involved in the growth of multicellular tumor spheroids. The physical-mathematical model proposed here to describe such a coupling and the respective numerical simulations, after validation through a quantitative comparison with experimental data, will be applied to support biological hypotheses previously formulated and to propose new themes of investigation.

The impedance of a positive column has been calculated at medium pressures i.e. at the regime of step ionization-ambipolar diffusion. Calculations were carried out for two cases: (a) metastable level decay by electron impact; (b) metastable level decay on the walls as a result of diffusion. In both cases the impedance has generally an inductive character. In the case of metastable level decay by electron impact, the impedance curve starts from the coordinate origin at $\omega =0 $. At low frequencies the PC has a negatron property, while the static volt-ampere characteristics of the stationary PC becomes parallel to the current axis. The module |Z| reaches its maximum value at frequencies of about the order of $\sqrt{ \tau_a^{-1}\alpha _{m}n_{0}}$. At very high frequencies $\omega \longrightarrow \infty $, the impedance reaches the real value of $Z=R_{0}$. In the case when metastable levels decay as a result of diffusion, the impedance curve starts from the negative real values at $\omega=0$. The volt-ampere characteristics of the stationary PC drops. The module |Z| reaches its maximum value at frequencies of about the order of $\sqrt{\tau_a^{-1} \tau^{-1}_{m}}$. At very high frequencies $\omega \longrightarrow \infty $, the impedance reaches the real value of $Z=R_{0}$. In both cases, impedance curves have single structured shapes in spite of existence of several characteristic time scales of different order.

The aim of this paper is to give a solution to unbalance problem of the input DC voltages of the five-level NPC-VSI used in high voltage and great power applications. For that, a Five-level PWM current rectifier – Five-level NPC VSI – PMSM cascade is presented. In the first part, we develop a knowledge model of the five-level NPC VSI and propose a space vector modulation of this converter using four bipolar carriers. The characteristics of this strategy are studied and the performances of the drive of the PMSM fed by this inverter are presented too. In the first case the input DC voltages of the multilevel inverter are supposed constant and equals. After that, we propose to study a new high voltage cascade five-level PWM current rectifier – Five-level NPC VSI – PMSM. This study shows particularly the problem of the stability of the DC voltages of the inverter and its consequence on the performances of the PMSM speed control. Then, we propose a solution to the problem by employed closed loop regulation using sliding mode. We add a Clamping bridge to stabilise the four DC input voltages of the Five-level NPC VSI. This cascade found applications in great power and high voltage fields as electrical traction.

At National Metrology Institute of Turkey (UME, Ulusal Metroloji Enstitüsü), luminous intensity unit of candela was realized using detector-based approach and photometric scale was re-established depending on this new realization. Candela was measured on photometric bench using interferometric distance measurement system and filter-radiometer traceable to UME primary level electrical-substitution cryogenic radiometer. Thermally stabilized filter radiometer, which has been designed for spectral irradiance measurements, is consists of trap detector, filter housing and precision aperture. Different measurement techniques were used to fully characterize each parameter of filter-radiometer; like effective aperture area, spectral transmittance of $V(\lambda)$ filter and responsivity of trap detector.

The final properties of cast materials depend greatly on the solidification process undergone by the material. In this paper, we study gold alloys dedicated to the watch industry and jewellery in the framework of a research collaboration with the Metalor Company. The aim is to improve the concentration homogeneity of the ingots by controlling the solidification step. It can be achieved by reducing segregations by a decrease in the grain size. For this purpose, we set up a multiphase electromagnetic stirring of the melt to favour the growth of finer grains and improve the homogeneity of the composition. We first design an electromagnetic stirrer by numerical simulation. The stirrer is then implemented on a model experiment. Eventually, the alloys are characterised by metallography and etching to evidence the grain structure. As expected, we obtain a substantial reduction of the grain size although, some work remains to be done to attain the final goal of even finer grains.