Common- and differential-mode HF current components in AC motors supplied by voltage source inverters

In this paper, an inverter-fed ac motor drive is analyzed in order to investigate the conducted electromagnetic interferences at both the input and output sides of the inverter. HF lumped equivalent circuits for the inverter and the motor stator windings are proposed. The overall circuit model allows time- and frequency-domain analysis to be performed with standard circuit simulators. The proposed model can also predict common- and differential-mode HF current components. The equivalent circuit is verified by experimental tests carried out on a prototype of ac motor drive.     

H,C, Pt NMR study on platinum(II) interaction with sulphur containing Amadori compounds

The NMR study on the interaction of Pt(II) with Amadori compounds is performed. The Amadori compounds are derived from the reaction of β-d-glucose with l-cystine leading to N,N′-di-(1-deoxy-β-fructos-1-yl)-l-cystine [FruCyscys], and with l-methionine leading to N-(1-deoxy-β-fructos-1-yl)-l-methionine [FruMet].     

Physico-chemical behaviour of sulpha drugs: VI. Electrochemical behaviour and electronic structure of sulphonamide derivatives

The electrochemical reduction of ØSO₂NH₂ and its ortho, para and meta amino derivatives was examined in aprotic medium (CH₃CN) with varying experimental conditions, i.e. drop time, concentration and temperature. It has been shown that the reduction process is irreversible and controlled by diffusion at small values of concentration and low drop times, while the whole process is controlled by an adsorption step at larger values of concentration and drop times. The reduction mechanism, proposed by Horner for sulphonamides of the type XØSO₂NR₁R₂, was confirmed and shown always to involve the S-N bond cleavage. Half-wave potentials and electrokinetic parameters were correlated with some theoretical and experimental structural indexes. Even if the correlation is fairly good and confirms the validity of the theoretical model assumed, it does not enable the pharmacological behaviour of the three isomers to be differentiated.     

Mercury(II) dibromo-bis-(3-amino-5-mercapto-1,2,4-triazole): synthesis,crystal structure,and infrared characterization

The title compound C₄H₈N₈S₂HgBr₂ was prepared and characterized by means of X-ray crystallography, and i.r. measurements. The crystals are orthorhombic, space group Pbcn (no. 60) witha=9.707(2),b=8.609(1),c=16.128(2) Å, andZ=4. The compound exhibits discrete monometallic units with the 1,2,4-triazole molecule acting as a monodentate ligand. The structure consists of units in which the mercury atom is coordinated in a distorted tetrahedral geometry by two sulfur and two bromine atoms. The NH and NH₂ group of the 3-amino-5-mercapto-1,2,4-triazole unit are involved in intermolecular hydrogen bonds. Infrared bands are diagnostic of the coordination environment around the metal atoms.     

Preferential protonation and methylation at the nitrogen atoms of N,N-dimethylamino derivatives of pyridine

The relative reactivity toward protonation and methylation of the two nitrogen atoms in N,N-dimethylaminopyridines has been examined by ¹H NMR. The ring position of the dimethylamino group has no influence on protonation, which occurs in all the derivatives at the heterocyclic nitrogen. The N-methylation reaction does not follow a homogeneous behaviour, occurring at the exocyclic nitrogen in the 2-substituted dimethylamino derivative. The electronic characteristics of the molecules, determined by MO calculations at a semi-empirical level, indicate that both protonation and methylation should occur at the heterocyclic nitrogen; the calculated relative stabilites, however, of the N-protonated and N-methylated forms are in full agreement with the experimental results, and it appears that the anomalous behaviour of 2-dimethylaminopyridine in the N-methylation reaction is caused by steric factors.     

Western European Broadcasting in Transition

The demands for public participation and decentralization of broadcasting structures are two forces which contribute to the changes in media organization and control.     

A phase field approach to solidification and solute separation in water solutions

We propose a phase field model for the solid–liquid phase transition in a water-salt (sodium chloride) solution in the absence of macroscopic motion, under possibly non-isothermal conditions. A thermodynamic approach based on a free energy functional is assumed. The model consists of three evolution equations: a time-dependent Ginzburg–Landau equation for the solid–liquid phase change, a diffusion equation of the Cahn–Hilliard kind for the solute dynamics and the heat equation for the temperature change. The proposed system is aimed to contribute to the modelling of the brine channels formation in the ice of the polar seas.     

Structural investigation of an amorphous Si24Nb76 alloy produced by mechanical alloying using reverse Monte Carlo simulations

The atomic structure of an amorphous Si₂₄Nb₇₆ alloy produced by mechanical alloying was investigated by using one X-ray total structure factor S(K) as input data for reverse Monte Carlo (RMC) simulations. The partial S_Si–Si(K), S_Si–Nb(K), S_Nb–Nb(K) structure factors and G_Si–Si(r), G_Si–Nb(r), G_Nb–Nb(r) pair probability functions were obtained from the RMC simulations. The structural parameters (interatomic distances and co-ordination numbers) for the first neighbors were extracted and compared with those found in the Nb₃Si compound. It was observed some resemblance between these phases.     

A thermodynamic approach to isotropic-nematic phase transitions in liquid crystals

We propose a dynamical model for (non-isothermal) phase transitions in liquid crystals. Macroscopic motions of the liquid crystal (LC) are neglected, while the coupling with the electromagnetic field is considered. The LC is described in terms of the classical order tensor Q, which is split as Q=s N, where N is a normalized tensor; two independent evolution laws are given for s and N. The model includes an evolutive equation for the temperature field obtained from an appropriate form of the energy balance, in which the internal powers associated to the equations for s and N are accounted for. The thermodynamic restrictions in the constitutive relations which ensure the Clausius–Duhem inequality have been pointed out.