Superparamagnetic nanoparticles are widely used as contrast agents for magnetic resonance imaging. We present the Proton Nuclear Magnetic Resonance Dispersion curves for colloidal suspension of iron oxide nanoparticles used as contrast agents.The systems studied are composed of iron oxide nanoparticles of two different sizes, 80–150 nm dextran coated and 300–400 nm silicon coated.Previous studies show that the longitudinal relaxation time dispersion as a function of the proton Larmor frequency is not easily obtained for the aqueous colloidal suspension of 300–400 nm diameter nanoparticles. We obtained this system longitudinal relaxation time dispersion over a broad range of magnetic fields in a viscous medium. A theoretical model that accounts for the relaxation rate of water protons under the influence of such colloidal superparamagnetic nanoparticles was fitted to the experimental data of both systems.The fit allows access to characteristic parameters of superparamagnetic nanoparticles such as the Néel relaxation time, the nanoparticle radius, particle's magnetic moment and translational correlation time, important parameters for the contrast agent efficiency.

Transparent Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics have been prepared, 32(SiO2) 9(AlO1.5) 31.5(CdF2) 18.5(PbF2) 5.5(ZnF2): 3.5(Yb-Er-TmF3) mol%, where the co-dopants partition mostly to the fluoride PbF2-based nano-crystals. A comparative study of the up-conversion luminescence in nano-glass-ceramics and its precursor glass indicates that these materials can be used as blue/green/red tuneable up-conversion phosphor, in particular for white light generation. A ratio between blue, green and red emission bands of the Tm3+ and Er3+ can be widely varied with nano-ceramming of the precursor glass and with changing a pump power of luminescence. The change in the ratio between the blue, green and red emission bands is explained to be due to substantial lowering phonon energy and shortening of inter-dopant distances with nano-ceramming of the precursor glass and due to change in the ratio of 2- and 3-photon up-conversion processes with pump power.

Most applications involving metallic nanoparticle labelling necessitate both fast imaging and local spectroscopy of individual beads. We present an imaging method based on a guided laser illumination associated to spatial modulation which allows the detection of gold particles down to 10 nm. Using an imaging spectrometer and white incoherent illumination, the same system delivers individual spectroscopy of several gold beads simultaneously, allowing a fast and selective discrimination between individual metal particles and aggregates or dust.

This paper deals with fault tolerant multiphase electrical drives. The quality of the torque of a vector-controlled Permanent Magnet (PM) Synchronous Machine supplied by a multi-leg Voltage Source Inverter (VSI) is examined in normal operation and when one or two phases are open-circuited. It is then deduced that a seven-phase machine is a good compromise allowing high torque-to-volume density and easy control with smooth torque in fault operation. Experimental results confirm the predicted characteristics.

The paper presents the possibilities to evaluate the health of an electrical machine by analyzing its electromagnetic emissions. Different piece of information can be detected according to the frequency range. First of all, a monitoring system sensitive to the degradation of the turn-to-turn insulation quality of the stator winding is presented; it is based on high frequency electromagnetic emissions. The second part of the paper is based on the medium and low frequency emission analysis. It explains how to detect turn-to-turn short circuits in stator windings or in the excitation coils of synchronous machines.

A considerable number of communities throughout the world, most of them isolated, need hybrid energy solutions either for rural electrification or for the reduction of diesel use. Despite several research projects and demonstrations which have been conducted in recent years, wind-diesel technology remains complex and much too costly. Induction generators are the most robust and common for wind energy systems but this option is a serious challenge for electrical regulation. When a wind turbine is used in an off-grid configuration, either continuously or intermittently, precise and robust regulation is difficult to attain. The voltage parameter regulation option, as was experienced at several remote sites (on islands and in the arctic for example), is a safe, reliable and relatively simple technology, but does not optimize the wave quality and creates instabilities. These difficulties are due to the fact that no theory is available to describe the system, due to the inverse nature of the problem. In order to address and solve the problem of the unstable operation of this wind turbine generator, an innovative approach is described, based on a different induction generator single phase equivalent circuit.

The increasing diffusion of power electronics in the electrical equipment induces harmonic perturbations which reduce the power quality of power systems. Moreover, the induction machine is widespread in the industrial applications and it is often supplied by speed drives which generate non sinusoidal voltages. In this context, this study deals with the frequential modelling of the induction machine in order to simulate the line current with its harmonic components. Some of the frequential models existing in the literature are presented and compared. Then a circuit model of the machine based on the superposition principle, an harmonic model, is proposed. The comparison of the simulation results with the experimental measurements allows electing the harmonic model associated to the identification test using a DC current as the most representative of the machine behaviour.

Efficient numerical models have been already developedin 2D to take into account the movement of electromagnetic deviceswith rotating parts in the framework of the Finite Element Method(FEM). When the movement becomes complex it leads to large meshdistortions. A remeshing step is then required which increases thecomputational complexity and can also lead, in some cases, tonumerical ripples on forces and torques due to the fieldprojections between old and new meshes. Moreover, remeshingprocedures in 3D remain an open topic. Meshless methods seem anappealing choice for alleviating the mesh constraints. The NaturalElement Method (NEM) which, has known a growing interest in thedomain of mechanics, allows to proceed in the meshless framework,avoiding one of the main drawbacks related to the vast majority ofmeshless techniques, as is the imposition of essential boundaryconditions. In this paper, a variant of the NEM, known asconstrained natural element method (C-NEM) is applied forsimulating electromagnetic machines involving rotating parts. Anew mixed strategy combining the finite element and theconstrained natural element methods is proposed and then tested byusing an appropriate error estimator.

Investigations on ion transport mechanism in the new Ag+ ion conducting quaternary solid electrolyte systems: (1 − x)[0.75AgI: 0.25AgCl]: xKI, where 0 < x < 1 in mol. wt.%, are reported. The quaternary systems were prepared by solid solution reaction of an alternate host: `a quenched [0.75AgI: 0.25AgCl] mixed system/solid solution', instead of the traditional host salt AgI, and KI. The compositional dependent conductivity studies on the quaternary systems identified the composition: 0.7[0.75AgI: 0.25AgCl]: 0.3KI, as the Optimum Conducting Composition (OCC) having conductivity σ ~ 5.9 × 10−3 S cm−1 at 27 °C. For direct comparison of the room temperature conductivity behaviour of the quaternary OCC, AgI-based ternary solid solution composition: 0.8AgI: 0.2KI, resulting into the well-known superionic system: KAg4I5, has also been synthesized in the identical manner which exhibited σ ~ 1.12 × 10−2 S cm−1 at 27 °C. The conductivity of newly synthesized quaternary OCC was slightly lower than that of as prepared ternary KAg4I5. However, in the open ambient conditions $\sigma $ of OCC sample remained practically stable for over hundred hours while that of KAg4I5 decreased by more than two orders of magnitude in the same duration. The phase identification and material characterization studies on the quaternary OCC have been carried out using XRD and DTA techniques. The ion transport mechanism has been characterized on the basis of experimental studies on some basic ionic parameters viz. conductivity ( $\sigma $ ), ionic mobility ( $\mu $ ), mobile ion concentration (n), ionic transference number (t ion ) and ionic drift velocity (v d ). Solid state batteries have been fabricated using the newly synthesized quaternary OCC as well as KAg4I5 as electrolytes, sandwiched between Ag/I2 electrode couple and the cell potential discharge performances have been studied under varying load conditions.

This paper deals with reliability of motor drive systems. It focuses on the switching power converter which is the weakest drive part. It investigates a new architecture which provides intrinsic redundancy. The method used in this fault switch detection and diagnosis is based on a sliding mode observer. The original aspect of this new approach is that the observer influences the control algorithm in order to rule out or accept the possibility of the device failure. This leads to the right decision which induces the rebuilding of the converter topology. This fault tolerant control strategy assures continuous operation even though one switch failure occurs.

To insure interoperability of transeuropean trains, new transmission systems (GSMR, Eurobalise) are developed in order to permit communications between trains and control centres. These systems have to be available and safe from an electromagnetic point of view, but the normalized methods to characterize electromagnetic noise in the railway environment are not convenient for these applications. This paper presents new experimental methods to characterize the electromagnetic noise on board trains which are studied in the framework of the European project “Railcom”. The results of measurements realized both in time and in frequency domains, are analysed and certain conclusions can be used as a first step to define a new standard for the considered systems.

A study on the characterization of small cracks by using eddy current testing (ECT) signal is presented. The significant parameters of the ECT data are selected using principal component analysis according to two approaches. The ECT signal inversion is then achieved using a parametric model trained with synthetic data obtained with a fast numerical simulation tool. The characterization procedure is then tested using experimental data. Results show that information can be obtained concerning the area of the cracks.

Primary power standards in the microwave domain are realized using a calorimetric technique, usually identified with the used measurement system, i.e., the microcalorimeter. It is adjusted for measurement of power ratios with a relative accuracy that, after an appropriate system calibration, is of order of 10−3, at least in the microwave domain (1 GHz–18 GHz). Hereby we describe the calibration process implemented at the Istituto Nazionale di Ricerca Metrologica (Italy) for realizing a coaxial power standard based on indirect heating thermocouples. Particular regard is devoted to describe the nearly ideal thermal load used for determining the microcalorimeter losses and their influence on the measurand accuracy.

The aim of this paper is to present a method of detection and isolation of intermittent misfiring in power switches of a three phase inverter feeding an induction machine drive. The detection and diagnosis procedure is based solely on the output currents of the inverter flowing into the machine windings. The measured currents aretransformed in the two dimensional frame obtained with the Concordia transform. The data are then treated by a time-average method. The results even promising lack of accuracy mainly in the fault isolation step. To enhance the fault detection and diagnosis by the use of the information enclosed in the data, a Principal Component Analysis classifier is applied. The detection of a fault occurrence is made by a two-class classifier. The isolation is a two-step approach which uses the Linear Discriminant Analysis; the first is to identify the faulty leg with a three-class classifier and the second one discriminates the faulty power switch. Both methods are evaluated with experimental data and pattern recognition method proves its effectiveness and accuracy in the faulty leg detection and isolation.

The rapid expansion of supercritical solution (RESS) is a promising process for the production of small particles with a narrow size distribution. It involves an expansion of a supercritical solution through a small nozzle to generate a rapid nucleation and then the formation of ultrafine particles. The particles are transported by a powerful jet developed in the expansion chamber. The particle size distribution (PSD) of the obtained fine powders depends on the hydrodynamic conditions in the pre- and post-expansion unit, the nature of solute-solvent system, as well as on the nozzle geometry, and diameter. In this work, we have developed a numerical simulation of both transport and Brownian coagulation of spherical particles in the expansion chamber by resolving the general dynamic equation (GDE). This simulation has permitted to control the temporal evolution of PSD characterizing each class of particles. These PSD field evolutions show that the particles of each class get round the Mach disk taking refuge on the jet boundaries where the Brownian coagulation is more pronounced. Therefore, these particles whose size depends on thermodynamic and geometrical conditions are deposited on the flat plate as a ring. We notice that the narrowest distribution function of the deposited particles on the flat plate is obtained for the largest nozzle orifice diameters and the lowest expansion pressure.

We report on the production of composite semiconductor CdZnS nanoparticles by adopting an inverse micellar route, using bis (2-ethylhexyl) sulfosuccinate (aerosol-AOT) as surfactant and with a degree of hydration w 0 = [ H2O]: [AOT] = 8.9. Prior to bioconjugation (conjugation with bovine serum albumin (BSA)), the hydrophobic surface of the nanocrystals were made hydrophilic with thiol treatment (reacting with mercapto acetic acid). We compare photophysical nature of as prepared, thio-stabilized and bioconjugated CdZnS nanoparticles using absorption/emission spectroscopy and ultrafast photoluminescence decay measurements. The change-over from nonzero anisotropy (untreated) to zero anisotropy (bioconjugated) is assigned to the depolarized emission due to the surface reconstruction owing to BSA adsorption into the surface vacancies. Exploration of the dynamics of photophysical features would be promising for biomolecular sensing, labeling, and imaging applications.