117,465 research outputs found
Alle origini dell'immaginario spaziale di Soleri: la fabbrica Solimene a Vietri sul mare
No full textGenesi e significato di uno degli edifici industriali più originali del dopoguerra italiano: la fabbrica di ceramiche Solimene a Vietri di Paolo Soler
Il coordinamento nei sistemi aziendali complessi. Finalità e strumenti
No full textNelle aziende moderne, le informazioni, le competenze, l'esperienza e le capacità creative indispensabili per la gestione e il governo aziendale non sono, per norma, detenute esclusivamente dagli organi costituenti il vertice aziendale, ma sono ampiamente diffuse nell'ambito dell'organizzazione. Vari fenomeni, operando a sistema, sviluppano nell'azienda una tensione potenziale verso l'"entropia positiva", verso il disordine, la disgregazione delle strutture, la perdita di coordinamento. Creatività e innovazione tendono a spegnersi e l'adattabilità all'ambiente diventa carente. Naturalmente l'entropia positiva aumenta in intensità a mano a mano che l'ambiente diventa più complesso. La tendenza all'entropia positiva è fronteggiata dal management con processi che hanno l'effetto di rivitalizzare la struttura organizzativa e di coordinare ed armonizzare la condotta dei vari centri aziendali. In particolare, nella quarta parte l'analisi è rivolta ad individuare come la leadership possa influenzare il comportamento aziendale e creare condizioni per sviluppare la creatività, la fantasia e l'energia degli uomini che compongono il sistema aziendale
Identification of DC thermal steady-state differential inductance of ferrite power inductors
No full textIn this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC–DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC–DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the magnetization curve up to the saturation. The obtained inductance profile can be adopted to simulate the current waveform of a saturable inductor in a DC–DC converter, providing accurate results under a wide range of switching frequency, input voltage, duty cycle, and out-put current values
The role of materials in the optimal design of magnetic components for DC–DC converters
No full textThis paper analyses the design of the output inductor of a DC–DC converter, comparing the performances achieved by three different core materials to reach the best trade-off between the total losses and the size of the magnetic component. The N87 ferrite, the Xflux60 silicon iron powder, and the Metglas 2605 SA-1 iron-based amorphous are considered in the present analysis. An equivalent non-linear reluctance model is adopted to compute the differential inductance profile of each design configuration. The total losses are estimated with analytical computations. Several considerations are presented in comparing the different core materials, and the optimum design criteria in different configurations are investigated
Saturable Ferrite Inductor Parameters Obtained through a Double Step Optimization
No full textThis paper deals with the modelling of ferrite inductors considering weak saturation operating conditions. The proposed methodology is based on a parametric representation of the magnetic characteristic of the inductor that is optimized through a double-step identification/optimization algorithm. The obtained magnetic characteristic is applied in a simulator to compute the inductor current. To demonstrate the effectiveness of this approach the inductor is tested in a DC-DC buck power converter. Two experimental cases are presented: the former regarding a low voltage, low current, MOSFETs buck converter; the second case regarding a 110W GaN-based buck converter up to 1MHz
Identification of material properties and optimal design of magnetically shielded rooms
No full textIn this paper, we propose an optimal design procedure for magnetically shielded rooms. Focusing on multi-layer ferromagnetic structures, where inner layers operate at very low magnetic field, we propose an identification method of the magnetic material characteristic in the Rayleigh region. A numerical model to simulate the shielding efficiency of a multi-layer ferromagnetic structure is presented and experimentally tested on different geometries and layer configurations. The fixed point iterative method is adopted to handle the nonlinearity of the magnetic material. In conclusion, the optimization of the design parameters of a MSR is discussed, using the Vector Immune System algorithm to minimize the magnetic field inside the room and the cost of the structure. The results highlight that a linear magnetic characteristic for the material is sufficient to identify the suitable geometry of the shield, but the nonlinear model in the Rayleigh region is of fundamental importance to determine a realistic shielding factor
X-ray imaging of horizontal jets in gas fluidised bed nozzles
No full textThe design of the fluidising air distributors, or nozzles, is one of the most important aspects influencing operation of fluidised beds at industrial scale. In this work, the study of the hydrodynamics in gas-solid fluidized beds where the primary gas injection is achieved through a nozzle-type gas distributor has been carried out, using an innovative X-ray imaging technique. Qualitative and quantitative results are reported, with particular focus on jets penetration length and their evolution. Results show that the lighter and the finer are the particles, the larger is the jet penetration. Since the experimental data do not match predictions available in literature, a new non-dimensional correlation based on hydrodynamic scaling and Froude number is also proposed. The new correlation takes into account the effects of jet velocity, particle density and particle size. A tentative mechanistic explanation for the departure from purely hydrodynamic scaling is offered
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