Quantum Treatment for Bose-Einstein Condensation in Non-Equilibrium Systems

We develop an approach based on stochastic quantum trajectories for an incoherently pumped system of interacting bosons relaxing their energy in a thermal reservoir. Our approach enables the study of the versatile coherence properties of the system. We apply the model to exciton polaritons in a semiconductor microcavity. Our results demonstrate the onset of macroscopic occupation in the lowest-energy mode accompanied by the establishment of both temporal and spatial coherence. We show that temporal coherence exhibits a transition from a thermal to coherent statistics and the spatial coherence reveals off-diagonal long-range order.Comment: 5 Pages, 3 figure

Studi sull\u2019accuratezza numerica di un solutore meshfree per l\u2019approssimazione di campi

L\u2019attivit\ue0 di ricerca \ue8 stata finalizzata allo studio di metodologie numeriche avanzate senza reticolazioni per l\u2019approssimazione di funzioni e sue derivate. In particolare si sono condotti studi sull\u2019accuratezza e convergenza del metodo Smoothed Particle Hydrodynamics riferendosi a campionamenti regolari e no

An Improved Solver for the M/EEG Forward Problem

Noninvasive investigation of the brain activity via electroencephalography (EEG) and magnetoencephalography (MEG) involves a typical inverse problem whose solution process requires an accurate and fast forward solver. We propose the Method of Fundamental Solutions (MFS) as a truly meshfree alternative to the Boundary Element Method (BEM) for solving the M/EEG forward problem. The solution of the forward problem is obtained, via the Method of Particular Solutions (MPS), by numerically solving a set of coupled boundary value problems for the 3D Laplace equation. Numerical accuracy and computational load are investigated for spherical geometries and comparisons with a state-of-the-art BEM solver shows that the proposed method is competitive

ODEF: an interactive tool for optimized design of EMI filters

The impact of EMI filters on volume and weight of power converters is significant. For this reason, filter’s size optimization is a strategic step towards the improvement of the power converter’s power density. An EMI filter design that follows a conventional procedure does not guarantee the selection of components/configuration leading to the best power density. Therefore, in order to help EMI engineers and scientists in pursuing a fast and effective choice of optimal discrete EMI filter components and configuration, a novel tool is proposed in this paper, namely ODEF (Optimized Design of EMI Filters). ODEF is an interactive software application running in Matlab® environment. It suitably improves a previously validated EMI filter design procedure that extends the conventional filter design method in order to achieve optimal power density. Features and operation of ODEF tool are illustrated. Moreover, the experimental assessment of an input EMI filter, designed according to the optimized procedure for an inverter-fed induction motor drive, is performed

Diffusion-controlled anisotropic growth of stable and metastable crystal polymorphs in the phase-field crystal model

The official published version of the article can be accessed from the link below - Copyright @ 2009 APSWe use a simple density functional approach on a diffusional time scale, to address freezing to the body-centered cubic (bcc), hexagonal close-packed (hcp), and face-centered cubic (fcc) structures. We observe faceted equilibrium shapes and diffusion-controlled layerwise crystal growth consistent with two-dimensional nucleation. The predicted growth anisotropies are discussed in relation with results from experiment and atomistic simulations. We also demonstrate that varying the lattice constant of a simple cubic substrate, one can tune the epitaxially growing body-centered tetragonal structure between bcc and fcc, and observe a Mullins-Sekerka-Asaro-Tiller-Grinfeld-type instability.This work has been supported by the EU FP7 Collaborative Project ENSEMBLE under Grant Agreement NMP4-SL-2008-213669, the Hungarian Academy of Sciences under contract OTKA-K-62588, the Academy of Finland via its COMP CoE grant, and by Tekes via its MASIT33 project. A. J. acknowledges financial support from the Finnish Academy of Science and Letters. T. P. acknowledges support from the Bolyai Ja´nos Grant

Time Evolution of Partial Discharges in a Dielectric Subjected to the DC Periodic Voltage

Partial discharge (PD) detection can be considered one of the most useful tools for assessing the insulation conditions of the power apparatus in high-voltage systems. Under AC conditions, this analysis is widely employed in online and offline tests, such as type tests or commissioning, and can be carried out by applying the phase-resolved PD (PRPD) method, since the patterns can give information about the defect classification. Under DC voltages, the classic pattern recognition method cannot be performed, and the measurements show complexities related to the nature of the phenomena. For this reason, to date, a standard for PD measurements under DC does not exist. In previous papers, a new method for PD detection under DC stress voltages has been proposed by the authors. It is based on the application of a direct current periodic (DCP) waveform useful in obtaining PRPD patterns. The dependence of partial discharge inception voltage (PDIV) and PD repetition rate (PDRR) on the \u3b4 shape parameter of the DCP for different materials, as well as the capability to recognize different discharge phenomena, provided valid indications on the behavior of PD in the transition from AC to DC. The aim of this paper is to evaluate the time dependence of PD occurring in a dielectric by applying the DCP waveform. In our previous studies, the investigations were focused on the PD behavior under different values of the DC voltage periodic part. In another work, the DCP waveform with both positive and negative polarity was applied to several dielectric materials. In the proposed work, instead, the DCP waveform is applied for a long time in order to observe its effect on the PD behavior for 72 h. In this way, due to the space charge accumulation phenomenon, the aging effect, also due to the space charge accumulation phenomenon, is evaluated. The methodological approach was to acquire PRPD patterns over time and evaluate their trends in comparison with the sinusoidal case. The experimental results show that, with a DCP waveform having \u3b4 = 0.6, the aging effect similar to that provided by pure DC stress is observed, while the acquired PRPD patterns are easily interpretated, as in the AC case

Airborne measurements of cloud-forming nuclei and aerosol particles in stabilized ground clouds produced by solid rocket booster firings

Airborne measurements of cloud volumes, ice nuclei and cloud condensation nuclei, liquid particles, and aerosol particles were obtained from stabilized ground clouds (SGCs) produced by Titan 3 launches at Kennedy Space Center, 20 August and 5 September 1977. The SGCs were bright, white, cumulus clouds early in their life and contained up to 3.5 g/m3 of liquid in micron to millimeter size droplets. The measured cloud volumes were 40 to 60 cu km five hours after launch. The SGCs contained high concentrations of cloud condensation nuclei active at 0.2%, 0.5%, and 1.0% supersaturation for periods of three to five hours. The SGCs also contained high concentrations of submicron particles. Three modes existed in the particle population: a 0.05 to 0.1 micron mode composed of aluminum-containing particles, a 0.2 to 0.8 micron mode, and a 2.0 to 10 micron mode composed of particles that contained primarily aluminum

PROGETTO DI FILTRI EMI AD ELEVATA POWER DENSITY MEDIANTE OTTIMIZZAZIONE MULTI-OBIETTIVO

L’impiego di filtri EMI ad elevata power densitycostituisce un importante ed inderogabile aspetto da tener in conto durante la fase di progetto di un qualunque convertitore elettronico di potenza o di apparato che ne preveda l’impiego per applicazioni in ambito automotiveo avionico, e comunque in tutte quelle applicazioni in cui pressante è la necessità di rispettare i vincolirelativi all’ingombro ed al peso, a parità di prestazioni dal punto di vista della complianceelettromagnetica

ADVANCED BIO-ELECTROMAGNETIC NUMERICAL MODELLING AND ICT FOR HUMAN BRAIN RESEARCH

Functional imaging is used in the research area neurological, neurophysiology and cognitive psychology, for the diagnosis of diseases metabolic and for the detection of thin / squamous lesions (eg Alzheimer's disease) and for the development of neural interfaces (brain-computer interfaces - BCI)

Optimized design of high power density EMI filters for power electronic converters

Nowadays, power density of power converters and related EMI filters is gaining more and more attention. This severely impacts on the design constraints in several application domains. A conventional design of the EMI filter does not guarantee the selection of components/configuration leading to the best power density. For this reason, an optimized design procedure of discrete EMI filters in terms of power density is proposed in this paper. It is based on a previously developed rule-based design procedure, introducing here additional features to obtain a more effective optimization of EMI filter's power density. The proposed approach has been validated in terms of EMI filter's performance and size reduction, by a comparison between an EMI filter designed using the optimized procedure and a conventionally designed one, for two different case studies