186,466 research outputs found
Preface: Special issue featuring papers from the International Conference on Nonequilibrium Carrier Dynamics in Semiconductors
No full textEnvironmental acoustic noise observations in Tethys Bay (Terra Nova Bay, Ross Sea, Antarctica)
No full textUnderwater acoustic measurements have been recently carried out in Tethys Bay (Ross Sea, Antarctica) during the XXIX Italian Antarctic Expedition to support acoustic propagation studies in the area and to investigate the environmental noise. Tethys Bay is a small deep cove close to the Antarctic Italian base Mario Zucchelli Station (Baia Terra Nova -74°42' S e 164°07' E) and covered with sea-ice for most of the year. During the period of the experiment (November 2013) the pack-ice had an almost constant thickness of about 2.2 m, so that the measurements were performed deploying the instruments into the sea from holes drilled through the pack ice. The holes were located along the bay axis at a distance of about 500 m each other. The sea depth was around 200 m except for the hole close to the coast, where the sea depth was only 25 m. An hydrophone RESON TC 4032 was located in the outermost hole, while the acoustic source, a transceiver transmitting FSK pulses at 11 kHz, was placed in sequence in the other three holes. Every time, the measurements were performed at 0, 20 and 45 m depth for each configuration. Furthermore during the experiment, sea temperature, salinity and currents, as well as the main meteorological parameters were continuously measured. The analysis here reported mainly focuses on the acquired acoustic passive data. The passive measurements evidenced that the signal was generally dominated by different sounds from seals, which was prevailing on the noise due to human activities. © 2014 IEEE
Effect of half-space and interface phonons on the transport properties of AlGaAs/GaAs single heterostructures
No full textWe present a detailed analysis of the influence of the various phonon modes characteristic of the single heterostructure AlxGa1-xAs/GaAs on its electronic transport by using a Monte Carlo simulation. The electronic states of the system are calculated by solving self-consistently the coupled Schrodinger-Poisson equations for the system. LO-phonon states are treated within the dielectric continuum model by using two different dielectric functions to describe the two semiconductors, the usual Lyddane-Sachs-Teller expression for GaAs and a generalized two poles expression for AlxGa1-xAs. Two sets of optical modes characterize the system, the half-space LO modes and the interface modes. The scattering rates for the interaction of these modes with the confined electrons are calculated from the Fermi golden rule. A Monte Carlo simulation is then used to study the effect of the electron-phonon interaction on the transport properties of a single AlxGa1-xAs/GaAs heterostructure in the presence of an electric field applied along the heterointerface. The results of simulations performed at 300 and 77 K compare favorably with available experimental data. Drag and heating effects related to nonequilibrium phonon effects are found and discussed
Effect of a perturbed acoustic-phonon distribution on hot-electron transport: a Monte Carlo analysis
No full textA Monte Carlo simulation code has been developed to study the effect of phonon perturbations in hot-electron transport in semiconductors. The modifications of carrier drift velocity and mean energy induced by the perturbed acoustic-phonon distribution are studied at low temperatures in p-Ge. Under appropriate conditions, current saturation is obtained as a result of the steady-state phonon perturbation. The Monte Carlo analysis has been complemented and compared with an analytical approach based on a heated and displaced Maxwellian distribution for the electron gas
Dati meteorologici acquisiti dalla stazione ENEA di S. Teresa (SP). Rapporto annuale 2019 e comparazione con dati climatologici
No full textDa Agosto 2003, presso il centro ENEA CRAM di S. Teresa (SP), è in funzione una stazione meteorologica con lo scopo di misurare i principali parametri meteorologici. I dati vengono raccolti secondo lo standard del World Meteorological Organization (WMO-No.8, 2014) ed archiviati. E’ possibile visionare i grafici delle variabili meteo in tempo reale (limitatamente all’ultima settimana di acquisizione) all’indirizzo web: http://www.santateresa.enea.it In questo rapporto sono riportate le osservazioni meteorologiche in forma grafica e tabellare per il 2019, con i valori minimi, medi, massimi, deviazioni standard delle grandezze misurate e rose dei venti mensili. Si è inoltre effettuato un confronto con dati climatici acquisiti in precedenza riportando le anomalie delle osservazioni meteorologiche.A meteorological station has been working in the S. Teresa CRAM ENEA Centre to measure the main meteorological parameters since August 2003. Data are acquired in accordance with World Meteorological Organization (WMO-No.8, 2014) standard and stored. Meteo variables in real-time (only for the last week of acquisition) at the web address: http://www.santateresa.enea.it are available. This report presents, in tabular and graphical form, the meteorological observations acquired during the year 2019 detailing the monthly average, minimum, maximum, standard deviation values of the measured data and monthly wind roses. This report also includes a comparison with previous meteorological observations and presents relative anomalies
EFFECT OF MARKOV AND NON-MARKOV CLASSICAL NOISE ON ENTANGLEMENT DYNAMICS
No full textWe analyze the effect of a classical noise into the entanglement dynamics between two particles, initially entangled, subject to continuous time quantum walks in a one-dimensional lattice. The noise is modeled by randomizing the transition amplitudes from one site to another. Both Markovian and non-Markovian environments are considered. For the Markov regime an exponential decay of the initial quantum correlation is found, while the loss of coherence of the quantum state increases monotonically with time up to a saturation value depending upon the degrees of freedom of the system. For the non-Markov regime the presence or absence of entanglement revival and entanglement sudden death phenomena is found or deduced depending on the peculiar characteristics of the noise. Our results indicate that the entanglement dynamics in the non-Markovian regime is affected by the persistence of the memory effects of the environment and by its intrinsic features
Quantum correlations in continuous-time quantum walks of two indistinguishable particles
No full textWe evaluate the degree of quantum correlation between two fermions (bosons) subject to continuous time quantum walks in a one-dimensional ring lattice with periodic boundary conditions. In our approach, no particle-particle interaction is considered. We show that the interference effects due to exchangesymmetry can result into the appearance of non-classical correlations. The role played onto the appearance of quantum correlations by the quantum statistics of the particles, the boundary conditions, and the partition of the systemis widely investigated. Quantum correlations have also been investigated in a model mimicking the ballistic evolution of two indistinguishable particles in a 1D continuous space structure.Our results are consistent with recent quantum optics and electron quantum optics experiments where the showing up of two-particle non-classical correlations has been observed even in the absence of mutual interaction between the particles
Monte Carlo analysis of hot-phonon effects on non-polar semiconductors transport properties
No full textAn iterative procedure to include phonon disturbance into a Monte Carlo algorithm is presented. Low temperature transport in p-Ge is considered. Calculations show that carrier drift velocity and mean energy increase as a result of the phonon amplification
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