340 research outputs found

    Opacity calculation for target physics using the ABAKO/RAPCAL code

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    Radiative properties of hot dense plasmas remain a subject of current interest since they play an important role in inertial confinement fusion (ICF) research, as well as in studies on stellar physics. In particular, the understanding of ICF plasmas requires emissivities and opacities for both hydro-simulations and diagnostics. Nevertheless, the accurate calculation of these properties is still an open question and continuous efforts are being made to develop new models and numerical codes that can facilitate the evaluation of such properties. In this work the set of atomic models ABAKO/RAPCAL is presented, as well as a series of results for carbon and aluminum to show its capability for modeling the population kinetics of plasmas in both LTE and NLTE regimes. Also, the spectroscopic diagnostics of a laser-produced aluminum plasma using ABAKO/RAPCAL is discussed. Additionally, as an interesting application of these codes, fitting analytical formulas for Rosseland and Planck mean opacities for carbon plasmas are reported. These formulas are useful as input data in hydrodynamic simulation of targets where the computation task is so hard that in line computation with sophisticated opacity codes is prohibitive

    Surface acoustic wave modulation of single photon emission from GaN/InGaN nanowire quantum dots

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    On-chip quantum information processing requires controllable quantum light sources that can be operated on-demand at high-speeds and with the possibility of in-situ control of the photon emission wavelength and its optical polarization properties. Here, we report on the dynamic control of the optical emission from core-shell GaN/InGaN nanowire (NW) heterostructures using radio frequency surface acoustic waves (SAWs). The SAWs are excited on the surface of a piezoelectric lithium niobate crystal equipped with a SAW delay line onto which the NWs were mechanically transferred. Luminescent quantum dot (QD)-like exciton localization centers induced by compositional fluctuations within the InGaN nanoshell were identified using stroboscopic micro-photoluminescence (micro-PL) spectroscopy. They exhibit narrow and almost fully linearly polarized emission lines in the micro-PL spectra and a pronounced anti-bunching signature of single photon emission in the photon correlation experiments. When the nanowire is perturbed by the propagating SAW, the embedded QD is periodically strained and its excitonic transitions are modulated by the acousto-mechanical coupling, giving rise to a spectral fine-tuning within a ~1.5 meV bandwidth at the acoustic frequency of ~330 MHz. This outcome can be further combined with spectral detection filtering for temporal control of the emitted photons. The effect of the SAW piezoelectric field on the QD charge population and on the optical polarization degree is also observed. The advantage of the acousto-optoelectric over other control schemes is that it allows in-situ manipulation of the optical emission properties over a wide frequency range (up to GHz frequencies).Comment: arXiv admin note: text overlap with arXiv:1902.0791

    Low temperature microwave emission from molecular clusters

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    We investigate the experimental detection of the electromagnetic radiation generated in the fast magnetization reversal in Mn12-acetate at low temperatures. In our experiments we used large single crystals and assemblies of several small single crystals of Mn12-acetate placed inside a cylindrical stainless steel waveguide in which an InSb hot electron device was also placed to detect the radiation. All this was set inside a SQUID magnetometer that allowed to change the magnetic field and measure the magnetic moment and the temperature of the sample as the InSb detected simultaneously the radiation emitted from the molecular magnets. Our data show a sequential process in which the fast inversion of the magnetic moment first occurs, then the radiation is detected by the InSb device, and finally the temperature of the sample increases during 15 ms to subsequently recover its original value in several hundreds of milliseconds.Comment: changed conten

    Implementation of activities for the evaluation of the specific instrumental transversal competence in subjects in the area of mechanical engineering

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    [EN] Most of the higher education frameworks work and evaluate transversal competences, to achieve the excellence of graduates, not only academically but also integrating social aspects, ethics, communication, teamwork, etc. To this end, the present work studies a common methodology both in the activities, to improve the acquisition of the ¿Specific Instrumental¿ transversal competence, as well as in its evaluation. In the practical sessions, the student uses a detailed tutorial with the procedure to obtain the numerical result. The evaluation of the ¿Specific Instrumental¿ transversal competence is deficient following this structure, since it does not show whether the student acquires autonomy to solve similar problems. Therefore, an unguided alternative activity was proposed at the end of each session, which allows to see the evolution of the student in the face of a different problem without guidelines. Experience shows that it is rash to expect the student to handle the program autonomously in the first session. For this reason, the delivery deadline for tasks will be extended by a few weeks. Obviously, guarantee of authenticity is lost, but responsibility for learning is transferred to the student. Allowing the student to spend the time necessary for deep learning, without the pressure of ending the session.Authors gratefully acknowledge the financial support of the Vicerrectorado de Estudios, Calidad y Acreditación and the Vicerrectorado de Recursos Digitales y Documentación of the Universitat Politècnica de València (project PIME B/19-20/165) and the Instituto de Ciencias de la Educación of the Universitat Politècnica de València (EICE INTEGRAL).Pedrosa, AM.; Sánchez Orgaz, EM.; Lozano-Mínguez, E.; Martinez-Sanchis, S. (2020). Implementation of activities for the evaluation of the specific instrumental transversal competence in subjects in the area of mechanical engineering. IATED Academy. 597-602. https://doi.org/10.21125/iceri.2020.0197S59760

    Técnicas SIG aplicadas al estudio del relieve de los Montes de León (NO de la Península Ibérica)

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    En este trabajo se presenta un método basado en el análisis de modelos digitales de elevación (MDE) a través de SIG, encaminado a realizar una cartografía preliminar de antiguas superficies de aplanamiento en los relieves que bordean la cuenca del Bierzo (oeste de la provincia de León, noroeste de la Península Ibérica). El área de estudio es un complejo sistema escalonado de niveles de aplanamiento elaborados sobre el basamento del Macizo Ibérico, constituyente de los relieves montañosos de la zona, deformado por la Orogenia Alpina durante el Cenozoico, en donde las superficies se encuentran elevadas, basculadas, fragmentadas y muy degradadas. Partiendo del MDE con paso de malla de 25 m del PNOA se realizó una caracterización general de la zona de estudio mediante la obtención de mapas derivados: pendientes, orientaciones de pendiente y sombreado, así como de la red de drenaje. Empleando la extensión EZ Profile para ArcGIS 9.3 se generaron 213 perfiles topográficos, sobre los principales cordales e interfluvios, con los que se localizaron y correlacionaron los elementos culminantes (indicios y restos de superficies de aplanamiento) presentes en toda la zona de estudio, lo que permitió reconstruir el relieve previo al desmantelamiento por parte de la red de drenaje. Una vez delimitadas las superficies de aplanamiento se procedió a su caracterización, agrupación y jerarquización, mediante el estudio de superficies de tendencia, el análisis de la red de drenaje y la relación con la actividad tectónica. Se realizó una reconstrucción teórica de cada uno de los aplanamientos a través de la interpolación de los puntos pertenecientes al antiguo relieve, generando así una superficie de tendencia de primer orden, de donde se obtuvo la orientación y pendiente de cada una de ellas. A su vez, se buscaron anomalías en los cauces de los ríos que atraviesan los aplanamientos, que pudieran indicar actividad tectónica reciente. Asimismo, se llevó a cabo un estudio de las cuencas de drenaje, sobre las que se realizaron cálculos de hipsometría y de asimetría (Factor de Asimetría). Por último, se calculó la incisión del drenaje sobre las superficies de aplanamiento cartografiadas. Como resultado se obtuvieron veinte superficies clasificadas en ocho niveles, desde los 1000m a los 2100m, en donde se observa cómo los distintos elementos de un mismo nivel se encuentran en extremos opuestos de la zona de estudio, ubicados en forma de orla perdiendo altura hacia la cuenca del Bierzo.Trabajo financiado por el proyecto de la Junta de Castilla y León LE311A12-2 y por el proyecto Consolider Ingenio 2006 CSD-2006, TopoIberia Geociencias en Iberia

    Quantum Magnetic Deflagration in Mn12 Acetate

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    We report controlled ignition of magnetization reversal avalanches by surface acoustic waves in a single crystal of Mn12 acetate. Our data show that the speed of the avalanche exhibits maxima on the magnetic field at the tunneling resonances of Mn12. Combined with the evidence of magnetic deflagration in Mn12 acetate (Suzuki et al., cond-mat/0506569) this suggests a novel physical phenomenon: deflagration assisted by quantum tunneling.Comment: 4 figure
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