Semianalytical calculation of the zonal-flow oscillation frequency in stellarators

Due to their capability to reduce turbulent transport in magnetized plasmas, understanding the dynamics of zonal flows is an important problem in the fusion programme. Since the pioneering work by Rosenbluth and Hinton in axisymmetric tokamaks, it is known that studying the linear and collisionless relaxation of zonal flow perturbations gives valuable information and physical insight. Recently, the problem has been investigated in stellarators and it has been found that in these devices the relaxation process exhibits a characteristic feature: a damped oscillation. The frequency of this oscillation might be a relevant parameter in the regulation of turbulent transport, and therefore its efficient and accurate calculation is important. Although an analytical expression can be derived for the frequency, its numerical evaluation is not simple and has not been exploited systematically so far. Here, a numerical method for its evaluation is considered, and the results are compared with those obtained by calculating the frequency from gyrokinetic simulations. This "semianalytical" approach for the determination of the zonal-flow frequency reveals accurate and faster than the one based on gyrokinetic simulations.Comment: 30 pages, 14 figure

Auditorías en seguridad clínica para centros de atención primaria. Estudio piloto

Objetivo: Detectar procesos organizativos, infracciones de normas o actuaciones profesionales que supongan niveles de inseguridad clínica. Diseno: ¿ Estudio descriptivo transversal mediante encuesta personalizada heteroadministrada de junio de 2008 hasta febrero de 2010. Emplazamiento: Trece de los 53 equipos de atención primaria (EAP) del ICS Costa de Ponent, Barcelona. Participantes: Trabajadores de 13 EAP agrupados en: director/a, adjunto/a, responsable del servicio de admisiones y médico/a centinela. Métodos: Selección no aleatoria, aparejando centros docentes/no docentes, urbanos/rurales, pequenos/grandes. ¿ Se evaluaron 33 indicadores: 15 de procedimientos, 9 de cultura y actitud, 3 de formación y 6 de comunicación. Criterios de exclusión: no colaboración. Resultados: Características de los 55 profesionales encuestados: 84,6% de centros urbanos, 46,2% docentes y 76,9% EAP grandes. Distribución por estamentos: 13 responsables de atención al usuario, 13 adjuntos de enfermería, 13 directores y 16 médicos centinelas. Nivel de inseguridad: < 50% respuestas afirmativas por indicador. Los EAP estudiados presentaron niveles de inseguridad en: recepción de nuevos profesionales médicos, administración de inyectables, sistema de recogida de domicilios por enfermería en fines de semana, interconsultas urgentes a especialistas, pacientes agresivos, presencia de incidentes críticos sobre las agendas de los médicos y barreras de comunicación en planes terapéuticos y con inmigrantes

Propiedades mecánicas y acústicas de hormigones con áridos reciclados y neumáticos fuera de uso

Industrial progress used to be linked to the produce of large waste volumes. These industrial by-products are deposited in landfills despite these ones could be used to manufacture others. In fact, the construction industry could incorporate these materials to contributing to greater environmental balance. This paper studies the manufactured of concrete using as aggregates two kind of different wastes: construction and demolition wastes as well as recycled tires rubber (NFU). Natural fine fraction is replaced by a 10% by volume of industrial products analyzed. The mechanical behaviour and the acoustic properties of concrete made with recycled aggregates are studied. Results show a reduction in mechanical properties by using recycled aggregates and NFU. Nevertheless, it is observed that concrete made with fine recycled aggregate fraction of NFU could be employed with all the guarantees to produce concrete for non-structural applications.El progreso industrial lleva asociado la generación de grandes volúmenes de residuos que, en la mayoría de los casos, acaban en los vertederos, desperdiciando su potencial como materias primas para otros sectores industriales, como es el sector de la construcción, por lo que debe considerarse su reutilización en nuevas aplicaciones e incorporación como subproducto en el campo de los materiales de construcción, dando lugar a materiales más ecoeficientes y respetuosos con el medioambiente. Este trabajo estudia el empleo de áridos reciclados procedentes de residuos de construcción y demolición, y caucho procedente de neumáticos fuera de uso (NFU) en la fabricación de hormigones. La fracción fina natural ha sido sustituida por un 10% en volumen de los subproductos industriales analizados. El comportamiento físico, mecánico y las propiedades acústicas de los hormigones ha sido comparado con los hormigones de referencia. En los resultados se observa una reducción de las resistencias mecánicas y del modulo de elasticidad por el empleo de áridos reciclados y NFU. Se muestra que los hormigones fabricados con la fracción fina de áridos reciclados y NFU podrían ser empleados con todas las garantías en hormigones para aplicaciones no estructurales

Turbulent transport of impurities in 3D devices

A large diffusive turbulent contribution to the radial impurity transport in Wendelstein 7-X (W7-X) plasmas has been experimentally inferred during the first campaigns and numerically confirmed by means of gyrokinetic simulations with the code stella. In general, the absence of strong impurity accumulation during the initial W7-X campaigns is attributed to this diffusive term. In the present work the diffusive contribution is also calculated in other stellarator plasmas. In particular, the diffusion (D) and convection (V) coefficients of carbon and iron impurities produced by ion-temperature-gradient (ITG) turbulence are obtained for W7-X, LHD, TJ-II and NCSX. The results show that, although the size of D and V can differ across the four devices, inward convection is found for all of them. For W7-X, TJ-II and NCSX the two coefficients are comparable and the turbulent peaking factor is surprisingly similar. In LHD, appreciably weaker diffusive and convective impurity transport and significantly larger turbulent peaking factor are predicted. All this suggests that ITG turbulence, although not strongly, would lead to negative impurity density gradients in stellarators. Then, considering mixed ITG/Trapped Electron Mode (TEM) turbulence for the specific case of W7-X, it has been quantitatively assessed to what degree pellet fueled reduced turbulence scenarios feature reduced turbulent transport of impurities as well. The results for trace iron impurities show that, although their turbulent transport is not entirely suppressed, a significant reduction of V and a stronger decrease of D are found. Although the diffusion is still above neoclassical levels, the neoclassical convection would gain under such conditions a greater specific weight on the dynamics of impurities in comparison with standard ECRH scenarios.Comment: 16 pages, 8 figure

Turbulent impurity transport simulations in Wendelstein 7-X plasmas

A study of turbulent impurity transport by means of quasilinear and nonlinear gyrokinetic simulations is presented for Wendelstein 7-X (W7-X). The calculations have been carried out with the recently developed gyrokinetic code stella. Different impurity species are considered in the presence of various types of background instabilities: ITG, TEM and ETG modes for the quasilinear part of the work; ITG and TEM for the nonlinear results. While the quasilinear approach allows one to draw qualitative conclusions about the sign or relative importance of the various contributions to the flux, the nonlinear simulations quantitatively determine the size of the turbulent flux and check the extent to which the quasilinear conclusions hold. Although the bulk of the nonlinear simulations are performed at trace impurity concentration, nonlinear simulations are also carried out at realistic effective charge values, in order to know to what degree the conclusions based on the simulations performed for trace impurities can be extrapolated to realistic impurity concentrations. The presented results conclude that the turbulent radial impurity transport in W7-X is mainly dominated by ordinary diffusion, which is close to that measured during the recent W7-X experimental campaigns. It is also confirmed that thermo-diffusion adds a weak inward flux contribution and that, in the absence of impurity temperature and density gradients, ITG- and TEM-driven turbulence push the impurities inwards and outwards, respectively.Comment: 19 pages, 10 figures, 2 table

Gyrokinetic simulations in stellarators using different computational domains

In this work, we compare gyrokinetic simulations in stellarators using different computational domains, namely, flux tube, full-flux-surface, and radially global domains. Two problems are studied: the linear relaxation of zonal flows and the linear stability of ion temperature gradient (ITG) modes. Simulations are carried out with the codes EUTERPE, GENE, GENE-3D, and stella in magnetic configurations of LHD and W7-X using adiabatic electrons. The zonal flow relaxation properties obtained in different flux tubes are found to differ with each other and with the radially global result, except for sufficiently long flux tubes, in general. The flux tube length required for convergence is configuration-dependent. Similarly, for ITG instabilities, different flux tubes provide different results, but the discrepancy between them diminishes with increasing flux tube length. Full-flux-surface and flux tube simulations show good agreement in the calculation of the growth rate and frequency of the most unstable modes in LHD, while for W7-X differences in the growth rates are found between the flux tube and the full-flux-surface domains. Radially global simulations provide results close to the full-flux-surface ones. The radial scale of unstable ITG modes is studied in global and flux tube simulations finding that in W7-X, the radial scale of the most unstable modes depends on the binormal wavenumber, while in LHD no clear dependency is found.Comment: submitted to Nuclear Fusio

Elaboració d’un pla de tutories per a la FIB

La majoria d'estudiants que accedeixen a la universitat, i en concret a la FIB, no són conscients del que comporta cursar una carrera universitària. Els estudis universitaris requereixen molta dedicació. Sovint els estudiants tenen mancances de coneixements, però també hàbits i actituds no adequats. En aquest sentit és interessant la figura del tutor, especialment en l’inici dels estudis, per tal de guiar i orientar els estudiants i estudiantes amb l’objectiu principal de facilitar la seva adaptació al mon universitari i millorar el seu rendiment acadèmic. Actualment les tutories són voluntàries a la FIB i hi ha pocs estudiants que demanin un tutor i pocs professors que s'impliquin en aquesta tasca. Per una banda, molts estudiants no veuen la necessitat de tenir un tutor. Per altra banda, hi ha professors que no disposen ni del material ni de la formació que seria desitjable per a fer aquesta tasca i d’altres que no creuen en la seva utilitat. L’objectiu d’aquest projecte és l’elaboració d’un Pla de Tutories per a la FIB amb les directrius i material necessari per a desenvolupar aquesta tasca. D’aquesta manera esperem captar més tutors i tutores i incidir en una millora del rendiment acadèmic.Peer Reviewe