Dynamics of a 1-D model for the emergence of the plasma edge shear flow layer with momentum conserving Reynolds stress

A one-dimensional version of the second-order transition model based on the sheared flow amplification by Reynolds stress and turbulence supression by shearing is presented. The model discussed in this paper includes a form of the Reynolds stress which explicitly conserves momentum. A linear stability analysis of the critical point is performed. Then, it is shown that the dynamics of weakly unstable states is determined by a reduced equation for the shear flow. In the case in which the flow damping term is diffusive, the stationary solutions are those of the real Ginzburg-Landau equation.Comment: 21 pages, 8 figure

Effects of Self-Consistent Flow on Island Generation in Interchange Mode

The time evolution of magnetic island in the nonlinear phase of the resistive interchange mode is examined in the cylindrical geometry. The effects of self-consistent uniform poloidal flow is taken into account. In this case, the reconnection of the magnetic field line occurs both at the saturation of the dominant unstable mode and at the saturation of the n = 0 mode, where n is the toroidal mode number, through the curvature change of perturbed poloidal flux surface

Quartz of C-Axis Fabric Variation at the Margins of a Shear Zone Developed in Schists from Cap de Creus (Spain)

By means of geometrical analysis it is established that the studied shear zone, although approaching closely the simple shear model, does not satisfy it completely. Slight departures must be taken into account, i.e. there is an heterogeneity of strain along the shear zone on decimetric to milimetric domains, this caused by the non isotropic character of the original rock. Furthermore, a slight flattening component, besides the dominant simple shearing has to be taken into account when considering the bulk type of strain acting on the outer margins of the shear zone. In the outer margin of the studied shear zone two incipient sets of extensional crenulations, nearly symmetnc about the regional schistosity, appear. In such low strain domains, a weak caxis preferred orientation is already present consisting in a pseudo-two-girdle pattern. Stili at the marginal domains, but approaching the inner part of the shear zone, the regional schistosity progressively rotates into a mylonitic foliation. At the same time one set of the crenulations tends to vanish, while the other becomes better developed but conserves about the same angular relationship with the foliation. This fact coincides with the rotation and strengthening of the preferred orientation c-axis fabric pattern and its progressively more asymmetnc character with regard to the foliation. The final fabric is a nearly single girdle which tends to remain perpendicular to the persisting set of extensional crendations or shear bands if present. The obliquity of the girdle with respect to the mylonitic foliation is by no means related to the amount of strain.El análisis geométrico de la zona de la cizalla estudiada permite evidenciar que la deformación global se aproxima sensiblemente al modelo de cizaiia simple si bien debe tenerse presente la existencia de un componente menor de aplastamiento no rotacional especialmente significativo en los márgenes externos de la zona de cizalla. Además debe tenerse en consideración la presencia de heterogeneidades en la deformación, en los dominios decimétricos o inferiores, a lo largo de la zona de cizalla y originadas por el carácter no isotrópico de la roca original. En los márgenes externos de la zona de cizalla existen dos sistemas incipientes de crendaciones extensivas dispuestas aproximadamente simétricas con respecto a la esquistosidad regional. En estos dominios externos en donde la deformación es débil se aprecia ya la existencia de orientaciones preferentes de los ejes c del cuarzo adoptando disposiciones del tipo: "pseudo-two-girdle". Todavía en las zonas marginales, pero en dirección al interior de la zona de cizalla, la esquistosidad regional gira progresivamente transformándose en una foliación milonítica. Al mismo tiempo un sistema de crenulaciones tiende a desaparecer, mientras que el segundo se acentúa, conservando aproximadamente la misma relación angular con la foliación. Este hecho coincide con la rotación y el refuerzo de la orientación preferente de los ejes "c" del cuarzo y con su asimetrización con respecto a la foliación. La fábrica final se asemeja a una guirnalda sencilla la cual tiende a permanecer en posición ortogonal al sistema de crenulaciones o de bandas de cizalla persistentes, cuando éstas existen. La oblicuidad de la guirnalda con respecto a la foliación milonítica en ningún caso puede ser correlacionada con el valor de la deformación

Silicon Nanocrystal Field-Effect Light-Emitting Devices

We describe the operation of a light-emitting device in which silicon nanocrystals are electrically pumped via the field-effect electroluminescence (EL) mechanism. In contrast to the simultaneous bipolar carrier injection used in conventional p-n junction light-emitting diodes, this device employs sequential unipolar programming of both electrons and holes across a tunneling barrier from the same semiconductor channel. Light emission is strongly correlated with the injection of second carriers into nanocrystals that have been previously programmed with charges of the opposite sign. The properties of this device are well described by the model of a charge injection through Coulomb field modified tunneling processes. We additionally consider limiting performance bounds for potential future devices fabricated from nanocrystals with different radiative emission rates

Distributed Generation and Resilience in Power Grids

We study the effects of the allocation of distributed generation on the resilience of power grids. We find that an unconstrained allocation and growth of the distributed generation can drive a power grid beyond its design parameters. In order to overcome such a problem, we propose a topological algorithm derived from the field of Complex Networks to allocate distributed generation sources in an existing power grid.Comment: proceedings of Critis 2012 http://critis12.hig.no

Seven years of marine environmental changes monitoring at coastal OOCS stations (Catalan Sea, NW Mediterranean)

Since March 2009 up to the present (more than 7 years now), the Operational Observatory of the Catalan Sea (OOCS; http://www2.ceab.csic.es/ oceans/) remains a witness of persistent marine environmental changes. The OOCS has two fixed observation stations at the head of the Blanes Canyon (200 m depth, 41.66°N; 2.91°E) and at the Blanes bay (20 m depth, 41.67°N; 2.80°E) in the Catalan Sea, NW Mediterranean. At the canyon station, a multi-parametric buoy presently installed delivers high frequency (by 30 min) and multi-parametric oceanographic (i.e. salinity, temperature, chlorophyll, turbidity, as well as light intensity in the PAR range for the upper 50 m depth) and atmospheric (air temperature, relative humidity, wind speed and direction and PAR) data. Subsurface photos and videos by an IP high resolution fisheye camera attached to the buoy are also delivered at 4-hour basis. Data and multimedia are transmitted in near real time for public access, via combined GSM/GPRS and 3G connections. At both stations, CTD profiles and water samples (collected for nutrients and picoplankton analyses) are carried out on board a research vessel at fortnightly basis. Numerical simulations along with the time series of in-situ observations show inter-annual seasonality anomalies possibly linked to global environmental changes. The lower-atmosphere and upper-sea environmental time series data collected prove the occurrence of shifting patterns of heat and matter fluxes impacting pelagic and benthic organisms.Peer Reviewe