On the use of TVD fluxes in ENO and WENO schemes

Very high order methods, such as ENO/WENO methods [21, 30, 19], Runge-Kutta Discontinuous Galerkin Finite Element Methods [12] and ADER methods [54,46] often use high order (e.g. fifth order) polynomial reconstruction of the solution of a lower (first) order monotone flux as the building block. In this paper we propose to use second order TVD fluxes in the framework of such methods and apply the principle to the finite-volume ENO, WENO and MPWENO schemes. We call the new improved schemes the ENO-TVD, WENO-TVD and MPWENO-TVD schemes respectively. They include both upwind and centred schemes with non-stuggered meshes. Numerical results suggest that our schemes are superior to original schemes with first order fluxes. This is especially so for long time evolution problems containing both smooth and non-smooth features

Optimized Hierarchical Control for an AC Microgrid Under Attack

Context: An inverter-based microgrid working in islanded mode can suffer cyber- attacks, these can be done against either the local controller or the communication links among the inverters. Secondary control is able to reject those attacks, however, a tertiary control action is necessary in order to stabilize the power flow among the microgrid. Method: Confidence factor technique allows to reject attacks in a microgrid acting directly over the secondary control, however, this technique omits other factor related to the power available. In this case, secondary control was complemented with a tertiary control that includes optimization criteria. Results: An inverter-based microgrid is simulated in Matlab for different scenarios and under cyberattack, this allows checking the correct response of the controller under attacks and the effective powersharing among inverters. Conclusions: The tertiary control allows stabilizing the active power of the system after the rejection of a cyber-attack by the secondary control. Each inverter supplies active power according to its máximum power rating without affecting the stability of the whole system

Neurocognitive mechanisms underlying working memory encoding and retrieval in Attention-Deficit/Hyperactivity Disorder

Working memory (WM) impairments in ADHD have been consistently reported along with deficits in attentional control. Yet, it is not clear which specific WM processes are affected in this condition. A deficient coupling between attention and WM has been reported. Nevertheless, most studies focus on the capacity to retain information rather than on the attention-dependent stages of encoding and retrieval. The current study uses a visual short-term memory binding task, measuring both behavioral and electrophysiological responses to characterize WM encoding, binding and retrieval comparing ADHD and non-ADHD matched adolescents. ADHD exhibited poorer accuracy and larger reaction times than non-ADHD on all conditions but especially when a change across encoding and test displays occurred. Binding manipulation affected equally both groups. Encoding P3 was larger in the non-ADHD group. Retrieval P3 discriminated change only in the non-ADHD group. Binding-dependent ERP modulations did not reveal group differences. Encoding and retrieval P3 were significantly correlated only in non-ADHD. These results suggest that while binding processes seem to be intact in ADHD, attention-related encoding and retrieval processes are compromised, resulting in a failure in the prioritization of relevant information. This new evidence can also inform recent theories of binding in visual WM.Fil: Ortega Toro, Rodrigo. Universidad de Chile; ChileFil: López, Vladimir. Pontificia Universidad Católica de Chile; ChileFil: Carrasco, Ximena. Universidad de Chile; ChileFil: Escobar, María Josefina. Universidad Adolfo Ibañez; ChileFil: García, Adolfo Martín. Universidad de San Andrés; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Neurociencia Cognitiva. Fundación Favaloro. Instituto de Neurociencia Cognitiva; Argentina. Universidad de Santiago de Chile; ChileFil: Parra, Mario. Universidad Autónoma del Caribe; ColombiaFil: Aboitiz, Francisco. Universidad de Chile; Chil

Regulation frequency improvements using the inertia increase of networked microgrids

El control por pendiente garantiza la regulación de frecuencia y el reparto de potencia activa entre los inversores de una microrred aislada, sin embargo, introduce desviaciones respecto a la frecuencia de referencia. Cuando un generador adicional basado en inversores se conecta a la microrred se reduce la desviación en frecuencia y se aumenta la capacidad de potencia de todo el sistema; lo mismo ocurre cuando se interconectan microrredes en modo isla. El control por pendiente ha mostrado ser efectivo en microrredes basadas en inversores, sin embargo, cuando uno o más generadores sincrónicos se conectan directamente a la microrred, cambian las condiciones de dicho control. Para analizar que ocurre cuando se interconectan microrredes en modo isla se analizan los casos cuando ambas microrredes constan únicamente de inversores, y cuando una microrred o ambas tienen al menos un generador sincrónico. De esta manera, los resultados de simulación presentados demuestran las mejoras de la regulación de frecuencia utilizando el aumento de inercia de microrredes Interconectadas.Droop control guarantee frequency regulation and power sharing among the inverters in an islanded microgrid, however, frequency deviations are introduced respect to reference values. When an aditional distributed generator base on inverters is connected to the microgrid, such deviations are reduced and the power capacity of the system is improved; same way happens when islanded microgrids are interconnected. Droop control has shown to be effective in inverter based microgrids, however, when one or more synchronous generators are directly connected to the microgrid the conditions of the controller change. To analaize what happen when islanded microgrids are interconected different cases are considered: first when both microgrid are based only in inverters and other case in which one microgrid has at least one synchronous generator. In this way, the simulation results show the regulation frequency improvements using the inertia increase of networked microgrids

Sistema de medición de sedimentos para uso en la zona de rompientes.

Se modificó el diseño de Kraus y Rosati (1989) y se realizó un diseño que aparte de las ventajas de este solucionara algunos inconvenientes del mismo. Se construyeron 2 trampas de sedimentos, la primera un diseño modificado del original y la segunda un diseño propio del CCCP. Así el sistema quedo compuesto por 2 correntómetros acústicos y por 2 trampas de sedimentos. Los resultados preliminares permiten definir el valor promedio para el diámetro medio (D50) del sedimento en la zona de estudio como 0.13mm y como origen del material el sur (Río Mira), debido a valores altos de tasas de transporte en ese lado de las trampas

Análisis Numérico y Experimental de las Técnicas de Control ZAD y FPIC para un Convertidor Buck

El objetivo principal de este trabajo es lograr concordancia entre los resultados numéricos, obtenidos vía modelización matemática, y los resultados experimentales en un convertidor reductor (convertidor buck) controlado con la técnica combinada de control: Zero Average Dynamics-Fixed Point Induced Control (ZAD-FPIC). El modelo matemático propuesto incluye: resistencias internas, resistencias de medida y la caída de voltaje en el diodo. El diseño ha sido validado experimentalmente, usando la plataforma digital dSPACE, en un convertidor DC-DC de baja potencia. Los diagramas de bifurcaciones, calculados numéri- camente en la etapa de diseño, concuerdan totalmente con los obtenidos en la etapa experimental. Cuando el sistema opera en zona estable se obtiene buen comportamiento a la salida (regulación en el caso DC- DC), con bajo error de estado estacionario.Palabras clave: Controlador ZAD-FPIC, convertidor buck, diagramas de bifurcaciones, resultados numé- ricos y experimentales.

Sensory hybrid host materials for the selective chromo-fluorogenic detection of biogenic amines

Pyrylium-containing mesoporous materials have been used for the chromo-fluorogenic sensing of biogenic amines in an aqueous environment.Amoros del Toro, Pedro Jose, [email protected]

Dark sectors 2016 Workshop: community report

This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years

Loss of quaternary structure is associated with rapid sequence divergence in the OSBS family

The rate of protein evolution is determined by a combination of selective pressure on protein function and biophysical constraints on protein folding and structure. Determining the relative contributions of these properties is an unsolved problem in molecular evolution with broad implications for protein engineering and function prediction. As a case study, we examined the structural divergence of the rapidly evolving o-succinylbenzoate synthase (OSBS) family, which catalyzes a step in menaquinone synthesis in diverse microorganisms and plants. On average, the OSBS family is much more divergent than other protein families from the same set of species, with the most divergent family members sharing <15% sequence identity. Comparing 11 representative structures revealed that loss of quaternary structure and large deletions or insertions are associated with the family’s rapid evolution. Neither of these properties has been investigated in previous studies to identify factors that affect the rate of protein evolution. Intriguingly, one subfamily retained a multimeric quaternary structure and has small insertions and deletions compared with related enzymes that catalyze diverse reactions. Many proteins in this subfamily catalyze both OSBS and N-succinylamino acid racemization (NSAR). Retention of ancestral structural characteristics in the NSAR/OSBS subfamily suggests that the rate of protein evolution is not proportional to the capacity to evolve new protein functions. Instead, structural features that are conserved among proteins with diverse functions might contribute to the evolution of new functions