Sensitivity Function Trade-offs for Networks with a String Topology

We present two sensitivity function trade-offs that apply to a class of networks with a string topology. In particular we show that a lower bound on the H-infinity norm and a Bode sensitivity relation hold for an entire family of sensitivity functions associated with growing the network. The trade-offs we identify are a direct consequence of growing the network, and can be used to explain why poorly regulated low frequency behaviours emerge in long vehicle platoons even when using dynamic feedback

Robust Scale-Free Synthesis for Frequency Control in Power Systems

The AC frequency in electrical power systems is conventionally regulated by synchronous machines. The gradual replacement of these machines by asynchronous renewable-based generation, which provides little or no frequency control, increases system uncertainty and the risk of instability. This imposes hard limits on the proportion of renewables that can be integrated into the system. In this paper we address this issue by developing a framework for performing frequency control in power systems with arbitrary mixes of conventional and renewable generation. Our approach is based on a robust stability criterion that can be used to guarantee the stability of a full power system model on the basis of a set of decentralised tests, one for each component in the system. It can be applied even when using detailed heterogeneous component models, and can be verified using several standard frequency response, state-space, and circuit theoretic analysis tools. Furthermore the stability guarantees hold independently of the operating point, and remain valid even as components are added to and removed from the grid. By designing decentralised controllers for individual components to meet these decentralised tests, every component can contribute to the regulation of the system frequency in a simple and provable manner. Notably, our framework certifies the stability of several existing (non-passive) power system control schemes and models, and allows for the study of robustness with respect to delays.Comment: 10 pages, submitte

Performance tradeoffs of dynamically controlled grid-connected inverters in low inertia power systems

Implementing frequency response using grid-connected inverters is one of the popular proposed alternatives to mitigate the dynamic degradation experienced in low inertia power systems. However, such solution faces several challenges as inverters do not intrinsically possess the natural response to power fluctuations that synchronous generators have. Thus, to synthetically generate this response, inverters need to take frequency measurements, which are usually noisy, and subsequently make changes in the output power, which are therefore delayed. This paper explores the system-wide performance tradeoffs that arise when measurement noise, power disturbances, and delayed actions are considered in the design of dynamic controllers for grid-connected inverters. Using a recently proposed dynamic droop (iDroop) control for grid-connected inverters, which is inspired by classical first order lead-lag compensation, we show that the sets of parameters that result in highest noise attenuation, power disturbance mitigation, and delay robustness do not necessarily have a common intersection. In particular, lead compensation is desired in systems where power disturbances are the predominant source of degradation, while lag compensation is a better alternative when the system is dominated by delays or frequency noise. Our analysis further shows that iDroop can outperform the standard droop alternative in both joint noise and disturbance mitigation, and delay robustness

The effects of hypnosis on flow states and three-point shooting performance in basketball players.

This study examined the effects of hypnosis on flow states and three-point shooting performance in 5 collegiate basketball players. The investigation uti- lized an ideographic single-subject multiple baselines across subjects design combined with a procedure that monitors the internal experience of the par- ticipants (Wollman, 1986). The method of intervention utilized in this study involved relaxation, imagery, hypnotic induction, hypnotic regression, and trigger control procedures. The results indicated that all five participants in- creased both their mean basketball three-point shooting performance and their mean flow scores from baseline to intervention. There were no overlapping data points between the baseline and intervention for either performance or flow state. Additionally, each participant indicated that they had felt the inter- vention was useful in keeping them confident, relaxed, and calm. These re- sults support the hypothesis that a hypnosis intervention can improve three- point shooting performance in basketball players and increase feelings and cognitions that are associated with flow

“I miss you, I forget you, I love you again”: The construction of love in Argentinian young adult literature

Recociendo que para analizar objetos literarios es necesario desbordar los límites del texto, este artículo apunta a indagar en las mediaciones existentes entre la literatura y el entramado social, es decir, los rasgos específicos del texto literario y la red de relaciones de la que es parte. En particular, se centrará en la literatura juvenil romántica argentina para preguntarse cómo está configurado este campo, qué matrices discursivas en torno del amor se construyen y cómo es leída y apropiada por parte del público lector juvenil. Para ello se analizarán los libros S.O.S. Tengo mi primera cita (Dritsos, 2014) y Diario de una ruptura (Dritsos, 2016).En primera instancia, se contextualizarán los libros seleccionados dentro del mercado editorial argentino y se recuperará la trayectoria de su autora para dar cuenta de sus condiciones sociales de producción. En segundo lugar, se desglosará el análisis de ambos libros en torno a los modos en que se construye el amor a partir de dos matrices discursivas: el amor romántico y el amor contingente. Finalmente, se reconstruirán los espacios por donde han circulado estos libros, así como también los modos en que han sido leídos y apropiados en Argentina.When we analyze literary objects, it is necessary to go beyond the limits of the text. This article aims to look at the mediations between the literary and social frameworks; that is to say, the specific features of the literary text and the relationship network to which it belongs. We shall focus specifically on Argentinian romantic young adult literature to reflect on how the literary field is built, what discursive matrices on love are constructed, and how it is read by young readers. To do so, Georgina Dritsos’ books S.O.S. Tengo mi primera cita (2014) and Diario de una ruptura (2016) shall be analyzed. First of all, these two books shall be set within to the Argentinian editorial market as well as the author’s literary career will be mentioned. Secondly, the ways in which love is constructed in both books will be analyzed following two discursive matrices: romantic love and contingent love. Finally, the places where the books have circulated and the ways they have been read in Argentina it shall be summarized.Fil: Pates, Giuliana Antonela. Universidad Nacional de La Plata. Facultad de Periodismo y Comunicación Social. Centro de Investigación en Problemáticas Socio-simbólicas Latinoamericanas "Aníbal Ford"; Argentin

What Kinds of Research Information Do Communications Practitioners Need?

Listen to a communicator attending any conference related to their work and one could conclude that the mission of the average communications office has become: Do more, do it better, do it with LESS!! Not only on less money...but less time! Now, if that isn\u27t the perfect recipe for frustration, it would be hard to find one. Unfortunately, it seems to be a feeling shared by many

A Damping Ratio Bound for Networks of Masses and Springs

The damping ratio is a key performance measure in systems that can be modelled as networks of masses and springs. We derive a lower bound on this quantity that applies to such networks when the masses are subject to viscous damping. The result allows the size of the damping ratio to be understood as a function of the system parameters. We use this to derive a decentralised criterion which, if satisfied, guarantees that all the modes of a swing equation power system model are sufficiently well damped, independently of its operating point and size