如果你忘记了我

I want you to know
one thing.
You know how this is：
if I look
at the crystal moon, at the red branch
of the slow autumn at my window,     

Continuous fixed-time convergent regulator for dynamic systems with unbounded disturbances

This paper presents a novel continuous fixed-time convergent control law for dynamic systems in the presence of unbounded disturbances. A continuous fixed-time convergent control is designed to drive all states of a multi-dimensional integrator chain at the origin for a finite pre-established (fixed) time, using a scalar input. The fixed-time convergence is established and the uniform upper bound of the settling time is computed. The designed control algorithm is applied to fixed-time stabilization of two mechatronic systems, a cart inverted pendulum and a single machine infinite bus turbo generator with main steam valve control.     

Fatigue does not conjointly alter postural and cognitive performance when standing in a shooting position under dual-task conditions

This study investigated the effects of fatigue on balance control and cognitive performance in a standing shooting position. Nineteen soldiers were asked to stand while holding a rifle (single task – ST). They also had to perform this postural task while simultaneously completing a cognitive task (dual task – DT). Both the ST and DT were performed in pre- and post-fatigue conditions. In pre-fatigue, participants achieved better balance control in the DT than in the ST, thus suggesting that the increased cognitive activity associated with the DT improves balance control by shifting the attentional focus away from a highly automatised activity. In post-fatigue, balance control was degraded in both the ST and DT, while reaction time was enhanced in the first minutes following the fatiguing exercise without affecting the accuracy of response in the cognitive task, which highlights the relative independent effects of fatigue on balance control and cognitive performance.     

Intelligent information retrieval: diagnosing information need. Part II. Uncertainty expansion in a prototype of a diagnostic IR tool

This article is part II of a three part series. In part I we described the theoretical framework for developing an “intelligent information retrieval” tool, based on three principles from medical diagnosis theory. In part II, the present article, we outline a prototype of an “intelligent” IR tool, whose purpose is to facilitate information access for an undergraduate seeking information for a history term paper. Our objective is to create a tool that will (i) draw-out the undergraduate's query to the information system by taking the student through the task of doing the term paper and (ii) diagnose the student's information need by measuring his or her degree of topic integration. The degree of integration indicates a class of information need. The classes of information need are based on Kuhlthau's six stage information search process (ISP) model (each stage is a separate information need, demanding different information to satisfy it). The measurement instrument is based on (i) principles from Shannon's mathematical theory of communication and (ii) principles of uncertainty expansion and reduction from differential diagnosis theory.     

Measuring systematic long-term trajectories of school effectiveness improvement

The objective of this study was to identify trajectories of school improvement experienced by Chilean elementary schools over the last decade. Using econometric analysis and controlling for potential confounding factors, we created an index of school performance combining outcome indicators focused on different school dimensions, and estimated the 2002/2010 evolution of school improvement for all Chilean schools with available data. Broadly, we estimated an average increase in the school performance of about 0.19 SD; nevertheless, while 41% of the schools increased their educational performance by at least 0.1 SD, 25% of the schools decreased it during the same period; we also found that improving school effectiveness was more probable among schools with lower student socioeconomic status (SES). Finally, we found that the observed school improvement trajectories tended to be non-linear; thus, we estimated that only 13.4% of the schools improved their performance in a systematic way during the entire decade.     

Using Drama to Promote Argumentation in Science Education

The purpose of this study was to use drama as a springboard for promoting argumentation among 91 first-semester undergraduate medical students (56 females and 35 males, 16–30 years old) in Colombia during a complete teaching–learning sequence (TLS) supervised by the same teacher. The drama used was the play Should’ve, written by Nobel laureate Roald Hoffmann. The data was derived from students’ written responses, audio and video recordings, and written field notes. This investigation provides evidence that an approach combining drama and argumentation could increase students’ awareness of the relevance of ethics in science as one of the features of science (FOS). The findings show that the play Should’ve can be useful for promoting students’ argumentation and is also appropriate for medical students. Future studies could include other science disciplines (e.g., astronomy, biology, chemistry, earth science, ecology, physics); students of other ages; and other plays and experiments in other parts of the world.     

Los espacios recreativos a principios del siglo XX en la capital argentina. Problemas,tensiones y pugnas sobre los múltiples sentidos de la diferencia sexual

RESUMEN

En las primeras décadas del siglo XX un conjunto de actores y grupos sociales percibieron la necesidad de construir espacios complementarios y, en algunos casos, alternativos al formato escolar estatalizado que estaba en pleno crecimiento. Entre los espacios pensados para transmitir e imponer ciertos tópicos, se destacaron los recreos infantiles. Más allá de las fuertes disputas ideológicas y políticas acaecidas en las primeras décadas del siglo XX en la Argentina, hubo un fuerte consenso sobre la necesidad de disponer de espacios recreativos para la población infantil. Sin embargo, los fines, los sentidos y los significados puestos en circulación entraron rápidamente en colisión dependiendo del grupo social de origen, de la ideología profesada y de la forma de concebir “lo político”. Grupos de socialistas, anarquistas y de diferentes congregaciones religiosas (por ejemplo, salesianas) implementaron recreos infantiles en la Argentina. Estos espacios de sociabilidad pusieron en circulación una serie de sentidos y significados sobre diferentes tópicos, entre ellos la “cuestión sexual”. El siguiente artículo indaga los significados que se produjeron, transmitieron y circularon en relación a la diferencia sexual, a la feminidad y a la masculinidad.     

Modelling mathematical argumentation: the importance of qualification

In recent years several mathematics education researchers have attempted to analyse students’ arguments using a restricted form of Toulmin’s [The Uses of Argument, Cambridge University Press, UK, 1958] argumentation scheme. In this paper we report data from task-based interviews conducted with highly talented postgraduate mathematics students, and argue that a superior categorisation of genuine mathematical argumentation is provided by the use of Toulmin’s full scheme. In particular, we suggest that modal qualifiers play an important and previously unrecognised role in mathematical argumentation, and that one of the goals of instruction should be to develop students’ abilities to appropriately match up warrant-types with modal qualifiers.     

The introduction of infinite durability to an information good and the decision to buy or rent: evidence from the film industry

Home entertainment markets have seen dramatic declines in revenues over the last 10 years due to the digital revolution, making new adaptation strategies of crucial importance to maintaining existing profitability. Recently, the film industry has worked with related firms to develop a standardized ecosystem for the sale and access to digital versions of their films. This system, known as UltraViolet, embodies infinite durability; the perpetual access to a purchased film across computing platforms and time. The author makes use of exogenous variation in the implementation of this system to study the effect the introduction of this new feature has had on the decision to buy or rent. His findings show that the inclusion of infinite durability creates enough value to spur increased purchasing behavior. Also, the inclusion of infinite durability creates a high degree of substitutability amongst products that include it in purchase markets. Lastly, the author found evidence that the lack of inclusion of infinite durability will spur consumers to rent rather than buy.