Natural surface design for sliding mode control with multiple discontinuous inputs

It is well known that sliding mode control is based on the definition of an invariant manifold, where the system dynamics are forced to in a finite time. Such a manifold is somewhat arbitrarily defined, as long as the system dynamics are stable on it. Computational and control effort may vary depending on selected manifold. Obviously, if a system has naturally acceptable stable dynamics around a desired equilibrium point, no control is needed unless uncertainties or disturbances are present. It would be desirable that if such a system had uncertainties or disturbances, the control effort be designed only to overcome the effect of such factors. For a system with first order dynamics and affine control input, designing a sliding mode control overcoming only such uncertainties or disturbances is a trivial task. When a higher order dynamics system is involved, unit control may be used, where the input control signals are not discontinuous, but when only discontinuous control inputs are available, a design approach is not readily available. In this paper, taking advantage of the natural stable dynamics of a system, a sliding mode control approach is introduced for designing multiple discontinuous control inputs, where the control effort overcomes only uncertainties, disturbances or unstable dynamics. Two illustrative examples are given in order to show the feasibility of the method.     

Accountability and the Framing Power of Visual Technologies: How Do Visualized Reconstructions of Incidents Influence Public and Political Accountability Discussions?

In this article visual technologies and their use in three reconstructions after an incident are linked with accountability issues. Conclusions are drawn on the relation between administration, the choice of technology to create and distribute visual occurrences, and society and how visualizations are used to frame accountability issues.     

How do your rivals’ releasing dates affect your box office?

In this paper, we study to what extent a movie’s box-office receipts are affected by the temporal distribution of rival films. We propose a reduced-form empirical model to measure and test competition effects among films released close to each other in a standard regression framework. Such an analysis is appealing in terms of its policy implication and may provide guidance to distributors to decide on their releasing dates of their firms. We estimate this model using information on the films released in five countries: the USA, the United Kingdom, Germany, France and Spain. The geographical dimension of our data set permits us to control for unobserved heterogeneity among films released using panel data techniques, which allows us to evaluate the individual and specific effects of each film. Thus we deal with one of the most relevant features of the movie market, namely the presence of highly differentiated products.     

Color characterization of roofing slates from the Iberian Peninsula for restoration purposes

Substitution of slate roofing tiles is a conventional operation during building restoration, since tiles are very difficult to restore or clean because of the high degree of alteration they suffer. Criteria for replacement of historical building stones must be based on geological, geotechnical and esthetic parameters, among which color is of great importance. In this sense, this paper constitutes a comprehensive and useful colorimetric study of roofing slates from the Iberian Peninsula, for the purposes of restoration. The color of 50 commercial varieties of roofing slate mined in quarries from the 12 mining districts in the Iberian Peninsula was analyzed with a spectrophotometer device, by considering the CIELAB color space. The results of the study were used to develop a protocol for characterizing the color of roofing slate and to define the color range of roofing slate from the Iberian Peninsula. In addition, the similarities and differences in the color and microstructure of the different commercial varieties of Iberian roofing slate were established and the limit of acceptability of replacement of one type of slate by another was determined. Parameter h_ab was found to be the most important CIELAB color coordinate as regards the formation of homogeneous color groups, and the specular component excluded (SCE) mode was most sensitive as regards detecting color differences between two samples.     

From shanzhai chic to Gangnam style: seven practices of cultural-economic mediation in China and Korea

ABSTRACT

This paper examines the social construction of ‘fashionability’ – namely, what is ‘desirable’ and ‘fashionable’ – with reference to the concept ‘cultural mediators’ that foregrounds agency, negotiation and the contested practices of market actors in cultural production. It zeroes in on the cultural mediators’ attitudes and positions in the two markets by drawing on 25 in-depth interviews with industry veterans. It shows that the mediators in South Korea and China increasingly occupy hybrid occupational roles and social positions across industries and sectors yet achieve limited success in countering the status quo of Western fashion through mediation. The analysis contributes to the literature with a categorisation of seven mediation practices that shape the valuation of fashion products (i.e. ‘fashionability’) in two ways. Empirically, this categorisation illuminates how cultural mediators make reference habitually to the broader social and cultural contexts to co-construct cultural-aesthetic objects. Theoretically, it advances a cultural-economic approach to the understanding of cultural mediation and challenges the reductionist viewpoint of actor–network theory through the notion of a matrix of cultural-economic agency.     

Can public arts education replace arts subsidization?

The debate about whether the arts should be supported or not is far from new, and most governments support the arts in one way or the other. The literature considers several arguments in favor of such interventions. Public education may seem to be an action which could, in the long run, lead to possible reductions of subsidies. Surveys show that those who have been exposed to the arts when young participate more when adult. However, the “non-market” transmission from parents to children generates an external effect, which has to be taken into account to reach first-best situations. We construct an overlapping generations model in which young consumers are exposed to both public education toward the arts and to non-altruistic transmission of such a taste from their parents. We show that the first-best can be reached only if there is both public cultural education and subsidization of arts consumption. Therefore, education cannot be considered as a substitute for subsidies to arts consumption. However, as is often the case in European countries, government intervention is usually below the first-best level. Using a model calibrated on French data, we show that it is then preferable to subsidize education, while consumption, especially of the older generations, should be taxed rather than subsidized.

Mathematics achievement and mathematics learning strategies: Cognitive competencies and construct differentiation

Responding to a survey requires cognitive abilities similar to those for any other linguistic task. We argue that, when faced with a cognitively challenging task, individuals respond by simplifying the task, declining it, or performing it poorly. Using the 2003 Program for International Student Assessment (PISA 2003) data sets, we document that the extent of construct differentiation in students’ mathematics learning strategies is strongly associated with their level of mathematics achievement. Likewise, the higher the level of mathematics achievement, the lower is the probability of a non-response to the mathematics learning strategy questions. Finally, the higher the students’ level of mathematics achievement, the more varied were their responses to the learning strategies items. These associations were examined across 40 participating countries.     

Application of a lexical-semantic intervention programme for students with Specific Language Impairment / Aplicación de un programa de intervención léxico-semántica en alumnado con Trastorno Específico del Lenguaje

The aim of this research has been to test the efficacy of an intervention programme on lexical-semantic problems in children with Specific Language Impairment (SLI). The sample consisted of 34 children diagnosed with SLI and 34 children with typical language development, all enrolled in different schools on the island of Tenerife (Canary Islands, Spain). For the selection of the sample, CELF-3, Peabody, ITPA Auditory Association and Visual Association subtests and the K-BIT IQ tests were used. The intervention programme consisted of 72 sessions of 30 minutes each, using noun and action naming activities along with conversation and categorization tasks in order to increase vocabulary and improve lexical semantic competence. Significant results were achieved in aspects related to the acquisition of vocabulary as well as in lexical semantics or related terms. The educational implications are clear insofar as lexical-semantic aspects are key in terms of activating other linguistic components and in improving the academic progress of SLI students.