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.     

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.     

Tweet Up? Examining Twitter's Impact on Social Capital and Digital Citizenship in Higher Education

Twitter is a highly accessible communication venue that is embraced by great numbers of traditionally aged and ethnically diverse college students. Danielle Morgan Acosta challenges us to turn our research and teaching attention to the potential of Twitter to support student learning.     

Simulating Oppression: Digital Gaming,Race and the Education of African American Children

Educational game designers and educators are using digital games as a platform for teaching academic content, including multicultural curriculum. However, it is unclear how well digital game-based learning can coexist with the goals of multicultural education for the purpose of meeting the needs of African American children. In this essay, we raise serious questions about the use of digital games to teach about social oppression in ways that privilege the psychological well-being of African American children. We argue that digital games that intend to recreate histories of racial oppression can be harmful to African American children if they reproduce popular and problematic notions of indigenous lives and experiences. We illuminate some of the dangers of such digital games through a preliminary exploration of one digital game designed to teach about facets of African American enslavement. Our essay concludes with recommendations for culturally relevant digital game-based learning design and instruction.     

Mental attention in gifted and nongifted children

The relationship between the construct of mental attention and “giftedness” is not well established. Gifted individuals could make effective use of their executive functions and this could be related to their mental attentional capacity. The dialectic constructivist model developed by Pascual-Leone introduced the concept of mental attention or “effort”, relating it to mental capacity. The aim of this study is to investigate whether the measurement of mental capacity (M-measurement) is differential for a group of children with high IQs. 110 students between 4 and 18 years old participated in this study. Some were Gifted (n=70) and others Non-Gifted (n=40). Wechsler-R Scale and the Figural Intersection Test were administered to all participants. An interesting pattern was found in the younger groups. The gifted scored higher than the non-gifted in the Figural Intersection Test and much higher than their theoretical M. The non-gifted scored quite close to their theoretical M (based on age). In the oldest group, the gifted again achieved higher scores, but now they scored at the theoretical level, and the non-gifted underperformed.     

Negotiating diversity: an empirical investigation into family,school and student factors influencing New Zealand adolescents’ science literacy

The purpose of this study was to examine a factor triad consisting of family, school and student variables contributing to New Zealand adolescents’ science literacy performance on Programme for International Student Assessment 2006. Results indicated that the selected variables in our study explained 25% of total differences in New Zealand students’ science achievement. Family socio-economic status (SES) as well as adolescents’ motivation to learn science and general value of science were influential factors in students’ science achievement. Findings also revealed a statistically significant interaction effect between SES and first-generation immigrant students but not between SES and second-generation immigrant students. Although parents’ perception of general value of science showed a positive effect on adolescents’ scientific performance, its predictive power was relatively weak.     

Shared academic values: testing a model of the association between Hong Kong parents’ and adolescents’ perception of the general value of science and scientific literacy

This study investigated parent general value of science operationalized in the 2006 questionnaire of the Programme for International Student Assessment (PISA), as a determinant of adolescents’ scientific literacy performance. The transmission of academic values literature is small. To the best of our knowledge, no previous studies to date have examined the transmission of valuing of science. Study data were drawn from PISA 2006, which focused on science. The study sample comprised 4645 15-year-old adolescents in Hong Kong. Results from the conceptual structural model indicated that parental academic values (general value of science): (a) positively and directly affected adolescents’ valuing of science and in turn further influenced adolescents’ science performance, (b) positively and directly affected adolescents’ science performance, and (c) stimulated adolescents’ motivation to study science and in turn further influenced their science performance. Implications for school-level policy and practice include: (a) promoting parental valuing of science via parent involvement and (b) producing culturally and contextually grounded evidence on strategies for enhancing the transmission of academic values using research methodologies such as action research.     

Hints for the improvement of quality teaching in introductory engineering statistics courses

In recent years there has been a spectacular increase in concern within society about problems of service and, in particular, that of university teaching. Teaching quality can be understood as a goal to be achieved in three nurtured phases: course planning; the adoption of a methodological approach; and the evaluation of the results. The teaching of statistics in engineering schools raises common problems as well as certain others specific to each qualification. In this article, proposals are made about how to improve the quality of teaching of statistics to undergraduate engineering students.     

A microfluidic device to study cancer metastasis under chronic and intermittent hypoxia

Metastatic cancer cells must traverse a microenvironment ranging from extremely hypoxic, within the tumor, to highly oxygenated, within the host''s vasculature. Tumor hypoxia can be further characterized by regions of both chronic and intermittent hypoxia. We present the design and characterization of a microfluidic device that can simultaneously mimic the oxygenation conditions observed within the tumor and model the cell migration and intravasation processes. This device can generate spatial oxygen gradients of chronic hypoxia and produce dynamically changing hypoxic microenvironments in long-term culture of cancer cells.