High-gain fractional disturbance observer control of uncertain dynamical systems

Disturbance observer-based control allows to compensate unknown inputs, however, in most cases, requiring their integer-order differentiability. In this paper, a novel disturbance observer-based state feedback controller is proposed to compensate a more general class of fractional-, but not necessarily integer-order, differentiable unknown inputs. The proposed fractional PI-like structure yields precise conditions for feedback gain tuning. Remarkably, the resulting controller rejects non-differentiable disturbances with a smooth controller, guaranteeing robustness, an outstanding features for tracking tasks, under a prescribed practical stability regimen. A comparison to a fractional sliding mode observer is conducted via simulations to highlight the reliability of the proposed scheme.     

An interdisciplinary and application-oriented approach to teach microfluidics

Microfluidics is a relatively novel interdisciplinary research area with broad applications in chemistry, physics, material science, and biology. Despite the rapid growth of the field, students'' exposure to microfluidic technologies is still limited and often insufficient to appreciate the advantages over other commonly used technologies. To this end, we designed a five-day course, “Microfluidics for microbial ecology,” in which students with very different backgrounds learn the basics of microfluidic technologies and sample a range of applications in microbial ecology. The course was created for Master and Ph.D. students interested in applying microfluidics to their research and, therefore, followed an application-oriented approach. The presentation of critical aspects of fluid flow phenomena at the microscale and an outline of the advantages and constraints of the technology provide students with the background to design and perform microfluidics-based experiments. In order to improve the effectiveness of learning in a class with diverse interests and backgrounds, two active learning exercises were implemented. The first comprised the design of an individualized microfluidics experiment in parallel with the lectures: students were guided to apply each module to their personalized application and discuss it in groups. The second was a group experimental activity, in which students jointly set up, performed, analyzed, and presented a microfluidics-based experiment. Given the multidisciplinary teaching context, the course was able to foster common conceptual ground and promote discussion among students. This application-oriented approach built upon experimental activities and in-class discussion is well suited to promote learning in a technology-related subject such as microfluidics.     

What do science teachers consider when selecting formative assessment tasks?

The purpose of this qualitative exploratory study was to identify factors that influenced prospective and experienced secondary level science teachers' reasoning as they evaluated or selected tasks to formatively assess their students' understanding of scientific concepts. The analysis of the coded written responses revealed two categories of factors that influenced the teachers' reasoning: (1) characteristics of the task and (2) characteristics of students or the curriculum. Characteristics of the task related to qualities of the task regardless of the learning environment in which it would be used, such as the level of student thinking demanded by a task. Characteristics of the students and the curriculum related to the learning environment in which an assessment task would be implemented, such as students' abilities to complete the task. Both prospective and experienced teachers' task evaluations were influenced by the same factors related to the characteristics of the task, although their interpretations of the meaning of each factor varied. In addition, experienced teachers' task evaluations were more likely than prospective teachers to be influenced by factors related to characteristics of students and the curriculum. The findings are discussed as a conceptual framework that presents the identified factors along three different dimensions: (1) the influence of task, student, and curriculum characteristics, (2) the influence of expectations for success, and (3) the influence of teaching experience. © 2008 Wiley Periodicals, Inc. J Res Sci Teach 45: 1113–1130, 2008     

Word problem solving approaches in mathematics textbooks: a comparison between Singapore and Spain

European Journal of Psychology of Education - Singaporean children are the best performers on international achievement tests in mathematics (i.e. the TIMSS). Their excellent results could be due...     

Contributions from the Philosophy of Science to the Education of Science Teachers

One of the most important topics on the international agenda in educational research is to gain an understanding of the processes of educational change in teachers and of the factors that favour or hinder it. Such understanding is, for instance, an essential element in planning and putting into practice initial and ongoing teacher education programs. This article reviews the research on science teachers’ educational change. To organize the information, an analogy is made with the process of scientific change, analyzing and evaluating the contributions of the different models taken from the philosophy of science – positivism, Popper’s principle of falsifiability, Lakatos’ scientific research programs, Laudan’s research traditions, Toulmin’s evolutionism, and Kuhn’s relativism. We conclude the article with the implications for science teacher education.     

A heterotopology of the academy: mapping assemblages as possibilised heterotopias

Heterotopias are counter-sites of enacted utopias through which reality is simultaneously represented, contested and inverted. They are physical or mental spaces where, although norms of behaviours are suspended, there are connections with a plethora of other spaces. This article constructs a collective biography as a heterotopology of the academy. Academic subjectivities are produced and often constrained within powerful Higher Education discourses. Constructing an affective assemblage of becomings as a heterotopology, the authors deploy poststructural philosophy to re-story academic life experiences and conceptualise agency in the academy. Taking licence with the notion of academicity and heterotopia, the article describes how spaces in the measured university can be deterritorialised through generative lines of flight. An affective assemblage is presented that ruptures the discursive orientation of category boundary work where academics are constituted as ‘productive metric-minded knowledge workers’. The collective biography research approach facilitates a mapping of affective cartographies as a heterotopology and a critique of the discursive production of selves. The subjectivations of identity politics in matricised assemblages may be, even if momentarily, evaded, refused and agentically resisted.     

Initiating running barefoot: Effects on muscle activation and impact accelerations in habitually rearfoot shod runners

Runners tend to shift from a rearfoot to a forefoot strike pattern when running barefoot. However, it is unclear how the first attempts at running barefoot affect habitually rearfoot shod runners. Due to the inconsistency of their recently adopted barefoot technique, a number of new barefoot-related running injuries are emerging among novice barefoot runners. The aim of this study was therefore to analyse the influence of three running conditions (natural barefoot [BF], barefoot with a forced rearfoot strike [BRS], and shod [SH]) on muscle activity and impact accelerations in habitually rearfoot shod runners. Twenty-two participants ran at 60% of their maximal aerobic speed while foot strike, tibial and head impact accelerations, and tibialis anterior (TA), peroneus longus (PL), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) muscle activity were registered. Only 68% of the runners adopted a non-rearfoot strike pattern during BF. Running BF led to a reduction of TA activity as well as to an increase of GL and GM activity compared to BRS and SH. Furthermore, BRS increased tibial peak acceleration, tibial magnitude and tibial acceleration rate compared to SH and BF. In conclusion, 32% of our runners showed a rearfoot strike pattern at the first attempts at running barefoot, which corresponds to a running style (BRS) that led to increased muscle activation and impact accelerations and thereby to a potentially higher risk of injury compared to running shod.