The Analysis of Students’ Conceptions as a Support for Designing a Teaching/Learning Sequence on the Acoustic Properties of Materials

We believe that finding out how students think about certain topics that are covered in science classes should not be ??the end of the story?? but the starting point for planning lessons and designing materials. From this perspective, the research study presented here is intended to explore secondary school (15?C18?year old) students?? preconceptions of sound attenuation, and of the properties and internal structure of materials. Specifically, we analysed students?? explanations for the fact that some materials attenuate sound more than others. This study was conducted within a particular scenario, in which 72 students participated in laboratory sessions aimed at developing students?? understanding of the nature, propagation and attenuation of sound. From the analysis of students?? explanations, we could identify some conceptions of sound attenuation in materials (e.g. as a result of hindering the entrance of sound, or as a result of capturing sound). The results of this study also indicate that the role of properties of a material and the role of the internal structure that students associate with its acoustic behaviour depend on their conceptions of sound attenuation. We used these results as support for the design of a research-based teaching/learning sequence on the Acoustic Properties of Materials, which is intended to facilitate students?? overcoming the specific conceptual difficulties identified in this research study and promote students?? development of conceptual models of sound attenuation.     

Numerical study of dc-biased ac-electrokinetic flow over symmetrical electrodes

This paper presents a numerical study of DC-biased AC-electrokinetic (DC-biased ACEK) flow over a pair of symmetrical electrodes. The flow mechanism is based on a transverse conductivity gradient created through incipient Faradaic reactions occurring at the electrodes when a DC-bias is applied. The DC biased AC electric field acting on this gradient generates a fluid flow in the form of vortexes. To understand more in depth the DC-biased ACEK flow mechanism, a phenomenological model is developed to study the effects of voltage, conductivity ratio, channel width, depth, and aspect ratio on the induced flow characteristics. It was found that flow velocity on the order of mm/s can be produced at higher voltage and conductivity ratio. Such rapid flow velocity is one of the highest reported in microsystems technology using electrokinetics.     

Cognitive,Motivational, and Volitional Dimensions of Learning: An Empirical Test of a Hypothetical Model

The principal aim of this research is to contrast empirically a hypothetical model developed on the basis of the fundamental assumptions of current self-regulated learning models. In line with evaluation criteria of model fit, a high rate of congruence between the hypothesized theoretical model and the empirical data was observed. Analysis of the effects between the variables of the model revealed the following relevant aspects: students' predisposition to feel responsible for the results of their academic behavior (internal attribution) is related to positive self-image (academic self-concept), both being important conditions for development of learning-oriented motivation (learning goals). All of this involves selection and use of learning strategies for deep information processing (deep learning strategies), which leads students to assume responsibility with high levels of persistence, perseverance, and tenacity so as to achieve goals defined by the motivational orientation. This persistence and effort to achieve the proposed goals has in turn a positive and significant effect on academic achievement.     

Detection of Misconceptions about Colour and an Experimentally Tested Proposal to Combat them

We study the misconceptions about colour that most people hold, determining the general phenomenological laws that govern them. Concept mapping was used to combat the misconceptions which were found in the application of a test specifically designed to determine these misconceptions, while avoiding the possible misleading inductions that could have arisen from the use of everyday language. In particular, care was taken to avoid the distorting effect that the use of the verb ‘to be’ applied to coloured objects could have on the responses. The misconceptions found were shown to have an internal consistency in the form of authentic mini-theories (implicit theories). We compared experimentally the results of two different teaching methods applied to combat these misconceptions. This study was conducted with 470 undergraduates of the University of Extremadura. We analysed the persistence over time of their learning made to overcome those misconceptions. The students were divided randomly into an experimental group (EG) and a control group (CG). To combat their misconceptions, EG were taught following a method based on the use of concept maps, and CG were taught following traditional teaching methods. The results of a pre-test and a post-test were compared for the two groups, finding statistically significant differences. The results allowed the principal working hypothesis to be accepted—concept maps are learning tools which foster conceptual change and allow misconceptions to be eradicated via meaningful learning maintained over time, i.e. EG acquired a relative long-lasting gain in learning that was superior to that acquired by CG.