Articulation of Conceptual Knowledge and Argumentation Practices by High School Students in Evolution Problems

The oral arguments of 12th grade students while solving tasks related to evolution are examined. Two groups (N = 45), taught by the same teacher, were studied during a complete teaching sequence. The paper focuses on data from the last sessions, devoted to solving problems in small groups, problems related to different dimensions of the evolutionary model. Data include video recordings, the students’ written productions and the researcher (first author) field notes. The objective is to examine the process of articulation of students’ argumentation practices with their use of evolutionary models. The results show that participants were able to apply notions such as common ancestors, radiation, or gradualism to different contexts. The arguments required the articulation of evolution notions with argumentative practices as coordinating evidence with claims at different epistemic levels. The influence of the teacher’s strategies in the students’ role is discussed.     

Personalizing and Contextualizing Multimedia Case Methods in University-based Teacher Education: An Important Modification for Promoting Technological Design in School Science

Results of various studies suggest that multimedia ‘case methods’ (activities associated with case documentaries) have many benefits in university-based teacher education contexts. They can, for example, help to ‘bridge the gap’ between perspectives and practices held by academic teacher educators and those held by student-teachers – who may adhere to perspectives and practices commonly supported in schools. On the other hand, some studies, along with theoretical arguments, suggest that there are limits to the effectiveness of multimedia case methods – because, for example, they can never fully represent realities of teaching and learning in schools. Furthermore, often missing from multimedia case methods is the student-teacher in the role of teacher. To address these concerns, we modified an existing multimedia case method by associating it with a special practice teaching situation in a school context. Qualitative data analyzed using constant comparative methods suggest that student-teachers engaged in this modified multimedia case method developed relatively deep commitments to encouraging students to conduct technology design projects – a non-traditional practice in school science. Factors that appeared to influence development of this motivation included student-teachers’ pre-instructional perspectives about science and the personalization and contextualization inherent to the modified multimedia case method.

How do secondary students approach different types of division with remainder situations? Some evidence from Spain

Division-With-Remainder (DWR) problems are particularly complex, as suggested in many studies. The purpose of this work was to establish whether students’ difficulties in DWR problems came from an inadequate initial representation or from an inadequate final interpretation of the numerical answers, and whether remainders could be grouped into two blocks depending on the kind of answer, either directly matching the terms of the division or not. Forty-five Spanish secondary students, aged 12–13, were requested to solve two Types of Division Situations (i.e., Equal Groups and Comparison), each one involving four Types of Remainder (i.e., Remainder-Not-Divisible, Remainder-Divisible, Remainder-as-the-Result, and Readjusted-Quotient-by-Partial-Increments). Our data showed that: (a) the selection of the correct solution procedure depended on the Type of Division Situations, being easier in Equal Groups than in Comparison problems; (b) correct interpretations were higher than the percentages reported in other researches; and (c) success in problems whose answers were the quotient or the remainder was higher than in Readjusted-Quotient-by-Partial-Increments problems. The results obtained suggest that students’ difficulties originate in the initial representation of the DWR problems and that it would be more adequate to refer to the difficulty of Readjusted-Quotient-by-Partial-Increments problems in particular, rather than to the difficulty of DWR problems in general.     

A Case Study of Relationships between Organizational Culture and Curricular Change in Engineering Education

We examined two curricular change efforts at a small, midwestern engineering and science college in order to explore how organizational culture influences curricular change processes. We found that the failure of one effort (measured by inability to sustain the curriculum over time) and the success of the other (the curriculum continues to be offered by the institution) were directly linked to how well the change strategies aligned with the culture of the institution.     

Adaptive control of bi-directionally coupled Lorenz systems with uncertainties

The bi-directionally coupled Lorenz systems are linked to the modeling of a coupled double loop thermosyphon system where the mass momentum and heat exchange are both considered. As the key parameters of the system, known as Rayleigh numbers, increase, the system of differential equations predicts typical flow dynamics in a thermosyphon from heat conduction to time-dependent chaos. In many applications including the thermosyphon systems, there are uncertainties associated with mathematical models such as unmodeled dynamics and parameter variations. Also, under the high heat environment for a thermosyphon, there exist external disturbances quantitatively linked to the Rayleigh numbers. All these sources constitute uncertainties to the dynamical system. Our objective is to design adaptive controllers to stabilize the chaotic flow in each thermosyphon loop with unknown system parameters and existence of uncertainties. The controllers consist of a proportional controller with an adaptive gain and a wavelet network that reconstructs the unknown functions representing the uncertainties. Explicit stability bounds and adaptive laws for the control parameters are obtained so that the coupled Lorenz systems are globally stabilized.     

Widely linear estimation for multisensor quaternion systems with mixed uncertainties in the observations

The optimal widely linear state estimation problem for quaternion systems with multiple sensors and mixed uncertainties in the observations is solved in a unified framework. For that, we devise a unified model to describe the mixed uncertainties of sensor delays, packet dropouts and uncertain observations by using three Bernoulli distributed quaternion random processes. The proposed model is valid for linear discrete-time quaternion stochastic systems measured by multiple sensors and it allows us to provide filtering, prediction and smoothing algorithms for estimating the quaternion state through a widely linear processing. Simulation results are employed to show the superior performance of such algorithms in comparison to standard widely linear methods when mixed uncertainties are present in the observations.