Diagnosing Students’ Understanding of the Nature of Models

Students’ understanding of models in science has been subject to a number of investigations. The instruments the researchers used are suitable for educational research but, due to their complexity, cannot be employed directly by teachers. This article presents forced choice (FC) tasks, which, assembled as a diagnostic instrument, are supposed to measure students’ understanding of the nature of models efficiently, while being sensitive enough to detect differences between individuals. In order to evaluate if the diagnostic instrument is suitable for its intended use, we propose an approach that complies with the demand to integrate students’ responses to the tasks into the validation process. Evidence for validity was gathered based on relations to other variables and on students’ response processes. Students’ understanding of the nature of models was assessed using three methods: FC tasks, open-ended tasks and interviews (N?=?448). Furthermore, concurrent think-aloud protocols (N?=?30) were performed. The results suggest that the method and the age of the students have an effect on their understanding of the nature of models. A good understanding of the FC tasks as well as a convergence in the findings across the three methods was documented for grades eleven and twelve. This indicates that teachers can use the diagnostic instrument for an efficient and, at the same time, valid diagnosis for this group. Finally, the findings of this article may provide a possible explanation for alternative findings from previous studies as a result of specific methods that were used.     

Residual stress analysis and bow simulation of crystalline silicon solar cells

The pressure to reduce solar energy costs encourages efforts to reduce the thickness of silicon wafers. Thus, the cell bowing problem associated with the use of thin wafers has become increasingly important, as it can lead to the cracking of cells and thus to high yield losses. In this paper, a systematic approach for simulating the cell bowing induced by the firing process is presented. This approach consists of three processes: (1) the material properties are determined using a nanoidentation test; (2) the thicknesses of aluminum (Al) paste and silver (Ag) busbars and fingers are measured using scanning electron microscopy; (3) non-linear finite element analysis (FEA) is used for simulating the cell bowing induced by the firing process. As a result, the bowing obtained using FEA simulation agrees better with the experimental data than that using the bowing calculations suggested in literature. In addition, the total in-plane residual stress state in the wafer/cell due to the firing process can be determined using the FEA simulation. A detailed analysis of the firing-induced stress state in single crystalline silicon (sc-Si), cast, and edge-defined film-fed growth (EFG) multi-crystalline silicon wafers of different thicknesses is presented. Based on this analysis, a simple residual stress calculation is developed to estimate the maximum in-plane principal stress in the wafers. It is also proposed that the metallization pattern, Ag busbars and fingers screen printed on the front of a solar cell, can be designed using this approach. A practical case of a 3-busbar Si solar cell is presented.     

The Nature of Scientific Practice and Science Education

There is, broadly speaking, an agreement within the international science education community that comprehension of the nature of science (NOS) should be a key element in the scientific literacy of citizens. During the last few decades, several didactic approaches have emerged concerning what and how to teach NOS. Also, one of the basic objectives of science education is for students to become familiar with the skills typical of scientific practice; however, there is little reference to their need to also acquire meta-knowledge about scientific practice (i.e., an understanding of the nature of scientific practice). Among other reasons, this may be due to NOS being essentially identified in most of the predominant proposals with the nature of scientific knowledge. But why not plan the teaching of science to be in tune with real scientific practice for students to learn about the nature of scientific practice at the same time as they are learning science? The answer to this question has given rise to a proposal grounded in ten essential pedagogical principles for the teaching and learning of science in secondary school. These are the principle of formulating questions, the principle of creativity and imagination, the principle of experimentation, the principle of procedural diversity, the principle of errors as opportunity, the principle of modeling, the principle of cooperation and teamwork, the principle of argumentation and discussion, the principle of communication, and the principle of evaluation. The purpose of this article is to present the justification and fundaments of these principles.     

Investigating further preservice teachers’ conceptions of multidigit whole numbers: refining a framework

This study was designed to investigate preservice elementary school teachers’ (PSTs’) responses to written standard place-value-operation tasks (addition and subtraction). Previous research established that PSTs can often perform but not explain algorithms and provided a four-category framework for PSTs’ conceptions, two correct and two incorrect. Previous findings are replicated for PSTs toward the end of their college careers, and two conceptions are further analyzed to yield three categories of incorrect views of regrouped digits: (a) consistently as 1 value (all as 1 or all as 10), (b) consistently within but not across contexts (i.e., all as 10 in addition but all as 1 in subtraction), and (c) inconsistently (depending on the task).     

Seismic force modification factor for ductile structures

INTRODUCTION In codes for seismic design of buildings of many developed countries, elastic response spectra are adopted to calculate the base shear forces. For exam-ple, the base shear defined in Japan code 1997 is: FEK=DsFesC0ZAiRtW (1) where Rt is the elastic design spectrum; Ds is the structural coefficient changing among 0.25 to 0.50 to take account of different ductility of different struc-tures; W is the total weight of a structure; the others are site coefficient, irregular…     

Teacher professional development through digital content evaluation

In this study, researchers designed and implemented a 1-year professional development (PD) program that focused on supporting teachers in evaluating and selecting digital learning contents. Participants in this investigation included 109 teachers who consented to the study amongst a total of 171 teachers from five school districts across central Ohio. In addition to their participation in the PD program, they completed surveys, interviews, and self-reflections in this mixed-method study. The results revealed that teachers’ perceived TPACK increased over time throughout the PD program, suggesting that training teachers to evaluate digital contents can be an effective PD model to improve teachers’ capacity in learning technology integration. The PD program was especially effective for teachers with less prior experience in technology integration or related training. Mathematics teachers, in comparison to teachers from other disciplines, began with low TPACK; however, these initial differences gradually diminished over the course of the PD program. In terms of their motivation in digital content evaluation, teachers’ expectancy for success increased significantly while their task values remained medium high. The qualitative analyses provided additional insights and revealed design suggestions for success in future PDs.     

Teacher management and educational reforms: Paradigm shifts

In the past 15 years, numerous reforms and initiatives in many countries in the Asia-Pacific region have aimed to change education and promote new learning to prepare the new generation for the future. Unfortunately, despite good intentions and huge investments of resources, many of these reforms have been found to be ineffective and unsustainable—if they succeed at all. Reflecting on the trends and waves of educational reform in the Asia-Pacific region, this paper introduces an international lesson on the emerging syndrome of educational reform across the region and illustrates its negative impacts on teacher ecology and teacher management. Then, the paper outlines the implications of this lesson and of a study of the world’s best-performing educational systems, using them to develop a holistic approach to managing teachers and planning for their sustainable professional development. Finally, it highlights the paradigm shifts in teacher management, reviewing the three waves of educational reform in the last two decades, and draws further implications for formulating teacher management policies in ongoing and future educational reforms to support students’ new learning and sustainable development.