Stress intensity factors under combined bending and torsion moments

This paper discusses stress intensity factor (SIF) calculations for surface cracks in round bars subjected to combined torsion and bending loadings. Different crack aspect ratios, a/b, ranging from 0.0 to 1.2 and relative crack depths, a/D, ranging from 0.1 to 0.6 were considered. Since the loading was non-symmetrical for torsion loadings, a whole finite element model was constructed. Then, the individual and combined bending and torsion loadings were remotely applied to the model. The equivalent SIF method, F*_EQ, was then used explicitly to combine the individual SIFs from the bending and torsion loadings. A comparison was then carried out with the combined SIF, F*_FE, obtained using the finite element analysis (FEA) under similar loadings. It was found that the equivalent SIF method successfully predicted the combined SIF for Mode I. However, discrepancies between the results determined from the different approaches occurred when F _III was involved. It was also noted that the predicted F*_FE using FEA was higher than the F*_EQ predicted through the equivalent SIF method due to the difference in crack face interactions.     

Cycle performance studies on a new HFC-161/125/143a mixture as an alternative refrigerant to R404A

In this paper, a new ternary non-azeotropic mixture of HFC-161/125/143a (0.15/0.45/0.40 in mass fraction), as a promising mixed refrigerant to R404A, is presented. The ozone depletion potential (ODP) of the new refrigerant is zero and its basic thermodynamic properties are similar to those of R404A, but its global warming potential (GWP) is much smaller than those of R507A and R404A. Meanwhile, theoretical calculations show that, under the working condition I (the average evaporation temperature: −23 °C, the average condensing temperature: 43 °C, the superheat temperature: 28 °C, the subcooling temperature: 5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.33% and 15.48% higher, respectively, than those of R404A. The coefficient of performance (COP) of the new mixture is 5.19% higher than that of R404A and the pressure ratio of the new mixture is 0.82% lower than that of R404A. Equally, under the working condition II (the average evaporation temperature: −40 °C, the average condensing temperature: 35 °C, the superheating temperature: 30 °C, the subcooling temperature: 5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.24% and 20.58% higher, respectively, than those of R404A. The COP of the new mixture is 4.60% higher than that of R404A and the pressure ratio of the new mixture is similar to that of R404A. The performances of the new mixture and R404A are compared in a vapor compressor refrigeration apparatus originally designed for R404A under several working conditions (condensing temperatures: 35–45 °C, evaporation temperatures: −40–−20 °C). Experimental results show that the new mixture can obtain a higher COP, by 6.3% to 12.1%, and a lower pressure ratio, by 1.8% to 6.6%, compared to R404A; although the discharge temperature of the new mixture is slightly higher than that of R404A. The advantages of the new mixture will be further verified in the actual system.     

Policy learning to internationalize European science: possibilities and limitations of open coordination

Mutual learning exercises have become increasingly employed in Europe over the last decade. This study examines the policy learning process in the area of internationalization of science and technology, which has been targeted as a priority for Europe. Through a case study of the open method of coordination expert group in this area, the analysis identifies policy learning drivers, mechanisms and outcomes operating at multiple levels, from individual to organizational. Different theoretical perspectives are employed to analyze the findings, highlighting both the social and instrumental aspects of policy learning. Using multiple conceptual approaches helps account for important contributions as well as limitations of open coordination for the internationalization of science and technology agenda in Europe.     

Teachers' self-esteem and self-efficacy

A web-based questionnaire was sent to all elementary and middle school teachers in Iceland. The population list, with e-mail addresses, was obtained from the teaching union. The teachers were asked to indicate their major, as well as their experience in teaching Icelandic as classroom teachers or subject teachers. They then rated their competence in teaching Icelandic on a scale from 1–10. Responses were received from 1033 elementary and middle school teachers. Of all teachers, 83.9% had taught Icelandic as classroom teachers and 37.3% had taught Icelandic as subject teachers. All teachers rated their competence as high. Statistically, Icelandic majors and older teachers were significantly more efficacious than others in teaching Icelandic. Those with the lowest competence ratings in teaching Icelandic were sports and home studies majors. However, teachers from all majors had taught Icelandic as classroom teachers, and a significant number of them had taught Icelandic as a subject.     

Waves of (Dis)Satisfaction: Effects of the Numerus Clausus system in Portugal

Access to higher education in Portugal is governed by a quota system (numerus clausus). The purpose of this article is to answer two questions: First, how does the numerus clausus system shape the demand for medical studies? Second, how do non-enrolled medical candidates influence the global allocation system and generate waves of dissatisfaction? The results show that students who do not succeed in entering medicine register in other programmes, such as pharmacy, veterinary medicine and dental studies, generating a first wave of dissatisfaction. Because students who are not placed in medicine occupy a large share of the places available in those other programmes, the wave of dissatisfaction propagates, with students being pushed to other programmes, especially biology and biochemistry. This process has also been analysed from a spatial perspective. Apparently, when students are competing to obtain a study place in a programme with prestige and good professional career perspectives such as medicine moving to a more peripheral region becomes more frequent.     

Children’s Models about Colours in Nahuatl-Speaking Communities

This paper presents the development and structure of indigenous children’s ideas about mixing colours as well as their ideas about each colour, derived from their traditions. The children were interviewed both at school and outside it, and an educational proposal was implemented. Ideas expressed in the school context were analysed using the partial possible model, which states that the inferences and explanations used to describe a subject consist of constricting ideas, rules of correspondence, and a set of phenomenological inferences about processes. After identifying these components in the children’s ideas, we developed models to describe their conceptions about mixing colours. We employed a different approach to analyse children’s ideas related to their cultural context. The results showed that children change from a conception that focuses on colours as entities that do not change and as properties of objects (model 1) to the idea that colour represents a quality of substances or objects that can be modified by mixing colours (model 2). Cultural context analysis showed that stories are independent from one another and that they are not connected to colour mixing processes, only to the actions of colour on people. We concluded that students generate independent constructions between school and cultural knowledge.     

Are teachers’ approaches to teaching responsive to individual student variation? A two-level structural equation modeling

In the framework of teacher’s approaches to teaching, this study investigates the relationship between student-related variables (i.e., study time, class absence, domain knowledge, and homework completion), students’ approaches to learning, and teachers’ approaches to teaching using structural equation modeling (SEM) with two independent data samples. The participants were 61 biology teachers and their corresponding 1,518 high school students (12th grade). The first sample was used to fit the model, and the second sample was used to analyze the consistency of the data derived from the first sample. Using a two-level SEM analysis, we established whether the effects found at the individual level varied significantly at class level. The students’ approaches to learning were related to the teachers’ approaches to teaching as a function of the hypotheses established in the model, although the effect size was smaller than expected. However, approximately 48 % of the variance of the surface approach and 46 % of the deep approach sat at class level. At the individual level, the results of this study suggest that students’ approaches to learning significantly explain their teachers’ approaches to teaching and, thus, constitute important contextual variables. At the class level, the way students learn appears to be closely associated with class-related variables. Our data stresses the importance of promoting educational opportunities (e.g., school-based courses) for teachers to reflect upon the teaching methodologies used in class.     

Founders’ Continuing Roles in Schools Supporting Self-Directed Learning

What should be the continuing role of founders in schools supporting self-directed learning? To answer this, the founders’ views of two North American schools for self-directed learners will be compared. One school is exam-focused and private; the other is, test-free and public. The founders of both schools have comparable beliefs regarding the importance of self-direction in education: Dr. Able, the founder of Able School, sees the primary value of the school as constructing a cohesive “tribe” based on the Socratic method of questioning. Dr. Green, influenced by A. S. Neill’s Summerhill in founding Unschool, considers freedom to live life as one chooses as the principle value. Although both founders played a substantial role in the formative years of their schools, only the founder of Able School still holds a prominent position in the school. Why does this discrepancy exist in the continuing role of the founders? What continuing role for a founder is most compatible with democratic society? The answers to these questions provided in this paper are based on personal communications with Dr. Green after a visit this founder of Unschool made to Able School December 12, 2013 to meet with Dr. Able. The names of the founders and their schools are pseudonyms.     

Incompatibility between pregnancy and educational projects,from the perspective of socially vulnerable adolescent women and men in Mexico

Research focused on adolescent pregnancy reports that this event acquires significance and has different consequences according to the context and social subjects who experience it. In this study, by means of a sample formed by adolescent women and men who are socially vulnerable in Mexico, with and without a history of pregnancy, we can see how this reproductive event turns into a factor of educational vulnerability and how their possibilities and expectations with respect to continuing in school are determined in a differentiated manner, according to gender. The findings show that adolescent pregnancy in vulnerable sectors is scarcely compatible with educational projects and that possibilities and expectations to continue in or re-enter the school system are determined by gender differences; these usually lead to fewer opportunities for adolescent women to return to school during or after pregnancy.