Lumped parameter model for resonant frequency estimation of a thermoacoustic engine with gas-liquid coupling oscillation

Gas-liquid coupling oscillation is a novel approach to reducing the resonant frequency and to elevating the pressure amplitude of a thermoacoustic engine. If a thermoacoustic engine is used to drive low-frequency pulse tube refrigerators, the frequency matching between the thermoacoustic engine and the refrigerator plays an important role. Based on an acoustic-electric analogy, a lumped parameter model is proposed to estimate the resonant frequency of a standing-wave thermoacoustic engine with gas-liquid coupling oscillation. Furthermore, a simplified lumped parameter model is also developed to reduce the computation complexity. The resonant frequency dependence on the mean pressure, the gas space volume, and the water column length is computed and analyzed. The impact of different working gases on the resonant frequency is also discussed. The effectiveness of the models is validated by comparing the computed results with the experimental data of the gas-liquid coupling oscillation system. An increase in the mean working pressure can lead to a rise in the resonant frequency, and a lower resonant frequency can be achieved by elongating the liquid column. In comparison with nitrogen and argon, carbon dioxide can realize a lower frequency due to a smaller specific heat ratio.     

Towards an understanding of the role of language in the science classroom and its association with cultural identity development in the context of Mozambique

I am reflecting here my struggle to understand the issue of language in the science classroom and in our lives from three different perspectives: before and after Mozambican independence and after completion of my doctoral research. The main method used is auto|ethnographic inquiry in which I use the events in my life to question what is happening in my society. I have used Maria Rivera Maulucci’s paper, Language experience narratives and the role of autobiographical reasoning in becoming an urban science teacher as a reference. This paper helps me to show how isolated and generalized is the Mozambican situation and the value of our struggle in giving value to local languages.     

How Often and for What Purposes Apprentices Seek Help in Workplaces: A Mobile Technology-Assisted Study

In the ‘dual’ system of vocational training, working in company represents the major part of training. At the workplace, apprentices are expected to acquire the typical skills of their profession but, at the same time, to contribute to the production of the company. For this reason apprentices are expected to carry out activities on their own from early on in their training and to ask for help only when they need it. Learning to ask questions and to seek help appropriately is, therefore, an important competence for learners to acquire during vocational training, just as it is important for the company to offer the learner every opportunity to ask for help when needed. In this study, we used mobile phones to follow at a distance 19 apprentices in car mechanics at the workplace. We then analyzed a corpus of approximately 77 hours of work, in search of all questions and requests they addressed during this time. Data show that requests for information are twice as frequent as requests for assistance (i.e. intervention or physical help) and that all together, requests are introduced more often by more advanced apprentices than by those in the early stages of their training. These findings are linked with the facts that: a) bringing apprentices to be autonomous early in their work is a deciding factor of the philosophy of work in many of the enterprises training apprentices, b) more advanced apprentices are given more complex tasks to work on, c) more advanced apprentices work more is often undertaken in collaboration with an expert car mechanics and d) questions and requests for help are more likely to be addressed when working collaboratively than when working alone. These findings are interpreted as evidences of a natural regulation which takes place at the workplace between the learner’s engagement and the workplace affordances.     

Relationship Reciprocation Modulates Resource Allocation in Adolescent Social Networks: Developmental Effects

Adolescence is characterized as a period of social reorientation toward peer relationships, entailing the emergence of sophisticated social abilities. Two studies (Study 1: N = 42, ages 13–17; Study 2: N = 81, ages 13–16) investigated age group differences in the impact of relationship reciprocation within school‐based social networks on an experimental measure of cooperation behavior. Results suggest development between mid‐ and late adolescence in the extent to which reciprocation of social ties predicted resource allocation. With increasing age group, investment decisions increasingly reflected the degree to which peers reciprocated feelings of friendship. This result may reflect social‐cognitive development, which could facilitate the ability to navigate an increasingly complex social world in adolescence and promote positive and enduring relationships into adulthood.     

Constructing the academic category of teacher educator in universities’ recruitment processes in Aotearoa,New Zealand

An examination of recruitment materials and interviews with personnel involved in the employment of teacher educators to positions in university-based New Zealand initial teacher education (ITE) courses reveals three constructions of teacher educator as academic worker: the professional expert, the dually qualified, and the traditional academic. However, this study’s analysis shows how these constructions allow universities to pursue a bifurcated approach for the employment of teacher educators, an approach that maintains binaries within teacher education and hinders development in the field. Furthermore, as the spectre of a major cultural shift in the provision of New Zealand ITE arises, the extent to which the professional expert and traditional academic constructions of teacher educator might serve the scope of work required of postgraduate ITE going forth is questioned.     

Enhancing large-class teaching: a systematic comparison of rich-media materials

Large cohorts (>200 students) are an ever-increasing presence in the UK higher education (HE) sector. Providing excellent teaching and learning to these large classes is an ongoing challenge for teaching faculty, a challenge intensified when the cohort comprises 85% non-native English speakers. This paper presents the findings of a project to supplement face-to-face lectures on a large campus-based taught MSc programme with a set of rich-media materials. These resources consisted of audio podcasts, audio-narrated slides, short video segments and full-video lecture capture. The aim of the study was to examine student usage of, and preference for, these different rich-media materials. Key findings are that students valued most highly the full-video lecture capture followed by the audio-narrated slides, using the materials primarily to consolidate their understanding and as revision aids. Students also emphasised the central importance of the face-to-face lecture – viewing the rich-media materials as complementary to, rather than as a replacement for the traditional lecture. Nor did the majority of students see the provision of videoed lectures as a reason for non-attendance at lectures. The findings of this study provide confirmatory evidence of the ongoing importance of the traditional lecture in large cohort HE teaching together with an acknowledgement of the benefits that rich-media materials can bring to the student learning experience.     

Challenges in embedding numeracy throughout the curriculum in three Queensland secondary schools

The Australian Curriculum identified seven General Capabilities, including numeracy, to be embedded in all learning areas. However, it has been left to individual schools to manage this. Whilst there is a growing body of literature about pedagogies that embed numeracy in various learning areas, there are few studies from the management perspective. A social constructivist perspective and a multiple case study approach were used to explore the actions of school managers and mathematics teachers in three Queensland secondary schools, in order to investigate how they meet the Australian Curriculum requirement to embed numeracy throughout the curriculum. The study found a lack of coordinated cross-curricular approaches to numeracy in any of the schools studied. It illustrates the difficulties that arise when teachers do not share the Australian Curriculum cross-curricular vision of numeracy. Schools and curriculum authorities have not acknowledged the challenges for teachers in implementing cross-curricular numeracy, which include: limited understanding of numeracy; a lack of commitment; and inadequate skills. Successful embedding of numeracy in all learning areas requires: the commitment and support of school leaders, a review of school curriculum documents and pedagogical practices, professional development of teachers, and adequate funding to support these activities.     

Maternal Unresponsiveness and Child Disruptive Problems: The Interplay of Uninhibited Temperament and Dopamine Transporter Genes

This study examined how and why dopamine transporter (DAT1) susceptibility alleles moderate the relation between maternal unresponsiveness and young children's behavior problems in a disadvantaged, predominantly minority sample of 201 two‐year‐old children and their mothers. Using a multimethod, multisource design, the findings indicated that a genetic composite of DAT1 susceptibility alleles (rs27072, rs40184) potentiated associations between maternal unresponsive caregiving and increases in children's behavior problems 2 years later. Moderator‐mediated‐moderation analyses further revealed that the DAT1 diathesis was more proximally mediated by the potentiating effects of children's uninhibited temperament in the pathway between maternal unresponsiveness and disruptive behavior problems. Results are interpreted in the context of supporting and advancing the biosocial developmental model (Beauchaine & Gatzke‐Kopp, 2012).