scholarly journals Two component thermal storage material study, Phase 2. Interim progress report, June 1976--December 1976

1977 ◽  
Author(s):  
E. Mehalick ◽  
A. Tweedie
2021 ◽  
Vol 4 (5(112)) ◽  
pp. 12-20
Author(s):  
Olga Khliyeva ◽  
Vitaly Zhelezny ◽  
Aleksey Paskal ◽  
Yana Hlek ◽  
Dmytro Ivchenko

Thermal energy storage (TES) plays an important role in solar heat power systems. The use of phase change materials (PCM) and selecting additives to increase the rate of heat accumulation is a promising way to increase the efficiency and reliability of such systems. The objects of the study were pure paraffin wax (PW) and composite PCMs based on it (containing aluminum and copper wool of 30 and 45 μm in diameter, respectively). An experimental setup with a cylindrical measuring cell was created, which was also considered as a model of a capsule with a thermal storage material. The rate of temperature change in the pure PW sample and samples of composite PCMs was experimentally measured. Two modes of heating and cooling were investigated: from 48 to 59 °C (mode with a phase change) and from 30 to 40 °C (mode without phase changes). Heating time from 48 to 59 °C for the PW sample was 13 min., for the PW samples with the content of aluminum wool of 0.00588 and 0.01780 m3·m-3 − 11 and 10.5 min., for the PW samples with the content of copper wool of 0.00524 and 0.01380 m3·m-3 − 11 and 8 min., correspondingly. The minimum heating time from 30 to 40 °C was 6 min. for the sample of PW with 0.01380 m3·m-3 of copper wool in comparison with 9 min. for the sample of pure PW. The expediency of using copper wool as an additive to thermal storage materials of PW to increase the charging and discharging rate of TES devices without significantly raising their price was confirmed. The presence of metal wool in molten PW suppresses bottom-up convective currents, so the main mechanism of heat transfer is thermal conductivity. This fact will contribute to a faster equalization of the temperature field by the height of heat storage capsules


2021 ◽  
Author(s):  
◽  
Loc Tan Nguyen

<p>Recent years have seen increasing research interest in the teaching of pronunciation in English as a second/foreign language classes (Thomson & Derwing, 2014), with particular strands of this research focused on understanding how pronunciation is represented in instructional materials and actual teaching practices in a range of settings and in teacher cognition (e.g., Couper, 2017; Derwing, Diepenbroek, & Foote, 2012; Foote, Trofimovich, Collins, & Urzúa, 2016). The study reported in this dissertation extends this research by investigating pronunciation teaching in a context where it has hitherto been under-researched, namely tertiary EFL in Vietnam.  The research involved two phases. Phase 1 was an introductory situation analysis which investigated pronunciation teaching practices of six Vietnamese tertiary EFL teachers teaching six intact classes at a Vietnamese university. First, the representation of pronunciation features in prescribed textbooks and supplementary materials of the EFL programme were analysed. Six ninety-minute lessons (one from each of the teachers) were then observed, and the teachers and 24 students across the six groups interviewed. The teacher interviews included both stimulated recall and general questions probing their beliefs about pronunciation teaching. Students were interviewed in focus groups (four each) regarding their teachers’ pronunciation teaching and their own pronunciation needs. The focus of Phase 1 was on how the teachers taught pronunciation, the factors shaping their pedagogical choices, and the students’ beliefs about their teachers’ pronunciation teaching and their instructional needs. The findings revealed that pronunciation was largely absent from course books and curriculum documents and that the teachers’ beliefs were in contrast with what they actually did in class. The teachers reported that they would follow deliberate steps if they taught pronunciation explicitly such as listening discrimination followed by explaining places of articulation and then practice. However, in the observed lessons, they only corrected their students’ pronunciation errors through recasts and/or prompts, with little if any explicit or pre-planned pronunciation teaching. In the interviews, the teachers confirmed that they never used any other techniques and that this was typically the only way they taught pronunciation in class.  The teachers’ pronunciation teaching was textbook-driven and was shaped by contextual factors including the curriculum and the learners. Decision making by all the teachers reflected a general commitment to strictly follow the mandated curriculum, with little evidence of pronunciation being taught explicitly. All the teachers reported a lack of initial training and professional learning in pronunciation pedagogy. In addition, there was a mismatch between the teachers’ and students’ preferences and beliefs about pronunciation teaching. Whereas the teachers believed error correction through recasts and/or prompts was effective, the students did not, and expressed a strong need for more explicit, communicative teaching of pronunciation. This pronunciation instructional need and the teachers’ lack of initial training and PL in pronunciation pedagogy motivated the Phase 2 study.  Phase 2 was an intervention study conducted with the same teachers teaching different classes. At the beginning of Phase 2, the teachers attended a teacher professional learning (TPL) workshop in which they were introduced to a pedagogic framework for teaching English pronunciation communicatively proposed by Celce-Murcia, Brinton, & Goodwin (2010). The teachers then planned communicative pronunciation teaching (CPT) lessons using this framework, and were subsequently observed implementing these lessons in their classes. Both the workshop and subsequent classes of this phase were audio-video recorded. A total of seven lesson plans and 24 classroom observations were made across the six teachers (four observations each). Right after the classroom observations, the teachers were interviewed to obtain their views of the TPL workshop and their implementation of the CPT lessons. Twenty-four students across the six groups were interviewed to reflect on their experience with the CPT lessons.  Observational data showed that the teachers understood and were able to translate what they learned about CPT from the workshop into actual classroom practice as reflected in their lesson planning and subsequent teaching. The lesson plans designed by the teachers closely followed the principles of the communicative framework. Interview data showed that the CPT model was favoured by both teacher and student participants. On the basis of the teachers’ implementation of the CPT lessons, both the teachers and students were confident that CPT has the advantages for promoting learners’ pronunciation knowledge, fostering their phonological ability, and developing their oral communication skills. They also reported that CPT can arouse learners’ interest and engagement in classroom learning.  Taken as a whole, this research highlights the need for pronunciation to be given a more explicit place in teaching and learning in tertiary EFL programmes in Vietnam, and for teachers to be better equipped for teaching pronunciation. Findings from interviews with teachers and learners in the study suggest that they would be receptive to such changes.</p>


2020 ◽  
Vol 28 ◽  
pp. 510-514 ◽  
Author(s):  
Nilesh Purohit ◽  
Mani Sankar Dasgupta

2019 ◽  
Vol 211 (4) ◽  
pp. 189
Author(s):  
Timothy ME Davis ◽  
Ashley E Makepeace ◽  
Kirsten Peters ◽  
Kevin Colclough ◽  
Wendy A Davis

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