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Abdelaziz Salhi,Salaheddine Sayouri,Lahoucine Hajji,TajEddine Lamcharfi 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.12
Nanocrystalline barium titanate (BT) was synthesized by the sol gel method. The dry gel obtained was first treated in themicrowave (MW) and then calcined at different temperatures. A pure tetragonal phase was obtained under heat treatmentat 750 oC which is a relatively low temperature. SEM image reveals a fairly dense and uniform microstructure. Dielectricmeasurements performed on the sintered BaTiO3 sample at 1200 oC revealed the presence of the resonance phenomenon atfrequencies lower than 2 MHz and the existence of a weak positive temperature coefficient of resistivity (PTCR) just abovethe Curie temperature. Electric impedance analysis shows the predominance of the grain boundary (gb) contribution andenables determination of activation energies of the gb and the bulk effect and their relative capacitance and resistanceelements.
Abdelhak El Ghandouri,Salaheddine Sayouri,TajEddine Lamcharfi,Lahoucine Hajji 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.2
Structural, dielectric and piezoelectric properties of nanopowders of pure and strontium-doped BaTiO3 (Ba1-xSrx)TiO3 (x =0.00; 0.10; 0.20; 0.30 and 0.40), synthesized by the sol gel process, have been investigated. The samples crystallize in the pureperovskite structure and transform from tetragonal to pseudocubic under doping with Sr. The calculated average crystallitesize was about 30 nm. Dielectric parameters (dielectric permittivity and losses) were determined. Sr doping gives rise to adecrease of the ferro-to-paraelctric transition temperature and to an enhancement of the Positive Temperature Coefficient ofResistivity (PTCR). Piezoelectric parameters were also determined and their thermal behavior investigated.
Zia Tajeddin,Ali Dabbagh 아시아테플 2015 The Journal of Asia TEFL Vol.12 No.4
Despite the international surge of interest in the measurement of L2 pragmatic competence, the washback of pragmatic test tasks has remained a noticeably under-researched issue. To bridge this gap, this study sought to investigate the washback of a written discourse completion task (WDCT), as a pragmatic measure, to L2 teachers and learners in two different testing contexts, i.e., one with the addition of WDCT as part of summative assessment (pragmatic testing context) and the other with no such addition to the tests (non-pragmatic testing context). Data from teacher and learner interviews and classroom observations were subjected to content analysis. The results revealed various aspects of pragmatic assessment washback. First, the added pragmatic test tasks in the pragmatic testing context enhanced learners’ noticing of pragmatic aspects of listening materials and teacher talk, whereas learners in the non-pragmatic testing context expressed more concern for lexical and grammatical features. Second, pragmatic context learners specified the production of pragmatically appropriate discourse as the ultimate objective of language learning. Finally, most teachers in the pragmatic testing context emphasized the utility of pragmatic-based teaching activities. The findings indicate that lowstakes pragmatic assessment has a positive washback to learning and teaching activities.
Zia Tajeddin,Amirhamid Forough Ameri 아시아테플 2018 The Journal of Asia TEFL Vol.15 No.4
A concern with identity has become remarkably widespread since the 1990s. An immense amount of research has been carried out to investigate the construct of identity, but few studies have been done to explore the construct of identity boundary, even less on the discursive construction of identity boundary. To fill this gap, this study explored how Iranian English as a foreign language (EFL) teachers construct identity boundaries between themselves and learners discursively. Semi-structured interviews were conducted with 58 Iranian EFL teachers (31 male and 27 female) to identify how they demarcate the boundaries between themselves and learners. Five significant themes emerged from the data analysis: teachers' knowledge and power as indicators of their identity, setting boundaries by drawing up classroom rules, creating boundaries and not walls, demarcating boundaries both discursively and non-discursively, and establishing boundaries more implicitly than explicitly. The findings indicate that four categories could be conceivable with regard to teachers’ identity boundary setting: discursive, explicit; discursive, implicit; non-discursive, explicit; and non-discursive, implicit. As the majority of the teachers in this study reported that they tended to demarcate their identity boundaries more implicitly and non-discursively, the implication might be that Iranian EFL teachers prefer to create the identity boundaries more indirectly so as not to cause any negative affective influences on their students.