The effect of silica polymorphs on the thermomechanical properties of 0, 5, 10, and 20 wt % silica particles-reinforced-based poly(ethylene glycol) (PEG) composites have been studied as a function of temperature using dynamic mechanical analysis (DMA). The silica polymorphs exhibited quartz (Q), cristobalite (C), and amorphous (A) phases, which were obtained by processing natural silica sand. The DMA thermomechanical properties were determined in tensile (E) and shear (G) modes. The maximum storage moduli (E 0 and G 0 ) were achieved by samples with 20 wt % silica for all type of fillers. These values increased approximately 12 times for PEG/Q, 10 times for PEG/A, and 11 times for PEG/C composites compared to the pure PEG. Furthermore, the Poisson's ratio values of the composites were filler phase dependent, that is, 0.39-0.47 for PEG/Q, 0.15-0.18 for PEG/A, and somewhat anomalous for PEG/C composites.
Polyethylene glycol (PEG)/quartz (denoted as BP/Q) composites have been investigated as candidates of phase change materials (PCMs) due to their thermomechanical properties around the glass transition temperature as well as thermal properties between 30 and 600 C. Quartz (q-SiO 2 ) powders were extracted from local sand in Tanah Laut, Pelaihari, South Kalimantan, Indonesia. The composites were prepared by dispersing q-SiO 2 powders in the PEG matrix followed by the wet mixing process. The thermal properties of the composites were characterized using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), while the thermomechanical properties were examined using a dynamic mechanical analyzer (DMA) in a three-point bending mode around the PEG glass transition temperature range (−100-50 C). The morphology and interface bonding were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). From the DSC measurement, the endothermic peak of the composites showed a shift of approximately 7-12 C toward higher temperatures than that of the pure polymer. The melting enthalpy values (ΔH m ) of the BP/Q composites covered the required PCM application range, that is, between 139 and 182 J/g. The TGA of the composites showed that thermal degradation occurs in the range of 250-450 C. We found that solid-solid PCMs (ssPCMs) were successfully fabricated with the addition of 10 and 20 wt% q-SiO 2 . From DMA characterization, the BP/Q 20 wt% composite exhibited the maximum E' and the minimum energy dissipation (E"). Its E' value was approximately 250 MPa more than that of the pure PEG. The glass transition (T g ) temperatures of PEG and BP/Q composites (5, 10, and 20 wt%) were around −24.5, −19.1, −17.1, and − 5.3 C, respectively. In addition, the E" and tan δ values decreased with q-SiO 2 filler content. Furthermore, the Cole-Cole plots of the BP/Q composites revealed a better interfacial bonding between the q-SiO 2 and the PEG matrix in the composites with higher silica content. A compact morphology was shown by the BP/Q 20 wt% composite due to high silica concentration.
The purpose of this study was to determine the effectiveness of distance learning during the Covid-19 pandemic in the management of English learning and to improve student achievement at SMA Muhammadiyah 3 Yogyakarta. The research approach used is descriptive qualitative, with data collection techniques through interviews and observations. The research subjects were English teachers and deputy principals of SMA Muhammadiyah 3 Yogyakarta. The results of the study are as follows. First, English education planning is prepared based on subjects, competency standards, basic competencies, learning objectives, teaching modules, procedures, time allocation, learning activities, learning resources/equipment, and evaluation of distance education students' learning outcomes during the Covid- 19. Second, the implementation of education that the teacher is trying has been guided by the latest updated syllabus and online learning implementation plan. English teachers have practised innovative education during the Covid-19 pandemic, such as Google Classroom, Zoom, WhatsApp, and many more. Distance learning that the teacher applies is to open lessons, deliver modules or teaching materials two days before learning activities occur, and discuss learning with students where learning is student-centred. The educational process places more emphasis on the cognitive and psychomotor domains. Third, learning assessment uses pre-test and post-test when online education takes place. The evaluation method used in learning applies direct observation, carries out tests/exercises at the end of the lesson so that the teacher knows the weaknesses and measurements of each student. Learning support facilities at Muhammadiyah 3 High School Yogyakarta are equipped with a language laboratory to facilitate the implementation of learning English more effectively.
Kreano 6 (1) (2015): 26-32 Kreano Ju r n a l M a t e m a t i k a K r e a t i f -I n o v a t i f http://journal.unnes.ac.id/nju/index.php/kreano AbstrakTujuan penelitian ini adalah membandingkan keefektifan model pembelajaran kooperatif tipe LC-5E (Learning Cycle 5E) dan tipe CIRC (Cooperative Integrated Reading and Composition) terhadap kemampuan pemecahan masalah matematika peserta didik. Populasi penelitian adalah peserta didik kelas X SMA Negeri 2 Ungaran. Sampel diambil secara cluster random sampling. Data akhir mengenai kemampuan pemecahan masalah peserta didik diambil menggunakan metode tes. Teknik analisis data menggunakan uji proporsi, uji Anava dan uji lanjut LSD. Hasil penelitian menunjukkan kelas yang dikenai perlakuan pembelajaran LC-5E dan CIRC mencapai ketuntasan belajar. Dari uji Anava diketahui bahwa ada perbedaan rata-rata yang signifikan. Selanjutnya dilakukan uji lanjut LSD menunjukkan Kelompok Eksperimen 1 paling baik. Simpulan dari penelitian ini adalah model pembelajaran LC-5E lebih efektif dibandingkan tipe CIRC terhadap kemampuan pemecahan masalah peserta didik. Saran yang dapat direkomendasikan adalah pembelajaran LC-5E dapat digunakan sebagai alternatif dalam mengembangkan kemampuan pemecahan masalah peserta didik. Abstract
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