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All Journal Jurnal Teknik Industri These proceedings represent the work of researchers participating in The International Conference on Elementary Education (ICEE) which is being hosted by the Elementary Education Study Programme School of Postgraduate Studies, Universitas Pendidikan
W Widyastuti, W
Center for Radioisotopes and Radiopharmaceuticals Technology, National Nuclear Energy Agency Puspiptek Area Serpong, Tangerang 15310, Indonesia
Humanities Decision Sciences, Operations Research & Management Economics, Econometrics & Finance Education Industrial & Manufacturing Engineering Languange, Linguistic, Communication & Media Mathematics Social Sciences

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SYNTHESIS OF NANOPARTICLE BARIUM HEX AFERRITE BY SOL GEL AUTO COMBUTIO Widyastuti, W; Yulian FF, Felly; Rochiem, Rochman; Purwaningsih, Hariyati
Jurnal Teknik Industri Vol 12, No 2 (2011): Agustus
Publisher : Department Industrial Engineering, University of Muhammadiyah Malang

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3424.509 KB) | DOI: 10.22219/JTIUMM.Vol12.No2.156-161

Abstract

Nanocrystalline of Barium Hexaferrite (BaFe12O19) powders have been synthesized using the sol gel auto combustion method. The ferrite precursors were obtained from aqueous mixtures of Barium nitrate and Ferric nitrate by auto combustion reaction from gel point. These precursors were sintered at different temperatures ranging from 700 to 1000oC for constant calcinations time 2,5 h in a static air atmosphere. Effects of Fe3+/Ba2+ mol ratios and sintering temperatures on the microstructure and magnetic properties were systematically studied. The powders formed were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and VSM. The results obtained showed that the phase BaFe12O19 powders were achieved by the Fe3+/Ba2+ mole ratio from the stoichiometric value 11, 11.5 and 12 at temperature 950OC. With increasing of temperature sintering, coercivity and magnetization value tends to rising. The maximum saturation magnetization (66.16 emu/g) was achieved at the Fe3+/Ba2+ mole ratio to 11.5 and the sintering temperature 950OC. The maximum coercivity value 3542 Oe achieved at mole ratio sample 12 with sintering temperature 950OC. Maximum saturation 6616 emu/g achieved at mole ratio sample 115 with the same temperature.
The 10th Grade Students’ Folding Back Process in Solving Contextual Mathematical Problem Widyastuti, W; Hasanah, A
International Conference on Elementary Education Vol. 2 No. 1 (2020): Proceedings The 2nd International Conference on Elementary Education
Publisher : Elementary Education Study Program School of Postgraduate Studies Universitas Pendidikan Indonesia in collaboration with UPI PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (808.654 KB)

Abstract

Mathematical contextual problem can be useful for students because it is able to evoke higher student’s thinking and good mathematization to apply mathematics in real world. However, many students have been difficult in solving mathematical contextual problems, and some of them even have difficulty in understanding mathematical contextual problems. The folding back process is a key feature of the Pirie-Kieren theory about layers of mathematical understanding. Folding back occurs when students cannot solve a problem at an outer level of understanding directly, so they return to the inner level and reconstruct their understanding using their new knowledge. The purpose of this study is to analyze the folding back process in 10th grade students’ mathematical understanding based on the Pirie-Kieren theory in solving mathematical contextual problems. Thus, this study used qualitative approach. The subjects of this study were two students of grade 10th in Jakarta. The data were collected by giving two items of mathematical contextual problem and interviewing with semi-structured interview. The result of this study showed that both of the subjects often folding back to the primitive knowing level and go forward to the next level. This study showed that primitive knowing level was a key factor to solve mathematical contextual problems
Co-Authors FELLY YULIAN FF, FELLY Hariyati Purwaningsih Hasanah, A Laihad, Fanny M Nastiti, Arlita Dewi Rochman Rochiem