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Wahyu Hidayat,Yun Ki Kim,Woo Seok Jeon,Ju Ah Lee,Ah Ran Kim,Se Hwi Park,Rohny S Maail,Nam Hun Kim 한국목재공학회 2017 목재공학 Vol.45 No.4
The objective of this study was to compare the wood anatomical characteristics of local tree species in Moluccas, Indonesia i.e., Moluccan ironwood (Intsia bijuga), linggua (Pterocarpus indicus), red meranti (Shorea parvifolia), and gofasa (Vitex cofassus). Qualitative evaluation was conducted by observing the anatomical structure in cross, radial, and tangential sections of each sample. For the quantitative evaluation, the dimensions of vessels, rays, and fibers were measured. Qualitative evaluation showed that crystals were observed in Moluccan ironwood, linggua, and gofasa, while resin canals were only observed in red meranti. Tyloses were frequently observed in gofasa but infrequently observed in linggua and red meranti. Quantitative evaluation showed that Moluccan ironwood with the higher density had thicker fiber wall, higher quantity of ray number, and wider rays than the other species. Red meranti had higher values of ray height and fiber length than the other three species. The results also revealed that linggua showed the highest values of relative crystallinity and crystallite width. Red meranti and gofasa showed similar values of relative crystallinity and crystallite width, while Moluccan ironwood showed the lowest values. The basic qualitative and quantitative anatomical characteristics discussed could provide useful information for further utilizations of such wood species.
Wahyu Hidayat,Yue Qi,Jae Hyuk Jang,Byung Ho Park,Irwan Sukri Banuwa,Fauzi Febrianto,Nam Hun Kim 한국목재공학회 2017 목재공학 Vol.45 No.2
Heat treatment of wood is an attractive alternative environmentally-friendly treatment to add value of less valuable woods by improving color, dimensional stability, and natural durability. To improve the color properties of Korean white pine (Pinus koraiensis) and royal paulownia (Pauwlonia tomentosa), we treated the woods at 160℃, 180℃, 200℃, and 220℃ for 2 hours. Color change after heat treatment was evaluated using the CIE-Lab color system and survey was conducted to determine the consumer preferences towards color of heat-treated wood. Lightness (L*) decreased with increasing temperature and the higher degree of change was obtained in royal paulownia. The red/green chromaticity (a*) in both wood decreased after heat treatment at 160℃, and constantly increased after heat treatment at 180℃ to 220℃. Yellow/blue chromaticity (b*) in Korean white pine tended to increase after heat treatment at 160℃, then decreased gradually afterwards. In royal paulownia, b* values linearly increased with increasing temperature. Overall color change (ΔE*) increased with increasing temperature with higher degree obtained in royal paulownia. Samples with the clamps in both wood species showed lower degree of the change in L*, a*, b and ΔE*. The results of the consumer preferences test showed that the darker colors of heat-treated woods were more preferred by consumers compared to the lighter colors of untreated woods. Consequently, heat treatment could enhance the color properties of Korean white pine and royal paulownia woods for value added products.
< 구두-A-06 > Characterisation of heat treated wood from Gmelina arborea and Melia azedarach
( Wahyu Hidayat ),( Byantara Darsan Purusatama ),( Fauzi Febrianto ),( Nam Hun Kim ) 한국목재공학회 2019 한국목재공학회 학술발표논문집 Vol.2019 No.1
Heat treatment of wood is an attractive alternative environmentally-friendly treatment to add value of less valuable woods by improving color property, dimensional stability, and natural durability. To improve the properties of Gmelina arborea and Melia azedarach woods, the present study heat treated the woods at 180°C and 210°C for 3 h under air atmosphere. Effect of mechanical restraint by using clamp during heat treatment on the color, physical and mechanical properties was evaluated. The results showed that color change (ΔE*) increased by increasing the temperature, showing greater DE* in Gmelina arborea than in Melia azedarach wood. The color of both woods gradually changed from original light color to a darker color similar to most tropical woods. The weight loss and volume shrinkage increased with the increase of temperature. It was found that weight loss and volume shrinkage in samples with clamp were lower than without clamp. Heat treated woods evidently absorbed less water than control, showing lower equilibrium moisture content. The wettability of woods decreased with heat treatment. In addition, Gmelina arborea showed higher degree of change in contact angles than Melia azedarach. Evaluation of mechanical properties showed that modulus of rupture (MOR) and modulus of elasticity (MOE) in both woods decreased with the increase of temperature. Clamping minimized strength reduction in both woods.
( Wahyu Hidayat ),( Jae Hyuk Jang ),( Yun-ki Kim ),( Woo-seok Jeon ),( Ju-ah Lee ),( Nam Hun Kim ) 韓國木材工學會 2017 한국목재공학회 학술발표논문집 Vol.2017 No.1
The objective of this work was to investigate the effect of heat treatment on color changes and to determine determine the consumer preferences towards color of heat-treated woods. Korean white pine (Pinus koraiensis) and royal paulownia (Pauwlonia tomentosa) woods were treated at 160°C, 180°C, 200°C, and 220°C for 2 hours. The evaluation of color changes using the CIE-Lab color system showed that lightness (L<sup>*</sup>) and red/green chromaticity (a<sup>*</sup>) in both woods decreased with increasing temperature. Yellow/blue chromaticity (b<sup>*</sup>) in Korean white pine tended to increase after heat treatment at 160°C, then decreased gradually afterwards. Overall color change (ΔE<sup>*</sup>) increased with increasing temperature with higher degree obtained in royal paulownia. The results of the consumer preferences test showed that the darker colors of heat-treated woods were more preferred by consumers compared to the lighter colors of untreated woods.
Problems and Constraints of Authentic Assessment among Children s Early Education Teachers
Wahyu Hidayat,Nur Asmawati Lawahid,Mujahidah The Pacific Early Childhood Education Research Ass 2021 Asia-Pacific journal of research in early childhoo Vol.15 No.2
Authentic assessment aims to plan the individual learning of children by identifying specific needs, assistance or services. The current study aims to identify constraints faced by them in implementing authentic assessment of teachers in early Childhood Education in North Aceh. This study was conducted through three phases, namely the first, the study of problems and constraints of teachers in implementing assessment practices on 70 early Childhood teachers; the second phase, reviewing the teacher documents on the six selected early Childhood teachers and the third examining the constraints from the perspective of five teachers in implementing authentic assessments. The first and second phase analyzes used descriptive statistics. The third phase study data were analyzed qualitatively. Findings show that 70 (100%) teachers get strong emphasis from parents to teach reading, writing and counting to their children. The findings, on the other hand, have identified the constraints faced by teachers, namely the influence and demand from families who want their children to be able to read, write and count as well as testing using written tests. Lack of instruction from the Ministry of Education is also a constraint in implementation.
( Wahyu Hidayat ),( Jaehyuk Jang ),( Yunki Kim ),( Wooseok Jeon ),( Juah Lee ),( Namhun Kim ) 韓國木材工學會 2016 한국목재공학회 학술발표논문집 Vol.2016 No.2
The objective of this work is to investigate the effect of heat treatment on color changes, wettability, physical and mechanical properties of Korean white pine (Pinus koraiensis) and Royal paulownia (Paulownia tomentosa). Samples were heat treated using an electric oven with a programmable controller at 160°C, 180°C, 200°C, and 220°C for 2 h. The results showed that the color of heat treated wood became darker with the increase of temperature. The weight loss and volume shrinkage increased with the increase of temperature. Heat treated wood evidently absorbed less water than control, showing lower equilibrium moisture content and water absorption. The wettability of wood decreased with heat treatment. In addition, Royal paulownia showed higher degree of change in contact angles than Korean white pine. Evaluation of mechanical properties showed that modulus of rupture (MOR) and modulus of elasticity (MOE) in both woods decreased with the increase of temperature. However heat treatment at 160°C tended to increase the MOE of wood.