• Journal of the Korean Chemical Society
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• v.51 no.2
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• pp.213-222
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• 2007

In this study, science history program was developed to enhance student's concepts toward the particulate nature of matter and the understanding about the nature of science. And the effects of its application was investigated in the lesson of ‘Composition of Matter' in middle school science class. This science history program was based on genetic approach and included the contents from the old Greek natural philosophers to Avogadro. Before instruction, the test of understanding about nature of science was administered, and the science scores of the previous course were obtained, which were used as covariates. During 24 class hours, this study was conducted with two classes(experimental and comparison group) in a middle school in Seoul. The experimental group was received lessons by science history programs and the comparison group was received traditional lessons. After instruction, the scientific concept test, the test of understanding about nature of science were administered. The result of this study indicates that the scientific concept scores of experimental group were significantly higher than comparison group at p <.01 level of significance. It means that the students in experimental group has more sound conceptions about the particulate nature of matter and less mis conceptions about matter than the students in comparison group. However, there was no significant difference between two groups in the score of understanding about the nature of science.

• Resources Recycling
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• v.11 no.6
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• pp.47-54
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• 2002

Copper concentrate particles were fed from the top of vertical reaction tube of 2.8 cm ID and 65 cm long with an $O_2$-$N_2$ gas mixture. The reaction tube was heated to 1000 K to 1400 K. The copper concentrate particles were very rapidly oxidized and melted down during their descent in the reaction tube. The particle temperature were calculated by combining an unreacted core model, mass transfer between gas and particles, and heat transfer between gas, particles and tube wall. The particle temperature reached its maximum at the height of 20 to 30 cm from the top of the reaction tube, and it attained about 1700 K at higher oxy-gen partial pressure. The most particles were melted at the oxygen partial pressure above 0.2 atm.

• Applied Microscopy
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• v.37 no.2
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• pp.83-91
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• 2007

The present study examined the epidermal changes of adhesive disks which occur during attachment in Parthenocissus tricuspidata using scanning and transmission electron microscopy. Several adhesive disks, each covered with a bract, develop from the shoot apical meristem during early development. In the initial stage, the adhesive disks are club-shaped and their upper and lower epidermis are indistinguishable. However, in the actively growing stage, they become spherical and both epidermis are clearly differentiated into the adventitious roots. Prior to wall attachment, the adhesive disks exhibit adaxial convex and abaxial concave shapes, and electron-dense substances are abundant in the vacuoles of epidermal cells. The peripheral area of the adhesive disk is adhered first to the wall surface, while the central area is drawn inward in a vacuum-like state during attachment. As the attachment progresses and the electron-dense substances continue to discharge, the upper and lower epidermis rapidly undergo deterioration and the disks shrink considerably. At this stage, structural changes of the lower epidermis occur much faster than in the upper one. The discharged substance is accumulated on the wall surface, and this aids the attachment of adhesive disks on the wall for long periods. In this manner, the shape and structure of the adhesive disk epidermis change drastically from initial growth to the mature stage. Further, the role of electron-dense substance and shrinkage of the disk during attachment has been discussed in Parthenocissus tricuspidata.