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정일용,정영관 ( Il Yong Chung,Young Gwan Chung ) 한국산림과학회 1984 한국산림과학회지 Vol.65 No.1
The purposes of this study are to analyze and forecast the domestic demand for papers by regression models with time-series data (1965-81). For the period of 1965-81, the real GNP of Korea grew at annual average increase rate of 8.8 percent. On the other hand, the domestic demand of papers grew at annual average increase rate of 17.9 percent in this period. Especially, the annual average increase rate for board-papers accounted to 25.8 percent. To analyze domestic demand for papers, GNP, per capita GNP, price findex of papers, production activity index of the major papers consuming industries and price index of substitutive goods were selected as independent variables. The expected values of domestic demand for papers were computed by forecasting equations as follows. T-values are in parentheses.
어린이 음료수가 레진관과 지르코니아 기성관의 색조에 미치는 영향
정일용,이석순,이한이,이대우,양연미,김재곤 대한소아치과학회 2017 大韓小兒齒科學會誌 Vol.44 No.3
The purpose of this study was to evaluate the effects of exposure to various children’s drinks on the color stability of anterior primary teeth and different esthetic restorative materials clinically used in pediatric dentistry. Exfoliated maxillary primary central incisors that had been unaffected by caries were chosen as control group. Maxillary primary central incisor-shaped specimens made of strip crown and Nu-smile zirconia crowns were chosen as test groups. Polished strip resin crowns were additionally prepared to compare with unpolished strip resin crown. Each specimen and teeth were divided into 4 groups in which the test samples (n=5 each) were immersed in 4 different drinks (distilled water, cola, grape juice, jelly juice) for 6 days. In all 4 drink groups, all specimens generally showed increasing ΔE * value (color difference) with time. Polished resin strip crown had higher ΔE * value than the unpolished in cola, grape juice and jelly juice groups. ΔE * value of zirconia crown in cola, grape juice and jelly juice groups were significantly different (p < 0.05). In conclusion, dietary control of children’s drinks is required for preventing discoloration of restorative materials. 이 연구는 유전치와 그 심미 수복에 사용되는 전장관의 어린이 음료수에 대한 색조 안정성을 평가하였다. 우식 및 변색 없이 자연탈락된 20개의 상악 우측 유중절치와 상악 우측 유중절치 모양의 resin strip crown 40개 및 Nu-smile zirconia crown 20개를 대상으로 하였다. 복합 레진의 연마 여부에 따른 색조 안정성을 비교하기 위해 40개의 resin strip crown 중 20개는 Sof-lex™ Contouring and Polishing Discs를 이용하여 연마하였다. 이 후 각각의 시편을 5개씩 나누어 증류수, 콜라, 포도주스, 젤리주스에 6일간 담갔다. 그 결과네 음료수 군에서 모든 시편의 색조 변화가 있었으며, 연마한 resin strip crown은 연마하지 않은 군에 비해 색조 변화가 컸고 콜라, 포도주스, 젤리주스에서 통계적으로 유의하였다(p < 0.05). Zirconia crown의 경우 포도주스와 콜라에서의 색조 변화 값은 통계적으로 유의하지 않았으나 젤리주스와 나머지 두 음료수 사이에서는 유의하였다(p < 0.05). 따라서 소아 유전치 수복에 사용하는 수복재료들도어린이 음료수에 노출될 경우 색조 변화가 있을 수 있으므로 어린이 음료수에 대한 식이 조절이 필요하다.
패키지 및 PCB 재료가 PDIP 열특성에 미치는 영향에 관한 연구
정일용,이규봉 대한기계학회 1994 대한기계학회논문집 Vol.18 No.3
A three-dimensional finite element model of a 20-pin plastic dual-in-line package(PDIP) plugged into a PCE has been developed by using the finite element code ANSYS. The model has been used for thermal characterization of the package during its normal operation under natural convection cooling. Temperature distributions in the package and PCB are obtained from numerical analysis and compared with experimentally measured data. Various cases are assumed and analyzed to study the effects of package and PCB materials on thermal characteristics of PDIP with and without aluminum heatspreader. Thermal dissipation capability of PDIP is greatly increased due to copper die pad/lead frame and heatspreader. However, thermally induced stresses in the package and fatigue life of chip are improved for PDIP with Alloy 42 die pad/lead frame and no heatspreader. It is also found that the role of PCB on thermal characteristics of PDIP is very imporatant.