• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.74-78
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• 1992

외부가 비축대칭인 튜브의 수방압출은 자동차와 항공기등의 복잡한 부품을 만드는데 많이 사용된다. 이런 후방압출 제품의 변형 상태는 저자들의 논문에서 이미 밝힌 바와 같이 복잡하다. 그래서, 외부가 비출대칭인 튜브형상의 후방압출은 근래에 와서 연구되었다. 본 연구에서는 저자들의 논문 에서 제시된 동적가용속도장을 수정하여 비축대칭인 소재에서 내부가 원형인 튜브의 후방압출의 최종 단계를 해석하 고자 한다. 해석의 적용예로서는 정다각형 소재와 모서리가 둥근 직사각형(rounded rectangle)소재를 택하였다 제시된 속도장으로부터 단면 감소율과 형상비(aspect ratio)에 대하여 압출 하중과 압출된 소재의 평균 높이가 결정된다. 이론적인 결과와 비교하기 위하여 퓰림처리된 AIST-2024 알루미늄 소재로 실험하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.2587-2593
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• 2014

Ceramic Injection Molding (CIM) is one of wide used processes in industry field and the applications are gradually being expanded to parts of medical and electric devices. In this study, the CIM process were analyzed with FEM and process parameters were studied and analyzed the effect on product quality. The shape of simple flat plate was compared to the shapes with the hole, with the round corner portion or with the side wall portion. If there are holes then the hole around the uneven density distribution and the defects such as weld lines could be occurred. The Large radius of the corners of the product give good formability and fluidity. Not only the shape parameters of product but also the process parameters during CIM are studied. The simulation results showed that the process parameters of temperature, initial fractions and velocity are important design parameters to improve the quality of products.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.408-413
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• 1996

A self-diagnostic, air-damped, piezoresitive, cantilever-beam microaccelerometer has been designed, fabricated and tested for applications to automotive electronic airbag systems. A skew-symmetric proof-mass has been designed for self-diagnostic capability and zero transverse sensitivity. Two kinds of multi-step anisotropic etching processes are developed for beam thickness control and fillet-rounding formation, UV-curing paste has been used for sillicon-to-glass bounding. The resonant frequency of 2.07kHz has been measured from the fabricated devices. The sensitivity of 195 $\mu{V}$/g is obtained with a nonlinearity of 4% over $\pm$50g ranges. Flat amplitude response and frequency-proportional phase response have been obserbed, It is shown that the design and fabricaiton methods developed in the present study yield a simple, practical and effective mean for improving the performance, reliability as well as the reproducibility of the accelerometers.

• Korean Journal of Crystallography
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• v.3 no.1
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• pp.1-8
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• 1992

The morphology of lead titanate powders prepared by sol-gel and coprecipitation techniques was investigated as a function of firing temperature and soaking time. PbTiO3 precursor powders were derived from a mixed solution of lead nitrate and titanium tetrachloride at 40℃ to 43℃ and pH of 9.0 to 9.7, and fired at temperatures 350-1000℃ for 1-10h in air. An increase of particle size and agglomeration with increasing calcination temperature and duration could be observed. By annealing sol-gel derived powder at 700℃, the tially-formed acicular(and/or prismatic) primary particles transformed to polyhedral shape with soaking time, and further soaking caused coarsening the polyhedral particles with rounded edges. However, the morphology of the coprecipitated powders was not varied during crystallization.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.33 no.4
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• pp.38-51
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• 2015

In the maps of the period, there were three large ponds called Dongji(東池), Seoji(西池) and Namji(南池) in Hanyang, the capital of Joseon Dynasty. They were different than the ponds found in the palace, civic buildings, and private dwellings. Dongji, Seoji and Namji were ponds relating to Fortress wall of Seoul, and all had lotuses cultivated in them. The purpose of this paper is to clarify the locational and spatial characteristics of these ponds and to detail the construction and reconstruction process and management conditions through maps, drawings, illustrations, historical records and literary works from the urban environmental perspective. The results are as follows. First, Seoji and Namji were intended for Bibo(裨補) which redeemed the geographical weaknesses of Hanyang, securement of bright court water(明堂水), supplement for fire energy(火氣), fire preventive water and waterscape facilities, while Dongji was emphasized on protecting water mouth(水口) besides Bibo and securement of bright court water. Second, Seoji was connected to mountain streams and Dongji and Namji were to ditches. The ponds connected to ditches had been difficult to fill and maintain. Third, Seoji and Namji were in urban areas, whereas Dongji was in farmlands, and these locational differences had an influence on the use of ponds. Fourth, the shapes of ponds, in contrast to the ponds in palace and civic buildings, which were perfectly square, were either freeform or square with rounded edges. Fifth, lotus ponds could be maintained by continuous management polices, earth filling and reconstructing process were repeated during the Joseon Dynasty. The lotus ponds of Fortress Wall of Seoul which had managed over 500 years, were built in, in accordance with the tenets of Bibo pungsu geomancy; however as time passed, they were maintained not only as public open spaces, but also a cultural attraction for residents and visitors.