• Journal of computational fluids engineering
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• v.2 no.1
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• pp.117-128
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• 1997

Effects of dam and weir on the fluid flow and behavior of inclusions in the continuous casting tundish have been studied using the CFD (Computational Fluid Dynamics) technique. Inclusions affecting the quality of steel products have been considered to be passive: the fluid flow has been obtained for unstaggered grid points defined on body-fitted generalized cuvilinear coordinates with no attention on inclusions, and the spatial propagation of inclusions has been determined by using the flow field data. The result show that the dam and weir direct the flow to the free surface and increase the residence time of inclusions significantly, and thereby that inclusions have much more chance to be floated to the free surface of the tundish where it is eliminated. It is also found that they offer more margin on the geometric design of exit nozzles connected to moulds. This finding is particularly important for twin casting operations where the quality of steel products from the two moulds be kept uniformly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.807-812
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• 2009

Most structure engineers give the casting components over-estimated factor of safety without any reasonable foundation due to the worries about the unavoidable defects such as shrinkages and porosity in castings; the engineers have little knowledge on the relation between the defect and structural behavior. And the workers in casting field also do not know how to control the defects by manufacturing; they do not know to where the defects move or until how size they reduce the defects. In this study, shrinkage defect was scanned by industrial computerized tomography instrument (CT), and subsequently was modeled to a spheroid primitive for structural analysis. Using these simplified models of shrinkage, we observed the effects of the defect on the results of the structural analysis. A commercial structural analysis code was used to do the analysis works. Considering the conclusions, it is possible to manage the shrinkages effectively in casting process and to design the products with more reliable

• Conservation Science in Museum
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• v.28
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• pp.65-88
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• 2022

The characteristics and behavior of bullets are important because they are directly related to the firearm performance. However, research related to bullets have been small. In this paper, scientific analysis was conducted to find out the materials and manufacturing process of metal bullets during the Joseon Dynasty, owned by Korea Army Museum, and the types of firearms available were classified and organized according to the bullet diameter. As a result, bullets were classified into iron bullets, lead bullets, and lead-coated iron bullets. Most of the iron bullets and lead bullets were made from casting. Some iron bullets were made from forging. And the lead-coated iron bullet was made by pouring molten lead after putting the iron bullet into the mold. Finally, the bullets could be used for Hand Cannon, Matchlock Musket, Frankish Cannon, Hyeon-ja Cannon, Dae-Wiwon Cannon, Small Cannon, and Hong-Yi Cannon.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.108-108
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• 2017

다양한 생체 재료들을 이용한 마이크로 및 나노 크기의 표면 구조 모사는 조직공학에서 세포의 성장 및 분화에 영향을 미치는 것으로 알려져 있다. 특히, 마이크로-나노 구조가 공존하는 계층적 표면 구조는 골 아세포의 증식과 분화에 탁월하여 뼈 조직 재생에 응용되어 왔다. 기존에는 화학적 처리 기법을 이용하여 마이크로 표면 구조가 제작 되었으나 미세 거칠기 및 계층적 표면 구조의 제어가 어려웠다. 현재 이러한 문제점들을 극복하기 위해 플라즈마를 이용한 애칭 기법이 주로 이용되고 있으나 높은 온도 공정 환경에 의한 재료 선택의 한계점 및 오랜 공정 시간에 의한 플라즈마 처리 효율이 감소되어 원하는 표면구조 및 거칠기를 얻을 수 없다는 단점이 있다. 본 연구에서는 이러한 문제점들을 극복하기 위해 마이크로/나노 주조 기법 이용하여 생체적합성 합성고분자 poly(${\varepsilon}$-caprolactone) (PCL) 위에 연꽃잎 구조를 모사한 후 플라즈마 애칭 기법을 이용하여 마이크로-($3.01-3.07{\mu}m$)와 나노크기 ($97{\pm}16nm$)를 동시에 갖는 계층적 구조를 제작하였다. 제작된 구조의 효능을 관찰하기 위해 조골세포를 배양한 결과 평평한 PCL 구조보다 제작된 계층적 구조가 높은 세포성장률 (>2.9배)및 세포 분화도(>2.1배)를 보였다. 이러한 결과는 새로운 표면 공학적 모델로서 손상된 뼈 및 치아조직 재생을 위한 적합한 거칠기 및 표면적인 환경을 제공해 빠른 재생 능력과 더불어 치료기간의 단축을 가져 올 수 있을 것으로 사료된다.

• 보존과학연구
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• s.12
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• pp.42-62
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• 1991

A.D. 5세기 전반기경으로 추정되는 황남대총 고분에서 발굴출토된 유물 중 도금 기법이 적용된 대표적인 형태 및 용도의 유물 시료 13점을 선정 SEM-EDS 및 금속현미경에 의해 분석한 결과,시료의 도금피복 기술은 수은(Hg)에 의한 아말감(amalgam) 도금법에 의한 것으로 판명되었으며, 도금피막의 두께는 $5.99∼12.97\mum$ (단, 소지가 은인 시료 No.C는 $19.96\mum$)로 균일하고 치밀하게 도포되었다. 소지금속은 금속현미경 조직검사 결과 대부분 단조로 제조된 4.7∼11.5%의 연(Pb)을 함유하고 약 1.7% 내외의 아연(Zn)을 함유한 동합금이었다. 또한 내재된 불순물이나 기공이 매우 적은 것으로 보아 당시의 소지금속인 동합금 주조기술이 상당한 수준임을 알 수 있었다.

• Journal of Conservation Science
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• v.20
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• pp.23-30
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• 2007

By analyzing the chemical compositions of bronze mirror presumably excavated from Mireuksaji temple site, Iksan, we have surveyed what alloy composition was used in casting the mirror, and also tried to estimate the manufacturing technique of the bronze mirror, through the observation of microstructure, as well as which region$^{\circ}{\emptyset}s$ galena the lead used in the mirror belonged to, by analyzing the ratio of the lead isotope. The content analysis result of bronze mirrors shows that it consists of 68.8 to 73.3wt% of Cu, 21.6 to 24.9wt% of Sn. In particular, the content of Pb of Mireuk 2 and 3 Samples are higher than those of Miruk 4. The observation result of microstructure demonstrates that Mireuk 2 and 3 consist of ${\alpha}$ and ${\alpha}+{\delta}$ eutectoide phase made through casting process. But Mireuk 4 show other process employed, such as quenching though martensite structure. In the analysis result of provenance though the lead isotope ratio, the origin of the used in bronze millers excavated from Mireuksaji temple site is presumed to be from galenas of Japen, like this those, the chemical competition, microstructure, and lead isotope ratio of bronze mirrors excavated from Mireuksaji can be utilized at fundamental data to compare mutually with other remains.

• Conservation Science in Museum
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• v.16
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• pp.56-81
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• 2015

Ring in the scroll painting is one of the mounting elements which are fixed string and tassel to hang, these differ widely in shape and produce a variety of metals. Most traditional shapes of ring have been lost, because of remount, there are used Japanese style rings in present.Therefore, this study examines to shape, production technique and analyze component traditional style rings of 19 traditional scroll paintings in National Museum of Korea for restoration of original style. Ring has been recorded official names; Wonhwan(Ring), Gukhwadong(Chrysanthemum shaped ornaments), Baemok(Ring-shaped nail) in Uigwe. Result of an optical microscope (Leica, M205A), Wonhwan has two type of production technique; one is cutting and bending a metal rod and other is cast. Baemok is made to forging process after metal rod or plate by casting alloy. Baemok decoration is metal plate cutting shape, and then decorates it with pattern by using kicking line engraving, chasing and so on. Component analysis result from portable X-ray fluorescence found various metals, such as, brass, iron silver-cooper. Brass based on copper and zinc used rings of 17 scroll painting. Baemok of Yun Sidal portrait is used iron and plated with a tin-lead alloy. Yi Seogu portrait is silver-cooper alloy in whole ring.

• Journal of the Korea Society of Computer and Information
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• v.17 no.11
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• pp.1-10
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• 2012

In this paper, the extension of the addressing mode in the 16-bit Thumb instruction set architecture is proposed to improve the performance of 16-bit Thumb code. The key idea of the proposed approach is the introduction of new addressing modes for more frequent instructions by using the saved bits from the reduction of the register fields in less frequently used instructions. The proposed approach adopts efficient addressing modes from the 32-bit ARM architecture, which is the superset of the 16-bit Thumb architecture. To speed up access to a data list, scaled register offset addressing mode and post-indexed addressing mode are introduced for load and store instructions. Experiments show that the proposed approach improves performance by an average of 8.5% when compared to the conventional approach.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.613-621
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• 2009

Except for traditional industrial art and history of design development, Korea jewelry industry before 1980's, had little meaning in the aspect of marketing and business. Domestic jewelry market which have changed from the value of goods to value of ornaments, faced important transition point for jewelry industry by the chance of in Asian Game held in 1986, and money of overseas traveler after 1980s. The rapidly-grown Jewelry field by the introduction of detail casting method to make it possible mass-production of the products before 1990's, began to change into new system, with introducing CAD/CAM after 1990's. Jewelry industry has changed from manual work called handmade to the detail casting industry based on master for mass-production. For this, the development of master, with the design development, have been suggested as important task to jewelry industry firms, and by the introduction of CAD/CAM, the diversification of design and master development has been made up. In this study, we would try to find out current status of domestic jewelry field and to understand CAD/CAM, and advantage of CAD/CAM, and through this, suggest good solution to precipitate domestic jewelry market.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3358-3365
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• 2012

This paper presents a scheduling scheme for die casting processes considering power usage. The scheduling problem of a shift-based die casting process is represented by a linear programming (LP) model that maximizes the average efficiency of melting furnaces in regard of the usage of molten alloy, where the product quantities of each shift are used as primary variables. In this research, we propose a novel LP model that considers power usage of foundries. The developed LP model can derive product plans in which the expended power of a casting shift does not exceed a prescribed limit, while optimizing the efficiency of alloy usage. The simulation result of a case study demonstrates the superiority and applicability of the proposed scheme. This paper serves as a basic research on the role of foundries as an intelligent costumer in smart grid environment where the limit of power usage should be fulfilled.