• 한국주조공학회지
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• 제27권1호
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• pp.42-47
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• 2007

Vacuum molding process(V-process) has several benefits such as a lower total production cost and a high quality casting comparing to the conventional sand molding. Influence of the gating design on the molten metal flow was investigated in this study. General criteria for the gating design of the castings and commercial codes for the flow and solidification analysis were used to attain the optimized gating design in V-process. Though mold cavity was filled smoothly under the low initial velocity of molten metal, molten metal dashed against the upper part of the mold before the completion of the mold filling with higher initial molten metal velocity and fell soon. This phenomenon may affect collapsing the mold shape, however it is thought that the possibility of burning out of the vinyl by the molten metal is not so high because vinyl is coated with refractory material.

• 한국주조공학회지
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• 제20권1호
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• pp.3-12
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• 2000

The lead content of drinking water has been restricted to less than 15 ppb by Environmental Protection Agency (EPA) in USA. This has led to extensive research and development work at the Materials Technology Laboratory (MTL) of CANMET, a Canadian Government research laboratory, on the development of low-lead and lead-free copper alloys for plumbing applications. Attentionhas also been focused on the environmentally friendly and energy efficient permanent mold casting process to minimize the disposal of foundry sand contaminated by lead due to the use of leaded alloys in the non-ferrous foundries. A new series of alloys called SeBiLOY contaning Bi and Se been introduced to replace lead in the leaded alloys. This paper addresses some important casting characteristics such as fluidity, hot tear resistance, mechanical properties and microstructure of lead-free alloys such as SeBiLOY III and low-lead alloys such as silicon brass, silicon bronze and yellow brass in gravity permanent mold casting.

• 한국주조공학회지
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• 제42권3호
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• pp.198-201
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• 2022

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2001년도 Proceedings of the 3rd Annual Meeting of Yellow Sea Environment
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• pp.1.1-5
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• 2001

High SPM concentrations(199.8~249.4${\mu}{\textrm}{m}$/㎥) were detected in the west Korea during the Yellow Sand Periods, 2000. Majority of the total SPM were composed of about 5${\mu}{\textrm}{m}$ sized coarse particles over the periods. However, fine particles sized about 1 ${\mu}{\textrm}{m}$ and coarse particles sized about 5-6${\mu}{\textrm}{m}$ showed peaks at the graph of SPM size distribution in the Non Yellow Sand Period. Airborne fungal spores at the SPM samples were cultured and identified. Full-grown colonies during the Yellow Sand Periods, Fusarium, Aspergillus, Penicillium and Basipetospora are hyphomycetes in the division Fungi imperfecti(Deuteromycota). And morphologically more diversified mycelia of hyphomycetes were grown on the sample captured from 1.1~2.1${\mu}{\textrm}{m}$ sized SPM than on other sized samples during the Yellow Sand Period. But no mold was observed on the sample of 1.1~2.1${\mu}{\textrm}{m}$ sized SPM in the Non Yellow Sand Period. It was thought that several sorts of fine sized fungal spores were suspended in the atmospheric environment of the west Korea during the Asian dust episodes.

• 한국자원식물학회지
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• 제19권4호
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• pp.517-520
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• 2006

봉의꼬리에 있어서 생육은 일반상토인 모래: 마사토 : 부엽토(2:5:3)와 피트모스 : 이끼(5:5) 조합에서 많았으므로 인공상토로는 피트모스에 이끼를 덮은 조합이 유리한 것으로 나타났다. 도깨비고비의 경우에는 전체적으로 배양토 적응성이 높게 나타났으며 역시 피트모스 : 펄라이트(7:3) 조합에서 생육량이 가장 많았다. 그러나 바크와 톱밥이 들어간 배양토에서는 생육이 저조하였다. 부싯깃고사리의 경우 초장과 엽수의 생육으로 볼 때 모래 : 마사토 : 부엽(2:5:3) 조합이 가장 크고 많았으며 그 다음이 피트모스 : 펄라이트(7:3, 5:5) 조합 순이었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.462-473
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• 2019

The effects of the location and dimension of the gate, location, and volume of the feeder, application of a chill, chill volume, and heating method of the feeder with respect to the effect of the mold-designing technologies on the defect status of the products are described. It is possible to increase the solidification time of the feeder by heating feeder. Furthermore, the pressure generated from the feeder is imposed on a product, and this decreases the generation of shrinkage porosities. In this study, two types of gating and feeding systems had been proposed: the bottom L-type junctions and the top L-type junctions. Additionally, solidification behaviors, such as solidification time, shrinkage porosities, weight percentage of chill system to product, hot spot, and solidification time ratio (=Solidification time of feeder/solidification time of product), are extensively analyzed by using commercial casting simulation software. Based on the solidification behaviors, reasonable mold design, feeding system, critical feeder heating temperature, and solidification time ratios are proposed in the sand casting process for the fabrication of carrier housing in order to reduce the casting defects and to increase the recovery rate.

• 한국주조공학회지
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• 제42권1호
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• pp.61-66
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• 2022

Hydraulic units are important components of agricultural and construction machinery, and thus require high-quality castings. However, gas defects occurring inside the sand cores of the castings due to the resin used is a problem. This study therefore aimed to develop a casting simulation method that can clarify the gas defect positions. Gas defects are thought to be caused by gas generated after the molten metal fills up the mold cavity. The gas constant is the most effective factor for simulating this gas generated from sand cores. It is calculated by gas generating temperature and analysis of composition in the inert gas atmosphere modified according to the mold filling conditions of molten metal. It is assumed that gases generated from the inside of castings remain if the following formula is established. [Time of occurrence of gas generation] + [Time of occurrence of gas floating] > [Time of occurrence of casting surface solidification] The possibility of gas defects is evaluated by the time of occurrence of gas generation and gas floating calculated using the gas constant. The residual position of generated gases is decided by the closed loops indicating the final solidification location in the casting simulation. The above procedure enables us to suggest suitable casting designs with zero gas defects, without the need to repeat casting tests.

• 한국조경학회지
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• 제32권6호
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• pp.103-108
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• 2005

본 연구는 실내에서의 관수주기, 상토종류, 배수층의 유$\cdot$무에 따른 가는쇠고사리의 생육을 살펴봄으로써 실내조경용 식물소재로 활용 및 관리 방법에 관한 자료를 제공하고자 수행하였다. 관수주기는 주 2회와 주 7회로 처리하였으며 배수층은 각 관수주기 처리별로 500mm 깊이의 마사토로 처리하였다. 상토는 자연토인 마사토:부엽토=1:1와 인공토인 피트모스:버미큘라이트:펄라이트=1:1:1을 사용하였다. 1. 2가지의 상토의 화학적인 특징을 분석한 결과 토양산도, 치환성 양이온함량은 피트모스:버미큘라이트:펄라이트=1:1:1 처리에서, 전기전도도, 유기물함량, 유효인산, 전질소함량, 양이온치환용량은 마사토:부엽토=1:1 처리에서 높은 수준을 보였다. 2. 관수주기에 있어 주 2회 관수처리가 주 7회 관수처리보다 가는쇠고사리의 생육과 실내 적응성이 높아 양치식물이 높은 수분환경을 선호함에도 불구하고 과도한 관수는 바람직하지 않는 것으로 사료된다. 3. 상토에 다른 가는쇠고사리의 생육과 실내 적응성은 마사토:부엽토=1:1 처리가 피트모스:버미큘라이트:펄라이트=1:1:1 처리에 비해 높았다. 그러나 실내에서는 자연토의 하중문제가 발생될 수 있으므로 추후 이를 대체할 수 있는 경량의 인공토양이 개발되어야 할 것이다. 4. 배추층의 유$\cdot$무에 의한 가는쇠고사리의 생육결과, 주 2회 관수처리에서는 배수층에 유$\cdot$무에 따른 생육적 차이가 크지 않았으나 주 7회 관수처리에서는 배수층이 있는 처리구가 생육과 실내 적응성이 높았다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.963-966
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• 2000

Plasma display panel (PDP) is a type of flat panel display utilizing the light emission that is produced by gas discharge. Barrier Ribs of PDP separating each sub-pixel prevents optical and electrical crosstalk from adjacent sub-pixels. Mold for forming barrier ribs has been newly researched to overcome the disadvantages of conventional manufacturing process such as screen printing, sand-blasting and photosensitive glass methods. Mold for PDP barrier ribs have stripes of micro grooves transferring stripes of glass-material wall. In this paper. Stripes of grooves of which width 48 um, depth 124um, pitch 274um was acquired by machining the material of WC with dicing saw blade. Maximum roughness of the bottom and sidewall of the grooves was respectively 120 nm, 287 nm. Maximum tilt angle caused by difference between upper-most width and lower-most width was 2$^{\circ}$. Maximum Radius of curvature of bottom was 7.75 ${\mu}{\textrm}{m}$. This results meets the specification for barrier ribs of 50 inch XGA PDP. Forming the glass paste will be followed by using mold in the near future.

• 한국정밀공학회지
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• 제17권7호
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• pp.124-131
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• 2000

Rapid Prototyping(RP) models are no longer used only for design verification. Currently, parts built utilizing layer manufacturing technology can be employed as functional prototypes and as patterns or tools for different manufacturing processes such as vacuum casting, investment casting, injection molding, precise casting and sand casting. This trend of Rapid Prototyping application meets the requirement of concurrent engineering and its range covers a more spreaded area. The aim of this paper is saving the manufacturing lead time and cost of plastic parts having hollow space shapes used by prototype-car. Using rapid prototype patterns, made by the Selective Laser Sintering(SLS) technique, a new approach of manufacturing resin-based blow mold is discussed. It has a great potential fur making prototype-car parts with the batch size of under 200 parts, in case of rapid modification due to a subsequent design changes in developing stage. So, the process proposed in this research shows reduction of process time and manufacturing cost when compared with the conventional process such as a Zinc Alloy fur Stamping(ZAS) mold.