• Proceedings of the KSME Conference
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• 2001.06c
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• pp.621-626
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• 2001

Microcellular foaming process was developed at MIT in 1980's to save a quantity of raw materials and improve mechanical properties. There are many process variables in appling microcellular foaming process to the conventional injection molding process. Of all process variables, part dimension control and shrinkage are the most influential on the post molded dimension. The post molding dimensional change of thermoplastic resins is important to tool designers for predicting the specific difference of molded part vs. actual mold cavity. Generally, articles injection molded are smaller in size than the cavity; hence, the term shrinkage factor is used to define the allowance a designer specifies. It is important to consider the factors that influence molded part dimension. According to ASTM Designation: D 955, shrinkage from mold dimensions of molded plastics was measured. In injection molding, the difference between the dimensions of the mold and of the molded article produced therein from a given material may vary according to the design and operation of the mold. In this paper, shrinkage data of molded plastic parts was obtained. It can be an important information for designing optimum mold system in a microcellular foaming injection molding process.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.71-71
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• 2003

최근 통신용 전자부품의 소형화, 저가격화, 고기능화의 요구가 점점 더 증대되고 있으며 이를 위해서 기판의 배선밀도를 높이는 것과 개별 부품 또는 모듈의 크기와 무게를 줄이는 것이 절실히 필요하다. 본 연구에서는 저융점의 phosphate계 유리 프릿의 첨가를 통해 LTCC (Low Temperature Co-fired Ceramic) 에 적용 가능한 조성을 개발하고자 하였다. 마이크로파 용 유전재료로서 널리 사용되고있는 BNT (BaO-Nd$_2$O$_3$-TiO$_3$) 계 세라믹스에 저융점 유리 프릿의 양을 10-30wt% 범위로 변화시키면서 900-110$0^{\circ}C$ 범위에서 소결하여 이에 따른 수축률 변화와 상대밀도의 변화를 조사하였다 유리 프릿으로 P$_2$O$_{5}$-ZnO-BaO-Nd$_2$O$_3$ 계, P$_2$O$_{5}$-SnO-ZnO 계 2가지 조성의 유리를 사용하였다 그 결과로 소결체의 상대밀도는 소성온도가 900-110$0^{\circ}C$ 로 증가함에 따라 85-96% 로 증가하였고, 그 수축률은 소결온도 100$0^{\circ}C$ 에서 급격히 증가하였다. 이러한 결과는 저온 동시소성 세라믹 조성의 사용을 위해 좋은 결과가 예상된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.164-167
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• 2003

In this study, we developed the mold for the plastic cavity filter which is a kind of a wireless communication device. Since the cavity filter is made of aluminium, the cost of fabrication is high and the production rate is low. But we can produce plastic cavity filter part by injection molding process with the mold which was designed by our team. The dimension and surface quality of plastic cavity filter was investigated by varying the molding method (conventional and MmSH process) and two different types of resin(PC/ABS and ABS). In case of ABS part, the shrinkage of the inner partition walls was decreased when we adopted MmSH method. The weight of both ABS and PC/ABS parts increased and the surface roughness decreased with MmSH process.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.97-97
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• 2012

비스코스 레이온 소재는 목재 펄프를 원료로 한 재생섬유로서 Drape성과 반발성은 탁월하나, 습식 방사에 따른 분자 구조적 불안정성으로 소비자가 일반 세탁 시 수축발생으로 종종 Dry Cleaning을 해야 하는 문제점들이 있음. 본 연구에서는 이와 같은 레이온의 단점을 극복하고 신축성 발현 및 형태안정성을 부여하기 위해 Rayon DTY사와 Spun T/R 40's를 개발하고 다양한 조직의 환편물을 제작하였으며, 기존의 레이온 제품 대비 수축률 등 형태안정성과 신축특성이 발현될 수 있는 염색가공 공정 조건을 설정하였음. 먼저 전처리시 균일하고 안정적인 수축이 발생하도록 하여 최종 생산품의 형태안정성과 신축성이 유지 될 수 있는 최적의 조건을 설정하였음. 전처리는 저온 축소 후 고온에서 정련하는 공정이 환편물의 조직에 관계없이 우수하였으며, 비교적 견뢰도가 우수하다고 판단되는 시판 분산염료 및 반응성염료를 사용하여 Polyester/Rayon의 2욕 2단 염색을 진행하였음. 또한 시제품의 품위를 높이기 위해 레이온 섬유의 고유한 특성을 부여할 수 있는 유연처방을 사용하여 총 13종의 환편물을 개발할 수 있었으며, 이렇게 개발된 원단은 형태안정성 -2.5~1.0%, 신장회복률 83% 이상, 필링성 4-5급의 결과를 나타내었음.

• Journal of the Korean Wood Science and Technology
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• v.43 no.3
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• pp.327-333
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• 2015

To measure the dimensional stability of three softwoods by vacuum pressurization of water soluble melamine-formaldehyde (MF) resin impregnation process, properties of resin treated compressed woods (compregs) were measured after impregnating the water soluble MF resin into three coniferous wood species for different impregnation times and resin concentrations. As the resin concentration was higher and impregnation time was longer, coefficients of volumetric shrinkage and anti-volumetric swelling efficiency increased, but coefficients of volumetric swelling, anti-volumetric swelling efficiency and absorption decreased. Also, weight percent gain increased remarkably as the resin concentration was high, but there was no uniform relationship with impregnation time.

• Analytical Science and Technology
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• v.6 no.2
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• pp.181-195
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• 1993

The purpose of this research is to improve the density and the hardness of the SUS alloys for wear resistant materials. The dependence of the density, shrinkage ratio and hardness of various alloys on the sintering temperature and composition were examined. Alloys added with 3% Ti shows the most proper sintering properties of shrinkage ratio and the hardness which is enough to substitute for existing high price materials.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.113-118
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• 2011

It is not easy to predict the shrinkage rate of a plastic injection mold in its design process. The shrinkage rate should be considered as one of the important performances to produce the reliable products. The shrinkage rate can be determined by using the CAE tools in the design produces. However, since the analysis can take minutes to hours, the high computational costs of performing the analysis limit their use in design optimization. Therefore this study was carried out to presume for mutual relation of analysis condition to get the optimum average shrinkage by regression analysis. The results shown that coefficient of determination of regression equation has a fine reliability over 87% and regression equation of average shrinkage is made by regression analysis.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.516-526
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• 2004

Polymerization shrinkage of photoinitiation type composite resin cause several clinical problems. The purpose of this study was to evaluate the shrinkage strain stress, linear polymerization shrinkage, compressive strength and microhardness of recently developed composite resins. The composite resins were divided into four groups according to the contents of matrix and filler type. Group I : $Denfil^{TM}$(Vericom, Korea) with conventional matrix, Group II : $Charmfil^{(R)}$(Dentkist, Korea) with microfiller and nanofller mixture, Group III : $Filtek^{TM}$ Z250(3M-ESPE, USA) TEGDMA replaced by UDMA and Bis-EMA(6) in the matrix, and Group IV : $Filtek^{TM}$ Supreme(3M-ESPE, USA) using pure nanofiller. Preparation of acrylic molds were followed by filling and curing with light gun. Strain gauges were attached to each sample and the leads were connected to a strainmeter. With strainmeter shrinkage strain stress and linear polymerization shrinkage was measured for 10 minutes. The data detected at 1 minute and 10 minutes were analysed statistically with ONE-way ANOVA test. To evaluate the mechanical properties of tested materials, compressive hardness test and microhardness test were also rendered. The results can be summarized as follows : 1. Filling materials in acrylic molds showed initial temporary expansion in the early phase of polymerization. This was followed by contraction with the rapid increase in strain stress during the first 1 minute and gradually decreased during post-gel shrinkage phase. After 1 minute, there's no statistical differences of strain stress between groups. The highest strain stress was found in group IV and followed by group III, I, II at 10 minutes-measurement(p>.05). In regression analysis of strain stress, group III showed minimal inclination and followed by group II, I, IV during 1 minute. 2. In linear polymerization shrinkage test, the composite resins in every group showed initial increase of shrinkage velocity during the first 1 minute, followed by gradually decrease of shrinkage velocity. After 1 minute, group IV and group III showed statistical difference(p<.05). After 10 minutes, there were statistical differences between group IV and group I, III(p<.05) and between group II and group III(p<.05). In regression analysis of linear polymerization shrinkage, group II showed minimal inclination and followed by group IV, III, I during 1 minute. 3. In compressive strength test, group III showed the highest strength and followed by group II, IV, I. There were statistical differences between group III and group IV, I(p<.05). 4. In microhardness test, upper surfaces showed higher value than lower surfaces in every group(p<.05).

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.915-918
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• 2008

Hydration heat and autogenous shrinkage are generated essentially by the same hydration. Many researchers have studied the close relationship between hydration temperature and autogenous shrinkage but hardly any research has been undertaken to explain the specific numerical relation. In this study, early age properties of hydration heat and autogenous shrinkage of specimen whose section size was changed were analyzed, and relationship between hydration heat and autogenous shrinkage was investigated. In the results of the study, inner temperature and autogenous shrinkage increased as the section size increased. And rise and rise ratio of hydration temperature and autogenous shrinkage in hydration heating section and autogenous shrinking section are increased too. Temperature rise and autogenous shrinkage rise increased respectively, as hydration heating velocity and autogenous shrinking velocity increased. And autogenous shrinkage rise and autogenous shrinking velocity increased as hydration heating velocity increased.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.561-564
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• 2010

의학과 기술 발달로 인해 질병과 사고에 의한 사망률은 줄어들었으나, 심장 관련 질환에 의한 사망률은 증가하였다. 심장 질환을 예방하는 데는 정기적인 검진을 통해 심장기능을 분석하고 관찰하는 것이 중요하다. 심장 기능의 분석은 이완기와 수축기 사이의 혈류량 및 심박구출률 계산을 통한 심장 운동능력 평가에 의해 이루어진다. 본 연구에서는 심장 단축 자기공명영상에서 좌심실 영역을 자동 분할하여 혈류량 및 심박 구출률을 계산하는 알고리즘을 제안한다. K평균 군집화 기법을 적용하여 좌심실을 분할하고, 그래프 탐색 기법에 기반하여 분할 오류를 수정하였다. 15명의 지원자에 대해 제안하는 알고리즘을 사용하여 혈류량과 심박구출률을 계산하였고, 수동윤곽검출 및 General Electronics 사의 MASS 소프트웨어와 비교하였다. 제안한 알고리즘의 수동윤곽검출과 차이는 혈류량의 경우 평균적으로 이완기에 $4.6mL{\pm}3.9$, 수축기에 $2.1mL{\pm}2.4$로 나타났고, 심박구출률은 $1.8%{\pm}1.7$이었다. 전반적으로 MASS소프트웨어에 비해 좋은 성능을 나타내었다.