• 한국재료학회지
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• 제13권1호
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• pp.6-10
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• 2003

Electroplated Ni and Ni-W micro-molds using LIGA-like process for replication of micro-components such as microfluidic parts and micro optical parts have been investigated. In general, it is hard to produce micro-parts using conventional mechanical processes. Micro-mold formed by LIGA-like process could fabricate micro-parts with high aspect ratio. In this paper, fabrication and properties of electroplated Ni molds with varying applied current types as well as those of Ni-W molds were investigated. Ni molds fabricated under pulse-reverse current showed the highest hardness value of about 160 Hv. Ni-W molds showed the hardness of about 500 Hv which was much harder than that of Ni electroplated molds. The above results suggested that high quality micro-molds could be fabricated by using Ni electroplating of pulse-reverse type for core molds and sequential Ni-W alloys coating.

• 한국주조공학회지
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• 제23권5호
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• pp.235-243
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• 2003

The collapsibility of sodium silicate-bonded sands mixed with the L.D converter slag powder to form a hardener were investigated. Five to six percent sodium silicate on the basis of silica sand and 30-40% L.D converter slag powder on the basis of sodium silicate, were mixed and the compressive strength, surface stability index(SSI), bench time, retained strength of the standard sand specimens were measured. The properties were similar to those of general inorganic bonded self-setting molds. The compressive strength and surface stability index were increased and the retained strength and bench time were decreased with increased amount of the L.D converter slag powder. The retained strength of sodium silicate-bonded self-setting molds with the L.D converter slag powder were decreased than $CO_2$ sand molds. The collapsibility of sodium silicate-bonded self-setting molds with the L.D converter slag powder were superior in comparison with $CO_2$ sand molds. The L.D converter slag powder could be used as hardener and collapse agent for the sodium silicate-bonded self-setting molds.

• 산업경영시스템학회지
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• 제41권4호
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• pp.248-255
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• 2018

Ensuring the quality of molds is one of the major issues in mass production. In general, securing the quality of the molds is achieved by repeating grinding and die spotting after machining the molds based on engineer's decision. However, this heuristic method is affected by the engineer's skill and working environment. Therefore, a lot of time and resources are needed in order to ensure quality. In this study, ensuring the quality of molds using grinding map which is generated using automatic measurement is proposed. An automatic measuring system based on CMM (Coordinate Measuring Machine) is developed for measuring the molds. This system generates the measurement path automatically using the 3D CAD model of products. CAD (ComputerAided-Design), CAM (Computer-Aided-Manufacturing), and CAQ (Computer-Aided-Quality) technology is integrated using DMIS (Dimensional Measuring Interface Standard) format in the automatic measuring system. After measuring the molds, a grinding map is generated using the gap between the CAD model and measured values of mold. The grinding map displays the machining tendency and the required amount of grinding with values on a 3D map. Therefore, the quality of molds can be ensured with exactness and quickness based on the grinding map. This study shows that integrating the planning, measuring, and analyzing based on computer technology can solve the problem of quality assurance of mold using the proposed method, therefore the productivity can be increased.

• 한국정밀공학회지
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• 제19권10호
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• pp.212-220
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• 2002

The finishing process for die and mold manufacturing is very important because it influences the final quality of products. Injection molds need higher quality surface than general purpose dies and molds. Conventional polishing can not make mold surface down to nanometer roughness efficiently because of their loading and glazing. This paper focused on the development of fixed abrasive pad using water swelling mechanism of polymer binder network. Self-conditioning was recognized as the long term polishing stabilization tool without any loading or glazing because water makes fixed abrasives free by swelling of the pad. Consequently, stable nano-polishing process has been applied on the injection mold, from the experimental results with polished surface roughness of Ra 15.1nm on STD-11 die steel.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.1859-1864
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• 2014

본 액화 실리콘 고무는 내열성 및 내화학적 우수성으로 전자 제품 및 다양한 제품에서 활용되고 있다. 하지만 초탄성 재료는 일반 금속재료와 다른 특성을 보인다. 초탄성 재료는 하중과 변형이 비선형 관계를 보이는 대변형 범위에서도 탄성거동을 나타내는 특성을 지니며, 비선형, 비압축성 및 대형의 특성을 지니고 있다. 이러한 특성 때문에 제품을 설계 및 생산 하기위해는 기능적 측면을 고려한 소재의 특성에 대한 물성 확보가 반드시 필요하기 때문에 현장에서 많은 어려움이 있다. 본 논문에서는 자동차용 방수커넥터 설계를 위해 소재의 인장, 압축 시험으로부터 구한 하중-변형관계를 이용하여 이를 유한 요소 해석에 적용한 결과를 비교하였으며, 해석결과와 제품의 성능 테스트 결과를 비교하여 방수커넥터용 씰의 경우 어떠한 소재특성을 적용할 경우 유용한 결과를 도출할 수 있는지를 확인하였으며, 이를 통해 제품 개발에 유용성을 확인하였다.

• 생명과학회지
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• 제8권6호
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• pp.648-653
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• 1998

1. 포장 또는 비포장의 부패된 어육연제품에서 분리된 미생물의 대부분(약 98%)은 Bacillus속을 비롯한 세균류였다. 특히 비포장어묵제품에서는 곰팡이도 약 0.1%검출되었다. 이들 부패미생물에 대한 계피추출물의 최저증식억제농도는 세균과 곰팡이에 대하여 각각 160~640$\mu\textrm{g}$/$m\ell$과 40~80$\mu\textrm{g}$/$m\ell$으로 나타났다. 2. 흰살어묵의 원료 배합시 계피추출물을 0.5% 첨가하면 첨가하지 않은 것에 비하여 $25^{\circ}C$에서 보존기간이 2일 연장되었다. 또한, 계피추출물과 ethanol을 1 : 3으로 혼합한 액을 튀김어묵표면에 분무한 것은 ethanol만 분무한 대조구에 비하여 곰팡이 발육이 2일간 지연되었다. 3. 샌드위치와 찹쌀떡의 표면에 계피추출물과 ethanol을 1 : 1 비율로 혼합한 액을 분무하여 $25^{\circ}C$에서 저장하면 곰팡이 발육이 대조구에 비하여 보존기간이 각각 5일과 7일정도 연장되었다.

• 한국식품영양과학회지
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• 제13권1호
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• pp.117-126
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• 1984

Aflatoxins are toxic and carcinogenic secondary metabolites which are produced by trains of A. flavus and A. parasiticus during their growth on foods and feedstuffs. Aflatoxins are a group of closely related heterocyclic compounds of which $B_1$, $B_2$, and $G_2$ are the major members. Aflatoxins are synthesized via a polyketide pathway in which the general steps are acetate, an-thraquinones, xanthone and aflatoxins. Aflatoxin formation is favored by high moisture or high $a_w$(0.95${\sim}$0.99). The limiting $a_w$ for aflatoxin production on agricultural commodities is 0.83. Optimum temperature for aflatoxin production by the molds is $25{\sim}30^{\circ}C$ and the incubation time for the maximum production of the toxin is 7${\sim}$15 days. The limiting temperatures for aflatoxin production are ${\leq}7.5^{\circ}C\;and\;\geq40^{\circ}C$. Cycling temperatures may or may not stimulate aflatoxin production depending on the amplitude of cycling, substrate and strains of molds. Aflatoxin pro-ducing molds are aerobic organisms and thus have a requirement for oxygen. A decreasing $O_2$ concentration and/or increasing concentrations of $CO_2$ or $N_2$ depress the mold growth and aflatoxin formation. A. flavus grows competitively or associatively in the presence of other microorganisms and occasionally loses the competition with other microorganisms. Some lactic acid bacteria have been shown to reduce growth and aflatoxin production by A. parasiticus. Carbon source is the most important nutritional factors affecting aflatoxin formation by the molds. Sucrose, fructose and glucose are the most favorable carbon sources. Food substrates of plant derived products which have high carbohydrate content such as agricultural commodities and their products are most vulnerable to contamination by aflatoxins.

• 열처리공학회지
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• 제36권5호
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• pp.270-276
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• 2023

In this study, we analyzed two types of cold forging dies commonly used for manufacturing general nuts and screws to investigate the differences in WC powder according to the lifespan. For both Type I and Type II dies, it was observed that as the lifespan of the molds increases, the area fraction of Co becomes larger and the size of the powder becomes smaller. Moreover, there is a trend where the strength also increases as the lifespan gets longer. Actually, the hardness value of the sample with the longest lifespan is ~ 131 HV higher than the specimen of the shortest lifespan, It is noted that the reduction in toughness of the WC-Co mold is caused by insufficient Co and the decrease in contact surface area of WC-Co results in a reduced bonding surface area. The lifespan of cold-working WC molds increases when the W content and the volume fraction of WC are high, and the size of the WC powder is small. The results can significantly enhance producing high-quality molds with an extended lifespan using WC powder for cold forging.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.126-127
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• 2014

At construction sites, due to the reason of inconvenience and difficulties of producing and using curing equipment and when it comes to measuring compression strength of the actual structure, strength of structure concrete according to general standards which are suggested in concrete standard specification are assessed. However, this method does not consider various variables of the sites such as kinds concretes and sizes of frame works so that it is not easy to measure proper curing period and strength. Thus, this study reviews description of strength development according to In-situ temperature system and analyzes and compares properties of strength development of the existing curing methods such as sealing curing so that it provides basic materials for period of removal of molds.

• 한국식품위생안전성학회지
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• 제2권1호
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• pp.29-34
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• 1987

건조 표고버섯의 위생적이고 안전한 품질 보존법 개발을 위하여 현행 방법인 ethylene oxide 훈증처리와 감마선조사가 저장 상대습도에 따른 시료의 미생물 및 조리시 재수화성과 관능적 특성에 미치는 영향을 비교 검토하였다. 일반 곰팡이의 생육한계 수분 환성도인 0.80과 내건성 곰팡이의 생육한계 최저 수분활성도인 0.64에 해당하는 건조 표고버섯의 평형 수분함량은 $25^{\circ}C$에서 17%, 27%였다. 건조 표고버섯의 미생물 오염은 전세균이 $1.27{\times}10^5/g,\;곰팡이가\;4.80{\times}10^3/g이며,\;대장균군은\;1.20{\times}10^2/g$이 검출되었는데 3 kGy의 감마선조사로서 2-3 log cycles 정도 격감되었고, 대장균은 완전 살균되었으며, 5 kGy 조사로서는 미생물 검출 한계 이하로 살균되어 실온에서 3개월 저장 후에도 이들의 생육은 거의 없었는데 반해 ethylene oxide 처리구는 곰팡이의 살균이 다소 불충분하였다. ethylene oxide 처리와 감마선조사된 건조 표고버섯의 수화도는 각 시험구 모두 첨지온도와 조사선량이 높을수록 흡수속도가 빨랐으며, ethylene oxide 처리구가 충분한 수화에 도달하기 위해서는 조사구에 비해 더 많은 시간이 필요하였다. 또한 조리적성 검토를 위한 관능 실험 결과에서 시료의 풍미는 처리구간에 유의적인 차이가 나타나지 않았으며, 조직감에서는 감마선조사구가 타 처리구에 비해 우수함을 보였다.