• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.41.1-41.1
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• 2009

최근 금형은 자동차뿐만 아니라 여러 산업에서 필수적이며 제품의 품질은 물론 제조원가에 막대한 영향을 미친다. 이러한 금형은 침탄, 질화, 고주파담금질등에 의해 표면처리 되어져 왔으나, 이와 같이 기존의 처리 방법은 모두 처리물 전체를 가열하거나 균일한 가열을 하지 못하기 때문에 변형의 문제와 처리후의 후가공의 경비 문제, 그리고 극히 일부분만 경화가 필요한 부품에는 적용하기 어려운 문제점이 있다. 이러한 문제를 해결할 수 있는 표면처리로서 레이저 표면처리 방법이 대두되고 있으며, 레이저 표면처리는 레이저 빔을 피처리물의 표면에 조사하고 적당한 속도로 이동을 하게 되면 레이저조사부위가 급속하게 가열되고 레이저빔이 통과한 후에는 표면의 열이 내부로 열전도 되어 급속히 자기냉각(Self-quenching)됨으로서 표면에 새로운 기계적 성질을 갖게 하는 표면처리법이다. 이와 같이 레이저를 이용한 표면처리로 기존의 CW Nd:YAG 레이저 열원보다 효율이 좋은 HPDL(High Power Diode Laser)를 이용한 고효율, 고기능 금형 표면처리 후 재료적 물성을 평가하고자 한다. 평가방법은 레이저빔의 조사속도 및 온도변화에 따른 표면처리부, 열영향부 그리고 모재 부분에 대한 경도특성 및 미세조직 변화를 관찰하였다. 또한 조사속도 및 온도변화에 대해 경화깊이를 관찰하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.291-291
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• 2011

플라즈마에 노출된 재료 표면의 온도 증가는 다음과 같은 요인에 의해서 결정된다. 이온의 충돌에 의한 역학적 에너지, 이온의 중성화, 라디칼의 안정화에 의한 에너지 방출(잠열, latent heat), 플라즈마에서 방출된 빛의 흡수. 이중 식각을 위한 기판 바이어스에 의해서 주로 결정되는 이온 충돌 에너지와 잠열의 방출이 300 mm wafer용 유도 결합 플라즈마 식각 장치에서 소스 전력과 바이어스 전력에 따라서 어떻게 변화하는지 전산 유체 역학 모사 프로그램인 CFD-ACE를 이용하여 상용 식각 장비인 AMAT사의 DPS II를 대상으로 온도 분포의 변화를 계산하였다. 실험 결과와 비교를 위하여 다섯 곳에(상, 하, 좌, 우, 중심) 열전대를 부착한 온도 측정 웨이퍼를 기판의 위치에 설치하고 여러 가지 실험 조건에 대해서 온도의 변화를 측정하였다. Ar 10 mTorr에서 2열 병렬 안테나의 전력을 300 W에서 시간에 따른 온도의 변화를 측정하였다. 이때 wafer의 평균 온도는 $28.9^{\circ}C$에서 $150^{\circ}C$까지 12분 내에 상승하였으며 최고 온도에 도달한 다음에는 거의 일정하게 유지 되었다. Si의 식각에서 온도의 영향을 가장 크게 받는 반응은 F 라디칼에 의한 Si의 직접 식각이며 Arrhenius 식의 형태로 표현하면 0.116*exp (-1250/T)의 형태로 된다. 문헌에 보고된 계수를 이용해서 $29^{\circ}C$의 식각 속도와 플라즈마에 의한 가열 최고 온도인 $150^{\circ}C$ 때의 값을 비교해보면 3.3배의 차이가 난다. 따라서 4%내의 식각 균일도를 목표로 하는 폴리 실리콘 게이트 식각 장비의 설계에서는 플라즈마에 의한 가열 불균일을 상쇄 할 수 있는 히터와 냉각 구조의 최적 설계가 필요하다.

• Resources Recycling
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• v.25 no.6
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• pp.3-12
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• 2016

In this study, Au distribution in F-PGA chip and W-BGA chip were examined to recover Au effectively from CPU chips. The result showed that 80.8% and 89.8% of Au exist in terminal of F-PGA chip and bare die of W-BGA chip, respectively. Based on the fact that Au exists in specific parts of the chips, an CPU chip dismantling apparatus was developed. The experimental variables were roller rotating speed, heat temperature of IR heater and heating time. Terminals of F-PGA chips were completely recovered under the temperature of $300^{\circ}C$ and the residence time of 90 s. Bare dies of W-BGA chips were completely recovered as well under the temperature of $300^{\circ}C$, the roller rotating rate of 90 rpm and the residence time of 90 s.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.72-73
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• 2000

단원자를 이용한 Cavity-QED 실험을 통해서 광자 수상태 및 sub-poissonian 광원 구현 및 비고 전적인 광 특성을 가지는 광원등을 구현 할 수 있다. 이를 위해서는 오랫동안 공진기 안에 포획하거나, 빔의 형태로 단원자들이 일정시간 동안 공진기를 지나게 해야 한다. 본 연구는 안정한 원자빔 속도제어 실험에 관한 것으로 자체 제작한 원자빔 오븐의 특성과 원자빔 속도 선택기의 제작, 속도 선택 결과에 대하여 논하고자 한다. (중략)

• Composites Research
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• v.31 no.2
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• pp.63-68
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• 2018

Thermoplastic composite has been limitedly used in high performance aerospace industry due to relatively low mechanical properties even though it has various advantages. But, thermoplastic aromatic polymer composite has recently been researched and utilized much. In this study, PEEK and PPS neat resin film as representative thermoplastic aromatic polymer were processed through continuous heating, cooling and reheating cycle. Property change such as glass transition temperature and melting temperature were identified and crystallinity variation by different cooling rate were evaluated. In the first (heating) run, polymer specimens were kept for 5 minutes at higher temperature than melting point to remove previous thermal history, and crystallization reaction was controlled by adjusting cooling rate to 2, 5, 10, 20 and $40^{\circ}C/minute$ in the second (cooling) run. In the third (heating) run, specimen crystallinity were verified by measuring the melting enthalpy. The initial specimens containing high portion of amorphous structure exhibited cold crystallization and clear glass transition in the first run whereas they did not show in the third run due to the increase of crystalline structure portion. As cooling rate decreases through the second cooling run, the crystallinity of the specimen increased. PEEK polymer had 21.9~39.3% crystallinity depending on cooling rate change whereas PPS polymer showed 29.1~31.2%.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.2
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• pp.277-284
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• 2005

Micro-filtration (MF) or ultra-filtration (UF) system with hollow-fiber cartridge was introduced in order to improve the Quality level of commercial foxtail millet Yakju, which has an off-flavour and/or undesired colour after the thermal treatment. The filtration effects of cartridges such as MF (0.65, 0.45, 0.2, 0.1 $\mu$m) and UF (500 K dalton) were investigated. The physicochemical and sensory characteristics of the Yakju were then evaluated during the 6 months storage at room temperature. The exclusion ability of microorganism in samples was confirmed in all cartridges, but 0.45 pm MF-cartridge was suitable in the Yakju manufacture due to its superior filtration rate and efficiency. Changes in reducing sugar and colour difference of foxtail millet Yakju untreated or treated by heat ($65^{\circ}C$${\times}$10 min) were observed during the storage; after 6 months the L-value of thermal-treatment sample was decreased and its b-value, however, significantly increased so that its color became dark, in comparison to non-thermal treatment sample. This decrease of reducing sugar is assumed that color change is associated with non-enzymatic browning reaction. Sensory Quality of foxtail millet Yakju produced by non-thermal treatment was better than that of thermal treatment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.212-218
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• 2020

The purpose of this study is to investigate the fire resistance of ultra-high-performance concrete according to the amount of polypropylene fiber. Different mixtures according to the amount of polypropylene fiber were exposed to a maximum temperature of 900℃; and explosive spalling, residual compressive strength, and ultrasonic velocity of each specimen were evaluated. Test results showed that the fire resistance can be improved by including a small amount of polypropylene fiber in ultra-high performance concrete. It was not observed that explosive spalling occur at a temperature of 900℃ when the polypropylene fibers over 0.4% were included. Residual compressive strength and ultrasonic velocity decreased by 48% and 44%, respectively, compared to those at room temperature.

• Korean Journal of Food Science and Technology
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• v.47 no.4
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• pp.474-479
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• 2015

In this study, five different Gochujang (a traditional Korean sauce prepared using fermented red pepper paste) sauces were heated at $100^{\circ}C$ for 5 min using a continuous ohmic heating system. Ohmic heating yielded greater reduction in microbial counts (90-95% reduction) than did conventional heating (65-75% reduction). The sterilization effect of the continuous ohmic heater increased with increasing sample flow rate and decreasing Reynolds number inside the pipe. Low-viscosity samples had higher electrical conductivity and were better suited for ohmic heating than were high-viscosity samples. The color and texture were also satisfactorily maintained after ohmic heating. Compared with conventional heating, ohmic heating provided rapid and uniform heating, which is more suitable for aseptic thermal processing of viscous foods.

• Korean Journal of Food Science and Technology
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• v.27 no.4
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• pp.582-592
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• 1995

To measure rheological properties of the starch dough, an Extrusion Capillary Viscometer(ECV) cell was self-made and attached to Instron machine(Model 1140). Apparent viscosities of corn and waxy corn starch doughs were measured and their gelatinization degrees were determined by enzymatic analysis. When corn and waxy corn starch doughs with $36{\sim}52%$ moisture content were heated at $60{\sim}100^{\circ}C$, come-up time of the cold point of doughs decreased from 220 sec to 140 sec with increased in the moisture content. In the measurement range of $36{\sim}52%$ moisture content and $60{\sim}100^{\circ}C$ heating temperature, both corn and waxy corn starch doughs showed pseudoplastic flow behaviors. At the same shear rate, both shear stress and viscosity of starch dough decreased as the moisture content increased. At the moisture content above 44%, the shear stress and viscosity of starch dough decreased as the heating temperature increased from $60^{\circ}C\;to\;70^{\circ}C$, but increased as the heating temperature increased from $80^{\circ}C\;to\;100^{\circ}C$. When the moisture content increased and heating temperature, the gelatinization degree of starch dough increased from about 10% to about 62%. The gelatinization degree of waxy corn starch dough was $15{\sim}20%$ higher than that of corn starch dough under the same gelatinization conditions. The effects of moisture content on the viscosity of starch dough were examined by Arrhenius equation. As the moisture content increased, viscosity of starch dough decreased. But the effect of moisture content was greater in the range of $80{\sim}100^{\circ}C$ than in the range of $60{\sim}70^{\circ}C$ heating temperature.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.2
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• pp.108-115
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• 2009