• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.10
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• pp.797-802
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• 2009

Large area crystallization of amorphous silicon thin-films on glass substrates is one of key technologies in manufacturing flat displays. Among various crystallization technologies, the Joule induced crystallization (JIC) is considered as the highly promising one in the OLED fabrication industries, since the amorphous silicon films on the glass can be crystallized within tens of microseconds, minimizing the thermally and structurally harmful influence on the glass. In the JIC process the metallic layers can be utilized to heat up the amorphous silicon thin films beyond the melting temperatures of silicon and can be fabricated as electrodes in OLED devices during the subsequent processes. This numerical study investigates the heating mechanisms during the JIC process and estimates the deformation of the glass substrate. Based on the thermal analysis, we can understand the temporal and spatial temperature fields of the backplane and its warping phenomena.

• Korean Journal of Food Science and Technology
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• v.27 no.3
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• pp.404-413
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• 1995

System parameters (extrusion temperature, extrusion pressure, specific mechanical energy, mean residence time) were analysed on three different screw configurations during twin-screw extrusion of wheat bran. Experiments were conducted over a screw speed of $280{\sim}380\;rpm$, feed rate of $22{\sim}38\;kg/hr$ and moisture content of $17{\sim}33%$ using screws assembled with 3, 4, and 5 reverse screw elements (RSE) adjacent to the heating zone of the barrel. Extrusion temperature increased with increasing RSE but it decreased with increasing feed rate and moisture content. Decreasing the filling ratio of the screw resulted in a lower extrusion pressure, and increasing the length of the RSE gave similar results due to the higher temperature and lower viscosity of melted dough. It was also observed that increasing the feed rate and decreasing moisture content resulted in the reduced extrusion pressure. Specific mechanical energy (SME) decreased when the feed rate and moisture content increased, and SME increased when using RSE posses from 3 to 5. Screw configuration posses with 4 RSE yielded the longest RT, and the smaller the die hole, the higher the RT. In contrast, RT decreased when the feed rate increased. With increasing moisture content RT for 3 RSE increased, but that for 4 and 5 RSE decreased.

• Journal of Life Science
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• v.32 no.7
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• pp.532-541
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• 2022

Obesity induced by high-fat diet (HFD) is verified as a strong risk factor and negative prognostic factor for prostate cancer in several genetically engineered mice although it was not examined in the normal mice. To investigate whether HFD-induced obesity can affect the development and progression of cancer in the prostate of normal mice, alterations in the weight and histological structure of the prostate as well as the expression of cancer-related proteins were analyzed in obese C57BL/6N mice fed with 60% HFD for 16 weeks. First, HFD-induced obesity, including an increase in organ weight, body weight, fat accumulation, and serum lipid profile, was successfully induced in C57BL/6N mice after HFD treatment. The total weight of the prostate significantly increased HFD-induced obesity in the model mice compared with the control group. Among the four lobes of the prostate, the weight of the ventral prostate (VP) and anterior prostate (AP) were higher in HFD-induced obesity model mice than in the control group, although the weights of the lateral prostate (DLP) and seminal vesicle (SV) were constantly maintained. In addition, the incidences of hyperplasia and non-hodgkin's lymphoma (NHL) in the histological structure were remarkably increased in HFD-induced obesity model mice, while the epithelial thickness was higher in the same group. A significant increase in the phosphorylation levels of key proteins in the AKT (protein kinase B) signaling pathway was detected in HFD-induced obesity model mice. Therefore, these results suggest that HFD-induced obesity can promote hyperplasia and NHL in the prostates of C57BL/6N mice through the activation of the AKT signaling pathway.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.143-143
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• 2003

최근 생활수준 및 생활환경의 향상에 힘입어 청결 및 쾌적을 추구하는 것이 사회적 현상으로 나타나고 있다. 요즘처럼 현대화된 시대에 '왜 항균제가 필요한 것일까' 라는 자연스러운 의문이 발생하게 되지만 현실은 항균제를 이용한 다양한 항균제품, 항균가전제품, 항균가공 내ㆍ건자재 및 항상 신선한 선도를 유지할 수 있는 제품 등이 호황을 누리고 있는 것이 현실이며 그 시장 규모는 3,000억원을 상회하고 있다. 이러한 항균 가공제품이 호평을 받는 사회적 배경은 우리를 둘러싼 주변 삶의 경제환경 신장에 따른 쾌적성 추구와 밀접한 관련이 있을 것이다. 이처럼 항균기능이 부여된 제품이 호평을 받고 있음에도 불구하고 국내에서는 항균제품의 주 기능 역할을 하는 항균제에 대한 개발은 초기단계로 국내 시장에서 많은 연구가 이루어지고 있는 실정이다. 국내의 경우, 유기 항균제의 사용이 전체 사용량의 80%를 차지하고 있고, 제올라이트나 인산염을 무기 담체로 항균성 금속 이온(Ag, Zn)을 물리적으로 결합시킨 무기 항균제가 개발된 것이 최근의 기술 수준이다. 이러한 유기 항균제는 미생물의 번식을 억제 또는 사멸시키기 위한 것이지만, 생체의 피부 세포에도 영향을 줄 수 있는 피부 자극원의 하나로 그 사용이 점차로 제한되고 있다. 무기 항균제는 안정성이나 항균력에서는 유기항균제 보다는 뛰어나지만 가격(경제성)이나 색(Color), 사용성 (Application)측면에서는 여러 가지 문제를 나타내고 있다. 귀금속이므로 가격이 고가이며, 금속고유의 색으로 회귀하려는 플라즈몬 효과에 의해 색(Color)의 조절이 불가능, 분말형태이므로 지류에 첨가시키는 방법 등이 큰 문제로 부각되고 있다. 이 러한 문제점을 해결할 수 있는 기술이 나노기술이다 나노기술(Nano-Technology)은 물질을 분자, 원자단위에서 규명하고 제어하는 기술로서 원자, 분자를 적절히 결합시킴으로서 기존 물질의 변형, 개조는 물론 신물질의 창출을 가능케 하는 기술이다. 나노기술은 여러분야로 세분화되지만 그중 산업화에 가장 접목이 용이한 기술이 나노입자(Nano-Particle)제어 기술이며, 나노입자는 통상적으로 입자크기가 수 nm에서 100nm이하 크기의 넓은 표면적을 가진 콜로이드 상의 불균일 분산입자를 말한다. 나노입자(Nano-Particle)는 기존의 입자($\mu\textrm{m}$)보다 물리적 및 광학적 성질이 우수하고 그 자체의 기능면에서도 탁월하기 때문에 국내외의 여러 산업에서도 기존제품의 품질 향상 및 기능성부여, 기존 공정의 개선 및 생산 원단위 절감 등 경제적, 생산적인 측면을 고려하여 적합한 나노입자를 채택, 적용하고자 하는데 많은 노력을 기울이고 있다. 이에 천연 항생제로 알려진 Ag, 즉 항균 및 탈취, 전기적 기능이 우수한 은(silver, Ag)을 나노(nm) 입자희 제조하고 이와 더불어 이산화티탄(TiO2) 복합 분체를 제조하여 제조된 나노 입자 및 복합 분체를 사용함으로써 환경 친화적이며 다양한 용도로 활용 가능한 소재 개발에 연구 내용을 두고 있다. 본 연구를 통한 기대 효과로서 환경성 측면에서는 환경 친화적인 나노 입자의 제조로 기능성 나노 입자에 친 환경성을 부여하여 유기계 항균제 대체 효과를 발현하고 이를 제품에 적용함으로써 다양한 기능을 가진 신소재 제조에 있다. 또한 경제적인 측면에서도 고부가 가치의 제품 개발에 따른 새로운 수요 창출과 수익률 향상, 기존의 기능성 안료를 나노(nano)화하여 나노 입자를 제조, 기존의 기능성 안료에 대한 비용 절감 효과등을 유도 할 수 있다. 역시 기술적인 측면에서도 특수소재 개발에 있어 최적의 나노 입자 제어기술 개발 및 나노입자를 기능성 소재로 사용하여 새로운 제품의 제조와 고압 기상 분사기술의 최적화에 의한 기능성 나노 입자 제조 기술을 확립하고 2차 오염 발생원인 유기계 항균제를 무기계 항균제로 대체할 수 있다. 이와 더불어 안료의 형상 균일화 기술을 확보하여 가격 경쟁력 및 부가가치 향상을 기대할 수 있다.

• Elastomers and Composites
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• v.47 no.4
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• pp.336-340
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• 2012

Residual stress in the injection molded part is originated from thermal shrinkage and shear stress during injection molding process. There are many measurement methods of residual stress in the plastic part. Residual stress in opaque products can be measured by chemical cracking test. This method enables the solvent and specimen to react and to cause cracks. Cracks developed according to the level of residual stress. Thus the stresses in plastic part can be quantitatively measured by counting the number of cracks or measuring the size of cracks. Relationship between stress and number of cracks in a plastic specimen has been investigated in this study. Bergen jig was used to give a strain in the specimens those were molded using PC/PBT and PC/ABS. Solvent for the chemical cracking test was prepared using tetrahydrofuran and methyl alcol with the ratio of 1 to 3. Stresses in the specimen can be calculated by strains those were imposed by Bergen jig. Cracks were developed for stress higher than certain level. The number of cracks increased by second order function for stress.

• Journal of Adhesion and Interface
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• v.25 no.1
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• pp.169-274
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• 2024

Recent attention has been drawn to materials that undergo reversible expansion and contraction in response to external stimuli, leading to morphological changes. These materials hold potential applications in various fields including soft robotics, sensors, and artificial muscles. In this study, a novel material capable of responding to high temperatures for protection or encapsulation is proposed. To achieve this, liquid crystal elastomer (LCE) with nematic-isotropic transition properties and polyimide (PI) with high mechanical strength and thermal stability were utilized. To utilize a solution process, a dope solution was synthesized and introduced into micro-printing techniques to develop a two-dimensional pattern of LCE/PI bilayer structures with sub-millimeter widths. The honeycomb-patterned LCE/PI bilayer mesh combined the mechanical strength of PI with the high-temperature contraction behavior of LCE, and selective printing of LCE facilitated deformation in desired directions at high temperatures. Consequently, the functionality of selectively and reversibly encapsulating specific high-temperature materials was achieved. This study suggests potential applications in various actuator fields where functionalities can be implemented across different temperature ranges without the need for electrical energy input, contingent upon molecular changes in LCE.

• Journal of Bio-Environment Control
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• v.7 no.1
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• pp.63-70
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• 1998

This study was carried out to investigate the interaction of selenate and sulfate ion in nutrient solution supplyed with selenate ion. At early growth stage, the growth of Mongolian wormwood was best at 3mM sulfate ion and 2mg/$\ell$Na$_2$SeO$_4$ treatment. As they were grown and matured, at the later growth stage, the effect of antagonism between selenate and sulfate ion on the growth of each plant decreased. At supplying with selenate ion in nutrient solution, the uptake of selenate by plant had negative correlation with sulfate ion concentration in nutrient solution. The higher sulfate ion concentration, the less selenium uptake. However, the effect of antagonistic interaction of selenate and sulfate ion on the selenium uptake increased with plant age. Whereas, the uptake of sulfate ion had positive correlation with sulfate ion concentration in nutrient solution at supplying with selenate ion in nutrient solution. The uptake of sulfate ion increased with increase of sulfate ion concentration in nutrient solution. The effect of this interaction with selenate and sulfate ion increased with growth and maturity of plant. However, at 3mM sulfate ion concentration in nutrient solution, sulfate ion concentration in plant tissue decreased markedly.

• Journal of Investigative Cosmetology
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• v.14 no.4
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• pp.455-462
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• 2018

This study aimed to investigate the antioxidant, antimicrobial and anti-inflammatory effects of Anemarrhena asphodeloides extracts using supercritical extraction. In the antioxidant test, the total concentration of polyphenol compounds was determined to be 22.58 mg/g (supercritical extraction), 18.75 mg/g (ethanol extraction) and 17.69 mg/g (hydrothermal extraction). The DPPH radical scavenging effects were 89.84% (ethanol extraction) and 64.86% (supercritical extraction) at 2000 mg/L. ABTS radical scavenging ability had an IC50 value at 250~500 mg/L for supercritical extraction, higher than that for hydrothermal and ethanol extractions. At 1000 mg/L, elastase inhibition rates were 64.08% for ethanol extraction and 45.84% for supercritical extraction. The antimicrobial effect of the supercritical extraction was higher than that of hydrothermal and ethanol extractions. NO production with stimulated LPS was decreased in a concentration-dependent manner and, at 20 ㎛/mL, NO production was reduced by 77% for supercritical extraction compared with 46% (ethanol extract) and 63% (hydrothermal extract). Here, we confirmed that superficial extracts of Anemarrhena asphodeloides displayed excellent antioxidant, antimicrobial and antiinflammatory effects and have potential to be used as a safe and natural cosmetic material in the future.