• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.294-295
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• 2018

유도가열은 전자기 유도 현상을 이용하여 금속체를 직접 가열하는 방식이며 높은 변환 효율로 전기에너지를 열에너지로 변환할 있다. 이로 인해 금속의 단조, 용해, 표면경화, 풀림 등 여러 응용분야를 통해 철강 및 기계 산업에 기여하고 있다. 단조용 유도가열기 전원장치는 높은 전력용량을 사용하여 주로 SCR을 이용한 위상제어 정류기를 적용한다. 하지만 입력단의 저 역률 및 전류의 THD가 높은 단점을 가진다. 따라서 본 논문에서는 이러한 단점을 보안하기 위해 단조용 유도가열 작업에 맞는 인터리브드 방식의 벅 컨버터와 전류원 인버터를 사용한 고효율 유도가열 전원장치를 제안한다.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.4
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• pp.235-239
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• 2001

급속 표면가열과 기존의 전기로 열처리에서 얻어지는 경화의 가장 중요한 차이점은 전자가 불균질한 오스테나이트를 생성할 수도 있다는 것이다. 즉, 오스테나이트에 미용해 탄화물이 존재할 수도 있고 탄소와 합금원소의 농도 구배가 존재할 수도 있다. 합금강에서, 이러한 탄화물은 합금성분이 비교적 높기 때문에 철 탄화물에 비해서는 좀 더 천천히 기지에 용해된다. 또한 망간, 크롬, 니켈 및 몰리브덴과 같은 치환형 합금원소는 천천히 확산한다. 따라서, 균일한 오스테나이트를 생성하기 위해서는 더 많은 시간과 더 높은 온도가 요구된다. 그러나 표면 구역의 낮은 경화능에도 불구하고 냉각속도가 마르텐사이트의 체적분율이 큰 미세조직을 확보할 만큼 충분히 크기 때문에 경도는 높게 된다.

• 대한치주과학회:학술대회논문집
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• 2006.11a
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• pp.52-52
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• 2006

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4A
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• pp.295-302
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• 2011

The setting time which is the important element for the determination of slip-up speed of Slip-Form system is the hardening time of early-age concrete when the in place concrete has minimum compressive strength before the concrete appears out of Slip-Form system. But it is very difficult to predict the setting time because it depends on not only the composition ratio of concrete but also various conditions of construction fields. Thus, the technique to estimate accurately and continuously the hardening time of early-age in place concrete during operating Slip-Form system is necessary to guarantee the safety of Slip-Form system and the maintenance of the shape of concrete. Ultrasonic wave-based nondestructive testing methods have the advantages which are accurate and continuous in estimating concrete compressive strength. Of such methods, the method using surface wave which propagates along the surface of material is effective for thick member such as a pylon. Thus, in this paper a study on the determination of slip-up speed for Slip-Form system using surface wave velocity is performed. The relation between the slip-up speed of Slip-Form system and the setting time is formulated, and the surface wave velocity is estimated from continuous wavelet transform of the numerical results for surface wave propagation. Finally, the accuracy of this method according to the distance between the wave source and receivers and the relation between the estimated surface wave velocity and the elastic modulus are investigated.

• Journal of the Korean Wood Science and Technology
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• v.42 no.3
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• pp.339-345
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• 2014

For enhancing productivity of glulam, high frequency (HF) curing technique was researched in this study. Heat energy is generated by electromagnetic energy dissipation when HF wave is applied to a dielectric material. Because both lamina and adhesives have dielectric property, internal heat generation would be occurred when HF wave is applied to glulam. Most room temperature setting adhesives such as phenol-resorcinol-formaldehyde (PRF) resin, which is popularly used for manufacturing glulam, can be cured more quickly as temperature of adhesives increases. In this study, dielectric properties of larch wood and PRF adhesives were experimentally evaluated, and the mechanism of HF heating, which induced the fast curing of glue layer in glulam, was theoretically analyzed. Result of our experiments showed relative loss factor of PRF resin, which leads temperature increase, was higher than that of larch wood. Also, it showed density and specific heat of PRF, which are resistance factors of temperature increase, were higher than those of wood. It was expected that the heat generation in PRF resin by HF heating would occur greater than in larch wood, because the ratio of relative loss factor to density and specific heat of PRF resin was greater than that of larch wood. Through theoretical approach with the experimental results, the relative strengths of ISM band HF electric fields to achieve a target heating rate were estimated.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.577-577
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• 2013

플라즈마를 이용하는 공정은 반도체 산업에서 박막트랜지스터, 평면 모니터와 LCD 등 다양한 반도체 및 디스플레이 소자를 제작하는데 중요한 기술 중 하나로 발전되어 왔다. 현재 플라즈마 공정 기술을 이용하여 소자의 크기를 수십 나노 이하로 공정함으로써 수율을 향상시킬 수 있었지만, 소자의 미세화는 그 한계점에 봉착하였다. 그러한 이유로 웨이퍼 사이즈의 크기를 대구경화 시킴으로써 이런 문제점을 극복하고자 하였지만, 대구경 웨이퍼 사이즈에 맞는 차세대 대면적 공정 장비와 그에 따른 플라즈마 소스의 개발과 이를 컨트롤 할 수 있는 능력이 매우 절실하게 되었다. 본 연구에서는 대구경 웨이퍼용 플라즈마 소스를 위해 상대적으로 낮은 압력과 고밀도 플라즈마를 발생시킬 수 있는 유도 결합형 플라즈마원을 사용하였다. 하지만 유도 결합형 플라즈마 소스의 경우 대구경화에 따른 안테나의 길이가 길어짐으로써 생기는 정상파 효과를 피할 수가 없게 되었다. 그러한 이유로, 본 연구에서는 정상파 효과를 줄일 수 있는 상대적으로 낮은 주파수를 사용하는 안테나의 형태를 이용하여 실질적인 공정 영역에 있어서의 균일도 문제를 해결하였다. 또한, 플라즈마의 특성조절을 위해 이중주파수를 사용함 으로써 플라즈마 특성 조절을 하였다. 이러한 형태의 이중주파수를 사용하는 플라즈마 소스를 이용하여 10 mTorr의 Ar/CF4 조건에서 양이온 종들을 PSM (Plasma Sampling Mass spectroscopy, HIDEN Inc.)을 통해 에너지를 분석하였다. 이중 주파수에 있어 전력비율에 따라 IEDs (Ion Energy Distributions)는 많은 변화가 관찰되었으며, 인가하는 입력전력에 따라 E-H mode 전이가 일어남을 관찰할 수 있었다.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.04a
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• pp.50-57
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• 2003

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.101-106
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• 2005

Photocurable modified 6 functional polyacrylate(PA-1) were prepared from dipentaerythritol derivatives (DPET) and acrylic acid, and 12 functional polymethacrylate(PA-2) were prepared from dipentaerythritol derivatives (DPET), trimellitic anhydride, and glycidyl methacrylate. And physical properties of photocurable modified poly(meth)acrylate were increased with increasing functionality of (meth)acrylate. Thermal stability of UV cured film obtained by using TGA was shifted to higher temperature as the increasing of functionality. Hardness, abrasion resistance and tensile strength of UV cured film were increased with increasing functionality of (meth)acrylate. Values of yellow index were increased with increasing functionality of (meth)acrylate.

• Journal of Nutrition and Health
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• v.53 no.1
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• pp.1-12
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• 2020

Purpose: Diabetic nephropathy is one of the most important diabetic complications prompted by chronic hyperglycemia, characterized by glomerulosclerosis, tubular fibrosis, and it eventually causes kidney failure. Nobiletin is a polymethoxyflavone present in tangerine and other citrus peels, and has anti-cancer and anti-inflammatory effects. This study investigated the effects of nobiletin on glomerular fibrosis through inhibition of the transforming growth factor (TGF)-β1-Src-caveolin-1 pathway. Methods: Human renal mesangial cells (HRMC) were incubated in media containing 33 mM glucose with or without 1-20 uM nobiletin for 3 day. The cellular expression levels of fibrogenic collagen IV, fibronectin, connective tissue growth factor (CTGF), TGF-β1, Src and caveolin-1 were all examined. In addition, TGF-β1, Src and caveolin-1 proteins were screened to reveal the relationship among TGF-β1-Src-caveolin-1 signaling in glomerular fibrosis. Results: High glucose promoted the production of collagen IV, fibronectin and CTGF in HRMC, which was inhibited in a dose dependent manner by 1-20 uM nobiletin. The Western blot data showed that high glucose elevated the expression of TGF-β1, Src, caveolin-1 and Rho GTPase. When nobiletin was treated to the HRMC exposed to high glucose, the expression of TGF-β1-Src-caveolin-1 was dampened. Finally, TGF-β1-Src-caveolin-1 signaling pathway was activated in high glucose-exposed HRMC, and such activation was encumbered by nobiletin. Conclusion: These result demonstrated that nobiletin blunted high glucose-induced extracellular matrix accumulation via inhibition of the TGF-β1-Src-caveolin-1 related intracellular signaling pathway. Nobiletin may be a potent renoprotective agent to counteract diabetes-associated glomerular fibrosis that leads to kidney failure.

• Korean Journal of Clinical Laboratory Science
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• v.53 no.2
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• pp.158-164
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• 2021

Hypertriglyceridemia is the main risk factor for atherosclerosis. It is reported that triglyceride (TG) induces macrophage cell death, and is involved in the formation of plaques and development of atherosclerosis. We previously reported that TG-induced cell death of macrophages is mediated via pannexin-1 activation, which increases the extracellular ATP and subsequent increase in potassium efflux, thereby activating the caspase-2/caspase-1/apoptotic caspases, including the caspase-8 pathway. Contrarily, some studies have reported that caspase-8 is an upstream molecule of caspase-1 and caspase-2 in several cellular processes. Therefore, this study was undertaken to investigate whether caspase-8 influences its upstream molecules in TG-stimulated macrophage cell death. We first confirmed that caspase-8 induces caspase-3 activation and poly ADP-ribose polymerase (PARP) cleavage in TG-treated macrophages. Next, we determined that the inhibition of caspase-8 results in reduced caspase-1 and -2 activity, which are upstream molecules of caspase-8 in TG-induced cell death of macrophages. We also found that ATP treatment restores the caspase-8 inhibitor-induced caspase-2 activity, thereby implying that caspase-8 affects the upstream molecules responsible for increasing the extracellular ATP levels in TG-induced macrophage cell death. Taken together, these findings indicate that caspase-8 potentiates the TG-induced macrophage cell death by activating its upstream molecules.