Thermal management is a critical issue for the development of high-performance electronic devices. In this paper, thermal conductivity values of mild steel and stainless steel(STS) are measured by light flash analysis(LFA) and dynamic thermal interface material(DynTIM) Tester. The shapes of samples for thermal property measurement are disc type with a diameter of 12.6 mm. For samples with different thickness, the thermal diffusivity and thermal conductivity are measured by LFA. For identical samples, the thermal resistance(Rth) and thermal conductivity are measured using a DynTIM Tester. The thermal conductivity of samples with different thicknesses, measured by LFA, show similar values in a range of 5 %. However, the thermal conductivity of samples measured by DynTIM Tester show widely scattered values according to the application of thermal grease. When we use the thermal grease to remove air gaps, the thermal conductivity of samples measured by DynTIM Tester is larger than that measured by LFA. But, when we did not use thermal grease, the thermal conductivity of samples measured by DynTIM Tester is smaller than that measured by LFA. For the DynTIM Tester results, we also find that the slope of the graph of thermal resistance vs. thickness is affected by the usage of thermal grease. From this, we are able to conclude that the wide scattering of thermal conductivity for samples measured with the DynTIM Tester is caused by the change of slope in the graph of thermal resistance-thickness.

본 연구에서는 영지버섯의 종류별 기능성 성분과 생리활성과의 상관관계를 분석하였다. 영지버섯은 담자 균류 민주름목 구멍장이 버섯과에 속하며 전세계에 분보하고 떡갈나무, 상수리나무 등 활엽수에서 주로 자생한다. 영지버섯은 색상과 형상에 따라서 적, 흑,자, 황, 백, 청, 녹각, 편목, 쓰가 영지로 구분을 하고 있다. 영지버섯은 한방에서 골을 강화하고, 치질과 신경쇄약, 소화불량 등 만성질환에 도움을 주며, 오미의 성분 준다고 나와있다. 영지버섯은 2010~2013년 영지버섯의 전국 생산량은 281 M/T(metric ton), 경기도, 충남, 전북에서 많이 생산되었고, 주요 성분으로 triterpene계(ganoderic acid A-T), steroid계(ganoderol A,B), 다당류 (예: ganoderan B), proteoglycan(예: GLIS) 등이 알려져 있다. 영지버섯의 생리활성으로서는 항종양작용, 심혈관계에 대한 작용, 세포보호작용, 면역증진, 항바이러스 작용 등의 약리효능을 나타내는 것으로 보고되고 있고, 본연구팀의 이전 연구 결과에서 항산화 효과 및 RAW 264.7 대식세포에 대한 항염증 효과를 돟물 실험을 통해 분석한 결과 우수한 효과를 나타낸 것을 보고한 바 있다. 또한, 본 연구팀은 영지버섯중 녹각 영지버섯 추출물의 엡스타인 바 바이러스에 대해서 위암세포 발달을 저해하는 효과를 나타내는 것을 동물 실험을 통해서 확인하였다. 이번 연구결과는 영지버섯류의 기능성 성분과 생리활성 상관관계를 분석하여 베타 글루칸이외의 성분들과 효능과의 상관관계를 분석함으로서 버섯을 이용한 고부가가치 산업화의 소재 개발의 기초를 마련하고자 하였다.

웰빙식품, 건강에 대한 관심 증대로 버섯의 소비량은 꾸준히 증가하고 있으나, 주로 생버섯으로 소비되 고 2차 가공식품의 기능성 구명으로 새로운 용도 개발 연구는 미진한 상황이다. 버섯의 고부가가치 창 출을 위해서는 버섯의 생산 및 단순가공형 산업에서 탈피하여 새로운 신기능성 구명 연구를 통해 새로 운 미래 바이오산업 확대를 위한 용도 창출을 위하여 본 연구를 수행하였다. 연구내용은 버섯류 35종 에 대한 전립선암세포내 PSA발현 억제 효능 및 이를 통해 확인된 버섯자원들의 함유성분 중 암에 관 련된 화합물들에 대한 구조적 상관관계를 분석하였다. 35종의 버섯류는 99% 에탄올 추출 및 물로 추출 후 동결건조하여 공시재료로 사용하였다. 그 결과 35종의 버섯중 느티만가닥(Hypsizigus marmoreus), 눈 꽃동충하초(Cordyceps takaomontana), 차가버섯(Inonotus obliquus), 동충하초(Cordyceps sinensis), 양송이 (Agaricus bisporus) 등에서 전립선암세포내 PSA 발현을 억제하는 효과를 보였다. 이들 버섯들은 면역력 을 높이는데 유효한 성분인 베타글루칸이 다량으로 함유되어 있어 면역력증진에 따른 전립선암세포의 증식 억제에 효과를 나타내고 있는 것으로 사료된다.

본 연구에서는 녹각영지버섯 추출물의 항산화 효과 및 lipopolysaccharide (LPS)/interferon (IFN)-γ로 자극 된 RAW 264.7 대식세포에서 항산화 효과 및 항염증 효과를 조사하였다. 녹각영지버섯의 항산화 활성 을 확인하기 위하여 1,1-diphenyl-2-picrylhydrazyl (DPPH)과 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radical 소거 활성 및 reactive oxygen species (ROS) 생성량을 측정한 결과, DPPH radical 및 ABTS radical 소거효과에 대한 IC50은 각각, 80.74, 52.28 ㎍/ml의 radical 소거능이 관찰되었으며 ROS 생성량은 농도 의존적으로 감소하는 것으로 나타났다. 그리고, RAW 264.7 대식세포를 이용하여 항산화 및 항염증 활성을 확인하기 위하여 ROS 및 nitric oxide (NO) 생성량을 측정한 결과, 활성산소 종 ROS와 염증 매개물질인 NO는 투여농도 의존적으로 감소하였다. 또한, 염증과 관련된 inflammatory cytokine의 발현을 농도 의존적으로 억제하여 항염증 활성을 나타내는 것을 확인할 수 있었다. 이상의 결과로부터 녹각영지버섯 추출물은 항산화 및 항염증을 지닌 기능성 소재로 활용이 가능할 것으로 사 료된다.

Glancing angle deposition (GLAD) is a powerful technique to control the morphology and microstructure of thin film prepared by physical vapor deposition. Chromium (Cr) thin films were deposited on a polymer substrate by a sputtering technique using GLAD. The change in thickness and Vickers microhardness for the samples was observed with a change in the glancing angle. The adhesion properties of the critical load (Lc) by a scratch tester for the samples were also measured with varying the glancing angle. The critical load, thickness and Vickers microhardness for the samples decreased with an increase in the glancing angle. However, the thickness of the Cr thin film prepared at a 90o glancing angle showed a relatively large value of 50 % compared to that of the sample prepared at 0o. The results of X-ray diffraction and scanning electron microscopy demonstrated that the effect of GLAD on the microstructure of samples prepared by sputter technique was not as remarkable as the samples prepared by evaporation technique. The relatively small change in thickness and microstructure of the Cr thin film is due to the superior step-coverage properties of the sputter technique.

In this study, the effects of cryogenic treatment cycles on the residual stress and mechanical properties of 7075 aluminum alloy (Al7075) samples, in the form of a tube-shaped product with a diameter of 500 nm, were investigated. Samples were first subjected to solution treatment at 470˚C, followed by cryogenic treatment and aging treatment. The residual stress and mechanical properties of the samples were systematically characterized. Residual stress was measured with a cutting method using strain gauges attached on the surface of the samples; in addition, tensile strength and Vickers hardness tests were performed. The detailed microstructure of the samples was investigated by transmission electron microscopy. Results showed that samples with 85 % relief in residual stress and 8% increase in tensile strength were achieved after undergoing three cycles of cryogenic treatments; this is in contrast to the samples processed by conventional solution treatment and natural aging (T4). The major reasons for the smaller residual stress and relatively high tensile strength for the samples fabricated by cryogenic treatment are the formation of very small-sized precipitates and the relaxation of residual stress during the low temperature process in uphill quenching. In addition, samples subjected to three cycles of cryogenic treatment demonstrated much lower residual stress than, and similar tensile strength compared to, those samples subjected to one cycle of cryogenic treatment or artificial aging treatment.

For heat exchanger applications, 2-ply clad materials were fabricated by rolling of aluminum (Al) and mild steel sheets. Effects of annealing temperature on interface properties, especially on inter-layer formation and softening of strain hardened mild-steel, for Al/mild steel clad materials, were investigated. To obtain optimum annealing conditions for the Al/mild steel clad materials, annealing temperature was varied from room temperature to 600˚C. At the annealing temperature about 450˚C, an inter-layer was formed in an island-shape at the interface of the Al/mild steel clad materials; this island expanded along the interface at higher temperature. By analyzing the X-ray diffraction (XRD) peaks and the energy dispersive X-ray spectroscopy (EDX) results, it was determined that the exact chemical stoichiometry for the inter-layer was that of Fe2Al5. In some samples, an X-layer was formed between the Al and the inter-layer of Fe2Al5 at high annealing temperature of around 550˚C. The existence of an X-layer enhanced the growth of the inter-layer, which resulted in the delamination of the Al/mild-steel clad materials. Hardness tests were also performed to examine the influence of the annealing temperature on the cold deformability, which is a very important property for the deep drawing process of clad materials. The hardness value of mild steel gradually decreased with increasing annealing temperature. Especially, the value of hardness sharply decreased in the temperature range between 525˚C and 550˚C. From these results, we can conclude that the optimum annealing temperature is around 550˚C under condition of there being no X-layer creation.

Saw wires have been widely used in industries to slice silicon (Si) ingots into thin wafers for semiconductor fabrication. This study investigated the microstructural and mechanical properties, such as abrasive wear and tensile properties, of a saw wire sample of 0.84 wt.% carbon steel with a 120 μM diameter. The samples were subjected to heat treatment at different linear velocities of the wire during the patenting process and two different wear tests were performed, 2-body abrasive wear (grinding) and 3-body abrasive wear (rolling wear) tests. With an increasing linear velocity of the wire, the tensile strength and microhardness of the samples increased, whereas the interlamellar spacing in a pearlite structure decreased. The wear properties from the grinding and rolling wear tests exhibited an opposite tendency. The weight loss resulting from grinding was mainly affected by the tensile strength and microhardness, while the diameter loss obtained from rolling wear was affected by elongation or ductility of the samples. This result demonstrates that the wear mechanism in the 3-body wear test is much different from that for the 2-body abrasive wear test. The ultra-high tensile strength of the saw wire produced by the drawing process was attributed to the pearlite microstructure with very small interlamellar spacing as well as the high density of dislocation.

Ultra-thin aluminum (Al) and tin (Sn) films were grown by dc magnetron sputtering on a glass substrate. The electrical resistance R of films was measured in-situ method during the film growth. Also transmission electron microscopy (TEM) study was carried out to observe the microstructure of the films. In the ultra-thin film study, an exact determination of a coalescence thickness and a continuous film thickness is very important. Therefore, we tried to measure the minimum thickness for continuous film (dmin) by means of a graphical method using a number of different y-values as a function of film thickness. The raw date obtained in this study provides a graph of in-situ resistance of metal film as a function of film thickness. For the Al film, there occurs a maximum value in a graph of in-situ electrical resistance versus film thickness. Using the results in this study, we could define clearly the minimum thickness for continuous film where the position of minimum values in the graph when we put the value of Rd3 to y-axis and the film thickness to x-axis. The measured values for the minimum thickness for continuous film are 21 nm and 16 nm for sputtered Al and Sn films, respectively. The new method for defining the minimum thickness for continuous film in this study can be utilized in a basic data when we design an ultra-thin film for the metallization application in nano-scale devices.

Carbon nanotube (CNT) cathodes were fabricated using nano-sized silver (Ag) powders as a bonding material between the CNTs and cathode electrodes. The effects of the powder size on the sintering behavior, the current density and emission image for CNT cathodes were investigated. As the diameter of the Ag powders decreases to 10 nm, the sintering temperature of the CNT cathode was lowered primarily due to the higher specific surface area of the Ag powders. In this study, it was demonstrated that nano-sized Ag powders can be feasibly used as a bonding material for a screen-printed CNT cathode, yielding a high current density and a uniform emission image.

공기역학적 현상중에서 물체에 작용하는 외부 공기력이 존재하지 않더라도 주기적인 물체의 진동에 의해 발생되는 유체에너지로부터 공기력이 생성된다. 이러한 메커니즘에 위해 생성되는 공기력을 자발공기력(self excited force)이라 하며 플러터 계수에 의해 산정된다. 유체흐름에서 발생되는 진동은 유속 이 작은 경우, 교량 단면에 생기는 미소 교란으로 인하여 탄성진동이 발생하여도 교량의 진동에 따라 일어나는 공기력에 의해 감쇠된다. 하지만 유속이 증가하여 임계 풍속에 도달하면 교량은 부감쇠를 가지게 되며 무한발산을 하게되며 결국 파괴에 이르게된다. 본 논문에서는 준정상 가정을 바탕으로 교량단면의 공기역학적 계수를 산정하며 기존 연구자들에 의해 제안된 산출식과 비교하고자 한다. 또한 대상단면(단면 1)에 대한 실험적 해석을 통해 각 연구자들의 산출식을 비교하였다.

본 연구는 바람의 난류에 의한 장대교량의 피로 및 사용성에 문제를 야기시킬수 있는 버페팅 현상에 대해 주파수 영역에서의 해석적 연구를 수행하였으며, 유한요소방법과 램던 이론에 의해 바람의 파워스펙트럼, 변동특성 및 교량 구조물의 응답을 산정하였다. 바람의 난류에 의한 버페팅 응답을 해석할 수 있는 전산 해석기술을 개발하였으며, 개발된 해석 프로그램을 통하여 예제를 수행하였다. 단순지지된 보 구조물에 대한 버페팅 응답을 수행하였으며, Scanlan의 해석방법과 비교, 검토한 결과 잘 일치하였다 . 끝으로 2경간 연속 사장교에 대한 해석을 수행하였다.