• 한국건축시공학회지
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• 제2권3호
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• pp.163-170
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• 2002

Recently, polishing tile(porcelain homogeneous polished tile) was used in the construction field as a finishing material. But, there happened some problems such as tile exfoliation by construction condition in early ages. Also, for use of polishing tile in the dry wall system which used to lightweight wall, the examination of adhesive stability of polishing tile is needed. In this study, adhesive strength of Polishing tile was investigated by tile bond types on gypsum board and non asbestos board coated by tar-urethane and Polymer modified cementitious waterproofing membrane(Series I). Then, the effect of heat stress and vibration was estimated on gypsum and non asbestos board(Series II). As the result of study are the follows; (1) Polishing tile(600$\times$400mm) construction on waterproofing layer : Both laboratory estimation and spot examination sieve were happened that fall of tile because their hardening speed is late. (2) To using powder style adhesives in the dry wail with waterproofing layer : Adhesive strength of tile is Influenced by interface bond area and base side condition. (3) Shock and heat stresses : obvious decline of adhesive strength is not happened

• 전기화학회지
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• 제10권1호
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• pp.36-42
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• 2007

전기 에너지를 가장 직접적으로 저장하는 기기로써 우리는 흔히 전지(battery)와 콘덴서(condenser)를 생각한다. 산업혁명 이후 과학과 기술의 엄청난 발전에 따라 여러 분야에서 다양한 문명이기의 개발과 활용이 있어왔지만 우리 생활에 밀접히 활용되고 있으며 각종 전기전자 시스템의 핵심 구성품인 이러한 전지나 콘덴서의 기술 발전 속도는 다른 분야에 비하여 상대적으로 뒤쳐진 상황이라고 볼 수 있다. 그러나 최근 10여년 동안 괄목할 만한 소재기술의 발전에 힘입어서 재래식의 콘덴서는 물론 니켈수소전지, 리튬이온전지, 리튬폴리머전지 등과 같은 최신형 2차전지들 조차도 갖지 못하는 장수명, 고출력 특성을 갖는 새로운 형식의 전기에너지 저장장치인 '전기화학커패시터(electrochemical capacitor)'의 개발이 실현되고 있다. 이에, 본 고에서는 전기화학커패시터에 대한 기본적인 이해와 이의 최신기술 동향에 대하여 간략히 소개하기로 한다.

• Steel and Composite Structures
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• 제35권4호
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• pp.463-474
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• 2020

In this paper, the influence of adding multi-walled carbon nanotube (MWCNT) on the pull behavior of steel and GFRP bars in ultra-high-performance concrete (UHPC) was examined experimentally and numerically. For numerical analysis, 3D nonlinear finite element modeling (FEM) with the help of ABAQUS software was used. Mechanical properties of the specimens, including Young's modulus, tensile strength and compressive strength, were extracted from the experimental results of the tests performed on standard cube specimens and for different values of weight percent of MWCNTs. In order to consider more realistic assumptions, the bond between concrete and bar was simulated using adhesive surfaces and Cohesive Zone Model (CZM), whose parameters were obtained by calibrating the results of the finite element model with the experimental results of pullout tests. The accuracy of the results of the finite element model was proved with conducting the pullout experimental test which showed high accuracy of the proposed model. Then, the effect of different parameters such as the material of bar, the diameter of the bar, as well as the weight percent of MWCNT on the bond behavior of bar and UHPC were studied. The results suggest that modifying UHPC with MWCNT improves bond strength between concrete and bar. In MWCNT per 0.01 and 0.3 wt% of MWCNT, the maximum pullout strength of steel bar with a diameter of 16 mm increased by 52.5% and 58.7% compared to the control specimen (UHPC without nanoparticle). Also, this increase in GFRP bars with a diameter of 16 mm was 34.3% and 45%.

• 대한본초학회지
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• 제31권5호
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• pp.41-46
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• 2016

Objectives : The Skin is composed of multiple layers, including the epidermis, dermis, and hypodermis. It provides a vital barrier structure that protects vertebrates from external environmental antigens, solvents, ultraviolet light, microorganisms, toxins, and weather conditions. Although several biological effects of Mori Follium have been reported, beneficial effects of Mori Follium in skin health remain unclear. In this study, we prepared water extract of Mori Follium (MLE) and evaluated the effects on melanin accumulation and expression levels of skin fibril-related proteins.Methods : The cytotoxicities of MLE in B16F10 melanoma and human skin fibroblasts (HSF) were examined by MTT assay. Inhibitory effect of MLE on the α-MSH- and IBMX-induced melanosis in B16F10 melanoma was examined. The expression levels of fibronectin, collagen 1α2, and CCN2 in MLE-treated HSF were analyzed by reverse transcription-polymer chain reaction (RT-PCR) and western blotting.Results : The MLE treatment for 24 h did not affect to the B16F10 and HSF at concentrations of 1, 10, 50, 100, 200, 400 and 800 ㎍/ml. The MLE treatment for 72 h significantly and dose dependently suppressed melanin accumulation in B16F10 melanoma. In addition, the MLE treatment up-regulated expression levels of skin fibril-related genes such as fibronectin, collagen 1α2, and CCN2 in HSF. Our western blot analysis revealed MLE-induced up-regulation of skin fibril-related genes required the activation of CCN2 protein.Conclusions : In conclusion, these findings suggest that the MLE could be used in development of cosmetic natural material of maintaining healthy skin.

• Smart Structures and Systems
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• 제17권4호
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• pp.593-610
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• 2016

In this study, an innovative and smart glass fiber-reinforced polymer (GFRP) hybrid bar was developed for stronger durability of concrete structures. As comparing with the conventional GFRP bar, the smart GFRP Hybrid bar can promise to enhance the modulus of elasticity so that it makes the cracking reduced than the case when the conventional GFRP bar is used. Besides, the GFRP Hybrid bar can effectively resist the corrosion of conventional steel bar by the GFRP outer surface on the steel bar. In order to verify the bond performance of the GFRP hybrid bar for structural reinforcement, uniaxial pull-out test was conducted. The variables were the bar diameter and the number of strands and pitch of the fiber ribs. Tensile tests showed a excellent increase in the modulus of elasticity, 152.1 GPa, as compared to that of the pure GFRP bar (50 GPa). The stress-strain curve was bi-linear, so that the ductile performance could be obtained. For the bond test, the entire GFRP hybrid bar test specimens failed in concrete splitting due to higher shear strength resulting in concrete crushing as a function of bar deformation. Investigation revealed that an increase in the number of strands of fiber ribs enhanced the bond strength, and the pitch guaranteed the bond strength of 19.1 mm diameter hybrid bar with 15.9 mm diameter of core section of deformed steel the ACI 440 1R-15 equation is regarded as more suitable for predicting the bond strength of GFRP hybrid bars, whereas the CSA S806-12 prediction is considered too conservative and is largely influenced by the bar diameter. For further study, various geometrical and material properties such as concrete cover, cross-sectional ratio, and surface treatment should be considered.

• Macromolecular Research
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• 제17권9호
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• pp.703-708
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• 2009

Silk fibroin scaffolds were examined as a biomaterial option for tissue-engineered cartilage-like tissue. In tissue engineering for cartilage repair using a scaffold, initial chondrocyte-material interactions are important for the following cell behaviors. In this study, the surface of nanofibrous silk fibroin (NSF) meshes was modified by a microwave-induced argon plasma treatment in order to improve the cytocompatibility of the meshes used as cartilaginous grafts. In addition, the effects of a plasma treatment on the cellular behavior of chondrocytes on NSF were examined. The plasma treatment resulted in an increase in the hydrophilicity of NSF meshes suggesting that the cytocompatibility of the mesh might be improved. Furthermore, the human articular chondrocytes showed higher viability on the surface-modified NSF meshes. These results suggest that the surface modification of NSF meshes by plasma can enhance the cellular behavior of chondrocytes and may be used in tissue engineering.

• Elastomers and Composites
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• 제48권2호
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• pp.125-132
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• 2013

본 고에서는 카본블랙 및 다양한 유기화합물의 혼합에 의해 제조되는 카본 마스터배치의 제조를 위한 신규 엔지니어링 시스템에 대하여 논의하고자 한다. 자동차 타이어와 일상 생활용품에서 각종 산업용품의 소재로 사용되는 고분자 수지는 색상 및 물성 조절을 위하여 대부분 충전제를 사용하고 있으며, 충전제로 카본블랙 또는 실리카가 가장 널리 사용되고 있다. 국내 부품소재산업은 원재료의 배합 등 재료개발의 측면에서는 비약적인 발전을 이루어 냈다. 하지만 제품의 대량생산을 위해 필수적인 요소인 엔지니어링 기술분야는 더딘 기술발전과 높은 해외의존도로 인해 산업적 측면에서 빠르게 성장하지 못하고 있는 실정이다. 따라서, 본 고에서는 카본 마스터배치 생산을 위한 제조 시스템으로 최근 국내 기업에서 개발된 신규 엔지니어링 기술에 대한 소개를 하고자 한다.

• 설비공학논문집
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• 제20권4호
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• pp.274-279
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• 2008

In the perspective of saving energy in buildings, high performance of insulation and air tightness for improving the heating and the cooling efficiency has brought the positive effect in an economical view. However, these building energy saving technologies cause the lack of ventilation, which is the direct cause of increasing the indoor contaminants, and it is also very harmful to residents because they spend over 90% of their time in the indoor area. Therefore, the ventilation is important to keep indoor environment clean and it can also save energy consumption. In this study, a HEPA type breathing wall is designed as a passive ventilation system to collect airborne particles and to supply fresh outdoor air. To make fine porous structures, polymer nano fibers which were made by electro spinning method are used as a precursor. The nano fibers are coated with SiO2 nano particles and finally the HEPA type breathing wall is made by sintering in the electric furnace at $300\sim500^{\circ}C$. The pressure drops of nano ceramic structure are 8.2, 25.5 and 44.9 mmAq at the face velocity of 2.0, 5.9 and 8.8 cm/s, respectively. Also the water vapor permeability is $3.6g/m^2{\cdot}h{\cdot}mmHg$. In this research, the porous nano ceramic structures are obtained and the possibility for the usage of a material for HEPA type breathing wall can be obtained.

• Macromolecular Research
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• 제17권2호
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• pp.128-132
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• 2009

Fucoidan, a sulfated polysaccharide derived from brown seaweed, is an important material valued for its various biological functions, including anti-coagulation, anti-aging, and immune system support. In this study, we examined the potential of fucoidan as a novel emulsifying agent in BSA (bovine serum albumin)-stabilized emulsion at a neutral pH. We measured the dispersed oil-droplet size, surface zeta-potential and creaming formation of 0.5 wt% BSA emulsion (20 wt% oil traction) in the absence and presence of fucoidan. The average particle size and zeta-potential value were 625.4 nm and -30.91 mV in only BSA-stabilized emulsion and 745.2 nm and -44.2 mV in 1.0 wt% fucoidan-added BSA emulsion, respectively. This result suggested that some positive charges of the BSA molecules interacted with the negative charges of fucoidan to inhibit the flocculation among the oil droplets. The creaming rate calculated from the backscattering data measured by Turbiscan dramatically decreased in 1.0 wt% fucoidan-added BSA emulsion during storage. Accordingly, the repulsion forces induced among the oil particles coated with 1.0 wt% fucoidan in emulsion solution resulted in significantly increased emulsion stability. The turbidity of the BSA-stabilized emulsion at 500 nm decreased during five days of storage. However, the fucoidan-added BSA emulsion exhibited a higher value of turbidity than the BSA-stabilized emulsion did. In conclusion, an anionic sulfated fucoidan lowered the surface zeta-potential of BSA-coated oil droplets via the electrostatic interaction, and subsequently inhibited the flocculation among the oil droplets, thereby clearly minimizing the creaming and phase separation of the emulsion.

• 한국자기학회지
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• 제16권1호
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• pp.66-70
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• 2006

본 연구에서는 음향화학법을 적용한 공침 기술을 이용, 균일한 마그네타이트 나노 입자를 합성하였다 이 방법을 통하여 합성된 마그네타이트 나노 입자를 이용하여 마그네타이트 나노 입자들이 균일하게 분산된 마이크로미터 크기의 키토산 미소구체를 제조하였다. 이 연구의 목적은 생분해성, 저독성, 생체친화성의 특징을 갖고 있는 키토산과 균일한 마그네타이트 나노 입자를 이용하여 자기공명 영상의 조영제와 혈관 폐색을 위한 혈관 색전물질 등에 활용 가능성 있는 초상자성 특성을 갖는 미소구체를 제조하는 것이다. 우리는 $1\%$ 아세트산 용액을 사용하여 키토산 용액을 제조, 마그네타이트 나노 입자들을 분산시켰다. 키토산이 알칼리 수용액에서 겔화되는 성질을 이용하여, 마그네타이트 나노 입자들이 분산된 키토산 용액을 알칼리 용액에 분무하여 초상자성 특성을 갖는 자성 키토산 미소구체를 제조하였다.