• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.372.1-372.1
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• 2016

Recently, there are a lot of diseases all around the world. Out of them, Atherosclerosis (AS) is the most common cause of stroke, cardiovascular mortality, and myocardial infarction. The macrophage-derived foam cell, which is formed by oxidized low-density lipoprotein (oxLDL), is the crucial marker for AS. In this study, we report a label-free capacitance imaging technique with multi-electrode array (MEA). The lipid-rich aorta arch lesions, which are derived from an apolipoprotein-E receptor-deficient (apoE-/-) mouse, exhibit higher capacitance than the lipid-free aorta arch, allowing the capacitance imaging of lipid region in atherosclerosis. To improve the contacts between MEA and tissue, polypyrrole(PPy)-coated multi walled carbon nanotubes (MWNTs) multi electrode array (PPy-MWNTs-MEA) was fabricated. Compared to TiN-MEA, PPy-MWNTs-MEA yielded lower contact impedance and better capacitance images. In addition, we have also developed a flexible MEA using single walled carbon nanotubes on a PET substrate. The lipid region could be discriminated in the capacitance images of the lipid-rich aorta arch lesions measured using flexible MEA, demonstrating a feasibility of in vivo applications.

• 한국생산제조학회지
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• 제22권3호
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• pp.414-420
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• 2013

Research on decreasing the weight of composite sandwich panels is in progress. This paper reports the experimental results for the mechanical behavior of a composite sandwich panel. The skins of sandwich panels were made of glass fiber sheets and plywood matrix composites. Their interior layers consisted of glass fiber pultrusion pipes and gold foam. Experimental tests were performed to obtain the mechanical properties and complex mechanical behavior. Before fatigue tests, tensile tests and 3-point bending tests were carried out to obtain the optimal design and determine their strength and failure mechanisms in the flat-wise position. After the static test, a fatigue test were conducted at a load frequency of 5 Hz, stress ratio (R) of 0.1, and endurance limit for the S-N curve. It showed that the failure modes were related to both the core design and skin failure.

• 한국분말재료학회지
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• 제26권6호
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• pp.502-507
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• 2019

Macro-porous carbon foams are fabricated using cured spherical phenolic resin particles as a matrix and furfuryl alcohol as a binder through a simple casting molding. Different sizes of the phenolic resin particles from 100-450 ㎛ are used to control the pore size and structure. Ethylene glycol is additionally added as a pore-forming agent and oxalic acid is used as an initiator for polymerization of furfuryl alcohol. The polymerization is performed in two steps; at 80℃ and 200℃ in an ambient atmosphere. The carbonization of the cured body is performed under Nitrogen gas flow (0.8 L/min) at 800℃ for 1 h. Shrinkage rate and residual carbon content are measured by size and weight change after carbonization. The pore structures are observed by both electron and optical microscope and compared with the porosity results achieved by the Archimedes method. The porosity is similar regardless of the size of the phenolic resin particles. On the other hand, the pore size increases in proportion to the phenol resin size, which indicates that the pore structure can be controlled by changing the raw material particle size.

• 한국전자파학회논문지
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• 제14권9호
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• pp.950-954
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• 2003

본 논문에서는 내부 전자파원에 의해 여기된 공동의 내벽 한 면에 손실 유전체를 설치한 경우 공동 내부로 공급된 전력과 반사계수를 계산하였으며, 손실 유전체에 의해 공동 내부의 전자계가 저감되는 특성을 검토하고있다. 이론 해석으로는 내부 전자파원의 전류 분포 및 손실 유전체 경계면에서의 전계분포에 관한 연립 적분방정식을 유도하고 Galerkin의 모멘트법으로 해석하여 공동체 공급된 전력과 반사계수를 구하고 있다. 이론해석 결과, carbon을 함유한 발포 폴리스티렌을 손실 유전체로 사용하여 유전체의 두께와 carbon 함유량을 조절함으로써 공동 내부 전자파원으로부터의 전자파 방사를 저감시킬 수 있음을 보이고 있으며, 공급 전력의 실험치와도 비교하여 이론 해석의 타당성을 확인하고 있다.

• 한국화재소방학회논문지
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• 제15권3호
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• pp.7-13
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• 2001

본 연구는 고분자재료 중 방염미처리된 합판, 방염처리된 합판, 경질PVC, 경질우레탄폼의 연소가스 독성평가를 위하여 열분해 온도 $600^{\circ}c$, $800^{\circ}c$, $1000^{\circ}c$에 따라 발생되는 연소가스를 가스텍(GASTEC) 가스검지관(Colorimetric gas detector tubes)을 이용하여 조사하였다. 연구결과 고분자재료의 연소시 발생되는 연소가스에 인간이 30달 동안 노출될 경우 사망에 이르는 독성지수를 갖고 있었으며, 열분해 온도 $800^{\circ}c$에서 독성지수는 경질 PVC가 31.94로 가장 높았다. 또한 열분해 온도에 관계없이 공통적으로 발생되는 연소가스는 이산화탄소($CO_2$)와 일산화탄소(CO)로. 나타났으며, 동일재료라도 열분해 온도에 따라 독성지수(T.I)는 차이가 있었다.

• 폴리머
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• 제37권6호
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• pp.685-693
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• 2013

반응 컴파운딩으로 개질한 poly(lactic acid)를 초임계 $CO_2(scCO_2)$를 사용하여 발포하였다. 발포는 $105{\sim}135^{\circ}C$와 12~24 MPa 범위에서 실시하였다. 발포체의 발포 배율과 셀 구조는 온도, 압력 및 감압 속도와 같은 발포 조건에 크게 영향을 받았다. 발포 온도와 포화 압력 증가에 따라서 발포 배율은 증가하다가 감소하였으며, 그 결과로 $120^{\circ}C$ 발포 온도 및 20 MPa 포화 압력에서 최대 발포 배율이 얻어졌다. 감압 속도가 느린 경우에는 셀이 장시간 동안 팽창함으로써 보다 큰 셀 구조를 가지는 발포체가 얻어졌다.

• 폴리머
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• 제36권1호
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• pp.34-40
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• 2012

초임계 $CO_2(scCO_2)$를 사용하여 poly(butylene succinate) (PBS)를 발포하였다. PBS는 용융 강도를 높이기 위하여 반응 컴파운딩 기법으로 개질하였다. $scCO_2$로 포화된 PBS를 강하 융점 이상의 온도에서 빠르게 압력을 낮춤으로써 미세기포 발포체를 제조하였다. 발포체의 구조는 공정 조건을 변화시켜 제어할 수 있었다. 다른 변수들은 고정하고 발포 온도만 변화시킨 실험은 발포 온도가 높을수록 셀 크기는 증가하고, 셀 밀도는 감소함을 보여주었다. 포화 압력이 클수록 기핵 밀도가 높아졌으며, 그 결과로 셀의 크기는 감소하였다. 감압 속도가 느린 경우에는 셀이 장시간 동안 팽창함으로써 보다 큰 셀이 얻어졌다.

• Korea-Australia Rheology Journal
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• 제16권1호
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• pp.47-54
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• 2004

Low Reynolds number, dilute, and surfactant-free bubble suspensions are prepared by mechanical mixing after introducing carbon dioxide bubbles into a Newtonian liquid, polyol. The apparent shear viscosity is measured with a wide-gap parallel plate rheometer by imposing a simple shear flow of capillary numbers(Ca) of the order of $10^{-2}$ ~ $10^{-1}$ and for various gas volume fractions ($\phi$). Effects of capillary numbers and gas volume fractions on the viscosity of polyol foam are investigated. At high capillary number, viscosity of the suspension increases as the gas volume fraction increases, while at low capillary number, the viscosity decreases as the gas volume fraction increases. An empirical constitutive equation that is similar to the Frankel and Acrivos equation is proposed by fitting experimental data. A numerical simulation for deformation of a single bubble suspended in a Newtonian fluid is conducted by using a newly developed two-dimensional numerical code using a finite volume method (FVM). Although the bubble is treated by a circular cylinder in the two dimensional analysis, numerical results are in good agreement with experimental results.

• 한국유체기계학회 논문집
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• 제15권6호
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• pp.11-17
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• 2012

The one way fluid structure interaction analysis on advanced propeller blade for next generation turboprop aircraft. HS1 airfoil series are selected as a advanced propeller blade airfoil. Adkins method is used for aerodynamic design and performance analysis with respect to the design point. Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. propeller geometry is generated by varying chord length and pitch angle at design point. Blade sweep is designed based on the design mach number and target propulsion efficiency. The aerodynamic characteristics of the designed Advanced propeller were verified by CFD(Computational Fluid Dynamic) and showed the enhanced performance than the conventional propeller. The skin-foam sandwich structural type is adopted for blade. The high stiffness, strength carbon/epoxy composite material is used for the skin and PMI(Polymethacrylimide) is used for the foam. Aerodynamic load is calculated by computational fluid dynamics. Linear static stress analysis is performed by finite element analysis code MSC.NASTRAN in order to investigate the structural safety. The result of structural analysis showed that the design has sufficient structural safety. It was concluded that structural safety assessment should incorporate the off-design points.

• 한국해양공학회지
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• 제35권4호
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• pp.247-256
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• 2021

In order to minimize carbon emissions and greenhouse gas, the Energy Efficiency Design Index (EEDI) has become a major factor to be considered in recent years in a ship's design and operation phases. Energy-Saving Devices (ESDs) improve the EEDI of a vessel and make them environmentally friendly. In this research, the performance of an equalizing duct-type ESD installed upstream of a Korea Research Institute of Ships & Ocean Engineering (KRISO) Container Ship (KCS) model's propeller was investigated by computational fluid dynamics (CFD). Open-source CFD libraries, OpenFOAM, were used for computational analysis of the KCS with and without the ESD to verify the performance improvement. The flow field near the stern region and propulsive coefficients were considered for comparison. The results showed a considerable improvement when an ESD was used on the model. Using different sizes of the duct, the performance of the ESD was also compared. It was observed that with an increased duct size, the propulsive performance was improved.