• Journal of Biosystems Engineering
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• 제32권1호
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• pp.57-62
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• 2007

The objectives of this study were to prepare a new artificial eardrum patch using water-insoluble chitosan for healing the tympanic membrane perforations and to investigate biomechanical properties and cyotoxicity of the chitosan patch scaffold (CPS). Tensile strength and elongation at the rupture point of CPSs were 2.49-74.05 MPa and 0.11-107.06%, respectively. As the biomechanical properties or CPSs varied with the concentration of chitosan and glycerol, the proper conditions for the CPS were found out. SEM analysis showed very smooth and uniform surface of CPSs without pores at x1000. The result of MTT test showed that CPSs had no cytotoxicity.

• 한국도로학회논문집
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• 제8권2호
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• pp.37-47
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• 2006

The structural response and performance of a flexible pavement can be improved through the use of geogrids as base course reinforcement. Current ongoing research at the University of illinois has focused on the development of a geogrid base reinforcement mechanistic model for the analysis of reinforced pavements. This model is based on the finite element methodology and considers not only the nonlinear stress-dependent pavement foundation but also the isotropic and anisotropic behavior of base/subbase aggregates for predicting pavement critical responses. An axisymmetric finite element model was developed to employ a three-noded axisymmetric membrane element for modeling geogrid reinforcement. The soil/aggregate-geogrid interface was modeled by the three-noded membrane element and the neighboring six-noded no thickness interface elements. To validate the developed mechanistic model, the commercial finite element program $ABAQUS^{TM}$ was used to generate pavement responses as analysis results for simple cases with similar linear elastic material input properties. More sophisticated cases were then analyzed using the mechanistic model considering the nonlinear and anisotropic modulus property inputs in the base/subbase granular layers. This paper will describe the details of the developed mechanistic model and the effectiveness of geogrid reinforcement when used in different quality unbound aggregate base/subbase layers.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.203-204
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• 2006

Studies on some biodegradable polymers and other materials such as hydrogels have shown the promising potential for a variety of surgical applications. Postoperative adhesion caused by the natural consequence of surgical wound healing results in problems of the repeated surgery. Recently, scientists have developed absorbable anti-adhesion barriers that can protect a tissue from adhesion in case they are in use; however, they are dissolved when no longer needed. Although these approaches have been attempted to fulfill the criteria for adhesion prevention, none can perfectly prevent adhesions in all situations. Overall of this work, a new method to fabricate an anti-adhesion membrane using biodegradable polymer and hydrogel has been developed. The ideal barrier for preventing postoperative adhesion would have the following properties; it should be (i) resorbable (ii) non-reactive (iii) easy to apply (iv) capable of being fixed in position. In order to fulfill these properties, we adopted solid freeform fabrication method combined with surface modification which includes the hydrogel coating, therefore, inner or outer structure can be controlled and the property of anti adhesion can be improved.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.85.1-85.1
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• 2011

In this study, Grafoil$^{TM}$ which has comparable electric resistance and chemical stability but is flexible, fragile, and cheap material was adopted as bipolar plates for proton exchange membrane fuel cell(PEMFC) having only one straight line flow channel. Because of its flexibility, pressurizations of cell with various pressures showed different operating characteristics compared to ordinary graphite-used PEMFC. While performances of both cells decreased as these were pressurized, investigation of ohmic and faradaic resistance by electrochemical impedance measurement indicated different tendency of change. Ohmic resistance of graphite-used cell increased with increasing pressure, which is reversed in Grafoil$^{TM}$-used cell. It is speculated that effective chemical reaction area is decreased with increasing pressure in case of graphite-used one, but because of flexible property of Grafoil$^{TM}$, gas diffusion layer in Grafoil$^{TM}$-used cell was well-activated. Different rate of change of faradaic resistances in both cells support this supposition. However, although optimum point of pressurization is found, it is required to investigate other operating conditions because of low performance compared to graphite-used cell.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.17-20
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• 2006

It often happen water leakage that roof membrane have a poor condition such as direct exposed to rain, ultraviolet lays, temperature change compare with other part of waterproofing. There are difficult to maintain the quality of waterproofing and durability due to use only few waterproofing materials in practical in spite of development and use the various waterproofing material as solution of these poor condition. Therefore, in this thesis, I would like to know the property to apply field and suggest other method to develop for this waterproofing method to adopt various field condition for roof tops, as searching exposed and complex waterproofing technology for roof tops which is reinforced sheet using rising system have a regular pitch, depth, space.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.55.2-55.2
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• 2009

A polymer electrolyte membrane (PEM) fuel cell has been getting large interest as a typical issue in useful applications. The PEMFC is composed of a membrane, catalyst and the bipolar plate. SnOx:F films on SUS316 stainless steel were prepared as a function of substrate with using electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) in order to achieve the corrosion-resistant and low contact resistance bipolar plates for PEM fuel cells. The SnOx:F films coated on SUS316 substrate at surface plasma treatment for excellent stability, before/after heat treatment for good crystalline structure and microwave power for were characterized by X-ray diffraction (XRD), auger electron microscopy (AES) and field emission-scanning electron microscopy (FE-SEM). The SnOx:F film coated on SUS316 substrate with various process parameters were able to observe optimum interfacial contact resistance (ICR) and corrosion resistance. It can be concluded that fluorine-doping content plays an important function in electrical property and characteristic of corrosion-protective film.

• 한국건축시공학회지
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• 제6권4호
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• pp.69-75
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• 2006

It often happen water leakage that roof membrane have a poor condition such as direct exposed to rain, ultraviolet lays, temperature change compare with other part of waterproofing. There are difficult to maintain the quality of waterproofing and durability due to use only few waterproofing materials in practical in spite of development and use the various waterproofing material as solution of these poor condition. Therefore, in this thesis, I would like to know the property to apply field and suggest other method to develop for this waterproofing method to adopt various field condition for roof tops, as searching exposed and complex waterproofing technology for roof tops which is reinforced sheet using rising system have a regular pitch, depth, space.

• 대한금속재료학회지
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• 제47권11호
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• pp.722-727
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• 2009

The bipolar plates are not only the major part of the polymer electrolyte membrane fuel cell (PEMFC) stack in weight and volume, but also a significant contributor to the stack costs. Stainless steels are considered to be good candidates for bipolar plate materials of the PEMFC due to their low cost, high strength and easy machining, as well as corrosion resistance. In this paper, 316L stainless steel with and without nitrogen ion implantation were tested in simulated PEMFC environments for application as bipolar plates. The results showed that the nitride formed by nitrogen ion implantation contributed the decrease of the interfacial contact resistance without degradation of corrosion property. The combination of excellent properties indicated that nitrogen ion implanted stainless steel could be potential candidate materials as bipolar plates in PEMFC. Current efforts have focused on optimizing the condition of ion implantation.

• 멤브레인
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• 제25권6호
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• pp.530-537
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• 2015

태양광 발전시스템은 태양복사에너지를 반도체의 광전효과를 이용하여 전기에너지로 직접 전환시키는 에너지변환 시스템이다. 태양전지의 내구성과 에너지변환율에 영향을 미치는 핵심소재로는 다층형 필름구조를 갖는 백시트를 들 수 있다. 대표적인 상용 백시트는 고내구성 poly(vinyl fluoride) (PVF) 필름이 중심축에 위치하고 가격저감을 위해 도입된 poly(ethylene terephthalate) (PET) 필름이 그 양쪽에 접합된 삼층구조로 구성된다. 하지만, PVF 필름의 높은 가격은 저렴한 고내구성 백시트를 요구하는 시장상황을 반영하기 어렵게 한다. 이를 위한 해결책으로는 PVF 필름을 결정성 PET 필름으로 대체한 탄화수소계 백시트가 될 수 있다. 하지만, PET 필름의 본질적인 가수분해에 대한 취약성으로 인해, 추가적인 수분에 대한 배리어성 부여는 필수적이다. 이를 위해 본 연구에서는 소수성 실리카 나노입자 분산기술을 활용한 수분차단성 폴리우레탄 접착제를 개발코자 하였다. 개발된 접착제는 내부에 위치한 PET 필름으로의 수분침투를 약화시켜, 가수분해속도를 지연시킬 것이라 기대되었다. 본 개념의 효용성을 확인하기 위해, 표준화된 온습도조건에 노출된 이후의 일반접착제와 수분차단성 접착제가 도입된 백시트의 기계적 강도 및 시간당 태양전지성능 변화가 비교평가되었다.

• 폴리머
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• 제27권4호
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• pp.307-312
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• 2003

고밀도 폴리에틸렌 (HDPE)과 초고분자량 폴리에틸렌 (UHMWPE)을 혼합하여 중공사막을 제조하고, 이의 형태구조와 물성 변화를 조사하였다. 분자량 측정과 FT-IR을 이용한 분석 결과, 상품화된 중공사막(Sterapore)은 고분자량의 HDPE로 제조되었으며, 표면은 친수성 고분자인 비닐 알코올/비닐 아세테이트 공중합체로 코팅되어 높은 수투과도를 갖는 이유를 규명하였다. HDPE/UHMWPE 블렌드에서 UHMWPE의 혼합 한계 조성비는 10 wt% 이하이며, UHMWPE의 분산성을 높이기 위하여 혼합과정에서 광유를 도입하여야 할 것으로 판단되었다. 제조된 HDPE/UHMWPE 블렌드 중공사의 기계적 물성과 막 구조는 Sterapore와 유사하였다.