• Journal of the Korean Electrochemical Society
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• v.9 no.4
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• pp.170-177
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• 2006

Optimum design of flow channel in the separation plate of Proton Exchange Membrane Fuel Cell is very prerequisite to reduce concentration over potential at high current region and remove the water generated in cathode effectively. In this paper, fully 3 dimensional computational model which solves anode and cathode flow fields simultaneously is developed in order to compare the performance of fuel cell with parallel and interdigitated flow channels. Oxygen and water concentration and pressure drop are calculated and i-V performance characteristics are compared between flows with two flow channels. Results show that performance of fuel cell with interdigitated flow channel is hi민or than that with parallel flow channel at high current region because hydrogen and oxygen in interdigitated flow channel are transported to catalyst layer effectively due to strong convective transport through gas diffusion layer but pressure drop is larger than that in parallel flow channel. Therefore Trade-off between power gain and pressure loss should be considered in design of fuel cell with interdigitated flow channel.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.40-40
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• 2011

반도체 소자의 미세화와 더불어 세정공정의 중요성이 차지하는 비중이 점점 커지고, 이에 따라 세정 기술 개발에 대한 요구가 증대되고 있다. 기존 세정 기술은 화학약품 위주의 습식 세정 방식으로 패턴 손상 및 대구경화에 따른 어려움이 있다. 따라서 건식세정 방식이 활발하게 도입되고 있으며 대표적인 것이 에어로졸 세정이다. 에어로졸 세정은 기체상의 작동기체를 이용하여 에어로졸을 형성하고 표면 오염물질과 직접 물리적 충돌을 함으로써 세정한다. 하지만 이 또한 생성되는 에어로졸 내 발생 입자로 인해 패턴 손상이 발생하며 이러한 문제점을 극복하기 위하여 대두되는 것이 가스클러스터 세정이다. 가스 클러스터란 작동기체의 분자가 수십에서 수백 개 뭉쳐 있는 형태를 뜻하며 이렇게 형성된 클러스터는 수 nm 크기를 형성하게 된다. 그리고 짧은 시간의 응축에 의해 수십 nm 크기까지 성장하게 된다. 에어로졸 세정과 다르게 클러스터가 성장할 환경과 시간을 형성하지 않음으로써 작은 클러스터를 형성하게 되며 이로 인해 패턴 손상 없이 오염입자를 제거하게 된다. 이러한 가스 클러스터 세정을 최적화하기 위해서는 설계 단계부터 노즐 내부 유동의 수치해석에 기반한 입자 크기 분포를 계산하여 반영하는 것이 필요하다. 따라서 본 연구에서는 상용 수치해석 프로그램을 이용하여 세정 환경을 조성하는 조건에서의 노즐 내부 유동을 해석하고, 이를 통해 얻어진 수치를 이용하여 aerosol general dynamic equation (GDE)를 계산하여 발생하는 클러스터의 크기 분포를 예측하였다. GDE 계산 시 입자의 크기 분포를 나타내기 위해서는 여러 가지 방법이 존재하나 본 연구에서는 각 입자 크기 노드별 개수 농도를 계산하였다. 노즐 출구에서의 가스 클러스터 크기를 예측하기 위하여 먼저, 노즐 내부 유속 및 온도 분포 변화를 해석하였다. 이를 통하여 온도가 급격하게 낮아져 생성된 클러스터의 효과적 가속 및 에너지 전달이 가능함을 확인할수 있었다. 이에 기반하여 GDE를 이용한 입자 크기를 예측한 결과 수 나노 크기의 초기 클러스터가 형성되어 온도가 낮아짐에 따라 성장하는 것을 확인할 수 있었으며, 최빈값의 분포가 실험적 측정값과 일치하는 경향을 가지는 것을 볼 수 있었다. 이는 향후 확장된 영역에서의 유동 해석과 증발 등 세부 요소를 고려한 계산을 통해 가스 클러스터 세정 공정의 최적화된 설계에 도움이 될 것이다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.4
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• pp.399-405
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• 2018

The multi-layered and compartmented hydrogel was designed to examine the self-transforming for developing a 4D mask pack. The hydrogel consisting of two layers with different expansion ratios were fabricated to have specific curvature by self-folding assembly. In addition, the hydrogel compartmented with three different geometries was designed by varying of expansion ratios. The compartmented hydrogel with 0.03, 0. $0,03mm^{-1}$ of curvatures at room temperature was self-transformed with 1.33, 0, $1.33mm^{-1}$of curvatures at $37^{\circ}C$, enhancing the facial adhesion. Overall, this new strategy to prepare the multi-layered and compartmented hydrogel would be actively used in developing the 4D mask pack to self-transform by each facial curvature.

• Korean Journal of Agricultural Science
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• v.34 no.2
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• pp.171-179
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• 2007

The new insecticidal active molecules from the based on the holographic quantitative structure-activity relationships (HQSAR) between a series of $1-(R_1)-2-(n-octyl)-3-(R_2)$, $3-(R_3)-pseudothiourea$ derivatives and their insecticidal activities against Diamond-back moth (Plutella Xylostella Linnaeus) were designed and discussed quantitatively. The most active molecule from the based graphical analyses of atomic contribution maps with the optimized HQSAR C-1 model ($q^2=0.764$ & $r^2{ncv}=0.942$) was 1-(n-butyl)-2-(t-butyl)-3,3-diisopropylpseudothiourea (P1: $pI_{50}=5.30$, $IC_{50}=1.397ppm$). Therefore, it is suggested that the new designed molecule would increased the activity as much as 23.5 times as compared to X=n-octyl substituent 17($pI_{50}=4.00$, $IC_{50}=32.86ppm$) which was the highest active molecule in training set compounds.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.483-490
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• 2008

Minimization of nozzle induces many flow losses in micro-propulsion system. In this study, we studied about thermal transpiration based micro propulsion system to overcome these losses. Thermal transpiration device(Knudsen pump) having no moving parts can self-pump the gaseous propellant by temperature gradient only (cold to hot). We designed, fabricated the Knudsen pump and analyzed pressure gradient efficiency of membrane according to Knudsen number under vacuum condition. Experimental results showed that thick membranes are more effective than thin membranes in transition flow regime, and pressure gradient efficiency according to Knudsen number is increased to maximum 82% apart from membrane thickness in free molecular regime.

• The Inventors News
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• no.45
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• pp.1-16
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• 2006

'2006 여성발명 창의교실' 첫 수료식 개최/2006 대한민국 여성발명품 박람회/제12회 여성발명 우수사례 발표회/신세대 인터넷 용어, 상표 출원 증가/독창성가진 화투, 특허품으로 인정/대학 강의실에도 특허 열풍 분다/차세대 분자전자 메모리 특허 증가/교통카드 특허 이용료 협상 골머리/국제지식재산연수원, WIPO 공식 연수기관 지정/PCT, 국내단계 진입기간 31개월까지로 연장/직무발명 보상에 대한 길 더 넓어져/특허.실용신안, 권리 강화 되다/'특허행정체험단' 통해 고객 감동 실현/신규 발명교실 설치 계획 안내/사랑 확인해 주는 '연인의 잔' 발명/'무공해 플라스틱'으로 환경 사랑 나선다/중국, R&D 기지로 급부상하다/특허출원 실적, 대학별 빈부 격차 심해져/삼성,SDI,OLED 특허 출원 세계 최다/한국여성발명협회, 홈페이지 전면 개편/특허청, 국방과학연구소와 업무협력협정 체결/브랜드 경영 열풍, 지자체에도 분다/'DMB 기술표준과 전략적 특허분석' 발간/지렁이로 화장품, 비누 발명/건강 상식/시중 은행, 월드컵 미끼상품 못판다/역사 속의 발명품/하루 10문 발명교실/특허Q&A/조정숙 코코허브 대표/수원 매현중학교 발명교실/파마머리 발명, 올해로 1백주년/아이디어 착상 및 발명 기법/창의성은 우리의 밥줄이다/야마모토의 추잉껌/PSP진동기술 특허소송 소니패배/내셔널반도체, 특허 장난꾼 잡는다/특허청, '제7회 반도체 설계 공모전' 개최/KAIST 학생들, 특허청에서 '연구노트' 작성법 전수/특허법원, 전국법원 중 처음으로 구술변론 도입/한국여성발명협회 회원사 발명품 가이드/'2006 전국 발명표어 공모대회' 공고

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.196-200
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• 2005

A theoretical model for the calculation of chemical equilibrium composition of propellant combustion product is briefly presented for the performance analysis of monopropellant hydrazine rocket engine. Analysis result is compared to that of test and evaluation of 1-lbf class thruster and is scrutinized primarily from the view point of ammonia dissociation fraction. Chemical equilibrium composition and average molecular weight is additionally depicted according to the variation of propellant inlet pressures and the varying nozzle area ratio. The theoretical analysis is tried as a way of derivation of design parameters for mid- and large-thrust class of monopropellant rocket engines.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.669-675
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• 2009

A study has been made on the preparation of liquid resin of non-solvent and non-discoloration type for replacement of the soft PVC at room temperature. A new synthetic process was developed by structure-control design of polyurethane synthesis using pre-polymer and polyols as curing agent. The optimum recipe was made according to macro-glycols, molecular weight and reaction conditions, and the final products indicated that the mechanical properties such as tensile strength, tear strength and flexibility was very excellent than PVC products. Also, viscosity, hardness and color operations of the final products can be controlled by this system. And yellowing property by UV and NOx gas was improved from the various additive experiment.

• Korean Journal of Materials Research
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• v.24 no.4
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• pp.175-179
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• 2014

Ti and Ti alloys have been extensively used in the medical and dental fields because of their good corrosion resistance, high strength to density ratio and especially, their low elastic modulus compared to other metallic materials. Recent trends in biomaterials research have focused on development of metallic alloys with elastic modulus similar to natural bone, however, many candidate materials also contain toxic elements that would be biologically harmful. In this study, new Ti based alloys which do not contain the toxic metallic components were developed using a theoretical method (DV-$X{\alpha}$). In addition, alloys were developed with improved mechanical properties and corrosion resistance. Ternary Ti-Ag-Zr alloys consisting of biocompatible alloying elements were produced to investigate the alloying effect on microstructure, corrosion resistance, mechanical properties and biocompatibility. The effects of various contents of Zr on the mechanical properties and biocompatibility were compared. The alloys exhibited higher strength and corrosion resistance than pure Ti, had antibacterial properties, and were not observed to be cytotoxic. Of the designed alloys' mechanical properties and biocompatibility, the Ti-3Ag-0.5Zr alloy had the best results.

• Korean Journal of Cognitive Science
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• v.14 no.2
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• pp.15-25
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• 2003

The Monkey and Banana Problem is an example commonly used for illustrating simple problem solving. It can be solved by conventional approaches, but this requires a procedural aspect when inferences are processed, and this fact works as a limitation condition in solving complex problems. However, if we use DNA computing methods which are naturally able to realize massive parallel processing. the Monkey and Banana Problem can be solved effectively without weakening the fundamental aims above. In this paper, we design a method of representing the problem using DNA molecules, and show that various solutions are generated through computer-simulations based on the design. The simulation results are obviously interesting in that these are contrary to the fact that the Prolog program for the Monkey and Banana Problem, which was implemented from the conventional point of view, gives us only one optimal solution. That is, DNA computing overcomes the limitations of conventional approaches.