• 한국정밀공학회지
• /
• 제24권12호
• /
• pp.119-127
• /
• 2007

Recently, microstructures fabricated using microstereolithography technology have been used in the biological, medical and mechanical fields. Microstereolithography can fabricate real 3D microstructures with fine features, although there is presently a limited number of materials available for use in the process. Deformation of the fine features on a fabricated microstructure remains a critical issue for successful part fabrication, and part deformation can occur during rinsing or during fabrication as a result of fluid flow forces that occur during movement of mechanical parts of the system. Deformation can result in failure to fabricate a particular feature by breaking the feature completely, spatial deflection of the feature, or attaching the feature to neighboring microstructures. To improve mechanical strength of fabricated microstructures, a clay nanocomposite can be used. In particular, a high-aspect ratio microstructure can be fabricated without distortion using photocurable liquid resin containing a clay nanocomposite. In this paper, a clay nanocomposite was blended with a photocurable liquid resin to solve the deformation problem that occurs during fabrication and rinsing. An optimal mixture ratio of a clay nanocomposite was found through tensile testing and the minimal allowable distance between microstructures was found through fabrication experimentation. Finally, using these results, high-aspect ratio microstructures were fabricated using a clay nanocomposite resin without distortion.

• 한국염색가공학회지
• /
• 제20권3호
• /
• pp.31-38
• /
• 2008

Regenerated composite fibers were prepared from solution of styela clava tunics(SC) and poly vinyl alchol(PVA) using N-methylmorpholine-N-oxide(NMMO)/water(87/13)(wt%/wt%) as a solvent by dry jet-wet spinning. Structure and physical properties of regenerated composite fibers were investigated through birefrngence, x-ray diffratograms, tenacity, fibrillation and SEM. Optimal blend ratio of SC/PVA for mechanical properties of composite fibers was 70/30 and total weight was 4wt% concentrations in NMMO/$H_2O$ solvent system. Crystallinity index of composite fibers were decreased as the PVA contents increased. Fibrillation of $10{\sim}20wt%$ PVA blended fibers were occurred less than pure SC fiber. Shape of composite fibers were a circle cross section within 10wt% PVA content. But the cross section of fibers were changed as crushed flat with the PVA contents increased.

• 한국응용과학기술학회지
• /
• 제28권4호
• /
• pp.508-516
• /
• 2011

Hydrotreated biodiesel(HBD) is paraffinic bio-based liquid, with the chemical structure $C_nH_{2n+2}$, originating from vegetable oil(the process can also be applied to animal fat). The oil or fat is treated in a number of process, the most important being hydrogenation, in order to create a bio-based liquid diesel fuel. During the hydrogenation, oxygen is removed from the triglyceride and converted into water. Propane is formed as a by product and can be combusted and used for energy production. HBD can be used in conventional diesel engines, pure or blended with conventional diesel, due to its similar physical properties to diesel. This study reports the quality characteristics with chemical and physical properties as an alternative diesel fuel. Especially, HBD showed higher cetane value and number than FAME, and it is consisted of $C_{15}$ - $C_{18}$ n-paraffinic compounds. We also describes quality characteristics of HBD blends(2, 5, 10, 20, 30, 40, 50 vol%) in automotive diesel. HBD blends(max. 20 vol%) were the limit by the Korean specification due to poor low temperature characteristics.

• 한국의류산업학회지
• /
• 제17권6호
• /
• pp.1020-1029
• /
• 2015

This paper investigated the wearing performance of knitted fabrics made of air vortex yarns using PTT/tencel/cotton fibres in comparison with ring and compact yarns for emotional garment. Wicking property of knitted fabric made of MVS yarns was worse than those by ring and compact yarns, however, drying property of knitted fabric made of MVS yarns was better than those by ring and compact yarns, which was explained as more water vapor transport due to larger openness between fibres in the MVS yarns than those in the ring and compact yarns. Thermal conductivity of knitted fabric made of MVS was lower than those of ring and compact yarns and maximum heat flow(Q_max) at the transient state of MVS knitted fabric was lower than those of ring and compact yarns, which may be attributed to MVS yarn structure that has parallel fibres in the core part of the yarn and fasciated fibre bundles on the sheath part with roughness on the yarn surface. However, pilling of MVS knitted fabric was better than those by ring and compact yarns, which was caused by less and shorter hairy fibres protruded from MVS yarn surface than those of ring and compact yarns. It was observed that tactile hand of MVS yarn knitted fabrics was stiffer than those of ring and compact yarns knitted fabrics. It was explained by low extensibility and compressibility and high bending and shear rigidities of the MVS yarn knitted fabrics, which resulted in bad wearing performance of MVS knitted fabric.

• 대한토목학회논문집
• /
• 제32권6A호
• /
• pp.427-435
• /
• 2012

본 연구는 보통 및 혼합시멘트계 모르타르의 황산염침식 저항성에 대한 노출조건의 영향을 평가하기 위하여 수행되었다. 모르타르를 제조한 후, 3종류 노출조건, 즉 1) 연속 완전침지, 2) 연속 반침지 및 3) 건습반복 조건에서 모르타르의 팽창, 강도, 밀도 등 역학적 성능변화를 52싸이클까지 주기적으로 관찰하였다. 실험결과에 따르면, 연속 반침지(Exposure B) 조건에 노출된 OPC 모르타르가 황산염침식에 의한 다량의 균열이 발생하므로써, 연속 완전침지 조건 및 건습반복 조건에 노출된 모르타르에 비하여 성능저하가 상대적으로 크게 나타났다. 그러나, 고로슬래그미분말 및 실리카퓸을 사용한 혼합시멘트계 모르타르는 낮은 투수성 및 조직구조의 밀실화효과에 의하여 노출조건에 관계없이 우수한 황산염침식 저항성을 보였다. 따라서, 콘크리트 구조물이 황산염침식 환경에 노출될 경우, 노출조건에 대한 고려가 반드시 이루어져야 할 것으로 판단된다.

• 접착 및 계면
• /
• 제9권3호
• /
• pp.27-33
• /
• 2008

무기계 킬레이트의 일종인 aluminum acetylacetonate (AlACA)를 점착제의 -COOH 당량비에 따라 0, 0.25, 0.5, 0.75, 1의 비율로 변화 시키고, 점착제는 acrylic acid의 함량을 3 wt%, 7 wt%, 10 wt%으로 변화를 시켜 그에 따른 경화거동을 살펴 보았다. 킬레이트의 함량이 증가하면서 가교 구조가 형성되고, 이에 따라 probe tack의 fibrillation이 줄어들고, peel strength도 줄어드는 경향을 보였다. SAFT의 경우 점착제의 acrylic acid 함량이 증가함에 따라 확연히 증가하였다. 본 연구 결과, aluminum acetylacetonate는 점착물성을 크게 변화시키지 않는 범위에서 점착제를 가교 시킬 수 있음을 확인하였다.

• Membrane and Water Treatment
• /
• 제7권3호
• /
• pp.257-275
• /
• 2016

The enantiomeric and racemic effects of tartaric acid (TA) on the properties of polysulfone (PSn) ultrafiltration membranes were studied in terms of morphology and hydrophilicity (HPCT) of membrane. Asymmetric membranes were prepared by direct blending of polyvinyl pyrrolidone (PVP) with D-TA and DL-TA in membrane casting solution. FTIR analysis was done for the confirmation of the reaction of PVP and TA in blended membranes and plain PSn membranes. Scanning electron microscope (SEM), field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM) were used for analyzing the morphology and structure of the resulting membranes. The membranes were characterized in terms of pure water flux (PWF), hydraulic permeability and HPCT. PWF increased from $52L/m^2h$ to $79.9L/m^2h$ for plain and D-TA containing PSn membrane, respectively. Water contact angle also found to be decreased from $68^{\circ}$ to $55^{\circ}$. In Additionally, permeation and rejection behavior of prepared membranes was studied by bovine serum albumin (BSA) solution. A considerable increase in BSA flux (from $19.1L/m^2h$ for plain membrane to $32.1L/m^2h$ for D-TA containing membrane) was observed. FESEM images affirm that the pore size of the membranes decreases and the membrane permeability increases from 0.16 to 0.32 by the addition of D-TA in the membrane. D-TA increases the HPCT whereas; DL-TA decreases the HPCT of PSn membrane. PVP (average molecular weight of 40000 Da) with D-TA (1 wt%) gave best performance among all the membranes for each parameter.

• 폴리머
• /
• 제37권1호
• /
• pp.34-40
• /
• 2013

아민 작용기를 가진 POSS에 toluene diisocyanate(TDI)와 caprolactam(CL)의 반응물을 반응시켜 POSS 기반의 하이브리드 충전제(POSS-(TDI+CL))를 합성하였고 이를 상업용 폴리아미드계 열가소성 탄성체인 PA-TPE에 블렌딩하여 PA-TPE/POSS-(TDI+CL) 복합체를 제조하였다. POSS계 충전제의 화학구조는 FTIR과 $^1H$ NMR을 사용하여 확인하였다. PA-TPE/POSS-(TDI+CL) 복합체는 충전제를 PA-TPE에 7 wt%까지 첨가하여 제조하였고 이들은 순수 PA-TPE와 변성되지 되지 않은 PA-TPE/octaphenyl POSS의 복합체보다 낮은 tension set 값을 보여 탄성회복력이 향상되었다. 또한 하이브리드 충전제의 함량이 증가함에 따라 인장강도와 모듈러스가 증가하였다. 결론적으로 하이브리드 충전제인 POSS-(TDI+CL)는 원래 PA-TPE의 탄성에 나쁜 영향을 미치지 않고도 기계적 물성을 향상시킬 수 있는 적절한 충전제라 볼 수 있다.

• 한국환경교육학회지:환경교육
• /
• 제21권2호
• /
• pp.25-39
• /
• 2008

The purpose of the study was to develop cyber in-service training contents regarding environmental literacy for entry-level environmental public servants. The blended type of contents were developed, through literature review, contents analysis of other programs, and expert conferences. The validity of the contents developed was ensured experts in environment. Major research findings were as followings: First, there is a lack of time for entry-level environmental public servants to participate in the environmental in-service training programs. Therefore, cyber training can be a good solution to the problems with environmental training courses. It improves access to educational opportunities as it overcomes the limitations of time and space and provides hands-on experiences through multimedia materials that reflect the real world. Second, directions for developing cyber environmental education contents were represented in three parts; 1) strategies for developing cyber environmental education contents, 2) Models for developing cyber environmental education contents, 3) Contents selection for developing cyber environmental education contents Third, the developed contents for entry-level environmental officers consist of 4 domains: (1) the introduction to environment; (2) the natural scientific understanding of environment; (3) the humanistic understanding of environment; and (4) the social scientific understanding of environment. Fourth, the program developed was evaluated by 7 environmental education experts according to 10 evaluation items of total contents and contents development structure. In result, the validity of the program was ensured. Based on the results, some recommendations were suggested.

• 한국진공학회지
• /
• 제22권4호
• /
• pp.211-217
• /
• 2013

$PCDTBT:PC_{71}BM$과 $PTB7:PC_{71}BM$을 유기고분자 활성층 재료로 이용한 Bulk Hetero-Junction (BHJ) 구조의 유기박막태양전지를 플라스틱 기판 위에 각각 제작하여, 시간변화에 따른 단락전류밀도($J_{SC}$), 개방전압($V_{OC}$), 곡선인자(FF) 및 전력변환효율(PCE) 등 출력특성의 변화에 대해 고찰하였다. 유기박막태양전지의 출력특성 파라메터는 시간 경과에 따라 모두 감소하는 경향을 나타내었으며, 특히 개방전압의 감소폭이 컸다. 이러한 개방전압 감소의 원인은 빛에 대한 장시간의 노출과 산소를 포함하는 수분과의 접촉에 의한 LUMO 준위와 HOMO 준위 차의 감소가 그 원인이라 생각되며, 그 메커니즘에 대해 고찰하였다. 또한 유기박막태양전지 소자의 직렬 및 병렬 저항 값은 감소하다가 다시 증가하는 경향을 보였다. 이는 LUMO 준위와 HOMO 준위 차가 감소함에 의한 것과 공액 고분자 활성층 내부에서의 열적과정 손실에 기인하여 전극과 고분자의 계면에서의 접촉저항의 증가 때문이라고 생각된다. 유기박막태양전지의 전력변환효율은 초기에 급격한 감소를 보이다가 시간이 지날수록 감소폭이 차츰 둔화되어 한계치에 도달한 후, 포화되는 경향을 보였다. 이것이 유기박막태양전지가 실제 구동에서 발생시킬 수 있는 최소 출력특성값인 것으로 판단된다.