• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.110-112
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• 2006

Membrane electrode assembly (MEA) for polymer electrolyte fuel cell (PEFC) are commonly prepared in the research laboratory by spraying, screen-printing and brushing catalyst slurry onto membrane or other support material like carbon paper or polyimide film in a batch style. These hand applications of the catalyst slurry are painstaking process with respect to precision of catalyst loading and reproducibility. It has been generally mentioned that the adoption of continuous process is very helpful to develop the reliable product. In the present work, we report the results of using continuous type coater with doctor-blade to coat catalyst slurry for preparing the MEA catalyst layers In a faster and highly reproducible fashion. We show that while expectedly faster than batch style, the machine coater requires the use of slurry of appropriate composition and a properly selected transfer decal material in order to achieve superior MEA plat lnw loading reproducibility. To make highly viscous catalyst slurry that is imperative for using coater, we use 40wt.% Nafion solution and minimize the content of organic solvent. And the choice of proper high surface area catalyst is important in the viewpoint of making well-dispersed slurry. After catalyst coating onto the support material, we transferred the catalyst layer to both sides of Nafion membrane by hot-pressing In this case, the degree of transfer was Influenced by hot-pressing condition including temperature, pressure, and time. To compare the transferring ability, we compared so many films and detaching papers. And among the support, polyethylene terephthalate(PET) film shows the prominent result.

• 한국운동역학회지
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• 제31권3호
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• pp.183-188
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• 2021

Objective: The purpose of this study was to develop a stretchable joint motion sensor that is based on silver nano-particle. Through this sensor, it can be utilized as an equipment for rehabilitation and analyze joint movement. Method: In this study, precursor solution was created, after that, nozel printer (Musashi, Image master 350PC) was used to print on a circuit board. Sourcemeter (Keithley, Keithley-2450) was used in order to evaluate changes of electric resistance as the sensor stretches. In addition, the sensor was attached on center of a knee joint to 2 male adults, and performed knee flexion-extension in order to evaluate accurate analysis; 3 infrared cameras (100 Hz, Motion Master 100, Visol Inc., Korea) were also used to analyze three dimensional movement. Descriptive statistics were suggested for comparing each accuracy of measurement variables of joint motions with the sensor and 3D motions. Results: The change of electric resistance of the sensor indicated multiple of 30 times from initial value in 50% of elongation and the value of electric resistance were distinctively classified by following 10%, 20%, 30%, 40% of elongation respectively. Through using the sensor and 3D camera to analyze movement variable, it showed a resistance of 99% in a knee joint extension, whereas, it indicated about 80% in flexion phase. Conclusion: In this research, the stretchable joint motion sensor was created based on silver nanoparticle that has high conductivity. If the sensor stretches, the distance between nanoparticles recede which lead gradual disconnection of an electric circuit and to have increment of electric resistance. Through evaluating angle of knee joints with observation of sensor's electric resistance, it showed similar a result and propensity from 3D motion analysis. However, unstable electric resistance of the stretchable sensor was observed when it stretches to maximum length, or went through numerous joint movements. Therefore, the sensor need complement that requires stability when it comes to measuring motions in any condition.

• 한국기계가공학회지
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• 제18권3호
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• pp.33-40
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• 2019

FDM 3D printers have become widespread, and investment in the 3D printer industry is increasing. Therefore, many 3D printers are released and the functions of products are emphasized. However, to lower unit prices, open-type 3D printers are sold in kit form, and their performance is very low. If the 3D printer has many heat sources and is sealed, there is the possibility that the main accessories (the main board, power supply, and motor) will be damaged by trapped heat. At the same time, if the ambient temperature is low due to the properties of the material, the output quality deteriorates. In this study, we analyzed the temperature rise of the main accessories and the quality of the output by the heat bed when a chamber was added to an open-type 3D printer. We also compared the quality of the output due to the air flow with the temperature rise of the main accessories. Moreover, we found the optimal value. As a result of the quality analysis, it was finally confirmed that the case with the chamber at $95^{\circ}C$ was the best for the printing condition. In addition, in the absence of the chamber, the bending of the specimen was found to be large, and in the case of the chamber, the degree of bending was slightly decreased by 0.05 mm.

• Composites Research
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• 제35권6호
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• pp.463-468
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• 2022

상용 FFF (Fused filament fabrication) 3D 프린터로 제조된 탄소 단섬유강화 나일론 복합재료 구조의 내부 채움 패턴(Infill pattern)의 높은 공극률은 프린팅 된 구조의 기계적 성능을 결정한다. 본 연구는 프린팅 된 구조의 내부 채움 패턴의 공극률을 줄여서 기계적 특성을 개선하기 위해 사각형 내부 채움 구조로 제작된 Onyx 복합 재료 시편의 열압밀 조건에 따른 시편의 기계적 성능을 실험적으로 평가하고, 가장 우수한 기계적 물성을 유도하는 열압밀 공정 조건(145℃, 4 MPa, 12 min)을 찾았다. 현미경 관찰결과 열압밀 후처리를 겪은 복합재료 시편의 내부 채움 공극률이 효과적으로 줄어듦을 확인하였다. 후처리된 시편의 기계적 성능을 확인하기 위해, 후처리를 하지 않은 대조군 시편과, 후처리 후 밀도와 치수를 동일하게 설정하여 출력한 시편과 함께 인장시험 및 3점 굽힘시험을 수행하여 기계적 물성을 비교한 결과 열압밀 후처리를 수행한 경우 기계적 물성이 효과적으로 개선되는 것을 확인하였다.

• Tribology and Lubricants
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• 제38권5호
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• pp.199-204
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• 2022

This paper presents a numerical investigation of the influence of water molecule thickness on frictional behavior at the nanoscale using molecular dynamics simulation. Three different models, comprising water thin films of various thicknesses, were built, and indentation and sliding simulations were performed using the models. Various normal loads were applied by indenting the Si tip on the water film for the sliding simulation to evaluate the interplay between the water thin film thickness and the normal load. The results of the simulations showed that the friction force generally increased with respect to the normal load and thickness of the water thin film. The friction coefficient varied with respect to the normal load and the water film thickness. The friction coefficient was the smallest under a moderate normal force and increased with decreasing or increasing normal loads. As the water film became thicker, the contact area between the tip and water film became larger. Under well-lubricated conditions, the friction force was proportional to the contact area regardless of the water film thickness. As the normal force increased above a critical condition, the water molecules beneath the Si tip spread out; thus, the film could not provide lubrication. Consequently, the substrate was permanently deformed by direct contact with the Si tip, while the friction force and friction coefficient significantly increased. The results suggest that a thin water film can effectively reduce friction under relatively low normal load and contact pressure conditions. In addition, the contact area between the contacting surfaces dominates the friction force.

• 대한토목학회논문집
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• 제29권6D호
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• pp.771-779
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• 2009

GIS의 자료기반이 되는 수치지도는 주로 재래식 항공사진측량에 의해서 제작되고 있다. 따라서 촬영된 아날로그 항공사진은 필름의 현상, 인화, 스캐닝 작업 과정을 거쳐 수치지도 제작에 이용되고 있다. 하지만 디지털 항측카메라의 개발로 촬영된 사진의 전처리과정 없이 직접 디지털 영상의 획득이 가능하여 항공사진의 효율성이 극대화 되고 있는 실정이다. 본 연구 에서는 면형방식 카메라인 DMC(Digital Modular Camera) 영상의 블록구성에 따른 기하적 안정성을 검증하기 위하여 횡스트립의 유무, GPS/INS 외부표정요소의 유무 및 지상기준점 수를 달리한 조건으로 블록조정을 수행하였다. 각 조건별 블록조정의 결과로 부터 외부표정요소에 대한 잔차의 변화를 계산하여 정확도를 상호 비교하였다. 연구 결과 횡스트립 추가 시 블록은 기하학적으로 약 30% 안정함을 알 수 있었고, 외부표정요소에서는 횡스트립 추가 시 표준편차의 평균에서 X축으로 2cm, Y축으로 3cm, Z축으로 3cm 더 우수하였으며, omega는 6", phi는 4", kappa는 3" 더 우수하게 나타났다.

• 대한치과보철학회지
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• 제57권2호
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• pp.110-117
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• 2019

목적: 본 연구의 목적은 적층 가공(additive manufacturing)법, 절삭 가공(subtractive manufacturing)법, 전통적인 방법에 따른 임시 수복용 레진의 마모 저항성을 조사하는 것이다. 재료 및 방법: 제작방법에 따라 4개의 군으로 나누었으며, 각 군은 전용의 임시 수복용 레진을 사용하였다: S3P군, Stereolithography apparatus (SLA) 3D 프린터 및 전용의 광경화성 수지로 제작한 군; D3P군, Digital Light Processing (DLP) 3D 프린터 및 전용의 광경화성 수지로 제작한 군; MIL군, Milling machine 및 밀링용 레진 블록으로 제작한 군; CON군, 전통적인 방법 및 자가중합형 레진으로 제작한 군. 한편, 3D 프린팅된 레진 시편을 제작함에 있어 적층 각도와 층 두께를 각각 $0^{\circ}$와 $100{\mu}m$로 설정하였다. 구강내 환경을 재현하기 위하여 열순환 처리와 수평, 수직운동이 가능한 2축 chewing simulator를 사용하였으며, 하부에는 한쪽면이 편평하게 제작된 임시 수복용 레진을, 상부에는 끝이 3 mm 직경을 가지는 원뿔형의 steatite를 고정하여 마모시험 진행하였다(5 kg, 30,000회, 0.8 Hz, $5^{\circ}C/55^{\circ}C$). 임시 수복용 레진의 마모량은 마모 전후의 Standard Triangulated Language (STL) 파일과 전용의 CAD software를 이용하여 부피를 계산하였고, 주사전자현미경으로 마모 양상을 비교하였다. 결과: S3P군, D3P군, MIL군의 마모량은 CON군보다 유의하게 작았으며 (P < .05), S3P군, D3P군, MIL군 사이에는 통계학적으로 유의한 차이가 없었다 (P > .05). 주사전자현미경으로 마모면을 관찰한 결과, S3P군과 D3P군에서는 대합치의 운동 방향에 대해 수직적으로 갈라진 흔적이 발견되었다. MIL군에서는 전반적으로 균일한 마모면이 보인 반면, CON군에서는 대합치 운동 방향으로의 뚜렷한 마모 흔적과 다수의 기포가 관찰되었다. 결론: 본 연구의 한계 내에서, 3D 프린팅된 임시 수복용 레진은 치과용으로서 적절한 마모저항성을 보였다.

• 한국콘텐츠학회논문지
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• 제17권7호
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• pp.67-78
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• 2017

본 연구는 중증장애인생산품 생산시설 실태분석을 통해 중증장애인생산품 판매를 활성화하고, 생산시설 운영을 성공적으로 지원하는 방안을 제시하는데 목적이 있다. 2016년 12월 현재 지정받은 생산시설 403개 중 289개를 대상으로 조사하였다. 연구결과, 첫째, 중증장애인생산품 생산시설 289개소 중 장애인보호작업장(57.1%), 장애인복지단체(29.8%), 장애인근로사업장(13.1%) 순으로 나타났다. 근로자는 총 8,358명으로 1개 시설 평균 28.92명이고, 이중 장애인근로자는 6,119명(평균 21.17명)으로 나타났다. 근로장애인 중 중증장애인이 85.8%로 기준인 60%보다 높은 것으로 확인되었고, 근로장애인의 시급은 평균 5,235원으로 최저임금보다 낮은 수준으로 나타났다. 둘째, 지정품목은 인쇄/광고(18.6%)가 가장 많았고, 식품(14.3%), 사무/문구(12.8%)순으로 나타났다. 셋째, 총매출액은 1개소당 17.8억원이고, 매출원가는 15.7억원이며 이익은 2.1억원으로 나타났다. 또한, 지정받은 기간이 길수록 매출액이 증가하는 것으로 확인되었다. 넷째, 지정을 통하여 매출 향상, 장애인고용 향상, 장애인근로자 임금향상, 근무조건 개선에 도움이 되는 것으로 나타났다. 마지막으로, 성공적인 운영을 위해서 우선구매비율 확대(19.4%), 구매가산점 확대(17.5%), 판로지원 확대(10.2%)가 필요한 것으로 확인되었다. 이를 근거로 개선방안을 제시하였다.

• Design & Manufacturing
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• 제14권1호
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• pp.1-7
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• 2020

In this study, the variation of the shrinkage in the thickness direction of the molded parts according to the gate size of the polymer core fabricated through the 3D printer using the SLS method was studied. The polymer cores are laser sintered and the powder material is nylon base PA2200. The polymer cores have lower heat transfer rate and rigidity than the metal core due to the characteristics of the material. Therefore, the injection molding test conditions are set to minimize the deformation of the core during the injection process. The resin used in the injection molding test is a PP material. The packing condition was set to 80, 90 and 100% of the maximum injection pressure for each gate size. The runner diameter used was ∅3mm, and the gates were fabricated in semicircle shapes with cross sections 1, 2, and 3 ㎟, respectively. Thickness measurement was performed for 10 points at 2.5 mm intervals from the point 2.5 mm away from the gate, and the shrinkage to thickness was measured for each point. The shrinkage rate according to the gate size tends to decrease as the cross-sectional area decreases as the maximum injection pressure increases. The average thickness shrinkage rate was close to 0% when the packing pressure was 90% for the gate area of 1mm2. When the holding pressure was set to 100%, the shrinkage was found to decrease by 3% from the standard dimension due to the over-packing phenomenon. Therefore, the smaller the gate, the more closely the molded dimensions can be molded due to the high pressure generation. It was confirmed that precise packing process control is necessary because over-packing phenomenon may occur.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.344-344
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• 2014

Transparent amorphous oxide semiconductors such as a In-Ga-Zn-O (a-IGZO) have advantages for large area electronic devices; e.g., uniform deposition at a large area, optical transparency, a smooth surface, and large electron mobility >10 cm2/Vs, which is more than an order of magnitude larger than that of hydrogen amorphous silicon (a-Si;H).1) Thin film transistors (TFTs) that employ amorphous oxide semiconductors such as ZnO, In-Ga-Zn-O, or Hf-In-Zn-O (HIZO) are currently subject of intensive study owing to their high potential for application in flat panel displays. The device fabrication process involves a series of thin film deposition and photolithographic patterning steps. In order to minimize contamination, the substrates usually undergo a cleaning procedure using deionized water, before and after the growth of thin films by sputtering methods. The devices structure were fabricated top-contact gate TFTs using the a-IGZO films on the plastic substrates. The channel width and length were 80 and 20 um, respectively. The source and drain electrode regions were defined by photolithography and wet etching process. The electrodes consisting of Ti(15 nm)/Al(120 nm)/Ti(15nm) trilayers were deposited by direct current sputtering. The 30 nm thickness active IGZO layer deposited by rf magnetron sputtering at room temperature. The deposition condition is as follows: a rf power 200 W, a pressure of 5 mtorr, 10% of oxygen [O2/(O2+Ar)=0.1], and room temperature. A 9-nm-thick Al2O3 layer was formed as a first, third gate insulator by ALD deposition. A 290-nm-thick SS6908 organic dielectrics formed as second gate insulator by spin-coating. The schematic structure of the IGZO TFT is top gate contact geometry device structure for typical TFTs fabricated in this study. Drain current (IDS) versus drain-source voltage (VDS) output characteristics curve of a IGZO TFTs fabricated using the 3-layer gate insulator on a plastic substrate and log(IDS)-gate voltage (VG) characteristics for typical IGZO TFTs. The TFTs device has a channel width (W) of $80{\mu}m$ and a channel length (L) of $20{\mu}m$. The IDS-VDS curves showed well-defined transistor characteristics with saturation effects at VG>-10 V and VDS>-20 V for the inkjet printing IGZO device. The carrier charge mobility was determined to be 15.18 cm^2 V-1s-1 with FET threshold voltage of -3 V and on/off current ratio 10^9.