• Composites Research
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• 제34권4호
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• pp.241-248
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• 2021

전기자동차 시장이 성장함에 따라 배터리 효율을 증가시키기 위해 차량 경량화 이슈가 대두되고 있다. 이에 전기자동차 배터리 모듈을 보호하는 배터리 모듈 커버를 기존 알루미늄 소재에서 알루미늄 대비 절반 수준의 무게를 가지는 고강도/고내열성 고분자 복합소재로 대체하고자 한다. 또한 복잡한 형상에 대한 제약이 없고, 다품종 소량생산에 유리한 3D 프린팅 기술을 접목하여 기술 변화가 빠른 초기 전기자동차 시장에 대응하고자 한다. 복합소재 역학에 기반하여 압출기를 통해 가공한 단섬유 GF(glass fiber)/PC(polycarbonate) 복합소재 내 유리섬유의 임계길이(critical length)가 453.87 ㎛임을 도출하였고, 사이드 피딩(side feeding) 방식의 가공법을 택함으로써 기존 365.87 ㎛이었던 잔류섬유길이를 향상시킴과 동시에 분산성을 향상시켰다. 이에 30 wt%의 GF가 함유된 GF/PC 복합소재로 인장강도(tensile strength) 135 MPa, 탄성계수(Young's modulus) 7.8 MPa의 최적의 물성을 구현하였다. 또한 3D 프린팅 필라멘트가 상용 필라멘트 규격인 두께 1.75 mm, 표준편차 0.05 mm를 만족하기 위해서 필라멘트 압출 조건(온도, 압출속도)을 최적화하였다. 제작된 필라멘트를 통해 기공률을 최소화하며 강도를 최대화하고, 동시에 생산성 향상을 위해 프린팅 속도를 최대화하는 다중 최적화 문제를 통해 3D 프린팅 공정조건(온도, 프린팅 속도)을 최적화하였고, 이로써 기존 상용화 되어있는 동일 소재 필라멘트 대비 인장강도 11%, 탄성계수 56%가 향상된 결과를 얻었으며, 출력물의 후처리(post-process)를 통해 후처리 전 대비 인장강도 5%, 탄성계수 18%를 추가로 향상시켰다. 끝으로 유한요소해석(finite element analysis, FEA) 기법을 활용하여 전기자동차 배터리 모듈 커버의 시험 규격(ISO-12405)의 Mechanical Shock test의 기준을 만족하도록 배터리 모듈 커버의 구조를 최적화하였고, 이로써 배터리 커버 시험규격을 만족하면서 동시에 알루미늄을 사용했을 때 대비 37%의 경량화를 달성하였다. 해당 연구 결과 및 연구 방법을 활용하여 향후 다양한 분야에 고분자 복합소재 3D 프린팅 기술이 활용될 수 있을 것으로 기대된다.

• 한국의류학회지
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• 제33권12호
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• pp.1883-1896
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• 2009

이 논문은 조선후기 보자기에 적용된 다양한 장식 특성을 연구한 것이다. 보자기는 물건을 싸거나 음식을 덮는 등 일차적으로는 실생활에 활용하기 위한 실용적 목적으로 제작되었지만, 보자기 제작은 전래된 상징적 문양의 표현을 통한 현세적 기원의 행위이기도 했으며, 또한 조선의 엄격한 유교 윤리 하에서 여성의 창작 욕구가 자유롭게 발현된 생활 속 여흥의 일부이기도 했다. 한국의 보자기에는 조각 잇기, 자수, 회염, 인염, 오려내기 세공 등 다양한 장식 기법이 활용되었다. 조각 잇기 기법이 활용된 조각보에서는 조선 여인들의 절약습관이 돋보이는데 이는 특히 자원의 재활용을 중시하는 오늘날의 가치와도 일맥상통하는 바가 있다. 자수가 놓인 수보에서는 상징적 문양의 표현을 통한 여인들의 소박한 바램이 읽혀진다. 한국 보자기는 회염이나 인염으로 장식되기도 했는데, 이들은 한국 복식 유물에서는 보기 어려운 장식 기법들이다. 농담을 조절한 다양한 색채의 당채 기법이나 단일색의 먹물 채색, 여러 종류의 도안이 새겨진 목판을 이용한 인염 기법 등이 이용되었다. 음식물이 묻지 않게 하기 위해 때로는 기름 종이로 보자기를 만들기도 했는데, 이러한 식지보에는 오려내기 세공이 장식 기법으로 활용되었다. 오려내기 기법의 원리는 스텐실 염색과 비슷하여 이를 또한 섬유제품 디자인에 활용할 수도 있다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1090-1093
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• 2004

In this paper, a problem of geometrically distorted images is considered. In particular, the paper discusses the detection of a watermark from a photographed image of the watermarked picture. The image is possibly obtained by using a digital camera. This watermark detection problem is made difficult by various geometric distortions added to the original picture through the printing and photographing processes. In particular, the paper focuses on the geometric distortion due to a projective transformation, as part of a camera 3D-to-2D imaging process. It is well-known that a cross ratio of collinear points is invariant under a perspective projection. By exploiting this fact, a projective-invariant digital watermarking technique is developed. By detecting the picture's corners, and the image center point at the intersection of two main diagonal lines, predefined cross ratios are used to compute the watermark embedded locations. From those identified embedding pixel locations, a watermark can be detected by performing a correlation between a watermark pattern and the image over those pixels. The proposed method does not require an inverse transformation on the distorted image, thus simplifying the detection process. Performance of the proposed method has been analyzed through computer experiments

• 한국측량학회지
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• 제17권1호
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• pp.69-78
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• 1999

최근 급속한 산업발전으로 환경오염에 대한 인식이 고조되고 있으며 오염방지에 대한 방법 및 기술 또한 다각적으로 연구되고 있다. 과거에는 환경오염에 대한 대응방향이 오염물질의 농도저감과 처리기술 개발등에 국한되어 왔으나 현재는 오염물질의 관리 및 평가와 같은 좀더 고차원적인 연구로 전환되고 있다. 본 연구에서는 환경정보 시스템구축에 대한 개념을 수립하고 그 기법을 제시하였으며 오염원과 오염부하량에 따른 환경정보의 데이터베이스 설계, 질의, 분석 그리고 출력기법을 개발하였다. 또한, LANDSAT TM 영상을 이용하여 토지이용도를 작성하였으며, PC상에서 Excel과 PC ArcView 프로그램간에 동적데이터교환을 이용하여 폐수배출시설허가관리대장 관리를 가능하게 하여 기존 GSIS용 프로그램의 문서관리에 대한 취약성을 극복할 수 있었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.39.2-39.2
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• 2011

With the steady increase in the demand for flexible devices, mainly in display panels, researchers have focused on finding a novel material that have excellent electrical properties even when it is bended or stretched, along with superior mechanical and thermal properties. Graphene, a single-layered two-dimensional carbon lattice, has recently attracted tremendous research interest in this respect. However, the limitations in the growing method of graphene, mainly chemical vapor deposition on transition metal catalysts, has posed severe problems in terms of device integration, due to the laborious transfer process that may damage and contaminate the graphene layer. In addition, to lower the overall cost, a fabrication technique that supports low temperature and low vacuum is required, which is the main reason why solution-based process for graphene layer deposition has become the hot issue. Nonetheless, a direct deposition method of large area, few-layered, and uniform graphene layers has not been reported yet, along with a convenient method of patterning them. Here, we report an evaporation-induced technique for directly depositing few layers of graphene nanosheets with excellent uniformity and thickness controllability on any substrate. The printed graphene nanosheets can be patterned into desired shapes and structures, which can be directly applicable as flexible and transparent electrode. To illustrate such potential, the transport properties and resistivity of the deposited graphene layers have been investigated according to their thickness. The induced internal flow of the graphene solution during tis evaporation allows uniform deposition with which its thickness, and thus resistivity can be tuned by controlling the composition ratio of the solute and solvent.

• Journal of Information Display
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• 제7권2호
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• pp.16-21
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• 2006

The effect of improvement on the surface morphology of screen-printed carbon nanotube (CND) films was studied by using the optically clear poly-dimethylsiloxane (PDMS) elastomer for surface treatment. After the PDMS activation treatment was applied to the diode-type CNT cathode, the entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field-emission characteristics over the as-deposited CNT film. Also, the cathode film morphology of a top gated triode-type structure can be treated by using the proposed surface treatment technique, which is a low-cost process, simple process. The relative uniform emission image showed high brightness with a high anode current. This result shows the possibility of using this technique for surface treatment of large-size field emission displays (FEDs) in the future.

• 한국의류산업학회지
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• 제6권4호
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• pp.433-439
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• 2004

Hanji costumes has four aspects that allow the creator or artist to create many variations. The pictorial effects of Hanji costumes are produced through variations in the dyes and brushes used for its application. The amount of water and texture of the Hanji mixture also influences the Hanji clothing. This effect was expressed using a dry brush technique, a dripping technique, India inks, and fragments from other Hanji works. A second aspect of Hanji clothing is the coloring effect in the Hanji costumes. The coloring is due to the fibers in the preparation mixture and the uniqueness of the dyes. The Hanji clothing was dyed various colors and patterns by dip dyeing, block dyeing, silk screens, digital printing. The third aspect of Hanji imagination in clothing is the decorative details. The details in Hanji clothing can be seen using frills, pleats, tucks and ribbons. The last variation of Hanji clothing can be expressed through crafting techniques. These techniques are the quality of paper string, cuts in the paper and paste ingredients. With Hanji cloth, it is possible to plait, roll, and crample into other flexible & useful materials.

• 한국군사과학기술학회지
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• 제13권1호
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• pp.114-119
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• 2010

There are a number of studies on chemically strengthened glass. Most of them are strengthened in molten salt bath below transformation range of glass. This research is distinguished from the aforementioned studies in that single $KNO_3$ powder was used by employing screen printing technique. In this study soda-lime-silicate(SLS) glasses for bulletproof glass application with various thicknesses were used. The maximum value of the bending strength is 791MPa heat treated at $480^{\circ}C$, which is about 4.3 times higher than the parent glass, which is the highest strength of all soda-lime glasses. In this study, it is also observed that Vickers hardness increased to $657H_v$, which is about 15% higher than the parent glass($568.7H_v$) and fracture toughness was not changed. Depth profiles measured by electron probe micro analyzer(EPMA) showed a correlation between the migrations of $K^+$ ions with bending strength of ion exchanged glasses.

• 복식문화연구
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• 제14권6호
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• pp.956-970
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• 2006

The purposes of this study was to analyze the characteristics of national races' costumes in Chinese contemporary costumes. For the purpose, this researcher concentrated on the relations between national races' costumes and Chinese contemporary costumes and discuss systematically depending on references such as fashion magazines, picture albums, and historical records. The results of study were as follows: First, the formation of fashion has been influenced by Man, Uighur, and Choson races. For example, Qipao, the tight style of Man race's fashion, Uighur race's bell style sleeve and cyclic skirt are applied to women's modern fashion. Second, weaving, printing, and embroidery technique of a minority race developed more than Han race, so applied still. Recently, Chinese contemporary costumes accepted the weaving technique of Miao and Uighur race through publicizing of a minority culture. Third, a national race's costumes are famous with splendid design and applied to modern fashion directly. They are commonly made to hair pin, necklace, earing, bracelet and so on. Recently, styles from a national race's costumes and old style are becoming popular to Chinese and it's easier to found such a fashion in market.

• Tribology and Lubricants
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• 제37권1호
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• pp.1-6
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• 2021

This paper presents the experimental results of hydrophobic surfaces developed using a stereolithography-based additive-manufacturing technique. The additive manufacturing technique can be used to manufacture objects with complex geometries from computer-aided design data. Several additive manufacturing methods, such as selective laser sintering, fused deposition modeling, stereolithography apparatus (SLA), and inkjet-based system, have been developed. The SLA is a form of three-dimensional printing technology used to create prototypes, patterns, and production parts in successive layers through photochemical processes. Light causes chemical monomers and oligomers to cross-link together to form objects composed of polymers. Moreover, this method is economical for fabricating surfaces with high output resolution and quality. Here, we fabricate various surfaces using different shapes using an SLA. The surfaces with micro-patterns are fabricated for 10 cases, including the biomimetic surface. The fabricated surfaces with various micro-patterns are evaluated for hydrophobicity performance based on the static contact angle. The contact angle is measured three times for each case, and the averaged value is used. The results indicate that the arrangements in a staggered structure have a larger contact angle than those in a line when the same micro-pattern is applied. Moreover, the mimetic surfaces exhibit more hydrophobic characteristics than those of artificial micro-patterns.