• 대한기계학회논문집
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• 제17권1호
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• pp.120-130
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• 1993

본 연구에서는 니켈의 가공시 나타나는 공구의 마멸에 대한 정량화 및 절삭변 수와의 연관성에 대한 연구는 그 자체가 마멸에 대한 데이터 베이스 측면에서 중요하 고, 이러한 접근방법으로는 연구가 거의 이루어지지 않았다는 측면에서도 큰 의미를 갖는다. 본 연구는 특히 경도가 큰 공구인 CBN, 소결 다이아몬드(poly crystal dia- mond 이하 PCD), 단결정 다이아몬드(single crystal diamond 이하 SCD)공구를 사용하 여 니켈의 절삭에서 나타나는 공구의 마멸에 대한 분석을 선행한 후 수집한 정보로부 터 절삭속도, 이송, 절삭깊이 및 공구의 nose반경이 공구의 마멸 및 표면의 성상(su- rface quality)에 미치는 영향에 대하여 고찰하였고 절삭조건의 변화에 따라 마멸에 대한 예상 곡선을 구하였다.

• 한국주조공학회지
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• 제15권3호
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• pp.272-282
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• 1995

Iron-based metal matrix composites have been recently investigated for the use of inexpensive abrasion resistance material. This paper carried out to investigate the in-situ reaction effects on the microstructural characteristics and the formation mechanism of tungsten carbides in a white cast iron matrix. The specimens of Fe-3.2%C-2.8%Si alloy cast-bonded with tungsten wire were cast in the metal mold and isothermally heat treated at $950^{\circ}C$ up to 48 hours. The typical microstructure of heat treated specimens showed the reaction layer of WC at the interface of tungsten wire and the carbon depletion zone between the WC layer and the matrix. During the formation of WC layer, if the carbon supply is insufficient due to the decarburization of matrix or the isolation of matrix by cast-bonded W wires, the reaction layer develops coarse hexagonal crystalline WC. From the microstructural investigation, it was found that the volume of WC layer and the carbon depletion zone increased linearly with the isothermal heat treating time. This results supported that the formation rate of WC in the white cast iron matrix is controlled by the interfacial reaction with a constant reaction rate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.631-631
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• 2013

Battery has major drawbacks including its size and life expectancy, and environmental problem. As an alternative, energy harvesting is emerging as a potential solution to replace battery along with more energy-efficient IT devices. The idea of harnessing energy from our living environment is sustainable, semi-permanent, and eco-friendly. Also, unlike battery, energy harvester does not require much space to store energy. Therefore, energy harvesting can provide a better source of power for small, portable, and wireless devices. Among various ways of harvesting energy from our surroundings, triboelectricity is chosen due to its potential to be miniaturized, and efficient. Triboelectric effect occurs as two different materials with different polarity of charge separation come into contact through friction, and then become separated so that electric potential difference is achieved. In this research, such characteristic of triboelectricity is used as a way to convert ambient mechanical energy into electric energy.Series of recent researches have shown promising results that the triboelectric energy harvester can be simple and cost effective. However, sufficient electricity level required to operate mobile devices has not yet been achieved.In this research, our group focuses on the design and optimization of triboelectric energy harvesting device to enhance its output. By using maskless lithography to pattern Kapton film and silicon substrate, which is used as a mold for PDMS thin layer, and sputtering metal electrodes on each side, we fabricate and demonstrate different designs of triboelectric energy harvester that utilizes the contact electrification between a polymer thin film and a metal thin foil. In order to achieve optimized result, the output voltage and current are measured under diverse conditions, which include different surface structure and pattern, material, and the gap between layers.

• Advances in nano research
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• 제13권2호
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• pp.199-206
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• 2022

We present the high-brightness large-area 10.1" in-cell polarizer display panel integrated with a wire grid polarizer (WGP) and metal reflector, from the initial design to final system development in a commercially feasible level. We have modeled and developed the WGP architecture integrated with the metal reflector in a single in-cell layer, to achieve excellent polarization efficiency as well as brightness enhancement through the light recycling effect. After the optimization of key experimental parameters via Taguchi method, the roll nanoimprint lithography employing a flexible large-area tiled mold has been utilized to create the 90 nm-pitch polymer resist pattern with the 54.1 nm linewidth and 5.1 nm residual layer thickness. The 90 nm-pitch Al gratings with the 51.4 nm linewidth and 2150 Å height have been successfully fabricated after subsequent etch process, providing the in-cell WGPs with high optical performance in the entire visible light regime. Finally we have integrated the WGP in a commercial 10.1" display device and demonstrated its actual operation, exhibiting 1.24 times enhancement of brightness compared to a conventional film polarizer-based one, with the contrast ratio of 1,004:1. Polarization efficiency and transmittance of the developed WGPs in an in-cell polarizer panel achieve 99.995 % and 42.3 %, respectively.

• 박물관보존과학
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• 제28권
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• pp.65-88
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• 2022

탄환의 특성과 거동은 화기 성능과 직결되므로 매우 중요하다. 그러나 전통 탄환과 관련된 연구 성과는 사실상 적은 편이다. 본고에서는 육군박물관 소장 조선시대 금속제 탄환의 재료와 제작 공정을 알아보기 위해 과학적 분석을 실시했다. 또한 탄환 직경에 따라 사용 가능한 조선시대 화기 종류를 분류하여 정리했다. 그 결과 탄환은 철환, 납환 및 수철연의환으로 구분되었다. 대부분의 철환과 납환은 주조로 제작되었다. 일부 철환은 단조로 제작되었다. 수철연의환은 철환을 주형에 넣은 후 용융된 납을 부어 주조하여 제작된 것으로 추정된다. 한편 탄환은 재료에 따라 비중이 확연히 구분되는 것을 확인할 수 있었다. 마지막으로 조사 대상 탄환은 소형 총통, 조총, 불랑기포, 현자총통, 대위원포, 소포, 홍이포 등에 사용 가능했다.

• 한국주조공학회지
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• 제43권4호
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• pp.187-193
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• 2023

쉘 중자 공법은 성형성, 탈사성에 있어서는 뛰어난 프로세스이나, 고온의 알루미늄 용탕이 중자와 접촉할 때 수지의 열분해에 의한 가스발생이 필연적이며, 이의 배출이 원활하지 못할 때에는 주물내부에 기공 등으로 남게 되어 주조품의 내기밀성에 직접 영 향을 미친다. 쉘 중자 이용 시 가스발생거동에 대해서는 일본에서 약간의 연구가 있었으나, 직접적인 예측 결과는 발표되지 않았고, 특 히 가스발생에 대한 모델링이 성립되어 있지 않아 이의 연구는 아주 미미한 상태이다. 개발되는 코어에 대한 온도-가스량과의 관 계를 고려한 발생 가스량 시뮬레이션 프로그램을 개발하고, 이를 이용하여 실린더 헤드 제품의 코어 금형 설계 및 저압주조 시 금속 용탕의 유동 및 응고 거동을 해석하고 주조결함 발생을 예측하여 결함발생을 최소화 하는 주조방안 도출하고자 한다.

• 한국정밀공학회지
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• 제31권11호
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• pp.975-979
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• 2014

Transparent conductive films (TCF) with excellent electrical properties and high mechanical flexibility have been widely studied because of their potential for application in optoelectronic devices such as light-emitting diodes, paper displays and organic solar cells. In this paper, we report on low-resistance and high-transparent TCF for flexible device applications. To fabricate a high-resolution roll imprinted TCF, the following steps were performed: the design and manufacture of an electroforming stamp mold, the fabrication of high-resolution roll imprinted on flexible film, the manufacture of Ag-nano paste which was filled into patterned film using a doctor blade process. Also, we was demonstrated with the successful application(ITO free organic photovoltaic) of the developed flexible TCF.

• 한국주조공학회지
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• 제20권5호
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• pp.344-353
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• 2000

In order to find out the casting conditions of the thin wall stainless steel exhaust manifold for automobile, the melt flow and solidification behavior simulated by the Z-CAST program were evaluated, and experimental casting result on the test casting and exhaust manifold of SSC13 alloy were investigated. From the results of this study, it was shown that the calculated results on fluid flow were in good agreement with practical thin wall test castings under the same casting conditions, as pouring metal is austenitic stainless steel(SSC13) and pouring temperature is 1575, 1630, and $1665^{\circ}C$ respectively. That calculated result with designed thin wall exhaust manifold was predicted filling up into the mold cavity, and practical casting was sound. The solidification simulation was predicted shrinkages at the bosses for original exhaust manifold, and designed it without bosses was predicted no defect. Therefore practical exhaust manifold casting was sound and in good agreement with calculated solidification results.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.631-636
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• 2002

The purpose of this study was to present the method to choose the optimization machining condition for the wire electric machine. This was completed by examining the ever- changing quality of the material and by improving the function of the wire electric discharge machine. Precision metal mold products and the unmanned wire electric discharge machining system were used and then applied in industrial fields. This experiment uses the wire electric discharge machine with brass wire electrode of 0.25mm. To measure the precision of the machining surface, average values are obtained from 3 samples of measures of center-line average roughness by using a third dimension gauge and a stylus surface roughness gauge. In this experiment, we changed no-node voltage to 7 and 9, pulse-on-time to $6\mu\textrm{s}$, $8\mu\textrm{s}$ and $10\mu\textrm{s}$, pulse-off-time to $8\mu\textrm{s}$, $10\mu\textrm{s}$ and $13\mu\textrm{s}$, and experimented on wire tension at room temperature by 1000gf, 1200gf, and 1400gf, respectively

• 한국생산제조학회지
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• 제23권1호
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• pp.64-68
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• 2014

This paper introduces the use of a crown-shaped (CR) lens to effectively diffuse the light from a light-emitting diode (LED) without any loss in the light intensity, in contrast to polymer-bulb-type diffusers. The diffusion lens was designed based on the Snell's law, which describes the physical path of a ray passing through the boundary between different media. CR lenses were fabricated by polydimethylsiloxane (PDMS) casting and UV-embossing processes, which used a pre-designed metal mold and UV-curable resin, respectively. Through experiments and optical evaluations, it was verified that the newly proposed CR lens not only decreased the vertical light strength and glare effect from an LED light source but also improved the diffusion characteristics while maintaining the quality of the LED's light intensity.