• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.749-750
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• 2012

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.1295-1296
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• 2010

• 한국생산제조학회지
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• 제18권3호
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• pp.307-314
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• 2009

Large area micro pattern replication has promising application potential in many areas. Rolling imprint process has been demonstrated as one of the most competitive processes for such micro pattern replication, because it has advantages in low cost, high throughput and high efficiency. In this paper, we developed a prototype of roll-to-flat(R2F) thermal imprint system for large area micro pattern replication process, which is one of the key processes in the fabrication of flexible displays. Experimental tests were conducted to evaluate the feasibility of system and the parameters' effect on the process, such as flat mold temperature, loading pressure and rolling speed. 100mm $\times$ 100mm stainless steel flat mold and commercially available polycarbonate sheets were used for the tests. The experimental results showed that the developed R2F system is suitable for fabrication of various micro devices with micro pattern over large area.

• 펄프종이기술
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• 제33권2호
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• pp.49-57
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• 2001

This study was performed to identify the effect of calendering variables on the properties of coated paper such as sheet gloss, surface roughness, opacity, etc. The effect of calendering variables including the number of nips, pressure, machine speed and moisture content on the properties of coated paper was investigated. The calender was installed with two steel rolls and one cotton-made roll. With this calender, the coated sheets were passed through the calender from 1 to 4 times, applying the linear pressure on calender rolls, 5 through 100kg/cm and operating the machine speed 3 to 12m/min. Also, the moisture content of coated sheet was varied about 5 and 10%. It was found that sheet gloss and surface roughness of coated paper was increased with increasing the number of passing nips, linear roll pressure and the moisture content of coated paper. But it was shown that the opacity and brightness of coated paper were decreased under the above conditions due to the blackening. It was also suggested that the soft nip possibly increased the thermoplasticity of coating layer with the heat of steel roll, resulting in the reinforcement of surface properties positively. The sheet gloss and surface roughness of coated paper could be improved by the longer dwell time over the rolls.

• 수산해양기술연구
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• 제40권1호
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• pp.65-72
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• 2004

This paper deals with an experimental study on the dynamical characteristics of ship motion during trawling job on the real sea. The experiments were carried out on the small stern trawler, and roll and pitch motion of the ship according to the wave directions were simultaneously recorded by P/C in the same sea conditions. From these data, the statistical properties and power spectra were obtained, and then the analysis of ship motion in trwal job was made. As a result, it was found that the pitch motions in trwal job were displayed low amplitudes on the whole, but the rolling motions were displayed high amplitudes relatively, and very high value on the beam and quartering sea especially. Also, the trial ship has a high extinction coefficient in the roll motion, compared with the rule of stability, but when wave height takes 2.5m over, it can induce the safety of ship to scare occasionally. Therefore, a usefull countermeasure for the safety of ship has to be made adequately.

• 한국주조공학회지
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• 제16권2호
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• pp.124-131
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• 1996

High temperature properties such as hot hardness and thermal fatigue resistance of high speed steel roll of hot finishing mill have been investigated. Two kinds of roll having compositions, Fe-1.75%C-5.9%Cr-1.74%Mo-4.94%V-2.03%W(A specimen) and Fe-2.27%C-8.86%Cr-2.91%Mo-3.92%V-1.86%W(B specimen)were prepared for investigating the microstructure and crack propagation mode. A specimen has greater amounts of $M_7C_3$ type carbides and less amounts of MC type carbides in comparison with B specimen. Hot hardness showed sudden decrease over $400^{\circ}C$, resulting in the hardness decrease of 50% at the temperature of $600^{\circ}C$, and showed little variation with time at $500^{\circ}C$ and $800^{\circ}C$. Thermal crack was developed at $550^{\circ}C$ in A specimen and $600^{\circ}C$ in B specimen.

• 소성∙가공
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• 제25권3호
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• pp.161-168
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• 2016

Sheet metals are often required to be formed into three dimensional curved shapes for use as skin structures. As a result various sheet metal forming methods, such as press die forming, stretch forming, and line heating have been used over the years in industrial production lines. Although they are extensively used in industry, these methods are not suitable for small quantity batch productions. Studies have been conducted to improve or replace these methods with plausible flexible forming technologies. As a part of these studies, we developed a new and more efficient forming device named flexibly-reconfigurable roll forming (FRRF). The current study presents the process development and experimental verification for the applicability of this device. To improve the efficiency of the FRRF apparatus, several hardware components were invented and a suitable operating program was developed using MFC of visual C++. The ways to make the FRRF apparatus fully functional are also described. Sheet metal was formed into three dimensional shapes using the FRRF apparatus and the final products are presented as evidence for the applicability of the developed device.

• 전기학회논문지
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• 제59권11호
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• pp.2073-2082
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• 2010

The 4-th generation of mobile communication aims to realize global, fast and mobile communication service. The satellite communication charges a key role in this field. In this study, an OTM(On-The-Move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite was addressed. Since vehicles move during communication, active antenna line-of-sight stabilization is a core technology to guarantee high satellite communication quality. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. Various disturbance torques such as static and dynamic mass imbalance torques, variation of moment of inertia according to elevation angle, friction torque related to vehicle motion, equivalent disturbance torque due to antenna roll motion, etc. were analyzed. As a robust stabilization control, rate feedback with sliding mode control and position feedback with proportional+integral control was suggested. To compensate antenna roll motion, a supplementary roll rate feed forward control was included beside of the feedback control loop. The feasibility of the analysis and the proposed control design were verified along with some simulation results.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.101-105
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• 2005

Hemming process, composed of flanging, pre-hemming and main hemming, is the last one of a series of forming processes conducted on the automotive panels, having a great influence on the outward appearance of them. The hem quality can be quantitatively defined by the hemming defects including turn-down, warp and roll-in. However, it is difficult to evaluate and predict the hem quality through the experimental measurement or the numerical calculation since the size of defects is very small. This study is focused on how to simulate in the finite element analysis (FEA) the same conditions as in the experiment. The FEA result on turn-down, that was obtained from a finite element model including the spring element linked to the flanging pad, had a good correlation with the experimental data. It was found that the radius of curvature of the flange deeply affects the final hem quality and therefore high rigidity of forming tools and tight assembling tolerance are highly recommended. An over-stroke of the main hemming punch is also proposed to reduce the turn-down.

• 생물환경조절학회지
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• 제6권3호
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• pp.133-142
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• 1997

본 연구는 권취식 창개폐기의 설계 및 개발에 필요한 자료를 제시하고자 수행되었다. 기존의 단순 이론모델식으로는 정확한 권취토크를 예측할 수 없기 전문에 모형시험과 현장시험을 통하여 새로운 권취식 창개폐장치의 소요토크 모델식을 개발하였다. 본 연구에서의 결과를 요약하면 다음과 같다. 1. 권취식 창개폐장치에 있어서 권취토크는 곡부 권취면의 경사각을 따라 증가하는 경향을 나타내고 있으며, 경사각이 90$^{\circ}$인 수직면에서 최대를 나타냈고 수편면에서 최소값을 나타냈다. 2. 온실의 길이에 따른 소요토크는 권취하중의 증가와 축파이프의 변형의 영향으로 지수함수적으로 늘어나는 경향을 나타냈다. 3. 권취식 창개폐장치의 소요토크 계산의 이론식은 T ＝ W.(r＋a).sin$\theta$＋W.Cr.cos$\theta$로 나타낼 수 있으며, 여기서 축파이프의 권취반경 r과 축변형보정계수 $\alpha$를 더한 (r＋$\alpha$)는 축파이프의 최대변형값인 $\delta$에 지수함수적으로 비례하는 경향이 나타났다. 4. 권취반경 r과 축변형보정계수 $\alpha$의 합인 (r＋$\alpha$)은 22.2mm 파이프에 0.1mm 비닐로 피복을 했을 때 (r＋$\alpha$)＝2.10338$\times$$10^{0.00779{\delta}}$ 로 구할 수 있으며, 25.4mm 파이프에서는 (r＋a)＝2.58063$\times$$10^{(0.00452{\delta})}$로 구할 수 있다. 5. 권취식 창개폐장치의 소요토크에서 천창 등 곡부의 개폐시 고려되어야 할 굴름저항 보정계수는 피복재의 상태에 따라 다소 다를 수 있으나 0.7~0.8 정도의 값을 적용시키면 될 것으로 판단되었다. 6. 실제 권취식 창개폐를 사용하는 온실에서 권취축 파이프의 허용 변형정도를 최대 40cm 이하로 하는 것이 타당할 것으로 판단되며, 이때의 예상소요토크는 110m 온실인 경우 25.4mm 파이프를 축파이프로 사용한 경우 344kg.cm이며, 22.2mm 파이프의 경우 287kg.cm 정도이므로 새롭게 개발된 차동링기어 유성치 차감속기도 적당할 것으로 판단된다.