• Tribology and Lubricants
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• 제8권2호
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• pp.64-72
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• 1992

The recent trends of rotating machinery demand high speed and high temperature operation, and the bearing with new material is required to be developed. Ceramic, especially silicon nitride, have been receiving attention as alternative material to conventional bearing steel. Ceramic ball bearing offers major performance advantages over steel bearing, for instance, high speed, maginal lubrication, high temperature, improved corrosion resistance and nonmagnetic capabilities etc.. In this paper, the mechanical characteristics of ceramic ball bearing (hybrid ceramic bearing and all ceramic bearing) were investigated, and the characteristics of ceramic bearing were compared with that of steel bearing. Deep groove ball bearing 6208 was taken the object of analysis. The main results of analysis were followings: the radial stiffness of hybrid and all ceramic bearing were 112% and 130% that of steel bearing, and the axial stiffness of all ceramic bearing was 110% that of steel bearing. According as rotating speed was up, the ball load, the contact angle, the contact stress and the spin-to-roll ratio between ball and raceway of ceramic bearing were far smaller than these of steel bearing. And there was not a significant difference between the minimum film thickness of ceramic bearing and steel bearing. It is expected that this research is contributed to enhanced fundamental technology for the practical applications of ceramic ball bearing.

• 동력기계공학회지
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• 제15권5호
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• pp.16-21
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• 2011

The large scale decisive battle will be gradually reduced on the sea in the future and surface combatant ship installed advanced weapon units as well as propulsion system will be continuously increased. The high level of military technology leads to appear state-of-the-art weapon system using high power energy. As a results, fossil fuel powered main prime mover as diesel engine and gas turbine which are composed of mechanical propulsion system should be decreased from combatant ship in the near future. The new building naval combatant ship with the latest technology has electric based propulsion method of the hybrid type combined with mechanical and electrical drive. U.S. and Royal Navy, especially, select the integrated fully electric based propulsion system for the next generation combat ship and play an important roll for developing them. In this context, this paper was focused on the deduction of implications through analyzing the combatant ship propulsion system using diesel and gas turbine engine which are promoted on the worldwide.

• 대한조선학회논문집
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• 제52권5호
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• pp.365-371
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• 2015

Hull plate consists of various types of curved plates and there also exists corresponding processing methods. Typically, curved plates can be divided into convex type and saddle type. Large amount of research has been conducted mainly focusing on application of processing method of convex type, saddle type and hybrid type, but research on determination and processing method application of the most difficult S-shaped curved plate that has inflection lines has not been carried out yet. In this paper, as the fundamental research of appropriate processing method application, a calculation method is proposed to calculate inflection lines on curved plates. In order to calculate inflection lines, normal curvature and information of fabricated curved plates should be utilized. We compare the workability of the fabrication for hull plate using inflection line.

• ETRI Journal
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• 제44권1호
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• pp.147-154
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• 2022

We demonstrate a new double-layer structure for stretchable interconnects, where the top surface of a serpentine polyimide support is coated with a thin eutectic gallium-indium liquid metal layer. Because the liquid metal layer is constantly fixed on the solid serpentine body in this liquid-on-solid structure, the overall stretching is accomplished by widening the solid frame itself, with little variation in the total length and cross-sectional area of the current path. Therefore, we can achieve both invariant resistance and infinite fatigue life by combining the stretchable configuration of the underlying body with the freely deformable nature of the top liquid conductor. Further, we fabricated various types of double-layer interconnects as narrow as 10 ㎛ using the roll-painting and lift-off patterning technique based on conventional photolithography and quantitatively validated their beneficial properties. The new interconnecting structure is expected to be widely used in applications requiring high-performance and high-density stretchable circuits owing to its superior reliability and capability to be monolithically integrated with thin-film devices.

• 한국정밀공학회지
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• 제30권6호
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• pp.589-595
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• 2013

Solution processed conjugated molecules enable to manufacture various electronic devices by unconventional and cost effective patterning methods as screen or gravure printing. Spin-coating is the most popularly used method to form conjugated polymeric film for various electronic devices. The coating method has certain disadvantages such as a large amount of unwanted wastes, difficulty forming a film with a large area, and impossible to apply roll-to-roll manufacturing. We present here a promising alternative coating method, bar-coating for conjugated polymer film and OLED with the bar coated light emitting layer. In this papers, we show atomic force microscope images of spin- and bar-coated Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) films on substrate. The bar-coated film showed a slight lower RMS roughness (1.058 [nm]) than spin-coated film (1.767 [nm]). It means the bar-coating is suitable method to form light emitting layers in OLEDs. By using bar-coating process, an OLED obtained with 4.7 [cd/A] in maximum current efficiency.

• 복식
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• 제53권2호
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• pp.101-118
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• 2003

This paper describes pop stars' fashion style by the changes of pop music from the 1950's of the formative Period of a rock-n-roll to the 1990's. The author could examine the features of pop music as follows : the 1950's rock-n-roll, the 1960's rock and Psychedelic rock. the 1970's punk rock, the 1980's new wave and the 1990's reggae·hip-hop. Based on the examination, the author could do sampling of the fashion style, on which current pop music had influence, by rock style, new wave style, and reggae hip-hop style. The rock style makes appearance again as a new style when it is recently accepted to be a fashion. The 1960's hippie, which contains long-cherished desire of antiwar and peace after September 11, 2001 Attack on America and the Afghan War. reappeared as luxurious hippie, and the hybrid punk has been made because barriers between cultures have been collapsed to mix items and combine contradicting components at fashion field. The new wave style destroys sex difference of clothes. and men's clothes style has introduced women's dress style, so that androgynous style, which has handsome boy image with womanlike hair style and makeup, and the lingerie style without distinction of underwear and outer garment has made appearance through new cloth wearing ways and overexposure. The reggae and hip-hop style makes appearance to overcome social strata, groups, ages, regions and gender, etc and become one of the 21s1 century culture codes. In conclusion, pop music have played very important roles until expansion and popularity of new fashion style, and has been quickly expanded by mass media development. When the pop music fashion styles are introduced to high fashion, fashion styles have become more polished and high-qualify to expand them at main fashion world again.

• Composites Research
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• 제29권6호
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• pp.353-357
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• 2016

B-stage 레진 필름에 탄소나노튜브(CNT) 등을 균일하게 분포시킨 뒤에 기타의 보강섬유 층과 함께 여러 겹으로 적층하여 하이브리드 형태의 복합재료를 만드는 방법은 유용하다. 본 연구에서는 CNT가 포함된 에폭시 레진으로부터 shear mixing 및 Three-roll mill 공정을 이용하여 B-stage 레진 필름을 제작하였다. 두 공정을 통해 형성된 CNT/레진 복합재 필름의분산도를 파단면의 SEM 관찰을통해분석하였다. 보다 효율적인 공정을 위해 Calendering pass 횟수에 따른 분산도를 평가하였다. Pass의 횟수에 따른 샘플을 제조하고 CNT 분산도는 SEM 이미지를 통해 확인하고, 전기 전도도 측정을 통해 분석하였다. 추가적으로 gap mode, force mode를 통해 제작한 각각의 샘플의 전기 전도도를 측정하여 CNT 분산도를 분석하였고 이를 통해 최적공정을 도출하였다.

• 대한조선학회논문집
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• 제35권3호
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• pp.26-37
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• 1998

본 논문에서는 시험선 $\ulcorner$나래$\lrcorner$에 적용된 자세 제어 기술 및 그 실해역 시험 결과를 보이고자 한다. $\ulcorner$나래$\lrcorner$는 하부 몰수체와 그에 부착된 제어판을 이용하여 선체를 일정량 부상시키는 복합 지지선형을 채택하여 건조된 선박으로서, 본 연구원의 자체 설계를 거쳐 건조된 유인 시험선이다. 이러한 선형의 선박은 부상 상태에서 Heave, Pitch Roll의 3자유도에 대해 복원력이 거의 작용하지 않기 때문에 정적 불안정성을 가지며, 그에 따라 자세 제어 시스템이 필수적으로 요구된다. 시험선 $\ulcorner$나래$\lrcorner$에는 제어판 구동을 위한 유압 구동 장치 및 선체 운동의 계측을 위한 각종 계측 장비가 설치되었다. 제어기로는 PID 제어기가 사용되었으며, 실시간 제어를 위해 Pentium급 산업용 PC가 탑재되었다. 약 3개월 여에 걸쳐 부상 시험 및 조종 시험을 포함한 실해역 시험이 수행되었으며, 만족스런 제어 성능이 발휘됨을 확인하였다.

• 한국해양공학회지
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• 제30권2호
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• pp.84-90
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• 2016

In this study, a six degree-of-freedom motion analysis of a wind-wave hybrid platform equipped with numerous wave energy converters (WECs) was carried out. To examine the effect of the WECs on the platform, an analysis of one-way coupling was carried out, which only considered the power take-off (PTO) damping of the static WECs on the platform. The equation of motion of a floating platform with mooring lines in the time domain was established, and the responses of the one-way coupled platform were then compared with the case of a platform without any coupling effects from the WECs. The hydrodynamic coefficients and wave exciting forces were obtained from the 3D diffraction/radiation pre-processor code WAMIT based on the boundary element method. Then, an analysis of the dynamic responses of the floating platform with or without the WEC effect in the time domain was carried out. All of the dynamics of a floating platform with multiple wind turbines were obtained by coupling FAST and CHARM3D in the time domain, which was further extended to include additional coupled dynamics for multiple turbines. The analysis showed that the PTO damping effect on platform motions was negligible, but coupled effects between multiple WECs and the platform may differentiate the heave, roll, and pitch platform motions from the one without any effects induced by WECs.

• 한국항공운항학회지
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• 제22권1호
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• pp.130-135
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• 2014

FOD(Foreign Object Debris) has the potential threat to damage aircraft during critical phases of take-off and landing roll with some objects including metal on the runway. FOD can be found anywhere on an airport's air operation areas such as runway, taxiway and apron. It can lead to catastrophic loss of life and airframe, and increased maintenance and operating costs. In this paper, we defined FOD and surveyed its riskiness and necessity of automatic FOD detection system. We compared the requirements of the environment in Korea to the FAA advisory circular. Also we analyzed operation methods of FOD detection systems already installed at some airports. Based on the surveys mentioned above, we propose hybrid type of FOD detection system considering the environment in Korea which uses millimeter wave radar, optical camera and thermal imaging camera to detect FOD efficiently. In management approach, fixed type of the system should be installed for real-time monitoring, and mobile type of the system can be used additionally.