• Tribology and Lubricants
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• 제11권4호
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• pp.45-52
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• 1995

The wear behavior of alumina short fiber reinforced tin-bronze matrix composites was studied at the room temperature and an elevated temperature. The effect of the composition of specimens and the variation of wear conditions on the wear properties was examined by a pin-on-disc type wear testing machine. The wear mechanism according to the compositon of specimens at various wear conditions was discussed by the observation of the microstructure and the analysis of the composition on the worn surfaces. A thicker oxide layer on worn surfaces led to a lower wear loss because of the lubricating effect of oxide layers between pin and disc. As the testing temperature was raised to 350$^{\circ}$C, the fiber reinforced composites exibited markedly increased wear resistance even at a higher applied load since the reinforcement of composites with alumina fibers was not affected to a large extent by raising temperature. The results obtained by AES and EDS analysis indicated that the oxide layer of the worn surfaces formed at 350$^{\circ}$C was proved as Fe-oxide. This was explained by the faster formation of Fe-oxide than Cu-oxide at 350$^{\circ}$C.

• Steel and Composite Structures
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• 제48권3호
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• pp.321-333
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• 2023

This paper proposes a comprehensive investigation on lateral stiffness of corner-supported steel modular frame using splice connection. A full-scale modular frame with two stacked steel modules under lateral load is tested. Ductile pattern in the transfer of lateral load is found in the final failure mode. Two types of lateral stiffness, including tangent stiffness and secant stiffness, are defined from the load-displacement due to the observed nonlinearity. The difference between these two types of stiffness is found around 20%. The comparisons between the experimental lateral stiffness and the predictions of classical methods are also conducted. The D-value method using hypothesis of independent case is a conservative option for predicting lateral stiffness, which is more recommended than method of contraflexural bending moment. Analyses on two classical short-rod models, including fix-rod model and pin-rod model, are further conducted. Results indicate that fix-rod model is more recommended than pin-rod model to simplify splice connection for simulation on lateral stiffness of modular frame in elastic design stage.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.772-779
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• 2000

The friction and wear behavior of short carbon fiber reinforced polyetheretherketone was studied experimentally under dry sliding conditions against SCM440(AISI 4140) disks with a different surface roughness and hardness at the low sliding speeds and the high pressures on a pin-on-disk apparatus. Under the low disk surface roughness value the earsplitting noise and stick-slip were occurred. The increased adhesion friction and wear factor with stick-slip made the friction and wear behavior worse. Under the high disk surface hardness the break and falling-off of carbon fibers were accelerated. The carbon fibers fallen off from the matrix were ground into powder between two wear surfaces and this phenomenon caused a abrasive friction and wear factor to increase. So the friction and wear behavior became worse. With the transfer film made of wear particles formed on a disk, the carbon powder film formed on a pin lowered a friction coefficient.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 춘계학술대회논문집
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• pp.110-120
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• 1996

A crank-slider mechanism is driven by the rotating disk with are crank-pin guide to be applied to the deep drawing and cold forging presses. Load characteristics for different presses are summarized to see the basics of deep drawing of sheet metal and forging in terms of load-stroke relationship. Several types of conventional deep drawing presses are also shown to be compared with the ratating disk-types press. Kinematic performances by thearc guide driving mechanism are anlayzed in terms of load capaicty, stroke, and slide velocity characteristics, and they are compared with those by conventional driving , e.g. Niagara-typepress and so on. Kinematically better performances is shown by arc guide drive than those by conventional ones. The new driving mechanism is also proven to be one of the best for mass production press in terms of short cycle time. Possible applications of the arc guide press to deep drawing and cold forging work are in terms of kinematics and load capacity.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2011년도 춘계학술논문발표회 논문집
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• pp.77-79
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• 2011

본 논 연구에서는 가전제품 중에서 야간 절전 버튼의 작동 불량 원인을 규명하여 제품의 성능 및 신뢰성 향상을 위한 객관적 근거를 제시하였다. 시판된 제품을 수거하여 불량품 검사(전기적 특성 및 decap)를 실시한 결과 절전 버튼 IC pin No.2의 단락(short)에 의한 오작동 요소를 밝힐 수 있었다. 동일한 사양의 재현실험에서 EOS(전기적 과도전압에 의한 스트레스)보다 정전기 방전에 스트레스에 의해서 소손되는 특성을 나타내는 것을 확인할 수 있었다. 오작동 요소로 확인된 IC pin 2번에 바리스터(Varistor)를 부착하고 11kV를 인가하여 시험한 결과 오작동 요소를 제거할 수 있었다.

• 한국안전학회지
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• 제28권3호
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• pp.69-73
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• 2013

The purpose of this paper is to analyze the carbonization pattern and operation characteristics of an MCCB. The MCCB is consisted of the actuator lever, actuator mechanism, bimetallic strip, contacts, up and down operator, arc divider or extinguisher, metal operation pin, terminal part, etc. When the actuator lever of the MCCB is at the top or the internal metal operation pin is in contact with the front part, the MCCB is turned on or off. It means trip state if the actuator lever or the internal metal operation pin moves to back side. In the UL 94 vertical combustion test, white smoke occurred from the MCCB when an average of 17~24 seconds elapsed after the MCCB was ignited and black smoke occurred when an average of 45~50 seconds elapsed. It took 5~6 minutes for the MCCB surface to be half burnt and took an average of 8~9 minutes for the MCCB surface to be entirely burnt. In the UL 94 test, the MCCB trip device operated when an average 7~8 minutes elapsed. If the MCCB trip has occurred, it may have been caused by an electrical problem such as a short-circuit, overcurrent, etc., as well as fire heat. From the entire part combustion test according to KS C 3004, it was found that the metal operation pin could be moved to the MCCB trip position without any electrical problems.

• 수면정신생리
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• 제8권2호
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• pp.129-137
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• 2001

목 적 : 일상생활에서 하루 밤의 수면박탈은 흔히 있을 수 있다. 저자들은 전산화 신경인지검사를 통하여 38시간의 수면 박탈이 상지의 미세 운동수행능력에 어떠한 변화를 주는지를 연구하고자 하였다. 방 법 : 고려대학교 의과대학에 재학중인 학생중 정신적, 신체적으로 건강한 지원자 24명(M:F=21:3, mean age : $24.67{\pm}1.37$)을 대상으로 하였으며 모두 오른 손잡이었다. 또한 수면일지를 작성하게 하여 평소에 수면부족을 보이는 군은 배제하였다. Vienna Test System에서 나타날 수 있는 학습효과를 최소화하기 위하여 검사 하루 전에 미리 같은 검사를 시행하였다. 검사 전날 밤에 피험자들은 충분한 수면을 취하였으며, 검사 당일 오전 6시경에 기상하였다. 실험 첫날 오전 6시부터 다음날 오후 8시까지 38시간동안 수면을 박탈하였으며, 검사 첫날과 둘째 날의 오전 7시와 오후 7시, 총 4차례 Vienna Test System중 Motor Performance Series를 시행하였다. 실험기간 중에 모든 피험자에게 수면에 영향을 줄 수 있는 약물의 복용은 금지되었으며, 과도한 운동도 금지되었다. 자료는 SPSS를 이용하여 피험자당 4회 시행한 검사 결과를 Repeated ANOVA를 시행하였으며, 일중리듬을 고려하여 각 아침, 저녁 session끼리의 검사 결과를 paired t-test를 시행하여서 비교하였다. 결 과 : Motor Performance Series에서 수면박탈에 따라서 상지의 오른손의 운동 기능에 있어 수행능력의 저하가 나타났다. 각 소검사를 보면 tapping의 total number(p<.005), line tracking의 number of misses(p<.05), length of misses (p<.05), inserting short pin의 total length(p<.01), inserting long pin의 total length(p<.05), aiming의 number of misses (p<.05)에서 통계적으로 유의미한 기능의 저하가 나타났다. 결 론 : 이상의 결과는 38시간의 수면박탈만으로도 유의미한 운동기능의 저하가 나타난다는 것을 보여준 것이며, 특히 가장 예민하게 미세 운동기능을 발휘할 수 있는 우세한 오른손에서 기능저하가 나타났다. Inserting long pin보다는 inserting short pin 검사에서 기능이 저하되었고, line tracking, aiming에서 검사 결과의 수행 저하가 두드러진 것으로 보아서, 미세한 운동기능일수록 영향을 많이 받는다고 할 수 있겠으며, line tracking에서 전체 검사 시간은 감소되며, 수행에서 실수가 늘어난 것으로 보아, 수면박탈에 따라서 조급한 수행이 이루어진다고 보여진다. 또한 주어진 32초간의 시간 안에 최대한의 속도로 펜을 두드리는 tapping 검사에서 두드러진 저하를 보인 점에서, 수면박탈에 의하여 근육의 피로가 쉽게 나타난다고 생각 할 수 있겠다.

• 아태비즈니스연구
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• 제9권1호
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• pp.77-89
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• 2018

Today, the sports teams are in a highly competitive environment where they don't know what may happen in the near future. While the front-runner teams suffer a serious slump, the teams in lower ladder stacks victories. This recent phenomenon proves that no team can secure the sustainable competitive edge over others. This is the time when a complete change of the mindset about the short-term competitive edge is needed. Therefore, we conducted the case study to the short-term competitive edges by selecting OK Savings Bank Rush & Cash volleyball team(hereafter referred to as OK Savings Bank). Thus, we presented the Transient Advantage Wave which describes the five stages of Initiating-Promotion-Utilization-Reconstruction-Withdrawal as a framework for the case study. Finally, we organized the results of the analysis and based on this result, we discussed the significance and the limitation of the short-term competitive edge that the sports team should pursue. This study contributed to the changes in strategies & tactics of various sports teams by suggesting the new strategy called short-term competitive edges that teams should utilize in order to get the best results in the sports league that has the strong quality of Time-based system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.95-96
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• 2006

ITO thin film is generally fabricated by various methods such as spray, CVD, evaporation, electron gun deposition, direct current electroplating, high frequency sputtering, and reactive DC sputtering. However, some problems such as peaks, bumps, large particles, and pin-holes on the surface of ITO thin film were reported, which caused the destruction of color quality, the reduction of device life time, and short-circuit. Chemical mechanical polishing (CMP) process is one of the suitable solutions which could solve the problems.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2004년도 추계학술대회
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• pp.5-8
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• 2004

In this paper, a novel 400MHz band small meander microstrip antenna is proposed the shape of the proposed antenna is a waved meander microstrip with a pair rf short pins on th￡ edge. the length of waved meander microstrip is $\lambda_g/4$ but it bends to half its size. Therefore, the total size of the proposed antenna is reduced to about 1/20 which is compared with a square patch antenna the simulated antenna gain is about 3dBi at 424MHz. the proposed antenna of -10dB impedance bandwidth is measured about $1.4\%$.