• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.174.3-174
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• 2001

Electric power collection is one of the most important factors for the high-speed trains' operation. For the stable current collection, the contact wire of a catenary and the panhead of a pantograph should maintain a constant contact each other. In this paper, the catenary was modeled as a spring with time-varying stiffness from the point of a pantograph moving along the catenary, and the pantograph was modeled as a 3-D.O.F. mass-spring-damper system. Using the adaptive control method, the desired control performance could be obtained with the modeling errors and the time varying parameters. Also the state estimator was used considering the difficulty of applying the sensors obtaining feedback signals. Simulations were accomplished in various ...

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.144-147
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• 1998

VCR is a back-up roll with a special contour which leads to the length of the contact line between back-up roll and work becones self adjustable in accordance with the width of the strip. The simulation of a finite element model and the on-line test at production mill demonstrate that the VCR roll may keep the crown of the roll gap relatively stable, and at same time, permit the rolling pressure to be adjusted over a wider range, and increase the effect of work roll bending on the roll gap. The VCR rolls have been successfully used at the first stands of two largest cold rolling mills in China, and on-line test has been done at a wide hot strip finishing train. The use of VCR roll has created favorable conditions for subsequent rolling passes and the achievement of better flatness quality.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1065-1068
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• 2001

Effects of compacting pressure on the electrical and sintering characteristics of Cu25Cr contact material have been investigated. Cu25Cr contact materials were prepared by solid and liquid-phase sintering methods varying compacting pressure. Influence of compacting pressure on electrical characteristics were investigated in the cylindrical stainless-steel vessel using L-C resonant circuit. The physical and electrical properties of solid-phase sintered Cu25Cr material were found to be improved by increased compacting pressure. On the other hand, it was found that compacting pressure had little influence in case of liquid-phase sintered Cu25Cr material. After conditioning, contact resistance of Cu25Cr material was decreased regardless of compacting pressure. With increased compacting pressure, interrupting ability was shown to be increased.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.299-305
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• 2017

Gate-lifting devices in small- to mid-sized sluice gates mostly employ the mechanical roller rack pinion (RRP) system. This RRP system, which consists of a rack-bar and a pinion, transforms a rotation motion into a linear one. The rack-bar has a series of roller trains that mesh with the pinion. In this study, we adopt an exact involute-trochoid tooth profile of the pinion to obtain a higher contact fatigue strength using the profile modification coefficient. Further, we determine the contact forces and investigate Hertz contact stresses to predict the pitting life of the pinion according to varying the shape design parameters. The results indicate that the design fatigue life of an RRP system for sluice gate can be achieved only when the design value of the profile modification coefficient reaches or exceeds a certain level.

• Proceedings of the KIEE Conference
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• summer
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• pp.1109-1111
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• 2004

This paper deals with the calculation of contact resistance depending on the applied force by modeling surface roughness. The true contact surface area is made up of many asperities of varying heights which is close to Gaussian distribution. The mean square deviation and the mean value of the Gaussian distributed asperity heights were determined in this paper. The elastic deformation of the surface asperities according to the increasing of applied force were considered. The contact resistance was also calculated by using the Greenwood analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.47-52
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• 2007

Organic field-effect transistors (OFETS) are of interest for use in widely area electronic applications. We fabricated a copper phthalocyanine (CuPc) based field-effect transistor with varying channel length. The CuPc FET device was made a top-contact type and the channel length was a $100\;{\mu}m,\;50\;{\mu}m,\;40\;{\mu}m,\;and\;30\;{\mu}m$ and the channel width was a fixed at 3 mm. We observed a typical current-voltage (I-V) characteristics in CuPc FET with varying channel length (L) and we calculated the effective mobility. Also, we measured a capacitance-voltage (C-V) by applied bias voltage with varying frequency at 43, 100, 1000 Hz.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.387-394
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• 2000

Theoretical and experimental study is conducted on the contact pressure distribution of a radial tire in motion under various camber angles. Tire construction is modelled by a spring bedded elastic ring, consisted of sidewall springs and a composite belt ring. The contact area is assumed to be a trapezoidal shape varying with camber angles and weighted load. The basic equation in a quasi-static form is derived for the deformation of a running belt with a constant velocity by the aid of Lagrange-Euler transformation. Galerkin's method and stepwise calculation are applied for solving the basic equation and the mechanical boundary condition along both sides of the contact belt part subjected to shearing forces transmitted from the sidewall spring. Experimental results on the contact pressure, measured by pressure sensors embedded in the surface of the drum tester, correspond well with the calculated ones for the test tire under various camber angles, running velocities and weighted loads. These results indicate that a buckling phenomenon of the contact belt in the widthwise direction occurs due to the effect of camber angle.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.461-465
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• 2016

n-type silicon shows the better tolerance towards metal impurities with a higher minority carrier lifetime compared to p-type silicon substrate. Due to better lifetime stability as compared to p-type during illumination made the photovoltaic community to switch toward n-type wafers for high efficiency silicon solar cells. We fabricated the front electrode of the n-type solar cell with AgAl paste. The electrodes characteristics of the AgAl paste depend on the contact junction depth that is closely related to the firing temperature. Metal contact depth with p+ emitter, with optimized depth is important as it influence the resistance. In this study, we optimize the firing condition for the effective formation of the metal depth by varying the firing condition. The firing was carried out at temperatures below $670^{\circ}C$ with low contact depth and high contact resistance. It was noted that the contact resistance was reduced with the increase of firing temperature. The contact resistance of $5.99m{\Omega}cm^2$ was shown for the optimum firing temperature of $865^{\circ}C$. Over $900^{\circ}C$, contact junction is bonded to the Si through the emitter, resulting the contact resistance to shunt. we obtained photovoltaic parameter such as fill factor of 76.68%, short-circuit current of $40.2mA/cm^2$, open-circuit voltage of 620 mV and convert efficiency of 19.11%.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.112-116
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• 2015

This work studied the thickness and contact angle of solder joints between SAC 305 lead-free solder alloy and a Copper (Cu) substrate. Intermetallic compound (IMC) thickness and contact angle of 3Sn-Ag-0.5Cu (SAC 305) leadfree solder were measured using varying aging times, at a fixed temperature at 30℃. The thickness of IMC and contact angle depend on the aging time. IMC thickness increases as the aging increases. The contact angle gradually decreased from 39.49° to 27.59° as aging time increased from zero to 24 hours for big solder sample. Meanwhile, for small solder sample, the contact angle increased from 32.00° to 40.53° from zero to 24 hours. The IMC thickness sharply increased from 0.007 mm to 0.011 mm from zero to 24 hours aging time for big solder. In spite of that, for small solder the IMC thickness gradually increased from 0.009 mm to 0.017 mm. XRD analysis was used to confirm the intermetallic formation inside the sample. Cu₆Sn₅, Cu₃Sn, Ni₃Sn and Ni₃Sn₂ IMC layers were formed between the solder and the copper substrate. As the aging time increased, the strength of the solder joint mproved due to reduced contact angle.

• Nuclear Engineering and Technology
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• v.22 no.1
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• pp.75-81
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• 1990

Experiments to predict the thermal contact conductance between the fuel pellet and cladding have been performed, which is important to determine the temperature distibution within the fuel rod. UO$_2$and Zircaloy-2 are used in these experiments. The measuring apparatus is composed of a presser which controls the contact pressure, a thermometer with 5.5 sheathed thermocouples, a vacuum pump, pellet and cladding rods, and two heating devices, etc. The thermal contact conductances were measured with varying the contact pressure and surface roughnesses of UO$_2$and Zircaloy-2 bars. The results show that an increase in the contact pressure and a decrease of surface roughness resulted in increase of the thermal contact conductance. Finally, a fitting correlation has been established and compared with widely-used correlations.