• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.429-430
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• 2002

In this study, three kinds of brake: discs including two coated brake discs and one steel disc were tested under the same experimental conditions on a reduced scale braking test bench. Plasma spray coating technique was used to coat ceramic powder on the discs. In the test, four commercial sintered brake pads were coupled with discs. Ceramic coated discs have shown good stability in friction coefficient at high speed and high energy braking conditions. However, ceramic coated discs caused more wear loss of pad mass than the steel disc. It was shown that thermal barrier effect in ceramic coated discs adjusted the thermal partition between pad and disc. Steel disc showed fluctuating friction coefficient at high speed but less wear loss of pad mass than ceramic coated discs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.733-739
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• 2010

We developed to have an automatic transferring function of a two-motors-driven electrical scooter for women or seniors to use conveniently it since it has been previously to operate it in manual only. The function would be implemented by using master and slave micro-control units(MCU) in the system with the given input and output signals. The simulation and test of the system results show that the transition conditions of either higher accelerating speed and/or higher torque are demonstrated at the worst conditions, which means that the transition points might be set either at the 70% of accelerating speed or from the 100% of load torque. The developed equipment is very useful and has good performance in the real test and would be used for top brand and might be applicable to any other types of green cars.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.2
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• pp.173-179
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• 1998

An experimental study was conducted on the effect of compressor capacity control range of heat pump on the seasonal energy efficiency ratio with variation of the maximum and minimum compressor input frequencies. To obtain seasonal energy efficiency ratio, steady state test at the maximum, minimum and intermediate compressor speed and cyclic test at the minimum compressor speed should be conducted. Maximum input frequency was varied to 95Hz, 105Hz, and 115Hz, and the minimum input frequency was varied to 35Hz, 45Hz, and 55Hz. The seasonal energy efficiency ratio increased as the input frequency of the compressor decreased. The maximum input frequency had only slight effects on the SEER.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.463-468
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• 2002

This study investigates the variations of shear force, displacement, and fracture surface with the shear speed and the number of reflows. The experimental data of shear tests indicate that the shear force increases as increasing the number of reflows and the shear speed due to the formation of a kind of intermetallic compound, Ni$_3$Sn$_4$, on Au/Ni/Cu pad, and the work-hardening. However, general trends show that the shear force decreases due to increasing the thickness of the intermetallic compound over 4x reflow. It is observed that the intermetallic compound which is formed between solder and pad increases according to increasing the number of reflows, and the growth rate of the intermetallic compound at central region on the interface is faster than one at edge part. The general tendencies of shear force and displacement with different shear speeds are almost identical as an increase of the number of reflows.

• Journal of Ocean Engineering and Technology
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• v.18 no.3
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• pp.44-49
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• 2004

Initial hull form of 10 G/T and 40 knots class coastal patrol boat is newly developed. The resistance performances are experimentally and numerically investigated by model test and CFD technique. The effect of initial trim and a fin attached at hull side are studied together. Wave patterns are observed to make clear the relation between the performance and the wave characteristics. It can be found that the initial trim plays a role in increasing the resistance performance above a certain velocity, and the CFD technique can be used at the initial design stage of a high-speed planning boats.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.158-163
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• 2003

Several simulation techniques have been developed which are not practical deformation processes but are designed to embody specific tribological aspects. Sliding rolling type friction test machine (Cold rolling tribosimulator) was developed to simulate the tribological phenomena at the roll bite in real mill by laboratory scale. A rolled material is fed at a low speed of Max. 1/20 to that of roll speed, so as to obtain simultaneous plastic deformation in the material during rotation of the rolls in simulator. New cold rolling tribe-simulator is effective for evaluation of the lubricity of lubricant in cold rolling process.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1214-1221
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• 2006

In this paper, development and performance characteristic of propulsion system(Converter/Inverter) using IPM(Intelligent Power Module) for 120km/h AC electric vehicle is proposed. The proposed propulsion system is comprised of IPM converter and inverter stack which uses natural air-cooling system, DC-Link, OVCRf unit and control unit. And also 2-Parallel operation of two PWM converter is adopted for increasing capacity of system and the VVVF inverter control is used a mixed control algorithm, where the vector control strategy at low speed region and slip-frequency control strategy at high speed region. The proposed propulsion system is verified by main line test results as well as combined test results.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.281-286
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• 2001

TiAIN was deposited onto ISO P2O Cutting Insert Tip substrate by FVAS at the substrate temperature of 80$^{\circ}C$. Cutting and wear test have been performed with TiAIN coated and uncoated WC cutting tools, respectively. Uncoated WC cutting tool has been tested under similar cutting condition for comparison. Cutting force and tool wear of coated and uncoated carbide cutting tools were investigated by cutting length. In cutting test, cutting force of the coated insert tip was larger than the uncoated insert tip by tool wear. Configuration and wear of the coated tool were more stable and resistant than the uncoated. In tool life by the tool wear, the coated cutting tool life was rather longer than the uncoated when tested at high speed (V=250 m/min) than low speed (V=200 m/min), Cutting force, tool wear and life were analysised by tool dynamometer amp(3ch) and oscilloscope.

• Women's Health Nursing
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• v.18 no.2
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• pp.149-158
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• 2012

Purpose: This study was done to test the effects of Oketani breast massage on breast pain and breast milk pH of mothers, and sucking speed of neonates. Methods: A nonequivalent control group and a pretest-posttest design was used. Postpartum mothers complaining of breast pain were recruited at a postpartum care center. The application of Oketani breast massage by an Oketani massage therapist was the experimental treatment. The control group received the conventional massage technique from a nurse at the postpartum care centre. The collected data were analysed using a $x^2$-test and a t-test with the SPSS WIN 12.0 program. Results: The participants were homogeneous in age, gestation period, and birth weight. Breast pain (t=8.384, p<.001) was significantly relieved, and breast milk pH (t=4.793, p<.001) was significantly increased in the experimental group compared to the control group. The sucking speed of the neonates in the experimental group was significantly increased compared to the control group (t=9.920, p<.001). Conclusion: These findings indicate that Oketani breast massage is effective in relieving breast pain and increasing breast milk pH as well as the sucking speed of neonates.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.268-276
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• 2016

This paper presents a study on the crashworthiness of the scaled-down stiffened panels used on a Korean icebreaker. In order to validate the crashworthiness of the panels, this paper provides various mechanical properties such as the results of a CVN test, quasi-static tensile test, and high-speed tensile test at arctic temperatures. Two types of steels (EH32 and FH32) were chosen for the material tests. CVN tests revealed that the two steels were equivalent up to −60℃ in terms of their impact energy absorption capacity. However, the toughness of FH32 was significantly superior to that of EH32. EH32 showed slightly higher flow stresses at all temperature levels compared to FH32. The improvement ratios of the yield strengths, tensile strengths, plastic hardening exponents, etc. for FH32, which were obtained from quasi-static tensile tests, showed an apparent ascending tendency with a decrease in temperature. Dynamic tensile test results were obtained for the two temperatures levels of 20℃ and −60℃ with two plastic strain rate levels of 1 s⁻¹ and 100 s⁻¹. A closed form empirical formula proposed by Choung et al. (2011;2013) was shown to be effective at predicting the flow stress increase due to a strain rate increase.