• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.57-61
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• 2007

We designed and fabricated square coils of 4 layered structure on a PCB board. The size of the coils were $1{\times}1cm^2\;and\;$2{\times}2cm^2$. The line width of the fabricated coils was $100{\mu}m$. By reciprocating a magnet on the surface of a fabricated square coil which is composed of 4 layers, an alternating output voltage was obtained. We changed the vibrational frequency from 0.5 to 7 Hz. The generated voltages were 62 mV at $1{\times}1cm^2$ and 245 mV at $2{\times}2cm^2$ when 5.5 Hz frequency. We rectified and stepped up the output voltage using a quadrupler circuit and $2{\times}2cm^2$ coil. Before using the step up circuit, the measured voltage was 320 mV at 7 Hz. After using the step up circuit, the measured voltage was 400 mV at 7 Hz.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.632-637
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• 2017

The vehicle lubricant occupies upto 35% in a total lubricant market and engine oil occupies upto 77% in the vehicle lubricant market in Korea. A suitable quality management of the circulating engine oil is necessary for driver and engine protection. But, KS and synthetic engine oil products (involved over 30% synthetic oil) are exempt to any quality management under Petroleum and Alternative Fuel Business Act. It is also known that synthetic oils such as PAO (poly alpha olefin) have excellent properties and performance like anti-wear, varnish control and oxidation stability than those of mineral oils. For this reason, PAO has been used for an engine oil, rotary screw and reciprocating compressor in addition to heavy duty and other extreme service applications. In this study, our research group analyzed the chromatogram pattern for the mineral oil, PAO and mineral oil involved a typical ratio of PAO using SIMDIST (simulated distillation). In the SIMDIST chromatogram, the mineral oil showed a broad peak, while PAO showed a sharp typical peak. Also the oil with a large viscosity grade exhibited a long retention time due to the heavy molecular weight and high boiling point. In particular, the blended mineral oil with 20% PAO sample showed a distinctly different pattern compared to that of using the conventional mineral oil. For monitoring PAO contents in distributing engine oils, we analyzed the SIMDIST for 27 kinds of engine oils which were popularly sold in Korea. The analytic results indicate that all kinds of engine oils showed that PAO contents were below 20% in engine oil products. Moreover, the PAO titled product was found to have a small amount of PAO. Thus, we conclude that the related laws for the proper quality management of synthetic oils are needed to be established.

• Tribology and Lubricants
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• v.31 no.3
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• pp.95-101
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• 2015

Carbon nanotubes (CNTs) are widely used in polymer composites as filler materials to enhance various characteristics of the composites because of their remarkable mechanical, electrical, and thermal properties. In this study, we investigate the effects of MWCNTs on the electrical and wear characteristics of high-impact polystyrene (HIPS) composites, and compare the results with the effects of carbon black (CB). The HIPS composites are classified as Bare-HIPS, MWCNT-HIPS composites containing 2, 3, 4, and 5 wt% MWCNTs, and CB-HIPS containing 17 wt% CB. Electrical characteristics are evaluated by measuring the surface resistance using a 4-point probe. Wear characteristics are evaluated using the reciprocating wear test, and a chrome steel ball with a curvature of 6.3 mm is used as the counterpart. The results show that the addition of MWCNTs or CB can improve the electrical and wear characteristics of HIPS composites. In the case of MWCNT-HIPS composites, surface resistance, friction coefficient, and specific wear rate decrease as the concentrations of MWCNTs increase. Moreover, the addition of MWCNTs is more effective in improving the electrical and wear characteristics of HIPS composites compared to the addition of CB. To fabricate the HIPS composite with appropriate electrical and wear characteristics, more than 4 wt% MWCNTs is added to HIPS.

• Tribology and Lubricants
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• v.30 no.5
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• pp.278-283
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• 2014

Carbon nanotubes (CNTs) are used in various composite materials to enhance electrical, thermal and mechanical properties of composite materials. In this study, we investigate the wear characteristics of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends containing multi-walled carbon nanotubes (MWCNTs). PC/ABS blends are commonly used in many industrial applications such as cellular phones and display cases and MWCNTs have been added to the PC/ABS blends to improve their electromagnetic interference shielding (EMS). We performed wear tests on PC/ABS blends containing MWCNTs under reciprocating linear sliding conditions with chrome steel balls as a counterpart material. The normal loads were 10, 30, 50, 70, 100 N, the sliding speed was 10 mm/s, the stroke length was 15 mm, and the tests lasted 900 s. The MWCNTs included in the PC/ABS blends lower the wear volume and friction coefficient of the composites. We analyzed the wear debris collected from the composites during the tests in terms of the MWCNT concentration using inductively coupled plasma optical emission spectroscopy. The results show that the quantity of MWCNTs in the debris is proportional to the concentration of MWCNTs in the composite, indicating that the exposure of the MWCNTs to environments by wear could be increased with their concentration in the composite.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.9-12
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• 2006

We have designed and fabricated micro power generators by electroplating which is important in MEMS(micro electro mechanical system) technique. We have electroplated MEMS coils on the glass substrates and have chosen one of these coils for experiments. The thickness, width, and length of the coil are $7{\mu}m,\;20{\mu}m$, and 1.6 m, respectively. We have analyzed the structure of MEMS coil by SEM. We have made a vibrating system for reproducible results in measurement. With reciprocating a magnet on the surface of a fabricated winding coil, the micro power generator produce an alternating voltage. We have changed the vibrational frequency from 0.5 Hz to 8 Hz. The generated voltage was 106 mV at 3 Hz and 198 mV at 6 Hz. We aim at the micro power generator which can change vibration energy to useful electric energy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.765-772
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• 2015

Cast iron is widely used in fields such as the transport and heavy industries. For parts where contact damage is expected to occur, it is necessary to understand the friction and wear characteristics of cast iron. In this study, we use cast iron plates as the specimens to investigate their friction and wear characteristics. We perform various experiments using a reciprocating type tribotester. We assess the frictional characteristics by analyzing the friction coefficient values that were obtained during the sliding tests. We observe the wear surfaces of cast iron and steel balls using a scanning electron microscope, confocal microscope, and 3d profiler. We investigate the friction and wear characteristics of cast iron by injecting sand and alumina particles having various sizes. Furthermore, we estimate the effect of temperature on the friction and wear characteristics. The results obtained are expected to aid in the understanding of the tribological characteristics of cast iron in industry.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.1
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• pp.6-13
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• 2012

HVOF thermal spray coating of 80%WC-CoFe powder is one of the most promising candidate for the replacement of the traditional hard chrome plating and hard ceramics coating because of the environmental problem of the very toxic $Cr^{6+}$ known as carcinogen by chrome plating and the brittleness of ceramics coatings. 80%WC-CoFe powder was coated by HVOF thermal spraying for the study of durability improvement of the high speed spindle such as air bearing spindle. The coating procedure was designed by the Taguchi program, including 4 parameters of hydrogen and oxygen flow rates, powder feed rate and spray distance. The surface properties of the 80%WC-CoFe powder coating were investigated roughness, hardness and porosity. The optimal condition for thermal spray has been ensured by the relationship between the spary parameters and the hardness of the coatings. The optimal coating process obtained by Taguchi program is the process of oxygen flow rate 34 FRM, hydrogen flow rate 57 FRM, powder feed rate 35 g/min and spray distance 8 inch. The coating cross-sectional structure was observed scanning electron microscope before chemical etching. Estimation of coating porosity was performed using metallugical image analysis. The Friction and wear behaviors of HVOF WC-CoFe coating prepared by OCP are investigated by reciprocating sliding wear test at $25^{\circ}C$ and $450^{\circ}C$. Friction coefficients (FC) of coating decreases as sliding surface temperature increases from $25^{\circ}C$ to $450^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.11
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• pp.1349-1354
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• 2013

Sealing structure to prevent flowing hot gas into the driving device, located between the driving shaft and the liner of On-Off valve for controlling the hot gas flow path was studied. Wear occurs due to the constant movement of the driving shaft controlled by actuator on graphite as the sealing material. In this paper, the dynamic wear behavior in high temperature of graphite(HK-6) to be used as sealing material was evaluated. Reciprocating wear test was carried out for the graphite(HK-6) to the relative motion between shaft materials(W-25Re). The results of friction coefficient and specific wear rate according to contact load, sliding speed at room temperature and $485^{\circ}C$ considering the actual operating environment were evaluated. Through the SEM analysis of the worn surface, third body as lubricant films were observed and lubricant effect of third body was considered.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1131-1136
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• 2015

In a diesel engine, the wear of the cylinder liner occurs because of the continuous reciprocating motion of the piston ring. This wear reduces the performance of the diesel engine and shortens its service life. This study evaluated the wear characteristics of GT metal and a conventional metal used for cylinder liners using a ship's diesel engine. Wear tests were performed at temperatures of $25^{\circ}C$, $175^{\circ}C$, and $325^{\circ}C$, and under loads of 10 N, 30 N, and 50 N. The amount of wear, specific wear rate, and friction coefficient were evaluated for each condition. To analyze the wear mechanism, observations were made on an SEM. In the case of both metals, abrasive and adhesion wear occurred on the wear surfaces at room temperature, and corrosion wear was observed at high temperatures. The amount of wear and the specific wear rate of the GT metal were lower than those of the conventional metal at all temperatures, and hence it can be concluded that the wear characteristics of the GT metal are much better.

• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.15-21
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• 2015

Natural gas fuel has known to be very promising in terms of abundancy and economic value. Therefore it is widely treated as research topics in a variety field of production, storage and utilization. Natural gas has become one of the major sources for the power generation by using internal combustion engines(ICE). Development of natural gas fuel injection device should be preceded to realize a reliable natural gas fuel supply system for a MW class power generation reciprocating ICE. In this research, an injection valve which consists of solenoid and body part with a moving plate was designed and its dynamic performance was experimented in the engine-like environment. As a result of the experiments, linearity of flow rate was obtained and overall around 2ms of response time was observed at the pressure difference of 1bar. In addition, more than 100Liter/min(@2Hz) of gas flow rate was witnessed, which is expected to be adequate for the fuel supply system of a MW class natural gas engine.