• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.253.1-253.1
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.777-778
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• 2010

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.6
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• pp.638-644
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• 2015

This paper describes the continuing effort to analysis and design on dynamic and electrical behavior of gamma-type free piston Stirling engine/generator with dual-opposed linear generator for domestic micro-CHP (Combined Heat and Power) system. The double acting Stirling engine/generator has one displacer and two power piston which are supported by flexure springs. Two power pistons oscillate with symmetric sinusoidal displacement and are connected with moving magnet type linear generators for power generation. To operate Stirling engine/generator, combustion heat of natural gas is supplied to hot-end and heat is rejected from cold-end by cooling water. The temperature difference across the displacer induces the oscillating motion, and it can be explained with mass-spring vibration system. The purpose of this paper is to describe the design process of linear generator for the double acting free-piston Stirling engine.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.193-193
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• 2008

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to-electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1445-1449
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• 2007

This paper presents the DOD (Drop-On-Demand) characteristic using the electrostatic field induced inkjet printing system. In order to achieve the DOD characteristic of electrostatic field induced inkjet printing, applied the bias voltage of 1.4 kV and the pulse voltage of $2.0\;kV\;{\sim}\;2.7\;kV$ using high voltage pulse generator. Electrostatic field induced droplet ejection is directly observed using a high-speed camera and for investigated DOD characteristic, CNT ink used. The electrostatic field induced inkjet head system has DOD characteristic using pulse generator which can be applied pulse voltage. The bias voltage has a good condition which form meniscus and has micro dripping mode for small size micro droplet. Also, the droplet size decreases with increasing the applied pulse voltage. This paper shows DOD characteristic at electrostatic field induced inkjet head system, Therefore. electrostatic DOD inkjet head system will be applied industrial area comparing conventional electrostatic inkjet head system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.878-881
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• 2005

A Stereolithography technology is based on stacking of sliced layer from STL file that is converted from 3-dimensional CAD data. A microstereolithography technology is evolved from conventional stereolithography to fabricate microstructures. In this technology, we have to consider influence of resin flow to make refresh surface. To generate new resin surface, stage has to be moved downward deeply and upward to desired position. At this time, resin flow affects to refresh surface of resin. And resin viscosity is the key factor in simulation of resin flow. By setting optimal refresh time for resin surface, total fabrication time is reduced and there is no damage to fabricated layers. In this research, we simulate resin flow using CFD software and derive optimal stage moving time and dwelling time.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.534-535
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• 2006

This study attempts to develope the micro-turbine generators which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could be alleviated and competition with other alternative energy sources in the changable design conditions could be attained. The micro turbine generator of a new concept was designed based on changable design conditions, hydrodynamics and theory of power transmission.

• Tribology and Lubricants
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• v.17 no.6
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• pp.467-475
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• 2001

Feasibility study of gas-lubricated bearing in micro gas turbine was performed. Based on Reynolds equation, finite difference method with coupled boundary was developed to analyze bearing characteristics, such as load capacity, mass flow rates and stiffness. By the bearing force and mass flow rates analysis with the variation of supply pressure, bearing clearance and capillary radius, acceptable range of design parameters were suggested in terms of load capacity and stiffness of bearings. Additionally, coupled boundary effect on pressure distribution was investigated and it is stated that coupling could reduce an excitation force due to narrow pressure distribution.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.273-281
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• 2001

Feasibility study of gas-lubricated bearing in micro gas turbine was performed. Based on Reynolds equation, finite difference method with coupled boundary was developed to analyze bearing characteristics, such as load-carrying capacity, mass flow rates and stiffness. By the bearing force and mass flow rates analysis with the variation of supply pressure, bearing clearance and capillary radius, acceptable range of design parameters were suggested in terms of load capacity and stiffness of bearings. Additionally, coupled boundary effect on pressure distribution was investigated and it is stated that coupling could reduce all excitation force due to narrow pressure distribution.

• Journal of Welding and Joining
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• v.19 no.1
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• pp.88-94
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• 2001

DUPIC (Direct use of spent PWR fuel in CANDU reactors) nuclear fuel is a CANDU fuel fabricated remotely from spent PWR fuel materials in a hot cell. The soundness of the end closure welds of nuclear fuel elements is an important factor for the safety and performance of nuclear fuel. To evaluate the soundness of the end closure welds of DUPIC fuel element, a precise X-ray inspection system is developed using a micro-focus X-ray generator with an image intensifier and a real time camera system. The fuel elements made of Zircaloy-4 and stainless steel by an Nd:YAG laser welding and a TIG welding aye inspected by the developed inspection system. The soundness of the welds of the fuel elements was confirmed by the X-ray inspection process, and the irradiation test of DUPIC fuel elements has been successfully completed at the HANARO research reactor.