• Journal of electromagnetic engineering and science
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• v.15 no.3
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• pp.194-198
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• 2015

Magnetic resonant coupling is more efficient than inductive coupling for transferring power wirelessly over a distance. However, a conventional resonant wireless power transfer (WPT) system requires a transmitter and receiver pair in exactly coaxial positions. We propose a resonator that can serve as an omnidirectional WPT system. A magnetic field will be generated by the current flowed through the transmitter. This magnetic field radiates omnidirectionally in the x-y plane because of the crisscross structure characteristic of the transmitter. The proposed resonator is demonstrated by using a single port. To check the received S21 and transfer efficiency, we moved the receiver around the transmitter at different distances (50-350 mm). As a result, the transmission efficiency is found to be 48%-54% at 200 mm.

• Tribology and Lubricants
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• v.17 no.3
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• pp.221-227
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• 2001

The effect of silver particles on the sliding behavior of bearing steels was studied experimentally by using a ball-on-disk tribometer. Tests were performed in ambient air, dry air and vacuum. Disks of AISI 52100 were silver-coated by a thermal evaporation method, and the effects of silver particle transfer on friction were analyzed. In order to understand further the mechanism of silver particle transfer and its effect on friction and wear, pre-compressed silver particles were artificially introduced into the friction interface and the results were compared to those of silver-coated specimens. Results showed that the introduced silver particles produced transfer layers and resulted in low friction. It also showed that this low friction is closely related to the characteristic behavior of transfer layers. Shakedown occurred at the friction interface affected the friction and wear.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.75-79
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• 2008

In this study, the numerical process for analyzing the automotive louver fin heat exchanger was developed with a 3D microscopic and semi-microscopic analysis. In the microscopic analysis, the simulation with the detailed meshes was performed for obtaining the characteristics of the heat exchanger. From this simulation, the numerical correlations of the heat transfer and flow friction were obtained. In the semi-microscopic analysis, the Semi-microscopic Heat Exchanger (SHE) method, which is characterized by a conjugate heat transfer and porous media analysis was used with the numerical correlation from the microscopic analysis. This analysis predicted the flow and heat transfer characteristics of the louver fin heat exchanger in the wind tunnel and vehicle. In the design of the louver fin heat exchanger, this numerical process can predict the performance and characteristic of the louver fin heat exchanger.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.2
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• pp.244-251
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• 1994

The purpose of this study was to analyze conductive convective and radiative heat transfer characteristic of the nonwovens were studied by measuring thermal conductance at atmospheric and low air pressure. The results obtained were as follows . 1) As thickness of air layer Increased, overall heat transfer was decreased by reducing conductive and radiative heat trasfer. 2) The conductive and convective heat trasfer by air were in the range of 79~8971 of overall heat transfer. 3) As thickness of nonwoven increased for a given solidity, overall heat trasfer was decresed by increasing total thickness of air layer and by reducing conductive and radiative heat transfer. 4) For a given weight, increasing thickness is more effective than increasing solidity.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.218-220
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• 2005

This paper shows the analysis of the inductive power transfer system in conjunction with series resonant converter operating variable high frequency. Of particular interest is the sensitivity of the complete system to variations in operational frequency and parameters. In inductive power transfer system, electrical power is transferred from a prima교 winding in the form of a coil or track, to one or more isolated pick-up coils that may relative to the primary. The ability to transmit power without contact enables high reliability and easy maintenance that allows inductive power transfer system to be implemented in hostile environments. This technology has found application in many fields such as electric vehicles, PRT(Personal Rapid Transit) etc. The coupling between the primary and secondary is then presented to include the effects of parameter and operational frequency variation.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.478-485
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• 2000

An experimental study of the absorption process of water vapor into lithium bromide solution was performed. For the purpose of development of high performance absorption chiller-heater utilizing Lithium Bromide solution as working fluid, the absorber is the most effective to improve the performance of an absorber because it requires the largest heat transfer area in an absorption chiller-heater system. This paper introduces bare tube and inner ribbed notched fin tube for the absorber of absorption chiller-heaters. Inner ribbed notched fin tube has about 10∼20% higher heat and mass transfer performance than bare tube conventionally used in absorbers and the it is expected to perform high heat and mass transfer. This paper will provide important information on the selection of absorber tubes in commercial absorption chill-heaters.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.9
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• pp.734-740
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• 2002

In the present study, heat transfer characteristics of oil flow over offset strip fins are predicted by the numerical methods. Oil flow in the plate-fin passage is idealized by 2 dimensions. Inlet velocity, Prandtl number and fin pitch ratio are chosen as parameters which affect the heat transfer of offset strip fins. The effect of parameters on pressure drops and convective heat transfer coefficients are described. Characteristic length is derived in case of 2 dimensional flow situation. Correlations for friction factor and convective heat transfer coefficient are derived.

• Proceedings of the KIEE Conference
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• summer
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• pp.1304-1306
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• 2004

Recently, the study for development of system having affinity for environment is on investigation. This issue is also applicable to transportation system. This paper suggested the inductive power transformer used for the road/railway applied to contactless power transfer system. The two secondary windings, large gaped magnetic structure and horizontal alignment between primary and secondary coil for that transformer approach a process for improvement of contactless power transfer system performance.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.59-66
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• 2000

An experimental study on the effect of silver particles on the sliding behavior of bearing steels was performed by using a ball-on-disk tribometer. Tests were carried out in ambient air, dry and vacuum. Disks of AISI 52100 were silver-coaled by a thermal evaporation method, and the effects of silver particle transfer on friction were firstly analyzed. In order to understand further the mechanism of silver particles transfer and its effect on friction and wear, pre-compressed silver particles were artificially introduced into the friction interface and the results were compared to those of silver-coated specimens. Results showed that the introduced silver particles produced transfer layers and resulted in low friction. It also showed that this low friction is closely related to the characteristic behavior of transfer layers. Shakedown and rachetting occurred at the friction interface and affected the friction and wear.

• Structural Engineering and Mechanics
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• v.28 no.2
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• pp.167-188
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• 2008

This study is concerned with the establishment of the characteristic equation of a combined system consisting of a cantilever beam with a tip mass and an in-span visco-elastic helical spring-mass, considering the mass of the helical spring. After obtaining the "exact" characteristic equation of the combined system, by making use of a boundary value problem formulation, the characteristic equation is established via a transfer matrix method, as well. Further, the characteristic equation of a reduced system is obtained as a special case. Then, the characteristic equations are numerically solved for various combinations of the physical parameters. Further, comparison of the results with the massless spring case and the case in which the spring mass is partially considered, reveals the fact that neglecting or considering the mass of the spring partially can cause considerable errors for some combinations of the physical parameters of the system.