• Proceedings of the KWS Conference
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• 2007.11a
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• pp.132-134
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• 2007

• The Journal of the Acoustical Society of Korea
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• v.4 no.3
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• pp.16-20
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• 1985

압전형 초음파 변환자의 특성을 압전체, matching layer, backing, 매질, tuning 및 구동 회로를 고려하여 해석하였다. 압전체는 KLM 모델을 이용하였고, 모델변수를 실험적으로 추정하여 시뮬레이션 에 대입하였다. 실험적인 RTIL은 면반사에 대한 pulse-echo를 측정하여 계산하였으며, 이론치와 비교할 때 20 dB 주파수 대역내에서 3 dB 이하의 오차가 관찰되었다.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.107-109
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• 1995

This paper considers backing structure of non-contact steel plate using magnectically levitation and aspect-quality factor is defined by estimation of electromagnet-aspect attraction steel plate. Characteristics of attraction power is studied in cylindrical electromagnet, U-type electromagnet, E-type electromagnet by aspect-quality factor. Designing and manufacturing electromagnet attraction steel plate, propriety of experimental results is confirmed.

• Tribology and Lubricants
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• v.34 no.2
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• pp.43-48
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• 2018

This paper presents the thermohydrodynamic analysis of tilting journal pad bearings supporting a power turbine rotor applied to a 250 kW super-critical $CO_2$ cycle. In the analysis, the generalized Reynolds equation and 3D energy equation are solved to predict oil film temperature and the 3D heat conduction equation is solved for pad temperature. The power turbine rotor is supported by two tilting pad bearings consisting of five pads with an oil supply block between the pads. Copper backing pads with higher thermal conductivity compared to steel backing pads are adopted to improve thermal management. The predicted maximum pad temperature is around $55^{\circ}C$ which is approximately $15^{\circ}C$ higher than oil supply temperature. In addition, the predicted minimum film thickness is 50 mm at a rotating speed of 5,000 rpm. These results indicate that there is no issue in the thermal behavior of the bearing. An operation test is performed with a power turbine module consisting of a power turbine, a reduction gear and a generator. Thermocouples are installed at the 75% position from the leading edge of the pad to monitor pad temperature. The power turbine uses compressed air at a temperature of $250^{\circ}C$ in its operation. The steady state pad temperatures measured in the test show good agreement with the predicted temperatures.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.481-487
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• 2002

Currently, the load transfer's mechanism from a beam to a column has yet to ve clarified in a concrete filled steel tubular (CFT) structure with a connection type of an exterior diaphragm. The loads for each floor are transferred to the concrete core from a steel beam through ha contacted face between an in-filled concrete and the interior surface of a steel tube. Thus, a Push-Out test was performed to investigate the load transfer mechanism. A total of 30 samples were tested to confirm the bond stress and/or axial load distribution between a steel tube and in-filled concrete for CFT column. The main parameters considered for this study included concrete type, steel tube-shape/length, and the effect of a weld joint wit ha backing strip for a column splice. Test results were summarized to confirm load transfer behavior between a concrete and steel tube for each experimental parameter, using the analytical approach to verify experimental results.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.65-70
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• 2022

A vacuum system is designed for thermal insulation of a 10 ton/day class air liquefaction cold box for liquid air energy storage. The vacuum system is composed of a turbomolecular pump, a backing pump and vacuum piping for the vacuum pumps. The turbomolecular pump is in combination with the backing pump for pumping capacity. The vacuum piping is designed with system installation conditions, such as distance from the cold box, connections to vacuum pumps and installation space. The capacity of the vacuum pump combination, namely pumping speed, is determined by analysis of the vacuum system, and pump-down time to 1×10^-5 mbar is estimated. Vacuum piping conductance, system pumping speed and outgassing rate are calculated for the pump-down time with the ultimate pumping speed range of the vacuum pump combination of 1400 - 2300 l/s. Although the pump-down time gets shorter by larger capacity vacuum pumps, it mainly depends on target vacuum degree and outgassing rate in the cold box. The pump-down time is estimated as 3 - 6 hours appropriate for cold box operation for the pumping speed range. Considering the outgassing rate has uncertainty, the vacuum pump combination with pumping speed of 1900 l/s is chosen for the vacuum system, which is middle value of the pumping speed range.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.267-270
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• 2008

Thermo-mechanical simulation of the friction stir butt welding process was performed for AA5083-H18 sheets, utilizing commercial FVM code, STAR-CCM+, which is based on Eulerian formulation. Temperature and strain rate histories along the material flow were calculated under the steady state condition and simulated temperature distributions (profiles and peak values) were compared with experiments for verification. It was found that by including proper thermal properties of the backing plate (anvil) the accuracy of the simulation results increased significantly.

• Journal of Ship and Ocean Technology
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• v.6 no.3
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• pp.37-45
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• 2002

A series of detailed study was performed to identify the sources of the propeller blade failure and resolve the problem systematically, by use of the theoretical tools and by the direct measurement and observation in the full-scale sea trials. The selection of inexperienced propulsion control system with a reversible gear system is shown to cause the serious damage to the propeller blades in crash astern maneuver, when the rotational direction of the propeller is changed rapidly. Quasi-steady analysis for propeller blade strength using FEM code in bollard backing condition indicates that the safety factor should be order of 18∼20 to avoid the structural failure for the selected propeller geometry and reduction gear system.

• Journal of KIISE:Information Networking
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• v.27 no.4
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• pp.489-497
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• 2000

주문형 비디오(Video On Demand)서버의 구현은 현재까지도 많은 부분에 한계를 가지고 있으며 이를 해결하기 위한 연구들이 활발히 진행되고 있다. 주문형 비디오 서비스의 한계는 대부분이 자원(디스크, 버퍼)의 제한 때문에 발생하고 있으며 디스크어레이(Disk Array)나, 메모리 뱅크(Memory Bank)와 같은 특수한 하드웨어를 사용하여 해결하고 있다. 또한 이와 아울러 그룹핑이나 버퍼 공유기법과 같은 소프트웨어적인 방법도 제안되었다. 본논문에서는 주분형 비디오 서버의 한계 중 디스크대역폭과 버퍼공간의 한계점에 의한 문제를 해결하기위하여 개선된 그룹핑 방법과 버퍼 공유 및 관리 방법을 제안한다. 제안하는 그룹핑 방법은 비디오의 인기도에 기반을 둔 방법을 사용하며 버퍼 공유방법은 버퍼의 크기 및 디스크의 대역폭 가용량에 따라 적응적으로 병합 분할하는 방법을 사용한다, 제안하는 병합 분할 방법은 피기백킹(piggy-backing)개념을 도입하였으며 시뮬레이션을 통해 제안하 방법의 우수성을 보였다.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.573-576
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• 2000

현재 사용되고 있는 CDMA 시스템에서는 기지국 내에 사용되는 고출력 증폭기(high power. amplifier)의 비선형 특성으로 인해, 시스템의 송신 신호는 심각한 비선형 왜곡을 겪게되고 이는 결국 시스템의 성능을 크게 악화시키는 요인으로 작용한다. 이러한 고출력 증폭기의 비선형성은 출력 신호 레벨을 선형 영역으로 충분히 backing-off 시킴으로써 감소시킬 수 있으나, 이는 송신 신호의 출력을 과도하게 감소시키게 되어 결국 fade margin을 감소시키는 결과를 가져온다. 본 논문에서는 이러한 고출력 증폭기에서 발생하는 비선형 왜곡을 보상할 수 있는 디지털 사전왜곡기를 하드웨어적으로 직접 구현하여 고출력 증폭기의 특성이 변할 때,LMS 알고리듬을 이용하여 LUT의 값을 갱신함으로써 보다 효과적인 적응 사전왜곡기를 설계하는데 목적이 있다.