• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1812-1818
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• 2005

Even though SMA actuators have high power to volume ratio, there exist disadvantages such as hysteresis and saturation. So the model identification for SMA actuators is very difficult. For the qualitative model identification, we described the behavior of SMA actuators using a so-called diagonal model, which can readily expect the turning point of an incomplete phase transformation. For the quantitative model identification, we developed the general dynamics of SMA actuators using the modified Liang's model. Using this dynamics we can describe the hysteresis and the saturation very well. It is also very important to notice that the modified Liang's model maintains a continuous martensite fraction at the change of the phase transformation but the original model cannot.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.459-460
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• 2011

본 논문에서는 산과 골이 있는 복잡한 형상의 기어를 일정한 깊이로 열처리하기 위한 효율적인 유도가열에 관한 연구이다. 이를 위해 동시에 이중주파수를 발생하면서 출력을 각각 제어할 수 있는 인버터를 설계하였으며 두개의 인버터로 구동되는 방식을 기준으로 해석, 설계 및 부하와 매칭을 위한 필터 설계를 수행하여, MF(Medium frequency)와 HF(High frequency에서 공진주파수 운전을 위한 최적의 인버터를 설계 및 제작하고자 한다.

• Journal of computational fluids engineering
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• v.10 no.1
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• pp.1-7
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• 2005

Three-dimensional numerical analysis of the flow around rectangular cylinders with various side ratios, D/H, from 0.2 to 2.0, was carried out for Reynolds number of 10³ by using a multi-directional finite difference method on a regular-arranged multi-grid. The predicted results are in good agreement with the experimental data. It is found that fluid dynamic characteristics of rectangular cylinders alternate between the high-pressure mode and the low-pressure mode of the base pressure for D/H=0.2-0.6. We show that this phenomenon is induced by the change of the flow pattern around rectangular cylinders.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.136-139
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• 1997

The active-clamped double forward-flyback converter is studied in this paper. The converter reduces the voltage stress of the switches and decreases switching loss, EMI. The energy stored in the magnetic core is transferred to both the input voltage source and the flyback output. This makes it possible the output circuit of the flyback to operate at CCM without complex control circuit. The MOSFET is used at output stage, which decreases switching loss.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1387_1388
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• 2009

High accurate and stable 132 kV potential transformers (PTs) including 66 kV & 22 kV PT with stability of less than 0.0033 % for 13 month and with ratio error within $\pm$ 0.024 % at full rated voltage have been developed. The PTs are useful as the reference PT of the PT comparator system in the voltage range of 11 kV to 132 kV PT.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.157-161
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• 2008

An optical sensor was developed to detect nanoparticles, turbid materials and microorganisms in water simultaneously. Three different light sources like UV-LED, NIR-LED and laser diode have been employed to develop the optical sensor based on the scattering light and fluorescence light. The sensor system has high selectivity and sensitivity, that it can be used to monitor the quality of drinking water.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 1986.12a
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• pp.522.3-523
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• 1986

A Screening test was carried out for chitin-decomposing bacteria. In 100 samples from soil, fesh water and sea water, 7 strains of Chitinolytic bacteria were isolated. 5-3K which exhibited the highest chitinase activity was identified as Aeromonas hydrophila and cultural conditions from maximum chitinase production were determined. Optimum Chitinase production was obtained at pH 7, 33eC and with chitin concentration greater tham 0.2% Under optimal conditions, high yields of Chitinase were obtained in 16-30 hours. Chitinase was purified by ammonium sulfate precipitation and sephadex G-100 gel-filtration from the culture filtrgte.

• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.187-190
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• 2007

To improve the power factor and reduce the harmonic contents of the system, the design of tunned filters for six-pulse thyrister converter which is used by electrolyzer system is discussed in this paper. Tunned filters are added to high-power rectifiers to keep the line current distortion within allowable limits and to improve the rectifier power factor. For electrolyzer system, the design procedure of tunned filters of AC 14.4kV power system are proposed by dynamic simulation. It is shown that these harmonic filters can meet most operational requirments. The the proposed design procedure is verified with the simulation and experimental results.

• Wind and Structures
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• v.11 no.2
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• pp.137-152
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• 2008

This paper discusses engineering aspects of the rear-flank downdraft that was recorded near Lubbock, Texas on 4 June 2002, and produced a gust wind speed nearly equal to the design value (50-year return period) for the region. The general characteristics of the storm, and the decomposition of the time histories into deterministic 'running mean' and random turbulence components are discussed. The fluctuating wind speeds generated by the event can be represented as a dominant low-frequency 'running mean' with superimposed random turbulence of higher frequencies. Spectral and correlation characteristics of the residual turbulence are found to be similar to those of high-frequency turbulence in boundary-layer winds. However, the low-frequency components in the running-mean wind speeds are spatially homogeneous, in contrast to the low-frequency turbulence found in synoptic boundary-layer winds. With respect to transmission line design, this results in significantly higher 'span reduction factors'.

• Proceedings of the Korean Nutrition Society Conference
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• 2002.05a
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• pp.102-102
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• 2002