• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.508-511
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• 2002

By defining a power distribution ratio (PDR) and coupling efficiency (CE) amenable to the rigorous analytical solutions of newly developed rigorous modal transmission-line theory (MTLT), we explicitly analyze the power coupling characteristics of TE modes propagating in GADCs. The numerical results reveal that the incident power is optimally coupled into the desired guiding channel if the powers of rigorous modes excited at the input boundary of grating-assisted coupler are equally partitioned.

• Journal of the Optical Society of Korea
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• v.8 no.4
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• pp.149-155
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• 2004

Newly developed modal transmission-line theory(MTLT) is used to analyze rigorously the optical power distribution in grating-assisted directional couplers(GADCs) with three guiding channels. By defining a novel coupling efficiency ${\eta}$ amenable to the rigorous analytical solutions of modal transmission-line theory, we explicitly evaluate the power coupling and distribution of TM modes. The results reveal that the incident power is sensitively partitioned through three output channels in terms of such grating parameters as the grating period, the duty cycle, and the operating wavelength.

• Journal of Power Electronics
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• v.3 no.4
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• pp.239-248
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• 2003

This paper presents a novel prototype of three-phase voltage source type zero voltage soft-switching inverter with the auxiliary resonant snubbers suitable for high-power applications with IGBT power module packages in order to reduce their switching power losses as well as electromagnetic conductive and radiative noises. A proposed single inductor-assisted resonant AC link snubber circuit topology as one of some auxiliary resonant commutation snubbers developed previously to achieve the zero voltage soft-switching (ZVS) for the three-phase voltage source type sinewave PWM inverter operating under the instantaneous space voltage vector modulation is originally demonstrated as compared with the other types of resonant AC link snubber circuit topologies. In addition to this, its operation principle and unique features are described in this paper. Furthermore, the practical basic operating performances of the new conceptual instantaneous space voltage vector modulation resonant AC link snubber-assisted three-phase voltage source type soft-switching PWM inverter using IGBT power module packages are evaluated and discussed on the basis of switching voltage and current waveforms, output line to line voltage quality, power loss analysis, actual power conversion efficiency and electromagnetic conductive and radiative noises from an experimental point of view, comparing with those of conventional three-phase voltage source hard-switching PWM inverter using IGBT power modules.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.227-231
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• 2001

A new primary-side-assisted zero-voltage and zero-current switching (ZVZCS) three-level DC-DC converter with flying capacitor is proposed. The three-level converters are promising in high voltage applications, and ZVZCS is a very effective means for reducing switching losses. The proposed DC-DC converter uses only one auxiliary transformer and two diodes to obtain ZCS for the inner leg. It has a simple and robust structure, and offers soft-switching capability even in short-switching conditions. The proposed converter was verified by experiments in a 6KW prototype designed for communication applications and operating at 100kHz.

• Journal of Navigation and Port Research
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• v.35 no.4
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• pp.303-316
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• 2011

With the development of mechatronics technology in the transporter industry, the electric power assisted steering (EPAS) system has many advantages compared to the hydraulic system. Many manufacturers are developing and applying EPAS systems to improve the performance of the transporter. Using the HILS system developed in the paper, an adaptable EPAS system was developed for real transporter. It was installed in a real, KIA Rio, and tested. Results indicated outstanding performance. Therefore, the developed EPAS can be applied via HILS system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.125-125
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• 2018

반도체 소자의 미새화에 따라 선폭이 10nm 이하로 줄어듦에 따라, 금속 배선의 저항이 급격하게 상승하고 있다. Cu는 낮은 저항과 높은 전도도를 가지고 있어 현재 배선물질로써 가장 많이 사용되고 있지만, 소자가 미세화됨에 따라 Cu를 미래의 배선물질로써 계속 사용하기에는 몇 가지 문제점이 제기되고 있다. Cu는 electron mean free path (EMFP)가 39 nm로 긴 특성을 가지기 때문에, 선폭이 줄어듦에 따라 surface 및 grain boundary scattering이 증가하여 저항이 급격하게 증가한다. 또한, technology node에 따른 소자의 operating temperature와 current density의 증가로 인해 Cu의 reliability가 감소하게 된다. 텅스텐은 EMFP가 19 nm로 짧은 특성을 가지고 있어, 소자의 크기가 줄어듦에 따라 Cu보다 낮은 저항 특성을 가질 수 있으며, 녹는점이 3695K로 1357K인 Cu보다 높으므로 배선물질로써 Cu를 대체할 가능성이 있다. 본 연구에서는 Inductively Coupled Plasma (ICP) assisted magnetron sputtering을 통해 매우 얇은 텅스텐 박막을 증착하여 저항을 낮추고자 하였다. 고밀도 플라즈마의 방전을 위해, internal-type coil antenna를 사용하였으며 텅스텐 박막의 증착을 위해 DC sputter system이 사용되었다. 높은 에너지를 가진 텅스텐 이온을 이용하여 낮은 온도에서 고품위 박막을 증착할 수 있었으며, dense한 구조의 박막 성장이 가능하였다. ICP assisted를 이용하여 증착했을 때와, 그렇지 않을 때를 비교하여 ICP 조건에 따라서 박막의 저항이 감소함을 확인할 수 있었을 뿐만 아니라 최대 약 65% 감소함을 확인할 수 있었다. XRD를 이용하여 ICP power를 인가했을 때, 높은 저항을 갖는 A-15 구조를 가진 ${\beta}$ peak의 감소와 낮은 저항을 갖는 BCC 구조를 가진 ${\alpha}$ peak의 증가를 상온과 673K에서 증착한 박막 모두에서 확인하였으며, 이를 통해 ICP power가 저항 감소에 영향을 미친다는 것을 확인하였다. 또한, 두 온도 조건에서 grain size를 계산하여 ICP power를 인가함에 따라 두 조건 모두 grain size가 증가하였음을 조사하였다. 또한, XPS 분석을 통해 ICP power를 인가하였을 때 박막의 저항에 많은 영향을 끼치는 O peak이 감소하는 것을 통해 ICP assisted의 효과를 확인하였다. 이를 통해, ICP assisted magnetron sputtering을 통해 텅스텐 박막을 증착함으로써 차세대 배선물질로써 텅스텐의 가능성을 확인할 수 있었다.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.273-279
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• 2020

In this study, conventional solvent extraction (CSE), microwave-assisted extraction (MAE), and ultrasound-assisted extraction (UAE) were compared for the recovery of paclitaxel from biomass. As a result of investigating the effect of the extraction solvent type (acetone, chloroform, ethanol, methanol, methylene chloride), methanol was the most suitable for all extraction methods. In the case of MAE and UAE using methanol, most of the paclitaxel (> 95%) was recovered by only one extraction. The recovery rate of paclitaxel increased with the increase of extraction temperature (25-45 ℃), microwave power (50-150 W), and ultrasonic power (180-380 W) for MAE and UAE. In addition, SEM analysis showed that the biomass surface structure was slightly corrugated in CSE, while in the MAE and UAE, it was very rough and destroyed by strong impact.

• Journal of Power Electronics
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• v.5 no.1
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• pp.29-35
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• 2005

This paper presents a novel prototype of an active auxiliary quasi-resonant snubber(Auxiliary Quasi-Resonant Commutation Block-Link; ARCB)-assisted three phase voltage source soft switching space voltage vector modulated PFC rectifier, which uses Zero Voltage Soft Switching (ZVS) commutation. The operating principles of this digitally-controlled three phase soft switching PWM-PFC rectifier system with an instantaneous power feedback scheme are illustrated and its steady-state performance is evaluated using computer-aided simulation analysis.

• Journal of the Korean Ceramic Society
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• v.54 no.1
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• pp.38-42
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• 2017

Vanadium nitride (VN) coatings were deposited using inductively coupled plasma (ICP) assisted sputtering at different ICP powers. Microstructural, crystallographic and mechanical characterizations were performed by FE-SEM, AFM, XRD and nanoindentation. The results show that ICP has significant effects on coating's microstructure, structural and mechanical properties of VN coatings. With an increase in ICP power, coating microstructure evolved from a porous columnar structure to a highly dense one. Single- phase cubic (FCC) VN coatings with different preferential orientations and residual stresses were obtained as a function of ICP power. Average crystal grain sizes of single phase cubic (FCC) VN coatings were decreased from 10.1 nm to 4.0 nm with an increase in ICP power. The maximum hardness of 28.2 GPa was obtained for the coatings deposited at ICP power of 200 W. The smoothest surface morphology with Ra roughness of 1.7 nm was obtained in the VN coating sputtered at ICP power of 200 W.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.1
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• pp.1-7
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• 1990

To investigate the influence of r.f. power and electrode distance on the TiN deposition, TiN films were deposited onto STC3, STD11 steel and Si-wafer from gas mixtures of $TiC_4/N_2/H_2$ using the radio frequency plasma assisted chemical vapor deposition. The crystallinity of TiN film could be improved by the increase of r.f. power and the decrease of electrode distance. The TiN coated layer contains chlorine, its content were decreased with increasing r.f. power as well as decreasing electrode distance. And the thickness of deposited TiN was largely affected by r.f. power and electrode distance. The hardness of deposited TiN reached a maximum value of about Hv 2,000.