• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.259-262
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• 2000

In this study, 3.1$\times$3.7$\times$0.365 $\textrm{mm}^2$ model of thickness-longitudinal vibration mode VHF ceramic resonator with (Pb,Ca)(Co,W,Ti)O$_3$ ceramics was simulated by ANSYS according to the electrode size. With the variations of electrode size of the model, fundamental and the third overtone dynamic ratio was investigated. At the ratio of electrode to model thickness(1/t) 2.5, third overtone dynamic ratio was largely increased. That model is suitable for 20 MHz resonator.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.423-426
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• 2000

The 3-D $31.5$\times$31.5$\times$2.5mm$^3$model of contour vibration mode piezoelectric transformer with Pb($Ni_{1/2}$$W_{1/2}$)$O_3$-Pb(Zr,Ti)$O_3$ ceramics was simulated by ANSYS according to the dot size 17, 18, 19, 20, 21 $mm\phi$ and analyzed the results. The mechanical quality factor of the 3-D model was decreased with the dot size and increased as 2605 at 20 $mm\phi$ and after then decreased again. The output voltage of that sample was 74123 [V] and the maximum stress of the dot electrode at that sample was 288[$10^7$N/$m^2$] and the maximum displacement of the ring electrode at that sample was 128 [$\mu\textrm{m}$].

• 정보처리학회논문지C
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• 제14C권6호
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• pp.519-524
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• 2007

제한된 자원을 가진 센서 노드들로 구성된 센서 네트워크에서 가장 중요한 이슈 중 하나는 주어진 에너지를 최대한 활용하여 네트워크 수명을 연장하는 것이다. 네트워크 수명을 연장하는 가장 대표적인 방법은 클러스터링 방법이며, 이는 단일홉 모드와 다중홉 모드로 분류된다. 단일홉 모드는 클러스터 내의 모든 센서 노드들이 CH(Cluster Head)와 단일홉 통신을 하는 것을 말하며, 반면 다중홉 모드는 중간 노드들의 중계를 통하여 센서 노드와 CH가 통신하는 방식을 말한다. 기존의 다중홉 클러스터링 방식에서 성능 상 가장 중요한 영향을 미치는 요소는 클러스터 크기이며, 노드의 분포가 균일하다고 가정하였다. 그러나 실제 네트워크에서의 노드 분포는 균일하지 않을 수 있으므로 이러한 환경에서의 최적의 클러스터 크기 계산은 아주 어렵다. 본 논문에서는 싱크 주변의 CH에 대한 트래픽 부하를 줄이기 위하여 싱크로부터의 거리를 기반으로 클러스터 크기를 동적으로 변화시키는 다중홉 클러스터링 방법을 제안한다. 또한 수학적 분석과 시뮬레이션을 통하여 제안된 동적크기 클러스터링 방식이 기존의 고정크기 클러스터링 보다 더 나은 성능을 가짐을 보였다.

• 한국전자파학회논문지
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• 제29권12호
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• pp.963-968
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• 2018

본 논문에서는 수동소자를 이용한 소형 공통 모드 필터를 설계 및 제작하였다. 주어진 주파수 응답을 갖는 공통 모드 필터를 설계하기 위해 차동 모드와 공통 모드에서 등가회로를 분석하였다. 제안된 구조는 기존의 ${\lambda}/4$ 공진기로 구현된 필터에 비해 60 %의 크기가 감소하였다. 또한, 제작된 공통 모드 필터는 ${\mid}S_{dd11}{\mid}$, ${\mid}S_{cc21}{\mid}$, ${\mid}S_{cc11}{\mid}$ < -10 dB를 만족하는 27.5 %의 공통 모드 흡수 대역폭에서 최대 1.2 dB의 차동 모드 삽입손실과 최소 78.2 %의 공통 모드 흡수 효율을 갖는다.

• 한국대기환경학회지
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• 제16권5호
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• pp.529-537
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• 2000

Several Pt-based oxidation catalysts with different loading were prepared with various metal precursor solutions and characterized with H$_2$ chemisorption and TEM for Pt particle size. V was added to Pt-based catalyst for inhibiting SO$_2$oxidation reaction, as result, Pt-V/Ti-Si catalyst prepared by ERMS(Free Reduced Metal in Solution) method showed high enough activity and better inhibition on SO$_2$oxidation than Pt only catalyst. Optimum Pt particle size for diesel oxidation reaction turned out to be the size of around 20 nm. A prototype catalyst was prepared for light=duty diesel passenger car, and teated for the emission reduction performance with Korean regulation test mode(CVS-75 mode) on chassis dynamometer. The catalyst shows the performance reduction of 75~94% for CO, 53~67% for HC and 10~31% for PM. In the case of heavy-duty diesel catalyst, the domestic formal regulation teat mode D-13 was adopted for both Na engine and Turbo engine. The conversions of CO and THC are high enough(86% and 41%) while the reductions of NOx and PM are relatively low(3~11%).

• 동력기계공학회지
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• 제12권1호
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• pp.5-12
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• 2008

We measured emission characteristics of CRDI diesel engine equipped with a commercial CPF. Experimental parameters adopted a neat diesel fuel, a blend of diesel fuel with 20% biodiesel, a blend of diesel fuel with 15% biodiesel and 5% ethanol. The experiments were carried out to measure the emission and engine performance according to ESC 13-mode cycles. The maximum torque with biodiesel blend fuel is slightly lower than that of neat diesel fuel in the entire the 13-mode cycles, and 5% ethanol and 15% biodiesel blend fuel is slightly higher than that of neat diesel fuel. THC and CO emissions of the biofuel blended diesel fuel were slightly increased and decreased, and mean conversion efficiencies of THC and CO on the commercial CPF were achieved about 70$\sim$87% in the ESC 13-mode. From the measurement by the Scanning Mobility Particle Sizer(SMPS), the total number and mass of nano-sized particles by a commercial CPF were decreased about 97.8% and 96.8 % in the range of the nano-size from 10.6 to 385nm, respectively.

• 전력전자학회논문지
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• 제25권3호
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• pp.188-194
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• 2020

This paper presents a high-efficiency Switch Mode Line Transformer (SMLT) composed of load-shared dual modules, which is based on the AC/AC LLC resonant converter. Given that the conventional adaptor is usually composed of two power stages, namely, the PFC and DC/DC converters, its system size can be increased according to the output power. However, given that the proposed SMLT can separate the PFC converter from the adaptor, the size reduction of the system can be achieved. Meanwhile, the SMLT with a single module has the limit of the size reduction because of a high resonant current. Thus, it can be configured with dual or multiple modules to reduce the resonant current. Then, their load sharing can be guaranteed by only the proposed transformer structure without an extra current controller. The validity of the proposed converter is proven through a 850-W prototype.

• 전력전자학회논문지
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• 제24권4호
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• pp.237-243
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• 2019

A high-efficiency and small-sized switched-mode line transformer (SMLT) is proposed in this study. The conventional structure of an adapter is composed of line transformer and rectifiers. This structure has a limit in miniaturizing due to low-frequency line transformer. Another structure is composed of power factor correction (PFC) and DC/DC converter. This structure has a limit in reducing volume due to two-stage structure. As the proposed SMLT is composed of an LLC resonant converter, a high-frequency transformer can be adopted to achieve isolation standards and size reduction. This proposed structure has different operation modes in accordance with line input voltage to overcome poor line regulation. In addition, the proposed SMLT is applied to the front of a conventional PFC converter, because the SMLT output voltage is restored to rectified sinusoidal wave by using a full-bridge rectifier in the secondary side. The design of the PFC converter is easy, because the SMLT output voltage is controlled as rectified sinusoidal wave. The validity of the proposed converter is proven through a 350 W prototype.

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2010년도 춘계학술대회
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• pp.96-97
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• 2010

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1989년도 춘계학술대회 논문집
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• pp.107-109
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• 1989

Based on the ferroelectric microstructural residual stress model, the relation between grain size and residual elastic energy was proposed. It was found that the residual elastic energy increased with decreasing grain size by modeling and DSC results. This residual elastic energy change with grain size which induce the phase transituion mode change was the cause of a diffuse phase transition in small grain size.