• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.71-71
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• 2012

As the critical dimensions of integrated circuits are scaled down, the line width and spacing between the metal interconnects are made smaller. The dielectric film used as insulation between the metal lines contributes to the resistance-capacitance (RC) time constant that governs the device speed. If the RC time delay, cross talk and lowering the power dissipation are to be reduced, the intermetal dielectric (IMD) films should have a low dielectric constant. The introduction of Cu and low-k dielectrics has incrementally improved the situation as compared to the conventional $Al/SiO_2$ technology by reducing both the resistivity and the capacitance between interconnects. Some of the potential candidate materials to be used as an ILD are organic and inorganic precursors such as hydrogensilsequioxane (HSQ), silsesquioxane (SSQ), methylsilsisequioxane (MSQ) and carbon doped silicon oxide (SiOCH), It has been shown that organic functional groups can dramatically decrease dielectric constant by increasing the free volume of films. Recently, various inorganic precursors have been used to prepare the SiOCH films. The k value of the material depends on the number of $CH_3$ groups built into the structure since they lower both polarity and density of the material by steric hindrance, which the replacement of Si-O bonds with Si-$CH_3$ (methyl group) bonds causes bulk porosity due to the formation of nano-sized voids within the silicon oxide matrix. In this talk, we will be introduce some properties of SiOC(-H) thin films deposited with the dimethyldimethoxysilane (DMDMS: $C_4H_{12}O_2Si$) and oxygen as precursors by using plasma-enhanced chemical vapor deposition with and without ultraviolet (UV) irradiation.

• 한국분말재료학회지
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• 제28권6호
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• pp.470-477
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• 2021

Energy storage systems should address issues such as power fluctuations and rapid charge-discharge; to meet this requirement, CoFe₂O₄ (CFO) spinel nanoparticles with a suitable electrical conductivity and various redox states are synthesized and used as electrode materials for supercapacitors. In particular, CFO electrodes combined with carbon nanofibers (CNFs) can provide long-term cycling stability by fabricating binder-free three-dimensional electrodes. In this study, CFO-decorated CNFs are prepared by electrospinning and a low-cost hydrothermal method. The effects of heat treatment, such as the activation of CNFs (ACNFs) and calcination of CFO-decorated CNFs (C-CFO/ACNFs), are investigated. The C-CFO/ACNF electrode exhibits a high specific capacitance of 142.9 F/g at a scan rate of 5 mV/s and superior rate capability of 77.6% capacitance retention at a high scan rate of 500 mV/s. This electrode also achieves the lowest charge transfer resistance of 0.0063 Ω and excellent cycling stability (93.5% retention after 5,000 cycles) because of the improved ion conductivity by pathway formation and structural stability. The results of our work are expected to open a new route for manufacturing hybrid capacitor electrodes containing the C-CFO/ACNF electrode that can be easily prepared with a low-cost and simple process with enhanced electrochemical performance.

• 센서학회지
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• 제30권6호
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• pp.436-440
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• 2021

The impact of the gate length (L_g) on the DC and high-frequency characteristics of indium-rich In_0.8Ga_0.2As channel high-electron mobility transistors (HEMTs) on a 3-inch InP substrate was inverstigated. HEMTs with a source-to-drain spacing (L_SD) of 0.8 ㎛ with different values of L_g ranging from 1 ㎛ to 19 nm were fabricated, and their DC and RF responses were measured and analyzed in detail. In addition, a T-shaped gate with a gate stem height as high as 200 nm was utilized to minimize the parasitic gate capacitance during device fabrication. The threshold voltage (V_T) roll-off behavior against L_g was observed clearly, and the maximum transconductance (g_{m_max}) improved as L_g scaled down to 19 nm. In particular, the device with an L_g of 19 nm with an L_SD of 0.8 mm exhibited an excellent combination of DC and RF characteristics, such as a g_{m_max} of 2.5 mS/㎛, On resistance (R_ON) of 261 Ω·㎛, current-gain cutoff frequency (f_T) of 738 GHz, and maximum oscillation frequency (f_max) of 492 GHz. The results indicate that the reduction of L_g to 19 nm improves the DC and RF characteristics of InGaAs HEMTs, and a possible increase in the parasitic capacitance component, associated with T-shap, remains negligible in the device architecture.

• 한국멀티미디어학회논문지
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• 제20권10호
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• pp.1678-1688
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• 2017

Infiltration is one of detrimental problems occurring in nursing or medical settings. Early detection of infiltration is essential to minimize the risk of injury from infiltration. To perform a preliminary study on the point of care and automated infiltration detection system, bioelectrical impedance was investigated using bioelectrical impedance analyzer. We would like to report experimental results that allow impedance parameters to effectively distinguish infiltration. Electrodes were attached to both sides of the transparent dressing on the fusion site where IV solution was being infused. Then, impedance parameters before and after infiltration were measured as a function of time and frequency. The experimental results are as follows. After infiltration was intentionally induced by puncturing the vein wall with a needle, the resistance gradually decreased with time. That is, when an alternating current having a frequency of 20 kHz was applied to the electrodes, the resistance gradually decreased with time, reflecting the accumulation of IV solution in the extracellular fluid since the current could not pass through the cell membrane. Impedance parameters and equivalent circuit model for human cell were used to examine the mechanism of current flow before and after infiltration, which could be used for early detection of infiltration.

• 전기화학회지
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• 제11권1호
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• pp.33-36
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• 2008

본 연구에서는 겔식 VRLA (valve regulated lead acid번지의 충전상태(SoC) 판단을 위해 임피던스 기법을 이용하여 조사하였다. 임피던스는 VRLA전지 (2V/1.2Ah)의 다양한 충전상태에서 진폭 10mV로 100kHz에서${\sim}$10mHz까지 측정하였다. 측정된 임피던스 데이터로부터 등가회로를 유도하고, CNLS (Complex Non-linear Least Squares) 법을 사용하여 분석하였다. 양극 쪽의 전하전이 저항과 전기이중층 커패시턴스가 음극보다 높았다. 겔 저항은 충전상태가 감소함에 따라 증가하며 이는 VRLA 전지의 충전상태를 판단하는데 중요한 파라미터임을 확인하였다.

• Applied Biological Chemistry
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• 제38권5호
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• pp.371-375
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• 1995

식물 병원성 사상균 F. oxysporum과 R. solani에 대하여 우수한 길항력을 갖는 Pseudomonas (P.) fluorescens를 작물 근권으로 부터 분리하여 생리, 생화학적 특성을 조사하였다. 이들 분리 근권길항 미생물중 한 균주인 Ps70과 plasmid pSV2-neo를 이용하여 electroporation에 의한 길항 미생물 P. fluorescens의 transformation 가능성과 최적 조건을 조사하였다. 그 결과 10% glycerol을 P. fluorescens buffer로 사용하여 2.5kV의 voltage, $200{\Omega}$의 resistance에서 최적의 electrotransformation 효과를 보였다. 또한, 이균주에 크기가 서로 다른 plasmid를 electroporation하여 transformation 효과를 비교한 결과 voltage, electroporation buffer의 조성, 그리고 resistance (time constant)가 transformation의 효과를 증진하는데 주요한 역할을 하는것으로 나타났으며, 또 다른 P. fluorescens 균주에 같은 실험을 반복한 결과 유사한 electrotransformation 효과를 보였다.

• 한국전자파학회논문지
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• 제26권12호
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• pp.1064-1071
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• 2015

본 논문에서는 마이크로대역에서 단층 및 다층 그래핀이 각각 결합된 인터디지털 커패시터의 전기적 특성을 비교 분석하였다. 그래핀이 결합된 커패시터의 등가회로에서 커패시터의 저항, 인덕턴스, 커패시턴스 성분들 간 차이가 분명하게 나타났다. 특히 단층 그래핀이 결합된 커패시터의 경우, 순수 커패시터와 다층 그래핀이 결합된 커패시터에 비해 추가적으로 인덕턴스와 저항 성분이 나타났고, 또한, 커패시터 전극의 저항 성분이 증가하였다. 한편, 커패시터의 자기공명주파수는 더 낮은 주파수대역으로 이동하였고, 0.5~4 GHz 주파수 대역에서 투과특성이 상당히 향상되었다. 반면, 다층 그래핀이 결합된 커패시터의 경우, 순수한 커패시터의 전기적 특성과 약간의 차이만 나타났다. 결과적으로 본 연구를 통해서 단층 그래핀이 다층 그래핀에 비해 인터디지털 커패시터의 전기적 특성과 성능에 더욱 민감한 영향을 줄 수 있음을 확인하였다.

• Journal of Power Electronics
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• 제10권6호
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• pp.749-761
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• 2010

The switching frequency of a power device is a very important parameter in the design of a parallel active power filter (PAPF), but so far, very little discussion has been conducted on it in a quantitative manner in previous publications. In this paper, an extensive analysis on the effects of the switching frequency on the performance of a PAPF is made, and a specification of the switching frequency values with different compensation results is presented. A first-order inertia element and a second-order oscillation element are considered as approximate models of a PAPF, respectively. The compensation characteristic for each order of harmonic current is obtained at different switching frequencies. Then, the THDs of each model for the system loads of a rectifier with resistance and inductance loads are proposed. The compensation results of a PAPF controlled as a first-order inertia element are better than those of a PAPF controlled as a second-order oscillation element. With two types of system loads which are rectifier with resistance and inductance loads and rectifier with resistance, inductance and capacitance loads, the THDs of the source current after compensation are presented with different switching frequencies. The compensation characteristics for the most widely used digital control system are investigated. The situation with an analog control is the theoretical characteristic and it is the best situation. The compensation characteristic of the digital control is worse than the compensation characteristic of the theoretical characteristic. Based on these analyses, the specifications of compensation characteristics with different switching frequencies are quite straightforward. Finally, a practical design example is studied to verify the application.

• 대한조선학회논문집
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• 제60권5호
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• pp.305-319
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• 2023

This study focuses on measuring the relative wave elevation around the KSUPRAMAX-O ship and comparing it with numerical analysis results (potential and computational fluid dynamics). The relative wave elevation is a good indicator of the pressure distribution on the ship's surface, which is affected by the ship's motion, incident waves, and distributed waves. Prior to measuring the relative wave elevation, a comparative test was conducted on resistance type, capacitance type, and ultrasonic type wave probe to measure the relative wave elevation, and it was confirmed that the resistance type wave probe was suitable for measuring the relative wave elevation. A model test was performed at low speed and design speed using resistance type wave probe and compared with the results of numerical analysis result. As for the motion response, it was confirmed that the result of experiments and the result of the numerical analysis were in good agreement. The relative wave elevation showed a similar trend between the experiment and the computational fluid dynamics, but the potential analysis result showed a difference from the experiment in design speed.

• 한국산학기술학회논문지
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• 제21권5호
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• pp.516-522
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• 2020

수트리의 진행과정은 십수년이 걸리며 보통 매우 오래된 지중케이블에서 발견된다. 이러한 지중케이블들은 이미 접근이 어려운 곳에 있어 수트리를 검출하기 위해서는 많은 비용과 시간이 소요된다. 이러한 지중케이블의 유지보수 비용과 시간을 절감하기 위해서는 수트리가 진행된 지중케이블이 전력망에 미치는 영향을 분석할 수 있는 수학적 모델링이 필요하고, 이를 이용한 수트리 탐지 기술개발이 매우 필요한 실정이다. 본 논문에서는 수트리가 포함된 XLPE 케이블 대한 수학적 모델링을 하고자 수트리의 복잡한 구조를 Vented tree의 확인된 특정 패턴 2가지를 기준으로 가정하여 단순화 하였다. 그리고 수트리의 발달에 따른 케이블 절연층의 캐패시턴스 및 레지스턴스를 계산 및 분석하기 위해 matlab으로 시뮬레이션을 실시하였으며, 모델링의 유용성을 검증하기 위해서 참고문헌 Burkes 논문의 케이블 데이터를 동일하게 적용하였다. 시뮬레이션 결과, 캐패시턴스 크기의 변화는 케이블에 수트리 영역이 절연층에 95%까지 진행되었을 때 정상대비 약 0.025×10^-13[Farads/mm] 증가됨을 확인하였다. 레지스턴스 값의 경우 정상대비 약 0.5×10¹⁶[ohm/m] 정도 감소되는 것을 확인하였다. 따라서, Burkes 논문의 물리적 모델링 시뮬레이션 결과와 비교하였을 때 그 변화값이 매우 유사하여 본 논문에서 제시한 수학적 모델링의 유용성을 검증하였다.