• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 추계학술대회 논문집
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• pp.3-4
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• 2015

본 논문에서는 SP 토폴로지를 가지는 무선전력전송 시스템에서 결합 계수 및 부하 변화에 따른 Zero phase angle (ZPA) 주파수 추종 제어 알고리즘을 제안한다. 제안한 알고리즘은 부가적인 아날로그 회로 없이 기존의 디지털 제어기에 적용되어 ZVS 영역에서 동작하도록 공진 주파수를 추종한다. PSIM 시뮬레이션 및 실험을 통해 주파수 추종 성능을 검증한다.

• Journal of Magnetics
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• 제20권2호
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• pp.114-119
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• 2015

This study explored the effect of pulsed magnetic field (PMF) stimulus on the improvement of blood stagnation by means of photoplethysmography (PPG). Our stimulus system was designed to generate PMF with a maximum intensity variation of 0.20 T at a transition time of $160{\mu}s$, with pulse intervals of 1 Hz. In order to quantitatively estimate vascular condition, indices such as blood vessel tension (BVT), stress power (SP), differential pulse wave index (DPI) and remained blood volume (RBV) were calculated from the second derivative of the PPG signal and power density spectrum (PDS). Our results showed that non-invasive PMF stimulus was effective in improving blood stagnation. Therefore, it may be concluded that appropriate PMF stimulus affects the blood circulatory system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.321-322
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• 2015

The aim of this paper is to propose a design method for the double-sided LCC compensation circuit for 6.6kW electric vehicle (EVs) wireless charger. The analysis and comparison with several compensation topologies such as SS, SP, PS, PP and the hybrid LCC compensation is presented. It has been found that the hybrid LCC compensation has superior performance in comparison with other topologies. The design procedure for the EV charger is presented and the PSIM simulation results are provided.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.68.1-68.1
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• 2012

The best part of graphene is - charge-carriers in it are mass less particles which move in near relativistic speeds. Comparing to other materials, electrons in graphene travel much faster - at speeds of $10^8cm/s$. A graphene sheet is pure enough to ensure that electrons can travel a fair distance before colliding. Electronic devices few nanometers long that would be able to transmit charge at breath taking speeds for a fraction of power compared to present day CMOS transistors. Many researches try to check a possibility to make it a perfect replacement for silicon based devices. Graphene has shown high potential to be used as interconnects in the field of high frequency electrical devices. With all those advantages of graphene, we demonstrate characteristics of electrical and optical properties of graphene such as the effect of graphene geometry on the microwave properties using the measurements of S-parameter in range of 500 MHz - 40 GHz at room temperature condition. We confirm that impedance and resistance decrease with increasing the number of graphene layer and w/L ratio. This result shows proper geometry of graphene to be used as high frequency interconnects. This study also presents the optical properties of graphene oxide (GO), which were deposited in different substrate, or influenced by oxygen plasma, were confirmed using different characterization techniques. 4-6 layers of the polycrystalline GO layers, which were confirmed by High resolution transmission electron microscopy (HRTEM) and electron diffraction analysis, were shown short range order of crystallization by the substrate as well as interlayer effect with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups on its layers. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation, and Fourier Transform Infrared spectroscopy (FTIR) and XPS analysis shows the changes in oxygen functional groups with nature of substrate. Moreover, the photoluminescent (PL) peak emission wavelength varies with substrate and the broad energy level distribution produces excitation dependent PL emission in a broad wavelength ranging from 400 to 650 nm. The structural and optical properties of oxygen plasma treated GO films for possible optoelectronic applications were also investigated using various characterization techniques. HRTEM and electron diffraction analysis confirmed that the oxygen plasma treatment results short range order crystallization in GO films with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups. In addition, Electron energy loss spectroscopy (EELS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation and XPS analysis shows that epoxy pairs convert to more stable C=O and O-C=O groups with oxygen plasma treatment. The broad energy level distribution resulting from the broad size distribution of the $sp^2$ clusters produces excitation dependent PL emission in a broad wavelength range from 400 to 650 nm. Our results suggest that substrate influenced, or oxygen treatment GO has higher potential for future optoelectronic devices by its various optical properties and visible PL emission.

• 한국안광학회지
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• 제9권2호
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• pp.291-299
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• 2004

ECR-PECVD 방법을 이용하여 ECR power, $CH_4/H_2$ 가스 혼합비와 유량, 증착시간을 고정 시켜놓고 기판 bias 전압을 변화 시켜가면서 유리 기판위에 DLC 박막을 제작하였다. Raman, FTIR 및 UV/Vis 스펙트럼을 측정하여 기판 bias 진압에 따른 이용 충돌이 박막의 특성 변화에 미치는 영향을 조사하였다. FTIR 분석결과로부터 기판 bias 전압을 증가시킬수록 이용충돌 현상이 두드러져 탄소와 결합하고 있던 수소원자들의 탈수소화 현상을 확인할 수 있었고, 박막의 두께는 bias 전압을 증가시킬수록 감소되었다. 그리고 Raman 스펙트럼으로부터 Gaussian curve fitting을 통하여 sp3/sp2의 결합수에 비례하는 D/G피크의 면적 강도비(ID/IG)는 기판 bias 전압을 증가시킬수록 증가하였다. 그리고 광 투과율은 증착시간을 길게 할수록, 기판 bias 전압을 크게할수록 감소하였으나, 박막의 밀도가 증가하고 더 매끄러운 DLC 박막이 형성되었다. 이 결과로부터 DLC 박막은 기판 bias 전압의 크기를 증가시킬수록 특성이 더 향상됨을 알 수 있었다.

• 한국항해항만학회지
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• 제28권10호
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• pp.955-960
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• 2004

선박에서 발생되는 밸러스트수를 전처리하기 위하여 수중에 포함되어 있는 미생물을 복극전해처리시스템을 이용하여 살균처하였다. 전해처리시스템에 유입되는 시료는 정량펌프를 사용하여 상향류로 전극판 사이를 통과하도록 하였으며, 반응시간별로 유량을 조절하여 체류시간을 다르게 하였다. 양극판은 티타늄에 이산화이리듐을 전착한 Ti/Ir02 극판으로 하였으며, 음극판은 스테인리스 스틸판을 사용하였다. 전원공급은 최대 전압이 250V, 전류가 100Amper의 맥류가 전혀 없는 트랜지스트 평활회로를 사용한 D.C. Power Supply를 사용하여 전류밀도를 조절하여 운전하였다. 반응시간에 따라 전류밀도를 0.1$\~$1.0A사이로 변화를 주어 실험한 결과 5초 이내에 E. coli, Bacteria, Bacillus sp.의 미생물이 사멸됨을 확인할 수 있었고, 전극간격은 75mm, 전류밀도 2.0A/dm2, 체류시간을 5초로 하였을 때 제거율이 $90\%$이상이였다. 연구결과를 통하여 밸러스트수 처리에 적용 가능한 기술임을 알 수 있었다.

• Korean Chemical Engineering Research
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• 제48권3호
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• pp.292-299
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• 2010

그래핀(graphene)은 $sp^2$ 탄소원자들이 벌집 격자를 이룬 형태의 2차원 나노시트를 의미하며, 높은 비표면적(이론치 $2600m^2\;g^{-1}$)과 우수한 전기전도도(전형치 $8{\times}10^5S\;cm^{-1}$) 및 기계적 강도로 인해 리튬이온전지의 음전극 활물질 및 초고용량 커패시터의 전극 활물질로서 사용 가능성이 높아지고 있다. 본 총설에서는 현재까지 알려진 그래핀 나노시트와 그래핀을 기반으로 하는 나노복합체의 제조법을 소개하고, 이를 리튬이온전지와 초고용량 커패시터의 전극소재로 적용하였을 때의 특성을 그 나노구조적 관점과 연관하여 논의하였다.

• KIEAE Journal
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• 제17권1호
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• pp.77-82
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• 2017

In power supply systems for urban areas, issues such as a progressive tax have escalated recently. In this regard, photovoltaic power generation, which is appraised as an alternative power generation system, is drawing attention increasingly for its high stability and applicability to existing infrastructure. This study assessed the realistic feasibility of photovoltaic power generation and also analyzed the economic benefits expected when it is linked with green roof, which is likely to promote ecological functions in urban areas, based on the Seoul solar map, RPS, and actual monitoring data. The economics analysis of 30kW photovoltaic power generation applied with the monthly average horizontal solar radiation of six grades in the Seoul solar map showed that positive NPV was up to grade 4, while grade 5 or poorer showed negative NPV and indicated that it is difficult to assure appropriate feasibility. Compared with non-afforestation, when green roof was applied, monthly average power improvement efficiency was 7.2% at highest and 3.7% at lowest based on yearly actual monitoring data. The annual average was 5.3%, and the efficiency was high relatively in summer, including September and November. As for the economic benefits expected when 30kw photovoltaic power generation is combined with green roof based on the average horizontal solar radiation of grade 1 in the Seoul solar map, SP has improved 0.2 years to 7.4 years, and EP has improved 0.5 years to 8.3 years.

• 마이크로전자및패키징학회지
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• 제21권3호
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• pp.7-17
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• 2014

Power electronics modules are semiconductor components that are widely used in airplanes, trains, automobiles, and energy generation and conversion facilities. In particular, insulated gate bipolar transistors(IGBT) have been widely utilized in high power and fast switching applications for power management including power supplies, uninterruptible power systems, and AC/DC converters. In these days, IGBT are the predominant power semiconductors for high current applications in electrical and hybrid vehicles application. In these application environments, the physical conditions are often severe with strong electric currents, high voltage, high temperature, high humidity, and vibrations. Therefore, IGBT module packages involves a number of challenges for the design engineer in terms of reliability. Thermal and thermal-mechanical management are critical for power electronics modules. The failure mechanisms that limit the number of power cycles are caused by the coefficient of thermal expansion mismatch between the materials used in the IGBT modules. All interfaces in the module could be locations for potential failures. Therefore, a proper thermal design where the temperature does not exceed an allowable limit of the devices has been a key factor in developing IGBT modules. In this paper, we discussed the effects of various package materials on heat dissipation and thermal management, as well as recent technology of the new package materials.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.49-54
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• 2000

Cr-Mo-V steel is widely used as a material for the turbine structural component in fossil power plants. It is well known that this material shows the various material degradation phenomenons such as temper embrittlement, carbide coarsening. and softening etc. or ins to the severe operation conditions as high temperature and high pressure. These deteriorative factors cause tile change of mechanical properties as reduction of fracture toughness. Therefor it is necessary to evaluate tile extent of degradation damage for Cr-Mo-V steel in life assessment of turbine structural components. In this paper. the electrochemical potentiokinetic reactivation(EPR) test in $50wt%-Ca(NO_3)_2$ solution is performed to develop the newly technique for degradation damage evaluation of Cr-Mo-V steel. The results obtained from the EPR test are compared with those in small punch(SP) tests recommended by semi-nondestructive testing method using miniaturized specimen. The evaluation parameters used in EPR test are tile reactivation current density$(I_R)$ and charge$(Q_{RC})$ reactivation rate$(I_R/I_{Crit},\;Q_R/Q_{Crit})$. The results suggest that $I_R/I_{Crit}$ in these parameters shows a good correlation with SP test results.