• E2M - 전기 전자와 첨단 소재
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• 제9권10호
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• pp.1060-1065
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• 1996

We have studied the magnetoresistance phenomena on spin valve thin films of antiferromagnetic NiO/CoO. Interlayer coupling oscillates between the antiferrocoupling and ferrocoupling with the variation of Cu thickness. The exchange coupling strength between NiO (antiferromagnetic) and NiFe(ferromagnetic) as a function of NiO texture and interface roughness is investigated by CoO insertion. CoO has significantly higher anisotropy in the (111) plane and interface roughness. It seems that the MR-ratio is increased by CoO inserted films. From the AFM and XRD data, the increase of MR-ratio and exchange field is influenced by the roughness of CoO.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.416-417
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• 2007

통신 및 IT 기술의 발달로 실시간 기반 전력계통 해석 기능은 점진적으로 발전하고 있으며, 우리나라도 2003년부터 상태추정, 상정고장 등 실시간 해석기반 계통해석을 수행하고 있다. Network Analysis(NA) 기능으로 언급되는 EMS 계통해석 기능은 실시간 전력계통의 안전도를 평가, 취약개소를 도출함으로써 비상시 신속하고 안정적인 계통운영에 활용되고 있다. 본 논문에서는 EMS NA 기능 중 실시간 무효전력 최적화 제어기능인 VVD(Voltage VAR Dispatch) 기능을 소개하고 이의 활용방안을 제시하고자 한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전력기술부문
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• pp.113-115
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• 2004

This year korea power system had recorded highest peak load for 6 times and finally it made new peak load 51,264MW at July 29th 3:00 PM. The new peak load is increased 8.2% from the last year peak load 47,385MW and korea power system entered 50,000MW load era. The Korea Power Exchange (KPX) snapped power system data at the peak load time using state estimation function in the EMS. And authors converted the power system data at peak load to PSS/E power flow format. Using this PSS/E peak load power flow data, this paper explains demand analysis result shun capacitor operation, voltage distribution at the peak load. And the paper shows the simulation result of 2 contingency analysis using the snapped PSS/E peak load data.

• 동력기계공학회지
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• 제10권4호
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• pp.31-37
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• 2006

In this study, the ability for the function of double pipe inserted liquid pipe with small diameter in the gas pipe with large diameter for the circulating of liquid of high temperature and high pressure and low temperature and low pressure at the same time is presented. And in this double pipe, liquid pipe of high temperature and pressure is used to connect condenser and expansion valve and gas pipe of low temperature is used to connect evaporator and compressor. Also, when liquid refrigerant of high temperature and gas refrigerant of low temperature is circulated by reversed flow in the double pipe. The contribution of liquid gas heat exchange pipe is studied by comparison of the effect of heat transfer by temperature difference when liquid pipe and gas pipe is installed separately.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.358-364
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• 2021

In this study, an anion exchange membrane water electrolysis (AEMWE) cell was operated for ~1000 h at a voltage bias of 1.95 V. Impedance spectra were regularly measured every ~ 100 h, and changes in the ohmic and non-ohmic resistance were traced as a function of time. While there was relatively little change in the I-V curves and the total cell resistance during the long-term test, we observed various electrochemical phenomena in the cell: 1) initial activation with a decrease in both ohmic and non-ohmic resistance; 2) momentary and non-permanent bubble resistance (non-ohmic resistance) depending on the voltage bias, and 3) membrane degradation with a slight increase in the ohmic resistance. Thus, the regular test protocol used in this study provided clear insights into the performance degradation (or improvement) mechanism of AEMWE cells.

• KIEE International Transactions on Power Engineering
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• 제3A권1호
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• pp.53-60
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• 2003

At present the electric power industry in Korea is going through a major restructuring process. The restructuring is motivated by a desire to reduce electricity supply costs, to attract new in-vestment in modern generation, transmission and distribution facilities, and to stimulate innovation in the wholesale production and the retail supply of electricity. The experience to date shows that restructuring of electric power industry in the US, however, is marred with a number of problematic market performances including unreasonably high prices at wholesale. This paper investigates the important role of Power Exchange for stabilizing electric power industry in transition by offering various financial products. These financial products are used for risk hedging by the market participants. The paper focuses on the risk hedging by an individual supplier and derives an explicit decision rule that incorporates the attitude towards the risks. In addition to providing the financial products for risk hedging by market participants, the Power Exchange plays another very important role of financial safeguard system. Because of its unique characteristics, the Power Exchange is well suited for financial surveillance where it performs the early detection of unsound financial (and to a large extent operational) practices on the part of any system users and protect the system integrity and the market participants from the consequences of a default in the clearing structure.

• Ocean and Polar Research
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• 제25권spc3호
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• pp.423-426
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• 2003

The seawater exchange breakwater equipped with an oscillating water channel and water transmitting pipes has a very spectacular function that seawater supply can be greatly increased due to the upsurge of the water surface inside the channel at resonance condition which can be reached when the incident wave period becomes close to the natural period of the channel. The variations of the water level and period inside the channel are very important factors in enhancing the efficiency of sea water exchange, especially when designing the breakwater cross-section in shallow water zone which requires longer resonance period with the elongated horizontal projection of the channel. In the present study, a hydraulic experiment was performed varying the length of the oscillating channel, and the resonance periods and water surface variations are analyzed in terms of water transmission through the pipes.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.961-965
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• 1997

1H NMR spectra of 3,3-dimethylpiperidine (1) at -70 to 30 ℃ exhibit gradual change from slow to rapid exchange between two alternate chair forms. The exchange rate constant was determined as a function of temperature by simulating the line shape of the signal from the two methyl groups using the modified Bloch equations. The resulting free energy of activation is ΔG* = 44.4±1.9 kJ mol-1 at 298 K. The 1H NMR spectrum of a D2O or dimethylsulfoxide-d6 (DMSO-d6) solution containing 1 and [SiW11CoⅡO39]6- exhibits separate signals for the free ligand and the complex, indicating that the ligand exchange is slow on the NMR time scale. In D2O the piperidine ring is frozen as a chair form even at room temperature with the cobalt ion bonded to the axial position of the nitrogen atom. When DMSO-d6 is added to the D2O solution, the NMR spectral change suggests that a rapid exchange occurs between the chair form and another conformer. It is proposed that the conformation of ^b1^b coordinated to [SiW11CoⅡO39]6- in DMSO-d6 is close to a twist form.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.226-230
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• 2003

V5.2는 ETSI/ITU-T표준으로써 로컬 교환기와 가입자망간의 개방형(Open) 인터페이스(SNI=Service Node Interface) 통합 액세스 네트웍 구조를 제공하는 프로토콜로 2Mbps 이하의 교환/전용회선 서비스를 제공한다. 본 논문에서는 차세대 통신망에 필수적인 V5.2 인터페이스 시스템이 U에 시설되면서 V5.2 프로토콜의 성능이 기존의 로컬 교환기에서 제공되는 서비스를 모두 가능한지 검증하였다. V5.2 프로토콜 검증을 위하여 ETSI에서 발표한 권고 안을 기준으로 실험하였다. V5.2 표준 권고 안에서는 V5.2 프로토콜 Start-up과 각 서브 프로토콜 속성별로 구분하여 검증할 수 있는 세부 실험 절차가 제시되어 있다. 실험에서 V5.2 프로토콜 스택은 TDX-100교환기에 적합하도록 구성되었으며 여러가지 측면에서 시스템 구조의 안정성을 검증하고 실험이 진행되면서 발생한 문제점 및 대책을 기술하였다.

• 융합보안논문지
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• 제22권5호
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• pp.95-105
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• 2022

육·해·공군은 다영역작전에서 활용할 수 있도록 4차 산업혁명 기술을 접목한 무기체계 개발을 위해 다양한 노력을 하고 있다. 새로운 기술이 적용된 무기체계를 통해 통합 전투력을 효과적으로 발휘하기 위해서는 각각의 무기체계가 정보를 원활하게 송·수신할 수 있는 네트워크 환경의 구축이 필요하다. 이를 위해선 각 무기체계의 정보교환요구량(IER, Information Exchange Requirement)에 대한 분석이 필수적이나, 현재까지 진행된 많은 정보교환능력 분석 연구는 실제 네트워크의 다양한 고려 요소를 충분히 반영하지 못하고 있다. 따라서 본 연구는 기존의 정보교환 요구능력분석 연구들의 연구 방법과 결과를 면밀하게 분석하여 IER 분석시에는 메시지 자체의 크기와 네트워크 프로토콜 헤더의 크기, 전술네트워크의 송수신 구조, 정보 유통 과정, 메시지의 발생 빈도 등을 고려해야 할 필요성을 제기한다. 이어서 향후 IER 예측시에 활용이 가능하도록 푸아송 분포와 확률생성함수를 이용하여 정보교환요구량을 확률 분포로 계산하는 기법을 제시한다. 메시지 목록과 네트워크 토폴로지의 샘플을 이용하여 확률 분포의 계산 결과와 Network Simulator 2를 활용한 시뮬레이션 결과를 상호 비교하여 이 기법의 타당성을 입증한다.