• KEPCO Journal on Electric Power and Energy
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• 제2권2호
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• pp.307-310
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• 2016

The operational cost for maintaining the superconductivity of high-temperature superconducting (HTS) cables needs to be reduced for feasible operation. It depends on factors such as AC loss and heat transfer from the outside. Effective operation requires design optimization and suitable operational conditions. Generally, it is known that critical currents increase and AC losses decrease as the operational temperature of liquid nitrogen ($LN_2$) is lowered. However, the cryo-cooler consumes more power to lower the temperature. To determine the effective operational temperature of the HTS cable while considering the critical current and AC loss, critical currents of the HTS cable conductor were measured under various temperature conditions using sub-cooled $LN_2$ by Stirling cryo-cooler. Next, AC losses were measured under the same conditions and their variations were analyzed. We used the results to select suitable operating conditions while considering the cryo-cooler's power consumption. We then recommended the effective operating temperature for the HTS cable system installed in an actual power grid in KEPCO's 154/22.9 kV transformer substation.

• 전자공학회논문지D
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• 제36D권1호
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• pp.1-7
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• 1999

본 논문에서는 마이크로 스트립 다중 전송 선로의 고속 디지털 펄스 신호에 대한 상호 결합 특성을 시간영역에서 해석하기 위해 FDTD법을 사용하였고, SPICE에 의한 결과 및 측정결과와 상호 비교하였다. 기존 SPICE에 의한 다중 전송 선로의 해석은 FDTD법에 비해 정확도가 저하되고, 손실 특성에 대한 해석을 할 수 없으므로, 본 논문에서는 FDTD법을 이용하여 무손실 및 손실을 고려한 다중 전송 선로의 디지털 전송 특성을 해석하고 누화 특성을 비교하여 나타냈다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.43-43
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• 2010

HTS(High Temperature Superconductor) cable has a high possibility of practical use due to the possibility of low voltage and high capacity transmission caused by its lower power loss than copper cable. On the other hand, when fault current occurred, resistance increase caused by superconductivity loss, the amount of power supplies has diminished, furthermore, it's necessary to take the possible danger of damage to HITS cable into account. Therefore, an effective plan for dealing with the above problem is to link HITS cable to SFCL. In this study, we researched the possibilities of normal transport current as well as the safety of HITS cable by analyzing the properties of transport current in HITS cable connected with SFCL.

• 전자공학회논문지A
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• 제32A권3호
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• pp.25-37
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• 1995

The phenomenological loss equivalence method incorporated into the wideband lossy transmission line model is applied to the characterization of high desity digital transmission lines. The pulse propagation characteristics are analyzed using the calculated frequency characteristics and the discrete Fourier transformation. This approach has been verified by comparing the calculated frequency characteristics with the FEM and the esperimental results. This method is very suitable for computer-aided analysis of high density/high speed interconnection circuits because of the simple calculation as well as the calculation accuracy. We have found that pulse ftransmission speed and dispersion of hgih density digital transmission lines can be optimized by managing the conductor and dielectric losses in addition to the impedance matching.

• 산업기술연구
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• 제31권A호
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• pp.109-112
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• 2011

In this paper, we proposed a planar reversed triangle monopole antenna for UWB(Ultra Wideband) communication. RF-60A substrate of 0.64 mm thickness and 6.15 relative permitivity and 0.035 mm conductor of thickness and loss tangent 0.0025 is used for implementation. We have used Ansoft $HFSS^{TM}$(High Frequency Structure Simulator) to simulate the proposed antenna. The proposed antenna showed return losses about -10 dB, nearly omni-directional radiation patterns and maximum gains are over -5 dBi at the frequency band from 3.1 GHz to 10.6 GHz for ultra wide band communication.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권12호
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• pp.586-591
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• 2005

Magnetization loss of high temperature superconductoring BSCCO tape and YBCO coated conductor(YBCO CC) is most important issue in the development of superconducting power devices. In this paper, the measured results of magnetization losses in BSCCO tape and YBCO CC are presented and compared with each other. Measurements of magnetization losses are performed under various angles of external magnetic field to consider the anisotropic characteristics of YBCO CC. Also, we present the compared results of magnetization losses measured at arbitrary directional magnetic fields and analyzed with perpendicular magnetic field components of those. The results show that magnetization loss of YBCO CC agree well with the analyzed value by it's perpendicular magnetic field component, but BSCCO tape is not.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.1-2
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• 2016

This paper presents frequency modulation method of zero-voltage-transition interleaved DC/DC converter using auxiliary coupled-inductor. In conventional ZVT interlaved converter without semi-conductor devices in auxiliary circuit, the peak-to-peak value of coupled-inductor current has fixed value despite the change of load current. Then, as the load is reduced, the efficiency is reduced because of the conduction loss. The proposed frequency modulation method can reduce the conduction loss by controlling the current of coupled-inductor as the load condition using frequency modulation. The proposed method is verified by experimental results.

• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.49-53
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• 2006

A high temperature superconductor (HTS) has been developed for power applications such as power cables, fault current limiters and superconducting magnetic energy storage devices. For such applications it is required to understand the DC voltage-current characteristic of the HTS. which is important in analyzing AC loss and flux flow loss quantitatively. In this work, we have experimentally investigated influence of several factors, e.g. critical current density. degradation and AC external magnetic field, on the DC voltage-current characteristic. The measured results have been discussed in engineering application point of view.

• 한국전자파학회논문지
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• 제15권11호
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• pp.1108-1115
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• 2004

본 논문에서는 밀리피터파 대역의 응용에 적용될 수 있는 새로운 형태의 로트맨 렌즈를 제시하였다. 본 논문에서 새로이 제시하는 유전판 로트맨 렌즈는 도체손실과 포트간 상호간섭(mutual coupling)을 감소시킬 수 있는 특성을 지니고 있으며 밀리미터 대역에서 구현이 보다 용이한 구조이다. 기존의 렌즈가 도체 평판 구조인데 반해 제안된 렌즈는 유전판과 슬롯으로 구성되어 있으며 TE$_{0}$모드로 구동한다. 중심주파수 15 GHz에서 9개의 빔 포트와 9개의 배열포트로 구성된 렌즈를 9개의 TSA(Tapered Slot Antenna) 배열과 더불어 설계 및 제작하였다. 측정결과에 따르면 빔폭은 13 GHz에서 약 15$^{\circ}$이며 효율은 약 34 %를 나타냈으며 포트간 상호간섭은 주파수가 상승함에 따라 점진적으로 감소함을 관찰할 수 있었다. 밀리미터 파 대 역에서 제작 및 측정 장비의 부족으로 인해 설계주파수를 15 GHz로 크게 낮추었음에도 불구하고 효율은 평행 도체판 구조의 렌즈와 대등한 값을 얻었다. 향후 밀리미터파 대역에서 고유전율 막(high dielectric thin film) 형태로 제작된다면 도체 손실파 상호간섭을 크게 감소시킬 것이 기대된다.

• 한국항해항만학회지
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• 제34권3호
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• pp.167-173
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• 2010

지그비 모듈용 소형 PCB안테나를 $30mm{\times}8mm$의 좁은 영역으로 제한된 공간에서 구현함과 동시에 안테나의 반사손실을 개선시키기 위하여, 기생소자로 접지면과 이격되는 도체를 가지는 미앤더 슬롯 안테나가 제안된다. 본 논문을 통해 설계되어 제작된 안테나의 공진주파수는 대략 2.44GHz이고, 대역폭은 113MHz(VSWR${\leq}$2)이다. 방사패턴은 동작주파수영역에서 다이폴 안테나의 방사특성과 거의 유사하고, 안테나의 효율 및 이득은 각각 60% 및 2.7dBi이상의 값을 가진다. 이러한 안테나의 모든 특성들은 지그비에 응용되기 위해 요구되어지는 규격을 모두 만족함을 알 수 있다. 본 논문이 제안하는 안테나의 타당성을 보여주기 위해 모의실험 결과 및 측정결과를 비교하여 제시하였다.