• 한국정보통신학회논문지
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• 제19권7호
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• pp.1639-1645
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• 2015

UHD 고속영상 전송 시스템에서 EMI 특성은 특정 주파수 대역의 신호가 전기적, 구조적으로 주파수가 일치될 때, 에너지가 집중되고 신호의 흐름을 방해하여 왜곡이 발생하므로 시스템이 불안정해지는 원인이 된다. 이러한 신호의 왜곡을 제거하기 위하여 전원 무결성 분석과 EMI 현상에 대한 고주파 설계기법이 요구되어진다. 따라서 본 논문에서는 다층인쇄회로기판(MLB : Multi-Layer Printed Circuit Board) 구조에서 발생하는 고주파 잡음을 최소화하고 신호 무결성과 전원 무결성을 개선하면서 EMI를 억제하는 최적의 MLB 설계방법을 제안한다. 제안한 MLB의 특성 임피던스 파라미터는 비유전율 ε_r = 4.3, 고속영상 차동신호(HSVDS : High-Speed Vih = 0.145deo Differential Signaling)의 선로 폭 w = 0.203, 패턴의 간격 d = 0.203, 패턴의 두께 t = 0.0175, 베타층 위의 높이 를 고려하여 특성 임피던스 Zdiff = 100.186Ω으로 설계하였다. 실험결과 아이패턴의 출력 크기가 672mV, 지터는 6.593ps, 전송 주파수가 1.322GHz, 신호 대 잡음비는 29.62dB로 전송 품질이 개선 전보다 약 10dB 향상 되었다.

• 조명전기설비학회논문지
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• 제26권2호
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• pp.99-105
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• 2012

This paper deals with the experimental results of the frequency-dependent resultant ground impedance of vertical ground electrodes installed with a regular n-polygon. In order to propose an effective method of installing the vertically-driven multiple ground electrodes used to obtain the low ground impedance, the resultant ground impedance of ground electrodes installed with a regular n-polygon were measured as functions of the number of ground electrodes and the frequency of test currents and the results were discussed based on the potential interferences among ground electrodes. As a consequence, the effect of potential interference on the resultant ground impedance of vertical ground electrodes is frequency-dependent and it is significant in the low frequency of a few hundreds [Hz]. The resultant ground impedance of multiple vertical ground electrodes is not decreased in linearly proportion to the number of ground electrodes due to the overlapped potential interferences. Also the distributed-parameter circuit model considering the potential interference, the frequency-dependent relative permittivity and resistivity of soil was proposed. The simulated results of the frequency-dependent resultant ground impedance of multiple vertical ground electrodes are in good agreement with the measured data.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 센서 박막재료
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• pp.18-22
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• 2001

Spinel $LiMn_{2-y}Mn_{y}O_4$ powder was prepared solid-state method by calcining the mixture of $LiOH{\cdot}H_2O$, $MnO_2$ and MgO at $800^{\circ}C$ for 36h. To investigate the effect of temperature for cycle behaviour of cathode material during cycling, charge-discharge experiments and initial impedance spectroscopy performed by the condition of the charge-discharge temperature. Initial charge-discharge capacity was gradually increased by rising charge-discharge temperature. However, capacity was suddenly decreased at high temperature during cycling. Capacity at low temperature was almost constant during cycling. It confirmed because Mn dissolution is more serious at high temperature than at low temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1505-1506
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• 2011

염료감응형 태양전지(Dye-Sensitized Solar Cell, DSSC)의 FTO 표면에 compact layer를 형성시켜 직접적인 마찰에 의한 전자의 재결합을 줄일 수 있다. 따라서 광전극에서의 compact layer의 효과를 최대화하기 위하여 $TiCl_4$ 용액에 acetic acid를 첨가하여 특성변화를 측정하였다. UV-Vis 분광기, I-V 특성곡선, EIS 분석장비를 이용하여 검토한 결과, UV-Vis 분광분석을 통해서 acetic acid를 첨가한 compact layer의 투과도가 현저하게 높아진 것을 확인하였다. 이 결과는 $TiCl_4$ 처리에 의하여 compact layer를 구성하고 있는 $TiO_2$ 입자의 응집현상이 개선되므로 표면특성이 향상되었기 때문이다. Acetic acid를 첨가한 compact layer가 입자응집으로 인한 표면저항의 감소를 유발하여, 전자의 이동이 원활해진 것을 내부 임피던스 분석을 통하여 확인하였다. Compact layer에 의해 재결합이 감소하여 효율이 향상된 것을 I-V 특성곡선을 분석하여 확인하였다.

• 전기학회논문지
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• 제59권1호
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• pp.102-107
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• 2010

Dye-sensitized solar cell (DSC) has been expected to be an alternative to the conventional silicon solar cell due to simple manufacturing process and low fabrication casts. In order to improve productivity of DSC, we attempted to optimize the required time of the adsorption process. According to the change in the adsorption time from 1 to 24h, We analyzed the output characteristics and the change of internal impedance. As a result, The outputs of DSC were continuously increased until 12h of the adsorption time and remained the same after that. Also, We reconfirmed this result that 12h was optimum adsorption by the analysis of the electrochemical impedance spectroscope because the internal impedance was similar to the output.

• KEPCO Journal on Electric Power and Energy
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• 제2권4호
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• pp.601-608
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• 2016

접지전극이 매설되는 토양의 전기적 특성은 지역, 계절, 환경적 요인에 따라 저항률이 다양하게 변화한다. 접지전극 주변에서의 전기적 방전현상은 매우 다르게 발생하고, 이는 접지의 성능에 큰 영향을 미친다. 접지시스템의 설계 시에 다양한 조건에서 토양의 방전 특성과 이온화 현상에 관한 분석이 필요하다. 본 연구의 목적은 토양의 이온화 현상과 과도접지임피던스의 상관관계를 파악하는데 있다. 본 논문에서는 뇌임펄스전압에 의해 접지극 주변에서 발생하는 토양의 이온화 작용과 관련된 파라미터와 과도적인 접지저항에 관한 실험적 연구결과를 기술하였다.

• 전기학회논문지
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• 제58권4호
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• pp.849-856
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• 2009

Truncal obesity associated with insulin resistance and metabolic syndrome increase the likelihood of hypertension, various cardiovascular diseases, hyperlipidemia and coronary heart diseases. International Diabetes Federation (IDF) experts recognized that it is necessary to develop the simple diagnostic tool which is applicable to diagnose truncal obesity worldwide, and proposed the method using a waist circumference but there is a limit to estimate subcutaneous fat distribution. However, waist line is also influenced by total fat capacity less than the intra abdominal fat. The more having severe obesity, the more correlation coefficient between waist line and intra abdominal fat is low. Therefore, this thesis defines a new abdominal impedance measurement position and impedance-index to analysis central obesity. This proposes the new model to estimate abdominal obesity using the abdominal impedance-index and CT images acquired fro 160 Korean subjects. The proposed model shows that the abdominal fat distribution has a higher correlation than waist line. (Adj R2=0.809, 0.667 and 0.687 with abdominal fat area, visceral fat area and subcutaneous fat area respectively).

• 전기학회논문지
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• 제62권10호
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• pp.1458-1464
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• 2013

This paper proposed a new real time catenary impedance estimation technique using synchronized power data from the measured data of operating vehicle and substation for catenary protective relay and fault locator setting. This paper presented estimation equation of catenary impedance using synchronized power data between substation and vehicle of AT feeding system for the performance verification of the proposed technique. Also AC feeding system is modeled through power analysis program and performance was verified through simulation according to various load changes. We verified that average 2.38%(distance equivalent 23.8 m) error appeared between the proposed estimation equation of catenary impedance and power analysis program simulation output in no connection double track system between up track and down track. Furthermore, We confirmed that estimation error is bigger depending on the increasing the distance from substation and vehicle impedance using only using vehicle current when calculating vehicle impedance in connection double track system between up track and down track. But, We confirmed that the proposed technique estimated accurately catenary impedance regardless of vehicle impedance and distance from substation.

• 전기학회논문지
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• 제66권9호
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• pp.1334-1340
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• 2017

In this paper, a tie-plate shape is optimized by using the numerical technique to reduce the stray load loss of the tie-plate which is a mechanical structure for assembling and supporting of the transformer core. The eddy current loss of the structure is calculated by an electromagnetic field FEM program and the results are compared with 4 different shapes of tie-plates. Since the thickness of the tie-plate is very thin, and the skin depth is very small, the number of FE elements for 3-D transformer model is too big to solve. So, the surface impedance boundary condition (SIBC) is used to reduce the system matrix size and its computing time. To verify the method a 2.5 MVA 22,900/380V distribution transformer is simulated using one objective function and three design variables with some constraints. The final optimized tie-plate has three slots of 6 mm width and 23 mm gap, and the loss is reduced by 75 %. Consequently, the proposed algorithm seems to be considerably applicable to electric machinery as well as power transformer.

• 전기학회논문지
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• 제67권2호
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• pp.325-330
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• 2018

In this paper, we investigated the impedance method for searching fault detection point in case of an accident in the AC electric railway AT feeding system. For this purpose, simulation circuit modeling and prototype hardware are made based on the known numerical analysis. As a result of simulation modeling of the feeding system based on the numerical analysis of the impedance method confirmed that the modeling was properly implemented with an average error rate of 0.07%. Also, as a result of fault event by hardware simulator, it was confirmed that the breaker operation time is shortened and the fault current is decreased while the voltage is close to the supply voltage in the transient state as the point of the fault accident moves away from the substation(SS).