• Geophysics and Geophysical Exploration
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• v.9 no.3
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• pp.231-240
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• 2006

A variety of geophysical well loggings have been conducted to investigate the geological characteristics for basaltic volcanic area in Jeju Island. Specially, there is no precedent case study using geophysical well loggings in Jeju Island. And so, the proper understandings for geological features of Jeju Island are the key to interpret geophysical well logs. Presently, seawater intrusion monitoring systems have been constructed for systematic development and conservation of groundwater resources. As the results of geophysical well loggings in this seawater intrusion monitoring boreholes, the responses of well logs for saturated zone have distinctly identified basalt sequences. In particular, neutron logging, gamma-gamma (density) logging, and resistivity logging have well exhibited the characteristics of lava flows and lithologic boundaries. In hyalocastite, porosity is high, and resistivity is low. Eventually, geophysical well logs are useful for securing sustainable development of groundwater in Jeju Island in that it has identified the characteristics of geological responses.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.23-30
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• 2019

Fiber-Reinforced Cement Composite (FRCC) is known to be effective in mechanical effects such as cracking width control as well as steel anticorrosive effect. In this study, we examined about steel anticorrosive effect by using metal fibers including zinc fibers by accelerated corrosion test. Moreover, it was examined for salt penetration, sacrificial anode effect and formation of electric circuit that was significant effect on the steel anticorrosive effect. As a result, Steel anticorrosive effect was confirmed with mixed metal fibers on FRCC. Especially, In the case of zinc fibers with a high sacrificial anode effect, it was confirmed that the suppression of penetration and corrosion resistance were improved.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.365-371
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• 2009

It is time-consuming to estimate chloride diffusivity of concrete by concentration difference test. For the reason chloride diffusivity of concrete is mainly tested by electrically accelerated method, which is accelerating the movement of chloride ion by potential difference. In this study, portland cement concrete and concrete containing with ground granulated blast-furnace slag (40 and 60% of cement by weight) with water-cementitious material ratio 40, 45, 50 and 60% were manufactured. To compare with chloride diffusivity calculated from the electrically accelerated test and immersed test in artifical seawater, chloride diffusivity tests were conducted. From the results of regression analysis, regression equation between accelerated chloride diffusivity and immersed chloride diffusivity was linear function. And the determinant coefficient was 0.96 for linear equation.

• Journal of the Korean earth science society
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• v.28 no.4
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• pp.478-490
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• 2007

With groundwater data of seawater intrusion monitoring network in coastal areas of Korea's main land, we analyzed types of seawater intrusion through the coastal aquifer. The data including groundwater level, temperature and electrical conductivity obtained from 45 monitoring wells at 25 watershed regions were evaluated. Based on statistical analysis, correlation analysis and variation type analysis, groundwater levels were mainly affected by rainfall and artificial pumping. About 78% of the monitoring wells showed average temperature higher than $15^{\circ}C$ and about 58% of them showed minimum variations less than $0.2^{\circ}C$. Electrical conductivities showed a large magnitude of variation and irregular characteristics compared with groundwater levels and temperatures. Average electrical conductivities lower than $2,000\;{\mu}S/cm$ were observed at 28 monitoring wells while those of higher than $10,000\;{\mu}S/cm$ were done at 9 monitoring wells. From the cross-correlation analysis, groundwater levels were mostly affected by precipitation while temperature and electrical conductivity showed very low correlation. Meanwhile tidal variations strongly affected the groundwater levels comparing to precipitation. We classified the long-term monitoring data according to variation types such as constant process, linear trend, cyclic variation, impulse, step function and ramp. Impulse type was dominant for variations of groundwater level, which was largely affected by rainfall or artificial pumping, the constant process was dominant for temperature. Compared with groundwater level and temperature, electrical conductivities showed various types like linear trend, step function and ramp. According to the discrepancy of variation characteristics for monitoring data at each well in the same region, periodical analysis of monitoring data is essentially required.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.66-68
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• 2005

This paper presents the reduction characteristics of penetrated electromagnetic fields through a narrow slot aperture in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the parallel plate connected on the slot. The magnitude of penetrated electromagnetic fields through a narrow slot is controlled by electric field distributions on the slot aperture. An integral equation for the aperture electric field on narrow slots is derived and solved by applying Galerkin's method of moments. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by installing the parallel plate on the slot aperture.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.214-217
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• 2007

This paper presents a reduction method of penetrated electromagnetic fields through a narrow slot with resistive sheet in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the parallel plates connected on the slot. The magnitude of penetrated electromagnetic fields through the narrow slot is controlled by the electric field distribution on the slot. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by installing the resistive plates on the slot.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.597-599
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• 2005

국내 지중배전계통에 사용되는 케이블은 경제성을 이유로 송전급 케이블에 준하는 신뢰성을 확보하지 못하고 있다. 초창기 CNCV 케이블로부터 지속적으로 성능이 향상되어 왔음에도 불구하고 여전히 수분침투에 의한 수트리 열화와 반도전층 계면의 전계집중으로 인한 케이블 고장이 많이 발생하고 있다. 이에 한전에서는 위 두 가지 고장원인을 제거하기 위하여 TR CNCE-W 케이블을 개발하였으며, 2005년 4월 규격을 제정하였다. 새로운 케이블은 지중 관로에 포석될 것이며 지중배전계통의 신뢰성을 한충 향상시키게 된 것이다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.244-247
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• 2002

In order to evaluate the water ingress to URD power cables with the jacketing materials and the cable structures, water vapor transmission (WVT) tests were carried out by the ASTM and the TEPCO's specification. All polyolefin compounds showed the superior water suppression to conventional PVC. Especially, linear polyethylenes have very low WVT. In case of cable structures, Allaminate cables showed the significant water suppression due to the watertight structure. Accordingly, it can be concluded that jacketing material and cable structure play an important role in the water suppression of URD power cables.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1503-1504
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• 2015

배전용 케이블은 수트리 억제, 화재예방, 경제성 등을 고려하여 구조와 재질이 지속적으로 변경되고 있다. 변경되는 추세를 살펴보면 경제성 측면에서 도체의 재질은 동에서 알루미늄으로 변경되었고, 수트리 억제를 위해 절연체의 재질은 XLPE에서 TR-XLPE로 변경되었다. 또한 외피의 재질도 난연성을 강화하고 수분침투를 억제하기 위하여 난연성 PE로 개선하였다. 중성선도 외부반도전층 위에 올려진 구조에서 외피 내부로 들어가는 충실형 구조로 변경되었다. 이와 같이 외피구조가 변경되면서 외부반도전층의 두께가 증가되었고 이로 인해 접속재 시공시 삼각형 모양의 공극이 커지게 되었는데, 본 논문에서는 케이블의 외부 반도전층 두께 증가가 접속재 부분방전에 미친 영향을 고찰하였다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1269-1270
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• 2015

외부에서 발생되는 전자파가 특정 구조물 내에 침투하는 경우, 특히 구조체가 도체로 이루어 졌을 때, 구조체의 크기에 따른 특정 주파수가 공진을 일으켜 내부 PCB(Printed Circuit Board), 회로 등에 악영향을 미친다. 본 논문에서는 개구면이 존재하는 공진기에 전자기파가 입사되는 상황을 모드매칭(MM: Mode Matching)을 이용해서 해석한다. 이때 외부 전자파로 인해 개구면에 생기는 새로운 소스를 표면 등가 이론(Surface equivalence theorem)을 이용하여 등가 자기전류로 모델링하여, 공진기 내 외부의 전자기장을 구한 후 개구면에서 접선성분의 경계조건을 적용시켰다. 본 논문에서 사용된 계산식의 검증을 위해 3차원 유한 요소법(FEM: Finite Element Method)기반의 프로그램인 HFSS를 이용 하였다.