• 대한전자공학회논문지TC
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• 제45권8호
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• pp.8-14
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• 2008

본 논문에서는 via가 있는 버섯구조를 이용한 ENG ZOR 안테나와 DGS 구조를 이용한 via-free ENG ZOR 안테나의 접지면 크기의 변화에 따른 입력저항, 대역폭, 방사효율의 영향에 대하여 이론적 연구를 수행하였다. Via-free ZOR 안테나가 via가 있는 버섯구조 ZOR 안테나보다 접지면 크기에 영향을 더 받는 것으로 확인되었다. DGS가 적절하게 동작하기 위해서는 최소 크기의 접지면이 요구되어지므로 via-free 안테나의 방사특성은 일정 크기 이상의 접지면이 확보되어야 좋아질 수 있다. Via가 있는 안테나는 기판의 높이가 높아질수록 대역폭과 방사효율이 좋아지고, via-fee 안테나의 경우 높이가 높아질수록 대역폭과 방사효율이 떨어지는 것으로 관찰되었다. 또한, via-free ZOR 안테나의 경우 via가 있는 버섯구조 ZOR 안테나와 비교하여 대역폭이 좁고 방사효율은 떨어지지만 소형화에 유리함을 알 수 있었다.

• 한국지반환경공학회 논문집
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• 제2권3호
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• pp.57-69
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• 2001

샌드파일 공법은 연약지반 개량을 위해 널리 사용되는 방법중의 하나이다. 샌드파일 설치에 의해 얻고자 하는 주된 목적은 압밀촉진에 있으나 이와 더불어 복합지반효과를 지니게 된다. 본 연구에서는 상대적으로 면적 치환비가 작은 연직배수재로서 적용된 샌드파일 설치지반에서의 복합지반효과를 파악하고자 하였다. 이를 위하여 원지반과 샌드파일의 지내력 확인을 위한 평판재하시험을 실시하였으며, 성토체와 지반과의 상호거동을 확인하기 위하여 토압계를 설치하여 계측관리를 실시하였다. 분석결과 면적치환비가 작은 샌드파일 설치지반에서 복합지반을 고려한 지지력은 원지반의 지지력과 비교하여 매우 작은 증가효과를 보였다. 그러나 원지반과 비교한 샌드파일 설치위치에서의 지지력 증가는 약 60% 로 나타났다. 이와 같이 샌드파일의 강성증대에 의한 파일설치 위치에서의 지지력 증대는 재하하중 작용에 의한 압밀진행 과정중 압밀특성 변화의 요인으로 작용하게 될 것이다. 따라서 샌드파일 강성증대에 따른 복합지반효과는 샌드파일 설치지반에서 압밀침하량이 감소하는 요인으로 평가될 수 있는 것으로 판단된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.93-99
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• 2000

Using the EMTP(Electro Magnetic Transient Program) for the analysis of lightning direct voltage on the railway system, the shielding effects of overhead grounding wire on the railway were studied quantitatively. Installation of overhead ground wire and gap-type arrester such as s-horn Provides a 6.6㎸ HV distribution line with good protection effects. Even severe lightning induced voltage were create, 6.6㎸ HV lines can be withstand.

• Computers and Concrete
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• 제9권3호
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• pp.195-213
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• 2012

This paper presents the investigation of the stochastic responses of seismically isolated bridges subjected to spatially varying earthquake ground motions including incoherence, wave-passage and site-response effects. The incoherence effect is examined by considering Harichandran and Vanmarcke coherency model. The effect of the wave-passage is dealt with various wave velocities in the response analysis. Homogeneous firm, medium and soft soil conditions are selected for considering the site-response effect where the bridge supports are constructed. The ground motion is described by filtered white noise and applied to each support points. For seismic isolation of the bridge, single and double concave friction pendulum bearings are used. Due to presence of friction on the concave surfaces of the isolation systems, the equation of motion of is non-linear. The non-linear equation of motion is solved by using equivalent linearization technique of non-linear stochastic analyses. Solutions obtained from the stochastic analyses of non-isolated and isolated bridges to spatially varying earthquake ground motions compared with each other for the special cases of the ground motion model. It is concluded that friction pendulum systems having single and double concave surfaces have important effects on the stochastic responses of bridges to spatially varying earthquake ground motions.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.809-814
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• 2009

Deep mixing method has been used for ground improvement and foundation system for embankment, port and harbor foundations, retaining wall, and liquefaction mitigations. It has attractive benefits because it is not only improved strength of soft ground but superior for prevention of settlement. However, the quality controls of improved mass affect to the efficiency of the deep mixing method is not properly established. These effects vary depending upon the construction environments and conditions of agitation in consideration of an agitator. The strength and shape of the improved column are not unique and these are affected by mechanical properties of agitators. In this study, in order to investigate the efficiency of deep mixing method for ground improvement on a soft clay ground, experimental studies are performed considering mechanical properties of agitator; the location of exit-hole of admixtures, an angle of mixing wing and a speed of revolution. The experiments are conducted with the simulated apparatus for deep mixing plant that reduced the scale in 1:8 of the real plant. According to the results, the diameter and shape of improved column mass vary depending on the mechanical properties and operating conditions of agitator. Its quality is better when the exit-hole of admixtures is located in the mixing wing, when an angle of mixing wing is large, and when the speed of revolution is rapid.

• Steel and Composite Structures
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• 제32권1호
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• pp.91-110
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• 2019

In the present study, the effects of six different ground motion scaling methods on inelastic response of nonlinear steel moment frames (SMFs) are studied. The frames were designed using energy-based PBPD approach with the design concept using pre-selected target drift and yield mechanism as performance limit state. Two target spectrums are considered: maximum credible earthquake spectrum (MCE) and design response spectrum (DRS). In order to investigate the effects of ground motion scaling methods on the response of the structures, totally 3216 nonlinear models including three frames with 4, 8 and 16 stories are designed using PBPD approach and then they are subjected to ensembles of ground motions including 42 far-fault and 90 near-fault pulse-type records which were scaled using the six different scaling methods in accordance to the two aforementioned target spectrums. The distributions of maximum inter-story drift over the height of the structures are computed and compared. Finally, the efficiency and reliability of each ground motion scaling method to estimate the maximum nonlinear inter-story drift of special steel moment frames designed by energy-based PBPD approach are statistically investigated, and the most suitable scaling methods with the lowest dispersion for two groups of earthquake ground motions are introduced.

• 한국안전학회지
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• 제30권4호
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• pp.46-50
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• 2015

This paper describes the measurement and analysis of ground impedance according to arrangement of auxiliary probe around ground grid using the fall-of-potential method and the testing techniques to minimize the measuring errors are proposed. The fall-of-potential method involves passing a current between a ground electrode and a current probe, and then measuring the voltage between a ground electrode and a potential probe. To minimize interelectrode influences due to mutual resistances, the current probe is a generally placed at a substantial distance from the ground electrode under test. In order to analyze the effects of ground impedance due to the arrangement of auxiliary probe and frequency, ground impedances were measured in case that the arrangements of auxiliary probe were straight line, perpendicular line, and horizontal line. The distance of current probe was located from 10[m] to 200[m] and the measuring frequency was ranged from 55[Hz] to 513[Hz]. As a consequence, the ground impedance increases with increasing the distance from the ground electrode to the point to be tested, but the ground impedance decreases with increasing the frequency.

• 한국토양비료학회지
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• 제44권1호
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• pp.38-47
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• 2011

This study focused on health risk assessment via multi-routes of As exposure to establish a target cleanup level (TCL) in abandoned mines. Soil, ground water, and rice samples were collected near ten abandoned mines in November 2009. The As contaminations measured in all samples were used for determining the probabilistic health risk by Monte-Carlo simulation techniques. The human exposure to As compound was attributed to ground water ingestion. Cancer risk probability (R) via ground water and rice intake exceeded the acceptable risk range of $10^{-6}{\sim}10^{-4}$ in all selected mines. In particular, the MB mine showed the higher R value than other mines. The non-carcinogenic effects, estimated by comparing the average As exposure with corresponding reference dose were determined by hazard quotient (HQ) values, which were less than 1.0 via ground water and rice intake in SD, NS, and MB mines. This implied that the non-carcinogenic toxic effects, due to this exposure pathway had a greater possibility to occur than those in other mines. Besides, hazard index (HI) values, representing overall toxic effects by summed the HQ values were also greater than 1.0 in SD, NS, JA, and IA mines. This revealed that non-carcinogenic toxic effects were generally occurred. The As contaminants in all selected mines exceeded the TCL values for target cancer risk ($10^{-6}$) through ground water ingestion and rice intake. However, the As level in soil was greater than TCL value for target cancer risk via inadvertent soil ingestion pathway, except for KK mine. In TCL values for target hazard quotient (THQ), the As contaminants in soil did not exceed such TCL value. On the contrary, the As levels in ground water and polished rice in SD, NS, IA, and MB mines were also beyond the TCL values via ground water and rice intake. This study concluded that the health risks through ground water and rice intake were greater than those though soil inadvertent ingestion and dermal contact. In addition, it suggests that the abandoned mines to exceed the risk-based TCL values are carefully necessary to monitor for soil remediation.

• 전기학회논문지
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• 제56권6호
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• pp.993-999
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• 2007

This paper discusses the effects of CD type superconducting cable operation in 22.9kV multi neutral grounded distribution system during L-G fault and counterplans to power system protection. In case of using the 3-phase CD-type superconducting cable, the inductance of superconducting cable system would be decreased due to the current of shield part of superconducting cable, which is opposite direction and nearly equal value with respect to main superconductor. However, when the shield circuit system is operated in shorted state, shield current decreases faulted ground current and give effects to power system protection scheme. This study examines the phenomena of single line to ground fault case in above mentioned system using the EMTDC program and discusses the right operation method of superconducting shield.

• 오토저널
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• 제13권4호
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• pp.76-84
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• 1991

The off-road tractive performance of tracked vehicles can be evaluated in terms of soil thrust, motion resistance and drawbar pull. The ability to predict accurately ground pressure distribution under track is of importance since the vehicle sinkage and motion resistance are closely related to it. While the formulation of the method for predicting ground pressure distribution follows closely in spirit the ideas outlined for the terrain with linear pressure- sinkage relation case by Garber and Wong, the analysis of various terrain stiffness is magnified by numerical implementation procedure. The effects of soil parameters on tractive forces can be introduced through the terrain-track interaction such as pressure-sinkage and shearing characteristics. It is illustrated by determining the drawber pull-slip relation and corresponding ground pressure distribution for the terrains typically chosen and by comparing the results with the conventional ones based on normal ground pressure. The factorial experiment method is finally adopted for checking the sensitivity of the values of soil parameters on the drawbar pull.