• 한국도로학회논문집
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• 제15권4호
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• pp.53-63
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• 2013

PURPOSES: The purpose of this study was to investigate the disintegration mechanism of concrete due to the infiltration of the moisture to the milling overlay pavement and to come up with a method to minimize the disintegration as well as verifying the effectiveness of the edge sealing and Fogseal method. METHODS : This study investigated the distress mechanism due to the infiltrated moisture remaining in the milling overlay pavement through chloride freezing test and verified the effectiveness of the sealing of the milling edge and fog seal methods, which have been devised to minimize the moisture infiltration, through laboratory water permeability test. Additionally, long-term pavement performance was compared for the effectiveness of the proposed method through under loading test, and field water permeability test was carried out to verify the field applicability of the proposed method. RESULTS: The result of the research confirmed that chloride deteriorates the concrete surface through disintegration and lowers its strength and that the laboratory moisture infiltration test verified the effectiveness of the milling edge sealing and fog seal methods in the deterrence of moisture infiltration to the overlay pavement with excellent long-term performance of the pavement treated with the proposed method. Although the field water permeability test revealed some deterrence of moisture infiltration of the milling edge sealing and fog seal methods to a certain extent, the difference was a little. CONCLUSIONS: The milling edge sealing and fog seal methods are limited in their effectiveness for the cases of improvident compaction management or mixture with large void, and it is believed that installation of subsurface drainage is more effective in these cases.

• 조명전기설비학회논문지
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• 제25권2호
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• pp.131-136
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• 2011

This paper aims to examine the possibility of using an environmentally friendly $N_2$ as an alternative gas to $SF_6$. For this purpose, we have investigated breakdown characteristics of $N_2$ under impulse voltages in a quasi-uniform electric field gap. The 1.2/50[${\mu}s$] lightning impulse voltage, switching impulse voltages and oscillatory impulse voltages were applied at the test gap. The electric field utilization factor ranges from 0.5 to 0.8. The experimental data of $SF_6$ and $N_2$ acquired in the same experimental condition are presented in parallel for comparison. As a result, the breakdown voltages in $SF_6$ and $N_2$ are linearly increased with the gas pressure, also the breakdown voltages in $N_2$ are increased with increasing the gap distance and electric field utilization factor. The positive breakdown voltages are higher than the negative breakdown voltages. The nagative basic lightning impulse withstand level of 150[kV] in $N_2$ of about 0.5[MPa] is nearly equal to that in $SF_6$ of 0.15[MPa]. It is seen from the results obtained in this work that $N_2$ can be used as an eco-friendly alternative gas to $SF_6$ in distribution power equipment.

• 조명전기설비학회논문지
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• 제23권1호
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• pp.141-149
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• 2009

본 논문에서는 준정적 FDTD 기법을 FORTRAN 프로그래밍을 통해 직접 구현하고 이를 이용해 중간주파수 대역의 인체유도전류 분포를 해석하였다. 제작된 프로그램의 타당성을 검증하기 위하여 기존 FDTD 기법을 적용하기 어려운 테스트 모델에 대한 계산결과를 이론적 해와 비교하고, 타임스텝이 크게($5.68{\times}10^6$배) 단축되는 것을 확인하였다. 검증된 수치해석 기법을 이용하여 20[kHz] 자기장과 1[MHz] 전기장에 노출된 3차원 고해상도 인체모델에 유기되는 유도전류의 분포를 계산하고, 양 발의 접지조건이 유도전류의 분포와 크기에 미치는 영향을 분석하였다. 본 연구는 인체유도전류의 안전성 평가, 생체전기 응용 진단장치 개발 등을 포함한 다양한 분야에서 활용될 것으로 기대된다.

• 조명전기설비학회논문지
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• 제24권8호
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• pp.126-132
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• 2010

본 논문은 준평등전계중에서 임펄스전압에 대한 $N_2$가스의 절연파괴특성에 관한 것으로 실험은 1.2/50[${\mu}s$] 표준뇌임펄스전압, 180/2500[${\mu}s$] 개폐임펄스전압과 500[ns]/1[MHz] 급준성 과도과전압이 인가된 전극계에서 이루어졌다. 구-평판 전극의 간격은 14[mm]이고, 전계이용률은 71.2[%]이었으며 가스압력은 0.2~0.6[MPa]범위로 하였다. 그 결과 절연파괴는 스트리머방전에 의하여 일어났으며, 절연파괴전압은 상승시간이 빠른 급준성 과도과전압에서 가장 높게 나타났다. 정극성 절연파괴전압이 부극성보다 높았으며, 정극성의 경우 절연파괴까지의 시간도 더 긴 것으로 나타났다.

• Geomechanics and Engineering
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• 제15권3호
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• pp.841-849
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• 2018

The purpose of a rock bolt is to improve the mechanical performance of a jointed-rock mass. The performance of a rock bolt is generally evaluated by conducting a field pullout test, as the analytical or numerical evaluation of the rock bolt behavior still remains difficult. In this study, wide range of field test was performed to investigate the pullout resistance of rock bolts considering influencing factors such as the rock type, water bearing conditions, rock bolt type and length. The test results showed that the fully grouted rock bolt (FGR) in water-bearing rocks can be inadequate to provide the required pullout resistance, meanwhile the inflated steel tube rock bolt (ISR) satisfied required pullout resistance, even immediately after installation in water-bearing conditions. The ISR was particularly effective when the water inflow into a drill hole is greater than 1.0 l/min. The effect of the rock bolt failure on the tunnel stability was investigated through numerical analysis. The results show that the contribution of the rock bolt to the overall stability of the tunnel was not significant. However, it is found that the rock bolt can effectively reinforce the jointed-rock mass and reduce the possibility of local collapses of rocks, thus the importance of the rock bolt should not be overlooked, regardless of the overall stability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.22-25
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• 2001

The research results on the superconducting magnet for whole body MRI are presented. The magnet consists of main coil with 6 solenoid coils, shielding coil with 2 solenoid coils and 6 sets of cryogenic shim coil. The ferromagnetic shim assembly is installed on the inside wall of the room temperature bore for shimming inhomogeneous field components generated due to manufacturing tolerances, installation misalignments and external ferromagnetic materials near the magnet. Also, the magnet is enclosed with the horizontal type cryostat with 80cm room temperature bore to keep the magnet under the operating temperature. The magnetic field distributions within the imaging volume were measured by the NMR field mapping system. Through the test, the central field of magnet was 1.5 Tesla and the field homogeneity of 9.3 ppm has been obtained on 40cm DSV(the diameter of spherical volume) and using this magnet, comparatively good images for human body, fruits and water phantoms have been achieved.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.330-337
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• 2002

The HANARO seismic monitoring system is classified as non-nuclear safety(NNS), seismic category I, and quality class T The seismic monitoring system installed at the instrument room consists of five field sensors and one monitoring cabinet. The field sensors are composed of three triaxial accelerometers which installed at base slab, free field and overhead crane support respectively, a seismic trigger and a seismic switch at base slab. The most parts of analog system except field sensors are not produced any more, the improvement of the system is to be needed. The analog system with magnetic tape recorder is not only out-of-date model but dependent upon foreign technology. So it is difficult to get the spare parts and the cost to buy them is increased. Therefore we have improved the analog seismic monitoring system into a new digital seismic monitoring analysis system(SMAS) except five field sensors. After the installation of the new SMAS, we have carried out the site acceptance test(SAT) to confirm the field functions. The results of SAT satisfy the requirements of the fabrication technical specification. This new SMAS is operating at HANARO instrument room to acquire and analyse the signal of earthquake.

• 한국유체기계학회 논문집
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• 제2권3호
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• pp.24-29
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• 1999

The ASME strainers have been newly installed at the suction side of each reactor coolant pump to get rid of the foreign materials which may damage the pump impeller or interfere with the coolant path of fuel flow tube or primary plate type heat exchanger. The strainer was designed in accordance with ASME SEC. III, DIV. 1, Class 3 and the structural integrity was verified by seismic analysis. The screen was designed in accordance with the effective void area from the result of flow analysis for T-type strainer. After installation of the strainer, it was confirmed through the field test that the flow characteristics of primary cooling system were not adversely affected. The pressure loss coefficient was calculated by Darcy equation using the pressure difference through each strainer and the flow rate measured during the strainer performance test. And these are useful data to predict flow variations by the pressure difference.

• 한국군사과학기술학회지
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• 제19권3호
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• pp.339-345
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• 2016

This paper is concerned with the numerical simulation result of pressure propagation to the main charge by warhead penetration into concrete targets. In this study, we developed on-line pressure measurement method in the main charge during warhead penetration. Using the on-line pressure measurement method, we successfully recorded the pressure-time history in the main charge during the field penetration test. Then we compared result of numerical simulations with test data and found that the simulation results are in good agreement with the test results. Finally, through the numerical calculations it is concluded that the installation of liner is effective in reducing pressure level produced in the main charge.

• 조명전기설비학회논문지
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• 제23권12호
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• pp.191-200
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• 2009

본 논문에서는 전력계통에서 발생하는 저주파 진동을 억제하여 계통에 댐핑력을 제공함으로써 계통 안정도를 향상시킬 수 있는 전력계통 안정화장치의 정수선정 기법과 현장시험을 통한 성능검증 방법을 제시하였다. 대상 발전기는 우리나라 계통에 설치되어 있는 612[MVA]급 화력발전기이며, 축 속도를 입력으로 하는 아날로그 전력계통 안정화장치를 적용대상으로 하였다. 본 논문에서는 먼저, 오프라인에서 선형 해석 및 고유치 해석을 통하여 최적정수를 선정하는 기법을 제시하고, 시간영역 과도 안정도 해석을 이용하여 선정된 정수를 검증하였다(Part I). 또한, 선정된 전력계통 안정화장치의 성능을 온라인 현장시험을 통하여 최종적으로 검증하였으며, 정수선정 전 후의 오프라인 시뮬레이션 결과와 온라인 시험결과를 비교 분석함으로써, 결정된 모델의 적정성을 확인하였다(Part II). 이를 통하여, 축 속도를 입력으로 하는 PSS의 정수선정 방법과 실 계통 현장시험을 통한 성능검증 방법을 제시하였다.