• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.149-159
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• 2014

In this study, we develop an algorithm to predict swell-like high waves on the east coast of Korea using the directional wave gauge which was installed near Sokcho. Using the numerical wave model SWAN, we estimate wave data in open sea from the wave data collected by using the directional wave gauge. Then, using the wave ray method and SWAN model with the open-sea wave data as offshore boundary conditions, we predict the swell-like high waves at several major points on the east coast of Korea. We verify the prediction methods with the SWAN and wave ray methods by comparing predicted data against measured one at Wangdolcho. We can improve the prediction of the swell-like high waves in the east sea of Korea using both the real-time wave measurement system and the present prediction algorithm.

• Journal of the Korean Geosynthetics Society
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• v.1 no.1
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• pp.43-51
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• 2002

In this study, free swell index of betonite was examined in several regeants; distilled water, leachate, seawater and 3% NaCl solution. Free swell index values of bontonite to be added Poly(acrlylic acid), PYA(Polyvinyl Alcohol) or SCMC (Sodium Carboxymethyl Cellulose) were evaluated and compared. From this, it was confirmed that hydraulic conductivities of GCL in seawater were examined and the hydraulic conductivities of GCL in seawater were compared to those in distilled water. The average values of free swell indices of bentonite were decreased in order of distilled water>leachate>seawater. It was shown that no significant differences were occurred for free swell index between seawater and 3% NaCl solution. For bentonite to be added PVA, the other reagents except distilled water didn't affect increase of swelling. Swelling properties of bentonite to be added SCMC were improved except 3% NaCl solution.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.290-292
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• 2009

본 연구에서는 배전계통의 전압 및 전류 품질을 통합적으로 개선할 수 있는 수동필터 연계형 Z-소스 전력품질 보상 시스템을 제안한다. 제안된 시스템의 주안점은 전압의 변동을 보상하는 직렬형 인버터와 고조파를 보상하는 병렬형 인버터에 각각 Z-소스 토폴로지를 적용하는 것이다. 전압 sag와 swell이 발생하는 과도상태에서 제안된 시스템의 성능을 검증하기 위하여 PSIM시뮬레이션을 하여 타당성을 입증하였다.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.146-148
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• 2009

본 논문에서는 새로운 Quasi Z-소스 순간전압 Sag-Swell 보상기를 제안한다. 제안된 시스템은 Quasi Z-소스 교류-교류 컨버터를 기반으로 하며, 입력단과 출력단이 공통 접지이며, 연속적인 입력전류로 동작하는 특징을 가지고 있다. 또한 평균치 제어 기법의 단점을 보완하기 위한 방법으로 실시간 샘플링 검출기법을 이용한 알고리즘을 적용하여 샘플링 구간 동안 평균치 값을 계산해서 순간전압 변동을 검출해 내는 기법을 적용했다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.9
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• pp.165-171
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• 2010

There are many researches on Power Quality Device to protect the critical load and power system as the nonlinear load and precision load are adopted into the power system recently. To analyze the voltage compensation of voltage sag and voltage swell by DVR, which is connected to the important load in series, this paper shows PSCAD/EMTDC simulation and its verification by comparing with the actual DVR output of 2MVA. DVR control scheme in this paper is applicable to compensate single-phase, 2-phases or 3-phases voltage sag as well as DVR for distribution system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.235-241
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• 2018

In this study, we collected cases of accidents caused by swell in the east coast of Korea from 2013 to 2017. The location of the accident, the season, the type of coast and the type of damage were classified and the correlation between the accident and the wave data was analyzed by collecting the observation data of the nearby area at the time of the accident. Also, based on the results of the coastal disaster vulnerability assessment of Korea Hydrographic and Oceanographic Agency, the vulnerability grades of swell accidents area were evaluated. In swell accident area, the average grade of the wave exposure index was 4.91, the wave sensitivity index was 3.87, and the wave impact index was 4.90. As a result, most of the swell accidents occurred in the 5 grade (very vulnerable level) of the wave impact index, and the area of the east coast (78.7%) of the same 5 grade was classified into five types according to the wave sensitivity index result. Finally, a countermeasures was taken for characteristics of each type.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.395-398
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• 2003

Geosynthetic Clay Liners(GCLs) have been widely used as hydraulic barrier in landfills and remediation projects of contaminated sites. The aim of this research is to modify GCLs for effective removal of contaminants. We perform the free swell test, hydraulic conductivity test, and contaminants (TCE, hexavalent chromium, and nitrate) removal test on the bentonite-ZVI mixture with various ZVI content. As the ZVI content increased, contaminants removal efficiencies and swell volume increased, and hydraulic conductivity decreased.

• Journal of Electrical Engineering and information Science
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• v.2 no.3
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• pp.66-70
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• 1997

The steam generator level is susceptible to the nonminimum phase in dynamics due to the thermal reverse effects known as "shrink and swell" in a pressurized water reactor. A state feedback assisted control concept is presented for the change of dynamic performance to the minimum phase the concept incorporates a nonlinear digital observer as a part of the control system. The observer is deviced to estimate the state variables that provide the true indication of water inventory by compensating for shrink and swell effects. The concept is validated with implementation into the steam generator simulation model.

• 대학교육
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• s.128
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• pp.101-104
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• 2004

• Geomechanics and Engineering
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• v.22 no.3
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• pp.227-236
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• 2020

Expansive soils are renowned for their swelling-shrinkage property and these volumetric changes resultantly cause huge damage to civil infrastructures. Likewise, subgrades consisting of expansive soils instigate serviceability failures in pavements across various regions of Pakistan and worldwide. This study presents the use of polypropylene fibers to improve the engineering properties of a local swelling soil. The moisture-density relationship, unconfined compressive strength (UCS) and elastic modulus (E₅₀), California bearing ratio (CBR) and one-dimensional consolidation behavior of the soil treated with 0, 0.2, 0.4, 0.6 and 0.8% fibers have been investigated in this study. It is found that the maximum dry density of reinforced soil slightly decreased by 2.8% due to replacement of heavier soil particles by light-weight fibers and the optimum moisture content remained almost unaffected due to non-absorbent nature of the fibers. A significant improvement has been observed in UCS (an increase of 279%), E₅₀ (an increase of 113.6%) and CBR value (an increase of 94.4% under unsoaked and an increase of 55.6% under soaked conditions) of the soil reinforced with 0.4% fibers, thereby providing a better quality subgrade for the construction of pavements on such soils. Free swell and swell pressure of the soil also significantly reduced (94.4% and 87.9%, respectively) with the addition of 0.8% fibers and eventually converting the medium swelling soil to a low swelling class. Similarly, the compression and rebound indices also reduced by 69.9% and 88%, respectively with fiber inclusion of 0.8%. From the experimental evaluations, it emerges that polypropylene fiber has great potential as a low cost and sustainable stabilizing material for widespread swelling soils.