• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.19-27
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• 2015

As the recent regulation of Internaional Maritime Organization (IMO) is enforced, the advanced technology of Ballast water treatment system (BWTS) is needed to meet its requirements. Until now, there are two kinds of the BWTS technologies such as physical methods (Membrane and UV) and chemical methods (Chlorin and Ozone). However, these conventional methods have some limitations of auxiliary power, low productivity, residual treatment and etc. In order to overcome these problems, this paper introduces the new kind of BWTS based on mechanical principle and investigates the effect of rotating disc shapes on flow characteristics between rotating and stationary discs by computational fluid dynamics (CFD). Planar and Step types can make the local cavitation generated along radius, and Circular type can increase the intensity of shear stress.

• Journal of the Korean Geotechnical Society
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• v.36 no.6
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• pp.17-34
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• 2020

In response spectrum analysis of pile-supported structure, an amplified seismic wave should be used as the input ground acceleration through the site-response analysis. However, each design standard uses different input ground acceleration criteria, which leads to confusion in determining the appropriate input ground acceleration. In this study, the ground accelerations were calculated through dynamic centrifuge model test, and the response spectrum analysis was performed using the calculated ground acceleration. Then, the moments derived from the test and analysis were compared, and a method for determining the appropriate input ground acceleration in response spectrum analysis was presented. Comparison of the experimental and simulated results reveals that modeling of the ground using elastic springs allows proper simulation of the natural period of the structure, and the use of a seismic wave that is amplified at the ground surface as the input ground acceleration provided the most accurate results for the response analysis of pile-supported structures in sands.

• Korean Journal of Food Science and Technology
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• v.11 no.2
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• pp.112-117
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• 1979

By using the existing caustic refining system with a minimum modification and by using a combination of various emulsifiers(0.2 % sodium hexametaphosphate. 0.05 % sodium lauryl sulfate and 0.001 % dioctyl sodium sulfosuccinate), a new economical dewaxing process for sunflower seed oil was developed in order to reduce the cost of the dewaxing process. The results indicate that the waxes can be removed satisfactorily from the sunflower seed oil by emulsifying. batchwise or continuously, the oil with the aqueous surfactant solution, followed by centrifugation at ambient temperatures $(16{\sim}27^{\circ}C)$. Dewaxing loss for the batch process was satisfactory for both low wax-and high wax-crude oil, whereas dewaxing loss for the continuous process needs to be improved. The results indicate that initial level of wax content (low wax vs. high wax) did not affect the loss for batch process (0.82 % vs. 0.62 %), but affected the loss for continuous processes, regardless of the type of mixing mode (2.28 % and 5.68 % for low wax-and high wax-oil, respectively). It was also noted that the type of mixing mode (centactor vs. static mixer) for the continuous process affected the loss, regardless of the wax content (5.2 % and 2.8 % for contactor and static mixer, respectively).

• Journal of the Korean Geotechnical Society
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• v.37 no.12
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• pp.57-71
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• 2021

The pile-supported wharf is the port structure in which the upper deck is supported by piles or columns. By installing batter piles in this structure, horizontal load such as earthquake loads can be partially delivered as axial forces. The codes suggests using the response spectrum analysis as a preliminary design method for seismic design of pile-supported wharf, and suggests modeling the piles using virtual fixed points or soil spring methods for this analysis. Recently, several studies have been conducted on pile-supported wharves composed of vertical piles to derive a modeling method that appropriately simulates the dynamic response of structures during response spectrum analysis. However, studies related to the response spectrum analysis of pile-supported wharves with batter piles are insufficient so far. Therefore, this study performed the dynamic centrifuge model test and response spectrum analysis to evaluate the seismic performance according to the modeling method of pile-supported wharves with batter piles. As a result of test and analysis, it is confirmed that modeling using the Terzaghi (1955) constant of horizontal subgrade reaction (n_h) most appropriately simulates the actual response in the case of the pile-supported wharf with batter piles.

• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.67-74
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• 2012

The arching effect of the active earth pressure acting on an excavation wall subjected to close excavation reduces lateral earth pressure acting on excavation wall. In this paper, the arching effect was estimated for varying width to excavation depth ratio and wall friction angle by analytical and numerical methods verified with centrifuge test results. The arching effect is significant when the width to excavation depth ratio and wall friction angle is decreased and increased, respectively. The analytical solution derived from the classical arching theory suggested by Handy(1985) shows good agreement with the numerical solution than the other solutions.

• Journal of the Korean GEO-environmental Society
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• v.4 no.3
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• pp.61-67
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• 2003

A new precess which consists of pre-dewatering device, post composting for solid phase and post sequencing batch reactor(SBR) for liquid phase was designed. Nitrogen in supernatants of dewatering device was removed by sequencing batch reactor. Experiments were carried out to investigate the SBR operation modes such as fill ratio, SRT, and operation cycle. The optimum fill ratio, SRT and aeration/non-aeration time were 1/12, 15days, and 2hr aeration / 1hr non aeraion, respectively. Methanol as an external carbon source increased denitrification when step feeding method was applied, not single feeding method.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.41-48
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• 2004

Several centrifuge modelling tests were performed to compare sand compaction pile (SCP) with gravel compaction pile (GCP) at the point of bearing capacity. SCP and GCP were installed as 30, 40, 50, 60, 70% of replacement ratio in cylindrical model tank (diameter = 20 cm, height = 40 cm), and the loading tests were carried out to analyze the bearing characteristics of soft clay ground reinforced by SCP and GCP. As a result of loading tests, the bearing capacities of soft grounds reinforced by SCP and GCP increase with increasing replacement ratio of pile, and a GCP reinforced ground has larger bearing capacity than that of a SCP reinforced ground. Several proposed bearing capacity equations for ground reinforced by SCP or GCP were compared with loading test results.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.214-222
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• 2001

The purpose of this research it to develop gas-air rotary heat exchanger using heat pipe and the performances were examined by way of the theoretical analysis and the experiment. Centrifugal force to return the working fluid in heat pipe elements with different radius was evaluated as a function of the revolution speed and inclination angle, and a rotary heat exchanger with 60 heat pipes in 3 rows was designed and manufactured. The inclination angle of a heat pipe relative to the revolving axis was designed to be 2$^{\circ}$and water was used as a working fluid. Experimental result showed the heat exchange rate was enhanced by 16% with compared to the calculated value.

• Restorative Dentistry and Endodontics
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• v.28 no.6
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• pp.467-474
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• 2003

복합레진에 의한 구치부 2급 와동의 수복에서 치은부 변연이 법랑-백아 경계 하방에 위치하는 경우 복합레진의 중합 수축에 의한 응력은 변연부의 폐쇄능력을 저하시키고 이로인한 미세누출은 2차적인 우식이나 술후과민증을 일으켜 임상에서의 성공을 위협한다. 본 연구에서는 2급 와동에서 복합레진으로 수복하기 전에 치은 변연부를 중합수축에 의한 응력을 완화시킬 수 있는 것으로 알려진 몇가지 재료들을 중간층으로 먼저 충전한 후 충전용 복합레진으로 충전한 뒤 치은부 변연에서 이들 중간층과 치질 사이의 미세누출의 정도를 비교하였다. 20개의 발거된 구치의 근, 원심면에 각각 상자 모양의 2급 와동을 형성하고 40개의 와동을 무작위로 10개씩, 4개의군으로 나누었다. 1군은 중간층의 수복없이 Clearfil SE Bond과 Clearfil AP-X로 충전하였으며 2, 3 및 4군은 중간층으로 각각 Revolution, Dyract그리고 FujiII LG를 먼저 충전한 후 1군과 동일한 방법으로 복합레진을 충전하였다. 충전된 시편은 열순환후 2% methylene blue 용액에 12시간 침잠시킨 후 색소의 침투도를 stereomicroscope로 관찰하였으며 실험결과는 Kruskal-Wallis non-parametric independent analysis 및 Mann-Whitney U test로 통계분석하여 다음의 결론을 얻었다. 1. 레진강화형 글라스아이오노머를 중간층으로 먼저 수복하고 복합레진으로 충전한 경우에서 더 적은 미세누출을 보였다(p<0.05). 2. 유동성 레진과 콤포머를 중간층으로 수복한 경우와 복합레진만으로 수복한 경우는 미세누출에 있어서 유의한 차이를 나타내지 않았다(p>0.05).

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.606-606
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• 2012

최근 지구 환경변화에 따른 기후변화의 영향으로 이상홍수 발생의 위험성이 증가하고, 상습적으로 홍수피해가 반복되고 있다. 홍수피해의 원인 중 하나인 하천제방의 붕괴는 월류, 침식, 제체불안정, 구조물에 의한 파괴 등으로 구분되고 이 중 월류 및 침식은 제방 파괴의 주된 원인으로 최근 통계자료에 보고되고 있다. 제방붕괴의 주된 원인 중 하나인 침식파괴로부터 제방을 보호하기 위해 제내지 사면에 호안공을 설치하며, 하천설계기준 해설(2009)에서는 제방 또는 하안을 유수에 의한 파괴와 침식으로부터 직접 보호하기 위해 제방 앞비탈에 설치하는 구조물로 정의하고 있다. 특히 사행하천의 만곡부에서는 제방파괴의 위험성이 높을 뿐만 아니라 국부적으로 집중되는 유속분포는 제방의 안정성을 위협한다. 또한 원심력, 2차류(secondary flow) 등에 의한 수위상승 등에 의해 제방이 파괴되고 월류되어 홍수피해가 발생할 가능성이 큰 취약지점이라고 할 수 있다. 본 연구에서는 2차원 수치모형을 이용하여 만곡부 흐름 특성을 분석하고 수리실험을 통해 측정된 유속 및 수위분포 결과와 비교하여 분석하였다. 또한 수리실험에서 도출된 호안 붕괴 시의 흐름을 구현하여 호안 붕괴 시 국부유속 및 전단응력을 계산하고 만곡부 호안의 안정성을 위한 설계인자를 분석하였다. 연구결과로 제시된 만곡부 안정성을 위한 설계인자는 국외 호안공 설계식과 비교하여 국부유속 및 전단응력의 설계인자의 적합성을 검토하고 국내 만곡부 호안의 안정성 설계기법개발에 도움이 될 수 있는 설계인자를 제시하고자 한다.