• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.217-222
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• 2015

There has been increased amount of atmospheric pollutants including NOx and SOx which cause acid rain and photochemical smog as a result of increased use of fossil fuels. In order to reduce the amount of pollutants produced by fossil fuel, wet scrubber system is introduced in this experiment. Wet scrubber system is applied to a diesel engine (3,298 cc) and the amount of smoke is measured before and after the application in terms of aspect ratio, filling rate, and flow rate. The result showed a lot of smoke reduction when wet scrubber system was applied, and also the aspect ratios and water spray flow rate were the important factors to improve smoke reduction.

• Journal of the Korean GEO-environmental Society
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• v.8 no.5
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• pp.47-55
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• 2007

The increment of impermeable land area due to widespread land development caused the adverse impact on urban disaster prevention because it could decrease the peak rate of runoff as well as increase the runoff and peak flow during rainy period. To date, little research has been conducted on the infiltration characteristics and quantitative analysis because of their highly dependence on construction method, paving material, surface permeability, and field condition. Hence, this study was performed to investigate the infiltration characteristics of runoff-reducing facilities according to the type of paving material, which were examined using experimental apparatus with varying paving material and rainfall intensity, and thus to provide fundamental research data for runoff-reducing infiltration facilities. In this study, the infiltration characteristics were examined under the rainfall intensity of 20, 30, 50, 80, 100, 200 mm/hr for a variety type of paving materials such as concrete, asphalt, sand, grassland, and permeable paving material. The infiltration rate for permeable paving material was observed to be more than 93% under the condition of less than 200 mm/hr of rainfall intensity. For the compacted earth and grassland, the ultimate infiltration rate was estimated to be about 13% to 67%. The permeable paving material was concluded to be the most appropriate one for the runoff-reducing infiltration facilities because it has more favorable advantages than others in the light of infiltration volume, disaster prevention, and river training.

• Journal of the Korean GEO-environmental Society
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• v.13 no.3
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• pp.53-58
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• 2012

In general, sand compaction pile(SCP) method and gravel compaction pile(GCP) method have been mainly used to reinforce soft soils such as soft clay or loose sandy ground. But the sand compaction pile method has problems such as lack of sand supply and destroying the nature while collecting sand, the gravel compaction pile method has a problem such as decreased permeability of the drainage material due to clogging. Recently, the study to replace sand with bottom ash which has similar engineering properties with sand is in active. As a fundamental research on bottom ash mixture compaction pile utilizing bottom ash, its behavioral characteristics depending on granular materials and replacement ratio has been simulated numerically. In particular, Settlement Reduction Ratio(SRR) according to the distance from the center of pile was calculated. The main findings were as follows. Change values of Mixture Compaction Pile's SRR according to granular materials showed similar patterns and stiffness of the composite soil is increased depending on the replacement ratio so SRR showed decreased patterns. Especially, when the replacement ratio is in 20~40%, it increase significantly. When the replacement ratio is over 40%, it increase slowly. When considering the economics, 30~40% replacement ratio is appropriate.

• Journal of Environmental Impact Assessment
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• v.25 no.5
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• pp.333-344
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• 2016

In this study, the efficiency of natural attenuation was evaluated through the hydrogeological characteristics such as monitoring and analyses, tracer tests, chemical composition analysis of the groundwater at a military site contaminated by petroleum hydrocarbon in korea. Also, based on the results, the natural attenuation rate by distance and the expressed biodegradation capacity(EBC) was evaluated. The regression slope of -0.0248($K/V_x$) and bulk attenuation rate of $1.7{\times}10^{-3}/day$ were calculated respectively. The range of total expressed biodegradation capacity(EBC) of BTEX was shown from 9.1 mg/L to 10.0 mg/L(average 9.7 mg/L). It was confirmed that the denitrification which was expressed about 63.6% in the total EBC is the largest influence redox process. Consequently, the biodegradation capacity is considered to be sufficient for remediation in the BTEX average concentration of 1.326 mg/L.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.2
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• pp.2-8
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• 1988

중대형 상용차에 널리 사용되어온 디젤엔진은 오일 쇼크 이후로 소형 상용차에까지 널리 탑재되고 있는 세계적인 추세이다. 디젤엔진은 높은 연소 압력 및 압력 상승율(Rate of Pressure Rice)로 운전되기 때문에 연소소음(Combustion Noise) 및 기계소음(Mechanical Noise)이 매우 크다. 차량 개발 개념에 있어 소음제어는 법적 규제와 소비자의 요구수준을 만족시키는 측면에서 고려되어야 한다. 차량 전체 소음에서 엔진 소음의 기여도는 약 40-50%정도이며 당연히 엔진소음 저감 대책의 필요성은 높다. 본고에서는 2.4리터 간접 분사식(IDI)디젤 엔진의 소음 저감을 위한 소음 저감 대책을 기술한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1231-1239
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• 2006

In this research magnetic field reduction effect of each passive loop was analyzed by using the scale down models of transmission lines. This paper examined magnetic field reduction effect of the passive loop that will be applied to actual facility through the experiment, which is about double vertical transmission line and horizontal transmission line. Consequently, by confirming the fact that magnetic field reduction effect can be obtained to 50 % by passive loop without reactive compensation, we insured technology about application of passive loop. And the case of 3 turns of loop showed two times reduction effect than that of 1 turns of loop in reducing magnetic field. Vertical passive loop is more efficient than horizontal passive loop in the aspect of reducing magnetic field on double vertical transmission lines. What is more, vertical passive loop showed good effect of reducing magnetic field in a far distance as well as in a short distance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.97-102
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• 2010

The objective of this paper is to explore the possibility of reuse of waste vegetable oil (WO) as an autogenous shrinkage reducer for high strength concrete and to compare the amount of autogenous shrinkage of the mortar using existing shrinkage reducing agent(SR) and expansive additives(EA). According to test results, as the dosages of WO increased, flow value exhibited to decrease, while the use of SR increased flow value. For the effect of WO on strength, although the use of SR and WO resulted in a slight decrease in compressive strength at early age, at 91 days they had similar strength level of the plain mixture. For autogenous shrinkage, as expected, the addition of WO, SR and EA resulted in a decrease of autogeneous shrinkage considerably especially, WO had superiority in autogenous shrinkage reducing effect compared with the case of SR and EA.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.434-445
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• 2020

In this study, the minimization of harbor oscillation using permeable breakwater was applied to the actual harbor and investigated an effect of minimization by computer simulation in order to take into account the water quality problems and measures of harbor oscillation by infragravity waves at the same time. The study site is Mukho harbor located at East coast of Korea that harbor oscillation has been occurred frequently. The infragravity waves obtained by analyzing the observed field data for five years focused on the distribution between wave periods of 40 s and 70 s and wave heights in less than 0.1 m was 94% of analyzing data. The target wave periods was 68.0 s. The most effective method of minimization of harbor oscillation by infragravity waves was to install a detached permeable breakwater with transmission coefficient of 0.3 on the outside harbor and replace some area of the vertical wall in the harbor with wave energy dissipating structure to achieve a reflectivity of 0.9 or less. The amplitude reduction rate of this method shown in 27.4%. And the effect of the difference in transmission coefficient of permeable breakwater on the reduction rate of the amplitude was not significant.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.2588-2595
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• 2013

In a traditional hydraulic elevator, elevator car is descended by down control valve, and the oil hydraulic energy must be lost during the descending stroke. In this paper, the performance characteristics of the hybrid type energy saving unit, is used to save the hydraulic energy which is lost during the descending stroke, for a hydraulic elevator are studied. The energy can be reused as the auxiliary power. The results show that the performance characteristics, such as the pressure, flow rate, output current and voltage, efficiency, and the energy recovery rate of the unit are stable and good as the energy recovery rate is 54%, and the energy saving unit is useful to reuse the saved energy during the descending stroke of elevator car. Also, it was confirmed that the energy saving unit can be deployed on a commercial scale.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1047-1051
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• 2006

우리나라는 산업화 이후 많은 인공 저수지를 건설하였으며, 이후 부영양화 등의 수질 악화로 하천 및 호소의 오염은 심각한 상황에 놓여있다. 이에 대해 점오염원에 대한 대책을 마련하였지만, 하천 및 호소의 오염저감에 한계를 드러내었으며 그 원인을 비점오염원에서 오염물질이 대량으로 하천 및 호소에 유입되기 때문인 것으로 추정하고 있다. 이에 본 연구에서는 화성호의 주요 유입하천(남양천, 자안천, 어은천) 유역의 오염원 조사와 유입하천의 강우시기별 수질 및 유량조사를 통하여 오염부하량의 산정 및 유입하천의 오염부하량 유달율을 산정함으로써, 비점오염원에 대한 보다 명확한 대책 마련을 위한 기초 자료로 활용하고자 하였다. 강우시 수질 및 유량조사 결과, 유입하천의 유량은 강우 사상과 매우 큰 관계를 지니며, 강우 강도 및 강우 지속 시간 등의 변화에도 많은 유출 특성의 변화가 일어나는 것으로 조사되었다. 월별 유달율 산정 결과 홍수기에 가장 높았으며, 이는 강우의 집중으로 인한 비점오염물질에 의한 영향으로 판단된다. 강우시의 유달율이 높게 나타난 것은 강우시에는 점 및 비점오염원 모두에서 비점오염 형태로의 유출 가능성이 커 이에 대한 집중적인 관리가 필요할 것으로 판단되며, 유달율 산정으로 하천 수계 특성에 적합한 소유역의 유달율 적용을 통해 점 및 비점오염원에 대한 효율적인 관리를 위한 자료로 이용함으로써 하천 및 수계 관리를 위해 보다 실효성 있는 관리 방안을 마련할 수 있을 것이다.