• 한국수자원학회논문집
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• 제52권12호
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• pp.1075-1086
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• 2019

최근 기후 온난화의 발생과 이상기후의 발생빈도가 증가함에 따라 강수량, 하천유량과 같은 수문학적 요소의 예측이 복잡해지고 있으며 물부족 발생 위험도 증가하고 있다. 따라서 본 연구에서는 중단기 하천 취수량을 예측하기 위한 모델을 개발하고자 하였다. 입력인자를 선정하기 위해 취수량과 기상인자들 간의 상관성분석을 수행한 결과 온도가 가장 영향이 큰 것으로 나타났다. 또한 취수량은 시계열에 따른 증가 경향과 계절적 특성이 뚜렷하게 나타나므로 시계열분해기법을 이용하여 전처리를 수행하고 잔차에 대해 서포트 벡터 머신(SVM)을 적용하여 취수량 예측 모델을 개발하였다. 이 모델은 평균적으로 4.1%의 오차율을 나타내며, 전처리를 하지 않은 SVM 모델에 비해 높은 정확도를 나타냈다. 특히, 1~2달에 대해 중단기 예측을 수행하였을 때 더 유리한 결과를 나타냈다. 본 연구에서 개발된 취수량 예측모델은 수자원의 지속가능하고 효율적인 관리를 위해 하천수 사용허가, 수질관리, 가뭄 대책 마련에 활용이 가능할 것으로 예상된다.

• Ocean Systems Engineering
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• 제5권1호
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• pp.1-19
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• 2015

The water jetting system for a jack-up spudcan requires the suitable design considering the platform/spudcan particulars, environments, and soil conditions, either the surficial clay or surficial sand. The usage of water jetting depends critically on soil conditions. The water jetting is usually used for the smooth and fast extraction of the spudcan in the surficial clay condition. It is also required for inserting spudcan up to the required depth in the surficial sand condition, which is investigated in this paper. Especially, it should be very careful to use the water jetting during an installation of spudcan in the surficial sand condition, because there is a risk of overturning accident related to the punch-through. Therefore, in this study, the effect of water jetting flow rate and time on the change of soil properties and penetration resistance is analyzed to better understand their interactions and correlations when inserting the spudcan with water jetting in surficial sand condition. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the multi layered soil (surficial sand overlaying clays) is considered as the soil condition. The environmental loading and soil-structure interaction (SSI) analysis are performed by using CHARM3D and ANSYS. This kind of investigation and simulation is needed to decide the proper water jetting flow rate and time of spudcan for the given design condition.

• 대한소아치과학회지
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• 제51권1호
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• pp.80-87
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• 2024

Silver diamine fluoride, which can arrest dental caries, is alkaline and may cause mild soft tissue irritation. Water-based silver fluoride has a neutral pH, which is closer to the physiological range, and is biocompatible for use in the oral environment. This study aimed to evaluate the effect of water-based silver fluoride on remineralizing early enamel lesions by comparing it with other fluoride agents through microhardness and quantitative light-induced fluorescence measurements. An in vitro study with intact bovine incisors was performed. Artificial enamel lesions were induced and subjected to microhardness and quantitative light-induced fluorescence testing. Specimens were randomly divided into 4 groups for treatment. The specimens in group I were treated with water-based silver fluoride and potassium iodide, group II with silver diamine fluoride and potassium iodide, group III with sodium fluoride varnish, and group IV with distilled water. After 8 days of pH cycling, the specimens were subjected to microhardness and quantitative light-induced fluorescence testing. Water-based silver fluoride and silver diamine fluoride showed the greatest increases in microhardness and quantitative light-induced fluorescence, with no significant differences between the two. Sodium fluoride varnish also exhibited a significant increase in microhardness and quantitative light-induced fluorescence, but the differences were smaller than those for water-based silver fluoride and silver diamine fluoride. Water-based silver fluoride is considered useful in a clinical setting for remineralizing enamel lesions, with the advantages of no risk of tissue burn and improved taste and smell.

• 대한토목학회논문집
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• 제28권5D호
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• pp.695-703
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• 2008

중국 수처리 시장의 지속적 성장세 가운데 국내 환경기업은 BOT 방식을 통한 환경산업의 중국진출이라는 측면에 많은 관심을 가지고 있다. 그러나 중국 시장은 2000년 이후 중국기업들의 급성장과 동시에 많은 해외기업이 후퇴한 결과 소수 해외기업의 시장 독점화 현상을 보이고 있다. 본 연구는 이러한 해외기업의 시장탈피 현상과 관련하여 해외기업의 중국 수처리 BOT시장 참여의사결정에 부정적 결과를 초래하는 주요 시장참여 위험요인을 도출하고 국내건설기업의 관점에서 개별 요인이 의사결정에 미치는 영향력을 분석하였다. 분석결과 고정수익 금지조항 발효 및 낮은 물 사용료와 같은 수익 불확실성과 관련된 요인들의 영향력이 가장 높은 것으로 조사되었고, BOT사업에서 EPC업체 선정시 경쟁입찰의 의무화와 건설법인의 설립 의무화 등도 주요 영향변수로 조사되었다. 후자가 문제시 되는 원인은 현지의 대표적 다국적 전문 수처리 기업은 BOT사업 모델을 투자를 수반한 운영사업으로 인식하는 반면에 국내기업은 대다수 시장후퇴 기업들과 마찬가지로 해외 BOT 진출시 EPC사업 수주를 통한 조기 투자회수를 목표로 하고 있다는 점에 기인하는 것으로 조사되었다. 중국 정부는 본 연구결과물을 근거로 중국내 중장기 수처리시설 수요목표를 달성하기 위한 시장경쟁률 향상 메커니즘에 대한 이해를 높일 수 있으며 국내기업은 중국내 수처리 BOT시장 진입시 주요 의사결정 판단기준과 사업 참여의사결정 시스템 개정 방안으로 활용할 수 있다.

• International Journal of Contents
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• 제14권3호
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• pp.53-60
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• 2018

Based on the previous studies on sinkholes and ground subsidence conducted until date, the factors affecting the occurrence of sinkholes can be divided into natural environmental factors and human environmental factors in accordance with the purpose of the study. Furthermore, to be more specific, the human environment can be classified into the artificial type and the social type. In this study, the assessment indices for assessing risks of sinkholes and ground subsidence were developed by performing AHP analysis based on the results of the study by Lee et al. (2016), who selected the risk factors for the occurrence of sinkholes by performing Delphi analysis targeting relevant experts. Analysis showed that the artificial environmental factors were of significance in affecting the occurrence of sinkholes. Explicitly, the underground factors were found to be of importance in the natural environment, and among them, the level of underground water turned out to be an imperative influencing factor. In the artificial environment, the underground and subterranean structures exhibited similar importance, and in the underground structures, the excessive use of the underground space was found to be an important influencing factor. In the subterranean ones, the level of water leakage and the erosion of the water supply and sewage piping system were the influential factors, and in the surface, compaction failure was observed as an imperative factor. In the social environment, the regional development, and above all, the groundwater overuse were found to be important factors. In the managemental and institutional environment, the improper construction management proved to be the most important influencing factor.

• Wind and Structures
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• 제38권3호
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• pp.171-191
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• 2024

Wind Driven Rain (WDR) poses a significant threat to the building environment, especially in hurricane prone regions by causing interior and content damage during tropical storms and hurricanes. The damage due to rain intrusion depends on the total amount of water that enters the building; however, owing to the use of inadequate empirical methods, the amount of water intrusion is difficult to estimate accurately. Hence, the need to achieve full-scale testing capable of realistically simulating rain intrusion is widely recognized. This paper presents results of a full-scale experimental simulation at the NHERI Wall of Wind Experimental Facility (WOW EF) aimed at obtaining realistic rain characteristics as experienced by structures during tropical storms and hurricanes. A full-scale simulation of rain in strong winds would allow testing WDR intrusion through typical building components. A study of rain intrusion through a sliding glass door is presented, which accounted for the effects of multiple wind directions, test durations and wind speeds; configurations with and without shuttering systems were also considered. The study showed that significant levels of water intrusion can occur during conditions well below current design levels. The knowledge gained through this work may enhance risk modeling pertaining to loss estimates due to WDR intrusion in buildings, and it may help quantify the potential reduction of losses due to the additional protection from shuttering systems on sliding glass doors during winds.

• Toxicological Research
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• 제35권2호
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• pp.131-136
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• 2019

Ethylhexyl dimethyl para-aminobenzoic acid (PABA) is an oily yellow liquid derivative of water-soluble PABA commonly used in sunscreen. Ethylhexyl dimethyl PABA is widely used as an ingredient in many cosmetics at an average concentration of 1.25% (0.5-2.0%) in Korea. Previous studies, including those involving animals, have demonstrated that ethylhexyl dimethyl PABA is toxic to the following four organs: testis, epididymis, spleen, and liver. In addition, experiments using human keratinocytes found that ethylhexyl dimethyl PABA inhibits cell growth and DNA synthesis at low concentrations, and halted the cell cycle of MM96L cells (human melanoma cell line) at the G1 phase. Despite limited clinical data in humans, many studies have confirmed increased mutagenicity of ethylhexyl dimethyl PABA following exposure to sunlight, which suggests that this molecule is likely to contribute to onset of sun-induced cancer despite protecting the skin through absorption of UVB. For risk assessment, the no observed adverse effect level (NOAEL) chosen was 100 mg/kg bw/day in a 4 weeks oral toxicity study. Systemic exposure dosage (SED) was 0.588 mg/kg bw/day for maximum use of ethylhexyl dimethyl PABA in cosmetics. Based on the risk assessment and exposure scenarios conducted in this study, the margin of safety (MOS) was calculated to be 180.18 for a sunscreen containing 8% ethylhexyl dimethyl PABA, which is the maximum level allowed by the relevant domestic authorities.

• 농업과학연구
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• 제48권1호
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• pp.33-43
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• 2021

Along with the widespread use of pesticides in the world, concerns over human health impacts are rapidly growing. There is a large body of evidence on the relationship between the exposure to pesticides and the elevated rate of chronic diseases such as different types of cancers, diabetes, neurodegenerative disorders like Parkinson, Alzheimer, and amyotrophic lateral sclerosis (ALS), birth defects, and reproductive disorders. This research assessed the health risk of pesticide residues by the dietary intake of vegetables collected from the agro-based markets of Dhaka, Bangladesh. As some of the banned pesticides were also found in vegetable samples, they may pose a higher risk because of cheaper availability and hence the government of Bangladesh should take strong measures to control these banned pesticides. Five organo phosphorus (chlorpyrifos, parathion, ethion, acephate, fenthion) and two carbamate (carbaryl and carbofuran) pesticide residues were identified in twenty four samples of two common vegetables (tomato and brinjal). The pesticide residues ranged from below a detectable limit (< 0.01) to 0.36 mg·kg^-1. Acephate, chlorpyrifos, ethion, and carbaryl were detected in only one sample, while co-occurrence occurred twice for parathion. Continuous monitoring and strict regulation should be enforced regarding the control of pesticide residues in fresh vegetables and other food commodities in Bangladesh.

• 대한원격탐사학회지
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• 제37권3호
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• pp.591-601
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• 2021

국내의 화학 산업이 지속적으로 발전이 이루어짐에 따라 화학물질의 취급량과 운송량은 매년 증가하고 있다. 우리나라 도로 화물운송은 90%이상을 차지하고 있으며, 화학물질 운송도 대부분 도로를 통해 이루어지고 있다. 이러한 화학물질 운송차량들은 사고가 발생하게 되면 대형사고로 이어질 수 있다. 운송차량은 1차 피해인 교통사고뿐만 아니라 2차 피해인 환경 피해 요인들인 수질오염, 토양오염 등을 발생시킬 가능성이 높다. 본 연구는 반포IC와 서초IC 구간을 연구지역으로 설정하여 염화수소 가스 누출에 대한 시나리오를 작성하여, ALOHA 프로그램을 사용하여 예측거리를 측정하고 거리에 따라 염화수소 가스가 도달한 시간을 분석하였다. 또한 GIS를 이용해 시간별로 발생한 피해 영역에 대해서 인구밀도를 이용한 리스크 평가를 수행하였다. 이를 통해 피해 영역에 대해서 예방·대응 방안의 필요성을 제시하였다.

• 한국농공학회논문집
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• 제49권4호
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• pp.13-22
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• 2007

The uncertainty in water quality model predictions is inevitably high due to natural stochasticity, model uncertainty, and parameter uncertainty. An integrated modeling system under uncertainty was described and demonstrated for use in watershed management and receiving-water quality prediction. A watershed model (HSPF), a receiving water quality model (WASP), and a wetland model (NPS-WET) were incorporated into an integrated modeling system (modified-BASINS) and applied to the Hwaseong Reservoir watershed. Reservoir water quality was predicted using the calibrated integrated modeling system, and the deterministic integrated modeling output was useful for estimating mean water quality given future watershed conditions and assessing the spatial distribution of pollutant loads. A Monte Carlo simulation was used to investigate the effect of various uncertainties on output prediction. Without pollution control measures in the watershed, the concentrations of total nitrogen (T-N) and total phosphorous (T-P) in the Hwaseong Reservoir, considering uncertainty, would be less than about 4.8 and 0.26 mg 4.8 and 0.26 mg $L^{-1}$, respectively, with 95% confidence. The effects of two watershed management practices, a wastewater treatment plant (WWTP) and a constructed wetland (WETLAND), were evaluated. The combined scenario (WWTP + WETLAND) was the most effective at improving reservoir water quality, bringing concentrations of T-N and T-P in the Hwaseong Reservoir to less than 3.54 and 0.15 mg ${L^{-1}$, 26.7 and 42.9% improvements, respectively, with 95% confidence. Overall, the Monte Carlo simulation in the integrated modeling system was practical for estimating uncertainty and reliable in water quality prediction. The approach described here may allow decisions to be made based on probability and level of risk, and its application is recommended.