• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.191-194
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• 2002

토양증기추출(Soil Vapor Extraction)법을 이용하여 대표적 휘발성 NAPL (Non-aqueous phase liquid)인 TCE (trichloroethylene)와 toluene을 토양으로부터 제거하는 칼럼 실험을 실시하였다. 토양특성 및 증기추출 조건들이 정화효율에 미치는 영향을 규명하는데, 균질한 Ottawa sand와 실제 오염지역의 토양들을 직경 2.5cm, 길이 30cm인 유리 칼럼이 충진시켰으며, 빨갛게 염색된 TCE 또는 toluene 4 g이 주입되었다 공기 유량계를 설치하여 0.03L/min의 일정한 속도로 공기가 주입되도록 하고, 퍼지장치를 설치하여 주입 공기의 습윤도를 99% 이상으로 유지하였다. 가스크로마토그래피로 유출 가스 농도를 분석하였다. Ottawa sand로 충진된 칼럼실험에서는 매질의 입자크기, 함수율, 토양 내 오염물 체류시간 등을 변화시켜 실험을 반복하였다. TCE로 오염된 세립질 Ottawa sand 칼럼실험에서 유출 공기의 최대 농도는 조립질 Ottawa sand 칼럼의 유출 농도보다 약 20% 정도 감소하였고, 오염지역의 실제토양 칼럼실험에서는 최대유출농도가 조립질 Ottawa sand 칼럼의 농도보다 약 50% 감소하였으나, 20 liter공기 주입 후부터는 모두 비슷한 농도감소 현상을 나타내었으며, 초기 주입량의 90 % 이상이 제거되었다. 함수율증가에 따른 유출공기의 농도 감소는 거의 나타나지 않았으며, TCE 주입 후 7일 동안 방치하였다가 SVE를 실시한 칼럼 실험에서도 잔류하는 TCE의 양이 약간 증가하였지만 20 liter 공기 추출 후에는 초기 주입량의 90% 가, 40 liter공기 추출 후에는 98% 이상이 제거되었다. Toluene으로 오염된 칼럼 실험에서도 TCE와 비슷한 제거 경향을 나타냈으며 200 liter 공기 추출 후에는 오염물 초기 주입량의 98% 이상이 제거되었다. 본 실험 결과로부터 증기추출법을 이용한 TCE, toluene 정화 효율성이 규명되었으며, 휘발성 NAPL로 오염된 실제 토양을 복원하기 위한 SVE법의 적용가능성을 확인할 수 있었다.

• Journal of Environmental Health Sciences
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• v.10 no.2
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• pp.61-68
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• 1984

공기 중에는 benzo(a)pyrene을 위시한 여러 가지 polynuclear aromatic hydrocarbons(PNAs)가 존재하고 있으며, 그 측정방법이 매우 복잡하여 아직 통일된 적절한 방법이 없다. 본 연구는 공기 중의 PNAs를 측정하기 위한 적절한 방법을 개발하기 위하여 여러 가지 실험을 실시하였고 또 실제로 근로자들을 대상으로 공기를 채취하여 분석한 결과는 다음과 같다. (1) 공기 중 PNAs의 채취방법으로는 Teflon filter와 Polyurethane foam 또는 XAD-2를 연결하여 사용하는 것이 가장 좋은 효과를 보였다. (2) 검체에서 PNAs를 추출하는 방법으로는 methylene chloride를 이용한 초음속진동법 (ultra sonication)이 효과적이었다. benzene과 cyclohexane은 추출효과가 methylene chloride보다 적었으며, 초음속진동시간은 15분이 가장 적절하였다. (3) 분석법으로는 high pressure liquid chromatograph(HPLC)가 적절하였다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1998.06a
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• pp.22-26
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• 1998

토양오염 정화방법의 하나인 토양증기추출법(soil vapor extraction, SVE)은 오염된 토양에 진공 또는 가압의 공기를 공급하여 연속적인 공기 흐름을 유도함으로써 토양의 기공에 잔류하는 유해화합물의 증발을 촉진하여 오염물질을 제거하는 공정이다. 본 연구에서는 토양증기추출법의 효율에 영향을 주는 인자들 가운데에서 토양의 수분함량과 오염물질의 종류가 오염물질의 제거효율에 미치는 영향에 대한 실험과 계산을 수행하였다. 인공토양으로 glass bead, sand, molecular sieve가 사용되었으며. 오염물질로는 톨루엔. 메틸에틸케톤, 트리클로로에틸렌이 사용되었다. 각 실험에 대하여 프로인들리히 등온식과 기공확산모델 등을 고려하여 계산을 수행한 결과, 수분이 없는 경우에는 탈착식에 의해, 수분이 있는 경우에는 interparticle에서의 확산 현상에 의해 오염물질의 제거속도가 지배됨을 알 수 있었다. 이러한 연구결과는 정화대상지역에 SVE를 이용한 적절한 정화방법을 설계하는데 기초자료로 이용할 수 있을 것이다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04b
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• pp.345-347
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• 2000

본 연구는 문서를 구성하고 있는 각 단락들(paragraphs)간의 단어공기정보(world co-occurrence)를 이용해 이들간의 관계를 바탕으로 중요단락을 추출하여 문서의 요약을 한다. 이같은 접근법 문서요약의 성능은 단락들간의 정보추출방법과 추출된 정보에 의한 중요단락 선택방법에 크게 좌우된다. 본 논문에서는 중요단락에 대한 선택을 할 때 기존의 방법론에서 발생하는 요약문의 가독성(readability)을 높이면서 또한 성능의 향상도 꾀할 수 있는 방법론을 제시한다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.242-251
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• 2020

In this study, the extraction efficiency and reflection coefficient by a two-dimensional OWC (Oscillating Water Column) WEC (wave energy converter) installed in front of a seawall was investigated for regular/irregular waves. The matched eigenfunction expansion method (MEEM) based on the linear potential theory was applied as an analytical tool. The diffraction problem by the incident wave in the open-chamber and the radiation problem by the oscillating pressure in the closed-chamber were solved to obtain the volume fluxes at the internal free-surface. Applying the volume fluxes into the continuity equation for the airflow in a chamber, we got the oscillating air pressure. The maximum extracted power and corresponding reflection coefficient were determined at the optimal turbine coefficient that maximizes the extracted power. OWC device designed for a high extracted efficiency simultaneously contributes to reduce reflected waves.

• Economic and Environmental Geology
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• v.46 no.5
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• pp.425-444
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• 2013

This study was carried out in order to determine the remediation of total petroleum hydrocarbons (TPHs), trichloroethylene (TCE), perchloroethylene (PCE), benzene, toluene, ethylbenzene and xylenes (BTEX) compounds for non-aqueous phase liquids (NAPLs) using in-situ air sparging (IAS) / vapor extraction (VE) with the marine sediments of Mandol, Hajeon, Sangam and Busan, South Korea. Surface sediment of Mandol area had sand characteristics (average particle size, 1.789 ${\Phi}$), and sandy silt characteristics (average particle size, 5.503 ${\Phi}$), respectively. Sangam surface sediment had silt characteristics (average particle size, 5.835 ${\Phi}$). Sediment characteristics before experiment in the Busan area showed clay characteristics (average particle size, 8.528 ${\Phi}$). TPHs level in the B1 column of Mandol, Hajeon, Sangam, and Busan sediments were 2,459, 6,712, 4,348, and 14,279 ppm. B2 (3 L/min) to B5 (5 L/min) columns reduced 99.5% to 100.0% of TCE and 93.2% to 100.0% of PCE. Removal rates of TCE, PCE, and BTEX are closely correlated (0.90-0.99) with particle sizes and organic carbon concentrations. However, TPHs (0.76) and benzene (0.71) showed the poorer but moderate correlations with the same parameters.

• Economic and Environmental Geology
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• v.35 no.3
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• pp.221-227
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• 2002

Column experiments were performed to evaluate the removal efficiency of soil vapor extraction (SVE) iota TCE (trichloroethylene) and toluene in soil. Homogeneous Ottawa sands and real soils collected from contaminated area were used to investigate the effect of soil properties and SVE operation conditions on the removal efficiency. In column teats with two different sizes of Ottawa sand, the maximum effluent TCE concentration in a coarse sand column was 442 mg/L and 337 mg/L in a fine sand column. However, after 20 liter gas flushing, the effluent concentrations were very similar and more than 90% of initial TCE mass were removed from the column. For two real contaminated soil columns, the maximum effluent concentration decreased 50% compared with that in the homogeneous Ottawa coarse sand column, but 99% of initial TCE mass were extracted from the column within 40 liter air flushing, suggesting that SVE is very available to remove volatile NAPLs in the contaminated soil. To investigate the effect of contaminant existing time on the removal efficiency, an Ottawa sand column was left stable for one week after TCE was injected and the gas extraction was applied into the column. Its effluent concentration trend was very similar to those for other Ottawa sand columns except that the residual TCE after the air flushing showed relatively high. Column tests with different water contents were performed and results showed high removal efficiency even in a high water content sand column. Toluene as one of BTEX compounds was used in an Ottawa sand column and a real soil column. Removal trends were similar to those in TCE contaminated columns and more than 98% of initial toluene mass were removed with SVE in both column.

• Journal of Biomedical Engineering Research
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• v.24 no.1
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• pp.9-13
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• 2003

An assist device was developed to identify the epidural space by continously monitoring the air-filled catheter pressure. The pressure signal appropriately amplified and filtered enabled to alarm the needle introduction into the epidural space by thresholding detection. Ten LEDs provided a visual change of catheter pressure before alarming for user convenience. Clinical trials were performed in 30 patients with 83% success rate at the first trial. When failed, the second trial was enough for successful anesthesia. The air volume introduced during each anesthesia was less than 1ml, causing side effects. Air filling of the catheter could also minimize infection possibility. Therefore, the present device guarantees safe anesthesia with user convenience.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.101-114
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• 1998

Soil vapor extraction (SVE) is known to be an effective process to remove the contaminants from the soils by enhancing the vaporization of organic compounds using forced vapor flows or applying vacuum through soils. Experiments are carried out to investigate the effects of the organic contaminants, types of soils, and water contents on the removal efficiency with operating time. In the study, simulated soils include the glass bead which has no micropore, sand and molecular sieve which has a large volume of micropores. As model organic pollutants, toluene, methyl ethyl ketone, and trichloroethylene are selected. Desorption experiments are conducted by flowing nitrogen gas. Under the experimental conditions, it is found that there are linear relationships between logarithm of removal efficiency and logarithm of number of pore volumes. The number of pore volumes are defined as the total amount of air flow through the soil column divided by the pore volume of soil column. For three organic compounds studied, the removal rate is slow for no water content, while the number of pore volumes for removal of organic compounds are notably reduced for water contents up to 37%. For the removal of dense organic compound, such as trichloroethylene, a large number of pore volumes are needed. Also, the effects of the characteristics of simulated soils on the removal efficiency of organic compounds are studied. After the characterization of soil surface, porosity of soil columns and types of contaminants, the results could provide a basis for the design of SVE process.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.1-8
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• 2004

In this study, the method of computing and extracting the generalized unsteady aerodynamic matrices using MSC/NASTRAN and MSC/NASTRAN DMAP ALTER has been suggested for the analysis and control of aeroelastic phenomena such as flutter and gust response analysis. In addition to that, the method of approximating the generalized unsteady aerodynamic matrices using minimum state approximation method has been proposed in order to cast the aeroelastic equations of motion in state space form for aeroelastic analysis and control application. Simplified aircraft wing box model has been used for the validation of the methods suggested in this study.