• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.112-115
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• 2003

쓰레기매립장의 침출수 누출 탐지를 위한 물리탐사법은 침출수의 전기전도도를 대상으로 한 전기탐사법이 주로 적용되어 왔다. 이 연구는 제주도에 위치한 비위생매립지를 대상으로 주변 수리지질환경 파악을 위한 전기비저항 탐사와 더불어 매립장 경계부와 토양층을 통한 침출수 누출 영역을 효율적으로 규명하기 위하여 다중주파수를 이용한 소형루프 전자탐사를 병행하여 수행하였으며, 아울러 오염지역의 천부 지하수 유동 방향을 추정하기 위하여 침출수의 유동에 의해 발생될 수 있는 자연전위를 모니터링 하였다. 전기비저항 탐사 및 자연전위 모니터링 결과 매립지 주변을 통한 침출수의 누출 가능성은 거의 없는 것으로 나타났으며, 이는 주변 하천에서 정기적으로 실시한 수질 분석 결과와 일치된다. 또한 소형루프 전자탐사 자료에 대하여 공간 필터링 및 1차원 역산법을 적용한 결과 매립장 경계부의 위치 및 매립장 내부의 심도별 매립물에 의한 저비저항 이상대를 효과적으로 도출 할 수 있었다.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.174-180
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• 2014

Experimental study of liquid nitrogen pool spread is carried out when it is continuously released. The liquid nitrogen spreads over a cement mortar plate with continuous release. Evaporation rate per unit area of the liquid nitrogen is measured using a digital balance, and a spreading distance of the liquid pool is measured by thermocouples. It is discovered that the evaporation rate per unit area of liquid nitrogen tends to decrease as the liquid pool spreads.

• Journal of Soil and Groundwater Environment
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• v.8 no.3
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• pp.1-7
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• 2003

A modified model was developed for solute transport in porous media that can consider the movement of an LNAPL above the water table. From the results of sensitivity analyses with and without considering LNAPL movement, there are some differences according to the hydraulic gradient, the quantity of oil leakage and dispersivity. The mean deviation between the model in this study and a conventional model without LNAPL movement increases as the hydraulic gradient decreases and the quantity of oil leakage increases. Variation of dispersivity has no influence on the magnitude of the mean deviation. However, the spatial distribution of the deviation between the two models is wider as dispersivity increases. Furthermore, groundwater is at high risk of contamination in the vertical direction in the case that transverse dispersion value is large. A conventional model underestimates the concentration of solute in an aquifer where the movement of an LNAPL cannot be negligible: Based on the study results, it is important to understand how fast the LNAPL moves on the water table for realistic prediction of solute transport in an aquifer with the movable LNAPL on the water table.

• Defense and Technology
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• no.10 s.272
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• pp.58-63
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• 2001

과거의 전쟁양상과는 달리 미래전은 전자전이 전쟁의 승패에 중추적 역할을 담당하게 될 것이다. 전자전 지원장비인 방탐장비는 주요국가들에게 고유의 모델과 기술로 제작 운용하고 있으며, 해외구입시 기술적 종속 및 정보누출의 위험에 노출될 수 있는 소지가 있다. 이 글에서는 방탐장비의 기본원리와 탐지기법 등 이론적인 설명을 하였으며, 주요 선진국의 방향탐지 장비현황 및 발전추세를 철저히 분석하여 우리 군이 미래전에 대비하여 나아가야 할 방향과 방법을 제시하였다.

• Korean Journal of Food Science and Technology
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• v.40 no.2
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• pp.228-233
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• 2008

Ultraviolet sterilizers (UVS) are widely used in restaurants, cafeterias and catering businesses in Korea. The proper application of UVS, however, is still questionable since no studies have clearly identified their efficacy and safety, while regulations and regulatory management systems are yet to be established. In the present study, the efficacy of UVS were investigated by measuring spatial UV intensity inside five commercially operated UVS. The operating safety parameters were also checked by measuring leaked UV intensity. The UV intensities were inversely proportional to distance from the UV lamp within 25 cm, and to the square of the distance exceeding 25 cm. The UV intensities in commercial UVS varied with the distance from UV lamp and the incident angle, highlighting efficacy and stability concerns. Notable leakage was detected through the door gaps of a studied UVS, which also brought about safety concerns. Allowable working distances for the UV leaking UVS were suggested based on international standards.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.2
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• pp.145-151
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• 2014

Purpose: The purpose of this study was to investigate the microleakage in class II cavity resin restorations used with resin-modified glass ionomer (RMGI) lining material depending on two different applying methods; classical delivery method using a dental explorer and a specially designed rotating bur. Materials and Methods: A total thirty-six extracted teeth were prepared with a class II proximal box, and randomly divided into three groups: 1) control group with no lining added and the proximal box restored (Group I), 2) the second group used RMGI as a lining material which was spread with an explorer (Group II), 3) the third group used a specially designed rotating bur to thin out RMGI (Group III). All teeth were restored with the same manner using incrementally placed resin composite. All 36 teeth were prepared and sectioned for the dye penetration test, and observed with a stereomicroscope for scoring the dye penetration. Results: When RMGI liners were used, both groups using an explorer and the special bur with the liner had significantly less microleakage than the control group with no liner (P < 0.05). The 50% of the group with RMGI liner using the bur showed no microleakage under a dye penetration test whereas all the teeth in control group showed microleakage of different degrees. However, there was no statistically significant difference between Group II and Group III. Conclusion: RMGI is an effective lining material to decrease microleakage in class II composite resin restorations regardless of applying methods.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.199-200
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• 2001

최근 연료 가격의 상승으로 자동차용 연료에 벤젠, 톨루엔 등을 혼합한 가짜휘발유가 많이 유통되고 있다. 가짜휘발유는 벤젠, 톨루엔 등의 방향족물질을 혼합하거나 경유, 등유 등을 혼합하여 사용한다. 방향족 화합물이 많이 함유된 휘발유를 장기간 사용할 경우 차량의 고무부품을 팽윤시켜 연료의 누출 등에 따른 화재 발생의 가능성이 높으며, 톨루엔은 열함량이 작기 때문에 연소효율 저하로 연비를 악화시킨다. 또한 자동차 연료의 조성은 배출가스에도 많은 영향을 주는 것으로 알려져 있다. 본 연구에서는 이러한 가짜휘발유 사용에 따른 배출가스 영향을 정확히 파악하기 위해 휘발유 중 방향족 함량이 다른 세종류의 연료를 사용하여 배출가스 및 연비에 대한 영향을 조사하였다. (중략)

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.504-511
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• 2001

Preventive resin restoration, extended concept of occlusal pit and fissure sealing, is procedure composed of as follows. Cavity preparation is limited to areas of initial caries The cavity is then restored with composite resin, while other sound pits and fissures are sealed with pit and fissure sealant. If pit and assure sealant with which microrestoration is possible is used, it may be of great benefit to both patient and operator in case of difficult-to-control children s treatment. However study on preventive resin restoration using this kind of materials have been scarce. The purpose of this study was to compare the microleakage of four different modes of preventive resin restoration. Restoration using only composite resin was compared together Fifty-five bicuspids were prepared with small class I cavity preparation on the occlusal surface, divided into the following groups and restored accordingly. Group 1 : Cavity was restored with Z-100 composite resin Group 2 : Cavity was restored with Z-100 composite resin. Pits and fissures were then sealed with Teethmate F-1 Group 3 : Cavity was restored with Z-100 composite resin Pits and fissures were then sealed with Ultraseal XT-plus Group 4 : Cavity and pits and fissures were restored with Ultraseal XT-plus altogrether Group 5 : Cavity was restored with Ultraseal XT-plus. Pits and fissures were then sealed with the same material. After restoration, the samples were thermocycled 500 times between $5^{\circ}C$ and $55^{\circ}C$ with a dwell time of 30 seconds. After thermocycling, the samples were dipped into 1% methylene blue solution for 24 hours, then rinsed with tap water. The teeth were then embedded in resin and cut buccolingually along the tooth axis and observed with a stereomicroscope to determine the degree of microleakage. The results were as follows : 1. Group 4 showed the greatest microleakage, while group 3, showed the least. The mean microleakage decreased in the following order:4>1>5>2>3. 2. There was no stastically significant difference between group 1 and group 5(p>0.05). However, group 1 showed significantly greater microleakage compared to group 2 and 3(p<0.05) Group 1 showed significantly less microleakage compared to group 4(p<0.05). 3. Group 2 showed no statistically significant difference compared to group 3(p>0.05). However group 2 showed significantly less microleakage compared to group 4 and 5(p<0.05) 4. Group 3 showed significantly less microleakage compared to group 4 and 5(p<0.05). 5. Group 5 showed significantly less microleakage than group 4(p<0.05).

• Journal of the Korea Society of Computer and Information
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• v.26 no.2
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• pp.119-124
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• 2021

In this study, we propose an antibacterial efficiency according to the direction of UV irradiation. In the experiment, we measured the effective irradiation angle of UVC using S.aureus, a Gram-positive bacterium, and the variation of the antibacterial region according to the distance according to the direction of ultraviolet irradiation. Also, as a method to increase the antibacterial efficiency during horizontal irradiation of ultraviolet rays, we tested reflecting leaking UVC. As a result, the angle of ultraviolet irradiation was measured smaller than the product description, and in the case of the antibacterial area according to the direction of ultraviolet irradiation, the distance from the sample was increased during vertical irradiation, and the antibacterial area was increased as the distance from the sample was closer during horizontal irradiation. In addition, it was confirmed that antibacterial efficiency can be increased by reflecting leaking UVC during horizontal irradiation of UVC.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.53-60
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• 2009

Statement of problem: At present, as the esthetic demands are on the increase, there are many ongoing studies for tooth-colored post and cores. Most of them are about fiber post and prefabricated zirconia post, but few about one-piece milled zirconia post and core using CAD/CAM (computer-aided design/computer-aided manufacturing) technique. Purpose: The objective of this study was to compare microleakage of endodontically treated teeth restored with three different tooth-colored post and cores. Material and methods: Extracted 27 human maxillary incisors were cut at the cementoenamel junction, and the teeth were endodontically treated. Teeth were divided into 3 groups (n=9); restored with fiber post and resin core, prefabricated zirconia post and heat-pressed ceramic core, and CAD/CAM milled zirconia post and core. After the preparation of post space, each post was cemented with dual-polymerized resin cement (Variolink II). Teeth were thermocycled for 1000 cycles between $5-55^{\circ}C$ and dyed in 2% methylene blue at $37^{\circ}C$ for 24 hours. Teeth were sectioned (bucco-lingual), kept the record of microleakage and then image-analyzed using a microscope and computer program. The data were analyzed by one-way ANOVA and Scheffe's multiple range test (${\alpha}=0.05$). Results: All groups showed microleakage and there were no significant differences among the groups (P>.05). Prefabricated zirconia post and heat-pressed ceramic core showed more leakage in dye penetration at the post-tooth margin, but there was little microleakage at the end of the post. Fiber post and resin core group and CAD/CAM milled zirconia post and core group indicated similar microleakage score in each stage. Conclusion: Prefabricated zirconia post and heat-pressed ceramic core group demonstrated better resistance to leakage, and fiber post and resin core group and CAD/CAM milled zirconia post and core group showed the similar patterns. The ANOVA test didn't indicate significant differences in microleakage among test groups. (P>.05)