• 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.

• Fire Science and Engineering
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• v.18 no.4
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• pp.16-21
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• 2004

This paper has investigated influences of pollutants in air-breathing on the respirators and it by year of disused air respirators that fire fighter is using in domestic cutting done air respirators after collection observed state of cylinder material through instrumental analysis, and cut open pipe to confirm pollution degree of pipe from cylinder of air respirators to airline mask and confirm pollution availability. The metal surface inside the air respirators was corroded by moisture included in the compressed air. The material generated by corrosion is white powder of less then 100㎛, which is analyzed as aluminum hydroxide corroded by moisture. This aluminum hydroxide powder may get into the lung while one breathes in, and it is easy to be attached to the lung so it will cause a serious influences to human health. This study suggests that Korea should set out the standards for components and composition of breathing air as soon as possible.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.326-329
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• 2003

본 연구에서는 유류 오염 토양의 복원에 효율적인 것으로 나타난 Biopile 공법을 오염 토양에 적용하였을 경우, 토양의 생물학적 복원이 가능한지 여부를 평가하고자 하였다. 45일간 의 Biopile 실험 결과, 공기 주입 및 영양분 주입 후 TPH의 감소율이 최대 64.75 %까지 나타났다. 또한 공기만을 주입하였을 경우에도 제거율이 약 33 %를 나타내었다. TPH가 6,000 mg/kg인 인공 오염 토양을 사용하여 Biopile 공법을 적용하였을 경우에는 30일 반웅 후 43.46 %의 높은 제거율을 나타내었다. 오염 토양의 균주를 순화/분리 하였을 때 오염 토양 내에 고 활성의 유류 분해 미생물이 확인되었으며, 이들의 유전자 역시 확인되어 자체적으로 생물학적 분해능을 가지고 있는 토양으로 나타났다.

• Membrane Journal
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• v.27 no.1
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• pp.43-52
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• 2017

The air injection nozzle tube was inserted inside of the tubular membrane module to reduce membrane fouling and improve the permeate flux. The average pore size of membrane was $0.1\;{\mu}m$ and the yeast was used as a foulant. All of permeate experiments were started without air injection for the module equipped with the nozzle tube, then carried out continuously with air injection. Finally, the nozzle tube was removed from the module and the permeate was measured without air injection. The measured permeate fluxes were compared to examine the effect of air injection. The fluxes for air injection were consistently maintained or increased. The fluxes of no-air injection with the nozzle tube were greater than those of the empty tubular module. As operating pressure decreased to 0.4 bar, the flux enhancement of air injection based on no-nozzle case increased to 21%. Flux enhancements of air injection were above 30% as the gas/liquid two-phase flow was changed from the stratified-smooth to the intermittent pattern due to increase of gas flowrate.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.179-188
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• 2023

Purpose. The purpose of this study was to evaluate the effect of surface treatments on the shear bond strength of two types of zirconia (3-TZP and 5Y-PSZ) with resin cement. Materials and methods. Two different types of zirconia specimens with a fully sintered size of 14.0×14.0×2.0 mm³ were prepared, polished with 400, 600, and 800 grit silicon carbide paper, and buried in epoxy resin. They were classified into four groups each control, sandblasting, primer, and sandblasting & primer. Cylindrical resin adhered to the surface-treated zirconia with resin cement. It was stored in distilled water (37℃) for 24 hours, and a shear bond strength test was performed. The normality of the experimental group was confirmed with the Kolmogorov-Smirnov & Shapiro-Wilk test. The interaction and statistical difference were analyzed using a two-way ANOVA. A post-hoc analysis was performed using Dunnett T3. Results. As a result of two-way ANOVA, there was no significant difference in shear bonding strength between zirconia types (P > .05), but there was a significant correlation in the sandblasting, primer, and alumina sandblasting & primer group (P < .05). Dunnett T3 post-test showed that, regardless of the type of zirconia, shear bonding strength was sandblasting & primer > Primer > sandblasting > control group (P < .05). Conclusion. There was no difference in shear bond strength between the types of zirconia. The highest shear bond strength was shown when the mechanical and chemical treatments of the zirconia surface was performed simultaneously.

• Korean journal of dermatology
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• v.56 no.9
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• pp.577-578
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• 2018

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.331-334
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• 2009

An air-independent propulsion (AIP) system based on fuel cell technologies was developed for space and underwater applications in the present study. Hydrogen peroxide was selected as an oxidizer for space and underwater power applications where air independence is a must. Catalytic decomposition of hydrogen peroxide was used to generate oxygen and water. The pure oxygen was provided to a fuel cell and the water was stored separately. Sodium borohydride in the solid state was used as a hydrogen source in the present study. Pure hydrogen can be generated by a catalytic hydrolysis reaction. A fuel cell system was fabricated to validate the fuel cell based air-independent power system and was evaluated at the various conditions.

• Journal of Biosystems Engineering
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• v.2 no.2
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• pp.1-14
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• 1977

현재 선진국에서 널리 이용되고있는 곡물의 화력건조는 곡물의 품질을 손상시킬 뿐만 아니라 손실을 증가시키고 있다. 화력에 의한 건조는 또한 연료의 절약면에서 볼 때 역시 문제점을 내포하고있다.l 이러한 문제점들을 해결하기 위하여 근래에는 실리카 젤과 같은 흡습성의 건조제를 사용한 곡물의 건조 실험이 진행 중에 있으며 좋은 결과를 보여주고 있다. 실리카겔은 그 자체무게의 40% 까지 동적 및 정적하에서 수분을 흡수하는 성질을 가지고 있으며 일단 포화상태가 되면 수천번 재생이 가능하다. 본 연구에서는 이와같은 실리카텍의 재생실험을 일차적으로 실내에서 공기의 온도를 일정하게 한 상태에서 실시하였으며 일반적으로 실리카 젤은 $300^{\circ}F$에서 완전재생이 가능하나 본 실험에서 사용된 재생온도는 평면식 태양열 집열기로부터 얻을 수 있는 $150^{\circ}F$ 내외에서 시도하였다. 본실험과 병행하여 건조중 공기와 실리카 젤의 에너지 및 질량변화에 따른 이론식을 만들어 주어진 여러 가지 조건에 대하여 4개의 미분방정식을 컴퓨터에 의하여 해결하였으며 건조(재생) 시간에 따른 공기의 온도와 흡습 및 실리카 젤의 함수량을 구하였다. 위의 이론적인 분석결과는 후에 태양열집열기를 이용한 재생실험을 분석하는데 적용될 것이다. 본 연구결과를 요약하면 다음과 같다. 1. 본 연구에서 유도한 이론식은 실리카 젤의 재생온도를 만족스럽게 표시하였으며 재생시간에 따른 공기의 온도와 흡습 및 실리카 젤의 함수량변화의 이론치는 실험치와 근사하였다. 2. 이론치와 실험치를 일치시키기위하여 흡착온도에서 산출된 열 및 질량 전달계수를 1/5로 조정 사용하였다. 3. 실리카 젤은 $120^{\circ}F$에서 9 %, $180^{\circ}F$에서 1% 내외로 재생이 가능하였다. 4. 본 연구에서 유도된 이론적 분석방법은 다른 여러 가지 형태의 물질 및 건조 또는 냉각 과정을 분석하는데 사용될 수 있다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.13-18
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• 1998

vortex tube는 간단한 구조의 관을 이용하여 어떠한 화학작용이나 연소작용 없이 압축유체를 저온 및 고온부분으로 분리하는 에너지 분리장치이다. 금속학자 Georges Joseph Ranque에 의해 vortex tube의 에너지분리 현상이 발견된 후 vortex tube는 공작기계에 의한 금속가공에 있어서 가공물의 열변형을 막기 위한 국소냉각, 금형제품의 급속냉각 또는 냉각복(air cooling jacket)에 사용하거나 공기공급식 호흡보호구의 공기공급시스템에 많이 활용되고 있다. vortex tube를 이용한 냉각복 및 호흡보호구는 소형, 경량으로서 근로자의 직접적인 조작이 간단하고, 열기가 신체에 직접적으로 닿지 않아 안전하고, 냉각효율이 높을 뿐만 아니라 매우 경제적이어서 그 이용률이 점차 확대될 전망이다. (중략)

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.23-27
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• 2013

In this study, efficiency of pre-treatment of turbid seawater was measured where micro-air bubbles were used to remove particles in seawater after input of natural coagulant PGA. Artificial seawater was prepared having the intended trubidity using marine sediments and microalgae. 73.7% of turbidity removal was achieved when 0.5g/L of $AlCl_3{\cdot}6H_2O$ was added in the artificial seawater, but 92.4% of turbidity removal was observed when 0.05g/L of PGA was added in the artificial seawater containing microalgae. In addition, much greater turbidity removal was achieved for microalage than sediments. For both cases, input of 0.1g/L PGA and following additional input of micro-air bubbles for 5 seconds resulted in the maximum removal efficiency where reaction time of coagulation was 1 min and flotation by micro-air bubbles was 10 min. From this study, we concluded that micro-air floation after coagulation could be a possible economical pre-treatment method for highly turbid seawater.