• The Journal of the Convergence on Culture Technology
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• v.6 no.1
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• pp.501-506
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• 2020

In this experimental study, we have analyzed aerodynamic performance of the four representative types of passenger car vehicles, different types of side window angles, different types of engine hood angles, and the angle difference of the roof line in order to comprehensively analyze how the aerodynamic performance varies with different shape of vehicle. Experiment results showed that the rear window falling at aa certain angle lowered aerodynamic performance, angle difference of the lowered roof line did not affect aerodynamic performance, and the back window line falling at certain angles had no visible effect on aerodynamic performance. Back window line leaning towards front side may help enhance styling aesthetics, but aerodynamic performance decreased. In case of rear diffuser installation, aerodynamic performance also decreased.

• Journal of the Korea Society of Computer and Information
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• v.28 no.1
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• pp.121-127
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• 2023

In this study, the design conditions and CFD analysis results are compared and reviewed in SCR that can optimally reduce nitrogen compounds. To this end, it was analyzed and compared using CFD to see if the design criteria were satisfied for the shell and tube areas of the boiler. In the SCR system, the analysis area is the gas/air heat exchanger on the shell side, and eight tubes of the gas/air heat exchanger on the tube side. Through CFD analysis, the gas velocity distribution on the primary catalyst side of the SCR system was designed to be 2.4%, and the NH3/NOx molar ratio distribution was 3.7%, which satisfied the design criteria. In addition, the uniformity of the temperature distribution was confirmed and the required condition of 260℃ or higher was satisfied. The angle of the gas entering the catalyst met the design conditions at 2.9 degrees, and the pressure loss that occurred also satisfied the design requirements. Through this CFD analysis, it was confirmed that it was designed and operated by satisfying the design conditions required for each area.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.334-339
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• 1996

Midloop 운전중 RHR 기능 상실사고를 모의 실험한 Bethsy 6.9d에 대해 CATHARE2 코드를 이용하여 해석하였다. 이 실험의 초기조건은 계통수위를 고온관 중간까지 낮추고, 그 윗부분은 비응축 가스로 차 있는 midloop 상태를 유지하는 것이다. 잔열은 원자로 정지 2일 후를 가정한 노심출력을 사용하였으며, 계통내 방출유로는 상부의 Upper head vent와 가압기 vent 및 고온관 1에 연결된 Letdown line과 수위지시계 방출유로가 열려 있다고 가정하였다. 또한 세 개의 loop중 증기발생기 한대만 이유 가능하고, 나머지 두 대는 이차측이 공기로 가득 차 있는 상태를 유지하였다. 이 연구의 주된 목적은 midloop 운전중 RHR 기능 상실사고에 대한 위와같은 상태에서 계통의 열수력적 현상을 실험을 통해 이해하고 코드 예측능력을 평가하는 것이다. CATHARE2 코드 계산결과 대체적으로 실험의 현상을 잘 모의하고 있으나 다음 사항에 대해서는 차이를 보이고 있다. 첫째 노심내 물의 혼합을 적절히 모의하지 못하여, 노심내 국부적 증기 발생 시점이 실험에 비해 약 250초 빨리 나타났다. 둘째 노심에서 고온관으로의 물의 유입이 많아 고온관에서 기포율이 실험에 비해 낮게 나타났다. 마지막으로 밀림관(surge line)에서 물의 유입에 의한 압력차가 실험보다 높게 나타났다.

• Journal of Environmental Health Sciences
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• v.23 no.4
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• pp.39-44
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• 1997

Propionaldehyde, n-Butyraldehyde, n-Valeraldehyde 수용액에 주파수 200 kHz, 출력 6.0 W/cm$^2$의 초음파조사후 그 분해반응에 관해 고찰했다. Aldehyde류는 초음파 조사에 의해 빠르게 분해되었고, 분해형태는 유사1차 반응을 나타내었다. 이들의 분해 속도는 Propionaldehyde

• Fire Science and Engineering
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• v.33 no.6
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• pp.35-42
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• 2019

The aim of this study is to investigate the direction of improvement of safety experience education through the analysis of the evacuation time experiment. For the study, test subjects were divided into groups of similar body size and weight. The test subjects were directly experienced four evacuation devices, and the experience time was measured. As a result of the analysis of the total time from the installation of the evacuation device to the escape, the time was measured in the order of Descending Life Line-Tilt-Down Rescue Line-Vertical Escape Chute-air safety mat. In the case of evaluating the evacuation time using evacuation mechanisms, the evacuation time was measured in the order of air safety mat-Tilt-Tilt-Down Rescue Line-Descending Life Line-Vertical Escape Chute. In the first and second experiments of the Descending Life Line, time differences were observed. The escape time using the Descending Life Line was reduced in the second experiment than in the first experiment. As shown in this result, education through experience has shown that behavioral confidence and time can be managed. The conclusion of this study is that the goal of safety education is to minimize human life and property damage. Therefore, in order to bring this effect to more people, it is necessary to make efforts to keep self-safe through experiential education.

• Korean Journal of Microbiology
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• v.48 no.1
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• pp.8-15
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• 2012

Bioaerosols generated from composting facilities and landfills may create health risks for workers and nearby residents. To determine the levels of culturable airborne bacteria and fungi in bioaerosols, samples were seasonally collected at a composting facility and a landfill in Ulsan, Korea with an impaction-type sampler. Concentrations of heterotrophic bacteria averaged (in $MPN/m^3$) $6.5{\times}10^3$ (range $1.5{\times}10^2-1.5{\times}10^4$) in the composting facility and $3.9{\times}10^3$ (range $6.0{\times}10^1-9.3{\times}10^3$) at the entrance of the facility. These concentrations were 460 and 280 times higher than those of reference sites. Coliform bacteria were detected both inside and entrance of the facility. On the landfill, heterotrophic bacterial concentrations averaged (in $MPN/m^3$) $4.9{\times}10^2$ (range $1.7{\times}10^2-1.0{\times}10^3$), while they averaged $3.7{\times}10^2$ (range $4.8{\times}10^1-1.3{\times}10^3$) at the parking lot of the landfill. These concentrations were 35 and 26 times higher than those of reference sites. When we isolated and tentatively identified heterotrophic bacteria, Pseudomonas luteola was the most dominant species in bioaerosols from the composting facility, whereas the most abundant one in reference samples was Micrococcus sp. Average concentrations of airborne fungi were measured between $4.8{\times}10^2$ and $7.9{\times}10^2\;MPN/m^3$ depending on sites, which were 2.1-3.4 times higher compared to those of reference sites. While Cladosporium, Alternaria, and Penicillium were commonly identified fungal genera, genus Aspergillus was identified only in bioaerosols from the composting facility.

• Food Science and Preservation
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• v.16 no.4
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• pp.573-578
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• 2009

Microbial contamination levels in a fresh-cut leafy vegetable processing plant were evaluated. Total plate counts of samples collected from the walls, equipment, and raw materials ranged from $10^1{\sim}10^2$ CFU/100 $cm^2$, $10^0{\sim}10^4$ CFU/100 $cm^2$, and $10^4{\sim}10^6$ CFU/g, respectively. No coliforms were detected on walls; however, equipment and raw materials contained coliforms in concentrations ranging from ND (not detected)to $10^2$ CFU/100 $cm^2$ and $10^4{\sim}10^5$ CFU/g, respectively. Additionally, total plate counts for falling and floating bacteria in the processing plant were $10^0{\sim}10^1$ CFU/plate and $10^1{\sim}10^3$ $CFU/m^3$, respectively. Pathogenic microorganisms such as Escherichia coli, Salmonella spp, Staphylococcus aureus, or Listeria monocytogenes were not detected on walls, equipment, or raw materials. Overall, the results of this study indicate that hygiene control in the fresh-cut processing plant should be improved.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.989-992
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• 2008

In this paper, we are presenting a case that integrates ultra high strength concrete(150MPa) with surface-exposed concrete. Ahead of the field application, we carried out laboratory experiment and B/P Test for a basic property of concrete(slump flow, air content, 50cm flow time, elapse time change and compression strength) and productivity. The next, we conducted Mock-up Test using simulation specimen to evaluate infilling, surface-finishing and hydration heat of concrete. We had satisfactory results for a basic property and hydration heat of concrete. However at the time of field application, it was occurred rupture of formwork because of high lateral pressure of concrete, and then formwork was reinforced and case-in-place time was adjusted. And regardless of low and high frequency vibration, it occurred to surface-pockmark. In case that applies ultra high strength concrete to surface-exposed concrete, we estimate that it is important of systematic management and improvement of construction.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.18-25
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• 2001

The results of systematic numerical experiments of secondary gas injection thrust vector control are presented. The effects of secondary injection system such as injection location and nozzle divergent cone angle onto the overall performance parameters such as thrust ratio, specific impulse ratio and axial thrust augmentation, are investigated. Complex nozzle exhaust flows induced by the secondary jet penetration is numerically analyzed by solving unsteady three-dimensional Reynolds-averaged Navier-Stokes equations with Baldwin-Lomax turbulence model for closure. Numerical simulations compared with the experiments of secondary air injection into the rocket nozzle of $9.6^{\cire}$ divergent half angle showed good agreement. The results obtained in terms of overall performance parameters showed that locating the secondary injection orifice further downstream of primary nozzle ensures the prevention of occurrence of reflected shock wave, therefore is suitable for efficient and stable thrust vectoring over a wide range of use.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.243-246
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• 2008

목질계 바이오매스 가스화 발전에 있어서는 가스화 가스중에 함유되어있는 타르를 가능한 한 가연성 가스로 전환하여 냉가스효율을 향상시키는 것 및 잔유하는 타르는 후단기기에 악영향을 초래할 우려가 있기 때문에 타르를 저감 제거하는 것이 바람직하다. 본 연구에서는 공기 수증기를 사용하여 타르개질 프로세스의 개선을 위해서 타르에서 가스성분으로의 전환에 관한 개질 실험을 실시하여 Wood chip 타르의 열분해 개질 생성물 거동에 대하여 검토하였다. Wood chip 열분해로 생성된 타르의 원소분석 및 $^1H$ NMR분석의 결과로 타르를 치환기를 가지지 않는 방향족, alkyl-기를 가지는 방향족, 산소 함유 방향족, 지방족의 4개로 분류하였다. 개질제에 의해 경질 타르, 중질 타르 모두 감소하였다. 개질 공기는 타르를 연소시키지만 그 속도는 가연성 가스와 경합하고 $900^{\circ}C$에서는 타르의 연소는 나타나지 않았다. alkyl-기를 가지는 방향족은 메탄과 치환기를 가지지 않는 방향족으로 전환되고, 치환기를 가지지 않는 방향족은 수소와 soot로 전환되고, 산소 함유 방향족은 일산화탄소와 치환기를 가지지 않는 방향족으로 전환되는 것을 알았다. 또한, 개질제에 의해alkyl-기를 가지는 방향족, 치환기를 가지지 않는 방향족, 산소 함유방향족 모두가 일산화탄소,이산화탄소로 전환되는 것을 알았다.