• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1346-1353
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• 2007

2003년 대구 지하철(중앙역) 화재 사건 당시의 화재 유동 및 승객 피난 시뮬레이션을 수행하였다. 화재 발생 첫 지점은 중앙역 지하 3층 객차 내부이며, 지하 3층과 지하 2층의 화재 및 연기 유동을 FLUENT 6.2를 이용하여 수치해석 하였다. 화재 객차 및 승강장에서의 이산화탄소 및 온도분포를 예측하였으며, 수치해석을 통하여 구해진 data는 승객 피난 시뮬레이션(EXODUS)의 입력 인자로 사용되었다. 수치해석에서 가장 높은 온도는 1500K로 조사되었다. EXODUS를 이용하여 지하 3층에서 지하1층까지 승객 피난 시뮬레이션이 수행되었으며, 총 피난 승객은 1000명으로 가정하였다. 이중 640명은 객차 내부에, 360명은 승강장에 존재하는 것으로 하고 계산을 수행하였다. 피난 시뮬레이션 결과 135명이 사망하였으며 이는 대구 화재 사고결과에 비교적 근접하는 수치이다. 또한 평균 피난 시간은 10분 19초로 조사가 되었다.

• Composites Research
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• 제26권6호
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• pp.355-362
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• 2013

복합재료 중 가장 많이 사용되는 탄소계 나노복합재의 성능 향상에 대한 연구가 수행되었다. 나노 사이즈의 탄소나노튜브(CNT)와 마이크로 사이즈의 그레파이트(Graphite) 입자를 일정한 형태로 배열하여 나노복합재를 제작하였다. 입자를 배열하기 위하여 전기장을 활용하였다. 일정한 방향 혹은 형태로 배열된 입자는 에폭시 기지 속에서 섬유강화 복합재 처럼 일정한 방향으로 강성의 향상을 나타낸다. 복합재의 구조적 강성이나 물리적 특성은 강화 입자의 배열상태에 따라 매우 달라지게 된다. 본 연구에서는 특히 탄소나노튜브와 그레파이트 강화입자의 전기장 배열에 의해서 만들어진 나노복합재의 강성 및 방사능 차폐특성을 규명하였다. 전기장에 의한 입자의 배열로 만들어진 탄소계 복합재는 구조적 성능뿐만 아니라 물리적인 방사능 차폐에서도 훌륭한 특성을 나타내었다.

• 한국환경복원기술학회지
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• 제15권3호
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• pp.1-15
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• 2012

The objective of this study is to analyze the distribution of urban parks and its problems in a city in Gyeonggi-do where new towns and old towns are mixed. The study will also analyze and understand the unbalanced deployment of urban parks - rest areas and carbon absorbers of an entire city - between old towns and new towns, suggest improvement opportunities and examine and suggest plans to create and expand urban parks in old cities that lack urban parks. Findings showed that first, new towns were 1.2~1.6 higher than old towns in the number of parks, park area, and per capita park area, indicating that parks were unbalanced across towns. Second, as for a plan for improving the unbalanced deployment of urban parks, when the use area needs to be changed in an urban development project, it was suggested to donate 10% of the project site to the city to create it into a park and it was suggested to identify and proactively improve alternative park resources that can replace parks such as rivers and recreational sites. Third, regarding a plan for improving urban parks in old towns, it was suggested to secure urban parks by attracting various urban development projects to old town areas. The amendment of related laws was proposed to double required park area to $6m^2$ per household. Amendments were also suggested for one law and four guidelines to specifically define the location of urban parks as well.

• 한국수산과학회지
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• 제36권6호
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• pp.700-707
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• 2003

Surface sediments in the mouth area of Jinhae Bay were investigated to evaluate the benthic environment in terms of geochemical criteria and macrobenthos abundance. Characteristics of the surface sediment distribution exhibited muddy sediments in the most part of study area. Some mixed sediments of coarse sand and mud were distributed along the coastal area of Geoje Island and around the Jeo Islands. Organic matter from ignition loss and total organic carbon from CHNS varied between $8.8-1.7\%,\;and\;4.62-0.77\%,$ respectively. The source of organic matter based on the C/S ratio was mixed with in situ biogenic and terrigenous organic matter. The C/S ratio of organic matter also suggested both an anoxic bottom condition in several parts of the study area. The content of hydrogen sulfide in surface sediment was extremely variable and showed spatio-temporal variation from site to site. In several locations, the content of hydrogen sulfide as an index of eutrophication was over the critical value (0.2 mg/g), suggesting that several parts of the study area were not favorable for the habitat of macrobenthos. The relationship among the number of individuals of marcrobenthos, hydrogen sulfide, and organic matter was not clear, but a potential negative relationship between individuals of marcrobenthos and hydrogen sulfide was indicated.

• 한국수소및신에너지학회논문집
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• 제25권4호
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• pp.378-385
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• 2014

In this research, we investigate electrical performance and electrochemical properties of graphene supported Pt (Pt/G) and PtM (M = Ni and Y) alloy catalysts (PtM/Gs) that are synthesized by modified polyol method. With the PtM/Gs that are adopted for oxygen reduction reaction (ORR) as cathode of proton exchange membrane fuel cells (PEMFCs), their catalytic activity and ORR performance and electrical performance are estimated and compared with one another. Their particle size, particle distribution and electrochemically active surface (EAS) area are measured by TEM and cyclic voltammetry (CV), respectively. On the other hand, regarding ORR activity and electrical performance of the catalysts, (i) linear sweeping voltammetry by rotating disk electrode and rotating ring-disk electrode and (ii) PEMFC single cell tests are used. The TEM and CV measurements demonstrate particle size and EAS of PtM/Gs are compatible with those of Pt/G. In case of PtNi/G, its half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production % are excellent. Based on data obtained by half-cell test, when PEMFC singlecell tests are carried out, current density measured at 0.6V and maximum power density of the PEMFC single cell employing PtNi/G are better than those employing Pt/G. Conclusively, PtNi/Gs synthesized by modified polyol shows better ORR catalytic activity and PEMFC performance than other catalysts.

• 대한환경공학회지
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• 제22권6호
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• pp.1063-1072
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• 2000

본 연구에서는 열중량 분석법을 이용하여 희분식 반응기에서 승온속도를 0.5, 1.0 및 $2.0^{\circ}C/min$로 변화시키면서 폐용활유와 polystyrene 혼합물의 열분해반응 속도실험을 수행하였다. 미분법을 이용하여 폐윤활유/polystyrene 혼합물의 열분해 전환율이 1%에서부터 100%일때까지의 활성화에너지 및 반응차수를 구하였다. 폐윤활유와 polystyrene을 혼합하여 열분해할 경우 각각을 열분해할 때보다 낮은 온도에서 열분해반응이 진행되었으며 열중량 변화곡선의 기울기변화는 크게 두 부분으로 구분되었다. 폐윤활유/polystyrene 혼합물의 열분해 생성 오일의 탄소수를 분석했을 때 styrene 단량체와 이량체에 해당하는 탄화수소화합물의 선택성이 매우 높게 나타났다.

• Ocean and Polar Research
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• 제41권2호
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• pp.47-61
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• 2019

The Dokdo coast is known for its high biodiversity. However, few studies have examined the biodiversity and macrobenthic community on the subtidal soft-bottom. Therefore, we collected macrobenthos (> 1 mm) using a Smith-McIntyre grab ($0.1m^2$) at 15 stations along the Dokdo coast in September 2016. The sediments consisted of badly sorted (1.7) coarse sand with gravel and the mean sediment grain size was $-0.4{\phi}$. In total, 177 macrobenthic species were collected; their mean density was $1,566ind./m^2$. The number of species and density of macrobenthic fauna decreased significantly with the mean grain size. The dominant species were the amphipods Melita denticulata (16.5%) and Melita shimizui (5.5%), polychaete Salvatoria clavata (5.4%), bivalve Glycymeris aspersa (4.4%), and ophiuroid Ophionereis dubia (4.3%). The dominant macrobenthos species on the subtidal soft-bottom differed from the coastal areas of the East Sea, suggesting that the difference in the sediment grain size affected the macrobenthos. Cluster analysis was performed to divide the study area into four groups, and environmental factors which correlated with species composition and distribution in the study area were the combination of the four parameters of salinity, dissolved oxygen, total organic carbon and depth. A future seasonal investigation is needed to understand the species composition and characteristics of the Dokdo macrobenthos.

• 청정기술
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• 제25권2호
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• pp.168-176
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• 2019

Spent coffee is one of biomass sources to be converted into bio-oil. However, the bio-oil should be further upgraded to achieve a higher quality bio-oil because of its high oxygen content. Deoxygenation under hydrotreating using different catalysts (catalytic hydrodeoxygenation; HDO) is considered as one of the promising methods for upgrading bio-oil from pyrolysis by removal of O-containing groups. In this study, the HDO of spent coffee bio-oil, which was collected from fast pyrolysis of spent coffee ($460^{\circ}C$, $2.0{\times}U_{mf}$), was carried out in an autoclave. The product yields were 72.16 ~ 96.76 wt% of bio-oil, 0 ~ 18.59 wt% of char, and 3.24 ~ 9.25 wt% of gas obtained in 30 min at temperatures between $250^{\circ}C$ and $350^{\circ}C$ and pressure in the range of 3 to 9 bar. The highest yield of bio-oil of 97.13% was achieved at $250^{\circ}C$ and 3 bar, with high selectivity of D-Allose. The carbon number distribution of the bio-oil was analyzed based on the concept of simulated distillation. The $C_{12}{\sim}C_{14}$ fraction increased from 22.98 wt% to 27.30 wt%, whereas the $C_{19}{\sim}C_{26}$ fraction decreased from 24.74 wt% to 17.18 wt% with increasing reaction time. Bio-oil yields were slightly decreased when the HZSM-5 catalyst and dolomite were used. The selectivity of CO was increased at the HZSM-5 catalyst and decreased at the dolomite.

• 대한환경공학회지
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• 제28권9호
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• pp.955-960
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• 2006

반회분식 반응기를 이용하여, 폐 고밀도 폴리에틸렌(HDPE)으로부터 가솔린을 제조하기 위하여 HZSM-5 촉매상에서 분해반응을 수행하였다. HZSM-5 촉매상에서 가솔린 분자 범위의 액상수율을 증가시키기 위하여 시판용의 Si/ZSM-5 촉매와, 인과 마그네슘을 HZSM-5 촉매에 첨가한 촉매를 사용하여 접촉분해반응 특성을 조사하였다. HZSM-5에 인과 마그네슘을 지지한 경우, 최적 지지량은 각각 0.5 wt%와 2.0 wt%이었다. 암모니아 TPD 실험 결과에서 인을 지지 시켰을 때는 강산점과 약산점이 전체적으로 크게 감소하였으며, 마그네슘을 지지 시켰을 때는 강산점은 완만하게 감소하였고 약산점은 크게 감소하였다. Si/ZSM-5 촉매에서는 산점은 거의 사라졌으며 분해반응도 크게 감소하여 액상생성물이 거의 생성되지 않았다. 액상생성물의 탄소수 분포는 인과 마그네슘이 지지되었을 때 탄소수가 낮은 쪽으로 이동되었고 성분의 100%가 가솔린 범위($C_5-C_{11}$)에 분포되어 있었다. Mg(2.0 wt%)/ZSM-5 촉매는 반응온도 $400^{\circ}C$E에서 액상 수율이 55.8%이었으며, 생성물의 분포가 100% 가솔린 범위에 있어서 유망한 촉매로 나타났다.

• 한국환경보건학회지
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• 제46권6호
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• pp.627-635
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• 2020

Objectives: Indoor air quality has become more important aspeople spend most of their times indoors. Since students spend most of their times at home or at school, they are more likely to be exposed to indoor air pollutants. Ventilation in school classrooms can affect health and learning performance. In this study, ventilation deficiency was evaluated in school classrooms using Monte Carlo simulation. Methods: This study used sensor-based monitoring for six months to measure carbon dioxide (CO2) concentrations in classrooms in elementary, middle, and high schools. The volume of the classroom and the number of students were investigated, and the students' body surface area was used to calculate the CO2 emission rate. The distribution of ventilation rates was estimated by measured CO2 concentration and a mass-balance model using Monte Carlo simulation. Results: In the elementary, middle, and high schools, the average CO2 concentrations exceeded 1000 ppm, indicating that the ventilation rates were insufficient. The ventilation rates were deficient from July to August and in December, but showed relatively high ventilation rates in October. Forty-three percent of elementary schools, 56% of middle schools, and 62% of high schools showed insufficient ventilation rates. Conclusions: The ventilation rates calculated in elementary, middle and high schools were found to be quite insufficient. Therefore, proper management is needed to overcome the lack of ventilation and improve air quality.