• Journal of Mechanical Science and Technology
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• 제14권11호
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• pp.1286-1295
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• 2000

The ventilation effectiveness is evaluated as a function of air exchange rate and supply / extract locations in a simplified model chamber using a tracer gas technique of CO$_2$ gas injected into a supply duct. Ventilation systems consist of supply and extract fans, a CO$_2$gas generator, a CO$_2$gas analyzer and a test chamber. The ventilation effectiveness is evaluated using a step-down method based on ASTM Standard E741-83. The room mean age of the model chamber is decreased with increasing air exchange rate fanged from 6to 10 air changes per hour. The ventilation effectiveness of the mechanical inlet/natural extract system is better than that of the mechanical extract system.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권3호
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• pp.109-118
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• 2013

Characteristics of the transport of zero-valent iron nanoparticles (nZVI) in an aquifer were investigated to evaluate an application of nZVI-based reactive zone technology. Main flow direction of groundwater was north. Preferential flow paths of the groundwater identified by natural gradient tracer test were shown northeast and northwest. The highest groundwater velocity was $4.86{\times}10^{-5}$ m/s toward northwest. When the breakthrough curves obtained from the gravity injection of nZVI were compared with the tracer curves, the transport of nZVI was retarded and retardation factors were 1.17 and 1.34 at monitoring wells located on the northeast and northwest, respectively. The ratios of the amount of nZVI delivered to the amount of tracer delivered at the two wells mentioned above were 24 and 28 times greater than that of the well on the main flow direction, respectively. Attachment efficiency based on a filtration theory was $4.08{\times}10^{-2}$ along the northwest direction that was the main migration route of nZVI. Our results, compared to attachment efficiencies obtained in other studies, demonstrate that the mobility of nZVI was higher than that of results reported in previous studies, regardless of large iron particle sizes of the current study. Based on distribution of nZVI estimated by the attachment efficiency, it was found that nZVI present within 1.05 m from injection well could remove 99% of TCE within 6 months.

• 한국환경복원기술학회지
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• 제9권4호
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• pp.52-59
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• 2006

This study was conducted to find end-members and tracers which are effective to be applied in the End Member Mixing Analysis (EMMA) model for runoff separation at the Gwangneung coniferous forest catchment (13.6ha), Gyeonggido, Korea. We monitored three successive rainfall events during two weeks from June 26, 2005 to July 10, 2005, and analysed chemical properties of rainfall, throughfall, stemflow, groundwater and soil water considered as main components of storm runoff. The followings are the results of analyses of each component and tracer. Groundwater, soil water and rainfall (or throughfall) were dominant runoff components. Rainfall and groundwater were selected as main components for the two components-one tracer mixing model, and groundwater, soilwater and throughfall were selected as main components for the three components-two tracers mixing model. Tracers were selected from anion ($Cl^-$ and ${SO_4}^{2-}$), cation ($Na^+$, $K^+$, $Mg^{2+}$, and $Ca^{2+}$) and Acid Neutralizing Capacity (ANC) in event 1, 2, and 3. $Na^+$, $Ca^{2+}$ and ANC were selected in the two components-one tracer mixing model and ${SO_4}^{2-}-K^+$, ${SO_4}^{2-}-Na^+$, ${SO_4}^{2-}-Ca^{2+}$, ${SO_4}^{2-}$-ANC, and $Ca^{2+}$-ANC were selected in the three components-two tracers mixing model. Selected main runoff components and tracers can provide basic information to determine the contribution rate of each runoff component and identify the runoff process in a forest watershed.

• 한국수자원학회논문집
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• 제36권4호
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• pp.673-689
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• 2003

사행이 있는 자연하천에서 횡혼합 특성을 분석하고 종ㆍ횡분산게수를 산정하기 위해 현장실험을 실시하였다. 이를 위해 남한강 지류인 섬강 및 청미천에서 사행구간을 선정하여 유속과 수심 측정 및 추적자실험을 수행하였다. 추적자로서는 미량으로도 관측이 용이한 방사성 동위원소를 사용하였으며 주입은 순간. 점주입 조건을 바랐다. 이를 통해 취득된 수리량 및 농도 자료를 이용하여 종ㆍ횡분산계수를 산정하였고, 이들을 기존의 추정식에 의한 결과와 비교, 분석하였다. 종분산계수는 해석해를 통해 산정하였는데 섬강은 약0.5 $m^2$/s, 청미천은 0.2 $m^2$/s 로 산정되었다. 횡분산계수는 해석해 및 모멘트방법을 이용하여 산정하였는데, 섬강은 약 0.01-0.06 $m^2$/s의 범위를 가지며 청미천은 약 0.0l-0.05 $m^2$/s의 범위를 갖는 것으로 산정되었다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.547-551
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• 1998

Reaeration coefficient is the physical absorption of oxygen from the atmosphere by water. It is the most important natural means by which a stream replaces the oxygen consumed in the biodegradation of organic wastes, and the rate constant describing this process is the reaeration coefficient, It. Reaeration coefficient is the dominant parameter affecting the use of water quality model. Therefore accurate estimation of the reaeration coefficient is essential for optimum water quality management. There is several method to estimate stream reaeration coefficient. In this study, it would be concluded that SI-peak method is of practical use when applied to small stream, and CRI method is adequate to large stream.

• 한국환경보건학회지
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• 제33권4호
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• pp.283-292
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• 2007

Atmospheric concentrations of radon had been continuously observed in Seoul, Korea since December 1999, as a tracer for long-range transport of air pollutants from China continent to Korea. In order to study radon as a tracer of long-range transport, it is important to know information about the atmospheric distribution and variation of radon concentration and its time variation. Atmospheric radon concentration are measured with electrostatic radon monitor(ERM) at Hanyang University located in Eastern area of Seoul. Air sample is taken into a vessel of ERM, and alpha particles emitted by radon daughters $Po^{218}$ are detected with ZnS(Ag) scintillation counter. Hourly mean concentrations and hourly alpha counts are recorded automatically. The major results obtained from time series observation of atmospheric radon were as follows : (1) The mean of airborne radon concentration in Seoul was found to be $7.62{\pm}4.11\;Bq/m^3$ during December $1999{\sim}January$ 2002. (2) The hourly variation of radon concentrations showed the highest in 8:00AM ($8.66{\pm}4.22\;Bq/m^3$) and the lowest in 3:00AM ($6.62{\pm}3.70\;Bq/m^3$) and 5:00AM ($6.62{\pm}3.39\;Bq/m^3$). (3) the seasonal variation of radon concentrations showed higher during winter-to-fall and lower during summer-to-spring. (4) Correlation between airborne radon concentration and the meteorological factors were -0.21 for temperature, 0.09 for humidity, -0.20 for wind speed, and 0.04 for pressure. (5) The mean difference of airborne radon concentration between Asian dust ($5.36{\pm}1.28\;Bq/m^3$) and non-Asian dust ($4.95{\pm}1.49\;Bq/m^3$) phenomenon was significant (p=0.08). We could identify time series distribution of radon concentration related meteorological factors. In addition, radon can be considered a good natural tracer of vertical dispersion and long-range transport.

• 한국수소및신에너지학회논문집
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• 제29권2호
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• pp.219-225
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• 2018

This study was carried out to investigate the injection characteristics of 800 kPa compressed natural gas compressed natural gas (CNG) injector developed in Korea. The CNG injector with multi-holes, employed in this experiment, was designed to inject CNG in the manifold at high pressure of 800 kPa. The spray macroscopic visualization test was carried out via Schlieren photography to study fuel-air mixing process. The fundamental spray characteristics, such as spray penetration, spray cone angle and spray velocity, were evaluated in the constant volume combustion chamber (CVCC) with varying the constant back pressure in CVCC from 0 to 1.8 bar. For the safety reason, nitrogen ($N_2$) and an acetone tracer were utilized as a surrogate gas fuel instead of CNG. The surrogate gas fuel pressures were controlled at 3, 5.5, and 8 bar, respectively. Injection durations were set at 5 ms throughout the experiment. The simulating events of the low engine speed were arranged at 1,000 rpm. The spray images were recorded by using a high-speed camera with a frame rate of 10,000 f/s at $512{\times}256pixels$. The spray characteristics were analyzed by using the image processing (Matlab). The results showed the significant difference that higher injection pressure had more effect on the spray shape than the lower injection pressure. When the injection pressure was increased, the longer spray penetration occurred. Moreover, the linear relation between speed and time are dependent on the injection pressure as well.

• 생명과학회지
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• 제20권1호
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• pp.1-8
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• 2010

본 연구자들의 앞선 연구에서는 햄스터 상구에서 AMPA 수용체의 아형인 GluR1과 GluR4의 분포와 눈 적출 이후 이들 수용체의 분포를 면역세포화학적 방법으로 연구하였다. 또한, 표지한 GluR1과 GluR4를 칼슘결합단백질인 calbindin D28K, calretinin, parvalbumin과 GABA로 표지하여 비교하였다. 본 연구에서 역행성이동추적물질(retrograde tracer)인 호스래디시퍼옥시다아제(horseradish peroxidase, HRP)를 상구의 각 주요 상행로와 하행로에 주입함으로써 GluR1- 면역반응 신경세포들과 GluR4- 면역반응 신경세포들이 투사신경세포(projection neurons)임을 밝혀내었다. Tecto-reticulospinal pathway (TRS)와 dorsal lateral geniculate nucleus (dLGN)으로 HRP 를 주입한후, 햄스터들은 회복을 위해 48시간 동안 살려둔 뒤 관류(perfusion)하였다. GluR- 면역반응 처리된 절편들은 역행성 표지된 신경세포를 지님을 확인하였다. HRP를 주입하였더니 단지 적은 수의 GluR1- 면역반응 신경세포들이 TRS (1.4%)와 dLGN (2.6%)으로 투사되었고, 반면에 많은 수의 GluR4- 면역반응 신경세포들이 TRS (32.7%)로 투사되었다. 사이/투사 신경세포(inter/projection neurons)들은 GluR 아단위들의 분류된 분포와 차별화된 양상을 보였고 이들의 이러한 분포는 칼슘결합단백질들과 GABA와는 겹쳐지지 않았으며, 일전에 발표했던 시각적 행동 반응에서 안구 적출 후 수용체 아단위들의 기능적 다양화와는 차별화된 양상을 보였다.

• 한국콘텐츠학회논문지
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• 제9권1호
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• pp.400-406
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• 2009

본 연구에서는 하천에 유입된 오염물질의 거동 및 확산 특성을 파악하기 위하여 실제 하천에서 RI(Radioactive Isotope) 추적자를 이용하여 오염물 확산을 실측하고 그 결과를 수치모형과 비교분석하였다. 연구대상 수로구간은 금강 상류지역의 용담댐 부근 합류지점으로부터 하류로 약 2km구간에서 실험을 하였으며, 수치모형으로는 RMA-2(Resource Modeling Associates-2), RMA-4를 사용하였다. RI를 이용한 현장실험은 모델링을 적용한 지역과 동일 지역에서 실험을 실시하였고, 각 구간의 간격은 1km로 정하되 현장 사정에 따라 차이를 조금 두어 RI계측기인 NaI계측기를 통한 1초 간격의 농도 데이터를 계측하였다. 계측결과는 수치모형의 결과와 실제 하천에서의 확산범위 및 확산에 큰 영향을 미치는 확산계수 변화에 따른 농도 분포를 비교 분석하였다.

• 교육시설
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• 제11권2호
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• pp.17-23
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• 2004

The purpose of this study concerns the improvement of air quality in school classrooms. Polluted indoor air is improved by efficient ventilation systems. So it is important to measure the amount of ventilation needed in classrooms. First, the amount of natural ventilation were measured through a tracer gas method. And we have established a heat recovery ventilation system from 4 cases of airflow in classrooms, and we have measured the change of $CO_2$ density. According to air quality measurements in the classrooms, the density of $CO_2$ is well above environmental standards which are acceptable. When the amount of ventilated airflow increases, indoor air quality is improved. It is surveyed that the most suitable amount of external inducted air is 770 CMH to satisfy $CO_2$ less than 1,000 ppm in classrooms. For improvement of air quality in classrooms, we must consider a suitable ventilation plan and installation of ventilation systems when constructing school buildings.