• Journal of Soil and Groundwater Environment
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• v.12 no.4
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• pp.25-31
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• 2007

Characterizing the risk posed by a mixture of chemicals is a challenging task due to the chemical interactions of individual components that may affect their physical behavior and hence alter their exposure to receptors. In this study, cell tests that represent subsurface environment were carried out using benz[a]anthracene (BaA) and p-xylene focusing on phasetransforming interaction to verify increased mobility and risk of highly sorbed pollutants in the presence of less sorbed, mobile liquid pollutants. A transport model was also developed to interpret results and to simulate the same process on a field scale. The experimental results showed that BaA had far greater mobility in the presence of p-xylene than in the absence of that. The main transport mechanisms in the vadose zone were by dissolution to p-xylene or water. The transport model utilizing Defined Time Steps (DTS) was developed and tested with the experimental results. The predicted and observed values showed similar tendency, but the more work is needed in the future study for more precise modeling. The field-scale simulation results showed that transport of BaA to groundwater table was significantly faster in the presence of NAPL, and the oral carcinogenic risk of BaA calculated with the concentration in groundwater was 15${\sim}$87 times larger when mixed with NAPL than when solely contaminated. Since transport rate of PAHs is very slow in the subsurface without NAPL and no degradation of PAHs was considered in this simulation during the transport, the increase of risk in the presence of NAPL is expected to be greater for the actual contaminated site.

• Journal of The Korean Association For Science Education
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• v.38 no.3
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• pp.393-405
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• 2018

In this study, we classified the group model construction types in the actual classroom situation implementing the instructional strategy mixed with individual model construction and group model construction types. The purpose of this study is to analyze the information flow and the individual construction types of each group model construction type to obtain implications for model co-construction in a real classroom environment. A two-session class on sound propagation was carried out for thirty-three 8th grade students in Seoul. A total of 65 individual model construction and 16 group model construction processes were collected and analyzed. The group model construction types were classified as unchanged, enumerated, and elaborated. The unchanged type was found in 8 groups, the enumerated type in 3 groups, and the elaborated type in 5 groups. The isolated individual and independent construction (i.I) were found mostly in the unchanged group construction type (50.0%) and enumerated group construction type (54.5%). In the unchanged type, the radial shape of flow in which one student's information is transmitted to all the members of the group appeared. In the enumerated type, the starting point of the information flow was observed from two individuals. In the elaborated type, linear information flow appeared and both the second dissemination and reflective construction (2d.R) contributed to the group model construction (58.3%). This study suggests a viewpoint that enables to understand the process of complex model construction in an actual classroom context rather than in an ideal situation. The result of this study suggests the necessity of a modeling strategy considering the characteristics of Korean small group culture. It is expected that the discussion will progress through further studies.

• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.4
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• pp.384-398
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• 2015

In this paper, the high-resolution Weather Research and Forecasting/Noah-MultiParameterization (WRF/Noah-MP) modeling system is configured for the Cheongmicheon Farmland site in Korea (CFK), and its performance in land and atmospheric simulation is evaluated using the observed data at CFK during the 2014 special observation period (21 August-10 September). In order to explore the usefulness of turning on Noah-MP dynamic vegetation in midterm simulations of surface and atmospheric variables, two numerical experiments are conducted without dynamic vegetation and with dynamic vegetation (referred to as CTL and DVG experiments, respectively). The main results are as following. 1) CTL showed a tendency of overestimating daytime net shortwave radiation, thereby surface heat fluxes and Bowen ratio. The CTL experiment showed reasonable magnitudes and timing of air temperature at 2 m and 10 m; especially the small error in simulating minimum air temperature showed high potential for predicting frost and leaf wetness duration. The CTL experiment overestimated 10-m wind and precipitation, but the beginning and ending time of precipitation were well captured. 2) When the dynamic vegetation was turned on, the WRF/Noah-MP system showed more realistic values of leaf area index (LAI), net shortwave radiation, surface heat fluxes, Bowen ratio, air temperature, wind and precipitation. The DVG experiment, where LAI is a prognostic variable, produced larger LAI than CTL, and the larger LAI showed better agreement with the observed. The simulated Bowen ratio got closer to the observed ratio, indicating reasonable surface energy partition. The DVG experiment showed patterns similar to CTL, with differences for maximum air temperature. Both experiments showed faster rising of 10-m air temperature during the morning growth hours, presumably due to the rapid growth of daytime mixed layers in the Yonsei University (YSU) boundary layer scheme. The DVG experiment decreased errors in simulating 10-m wind and precipitation. 3) As horizontal resolution increases, the models did not show practical improvement in simulation performance for surface fluxes, air temperature, wind and precipitation, and required three-dimensional observation for more agricultural land spots as well as consistency in model topography and land cover data.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.5
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• pp.595-602
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• 1996

The antimicrobial effects of two disinfectants commonly used in food industry on Listeria monocytogenes ATCC 15313 were studied. The two disinfectants tested were commercial benzalkonium chloride (BAC) and sodium hypochlorite (NaOCl). Their effects were studied on cells suspended in disinfectants (in vitro) and in the sponge model with the disinfectants (in vivo). When cells were exposed to $0\~0.1\%$ BAC and $0\~150\;ppm$ NaOCL for 20 minutes, BAC and NaOCl concentration more than $0.25\%$ and 100 ppm showed the antimicrobial effects respectively. This organism decreased rapidly during the first $0.5\~1$ minute followed by a slower decrease during the rest of the exposure time. Fifteen ml of cell solution $(about\;10^7\;CFU/ml\;in\;the\;TSB)$ was mixed with 15 ml of disinfectants in the sponge $(6.0{\times}4.0{\times}4.0cm)$, BAC and NaOCl concentration more than $0.1\%$ and 300 ppm showed the antimicrobial effects, and at $0.25\%$ and 800 ppm diminished in cell numbers 3-log cycles during the first 20 minutes. In the case of sponge model, 15 ml of cell solution and 15 ml of disinfectants $(0.25\%\;of\;BAC,\;800\;ppm\;of\;NaOCl)$ were suspended in the sponge during 20 minutes, washing with 200 ml of sterilized distilled water, and this sponge was transfered in the 100 ml TBS, and then incubated at various temperature. The cells were increased about 1-log cycle during 24 hrs at $5\~15^{\circ}C$. And the others temperature, the cells growth was in proporation to storage tepmerature and the cells were about $10^9\;CFU/ml$ after $1\~3$ days incubations.

• Journal of the Korean Institute of Landscape Architecture
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• v.49 no.5
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• pp.79-96
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• 2021

Green infrastructure planning represents landscape planning measures to reduce particulate matter. This study aimed to derive factors that may be used in planning green infrastructure for particulate matter reduction using text mining techniques. A range of analyses were carried out by focusing on keywords such as 'particulate matter reduction plan' and 'green infrastructure planning elements'. The analyses included Term Frequency-Inverse Document Frequency (TF-IDF) analysis, centrality analysis, related word analysis, and topic modeling analysis. These analyses were carried out via text mining by collecting information on previous related research, policy reports, and laws. Initially, TF-IDF analysis results were used to classify major keywords relating to particulate matter and green infrastructure into three groups: (1) environmental issues (e.g., particulate matter, environment, carbon, and atmosphere), target spaces (e.g., urban, park, and local green space), and application methods (e.g., analysis, planning, evaluation, development, ecological aspect, policy management, technology, and resilience). Second, the centrality analysis results were found to be similar to those of TF-IDF; it was confirmed that the central connectors to the major keywords were 'Green New Deal' and 'Vacant land'. The results from the analysis of related words verified that planning green infrastructure for particulate matter reduction required planning forests and ventilation corridors. Additionally, moisture must be considered for microclimate control. It was also confirmed that utilizing vacant space, establishing mixed forests, introducing particulate matter reduction technology, and understanding the system may be important for the effective planning of green infrastructure. Topic analysis was used to classify the planning elements of green infrastructure based on ecological, technological, and social functions. The planning elements of ecological function were classified into morphological (e.g., urban forest, green space, wall greening) and functional aspects (e.g., climate control, carbon storage and absorption, provision of habitats, and biodiversity for wildlife). The planning elements of technical function were classified into various themes, including the disaster prevention functions of green infrastructure, buffer effects, stormwater management, water purification, and energy reduction. The planning elements of the social function were classified into themes such as community function, improving the health of users, and scenery improvement. These results suggest that green infrastructure planning for particulate matter reduction requires approaches related to key concepts, such as resilience and sustainability. In particular, there is a need to apply green infrastructure planning elements in order to reduce exposure to particulate matter.