• Journal of Environmental Impact Assessment
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• v.30 no.3
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• pp.141-154
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• 2021

In this study, the effect of the restoration of Yaksa stream and the construction of an apartment complex by the urban renewal project in the Yaksa district of Chuncheon on air quality in the surrounding area was evaluated using computational fluid dynamics (CFD) model simulations. In orderto compare the impact of the project, wind and pollutant concentration fields were simulated using topographic data in 2011 and 2017, which stand for the periods before and after the urban renewal project, respectively. In the numerical experiments, the scenarios were set to analyze the effect of the construction of the apartment complex and the effect of stream restoration. Wind direction and wind speed data obtained from the Chuncheon Automated Synoptic Observing System (ASOS) were used as the inflow boundary conditions, and the simulation results were weighted according to the frequencies of the eight-directional inflow wind directions. The changes in wind speed and NO_X concentration distribution according to the changes in building and terrain between scenarios were compared. As a result, the concentration of NO_X emitted from the surrounding roads increased by the construction of the apartment complex, and the magnitude of the increase was reduced as the result of including the effect of stream restoration. The concentration of NO_X decreased around the restored stream, while the concentration increased significantly around the constructed apartment complex. The increase in the concentration of NO_X around the apartment complex was more pronounced in the place located in the rear of the wind direction to the apartment complex, and the effect remains up to the height of the building. In conclusion, it was confirmed that the relative arrangement of apartment complex construction and stream restoration in relation to the main wind direction of the target area was one of the major factors in determining the surrounding air quality.

• The Korean Journal of Nuclear Medicine
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• v.37 no.6
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• pp.364-373
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• 2003

Purpose: For good quality of myocardial perfusion images, an approximately 30 min to 1 hour of waiting time after radiopharmaceutical injection and ingestion of fatty meal are asked of the patients. The aim of this study was to investigate the shortening of waiting time after radiopharmaceutical injection and improvement of image quality using natural plant extracts that promote bile excretion. Materials and Methods: Ten volunteers participated in protocol 1 (7 men, 3 women; mean age, $24.1{\pm}2.4$ years) and protocol 2 (8 men, 2 women; mean age, $26.1{\pm}2.9$ years), respectively. For the modified method of both protocols, subjects took natural plant extracts 15 minutes before the first injection of $^{99m}Tc$ MIBI without laking fatty meals. Control (Conventional) methods were peformed with intake of a fatty meal 20 to 30 minutes after $^{99m}Tc$ MIBI injection. Results: As the results of protocol 1 and 2, the ratio of myocardial to lung ratio were not different between modified and conventional method. Liver to lung ratio of modified method showed significantly lower value than that of conventional method. In modified method, myocardial to liver ratio was higher persistently. In protocol 2, natural plant extracts took before the first injection of $^{99m}Tc$ MIBI exerted accelerating effect of excretion of bile juice into Intestine until the end of examination. Conclusion: These results represent that natural plant extracts for facilitation of bile excretion before injection of $^{99m}Tc$ MIBI may provide better quality of myocardial perfusion images without the need for preparations such as ingestion of fatty meal within the 2 hours compared with conventional method.

• Journal of Korean Society of Forest Science
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• v.90 no.4
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• pp.431-436
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• 2001

The extractable sulfate content and sulfate adsorption capacity in soils of four Pinus densiflora stands were measured to assess the soil acidification sensitivity to acid deposition. The soluble sulfate content in organic horizon which reflects the previous deposition of sulfur oxides was much higher for Namsan and Ulsan than Kanghwa and Hongcheon. In mineral soils, however, the extractable sulfate content was the greatest for Ulsan followed by Kanghwa, Namsan and Hongcheon due to the interactive effect of previous deposition and soil adsorption of sulfate. Adsorption rates of specifically adsorbed sulfate(proportion of insoluble sulfate to total extractable sulfate) for Namsan, Kanghwa and Ulsan affected by acid deposition were 16.6%, 56.8% and 37.4%, respectively, so that the soil in Namsan had the highest acidification sensitivity to acid deposition. For sulfate adsorption isotherm($RE=mX_i-b$), the significantly positive correlations between added sulfate($X_i$) and adsorbed sulfate(RE) were found only in mineral soil(p<0.05) over all regions. The regression coefficient(m) that means soil sulfate adsorption capacity by 0-30cm depth was 0.16, 0.24, 0.25 and 0.32 in $mmol_c\;kg^{-1}$ for Namsan, Kanghwa, Ulsan and Hongcheon, respectively, indicating that soil acidification sensitivity is the highest for Namsan. The added sulfate($X_i$) that could make the adsorbed sulfate(RE) null was 3.81, 2.17, 4.96 and 0.65 in $mmol_c\;kg^{-1}$ for Namsan, Kanghwa, Ulsan and Hongcheon, respectively and the values of former three regions considerably exceeded the realistic sulfate deposition.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.250-256
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• 2013

Gasoline generates organic acid and polymer (gum) by hydrocarbon oxidation depending on the storage environment such as temperature and exposure to sunlight, which can cause metal corrosion, rubber and resin degradation and vehicle malfunction caused by accumulation in fuel supply system. The gasoline which has not been used for a long time in bi-fuel (LPG-Gasoline) vehicle causes problems, and low octane number gasoline have evaporated into the field, but the exact cause has not been studied yet. In this study, we suggest a plan of quality management by investigating the gasoline oxidation behavior. In order to investigate the oxidation behavior of gasoline, changes of gasoline properties were analyzed at various storage conditions such as storage time, storage vessel type (vehicle fuel tank, PE vessel and Fe vessel) and storage circumstances (sunlight exposure and open system, etc.). Currently distributing gasoline and bioethanol blended fuel (blended 10%) were stored for 18 weeks in summer season. The sample stored in PE vessel was out of quality standard (octane number, vapor pressure, etc.) due to the evaporation of the high octane number and low boiling point components through the vessel cap and surface. Especially, the sunlight exposure sample stored in PE vessel showed rapid decrease of vapor pressure and increase of gum. Bioethanol blended fuel showed similar results as gasoline.

• Journal of Environmental Policy
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• v.14 no.2
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• pp.133-148
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• 2015

The number of used oil refining companies has been increased and it causes shortage of the volume of used oil per recycling company. In addition, the number of used oil collecting companies has been increased and it caused excessive competition among companies with excessive costs. Companies use not only proper used oil but also low quality used oil because of shortage of supply. It is the reason of environmental pollution. Also excessive competition brings high cost of refined oil and it becomes a burden on the consumer. Therefore, the recycling improvement plans of used oil is needed because of these causes. First of all, importing used oil from the developed countries of OECD is the one of solution to secure a used oil supply. However, imported used oil should meet the international quality standards and it is examined twice by international authority institute such as K-petro in both exporting and importing countries. Second, the cost would be reduced with the relaxation on regulations of used oil refinement. However, regulation to sediment and water should be separated. Sediment should be kept within 2% and water should be kept within 5%. It is the way to relax the regulations of used oil refinement with preventing environmental pollutions. Finally, the standard of used oil for heater should be regulated strictly. To prevent pollutions, used oil for heater is limited to high quality waste lubricating oil. Also the air pollution prevention device has to be installed on heater.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.315-324
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• 2016

Because of a fissility characteristics of shale in the Gyoungsang super-group, it breaks down to debris when daylighted by construction work and causes a slope unstability. To assess the durability property of shale, a series of slake durability tests was conducted by controlling test conditions such as shape of specimen, number of specimen, revolution speed, revolution number, drying temperature and pH of submerging liquid. For the specimen shape, cube one showed relatively lower durability index than cuboid and/or fan shape one. The test with the more number of specimens showed the less durability index because of a higher friction among specimens in the drum. The durability index is linearly decreased by increasing the total number of revolution, while the revolution velocity could not affect the index. And the durability index is also decreased by increasing the drying temperature of specimen and by decreasing the pH of submerging liquid. Because the durability index of shale is almost similar to that of crystalline rocks, the disintegration characteristics of shale could not be assessed by the slake durability test recommended by ISRM, and thus a new test method by changing the total revolution number may be required for the shale having fissility characteristics.

• Journal of the Korean Society of Radiology
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• v.3 no.1
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• pp.17-21
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• 2009

The Recently, large area matrix-addressed image detectors are investigated for X-ray imaging with medical diagnostic and other applications. In this paper, a new flat panel gas detector for diagnostic X-ray imaging is proposed, and its characteristics are investigated. The research of flat panel gas detector is not exist at all. Because of difficulty to inject gas against to atmospheric pressure. So almost gas detector made by chamber shape. We made flat panel sample by display technique. (ex: PDP, Fed, etc.) The experimental measurements, the transparent electrodes, dielectric layer, and the MgO protection layer were formed in front glass. And, the X-ray phosphor layer and address electrodes are formed in the rare glass. The dark current, the x-ray sensitivity and linearity as a function of electric field were measured to investigate the electrical properties. From the results, the stabilized dark current density and the significant x-ray sensitivity were obtained. And the good linearity as a function of exposure dose was showed in wide diagnostic energy range. These results means that the passive matrix-addressed flat panel gas detector can be used for digital x-ray imaging.

• Journal of Korea Technology Innovation Society
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• v.21 no.3
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• pp.1101-1126
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• 2018

As incipient organizations progress from formation to become larger entities, the procedures and rules that provided managerial and structural advantages in having established the organizations and promoting the growth impede the innovation and creativity vital to maintain the competitive advantage. Adopting Corporate Entrepreneurship (CE), large corporations have tried to overcome the dilemma and to sustain the innovation and creativity in order to effectively cope with harsh competitive realities. Recently, some advanced corporations are trying to enhance CE by setting up an internal venture program as a seed organization for CE. By making an in-depth analysis of the internal venture program, 'C-Lab' of Samsung that is promoting CE-related characteristics for enhancing CE, we attempt to shed light on (1) what kinds of environments should be built around the seed organization for CE (2) what are the major characteristics that should be promoted through the seed organization in relation to CE (3) What kinds of achievements can be made from the promoted characteristics (4) How the characteristics are spread over the entire organization. Based on the analysis, we suggest a generalized process in which CE can be enhanced. Since different approaches should be taken for managing the seed organization and spreading the characteristics depending on the strengths and weaknesses of a corporation, there must be the step, 'evaluation of corporate internal capabilities' in the process. We believe that each corporation can enhance CE by taking advantage of the process with reference to the C-Lab case study.

• Membrane Journal
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• v.29 no.3
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• pp.173-182
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• 2019

Much research has been made for finding new and eco-friendly alternative sources of energy to solve the problems related with the pollution caused by emissions of greenhouse gases such as carbon dioxide as the use of fossil fuels increases worldwide. Among them, fuel cells draws particular interests as an eco-friendly energy generator because only water is obtained as a by-product. Anion exchange membrane-based alkaline fuel cell (AEMFC) that uses anion exchange membrane as an electrolyte is of increased interest recently because of its advantages in using low-cost metal catalyst unlike the PEMFC (potton exchange membrane fuel cell) due to the high-catalyst activity in alkaline conditions. The main properties required as an anion exchange membrane are high hydroxide conductivity and chemical stability at high pH. Recently we reported a chemically crosslinked poly(2-dimethyl-1,4-phenylene oxide) (PPO) by reacting PPO with N,N,N',N'-tetramethyl-1,6-hexanediamine as novel anion exchange membranes. In the current work, we further developed the same crosslinked polymer but having enhanced physicochemical properties, including higher conductivity, increased mechanical and dimensional stabilities by using the PPO with a higher molecular weight and also by increasing the crosslinking density. The obtained polymer membrane also showed a good cell performance.

• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.3
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• pp.227-235
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• 2015

Using eddy covariance method, net ecosystem exchange (NEE) of $CO_2$ ($F_{CO_2}$), $H_2O$ (LE), and sensible heat (H) can be approximated as the sum of eddy flux ($F_c$) and storage flux term ($F_s$). Depending on strength and distribution of sink/source of scalars and magnitude of vertical turbulence mixing, the rates of changes in scalars are different with height. In order to calculate $F_s$ accurately, the differences should be considered using scalar profile measurement. However, most of flux sites for agricultural lands in Asia do not operate profile system and estimate $F_s$ using single-level scalars from eddy covariance system under the assumption that the rates of changes in scalars are constant regardless of the height. In this study, we measured $F_c$ and $F_s$ of $CO_2$, $H_2O$, and air temperature ($T_a$) using eddy covariance and profile system (i.e., the multi-level measurement system in scalars from eddy covariance measurement height to the land surface) at the Chengmicheon farmland site in Korea (CFK) in order to quantify the differences between $F_s$ calculated by single-level measurements ($F_s_{-single}$ i.e., $F_s$ from scalars measured by profile system only at eddy covariance system measurement height) and $F_s$ calculated by profile measurements and verify the errors of NEE caused by $F_s_{-single}$. The rate of change in $CO_2$, $H_2O$, and Ta were varied with height depending on the magnitudes and distribution of sink and source and the stability in the atmospheric boundary layer. Thus, $F_s_{-single}$ underestimated or overestimated $F_s$ (especially 21% underestimation in $F_s$ of $CO_2$ around sunrise and sunset (0430-0800 h and 1630-2000 h)). For $F_{CO_2}$, the errors in $F_s_{-single}$ generated 3% and 2% underestimation of $F_{CO_2}$ during nighttime (2030-0400 h) and around sunrise and sunset, respectively. In the process of nighttime correction and partitioning of $F_{CO_2}$, these differences would cause an underestimation in carbon balance at the rice paddy. In contrast, there were little differences at the errors in LE and H caused by the error in $F_s_{-single}$, irrespective of time.