• Polymer(Korea)
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• v.39 no.3
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• pp.359-364
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• 2015

A self-oscillating interpenetrating polymer network (IPN) poly(acrylic acid)/poly(ethylene glycol) (PAA/PEG) hydrogel was prepared by using radical polymerization with a two-step method. The IPN hydrogel was characterized by FTIR spectroscopy and morphological analysis. The results indicated that the chains of PEG and PAA twined to form porous structure which is beneficial to water molecules entering inside of the hydrogel. In addition, the pH-responsive behavior, salt sensitivity, swelling/de-swelling oscillatory behaviors and self-oscillation in a closed pH oscillator were also studied. The results showed that the prepared hydrogel exhibited pH-sensitivity, good swelling/de-swelling reversibility and excellent salt sensitivity. The self-oscillating behavior of swelling/de-swelling for the prepared hydrogel was caused by pH alteration coupled with the external media. This study may create a new possibility as biomaterial including new self-walking actuators and other related devices.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1151-1152
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• 2006

In this paper, we examined 10 domestic samples of three different model using thermal, humidity freeze, thermal-endurance and damp heat test under IEC61215 photovoltaic module environmental endurance test condition. Three was almost no changes on power generation. Insulation resistance capacity was much higher than judgement standard but, showed unstable results depending on environmental test items. On external appearance test, there were two models which showed bubble, humidity penetration, seal melted frame phenomenon. From this results, the degree of aging under the external environment is a main cause that shortens photovoltaic module life time. So it is considered that the efforts for finding optimum condition of manufacturing process should be needed.

• Journal of Applied Reliability
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• v.13 no.2
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• pp.141-151
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• 2013

The study of environmental stress cracking (ESC) by contact with plastic rulers and PVC erasers which was artificially added to the external stress was carried out in order to accelerate the chemicals crack. To analyze a blooming plasticizer that migrates from the inside of blended eraser to the surface of the eraser, the ESC experiments were carried out at room temperature and $50^{\circ}C$ conditions. The chemicals crack shape caused by the plasticizer and the brittle fracture shape resulted from the external stress were observed in consequence with the cross-sectional surface analysis of the ruler crack by the ESC. The bending strength of the plastic rulers were fractured prior to the yield point and it had low bending flexure stress. We presented that ESC of polymer materials was affected by the polarity of the chemicals and polymer, the exposure time to chemicals, the exposure temperature and the level of strain on the polymer.

• Journal of Korean Society on Water Environment
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• v.36 no.2
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• pp.116-124
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• 2020

This study aims to identify the characteristics of organic matter and pollutant sources using water quality and stable isotope ratios (δ¹⁵N, δ¹³C) of the two inflow tributaries (Gulpo (GP) and Anyang (AY) streams). Water samples were analyzed in June and September 2018, and the results showed that the concentrations of nutrients, such as TN and NO₃-N, were increased at GP4, which is located at the downstream of sewage treatment facilities(STFs). TOC and TN ratios showed a strong positive correlation (R² = 0.77, p<0.01) at all points except for GP4. The results of GP's stable isotope ratio analysis do not appear to be a constant cluster compared to AY because GPs with large amounts of pollutants from the industry (metal processing companies, etc.) have less tributary, shorter waterway and significantly different external sources. This could be attributed to different sources of external inflow despite its smaller number of tributaries and shorter waterways than AY. In the first half of the year, the δ¹⁵5N of GP4 was affected by discharge of STFs, while AY3 seemed to have an influence of tributary than the discharge of STFs. Consequently, using water quality, stable isotope ratio and C/N, the sources of contamination in two streams with different contaminants were identified and origin was estimated.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.12
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• pp.1245-1254
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• 2008

Proposing a method for the estimation of the social cost for global warming impact (external cost) is the aim of this paper. Both the endpoint approach and conjoint analysis were applied to estimating the social cost for global warming. The endpoint approach was used to assess the damage on the safeguard subjects by global warming due to the emission of greenhouse gases into the atmosphere. The conjoint analysis was used to estimate the economic values for safeguard subjects which measure the social preferences and willingness to pay (WTP) on safeguard subjects. The economic values of human health and social asset were estimated at 62,261,700 Won / DALY (yr) and 10,000 Won / 10,000 Won, respectively. Moreover, cost factors of GHGs were calculated by multiplying the damage factor which is quantified the unit damage on safeguard subject and the economic value. In the case of CO$_2$, the cost factor was calculated at 13.52 Won / kg (13,520 Won / ton). External cost of products or services can be calculated by multiplying the GHG inventory result of products or services by the cost factor of each GHG. inventory.

• The Korean Journal of Food & Health Convergence
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• v.8 no.6
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• pp.11-17
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• 2022

Emergency transport is directly related to the life of the patient, and rapid transport to the hospital is crucial. However, external environmental factors such as traffic or weather, interfere with hospital transport. In this study, we investigated the external environment affecting hospital transport time. We examined the transfer time and patient treatment time of emergency patients in an area of northern Gyeonggi-do from 2018 to 2020. Diagnosis after arrival at the hospital was used, and on-site treatment time was measured from paramedic arrival time at the scene to departure. Furthermore, we examined whether there was a correlation between the time paramedics left the scene and hospital arrival time through the reason for the delay as recorded in the emergency log. Traffic jams had the greatest impact on patient transport, while transport delays occurred due to heavy rain, but not snow. Among injured patients, electrical accidents were the most problematic in terms of on-site treatment time. This was because a lot of first aid is needed in electrical accidents. It must be necessary to mobilize two ambulances in an emergency through the expansion of infrastructure, prepare a plan for rapid transport in heavy rain, and implement strong laws against transport obstruction.

• The Korean Journal of Health Service Management
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• v.5 no.1
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• pp.133-145
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• 2011

The purpose of this study is to analyze the influence of external environment, organizational characteristics on informatization level in hospital settings, and to provide suggestions to improve the informatizaiton level of strategic information system of hospitals. In order to achieve study purpose, causal model was developed and empirically tested. Data were collected from 716 managers of 89 hospitals keeping information system in Busan and KyungNam Province using self-administered structured questionnaire. Major results of this study were as follows; First, among hospitals which had information training programs, informatization capacity was significantly higher. Moreover, informatization capacity was significantly varied by ownership type, institutional level, and number of beds of hospitals. Second, environmental uncertainty, intra-industry competition intensity, decision-making concentration, work standardization variables and perceived benefits were found to be significant affecting factors on informatization capacity as a result of path analysis. Third, support of top-management and perceived benefits were found to be significant affecting factors on informatization capability as a result of path analysis. Especially, informatization capability was positively affected by informatization capacity. Finally, perceived benefits was found to be significant affecting factors on informatization competency as a result of path analysis. Especially, informatization competency was positively affected by informatization capability.

• IE interfaces
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• v.22 no.4
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• pp.336-346
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• 2009

One of primary assumptions on DEA is that all DMUs for evaluation should be homogeneous. In comparative analysis among DMUs with relative efficiency measurement, it should be evaluated under identical conditions by ruling out external environmental influences. In this study, a measurement of innovation efficiency using the three-stage approach is performed. The approach employs DEA to measure relative efficiency and Tobit regressions to control external variables affecting innovation activity. The approach applied to firms in Korean Innovation Survey: Service Sector 2003 and 2006. Final efficiency scores of the approach represent net efficiency of the innovation. This study found that there is a increasing on technical efficiency of third stage, and it has difference with first stage significantly. Besides, a decrease on standard deviation of third stage is found. It means DMUs biased lower due to unfavorable condition and ones biased higher due to favorable condition are fallen into an identical operating environment through the approach. A measurement of net efficiency, excluding external effects, ensures the homogeneity of DMUs so that improves the reliability in terms of its analysis results. This study is expected to provide a direction and to be a valuable reference to further evaluation of innovation performance in Korean service sector.

• Journal of Korean Society of Transportation
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• v.33 no.6
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• pp.520-530
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• 2015

This paper formulates the methodologies to estimate optimal congestion tolls from long-run and short-run perspectives and applies them to the highways of Seoul. An optimal long-run congestion toll is estimated with an optimal volume-capacity-ratio to minimize the total costs which consist of two components: road construction and maintenance costs and traveler costs. By contrast, an optimal short-run congestion toll is estimated with a supply-demand equilibrium which is determined by using a speed-flow function and a disaggregate modal choice model. The results of a long-run analysis for the Seobu urban expressway suggest the optimal volume-capacity-ratio of 1.35 and the optimal congestion toll of 503 Won per automobile kilometer. By contrast, those of a short-run analysis for the Mia-ro urban arterial suggest 1.31 and 420 Won, respectively. Although our results are to some degree dependent on the interest rate and time value assumed, one basic conclusion holds up: the congestions toll tested could generate substantial gains in social welfare if applied to Seoul.

• Journal of the Korean Institute of Rural Architecture
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• v.21 no.3
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• pp.61-68
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• 2019

Dramatic increase of population migrating from suburban area to metropolitan area which started in 1990s resulted in the increase of aging population among this area. Centralized population also causes decreased number of students in suburban areas which in turn affects environmental facilities such as school and brings social issue. Additionally, compared to the alternative analysis and data regarding internal spatial arrangement of high school, there are not enough data or information on external spatial arrangement and how to construct such space. Therefore, the main purpose of this thesis is to provide fundamental data which can be used as a reference in improving educational environment of suburban high school by analyzing and investigating various factors including location, accessibility, facility status, and external spatial arrangement based on arrangement type of 8 normal high schools located across Jeju Island where the trend of decreasing number of students is prominent. Following is the result of such investigation. Despite the fact that high schools from suburban areas in Jeju Island possess diversity based on local characteristic, construction of external space is rather inconsistent as the plans regarding external space is not organized. Therefore, there is a need for preparing external spaces appropriate for each school based on the number of students and the characteristic of gymnasium.