• Journal of Korean Society of Transportation
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• v.34 no.1
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• pp.43-54
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• 2016

Although there are continuous demands for activating BSSs(Bicycle Sharing Systems) due to the convenience and positive health effects, it is difficult to make a decision to support the existing systems and build more systems because of the deficit resulting from the operation of BSSs. Consequently, this study estimated the economic effects(WTP; Willingness to Pay) of BSS and analyzed the impact factors of WTP to support the above decision making in Daejeon. For this, we conducted a survey and collected 668 samples from the users and non-users of TASHU that is the BSS operated in Daejeon. Also, we used CVM(Contingent Valuation Method) for the estimation of WTP. The results show that the number of bicycle uses is a determinant factor having a positive relationship with WTP and car ownership and age are also determinant factors having a negative relationship with WTP. On the other hand, income and sex have no significant statistical relationship with WTP. Also, the economic benefit of TASHU was estimated as much as 49.9 billion KRW to 63.6 billion KRW. Considering the operation cost of 2.5 billion KRW, it is quite big benefit. Based on the results, it needs to support TASHU from a user perspective for the efficient operation of the system.

• Environmental and Resource Economics Review
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• v.12 no.4
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• pp.637-661
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• 2003

This paper analyzes the impact of import liberalization of petroleum product market in 1997 on the behavior of a domestic industry, regarded as a typical oligopoly. Based on the theory of implicit cartel, two regression equations were formulated and estimated for domestic production and refinery margin using monthly data for the period from Jan. 1994 to June 2003. Estimation results show that not only did domestic production rise sharply but also the refining cost fell substantially throughout 1996 before the actual liberalization of imports, Such a response is clearly consistent with the implicit cartel theory, which suggests that once the difficulty of maintaining a cartel in the future is recognized, the cartel immediately collapses and anticipation of import liberalization can cause immediately lowering market price as well as an immediate expansion of the supply by a domestic industry. However, the significant reduction of refinery cost accompanied by a large contraction in domestic output after the actual implementation of import liberalization can be explained by the collapse of implicit cartel caused by the anticipated liberalization of imports. Thus, import liberalization in the sense of allowing entry of foreign producers into domestic market has seemed to be an effective means to weaken market power and induce more competitive conduct of domestic firms.

• Journal of Energy Engineering
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• v.22 no.4
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• pp.370-375
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• 2013

This paper attempts to estimate the city gas demand function in Korea over the period 1981-2012. As the city gas demand function provides us information on the pattern of consumer's city gas consumption, it can be usefully utilized in predicting the impact of policy variables such as city gas price and forecasting the demand for city gas. We apply lagged dependent variable model and ordinary least square method as a robust approach to estimating the parameters of the city gas demand function. The results show that short-run price and income elasticities of the city gas demand are estimated to be -0.522 and 0.874, respectively. They are statistically significant at the 1% level. The short-run price and income elasticities portray that demand for city gas is price- and income-inelastic. This implies that the city gas is indispensable goods to human-being's life, thus the city gas demand would not be promptly adjusted to responding to price and/or income change. However, long-run price and income elasticities reveal that the demand for city gas is price- and income-elastic in the long-run.

• Journal of Wetlands Research
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• v.18 no.4
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• pp.404-412
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• 2016

This paper not only aims to establish a plan to acquire the water stage data in a constant and proper manner by using limited manpower and costs, but also establishes the fundamental technology for acquiring the water level observation data or the stage data. For this, this paper focuses on how to acquire the stage data, in a uniform manner, that can represent each basin by developing the technology for establishing the optimal observational network. For that, this paper identifies the current status of the stage gauge stations installed in the ChungJu dam including wetland basin mainly along the national rivers. Then, thus obtained factors are used to develop the representative unit hydrograph. After that, the data are converted into the probability density function. Then, the stations are calculated information transfer amount. As a last step, we establish the optimized stage gauge network by the location of the stage station and space impact that takes into account for the combinations of the number of the stations. In other words, we consider the combination of the stage gauge station with information transfer amount and spatial correlation analysis for estimation.

• Journal of Distribution Science
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• v.14 no.1
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• pp.93-102
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• 2016

Purpose - The purpose of paper is studying the static and dynamic side for long-term memory storage properties, and increase the explanatory power regarding the long-term memory process by looking at the long-term storage attributes, Korea Composite Stock Price Index. The reason for the use of GPH statistic is to derive the modified statistic Korea's stock market, and to research a process of long-term memory. Research design, data, and methodology - Level shifts were subjected to be an empirical analysis by applying the GPH method. It has been modified by taking into account the daily log return of the Korea Composite Stock Price Index a. The Data, used for the stock market to analyze whether deciding the action by the long-term memory process, yield daily stock price index of the Korea Composite Stock Price Index and the rate of return a log. The studies were proceeded with long-term memory and long-term semiparametric method in deriving the long-term memory estimators. Chapter 2 examines the leading research, and Chapter 3 describes the long-term memory processes and estimation methods. GPH statistics induced modifications of statistics and discussed Whittle statistic. Chapter 4 used Korea Composite Stock Price Index to estimate the long-term memory process parameters. Chapter 6 presents the conclusions and implications. Results - If the price of the time series is generated by the abnormal process, it may be located in long-term memory by a time series. However, test results by price fixed GPH method is not followed by long-term memory process or fractional differential process. In the case of the time-series level shift, the present test method for a long-term memory processes has a considerable amount of bias, and there exists a structural change in the stock distribution market. This structural change has implications in level shift. Stratum level shift assays are not considered as shifted strata. They exist distinctly in the stock secondary market as bias, and are presented in the test statistic of non-long-term memory process. It also generates an error as a long-term memory that could lead to false results. Conclusions - Changes in long-term memory characteristics associated with level shift present the following two suggestions. One, if any impact outside is flowed for a long period of time, we can know that the long-term memory processes have characteristic of the average return gradually. When the investor makes an investment, the same reasoning applies to him in the light of the characteristics of the long-term memory. It is suggested that when investors make decisions on investment, it is necessary to consider the characters of the long-term storage in reference with causing investors to increase the uncertainty and potential. The other one is the thing which must be considered variously according to time-series. The research for price-earnings ratio and investment risk should be composed of the long-term memory characters, and it would have more predictability.

• Restorative Dentistry and Endodontics
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• v.27 no.4
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• pp.403-410
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• 2002

Several ways of curing are being tried to improve material's properties and reduce marginal gap. However, all are considering about the pattern of light intensity. It was noted from the preliminary study the change of light wavelength from filter changing may give an impact on material's property and microleakage. The object of this study was to verify the effect of filters with various wavelength width on the microhardness and microleakage of composite resin ; hybrid type of DenFil and submicron hybrid type of Esthet X. Composite resins were cured using 3 kinds of filter; narrow-banded(465-475 nm), mid-banded(430-470 nm), wide-banded(400-500 nm). After the estimation of microhardness. degree of dye penetration and the maximum gap from SEM evaluation were done between 4 groups that showed no difference in microhardness value of the lower surface . The results were as follows : 1 Adequate microhardness could not be gained with a narrow-banded filter irrespective of curing time. At the upper surface, DenFil should be polymerized with middle or wide-banded filter for 20 seconds at least, while Esthet X be col$.$ed with middle or wide-banded filter for 30 seconds at least to get simitar hardness value to control group. 2. There was little dye penetration in enamel margin, but all dentin margins skewed much more dye penetration irrespective of curing conditions. Although there was no statistical difference, groups cured with mid-banded filter for 40 seconds and with wide-width filter for 20 seconds showed relatively less dye penetration. 3. It was revealed from the SEM examination that group cured with wide-banded filter had the smallest gap without statistical significance. Spearman's rho test showed that the correlation between the results of dye penetration and SEM examination was very low. From these results, it could be concluded that curing with wide-width filter would be better than the other techniques, even though the curing technique using mid-width filter seems to have its own unique advantage.

• Journal of the Korean earth science society
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• v.35 no.4
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• pp.215-224
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• 2014

Data assimilation effect of mobile rawinsonde observation was evaluated using Unified Model (UM) with a Three-Dimensional Variational (3DVAR) data assimilation system during the intensive observation program of 2013 summer season (rainy season: 20 June-7 July 2013, heavy rain period: 8 July-30 July 2013). The analysis was performed by two sets of simulation experiments: (1) ConTroL experiment (CTL) with observation data provided by Korea Meteorological Administration (KMA) and (2) Observing System Experiment (OSE) including both KMA and mobile rawinsonde observation data. In the model verification during the rainy season, there were no distinctive differences for 500 hPa geopotential height, 850 hPa air temperature, and 300 hPa wind speed between CTL and OSE simulation due to data limitation (0000 and 1200 UTC only) at stationary rawinsonde stations. In contrast, precipitation verification using the hourly accumulated precipitation data of Automatic Synoptic Observation System (ASOS) showed that Equivalent Threat Score (ETS) of the OSE was improved by about 2% compared with that of the CTL. For cases having a positive effect of the OSE simulation, ETS of the OSE showed a significantly higher improvement (up to 41%) than that of the CTL. This estimation thus suggests that the use of mobile rawinsonde observation data using UM 3DVAR could be reasonable enough to assess the improvement of prediction accuracy.

• Journal of Environmental Health Sciences
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• v.44 no.3
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• pp.217-226
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• 2018

Objectives: Despite the positive effects of Off-site risk assessment (ORA) system such as prevention of chemical accidents, some problems have been constantly raised. The purpose of this study is to analyze the problems that have occurred through the implementation of the ORA system for the past three years and to suggest reasonable directions for improvement in the future. Methods: In order to identify the problems with the methodology and procedure of ORA system, we analyzed statutes, administrative rules and documents related to the ORA system. A survey of ORA reviewers in National Institute of Chemical Safety was conducted to investigate the weight of determinants considered when judging the level of total risk in ORA. Results: In this study, we found out the uncertainty of the estimation of the number of people in the impact range in the procedure of the risk assessment of individual handling facilities, the lack of quantitative risk analysis methods for environmental receptors, and the ambiguity of the criteria for the total risk. In addition to suggesting solutions to the problems mentioned above, we also, suggested a decision tree for total risk in ORA. Conclusion: We anticipate that the solutions including the systematic decision tree for total risk suggested will contribute to the smooth operation of the ORA system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.283-293
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• 2006

The purpose of this study is to quantitatively estimate the erosional properties for cohesive sediments on Keum Estuary. Then the spatial variation was evaluated, through analyzing and comparing the seasonal variation of the erosional properties in Keum Estuary with that of the erosional properties in the other sites. As erosional properties of cohesive sediments are also influenced largely by basic physico-chemical property of cohesive sediments themselves, the impact that the basic physico-chemical property has on the erosional properties is analyzed in this study. Erosional tests are performed under the condition of uniform beds. Total 8 times of tests using an annular flume are also conducted in a location, low times respectively by seasons: the fall, winter. Experimental results of erosional tests show that the critical shear stress for erosion varies in the range of $0.12{\sim}0.36N/m^2$ and the coefficient of erosion rate varies in the range of $120.91{\sim}6.72mg/cm^2{\cdot}hr$, over the corresponding bulk-density range $1.15{\sim}1.34g/cm^3$. Although the calculated parameters of erosional properties are remarkably different in quantity compared with those of other cohesive sediments(lake Okeechobee) and Kaolinite, their seasonal variabilities within Keum Estuary appear to be insignificant.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.5
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• pp.716-721
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• 2010

LCA (Life Cycle Assessment) carried out to estimate carbon footprint and to establish of LCI (Life Cycle Inventory) database of rice production system. The results of collecting data for establishing LCI D/B showed that organic fertilizer and chemical fertilizer input to 4.29E-01 kg $kg^{-1}$ rice and 2.30E-01 kg $kg^{-1}$ rice for rice cultivation. It was the highest value among input for rice cultivation. And direct field emission was 3.23E-02 kg $kg^{-1}$ during rice cropping. The results of LCI analysis focussed on greenhouse gas (GHG) was showed that carbon footprint was 8.70E-01 kg $CO_2$-eq. $kg^{-1}$ rice. Especially for 80% of $CO_2$ in the GHG and 7.02E-01 kg of its $CO_2$-eq. $kg^{-1}$ rice. Of the GHG emission $CH_4$, and $N_2O$ were estimated to be 13% and 5%, respectively. With LCIA (Life Cycle Impact Assessment) for rice cultivation system, it was observed that fertilizer process might be contributed to approximately 80% of GWP (global warming potential).