• KDI Journal of Economic Policy
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• v.36 no.4
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• pp.135-169
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• 2014

This study empirically analyzes changes in production patterns of farmers by agricultural disaster insurance. The aim of this project is to achieve stability of farm management by paying insurance in case of a natural disaster. However, it causes farmers to change production patterns in the direction of increasing production, and leads the crop price to drop. This can be explained by producers' risk reduction through the disaster insurance. The empirical analysis is based on IV approach with using two stage least squares method. The first stage estimates by difference-in-differences methodology indicate that the production of insurable crops increases more about 80,000ton on average than that of non-insurable crops. In addition, to solve the endogeneity problem caused by general supply and demand model, I use the first stage estimates and find that the price index of the crops drops about 2.3% according to the production increase by 10,000ton. The credibility of these results is also attained by various robustness checks. These findings suggest that it is necessary for government to analyze the whole economy which consists of producer and consumer welfare when it determines the policy. Besides, it implies that it is essential to develop a new market to cope with the unintended effect.

• Korean Journal of Remote Sensing
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• v.34 no.3
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• pp.481-494
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• 2018

The accurate radiative transfer model simulation is essential for an accurate ozone profile retrieval using optimal estimation from backscattered ultraviolet (BUV) measurement. The input parameters of the radiative transfer model are the main factors that determine the model accuracy. In particular, meteorological parameters such as temperature and surface pressure have a direct effect on simulating radiation spectrum as a component for calculating ozone absorption cross section and Rayleigh scattering. Hence, a sensitivity of UV ozone profile retrievals to these parameters has been investigated using radiative transfer model. The surface pressure shows an average error within 100 hPa in the daily / monthly climatological data based on the numerical weather prediction model, and the calculated ozone retrieval error is less than 0.2 DU for each layer. On the other hand, the temperature shows an error of 1-7K depending on the observation station and altitude for the same daily / monthly climatological data, and the calculated ozone retrieval error is about 4 DU for each layer. These results can help to understand the obtained vertical ozone information from satellite. In addition, they are expected to be used effectively in selecting the meteorological input data and establishing the system design direction in the process of applying the algorithm to satellite operation.

• The Journal of Information Technology
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• v.3 no.2
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• pp.73-85
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• 2000

The efficient algorithms are suggested in this study for solving the multicommodity network flow problems applied to Communications Systems. These problems are typical NP-complete optimization problems that require integer solution and in which the computational complexity increases numerically in appropriate with the problem size. Although the suggested algorithms are not absolutely optimal, they are developed for computationally efficient and produce near-optimal and primal integral solutions. We supplement the traditional Lagrangian method with a price-directive decomposition. It proceeded as follows. First, A primal heuristic from which good initial feasible solutions can be obtained is developed. Second, the dual is initialized using marginal values from the primal heuristic. Generally, the Lagrangian optimization is conducted from a naive dual solution which is set as ${\lambda}=0$. The dual optimization converged very slowly because these values have sort of gaps from the optimum. Better dual solutions improve the primal solution, and better primal bounds improve the step size used by the dual optimization. Third, a limitation that the Lagrangian decomposition approach has Is dealt with. Because this method is dual based, the solution need not converge to the optimal solution in the multicommodity network problem. So as to adjust relaxed solution to a feasible one, we made efficient re-allocation heuristic. In addition, the computational performances of various versions of the developed algorithms are compared and evaluated. First, commercial LP software, LINGO 4.0 extended version for LINDO system is utilized for the purpose of implementation that is robust and efficient. Tested problem sets are generated randomly Numerical results on randomly generated examples demonstrate that our algorithm is near-optimal (< 2% from the optimum) and has a quite computational efficiency.

• Journal of Food Hygiene and Safety
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• v.14 no.3
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• pp.249-254
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• 1999

The present study was performed to investigate biodegradation rate of BPMC(2-sec-butylphenyl methyl carbamate) and chlorothalonil. In the biodegradation test of two pesticides by the modified river die-away method from June 17 to August 22, 1998, the biodegradation rate constants and half-life were determined in Nakdong(A) and Kumho River(B). Bio- degradation rate of BPMC was 27% in A sampling point, 40% in B sampling point after 7 days. Biodegradation rate constants and half-life of BPMC were 0.0460 and 15.1 days in A sampling point, 0.0749 and 9.3 days in B sampling point, respectively. Biodegradation rate of chlorothalonil was 100% in A and B sampling points after 7 days. Biodegradation rate constants and half-life of chlorothalonil were 0.1416 and 4.9 hours in A sampling point, 0.1803 and 3.8 hours in B sampling point, respectively. Biodegradation rate of chlorothalonil was faster than that of BPMC. Correlation analysis between biodegradation rate constants of pesticides and water quality(DO, BOD, SS, ABS, $NH_3-N\;and\;NO_3-N$) showed significant correlation with BOD, SS and $NH_3-N$. Furthermore, regression analysis with BOD, SS and $NH_3-N$ as independent variable and biodegradation rate constant as independent variable showed a significant linear equation. These results suggested that BPMC and chlorothalonil were mainly degraded by biodegradation, and the difference in biodegradation of two pesticides was due to difference of water quality.

• Journal of the Korean Data and Information Science Society
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• v.26 no.2
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• pp.355-365
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• 2015

As the global climate has dramatically changed over the past decades, there has been active research on evaluating its effects on food security, which has been recognized as one of the most important issues in the field. In this study, we analyzed the impact of the climate change on the Korean agriculture using meta-analysis methods. Especially, our research focus is on estimating the effect of CO2 concentration and two adaptations (planting-date and cultivar adjustments)on rice that accounts for a larger proportion of the Korean domestic agriculture. Unlike traditional general meta-analysis methods that use summary statistics of effects of interest, meta analysis specific to the agriculture literature was conducted by integrating the data on rice yield that were generated under various CO2 emission scenarios and general circulating models of the 6 collected individual studies. As a modeling approach, the rice yield change ratio was set as the dependent variable and the main and interaction effects of CO2 concentration and adaptation were considered as independent variables in a regression model, As a result, CO2 is estimated to have opposite effects on rice yield depending on whether any of the two adaptations is applied or not; decreasing effect without adaptation and increasing effect with adaptation. In addition, it turns out that the cultivar adjustment has a higher increasing effect on rice yield than the planting-date adjustment. The results of the study are expected to be used as basic quantitative data for establishing responsive polices to the future climate changes.

• Journal of Korean Society of Forest Science
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• v.96 no.4
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• pp.387-392
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• 2007

Characteristics of needle morphology and anatomy were examined in 14 populations of Abies nephrolepis (Trautv.) Maxim. and A. koreana Wilson. Additionally we studied the classification index to distinguish between the species by the method of discriminant analysis. Characteristics of needle for A. nephrolepis could be distinguished from those for A. koreana by flatten arrangement, thin and long length for needle form, many stomata row, and marginal position of resin duct Nested ANOVA showed that there were statistically significant differences among populations as well as among individuals within populations in all 9 needle traits. For the needle indices such as needle thickness, number of stomata row, and the distance between resin duct and vascular for both species, variance components among populations were larger than those among individuals within populations. The characteristics that contributed most to the separation of A. nephrolepis and A. koreana according to the discriminant analysis using stepdisc procedures were needle index and thickness of needle, needle arrangement index, distance between resin duct and vascular, and number of stomata row.

• Journal of Convergence Society for SMB
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• v.3 no.2
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• pp.1-8
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• 2013

This study examine the relation between small and medium firm's stability and tax avoidance. We use some financial data of small and medium IT firms in KOSDAQ during 2001 to 2009. Following previous research(Desai and Dhamapala 2006), we estimate corporate tax avoidance. And we use quick ratio and current ratio as a short-term stability and equity ratio as a long-term stability. Empirical results follows as. First, It was not significant statistically between short-term stability and corporate tax avoidance. Second, it was significant statistically between the long-term stability and corporate. As corporate tax avoidance increases, the long-term stability(equity ratio) was low. Our analysis provides the empirical evidence between long-term stability and tax avoidance. It offers implications of corporate tax avoidance to small and medium IT firms in KOSDAQ. But this results is difficult generalization because of sample limits.

• Journal of Korea Port Economic Association
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• v.29 no.3
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• pp.159-174
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• 2013

This paper mainly deals with the appropriation of ship voyage allocation, using a heuristic regression model, in order to reduce total costs incurred in port, yard and at sea under the specific port condition. Because of different behavior of costs incurred in port, yard and at sea, an effort to minimize these costs by adjusting the number of voyages for three ship classes(50,000, 100,000, and 150,000-ton) should be made. For instance, if the port managers attempt to reduce the sea transport cost by increasing the annual allocated number of ship voyages classed 150,000-ton for economies of scale, they have no choice but to suffer a significant increase in queueing cost due to port congestion. To put it differently, there are trade-off relationships among the costs incurred in port, yard, and at sea. We utilized a computer simulation result to perform a couple of regression analyses in order to figure out the appropriate range of allocated number of voyages of each ship class using a heuristic approach. The detailed analytical results will be shown at the main paper. We also suggested a net present value(NPV) model to make a proper investment decision for an additional berth of 200,000-ton class that alleviates port congestion and reduces transport cost incurred both in port and at sea.

• Journal of The Korean Dental Society of Anesthesiology
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• v.11 no.2
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• pp.141-145
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• 2011

배경: 협조가 불가능하거나 진정법 하 치과치료가 여의치 않을 경우 전신마취 하 치료를 계획하게 된다. 하지만 전신마취 하 치료시 기관내 삽관이 여의치 않은 경우를 종종 경험하게 된다. 이와같은 경우 기관지경을 이용한 기관내 삽관을 시행한다. 기관지 내시경을 환자의 성문에 근접하게 전진시킬 경우 기관지 내시경 하 시야확보가 용이한 점을 감안 시 비공 - 성대간 거리를 예측하는 것은 매우 유용할 것으로 생각된다. 또한 비공 - 성대간 거리를 추정하게 되면 맹목적 비강내 기관내 삽관을 하는데도 도움이 된다. 방법: 본 연구는 전신마취하 치과치료가 예정되어 있는 62명의 소아환자들을 대상으로 하여 신체변수와 비공 - 성대거리와의 관계를 확인해보고자 하였다. 선형회귀분석을 시행하여 다음과 같은 결론을 도출하였다. 결과: 소아환자들에 있어 비공 - 성대간 거리는 환아의 신장, 체중, 연령 등과 상관관계를 나타내었다. 비공 - 성대간 거리와 상관관계를 보인 변수들 중 에서 신장과의 상관계수가 가장 높았다. 선형회귀분석을 통해 비공 - 성대간 거리를 예측하는 다음과 같은 회귀식을 구하였다. 비공 - 성대간 거리 = (4.8 + 신장(cm)) ${\times}$ 0.07 고찰: 본 연구에서 구해진 회귀식을 이용하여 기도유지가 어려운 소아의 기도유지 하는데 큰 도움이 될 것으로 생각된다.

• Journal of Korea Port Economic Association
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• v.38 no.3
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• pp.29-51
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• 2022

The International Maritime Organization (IMO) designated the Emission Control Area (ECA) in Northern Europe to reduce the NOx and SOx emissions from ships in the coastal areas. This study used Network slack-based measure (SBM) Data Envelopment Model (DEM) and Bootstrop Truncated Regression (BTR) model to analyze the ECA's impact on ferry companies' financial performances based on the financial data from eight ferry carriers in Northern Europe, the Mediterranean and North America from 2004 to 2017. To alleviate the problem of arbitrary variable selection in DEA, the variable selection criteria proposed by Dyson et al. (2001) were applied; the size of the company was considered through the Network SBM DEA model; and the company's profit-generating process was divided into stages to measure financial performance in more detail. In addition, the BTR model was applied to derive results that minimize the bias of the data. The study found that ECA regulations did not always negatively affect the shipping companies' financial performance. Rather, a steady increase in efficiency was observed for Northern European ferry companies which were subject to the strongest regulations. For North American ferry companies, government subsidies were found to have a significant impact on efficiency, and relatively small impact on efficiency due to the ECA and oil prices. For the Mediterranean ferry companies, efficiency values have decreased since the implementation of ECA regulation despite the lowest level of regulation in the region.