• Journal of Korea Port Economic Association
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• v.23 no.4
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• pp.228-243
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• 2007

This study porvides an empirical overview of the import patterns of Incheon port using an Engle-Granger cointegration technique and Johansen's multivariate cointegraion methodology test to check the stationarity of the model. The empirical results show that the import in Incheon port related to the economic variables. This paper also applies rolling regression to our model, indicating that import are endogeneous to the economic variable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1471-1477
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• 2014

This paper addresses the development on supply-demand outlook model of Jeju winter radish and introduces a projection of supply-demand and market prices during 2014-2018 using the model. The supply-demand outlook model is specified as a partial equilibrium model of Jeju winter radish. Each equation in the model is estimated by using the econometric techniques. A review of the model stability is also carried out by the references based on RMSPE, MAPE, and Theil's inequality coefficients. According to the reference of RMAPE, the error rates of the forecasting values of the cultivation ares, production quantity, and consumption quantity show less than 4% and the error rate of market price is below 10%. The cultivation area and production quantity are projected respectively to be increased to 6,650ha and 433,310MT in 2018.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.846-853
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• 2004

This paper introduces implementation of a traffic distributed processing system on the Web Sever Networking. The study used two software packages （Packet Capture and Round-Robin Test Package） to check packet quantity from Virtual Network Structure (data generator, virtual server, Serve. 1, 2, 3), and could find out traffic distribution toward Server 1, 2, and 3. The functions of implemented Round-Robin Load Balancing Monitoring System include Round-Robin testing, system monitoring, and graphical indication of data transmission/packet quantity (figures ＆ diagram). As the result of the study shows, Round-Robin Algorithm ensured definite traffic distribution, unless incoming data loads differ much. Although error levels were high in some cases, they were eventually alleviated by repeated tests for a long period of time.

• The Korean Journal of Applied Statistics
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• v.36 no.5
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• pp.473-488
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• 2023

Gangwon-do is one of Korea's most popular tourist destinations, with varying tourism demands and trends across its subregions. It is crucial to identify the characteristics of tourism in each area and compare the tourism patterns over time to devise policies that revitalize tourism in each local government and promote balanced development across regions. In this paper, we classify the regions in Gangwon-do based on tourism data from the last four years and analyze the tourism pattern of each region using the non-Euclidean additive model proposed by Jeon et al. (2021). The model incorporates the proportions of visitors by age groups and the proportions of navigation searches by destination types as two covariates, and the proportions of tourism expenditure types as a response variable. We estimate the model using the smooth-backfitting method and coordinate-wise bandwidth selection. The results are visualized in ternary plots, and changes in tourism patterns over time are analyzed by comparing the ratios of prediction errors to fitting errors.

• Environmental and Resource Economics Review
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• v.16 no.2
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• pp.213-237
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• 2007

Discussions on regionalization of the world crude oil markets have provided important implications for the establishment of national energy policies. In particular, due to arbitrage trading, if these markets are regionalized, Korea who imports approximately 80% of the annual oil consumption from a single region may be faced with a crucial problem. Therefore, in this study, we analyzed regionalization of the world crude oil markets using causality analysis as well as cointegration method to consider temporal relationship and time lags. To analyze regionalization, we chose Dubai price for the Middle East market, Brent for the European, WTI for the U.S., and Tapis for the East Asian. For the case that long-run equilibrium existed between market prices, we used vector error correction model to analyze causal relationship, and for the case that equilibrium did not exist, we used Hsiao (1981)'s framework that can consider asymmetric time lags in the model for causality analysis. By the results of cointegration analysis, there did not exist long-run equilibrium among Dubai price and the other prices. However, we found the causal relationship among Dubai price and the other prices with one to four weeks time lags. Therefore, in effect, we could conclude that the world crude oil markets are unified supporting Adelman (1984)'s hypothesis.

• Korea Trade Review
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• v.43 no.4
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• pp.155-175
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• 2018

This study estimates the technical efficiency and total factor productivity(TFP) of and analyzes the relationship between TFP and exports for Korean manufacturing companies from 2000 to 2016. Specially, TFP is decomposed into Technical Change(TC), Technical Efficiency Change (TEC), and Sale Effect(SE), and compared between large and small enterprises. First, in the case of technical efficiency, the Korean economy has been very vulnerable to external shocks, such as the sharp decline following the 2008 financial crisis. The efficiency of the electronics, automobile, and machinery sectors is low and needs to be improved. In addition, the technological efficiency of large enterprises is higher than that of SMEs in most manufacturing sub-sectors except for non-ferrous metals. In the case of TFP, most changes are due to TC, and the effective combination of labor, capital and the effect of scale have little effect, suggesting that improvement of internal structure is urgent. In addition, volatility due to the impact of the financial crisis in 2008 was much larger in SMEs than in large companies, so external economic impacts are more greater for SMEs than large enterprises. The relationship between TFP decomposition factors and exports shows that TC has a positive effect only on exports of SMEs. Therefore, in order to increase exports, in the case of SMEs, R&D support to promote technological development is needed. In the case of large companies, it is necessary to establish differentiated strategies for each export market, competitor company, and item to link efficiency and scale effect of exports.

• Journal of Korea Port Economic Association
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• v.39 no.2
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• pp.41-57
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• 2023

The drybulk shipping market has high freight rate volatility in the chartering market and various and complex factors affecting the market. In the unstable economic situation caused by the COVID-19 pandemic in 2020, the BDI plunged due to a decrease in trade volume, but turned from the end of 2020 and maintained a booming period until the end of 2022. The main reason for the market change is the decrease in the available fleet that can actually be operated for cargo transport due to port congestion by the COVID-19 pandemic, regardless of the fleet and trade volume volatility that have affected the drybulk shipping market in the past. A decrease in the actual usable fleet due to vessel waiting at port by congestion led to freight increase, and the freight increase in charting market led to an increase in second-hand ship and new-building ship price in long-term equilibrium relationship. In the past, the drybulk shipping market was determined by the volatility of fleet and trade volume. but, in the future, available fleet volume volatility by pandemics, environmental regulations and climate will be the important factors affecting BDI. To response to the IMO carbon emission reduction in 2023, it is expected that ship speed will be slowed down and more ships are expected to be needed to transport the same trade volume. This slowdown is expected to have an impact on drybulk shipping market, such as a increase in freight and second-hand ship and new-building ship price due to a decrease in available fleet volume.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.11
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• pp.63-67
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• 1995

신체 자세균형의 안정도를 반영하는 압력중심(COP)을 계측하기 위해 정삼각형 모양의 평형판 시스템을 설계, 제작하였고 그 유용성을 평가하였다. 재질로는 강도와 가공성이 뛰어난 듀랄루민을 사용하였고 압력중심(COP)의 위치를 계측하는 힘센 서로는 공업용 로드셀 3개를 사용하였다. COP신호를 검출하는 전자회로를 제작하여 실험한 결과 평형판의 COP 위치측정 오차는 2% 미만이었다. 시스템의 임상응용가능성을 평가하기 위하여 정상인 10명과 이학적 평가가 정상인 환자 4명을 대상으로 임상실험을 수행하였다. 자세안정도를 반영할 척도로써 COP신호의 표준편차($SD_x,\;SD_y,\;SD_r$)를 설정하여 자세가 불안정해짐에 따라, 그리고 시각의 영향이 배제됨에 따라 이 값들이 증가하는 것을 관찰하였다. 또한 환자의 경우에는 정상인과 현저한 차이를 보였다. 즉, 본 평형판시스템이 자세안정도를 정량적이고 예민하게 계측할 수 있음을 확인하였고 임상적 실용성을 검증하였다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.1
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• pp.33-41
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• 2002

In this paper, we present a frequency weighted model reduction using LMIs for minimizing the H$\infty$ weighted model error compared with the methods of frequency weighted balanced truncation and frequency weighted Hankel norm approximation. The proposed algorithm, its form is equal to the sufficient condition of performance preserving controller approximation, is based on an iterative two-step LMI scheme induced from bound real lemma. So, it can be applied to the problem of the performance preserving controller approximation. The controller reduction is useful in a practical control design and ensures its easy implementation and high reliability The validity of the proposed algorithm is shown through numerical examples. Additionaly, we extend the proposed algorithm to performance preserving controller approximation by applying to the HIMAT(highly maneuverable aircraft technology) system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.347-352
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• 2009

Pneumatic system is widely applied to ground facility and launcher on-board system. The main requirements of pneumatic system is to meet pressure and flow requirements of gas consumers. For launcher related applications, different from other applications, very high flow is required which can leads to supply pressure drop against required setting pressure. The supply pressure decrease is closely related to regulator characteristics. In this paper, the characteristics of pneumatic regulator related to supply pressure decrease and the control methods for reducing the pressure offset are reviewed.