• KDI Journal of Economic Policy
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• v.27 no.2
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• pp.123-154
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• 2005

Using Korean household data, this paper examines how consumption of durable goods is determined. Previous studies report that the standard Permanent Income Hypothesis (PIH), while being broadly consistent with non-durable goods consumption, provides little explanation for durable goods consumption. In this paper, we consider the (S, s) model as an alternative to the standard PIH. The (S, s) model predicts that, because of fixed adjustment costs, consumers make no adjustment to the durable goods stock until deviation from the optimal level becomes large. When the adjustments are made, the durable goods stock attains the optimal level. In order to test this prediction, we examine the intra-temporal relationship between non-durable goods and durable goods consumption and intertemporal changes in durable goods consumption, using data from the Korean Household Panel Study. The results show that, while the standard PIH is rejected by the data, the (S, s) model is not.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.36-42
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• 2018

This paper considers the Marine Traffic Risk Assessment for fixed and moving targets, which threaten officers during a voyage. The Collision Risk Assessment Formula was calculated based on a dynamic ship domain considering the length, speed and maneuvering capability of a vessel. In particular, the Navigation Risk Assessment Model that is used to quantitatively index the effect of a ship's size, speed, etc. has been reviewed and improved using a hybrid combination of a vessel's dynamic area and the Collision Risk Assessment Formula. Accordingly, a new type of Marine Traffic Risk Assessment Model has been suggested giving consideration to the Speed Length Ratio, which was not sufficiently reflected in the existing Risk Assessment Model. The larger the Speed Length Ratio (dimensionless speed), the higher the CJ value. That is, the CJ value is presented well by the Speed Length Ratio. When the Speed Length Ratio is large, states ranging from [Caution], [Warning], [Dangerous] or [Very Dangerous] are presented from a greater distance than when the Speed Length Ratio is small. The results of this study, can be used for route and port development, including dangerous route avoidance, optimum route planning, breakwater width, bridge span, etc. as well as the development of costal navigation safety charts. This research is also applicable for the selection of optimum ship routing and the prevention of collisions for smart ships such as autonomous vessels.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.16-29
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• 1995

Choosing initial codevectors in the LBG algorithm controls the performance of a codebook, because it only guarantees a locally optimal codebook. In this paper, we propose the decision method of initial codevectors by a decision radius which takes for feature vectors DC, low frequency, medium frequency and high frequency terms generated by a DCT. The more the decision radius is increased in order to decide initial codevectors, the more the number of membership vectors and the standard deviation for distance among the initial codevectors are increased. To obtain improved performance for a codebook, the decision radius for DC term is required above 0.9 of the membership rate and those for low frequency, medium frequency and high frequency terms under 0.6 of it.

• Journal of Korea Port Economic Association
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• v.37 no.3
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• pp.75-91
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• 2021

Due to increased competition in supply side to reduce operational costs, port professionals have experienced extreme pressure, which demanded academicians to develop the model for efficient port operations from the industry perspective. Among many ports in the world, U.S. ports are our primary interest to analyze in our study for its high volume of cargoes transacted in the U.S. ports. We primarily employed DEA (Data Envelopment Analysis) technique to research the productivity of U.S. ports and applied the algorithm of double bootstrapped DEA proposed by Simar & Wilson (2007) to further investigate the driving forces of the performance of U.S. port operations. The external variables employed in our study comprise onDock Rail, Channel Depth, Location, Area, Acres, ForeignCargoRatio, and TEUChange, out of which onDock Rail, Acres, ForeignCargoRatio, and TEUChange were significant. In order to evaluate the effects of methodology selection, we conducted the same analysis applying the Censored model (Tobit) and contrasted the outcomes drawn from the two different techniques. Based on the findings from this work we proposed managerial implications and concluded.

• Journal of Navigation and Port Research
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• v.41 no.3
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• pp.137-148
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• 2017

Port service level is a metric of competitiveness among ports for the operating/managing bodies such as the terminal operation company (TOC), Port Authority, or the government, and is used as an important indicator for shipping companies and freight haulers when selecting a port. Considering the importance of metrics, we developed software to objectively define and manage six important service indicators exclusive to container and bulk terminals including: berth occupancy rate, ship's waiting ratio, berth throughput, number of berths, average number of vessels waiting, and average waiting time. We computed the six service indicators utilizing berth 1 through berth 5 in the container terminals and berth 1 through berth 4 in the bulk terminals. The software model allows easy computation of expected ship's waiting ratio over berth occupancy rate, berth throughput, counts of berth, average number of vessels waiting and average waiting time. Further, the software allows prediction of yearly throughput by utilizing a ship's waiting ratio and other productivity indicators and making calculations based on arrival patterns of ship traffic. As a result, a TOC is able to make strategic decisions on the trade-offs in the optimal operating level of the facility with better predictors of the service factors (ship's waiting ratio) and productivity factors (yearly throughput). Successful implementation of the software would attract more shipping companies and shippers and maximize TOC profits.

• Korean Journal of Food Science and Technology
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• v.43 no.6
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• pp.783-786
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• 2011

Various mushroom extracts were examined for their anti-Streptococcus mutans and anti-glucosyltransferase (GTase) activities. Mushrooms were extracted with chloroform, methanol, acetone, ethyl acetate, and distilled water. The chloroform, methanol, and ethyl acetate extracts showed higher antimicrobial activity than that of the others. The inhibitory effects of the chloroform, methanol, and ethyl acetate extracts of Lyopyllum ulmarium, which have high anti-microbial and GTase activities, on the growth of S. mutans were examined and the optimal ratio of solvents was also evaluated to investigate the influence of solvents using a simplex centroid design. The anti-cariogenic effects of the L. ulmarium extract on S. mutans was influenced by the solvent, and the optimum anti-cariogenic activity of the extract was obtained with the ratio of chloroform:methanol:ethyl acetate=1:1:1 (v/v/v). These results suggest that solvent selection is an important factor to extract anti-cariogenic materials effectively from mushrooms.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2855-2857
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• 2005

디지털 선박(Digital Ship)이란 항해의 안전과 효율적 운행을 위해 항해, 조정, 상태감시 등 선박운행에 대한 전반적인 내용들을 컴퓨터를 통해서 구현하고 위성통신을 통해서 육상에서도 제어할 수 있는 완전 자동화 및 네트워크화 된 시스템을 의미하며 궁극적으로 무인화된 선박을 지향한다. 또한 통한항해시스템이란 선박의 경제적이고 안전한 운항을 위해 전자해도와 레이더를 이용하여 선박의 항로를 계획하고 감시하며 최적 항로 분석, 충돌/좌초방지 및 자동항법시스템과 연계한 자동항해 기능을 수행한다. 본 논문은 디지털 선박을 위하여 항해정보시스템과 항해 장비 통합장치 및 통신서버를 기반으로 한 전자해도와 레이더, 자동항법장치(autopilot) 및 각종 항해센서의 다기능 표시장치의 기능과 인터페이스 방안을 제시하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.920-927
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• 1998

This paper presents a synthetic control algorithm that generates the rudder command angle to track the optimal route which is composed of straight-lines among way-points with keeping a required error limit. The control algorithm comprises three main lgorithms that is a course-keeping algorithm that eliminates the yaw angle difference between optimal route and current route a track-keeping algorithm that tracks the optimal route among way-points and a turning-control algorithm that includes the generation of optimal turning routes and control method. The effectiveness of the proposed control algorithm is assured through computer simulation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.34-36
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• 2013

부산항 및 부산신항 개발의 특징은 매립으로 인하여 가항수역은 협소화되는 반면에 선박은 대형화되면서 흘수가 증가함으로 인하여 점점 더 깊은 수심을 필요로 하게 되었다. 따라서 초대형선들은 출입항선 상호간의 간섭이 증가하고, 심흘수화로 인한 조종성능의 저하와 비상시 대응책의 한계를 드러내는 등의 문제점을 안고 있다. 또한 전반적인 선박 통항량의 증가는 거대형 컨테이너선이 부두전면에서 회두하거나 감속, 접근하는데 소요되는 시간에 따라서 항만의 효율성뿐만 아니라 주변수역의 안전에도 크게 영향을 미치고 있다. 따라서 본 연구에서는 항만의 안전과 효율성을 제고하기 위하여 초대형 선박의 조종특성과 주변 여건을 다각도로 고려한 최적의 표준 조선방법 및 응급조선을 2D베이스로 개발된 선박조종시뮬레이터를 이용하여 모색해 보고자 한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.12a
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• pp.237-241
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• 2001

본 논문에서는 TSK (Takagi-Sugeno-Kang) 형태의 퍼지모델을 유도하는데 있어서, 동적시스템의 비선형 미분방정식을 선형화시 off-equilibrium에서 발생할 수 있는 상수항을 배제하고, TSK 퍼지 모델의 전건부 소속함수들을 GA(Genetic Algorithm)을 이용하여 최적화한후 이를 퍼지를 이용하여 합성함으로써, 실제 동적시스템을 묘사하는 비선형 미분방정식에 최적 근사화된 TSK 퍼지 모델링기법을 제시한다.