• 한국철도학회논문집
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• 제13권4호
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• pp.447-454
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• 2010

레일 피로 열화손상유형들은 크게 레일표면에서 발생하는 결함들과 레일내부에서 진전되어 발생하는 결함들로 구분되어질 수 있다. 본 연구에서는 국내에서 연간 누적통과톤수가 가장 많은 도시철도의 운행조건을 고려하여 현장측정을 통해 레일표면 요철성장률을 분석하였으며, 연마 후 누적통과톤수에 따른 시험편을 현장에서 발췌하여 현미경을 이용한 조직검사, 화학성분검사, 마이크로 비커스 경도시험을 수행하였다. 시험결과 신품레일의 경우 유효탈탄층 제거를 위해 약 0.3mm의 초기연마를 시행해야하며, 예방연마의 경우 전구간을 일괄적으로 연마할 경우와 특정 구간별로 구분하여 연마할 경우에 대하여 2가지 방안을 제시하여 레일표면에서 발생하는 RCF결함을 예방하거나 제거할 수 있도록 제시하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.333-347
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• 2013

The present study numerically models the interaction between a regular wave and the roll motion of a rectangular floating structure. In order to simulate two-dimensional incompressible viscous two-phase flow in a numerical wave tank with the rectangular floating structure, the present study used the volume of fluid method based on the finite volume method. The sliding mesh technique is adopted to handle the motion of the rectangular floating structure induced by fluid-structure interaction. The effect of the wave period on the flow, roll motion and forces acting on the structure is examined by considering three different wave periods. The time variations of the wave height and the roll motion of the rectangular structure are in good agreement with experimental results for all wave periods. The present response amplitude operator is in good agreement with experimental results with the linear potential theory. The present numerical results effectively represent the entire process of vortex generation and evolution described by the experimental results. The longer wave period showed a different mechanism of the vortex evolution near each bottom corner of the structure compared to cases of shorter wave periods. In addition, the x-directional and z-directional forces acting on the structure are analyzed.

• 한국항만경제학회지
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• 제38권2호
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• pp.49-67
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• 2022

본 연구는 Diebold and Yilmaz (2012, 2014, 2016)의 분석방법을 적용하여 2007년 7월 19일부터 2022년 3월 31일까지 해상운임지수(BDI, BDTI, BCTI)에너지(원유, 천연가스, 석탄), 곡물(대두, 옥수수, 밀)을 대상으로 연계성을 분석하였다. 본 논문의 주요 분석결과는 다음과 같다. 첫째, 네트워크 분석 결과에 따르면 전체 분석기간의 경우 총 연계성은 20.43%로 측정되어, 해상운임지수와 상품가격 사이에 상호 연관성이 낮은 것으로 나타났다. 또한, 방향 연계성 결과를 살펴보면, 영향력이 가장 큰 변수는 옥수수로 나타났으며, 그 반대로 BDI가 가장 낮은 변수로 나타났다. 마지막으로 시기별로 구분하였을 때, COVID-19 기간에만 BCTI가 주도적인 역할을 하는 것으로 나타났다. 둘째, 표본이동분석결과에 따르면, 총 연계성이 금융위기, 무역전쟁, COVID-19 등과 같이 경제 상황의 변화와 특정 사건이 발생할 때 서로 간의 상호 연관성이 높은 것으로 나타났다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.63-66
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• 1996

Cold rolling mill process in steel works uses stands of rolls to flatten a strip to a desired thichness. At Pohang Iron and Steel Company (POSCO) in Pohang, Korea, precalculation determines the mill settings before a strip actually enters the mill and is done by an outdated mathematical model. A corrective neural network model is proposed to improve the accuracy of the roll force prediction. Additional variables to be fed to the network include the chemical composition of the coil, its coiling temperature and the aggregated amount of processed strips of each roll. The network was trained using a standard backpropagation with 2,277 process data collected form POSCO from March 1995, then was tested on the unseen 200 data from the same period. The combined model reduced the prediction error by 55.4% on average.

• 한국생산제조학회지
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• 제24권6호
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• pp.653-659
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• 2015

The aim of this study is to develop a technique for the accelerated life test of the capacitor in a propulsion control device of a traction inverter used for a high-speed train. Using this technique, the accelerated life test can possibly estimate the life cycle of a capacitor under various temperature conditions and irregularly applied voltage. The accelerated life test is conducted for the capacitor of the traction inverter. The common proceedings of this test are selection of failure mechanism, determination of accelerated stress, range determination of the accelerated stress, determination of the test condition, and distribution and determination of the sample. From this result, the continuous applied voltage was not considered for the acceleration factors anymore. Therefore, the final result having an acceleration factor of 9.4 (= 13,626/1,445) was observed. Furthermore, the life-shortening acceleration effect for the irregular applied voltage condition can be applied to various situations.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.306-312
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• 2005

Gates for the purpose of drainage are classified following the types of structure as: Radial Gate, Sluice Gate, Rolling Gate, Drum Gate. In many cases of the reclamation project the sluice type of gates are applied. Different from this general trend, however the radial type of gate was adopted in the Saemangeum project. In this case the discharge coefficients which are used for the sluice type of gate was applied. To estimate the correct amount of discharge which will be evacuated through the gates, therefore the proper discharge coefficients should be estimated before the operation of the gates. The discharge coefficients were estimated through the physical hydraulic modeling, and we got the results as: $0.72{\sim}0.84$ for the submerged condition on the both sides of upstream and downstream, $0.62{\sim}0.83$ for the free surface condition on the downtream side only, and $1.04{\sim}1.12$ for the free surface condition on the both sides of upstream and downstream. The discharge coefficients obtained from the experiments are greater than those of the sluice gates in the design criteria. From the results of the study we may expect that in the Saemangeum project the radial gates could evacuate larger amount of discharge than the originally designed discharge, so that we may sure that the Saemangeum gates have enough capability to control the evacuation of water not only in the usual period but also in the flooding season.

• 패션비즈니스
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• 제17권5호
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• pp.31-44
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• 2013

This study is aimed to examine the wearing, the clothing satisfaction and the actual purchase conditions of dance sportswear for females in their 20s~50s in order to provide a basic resource for the development of motion functionality and emotionally suitable dance sportswear. As a result, females in their 50s are considered with higher percentages of participation and more than half of them participated in the Latin American sports dance. As for the frequency of activities per week, 1~2 times per week is the largest portion with the main purpose of health and diet for all age levels. Participants with more than 3 years of experience have more proper clothing as compared with those less than 1 year of experience. The most inconvenient point is the rolling up of the upper clothes in the case for two pieces of clothing. The purchase frequency of dance sportswear is once or twice per year which shows no differences for all age levels and the repurchase period is considered to be long. As for price, items less than 50,000 won hold the highest portion which meant that they preferred low priced clothing. When they purchase dance sportswear, more than 80% of the participants consider design and materials as the most important factors.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1458-1465
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• 2008

With 34 years of accumulated operating experience, Seoul Metro has launched a project aimed at exporting second-hand trains(used EMU cars) to Vietnam while seeking measures for diversifying its business such as the construction of the metropolitan railways both at home and abroad, and operating business as a way of fiscal consolidation and management improvement. Therefore, Seoul Metro has moved ahead with this plan considering that there's no legal constraints on durable period of rolling stocks in advanced countries where the vehicles have been used for 35 years or longer than 40 years through renovation such as safety inspection and comprehensive maintenance program, and the railway systems for the replacement are expected to reach 838 cars by 2015 with growth of 100 cars a year. Seoul Metro strives to create value for boosting revenues and recycling resources by sending used EMUs to Vietnam. Seoul Metro will also provide under-developed countries with cars at a low price as well as share the accumulated railway technical know-how so that it can promote the national image and obtain the pre-emptive effect of metro railways in Vietnam.

• 한국해양공학회지
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• 제24권3호
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• pp.64-71
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• 2010

This paper summarizes the development of an ART control system panel with a touch screen and sensors to measure the roll and roll rate of ships. The control system hardware consists of two micro-processors, analog and digital I/O circuits, various relay circuits, etc. Sensor fusion and moving cross algorithms are implemented to accurately estimate the roll angle and roll period. In addition, the control system adopts a fault detection algorithm to inform users of ART system faults. A touch screen in the control panel can display the ART system states and faults. The performance of the developed system was verified on real sea trials.

• The Journal of Asian Finance, Economics and Business
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• 제9권5호
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• pp.19-27
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• 2022

The size of the government is one of the most fundamental debates of open economies. In any economy, government plays an important role, but a pertinent level of economic prosperity has never been obtained in history without government. Therefore, the objective of this paper investigates the association of government size, economic volatility, and institutional quality for 182 economies from the time period 1996-2016 is collected from the World Bank database. GE is defined as the General government's final consumption expenditure. Health expenditure is represented by HE. Government expenditure on education is denoted by EDUEXP. The economic volatility is measured by the rolling standard deviation of GDP per capita growth rate, Population growth, Trade openness, GINI represented Gini index which measures the degree to which the income distributed or consumption expenses among citizens deviates from a perfectly equal distribution. The results proposed that economic volatility has a significant effect on government size and institutional qualities. Moreover, the paper extends the investigation by finding the link between economic volatility with government health and education expenditure separately. The policy implication drawn from this analysis is that controlling economic volatility may reduce the size of government and also significantly affect health and education expenditures.