• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2600-2608
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• 2011

The dynamic stability of railway vehicle has been one of the important issues in railway safety. The dynamic simulator has been used in the study about the dynamic stability of railway vehicle and wheel/rail interface. Especially, a small scale simulator has been widely used in the fundamental study in the laboratory instead of full scale roller rig which is not cost effective and inconvenient to achieve diverse design parameters. But the technique for the design of the small scale simulator for the fundamental study about the dynamic characteristics of the wheel-rail system and the bogie system has not been well developed in Korea. Therefore, the research about the development of the small scale simulator and the bogie has been conducted. As this paper, To predict the dynamic behavior of railway vehicle, we studied running stability test of 1/5 scaled bogie that similarity laws is applied using small scale derailment simulator. For the operation of the small scale derailment simulator, it is required to investigate the performance and characteristics of the system. This could be achieved by a comparative study between an analysis and an experiment. This paper presented the analytical model which could be used for verifying of the test results and understanding of the physical behavior of the dynamic system comprising the small scale bogie and the simulator.

• 동력기계공학회지
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• 제8권2호
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• pp.5-11
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• 2004

The failure frequency of the Emergency Diesel Generator(EDG) at Nuclear Power Plants(NPPs) is not so much lower than that of the Marine engines, whereas the running hours of the diesel engine at NPPs is much less than those of the engines for commercial service. The primary factor results from the severe surveillance test requirements such as fast start, large number of starting test, fast load-run, high load running, etc. The other factor comes from the excessive maintenance based on the engine maker's instruction manual that did not incorporate the peculiar characteristics of the diesel engines at NPPs. In this paper, the present preventive maintenance program on the basis of the Pielstick diesel engines was reviewed for the purpose of securing the reliability of the emergency diesel generator at NPPs and the ways for its improvement were presented by referring to the overseas cases for their applications.

• 대한조선학회논문집
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• 제52권6호
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• pp.494-500
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• 2015

It has been reported that a ship sailing in shallow water possesses better straight-line stability due to the change of fluid flow around the ship. This tendency affects manoeuvring characteristics of the ship. To investigate this phenomenon, indoor free running model test(FRMT) on KVLCC2 was carried out in three water depth conditions(H/T = 1.2, 1.5 & 2.0). Turning circle tests(± 35° ) and zigzag tests(± 20° /5° and ± 20° /10° ) were conducted with newly developed indoor FRMT system, and the manoeuvring results were compared with test results from other institutes. As the water depth decreased, the yaw rate of the ship decreased, and the distances of circular trajectories at the same heading angle increased in the turning circle tests. The first overshoot angles of the zigzag tests decreased. From both tests, the time for course change increased as the water depth decreased. These manoeuvring characteristics show that KVLCC2 in shallow water becomes more stable in terms of straight-line stability.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.557-570
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• 2000

It is necessary to perform a study on the interrace between a G7 pantograph and a KTX catenary system prior to G7 on-line tests in the Korea High Speed Test Track in order to predict how high current collection quality can be obtained during the on-line tests and check if safety problems shall be caused b)Y the tests or not. According to the simulation results, current collection quality of the G7 pantograph at 350km/h is lower than that of a GPU pantograph at 300km/h, but the contact wire uplifts and average contact forces are within the safe-zone. In addition, the ratio of running speed (350km/h) to safe running. Therefore, the G7 on-line tests at 350km/h in the Korea High Speed Test Track is expected not to cause the safety problem.

• 대한토목학회논문집
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• 제8권2호
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• pp.41-50
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• 1988

본(本) 논문(論文)에서는, 국내(國內)에 가설(架設)되어 있는 30개(個) 교량(橋梁)들에 대한 정동적시험(靜動的試驗)으로부터 얻어진 동적특성(動的特性)에 관한 기본자료(基本資料)를 정리(整理)하여, 교량진동(橋梁振動)의 주(主)된 원인이 되는 사항에 대해 살펴보았다. 시험(試驗)은 교량(橋梁)의 중앙하부(中央下部)에 변위측정기(變位測定機)와 변형(變形)게이지를 설치(設置)한 뒤 단일만재차량(單一滿載車輛)을 주행(走行)시켜 실시(實施)하였으며, 이때 얻어지는 동적(動的)데이타는 강제진동(强制振動)과 자유진동(自由振動)으로 구분(區分)하여 시간영역해석(時間領域解析)을 통하여 분석(分析), 교량(橋梁)의 진동특성(振動特性)을 연구(硏究)하였다. 여기서 얻어진 자료(資料)는 국내(國內)에서 초보적 단계에 있는 도로교(道路橋)의 진동거동예측(振動擧動豫測)에 귀중한 자료(資料)를 제시할 것이다.

• 패션비즈니스
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• 제6권2호
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• pp.93-109
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• 2002

This study measured the accompanying rating, recall, and recognition of advertisements, which were run with different methods of spacing in the magazines. To achieve this objective the study chose a qualitative research and performed a reliable test. After the survey was completed, the advertisement recall test was performed. In addition, two days later, the recognition test was performed to the survey respondents and data on the memory of respondents on the advertisements was collected. As a result, rating, recall and recognition of the advertisement's were significantly different by the various forms of advertisements in the magazines. In the advertisement rating and recall by the advertisement printing forms, rather than the regular printing form of running the target advertisement for two pages in a role and the irregular printing form, the continuous printing form was confirmed to be more effective. In addition to that, in the form of running continuous target advertisements for six pages in a role, the effects of the advertisements recall and the recognition were increased. A continuous printing form had higher outcomes on the rating, recall and recognition of advertisements. Therefore, conclusively, it gave more effects in increasing the memory of the advertisement for the consumers. The conclusion of the study provided suggestions on the forms of advertisement to stimulate the memory of consumers in the magazine advertisement.

• Tribology and Lubricants
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• 제21권3호
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• pp.114-121
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• 2005

As fuel cell system is environmental friendly generator, its performance depends on its air supply system. Because, fuel cell stack generates electrical energy by electron and the electron is generated by reacting between air and hydrogen. So, more and more compressed air is supplied, more and more the energy can be obtained. In this study, turbo-expander supported by air foil bearing is introduced as the air supply system used by fuel cell systems. The turbo-expander is a turbo machine which operates at high speed, so air foil bearings suit its purpose for the bearing elements. Analysis for confirming the stability and endurance is conducted. Based on FDM and Newton-Raphson method, characteristics of air foil bearing, dynamic coefficients, pressure field and load capacity, are obtained. Using the characteristics of air foil bearing, the rotordynamic analysis is performed by finite element method. The analysis (stability analysis and critical speed map) shows that turbo-expander is stability at running speed. After the analysis, the test process and results are presented. The goals of test are running up to 90,000 RPM, flow rate of 150 $m^3/h$ and pressure ratio of 1.15. The test results show that the aerodynamic performance and stability of turbo-expander are satisfied to the primary goals.

• The Journal of Asian Finance, Economics and Business
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• 제8권1호
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• pp.23-36
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• 2021

The study explores the nexus between foreign direct investment (FDI), financial innovation, and exchange rate volatility in selected South Asian countries for 1980 to 2017. The study applies the unit root test, Autoregressive Distributed Lagged, nonlinear ARDL, and causality test following Toda-Yamamoto. Unit root tests ascertain that variables are integrated in a mixed order; few variables are stationary at a level and few after the first difference. Empirical model estimation with ARDL, Long-run cointegration revealed with the tests of FPSS, WPSS, and tBDM by rejecting the null hypothesis of "no cointegration." This finding suggests that, in the long-run financial innovation, FDI inflows, and exchange rate volatility move together. Moreover, study findings established adverse effects running from FDI inflows and financial innovation to exchange rate volatility in the long run. These findings suggest that continual FDI inflows and innovativeness in the financial system assist in lessening the volatility in the foreign exchange market. Furthermore, nonlinear ARDL confirms the presence of asymmetric cointegration in the model. The standard Wald test established asymmetric effects running from FDI inflows and financial innovation to exchange rate volatility, both in the long and short run. Directional causality unveils feedback hypothesis holds for explaining causality between FDI, financial innovation, and exchange rate volatility.

• 대한조선학회논문집
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• 제58권6호
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• pp.415-423
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• 2021

There have been many experimental studies on the manoeuvrability of KRISO Container Ship (KCS). However, the scale ratio of the model ship and the test procedure for each institute are slightly different, so direct comparison for the data is technically difficult to perform. This paper presents the manoeuvrability of the ship with different scale ratios: 1/65.8, 1/42.0, and 1/31.6 in model scale. KRISO conducted Free Running Model Tests (FRMT): 35° turning circle tests and 20/20(10/10) zigzag manoeuvring tests. The test results indicated that advance and tactical diameter in turning circle tests were similar, and overshoot angles in two zigzag manoeuvring tests increased as the model ship size increased. In addition, a basic concept for the FRMT method with an auxiliary X-thrust device was proposed so that the scale effect could be considered in model ship tests.

• 무역학회지
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• 제45권3호
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• pp.119-132
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• 2020

In this paper we explore the two analyses to know the urbanization effect on trade. First, the granger causality test to examine the relationship between trade and urbanization. The Granger causality test is a statistical hypothesis test for determining whether one time series is useful for forecasting another. The results indicated that the existence of a bidirectional causality running from trade to urbanization when six lags were applied. When eight lags were applied, we found unidirectional causality running from urbanization to trade. Second, gravity models were used to investigate the urbanization effect on trade. The production cost and specification are affected by the economies of scale, and the economies of scale increased as the greater geographically agglomeration. However, the gravity model to explain the bilateral trade flows ignores the urbanization variables. Therefore we added the urbanization variable represented as the geographically agglomeration into gravity model. The results show that the degree of urbanization of both countries has statistically positive effect on trade (export and import) and the bigger coefficients of trade partner's urbanization. The reason is that the trade share of industrial supplies, intermediate goods and capital goods is much higher than finished consumer goods. The urbanization is more important the improved the efficiency of production than demand market.