• 수산해양기술연구
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• 제44권2호
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• pp.148-156
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• 2008

In this study it will be discussed how to solve the problem of discomfort from rolling motion on the fishing boats. Most discomfort is caused by the short cycle of rolling due to the light weight of the boats. The light weight is due to the FRP material which dries a boat. A way to improve the feeling of boarding by using fish hold was researched. The experiment was done on experimental fishing boat made by FRP in Jeju. An existing fish hold was designed and manufactured through the rolling test and that was used for a marine experiment. The rolling condition of the U-tank boat ideally designed was compared to that of an existing fishing boat using the same conditions. The experiments were carried out two times on the stop engine in the outward Sehwa fishing port, which the experimental data had analysed for effects of rolling reduction to compare the U - tank with the of exiting fish hold. The results were confirmed that the U-boat tank in the roll period and GoM were more safe than the existing fish hold and the average amplitude and significant of rolling angles were decreased relatively.

• 벤처창업연구
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• 제7권4호
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• pp.41-47
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• 2012

철도차량은 사용기간이 길고 철로 위를 달리기 때문에 마모, 진동이 심하여 다른 교통수단에 비해 정비비용이 많이 소요된다. 이에 따라 정비최적화는 매우 중요하다. 본 연구에서는 코레일에서 운용하고 있는 철도차량 정비현황을 분석해 보고 개선방안을 찾고자 하였다. 특히, 차량정비인력이 많이 소요되는 일상검수에 대해 가장 효율적인 정비 주기와 방법을 적용하고자 하였다. 철도차량은 컴퓨터시스템 적용으로 자가진단이 가능하고 과거에 비해 차량의 품질이 많이 향상되었으나, 현행 일상검수는 관례적으로 짧은 기간 시행해야 한다는 측면에서 현재 비효율적인 측면을 시급히 개선해야 함은 당연하다. 따라서 본 연구에서는 차량의 상태를 반영한 개선된 일상검수 주기를 적용하여 차량의 신뢰성 확보와 정비비용을 최소화하고자 한다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1642-1649
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• 2010

At present, KORAIL is in the middle of renovating. All steps exert great effort at cost reduction and a profit improvement. Especially to improve maintenance method and inspection period at the rolling-stock division lots of research is under progress. Daily inspection of rolling stocks is to operate the rolling stock normally. Daily inspection items are driving control device, coupling device, brake system, water system and air conditioning system, electrical system etc. Half of the maintenance manpower are inputted at daily inspection. Strengthens the quality and optimize the proportion of daily inspection are urgent problem. Daily inspection period extension aim is as follows. KTX from 3,500km to 5,000km, passenger car from 1st to 3,500km, new style electric locomotive from 2nd to 5,000km, the diesel locomotive is 2,800km from 1,200km. In this paper, the optimal daily inspection period and methods are considered including expected problem and counter measures.

• 대한조선학회논문집
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• 제40권1호
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• pp.1-7
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• 2003

The effect of the passive anti-rolling tanks(ART) decreases when the roll period of the vessel does not match the designed oscillating period of the fluid in the tank. In order to improve the effect of the passive ART, the damping plates are installed in the lower duct of the ART to adjust the oscillating period of the fluid. The effects of the damping plates on the oscillating period of the fluid and the changes of the stabilizing moments are examined through the series of bench tests. Acryl model tank larger than 1m breadth is made to minimize the viscous effect of the tank and the stabilizing moments of the tank are measured for various roll angles. Using the obtained tank damping coefficient, RAO(Response Amplitude Operator) value in the resonance range is computed and the stabilizing effect of a ART has been estimated.

• 대한조선학회논문집
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• 제52권2호
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• pp.135-142
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• 2015

The Anti-Rolling Tank(ART) has an advantage over the other roll stabilizing devices, when ship is staying and working at one site of sea. An important design point of ART is the tank tuning, that is, matching the tank natural period to the ship's roll natural period. Since the load condition and consequently the roll natural period of ship is to be changed widely, the natural period of ART also has to be changed widely. In case of the existing U-tube type ART with a single layer duct, the tank natural period can be changed in a relatively narrow range. This paper suggests a new U-tube type ART system using a double layer duct to enable wide change of ART natural period. Through the roll experiments performed in regular beam waves for a box-type model ship, it is shown that the double layer duct ART has about two times wider period range and a better reducing effect of roll magnitude than the single layer duct ART.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1627-1633
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• 2004

Safety and punctuality in the subway are considered as critical factors. This system is composed of many factors like signals, rails, electrical power sources, rolling stocks. The effective inspection should be carried out at all the times for the safety and punctuality. Purpose of the rolling stocks maintenance is to offer the optimum condition of vehicles, and minimize the maintenance expenses. This paper suggests appropriate maintenance period of rolling stocks to enhance the utility efficiency in SMSC.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.520-529
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• 2020

Experimental investigations were attempted to simultaneously observe the vapor behaviors and critical heat flux under static and rolling conditions. From visualization results, vapor initiated, grew, and detached individually in a vertical direction from the static heated surfaces (at 10, 20, and 30°). While under rolling motion, initiated vapor grew, and interacted with each other, resulting in forming a wider dry spot on the heated surface. Also, it was observed that the vapor drifted upward and stayed on the heated surface longer compared to under static condition. The faster the platform rolls, the longer the vapor stay on the heated surface, significantly decreasing the CHF. On the other hand, as the platform rolls slower (at high rolling period), CHF increases. CHF was decreased with increasing maximum rolling amplitude and inclination angle under both conditions (static and rolling). CHF under rolling conditions was noticed to be lower than under static condition except at maximum rolling amplitude of 10°. The bubble departure frequency at a maximum rolling amplitude of 10° was the highest among all of rolling amplitudes, thereby enhancing the CHF. These results indicate that rolling motion significantly affects vapor behaviors and CHF.

• 수산해양기술연구
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• 제45권4호
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• pp.267-275
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• 2009

According to the recent statistics of marine casualties in Korea, fishing boats are more likely to be ended in the casualties, and small fishing boats especially cause much more accidents in sinking and capsizing than any other big vessels. These casualties were mainly produced from the ignorance on the lack of own ship stability. From this view, this study aims to analyze the characteristics of stability on the crab trap fishing boat receiving transverse wave by means of carrying out the water tank test. The rolling angle of the model ship was affected largely with the displacement and the wave period of it, and the trends were shown that the magnitude of the angle was proportional to the displacement, but inversely to the wave period. And the wave height had effect on the rolling angle just in the specific range of the wave period. The force of steady wind didn't have influence on the rolling variation significantly.

• Earthquakes and Structures
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• 제11권1호
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• pp.25-43
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• 2016

The uneven distribution of rolling friction coefficient may lead to great uncertainty in the structural seismic isolation performance. This paper attempts to improve the isolation performance of a spring-damper-rolling isolation system by artificially making the uneven friction distribution to be concave. The rolling friction coefficient gradually increases when the isolator rolls away from the original position during an earthquake. After the spring-damper-rolling isolation system under different ground motions was calculated by a numerical analysis method, the system obtained more regular results than that of random uneven friction distributions. Results shows that the concave friction distribution can not only dissipate the earthquake energy, but also change the structural natural period. These functions improve the seismic isolation efficiency of the spring-damper-rolling isolation system in comparison with the random uneven distribution of rolling friction coefficient, and always lead to a relatively acceptable isolation state even if the actual earthquake significantly differs from the design earthquake.

• 한국운동역학회지
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• 제17권3호
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• pp.189-195
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• 2007

The purpose of this study was to analyze the effects of shoes with curved out-sole on the pressure, reaction force(sum of pressure) on foot and relations between the rolling speeds and pronation of foot. The foot pressure, reaction force and pressure center on the foot surface of shoe were measured with NOVEL padar system, and 3 type shoes were used to compare the position and speed of pressure center and the foot reaction force, which were s(target) shoe with soft cushions in middle part of out-sole and curved out-sole, m shoes with two type- soft, hard, hardness out-sole and curved out-sole and n shoes with flat out-sole. The subjects were 13 female university students, had weared the 3 type shoes for 6 weeks on two-weeks shifts for adaptation before experiment and put on 3-type shoes repeatedly and randomly and walked on treadmill with 3.5km/h and 80 steps/min. The data were captured with 30Hz and readjusted with 5kgf threshold reaction force. The results can be summarized as follow. 1. There were no difference in maximum reaction force on initial contact period and total foot impact, but statistical difference in maximum reaction force on takeoff period : s, m, n in ascending order. 2. There were some difference in rolling speeds for support periods. At initial contact, the rolling speed of s shoes was fastest but at periods between first and second maximum reaction force, that of m shoes fastest. 3. There was a negative relation between rolling speeds and the length of lever arm on initial reaction force related to pronation. It seems shoes with various curved shapes and hardness could make effects on the rolling features and the rolling speed also have some relationships with walking efficiency, absortion of impact and pronation.