• Journal of Navigation and Port Research
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• v.32 no.1
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• pp.15-22
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• 2008

A ship in a sea cruises with rolling, pitching, heaving etc because of environmental causes such as wind and wave. Those motions make crews or passengers feel inconvenience and they feel acceleration changes. Therefore, if lateral and vertical accelerations can be measured at a specific position in a ship, it can be known how discomfortable crews or passengers are. The motion monitoring system developed in this paper consists of measuring and communicating part including five accelerometers and gyro and a main computer which acquires measuring data and calculates motion indices. MSI(Motion Sickness Incidence) and MII(Motion Induced Interrupt) are calculated in real time using measured acceleration and angular rate. The validity of the developed system was confirmed through the real ship test of Hannara which is the school ship of Korea Maritime University.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.55-62
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• 2011

In this paper, a temporal color and luminance variation suppression algorithm for a digital video sequence is proposed by considering time-varying light source. When a video sequence is sampled with the periodically emitting illuminant and with a short exposure time, the color rolling phenomenon occurs, where the color and the luminance of the image periodically change from field to field. In conventional signal processing techniques, the luminance variation remaining in the resultant video sequence degrades the constancy of the image sequence. In the proposed method, we obtain video sequences with constant luminance and color by compensating for the inter-field luminance variation. Based on a motion detection technique, the amount of the luminance variation for each channel is estimated on the background of the sequence without the effects of moving objects. The experimental results clearly show that our strategy efficiently estimated the illuminant change without being affected by moving objects, and the variations were efficiently reduced.

• Journal of Fisheries and Marine Sciences Education
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• v.9 no.2
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• pp.167-178
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• 1997

It has been expected not only for crew but also for passengers to realize a ship whose rolling and other motions are small as much as possible. Restricting our consideration to the roll reduction, the conventional roll stabilization system, fins or anti-rolling tanks hve been utiized as the actuator. Excessive motions would interfere with the recreational activities of passengers on a cruise ship. Often more than half of the load of a containership is stowed above deck where it is subjected to large acclerations due to rolling. In some situations this may cause some internal damage to the contents of the containers; in more severe situations failure of the lashing can occur and containers may be lost over-board. Underdeck cargo in ordinary cargo ships and bulk commodities in colliers, ore ships and grain ships can shift if the motions become too severe. The purpose of this study is to concentrate on the additions. either internal or external to the hull, that reduce or otherwise improve the motion responses of the hull. It is assumed that the additions are such that their benefit to the motions of the ship outweights any impact on the ability of the ship to perform its assigned task. It is particularly challenging to obtain large improvements in the motion characteristics of existing ships that are being rebuilt or modified for some task not anticipated in their original design. Further the authors will statistically analyze the influence of ruder-roll-yaw coupling motion in the case of application of this advanced control method to various kinds of ship.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.2
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• pp.147-153
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• 2014

The purpose of this paper is to examine the roll damping characteristics by bilge keels on the fishing vessel. Unlike other degree of freedom motions, roll motion is highly nonlinear. However the quantitative evaluation of roll damping combined with waves is very important for the fishing vessel. To reduce roll motion, roll motion stabilizers such as a bilge keel is used due to easy made and cheap cost rather than anti-rolling tank and fin-stabilizer. Authors paid attention to the shape of bilge keel and waves to grasp the roll damping for the fishing vessel and studied about the difference of tendencies of roll angle following the shapes of bilge keel. The model ship was the offshore large purse seiner and four types of bilge keel were used. The data from the experiments were provided and analyzed to investigate the rolling characteristics of the model ship being affected by the wave height, wave period and bilge keel shape. The results of the study showed that three types of the bilge keel have little effective, but only one has an effect on the roll damping. So bilge keel shape and its attachment method need to be a future study for the practical use in fishing vessel.

• Structural Engineering and Mechanics
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• v.47 no.4
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• pp.455-470
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• 2013

This paper presents a theory concerning the beam element subjected to an eccentric rolling disk (or simply called the eccentric-disk-loaded beam element) such that the dynamic responses of a beam subjected to an eccentric rolling disk with its inertia force, Coriolis force and centrifugal force considered can be easily determined. To this end, the property matrices of an eccentric-disk-loaded beam element are firstly derived by means of the Lagrange's equations. Then, the overall property matrices of the entire vibrating system are determined by directly adding the property matrices of the eccentric-disk-loaded beam element to the overall ones of the entire beam itself. Finally, the Newmark direct integration method is used to solve the equations of motion for the dynamic responses of a beam subjected to an eccentric rolling disk. Some factors relating to the title problem, such as the eccentricity, radius and rotating speed of the rolling disk, and the Coriolis force and centrifugal force induced by the rolling disk are investigated. Numerical results reveal that the influence of last factors on the dynamic responses of the pinned-pinned beam is significant except the centrifugal force.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.11 s.254
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• pp.1461-1471
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• 2006

This paper presents the mathematical model for rolling behaviors of a small regular polygonal part on an inclined plane. Throughout the numerical analysis performed with the simulation program which has been experimentally validated, it is shown that the number of edges of the rolling polygonal part can be a measure for the energy dissipation rather than the coefficient of friction. The appropriate slope angle has been found to be around 20 degree for roughness-separation as well as shape-separation of polygonal parts which have small number of edges. In additions, the vibratory motion applied to the inclined plane is able to cause mixed parts to be separated more effectively according to the shape or the roughness. Finally, a couple of parts separation methods based on the analysis results are presented, and are validated through the numerical simulation.

• Journal of Navigation and Port Research
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• v.34 no.2
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• pp.123-129
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• 2010

The object of this study is to develop the method of safe conducting of a vessel through stormy sea when we encounter typoon or hurricane on ocean. The scope of investigation in this paper will be limited to safe maneuvering related only with rolling motions of a vessel. The processes of investigations are as follows; Firstly, we decide a CPA(Closest Point of Approach) with the center of the storm and decide significant wave height($H_{1/3}$) by SMB method and then calculate wave height of the highest of 1000 waves($H_{1/1000}$) and other data. Secondly, we make mathematical model of rolling motions of the vessel on the stormy sea and calculate the biggest rolling angle of the vessel and etc. Thirdly, we decide the most safe maneuvering method to ride out the stormy sea. By the above mentioned method we are able to calculate the status of the stormy sea and ships motions to be encountered and ride out safely through violently rough sea.

• Computational Structural Engineering
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• v.10 no.2
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• pp.161-169
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• 1997

It is known that tire plays an important role to the dynamic performances of a vehicle such as noise, vibration, ride and handling. Therefore, force and moment measurements have been a part of the traditional tire engineering process. In this paper, a computational analysis technique has been explored. A FE model is made to simulate inflation, vertical load due to the vehicle weight, and the slow rolling of a radial tire. A rigid surface with Coulomb friction is included in the model to simulate the slow rolling contact. The tire slip during the in-plane motion of the rigid surface is calculated. Results are presented for both lateral and vertical loads, as well as straight ahead free rolling. The calculated and measured tire slips are in good correlation. A Study on slow Rolling Tire for perdiction of tire Forces and Moments.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.323-327
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• 2002

In order to control the railway noise, the radiation characteristic of the noise during the train passage should be analyzed. Generally, the major noise sources for Korean Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic. The calculation results are compared with short distance measurement. It is shown that the radiation characteristic of the rolling noise is dipole type. The noise generated by the power unit is radiated as the cosine type. The noise level at an observer is increased in the direction of motion and reduced in the direction opposite to the motion with increasing of the train speed. The calculation results including the moving effect of the noise source at 300km/h show in good agreement.

• Bulletin of the Society of Naval Architects of Korea
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• v.8 no.2
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• pp.35-44
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• 1971

In terms of this paper, concerning primarily with the U-tube tank stabilizer, the authors' aim is to clarify and consolidate the theory as it has been developed thus far, and to provide with the certain additions which will make it more complete, more accurate, and more practical. And then we can know that the effect of the vertical tank position from the C.G., $a_{st}=1-w^2/{w^2}_{st}$, is very important, on account for the fact that the position factor, $a_{st}$, increase when the anti-rolling tank attaches to higher position vertically, but $a_{st}$ does not increase in proportion to the distance of the tank position. Measuring many characteristic coefficients by experiment, in the equation of the ship-tank system motion, such as the inertia coefficient, the damping coefficient, the natural frequency and so on, they can also give a guess that the higher position will accompany the non-linear motion of the tank water, but the non-linear effect will decrease the tank ability. In this study, they deal with not only the optimum damping coefficient of tank, which has very simply been expressed by the strength ratio, $\lambda$, but also the effect of the tank top, which has experimentally been treated when the water has hit the tank top. As this result, we can immediately find that the ability of the anti-rolling tank decrease at w/ws=0.9 generally low frequency.