• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.385-393
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• 2018

In this study, the analysis of 2DOF (2 Degree Of Freedom) motion and added resistance of a ship in regular head waves is carried out using RANS (Reynolds Averaged Navier-Stokes) approach. In order to improve the accuracy for large amplitude motions, the dynamic overset scheme is adopted. One of the dynamic overset schemes, Suggar++ is applied to WAVIS which is the in-house RANS code of KRISO (Korea Research Institute of Ships and Ocean Engineering). The grid convergence test is carried out using the present scheme before the analysis. The target hull form is KRISO VLCC tanker (KVLCC2) and 13 wave length conditions are applied. The present scheme shows the improved results comparing with the results of WAVIS2 in the non-inertial reference frame. The dynamic overset scheme is confirmed to give the comparatively better results for the large amplitude motion cases than the non-inertial frame based scheme.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.483-491
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• 2004

Clusters of galaxies are storage rooms of cosmic rays. They confine the hadronic component of cosmic rays over cosmological time scales due to diffusion, and the electron component due to energy losses. Hadronic cosmic rays can be accelerated during the process of structure formation, because of the supersonic motion of gas in the potential wells created by dark matter. At the shock waves that result from this motion, charged particles can be energized through the first order Fermi process. After discussing the most important evidences for non-thermal phenomena in large scale structures, we describe in some detail the main issues related to the acceleration of particles at these shock waves, emphasizing the possible role of the dynamical backreaction of the accelerated particles on the plasmas involved.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.4 no.1
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• pp.1-9
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• 2001

An oscillating body motion with extremely large amplitude has been studied using the viscous flow solver. Time simulations of oscillating ship hull in prescribed heave and roll motions are presented using RANS method with FAM approach (Chen, 1995). For viscous flows, laminar flow and turbulent flow with $textsc{k}$-$\varepsilon$ model are considered and compared. The viscous flow solver of RANS method is performed together with a Chimera type of multi-block grid system to demonstrate the advantage of accurate and efficient zonal approach. In the present study, effects of viscosity and oscillation degree are discussed using Re=1000 and Re=1000000. Large motion of oscillating body shows clear vortex propagation that is not possible for inviscid flow to present.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.155-158
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• 1996

Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation of small scale power. The current status of these difficulties is discussed. The resolution could depend on the nature of the saturated field produced by the small scale dynamo. We argue that the small scale fields do not fill most of the volume of the fluid and instead concentrate into intermittent ropes, with their peak value of order equipartition fields, and radii much smaller than their lengths. In this case these fields neither drain significant energy from the turbulence nor convert eddy motion of the turbulence on the outer scale to wave like motion. This preserves the diffusive effects needed for the large scale dynamo operation.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.31.1-31.1
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• 2011

We present wide-field near-IR imaging polarimetry of 30 Doradus in the Large Magellanic Cloud, using the InfraRed Survey Facility (IRSF). We obtained polarimetry data in J, H, and Ks bands using the JHKs-simultaneous imaging polarimeter SIRPOL. Since many Galactic field stars along the line-of-sight to the Large Magellanic Cloud are contaminated in our data, we developed methods to identify the foreground sources using the proper motion data. We investigated polarimetric properties between the Galactic foreground stars and the stars in the LMC.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.317-319
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• 1996

Utilizing a Calcium filter, a large two ribbon flare of an importance 2.5Xj31? was recorded at. King Abdul-Aziz University Solar Observatory (KAAUSO) at the 30th of October 1991. This chromosphenc flare observation, which is of special importance since it is rarely reported, was for a flare that occurred near the south west of the equator at the vicinity of a large sunspot group on an active region known as AR 6891. The observed foot points of this flare had a strange behavior in which the separating motion of the ribbons were not typical of most flares, rather were nearly orthogonal. In this article we present the characteristics of the main sunspot group of this active region and try to investigate its evolution and fragmentation with time. Information regarding magnetic fields and velocity fields are necessary to understand the restructuring of the magnetic field pattern and plasma motion, and hence the changes that could lead to the occurrence of such an interesting flare.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.35-40
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• 2016

In this study, the thermal and fluid dynamic characteristics for the coating process of large-sized water pipes was studied by heating the inside of a pipe directly with a gas burner. Heat and flow analyses were performed on large pipes with various inlet shapes. Using large pipes for coating was shown to be the proper shape for heating large pipes uniformly. This type has a screw with a diameter of 200 mm installed at the inlet to provide a rotational motion to the heating air. The rotational motion resulted in a uniform temperature distribution that ranged from $289.1^{\circ}C$ to $352.1^{\circ}C$ The optimized geometric configuration of the inlet of the pipe successfully and uniformly enhanced the thermal characteristics of the devised temperature limit.

• Ocean Systems Engineering
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• v.11 no.1
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• pp.59-81
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• 2021

The nonlinear formulation using the principle of virtual work-energy for free vibration of a large-sag extensible catenary riser in two dimensions is presented in this paper. A support at one end is hinged and the other is a free-sliding roller in the horizontal direction. The catenary riser has a large-sag configuration in the static equilibrium state and is assumed to displace with large amplitude to the motion state. The total virtual work of the catenary riser system involves the virtual strain energy due to bending, the virtual strain energy due to axial deformation, the virtual work done by the effective weight, and the inertia forces. The nonlinear equations of motion for two-dimensional free vibration in the Cartesian coordinate system is developed based on the difference between the Euler's equations in the static state and the displaced state. The linear and nonlinear stiffness matrices of the catenary riser are obtained and the eigenvalue problem is solved using the Galerkin finite element procedure. The natural frequencies and mode shapes are obtained. The results are validated with regard to the reference research addressing the accuracy and efficiency of the proposed nonlinear formulation. The numerical results for free vibration and the effect of the nonlinear behavior for catenary riser are presented.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.2
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• pp.35-44
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• 2002

The translation and the rotation of camera occur global motion which affects all over the frame in video sequence. With the video sequences containing global motion, it is practically impossible to extract exact video objects and to calculate genuine object motions. Therefore, high compression ratio cannot be achieved due to the large motion vectors. This problem can be solved when the global motion compensated frames are used. The existing camera motion estimation methods for global motion compensation have a large amount of computations in common. In this paper, we propose a simple global motion estimation algorithm that consists of linear equations without any repetition. The algorithm uses information .of symmetric points in the frame of the video sequence. The discriminant conditions to distinguish regions belonging to distant view from foreground in the frame are presented. Only for the distant view satisfying the discriminant conditions, the linear equations for the panning, tilting, and zooming parameters are applied. From the experimental results using the MPEG test sequences, we can confirm that the proposed algorithm estimates correct global motion parameters. Moreover the real-time capability of the proposed technique can be applicable to many MPEG-4 and MPEG-7 related areas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1343-1355
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• 1997

Full motion video data is the most effective data type that transmits information in multimedia enviornment. VOD service is system that uses network to transmit full motion video data interactively. Therefore VOD service system must satisfy the following requirements. First, it should transmit high quality full motion video. Second, it should be able to control a large quantity of full motion video. Third, a user should be able to retrieve the full motion vide effectively. However the existing VOD service system is established based n file system that not only does it have disadvantages in managment such as transaction control but also it is not suitable for distributed multimedia environment. The goal of this research is to build a VOD service system that provides high-quality full motion video assuming information retrieval. In order to mainly search video data's bibliographical information and to manage related information, VOD service system and DBMS system are to be closely related. Also, to transmit high quality full motion video data, we use MTP$^{TM}$(Media Transfer Protocol) developed by StarLight. MTP$^{TM}$ guarantees high bandwidth that is necessary to tansmit high quality full motion video data effectively. In other hand TCP/IP which is used for information search does not guarentee high bandwidth as that in MTP$^{TM}$. Therfore VOD service system that seraches information managed by DBMS and transmits requried full motion video data should control different kinds of protocol simultaneously. This paper describes the configuration of VODB system that has solved these problems, implementation and efficiency of data applied system.stem.