• The KSFM Journal of Fluid Machinery
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• v.6 no.1 s.18
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• pp.37-43
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• 2003

Natural convection of a magnetic fluid is different from that of Newtonian fluids because a magnetic body force exists in an addition to gravity and buoyancy forces. In this paper, the natural convection of a magnetic fluids (W-40) in a rectangular enclosure is investigated by numerical and experimental methods. One side wall is kept at a constant temperature ($25^{\circ}C$), and the opposite side wall is also kept at a constant temperature ($20^{\circ}C$), Under above conditions, the magnitude of the magnetic fields were varied and applied. GSMAC scheme is used for the numerical method, and the thermo-sensitive liquid crystal film (R20C5A) is utilized in order to visualize wall-temperature distributions as an experimental verification. This study has resulted in the following fact that the natural convection of a magnetic fluid is controlled by the direction and intensity of the magnetic fields.

• Publications of The Korean Astronomical Society
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• v.10 no.1
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• pp.91-108
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• 1995

We have intensively examined the structure of photospheric magnetic fields obtained from the calculation of the polarized radiation transfer for the model atmosphere. To determine more reliable magnetic field in the photospheric region composed of umbra, penumbra and quite area, we have calculated the polarized radiative transfer for a magnetically sensitive spectral line, FeI $6302.5{\AA}$, using our composite model representing three kinds of the atmospheric area distinguished by the pixel value of the Stokes I image over the region. Polarization data of the full Stokes parameters, used in this paper had been obtained from the vector magnetograph on Solar Flare Telescope of National Astronomical Observatory at Mitaka(MTK) in Japan. According to our investigation on the active region in the photosphere, it has been found that the large current density(${\geq}8{\times}10^2A/km^2$) and shear angle(${\geq}85^{\circ}$) should be distributed along the magnetic neutral line. To be compared with the results of MTK, our results in transverse magnetic field strength and direction are similar with those of MTK, however our longitudinal field strength at the center of the spot is somewhat(${\sim}1000$ Gauss) larger than MTK.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.1-4
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• 2005

A higher order zig-zag shell theory is developed to refine accurately predict deformation and stress of smart shell structures under the mechanical, thermal, and electric loading. The displacement fields through the thickness are constructed by superimposing linear zig-zag field to the smooth globally cubic varying field. Smooth parabolic distribution through the thickness is assumed in the transverse deflection in order to consider transverse normal deformation. The mechanical, thermal, and electric loading is applied in the sinusoidal distribution function in the in-surface direction. Thermal and electric loading is given in the linear variation through the thickness. Especially, in electric loading case, voltage is only applied in piezo-layer. The layer-dependent degrees of freedom of displacement fields are expressed in terms of reference primary degrees of freedom by applying interface continuity conditions as well as bounding surface conditions of transverse shear stresses. In order to obtain accurate transverse shear and normal stresses, integration of equilibrium equation approach is used. The numerical examples of present theory demonstrate the accuracy and efficiency of the proposed theory. The present theory is suitable for the predictions of behaviors of thick smart composite shell under mechanical, thermal, and electric loadings combined.

• The Journal of Korea CHUNA Manual Medicine
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• v.5 no.1
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• pp.67-76
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• 2004

Objectives : The purpose of this study is to research trends In the study of osteoporosis and to establish the future direction for its study. Methods: We reviewed oriental medicine papers published in last twelve years (1990-2002). Methods : We reviewed oriental medicine papers published in last twelve years (1990-2002). Results : 1. We researched 42 papers in 12 journals and patterns of study were as follows: experimental studies were 30 (71%), reviewed studies were 8(19%), clinical studies were 2 (5%) and etc were 2 (5%). 2. The experimental studies(30) were divided into papers on efficiency testing of herbal medications (22) and herbal acupuncture (7) and etc (1). 3. The reviewed studies showed that research has been carried out in the fields of cause, pathogenesis, principles for treating disease, herbal medication, herbal acupuncture, acupuncture and moxibustion, exercise to osteoporosis. 4. The clinical studies showed that the research was carried out in the fields of follow up surveys for the herbal medication efficiency testing, the relativity of osteoporosis to other diseases. 5. In consequence of researching the case reports, there was no prescription used meaningfully. Conclusions: We need more studies of osteoporosis by reaching for specific therapy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.84-94
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• 2003

It is known that tip clearance flows reduce the pressure rise, flow range and efficiency of the turbomachinery. So, the clear understanding about flow fields in the tip region is needed to efficiently design the turbomachinery. The Navier-Stokes code with the proper treatment of the boundary conditions has been developed to analyze the three-dimensional steady viscous flow fields in the transonic rotating blades and a numerical study has been conducted to investigate the detail flow physics in the tip region of transonic rotor, NASA Rotor 67. The computational results in the tip region of transonic rotors show the leakage vortices, leakage flow from pressure side to suction side and their interaction with a shock. Depen ding on the operating conditions, toad distributions and the position of shock-wave on the blade surface are very different close to the blade tip of the transonic compressor rotor. The load distribution and the shock-wave position close to the blade tip had the close relationship with the starting position of leakage vortex and the direction of leakage flow.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.3
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• pp.249-261
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• 2003

A three-dimensional mesoscale atmospheric dispersion modeling system consisting of the Lagrangian particle dispersion model (LPDM) and the meteorological mesoscale model (MM5) was employed to simulate the transport and dispersion of non-reactive pollutant during the nuclear spill event occurred from Sep. 31 to Oct. 3, 1999 in Tokaimura city, Japan. For the comparative analysis of numerical experiment, two more sets of foreign mesoscale modeling system; NCEP (National Centers for Environmental Prediction) and DWD (Deutscher Wetter Dienst) were also applied to address the applicability of air pollution dispersion predictions. We noticed that the simulated results of horizontal wind direction and wind velocity from three meteorological modeling showed remarkably different spatial variations, mainly due to the different horizontal resolutions. How-ever, the dispersion process by LPDM was well characterized by meteorological wind fields, and the time-dependent dilution factors ($\chi$/Q) were found to be qualitatively simulated in accordance with each mesocale meteorogical wind field, suggesting that LPDM has the potential for the use of the real time control at optimization of the urban air pollution provided detailed meteorological wind fields. This paper mainly pertains to the mesoscale modeling approaches, but the results imply that the resolution of meteorological model and the implementation of the relevant scale of air quality model lead to better prediction capabilities in local or urban scale air pollution modeling.

• Journal of the korean society of oceanography
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• v.32 no.1
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• pp.1-7
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• 1997

Surface current fields in the eastern East China Sea (ECS) were constructed by analyzing trajectories of 58 satellite-tracked surface drifters released during 1991-1996. Composite trajectories and 20-minute-by-20-minute box-averaged current vectors show that the basic current pattern composes of: the Kuroshio main stream, which turns eastward toward the Tokara Strait; a northward branch current of the Kuroshio on the ECS outer shelf deeper than 100 m; and an anticyclonic circulation in the northern Okinawa Trough west of Kyushu. The northward branch current sharply changes its direction to the northeast when it crosses a line connecting Cheju Island, Korea and Goto Islands, Japan. The basic pattern of current field changes slightly from winter to summer, and the main axis of the Tsushima Current in the Korea Strait is found to shift seasonally. The drifter experiment does not support the claim that the Yellow Sea Warm Current is separated from the northward branch current on the outer shelf southeast of Cheju Island. We suggest that the use of the term 'Tsushima Current' be limited to the northeast channel flow in the Korea Strait. The new term 'Kuroshio Branch Current' is suggested for the northward branch current on the outer shelf south of Cheju-do, which is separated from the Kuroshio.

• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.7-12
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• 2015

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.

• Journal of the Korea Society of Computer and Information
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• v.19 no.7
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• pp.27-35
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• 2014

Motion Graphic developed in the visual fields such as film and TV is widely used from the fields of arts such as applied paintings to interactive media such as web sites. In particular, Motion Graphic is actively used in the film's promotion websites with the form of a mixture between characteristics of visual media and characteristics of websites. In this study, we analyze the characteristics of film's promotion websites, investigate previous studies for Motion Graphic analysis. And present a model for the analysis of websites including visual elements, media elements and motion elements as main elements. We select some of promotion websites for films among 2013 domestic hot films, carry out a case analysis, and present the direction of development on the base of the results.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.23-29
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• 2010

Korean shipbuilding companies have sometimes carried out sea trials to measure a vessel's speed performance around the western channel of the Straits of Korea, where the flow fields are very complicated because of the effect of various flows such as sea, tidal, geostrophic, and wind-driven currents. Because these flows seem to present significant interference to a ship, the numerical reproduction of the flow-fields in the vicinity of the target sites could provide a better understanding of the sea environments while performing sea trials. In this study, we used the MEC ocean model to simulate the tidal currents around Tsushima Island and compared the simulated tidal amplitudes and currents with the measurements of Teague et al. (2001). The tidal amplitudes of the present simulation results agreed well with the observations. Based on the numerical simulation, the optimal direction and proper sites for a speed trial are described.