• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.339-340
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• 1996

In the present study we examine physical characteristics of a thin and rigid magnetic flux tube with a steady flow inside, which is embedded vertically upward in the solar atmosphere. We found from this study that (1) The downward material flow gives rise to a dominant heating in the flux tube which works with the conductive heating in the same direction. However, the upflow flow creates a dominant cooling which works against the conductive heating, resulting in a steeper temperature gradient with a shallower transition region. (2) Since the thickness of the transition region determines the material content in the transition region, a broader transition region of the downflow tube produces a larger differential measure.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1512-1517
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• 2003

Augmentation of CHF by ultrasonic is experimentally studied under subcooling pool boiling condition. Experiment is carried out for downward-facing plate with and without the ultrasonic. The working fluid is distilled water. Experimental apparatus is composed of a bath, power supply, test section, ultrasonic generator, DAQ system. Experiment is performed with the subcooling temperature of $5^{\circ}C$, $20^{\circ}C$, $40^{\circ}C$ and the inclined angle of $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $45^{\circ}$, 90. From the experimental results, it is found that ultrasonic effect enhances CHF of the downward-facing plate. As increasing the degree of subcooling, the rate of CHF increase is enhanced. As increasing the inclined angle, the rate of CHF increase decreases. Also, we can see that the heat transfer mechanism of CHF augmentation is closely connected with the dynamic behavior of bubble generation and departure.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.227-235
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• 2007

The railway catenary is softer in the middle of a span than at the end. This stiffness variation induce the vertical motion of a moving pantograph, which results in the large variation of contact forces. To reduce the vertical motion of a pantograph, we can introduce a pre-sag of the contact wire. The pre-sag changes merely equilibrium position of the contact wire. Because the pantograph must follow the sag added to the motion of the contact wire, the sag gives downward forces to the pantograph. If the pre-sag is proper, the variation of the vertical motion of the pantograph is reduced. However, excessive sag worses the current collection performance because the pantograph receives too large downward forces by the contact wire. The objective of the paper is to establish the theoretical basis to understand how the pre-sag affect the contact force variation and to propose the proper sag for the railway catenary for the train speed up to 200 km/h.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11a
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• pp.224-229
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• 1996

An experimental study on critical heat flux (CHF) and two-phase flow visualization has been performed for water flow in internally-heated, vertical, concentric annuli under near atmospheric pressure. Tests have been done under stable forced- circulation, upward and downward flow conditions with three test sections of relatively large gap widths (heated length = 0.6 m. inner diameter = 19 mm, outer diameter = 29, 35 and 51 mm). The outer wall of the test section was made up of the transparent Pyrex tube to allow the observation of flow patterns near the CHF occurrence. The CHF mechanism was changed in the order of flooding, chum-to-annular flow transition, and local dryout under a large bubble in churn flow as the flow rate was increased from zero to higher values. Observed parametric trends are consistent with the previous understanding except that the CHF for downward flow is considerably lower than that for upward flow.

• Journal of the Korean Institute of Gas
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• v.19 no.1
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• pp.51-56
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• 2015

To assess downward positions of water spray for the small-scale release of chlorine gas, dispersion coefficients for the Gaussian dispersion model were validated at the small-scale release experiment. And the downwind distances of water spray were assessed with the simulated results. As results, the Gaussian plume model using the Briggs' dispersion coefficient well estimated the dispersed characteristics for small-scale release of chlorine gas. The best adequate downwind position of water spray is the position of the maximum concentration of chlorine at the ground level. And the adequate vertical and horizontal dimensions of water spray consider the maximum width and height of cloud.

• Journal of Korea Multimedia Society
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• v.20 no.7
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• pp.1014-1023
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• 2017

In this paper, we propose a method for estimating the human height by using downward depth images. We detect a point with the lowest depth value in an object as top of the head and estimate the height by calculating the depth difference with the floor. Since the depth of the floor varies depending on the angle of the camera, the correction formula is applied. In addition, the binarization threshold is variably applied so that height can be estimated even when several people are adjacent. Simulation results show that the proposed method has better performance than the conventional methods. The proposed method is expected to be widely used in body measurement, intelligent surveillance, and marketing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2008.05a
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• pp.27-30
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• 2008

For the purpose of developing economical and time-efficient formwork for Top-down construction, a Non-Supporting Form System has been proposed. The system is consisted of two parts: a hanging part to support a steel frame and a section of concrete slab, and the other hanging part to lower the steel frame. In this paper, the proposed system is compared to two existing systems of Non Supporting Top-down Method and Bracket Supported R/C Downward Method. It is expected that this system can be used in Top-down construction with further development.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.1
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• pp.26-32
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• 1988

A study has been conducted experimentally on the natural convection heat transfer characteristics of fin arrays on a horizontal flat plate in air. The effects of fin heights and Rayleigh numbers are mainly investigated. The experimental results are as follows; 1. The mean fin and mean total Nusselt numbers increase as dimensionless fin heights increase at 0.67.leg.H/s.leg.1.67. The mean plate Nusselt numbers increase in case of upward facing fins, but they decrease in case of downward facing fins. 2. The mean Nusselt numbers increase as Rayleigh numbers increase. 3. The mean fin surface Nusselt numbers has its maximum outside surface (Y$_{1}$) where there is no interference from each other fin. 4. The mean total Nusselt numbers in case of upward facing fins increase by 47% and 26%, respectively at H/S=0.67 and 1.67 than those in case of downward facing fins for Ra$_{s}$=6.50*10$^{3}$.>.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.110-114
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• 1997

The major object in this report is the curvature prediction of front end downward bending in plate rolling. Because of relations front end shape and curvature in plate, many simulations were carried out to obtain empirical model. Simulation conditions, for example the position and the size of bottom stripper or roller table etc., were limited to the POSCO conditions. Though the result in this report can be applied to the special case, the tendency of this result is similar to the many cases. So the empirical model equation can be improved or expanded to many simulation conditions.

• Journal of the Korean Society of Clothing and Textiles
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• v.5 no.2
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• pp.63-68
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• 1981

Succeding to Report I, to determine the effect of opening conditions and areas of clothes ($10\%,\;20\%,\;30\%,\;40\%$ of total area) on the warmth keeping properties, cooling method was employed by using Latin Square Design, The following results were obtained: 1) The warmth keeping ratio was varied with the opening conditions and the: order was downward, upward, horizontal and up & downward opening 2) The size of opening areas was in inverse proportion to the warmth keeping ratio, 3) In the horizontal opening, the thickness of air layers in clothes did not effect on the warmth keeping ratio.