• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.130-138
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• 1996

The transient incompressible flow behind the widely-spaced co-axial jet is numerically simulated using the random vortex method(RVM). This numerical approach is based on the Lagrangian approach for the vorticity formulation of the unsteady Navier-Stokes equations, utilizing vortex elements to account for the convection and diffusion processes. The effects of the mass flow rate of an annular air jet and a central fuel jet on the co-axial jet flow dynamics is investigated. To validate the present procedure, the numerical results are compared with the available experimental data the present procedure, the numerical results are compared with the available experimental data in terms of the centerline and off-centerline profiles of the mean axial velocity. Discrepancies between the RVM results and the measurements are discussed in detail.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.3
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• pp.184-192
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• 1991

In many combustion systems, swirling combustion air is extensively applied as an aid for stabilization of high intensity combustion pocesses. Swirl, generally, causes significant effects on the flow field which, in turn, determines the size, shape, and stability of flames, and combustion intensity. The purpose of this study is to investigate the effect of swirls on flames produced from a model combustor designed in this paper. In order to impart swirls to the combustion air, a movable block swirl generator was used. Temperature distribution and radiative heat flux along the centerline of the swirling flame were measured. Data obtained from these swirl flows can be used as design data for high intensity or high efficiency combustion systems. The results obtained are summarized as follows: 1. Flame temperature profiles were measured at various swirl number. 2. The axial distance for maximum temperature from the centerline of burner increased as the swirl number increased. 3. Radiative heat flux increased as the swirl number and axial distance from burner increased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.30-33
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• 2007

DSMC method is now widely accepted CFD approach to compute and simulate the nozzle plume in rarefied regimes. In this study, using SMILE(Statistical Modeling in Low-density Environment) code which was developed in ITAM, Russia and coded using DSMC method, the internal flow of the Rothe micronozzle was simulated. Moreover, to show the validity of the SMILE code, the centerline temperatures according to the Reynold's number were compared with the ones obtained by the Rothe's experiment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3166-3178
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• 1993

The turbulent flow characteristics of impinging jet have been investigated by the hot wire anemometry with a movable impinging wall. Turbulences were generated by the meshed jet as well as the typical round jet and their characteristics were compared, of mean velocity profiles, turbulent intensities. Reynolds stresses, similarities and their centerline flow behaviors. The meshed jet tends to make shear layer wider than the normal one in the initial region and the velocity profiles of the normal jet is rather contractive being compared with those of the meshed one near the wall. The effect of meshed exit appears only within 4D at the begining of jets and the cascading process of the meshed one marches more rapidly than that of the normal jet. The wall effects appear in the downstream of about 0.85 H to the impinging wall for every case of wall positions in both nozzles.

• Journal of Multimedia Information System
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• v.7 no.4
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• pp.257-262
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• 2020

In this paper, a method of detecting the emergency situations such as body fall is proposed by using color images. We detect body areas and key parts of a body through a pre-learned Mask R-CNN in the images captured by a camera. Then we find the centerline of the body through the joint points of both shoulders and feet. Also, we calculate an angle to the center line and then calculate the amount of change in the angle per hour. If the angle change is more than a certain value, then it is decided as a suspected fall. Also, if the suspected fall state persists for more than a certain frame, then it is determined as a fall situation. Simulation results show that the proposed method can detect body fall situation accurately.

• Journal of the Korean Society of Visualization
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• v.19 no.3
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• pp.22-30
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• 2021

Ventilated cavity shapes by varying angle of attack of a circular cavitator were predicted based on Logvinovich's Independence Principle in order to verify the cavity shape prediction method. The prediction results were compared with model experiments conducted in the high-speed cavitation tunnel. In the prediction of the cavity centerline, the movement of the cavity centerline due to the effect of gravity and cavitator's angle of attack were well predicted. In the prediction of the cavity contour, it was found that the cavity edge prediction error increased as the angle of attack increased. The error of the upper cavity contour was small at the positive angle of attack, and the error of the lower cavity contour was small at the negative angle of attack.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.11a
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• pp.301-302
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• 2018

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.444-451
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• 2013

The purpose of this study was to investigate the changes in temporospatial variables in healthy elderly and healthy adults during usual walking, narrow base walking and centerline-guided walking. Twenty healthy elderly and nineteen healthy adults were participated in this study. In each conditions, the subjects were walked on a 6m walkway at comfortable self-selected speeds under three conditions : (1) usual walking, (2) walking within a 50% of the distance between the subject's ASIS (3) walking along a centerline. GAITRite system was used for kinematic analysis to assess the temporospatial variables. There were no significant changes in healthy adults(p>.05), but walking speed, cadence, H-H base support, functional ambulation performance were significantly decreased progressively as pathway narrowed in elderly adults(p<.05). The results show that elderly people had more difficulty with walking on narrow pathway for fear of falling. This study provides data for use in basic research into safe walking and preventing falling for elderly.

• Journal of the Korean Geographical Society
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• v.39 no.4
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• pp.633-642
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• 2004

This study tries to generalize the stream network by constructing rule-based modelling. A study on the map generalization tends to be concentrated on development of algorithms for modification of linear features and evaluations to the limited cartographic elements. Rule-based modelling can help to improve previous algorithms by application of generalization process with the results that analyzing mapping principles and spatial distribution patterns of geographical phenomena. Rule-based modelling can be applied to generalize various cartographic elements, and make an effective on multi-scaling mapping in the digital environments. In this research, nile-based modelling for stream network is composed of generalization rule, algorithm for centerline extraction and linear features. Before generalization, drainage pattern was analyzed by the connectivity with lake to minimize logical errors. As a result, 17 streams with centerline are extracted from 108 double-lined streams. Total length of stream networks is reduced as 17% in 1:25,000 scale, and as 29% in 1:50,000. Simoo algorithm, which is developed to generalize linear features, is compared to Douglas-Peucker(D-P) algorithm. D-P made linear features rough due to the increase of data point distance and widening of external angle. But in Simoo, linear features are smoothed with the decrease of scale.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.5
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• pp.1671-1678
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• 1996

In external chemical vapor deposition processes including VAD and OVD the distribution of flame-synthesized silica particles is determined by heat and mass transfer limitations to particle formation. Combustion gas flow velocities are such that the particle diffusion time scale is longer than that of gas flow convection in the zone of particle formation. The consequence of these effects is that the particles formed tend to remain along straight smooth flow stream lines. Silica particles are formed due to oxidation and hydrolysis. In the hydrolysis, the particles are formed in diffuse bands and particle formation thus requires the diffusion of SiCl$\_$4/ toward CH$\_$4//O$\_$2/ combustion zone to react with H$\_$2/O diffusing away from these same zones on the torch face. The conversion kinetics of hydrolysis is fast compared to diffusion and the rate of conversion is thus diffusion-limited. In the language of combustion, the hydrolysis occurs as a Burke-Schumann process. In selected conditions, reaction zone shape and temperature distributions predicted by the Burke-Schumann analysis are introduced and compared with experimental data available. The calculated centerline temperatures inside the reaction zone agree well with the data, but the calculated values outside the reaction zone are a little higher than the data since the analysis does not consider diffusion in the axial direction and mixing of the combustion products with ambient air. The temperatures along the radial direction agree with the data near the centerline, but gradually diverge from the data as the distance is away from the centerline. This is caused by the convection in the radial direction, which is not considered in the analysis. Spatial distribution of silica particles are affected by convection and diffusion, resulting in a Gaussian form in the radial direction.