• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.823-829
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• 1986

The Large-scale structure of the circular jet in the transition region, which influences the subsequent flow in the turbulent region, was studied experimentally. Measuring equipments are composed of the two channel hot-wire anemometer, the computer controlled two-directional traverse mechanism, the data acquisition system, and FFT-analyzer. The circular jet has 50mm diameter. The mean velocity distribution, the velocity fluctuation, the auto 'cross correlations and the power spectra were acquired at moderate Reynolds number of 10$^{4}$. And the VITA method was used to measure the convection velocity of Large-scale eddy. The phase of u'is in advance of that of v'in all regions. .over bar. $R_{u}$(.tau.=0) is approximately zero in the potential core region, but a small regular deviation is observed. At a position in the mixing layer region the convection velocity is different along the part of the eddy, and in this experiment the convection velocity of the inner region is larger than the outer region. The averge convection velocity of the eddy along y/D=0 was approximately constant in the transition region.D=0 was approximately constant in the transition region.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.426-432
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• 2004

Large-Eddy Simulation (LES) is applied for the simulation of compressible flat plate boundary with Reynolds number up to 5 X 10$^{5}$ . Numerical examples include shock/boundary layer interaction and boundary layer transition, aiming future application to the analysis of transonic fan/compressor cascades. The present LES code uses hybrid com-pact/WENO scheme for the spatial discretization and compact diagonalized implicit scheme for the time integration. The present code successfully predicted the bypass transition of subsonic boundary layer. As for supersonic turbulent boundary layer, mean and fluctuation velocity of the attached boundary, as well as the evolution of the friction coefficient and the displacement thickness both upstream and downstream of the separation region are all in good agreement with experiment. The separation point also agreed with the experiment. In the simulation of the shock/laminar boundary layer interaction, the dependence of the transition upon the shock strength is reproduced qualitatively, but the extent of the separation region is overpredicted. These numerical examples show that LES can predict the behavior of boundary layer including transition and shock interaction, which are hardly managed by the conventional Reynolds-averaged Navier-Stokes approach, although there needs to be more effort before achieving quantitative agreement.

• Journal of Welding and Joining
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• v.7 no.3
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• pp.28-35
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• 1989

It was reported that the toughness for welded region was influenced by various factors such as the gradient for prior austenite grain size, the variation of microhardness and the characteristic microstructure depending on distance from the fusion boundary. Therefore, in order to evaluate the fracture strength of the weldment in which the microstructures change continuously, it is important to assess the peculiar strength of each microstructure in welded region. It was known that the small punch(SP) test technique which was originally developed to study the irradiation damage effect for the structures of nuclear power plant was also useful to investigate the strength evaluating of nonhomogeneous materials. In this paper, by means of a small punch test technique the possibility of evaluating strength of parent and welded region in SS41 and SM53B steels was investigated. The obtained results are summerized as follows: 1) The small punch test which showed markedly the ductile-brittle transition behavior in this experiment may be applied to evaluation for the fracture strength of welded region. 2) It was shown that the ductile-brittle regime lied in Region III(plastic membrane stretching region) of the flow characteristics observed in SP test. 3) The SP test technique which shows a more precipitous energy change transition behavior than the other test technique is able to estimate the more precise transition temperature. 4) It could be seen that in comparision with the structure of parent the structure of weld HAZ in SS41 steel was improved while it in SM53B steel was deteriorated.

• Journal of the Korean Society of Visualization
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• v.20 no.1
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• pp.29-37
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• 2022

We carried out a laboratory experiment about the thermo-fluidic characteristics of natural convection boundary layer over a vertical heated plate under constant heat flux condition. Particle image velocimetry has been applied to observe the surface convection velocity close to the vertical plate submerged in the water chamber with the condition of Ra = 7 × 10⁹ and Pr = 8.1. The velocity distributions indicate that the distinct stripe-like structures appears in the upstream (earlier transition region) and the distinct negative-positive and Λ(λ)-shaped flow structures in the downstream (mid-transition region). In addition, the temporal variation of spanwise and streamwise velocity is also presented.

• Journal of Broadcast Engineering
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• v.26 no.5
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• pp.543-552
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• 2021

The story is formed by the flow of the development and resolution of the conflict between the characters. Namely, the story consists of conflict setting, development, and resolution. Character region is an important expression technique to describe the emotions or states of characters and the relationship between characters and the environment. The purpose of this paper is to propose a method for detecting the transition of conflict from the graph of character region's change. To this end, we present a method of generating a change graph of a character region in a movie by calculating the character region and a method of detecting a conflict transition scene from a graph of character region's change. To verify the performance of the proposed method, an experiment was conducted to extract conflict transition scenes for 7 movies, and performance evaluation results of 73.57% accuracy and 77.26% recall were obtained. This proves that it is possible to extract conflict transition scenes based on the character region.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.21-31
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• 2017

In the present study, theoretical and numerical analyses have been carried out to investigate the detailed flow characteristics during the mode transition. The theoretical analysis rearranged the knowledge of gasdynamics and the previous studies, and the numerical analysis has conducted to solve the 2D unsteady compressible Navier-Stokes equations with a fully implicit finite volume scheme. To validate the numerical analysis, the experiment was compared with it. The total temperature at the inlet of isolator and the hydrogen fuel equivalent ratio were changed to investigate their effects on the mode transition phenomenon. As the results, the numerical analysis reproduced well the experiment qualitatively, the increment in the hydrogen fuel equivalent ratio induced the scram-mode to ram-mode transition which is discontinuous with a non-allowable region, and the variation in the total temperature changed the boundary of the mode transition.

• Korean Journal of Medicinal Crop Science
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• v.14 no.3
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• pp.178-182
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• 2006

This study was conducted to investigate the variation in sequence, the base composition and the sequence similarity of 18S rDNA (18S ribosomal RNA coding region) in the 10 Polygonatum spp. collections. The entire 18S rDNA region of 10 Polygonatum spp. collections ranged from 913 bp to 914 bp. There were 8 variable sites in the entire 18S region, and they were attributable to nucleotide substitution and deletion. $T{\rightarrow}C$ transition happened in 4 sites, and $A{\rightarrow}G$ transition happened in 1 site. $C{\rightarrow}A$ transversion happened in 1 site, and deletion happened in 2 sites. Transition rates were five times that of transversion. Base compositions of 18S rDNA were $23.09{\sim}23.33%$ in adenine, $23.33{\sim}23.52%$ in guanine, $25.60{\sim}25.85%$ in thymine and $27.38{\sim}27.79%$ in cytosine. The A + T content of 18S rDNA of 10 Polygonatum spp. collections averages 48.99%, ranging from 48.80% to 49.18%, and the G + C content averages 51.01%, ranging from 50.82% to 51.20%. Pairwise sequence comparisons indicated that 18S rDNA sequence similarity ranged from 99.7% to 100%.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.4
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• pp.280-286
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• 2002

It has been long suspected that the transition region may give rise to local pressure fluctuations and radiated sound that are different from those created by the fully-developed turbulent boundary layer at equivalent Reynolds number. Experimental investigation described in this paper concerns the characteristics of pressure fluctuations at the transition. Flush-mounted microphones and hot wires are used to measure the pressure fluctuations and local flow velocities within the boundary layer in the low noise wind tunnel. From this experiment we could observe the spatial and temporal development process of T-S wave using Wigner-Ville method and find the relations between the characteristic frequency of T-S wave and free stream velocity and the boundary layer thickness based on nondimensional pressure spectra scaled on outer variables.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.331-336
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• 1996

The effects of a mixing vane on air-water mixed flow have been experimentally studied in this work, to investigate the basic mechanisms that the mixing vane affects critical heat flux (CHF). Experiment was performed for various flow rates focusing on bubbly flow and annular flow patterns. Acrylic tube (1.7m long, 11 mm I.D.) and the split vane type mixing vane were used, and ring-type conductance probes were used to measure the liquid film thickness in annular flow. Experimental results show that, (a) bubbly-to slug flow transition and churn-to-annular flow transition occur respectively near the mixing vane compared to the tests without mixing vane, (b) in bubbly flow region, the mixing vane breaks the bubbles into smaller ones and forwards bubbles to the center region of the tube by the centrifugal force, (c) the liquid film thickness in annular flow is decreased near the mixing vane for mass fluxes.

• International Journal of Control, Automation, and Systems
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• v.2 no.3
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• pp.354-361
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• 2004

To improve fault isolation performance of the Bayes isolator, this paper proposes the Fuzzy-Bayes isolator, which uses the Fuzzy-Bayes classifier as a fault isolator. The Fuzzy-Bayes classifier is composed of the Bayes classifier and weighting factor, which is determined by fuzzy inference logic. The Mahalanobis distance derivative is mapped to the weighting factor by fuzzy inference logic. The Fuzzy-Bayes fault isolator is designed for the BLDC motor fault diagnosis system. Fault isolation performance is evaluated by the experiments. The research results indicate that the Fuzzy-Bayes fault isolator improves fault isolation performance and that it can reduce the transition region chattering that is occurred when the fault is injected. In the experiment, chattering is reduced by about half that of the Bayes classifier's.