• The Journal of the Korea Contents Association
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• v.22 no.5
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• pp.527-541
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• 2022

This study analyzed the structural relationship between motivation to participate in online lifelong education through YouTube, academic self-efficacy, and learning flow, where learners are rapidly increasing due to the spread of COVID-19. For this study, an online survey was conducted from July 16 to 30, 2021 for adult learners living in the metropolitan area. A total of 428 people participated in the survey, and a total of 409 copies of the results were analyzed, excluding 19 insincere responses. The main analysis results are as follows. First, The fitness of the research model was verified to be suitable for all analysis. Second, as a result of confirming the coefficients and statistical significance of each pathway in the research model, the motivation to participate in YouTube lifelong education was learning flow and academic self-efficacy, and academic self-efficacy also had a positive effect on learning flow. Third, it was confirmed that the effect of participation motivation in YouTube lifelong education on learning flow through academic self-efficacy was a statistically significant partial mediation. This study is meaningful in that it verified the structural relationship analysis between participation motive, academic self-efficacy, and learning flow in online lifelong education using YouTube reflecting the digital transformation of lifelong education due to COVID-19. Reflecting the need for re-regulation of lifelong education formed after COVID-19 and the flow of digital transformation through the research results, we discussed how lifelong education can enhance learners' motivation to participate and strengthen learning flow through academic self-efficacy as a medium.

• Journal of The Korean Association For Science Education
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• v.40 no.1
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• pp.13-28
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• 2020

This study attempted to understand the characteristics of images of scientific experiments represented and consumed on YouTube, a representative of today's new media. In particular, this paper analyzes the case studies of YouTube's hydrogen peroxide decomposition experiment based on Baudrillard's theory of Simulation and Simulacra, which discusses the strong status of images and the ambiguity of the boundary between virtual and reality. A total of 14 YouTube videos related to hydrogen peroxide decomposition experiments were analyzed. In those videos, hydrogen peroxide decomposition experiments were typically conducted with several signs representing scientific experiments, but the most important sign in the videos were bubbles produced through experiments. For more public consumption of the content, the bubbles resulted from hydrogen peroxide decomposition reproduced in YouTube have been transformed into a more spectacular image as 'super-huge' and 'explosive' bubble. Considering the influence of new media that can be accessed by students anytime and anywhere, it is positive that science experiments in new media enhance students' intimacy and access to science. At the same time, however, it is also important to note the danger that the purpose of scientific experiments will be limited to only 'showing specular images', due to the nature of new media, which mainly deals with immediate and superficial images. Furthermore, this study argues that improving students' science media literacy is required to critically examine the science-related images represented in the new media based on understanding the characteristics and limitations of new media that deeply affect daily life.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.907-913
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• 2011

Swirling flows are related to the spiral motion in the tangential direction in addition to the axial and radial direction using several swirl generators. These type of flows are used in combustion chambers to improve flame stability, heat exchanger to enhance heat transfer coefficients, agricultural spraying machines and some vertical pipes to move slurries or transport of materials. However, only a few studies three dimensional velocity profiles in a vertical pipe have been reported. In this present paper, 3 dimension particle image velocimetry(PIV) technique was employed to measure the velocity profiles in water along a vertical circular pipe with Reynolds number from 6000 to 13,000. A tangential inlet condition was used as the swirl generator to produce the required flow. The velocities were measured with swirling flow in the water along the test section using the PIV technique.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.26-36
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• 1996

The fully developed turbulent momentum and heat transfer induced by the square-ribbed roughness elements on both the inner and outer wall surfaces in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fuid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity positions and friction factors, and etc. shown in Fig.1. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt bumber and Prand시 number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view by investigating turbulent flows and heat transfer in Fig.1.

• Journal of Korea Foundry Society
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• v.30 no.3
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• pp.94-99
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• 2010

When the returned scrap of bulk amorphous alloy is remelted, impurities such as oxides and intermetallic compounds increase. Glass forming ability of its scrap is deteriorated remarkably. Melt fluxing technique is introduced to enhance the glass forming ability during melting and freezing of bulk amorphous alloys. Cu and Zr based alloys are chosen. Small pieces of these alloy scraps and $B_2O_3$ flux are put together in a quartz tube. Cyclic heating and cooling are done by induction heating and water quenching or air cooling. Melting fluxing was effective for both Cu-based and Zr-based alloy, and their glass forming abilities were improved with increasing the number of fluxing.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.77-79
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• 1998

Metallic chromium was diffused in the{0001},{1120} white sapphires which were grown by the Verneuil method to enhance the physical properties of the sapphires. Chromium metal vapour pressure and {{{{ { N}_{2 } }}}} pressure were kept by {{{{ { 1$\times$10}^{-4 } }}}} torr at 21 50 $^{\circ}C$ and 6 atm in the quartz-tube, respectively. The color do the Cr-doped sapphires was changed to light red. Chromium was diffused faster in the {1120} than 수 the {0001} plane. It was speculated that the planar density was one the factors determining diffusion coeffcient

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.273-280
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• 1997

Rotary swaging is a process for reducing the cross-sectional area or changing the shape of bar, tube or wires by repeated radial blows with one or more parirs of opposed dies. The present study is concerned with investigation the effect of process parameters upon product quality(hardness, roughness, precision of dimension). To enhance the product quality, experimental works are carried out for some process parameters such as forming speed, billet shape, lubrication, reduction of area and ratio of t/D. Rod shift formed by RSM25 under cold conditions has good surface quality, hardness and precision of dimension. The recommendable process conditions are suggested for solid and tubular products.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.341-346
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• 2000

This experimental study investigated the flow motion of the working fluid for various diameters of miniature thermosyphons and the performance characteristics for the various amount of the working fluid. The temperatures of condenser surface were measured and visual observations were conducted. The test results show that some fluid condensed in the tube diameters of 0.18cm and 0.22cm is not returned to the evaporator section due to capillary effect so that large temperature gradients are measured. To enhance returning the working fluid, one copper wire of 0.5mm diameter was inserted and the test results show good performance. When the liquid charge was less than 10% in volume dry-out was occurred fur the thermosyphons of the inner diameter of 1.8mm and 2.2mm.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.165.1-165.1
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• 2011

In this paper, it is intended to study about deferences of design and operation properties between large and small hydro-power house's turbine which type is reaction. In generally, turbine of large hydro-power has a more safe and effective energy output mechanisms than small hydro-power's because the turbine of small hydro-power is more sensitive to hydraulic losses. But, it is more effective for the all energy market to improve the capability and efficiency of small hydro-power in the present status of increasing construction of small hydro-power than large hydro-power. Therefore, we intend to investigate and introduce the way to enhance the efficiencies of reaction turbine adopted to small hydro-power.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.10
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• pp.649-656
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• 2010

The aim of this study is to investigate the influence of the secondary fluid flow rate through GLHX on a GSHP system with vertical single U-tube type GLHXs. The COP of a GSHP system with large flow rate was lower than it with small flow rate due to large power consumption of ground loop circulating pump. It is suggested that the heat pump unit with high COP and low flow rate through the GLHX have to be selected in order to enhance the performance of the system and reduce the length of GLHX.