• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.386-391
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• 2006

This study presents experimental results of sloshing phenomenon done on rectangular box. A simple harmonic excitation was done on the box. Two kinds of filling ratio, 20% and 30% of height, were tested. A total of 15 pressure sensors were installed to monitor the impact pressure. Each test was repeated for 20 times to ensure the repeatability. The high speed camera captured the flaw filed and the corresponding pressure were synchronize with video signal so that the video image can help the interpretation of the impact pressure. The two filling ratio made difference in the flaw characteristic and impact pressure. The use of high speed camera made it possible to understand the bubble generation mechanism. The pressure time histories were presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.47-53
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• 2007

To suppress the bubble generated in the liquid LPG direct injector is the most important to develop the LPDi engine. It was found in the previous study that bubbling phenomenon in the injector of the LPDi engine is decisively influenced by pressure of fuel and temperature around the injector. Therefore, in this study, the effect on suppressing the bubbling in the LPDi injector by high pressurization of fuel is analyzed and the spray characteristics are also studied. As a result, it is found that the bubbling in the LPDi injector is radically suppressed when the pressure of fuel is over 50MPa. The bubbling is suppressed when the pressure of fuel is over 3MPa if the inserted position of the injector is considered. Also, it is confirmed that the higher the pressure of fuel is the longer spray tip penetration and is the larger spray angle. As the ambient pressure increases, spray tip penetration decreases and spray angle increases due to the increase of drag force.

• The Korean Journal of Mycology
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• v.31 no.2
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• pp.89-93
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• 2003

In order to select suitable bioreactor type inhibiting cell stress during submerged culture of Tricholoma matsutake mycelium, the growth characteristics and ergosterol contents were investigated using the external-loop type of air-lift bioreactor (ETAB), balloon type of air bubble bioreactor (BTBB) and column type of air bubble bioreactor (CTBB). Dry weights of the T. matsutake in the BTBB, ETAB and CTBB were 12 g, 11.4 g, and 9.5 g per 1 litter, respectively. BTBB, ETAB and CTBB reached stagnant phases 16, 20, and 24 days after cultivation, respectively, The BTBB was more suitable for liquid culture of T. matsutake mycelium compared to other bioreactors owing to much mycelia product and short culture period. The ergosterol contents produced by the mycelium in the bioreactors were in sequence of BTBB, CTBB, and ETAB at every growth phase. BTBB might affect the mycelium on producing the smallest size of pellets. BTBB and CTBB got the mycelium precipitated and coagulated under operation of bioreactor sparser, whereas ETAB shown no effect of above phenomenon. A renovated bioreactor combined between a balloon shape of BTBB and an external-loop of ETAB was developed to enhance the efficiency of culture technique.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.1-10
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• 2021

This study empirically confirmed 'the political bias of the YouTube recommendation algorithm' and 'the selective exposure of user' to verify the Filter Bubble phenomenon of YouTube. For the experiment, two new YouTube accounts were opened and each account was trained simultaneously in a conservative and a liberal account for a week, and the "Recommended" videos were collected from each account every two days. Subsequently, through the text mining method, the goal of the research was to investigate whether conservative videos are more recommended in a righties account or lefties videos are more recommended in a lefties account. And then, this study examined if users who consumed political news videos via YouTube showed "selective exposure" received selected information according to their political orientation through a survey. As a result of the Text Mining, conservative videos are more recommended in the righties account, and liberal videos are more recommended in the lefties account. Additionally, most of the videos recommended in the righties/lefties account dealt with politically biased topics, and the topics covered in each account showed markedly definitive differences. And about 77% of the respondents showed selective exposure.

• The Journal of the Korea Contents Association
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• v.18 no.4
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• pp.27-37
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• 2018

A satirical cartoon is a time-limited medium in the context of specific social phenomena. On the other hand, satirical cartoons based on 'Sewolho' was published with 74 works by Kyunghyang Shinmun and 46 works by Joongang Ilbo. This is because it is a social phenomenon with a special meaning that satirical cartoons based on 'Sewolho' is a political issue that is called out of time constraints. In this study, I compared and analyzed the expressive elements of Kyunghyang Shinmun and Joongang Ilbo in the social phenomenon 'Sewolho'. The elements of the character, frame, and speech bubble which are the picture elements of satirical cartoons, combine to form the narrative structure. And the elements of the Speech, name and commentary which are also the same. The results of this study are meaningful that the analysis of the narrative structure through the expressive elements of satirical cartoons is meaningful by comparing and analyzing the satirical cartoons of two newspapers with different tendencies.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.9
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• pp.605-613
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• 2017

Recently, efficient heat dissipation has become necessary because of the miniaturization of devices, and research on boiling on micro-channels has attracted attention. However, in the case of micro-channels, the friction coefficient and heat transfer characteristics are different from those in macro-channels. This leads to large errors in the micro scale results, when compared to correlations derived from the macro scale. In addition, due to the complexity of the mechanism, the boiling phenomenon in micro-channels cannot be approached only by experimental and theoretical methods. Therefore, numerical methods should be utilized as well, to supplement these methods. However, most numerical studies have been conducted on macro-channels. In this study, we applied the lattice Boltzmann method, proposed as an alternative numerical tool to simulate the boiling phenomenon in the micro-channel, and predicted the bubble growth process in the channel.

• Journal of Korean Neurosurgical Society
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• v.56 no.6
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• pp.521-526
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• 2014

The authors report a case of symptomatic epidural gas accumulation 2 weeks after the multi-level lumbar surgery, causing postoperative recurrent radiculopathy. The accumulation of epidural gas compressing the dural sac and nerve root was demonstrated by CT and MRI at the distant two levels, L3-4 and L5-S1, where vacuum in disc space was observed preoperatively and both laminectomy and discectomy had been done. However, postoperative air was not identified at L4-5 level where only laminectomy had been done in same surgical field, which suggested the relationship between postoperative epidural gas and the manipulation of disc structure. Conservative treatment and needle aspiration was performed, but not effective to relieve patient's symptoms. The patient underwent revision surgery to remove the gaseous cyst. Her leg pain was improved after the second operation.

• Transactions of Materials Processing
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• v.21 no.2
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• pp.101-106
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• 2012

Generally, rapid cure reaction of LED encapsulation silicone resin causes serious defects in cured resin products such as warpage, residual bubbles, and reduced wettablility. In order to prevent residual bubbles in silicone resin, the step cure process was examined in the present paper. Three kinds of step cure processes were applied, and bubble-free phenomenon was observed. Most of the bubbles were removed under $70^{\circ}C$, the minimum temperature for activating cure reaction. In addition, degree of cure(DOC) and temperature distribution were predicted by using FEM analysis of heat transfer. It was concluded that maintaining cure temperature which provide a DOC under 0.5~0.6 effectively reduces residual bubbles.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.269-270
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• 2006

A finite difference lattice Boltzmann model which allows us to simulate gas-liquid two-phase flows with large density difference, for instance, 800 times for air and water is considered. Two-particle model is used and the density difference is introduced by changing the acceleration according to the fluid density. Numerical measurement of surface tension agrees well with theoretical predictions. Simulations of two-phase phenomenon for phase-transition is carried out, showing applicability of the model for two-phase flows. The two-dimensional cavitating flow around a board set up in the fluid way is also simulated. As a result, it was confirmed that the FDLB method with two-particle model was effective in numerical simulation of cavitating flow and the bubble periodically grew up at the low pressure area behind the board, in which the fluid condition was influenced by the cavitation number.

• Journal of Mechanical Science and Technology
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• v.14 no.5
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• pp.562-568
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• 2000

The pressure in a water-entry induced cavity, is analyzed up to the closed cavity (bubble). Water-entry is a highly transient phenomenon, and the evolution of the water-entry cavity must be explained by considering the entry speed, shape of the solid body, atmosphere pressure, and cavity pressure as the primary variables. This work is an extension of the cavity dynamics model recently reported by Lee (l997a). To extend the model for a wide range of entry speeds the cavity pressure is calculated from a one-dimensional quasi-steady flow model. The estimation of the cavity pressure allows us to explain the experimentally observed surface closure phenomena at low entry speeds. Predictions for the time of surface closure are compared with the published experimental data.