• Journal of the Korean Society of Safety
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• v.20 no.1 s.69
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• pp.42-48
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• 2005

The present study investigates the effect of balcony on external smoke movement of high rise building through the fire tests of the 1/10 reduced model scale using Froude scaling. A hexane pool fire is used to examine the smoke movement for various opening sizes of balcony and temperature distributions are measured by T-type thermocouples. Also, hydrogen bubble technique is applied to visualize the smoke movement near the balcony. Measured temperatures of the closed balcony is 2.5 times higher than those of the open balcony because the external smoke in case of the closed balcony rise along the vertical wall. The maximum vertical temperature of partially closed balcony is similar with fully closed balcony and mean temperature inside of balcony increases as opening size of balcony decreases. The experimental results show that the balcony space plays an important roles in preventing fire propagation and cooling of smoke layer. In order to ensure the fire safety in high rise building design, a series of systematic researches are required to examine the various type of balconies.

• Journal of Electrical Engineering and Technology
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• v.2 no.2
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• pp.257-262
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• 2007

In this paper the experiments of breakdown characteristics by temperature change of $SF_6$ gas($GSF_6$), and $SF_6$ liquid ($LSF_6$) in model GIS (Gas Insulated Switchgear) are described. From the experiment's results, the breakdown characteristics classify the vapor stage of $SF_6$ according to Paschen's law, in which the gas & liquid coexisted stage of voltage value increases, resulting in much deviation and the breakdown of voltage ($V_B$) low stage as the interior of the chamber gets filled with a mixture of $SF_6$ that is not liquefacted and remaining air that cannot be ventilated. The ability of $LSF_6$ insulation is higher than the high-pressurized $SF_6$ gas. The breakdown characteristics of $LSF_6$ were produced by bubble formed evaporation of $LSF_6$ and bubbles caused by high electric emission. It is considered in this paper that the results are fundamental data for electric insulation design of superconductor and cryogenic equipments machinery that will be studied and developed in the future.

• Nuclear Engineering and Technology
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• v.32 no.5
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• pp.433-445
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• 2000

The interfacial area concentration (IAC) is one of the most important parameters in the two-fluid model for two-phase flow analysis. The IAC can be measured by a local conductivity probe method that uses the difference of conductivity between water and air/steam. The number of sensors in the conductivity probe may be differently chosen by considering the flow regime of two-phase flow. The four sensor conductivity probe method predicts the IAC without any assumptions of the bubble shape. The local IAC can be obtained by measuring the three dimensional velocity vector elements at the measuring point, and the directional cosines of the sensors. The five sensor conductivity probe method proposed in this study is based on the four sensor probe method. With the five sensor probe, the local IAC for a given referred measuring area of the probe can be predicted more exactly than the four sensor probe. In this paper, the mathematical approach of the five sensor probe method for measuring the IAC is described, and a numerical simulation is carried out for ideal cap bubbles of which the sizes and locations are determined by a random number generator.

• Transactions of the Korean Society of Mechanical Engineers
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• v.4 no.3
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• pp.96-104
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• 1980

유압이 변화할 때 증기기포의 크기를 구하는 공식을 제시하였다. 이 공식은 변화하는 유압하에서 기포의 크기를 상한과 하한으로 표시한 Hopper, Faucher 및 Eidlitz가 제시한 공식과, Plesset과 Zwick이 해결한 일정유압하에서 성립하는 기포에 관한 간단한 asymptotic 공식을 모두 대체 하기 위한 것이다. 여기에 제시한 새로운 공식의 정확성을 검토하기 위하여 Hooper, Faucher 및 Eidlitz가 보고한 실험결과와 이론적으로 얻은 결과와를 비교하여 보았다.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.11
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• pp.810-819
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• 2006

This paper proposes an Adaptive Double Buffer Model. As a new FIFO buffer model, this technique minimizes packet losses from network congestion by logically managing buffers. It allocates the spare spaces of non-congested buffers to congested buffers by allowing receive/send buffers to share two queues, and hence it minimizes packet losses. In contrast to the buffer model utilizing a free list, this buffer model can prevent the bubble phenomenon caused by a memory leak and thereby apply to a network buffer in a restricted environment. Also, compared with the model using an way, this model brings maximum 100 percent improvement in accepting packets and compared with the model utilizing a free list, this model has the similar efficiency Results of the performance test on Adaptive Double Buffer Model, shows that this proposed model decreases packet losses and enhances memory efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.10
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• pp.1114-1122
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• 2005

This research investigates the effects of sonication mode, reaction temperature and volume on sonolysis of 1,4-dioxane in order to increase the degradation efficiency and kinetics. The degradation efficiency in case with pulse mode was about 10 % higher than that in case with continuous mode. The degradation profiles in both cases, which were performed without the control of reaction temperature and in 1000 mL, were composed of three steps. However, 1,4-D was mainly degraded in the initiation step as the first portion and the acceleration step as the second portion. The initial step agreed with zero-order expression well, while the acceleration step could be fitted with pseudo 1st-order expression. The kinetic model in case with $5^{\circ}C$ and 300 mL conformed to pseudo 1st-order, while that in cases with $10^{\circ}C$ to $40^{\circ}C$ agreed with zero-order expression. The degradation efficiency and profile of 1,4-D in the experiment with $20^{\circ}C$ and 300 mL was higher and simpler than that in case with $20^{\circ}C$ and 1000 mL. The reaction temperature and volume influence bubble intensity, which was produced in sonication. The increase of bubble intensity induced to augment the production of OH radical in sonication.

• The Journal of the Korea Contents Association
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• v.22 no.5
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• pp.56-66
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• 2022

Due to the recent increase in information encountered on social media, algorithm-based recommendation formats selectively provide information based on user information, which often causes a filter bubble effect by an Echo Chamber. Eco-chamber refers to a phenomenon in which beliefs are amplified or strengthened by communication only in an enclosed system, and filter bubbles refer to a phenomenon in which information providers provide customized information according to users' interests, and users encounter only filtered information. The purpose of this study is to propose a method of efficiently selecting information as a way to improve the filter bubble phenomenon by such an echo chamber. The research progress method analyzed recommended algorithms used on YouTube, Facebook and Amazon. In this study, humanities solutions such as training critical thinking skills of social media users and strengthening objective ethical standards according to self-preservation laws, and technical solutions of model-based cooperative filtering or cross-recommendation methods were presented. As a result, recommended algorithms should continue to supplement technology and develop new techniques, and humanities should make efforts to overcome cognitive dissonance and prevent users from falling into confirmation bias through critical thinking training and political communication education.

• Resources Recycling
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• v.33 no.3
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• pp.38-47
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• 2024

Molybdenite is the primary molybdenum resource and is extracted via flotation due to its unique hydrophobic surface. Meanwhile, the grade and crystal size of mined molybdenite are decreasing. As a result, the size of the molybdenum ore required for liberation is decreasing, and the flotation process's feed size input is also decreasing. Therefore, in order to secure molybdenum, it is necessary to perform research on the flotation for the fine molybdenite. In this study, we developed a method to enhance the flotation efficiency of fine molybdenite particles in the range of 5-30 ㎛. The methodology involved implementing bubble size reduction and particle aggregation. Through simulations of bubble-particle collision probability and flotation experiments, we were able to find the ranges of bubble size and particle aggregate size that make fine particles float more effectively. This range provided the conditions for effective flotation of fine molybdenite particles. Therefore, we will implement the flotation conditions established in this study for fine molybdenum ore to improve the flotation process in molybdenum mineral processing plants in the future.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.407-410
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• 2006

This study describes a simulation of two-dimensional bubble forming and motion by the Lattice Boltzmann Method with the phase field equation. The free energy model is used to treat the interfacial force and deformation of binary fluids system, drawn into a T-junction the micro channel. A numerical simulation of a binary flow in a cross-junction channel is carried out by using the parallel computation method. The aim in this investigation is to examine the applicability of LBM to numerical analysis of binary fluid separation and motion in the micro channel.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.67-74
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• 1998

Reducing drag of vehicles are the main concern for the body shape designers in order to lower fuel consumption rate and to aid the driving stability. The drag of bluff bodies like transportation vehicles is mostly pressure drag due to the flow separation, which can minimized by controlling the location and size of the separation bubble. In the present study, the TURBO-3D code is incorporated with optimal algorithm based on analytical approximation method to obtain optimal afterbody shape of the MIRA Model corresponding to the lowest drag coefficient. For this purpose three mutually independent afterbody angles are chosen as design variables, while the drag coefficient is chosen as an objective function. It is demonstrated in the present study that an optimal body shape having lowest drag coefficient which is about $6\%$ lower than that of the original shape has been successfully obtained within number of iterations of the optimal design loop.