• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.119-125
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• 2004

Radiant tube heaters are widely used for indirect heating in heat treatment processes such as continuous annealing line(CAL) or continuous galvanizing line(CGL). Main issues for radiant tube are temperature uniformity, lifetime, thermal efficiency. To achieve higher heat release, the radiant tubes are fired at a higher fuel rate and therefore local overheating occur. A numerical simulation based on a commercial code FLUENT has been performed to investigate local overheating of radiant tube heaters. To minimize local overheating, the effects of radiating fins, flue gas recirculation(FGR), two-stage combustion were investigated. More uniform temperature distribution was achieved in the longitudinal direction within the tube with radiating fins and this contributed to increase the life of radiant tubes. Furthermore, the radiant tube with radiating fins was proven to be more efficient than the one without fins. The effects of flue gas recirculation and two stage combustion on the efficiency of the radiant tube were also considered and the results were presented.

• Entomological Research
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• v.48 no.5
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• pp.354-361
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• 2018

Plant essential oils (EOs) exhibit an array of biological activities against insect pests. However, their negative influences on the pheromonal activity of azuki bean beetle (ABB), Callosobruchus chinensis L. have not received research attentions. ABB is a field-to-storage pest of legumes, and its female produces the sex pheromone known as homofarnesal with two isomeric components: 2E- and 2Z-homofarnesal, (2E,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienals and (2Z,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienals. We evaluated the effects of three EOs and their two major components on the attractiveness of male ABBs to synthetic homofarnesal (2E-:2Z-homofarnesal = 6:4) using Y-tube olfactometry in laboratory and rocket traps in the semi-open polyhouse. Y-tube olfactometry showed the significant negative effect of EOs of Illicium verum, Croton anisatum at 10 and 100 ng, and Gaultheria fragrantissima at 100 ng against homofarnesal (100 ng) in attracting male ABBs. Similarly trans-anethole (at 10 and 100 ng) and methyl salicylate (at 100 ng) also ascertained significant negative effect against homofarnesal (100 ng) in Y-tube olfactometry. When 10 mg of each of trans-anethole and methyl salicylate was released at the downstream of 30 mg homofarnesal lure in rocket traps, highly significant effect was achieved against attractiveness of homofarnesal to ABB males. This study ascertained significant level of negative effect of the tested EOs and their major components to homofarnesal, tracing out a new opportunity of integrating them in ABB management programs both in field and storage.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.15 no.2
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• pp.64-70
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• 2019

In recent years, attention has been paid to the integrity of steam generator (SG) tubes due to severe accident and beyond design basis accident conditions. In these transient conditions, steam generator tubes may be damaged by high temperature and pressure, which might result in a risk of fission products being released to the environment due to the failure. Alloy 690 which has increased the Cr content has been replaced for the SG tube due to its high corrosion resistance against stress corrosion cracking (SCC). However, there is lack of research on the high temperature creep rupture and life prediction model of Alloy 690. In this study, creep test was performed to estimate the high temperature creep rupture life of Alloy 690 using tube specimens. Based on manufacturer's creep data and creep test results performed in this study, creep life prediction was carried out using the Larson-Miller (LM) Parameter, Orr-Sherby-Dorn (OSD) parameter, Manson-Haford (MH) parameter, and Wilshire's approach. And a hyperbolic sine (sinh) function to determine master curves in LM, OSD and MH parameter methods was used for improving the creep life estimation of Alloy 690 material.

• The Research Journal of the Costume Culture
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• v.28 no.3
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• pp.389-407
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• 2020

With YouTube's overwhelming share of the market, research on analyzing the types of content on YouTube is essential. An analysis of major global fashion YouTubers that the types of video content could be largely classified into three main categories: Fashion, beauty and daily life. The fashion category was subdivided into styling and fashion product review content type. The beauty category was subdivided into tutorials, beauty product reviews, and beauty tip content types. The daily life category was subdivided into daily sharing, consultation, and Q & A content types. Video content within fashion YouTuber channels is accompanied by expertise in fashion and beauty. At the same time, videos on daily life are uploaded, and through interactive communication with viewers, YouTubers form an intimate bond with subscribers. Content emphasizing entertainment, not just information delivery that introduces fashion products, is attracting growing interest among subscribers. This study analyzed the content of the increasingly popular fashion YouTuber channels and determined its important characteristics. The study makes a significant contribution to academic research by laying a foundation for future studies of YouTube content in the fashion field. Since differences in country of birth and race among YouTubers may influence content production, follow-up research will be conducted on the types and characteristics of domestic fashion YouTubers.

• Fashion & Textile Research Journal
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• v.23 no.2
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• pp.212-225
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• 2021

With the recognition of YouTube as an information search tool, YouTube creators have subsequently become sources of information to consumers. Accordingly, this study aims to analyze the consumers' response of famous fashion YouTubers in Korea, and to identify differences in consumer response based on the gender and generation of YouTubers. During the period from the opening of fashion creators' YouTube channels, we collected postings on blogs and Internet cafes using textom. As a result of preliminary investigation, six fashion YouTubers were selected. First, all the selected fashion YouTubers were well recognized by consumers as fashion informants. However, Milanonna has been shown to act as a life advisor and as an informant for luxury brands at the same time. Second, female fashion YouTubers were perceived with themes related to daily life, beauty, emotions, and mood rather than fashion itself; whereas, male fashion YouTubers appeared to be more interested in fashion accessories, especially with respect to the basic style. Third, Generation Z fashion YouTubers used the most non-fashion keywords, and their Millennial counterparts used keywords related to fashion items and product purchase properties. However, consumer response to OPAL fashion YouTubers have emerged with items such as life experiences, wisdom, and advice. Moreover, OPAL fashion YouTubers showed a variety of consumer assessments and the YouTuber's personal background. This study's analysis of the differences in the consumer response to fashion YouTubers based on gender and age enables the establishment of an appropriate strategy to attract target consumers and identify their appeal points.

• Journal of Digital Convergence
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• v.20 no.2
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• pp.299-309
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• 2022

YouTube videos secure the latest trends in the field and provide viewers' preferences and non-preferences. This study analyzes the discussion of death in recent YouTube videos and explores the relationship between life, well-dying, and well-aging. The purpose of this study is to contribute to the establishment of a healthy life for Koreans by exploring relevance. The survey period and target are 13 videos uploaded on YouTube from 2019 to 2021. As a result of the investigation, it was possible to encompass 25 speakers who were discussing death centered on doctors. Video speakers in charge of various areas conducted various discussions on death from the perspective of experts. The key points are the true value of life, death that you don't need to fear, the importance of hope, the naturalness of death, etc. 11 expert perspectives are measured into 4 types based on 4 criteria: life, death, well-aging, and well-dying. Despite the limitations of studying 13 extracted at a specific time, this study revealed that YouTube videos are a place for free communication. It can contribute in part to maintaining and improving the health of our lives in the future and researching convergence.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.3
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• pp.281-287
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• 2012

The internal oxide scale of twelve superheater and reheater tubes were tested which were serviced for 30,000~120,000 hours in thermal power plants. The oxide scale was formed in three layers. The Cr-rich area was observed beneath the original metal surface. The hematite ($Fe_2O_3$) phase was formed on the outer surface. The intermediate layer was magnetite ($Fe_3O_4$). The thickness of Cr-rich layer was about half of the total scale. All layers grew during the operation hour of the plant. The thickness of thickest scale was 0.2mm in superheater tubes. This can increase the tube metal temperature about $7^{\circ}C$ more than initial state. $7^{\circ}C$ tube metal temperature can reduce tube life about 30%, but the boiler tube's design margin is big enough therefore it has been analyzed that it would not effect on the life span.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.4
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• pp.208-216
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• 2020

With the spread of smart manufacturing, one of the key topics of the 4th industrial revolution, manufacturing systems are moving beyond automation to smartization using artificial intelligence. In particular, in the existing automatic machining, a number of machining defects and non-processing occur due to tool damage or severe wear, resulting in a decrease in productivity and an increase in quality defect rates. Therefore, it is important to measure and predict tool life. In this paper, ν-ASVR (ν-Asymmetric Support Vector Regression), which considers the asymmetry of ⲉ-tube and the asymmetry of penalties for data out of ⲉ-tube, was proposed and applied to the tool wear prediction problem. In the case of tool wear, if the predicted value of the tool wear amount is smaller than the actual value (under-estimation), product failure may occur due to tool damage or wear. Therefore, it can be said that ν-ASVR is suitable because it is necessary to overestimate. It is shown that even when adjusting the asymmetry of ⲉ-tube and the asymmetry of penalties for data out of ⲉ-tube, the ratio of the number of data belonging to ⲉ-tube can be adjusted with ν. Experiments are performed to compare the accuracy of various kernel functions such as linear, polynomial. RBF (radialbasis function), sigmoid, The best result isthe use of the RBF kernel in all cases

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.13-18
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• 1998

In this study. the fatigue lives of two kinds of specimens made by $CO^2$ gas weld were assessed. The materials for two kinds of specimens were taken out of the virgin carbon steel tubes and the used carbon steel tubes respectively. As a result, it was found that the fatigue lives of two groups of specimens were in the same order of magnitude.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.651-655
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• 2000

The objective of present work is to investigate experimentally the characteristics of heat transfer. A fluidized bed combustion has advantages of pollution control, fuel flexibility and excellent heat transfer. The present study investigates fundamental phenomena of bed-to-surface heat transfer in high temperature fluidized beds to improve design of immersed tube surface. The tested operating variables are bed temperature, supeficial velocity, mean size of bed material, and the rake angle of fin. Generally, heat transfer rates between the fluidized bed and immersed finned-tube are much higher than those of a smooth tube. A life time of finned-tube is generally longer than that of smooth tube.