• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.209-216
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• 2016

Holes of rivets, bolts and nuts may cause stress concentration on the plates used in aircraft, ship and other structures. Excessive stress concentration may lead to severe breakage of the plates. Thus, accurate analysis of the stress concentration at the design stage will be important. In this paper, accuracy of EDISON program in stress concentration analysis was examined. By changing hole size on a narrow plate, the change of the stress concentration factor(K) was investigated. Additionally, the same experiment was conducted about series of holes on plate to investigate the interaction between adjacent holes. Then, these numerical results were compared with the analytic prediction. EDISON program showed very high accuracy about stress concentration, since the numerical results was correlated well with the analytic prediction.

• Clinical and Experimental Pediatrics
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• v.56 no.5
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• pp.202-204
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• 2013

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.4
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• pp.323-332
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• 2013

Objectives: This study was conducted in order to investigate the diesel exhaust particle(DEP) concentrations in the thirteen parking lots of large shopping complex. Methods: The real-time black carbon(BC) concentration was determined using an Aethalometer, and elemental/organic carbon concentration was determined according to the method of the National Institute for Occupational Safety and Health(NIOSH) 5040. The particle number concentration(NC), lung deposited surface area concentration(LDSA) and geometric mean diameter(GMD) were determined using a DiSCmini aerosol monitor. Results: The average concentration of BC, EC, OC, NC, LDSA and GMD were $19.1{\mu}g/m^3$, $12.6{\mu}g/m^3$, $51.5{\mu}g/m^3$, $94,000particles/cm^{-3}$, $298{\mu}m^2/cm^{-3}$ and 57 nm in all parking lots, respectively, approximately 3-fold higher than those found in the urban outdoor. The average concentration of BC were $21.3{\mu}g/m^3$ in underground parking lots, 3-fold higher than above parking lots. Conclusions: Therefore, the parking lots at the large shopping complex can be considered a potentially dangerous environment with a high concentration of DEP nanoparticles.

• Korean Journal of Plant Resources
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• v.10 no.3
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• pp.221-226
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• 1997

Improvement of seed protein quality might be an essential issus in soybean and would give more profit directly to both farmers and users. This study was carried out to investigate the effects of reduced-S form(s) on seed storage protein components in soybean during seed filling stages. The reduced-S forms during seed fill were sodium thiosulfate, sodium sulfite, sodium sulfide, thioaceteat, $\beta$-mercaptoethanol, thiourea, thiamine-HCI, L-cysteine, L-cystine, and L-methionine. Seed storage protein concentration did not appear to be affected by any reduced-S forms. However, glycinin and $\beta$-conglycinin concentration seemed to be changed greatly by L-methionine. This resulted in the increase in the 11S/7S ratio(3.58). Among the $\beta$-conglycinin, $\beta$-subunit was not accumulated at all. $\alpha$-subunit concentration appeared to be decreased and $\alpha'$-subunit concentration was not altered in comparison with sulfate control. Also, $\beta$-conglycine concentration, especially $\beta$-subunit concentration, tended to be decreased with L-cystine treatment, resulting in an increase in the 11S/7S ratio(1.83). The glycinin concentration tended to be increased at the expense of the decrease in the $\beta$-conglycinin concentration. Therefore, it is suggested that enhancing soybean protein quality would be achieved by improving metabolic pathways of S assimilation in soybean plants during seed filling period under sulfate-sufficient condition.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.3
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• pp.273-282
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• 2018

Objectives: Dustiness of nanomaterials is considered as exposure index of essential material. Research on dustiness of nanomaterial is needed to control exposure in workplaces. Method: Dustiness measurement using vortex shaker were installed in the laboratory. Nanomaterials, 1 g, was put in the glass test tube and shaked using vortex shaker. Aerosol dispersed was measured using scanning mobility particle sizer(SMPS) and optical particle counter(OPC). Mass concentration using PVC filter and cassette was measured and TEM grid sampling was conducted. Total particle concentration and size distribution were calculated. Image and chemical composition of particles in the air were observed using transmission electron microscopy and energy dispersive X-ray spectrometer. Eleven different test nanomaterials were used in the study. Results: Rank of mass concentration and particle number concentration were coincided in most cases. Rank of nanomateirals with low concentration were not coincided. Two types of fumed silica had the highest mass concentration and particle number concentration. Indium tin oxide, a mixture of indium oxide and tin oxide, had high mass concentration and particle number concentration. Indium oxide had very low mass concentration and particle number concentration. Agglomeration of nanoparticles in the air were observed in TEM analysis and size distribution. In this study, mass concentration and particle number concentration were coincided and two index can be used together. The range of dustiness in particle number concentration were too wide to measure in one method. Conclusion: Particle number concentration ranged from low concentration to high concentration depend on type of nanomaterial, and varied by preparation and amount of nanomaterial used. Further study is needed to measure dustiness of all nanomaterial as one reference method.

• Journal of Environmental Science International
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• v.26 no.1
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• pp.55-65
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• 2017

Average concentration of PM in Seoul metropolitan area satisfied the Korean air quality standard in 2010. Furthermore, concentration of PM in all boroughs across Seoul met the air environment standard in 2012. $PM_{10}$ concentration was relatively higher in center of Seoul in comparison to the rest, while $PM_{2.5}$ concentration showed exactly the contrary result. We analyzed the effect that PM emissions from vehicles would have on PM concentrations across Seoul. The results showed that average annual PM concentration recently decreased in Seoul although the number of vehicles registered annually continued its upward trend. By contrast, average fine dust concentrations in Seoul showed a decline which suggested that correlation between annual average PM concentrations and number of registered vehicles remained low. However, year-on-year vehicle registration rate recently showed a declining tendency in the same way as the trend of changes in average PM concentrations. Particularly, the upward trend in annual average PM concentrations in 2002 and 2007 was consistent with the increase in vehicle registration rate, suggesting that vehicle registration rate was closely associated with changes in PM concentrations.

• Journal of the Korean housing association
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• v.26 no.4
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• pp.55-62
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• 2015

The international concern on the inhalable fine dust is continuing to increase. In addition to the toxic properties of the fine dust itself, it can be more dangerous than other environmental factors since the dust pollution is hard to be detected by human sense. Although the information on outdoor air condition can be acquired easily, the indoor dust concentration is another problem because the indoor air condition is influenced by the architectural environment and human activity. It means occupants may be exposed to indoor dust pollution over a long period without being aware. Therefore the indoor dust concentration should be measured separately and visualized as an intuitive information. By visualizing, the indoor dust concentration in each space can be recognized practically in compare with the degree of pollution in adjacent spaces. Besides the visualization outcome can be used as base data for related research such as an analysis of the relation between indoor dust concentration and architectural environment. Meanwhile, with the development of network and micro sensing devices, it became possible to collect wide range of indoor environment data. In this regards, this paper suggests a system for visualization of indoor dust concentration and demonstrates it on an actual space.

• Journal of Korea Society of Digital Industry and Information Management
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• v.18 no.4
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• pp.67-75
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• 2022

Recently, e-learning has been attracting significant attention due to COVID-19. However, while e-learning has many advantages, it has disadvantages as well. One of the main disadvantages of e-learning is that it is difficult for teachers to continuously and systematically monitor learners. Although services such as personalized e-learning are provided to compensate for the shortcoming, systematic monitoring of learners' concentration is insufficient. This study suggests a method to evaluate the learner's concentration by applying machine learning techniques. In this study, emotion and gaze data were extracted from 184 videos of 92 participants. First, the learners' concentration was labeled by experts. Then, statistical-based status indicators were preprocessed from the data. Random Forests (RF), Support Vector Machines (SVMs), Multilayer Perceptron (MLP), and an ensemble model have been used in the experiment. Long Short-Term Memory (LSTM) has also been used for comparison. As a result, it was possible to predict e-learners' concentration with an accuracy of 90.54%. This study is expected to improve learners' immersion by providing a customized educational curriculum according to the learner's concentration level.

• Journal of the Korean Institute of Navigation
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• v.5 no.1
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• pp.49-70
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• 1981

This article is divided into five chapters: chapter I is the introduction on the subject under examination; chapter II is devoted to explaining the phenomenon of concentration of capital. The writer has attempted here to show the degree of capital concentration in Korean shipping in 1974 and 1979 and made a comparison with that of the selected leading maritime nations; chapter III has been devoted to the economies of scale and the optimum size of shipping firm, firstly introducing empirical studies of the British shipping firms, which had been conducted by American and British economists in the early 1960's, and secondly made a survey of Korean shipping activity during 1974-1979 in terms of economies of scale; chapter IV deals with the reasons of concentration of shipping in light of recent advances of ship technology; chapter V sets forth conclusion.

• International Journal of Oral Biology
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• v.30 no.2
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• pp.65-69
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• 2005

Periodontitis is a multi-microbial disease and the comparison of a series of periodontopathogenic and non-periodontopathogenic bacteria in terms of microbe-host interaction may provide clues to understand the microbial etiology of the disease better. When we deal with twenty different bacterial species in a study, the first technical issue is how to measure the accurate concentration and use the same number of bacterial cells. We measured bacterial concentration by enumerating bacteria stained with SYTOX green for constant time using a flow cytometer and compared the results with those obtained by plate counting. Concentrations calculated by two different methods were very close. Therefore, flow cytometric counting allowed the rapid analysis of live/dead bacteria, offering the advantage of turbidity measurement and that of colony counting together.