• Korean Journal of Ichthyology
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• v.33 no.4
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• pp.278-286
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• 2021

The habitat characteristics and feeding ecology of the Siberian stone loach Barbatula toni were investigated in Bukcheon (Stream), Eocheonri, Ganseong-eup, Goseong-gun, and Gangwon-do, Korea from January to December 2013. B. toni lived in rapids or slow rapids from the upper stream to downstream, with the largest number of inhabitants in the middle-downstream regions. As a result of analyzing habitat preferences by age, 0+ and 1+ to ≥3+ showed differences. Ages of 0+(juveniles) lived mainly in rapidly flowing water (37.6±26.79 cm/sec) and low water depths (13.3±9.47 cm) in the pebble bottoms (substratum particle size 9.5±6.66 cm), but ages 1+ to ≥3+ lived mainly in relatively slowly flowing water (13.3±17.33 cm/sec) and relatively deep depths (25.9±10.31 cm) in stone and large stone bottoms (substratum particle size 18.0±7.63 cm). B. toni was mainly eaten from March to December when the temperature was above 5℃, and the amount of food eaten peaked in June and October. Their main food sources analyzed by the index of relative importance (IRI) included Diptera (57.0%), Ephemeroptera (29.3%), and Trichoptera (13.5%). The juveniles (age 0+) fed on small-sized prey such as Diptera and Trichoptera whales, but as they grew, they mainly ate large-sized Ephemeroptera. These feeding habits and changes in food according to the growth of B. toni were very similar to those of sibling species, B. nuda.

• Advances in nano research
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• v.16 no.4
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• pp.375-394
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• 2024

The extensive utilization of concrete has given rise to environmental concerns, specifically concerning the depletion of river sand. To address this issue, waste deposits can provide manufactured-sand (MS) as a substitute for river sand. The objective of this study is to explore the application of machine learning techniques to facilitate the production of manufactured-sand concrete (MSC) containing stone nano-powder through estimating the splitting tensile strength (STS) containing compressive strength of cement (CSC), tensile strength of cement (TSC), curing age (CA), maximum size of the crushed stone (Dmax), stone nano-powder content (SNC), fineness modulus of sand (FMS), water to cement ratio (W/C), sand ratio (SR), and slump (S). To achieve this goal, a total of 310 data points, encompassing nine influential factors affecting the mechanical properties of MSC, are collected through laboratory tests. Subsequently, the gathered dataset is divided into two subsets, one for training and the other for testing; comprising 90% (280 samples) and 10% (30 samples) of the total data, respectively. By employing the generated dataset, novel models were developed for evaluating the STS of MSC in relation to the nine input features. The analysis results revealed significant correlations between the CSC and the curing age CA with STS. Moreover, when delving into sensitivity analysis using an empirical model, it becomes apparent that parameters such as the FMS and the W/C exert minimal influence on the STS. We employed various loss functions to gauge the effectiveness and precision of our methodologies. Impressively, the outcomes of our devised models exhibited commendable accuracy and reliability, with all models displaying an R-squared value surpassing 0.75 and loss function values approaching insignificance. To further refine the estimation of STS for engineering endeavors, we also developed a user-friendly graphical interface for our machine learning models. These proposed models present a practical alternative to laborious, expensive, and complex laboratory techniques, thereby simplifying the production of mortar specimens.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.38 no.1
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• pp.44-49
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• 2012

Introduction: Sialolithes are initiated by localized deposition of calcified material in the salivary glands. And that may even cause various symptom especially swelling and pain. This study purposes to collect statistical data of sialolithiasis for clinical analysis. Materials and Methods: Among forty seven patients who have visited Seoul National University Dental Hospital during 2004-2009, patients' age, sex, location and size of stone, radiodensity of stone, symptom, surgical procedure were investigated. Statistical correlation between size, location, symptom was evaluated. Chemical composition was analyzed for 3 sialolithes. Results: The average age was 41.4 years. Sialolithiasis had slight female predilection (57.4%). Most cases occurred in the submandibular glands (91.5%). And most cases had radiopaque features (95.8%). The average size was 7.17 mm. The most frequent location of the stones were the duct orifice and the submandibular gland hilum (16 cases in each), followed by the middle part of the duct (n=8), the intraglandular area (n=4), and the proximal part of the duct (n=3). Eleven cases were asymptomatic. Thirty six cases had complaints of pain, swelling, hardness, and decrease in saliva flow (multiple symptoms). Various methods of surgery was performed. Two cases were self-removed. Thirty seven cases underwent procedure involving stone removal alone. Six cases underwent gland extirpation, and two cases underwent ductoplasty. Conclusion: There was no statistical correlation between size, location, and symptoms. Sialolith was composed of Ca (58.5-69.3%), P (30.7-35.7%), organic material, and trace inorganic material.

• Journal for History of Mathematics
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• v.19 no.1
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• pp.43-54
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• 2006

The purpose of this paper, followed by 'Nature$\cdot$Human, and Golden Section I ', is to study aesthetic consciousness, mentality model and body proportion of human, and the golden section applied to architecture and hand axe of stone age. In particular, handaxes of one million years ago have shown that they had critical competency to the basis of art and mathematics in the future. Furthermore, without pen, paper and ruler, the existence of mentality model made fundamental conversion of mathematics possible. Different sizes of handaxes were made by maintaining the equal golden section. This was the first example in relation to the principle mentioned in 'Stoicheia' by Euclid which was published hundred thousands of years later.

• Advances in nano research
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• v.15 no.6
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• pp.533-539
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• 2023

This study aims to examine four machine learning (ML)-based models for their potential to estimate the splitting tensile strength (STS) of manufactured sand concrete (MSC). The ML models were trained and tested based on 310 experimental data points. Stone nanopowder content (SNPC), curing age (CA), and water-to-cement (W/C) ratio were also studied for their impacts on the STS of MSC. According to the results, the support vector regression (SVR) model had the highest correlation with experimental data. Still, all of the optimized ML models showed promise in estimating the STS of MSC. Both ML and laboratory results showed that MSC with 10% SNPC improved the STS of MSC.

• Korean Journal of Child Studies
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• v.25 no.3
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• pp.27-39
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• 2004

This study was to find out children's Negotiation Levels(NLs) according to their age and gender. The subjects for this study were 143 children of 7, 9, 12 years. Two children dyads participated in the experimental play situation with Rokenbok Electronic Toy Systems. The NLs in children's interactive dialogue & actions were scored with Stone, Robinson & Taylor(1980)'s 'Negotiation of Task Completion Coding Manual'. They were coded into Level 0(no interaction), Level l(one way interaction), Level 2(reciprocally interaction), Level 3(mutual or cooperative interaction). The results were as follows; 1) 12-year-old children negotiated with higher level than 7-and 9-year old children 2) Boys' NLs average were higher than girls'. These results imply that 1) the fluctuation of NLs in childhood, especially around 10 years, should be interpreted carefully, 2) various measuring kits for negotiation should be developed considering children's characteristics, such as age, gender etc.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.197-200
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• 2002

This study is performed to examine the non-destruction properties of the Hwangtoh mortar. The absorption ratio is in the range of $8.25%{\sim}18.16%$, it tend to increase with increase using the stone dust and Hwangtoh. The pulse velocity and dynamic modulus at the curing age 7 and 28days are in the range of $2,290m/s{\sim}4,140m/s,\;2,976m/s{\sim}4,219m/s\;and\;105{\times}10^3kgf/cm^2{\sim}293{\times}10^3kgf/cm^2,\;137{\times}10^3kgf/cm^2{\sim}318{\times}10^3kgf/cm^2$, respectively. They tend to decrease with increase using the stone dust and Hwangtoh.

• Safety and Health at Work
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• v.5 no.3
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• pp.136-139
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• 2014

Background: Occupational injuries cause major health problems, which the developed, developing, and underdeveloped nations worldwide are facing today. The present study aimed to assess dental caries, periodontal health of stone mine workers, and the relationship between wasting diseases and the years of working experience. Methods: The study population comprised 510 men, selected based on the stratified cluster sampling procedure. Clinical oral examinations were carried out, and periodontal disease, dental caries, and wasting diseases were recorded. Results: Workers were in the age group of 17-56 years; the prevalence of dental caries in the workers was found to be 74%, with a mean decayed, missing, filled teeth index of 2.89. A periodontal pocket of more than 6 mm was observed in 6% of the workers. Conclusion: The oral health of mine workers is in a poor state; steps should be taken so as to provide basic medical and dental care facilities.

• Journal of Conservation Science
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• v.1 no.1 s.1
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• pp.40-59
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• 1992

Stone-monuments, distributed in this area, have been investigated and studied in geological and conservational points of view. They are seemed to have been built from the Shilla to Koryeo Kingdoms, although more systematic studies are needed. The used rocks in these monuments are mainly biotite granite of Jurassic age. They are strongly weathered and partly exfoliated along igneous lineation about 1-2 mm(maximum up to 5 mm). They are mainly effected by chemical weathering to be selectively dissolved and by various kind of moss. For conservation, it must be scientifically considered based on characteristics and kind of rock phase, factors on weathering process, situation and protection.

• Journal of the korean academy of Pediatric Dentistry
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• v.8 no.1
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• pp.25-36
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• 1981

The purpose of this longitudinal study was to measure and analyze the width and length changes of dental arches at age 7 to 9. 66 children were selected for this study. Stone models obtained from these children were measured and analyzed annually. The results were as follow. 1. The widths of upper arch increased by age both in males and females except the region of second deciduous molars. 2. The widths of lower arch increased by age significantly both in males and females. 3. The lengths of dental arches increased by age both in males and females at anterior portion. ; did not increase at Posterior portion. 4. The upper widths of males were wider than those of females at age 9, but no significant difference were present at age 7 and 8. 5. The differences of the lower widths between males and females were not present except the region of the second deciduous molars (E-E) at age 7. 6. There were few differences between the lengths of males and females except the posterior lengthes at age 7. 7. The widths and lengths of upper arches were difinitely wider and longer than lower arches.