• Computers and Concrete
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• v.19 no.4
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• pp.357-363
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• 2017

This paper conveys the effects of fly ash and silica fume incorporated in concrete at various replacement ratios on the durability properties of concretes. It is quite well known that concrete durability is as much important as strength and permeability is the key to durability. Permeability is closely associated with the voids system of concrete. Concrete, with less and disconnected voids, is assumed to be impermeable. The void system in concrete is straightly related to the mix proportions, placing, compaction, and curing procedures of concrete. Reinforced concrete structures, particularly those of subjected to water, are at the risk of various harmful agents such as chlorides and sulfate since the ingress of such agents through concrete becomes easy and accelerates as the permeability of concrete increases. Eventually, both strength and durability of concrete reduce as the time moves on, in turn; the service life of the concrete structures shortens. Mineral additives have been proven to be very effective in reducing permeability. The tests performed to accomplish the aim of the study are the rapid chloride permeability test, pressurized water depth test, capillarity test and compressive strength test. The results derived from these tests indicated that the durability properties of concretes incorporated fly ash and silica fume have improved substantially compared to that of without mineral additives regardless of the binder content used. Overall, the improvement becomes more evident as the replacement ratio of fly ash and silica fume have increased. With regard to permeability, silica fume is found to be superior to fly ash. Moreover, at least a 30% fly ash replacement and/or a replacement ratio of 5% to 10% silica fume have been found to be highly beneficial as far as sustainability is concerned, particularly for concretes subjected to chloride bearing environments.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.3
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• pp.454-466
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• 2017

North Korea intended to increase the power of its nuclear weapons and standardize warhead to be loaded in ballistic missiles through the $4^{th}$ and $5^{th}$ nuclear tests. In this study, three kinds of nuclear weapons that North Korea might have used in the $4^{th}$ and $5^{th}$ nuclear tests to achieve their technical goals were suggested. Monte Carlo modeling and various technical assessments have shown that boosted fission weapons are most likely to be used. Also, using the empirical formula considering the burial depth of explosion, we found that the yield of the $4^{th}$ and $5^{th}$ nuclear tests is at least twice as strong as that is expected it could be and the initial design power could reach 8kt before amplification. This means that North Korea has already achieved a substantial level of nuclear fusion technology through the $4^{th}$ test and has made a breakthrough in the miniaturization of nuclear weapons through the $5^{th}$ test. After two or three additional tests, North Korea is expected to have nuclear missiles equipped with nuclear warhead by 2020, which is expected to complete ballistic missile development.

• Journal of Conservation Science
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• v.4 no.1 s.4
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• pp.3-10
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• 1995

This study focused on the reconstructional point of Shinan ship-wreck that was excavated between $1976\~1984$. The wreck, which might be sunk in the beginning of the 14th century, is regarded as a vessel of Yuan dynasty, China. This paper tried to find out some structural characteristics and principal dimensions for restoration. The Shinan shipwreck's structural characteristics are summarized as follow, 1) The Shinan shipwreck is formed V-shaped cross section with bar keel, 2) The vessel is divided 8 holds by 7 bulkheads. 3) The ship has flat type stem and transome stern. 4) A rabbeted clinker -built is basically adopted on planking joint. 5) A wooden sheathing, which means a sort of protecting board against marine insects, is covered outside of the main hull, 6) For making an watertight structure, oakum and lime mixtured t'ung-oil are used along the seam of planking and bulkhead. 7) A V-shaped deep water-way exists at both deck side. 8) The shipwreck is believed to have 2 masts at least. 9) The shiptimbers are classified as Chinese Red Pine(Pinus Massonina) which is mainly grown in the southern part of China. Considering as mentioned above the structural characteristics, Shinan ship-wreck could be classified as Chinese Fu-chuan type(복선형) of sea-going ship. The Shinan ship's principal dimensions which are calculated on the basis of Chinese traditional shipbuilding custom, are as follow, Length overall(L.O.A). : 34.80m Length water line(L.W.L) : 24.90m Breadth(B.max.) : 11m Breadth(B) : 10m Depth at keel line(H) : 3.75m Draft(D). : 3.15m Freeboard(F) : 0.65m Ratio, length/breadth(L/B). : 2.26 Ration, breadth/depth(B/D) : 3.5 Height of stem : 7m Height of stern : 10m Displacement : ab.340ton.

• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.1-8
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• 2007

In Norway, about 30 subsea tunnels have been constructed over the last 20 years. The minimum depth of 17 subsea tunnels is 56 m and rock cover are between 23 and 49 m. As the project areas for subsea tunnel are covered by water, special investigation techniques need to be applied and the investigation results are more uncertain than that of most conventional tunnel projects. The indefinite potential of water inflow and the salinic character of ingress water represent considerable problems for tunnel equipment and rock support materials. The least stable conditions are represented by major faults or weakness zones containing heavily crushed rock and clay gouge. This paper introduces the Oslofjord subsea tunnel project including minimum rock cover requirement, risk of water inflow, investigation costs, construction costs, and traffic & operation costs.

• Imaging Science in Dentistry
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• v.43 no.4
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• pp.219-225
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• 2013

Purpose: The purpose of this study was to determine the prevalence of missing and impacted third molars in people aged 25 years and above. Materials and Methods: The study sample of 3,799 patients was chosen randomly from patients who visited Pusan National University Dental Hospital and had panoramic radiographs taken. The data collected included presence and impaction state, angulation, and depth of impaction of third molars, and radiographically detected lesions of third molars and adjacent second molars. Results: A greater percentage of men than women retained at least one third molar. The incidence of third molars decreased with increasing age. The incidence of partially impacted third molars greatly declined after the age of 30. Vertically impacted maxillary third molars and horizontally impacted mandibular third molars were most frequent in all age groups. Among the maxillary third molars, those impacted below the cervical line of the second molar were most frequent in all age groups, and among the mandibular third molars, deeply impacted third molars were most frequent in those aged over 40. Dental caries was the most common radiographic lesion of the third molars. Mesioangularly impacted third molars showed radiographic lesions in 13 (9.5%) adjacent maxillary second molars and 117 (27.4%) mandibular second molars. Conclusion: The number of remaining third molars decreased and the percentage of Class C depth increased with age. Caries was the most frequent lesion in third molars. Partially impacted mesioangular third molars showed a high incidence of caries or periodontal bone loss of the adjacent second molar. Regular oral examination will be essential to keep asymptomatic third molars in good health.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.119-126
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• 2001

The potential pollution problems resulting from tanker collision necessitate the requirement for an effective structural design and the development of relevant safety regulation. During a few decades, the great effort has been made by International Maritime Organization and the Administration, etc, to reduce oil spillage from collision accidents. However there is still a need for investigation in the light of structural evaluation method for the experiments and rational analysis, and design development for an operational purpose of ships. This study is aimed at investigating a complicated structural response of bow structures of oil carriers for assessing the energy dissipation and crushing mechanics of striking vessel through a methodology of the numerical analysts for the various models and its design changes. Through this study an optimal bow construction absorbing great portion of kinetic energy in the least penetration depth prior to reach to the cargo area and an effective location of collision bulkhead are investigated. In order to obtain a rational results in this study, three stages of response analysis procedures are performed as follows; 1). 16 simplified ship models are used to investigate the structural response against bow collision with variation of primary and secondary members. Mass and speed are also varied in two conditions. 2). 21 models conisted of 5 size of full scaled oil carriers are used to perform the collision simulation with the various sizes and deadweight delivered in a recent which are complied with SOLAS and MARPOL. 3). 36 models of 100k oil carrier are used to investigate the structural response and its influence to the collision bulkhead against bow collision in variation with location of collision bulkhead, primary mombers, framing system and colliding conditions, etc.

• Journal of Periodontal and Implant Science
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• v.39 no.1
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• pp.53-58
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• 2009

Purpose: The resective treatment in mandibular Degree III furcation areas includes root resection and tunnel preparation. The purpose of this retrospective study is to evaluate which treatment procedure(root resection vs tunnel preparation) has more favorable prognosis in mandibular Degree III furcation involvement. Materials and methods: The subjects of this study were patients who were treated their mandibular posteriors with either root resection(22 teeth on 22 patients) or tunnel preparation(24 teeth on 22 patients) and have participated in periodic recall check program for at least 2 years. Failure rate, plaque index, bleeding on probing and probing pocket depth were measured and the results were compared and statistically analysed. Results: Failure rates of root resection and tunnel praparation were 13.6% and 16.7%, respectively, and showed no significant difference between two procedures. No significant differences were observed between two procedures with respect to plaque index, bleeding on probing and probing pocket depth. Conclusion: root resection and tunnel preparation are both effective procedures to treat mandibular posterior furcation involvement, if adequate treatment of choice is made and patient's cooperation is accompanied. However, tunnel preparation is more preservative procedure in mandibular posterior furcation involvement since root canal treatment and prosthetic restoration are needed additionally, in case of root resection.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.2
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• pp.79-84
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• 2000

The aim of this study was to evaluate the chemical properties of orchard soils through which their soil fertilities were discriminated. Total 877 soil samples in major orchard area, i.e. from 239 apple, 369 pear, 168 grape, 101 peach orchards, were examed on the basis of temporary optimal range for each component. The levels of fertility were ranged from 3.0 to 65.2% compared to optimum fertility, suggesting that almost orchard soils contained inadequately soil components. The contents of chemical component have a tendency to decrease with soil depth gradually from surface to subsoil. This meaned that the contents of various components in subsoil could be estimated on the basis of analysis of surface soil, using the linearly fitted equations of the relationship between component in subsoil and in surface at least to which fertility were samely managed. Furthermore, even when only the content of components in 20cm depth surface soil was analyzed, it could be determined whether the amount of each component in the surface soil is surplus or deficient.

• Journal of Periodontal and Implant Science
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• v.49 no.2
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• pp.90-104
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• 2019

Purpose: The aim of this study was to evaluate clinical and radiographic changes and the survival rate after periodontal surgery using deproteinized bovine bone mineral (DBBM) with 10% collagen or DBBM with a collagen membrane in endo-periodontal lesions. Methods: A total of 52 cases (41 patients) with at least 5 years of follow-up were included in this study. After scaling and root planing with or without endodontic treatment, periodontal regenerative procedures with DBBM with 10% collagen alone or DBBM with a collagen membrane were performed, yielding the DBBM + 10% collagen and DBBM + collagen membrane groups, respectively. Changes in clinical parameters including the plaque index, bleeding on probing, probing pocket depth, gingival recession, relative clinical attachment level, mobility, and radiographic bone gains were evaluated immediately before periodontal surgical procedures and at a 12-month follow-up. Results: At the 12-month follow-up after regenerative procedures, improvements in clinical parameters and radiographic bone gains were observed in both treatment groups. The DBBM + 10% collagen group showed greater probing pocket depth reduction ($4.52{\pm}1.06mm$) than the DBBM + collagen membrane group ($4.04{\pm}0.82mm$). However, there were no significant differences between the groups. Additionally, the radiographic bone gain in the DBBM + 10% collagen group ($5.15{\pm}1.54mm$) was comparable to that of the DBBM + collagen membrane group ($5.35{\pm}1.84mm$). The 5-year survival rate of the teeth with endo-periodontal lesions after periodontal regenerative procedures was 92.31%. Conclusions: This study showed that regenerative procedures using DBBM with 10% collagen alone improved the clinical attachment level and radiographic bone level in endo-periodontal lesions. Successful maintenance of the results after regenerative procedures in endo-periodontal lesions can be obtained by repeated oral hygiene education within strict supportive periodontal treatment.

• Korean Journal of Remote Sensing
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• v.37 no.4
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• pp.777-788
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• 2021

Since aerosol has a relatively short duration and significant spatial variation, satellite observations become more important for the spatially and temporally continuous quantification of aerosol. However, optical remote sensing has the disadvantage that it cannot detect AOD (Aerosol Optical Depth) for the regions covered by clouds or the regions with extremely high concentrations. Such missing values can increase the data uncertainty in the analyses of the Earth's environment. This paper presents a spatial gap-filling framework using a univariate statistical method such as DCT-PLS (Discrete Cosine Transform-based Penalized Least Square Regression) and FMM (Fast Matching Method) inpainting. We conducted a feasibility test for the hourly AOD product from AHI (Advanced Himawari Imager) between January 1 and December 31, 2019, and compared the accuracy statistics of the two spatial gap-filling methods. When the null-pixel area is not very large (null-pixel ratio < 0.6), the validation statistics of DCT-PLS and FMM techniques showed high accuracy of CC=0.988 (MAE=0.020) and CC=0.980 (MAE=0.028), respectively. Together with the AI-based gap-filling method using extra explanatory variables, the DCT-PLS and FMM techniques can be tested for the low-resolution images from the AMI (Advanced Meteorological Imager) of GK2A (Geostationary Korea Multi-purpose Satellite 2A), GEMS (Geostationary Environment Monitoring Spectrometer) and GOCI2 (Geostationary Ocean Color Imager) of GK2B (Geostationary Korea Multi-purpose Satellite 2B) and the high-resolution images from the CAS500 (Compact Advanced Satellite) series soon.