• Journal of Korean Society of Water and Wastewater
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• v.21 no.6
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• pp.689-699
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• 2007

The accurate estimation of water pipe deterioration is indispensable to prevent pipe breakage and manage in advance. In this study, corrosion of water pipe is adopted, which is relatively underestimated although it takes most part of deteriorating pipeline. Predicting corrosion rate and corrosion depth of a pipe can make an increase the life span of the pipeline, which is laid under the ground according to characteristics of soil and water corrosion. For the purpose, mathematical models that can presume nominal depth through estimation of pit corrosion and corrosion rate is introduced. As comparison of results with conventional methods in other foreign countries, it is evaluated that the external corrosion depth is estimated less than the models, proposed by other researchers and the internal corrosion rate was processed faster than the external corrosion rate.

• Korean Journal of Ecology and Environment
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• v.44 no.4
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• pp.385-395
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• 2011

The adjustment processes and responses of a series of mining pits by sand or gravel mining were investigated by laboratory experiments. The filling processes of the two pits were affected by the bars developed in the upstream of the channel. However, the bars were not developed and the bed was degradated in the downstream of the pits due to little sediment flow, which was trapped in the pits. The submerged angle of repose in the pits was nearly constant when the pits were being filled. After the filling processes of the pits were finished, the pit was speedily filled with sediment, and the bed was aggradated and migrated with speed. However, the angle of repose decreased. As the distance between the upstream pit and the downstream pit increased, the bed of the pit downstream was tailcutted and degradated. The migration speed of the pit decreased. However, the dimensionless pit depth increased as the distance between the pits increased. The dimensionless pit depth increased with time.

• Journal of the Korea Furniture Society
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• v.29 no.1
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• pp.1-7
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• 2018

A study was carried out to observe the 1% aqueous safranine solution flow speed in longitudinal and radial directions of softwood Metasequoia glyptostroboides, diffuse-porous wood Anthocephalus cadamba and ring-porouswood Fraxinus rhynchophylla. In radial direction, ray cells and in longitudinal direction, tracheids, vessel and wood fiber were considered for the measurement of liquid penetration speed at less than 12% moisture contents (MC). The length, lumen diameter, pit diameter, end wall pit diameter and the numbers of end wall pits determined for the flow rate. The liquid flow in the those cells was captured via video and the capillary flow rate in the ones were measured. Vessel in hardwood species and tracheids in softwood was found to facilitate prime role in longitudinal penetration. Anatomical features like the length and diameter, end-wall pit numbers of ray parenchyma were found also responsible fluid flow differences. On the other hand, vessel and fiber structure affected the longitudinal flow of liquids. Therefore, the average liquid penetration depth in longitudinal tracheids of Metasequoia glyptostroboides was found the highest among all cells considered in Anthocephalus cadamba and Fraxinus rhynchophylla In radial direction, ray parenchyma of Metasequoia glyptostroboides was found the highest depth and the one of Fraxinus rhynchophylla was the lowest. The solution was penetrated lowest depth in the wood fiber of Fraxinus rhynchophylla. The large vessel of Fraxinus rhynchophylla was found the lowest depth among the vessels. The solutin was penetrated to the wood fiber of Anthocephalus cadamba higher than the one of Fraxinus rhynchophylla.

• Journal of the Korea Furniture Society
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• v.28 no.1
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• pp.88-93
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• 2017

A study was carried out to observe the 1% aqueous safranine solution flow speed in longitudinal and radial directions of softwood Larix kaempferi (Lamb.)Carriere, diffuse-porous wood Betula davurica Pall.. and ring-porouswood Castanea crenata S.etZ. In radial direction, ray cells and in longitudinal direction, tracheids, vessel and wood fiber were considered for the measurement of liquid penetration speed at less than 12% moisture contents (MC). The length, lumen diameter, pit diameter, end wall pit diameter and the numbers of end wall pits determined for the flow rate. The liquid flow in the those cells was captured via video and the capillary flow rate in the ones were measured. Vessel in hardwood species and tracheids in softwood was found to facilitate prime role in longitudinal penetration. Anatomical features like the length and diameter, end-wall pit numbers of ray parenchyma were found also responsible fluid flow differences. On the other hand, vessel and fiber structure affected the longitudinal flow of liquids. Therefore, the average liquid penetration depth in longitudinal tracheids of Larix kaempferi was found the highest among all cells considered in Betula davurica and Castanea crenata, In radial direction, ray parenchyma of Larix kaempferi was found the highest depth and the one of Betula davurica was the lowest. The solution was penetrated lowest depth in the wood fiber of Castanea crenata. The large vessel of Castanea crenata was found the lowest depth among the vessels. The solutin was penetrated to the wood fiber of Betula davurica higher than the one of Castanea crenata.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1503-1512
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• 1992

The strength evaluation and life prediction on the corrosion part of structure is one of the most important subjects, as a viewpoint of reducing economic loss by regular inspection, maintenance, repair and replace. For this purpose, it has been difficult to obtain the available data on growth of pit depth or growth rate of each pit which depends on time. In this paper, the life prediction and strength evaluation method was suggested for the structure with irregular stress concentration part by surface corrosion. The statistical distribution pattern of corrosion depth and the degree of fatigue strength decline were confirmed according to corrosion period by artificial corrosion of SS41 steel. The life prediction and the fatigue strength evaluation of materials with consideration of the corrosion period on the extreme value statistic analysis by the data of maximum depth of corrosion and on random variable was studied.

• Geomechanics and Engineering
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• v.31 no.5
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• pp.489-503
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• 2022

A 1257-m-long irregular deep foundation pit located in the central of Nanjing, China was constructed using the combined full-width and half-width top-down method. Based on the long-term field monitoring data, this study analyzed the evolution characteristics of the vertical movement of the columns, internal force of the struts, and axial force of the structural beam and slab. The relevance of the three mentioned above and their relationship with the excavation process, structural system, and geological conditions were also investigated. The results showed that the column uplift was within the range of 0.08% to 0.22% of the excavation depth, and the embedded depth ratio of the diaphragm wall and the bottom heave affected significantly on the column uplift. The differential settlement between the column and diaphragm wall remained unchanged after the base slab was cast. The final settlement of the diaphragm wall was twice the column uplift. The internal force of the struts did not varied monotonically but was related to numerous factors such as the excavation depth, number of struts, and environmental conditions. Additionally, the dynamic force and deformation of the columns, beams, and slabs were analyzed to investigate the inherent relationship and variation patterns of the responses of different parts of the structure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.2
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• pp.41-46
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• 2020

The characteristics of the residual stress on the types of the substrate was investigated with adjusting the V/III ratio during GaN growth via the HVPE method. GaN single crystal layers were grown on a sapphire substrate and a GaN template under the conditions of V/III ratio 5, 10, and 15, respectively. During GaN growth, multiple hexagonal pits in GaN single crystal were differently revealed in accordance with growth condition and substrate type, and their distribution and depth were measured via optical microscopy(OM) and white light interferometry(WLI). As a result, it was confirmed that the distribution area and depth of hexagonal pit tended to increase as the V/III ratio increased. Moreover, it was found that the residual stress in GaN single crystal decreased as the distribution area and depth of the pit increased through measuring micro Raman spectrophotometer. In the case of GaN growth according to substrate type, the GaN on GaN template showed lower residual stress than the GaN grown on sapphire substrate.

• The Journal of the Korea Contents Association
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• v.22 no.3
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• pp.586-592
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• 2022

In this study cerium nano particles(CNPs) with 0-4.0 wt% was incorporated to the conventional dental pit and fissure sealant(ConciseTM) to produce new pit and fissure sealant the physical properties and cytotoxicity. The physical properties were measured for polymerizing depth the degree of water absorption and solubility. The cytotoxicity of cell viability was analyzed by MTT assay using immortalized human oral keratinocyte(IHOK). As a result of this preceding study the polymerizing depth was decreased by the increasing of the amount of CNPs. The solubility degree of the sealant added CNPs with 2.0 wt% showed was the lower and the water absorption showed no significantly difference with the control groups(p>0.05). The cytotoxicity test results showed high survival rates in all experimental groups. Therefore, pit and fissure sealant by the addition of CNPs excellent cell viability be produced without weaken the physical property of the cell viability fissure sealant containing CNPs does not weaken physical properties and has no cytotoxic effects biocompatibility. Considering its properties effect of CNPs, further studies are required for distribution technology application.

• Steel and Composite Structures
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• v.46 no.3
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• pp.385-401
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• 2023

Steel is becoming increasingly popular due to its high strength, excellent ductility, great assembly performance, and recyclability. In reality, steel structures serving for a long time in atmospheric, industrial, and marine environments inevitably suffer from corrosion, which significantly decreases the durability and the service life with the exposure time. For the mechanical properties of corroded steel, experimental studies are mainly conducted. The existing numerical analyses only evaluate the mechanical properties based on corroded morphology at the isolated time-in-point, ignoring that this morphology varies continuously with corrosion time. To solve this problem, the relationships between pit depth expectation, standard deviation, and corrosion time are initially constructed based on a large amount of wet-dry cyclic accelerated test data. Successively, based on that, an in-situ pitting evolution method for evaluating the residual tensile strength of corroded steel is proposed. To verify the method, 20 repeated simulations of mass loss rates and mechanical properties are adopted against the test results. Then, numerical analyses are conducted on 135 models of corrosion pits with different aspect ratios and uneven corrosion degree on two corroded surfaces. Results show that the power function with exponents of 1.483 and 1.091 can well describe the increase in pit depth expectation and standard deviation with corrosion time, respectively. The effect of the commonly used pit aspect ratios of 0.10-0.25 on yield strength and ultimate strength is negligible. Besides, pit number ratio α equating to 0.6 is the critical value for the strength degradation. When α is less than 0.6, the pit number increases with α, accelerating the degradation of strength. Otherwise, the strength degradation is weakened. In addition, a power function model is adopted to characterize the degradation of yield strength and ultimate strength with corrosion time, which is revised by initial steel plate thickness.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.3
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• pp.253-263
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• 2022

A buccal pit is a prominent point-like depression that appears at the cervical end of the mandibular molar developmental grooves. A defective buccal pit can be defined as a buccal pit in which the continuity of the dentinoenamel junction is broken and the pit extends to the dentinal level. This study aimed to determine the frequency of buccal pits and defective buccal pits in un-erupted mandibular first and second molars using cone-beam computed tomography (CBCT). The analysis was performed on CBCT images taken from 417 Korean children and adolescents who visited the Department of Pediatric Dentistry, Yonsei University Dental Hospital between 2004 and 2020. Based on cross-sectional views of CBCT images, buccal pits were categorized into 4 classes according to the depth of the pits. The expression rate of the buccal pits was 29.1%. The prevalence of defective buccal pits was 7.9%. The buccal pits tended to develop bilaterally. To date, this is the most comprehensive study on the frequency of buccal pits with the largest sample size. This was the first attempt worldwide to analyze the depth of the buccal pit using CBCT images and to define a defective buccal pit worldwide.