• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.76-81
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• 2003

Non-linear anisotropic materials were used to simulate the effects of tensile stress in 3D finite element analysis (FEA). FEA was used to calculate the effects of far and near-side pit depth and tensile stress on magnetic flux leakage (MFL) signals. The axial and radial MFL signals were depended on far and near-side double circular pit depth and on the stress, but the circumferential MFL signal was not depended on them. The axial and radial MFL signals increased with greater pit depth and applied stress, but the circumferential MFL signal was scarcely changed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.2
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• pp.144-150
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• 2006

The purpose of this study is to predict outlet temperature and humidity through underground pit for the reduction of cooling load and heating load. Commonly, the underground temperature is lower than outdoor in summer but the reverse happens in winter. When the outdoor average air temperature is $25.7^{\circ}C$ during cooling periods, the average outlet air temperature through underground pit is $23.6^{\circ}C$ with 3 m-depth and 60m-length and is $22.2^{\circ}C$ with 3 m-depth and 150 m-length. When the outdoor average air temperature is $4.9^{\circ}C$ during heating periods, the average outlet air temperature through underground pit is $7.7^{\circ}C$ with 3m-depth and 60 m-length and is $10.8^{\circ}C$ with 3 m-depth and 150 m-length. The outlet air temperature is affected by more length than depth of underground pit. The diffusion ratio of outdoor humidity is $-7.7\times10^{-8}kg/s$ in cooling periods and $9.29\times10^{-7}kg/s$ in heating periods.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.267-272
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• 2002

Pitting corrosion is a very common occurrence in marine structures. Therefore, the 3-D finite element analysis is carried out to determine the stress intensity factors at the pit depth and also at the surface of the pit. The pits are modeled as a part of sphere, based on the pit depth and the pit diameter as specified by the Ship Structural Committee. The pit depth and pit diameter are function of the percentage of pitting that the plate is subjected to. A dog-bone shaped specimen is subjected to different intensities of pitting and the stress intensity factors are determined under axial tensile loads.

• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.70-75
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• 2003

Non-linear anisotropic materials were used to simulate the effects of bulk tensile stress in 3D finite element analysis (FEA). FEA was used to calculate the effects of near and far-side racetrack pit depth and simulated bulk tensile stress on magnetic flux leakage (MFL) signals. The axial and radial MFL signals were depended on near and far-side racetrack pit depth and on the bulk stress, but the circumferential MFL signal was not depended on them. The axial and radial MFL signals increased with greater pit depth and applied bulk stress, but the circumferential MFL signal was scarcely changed.

• Journal of Korea Water Resources Association
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• v.43 no.7
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• pp.657-666
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• 2010

The adjustment processes of mining pits in the disturbed channels by sand or gravel mining were investigated by laboratory experiments in this study. The pit migrated with speed when the river bed was steep. The pit migrated slow and steady when the pit was filling with sand, but the pit migrated with speed after the filling processes was finished. The submerged angle of repose in the pit was nearly constant during the pit was filling. The pit was filled with sand with speed as the channel slope was increased. It took time for the pit to be filled with sand as the pit dimension was increased. This meant that the disturbed channels by sand or gravel mining to adjust the new environment was dependent on the slope of the channels and the dimension of the pits. The dimensionless pit length was short and the dimensionless pit depth was shallow as the time was increased. The dimensionless pit depth was shallow, but the dimensionless pit migration speed was increased as the dimensionless shear velocity and the migration speed of the pit were increased. The dimensionless pit depth was increased with the dimensionless bar migration speed. The shape of the pit was deformed and migrated downstream in accordance with the location and shape of the biased bar front which was developed upstream.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.3
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• pp.263-269
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• 2003

Magnetic flux leakage (MFL) signals were used for corrosion inspection of buried oil and gas pipeline. 3D finite element analysis was used to examine the effects of far and near-side pit depth and tensile stress on MFL signals. Anisotropci materials were used, and the effects of simulated tensile stress on MFL were investigated. The axial and radial MFL signals depended on far and near-side single pit depth and on the bulk stress, but the circumferential MFL signal did not depend on them. The axial and radial MFL signals increased with increasing pit depth and the bulk stress, but the circumferential MFL signal was scarcely changed.

• Journal of Ocean Engineering and Technology
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• v.2 no.2
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• pp.78-86
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• 1988

In order to investigate the corrosion pit occurrence and growth characteristic of M.E.F.(martensite encapsulated islands of ferrite) dual phase steel was made with a suitable heat treatment of raw material(SS41), a corrosion fatigue test was performed under rotary bending in the salt solution having a concentration from 0.01 wt percent to 3.5 wt percent. The fatigue strength of dual phase steel was remarkably decreased with an increase in concentration of salt solution; approximately from 63% to 80% in case of dual phase steel and from 40% to 71% in case of raw material. Corrosion pit occurred in the martensite phase and fatigue cracks from corrosion pits were selectively propagated in martensite phases. In the observation of corrosion pits at the origin of fatigue cracks, it had been found that corrosion pits were grown into hemispherical pits and a/c(the surface diameter, 2c and the depth, a of corrosion pit)was about 1.0-1.5regardless of the variation of salt solution concentration. The difference of corrosion pit depth growth rate was increased with an increase in concentration of salt solution according to an increase in stress level.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.4
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• pp.849-857
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• 1998

The purpose of this study was to investigate whether fluoride-releasing pit and fissure sealant was more effective in preventing caries than conventional non-fluoride-releasing sealant. Specimens 8mm in diameter were made from sound bovine enamel. Fluoride-releasing pit and fissure sealant(Helioseal F, Vivadent, Schaan, Liechtenstein) and non-fluoride-releasing sealant(Helioseal, Vivadent, Schaan, Liechtenstein) were applied to the specimens and artificial caries was induced. Microhardness and the depth of the carious lesion was measured. The following results were obtained: 1. In group 2, sealed with fluoride-releasing sealant, there was a 58.4% decrease in microhardness. This was significantly less than the 84.4% decrease observed in group 1, sealed with non-fluoride-releasing sealant(p<0.01). 2. The average depth of the artificial carious lesion in group 2 was $30.1{\pm}9.8{\mu}m$. In group 1, sealed with non-fluoride-releasing sealant, the lesion was significantly deeper with an average depth of $58.5{\pm}4.9{\mu}m$(p<0.01). 3. Fluoride-releasing pit and fissure sealant was more anticariogenic compared to non-fluoride-releasing sealant.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.4
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• pp.308-320
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• 2006

An analytic solution to the mild-slope equation is derived for waves propagating over an axi-symmetric pit. The water depth inside the pit varies in proportion to a power of radial distance from the pit center. The governing equation is transformed into ordinary differential equations by using separation of variables, and the coefficients of the equations are transformed into explicit forms by using Hunt's (1979) approximate solution. Finally, by using the Frobenius series, the analytic solution is derived. Due to the feature of Hunt's equation, the present analytic solution is accurate in shallow and deep waters, while it is less accurate in intermediate depth water. The validity of the analytic solution is demonstrated by comparison with numerical solutions. The analytic solution is also used to examine the effects of pit geometry and relative depth on wave transformation.

• Corrosion Science and Technology
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• v.22 no.1
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• pp.55-63
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• 2023

The aim of this study was to propose a multiple linear regression (MLR) equation to predict ultimate tensile strength (UTS) of 316L stainless steel with unspecified pit corrosion. Tensile specimens with pit corrosion were prepared using a potentiostatic acceleration test method. Pit corrosion was characterized by measuring ten factors using a confocal laser microscope. Data were collected from 22 tensile tests. At 85% confidence level, total pit volume, maximum pit depth, mean ratio of surface area, and mean area were significant factors showing linear relationships with UTS. The MLR equation using these three significant factors at a 85% confidence level showed considerable prediction performance for UTS. Determination coefficient (R²) was 0.903 with training and test data sets. The yield strength ratio of 316L stainless steel was found to be around 0.85. All specimens with a pit corrosion presented a yield ratio of approximately 0.85 with R² of 0.998. Therefore, pit corrosion did not affect the yield ratio.