• International Journal of Ocean System Engineering
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• v.2 no.3
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• pp.176-184
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• 2012

Installing floating structures in a coastal area requires careful observation of the finite-depth effect. In this paper, a Rankine panel method that includes the finite-depth effect is developed in the time domain. The bottom boundary condition is satisfied by directly distributing Rankine panels on the bottom surface. A stepwise analysis is performed for the radiation diffraction problems and consequently freely-floating motion responses over different water depths. The hydrodynamic properties of two test hulls, a Series 60 and a floating barge, are compared to the results from another computation program for validation purposes. The results for both hulls change remarkably as the water depth becomes shallower. The important features of the results are addressed and the effects of a finite depth are discussed.

• Journal of Ocean Engineering and Technology
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• v.36 no.2
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• pp.83-90
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• 2022

This paper presents the minimum submergence depth of an underwater vehicle that can remove the effect of free surface on the resistance of the underwater vehicle. The total resistance of the underwater vehicle in fully submerged modes comprises only viscous pressure and friction resistances, and no wave resistance should be present, based on the free surface effect. In a model test performed in this study, the resistance is measured in the range of 2 to 10 kn (1.03-5.14 m/s) under depth conditions of 850 mm (2.6D) and 1250 mm (3.8D), respectively, and the residual resistance coefficients are compared. Subsequently, resistance analysis is performed via computational fluid dynamics (CFD) simulation to investigate the free surface effect based on various submergence depths. First, the numerical analysis results in the absence of free surface conditions and the model test results are compared to show the tendency of the resistance coefficients and the reliability of the CFD simulation results. Subsequently, numerical analysis results of submergence depth presented in a reference paper are compared with the model test results. These two sets of results confirm that the resistance increased due to the free surface effect as the high speed and depth approach the free surface. Therefore, to identify a fully submerged depth that is not affected by the free surface effect, case studies for various depths are conducted via numerical analysis, and a correlation for the fully submerged depth based on the Froude number of an underwater vehicle is derived.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.225-233
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• 2001

Distortion of Secondary Ion Mass Spectrometry(SIMS) depth profile, which is usually observed when the analysis is made using oxygen flooding on the surface of Si with oxide on it, has been corrected. The origin of distortion has been attributed to depth calibration error due to sputter rate difference and concentration calibration error due to relative sensitivity factor(RSF) difference between $SiO_2$ and Si layers, In order to correct depth calibration error, artifact in analysis of sodium ion on oxide was used to define the interface in SIMS depth profile and oxide thickness was measured with SEM and XPS. The differences of sputter rate and RSF between two layers have been attributed to volume swelling of Si substrate occurred by oxygen flooding induced oxidation. The corrected SIMS depth profiles showed almost the same results with those obtained without oxygen flooding.

• International Journal of Highway Engineering
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• v.19 no.2
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• pp.1-6
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• 2017

PURPOSES : Pavement textures can be categorized into four according to wavelength: microtexture, macrotexture, megatexture (roads), and roughness. Pavement surface texture influences a number of aspects of tire-pavement interaction such as wet-weather friction, tire-pavement noise, splash, spray, tire-wear, and rolling resistance. In particular, macrotexture is the pavement surface characteristic that considerably impacts tire-pavement noise. In general, it can be demonstrated that tire-pavement noise increases with the increase of texture depth and wavelength. Recently, mean profile depth (MPD) and wavelength have been used to evaluate tire-pavement noise. This study aimed to identify the relationship between mean profile depth and average wavelength for asphalt pavement based on the information obtained on a number of asphalt pavement sections. METHODS : Profile data were collected from a number of expressway sections in Korea. In addition, mean profile depth and average wavelength were calculated by using this profile data. Statistical analysis was performed to determine the correlationship between mean profile depth and average wavelength. RESULTS:This study demonstrates a linear relationship between mean profile depth and average wavelength for asphalt concrete pavement. CONCLUSIONS :The strong relationship between mean profile depth and average wavelength of asphalt pavement was determined in this study.

• Journal of Industrial Technology
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• v.29 no.A
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• pp.67-75
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• 2009

In this study, the investigation of hydraulic characteristics and the pier data for the rivers in Youngseo area of Gangwon Province was carried out and the evaluation and comparison between the values from existing formulas and the values from the model tests was conducted, along with the statistical sensitivity analysis of the elements influencing the scour. As a result, the deviation between the values calculated from the existing formulas and the model tests appeared to be 1.09%~63.98% as the piers were getting larger, which indicated that the existing formulas were not appropriate to estimate the scour in the rivers in Gangwon area. And the formula which estimates the scour with the size of the pier only, among the existing ones, was far behind in estimating the sensitivity because of insufficient incorporation of the hydraulic characteristics, though it is convenient to estimate the value. The sensitivity analysis of the value from the model tests and the depth of the scour proved the significant impact on scour by the size of the pier and water depth, indicating 64% and 36%, respectively. In this study, the formula developed through the regression analysis performed based on the values from the model tests, which appeared to be appropriate for the rivers in Gangwon Province, was proposed.

• Journal of Digital Contents Society
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• v.16 no.4
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• pp.645-650
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• 2015

In this paper, we propose the method for creating a stable stereoscopic 3D contents with the production guidelines by removing the excessive depth value and scene changes for high quality. We have developed a three-dimensional depth analysis tool for detecting the scene changes out of the production guidelines and the depth value changes excessively. The Scenes detected by depth analysis tool can be modified at the post production and it helps to make a stable stereoscopic 3D contents.

• Geomechanics and Engineering
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• v.29 no.5
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• pp.583-598
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• 2022

The Compaction effect is important for evaluating the subgrade construction. However, there is little research exploring the compaction quality of deep soil using hydraulic compaction. According to reinforcement effect analysis, dimensional analysis is adopted in this work to analyze subgrade compactness within the effective reinforcement depth, and a prediction model is obtained. A hydraulic compactor is then employed to carry out an in-situ reinforcement test on gravel soil subgrade, and the subgrade parameters before and after reinforcement are analyzed. Results show that a reinforcement difference exists inside the subgrade, and the effective reinforcement depth is defined as increasing compactness to 90% in the depth direction. Layered compactness within the effective reinforcement depth is expressed by parameters including the drop distance of the rammer, peak acceleration, tamping times, subgrade settlement, and properties of rammer and filler. Finally, a field test is conducted to verify the results.

• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.997-1005
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• 2018

The regulatory periodic safety inspection system is one of the most important methods for confirming the safety of nuclear power plants and the defense in depth in nuclear safety is the most important basic means for accident prevention and mitigation. Recently, a new regulatory technology based on risk-informed and safety performance has been developed and used in advanced countries. However, since the domestic periodic inspection system is being used in the same way over 30 years, it is necessary to know how the inspection contributes to the safety confirmation of the nuclear power plants. In this study, the domestic periodic inspection system currently in use was analyzed from the perspective of defense in depth in nuclear safety. In addition, the analysis results were compared to the U.S. NRC's safety inspection system to obtain consistency and lessons in this study. As a result of analysis, the NRC's safety inspections were distributed almost evenly at the all levels of defense in depth, while in the case of domestic inspection, they were heavily focused on the level 1 of defense in depth. Therefore, it appeared urgent to improve the inspection system to strengthen the other levels of defense in depth in nuclear safety.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.243-244
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• 2021

In this study, we develop diagnostic technology for damage depth of fire-damaged concrete and propose methods for damage caused by fire by drying damaged concrete after immersion. As a result of the test, the damaged depth was clearly found when evaluating the depth of impurities caused by fire in a drying method after water had permeated, and it could be verified using thermogravimetric analysis.

• Ocean Systems Engineering
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• v.6 no.4
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• pp.305-324
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• 2016

Wave load prediction at zero forward speed using finite depth Green function is a well-established method regularly used in the offshore and marine industry. The forward speed approximation in deep water condition, although with limitations, is also found to be quite useful for engineering applications. However, analysis of vessels with forward speed in finite water depth still requires efficient computing methods. In this paper, a method for analysis of wave induced forces and corresponding motion on freely floating three-dimensional bodies with low to moderate forward speed is presented. A finite depth Green function is developed and incorporated in a 3D frequency domain potential flow based tool to allow consideration of finite (or shallow) water depth conditions. First order forces and moments and mean second order forces and moments in six degree of freedom are obtained. The effect of hull flare angle in predicting added resistance is incorporated. This implementation provides the unique capability of predicting added resistance in finite water depth with flare angle effect using a Green function approach. The results are validated using a half immersed sphere and S-175 ship. Finally, the effect of finite depth on a tanker with forward speed is presented.