• Ocean Systems Engineering
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• v.7 no.4
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• pp.399-412
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• 2017

The Gauss-Legendre integral method is applied to numerically evaluate the Green function and its derivatives in finite water depth. In this method, the singular point of the function in the traditional integral equation can be avoided. Moreover, based on the improved Gauss-Laguerre integral method proposed in the previous research, a new methodology is developed through the Gauss-Legendre integral. Using this new methodology, the Green function with the field and source points near the water surface can be obtained, which is less mentioned in the previous research. The accuracy and efficiency of this new method is investigated. The numerical results using a Gauss-Legendre integral method show good agreements with other numerical results of direct calculations and series form in the far field. Furthermore, the cases with the field and source points near the water surface are also considered. Considering the computational efficiency, the method using the Gauss-Legendre integral proposed in this paper could obtain the accurate numerical results of the Green function and its derivatives in finite water depth and can be adopted in the near field.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1522-1529
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• 2009

When a shaft is excavated in Korea, the mechanized method such as RBM(Raise Boring Machine) or RC(Raise Climber) is used independently of depth. But usually, the mechanized method is useful for the deep depth. On the contrary, when the depth of shaft is short, the cost of excavation increase. So in the case of shaft constructon less than 100m, we need to consider more suitable method of shaft construction such as Stage-cut which is one of blasting methods. Stage-Cut is widely used in the field of shaft construction in Japan as a tool of rock excavation. The main purpose of this study is to provide technical guidance for design and construction of shafts in rock, using Stage-cut method which is suitable for 20m~80m depth shaft. In this study, Blasting tests was performed in field, according to rock classification. Finally, the stage-cut method which is suitable for the geology of Korea was developed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.329-334
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• 2012

The distribution submarine cables are normally used for power supply at island, which are mostly installed in the southern coast of KOREA, and partially installed in the west coast and Jeju-Island. There are two way of submarine cable burying system, buried and unburied type. Since 2003, KEPCO is entirely being constructing the distribution submarine cable by buried type. In this case, 'burial depth' is key index for evaluating the suitability of the buried situation. Therefore, the measurement accuracy of 'burial depth' is a big issue for burying system in the distribution submarine cable. This paper demonstrates the measurement error of burial depth that is affected by electrical factor such as grounding type of submarine cable in case of magnetic field detection method, and indicates the method to reduce the measurement error in buried type of distribution submarine cable system.

• Journal of Korea Multimedia Society
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• v.23 no.8
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• pp.1088-1098
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• 2020

This paper proposes an obstacle avoidance method using a depth polar grid. Depth information is a crucial factor for determining the safe path for collision-free navigation of unmanned aerial vehicles (UAVs) as it can perceive the distance to the obstacles effectively. However, the existing depth-camera-based approaches for obstacle avoidance require computational y expensive path planning algorithms. We propose a simple navigation method using the polar-grid of the depth information obtained from the camera with narrow field-of-view(FOV). The effectiveness of the approach was validated by a series of experiments using software-in-the-loop simulation in a realistic outdoor environment. The experimental results show that the proposed approach successfully avoids obstacles using a single depth camera with limited FOV.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.398-407
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• 1999

In the present image processing technique, the concept of the gradient indicator(GI) has been introduced to find out the depth-of-field in sizing large particles ranging from $30{\mu}m$ to $30{\mu}m$ where using of the concept of the normalized contrast value(VC) is not appropriate. The gradient indicator is defined as the ratio of the local value to the maximum possible value of the gray-level gradient in an image frame. The gradient indicator decreases with the increases of the particle size and the distance from the exact focal plane. A particle is considered to be in focus when the value of the gradient indicator at its image boundary stays above a critical value. This critical gradient indicator($GI_{critical}$) is defined as the maximum gradient indicator($GI_{max}$) subtracted by a constant ${\Delta}GI$ which is to account for the particle-size effect. In the present ca.so, the value of ${\Delta}GI$ was set to 0.28 to keep the standard deviation of the measured particles mostly within 0.1. It was also confirmed that, to find the depth-of-field for small particles(${\leq}30{\mu}m$) with the same measurement accuracy, tho concept of the critical normalized contrast($VC_{critical}$) is applicable with 85% of the maximum normalized contrast value($VC_{max}$). Finally, the depth-of-field was checked for the size range between $10{\mu}m$ and $300{\mu}m$ when the both in-focus criteria ($GI_{critical}$ and $VC_{critical}$) were adopted. The change of the depth-of-field with the particle size shows good linearity in both the VC-applicable and the GI-applicable ranges with a reasonable accuracy.

• Wind and Structures
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• v.37 no.1
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• pp.25-38
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• 2023

Due to the complexity and difficulty in meeting the multiphase flow complexity, similarity, and multiscale characteristics, the mechanism of snow drift is so complicated that the snow deposition prediction is still inaccurate and needs to be far improved. Meanwhile, the validation of prediction methods is also limited due to a lack of field-measured data about snow deposition. To this end, a field measurement activity about snow deposition around a cube with time was carried out, and the snow accumulation process was measured under blowing snow conditions in northwest China. The maximum snow depth, snow profile, and variation in snow depth around the cube were discussed and analyzed. The measured results indicated three stages of snow accumulation around the cube. First, snow is deposited in windward, lateral and leeward regions, and then the snow depth in windward and lateral regions increases. Secondly, when the snow in the windward region reaches its maximum, the downwash flow erodes the snow against the front wall. Meanwhile, snow range and depth in lateral regions have a significant increase. Thirdly, a narrow road in the leeward region is formed with the increase in snow range and depth, which results in higher wind speed and reforming snow deposition there. The field measurement study in this paper not only furthers understanding of the snow accumulation process instead of final deposition under complex conditions but also provides an important benchmark for validating prediction methods.

• Geophysics and Geophysical Exploration
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• v.14 no.1
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• pp.50-57
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• 2011

For effective and accurate prediction of overpressure in the Efomeh field, located in the Niger delta basin of Nigeria, integrated seismic and borehole analyses were undertaken. Normal and abnormal pore pressure zones were delineated based on the principle of normal and deviation from normal velocity trends. The transition between the two trends signifies the top of overpressure. The overpressure tops were picked at regular intervals from seismic data using interval velocities obtained by applying Dix's approximation. The accuracy of the predicted overpressure zone was confirmed from the sonic velocity data of the Efomeh 01 well. The variation to the depth of overpressure between the predicted and observed values was less than 10mat the Efomeh 01 well location, with confidence of over 99 per cent. The depth map generated shows that the depth distribution to the top of the overpressure zone of the Efomeh field falls within the sub-sea depth range of 2655${\pm}$2m (2550 ms) to 3720${\pm}$2m (2900 ms). This depth conforms to thick marine shales using the Efomeh 01 composite log. The lower part of the Agbada Formation within the Efomeh field is overpressured and the depth of the top of the overpressure does not follow any time-stratigraphic boundary across the field. Prediction of the top of the overpressure zone within the Efomeh field for potential wells that will total depth beyond 2440m sub-sea is very important for safer drilling practice as well as the prevention of lost circulation.

• Journal of Digital Contents Society
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• v.9 no.2
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• pp.187-192
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• 2008

This study carried out researches on the techniques which are applicable to express sense of depth in the process of producing lofty image contents, and it's verification. Techniques for expression of sense of depth are how to use highlight and shadow, how to use depth of field and lenses, and how to use camera motion, zoom and dolly. For the practical application in all cases, I examine the preference frequency, and most of the pictures that techniques are adapted are selected. As a result we can verify the way of using lenses is the most convenient way in the expression of 'sense of depth'.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.21-32
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• 2011

The frost penetration depth of pavement is usually estimated from the freezing index that made temperature data analysis of 30 years and decided the thickness of anti-frost layer. The field monitoring region in study was divided into five regions by freezing index 550~650$^{\circ}C{\cdot}$day, 450~550$^{\circ}C{\cdot}$day and 350~450$^{\circ}C{\cdot}$day. Each region has three-section of road pavement such as cutting area, boundary area of cutting and banking, and lower area of banking. The field monitoring system was established both in the section of anti-frost layer and in the section without anti-frost layer. The data analysis was conducted for determination of frost penetration depth within the paved road by the field monitoring system. The result showed that The temperature of subgrade without anti-frost layer shows below zero in centigrade for the region of freezing index 550~650$^{\circ}C{\cdot}$day, up and down around zero degree in subgrade for the region of freezing index 450~550$^{\circ}C{\cdot}$day, and there is no place existed below zero degree in subgrade for the region of freezing index below 450$^{\circ}C{\cdot}$day. With comparison of field frost penetration depth for the cross-sections of pavement, the cutting area shows the greatest frost penetration depth, and less influence of frost penetration depth for the boundary area of cutting and banking, and the least influenced for the lower area of banking.

• Journal of the Korean Society of Safety
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• v.30 no.6
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• pp.102-109
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• 2015

In this study, on the basis of the results of the field survey and the theoretical consideration for Korean Standard Specification for concrete durability and maintenance, the following conclusions are derived. From the survey, the prediction equation of carbonation depth for the southwest region in Korea is experimentally proposed, $y_p=5.865{\sqrt{t}}$, which predicts about 60mm of the carbonation depth for the concrete structures of 100 years, a 1st class of target endurance period, under a combined deterioration environment like a marine environment. Considering that the marginal value for a carbonation depth limitation under very severely marine environment is 25mm, in accordance with the Specification, it is found that the predicting carbonation depth for the concrete cover depths, 100mm and 60mm are 63mm and 29.4mm, respectively. In conclusion, according to the equation and the Specification, it is strongly required that the reinforced concrete structures with the cover depth under 100mm have to make a protection from combined deterioration factors by any methods like a surface coating, an increment of cover depth or an application of a special concrete.