• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.235-244
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• 1993

The present study was made based on the zero extension line theory and the well-known Mononobe-Okabe's to determine the dynamic earth pressures acting on the retaining walls. The zero extension line theory, which was proposed by Roscoe et al., assumes the coincidence between the loci of failure and the zero extension lines in soil mass. ln order to compute the dynamic earth pressure developed by an earthquake, it was assumed that for the vertical retaining walls with no surcharge, the backfill materials are dense and cohesionless sandy soils, there are no changes in soil parameters during earthquake, and the horizontal earthquake intensity is considered. The effects of horizontal earthquake intensity, internal friction angle of soil, wall friction angle and dilation angle, on the earth pressure coefficients were analysed. Final1y, the presented theories were successfully compared with the Mononobe-Okabe's as well.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.7
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• pp.76-81
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• 2011

A new via cutting structure in 2-layer DRAM package substrate has been fabricated to lower its power distribution network(PDN) impedance. In new structure, part of the via is cut off vertically and its remaining part is designed to connect directly with the bonding pad on the package substrate. These via structure and substrate design not only provide high routing density but also improve the PDN impedance by shortening effectively the path from bonding pad to VSSQ plane. An additional process is not necessary to fabricate the via cutting structure because its structure is completed at the same time during a process of window area formation. Also, burr occurrence is minimized by filling the via-hole inside with a solder resist. 3-dimensional electromagnetic field simulation and S-parameter measurement are carried out in order to validate the effects of via cutting structure and VDDQ/VSSQ placement on the PDN impedance. New DRAM package substrate has a superior PDN impedance with a wide frequency range. This result shows that via cutting structure and power/ground placement are effective in reducing the PDN impedance.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.107-122
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• 2009

Insufficient reinforcement for maximizing payability and benefits in mining cavities causes subsidence problems and it threatens residents' lives and properties. So many reinforcement management methods are developed and now various methods are being applied in the field. Among them, a filling method which sends reinforcement materials in the cavities is used extensively. However, domestic geological condition and coal mining methods are so complicate that make many steep cavities. Because of those problems, it is difficult to apply foreign methods directly, which is valid for horizontal cavities. In this study, the injection volume of quick setting grouting material which is developed for filling cavities in domestic condition and the shape of consolidated bodies are investigated. And a programming method for estimating proper injection amounts of filling materials is proposed. The results are verified by numerical analysis using UDEC.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.105.1-105.1
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• 2012

고온가압소결으로 제조된 SiCf/SiC 복합체는 부식과 침식에 강하고 우수한 열적 성질과 고온에서의 높은 기계적 강도를 유지하는 장점을 가진 복합체다. 복합체의 파괴인성은 섬유와 기지 사이에 존재하는 열분해탄소 (PyC) 계면층에 의해 큰 영향을 받는데, 고온가압소결중 첨가되는 소결조제 ($Y_2O_3$, MgO, $Al_2O_3$)와 반응하여 계면이 손상되어 복합체의 기계적 특성치가 낮아지는 결과를 보였다. 본 연구에서는 계면의 손상을 보호하고자 PyC 계면상 위에 SiC 층을 증착하였는데 계면층과 SiC 층의 증착은 화학기상 증착법(CVD)을, 기지채움 공정은 전기영동법(EPD)과 고온가압소결방법(Hot Pressing)을 이용하여 복합체를 제조하였다. Tyranno-SA 섬유에 소스가스인 메탄을 열분해 하여 200nm 두께로 PyC 계면상을 증착하고, 두께를 달리하여 보호층으로써의 SiC 층을 single 과 double layer로 증착하였다. SiC 나노분말과 소결 첨가제인 $Y_2O_3$, $Al_2O_3$, MgO를 첨가한 슬러리를 전기영동법(EPD)을 이용하여 섬유내부에 슬러리를 함침시켰고, 이러한 프리폼을 $1750^{\circ}C$/20MPa의 조건으로 고온 가압소결 하여 $SiC_f$/SiC 복합체를 제조하였다. 이렇게 single layer와 double layer로 제조된 $SiC_f$/SiC 복합체에 대해 밀도와 미세구조를 관찰하였고, 기계적 특성을 비교하여 보호층으로써의 SiC 증착효과를 고찰하고자 하였다.

• Journal of the Korean Geosynthetics Society
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• v.2 no.2
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• pp.3-11
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• 2003

Researches on the induced trench method using compressible materials such as clay, mud, straw, or EPS block have been performed to reduce the load acting on buried conduits under a high fill. The induced trench method has the problems that the arching area due to the compressible arching material is one dimensional or localized in a narrow zone. The main purpose of this study is to solve the problems of the induced trench method mentioned above. The various types of laboratory model tests are conducted to find the effects of the variations of EPS block width, multilayer application, soil density, and diameter of the flexible steel pipe. A series of model tests was conducted to evaluate the reduction of earth pressure on conduits using EPS block. Based on modeling test it is found that the magnitude of vertical earth pressure on conduits was reduced about 60% compared with conventional flexible conduit systems.

• Journal of Digital Contents Society
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• v.18 no.4
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• pp.739-745
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• 2017

This paper presents and discusses an implementation of the GPU shifted sorting method to find approximate k nearest neighbors which executes within "warp", the minimum execution unit in GPU parallel architecture. Also, this paper presents the comparison results with other two common nearest neighbor searching methods, GPU-based kd-tree and ANN (Approximate Nearest Neighbor) library. The proposed implementation focuses on the cases when k is small, i.e. 2, 4, 8, and 16, which are handled efficiently within warp to consider it is very common for applications to handle small k's. Also, this paper discusses optimization ways to implementation by improving memory management in a loop for the CUB open library and adopting CUDA commands which are supported by GPU hardware. The proposed implementation shows more than 16-fold speed-up against GPU-based other methods in the tests, implying that the improvement would become higher for more larger input data.

• Journal of Digital Convergence
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• v.11 no.1
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• pp.243-248
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• 2013

In this paper, depth of foreground is analysed by focus and color analysis grouping for 2D/3D video conversion and depth of foreground progressing method is preposed by using focus and motion information. Candidate foreground image is generated by estimated movement of image focus information for extracting foreground from 2D video. Area of foreground is extracted by filling progress using color analysis on hole area of inner object existing candidate foreground image. Depth information is generated by analysing value of focus existing on actual frame for allocating depth at generated foreground area. Depth information is allocated by weighting motion information. Results of previous proposed algorithm is compared with proposed method from this paper for evaluating the quality of generated depth information.

• Korean Journal of Optics and Photonics
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• v.33 no.6
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• pp.245-251
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• 2022

We have developed a multi-channel fiber laser for tiled laser beam combining and a laser output array system for multi-beam alignment. The fiber laser is a master oscillator power amplifier configuration that has a common seed, a preamplifier, and a 7-channel amplifier. The output power of each channel is more than 10 W. The laser output array system is a packed cylindrical configuration for a high fill-factor, and it has capabilities for collimation and tilt control with built-in PZT. Multi-beam alignment to a target is successfully implemented using PZT controlled with a stochastic parallel gradient descent (SPGD) algorithm.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.13-20
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• 2011

The main objective of this paper is finding the influence factors and their degree of importance to steel liner's safety by investigating and evaluating the buckling incidents of steel tunnel liner under external water pressure. The study was based on the detailed investigation to the design conditions and incident shapes at 2m diameter waterway tunnel with a partially buckled internal steel liner and concrete backfilled lining as the raw water transmission pipe line of regional water supply project. Appropriate buckling theory capable of applying this incident points was selected by referring the existing literature and compared with the results of investigation. Also, hydrogeological characteristics of this site on buckling pressure was evaluated. The result of this study was shown that both the hydrogeological characteristics of upper geologic layers and proper tunnel construction are important factors on buckling at steel liner, and hydraulic gradient level should be decided according to the hydrogeological characteristics. This incident case analysis on steel liner of pressurized waterway tunnel was expected to provide more information for realizing the problems and improvements at each design, construction and maintenance stages.

• Journal of the Korean Geotechnical Society
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• v.23 no.4
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• pp.113-123
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• 2007

In order to ensure the stability of reinforced structures backfilled with low permeability soil, it is very important to determine the change in undrained pullout capacity compared to drained pullout capacity prior to design. In this research, a series of numerical analyses on laboratory pullout tests have been performed on different materials (clean sand, 5, 10, and 15% silty sand), different overburden pressures (30, 100 and 200 kPa), and different drainage conditions (drained and undrained) in order to compare drained pullout capacity with undrained pullout capacity. The results of numerical analysis also have been compared with the results of the laboratory pullout tests. The analysis results show that both drained and undrained pullout capacity are influenced by silt contents and increase with increase of friction angle of the soil and overburden pressure. In undrained condition, the effective stresses acting on the reinforcement decrease as excessive pore pressures are generated, resulting in decrease in pullout capacity; 57% for 30 kPa, and 70% for 100 and 200 kPa. These results show a good agreement with the results of the laboratory pullout tests performed under the same condition.