• Journal of Advanced Research in Ocean Engineering
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• 제3권1호
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• pp.1-14
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• 2017

The safety analysis of an earthquake is carried out during the operation of a subsea pipeline and an onshore pipeline. Several cases are proposed for consideration. In the case of a buried pipeline, permanent ground deformation by the earthquake and an increase of internal pressure by the acceleration of the earthquake should be considered. In the case of a subsea pipeline, a bending moment is caused by liquefaction of the backfill material on a trenched seabed, etc., which results in a high bending moment of the buried pipeline. The bending moment causes the collapse of the subsea pipeline or a leak of crude oil or gas, which results in economic loss due to enormous environmental contamination and social economic loss owing to operation functional failure. Thus, in order to prevent economic loss and operation loss, structurally sensitive design with regard to seismic characteristics must be performed in the buried pipeline in advance, and the negative impact on the buried pipeline must be minimized by conducting a thorough analysis on the seabed and backfilling material selection. Moreover, it is proposed to consider the selection of material properties for the buried pipeline. A more economical review is also required for detailed study.

• 대한전자공학회논문지TC
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• 제37권3호
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• pp.58-63
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• 2000

본 논문에서는 고집적 3차원 초고주파 소자 및 모듈에서 발생되는 수직 전이 구조의 효과적인 연결을 위하여 방사형 스터브 (radial stub)를 사용한 접지 방법을 제시하였다. 제안된 구조는 완전 해석법 (full-wave analysis)인 유한 요소법 (finite element method)을 이용하여 해석하였고 제작을 통하여 그 결과를 검증하였다. 해석결과, 2.S~6.3 GHB 주파수 범위에서 반사손실 (return loss) IS dB 이상, 삽입손 실 (insertion loss) 0.5 dB 이하의 특성을 가짐을 확인하였다. 본 해석 결과는 고집적, 소형화를 위한 3차 원 구조를 갖는 초고주파 소자 및 모듈의 공통 접지 연결을 위해 유용하게 사용될 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권7호
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• pp.2547-2567
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• 2021

It has been widely acknowledged that occlusion impairments adversely distress many face recognition algorithms' performance. Therefore, it is crucial to solving the problem of face image occlusion in face recognition. To solve the image occlusion problem in face recognition, this paper aims to automatically de-occlude the human face majority or discriminative regions to improve face recognition performance. To achieve this, we decompose the generative process into two key stages and employ a separate generative adversarial network (GAN)-based network in both stages. The first stage generates an initial coarse face image without an occlusion mask. The second stage refines the result from the first stage by forcing it closer to real face images or ground truth. To increase the performance and minimize the artifacts in the generated result, a new refine loss (e.g., reconstruction loss, perceptual loss, and adversarial loss) is used to determine all differences between the generated de-occluded face image and ground truth. Furthermore, we build occluded face images and corresponding occlusion-free face images dataset. We trained our model on this new dataset and later tested it on real-world face images. The experiment results (qualitative and quantitative) and the comparative study confirm the robustness and effectiveness of the proposed work in removing challenging occlusion masks with various structures, sizes, shapes, types, and positions.

• Geomechanics and Engineering
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• 제33권5호
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• pp.439-451
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• 2023

The construction of shield tunnelling in urban sites is facing serious risks from complex and changeable underground conditions. Construction problems in the sand-clay mixed ground have been more reported in recent decades for its poor control of soil loss in tunnel face, ground settlement and supporting pressure. Since the limitations of observation methods, the conventional physical modelling experiments normally simplify the tunnelling to a plane strain situation whose results are not reliable in mixed ground cases which exhibit more complicated responses. We propose a new method for the study of the mixed ground tunnel through which mixed lays are simulated with transparent soil surrogates exhibiting different mechanical properties. An experimental framework for the transparent soil modelling of the mixed ground tunnel was established incorporated with the self-developed digital image correlation system (PhotoInfor). To understand better the response of face stability, ground deformation, settlement and supporting phenomenon to tunnelling excavation in the sand-clay mixed ground, a series of case studies were carried out comparing the results from cases subjected to different buried depths and mixed phenomenon. The results indicate that the deformation mode, settlement and supporting phenomenon vary with the mixed phenomenon and buried depth. Moreover, a stratigraphic effect exists that the ground movement around mixed face reveals a notable difference.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.124-128
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• 1997

In order tohave a betterunderstanding of thefavorable effect ofground granulated blast-furnace slag and fly ash, slump loss, temperature risingand compressive strength of concrete were investigated into diffrent conditions. When slag was mixed with ordinary portland cement as30%, slump loss gotto some 18% at 60min, maximum temperatureto some $43^{\cire}C$ at 180min, compressive strength similar to that of ordinary portland concrete at 28 days. Therefore it wasnoted thatslump loss andmaximum teaperaturerising of concrete were very reduced according to ground granulated blast-furnace slag and fly ash mixed with ordinary portland cement.

• 한국지반환경공학회 논문집
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• 제24권11호
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• pp.19-24
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• 2023

그라운드 앵커 공법은 최근 깎기 비탈면과 교대 등의 보강을 목적으로 사용이 증가하고 있다. 그라운드 앵커는 구조물의 사용연한 이상의 내구성을 확보하여야 하지만 국내 고속도로에 시공된 대부분의 앵커에서 장기적인 긴장력 손실이 발생하여 안정성이 문제가 있는 것으로 나타났다. 본 연구에서는 실규모 모형실험을 통하여 긴장력 감소원인에 대한 분석을 수행하였다. 실험결과 물-결합재 비가 55%가 되는 시점부터 부착력의 감소현상이 나타났으며, 인장쐐기의 영향으로 강연선 파단강도의 14%의 감소현상이 나타났다. 지반강도, 앵커형식, 지하수의 유무에 따라 극한인발력이 차이를 보였으며, 특히 지하수의 유무는 그라우트의 강도 및 품질에 관여하여 앵커의 거동특성에 미치는 영향이 가장 높은 것으로 나타났다. 장기거동에서는 초기 정착이 안정되는 시점까지 급격하게 하중이 감소하다가 이후에는 일정하게 긴장력이 감소하는 것으로 나타났다.

• 한국터널지하공간학회 논문집
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• 제8권4호
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• pp.365-375
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• 2006

일반적으로 터널2차라이닝의 구조해석에는 골조해석모델이 적용되고 있다. 본 모델은 경험적 방법에 의한 지반 이완하중을 고려하고 있으나 주관적이고 과대평가되는 경향이 있다. 2차라이닝에 작용하는 지반하중은 숏크리트 및 록볼트와 같은1차지보재의 지지력 상실에 기인한다. 그러므로 2차라이닝에 작용하는 지반하중 산정에는 1차지보재와 지반의 평형상태가 고려되어야 한다. 지반-라이닝 상호작용(Ground-Lining Interaction, GLI)모델은1차지보재의 지지력 상실에 의해 야기된 지반의 변형을2차라이닝이 지지하는 개념을 토대로 수립되었다. 따라서 GLI모델은 복잡한 지반조건과 1차 지보재의 설치조건을 합리적으로 반영한 지반하중을 고려할 수 있다. 2차라이닝에 작용하는 하중은 지반하중 외에 지하수압, 지진하중 등이 있다. 극한강도 설계법을 이용한 라이닝 구조보강을 위해서는 계수하중 및 다양한 하중조합이 고려되어야 한다. GLI모델은 계수하중을 고려하기 곤란하기 때문에 개별 하중에 대해 산정된2차라이닝 단면력에 하중계수를 곱하는 중첩의 원리를 적용하였다. 끝으로, 본 연구에서 제시된 GLI모델을 이용한 2차라이닝 설계방법을 저심도 지하철 터널에 적용하였다.

• Interaction and multiscale mechanics
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• 제1권1호
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• pp.157-175
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• 2008

A brief review of the research works on ground vibrations caused by trains moving in underground tunnels is first given. Then, the finite/infinite element approach for simulating the soil-tunnel interaction system with semi-infinite domain is summarized. The tunnel is assumed to be embedded in a homogeneous half-space or stratified soil medium. The train moving underground is modeled as an infinite harmonic line load. Factors considered in the parametric studies include the soil stratum depth, damping ratio and shear modulus of the soil with or without tunnel, and the thickness of the tunnel lining. As far as ground vibration is concerned, the existence of a concrete tunnel may somewhat compensate for the loss due to excavation of the tunnel. For a soil stratum resting on a bedrock, the resonance peak and frequency of the ground vibrations caused by the underground load can be rather accurately predicted by ignoring the existence of the tunnel. Other important findings drawn from the parametric studies are given in the conclusion.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.705-708
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• 2001

The effect of grinding on the synthesis of LaAO$_3$ceramics was investigated. The mixture ground by plantary ball mill showed 70nm particle size (wet ball mill or unground=0.5 $\mu$m). Monophase LaAlO$_3$powders were formed when ground samples were heated at 100$0^{\circ}C$, however unground samples required temperatures above 130$0^{\circ}C$. Density of the ground samples sintered at 140$0^{\circ}C$ showed 98.3% of theoretical density (unground=93.5% at 150$0^{\circ}C$). Dielectric constant of the ground samples($\varepsilon$r=22.4) showed higher values than that of the unground samples($\varepsilon$r=20.32). Temperature coefficient of capacitance($\tau$$_{c}$) and dielectric loss (tan$\delta$) of the ground samples were similar to those of unground samples.s.

• 한국지반환경공학회 논문집
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• 제15권11호
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• pp.29-42
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• 2014

This paper investigates the effects of micro-tunneling on buried pipelines parametrically. A simplified numerical approach was developed and various parametric studies have been conducted to evaluate the effects of ground settlements on the response of buried pipelines. The controlled parameters included the pipe stiffness, ground loss magnitude, and pipe location with respect to a micro-tunnel. Maximum settlement and curvature along a pipeline have been investigated and compared among others for different conditions. In addition, the numerical results have been compared with a theoretical method by Attewell et al. (1986), which is based on a Winkler type linear-elastic solution. The comparison indicated that the response of buried pipes to micro-tunneling-induced ground settlements highly depends on the soil-pipe interaction including the separation and slippage of pipe from soil with the effects of the investigated parameters. Therefore, rather than using the theoretical method directly, it would be a better assessment of the response of buried pipelines to consider the soil-pipe interaction in more realistic conditions.