• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.475-476
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• 2019

L-shaped tunneling field-effect-transistor (LTFET) is considered a superior device over conventional TFETs. However, experimentally demonstrated LTFET demonstrated poor subthreshold characteristics which was attributed to trap-assisted-tunneling (TAT) caused by presence of trap states. In this paper, TAT mechanism in the experimentally demonstrated LTFET is investigated with the help of band diagram and TAT recombination rate (GTAT).

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.6
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• pp.695-702
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• 2015

Recently, the improvement of mechanical and theoretical issues in geo-centrifuge test enhances the applicability and accuracy of the test. Geo-centrifuge test is appropriate to simulate the behaviors of underground structures like tunnel, since tunnel interacts with the soil and/or rock around it and the test can embody the in-situ stress conditions effectively. In this study, the seismic behaviors of twin tunnel were analyzed based on geo-centrifuge test. Flexible segment to mitigate seismic acceleration were implemented in the model with thin and thick thickness. Based on the test results, it was found that flexible segment can decrease the peak acceleration generally, however, thin flexible segment was not able to reduce peak acceleration in short-period seismic wave. Thick flexible segment was more effective in case of high bedrock acceleration condition. Additionally, 3-dimensional numerical analysis was performed to verify the characteristics of seismic behavior and the effect of flexible segment. Consequently, the numerical analysis result showed good agreement with the test result.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.687-687
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• 2004

예술의 전당 하부를 통과하는 우면산터널은 예술의 전당 자료관, 오페라하우스, 음악당, 서예관, 미술관 등의 건물과 인접하여 설계되었다. 이들 건물은 진동의 전달경로에 따라 구조-구조의 전달경로인 자료관과 구조-지반-구조의 전달경로인 오페라하우스, 음악당, 서예관으로 분류할 수 있다. 자료관은 하부의 기조 중 일부가 우면산 터널의 통과를 위해 설치한 박스(box) 터널 상부와 구조계를 형성하고 있고, 오페라하우스와 음악당 및 서예관 주변으로는 우면산 터널의 상행선과 하행선이 각각 인접하여 통과하는 구조계를 형성하고 있다. 본 연구는 서울시 서초구 서초동～우면동에 이르는 우면산 터널에 실험 차량이 통과할 때 차량 통행으로 인해 발생하는 진동이 예술의전당 자료관, 오페라하우스, 음악당, 서예관 등의 건축구조물에 전달되는 고체전파음의 발생특성 파악하고, 예술의전당 통과구간에 방진패드에 의한 도로포장 공사 후 그에 대한 효과를 비교하였다. 또한, 우면산 터널 예술의 전당 통과구간에 대하여 다공성 아스팔트로 도로포장한 후 그에 대한 효과도 파악하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.2
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• pp.91-100
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• 2002

This paper presents the results of laboratory investigation on the deformation behavior of tunnel face reinforced with longitudinal pipes. A series of reduced-scale model tests was carried out to investigate the effect of reinforcement layout on the tunnel face axial displacement as well as the surface settlement. Among other things, the results of the model tests indicate that the axial displacement of tunnel face as well as the ground surface settlement can significantly be reduced by pre-reinforcing the tunnel face with longitudinal pipes, suggesting that the pre-reinforcing technique may effectively be used as a positive ground control method in the urban environments. Also illustrated is that the reinforcing effect is significantly influenced by the reinforcement layout. The implications of the findings from this study are discussed in a great detail.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.4
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• pp.341-347
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• 2010

The performance of water spray system installed to reduce risks of tunnel fire is investigated by a real tunnel fire test. In case of A class fire, Pool fire, and car fire, the nozzle of water spray has had a marvelous effect to reduce the temperature of hot smoke. And it is verified to have remarkable cooling effects when there is the air flow in a tunnel. Though this results, water spray system will be able to prevent a fire jump to decrease the air temperature in a tunnel and to protect tunnel facilities by the fire control.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.173-180
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• 2001

This research is aimed at investigating the dynamic response of cut-and-cover tunnel to seismic waves. We carried out shaking table test which is used a 1/40-scale(the width of prototype tunnel is about 14.2m, the height is about 8.5m) model for this research, and we analyzed the effect of depth of tunnel and slope of the ground in relation to the dynamic responses of tunnel. As a result of the test, the stress and acceleration along the tunnel decreased accordingly to the depth of increment, and this phenomenon is caused by the increase of the confining effect of ground. Also, the dynamic responses of tunnel showed a tendency to rise according as ground declined gently. In comparison the result of shaking table test with that of structural analysis on ordinary condition, we conclude that seismic waves do not affect cut-and-cover tunnel when the depth of tunnel is over the diameter of tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.999-1012
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• 2017

Theoretical, empirical and numerical methods are used to evaluate the rock load due to tunnelling. Theoretical and empirical methods do not consider ground conditions, tunnel shape, and construction conditions. However, through numerical analysis, it is possible to analyze the displacement and stresses around tunnel due to its excavation, and evaluate the rock load considering ground and construction conditions. The stress transfer ratio(e) which is defined as a ratio of the difference between the major and minor principal stresses to major principal stress is used in order to understand the stress transfer effect around the tunnel excavation using numerical analysis results. The loosend area around tunnel periphery was found based on this approach. The difference of rock load from stress transfer effect was found according to the ground grade. From comparison, rock load obtained from stress transfer effect (e = 10%) were somewhat larger than the results obtained from the critical strain method, but smaller than those obtained from theoretical and empirical methods. The stress transfer effect approach considers the ground condition, tunnel shape; therefore, it can be applied to evaluate the rock load in concrete lining design.

• Journal of the Korean Magnetics Society
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• v.3 no.1
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• pp.29-33
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• 1993

Magnetoresistance was studied for the ferromagnetic tunneling junction in $Permalloy/Al_{2}O_{3}/Co$ prepared by evaporation in a vacuum of $1{\times}10^{-6}$Torr. We measured voltage-current characteristic and magnetic valve effect of prepared ferromagnetic tunneling junction sample. We investigated field-dependency of tunnel resistance by Wheat-stone bridge method and measured magnetic hysteresis curve by vibrating sample magnetometer. The tunneling is confirmed by measuring voltage-current characteristic. The hysteresis curve of magnetoresistance corresponds well with that of magnetization. The magnetoresistance ratio ${\Delta}R/R$ is 0.6% at room temperature.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.5
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• pp.359-368
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• 2010

Unlike in Korea where steel pipe-reinforced multistep grouting is of commonly used methods for tunnel reinforcement, face bolt method is more widely used due to its better workability and lower construction cost in other countries. In this paper, the effects of both methods after tunnel failure were numerically analyzed and verified based on the oversea construction experiences. As a result it is concluded that the face bolt method may be effective to reinforcement especially when there are some fractured zones developed in the face of tunnel.

• Tunnel and Underground Space
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• v.11 no.4
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• pp.339-343
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• 2001

Shield tunnel having circular section located in the soil or soft rock layer is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately during earthquakes. Based on this knowledge, the ground-tunnel interaction effect for this particular vibration mode is investigated. The ground surrounding a tunnel is assumed to be a homogeneous elastic medium. The bonded boundary condition on the ground-tunnel interface is considered. This suggests a firm bond between the ground and the tunnel lining. As Poisson's ratio and stiffness of the ground increases, the strain induced within the tunnel lining increases.