• Title/Summary/Keyword: Tunnel current effect

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A study on the behaviour of pre-existing single piles to adjacent shield TBM tunnelling from three-dimensional finite element analyses (3차원 유한요소해석을 통한 shield TBM 터널 근접시공에 의한 인접 단독말뚝의 거동에 대한 연구)

  • Jeon, Young-Jin;Jeon, Seung-Chan;Jeon, Sang-Joon;Lee, Cheol-Ju
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.22 no.1
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    • pp.23-46
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    • 2020
  • In the current work, a series of three-dimensional finite element analyses have been carried out to understand the behaviour of pre-existing single piles to adjacent tunnelling by considering the tunnel face pressures and the relative location of pile tips with respect to the tunnel. The numerical modelling has analysed the effect of the face pressures on the pile behaviour. The analyses concentrate on the ground settlements, the pile head settlements, the axial pile forces and the shear stress transfer mechanism at the pile-soil interface. The head settlements of the pile (the vertical distance between the pile and the tunnel: 0.25D, where D is the tunnel diameter) directly above the tunnel crown with the face pressure 50% of the in-situ horizontal soil stress at the tunnel springline decreased by about 38% compared to corresponding settlements with a face pressure 25% of the in-situ horizontal soil stress at the tunnel springline. Furthermore, it was found that the smaller the face pressure, the larger the tunnelling-induced ground movements and the axial pile forces were and the higher the degree of the shear strength mobilisation at the pile-soil interface. When the piles were outside the tunnel influence zone, compressive pile forces were developed due to tunnelling. It has been found that the ground settlements and the pile settlements are heavily affected by the face pressures and the position of the pile tip relative to the tunnel. In addition, the computed results have been compared with relevant studies previously reported in literature. The behaviour of the piles has been extensively examined and analysed by considering the key features in great detail.

A Study on the Excavation of Tunnel Portal Zone Located at High Steep Slope (급경사 지형에 위치하고 있는 갱구부의 굴착 방안 연구)

  • Kim, Woo-Sung;Lee, Sang-Eun
    • Explosives and Blasting
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    • v.26 no.2
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    • pp.38-44
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    • 2008
  • Recently, planning road construction in South Korea is focused on upgrading of the existing road by rerouting or restructuring. For this, roads under current construction in Korea go for more straight in its alignments and routing. Straight routing makes it all the more required to construct many mountain tunnels and bridges in Korea where mountains are so widely spread. Some portal of mountain tunnel is not rarely planed at high steep slope of mountain valley where it is not easy to secure working space for tunnel excavation. Reverse excavation is an alternative measure for excavation of tunnel portal at high steep slope. Construction in reverse excavation method has three important points requiring careful consideration: 1)planning of pilot tunnel in proper width, height, and length etc., 2)measure against the effect of one-side earth pressure to the direction of tunnel portal, 3)securing tunnel safety against shallow ground condition at portal zone. This paper intends to suggest applicable range of pilot tunnel for reverse excavation at the portal zone located at high steep slope, and shows result of study on the appropriateness of a reverse excavation by means of 3D numerical analysis. Result of 3D numerical analysis for reverse excavation at high steep slope shows that pilot tunneling will be applicable to start from the point $20{\sim}25m$ before the portal from inside the tunnel.

Passivation Properties of Phosphorus doped Amorphous Silicon Layers for Tunnel Oxide Carrier Selective Contact Solar Cell (터널 산화막 전하선택형 태양전지를 위한 인 도핑된 비정질 실리콘 박막의 패시베이션 특성 연구)

  • Lee, Changhyun;Park, Hyunjung;Song, Hoyoung;Lee, Hyunju;Ohshita, Yoshio;Kang, Yoonmook;Lee, Hae-Seok;Kim, Donghwan
    • Current Photovoltaic Research
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    • v.7 no.4
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    • pp.125-129
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    • 2019
  • Recently, carrier-selective contact solar cells have attracted much interests because of its high efficiency with low recombination current density. In this study, we investigated the effect of phosphorus doped amorphous silicon layer's characteristics on the passivation properties of tunnel oxide passivated carrier-selective contact solar cells. We fabricated symmetric structure sample with poly-Si/SiOx/c-Si by deposition of phosphorus doped amorphous silicon layer on the silicon oxide with subsequent annealing and hydrogenation process. We varied deposition temperature, deposition thickness, and annealing conditions, and blistering, lifetime and passivation quality was evaluated. The result showed that blistering can be controlled by deposition temperature, and passivation quality can be improved by controlling annealing conditions. Finally, we achieved blistering-free electron carrier-selective contact with 730mV of i-Voc, and cell-like structure consisted of front boron emitter and rear passivated contact showed 682mV i-Voc.

Numerical evaluation of the effect of multiple roughness changes

  • Abdi, Daniel S.;Bitsuamlak, Girma T.
    • Wind and Structures
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    • v.19 no.6
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    • pp.585-601
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    • 2014
  • The effect of multiple roughness changes close to a building site was examined through three dimensional computational fluid dynamics (CFD) simulations conducted in a virtual boundary layer wind tunnel (V-BLWT). The results obtained were compared with existing wind speed models, namely ESDU-82026 and Wang and Stathopoulos (WS) model. The latter was verified by wind tunnel tests of sixty nine cases of multiple roughness patches, and also with a simplified 2D numerical model. This work extends that numerical study to three dimensions and also models roughness elements explicitly. The current numerical study shows better agreement with the WS model, that has shown better agreements with BLWT tests, than the ESDU model. This is in contrast to previous results of Wang and Stathopoulos, who concluded that CFD shows better agreement with the ESDU model. Many cases were simulated in a V-BLWT that has same dimensions as BLWT used in the original experiment and also in a reduced symmetrical version (S-BLWT) that takes advantage of regular arrangement of roughness blocks. The S-BLWT gives results almost identical to V-BLWT simulations, while achieving significant reduction on computational time and resources.

Wind tunnel test of wind loads and current loads acting on FLBT and LNG bunkering shuttles in side-by-side configuration and comparison with empirical formula (병렬 배치된 FLBT 및 LNG-BS에 작용하는 풍하중 및 조류하중에 대한 풍동 시험 및 경험식 비교 연구)

  • Park, Byeongwon;Jung, Jae-Hwan;Hwang, Sung-Chul;Cho, Seok-Kyu;Jung, Dongho;Sung, Hong Gun
    • Journal of Ocean Engineering and Technology
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    • v.31 no.4
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    • pp.266-273
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    • 2017
  • In recent years, LNG bunkering terminals are needed to supply LNG as fuel to meet the emission requirements of the International Maritime Organization (IMO). A floating LNG bunkering terminal (FLBT) is one of the most cost-effective and environmentally friendly LNG bunkering systems for storing LNG and transferring it directly to an LNG fuel vessel. The FLBT maintains its position using mooring systems such as spread mooring and turret mooring. The loads on the vessel and mooring lines must be carefully determined to maintain their positions within the operable area. In this study, the wind loads acting in several side-by-side arrangements on the FLBT and LNG-BS were estimated using wind tunnel tests in the Force Technology, and the shielding effect due to the presence of ships upstream was evaluated. In addition, the empirical formulations proposed by Fujiwara et al. (2012) were used to estimate the wind force coefficients acting on the FLBT and those results were compared with experimental results.

Electrical Resistivity Imaging for Upper Layer of Shield TBM Tunnel Ceiling (쉴드 TBM터널 상부 지반 연약대 전기탐사)

  • Jung, Hyun-Key;Park, Chul-Hwan
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.401-408
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    • 2005
  • Recently shield TBM tunnellings are being applied to subway construction in Korean cities. Generally these kinds of tunnellings have the problems in the stability of ground such as subsidence because urban subway is constructed in the shallow depth. A sinkhole occurred on the road just above the tunnel during tunneling in Kwangju, so a survey for upper layer of the tunnel was needed. But conventional Ground Probing Radar can't be applicable due to the presence of steel-mesh screen in the shield segment, so no existent geophysical method is applicable in this site. Because the outer surface of each shield segment is electrically insulated, dipole-dipole resistivity method which is popular in engineering site investigation, was tried to this survey for the first time. Specially manufactured flexible ring-type electrodes were installed into the grouting holes at an interval of 2.4 m on the ceiling. The K-Ohm II system which has been developed by KIGAM and tested successfully in many sites, was used in this site. The system consists of 1000Volt-1Ampere constant-current transmitter, optically isolated 24 bit sigma-delta A/D conversion receiver - maximum 12 channel simultaneous measurements, and graphical automatic acquisition software for easy data quality check in real time. Borehole camera logging with circular white LED lighting was also done to investigate the state of the layer. Measured resistivity data lack of some stations due to failing opening lids of holes, shows general high-low trend well. The dipole-dipole resistivity inversion results discriminate (1) one approximately 4 meter diameter cavity (grouted but incompletely hardened, so low resistivity - less than $30{\Omega}m$), (2) weak zone (100-200${\Omega}m$), and (3) hard zone (high resistivity - more than 1000${\Omega}m$) very well for the distance of 320 meters. The 2-D inversion neglects slight absolute 3-D effect, but we can get satisfactory and useful information. Acquired resistivity section and video tapes by borehole camera logging will be reserved and reused if some problem occurs in this site in the future.

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The Study of Electromagnetic Force by Three Phase Short-Circuit Test of Cable (케이블 삼상단락 실증시험을 통한 전자력 영향 검토)

  • Hong, Dong-Suk;Kim, Hae-Jun;Park, Sung-Min;Chang, Woo-Suk;Park, Heong-Suk;Jang, Tae-In;Kang, Ji-Won
    • Proceedings of the KIEE Conference
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    • 2009.07a
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    • pp.395_396
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    • 2009
  • This paper handles with effect of electromagnetic force on the cables by fault current accompanied by accident of underground transmission cable. Even though underground transmission cable is an essential transmission method to supply stable power for downtown and population center, interaction of electromagnetic force from fault current is very large comparing to overhead transmission line due to restricted installation space such as tunnel, etc. and close consideration is required for it. This paper describes the effect of electromagnetic force through results of three phase short-circuit test and electromagnetic force analysis using theoretical calculations and electrical evaluation test after three phase short-circuit test, which will be utilized as basic materials for improvement and development of cleat, hanger, etc. to reduce and release effect of electromagnetic force in the future.

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Wind engineering for high-rise buildings: A review

  • Zhu, Haitao;Yang, Bin;Zhang, Qilin;Pan, Licheng;Sun, Siyuan
    • Wind and Structures
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    • v.32 no.3
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    • pp.249-265
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    • 2021
  • As high-rise buildings become more and more slender and flexible, the wind effect has become a major concern to modern buildings. At present, wind engineering for high-rise buildings mainly focuses on the following four issues: wind excitation and response, aerodynamic damping, aerodynamic modifications and proximity effect. Taking these four issues of concern in high-rise buildings as the mainline, this paper summarizes the development history and current research progress of wind engineering for high-rise buildings. Some critical previous work and remarks are listed at the end of each chapter. From the future perspective, the CFD is still the most promising technique for structural wind engineering. The wind load inversion and the introduction of machine learning are two research directions worth exploring.

Analytical Surface Potential Model with TCAD Simulation Verification for Evaluation of Surrounding Gate TFET

  • Samuel, T.S. Arun;Balamurugan, N.B.;Niranjana, T.;Samyuktha, B.
    • Journal of Electrical Engineering and Technology
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    • v.9 no.2
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    • pp.655-661
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    • 2014
  • In this paper, a new two dimensional (2D) analytical modeling and simulation for a surrounding gate tunnel field effect transistor (TFET) is proposed. The Parabolic approximation technique is used to solve the 2-D Poisson equation with suitable boundary conditions and analytical expressions for surface potential and electric field are derived. This electric field distribution is further used to calculate the tunneling generation rate and thus we numerically extract the tunneling current. The results show a significant improvement in on-current characteristics while short channel effects are greatly reduced. Effectiveness of the proposed model has been confirmed by comparing the analytical results with the TCAD simulation results.

Analysis of the Temperature Distribution at Micromachining Processes for Microaccelerometer Based on Tunneling Current Effect (턴널전류 효과를 이용한 미소가속도계의 마이크로머시닝 공정에서 온도분포 해석)

  • 김옥삼
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.9 no.5
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    • pp.105-111
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    • 2000
  • Micronization of sensor is a trend of the silicon sensor development with regard to a piezoresistive silicon pressure sensor, the size of the pressure sensor diaphragm have become smaller year by year, and a microaccelerometer with a size less than 200~300${\mu}{\textrm}{m}$ has been realized. Over the past four or five years, numerical modeling of microsensors and microstructures has gradually been developed as a field of microelectromechanical system(MEMS) design process. In this paper, we study some of the micromachining processes of single crystal silicon(SCS) for the microaccelerometer, and their subsequent processes which might affect thermal and mechanical loads. The finite element method(FEM) has been a standard numerical modeling technique extensively utilized in structural engineering discipline for component design of microaccelerometer. Temperature rise sufficiently low at the suspended beams. Instead, larger temperature gradient can be seen at the bottom of paddle part. The center of paddle part becomes about 5~2$0^{\circ}C$ higher than the corner of paddle and suspended beam edges.

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