• Wind and Structures
• /
• 제17권1호
• /
• pp.69-85
• /
• 2013

With the sustainability movement, vegetated building envelopes are gaining more popularity. This requires special wind effect investigations, both from sustainability and resiliency perspectives. The current paper focuses on wind load estimation on small- and full-scale trees used as part of green roofs and balconies. Small-scale wind load assessment was carried out using a wind tunnel testing in a global-effect study to understand the interference effects from surrounding structures. Full-scale trees were investigated at a large open-jet facility in a local-effect study to account for the wind-tree interaction. The effect of Reynolds number combined with shape change on the overall loads measured at the base of the trees (near the roots) has been investigated by testing at different model-scales and wind speeds. In addition, high-speed tests were conducted to examine the security of the trees in soil and to assess the effectiveness of a proposed structural mitigation system. Results of the current research show that at relatively high wind speeds the load coefficients tend to be reduced, limiting the wind loads on trees. No resonance or vortex shedding was visually observed.

• Geomechanics and Engineering
• /
• 제21권2호
• /
• pp.187-200
• /
• 2020

In the current work, a series of three-dimensional finite element analyses have been conducted to investigate the behaviour of pre-existing single piles in response to adjacent tunnelling by considering the tunnel face pressures and the relative locations of the pile tips with respect to the tunnel. Via numerical modelling, the effect of the face pressures on the pile behaviour has been analysed. In addition, the analyses have concentrated on the ground settlements, the pile head settlements and the shear stress transfer mechanism at the pile-soil interface. The settlements of the pile directly above the tunnel crown (with a vertical distance between the pile tip and the tunnel crown of 0.25D, where D is the tunnel diameter) with a face pressure of 50% of the in situ horizontal soil stress at the tunnel springline decreased by approximately 38% compared to the corresponding pile settlements with the minimum face pressure, namely, 25% of the in situ horizontal soil stress at the tunnel springline. Furthermore, the smaller the face pressure is, the larger the tunnelling-induced ground movements, the axial pile forces and the interface shear stresses. The ground settlements and the pile settlements were heavily affected by the face pressures and the positions of the pile tip with respect to the tunnel. When the piles were inside the tunnel influence zone, tensile forces were induced on piles, while compressive pile forces were expected to develop for piles that are outside the influence zone and on the boundary. In addition, the computed results have been compared with relevant previous studies that were reported in the literature. The behaviour of the piles that is triggered by adjacent tunnelling has been extensively examined and analysed by considering the several key features in substantial detail.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2018년도 추계학술대회
• /
• pp.381-382
• /
• 2018

무접합 나노선 터널 전계 효과 트렌지스터(junctionless nanowire tunnel field-effect transistor; JLNW-TFET)에서 소스(p+), 채널(i), 드레인(n) 물질으로 실리콘 및 게르마늄을 사용하여 이 구조에 대한 문턱전압 이하 기울기(subthreshold swings; SS)와 구동전류를 관찰했다. 소스-채널을 게르마늄-실리콘일 때 실리콘-실리콘, 실리콘-게르마늄, 게르마늄-게르마늄 구조보다 구동전류가 최대 1000배 증가하였고, 실리콘-실리콘 구조가 다른 구조에 비해 최소 SS가 최대 5배 이상 감소하였다.

• 한국정보통신학회논문지
• /
• 제21권5호
• /
• pp.869-875
• /
• 2017

본 연구에서는 TCAD 시뮬레이션을 이용하여 4가지 터널링 전계효과 트랜지스터(Tunnel Field-Effect Transistors; TFETs) 구조에 따른 특성을 조사하였다. 단일게이트 TFET(SG-TFET), 이중게이트 TFET(DG-TFET), L-shaped TFET(L-TFET), Pocket-TFET(P-TFET)의 4가지 TFET를 유전율과 채널 길이를 변화함에 따라서 드레인 전류-게이트전압 특성을 시뮬레이션해서 문턱전압이하 스윙(Subthreshold Swing; SS)과 구동 전류(On-current)면에서 비교하였다. 고유전율을 가지며 라인 터널링을 이용하는 L-TFET 구조와 P-TFET 구조가 포인트 터널링을 이용하는 SG-TFET와 DG-TFET보다 구동전류면에서 10배 이상 증가하였고, SS면에서 20 mV/dec이상 감소하였다. 특히, 고유전율을 가진 P-TFET의 주 전류 메카니즘이 포인트 터널링에서 라인터널링으로 변화하는 험프현상이 사라지면서 SS가 매우 향상되는 것을 보였다. 4가지 TFET 구조의 분석을 통해 포인트터널링을 줄이고 라인터널링을 강조하는 새로운 TFET 구조의 가이드 라인을 제시한다.

• Progress in Superconductivity
• /
• 제3권1호
• /
• pp.41-44
• /
• 2001

We report the current transport properties of a normal metal/organic conductor/ superconductor tunnel junction as a novel high- $T_{c}$ superconducting three terminal device. The organic copper (II) phthalocyanine (Cu-Pc) layer was used far a polaronic quasiparticle (QP) injector. The injection of polaronic QP from the Cu-Pc interlayer into a superconductor $Bi_2$$Sr_2$$CaCu_2$ $O_{8+}$ $\delta$/(BSCCO) thin film generated a substantially larger nonequilibrium effect as compared to the normal QP injection current. The tunneling spectroscopy of an Au/cu-PC/BSCCO junction exhibited a zero bias conductance peak which may be due to Andreev reflection at a Cu-Pc/d-wave superconductor junction.n..

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제15권6호
• /
• pp.585-593
• /
• 2015

In the nanoscale regime, many multigate devices are explored to reduce their size further and to enhance their performance. In this paper, design of a novel device called, Triple Material Surrounding Gate Tunnel Field effect transistor (TMSGTFET) has been developed and proposed. The advantages of surrounding gate and tunnel FET are combined to form a new structure. The gate material surrounding the device is replaced by three gate materials of different work functions in order to curb the short channel effects. A 2-D analytical modeling of the surface potential, lateral electric field, vertical electric field and drain current of the device is done, and the results are discussed. A step up potential profile is obtained which screens the drain potential, thus reducing the drain control over the channel. This results in appreciable diminishing of short channel effects and hot carrier effects. The proposed model also shows improved ON current. The excellent device characteristics predicted by the model are validated using TCAD simulation, thus ensuring the accuracy of our model.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제11권4호
• /
• pp.287-294
• /
• 2011

In this paper, two competing mechanisms determining drain current of tunneling field-effect transistors (TFETs) have been investigated such as band-to-band tunneling and drift. Based on the results, the characteristics of TFETs have been discussed in the tunneling-dominant and drift-dominant region.

• Journal of information and communication convergence engineering
• /
• 제14권2호
• /
• pp.115-121
• /
• 2016

Currently there is a lack of literature on SPICE-level models of double-gate (DG) tunnel field-effect transistors (TFETs). A DG TFET compact model is presented in this work that is used to develop a SPICE model for DG TFETs implemented with Verilog-A language. The compact modeling approach presented in this work integrates several issues in previously published compact models including ambiguity about the use of tunneling parameters A_k and B_k, and the use of a universal equation for calculating the surface potential of DG TFETs in all regimes of operation to deliver a general SPICE modeling procedure for DG TFETs. The SPICE model of DG TFET captures the drain current-gate voltage (I_ds-V_gs) characteristics of DG TFET reasonably well and offers a definite computational advantage over TCAD. The general SPICE modeling procedure presented here could be used to develop SPICE models for any combination of structural parameters of DG TFETs.

• Progress in Superconductivity
• /
• 제4권2호
• /
• pp.99-103
• /
• 2003

We studied the nonequilibrium superconductivity due to tunnel injection of polaronic quasiparticle (QP) from organic photoconductor. The transport properties of an organic copper (II) phthalocyanine (Cu -Pc)/d-wave superconductor were investigated in dark and under ultraviolet (UV) radiation for performance of a novel $high -T_{c}$ superconducting three terminal device. We observed that the injection of polaronic QP from the organic Cu -Pc film into the $Bi_2$S $r_2$$CaCuO_{8+{\delta}}$ film generated a substantially larger nonequilibrium effect as compared to the normal QP injection current. We could increase the current gain by UV excitation of the organic photoconductor injector. The tunneling spectroscopy of a Cu -Pc/BSCCO junction exhibited a small enhancement of the zero bias conductance peak under the W excitation. The above phenomena are of importance in developing optically controlled three terminal superconducting device.e.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2017년도 추계학술대회
• /
• pp.454-456
• /
• 2017

다양한 양자모델(Quantum model)을 적용한 터널 전계 효과 트랜지스터(tunnel field effect transistor; TFET)의 전류 및 커패시턴스(Capacitance)-전압 특성을 조사하였다. 사용된 양자 모델은 density gradient, Bohm Quantum Potential(BQP), Vandort quantum correction 모델을 슈뢰딩거-푸아송 모델과 calibration하여 사용하였다. BQP, Vandort, density gradient 모두 구동전류는 감소하였다. BQP를 단독으로 사용한 경우에 SS(subthreshold swing)와 on-set 전압($V_{onset}$)은 일정하지만 구동전류에서만 약 3배 전류가 감소하였으며, BQP와 Vandort 사용한 경우와 density gradient를 사용한 경우에 모두 $V_{onset}$이 약 0.07 eV 이동하였으며, SS가 40 mV/dec 이상으로 증가하였다.