• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.742-753
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• 2008

Currently an increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method (NATM). Therefore, a possibility of a tunnel collapse during excavation is getting higher in a proportionate manner. This paper will analyze causes the failure mechanism of a shallow NATM tunnel for different geological conditions, ground-water and invert solutions by investigation typical collapse site during tunnel construction. In this paper, this analysis performed two phase, firstly, the field investigation considering displacement measurement, ground-water level, geological characteristic, secondly, the numerical simulation considering the exist of invert construction and the effect of ground-water. It has been found that environmental factors such as state of underground water or construction sequences could influence failure mechanism of a shallow tunnel.

• Archives of Reconstructive Microsurgery
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• v.25 no.1
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• pp.1-6
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• 2016

Purpose: The external ear is a common area of trauma on the body prone to exposure of ultraviolet light, which can lead to skin cancer. Thus, variable techniques have been developed and used for reconstruction of the external ear. The aim of this study is to review the surgical method, its area of application, as well as advantages and pitfalls of reconstruction of the external ear with inferior based retroauricular flaps. Materials and Methods: Eight patients underwent external ear reconstruction with inferior based retroauricular flap for external ear defects in our institute from September 2012 to June 2015. According to the area of the defect, patients were classified as middle 1/3 (n=4), inferior 1/3 (n=2), superior auroculo-cephalic sulcus (n=1), and external auditory canal (n=1). Results: All of the flaps survived the operation and there was no marginal necrosis. Mean size of the defect was $2.8{\times}1.8cm$ and mean size of the retroauricular flap was $5{\times}2cm$. For insetting of the flap, a subcutaneous tunneling technique was used in 6 cases and rotation without subcutaneous tunneling was used in 2 cases. Transient paresthesia occurred in 3 cases. Two cases recovered within 3 months but one case did not recover until 6 months. Conclusion: The inferior based retroauricular flap is an available technique in external ear reconstruction with one stage operation.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.114-114
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• 2000

III-nitride 게 물질들은 blue와 UV 영역의 LED, LD와 같은 광소자뿐만 아니라 HBT, FET와 같은 전자소자로도 널리 응용되고 있다. 이와 같은 물질을 이용한 소자를 제작할 경우 낮은 저항의 ohmic contact은 필수적이다. p-GaN의 ohmic contact은 아직까지 많은 문제점을 내포하고 있다. 그 중의 하나는 높은 doping 농도(>1018cm-3)의 p-GaN 박막을 성장하기가 어렵다는 것이며, 또 하나는 낮은 접촉 비저항을 얻기 위해선 7.5eV 이상의 큰 재가 function을 지닌 금속을 선택해야 한다. 그러나 5.5eV 이상의 재가 function을 갖는 금속은 존재하지 않는다. 위와 같은 문제점들은 p-GaN의 접촉 비저항이 10-2$\Omega$cm2이상의 높은 값을 갖게 만들고 있으며 이에 대한 해결방안으로는 고온의 열처리를 통하여 p-GaN와 금속사이에서 화학적 반응을 일으킴으로써 표면근처에서 캐리어농도를 증가시키고, 캐리어 수송의 형태가 tunneling 형태로 일어날 수 있도록 하는 tunneling current mechaism을 이용하는 것이다. 이에 본 연구에서는 MOCVD로 성장된 p-GaN 박막을 Mg의 activation을 증가시키기 위해 N2 분위기에서 4분간 80$0^{\circ}C$에서 RTA로 annealing을 하였으며, ohmic 접촉을 위한 금속으로 높은 재가 function과 좋은 adhesion 그리고 낮은 자체저항을 가지고 있는 Ni/ZSi/Ni/Au를 ohmic metal로 하여 contact한 후에 $700^{\circ}C$에서 1분간 rapid thermal annealing (RTA) 처리를 했다. contact resistance를 계산하기 위해 circular-TLM method를 이용하여 I-V 특성을 조사하였고, interface interaction을 알아보기 위해 SEM과 EDX, 그리고 XRD로 분석하였다. 또한 추가적으로 Si 계열의 compound metal인 PdSi와 PtSi에 대한 I-V 특성도 조사하여 비교하여 보았다.

• Journal of Magnetics
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• v.10 no.2
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• pp.66-70
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• 2005

The junction properties between the ferromagnet (FM) and two-dimensional electron gas (2DEG) system are crucial to develop spin electronic devices. Two types of 2DEG layer, InAs and GaAs channel heterostructures, are fabricated to compare the junction properties of the two systems. InAs-based 2DEG layer with low trans-mission barrier contacts FM and shows ohmic behavior. GaAs-based 2DEG layer with $Al_2O_3$ tunneling layer is also prepared. During heat treatment at the furnace, arsenic gas was evaporated and top AlAs layer was converted to aluminum oxide layer. This new method of forming spin injection barrier on 2DEG system is very efficient to obtain tunneling behavior. In the potentiometric measurement, spin-orbit coupling of 2DEG layer is observed in the interface between FM and InAs channel 2DEG layers, which proves the efficient junction property of spin injection barrier.

• Polymer(Korea)
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• v.25 no.2
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• pp.293-301
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• 2001

Electrically conductive carbon fiber/high density polyethylene (CF/HDPE) composite films were fabricated by new method, so called electron-ion technology (EIT) and the effects of CF epoxy sizing on the volumetric resistivity. tensile strength and interphase properties of the films were investigated. While epoxy sizing increased conductivity of composite films resulting from enhanced tunneling effect it reduced interphase adhesion between CF and HDPE because polar epoxy sizing and nonpolar HDPE are incompatible. Consequently epoxy sized CF(CF(S)) caused significant reduction in the volumetric resisitivity and tensile strength of composite films when compared with unsized CF(CF(U)). Epoxy sizing reduced nucleating efficiency of CF(S), therefore CF(S)/HDPE composite films showed nonuniform transcrystalline layer when compared with CF(U)/HDPE composite films.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.7
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• pp.51-57
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• 1995

The theoretical analysis for AlInAs/GaInAs resonant tunneling diodes (RTDs), which have shown the improved negative differential resistance (NDR) characteristics, has scarcely been made in comparison with AlGaAS/GaAs RTDs. In this paper, the static current-voltage relation of Al$_{0.48}In_{0.52}As/Ga_{0.47}In_{0.53}$As RTDs were numerically estimated by using a self-consistent method. Assuming a simplified RTD with single quantum well structure and spacer layers, the peak current density (J$_{P}$) and the peak-to-valley current ratio (PVCR) were analysed as the function of the thickness of the well, the barrier and the spacer layer, and temperature. As the results, the peak current density and the peak-to-valley current ratio indicated a reciprocal relation roughly in respect to the thicknesses of the well and the barrier, and it was theoretically predicted that it be not attainable to provide a high peak current desity (J$_{P}$) over 1${\times}10^{5}A/cm^{2}$ as well as the large peak-to-valley current ratio (PVCR) over 10 that were the the critical conditions for the practical use.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.727-736
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• 1995

This paper examines the characteristics and physical properties of the scaled MONOS nonvolatile memory device for low programming voltage EEPROM. The capacitor-type MONOS memory devices with the nitride thicknesses ranging from 41.angs. to 600.angs. have been fabricated. As a result, the 5V-programmable MONOS device has been obtained with a 20ms programming time by scaling the nitride thickness to 57.angs. with a tunneling oxide thickness of 19.angs. and a blocking oxide thickness of 20.angs.. Measurement results of the quasi-static C-V curves indicate, after 10$\^$6/ write/erase cycles, that the devices are degraded due to the increase of the silicon-tunneling oxide interface traps. The 10-year retention is impossible for the device with a nitride less than 129.angs.. However, the MONOS memory device with 10-year retentivity has been obtained by increasing the blocking oxide thickness to 47.angs.. Also, the memory traps such as the nitride bulk trap and the blocking oxide-nitride interface trap have been investigated by measuring the maximum flatband voltage shift and analyzing through the best fitting method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.6
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• pp.321-326
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• 2016

Minimizing the carrier recombination and electrical loss through surface passivation is required for high efficiency c-Si solar cell. Usually, $SiN_X$, $SiO_X$, $SiON_X$ and $AlO_X$ layers are used as passivation layer in solar cell application. Silicon oxide layer is one of the good passivation layer in Si based solar cell application. It has good selective carrier, low interface state density, good thermal stability and tunneling effect. Recently tunneling based passivation layer is used for high efficiency Si solar cell such as HIT, TOPCon and TRIEX structure. In this paper, we focused on silicon oxide grown by various the method (thermal, wet-chemical, plasma) and passivation effect in c-Si solar cell.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1265-1267
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• 1993

The switching and the retention characteristics with the injection conditions(pulse height and pulse width) were investigated in the nonvolatile MNOS memories with thin oxide layer of $23{\AA}$ thick. The shift of flatband voltage was measured using the fast ramp C-V method and experimental results were analized using the previously developed models. It was shown that the experimental results were described quit well by the trap-assisted and modified Fowler-Nordheim tunneling models for the voltage pulse of $15V{\sim}19V,\;24V{\sim}25V$, respectively. However, the direct tunneling model was agreement with experimental values in all range of pulse height. As increasing the initial shift of the flatband voltage, the decay rate was increased. But for the same initial shift of the flatband voltage, the decay rate was smaller for low and long pulse than for high and short one.

• Journal of the Korean GEO-environmental Society
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• v.22 no.11
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• pp.39-47
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• 2021

Tunneling is widely increased in rail-road construction due to the large portion of mountainous regions in Korea as well as the improving running performance of train. Tunneling under poor rock condition, shallow overburden, or existing fault zone has high risk for collapse. Therefore, this study presents the stability of tunnel under unfavorable geological conditions using finite element methods.