• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.140-148
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• 2014

A storm surge barrier is a specific type of floodgate, designed to prevent a storm surge or spring tide from flooding the protected area behind the barrier. A surge barrier is almost always part of a larger flood protection system consisting of floodwalls, dikes, and other constructions. Surge barriers allow water to pass under normal circumstances but, when a (storm) surge is expected, the barrier can be closed. Among the various means of closing, buoyant flap typed storm surge barrier which was indicated by MOSE project in Italy is chosen for Masan bay protection, and the motion of the surge barrier under the action of storm surge and wave is examined using FLOW-3D, a computational fluid dynamics software analyzing various physical flow processes. Numerical result shows that storm surge barrier is successfully operated under wave height 3 m, and tidal range 2 m.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.888-891
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• 2011

In this paper, drain induced barrier lowering(DIBL) has been analyzed as one of short channel effects occurred in double gate(DG) MOSFET. The DIBL is very important short channel effects as phenomenon that barrier height becomes lower since drain voltage influences on potential barrier of source in short channel. The analytical potential distribution of Poisson equation, validated in previous papers, has been used to analyze DIBL. Since Gaussian function been used as carrier distribution for solving Poisson's equation to obtain analytical solution of potential distribution, we expect our results using this model agree with experimental results. The change of DIBL has been investigated for device parameters such as channel thickness, oxide thickness and channel doping intensity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1125-1128
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• 2007

In order to improve the acoustic performance of a noise barrier without increasing its height, various type of acoustic devices are suggested but, there is no proper method to estimate the performance in Korea. For this, an outdoor test facility was established in Expressway and Transportation Technology Institute(ETTI) of Korea Expressway Corporation for testing the acoustical performance of noise reducing devices installed on the top of a noise barrier. Noise measurements before and after installation of the noise reducing devices were carried out by using sound pressure level for long distance range from the barrier, from 10m to 40m. For considering the directivity effects of noise reducing devices, multivariate regression analysis was attempted.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.579-584
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• 2012

In this paper, drain induced barrier lowering(DIBL) has been analyzed as one of short channel effects occurred in double gate(DG) MOSFET. The DIBL is very important short channel effects as phenomenon that barrier height becomes lower since drain voltage influences on potential barrier of source in short channel. The analytical potential distribution of Poisson equation, validated in previous papers, has been used to analyze DIBL. Since Gaussian function been used as carrier distribution for solving Poisson's equation to obtain analytical solution of potential distribution, we expect our results using this model agree with experimental results. The change of DIBL has been investigated for device parameters such as channel thickness, oxide thickness and channel doping concentration.

• Journal of Magnetics
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• v.10 no.4
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• pp.137-141
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• 2005

We confirmed that the improvement in properties of magnetic tunnel junctions prepared by radical oxidation after thermal treatment was mostly resulted from the redistribution of oxygen at the $AIOx/Co_{90}Fe_{10}$ interface. The as-deposited Al oxide barrier was oxygen-deficient but most of it re-oxidized into $Al_2O_3$, the thermodynamically stable stoichiometric phase, through thermal treatment. As a result, the effective barrier height was increased from 1.52 eV to 2.27 eV. On the other hand, the effective barrier width was decreased from 8.2 ${\AA}$ to 7.5 ${\AA}$. X-ray absorption spectra of Fe and Co clearly showed that the oxygen in the CoFe layer diffused back into the Al barrier and thereby enriched the barrier to close to a stoichiometirc $Al_2O_3$ phase. The oxygen bonded with Co and Fe diffused back by 6.8 ${\AA}$ and 4.5 ${\AA}$ after thermal treatment, respectively. Our results confirm that controlling the chemical structures of the interface is important to improve the properties of magnetic tunnel junctions.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.197-204
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• 2007

Ultra thin Er-silicide layers formed by Er deposition on the clean p-silicon and in situ post annealing technique were investigated with respect to change of the Schottky barrier height. The formation of Er silicides was confirmed by XPS results. UPS measurements revealed that the workfunction of the silicide decreased and was saturated as the deposited Er thickness increased up to $10{\AA}$. We found that the silicides were mainly composed of Er5Si3 phase through the XRD experiments. After Schottky diodes were fabricated with the Er silicide/p-Si junctions, the Schottky barrier heights were calculated $0.44{\sim}0.78eV$ from the I-V measurements of the Schottky diodes. There was large discrepancy in the Schottky barrier heights deduced from the UPS with the ideal junction condition and the real I-V measurements, so that we attributed the discrepancy to the $Er_5Si_3$ phase in the Er-silicides and the large interfacial density of trap state of it.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.5
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• pp.627-634
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• 2018

In the study, computational fluid dynamics analysis was performed to estimate wind force coefficients for a box-type concrete girder bridge under the influence of wind. The drag, lift and pitching moment coefficients were obtained for the bridge section without noise barrier and compared with those of the bridge section with noise barriers of various heights. The shear stress transport $k-{\omega}$ turbulence model was employed to estimate the wind force coefficients, and the contribution of the friction drag force to the total drag force was investigated. It was found from the study that the drag force coefficients increased as the height of noise barrier increased when a wind blew horizontally, and that the contribution of the friction drag force was highest for the bridge section without noise barrier. It is concluded that the impact of the height of noise barriers should be considered in the design of bridges, and the friction force played an important role in evaluating wind forces on bridges.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.115-115
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• 1999

GaN는 직접천이형 wide band gap(3.4eV) 반도체로서 청색/자외선 발광소자 및 고출력 전자장비등에의 응용성 때문에 폭넓게 연구되고 있다. 이러한 넓은 분야의 응용을 위해서는 열 적으로 안정된 Ohmic contact을 반드시 실현되어야 한다. n-type GaN의 경우에는 GaN계면에서의 N vacancy가 n-type carrier로 작용하기 때문에 Ti, Al, 같은 금속을 접합하여 nitride를 형성함에 의해서 낮은 접촉저항을 갖는 Ohmic contact을 하기가 쉽다. 그러나 p-type의 경우에는 일 함수가 크고 n-type와 다르게 nitride가 형성되지 않는 금속이 Ohmic contact을 할 가능성이 많다. 시료는 HF(HF:H2O=1:1)에서 10분간 초음파 세척을 한 후 깨끗한 물에 충분히 헹구었다. 그런 후에 고순도 Ar 가스로 건조시켰다. Pd와 Ni은 열적 증착법(thermal evaporation)을 사용하여 p-GaN에 상온에서 증착하였다. 현 연구에서는 열처리에 의한 Pd의 clustering을 줄이기 위해서 wetting이 좋은 Ni을 Pd 증착 전과 후에 삽입하였으며, monchromatic XPS(x-ray photoelectron spectroscopy) 와 SAM(scanning Auger microscopy)을 사용하여 열처리 전과 40$0^{\circ}C$, 52$0^{\circ}C$ 그리고 695$0^{\circ}C$에서 3분간 열처리 후의 온도에 따른 morphology 변화, 계면반응(interfacial reaction) 및 벤드 휨(band bending)을 비교 연구하였다. Nls core level peak를 사용한 band bending에서 Schottky barrier height는 Pd/Ni bi-layer 접합시 2.1eV를, Ni/Pd bi-layer의 경우에 2.01eV를 얻었으며, 이는 Pd와 Ni의 이상적인 Schottky barrier height 값 2.38eV, 2.35eV와 비교해 볼 때 매우 유사한 값임을 알 수 있다. 시료를 후열처리함에 의해 52$0^{\circ}C$까지는 barrier height는 큰 변화가 없으나, $650^{\circ}C$에서 3분 열처리 후에 0.36eV, 0.28eV 만큼 band가 더 ？을 알 수 있었다. Pd/Ni 및 Ni/Pd 접합시 $650^{\circ}C$까지 후 열 처리 과정에서 계면에서 matallic Ga은 온도에 비례하여 많은 양이 형성되어 표면으로 편석(segregation)되어지나, In-situ SAM을 이용한 depth profile을 통해서 Ni/Pd, Pd/Ni는 증착시 uniform하게 성장함을 알 수 있었으며, 후열처리 함에 의해서 점차적으로 morphology 의 변화가 일어나기 시작함을 볼 수 있었다. 이는 $650^{\circ}C$에서 열처리 한후의 ex-situ AFM을 통해서 재확인 할 수 있었다. 이상의 결과로부터 GaN에 Pd를 접합 시 심한 clustering이 형성되어 Ohoic contact에 문제가 있으나 Pd/Ni 혹은 Ni/Pd bi-layer를 사용함에 의해서 clustering의 크기를 줄일 수 있었다. Clustering의 크기는 Ni/Pd bi-layer의 경우가 작았으며, $650^{\circ}C$ 열처리 후에 barrier height는 Pd/Ni bi-layer의 경우에도 Ni의 영향을 받음을 알 수 있었다.

• Journal of Trauma and Injury
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• v.18 no.2
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• pp.101-106
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• 2005

Purpose: The number of the deceased from free-fall is increasing nowadays. Free-fall comes to a great social problem in that even the survivor will be suffering for cord injury or brain injury, and so on. We analyzed the cases of free-fall patients to find out whether the injury severity is mainly correlated with the height of fall. Methods: We retrospectively investigated the characteristics of patients, who fall from the height above 2m from January 2000 to August 2004. We excluded the patients who transferred to other hospital, transferred from other hospital, and not known the height of fall. 145 patients were evaluated. Variables included in data analysis were age, height of fall, injury severity score (ISS), the being of barrier, and the survival or not. To find out the correlation between height of fall and death, we used receive operating characteristics (ROC) curve analysis. Results: The mean age of patients was $36.5{\pm}19.4$ years old. 110 were male and 35 were female. Mean height of fall was $11.1{\pm}8.5m$. 51 patients (35.2%) were died and 30 patients of them (58.9%) got emergency room on dead body. The mean height of fall is $8.9{\pm}5.8m$ for 94 survivors and $15.2{\pm}11.0m$ for the 51 deceased (p<0.001). The area under the ROC curve was 0.646, which means the height of fall was not adequate factor for predicting for death. At 13.5m, as cut?off value, sensitivity is 52.9%, specificity is 86.2%, positive predictive value is 67.5% and negative predictive value is 77.1%. There were statistical differences in mortality rate and ISS between 'below 13.5m group' and 'above 13.5m group', but there was not statistical difference in head and neck AIS. Conclusion: The height of fall is not adequate factor for prediction of death. So other factors like intoxication or not, the being of barrier or protection device need to be evaluated for predicting of free-fall patient's death.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.4
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• pp.261-265
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• 2011

This paper describes the fabrication and characteristics of a Au/Ni/Ti/3C-SiC Schottky diode with field plate (FP) edge termination. The Schottky contacts were annealed for 30 min at temperatures ranging from 0 to $800^{\circ}C$. At annealing temperature of $600^{\circ}C$, it showed an inhomogeneous Schottky barrier and had the best electrical characteristics. However, the annealing of $800^{\circ}C$ replaced it with ohmic behaviors because of the formation of many different types of nickel silicides. The fabricated Schottky diode had a breakdown voltage of 200 V, Schottky barrier height of 1.19 eV and worked normally even at $200^{\circ}C$.