• Journal of Sensor Science and Technology
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• v.12 no.2
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• pp.79-87
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• 2003

In this paper, we propose a method to obtain a linear characteristic using soft computing for systems which have array sensors of nonlinear characteristics. Also a procedure utilizing the pattern information of array sensors without additional sensors is proposed to reduce disturbance effects. For a typical example, even a single CdS cell for CdS array has nonlinear characteristics. Overall linear characteristic for CdS array is obtained using fuzzy logic for each cell and overlapped portion. In addition, further improvement for linearization is obtained applying genetic algorithms for the parameters of membership functions. Also the effect of disturbing external light changes to the CdS array can be reduced without using any additional sensors for calibration. The proposed method based on fuzzy logic shows improvements for position measurements and disturbance reduction to external light changes due to the fuzziness of the shadow boundary as well as the inherent nonlinearity of the CdS array. This improvement is shown by applying the proposed method to the ball position measurements of a magnetic levitation system.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.142-142
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• 2010

본 논문은 단결정 및 다결정 실리콘 기판 상에 아산화질소 플라즈마 처리를 통하여 형성한 초박형 실리콘 옥시나이트라이드 박막의 특성과 이의 어플리케이션에 관한 것이다. 초박형 절연막은 현재 다양한 전자소자의 제작과 특성 향상을 위하여 활용되고 있으나 일반적인 화학 기상 증착 방법으로는 균일도를 확보하기 어려운 문제점을 가지고 있다. 디스플레이의 구동소자로 활용되는 박막 트랜지스터의 특성 향상과 비휘발성 메모리 소자의 터널링 박막에 응용하기 위하여 초박형 실리콘 옥시나이트라이드 박막의 증착과 이의 특성을 분석하였고, 실제 어플리케이션에 적용하였다. 실리콘 산화막과 실리콘 계면상에 존재하는 질소는 터널링 전류와 결함 형성을 감소시키며, 벌크 내에 존재하는 질소는 단일 실리콘 산화막에 비해 더 두꺼운 박막을 커패시턴스의 감소없이 이용할 수 있는 장점이 있다. 아산화질소 플라즈마를 이용하여 활성화된 질소 및 산소 라디칼들이 실리콘 계면을 개질하여 초박형 실리콘 옥시나이트라이드 박막을 형성할 수 있다. 플라즈마 처리 시간과 RF power의 변화에 따라 형성된 실리콘 옥시나이트라이드 박막의 두께 및 광학적, 전기적 특성을 분석하였다. 아산화질소 플라즈마 처리 방법을 사용한 실리콘 옥시나이트라이드 박막을 시간과 박막 두께의 함수로 전환해보면 초기적으로 증착률이 높고 시간이 지남에 따라 두께 증가가 포화상태에 도달함을 확인할 수 있다. 아산화질소 플라즈마 처리 시간의 변화에 따라 형성된 박막의 전기적인 특성의 경우, 플라즈마 처리 시간이 짧은 실리콘 옥시나이트라이드 박막의 경우 전압의 변화에 따라 공핍영역에서의 기울기가 현저히 감소하며 이는 플라즈마에 의한 계면 손상으로 계면결합 전하량이 증가에 기인한 것으로 판단된다. 또한, 전류-전압 곡선을 활용하여 측정한 터널링 메카니즘은 2.3 nm 이하의 두께를 가진 실리콘 옥시나이트라이드 박막은 직접 터널링이 주도하며, 2.7 nm 이상의 두께를 가진 실리콘 옥시나이트라이드 박막은 F-N 터널링이 주도하고 있음을 확인할 수 있다. 결론적으로 실리콘 옥시나이트라이드 박막을 활용하여 전기적으로 안정한 박막트랜지스터를 제작할 수 있었으며, 2.5 nm 두께를 경계로 터널링 메커니즘이 변화하는 특성을 이용하여 전하 주입 및 기억 유지 특성이 효과적인 터널링 박막을 증착하였고, 이를 바탕으로 다결정 실리콘 비휘발성 메모리 소자를 제작하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3247-3252
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• 2013

The convergence of ICT and cloud computing is treated as a main issue all over the fields including education. This development leads to change from e-learning to u-learning and smart education. Therefore, we need to study in term of the systematic and a long-term viewpoint how smart education environment have an influence on the practical space. And we need a concrete study for smart education space based on property of space. Under these critical mind, this study understands the smart education space in terms of the convergence of computing space and physical space. As a Result, smart education space have major property such as flexibility, communication, polyvalence.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.36-41
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• 2012

Total external reflection (TER), which does not occur on a dielectric interface, is a unique feature of surface plasmon-polaritons (SPP). We propose an SPP-TER waveguide structure consisting of low-index dielectric nanocore covered with high-index dielectric on a flat metal surface. The SPP mode confined in the nanocore by the TER effect has a mode size much smaller than wavelength scale. Numerical comparison of mode characteristics between the SPP-TER waveguides and other total-internal-reflection-based waveguides such as metal or high-index dielectric nanowires show that the SPP-TER structures can possess higher modal gain for applications of nanocavity lasers.

• Journal of the Korea Construction Safety Engineering Association
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• s.45
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• pp.60-70
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• 2008

Mechanized tunnelling by TBMs has been extensively adopted for last two decades. Nevertheless, only few case histories have been reported. Unlike NATM tunnels, the case histories of the weak zone have been seldom reported for the mechanized tunnelling, even in the other countries. In this study, a collapse of TBM tunnel occurred in the severely altered weak rock zones between volcaniclastic rocks and granitic rocks was briefly described. A systematic geotechnical investigation, which was performed to examine the cause of the collapse, was carried out at the site and then characteristics of the rocks in the zones were evaluated. Moreover, This study propose a guide line of estimateing the possibility of collapse in TBM tunnels through comparing experimental results with surveying results of general rocks.

• Composites Research
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• v.15 no.2
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• pp.1-10
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• 2002

The strength of glass/epoxy fabric joints under pin-loading is estimated based on the characteristics length method and experiment. To investigate the effect of finite element idealization for the contact between pin and laminate, three modeling cases are analyzed; assuming the cosine load distribution around the contact area, constraining the radial displacement at the hole boundary, and using the contact element. To study the effect of failure criteria, Tsai-Wu and Yamada-Sun methods are applied on the characteristic curve. The results of the nonlinear analysis using the contact element showed good agrements with experimental data in both laminates made of uni-directional prepreg tapes and fabrics. In terms of failure criteria, Tsai-Wu method showed better agreement with experimental results than the one by Yamada-Sun laminate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4C
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• pp.109-116
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• 2011

In this study, dynamic response of a vertical shaft subjected to seismic loads was evaluated by three-dimensional Finite Element (FE) approach. The emphasis was on quantifying the ground conditions, input motions and direction of motions. A series of parametric analyses were carried out. From the results of FE analysis, more than 1.7 times increase in shear force and bending moment is obtained when the stiff layer was thinker than the soft layer. And all of the maximum values were occurred near the interface between the soil layers. The dynamic behavior of vertical shaft was significantly influenced by the different frequencies of the input motion, and normalized acceleration of surrounding soil was 3 times larger than vertical shaft.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1621-1625
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• 2006

하천은 여러 하천의 연결망으로 구성되어 있으며, 연결부는 절점으로 이루어져 있고, 이 절점은 하천이 합류하는 곳으로서 하천의 시스템을 구성하는 가장 중요한 요소이다. 최근에 친자연 하천 복원 등의 많은 사업을 하고 있음에도 불구하고 이에 대한 검토가 거의 이루어지지 않고 있으며, 이를 검토하고 이해하는 것이 하천을 복원하고 관리하는데 매우 중요하다. 본 연구는 본류와 지류의 하상경사 및 하상고가 다르고, 유사 유입조건이 다른 비평형 유입조건을 갖고 있으며, 하폭이 넓고 수심이 상대적으로 얕은 합류부에서 흐름 및 하상변동에 관하여 수치모의를 수행하여 그 특성을 파악하는데 그 목적이 있다. 적용 대상지역은 금강과 미호천의 합류부로서, 흐름 특성 및 하상변동을 모의하기 위하여 RMA-2와 SED2D를 이용하였다. 유량의 증가에 따라 흐름에 대한 유속이 증가하며, 전단층의 길이가 증가하고, 합류부의 우안의 정체수역에서 발생하는 와(vortex)의 크기도 증가하였다. 부유사의 농도는 실제 상황에 맞도록 비평형 유입조건을 사용하였으며, 미호천에서 유입되는 유사의 농도에 영향을 받아, 합류직후에도 유사의 농도가 높으며, 전단층을 경계로 하여 농도 띠가 하류로 유지되었으며, 합류 후에는 우안에서는 하상이 상승되었다.

• Composites Research
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• v.13 no.2
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• pp.1-7
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• 2000

A new ultrasonic test method is proposed to obtain elastic constants of unidirectional composite materials nondestructively. In the proposed test method, only longitudinal transducers are used to measure wave velocities by through-transmission method. An aluminum wedge and a flat aluminum rectangular block are placed on each side of the test specimen. Oblique incident longitudinal wave is transmitted from a wedge to the specimen and the mode conversions are occurred sequentially at two interfaces between the specimen and aluminium. Measuring wave velocities converted to longitudinal waves in the rectangular block give all information to determine elastic constants of the composites. In order to determine shear stiffness coefficients, transverse wave velocity is measured indirectly from received longitudinal wave. Effects of anisotropy on waves are also considered in this study.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.48-53
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• 2007

The objective of this paper is to investigate the influence of impact conditions on the impact characteristics of the stainless sheet for the case of the fixed boundary conditions. In order to examine impact characteristics of the sheet, three-dimensional finite element analyses and impact tests have been performed. High speed tensile tests have been carried out to obtain strain-stress relationships including the effects of the strain rate. In order to improve an accuracy of the FE analysis, the hyper-elastic model and the damping factor have been introduced. The results of the FE analyses and the impact tests have been shown that the diameter of the impact head does not affect the absorption energy of the stainless sheet. In addition, it has been shown that the absorption rate of energy maintains almost $82.5\;\sim\;83.5\;%$ irrespective of the impact energy level and the diameter of the impact head. From the results of FE analyses, the variation of stress and strain energy in the stainless sheet has been quantitatively examined.