• Journal of Korean Society of Steel Construction
• /
• v.13 no.5
• /
• pp.587-597
• /
• 2001

The structural system that discreterized continuous shells is frequently used to make dome-type structures and these structures show the unstable phenomena by snap-through or bifurcation when a load level reaches certain critical value. The characteristic structural behaviour of a cable dome shows a strong nonlinearity and very sensitive according to the initial imperfection. In this study the shape finding problem by applying initial tension stress is investigated and using this the unstable phenomena of perfectly shaped and initially imperfected shape model by external forces are examined to grasp the unstable behavior of cable dome using the Geiger-type model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.475-481
• /
• 2017

In this paper, high speed camera images were used to analyze the supercritical injection behavior of liquid hydrocarbon compounds used as main components of propellant fuel. Decane and Methylcyclohexane (MCH), which have different critical points among kerosene constituents, were selected as experimental fluid and Shadowgraphy technique was used for the analysis. The difference in the temperature variation from the initial injector state of the subcritical condition until the vaporization occurs was represented by the different behaviors of Decane and MCH. However, under the Supercritical conditions, the enthalpy of vaporization near the critical point approaches zero and the phase change to the Supercritical phase occurs instead of vaporization process. In the phase change of the Supercritical system, there was no rapid density change, so the liquid state image was observed in both the Decane and MCH.

• Korean Journal of Food Science and Technology
• /
• v.31 no.1
• /
• pp.164-170
• /
• 1999

Cracking of rice caused by moisture migration during storage under different relative humidity conditions was investigated for the establishment of safe storage condition of rice. Rice was cracked when a large difference in equilibrium relative humidity $({\Delta}ERH)$ between the rice and the environment was present. External and internal cracks were generated as the results of moisture desorption and adsorption, respectively. The external cracks by moisture desorption generated in all directions and shaped irregularly, while the internal cracks by moisture adsorption did in radial direction and showed a typical shape. The cracking trend could be analyzed by the Weibull function, and the cracking constant increased with ${\Delta}ERH$. The frequency of cracked rice increased linearly with In $({\Delta}ERH)$. The critical crack-inducing ${\Delta}ERH$ was $11.3{\sim}16.4%$ during desorption and $10.8{\sim}17.1%$ during adsorption. A diagram for the safe storage of rice was developed with respect to the initial moisture content and the water activity of rice.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.2 s.35
• /
• pp.201-209
• /
• 1998

The presence of elevated temperature can alter significantly the structural response of fibre-reinforced laminated composites. A thermal environment causes degradation in both strength and constitutive properties, particularly in the case of fibre-reinforced polymeric composites. Furthermore, associated thermal expansion, either alone or in combination with mechanically induced deformation, can result in buckling, large deflections, and excessively high stress levels. Consequently, it is often imperative to consider environmental effects in the analysis and design of laminated systems. Exact analytical solutions of higher-order shear deformation theory is developed to study the thermal buckling of cross-ply and antisymmetric angle-ply rectangular plates. The buckling behavior of moderately thick cross-ply and antisymmetric angle-ply laminates that are simply supported and subject to a uniform temperature rise is analyzed. Numerical results are presented for fiber-reinforced laminates and show the effects of ply orientation, number of layers, plate thickness, and aspects ratio on the critical buckling temperature and compared with those obtained using the classical and first-order shear deformation theory.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.628-628
• /
• 2015

유역의 형상은 강우, 산사태 등과 같은 지배적인 침식작용과 더불어 지형 지질학적 요인들에 의해 결정되어 진다. 그러므로 유역형상에 대한 공간특성 분석을 위해서는 지형학적 요인과 다양한 침식작용에 대한 분석이 필요하다. 국내 외 많은 연구결과에 의하면 지형학적 인자에 의한 침식 형태는 국부경사와 집수면적의 크기에 의해 다양한 구간으로 나뉘며, 그 특성에 따라 지표침식, 세굴, 산사태 등으로 구분되는 것으로 연구된 바 있다. 일례로 유역 내 세굴과 관련된 지배인자는 집수면적보다는 국부경사에 반대로 지표침식, 산사태는 국부경사보다는 집수면적의 크기에 따라 영향을 받는다. 따라서 지형학적 인자(국부경사, 집수면적)의 임계치(threshold) 산출을 통해 침식특성(불안정지역)을 검토할 수 있으며, 이에 대한 물리적 검증은 여러 연구를 통해 물질플럭스(유량, 에너지)에 대한 Power Law로써 검증된바 있다. 본 연구에서는 이러한 지형학적 침식특성 분석을 위하여 2006년 집중호우에 의해 광역적 산사태가 발생한 강원도 평창군 진부면 일대의 $10m{\times}10m$ DEM로부터 국부경사, 집수면적을 산출하고 경사-면적한계곡선(Slope-Area Threshold Curve, SATC), 배수면적 확률분포곡선(Probability distribution of Drain Areas Curve, PDAC), 에너지지수 확률분포곡선(Probability distribution of Energy Index Curve, PEIC)를 실제 산사태지점과 중첩하여 도시하였다. 그 결과, 특정 임계구간(Threshold Area, Unstable area, 2~3권역)내에서 산사태 발생지점이 분포하는 것으로 분석되었다. 이를 통해 지형학적 인자만을 고려하여 미계측 유역에 대한 잠재적 불안정지역의 판별이 가능할 것으로 판단되며, 추후 광역적 사면안정해석에 적용 가능할 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.2
• /
• pp.43-54
• /
• 1992

For shallow arches with large dynamic loading, linear analysis is no longer considered as practical and accurate. In this study, a method is presented for the dynamic analysis of shallow arches in which geometric nonlinearity must be considered. A program is developed for the analysis of the nonlinear dynamic behavior and for evaluation of critical buckling loads of shallow arches. Geometric nonlinearity is modeled using Lagrangian description of the motion. The finite element analysis procedure is used to solve the dynamic equation of motion and Newmark method is adopted in the approximation of time integration. A shallow arch subject to radial step loads is analyzed. The results are compared with those from other researches to verify the developed program. The behavior of arches is analyzed using the non-dimensional time, load, and shape parameters. It is shown that geometric nonlinearity should be considered in the analysis of shallow arches and probability of buckling failure is getting higher as arches are getting shallower. It is confirmed that arches with the same shape parameter have the same deflection ratio at the same time parameter when arches are loaded with the same parametric load. In addition, it is proved that buckling of arches with the same shape parameter occurs at the same load parameter. Circular arches, which are under a single or uniform normal load, are analyzed for comparison. A parabolic arch with radial step load is also analyzed. It is verified that the developed program is applicable for those problems.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2004.10a
• /
• pp.391-395
• /
• 2004

본 논문은 맞춤형 신발제작을 위하여 맞춤형 신발에 필요한 화형제작용 데이터를 위한 3차원 측정 장치를 통해 획득한 발의 형상을 인공지능 기법을 기반으로 하는 최적화된 형상을 복원하는 방법을 제시하고자 한다. 본 연구를 위해 개발된 시스템은 PC를 기반으로 하는 기존의 3차원측정 방식을 이용하여 상, 하, 좌, 우로 각각 장착된 8대의 CCD 카메라와 4대의 레이져를 통해 화형 및 발의 형상 데이터를 획득한다 획득된 데이터들은 인공지능 기법을 이용한 영상처리 알고리즘으로 처리되며, 처리 결과는 기존의 지능 기법을 도입하지 않은 시스템에 비해 노이즈제거 특성이 향상되었고, 후처리과정을 간소화 할 수 있다. 따라서 본 논문에서는 3차원 측정을 위해 기구적인 부분과 하드웨어적인 부분의 시스템을 구성하고, 데이터 처리용 소프트웨어에서 입력영상의 전처리 과정 중 영상의 이진화 단계에서 임계값을 결정하기 위하여 간단한 신경망을 사용하였으며, 이에 대한 결과를 제시하고자 한다.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.3 s.32
• /
• pp.323-332
• /
• 1997

This study is aimed at investigating the buckling characteristics of single layer latticed domes with triangular network pattern under the partially concentrated equipment loading in the cases of both having a geometrical imperfection and not having.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.5 no.4
• /
• pp.175-179
• /
• 2012

In this paper, we proposed the modified block structures with enhanced electromagnetic shielding properties for mobie communications and ETC frequency bands. As the result of measurement, this block structure with optimized design has the shielding properties of 30 dB, and can be used for electromagnetic safety and EMI.

• Computational Structural Engineering
• /
• v.7 no.1
• /
• pp.69-81
• /
• 1994

This paper summarizes a dynamic analysis of the shallow circular arches under dynamic loading, considering the geometric nonlinearity. The major emphasis is placed on the development of computer program, which is utilized for the analysis of the nonlinear dynamic behavior and for the evaluation of the critical buckling loads of the shallow circular arches. Geometric nonlinearity is modeled using Lagrangian description of the motion and a finite element analysis procedure is used to solve the dynamic equation of motion. A circular arch subject to normal step load is analyzed and the results are compared with those from other researches to verify the developed program. The critical buckling loads of arches are estimated using the non-dimensional time, load and shape parameters and the results are also compared with those from the linear analysis. It is found that geometric nonlinearity plays and important role in the analysis of shallow arches and the probability of buckling failure is getting higher as arches become shallower.