• Structural Engineering and Mechanics
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• 제45권3호
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• pp.355-371
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• 2013

Single- and multi-span orthotropic functionally graded hollow cylinders subjected to axisymmetrical bending are investigated on the basis of a unified shear deformable shell theory, in which the transverse displacement is expressed by means of a general shape function. To approach the through-thickness inhomogeneity of the hollow cylinder, a laminated model is employed. The shape function therefore shall be determined for each fictitious layer. To improve the computational efficiency, we resort to a transfer matrix method. Based on the principle of minimum potential energy, equilibrium equations are established, which are then solved analytically using the transfer matrix method for arbitrary boundary conditions. Numerical comparisons among a third-order shear deformable shell theory, an exact elastic theory and the present theory are provided for a simply supported hollow cylinder, from which the present theory turns out to be superior in stress estimation. Distributions of displacements and stresses in single- and three-span hollow cylinders with different boundary conditions are also illustrated in numerical examples.

• Steel and Composite Structures
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• 제24권5호
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• pp.569-578
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• 2017

In this research work, a simple and accurate hyperbolic plate theory for the buckling analysis of functionally graded sandwich plates is presented. The main interest of this theory is that, in addition to incorporating the thickness stretching effect (${\varepsilon}_z{\not=}0$), the displacement field is composed only of 5 unknowns as the first order shear deformation theory (FSDT), instead of 6 like in the well-known "higher order shear and normal deformation theories". Thus, the number of unknowns and governing equations for the present theory is reduced, significantly facilitating engineering analysis. Governing equations are obtained by employing the principle of minimum total potential energy. Comparison studies are performed to verify the validity of present results. A numerical investigation has been conducted considering and neglecting the thickness stretching effects on the buckling of sandwich plates with functionally graded skins. It can be concluded that the present theory is not only accurate but also simple in predicting the buckling response of sandwich plates with functionally graded skins.

• Communications for Statistical Applications and Methods
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• 제13권2호
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• pp.389-407
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• 2006

Extreme value theory has been used widely in many areas of science and engineering to deal with the assessment of extreme events which are rare but have catastrophic consequences. The potential of extreme value theory has only been recognized recently in finance area. In this paper, we provide an overview of extreme value theory for estimating and assessing value at risk and expected shortfall which are the methods for modelling and measuring the extreme financial risks. We illustrate that the approach based on extreme value theory is very useful for estimating tail related risk measures through backtesting of an empirical data.

• Advances in nano research
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• 제7권1호
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• pp.63-75
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• 2019

This article represents a quasi-3D theory for the buckling investigation of magneto-electro-elastic functionally graded (MEE-FG) nanoplates. All the effects of shear deformation and thickness stretching are considered within the presented theory. Magneto-electro-elastic material properties are considered to be graded in thickness direction employing power-law distribution. Eringen's nonlocal elasticity theory is exploited to describe the size dependency of such nanoplates. Using Hamilton's principle, the nonlocal governing equations based on quasi-3D plate theory are obtained for the buckling analysis of MEE-FG nanoplates including size effect and they are solved applying analytical solution. It is found that magnetic potential, electric voltage, boundary conditions, nonlocal parameter, power-law index and plate geometrical parameters have significant effects on critical buckling loads of MEE-FG nanoscale plates.

• 한국지반공학회지:지반
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• 제13권1호
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• pp.137-146
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• 1997

A Study on the 본 연구에서는 플라스틱드레인을 이용하여 진공수평배수에 의해 개량된 준설 점토 지반의 압밀거동을 파악하기 위하여 대형 압밀시험을 실시하였으며, 실험 결과가 포텐결중공원주의 압밀이론을 이용한 수치해석에 의해 비교 검토되었다. 본 연구 실험결과에 의하면 수평배수진공압밀시험은 점토층 내부의 함수비 및 간극수압과 드레인 배수 속도 등이 진공압밀 시간 경과에 따라 감소되어 압밀이 급속하게 진행되고 있음이 확인되었다. 점토층 중공원주의 방사류에 대한 선형포텐샬압밀이론을 이용하여 수치 압밀해석 결과 간극수압은 확산 형태보다 흙의 변형과 투수에 의해 크게 좌우되고 있으므로, 지표면 부근에서의 실측 침하량은 압밀응력증가율 a가 -0.5정도에서 수치해석과 일치하며 또한 드레인 설치 부근에서의 점토층 침하량은 Baryon 압밀이론과 유사한 거동을 나타내고 있다. 최종적으로 수평 배수에 대한 적당한 선택과정을 포함한 설계 및 시공관리가 시험결과에 의하여 설명 되었으며 포텐셜압밀이론은 진공배수시 수평드레인에 의한 압밀거동을 정확하게 예측할 수 있다.

• 전자공학회논문지CI
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• 제40권3호
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• pp.127-136
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• 2003

본 논문에서는 템플릿 변형과 Level-Set 이론을 사용하여 모델과 에지 기반의 객체 추적 방법을 제안한다. 제안된 방법은 배경의 변화, 객체 자체의 모양변화, 객체간의 겹침 등이 있는 경우에도 객체를 추적할 수 있다. 먼저, 객체 추적을 위해 템플릿과 목적 프레임간의 상호 영역 차이(Inter-region distance)와 에지 값으로 구성된 에너지 함수 PDEF(Potential Difference Energy Function)를 새롭게 정의한다. 이 함수는 객체 위치 및 경계 예측과 객체 모양 재결정 단계에서 사용된다. 객체 위치 및 경계 예측 단계에서는 객체의 변화가 어파인(affine) 변형을 따른다는 가정 하에 객체의 대략적인 모양 및 위치를 예측한다. 객체 모양 재결정 단계에서는 퍼텐셜 에너지 지도(Potential energy map)와 수정된 Level-Set 운동 함수를 사용하여 객체의 정확한 형태를 재결정한다. 실험결과에서 제안된 방법은 기존의 방법보다 배경의 변화가 큰경우, 객체 자체의 모양변화가 심한 경우, 객체간의 겹침이 있는 경우 등 다양한 상황이 포함된 동영상에서 정확하게 객체를 추적할 수 있음을 확인할 수 있다.

• 한국물환경학회지
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• 제26권1호
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• pp.89-95
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• 2010

The electrokinetic potential of $CaCO_3$, which takes an important part in aquatic system, has been measured and the variation of total energy between $CaCO_3$ particles with the distance of particles was estimated based on DLVO theory. The electrokinetic potential of particles was observed to increase to positive direction as the charge valence of cations which was added to suspension was increased. Also, the total interaction energy between particles was estimated to be more negative as the charge valence of cation was higher and its concentrations was raised. When a mixture of cations with different charge valences was added, the influence of cation with a higher charge valence was more significant on the total interaction energy between particles. When anion was added to the suspension of $CaCO_3$, the total energy estimated by DLVO theory was examined to move to positive direction and the electrokinetic potential of particles became more negative. Likewise cations, the effect of anions on the electrokinetic potential of particles and total interaction energy between them was observed to be proportional to their charge valence and the influence of the mixture of anions with different charge valence became more remarkable as the mixing ratio of the anion with a higher charge valence was increased.

• 한국건설관리학회논문집
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• 제24권6호
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• pp.36-44
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• 2023

입찰담합에 따른 공공재정 손실, 경쟁 저해, 신뢰 하락 등의 문제에 대응하기 위해, 공공 건설공사 입찰실무자의 담합 가능성을 예측하고 대응 방안을 개발하는 것을 목적으로 한다. 이를 위해 FTT (Fraud Triangle Theory)의 기회, 압력, 합리화 요인을 분석하여 입찰담합 예방 및 대응 방안을 도출한다. 종합·전문 건설업체의 입찰실무자를 대상으로 한 설문 조사를 통해 FTT 연구모형을 검증하고, 결과를 통해 입찰실무자의 담합 가능성을 예측하는 데 활용한다. 연구 결과, 압력이 높을수록, 기회가 많을수록, 합리화가 강할수록 개인의 담합 가능성이 커지는 것을 확인하였다. 또한, 기회가 많을수록, 합리화가 강할수록 타인의 담합 가능성도 커지는 것을 알 수 있었다. 이러한 현상을 이해하여 입찰담합 예방을 위한 정책 개발에 기여할 것으로 기대된다.

• Bulletin of the Korean Chemical Society
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• 제11권1호
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• pp.34-41
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• 1990

The second order ab initio effective valence shell Hamiltonian is calculated for the valence state potential energy curves of NH and $NH^+$. From the potential energy curves various spectroscopic constants of valence states are determined. The results are in good agreement with experiments and configuration interaction calculations. They show the composite picture of potential energy curves and also indicate that the second order effective Hamiltonian theory is adequate for describing various valence states of a molecule and its ions simultaneously.

• 대한수학회논문집
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• 제34권3호
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• pp.757-769
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• 2019

A solution of the heat equation with a distribution-valued potential is constructed by regularization. When the potential is the generalized derivative of a $H{\ddot{o}}lder$ continuous function, regularity of the resulting solution is in line with the standard parabolic theory.