• Nuclear Engineering and Technology
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• 제46권1호
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• pp.101-108
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• 2014

About 40% of reactors in the world are being operated beyond design life or are approaching the end of their life cycle. During long-term operation, various degradation mechanisms occur. Fatigue caused by alternating operational stresses in terms of temperature or pressure change is an important damage mechanism in continued operation of nuclear power plants. To monitor the fatigue damage of components, Fatigue Monitoring System (FMS) has been installed. Most FMSs have used Green's Function Approach (GFA) to calculate the thermal stresses rapidly. However, if temperature-dependent material properties are used in a detailed FEM, there is a maximum peak stress discrepancy between a conventional GFA and a detailed FEM because constant material properties are used in a conventional method. Therefore, if a conventional method is used in the fatigue evaluation, thermal stresses for various operating cycles may be calculated incorrectly and it may lead to an unreliable estimation. So, in this paper, the modified GFA which can consider temperature-dependent material properties is proposed by using an artificial neural network and weight factor. To verify the proposed method, thermal stresses by the new method are compared with those by FEM. Finally, pros and cons of the new method as well as technical findings from the assessment are discussed.

• 한국항공우주학회지
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• 제31권1호
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• pp.34-41
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• 2003

경사기능재료 판에 대한 열탄성 변형과 응력 해석을 위해 Green 함수 방법이 채택되었다. 3차원 정상 온도분포에 대한 해는 적층판 이론에 의해 얻어진다. 열탄성 문제에 대한 기본 방정식은 각각 평면의(out-plane) 변형과 평면내(in-plane) 힘에 의해 유도되었다. 굽힙과 평면내 힘으로 인한 열탄성 변형과 응력분포는 Galerkin 방법에 근거한 Green 함수를 이용하여 해석되었다. 열탄성 변형과 응력분포 해석을 위한 Galerkin Green 함수의 특성함수들은 사각판의 제차 경계조건을 만족시키는 허용함수들의 급수 형태로 근사화 되었다. 수치예제가 수행되었으며, 경사기능재료의 물성치가 판의 열탄성 거동에 미치는 영향이 검토되었다.

• 한국항공운항학회지
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• 제15권2호
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• pp.9-17
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• 2007

A Green's function approach based on the laminate theory is adopted for solving the two-dimensional unsteady temperature field and the associated thermal stresses in an infinite plate made of functionally graded material (FGM). All material properties are assumed to depend only on the coordinate x (perpendicular to the surface). The unsteady heat conduction equation is formulated into an eigenvalue problem by making use of the eigenfunction expansion theory and the laminate theory. The eigenvalues and the corresponding eigenfunctions obtained by solving an eigenvalue problem for each layer constitute the Green's function solution for analyzing the two-dimensional unsteady temperature. The associated thermoelastic field is analyzed by making use of the thermal stress function. Numerical analysis for a FGM plate is carried out and effects of material properties on unsteady thermoelastic behaviors are discussed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.275-278
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• 1995

In this paper, we consider a dynamic shape control problem with an example of controlling a flexible beam shape. Mathematical formulations are obtained by employing the Green's function approach. Necessary conditions for optimality are derived by considering the quadratic performance criteria. Numerical results for both of the dynamic and the static cases are obtained and compared.

• Structural Engineering and Mechanics
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• 제54권4호
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• pp.623-648
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• 2015

A numerical approach is presented for the analysis of the forced vibration of a rigid surface foundation with arbitrary shape. In the analysis, the foundation is discretized into a number of sub squaree-lements. The dynamic response within each sub-element is described by the Green's function, which is obtained by the Fourier-Bessel transform and Precise Integration Method (PIM). Incorporating the displacement boundary condition and force equilibrium of the foundation, it obtains a system of linear algebraic equation in terms of the contact forces within each sub-element. Solving the equation leads to the desired dynamic impedance functions of the foundation. Numerical results are obtained for foundation not only with simple geometrical configurations, such as rectangular and circular foundation, but also the case of irregularly shaped foundation. Several comparisons between the proposed approach and other methods are made. Very good agreement is reached. Also, parametric studies are carried out on the dynamic response of foundation. Addressed in this study are the effects of Poisson's ratio, material damping and contact condition of soil-foundation interface. Several conclusions are drawn the significance of the factors.

• 한국실내디자인학회논문집
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• 제28호
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• pp.51-59
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• 2001

This Study tried to approach with a new Point of view about Green Design that had been studied on just Aesthetics and Function and it focused on creating a pleasant environment In the Interiors combing with Horticultural therapy as advanced study in Green Design. This study is barred on understanding that nature, human and space should continue to coexist through realizing relationship between nature and human and overcoming denaturalization and dehumanization and have an opportunity to know what a pleasant space for human is. Although pleasant space can be made by many different methods, this study start from the thought that a space with plants is the best to satisfy human's basic emotion. The method of study is through research and analysis with many kinds of references and examples, and then the results were used to make design guide which introduces Green Amenity Space in residential space. The pleasant space that human pursuits should be the human-centered space as well as the space giving them mental and physical satisfaction beyond space with just function and beauty. Therefore Green Amenity Space is the best space with which human is familiar.

• 한국항공우주학회지
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• 제32권8호
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• pp.91-100
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• 2004

경사기능재료 판에 대한 열탄성 변형과 응력 해석을 위해 Green 함수 방법이 채택되었다. 3 차원 비정상 온도분포에 대한 해는 적층판 이론에 의해 얻어진다. 열탄성 문제에 대한 기본 방정식은 각각 평면외 (out-plane) 변형과 평면내 (in-plane) 힘에 의해 유도되었다. 굽힘과 평면내 힘에 의한 열탄성 변형과 응력분포는 Galerkin 방법에 근거한 Green 함수를 이용하여 해석하였다. 열탄성 변형과 응력분포 해석을 위한 Galerkin Green 함수의 특성함수들은 사각판의 제차 경계조건을 만족시키는 허용함수들의 급수 형태로 근사화되었다. 단수지시된 사각 판에 대한 수치해석이 수행되었으며, 정사기능재료의 물성치가 판의 비정상 열탄성 거동에 미치는 영향이 검토되었다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권1호
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• pp.1-9
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• 2006

We introduce our in-house program, NANOCAD, for the modeling and simulation of carrier transport in nanoscale MOSFET devices including quantum-mechanical effects, which implements two kinds of modeling approaches: the top-down approach based on the macroscopic quantum correction model and the bottom-up approach based on the microscopic non-equilibrium Green’s function formalism. We briefly review these two approaches and show their applications to the nanoscale bulk MOSFET device and silicon nanowire transistor, respectively.

• 대한기계학회논문집A
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• 제21권9호
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• pp.1441-1451
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• 1997

This paper addresses method which can be used for analyzing thermal stresses of a functionally graded material(FGM) using semi-analytical approach. FGM is a nonhomogeneous material whose composition changes continuously from a metal surface to a ceramic surface. An infinite one dimensional FGM plate is considered. The temperature distribution in the FGM is obtained by approximate Green's function solution. To expedite the convergence of the solutions, alternative Green's function solution is derived and shows good agreement with results from finite difference method. Thermal stresses are calculated using temperature distribution of the plate.

• 대한기계학회논문집A
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• 제22권1호
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• pp.16-22
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• 1998

This paper addresses a method which can be used for analyzing thermal stresses of a functionally graded material(FGM) using semi-analytical approach. FGM is a nonhomogeneous material whose composition is changed continuously from a metal surface to a ceramic surface. An infinite one dimensional FGM plate is considered. The temperature distribution in the FGM is obtained by approximate Green's function solution. To expedite the convergence of the solutions, alternative Green's function solution is derived and shows good agreement with results from finite difference method. Thermal stresses are calculated using temperature distribution of the plate.