• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(1)
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• pp.79-86
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• 1998

The nonlinear analytic function expansion nodal (AFEN) method is applied to the solution of the time-dependent neutron diffusion equation. Since the AFEN method requires both the particular solution and the homogeneous solution to the transient fixed source problem, the derivation solution method is focused on finding the particular solution efficiently. To avoid complicated particular solutions, the source distribution is approximated by quadratic polynomials and the transient source is constructed such that the error due to the quadratic approximation is minimized. In addition, this paper presents a new two-node solution scheme that is derived by imposing the constraint of current continuity at the interface corner points. The method is verified through a series of applications to the NEACRP PWR rod ejection benchmark problem.

• 한국주조공학회지
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• 제20권2호
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• pp.129-140
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• 2000

This study aims at the phase-field modeling of the phase transformation in graphitization of the cast iron. As the first step, we constructed a phase-field model including the phases with negligible solubility. Under the dilute regular solution approximation, a simplified version of the phase-field model was obtained, which can be used for the phase transformation related with the stoichiometric phases. The results from the numerical calculation of the phase-field model was in good agreement with the exact analytic solution. The compositional shift due to Gibbs-Thomson effect can be reproduced within 0.5% error in the numerical calculation. The interface velocity, whereas, in numerical calculation of phase-field model appeared to be 15% larger than that from the analytic solution. This error is due to the shift of the interface position in phase-field model from the position with ${\phi}=0.5$.

• Bulletin of the Korean Chemical Society
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• 제14권1호
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• pp.63-71
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• 1993

By use of cluster orbitals, analytic solutions of finite face-centered cubic clusters are obtained. Taking interactions between up to the second nearest neighbors into account, the forms of all the elements of the Hamiltonian matrix are found explicitly within Huckel approximation. By adopting $D_{2k}$ point group to the cluster, the matrix is simplified. We assume that the cluster orbitals can mix together only when their state indices are indentical. It is then possible to calculate various physical properties of face-centered cubic metal clusters and example are shown for palladium clusters. The results show that density of states and projected density of states are similar, qualitatively, with those obtained by extended Huckel calculation.

• 대한수학회보
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• 제41권1호
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• pp.27-43
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• 2004

Let he(x) and $h_{o}(x)$ denote the limits of the sequences $\{^{2n}x\}\;and\;\{^{2n+1}x\}$, respectively. Asymptotic formulas for the functions E\$h_e\;and\;h_o$ at the points $e^{-e}$ and 0 are established.

• 대한수학회보
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• 제49권5호
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• pp.899-910
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• 2012

Let $\mathcal{H}$ be a complex separable infinite dimensional Hilbert space. In this paper, a necessary and sufficient condition is given for an operator T on $\mathcal{H}$ to satisfy that $f(T)$ obeys generalized Weyl's theorem for each function $f$ analytic on some neighborhood of ${\sigma}(T)$. Also we investigate the stability of generalized Weyl's theorem under (small) compact perturbations.

• 대한수학회논문집
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• 제28권3호
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• pp.615-633
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• 2013

We use a power series expansion method to get an analytic approximation value for the quanto option price under the Hull and White stochastic volatility model, which turns out to be accurate enough by comparing with the simulation prices using Monte Carlo method.

• 대한수학회지
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• 제38권2호
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• pp.321-336
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• 2001

A Feynman functional formulation is given for the Global Positioning System, GPS. Both the sequential and analytic Feynman functionals are presented for the classical, exterior, gravity problems which included rigid body rotations, special relativity and some general relativity corrections. A mathematically rigorous approach is introduced whose solutions exist, are unique and which depend continuously on the intial data. This formulation is convergent and has the finite approximation property. It is emphasized that all of the problems studied are classical (not quantum) evolution systems.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.230-237
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• 2020

In this part, an implicit time dependent solution is presented for the Boltzmann transport equation discretized by the analytic coarse mesh finite difference method (ACMFD) over the spatial domain as well as the simplified P₃ (SP₃) for the angular variable. In the first part of this work we proposed a SP₃-ACMFD approach to solve the static eigenvalue equations which provide the initial conditions for temp dependent equations. Having solved the 3D multi-group SP₃-ACMFD static equations, an implicit approach is resorted to ensure stability of time steps. An exponential behavior is assumed in transverse integrated equations to establish a relationship between flux moments and currents. Also, analytic integration is benefited for the time-dependent solution of precursor concentration equations. Finally, a multi-channel one-phase thermal hydraulic model is coupled to the proposed methodology. Transient equations are then solved at each step using the GMRES technique. To show the sufficiency of proposed transient SP₃-ACMFD approximation for a full core analysis, a comparison is made using transport peers as the reference. To further demonstrate superiority, results are compared with a 3D multi-group transient diffusion solver developed as a byproduct of this work. Outcomes confirm that the idea can be considered as an economic interim approach which is superior to the diffusion approximation, and comparable with transport in results.

• 한국진공학회지
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• 제6권2호
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• pp.109-113
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• 1997

MBE로 성장한 AlGaAs/GaAs multiple-quantum well(MQW)에 대하여 pump source를 He-Ne laser와 Ar laser를 사용하여 상온에서 PR(photoreflectance)측정을 수행한 결과 여러 subband transition peak을 관찰하였다. PR결과를 standard analytic line shape으 로 fitting하여n=1의 conduction band와 heavy hole 그리고 light hole transition peak인 Cl-Hl, Cl-Ll에 대한 energy값들을 얻었다. 또한 상온에서의 PL(photoluminescence)측정에 서 Cl-Hl, Cl-Ll과 관련된 main peak와 shoulder를 관찰하였다. 이 값은 PR측정값과 잘 일 치함으로써 PL에서의 main peak와 should가 Cl-Hl, Cl-Ll과 관련된 peak임을 확인할 수 있 었다. 또한 envelope function approximation(EFA)을 이용하여 구한 이론값과 PR과 PL에서 측정된 실험값들을 비교하였다.

• 한국융합학회논문지
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• 제12권12호
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• pp.59-64
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• 2021

본 논문에서는 기계적 결함에 따른 실제 진폭비와 명목상 진폭비의 차이를 정규분포를 갖는 랜덤변수로 모델링할 때, crosse-eye의 재밍 효과의 성능 분석을 다룬다. 수치 적분 기반 접근법을 사용하여 구한 mean square difference (MSD)를 제안한다. 수치 적분 기반 접근법을 사용하여 구한 MSD는 1차 테일러 근사 기반성능 분석 방법과 2차 테일러 근사 기반 해석적 성능 분석 방법을 이용하여 계산한 analytic 기반 MSD보다 근사하지 않은 Monte-Carlo 기반 Simulation MSD에 가깝다. 이는 수치 적분 기반 MSD가 정확성이 더 높은 것을 뜻한다. 계산비용이 큰 Monte-Carlo 기반 Simulation을 이용하지 않아도 수치적분을 통하여 MSD로 주어지는 진폭비 섭동이 성능 저하에 미치는 영향을 구할 수 있음을 보인다.