• Publications of The Korean Astronomical Society
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• v.13 no.1 s.14
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• pp.167-180
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• 1998

We have carried out high precision orbit calculation, by using various numerical techniques with accuracy of higher than fourth order, in order for exact prediction on position and velocity of celestial bodies and artificial satellites. General second order ordinary differential equation has been solved numerically to test the performance for each of numerical methods. We have compared computed values with exact solution obtained by using universal variables for two body problem and discussed overall results of numerical methods used in our calculation. As a result, it is found that high order difference table method called as Gauss-Jackson method is best one with easiness and efficiency in the increase of accuracy by number of initial values.

• Journal of Korean Port Research
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• v.11 no.2
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• pp.257-271
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• 1997

The calculation of earthwork plays a major role in plan or design of many civil engineering projects and thus it has become very important to advanced the accuracy of earthwork calculation. The purpose of this paper is to calculate the excavation volume of terrain using a proposal area formular in eathwork volume determination for reclamation of the harbor. A proposal area formular by first and third equation is compared with end area, middle area, prismoidal formula by trapezoidal, simpson formular to excavation volume for an experimental terrian $1\sim12$. As a result of this study, algorithm of a proposal area formula by prismoidal formula should provide a better accuracy than end area, middle area, prismoidal formula by trapezoidal formular, simpson formular.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.30-43
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• 2021

In the 2D/1D method, a global adjoint CMFD based on the generalized equivalence theory is built to synthesize the 2D radial MOC adjoint and 1D axial NEM adjoint calculation and also to accelerate the iteration convergence of 3D whole-core adjoint transport calculation. Even more important, an advanced yet accurate two-level (TL) CMFD acceleration technique is proposed, in which an equivalent one-group adjoint CMFD is established to accelerate the multi-group adjoint CMFD and then to accelerate the 3D whole-core adjoint transport calculation efficiently. Based on these method, a new code is developed to perform 3D adjoint neutron flux calculation. Then a set of VERA and C5G7 benchmark problems are chosen to verify the capability of the 3D adjoint calculations and the effectiveness of TL CMFD acceleration. The numerical results demonstrate that acceptable accuracy of 2D/1D adjoint calculations and superior acceleration of TL CMFD are achievable.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1688-1695
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• 2008

Recently, it is common in a distribution system of Korea Electric Power Corporation (KEPCO) to find instances where distribution lines are parallel. A traditional method of an induced voltage calculation is not suitable for parallel distribution lines. For more actual analysis of induced voltage on telecommunication lines in parallel distribution lines, a new calculation method is needed. This paper presents a new calculation method of an induced voltage on telecommunication line using equivalent ${\pi}$ circuits matrix in parallel distribution lines. The advantages of the calculation method are using actual neutral current value and not using screening factor for considering the overhead ground wire and the neutral wire. To verify the effectiveness and the accuracy of the method, various case studies are performed with EMTP(Electro-Magnetic Transients Program).

• Journal of computational fluids engineering
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• v.9 no.1
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• pp.48-56
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• 2004

The numerical simulations with unstructured mesh by cell-centered and vertex-centered approaches were peformed for the quadrilateral and triangular meshes. For 2-D inviscid supersonic vortex flow, the simulation results and the analytic solution were compared and the accuracy was assessed. The calculation efficiency was measured by the parameter defined by the consumed CPU time multiplied by absolute error As a results, equilateral triangular mesh yielded the best accuracy and efficiency among the tested meshes. Cell-centered approach gives a little better efficiency than vertex - centered approach.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.5 no.1
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• pp.40-45
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• 2002

The calculation of earthwork plays a major role in the planning and design phases of many civil engineering projects, such as seashore reclamation; thus, improving the accuracy of earthwork calculation has become very important. In this paper, we propose an algorithm for finding a cubic spline surface with the free boundary conditions, which interpolates the given three-dimensional data, by using B-spline and an accurate method to estimate pit-excavation volume. The proposed method should be of interest to surveyors, especially those concerned with accuracy of volume computations. The mathematical models of the conventional methods have a common drawback: the modeling curves form peak points at the joints. To avoid this drawback, the cubic spline polynomial is chosen as the mathematical model of the new method. In this paper, we propose an algorithm of finding a spline surface, which interpolates the given data, and an appropriate method to calculate the earthwork. We present some computational results that show the proposed method, of the Maple program, provides better accuracy than the method presented by Chen and Lin.

• The Korean Journal of Applied Statistics
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• v.37 no.4
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• pp.445-453
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• 2024

For Markov processes whose stationary probabilities are difficult to obtain in the analytical form, approximate solutions can be considered using numerical methods such as a matrix operation method or an iterative calculation method. In this paper we perform the study to verify the accuracy of a numerical iteration formula which calculate the stationary probabilities of Markov chains or processes. Especially, the convergence and accuracy of the numerical method are investigated by using Markov models for system availability. We compare the values of the system availability based on the numerical calculation and those based on the complicated but analytical solutions. We also calculate the iteration numbers necessary for the convergence of the numerical solutions. The accuracy and usefulness of the numerical iterative calculation method can be ascertained through this study.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.19-29
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• 2022

The 2D/1D method has become the mainstream of the direct transport calculation considering the balance of accuracy and efficiency. However, the 2D/1D method still suffers from stability issues. Recently, a quasi-3D method has been proposed with axial Legendre expansion. Analysis and comparison of the 2D/1D and quasi-3D method is conducted in theory from the equation derivation. Besides, the C5G7 benchmark, the KUCA benchmark and the macro BEAVRS benchmark are calculated to verify the theory comparisons of these two methods with the direct transport code SHARK. All results show that the quasi-3D method has better stability and accuracy than the 2D/1D method with worse efficiency and memory cost. It provides a new option for direct transport calculation with the quasi-3D method.

• Progress in Medical Physics
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• v.32 no.1
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• pp.18-24
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• 2021

Purpose: Kilovoltage computed tomography (kV-CT) is essential for radiation treatment planning. However, kV-CT images are significantly distorted by artifacts when a metallic prosthesis is present in the patient's body. Thus, the accuracies of target delineation and treatment dose calculation are inevitably lowered. We evaluated the accuracy of the calculated doses using an image restoration method with hybrid CT, which was introduced in our previous study. Methods: A cylindrical phantom containing four metals, namely, silver, copper, tin, and tungsten, was scanned using kV-CT and megavoltage CT to produce hybrid CT images. We created six verification plans for three head and neck patients on kV-CT and hybrid CT images of the phantom and calculated their doses. The actual doses were measured with film patches during beam delivery using tomotherapy. We used the gamma evaluation method to compare dose distribution between kV-CT and hybrid CT with three gamma criteria, namely, 3%/3 mm, 2%/2 mm, and 1%/1 mm. Results: The gamma pass rates decreased as the gamma criteria were strengthened, and the pass rate of hybrid CT was higher than that of kV-CT in all cases. When the 1%/1 mm criterion was used, the difference in gamma pass rates between them was up to 13%p. Conclusions: According to our findings, we expect that the use of hybrid CT can be a suitable approach to avoid the effect of severe metal artifacts on the accuracy of dose calculation and contouring.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.506-510
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• 2012

This study suggested an improved algorithm of urban energy consumption estimation on the urban planning stage which concerns calculation accuracy. The results are as follows. (1) Urban energy consumption was estimated and managed per unit space using E-GIS DB which contains facility information per mesh. (2) Urban energy consumption was reflected by the urban facility classified and standardized by the characteristics of energy use. (3) Calculation accuracy of energy consumption was approached by separately suggested as summer algorithm reflecting urban heat island on summer energy use and winter algorithm reflecting heating system normally used in Korea.