• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.168-171
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• 2003

IEEE 802.16 Wireless MAN standard specifies the air interface of fixed point-to-multipoint broadband wireless access systems providing multiple services. Among the service classes supported by the wireless MAN, the best effort service class is ranked on the lowest position in priority and is assisted by a MAC scheme based on reservation ALOHL Such MAC scheme must include a number of components, while many of them are not specified in the standard. In this paper, we thus reveal main components of a MAC scheme supporting the best effort service and present candidate schemes implementing such components. Combining schemes for implementing components, we then construct distinctive MAC schemes supporting best effort service. In designing a MAC scheme, the delay performance induced by the scheme should be considered since scarce resource may be available for the best effort service after the preemptive resource occupation by other service classes. In this paper, we focus on the delay fairness among the subscriber stations using the best effort service. For evaluating a MAC scheme in delay fairness, we present two definitions of delay fairness and provide a criterion for optimal MAC scheme according to each definition of delay fairness. Using a simulation method we investigate the mean delay performance exhibited by each MAC scheme arid find an optimal scheme in delay fairness. From numerical examples, we observe that SR/ED/PG＋P scheme has strong delay fairness compared with MR/ED/PG＋P and SR/ED/PG＋D schemes according to a definition of delay fairness. However, other schemes are rather shown to have better delay fairness when the other definition is adopted.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.290-297
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• 2009

A two-phase (gas and liquid) flow analysis solver, named CUPID, has been developed for a realistic simulation of transient two-phase flows in light water nuclear reactor components. In the CUPID solver, a two-fluid three-field model is adopted and the governing equations are solved on unstructured grids for flow analyses in complicated geometries. For the numerical solution scheme, the semi-implicit method of the RELAP5 code, which has been proved to be very stable and accurate for most practical applications of nuclear thermal hydraulics, was used with some modifications for an application to unstructured non-staggered grids. This paper is concerned with the effects of interpolation schemes on the simulation of two-phase flows. In order to stabilize a numerical solution and assure a high numerical accuracy, the second-order upwind scheme is implemented into the CUPID code in the present paper. Some numerical tests have been performed with the implemented scheme and the comparison results between the second-order and first-order upwind schemes are introduced in the present paper. The comparison results among the two interpolation schemes and either the exact solutions or the mesh convergence studies showed the reduced numerical diffusion with the second order scheme.

• Communications of the Korean Mathematical Society
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• v.11 no.4
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• pp.1175-1185
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• 1996

We study the computation of sparse null bases of equilibrium matrices in the context of structural optimization and incompressible fluid flow. In our approach we emphasize the parallel computatin and examine the applications. New block decomposition and node ordering schemes are suggested, and numerical examples are considered.

• Journal of the Korean Mathematical Society
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• v.32 no.1
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• pp.115-139
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• 1995

Our purpose in this paper is to prove a new version of the nonlinear Chernoff theorem and to discuss the equivalence between resolvent consistency and converge nce for nonlinear algorithms acting on different Banach spaces. Such results are useful in the numerical treatment of partial differential equations via difference schemes.

• Korean Journal of Hydrosciences
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• v.1
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• pp.15-25
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• 1990

Spatially varied unsteady flow in a groave-like channel of a sloping roof is analyzed by numerical solution of Saint Venant equations. Depth variations are discussed with different slopes and bed roughness of the channel. Time to equilibrium is found to be inversely proportional to the kinematic flow number. The design of roof drainage system by different schemes is included.

• Water for future
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• v.28 no.4
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• pp.125-136
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• 1995

ELM, a characteristic line based method, was applied to advection-dispersion equation, and the results obtained were compared with those of Eulerian schemes(Stone-Brian and QUICKEST). The calculation methods consisted of Lagrangian interpolation scheme and cubic spline interpolation scheme for the advection calculation, and the Crank-Nicholson scheme for the dispersion calculation. The results of numerical methods were as follows: (1) for Gaussian hill: ELM, using Lagrangian interpolation scheme, gave the most accurate computational result, ELM, using cubic spline interpolation scheme, and QUICKEST scheme gave numerical damping for Peclet number 50. Stone-Brian scheme gave phase shift introduced in the numerical solution for Peclet number 10 and 50. (2) for advanced front: All schemes gave accurate computational results for Peclet number 1 and 4. ELM, Lagrangian interpolation scheme, and Stone,Brian scheme gave dissipation error and ELM, using cubic spline interpolation scheme, and QUICKEST scheme gave numerical oscillation for Peclet number 50.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.529-531
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• 2009

To construct the wind map for mainland Korea, the well designed atmospheric numerical modeling system was used. Three nest domains were construced with spatial resolutions between $10{\times}10km$ up to the hightest resolution of $1{\times}1km$. Parameterization schemes like MRF(PBL), RRTM(radiation), Grell(cumulus) were chosen since wind data simulated is in better agreement with the observed wind data. High-resolution atmospheric numerical model was applied to simulate the motion of the atmosphere and to produce the wind map around the South Korea. The results of several simulations were improved compare to the past system, because of using the fine geographical data, such as terrain height and land-use data, and the meteorological data assimilation.

• Journal of applied mathematics & informatics
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• v.22 no.1_2
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• pp.49-65
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• 2006

A robust numerical method for a singularly perturbed second-order ordinary differential equation having two parameters with a discontinuous source term is presented in this article. Theoretical bounds are derived for the derivatives of the solution and its smooth and singular components. An appropriate piecewise uniform mesh is constructed, and classical upwind finite difference schemes are used on this mesh to obtain the discrete system of equations. Parameter-uniform error bounds for the numerical approximations are established. Numerical results are provided to illustrate the convergence of the numerical approximations.

• Computers and Concrete
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• v.25 no.5
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• pp.461-470
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• 2020

This paper presents a numerical study on structural behavior of hammer head pier cap beams, extended on verges and reinforced with carbon fiber reinforced polymer (CFRP) plates. A 3-D finite element (FE) model along with a simplified analytical model are presented. Concrete damage plasticity (CDP) was adapted in the FE model and an analytical approach predicting the CFRP anchor strength was adapted in both FE and analytical model. Total five quarter-scaled pier cap beams with various CFRP reinforcing schemes were experimentally tested and analyzed with numerical approaches. Comparison between experimental results, FE results, analytical results and current ACI guideline predictions was presented. The FE results showed good agreement with experimental results in terms of failure mode, ultimate capacity, load-displacement response and strain distribution. In addition, the proposed strut-and-tie based analytical model provides the most accurate prediction of ultimate strength of extended cap beams among the three numerical approaches.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.12 no.1
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• pp.41-53
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• 2008

Polynomials are one of most important and widely used numerical tools in dealing with a smooth function on a bounded domain and trigonometric functions work for smooth periodic functions. However, they are not the best choice if a function has a bounded support in space and in frequency domain. The Prolate Spheroidal wave function (PSWF) of order zero has been known as a best candidate as a basis for band-limited functions. In this paper, we review some basic properties of PSWFs defined as eigenfunctions of bounded Fourier transformation. We also propose numerical inversion schemes based on PSWF and present some numerical examples to show their feasibilities as signal processing tools.