• Journal of the Korean Society of Safety
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• v.10 no.3
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• pp.3-10
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• 1995

For most engineering materials are influenced by the dominant mechanism resisting crack extention under large scale yielding conditions. Continuum mechanics analysis shows that fracture toughness, in addition to depending on young's modulus, flow stress strain hardening exponent, and yield strain, should be nearly proportoinal to the effective fracture ductility obtained for the stress state characteristic for region ahead of the crack; plane stress or plane strain. It's known that, in most ductile materials, crack propagation of the material strongly governed by the $J_{IC}$ value, which is still difficult to determine for it's complicate and treble-some determinative process. This paper, on the assumption that, initiation of crack tip strain field reaches on the relationships between the critical value of J-integral ($J_{IC}$) and the local fracture strain(${\varepsilon}_c$) in uniaxial tensile test in the region of maximun reduction areas was described.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.180-182
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• 1993

A distance protection algorithm for detecting faults at power transmission lines is presented in this paper. The algorithm is based on the differential equation related to the voltage and the current at an equivalent circuit of a transmission line which is composed of the lumped resistance and inductance. The presented integration method has high performance at though the fault voltage and the current are heavily distorted with the DC offset and harmonics which occurred at transient states after faults.

• Journal of the Korean Society of Combustion
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• v.1 no.2
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• pp.51-58
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• 1996

The coherent flamelet model(CFM) is applied to symmetric counterflow turbulent premixed flames. The flame source term is set proportional to the turbulence intensity to reproduce the experimental correlation of Abdel-Gayed et al. for the turbulent burning velocity. Flame quenching by the turbulent rate of strain is modeled by an additional multiplication factor to the flame source term. A modified form of CFM is employed to consider coexistence of burned and unburned premixture with ambient air. The predicted flame position and turbulent flow field coincide well with the experimental data of Kostiuk et al., although there is some discrepancy in the radial rms velocity component and integral length scale near the symmetric plane.

• Journal of the Korean Society of Safety
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• v.11 no.1
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• pp.11-15
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• 1996

For the assessment of fracture behaviors of structural components, various fracture mechanics parameters have been applied to date. New approaches to analyze structural fracture performance under elastic-plastic condition have been proposed by the development of testing methods for characterization of material behavior which is defying to the analysis by conventional fracture parameters. In this study, on the assumption that, initiation of crack propagation of a piping materials occurs when the crack tip strain field reaches "the local fracture strain", following two major issues are discussed ; 1) The relationship between the critical value of J-integral($J_{IC}$) and the local fracture strain (${\varepsilon}_c$) in uniaxial tensile test in the region of maximum reduction area was described. 2) To proved the validity of above relations a series of tests were performed under various temperature and on the different piping materials.materials.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.739-741
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• 1993

This paper deals with the Improvement of inverter output waveform with space vector modulation using the DSP-chip. The proposed scheme can be considered as a alternative of the conventional, subharmonic method. This scheme features a maximum output voltage that is 15% greater. The number of switchings is also 30% less than the one obtained by subharmonic modulation method(SHM) A performance function(PF) which is the time integral function of the inverter output voltage is introduced in this paper. An optimal PWM pattern is obtained by minimizing the distortion factor of performance function. The experiment was carried out with an TMS320C25.

• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1226-1233
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• 2017

Measurements of the isotopic contents of spent nuclear fuel provide experimental data that are a prerequisite for validating computer codes and nuclear data for many spent fuel applications. Under the auspices of the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) and guidance of the Expert Group on Assay Data of Spent Nuclear Fuel of the NEA Working Party on Nuclear Criticality Safety, a new database of expanded spent fuel isotopic compositions has been compiled. The database, Spent Fuel Compositions (SFCOMPO) 2.0, includes measured data for more than 750 fuel samples acquired from 44 different reactors and representing eight different reactor technologies. Measurements for more than 90 isotopes are included. This new database provides data essential for establishing the reliability of code systems for inventory predictions, but it also has broader potential application to nuclear data evaluation. The database, together with adjoint based sensitivity and uncertainty tools for transmutation systems developed to quantify the importance of nuclear data on nuclide concentrations, are described.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.24 no.3
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• pp.293-303
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• 2020

The present work aims to analyzed the transient thermoelastic stress analysis of a thin circular plate with uniform internal heat generation. Initially, the plate is characterized by a parabolic temperature distribution along the z-direction given by T = T₀(r, z) and perfectly insulated at the ends z = 0 and z = h. For times t > 0, the surface r = a is subjected to convection heat transfer with convection coefficient h_c and fluid temperature T_∞. The integral transform method used to obtain the analytical solution for temperature, displacement, and thermal stresses. The associated thermoelastic field is analyzed by making use of the temperature and thermoelastic displacement potential function. Numerical results are carried out with the help of computational software PTC Mathcad Prime-3.1 and shown in figures.

• Communications of the Korean Mathematical Society
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• v.31 no.4
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• pp.869-878
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• 2016

This paper presents an ecient fractional shifted Legendre polynomial method to solve the fractional Volterra's model for population growth model. The fractional derivatives are described based on the Caputo sense by using Riemann-Liouville fractional integral operator. The theoretical analysis, such as convergence analysis and error bound for the proposed technique has been demonstrated. In applications, the reliability of the technique is demonstrated by the error function based on the accuracy of the approximate solution. The numerical applications have provided the eciency of the method with dierent coecients of the population growth model. Finally, the obtained results reveal that the proposed technique is very convenient and quite accurate to such considered problems.

• Bulletin of the Korean Chemical Society
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• v.15 no.1
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• pp.45-52
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• 1994

We present a theoretical study of the non-symmetrical A/BC polymeric system. The polymer blends consist of two phases, a pure polymeric phase A on one side and a mixture of polymers B as a compatibilizer and C on the other. The adsorption of homopolymer B to the interface improves the interfacial adhesion between two phases. By employing the functional integral techniques, we derive the mean-field equations and solve them numerically to obtain the interfacial properties including the concentration profiles in the limit of infinite molecular weight for the polymers. Thecalculations of the interfacial properties are performed for typical values of the Flory X parameters and the volume fraction of polymer B in the asymptotic mixture phase. The interfacial adsorption of polymer B and the degrees of the specific interaction between the polymers play an important role in modification of the interfacial properties.

• Journal of applied mathematics & informatics
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• v.39 no.5_6
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• pp.617-622
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• 2021

Let R be a commutative ring with identity, R[X] the polynomial ring over R and S a multiplicative subset of R. Let U = {f ∈ R[X] | f is monic} and let N = {f ∈ R[X] | c(f) = R}. In this paper, we show that if S is an anti-Archimedean subset of R, then R is an S-Noetherian ring if and only if R[X]_U is an S-Noetherian ring, if and only if R[X]_N is an S-Noetherian ring. We also prove that if R is an integral domain and R[X]_U is an S-principal ideal domain, then R is an S-principal ideal domain.