• Kyungpook Mathematical Journal
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• v.61 no.2
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• pp.383-393
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• 2021

In this paper, numerical techniques are presented for solving initial value problems of fractional differential equations with variable coefficients. The method is derived by applying a Taylor vector approximation. Moreover, the operational matrix of fractional integration of a Taylor vector is provided in order to transform the continuous equations into a system of algebraic equations. Furthermore, numerical examples demonstrate that this method is applicable and accurate.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.77-83
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• 1994

In this paper we numerically approximated the field-effect mobility of a-Si:H TFT. Field-effect mobility, based on the charge-trapping model and new effective capacitance model in our study, used Chebyshev approximation was approximated as the function of gate potential(gate-to-channel voltage). Even though various external factors are changed, this formula can be applied by choosing the characteristic coefficients without any change of the approximation formula corresponding to each operation region. Using new approximated field-effect mobility formula, the dependences of field-effect mobility on materials and thickness of gate insulator, thickness of a-Si bulk, and operation temperature in inverted staggered-electrode a-Si:H TFT were estimated. By this was the usefulness of new approximated mobility formula proved.

• Journal of the Korean Mathematical Society
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• v.51 no.2
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• pp.267-288
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• 2014

We propose and analyze two-scale product approximation for semilinear heat equations in the mixed finite element method. In order to efficiently resolve nonlinear algebraic equations resulting from the mixed method for semilinear parabolic problems, we treat the nonlinear terms using some interpolation operator and exploit a two-scale grid algorithm. With this scheme, the nonlinear problem is reduced to a linear problem on a fine scale mesh without losing overall accuracy of the final system. We derive optimal order $L^{\infty}((0, T];L^2({\Omega}))$-error estimates for the relevant variables. Numerical results are presented to support the theory developed in this paper.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.91-107
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• 2009

In order to compute linear wave transformation over a single step bottom, both variational approximation and eigenfunction expansion method are used. Both numerical results are in good agreement for reflection and transmission coefficients, surface displacement respectively. However x velocity profiles at the boundary of step are seen to be different to each other even though x velocity matching condition is used.

• International Journal of Reliability and Applications
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• v.8 no.1
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• pp.1-16
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• 2007

In this paper, we derive exact explicit expressions for the triple and quadruple moments of the lower record values from inverse the Weibull (IW) distribution. Next, we present and calculate the coefficients of the best linear unbiased estimates of the location and scale parameters of IW distribution (BLUEs) for different choices of the shape parameter and records size. We then use the higher order moments and the calculated BLUEs to compute the mean, variance, and the coefficients of skewness and kurtosis of certain linear functions of lower record values. By using the coefficients of the skewness and kurtosis, we develop approximate confidence intervals for the location and scale parameters of the IW distribution using Edgeworth approximate values and then compare them with the corresponding intervals constructed through Monte Carlo simulations. Finally, we apply the findings of the paper to some simulated data.

• Journal of the Korean Mathematical Society
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• v.33 no.4
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• pp.955-982
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• 1996

In surface compression applications, one of the main issues is how to efficiently store and calculate the computer representation of certain surfaces. This leads us to consider a nonlinear approximation by box splines with free knots since, for instance, the nonlinear method based on wavelet decomposition gives efficient compression and recovery algorithms for such surfaces (cf. [12]).

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.685-692
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• 1995

The electron transport coefficients in argon gas is studied over the range of E/N values from 85 to 566 Td by the Monte Carlo method considering the latest cross section data. The result of the Monte Carlo method analysis shows that the value of the electron transport coefficients such as the electron drift velocity, the ratio of the longitudinal and transverse diffusion coefficients to the mobility. It is also found that the electron transport coefficients calculated by the two-term approximation analysis agree well with those by Monte Carlo calculation. The electron energy distributions function were analysed in argon at E/N=283, and 566 Td for a case of the equilibrium region in the mean electron energy. A momentum transfer cross section for the argon atom which was consistent with both of the present electron transport coefficients was derived over the range of mean electron energy from 10.3 to 14.5 eV, also suggested as a set of electron cross section for argon atom. The validity of the results obtained has been confirmed by a Monte Carlo simulation method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.525-529
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• 1996

Decision environments involve a high degree of uncertainty as well as multiple, conflicting goals. Although traditional goal programming offers a means of considering multiple, conflicting goals and arrives at a satisficing solution in a deterministic manner, its major drawback is that decision makers often specify aspiration level of each goal as a single number. To overcome the problem of setting aspiration levels, chance constrained programming can be incorporated into goal programming formulation so that sampling information can be utilized to describe uncertainty distribution. Another drawback of goal programming is that it does not provide a systematic approach to set priorities and trade-offs among conflicting goals. To overcome this weekness, the analytic hierarchy process(AHP) is used in the model. Also, most goal programming models in the literature are of a linear form, although some nonlinear models have been presented. Consideration of risk in technological coefficients and right hand sides, however, leads to nonlinear goal programming models, which require a linear approximation to be solved. In this paper, chance constrained reformulation with linear approximation is presented for a 0-1 goal programming problem whose technological coefficients and right hand sides are stochastic. The model is presented with a numerical example for the purpose of demonstration.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.43-51
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• 2001

The unsteady problems of ships in waves are analyzed by a low order panel method with Rankine source. Considering the basic flow as the uniform incoming flow(so called Kelvin flow) and also the double body flow. the solutions to satisfy the governing equation with the boundary conditions are obtained, and these two results are compared. The hydrodynamic coefficients for the modified Wigley hull and Series 60($C_B=0.7$) are computed and compared with the experimental data available and also other computational results published. It is shown that the computational results by the double body approximation agree well with the experimental results compared with those by the uniform Kelvin flow approximation.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.40-46
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• 2014

We introduce a parameter estimation algorithm by using pole-zero coefficients of Pade approximation for radar active cancellation. Proposed scheme is based on relation among pole-zero coefficients of Pade approximation, parameters, and samples of received signal. A closed form solution for parameter estimation is achieved with a few samples of received signal and a simple comparison. Also, stepwise estimation algorithm is proposed to suppress beat effect which is occurred by active cancellation over long time with imperfectly estimated parameters. Simulation results show that proposed scheme performs faster radar active cancellation with lower computational complexity than the conventional schemes.