• Structural Engineering and Mechanics
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• v.59 no.5
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• pp.901-920
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• 2016

MeshFree methods have become popular owing to the ease with which high stress gradients can be identified and node density distribution can be reformulated to accomplish faster convergence. This paper presents a strategy for nodal density refinement with strain energy as basis in Element-Free Galerkin MeshFree technique. Two popular flat plate problems are considered for the demonstration of the proposed strategies. Issue of integration errors introduced during nodal density refinement have been addressed by suggesting integration cell refinement. High stress effects around two symmetrical semi-circular notches under in-plane axial load have been addressed in the first problem. The second considers crack propagation under mode I and mode II fracture loading by the way of introducing high stress intensity through line crack. The computational efficacy of the adaptive refinement strategies proposed has been highlighted.

• Structural Engineering and Mechanics
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• v.85 no.1
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• pp.135-145
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• 2023

This study presents the free vibrational responses of bi-directional axially graded cylindrical shell panels using 3D graded finite element approximation under a temperature field. The cylindrical shell panel is graded in two directions and made of metal-ceramic materials. To extract material properties, the Voigt model is combined with a Power-law material distribution. Convergence and validation studies are performed on the developed computational model to ensure its accuracy and effectiveness. Furthermore, a parametric study is performed to evaluate the developed model, which demonstrates that geometrical parameters, imperfect materials (porosity), support conditions, and surface temperature all have a significant impact on the free vibration responses of a bi-directional axially graded cylindrical shell panel in a thermal environment.

• Journal of Mechanical Science and Technology
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• v.17 no.10
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• pp.1458-1465
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• 2003

An eigenvalue analysis of the circular Mindlin plates with free boundary conditions is presented. The analysis is based on the Chebyshev-Fourier pseudospectral method. Even though the eigenvalues of lower vibration modes tend to convergence more slowly than those of higher vibration modes, the eigenvalues converge for sufficiently fine pseudospectral grid resolutions. The eigenvalues of the axisymmetric modes are computed separately. Numerical results are provided for different grid resolutions and for different thickness-to-radius ratios.

• Journal of applied mathematics & informatics
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• v.16 no.1_2
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• pp.165-181
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• 2004

Based on Landau-type transformation, a Stefan problem with non-linear free boundary condition is transformed into a system consisting of parabolic equation and the ordinary differential equations. Semidiscrete approximations are constructed. Optimal orders of convergence of semidiscrete approximation in $L_2$, $H^1$ and $H^2$ normed spaces are derived.

• Journal of the Korea Convergence Society
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• v.11 no.5
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• pp.209-217
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• 2020

The background of the research is the following. With the prosperity of drone industry, the government has been actively promoting measures to nominate 'drone photographing free areas'. However, existing laws, and procedures are rather unclear with related environmental factors in discordance with one another. Hence, voices in need for establishing a clear precondition for nominating drone photography free area have been rising. The purpose of the research is to provide measures for the preconditions to establish photography free areas for convenient drone photographing. The research utilizes literary methods, conducting focus group interviews to coordinate with specialists who can participate and discuss so that they can provide improvement measures. The research renders improvement measures in different sectors including 2x items in aviation security law, 8x items in free area nomination and procedure, 4x items in infrastructure establishment and information management area. The expected effects are the following: by attaching drone photography with aviation security law, nominating photography free area can be linked up with the Ministry of Land Infrastructure and Technology. Secondly, by enlarging photography restricted area to upper mid-air, a three dimensional drone security will be possible. Thirdly, by providing a 'Yongin area standard model', free area nomination will become more easy. Future research will focus on enhancing aviation security law regarding drone photographing. In addition, the promotion to nominate free areas for 33x responsible areas in accordance with the National Intelligence service will be required.

• Communications of the Korean Mathematical Society
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• v.12 no.2
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• pp.467-478
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• 1997

A nonlinear Galerkin method for the Burgers equation is considered. Due to the lack of the divergence free condition, the nonlinear term is treated differently compared to that of the Navier-Stokes equations. Strong convergence results are proved for the nonlinear Galerkin method.

• ETRI Journal
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• v.29 no.6
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• pp.835-837
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• 2007

A multi-bit sigma-delta modulator architecture is described for low-distortion performance and a high-speed operation. The proposed architecture uses both a delayed code and a delayed differential code of analog-to-digital converter in the feedback path, thereby suppressing signal components in the integrators and relaxing the timing requirement of the analog-to-digital converter and the scrambler logic. Implemented by a 0.13 ${\mu}m$ CMOS process, the sigma-delta modulator achieves high linearity. The measured spurious-free dynamic range is 89.1 dB for -6 dBFS input signal.

• Bulletin of the Korean Mathematical Society
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• v.55 no.4
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• pp.1241-1261
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• 2018

We derive discrete time model of the geometric fractional Brownian motion. It provides numerical pricing scheme of financial derivatives when the market is driven by geometric fractional Brownian motion. With the convergence analysis, we guarantee the convergence of Monte Carlo simulations. The strong convergence rate of our scheme has order H which is Hurst parameter. To obtain our model we need to convert Wick product term of stochastic differential equation into Wick free discrete equation through Malliavin calculus but ours does not include Malliavin derivative term. Finally, we include several numerical experiments for the option pricing.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.230-232
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• 2005

This paper proposes a Distributed Transaction models based on the multimedia framework (MPEG-21) in digital convergence environment. Digital media market is growing up rapidly according to the extension of internet and universality of multimedia contents. So, importance of the effective management with the production and distribution of produced multimedia contents is becoming larger. For effective management of multimedia contents, the multimedia contents which are represented with different standard each other can be processed adaptively in the variable network environment. A free compatibility among the different terminals and standards are the essential particular should be offered for the digital convergence environment. A multimedia framework supports this compatibility and various multimedia services. In this paper, the Distributed Transaction models that multimedia contents can be circulated among the individual users safely and freely are proposed and the relation technologies are described.

• IEMEK Journal of Embedded Systems and Applications
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• v.16 no.6
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• pp.307-312
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• 2021

This paper proposes an adaptive time-delayed control approach with the integral sliding-mode surface for the fast convergence rate of robot manipulators. Adaptive switching gain aims to guarantee the system stability in such a way as to suppress time-delayed estimation error in the proposed control approach. Moreover, it makes an effort to increase the convergence ability in reaching the phase. An integral sliding-mode surface is employed to achieve a fast convergence rate in the sliding phase. The stability of the proposed one is proved to be asymptotically stable in the Lyapunov stability. The efficiency of the proposed control approach is illustrated with a tutorial example in robot manipulator, which is compared to that of the existing control approach.