• Proceedings of the International Microelectronics And Packaging Society Conference
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• 1999.11a
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• pp.33-36
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• 1999

In this paper, we proposed a simultaneous switching noise(SSN) reduction technique in muti-layer beards(MLB) for high-speed digital applications and analyzed them using the Finite Difference Time Domain(FDTD) method. The new method by conductive dielectric substrates reduces SSN couplings and resonances, significantly, which cause series malfunctions in the modem high-speed digital applications.

• Computers and Concrete
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• v.2 no.3
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• pp.177-188
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• 2005

This paper presents a numerical model developed to evaluate the load-deflection and moment-curvature relationship for concrete beams strengthened externally with four different Fiber Reinforced Polymer (FRP) composite systems. The developed model considers the inelastic behavior of concrete section subjected to a combined axial force and bending moment. The model accounts for tensile strength of concrete as defined by the modulus of rupture of concrete. Based on the adopted material constitutive relations, the model evaluates the sectional curvature as a function of the applied axial load and bending moment. Deflections along the beam are evaluated using a finite difference technique taking into account support conditions. The developed numerical technique has been tested on a cantilever beam with a transverse load applied at its end. A study of the behavior of the beam with tension reinforcement compared to that with FRP areas giving an equivalent ultimate moment has been carried out. Moreover, cracking of the section in the tensile region at ultimate load has also been considered. The results indicated that beams reinforced with FRP systems possess more ductility than those reinforced with steel. This ductility, however, can be tuned by increasing the area of FRP or by combining different FRP layers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.776-787
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• 1998

This paper analyzes the local specific absorption rates (SAR's) averaged over 1 g and 10 g in a human head model in contact with a mobile phone operating at 835 MHz. The used numerical method is a total field finite-difference time-domain (FDTD) technique. The phone was simulated with a conducting box, a plastic case, and a whip antennal composed of a monopole and a helix. The discrete human model of the spatial resolution 3 mm is based on Magnetic Resonance Imaging (MRI), computerized tomography (CT) and anatomical images. The near field and far field and far field patterns were analyzed for extended and retracted phone. The two methods to take the volumes of the weights, 1 g or 10 g in tissue are proposed and compared to offer a reproductive technique for SAR estimations.

• Journal of applied mathematics & informatics
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• v.35 no.3_4
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• pp.277-302
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• 2017

In this paper, we have proposed a numerical method for Singularly Perturbed Boundary Value Problems (SPBVPs) of reaction-diffusion type of third order Ordinary Differential Equations (ODEs). The SPBVP is reduced into a weakly coupled system of one first order and one second order ODEs, one without the parameter and the other with the parameter ${\varepsilon}$ multiplying the highest derivative subject to suitable initial and boundary conditions, respectively. The numerical method combines boundary value technique, asymptotic expansion approximation, shooting method and finite difference scheme. The weakly coupled system is decoupled by replacing one of the unknowns by its zero-order asymptotic expansion. Finally the present numerical method is applied to the decoupled system. In order to get a numerical solution for the derivative of the solution, the domain is divided into three regions namely two inner regions and one outer region. The Shooting method is applied to two inner regions whereas for the outer region, standard finite difference (FD) scheme is applied. Necessary error estimates are derived for the method. Computational efficiency and accuracy are verified through numerical examples. The method is easy to implement and suitable for parallel computing. The main advantage of this method is that due to decoupling the system, the computation time is very much reduced.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.227-236
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• 1999

The finite difference time domain method (FDTD) is widely applied to the analysis of various microwave circuits. However, previous source modeling techniques have a lot of constraints and difficulties to apply for general geometries. Therefore, the internal resistive source modeling technique is suggested for efficiently analyzing various types of microwave circuit in this paper. Its efficiency is proved by comparing the computation time with that of hard source modeling. Accuracy is also verified by comparing the scattering parameters with those of previous source modeling methods and measurements for several microwave circuits.

• Journal of Ocean Engineering and Technology
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• v.2 no.2
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• pp.96-103
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• 1988

The stress distribution in the vicinity of the crack tip in the fracture mechanics is ordenarily indicated by the stress intensity factor. In the analysis of stress intensity factors, there are many theoretical and experimental methods. The stress analysis in photoelastic technique is usually made by using the difference of the principal stress of isochromatic fringe patterns. In this paper, the teflon molding technique is adopted to make a test specimen with a circular arc-crack, and that upgraded the accuracy of experiment. As the result, the experimental values of the stress intensity factors for the circular disk with a straight crack are coincided with the theoretical values. But, there is quite a difference between this expermental results on the finite plate for circular arc-crack and its theoretical values on the infinite one. Therefore, a boundary condition with regard to the loading condition on finite disk must be considered.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.11
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• pp.2773-2781
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• 1993

Laplace's equation is, perhaps, the most important equation, which governs various kinds of physical phenomena. Due to its importance, there have been several numerical techniques such as the finite element method, the finite difference method, and the boundary element method. However, these techniques do not appear very effective as they require a substantial amount of numerical calculation. In this paper, we develop a new most efficient technique based on analytic solutions for Laplace's equation in some convex polygons. Although a similar approach was used for the same problem, the present technique is unique as it solves directly Laplace's equation with the utilization of analytical solutions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1920-1929
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• 1994

The stochastic finite element method(SFEM) based structural optimal design is presented. Random system response including uncertainties for the design variable is calculated with first order perturbation method. A method for calculating the sensitivity coefficients is developed using the equilibrium equation and first-order perturbed equation. Numerical results are presented for a truss, frame and plate structures with displacement and stress constraints. The sensitivity calculation proposed here is compared with finite difference method. A nonlinear programming technique is used to solve the problem. The procedure is easily incorporated with existing deterministic structural optimization.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.7
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• pp.31-39
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• 2014

Recently, as Intelligent Transportation System (ITS) and self-driving system become influential in the ground transportation system, automotive radar systems have been actively studied among the various radar systems to implement the vehicle collision detection system and distance measurement system between vehicles. Most of the automotive radars are Frequency Modulated Continuous Wave (FMCW) radar type which can calculate distance and velocity of target by estimating the frequency difference between the transmitted signal and received signal. Therefore, accurate frequency estimation is very important in the FMCW radar system. For this reason, to improve the measurement accuracy of the FMCW radar, Reverse Directional FRI (RD-FRI) Super-Resolution technique which has high frequency estimation accuracy is applied to the FMCW radar system. The feasibility of the proposed technique is evaluated with simulation results and compared with FFT and conventional Super-Resolution techniques. The simulation results show that the proposed technique estimates the frequency with high accuracy and the distance with centimeter accuracy.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.12 no.4
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• pp.201-202
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• 2008

Because of the importance of suction or injection in the fields of aerodynamics, space science and many other industrial applications, our present study is motivated. The effect of natural convection on MHD flow past a vertical plate with suction or injection is studied. We have tried to solve the dimensionless governing equations by using finite difference scheme. To ensure the validity of our numerical solutions, we have compared our numerical solutions for temperature and velocity for the case of suction and injection for unit Prandtl number with the available exact solutions in the literature. The corresponding codes were written in Mathematica 5.0 for calculating numerical solutions for temperature and velocity and the comparison between the exact and numerical solutions. For the purpose of discussing the results some numerical calculations are carried out for non-dimensional temperature T, velocity u, skin friction ${\tau}$ and the Nusselt number $N_u$, by making use of it, the rate of heat transfer is studied.