• Water Engineering Research
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• v.1 no.1
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• pp.63-74
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• 2000

This paper presents a two- phase search scheme for optimal pipe expansion of expansion of existing water distribution systems. In pipe network problems, link flows affect the total cost of the system because the link flows are not uniquely determined for various pipe diameters. The two-phase search scheme based on stochastic optimization scheme is suggested to determine the optimal link flows which make the optimal design of existing pipe network. A sample pipe network is employed to test the proposed method. Once the best tree network is obtained, the link flows are perturbed to find a near global optimum over the whole feasible region. It should be noted that in the perturbation stage the loop flows obtained form the sample existing network are employed as the initial loop flows of the proposed method. It has been also found that the relationship of cost-hydraulic gradient for pipe expansion of existing network affects the total cost of the sample network. The results show that the proposed method can yield a lower cost design than the conventional design method and that the proposed method can be efficiently used to design the pipe expansion of existing water distribution systems.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.93-98
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• 2020

Effective control of the heat generated from electronics and semiconductor devices requires a high thermal conductivity and a low thermal expansion coefficient appropriate for devices or modules. A method of reducing the thermal expansion coefficient of Cu has been suggested wherein a ceramic filler having a low thermal expansion coefficient is applied to Cu, which has high thermal conductivity. In this study, using pressureless sintering rather than costly pressure sintering, a polymer solution synthesis method was used to make nano-sized Cu powder for application to Cu matrix with an AlN filler. Due to the low sinterability, the sintered Cu prepared from commercial Cu powder included large pores inside the sintered bodies. A sintered Cu body with Zn, as a liquid phase sintering agent, was prepared by the polymer solution synthesis method for exclusion of pores, which affect thermal conductivity and thermal expansion. The pressureless sintered Cu bodies including Zn showed higher thermal conductivity (180 W/m·K) and lower thermal expansion coefficient (15.8×10^-6/℃) than did the monolithic synthesized Cu sintered body.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.50-56
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• 2021

An accurate evaluation of three-dimensional (3D) Time-Domain Green Function (TDGF) in infinite water depth is essential for ship's hydrodynamic analysis. Various numerical algorithms based on the TDGF properties are considered, including the ascending series expansion at small time parameter, the asymptotic expansion at large time parameter and the Taylor series expansion combines with ordinary differential equation for the time domain analysis. An efficient method (referred as "Present Method") for a better accuracy evaluation of TDGF has been proposed. The numerical results generated from precise integration method and analytical solution of Shan et al. (2019) revealed that the "Present method" provides a better solution in the computational domain. The comparison of the heave hydrodynamic coefficients in solving the radiation problem of a hemisphere at zero speed between the "Present method" and the analytical solutions proposed by Hulme (1982) showed that the difference of result is small, less than 3%.

• Journal of applied mathematics & informatics
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• v.28 no.5_6
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• pp.1431-1437
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• 2010

We use the (G'/G)-expansion method to seek the traveling wave solution of the Seventh-order Sawada-Kotera Equation. The solutions that we get are more general than the solutions given in literature. It is shown that the (G'/G)-expansion method provides a very effective and powerful mathematical tool for solving nonlinear equations in mathematical physics.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.412-416
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• 2003

This paper introduces a new joint signed expansion method for computing simultaneous scalar multiplication on an elliptic curve and a modified binary algorithm for efficient use of the new expansion method. The proposed expansion method can be also be used in cryptosystems such as RSA and EIGamal cryptosystems.

• Journal of the Chungcheong Mathematical Society
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• v.24 no.2
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• pp.359-370
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• 2011

In this work, we obtain new solitary wave solutions for some nonlinear partial differential equations. The Jacobi elliptic function rational expansion method is used to establish new solitary wave solutions for the combined KdV-mKdV and Klein-Gordon equations. The results reveal that Jacobi elliptic function rational expansion method is very effective and powerful tool for solving nonlinear evolution equations arising in mathematical physics.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.2
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• pp.97-101
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• 2013

Bit-depth expansion is a process of enhancing the image quality by increasing the number of intensity levels. To solve this problem, a hybrid method is proposed, where the pixels are categorized into smooth and complex regions, and are processed using different methods. The pixels in the smooth region are reconstructed with a smooth prior, and a Bayesian estimator is used for the pixels in the complex region. The proposed method effectively removes the false contour artifacts while requiring less computation than conventional methods. In addition, the method shows good quantitative performance, and the PSNR gains over the best existing method are 1.45 dB and 0.26 dB for 4 bits and 3 bits expansion cases, respectively.

• Honam Mathematical Journal
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• v.33 no.2
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• pp.247-259
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• 2011

In this paper, the $(\frac{G'}{G})$-expansion method is used to construct new exact travelling wave solutions of some nonlinear evolution equations. The travelling wave solutions in general form are expressed by the hyperbolic functions, the trigonometric functions and the rational functions, as a result many previously known solitary waves are recovered as special cases. The $(\frac{G'}{G})$-expansion method is direct, concise, and effective, and can be applied to man other nonlinear evolution equations arising in mathematical physics.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.772-784
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• 2024

The hexagonal nodal code RENUS has been enhanced to handle irregularly deformed hexagonal assemblies. The underlying RENUS methods involving triangle-based polynomial expansion nodal (T-PEN) and corner point balance (CPB) were extended in a way to use line and surface integrals of polynomials in a deformed hexagonal geometry. The nodal calculation is accelerated by the coarse mesh finite difference (CMFD) formulation extended to unstructured geometry. The accuracy of the unstructured nodal solution was evaluated for a group of 2D SFR core problems in which the assembly corner points are arbitrarily displaced. The RENUS results for the change in nuclear characteristics resulting from fuel deformation were compared with those of the reference McCARD Monte Carlo code. It turned out that the two solutions agree within 18 pcm in reactivity change and 0.46% in assembly power distribution change. These results demonstrate that the proposed unstructured nodal method can accurately model heterogeneous thermal expansion in hexagonal fueled cores.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1413-1421
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• 1997

A new control method to alleviate the impulsive noise at the exit of high-speed railway tunnel was applied to the compression wave at the entrance of the tunnel. This method uses the interaction phenomenon of unsteady expansion wave and unsteady compression wave. Unsteady expansion wave was assumed to be made instantaneously by the simple theory of shock tube. Total Variation Diminishing method was employed to solve the axisymmetric unsteady compressible flow field with a specified compression wave. Numerical results show that the maximum pressure gradient of the propagating compression wave decreases with increase of the wave length of the unsteady expansion wave. It is found that the impulsive noise reduction can be obtained when the unsteady expansion wave with a large wave length is emitted just before the train enters the tunnel. The present results give the possibility to reduce the impulsive noise at the exit of tunnel.