• Journal of the Korean Mathematical Society
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• v.36 no.2
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• pp.355-367
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• 1999

We prove the existence of 2N-1 distinct ordered positive solutions of a class of semilinear elliptic Dirichlet boundary value problems on Rn when the forcing term has N distinct positive stable zeros and the coefficient function decaying to the zero at infinity.

• Journal of Biomedical Engineering Research
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• v.11 no.1
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• pp.179-186
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• 1990

A numerical analysis of crutch walking cycle has been performed to determine the transmissibility of a single-degree-of-freedom crutch system when a non-harmonic periodic forcing function is acting on the spring-damping-mass system. The results indicate that the damping factor which can reduce the forces transmitted to the human body plays an important role. In crutch walking, the stride angle of dynamic crutches must be limited for the comfortable walking.

• Journal of the Korea Fashion and Costume Design Association
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• v.14 no.1
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• pp.151-160
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• 2012

The Purpose of this study is to examine the inner symbolic meaning of the revenge movies, forcing on , , by producer Chan-Wook Park. This study was analyzed with theoretical frames of Greimas's and Lacan's desire theory. The results of this study is as follows: Main characters of these films were tangled each their with love, desire, angry, hate and revenge. They also had desires and needs of revenge caused by deficiency. These films represented blue as sorrow, depression, frigidness, loneliness and deficiency, red as love, desire, angry, hate and revenge, black as strong will, till-eat, death, violence and bloody-mindedness and white as forgiveness, expiation and salvation. The function of colors in conveying meaning was very effected to analyzing the visual power implications and psychological effects on human feelings that colors have in the movie.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.6
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• pp.619-627
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• 2004

In most industrial applications, the geometrical complexity is combined with the moving boundaries. These problems considerably increase the computational difficulties since they require, respectively, regeneration and deformation of the grid. As a result, engineering flow simulation is restricted. In order to solve this kind of problems the immersed boundary method was developed. In this study, the immersed boundary method is applied to the numerical simulation of stationary, rotating and oscillating cylinders in the 2-dimensional square cavity. No-slip velocity boundary conditions are given by imposing feedback forcing term to the momentum equation. Besides, this technique is used with a second-order accurate interpolation scheme in order to improve the accuracy of flow near the immersed boundaries. The governing equations for the mass and momentum using the immersed boundary method are discretized on the non-staggered grid by using the finite volume method. The results agree well with previous numerical and experimental results. This study presents the possibility of the immersed boundary method to apply to the complex flow experienced in the industrial applications. The usefulness of this method will be confirmed when we solve the complex geometries and moving bodies.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.916-921
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• 2003

In most industrial applications, the geometrical complexity is combined with the moving boundaries. These problems considerably increase the computational difficulties since they require, respectively, regeneration and deformation of the grid. As a result, engineering flow simulation is restricted. In order to solve this kind of problems the immersed boundary method was developed. In this study, the immersed boundary method is applied to the numerical simulation of stationary, rotating and oscillating cylinders in the 2-dimensional square cavity. No-slip velocity boundary conditions are given by imposing feedback forcing term to the momentum equation. Besides, this technique is used with a second-order accurate interpolation scheme in order to improve the accuracy of flow near the immersed boundaries. The governing equations for the mass and momentum using the immersed boundary method are discretized on the non-staggered grid by using the finite volume method(FVM). This study presents the possibility of the immersed boundary method to apply to the complex flow experienced in the industrial applications.

• Smart Structures and Systems
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• v.26 no.6
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• pp.681-692
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• 2020

Conventional Piezoelectric Energy Harvesters (CPEH) have been extensively studied for maximizing their electrical output through material selection, geometric and structural optimization, and adoption of efficient interface circuits. In this paper, the performance of Stepped Piezoelectric Energy Harvester (SPEH) under harmonic base excitation is studied analytically, numerically and experimentally. The motivation is to compare the energy harvesting performance of CPEH and SPEHs with the same characteristics (resonant frequency). The results of this study challenge the notion of achieving higher voltage and power output through incorporation of geometric discontinuities such as step sections in the harvester beams. A CPEH consists of substrate material with a patch of piezoelectric material bonded over it and a tip mass at the free end to tune the resonant frequency. A SPEH is designed by introducing a step section near the root of substrate beam to induce higher dynamic strain for maximizing the electrical output. The incorporation of step section reduces the stiffness and consequently, a lower tip mass is used with SPEH to match the resonant frequency to that of CPEH. Moreover, the electromechanical coupling coefficient, forcing function and damping are significantly influenced because of the inclusion of step section, which consequently affects harvester's output. Three different configurations of SPEHs characterized by the same resonant frequency as that of CPEH are designed and analyzed using linear electromechanical model and their performances are compared. The variation of strain on the harvester beams is obtained using finite element analysis. The prototypes of CPEH and SPEHs are fabricated and experimentally tested. It is shown that the power output from SPEHs is lower than the CPEH. When the prototypes with resonant frequencies in the range of 56-56.5 Hz are tested at 1 m/s2, three SPEHs generate power output of 482 μW, 424 μW and 228 μW when compared with 674 μW from CPEH. It is concluded that the advantage of increasing dynamic strain using step section is negated by increase in damping and decrease in forcing function. However, SPEHs show slightly better performance in terms of specific power and thus making them suitable for practical scenarios where the ratio of power to system mass is critical.

• Korean Journal of Mathematics
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• v.28 no.2
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• pp.223-240
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• 2020

The paper is concerned with periodic linear evolution equations of the form x"(t) = A(t)x(t)+f(t), where A(t) is a family of (unbounded) linear operators in a Banach space X, strongly and periodically depending on t, f is an almost (or asymptotic) almost periodic function. We study conditions for this equation to have almost periodic solutions on ℝ as well as to have asymptotic almost periodic solutions on ℝ⁺. We convert the second order equation under consideration into a first order equation to use the spectral theory of functions as well as recent methods of study. We obtain new conditions that are stated in terms of the spectrum of the monodromy operator associated with the first order equation and the frequencies of the forcing term f.

• Journal of Theoretical and Applied Mechanics
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• v.1 no.1
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• pp.29-67
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• 1995

A procedure is formulated, in this paper, to compute the bifurcation modes born by the stability change of normal modes, and to compute the forced responses associated with bifurcation modes in inertially and elastically coupled nonlinear oscillators. It is assumed that a saddle-loop is formed in Poincare map at the stability chage of normal modes. In order to test the validity of procedure, it is applied to one-to-one internal resonant systems in which the solutions are guaranteed within the order of a small perturbation parameter. The procedure is also applied to the exact system in which normal modes are written in exact form and the stability of normal modes can be exactly determined. In this system the stability change of normal modes occurs several times so that various types of bifurcation modes are created. A method is described to identify a fixed point on Poincare map as one of bifurcation modes. The limitations and advantage of proposed procedure are discussed.

• The KIPS Transactions:PartA
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• v.13A no.3 s.100
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• pp.199-204
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• 2006

The kernel hardening function is necessary in terms of kernel stability to reduce the system error or panic due to the kernel code error that is made by program developer. But, the traditional kernel hardening method is difficult to implement and consuming high cost. The suggested kernel hardening function that makes high availability system by changing the panic() function of inside kernel code guarantees normal system operation by recovering the incorrect address of the kernel stack frame. We experimented the kernel hardening function at the network module of the Linux by forcing panic code and confirmed the proposed design mechanism of kernel hardening is working well by this experiment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.173-180
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• 2007

This paper designs the kernel hardening function by recovering the kernel stack fame to reduce the system error or panic due to the kernel code error. The suggested kernel hardening function guarantees normal system operation by recovering the incorrect address of the kernel stack kernel. The suggesting kernel hardening mechanism is applied to the network module of Linux which is much using put. I experimented the kernel hardening function at the network module of the Linux by forcing panic code.