• Journal of the Korean Mathematical Society
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• v.37 no.5
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• pp.707-720
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• 2000

Conley index is used study bifurcation from equilibria of full bounded solutions to parameter dependent families of ordinary differential equations of the form {{{{ {dx} over {dt} }}}} =$\varepsilon$F(x, t, $\mu$). It is assumed that F(x, t,$\mu$) is uniformly almost periodic in t.

• Korean Journal of Mathematics
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• v.17 no.3
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• pp.331-340
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• 2009

We show the existence of nonconstant periodic solution for the nonlinear Hamiltonian systems with some nonlinearity. We approach the variational method. We use the critical point theory and the variational linking theory for strongly indefinite functional.

• Journal of applied mathematics & informatics
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• v.28 no.3_4
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• pp.797-804
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• 2010

The aim of this paper is to investigate the global stability, periodic nature, oscillation and the boundedness of solutions of the difference equation $x_{n+1}\;=\;\frac{A+Bx_{n-1}}{C+Dx_n^2}$, n = 0, 1, 2, ... where A, B are nonnegative real numbers and C, D > 0.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.2 no.1
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• pp.1-14
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• 1998

Multiplicity results of doubly-periodic solution for semilinear heat equations having coercive nonlinearity are discussed. Our proofs rely on Mawhin's continuation theorem.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.597-607
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• 2006

This paper presents a numerical simulation of the behavior of the LiBr solution droplets and falling films in horizontal tube banks of absorber. The model developed here accounts for the details of the droplets formation and impact process for absorption on horizontal tubes including the heat transfer from solution film to the tube wall. Especially. the characteristic of unsteady behavior of solution flow has been investigated. Flow visualization studies shown that the solution droplets and falling films have some of the complex characteristics. It is found that. with the numerical conditions similar to the operating condition of an actual absorption chiller/heater, the outlet solution temperature and heat flux from solution film to the tube wall have a stable periodic behavior with time. The solution droplets and falling films in horizontal tube banks of absorber is a periodic unsteady flow. The results from this model are compared with previous experimental observation taken with a high-speed digital video camera and shown good agreement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.6 s.261
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• pp.694-700
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• 2007

Recently, a new cellular metal, WBK(Wire woven Bulk Kagome) has been introduced. WBK is fabricated by assembling metal wires in six directions into a Kagome-like truss structure and by brazing it at all the crossings. Wires as the raw material are easy to handle and to attain high strength with minimum defect. And the strength and energy absorption are superior to previous cellular metals. Therefore, WBK seems to be promising once the fabrication process for mass production is developed. In this paper, an upper bound solution for the mechanical properties of the bulk WBK under compression is presented. In order to simulate uniform behavior of WBK consisted of perfectly uniform cells, a unit cell of WBK with periodic boundary conditions is analyzed by the finite element method. In comparison with experimental test results, it is found that the solution provides a good approximation of the mechanical properties of bulk WBK cellular metals except for Young's modulus. And also, the brazing joint size does not have any significant effect on the properties with an exception of an idealized thin joint.

• Management Science and Financial Engineering
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• v.1 no.1
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• pp.39-66
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• 1995

This article presents a new model called the periodic square wave(PSW) to describe the material flow of periodic processes involving an intermediate buffer. The material flows into and out of the intermediate buffer are assumed to be periodic square shaped. By using this model, It is proved that the classical economic lot size model with finite supply rate, the so-called EPQ model, can be applicable to the arbitrary periodic demand case. This new model relaxes the original assumption of the constant demand. It is shown, as a unique application example, that the explicit solution for determining both upstream and downstream economic lot size can be obtained with the aid of the PSW model. The PSW model provides more accurate information on analyzing the inventory and production system than the classical approach, without losing simplicity and increasing the computational burden.

• The Pure and Applied Mathematics
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• v.19 no.2
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• pp.103-109
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• 2012

The existence and uniqueness of T-periodic solutions for the following p-Laplacian equations: $$({\phi}_p(x^{\prime}))^{\prime}+{\alpha}(t)x^{\prime}+g(t,x)=e(t),\;x(0)=x(T),x^{\prime}(0)=x^{\prime}(T)$$ are investigated, where ${\phi}_p(u)={\mid}u{\mid}^{p-2}u$ with $p$ > 1 and ${\alpha}{\in}C^1$, $e{\in}C$ are T-periodic and $g$ is continuous and T-periodic in $t$. By using coincidence degree theory, some existence and uniqueness results are obtained.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.209-211
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• 2008

In this paper, a segregated finite element program for the analysis of an axisymmetric steady flow has been developed in order to investigate the flow inside an annular pipe with a periodic obstacle. For the verification of the developed code, a developing pipe flow has been solved and the solution is in a good agreement with the existing results. For the analysis of the flow inside an annular pipe with a periodic obstacle, three types of periodic obstacle are considered. From the present numerical analysis, various physical variables including flow pattern, pressure distribution and residence time are investigated as a preliminary study to the heat transfer analysis of an annular pipe flow with a periodic obstacle.

• Structural Engineering and Mechanics
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• v.4 no.5
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• pp.553-568
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• 1996

Finite element stiffness matrix methods are presented for finding natural frequencies (or buckling loads) and modes of repetitive structures. The usual approximate finite element formulations are included, but more relevantly they also permit the use of 'exact finite elements', which account for distributed mass exactly by solving appropriate differential equations. A transcendental eigenvalue problem results, for which all the natural frequencies are found with certainty. The calculations are performed for a single repeating portion of a rotationally or linearly (in one, two or three directions) repetitive structure. The emphasis is on rotational periodicity, for which principal advantages include: any repeating portions can be connected together, not just adjacent ones; nodes can lie on, and members along, the axis of rotational periodicity; complex arithmetic is used for brevity of presentation and speed of computation; two types of rotationally periodic substructures can be used in a multi-level manner; multi-level non-periodic substructuring is permitted within the repeating portions of parent rotationally periodic structures or substructures and; all the substructuring is exact, i.e., the same answers are obtained whether or not substructuring is used. Numerical results are given for a rotationally periodic structure by using exact finite elements and two levels of rotationally periodic substructures. The solution time is about 500 times faster than if none of the rotational periodicity had been used. The solution time would have been about ten times faster still if the software used had included all the substructuring features presented.