• Journal of applied mathematics & informatics
• /
• v.19 no.1_2
• /
• pp.261-280
• /
• 2005

We study the existence and nonexistence of positive periodic solutions of a non-autonomous functional differential equation with impulses. The equations we study may be of delay, advance or mixed type functional differential equations and the impulses may cause the existence of positive periodic solutions. The methods employed are fixed-point index theorem, Leray-Schauder degree, and upper and lower solutions. The results obtained are new, and some examples are given to illustrate our main results.

• Communications of the Korean Mathematical Society
• /
• v.10 no.3
• /
• pp.751-758
• /
• 1995

We prove the existence of solution for a Dirichlet singular boundary value problem. The proofs are based on the method of upper and lower solutions.

• Journal of applied mathematics & informatics
• /
• v.24 no.1_2
• /
• pp.209-220
• /
• 2007

In this paper, the existence and multiplicity of solutions of three-point p-Laplacian boundary value problems at resonance with one-sided Nagumo condition are studied by using degree theory and upper and lower solutions method. Some known results are improved.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.32 no.1
• /
• pp.77-91
• /
• 2007

In this paper, we present a symbiotic evolutionary algorithm for multi-objective optimization. The goal in multi-objective evolutionary algorithms (MOEAs) is to find a set of well-distributed solutions close to the true Pareto optimal solutions. Most of the existing MOEAs operate one population that consists of individuals representing the entire solution to the problem. The proposed algorithm has a two-leveled structure. The structure is intended to improve the capability of searching diverse and food solutions. At the lower level there exist several populations, each of which represents a partial solution to the entire problem, and at the upper level there is one population whose individuals represent the entire solutions to the problem. The parallel search with partial solutions at the lower level and the Integrated search with entire solutions at the upper level are carried out simultaneously. The performance of the proposed algorithm is compared with those of the existing algorithms in terms of convergence and diversity. The optimization problems with continuous variables and discrete variables are used as test-bed problems. The experimental results confirm the effectiveness of the proposed algorithm.

• Bulletin of the Korean Mathematical Society
• /
• v.51 no.2
• /
• pp.329-338
• /
• 2014

In this paper, we study the method of upper and lower solutions and develop the generalized quasilinearization technique for the existence and approximation of solutions to some three-point nonlocal boundary value problems associated with higher order fractional differential equations of the type $$^c{\mathcal{D}}^q_{0+}u(t)+f(t,u(t))=0,\;t{\in}(0,1)$$ $$u^{\prime}(0)={\gamma}u^{\prime}({\eta}),\;u^{\prime\prime}(0)=0,\;u^{\prime\prime\prime}(0)=0,{\ldots},u^{(n-1)}(0)=0,\;u(1)={\delta}u({\eta})$$, where, n-1 < q < n, $n({\geq}3){\in}\mathbb{N}$, 0 < ${\eta},{\gamma},{\delta}$ < 1 and $^c\mathcal{D}^q_{0+}$ is the Caputo fractional derivative of order q. The nonlinear function f is assumed to be continuous.

• Journal of applied mathematics & informatics
• /
• v.29 no.1_2
• /
• pp.191-200
• /
• 2011

This paper deals with second order differential equations with different deviated arguments ${\alpha}$(t) and ${\beta}$(t, ${\mu}$(t)). We investigate the existence of solutions of such problems with nonlinear mixed boundary conditions. To obtain corresponding results we apply the monotone iterative technique and the lower-upper solutions method. Two examples demonstrate the application of our results.

• Journal of the Chungcheong Mathematical Society
• /
• v.7 no.1
• /
• pp.227-236
• /
• 1994

• Journal of electromagnetic engineering and science
• /
• v.1 no.2
• /
• pp.156-160
• /
• 2001

Very convenient equivalent circuits fur the design of bandpass filters with an attenuation pole in the lower or upper stopband are provided together with necessary closed-form solutions. The proposed approach gives us much flexibility and simplifies the design of inserting attenuation poles.

• Nonlinear Functional Analysis and Applications
• /
• v.23 no.4
• /
• pp.779-795
• /
• 2018

In this paper, we establish the sufficient conditions for the existence of solutions for multi-valued equilibrium problems.

• Journal of the Korean Society of Safety
• /
• v.14 no.3
• /
• pp.120-126
• /
• 1999

This study was accomplished by measuring the lower and upper flash point with air blowing method and grasping the characteristics of flammability for the three component systems, which are made up of the Benzene-Toluene-o-Xylene and Methylethylketone-Toluene-o-Xylene. These three component systems are widely used in the various industrial fields together with the development of industry. The results are as follows ; 1 ) Isothermal line is plotted on the triangular diagram for flash points determined in each solutions. From this line, the mixed compositions which indicated the same lower and upper flash points in each different composition could be read on this diagram, if the composition of mixtures are known. 2) Lower and upper explosion limits obtained from the flash points determined for the three component solution are compared with the value calculated from Le Chatelier's law. Especially the lower explosion limits are in a good agreement with the calculated values.