• 한국경영과학회지
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• 제29권3호
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• pp.145-155
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• 2004

The design of a communication network has long been a challenging optimization problem. Since the optimal design of a network topology is a well known as a NP-complete problem, many researches have been conducted to obtain near optimal solutions in polynomial time instead of exact optimal solutions. All of these researches suggested diverse heuristic algorithms that can be applied to network design problems. Among these algorithms, a simulated annealing algorithm has been proved to guarantee a good solution for many NP-complete problems. in applying the simulated annealing algorithms to network design problems, generating mechanisms for initial solutions and candidate solutions play an important role in terms of goodness of a solution and efficiency. This study aims at analyzing these mechanisms through experiments, and then suggesting reliable mechanisms.

• Kyungpook Mathematical Journal
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• 제57권2호
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• pp.287-299
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• 2017

In this paper, we develop an enhanced Chebyshev collocation method based on an integration scheme of the generalized Chebyshev interpolations for solving stiff initial value problems. Unlike the former error embedded Chebyshev collocation method (CCM), the enhanced scheme calculates the solution and its truncation error based on the interpolation of the derivative of the true solution and its integration. In terms of concrete convergence and stability analysis, the constructed algorithm turns out to have the $7^{th}$ convergence order and the A-stability without any loss of advantages for CCM. Throughout a numerical result, we assess the proposed method is numerically more efficient compared to existing methods.

• 한국환경과학회지
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• 제13권6호
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• pp.599-603
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• 2004

In a batch reactor, the characteristics of photocatalytic degradation of brilliant blue FCF in titanium dioxide suspension was studied under the irradiation of ultra-violet ray. Photocatalytic degradation in anatase type of TiO$_2$ was more effective than in rutile type of $TiO_2$ below the dosage of 5g. The degradation rate was slightly increased with decreasing initial pH of brilliant blue FCF aqueous solution, but rapidly increased with the addition of oxidant. Potassium bromate acted as more effective oxidant than ammonium persulfate. The photocatalytic degradation rate of brilliant blue FCF was pseudo-first order with rate constants of 0.012, 0.006 and $0.003min^{-1}$ at initial pH 3.1, 5.2 and 7.1 of brilliant blue FCF solution, respectively.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.601-606
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• 1992

In this paper, we consider an optimal guidance problem with both the terminal impact angle and control constraints in addition to the usual zero miss distance constraint. We first present the optimal solution of the problem for the missile of an arbitrary order, and show that it is a linear combination of a step response and a ramp response of the missile. Therefore the usual practice of using the control obtained by saturating the optimal solution for the case of unlimited control may result in a large terminal miss. A method called the initial command saturation is suggested to reduce this terminal miss, where the control in the initial phase of guidance is forced to be saturated until a certain condition for a guidance variable is met.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제15권2호
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• pp.143-150
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• 2011

We consider the global existence of strong solutions of the 3D incompressible Navier-Stokes equations in a thin periodic domain. We present a simple proof that a strong solution exists globally in time when the initial velocity in $H^1$ and the forcing function in $L^p$(0,${\infty}$;$L^2$), $2{\leq}p{\leq}{\infty}$ satisfy certain condition. This condition is basically similar to that by Iftimie and Raugel[7], which covers larger and larger initial data and forcing functions as the thickness of the domain ${\epsilon}$ tends to zero.

• 산업공학
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• 제22권3호
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• pp.263-277
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• 2009

This research deals with a task assignment problem to worker group which consists of one master and one assistant. Each task must be assigned to only one worker group and it is possible to make a pair of each master and each assistant to organize a worker group. A worker group may have more than one task assigned to it, but the workloads of each worker group must be balanced within the allowable range. This problem can be formulated mathematically using the Mixed Integer Programming(MIP), where the objective function is to minimize the total assignment cost. A two phase heuristic algorithm is suggested in order to find approximate solutions. The first phase is to obtain an initial solution, where the initial assignment is performed to follow the workload adjustment. In the second phase, the solution is improved through the repeated process of the exchange and the assignment adjustment. Numerical experiments have been performed to evaluate the performance of the heuristic algorithm.

• 대한수학회지
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• 제49권2호
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• pp.315-324
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• 2012

We consider the global existence of strong solutions of the 3D incompressible Navier-Stokes equations in a long periodic domain. We show by a simple argument that a strong solution exists globally in time when the initial velocity in $H^1$ and the forcing function in $L^p$([0; T);$L^2$), T > 0, $2{\leq}p{\leq}+\infty$ satisfy a certain condition. This condition common appears for the global existence in thin non-periodic domains. Larger and larger initial data and forcing functions satisfy this condition as the thickness of the domain $\epsilon$ tends to zero.

• 한국염색가공학회지
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• 제11권4호
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• pp.24-30
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• 1999

Cotton fabric was dyed with indigo at different pHs, dye concentrations, and repeated dyeings. And the K/S value and dye uptake of the dyed materials at those conditions were determined. The decrease of pH during the reduction process of indigo stock solution was observed. As a result the decrease of pH of the dye stock solution depended on the dye concentration and initial pH. The highest K/S value was shown at fabric dyed at pH 11 and the relationship between K/S value and dye uptake depended on initial pH of reduction bath and the slope was lower as the pH increased to 13.

• 산업경영시스템학회지
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• 제35권4호
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• pp.171-178
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• 2012

A possible heuristic to solve metropolitan area vehicle routing problems with variable vehicle speeds is suggested in this research. Delivery hours are classified into 4 different time zones to make variable vehicle speeds no change within the same time zone to make TDVRP simple to solve. The suggested heuristic consists of 2 stages such as initial solution development step and initial solution improvement step. A computer program using C++ is constructed to evaluate the suggested heuristic. Randomly generated vehicle routing problems are used for the experiments. This heuristic could be helpful to logistics companies by increasing delivery efficiencies since the 4 zone classification is taken from the observed traffic information offered by a local government.

• Journal of Microbiology and Biotechnology
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• 제11권1호
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• pp.97-105
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• 2001

The viability of Bifidobacterium longum KCTC 3128, entrapped in calcium alginate beds in simulated gastroenteric juices (gastric and bile salt solution), was tested to evaluate the influences of several parameters (gel concentration, bead size, and initial cell number). The death rate of B. longum in beads after being sequentially exposed to simulated gastric juices and bile salt solution decreased propertionally with increasing both the alginate gel concentration and bead size. The number of initial cell loading in beads affected the numbers of survivors after being exposed to these solutions, while the death rate of the viable cells were not affected. From the results obtained, the influence of entrapment parameters on the survival of bifidobacteria was quantitatively and systematically evaluated by using a mathematical method.