• Journal of Korea Water Resources Association
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• v.42 no.12
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• pp.1079-1089
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• 2009

The objective of this study is to develop the accurate, robust and high resolution two-dimensional numerical model that solves the computationally difficult hydraulic problems, including the wave front propagation over dry bed and abrupt change in bathymetry. The developed model in this study solves the conservative form of the two-dimensional shallow water equations using an unsplit finite volume scheme and HLLC approximate Riemann solvers to compute the interface fluxes. Bed-slope term is discretized by the divergence theorem in the framework of FVM for application of unsplit scheme. Accurate and stable SGM, in conjunction with the MUSCL which is second-order-accurate both in space and time, is adopted to balance with fluxes and source terms. The exact C-property is shown to be satisfied for balancing the fluxes and the source terms. Since the spurious oscillations in second-order schemes are inherent, an efficient slope limiting technique is used to supply TVD property. The accuracy, conservation property and application of developed model are verified by comparing numerical solution with analytical solution and experimental data through the simulations of one-dimensional dam break flow without bed slope, steady transcritical flow over a hump and two-dimensional dam break flow with a constriction.

• Journal of fish pathology
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• v.26 no.2
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• pp.65-75
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• 2013

Population growth equation of scuticociliate Miamiensis avidus was obtained from the experimental results of in vitro culture condition to estimate the growth rate and carrying capacity from the growth equation. In addition, intraperitoneal infections into olive flounder Paralichthys olivaceus were carried out into 2 different conditions: different concentrations of M. avidus in same water temperature and same concentration of M. avidus in different water temperatures. Olive flounder mortality was threshold dependent with both the temperature and M. avidus density parameters. In this paper, we propose a mathematical model to study M. avidus growth in olive flounder based upon the interactions between parasite and host. The mathematical model was logistic growth differential equation (1.2). The parameters were found with Matlab program through the Levenberge-Marquardt method. In theorem, equilibrium values between the infected fish population and dead population could found. Our equilibrium points were a stable equilibrium and an unstable equilibrium. From the equation (1.6), it was possible to predict the amount of cumulative mortality of olive flounder along with the time after M. avidus infection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11A
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• pp.878-891
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• 2011

We consider the throughput-maximization problem for both the up- and downlink in a wireless network with interference channels. For this purpose, we design an iterative and distributive uplink algorithm based on Lagrangian relaxation. Using the uplink power prices and network duality, we achieve throughput-maximization in the dual downlink that has a symmetric channel and an equal power budget compared to the uplink. The network duality we prove here is a generalized version of previous research [10], [11]. Computational tests show that the performance of the up- and downlink throughput for our algorithms is close to the optimal value for the channel orthogonality factor, ${\theta}{\in}$(0.5, 1]. On the other hand, when the channels are slightly orthogonal (${\theta}{\in}$(0, 0.5]), we observe some throughput degradation in the downlink. We have extended our analysis to the real downlink that has a nonsymmetric channel and an unequal power budget compared to the uplink. It is shown that the modified duality-based approach is thoroughly applied to the real downlink. Considering the complexity of the algorithms in [6] and [18], we conclude that these results are quite encouraging in terms of both performance and practical applicability of the generalized duality theorem.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.45-53
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• 1991

The underground structure, which has infinite or semi-infinite boundary conditions, is subjected by body forces and in-situ stresses. It also has stress concentration, which causes material nonlinear behavior, in the vicinity of the excavated surface. In this paper, some methods which can be used to transform domain integrals into boundary integrals are reviewed in order to analyze the effect of the body forces and the in-situ stresses. First, the domain integral of the body force is transformed into boundary integral by using the Galerkin tensor and divergence theorem. Second, it is transformed by writing the domain integral in cylindrical coordinates and using direct integration. The domain integral of the in-situ stress is transformed into boundary integral applying the direct integral method in cylindrical coordinates. The methodology is verified by comparing the results from the boundary element analysis with those of the finite element analysis. Coupling the above boundary elements with finite elements, the nonlinear behavior that occurs locally in the vicinity of the excavation is analyzed and the results are verified. Thus, it is concluded that the domain integrals of body forces and in-situ stresses could be performed effectively by transforming them into the boundary integrals, and the nonlinear behavior can be reasonably analyzed by coupled nonlinear finite element and boundary element method. The result of this research is expected to he used for the analysis of the underground structures in the effective manner.

• Management & Information Systems Review
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• v.34 no.1
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• pp.65-80
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• 2015

In previous studies concerning turnover, they argue individual stock's turnover must be identical to market portfolio's turnover under one condition where 2 funds separation theorem holds. In this kind of world, all market participants hold and trade the same portfolio and this should be only market portfolio. If one's trading portfolio's shape is different from market portfolio's, this would mean he or she has an advantage over others in information and this kind of information would be private. In accordance with this theory, we develop a metric which measures how far one's trading portfolio from market's and name it as Stock Selection by Investor(SSI). We apply this measurement to the various types of investor groups classified as individual, institutional and foreign who participate in Korea stock market. To test the validity of measure, we regress price ratio on this measurement using SUR method. As a result, individual investor group shows large number in SSI, but the coefficient in regression is not significant and economically meaningless. In case of institutional investor group, the coefficient proves to be significantly negative. We can infer from this fact that their trading is somehow far from informed trading. Stock selection activity by foreign investor groups proves to be informed trading by showing significantly positive coefficient and the magnitude of coefficient is economically meaningful, especially in sell activity.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.205-214
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• 2012

The main thing that IT operation managers consider is protecting assets of corporation from system failure and disaster. Therefore, this research proposed a backup system for a disaster recovery. Previous backup method is that if database update occurs, this record is saved in redo log, and if the size of record file is over than expected, this file is saved in archive log in order. Thus, it is possible to occur errors of data loss from the process of data backup which change in real time while changes of database occur. Suggested backup system is back redo log up to database of transaction log in real time, and back a record that can be omitted from previous backup method up to archive log. When recover the data, it is possible to recover redo log in real time online, and it minimizes data loss. Also, throughout multi thread processing method data recovery is performed and it is designed that system performance is improved. To verify stability of backup system CPN(Coloured Petri Net) is introduced, and each step of backup system is displayed in diagram form, and th e stability is verified based on the definition and theorem of CPN.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.773-783
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• 2007

A simple unbonded-type shear strengthening technique for reinforced concrete beams using wire rope units is developed. Six two-span continuous T-beams externally strengthened with wire rope units and an unstrengthened control beam were tested. The main variables investigated were the amount and prestressing force of wire rope units. All specimens had the same geometrical dimension and arrangement of internal reinforcement. Influence of the distribution of vertical stresses in beam web owing to the prestressing force of wire rope units on the diagonal shear cracking load and the ultimate shear capacity of beams tested is presented. Based on the current study, it can be concluded that the amount and initial prestress of wire rope should be limited to be above 2.5 times the minimum shear reinforcement ratio specified in ACI 318-05 and below 0.6 times its own tensile strength, respectively, to ensure the enhancement of shear capacity and ductile failure mode of the strengthened beams. A numerical analysis based on the upper-bound theorem is developed to assess the shear capacity of continuous T-beams strengthened with wire rope units. From the comparisons of measured and predicted shear capacities, a better agreement is achieved in the proposed numerical analysis than in empirical equations recommended by ACI 318-05.

• School Mathematics
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• v.16 no.3
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• pp.585-611
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• 2014

The purpose of this study is to understand the decision-making behavior of a mathematics teacher in science academy of Korea by applying the framework of class analysis through the theory of goal-oriented decision-making. To this end, we selected as the participant a mathematics teacher in charge of the class of basic calculus of science high school for the gifted in the metropolitan area, and observed the teacher's lesson. Based on a questionnaire derived from previous studies, we analyzed goals, orientations and resources of the teacher. Research results show that there are certain teaching routines by analyzing the behavior patterns that appear repeatedly in the teacher's lesson. Also we understand that it can be used on goals, orientations and resources of the teacher to adequately explain his teaching routine. In the present study, in particular, it was found to have a similar but partially different routines to the teaching routines shown in the study of Schoenfeld. From these findings, We can derive the implications that the theory of goal-oriented decision making can be suitably used as analytical tool for understanding the behavior of the teacher who pursue a productive interaction in mathematics lesson in Korea.

• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.13-20
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• 2010

Seismic risk assessment of railway bridges is an important issue for a transportation network, because loss of functionality of railway bridges could result in severe disruption of the railway line, as no redundant routing systems generally exist. Although many studies have been conducted by numerous researchers regarding fragility analyses of bridge structure, little or no studies have been done for fragility analyses of a class of bridge structures considering their geometric variability. This study performs a fragility analysis for Track-on Steel-Plate-Girder (TOSPG) railway bridges in Korea considering their span variability. Seismic fragility curves are developed for a series of bridges with different spans varying from 2 to 15. At last, the fragility curves for the whole TOSPG bridges in Korea are also developed using the total probability theorem. This study is expected to effectively contribute to the seismic risk assessment of railway lines, where a number of bridges are present.

• Journal of Educational Research in Mathematics
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• v.20 no.1
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• pp.85-102
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• 2010

Linear programming(LP) is useful for finding the best way in a given condition for some list of requirements represented as linear equations. This study analysed LP in mathematics contexts and LP in school mathematics contexts, considered learning process of LP from an epistemological point of view, and explored a hypothetical learning trajectory of LP. The differences between mathematics contexts and school mathematics contexts are whether they considered that the convex polytope $\Omega$ is feasible/infeasible or bounded/unbounded or not, and whether they prove the theorem that the optimum is always attained at a vertex of the polyhedronor not. And there is a possibility that students could not understand what is maximum and minimum of a linear function when the domain of the function is limited. By considering these three aspects, we constructed hypothetical learning trajectory consisted of 4 steps. The first step is to see a given linear expression as linear function, the second step is to partition a given domain by straight lines, the third step is to construct the conception of y-intercept by relating lines and the range of k, and the forth step is to identify whether there exists the optimum in a given domain or not.