• Korean Journal of Mathematics
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• v.18 no.3
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• pp.323-334
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• 2010

We give a theorem for the existence of at least three solutions for the fourth order elliptic boundary value problem with the square growth variable coefficient nonlinear term. We use the variational reduction method and the critical point theory for the associated functional on the finite dimensional subspace to prove our main result. We investigate the shape of the graph of the associated functional on the finite dimensional subspace, (P.S.) condition and the behavior of the associated functional in the neighborhood of the origin on the finite dimensional reduction subspace.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.6
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• pp.246-251
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• 2003

We report the theory of thin-sample Z -scan for materials, viz. diffusion-dominated photorefractives, having a nonlinearly induced phase that may be proportional to the spatial derivative of the intensity profile. The on-axis far-field intensity is approximately an even function of the scan distance on different positive and negative values for phase shift $\Delta$$\Phi$$_{o}$. In case of positive phase shift, the Z -scan graph shows a minimum and two maxima, while for the negative value, only one minimum is observed. The fact is that far-field beam profiles display beam distortion and shift of the peak as compared with Kerr-type or photovoltaic nonlinearities.s.

• The Journal of Information Systems
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• v.8 no.1
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• pp.109-129
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• 1999

This study deals with the problem of information dissemination in a communication network, which is defined to be the process whereby a set of messages, generated by an originator, is transmitted to all the members within the network. Since this type of message generally includes control data to manage the network or global information that all members should know, it is to be required to transmit it to all the members as soon as possible. In this study, it is assumed that a member can either transmit or receive a message and an informed member can transmit it to only one of its neighbors at time. This type of transmission is called 'local broadcasting' Several schemes of call sequencing are designed for a general-type network with nonuniform edge transmission times, and then computer simulations are performed. Some heuristics for information dissemination are proposed and tested. For this, optimal call sequence in a tree-type network, sequencing theory and graph theory are applied. The result shows that call sequencing based on the shortest path tree is the most desirable.

• Journal for History of Mathematics
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• v.18 no.4
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• pp.101-112
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• 2005

In this article, we introduce a generous but eccentric genius in mathematics, Paul Erdos. He invented probabilistic methods, pioneered in their applications to discrete mathematics, and estabilshed new theories, which are regarded as the greatest among his contributions to mathematical world. Here we introduce the probabilistic methods and random graph theory developed by Erdos and look at his life in glance with great respect for him.

• Journal of the Korea Society of Computer and Information
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• v.24 no.10
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• pp.205-213
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• 2019

Network robustness is one of the most important characteristics needed as the network. Over the military tactical communication network, robustness is a key function for maintaining attack phase constantly. Tactical Information Communication Network, called TICN, has mixed characteristics of lattice- and tree-type network topology, which looks somewhat weak in the viewpoint of network robustness. In this paper, we search articulation points and bridges in a current Tactical Information Communication Network using graph theory. To improve the weak points empirically searched, we try to add links to create the concrete network and then observe the change of network-based verification values through diminishing nodes. With these themes, we evaluate the generated networks through SNA techniques. Experimental results show that the generated networks' robustness is improved compared with current network structure.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.83-87
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• 2004

In this paper, an electrical equivalent circuit is derived by solving system equations. A frequency characteristics graph is calculated and the characteristics curve of the linear Actuator Model System are simulated by the Matlab program The frequency characteristics of a linear actuator are analyzed on the structure of the linear Actuator Model System This paper proposed and analyzed the linear Actuator Model(LAM) by using Matlab program with linear actuator was verified computer simulation based on the energy conversion theory.

• Journal of the Korean Institute of Intelligent Systems
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• v.9 no.4
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• pp.451-456
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• 1999

All the teaching items in a textbook are normally arranged in a prescribed teaching order. However, one can easily find that the textbooks of the same kind, even with the same teaching items, show different arrangements. Without learning preceding teaching items, students may have a difficulty in understanding the teaching items. In this sense, it is very important to decide how to arrange teaching items in terms of teaching sequence. As a solution to this problem, lsamu Matsubara presents a method based on the graph theory. The four types defined in his method are the straight type, the group type, the branch type, and the independent type. Among these, the three types except the straight type lack the objectivity. An objective solution to these three types, based on the fuzzy theory. is propopsed in this paper.

• Educational Technology International
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• v.13 no.1
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• pp.145-173
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• 2012

The purpose of this study is to develop collaboration scripts as an instructional means to facilitate argumentation in computer-supported collaborative learning, and to analyze their effects. To develop collaboration scripts for argumentation, researchers used activity theory as a conceptual framework and refined the design principles by design-based research. Using LAMS, collaboration scripts for argumentation were developed based on the ArgueGraph. To examine their effects, 72 participants were divided into two groups by internal scripts and randomly allocated to one of three external scripts. Applying mixed methods, researchers analyzed argumentation competence related to the cognitive aspect, examined self-efficacy related to the motivational aspect, and identified the factors influencing collaborative learning processes and outcomes. Researchers found that the internal script is a critical factor to determine the dimensions, degrees, and duration of improvement in argumentation competence. That is, learners with higher internal scripts improved highly in the quality of single arguments, while learners with lower internal scripts improved continuously in the quality of argumentation sequences. The effects of the external scripts varied with the internal script levels and supporting periods. Besides, collaboration scripts for argumentation had positive effects on learners' self-efficacy, and learners with higher internal scripts had better self-efficacy. The factors influencing collaborative learning processes and outcomes showed different results depending on the learning context. Therefore, when scripting learner's interaction in CSCL, researchers should design the scripts adaptable to a natural context of activities.

• Korean Institute of Interior Design Journal
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• v.19 no.6
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• pp.112-120
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• 2010

Human can recognize the environment by detecting spatial perception, and most of environmental perception depends on visual perception. In view that the acquisition of spatial information is accomplished through visual recognition, analysis of visual structure contained in the space is thought to be very important sector in studying the characteristic of the space. The history of studies on visual structure of space, however, wasn't too long, and furthermore most of the theories up to now focused on static and planar principles. Under this circumstance, this study is intended to suggest new theory by combining Isovist theory and VGA theory that have been actively discussed as the theory on visual perception-based spatial structure and supplementing them between each other to expand into 3-dimensional model. The suggested theory is a complex principle in dimensional and dynamic form in consideration of visual direction, which forms 3-dimentional virtual model that enables visualization of the property of spatial structure as the routine discriminating whether visual connection is made between viewing point and target point, and the target point is included in the visual field quadrangular pyramid or not. Such model was built up by an analysis application where four probe paths were applied to simulate the visual structure that occurs in virtual space, and then the characteristics were analyzed through quantification. In result, in spite of the path with equal space and equal length, significant difference in the acquired quantity of spatial information could be found depending on the probe sequence. On the contrary, it was found that probe direction may not affect the acquired quantity of information and visual property of the space.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.3 no.6
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• pp.612-627
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• 2009

The high-level contribution of this paper is to illustrate the effectiveness of using graph theory tree traversal algorithms (pre-order, in-order and post-order traversals) to generate the chain of sensor nodes in the classical Power Efficient-Gathering in Sensor Information Systems (PEGASIS) data aggregation protocol for wireless sensor networks. We first construct an undirected minimum-weight spanning tree (ud-MST) on a complete sensor network graph, wherein the weight of each edge is the Euclidean distance between the constituent nodes of the edge. A Breadth-First-Search of the ud-MST, starting with the node located closest to the center of the network, is now conducted to iteratively construct a rooted directed minimum-weight spanning tree (rd-MST). The three tree traversal algorithms are then executed on the rd-MST and the node sequence resulting from each of the traversals is used as the chain of nodes for the PEGASIS protocol. Simulation studies on PEGASIS conducted for both TDMA and CDMA systems illustrate that using the chain of nodes generated from the tree traversal algorithms, the node lifetime can improve as large as by 19%-30% and at the same time, the energy loss per node can be 19%-35% lower than that obtained with the currently used distance-based greedy heuristic.