• Korean Journal of Computational Design and Engineering
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• v.14 no.3
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• pp.207-216
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• 2009

Modern engineering design problems involve complexity of disciplinary coupling and difficulty of problem formulation. Multidisciplinary design optimization can overcome the complexity and design optimization software or frameworks can lessen the difficulty. Recently, a growing number of new multidisciplinary design optimization techniques have been proposed. However, each technique has its own pros and cons and it is hard to predict a priori which technique is more efficient than others for a specific problem. In this study, a software system has been developed to directly solve MDO problems with minimal input required. Since the system is based on MATLAB, it can exploit the optimization toolbox which is already developed and proven to be effective and robust. The framework is devised to change an MDO technique to another as the optimization goes on and it is called a reconfigurable MDO framework. Several numerical examples are shown to prove the validity of the reconfiguration idea and its effectiveness.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.841-844
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• 2009

Recently our society is changing from an information era to an ubiquitous era. The centralization of an ubiquitous city has been developing among the countries and cities competitively. At this point, a reconfiguration of proper network environment is very important factor for a city competitive power. The centralization of an ubiquitous city is progressing with two kinds of category divided into existing cities and new cities. For example, Unlike new cities, the existing cities should consider the physical space restriction of communication network configuration because they can not design an underground cord lining. This paper describes the comparison and analysis of ubiquitous proceeding cases between the existing cities and new cities. And also, we investigated infrastructure features of proceeding ubiquitous city which is regarded as a reviving concept for the existing cities. In addition, a political proposal of wireless network configuration is suggested to solve these problems for the ubiquitous city.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.1
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• pp.89-96
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• 2015

The various services applied internet have been provided by the rapid development of wireless networks and providing multimedia contents are also increasing. It is caused a number of problems such as increasing of network traffic rapidly. P2P technique is gaining popularity for solving these problems. In particular, P2P technique in a wireless network environment has gained much popularity. Among them, MANET-based P2P techniques has been studied actively. It is not easy to be applied the existing technique as it is due to the dynamic topology and low bandwidth by moving nodes in MANET that is consisted of only mobile nodes. In this paper, we proposed sharing group construction technique for providing a stable connection between mobile nodes and reducing the load of network traffic and overhead of sharing group reconfiguration in order to improve data transmission performance between mobile nodes. The sharing group member nodes applied virtual sharing group generation technique with neighboring nodes of 1-hop distance in order to reduce traffic for file sharing. We performed comparative experiments with DHT technique to evaluate the performance of the proposed technique in this paper and the excellent performance is confirmed through experiments.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.285-290
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• 2011

This paper presents an algorithm that can provide initial conditions for formation flying at the beginning of a region of interest to maximize scientific mission goals in the case of a tetrahedral satellite formation. The performance measure is to maximize the quality factor that affects scientific measurement performance. Several path constraints and periodicity conditions at the beginning of the region of interest are identified. The optimization problem is solved numerically using a direct transcription method. Our numerical results indicate that there exist an optimal configuration and states of a tetrahedral satellite formation. Furthermore, the initial states and algorithm presented here may be used for reconfiguration maneuvers and fuel balancing problems.

• Journal of Astronomy and Space Sciences
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• v.21 no.3
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• pp.209-220
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• 2004

Some methods have been presented to get optimal formation trajectories in the step of configuration or reconfiguration, which subject to constraints of collision avoidance and final configuration. In this study, a method for optimal formation trajectory-planning is introduced in view of fuel/time minimization using parameter optimization technique which has not been applied to optimal trajectory-planning for satellite formation flying. New constraints of nonlinear equality are derived for final configuration and constraints of nonlinear inequality are used for collision avoidance. The final configuration constraints are that three or more satellites should be placed in an equilateral polygon of the circular horizontal plane orbit. Several examples are given to get optimal trajectories based on the parameter optimization problem which subjects to constraints of collision avoidance and final configuration. They show that the introduced method for trajectory-planning is well suited to trajectory design problems of formation flying missions.

• Korean Journal of Computational Design and Engineering
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• v.8 no.3
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• pp.184-188
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• 2003

The harness design process consists of repetitious routines to decide the wire configuration in its interior. A slight change in one of the wire's configuration will require a total reconfiguration of the entire wire system. Therefore, the harness design is extremely time consuming and is vulnerable to human errors by an engineer. Based on both electrical and mechanical area, Wiring Harness system is in complicated area. Existing systems are, therefore, not exactly suitable for practical use. This paper presents a novel framework for ameliorating existing system's defects. In this paper, Visio and Visual Basic was interfaced to process wire bundle information and wire bundle location to alleviate problems mentioned beforehand concerning harness design; at the same time developing the automation of the entire design process based on the feature based design method, optional print, and management of documents for reuse.

• Kyungpook Mathematical Journal
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• v.56 no.3
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• pp.647-655
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• 2016

Let H be a graph, and $k{\geq}{\chi}(H)$ an integer. We say that H has a cyclic Gray code of k-colourings if and only if it is possible to list all its k-colourings in such a way that consecutive colourings, including the last and the first, agree on all vertices of H except one. The Gray code number of H is the least integer $k_0(H)$ such that H has a cyclic Gray code of its k-colourings for all $k{\geq}k_0(H)$. For complete bipartite graphs, we prove that $k_0(K_{\ell},r)=3$ when both ${\ell}$ and r are odd, and $k_0(K_{\ell},r)=4$ otherwise.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.160.1-160.1
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• 2012

We present an alternative approach for satellite formation reconfiguration by an optimal impulsive-thrust strategy to minimize the total characteristic velocity in a near-circular-orbit. Linear transformation decouples the Hill-Clohessy-Wiltshire(HCW) dynamics into a new block-diagonal system matrix consisting of 1-dimensional harmonic oscillator and 2-dimensional subsystem. In contrast to a solution based on the conventional primer vector theory, the optimal solution and the necessary conditions are represented as times and directions of impulses. New analytical expression of the total characteristic velocity is found for each sub systems under general boundary conditions including transfer time constraint. To minimize the total characteristic velocity, necessary conditions for times and directions of impulses are analytically solved. While the solution to the 1-dimensional harmonic oscillator has been found, the solution to the 2-dimensional subsystem is currently under construction. Our approach is expected to be applicable to more challenging problems.

• Journal of Information Technology Services
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• v.10 no.1
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• pp.117-133
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• 2011

In this paper, we present a frequency reassignment problem (FRP) arising from the reconfiguration of radio networks such as adding new base stations (BSs) and changing the number of frequencies assigned to BSs. For this problem, we develop an integer programming (IP) model that minimizes the sum of frequency reassignment cost and the cost for unsatisfied frequency demands, while avoiding interference among frequencies. To obtain tight lower bounds, we develop some valid inequalities and devise an objective function relaxation scheme. Also, we develop a simple but efficient heuristic procedure to solve large size problems. Computational results show that the developed valid inequalities are effective for improving lower bounds. Also, the proposed tabu search heuristic finds tight upper bounds with average optimality gap of 2.3%.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.800-803
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• 1996

This paper proposes the algorithm to solve emergency service restoration problems using efficient reconfiguration method in distribution system. In this algorithm, we try to avoid the blackout of important loads by considering service rank. It is possible to reconfigurate the system by using fuzzy inference results in which was reflected the expected distribution power, line capacity and service rank. A 27-bus, 32-branch model system is used to demonstrate the effectiveness of the proposed algorithm.