• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.340-345
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• 2001

Electric power market in Japan is now on the trend of deregulation and privatization just like in Europe and the United States. And various approaches for risk management have been investigated taking the electric power price fluctuation after the deregulation into account. The behavior of the investment in power generation plants has not, however, been studied in detail yet due to the complexity of the problem. The problem of the investment in the deregulated power market is that of autonomous decentralized decision-making system, which includes various kinds of decision-makers, that is, power producers called IPPS Each generator has its own criteria for plant investment. Therefore, the total behavior of the decentralized power market will be so complicated, and normative approach will not be applicable fur this analysis. We have developed a simulation-based system fur behavioral analysis and also the framework design of the decentralized power market.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.30-35
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• 1992

Since many design problems in the railroad, aerospace and machine structures involve considerations of the effect of cyclic loading, manufacturing and quality control processes must fully account for fatigue of critical components. Due to the sensitivity of the Paris law, it is very important to calculate the ΔK numerically to minimize the error of predicted fatigue life in cycles. It is shown that the p-version of FEM based on LEFM analysis is far better suited for computing the stress intensity factors than the conventional h-version. To demonstrate the proficiency of the proposed scheme, the welded T-joint with crack problem of box car body bolster assembly and a crack problem emanating Iron a circular hole in finite strip have been solved.

• Structural Engineering and Mechanics
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• v.4 no.3
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• pp.277-301
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• 1996

A finite element model of a beam element with flexible connections is used to investigate the effect of the randomness in the stiffness values on the modal properties of the structural system. The linear behavior of the connections is described by a set of random fixity factors. The element mass and stiffness matrices are function of these random parameters. The associated eigenvalue problem leads to eigenvalues and eigenvectors which are also random variables. A second order perturbation technique is used for the solution of this random eigenproblem. Closed form expressions for the 1st and 2nd order derivatives of the element matrices with respect to the fixity factors are presented. The mean and the variance of the eigenvalues and vibration modes are obtained in terms of these derivatives. Two numerical examples are presented and the results are validated with those obtained by a Monte-Carlo simulation. It is found that an almost linear statistical relation exists between the eigenproperties and the stiffness of the connections.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.458-461
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• 2006

Early age cracking of concrete is a widespread and complicated problem, and diverse applications in practical engineering have focused on this issue. Since massive concrete base slab composes the infrastructure of other concrete structures such as pier, concrete dam, and high rise buildings, early age cracking of that is considered as a crucial problem. In this study, finite element analysis (FEA) implemented with the age-dependent microplane model was performed. For a massive concrete base slab, cracking initiation and propagation, and deformation variation were investigated with concrete age. In massive concrete slab, autogenous shrinkage increases the risk of early age cracking and it reduces reinforcement effect on control of early age cracking. Gradual crack occurrence is experienced from exterior surface towards interior of the slab in case of combined hydration heat and autogenous shrinkage. FEA implemented with enhanced microplane model successfully simulates the typical cracking patterns due to edge restraint in concrete base slab.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.7
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• pp.633-640
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• 2001

In this paper we examine the machine learning issues raised by the domain of the Intrusion Detection Systems(IDS), which have difficulty successfully classifying intruders. There systems also require a significant amount of computational overhead making it difficult to create robust real-time IDS. Machine learning techniques can reduce the human effort required to build these systems and can improve their performance. Genetic algorithms are used to improve the performance of search problems, while data mining has been used for data analysis. Data Mining is the exploration and analysis of large quantities of data to discover meaningful patterns and rules. Among the tasks for data mining, we concentrate the classification task. Since classification is the basic element of human way of thinking, it is a well-studied problem in a wide variety of application. In this paper, we propose a classifier system based on genetic algorithm, and the proposed system is evaluated by applying it to IDS problem related to classification task in data mining. We report our experiments in using these method on KDD audit data.

• Journal of the Korean Data and Information Science Society
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• v.18 no.4
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• pp.859-868
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• 2007

The present paper deals with the ordering problem for how to teach mathematical concepts successfully. Main object is the concept of continuous functions which is fundamental in analysis and topology. At first, the theoretical organization of this concept is investigated through several texts in related field, calculus, analysis and topology. And next, the historical order for this concept from the viewpoint of problem-solving is considered. Based on these two materials, we suggest a lecturing organization order in order to establish a balanced unification of three concepts - intuitive, logical and formal concepts.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1448-1454
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• 1994

Data which gathered and used in the field of fatigue and fracture mechanics have a lot of uncertainties. In this case, those uncertainties will make scatter band in evaluation of fatigue life and fracture toughness. Thus, the probabilistic analysis of these data will be needed. For determining the fatigue life in mixed mode, using crack direction law and fatigue crack growth law, the problem is studied as a constrained life minimization. Stress intensity factor(SIF) is computed by approximate solution table(Ewalds/Wanhill 1984) and 0th order PFEM. The variance of fatigue life and SIF are computed by differentiation of tabulated approximate solution and 1st order PFEM. And these are used for criterion of design values, principal parameter determination and modelling. The problem of center cracked plate is solved for checking the PFEM model which is influenced by various parameters like as initial crack length, final crack length, two fatigue parameters in Paris Equation and applied stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.850-858
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• 1997

A new a posteriori error estimator is introduced and applied to variational inequalities occurring in problems of flow through porous media. In order to construct element-wise a posteriori error estimates the global error is localized by a special mixed formulation in which continuity conditions at interfaces are treated as constraints. This approach leads to error indicators which provide rigorous upper bounds of the element errors. A discussion of a compatibility condition for the well-posedness of the local error analysis problem is given. Two numerical examples are solved to check the compatibility of the local problems and convergence of the effectivity index both in a local and a global sense with respect to local refinements.

• Journal of applied mathematics & informatics
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• v.13 no.1_2
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• pp.323-334
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• 2003

This paper presents a goal-programming (GP) model for management decision-making for sugarcane fertilizer mix problems. Sensitivity analysis on the priority structure of the goals has been performed to obtain all possible solutions. The study uses Euclidean distance function to measure distances of all possible solutions from the ideal solution. The optimum solution is determined from the minimum distance between the ideal solution and other possible solutions of the problem. The optimum solution corresponds to the appropriate priority structure of the problem in the decision-making context. furthermore, the results obtained from sensitivity analysis on the cost of combination of fertilizers confirm the priority structure.

• Fashion & Textile Research Journal
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• v.10 no.4
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• pp.436-444
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• 2008

Recycle fashion is suggested to the suitable alternative of the environmental problem and the exhaustion of natural resources. The purpose of this study is focused on trying to comprehend between design characteristics and aesthetic values of recycle fashion design and those from fashion brands, fashion designers, and the public. For such purpose, 1553 photos of recycle fashion design which appeared in web-site, newspaper, fashion magazines between 2002 and 2007 were analyzed. Method of analysis did content analysis. The results of the research can be summarized as follows. First, design characteristics of recycle fashion were expressed by Junk Recycle Look, Vintage Recycle Look, Contemporary Recycle Look, Artisanal Recycle Look. Second, the expression methods of recycle fashion were presented reuse, reform, and regeneration. Third, aesthetic values of recycle fashion can be explained by the promotion of environment, the variableness, and the deconstruction.