• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.4
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• pp.369-374
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• 2015

In order to efficiently optimize the problem involving complex computer codes or computationally expensive simulation, surrogate models are widely used. Because their accuracy significantly depends on sample points, many experimental designs have been proposed. One approach is the sequential design of experiments that consider existing information of responses. In earlier research, the correlation coefficients of the kriging surrogate model are introduced as weight parameters to define the scaled distance between sample points. However, if existing information is incorrect or lacking, new sample points can be misleading. Thus, our goal in this paper is to propose a weight function derived from correlation coefficients to generate new points robustly. To verify the performance of the proposed method, several existing sequential design methods are compared for use as mathematical examples.

• Journal of Elementary Mathematics Education in Korea
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• v.18 no.2
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• pp.297-318
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• 2014

This study is designed for helping elementary school teachers have an insight into making or choosing questions of descriptive assessment in mathematics. For this, it is analyzed 30 descriptive mathematical questions produced by Gyeonggi Provincial Office of Education in 2011 and 2012 and 3rd to 6th grade students' papers marked by their teachers in charge from 2 elementary schools located in Gyeonggi Province. The main focus of analysis is the errors of students' answers and teachers' marking not from their own mistakes but from the defects of questions themselves. As a result of analysis, 7 cases of problematic situations are induced and they are reorganized into 3 categories as follow: i) case of not performing unique purpose of descriptive assessment, ii) case of inducing the problem of fairness of grading, iii) case of leading students erroneous direction.

• Journal of Educational Research in Mathematics
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• v.17 no.3
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• pp.253-270
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• 2007

by A.C. Clairaut was written based on the historico-genetic principle such as his . In this paper, by analyzing his we can induce six principles that Clairaut adopted to teach algebra: necessity and curiosity as a motive of studying algebra, harmony of discovery and proof, complementarity of generalization and specialization, connection of knowledge to be learned with already known facts, semantic approaches to procedural knowledge of mathematics, reversible approach. These can be considered as strategies for teaching algebra accorded with beginner's mind. Some of them correspond with characteristics of , but the others are unique in the domain of algebra. And by comparing Clairaut's approaches with school algebra, we discuss about some mathematical subjects: setting equations in relation to problem situations, operations and signs of letters, rule of signs in multiplication, solving quadratic equations, and general relationship between roots and coefficients of equations.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.1921-1929
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• 2015

The smart substation is the heart of a transmission system, which is particularly emphasized as the most significant composition of smart grids in China. In order to assess the functionality performance of substation technologies, this paper presents methods used to identify the most promising solutions for smart substation design and to evaluate the technical levels of available technologies. The multi-index optimization model is presented to address the issue of smart substation planning. A mathematical model of the planning decision problem is established with multiple objectives consisting of economic, reliability, and green key indices, and many kinds of concerns including physical and environmentally friendly operations are formulated as a set of constraints. With respect to the assessment of the technical level regarding integration of advanced technologies into a substation, a modified grey whitenization weight function is adopted to structure a novel grey clustering method. The proposed grey clustering approach is used to overcome the difficulty of insufficient quantitative assessment capacity for traditional methods. The evaluation of technical effects provides the classification definition for the development phase and the maturity level of the smart substation. The effectiveness of the proposed approaches in planning decision-making and evaluation of construction efforts is demonstrated with case studies involving the actual smart substation projects of Wenchongkou substation in China Southern Power Grid (CSG) and Mengzi substation in State Grid Corporation of China (SGCC).

• Industrial Engineering and Management Systems
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• v.7 no.3
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• pp.189-196
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• 2008

This paper proposes a way of designing of a global logistics system for "the international cooperative global complementary production system" (ICGCPS) constructed in ASEAN region. ICGCPS is a global production system with several production bases located in a number of countries. In order to assemble the final products and sell them in the domestic market, each production base produces only special kinds of components and parts with the total demand required all the participating countries, and supplies them to the other production bases each other. In the ICGCPS, there are a number of important decision-making problems such as identifying which countries are suitable to produce specified components and parts, and deciding how to transport components and parts between the production bases. In the initial period of this system, each production base focused on its domestic market so that the final products it produced were sold only in the country where the base was located. Recently, some production bases have expanded sales to overseas markets. Taking this fact into account, we propose a production and transportation planning model in this paper that takes into account the export quantity of the final products, formulating it into a mathematical programming problem. Using this, we propose a way for managing the supply chain processes of the ICGCPS in order to improve performance measurements such as the total lead-time, the inventory quantity at the depot and the average rate of loading. A numerical example is presented to clarify the procedure proposed in this paper.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.749-758
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• 2017

In structural mechanics, traditional analyses methods usually employ matrix operations for obtaining displacement and internal forces of the structure under the external effects, such as distributed loads, earthquake or wind excitations, and temperature changing inter alia. These matrices are derived from the well-known principle of mechanics called minimum potential energy. According to this principle, a system can be in the equilibrium state only in case when the total potential energy of system is minimum. A close examination of the expression of the well-known equilibrium condition for linear problems, $P=K{\Delta}$, where P is the load vector, K is the stiffness matrix and ${\Delta}$ is the displacement vector, it is seen that, basically this principle searches the displacement set (or deformed shape) for a system that minimizes the total potential energy of it. Instead of using mathematical operations used in the conventional methods, with a different formulation, meta-heuristic algorithms can also be used for solving this minimization problem by defining total potential energy as objective function and displacements as design variables. Based on this idea the technique called Total Potential Optimization using Meta-heuristic Algorithms (TPO/MA) is proposed. The method has been successfully applied for linear and non-linear analyses of trusses and truss-like structures, and the results have shown that the approach is much more successful than conventional methods, especially for analyses of non-linear systems. In this study, the application of TPO/MA, with Harmony Search as the selected meta-heuristic algorithm, to cables net system is presented. The results have shown that the method is robust, powerful and accurate.

• Journal of Korea Multimedia Society
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• v.12 no.1
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• pp.31-40
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• 2009

Call centers have become the prevalent contact points between companies and their customers. By virtue of recent advances in communication technology, the number and size of call centers have grown dramatically. As a large portion of the operating costs are related to the labor costs, efficient design and workforce staffing are crucial for the economic success of call centers. Therefore it is very important to determine the adequate number of agents. In this context, the workforce staffing level can be modeled as mathematical optimization problem using queueing theory. In this paper, we deal with an approximate analysis of an N-design call center with two finite queues and two types of reneging customers by using the state decomposition method. We also represent some numerical examples and show the impact of the system parameters on the performance measures of the call center.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.04a
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• pp.217-224
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• 2004

Open-coast storm surge computations are of value in planning and constructing engineering works, especially in coastal regions. Prediction of typhoon surge elevations is based primarily on the use of a numerical model in this study, since it is difficult to study these events in real time or with use of physical models. A simple quasi-two dimensional numerical model for storm surge is considered. In order to understand the model's underlying assumptions, range of validity, and application, we discussed several aspects of typhoons and the physical factors governing storm generation processes. We also followed the basic governing equation, together with the assumption generally taken in their development, to see the principle characteristics of the model from a physical as well as a mathematical point of view. The equations consistent with the model described here are reduced forms of the basic equations and their effects on the resulting numerical scheme are discussed. Finally we applied the model discussed above to a storm surge problem at Masan Bay, the south coast of Korea Effects of astronomical tide, initial water level, and atmospheric pressure setup are considered. We then analyzed the flood at the coastal city and proposed a reasonable way of flood control.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.3
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• pp.689-696
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• 2015

In this study, a learning system based on smart learning is proposed so that students with learning disabilities can learn the effective use of meta-cognitive to solve problems arising during the learning process. The features of the proposed system are as follow. First, it is possible to achieve students' individualized learning by use of smart devices and smart education system. Second, it is possible to provide the constant repetition learning for students. Third, students can improve their achievement using the proposed app. The proposed smart education system using meta-cognition was applied to some learning disabilities students. The following results were obtained. First, the disabled students could have an interest in learning math and improve confidence. Second, the student's mathematical problem-solving skills have improved. Third, students' individualized and self-directed learning was achieved.

• The Korean Journal of Applied Statistics
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• v.24 no.5
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• pp.769-789
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• 2011

The life table is a statistical model for life expectancy and reflects mortality experiences exposed to a particular group of people. The following three issues are prerequisite for constructing the life table : a selection of how to estimate the death probability from observed death rates, a graduation method to smooth irregularity of the death probabilities, and an extension method of the death probabilities for oldest-old ages. To construct the life table that is fittest to Korean mortality experiences, we examine five estimation methods such as Chiang's and Greville's for the death probability, three graduation techniques including Beer's and Greville's formulae, and twelve mathematical functions for the extension of death probabilities for oldest-old ages. We also propose a method to resolve the cross-over problem arising from construction the life table.