• Journal of KIISE:Information Networking
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• v.32 no.5
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• pp.574-582
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• 2005

Localization in wireless sensor networks is essential to important network functions such as event detection, geographic routing, and information tracking. Localization is to determine the locations of nodes when node connectivities are given. In this paper, centroid approach known as a distributed algorithm is extended to a centralized algorithm. The centralized algorithm has the advantage of simplicity. but does not have the disadvantage that each unknown node should be in transmission ranges of three fixed nodes at least. The algorithm shows that localization can be formulated to a linear system of equations. We mathematically show that the linear system have a unique solution. The unique solution indicates the locations of unknown nodes are capable of being uniquely determined.

• Education of Primary School Mathematics
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• v.19 no.4
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• pp.277-289
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• 2016

Fraction is one of the concepts which are difficult to elementary school students. So, many researches about fraction were performed in mathematics education research. In special, fraction has so many subordinative concepts-proper fraction, improper fraction, mixed number. We have to concentrate on the conceptual understanding in teaching of fraction. In this case, a mixed number and improper fraction are concepts which can convert respectively. And there are methods that a mixed number and improper fraction can be converted. So, it's needed to analyze the converting methods in textbooks for getting the implication of teaching in this areas. In this study, I analyzed the Korean and foreign's textbooks. I certified the methods-using addition expression, using part-whole model in the textbooks. For the conceptual understanding, I suggested to use the fusion of the various part-whole fraction models and addition expression more than the algorithm in converting between a mixed number and improper fraction. It's reason that the use of models in converting between a mixed number and improper fraction is important for the relational understanding.

• School Mathematics
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• v.18 no.3
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• pp.625-645
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• 2016

This study clarified the big ideas related to teaching addition and subtraction of fractions with different denominators based on quantitative reasoning with unit and recursive partitioning. An analysis of this study urged us to re-consider the content related to the addition and subtraction of fraction. As such, this study analyzed textbooks and teachers' manuals developed from the fourth national mathematics curriculum to the most recent 2009 curriculum. In addition and subtraction of fractions with different denominators, it must be emphasized the followings: three-levels unit structure, fixed whole unit, necessity of common measure and recursive partitioning. An analysis of this study showed that textbooks and teachers' manuals dealt with the fact of maintaining a fixed whole unit only as being implicit. The textbooks described the reason why we need to create a common denominator in connection with the addition of similar fractions. The textbooks displayed a common denominator numerically rather than using a recursive partitioning method. Given this, it is difficult for students to connect the models and algorithms. Building on these results, this study is expected to suggest specific implications which may be taken into account in developing new instructional materials in process.

• Journal of Educational Research in Mathematics
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• v.22 no.4
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• pp.477-494
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• 2012

This study is to review the content organization and developmental ways of the unit on the mixed calculations and explore the alternatives on the basis of students' responsive examples and error patterns with relation to the mixed calculations, mnemonics of PEMDAS and historical context with relation to the order of operations. Then I analyzed the textbook and manual for teachers of the unit of mixed calculations of fourth grade and improvement about teaching the mixed calculations. First, I pointed out illogical connection between practical problem and rules of order of operations. Second, I suggested constructing a textbook by considering conventional character of order of operations. Third, I pointed out the importance of structural understanding of an expression of mixed calculations and various strategies with relation to teaching and learning. This study is suggestive for textbook development of the mixed calculations.

• Journal of Educational Research in Mathematics
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• v.17 no.2
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• pp.111-125
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• 2007

In this article, we introduce an example about 'computers and mathematics education' and discuss its educational meaning. First, we survey two microworlds of Logo and DGS, which are two different representation systems for geometric phenomena. And we propose needs of connecting two microworlds with common perspective. And we suggest a mediation model that connects two representations in a microworld. Using this mediation model(Circle model), we construct a circle, a ellipse, and a cardioid with two different representations. It is important that the mediation model makes it possible that we translate descriptions from one representation into the other, and guess perimeters of planar curves. We also discuss roles and mathematical implications of this mediation model by error case in calculating perimeters of ellipses.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.144-149
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• 1999

발전소의 안정적 운영을 위한 발전소 운전원의 훈련에는 기준 발전소 주제어실의 각종 패널라 계기들을 기계적으로 동일하게 만들고 정확한 수학적 모델로 발전소 시스템을 모사한 전 범위 시뮬레이터가 주로 이용된다. 전범위 시뮬레이터는 실제 현장을 모사하는 시뮬레이션 컴퓨터와 주제어실의 패널 계기들을 연결시켜 주는 I/O 인터페이스 시스템을 필요로 한다. 기 설치 운용되고 있는 선행 호기 시뮬레이터를 보면 주 공급업체는 모델링 기술을 가지고 있는 업체가 맡고, I/O 인터페이스 시스템은 I/O 모듈과 네트웍 프로토콜까지 협력업체나 자사의 독자 모델을 취하고 있다. 그러나 I/O 모듈의 제작사가 대부분 외국의 특정 업체여서 예비품의 입수가 용이하지 않아 유지보수가 어렵고, 많은 비용을 지불해야 하는 단점을 가지고 있다. 따라서, 유지보수 용이성과 경제적 측면에서 특정 벤더 규격에 종속되지 않고 일반적인 표준을 따르는 off-the-shelf 제품을 이용하는 발전소 시뮬레이터 I/O 인터페이스 시스템의 구축이 요구된다. 본 논문에서는 화력 발전소와 원자력 발전소를 대상으로 시뮬레이터 I/O 인터페이스 시스템의 요구사양을 소개하고, 네트웍에서 시스템 아키텍처까지 개방형 인터페이스 방식의 상용 제품을 채용하는 PC기반 시뮬레이터 I/O 인터페이스 시스템 구축방안을 제시하고, 성능 예측을 통해 제안한 시스템 구축 방안의 효용성을 보인다.

• Journal of Educational Research in Mathematics
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• v.16 no.4
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• pp.367-386
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• 2006

There are two strands for considering tile relationships between education and technology. One is the viewpoint of 'learning from computers' and the other is that of 'learning with computers'. In this paper, we call mathematics education with computers as 'computers and mathematics education' and this computer environments as microworlds. In this paper, we first suggest theoretical backgrounds ai constructionism, mathematization, and computer interaction. These theoretical backgrounds are related to students, school mathematics and computers, relatively As specific strategies to design a microworld, we consider a physical construction, fuctiionization, and internet interaction. Next we survey the different microworlds such as Logo and Dynamic Geometry System(DGS), and reform each microworlds for mathematical level-up of representation. First, we introduce the concept of action letters and its manipulation for representing turtle actions and recursive patterns in turtle microworld. Also we introduce another algebraic representation for representing DGS relation and consider educational moaning in dynamic geometry microworld. We design an integrating microworld between Logo and DGS. First, we design a same command system and we get together in a microworld. Second, these microworlds interact each other and collaborate to construct and manipulate new objects such as tiles and folding nets.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.29-41
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• 2007

Structural design, like other complex decision problems, involves many trade-offs among competing criteria. Although mathematical programming models are becoming increasingly realistic, they often have design limitations, that is, there are often relevant issues that cannot be easily captured. From the understanding of these limitations, a decision-support system is developed that can generate some useful alternatives as well as a single optimum value in the optimization of steel frame structures. The alternatives produced using this system are "good" with respect to modeled objectives, and yet are "different," and are often better, with respect to interesting objectives not present in the model. In this study, we created a decision-support system for designing the most cost-effective moment-resisting steel frame structures for resisting lateral loads without compromising overall stability. The proposed approach considers the cost of steel products and the cost of connections within the design process. This system makes use of an optimization formulation, which was modified to generate alternatives of optimum value, which is the result of the trade-off between the number of moment connections and total cost. This trade-off was achieved by reducing the number of moment connections and rearranging them, using the combination of analysis based on the LRFD code and optimization scheme based on genetic algorithms. To evaluate the usefulness of this system, the alternatives were examined with respect to various design aspects.

• Journal of Educational Research in Mathematics
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• v.26 no.2
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• pp.247-267
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• 2016

It has been pointed out that the mathematics textbooks according to 2009 revised national curriculum cause difficulty not by mathematical knowledge but concomitantly by words and sentences for the first graders who just started learning Korean alphabets. This study focused on the suitability of words and sentences in mathematics textbooks for elementary first grade. We analyzed the degree of difficulty and familiarity in terms of words and the structure, length, and expression in terms of sentences. The results show some causes that lead the first graders to the difficulty. In more detail, we found 108 difficult words and 6 unfamiliar words for the first graders. And it is noticed that the textbooks contain 37 compound sentences, 727 complex sentences, and 38 compound-complex sentences. They also contain 237 long sentences that are composed of 9 words or more, 168 sentences that assign two activities or more, and 52 sentences that contain three nouns or adjectives or more successively. Based on these results and discussions, we suggested several implications for writing mathematics textbooks for the lower grades in elementary school.

• Journal of the Korean School Mathematics Society
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• v.18 no.4
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• pp.411-429
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• 2015

In this study we investigated the effects of using GSP in solving geometric problems. Especially we focused the effects of GSP in leveled students' connection of geometry and algebra. High leveled students prefer to use algebraic formula to solve geometric problems. But when they did not know the geometric meaning of their algebraic formula, they could recognize the meaning after using GSP. Middle and low leveled students usually used GSP to obtain hints to solve the problems. For the low leveled students GSP was usually used to understand the meaning of the problem, but it did not make them solve the problem.