• Journal of the Korean School Mathematics Society
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• v.17 no.4
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• pp.613-627
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• 2014

Elementary textbook ${\ll}Mathematics\;4-2{\gg}$ first published in 2014 according to the 2009 elementary mathematics curriculum has been dealing with concave polygons which were not treated in elementary textbooks according to the previous curriculum. However, n the present paper, to show that there is a need to reconsider the handling of the concave polygons, after discussions about the polygon, problems in handling the concave polygons were discussed in next two viewpoints: Does 2009 elementary mathematics curriculum allow handling of the concave polygons? are there any logical leaps in handling of the concave polygon? And the following reasons to reconsider the handling of the concave polygons are presented as conclusions. First, there was no process of publicizing the handling of the concave polygon. Second, the evidences that will justify the handling of the concave polygon can not be found in 2009 elementary mathematics curriculum. Third, there are logical leaps in the handling of the concave polygons. Fourth, there is no consistency in handling the concave polygons.

• Communications of Mathematical Education
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• v.38 no.2
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• pp.215-230
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• 2024

Congruences and symmetry are familiar concepts that can be encountered in everyday life. In order to effectively understand and acquire these concepts, the role of appropriate visual examples is important. This analysis examined various visual examples used in the process of learning the concepts of congruence and symmetry in elementary mathematics textbooks and focused on the use of convex polygons and concave polygons. As a result of the analysis, various types of polygons were used as visual examples for teaching and learning of congruence and symmetry in textbooks. The frequency of use of concave polygons was higher in the order of congruence, line symmetry, and point symmetry, and it was confirmed that it was used more frequently in the process of exploring properties than in the introduction of the concept. Based on these results, a plan to utilize concave polygons in teaching and learning of congruence and symmetry was sought.

• School Mathematics
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• v.15 no.3
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• pp.569-583
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• 2013

In Korea, the school mathematics curricula have been revised in every average 6 years by the government. From the year 2013, the new revised curricula called 2009 version are implied. The subject of elementary mathematics in this new curricula contains four issues to be improved. First, it should be allowed to call the basic figures such as box, cylinder, ball, quadrilateral, triangle and circle in verbal languages. Second, the name of the activities to define mathematical concepts should be changed from 'Yaksok', which means 'promise' in English, to a better and more honest one. Third, the concave polygons should be treated together with the convex ones. Fourth, the calculations of fractions should be weakened as much as possible for the elementary school children.

• School Mathematics
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• v.18 no.1
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• pp.1-14
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• 2016

In this paper, in order to lay the foundation for clearly determining the scope of contents handled in elementary math textbooks in Korea, what may be issues are discussed with respect to the contents handled in the current math textbooks. First of all, handling of percent point, concave polygons, and possibilities of event that will happen are discussed, the handling of them can be a issue in the sense of inconsistencies to the curriculum. Next, handling of fractions attaching units of discrete quantities and fractions attaching 'times' are discussed, the handling of them can be a issue in the sense of gap between everyday life and definition in math textbooks. Finally, handling of representing natural numbers into fractions and the positional relationship of geometrical figures are discussed, the handling of them can be a issue in the sense of a logical jump. The following three implications obtained from these discussions are presented as conclusions. First, it is necessary to establish clearly the relationship of textbooks and curriculum. Second, it is necessary to give attention to using the way to define or deal with concepts in math textbooks mixed with the way to use them in everyday life. Third, it is necessary to identify and eliminate the logical jumps in math textbooks.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_1
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• pp.483-491
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• 2013

By a development of car navigation systems and mobile or positioning technology, it increases interest in location based services, especially pedestrian navigation systems. Updating of digital maps is important because digital maps are mass data and required to short updating cycle. In this paper, we proposed change detection for different network data-sets based on areal feature matching. Prior to change detection, we defined type of updating between different network data-sets. Next, we transformed road lines into areal features(block) that are surrounded by them and calculated a shape similarity between blocks in different data-sets. Blocks that a shape similarity is more than 0.6 are selected candidate block pairs. Secondly, we detected changed-block pairs by bipartite graph clustering or properties of a concave polygon according to types of updating, and calculated Fr$\acute{e}$chet distance between segments within the block or forming it. At this time, road segments of KAIS map that Fr$\acute{e}$chet distance is more than 50 are extracted as updating road features. As a result of accuracy evaluation, a value of detection rate appears high at 0.965. We could thus identify that a proposed method is able to apply to change detection between different network data-sets.