• Journal of Internet Computing and Services
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• v.15 no.6
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• pp.125-132
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• 2014

Since frequent pattern mining was proposed in order to search for hidden, useful pattern information from large-scale databases, various types of mining approaches and applications have been researched. Especially, frequent graph pattern mining was suggested to effectively deal with recent data that have been complicated continually, and a variety of efficient graph mining algorithms have been studied. Graph patterns obtained from graph databases have their own importance and characteristics different from one another according to the elements composing them and their lengths. However, traditional frequent graph pattern mining approaches have the limitations that do not consider such problems. That is, the existing methods consider only one minimum support threshold regardless of the lengths of graph patterns extracted from their mining operations and do not use any of the patterns' weight factors; therefore, a large number of actually useless graph patterns may be generated. Small graph patterns with a few vertices and edges tend to be interesting when their weighted supports are relatively high, while large ones with many elements can be useful even if their weighted supports are relatively low. For this reason, we propose a weight-based frequent graph pattern mining algorithm considering length-decreasing support constraints. Comprehensive experimental results provided in this paper show that the proposed method guarantees more outstanding performance compared to a state-of-the-art graph mining algorithm in terms of pattern generation, runtime, and memory usage.

• Journal of The Korean Association For Science Education
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• v.25 no.2
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• pp.122-132
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• 2005

Graphing abilities are critical to understand and convey information in science. And then, to what extent are secondary students in science courses able to understand line graphs? To find clues about the students' interpretation processes of the information in science-related line graphs, this study has the following research question: Is there a difference between the levels of complexity of good and poor readers as they use the thinking aloud method for studying cognitive processes? The present study was designed to provide evidence for the hypothesis that good line graph readers use a specific graph interpretation process when reading and interpreting line graphs. With the aid of the thinking aloud method we gained deeper insight into the interpretation processes of good and poor graph readers while verifying verbal statements with respect to line graphs. The high performing students tend to read much more information and more trend-related information than the low performing students. We support the assumption of differential line graph schema existing in the high performing students in conjunction with general graph schema. Also, high performing students tend to think aloud much more metacognitively than low performing students. High performing students think aloud a larger quantity of information from line graphs than low performing students, and more trend-related sentences than value-related sentences from line graphs. The differences of interpretation processes revealed between good and poor graph readers while reading and interpreting line graphs have implications for instructional practice as well as for test development and validation. Teaching students to read and interpret graphs flexibly and skillfully is a particular challenge to anyone seriously concerned with good education for students who live in an technological society.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.271-279
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• 2016

Pantograph aerodynamic noise is a major cause of noise that occurs when a train is traveling at high speeds. In this study, in order to analyze the contribution of pantograph aerodynamic noise, real train tests using HEMU-430X were carried out. In order to analyze the frequency characteristic of the noise of the pantograph in an actual vehicle, a sound field visualization has been carried out using a 144-channel microphone array at train speeds of 350 and 400km/h. As a result, it was confirmed that the low frequency noise in the 250~400Hz bandwidth provides the main contribution to the pantograph noise. And, in order to estimate the noise contribution of the pantograph, the noise level difference between cases in which the pantograph is ascending and those in which it is descending were compared in single microphone experiments. The frequency analysis in the single microphone tests showed that the bands of 315~400Hz and 1000~1250Hz are the main frequency characteristics of pantograph noise. These results show quite good agreement with those of previous studies and with results of sound field visualization.

• Journal of Educational Research in Mathematics
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• v.27 no.1
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• pp.23-49
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• 2017

This study examined two current learning models for covariational reasoning(Carlson et al.(2002), Thompson, & Carlson(2017)), applied the models to teaching two $9^{th}$ grade students, and analyzed the results according to the types of graphs(a quantitative graph or qualitative graph). Results showed that the model of Thompson and Carlson(2017) was more useful than that of Carlson et al.(2002) in figuring out the students' levels in their quantitative graphing activities. Applying Carlson et al.(2002)'s model made it possible to classify levels of the students in their qualitative graphs. The results of this study suggest that not only quantitative understanding but also qualitative understanding is important in investigating students' covariational reasoning levels. The model of Thompson and Carlson(2017) reveals more various aspects in exploring students' levels of quantitative understanding, and the model of Carlson et al.(2002) revealing more of qualitative understanding.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.975-983
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• 2010

In this paper, we introduce extended problems of Tower of Hanoi (ToH) and propose a novel visualization method to express a state space of ToH. As for the extended problems, we introduce multi-peg ToH, multi-stack ToH, and regular state ToH. The novel visualization method in this paper is a natural extension of Hanoi graph visualization. In the proposed method, we assign one Cartesian coordinate point per each disk to provide an unified visualization that the marks on a link and the changes of a state should correspond with a peg position of a disk. Compared with Hanoi graph, the generated graph by the proposed method is isomorphic if we remove links of forbidden move, which indicates that our method is a generalization of Hanoi graph and thus is more expressive. To help the understanding of the readers, we show the generated graphs by our method when the number of disks is 2 and 3.

• Journal of Korean Society of Archives and Records Management
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• v.23 no.4
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• pp.159-178
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• 2023

A digital archive is an online platform for preserving and utilizing digital records worthy of continued preservation. However, there are no shared standards for functionality, metadata, or data technical principles across digital archives in Korea. These issues create challenges in linking distributed digital records. This study proposes a common vocabulary for digital archives to enhance the interoperability of digital records and evaluates the interoperability of the digital archive built with the common vocabulary. We collect and analyze data from the digital archive on the Korean financial crisis of 1997 to construct a knowledge graph and compare its interoperability with the knowledge graph built with RiC-O. The archive and the knowledge graph underwent evaluation using the FAIR data principles evaluation framework. The constructed knowledge graph links various objects in the archive and provides contextual information to aid in understanding the archive. The results demonstrate that a knowledge graph built with a common vocabulary significantly improves the linkage, search, and interoperability of digital records compared to a traditional archive.

• Communications of Mathematical Education
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• v.36 no.4
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• pp.559-587
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• 2022

The purpose of this study is to derive implications for the development of the next curriculum and textbooks by comparing and analyzing the textbooks of the 2015 revised high school mathematics curriculum <Mathematics for Economics> and social studies curriculum <Economics>. In the <Mathematics for Economics> textbooks, economic terms and function notations should be introduced. Additionally, the use of graphs for economic-related functions is different from the use of graphs in mathematics in the <Mathematics for Economics> textbooks. For these reasons, the usage of economic terms, function notations, and function graphs covered in the <Mathematics for Economics> textbooks were compared and analyzed with the usage in the <Economics> textbooks. In the <Mathematics for Economics> textbooks, economic terms that are highly related to mathematics are defined and presented. Contrary to the conventions of mathematics and economics, the function notations in the <Mathematics for Economics> textbooks were used inconsistently because uppercase and lowercase letters were mixed in the function notations. Function graphs in the <Mathematics for Economics> textbooks had differences in the range of values represented by the variables regarding axes and scaling. The <Mathematics for Economics> textbooks did not provide a mathematical interpretation of the translation or slope. In the course of <Mathematics for Economics>, it is necessary to specify considerations for teaching and learning, and assessment in the curriculum to promote students' understanding of mathematics and economics. The descriptions in the curriculum document and textbooks of <Mathematics for Economics> should be supplemented to provide learning opportunities for mathematical interpretation of economics-related contents.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10b
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• pp.123-125
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• 1998

지리 정보 시스템이서 다중 공간 조인과 같은 많은 기하 계산을 필요로 하는 질의를 처리하기 위해서는 질의에 대한 병렬화 작업을 통해 실행 시간을 최소화 하는 것이 필수적이다. 다중 공간 조인은 정제에서 많은 시간을 소비하므로 여과와 정제를 분리하여 각각을 수행하는 것이 정제 시간을 단축하게 되고 따라서 좋은 성능을 나타낼 수 있다. 그러므로 다중 공간 조인을 병렬화 하기 위해서는 다중 공간 여과와 정제 각각에 대해 병렬 실행 계획을 세우는 것이 중요하다. 이 논문에서는 우선적으로 병렬 공간 여과를 수행하기 위한 두가지 알고리즘, 즉 blush tree을 사용한 다중 공간 여과와 pipelining을 사용한 다중 공간 여과의 병렬화를 비교한다. 그리고, 다중 공간 여과의 결과로서 생성되는 중간 결과 테이블에서 데이터의 중복에 따라 정제 성능의 저하가 발생되는데, 이를 효율적으로 제거하기 위한 두가지 그래프 생성 알고리즘을 제안하고 이를 비교한다. 그리고, 생성된 그래프에서 병렬 정제를 수행하기 위한 여러 가지 분할 알고리즘을 제안하고 이를 비교 평가한다. 이런 일련의 작업을 통해 우수한 성능의 병렬 다중 공간 조인 방법을 제안하고 성능 평가를 통해 최적의 병렬 수행 방법을 도출한다.

• The Korean Journal of Applied Statistics
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• v.19 no.3
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• pp.447-460
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• 2006

This paper develops a multiple comparison method for finding an optimal ordering of K geometric means of exponential parameters. This is based on the paired comparison experimental arrangement whose results can naturally be represented by a completely oriented graph. Introducing posterior preference probabilities and stochastic transitivity conditions to the graph, we obtain a new graphical model that yields criteria for the optimal ordering in the multiple comparison. Necessary theories involved in the method and some computational aspects are provided. Some numerical examples are given to illustrate the efficiency of the suggested method.

• 월간산업보건
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• s.84
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• pp.25-30
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• 1995