• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1786-1792
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• 2015

Random linear network coding (RLNC) is widely employed to enhance the reliability of wireless multicast. In RLNC encoding/decoding, Galois Filed (GF) arithmetic is typically used since all the operations can be performed with symbols of finite bits. Considering the architecture of commercial computers, the complexity of arithmetic operations is constant regardless of the dimension of GF m, if m is smaller than 32 and pre-calculated tables are used for multiplication/division. Based on this, we show that the complexity of RLNC inversely proportional to m. Considering additional overheads, i.e., the increase of header length and memory usage, we determine the practical value of m. We implement RLNC in a commercial computer and evaluate the codec throughput with respect to the type of the tables for multiplication/division and the number of original packets to encode with each other.

• School Mathematics
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• v.8 no.2
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• pp.139-160
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• 2006

It seems that North Korea has been trying to reorganize its educational system as well as its economic system on a large scale since July 1, 2002. There has been a decrease in quantity of math textbooks by about 30% decrease. Until the 1990's, geometry and algebra had been kept apart from each other in North Korea, but they are put together now. Moreover many changes have been made in both contents and methods of teaching. For example, an area model is used in North Korea to teach operation of fraction, which makes the learning period shorter. This idea will provide us with many implication when we need to ready for decreasing the quantities in the future. Moreover teaching methods of division algorithms need to be reconsidered since the visual algorithm of division could help save the thinking in problem solving.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.12
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• pp.1904-1913
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• 2021

With the proliferation of smart phones and the development of IoT technology, it has become possible to collect personal data for public purposes. However, users are afraid of voluntarily providing their private data due to privacy issues. To remedy this problem, mainly three techniques have been studied: data disturbance, traditional encryption, and homomorphic encryption. In this work, we perform simulations to compare them in terms of accuracy, message length, and computation delay. Experiment results show that the data disturbance method is fast and inaccurate while the traditional encryption method is accurate and slow. Similar to traditional encryption algorithms, the homomorphic encryption algorithm is relatively effective in privacy preserving because it allows computing encrypted data without decryption, but it requires high computation costs as well. However, its main cost, arithmetic operations, can be processed in parallel. Also, data analysis using the homomorphic encryption needs to do decryption only once at any number of data.

• School Mathematics
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• v.15 no.2
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• pp.289-314
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• 2013

Achievement profile by attribute in Korean students' mathematics was analyzed by applying cognitive diagnostic model, which is the newest measurement theory, to 2011 NAEA(National Assessment of Educational Assessment) results. The results are as follows. As the level of school is higher from 6th grade, 9th grade to 11th grade, the percentage of students mastering cognitive attribute 9(expressions using picture, table, graph, formula, symbol, writing, etc) drastically declined from 78%, 35% to 26%. It is necessary to have learning strategies to reinforce their abilities of expressing table, graph, etc. that higher graders in mathematics are more vulnerable to. Next, the property of mastering cognitive attributes according to gender, multi-cultural family was analyzed. In terms of mathematics, the percentage of girls mastering most of the attribute generally is higher than that of boys from 6th grade to 9th grade, however, boys show higher mastery in almost attributes than girls in the 11th grade. Compared to boys, the part where girls have the most trouble is attribute 9 in mathematics(expressions using picture, table, graph, formula, symbol, writing, etc). As international marriage, influx of foreign workers, etc. increase, the number of students from Korea's multi-cultural families is expected to be higher, therefore, identifying the characteristics of their educational achievement is significant in reinforcing Korea's basic achievement. In mathematics, gap of mastery level of attributes between multi-cultural group and ordinary group is more severe in higher grade and the type of multi-cultural group that needs supports for improving achievement most urgently changed in 6th grade, 9th grade and 11th grade respectively. In the 6th and 11th grade, migrant students from North Korea show the lowest level of mastering attributes, however, in the 9th grade, the mastery rate of immigrant students is lowest. Therefore, there is an implication that supporting plans for improving achievement of students from multi-cultural family should establish other strategies based on the characteristics of school level.

• Journal of Elementary Mathematics Education in Korea
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• v.14 no.1
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• pp.43-64
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• 2010

This study aimed to foster the learning abilities of mathematics, that is, along with the formation of a sure mathematical concept, extending the powers of doing mathematics, and bringing the creativities for 3rd grade elementary school children. In order to achieve these objects, we have executed mathematical classes for two consecutive hours of 16 times using the teaching model of [Learning contents in textbook]$\rightarrow$[The first problem Posing]$\rightarrow$[Problem solving to childrens' posing some problems]$\rightarrow$[Advanced problem posing] to 3rd grade school children during the first semester of 2009. In this paper, we analyzed problems that are made by children focusing on the four fundamental rules +, -, ${\times}$, $\div$ of arithmetic, with the view points of problem's completion, fluencies, flexibilities, buildings of concept, originalities and using materials. As a result of the comparative analysis of the first problems and advanced problems made by the children, the first problems were revealed to be rather better in of problem's completion and fluencies. And the flexibilities were improved in the division and multiplication classes carried on. Setting up the experimental and comparative class, we compared to the scholastic achievement of two classes for the beginning and end in the first semester. In the result, the former was improved in the scholastic achievement more than the latter.