Gyeongin National University of Education
Incheon, South Korea

Gyeongin National University of Education is a national institution which provides training for future public elementary school teachers in South Korea. It was founded on May 23, 1946 under the name of Gaeseong School of Education in Gyeonggi-do. In 2003, the institution changed its name from Inchon National University of Education to Gyeongin National University of Education. The university is the largest educational institute for training future elementary school teachers in Korea. The university has two campuses: Incheon campus in Gyesan-dong, Gyeyang-gu, Incheon, and Gyeonggi campus in Seoksu-dong, Manan-gu, Anyang in Gyeonggi-do. The university offers graduate and undergraduate programs, and has an attached elementary school. Wikipedia.

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Lee S.,Gyeongin National University of Education
Lecture Notes in Electrical Engineering | Year: 2017

In collaborative filtering-based recommender systems, items are recommended by consulting ratings of similar users. However, if the number of ratings to compute similarity is not sufficient, the system may produce unreliable recommendations. Since this data sparsity problem is critical in collaborative filtering, many researchers have made efforts to develop new similarity metrics taking care of this problem. Jaccard index has also been a useful tool when combined with existing similarity measures to handle data sparsity problem. This paper proposes a novel improvement of Jaccard index that reflects the frequency of ratings assigned by users as well as the number of items co-rated by users. Performance of the proposed index is evaluated through extensive experiments to find that the proposed significantly outperforms Jaccard index especially in a dense dataset and that its combination with a previous similarity measure is superior to existing measures in terms of both prediction and recommendation qualities. © Springer Nature Singapore Pte Ltd. 2017.

Park N.H.,Anyang University, South Korea | Joo K.H.,Gyeongin National University of Education
International Journal of Multimedia and Ubiquitous Engineering | Year: 2014

The conventional researches on a distributed On-Line Analytical Processing (OLAP) system have been in hardship to be adapted to real business environment. However, the recent spread of Cloud PaaS (Platform as a Services) provides new chances in the field of a distributed OLAP. OLAP query execution costs many minutes by its enormous data and OLAP query properties. On the other hand, MOLAP has fast responses. But it has a physical space limit to materialize all cells in possible combinations. Therefore, MOLAP is unsuited to analyze large data. In this paper, to provide not only flexibility and expandability of ROLAP but also the speediness of MOLAP, the cloud server architecture is proposed which shares clients' cube cache by P2P and manages central index on cube data on P2P nodes. In this paper, each node acts as not only a P2P duplicator of aggregated data cubes but also a hybrid server to process queries on sub-cubes. Also, the requests on server are confined to non-aggregated areas and multiple client nodes exchange data simultaneously and asynchronously in the proposed Cloud P2P OLAP. In particular, data are retrieved from physically or logically adjacent nodes. With time series properties, the volume of requested data is minimized and the reuse of past cache data is focused. While central managed P2P has blocked the extendibility, Cloud P2P OLAP guarantees the performance and the extendibility. While Grid OLAP should keep self-distributed system, Cloud use services as much as used by public services. Therefore, Cloud P2P OLAP solves a lot of theoretical limits of conventional distributed OLAP. © 2014 SERSC.

Hong S.-I.,Gyeongin National University of Education | Hong S.-C.,Korea University
European Journal of Physics | Year: 2014

We obtain generalized formulae for the moments of inertia of D( 2)-dimensional uniform solid spheres and spherical shells without actual integration. The derivation is based on the parallel axis theorem and the (generalized) perpendicular axis theorem along with rotational symmetry. © 2014 IOP Publishing Ltd.

Joo Y.-I.,Korea University | Hur K.,Gyeongin National University of Education
Wireless Personal Communications | Year: 2014

Merits of distributed medium access control specified by WiMedia Alliance such as distributed nature and high data rate make it a favorite candidate standard for high rate wireless personal area network. However, the current WiMedia MAC standard has not considered supporting Quality of Service (QoS) even though QoS parameters such as a range of service rates are provided to each traffic stream (TS). Therefore, we propose a fair and QoS-aware resource allocation method that provides a fair and maximized QoS for all TSs according to the current traffic load condition and differentiates SoQ among different QoS classes while guaranteeing fairness of SoQ within a QoS class in a fully distributed manner. Even in case that the traffic load varies, each device independently recognizes the changes and calculates fair and maximum allowable service rates for TSs. From the simulation results, it is proven that the proposed method achieves high capacity of TSs and fair QoS provisioning under various traffic load conditions. © 2013 Springer Science+Business Media New York.

Lee S.,Gyeongin National University of Education
Computers in Human Behavior | Year: 2015

With the growing speed of SNS accelerated recently, there are increasing concerns about the possibility of young students doing negative SNS behavior. This study tried to discover the relationship between various variables such as gender, grade, SNS usage time, motives to use SNS, degree of using advanced functions of SNS, SNS dependency, and perceptions about SNS with negative SNS behaviors among elementary and middle school students. The analyses revealed that regardless of gender and grade, the most frequently committed negative behavior is 'stealing others' private information' and the least is 'cyber bullying', while 'contacting strangers' showing the most significant increase with the age. With the seriousness of negative SNS behaviors classified into four levels, it was found that the biggest significant difference across the levels appears on illegal use of photos and videos, followed by on verbal abuse and on cyber bullying. It was also found that a significant positive correlation exists between each of the factors considered and the negative SNS behavior. Based on these findings, a regression analysis was conducted to successfully extract several factors as significant predictors of the negative SNS behaviors. Furthermore, factors distinguishing the lowest level from the highest level of the negative SNS behaviors were identified to be gender, SNS dependency, utilization of advanced SNS functions, and grade, with its accuracy rate reaching as high as 85.6%. © 2014 Elsevier Ltd. All rights reserved.

Hong S.-I.,Gyeongin National University of Education
Physics Education | Year: 2016

A comic strip about a plane mirror was used in a high school optics test, and it was perceived that a large portion of the students believed that the mirror should be larger than the object so the virtual image could be entirely visible. Inspired on the comic strip, an experimental demonstration with flat mirrors was developed, in order to readdress this topic learning. Students were encouraged to create their own investigation of the phenomenon with a simple instrumental apparatus and also suggest different experimental approaches. © 2016 IOP Publishing Ltd.

Joo K.H.,Gyeongin National University of Education
Contemporary Engineering Sciences | Year: 2014

To make use of the recent distributed OLAP environment, researches on P2P (Peer-to-Peer) OLAP with the dynamic hybrid tree (DHT) and Grid OLAP are actively proposed. In addition, OLAP query execution costs many minutes by its enormous data and OLAP query properties. To adapt OLAP systems to the cloud computing environment, P2P OLAP has problems on executing multi-dimensional range queries because of P2P properties. In this paper, the central management Cloud P2P OLAP is proposed to provide an efficient cloud computing environment which query results are able to be reused with the time-series properties by various users. The Cloud P2P OLAP is grafted onto hierarchical hybrid P2P for fast query results and multi-dimensional range query, so that the index loads are distributed and the performance is improved. © 2014 Kil Hong Joo.

Ahn S.,Gyeongin National University of Education
Proceedings - 2014 International Conference on Soft Computing and Machine Intelligence, ISCMI 2014 | Year: 2014

In this paper, I research about if the digital textbook has an effect on ability of self-directed learning that many Korean has an interest in. In order to know if the digital textbook has an effect on ability of self-directed learning, I measure the ability of self-directed of students up twice. I found that digital textbook have a effect on ability of selfdirected learning. © 2014 IEEE.

Lee S.,Gyeongin National University of Education
Lecture Notes in Electrical Engineering | Year: 2015

Similarity is a most critical index in collaborative filteringbased recommdender systems, which suggest items to their customers by consulting most similar neighbors. Current popular similarity measures may mislead the user to unwanted items in certain cases, due to their inherent properties. This study suggests a novel idea to significantly decrease such occurrences by enforcing qualifying conditions to neighbors using some simple criteria, to make consultations for their ratings. From extensive experiments, the proposed idea is found to substantially improve prediction performance of collaborative filtering based on existing similarity measures. This result is noticeable considering that such improvements are achieved by simply consulting only those neighbors satisfying the given criteria, without adopting any sophisticated similarity measure. © Springer-Verlag Berlin Heidelberg 2015.

Hong S.-I.,Gyeongin National University of Education
European Journal of Physics | Year: 2015

Due to reversibility of light rays, th.e thin-lens equation (TLE) is symmetric under the exchange of the object distance and the image distance. To measure the focal length of a converging lens, the displacement method (or Bessels method) utilizes the two different configurations of the real object, the converging lens and the real image which correspond to the two symmetric solutions of the TLE. Theoretically, we show that this method can be generalized to all possible pairs of symmetric solutions of the TLE for both converging and diverging lenses. © 2015 IOP Publishing Ltd.

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