• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.11-19
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• 2004

P2P network environments provide users with direct data transmission and sharing facilities and those environments can be classified into hybrid P2P network environments and pure P2P network environments according to the arbitration mechanism among the peers in the network. In hybrid P2P network environments, there exists a server that maintains index information for the data to be shared and network isolation does not occur because every peer always keeps connection to the server. In pure P2P network environments, however, each peer directly connects to another peer and gets services without server intervention, and so, network isolation can occur when the mediating peer fails to work. In this paper. we propose a scheme for each peer to keep connection to other peers continuously by maintaining IP addresses of its neighbor peers and connecting to the peers when the mediating peer fails to work. Although the P2P application that uses our proposed framework should obtain one or more IP addresses of the neighbor peers manually, after instantiation, the application can do its job while maintaining connection to the network continuously and automatically. To evaluate our proposed scheme, we measured and analyzed the time for a peer to reconnect to the network when the mediating peer fails and the network isolation occurs.

• Journal of Science Education
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• v.41 no.3
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• pp.462-479
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• 2017

This study classified the visualization's materials presented in two types of middle school science textbooks to data visualization and infographics, thereafter characteristics of infographics according to science content's domains were analyzed using an analytical framework for infopraphics. The results of this study are as follows : First, visualization materials in middle school science textbooks had more data visualization (23.2%) than infographics (76.8%). Second, there were many differences in information content's category among the science subject's domains. The relationship type of information content in the domain of energy and matter, the function type in life domain, and the location type in the earth domain were prominent. In visual representation's category, the illustration type and comparative analysis type were the most dominant in the all science domains. The horizontal type in layout category occupied the largest proportion in all science domains. Therefore, it is necessary to present the visualization materials with the infographics conveying many informations than the data visualization in middle school science textbooks. And the infographics need to be developed and distributed in various formats in each science domain.

• The Journal of the Korea Contents Association
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• v.17 no.10
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• pp.472-482
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• 2017

In this study, discrete mathematical items were classified into analytical items and mathematical items were analyzed on the basis of analytic framework items of mathematics and the past items of mathematics subject contents of the period 2011-2017 school year. First, the discrete mathematics evaluation areas and evaluation contents proposed by the Korea Institute for Curriculum and Evaluation should be evenly distributed. Second, the items of measuring metacognitive knowledge as a strategic knowledge on the use of cognitive methods should be given. Third, the ratio of the number of items in discrete mathematics to the number of that was 3.8%~6.8%, and the ratio according to the item weighting was 2.2%~6.3%. Fourth, it is analyzed that all the items are suitable for the evaluation goal and the pre-service math teachers who have faithfully implemented the curriculum have maintained the appropriate level of difficulty to solve. Finally, the content items such as the method of counting the discrete mathematics curriculum, the Recurrence Relation, the generation function, and the graph are matched with the teacher certification examination and the mathematics education curriculum of each teachers college. By these reasons, we conclude that the contribution of pre-service teachers to the motivation of learning is obtained and implications.

• Journal of KIISE:Software and Applications
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• v.34 no.9
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• pp.817-827
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• 2007

In the age of ubiquitous environment, huge number of devices and computing services are provided to users. Personalized service, which is modeled according to the character of each and every individual is of particular need. In order to provide various dynamic services according to user's movement, service unit and operating mode should be able to operate automatically with minimum user intervention. In this paper, we discuss the steps of offering approximate service based on user's request in ubiquitous environment. First, we present our simulator designed for modeling the physical resource and computing object in smart space - the infrastructure in ubiquitous. Second, intelligent agents, which we developed based on a FIPA specification compliant multi-agent framework will be discussed. These intelligent agents are developed for achieving the service goal through cooperation between distributed agents. Third, we propose an automated service discovery and composition method in heterogeneous environment using semantic message communication between agents, according to the movement by the user interacting with the service available in the smart space. Fourth, we provide personalized service through agent monitoring anytime, anywhere from user's profile information stored on handhold device. Therefore, our research provides high quality service more than general automated service operation.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.72-83
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• 2010

Group communication in a wireless mesh network is complicated due to dynamic intermediate mesh points, access control for communications between different administrative domains, and the absence of a centralized network controller. Especially, many-to-many multicasting in a dynamic mesh network can be modeled by a decentralized framework where several subgroup managers control their members independently and coordinate the inter-subgroup communication. In this study, we propose a topology-matching decentralized group key management scheme that allows service providers to update and deliver their group keys to valid members even if the members are located in other network domains. The group keys of multicast services are delivered in a distributed manner using the identity-based encryption scheme. Identity-based encryption facilitates the dynamic changes of the intermediate relaying nodes as well as the group members efficiently. The analysis result indicates that the proposed scheme has the advantages of low rekeying cost and storage overhead for a member and a data relaying node in many-to-many multicast environment. The proposed scheme is best suited to the settings of a large-scale dynamic mesh network where there is no central network controller and lots of service providers control the access to their group communications independently.

• KIPS Transactions on Software and Data Engineering
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• v.6 no.6
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• pp.309-314
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• 2017

In general, there are many difficulties in collecting, storing, and analyzing SNS (social network service) data, since those data have big data characteristics, which occurs very fast with the mixture form of structured and unstructured data. In this paper, we propose a new data visualization framework that works on Apache Storm, and it can be useful for real-time and dynamic analysis of SNS data. Apache Storm is a representative big data software platform that processes and analyzes real-time streaming data in the distributed environment. Using Storm, in this paper we collect and aggregate the real-time Twitter data and dynamically visualize the aggregated results through the tag cloud. In addition to Storm-based collection and aggregation functionalities, we also design and implement a Web interface that a user gives his/her interesting keywords and confirms the visualization result of tag cloud related to the given keywords. We finally empirically show that this study makes users be able to intuitively figure out the change of the interested subject on SNS data and the visualized results be applied to many other services such as thematic trend analysis, product recommendation, and customer needs identification.

• Management & Information Systems Review
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• v.36 no.4
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• pp.129-148
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• 2017

Conventional exhibition management information systems recommend tourist attractions that are close to the place in which an exhibition is held. Some recommended attractions by the location-based recommendation could be meaningless when nothing is related to the exhibition's topic. Our goal is to recommend attractions that are related to the content presented in the exhibition, which can be coined as content-based recommendation. Even though human exhibition curators can do this, the quality is limited to their manual task and knowledge. We propose an automatic way of discovering attractions relevant to an exhibition of interests. Language resources are incorporated to discover attractions that are more meaningful. Because a typical single machine is unable to deal with such large-scale language resources efficiently, we implemented the algorithm on top of Apache Spark, which is a well-known distributed computing framework. As a user interface prototype, a web-based system is implemented that provides users with a list of relevant attractions when users are browsing exhibition information, available at http://bike.snu.ac.kr/WARP. We carried out a case study based on Korean Tourism Organization Linked Open Data with Korean Wikipedia as a language resource. Experimental results are demonstrated to show the efficiency and effectiveness of the proposed system. The effectiveness was evaluated against well-known exhibitions. It is expected that the proposed approach will contribute to the development of both exhibition and tourist industries by motivating exhibition visitors to become active tourists.

• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.1-5
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• 2006

Lithium titanium oxide $(Li_4Ti_5O_{12})$ with spinel-framework structures as anode material for lithium-ion battery was prepared by sol-gel and high energy ball milling (HEBH) method. According to the X-ray diffraction (XRD), Particle Size Analyses(PSA) and scanning electron microscopy (SEM) analysis, uniformly distributed $Li_4Ti_5O_{12}$ particles with grain sizes of 100 nm were observed. Half cells, consisting of $Li_4Ti_5O_{12}$ as working electrode and lithium foil as both counter and reference electrodes showed the high performance of high rate discharge capacity and 173 mAh/g at 0.2C in the range of $1.0\sim2.5 V$. Furthermore, the crystalline structure of $Li_4Ti_5O_{12}$ didn't transform during the lithium intercalation and deintercalation process.

• Journal of the Korea Computer Graphics Society
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• v.13 no.4
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• pp.7-12
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• 2007

With the advent of digital cinema, more and more movies are digitally produced, distributed via digital medium such as hard drives and network, and finally projected using a digital projector. However, digital cameras capable of shotting at 2K or higher resolution for digital cinema are still very expensive and bulky, which impedes rapid transition to digital production. As a low-cost solution for acquiring high resolution digital videos, we propose a hybrid camera consisting of a low-resolution CCD for capturing videos and a high-resolution CCD for capturing still images at regular intervals. From the output of the hybrid camera, we can synthesize high-resolution videos by software as follows: for each frame, 1. find pixel correspondences from the current frame to the previous and subsequent keyframes associated with high resolution still images, 2. synthesize a high-resolution image for the current frame by copying the image blocks associated with the corresponding pixels from the high-resolution keyframe images, and 3. complete the synthesis by filling holes in the synthesized image. This framework can be extended to making NPR video effects and capturing HDR videos.

• Journal of The Korean Association For Science Education
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• v.16 no.3
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• pp.314-328
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• 1996

This study investigated the literature about science process skills' evaluation to analyse transition of evaluation objectives before and after a Scholastic Ability Test for College Entrance. In the literature survey the researcher established a 3 dimensional science assessment framework with X axis as science concept, Y axis as science process skills and Z axis as problem context. In order to analysis and compare each items the researcher selected 210 items from the 1st to the 7th trials and 138 items from the 1st to 4th Scholastic Ability Test for College Entrance and sampled 2873 science achievement test items from 10 high schools. In accordance with this taxonomy the researcher analysed and compared science process skills item forms. The following results were drawn : The items were evenly distributed in all the four areas(Earth Science, Biology, Physics and Chemistry) of the science concept domain, but they were heavily concentrated on data analysis and drawing a conclusion in science process domain. In the domain of problem context school context was the majority. In spite of distribution like this the ratio on science process skills measurement items and science achievement test items was increased after the Scholastic Ability Test for College Entrance was given. Also the ratio on item expression type was increased. Item form was almost 5 options selection type in the national level test. Although there were 4 options selection type, 5 options selection type, short answer type, essay type in school level test, rising from 33.1% to 65.5% on 5 options selection type is exhibited. This study showed that the school level item form was better various than the nation level. This point like this is the evidence for the improvement toward the science process skills test and influenced by Scholastic Ability Test for College Entrance. The ratio on the item which joined with the 3 axes had a mean of 99.3% in nation level test and mean 44.9% in school achievement test level. But the ratio in the school achievement test level increased after the Scholastic Ability Test for College Entrance was given. In view of this study we must furthermore study the item types which can evaluate valjdately science process skill's five stage each and evaluation method by the high school students' problem solving patterns and features in scientific inquiry on all science process skills elements.