• Journal of Convergence for Information Technology
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• v.10 no.1
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• pp.22-27
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• 2020

With the deployment of 5G infrastructure, content delivery network (CDN) will be a key role to provide explosive growing services for the independent media and YouTube which contain high-speed mobile contents. Without a local cache, the mobile backhaul and fronthaul should endure huge burden of bandwidth request for users as the increase number of direct accesses from contents providers. To deal with this issue, this paper fist presents both fronthaul solutions for CDN that use dark fibers and a passive optical network (PON). On top of that, we propose the aggregated content request specialized for PON caching and evaluate and compare its performance to legacy schemes through the simulation. The proposed PON caching scheme can reduce average access time of up to 0.5 seconds, 1/n received request packets, and save 60% of backhaul bandwidth compared to the no caching scheme. This work can be a useful reference for service providers and will be extended to further improve the hit ratio of cache in the future.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.78-87
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• 2008

Digital image find own level core media in multimedia as image restoration technology fields, which remove degradation factor for image enhancement, have been growing. Linear space-invariant image restoration algorithm often introduce ringing artifacts near sharp intensity transition areas. This paper presents a new adaptive post-filtering algorithm for reducing ringing artifact. The proposed method extracts an edge map of the image using wavelet transform Based on the edge information, ringing artifacts are detected, and removed by an adaptive bilateral filter. Experimental results show that the proposed algorithm can efficiently remove ringing artifacts with edge preservation.

• The Korean Journal of Mycology
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• v.26 no.1 s.84
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• pp.25-30
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• 1998

Present expriments were conducted to determine the possibility of cultivation of Coriolus versicolor selected among the higher fungi growing in Korea. Dried apple sawdust used in this study consisted of 31.5% C, 0.54% N, 2.41 % CaO, 0.05% $P_2O_5$, 0.48% MgO and 0.81% $K_2O$(pH 5.6). Coriolus versicolor mushrooms were cultivated on the sawdust media; apple sawdust; rice bran=80:20 in 850cc polypropylene bottles. The isolate of Coriolus versicolor used was YCV collected from an Apple farm in Youngchun district. It took 34 days to make fruitbody from spawning. The fruit bodies produced the total fresh weight 28 g in a bottles, and converted to 64% of fresh weight.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.65-74
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• 2016

Ship ad-hoc network (SANET) extends the coverage of the maritime communication among ships with the reduced cost. To fulfill the growing demands of real-time services, the SANET requires an efficient clock time synchronization algorithm which has not been carefully investigated under the ad-hoc maritime environment. This is mainly because the conventional algorithms only suggest to decrease the beacon collision probability that diminishes the clock drift among the units. However, the SANET is a very large-scale network in terms of geographic scope, e.g., with 100 km coverage. The key factor to affect the synchronization performance is the signal propagation delay, which has not being carefully considered in the existing algorithms. Therefore, it requires a robust multi-hop synchronization algorithm to support the communication among hundreds of the ships under the maritime environment. The proposed algorithm has to face and overcome several challenges, i.e., physical clock, e.g., coordinated universal time (UTC)/global positioning system (GPS) unavailable due to the atrocious weather, network link stability, and large propagation delay in the SANET. In this paper, we propose a logical clock synchronization algorithm with multi-hop function for the SANET, namely multi-hop clock synchronization for SANET (MCSS). It works in an ad-hoc manner in case of no UTC/GPS being available, and the multi-hop function makes sure the link stability of the network. For the proposed MCSS, the synchronization time reference nodes (STRNs) are efficiently selected by considering the propagation delay, and the beacon collision can be decreased by the combination of adaptive timing synchronization procedure (ATSP) with the proposed STRN selection procedure. Based on the simulation results, we finalize the multi-hop frame structure of the SANET by considering the clock synchronization, where the physical layer parameters are contrived to meet the requirements of target applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.217-225
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• 2015

Recently, as the supply of smart phone is spreading and the exhibition industries are rapidly growing, future exhibitions are evolving toward active, customized, interactive, tangible services, which can give more satisfaction to visitors. To realize this services, the indoor localization in the exhibition of visitors is very important and according to the accuracy of localization the quality of services for exhibition are also different. In this paper, state-of-the art indoor localization techniques are investigated and new localization method are proposed. To achieve this goal, future exhibition service types are proposed, which are connected with IT technology. And also, BLE(Bluetooth Low Energy) technology including comparison of specifications and representative localization technologies are analysed. Furthermore we performed comparison study and simulation between RF and VLC channels. Finally based on this, we proposed converged VLC and RF(Wi-Fi and BLE) localization technique for exhibition.

• Journal of the Korean Society for information Management
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• v.27 no.2
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• pp.61-74
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• 2010

The knowledge sharing in a knowledge management process is much affecting generation and distribution of knowledge. Especially, the knowledge distribution is being revitalized with the center of social media service like twitter and library service 2.0 in the knowledge-based IT (Information Technology) environment. The present research analyzed the structure and characteristics of a social network inside an organization that is growing like an organism through self-organization through tools for SNA (Social Network Analysis) and multiple regression analysis of independent variables such as 1) a relationship between social network's structure and knowledge sharing, 2) a relationship between structural holes and knowledge sharing influence of centrality, 3) a relationship between individual ability and knowledge sharing of information technology and work recognition.

• Journal of the Korean Institute of Landscape Architecture
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• v.42 no.6
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• pp.50-59
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• 2014

This experiment was performed in order to study the relationship between physical properties of soil and the growth characteristics of Sedum reflexum. A correlation analysis and multiple regression analysis were performed using SPSS Ver 19.0 for Windows. The multiple regression analysis results of soil physical properties and growth characteristics were as follows. The regression equation: The length=$.993-14.070^*$(soil bulk density)+$.233^*$(solid phase)+$.038^*$(liquid phase)+$.068^*$(permeability). The significance of soil bulk density and solid phase was great. The width=$2.931-33.925^*$(soil bulk density)+$.566^*$(solid phase)+$.206^*$(liquid phase)+$.027^*$(permeability). The significance of soil bulk density and solid phase was great. The wet weight and dry weight of the upper and lower and soil physical properties did not have a direct relationship.

• KIISE Transactions on Computing Practices
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• v.22 no.5
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• pp.246-251
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• 2016

Recently, the influence of SNS and online media is rapidly growing with a consequent increase in the interest of marketing using these tools. Blog marketing can increase the ripple effect and information delivery in marketing at low cost by prioritizing keyword search results of influential portal sites. However, because of the tough competition to gain top ranking of search results of specific keywords, long-term and proactive efforts are needed. Therefore, we propose a new method that recommends associated keyword groups with the possibility of higher exposure of the blog. The proposed method first collects the documents of blog including search results of target keyword, and extracts and filters keyword with higher association considering the frequency and location information of the word. Next, each associated keyword is compared to target keyword, and then associated keyword group with the possibility of higher exposure is recommended considering the information such as their association, search amount of associated keyword per month, the number of blogs including in search result, and average writhing date of blogs. The experiment result shows that the proposed method recommends keyword group with higher association.

• KIISE Transactions on Computing Practices
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• v.21 no.8
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• pp.543-548
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• 2015

Recently, volume of data has been growing dramatically along with the growth of social media and digital devices. However, the existing disk-based distributed file systems have limits to their performance of data processing or data access, due to I/O processing costs and bottlenecks. To solve this problem, the caching technique is being used to manage data in the memory. In this paper, we propose a cache management scheme to handle load balancing in a distributed memory environment. The proposed scheme distributes the data according to the memory size, n distributed environments with different memory sizes. If overloaded nodes occur, it redistributes the the access time of the caching data. In order to show the superiority of the proposed scheme, we compare it with an existing distributed cache management scheme through performance evaluation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.336-342
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• 2015

Fall-related injuries are the most common cause of accidental death for the elderly and the most frequent work-related injuries in construction sites. Due to the growing popularity of smartphones, there has been a number of research work related to the use of sensors embedded in the smartphone for fall detection. Falls can be detected easily by measuring the magnitude and direction of acceleration vectors. In general, the direction of the acceleration vector does not show the object movement, but the velocity vector directly indicates the tangential direction in which the object is moving. In this paper, we proposed a new method for computing the fall direction based on the characteristics of the velocity vector extracted from the accelerometer.