• Journal of Broadcast Engineering
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• 제17권1호
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• pp.95-107
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• 2012

Network coding was proposed to increase the achievable throughput of multicast in a network. Recently, combining network coding into user cooperation has attracted research attention. For cooperative transmission schemes with network coding, users combine their own and their partners messages by network coding. In previous works, it was shown that adaptive DF with network coding can achieve diversity gain and additional throughput gain. In this paper, to improve performance of conventional protocols and maximize advantage of using network coding, we propose a new network coding based user cooperation scheme which uses adaptively amplify-and-forward and decode-and-forward according to interuser channel status. We derive outage probability bound of proposed scheme and prove that it has full diversity order in the high SNR regime. Moreover, based on the outage bound, we compute optimal power allocation for the proposed scheme.

• The KIPS Transactions:PartA
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• 제8A권4호
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• pp.367-374
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• 2001

Recently, LINUX cluster file systems based on the storage area network (SAN) have been developed. In those systems, without using a central file server, multiple clients sharing the whole disk storage through Fibre Channel can freely access disk storage and act as file servers. Accordingly, they can offer advantages such as availability, load balancing, and scalability. In this paper, we describe metadata management schemes designed for a new SAN-based LINUX cluster file system. First, we present a new inode structure which is better than previous ones in disk block access time. Second, a new directory structure which uses extendible hashing is described. Third, we describe a novel scheme to manage free disk blocks, which is suitable for very large file systems. Finally, we present how we handle metadata journaling. Through performance evaluation, we show that our proposed schemes have better performance than previous ones.

• Journal of Advanced Navigation Technology
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• 제23권5호
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• pp.400-407
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• 2019

In this paper, the shadow detection and reconstruction method are proposed using intrinsic image, which does not change the essential characteristics under the influence of various illuminance, and multi-scale gamma correction. The shadow detection was estimated by the pixel change information between a grayscale and an intrinsic image of the color image, and the brightness of the image were adjusted by gamma correction in the shadow restoration process. Multi-scale gamma correction is performed for each channel of a color image due to the fact that the saturation can be changed by nonlinear adjustment to individual pixel values. Multi-scale gamma values are estimated based on the information of the crossed edge between shadows and non-shadowed regions in the color image, as a result, the shadows are reconstructed by correcting different region features with multi-scale gamma values. Experimental results show that the proposed method effectively reconstructs shadows in a single natural image.

• Journal of the Korea Society of Computer and Information
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• 제18권11호
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• pp.107-113
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• 2013

Mobile mobility and data reliability should be guaranteed as well as amounts of data services are essential in the era of smart media. In order to improve the reliability of high-speed data, strong channel coding and modulation techniques are required. In this paper, the structure of Turbo TCM decoder, applying high-order modulation techniques and the DPSAM method which improves performances in time-selective fading channels in the case of burst errors are suggested through the optimal decoding method and iteration decoding so as to improve bandwidth efficiency in Turbo Codes with excellent encoding gain. The proposed method in comparison with the existing method is that 3dB is superior in case that BER is $10^{-2}$ and the number of iterations is 3. In addition, the function is improved at approximately 6dB in case that BER is $10^{-3}$ and the number of iterations is 7. The proposed method requires additional bandwidth; however, the bandwidth loss can be overcome through Turbo TCM technology on the additional bit rate from the bandwidth loss.

• The Journal of Advanced Prosthodontics
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• 제11권2호
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• pp.105-111
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• 2019

PURPOSE. Limited data is available regarding the differences for possible microleakage problems and fitting accuracy of zirconia versus titanium abutments with various connection designs. The purpose of this in vitro study was to investigate the effect of connection design and abutment material on the sealing capability and fitting accuracy of abutments. MATERIALS AND METHODS. A total of 42 abutments with different connection designs [internal conical (IC), internal tri-channel (IT), and external hexagonal (EH)] and abutment materials [titanium (Ti) and zirconia (Zr)] were evaluated. The inner parts of implants were inoculated with $0.7{\mu}L$ of polymicrobial culture (P. gingivalis, T. forsythia, T. denticola and F. nucleatum) and connected with their respective abutments under sterile conditions. The penetration of bacteria into the surrounding media was assessed by the visual evaluation of turbidity at each time point and the number of colony forming units (CFUs) was counted. The marginal gap at the implant- abutment interface (IAI) was measured by scanning electron microscope. The data sets were statistically analyzed using Kruskal-Wallis followed by Mann-Whitney U tests with the Bonferroni-Holm correction (${\alpha}=.05$). RESULTS. Statistically significant difference was found among the groups based on the results of leaked colonies (P<.05). The EH-Ti group characterized by an external hexagonal connection were less resistant to bacterial leakage than the groups EH-Zr, IT-Zr, IT-Ti, IC-Zr, and IC-Ti (P<.05). The marginal misfit (in ${\mu}m$) of the groups were in the range of 2.7-4.0 (IC-Zr), 1.8-5.3 (IC-Ti), 6.5-17.1 (IT-Zr), 5.4-12.0 (IT-Ti), 16.8-22.7 (EH-Zr), and 10.3-15.4 (EH-Ti). CONCLUSION. The sealing capability and marginal fit of abutments were affected by the type of abutment material and connection design.

• Journal of Broadcast Engineering
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• 제26권2호
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• pp.132-142
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• 2021

The purpose of this study is to present an effective methodology that can measure heart rate, heart rate variability, oxygen saturation, respiration rate, mental stress level, and blood pressure using mobile front camera that can be accessed most in real life. Face recognition was performed in real-time using Blaze Face to acquire facial image data, and the forehead was designated as ROI (Region Of Interest) using feature points of the eyes, nose, and mouth, and ears. Representative values for each channel of the ROI were generated and aligned on the time axis to measure vital signs. The vital signs measurement method was based on Fourier transform, and noise was removed and filtered according to the desired vital signs to increase the accuracy of the measurement. To verify the results, vital signs measured using facial image data were compared with pulse oximeter contact sensor, and TI non-contact sensor. As a result of this work, the possibility of extracting a total of six vital signs (heart rate, heart rate variability, oxygen saturation, respiratory rate, stress, and blood pressure) was confirmed through facial images.

• The Korean Journal of Franchise Management
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• 제11권2호
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• pp.23-39
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• 2020

Purpose: Social Network Sites(SNS) have been grown up as a public communication channel consumer frequently participate in. Most of food service brands are utilizing social media for advertising recently. As a result of SNS marketing, food service brands anticipate positive outputs from SNS engagement and consumer brand engagement so that we need to verify structural relationship among SNS characteristics, SNS engagement and consumer brand engagement. Research design, data, and methodology: This study identifies that SNS characteristics have effects on SNS engagement and examines relationship between SNS engagement and behavioral engagement. We conceptualize SNS characteristics as information quality, hedonic level and interaction. Furthermore, SNS engagement is composed of SNS participation, positive word of mouth(WOM). In order to verify the purposes of this research, research model and hypotheses were developed. All constructs were measured with multiple items developed and tested in the previous studies. Sample data were collected from 433 online survey panels and analyzed by using SmartPLS 3.2.9. Result: The findings of this research are as follows. First, information quality is positively related with SNS participation. Hedonic level and interaction have impacts on SNS participation and positive WOM respectively. Second, SNS participation has positive effects on positive WOM. Third, both SNS participation and WOM influence behavioral engagement respectively. Conclusions: The implications demonstrate that SNS characteristics such as information quality and hedonic level and interaction exert effects for consumer to participate in SNS brand page. Meanwhile, hedonic level and interaction influence on positive WOM but information quality doesn't. SNS participation and positive WOM affect consumer to engage in specific brand behaviorally as well. Therefore, food service brand marketer is required to manage SNS information quality and hedonic level and interaction among members to encourage SNS participation and positive WOM. As SNS participation and positive WOM increases behavioral engagement of consumer, marketer needs to incentivize SNS participation and look after situation of positive WOM and respond swiftly.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제23권11호
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• pp.1321-1329
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• 2019

With the development of social information networks, the marketing methods are also changing in various ways. Unlike successful marketing methods based on existing celebrities and financial support, Influencer-based marketing is a big trend and very famous. In this paper, we first extract influencer features from more than 54 YouTube channels using the multi-dimensional qualitative analysis based on the meta information and comment data analysis of YouTube, model representative themes to maximize a personalized video satisfaction. Plus, the purpose of this study is to provide supplementary means for the successful promotion and marketing by creating and distributing videos of new items by referring to the existing Influencer features. For that we assume all comments of various videos for each channel as each document, TF-IDF (Term Frequency and Inverse Document Frequency) and LDA (Latent Dirichlet Allocation) algorithms are applied to maximize performance of the proposed scheme. Based on the performance evaluation, we proved the proposed scheme is better than other schemes.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제25권8호
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• pp.1088-1094
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• 2021

This paper proposes a partial BMA (Broadcasting Multiple Access) network structure and D-ARP (Distributed Address Resolution Protocol) method in order to support full mesh routing function in the DAMA (Demand Assigned Multiple Access)-based MF-TDMA (Multi Frequency-Time Division Multiple Access) satellite system. The partial BMA network enables legacy router devices and routing protocols to be adopted in the satellite communication system, and decreases the amount of routing protocol overhead. In addition, we introduce the D-ARP method that help a spoke satellite node acquiring the MAC (Media Access Control) address from remote satellite nodes in none BMA satellite network. The D-ARP method provides the MAC address of remote nodes to each other nodes through the broadcasting-enabled satellite channel. And we lastly evaluate and analysis the network performance of the proposed approach.

• The Journal of Information Systems
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• 제31권1호
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• pp.147-173
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• 2022

Purpose As the use of social network services has become common, it has become possible to freely communicate and establish relationships with other people anytime, anywhere for communication and information sharing. Influencers who have a strong influence on consumers' perceptions and attitudes through their own opinions and stories have appeared on various social media channels such as YouTube. Recently, companies utilize influencers with a large number of followers to check interactions with customers to understand customer attitudes and opinions about products in real time. Start-ups with insufficient resources need to quickly examine customer responses to reduce the probability of failure after product planning. The Lean process of creating an MVP and quickly confirming and learning the market response should be repeated over and over again. Findings In this paper, we try to suggest that the YouTube platform can play a sufficient role as a customer experiment space through examples. The case company is a company that has successfully commercialized products by continuously interacting with customers through the YouTube platform for the first four months of its founding. This paper is expected to be helpful in the experimental process for prospective founders and early founders to examine customer responses to reduce the probability of market failure before commercialization. Design/methodology/approach This paper analyzed the YouTube channel data of case companies based on the netnography methodology and presented the contents of the lean process management carried out in the experimental stage and the post-production stage through interview research.