• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.1
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• pp.85-92
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• 2000

Channel management is critical in designing a cellular mobile system that offers high capacity and high quality. In this paper, an integrated channel management scheme is proposed, which consists of a dynamic channel allocation scheme and an admission control scheme. The dynamic channel allocation scheme allocates a call request the channel which minimizes the impact on its interfering cell, and consists of two types of channel allocation strategies : nominal channel allocation strategy and non-nominal channel allocation strategy. The admission control scheme named the variable cutoff priority scheme reserves some frequency channels for handoff cells in each cell the number of which varies according to the blocking probability of handoff class in that cell. Computationl tests are performed to evaluate the performance of the proposed scheme in terms of overall blocking probability, defined by the weighted value of the blocking probabilities of new calls and handoff calls. The results show that the proposed scheme yields better performance than other compared schemes.

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.78-85
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• 2006

Selection of flow channel in the separation plate of PEMFC is very important parameter to improve its performance and reduce parasite loss. Flow patterns in the channel have great influence on the transport of hydrogen and air and removal of water generated from electrochemical reaction in diffusion layer. In this study. fluid flow in flow channel with parallel and interdigitated patterns are simulated three dimensionally on full flow domain including anode and cathode channel together. The numerical results show that the fuel cell with interdigitated flow channel represents better performance than that with parallel flow channel due to its strong convective transport across the gas diffusion layer. But the pressure drop in parallel flow channel is much more than that in interdigitated flow channel. And effects of temperature and stoichiometric number on performance can be calculated and analyzed as well. Nomenclature.

• ETRI Journal
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• v.38 no.5
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• pp.952-961
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• 2016

In this paper, we study a spectrum sharing network (SSN) where a spectrum sharing device (SSD) coexists with multiple wireless communication systems (WCSs) in the same channel. The SSD can operate with either a duty cycle (DC) channel access mechanism or a listen-before-talk (LBT) channel access mechanism, whereas WCSs operate with an LBT mechanism. An opportunistic channel selection scheme for the SSD in the SSN is first proposed to minimize the outage probability. The optimal data transmission time for the DC-based SSD is derived to further improve the outage probability. We also derive the exact and closed-form outage probability of the proposed channel selection in the SSN by assuming that the number of WCSs operating in each channel is uniformly distributed. The simulation results show that the proposed channel selection scheme outperforms other channel selection schemes. It was also observed that a DC-based SSD with an optimal data transmission time provides a better outage performance than an LBT-based SSD. As the number of available channels increases, the channel selection scheme plays an important role in minimizing the outage probability of the SSNs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.911-923
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• 2014

Ad hoc cognitive radio wireless sensor networks allow secondary wireless sensor nodes to recognize spectrum opportunities and transmit data. Most existing protocols proposed for ad hoc cognitive radio wireless sensor networks require a dedicated common control channel. Allocating one channel just for control packet exchange is a waste of resources for channel-constrained networks. There are very few protocols that do not rely on a common control channel and that exchange channel-negotiation control packets during a pre-allocated time on the data channels. This, however, can require a substantial amount of time to access the channel when an incumbent is present on the channel, where the nodes are intended to negotiate for the data channel. This study examined channel access delay on cognitive radio wireless sensor networks that have no dedicated common control channel.

• Journal of Distribution Research
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• v.13 no.3
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• pp.27-54
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• 2008

This study explored the relationship between information search and purchasing behavior across in-home shopping channels to give multi-channel retailer an implication of multichannel customer management. We analyzed the relationship between consumer's information search and purchase behavior (choice, frequency, and expenditure) with a view to channel lock-in and cross-channel synergy. This study was carried out using survey data about in-home shopping behavior of housewives. Results of the study showed that (1) there was channel lock-in between information search and purchase behavior across in-home shopping channels, (2) catalog channel and the Internet channel were a alternative channels of TV home shopping channel and (3) catalog channel and the Internet channel were an complementary channels. This results can provide meaningful implication for multi-channel retailers.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.842-845
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• 2009

Wireless ad hoc networks often suffer from rapidly degrading performance with the number of user increases in the network. One of the major reasons for this rapid degradation of performance is the fact that users are sharing a single channel. Obviously, the problem of using single shared channel schemes is that the probability of collision increases with the number of nodes. Fortunately, it is possible to solve this problem with multi-channel approaches. Due to the especial properties of multiple channels, using the multiple channels is more efficient than single channel because it enhances the capacity of the channel and reduces the error rate during data transmission. Some multi-channel schemes us one dedicated channel for control packets and one separate channel for data transmissions. On the other hand, another protocols use more than two channels for data transmissions. This paper summarizes six multiple channel protocols based on these two kinds of schemes. Then we compare them and discuss the research challenge of multiple channel protocols.

• Asia Marketing Journal
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• v.19 no.4
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• pp.37-59
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• 2018

This study investigates the effects of the distribution channel structure on quality decisions under duopoly competition. I considers a set-up in which two retailers compete on product quality and retail price. In the set-up, the integrated retailer has the power to determine the quality of its exclusive product, while the decentralized retailer does not. For the decentralized retailer, the supplier determines product quality. I find that asymmetric pairs of a decentralized channel by one retailer and an integrated channel by the other retailer can be a Nash equilibrium in a simultaneous-channel-choice model. The two retailers select different levels of quality, and this quality competition benefits retailers by softening price competition. In a sequential-channel-choice model, I find that the leader can obtain a first-mover advantage. From the perspective of the supplier, which can decide the distribution channel structure and level of quality, both suppliers choose the decentralized channel in equilibrium.

• Journal of Distribution Science
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• v.18 no.1
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• pp.5-13
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• 2020

Purpose: The purpose of this study is to examine the growth and change process of Korean cosmetic market that has grown more than three times since 2000. It also examined how the growth and decline of the cosmetics brands are related to the change of the cosmetic distribution structure. Research methodology: This study tried to classify the change of the Korean cosmetics market into four stages based on the market sales information. It analyzed the sales information of Korean cosmetic companies and the relationship with the sales of the brands by distribution channel. Results: One-brand store channel had played a leading role in the market growth, and multi-brand stores have grown and a number of brands also grew through that channel since 2013. Since 2016, multi-brand stores have continued to grow and have dominated the market beyond one-brand store channel. Conclusions: The changes in sales of domestic cosmetics companies have been classified based on the distribution channel type in four stages: the emergence of one-brand store, the growth of one-brand store channel, the growth of multi-brand store channel, and the decline of one-brand store channel. In conclusion, multi-brand store channels have recently grown in the Korean cosmetics market, and this trend is expected to continue.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.418-424
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• 2007

This paper proposes a scheme to track channel response in OFDM systems with null sub-carriers. The proposed channel tracking scheme estimates the channel response first in the frequency domain by using the decision directed data. The time domain channel estimation is then performed to remove additive white Gaussian noise (AWGN) components further. Due to the channel estimation in the frequency domain, no inverse matrix calculation is required in the time domain channel estimation. Computational reduction in the proposed method is about 93%, compared with the conventional time domain channel estimation method. Mean square error (MSE) and bit error rate (BER) performances are evaluated by using computer simulation. The proposed method shows the same performance as that of the conventional time domain channel estimation even though the significant computational reduction.

• Nuclear Engineering and Technology
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• v.20 no.2
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• pp.80-87
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• 1988

Predicted in this paper are flow distributions in average and hot channels of the reactor core during small and large break LOCAs. Also estimated based on REALP5/MOD2 calculations are the effects of cross flow between channels on LOCA analysis results. It has been so far generally accepted that a single average channel is sufficient for small break LOCA core hydraulic modelling. However, based on these calculation results, hot channel modeling (two channel modeling) is found necessary in order to guarantee more reliable and conservative results. In large break LOCA blowdown phase, the hot channel thermal hydraulics is worse than that of average channel in both cases with the without consideration of cross flow.