• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.289-304
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• 2010

This paper proposes a novel scheme for cooperative spectrum sensing on distributed cognitive radio networks. A fuzzy logic rule - based inference system is proposed to estimate the presence possibility of the licensed user's signal based on the observed energy at each cognitive radio terminal. The estimated results are aggregated to make the final sensing decision at the fusion center. Simulation results show that significant improvement of the spectrum sensing accuracy is achieved by our schemes.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.467-476
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• 2009

As web technology and educational environments are in rapid progress, web-based cooperative learning systems have gained a lot of interests. Recently some studies have attempted to combine a learning system and simple games that enable learners to actively participate and have high interests in learning. These studies are based on TGT model, a cooperative learning model using games, and mostly remain system design levels. A few implemented systems have many problems because they focus only on pure TGT model. To solve these problems, this paper builds a extended TGT model and a new web-based cooperative learning system using this new model. The extended part contains ideas such as expert learning from Jigsaw II model, improvement scores from STAD model and making game problems by learners. A system using pure TGT model and a suggested system are implemented and used by two classes of middle school students to evaluate our system. The experimental results show that our system outperforms the other system.

• Korean Journal of Childcare and Education
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• v.16 no.1
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• pp.1-20
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• 2020

Objective: The purpose of this study was to explore the application of the multidisciplinary model, which is customized evidence-based counseling for abused preschool children done by a day care center teacher. Methods: The participants were 16 preschool children which were abused by a day care center teacher and their parents. The data were analyzed by using the Wilcoxon Signed-rank test. Results: The multidisciplinary cooperative service model based on customized evidence-based counseling for abused preschool children, their parents, and day care center teachers was developed. Based on this model, customized evidence-based Post-Traumatic Stress Disorder (PTSD) emergency intervention was provided to preschool children abused by a day care teacher in Incheon. The multidisciplinary cooperative emergency intervention service proved to be effective in reducing emotional and behavioral problems of abused preschool children and enhancing the mental health of parents. Conclusion/Implications: The results of this study indicated that the customized evidence-based counseling for abused preschool children done by a day care center teacher using the multidisciplinary cooperative linkage system would be effective, and that child abuse prevention by day care center teachers and intervention services should be provided systematically at the national level.

• Journal of Distribution Research
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• v.2 no.1
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• pp.143-174
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• 1997

The model applied in this paper is based on the theory of economic order quantity (EOQ). EOQ model is introduced to explain the improvement of the transaction efficiency through the cooperative purchase. We examine explicitly how horizontal cooperation affects vertical transactions. A result of the analysis is that a seller can prefer transacting with a cooperative rather than with each buyer separately, even if he reduces the selling price of the product. Without increasing the demand for the product, this result is that dealing with a cooperative, rather than separately with each buyer, decreases the transaction cost for the seller-buyers system, the cost reduction more than off-setting the effect of price decrease on the sellers profit. For a coopative consisting of any number of buyers, Pareto efficient ordering policies that maximize the joint cost saving for the seller-buyers system are identified. We then discuss the conditions under which a cooperative under consideration can be modified to increase efficiency gain. Next, we relax the assumption that all buyers participate in a single cooperative and examine the issue of how many cooperatives, each consisting of a subset of the buyers, should be formed to maximize the total cost saving for the seller-buyers system. Finally, the issue of shapley value to divide the cooperatives gain among its members is discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8A
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• pp.769-774
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• 2006

Based on the performance of a cooperative diversity with selection combining in Rayleigh fading, the power control range of a relay node is investigated. Also the effect of the power-limited relay node to the system performance is investigated. If the average signal-to-noise ratio(SNR) of each signal path is equal, the single relay cooperative diversity is obtained 13.5dB gain at the outage probability of $1{\times}10^{-3}$ in Rayleigh fading. We noticed that the limited power of a relay node severely degrades the system performance. Therefore the node with limited power in ad-hoc network is not recommended as a relay node in cooperative diversity system.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.1
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• pp.135-144
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• 2015

This study aims to propose an evaluation model that enables cooperative learning using e-Learning system. Even if the teacher and the student are not in the same place at the same time, the team project deliverable submitted by the student to the online system can be viewed by the teacher, enabling the teacher to assess the student not only based on the project but also in many other aspects. The proposed e-learning cooperative learning model allows the development of assessment factors, using such factors in assessment of the student's activities which are performed through the e-learning system, and the feedback of the results to the student so that the student is further motivated for learning. The teacher performs a comprehensive assessment of such factors, which is considered in conjunction with the student's assessment. Implementing the cooperative learning model proposed in this study in various e-learning systems such as Moodle is expected to motivate the student for learning, produces better cooperative learning results, provides greater convenience of assessment to the teacher, and improves fairness of assessment by showing the student's activities in real time.

• Journal of Communications and Networks
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• v.13 no.3
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• pp.240-249
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• 2011

Cooperative diversity protocols have attracted a great deal of attention since they are thought to be capable of providing diversity multiplexing tradeoff among single antenna wireless devices. In the high signal-to-noise ratio (SNR) region, cooperation is rarely required; hence, the spectral efficiency of the cooperative protocol can be improved by applying a proper cooperation selection technique. In this paper, we present a simple "cooperation selection" technique based on instantaneous channel measurement to improve the spectral efficiency of cooperative protocols. We show that the same instantaneous channel measurement can also be used for relay selection. In this paper two protocols are proposed-proactive and reactive; the selection of one of these protocols depends on whether the decision of cooperation selection is made before or after the transmission of the source. These protocols can successfully select cooperation along with the best relay from a set of available M relays. If the instantaneous source-to-destination channel is strong enough to support the system requirements, then the source simply transmits to the destination as a noncooperative direct transmission; otherwise, a cooperative transmission with the help of the selected best relay is chosen by the system. Analysis and simulation results show that these protocols can achieve higher order diversity with improved spectral efficiency, i.e., a higher diversity-multiplexing tradeoff in a slow-fading environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5149-5173
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• 2016

Cooperative forwarding has shown a substantial network performance improvement compared to traditional routing in multi-hop wireless network. To further enhance the system throughput, especially in the presence of highly congested multiple cross traffic flows, a promising way is to incorporate the multi-radio multi-channel (MRMC) capability into cooperative forwarding. However, it requires to jointly address multiple issues. These include radio-channel assignment, routing metric computation, candidate relay set selection, candidate relay prioritization, data broadcasting over multi-radio multi-channel, and best relay selection using a coordination scheme. In this paper, we propose a simple and efficient cluster-based cooperative data forwarding (CCDF) which jointly addresses all these issues. We study the performance impact when the same candidate relay set is being used for multiple cross traffic flows in the network. The network simulation shows that the CCDF with MRMC not only retains the advantage of receiver diversity in cooperative forwarding but also minimizes the interference, which therefore further enhances the system throughput for the network with multiple cross traffic flows.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.6
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• pp.13-19
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• 2008

In this paper, the new cooperative communication techniques is proposed for multi-input multi-output(MIMO)-orthogonal frequency division multiplexing (OFDM) system using the relay with multiple antenna. As the MIMO channel is formed by space time coding at the MS(mobile station)-RS(relay station) and RS-BS(base station), we can get the cooperative diversity and MIMO diversity gain simultaneously. Therefore, the performance of MIMO-OFDM system using the relay with multiple-antennas is very improved. And the simple power allocation technique is Proposed for the transmitting power of the mobile station and the relay.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.648-651
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• 1997

This paper proposes methods for the cooperative control of multiple mobile robots and constructs a robotic soccer system in which the cooperation will be implemented as a pass play of two robots. To play a soccer game, elementary actions such as shooting and moving have been designed, and Q-learning, which is one of the popular methods for reinforcement learning, is used to determine what actions to take. Through simulation, learning is successful in case of deliberate initial arrangements of ball and robots, thereby cooperative work can be accomplished.