• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.237-245
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• 2012

This paper describes an acoustic echo canceller with double-talk by the blind signal separation. The acoustic echo canceller is deteriorated or diverged in the double-talk period. So we use the blind signal separation to estimate the near-end speech signal and to eliminate the estimated signal from the residual signal. The blind signal separation extracts the near-end signal with dual microphones by the iterative computations using the 2nd order statistical character. Because the mixture model of blind signal separation is multi-channel in the closed reverberation environment, we used the copied coefficients of echo canceller without computing the separation coefficients. By this method, the acoustic echo canceller operates irrespective of double-talking. We verified performances of the proposed acoustic echo canceller by simulations. The results show that the acoustic echo canceller with this algorithm detects the double-talk periods thoroughly, and then operates stably in the normal state without the divergence of coefficients after ending the double-talking. And it shows the ERLE of averagely 20dB higher than the normal LMS algorithm.

• Journal of Digital Convergence
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• v.16 no.1
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• pp.327-336
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• 2018

The purpose of this study was to analyze the coupon attitude plays a mediating in the relationship between brand image, brand preference, and information reliability of 'KakaoTalk Plus Friend' and also the coupon attitude plays a mediating role in the relationship between user satisfaction and continuous usage intention. A questionnaire was used the samples of totally 170 people, who is currently using the 'KakaoTalk Plus Friend'. According to analysis, first, the coupon attitude has been shown to be partly mediating effect on the relationship between brand image and information reliability. Second, the coupon attitude has been shown to be not mediating effect on the relationship between brand preference and use satisfaction. Third, the coupon attitude has been shown to be partial mediating effect in relation to user satisfaction. As a result, the coupon attitude has been shown to be mediating effect on the user attitude. This result can help the understanding user attitude and the coupon attitude in the 'KakaoTalk Plus Friend'.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.921-929
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• 2010

Group communication that involves the setup of a list of users has been a topic of interest in mobile industry. Push to Talk over Cellular (PoC), a group communication service for cellular phone network, is a type of half duplex communications that allows a single person to reach an active talk group without making several calls, but a single button press. Based on this service, we build a new protocol called Push to Talk over Mobile Wimax that uses group communication service in 802.16e network. Also, weper formed simulation to verify and evaluate performance of the designed service in Mobile Wimax network. From the results of performance evaluation, network administrators can evaluate the stability of network and make a better of network's shortcoming and have decision to build the robust network.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.1
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• pp.7-14
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• 2017

Theoretically, it is known that common beliefs and/or common knowledge cannot be attained in asynchronously distributed multiagent environments, however, it show that some propositions with deadlines can be attained as common beliefs among a set of fully trusted agents even when they communicate to each other asynchronously. Generally, in the multiagent environment, the attainment of common beliefs is approached as a problem of communication, and for the common beliefs paradox that the common beliefs is not attained on a system without communication time restriction is applied to loose coarser granularity and it prove that forming common beliefs is possible by relaxing necessary requirements through the KakaoTalk chatting model. I also experimented with the reasoning function that confirms the common beliefs by inquiring about the common belief generated by implementing the inference function in each agent of the KakaoTalk chatting model. Through utilizing metalogic programming, a formalization of the presentation and reasoning of common beliefs has been achieved, and the group chatting model of KakaoTalk was adopted in experiments to show that common beliefs can be formed among distributed agents using asynchronous communication.

• Journal of IKEEE
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• v.23 no.1
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• pp.91-98
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• 2019

LTE's extension for unlicensed spectrum called Licensed Assisted Access (LAA) is equipped with Listen-Before-Talk (LBT) designed similar with the backoff mechanism of Wi-Fi for coexistence. However, Wi-Fi's backoff mechanism has not evolved from its old design for compatibility with legacy devices, thus LAA's LBT is not efficient either in utilizing spectrum. If LAA operates with no Wi-Fi systems in proximity, it can run more efficient LBT. In this paper, we propose Narrowband Clear Channel Assessment (NCCA) for narrowband transmission. In NCCA, an LAA node performs LBT in either wide or each narrow bandwidth segment. This allows multiple LAA nodes to perform simultaneous transmissions in orthogonal bandwidth segments in the same time slot. We design four variants of NCCA implementation and model their performance using a mathematical model. The coexistence performance of NCCA with conventional wideband nodes and the accuracy of the model are shown via simulation.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.56-61
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• 2002

In piezoelectric ultrasonic linear array transducers widely used for diagnosis, the cross talk caused by the structural cross-coupling between adjacent elements inside the transducer affects the probe performance in a significant manner. In this study, we constructed a finite element model of a piezoelectric ultrasonic transducer, and analyzed its cross talk level with respect to the shape of and materials inside the kerf, The results of this work can be utilized in optimal design of the transducers for medical diagonosis and treatment as well as W applications.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.8.2-8.2
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• 2011

This talk demonstrates diverse patterned structures utilizing in-situ self-organization and phase separation of the materials into an ordered fashion. The patterned structures in this talk include electrospun nanofibers and electrosprayed microparticles embedding small particles. The positions of the small particles are in-situ controlled during the electrohydrodynamic process by the interaction with the polymer matrix. Another topic of the talk includes selective deposition of spin-coated materials on a corrugated surface that was prepared by buckling of polymer thin films. Solution are strong tendency to be positioned in the trench area of the surface, which facilitates the fabrication of micropatterns of diverse materials.

• Journal of the Korean Operations Research and Management Science Society
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• v.14 no.1
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• pp.97-107
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• 1989

In this study three types of aggregation methods such as the Estimate-Talk-Consensus (ETC) process, the Estimate-Talk-Estimate (ETE) process, and as a new approach the Estimate-Talk-Leader's Estimate (ETLE) process are compared to find which one of the three group processes considered is more effective than others. We, also, investigate the effect of group size on the performance of the group processes. Some experiments were conducted. It was shown that both the ETC and the ETLE processes performed better than the ETE process in approaching correct estimates in this judgmental task. As the size group increased, only the ETC and the ETC processes were shown to result in positive effect.

• Journal of the Korean Home Economics Association
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• v.40 no.6
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• pp.213-221
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• 2002

This study investigated talk about mental states in pretend play, to whom mental states were attributed, and function of mental-state terms. Also, frequency of mental-state terms of pretend versus non-pretend turns was examined. Thirty 4 year old preschoolers, each paired with a self-chosen peer, were observed and videotaped during a 20-minute play session. The observations presented the following conclusions: Knowing and pretending were the most frequently expressed. Children attributed a large proportion of mental state to themselves. The mental-state terms were used to refer his or another's thoughts and beliefs, to direct interaction, and to attract the other child's attention. Mental-state talk occurred within pretend more often than within non-pretend turns.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.891-894
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• 2008

Here we describe the new structured electrochromic(EC) materials to improve the three primary colors (RGB). We also report the simply isolated electrochromic unit cell using gel type electrolyte and show cross-talk' free driving of EC display device.