• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.3
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• pp.1-7
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• 1999

일대다 형상을 갖는 통신시스템에서 많이 고려되는 예약 알로하 방식 매체접속제어 프로토콜의 성능은 예약 채널과 데이터 채널의 분배 양식에 의해 달라진다. 본 논문에서는 이 프로토콜을 직렬 2단 대기열 모델로 근사화하고, 데이터의 지연을 성능 척도로 하여 이를 줄이는 세가지 채널 할당 방식을 제시하였다. 그리고 이들에 대한 모의실험을 통해 그 동작 특성을 규명하고 성능을 평가하였다. 그 결과 이들의 성능은 트래픽의 특성, 특히 데이터 길이의 분산에 크게 의존하며, 일반적으로는 데이터에 우선권을 주는 방식이 우수하나, 데이터 길이의 분산이 큰 경우에는 비례배분 할당 방식이 우수한 것으로 평가되었다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.297-302
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• 1998

본 논문에서는 CDMA(Code Division Multiple Access) 채널을 통과하면서 여러 가지 형태로 손상된 음성에 대한 주관적 음질 평가를 할 수 있는 객관적 척도에 대한 연구를 수행하였다. 즉, CDMA 채널을 통과한 음성 신호에 대하여 주관적 음질 평가 방법 중 가장 많이 사용되고 있는 MOS(Mean Opinion Score) 테스트를 수행하고, 이 MOS 테스트 결과를 추정할 수 있는 객관척도 알고리즘을 시뮬레이션 하였다. 이러한 연구 결과로 PSQM(Perceptual Speech Quality Measure)을 CDMA 채널 환경에 맞게 수정하여 우수한 성능의 객관적 음질 평가 방법을 얻었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.8-18
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• 2009

CableLAB published DOCSIS 3.0 Specifications to supply broadband access to homes and small businesses. The primary technique of DOCSIS 3.0 Specification is channel bonding which provides cable operators with a flexible way to significantly increase up/downstream speeds. In this paper, we propose the upstream scheduler that serves channel bonding. Proposed scheduler consists of two sub-scheduler: bonding group scheduler and channel scheduler. Also, we propose three scheduling algorithms to allocate request bandwidth of CM to each bonding channel: equivalent scheduling algorithm, current request-based scheduling algorithm, and last grant-based scheduling algorithm. In order to evaluate the performance of these algorithms and DOCSIS 3.0 MAC protocol, we develop the DOCSIS 3.0 simulator with the network simulator, OPNET, to model DOCSIS network, CMTS, and CM. Our results show that equivalent scheduling algorithm is superior to others in the view of transmission delay and throughput and DOCSIS 3.0 protocol provides higher throughput than pre-DOCSIS 3.0 protocol.

• The Journal of the Korea Contents Association
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• v.18 no.8
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• pp.300-314
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• 2018

This study, expending the existing concept of hostile media perception to biased media perception, empirically examined the effects of TV audience's political disposition(liberal, neutral, conservative) and broadcasting company's political disposition perceived by the audience(liberal, neutral, conservative) on evaluations of the broadcasting channel(interestedness, diversity, creativity, reliability, usefulness, fairness, public interest). With the nationwide online survey data from 624 adult audiences, a broadcasting company evaluated as the most neutral in political disposition at the moments of data gathering was selected and respondents' evaluations of the broadcasting channel were analyzed in a two-way factorial multiple analysis of covariance(MANCOVA). The results showed that the perceived political disposition of the broadcasting company affects audiences' evaluations of the channel while audiences' their own political dispositions do not. In addition, due to the interaction effects between audience's and broadcasting company's political dispositions, congruency in political dispositions led to positive evaluations(congenial media perceptions) while incongruency led to negative ones(hostile media perceptions). Based on these results, theoretical and empirical implications were discussed in terms of the formation of attitudes toward TV broadcasting channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.794-801
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• 2000

In this paper, the efficient new performance evaluation method for digital communication channels is suggested and verified its efficiency in terms of simulation run-tim for the digital satellite broadcasting satellite TV channel. In order to solve the difficulties of the existing Importance Sampling(IS) Technics, we adopted the discrete probability mass function(PMF) in the new method for estimating the statistical characteristics of received signals from the measured Nth order central moments. From the discrete probability mass function obtained with less number of the received signal than the one required in the IS technic, continuous cumulative probability function and its inverse function are exactly estimated by using interpolation and extrapolation technic. And the overall channel is simplified with encoding block, inner channel performance degra-dation modeing block which is modeled with the Uniform Random Number Generator (URNG) and concatenated Inverse Cummulative Pr bility Distribution function, and decoding block. With the simplified channel model, the overall performance evaluation can be done within a drastically reduced time. The simulation results applied to the nonlinear digital satellite broadcasting TV channel showed the great efficiency of the alogrithm in the sense of computer run time, and demonstrated that the existing problems of IS for the nonlinear satellite channels with coding and M-dimensional memory can be completely solved.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.271-271
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• 2014

본 연구에서는 최근 다양한 전자 소자로써의 연구가 진행되고 있는 그라핀을 SiO2/Si 기판 위에 전자빔 식각(Electron-Beam Lithography)을 이용하여 후면 게이트 전극 구조의 그라핀 채널을 갖는 삼단자 소자를 형성하고 가스 유입이 가능한 진공 Probe Measurement System을 이용하여 금속 전극과 그라핀 간의 접촉저항 (Rc) 및 길이가 다른 채널저항(Rch)를 구하고, 채널 길이, 가스 유량, 온도, 게이트 전압에 따른 I-V 변화를 측정함으로써, 후면 게이트 전극 구조의 그라핀 채널을 갖는 삼단자 소자의 가스 센서로서의 가능성을 연구하였다. 후면 게이트 전극 구조의 그라핀 채널을 갖는 삼단자 소자는 전자빔 식각(Electron-Beam Lithography)에 의해 패턴을 제작하고 Evaporator를 이용하여 전극을 증착 하였다. 소자의 소스 (Source)와 드레인 (Drain)은 TLM (Transfer Length Method)패턴을 이용하여 인접한 두 개의 전극간 범위를 변화시키는 형태로 제작함으로써 소스-드레인간 채널 길이가 다르게 하였다. 이 때 전극의 크기는 가로, 세로 각각 $20{\mu}m$, $40{\mu}m$이며 전극간 간격은 $20/30/40/50/60{\mu}m$로 서로 다르게 배열 하였다. 제작된 그라핀 소자는 진공 Probe Measurement System 내에서 게이트 전압(VG)를 변화시킴으로써 VG 변화에 따른 소자의 특성을 평가하였는데, mTorr 상태의 챔버 내로 O2 가스를 주입하여 그라핀의 Dangling bond 및 Defect site에 결합 된 가스로 인한 전기적 특성의 변화를 측정하고, 이 때 가스의 유량을 50 sccm에서 500 sccm 까지 변화시킴으로써 전기적 특성 변화를 측정하여 센서 소자의 민감도를 평가하였다. 또한, 서로 다르게 배열한 소스-드레인 간의 채널 길이로 인하여 채널과의 접촉 면적에 따른 센서 소자의 민감도 또한 평가할 수 있었다. 그리고 챔버 내 온도를 77 K에서 400 K까지 변화시킴으로써 온도에 따른 소자의 작동 범위를 확인하고 소자의 온도의존성을 평가하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1113-1120
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• 2016

The purpose of this study is to find the important travel agency service quality factors in relation to the amount of information search efforts through major information channels of customers such as interpersonal source, retailer source, and external media source. Factor analysis using varimax rotation was performed and 20 service attributes of travel agent was reduced to 6 factors; convenience system, personal service, customer maintaining service, reputation, atmosphere and accessibility. According to MANOVA analysis there are significant differences in the service quality factor due to the type of source and amount of efforts of information search.

• Journal of Digital Contents Society
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• v.7 no.1
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• pp.47-52
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• 2006

This paper proposes an algorithm for human sensibility evaluation using 4-channel EEG signals of the prefrontal and the parietal lobes. The algorithm uses an artificial neural network and the multiple templates. The linear prediction coefficients are used as the feature parameters of human sensibility. Comfortableness and temperature/humidity are evaluated. Many conventional researches have emphasized that a wave of left prefrontal lobe is activated in case of positive sensibility and that of right prefrontal lobe is activated in case of negative sensibility. So the power ratio of n wave is obtained from for computation and the results are compared. The results of the comfortableness evaluation for temperature and humidity showed that the outputs of the proposed algorithm coincided with corresponding sensibilities depending on the task of the temperature and the humidity. The conventional method using a wave is hardly related with comfortableness. And it is also observed that the uncomfortable state due to the high temperature and humidity can be easily changed to the comfortable state by small drop of the temperature and the humidity.

• The Journal of the Acoustical Society of Korea
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• v.21 no.3
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• pp.245-255
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• 2002

This thesis deals a method to deliver more realistic sound by cancelling the cross-talk which is inherent to the 5.1 channel speaker system. The acoustical model for cross-talk cancellation is the free field model. This model minimizes distortion of sound. I used the bark scale sound quality compensation which based on psycho-acoustic. For the surround channels, band-limited sound quality compensation is performed in the frequency domain. I also performed the sound quality assessment test on the traditional 2 channel stereo and 5.1 channel system. This test is performed in the test chamber which satisfies the ITU-R specifications. I uses the IACC (Inter-Aural Cross-Correlation) to determine the preferences of the amateur and the golden ear experts to asses the trans-aural filter. According to the result from the proposed method, I got more the 38 dB separation rates with the Dolby standard speaker array. The results on the diffusion by the subjective test with the experts shows 0.4 point increased then before.

• The KIPS Transactions:PartB
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• v.11B no.3
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• pp.345-352
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• 2004

This paper deals a method to deliver more realistic sound by cancelling the cross-talk which is inherent to the 5.1 channel speaker system. The acoustical model for cross-talk cancellation is the free field model. This model minimizes distortion of sound. 1 used the bark scale sound quality compensation which based on psycho-acoustic. For the surround channels, band-limited sound quality compensation is performed in the frequency domain. I also performed the sound qualify assessment test on the traditional 2 channel stereo and 5.1 channel system. This test is performed in the tort chamber which satisfies the ITU-R specifications. 1 uses the IACC(Inter-Aural Cross-Correlation) to determine the preferences of the amateur and the golden ear experts to asses the trans-aural filter. According to the result from the proposed method, I got more the 38dB separation rates with the Dolby standard speaker array. The results on the diffusion by the subjective test with the experts shows 0.4∼0.5 point Increased then before.