• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.226-229
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• 2003

Under the prsence of the frequency and timing offset, we evaluate the BER performance of the FFH-MA system using noncoherent M-ary FSK modulation in the Rayleigh fading channel. The numerical resuts show that while the frequency and timing offset increases at a given SNR, the BER is severely degraded. The threshold level used in the envelope detector increases with the increase of the frequency and timing offset, and with the proper selection of the threshold level, the BER can be improved under the presence of such offsets.

• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.1
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• pp.135-145
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• 1992

The relationships among leadershipm leader-subordinate interpersonal communication and outcomes in research teams were investigated for six research institutes sponsored by the Korean Government, Consideration and initiating structure of leader behavior were used as leadership dimensions. Subordinate satisfaction with supervision and with work, and project success were considered as outcomes in research team. Leader-subordinate interpersonal communication was positively related to both of consideration and initiating structure of leader behavior. Outcomes in a research team were differently related to the communication according to leadership types. Finally, several theoretical and managerial implications are discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.12
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• pp.3003-3017
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• 2013

In this paper, we investigate the outage performance of a cognitive relay network. We consider mutual interference in an independent, non-identically distributed Nakagmai-m fading environment. We first derive the close-form outage probability expression, which provides an efficient means to evaluate the effects of several parameters. This allows us to study the impact of several parameters on the network's performance. We then derive the asymptotic expression and reveal that the diversity order is strictly determined by the fading severity of the cognitive system. It is not affected by the primary network. Moreover, the primary network only affects the coding gain of the cognitive system. Finally, Monte Carlo simulations are provided, which corroborate the analytical results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.399-403
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• 2006

Software-based GNSS receivers have the great advantage in flexibility compared with conventional receivers. But it has some problems to processing IF level Signal RAW data, need long time to process long term data and TTFF is long because the process is too slow. So this time, we concentrated on the signal acquisition, and examined the speedup technique. Using this technique, the acquisition was speedup dramatically, and signal-to-noise ratio was improved.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.57-59
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• 2006

In order to apply the network adjustment, the correct ambiguities between each of reference stations must be calculated. This paper focused on the comparison of ambiguity resolution between the reference stations. Three hours test data with different baseline length from 20 km to 60 km have been analyzed. The results show that the time-to-fix between 20 km and 40 km is typically under 1 minute. However, over 60km baseline, the time-to-fix performance degrades.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.1001-1004
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• 2015

소설미디어의 급증과 함께 온라인 리뷰의 의존성이 급증하는 가운데 사용자의 올바른 의사결정을 저해하는 기만적 의견 스팸 이슈가 새롭게 주목받고 있다. 기존의 의견 스팸 연구는 실제 리뷰와 의견 스팸 간의 차이를 어휘, 품사 또는 감정단어와 같은 표면적 자질을 통해 설명하였으나 그들간의 의미적 연결관계는 고려하지 않았다. 본 논문에서는 1) 의미적 프레임 기반의 텍스트 분석기법을 제안하고, 이를 바탕으로 2) 의견 스팸과 실제 리뷰간의 의미적 차이가 있음을 규명하며 3) 새로운 의미적 프레임 자질을 사용하여 기존의 의견 스팸 분류 성능을 향상시킬 수 있음을 보인다.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.937-940
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• 2004

프로세서 자원, 데이터 저장장치 자원을 제공하면서 가상기관(Virtual Organization)을 구성하는 각 사이트는 사용할 수 있는 네트윅 자원이 한정된 상황에서 애플리케이션 처리량을 극대화하는 최적화된 데이터그리드 시스템을 기대한다. 본 논문에서는 크기가 제한적이며 지리적으로 분산된 데이터 저장공간에서 적응적 데이터 복제 기법을 제안하고 Replica의 지리적 분배를 위한 평가 모델을 제안한다. 이를 위해 논리 시간 데이터 접근 기록 및 통계를 적용하여 복제할 파일들을 구분 하는 이산적 결정 모델을 제안하고 삭제할 Replica 결정에 논리 시간 접근 기록을 적용한다.

• International Journal of Computer Science & Network Security
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• v.21 no.3
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• pp.48-54
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• 2021

Security is an important issue for wireless communications and poses many challenges. Most security schemes have been applied to the upper layers of communications networks. Since in a typical wireless communication, transmission of data is over the air, third party receiver(s) may have easy access to the transmitted data. This work examines a new security technique at the physical layer for the sake of enhancing the protection of wireless communications against eavesdroppers. We examine the issue of secret communication through Rayleigh fading channel in the presence of an eavesdropper in which the transmitter knows the channel state information of both the main and eavesdropper channel. Then, we analyze the capacity of the main channel and eavesdropper channel we also analyze for the symbol error rate of the main channel, and the outage probability is obtained for the main transmission. This work elucidate that the proposed security technique can safely complement other Security approaches implemented in the upper layers of the communication network. Lastly, we implement the results in Mat lab

• Current Optics and Photonics
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• v.6 no.1
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• pp.15-22
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• 2022

This paper describes the construction of a phase shifter with low loss and small volume. To construct it, we use the two graphene layers that are separated by a hexagonal boron nitride (hBN) and embedded in a silicon waveguide. The refractive index of the waveguide is adjusted by applying a bias voltage to the graphene sheet to create an optical phase shift. This waveguide is a compact device that only has a radius of 5 ㎛. It has a phase shift of 6π. In addition, the extinction ratio (ER) is 11.6 dB and the insertion loss (IL) is 0.031 dB. Due to its unique characteristics, this device has great potential in silicon on-chip optical interconnection and all-optical multiple-input multiple-output processing.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.957-960
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• 2009

의료영상기기의 발달과 등장으로 진단과 치료목적으로 생성된 의료영상은 기하급수적으로 증가하고 있다. 게다가 의료 환경이 보다 전문화, 집중화 되면서 의료기관 간의 협업의 중요성이 강조되고 있다. 의료기관간의 효과적인 의료협업을 위해서는 의료정보의 원활한 가시화와 이를 지원하기 위한 정보 처리는 필수적이다. 의료기관간의 의료정보를 가시화하기 위해서는 안정적이고 다양한 의료정보를 표현하기 위한 플랫폼이 필요하다. 본 연구에서는 다양한 의료정보 협업을 지원하는 의료협업 플랫폼을 제안하고 기존의 PACS-Grid 와 서비스 기반의 의료정보 협업 가시화 서비스를 설명하고자 한다.