• 한국과학교육학회지
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• 제24권6호
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• pp.1206-1215
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• 2004

본 연구에서는 오프라인과 온라인으로 진행된 물리탐구 토론에 참여한 학생들을 대상으로 실시된 설문과 면담을 통하여 온라인 물리탐구토론 학습체제에 대한 학생들의 인식을 알아보고, 이를 통하여 온라인 물리탐구토론 학습 체제의 특징을 알아보았다. 분석은 온라인 물리탐구토론 학습체제의 사용자 편리상 온라인 탐구토론의 비동시성, 글쓰기와 관련된 온라인 탐구토론, 온라인 탐구토론의 시각적 표현과 물리적 존재감, 온라인 탐구토론의 선호도의 다섯 가지 범주로 실시되었다. 학생들은 온라인 탐구토론에서 시공간을 초월하여 접근할 수 있고, 비동시성으로 인하여 충분한 사고 후에 논쟁에 참여할 수 있다는 점을 온라인 탐구토론의 가장 큰 장점으로 여기고 있었다. 또한 온라인 활동이 학생들 스스로의 참여로 수행되지만, 학생들의 활발한 참여를 위해서는 온라인 교육 시스템의 기술적인 부분이외에도 학부모와 교사의 역할이 더없이 중요하다.

• 한국통신학회논문지
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• 제38B권10호
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• pp.832-842
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• 2013

Cognitive Radio has attracted intensive interests of the researchers, recently. The data rate always increases in the emerging technologies. The increased data rate poses mainly two challenges for spectrum sensing. One is that the state of primary user (PU) is fast and alternatively varying between "on/off" in a spectrum sensing window. The other is that the asynchronicity among the reports in a cooperative spectrum sensing setting becomes more apparent. Both of them would deteriorate the spectrum sensing performance. Thus, we propose an asynchronous cooperative spectrum sensing method to cope with these two challenges. A likelihood ratio test based spectrum sensing is developed for a single cooperator. The likelihood ratio is obtained in the setting of fast varying PU state. The likelihood ratio test is uniformly powerful according to the Neyman-pearson lemma. Furthermore, the asynchronicity among the cooperators are studied. Two sets of fusion weights are discussed for the asynchronous time among cooperators. One is designed based on the condition probability of the PU state variation and the other one is designed based on the queueing theory. The simulation results are provided with different fusion methods. The performance improvements are demonstrated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 춘계학술대회 논문집
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• pp.409-414
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• 1994

A FMS is a typical discrete event system exhibiting concurrency, asynchronicity and non-determinism. Torepresent a FMS with those chatcteristics, Colored and Timed Petri Nets is defined and the modeling procedure is provided in this paper. Toanalyze and evaluate the performance of a FMS, a simulation software is developed and applied to SNU FMS/CIM Center. This software enables to detect the bottleneck machine and decide the optimaldirection in case of the expansion of a FMS.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.336-341
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• 1993

Automatic Assembly Systems(AAS) are a class of systems exhibiting concurrency, asynchronicity and distributedness, and can be modeled by Petri Nets. In this paper, we design two types of configuration of part-assembly system in the car manufacturing line, as an example of AAS. And, we make a modeling the system by utilizing Extended Petri Nets, simulation as varying machine parameters, and analysis of operation status. These enable to present the information of optimal status and various problems occurring in the system for achieving high production rate.

• 한국정밀공학회지
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• 제11권4호
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• pp.174-181
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• 1994

A FMS is a typical discrete event system exhibiting concurrency, asynchronicity and non-determinism. To represent a FMS with those characteristics, Colored and Timed Petri Nets is defined and the modeling procedure is provided in this paper. To analyze and evaluate the performance of a FMS, a simulation software is developed and applied to SNU FMS/CM Center. This software enables to detect the bottleneck machine and decide the optimal direction in case of the expansion of a FMS.

• Journal of Communications and Networks
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• 제5권2호
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• pp.150-156
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• 2003

In this paper, an uplink MC-CDMA system incorporating multiuser detection and smart antennas has been considered. The performance of asynchronous as well as synchronous system is studied over a correlated Rayleigh multipath slow fading channel. A simplified array-processing algorithm suitable for slow fading situation is investigated to overcome the heavy computational complexity associated with Eigen solutions. The effect of variable data rate in the system performance is considered and effectiveness of antenna array to handle high data rate is discussed. A brief investigation on the system performance degradation due to correlated channel is also carried out. Based on the extensive simulation carried out, the performance of the asynchronous uplink system is found dramatically improved with antenna array and multiuser detection. Asynchronicity and channel correlation are found to affect the system performance significantly. The investigated simpli- fied algorithm produces similar results as Eigen solutions in slow fading situation with much reduced complexity.

• Bulletin of the Korean Chemical Society
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• 제24권9호
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• pp.1345-1350
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• 2003

Principal component analysis based two-dimensional (PCA-2D) correlation analysis is applied to FTIR spectra of polystyrene/methyl ethyl ketone/toluene solution mixture during the solvent evaporation. Substantial amount of artificial noise were added to the experimental data to demonstrate the practical noise-suppressing benefit of PCA-2D technique. 2D correlation analysis of the reconstructed data matrix from PCA loading vectors and scores successfully extracted only the most important features of synchronicity and asynchronicity without interference from noise or insignificant minor components. 2D correlation spectra constructed with only one principal component yield strictly synchronous response with no discernible a asynchronous features, while those involving at least two or more principal components generated meaningful asynchronous 2D correlation spectra. Deliberate manipulation of the rank of the reconstructed data matrix, by choosing the appropriate number and type of PCs, yields potentially more refined 2D correlation spectra.