• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1819-1824
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• 2004

The common method to improve heat transfer in Nuclear fuel rod bundle is install a mixing vane in space grid. The previous split mixing vane is guides cooling water to swirl flow in sub-channel of fuel assembly. But, this swirl flow decade rapidly after mixing vane and the effect of enhancing the heat transfer vanish behind this short region. The large scale secondary vortex flow was generated by rearranging the inclined angle direction of mixing vanes to the coordinated directions. This LSVF mixing vanes generate the most strong secondary flow vortices which maintain about 35 $D_H$ after the spacer grid and the streamwise vorticity in subchannel with LSVF mixing vane sustain two times more than that in subchannel with split mixing vane. The turbulent kinetic energy and the Reynolds stresses generated by the mixing vanes have nearly same scales but maintain twice more than previous type.

• Current Optics and Photonics
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• 제1권5호
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• pp.440-455
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• 2017

In this paper, we carry out a performance analysis of a two-user free-space optical (FSO) communication system with photodetector multiplexing, in which the two users are defined as the primary user (PU) and secondary user (SU). Unlike common single-user FSO systems, our photodetector multiplexing FSO system deploys a shared detector at the receiver and enables PU and SU to send their own data synchronously. We conduct the performance analysis of this FSO system for two cases: (1) in the absence of background radiation, and (2) in the presence of background radiation. Decision strategies for PU and SU are presented according to the two scenarios above. Exact and approximate conditional symbol-error probability (SEP) expressions for both PU and SU are derived, in an ideal channel with no fading. Average SEP expressions are also presented in the no-background-radiation scenario. Additionally, in some particular cases where the power ratio tends to 0.5 or 1, approximate SEP expressions are also obtained. Finally, numerical simulations are presented under different conditions, to support the performance analysis.

• 전자공학회논문지B
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• 제28B권10호
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• pp.790-798
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• 1991

The congestion control methods of an integrated heterogeneous traffic multiplexer are studied. The real-time traffics have preemptive priority over nonreal-time traffics in capturing the common output link. Also real-time traffics are transmitted with bandwidth reduction when the nonreal-time traffics are over the buffer threshold. The proposed model formulated the system as a continous time Markov process and is analysed using matrix equation. Time delay and average number of used channel are applied for performance parameters. In this study, a new control method with the sizable buffer threshold is introduced and the optimal congestion control can be obtained.

• International Journal of Internet, Broadcasting and Communication
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• 제10권3호
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• pp.81-87
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• 2018

It is common practice to display high-quality video images on the large display among the methods of developing tourist attractions and culture in the region as experience contents differentiation is required. This paper combines the local attractions with the OLED dual layer display system and the extended image implementation and augmented interaction technique to give the experiencer a realistic space, such as directing to new experiences and beautiful sights. In this paper, we added UI layer to additional layers of images to enable users to experience sightseeing information, weather, maps, accommodation, festivals and photo materials with images. It is implemented to add fun through interlocking. We also developed transparent OLED and dual layer panel and 3-channel multi-image playback technique.

• Journal of Communications and Networks
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• 제7권1호
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• pp.13-20
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• 2005

In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.

• Journal of Communications and Networks
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• 제9권2호
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• pp.128-135
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• 2007

A combined opportunistic multiple beamforming method is presented that the first beam is designed with an aid of channel state information using uplink mid-amble and other beams are orthogonally generated to the first beam sequentially. The power allocation with SINR feedback increases overall throughput for the decentralized systems. The advantages of the proposed scheme is that the first beam is not interfered by other beams guaranteeing quality of service (QoS) and other orthogonal beams are operated opportunistically to obtain multi user diversity. The computer simulation demonstrates that the proposed scheme is effective at a small number of users, which is common in cellular systems, and outperforms conventional spatial division multiple access (SDMA) opportunistic beamforming methods.

• Journal of electromagnetic engineering and science
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• 제12권2호
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• pp.148-154
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• 2012

In this paper, we propose an algorithm to conserve resources of the common control channel in a cognitive radio network by rejecting the redundant users using cooperative spectrum sensing. The proposed scheme is investigated under the paradigm of active spectrum sensing and a sequential detection technique. The algorithm is based on the J-divergence between the hypotheses of non primary user operation and the otherwise case. We select the most significant eigenvalues, which primarily affect the global statistical test. For the case where interference is from a secondary system transmission, a match filter is first employed to remove the degradation, and then the proposed algorithm is employed to remove the cooperative sensing nodes. Numerical results are provided and compared with conventional cases in order to validate the performance of the proposed algorithm.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.482-485
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• 2006

다채널 시각비교 수신기(R100-40T, Euro-80)를 이용한 GPS C/A 코드 시각비교 데이터와 Ashtech Z12T 수신기를 이용한 P3 코드 시각비교 데이터를 통합 모니터링함으로서, 간편하게 시각비교 결과를 확인 할 수 있게 GUI(Graphic User Interface) 환경으로 구현하였다. 수신기들은 현재 KRISS(Korea Research Institute of Standards and Science)에서 사용 중인 위성이용 시각비교 수신기들이다. 본 시각비교 통합 모니터링 프로세스를 통해서 GPS C/A code 시각비교 데이터와 P3 code 시각비교 데이터 각각을 비교 분석함으로써 시각비교 결과의 신뢰성을 검증하는데 사용한다.

• Industrial Engineering and Management Systems
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• 제12권2호
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• pp.118-129
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• 2013

In this study, we intend to identify key financial variables that can accurately classify Green IT leaders against Green IT followers. In particular, we build and compare single and meta-classifiers to identify the relationship between environmental performance and financial performance, while focusing on selecting and interpreting a final prediction model with a smaller set of financial performance indicators. Our experimental results demonstrate that several key variables representing the size, financial resources, operational efficiency, and risk-taking tendency of an organization can successfully identify Green IT leaders with approximately 90% of accuracy. In addition, we find that Green IT leaders show a higher utilization rate of Web pages as a green marketing channel than Green IT followers while they share common layouts of Web publication to build green IT brands with some differences.

• 한국항해학회지
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• 제18권4호
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• pp.1-9
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• 1994

Assessment of the safety of ship's transit in the narrow channel consist of the maneuvering safety determined by the chance of running aground, the maneuvering difficulty determined by ship's workload and master's subjective evaluation. To examine the relation between master's subjective evaluation and maneuvering safety, this utilizes a real-time and full-mission shiphandling simulator in the Korea Marine Training & Research Institutes(KMTRI). The vessel chosen was 60,000-ton, Panamax-type ship. The findings regarding master's subjective evaluation were as follows: -Relation between master's subjective evaluation and common logarithms of stranding probability is linear. -Stranding probability with more than 0.001 is master's subjective evaluation with more than 5.