• 천문학회보
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• 제42권1호
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• pp.55.2-55.2
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• 2017

We study the effect of driving scheme on the density-magnetic field correlation. We numerically investigate how the correlation time of driving affects the correlation between density and magnetic field. We performed MHD turbulence simulation using two different driving schemes - a finite-correlated driving and a delta-correlated driving. In the former, the forcing vectors change continuously with a correlation time comparable to the large-eddy turnover time. In the latter, the direction and amplitude of driving changes in a very short time scale.

• Journal of information and communication convergence engineering
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• 제2권2호
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• pp.61-66
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• 2004

This paper presents a way to maximize transmission efficiency and reception ability through transmission diversity technology, which can be adapted to wireless multimedia Wireless LAN system. The presented method is a comparative analysis between a case where parameter a for time average is 0.3.1 with consideration of channel presumption with two types of rms delayed spread, which is 50nsec. 150nsec, for the performance analysis of STTC (Space-Time Trellis Code) adopting time-space ciphering method appropriate for MIMO channel, and performance in the case where presumed channel value from long training column section is applied to according frame in a single frame. The result showed that BER brought SNR improvement of l.0dB in $10^{-3}$ when a was 0.3 than adopting only the long training column, and showed increase of general performance improvement for the sake of time average rather than the case without.

• 한국멀티미디어학회논문지
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• 제24권3호
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• pp.468-480
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• 2021

Realistic real-time rain streaks rendering has been treated as a very difficult problem because of various natural phenomena. Also, in creating and managing a large number of particles, a large amount of computer resources had to be used. Therefore, in this paper, we propose a more efficient real-time rain streaks rendering algorithm by generating view-dependent rain particles and expressing a large amount of rain even with a small number. By creating a 'rain space' dependent on the field of view of the camera moving in real time, particles are rendered only in that space. Accordingly, even if a small number of particles are rendered, since the rendering is performed in a limited space, an effect of rendering a very large amount of particles can be obtained. This enables very efficient real-time rendering of rain streaks.

• 한국실내디자인학회논문집
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• 제15권5호
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• pp.247-254
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• 2006

The museum has steadily been evolved by time with its function and social idea differently. As the museum makes its evolution, its architecture has also been changed. This study aims to find out the characteristics of museum architecture by applying Space Syntax for space correspondence of museum architecture changed by the time. And the characteristics could be used as project guide by making data for building up museum architecture changed by social concept with efficient and functional system. The method of the study is to divide the museum into three generations, and give case for each generation. And the each chosen case was analyzed by convex space of space syntax. The order of the analysis is to divide the case as the unit space, make out the Convex Map. And finally get the analysis variable by carrying out a mathematical operation. The characteristics found in these operations are as follows. First, the major space has been planed for convenience of spectators. Second, exhibition space located on specific area in entire plot planning makes spectators easy to recognize in terms of the line of flow toward exhibition space and also relieves character of major and exhibition space. Third, it is getting hard to comprehend the entire space as forming diverse space in process that museum accepts many request from spectators.

• Journal of electromagnetic engineering and science
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• 제6권2호
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• pp.83-91
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• 2006

In this paper, we develop space-time(ST) Rake receivers for Time Division Synchronous Code Division Multiple Access(TD-SCDMA) base stations(BS). The beamforming of BS transforms the uplink MIMO channel space into many sub-sectors' channels to be nearly orthogonal, thus, well established 1-D Rake technology can be used to TD-SCDMA base station to construct ST Rake, which simplified the system's implementation as well as enlarged users' capacity by the beamforming. The construction and capacity of MIMO sub-sectors by multi-beamforming have been presented. The proposed ST Rake algorithm include the multi-beamforming algorithm for MIMO sub-sectors and classical 1-D Rake algorithm. The calculating formulas for interference plus noise ratio(SINR) and bit error rate(BER) have been derived. Simulations verify that the proposed ST Rake receiver for BS is effective, and the BS systems can get higher system capacity and can be of better performance than presented TD-SCDMA systems.

• Journal of Positioning, Navigation, and Timing
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• 제9권4호
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• pp.327-336
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• 2020

This study presents signal availability of inter-operable global navigation satellite system (multi-GNSS) combined with future Korean Positioning System (KPS), specifically at geosynchronous orbit (GSO). The orbit of KPS, which is currently under conceptual feasibility study, is first introduced, and the grid points for evaluating space service volume (SSV) at GSO are generated. The signal observabilities are evaluated geometrically between those grid points and KPS/GNSS satellites. Then, analyzed are the visibility averaged over time/space and outage time to not access one or four signals. The reduction of maximum outage time induced by KPS are presented with different maximum off-boresight angles depending on L1/E1/B1 and L5/L3/E5a/B2 frequencies. Our numerical analysis shows that the SSV of multi-GNSS combined with KPS provides up to 7 additional signals and could provide continuous observation time (zero outage time) of more than four GNSS or KPS signals for 3.20-14.83% of SSV grid points at GSO. Especially at GSO above North/South America and Atlantic region, the introduction of KPS reduces the outage duration by up to 63 minutes with L1/E1/B1 frequency.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 추계종합학술대회
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• pp.1037-1040
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• 2005

본 논문에서는 다중 안테나 방식인 시공간 블록코드를 HDR-WPAN 시스템에 적용하여 페이딩 채널 환경에서 그 성능을 분석하였다. 다중 안테나 방식은 안테나마다 다른 페이딩을 겪은 신호를 다수의 송/수신 안테나에 의해 결합함으로써 경로 간의 채널 골을 서로 보완시켜 수신 성능을 향상시키는 기술이다. 시공간 블록코드는 최대 공간 다이버시티 이득을 얻을 수 있고 간단한 선형 처리만으로도 최대 근사화(ML) 수신기 구현이 가능한 시공간 다이버시티 기법이다. HDR-WPAN 시스템에 시공간 블록코드를 적용하였을 경우 페이딩 채널 환경에서 기존 시스템보다 10$^{-4}$ 의 BER(bit error rate) 기준에서 최대 14dB의 다이버시티 이득을 가졌다. 시뮬레이션 결과를 통해 HDR-WPAN 시스템에 시공간 블록코드를 적용하였을 경우 적은 전력으로도 신뢰성 있는 통신을 할 수 있음을 확인하였다.

• ETRI Journal
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• 제26권6호
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• pp.622-634
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• 2004

In this paper, we discuss the design problem and the robustness of space-frequency trellis codes (SFTCs) for multiple input multiple output, orthogonal frequency division multiplexing (MIMO-OFDM) systems. We find that the channel constructed by the consecutive subcarriers of an OFDM block is a correlated fading channel with the regular correlation function of the number and time delay of the multipaths. By introducing the first-order auto-regressive model, we decompose the correlated fading channel into two independent components: a slow fading channel and a fast fading channel. Therefore, the design problem of SFTCs is converted into the joint design in both slow fading and fast fading channels. We present an improved design criterion for SFTCs. We also show that the SFTCs designed according to our criterion are robust against the multipath time delays. Simulation results are provided to confirm our theoretic analysis.

• Journal of Communications and Networks
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• 제5권2호
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• pp.174-183
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• 2003

Space-Time (ST) codes are known to provide high transmission rates, diversity and coding gains. In this paper, a tight upper bound on the error probability of ST codes over rapid fading channels is presented. Moreover, ST codes suitable for rapid fading channels are presented. These codes are designed using the QPSK and 16-QAM signal constellations. The proposed codes are based on two different encoding schemes. The first scheme uses a single trellis encoder, whereas the second scheme uses the I-Q encoding technique. Code design is achieved via partitioning the signal space such that the design criteria are maximized. As a solution for the decoding problem of I-Q ST codes, the paper introduces a low-complexity decoding algorithm. Results show that the I-Q ST codes using the proposed decoding algorithm outperform singleencoder ST codes with equal complexity. The proposed codes are tested over fading channels with different interleaving conditions, where it is shown that the new codes are robust under such imperfect interleaving conditions.

• 한국주거학회논문집
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• 제14권6호
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• pp.87-93
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• 2003

The purpose of this study is to investigate the characteristics of the spatial composition at the Modern Korean houses after the time of the enlightenment in Daegu province. The orientation of the houses, way of the entrance and its relation to the inner house(An-Chae), the type of floor plan, the compositional methods of exterior space, and the usage of exterior space are investigated. As the results, the Modern Korean houses after the time of the enlightenment in Daegu province are showed the symptom of the modernization in aspect of the site plan and the compositional methods of exterior space.