• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.9-12
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• 2001

In this paper, the natural space-time coding is applied for a DS-CDMA system with multiple transmit/receive antennas in a Rayleigh fading channel. With difference of arrival times from transmit antennas a modified maximum likelihood (ML) decoding algorithm is proposed for the space-time coded DS-CDMA system. The proposed decoding algorithm performs ML decoding over the transition of two consecutive branches by using a modified branch metric with the partial autocorrelation. By simulation, it is shown that the proposed decoding algorithm achieves significant performance improvement over the ML decoding algorithm without the modified branch metric.

• The Journal of Korean Physical Therapy
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• v.14 no.4
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• pp.45-54
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• 2002

The purpose of this study was to describe the gait pattern and parameters of the healthy elderly over 65years of age by the GATERite system. The subjects were sorted into two groups, depending on their sex: male and female. And female subjects were sorted into three groups, depending on their age. From time parameters and space parameters of gait cycle, between groups, the following results were made. The time parameters such as cadence, velocity, step time, single support and double support were the less the male than the female. And the higher age, the lower value except 80 age group, while no statistically significant. The space parameters(step length and stride length) were the longer the male than the female, and the higher age, the lower value while no statistically signigicant. The functional ambulation profile was high correlation with time and space parameters statistically significant.

• Communications for Statistical Applications and Methods
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• v.10 no.1
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• pp.19-30
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• 2003

Spatiotemporal statistical models are used for analyzing space-time data in many fields, such as environmental sciences, meteorology, geology, epidemiology, forestry, hydrology, fishery, and so on. It is well known that classical spatiotemporal process modeling requires the estimation of space-time variogram or covariance functions. In practice, the estimation of such variogram or covariance functions are computationally difficult and highly sensitive to data structures. We investigate a Bayesian hierarchical model which allows the specification of a more realistic series of conditional distributions instead of computationally difficult and less realistic joint covariance functions. The spatiotemporal model investigated in this study allows both spatial component and autoregressive temporal component. These two features overcome the inability of pure time series models to adequately predict changes in trends in individual sites.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.874-879
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• 2014

This study is aimed to evaluate the acoustic performances of outdoor apartment complex and to analyze acoustic performances change based on greening conditions. The object space located in Seoul, Yangcheon-gu, Sinjung-dong and classified according to type of space-form. The measurement reverberation time at 500 Hz is 0.86~1.84sec. The simulated reverberation time at 500 Hz is decreased from 1.57sec to 0.57sec in ㅁshape type of 69% treatment with greening and 1.7sec to 0.89sec in ㄷshape type of 70% treatment and 1.05sec to 0.53sec in ㄴshape type of 61.6% treatment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2341-2350
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• 2012

Face detection is the first step of vision-based driver fatigue detection method. Traditional face detection methods have problems of high false-detection rates and long detection times. A space-time restrained Adaboost method is presented in this paper that resolves these problems. Firstly, the possible position of a driver's face in a video frame is measured relative to the previous frame. Secondly, a space-time restriction strategy is designed to restrain the detection window and scale of the Adaboost method to reduce time consumption and false-detection of face detection. Finally, a face knowledge restriction strategy is designed to confirm that the faces detected by this Adaboost method. Experiments compare the methods and confirm that a driver's face can be detected rapidly and precisely.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.5
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• pp.1-8
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• 2018

This paper proposes a simple encryption technology for space-time block coding algorithm. Space-time block coding algorithm uses two antennas in transmitting data which consists of original data and transformed data for the purpose of combining in the receiver. This kind of two transmission antenna data could be exchanged and transmitted on each other's antenna individually, which can be used as a simple encryption algorithm. Encryption timing control informations should be shared between transmitter and receiver beforehand. It is shown that the proposed architecture can give performance enhancement compared with no encryption cases.

• ETRI Journal
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• v.28 no.5
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• pp.680-683
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• 2006

One objective in developing the next generation of wireless communication systems is to increase data rates and reliability. A promising way to achieve this is to combine multiple-input and multiple-output signal processing with a space-time coding scheme, which offers higher coding and diversity gains and improves the spectrum efficiency and reliability of a wireless communication system. It is noted, however, that time delay differences and phase differences among different channels increase symbol interference and degrade system performance. In this letter, we investigate phase differences and their effects on multiple-input and multiple-output systems, and propose a compensation algorithm for the Rayleigh fading model to minimize their effects.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.177-184
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• 2007

Alamouti space-time code (STC) is a part of the UMTS-WCDMA standard. However, up to the best of our knowledge no exact closed-form outage and bit error probability (BEP) formulas for this famous code exists. Evaluating its performance through simulations is time-consuming and therefore, there should be analytical performance graphs to serve as a reference which are derived in this paper for coherently MPSK-modulated data. Additionally, analytical results take into account different channel fading levels from transmit antennas to receive ones.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.60.2-60.2
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• 2019

Based on our experience on exoplanet transit observation, we propose the exoplanet science cases with Small Telescope Network. One is the follow-up observation for validation of exoplanet candidates. TESS(Transiting Exoplanet Survey Satellite) is pouring out exoplanet candidates in bright stars(V<15) on all the sky. Since Small Telescope Network will consist of 0.5-1m telescopes, we will expect to produce promising outcomes from the follow-up observation of bright candidates. Next is the transit time observation. By spectroscopy of space and large telescopes during transit event, it can be possible to find the bio signatures in exoplanet atmosphere. So, in terms of cost, it is critical to determine the exact time of transit event. In addition, detecting the variation of transit time can reveal another exoplanet and exomoon in the system. In order to determine the transit time and its variation, the accumulation of transit event data is more important than the quality of photometric data. We expect that it can be a challenging project of Small Telescope Network.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.67-72
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• 2014

The next generation small satellite-1 (NEXTSat-1) program has been kicked off in 2012, and it will be launched in 2016 for the science missions and the verification of space core technologies. The payloads for these science missions are the Instrument for the Study of Space Storms (ISSS) and NIR Imaging Spectrometer for Star formation history (NISS). The ISSS and the NISS have been developed by Korea Advanced Institute of Science and Technology (KAIST) and Korea Astronomy and Space science Institute (KASI) respectively. The ISSS detects plasma densities and particle fluxes of 10 MeV energy range near the Earth and the NISS uses spectrometer. In order to verify the spacecraft core technologies in the space, the total of 7 space core technologies (SCT) will be applied to the NEXTSat-1 for space verification and those are under development. Thus, the operation modes for the ISSS and the NISS for space science missions and 7 SCTs for technology missions are analyzed for the required operation time during the NEXTSat-1's mission life time of 2 years. In this paper, the operational concept of the NEXTSat-1's science missions as well as the verification of space core technologies are presented considering constraints of volume, mass, and power after launch.