• Journal of Positioning, Navigation, and Timing
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• v.6 no.1
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• pp.35-41
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• 2017

Precise Point Positioning (PPP) method is based on dual-frequency data of Global Navigation Satellite Systems (GNSS). The recent multi-constellations GNSS (multi-GNSS) enable us to bring great opportunities for enhanced precise positioning, navigation, and timing. In the paper, the multi-GNSS PPP with a combination of four systems (GPS, GLONASS, Galileo, and BeiDou) is analyzed to evaluate the improvement on positioning accuracy and convergence time. GNSS observations obtained from DAEJ reference station in South Korea are processed with both the multi-GNSS PPP and the GPS-only PPP. The performance of multi-GNSS PPP is not dramatically improved when compared to that of GPS only PPP. Its performance could be affected by the orbit errors of BeiDou geostationary satellites. However, multi-GNSS PPP can significantly improve the convergence speed of GPS-only PPP in terms of position accuracy.

• Journal of The Korean Digital Architecture Interior Association
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• v.6 no.2
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• pp.47-54
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• 2006

Chang Hyon-Gwang(1554-1637) compared the relationship between Ipam and the 28 places with that of the Polestar and 28 constellations. And he considered the ipam to be the core of the universe. This paper aims to identify the meaning of christening to the places for him. I analyzed contents of Chang's , and which preserved the traditional view of the site and writings. As a result, christening to the natural places mean that promote the environment for housing. It is a architecture by itself.

• Journal of Communications and Networks
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• v.14 no.3
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• pp.243-251
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• 2012

Under the power-based capture model, a transmission is successfully received at the destination, even in the presence of other transmissions and background noise, if the received signal-to-interference-plus-noise ratio exceeds a capture threshold. We evaluate the spectral efficiency of simple multi-user channels by combining the basic capture model with a communication-theoretic model. The result is a more refined capture model that incorporates key system design parameters (such as achievable bit rate, target bit error rate, channel bandwidth, and modulation signal constellations) that are absent from the basic capture model. The relationships among these parameters can serve as a tool for optimizing the network performance.

• Journal of the Korean Society of Earth Science Education
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• v.5 no.2
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• pp.166-174
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• 2012

This study is purposed to survey on astronomical observation experiences of elementary students and teachers. Survey samples are 182 elementary students and 51 elementary teachers, and 8 students and 2 teachers among them are interviewed. The results of this study show that most elementary students are not interested in observing constellations, planets, and moon. Also most elementary students and teachers are not taught to observe astronomical objects. Finally, regarding the difficulty of astronomical practice, teachers pointed out that lack of knowledge about astronomy.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.179-182
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• 1988

Since the bits in any encoded PCM word are of different importance to the bit positions, in order to improve the signal to noise ratio the technique that the encoded signal bits are weighted for the QPSK transmission system, is presented. Also the erasure zone is established at the detector, such that if the output falls into the erasure zone, the regenerated sample is replaced by interpolation. Two weighting methods are shown here. One is the method that the same weighting profile is used to Q and I dimension in QPSK signal constellations. The other is diferent weighting to Q and I dimension. The gains of this new technique in overall signal s/n compared to conventional QPSK transmission system were 5 db and 2db, respectively.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.206-212
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• 2012

In this paper, in order to effectively apply unitary space-time modulation to the direct-sequence spread-spectrum multiple-access (DSSS-MA) networks, we propose a low-rate, noncoherent, unitary, and space-time modulated DSSS system supporting any number of transmit antennas based on Walsh matrices. The proposed scheme simultaneously performs bandwidth spreading and space-time coding and outperforms those using high-rate, conventional unitary space-time constellations. Furthermore, the proposed scheme allows for a simple detector structure based on fast Walsh transforms.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.167-176
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• 2007

In multimedia communication systems, efficient transmission system design should incorporate the use of matching unequal error protection (UEP), since source coders exhibit unequal bit error sensitivity. In this paper, we present UEP schemes which exploit differences in bit error protection levels in orthogonal frequency division multiplexing (OFDM) systems over frequency selective fading channels. We introduce an UEP scheme which improves the link performance with multiple transmit and receive antennas. Especially, we propose a new receiver structure based on two stage Maximum Likelihood detection (MLD) schemes which can approach the performance of a full search MLD receiver with much reduced computational complexity. In the performance analysis, we derive a generalized pairwise error probability expression for the proposed UEP schemes. Simulation results show that the proposed schemes achieve a significant performance gain over the conventional equal error protection (EEP) scheme.

• Bulletin of the Korean Mathematical Society
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• v.59 no.6
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• pp.1409-1422
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• 2022

A 3-fold quotient terminal singularity is of the type $\frac{1}{r}(b,1,-1)$ with gcd(r, b) = 1. In [6], it is proved that the economic resolution of a 3-fold terminal quotient singularity is isomorphic to a distinguished component of a moduli space 𝓜_𝜃 of 𝜃-stable G-constellations for a suitable 𝜃. This paper proves that each connected component of the moduli space 𝓜_𝜃 has a torus fixed point and classifies all torus fixed points on 𝓜_𝜃. By product, we show that for $\frac{1}{2k+1}(k+1,1,-1)$ case the moduli space 𝓜_𝜃 is irreducible.

• Journal of the Korean Society of Earth Science Education
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• v.16 no.2
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• pp.302-318
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• 2023

The purpose of this study was to study to the effect of presenting SBF questions on the level of conceptual achievement and eye movement of elementary students in seasonal constellation learning that requires systems thinking. In this study, the effectiveness of SBF questions was divided into experimental groups and comparison groups, and scientific texts with different question types were presented to analyze the level of conceptual achievement and differences in eye movement of sixth-grade elementary students. Data analysis quantitatively analyzed the pre- and post-test results of the developed concept test paper and the eye movement data when learning scientific texts related to seasonal constellations. As a result of the study, first, the SBF question was a valid learning strategy for learning seasonal constellations. The SBF question showed a statistically significant difference (p<0.05) in the pre- and post-test between groups, and a statistically significant difference (p<0.001) in the pre- and post-test within the group. Second, SBF questions had a positive effect on students' learning by inducing learners with low preconceptions to area of interest that help them achieve concepts. In other words, when presenting SBF questions with visual data from a space-based perspective, it was confirmed based on the results of eye movement analysis that there was a significant difference in total fixation count (p<0.01) of learners. On the other hand, for learners with high scientific preconceptions, the effect of exploration was not significant because the preconceptions of the learners themselves acted as a hard core rather than the effect of SBF questions. This study is different from existing seasonal constellation learning studies in that it provides quantitative data through pre- and post-test and eye movement analysis in the seasonal constellation learning process, and can help elementary students learn seasonal constellations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.12
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• pp.1258-1268
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• 2014

In this paper, we propose and design IBFD system based on DCR. And then, we analyze effect of DC offset by self-interference in the proposed system. Also, we evaluate BER performance of the proposed system according to DC offset. As a result of the simulation, we can confirm that when the self-interference is not completely cancelled by the RF cancellation, linearity of desired signal and self-interference is distorted by DC offset. Also, in the proposed system using m-QAM modulation, DC offsets of multi-level are caused by self-interference with m-QAM modulation. As a result, constellations of desired signal and self-interference are greatly distorted. In contrast, in the proposed system using m-PSK modulation, DC offset of single level is caused by self-interference with m-PSK modulation. In this condition, we confirm that distortion of constellations of desired signal and self-interference is less than when using m-QAM modulation. That is, we can confirm that m-PSK modulation is effective than m-QAM modulation in DCR based IBFD system. Also, we can confirm that it is important to cancel self-interference as much as possible in RF-stage.