• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.12
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• pp.1091-1099
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• 2015

UFMC(Universal-Filtered Multi-carrier) and FBMC(Filter Bank Multi-carrier) system are receiving attention as candidate waveforms for 5G mobile communication system. But, these systems have high PAPR(Peak to Average Power Ratio) problem because these systems use a number of subcarrier. In this paper, we propose DFT(Discrete Fourier Transform) spreading based DFT-s(spreading)-UFMC system and DFT-s-FBMC system in order to overcome the PAPR drawback. In order to evaluate PAPR performance of the proposed systems, we design and simulate OFDM(Orthogonal Frequency Division Multiplexing), UFMC, FBMC, DFT-s-OFDM, DFT-s-UFMC, DFT-s-FBMC system. As simulation results, each PAPR performance of DFT-s-OFDM system, DFT-s-UFMC system, and DFT-s-FBMC system rise by 2.7 dB, 2.8 dB, and 1.1 dB respectively by DFT spreading technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.440-446
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• 2007

This paper addresses a new representation of DFT matrix via the Jacket transform based on the element inverse processing. We simply represent the inverse of the DFT matrix following on the factorization way of the Jacket transform, and the results show that the inverse of DFT matrix is only simply related to its sparse matrix and the permutations. The decomposed DFT matrix via Jacket matrix has a strong geometric structure that exhibits a block modulating property. This means that the DFT matrix decomposed via the Jacket matrix can be interpreted as a block modulating process.

• Journal of the Korean Chemical Society
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• v.48 no.5
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• pp.537-541
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• 2004

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.4
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• pp.7-12
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• 1984

A composite - discrete courier transform (CDFT) is developed, which can diagonalize a real symmetric circulant matrix. In general the circulant matrices can be diagonalized by the discrete Fourier transform (DFT). With the analysis of the variance distributions of the DFT and CDFT for the general symmetric covariance matrix of real signals, the DFT and CDFT are compared with respect to the rate distortion performance measure. The results show that the CDFT is more efficient than the DFT in bit rate reduction. In addition, for a particular 64$\times$64 points covariance matrix (f(q)=(0.95)q), the amount of the relative average bit rate reduction for the CDFT with respect to the DFT is obtained by 0.0095 bit with a numerical calculation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.4
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• pp.470-476
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• 2002

This paper presents an analysis of the performance degradation of coefficient approximation and frequency deviation in phase measurement algorithm based on Sliding-DFT. The analytic derivation is based on the statistics of the error dynamic equation that describes the error propagation of the recursion. The analysis result is intended to obtain a closed-form equation of error variance in terms of the number of bits used in coefficient approximation, the length of the DFT data block, and noise. It is verified with data obtained from the computer simulations.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.5
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• pp.218-224
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• 2001

This paper describes the identification of torsional modes and power oscillation modes including the inter-area modes and local modes of KEPCO using the proposed DFT analysis algorithm which is applied to the digitally recorded RMS values of power system variables such as steady-state measured active power, load angle and so on. As a result, the inter-area mode of 0.65Hz and the local modes of the three different generators were identified. In addition the torsional modes of two steam-turbo generators were analyzed by applying the DFT algorithm. Thus, this paper clearly shows the availability of the proposed DFT algorithm that can analyze the digitally recorded effective values measured from the equipment such as PMU of DSM.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.610-615
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• 2014

Filterbanks have been widely used in the field of multi-channel signal processing for their simple efficient implementation architectures. Especially, the polyphase DFT(Discrete Fourier Transform) filterbank is the most preferred filterbank for the uniform spaced multi-channel processing due to its simplicity. In frequency hopped communication systems, however, the use of the polyphase DFT filterbank is limited due to its undesirable transient response from hop-to-hop transitions. In this paper, the transient response of polyphase DFT filterbanks in the hop-to-hop transition was analyzed, and the efficient methods to overcome such a problem was proposed. Simulation results showed that the proposed schemes could resolve this issue efficiently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10A
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• pp.941-948
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• 2008

In this paper, the effect of unobtainable channel frequency response (CFR) inside virtual subcarreiers on DFT-based channel estimation is derived and introduced numerically because the CFRs cause the leakage to the estimated channel and degrade the estimation performance. In addition, the performance of DFT-based channel estimation is analyzed with respect to the number of virtual subcarriers, pilot spacing and the number of unobtainable CFRs at equi-distance subcarriers inside virtual subcarriers.

• Journal of the Korean Chemical Society
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• v.57 no.1
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• pp.20-24
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• 2013

The effect of the DFT methods and basis sets on harmine molecule has been investigated. 26 DFT methods with 6 basis sets were used. Two main comparison chosen DFT methods in this work has been investigated. It is concluded that this contribution is very important and cannot be neglected. In the following analysis, changes in energy levels were investigated by two different methods. Considering a specific basis set, changes in energy levels were obtained using different DFT methods. A specific DFT method is chosen and changes in energy levels have been investigated by means of various basis sets. Effect of the choice of basis sets on geometrical parameters on harmine molecule has also been investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.87-94
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• 2007

A structural dynamic analysis can be divided into a time domain analysis and a frequency domain analysis. The time domain analysis makes use of a direct integration method or a mode superposition method and the frequency domain analysis applies a DFT method. Generally the DFT method is more effective method in case of calculating response of periodic excitation. But in case of transient excitation exact solution can not be acquired. So, by modifying the response or increasing the period accuracy of solution can be enhanced. Accordingly this study analyzed dynamic responses of structures under aperiodic moving load in time domain and frequence domain. Consequently it is concluded that exact solution would be get enough using DFT method by increasing the duration of free vibration or modifying the dynamic response.