• Bulletin of the Korean Chemical Society
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• v.19 no.4
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• pp.471-475
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• 1998

Phase shift spectroscopy is applied to Eu(Ⅲ) luminescence from $Eu^{3+}$-exchanged Y zeolite. The phase shift and intensity modulation of luminescence following intensity-modulated excitation are measured as a function of modulation frequency and they are fitted into a double exponential decay. The fast decay component, compared with the slow one, has narrower spectral bandwidth and is emitted from the $Eu^{3+}$ that has more polar and definite environment with higher symmetry and that interacts more easily with hydrated water molecules. The fast decay component is attributed to $Eu^{3+}$ at site Ⅱ' while the slow one to $Eu^{3+}$ at sites Ⅰ' and Ⅰ.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.2009-2019
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• 2013

In this paper, we propose an automatic modulation recognition algorithm based on cyclic moment and new modified cumulant for analog and digital modulation signals. It is noteworthy that each modulated signal has different cycle frequency characteristics according to its order of cyclic moment. By means of this characteristics as classification features, various modulated signals can be efficiently classified. Also, to identify modulated signals having the same cycle frequency characteristics, we take advantage of the additional classification factors such as variations of envelope and phase as well as modified cumulant. The proposed algorithm was evaluated by considering the number of symbols, SNR, and frequency offset. In the simulation condition where the number of gathered symbols was about 819, and SNR and frequency offset were above 10dB and below 25%, respectively, the average accuracy of the proposed algorithm was more than 95%.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.1204-1208
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• 1991

This paper describes the 2-channel telemeter system using AM(Amplitude Modulation) - FM (Frequency Modulation) techniques suitable for measurement of spindle torque by strain gage. In order to evaluate the developed system, the model tests were performed for test specimens. The developed system was installed on the plate mill and it was possible to measure and analyze the torque signal of spindle,

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.36-39
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• 2000

The adaptive learning circuit is designed the basis of modeling of MFSFET (Metal-Ferroelectric-Semiconductor FET) and the numerical results is analyzed. The output frequency of the adaptive learning circuit is inversely proportioned to the source-drain resistance of MFSFET and the capacitance of the circuit. The output frequency modulation of the adaptive learning circuit is investigated by analyzing the source-drain resistance of MFSFET as functions of imput pulse numbers in the adaptive learning circuit and the dimensionality factor of the ferroelectric thin film. From the results, the frequency modulation characteristics of the adaptive learning circuit, that is, adaptive learning characteristics which means a gradual frequency change of output pulse with the progress of input pulse are confirmed.

• Journal of electromagnetic engineering and science
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• v.5 no.1
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• pp.36-42
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• 2005

In this paper, the optimal position of optical phase conjugator(OPC) excellently compensating distorted WDM channels with initial frequency chirp due to both chromatic dispersion and self phase modulation(SPM) is numerically investigated. Highly-nonlinear dispersion shifted fiber(HNL-DSF) is used as a nonlinear medium of OPC in order to widely compensate WDM signal band. It is confirmed that if the OPC position was shifted from mid-way of total transmission length dependence on the initial frequency chirp as well as modulation format and fiber dispersion coefficient, it is possible to cancel the performance degradation owing to the initial frequency chirp. Using proposed configuration, it is possible to remove all in-line dispersion compensator, reducing span losses and system costs in the long-haul broadband WDM systems.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.600-604
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• 1991

In this paper, an advanced PWM modulation strategy for driving a variable-speed induction motor is introduced. According to this method, the technique of efficiently eliminating harmonics component is achived. A switching pattern was computed making use of the near-proportionality of voltage and frequency in AC machines operating with constant flux. At low magnitudes and low frequencies of the foundamental, many more harmonics are eliminated than at high magnitudes and frequencies. In order to keep the inverter switching frequency constant over the output frequency range, chopping times diminishes as the frequency of the fundamental increases.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.3
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• pp.24-38
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• 1994

In this paper we develop the software simulator written in a C language for a frequency modulation synthesis and the approximate range of parameters, for a musically satisfactory timbre, obtained by using the software simulator will be applied to develop an algorithm for parameter extraction. For a frequency modulation synthesis, we also develop an algorithm for parameter extraction through waveform analysis in the time domain as well as spectrum analysis using a FFT in the frequency domain. To verify the validity of the developed algorithm as well as software simulator experimentally, we extract parameters for the several music instruments using the suggested algorithm and analyze the synthesized sound by applying the parameters to the software simulator. The evaluation of the synthesized sound is first done by listening the sound directly as a subjective testing. Secondly, to evaluate the synthesized sound objectively with an engineering sense, we compare the synthesized sound with an original one in a time domain and a frequency domain.

• Journal of Power Electronics
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• v.14 no.2
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• pp.282-291
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• 2014

This paper presents a detailed theoretical analysis and performance assessment of the capacitor voltage balancing strategies for staircase modulated modular multilevel converters (MMC) in terms of the algorithm structures, voltage balancing effect, and switching frequency. A constant-frequency redundancy selection (CFRS) method with minimal switching loss is proposed and the function realization of specific modules of the algorithm is given. This method is simple and efficient in both switching frequency and regulation capacity. Laboratory results show very good agreement with the theoretical analysis and numerical simulations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.7
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• pp.49-57
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• 2008

This paper presents a voltage source type half-bridge series resonant high frequency (HF) inverter for induction heated fixing roller in copy machines. This high-frequency inverter works under zero current soft switching (ZCS) commutation and has wide power regulation range due to employing a pulse density modulation (PDM) scheme. Transient and steady state operating modes of the inverter are presented in this paper together with its PDM-based power regulation system. Experimental operating performances of the developed HF-ZCS inverter as well as power losses and actual efficiency are discussed and compared with computer simulation results.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.226-229
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• 2003

Under the prsence of the frequency and timing offset, we evaluate the BER performance of the FFH-MA system using noncoherent M-ary FSK modulation in the Rayleigh fading channel. The numerical resuts show that while the frequency and timing offset increases at a given SNR, the BER is severely degraded. The threshold level used in the envelope detector increases with the increase of the frequency and timing offset, and with the proper selection of the threshold level, the BER can be improved under the presence of such offsets.