• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.2
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• pp.192-199
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• 2000

This paper describes a Phase-Shift Pulse Modulation(PSPM) and Frequency Trad이ng Pulse Modulation(FTPM) s series resonant high-frequency inverter using IGBT for the power control of high-frequency induction heating u using Neuro-Fuzzy, which is practically applied for 20kHz~500kHz induction-heating and melting power supply in i indust껴aJ fields. The adaptive frequency tracking based on the PSPM(phase-shifting pulse modulation) r regulation scherne is presented in or$\tau$ler to l11lmmlZe svvitching losses. The trially-produced breadboards using N Neuro Fuzzy controller are successfully demonstrated cUld cliscussed.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.2
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• pp.221-225
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• 2008

In this paper, to avoid the frequency analysis requiring a high sampling rate, time-warped similarity measure algorithms, which are able to classify objects even with a low-rate sampling rate as time- series methods, are presented and proposed the DTW-Cosine algorithm, as the best classifier among them in wireless sensor networks. Two problems, local time shifting and spatial signal variation, should be solved to apply the time-warped similarity measure algorithms to wireless sensor networks. We find that our proposed algorithm can overcome those problems very efficiently and outperforms the other algorithms by at least 10.3% accuracy.

• Journal of Biomedical Engineering Research
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• v.20 no.3
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• pp.275-281
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• 1999

Conventional PW Doppler systems suffer from the ambiguity of measured blood velocities due to the spectrum aliasing when the corresponding Doppler frequencies are greater than the Nyquist frequency. Base-line shift is a customary method for dealiasing the Doppler spectrums. I lowever, Doppler audio signals still remain unchanged even when the base-line shift method is applied. This paper de scribes an method for dealiasing both the Doppler spectra and audio signals by using sampling rate expansion, frequency shifting, and filtering poerations. For undirectional flows, the method can increase the maximum detectable Doppler frequency from the Nyquist limit of one-half of the Pulse Repetition Frequency(PRF) to the PRF. Experiments with real data have been performed to verify the proposed method.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.391-400
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• 2008

Multi-pulse topology of converters using elementary six-pulse GTO - VSC (gate turn off based voltage source converter) operated under fundamental frequency switching (FFS) control is widely adopted in high power rating static synchronous compensators (STATCOM). Practically, a 48-pulse ($6{\times}8$ pulse) configuration is used with the phase angle control algorithm employing proportional and integral (PI) control methodology. These kinds of controllers, for example the ${\pm}80MVAR$ compensator at Inuyama switching station, KEPCO, Japan, employs two stages of magnetics viz. intermediate transformers (as many as VSCs) and a main coupling transformer to minimize harmonics distortion in the line and to achieve a desired operational efficiency. The magnetic circuit needs altogether nine transformers of which eight are phase shifting transformers (PST) used in the intermediate stage, each rating equal to or more than one eighth of the compensator rating, and the other one is the main coupling transformer having a power rating equal to that of the compensator. In this paper, a two-level 48-pulse ${\pm}100MVAR$ STATCOM is proposed where eight, six-pulse GTO-VSC are employed and magnetics is simplified to single-stage using four transformers of which three are PSTs and the other is a normal transformer. Thus, it reduces the magnetics to half of the value needed in the commercially available compensator. By adopting the simple PI-controllers, the model is simulated in a MATLAB environment by SimPowerSystems toolbox for voltage regulation in the transmission system. The simulation results show that the THD levels in line voltage and current are well below the limiting values specified in the IEEE Std 519-1992 for harmonic control in electrical power systems. The controller performance is observed reasonably well during capacitive and inductive modes of operation.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1221-1229
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• 2022

In this work, the guided wave de-bonding area-detecting technique was studied for application to containment liner plates in nuclear power plant areas. To apply this technique, an appropriate Lamb wave mode, symmetric and longitudinal dominance, was verified by the frequency shifting technique. The S0 2.7 MHz mm Lamb wave mode was chosen to realize quantitative experimental results and their visualization. Results of the bulk wave, longitudinal wave mode, and comparison experiments indicate that the wave mode was able to distinguish between the de-bonded and bonded areas. Similar to the bulk wave cases, the bonded region could be distinguished from the de-bonded region using the Lamb wave approach. The Lamb wave technique results showed significant correlation to the de-bonding area. As the de-bonding area increased, the Lamb wave energy attenuation effect decreased, which was a prominent factor in the realization of quantitative tomographic visualization. The feasibility of tomographic visualization was studied via the application of Lamb waves. The reconstruction algorithm for the probabilistic inspection of damage (RAPID) technique was applied to the containment liner plate to verify and visualize the de-bonding condition. The results obtained using the tomography image indicated that the Lamb wave-based RAPID algorithm was capable of delineating debonding areas.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.6 s.348
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• pp.1-8
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• 2006

In the asynchrous OFCDM(Orthogonal Frequency and Code Division Multiplexing) system, a three-step cell search algorithm is performed for the initial synchronization in the following three steps: OFCDM symbol timing, i.e., Fast Fourier Transform(FFT) window timing is estimated employing guard interval (GI) correlation in the first step, then the frame timing and CSSC (Cell Specific Scrambling Code) group is detected by taking the correlation of the CPICH(Common Pilot Channel) based on the property yeilded by shifting the CSSC phase in the frequency domain. Finally, the CSSC phase within the group is identified in the third step. This paper proposes a modification code(PCSSCG:Patial Cell Specific Scrambling Code Group) of the conventional CPICH based cell search algorithm in the second step which offers MS(Mobile Station) complexity reductions with the nearly same performance. The proposed method is to be compared and verified through the computer simulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.139-149
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• 2007

Asynchronous OFCDM(Orthogonal Frequency and Code Division Multiplexing) systems must have a cell search process necessarily unlike synch개nous systems. this process is hewn initial synchronization and a three-step cell search algorithm is performed for the initial synchronization in the following three steps: OFCDM symbol timing, i.e., Fast Fourier Transform(FFT) window timing is estimated employing guard interval (GI) correlation in the first step, then the frame timing and CSSC(Cell Specific Scrambling Code) group is detected by taking the correlation of the CPICH(Common Pilot Channel) based on the property yielded by shifting the CSSC phase in the frequency domain. Finally, the CSSC phase within the group is identified in the third step. This paper proposes a modification group code with two or three block of the conventional CPICH based cell search algorithm in the second step which offers MS(Mobile Station) complexity reductions. however, the effect of the reduction complexity leads to degradation of the performance therefore, look for combination to have the most minimum degradation. the proposed block type group code with suitable combinations is the nearly sane performance as conventional group code and has a complexity reduction that is to be compared and verified through the computer simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.6 s.348
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• pp.9-17
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• 2006

We proposed a new High-speed CMOS Level Up/Down Shifter circuits that can be used with Dynamic Voltage and Frequency Scaling(DVFS) algorithm, for low power system in the SoC(System-on-Chip). This circuit used to interface between the other voltage levels in each CMOS circuit boundary, or between multiple core voltage levels in a system bus. Proposed circuit have advantage that decrease speed attenuation and duty ratio distortion problems for interface. The level up/down shifter of the proposed circuit designed that operated from multi core voltages$(0.6\sim1.6V)$ to used voltage level for each IP at the 500MHz input frequency The proposed circuit supports level up shifting from the input voltage levels, that are standard I/O voltages 1.8V, 2.5V, 3.3V, to multiple core voltage levels in between of $0.6V\sim1.6V$, that are used internally in the system. And level down shifter reverse operated at 1Ghz input frequency for same condition. Simulations results are shown to verify the proposed function by Hspice simulation, with $0.6V\sim1.6V$ CMOS Process, $0.13{\mu}m$ IBM CMOS Process and $0.65{\mu}m$ CMOS model parameters. Moreover, it is researched delay time, power dissipation and duty ration distortion of the output voltage witch is proportional to the operating frequency for the proposed circuit.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.178-203
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• 2018

In this paper, authors have been evaluated the Frame Error Rate (FER) performance of IEEE 802.11 a/g/p standard 5 GHz frequency band WLAN over Rayleigh and Rician distributed fading channels in presence of Additive White Gaussian Noise (AWGN). Orthogonal Frequency Division Multiplexing (OFDM) based transceiver is implemented by using real-time signal processing frameworks (IEEE 802.11 Blocks) in GNU Radio Companion (GRC) and Ettus USRP N200 is used to process the symbol over the wireless radio channel. The FER is calculated for each sub-carrier conventional modulation schemes used by OFDM such as BPSK, QPSK, 16, 64-QAM with different punctuated coding rates. More precise SNR is computed by modifying the SNR calculation process of YANS and NIST error rate model to estimate more accurate FER. Here, real-time signal constellations, OFDM signal spectrums etc. are also observed to find the effect of multipath propagation of signals through flat and frequency selective fading channels. To reduce the error rate due to the multipath fading effect and Doppler shifting, channel estimation (CE) and equalization techniques such as Least Square (LS) and training based adaptive Least Mean Square (LMS) algorithm are applied in the receiver. The simulation work is practically verified at GRC by turning into a pair of Software Define Radio (SDR) as a simultaneous transceiver.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.209-215
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• 2006

Circular Bragg gratings(CBGs) canbe incorporated in most of the semiconductor laser devices because of the frequency-selective property applicable as an optical narrowband-pass filter in DWDM optical communications. In this paper, the optical filtering characteristics of CBGs are evaluated by a novel and simple analytic modal transmission-line theory(MTLT), which is based on Floquet-Babinet's principle. The numerical results reveal that this method offers a simple and convenient algorithm to analyze the filtering characteristics of CBGs as well as is extended conveniently to evaluate the guiding problems of circular multi-layered periodic structures.