• Proceedings of the KSR Conference
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• 2008.06a
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• pp.691-706
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• 2008

ATP(Automatic Train Protection) system in railway signaling system is the important one grasping the position and velocity of a train. The wayside transmitter of ATP system is installed between rails. In concrete slab track, the signal current using wayside transmitter of ATP system is influenced by reinforcing bars. The magnetic coupling between reinforcing bars and wayside transmitter of ATP system as a filter makes an input current distorted. So, it makes an alternating current signal with a desirable size not transmit to on-board system of a train. Way to decrease the distortion of an input current signal frequency is to avoid maximum induction current frequency. And the induction phenomenon between reinforcing bars insulated and wayside transmitter of ATP system does not occur. In this paper, we represent the model about wayside transmitter of ATP system and reinforcing bars on the concrete slab tracks, and calculated the parameters demanded for the model. Also, we demonstrated it through the Maxwell program. Furthermore, we calculated impedance on wayside transmitter used in KVB system and ERTMS/ETCS system which are a kind of ATP system, frequency response of induction current, using the Matlab, and demonstrated the validity of it, using the PSpice program.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.1018-1020
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• 2013

Conventionally, PCB fabrication processes detects simply electrical characteristics of TCP and COF by automatic manufacturing system and additionally, by introducing human visual detection, those are very ineffective in view of low cost implementation. So, this paper presents an efficient detection algorithm for short and protrusion-type defects based on reference images by using local binary pattern analysis. The proposed methods include several preprocessing techniques such as histogram equalizing, the compensation of spatial position and maximum distortion coordination Through several experiments, it is shown that the proposed method can improve the defect detection performance compared to the conventional schemes.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.5
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• pp.358-368
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• 2020

Grid-connected inverters (GCIs) based on renewable energy sources play an important role in enhancing the sustainability of a society. Harmonic standards, such as IEEE 519 and P1547, which require the total harmonic distortion (THD) of the output current to be less than 5%, should be satisfied when GCIs are connected to a grid. However, achieving a current THD of less than 5% is difficult for GCIs with an output filter under a distorted grid condition. In this study, a novel harmonic compensation method that uses a digital lock-in amplifier (DLA) is proposed to eliminate harmonics effectively at the output of GCIs. Accurate information regarding harmonics can be obtained due to the outstanding performance of DLA, and such information is used to eliminate harmonics with a simple proportional-integral controller in a feedforward manner. The validity of the proposed method is verified through experiments with a 5 kW single-phase GCI connected to a real grid.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.1
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• pp.61-67
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• 2020

This study deals with the modulation index (MI) of a voltage source converter (VSC) HVDC system based on a modular multilevel converter (MMC). In the two-level converter, the purpose of the MI is to maximize the achievable AC voltage of the converter from a fixed DC voltage. Unlike that in a two-level converter, the MI in the MMC topology plays a role in making the converter a voltage source using a capacitor. The circulating current in the MMC distorts the AC voltage reference, and the distortion affects the MI. In addition, the AC network conditions, such as AC voltage variation and reactive power, affect the MI. Therefore, the MI should be optimized with consideration of internal and external factors. This study proposes a method to optimize the MI of an MMC HVDC system.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.1009-1015
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• 2014

Chalcopyrite $CuInSe_2$ (CIS) thin films were prepared without Se- / S-containing gas by co-sputtering using $CuSe_2$ and $InSe_2$ selenide-targets and rapid thermal annealing. The grain size increased to a maximum of 54.68 nm with a predominant (112) plane. The tetragonal distortion parameter ${\eta}$ decreased and the inter-planar spacing $d_{(112)}$ increased in the RTA-treated CIS thin films annealed at a $400^{\circ}C$, which indicates better crystal quality. The increased carrier concentration of RTA-treated p-type CIS thin films led to a decrease in resistivity due to an increase in Cu composition at annealing temperatures ${\geq}350^{\circ}C$. The optical band gap energy ($E_g$) of CIS thin films decreased to 1.127 eV in RTA-treated CIS thin films annealed at $400^{\circ}C$ due to the improved crystallinity, elevated carrier concentration and decreased In composition.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.48-54
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• 2017

In this paper, hysteresis voltage control method is proposed to an unidirectional inverter control for piezoelectric load. Piezoelectric load has electrically RC characteristic, and is driven by the inverter to control the output voltage waveform. When controling the output waveform by PI control, appropriate gains need to be selected. However, hysteresis control may minimize the output distortion because it has maximum proportional gain. In addition, Hysteresis control algorithm has simple structure to realize and the response is fast. Although the switching frequency of the inverter by hysteresis control varies, the switching frequency for the piezoelectric load is lower than that by PI control for equivalent performance. In particular, on implementing the algorithm using FPGA, the algorithm can be implemented in fewer pabrics and the processing time can be reduced. The superiority of the proposed hysteresis voltage control was proved for piezoelectric load through simulation and experiment.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.3
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• pp.15-20
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• 2003

For some applications such as teleconference or telecommunication systems using a distant-talking hands-free microphone, the near-end speech signals to be transmitted is disturbed by an ambient noise and by an echo which is due to the coupling between the microphone and the loudspeaker. Furthermore, the environmental noise including channel distortion or additive noise is assumed to affect the original input speech. In the present paper, a new approach using echo canceller and maximum a posteriori(MAP) estimation is introduced to improve the accuracy of hands-free speech recognition. In this approach, it was shown that the proposed system was effective for hands-free speech recognition in ambient noise environment including echo. The experimental results also showed that the combination system between echo canceller and MAP environmental adaptation technique were well adapted to echo and noise environment.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.3
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• pp.220-227
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• 1995

An underwater speaker was designed and used as sound source for thronging shoal of squid in squid angling gear operation. The frequency characteristics of the designed speaker was analyzed experimentally and the thronging response of shoals of squid which may be a key parameter for a new sound catching method, was characterized in audible frequency. The field experiment was carried out in the coast of Cheju Island. The results of this study are summarized as follows; 1. Amplitude response of the speaker shows a maximum in their the frequency of 500Hz. 2. The output waveform distortion is not measured in the frequency range of 250~600Hz. 3. A underwater noise of shoals of squid which were thronged by fish lamp in night appeared the center frequency of 300~400Hz. 4. The shoals of squid shows a thronging response, when a manufactured underwater speaker transmits a intermittent audible sound of 300~400Hz in 10m depth of water.

• Journal of Multimedia Information System
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• v.8 no.3
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• pp.147-158
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• 2021

Versatile Video Coding (VVC) is the latest video coding standard developed by Joint Video Exploration Team (JVET). In VVC, the quadtree plus multi-type tree (QT+MTT) structure of coding unit (CU) partition is adopted, and its computational complexity is considerably high due to the brute-force search for recursive rate-distortion (RD) optimization. In this paper, we aim to reduce the time complexity of inter-picture prediction mode since the inter prediction accounts for a large portion of the total encoding time. The problem can be defined as classifying the split mode of each CU. To classify the split mode effectively, a novel convolutional neural network (CNN) called multi-level tree (MLT-CNN) architecture is introduced. For boosting classification performance, we utilize additional information including inter-picture information while training the CNN. The overall algorithm including the MLT-CNN inference process is implemented on VVC Test Model (VTM) 11.0. The CUs of size 128×128 can be the inputs of the CNN. The sequences are encoded at the random access (RA) configuration with five QP values {22, 27, 32, 37, 42}. The experimental results show that the proposed algorithm can reduce the computational complexity by 11.53% on average, and 26.14% for the maximum with an average 1.01% of the increase in Bjøntegaard delta bit rate (BDBR). Especially, the proposed method shows higher performance on the sequences of the A and B classes, reducing 9.81%~26.14% of encoding time with 0.95%~3.28% of the BDBR increase.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.10
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• pp.15-26
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• 1998

The role of the Engineer in the era of nano-technology is explored, a trend in manufacture which is expected to yield a ＄20-30 billion per annum business throughout the world by the year 2020. The engineers who will be working in this subject will be required to have broadly based experience, over a range of traditional disciplines, such as physics. electronics, software engineering, control and mechanical engineering. As well as having an appreciation of other disciplines such as air conditioning, vibration analysis and its minimisation, the selection of materials for maximum stability and minimal thermal distortion as well as an understanding of ultra precision design and nano tribology. In other words the engineer who is to be successful in this new and emerging field, will have to be broader based than engineers of the past, where it was traditional to break up the elements of a discipline to smaller subsets. But as nano-technology advances and the subject brings about the evolution of nanotronics to provide a successful solution to emerging problems, it will be essential for a breed of engineers to develop who can consider the subject in a holistic manner. This paper therefore considers the emergence of nano-technology, predicts the subsets of the development and places them in context of the new engineer which will be required in increasing numbers. The paper summarises the skills of the proposed nanotronics engineer and provides a basis for their training and development.