• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.604-608
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• 2003

In this paper, we studied the radiated electric field of power-line with DMT signal source in the frequency range of $1.7{\sim}30 MHz$. First, we made the midium voltage power-line communication model for PLC and calculated the current through the power-line using the impedance of the power-line model. Second, we calculated the radiated electric field in power range $-50{\sim}-30 dBm$ using the calculated current. Consequently, the calculated emissive electromagnetic field from the DMT signal is similar to the measured result. So this study is applicable to the standard regulation of electromagnetic interference for PLC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1258-1259
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• 2008

In this paper, the variable tendency of the piezoelectric constant and resonance characteristics of the piezoelectric ceramics due to the electric field is studied. The practical application of piezoelectric ceramics is not only applied in field of small signal. For example, in case of an ultrasonic motor, 120 ${\sim}$ 130Vrms of driving voltage is needed. Therefore, to examine the characteristics of piezoelectric ceramics in large signal contributes to reducing the susceptibility to the multifarious application and securing the ease of the production of control circuit. These contributions may be connected to the expansion of industrial application. We fabricated disk-type piezoelectric ceramic samples by using conventional method and measured the resonance characteristics of these samples under from low to high voltage driving conditions. According to increasing the value of the input voltage, we measured the resonance frequency of the piezoelectric ceramic, and inquired into the cause of these phenomena.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.685-686
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• 2015

This paper describes design results of the measurement system to test the properties of broadband AC magnetic field sensors used in weapon system. This measurement system consists of 3-axis helmholtz coil, signal generator, signal amplifier, sensor data acquisition unit and measurement & analysis controller including the operating software. This system is able to measure various properties of AC magnetic field sensor such as sensitivity, linearity and dynamic response in the frequency of 1 Hz to 10 kHz. The performance of this system was verified by measuring and analyzing the property of a MAG 639, standard magnetic field sensor of bartington instruments, with this developed system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.182-185
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• 1998

This paper describes a field orientation control of an induction motor without any speed transducer and proposes a wide-range speed control strategy with the field orientation algorithm. The difference at impedances between the direct and quadrature axis at the injected signal is used for the sensorless field orientation control. But this algorithm has some limitations and should be supported by other method at high speed. In this paper, a sensorless speed control at an induction motor for wide speed range operation is proposed. The proposed algorithm is verified by experimental results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.545-550
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• 2005

A parametric loudspeaker is a device to generate highly directional sound using ultrasounds. The parametric loudspeaker could be used to focus sound in a limited space, so it is important to study the characteristics of the parametric loudspeaker in near-field. Mechanism of the audible sound generation in the parametric loudspeaker is explained by nonlinear interaction of the ultrasounds and is modeled as KZK equation, the nonlinear wave equation which contains attenuation, nonlinearity and diffraction. To measure the directional characteristics of the parametric loudspeaker precisely, a method to reduce the spurious signal which taints the measured signal was invented. With the method, directivity patterns of the parametric loudspeaker were measured and compared to the approximated solution and piston sources.

• 한국안전학회지
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• 제38권2호
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• pp.104-111
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• 2023

Rolling stock maintenance, which focuses on preventive maintenance, is typically implemented considering the potential harm that may be inflicted to passengers in the event of failure. The cost of preventive maintenance throughout the life cycle of a rolling stock is 60%-75% of the initial purchase cost. Therefore, ensuring stability and reducing maintenance costs are essential in terms of economy. In particular, private railroad operators must reduce government support budget by effectively utilizing railroad resources and reducing maintenance costs. Accordingly, this study analyzes the reliability characteristics of components using field data. Moreover, it resolves the problem of determining an economical replacement interval considering the timing of scrapping railroad vehicles. The procedure for determining the optimal replacement interval involves five steps. According to the decision model, the optimal replacement interval for the onboard signal device components of the "A" line train is calculated using field data, such as failure data, preventive maintenance cost, and failure maintenance cost. The field data analysis indicates that the mileage meter is 9 years, which is less than the designed durability of 15 years. Furthermore, a life cycle in which the phase signal has few failures is found to be the same as the actual durability of 15 years.

• 한국통신학회논문지
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• 제18권3호
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• pp.318-326
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• 1993

현재 TDX 교환기에서 사용하고 있는 신호수신 장치의 알고리즘은 field에 설치될 교환기가 지속적인 상용운용 과정을 거치면서 수신 알고리즘의 미세 조정을 필요로 한다. 따라서 신호 서비스 장치에 문제가 발생하였을 때 신속한 원인 규명이 어렵다. 이러한 문제를 해결하는 방법으로 신호서비스 장치에서 입출력되는 신호를 획득하여 R2MFC/DTMF/CCT/VOICE중 어느 것인지를 분석하는 시스템을 개발하였다. 본 논문은 이러한 시스템의 유지보수를 위해 개발한 PCM 신호획득 장치를 통해 원하는 채널의 PCM신호를 획득하고, CZT(chirp A-transform) 알고리즘을 적용하여 주파수를 구한 뒤 그에 대한 전력레벨 스펙트럼을 분석하므로서 획득한 신호가 어떤 종류의 속하는 신호인지, 신호상태를 분석, 판정하는 알고리즘을 논한다.

• International Journal of Aeronautical and Space Sciences
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• 제17권4호
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• pp.467-475
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• 2016

Ultrasonic propagation imaging (UPI) has shown great potential for detection of impairments in complex structures and can be used in wide range of non-destructive evaluation and structural health monitoring applications. The software implementation of such algorithms showed a tendency in time-consumption with increment in scan area because the processor shares its resources with a number of programs running at the same time. This issue was addressed by using field programmable gate arrays (FPGA) that is a dedicated processing solution and used for high speed signal processing algorithms. For this purpose, we need an independent and flexible block of logic which can be used with continuously evolvable hardware based on FPGA. In this paper, we developed an FPGA-based ultrasonic propagation imaging system, where FPGA functions for both data acquisition system and real-time ultrasonic signal processing. The developed UPI system using FPGA board provides better cost-effectiveness and resolution than digitizers, and much faster signal processing time than CPU which was tested using basic ultrasonic propagation algorithms such as ultrasonic wave propagation imaging and multi-directional adjacent wave subtraction. Finally, a comparison of results for processing time between a CPU-based UPI system and the novel FPGA-based system were presented to justify the objective of this research.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.415-415
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• 2013

We have investigated the optical and electrical properties of the CIGS thin film solar cells by the electroreflectance (ER), photoreflectance (PR), photoluminescence (PL), and photocurrent (PC) spectroscopies at room temperature. The ER spectrum had two narrow signal regions and one broad signal region. We measured PL and PC to confirm the signals at low energy region (1.02~1.35 eV), so these signals are related to the CIGS thin film, and the high energy region (2.10~2.52 eV) is related to the CdS bandgap energy. The broad signal region (1.35~2.09 eV) is due to the internal electric field by the p-n junction from the comparison between PR and ER spectra, and we calculated the internal electric field by the p-n junction. In the high efficiency solar cell, the CdS signal of ER spectrum is narrower than the lower efficiency solar cells.

• 대한전자공학회논문지SD
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• 제48권7호
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• pp.82-90
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• 2011

본 논문은 실험적 고찰을 통해 고주파 전송선 회로의 시그널 인테그러티를 정확하게 검증하는 방법을 제시하였다. 패키지 공정을 이용하여 제조한 배선의 공정편차, 표면 거칠기 효과, 표피 효과, 시뮬레이션을 위한 경계조건 등은 시뮬레이션의 정확도에 상당한 영향을 끼친다. 이러한 영향을 장해석기(HFSS)에 적용할 수 있는 변수로 변환하여 보다 정확하게 시그널 인테그러티를 검증 할 수 있도록 한다. 단일 신호선과 두 개의 전자기적으로 결합된 신호선에서의 신호 천이 특성을 측정 데이터와 제안하는 방법의 시뮬레이션 결과와 비교를 통해 제안한 방법의 정확성을 검증하였다.