• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.290-292
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• 1999

핵연료봉이나 제어봉과 같은 봉구조물의 검사를 위하여 원격장와전류 효과를 낼 수 있는 탐촉자를 설계하고 탐상주파수를 유한요소해석을 통해 설정하였다. 핵연료봉을 대상으로 한 해석에서 exciter coil 주변을 차폐하고 500kHz의 주파수를 사용한 결과 전위계곡과 위상매듭의 존재가 나타나 원격장와전류 효과가 구현되었음을 확인하였다. exciter와 sensor coil로 이루어진 탐촉자를 이동시키면서 예측한 탐상신호에서는 센서를 원격장 의치에 고정시켰을 때, 결함이 센서를 지날 때의 위상신호와 결함이 exciter를 지날 때의 위상신호가 서로 달리 나타났다. 또한, 외부결함과 내부결함이 센서를 지날 때의 위상지연은 작지만 서로 반대의 경향으로 나타났으며, 두 종류의 결함이 exciter를 지날 때는 위상지연이 상대적으로 크게 줄어들고 외부/내부 결함에 상관없이 신호가 비슷하게 나타남을 볼 수 있었다. 이러한 신호형태는 자성체 관의 탐상에서 내, 외부 결함신호가 구별이 안되고, 동일한 위상신호가 항상 쌍으로 나타나는 것과 비교할 때, 신호해석을 훨씬 수월하게 해 줄 수 있을 것이라고 판단된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.69-76
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• 2020

The sound signal radiated from an underwater source is received by the hydrophone of the system, including multi-path time-delay and multi-path signal by sea surface and bottom reflection. The system using a time-delay between received signals for the source localization shows performance degradation due to incoherence by the multi-path propagation environment and the disturbance of a marine environment. Various types of array and signal processing have been used for robust source range and bearing estimation in this environment. In this paper, we use a line array composed of doublet array and an estimated time-delay correction method for robust localization performance in a multi-path propagation environment. Three doublet arrays are located on the same line, and the time-delay between signals received on each doublet array is estimated in a two-step procedure. The estimated time-delay value is obtained by the cross-correlation function and corrected by the interaction formula between the center-frequency of received signal and the geometry of the array with respect to aperture. By this proposed procedure, the range and bearing of source from array were calculated. In order to confirm the validity of the proposed method and array, we simulated localization and estimation using the Monte-Carlo method.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.271-275
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• 2018

There are several methods for estimating the time delay between incoming signals to two sensors. Among them, the GCC-PHAT (Generalized Cross Correlation-Phase Transform) method, which estimates the relative delay from the signal whitening and the cross-correlation between the different signal inputs to the two sensors, is a traditionally well known method for achieving stable performance. In this paper, we have identified a part of GCC-PHAT that can improve the periodicity. Also, we apply the auto-correlation method that is widely used as a method to improve the periodicity. Comparing the proposed method with the GCC-PHAT method, we show that the proposed method improves the mean square error performance by 5 dB ~ 15 dB at the SNR above 0 dB for white Gaussian signal source and also show that the method improves the mean square error performance up to 15 dB at the SNR above 2 dB for the color signal source.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.6
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• pp.81-90
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• 2004

For deep submicron (DSM) very large scale integrated circuits (VLSI), it is well known that interconnects have become the dominant factor in determining the overall circuit performance. Buffer insertion is an effective technique of interconnect optimization. When a net has an excessive propagation delay, one or more buffers can be inserted to reduce the delay. Buffers also reduce the crosstalk between neighboring wires. While many conventional methods insert buffers net by net. we have developed new techniques in which buffer locations are simultaneously optimized for all nets. This is to avoid the difficulties in finding the right ordering of nets for buffer insertion. since several nets may compete for a buffer location. We also study buffer insertion with multiple fan-out nets to optimize critical path delay. Elmore delay model is used for delay calculation and the number of buffers for each net is determined to optimize the delay.

• Proceedings of the Acoustical Society of Korea Conference
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• 1984.12a
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• pp.70-72
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• 1984

본 논문에서는 음성신호에 섞인 잡음을 효과적으로 제거하기 위해 Two-sided Transversal Filter를 이용하는 방법을 제시하였다. 이 방법은 기존의 방법과는 달리 신호의 단기자기상관관계(short-term autocorrelation)을 충분히 이용하기 위해 적응 필터의 입력으로, 지연된 신호뿐만 아니라 미래의 신호도 이용하도록 하였다. 이 결과 음성신호에 섞인 잡음(백색잡음, 유색잡음)을 아주 효과적으로 제거함을 알 수 있다.

• Journal of Astronomy and Space Sciences
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• v.16 no.1
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• pp.61-68
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• 1999

The radio waves transmitted from GPS satellites is delayed by the troposphere as they propagate to Earth-based GPS receivers. The troposphere delay is usually divided into two parts, the dry delay due to the atmospheric gases and the wet delay due to the water vapor. In this study for the month of May in 1998 the GPS data from two stations(Taejon, Suwon) were used to estimate the total troposphere delay in the zenith direction by the least square method. The dry delay in the zenith direction can be evaluated by using surface pressure values at the station, then the zenith wet delay is obtained by removing the zenith dry delay from the total delay. The zenith wet delay is strongly correlated with the total precipitable water. The quality of the estimate has been assessed by comparison with radiosonde data at Osan. We found the food agreement in precipitable water of the GPS estimates and the radiosonde data. The standard deviation of the difference of the difference between the GPS and radiosonde observations was 3.68mm at Suwon.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.243-249
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• 2018

In this paper, we analyzed the effect of modulation scheme and modulation scheme on the dimming level of visible light communication system and studied the effect of distortion due to delayed signal. Currently, the modulation schemes most commonly used in visible light communication result in increasing the communication performance but reducing the brightness of the entire illumination. Continuous Burst Zero Duration will severely degrade lighting. This degrades not only the illumination but also the performance of the whole system and causes Flicker phenomenon. In this paper, we analyze the relationship between modulation technique and illumination - communication performance and investigate the effect of signal delay on visible light communication system. Through simulation, we analyze the performance of IPI-OOK which has the best communication-lighting performance and propose future research directions accordingly.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.85-90
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• 2001

In this paper, we analyzed the envelope correlation of wideband signals modulated on two separate subcarriers in a Nakagami-Rice fading channel with exponential power delay profile. The results show that the envelope correlation of resolvable paths is implicated by the ratio of the specular wave power to the mean multipath power as well as the signal bandwidth and the rms delay spread of the multipath waves.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.170-175
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• 1999

본 논문에서는 국내에서 운전 중인 한 가스터빈 출력제어 회로의 구성을 살펴보고 현장에서 취득한 자료를 근거로 하여 가스터빈의 모델과 제어기의 조정, 그리고 MW 신호 피이드백 회로에 필터의 사용효과를 시뮬레이션을 통해 살펴보았다. 전력계통의 주파수가 가스터빈 출력제어계의 시상수에 비해 상당히 빠르게 변하므로 자동 주파수 추종을 할 경우 제어계가 쉽게 불안정해진다. 이 출력제어계의 MW 피이드백 회로의 1차지연 요소를 사용하면 안정성 향상에 좋은 효과가 있으며, 이 지연요소의 시상수를 크게 할수록 안정도는 더 향상되며 Open Loop의 특성을 보이게 된다. 그러나, 주파수 추종운전이 아닌 운전원의 출력 증감발 요구에는 시간지연 없이 응답을 하여야 하므로 적절한 설정을 할 필요가 있다. 가스터빈의 연료제어 계통을 포함한 출력제어계에 순수 시간지연 요소가 없으면 피이드백 회로에 1차지연 요소를 사용하지 않는 것이 더 좋은 출력제어 응답을 나타낸다. 그러나 실제 모들 가스터빈에는 다소 시간지연 요소를 포함하고 있으므로 일반적으로 피이드백 회로에 시간지연 요소를 사용하므로써 안정성을 향상시킬 수 있다.

• Journal of Satellite, Information and Communications
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• v.10 no.4
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• pp.101-106
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• 2015

In this paper, a shared band transmission, in which downlink signals from satellite to both earth station and user terminal are transmitted in the same frequency band, is considered. For proper operation of such shared band transmission, self-interference caused by the transmitted signal from its own transmitter should be cancelled and the desired signal from the other transmitter should be obtained. The self-interference is sent by its own transmitter and it can be easily regenerated with the estimated round-trip delay. In addition to this delay, non-linearity effects caused by power amplifiers at the earth station and satellite should be exploited. The proposed interference canceller divided into two parts: one is subtraction of the transmitted signal with delay and non-linearity effects, and the other is adoptive filter to suppressed the residual interference. Through computer simulations, the effectiveness of the proposed system is verified.