• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.93-100
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• 2021

The purpose of this study is to find out the factors that affect the patient's exposure dose during the abdominal CT scan using the bolus tracking technique, and reducing the radiation exposure to the patient during the abdominal CT scan using the bolus tracking technique by adjusting the delay time according to the corresponding factor. The experiment was divided into two parts, and the first experiment was conducted with 300 patients There were 188 males and 112 females, and their average age was 58±12.18(19~85). In the second experiment, 150 subjects (100 males and 50 females) who were undergoing their follow-up examination among the first experiment subjects, and the difference in dose before and after was compared by applying the delay time according to the influencing factor. As a result of the first experiment, there was a relationship between the arrival time of the contrast media and the heart rate, and it was found that the arrival time decreased as the heart rate increased for both men and women. As a result of the second experiment, the average dose of CTDIvol and DLP before/after applying the delay time according to the heart rate decreased 4.98 mGy and 5.33 mGy·cm in the male group, and 3.54 mGy and 3.88 mGy·cm in the female group. By applying proper delay time according to the patient's heart rate during abdominal CT scan with the bolus tracking technique, the radiation exposure dose of the patient can be reduced.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05a
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• pp.221-226
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• 1998

과잉온도 차온(Overtemperature $\Delta$T) 및 과잉출력 차온(Overpower $\Delta$T)트립에 쓰이는 온도 측정계통 총 지연시간은 6초로 구성되며 RTD 우회배관 제거시 4.5초의 RTD 응답시간(일차지연 상수로 가정)과 1.5초의 순수지연시간(전자회로 지연시간 + 그립퍼 풀림시간등)으로 구성된다. 그러나 RTD우회배관 제거전 사고분석을 일차지연상수를 3.5초, 순수지연을 2.5초로 모델링하였으므로 Simulink를 통한 영향분석과 Rack 응답시험 계단파 입력신호의 타당성을 평가하였다. RTD 응답시간은 전형적인 1차 지연요소로 나타내며 계전기나 제어봉 Gripper Release 시간 등은 순수 지연으로 가정하고 분석을 수행하고 기타 지연/지상 필터를 발전소와 동일하게 모델링하여 분석하므로써 발전소에서 일어나는 과도현상을 묘사할 수 있다는 점을 고려할 때 RTD우회배관 제거후 응답시간 지연상수가 바뀌더라도 안전하다는 결론에 도달했다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.45-47
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• 1999

이동 컴퓨터 환경에서의 멀티미디어 스트림을 전송하는 경우에는 무선 네트웍의 높은 오류 발생률(error rate)과 잦은 단절(disconnection)로 인하여 데이터의 도달시간이 불규칙하게 되므로 데이터가 자연스럽게 재생되지 못한다. 따라서 시간의 영향을 많이 받는 멀티미디어 데이터를 자연스럽게 재생하기 위해서는 데이터 도달 지연시간의 영향을 최소화하는 것이 필요하다. 본 논문에서는 이동 컴퓨팅 환경에서 멀티미디어 스트림을 전송하기 위한 기법을 제안한다. 이를 위해 프락시를 사용한 효과적인 버퍼링 방법을 사용하여 데이터의 도달시간을 일정하게 유지시키는 방법과, 사용자가 요구하는 서비스 품질(Quality of Service: QOS)을 만족시키면서 프레임의 지연에 좀 더 유연하게 대처할 수 있는 재생 제어방법을 제안하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.499-502
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• 1998

본 논문에서는 한 쌍의 수동소나를 이용하여 미지의 잠항물체의 존재 유무를 확인하고 각 센서에 도달하는 시간지연의 차를 평가하는 Detection과 Tracking 알고리즘을 연구한다. 이 과정에서 이동하는 표적의 속력에 의한 도플러효과를 보상하는 2차원 확률분포 함수를 적용함으로 보다 정확한 결과를 도출한다. 관측신호의 Cross-Correlation과 Bayesian Method를 이용하여 계산한 시간지연과 도플러효과 비의 이차원 Likelihood 함수로부터 사후확률 (Posterior Probability)을 구하여 발견 평가와 추적을 수행한다.

• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.178-183
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• 2024

This study introduces an enhanced sound source localization technique, bolstered by a data-driven deep learning approach, to improve the precision and accuracy of direction of arrival estimation. Focused on refining Time Difference Of Arrival (TDOA) based sound source localization, the research hinges on accurately estimating TDOA from cross-correlation functions. Accurately estimating the TDOA still remains a limitation in this research field because the measured value from actual microphones are mixed with a lot of noise. Additionally, the digitization process of acoustic signals introduces quantization errors, associated with the sampling frequency of the measurement system, that limit the precision of TDOA estimation. A deep learning-based approach is designed to overcome these limitations in TDOA accuracy and precision. To validate the method, we conduct comprehensive evaluations using both two and three-microphone array configurations. Moreover, the feasibility and real-world applicability of the suggested method are further substantiated through experiments conducted in an anechoic chamber.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.130-137
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• 2010

An uplink indoor positioning system is proposed in the present work, where the acoustic signals are solely used for positioning. The underlying acoustic signals include whistle, finger snap, and hands-clapping. In the proposed method, positioning is achieved by finding the time-difference-of-arrivals using several self-generating sounds. To evaluate the feasibility of the signals and their positioning accuracies, the database of 100 persons about self-generating acoustic signals is built up. The results show that the hands-clapping sound is the most suitable for acoustic-based indoor positioning.

• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.370-375
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• 2004

This paper proposes an algorithm that estimates three dimensional array shape calibration about the bottom-mounted sensor array. under the assumption that the active sources are in the far-field with unknown positions. Under some assumptions. we calculate the sensor positions via an algebraic solutions of a least squares problem that the linear equations are related to the sensor positions and directions or arrival. We give examples of algorithm performance from both computer simulations and sea test. We also illustrate the performance of sensor positions estimation as a function of time delay estimation variance and the distribution of the localizing sources.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.84-90
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• 2000

The bearing detection of radiated target noise is very important at underwater acoustic measurement and passive detection. It differs the arrival tines of received signal at each sensor. Therefore, the bearing can be obtained from the time delay. This paper proposes a new algorithm using the RLSL adaptive filter for TDE. The proposed method is particularly attractive when there is a limitation of priori information about the received signal spectra and when the delay is subject to variation. As the simulation results, it is shown that the proposed algorithm has better convergence characteristics and TDE speed, and so that the usefulness of proposed algorithm is confirmed.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.887-888
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• 2008

본 논문은 여러 음향신호의 도달각에 기반한 실내측 위성능을 분석한다. 도달각 측정을 위해 송출전력이 같은 총성, 벨소리, 그리고 의사충격음을 사용하였다. 음향 신호는 약 32 평방미터의 실험실에서 한 개의 음원 스피커를 통해 송출되고, 두 쌍의 서로 동기가 맞는 배열 마이크를 통해 수신된다. 수신된 음향신호로부터 한 마이크 쌍 사이의 도달지연시간차가 측정되고, 이로부터 도달각이 산출된다. 끝으로, 음원 스피커의 최종 위치는 도달각의 교점으로 결정된다. 본 논문은 설치한 실험환경에서의 참 도달각과 측정 도달각의 평균절대오차와 측위오차의 상보누적분포를 보이고, 이에 대한 성능특성을 분석한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.138-142
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• 2006

Time Difference of Arrival (TDOA) algorithm was applied to sound source positioning. Using measured microphones signal, difference of distance from source to sensors were estimated by TDOA and speed of sound, and taken by navigational measurements. And iteration procedures were induced to find the actual source location. For the case of stationary and moving sound source, validation test were performed in the anechoic room. In the stationary case, the error of positioning is less then 1.3% in length scale, and it could be seen proper filtering processes were required in the application of moving sound source.