• Title/Summary/Keyword: Period Detection

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Coastal upwelling observed off the East coast of Korea and variability of passive sound detection environment (동해 연안에서 관측된 용승현상과 수동 음탐환경의 변화)

  • Sang-Shin, Byun;Chang-Bong, Cho
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.6
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    • pp.601-609
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    • 2022
  • In August 2007, coastal upwelling occurred off the east coast of Korea, and vertical water temperature and salinity data were obtained from a real-time surface ocean buoy. Based on the time series observation data, a vertical sound velocity structure was calculated before, during, and after the occurrence of the coastal upwelling, and how the coastal upwelling affects the sound propagation and detection environment through acoustic modeling considering the horizontal scale and actual seabed topography. As a result of comparing and analyzing the low-frequency (500 Hz) sound transmission loss and the target detection range by depth using the parabolic equation model, it was analyzed that if coastal upwelling occurs, a detection gain of up to about 10 dB can be expected. In addition, through this study, it was confirmed that the characteristics of sound propagation can be greatly changed even in a short period of about 2 to 3 days before and after coastal upwelling.

Agent-target Detection Problem Considering Change in Probability of Event Occurrence (사건 발생 확률 변화를 고려한 에이전트-타깃 감지 문제)

  • Gwang Kim
    • Journal of Korea Society of Industrial Information Systems
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    • v.29 no.4
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    • pp.67-76
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    • 2024
  • In this study, we address the problem of target detection using multiple agents. Specifically, the detection problem involving mobile agents necessitates additional strategies for path planning. The objective is to maximize the total utility derived from the detection process over a specific period. This detection problem incorporates realistic utility values by considering a stochastic process based on the Poisson process, which accounts for the changing probability of target event occurrence over time. The objective function is nonlinear and is classified as an NP-hard problem. To identify an effective solution within an efficient computation time, this study demonstrates that the objective function possesses the characteristic of submodularity. Using this property, we propose a heuristic algorithm designed to obtain a reasonable strategy with relatively low computational time. The proposed algorithm shows solution performance and the ability to generate solutions within an appropriate computation time through theoretical and experimental results.

Real-Time Step Count Detection Algorithm Using a Tri-Axial Accelerometer (3축 가속도 센서를 이용한 실시간 걸음 수 검출 알고리즘)

  • Kim, Yun-Kyung;Kim, Sung-Mok;Lho, Hyung-Suk;Cho, We-Duke
    • Journal of Internet Computing and Services
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    • v.12 no.3
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    • pp.17-26
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    • 2011
  • We have developed a wearable device that can convert sensor data into real-time step counts. Sensor data on gait were acquired using a triaxial accelerometer. A test was performed according to a test protocol for different walking speeds, e.g., slow walking, walking, fast walking, slow running, running, and fast running. Each test was carried out for 36 min on a treadmill with the participant wearing an Actical device, and the device developed in this study. The signal vector magnitude (SVM) was used to process the X, Y, and Z values output by the triaxial accelerometer into one representative value. In addition, for accurate step-count detection, we used three algorithms: an heuristic algorithm (HA), the adaptive threshold algorithm (ATA), and the adaptive locking period algorithm (ALPA). The recognition rate of our algorithm was 97.34% better than that of the Actical device(91.74%) by 5.6%.

Optimization of Design Variables of Detection Algorithm for Loss of Balance Using a Linear Internal Model (균형상실의 검출 성능 향상을 위한 내부 모델의 설계변수 선정 및 민감도 평가)

  • Kim, Kwang-Hoon;Kim, In-Su;Son, Kwon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.9
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    • pp.1153-1160
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    • 2010
  • The detection algorithm for loss of balance had three main parts: one for processing data, another for constructing an internal model, and a third for detecting the loss of balance. The part related to the internal model is the most important part of the algorithm. The purpose of this study is to evaluate the effect of variables associated with the internal model on the success rate of the algorithm. The internal model depends on the type of linearization adopted and the operating period of the algorithm. The design variables were evaluated by performing sensitivity analysis of the variables of the internal model in order to obtain the success rate of the algorithm. The results showed that the most sensitive variable was the period and the period of 0.3 s yielded the highest success rate of 97.1%. Further, the ranges of the design variables that can facilitate a success rate of over 95% are presented.

The measurement of the half period modulated pulse on earth for detection of a underground electric leakage point (지중선로 누전점 탐지를 위한 반주기 변조된 대지 펄스 측정)

  • Kim, Jae-Hyun;Jeon, Jeong-Chay;Yoo, Jae-Geun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.11
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    • pp.5123-5127
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    • 2011
  • Research and development for the technology, that is about maintenance and accidents prevention of underground power distribution line, are demanding. The precise detection of leakage point of underground power line is very important, because it is difficult to detect the exact location of a fault in underground power line and to repair faults. When earth electric potential is measured to detect underground electric leakage point after transmitting AC electric pulse wave to underground power line, it must be measured in a specific half period of AC pulse wave because the distribution of the electric earth potential varies with the polarity of the transmitted wave. In this paper we proposed the measurement of half period modulated earth potential as a method to detect a underground leakage point. And We compared the proposed method with other methods. Through experiments we verified that the proposed method can be implemented and operated properly.

Fundamental Frequency Estimation of Voiced Speech Signals Based on the Inflection Point Detection (변곡점 검출에 기반한 음성의 기본 주파수 추정)

  • Byeonggwan Iem
    • Journal of IKEEE
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    • v.27 no.4
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    • pp.472-476
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    • 2023
  • Fundamental frequency/pitch period are major characteristics of speech signals. They are used in many speech applications like speech coding, speech recognition, speaker identification, and so on. In this paper, some of inflection points are used to estimate the pitch which is the inverse of the fundamental frequency. The inflection points are defined as points where local maxima, local minima or the slope changes occur. The speech signal is preprocessed to remove unnecessary inflection points due to the high frequency components using a low pass filter. Only the inflection points from local maxima are used to get the pitch period. While the existing pitch estimation methods process speech signals in blockwise, the proposed method detects the inflection points in sample and produces the pitch period/fundamental frequency estimates along the time. Computer simulation shows the usefulness of the proposed method as a fundamental frequency estimator.

An Analysis and Comparison on Efficiency of Load Distribution Algorithm in a Clustered System (클러스터 시스템의 부하분산 알고리즘의 효율성 비교분석)

  • Kim, Seok-Chan;Rhee, Young
    • Journal of KIISE:Computing Practices and Letters
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    • v.12 no.2
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    • pp.111-118
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    • 2006
  • In this thesis, we analyze the efficiency of the algorithm to distribute the load in the clustered system, by comparing with the existed algorithm. PWLC algorithm detects each server's load in the system at weighted period, and following the detection of the loads, a set of weights is given to each server. The system allocates new loads to each server according to its weight. PWLC algorithm is compared with DWRR algorithm in terms of variance, waiting time by varying weighted Period. When the weighted period is too short, the system bears a heavy load for detecting load over time. On the other hand, when the weighted period is too long, the load balancing control of the system becomes ineffective. The analysis shows PWLC algorithm is more efficient than DWRR algorithm for the variance and waiting time.

Risk Evaluation Based on the Time Dependent Expected Loss Model in FMEA (FMEA에서 시간을 고려한 기대손실모형에 기초한 위험 평가)

  • Kwon, Hyuck-Moo;Hong, Sung-Hoon;Lee, Min-Koo;Sutrisno, Agung
    • Journal of the Korean Society of Safety
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    • v.26 no.6
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    • pp.104-110
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    • 2011
  • In FMEA, the risk priority number(RPN) is used for risk evaluation on each failure mode. It is obtained by multiplying three components, i.e., severity, occurrence, and detectability of the corresponding failure mode. Each of the three components are usually determined on the basis of the past experience and technical knowledge. But this approach is not strictly objective in evaluating risk of a given failure mode and thus provide somewhat less scientific measure of risk. Assuming a homogeneous Poisson process for occurrence of the failures and causes, we propose a more scientific approach to evaluation of risk in FMEA. To quantify severity of each failure mode, the mission period is taken into consideration for the system. If the system faces no failure during its mission period, there are no losses. If any failure occurs during its mission period, the losses corresponding to the failure mode incurs. A longer remaining mission period is assumed to incur a larger loss. Detectability of each failure mode is then incorporated into the model assuming an exponential probability law for detection time of each failure cause. Based on the proposed model, an illustrative example and numerical analyses are provided.

A Study on Orthogonal Image Detection Precision Improvement Using Data of Dead Pine Trees Extracted by Period Based on U-Net model (U-Net 모델에 기반한 기간별 추출 소나무 고사목 데이터를 이용한 정사영상 탐지 정밀도 향상 연구)

  • Kim, Sung Hun;Kwon, Ki Wook;Kim, Jun Hyun
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.40 no.4
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    • pp.251-260
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    • 2022
  • Although the number of trees affected by pine wilt disease is decreasing, the affected area is expanding across the country. Recently, with the development of deep learning technology, it is being rapidly applied to the detection study of pine wilt nematodes and dead trees. The purpose of this study is to efficiently acquire deep learning training data and acquire accurate true values to further improve the detection ability of U-Net models through learning. To achieve this purpose, by using a filtering method applying a step-by-step deep learning algorithm the ambiguous analysis basis of the deep learning model is minimized, enabling efficient analysis and judgment. As a result of the analysis the U-Net model using the true values analyzed by period in the detection and performance improvement of dead pine trees of wilt nematode using the U-Net algorithm had a recall rate of -0.5%p than the U-Net model using the previously provided true values, precision was 7.6%p and F-1 score was 4.1%p. In the future, it is judged that there is a possibility to increase the precision of wilt detection by applying various filtering techniques, and it is judged that the drone surveillance method using drone orthographic images and artificial intelligence can be used in the pine wilt nematode disaster prevention project.

Bubble-type Motion Detector Using a Pulsed-mode Oscillator and Delay Line (펄스 모드 발진기와 지연선로를 이용한 버블형 동작감지기)

  • Lee, Ik-Hwan;Kim, Dong-Wook
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.3
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    • pp.342-348
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    • 2015
  • This paper presents a new motion detector that has a bubble-layer detection zone using a pulsed-mode oscillator and delay line. The proposed motion detector controls the bubble-layer detection zone with pulse width of transmitted signals and creates IF signals only by reflected signals from the target within the detection zone whose position is determined by time delay of the delay line. The fabricated motion detector uses the pulsed-mode voltage controlled oscillator as a signal source which has a center frequency of 8 GHz, pulse width of 2 nsec and pulse period of 30 nsec. It successfully makes the bubble-layer detection zones at 1 m, 3 m and 5 m distant from itself using two delay lines with 7 nsec and 12 nsec delay, and is also demonstrated to detect the target within the detection zones.