• Title/Summary/Keyword: 신호인자

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Time-Domain Geoacoustic Inversion via Light Bulb Source Signal Matching (전구음원 신호를 이용한 시간영역 지음향학적 인자 역산)

  • Kim Kyungseop;Park Cheolsoo;Kim Seongil;Seong Woojae
    • The Journal of the Acoustical Society of Korea
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    • v.24 no.6
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    • pp.334-342
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    • 2005
  • In this Paper. a time-domain geoacoustic inversion was performed using the bulb signals measured during MがU. 04 experiment conducted in the East Sea of Korea in 2004. An obiective function was defined as a direct cross-correlation between the measured and the simulated signals in time domain. The ray theory was used to model the wave propagation in time domain and optimizations were Performed using VFSA (very fast simulated annealing) algorithm. Comparison of inversion results with those from transmission loss matching (an accompanying paper in this issue of the Journal of the Acoustical Society of Korea) shows that Parameters are consistently inverted. Direct time series comparisons between the measured signals and the simulated signals are Presented based on inversion results.

Sensitivity Study on the Infra-Red Signature of Naval Ship According to the Composition Ratio of Exhaust Plume (폐기가스 조성 비율이 적외선 신호에 미치는 영향 연구)

  • Cho, Yong-Jin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.103-110
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    • 2018
  • Infrared signatures emitted from naval ships are mainly classified into internal signatures generated by the internal combustion engine of the ship and external signatures generated from the surface of the ship heated by solar heat. The internal signatures are also affected by the chemical components ($CO_2$, $H_2O$, CO and soot) of the exhaust plumes generated by the gas turbine and diesel engine, which constitute the main propulsion system. Therefore, in this study, the chemical composition ratios of the exhaust plumes generated by the gas turbines and diesel engines installed in domestic naval ships were examined to identify the chemical components and their levels. The influence of the chemical components of the exhaust plumes and their ratios on the infrared signatures of a naval ship was investigated using orthogonal arrays. The infrared signature intensity of the exhaust plumes calculated using infrared signature analysis software was converted to the signal-to-noise ratio to facilitate the analysis. The signature analysis showed that $CO_2$, soot and $H_2O$ are the major components influencing the mid-wave infrared signatures of both the gas turbine and diesel engine. In addition, it was confirmed that $H_2O$ and $CO_2$ are the major components influencing the long-wave infrared signatures.

Estimation of Phase Variance of Acoustic Signals Depending on Turbulence Strength Near the Mukho Port in the East Sea of Korea (동해 묵호항 근처에서의 난류세기인자에 따른 음향수신신호의 위상분산 추정)

  • Kim, Jung-Hun;Bok, Tae-Hoon;Paeng, Dong-Guk;Shim, Tae-Bo;Kim, Young-Kyu;Park, Joung-Soo
    • The Journal of the Acoustical Society of Korea
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    • v.28 no.4
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    • pp.328-335
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    • 2009
  • Phase variance of the acoustic signals has to be investigated with the research of the medium, because the phase of the acoustic signals carries the information of the medium. The phase compensation of the received signals is required for the signal processing of SAS (Synthetic Aperture Sonar) and underwater communication. In this paper, the phase variance of the acoustic signals was studied depending on the micro-scale-turbulence of ocean. The turbulence strength of the locally isotropic and homogeneous turbulence was calculated, and the phase variance affected by the turbulence strength was computed along the ray paths. The CTD and ADCP data were acquired from a buoy system near the Mukho port in the East Sea of Korea and the ray paths were calculated by the Bellhop algorithm. As a result, the turbulence strength was mainly determined by the variation of temperature and flow speed, changing the phase variance of the received signals. Hence, we thought the phase variance should be considered in the sonar operating system.

Spectral Estimation of Nonstationary Signals Using RLS Algorithm with a Variable Forgetting Factor (시변 망각 인자를 갖는 RLS 알고리즘을 이용한 Nonstationary 신호의 스펙트럼 추정)

  • 조용수
    • The Journal of the Acoustical Society of Korea
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    • v.12 no.1E
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    • pp.56-64
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    • 1993
  • 본 논문은 공간적으로 변하는 스펙트럼을 추정하는 새로운 적응 방법을 제안한다. 제안한 방법에서는 오래된 upstream의 데이터를 망각함으로서 신호의 nonstationarity를 고려해주는 시변망각인자의 개념을 recursive least square(RLS) 알고리즘에 도입하였으며, 관심이 있는 공간영역에서 탐사침을 천천히 움직여 얻은 하나의 데이터 군으로부터 downstream 스펙트럼을 추정하였다. 제시한 방법의 실현 가능성은 실제 실험(wind tunnel 이용)을 통해서 얻은 공간적으로 변하는 nonstatonary 신호의 스펙트럼을 추정하는 과정에서 입증되며 또한 기존의 방법들과 비교함으로서 그 우수성을 보인다.

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Optimizations of 3D MRI Techniques in Brain by Evaluating SENSE Factors (삼차원 자기공명영상법의 뇌 구조 영상을 위한 최적화 연구: 센스인자 변화에 따른 신호변화 평가)

  • Park, Myung-Hwan;Lee, Jin-Wan;Lee, Kang-Won;Ryu, Chang-Woo;Jahng, Geon-Ho
    • Investigative Magnetic Resonance Imaging
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    • v.13 no.2
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    • pp.161-170
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    • 2009
  • Purpose : A parallel imaging method provides us to improve temporal resolution to obtain three-dimensional (3D) MR images. The objective of this study was to optimize three 3D MRI techniques by adjusting 2D SESNE factors of the parallel imaging method in phantom and human brain. Materials and Methods : With a 3 Tesla MRI system and an 8-channel phase-array sensitivity-encoding (SENSE) coil, three 3D MRI techniques of 3D T1-weighted imaging (3D T1WI), 3D T2-weighted imaging (3D T2WI) and 3D fluid attenuated inversion recovery (3D FLAIR) imaging were optimized with adjusting SESNE factors in a water phantom and three human brains. The 2D SENSE factor was applied on the phase-encoding and the slice-encoding directions. Signal-to-noise ratio(SNR), percent signal reduction rate(%R), and contrast-to-noise ratio(CNR) were calculated by using signal intensities obtained in specific regions-of-interest (ROI). Results : In the phantom study, SENSE factor = 3 was provided in 0.2% reduction of signals against without using SENSE with imaging within 5 minutes for 3D T1WI. SENSE factor = 2 was provided in 0.98% signal reduction against without using SENSE with imaging within 5 minutes for 3D T2WI. SENSE factor = 4 was provided in 0.2% signal reduction against without using SENSE with imaging around 6 minutes for 3D FLAIR. In the human brain study, SNR and CNR were higher with SENSE factors = 3 than 4 for all three imaging techniques. Conclusion : This study was performed to optimize 2D SENSE factors in the three 3D MRI techniques that can be scanned in clinical time limitations with minimizing SNR reductions. Without compromising SNR and CNR, the optimum 2D SENSE factors were 3 and 4, yielding the scan time of about 5 to 6 minutes. Further studies are necessary to optimize 3D MRI techniques in other areas in human body.

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An Analysis of Saturation Headway at Signalized Intersections by Using Fuzzy Inference (퍼지추론을 이용한 신호교차로에서의 포화차두시간 분석)

  • Kim, Kyung-Whan;Ha, Man-Bok;Kang, Duk-Ho
    • Journal of Korean Society of Transportation
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    • v.22 no.1 s.72
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    • pp.73-82
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    • 2004
  • 신호 교차로에서 포화차두시간에 영향을 미치는 영향인자는 도로조건, 교통조건, 환경조건으로 분류된다. 이러한 요인들의 복합적인 관계가 포화차두시간에 영향을 미친다. 현재 포화교통류율은 이상적인 조건일 때의 포화차두시간을 산출하고, 이를 이용해서 기본 포화교통류율을 구하고, 여기에 좌 우회전, 차로폭, 경사, 중차량 보정계수을 고려함으로써 특정 차로군의 포화교통류율을 산정하고 있다. 포화차두시간에 영향을 미치는 인자들 중에서 정량적으로 나타내기 어려운 인자 즉, 퍼지적 성격을 가진 인자들은 고려하지 않고 있다. 따라서 본 연구에서는 퍼지 근사추론 방법을 이용하여 정성적 인자의 영향을 고려한 모형을 구축하였다. 모형의 입력자료는 강우조건과 주변밝기의 정도, 중차량 구성비의 언어적 표현를 사용하였다. 이러한 변수들에 대하여 설문조사를 통해서 퍼지집합의 멤버쉽함수를 설정하였으며. 이에 기초하여 교차로에서 각 조건별로 포화차두시간을 관측하였다. 이러한 현장 관측치를 바탕으로 퍼지 제어규칙을 설정하고 모형을 구축하였다. 모형의 평가는 추론치와 실측치를 비교함으로써 이루어 졌으며, 결정계수인 $R^2$와 평균절대오차(MAE)와 평균제곱오차(MSE)를 사용하여 분석한 결과 본 모형의 설명력이 높은 것으로 평가되었다. 본 연구의 과정에서 강우에 의한 교통용량 감소는 중차량 구성비가 클수록 주변밝기의 정도가 나쁠수록 더욱 큰 것으로 나타났으며 그 감소율은 5.3%에서 21.8%에 이르는 넓은 범위의 값을 보였고. 주변밝기 정도에 따른 교통용량 감소는 4.7$\sim$7.5% 수준으로 나타났다.

Inference of The Sub-bottom Parameters using Ship-radiated Low Frequency Signal (저주파 선박 신호를 이용한 해저면 하부 인자 추정)

  • Kim Youngsun;Oh Jeongsoo;Na Jungyul;Kim Youngsun;Park Jeongsoo;Lee Philho;Choi Jinhyuk
    • Proceedings of the Acoustical Society of Korea Conference
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    • autumn
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    • pp.261-264
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    • 2000
  • 선박 신호를 이용한 퇴적을 인자 추정 가능성 고찰을 위해 천해에서 실험을 수행하였다. 실험 결과와 모델 결과의 비교를 통해 저주파 대역의 신호는 해저면 특성의 변화와 밀접한 관련이 있고 이러한 특성을 활용하면 해저면 인자 추정이 가능함을 확인하였다.

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Tonal Signal Detection for Acoustic Targets using ASM Neural Network (ASM 신경망을 이용한 음향 표적의 토날 신호 탐지)

  • 이성은
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1996.06a
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    • pp.22-28
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    • 1996
  • 수동 소나 시스템에서 표적을 탐지, 식별하는데 가장 중요한 인자는 표적에서 발생되는 토날 신호 성분이다. 수중의 주변잡음과 표적소음이 복합된 환경하에서 표적의 토날 신호성분을 정확히 추출하는데는 신호 탐지 준위 설정이나 주변 잡음의 변화에 의해 어려움이 있다. 본 논문에서는 ASM 신경망을 이용하여 신호 탐지 준위 설정이나 주변잡음의 변화에 강인한 음향 표적의 토날 신호 탐지 방식을 제안한다. 모의 시뮬레이션 및 실제 표적 신호에 적용하여 우수한 토날 신호 탐지 성능을 보인다.

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Alternative optimization procedure for parameter design using neural network without SN (파라미터 설계에서 신호대 잡음비 사용 없이 신경망을 이용한 최적화 대체방안)

  • Na, Myung-Whan;Kwon, Yong-Man
    • Journal of the Korean Data and Information Science Society
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    • v.21 no.2
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    • pp.211-218
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    • 2010
  • Taguchi has used the signal-to-noise ratio (SN) to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. Many Statisticians criticize the Taguchi techniques of analysis, particularly those based on the SN. Moreover, there are difficulties in practical application, such as complexity and nonlinear relationships among quality characteristics and design (control) factors, and interactions occurred among control factors. Neural networks have a learning capability and model free characteristics. There characteristics support neural networks as a competitive tool in processing multivariable input-output implementation. In this paper we propose a substantially simpler optimization procedure for parameter design using neural network without resorting to SN. An example is illustrated to compare the difference between the Taguchi method and neural network method.

Acoustic Target of Interest Tracking Algorithm Using Classification Feedback (표적 식별 정보 피드백을 통한 관심 음향 표적 추적 기법)

  • Choi, Kiseok
    • The Journal of the Acoustical Society of Korea
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    • v.33 no.4
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    • pp.225-231
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    • 2014
  • This paper suggests an algorithm to improve the tracking performance for an underwater acoustic target using the feedback information of acoustic feature of a target. While conventional tracking algorithms use detected acoustic signals only, the proposed algorithm uses detected acoustic signals and target feature information as well. Since the proposed algorithm tracks only the selected measurements using target feature information, it prevents onset of unnecessary tracks and improves tracking performance for target of interest. Furthermore, it optimizes tracking parameters for the target of interest and guarantees robustness and consistency of the track. Some simulations are performed to demonstrate the improved tracking performance of the proposed algorithm.