• Title, Summary, Keyword: Acoustic Doppler Current Profiler

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Variability of Vertical Distribution of Volume Scattering Observed in the Shallow Water (천해 체적 산란강도의 수직분포 변동성)

  • 박경주;김은혜;강돈혁;나정열
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.1
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    • pp.69-77
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    • 2003
  • Measurements of backscattered intensity were made over a shallow water using 300 ㎑and 1200 ㎑ bottom mounted ADCP (Acoustic Doppler Current Profiler) to determine the temporal variability of vertical distribution of high-frequency volume scattering strength (Sv). The variability of Sv in relatively deep water column(85 m and 113 m was due to the daily vertical migration, probably of larger zooplankton. However it was not found with 1200㎑ data at shallow water column. From the empirical orthogonal function (EOF) analysis using 1200㎑ data, the vertical distribution of the first mode eigenvectors of Sv is characterized by the presence of the maximum values near the bottom of the water.

Swimming speed measurement of Pacific saury (Cololabis saira) using Acoustic Doppler Current Profiler (음향도플러유향유속계를 이용한 꽁치어군의 유영속도 측정)

  • Lee, Kyoung-Hoon;Lee, Dae-Jae;Kim, Hyung-Seok;Park, Seong-Wook
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.46 no.2
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    • pp.165-172
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    • 2010
  • This study was performed to estimate the swimming velocity of Pacific saury (Cololabis saira) migrated offshore Funka Bay of Hokkaido using an acoustic Doppler current profiler (OceanSurveyor, RDI, 153.6kHz) established in T/S Ushio-maru of Hokkaido University, in September 27, 2003. The ADCP's doppler shift revealed as the raw data that the maximum swimming velocity was measured 163.0cm/s, and its horizontal swimming speed and direction were $72.4{\pm}24.1\;cm/s$, $160.1^{\circ}{\pm}22.3^{\circ}$ while the surrounding current speed and direction were $19.6{\pm}8.4\;cm/s$, $328.1^{\circ}{\pm}45.3^{\circ}$. To calculate the actual swimming speed of Pacific saury in each bins, comparisons for each stratified bins must be made between the mean surrounding current velocity vectors, measured for each stratified bin, and its mean swimming velocity vectors, assumed by reference (threshold > -70dB) and 5dB margin among four beams of ADCP. As a result, the actual averaged swimming velocity was 88.6cm/s and the averaged 3-D swimming velocity was 91.3cm/s using the 3-D velocity vector, respectively.

A Study on Spectrum Moment Estimation in an Acoustic Doppler Current Profiler (ADCP에서의 스펙트럼 모멘트 추정에 관한 연구)

  • Lee, Jonggil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.8
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    • pp.1790-1795
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    • 2013
  • The current velocity and turbulence information in each range cell can be obtained from the first and second Doppler spectrum moment estimates. However, the very widely used correlation method often called as the pulse-pair method has the inherent restrictions under the highly turbulent conditions since it does not satisfy the assumptions that the return Doppler spectrum should be symmetric and have a single peak value. Therefore, in this paper, the quality of pulse-pair estimates were compared with that of FFT estimates for problem analysis using various shapes of simulated Doppler spectra. It can be known that the pulse-pair method often yields meaningless results if the received signals are severely biased or multi-peak Doppler spectra in the Doppler frequency domain.

Improvement of Current Velocity Estimation Method in an ADCP (ADCP에서의 유속 추정 방법 개선에 관한 연구)

  • Lee, Jonggil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.21 no.9
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    • pp.1818-1825
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    • 2017
  • An Acoustic Doppler Current Profiler(ADCP) measures the current velocity and analyzes the degree of turbulence using Doppler effects of ultrasonic waves. Therefore, the autocorrelation or FFT spectrum estimates are obtained for extraction of current velocity in each spatial region. However, if the correlation method does not satisfy the assumption that the return signal spectra are symmetric Gaussian, the large bias errors can occur. Also, the accurate estimation of autocorrelation or FFT spectrum is difficult due to the short acquisition interval when the rapid changes of current velocity occur. Thus, in this paper, the estimation method of the autoregressive spectrum peak is suggested for the accurate current velocity measurement of both symmetric and asymmetric spectra. It is shown that estimation quality can be improved using the suggested method comparing with the conventional methods. Many return signals under the various environment are simulated and the results are compared and analyzed for evaluation of the suggested method.

Acoustic Signal Processing for ADCP using Zoom FFT Method to increase Frequency Resolution (주파수 해상도 증가를 위해 Zoom FFT 기법을 사용한 ADCP 음향신호처리)

  • Han, Jin-Hyun;Shim, Tae-Bo
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.47 no.5
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    • pp.229-234
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    • 2010
  • This paper proposed the acoustic signal processing techniques, which are applicable even in the shallow river, and will enhance the frequency resolution of the ADCP (Acoustic Doppler Current profiler). ADCP is a device that measures the velocity of a moving fluid. ADCP, in general, can be operated at ~300 Khz of center frequency due to no depth limit in the sea. However, it can hardly be used due to water depth of 30cm or shallower during the dry season in the river. Therefore, existing signal processing methods are not suitable to use in the shallow river. We are proposing an alternative acoustic signal processing method using Zoom FFT. Simulation results show that errors are reduced ${\pm}62\;cm/s$ in theory, and ${\pm}93\;cm/s$ in the experiment. The existing algorithm could not estimate the current speed at the shallow river below 30 cm, but proposed algorithm estimated the current speed that was faster than 20 cm/s at the shallow river below 30 cm.

Observation of suspended sediment concentration profiles from ADP (음향도플러유속계(ADP)를 이용한 부유사 농도 관측)

  • 오병철;추용식;정병순
    • Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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    • pp.294-297
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    • 2002
  • ADP(Acoustic Current Profiler)는 수중에서 음파를 발사하여 해수와 함께 유동하는 부유입자에 의하여 반사되는 음향의 Doppler 효과를 이용하여 여러 개의 수층에서 유속과 유향을 측정하는 장비이다. Doppler 효과에 의한 반사음향의 주파수 천이가 부유입자의 속도에 따라 달라지는 것을 이용하여 해수의 흐름을 관측할 수 있다. (중략)

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Variation of Current by the Building of Artificial Upwelling Structure(II) (인공용승구조물 설치에 의한 유동변화(II))

  • Hwang, Suk-Bum;Kim, Dong-Sun;Bae, Sang-Wan;Kheawwongjan, Apitha
    • Proceedings of KOSOMES biannual meeting
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    • pp.9-14
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    • 2007
  • To illusσ'ate the variation of current around artificial upwelling structure which is located in the South sea of Korea, current measurements using ADCP (Acoustic Doppler Current Profiler) during neap and spring tides were carried out on 27th July(summer), 14th October and 30th November(Autumn), 2006. Current after the set up of artificial upwelling structure were shown different in the upper and lower layer, the boundary between the upper and lower layer was at $27{\sim}30m$ depth in summer. And the boundary layer was formed structure of three layer in Autumn. Upwelling and downwelling flow were occurred around the seamount, and these vertical flows were connected from surface to bottom The distribution of vertical shear and relative vorticity support the vertical flow around the seamount. The strength of vertical shear was higher and the direction of relative vorticity was anticlockwise (+) around the upwelling area.

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Vertical Migration of Sound Scatterers in the Southern Yellow Sea in Summer

  • Lu, Lian-Gang;Liu, Jianjun;Yu, Fei;Wu, Wei;Yang, Xiaodong
    • Ocean Science Journal
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    • v.42 no.1
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    • pp.1-8
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    • 2007
  • Acoustic volume backscattering strength data were collected and Conductivity Temperature Depth (CTD) measurements were conducted in the southern Yellow Sea in summer 2005 and 2006. The high temporal and vertical resolution acoustic data measured with a 307 kHz Acoustic Doppler Current Profiler (ADCP) and a 250 kHz acoustic Doppler profile (ADP) had dominant diel variation, which resulted from vertical migration of sound scatterers. Some scatterers congregating in the bottom layer in the daytime migrated upward at dusk, and migrated downward into the bottom layer at dawn. The migration speeds were estimated. More than 33 days data show that the diel migration varies with time. The feature of migration measured with ADCP and ADP is consistent to some extent with what is described in the study on vertical migration of zooplankton in the southern Yellow Sea with conventional net samples.

Acoustical Estimation of Zooplankton Distributions From the Backscattered Signal of the Acoustic Doppler Current Profiler in the Korea Strait (한국 해협에서 ADCP(Acoustic Doppler Current Profiler)의 음파 산란신호에 의한 동물플랑크톤 분포의 추정)

  • Na, Jung Yul;Park, Joung Soo
    • 한국해양학회지
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    • v.24 no.4
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    • pp.172-183
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    • 1989
  • Acoustical estimation of vertical distributions of zooplankton was carried out by using the backscattered signals of ADCP which was deployed in the Korea Strait in September, 1978. the backscattered signals of ADCP represents the total backward sound intensity caused by the scatters existing within the insonified water column of 8m deep. Based on these backscattered intensities, the estimated number of individual zooplankton (namely, Copepods) varies with depth such that in the surface layer above the thermocline, the numbers are exceedingly larger than the lower layer. It is also shown that a relatively larger number of individuals exists in the bottom cold water layer in the centeral part of the Strait. The horizontal distribution of the zooplankton in the surface layer across the west channel of the Strait shows that the number is higher in the coastal zone of the Korea and it decreases toward the central and then remains constant up to the vicinity of the Tsushima Island where it increases again. This type of distributions is well fitted to the one obtained at several stations by the conventional method at least in qualitative way. Therefore, it is quite plausible to use the ADCP data for monitoring the spatial and temporal distributions of zooplankton.

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