• The Journal of the Acoustical Society of Korea
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• v.19 no.7
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• pp.77-84
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• 2000

In measurement of ship speed with a Doppler log sensor, we encounter the nonhorizontal movement of a ship, i.e. pitching and rolling, and that causes inaccuracy of the measurement. In this study, we develop a Janus type ultrasonic transducer that can resolve the problems in accuracy due to the pitching and other environmental factors of common ultrasonic sensors attributed to the underwater usage. For the development, we analyze the operation mechanism of the transducer, fabricate a prototype of the sensor, and evaluate its performance through experiments.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.377-380
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• 2000

도플러 로그용 센서를 이용하여 선박의 속도를 측정하면, 선박의 수평방향 이외의 움직임, 즉 핏칭이나 롤링 등에 의한 측정 속도의 부정확성이 문제가 된다. 본 연구에서는 이러한 핏칭과, 수중이라는 환경요인에 기인하여 다른 속도 측정용 센서들이 가지는 문제점을 극복할 수 있도록 진동판을 수평축에서 일정한 각을 가지도록 두 개 또는 네 개를 등 간격으로 배열한 야누스형 초음파 트랜스듀서를 개발하였다. 트랜스듀서 개발을 위하여 그 작동 구조를 해석하고 그에 따라 시제품을 제작한 후, 실험적인 성능 평가를 수행하였다. 시제작된 초음파 트랜스듀서는 지향성 및 감도가 우수하고, 대역폭이 넓은 성능을 가지고 있어, 실제 선박에 장착되어 도플러 로그용 초음파 트랜스듀서로 사용될 수 있는 가능성이 확인되었다.

• The Journal of the Acoustical Society of Korea
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• v.9 no.3
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• pp.48-55
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• 1990

We analyze the effect of second-order sampling on estimating the mean frequency of the Doppler signal. In order to reduce the sampling frequency of analogue-to-digital converter, it is possible to obtain the Doppler signal by sampling the radio frequency echo signal with the low frequence of $4f_0$/5 or $4f_0$/9 instead of $4f_0$, where $f_0$ is the center frequency of the transmitted signal. The computer simulation and experiments show that if the narrowband signal is transmitted as is usual in the Doppler system, the error of the mean frequency estimates due to the low sampling frequency is negligible.

• The Journal of the Acoustical Society of Korea
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• v.38 no.4
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• pp.433-441
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• 2019

In this paper, a method of estimating speech parameters for ultrasonic Doppler signals reflected from the articulatory muscles using LSTM (Long Short Term Memory) RNN (Recurrent Neural Networks) was introduced and compared with the method using MLP (Multi-Layer Perceptrons). LSTM RNN were used to estimate the Fourier transform coefficients of speech signals from the ultrasonic Doppler signals. The log energy value of the Mel frequency band and the Fourier transform coefficients, which were extracted respectively from the ultrasonic Doppler signal and the speech signal, were used as the input and reference for training LSTM RNN. The performance of LSTM RNN and MLP was evaluated and compared by experiments using test data, and the RMSE (Root Mean Squared Error) was used as a measure. The RMSE of each experiment was 0.5810 and 0.7380, respectively. The difference was about 0.1570, so that it confirmed that the performance of the method using the LSTM RNN was better.

• Journal of Fisheries and Marine Sciences Education
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• v.9 no.2
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• pp.179-187
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• 1997

Doppler log and current meter are based on the measurment of the doppler effect. Ship's speed over the ground measured by means of doppler log effect of underwater ultrasonic intends to get infulence by the difference of sound velocity, the ship's course, the sea bottom inclination, the trim and tranducer installation etc. This paper investigated on the error of speed over the ground by change of the trim comparing the real speed obtained by the mile post with the speed of single beam type doppler log on the trainning ship Kyeongyangho. The results are as follows ; 1. Indicating speed of doppler log is very much greatly influenced on variation of trim, but the real speed is less affected variation by trim. 2. The range of variation and error of speed over ground are smallest when ship's trim is 2.15m trim by the stern.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.1
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• pp.6-14
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• 1996

In this paper we present an algorithm to discriminate an underwater target under track against an acoustic counter-measure(ACM) source, based on a sequential hypothesis test. The ACM source is separated from the target under track and generates, while drifting, measurements with false range and Doppler information. The purpose of the ACM is to mislead the target-tracking and to help the true target evade a pursuer. The algorithm uses as a test statistic a function of the innovation sequences from extended Kalman filters to estimate the target dynamics and the drifting position of the ACM source. Numerical experiments on various scenarios show that the proposed algorithm discriminates the target against an ACM source very fast with a high probability of success.

• Tuberculosis and Respiratory Diseases
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• v.56 no.1
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• pp.67-76
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• 2004

Background : Pulmonary hypertension is a poor prognostic factor in patients with chronic respiratory disease. However, diagnosing pulmonary hypertension is a difficult procedure which often requires an invasive test. Thus new alternative biochemical markers would be useful in clinical field and are in search. We sought to assess the role of plasma N-terminal pro-brain natriuretic peptide(NT-proBNP) in patients with pulmonary hypertension. Method : We measured plasma NT-proBNP level in twenty nine patients suspected for pulmonary hypertension. Pulmonary hypertension was defined as being right ventricular systolic pressure more than 35 mm Hg estimated by Doppler echocardiography. Plasma NT-proBNP level was measured by electrochemiluminescence sandwich immunoassay. Results : The log-transformed values for plasma NT-proBNP levels showed a linear correlation (correlation coefficiency: 0.783, p-value <0.001) with right ventricular systolic pressure. Plasma NT-proBNP levels closely correlated with right ventricular systolic pressure, right ventricular hypertrophy, interventricular septal flattening and right ventricular dilatation. Conclusion : Our results suggest that the measurement of plasma NT-proBNP level is an useful marker of the presence of pulmonary hypertension.