• 한국통신학회논문지
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• 제37권6C호
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• pp.453-461
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• 2012

본 논문에서는 진폭 변조 거리 측정 시스템에 적용 가능한 개선된 위상 추정 기법을 제안한다. 기존 위상 측정 방법은 이동 목표물의 도플러 천이에 의해 위상 측정 오차가 발생한다. 제안된 위상 추정 기법은 도플러 천이에 대해 적응 도플러 보정(Adaptive Doppler Correction)을 사용하여 위상 추정 오차를 보정하므로 거리 측정 정확도를 향상 시킬 수 있다. 모의실험 결과 도플러 주파수 천이 보정은 기존 방식보다 94.7% 향상된 성능을 보이며, 거리 측정 정확도는 50%로 향상되었다. 음향 수조에서는 오차가 7.7cm로 추정되어 해양 환경에서 음파를 이용하여 거리 추정에도 적용 가능함을 확인하였다.

• 한국분무공학회지
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• 제3권1호
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• pp.1-9
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• 1998

Two measurement techniques of droplet sizing, an imaging technique(PMAS) and a phase-Doppler measurement technique (PDPA), have been compared using a water spray from a pressurized-type swirl nozzle. The result showed that SMD measured by PDPA was larger than that measured by PMAS by about 40 %. Such discrepancy of SMD could be explained by the fact that the light signal intensity used by PDPA can be biased towards larger particles. On the other hand there could be lower opportunity to capture the images of the large particles with PMAS, since the large particles could be out of sight due to their high speed.

• 대한의용생체공학회:의공학회지
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• 제8권1호
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• pp.75-80
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• 1987

With the conventional CW Doppler velocity meter, bl-directional velocities cannot be separated. The new CW Doppler system uses quadrature detection and phase rotation to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction, is fabricated. Specially, this system shows that phase rotation method for flow direction separation provides easy and satisfactory feature. From in vivo blood flow measurement, we can easily differentiate typical artery flow from vein flow, and measure both velocity characteristics qualitatively.

• 센서학회지
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• 제14권5호
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• pp.313-321
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• 2005

Spray combustion has been used in many industrial fields, for instance, such as diesel engines, gas turbines and industrial furnaces, and furthermore various measurement techniques have been applied to elucidate the phenomenon of spray combustion. In order to measure simultaneously the droplet velocity and the droplet size of spray, phase doppler anemometry (PDA) was frequently used in spray combustion. However, the measurement error is occurred due to existence of flame, which is considered as influencing the precision of measurement. Therefore, the purpose of this study is experimentally to conduct the systematic evaluation on the measurement error when PDA measurement is applied to combustion field.

• International Journal of Vascular Biomedical Engineering
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• 제1권1호
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• pp.3-12
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• 2003

Ultrasonic pulsed Doppler velocimetry has become a standard international method of classifying carotid disease. Because the measured angle adjusted velocity increases as the Doppler angle increases, examinations should be performed at a convenient standard Doppler examination angle. An angle of 60 degrees is achievable throughout most examinations. Multiple Doppler viewing angles allow the acquisition of velocity vectors during the cardiac cycle, revealing the complex velocity patterns. Ultrasonic velocimetry (whether Doppler or time domain) is based on changes in the phase of the ultrasound echo. Other examinations can be done based on the echo phase. Slow motions of organs such as the brain can be used to monitor changes in edema. Measurements of tissue strain due to the pulsatile filling of the arterioles. This plethysmographic imaging method can display differences in tissue perfusion because of different tissue types and changes in autonomic activity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.705-708
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• 1988

Ultrasound Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. Pulsed Doppler System uses Phase detector and zerocrossing method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time domain, had been fabricated. But time-domain analyzing such as audio evaluation and zerocrossing detection for instantaneous and mean frequency measurement doesn't, provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency domain technique to improve system performance. In this paper, we describe a unit which is composed of Pulsed Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of blood Signal.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.709-712
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• 1988

Ultrasonic Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. CW(Continuous-Wave) Doppler System uses quadrature detection and phase rotation method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time-domain, had been fabricated. But time-domain analyzing such as audio evaluation and zero- crossing detection for instantaneous and mean frequnecy measurement do not provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency-domain technique to improve system performance. In this paper, we describe a unit which is composed of CW Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of Blood signal.

• 대한기계학회논문집
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• 제18권4호
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• pp.1039-1049
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• 1994

The intermitternt and transient fuel spray have been investigated from the simultaneous measurement of droplet sizes and velocities by using Phase/Doppler Particle Analyzer(PDPA). Measurement have been done on the spray axis and at the edge of the spray near nozzle at various gas-to-liquid density ratios(.rho./sub g//.rho./sub l/) that ranges from those found in free atmospheric jets to conditions typical of diesel engines. Probability density distributions of the droplet size and velocity were obtained from raw data and mathematical probability density functions which can fit the experimental distribations were extracted using the principle of maximum likelihood. In the near nozzle region on the spray axis, droplet sizes ranged from the lower limit of the measurement system to the order of nozzle diameter for all (.rho./sub g/ /.rho./sub l/) and droplet sizes tended to be small on the spray edge. At the edge of spray, average droplet velocity peaked during needle opening and needle closing. The rms intensity is greatly incresed as the radial distance from the nozzle is increased. The probability density function which can best fit the physical breakage process such as breakup of fuel drops is exponecially decreasing log-hypebolic function with 4 parameters.

• 한국정밀공학회지
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• 제19권9호
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• pp.172-178
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• 2002

One of the ever-increasing demands on the performances of heterodyne interferometers is to improve the measurement resolution, of which current state -of-the-art reaches the region of sub-nanometers. So far, the demand has been met by increasing the clock speed that drives the electronics involved fur the phase measurement of the Doppler shift, but its further advance is being hampered by the technological limit of modem electronics. To cope with the problem, in this investigation, we propose a new scheme of phase -measuring electronics that reduces the measurement resolution without further increase in clock speed. Our scheme adopts a super-heterodyne technique that lowers the original beat frequency to a level of 1 MHz by mixing it with a stable reference signal generated from a special phase- locked-loop. The technique enables us to measure the phase of Doppler shift with a resolution of 1.58 nanometer at a sampling rate of 1 MHz. To avoid the undesirable decrease in the maximum measurable speed caused by the lowered beat frequency, a special form of frequency up-down counting technique is combined with the super-heterodyning. This allows performing required phase unwrapping simply by using programmable digital gates without 2n ambiguities up to the maximum velocity guaranteed by the original beat frequency.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1801-1807
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• 2001

In multiphase flne the bubble size and velocity. To achieve this, one of approaches is to utilize laser phase-Doppler anemometry. However, it was found that the second order refraction has great impact on PDA sizing method when the relative refractive index of media is less than one. In this paper, the problem of second order refraction is investigated and a model of phase-size correlation to eliminate the measurement errors is introduced for bubble sizing. As a result, the model relates the assumption of single scattering mechanism in conventional phase-Doppler anemometry. The results of simulations based on this new model by using Generalized Lorenz Mie Theory (GLMT) are compared with those based on the conventional method. An optimization method for accurately sizing air-bubble in water has been suggested.