• 한국정보통신학회논문지
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• 제16권10호
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• pp.2101-2107
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• 2012

하천 및 강등의 유속 측정을 위한 레이다에서는 수면에서 반사 또는 산란되는 전자파로부터 도플러 주파수를 추정함으로서 이에 대응하는 유속 정보를 추출하게 된다. 그러나 수면으로부터 수신되는 전자파 신호들의 도플러 스펙트럼은 측정 환경 및 기상 상태에 따라 매우 다른 형태를 나타낼 수 있다. 따라서 이러한 다양한 도플러 스펙트럼들의 존재로 인하여 레이다 센서에서의 유속정보 추출 알고리즘의 정확도 및 신뢰성에 심각한 문제가 발생할 수 있다. 따라서 본 논문에서는 수면으로부터 수신되는 매우 다양한 도플러 신호 스펙트럼을 적절하게 모의 구현할 수 있는 도플러 스펙트럼 모델을 제안하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.596-600
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• 2011

In this numerical analysis, the distortion of flow measurement by inlet velocity profile of orifice flowmeter was investigated. To validate the numerical method, the convergence was monitored and the grid dependency was also checked. realizable k-e model was selected and y+ was about 50 in this calculation. the results shows that the pressure at the pressure tab near pipe wall was changed by inclined inlet velocity profile and it leads to distorted a measurement values of flow through the orifice plate from -3.8% to 9%. Therefore, the fully developed inlet flow was required for accurate flow measurement by orifice flowmeter. If not, the orifice plate installed at wrong location should be re-installed or additional actions should be taken.

• 센서학회지
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• 제32권5호
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• pp.307-312
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• 2023

To measure the flow velocity and direction in the near field of an unmanned underwater vehicle, an optical measurement unit containing an image sensor and a phosphor-integrated pillar that mimics the neuromasts of a fish was constructed. To analyze pillar movement, which changes with fluid flow, fluorescence image analysis was conducted. To analyze the flow velocity, mean force analysis, which could determine the relationship between the light intensity of a fluorescence image and an external force, and length-force analysis, which could determine the distance between the center points of two fluorescence images, were employed. Additionally, angle analysis that can determine the angles at which pixels of a digital image change was selected to analyze the direction of fluid flow. The flow velocity analysis results showed a high correlation of 0.977 between the external force and the light intensity of the fluorescence image, and in the case of direction analysis, omnidirectional movement could be analyzed. Through this study, we confirmed the effectiveness of optical flow sensors equipped with phosphor-integrated pillars.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.605-610
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• 2014

Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.521-526
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• 2004

In order to evaluate the effect of blasting vibration in buildings and it's resident located around blasting construction field in urban area, blasting vibration characteristics were measured the vibration level, vibration velocity. The 250g and 750g of charged powder were used at the apartment and at the ground, respectively. In the measurement of the ground, Z(perpendicularity) axis was the highest value in vibration level, but vertical axis was the highest value at 25m point and longitudinal axis was the highest value at 50m point in vibration velocity. The amount of measurement was high value when measuring point is higher than blasting source, while that of measurement was low value when measuring point is lower than blasting source. In the measurement of the apartment, 2 axis was the highest value in vibration level, but in vibration velocity transverse axis was the highest value at ground, was vertical axis at 1st floor, was longitudinal axis at 3rd floor and was vertical and longitudinal axis at 5th floor. The vibration level and the vibration velocity of 50m point showed higher correlation value than 25m point at the ground, but those of 25m point showed higher correlation value than 50m point at the apartment.

• 한국소음진동공학회논문집
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• 제14권7호
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• pp.632-638
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• 2004

In order to evaluate the effect of blasting vibration in buildings and it's resident located around blasting construction field in urban area, blasting vibration characteristics were measured by the vibration level, vibration velocity. The 250g and 750g of charged powder were used at the apartment and at the ground, respectively. In the measurement of the ground, 2 (perpendicularity) axis was the highest value in vibration level, but vertical direction was the highest value at 25 m point and longitudinal direction was the highest value at 50 m point in vibration velocity. The amount of measurement was high value when measuring point is higher than blasting source, while that of measurement was low value when measuring point is lower than blasting source. In the measurement of the apartment, Z axis was the highest value in vibration level, but in vibration velocity transverse direction was the highest value at ground, was vertical direction at 1st floor, was longitudinal direction at 3rd floor and was vertical and longitudinal direction at 5th floor. The vibration level and the vibration velocity of 50 m point showed higher correlation value than 25 m point at the ground, but those of 25 m point showed higher correlation value than 50 m point at the apartment.

• 로봇학회논문지
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• 제5권4호
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• pp.309-317
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• 2010

This paper proposes an efficient measurement system for the velocity and direction of the wind using the dual rotor wind power generator in vessel. Conventional digital measurement system recognizes the direction and the velocity of the wind using the electric compass or synchronous motor and Vane probe method using hall sensors. But each system has its own short-comings: the synchronous motor has a larger measurement error than the magnetic compass and magnetic compass is weak for the external disturbances such as fluctuation of the vessel. To compensate these short-comings, this paper proposes a new compensation algorithm for the fluctuation errors according to the external interference and the unexpected movement of the vessel along the roll and pitch directions. The proposed system is implemented with the dual compasses and a synchronous motor. The proposed independent power generation system can be operated by itself and can raise the efficiency of the wind power generation systems of 30 ~ 400 W installed along the vertical and horizontal axes. The proposed system also realizes the efficient and reliable power production system by the MPPT algorithm for the real-time recognition of the wind direction and velocity. An advanced switching algorithm for the battery charging system has been also proposed. Effectiveness of the proposed algorithm has been verified through the real experiments and the results are demonstrated.

• 대한임상검사과학회지
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• 제42권3호
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• pp.155-160
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• 2010

Transcranial Doppler ultrasonography (TCD) allows measurement of blood flow velocity to be made from the basal intracerebral vessels. Blood flow velocity in TCD is highly affected not only by blood vessel diameter, blood flow volume, blood viscosity, but also age and sex. Therefore, the study is focused on the correlation between TCD measurement index and sex/age. Subjects were 214 (male 147, famale 67) who had TCD for headache and stroke evaluations at Dongguk University Ilsan Hospital neurology department from December 2009 to April 2010. Sex did not show significant differences with mean flow velocity (MFV), peak systolic flow velocity (PSFV), end diastolic flow velocity (EDFV), pulsatility index (PI) and resistance index (RI) in middle cerebral artery (MCA). Although age also did not show significant differences with MFV and PSFV, EDFV has statistically decreased with age, and PI and RI has statistically increased with age. In addition, age showed significant correlation with MFV, EDFV, PI and RI, but not with PSFV. Therefore, TCD is definitely correlated with age and sex, so that those influencial factors must be considered when being tested.

• 전기학회논문지
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• 제67권7호
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• pp.840-845
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• 2018

BLDC motor is widely used as a servo motor due to high efficiency, high power density, low inertia, and low maintenance. However, BLDC motor generally needs position and velocity sensors to control actuation system. Usually, analog tachometers and encoders have been used for velocity feedback sensors. However, using these types of sensors have problems such as the cost, space, and malfunction. So, This paper is to propose a new velocity measurement method using linear hall-effect and enhanced differentiator for BLDC motor. In order to verify the feasibility of the proposed method, several simulations and experiments are performed. It is shown that the proposed velocity measurement method can satisfy the requirements without using of velocity sensor.

• 한국음향학회지
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• 제31권4호
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• pp.253-259
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• 2012

Goldingham's measurement of the velocity of sound undertaken in the early nineteenth century was the first large-scale measuring enterprise which considered various meteorological factors such as temperature, humidity, atmospheric pressure, the direction of the wind, etc. Goldingham's successful performance of measuring the velocity of sound by employing the sounds of cannons as sound source in Madras (now Chennai), a colonial region of India, for one and a half years was supported by material, institutional and social resources. As the official astronomer at the Madras Observatory, he was benefitted by the undemanding employment of accurate measuring instruments under the support of the Madras Army enabled him to gain reliable data and his reputation as professional experimentalist facilitated the acknowledgment of their trustworthiness.