• Journal of Advanced Marine Engineering and Technology
• /
• 제20권2호
• /
• pp.116-116
• /
• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw and total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• Journal of Advanced Marine Engineering and Technology
• /
• 제20권2호
• /
• pp.48-56
• /
• 1996

This paper is concerned with a method for calibrating five-hole probes of both angle-tube and prismatic geometries to measure local total and static pressures and the magnitude and direction of the mean velocity vector. Descriptions of the calibration technique, the typical calibration data, and an accompanying discussion of the interpolation procedure are included. The flow properties are determined explicitly from measured probe pressures using calibration data. Flow angles are obtained within the deviation angle of 1.0 degree and dynamic pressures within 0.03 with 95% certainty. The variations in the calibration data due to Reynolds number are also discussed. For the range of Reynolds number employed, no effect was detected on the pitch, yaw abd total pressure coefficients. However, the static pressure coefficient showed change to cause minor variations in the magnitude of the calculated velocity vector. To account for these variations, average correction factors need to be incorporated into the static pressure coefficient.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2019년도 학술발표회
• /
• pp.155-155
• /
• 2019

The Agricultural Policy/Environmental eXtender (APEX) models have been developed for assessing agricultural management efforts and their effects on soil and water at the field scale as well as more complex multi-subarea landscapes, whole farms, and watersheds. National Academy of Agricultural Sciences, Wanju, Korea, has modified a key component of APEX application, named APEX-Paddy for simulating water quality with considering appropriate paddy management practices, such as puddling and flood irrigation management. Calibration and validation are an anticipated step before any model application. Simple techniques are essential to assess whether or not a parameter should be adjusted for calibration. However, very few study has been done to evaluate the ability of APEX-Paddy to simulate the impact of multiple management scenarios on nutrients loss. In this study, the observation data from experimental fields at Iksan in South Kora was used in calibration and evaluation process during 2013-2015. The APEX auto- calibration tool (APEX-CUTE) was used for model calibration and sensitivity analysis. Four quantitative statistics, the coefficient of determination ($R^2$),Nash-Sutcliffe(NSE),percentbias(PBIAS)androotmeansquareerror(RMSE)were used in model evaluation. In this study, the hydrological process of the modified model, APEX-Paddy, is being calibrated and tested in predicting runoff discharge rate and nutrient yield. Field-scale calibration and validation processes are described with an emphasis on essential calibration parameters and direction regarding logical sequences of calibration steps. This study helps to understand the calibration and validation way is further provided for applications of APEX-Paddy at the field scales.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
• /
• pp.603-605
• /
• 2005

In this paper, we deal with a calibration method for low cost motion capture sensor using PSD (Position Sensitive Detection). The PSD sensor is employed to measure the direction of incident light from moving markers attached to motion body. To calibrate the PSD optical module, a conventional camera calibration algorithm introduced by Tsai. The 3-dimensional positions of the markers are measured by using stereo camera geometry. From the experimental results, the low cost motion capture sensor can be used in a real time system.

• 천문학회지
• /
• 제39권4호
• /
• pp.151-155
• /
• 2006

Long slit spectrometers are widely used in optical and infrared bands in astronomy. Absolute flux calibration for extended sources, however, is not straightforward, because a portion of the radiation energy from a flux calibration star is blocked by the narrow slit width. Assuming that the point spread function(PSF) of the star is circularly symmetric, we develop a robust method to extrapolate the detected stellar flux to the unobscured flux using the measured PSF along the slit-length direction. We apply this method to our long slit data and prove that the uncertainty of the absolute flux calibration is less than a few percents.

• 한국가시화정보학회지
• /
• 제18권3호
• /
• pp.122-128
• /
• 2020

In the field of experimental fluid dynamics, the 5-hole probe is one of the most widely used tools to measure flow velocity and pressure. We hereby describe the development of an inexpensive laboratory-based flow calibration system for 5-hole probes. The system is applied to a custom L-shaped probe, and the probe performance is compared against a standard commercial probe in a custom wind tunnel. The setup allows rotation of the probe around the yaw and pitch axes. Static and total pressure values are calculated, and then calibration maps are constructed based on the yaw and pitch angles. Using these maps, errors of the custom probe are found to be ±5% for velocity magnitude and ±3° for direction, compared to the commercial probe, when both pitch and yaw angles are within 40°.

• 한국통신학회논문지
• /
• 제29권1A호
• /
• pp.18-30
• /
• 2004

본 논문에서는 비동기 CBMA 시스템에서 발생하는 배열 안테나 소자의 오차 보정(calibration) 문제를 다룬다. 수신기치 주파수 오프셋 오차가 있을 경우에 적용 가능한 새로운 순차적인 오차 보정 알고리즘을 제안한다. 제안된 알고리즘은 비선형 배열 안테나에도 적용가능하며, 사전에 알고 있는 신호를 사용하여 보정하는 것이 아니라, 셀 내의 임의의 사용자 PN code 만을 사용하여 온라인으로 오차 보정을 수행한다. 제안된 알고리즘은 채널과 주파수 오차를 추정하는 부분과 배열안테나 보정을 추정하는 부분으로 구성되어 있으며, 컴퓨터 모의 실험과 W-CDMA용 스마트 안테나 테스트 베드에서 얻어진 실측 데이터를 이용한 실험을 통하여 그 성능이 검증되었다.

• 한국통신학회논문지
• /
• 제34권2A호
• /
• pp.139-146
• /
• 2009

본 논문은 TDD(Time Division Duplex) 배열안테나 시스템에서 빔형성을 할 때와 송신 전력을 할당하는 경우에 필요한 송수신 RF 단의 진폭과 위상 오차를 교정하는 평균자동내부순환교정 방법을 제안한다. 제안된 기술은 기존의 부가적인 내부 신호발생기나 외부의 기준신호를 필요로 하지 않으며 송수신기 내부의 스위치와 커플러를 이용하여 배열안테나 RF단을 교정할 수 있는 방법이다. 또한 한 개의 송수신 RF단을 사용한 교정에 의한 오차를 줄이기 위해서 평균송수신 RF단 교정 방법을 제안하였다. 전산모의실험을 통해 DOA(Direction of Arrival)추정 빔형성 알고리즘이 송수신 RF단 교정에 의해 정확한 빔형성이 되는 것을 보였고 송신 전력 할 당시에도 제안된 교정에 의해 비트오류율이 낮아짐을 보였다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2010년도 추계학술대회
• /
• pp.40-43
• /
• 2010

This paper deals with a new two dimensional clinometer based on dual axis micromachined accelerometers. The clinometer is a small and low-cost product, which is mainly developed to help golfers read easily the tilt of a putting green. First, this paper proposes the principle of two dimensional clinometer and also a calibration method with respect to the offset voltage and sensitivity of a accelerometer. Experimental results on the developed clinometer show that the proposed clinometer can provide useful information on the tilt angle and direction of an inclined plane.

• 제어로봇시스템학회논문지
• /
• 제16권5호
• /
• pp.463-468
• /
• 2010

An obstacle avoidance method for a mobile robot is proposed in this paper. Our research was focused on the obstacles that can be found indoors since a robot is usually used within a building. It is necessary that the robot maintain the desired direction after successfully avoiding the obstacles to achieve a good autonomous navigation performance for the specified project mission. Sensors such as laser, ultrasound, and PSD (Position Sensitive Detector) can be used to detect and analyze the obstacles. A PSD sensor was used to detect and measure the height and width of the obstacles on the floor. The PSD sensor was carefully calibrated before measuring the obstacles to achieve better accuracy. Data obtained from the repeated experiments were used to plot an error graph which was fitted to a polynomial curve. The polynomial equation was used to navigate the robot. We also obtained a direction-error model of the robot after avoiding the obstacles. The prototypes for the obstacle and direction-error were modeled using a neural network whose inputs are the obstacle height, robot speed, direction of the wheels, and the error in direction. A mobile robot operated by a notebook computer was setup and the proposed algorithm was used to navigate the robot and avoid the obstacles. The results showed that our algorithm performed very well during the experiments.