• Title/Summary/Keyword: Radial Velocity

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RADIAL VELOCITY ESTIMATION OF EX Leo USING BF ALGORITHM (BF 방법을 이용한 EX Leo의 시선속도 추정)

  • Kang, Dong-Il;Park, Hong-Suh;Han, In-Woo;Kim, Kang-Min
    • Publications of The Korean Astronomical Society
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    • v.22 no.2
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    • pp.35-41
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    • 2007
  • We present the result of radial velocity observation of a W UMa type binary star EX Leo. We observed the star on February 16, 2003, using Long-Slit spectrograph of BOAO(Bohyunsan Optical Astronomical Observatory). Since the spectral lines are broad due to its fast rotation, it is difficult to distinguish two radial velocities from cross correlation function. Instead of cross correlation function, we used broadening function to develop our own code which estimate the radial velocity of the broadened line spectra. With our own code, radial velocities of primary and secondary stars are derived simultaneously. From the radial velocity curve fit, we obtained $K_1=50.24{\pm}8.29km/s$ and $K_2=254.05{\pm}20.984km/s$ respectively.

A Study on Radial Velocity Transformation and Uncertainty Propagation (시선속도 변환과 불확도 전파에 관한 연구)

  • Ryu, Chung-Ho;Hwang, Gyu-Hwan;Jang, Yong-Sik;Kim, Moon-Ki;Choi, Ik-Hwan
    • Journal of the Korea Institute of Military Science and Technology
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    • v.16 no.2
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    • pp.199-206
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    • 2013
  • In general, radial velocity of a target can be obtained by acquiring doppler frequency shift in case of a doppler radar, or can be obtained by acquiring range rate in case of a pulse radar. Then radial velocity can be converted to tangential velocity using aspect angle or position variation per unit time. These two ways have the same meaning in physically, but result in different uncertainty finally. In this paper, it is described not only the two transformation procedures to calculate tangential velocity from radar measurement data, but also the result of combined uncertainty comparison between these two procedures.

The Relation of Time Resolution and Radial Velocity Accuracy of a CW Doppler Radar (CW 도플러 레이더의 시각 분해능과 시선 속도 정확도의 관계)

  • Ryu, Chung-Ho;Jang, Yong-Sik;Choi, Ik-Hwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.23 no.7
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    • pp.815-821
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    • 2012
  • A CW Doppler radar can measure radial velocity of an object. It detects a Doppler frequency shift that is proportioned to radial velocity of a moving object. To detect a Doppler frequency shift, FFT(Fast Fourier Transform) is conducted. In this process, the time domain received signal is transformed to a frequency domain. A number of FFT affects not only the time resolution but also signal to noise ratio of received signal. So finally it is related with a radial velocity accuracy. Therefore in this paper, it is described the relation of time resolution and the radial velocity accuracy.

AN ANALYSIS OF THE LIGHT AND RADIAL VELOCITY CURVES OF DO CAS (식쌍성 DO Cas의 광도곡선과 시선속도곡선의 분석)

  • 안영숙;김호일;이우백
    • Journal of Astronomy and Space Sciences
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    • v.17 no.2
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    • pp.181-188
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    • 2000
  • DO Cas is a short period (P=0.68day) eclipsing binary star and is classified as a near-contact binary by Shaw(1990). There is no published radial velocity curve for this short period binary after Mannino(1958). Hill(1991) suspected that Mannino's radial velocity curve had some serious mistake. So, we scanned the original plates used by Mannino with PDS and the spectra were employed to IRAF packages to estimate the radial velocities. The radial velocity curve and the BVR light curves made by us in 1998 were analyzed simultaneously with Wilson-Devinney code. We found that DO Cas is a contact or near-contact binary which the primary component fills its Roche lobe and we also estimated the absolute dimensions of each components of this system.

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Flow Characteristics of Centrifugal Impeller Exit under Rotating Stall (선회실속하의 원심 임펠러 출구 유동 특성)

  • Shin, You-Hwan;Kim, Kwang-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.2 no.2 s.3
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    • pp.5-12
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    • 1999
  • This study presents the measured unsteady flctuation of impeller discharge flow for a centrifugal compressor in an unstable operating region. The characteristics of the blade-to-blade flow at rotating stall onset were investigated by measuring unsteady velocity fluctuations at several different diffuser axial distances using a hot wire anemometer. The flow characteristics in terms of the radial and tangential velocity components and the flow angle distribution at the impeller exit were analyzed using phase-locked ensemble averaging techniques. As a result, increase or decrease of the radial velocity component during the rotating stall is dominated by that of the suction side. The radial velocity distributions show the opposite trends in the regions where the radial velocity during rotating stall onset increases and decreases.

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Flow Characteristics of centrifugal Impeller Exit Under Rotating Stall (선회실속하의 원심 임펠러 출구 유동 특성)

  • Shin, You-Hwan;Kim, Kwang-Ho
    • 유체기계공업학회:학술대회논문집
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    • 1998.12a
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    • pp.129-134
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    • 1998
  • This study presents the measured unsteady fluctuation of impeller discharge flow for a centrifugal compressor in unstable operating region. The characteristics of the blade-to-blade flow at rotating stall onset were investigated by measuring unsteady velocity fluctuations at several different diffuser axial distances using a hot wire anemometer. The flow characteristics in terms of the radial and tangential velocity components and the flow angle distribution at the impeller exit were analyzed using phase-locked ensemble averaging techniques. As a result, increase or decrease of the radial velocity component during the rotating stall is dominated by that on the suction side. The radial velocity distributions show the opposite trends in the regions where the radial velocity during rotating stall onset increases and decreases.

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Peripheral Blood Flow Velocity and Peripheral Pulse Wave Velocity Measured Using a Clip-type Pulsimeter Equipped with a Permanent Magnet and a Hall Device

  • Kim, Keun-Ho;Lee, Sang-Suk
    • Journal of Magnetics
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    • v.20 no.1
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    • pp.47-51
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    • 2015
  • We measured radial arterial pulse signals using a prototype of a clip-type pulsimeter equipped with a permanent magnet and a Hall device, which produced signals through a voltage-detecting circuit. The systolic peak time and the reflective peak time for a temporally pulsed signal were analyzed for an arbitrary pulse wave at one position of a small permanent magnet. The measured value of the peripheral pulse wave velocity was about 1.25-1.52 m/s, demonstrating the accuracy of this new method. To measure the peripheral blood flow velocity, we simultaneously connected the radial artery pulsimeter to a photoplethysmography meter. The average value of the peripheral blood flow velocity was about 0.27-0.50 m/s.

On the Optimum Modelization for a Spray Column Direct Contact Heat Exchanger (분사칼럼식 직접접촉 열교환기의 최적 모델링을 위한 연구)

  • Yoon, S.M.;Kang, Y.H.;Kim, C.B.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.3 no.1
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    • pp.1-10
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    • 1991
  • The purpose of this study is to lay groundwork for a complete analysis of two component flow by analyzing a single component flow made of continuous fluid without dispersed phase. In order to achieve uniform velocity distributions which are desirable in designing an optimum spray column direct contact heat exchanger, the influence of injection nozzle orientation has been investigated for axial and radial injections. The results that radial injection ensures more uniform velocity distributions compared to the axial case. The flow characteristics in a spray column have been investigated with various L/D values and inlet velocities, the most uniform internal velocity distributions have been obtained for the case of L/D=10 and 0.1m/sec. In the present investigation, it is shown that radial injection method for the continuous flow is advantageous in obtaining desirable uniform velocity distributions in a spray column. It is also found that as the value of L/D increases and the inlet velocity decreases, the flow improves to be better uniform velocity distributions.

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Modeling of the Velocity of the Ceiling Jet Front (연기선단의 전파속도 모델에 관한 연구)

  • 김명배;한용식
    • Fire Science and Engineering
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    • v.15 no.2
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    • pp.91-95
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    • 2001
  • Decays of the ceiling jet front velocity under a circular ceiling are investigated. To simulate the ceiling jet in fires He and $N_2$gas were injected from a nozzle to the center of the ceiling. The jet fronts in the form of turbulent eddies were traced by a high-speed camera system. The instantaneous locations of the front were obtained from visual readings of visualized front, and the radial velocity was calculated from the information of the time and the location with respect to the front. The similarity and dimensional analysis were also carried out to reveal the relationship between the velocity decay and the radial distance. It was shown that the radial velocity of the front was inversely proportional to the radial distance in the fully developed region from the experimental results and the theoretical analysis.

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THE VELOCITY INHOMOGENEITY IN THE COMA CLUSTER OF GALAXIES

  • KIM KWANG TAE
    • Journal of The Korean Astronomical Society
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    • v.28 no.1
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    • pp.15-30
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    • 1995
  • A velocity inhomogeneity, which is defined as a regional preponderence of either radial or tangential orbits, is searched with a new technique for the Coma cluster of galaxies. It is found within $\~2h^{-1}$ Mpc from the cluster center that the Coma shows conspicuous inhomogeneities in velocity and that the inhomogeneities are real at a $99\%$ level of confidence. Even in the central region (7' - 30' from the center), zones that are dominated by radial and tangential orbits are distinguishable. Defining the cluster's 'equator' as the direction defined by the Coma-A1367 supercluster, tangential orbits dominate the 'polar' zones in the central region. Galaxies that are located in 30'-100' also inhomogeneous in velocity in that the 'polar' zones are mostly radial while the rest is nearly homogeneous. These results indicate that the Coma galaxies are exceedingly more radial in orbit, implying that merging or infalls are either still going on or an earlier virialization is likely to have occurred preferentially near the 'equator'. Incorporating the velocity inhomogeneity into mass estimators, the most appropriate mass is turned out to be $0.4\times10^{15}h^{-1}M_\bigodot(R\;\leq\;0.6h^{-1} Mpc),\;and\;1.0\times10^{15}h^{-1} M_\bigodot(R\;\leq\;2.1h^{-1}Mpc)$. The corresponding mass to blue light ratio on the average is $\~$300h. These estimates are consistent with Merritt (1987) and Hughes (1989) and the MILE is seemed to favour the mass-follows-light models than the uniform spread of dark matter throughout the cluster.

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