1,721,251 research outputs found
Evaluation of methods for assessing spectra from laser Doppler velocimetry signals
No full textA critical evaluation is made of the spectral bias which occurs in the use of a laser Doppler velocimeter (LDV). In order to accommodate the highly turbulent random sampled LDV data, a doubly stochastic Poisson process is generated. Four well-known processing algorithms, i.e., the direct transform (RG), the transit-time weighting method (TW), the sample-and-hold method (SH), and the modified Shannon sampling technique (SR), are evaluated and compared with the theoretical spectra for various sampling and flow conditions. Assessment of these algorithms is made for varying data densities (0.05 ≤ d.d. ≤ 5.0) and turbulence levels (t.i. = 30% and 100%). Furthermore, the effects of the Reynolds stress coefficients and of the transversal standard deviations on the spectral bias are examined. © 1995
Assessment of LDV spectral bias based on three-dimensional velocity fields
No full textAn extensive evaluation is made of the spectral bias in the use of a burst-type laser Doppler velocimeter (LDV). An improved version of the autoregressive vector model (ARV) to handle the full three-dimensional velocity fields is proposed. The particle arrival time statistics are modeled as a doubly stochastic Poisson process. Four well-known spectral algorithms, i.e., the direct transform method (RG), the transit time-weighting method (TW), the sample and holds interpolation method (SH), and the nonuniform Shannon reconstruction technique (SR), are evaluated and compared with the theoretical spectra for various sampling and flow conditions. Assessment is made of these processing algorithms over a broad range of data densities (0.05 ≤ d.d. ≤ 5.0) and turbulence levels (t.i. = 0.3, 1.0). In order to move closer to realistic experimental conditions, the influences of the ratio of the minimum number of periods required for frequency estimation to the maximum fringe number of the measuring volume (Q = 0.57), and the relative velocity by frequency shifting (R = 5.0) on spectral distortion are examined. Furthermore, the effect of the Reynolds stress coefficients on spectral bias is scrutinized. © 1997 Elsevier Science Ltd
A robust quantitative method for element analysis by laser-induced breakdown spectroscopy
No full text
Spectral Analysis of Randomly Bursted Data from a Laser Doppler Velocimeter in Turbulent Recirculating Flows
No full text
Formation Flying of Small Satellites using Coulomb Forces
No full textMinistry of science and Technology, Kore
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