Frequency-domain photon density wave setup with multicolor illumination at 684, 794, and 1060 nm

2007 ◽  
Author(s):  
Vladimir I. Plehanov ◽  
Ilya V. Turchin ◽  
Ekaterina A. Sergeeva ◽  
Vladislav A. Kamensky
Keyword(s):  
Frequency Domain ◽  
Density Wave ◽  
Photon Density ◽  
Wave Setup

An Improved Model to Study the Density Wave Oscillation in Tubes by Using Frequency Domain Method

2014 ◽  
Author(s):  
Yifan Zhang ◽  
Huixiong Li ◽  
Tai Wang ◽  
Weiqiang Zhang ◽  
Tianyou Sheng
Keyword(s):  
Heat Flux ◽  
Frequency Domain ◽  
Present Model ◽  
Heat Storage ◽  
Tube Wall ◽  
Density Wave ◽  
Wall Heat Flux ◽  
Frequency Domain Method ◽  
Conventional Model ◽  
Domain Method

Density Wave Oscillation (DWO) in tubes was usually studied by using the frequency domain method. However, in the conventional model, the heat storage of wall metal was usually neglected to simplify the complex solving process of transfer functions, which might cause unreasonable results when the tube wall had a thick wall or complex geometry structures. Hence, in the present paper, an improved mathematical model was proposed based on the frequency domain theory to theoretically study the DWO in tubes. The present model was an improvement of the conventional model. The most notable improvement in the present model was that the heat storage of the tube wall metal, the internal wall heat flux and the external wall heat flux were all considered as dynamic parameters. Based on the improvement, the prediction of the DWO in tubes by using the present model might be more accurate and reasonable than that by using the conventional model, and this was proved by the comparison of the results obtained with the two models to the experimental results gained from literature. In the present study, it was shown that both the present model and the conventional model could predict the DWO in tubes well when the tube wall was thin, and it was also found that the present model was more appropriate than the conventional model when the tube wall was thick. Both the thickness of the tube wall and the specific heat of tube wall metal play negative roles in the system stability.

Investigation of total diffuse-photon-density-wave field in semi-infinite turbid media based on the extrapolated Beer–Lambert law

2020 ◽  
Vol 127 (12) ◽  
pp. 123102
Author(s):  
Zhi-Tao Luo ◽  
Jian Wang ◽  
Fei-Long Mao ◽  
Lang Shen ◽  
Sheng Wang ◽  
...  
Keyword(s):  
Wave Field ◽  
Density Wave ◽  
Turbid Media ◽  
Photon Density

An Advanced Frequency-Domain Code for BWR Stability Analysis and Design

2013 ◽  
Author(s):  
Behrooz Askari ◽  
George Yadigaroglu
Keyword(s):  
Steady State ◽  
Frequency Domain ◽  
Transfer Functions ◽  
Density Wave ◽  
System Stability ◽  
Reactor Kinetics ◽  
Analysis And Design ◽  
Drift Flux ◽  
Reactor Transfer ◽  
Phase Instabilities

Density Wave Oscillations in BWRs are coupled with the reactor kinetics. A new analytical, frequency-domain tool that uses the best available models and methods for modeling BWRs and analyzing their stability is described. The steady state of the core is obtained first in 3D with two-group diffusion equations and spatial expansion of the neutron fluxes in Legendre polynomials. The time-dependent neutronics equations are written in terms of flux harmonics (nodal-modal equations) for the study of “out-of-phase” instabilities. Considering separately all fuel assemblies divided into a number of axial segments, the thermal-hydraulic conservation equations are solved (drift-flux, non-equilibrium model). The thermal-hydraulics are iteratively fully coupled to the neutronics. The code takes all necessary information from plant files via an interface. The results of the steady state are used for the calculation of the transfer functions and system transfer matrices using extensively symbolic manipulation software (MATLAB). The resulting very large matrices are manipulated and inverted by special procedures developed within the MATLAB environment to obtain the reactor transfer functions that enable the study of system stability. Applications to BWRs show good agreement with measured stability data.

The application of pulsation ratio preprocessing method in researching density wave instability

2018 ◽  
Vol 10 (3) ◽  
pp. 140-145
Author(s):  
Yefei Liu ◽  
Yang Liu ◽  
Xingtuan Yang ◽  
Haijun Jia
Keyword(s):  
Frequency Domain ◽  
Density Wave ◽  
Annular Channel ◽  
Frequency Domain Analysis ◽  
Wave Instability ◽  
Two Phase ◽  
Transform Method ◽  
Modified Method ◽  
Fast Fourier Transform Method ◽  
Dc Component

A modified Fast Fourier Transform method based on the pulsation ratio preprocessing is carried out in this study. When the density wave instability occurs, the method is applied to capture the characteristic signals in the frequency domain. Thus, the stable boundary in two-phase flow can be recognized accurately. In this paper, experiments are conducted in a system based on a narrow annular channel. The method is verified through two groups of experimental data collected in different conditions. The results indicate that the modified method can avoid the problem of DC component spectrum leakage in traditional frequency-domain analysis with the false value interference eliminated. Accordingly, it can improve the accuracy of boundary identification effectively when the instability occurs.

scholarly journals Exploring tissue dynamics by photon-density-wave fluctuation correlation spectroscopy

1999 ◽  
Author(s):  
Vlad Toronov ◽  
Mattia A. Filiaci ◽  
Maria-Angela Franceschini ◽  
Sergio Fantini ◽  
Enrico Gratton
Keyword(s):  
Density Wave ◽  
Correlation Spectroscopy ◽  
Photon Density

Oximetry based on diffuse photon density wave differentials

2000 ◽  
Vol 27 (2) ◽  
pp. 410-421 ◽  
Author(s):  
Vasilis Ntziachristos ◽  
Matthias Kohl ◽  
Honyan Ma ◽  
Britton Chance
Keyword(s):  
Density Wave ◽  
Photon Density
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