scholarly journals Smoothed Temporal Variance Spectrum: weak line profile variations and NRP diagnostics

2016 ◽  
Vol 458 (2) ◽  
pp. 1604-1617 ◽  
Author(s):  
A. F. Kholtygin ◽  
N. P. Sudnik
Keyword(s):  
Line Profile ◽  
Weak Line ◽  
Temporal Variance ◽  
Variance Spectrum

Contrast of Filament Bright Rims

1994 ◽  
Vol 144 ◽  
pp. 365-367
Author(s):  
E. V. Kononovich ◽  
O. B. Smirnova ◽  
P. Heinzel ◽  
P. Kotrč
Keyword(s):  
High Altitude ◽  
Line Profile ◽  
Line Center ◽  
Magnetic Structures ◽  
The Mean

AbstractThe Hα filtergrams obtained at Tjan-Shan High Altitude Observatory near Alma-Ata (Moscow University Station) were measured in order to specify the bright rims contrast at different points along the line profile (0.0; ± 0.25; ± 0.5; ± 0.75 and ± 1.0 Å). The mean contrast value in the line center is about 25 percent. The bright rims interpretation as the bases of magnetic structures supporting the filaments is suggested.

Frequency Redistribution Effects in the Formation of Lyman α in Prominences and Their Influence on the Ratio of Hα to Lα

1979 ◽  
Vol 44 ◽  
pp. 53-55
Author(s):  
R.W. Milkey ◽  
J.N. Heasley ◽  
E.J. Schmahl ◽  
O. Engvold
Keyword(s):  
Line Profile ◽  
Large Fraction ◽  
Partial Frequency ◽  
Frequency Redistribution ◽  
Partial Frequency Redistribution ◽  
Emergent Intensity

The effect of partial frequency redistribution in the formation of Lyman α in the chromosphere has been discussed by Milkey and Mihalas (1973) and others, and it has been shown that in this case the coherency of scattering in the wings of the line substantially influences the line profile. Although there are non-negligible sources for La photons within a prominence, a large fraction of the emergent line photons are due to scattering of photons incident on the surface of the prominence so that one expects that in a prominence the frequency redistribution processes will play an important role in determining the emergent intensity.

Microstructure of post-deformed ECAP-Ti investigated by Multiple X-Ray Line Profile Analysis

2006 ◽  
Vol 2006 (suppl_23_2006) ◽  
pp. 129-134 ◽  
Author(s):  
E. Schafler ◽  
K. Nyilas ◽  
S. Bernstorff ◽  
L. Zeipper ◽  
M. Zehetbauer ◽  
...  
Keyword(s):  
Line Profile ◽  
Profile Analysis ◽  
Line Profile Analysis ◽  
X Ray

Emission-Line Diagnostics of T Tauri Magnetospheric Accretion. I. Line Profile Observations

1998 ◽  
Vol 116 (1) ◽  
pp. 455-468 ◽  
Author(s):  
James Muzerolle ◽  
Lee Hartmann ◽  
Nuria Calvet
Keyword(s):  
Emission Line ◽  
Line Profile ◽  
T Tauri ◽  
Magnetospheric Accretion

scholarly journals Quantifying ionospheric effects on global 21-cm observations

2021 ◽  
Vol 503 (1) ◽  
pp. 344-353
Author(s):  
Emma Shen ◽  
Dominic Anstey ◽  
Eloy de Lera Acedo ◽  
Anastasia Fialkov ◽  
Will Handley
Keyword(s):  
Parameter Space ◽  
Spatial Model ◽  
Ionospheric Effects ◽  
Temporal Variance ◽  
Foreground Calibration ◽  
Over Time

ABSTRACT We modelled the two major layer of Earth’s ionosphere, the F-layer and the D-layer, by a simplified spatial model with temporal variance to study the chromatic ionospheric effects on global 21-cm observations. From the analyses, we found that the magnitude of the ionospheric disruptions due to ionospheric refraction and absorption can be greater than the expected global 21-cm signal, and the variation of its magnitude can differ, depending on the ionospheric conditions. Within the parameter space adopted in the model, the shape of the global 21-cm signal is distorted after propagating through the ionosphere, while its amplitude is weakened. It is observed that the ionospheric effects do not cancel out over time, and thus should be accounted for in the foreground calibration at each timestep to account for the chromaticity introduced by the ionosphere.

Real-time subsurface scattering with single pass variance-guided adaptive importance sampling

2020 ◽  
Vol 3 (1) ◽  
pp. 1-21
Author(s):  
Tiantian Xie ◽  
Marc Olano ◽  
Brian Karis ◽  
Krzysztof Narkowicz
Keyword(s):  
Real Time ◽  
Adaptive Sampling ◽  
Monte Carlo Sampling ◽  
Diffusion Profile ◽  
Correct Result ◽  
Subsurface Scattering ◽  
Stochastic Sampling ◽  
Light Gradient ◽  
Temporal Variance ◽  
Importance Function

In real-time applications, it is difficult to simulate realistic subsurface scattering with differing degrees translucency. Burley's reflectance approximation by empirically fitting the diffusion profile as a whole makes it possible to achieve realistic looking subsurface scattering for different translucent materials in screen space. However, achieving a physically correct result requires real-time Monte Carlo sampling of the analytic importance function per pixel per frame, which seems prohibitive to achieve. In this paper, we propose an approximation of the importance function that can be evaluated in real-time. Since subsurface scattering is more pronounced in certain regions (e.g., with light gradient change), we propose an adaptive sampling method based on temporal variance to lower the required number of samples. We propose a one phase adaptive sampling pass that is unbiased, and able to adapt to scene changes due to motion and lighting. To further improve the quality, we explore temporal reuse with a guiding pass prior to the final temporal anti-aliasing (TAA) phase that further improves the quality. Our local guiding pass does not constrain the TAA implementation, and only requires one additional texture to be passed between frames. Our proposed variance-guided algorithm has the potential to make stochastic sampling algorithm effective for real-time rendering.

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