Thought controlled IRCC using cross-correlation of different frequency band sequence

AbstractS5 0716+714 is a well-studied BL Lac object in the sky. Verifying the existence of correlations among the flux variations in different bands serves as an important tool to investigate the emission processes. To examine the possible existence of a lag between variations in different optical bands on this source, we employ a discrete correlation function analysis on the light curves. In order to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties, we perform Monte Carlo simulations called ‘flux redistribution/random subset selection’. Our analysis confirms that the variations in different optical light curves are strongly correlated. The time lags show a hint of the variations in high frequency band leading those in low frequency band of the order of a few minutes.

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Time Correction of Ocean-Bottom Seismometers Using Improved Ambient Noise Cross Correlation of Multicomponents and Dual-Frequency Bands

Seismological Research Letters ◽

10.1785/0220200358 ◽

2021 ◽

Author(s):

Jinyu Tian ◽

Jian Lin ◽

Fan Zhang ◽

Min Xu ◽

Yayun Zhang ◽

...

Keyword(s):

Frequency Band ◽

Ambient Noise ◽

Cross Correlation ◽

Single Frequency ◽

Ocean Bottom ◽

Ocean Bottom Seismometer ◽

Dual Frequency ◽

General Applicability ◽

Time Correction ◽

Noise Cross Correlation

Abstract An effective approach was developed for identifying and correcting ocean-bottom seismometer (OBS) time errors through improving ambient noise cross-correlation function (NCCF) analysis and combination with other methods. Significant improvements were illustrated through analyzing data from a passive-source seismic experiment in the southwestern sub-basin of the South China Sea. A novel method was first developed that can effectively identify errors in the sampling frequency of the OBS instruments. The traditional NCCF method was then expanded by increasing the analyzed data spectrum from a single-frequency band to dual-frequency band pairs, thus doubling the number of available data points and substantially improving the time correction quality. For data with relatively low signal-to-noise ratios, the average time errors were reduced from the original average values of 60–80 ms by the conventional methods to <40 ms using the improved approaches. The new multistep procedure developed in this study has general applicability to analysis of other OBS experiments. The demonstrated significant improvements in the data quality are critical for advancing seismic tomography and other modern marine geophysical studies that require high accuracy in the OBS data.

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Artefact in 20Å-Resolution Electron Images of Negatively Stained Twodimensional Membrane Protein Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053231 ◽

1982 ◽

Vol 40 ◽

pp. 92-93

Author(s):

Douglas L. Dorset ◽

Barbara Moss

Keyword(s):

Electron Scattering ◽

Cross Correlation ◽

Transmission Function ◽

Group Symmetry ◽

Asymmetric Structure ◽

Object Model ◽

Phase Object ◽

Computing Systems ◽

Resolution Electron ◽

Plane Group

A number of computing systems devoted to the averaging of electron images of two-dimensional macromolecular crystalline arrays have facilitated the visualization of negatively-stained biological structures. Either by simulation of optical filtering techniques or, in more refined treatments, by cross-correlation averaging, an idealized representation of the repeating asymmetric structure unit is constructed, eliminating image distortions due to radiation damage, stain irregularities and, in the latter approach, imperfections and distortions in the unit cell repeat. In these analyses it is generally assumed that the electron scattering from the thin negativelystained object is well-approximated by a phase object model. Even when absorption effects are considered (i.e. “amplitude contrast“), the expansion of the transmission function, q(x,y)=exp (iσɸ (x,y)), does not exceed the first (kinematical) term. Furthermore, in reconstruction of electron images, kinematical phases are applied to diffraction amplitudes and obey the constraints of the plane group symmetry.

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Application of cross correlation to HREM images of surfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100128080 ◽

1987 ◽

Vol 45 ◽

pp. 754-755

Author(s):

D. E. Luzzi ◽

L. D. Marks ◽

M. I. Buckett

Keyword(s):

Cross Correlation ◽

A Priori ◽

Matrix Material ◽

Correlation Method ◽

Accurate Knowledge ◽

Complex Image ◽

Fourier Filtering ◽

The Matrix ◽

Low Pass ◽

Data Reduction Technique

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.

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