Related Experiment Video
Updated: Jul 1, 2026
19:16
Live Cell Imaging of F-actin Dynamics via Fluorescent Speckle Microscopy (FSM)
Published on: August 5, 2009
Identifying non-stationarities in random EM fields: are speckles really disturbing?
John Broky1, Jeremy Ellis, Aristide Dogariu
1College of Optics and Photonics, CREOL, University of Central Florida, Orlando, Florida 32816, USA.
Optics Express
|September 17, 2008
Summary
Ensemble averaging is common for random electromagnetic fields. However, this study shows enhanced backscattering and other spatial non-stationarities can be found from a single field snapshot.
Area of Science:
- Wave propagation
- Electromagnetic fields
- Statistical physics
Background:
- Ensemble averaging is a standard technique for analyzing random electromagnetic (EM) fields.
- Characterizing spatial non-stationarities in wave interactions with random media typically requires multiple field realizations.
Purpose of the Study:
- To demonstrate that spatial non-stationarities, like enhanced backscattering, can be identified from a single snapshot of random EM fields.
- To show that fourth-order correlations provide sufficient information for this analysis.
Main Methods:
- Analysis of a single realization (snapshot) of wave interaction with a random medium.
- Calculation of fourth-order correlations between field components at two distinct spatial points.
Main Results:
- Spatial non-stationarities, including enhanced backscattering, are detectable from a single field snapshot.
- Fourth-order field correlations contain the necessary information to identify these non-stationarities.
Conclusions:
- The findings challenge the necessity of ensemble averaging for identifying certain spatial non-stationarities in random EM fields.
- Fourth-order correlation analysis offers a viable alternative for characterizing wave phenomena in random media from limited data.
Related Concept Videos
01:04Random Error
Random or indeterminate errors originate from various uncontrollable variables, such as variations in environmental conditions, instrument imperfections, or the inherent variability of the phenomena being measured. Usually, these errors cannot be predicted, estimated, or characterized because their direction and magnitude often vary in magnitude and direction even during consecutive measurements. As a result, they are difficult to eliminate. However, the aggregate effect of these errors can be...
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
01:08Outliers and Influential Points
An outlier is an observation of data that does not fit the rest of the data. It is sometimes called an extreme value. When you graph an outlier, it will appear not to fit the pattern of the graph. Some outliers are due to mistakes (for example, writing down 50 instead of 500), while others may indicate that something unusual is happening. Outliers are present far from the least squares line in the vertical direction. They have large "errors," where the "error" or residual is the vertical...
01:14NMR Spectrometers: Resolution and Error Correction
When magnetic nuclei in a sample achieve resonance and undergo relaxation, the signal detected in NMR is an approximately exponential free induction decay. Fourier transform of an exponential decay yields a Lorentzian peak in the frequency domain. Lorentzian peaks in an NMR spectrum are defined by their amplitude, full width at half maximum, and position, where the peak width is governed by the spin-spin relaxation time alone. In real experiments, however, the applied magnetic field is rendered...
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
01:20Random and Systematic Errors
Scientists always try their best to record measurements with the utmost accuracy and precision. However, sometimes errors do occur. These errors can be random or systematic. Random errors are observed due to the inconsistency or fluctuation in the measurement process, or variations in the quantity itself that is being measured. Such errors fluctuate from being greater than or less than the true value in repeated measurements. Consider a scientist measuring the length of an earthworm using a...