Scattering and information

The paper discusses some aspects of scattering of electromagnetic radiation in inhomogeneous media from the point of view of information theory. A theory is developed, based on a concrete model of a typical scattering experiment, which takes into account the finiteness of the scattering volume and the coherence characteristics of the radiation; as a conclusion, the speckle noise which is superimposed over the signal is brought into evidence. More exactly, it is shown that the spurious oscillations are due to the non-vanishing character of the convolution square of the inhomogeneity distribution function at the point of truncation in the primary space. Subsequently, the structural information of scattering experiments is examined and the finite logoncontent determined. The sampling interval is established and the resolution achievable in scattering measurements is deduced; also the means by which it can be improved are examined. An analysis of the quantitative information obtainable is pursued and the desirability of filtering is suggested. Finally, the way in which the partial coherence effectively acts as a low-pass filter is studied.

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Models of the Bouguer gravity and geologic structure at Yucca Flat, Nevada

Geophysics ◽

10.1190/1.1442458 ◽

1988 ◽

Vol 53 (2) ◽

pp. 231-244 ◽

Cited By ~ 18

Author(s):

John F. Ferguson ◽

Roger N. Felch ◽

Carlos L. V. Aiken ◽

John S. Oldow ◽

Holly Dockery

Keyword(s):

Structural Information ◽

Three Dimensional ◽

Structural Features ◽

Bouguer Gravity ◽

Three Dimensional Model ◽

Geologic History ◽

The West ◽

Pass Filter ◽

Low Pass Filter ◽

Low Pass

The Bouguer gravity anomaly at Yucca Flat, Nevada, has been modeled by two different techniques: the Cordell‐Henderson and Parker‐Oldenburg methods. The three‐dimensional model has incorporated known density and structural information where possible. These models predict the structural relief on the Cenozoic‐Paleozoic contact to within 150 m or about 15 percent of the actual depth. The three‐dimensional Parker‐Oldenburg method has been found to be efficient in an application involving a large (9000 sample) data base. Numerical stability was ensured by the application of a consistent regularization (a low‐pass filter tuned to suppress the noise‐dominated portion of the data spectrum) of the downward continuation operator. The use of a single regularizing filter for the entire model is not completely satisfactory due to the oversmoothing of shallow regions of the basin. The model is useful in the delineation of the geologic history of the area. Structural features in the model support the hypothesis that regional stress fields rotated significantly during the Tertiary. Major structural elements of the basin are well defined on the Cenozoic‐Paleozoic interface. The principal basin‐bounding fault is the large‐throw Carpetbag fault on the west. This fault was most active during the earliest phases of subsidence. The Yucca fault is seen to be a much smaller feature in the model presented here. The basin is rotated down to the west, with normal hinge faults on the eastern margin.

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Filtering of Electronic Speckle Correlation Fringes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.198-199.1202 ◽

2012 ◽

Vol 198-199 ◽

pp. 1202-1207

Author(s):

Fei Guo ◽

Mei Zhao ◽

Xiu Ying Fan ◽

Jin He Bao ◽

Wen Bang Sun

Keyword(s):

Frequency Domain ◽

Speckle Noise ◽

Filter Medium ◽

Space Domain ◽

Pass Filter ◽

Low Pass Filter ◽

Speckle Correlation ◽

Low Pass ◽

Mean Filter

Speckle correlation fringes include a large quantity of speckle noise. It is first to consider how to reduce speckle noise before using phase formula to calculate. Filter is usually used to reduce speckle noise. From two aspects of frequency domain and space domain, we adopted mean filter, medium filter, Butterworth low-pass filter and homomorphism filter to process the speckle correlation fringes obtained by experiment. It is shown that the speckle correlation fringes are clearer and more easily interpreted and automatic processed after being filtered.

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Trajectory tracking compensation for teleoperation with transmission delays

Robotica ◽

10.1017/s0263574711000075 ◽

2011 ◽

Vol 29 (6) ◽

pp. 863-871 ◽

Cited By ~ 5

Author(s):

Lingyan Hu ◽

Xiaoping P. Liu ◽

Guoping Liu ◽

Shaoping Xu

Keyword(s):

Trajectory Tracking ◽

Time Delays ◽

Point Of View ◽

Pass Filter ◽

Low Pass Filter ◽

Transmission Delays ◽

Additional Signal ◽

Wave Variables ◽

Reference Velocity ◽

Low Pass

SUMMARYThe proper transmission of wave variables rather than power variables in teleoperation with time delays ensures system passivity – rendering the entire system stable, but the introduction of wave variables leads to distortion between the velocities/positions of the master and slave, and the performance deteriorates significantly with the increase of time delays. This paper presents a new compensating scheme implemented at the slave side to remove or cancel partially the distortion. The system passivity can still be maintained by tuning a properly designed low-pass filter. Compared with previous work, the main contribution of this work exists in two points: first, it is the actual velocity/trajectory of the slave rather than the reference velocity/trajectory of the slave that tracks the master one, so the quality of tracking is better and converges faster; second, the proposed compensator does not require any additional signal from the master side, minimizing the amount of data transmitted over the channel, which is very important from the practical point of view. The simulation and experiment results show that the velocity (or trajectory) tracking is significantly improved under the condition of stability, and the force presented to the user is close to the environment one, meaning a high degree of system transparency is achieved.

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Application of Empirical Wavelet Transform in Digital Image Watermarking

Traitement du signal ◽

10.18280/ts.370517 ◽

2020 ◽

Vol 37 (5) ◽

pp. 839-845

Author(s):

Mohammad Keivani ◽

Amir Mahdi Sazdar ◽

Jalil Mazloum ◽

Akram Esvand Rahmani

Keyword(s):

Wavelet Transform ◽

Image Watermarking ◽

Low Cost ◽

Original Data ◽

Point Of View ◽

Security Requirements ◽

Pass Filter ◽

Low Pass Filter ◽

Empirical Wavelet Transform ◽

Low Pass

Nowadays, rapid growth of the Internet and digital multimedia technologies make it possible to duplicate data without any loss of quality and at a very low cost. In this regard, manipulation of documents will easily be accomplished by applying digital art and without the copyright owner's permission. To deal with situation, more diverse security requirements are introduced every day. Watermarking is considered as one of the methods used for achieving this purpose. Watermarking is focused on inserting a subtle signal between the host media data somehow it does not change the original data, but they can be extracted if necessary. They are also used as a claim for ownership of the digital effect. Various methods have been presented for watermarking so far. These methods have been developed to overcome the weaknesses of previous methods. Empirical wavelet transform is taken into account as a new method for hiding and extracting military digital images with respect to alpha composition. As such, it is resistant to noise, low pass filter and compression. Analytical studies showed that this method is more efficient than other methods from quantitative and qualitative point of view.

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