Showing 3 results for Attenuation
H Gh, H Sadeghi,
Volume 7, Issue 1 (8-2013)
Abstract
Wave velocity and attenuation are among the most important attributes of stress waves that propagate through geomaterials. Utilizing these attributes, it is possible to acquire useful information about porous geomaterials such as soil and rock and also the fluids that saturate the pores of geomaterials. The key point in order to gain this information is to establish an accurate link between field measurements of wave attributes and physical properties of geomaterials’ skeleton and pore fluid. The pore fluids and their inhomogeneous distribution fluid are among factors that affect wave velocity and attenuation to a considerable extent. Patchy saturation of pores which occurs on the scale larger than grains size but smaller than wavelength is one of the reasons that causes inhomogeneity in pore fluid distribution. The influence of such inhomogeneity is studied in present paper. Two different attenuation mechanisms including relative movement of fluid with respect to solid phase and also attenuation caused by grain to grain contact are implemented to fully assess wave attenuation. It is observed that the former attenuation is more dominant at higher frequencies compared to the latter attenuation.
Alimohammad Ajorloo, A. Yadolahi, A.r. Zolfaghari,
Volume 9, Issue 4 (3-2016)
Abstract
The use of heavy concrete as a protective shield against high-energy gamma rays is very common. It is also an effective, versatile and economical material. The heavy concrete production can use lead slag as raw materials. The use of lead slag in the production of concrete blocks saves natural resources and reduces the environmental problems caused by the accumulation of industrial waste. However, concrete production, due to the presence of heavy metals with high atomic number can be used as an effective shield against gamma radiation. This study examines the use of lead slag produced in the battery recycling process as concrete aggregates. For this purpose, strength and gamma-ray attenuation coefficient for concrete samples prepared by replacing 40 to 60 percent lead slag instead of natural aggregate. The effect of 1 to 5 percent lead powder in setting time of concrete was measured. The results showed that by increasing the amount of lead slag, density, mechanical strength and gamma-ray attenuation coefficient for concrete samples increased significantly, but lead powder delays setting time of cement paste. In general, appropriate lead slag concrete construction with minimal thickness, reduce the cost of protection and provides the highest level of attenuation
Mr. Ehsan Pegah, Mr. Behrang Feiz Aghaei,
Volume 18, Issue 3 (12-2024)
Abstract
Random noise reduction has always been one of the most important issues in seismic data processing. This study investigates one of the most effective random noise reduction methods, the 2D multi-stage median filter. This filter is applied to seismic data by applying a series of 1D median filters in different directions and then selecting the output value corresponding to the center of the 2D window. By applying a 2D multi-stage median filter to both synthetic and real data, it is shown that the filter can effectively attenuate random spike-like noise in both pre-stack and post-stack data. Similarly, based on spectral analysis, it is shown that this filter does a good job of reducing the level of high frequency random noise in both synthetic and real data. In this study, a 2D median filter is applied to synthetic data containing random noise with a density of 10%. Since increasing the filter length can damage useful signals in addition to attenuating random noise, it is important to specify an appropriate filter length. For synthetic data, the error ratio plot shows that a filter length of 9 points is appropriate for the first stage. In the second stage, a 2D median filter with a length of 7 points was applied to the output of the first stage filter. The effect of this filter on random noise suppression can then be observed by spectral analysis. In addition, median filters of 7 points and 5 points were applied to the pre-stack and post-stack real data, respectively. The effect and efficiency of this filter is assessed by examining the resulting difference plots, sections and spectral analysis.
