An in situ experimental study of variations of compressional wave speed and attenuation with depth in natural coral sands has been made offshore of Oahu, Hawaii. In situ data were collected at a center frequency of 7.5 kHz. Compressional wave speed averages around 1620 m/s and attenuation ~expressed as Qp , the reciprocal of the quality factor! decreases from 0.04 at the seafloor to 0.01 at 2 m...

This paper presents several fundamental frequency-domain bounds for a non-negative impulse response (NNIR) filter. Upper-bounds on power spectral attenuation and power spectral gain in geometrically spaced frequency regions are derived, when power spectral attenuation near frequency zero is limited. By analyzing the tightnesses of these bounds, the relationship between the maximally allowable p...

UNLABELLED Present attenuation-correction algorithms in whole-body PET/MRI do not consider variations in lung density, either within or between patients; this may adversely affect accurate quantification. In this work, a technique to incorporate patient-specific lung density information into MRI-based attenuation maps is developed and compared with an approach that assumes uniform lung density....

background and aims. cone-beam computed tomography (cbct) is an imaging system which has many advantages over computed tomography (ct). in ct scan, hounsfield unit (hu) is proportional to the degree of x-ray attenuation by the tissue. in cbct, the degree of x-ray attenuation is shown by gray scale (voxel value). the aim of the present study was to investigate the relationship between gray scale...

Golsar is located in north-west of Rasht the capital city of Guilan province. This region, according to standards 2800, is identified among the regions with relatively high risk of earthquake. A set of historical and instrumental seismicity data used in radius of 200 km which covers the period twelveth century until now. Kijko method has been applied for estimating for parameters considering of...

The Relationship between rain attenuation and depolarization at frequencies above 10GHz is useful for designing high-speed out-door wireless systems, such as satellite communication, millimeter FWA(Fixed Wireless Access) system and so on. Due to rapid growth of and strong demand for high speed communication, usage of millimeter wave bands in wireless system becomes in reality. The objective of ...

We review theoretical models to show that contrast reduction at a specific wavelength in the horizontal direction depends directly on the beam attenuation coefficient at that wavelength. If a black target is used, the inherent contrast is always negative unity, so that the visibility of a black target in the horizontal direction depends on a single parameter only. That is not the case for any o...

A correlation between near-infrared atmospheric attenuation measurements made by the Atmospheric Visibility Monitor (AVM) at the Table Mountain Facility and airport surface weather observations at Edwards Air Force Base has been performed. High correlations (over 0.93) exist between the Edwards observed sky cover and the average AVM measured attenuations over the course of the 10 months analyze...