Although is not a major error source at C-band, attenuation may degrade the radar measurement to a considerable degree in situations like a precipitation event in the radar shadow of a strong convective cell, or may affect precipitation accumulation estimates at distances far from the radar site. For C-band radars, attenuation can be corrected using different methods depending on the type of me...

Reliable attenuation correction methods for quantitative emission CT (ECT) require accurate delineation of the body contour and often necessitate knowledge of internal anatomic structure. Two broad classes of methods have been used to calculate the attenuation map: transmission-less and transmission-based attenuation correction techniques. Whereas calculated attenuation correction belonging to ...

In this paper, the link quality in SHF and EHF ranges are studied. In order to achieve high data rate higher frequencies must be used – centimeter waves (SHF), millimeter waves (EHF) or optical range. However, there are significant problem when a radio link work in that diapason – rain attenuation and attenuation in earth’s atmosphere. Based on statistical rain rates data for Bulgaria, the link...

There is growing interest in using seismic attenuation for reservoir characterization. We measure limestone samples in the laboratory to analyze attenuation and elastic moduli as a function of frequency from 3 Hz to ultrasonic. We observe that there is a positive correlation between bulk modulus dispersion and permeability. We also measure different modes of attenuation and find that the attenu...

In this work an N-state Markov Chain model is attempted to validate, which is used to generate an attenuation time series. The model is applicable for estimating the CCDFs (complement cumulative distribution function) of attenuation. The state transition probability parameters of the model is determined from fade slope statistics of attenuation. The conditional probability density function of f...

PURPOSE To utilize Gaussian mixture model (GMM) for the quantification of chronic obstructive pulmonary disease (COPD) and to evaluate the combined use of multiple types of quantification. MATERIALS AND METHODS Eighty-seven patients (67 men, 20 women; age, 67.4 ± 11.0 years) who had undergone computed tomography (CT) and pulmonary function test (PFT) were included. The heterogeneity of CT att...

UNLABELLED PET/MR offers potential advantages over PET/CT that are currently under investigation. One of the challenges of PET/MR is attenuation correction, as there is no simple correlation between MR signal intensity and the attenuation of 511-keV photons detected in PET. Currently, dedicated MR sequences are used to segment voxels into categories that are then assigned a predetermined attenu...

Measurements of minimum and average total tissue thicknesses overlying the fetus during the third trimester were taken on 52 patients between 24 and 40 weeks gestation. Minimum total thickness of tissues constantly along the ultrasound path had a mean value of 1.75 cm, ranging from 0.40 to 3.70 cm. This corresponded to a mean attenuation of 0.87 dB MHz-1, ranging from 0.30 to 1.68 dB MHz-1. Ave...