Sökning: "attenuation coefficients"

Visar resultat 1 - 5 av 18 avhandlingar innehållade orden attenuation coefficients.

1. 1. Colour Correction of Underwater Images Using Spectral Data

   Författare :Julia Åhlén; Ewert Bengtsson; Jussi Parkkinen; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Bildanalys; Colour; Correction; Attenuation; Coefficient; Underwater; Bildanalys; Image analysis; Bildanalys; Computer science;

   Sammanfattning : For marine sciences sometimes there is a need to perform underwater photography. Optical properties of light cause severe quality problems for underwater photography. Light of different energies is absorbed at highly different rates under water causing significant bluishness of the images. LÄS MER

3. 2. Scattering of elastic waves by an anisotropic sphere

   Författare :Ata Jafarzadeh; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Sphere; T matrix; Effective wave number; Distribution of inclusions; Phase velocity.; Anisotropy; Attenuation; Scattering;

   Sammanfattning : Scattering of a plane wave by a single spherical obstacle is the archetype of many scattering problems in physics and geophysics. Spherical objects can provide a good approximation for many real objects, and the analytic formulation for a single sphere can be used to investigate wave propagation in more complicated structures like particle composites or grainy materials, which may have application in non-destructive testing, material characterization, medical ultrasound, etc. LÄS MER

4. 3. Scattering of elastic waves by an anisotropic sphere with application to polycrystalline materials

   Författare :Ata Jafarzadeh; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Spherical obstacle; Anisotropy; Attenuation; Polycrystalline materials; Effective wave number; T matrix; Phase velocity; Scattering;

   Sammanfattning : Scattering of a plane wave by a single spherical obstacle is the archetype of many scattering problems in various branches of physics. Spherical objects can provide a good approximation for many real objects, and the analytic formulation for a single sphere can be used to investigate wave propagation in more complex structures like particulate composites or grainy materials, which may have applications in non-destructive testing, material characterization, medical ultrasound, etc. LÄS MER

5. 4. Methods Used in Quality Assurance and Optimization in Nuclear Medicine Imaging and Imaging Systems

   Författare :Sven-Åke Starck; Sten Carlsson; Göteborgs universitet; []
   Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; phantom; image quality; attenuation coefficients; detective quantum efficiency DQE ; digital filtering; iterative reconstruction; bone scintigraphy; bone SPECT; visual grading analysis VGA ; ROC-analysis;

   Sammanfattning : .... LÄS MER

7. 5. Magnetic resonance imaging with ultrashort echo time as a substitute for X-ray computed tomography

   Författare :Adam Johansson; Tufve Nyholm; Karlsson Mikael; James Balter; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; magnetic resonance imaging; computed tomography substitute; ultrashort echo time; parallel imaging; radial imaging; radiofysik; radiation physics;

   Sammanfattning : Radiotherapy dose calculations have evolved from simple factor based methods performed with pen and paper, into computationally intensive simulations based on Monte Carlo theory and energy deposition kernel convolution.Similarly, in the field of positron emission tomography (PET), attenuation correction, which was originally omitted entirely, is now a crucial component of any PET reconstruction algorithm. LÄS MER