Sökning: "attenuation"

Visar resultat 6 - 10 av 408 avhandlingar innehållade ordet attenuation.

1. 6. Assessment of attenuation correction methods for quantitative neuro-PET/MR

   Författare :Joao M. Sousa; Mark Lubberink; Lieuwe Appel; Håkan Ahlström; Mathias Engström; Ivo Rausch; Radiologi Uppsala universitet; []
   Nyckelord :MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; PET; MRI; attenuation correction; 68Ge transmission; quantification; 11C-PE2I; MRAC; DAT; CBF; Medicinsk radiofysik; Medical Radiophysics;

   Sammanfattning : Hybrid PET/magnetic resonance (MR) can provide physiological, functional, and structural information simultaneously, facilitating research in neurological disorders. For quantitative PET, correction for photon attenuation (AC) is necessary. LÄS MER

3. 7. Novel computational methods for image analysis and quantification using position sensitive radiation detectors

   Författare :Alejandro Sanchez Crespo; Stig A. Larsson; Magnus Dahlbom; Stockholms universitet; []
   Nyckelord :LANTBRUKSVETENSKAPER; AGRICULTURAL SCIENCES; SPET; PET; CMOS; spatial resolution; photon depth of interaction; positron annihilation; positron range; non-collinearity; scatter; attenuation; lung ventilation; lung perfusion; breast tumour; Medicine; Medicin;

   Sammanfattning : The major advantage of position sensitive radiation detector systems lies in their ability to non invasively map the regional distribution of the emitted radiation in real-time. Three of such detector systems were studied in this thesis, gamma-cameras, positron cameras and CMOS image sensors. LÄS MER

4. 8. Longer Wavelength GaAs-Based VCSELs for Extended-Reach Optical Interconnects

   Författare :Ewa Simpanen; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; vertical-cavity surface-emitting laser; high-speed modulation; reach; chromatic dispersion; single-mode; multi-mode; attenuation; optical interconnect;

   Sammanfattning : Data centers of today are increasing in size and are built to accommodate strong traffic demands while providing sustainably by having clients sharing resources under one roof. Their massive scale puts pressure on the server network topology and has incited a need for data transmission links that are energy efficient and capable of operation at high bit rates with reach up to a few kilometers. LÄS MER

5. 9. Basin-scale change in water availability and water quality under intensified irrigated agriculture

   Författare :Rebecka Törnqvist; Jerker Jarsjö; Marcel van der Perk; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Irrigation; Hydrology; Land-use change; Basin-scale; Central Asia; Aral Sea; Semi-arid; Return flow; Water saving; Health risk; Water quality; Surface water; Groundwater; Nitrogen; Attenuation; Recirculation; Climate change; Physical Geography; naturgeografi;

   Sammanfattning : Changes in land use and water use can greatly impact the cycling of water and water-borne substances. Increased redistribution of river water to irrigated fields can cause enhanced evapotranspiration and decreased river discharge. LÄS MER

7. 10. 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