Sökning: "wave number"

Visar resultat 1 - 5 av 362 avhandlingar innehållade orden wave number.

1. 1. Three-wave mixing in Josephson travelling-wave parametric amplifiers

   Författare :Hampus Renberg Nilsson; Chalmers University of Technology; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; three-wave mixing; lumped-element; four-wave mixing; SNAIL; Josephson junction; travelling-wave parametric amplifier; parametric amplifier; parametric amplification; resonant phase matching.; rf-SQUID;

   Sammanfattning : This work explores possibilities of building a wide-band, quantum-limited low-noise amplifier by means of three-wave mixing (3WM) in different kinds of Josephson travelling-wave parametric amplifiers (TWPAs). We extend the theory of the continuous three-mode model to include any number of up-converted modes in the small frequency limit where the frequency dispersion is close to linear. LÄS MER

3. 2. Experimental Determination of Aeracoustic Sources in Low Mach Number Internal Flows

   Författare :Andreas Holmberg; Hans Bodén; Lars Enghardt; KTH; []
   Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Aeracoustics; ducts; N-ports; scattering matrix; wave decomposition; source determination; over-determination; flow noise; fluid-acoustic interaction; fluid-structure-acoustic interaction; wave number; T-junction; power balance; grazing-bias flow; Acoustics; Akustik; Vehicle engineering; Farkostteknik;

   Sammanfattning : In this thesis, the in-duct experimental methods for determining aeroacoustic N-ports of in-duct elements are discussed and improved. The scattering matrix determination methods and the related wave decomposition methods are evaluated from measurements in an empty duct carrying a mean flow. LÄS MER

4. 3. Ultrasound based shear wave elastography of the liver : a non-invasive method for evaluation of liver disease

   Författare :Marie Byenfeldt; Anders Elvin; Per Fransson; Odd Helge Gilja; Umeå universitet; []
   Nyckelord :MEDICAL AND HEALTH SCIENCES; MEDICIN OCH HÄLSOVETENSKAP; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; Anthropometric measurement; diagnostic imaging; elasticity imaging technique; blood supply; BMI; body position; fatty liver; liver disease; hepatic steatosis; liver fibrosis; liver stiffness; obesity; postural change; pressure; probe; sex characteristic; shear wave elastography; skin-to-liver capsule distance; transducer and ultrasonography; Radiography; radiografi;

   Sammanfattning : Background: Detecting liver disease at an early stage is important, given that early intervention decreases the risk of developing cirrhosis and subsequently hepatocellular cancer (HCC). The non-invasive ultrasound-based shear wave elastography (SWE) has been used clinically for a decade to assess liver stiffness. LÄS MER

5. 4. Millimeter-wave Networking : Fundamental Limits, Scalable Algorithms, and Design Insights

   Författare :Hossein Shokri-Ghadikolaei; Carlo Fischione; Gabor Fodor; Muriel Madard; KTH; []
   Nyckelord :ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; Electrical Engineering; Elektro- och systemteknik;

   Sammanfattning : The current demands for extremely high data rate wireless services and the spectrum scarcity at the sub-6 GHz bands are forcefully motivating the use of the millimeter-wave (mmWave) frequencies. The main characteristics of mmWave communications are severe attenuation, sparse-scattering environment, huge bandwidth, vulnerability to obstacles and antenna misalignment, massive beamforming, and possible noise-limited operation. LÄS MER

7. 5. Millimeter-Wave Photonics: Signal Sources and Transmission Links

   Författare :Andreas Wiberg; Chalmers University of Technology; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; microwave photonics; mm-wave generation; radio over fiber; photonic frequency multiplication; millimeter-wave photonics; millimeter-waves; millimeter-wave communication system;

   Sammanfattning : With the use of higher and higher frequencies in a number of current and future wireless millimeter-wave applications it is beneficial to use photonics for several reasons. The use of optical fibers is an advantageous way to transport millimeter-waves in terms of loss, mechanical flexibility, weight, and insensitivity to electromagnetic interference. LÄS MER