Sökning: "high frequency characterization"

Visar resultat 16 - 20 av 229 avhandlingar innehållade orden high frequency characterization.

  1. 16. Experimental verification of tomographic measurement methods in ultrasound

    Författare :Monica Almqvist; Avdelningen för Biomedicinsk teknik; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; airborne.; high resolution; characterization; tomography; light diffraction; doppler; ultrasound; vector tomography; Instrumentation technology; Mät- och instrumenteringsteknik;

    Sammanfattning : This thesis describes two different measurement methods applied to ultrasound. The first method, Ultrasound doppler vector tomography, uses ultrasound to measure blood flow and the second method, Light diffraction tomography, measures the pressure field in an ultrasound beam with laser light. LÄS MER

  3. 17. Enhancements in Dielectric Response Characterization of Insulation Materials

    Författare :Xiangdong Xu; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; harmonic limited waveform; air reference method; contact-free electrode; geometric corrections.; frequency domain spectroscopy; Dielectric characterization;

    Sammanfattning : The increasing demand of integrating various renewable energy recourses in power system requires extensive use of power electronic solutions, such as HVDC and FACTS, as these techniques allow energy conversion between different frequencies and serves to stabilize the network. Consequently, electric stresses other than traditional 50/60 Hz sinusoidal voltage stress are acting on high voltage insulation materials. LÄS MER

  4. 18. Characterization of Microwave Transistors for Robust Receivers and High Efficiency Transmitters

    Författare :Mattias Thorsell; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; noise modeling; access resistance; self-heating; AlGaN GaN HEMT; thermal characterization; active load-pull; load modulation;

    Sammanfattning : The next generation of integrated transceiver front-ends needs both robustlow noise amplifiers and high power amplifiers on a single-chip. The AluminiumGallium Nitride / Gallium Nitride (AlGaN/GaN) High Electron MobilityTransistors (HEMT) is a suitable semiconductor technology for this purposedue to its high breakdown voltage and high electron mobility. LÄS MER

  5. 19. Effect of Dielectric and Magnetic Material Characteristics on Frequency Response of Power Transformers

    Författare :Nilanga Abeywickrama; Chalmers tekniska högskola; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; frequency response analysis; dielectric insulation; Complex permeability; core magnetization; finite element method; transformer diagnosis.; high frequency modelling; magnetic viscosity; silicon steel;

    Sammanfattning : Frequency response analysis (FRA) technique has become increasingly popular for the assessment of mechanicalintegrity in power transformers. This method is based on the fact that the shape of the frequency response at higher frequencies is uniquely determined by the geometrical construction of the transformer. LÄS MER

  7. 20. Remote Acoustic Characterization of Thin Sheets

    Författare :Etienne Mfoumou; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Remote acoustic excitation; material characterization; acoustic NDT; vibration-based technique; sheet material evaluation; fracture toughness.;

    Sammanfattning : There is a need to monitor the existence and effects of damage in structural materials. Aircraft components provide a much publicized example, but the need exists in a variety of other structures, such as layered materials used in food packaging industries. LÄS MER